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AMUDA and IBRAHIM 2006 Industrial Wastewater Treatment Using Natural Material as Adsorbent

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AMUDA and IBRAHIM 2006 Industrial Wastewater Treatment Using Natural Material as Adsorbent
African Journal of Biotechnology Vol. 5 (16), pp. 1483-1487, 17 August 2006
Available online at http://www.academicjournals.org/AJB
ISSN 1684–5315 © 2006 Academic Journals
Full Length Research Paper
Industrial wastewater treatment using natural material
as adsorbent
Amuda O.S.* and Ibrahim A.O.
Department of Pure and Applied Chemistry, Ladoke Akintola University of Technology, Ogbomoso, 210001, Nigeria.
Accepted 30 September, 2005
Attempts were made to compare the adsorption efficiency of coconut shell-based granular activated
carbon with the adsorption efficiency of commercial carbon, Calgon carbon F-300, with respect to
adsorption of organic matter from a beverage industrial wastewater. Freundlich adsorption isotherm
was used to analyze the adsorption efficiencies of the two activated carbons. These studies indicate
that acid-activated coconut shell carbon had higher adsorption for organic matter expressed as
chemical oxygen demand, (COD), than barium chloride-activated coconut shell carbon and Calgon
carbon (F-300) at all carbon dosages used. Thus, the potential for using agricultural waste (coconut
shell) that litter our environment may be valuable resources for removal of organic matter from
industrial wastewater.
Key words: Coconut shell, activated carbon, COD, beverage industrial wastewater.
INTRODUCTION
Population explosion, haphazard rapid urbanization,
industrial and technological expansion, energy utilization
and waste generation from domestic and industrial
sources have rendered many waters unwholesome and
hazardous to man and other living resources. There are
little or no stringent laws guiding environmental pollution
in Nigeria. Hence, many industries discharge untreated
or inadequately treated wastewater into water ways.
A number of technologies have been developed over
the years to remove organic matter (expressed as
chemical oxygen demand, COD) from industrial
wastewater. The most important technologies include
coagulation/flocculation process (Amuda et al., 2006;
Bromley et al., 2002), membrane filtration (Galambos et
al., 2004), oxidation process (Marrtinez et al., 2003;
Peres et al., 2004). These methods are generally
expensive, complicated, time consuming and requires
skilled personnel. The high cost of coal-based activated
carbons has stimulated the search for cheaper
alternatives. Low cost and non-conventional adsorbents
*Corresponding authors E-mail:
[email protected] Tel: 2348034402907.
include agricultural by products such as nut shells, wood,
bone, peat processed into activated carbons (Okieimen
et al., 1985; Girigis et al., 1994; Tam et al., 1999;
Ahmedna et al., 1997; Toles et al., 1998; John et al.,
1998, 1999; Ahmedna et al., 2000a,b; Dastgheib and
Rock Straw, 2001; Ng, 2002a,b; Bansode et al., 2004;
Nomanbhay and Palanisamy, 2005), and biomass such
as Aspergillus tereus (Azab and Peterson, 1989),
Pseudomonas sp. (Husseein et al., 2004), Rhizopus
arrhizus (Preetha and Viruthagiri, 2005) have been
reported to be important adsorbents for the removal of
metals and organics from municipal and industrial
wastewater.
Activated carbon is a commonly used adsorbent in
sugar refining, chemical and pharmaceutical industries,
water and wastewater treatment, and as an adsorbent in
point-of-use (POU) and point-of-entry (POE) home water
filtration systems (Ng et al., 2003). Increasing
requirements for clearer and more polished effluent from
many processes suggest that, barring the development
of new technologies, industrial need for activated carbon
will only increase in future (Ng et al., 2003).
In Nigeria, coconut shells litter around streets
especially in the suburban areas and they constitute
environmental nuisance. It is anticipated that this work
1484
Afr. J. Biotechnol.
Table 1. Characteristics of the coconut shell based activated carbons and commercial activated carbon.
Characteristics
2
Surface area (m /g)
3
Density (g/cm )
pH
Conductivity (µm)
CSA
Activated Carbon
CSB
F-300
668±11.00
0.63±0.0
5.80±0.71
51.00±0.60
632.00±9.00
0.58±0.00
6.20±0.01
37.20±1.00
628.00±12.00
0.51±0.00
7.20±0.32
6.10±0.22
CSA = coconut shell-based acid activated carbon
CSB = Coconut shell-based barium chloride activated carbon
F-300 = Calgon Carbon F-300 (Calgon Carbon Inc.)
would abate the environmental nuisance if the coconut
shell are been processed into granulated activated
carbon (GAC) for the removal of different contaminants
likely to be encountered in municipal and industrial
wastewaters. Hence, agricultural wastes such as coconut
shell could be important for the removal of contaminants
in wastewater.
