Arab Journal of Basic and Applied Sciences

ISSN: (Print) 2576-5299 (Online) Journal homepage: https://www.tandfonline.com/loi/tabs20

Powdered activated carbon prepared from

Leucaena leucocephala biomass for cadmium
removal in water purification process

Wan Muhammad Hilmi Wan Ibrahim, Mohd Hazim Mohamad Amini, Nurul
Syuhada Sulaiman & Wan Rashidah A. Kadir

To cite this article: Wan Muhammad Hilmi Wan Ibrahim, Mohd Hazim Mohamad Amini, Nurul
Syuhada Sulaiman & Wan Rashidah A. Kadir (2019) Powdered activated carbon prepared from
Leucaena�leucocephala biomass for cadmium removal in water purification process, Arab Journal
of Basic and Applied Sciences, 26:1, 30-40, DOI: 10.1080/25765299.2018.1533203

To link to this article: https://doi.org/10.1080/25765299.2018.1533203

© 2019 The Author(s). Published by Informa Published online: 07 Feb 2019.

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Group on behalf of the University of Bahrain

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ARAB JOURNAL OF BASIC AND APPLIED SCIENCES University of Bahrain
2019, VOL. 26, NO. 1, 30–40
https://doi.org/10.1080/25765299.2018.1533203

ORIGINAL ARTICLE

Powdered activated carbon prepared from Leucaena leucocephala biomass

for cadmium removal in water purification process
Wan Muhammad Hilmi Wan Ibrahima, Mohd Hazim Mohamad Aminia, Nurul Syuhada Sulaimanb and
Wan Rashidah A. Kadirc
a
Faculty of Bio-Engineering and Technology, Universiti Malaysia Kelantan, Jeli, Kelantan, Malaysia; bSchool of Industrial
Technology, Universiti Sains Malaysia, Penang, Malaysia; cForest Research Institute Malaysia, Kepong, Selangor, Kuala
Lumpur, Malaysia

ABSTRACT ARTICLE HISTORY

Activated carbons (ACs) were prepared from Leucaena leucocephala biomass. This is an agri- Received 15 October 2017
cultural solid waste by-product, as well as easily grown species available abundantly in Revised 3 October 2018
Southeast Asia. In this work, activated carbon derived from Leucaena leucocephala biomass Accepted 3 October 2018
was prepared for sequestration of cadmium from aqueous solutions. The activated carbon
KEYWORDS
was produced by a NaOH chemical activation process using NaOH:char ratios (w/w) of 1:1, Activated carbon; Leucaena
2:1 and 3:1 at 800
C. The activated carbon’s BET surface areas were determined as 185, 595, leucocephala; cadmium;
and 776 m2 g1 for the NaOH:char ratios of 1:1, 2:1, and 3:1, respectively. At initial concen- adsorption; isothermic;
tration of 30 mg/l, maximum cadmium adsorption was achieved within 40 min. The adsorb- kinetic
ent also showed good sorption of cadmium at pH 7.0 with solution temperature of 30
C.
Isothermic studies showed the adsorption process best fitted to Langmuir isotherm which
indicates monolayer adsorption had happened while kinetic studies showed physisorption
process was favorable, determined by pseudo-first order kinetic model. Maximum adsorption
capacity was found to be 70.423 mg/g for NaOH:char ratios of 3:1.

