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BAGASSE FLY ASH UTILIZATION AS AN ADSORBENT TO REDUCE

H2S LEVEL IN TOFU WASTE BIOGAS

Thesis

This thesis is submitted in fulfilment of the partial requirements for the

awards of the Master Degree of :

Master Program of System Engineering

Joint Program

Arranged By :

Rizki Triana Putri

09/305576/PTK/06798

TO

POSTGRADUATE PROGRAM

GADJAH MADA UNIVERSITY

YOGYAKARTA

2012

iv

ACKNOWLEDGEMENTS

First, I would like to say thanks to the Almighty Allah SWT, my Lord who

has given me the mercy and blessing, so my Thesis with title “Bagasse Fly Ash

Utilization As An Adsorbent To Reduce H2S Level in Tofu Waste Biogas”

could finish well. Sholawat and salam may be given to my prophet, Muhammad

SAW.

During writing this thesis I was helped by many people who have been

ready in handing over helps I needed, anywhere. Herewith I would like to say

thanks to:

1. Dr. Ir. Suhanan, DEA as Head of Master of Engineering System, Gadjah

Mada University, Yogyakarta.

2. Dr. Ir. Sarto, M.Sc. as my major advisor, for his guidance.

3. Ir. Ambar Pertiwiningrum, M.Si., Ph.D., as my minor advisor, for her

helpfull insights.

4. My lovely mother, mother, mother, father, for your prayer and support.

When I look back on this time and the dreams we left behind, I will be

glad because I was blessing to get and to have you in my life.

5. My sisters and brothers, Dani Ukasah, for all your support and advises

6. Mr Muh. Soleh, Mr. Jumiya, all member of JP 3, and all academic staff of

MTS UGM (Mr. Ahmad, Mas Syukron, Mas Andri, etc), thanks for all

your help and knowledge that was given.

7. Everyone I could not mention here.

The writer is aware if this paper is still far from being perfect, so any

suggestions and criticism for better improvement of the paper are welcomed. The

writer hopes this paper will give benefit for many people. Amien.

Wassalamu’alaykum Wr. Wb.

Yogyakarta, Februari 2012

Rizki Triana Putri

v

TABLE OF CONTENTS

TITLE ......................................................................................................................... i

ENDORSEMENT ...................................................................................................... ii

STATEMENT ............................................................................................................ iii

ACKNOWLEDMENT ............................................................................................... iv

TABLE OF CONTENTS ........................................................................................... v

LIST OF TABLES ..................................................................................................... vii

LIST OF FIGURES ................................................................................................... viii

LIST OF APPENDIX ................................................................................................ ix

LIST OF NOTATIONS ............................................................................................. x

ABSTRACT ............................................................................................................... xi

CHAPTER I INTRODUCTION ........................................................................... 1

1.1. Background ................................................................................................... 1

1.2. Problem Formulation ..................................................................................... 3

1.3. Research Objectives ....................................................................................... 3

1.4. Research Benefits ........................................................................................... 3

1.5. Research Authenticity .................................................................................... 4

CHAPTER II LITERATURE STUDY AND THEORY BASES…………………5

2.1. Literature Study ............................................................................................. 5

2.2. Theory Bases .................................................................................................. 20

2.3. Hipothesis ....................................................................................................... 22

CHAPTER III RESEARCH METHODOLOGY…………………………………..23

3.1. Research Material ........................................................................................... 23

3.2. Research Equipment ....................................................................................... 23

vi

3.3. Research Process ............................................................................................ 24

3.4. Research Variable ........................................................................................... 26

3.5. Result Analysis ............................................................................................... 27

CHAPTER IV RESULT AND DISCUSSION……………………………………..28

4.1. Hydrogen Sulfide Analysis ............................................................................ 28

4.2. Models Linearization ...................................................................................... 32

4.3. Analysis of Model Adams Bohart, Thomas, Yan .......................................... 35

4.4. Analysis of Adsorption Capacity and Breakthrough Curve ........................... 37

CHAPTER V CONCLUSION AND SUGGESTION…………………………….45

5.1. Conclusion ..................................................................................................... 45

5.2. Suggestion ..................................................................................................... 46

REFERENCES ........................................................................................................... 47

APPENDIX ................................................................................................................ 50

vii

LIST OF TABLES

Table 1. Biogas Composition ..................................................................................... 8

Table 2. Physical,Chemical,and Safety Characteristics Hydrogen Sulfide ............... 8

Table 3. Composition of Bagasse Fly Ash ................................................................. 11

Table 4. H2S Concentration with BFA 1 .................................................................... 28




Table 8. Adams-Bohart Analysis ............................................................................... 35

Table 9. Thomas Analysis .......................................................................................... 36

Table 10. Yan Analysis .............................................................................................. 36

Table 11. Model Analysis .......................................................................................... 37

Table 12. Resume of Adsorption Capacity ................................................................ 40

viii

LIST OF FIGURES

Figure 1. Tofu Production Process ............................................................................. 5

Figure 2. Sugarcane Milling Process ......................................................................... 10

Figure 3. Structure of Oxygen Functional Group ...................................................... 13

Figure 4. Structure of Nitrogen Functional Group ..................................................... 13

Figure 5. Skecth of Concentration Profile, Mass Transfer, and Breakthrough

Curve ......................................................................................................... 16

Figure 6. Research Equipment ................................................................................... 23

Figure 7. Research Diagram ....................................................................................... 24

Figure 8. Adams-Bohart Linearization ...................................................................... 32

Figure 9. Thomas Linearization ................................................................................. 33

Figure 10. Yan Linearization ..................................................................................... 34

Figure 11. Breakthrough Curve of BFA 1 ................................................................. 38




Figure 15. Curve of All Variables .............................................................................. 43

ix

LIST OF APPENDIX

1. Appendix A Result of H2S Analysis

2. Appendix B Methods of H2S Sampling

x

LIST OF NOTATIONS

Co : Inlet H2S concentration

C : Effluent H2S concentration

kAB : Adams-Bohart kinetics constanta, ml/mg/min

kTH : Thomas kinetics constanta, ml/mg/min

kY : Yan kinetics constanta, ml/mg/min

Q : Flow rate, ml/min

qAB : Adsorption capacity for Adams-Bohart model, mg/L

qTH : Adsorption capacity for Thomas model, mg/L

qY : Adsorption capacity for Yan model, mg/L

t : Flow time, minute

W : Adsorbent weight, gram

τ : Residence time in column, minute

Z : Height of column, cm

U : Superficial velocity, cm/min

N0 : Saturation concentration in Adams-Bohart model, mg/l

Veff : Effluent volume, ml

xi

ABSTRACT

The objectives of this research was to evaluate bagasse fly ash ability to reduce the number of H2S, to evaluate the effect of chemical treatment and the effect of size to BFA adsorption ability, to obtain mathematical model that is suitable to describe H2S reducing in tofu waste biogas that occured in fixed bed column, and also to evaluate the adsorption ability from recycle bagasse fly ash.

