treatment of dairy wastewater

Treatment of Dairy Wastewater implementing

Coagulation and Adsorption.

Treatment of Dairy Wastewater implementing

Coagulation and Adsorption

A Thesis submitted in partial fulfillment of the requirements for the

degree of

Master of Engineering

In

Chemical Engineering

By

Uttarini Pathak

(Roll No. 001310302007

Regn N0.-124704

Exam Roll No. M4CHE1507

Under the supervision and guidance of

Dr. Siddhartha Datta , Sri. Prasanta K. Banerjee

Department of Chemical Engineering

Jadavpur University

Kolkata 700032

CERTIFICATE

This is to certify that the thesis entiled Treatment of Dairy Wastewater implementing Coagulation and adsorption is submitted by Uttarini Pathak student of Chemical Engineering Department of registration year 2013- 2014 to

this institute in partial fulfillment of the requirement for the award of the degree of

Master of Engineering by Research.

This report is a bona-fide record of the work carried out by her under my

supervision and guidance at the Department of Chemical Engineering,

JADAVPUR UNIVERSITY, Kolkata-700032.It is further certified that no part of

this thesis is submitted for the award of any degree.

Sri. Prasanta K. Banerjee Dr. Siddhartha Datta

Department of Chemical Engineering Department of Chemical Engineering

Jadavpur University Jadavpur University

APPROVAL

The following thesis is hereby approved as a credible study of a Engineering

subject and presented in a manner satisfactory to warrant its acceptance as a

perquisite to the degree for which it has been submitted. It is to be understood that

by this approval, the undersigned do not necessarily endorse or approve any

statement made, opinion expressed or conclusion drawn there in, but approve the

thesis only for the purpose for which it has been submitted.

Department of Chemical Engineering

Jadavpur University

HOD (Department of Chemical Engineering)

Dean (FET)

ACKNOWLEDGEMENT

I am grateful to Chemical Engineering Department, Jadavpur University, Kolkata for providing an opportunity to undertake this Project Work. While doing this project, I have come across many erudite personalities who had helped me a lot in doing and finishing this project simultaneously. It is their kind help and untiring effort that has resulted in completion of this project. I would like to express my heartful gratitude to Prof. Dr. Siddhartha Datta and Sri. Prasanta K. Banerjee of Chemical Engineering Department of Jadavpur University, Jadavpur for allowing me to complete this work under their elegant supervision and guidance. Their encouragement throughout the times of difficulties was something that cannot be expressed with mere words.I am deeply indebted to them.

I am very grateful to Prof. Dr. Papita Das & Head of the Department, Chemical Engineering Department, Jadavpur university and all other faculty members for their help and cooperation. I would like to extend my thanks to our Lab assistant who has helped me a lot all throughout my work. My sincere appreciation also extends to all my colleagues and others who have provided assistance at various occasions; it is not possible to list all of them in this limited space. I am grateful to my parents who encouraged and supported me all through and helped me in all respect.

UTTARINI PATHAK

ABSTRACT

Dairy industry is one of the largest food processing industry which causes severe environmental

problems due to the generation of wastewater containing high Solid concentration, high BOD

and COD . Of all industrial activities, this food sector has one of the highest consumptions of water and is one of the biggest producers of effluent per unit of production in addition to

generating, besides to generate a large volume of sludge in biological treatment. Effluent from

milk processing unit contains soluble organics, suspended solids, trace organics which releases

gases, causes taste and odor, impart colour and turbidity, and promote eutrophication. The casein

precipitation from waste decomposes further into highly odorous black sludge. .In this study after determination of the preliminary parameters like pH, BOD, COD, Oil and Grease, alkanity

and many more it was subjected to coagulation using alum, lime, Ferric Chloride and Ferrous

Sulfate. It was found that efficient removal of COD as much as 92 % could be brought using a

combination of lime and Ferrous Sulfate. Moreover further studies was done to check whether

coagulation followed by adsorption process could be adopted which resulted in increased value

of COD. Thereby Adsorption Batch studies using nano composites (Graphene Oxide and

Hydroxyapatite nano particles) and plant adsorbents were performed ( Ricehusk and Sawdust). Batch adsorption studies are carried out as a variation of adsorbent dosage solution pH, contact

time, initial COD concentration and temperature. Results obtained clarified that nano particles

would be more preferable compared to agro based adsorbents. But all four showed a same

pattern of maximum removal at conditions of Low temperature(20 -25 deg C) and Low pH (2 4). Further Fitting of Isotherms and evaluation of kinetics and thermodynamics were done which

showed that Langmuir isotherm favoured the process followed by an exothermic reaction with

second order kinetics taking place.

CONTENTS

1.0 INTRODUCTION

2.0 LITERATURE REVIEW

2.1.1 Biological oxygen demand (BOD)

2.1.2 Chemical oxygen demand (COD)

2.1.3 pH

2.2 New Technologies in the Dairy Industry Waste Water Treatment

2.2.1 Ion Exchange

2.2.2 Chemical Oxidation

2.2.3.Membrane Filtration

2.2.4 Ozonization

2.2.5 Biodegradation

2.2.5 Solvent Extraction

2.3 CHEMICAL PRECIPITATION (Coagulation and Flocculation)

2.4 ADSORPTION

2.4.1 Fundamentals of the adsorption

2.4.2 Physical Adsorption

2.4.3 Chemical Adsorption

2.4.4 Adsorption Mechanism

2.5 ADSORBENTS

2.5.1 Sawdust

2.5.2 Ricehusk

2.5.3 Graphene Oxide

2.5.4 Hap Nano-Composites

2.6 ADSORPTION ISOTHERMS

2.6.1 Langmuir Isotherm

2.6.2 Freundlich Isotherm

2.7 Adsorption Kinetics

2.8 Adsorption Thermodynamics

3.0 MATERIALS AND METHODS

3.1 Coagulation- Coagulants and Procedure

3.1.1 Preparation of Coagulant Solution

3.1.2 COD Estimation

3.2 Adsorbent preparation 3.3 Batch sorption experiments

4.0 RESULTS AND DISCUSSIONS

4.1 Characterisation of Dairy Wastewater

4.2 Results obtained after Treatment of Wastewater with Coagulants

4.3 Results obtained after Treatment of Wastewater with Coagulation followed by

Adsorption.

4.4 Rate of Settling

4.5 Batch Adsorption study using Graphene Oxide as Adsorbent

4.5.1 Effect of Adsorbent Dosage

4.5.2 Effect of pH

4.5.3 Effect of Temperature

4.6 Batch Adsorption Study Using HAP Nano-Composites As Adsorbent


4.6.2 Effect of pH


4.6.4 Effect of Concentration

4.6.5 Adsorption Isotherms

4.6.6 Adsorption Thermodynamics

4.6.7 Adsorption Kinetics

4.7 Batch Adsorption study using Ricehusk as Adsorbent


4.7.2 Effect of pH






4.8 Batch Adsorption study using Sawdust as Adsorbent


4.8.2 Effect of pH



4.8.5 Effect of Adsorbent Size

4.9 Conclusion

5.0 References

LIST OF TABLES

1. Characteristics of Dairy Wastewater

2. Effect of Different Coagulant Treatment on Different Parameters

3. Effect of Coagulation Followed By Adsorption

4. Percentage Removal at different Adsorbent Dosage onto Graphene Oxide

5. Percentage Removal at different pH onto Graphene Oxide

6. Percentage Removal at different Temperature For Adsorption onto

Graphene Oxide

7. Percentage Removal at different Dosage For Adsorption onto HAP

8. Percentage Removal at different pH For Adsorption onto HAP

9. Percentage Removal at different Temperature For Adsorption onto HAP

10. Percentage Removal at different Concentration For Adsorption onto HAP

11. Isotherm parameters for Adsorption onto HAP

12. Thermodynamic Parameters for adsorption onto HAP .

13. Percentage Removal at different Adsorbent Dosage For Adsorption onto

Ricehusk

14. Percentage Removal at different pH For Adsorption onto Ricehusk

15. Percentage Removal at different Temperature For Adsorption onto

Ricehusk

16. Percentage Removal at different Concentration For Adsorption onto

Ricehusk

17. Isotherm parameters for Adsorption onto Ricehusk

18. Thermodynamic Parameters for adsorption onto Ricehusk

19. Percentage Removal at different Dosage For Adsorption onto Sawdust.

20. Percentage Removal at different pH For Adsorption onto Sawdust.

21. Percentage Removal at different Temperature For Adsorption onto Sawdust.

22. Percentage Removal at different Concentration For Adsorption onto

Sawdust.

