Afolabi et al.

(2022) FJPAS Vol 7(1) ISSN: 2616-1419

FUOYE Journal of Pure and Applied Sciences

Available online at http://fjpas.fuoye.edu.ng/index.php/

Removal of Indigo Blue Dye from Aqueous Medium (or Industrial Effluent) using Chemically
Treated Empty Palm Fruit Bunch Wastes

S.O. Afolabi 1, B.M. Babalola1*, A.O. Babalola2, V.O. Afolabi3, I.O. Arogundade1 and A.O. Adefisan1
1
Department of Chemistry, Federal University Oye-Ekiti, Ekiti State, Nigeria
2
Ekiti State Ministry of Works and Infrastructures, Ado Ekiti, Ekiti State, Nigeria
3
Teaching Service Commission, Ekiti State

A R T I C L E I N F O

Received: Jan 2022 Abstract

Accepted: Apr. 2022

Different treatment methods have been adopted for the removal of dyes from wastewaters in order to
prevent or reduce their hazardous effects on living organisms and on the environment. This work was
Keywords: carried out on the empty palm fruit bunch fibers to investigate the effects of various chemical
Adsorption, modification, treatments on its ability to remove indigo blue dye from aqueous solutions. The untreated empty palm
adsorbent, Kinetics, fruit bunches (UEFB) were subjected to three different chemical treatments (acetylation,
Thermodynamics mercerization and bleaching) geared towards improving specific properties such as surface
morphology and thereafter, characterized by the scanning electron microscopy (SEM) and Fourier
Corresponding author: transform infrared spectroscopy (FTIR). The values of the maximum dye uptake (UEFB: 39.37
bolanle.babalola@fuoye.edu.ng mg/mL; acetylation (AEFB): 84.75 mg/mL; bleaching (BEFB): 135.14 and mercerization (MEFB):
117.65 mg/mL) showed that all the treated fibers were able to considerably improve the sorptive
DOI: 10.55518/fjpas.YSEI7794 ability of the adsorbent. The data obtained were well fitted to the Freundlich Isotherm while the
Langmuir Isotherm could be applicable to UEFB. Chemical treatments of the fiber resulted in a
reduction in change in enthalpy of the adsorption system and the modified fibers performed better
than the unmodified fiber with BEFB which has the highest uptake of indigo blue dye and AEFB had
the least uptake. The improved uptake is as a result of the chemical treatment that the adsorbents have
undergone and this makes the bleached adsorbent with highest adsorptive ability suitable for treating
indigo blue laden wastewater. The results obtained showed that chemical modification, such as
mercerization and bleaching of adsorbents is a good means of improving the surface morphology and
the uptake ability of the empty fruit bunch.

1.0 Introduction having complex aromatic structures with different

In all ages, colours have always appealed to man, functional groups and a wide range of usage in
as seen in his attempt to give different colour various industries like textile, leather, plastic, food,
shades to his clothes, utensils, food and body parts printing, cosmetic, pharmaceutical, paper and pulp
such as nails, palms, hair and so on. And with it has industries, and other manufacturing industries [3],
come the concept of dyeing of various materials [4]. When some of these dyes are discharged from
using dyes, especially in the textile industry which the wastewaters of these industries into the aquatic
results in many such dyes in its wastewater [1], [2]. bodies, they become sources of water pollution as
Dye removal is a major part of textile wastewater most of the dyes and their degradation products are
treatment. Most dyes are organic compounds highly toxic, carcinogenic, mutagenic, and

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 Afolabi et al. (2022) FJPAS Vol 7(1) ISSN: 2616-1419