1. Introduction Comparatively, adsorption is one of the applicable

methods because of convenience, ease of operation or
Heavy metals receive great concern due to their
production and simplicity of design (Yaacoubi, Zidani,
potential risk as common environmental pollutants.
Mouflih, Gourai, & Sebti, 2014).
Heavy metal contamination of water is not only
Adsorption using activated carbon is one of the
harmful to aquatic life but also adversely affects
ways to eliminate this problem. However, the high
human health. Heavy metal contamination comes
cost of producing activated carbon is a limiting fac-
from electronic, metal smelting and automotive
tor. The properties of normally activated carbon are
industries (Ahmad Khan, Ibrahim, & Subramaniam,
still not sufficient to ensure efficient heavy metal
2004; Bailey, Olin, Bricka, & Adrian, 1999). One of the uptake from waste water. Therefore, chemical activa-
heavy metals involved is cadmium. Cadmium (Cd) is tion of the activated carbon needs to be employed
a metal identified for its high degree of toxicity. The to further increase the effectiveness of water treat-
presence of Cd as an impurity in zinc of galvanized ment. Phosphoric acid, sulfuric acid, zinc chloride,
pipes or Cd-containing solders in fittings, water cool- sodium hydroxide and potassium hydroxide are
ers, water heaters and taps leads to contamination among the dehydrating agents usually used in
of drinking water. Long-term consumption leads to chemical activation (Regti, Laamari, Stiriba, & El
Cd accumulation in the human body especially in Haddad, 2017). Recent research has been conducted
the kidneys where dysfunctioning of the organ by Devi et al. (2017) using nano particles or other
results in a worst case scenario (Bernard, 2008). products resulting from the development of nano-
The various methods that are used for water treat- technology as an effective adsorbent for removal of
ment have been developed to be applied for heavy cadmium. Other adsorbents used for sequestration
metal removal (Ali et al., 2018). These methods include of the cadmium ion from water are given in Table 1.
filtration, screening, oxidation, sedimentation, distilla- Activated carbon is a popular choice of adsorbent
tion, evaporation, reverse osmosis, electro-chemical, ion for contaminants removal, especially heavy metal
exchange and adsorption (Basheer, 2018). and dye from wastewater (Babel & Kurniawan, 2003).

CONTACT Mohd Hazim Mohamad Amini hazimamini@gmail.com Faculty of Bio-Engineering and Technology, Universiti Malaysia Kelantan,
Jeli, Kelantan, Malaysia
ß 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of the University of Bahrain.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits
unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
 ARAB JOURNAL OF BASIC AND APPLIED SCIENCES 31

Table 1. Some adsorbents used for removal of cadmium ion from water.
Adsorbent Reference
Cucumber peel activated carbon (Basu, Guha, & Ray, 2018)
Humic acid-based carbon materials (Jin et al., 2018)
nano-montmorillonite (Liu et al., 2018)
Punica granatum (pomegranate) carpel- (Saini, Kumar, Chawla, & Kaur, 2017)
lary membrane
Rice husk (Khan, Khan, Ding, Khan, & Alam, 2018)
Lotus seedpod-derived biochar (Chen et al., 2018)
Magnetite/carbon nanocomposites (Andelescu, Nistor, Muntean, & R
adulescu-Grad, 2018)
Aguaje (Mauritia flexuosa) based activated carbon. (Obregon-Valencia & Sun-Kou, 2014)

