Treatment of Aqueous Solution of Lead Content by using Natural Mixture of Kaolinite-Albite-Montmorillonite-Illite Clay
Jean Aubin Ondo,
Joseph Ndong Nlo,
Raphinos Kouya Biboutou
Benjamin Kouassi Yao
The possible use of clay from Bikougou (Gabon), as an adsorbent, for the removal of lead from waterwaste was investigated. The experiments were conducted using batch technique at 308 K and pH 4. The adsorption of Pb (II) ions in aqueous solution on clay has been studied as function of pH, concentration, time and temperature. Its efficiency increased with increasing of pH (from 2 to 8), Pb (II) ions in aqueous solution (pH higher 3), contact time of equilibration and temperature. The experimental data follow the Langmuir isotherm with correlation coefficient higher than 0.99 and maximum adsorption capacities varying between 24.12 to 25.64 mg g-1 at pH 4 and temperatures ranged between 308 and 318 K. Adsorptions kinetics obeys to a pseudo-second-order model with linear correlation coefficient higher than 0.96. Calculated and experimental amounts of Pb (II) ions adsorbed are in the same order. The negative Gibbs free energy value corresponds to a simultaneous process. The great capability of Bikougou clay to remove Pb (II) ions from aqueous solution demonstrated its potential as a low cost effective way to remediate Pb-contaminated water.
to cite this article:
Francois Eba, Jean Aubin Ondo, Soumahoro Gueu, Joseph Ndong Nlo, Raphinos Kouya Biboutou and Benjamin Kouassi Yao, 2011. Treatment of Aqueous Solution of Lead Content by using Natural Mixture of Kaolinite-Albite-Montmorillonite-Illite Clay. Journal of Applied Sciences, 11: 2536-2545.
Received: December 14, 2010;
Accepted: April 01, 2011;
Published: June 07, 2011
Lead is a heavy metal widely disseminated in the nature, particularly in the
human environment. Gas from fuel combustion, paint, battery, glass and mining
industries release lead in their effluents (Gueu et al.,
2007; Zhu et al., 2008). Now, lead is not
biodegradable and also found presenting adverse metabolic effects such as poisoning
of red blood cells, nervous system attack and kidneys damage (Wang
et al., 2007; Garcia and Corredor, 2004;
Frisbie et al., 2002). Then, the removal of lead
from industrial effluents is becoming a great concern for scientific community.
Taking into account all the above, a number of technologies for the removal
metal ions from aqueous solutions have been developed over the years. The most
important of them, include chemical precipitation, ultrafiltration, electrochemical
deposition, ion exchange and reverse osmosis (Ahmad et
al., 2009). But these technologies do not seem to be economically generalizable
because of their high costs and that developing countries may not afford such
technologies. In the last few years, adsorption has been shown to be an alternative
method for removing dissolved metal ions from wastewaters (Bayat,
2002). The adsorption process is a phenomenon known since the 17th century
when, it was discovered that porous materials have the property to adsorbing
gas and subsequently, the same behaviour is observed for solutions (Brunauer,
2007). Inactivated charcoals and activated carbons were firstly used as
adsorbents but their high cost has limited their use. In order to minimise processing
costs, several investigations have focused on the search of low-cost adsorbents
of agricultural and biological origin (Babel and Kurniawan,
2003). Among them, clays and clays materials considered as low-cost materials
have proved their efficiency as adsorbent in a treatment of aqueous solution
of metal ions content (Eba et al., 2010). For
instance, using a review of lead adsorption results by low-cost adsorbents,
from contaminated water. Babel and Kurniawan (2003)
reported that montmorillonite, kaolinite, illite and bentonite may remove respectively,
0.68, 0.12, 1.41, 4.29 and 0.68 mg g-1 of lead as given by Langmuir
model. Gupta and Bhattacharyya (2008) showed that kaolinite
and montmorillonite allow to uptake respectively 11.5 and 31.1 mg g-1.