allergenic [5], [6]. The dyes in water effluents have parameters on the temperature [20]. This
a very injurious impact on the natural environment, phenomenon of sorption of fluids or solutes by
thus they become unfit for human and aquatic life, solid or liquid surfaces is because the molecules or
resulting in chronic and acute diseases of health atoms on the solid surface have residual surface
concern [7]. It is thus important that the dyes energy due to unbalanced forces. Based on
wastewaters discharged from textile and dyestuff differences in adsorption forces, the adsorption
industries or any other source have to be treated process can be divided into two categories:
before they are released to the aquatic habitat [8]. physical adsorption and chemical adsorption.
Different treatment methods have been adopted for Physical adsorption is produced by the interaction
the removal of dyes from wastewaters in order to of intermolecular forces (i.e., van der Waals forces)
prevent or reduce their hazardous effects on living which is generally carried out at a low temperature,
organisms and the environment. The various and fast adsorption rate, low adsorption heat, and
methods used for removing dyes from wastewaters nonselective [21]. As the effect of intermolecular
include electro-floatation, flocculation, chemical attraction is weak, the structure of the adsorbate
precipitation, electro-kinetic, ion exchange, molecules hardly changes, the adsorption energy is
coagulation, microbial biodegradation small, and the adsorbed substance is easily
electrochemical destruction, irradiation, zonation, separated again. The adsorption due to the action
and membrane filtration [9],[10] nano-filtration, of chemical bonds is chemical adsorption which
biological oxidation/chemical precipitation [11], includes the formation and destruction of chemical
co-precipitation, solvent extraction, bonds. The absorption or release of adsorption heat
bioremediation [12],[13], adsorption, coagulation is larger, and the activation energy required is also
followed by flocculation and advanced treatment larger. Physical adsorption and chemical
techniques such as membrane separation, adsorption are not isolated and often occur
electrochemical degradation [14], but the together. In wastewater treatment technology, most
application of these methods is restricted by many of the adsorption is the result of several kinds of
disadvantages such as high reagent and energy adsorption processes. Due to the influence of
requirements, generation of toxic sludge, or other adsorbents, adsorbates, and other factors, some
waste products that require disposal or further kind of adsorption may play a leading role [22].
treatment [6],[15]. Among these techniques, Readily available and cheap materials such as
adsorption is considered to be simple in design, natural fibers (mainly lignocelluloses), with large
efficient [4]; applicable in many wastewaters surface pores, lend themselves well to the
sources, does not produce any sludge [7], [16] easy adsorption process as a good alternative to
recovery, regeneration capacity [17] and low cost activated carbon that has always been commonly
technique for dye contamination treatment in used as adsorbent material in wastewater treatment
comparison with other used techniques [18]. due to its abundant microporous structure, large
Adsorption is largely a surface area and surface specific surface area, and high hydrophobicity, but
pore process that leads to transfer of molecules also relatively more costly. They contain different
from a fluid bulk – adsorbate - (liquid or gas or functional groups like phenolic groups, carbonyl
solutes) to solid or liquid surface – adsorbent - due groups, hydroxyl groups, amino, acetamido and
to physical forces or by chemical bonds. Usually, sulfhydryl groups which are active binding sites
it is reversible (the reverse process is called [23], [24], [25]. Adsorption of some dyes onto
desorption) [19]. In most cases, this process is natural fiber materials such as rice husk, orange
described at the equilibrium by means of some peel, coconut husk, barley husks, peanut hull,
equations that quantify the amount of substance cocoa shell [16], hazelnut shells [26], olive stone
attached on the surface given the concentration in [27], sugarcane bagasse [28] palm tree trunk [4],
the fluid. These equations are called isotherms (the and wood sawdust [29], corn cob, olive oil by-
most famous are the Langmuir and the Freundlich products, sawdust, forest by-products and waste
equations) because of the dependence of their have been researched and all of these showed some
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degree of effectiveness for dye removal. More so, Village, near Akure, Ondo State. Analytical grade
recent research is constantly being geared towards of chemicals purchased from Sigma-Aldrich were
the improvements of the material surfaces for used as received in the experiments; ≥97.0%
optimum adsorption capacities. Some works Sodium hydroxide (NaOH), ≥99% acidified acetic
mentioned that the modification of biosorbents anhydride (CH3CO)2O, >90% alkaline hydrogen
with nanoparticles and cellulosic derivatives is a peroxide (H2O2); 85% Indigo Blue dye, 96%
brilliant alternative to enhance its adsorption ethanol (C2H5OH), >88% Disodium dithionite
capacity for dyes while some literatures asserted (Na2S2O4) and >99.0% Sodium Chloride (NaCl).
that modification of biosorbent with cationic
surfactants is an effective technique to enhance the 2.2 Methods
adsorption capacity of biosorbents for dyes
[30],[31],[32]. 2.2.1 Pre-treatment of the empty fruit bunch
fibers
In this study, empty fruit bunch fiber – EFB, which The empty fruit bunch fibers were cut into small
belongs to the category of natural fibers known as sizes from 2 cm to 8 cm, scoured with 2% hot
fruit fibers and also called oil palm fiber is detergent solution (1:100), rinsed thoroughly with
extracted from ripe palm fronds after processing distilled water and oven dried at 1050C until a
for palm oil. It is a low cost, low density, constant weight was achieved. The empty fruit
biodegradable, non-abrasive and largely abundant bunch fibers were ground into fine powder and
fiber materials with good surface properties. This treated with sodium hydroxide, acidified acetic
work is an attempt to follow more recent trends of anhydride and alkaline hydrogen peroxide so as to