Various researches have been conducted, aiming to kept in a closed container for further use (Rafatullah,
reduce the cost of activated carbon production with- Sulaiman, Hashim, & Amini, 2011).
out sacrificing the efficiency of the material in the
removal of heavy metals from waste water. Low-cost
2.2. Activated carbon preparation
adsorbents are a very popular material and receive
much attention for adsorption of pollutants such as Carbonization was carried out using a pyrolyzer to pro-
heavy metals and dyes (Sadegh, Mazloumbilandi, & duce a large quantity of charcoal. Carbonized Leucaena
Chahardouri, 2017). Therefore, this work on Leucaena leucocephala biomass particles were activated by a
leucocephala as a low-cost material for activated car- chemical process where the carbonized sample was
bon production, has been processed by chemical impregnated with NaOH at the NaOH:carbonized sam-
means to obtain highest possible adsorp- ple ratios of 3:1, 2:1 and 1:1. Approximately 10 g of car-
tion capacity. bonized sample were homogenized with 30 g of NaOH
Leucaena leucocephala, which is also known locally in 100 mL distilled water in a vertical stainless steel
as the Petai Belalang tree is native to southern Mexico reactor under continuous magnetic stirring for 2 h
and northern Central America and is widespread in the before drying in an oven at 105
C for 24 h (Cazetta
Asian tropics and Malaysia. Parts of the Leucaena leuco- et al., 2011). After heating for 24 h, the sample was
cephala plant are commonly used for animal food and placed in the muffle furnace for the activation process.
as a vegetable for human consumption. Leucaena leu- The sample was heated at 800
C under a nitrogen
cocephala is widely grown all over Malaysia and can flow of 150 cm3/min for 90 min during the process.
be easily cultivated. The abundance of this plant offers
a new opportunity to utilize its biomass in many fields. 2.3. Surface area analysis
It is a fast-growing species reaching 10 m in height
after 24 months of cultivation. The wood volume pro- Surface area analysis was carried out using
duced after 24 months of planting can rise to 91.3 m3 Micromeritics (ASAP 2010) analyzer. The activated car-
per hectare (MacDicken & Brewbaker, 1988; Rasat bon was degassed at 300
C before nitrogen adsorp-
et al., 2016). Utilization of Leucaena leucocephala can tion was carried out at –196
C. Surface area was
reduce production cost as it is a wild tree and can be calculated using Brunauer–Emmett–Teller (BET) analysis
grown without specific silviculture techniques. software provided with the instrument {Sudaryanto,
Studies on the adsorption behavior of the adsorb- 2006 #4745}.
ent materials towards heavy metals are important to
evaluate the optimum condition, thus increasing the 2.4. Scanning electron microscope (SEM)
efficiency of the water treatment process. Due to lack observation
of information on activated carbon prepared from
The raw Leucaena leucocephala and activated carbon
Leucaena leucocephala biomass, this work explores the
samples were sieved to obtain 35–60 mm sized frac-
potential of this new raw material together with its
tions. The particles were sprinkled onto the tub with
performance in the water purification process.
carbon glue before gold-plating with a vacuum elec-
troplating machine for about 60 s. The samples were
2. Experimental then analyzed using an SEM (JSM-IT100 JEOL Co.)
microscope at 150x and 550x magnifications.
2.1. Material preparation
Samples from wild Leucaena leucocephala were col-
2.5. Batch adsorption studies
lected around Selangor, Malaysia. The samples were
left to air dry until the moisture content became less Approximately 0.5 g of the prepared activated carbon
than 10%. The dried sample was cut into a smaller was mixed with 100 ml of the aqueous solutions of
size before being ground to produce particles cadmium inside a conical flask, continuously shaken
between 1 and 2 mm size. The wood particles were using a temperature-controlled water bath shaker for a
32 W. M. H. W. IBRAHIM ET AL.

