dissertation print copy

LEAD SORPTION FROM INDUSTRIAL EFFLUENTS USING

AGRICULTURAL WASTES: IDENTIFICATION OF THE

BEST METHOD FOR NIGERIA.

BY

LAIYEMO, MICHAEL ADEMOLA

(STUDENT ID: 1123956)

A DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE AWARD OF

A MASTERS OF SCIENCE DEGREE IN ENVIRONMENTAL SCIENCE:

LEGISLATION AND MANAGEMENT

SUPERVISOR: DR. ABDUL CHAUDHARY

SEPTEMBER 2012

Laiyemo, Michael A. 1123956

DEDICATION

I dedicate this dissertation to my parents Mr Omololu and Mrs Feyisara Laiyemo, for whom

God has used to be my pillar of support during my course of study. Just to let you know that

out of a billion parents, I will choose both of you over and over again and this work would not

have been possible without you. Thank you very much.

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ACKNOWLEDGEMENT

“Instruct the wise and they will be wiser; teach the righteous and they will add to their learning” Prov. 9: 9.

Most supervisors fix appointments for consultation but an exception is Dr. Abdul Chaudhary whose door is always opened for students. My greatest appreciation goes to my supervisor, Dr. Abdul Chaudhary because of his magnificent support and guidance during this dissertation.

I appreciate the support of my sisters; Kofo, Kemi and especially Lamide who has significantly been part of my educational progress.

My brothers from another mother; Mayowa Oshin and Godwin Nwokobia, thank you guys for the moral support, and being there for me in times of need. May God reward you abundantly.

To the almighty God, who has brought me this far in life, continue to guide and protect me in all my ways of life.

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CERTIFICATE OF AUTHORSHIP

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“I, Laiyemo Michael A., hereby certify that:

Each and every quotation, diagram or other piece of exposition which is copied from or based upon the work of others has its source clearly cited and referenced in the text at the place where it appears.

All research studies in this report have been carried out by me with no more assistance from members of the institution than has been specified.

Name: Laiyemo, Michael A.

Signature:

Date: 21st September, 2012


ABSTRACT

This study demonstrates why Nigeria as a developing country and having series of lead pollution problems by processing industries should implement a cheap and efficient technology for lead removal from industrial effluent. The Federal Environmental Protection Agency (FEPA) set down policies for processing industries to engage in the best available technology (BAT) during effluent treatment and there has to be reduction of toxic chemicals to a minimum level before effluents are discharged into receiving waters.

So despite the numerous methods to remove lead from a solution, biosorption technology is the most cost effective and environmentally friendly because it makes use of reusable low cost agricultural waste as adsorbent.

In this study, comparative analysis of selected agricultural wastes used in the preparation of adsorbents for the biosorption of lead from industrial effluent was done. The agricultural wastes compared are orange peels, sugarcane bagasse, rice husk and maize cob. The study was performed in order to identify the best agriculture waste in terms of adsorption efficiency and cost effectiveness that can be introduced in the biosorption of lead from industrial effluents in Nigeria.

Each selected agricultural wastes was subjected to SWOT and PEST analyses in which the analyses were based on adsorption capacity of the adsorbent, the adsorption rates, equilibrium time for lead removal, availability of the agricultural waste in Nigeria, desorption rate of the adsorbed lead from the adsorbent, the social and environmental impact and finally the political implications of using the agricultural wastes.

Work done by researchers (secondary data) were used throughout this study and it was discovered that adsorption capacity of the agricultural wastes differ depending on the adsorbent treatment, temperature of reaction, pH of the solution, contact time and adsorbent loading.

However based on the available data, the research showed that modified adsorbents show better adsorption capacities than unmodified adsorbents. Triethylene-tetramine modified sugarcane bagasse has the highest adsorption capacity of 313mg/g compared to the other wastes and further evaluation of the comparative parameters highlighted that triethylene-tetramine modified bagasse is the best method that can be used in lead biosorption from industrial effluents in Nigeria.

Keywords: Adsorbent; Agricultural wastes; Biosorption; Lead; Industrial effluent; Nigeria;

Adsorption capacity; SWOT analysis; PEST analysis.

CONTENTS

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Title PageACKNOWLEDGEMENT...........................................................................................................................3

ABSTRACT..................................................................................................................................................5

LIST OF ABBREVIATIONS.....................................................................................................................9

LIST OF FIGURES...................................................................................................................................10

LIST OF TABLES.....................................................................................................................................11

CHAPTER 1: INTRODUCTION.............................................................................................................12

1.1 Background.................................................................................................................................12

1.2 Hypothesis..................................................................................................................................14

1.3 Aim of study...............................................................................................................................14

1.4 Objectives of study.....................................................................................................................14

1.5 Scope of study.............................................................................................................................15

1.6 Importance of the study...............................................................................................................15

1.7 Summary of the Report...............................................................................................................15

1.7.1 Introduction..........................................................................................................................15

1.7.2 Literature Review.................................................................................................................15

1.7.3 Methodology........................................................................................................................16

1.7.5 Conclusion and Recommendation........................................................................................16

CHAPTER 2: LITERATURE REVIEW.................................................................................................17

2.1 Lead and its toxicity....................................................................................................................17

2.2 Sources of lead pollution.............................................................................................................18

2.3.1 The Federal Environmental Protection Agency....................................................................21

2.3.2 Water pollution in Nigeria....................................................................................................22

2.4 Conventional methods for lead removal from an aqueous solution.............................................24

2.4.1 Ion exchange........................................................................................................................24

2.4.2 Precipitation method............................................................................................................24

2.4.3 Reverse osmosis...................................................................................................................24

2.4.4 Flocculation/Coagulation.....................................................................................................24

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2.5 Biosorption.................................................................................................................................25

2.6.1 Characterization of the adsorbents.......................................................................................27

2.6.2 Preparation of adsorbents for experiment.............................................................................30

2.6.3 Biosorption experimental procedure....................................................................................31

2.6.3.1 Kinetic studies...................................................................................................................32

2.6.3.2 Adsorption isotherm..........................................................................................................33

2.6.3.2.1 Freundlich isotherm.......................................................................................................33

2.6.3.2.2 Langmuir isotherm.........................................................................................................33

2.6.4 Desorption............................................................................................................................34

2.8 Conclusion..................................................................................................................................37

CHAPTER 3: Methodology......................................................................................................................39

3.1 Methodology...............................................................................................................................39

3.2 Analytical Tools..........................................................................................................................40

3.2.1 SWOT analysis....................................................................................................................40

3.2.3 Justification in using SWOT and PEST analytical tools.......................................................41

CHAPTER 4: Results and Discussion......................................................................................................43

4.1 Availability of the selected agricultural wastes...........................................................................43

4.1.1 Availability of Orange peel in Nigeria.................................................................................43

4.1.2 Availability of Sugarcane bagasse in Nigeria.......................................................................44

4.1.3 Availability of Rice husk in Nigeria.....................................................................................44

4.1.4 Availability of Maize cob in Nigeria....................................................................................44

4.2 Description of other comparison parameters...............................................................................44

4.2.2 Equilibrium time..................................................................................................................45

4.2.3 Adsorption rate.....................................................................................................................45

4.2.4 Desorption rate.....................................................................................................................45

4.3 Data collected.............................................................................................................................45

4.4 SWOT and PEST analysis of the selected agricultural wastes used for lead biosorption............48

4.5 Discussion...................................................................................................................................54

4.5.1 Outcome of the SWOT analyses..........................................................................................54

4.5.1.1 Orange peel.......................................................................................................................55

4.5.1.2 Rice husk...........................................................................................................................56

4.5.1.3 Sugarcane bagasse.............................................................................................................56

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4.5.1.4 Maize cob..........................................................................................................................57

4.5.2 Outcome of the PEST analyses............................................................................................58

CHAPTER 5: CONCLUSION AND RECOMMENDATION..............................................................60

5.1 Conclusion..................................................................................................................................60

5.2 Recommendation........................................................................................................................60

REFERENCES...........................................................................................................................................62

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LIST OF ABBREVIATIONS

AAS Atomic Absorption Spectrometer

ATSDR Agency for Toxic Substance and Disease Registry

BAT Best Available Technology

BOD Biological Oxygen Demand

COD Chemical Oxygen Demand

CSTR Continuously Stirred Tank Reactor

EDTA Ethylene diamine tetra-acetic acid

FEPA Federal Environmental Protection Agency

FTIR Fourrier Transfer Infrared Spectroscopy

SEM Scanning Electron Microscopy

SWOT Strength, Weakness, Opportunity and Technology

TOC Total Organic Carbon

PEST Political, Environmental, Social and Technological

UNEP United Nations Environmental Protection

WHO World Health Organisation

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LIST OF FIGURES

Figure Title Page

2.1 Schematic flow diagram showing the biosorption of heavy metalsindustrial wastewater using adsorbents…………………………………………36

3.1 Overview of the research study……………………………………………….39

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LIST OF TABLES

Table Title Page

3.1 The template of the SWOT matrix…………………………………………............40

4.1 Work done by researchers on the removal of lead from aqueous solution…………46 using the selected agricultural wastes

4.2 SWOT matrix for orange peel adsorbent used for lead biosorption………………..48

4.2.1 PEST analysis for orange peel adsorbent used for lead biosorption………………..49

4.3 SWOT matrix for rice husk adsorbent used for lead biosorption……………………50

4.3.1 PEST analysis of rice husk adsorbent used for lead biosorption…………………….51

4.4 SWOT matrix for sugarcane bagasse adsorbent used for lead biosorption………….51

4.4.1 PEST analysis of sugarcane bagasse adsorbent used for lead biosorption…………..52

4.5 SWOT matrix for maize cob adsorbent used for lead biosorption……………………53

4.5.1 PEST analysis of maize cob adsorbent used for lead biosorption…………………….54

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CHAPTER 1: INTRODUCTION

1.1 BackgroundWater is termed a universal solvent because it supports all life forms and it is the most useful

natural resource on earth (Iqbal and Gupta, 2009). Various uses of water include; agricultural

irrigation, household duties, industrial duties, transportation, power application and it can be

used as a method for waste dumping by manufacturing or processing industries (Rashed,

2001).

However, a report by Bartram and Helmer (UNEP/WHO, 1996) discussed that the use of toxic

chemicals and the implementation of agricultural drainage methods introduce contaminants

into the aquatic environment and therefore contribute to the degradation in water quality.

Hence this consequentially affects the aim of obtaining a sustainable socio-economic

development.

Moreover, pollution in water is mainly due to industrial effluents coming out of sewage

treatment plants (Rashed 2001) and of great concern are heavy metals like Iron (Fe), Copper

(Cu), Mercury (Hg), Manganese (Mn), Zinc (Zn), Cadmium (Cd) and Lead (Pb) because they

are the most significant liable for water contamination (Rashed, 2001). Hence they dissolve in

water and bio-accumulate in the food web thereby causing danger to both terrestrial and

ecological health (Alluri, et al., 2007).