Gupta and Bhattacharyya (2005) have also found that
kaolinite and montmorillonite modified clays are able to absorb respectively
5.44 and 31.44 mg g-1 of lead at 303 K. This study is undertaken
to study the potential of clay from Bikougou (Gabon) to adsorb lead (II) ions
from aqueous solution. The effect of the solution pH, contact-time and temperature
on the removal of Pb (II) ions was investigated. The adsorption isotherm and
probable mechanism was explained. The thermodynamic parameters for the adsorption
Pb (II) ions have been also computed and discussed.
MATERIALS AND METHODS
Adsorbent characterization: The clay material taken from Bikougou deposit
(Gabon 11°37'E and 1°58'N) was used as adsorbent in this work. It was
characterized for its clay minerals content (X-rays) (Fig. 1,
2), composition in major (as oxides) and traces elements (Table
1). Clay values of Surface Specific Area (SSA) were performed using the
method of methylene blue (Hang and Brindley, 1970).
Its Cation Exchange Capacity (CEC) was determined using the ammonium acetate
method at pH 7 (Remi and Orsini, 1976). The acidity
of surface was evaluated by means of Boehm titration method (Mukana
and Kifuani, 2000). The point of zero charge was given by the use of potentiometric
titrations (Ijagbemi et al., 2009) (Table
The X-ray powder diffractograms of the crude clay (Fig. 1)
shows the presence of four clayey minerals with some impurities: (i) Kaolinite,
identified by its ray at 7.19Å in crude clay (ii) Montmorillonite recognized
for its typical rays at 14.93 Å (iii) Illite known for the displaying
a doo1 at 9.92 Å ; other illite rays are at 5.04, 4.45, 3.38, 3.65, 3.34,
2.87 and 2.54 Å in Fig. 1. (iv) Feldspars are revealed
by reflections at 3.18, 3.21, 4.04 Å. The pattern is typical of andesine
or albite. The other mineral species identified are (Fig. 1):
Quartz (rays at 3.34, 3.18 and 2.56 Å); carbonates calcite mineral (rays
at 3.05, 2.93 Å) and as gaylussite (rays at 3.205, 6.39 and 2.63 Å);
anatase (rays at 3.51, 2.37 and 1.89 Å); maghemite (rays at 2.93, 2.56
Å); Ba, Sr-hydroxyapatite (rays at 4.45, 3.76, 1.82, 2.13 and 2.93 Å).
The X-ray diffractogram of the crude material is completed by the diffractrogram of the clay fraction from which three minerals are identified. (i) Kaolinite identified by its ray at 7.21 Å in untreated fraction (curve U) which is shifted at 10.40 Å by hydrazine saturation from clay fraction (curve H). (ii) Montmorillonite recognized for its typical ray at 15.13 Å. (curve U) which is shifted at 17 Å (curve G) with the ethylene-glycol treatment or reduced to 9.80 Å (curve C) on heating at 490°C. (iii) Illite known for the displaying a doo1 at 10.02 Å (curve U) which is not affected by the above mentioned treatments (Fig. 2).
Many constituents present in the crude clay such as albite, carbonate, maghemite, anatase, quartz and Ba, Sr- hydroxyapathite have been not found in the clay fraction. The clay fraction was extracted with Robinson pipette, according to stokes law, from whole-rock aqueous suspension, after oxidation of organic matter using H2O2 and destruction of acid soluble minerals using HNO3 (5%).
Adsorbate and aqueous solution: Pb (II) ions used in this study have been obtained from Pb (NO3)2 (Prolabo Analytical grade), it was used without further purification. Aqueous solutions of Pb (II) were prepared by dissolving an accurately weighed amount of Pb (NO3)2 in deo-ionised water to achieve concentration of Pb (II) (ranged from 19 to 120 mg L-1).