researchers in improving the surface properties of improve its surface properties for efficient removal
EFB for better adsorption of indigo dye. NaOH of indigo blue dye from solution. The surface
treatment (mercerization), acetic acid/acetic morphology and functional groups of both treated
anhydride treatment (acetylation) and H2O2 and untreated fibers were examined using SEM
treatment (bleaching) are the three different (Nova Nano SEM 230) and Nicolet 380 FTIR
treatments carried out in this work. It examined the respectively and their adsorption abilities for
efficiency and capacity of both the unmodified and Indigo Blue dye liquor was investigated.
modified EFB for the removal of indigo dye from
polluted water. Three different modified empty 2.2.2 Mercerization
fruit bunch fibers (EFBs) were used for the 0.5 g of the dried empty fruit bunch fibers was
removal of indigo blue dye from prepared indigo weighed and subjected to chemical treatment with
dye liquor: acetylated, bleached and mercerized 100 mL of 5% sodium hydroxide for 2 hours at
empty fruit bunch fibers. The outcome of this room temperature; the suspension was stirred
research would be of great benefit to most continuously throughout the period of treatment;
industries in the developing countries of the world, after which, the powder was rinsed thoroughly with
especially where the wastewater industrial distilled water and oven dried at 1050C for 1 hour
effluents are generated. The adsorbent would serve [33].
as a cheaper adsorbent for the removal of Indigo
Blue and other dye stuff from wastewater. 2.2.3 Alkaline bleaching
The procedure outlined by [34] was employed in
2.0 Materials and methods the alkaline bleaching of the powder obtained from
the pre-treated empty fruit bunch fibers. 0.5 g of
2.1 Materials the fiber was treated with alkaline hydrogen
The empty fruit bunch fibers of palm trees were the peroxide (2% hydrogen peroxide in 25% sodium
natural fiber materials of choice used for this work. hydroxide solution) at room temperature for 2
It was obtained from ripe palm fronds after hours with continuous stirring on a magnetic stirrer
processing for palm oil in an oil mill at Ikota at room temperature. The resulting fibers were
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washed thoroughly several times with distilled (MEFB), Bleached empty fruit bunch fibers
water and oven dried at 105oC for 1 hour. (BEFB) and Acetylated empty fruit bunch fibers
(AEFB) were added to 250 mL conical flasks
2.2.4 Acetylation containing 100 mL of 100 ppm the prepared dye
Acetylation of the empty fruit bunch fibers was liquor and shaken on a Gallan Kamp orbital shaker
carried out by treating 0.5 g of powder obtained at 100 rpm at room temperature (30oC) for specific
from the empty fruit bunch fibers with 20 % acetic contact time (3 hours). At the end of the
acid/ acetic anhydride solutions with 1 hour stirring experiments, the content was filtered with
in 10 % acetic acid catalysed with a drop of conc. Whatman filter paper No 42 and the absorbance of
H2SO4 before finally treated with 10% acetic the filtrate was obtained at 410 nm against reagent
anhydride for another 1 hour all steps were carried blank with UNICAM UV HELIOS in order to
out at room temperature. At the end of the 2 hours determine the quantity of indigo dye left
treatment, the fibers were washed with distilled unadsorbed [37]. The contact time study was
water to free them from the chemicals and they carried out by varying the time of contact at which
were subsequently oven dried for 1 hour at 105oC the adsorbate, the dye liquor and the adsorbents
[35]. were shaken, between 0.5, 1.0, 1.5, 2.0, 2.5, 3.0,
3.5 and 4.0 hours while other conditions were
2.2.5 Preparation of Indigo Blue dye Liquor constant. The effect of initial concentration on the
The dye liquor was prepared by accurately sorption process was done by varying the initial
weighing 1 g of indigo dye into 250 mL conical concentration of the dye liquor (10, 20, 50, 100,
flask and adding 20 mL of 96% ethanol to make a 200 500 and 1000 ppm) with other conditions
paste. To the paste was added a solution containing constant. Studying the effect of temperature on the
100 mg of Na2S2O4. 10 mg of NaCl and 10 mg of adsorption of indigo dye by the various adsorbents
NaOH. For total dissolution of dye, the content in involved changing the temperature at which the
the conical flask was continuously stirred and the adsorption experiments were performed from 30oC
temperature raised to between 50oC and 60oC. (303K) to 70oC (343K) and the time to 100 mins
After total dissolution of dye is accomplished, the while all other factors were kept constant. The
dye solution was carefully transferred to 1 L study on adsorbent dosage was done by varying the
volumetric flask and made up to the mark with amount of each adsorbent between 0.5, 1.0, 1.5, 2.0
distilled water [36]. Desired working and 2.5 g for the specified contact time and
concentrations of 50, 100, 200, 500 ppm were adsorbate concentration [38].
obtained from this 1000 ppm stock solution by
serial dilution. 2.2.7 Quantification of results
The amount of Indigo dye adsorbed by unit mass
2.2.6 Adsorption experiments of the adsorbents was calculated using Equation 1
Batch adsorption procedure was employed and 1g 𝑄𝑒 = (𝐶𝑜 − 𝐶𝑒 ) 𝑉⁄𝑚 (1)
of each adsorbent (i.e. Unmodified empty fruit Co and Ce are the initial and final indigo dye
bunch (UEFB), Mercerized empty fruit bunch concentration (mg/L); V is the volume of the
(MEFB), acetylated empty fruit bunch (AEFB) and adsorbate used (L) and m represent the mass of the
bleached empty fruit bunch (BEFB)), was added to adsorbent (g)
250 mL conical flasks, 100 mL of the prepared dye
liquor (100 ppm) was added and the suspension 3.0 Results
was shaken on a Gallan Kamp orbital shaker at 100
rpm at room temperature (30oC) for contact time (3 3.1 Characterization of the adsorbents
hours). This procedure was done in batch process Micrographs result of the characterization of both
whereby a certain amount (1 g) of the different untreated and treated fibers of the empty fruit
adsorbents: Untreated empty fruit bunch fibers bunch obtained from Scanning Electron
(UEFB), Mercerized empty fruit bunch fibers Microscope (SEM) and Spectrographs of the
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Fourier Transform Infra-Red Spectroscopy (FTIR)