There is not a known definition of heavy metals in most peer review reports but Heavy metals

are often described to have densities five times greater than water and they can be found in the

earth’s crust because they are naturally occurring elements (Neustadt and Pieczenik 2007).

But, small amounts of zinc, copper, iron, and manganese are useful to living organisms in

such a way that they act as metalloenzymes but their toxicity is exercised if they are in high

concentration. For these reasons, they are called trace elements (Harmanescu, et al., 2011).

However, lead and cadmium have no usefulness to living organisms but they tend to be toxic

at low concentration when in contact with organisms (Harmanescu, et al., 2011), giving an

indication that the principle hazard of heavy metals lies within the context of exposure to Lead

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or Cadmium (Jarup, 2003). Furthermore, Adebisi and Fayemiwo (2010) discussed the

significance of improved industrialization as partly the cause of environmental pollution

because industrial effluents containing heavy metals are introduced into sewers and water

bodies thereby causing contamination of in the surroundings.

In view of the foregoing, there is a consistent stress on water quality and availability therefore,

a concise regulation of water bodies is necessary. Hence, an irregularity in the standards set

for water protection may be detrimental to both ecological and environmental health (Ibrahim

and abdullahi, 2008).

As part of the regulation set by governments, industrial effluents need to be pre-treated for

heavy metal removal or reduction before they are dumped into the environment (Volesky,

2000). The methods that could be used to remove metals from solutions could be chemical

processes like precipitation, ion exchange process and reverse osmosis but these methods

could be less effective, costly and may need a lot of energy during operations (Saikaew, et al.,

2009).

Consequentially, the technology for metal Biosorption was initiated during 1980s (Volesky,

2001), and according to Saikaew et al (2009), the interest for the development of the

biosorption technology was heightened because there was the need for a more economical and

efficient separation technologies to remove heavy metals from waste water. Hence it is

envisaged to be a promising sustainable development technology where heavy metals are

removed from a solution, because there is a massive growth in the activities of the

metallurgical industries and they contribute to the increase of heavy metals polluting the water

resources (Shafaghat, et al., 2012).

Economically viable biosorption process involves the use of various types of adsorbents

including agricultural wastes. For biosorption process the adsorbent must be low cost,

abundant in the environment, or maybe a by-product or a waste product from an industry.

Therefore, most researchers have engaged in the use of various agricultural wastes in the

removal of heavy metals from solutions because of their availability or reduced cost and their

environmental friendliness (Shafaghat, et al., 2012).

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1.2 HypothesisDoes adsorption capacity of low cost agricultural wastes differ in removal of lead ion from

aqueous solutions? At which conditions is it most efficient in lead ion removal?

1.3 Aim of studyThe aim of this project is to investigate which low cost agricultural waste can best be used as

adsorbent for the removal of lead ion from aqueous solutions in Nigeria.

1.4 Objectives of studyThe following objectives have been highlighted to help achieve the aim of the research by

using S-W-O-T and P-E-S-T analysis;

To characterize the agriculture adsorbent materials to collect their chemical and

physical properties.

To detect the best conditions for lead ion removal in terms of temperature, pH,

adsorbent loading, and contact time.

To compare the adsorption capacities of selected low cost agricultural wastes.

To quantify the adsorption rate of lead ion.

To determine the potential for lead recoverability.

To determine the Nigerian legislation and policy that can drive the biosorption

technology.

To determine the socio-economic and environmental impact of each adsorbent.

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1.5 Scope of studyThis study is limited to the application of agricultural wastes as adsorbents to remove lead

present in industrial effluents in Nigeria. Furthermore, comparison will be made between

orange peels, sugarcane bagasse, maize cobs and rice husk for the biosorption technology in

order to determine which agricultural waste’s method is more sustainable for Nigeria.

1.6 Importance of the study Nigeria like any developing country is constraint with funds, the importance of this study is

therefore to find an environmental friendly way where lead extraction could be achieved

relatively in a cheaper means. By implementing such adsorbent in an industrial effluent

treatment process, it will save cost, energy, reduce carbon foot print and reduce environmental

pollution.

1.7 Summary of the ReportThis section discusses the format and stages involved in order to achieve the aim and

objectives of this study. The stages include: (i) Introduction (ii) Literature review (iii)

Methodology (iv) Results & Discussion and (v) Conclusion and Recommendation.

1.7.1 IntroductionThe background information leading to the study is discussed in this chapter, the importance

and scope of this study is also highlighted in this chapter. Also incorporated in this chapter are

the aims and objectives of the study.

1.7.2 Literature ReviewThis chapter discusses the relevant studies on the subject by analysing peer reviewed papers

and case studies relating to the research. Studies on lead and its toxicity, sources of

contamination, biosorption method of removal, and studies on the adsorbent characterisation

are evaluated in this chapter in order to meet the aim and objectives set out in chapter 1. In

addition, the area of study and the required regulation are discussed.

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1.7.3 MethodologyThe methods used to gather information and interpret the data used for the research objectives

are discussed in this chapter. The justification for opting for such method is presented and also

the reasons for nominating the scope of study are discussed.

1.7.4 Results and Discussion

This chapter highlights the results of findings from the study of literature review and critical

analysis and discussion is carried out for the intention of identifying the best agricultural

waste for biosorption method.

1.7.5 Conclusion and RecommendationA summary of the findings gotten from the research process is presented in this chapter. The

possibility and areas of further research is highlighted in this chapter and recommendations

are proposed in other to achieve the desired option for the study.

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CHAPTER 2: LITERATURE REVIEW

2.1 Lead and its toxicityIn physicochemical terms, lead is described as a soft metallic element having an atomic

number of 82, coupled with density of 11.34 g/cm3 and melting point of about 327.5 °C

(Pokras and Kneeland, 2008). The occurrence of lead in the environment is either through its

natural existence or by man’s anthropogenic activities which will be discussed later in this

report.

Lead was reported to be amongst the most investigated industrial and environmentally

harmful substance because its usage for industrial purposes was dated as far back as the

Roman Empire era (Gidlow, 2004). Also, Graeme and Pollack (1998) argued that; “lead

poisoning extracted from boiling grape juice in lead pots and from storing and curing

beverages in lead-lined containers may have contributed to the fall of the Roman Empire”.

Therefore as illustrated above, the toxicity of lead has been a prevalent issue since the

beginning of civilisation.

Although, some heavy metals are seen to be essential for living organisms at low

concentrations but studies have shown that even at low concentration, lead is highly toxic.

Even in recent times, the World Health Organisation (WHO, 2010) reported that 0.6% of the

worldwide threatening diseases are due to lead toxicity and as part of the health concerns,

WHO on four different occasions was able to carry out health risk assessment on lead

contaminated food in 1972. Various workshops for guidance on lead poisoning were also

initiated by WHO and these have been going on for over 38 years.

According to Agency for Toxic Substances and Disease Registry (ATSDR, 2007), the toxicity

on humans depends on various conditions like age, diet and the duration of exposure.

Furthermore, ATSDR discussed lead and dietary experiments involving adults who were

exposed to lead just after eating and it was discovered that the lead absorbed into their

bloodstreams was 6%. This is a very low rate compared to adults that have not eaten for a day,

and have about 60 to 80% absorption rate of lead into their blood stream.

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As a result of lead absorbed into the blood stream, the erythrocytes are the first target for

absorbed lead in humans and then it distributes all over the body tissues and the bone marrows

where almost all the absorbed lead is deposited. Studies have shown that lead conjugates to

give glutathione and up to 99% are excreted in adults but only 32% are excreted in children

giving an indication that children are more prone to lead poisoning. However, continuous

exposure to lead results in lead accumulation in the body either in adults or children and

increase in blood lead concentration will result in chronic lead poisoning (Kimani, 2005).

Various effects of lead poisoning in humans have been observed through experiments, Pokras

and Kneeland (2008) reported that absorbed lead replaces the body essential metallic elements

like calcium, magnesium and zinc thereby disrupting the usual body metabolism.

Furthermore, they explained how lead toxicity affects nervous system, giving rise to stomach

pain, and also causing anaemia due to reduction in red blood cells when the bone marrow is

being attacked. Additionally mental developments in children have been affected negatively

by low level of lead at about 10µg/dl because it reduces their intelligence and also distorts

coordination in children (Johnson, et al., 2009).

Lead toxicity was further illustrated by Zaki et al (2010) after exposing 8 Marino sheeps to

lead and the animals showed symptoms of depression, inflammatory eyeballs, blindness, and

reduction in their testosterone level. Also, Wister rats treated with dosage of lead showed

kidney malfunction, loss of appetite and reduction in growth rate (Missoun, et al., 2010).

Hence, by extrapolation these symptoms could also be linked to human poisoning by lead.

Basically the toxicity of lead goes a long way in affecting the body functions and as the saying

goes prevention is better than cure so instead of focussing on the treatment for affected

people, the best solution is to prevent lead contamination in the environment by limiting the

amount of lead fed into the environment.

2.2 Sources of lead pollutionAs discussed earlier, lead exists in the environment by its natural existence on earth or by

man’s anthropogenic activities. But studies have declared that most of its pollution is caused

by anthropogenic activities. According to a report by Weiss et al (1999), the global

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anthropogenic emission rates of lead is about 332 × 109 g/year and the global natural

emissions sum up to about 12 × 109 g/year. Comparing the two values, it is obvious that

human activities, contribute more to lead’s existence in the environment.

Furthermore, Weiss et al (1999) argued that by calculating interference factor (IF) of heavy

metals which is the ratio of global anthropogenic emission rates to global natural emission

rates, lead was discovered to have a high interference factor compared to the rest of the heavy

metals.

Leaded petrol was a major cause of lead pollution in the society but most countries have put a

stop to its use as part of lead pollution controls (Makokha, et al., 2008). Also, house paints

containing lead have been recently phased out in most countries because it was discovered

that lead contamination occurs when applying or removing the paint on the walls (WHO

2010).

Nevertheless, environmental contamination by lead is still on the rise due to increase in

industrialization in countries, especially developing countries. Despite the various ways of

lead contamination, contamination caused by effluents coming from process industries

contributes immensely to lead pollution (Nasrullah, et al., 2006).

However, this study is limited to the presence of lead in aqueous solution, and in practical

sense aqueous solution can be interchanged for industrial effluents. Manufacturing industries

that participate in battery production, metal plating, paint production, mining and smelting

contribute immensely to lead pollution (Gupta, et al., 2001) because the industrial effluents

coming out from these industrial processes are dumped into surface waters without adequate

treatments to remove the heavy metal (Nasrullah, et al., 2006).

Apparently, the constituents of these effluents are the dissolved part of the raw materials used

in production and also its by-products that are also referred to as waste product. For instance

lead smelting which involves separating lead from its ore (primary smelting) or from lead

products (secondary smelting), is done using a blast furnace in the reactor thereby producing a

high temperature during the process (World bank group, 1998). Hence, cooling water is used

19


during the production process which will in turn be discarded as waste water containing lead

and also, the removal of air pollutants by water scrubber solution contributes to the waste

water generated (Woodard & Curran, 2006).