Adsorption procedure: The adsorption of Pb (II) ions on to clay was
studied by means of batch technique. A known weight (0.25 g) of clay was equilibrated
with 50 mL of the spiked lead solution of known concentration, in a stopped
propylene flask, at a fixed temperature and in a thermostatic shaker for known
period time. After the equilibration using a constant stirring speed, the suspension
was filtered out and analyzed for its lead concentration, using an atomic adsorption
spectrometer (Analyst 100 Perkin Elmer, Varian AA 20). The effects of several
parameters such as pH, contact-time, initial concentration of lead solutions
and temperature on the adsorption were studied.
|| Chemical composition of clay material from Bikougou
|Major elements expressed in weight percentage; Trace elements
in ppm; L.D: Limit of detection; LOI: Loss of ignition
|| Characteristics of Bikougou clay deposit
|| XRD patterns of crude clay from Bikougou deposit
|| XRD patterns of clay fraction from Bikougou deposit
Calculation: The amount of lead (II) ions adsorbed per unit mass of adsorbent and percentage of Pb (II) ions adsorbed (% ads) were calculated by using respectively the Eq. 1 and 2:
where, Co and Ct are the initial concentration and concentration
after any time of interaction adsorbate-adsorbent of lead in aqueous solutions,
V is the volume of lead solution and m is the mass of clay.
Adsorption results models: The adsorption process is normally described
in this study by the use of Langmuir and Dubinin-Kaganer-Radushkevich (DKR)
isotherms (Langmuir, 1918; Gupta
and Bhattacharyya, 2005; Karapinar and Donat, 2009).
These adsorption isotherm models serve to characterize the interaction of Pb
(II) with the clay from Bikougou. Each of them, provides a relationship between
the Pb (II) concentration in the solution and the uptake of Pb (II) adsorbed
onto the solid phase when the two phases are at equilibrium. The adsorption
experimental data obtained for equilibrium condition are analyzed by using the
linear forms of Langmuir and DKR adsorption isotherms.
Langmuir isotherm is applicable if the monolayer coverages of adsorbent by
adsorbate takes place on an homogeneous adsorbent surface. The Langmuir coefficients
b and qm representing respectively the adsorption equilibrium constant
and the monolayer maximum adsorption capacity are determined from the intercepts
and the slopes of the plots Ce/qe vs Ce. A
further analysis of Langmuir equation can be made on the basis of a dimensionless
separation constant RL (Juang et al.,
1997). For favourable adsorption 0 < RL< 1 and RL
> 1 represents unfavorable adsorption, RL = 1 linear adsorption
and RL = 0 corresponds to an irreversible process (Kadirvelu
and Namasivayama, 2003).
The DKR equation is used to explain the energetic heterogeneity of solid at low coverages as monolayer region in micopores. The DKR parameters Xm and β representing respectively, the maximum adsorption capacity and the coefficient of mean energy may be obtained from the intercepts and slopes of plots lnqe vs ε2.
When the kinetics of the adsorption follows the pseudo-second-order kinetics
(Tien and Huang, 1991; Ho and McKay,
1999c; Ho et al., 2001) the plot t/qe
vs. t gives a linear relationship which allows computation of the amount of
Pb (II) ions adsorbed per unit mass of clay at equilibrium (qe) and
the second order rate constant (k2).
Thermodynamic parameters such as enthalpy and entropy changes are estimated
using the Langmuir constant b at plotting lnb vs 1/T (K) (Eba
et al., 2010). The Gibbs free energy of the reaction is then computed
as ΔG0 = ΔH0-TΔS0.
RESULTS AND DISCUSSION
Properties of the used clay: Table 1 shows the mineral
composition of the clay used. The main constituent of the crude clay is SiO2
(54.32 w.t. %), Al2O3 is the next main constituent (24.64
w.t. %) followed by notable amounts of Fe2O3 (3.87 w.t.