The objectives of this study were to compare the
adsorption efficiency of coconut shell based activated
carbon and that of commercial carbon, Calgon carbon
(F-300) in the treatment of a beverage industrial
wastewater for the removal of organic matter. Secondly,
to apply Freundlich adsorption isotherm in the
comparison of the adsorption efficiencies of the coconut
shell based activated carbon and commercial activated
carbon.
MATERIALS AND METHODS
Materials
The commercial carbon, Calgon carbon (F-300), was obtained from
Calgon carbon Inc., Pittsburgh, PA, USA. The COD test vials were
obtained from HACH (Loveland, CO.). Raw industrial wastewater
was collected from Fumman Beverage industry, Ibadan Nigeria,
which produces agricultural based juice. The wastewater was
filtered using Whatman No. 1 filter paper to remove suspended
solids particles. The filtered wastewater was used immediately.
overnight in an oven at 110°C, cooled at room temperature, and
stored in a dessicator until use. A yield of 37% of the initial mass of
shells was obtained.
For barium chloride activation, the earlier described method of
kadirvelu et al. (2001) was employed. The pulverized coconut shell
was washed with double distilled deionized water. The samples
was then treated with 2% (w/v) BaCl2 in an incubator at 110°C for
24 h to remove moisture and then soaked with double distilled
deionized water until the solution pH was stable. The adsorbent
was washed with 2% HCl (v/v), followed by double distilled
deionized water to remove any residual BaCl2 and HCI. The BaCl2activated carbons obtained were dried overnight in an oven at
110°C, cooled at room temperature, and stored in a dessicator until
use. A yield of 38% of the initial mass of shells was obtained.
Batch adsorption experiment
All reagents used were of analytical grade (Aldrich). The particle
size used for adsorption was <45 µm. Particles of this size have
been reported as the rate-limiting step for adsorption (Randtke and
Snoeyink, 1983). Carbon dosages ranging from 0 to 3 g per 100
mL of wastewater were used for adsorption. The reaction mixture
was agitated at 150 rpm using a Teflon coated half-inch bar on a
Corning magnetic stirrer for 2 h to ensure equilibrium. After this
period of adsorption, the sample was filtered using Whatmann no.
1 filter paper, and the filtrates were analyzed for residual COD in
the wastewater using colorimetric method (5220D) recommended
by the Standard Method for Examination of Water and Wastewater
(Clesceri et al., 1998).
RESULTS AND DISCUSSION
Preparation of char from coconut shell
Coconuts shells were pulverized and sieved to 2.0 to 3.0 mm
particles size. Pulverized sample (15 g) was pyrolyzed in a furnace
(Carbolite, CTE 12/75). During pyrolysis, nitrogen at a flow rate of
0.1 m3/h was used as purge gas. The furnace temperature of
600°C was maintained for 2 h. The weight before and after
pyrolysis gave the weight loss of the sample. The pyrolyzed sample
was crushed into powder form.
For sulfuric acid activation, the earlier described method of
Kadirvelu et al. (2001) was employed. The pulverized coconut shell
was washed with double distilled deionized water until any
leachable impurity due to free acid and adherent powder were
removed. The sample was then treated with 2% (v/v) H2S04 in an
incubator at 110°C for 24 h and soaked with double distilled
deionized water until the solution pH was stable. Then the
adsorbent was soaked in 2% (w/v) NaHC03 till any residual acid left
was removed. The acid activated carbon obtained was dried
Characteristics of the activated carbons
The activated carbons characteristics (surface area,
density, pH and conductivity) were determined using the
methods described by Ahmedna et al. (1997). Table 1
gives the characteristics of the activated carbons. From
the table, it can be observed that coconut shell-based
acid-activated carbon (CSA) gave the highest surface
2
area of 668 m /g followed by coconut shell-based barium
2
chloride-activated carbon (CSB) with 632 m /g as it
surface area. Whereas, the commercial carbon (F-300)
2
had surface area of 628 m /g.
The density of CSA activated carbon was higher than
the densities of CSB and F-300. From the table, the pH
values of the activated carbons describe acidic, alkaline
Amuda and Ibrahim
Removal efficiency (%)
100
90
CSA
CSB
F-300
80
70
60
50
40
30
20
10
0
0.0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0
Carbon dosage (g/100 mL)
the CSA activated carbon recorded highest removal
efficiency of organic matter expressed as COD, followed
by CSB activated carbon and the least COD removal
efficiency was recorded by F-300. This is excepted due
to the fact that adsorption of the organic matter in the
wastewater is a function of carbon surface area
(Bansode et al., 2004). The highest surface area
2
recorded by CSA activated carbon (668 m /g) conferred
on it higher adsorption capacity. The adsorption
capacities of carbons are in the following order:
CSA>CSB> F-300 and thus reflected in the COD
removal efficiencies of the carbons.
Adsorption measurements
Figure 1. Removal efficiency of COD by the activated carbons.
Table 2. Freundlich isotherm constants for COD adsorption.