Furthermore, Malakootian et al (2008) reported that pigments are one of the primary raw

materials during paint production and these pigments are made up of lead compounds so

consequently, the effluent from the paint production process also contributes to the

environmental contamination of lead.

Another illustration demonstrating sources of industrial effluents that causes lead pollution is

the waste water produced during the manufacture of lead-acid batteries. The stages in the

battery production that produces most waste water are the pasting process, the electrode

developing process and washing of the manufactured lead-acid batteries (Woodard & Curran,

2006). However these waste waters are discharged as effluents from the waste water treatment

plants into the river or sewers, and if not properly discarded by reducing the level of lead

content to the required amount set by regulations, there will be contamination of the food

chain in the environment because lead is non-biodegradable in the environment but ironically

it undergoes a process called bio-magnification (Alluri, et al., 2007).

So it is highly desirable to carry out a pre-treatment process on the waste water in order to

remove or reduce the lead present in the waste water before waste water treatment takes place.

2.3 Nigeria

Nigeria is a country situated in the western part of Africa on a coastal plain however, its size

of approximately 923,768 km2, and its population of 170 million made it known to people as

Africa’s most populous country (UNEP/OCHA, 2010). Furthermore, Nigeria’s geography is

diverse in nature due to its location, expanse and specific features. The tropical rain forest is

seen along the coast of the country and the northern region is known to have the Sahel

climatic condition (Ayinde, 2010).

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Hence, water resources is in abundance in Nigeria but not equally distributed and this can also

be attributed to the fact that there is high precipitation of about 3,000mm yearly in the south

eastern part and there is reduction in the annual precipitation in the northern part of the

country which is averagely 500mm yearly. Ironically, while there is frequent flooding in the

southern parts of Nigeria, the northern parts experience extreme water shortages (Anukam,

WHO/UNEP, 1997). As discussed by Okunola and Ikuomola (2010), the land which

Nigerians thrive on is richly blessed and also, the climate is quite favourable for the

production of different types of food and cash crops like maize, rice, cassava, cocoa, orange,

rubber, sugarcane and cotton.

Also the abundance of some natural resources like crude oil, natural gas, coal, bauxite, lead,

tin, gold, salt, kaolin etc. are not farfetched. The minerals present in Nigerian soil are mined

on regular basis and various farming activities coupled with agriculture are predominantly

means of lively hood amongst the Nigerian people (UNEP/OCHA, 2010).

However, even with the abundance of natural resources and good climatic condition, Nigeria

still has the problems of environmental pollution, poor technological know-how, and financial

constraints. These problems persist even with the drive of increasing industrialization in the

country, and these have negative impacts on the socio-economic and environmental sectors

within the country.

2.3.1 The Federal Environmental Protection AgencyThe Federal Environmental Protection Agency (FEPA) was introduced by the Nigerian federal

military government in 1988 for the purpose of overall environmental protection in Nigeria.

Various duties and responsibilities that were assigned to this body include the prevention and

the control of emitting dangerous and hazardous substances to air, water and soil, it also

functions as the national body that get involves in international environmental activities with

other countries or international bodies. Setting standards for emissions into air, water and

noise pollution is also a major function of FEPA and enforcing these standards by FEPA is

also required by law (Ekubo and Abowei, 2011).

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FEPA was able to set out regulations for industrial effluents and these are reflected in The

Federal Environmental Protection Agency Act (Cap 131 LFN) (Effluent Limitation)

Regulations 1991.

Section 1(1) of the act states that; “Every industry shall install anti-pollution equipment for

the detoxification of effluent and chemical discharges emanating from the industry”.

Section 1(2) compliments paragraph 2 in terms of technology by stating that; “An installation

made pursuant to paragraph (1) of this regulation shall be based on the Best Available

Technology (BAT), the Best Practical Technology (BPT) or the Uniform Effluent Standards

(UES)”.

Section 3(1) of the FEPA Act 1991 states that; “An industry which discharges effluent shall

treat the effluent to a uniform level as specified in Schedule 2 to these regulations to ensure

assimilation by the receiving water into which the effluent is discharged”.

According to Schedule 2 of the FEPA Act 1991 in the effluent limitation guidelines in Nigeria

for all categories of industries, the lead limit for discharge into surface water is less than 1mg/l

and that for specific industries like automotive battery industries, metal working plating and

finishing industries, their lead limit is 0.01µg/l, for petrochemicals, their lead limit is 0.05µg/l.

These regulations are simple, straight forward and if not violated it would help to protect the

environment from industrial waste water to a large extent, but the problem of heavy metal

contamination due to industrial effluents still persists despite the set regulations. Further into

this study, discussions will identify where the problem lies and possible solutions will be

nominated.

2.3.2 Water pollution in NigeriaPollution in the aquatic water affects both rural and urban areas in Nigeria, because most

industries in Nigeria decide to locate their factories on river banks in order to have easy access

to industrial effluent disposal through river dumping and they do not consider the effects this

would have on aquatic life. The aquatic environment in Nigeria can be considered as a home

22


to various animals like fishes, sea turtles, whales, crocodiles, crustaceans, snakes etc. and can

also be a source of food within the entire ecosystem. Industries considered to be prominent for

water pollution in Nigeria are, petroleum industries, mining industries, plastics industries,

paint industries, textile industries, pharmaceutical industries, iron and steel industries, and

distillery industries (Anukam, WHO/UNEP, 1997).

A part of the motivation for this study is because there have been various reports on lead

contamination in Nigeria, for instance the joint UNEP/OCHA environment unit (2010) carried

out an emergency investigation in Zamfara state which is in the northern part of Nigeria. The

investigation was initiated by an international medical relief organisation called Médecins

sans Frontières because it was discovered that unexpected deaths occurred amongst the people

living in that area especially amongst children under five years old.

It was revealed during the investigation that the deaths were as a result of acute lead poisoning

which was caused by environmental contamination from processing of gold gotten from an

ore rich in lead and further studies discovered that the 10 µg/dl limit of lead in drinking water

set by WHO and the federal government was highly exceeded. Furthermore, ponds were also

found to be contaminated by lead and other investigations made the joint UNEP/OCHA

conclude that the lead contamination was as a result of lead processing.

In view of the forgoing, Ogunseitan and Smith (2007) reported that the mean blood

concentration of lead amongst children acquired from different locations in Nigeria to be 11.4

– 25 µg/dl and this level is very unacceptable according to the 10µg/dl level set by the World

Health Organisation (WHO). They further discussed industrial sources as partly the cause of

such high level of blood contamination in children.

Considering the above reviews, it is obvious that a major problem in Nigeria is the

contamination of lead through processing and industrial uses. However, as discussed earlier

waste water treatment is a major factor aiding the pathway through which lead gets into the

environment so therefore lead removal from effluent is inevitable and Nigeria being a

developing country with financial constraints need a cheaper and effective means of lead

23


removal. Nevertheless, there is the need to discuss the different techniques of lead extraction

from a solution and also give reasons why biosorption is a viable and sustainable method for

Nigerian use. Furthermore, discussion will progress into the various agro wastes for

biosorption and the best agro waste will be highlighted.

2.4 Conventional methods for lead removal from an aqueous solutionThe conventional methods used in lead removal from solutions may involve chemical,

physical and biological processes, a few of the are explained in the subsections below;

2.4.1 Ion exchange A bed of resins is used to selectively remove undesired ions passing through the resin fitted

column and these ions can therefore be recovered from the resin. However there are

limitations in using such method because studies have discovered that other waste water

materials have destructive effects on the resins and also considered as a disadvantage is the

high cost of acquiring resins (Fu and Wang, 2011).

2.4.2 Precipitation method It involves using alkali agents to precipitate soluble heavy metals from a solution in which an

insoluble metal compound is formed. The usual alkali precipitating agents are caustic soda,

lime and magnesium hydroxide, whereby the metal is precipitated as a hydroxide. Despite

being an easy technology, it is not effective in removing lead ions in the presence of

complexing agents, it requires pH adjustment so there is increase in cost due to purchase of

pH adjustment chemicals and the quantities of sludge formed after precipitation is massive

thereby giving rise to disposal problems (Eisazadeh, 2008).

2.4.3 Reverse osmosis This technology involves passing the aqueous solution through a semi permeable membrane

and the unwanted ions are being block from passing through the membrane. However, its

limitation is that it requires a high energy to power the pump for pressure input and to restore

the degrading membrane (Fu and Wang, 2011).

2.4.4 Flocculation/CoagulationThis employs the use of ferric salts like ferric chloride to precipitate the metal ions but this is

achieved only after a polymer was used to separate oil from the solution. However, this

24


method is effective when dealing with low volume of solution and a massive sludge is

produced which gives rise to disposal problems (Patoczka, et al., 1998).

In view of the foregoing some of the processes are efficient but they either need a lot of

energy to meet their required demands or they operate at increased cost, and some are not

effective in extracting metal ions. Moreover in modern times, industries are required to engage

in sustainable development practices in their respective organisations, so an economically

viable and environmentally friendly method of lead removal from industrial effluents was

initiated and this is explained in the next section.

2.5 BiosorptionMost peer reviews acknowledged biosorption as the best method for heavy metal removal

from aqueous solution in terms of cost effectiveness and environmental friendliness because it

makes use of naturally available materials or perhaps materials that are considered as waste to

remove heavy metals present in industrial effluents. It is of big advantage to discover a

process of employing naturally occurring wastes to reduce heavy metal contamination because

these wastes are inexpensive to acquire and despite being termed wastes, they term to be

useful in environmental protection.

Biosorption method has a great advantage over the other conventional methods in the sense

that it has high removal efficiency, the method of removal is low cost, it produces low sludge,

metal recovery and regeneration of the adsorbent is possible (Yeneneh, et al., 2011).

The technique of biosorption as described by Das et al., (2008) is that it involves a sorbent

which is the solid medium and the liquid medium which is the aqueous solution, and also

present in the liquid medium is the dissolved metal ion. The metal ion is removed from the

liquid medium due to the fact that the sorbent has a great attraction for the metal ions.

However Das et al., (2008) further explained that various mechanisms are used during the

sorption process depending on the sorbent and the process stops when equilibrium is attained

between the adsorbed metal ion and the metal ion which is remained in the liquid medium.

25


Different sorbents can be used for biosorption, they include biomasses such as; bacteria, fungi,

agricultural wastes, algae and yeast (Wang and Chen, 2009), but the focus of this study is

limited to Biosorption using agricultural wastes.

The mechanism behind using agricultural wastes as sorbent is due to the fact that these

agricultural wastes contain carbonyl, phenolic, amido, amino, acetamido or hydroxyl

functional groups on their surfaces and these groups have affinity for the positively charge

metal ions to form complex compounds (Sud, et al., 2008). And indeed, the presence of such

variety functional sites enhances the ability for different metal bindings by adsorption,

chelation and ion exchange (Ogali, et al., 2008).

2.6 Agricultural wastes as adsorbent

As discussed by Yeneneh et al (2011), the most viable agricultural wastes for heavy metal

removal should be eco-friendly, their chemical composition must be specific for the purpose

of binding with metal ion, they must be abundant in nature, low cost, and they must be very

efficient in heavy metal removal. Various researchers have demonstrated the competence of

agricultural wastes in lead uptake at different conditions.