23. Percentage Removal at different Adsorbent size For Adsorption onto

Sawdust.

1.0 INTRODUCTION

Water used in domestic and industrial applications become polluted to a greater or lesser

extent. Water is also used as a transport medium to carry away waste products. As awareness of

the importance of improved standards of water treatment grows, process requirements become

increasingly exacting. The food industry contributes to a great extent to pollution, particularly as

the pollutants are of organic origin. Organic pollutants normally consist of 1/3 dissolved, 1/3

colloidal and 1/3 suspended substances, while inorganic materials are usually present mainly in

solution[1]. Large amounts of water are used during production process producing effluents containing dissolved sugars and proteins, fats, and possibly residues of additives. Wastewater from dairies and cheese industries contain mainly organic and biodegradable materials that can disrupt

aquatic and terrestrial ecosystems. Due to the high pollution load of dairy wastewater, the milk-

processing industries discharging untreated/partially treated wastewater cause serious

environmental problems. Moreover, the Indian government has imposed very strict rules and

regulations for the effluent discharge to protect the environment.

Dairy effluent contains soluble organics, suspended solids, trace organics. All these

components contribute largely towards their high biological oxygen demand (BOD) and

chemical oxygen demand (COD). Dairy wastes are white in colour and usually slightly alkaline

in nature and become acidic quite rapidly due to the fermentation of milk sugar to lactic acid.

The suspended matter content of milk waste is considerable mainly due to fine curd found in

cheese waste. The pollution effect of dairy waste is attributed to the immediate and high oxygen

demand. Decomposition of casein leading to the formation of heavy black sludges and strong butyric acid odors and characterize milk waste pollution( Shete et al.,).

Coagulation is an essential process in water and industrial wastewater treatment.

Coagulation has been subject of many research, most of which has been related to wastewater

treatment, however, it may differ from depending on chemical and physical parameters of

contaminants. The particles to be removed include organic material, which can react differently

to a coagulant[Sahu et al., (2013)]. Coagulation/flocculation is a commonly used process in

water and wastewater treatment in which compounds such as lime, alum, ferric chloride and

ferrous sulfate [Parmar et al.,(2011)] are added to wastewater in order to destabilize the

colloidal materials and cause the small particles to agglomerate into larger settleable flocs

[Jopson and Hector(2004)].

Aluminum sulfate (alum), ferrous sulfate, ferric chloride and ferric chloro-sulfate were

commonly used as coagulants [Affrin et al.,]. Additionally, high COD removal capacities have

been observed during the combined action of alum and lime for the treatment of stabilized

leachates. The coagulation process with alum as the sole coagulant is capable of achieving

significant organic removal. The pH of the water during coagulation has profound influences on

effectiveness of coagulation for organic removal. Organic removal is much better in slightly

acidic condition. The optimum pH for alum coagulation is influenced by the concentration of

organic matter in the water.

Adsorption is typically used in wastewater treatment to remove toxic or recalcitrant organic

pollutants (especially halogenated but also non-halogenated), and to a lesser extent, inorganic

contaminants, from the wastewater. Adsorption finds applications in tertiary wastewater

treatment as a polishing step before final discharge. Adsorption is commonly used in the

treatment of industrial wastewaters containing organic compounds not easily biodegraded during

secondary (biological) treatment or toxic.

Many industrial wastewaters contain substances that:

are difficult to remove via conventionally secondary treatment are toxic or hazardous are volatile and cannot be transferred to the atmosphere. have the potential for creating noxious vapors or odors, or for imparting color to the

wastewater.

are present is very small concentrations that make their removal via other methods difficult.

There are various methods including chemical precipitation, membrane process, ion

exchange, liquid extraction and electrodialysis (Verma et al., 2006).. These methods are non-

economical and have many disadvantages such as incomplete metal removal, high reagent and

energy requirements, generation of toxic sludge or other waste products that require disposal or

treatment.

Biosorption, a technically feasible and economical process, has gained increased credibility

during recent years (Loukidou et al., 2004)..Plant wastes are inexpensive as they have no or very

low economic value and it is abundant in nature. Some of the advantages of using plant wastes

for wastewater treatment include simple technique, requires little processing, good adsorption

capacity, selective adsorption of heavy metal ions, low cost, free availability and easy

regeneration. The commonly used biosorbents in this study are: Rice husk, Saw dust.

However, the application of untreated plant wastes as adsorbents can also bring several

problems such as low adsorption capacity, high chemical oxygen demand (COD) and biological

chemical demand (BOD) as well as total organic carbon (TOC) due to release of soluble organic

compounds contained in the plant materials. The increase of the COD, BOD and TOC can cause

depletion of oxygen content in water and can threaten the aquatic life.

Carbon nanostructures have been extensively studied due to their excellent properties and

numerous applications [Geim and Novoselov (2007) and Saxena et al.,]. Graphene Oxide is a

single-atomic-layered material made by the oxidation of graphite crystals, which are inexpensive

and abundant. It is dispersible in water, and as a result is easy to process. Most importantly, it

can be converted into graphene. Graphene Oxide is one of the first commercial graphene

materials and one of the most popular products in the Graphene Supermarket.

Hydroxyapatite [Ca10(PO4)6(OH)2, HAP], a main inorganic constituent of the hard tissues

(bone and teeth) in human body, has marked potential in adsorption of various ions, organic

molecules and polymers (Jang et al.,(2008). HAP is also capable of establishing bonds with

organic molecules of different size. However, HAP is usually provided in powder or calcined

pellets form, which limits its industrial applications.

2.0 LITERATURE REVIEW Wastewater from dairies and cheese industries contain mainly organic and biodegradable

materials that can disrupt aquatic and terrestrial ecosystems. Due to the high pollution load of

dairy wastewater, the milk-processing industries discharging untreated/partially treated

wastewater cause serious environmental problems. Hence the importance of carrying out a whey

treatment as a starting point in order to optimize a simple and economic method to treat the

whole dairy effluent. Moreover, the Indian government has imposed very strict rules and

regulations for the effluent discharge to protect the environment.

Industrial waste water emanates from spillage of milk and products thereof, and from cleaning of

equipment that has been in contact with milk products. The concentration and composition of the

waste depends on the production programme, operating methods and the design of the processing

plant.