are presented in Figures 1 and 2 respectively.

Figure 1: Scanning Electron Microscope (SEM) micrographs of unmodified and modified

Empty Fruit Bunch

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Figure 2: FTIR Spectrum of unmodified and modified Empty Fruit Bunch

3.2 Effect of initial dye concentration and adsorbents in the isotherms are represented in
isothermal study Figures 4a and 4b respectively and the
The result in Figure 3 for the effect of initial constants are shown in Table 1 and 2. It is
concentration of Indigo Blue dye on its expected in most cases that an increase in the
uptake by the unmodified and the various concentration of adsorbate should
modified forms of EFB revealed that with subsequently lead to an increase in the
increase in initial concentration of the dye quantity of dye removed, this is because
solution, the uptake of Indigo blue onto the increase in concentration of adsorbate
adsorbents increased. The result of the brought about increase in competition of
experimental data which was thereafter adsorbate molecules for the few available
modelled by the Langmuir and Freundlich binding sites on the surface of the adsorbent.
Isotherm models and the plot for each of the

35
Quantity adsorbed (mg/g)

30
25
UEFB
20
AEFB
15
BEFB
10
MEFB
5
0
0 200 400 600 800 1000 1200
concentration (ppm)

Figure 3: Effect of Indigo Blue Dye concentration on its adsorption by unmodified and modified
empty fruit bunch
**Unmodified empty fruit bunch (UEFB), Mercerized empty fruit bunch (MEFB), acetylated
empty fruit bunch (AEFB) and bleached empty fruit bunch (BEFB)

Table 1: Parameters for Langmuir Isotherm of unmodified and modified Empty Fruit Bunch
Fiber Qmax (mg/g) B (L/g) R
UEFB 39.37 1.828 * 10-3 0.8459
-4
AEFB 84.746 6.240*10 0.5722
BEFB 135.135 3.767*10-4 0.2186
MEFB 117.647 5.048*10-4 0.6071
**Unmodified empty fruit bunch (UEFB), Mercerized empty fruit bunch (MEFB), acetylated
empty fruit bunch (AEFB) and bleached empty fruit bunch (BEFB)

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Table 2: Parameters of Freudlich Isotherm of unmodified and modified Empty Fruit Bunch
Fiber Kf 1/n R2
UEFB 0.1 0.8636 0.9705
AEFB 0.073 0.9 0.9969
BEFB 0.073 0.901 0.9934
MEFB 0.072 0.9342 0.9954
**Unmodified empty fruit bunch (UEFB), Mercerized empty fruit bunch (MEFB), acetylated
empty fruit bunch (AEFB) and bleached empty fruit bunch (BEFB)

40
UEFB
35
y = 0.0074x + 19.646 AEFB
30 y = 0.0118x + 18.91
R² = 0.2186
R² = 0.5722 BEFB
25
Qe/Ce)

MEFB
20 y = 0.0085x + 16.839
R² = 0.6071 Linear (UEFB)
15 y = 0.0254x + 13.897
R² = 0.8459 Linear (AEFB)
10
Linear (BEFB)
5
Linear (MEFB)
0
0 200 400 600 800 1000
Ce (ppm)

Figure 4a: The plot of Langmuir Isotherm model for the adsorption of Indigo Blue Dye using
unmodified and modified empty fruit bunch
**Unmodified empty fruit bunch (UEFB), Mercerized empty fruit bunch (MEFB), acetylated
empty fruit bunch (AEFB) and bleached empty fruit bunch (BEFB)

