• 1 .·

PREPARATION AND CHARACTERISATION OF TREATED AGRICULTURAL WASTES AS BIOSORBENTS

Siti Nor Sihariddh Binti Samsudin

TD 930 S613 Bachelor of Science with Honours 2012 (Resource Chemistry)

2012

Pusat Khidmat MaklumatAkademik VNlVERSm MALAVSIA SARAWAK

Preparation and Characterisation of Treated Agricultural Wastes as Biosorbents

P.KHIDMAT MAKLUMAT AKAD!MIK

111111111 r0111 111111 III 1000235647

Siti Nor Sihariddh Binti Samsudin (25091)

Thesis submitted in fulfillment of the requirements for the degree of

Bachelor of Science

Supervisor: Dr Sim Siong Fong

Resource Chemistry

Chemistry Department

Faculty of Resource Science and Technology

University Malaysia Sarawak

2012

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ACKNOWLEDGEMENT

First and foremost, all praises and thanks to Allah (S.W.T) for giving me

strength and patience throughout my study and completing my Final Year Project. I would

like to express my heartiest gratitude to my hardworking supervisor, Dr. Sim Siong Fong,

for her patience, humble supervision, guidance, encouragement and advice. Her kindness

and generosity in sharing knowledge and experience is much appreciated. Words are not

enough to express my gratitude towards you. I would also express my appreciation to the

laboratory assistants for their help.

Million thanks to my parents, especially to my mother, Mrs. Maimunah bt Abu

Bakar and other family members for their continuous support, pray, love and

understanding. Last but not least, thank to all my friends, for their enormous help and

guidance and also not forgetting my bestfriends for lending their ears and become a good

listener to all my problems. Only God can repay all your kindness toward me. Thank you

very much.

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DECLARATION

I hereby declare that this thesis entitled "preparation and characterisation of treated

agricultural wastes as biosorbents" is my own research except as cited in the references.

This thesis has not been accepted for any degree and concurrently it is submitted as partial

fulfillments of the requirement of degree of BSc. resource chemistry in order to be

graduated.

Siti Nor Sihariddh Binti Samsudin

Resource Chemistry

Faculty of Resource Science and Technology

Universiti Malaysia Sarawak

ii

Pusat Khidmat MakJumat Akademik "'nT~sm MALAYSIA SARAWAK

T ABLE OF CONTENTS

\ I I (: . '

Acknowledgement. ... . .. . ................................................... . .. . ..... . .. '" ....... .

Declaration... . ............. . ..... . ............... . ... . .................................. ~ ... , . . ...... 11

Table of Contents.

Abstract................................ . ............... . ...... . ........ .. ........... . ............ . .. . Vll

.......... . .. . ..... . ...................................................... . ....... iii

List of Abbreviations ........ . ......... . ..................... . ................... . . . .. . ... . .. ... ..... v

List ofTables and Figures . ............................... . ............ . ............ . ...... . .. . .... VI

1. Introduction ...... . ....... . ......................... . .................... ..... . ......... . ........ 1

1.1. Objective. . .. . ................... . .. . .. . ..... . ... . ..... . ............ . .. . . . ......... . ........ 2

2. Literature Review .... ...... . ................. . ... .. ... . ........ ............. . ......... . ......... 3

2.1. Overview of Pretreatments ... . .... . ... . ...................... . ......... . ............... . . 3

2.2. Chemical Pretreatment. ............... . . . .......... . ............ . .. .. ................. . ... 4

2.2.1. Alkali Pretreatment. . .. . ..... . ......... . ........................... . ............... 4

2.2.2. Acid Pretreatment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... 5

2.3. Biosorbents ..... . ...................... .. .... . ...... . .... .. ... .. ............. . ...... . ........ 6

2.3.1. Effect of Chemical Pretreatment on Adsorbents . ....................... .. ..... 6

3. Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8

3.1. Sample Preparation ............ . ... .. ............... . ........................ . ... . ... . ..... 8

3.2. Pretreatments .......... . ..... . .. . ............... . ......... . . . .... . ............. . ............ 8

3.2.1. Pretreatment with H2S04 ...... . ........... . .. .. .. . ...... . .. . .... . .... . .... . .... . . 8

3.2.2. Pretreatment with NaOH .................. . ............. . .... . .. . .. . .. . ... . ...... 9

3.3. Physico-chemical Properties ... . .. . . .. ......... . .. . ...................... ............. . .. 9

3.4. Iodine Number . .. ........ , ......... . .. .. ................. .. .................. . ............. 10

3.5. Fourier Transform Infrared. .. ............................................................ 11

iii

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t t ( f ~.."