Studies have shown that activated carbon treated Korean mandarine orange peel is a

promising agricultural waste that can be used to remove lead ion and this was demonstrated by

Park (2011). Using adsorbent weight of 0.2g at a concentration of 41.4 mg/l, at temperature of

30ºC and pH 5 gave lead ion adsorption rate of 44.2%. The best adsorption rate was 99.9% at

pH 9.

Sometimes, these adsorbents are modified to increase their adsorption rate. For instance,

Martín-Lara et al (2010) carried out experiments to remove lead ion from aqueous solution

using treated and untreated sugar cane bagasse. The sugar cane was treated with hydrogen

tetrasulphate (V1) acid to increase the sorption capacity for lead and to remove the soluble

substances on the surface. The overall result gave lead to be well removed by the treated sugar

cane bagasse with sorption capacity of 7.297 mg/g, and the untreated bagasse with sorption

capacity of 6.366 mg/g at temperature of 25 °C and pH 5 (Martín-Lara, et al., 2010).

26


Usually all experiments for metal adsorptions are executed with variations in adsorbent

loading, pH, contact time or temperature and the rate of adsorption is calculated using the

Langmuir or Freundlich isotherm.

Furthermore, Elham et al (2010) investigated the used of rice husk to remove zinc and lead

ions with variations in contact time, adsorbent load, and pH value of waste water. Results

gave 19.617 and 0.6216 mg/g, respectively as the adsorption capacity for zinc and lead and

the adsorption was strongly enhanced at pH 7 for zinc and pH 9 for lead. The maximum

percentage of removing lead was 96%.

Another experiment done to remove lead from an aqueous solution and effluents from battery

and paint industries was performed by Opeolu et al (2009) using maize cob as an adsorbent.

Dowex an ion exchange resin was added to another portion of the effluents as control

parameter. The experiment was analysed using Langmuir isotherm and it gave the removal of

lead to be 99.9% from the battery effluent and 47.38% with the effluent that was treated with

Dowex. However the removal rates for lead in paint effluents were 66.16% and 27.83% for

the Dowex controlled effluent.

Although these adsorbents are relatively cheap and readily available, Khan et al (2004)

discussed the importance of comparing the adsorbents in terms of cost and explained that

costs is being determined by the adsorbents degree of processing and their availability to the

area of research. Furthermore Khan et al (2004) emphasized that enhancement in their ability

to adsorb metals may compensate for the costs of any modification done on the adsorbent. So

therefore it is paramount to study the sources of these adsorbents and their ability to remove

heavy metals from aqueous solutions.

2.6.1 Characterization of the adsorbentsSometimes, it is important to subject some agricultural wastes to chemical treatment before

being used as adsorbents. Untreated wastes may not be effective in removing heavy metals

and may also distort the physicochemical properties of the aqueous solution by discharging its

27


organic soluble compounds into the solution and thereby increasing its chemical oxygen

demand (COD), biological oxygen demand (BOD) and total organic carbon (TOC).

Consequently, the increase in these physicochemical properties will reduce the oxygen level in

the solution and this will be detrimental to the aquatic ecosystem (Feng and Guo, 2012).

Nonetheless modified adsorbents can enhance the efficiency for lead removal, but there

should be consideration on the cost of acquiring chemicals for such modification and the cost

of methods used because the main purpose of using adsorbents is to achieve a low cost

method for biosorption. However, characterization studies on the changes in properties of the

modified adsorbents should be carried out to ascertain if it is necessary to modify the

adsorbent or to use it in its natural form (Ngah and Hanafiah, 2007).

Hence since the basic characteristics of adsorbents that favour and increase the efficiency for

metal binding include large surface area, porous structure, increased adsorption capacity and

an activated surface (Daffalla, et al., 2010), there should be studies on these characteristics to

achieve the aim of low processing cost (Ngah and Hanafiah, 2007).

Feng and Guo (2012) discussed the necessity to modify orange peels for adsorption purpose.

The constituents of orange peels which are; cellulose, lignin, pectin and hemicellulose where

reported to contain methyl esters and are known to have a no effect on metal binding.

However, due to findings that carboxyl groups enhance metal binding, the orange peels can be

treated with a base like sodium hydroxide to give a carboxylate functional site to facilitate

metal binding. Additionally, treating the orange peel with calcium chloride is credible because

calcium precipitates polysaccharides such as pectin if the contain carboxyl groups in them and

therefore make the pectin insoluble.

Furthermore, modification of orange peels using sodium hydroxide and calcium chloride by

Feng and Guo (2012) changed the surface morphology of the peel, and an indication for an

increased adsorption capacity was noticed because the structure of the modified orange peel

was uneven and porous compared to the natural orange peel. The surface areas for the

modified orange peel and the natural orange peel were 1.496m2/g and 0.828m2/g respectively.

28


The larger surface area provides larger binding sites for the metal ions, hence adsorption

experiment by Feng and Guo (2012) gave a 30% increase in adsorption rate of lead (Pb2+)

after modifying the orange peels.

Similarly, Yeneneh et al (2011) investigated the role played by chemical modifiers, heat and

size on both rice husk and sugarcane bagasse. The chemical modifiers where chosen

according to the functional site that will be fixed to the adsorbents, and the adsorbents where

treated with 0.1M potassium hydrogen phosphate and 0.1M sodium oxalate at a temperature

of 800 °C for 24 hours. As part of the adsorbent characterisation, the natural and treated rice

husk and sugarcane bagasse where grounded and sieved to particle sizes ranging from (500-

1000µm) to (45-63µm) and different lead removal experiments where carried for each natural

and treated adsorbents. To test for the effect caused by thermal modification, two grams of the

treated adsorbents were burned in a furnace at a temperature of 700 °C and analysed with

Scanning Electron Microscope (SEM), and Fourrier Transform Infra-Red Spectroscopy

(FTIR).

Yeneneh et al., (2011) discovered that potassium hydrogen phosphate increased the efficiency

of rice husk in removing lead ion with the removal capacity of 87.53 mg/g and sodium oxalate

gave 75.40 mg/g as the removal capacity. However, the treated sugarcane bagasse gave a

capacity of 100mg/g when potassium hydrogen phosphate was used as a modifier and sodium

oxalate treated sugarcane bagasse gave 98.53 mg/g removal capacity.

Additionally, it was also ascertained that particle sizes play a big role in lead uptake from a

solution because it was discovered that the smaller particle sizes ranging from 45-63µm for

both adsorbents gave a higher sorption properties compared to the bigger adsorbents sizes.

This was due to the fact that surface area and the affinity for metal binding increases with

decrease in size and obviously, there will be increase in the sorption capacity. The thermal

modification also increased the surface area for both adsorbents with the improvement of the

surface morphology and there was also increase in the roughness of the surfaces, hence

sugarcane bagasse and rice husk gave lead removal efficiencies of 84.1% and 80.5%

respectively.

29


2.6.2 Preparation of adsorbents for experimentBesides pre-treatment, processing adsorbents for biosorption of heavy metals takes almost the

same pattern for all adsorbents as described by most researchers. For instance the biosorption

experiment was carried out by El-Said (2010) for lead ion removal using rice husk and rice

husk ash, the rice husk was gotten from a rice mill factory and they were grounded to smaller

particles in order to increase its surface area. Furthermore, the particles were sieved to specific

sizes of 0.180, 0.355, and 0.855 using mesh sieves of those particular sizes.

Following the particle preparation, distilled water was used to wash the particles to remove the

impurities present and then the particles were dried in an oven at about temperature of 100 ºC.

The heating of the particle stopped until a constant weight was achieved, this ensured that the

particles were free of all impurities. The prepared absorbent was then stored for further use

during the Biosorption experiment. However, El-Said (2010) further explained that the rice

husk ash was prepared from the dried rice husk by heating it in an oven at a temperature of

600 ºC for about three hours.

Similarly, the preparation of modified sugarcane bagasse for the removal of lead ion from an

aqueous solution was discussed by Osvaldo et al (2007). The bagasse was dried in an oven at

a temperature of about 100 °C for 24hours and the dried bagasse was grounded and sieved

with 10, 30 45 and 60 mesh sizes. Furthermore, distilled water was used to wash the grounded

adsorbent and simultaneously being stirred at a temperature of 65ºC for about an hour and

dried again in an oven.

This procedure prepares the bagasse for the adsorption process. However, further processing

is necessary to develop a modified sugarcane bagasse. Osvaldo et al (2007) treated the washed

and dried adsorbent with succinic anhydride, 1M of acetic acid, 0.1 M of hydrogen chloride,

95% ethanol and distilled water were added to the solution, and then dried in an oven for

30mins at a temperature of about 100 ºC after all these procedure, the adsorbent was ready to

be used for the biosorption process.

30


2.6.3 Biosorption experimental procedureVarious researchers have carried out biosorption experiments and usually the procedures are

similar in the sense that the primary motive for the experiment is to bring both the adsorbent

and the metal ions together so that adsorption can take place. However, the adsorbent

preparation like granulation, washing and drying is highly needed for easy and accurate

experiment.

Usually, the adsorption experiment is carried out at different circumstances, for instance it

could be carried out at different pH, temperature, adsorbent loading and contact time.

A detailed example of such research was carried out by Elham et al., (2010) in which rice

husk was used to extract lead ion from industrial wastewater. The preparation of the rice husk

began the experimental procedure; the husks were washed with distilled water and dried at a

temperature of 100ºC in an oven.

The lead ion concentrated solution was obtained from dairy waste water and the initial

concentration of the lead ion before adsorption was determined using an atomic absorption

spectrometer (AAS). Also, to carry out the experiment at different pH, the pH adjustment was

done by adding either 0.1 M HCl or 0.1 M NaOH to the initial pH of the solution. The HCl

reduces the pH and the NaOH increases the pH level of the solution and however the pH

ranging from 2-9 was obtained for the process.

30 ml of the waste water was made to be in contact with different adsorbent weights ranging

from 0.5 to 3grams and also, the contact time was varied between 5 to 70 minutes. The reason

for these variations is to study the effects of the varying parameters on lead ion extraction by

rice husk.

Furthermore, the adsorbent and the wastewater were kept in 100ml beaker and shaken

rigorously for the specific required time of observation. Afterwards, the solution was filtered

using a filter paper and the solution was analysed using the AAS to determine the lead ion

concentration remaining in the solution and obviously to determine the amount of lead ion

adsorbed by the adsorbent.

Elham et al (2010) calculated the metal ion adsorbed with the formula below;

31


% Adsorption: Ϲ o−C e

C o×100 , where Co is the initial concentration of lead ion in solution

before adsorption in mol/m3 and Ce is the equilibrium concentration or the final concentration

of lead ion in the solution after adsorption in mol/m3.

Furthermore, the amount of lead ion adsorbed per kilogram of the rice husk at equilibrium was

calculated as;

qe = (Co – Ce)Vm , where qe is the adsorbed lead ion on the surface of the adsorbent in

mol/Kg adsorbent, V is the volume of waste water or metal solution in m3, m is the weight of

adsorbent used for the particular experiment in Kg, Co is the initial concentration of lead ion

in solution before adsorption and Ce is the final concentration of metal ion in the solution.