2.1 Organic pollutants

2.1.1 Biological oxygen demand (BOD) Oxygen demand is measured in terms of the quantity of oxygen consumed by micro-organisms

over a period of five days (BOD5) or seven days (BOD7 ), in decomposing the organic pollutants

in waste water at a temperature of 20C. BOD is measured in mg oxygen/l or g oxygen/m3.

2.1.2 Chemical oxygen demand (COD) COD indicates the quantity of the pollutants in waste water that can be

oxidised by a chemical oxidant. The normal reagents used for this purpose are strongly acid

solutions (to ensure complete oxidation) of potassium dichromate or potassium permanganate at

high temperature. Consumption of oxidant provides a measure of the content of organic

substance and is converted to a corresponding quantity of oxygen, expressing the result as mg

oxygen/l or g oxygen/m3.

The COD/BOD ratio indicates how biologically degradable the effluent is.Low values, i.e. < 2,

indicate relatively easily degradable substances, while high values indicate the contrary.

However, this relationship cannot be used generally, but a typical value of COD/BOD for

municipal sewage effluent is often < 2.

2.1.3 pH The pH of dairy effluent varies between 2 and 12 as a result of the use of acid and alkaline

detergents for plant cleaning.Both low and high pH values interfere with the activity of the

micro-organisms that break down organic pollutants in the biological treatment stage of the

sewage treatment plant, transforming them into biological sludge (cell detritus).Used detergents

are therefore normally collected in a mixing tank, often located close to the cleaning plant, and

the pH is measured and regulated to, say, pH 7.0 before it is discharged to drain.

2.2 New Technologies in the Dairy Industry Waste Water Treatment

Treatment of Dairy Industry Wastewater by Reverse Osmosis for Water Reuse

Anaerobic Filter Reactor for the Treatment of Complex Dairy Wastewater at Industrial Scale

Use of Nanofiltration and Reverse Osmosis Membranes in Dairy Wastewater Treatment

Anaerobic Treatment of Dairy Wastewaters

Electrochemical Technologies in Wastewater Treatment.

2.2.1 Ion Exchange

Ion exchange means the removal of an ion from aqueous solution by replacing another ionic

species. There are natural and synthetic materials available which are specially designed to

enable ion exchange operations at high levels. So ion exchangers are used to perform this ion

exchange for removal of organic and inorganic pollutants along with other heavy metals for

purification and decontamination of industrial effluents. The main disadvantages associated with

ion exchange methods are the high cost of the ion exchange resins and each resins must be

selectively removes one type of contaminant only. Further, complete removal of the contaminant

is not possible. Besides, it can be used for limited cycles only as by passing concentrated metal

solution the matrix gets easily owned out by organics and other solids in the wastewater after

several uses. Moreover ion exchange is also highly sensitive to pH of the solution [Liotta et al.,

2009 and Sapari et al., (1996)].

2.2.2 Chemical Oxidation

In this process the waste materials from the industrial waste water are removed by the help of

chemical oxidation by the use of various chemicals mainly hydrogen peroxide is widely used for

this purpose as reported [Dias-Machado et al., 2006 and Ksibi, (2006)]. There are many

disadvantages associated with this process like the high cost of the chemicals, emission of

various harmful by products, it creates hazardous constituent like secondary effluent problem

along with the production of harmful gases.

2.2.3.Membrane Filtration

Membrane filtration technique has received a significant attention for the waste water treatment.

It considers the application of hydraulic pressure to bring about the desired separation through

the semi permeable membrane [Chen et al., (2004)]. Important examples of membrane process

applicable to inorganic wastewater treatment include Ultra-filtration, Nanofiltration,

electrodialysis and Reverse osmosis reported by [Chauhan and Rekha, 2004 and Al-Rekabi et al.,

(2007)]. This process involve ionic concentration by the use of selective membrane with a

specific driving force. For reverse osmosis, pressure difference is employed to initiate the

transport of solvent across a semi-permeable membrane and electrodialysis relies on ion

migration through selective permeable membranes in response to a current applied to electrodes.

The main problem associated with this process is incomplete removal of contaminants, high

energy requirement, and high cost of the membrane and longevity of the membrane. After long

term use the membrane get clogged with the contaminants present in the waste water and is

damaged due to extra pressure on the membrane.

2.2.4 Ozonization

Chemical oxidation with ozone can be used to treat organic pollutants or act as disinfectants

agents. Ozone is a powerful oxidants that can oxidize a great number of organic and inorganic

materials Ozone based technologies research is also being focused on the catalytic ozonation

where the presence of catalyst significantly improved the oxidation rate of organic compounds

compared to non-catalytic ozonations. The ozonation processes are possibly one of the most

effective methods for the treatment of wastewater containing organic products effluents from

chemical and agrochemical industries, textile industry, paints, etc. [Guendy,(2007)]. The

disadvantages associated with the process are high operating cost. The cost of the equipment is

very high and also it requires high voltage and electricity for its operation [Gharbani et al.,

(2010)].

2.2.5 Biodegradation

Biodegradation is the process of decaying or reduction of different organic materials and toxic

metals to their non-toxic form with the help of microorganisms. In this process complete

mineralization of the starting compound to simpler ones like CO2, H2O, NO3 and other inorganic

compounds takes place[Atlas and Bartha, (1998)]. It is an eco-friendly and cost effective process

that requires low capital and operating cost. Being environmentally friendly process it produces

no harmful end products. The main disadvantage of this process is that it requires high

maintenance of various parameters like temperature, pH, source of carbon and other

microelements etc.

2.2.5 Solvent Extractions

Liquid-liquid extraction of heavy metals from solutions on a large scale is widely practiced. It

involves an organic and an aqueous phase. The aqueous solution containing the metal or metals

of interest is mixed with the appropriate organic solvent and the metal passes into organic phase.

In order to recover the extracted metal, the organic solvent is contacted with aqueous solution

whose composition is such that the metal is stripped from the organic phase and re-extracted into

stripping solution. Once the metal of interest has been removed, the organic solvent is recycled

either directly or after a fraction of it has been treated to remove the impurities .The disadvantage

associated with this process is high maintenance cost.

2.3 Chemical Precipitation (Coagulation and Flocculation)

Precipitation of metals is achieved by addition of coagulations such as alums, lime, iron

salts and other organic polymers.

In wastewater treatment, coagulation/flocculation processes are mainly used for the

removal of colloidal material, which cause color and turbidity by bringing suspended

matter together for the purpose of settling and for the preparation of the water for

filtration. Coagulation involves three specific steps which are Coagulation, Flocculation,

and Sedimentation. Coagulation can be a simple and in expensive way to improve the

quality of wastewater. Coagulation can improve the quality of water. This improves taste

and odor, makes the water safer for chlorination, and makes the water easier to treat for

domestic purposes.

Coagulation and flocculation processes are intended to form particles large enough to be

separated and removed by subsequent sedimentation, or alternative clarification

processes. The coagulation stage occurs when a coagulant, such as alum, is added to the

water to neutralize the charges on the colloidal particles in the raw water, thus bringing

the particles closer together to allow a floc to begin to form. The flocculation process,

following coagulations, allows smaller particles formed during the rapid coagulations

stage to agglomerate into larger particles to form flocculation aids, including alum

[Al2(SO4)3.18H2O], ferric chloride[FeCl3.6H2O], ferric sulphate[Fe2(SO4)2], ferrous

sulphate[FeSO4. 7H2O] and lime [Ca(OH)2]. These coagulants when used in

combinations gives better result in wastewater treatment, such as Lime +Alum, Lime +

Ferric Chloride + Alum, lime + Ferrous Sulphate, Lime + Ferrous Sulphate+ Ferric

Chloride etc.