3.6. Scanning Electron Microscopy ............................................................ 11

3.7. Principal Component Analysis ............................................................ 12

4. Results and Discussion ......................................................................... 13

4.1. Physico-chemical Properties .... . ... . .......... . ........ . ................................ 13

4.2. Iodine Number...... ......... ......... ......... ......... ......... ...... . ........ . ..... ..... 17

4.3. Fourier Transform Infrared ............................................. '" ............... 18

4.4. Principal Component Analysis ................................................ .. ...... '" 21

4.5. Scanning Electron Microscopy .............. . ........................................... 25

5. Conclusions and recommendations ............................................................ 27

6. References ....................................................................................... 28

iv

NH3

BT

Ca(OHh

CH

DMSO

FTIR

HCI

H202

EFB

PCA

RH

SW

SEM

Na2C03

NaHC03

NaOH

NaHCI03

H2S04

LIST OF ABBREVIATIONS

Ammonia

Banana trunk

Calcium hydroxide

Coconut husk

Dimethyl sulfoxide

Fourier Transform Infrared Spectroscopy

Hydrochloric acid

Hydrogen Peroxide

Oil palm empty fruit bunch

Principal Component Analysis

Rice husk

Sago ham pas

Scanning Electron Microscopy

Sodium carbonate

Sodium hydrogen carbonate / Sodium

bicarbonate

Sodium hydroxide

Sodium hypochlorite

Sulfuric acid

v

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No.

Table 1:

Table 2:

Table 3:

Table 4:

Table 5:

Table 6:

Figure 1: I

Figure 2:

Figure 3(a): [,

Figure 3(b):

Figure 3(c):

Figure 4:

Figure 5:

LIST OF TABLES AND FIGURES

Title Page

The moisture content of acid and alkali treated agricultural wastes 13

The ash content of acid and alkali treated agricultural wastes 14

pH of the treated agricultural wastes 15

Electrical conductivity of treated agricultural wastes 16

Iodine number of treated agricultural wastes 17

The common adsorption bands present in the treated and untreated 20 agricultural wastes

The purpose of pretreatment 3

The FTIR spectra of (a) untreated, (b) H2S04 and (c) NaOH treated 19 agricultural wastes

The scores plot ofPC2 against PCl according to treatments 22

The scores plot ofPC2 against PCl according to agricultural wastes 22

The scores plot ofPC2 against PCl according to the loading plots 23

of PC2 against PC 1

Distribution of several absorption bands 24

SEM images of various treated and untreated biomass 26

vi

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Preparation and Characterisation of Treated Agricultural Wastes as Biosorbents

Siti Nor Sihariddh Binti Samsudin

Resource Chemistry Faculty of Resource Science and Technology

Universiti Malaysia Sarawak

ABSTRACT

This study characterizes the agricultural wastes i.e., coconut husk, banana trunk, sago hampas, rice husk and oil palm empty fruit bunch treated with sulfuric acid (H2S04) and sodium hydroxide (NaOH). The pretreatment was done to improve the adsorption capacity and enhance the porosity structures. The physicochemical properties, functional characteristics and morphological structure of treated biomass were characterized. The treated samples were characterized by a low pH with high ash content. Principal Component Analysis (PCA) suggested that the treated and untreated samples are distinguishable with acid and alkali treated coconut husk demonstrating similar functional characteristics. Morphologically, the treated samples showed better developed microporous structures.