%), Na2O (3.09 w.t. %) and CaO (2.53 w.t. %). Among the analyzed
43 trace elements, prevailing elements are Sr (506 ppm), Ba (558 ppm). Other
elements contents are <100 ppm. The constrained multilinear calculation realized
by combining X-rays results and whole-rock chemical analyses was used to quantify
the percentage of each mineral in the crude clay (Njopwouo,
1984; Yvon et al., 1990).
The results presented in the Table 3 show the mineralogical composition of the crude clay material. The whole rock comprises kaolinite (29.1%), albite (20.3%), montmorillonite (15.2%) and illite (10.9%).
The data reported in the Table 2 show the surface properties
of clay. The CEC value (12.87 meq/100 g) which is similar to that of pure illite
(10-15 meq/100 g) (Baeyens and Bradbury, 2004), is higher
than those for standard technical kaolinites (5 meq/100 g) (Ma
and Eggleton, 1999) and lower than that of pure montmorillonite (40-100
meq/100 g) (Maes et al,. 1979). A simulation
accounting for the estimated modal compositions yielded a CEC value of 12.45
meq/100 g; implying that the CEC of the present material is the balance sum
of the CECs of its contrasted constitutive clay minerals. The SSA value (170
m2 g-1), is higher than those for illite (Oswego illite
78 m2 g-1) or of kaolinite (Florida kaolinite 35 m2
g-1) and lower than that of montmorillonite (700-410 m2
g-1) (Santamarina et al., 2002). It
is to be noted that specific surface area cannot represent a general characteristics
of a particular type of material, because its value depends of particle size,
particle shape, number distribution of cracks and pores in the material (Gupta
and Bhattacharyya, 2008). The PZC value (3) is higher than for kaolinite
(2.8) (Appel et al., 2003) and lower than for
montmorillonite (3.5) (Ijagbemi et al., 2009).
The Acidity Neutralization(AN) values are higher than that for kaolinite (Florida
kaolinite 0.1 meq g-1) (Baker et al.,
|| Mineralogical composition of clay from Bikougou
|Composition of untreated clay material and its fraction (wt
%). The composition of untreated clay is determined by combining qualitative
X-ray data and chemical analysis while the composition of clay fraction
is determined from X-ray pattern intensities measurements without absorption
|| Amounts (qe (mg g-1)) and percentage
(ads (%)) of Pb (II) ions adsorbed as function of pH and salt initial concentration
|where: qe, in mg g-1, is the equilibrium
amount of Pb (II) adsorbed per specified amount of adsorbent; ads is the
percentage of Pb (II) adsorbed
The neutralization of the acids on the surface with NaOH, NaHCO3 and
Na2CO3 translated the presence of functional group, such
-OH¯,-C = O and -COOH (Boehm, 1994). Clay characteristics
from this study, are not in agreement with those of single clay species, because
those for clay from Bikougou are the balance sum of characteristics, of its
constitutive clay minerals. All these parameters allow to assess the potential
of clay as adsorbent.
Effect of pH: The experiments for the effect of pH on adsorption capacities
of clay for Pb (II) ions were performed using different initial concentrations
varying from 20 to 40 mg L-1 of lead content and 250 mg of clay,
at various pH between 2 and 8 during 90 min. Table 4 reports
the pH influence of Pb (II) ions adsorption onto clay surface. Its is observed
that the adsorption capacity of clay increases greatly with the increase in
pH from 2 to 4 and the adsorption high level obtained from a pH of 4 increases
weakly as far as pH 8. When initial concentrations are below 25 mg L-1,
all the Pb (II) ions are adsorbed on clay assuming that the number of sites
adsorbing is higher than the amount of Pb (II) ions to be adsorbed, this gives
the impression that the adsorption is constant from pH 4 to 8. In agreement
with this work (for high concentration than 25 mg L-1), a continuous
increase of adsorption amounts of lead (II) ions with the increase in pH has
been reported by Wang et al. (2007) using MnO2/CNTS
as adsorbent, Potgieter et al. (2006) with palygorskite
as adsorbent, Zhu et al. (2008) using bentonite
as adsorbent and Gupta and Bhattacharyya (2005) with
kaolinite and montmorillonite as adsorbents. The observed changes in lead uptake
as function of pH could be explained from the hypothesis of a competition between
H3O+ and Pb (II) ions for the approach of available adsorption
sites on adsorbent surface (Gueu et al., 2006).