The theoretical reaction when coagulants added to water are:

Al2SO4.14.3H2O+3Ca(HCO3)2=2Al(OH)4+3CaCO4+14.3H2O+6CO2

Ca(OH)2 + H2CO3= CaCO3 + 2 H2O

Ca(OH)2 + Ca(HCO3)2= 2 CaCO3 + 2 H2O

FeSO4 +2 HCO3- = Fe (OH) 2 +SO4 -2 +2CO2

2.4 ADSORPTION

2.4.1 Fundamentals of the adsorption

Adsorption is a process in which a substance (adsorbate), in gas or liquid phase, accumulates on

a solid surface. It is based on the capability of porous materials with large surfaces to selectively

retain compounds on the surface of the solid (adsorbent). There are two types of adsorption;

physical and chemical adsorptions.

2.4.2 Physical Adsorption

Physical adsorption is achieved by Van der Waals forces, dipole interactions, and hydrogen

binding. There is no electron exchange between adsorbent and adsorbate. Because there is no

activation energy required for physical adsorption, the time needed to reach equilibrium is very

short. Physical adsorption is a nonspecific and a reversible process.

2.4.3 Chemical Adsorption

Chemical adsorption results from the chemical link between adsorbent and adsorbate molecule,

therefore it is specific as well as irreversible and chemical as well as electronic properties of

adsorbent are changed. Binding between adsorbent and adsorbate by covalent bond is called

weak chemical adsorption, and that by ionic bonds is called strong chemical adsorption.

2.4.4 Adsorption Mechanisms

The adsorption process of the adsorbate molecules from the bulk liquid phase into the adsorbent

surface is presumed to involve the following stages :

Mass transfer of the adsorbate molecules across the external boundary layer towards the solid particle.

Adsorbate molecules transport from the particle surface into the active sites by diffusion within the porefilled liquid and migrate along the solid surface of the pore.

Solute molecules adsorbtion on the active sites on the interior surfaces of the pores. Once the molecule adsorbed, it may migrate on the pore surface trough surface diffusion.

2.5 ADSORBENTS

2.5.1 SAWDUST

Sawdust is a waste by-product of the timber industry that is either used as cooking fuel or a

packing material; however, it can be used as a low-cost adsorbent of heavy metals, principally

due to its lignocellulosic composition. It is mainly composed of cellulose (4550%) and lignin

(2330%).

2.5.2 RICEHUSK

Rice husk, which is a relatively abundant and inexpensive material, is currently being investigated as an

adsorbent for the removal of various pollutants from water and wastewaters. Various pollutants, such as

dyes, phenols, organic compounds, pesticides, inorganic anions, and heavy metals can be removed very

effectively with rice husk as an adsorbent. Rice husk contains 75-90 % organic matter such as

cellulose, lignin etc. and rest mineral components such as silica, alkalis and trace elements

(Madhumita et al.,).

2.5.3 GRAPHENE OXIDE

GO has two important characteristics:(a) it can be produced using inexpensive graphite as

raw material by cost-effective chemical methods with a high yield, and (b) it is highly

hydrophilic and can form stableaqueous colloids to facilitate the assembly of macroscopic

structures by simple and cheap solution processes, both of which are important to the large-scale

uses of graphene. Graphite oxide has a similar layered structure to graphite, but the plane of

carbon atoms in graphite oxide is heavily decorated by oxygen-containing groups, which not

only expand the interlayer distance but also make the atomic-thick layers hydrophilic. As a

result, these oxidized layers can be exfoliated in water [ Shahriary and Anjali(2014)].

2.5.4 HAP NANO-COMPOSITES

Calcium hydroxyapatite (HAP), Ca10(PO4)6(OH)2, is an important inorganic material in biology

and chemistry (Elliott, 1994; LeGeros, 1991; Arends et al., 1987). Their availability structure,

ionic exchange property, adsorption affinity, and their characteristic to establish bonds with

organic molecules of different sizes have conferred to this material to attract more attention

during the last two decades. Calcium phosphates, especially apatites, are widely used for

chromatographic purposes (Kawazaki, 1991; Gorbuno_, 1984) and are suitable for a number of

biomedical applications, e.g., artificial bone and roofs of teeth, as well as a carrier for drug

delivery (Barroug and Glimcher, 2002; Cannon and Bajpai, 1995; Aoki, 1994). In addition, this

material can be a matrixes efficient of water purification.

2.6 ADSORPTION ISOTHERMS

Adsorption isotherms ,which are the presentations of the amount of the solute adsorbed per unit

of the adsorbent as a function of equilibrium concentration in bulk solution at constant

temperature .If a quantity q of adsorbate is adsorbed by a porous solid adsorbent at constant

temperature and the steady state equilibrium concentration , then the function q describes the

adsorption isotherm. The isotherm rises in the initial stages with higher slope at low Ce and qe

values.This indicates that initially there are numerous readily accessible sites.This confirms the

monolayer coverage of adsorbate onto adsorbent particles.A variety of isotherm equations have

been in use some of which have a theoretical foundation and some being of more empirical

nature.

2.6.1 Langmuir Isotherm

A basic assumption of the Langmuir theory is that the sorption takes place at specific

homogenous sites within the adsorbent . It is then assumed that once a ion or molecules occupies

a site no further sorption can take place at that site. The rate of sorption to the surface should be

proportional to a driving force multiplied by are. The driving force is the concentration in the

solution and the area is the amount of bare surface.

Ce/qe = 1/ KL Qo + Ce/ Qo

Where Ce is the equilibrium concentration , qe is the amount of ions or molecules adsorbed

(mg/g) ,Qo is qe for a complete monolayer ( mg/g) ,KL is sorption equilibrium constant . A plot of

Ce/qe versus Ce should indicate a straight line of slope 1/ Qo and an intercept of 1/ KL Qo.

2.6.2 Freundlich Isotherm

Freundlich Isotherm assumes that the uptake of ions occur on a heterogenous surface by

multilayer adsorption and that the amount of adsorbate adsorbed increases infinitely with an

increase in concentration . It is the most popular model for a single solute system, based on the

distribution of solute between the solid phase and aqueous phase at equilibrium.

Linear Equation of Freundlich Isotherm is

Log qe = log Kf + (1/n) log Ce

Where Ce is the equilibrium concentration , qe is the amount of ions or molecules adsorbed

(mg/g), Kf and n are Freundlich constants related to the adsorption capacity and adsorption

intensity ,respectively. A plot of Log qe versus log Ce gives a linear trace with a slope of 1/n and

intercept of log Kf . When 1/n > 0 , the change is adsorbed on concentration is greater than the

change in ion concentration in solution. It is often found that the Freundlich equation is fitted

well to the data at higher and intermediate concentrations , since the Freundlich equation does

not approach Henry s Law of ideal dilute solutions.

2.7 Adsorption Kinetics

Several Kinetic models are in use to explain the mechanism of the adsorption processes. A

simple pseudo second order equation was used.

t/qt = 1/K2qe2 + t/qe

where qt and qe are the amount of adsorption at equilibrium and at time t respectively and K2 is

the rate constant of the pseudo second order adsorption process.

The rate parameters K2 and qe can be directly obtained from the intercept and slope of the plot of

t/qt versus t.The values of rate constant are obtained graphically for both adsorption models.

2.8 Adsorption Thermodynamics

The thermodynamics of an adsorption process is obtained from a study of the influence of

temperature on the process. The standard Gibbs Energy was

G = RT ln Kc The equilibrium constants Kc was evaluated at each temperature using the following relationship

Kc = Ca/Ce

Kc = distribution coefficient for adsorption.