Keywords: Agricultural wastes, pretreatment, sulfuric acid, sodium hydroxide and adsorption

ABSTRAK

Bahan buangan pertanian iaitu sabut kelapa, batang pisang, hampas sagu, sekam padi dan tandan kosong buah kelapa sawit yang dirawat dengan asid su((urik (H2S04) dan natrium hidroksida (NaOH) telah dicirikan. Rawatan bahan buangan terse but dilakukan untuk meningkatkan keupayaan penyerapan dan meningkatkan struktur liang berongga. Sifat-sifat jiziko-kimia, kumpulan berfungsi dan structur moifologi telah dikaji. Sampel yang dirawat menunjukkan pH yang lebih rendah dengan kandungan abu yang tinggi. peA menunjukkan bahawa biojisim yang telah dirawat dapat dibezakan daripada biojisim asal di mana sabut kelapa (dirawat dengan asid dan alkali) menunjukkan ciri kumpulan beifungsi yang berhampiran. Dari segi morfologi, sampel yang dirawat menunjukkan struktur microporous yang lebih baik.

Kata kunci: Bahan buangan pertanian, pra-rawatan, asid su/jurik, natrium hidroksida dan penyerapan

vii

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1.0 Introduction

In recent years, the increase in waste materials disposal have been of concern

due to the large amount of solid waste produced from the agricultural industry worldwide

(Bhatnagar & Minocha, 2006). Intensive research is continuously undertaken to provide

possible alternatives for recycling agricultural wastes. These agricultural wastes have been

investigated for various purposes for example as biosorbents for removal of heavy metals

from wastewater. Low cost agricultural wastes either without or with processing have high

surface areas with encouraging microporous characteristics and surface chemical nature to

be used as adsorbents for heavy metals (Demiral et ai., 2008). They have been known as

potential low cost biosorbents.

In general, a low cost biosorbent is defined as a by-product that is available

abundantly in nature with a reasonable adsorption potential (Saikaew et ai., 2009). Many

agricultural wastes have revealed promising adsorption ability; this includes orange wastes

(Prez-Marin et ai., 2008), olive stones (Bla'zquez et ai., 2005), papaya wood (Asma et ai.,

2005), grape stalk waste, peas, broad bean, and medlar peels (BenaIssa, 2006), lemon peels,

orange peels, grapefruit peels, apple peels, apple kernel, apple core, and grape skins

(Schiewer & Patil, 2008), coconut shell powder (Pino et ai., 2006), coconut copra meal

(Augustine & Yuh-Shan, 2007), coconut husk (Chand et ai., 1994; Ayub et ai., 2001b),

neem bark (Ayub et ai., 2001a) and more.

The agricultural wastes are mainly composed lignocellulosic components which

refer to lignin, cellulose and hemicelluloses. They possess numerous functional groups i.e.;

carboxylic acids, phenolic, carboxyl and hydroxyl that act as the precursor for adsorption,

In addition, their spongy and buoyancy properties have· also enabled the adsorption

process to occur easily. The agriculture wastes are viable biosorbents because they are

1

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abundantly available, low cost and environmental friendly which generate very low

greenhouse emissions.

The adsorption capacity of agricultural wastes can often be improved by

incorporation of various pretreatment approaches for example chemical pretreatments.

Previous studies have reported chemical treatments with sulfuric acid. Other possible

pretreatment processes using phosphoric acids (Israilides et at., 1978; Goldstein et at.,

1983), hydrochloric acid (Israilides et at., 1978), nitric acids (Brink 1993 as cited in Mosier

et at., 2005) as well as alkaline solutions have also been investigated for removal of lignin

and to increase the active sites.

1.1 Objective

The main objective of this study is to treat and characterize the locally sourced agricultural

wastes; coconut husk, banana trunk, sago hampas, rice husk and oil palm empty fruit

bunch.

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2.0 Literature Review

1.1 Overview of Pretreatments

Pretreatment of agricultural wastes depends on the option of biomass because

they have different compositions of lignin, hemicelluloses and cell uloses. The treatment

processes can be categorized into mechanical, physicochemical, physical, chemical,

thermal and biological. The objectives of the pretreatments are 1) to alter the structures and

compositions that caused hindrance to hydrolysis and degradation processes (Hendriks &

Zeeman, 2009) and 2) to enhance the porosity of the cellulose. Pretreatment using acids,

alkali and oxidizing agents fundamentally disrupts the crystalline structure of cellulose so

that lignin and hemicelluloses can be removed. Figure 1 illustrates the pretreatment process.