Variable used in this research are bagasse fly ash particle size and bagasse fly ash chemically treatment. Bagasse fly ash particle size are -60+100 mesh and -200 mesh. Chemically treatment given namely activation using hydrogen peroxide (H2O2) 3%. This treatment is given for bagasse fly ash with particle size -60+100 mesh. The experiment done in fixed bed column and had a continous flow type. Concentration data of effluent and time data obtained are used to evaluate some parameters from Adams Bohart, Thomas, and Yan equation. The suitable model was evaluated using correlation coefficients.

The research showed that activated bagasse fly ash had a better ability to reduce H2S level better than non-activated bagasse fly ash. Smaller particle size of bagasse fly ash also had a better ability to adsorp H2S. This research show that Thomas model was the most suitable model to describe the reducing of H2S level in fixed bed column. The best result was obtained by activated bagasse fly ash -60+100 mesh at flow rate 200 min/minute and initial inlet concentration 154 ppm. The Thomas kinetics constant (kT) and the adsorption capacity (qT) were 0.36 ml/mg/min and 2.42 mg/g and the correlation coefficient obtained was 0.869. Keywords: Hydrogen Sulfide, biogas, tofu waste, activation, bagasse fly ash, adsorption.

1

CHAPTER I

INTRODUCTION

1.1. Background

Domestic energy demand is more and more increasing. Therefore, according

to national energy policy, we need to develop renewable energy as an alternative

energy that can fulfill energy demand from the society. Based on study which has

been done by PLN and team, Indonesia is very potential to develop about one

million unit of biogas installation. It number is similar with saving of 900 million

litres of fossil oil or 700 tons of LPG each year.

(http://www.pln.co.id/pro00/news/aktivitas/76/225.html).

Biogas is one of alternative energy that is applied in society, especially for

animal husbandry society. Biogas is produced from anaerobic process which is

occured inside the reactor (biodigester). Anaerobic process cause organic

compound degradation without presence of oxygen, where the process would be

produce by biogas that consist of methane, carbondioxide, and hydrogen sulfide .

Tofu industry’s waste water contain a very high organic substance, if it

discharge to the environment without any treatment, it makes a negative effect

that is descending of water quality. The number of tofu industry in Indonesia are

84.000 unit. And the maximum production capacity are 2,56 millions ton each

year, these industries produce more than 20 millions metre cubic each year and

also produce emission similar to 1 million ton CO2 (http://hendrik-

perdana.web.id/artikel/umum/242-biogas-dari-limbah-tahu).

2

Tofu liquid waste still contains organic materials that contain nutrients that

are good enough for methanogenic bacterial growth. The presence of bacteria in

the reactor can cause methanogenesis process that can produce methane gas. The

result of methane gas can be utilized as an energy alternative which can reduce the

impact of global warming.

The composition of gasses commonly found in tofu waste are nitrogen (N2),

oxygen (O2), hydrogen sulfide (H2S), amonia (NH3), carbondioxide (CO2), and

methane (CH4). These gases come from the decomposition of organic substances

which is in waste water (Herlambang, 2002). The levels of methane in biogas is

only 65%, but we can increase the purity of biogas by reducing the concentration

levels of H2S, CO2 and other impurities. Emissions from the biogas can make the

environment is threatened by the presence of hydrogen sulfide which is harmful to

humans and the environment. Therefore, if we can purify biogas levels, then we

can reduce the risk of biogas which can be harmful emissions and to increase the

methane content in biogas. If the methane content increases, the heating value of

biogas will also be increased. One of the methods used to improve the

performance of biogas is the adsorption method, and it is to reduce the levels of

H2S.

Bagasse fly ash (BFA) is waste of combustion from boilers in sugar mills

which is collected by a special instrument, it iscalled a dust collector. BFA has

potential as an adsorbent because it’s pores and high organic carbon content

(Prasetya, 2007). Currently, BFA is only used as an adsorbent for liquid waste, if

it is used in biogas, it needs further assessmentit is utilization of BFA as an

3

adsorbent to reduce the level of H2S in biogas. This study will examine that in the

presence of BFA on biogas installations can reduce the level of H2S in tofu waste

biogas.

1.2. Problem Formulation

Generally, the problem formulation on this research is the unknown effect

of the presence of BFA to the reduction of H2S levels in the biogas. H2S reduction

are expected to decrease the bad impact from the H2S with the presence of BFA as

an adsorbent.

1.3. Research Objectives

Based on problem formulation above, the research objectives on this study

can be formulated as follows :

1. To evaluate the adsorption ability from BFA to reduce H2S level in tofu

waste biogas.

2. To evaluate the effect of chemical treatment and effect of particle size to

BFA adsorption ability.

3. To know the regeneration ability from BFA.

1.4. Research Benefits

Utilization of BFA as an adsorbent are expected to give these kinds of

benefits :

1. To provide an alternative solution to utilize BFA which had dumped in a

big number.

2. Increasing the biogas purity by reducing the H2S level

4

1.5. Research Authenticity

Research with idea :

“Bagasse Fly Ash Utilization As An Adsorbent To Reduce H2S Level in

Tofu Waste Biogas” as the author's knowledge has never been done, except that

has been mentioned in references in this research.

5

CHAPTER II

LITERATURE STUDY AND THEORY BASIS

2.1. Literature Study

2.1.1. Tofu Waste

Tofe waste is generated from tofu production process. Tofu production

process is shown in figure 1 :

Figure 1. Tofu Production Process

6

Tofu waste generally consist into two forms, they are solid waste and

liquid waste. Solid tofu waste is from which are manure from soybean

soaking and washing (fine rock, soil, peels, and other solid attached on

soybean) and also the remaining filter soybean porridge. solid waste that

which is occurred are not too much (0.3% of the raw material of soybean).

While the solid waste in the form of tofu waste occurs in the filtering of

soybean porridge.