pre-determined period. The mixtures were filtered with Into linear Equation 4:
filter paper to separate the treated cadmium solution K1
from the adsorbent. The metal ion concentration was log ðqe  qt Þ ¼ log ðqe Þ  t (4)
2:303
determined by inductively coupled plasma optical
emission spectrometry, ICP-OES at Forest Research where qe and qt are the amount of ions adsorbed
Institute of Malaysia. All the experiments were per- (mg/g) at the equilibrium and at time t, respectively.
formed in triplicate to reduce errors (Sulaiman, Amini, K1 represents the rate constant of pseudo-first order
Rafatullah, Hashim, & Ahmad, 2010). reaction. A plot of log (qe – qt) against t was plotted
to obtain K1 from the slope and qe from
the intercept.
2.6. Isothermal studies
2.6.1. Langmuir isotherm 2.7.2. Pseudo- second order kinetics model
The Langmuir isotherm model suggested an ideal While the pseudo- second order kinetics model is
monolayer adsorption onto a homogenous surface. expressed by Equation 5:
Three temperatures of the reaction were used, prede- dqt
¼ K 2 ðq e  q t Þ2 (5)
termined at 30, 40, and 50
C. The following Equation qt
1 was used:
Integration of Equation 5 generates linearized
1 1 1
¼ þ (1) Equation 6:
qe qm K a q m Ce
t 1 1
¼ þ t (6)
where qe is the amount of adsorbate adsorbed at qt 2
K2 q e qe
equilibrium per gram of sample (mg/g), qm is the
saturated amount of adsorbate adsorbed in mg/g, where K2 is the rate constant of pseudo-second
Ce is the equilibrium concentration of cadmium in order reaction. K2 and qe can be determined from
mg/l, and Ka is the Langmuir adsorption constant the intercept and slope of a linear plot of t/qt versus
in l/mg. A 1/qe versus 1/Ce plot was made, showing t, respectively (Borah et al., 2018).
a straight line with a slope of 1/Kaqm and an inter-
cept of 1/qm Ka was then calculated by the for- 3. Results and discussion
mula (Lee, Amini, Sulaiman, Mohamed, &
Boon, 2018). 3.1. Surface area of activated carbon
The BET surface areas of Leucaena leucocephala acti-
2.6.2. Freundlich isotherm vated carbon were measured to be 185, 595 and
Freundlich isotherm assumes that heterogenous and 776 m2g1 for the NaOH:carbonized sample ratios of
multilayer adsorption occurred on the adsorbent sur- 1:1, 2:1 and 3:1, respectively. While increasing surface
€ket Tirtom, 2018), calcu-
face (Çetinkaya, Targan, & Nu area results in higher adsorption capacity, it also
lated using Equation 2: contributes to the reduction in bulk density and
1 physical strength of activated carbons. For harsh cyc-
lnqe ¼ lnKF þ lnCe (2) lic adsorption applications where high volumetric
n
capacity is needed, this characteristic could be
where KF is Freundlich equilibrium constant, n is an
potentially a disadvantage (Lee, Byamba-Ochir, Shim,
empirical constant and others as stated in Equation
Balathanigaimani, & Moon, 2015). Hence, the activa-
1. Thus, a plot of ln qe vs. ln Ce should provide a
tion process should be controlled correctly to obtain
straight line with a slope of (1/n) and an intercept
an excellent adsorbent with suitable capacity and
of lnKF
bulk density for specific applications. The total pore
volume and mesopore fraction were known to have
2.7. Kinetic studies positive relationship with the increment of mass
Adsorption kinetics which investigate the rate and ratio of the activating agent: raw material until a cer-
mechanism of the adsorption process pseudo-first- tain optimal point.
order kinetic model and pseudo-second order kinet- Among the most important parameters that
ics model. determine the adsorption capacity of an adsorbent
are the pore structure, the specific surface area and
2.7.1. Pseudo-first-order kinetic model the total number of micropores and mesopores
Pseudo-first-order kinetic model was derived from (Carrott & Carrott, 2007; Caglar et al., 2013). The
Equation 3: International Union of Pure and Applied Chemistry
(IUPAC) classifies ultramicropores for pore width less
dqt
¼ K1 ðqe  qt Þ (3) than 0.7 nm, supermicropores for pore width
qt between 0.7 nm and 2 nm, mesopores for pore width
 ARAB JOURNAL OF BASIC AND APPLIED SCIENCES 33

Figure 1. SEM images of (a) the raw material of Leucaena leucocephala at magnification 150x, (b) the raw material of
Leucaena leucocephala at magnification 550x, (c) activated carbon at magnification 150x and (d) activated carbon at magnifica-
tion 550x.