To get a better understanding of the experimental results and to characterize the efficiency of

an adsorbent, the kinetics sorption has to be studied (Abia and Asuquo, 2006). Graphs of

percentage lead ion absorbed are being plotted against their corresponding values varied

within the parameters such as contact time, pH, and absorbent loading.

For instance, Elham et al (2010) discovered that 60% of lead was removed after 5 minutes and

equilibrium adsorption capacity of 49% was achieved after 60 minutes. Similarly, a graph of

metal adsorbed and adsorbent weight was plotted by Elham et al (2010) and it was easy to

interpret the rate of adsorption in relation to adsorbent loading.

2.6.3.1 Kinetic studiesThere are different models that can be used to assess the kinetics of adsorption process but the

most widely used are the Lagergren’s pseudo-first-order rate or the pseudo-second –order rate

equation.

Pseudo-first-order rate equation is expressed as;

ln (1-qt/qe) = -K1t, where qt is the amount of metal ion adsorbed per gram of the adsorbent

at any time t (mg/g), qe is the amount of metal ion adsorbed at equilibrium (mg/g) and K1 is the

pseudo-first-order rate equation constant (Saikaew, et al., 2009).

32


The pseudo-second –order rate equation is expressed as t/qt = (1/K2qe2) + (t/qe), where qt is

the amount of metal ion adsorbed per gram of the adsorbent at any time t (mg/g), qe is the

amount of metal ion adsorbed at equilibrium (mg/g), and K2 is the pseudo-second –order rate

equation constant (Saikaew, et al., 2009).

2.6.3.2 Adsorption isothermTo analyse the adsorption capacity of adsorbents, the equilibrium studies are required and the

equilibrium correlations between the adsorbent and the metal ion are justified using adsorption

isotherms. Moreover, Freundlich and Langmuir adsorption isotherm are often used to show

the relationship between the amount of the adsorbed metal and the amount of the metal

remaining in the solution at a particular temperature and at equilibrium (Hussein, et al., 2004).

2.6.3.2.1 Freundlich isothermThe adsorption on heterogeneous surfaces is explained using Freundlich Isotherm, and the

equation for the Freundlich isotherm is;

logqe = l og K+ 1n

log Cₑ , where qe is the amount of metal ion adsorbed by the adsorbent at

equilibrium (mg/g), Ce is the concentration of the metal ion at equilibrium (mg/l), K and 1n are

the Freundlich isotherm constants and they are the values of the intercept and the slope

respectively determined from the linear curve graph of logqe against logCe (John, et al.,

2011).

The K value is related to the adsorption capacity in the sense that a larger K value indicates a

high adsorption capacity and the 1n value describes the change in the effectiveness of the

adsorbent if the equilibrium concentration is changed (Mamman, et al., 2011).

2.6.3.2.2 Langmuir isothermThe Langmuir isotherm is suitable for single layer adsorption on the adsorbent surfaces

containing adsorption sites that are similar (Karaca, et al., 2010).

Langmuir isotherm is described by the equation;

33


Cₑqₑ

= 1q˳ K ˳

+ Cₑq ˳ , Where qe is the amount of lead extracted at equilibrium (mg/g),

q˳ is the maximum adsorbent uptake capacity during saturation (mg/g), Ce is the equilibrium

concentration of metal in the solution (mg/l), and K˳ is the Langmuir constant (John, et al.,

2011).

If the graph of Cₑqₑ against Ce is plotted and it gives a linear curve, then the adsorption

approaches the Langmuir model. Furthermore, the slope of the curve is the q˳ value which is

the maximum capacity for lead uptake by the adsorbent and the K˳ is determined as the

intercept of the curve (Mamman, et al., 2011). The Langmuir isotherm is widely acceptable

due to the fact that it is used to quantify the adsorption capacities of agricultural wastes so it is

considered the most useful in the course of this study (Dos Santos, et al., 2010).

2.6.4 Desorption Desorption is a process whereby the lead ion saturated adsorbent is subjected to treatment in

order to separate the adsorbent from the lead ion. In other words, the adsorbent is regenerated

for further use and the metal ion is recovered from the liquid medium. The application of

desorption in an industry practising the biosorption process helps in keeping the cost of

processing down and imbibes the phenomenon of sustainable development practice in such

industry because the metal can also be recovered and used for other purposes.

However, biosorption process is described to be a complete economically viable process for

industrial use if it is possible to regenerate the used adsorbent for further biosorption

processes. (Acheampong, et al., 2009). Basically, the desorption process makes use of a

suitable solution to wash the saturated adsorbent, in which a suitable solution is that which is

selective in allowing the metal ion to dissolve in the solution and an equilibrium is achieved

between the dissolved metal ion and the ions that are still adhered to the adsorbent (Volesky,

2000).

34


In identifying a suitable solution for desorption, there must be considerations on the type of

adsorbent, the mechanism behind the biosorption process and the solution must be

environmentally friendly, low cost and must not have a destructive nature towards the

adsorbent. Solutions that could be used for desorption include acids, chelating agents, and

alkalines (Acheampong, et al., 2009). After the desorption process, there will be few lead ions

that will still be present on the adsorbent surface but the advantage of desorption is that it

provides free active sites for metal biosorption to take place after the adsorbent had been used

on the first instance.

A few literature review on desorption of heavy metals exists but Akissi et al (2010) took part

in desorption study after sawdust was used as an adsorbent to remove Pb (II) from aqueous

solution. The solutions tested for desorption include; double distilled water, ethylene di-amine

tetra acetic acid (EDTA), sulphuric acid (H2SO4), calcium chloride (CaCl2), sodium chloride

(NaCl), 0.2 M hydrochloric acid (HCL), and nitric acid (HNO3).

The mixtures of the metal ion bounded adsorbent and the desorption solutions were shaken

vigorously for about 45 minutes and then filtered, the filtrate which is the saw dust was

analysed to determine the amount of lead ions left after desorption. However, the experiment

was repeated four times using the same adsorbent.

Akissi et al (2010) reported the desorption ratio to be calculated as the amount of lead ion

desorbed/amount of lead ion adsorbed.

The result of the experiment showed that EDTA had the highest percentage of desorption of

about 77.29% and the lowest rate of desorption was double distilled water which was 2.11%.

Further adsorption with the same sawdust reduced the amount of lead ion adsorbed due to the

fact that some lead ions where still present after the desorption process.

35


2.7 Industrial application of the biosorption method for lead ion removal from an aqueous solution

36

Metal ion

Acid or Base solutionpH control

Adsorbent vessel

CSTR

Temp guage

pH meter

Desorption solution

Filtration tank

CSTR

Heavy metal solution tank

Treated waste water tank

Filtration tank

Temp. guage

pH

m

tre

Adsorbent recycle

Figure 2.1: Schematic flow diagram showing the biosorption of heavy metals from industrial wastewater using adsorbents

Source: Igwe and Abia (2006)


The above flow diagram is the schematic representation of the industrial application of the

biosorption method by removing metal ions from industrial wastewater using an adsorbent as

discussed by Igwe and Abia (2006). It can be seen from the diagram that the wastewater

containing the metal ion for an example, lead ion is introduced into the reactor and also the

adsorbent is introduced into the continuously stirred tank reactor (CSTR). The adsorbent could

have been pre-treated or modified if necessary, and after the introduction of both wastewater

and adsorbent into the CSTR, they are both stirred continuously for a period of time in the

reactor and the adsorption of the metal ion onto the adsorbent takes place. After equilibrium

has been attained for the adsorption process, the adsorbent becomes saturated and no more

metal ion is adsorbed on its surface. The solution goes into the filtration tank and it is filtered

thereby separating the adsorbent saturated with metal ion from the wastewater, the resultant

wastewater is collected in a tank and the adsorbent is ejected into another CSTR for the

purpose of desorption. Furthermore, after the completion of the desorption process, filtration

takes place and gives heavy metal ion solution which is kept in a tank for further purification

and the used adsorbent is recycled for re-use.

Igwe and Abia (2006) concluded by ascertaining that previous experimental data gotten from

isotherm calculations, kinetics studies and intra particle studies are useful in calculating

energy balances and material balances, and the plant specifications for the development of an

industrial biosorption plant. However, as stated by Igwe and Abia (2006), more research is

required for the implementation of such technology in industries.

2.8 ConclusionThe literature review highlighted the importance of using agricultural wastes for heavy metal

removal from industrial effluents in Nigeria, moreover various investigations carried out by

researchers showed that rice husk, orange peel, maize cob and sugarcane bagasse are suitable

agro wastes for the sorption of lead from aqueous solution regardless if untreated or treated.

But their rate of absorption and adsorption capacities differs depending on various factors like

adsorbent pre-treatment methods, their surface characteristics, pH of the solution, adsorbent

loading, contact time and temperature.

37


However, as the aim of this study depicts, the best method in terms of using agricultural

wastes need to be identified for easy implementation of the biosorption method in Nigeria.

In order to achieve this aim, absorption capacities of these selected wastes have to be

considered in relation to cost effectiveness, also social and political impacts of implementing

this method in Nigeria have to be studied.

The next chapter discusses the methods used for the critical analysis in identifying the best

agricultural waste that is suitable for Nigeria.

38


CHAPTER 3: Methodology

3.1 MethodologyIn this study, extensive secondary data will be sourced and analysed to generate a clear

understanding of the aim and objectives. Figure 3.1 below illustrates the overview of the

research study. From various agricultural wastes used as adsorbents for the biosorption

process, four of them, namely; orange peels, rice husk, sugarcane and maize cob were selected

for the study.

Secondary data will be used to undergo comparison between different parameters involved in

the process of biosorption of lead, such parameters include; adsorption capabilities of the low

cost agricultural wastes, their adsorption rates, modification methods, equilibrium time for the

experiment and the availability of the selected adsorbents in Nigeria. Similarly, various

reports and peer review papers that have discussed the removal of lead using the selected

agricultural wastes at different conditions will be sourced. Furthermore, the comparison will

also involve the use of statistical analysis obtained from secondary sources.

Papers from chemistry journals are sourced to characterize the adsorbent surfaces and to

gather information on their physicochemical properties.

Figure 3.1: Overview of the research study

39

BiosorptionProcess

Sugarcane bagasse

Rice husk

Orange peels

Secondary data collection

SWOT analysis

PEST analysis

Nigeria

Results Best method identification

Agricultural wastes

MaizeCobs


3.2 Analytical ToolsThe tools that will be used to make comparison between the selected agricultural wastes are S-

W-O-T and P-E-S-T analytical tools.

3.2.1 SWOT analysisBasically SWOT is an acronym for strength, weakness, opportunity and threats, and it is used

as a method for choosing a suitable strategy for embarking on a project by considering the

projects internal capacity (strength and weakness) and its external situation (opportunity and

threats) (Oetomo and Ardini, 2009). However after identifying SWOTs, the strength can be

used as an advantage over weakness and the threats can be converted to opportunities (Miller,

2006).