Ca = equilibrium concentration on the adsorbent.

Ce = equilibrium concentration in solution.

Other thermodynamic parameters such as change in standard enthalpy H and standard entropy S were determined using the following equations.

G = H TS

G = Gibbs free energy change H = enthalpy of reaction.

H and S were obtained from the slope and intercept of the Vant Hoff s plot of ln keq versus 1/T , Negative value of H indicates that the adsorption process is exothermic.The negative values of G reflect the feasibility of the process and the values become more negative with increase in temperature. Standard entropy determines the disorderliness of the adsorption at

solid-liquid interface. The positive value if S shows that increasing randomness at the solid-liquid interface during the adsorption process.

3.0 MATERIALS AND METHODS

Wastewater sample was collected from outfall of a dairy industry at Dankuni near Durgapur

express Highway. Wastewater sample collected from the plant was placed in plastic containers to

be transported to the laboratory and stored at 4C in a refrigerator. pH, oil and grease, COD,

BOD, Chlorides, Alkalinity were analysed in the laboratory according to the methods given in

the Standard Methods. Closed reflux colorimetric method was used for COD analysis and was

analysed as dictated by Standard Methods [APHA (2005)]. All the chemicals were of analytical reagent grades and used as received, without further purifications.

3.1 Coagulation- Coagulants and Procedure Coagulants included lime, alum, ferric chloride and ferrous sulfate were all supplied by Merck

India. Coagulation-flocculation and precipitation studies were performed in a conventional jar-

test apparatus [Ayeche (2012)], equipped with beakers of 500 mL volume. Before

coagulation/flocculation process, wastewater sample was thoroughly shaken to avoid possibility

of settling solids. The experimental process consisted of the initial rapid mixing stage that took

place for 5 min at 150 rpm, the following slow mixing stage for 30 min at 30 rpm and the final

settling step for 1 h. After 1 hour settling period, samples were withdrawn from supernatant for

analyses. Process performance was monitored by using COD values[Murali et al., (2013)].

3.1.1 Preparation of Coagulant Solution

Coagulants used for the removal of colour, COD, etc. in the experiment were Lime, Alum, Ferric

Chloride and Ferrous Sulphate. These coagulants were used in combination to enhance of COD.

The combination of the coagulants used was:

i. Lime (10%) + Alum (10%)

ii. Lime (10%) + Ferric Chloride (10%)

iii. Lime (10%) +Ferrous Sulfate (10%)

iv. Lime (10%) + Ferric Chloride (10%) + Alum (10%)

v. Lime (10%) + Ferrous Sulfate (10%)+ Ferric Chloride (10%)

Coagulation process Followed by Adsorption

The different combination of coagulants was added to the dairy wastewater according to the

procedure mentioned below:

i. Lime (10%) + Alum (10%)

100 ml of dairy wastewater was taken in 500 ml conical flask and the pH was

measured.

Lime (10%) solution (about 5 ml) was added to the sample to adjust the pH to

8.3.

Alum (10%) solution (about 5 ml) was added to adjust pH 7.83.

Then the flask was kept in rotary shaker at a high agitation of 150 rpm for 5

minutes and then at low agitation of 30 rpm for 30 minutes.

After that, it is allowed to settle down and the rate of settling was observed

with time.

The supernatant was collected and the parameters like COD, pH were

analysed.

The sludge volume was also measured.

ii. Lime (10%) + Ferric Chloride (10%) + Alum (10%)

100 ml of dairy wastewater was taken in 500 ml conical flask and the pH

was measured.

Lime (10%) solution (about 5ml) was added to the sample to adjust the pH

to 8.3.

Ferric Chloride (10%) solution (about 5 ml) was added to adjust pH 7.43.

No precipitate or settling was observed, then Alum (10%) solution (5 ml)

was added until precipitate was formed.

Then the flask was kept in rotary shaker at a high agitation of 150 rpm for

5 minutes and then at low agitation of 30 rpm for 30 minutes.


with time.


analysed.


iii. Lime (10%) + Ferrous Sulfate (10%)


was measured.

Lime (10%) solution (about 5 ml) was added to the sample to adjust the pH

above 8.3.

Ferrous Sulfate (10%) solution (5 ml) was added to adjust pH 7.31.




with time.


analysed.


iv. Lime (10%) + Ferrous Sulfate (10%) + Ferric Chloride (10%)


was measured.

Lime (10%) solution (about 5 ml) was added to the sample to adjust the pH

to 8.3.

Ferric Chloride (10%) solution (5 ml), Ferrous Sulfate(10%) solution (5

ml), was added to bring the pH to 7.21.

Due to the addition of ferric chloride, ferrous sulfate and sulfuric acid pH

comes nearly to 5. So lime (10%) was added to adjust the pH to 7.




with time.


analysed.


After the coagulation process, the supernatant of each flask was collected and sawdust was

added to the supernatant and kept in rotary shaker for 2 hrs. for adsorption process. After 2

hours, samples were taken COD were analysed using respective instruments and procedure.

3.1.2 COD Estimation

For the estimation of COD standard procedure was followed 2.5 ml of the collected samples was

poured to the COD vials along with 1.5 ml digestion mixture and 3.5 acid mixture. Then it is

kept in COD digestor for 2 hours at 148C. After 2 hour, the COD was calculated as

( a b ) N x 8000 COD mg/l = --------------------------------- ml sample where,

a = ml Fe(NH4)2(SO4)2 used for blank

b = ml of Fe(NH4)2(SO4)2 used for sample

N = normality of Fe(NH4)2(SO4)2

3.2 Adsorbent preparation Sawdust and Ricehusk were used for the adsorption process. Sal Sawdust was collected from a

nearby sawmill and ricehusk was collected from a local agro industry.All the adsorbents were

washed several times with hot distilled water and dried at room temperature for several days.

They were sieved using meshes to get the desired adsorbent size of

4.0 RESULTS AND DISCUSSIONS

4.1 Characterisation of Dairy Wastewater

The Dairy wastewater collected from the input of an effluent treatment section has the following

characteristics :-

Table 1 : Characteristics of Dairy Wastewater

Initial parameters of waste water

COD 468 mg/l.

BOD 210 mg/l.

OIL AND GREASE 240 mg/l.

CHLORIDES 136 mg/l. (less than 250 ppm).

ALKALINITY 462.5 mg/l CaCo3 equivalent

PH 7.34-7.38

TSS 942 mg/l

TDS 680 mg/l

Conductivity 1200 mS/cm

4.2 Results obtained after Treatment of Wastewater with Coagulants

Effects of different coagulants on COD removal, pH, sludge produced were studied and the

results observed below. Maximum removal of 92 % was obtained using Lime and Ferrous

Sulfate combination. But the main problem behind using Iron based Coagulants was the amount

of sludge produced. So Lime and Alum was more preferable.

Coagulant COD Percentage

removal (COD)

pH Sludge

produced

(mg/100ml)

Lime + Alum 72 84% 7.83 616.23

Lime +Ferric Chloride 80 82.9% 7.12 779.67

Lime+Ferrous Sulfate 26 92% 7.31 747.77

Lime+Ferrous Sulfate+ Ferric

Chloride 236 50% 7.21 578.47

Lime + Alum+ Ferric Chloride 411.86 12% 7.43 746

Table 2 : Effect of Different Coagulant Treatment on Different Parameters

4.3 Results obtained after Treatment of Wastewater with Coagulation

followed by Adsorption. The supernatant obtained after Coagulation were subjected to equal amount of dosage of the

adsorbent for equal interval of time and rotation in the shaker. The results showed that

coagulation followed by adsorption could not be adopted in case of Dairy Wastewater since it

resulted in massive increase of COD of wastewater as compared to the removal using only

coagulation technique. This may be due to the due to release of soluble organic compounds

contained in the adsorbents which added up to the proteins and Casein which was already present

in the wastewater.