Liquid waste in tofu production process derives from soaking, washing,

filtering, and tofu’s printing out. Most of the waste liquid is viscous liquid

(apart from clumps) which is called whey. This fluid contains high levels of

protein and can be decomposed. This waste is often discharged directly

without any treatment resulting stench and pollute the environment.

Organic ingredients contained in the tofu industry are very high.

Organic compounds in waste water can be proteins, carbohydrates, fats, and

oils. Among these compounds protein and fat are the greatest in number.

Protein reaches 40-60%, carbohydrates 25-50%, and 10% fat. The quality of

waste water is depend on the process which is used by its industry. If the

process is good, then the content of organic matter in effluent is usually low.

The largest component from tofu waste water is protein (N-total) as much

226,06-434,78 mg/l, if this waste water come into the environment it will

increase a number of nitrogen on that area (Herlambang, 2002).

7

Common gasses found in tofu waste are nitrogen (N2), Oxygen (O2),

hydrogen sulfide (H2S), amonia (NH3), carbondioxide (CO2) and methane

(CH4). The gasses come from organic substance decomposition in waste

water. (Herlambang, 2002).

Industrial solid waste is out of soy and tofu skin. The tofu still

contains a high enough protein which can be used as animal feed ingredients

and fish. However, the water content of tofu waste is still high and it is

inhibiting the using of tofu waste as animal feed.

2.1.2 Biogas

Generally, anaerobic process will produce methane gas (biogas).

Biogas is gas which is produced by decaying organic material by bacteria in

anaerobic conditions (without oxygen). Biogas is a mixture of various gases

such as nitrogen gas (N2), oxygen (O2), hydrogen sulfide (H2S), ammonia

(NH3), carbon dioxide (CO2), and methane (CH4). These gases come from

the decomposition of organic substances contained in waste water

(Herlambang, 2002). The Important properties of this methane gas are

odorless, colorless, poisonous, and flammable. The table 1 show the biogas

composition :

8

Table 1. Biogas Composition

Gas Formula % Volume

Methane CH4 54-70

Carbondioxide CO2 27-45

Nitrogen N2 0-1

Hydrogen H2 0-1

Carbonmonoxide CO 0.1

Oxygen O2 0.1

Hydrogen Sulfide H2S Small amount

Hydrogen sulfide is poisonous, odorous, and very corrosive. Some

characteristics from H2S will be described in table 2. Because of its

characteristics, the gasses usually occur on biogas production site.

Table 2. Physical, Chemical, and Safety Characteristics H2S (OSHA, 2002) Molecule weight Specific gravity Temperature Explosive range in air Odor treshold 8 hours-weight average 15minutes-exposure limit Immediately Fdangerous to Life of Health (IDLH)(OSHA)

34.08 1.192 2500 C

4.5-45.5% 0.47 ppb 10 ppm 15 ppm 300 ppm

With anaerobic biogas system, the gas which is produced depends on

the content of protein, fat, and carbohydrate which is contained in the waste,

length of time to decay at least 30 days, the longer time of decay process it

will be good.

2.1.3 B

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ced brownis

volumes wil

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F

he average w

sugar cane p

s of potentia

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ts own baga

per mills as

ste Sugarca

residue from

h is produc

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e bagasse.

h yellow, th

ll produce s

in figure 2:

Figure 2. Sug

waste gener

production i

al waste gen

t on every pl

tion, sugar

gas. Solid w

gasse is the

its sap. This

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ane)

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In the first

hen the milli

sap that is

garcane Mill

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nerated abou

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waste that is:

solid waste

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not the sam

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bagasse, bo

which is de

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Solid waste

sugar cane (

removing fr

n order to o

bagasse.

imes milling

d milling the

of the third,

me. Sugarca

ess is 32% s

mounted to

tons of pulp

gasse as boile

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erived from

f fiber and co

ing fuel, and

is the secon

9

saccharum

rom sap in

btain large

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fourth and

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sugar cane.

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p per year.

er fuel.

nsisting of

d sugarcane

m sugarcane

ork. Other

d it is used

nd form of

10

sugarcane, which is produced by sediment (waste purification sap) before

cooking and crystallized into sugar. Its shape like a black sandy soil, it has

an unpleasant smell if it is still wet.

Based on dry material, bagasse is composed of elements of C (carbon)

47%, H (Hydrogen) 6.5%, O (Oxygen) 44% and ash 2.5%. Excess waste

(bagasse) bring an issue for the sugar cane sugar mill, the pulp is bulky

(pour) so as to save them need large areas. it is Flammable because the

contains are water, sugar, fiber, and microbes, so when stacked, it will be

fermented and releases heated.

2.1.4 Bagasse Fly Ash (BFA)

Bagasse Fly Ash (BFA) is the result of chemical changes of pure

bagasse combustion. Bagasse is used as fuel for heating boilers with a

temperature of 550 0 -600 0 C and a long burning every 4-8 hours then

expenditures made transporting ash from the boiler, because if is left

without cleaning it will occur that will disrupt the next process as an impact

from accumulation of combustion of bagasse. BFA has a perfect pores and

potential to serve as the adsorbent (Prasetya, 2007). Composition of BFA

elements is shown on table 3:

11

Tabel 3. Composition of Bagasse Fly Ash (Prasetya, 2007) Element %berat Element kadar (ppm)

CH (organic carbon) 36,5 Cl 659 Al₂O₃ 2,2 V 20 CaO 2,78 Co 23 Fe₂O₃ - Ni 8 MgO 1,645 Sn 11 SiO₂ 49,98 Mo 5 FeO 1,218 W 47 K₂O 3,97 Rb 113 Pb 0 Sr 140 Ag 0 Ba 96 Bi 0 Y 11 Na₂O 0,23 Zr 19 TiO₂ 0,106 Nb 4 MnO 0,092 Th 9 P₂O₅ 0,906 Hg 0 S 0,2413 Cd 0 Cu 0,0058 As 8 Zn 0,0056 Sb 0

2.1.5 Adsorbent Activation

Activated carbon is utilized to remove organic material and metal ions

from drinking water and waste water. Wood, lignite, coconut shell, and peat

are materials which are currently widely used as raw material for making

activated carbon (Hendawy, 2003).

Adsorption of gas to the surface of activated carbon mainly is

influenced by the morphology of adsorbent material porous, while an

important role in the process of fluid adsorption into the surface of activated

carbon is the chemical nature of the surface of the adsorbent material

(Lahaye, 1998). Oxidation is the most popular treatments to improve the

functional groups of activated carbon surface. The oxidation process can be

12

performed in the gas phase using oxygen, ozone, and nitrogen oxides, or in

the liquid phase using hydrogen peroxide, nitric acid, perchloric acid, and

other oxidizing agents. The degree of oxidation of carbon and the type of

surface groups formed during the oxidation process depend on many factors

including the nature of the chemical oxidizing agent, oxidation temperature,

time, carbon chemical composition, surface properties, and porosity (Choma

et al., 1999).