between 2 nm and 50 nm, and macropores for pore emergence of the pores in the interlayer spacings of
width bigger than 50 nm. Activation process type the samples during the activation process through
and parameters affect the total number of micro- heating (Caglar, Afsin, Tabak, & Eren, 2009).
pores and mesopores, which leads to significant
changes in the surface area and porosity, and dir-
3.3. Batch adsorption studies
ectly influences the adsorption rate of the adsorbate.
The internal surface of activated carbon was 3.3.1. Effect of contact time on the cadmium
mainly contributed by the micropores which com- adsorption
prise the main portion of the total surface area, Effects of contact time, initial concentration, pH
while mesopores, macropores and the non-porous and temperature on the removal of cadmium by
surface represent the external surface of the sample. the activated carbon sample prepared from
Micropores usually act as adsorption sites, whereas Leucaena leucocephala were studied. Figure 2
the mesopores and macropores give rise to channels shows the removal of cadmium at the activation
for the adsorbate to reach the micropores. The temperature of 800
C for NaOH:carbonized sample
enlarged radii of the mesopores and macropores, on ratios of 1:1, 2:1 and 3:1 after different contact
the other hand, allow the multilayer adsorption times between 10 min and160 min with the initial
to occur. Cd2þ concentration of 30 mg/l. Approximately 0.5 g/
l of adsorbent dosage was used at pH 7.0 of the
solution. Adsorption equilibrium was established
3.2. Surface morphology analysis
within 40 min of treatment. At 160 min of contact
Figure 1 shows 150x (a) and 550x (b) magnified SEM time, the maximum amounts of adsorption of the
photos of the activated carbon between the raw samples were found as 99.86%, 99.82% and 99.97%
material of Leucaena leucocephala and activated car- for NaOH:carbonized sample ratios of 1:1, 2:1 and
bon. It may be seen in Figure 1 that the raw material 3:1, respectively. The higher the ratio of
sample had some tiny holes between activated car- NaOH:carbonized sample used for chemical activa-
bon samples. The SEM images of activated carbon tion, the higher the adsorption efficiency for cad-
obtained from Leucaena leucocephala (Figure 1(c,d)) mium removal as reflected from the larger surface
demonstrate that activated carbon possessed higher area obtained by the higher NaOH:carbonized sam-
amounts of tiny and large holes than the raw mater- ple ratios in BET surface area analysis. No significant
ial samples which can be explained by the increment on the amount of removal of solute
34 W. M. H. W. IBRAHIM ET AL.

100.00

99.80

99.60 Sample
(NaOH:carbonized

Adsorption (%)
material):
99.40
1:1
99.20 2:1

3:1
99.00

98.80

98.60
10 20 40 80 160
Contact time, minutes
Figure 2. Removal of cadmium at a different contact time.

from the solutions was recorded beyond the max- of cadmium ions by surface functional groups was
imum point where the system reaches equilibrium. the pH value. Figure 4 previously only indicated
the cadmium removal at the same pH and initial
3.3.2. Effect of initial adsorbate concentration concentration. Experimental studies were con-
on the cadmium adsorption ducted for 40 min of contact time with 40 mg/l ini-
The effect of initial concentration on the removal of tial cadmium ion concentration and 0.5 g/l of the
cadmium by Leucaena leucocephala activated carbon adsorbent dose at a different pH range. The high
was investigated at different sorbate solution con- pH value of the solution leads to increase in the
centrations (10, 20, 30, 40 and 50 mg/L) using 0.5 g negative charge on the adsorbent surface (Gupta
adsorbent dose at pH 7.0. The percentage of cad- & Sharma, 2002; Krishnan & Anirudhan, 2003).
mium removal decreased with the increase in the Therefore, the electrostatic interactions between
initial concentration of the solution. The surface area positive charged Cd2þ ions and the layer of nega-
and the number of available active sites were rela- tively charged adsorbent material, cause a more
tively high compared to the adsorbate ions to be powerful affinity, thus increasing the amount of
retained at low initial concentration. Thus, the cad- Cd2þ ions adsorbed onto the adsorbent (Banerjee
mium ions were easily adsorbed and removed. On & Chattopadhyaya, 2017). In contrast, where the
the other hand, the total number of available pH was lowered to pH 5 and pH 3, the percentage
adsorption sites is smaller than the amount of of Cd2þadsorption was decreasing, which may be
adsorbate ions when the initial solution concentra- ascribed to the competition between H3Oþ and
tion is higher, thus decreasing the percentage of Cd2þ ions in acidic media (Zheng et al., 2017).
cadmium removal. The adsorption percentage for all
samples was comparably high at relatively low con- 3.3.4. Effect of temperature on the cadmium
centrations of 10 mg/L and 20 mg/L as shown in adsorption
Figure 3. At the concentrations of 30 mg/L, 40 mg/L The effect of temperature on the removal of cad-
and 50 mg/L, NaOH:carbonized sample for the ratio mium by the prepared activated carbon is shown in
3:1 showed better performance than for the ratios of Figure 5. The experiment was carried out for the
2:1 and 1:1. These results clearly indicate that the contact time of 40 min, the initial cadmium ion con-
maximum adsorption percentage of metal ions by centration of 40 mg/l using 0.5 g/l of the adsorbent
activated carbon was affected by the initial metal dose at different temperatures. Figure 5 shows the
ion concentration. Higher initial concentration gives highest adsorption percentage for all samples was at
rise to lower adsorption rate due to the higher 30
C. Adsorption percentages dropped for all sam-
adsorbate: adsorption site ratio. ples as the temperature was increased from 40
C to
50
C, 60
C, and 70
C. Therefore, it can be con-
3.3.3. Effect of pH on the cadmium adsorption cluded that the adsorption percentage of cadmium
Rao, Rao, Seshaiah, Choudary, and Wang (2008) decreases in contrast with the temperature rise and
stated that the most crucial parameter controlling 30
C may be considered as the equilibrium tempera-
the adsorption process which affects the binding ture of the system. This result seems to be in
 ARAB JOURNAL OF BASIC AND APPLIED SCIENCES 35