Figure1: Effect of Coagulants on

Percentage Removal.

Figure2: Effect of Coagulants on

Sludge Produced.

Table 3 : Effect of Coagulation Followed By Adsorption

After coagulation COD value mg/l

After coagulation + adsorption with SAWDUST COD value mg/l

After coagulation + adsorption with RICEHUSK COD value mg/l

After coagulation + adsorption with GRAPHENE OXIDE COD value mg/l

Lime +alum 72 392 140 180

Lime +ferric chloride

80 444 440 432

Lime + ferrous sulfate

36 420 360 220

Lime + ferric chloride+ ferrous sulfate

236 252 380 Not done

4.4 Rate of Settling

The rate of Settling was observed for different coagulants on treatment of the wastewater .It was

observed

0

2

4

6

8

10

12

14

16

18

0 20 40 60 80 100 120 140

Hei

ght

Time

Lime+FeCl3

Lime+alum

Lime+FeSO4

Figure3: Rate of Settling of

Different Coagulants

Figure 4: Rate of Settling of

Different Coagulants

4.5 Batch Adsorption study using Graphene Oxide as Adsorbent

4.5.1 Effect of Adsorbent Dosage :. At this stage, the experiments were done under the conditions of constant temperature (30 C), agitation speed (150 rpm), constant pH of 2 and

variable adsorbent dose (0.5, 1, 1.5 , 2 , 2.5 g/L). The effect of adsorbent dose on the adsorption

in Fig.(5). are explained. It was observed that the percentage removal increased with an increase

in adsorbent dose. The correlation between adsorbent dose and percentage removal can be

related to an increase in the adsorbent surface area and availability of more adsorption sites.

Adsorbent Dosage in g/L Percentage Removal ( % )

0.5 94.14

1 94.63

1.5 95.36

2 96.34

2.5 96.5

4.5.2 Effect of pH The pH of the aqueous solution is clearly an important parameter that controlled the adsorption

process. The experiments of this stage were done under the conditions described above with

adsorbent dose (1.1 g/L). The experimental results of this stage are presented in Fig (6). At lower

pH there was a increase in percentage removal with time. But at pH 10 after a certain time there

was a drastic reduction in percentage removal.This suggests that the adsorption process was

favoured at lower pH.

pH Percentage Removal ( % )

2 97.578

4 97.31

6 96.34

10 96.09

Figure 5: Effect of Dosage on

Percentage Removal using

Graphene Oxide.

Table 4: Percentage Removal at

different Adsorbent Dosage For

Adsorption onto Graphene Oxide


different pH For Adsorption onto

Graphene Oxide

4.5.3 Effect of Temperature Figure (7) displays the effect of temperature on the adsorption process keeping other parameters

same as before. As seen from the figure, the percentage removal decreased with increasing

temperature. At a temperature of 20C the percentage removal was maximum of about

98%.Thus it concluded that the process was favoured by a lower temperature. Since the sorption

capacity of the adsorbent was greater at lower temperature, it can also be said that the sorption

might be an exothermic process. The binding capacity decreases with increasing temperature

which may be due to weakening of the bonds between the molecules and the binding sites of the

adsorbent.

Temperature ( K) Percentage Removal ( % ) 293 98.04

298 96.09

308 95.36

313 93.9

Figure 6: Effect of pH on


Graphene Oxide.

Figure 7: Effect of Temperature

on Percentage Removal using

Graphene Oxide.

Table 6:Percentage Removal at

different Temperature For

Adsorption onto Graphene Oxide

4.6 Batch Adsorption Study Using HAP Nano-Composites As Adsorbent

4.6.1 Effect Adsorbent Dosage : Result on the effect of adsorbent dose at temperature of 30C, Ph 7.38 and agitation 172 rpm is presented in table. The percentage removal increased

with an increase in adsorbent dose. The removal efficiency increases with increase in adsorbent

dose, as contact surface of adsorbent particles and the availability of more binding sites increase

for adsorption.

Adsorbent Dosage (g/L) PERCENTAGE REMOVAL (%)

4 91.67

6 92.09

8 92.57

10 93.38

12 93.4

4.6.2 Effect of pH : Result on the effect of pH at temperature of 30C, adsorbent dosage of 11 gm/l and agitation 172 rpm is presented. The removal was favoured at a lower pH and there

is a sharp decrease in the removal capacity with the increase of pH.. At higher pH, the adsorbent

surface carries a net negative charge while at lower pH a net positive charge.The Casein has a

negative charge resulting in electrostatic repulsion between the molecules and the binding sites

in alkali medium.This might be due to the weakening of electrostatic force of attraction between

the oppositely charged adsorbate and adsorbent that ultimately lead to the reduction in removal.

pH PERCENTAGE REMOVAL (%)

2 93.54

4 93.14

6 92.02

8 91.38

10 91.22



Hydroxyapatite Particles.


different Dosage For Adsorption onto

HAP

Table 8: Percentage Removal at different

pH For Adsorption onto HAP

4.6.3 Effect of Temperature: Figure(10) below displays the effect of temperature on the adsorption process keeping other parameters same as before. Thus it concluded that the process

was favoured by a lower temperature and the sorption might be an exothermic process. The

binding capacity decreases with increasing temperature which may be due to weakening of the

bonds between the molecules and the binding sites of the adsorbent.

TEMPERATURE (K) PERCENTAGE REMOVAL (%)

293 99.84

298 96.44

308 90.65

313 88


The concentration of the wastewater was varied by the method of percent dilution keeping the

other parameters same as above. It was observed that on increasing the dilution or reducing the

concentration the percentage removal increased. It is evident from this figure that,removal

efficiency decreases with the increase in initial Concentration. In case of lower concentrations,

the ratio of the initial number of moles of ions to the available surface area of adsorbent is large









Adsorption onto HAP

and subsequently the fractional adsorption becomes independent of initial concentration.

However, at higher concentrations, the available sites of adsorption become fewer, and hence the

percentage removal of decreases.

Concentration (mg/L) PERCENTAGE REMOVAL (%)

231.8 90.8

219.6 92.49

207.4 93.04

195.4 93.27

183 93.03

4.6.5 Adsorption Isotherms : Data for Langmuir, Freundlich were plotted for adsorption of molecules into the nano-adsorbent.It was observed that Langmuir isotherm was found

suitable.The plots are shown below. Table 11 :Isotherm parameters for Adsorption onto HAP Langmuir Freundlich

Ce Ce /qe Log Ce Log qe 25.97 1.388 3.256 2.929

21.27 1.179 3.057 2.892

19.7 1.154 2.98 2.836

Ce/qe=1/Qob + 1/Qo Ce

Slope = 0.039

Q0=KL/aL= 25.6410

1/Qo = 0.039

Qo= 25.6410 Intercept = 0.370

1/KLQo = 0.370

KL= 0.1054

1/Qob=0.370, b=0.1054

RL =0.0866, 0< RL


The thermodynamic parameters such as Gibbs energy (G),enthalpy (H) and entropy changes

(S) for the adsorption process can be determined using Vant Hoff equation. The enthalpy

change is determined graphically by plotting ln(keq) versus 1/T which gives a straight line and the

values of G and S computed numerically. Gibbs energy values are negative and large and

increases with increase of temperature. This indicated that better removal is obtained at lower

temperature.Negative value of H indicate that the process is exothermic.The positive value of

S shows the feasibility of the adsorption and the increased randomness at the sorbent /solution

interface during the adsorption of molecules onto HAP.