Functional groups on carbon surface functions can be oxygenated and

nitrogenated functions. Structure of functional groups that have been

proposed for the oxygen of which are shown in Figure 3 and for nitrogen is

shown in Figure 4.

Toles et al., (1999) reported that the activated carbon is made from

peanut shells which are activated with phosphoric acid and oxidation with

air has the ability to absorb metals better than the activated carbon that is

not oxidized. El-Hendawy Research (2003) showed that the activated

carbon-based corn cobs are oxidized with nitric acid has a greater ability to

absorb ions Pb 2 + but smaller in absorb phenol. Gupta and Sharma (2003)

stated that bagasse fly ash without oxidized, the adsorption ability is not

good. They do the activation bagasse fly ash with 30% hydrogen peroxide

to improve its adsorption abilities. The interesting thing was reported by

Choma et al., (1999) that when activated carbon oxidation carried out with

concentrated nitric acid on its boiling temperature, the adsorption capacity

13

decreases. Figure 3 shows oxygen functional structure in active carbon

surface :

Figure 3. Structure of oxygen functional group in active carbon surface are :

(a) carboxyl group; (b) carbonyl group; (c) carboxylic anhydrid; (d) lactone

group; (e) phenolic group; (f) ether group; (g) lactol; (h) quinone group

(Lahaye, 1998).

Figure 4. Structure of nitrogen functional group in active carbon surface

are: (a) amide group; (b) imide group; (c) pyrrolic group; (d) lactame group;

(e) pyridinic group (Lahaye, 1998).

ba d c

h

fe

g

cba

14

2.1.6 Adsorption

Adsorption is a term to describe the tendency of molecules are attached

to the surface of solids from the fluid phase (Ruthven, 1998). Adsorption is

the process of a liquid or gas binding to a solid adsorbent. This definiton is

used to explain the accumulation of gas molecules that occured on solid

surface.

Adsorption process occurs when the adsorbent is in contact with the

surrounding fluid with a specific composition, and after quite a long time to

reach equilibrium adsorbent and its surroundings (Suzuki, 1990).

Adsorption equilibrium depends on the interaction between adsorbate-

adsorbent (the nature of polar, non polar, hydrophobic, hydrophilic, etc.)

and operating conditions such as temperature, pressure, and concentration

(Crittenden and Thomas, 1998).

The process of adsorption depending on the specific area or surface area

of solids, the balance concentration of the adsorbent dissolved substances or

gases adsorption pressure, the temperature at the time the process takes

place and the nature of the adsorbat or adsorbent itself. Greater surface area,

the adsorption capacity will increase. The characteristics of adsorption on

the surface of solids is very selective , the meaning on a mixture of

substances is only one component of the adsorbing species by certain solids.

In some process of adsorption time contact between adsorbat and adsorbent

will effect to adsorption capacity (Laksono, 2002).

15

Adsorption may occur by three different mechanisms, namely (Do,

1998):

1. Steric mechanism

This mechanism based on the difference size of adsorbed molecules.

Adsorbent has a specific pore size so that the adsorbate molecules smaller

size can get into the pores while larger than the pore size can not enter the

pores.

2. Equilibrium Mechanism

This mechanism based on the ability of adsorbent in adsorb adsorbate

molecule. If the adsorbate are traped strongly, it will be more easier to be

separated.

3. Kinetic mechanism

This mechanism depends on the velocity of diffusion of each adsorbate

into the pores of the adsorbent. Molecules that have faster diffusion

velocity in solids will be easier to adsorb.

2.1.7 Fixed Bed Adsorption

Continuous adsorption process can be done in a variety of equipment,

namely fixed bed, moving bed, rotary bed, and fluidized bed (Richardson et

al., 2002). Each device has advantages and disadvantages. Fixed bed has

advantages such as simple, inexpensive manufacture, and adsorbent only

slightly eroded because the position is in column (Crittenden and Thomas,

1998).

16

Mass transfer of fluid to the adsorbent in the fixed bed occurs on the

area is called mass transfer zone (MTZ). The adsorption occurs start from

the entry area and over time move to the area of effluent is shown in Figure

4. If levels of the adsorbate on the effluent is calculated continuously,

breakthrough curve will be obtained when MTZ reaches the effluent area

(Suzuki, 1990). At any given time, adsorbent particles before and after

MTZ does not participate in the process of mass transfer.The section before

the MTZ has undergone equilibrium so no longer able to absorb molecules

of adsorbate, while the part after the MTZ has not been in contact with the

adsorbate (Crittenden and Thomas, 1998). Figure 5 is show about the

phenomenon :

Figure 5. A sketch showing the concentration profile, mass transfer and

Breakthrough curves in fixed bed (Crittenden and Thomas, 1998).

feed

Saturated adsorbent

Fresh adsorbent

adsorbat concentration of

effluent

waktu

Breakthroughcurve

17

C)f(q,tq=

∂∂

The success of adsorption column design requires prediction of the

concentration-time profile or breakthrough curve of effluent. Creating a

model that can accurately describe the dynamic behavior of the fixed bed

adsorption process is difficult because both the concentration of adsorbate in

fluid phase or solid phase at a certain position are change over time.

The translation of the mass balance adsorbate in the liquid phase can be

obtained from Equation (1) follows (Crittenden and Thomas, 1998):

(1)

The rate of adsorption in general can be expressed by equation (2):

(2)

The rate of adsorption depends on the mechanism of adsorption. This

mechanism can be controlled by mass transfer adsorbate to the adsorbent

surface, or diffusion and reaction within the adsorbent particles.

Equation (1) and (2), together with the equation of equilibrium

adsorption isotherm is solved simultaneously. Generally, the analytical

solution of partial differential equations above is difficult to do, it must be

completed in numerical (Souza et al., 2008). The following is a

simplification of Equation models (1) and (2) by taking several different

assumptions:

a. Adams-Bohart Model

0tq

ee1ρ

tC

z(UC)

zCD- 2

2

L =∂∂

⎟⎠⎞

⎜⎝⎛ −

+∂∂

+∂

∂+

∂∂

18

Fundamental equations that describe the relationship between C /

Co and t in the continuous system has been developed by Adams and

Bohart (1920) for adsorption of chlorine with charcoal. Although

originally is developed equations that are applied to gas-solid system

but the overall approach can be applied well in other systems (Aksu and

Gonen, 2004). This model assumes that the adsorption rate can be

approximated by a quasi-chemical kinetics speed (Ruthven, 1984).