At low pH than that of Point of Zero Charge (PZC), there is a large excess of
H3O+ ions which compete repulsively with Pb (II) ions
for the attainment of adsorption available sites on adsorbent surface. The number
of Pb (II) ions reaching adsorption sites is weak. The result is now a weak
level of Pb (II) ions uptake. When pH is higher than that of PZC, the amount
of H3O+ ions is negligible and more Pb (II) ions could
reach available adsorption sites on clay surface. The level of Pb (II) ions
adsorbed increases then, considerably. The literature reports similar views
about the effect of pH on Pb (II) adsorption by silicate minerals (Zhu
et al., 2008; Ayari et al., 2007).
The maximum sorption efficiency in the pH range 4-8 may be due also to the combination
between adsorption process and lead hydroxide precipitation. Gupta
and Bhattacharyya (2008) and Jain and Ram (1997)
observed this behavior of continuous increase of adsorption capacity of Pb (II)
ions on kaolinite and on montmorillonite with the increase in pH from 2 to 6
and appearance from pH 6 of the lowly soluble Pb (II) hydroxide. Instead that,
experiments in this work were realized at pH 4.
Adsorption isotherms studies: The adsorption isotherms for Pb (II) removal
were studied using initial concentration of Pb (II) ions such as 67.978, 74.202,
78.03 and 80.186 mg L-1 and adsorbent mass of 0.1 g at 308, 313 and
318±1K. Amounts of Pb (II) ions adsorbed per unit mass of clay increased
gradually with increasing concentration of lead (Table 5).
Similar results have been reported by Ayari et al.
(2007) and Gupta and Bhattacharyya (2008) for the
Pb (II) adsorption from aqueous solution onto bentonite and montmorillonite,
respectively. These results are related to number of Pb (II) ions capable to
react with available numerous adsorption sites on the adsorbent surface, this
number of Pb (II) ions is growing with the increase of concentration of Pb(II)
The data obtained are used to trace the Langmuir plots isotherms: Ce/qe
as function of Ce (Fig. 3) and DKR (Erdem
et al., 2004) plots isotherms: lnqe as function of ε2
(Fig. 4). From these plots (Fig. 3,
4), the corresponding parameters of the two models and their
linear correlation coefficients (R2) are determined and conclusion
could be drawn about the adherence of each isotherm model to adsorption experimental
data. The results are presented in the Table 6.
The adsorption data follow the Langmuir isotherm model, because, its correlation
coefficients from 308 K to 318 K are higher than 0.99. The equilibrium constant,
b, varies from 3.196 at 308 K to 7 at 318 K. The large values of constant, b
are an indication of the high strength of the interactions adsorbent- adsorbate,
most probably chemisorptions.
||Plot of variations of the ratio of the equilibrium concentration
(Ce, mg L-1) on amount adsorbed specified amount of adsorbent
(qe, mg g-1) as a function of equilibrium concentration for Pb
(II) ions adsorption on clay at 308K (initial concentration 67.94, 74.20,
78.03 and 80.19 mg L-1, pH 4)
||Plot of variations of the logarithm of amount adsorbed per
specified amount of adsorbent (qe, mg g-1) as a function
of the square of Polanyi potential (ε2 (kj/mol)2)
for Pb (II) ions adsorption on clay at 308K (initial concentration 67.94,
74.20, 78.03 and 80.19 mg L-1, pH 4)
||Amount of Pb(II) ions adsorbed per unit mass of clay at different
The adsorption capacity, qm, is found appreciably large with values
of 25.64 mg g-1 (308 K) to 24.63 mg g-1 (318 K) .The separation
factor, RL,with its values remained between 0.0046-0.0039 (308 K)
and 0.00178-0.0021 (318 K) corresponds to the case of favourable adsorption
of Pb (II) ions on the clay adsorbent (Juang et al.,
1997) in conformity with the requirement RL<1(Lin
and Juang, 2002) .The large values of Langmuir parameters from 308 to 318
K, imply that the adsorption of Pb (II) ions is limited to monolayer coverage
and also that adsorbent surface is energetically homogeneous.