Figure 12: Langmuir Isotherm

Plot for adsorption onto HAP

Figure 13: Freundlich Isotherm

Plot for adsorption onto HAP

Temperature (K) G (J /mole) H ( J/mole ) S (J/mole K )

293 - 4.3840 -673.2 2.298

298 -104.305

308 -293.969

313 -390.3423


Data for pseudo second order kinetic model for the adsorption of ions onto the nano- adsorbent

surface at temperature 30C , pH 7.38 and agitation 172 rpm and dosage of 11 g/L is presented.

Figure 14: Vant Hoff Plot for

estimation of thermodynamic

parameters for adsorption onto

HAP

Figure 15: Pseudo Second Order

Kinetic Model for adsorption

onto HAP

Table 12: Thermodynamic

Parameters for adsorption

onto HAP .

4.7 Batch Adsorption study using Ricehusk as Adsorbent

4.7.1 Effect of Adsorbent Dosage: The experiments were done under the conditions of

constant temperature (30 C), agitation speed ( >150 rpm), constant pH of 7.38 and variable

adsorbent dose (4,6,8,10 g/L).The percentage removal was found to be decreasing with increase

in dosage.This increase in COD value may be due to the release of soluble organic compounds

contained in the plant materials.

Adsorbent Dosage ( g/L) PERCENTAGE REMOVAL (%)

4 89.95

6 85.6

8 83.49

10 83.47

4.7.2 Effect of pH : The pH of the solution is an important monitoring parameter in biosorption studies. It influences not only the surface charge of the biosorbent but also the degree

of ionization of the organic substance present in the solution. Result on the effect of pH at

temperature of 30C, adsorbent dosage of 5 gm/l and agitation( >150 rpm), is presented. The

removal was favoured at a lower pH. At higher pH, the adsorbent surface carries a net negative

charge while at lower pH a net positive charge. The Casein has a negative charge resulting in

electrostatic repulsion between the molecules and the binding sites in alkali medium.

pH PERCENTAGE REMOVAL (%)

2 93.54

4 91.35

6 89.16

8 85.11

10 74.2



Ricehusk.


different Adsorbent Dosage For

Adsorption onto Ricehusk



Ricehusk

4.7.3 Effect of Temperature: Figure below displays the effect of temperature on the adsorption process keeping other parameters same as before. The percentage removal decreased

with increasing temperature. Since the sorption capacity of the adsorbent was greater at lower

temperature, it can also be said that the sorption might be an exothermic process. With regard to

the effect of temperature on the adsorption, an increasing uptake of organic molecules is

expected when the adsorption temperature decreases because adsorption is a spontaneous

process. The binding capacity decreases with increasing temperature which may be due to

weakening of the bonds between the molecules and the binding sites of the biosorbent.

TEMPERATURE (K) PERCENTAGE REMOVAL (%)

293 91.49

298 88.5

308 84.05

313 83.34



Ricehusk.



Ricehusk.





The concentration of the wastewater was varied by the method of percent dilution keeping the

other parameters same as above. It was observed that on increasing the dilution or reducing the

concentration the percentage removal increased. It is evident from this figure that,removal

efficiency decreases with the increase in initial Concentration. In case of lower concentrations,

the ratio of the initial number of moles of ions to the available surface area of adsorbent is large

and subsequently the fractional adsorption becomes independent of initial concentration.

However,at higher concentrations, the available sites of adsorption become fewer, and hence the

percentage removal of decreases.

Concentration (mg/L) PERCENTAGE REMOVAL (%)

231.8 91.023

219.6 91.741

207.4 92.458

195.4 93.8

183 94.011


Data for Langmuir, Freundlich were plotted for adsorption of molecules into the Ricehusk.It was

observed that Langmuir isotherm was found suitable.The plots are shown below

Langmuir Freundlich

Ce Ce /qe Log Ce Log qe 25.433 0.6162 3.2360 3.7202

23.4 0.5963 3.1527 3.6696

21.367 0.558 3.0618 3.616

17.567 0.4944 2.8660 3.5702

16.967 0.501 2.8312 3.5027

Figure 19: Effect of

Concentration on Percentage

Removal using Ricehusk.


different Concentration For


Ce/qe=1/Qob + 1/Qo Ce

Slope = 0.014

Q0=KL/aL= 71.4285

1/Qo = 0.014

Qo= 71.4285

Intercept = 0.241

1/KLQo = 0.241

KL= 0.0580

RL = 0.1470 ,0< RL

S shows the feasibility of the adsorption and the increased randomness at the sorbent /solution

interface during the adsorption of molecules onto ricehusk.

Temperature (K) G (J /mole) H ( J/mole ) S (J/mole K )

293 - 253.100 -554.1 1.997

298 -354.7883

308 -524.177

313 -585.253


Data for pseudo second order kinetic model for the adsorption of ions onto the Ricehusk surface

at temperature 30C , pH 7.38 and agitation >150 rpm and dosage of 5 g/L is presented.

Figure 23 : Pseudo Second Order

Kinetic Model for adsorption

onto Ricehusk

Figure 22: Vant Hoff Plot for

estimation of thermodynamic

parameters for adsorption onto

Ricehusk

Table 18: Thermodynamic

Parameters for adsorption

onto Ricehusk

4.8 Batch Adsorption study using Sawdust as Adsorbent

4.8.1 Effect of Adsorbent Dosage: The experiments were done under the conditions of

constant temperature (30C), agitation speed ( >150 rpm), constant pH of 7.38 and variable

adsorbent dose of (5,10,15 g/L).The percentage removal was found to be decreasing with

increase in dosage.This increase in COD value may be due to the release of soluble organic

compounds contained in the plant materials.

Time (min) Variation of Dosage in g/L

5 10 15

3 78.9 66 54.2

6 57.14 25.71 18.57

9 54.57 21.74 15.71

12 51.14 15.85 12.85

15 19.7 10.85 8.85

4.8.2 Effect of pH : Result on the effect of pH at temperature of 30C, adsorbent dosage of 6 gm/l and agitation >150 rpm rpm is presented. The removal was favoured at a lower pH and

there is a sharp decrease in the removal capacity with the increase of pH.. At higher pH, the

adsorbent surface carries a net negative charge while at lower pH a net positive charge.The

Casein has a negative charge resulting in electrostatic repulsion between the molecules and the

binding sites in alkali medium.Thus due to the weakening of electrostatic force of attraction

between the oppositely charged adsorbate and adsorbent that ultimately lead to the reduction in

removal.



Sawdust.


different Dosage For Adsorption

onto Sawdust.

Time

(min)

Variation of pH

2 4 6 9

3 99.14 96.42 78.28 61.14

6 99.71 94.62 72.85 45.42

9 99.04 74.6 69.42 32

12 97.14 70.2 64.57 24.57

15 98.28 53.46 47.42 15.71

4.8.3 Effect of Temperature: Figure below displays the effect of temperature on the adsorption process keeping other parameters same as before. Thus it concluded that the process

is exothermic and was favoured by a lower temperature. With regard to the effect of temperature

on the adsorption, an increasing uptake of organic molecules is expected when the adsorption

temperature decreases because adsorption is a spontaneous process.