Adams-Bohart model is used to describe the initial part of breakthrough

curve. The mass transfer rate obey the following equation (3) and (4)

following (Aksu and Gonen, 2004):

(3)

(4)

Settlement of differential equations above yield equation (Aksu and

Gonen, 2004):

(5)

b. Thomas Model

According to the Aksu and Gonen (2004), completion of Thomas,

including one of the most common and widely used in column

performance theory. Thomas model assumes the adsorption process

C qkdtdq

AB−=

⎟⎠⎞

⎜⎝⎛ −=

UzqktCkexp

CC

AB AB o ABo

C/U qkdzdC

AB−=

19

follow the Langmuir model and no axial dispersion and the driving

force to follow the kinetics of order two. This model form is shown in

Equation (6):

(6)

c. Yan Model

Empirical equation to fix the model is proposed by Yan Thomas,

et al., 2001. Yan model written as follows (Pokhrel and Viraraghavan,

2008) :

(7)

Where :

(8)

(9)

⎟⎟⎠

⎞⎜⎜⎝

⎛−+

=VCWq(

Qkexp 1

1CC

oThTho

a0

fV1

1 - 1CC

⎟⎠⎞

⎜⎝⎛+

=

Q Wq k

f YY=

Q C k

a 0Y=

20

2.2 Theory Basis

Adsorption is the process of a liquid or gas binding to a solid adsorbent.

This definiton is used to explain the accumulation of gas molecules that

occured on solid surface.

Adsorbent that often used are silica, Mg(OH)2, Ca3(PO4)2, etc. The

purpose of the adsorption process is to eliminate the taste, color, and

undesirable odors and organic materials that are toxic.

Adsorption process of H2S in tofu waste biogas using BFA adsorbent

continously can be approach with Adams-Bohart, Thomas, and Yan model.

a. Adams-Bohart Model

Linierization equation (5) result:

(10)

From equation (10), constants number from kAB and qAB can be search

by making a relationship graph between ln C/Co vs t.

b. Thomas Model

Linearization of equation (6) result equation as follow :

(11)

Where :

t = V/Q (12)

Thomas model constant kTh and qTh obtained by making a relationship

graph between ln (Co/C-1) vs t according to equation (11).

tCkWqQk1

CCln oThTh

Tho−=⎟

⎠⎞

⎜⎝⎛ −

UzqktCk

CCln AB AB o AB

o−=

21

c. Yan Model

Linearization of equation (7) result:

(13)

Model Yan constant kY and qY are obtained by making a graph of

relationship between ln (C/(Co-C)) vs ln V according to equation (13),

then a and f value obtained is inserted to equation (8) and (9) to obtain

kY and qY value.

The selection of suitable model among Adams-Bohart model, Thomas,

and Yan are done by calculating the correlation coeffisient of Linear

regression of experimental data into equation (10), (11), and (13) using

Microsoft Excel software.

One important factor affecting the adsorption process is the adsorbent.

According to Do (1998) adsorbent that both must have the following

properties:

1. Adsorbent must have a large effective surface area

2. Adsorbent must have a large number of pore network as a way for

molecules leading to the adsorbent.

Bagasse fly ash can be used as an adsorbent due to meet those two criteria.

This is because the main component of BFA which is a silicate. Silicate

framework structure is a polymer of tetrahedral SiO 4, the tetrahedral chain

is polihedral three-dimensional network formed through bonds between

fln aVln aCC

Cln 0

−=⎟⎟⎠

⎞⎜⎜⎝

⎛−

22

the oxygen in a tetrahedral atom in the tetrahedral silicate other.

Polihedral formed and merged with one another in the same manner to

form a framework silicate. Due to the formation of silicate framework, it

will have pores and channels which are quite open, allowing other

molecules through the process of adsorption (Hadi et al., 2002).

2.3 Hypothesis

From the problem formulation exist, it can be arranged some hipotesis i.e :

1. The presence of BFA as an adsorbent can reduce H2S level in tofu waste

biogas.

2. Chemically treatment and particle size have an effect to BFA adsorption

ability performance.

3. BFA has an ability to re-generate by BFA re-activating.

23

CHAPTER III

RESEARCH METHODOLOGY

3.1. Research Material

1) Bagasse Fly Ash (BFA) is from PT. Madubaru Yogyakarta

2) Tofu Waste Biogas is from tofu industri which is located in Ds.

Margoagung, Seyegan, Sleman, Yogyakarta

3) H2O2 is 3%

4) Aquades

5) Flour

3.2 Research Equipment

Series of adsorption column, can be seen in figure 6, that is consist of

adsorption column with diameter 2.5 inch which is filled by BFA that have

been formed into granules, flowmeter, plastic connector, oven, sieving, and

erlenmeyer. The research installation is shown on figure 6 below.

Figure 6. Research Installation

24

3.3. Research Process

The process of research is shown on this figure 7:

Figure 7. Research Diagram

3.3.1. Field Study

Field study are needed to know the condition and situation in research

field. Operation process and also the biogas installation there need to

know.

25

3.3.2. Column of Adsorption Preparation

Column adsorption diameter and length will have an effect for adsorbent

saturated time. In this research, column diameter is 2.5 inch and the

column height is 30 cm.

3.3.3. BFA Preparation and BFA Modification

BFA are sieved -60+100 mesh and also -200 mesh. Then BFA will give

some treatment as follow :

a. Non Activated

BFA is washed using aquades, then it is heated in oven on

temperature 100o C until water content inside BFA are loss (till

BFA’s weight are constant).

b. Activated BFA

BFA are submerged into H2O2 3% for at least 5 hours. Then it is

washed by aquades. After that, it is heated by oven until dry.

Hydrogen peroxide (H2O2) is strong oxidizing properties. H2O2

colourless and has a distinctive smell like acid. H2O2 dissolve very

well in water. Under normal conditions hydrogen peroxide is very

stable, with a very low rate of decomposition. The advantage from

H2O2 compared with another oxidizing is because of it’s nature that

environmentally friendly. The residue that leave are hydrogen and

oxygen.

26

c. Recycle BFA

BFA recycling is obtained by re-heating BFA that ever used in

experiment on the oven with specific temperature (1500 C). BFA

recycle derived from BFA activated -60+100 mesh that had been

saturated in experiment.