The Dubinin-Kaganer-Radushkevich (DKR) equation, has been found to describe
the sorption of Pb (II) ions on clay. The linear correlation coefficients remained
between 0.8401 and 0.9998 (in the ranges 308-318 K of temperature), correspond
to the level of monolayer coverage of microspores on the adsorbent surface.
Values of Xm (DKR monolayer capacity) are ranged from 5.92 mg g-1
to 8.57 mg g-1 with the increase in temperature from 308 to 318 K.
These high values of Xm indicate the nature favourable of the adsorption
of Pb (II) on clay. The adsorption energy E reveals the nature of adsorption.
If the E value is ranged between -1 and -8 kJ mol-1, adsorption process
is physical and if the E value is ranged between -9 and -16 kJ mol-1,
it is chemically controlled adsorption. The E values for the present study,
decrease from, -9.407 kJ/mol at 308 K, to -10.425 kJ mol-1 at 313
K and to -10.20 kJ mol-1 at 318 K That corresponds to an ion-exchange
mechanism (Hellferich, 1962; Kwon
et al., 1998). This sorption chemically controlled process was also
reported by Saeed et al. (2003).
Other workers have reported values of the adsorption parameters in similar
ranges. Gupta and Bhattacharyya (2008) from studies
of adsorption of Pb (II), Cd (II) and Ni (II) on kaolinite and montmorillonite,
found Langmuir adsorption capacity, qm, between 11.5 to 31.1 mg g-1
at 303 K and pH 5.7, RL ranged between 0.0021 to 0.0003 and R2
remained from 0.98 to 0.99 for Pb (II) adsorption. Lin and
Juang (2002) have reported DKR Adsorption capacity, Xm, of 5.27
and of 2.09 mg g-1, adsorption energy E of: -13.8 and -12.6 kJ mol-1
and correlation coefficients R2 of 0.962 and of 0.978 for Cu (II)
and Zn (II), respectively from the adsorption studies of these ions on surfactant-modified
Thermodynamics studies: In order to determine the thermodynamic feasibility
and the thermal effects accompanying the adsorption process, the amounts of
Pb (II) ions adsorbed (qe (mg g-1)) and equilibrium concentration
(Ce (mg L-1)) of Pb (II) ions in aqueous solution were determined
at 308, 313 and 318 K. Pb (II) adsorption on the clay increases with the increase
in temperature. The interaction is endothermic. Similar results have been reported
by Gupta and Bhattacharyya (2008) for adsorption of
Pb (II) on montmorillonite and/or kaolinite.
||Langmuir and DKR isotherm fitted parameters for the adsorption
of Pb (II) onto clay from Bikougou (pH 4, initial concentrations 67.98,
74.202, 78.2 and 80.18 mg L-1 clay 2 g L-1)
|Where: T is the temperature in Kelvin; qm is the
Langmuir monolayer maximum capacity; b is the Langmuir equilibrium constant;
RL is the Langmuir dimensionless factor; R2 is the
correlation coefficient; Xm is the DKR maximum adsorption capacity;
β is the activity coefficient related to the mean energy; E is the
adsorption mean energy
||Plot related to the variations of Langmuir equilibrium constant
(b, L/g) as a function of the temperature reverse (1/T, K-1)
for Pb (II) ions adsorption on clay at pH 4
The plot of lnb versus I/T (Fig. 5) gives effectively, a linear relationship with regression coefficient of equal to 0.86.