100.0

99.5

99.0 Sample

Adsorption (%)
(NaOH:carbonized
material):
98.5
1:1

98.0 2:1

3:1
97.5

97.0
30 40 50 60 70
Solution temperature (°C)
Figure 3. Initial concentration versus removal of cadmium.

100.0

99.0

98.0
Sample
97.0 (NaOH:carbonized
Adsorption (%)

material):
96.0

95.0 1:1

94.0 2:1

93.0 3:1

92.0

91.0

90.0
3 5 7 8
Solution pH
Figure 4. Solution pH versus removal of cadmium.

100.0

99.5

99.0 Sample
Adsorption (%)

(NaOH:carbonized
material):
98.5
1:1

98.0 2:1

3:1
97.5

97.0
30 40 50 60 70
Solution temperature (°C)
Figure 5. Effect of temperature on removal of cadmium.

conformity with the previous study by Kumar, 3.4. Isothermal studies

Ramakrishnan, Kirupha, and Sivanesan (2010), report-
ing the decrease of adsorption rate from 86.87 to 3.4.1. Langmuir isotherm
76.25% for 50 mg/L of the cadmium ion concentra- Figure 6 shows 1/qe vs 1/Ce plot of Langmuir iso-
tion within the temperature range from 25
C therm for Cd(II) ion adsorption for the sample
to 55
C. NaOH:carbonized sample ratios of 3:1 (a), 2:1 (b) and
36 W. M. H. W. IBRAHIM ET AL.

(a) 0.25

0.2 Linear equation

Temperature: Temp:
3:1 (a) 2:1 (b) 1:1 (c)
0.15 y = 0.0051x y = 0.003x y = 0.0039x
1/qe 30 °C
30 °C + 0.0185 + 0.0244 + 0.0321
y = 0.006x y = 0.0044x y = 0.0058x
0.1 40 °C
+ 0.0156 + 0.0198 + 0.0318
40 °C
y = 0.0043x y = 0.0035x y = 0.009x
50 °C
0.05 + 0.0142 + 0.0188 + 0.0053
50 °C
0
0 20 40 60
1/Ce

(b) 0.25 (c) 0.25

0.2 0.2
1/qe

0.15 0.15

1/qe
0.1 0.1

0.05
0.05

0
0 20 40 60 80 0
0 20 40 60
1/Ce 1/Ce
Figure 6. 1/qe vs 1/Ce plot of Langmuir isotherm of Cd(II) ion adsorption for NaOH:carbonized sample ratios of 3:1 (a), 2:1 (b)
and 1:1 (c).

Table 2. Isothermic and kinetics models for the adsorption of Cd2þ by Leucaena leucocephala based activated carbon.
Langmuir Isotherm Freundlich Isotherm

2
Sample Temperature, C qm (mg/g) KL (l/mg) R KF l/n R2
1:1 30 31.153 8.231 0.9671 3.8763 0.9878 0.8265
40 31.447 5.483 0.9655 3.8045 1.0455 0.7990
50 31.67 0.589 0.9542 5.1123 2.3296 0.9003
2:1 30 40.984 8.133 0.9855 5.6249 2.1227 0.9703
40 50.505 4.500 0.9783 4.7040 1.5924 0.9000
50 53.191 5.371 0.9707 4.8970 1.6174 0.8874
3:1 30 54.054 3.627 0.9627 4.8448 1.7987 0.9401
40 64.013 2.600 0.9609 4.2177 1.2863 0.7513
50 70.423 3.302 0.9873 5.7397 2.3551 0.9701