3.3.4. Granule’s Making

Granular BFA is BFA which is pelletized form which is prepared by

granulation of pulverized BFA powders by binders i.e flour and water

with specific composition. For gas phase adsorption, cylindrically

extruded pellets of between 4 to 6 mm are made.

3.3.5. Fixed Bed Column Experiment

This experiment was performed in small scale cylindrical fix-bed

columns,with diameter 2.5 inch and height 30 cm. The column were

packed with 500 gram granules of bagasse fly ash with different size and

different treatment. The effluent was then collected to evaluate the

hidrogen sulfide concentration. The sampling of effluent are taken and

analyzed in Balai Besar Teknologi Lingkungan, Yogyakarta. Method of

sampling is completely described in appendix.

3.4. Variable

Variables which are used in this research are :

a. Independent Variable

BFA modification (activated, non activated) and BFA size (-60+100

mesh and -200 mesh).

27

b. Dependent Variable

H2S concentration in biogas.

3.5. Result Analysis

Result analysis which is done by H2S level testing before and after

adsorption process. The effluent sampling was taken and analyzed in BTKL.

The sampling method is decsribed completely in appendix.

These research used Adams-Bohart, Thomas, and Yan model to know the

BFA’s adsorption capacity.

28

CHAPTER IV

RESULT AND DISCUSSION

4.1. Hydrogen Sulfide Analysis

Hydrogen Sulfide analysis for each variables on these research has been

done at Balai Besar Teknologi Kesehatan Lingkungan (BTKL), Yogyakarta.

The hydrogen sulfide analysis results are :

4.1.1. BFA (activated) and Size -60+100 mesh (BFA 1)

When this data was taken, biogas flow rate (Q) was 0.2 L/min and

initial concentration (Co) was 154 ppm. Table 4 shows the biogas

concentration after adsorption :

Table 4. H2S Concentration with BFA 1

No t(minute) C(ppm)

1 0 154

2 13 19.38

3 26 65.13

4 39 91.69

5 64 115.08

6 89 154

The initial concentration of H2S, when t = 0 minutes, was 154 ppm.

After 13, 26 , 39 , 64, and 89 minutes, the effluent concentration through the

adsorption column were measured. And the result respectively were 19.38

ppm, 65.13 ppm, 91.69 ppm, 115.08 ppm, and 154 ppm.

29

4.1.2. BFA (non-activated) and Size -60+100 mesh (BFA 2)


initial concentration (Co) was 261.86 ppm. Table 5 shows the biogas


Table 5. H2S Concentration with BFA 2 No t(minute) C(ppm)

1 0 261.86

2 5 173.73

3 10 206.7

4 15 254.75

5 20 261.5

6 25 261.8

The initial concentration of H2S, when t = 0 minutes, was 261.86 ppm.



ppm, 206.7 ppm, 254.75 ppm, 261.5 ppm, and 261.8 ppm.

4.1.3. BFA (non-activated) and Size -200 mesh (BFA 3)


initial concentration (Co) was 215.55 ppm. The table 6 shows the biogas


30


1 0 215.55

2 10 87.97

3 20 160.27

4 25 186.05

5 35 215

The initial concentration of H2S, when t = 0 minute, was 215.55 ppm.



ppm, 160.27 ppm, 186.08 ppm, and 215 ppm.

4.1.4. BFA Recycle (from Activated BFA -60+100 mesh / BFA 4)


initial concentration (Co) was 348.44 ppm. Table 7 shows the biogas



1 0 348.44

2 2 266.9

3 4 283.33

4 6 284.44

5 7 320.25

6 8 331.33

7 10 348

31

The initial concentration of H2S, when t = 0 minutes, was 348.44 ppm.

After 2, 4 , 6, 7, 8, and 10 minutes, the effluent concentration through the


ppm, 283.33 ppm, 284.44 ppm, 320.25 ppm, 331.33 ppm, and 348 ppm.

4

‐2,5

‐2

‐1,5

‐1

‐0,5

0

ln (C

/Co)

‐1

‐0,8

‐0,6

‐0,4

‐0,2

0

0,2

ln (C

/Co)

4.2. Model

Line

value for

4.2.1 A

A

breakt

qAB ob

done i

shown

y = 0,R

0 20

T

a.

y = 0,0R² =

0

Tim

c.

l’s Lineariz

arization of

each variab

dams-Boha

dams-Bohar

through curv

btained from

if range C/C

n in figure 8

,031x ‐ 2,052R² = 0,744

40

Time (minute)

BFA 1

35x ‐ 1,134= 0,887

20

me (minute)

BFA 3

zation

experiment

le.

art’s Model

rt’s Model w

ve. The param

m relation g

C0 is up from

:

60 80

)

40

Figure 8. A

result is ne

which is ap

meters from

graph betwe

m 0. Lineari

0

ln (C

/Co)

Ln (C

/Co)

dams-Bohar

eeded in ord

llied to des

adams boha

een t and ln

ization resul

‐0,5

‐0,4

‐0,3

‐0,2

‐0,1

0

0,1

0

y

‐0,3

‐0,25

‐0,2

‐0,15

‐0,1

‐0,05

0

0

rt Linearizati

der to know

cribe initial

art equation

n (C/C0). Lin

lt for each v

y = 0,028xR² = 0,

10

Time (minut

b. BFA 2

y = 0,034x ‐ 0,3R² = 0,909

5

Time (m

d. BFA

ion

32

correlation

l part from

i.e kAB and

nearization

variables is

x ‐ 0,527,929

20

te)

2

350

10

minute)

A 4

30

15

33

4.2.2. Thomas Model

The experiment data from column adsorption experiment determine

parameter of Thomas kinetics constanta (kTH) and maximum capacity of

column (qTH). Linearization are done by made relation between t and ln

(C/C0-1). Linearization occured when C/C0 is up from 0 and less then 1.