The SWOT analysis will be aided by the use of a SWOT matrix shown in Table 3.1 below, in

which the strengths, weaknesses, opportunities and threats of each method will be highlighted

upon, and the possible solutions to combat this weaknesses and threats by making use of the

existing opportunities and strengths will be discussed. Further to the discussion, the best

method that is most viable in the Nigerian context will be determined.

Table 3.1: Template of the SWOT matrix

STRENTHS WEAKNESSES

C Strength 1

Strength 2

Strength 3

D Weakness 1

Weakness 2

Weakness 3

OPP

OR

TUN

ITIE

S A Opportunity 1

Opportunity 2

Opportunity 3

E F

40


T

HR

EATS

B Threat 1

Threat 2

Threat 3

G H

Box A represents the opportunities involved in making use of the agricultural waste for the

biosorption process, box B contains the threats associated with the usage of the agricultural

waste, box C is the strength of the particular agricultural waste, and box D contains the

weaknesses of the agricultural waste. As part of the analysis, box E contains the processes

initiated to take advantage of the opportunities by making use of the strength possessed by the

agricultural waste, box F represents the processes involved to reduce the adsorbent

weaknesses by making use of the opportunities, box G contains suggestions in which the

strength can be used to anticipate or reduce the threats involved in using the adsorbent, and

box H contains the suggestions for reducing the weaknesses possessed by the adsorbent and

also to reduce the threats of using the adsorbent.

3.2.2 PEST analysis

PEST is an acronym for political, economic, social and technology. It is an analytical tool for

comprehending the political, economic, social and technological aspects of an operation

(CIMA, 2007). It is perceived that the PEST analysis coupled with SWOT analysis will give a

better understanding of the scenario being analysed and will in turn produce a better

judgement.

3.2.3 Justification in using SWOT and PEST analytical toolsThese methods of analysis where employed because they are believed to be most applicable

for the caparison between the agricultural wastes for the biosorption process. In addition,

SWOT and PEST analysis best explains thoroughly the strength, weakness, opportunity and

threats involved with the use of the selected agricultural wastes as well as the political,

economic, social and technological views of their application in the Nigerian community.

41


More so, this approach facilitates judgements based on key factors identified by the SWOT

and PEST analysis, and consequentially a critical evaluation of these factors will bring to a

conclusion of identifying the best agricultural waste method that suits industrial effluent

treatment in Nigeria.

42


CHAPTER 4: Results and Discussion

The following parameters are used to identify the data for the SWOT and PEST analysis of

orange peels, sugarcane bagasse, maize cobs and rice husk;

(i) Availability in Nigeria

(ii) Absorption capacities

(iii) Equilibrium time for adsorption

(iv) Adsorption rate

(v) Adsorbent treatment methods

(vi) Desorption rate (Metal recovery)

(vii) Social and environmental impact

4.1 Availability of the selected agricultural wastesIt is of great importance that the agricultural waste for the biosorption process must be

indigenous to Nigeria and as part of the data collection for the analysis of the different

methods for biosorption in Nigeria, the geographical distribution and availability of these

agricultural wastes are required. Hence, the following sections identifies the agricultural

wastes and there availability in Nigeria;

4.1.1 Availability of Orange peel in NigeriaCitrus fruits are well grown in Nigeria but the most produced citrus fruit is the sweet orange

which is grown and cultivated in fifteen states of Nigeria. However it has been reported that

about 0.3 million tonnes orange wastes yearly are generated in Nigeria which implies that the

wastes in form of peels will be in high volume and if not in use will constitute environmental

pollution. (Oluremi, et al., 2006, Ezejiofor, et al., 2011). Moreover to make these waste

materials useful, they can be turned into adsorbent for the biosorption process.

Although peels are thought to be a source of food for livestock, but its low nutrient contents

and bitter taste makes its usefulness limited in that aspect (Oluremi et al 2006), and thereby

give room for such a chunk of produced orange waste to be used in processes like biosorption.

43


4.1.2 Availability of Sugarcane bagasse in NigeriaSugarcane bagasse is the bit left after the juice of the sugarcane has been sucked out

(Alsharief 2012). Nigeria’s main raw material for sugar production is sugarcane, hence the

availability of bagasse as waste is linked to places with sugar production (Rossi, et al., 2002,

Abgoire, et al., 2002).

4.1.3 Availability of Rice husk in NigeriaErenstein et al., (2003) reported that rice is a cash crop produced mainly for commercial

purposes in Nigerian, but due to the fact that rice production yields a low return, there is

reduction in its productivity and consequentially increase in the cost of production.

Furthermore, policies have not been able to procure a place in the market for locally produced

rice merchants, so rice imports in Nigeria have been reported to have a giant share in the

statistics of imported agricultural produce into Nigeria (Erenstein et al., 2003, Nigerian

Tribune, 2010). Since rice is majorly imported in Nigeria, the existence of rice husk is limited

and therefore be a constraint for its use in biosorption process.

4.1.4 Availability of Maize cob in NigeriaNigeria is regarded as the second largest producer of maize in Africa, moreover the Nigerian

climatic condition favours maize growth. Cob, a part of the maize that bears the grain

represents 30% of maize agricultural wastes and being that about 8 million tonnes of maize is

produced in Nigeria annually with an increase of 23% in the production prediction between

2010 and 2015, there is an indication that corn cobs are produced in large volumes in Nigeria

(Akinfemi and Ladipo, 2011, Saliu and Sani, 2012, Ogunbode and Apeh, 2012).

4.2 Description of other comparison parametersTo understand the significance of the data acquired from work done by researchers used in

this study, it is paramount to understand the following terms;

44


4.2.1 Adsorption capacity

This is the maximum value of the amount of lead that is adsorbed per gram of the agricultural

waste (adsorbent) at equilibrium time (Knaebel 1995).

4.2.2 Equilibrium timeThis is the time at which the concentration of the metal ions being adsorbed by the adsorbent

is equal to the concentration of the exchanged ions leaving the surface of the adsorbent. At

this time, the surface of the adsorbent becomes saturated and cannot accept any more metal

ions (Site, 2000).

4.2.3 Adsorption rateThe percentage ratio of the adsorbed lead concentration to the total concentration of lead

present in the aqueous solution is termed adsorption rate. So therefore, it is the total amount of

lead adsorbed from aqueous solution by the adsorbent (Site, 2000).

4.2.4 Desorption rateThis is the percentage of removing the adsorbed metal ion from the adsorbent by using a

suitable reagent. The efficiency of the desorption process is known by the difference between

the quantity of lead in the desorption solution and the quantity of lead adsorbed by the

adsorbent (Akissi, et al., 2010).

4.3 Data collectedTable 4.1 below shows the data collected from the work done by researchers comprising of

the comparison parameters described above. All experiments by the researchers were done at

room temperature and they all stated that the adsorption capacities were pH dependent, in the

sense that increase in pH increases the adsorption capacities. The optimum pH whereby the

best lead adsorption occurred has been indicated in Table 4.1. However, pH higher than the

optimum values will encourage the precipitation of lead hydroxide which will hinder the rate

of lead adsorption.

45


Table 4.1: Work done by researchers on the removal of lead from aqueous solution using the Selected agricultural wastes

Agricultural

wastes;

unmodified/

modified.

Modifica-

tion

methods.

Adsorption

capacity

(mg/g).

Adso-

rption

rate

(%).

Equilibrium

time (min).

Desorp-

tion

rate

(%).

Optimum

pH

Sources

Orange peel

113.5

55.52

64.3

73.5

10

500

-

35.9

5.5

5

Feng and

Guo, 2012

De Souza et al., 2012

Modifiedorange peel

NaOH-

CaCl2

NaOH-Citric acid

209

84.53

99.4

74.9

10

500

-

38.0

5.5

5

Feng and

Guo, 2012

De Souza et al., 2012

Korean mandarin

orange peel 13.5 44.2 50 5 Park,

2010

Rice husk 0.06216 96.8 60 - Elham,et al., 2010

Modified rice Tartaric - 5.3 Wong,

46


Husk acid

15% alkali

treatment with

autoclave (Biomatri

x)

108

58.1

93

80

120

120-150-

(5.5˗6) ± 0.1

et al., 2003

Krishnani, et al.,

2008

Sugarcane bagasse

6.366 100 120 5 Martín Lara, et al., 2010

ModifiedSugarcane

bagasse

Sulphuric acid

Citric

acid

Triethylen

e-

tetramine

7.297

52.63

313

100

-

-

120

1440

50

-

98

-

5

-

5

Martín Lara, et al., 2010

Dos Santos, et al., 2010

Osvaldo, et al., 2007

Maize cob 1.09 - 90 - 5 Jonglertjunya,2008

Modified maizeCob

Natural fungi

growth

H3PO4

14.75

3.150

-

-

90

90

-

-

5

5

Jonglertjunya,2008

Nale, et al.,

2012

47


EDTA 144.93 - 60 - 7.5 Igwe and

Abia, 2007

4.4 SWOT and PEST analysis of the selected agricultural wastes used for lead biosorption.As discussed earlier in chapter 3, the SWOT analysis will be aided by a SWOT matrix for a

complete evaluation of each agricultural waste, and to compliment this method of analysis is

the inclusion of PEST analysis.

Table 4.2: SWOT matrix for orange peel adsorbent used for lead biosorption

STRENGHTS WEAKNESSESC •Unmodified orange peel has high adsorption capacities of 113.5 mg/g and 55.2 mg/g according to research by Feng and Guo, (2012) and De Souza et al., (2012) respectively.

•Adsorption rate is also high for unmodified orange peel.

•Equilibrium time for maximum adsorption is 10 minutes according to Feng and Guo, (2012) and this is low compared to other waste adsorbents.

•Modifying with NaOH-CaCl2 gives adsorption capacity of 209mg/g which is relatively higher than some of the adsorbents being compared.

D •Equilibrium time is 500 minutes according to a study by De Souza et al., (2012), and this is relatively high compared with the other agro-wastes.

•The rate of metal recovery is 35.9% which is quite low as indicated by the desorption studies carried out by De Souza et al., 2012.

48


O

PPO

RTU

NIT

IES

A •Orange peel wastes are in abundance in Nigeria and they are readily available.

•It can be modified with NaOH-CaCl2 for better efficiency.

•When implemented with the biosorption process, it is cheaper than other conventional processes.

•Policies are available for its implementation.

E •Being a cheap method for lead extraction, and because it has a high adsorption capacity and absorption rate for lead removal and coupled with a low equilibrium time makes it a potential adsorbent for the biosorption method even when used untreated.

•Modification with NaOH-CaCl2

gives a better adsorption rate, higher adsorption capacity and low equilibrium time.

F •Modifying the orange peel with sodium hydroxide and citric acid before the biosorption process, increases the desorption rate to 38% which still indicates a low metal recovery rate.

TH

REA

TS

B •Few researchers have carried out studies on the desorption rate of lead from orange peel.

•It may require permits or licencing for implementation and the process of acquiring them may be tasking or expensive.