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UEFB AEFB BEFB

2 MEFB Linear (UEFB) Linear (AEFB)
1.5 y = 0.9x - 1.1358
R² = 0.9969 y = 0.9342x - 1.1407
1 R² = 0.9954
Log Qe

y = 0.8636x - 1.0015
0.5 R² = 0.9705
0 y = 0.901x - 1.1341
0 0.5 1 1.5 R² = 20.9934 2.5 3 3.5
-0.5

-1
Log Ce

Figure 4b: The plot of Freundlich isotherm model for the adsorption of Indigo Blue Dye using
unmodified and modified empty fruit bunch
**Unmodified empty fruit bunch (UEFB), Mercerized empty fruit bunch (MEFB), acetylated
empty fruit bunch (AEFB) and bleached empty fruit bunch (BEFB)

3.3 Kinetics and contact time study models used are in Figures 6a and 6b while
Experiment conducted to study the effect of the equations and parameters obtained for
contact time shown in Figure 5 revealed each of the models on different adsorbent is
increase in uptake of Indigo Blue dye by each represented in Table 3. The time of contact
of the adsorbents as time of contacting was between the adsorbate and the adsorbent will
increased up to 3 hours and afterwards a affect the efficiency of the adsorption
decrease was observed. The plots for the process.

7
Quantity adsorbed (mg/g)

6
5 UEFB
4 AEFB
3 BEFB
2 MEFB

1
0
0 1 2 Time (hour) 3 4 5

Figure 5: Time Dependence plot for the adsorption of Indigo Blue Dye using unmodified and
modified empty fruit bunch
**Unmodified empty fruit bunch (UEFB), Mercerized empty fruit bunch (MEFB), acetylated
empty fruit bunch (AEFB) and bleached empty fruit bunch (BEFB)

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Table 3: Kinetic Parameters of unmodified and modified empty fruit bunch

Model/ Adsorbents UEFB AEFB BEFB MEFB
First Order: 𝐿𝑛(𝑄𝑒,1 − 𝑄𝑡 ) = −𝑘1 𝑡 +
𝐿𝑛𝑄𝑒,1

k1 (min-1) 0.2311 0.3523 0.3269 0.2801

Qe,1 (mg/g) 1.2229 1.8502 1.5360 1.8834
R2 0.4967 0.7274 0.6016 0.8015
𝑡 1 𝑡
Second Order: 𝑄 = 𝑘 +
𝑡 2 𝑄𝑒,2 ² 𝑄𝑒2
K2 (g/mg/min) 0.6269 0.295 0.4538 0.196
Oe,2 (mg/g) 3.834 6.4809 5.571 6.8166
2
R 0.9847 0.984 0.9915 0.9639
1/2
Intra-particle Diffusion : Qt = k id t
kid: (mg/min1/2/g) 1.0054 1.5861 1.2764 2.0034
2
R 0.8486 0.92 0.9081 0.8821
*k1, k2 and kid = rate constants for First order, Second order and Intra-particle diffusion model
respectively
**Unmodified empty fruit bunch (UEFB), Mercerized empty fruit bunch (MEFB), acetylated
empty fruit bunch (AEFB) and bleached empty fruit bunch (BEFB)
***Qe,1, Qe,2 and Qt = the sorption uptake at equilibrium for the 1st and 2nd order model and at any
time t respectively

UEFB AEFB BEFB MEFB

1.4
Linear (UEFB) Linear (AEFB) Linear (BEFB) Linear (MEFB)
1.2

1 y = 0.2608x + 0.1085 y = 0.1795x + 0.071

R² = 0.9847 R² = 0.9915
0.8
T/Qt

y = 0.1467x + 0.1098
0.6 R² = 0.9639
0.4
y = 0.1543x + 0.0807
0.2
R² = 0.984
0
0 1 2 3 4 5
Time (hour)

Figure 6a: Pseudo-second order kinetic model plot for the adsorption of Indigo Blue Dye using
unmodified and modified empty fruit bunch
**Unmodified empty fruit bunch (UEFB), Mercerized empty fruit bunch (MEFB), acetylated
empty fruit bunch (AEFB) and bleached empty fruit bunch (BEFB)

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UEFB AEFB BEFB MEFB

7
Linear (UEFB) Linear (AEFB) Linear (BEFB) Linear (MEFB)
6 y = 2.0034x + 1.9251
R² = 0.8821
5 y = 1.2764x + 2.6791
y = 1.5861x + 2.704 R² = 0.9081
R² = 0.92
4
Qt

2 y = 1.0054x + 1.6235
R² = 0.8486
1

0
0 0.5 1 1.5 2 2.5
T1/2

Figure 6b: Intra-particle diffusion plot for the adsorption of Indigo Blue Dye using unmodified
and modified empty fruit bunch
**Unmodified empty fruit bunch (UEFB), Mercerized empty fruit bunch (MEFB), acetylated
empty fruit bunch (AEFB) and bleached empty fruit bunch (BEFB)