Linearization result for each variables is shown in figure 9 :

a. BFA 1 b. BFA 2

c. BFA 3 d. BFA 4

Figure 9. Thomas Linearization

y = ‐0,055x + 2,163R² = 0,869

‐2‐1,5‐1

‐0,50

0,51

1,52

2,5

0 20 40 60 80ln (C

o/C‐1)

Time (minute)

y = ‐0,399x + 1,954R² = 0,932

‐7

‐6

‐5

‐4

‐3

‐2

‐1

0

0 5 10 15 20 25

ln (C

o/C‐1)

Time (minute)

y = ‐0,249x + 3,495R² = 0,913

‐7‐6‐5‐4‐3‐2‐1012

0 10 20 30 40

ln (C

o/C‐1)

Time (minute)

y = ‐0,604x + 1,022R² = 0,702

‐8

‐7

‐6

‐5

‐4

‐3

‐2

‐1

0

0 5 10 15

ln (C

o/C‐1)

Time (minute)

34

4.2.3. Yan Model

The experiment data from column adsorption experiment determine

parameter of Yans kinetics constanta (kY) and maximum capacity of column

(qY). Linearization are done by made relation between ln V and ln (C/C0-C).

Linearization occured when C/C0 is up from 0 and less then 1. Linearization

result for each variables is shown in figure 10 below :

a. BFA 1 b. BFA 2

c. BFA 3

d. BFA 4

Figure 10. Yan Linearization

y = 3,995x ‐ 31,43R² = 0,785

‐101234567

7,5 8 8,5 9 9,5

ln(C/(Co

‐C))

ln V

y = 1.905x ‐ 16.79R² = 0.984

‐2,5‐2

‐1,5‐1

‐0,50

0,51

1,5

0 5 10ln (C

(Co‐C))

ln V

y = 4,537x ‐ 37,45R² = 0,780

‐2‐101234567

7,5 8 8,5 9 9,5

ln (C

(Co‐C))

ln V

y = 2,504x ‐ 17,11R² = 0,499

012345678

0 5 10

ln (C

/(Co

‐C))

ln V

35

4.3. Analysis of Model Adams - Bohart, Thomas, dan Yan

The analysis of each model is about the influence of operating conditions

when the samples taking for adsorption capacity of BFA’s columns.

4.3.1. Adams - Bohart Model

From the data which is obtained, there is a trend if the value of the flow

rate is high, then the concentration of inlet also will be even greater. Table 8

shows the results from an experiment using model Adams-Bohart

approachment :

Table 8. Adams-Bohart Analysis

Variable Co Q Ρ KAB qAB

R² (mg/L) (mL/men) (g/L) (mL/mg/men) (mg/g)

BFA 1 154 200 526.06 0.201 4.08 0.744

BFA 2 261.86 500 526.06 0.107 4.93 0.929

BFA 3 215.55 300 526.06 0.162 4.19 0.887

BFA 4 348.44 500 526.06 0.098 3.59 0.909

4.3.2. Thomas Model

From the data which is obtained by Thomas model approach, there is a

trend, if flowrate is getting higher then the adsorption capacity is getting

smaller. However, if the value of the flowrate is high, then the inlet

concentration will be greater. Table 9 shows the result according to Thomas

model approachment :

36

Table 9. Thomas Analysis

Variable Co Q Ρ KTH qTH


BFA 1 154 200 526.06 0.35714 2.42 0.869

BFA 2 261.86 500 526.06 1.52 1.28 0.932

BFA 3 215.55 300 526.06 1.16 1.81 0.913

BFA 4 348.44 500 526.06 1.73 0.59 0.702

4.3.3. Model Yan

From the data which is obtained by the Yan model approach, there is a

trend, that more higher the biogas flowrate, the adsorption capacity of

adsorbent is getting smaller. However, if the value of the flow rate is high,

then the inlet concentration will be greater also. Table 10 shows the results

of an experiment with Yan model approach :

Table 10. Yan Analysis

Variabel Co Q Ρ ky qy


BFA 1 154 200 526.06 0.96 2.79 0.984

BFA 2 261.86 500 526.06 7.06 0.33 0.785

BFA 3 215.55 300 526.06 6.30 0.37 0.78

BFA 4 348.44 500 526.06 3.59 0.26 0.499

37

4.4. Analysis of Adsorption Capacity and Breakthrough Curve

From the analysis results of each model, then it can be choosen the most

appropriate models to represent the data of the experiment results in

accordance with the pre-defined variables, i.e. BFA 1, BFA 2, BFA 3, and

BFA 4. The best Model is determined by choosing the most correlation values

close to one. Having obtained the best model, then we can determine the value

for the adsorption capacity of each variable. Table 11 shows the correlation

value for each of the respective variable:

Table 11. Model Analysis

Model Co (mg/l)

Q (ml/men)

K (mL/mg/men)

q (mg/g) R²

Model Adams-Bohart 154 200 0.20 4.08 0.744 Model Thomas 154 200 0.36 2.42 0.869 Model Yan 154 200 0.96 2.79 0.984

Model Co (mg/l)

Q (ml/men)

K (mL/mg/men)

q (mg/g) R²

Model Adams-Bohart 261.86 500 0.11 4.93 0.929 Model Thomas 261.86 500 1.52 1.28 0.932 Model Yan 261.86 500 7.06 0.33 0.785

Model Co (mg/l)

Q (ml/men)

K (mL/mg/men)

q (mg/g) R²


Model Co (mg/l)

Q (ml/men)

K (mL/mg/men)

q (mg/g) R²


BFA 1

BFA 2

BFA 3

BFA 4

38

From the table 11, it can be concluded that BFA 2 and 3, Thomas Model

has the closest correlation value to 1. Although at variable BFA 1 and BFA 4,

the largest correlation value is not on the model of Thomas, but because

Thomas model has a correlation value > 0.5, so it is considered to have a strong

correlation (Sarwono, 2006). So that’s why, Thomas model is a model that can

be represent all the variables exist. According to Aksu and Gonen (2004)

Thomas model is a solution that generally and widely used to solve column

performance theory. Figure 11, 12, 13, and 14 show the breakthrough curve for

each variable and show that Thomas model approachment is closer to

experimental data.

Figure 11. Breakthrough Curve of BFA 1

0

0,5

1

1,5

2

2,5

0 5 10 15 20 25 30

Experimental data

Adams‐Bohart

Thomas

Yan

C/Co

39



0

0,2

0,4

0,6

0,8

1

1,2

1,4

0 5 10 15 20

Experimental DataAdams‐BohartThomasYan

t/τ

C/Co

0

0,2

0,4

0,6

0,8

1

1,2

0 5 10 15 20

Experimental Data

Adams‐Bohart

Thomas

Yan

t/τ

C/Co

40


According to Thomas model, adsorption capacity for each variables and its

operation condition are shown on the table 12. The adsorption capacity were

obtained from model Thomas analysis. First step is linearization, then determine

parameter of Thomas kinetics constanta (kTH). The parameter kTH is used to define

adsorption capacity (qTH) using equation 6.