Time

(min)

Variation of Temperature (K)

293 298 308 313

3 74.28 68.28 63.34 60.25

6 56.85 51.24 46.57 42.67

9 46.28 43.45 38 36.58

12 44 40.56 37.14 33.14

15 41 28 22.57 20.714



Sawdust.



Sawdust.



Adsorption onto Sawdust.

4.8.4 Effect of Concentration: The concentration of the wastewater was varied by the method of percent dilution keeping the other parameters same as above. It was observed that on

increasing the dilution or reducing the concentration the percentage removal increased. It is

evident from this figure that,removal efficiency decreases with the increase in initial

Concentration. In case of lower concentrations, the ratio of the initial number of moles of ions to

the available surface area of adsorbent is large and subsequently the fractional adsorption

becomes independent of initial concentration. However,at higher concentrations, the available

sites of adsorption become fewer, and hence the percentage removal of decreases.

Time

(min)

Variation of Concentration(mg/L)

231.8 219.8 195.2 183

3 45.41 53.83 57.58 65.58

6 36.58 40.41 46.08 52.25

9 17.5 29.34 34.67 41.91

12 10.5 15.75 19.16 33.59

15 4.5 6.25 11 14.6

Figure 26: Effect of temperature


Sawdust.

Figure 27: Effect of

Concentration on Percentage

Removal using Sawdust.


different Concentration For


4.8.5 Effect of Adsorbent Size :

Data for the effect of variation of different adsorbent size keeping other parameters same as

above indicates that with increase in adsorbent size the removal efficiency decreases. These

phenomena might be due to the fact that the smaller particles offer comparatively larger surface

areas and greater numbers of adsorption sites.

Time(min) Variation of Adsorbent Size (MIC)

60

3 45.9 38.75 29.16

6 39.58 18.75 16.67

9 26.25 16 10.41

12 17.5 11.666 9.16

15 9 8 5.83

Figure 28: Effect of adsorbent

size on Percentage Removal

using Sawdust.


different adsorbent size For


4.9 Conclusion

The present study shows that Nano composites especially Hydroxyapatite particle can be

effectively used as a adsorbent for treatment of Dairy Wastewater as it could bring about a

removal upto 96 % as compared to plant based adsorbents since the application of untreated

plant wastes as adsorbents can also bring several problems. With time the percentage removal

decreases which indicates to be a time saving process. Moreover it is a cost effective process

since all the nano composites were prepared from cheaply available raw materials.Casein is the

main component of Dairy Wastewater. Decomposition of casein leading to the formation of

heavy black sludges and strong butyric acid odors and characterize milk waste pollution. It is

relatively hydrophobic, making it poorly soluble in water. The caseins in the micelles are held

together by calcium ions and hydrophobic interactions. Casein has a negative charge in milk.

The purified protein is water insoluble. While it is also insoluble in neutral salt solutions, it is

readily dispersible in dilute alkalis and in salt solutions such as sodium oxalate and sodium

acetate which makes it unavailable for adsorption. The results showed that coagulation followed

by adsorption could not be adopted in case of Dairy Wastewater since it resulted in massive

increase of COD of wastewater as compared to the removal using only coagulation technique.

Only coagulation could bring about a reduction as high as 92 % using ferrous sulfate for efficient

removal of oil and grease. But Iron based coagulants causes sludge problem and inproper

removal of colour of the wastewater. Thus lime and alum was a preferable combination.

The entire process was favoured at lower temperature and lower pH with a little adsorbent

dosage . The solution pH controls the adsorptiveadsorbent and adsorptiveadsorptive

electrostatic interactions, which can have a profound effect on the adsorption process. Thus,

solution pH determines the carbon surface charge and the dissociation or protonation of the

pollutants or ions present. The removal was favoured at a lower pH and there is a sharp decrease

in the removal capacity with the increase of pH. At higher pH, the adsorbent surface carries a net

negative charge while at lower pH a net positive charge.The Casein has a negative charge

resulting in electrostatic repulsion between the molecules and the binding sites in alkali medium.

The organic removal was favoured at lower temperature which concluded that the process is

exothermic and was favoured by a lower temperature. With regard to the effect of temperature on

the adsorption, an increasing uptake of organic molecules is expected when the adsorption

temperature decreases because adsorption is a spontaneous process. Langmuir isotherm and

pseudo second order models fitted most. It can be concluded that the developed methods can be

effectively applied for the COD removal from the effluent. The present finding can be further

exploited for the possible utilization of the selected adsorbents in the industrial sector for large

scale practical applications.

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2.4 ADSORPTION2.4.1 Fundamentals of the adsorption2.4.2 Physical Adsorption2.4.3 Chemical Adsorption2.4.4 Adsorption Mechanism2.5 ADSORBENTS2.5.1 Sawdust2.5.2 Ricehusk2.5.3 Graphene Oxide2.5.4 Hap Nano-CompositesWastewater from dairies and cheese industries contain mainly organic and biodegradable materials that can disrupt aquatic and terrestrial ecosystems. Due to the high pollution load of dairy wastewater, the milk-processing industries discharging untrea... Treatment of Dairy Industry Wastewater by Reverse Osmosis for Water Reuse Anaerobic Filter Reactor for the Treatment of Complex Dairy Wastewater at Industrial Scale Use of Nanofiltration and Reverse Osmosis Membranes in Dairy Wastewater Treatment Anaerobic Treatment of Dairy Wastewaters Electrochemical Technologies in Wastewater Treatment.2.4 ADSORPTION2.4.1 Fundamentals of the adsorptionAdsorption is a process in which a substance (adsorbate), in gas or liquid phase, accumulates on a solid surface. It is based on the capability of porous materials with large surfaces to selectively retain compounds on the surface of the solid (adsorb...2.4.2 Physical AdsorptionPhysical adsorption is achieved by Van der Waals forces, dipole interactions, and hydrogen binding. There is no electron exchange between adsorbent and adsorbate. Because there is no activation energy required for physical adsorption, the time needed ...2.4.3 Chemical AdsorptionChemical adsorption results from the chemical link between adsorbent and adsorbate molecule, therefore it is specific as well as irreversible and chemical as well as electronic properties of adsorbent are changed. Binding between adsorbent and adsorba...2.4.4 Adsorption MechanismsThe adsorption process of the adsorbate molecules from the bulk liquid phase into the adsorbent surface is presumed to involve the following stages : Mass transfer of the adsorbate molecules across the external boundary layer towards the solid particle. Adsorbate molecules transport from the particle surface into the active sites by diffusion within the porefilled liquid and migrate along the solid surface of the pore. Solute molecules adsorbtion on the active sites on the interior surfaces of the pores. Once the molecule adsorbed, it may migrate on the pore surface trough surface diffusion.2.5 ADSORBENTS2.5.1 SAWDUSTSawdust is a waste by-product of the timber industry that is either used as cooking fuel or a packing material; however, it can be used as a low-cost adsorbent of heavy metals, principally due to its lignocellulosic composition. It is mainly composed ...2.5.2 RICEHUSKRice husk, which is a relatively abundant and inexpensive material, is currently being investigated as an adsorbent for the removal of various pollutants from water and wastewaters. Various pollutants, such as dyes, phenols, organic compounds, pestici...2.5.3 GRAPHENE OXIDE2.5.4 HAP NANO-COMPOSITES

treatment of dairy wastewater

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