During the process, chemical and physical properties of agricultural biomass may be

altered where the active sites are increased. The destruction of hydrogen bonds on cellulose

further renders them structurally stable. The chemical reactions usually take place at the

glycosidic bonds and hydroxyl groups of cellulose molecules.

Cellulose Lignin---.. I

.....;!:."OJ,\Amorpholls {

Region ~" Ill1\..w~j Pretreatment ~~ ~."

Crystalline { R(>gioll ,[ j

Hemicellulose

Figure 1: The purpose of pretreatment (adopted from Mosier et al., 2005).

3

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2.2 Chemical Pretreatment

Sustainability and cost are important criteria to be considered in pretreatment of

agricultural wastes. Various chemicals have been utilized to treat the agricultural biomass

for example alkali pretreatment, acid pretreatment, ozonolyis, organic solvents

pretreatment (organosolv processes) and oxidative pretreatment. The pretreatment

processes could result in increase in pore size and surface area (Khosravi-Darani & Zoghi,

2008; Rabelo et at., 2008; Martin et at., 2007). Sulphuric acid (H2S04) and sodium

hydroxide (NaOH) are most commonly used (Mosier et at., 2005). The delignification and

recalcitrant of lignin structure requires high temperatures, combination of chemicals for a

period of time and other harsh pretreatment conditions (Baucher et at.. 2003).

2.2.1 Alkali Pretreatment

According to Sun and Cheng (2002), oxidizing agents such as hydrogen

peroxide (H20 2) and ozone are effective for removal of lignin (Mtui, 2009). Other alkaline

solutions such as NaOH, calcium hydroxide (Ca(OHh), NaOH-urea, and sodium carbonate

(Na2C03) have also been investigated for hydrolysis of agricultural wastes. When the

pretreatments are done using 0.5-2.0 M alkali at a temperature between 120 and 200°C, the

enzymatic hydrolysis of lignocellulosic wastes is improved and the saccharification is

facilitated substantially (Mtui, 2009). Pretreatment using NaOH, H20 2, and sodium

hypochlorite (NaHCI03) could enhance the crystalinity of the cellulosic biomass (Malik,

Mukhtar & Haq, 2010) with alkali pretreatment processes required lower temperature and

pressure compared to other pretreatment methods (Mosier et at., 2005).

4

Pusat KhldmatMlldumat AkademikI .

UNlVERSm MALAYSIA SARAWAK

Solvation and saponification are two reactions that take place in alkali

pretreatment process that causes the lignocelluloses structure to swell and decrease in

degree of polymerization (Hendriks & Zeeman, 2009). Damisa et al. (2008) further

revealed that pretreatment of lignocellulosic waste can be more effective when acids are

combined with alkali compared to acids or alkali alone (Mtui, 2009).

2.2.2 Acid Pretreatment

Concentrated minerals acids (H2S04, hydrochloric acid or HCI), ammonia based

solvents (ammonia or NH3 and hydrazine), approtic solvents (dimethyl sulfoxide or

DMSO), metal complexes (ferric sodium tatrate, cadoxen and cuoxan) and wet oxidation

can be used for cellulose crystallization and disruption of lignin (Mosier et al., 2005).

According to Hendriks and Zeeman (2009), the accessibility of cellulose to enzymatic

hydrolysis is increased by hemicelluloses solublisation.

The pretreatment process with dilute acids is often conducted under high

temperature and pressure. This process requires shorter time compared to the concentrated

acid. In addition, it requires lower temperature and pressure for degradation of cellulose.

The concentrated acids can be powerful and strong agents for ceHulose hydrolysis but they

are highly reactive, toxic and corrosive therefore reactor resistant to corrosion is needed

that renders the process costly. Recovery of concentrated acid is necessary to make the

process economical and effective (Sun & Cheng, 2002). Nevertheless, the cost for acid

recovery system is usually high.

5

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Sulphuric acid pretreatment is employed in manufacturing of furfural where

dilute sulphuric acid is added into cellulosic materials at temperature of 160-200°C (Mosier

et al., 2005). Dilute acids seem to be effective in hydrolysis of agricultural wastes.

However the neutralization of the acids can be expensive (Estghlalian et al., 1997). Del

Campo et al. (2006) and Karimi et al. (2006) revealed that 0.5% of H2S04 is optimal for

rice straw treatment.