1:1 (c). The value of the correlation coefficient for increment of NaOH:carbonized sample ratio as
the NaOH:carbonized sample ratios of 1:1 are 0.9671, obtained by Karthikeyan, Rajgopal, and Miranda
0.9542 and 0.9655 at 30
C, 40
C and 50
C, respect- (2005). Comparison of the adsorption capacity of the
ively. NaOH:carbonized sample ratios of 2:1 and 3:1 Leucaena leucocephala activated carbon compared to
showed the same high values of correlation coeffi- other adsorbents for cadmium removal from water
cient with the lowest value of 0.9542 recorded. The in Table 3 showed that this adsorbent performs
high R2 values showed the adsorption process fol- above average with the maximum adsorption reach-
lows Langmuir isotherm which suggested a mono- ing 70.423 mg/g.
layer type of adsorption.
Table 2 shows the calculated values and constant 3.4.2. Freundlich isotherm
of the Langmuir equation. The qm, which is the Figure 7 shows the plots of linearized equations by
measure of the adsorption capacity to form a mono- Freundlich for the adsorption of cadmium at 800
C
layer, is recorded to be as high as 70.423 mg/g at activation temperature. The Freundlich model is
50
C. Constant KL, which denotes adsorption energy, applicable for non-ideal sorption on heterogeneous
for the corresponding adsorption capacity, ranged surfaces and multilayer sorption processes. Table 1
between 0.589 and 3.627 l/mg. The maximum mono- also shows the difference of R2 value for both
layer adsorption capacity, qm (mg/g) was found to Langmuir and Freundlich isotherm. The R2 value for
increase with the increment of temperature and this activation temperature shows that the Langmuir
 ARAB JOURNAL OF BASIC AND APPLIED SCIENCES 37

Table 3. Comparison of different adsorption capacity for different cadmium adsorbent.

Adsorbent Maximum adsorption (mg/g) Reference
Leucaena leucocephala activated carbon 70.42 This work
Humic acid-based carbon materials 26.3 (Jin et al., 2018)
Nano-montmorillonite 17.61 (Liu et al., 2018)
Punica granatum (pomegranate) carpel- 111.11 (Saini et al., 2017)
lary membrane
Lotus seedpod-derived biochar 51.18 (Chen et al., 2018)
Magnetite/carbon nanocomposites 76.67 (Andelescu et al., 2018)
Aguaje (Mauritia flexuosa) based activated carbon. 26.33 (Obreg
on-Valencia & Sun-Kou, 2014)

(a)
1.6
1.4 Linear equation
Temp:
1.2 3:1 (a) 2:1 (b) 1:1 (c)
1 y = 0.5081x y = 0.814x y = 0.5422x
30 °C
+ 1.3472 + 1.838 + 1.6926
ln qe

0.8 y = 0.4900x y = 0.5110x y = 0.4282x

40 °C
0.6 Temperature: + 1.2490 + 1.2491 + 1.2187
30 °C y = 0.7849x y = 0.4121x y = 0.5025x
0.4 50 °C
40 °C + 1.4922 + 1.2939 + 1.4857
0.2 50 °C
0
-1.5 -1 -0.5 0 0.5 1
ln Ce
(b) (c)
1.6
1.6
1.4
1.4
1.2
1.2
1
1
ln qe

ln qe

0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
0 -2 -1.5 -1 -0.5 0 0.5 1
-1.5 -1 -0.5 0 0.5
ln Ce
ln Ce
Figure 7. ln qe vs ln Ce linear plot of Freundlich isotherm of Cd(II) ion adsorption for NaOH:carbonized sample ratios of 3:1
(a), 2:1 (b) and 1:1 (c).