3.4 Effect of Temperature on the the systems could be calculated. Temperature

adsorption of Indigo Blue dye of the solution may likely affect the
Figure 7 showed the result obtained from the solid/liquid interfaces, the swelling property
study of the effect of temperature on the pf the adsorbents and the mobility of dye
adsorption process to determine how the ions. From temperature study, it is possible to
reactions proceeded. In Figure 8, the plot of determine thermodynamic parameters that
Vant Hoff’s equation is shown from this plot indicate the nature of the adsorption process.
change in enthalpy (∆H) and entropy (∆S) of

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5
4.5
Quantity adsorbed (mg/g) 4
3.5
UEFB
3
2.5 AEFB
2 BEFB
1.5
MEFB
1
0.5
0
300 310 320 330 340 350
Temperature (K)

Figure 7: Effect of temperature on the adsorption of Indigo Blue dye using unmodified and
modified empty fruit bunch
**Unmodified empty fruit bunch (UEFB), Mercerized empty fruit bunch (MEFB), acetylated
empty fruit bunch (AEFB) and bleached empty fruit bunch (BEFB)

0
0.0028 0.0029 0.003 0.0031 0.0032 0.0033 0.0034
-0.5
-1 UEFB
-1.5 AEFB
Ln k

-2 BEFB
-2.5 MEFB
-3
-3.5
1/T (K -1)

Figure 8: Plot of Ln k against 1/T for the adsorption of Indigo Blue dye using unmodified and
modified empty fruit bunch
**Unmodified empty fruit bunch (UEFB), Mercerized empty fruit bunch (MEFB), acetylated
empty fruit bunch (AEFB) and bleached empty fruit bunch (BEFB)

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Table 4: Thermodynamic parameters of unmodified and modified empty fruit bunch

Fiber ∆H ∆S (J/mol) ∆G (KJ/mol)

(kJ/mol)
303K 313K 323K 333K 343K
UEFB 9273.98 2.74 8443.76 8416.36 8388.96 8361.56 8334.16
AEFB 9503.42 5.31 7895.16 7842.08 7789.00 7735.93 7682.85
BEFB 8798.48 3.60 7709.10 7673.15 7637.20 7601.24 7565.29
MEFB 9403.67 7.33 7182.55 7109.25 7035.95 6962.64 6889.34
**Unmodified empty fruit bunch (UEFB), Mercerized empty fruit bunch (MEFB), acetylated
empty fruit bunch (AEFB) and bleached empty fruit bunch (BEFB)

3.5 Effect of Adsorbent dosage on the determines the potential of adsorbent in

adsorption of Indigo Blue dye removing ions from wastewater at an initial
The plot in Figure 10 showed the result of the concentration. Increasing the adsorbent
effect of adsorbent dosage on the uptake of dosage at a particular initial adsorbate
Indigo Blue dye. The adsorbent provides concentration provides greater more binding
binding sites for sorption, its concentration surface leading to more adsorbate ion
will affect the sorption of adsorbate from removal.
solution. The amount of adsorbent used

5
4.5
Quantity adsorbed (mg/g)

4
3.5
UEFB
3
AEFB
2.5
BEFB
2
1.5 MEFB

1
0.5
0
0 0.5 1 1.5 2 2.5 3
Dosage (g)

Figure 9: Effect of adsorbent dosage on the adsorption of indigo blue dye using unmodified and
modified empty fruit bunch
**Unmodified empty fruit bunch (UEFB), Mercerized empty fruit bunch (MEFB), acetylated
empty fruit bunch (AEFB) and bleached empty fruit bunch (BEFB)

4.0 Discussion cleansed by the chemical treatment with

From the SEM micrographs in Figure 1, the acetic acid/acetic anhydride, alkaline
untreated fibers clearly have rough and dirtier hydrogen peroxide and sodium hydroxide
outer surface layers which were thoroughly [40]. On removal of this outer layer, a