2.3 Biosorbents

Agricultural wastes are abundant. Transformation of agricultural wastes into

valuable products is due to the advancement in industrial biotechnology. In recent years,

various renewable value-added products have been produced from lignocellulose wastes

(Pandey et al., 2000; van Wyk, 2001; Howard et al., 2003). Mtui (2009) reported that

agricultural wastes have high absorption properties due to its ions exchange ability; they

can potentially be used as biosorbents to replace the conventional methods for removal of

pollutants such as heavy metals ions, dyes, ammonia and nitrates. Orlando et al. (2002) and

Kishore et al. (2006) reported the application of agricultural wastes as adsorbent materials

or ion exchangers to remove ammonia and nitrate. Bhatnagar and Minocha (2006)

similarly employed biological materials for removal of metal ions.

2.3.1 Effect of Chemical Pretreatment on Adsorbents

Chemical activation or chemical pretreatment processes are often incorporated to

enhance the adsorption capacity of agricultural biomass. Fernando et al. (2009) revealed

that a higher percentage of zinc was removed with biosorbents treated with NaOH due to

the improved surface properties however pretreatment with sulfuric acid has demonstrated

6

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a decrease in the adsorption capacity. As the alkali pretreatment, acid treatment has

improved the surface area and microporosity but the low pH or acidic properties has

deteriorated the removal efficiency. In addition, degradation of the biomass might have

occurred lowering the active site for adsorption process (Fernando et al., 2009).

7 .<10

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3.0 Materials and Methods

3.1 Sample preparation

In this study, locally sourced agricultural wastes used include coconut husk (CH),

banana trunk (BT), sago hampas (SW), rice husk (RH) and oil palm empty fruit bunch

(EFB) were used. The agricultural wastes were cut into smaller pieces and washed

extensively with running tap water to remove dirt and other particulate matter. The washed

materials were dried in an oven at 105°C for 24 hours. The products were then ground and

stored in airtight containers.

3.2 Pretreatments

The agricultural wastes were treated with concentrated H2S04 and NaOH.

3.2.1 Pretreatment with H2S04

The raw materials were mixed with 97% concentrated H2S04 in a ratio of 1: 1

and heated in an oven at 200°C for 24 hours. The samples were then allowed to cool to

room temperature, washed with distilled water and soaked in 1 % NaHC03 solution for 1

hour to remove any remaining acid. The samples were washed with distilled water for a

few times until pH of the material reaches 6.5. The samples were placed in an oven at 105

°C for 24 hours and stored in airtight containers.

8

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3.2.2 Pretreatment with NaOH

The raw materials were mixed with 0.25 M of NaOH in a ratio of 1: 10 ratio and

left for 1 hour. The samples were then neutralized with Hel and washed thoroughly with

distilled water. The washed material was dried at 105 °e in an oven for 24 hours. The

products were stored in airtight containers.

3.3 Physico-chemical properties

The treated agricultural wastes were subjected to physico-chemical analyses

including pH, electrical conductivity, ash and moisture content. For moisture content, 0.5 g

of sample was dried in an oven at 105 °e for 24 hours in six replicates. The drying sample

was constantly reweighed until a constant weighed was obtained. The percentage of

moisture content is calculated with the following formula:

% Moisture content = Wwt-Wdt x 100%

Wwt

Where:

Wwt = the weight of the moisture specimen with tare

Wdt = the weight of the dried specimen with tare

The ash content was determined by combustion at 550 °e for 4 hours. 0.5 g of

sample was weighed in six replicates and placed in a furnace. The crucibles and their

contents were aUowed to cool to room temperature and weighed. The percentage of ash

content was calculated with the following formula:

9

% Ash content = Weight after heated - Crucible weight x 100%

Sample weight

The standard test method for determination pH and electrical conductivity was

used. 1.0 g of each sample was weighed and transferred into a beaker. 100 mL of distilled

water was measured and added. Before the pH of the samples were measured using a pH

meter, they were allowed to stabilize. The samples were run in six replicates. After the pH

was measured, electrical conductivity was measured using a conductivity meter. Electrical

conductivity test was done to measure how well a solution conducts electricity.