Table 12. Resume of Adsorption Capacity

Variable Chemical Treatment

Size (mesh)

Initial Concentration (ppm)

Flow Rate (ml/minute)

Adsorption Capacity (q)

BFA 1 √ -60+100 154 200 2.42 BFA 2 - -60+100 261.86 500 1.28 BFA 3 - -200 215.55 300 1.81 BFA 4 Recycling -60+100 348.44 500 0.59

From data on table 12, it can be concluded that qBFAactivated -60+100mesh >

qBFAnonactivated -200mesh > qBFAnonactivated -60+100mesh > qBFArecycle . There are some

reasonable explanations and some factor that are support why each BFA has a

0

0,2

0,4

0,6

0,8

1

1,2

0 1 2 3 4 5 6

Experimental Data

Adams‐Bohart

Thomas

Yan

t/τ

C/Co

41

different capacity of adsorption. Contribution of some factors that is explained in

these research are chemical treatment effect, adsorbent size effect, flow rate

effect, and also H2S initial concentration effect.

4.4.1. Effect Of Chemical Treatment

Chemical treatment has an effect for the adsorption capacity. On

chemical treatment with hydrogen peroxide was observed that adsorption

capacity for activated BFA size -60+100 mesh is higher compare with BFA

non-activated size -60+100 mesh, 2.42 mg/g and 1.28 mg/gram. The

differences for adsorption capacity between activated BFA and non-

activated BFA can be attributed to the fact that acid treatment may dissolve

the mineral or other impurities from the adsorbent surfaces, thus increases

the pore volume and surface area of the sorbents (Shaobin et al., 2005).

Activated BFA has a greater adsorption capacity than non-activated BFA.

According to Lingga et al., 2010, activation of chemically performed with

the purpose to clean the pores of the surface, clean the impurities, and

compound reordered the position of the exchanged atoms. Gupta and

Sharma (2003) perform activation of bagasse fly ash with hydrogen

peroxide to improve its adsorption capacity.

4.4.2. Effect of Size

Adsorbent particle size has significant influence on the kinetic of

adsorption due to change in number of adsorption sites. According to

Benefield (1982), the size of particle influence the level of adsorption

42

capacity, the adsorption capacity will increase similar with the decrease of

particle size.

Based on some experiment that have been done by any researcher :

M.Rao (2002), Kasam dkk (2005), etc., said that smaller particle has greater

of surface area that is available to adsorbat removal. So, the particle size

differences on these research also have a contribution in adsorption

capacity. Non-activated BFA with a smaller particle size, namely -200

mesh has more greater adsorption capacity compare with BFA with the

bigger size (60+100 mesh). The adsorption capacity for BFA -200 mesh is

1.81 mg/gram and for BFA -600+100 mesh is 1.28 mg/gram.

4.4.3. Effect of Flow Rate

Gas inlet has a certain concentration flowthrough the column. As figure

15 which is shown, it was seen that the breakthrough time was shortened

with the flow rate increasing. An increase in flow rate reduce the volume of

effluent treated. At higher flow rate, film surrounding the particle breaks

thereby reducing the adhesion of adsorbate to the adsorbent particle (Aksu

and Gonen, 2004). As can be seen on table 12 the adsorption capacity of

H2S is decreased with the increase in flow rate. The breakthrough capacity

of the adsorbent decrease with increasing of flow rate. As the rate through

the bed decreased, the depth of the adsorption zone decreased because there

was more to adsorption occur. In these research, the experiment for BFA 2

and BFA 4 that has a biggest flow rate i.e 500 ml/min had a poor adsorption

43

capacity, namely 1.28 mg/g and 0.59 mg/g, compare with BFA 1 and BFA

4, namely 2.42 mg/g and 1.81 mg/g.

Figure 15. Curve of All Variable

4.4.4. Effect of Hydrogen Sufide Initial Concentration

A change in the inlet sorbat concentration affected the operating

characteristics of the fixed bed column. At low initial concentration,

breakthrough occured late and the treated volume were higher since the

lower concentration gradient caused a slower transport due to decreased

diffusion coefficient or mass transfer coefficient. The adsorbent gets

saturated early at high initial concentration because binding sites become

more quickly saturated in the system (Aksu and Gonen, 2004). In this

research, the variety of H2S is initial concentration for each BFA have a

contribution to the difference of adsorption capacity. BFA 4 has the highest

initial concentration, it is 348.4 ppm and BFA 1 has the lowest initial

0

0,2

0,4

0,6

0,8

1

1,2

0 50 100 150

BFA 1; Q=200ml/min; qo=154 ppm

BFA2; Q=500ml/min; qo=261.8ppm



t (minute)

C/Co

44

concentration 154 ppm, they both had an adsorption capacity 0.59 mg/gram

and 2.42 mg/gram. BFA 4 also get saturated early compare with others

BFA. BFA 4 get saturated only in 10 minutes and BFA 1 get saturated after

89 minutes.

45

CHAPTER V

CONCLUSION AND SUGGESTION

5.1. Conclusion

Some conclusions that can be obtained from this research are :

1. Bagasse fly ash (BFA) has an ability to reduce the H2S concentration in

biogas. Activated BFA has the higher adsorption capacity compare to non

activated BFA because activation chemically can clean the pores of the

surface, clean the impurities, and compound reordered the position of the

exchanged atoms. Smaller size of BFA also perform better ability to

adsorp H2S than the bigger one because surface area from smaller particle

are more lot than the bigger size particle.

2. The best performance in adsorption capacity is shown by BFA 1, BFA

that has a chemical treatment before, with the operation conditions as

follow : initial concentration of H2S is 154 ppm and gas flow rate is 200

ml/min. In this research, the lowest initial concentration of H2S and the

slowest gas flow rate are the operation condition that is support BFA 1 to

get highest adsorption capacity compare with others.

3. Recycle bagasse fly can be reused as an adsorbent after heating in oven

with high temperature (1500 C). Even the performance of its BFA is not

better than fresh BFA.

46

5.2. Suggestion

The suggestion that can gived according to these research result are :

1. Bagasse fly ash as a solid waste comes from sugar factory can be utilized

as an adsorbent to reduce H2S level in biogas. But it needs further

investigation to know the possibility if there are others gasses also adsorp

into BFA.

2. Bagasse fly ash proved that it can reduce H2S level in biogas, but it needs

more research to know BFA presence effect to reduce the number of H2S

in liquid waste ( ex. liquid waste from leather industry).

47

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