K
1/n
Correlation coefficient
CSA
146.30
0.59
0.973
CSB
95.90
0.62
0.951
F-300
66.10
0.72
0.953
Activated Carbon
1485
and neutral activated carbons. CSA activated carbon
displayed higher conductivity activated carbon followed
by CSB activated carbon and F-300 had the least
conductivity as a result of its neutral nature as shown by
its pH value (7.20).
Effect of carbon dosage on COD removal efficiency
The effect of activated carbon dosage on COD removal
was expressed as the removal efficiency of the carbon
on COD; which was defined as
–
E (%) = [Ci Cf / Ci] x 100
Where Ci and Cf are the initial and equilibrium
concentration of COD (mg/L), respectively. The initial
concentration of COD was determined colorimetrically
according to standard methods (Clesceri et al., 1998).
The initial concentration of COD of the untreated
beverage industrial wastewater ranged from 620 to 3470
mg/L and the corresponding pH was between 7.22 and
7.24. The dosage of carbons employed for adsorption
ranged from 0.0 to 3.0 g of carbon/100 mL of
wastewater.
Figure 1 presents the COD removal efficiencies by the
three activated carbons. From the figure, it is observed
that removal efficiency of the activated carbons generally
improve with increasing dose. Also, it is observed that
The relation between the concentration of organic matter
(expressed as COD) adsorbed by the activated carbons
and COD equilibrium concentration in wastewater is
given by Freundlich adsorption isotherm:
Log Ca = Log k + (1/n) log Ce
In this equation, Ca is the amount of COD adsorbed per
carbon dosage, Ce is the equilibrium concentration of
COD in solution, k and 1/n are empirical constants
(Freundlich parameters), the values of which are equal to
the intercept and slope of the plot of log Ca versus log
Ce. The effects of different activated carbon dosages on
the adsorption of COD were found to correspond to the
Freundlich adsorption isotherm. The Freundlich constants
(k and 1/n) and correlation coefficients for COD by the
activated carbons are given in Table 2.
The fitted equilibrium data in Freundlich isotherm
expression is shown in Figure 2. From the figure, it is
observed that the equilibrium data fitted very well in
Freundlich expression with a very high correlation
coefficients value of 0.973, 0.961 and 0.95 for CSA, CSB
and F-300, respectively. The very high correlation
coefficient confirms the applicability of the isotherm. In
Figure 2, log Ca values represent the relative adsorption
efficiency of the activated carbons, whereas log Ce
values represent the residual concentration of the organic
solutes in the treated wastewater. From the figure, it can
be observed that CSA activated carbon had highest log
Ca ratio at a given log Ce value, whereas the commercial
carbon, F – 300, had the least log Ca values.
The values of k and 1/n are empirical constants
(Freundlich parameters), the values of which are equal to
the intercept and slope of the plot of log Ca versus log
Ce. A larger value of k indicates good adsorption efficiency for the particular activated carbon, while a larger value
of 1/n indicates a larger change in effectiveness over
different equilibrium concentrations. In these studies,
CSA activated carbon had the highest k value (146.3),
the k value of CSA activated carbon is 55% more than
that of the commercial carbon, F-300 (66.1) and 35%
more than the k value of CSB activated carbon (95.9).
1486
Afr. J. Biotechnol.
3.0
2.5
CSA
CSB
0.3
0.6
F-300
Log Ca
2.0
1.5
1.0
0.5
0.0
0
0.9
1.2
1.5
1.8
2.1
Log Ce
Figure 2. Adsorption isotherms for the adsorption of COD by the
coconut shell-based activated carbons and commercial carbon.
This confirms the adsorption effectiveness of CSA
activated carbon over CSB activated carbon and F-300.
F-300 had the highest values of 1/n (0.72) indicating
that it has the highest rate of adsorption of COD in the
wastewater followed by CSB with 1/n value of 0.61 and
the least is CSA, having 1/n value of 0.59. The
implication is that, although, the rate at which F-300
adsorbed organic matter in the wastewater is high, its
adsorption capacity for the organic matter is minimal. The
higher values of correlation coefficients (>0.95) recorded
for the three activated carbons may be an indication that
the Freundlich adsorption isotherm applied is valid for the
carbon dosage used as exemplified by the linear graphs
on Figure 2.
CONCLUSION
From these studies, coconut shell-based activated
carbon was found to effectively adsorb organic matter.
Chemical activation was found to affect adsorptive
capacity of the carbon based upon variations in the
characteristics of the carbons such as surface area,
density, pH and conductivity. Coconut shell-based acid
activated carbon (CSA) had higher adsorption capacities
than coconut shell-based barium chloride activated
carbon (CSB) and commercial carbon (F-300) at all the
carbon dosages employed for the treatment. This may be
as a result of high surface area of the CSA compared to
CSB and F-300. Using coconut shell to produce granular
activated carbons potentially provide a less expensive
raw material than the commercial coal, as well as
producing an active carbon processed from a renewable
material instead of a non-renewable one.
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