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smoother and more ordered structure with modified adsorbents, the noticeable increased
wider pore sizes is revealed because their continued. This might be as a result of the
hemicellulose and lignin content have been different type of chemical treatment they
removed. The neater and more ordered have been subjected to so as to increase and
structure indicates higher crystalinity in line or expose the active sites for binding [46].
with the findings of [41]. This change in the The mercerized adsorbent (MEFB) showed
surface topography of the fibers and their better uptake ability over the other two types
crystallographic structure is due to the while the acetylated adsorbent (AEFB)
removal of tyloses from the surface as a result showed the lowest uptake.
of the chemical treatment as reported by [42]. The result of the experimental data was
[43] and [44] reported that chemical thereafter modelled by the Langmuir and
modification resulted in a change in surface Freundlich Isotherm models and the plot for
morphologies of coir fiber and hemp fiber each of the adsorbents in the isotherms are
respectively. It was reported on the surface represented in Figures 4a and 4b respectively.
morphology of treated and untreated flax The Langmuir equation which is typical for
fibers by [45] that the untreated fiber surfaces monolayer adsorbent is represented in
are rough, exhibiting waxy and protruding Equation 2; the data did not fit adequately
parts, which are removed by the chemical well to the Langmuir isotherm as shown in
treatment. Figures 4 and Table 1. The higher correlation
The FTIR micrographs shown in Figure 2 obtained with UEFB might be as a result of
revealed the presence of specific functional the fact that the surface of the unmodified
groups which are points or sites of adsorption adsorbent has not been altered or changed by
on the various adsorbents. chemical treatment and so sorption unto the
The absorption bands obtained from the monolayer surface was more feasible.
FTIR spectra for the various adsorbents 𝐶𝑒 1 𝐶
= 𝑘𝑄 + 𝑄 𝑒 Equation 2
𝑄
revealed that certain functional groups are 𝑒 𝑒 𝑚𝑎𝑥

present in the adsorbents. The peaks below Qe and Ce is the quantity of adsorbate (Indigo
1000 cm-1 stands for =C-H groups. Bands in Blue dye) adsorbed per unit gram of the
the region between 1050 and 1085 cm-1 adsorbent and the final concentration of the
represent the alcoholic groups (C-O) while adsorbate in the solution at the end of the
those between 1310 and 1340 cm-1 are for the adsorption experiment respectively, while k
-CH2 group. The absorption bands at 2900 to and Qmax are the Langmuir constants related
3000 cm-1 represent the vibration of -CH in to the sorption energy and monolayer
the cellulose ring; the vibration at 1500 to adsorption capacity respectively.
1510 cm-1 and 1600 to 1680 cm-1 are for
respectively -C-C- and -C=C- in the lignin The Freundlich Isotherm represented in its
ring; while those observed between 1720 and linear form in Equation 3 is used to describe
1740 are symbolic of -C=O group in the sorption onto heterogeneous surface and its
hemicellulose and lignin. The stretching constants; adsorption capacity of the
vibrations observed at 3200 to 3500 cm-1 adsorbent, Kf (mg/g (L/mg)1/n) and the
represent –OH (moisture). constant related to the efficiency of the
For the concentration study, there was an adsorption (1/n) are obtained from the plots
observed increase in the quantity adsorbed, of Log Qe against Log Ce [47].
1
and the increase occurred in all adsorbent 𝐿𝑜𝑔 𝑄𝑒 = 𝐿𝑜𝑔 𝐾𝑓 + 𝑛 𝐿𝑜𝑔 𝐶𝑒 (Linear
types from 10 ppm to 500 ppm, but a further form) Equation 3
increase in concentration showed a decrease Qe and Ce are respectively the quantity of
uptake of the dye unto UEFB while for the adsorbate (Indigo Blue dye) adsorbed per

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unit gram of the adsorbent and the final important information into understanding of
concentration of the adsorbate in the solution the mechanism involved in the sorption
at the end of the adsorption experiment. The process. The pseudo first order model could
plot of the Freundlich isotherm is shown in be fairly used in explaining the sorption of
Figure 5b and the favourability of the process Indigo Blue dye unto MEFB, AEFB AND
is depicted by values of 0 < 1/n <1. BEFB as the correlation coefficient for each
Values obtained for these constants are was greater than 0.6 while for UEFB R2
shown in Table 2, the 1/n values obtained approximately 0.5 (0.4967).
were all less than unity (1); showing that the The pseudo second order provided a better fit
adsorption process of Indigo Blue is to the experimental data for the four
favourable onto all the adsorbents [48]. adsorbents considered, its R2 were greater
Furthermore, the results presented in Table 2, than 0.96, thus we could conclude from this
showed that the Freundlich isotherm fitted that the sorption process is primarily
well for describing the experimental data governed by sharing of electrons or ion
because the correlation coefficients is high exchange; the applicability of the second
and it is seen that all the modified forms of order model to the sorption is further
the adsorbent gave better correlation; with established by the linearity obtained from
the acetylated fiber taking the first place, their respective plots shown in Figure 6a.
followed by the mercerized fiber while the Considering the third model used in this
bleached fiber came the third place. work, shown in Figure 6b, we found out that
The result of the contact time study shown in the R2 for sorption unto all adsorbents were
Figure 5 revealed that there was steady greater than 0.84, this is an indication that
increase in dye uptake from 30 minutes part of the sorption process was also
contact to 3 hours when each adsorbent had governed by intra-particle diffusion.
its maximum possible uptakes. We also have According to Webber and Morris equation
it that UEFB recorded the lowest value at this for intra-particle diffusion, the plot is
contact time when compared with other expected to be linear if intra particle diffusion
adsorbents while both AEFB and MEFB is the only mechanism applicable in the
have the highest uptake values. Thus, the sorption process but from Figure 6b, it seen
experimental contact time for this study was than the plots are not entirely linear over the
3 hours, the time at which there was no period of time covered, thus suggesting that
further increase in uptake of the dye. other mechanisms also have a part to play in
Data obtained from the contact time study the sorption of Indigo Blue dye unto the
was used in determining which kinetic model unmodified and the modified empty fruit
was better suited for the adsorption of Indigo bunch.
Blue dye unto each of the four adsorbents From the temperature study, Figure 7 showed
used in this study. The Pseudo first order, that an increase in temperature (from 303 K
Pseudo second order and the intra-particle to 343 K) of the system subsequently resulted
diffusion kinetic models were engaged for in increased uptake of Indigo Blue dye by the
modelling the process. The Figures for adsorbents, suggesting the process to be
Pseudo second order and the intra-particle endothermic. Applying the Vant Hoff’s
diffusion kinetic models are respectively equation shown in Equation 4, change in
presented in Figures 6a and 6b. The equations enthalpy (∆H) and entropy (∆S) of the
and parameters obtained for each of the systems could be obtained from the slope and
models on different adsorbent is represented intercept of the plots of Ln K against inverse
in Table 3. It was observed from the result of Temperature (1/T) shown in Figure 8.
that the three models could be used to provide ∆S ∆H
ln 𝑘 = 𝑅 − 𝑅𝑇 Equation 4