model exhibits a higher R2 value than the Freundlich shown in Table 4. The adsorption process was
model which suggests that the adsorption was a severely fitted to pseudo-second order kinetics
better fit to the Langmuir isotherm. It was stated by model where the R2 value goes as low as 0.0004.
Annadurai, Ling, and Lee (2008) that the value of the The pseudo-first-order kinetic model assumed that
exponent 1/n indicates the favorability and capacity the adsorption process depends only on the two
of the adsorbent/adsorbate system. Most of the sam- factors which are the number of metal ions present
ples showed n > 1 which indicates favorable adsorp- in the aqueous solution and the available binding
tion conditions where in most cases the exponent sites on the adsorbent at any particular period,
between 1 < n < 10 shows beneficial adsorption. which explain the physisorption nature of the
adsorption process. Meanwhile, the pseudo-
second-order kinetic model assumed that the rate
3.5. Kinetic studies controlling step of an adsorption process is the
3.5.1. Pseudo-first-order kinetic model and chemical adsorption (Manirethan, Raval, Rajan,
pseudo-second order kinetics model Thaira, & Balakrishnan, 2018).
Figure 8 shows log (qe-qt) vs. t linear plot of pseudo-
first-order (a) and t/qt vs. t linear plot of pseudo-
second-order (b) kinetic model of Cd(II) ion
4. Conclusions
adsorption using Leucaena leucephala activated car- Three activated carbon (AC) samples with different
bon. The R2 values showed the adsorption process characteristics were prepared using chemical activa-
followed the pseudo-firstorder kinetic model, as tion using the NaOH:carbonized sample ratios of 1:1,
38 W. M. H. W. IBRAHIM ET AL.

(a)
1.4
1.3 Sample
(NaOH:carbonized
1.2 material):
log (qe - qt) 1.1 1:1

1 2:1

0.9 3:1

0.8
0.7
0.6
5 15 25 35 45
t, minutes
(b)
2.05
Linear equation
2.04 Sample: Pseudo-first Pseudo-second
order (a) order (b)
2.03
y = -0.019x + y = 9E-05x +
1:1
2.02 1.5261 2.0129
y = -0.0188x y = -3E-05x +
2:1
t/qt

2.01 + 1.5264 2.0134

y = -0.0196x y = 0.0009x +
2 3:1
+ 1.5237 1.9963
1.99

1.98

1.97
0 20 40 60
t, minutes
Figure 8. log (qe-qt) vs t linear plot of pseudo first order (a) and t/qt vs t linear plot of pseudo second order (b) kinetic
model of Cd(II) ion adsorption using Leucaena leucephala activated carbon.

Table 4. Kinetic models for Cd(II) ion adsorption using results that the AC sample obtained from Leucaena
Leucaena leucephala activated carbon. leucocephala biomass at the NaOH:carbonized sam-
Pseudo first order Pseudo second order ple ratio of 3:1 could be the best to be used effi-
Sample qe (mg/g) K1 R2 qe (mg/g) K2 R2 ciently for removal of cadmium from
-8 15
1:1 33.58 0.0438 0.9650 2.0 x 10 1.24 x 10 0.3376 contaminated water.
2:1 33.6 0.0433 0.4851 2.0 x 10-4 12.42 x 10-6 0.1391
3:1 33.4 0.0451 0.8521 1111.1 4.06 x 10-7 0.1092
Disclosure statement
No potential conflict of interest was reported by
2:1 and 3:1 in the present study. Each sample exhib-
the authors.
ited different adsorption percentage during batch
adsorption studies. Considering the effect of contact
time on Cd2þ removal, the highest adsorption per- Funding
centage was observed for the ratio of 3:1. The The authors acknowledged the Ministry of Education of
adsorption equilibrium was reached within 40 min at Malaysia for MyMaster scholarship to Wan Muhammad
the initial Cd2þ concentration of 30 mg/l. The con- Hilmi bin Wan Ibrahim and Universiti Malaysia Kelantan
centration, pH, and temperature also gave rise to the for Short Term Grant (R/SGJP/A08.00/01046A/001/2015/
highest adsorption rate for the NaOH:carbonized 000242) awarded to Mohd Hazim Mohamad Amini.
sample ratio of 3:1. The higher the initial concentra-
tion, the lower the level of adsorption performance.
The higher adsorption equilibrium was established at References
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