•Modifying the orange peel may increase the operating cost of the process.

G •Workshops in the form ofdevelopment programs should be initiated and it will make people including government officials perceive the importance of using orange peel for the biosorption process. This will reduce any tariff or licence levy placed on its implementation.

H •Because few researchers have studied the desorption rate of lead from orange peel, other researchers should utilize the opportunity by investigating other avenues for increasing the rate of the metal recovery from orange peel.

Table 4.2.1: PEST analysis for orange peel adsorbent used for lead biosorption

POLITICAL

•There are available policies to implement the biosorption technology using orange peel as an adsorbent in Nigeria.

ECONOMIC

•It is considered as less expensive and an economically viable method of lead extraction from waste water.•Further treatment is required to dispose the metal binded adsorbent due to its low desorption rate, and this increases the operating cost.

SOCIAL

•The method is perceived to be accepted by the people because it is environmentally friendly.

•Reduces environmental pollution caused by orange peels.

TECHNOLOGY

•Biosorption is a new technology that is yet to be implemented at an industrial level.

49


Table 4.3: SWOT matrix for rice husk adsorbent used for lead biosorption

STRENGHTS WEAKNESSES

C •High adsorption rate of 96.8% for unmodified rice husk.

•Equilibrium time for maximum adsorption is low for both modified and unmodified rice husk.

•Treatment with tartaric acid or biomatrix formation gives adsorption capacities of 108mg/g and 58.1mg/g respectively.

•Adsorption rate is high for both modification of rice husk.

D •The adsorption capacity is 0.06216 mg/g for unmodified husk which is the least compared with the selected agro wastes.

OPP

OR

TUN

ITIE

S

A •It can be modified for better efficiency by treatment with tartaric acid, and forming a rice husk bio matrix also increases its efficiency.

• There are available policies to implement the biosorption technology using orange peel as an adsorbent.

E •It will be a suitable adsorbent upon treatment with tartaric acid because its adsorption rate and capacity will increase.

F •Modifying the rice husk with tartaric acid will increase its lead adsorption capacity.

•Available policies indicate government’s interests in such environmentally friendly project, so therefore the government can be asked to partly fund the project. This shifts the burden of rice husk treatment cost away from the industry.

T

HR

EATS

B •Abundance of rice husk wastematerials are not certain because of reduced rice production in Nigeria compared with other agricultural produce.

• Few researchers have carried out studies on the biosorption of lead using rice husk.

•If modified with chemical reagents or heat, it may increase the cost of the biosorption process compared to unmodified wastes.


G •The high adsorption rate or low equilibrium time may offset the cost incurred during modification of the rice husk with tartaric acid.

H •More investigation is needed for biosorption of lead using tartaric acid treated rice husk to determine the desorption rate.

50


Table 4.3.1: PEST analysis of rice husk adsorbent used for lead biosorption

Table 4.4: SWOT matrix for sugarcane bagasse adsorbent used for lead biosorption

STRENTHS WEAKNESSES

C •High rate of adsorption by untreated bagasse.•Equilibrium time is low for untreated bagasse and triethylene-tetramine modified bagasse.

•Treatment with citric acid and triethylene-tetramine increases its adsorption capacity as reported by Dos Santos et al., (2010) and Osvaldo, et al., (2007) respectively.

•Desorption studies by Dos Santos et al., (2010) confirm the metal recovery rate to be 98% which is very high compared to other methods.

D •Untreated sugarcane bagasse gives a low adsorption capacity for lead.

•Treatment with sulphuric acid still gives a low adsorption capacity.

•Equilibrium time is high with the citric acid treated bagasse.

51

POLITICAL

•There are available policies to implement the biosorption technology using rice husk as an adsorbent in Nigeria.

•Major importation of rice by selected people due to political motives threatens the abundance of rice husk required in the biosorption process.

ECONOMIC

•Lead adsorption by rice husk adsorbent requires treatment of the adsorbent in other to achieve a desirable result. However, the treatment is done using chemical reagents and heat. The chemicals contribute additional cost for the project and the heating will increase the energy consumption during the process and will in turn increase the cost.

SOCIAL

• Reduces environmental pollution caused by rice husk.

TECHNOLOGY

• Biosorption is a new technology that is yet to be implemented at an industrial level.

•it is perceived to be an easy and straight forward technology in reducing environmental impact caused by industrial processes.


OPP

OR

TUN

ITIE

S

A •Sugarcane bagasse wastes are readily available in Nigeria in millions of tonnes.

•There are available policies to implement the biosorption technology using sugarcane bagasse as an adsorbent.

•It can be modified with triethylene-tetramine and citric acid for better efficiency.

E •Potentially, sugarcane bagasse can be used for biosorption due to its abundance, and because there are available policies requiring the best available technology for effluent treatment and its tendency to be modified with triethylene-tetramine or citric acid for better efficiency.

F •The adsorption capacity is increased upon treatment with triethylene-tetramine or citric acid but treatment only with triethylene-tetramine gives a low equilibrium time of 50 minutes.

T

HR

EATH

S

B •If modified with triethylene-tetramine or citric acid, it may increase the cost of the biosorption process compared to unmodified wastes.


G •The high adsorption capacity and the high metal recovery rate for citric acid treated bagasse may offset the cost incurred during modification of the sugarcane bagasse because the metal recovered can be recycled and used as raw materials for other industrial processes and the adsorbent can also be reused over again which makes the process cost effective.

H •Workshops in the form of development programs should be initiated and it will make people including government officials perceive the importance of using modified sugarcane bagasse for the biosorption process. This will reduce any tariff or licence levy placed on its implementation.

•Movement to seek for government funding will reduce the cost involved in the adsorbent treatment method.

•Increasing the low absorption capacity and reducing the equilibrium time will be achieved by modifying the bagasse with triethylene-tetramine.

Table 4.4.1: PEST analysis of sugarcane bagasse adsorbent used for lead biosorption

52

POLITICAL

•There are available policies to implement the biosorption technology using sugarcane bagasse as an adsorbent in Nigeria.

ECONOMIC

•It is considered as less expensive and an economically viable method of lead extraction from waste water.

SOCIAL

• Reduces environmental pollution caused by sugarcane bagasse.

•it is perceived to be a totally acceptable technology due to its environmental friendliness and cost effectiveness compared to other conventional methods of lead extraction.

TECHNOLOGY

•It is perceived to be an easy and straight forward technology in reducing environmental impact caused by industrial processes.



Table 4.5: SWOT matrix for maize cob adsorbent used for lead biosorption

STRENTHS WEAKNESSESC •Low equilibrium time if unmodified.

•Adsorption capacity of 144.3mg/g when treated with ethylene diamine tetra-acetic acid (EDTA).

•A low equilibrium time of 60 minutes when treated with EDTA.

D •Low adsorption capacity if unmodified.

•Increased adsorption capacity when treated with natural fungi growth but it is still low compared to other selected wastes.

•Low adsorption capacity when modified with H3PO4.

OPP

OR

TUN

ITIE

S

A •There is abundance of maize cob due to availability of maize crop in Nigeria.

•It can be modified with a natural fungal growth, EDTA, and H3PO4 for better efficiency.

• There are available policies to implement the biosorption technology using maize cob if considered as the best available technology (BAT).

E •It should be modified with EDTA in order to increase its adsorption capacity, to reduce its equilibrium time and the abundance of maize crop makes its cob to be a potential adsorbent in the biosorption process.

F •From the data obtained, to have increased adsorption capacity comparable to other agricultural wastes, the maize cob has to be treated with EDTA.

T

HR

EATH

S

B •There is no information on the adsorption and desorption rate of lead when using maize cob as the adsorbent. So therefore there is limited data on its usage.

•Modifying with natural fungal growth, EDTA, and H3PO4 may increase operating cost.


G •Further research is necessary to determine the desorption rate of EDTA treated maize cob.

•The high adsorption capacity and the low equilibrium time may offset the cost incurred during modification of the maize cob.

H • To reduce the weakness and threats identified, it is important to treat the maize cob with EDTA.

•More research is needed to gather information on the biosorption process using maize cob as adsorbent.

•Workshops in the form ofdevelopment programs should be initiated and it will make people including government officials perceive the importance of using modified maize cob for the biosorption process. This will reduce any tariff or licence levy placed on its implementation.

Table 4.5.1: PEST analysis of maize cob adsorbent used for lead biosorption

53


4.5 Discussion

4.5.1 Outcome of the SWOT analysesThe SWOT matrix helped in highlighting the main points to consider when using each

individual agricultural waste for the biosorption process. These points are discussed in the

following sections below;

4.5.1.1 Orange peelAbundance of orange peel in Nigeria suggests the potentiality of it to be a good adsorbent for

the biosorption of lead. However, the SWOT matrix pin pointed out the factors that made

orange peel to be potentially viable for the biosorption process and ironically also shows the

limitation to be encountered if it is implemented in the biosorption process.

For instance, lead adsorption with orange peel was studied by Feng and Guo, (2012) and De

Souza et al., (2012) and they had its adsorption capacities to be of 113.5 mg/g and 55.2 mg/g.

These are good values because they simply depict the amount in grams of lead adsorbed by 1

gram of orange peels and having the values of 113.5 and 55.2mg/g shows that a substantial

amount of lead is adsorbed by orange peel. However, not just the adsorption capacity is to be

considered for viability because equilibrium time for the reaction is also an important factor to

54

POLITICAL

•There are available policies to implement the biosorption technology using sugarcane bagasse as an adsorbent in Nigeria.

ECONOMIC

•It is considered as less expensive and an economically viable method of lead extraction from waste water.

•Lead adsorption by maize cob adsorbent requires treatment of the adsorbent in other to achieve a desirable result. However, the treatment is done using EDTA and the chemicals may impose additional cost towards the project.

SOCIAL

•Reduces environmental pollution caused by maize cob wastes.

•It is perceived to be a totally acceptable technology due to its environmental friendliness and cost effectiveness compared to other conventional methods of lead extraction.

TECHNOLOGY


• It is perceived to be an easy and straight forward technology in reducing environmental impact caused by industrial processes.


consider in the sense that a low equilibrium time shows that the reaction goes at a faster rate

and saves time spent on waste water treatment.

The equilibrium time of 10 minutes determined by Feng and Guo, (2012) shows good

efficiency unlike that determined by De Souza et al., (2012) which is 500 minutes. This

denotes a longer process for the research by De Souza et al., (2012) to achieve a 55.2mg/g

adsorption rate. But the best value obtained for the biosorption process was using NaOH-

CaCl2 treated orange peel which gave 209 mg/g adsorption capacity, 99.4% adsorption rate

and 10 minutes equilibrium time. This favourable values of the comparison parameters for

orange peel doesn’t mean it is better than the other adsorbent because according to a report by

Ngah and Hanafiah (2008), which stated clearly that chemically modified adsorbent may have

high adsorption capacity for metal ions but in other to realise the motive of obtaining a low

cost adsorbent, there has to be caution on the amount spent on modification chemicals and

treatment methods.