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 Afolabi et al. (2022) FJPAS Vol 7(1) ISSN: 2616-1419

K referred to as the distribution coefficient of concluded that mercerization, as a method of

the adsorbate (L/g); ∆H is the enthalpy of the chemical treatment, considerably improved
reaction (kJ/mol); ∆S is the entropy of the the adsorption ability of adsorbents and
system (J/mol); R and T represent the Molar bleaching, which is not as rigorous in
gas constant (8.313 J/K/mol) and temperature operation as mercerization also provides a
(K) respectively. comparable result.
Table 4 is a representation of the values of
∆H and ∆S obtained for each adsorbent. The Declarations
calculated Gibb’s free energy (using
Equation 5) for each system at various Ethics approval and consent to participate
temperature is also shown in Table 4. Not applicable
∆𝐺 = ∆𝐻 − 𝑇∆𝑆 Equation 5
From Table 4, the value of ∆G decreased Consent for publication
slightly with temperature rise showing the Not applicable’
sorption might be slightly spontaneous and
better sorption of Indigo Blue dye unto the Availability of data and materials
adsorbents at high temperatures [49]. The ∆H All data generated during this study are
for the modified adsorbents (BEFB and included in this published article
MEFB) were greatly reduced when compared
to the unmodified adsorbent; implying that Competing interests
the chemical treatment of bleaching and The authors declare that they have no
methylation had reduced the required ∆H for competing interest
sorption of Indigo Blue dye unto them while
acetylation of the unmodified adsorbent led Funding
to an increase in ∆H of the process. Result of No Funding was received for this work.
the effect of adsorbent dosage on the uptake
of Indigo Blue dye shown in Figure 9 Authors' contributions:
revealed the UEFB had the lowest uptake ASO was involved in investigation and
value whatever the dosage applied; while experimental design as well as proof reading
MEFB had the highest. The result also of original draft of the manuscript; BBM
showed that increasing the dosage of the carried out analysis of results, reviewing and
adsorbent resulted in increased dye uptake by editing of original draft of the manuscript;
each adsorbent. BAO was involved in sample collection,
result analysis and writing the original draft
5.0 Conclusion of the manuscript; AVO was involved in the
Empty palm fruit bunch fiber was subjected investigation and experimental work; AIO
to three different chemical modifications did the characterization of the various
(mercerization, acetylation and bleaching). adsorbents and was also involved in writing
These various modifications were found to the original draft of the manuscript; AAO
have improved certain specific properties of wrote the original draft of the manuscript.
interest, such as surface morphology and All authors approved the final draft of the
hydrophobicity of the adsorbent. The results manuscript.
obtained showed that the chemical
modifications of adsorbent has proven to be a
very good means of improving the surface Acknowledgments
morphology and the dye uptake ability of the The authors xpress their gratitude to the
empty fruit bunch fiber. Thus, the authors Chemistry Department, The Federal

15
 Afolabi et al. (2022) FJPAS Vol 7(1) ISSN: 2616-1419

University of Technology Akure, Nigeria for of the Taiwan Institute of Chemical

the assess we had to use the laboratory. Engineers. 44(1): 81-88.
[7] Ngah, W.W. and Hanafiah, M.M.
(2008). Removal of heavy metal ions
from wastewater by chemically modified
plant
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