3.4 Iodine Number

Iodine number is a relative indicator of porosity and it indicates the extent of

micropore in the activated carbon. It was determined by using a 0.1 N standardized iodine

solution and the titrant used was 0.1 N sodium thiosulphate. 0.2 g of sample was weighed

accurately in three replicates. 40 mL of 0.1 N iodine solution was added to the sample in a

conical flask. The conical flask was shaked for 4 minutes and filtered. 10 mL of filtrates

were titrated with 0.100 N of standardized sodium thiosulfate until the solution turned pale

yellow. 1 mL of starch indicator was added and the titration was continued with sodium

thiosulfate until the solution is colorless. The volume of sodium thiosulfate used was

recorded. The iodine value was calculated with the following formula:

Iodine Value = C x Conversion factor (mg/g)

Conversion factor = Mol wt. of iodine (127) x Normality of iodine x 40

wt. of carbon x Blank reading

C=B-A

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Where

A =Reading after added starch

B =Blank reading

3.5 Fourier Transform Infrared (FTIR)

The functional characteristics of the treated biomass were analyzed using the

FTIR. All spectra were obtained on a Perkin Elmer FTIR system using the potassium

bromide (KBr) disc method with 2 mg sample in 100 mg KBr. The scanning range was

4000-400 cm- 1 at a resolution of 4 cm-1with 16 scans. For each sample, six replicates were

scanned. The spectra were analyzed according to Sim and Ting (2012) where the

adsorption peaks and the corresponding peak areas were recorded into a peak table with

rows representing samples and column designating variables (wavenumber, cm- I) . The

peak area is readily available for multivariate analysis.

3.6 Scanning Electron Microscopy (SEM)

The surface pore structures of activated carbon were observed using Analytical

Scanning Electron Microscope (Model JEOL JSM-6390LA, Japan). Specimens were

coated with thin film of conducting materials before they were examined under the

scanning electron microscope (SEM). Materials coating on specimens was done by

vacuum evaporation to obtain uniform thickness for analysis.

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3.7 Principal Component Analysis (PCA)

The peak table was standardised and subjected to PCA using Microsoft Excel

with the add-in tool developed by the Chemometrics group in the University of Bristol.

Standarization ensures each variable has a similar influence so that variables of low

intensity assume equal significance to those of high intensity.

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4.0 Results and Discussion

4.1 Physico-chemical Properties

The treated agricultural wastes consist of an average of 0.14% moisture and 29.7% ash.

Table 1 below shows the moisture content of acid and alkali treated agricultural wastes.

Table 1: The moisture content of acid and alkali treated agricultural wastes

Sample % Moisture Content

H2S04 Treatment NaOH Treatment

CH 0.017 0.011

BT 0.056 0.029

SW 0.097 0.013

RH 0.013 0.098

EFB 0.018 1.01

The acid treated sample appears to demonstrate higher ash content (30-42%) than the alkali

treated samples (18-27%). Table 2 shows the ash content of the acid and alkali treated

agricultural wastes. In comparison to the raw materials (5.57%), the treated sample is

characterized by much higher ash content.

13 ,<.

Table 2: The ash content of acid and alkali treated agricultural wastes

Sample % Ash Content

H2S04 Treatment NaOH Treatment

CH 33.56 19.89

BT 30.65 25.68

SW 41.98 17.92

RH 38.69 26.61

EFB 37.91 23.77

Ash is the inorganic residue remains after the removal of water and organic matter by

heating. The ash content is used to measure the mineral content left after the chemical

treatment process. Ash content can affect the treated agro-wastes by reducing the overall

activity. The treatment processes using chemicals have apparently added to the total

amount of the inorganic residues. The treated agricultural wastes are generally acidic

where the pH is in the range of 3 and 6.4 with the alkali treated biomass characterized by a

lower pH (Table 3).

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Table 3: The pH of the treated agricultural wastes

Sample pH

NaOH Treatment H2S04 Treatment

CH 3.28 3.71

BT 3.50 3.21

SW 3.37 4.22

EFB 2.96 6.35

RH 3.15 5.15

The pH is a measure of the hydrogen ion concentration in water. The surface charges of the

adsorbents vary depending on their pH. Suzuki (1990) revealed that the acidity measured

originates from the acidic functional groups from the surface of the treated agro-wastes (as

cited in Tsai et ai., 2001).

15