Desorption is the recoverability of the metal ion from the adsorbent and this is important for

the re-use of the adsorbent, to recover the metal for use in other manufacturing purposes and

lastly to avoid discarding the adsorbent and the adsorbed metal into the environment because

by doing so, it may generate into a more toxic substance and cause harm to the environment.

So very few literature reviews have discussed the desorption rate of lead adsorbed orange peel

except for De Souza et al., (2012) in which the desorption rate was as low as 35.9%.

4.5.1.2 Rice husk Amongst the few researchers that have carried out research on the use of rice husk adsorbent

for the removal of lead from aqueous solution, Wong, et al., (2003) gave the best result which

shows 108mg/g adsorption capacity, 93% adsorption rate of lead, and 120 minutes of

equilibrium time upon treatment of the rice husk with tartaric acid. There is no known amount

of desorption rate attached to lead binded rice husk. However, rice husk has limitations on its

use as adsorbent because of its availability in Nigeria. For an agricultural waste to be used as

an adsorbent for biosorption, it should be indigenous and readily available in the area where

55


the biosorption process is being implemented, and the adsorbent should have little or no

economic value.

Rice crop in Nigeria was discovered to be a crop of political importance because there is

inconsistency in the government policies concerning rice crop, this is a bid by the government

to favour some people of high calibre in the society. So this makes the local farmers to switch

to production of other crops and the only way to meet the country’s demand for rice is by

importation (Daramola 2005). Due to this reason, availability of rice husk becomes an aspect

to consider, because if there is a problem with rice importation in the future, obviously

shortage of rice husk occurs and this will hinder the progress of the biosorption technology.

4.5.1.3 Sugarcane bagasseLike other agro wastes, sugarcane bagasse is readily available in Nigeria because its crop

grows in the wide range of climatic condition present in Nigeria and sugarcane is the major

raw material for sugar production in Nigeria.

Unmodified sugarcane bagasse shows little adsorption capacity for lead from the study

conducted by Martín Lara, et al., (2010), however the best adsorption capacity was achieved

during studies conducted by Osvaldo, et al., (2007) whereby triethylene-tetramine was used to

modify sugarcane bagasse and adsorption capacity of 313mg/g was obtained with equilibrium

time of 50 minutes. The data obtained for sugarcane bagasse adsorption of lead shows that to

obtain the best efficiency of sugarcane bagasse as adsorbent, it has to be modified with

chemicals like citric acid or triethylene-tetramine. Citric acid modified bagasse gave a very

good desorption rate of 98%, implying that almost all the metal adsorbed by the bagasse were

recovered and liable for other processes in the industry but its equilibrium time is relatively

high compared to other adsorbents. There was no information gathered on the desorption rate

of lead adsorbed by triethylene-tetramine modified bagasse, in which if such information was

known and happens to be a high rate of desorption, then it will be a fair judgement to decided

that triethylene tetramine modified sugarcane bagasse is the best agricultural waste for

biosorption process in Nigeria.

56


Nonetheless, the citric acid and triethylene tetramine modified bagasse biosorption process

where done using the same agricultural waste but the process conditions and the treatment

chemicals are different for both methods. In view of the foregoing, there is every possibility

that if more research is undertaken for the desorption rate of lead from the triethylene

tetramine modified bagasse, there is every possibility of achieving a high rate of metal

recovery

4.5.1.4 Maize cobStudies highlighted the importance of Nigeria to maize production in Africa, it was reported

by Akinfemi and Ladipo, (2011) that Nigeria is the second largest producer of maize in

Africa. For this reason, maize cob wastes should not be farfetched in the Nigerian

communities. Maize cob can be prepared into adsorbent for lead biosorption process but from

the data gathered, the best efficiency is achieved when maize cob is modified with a chelating

agent like ethylene diamine acetic acid (EDTA). Gathered from the report by Igwe and Abia,

(2007), EDTA modified cob gave adsorption capacity of 144.93mg/g with equilibrium time of

about 60 minutes. Investigation carried out by Nale, et al., (2012) whereby phosphoric acid

(H3PO4) was treated with maize gave a low adsorption capacity and also a study by

Jonglertjunya, (2008), in which natural fungi growth occurred on the surface of the cob and it

was used for lead biosorption gave adsorption capacity of 14.75mg/g.

A huge limitation for maize cob adsorbent is that data on other comparison parameters like

adsorption rate and desorption rate are not available in literature reviews.

4.5.2 Outcome of the PEST analysesDespite the pros and cons of each agricultural waste discussed during the SWOT analyses, the

PEST analyses was able to show that implementing each of the agricultural wastes in an

environmental pollution remediation process like biosorption, it is like killing two birds with a

stone because the process will reduce environmental pollution caused by the agricultural

wastes themselves and also reduce environmental pollution caused by lead metal.

57


Nevertheless, the four methods are perceived to be socially acceptable by the public and

government because they are environmentally friendly and the methods show a reduction in

operating cost compared to other convention methods. A significant reason for the reduced

operating cost is because the agricultural wastes do not have economic values due to the fact

that they are readily available in the environment and also, processing industries like fruit

juice, sugar, and cereal manufacturing industries have these agricultural wastes in abundance.

So therefore these industries relieve their selves of disposal problems and the cost of involved

in disposing the agricultural wastes by utilizing the wastes in the biosorption process.

However, it was discovered that rice husk, sugarcane bagasse and maize cob require

treatments in other to modify their chemical and physical structure for better adsorption

capacities and rates.

These treatment methods involve the use of chemicals, reagents and heat, so therefore the

treatments incur additional cost on the process’s operating cost. But from another perspective,

the increased adsorption efficiency achieved from the modified agricultural wastes may offset

the cost incurred during treatment because more lead ions are adsorbed per unit mass of

adsorbent and there is little time spent on the process due to increase in adsorption rate of

lead and reduction in equilibrium time.

Pest analyses also showed the importance of metal recovery after the whole biosorption

process. If the method has a low desorption rate like orange peel, there is every possibility of

spending more money on further treatments and disposal of the saturated adsorbent and the

adsorbed lead.

Furthermore, there are established policies for implementing a technology like the biosorption

process in the Nigerian community. Moreover, the policies which were established by FEPA

(1991) have been discussed in chapter 2 of this study but in summary, it explains the

requirement by every industry to detoxicate effluents and chemicals coming out of the

industry into the environment. In addition, the policy requires the implementation of the best

58


available technology (BAT) for the detoxification process, so this justifies the reason for

carrying out the study of identifying the best method for lead biosorption using agro wastes.

CHAPTER 5: CONCLUSION AND RECOMMENDATION

5.1 ConclusionAfter a brain storming SWOT and PEST analysis of the secondary data obtained, the best

method for lead removal from industrial effluent in Nigeria is by using triethylene tetramine

modified sugarcane bagasse as an adsorbent in a biosorption process.

Triethylene tetramine modified bagasse has the highest adsorption capacity of 313mg/g, with

the least equilibrium time of 50 minutes and because it has the tendency to achieve 98%

desorption rate just like citric acid modified bagasse if properly researched, it is therefore the

most cost efficient and reliable agricultural waste adsorbent for the biosorption of lead

59


Based on the research done there are data gaps which suppressed the efficiency of the other

selected agricultural wastes compared to the modified sugarcane bagasse. However, it was

discovered that adsorption capacities of the agricultural wastes differ depending on their

treatment methods and the best adsorption capacities are achieved if the wastes are modified

with suitable reagents.

Missing in most of the analysis data obtained for the selected wastes are desorption and

adsorption rate of lead. Furthermore, there is need for more research on desorption and

adsorption rates of all the selected agricultural wastes in order to objectively decide which

method is the best for lead biosorption in Nigeria.

5.2 RecommendationThe proposed recommendations below will give some headway towards implementing

triethylene tetramine modified sugarcane bagasse biosorption technology by processing

industries in Nigeria;

Further studies are necessary in order to actually implement the biosorption technology

in industrial process units.

Workshops in the form of development programs should be initiated and it will make

people including government officials perceive the importance of using modified

sugarcane bagasse for the biosorption process and also it will reduce any tariff or

licence levy placed on the biosorption technology implementation.

Government funding should be sourced for further research on using the modified

sugarcane bagasse adsorbent for the biosorption technology. This will aid the

improvement in its design and its technology knowhow.

There should be more research done on the use of the other comparative agricultural

wastes for the biosorption process in order to achieve enhanced adsorption efficiency

with the wastes and to diversify the methods used for lead biosorption.

60


Strict monitoring of industrial effluents discharged into receiving waters is necessary,

and the monitoring team should make sure there is compliance with the standard set by

the Nigerian government with heavy penalty imposed on violators.

Other sources of lead pollution in Nigeria should be identified and assessed for studies

on ways to prevent them from harming the environment.

REFERENCES

Acheampong, M.A., Meulepasa, R.J., and Lensa, P.N. (2010). Removal of heavy metals and cyanide from gold mine wastewater. J. Chem Technol Biotechnol Vol 85, pp. 590–613. Society of Chemical Industry.

Adebisi, Akanmu, S. and Fayemiwo, K.A. (2010). Pollution of Ibadan soil by industrial effluents. New York Science Journal. Vol 3, No. 10, pp. 37.

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Agboire, S., Wada, A.C., and Ishaq, M.N. (2004). Evaluation and characterisation of sugar cane germplasm accessions for their breeding values in Nigeria. The journal of Food Technology in Africa. Vol 7, No 1.

Agency for Toxic Substances and Disease Registry (ATSDR). (2007). Toxicological profile for lead. U.S department of health and human services. Public health services.

Ajaelu C.J., Ibironke, O.L., Adedeji, V., and Olafisoye, O. (2011). Equilibrium and kinetic studies of the biosorption of heavy metal (Cadmium) on Cassia siamea bark. American-Eurasian Journal of Scientific Research Vol 6, No. 3, pp. 123-130.

Akinfemi, A., and Ladipo, M.K. (2011). Effect of Fungal Treated Maize Cob on the Performance of West African Dwarf Rams. Conference on International Research on Food Security, Natural Resource Management and Rural Development. Tropentag, University of Bonn, October 5 – 7.

Alluri, H.K., Ronda, S.R., Settalluri, V.S., Bondili, J.S., Suryanarayana, V., and Venkateshwar. P. (2007). Biosorption: An eco-friendly alternative for heavy metal removal.African Journal of Biotechnology Vol. 6, No 25, pp. 2924-2931.

Alsharief, H. (2012). Sugarcane as a tool for development in Nigeria. Kenana Engineering and Technical Services West Africa Ltd, 15 A Ndjamena Street, Wuse 2 Abuja.

Aluko, B. High expectations as Nigeria plans increased rice production. http://www.tribune.com.ng/index.php/features/3580-high-expectations-as-nigeria-plans-increased-rice-production (date accessed 24/08/2012).

Anukam, C.L. (WHO/UNEP 1997). Water Pollution Control - A Guide to the Use of Water Quality Management Principles. Case Study IV – NigeriaAyinde, O. E. (2010). Empirical analysis of agricultural production and climate change: A case study of Nigeria. Journal of sustainable development in Africa. Volume 12, No.6.

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