The Gibbs free energy values decrease from -3.205 kJ mol-1 at 308
K, to -4.290 kJ mol-1 at 313 K and to -5.375 kJ mol-1
at 318 K indicating that the process is spontaneously more feasible with the
increase in temperature. The positive value of enthalpy changes (63.655 kJ mol¯1)
corresponds to endothermic interactions Pb (II)-clay. The considerably high
values of ΔH0 suggest strong interactions corresponding to a
controlled chemical process, between Pb (II) ions and the clay. In the other
hand, the positive value of ΔS0 (0.217078 kJ/mol/K) indicates
that Pb (II) ions in aqueous solution are in a much more ordered state compared
to the chaotic distribution when adsorbed on clay. Thermodynamic data on Pb
(II) adsorption have been obtained through other works. In agreement with the
results of the present work, for the adsorption of Pb (II) on peat and on activated
carbons from coconut and seed hull of palm tree respectively, Ho
and McKay(1999a, b) and Gueu
et al. (2007) found a positive value of the adsorption enthalpy.
Wang et al. (2007) have reported that ΔH0,
ΔS0, ΔG0 for sorption of Pb (II) on manganese
dioxide coated carbon nanotubes have values of 0.3530 l, 0.02297 and -6.496
kJ mol-1. Ahmad et al. (2009) have
obtained the values of enthalpy, entropy and Gibbs free energy changes, respectively
of 120.02, 0.13 and -20.99 kJ mol-1 at 303 K for adsorption of Pb
(II) on sawdust of Meranti wood. In opposite case, exothermic adsorption of
Pb (II) of -58.9 and -31.5 kJ mol-1, negative values of the entropy
change of -209.7 and -116.3 J/mol/K and Gibbs free energy value of -64.6 and
-35.8 kJ mol-1, respectively have been obtained on kaolinite and
also on montmorillonite by Gupta and Bhattacharyya (2008).
The convergence is linked to thermodynamic behavior with respect to the adsorption
of Pb (II) ions and not to the values obtained on the thermodynamic parameters
because of not identity of adsorbents used.
Kinetic studies: Assuming a pseudo-second-order kinetic model, the experimental
data were subjected to the integrated form of law of pseudo-second-order model
(Ho and McKay, 1999c). One can immediately observe the
fast increase in Pb (II) uptake in just five minutes. This fast reaction implies
the strong electrostatic interaction between the negatively charged clay surface
and Pb (II) ions. The removal equilibrium of lead by clay is attained at about
of twenty-thirty minutes (Jain and Ram, 1997). The linear
plots in the system of coordinates t/qt versus t presented in Fig.
6, illustrate the fit of the pseudo-second-order kinetic model to experimental
The pseudo-second-order kinetics parameters k2, qe and R2 are reported in the Table 7.
The correlation coefficients for the linear plots are greater than 0.999 at
308K and than 0.96 at 313 and 318 K, in conformity with the requirement (R2
= 1) of the validity of a kinetics model (Al-Futaisi et
The kinetic constants k2 (g mg-1*min) vary in a random
way with the initial concentration of Pb (II) solution, decreasing with the
increase in initial concentration at 308 and 313 K and no known rule at 318
K. An examination of the temperature effect (Table 7) shows
that the values of constant rate decrease with the increase in temperature from
308 to 313K. The great level of rate constants (0.6 g/(mgxmin)≤k2≤4.038
g/(mgxmin) is an evidence of strong interaction between Pb (II) ions and adsorption
sites on the adsorbent. This is a characteristic of a chemical reaction also
called irreversible process.
||Plots related to variations of the ratio between adsorbent-adsorbate
contact time (t, min) on the amount adsorbed per specified amount of adsorbent
(qe, mg g-1) as a function of time for Pb (II) ions adsorption
on clay at 308 K for different initial concentration (67.74, 74.2, 78 and
80.186 mg L-1) at pH 4
||Pseudo-second-order kinetic parameters for the adsorption
of Pb (II) on clay (pH 4)
|Where: T is the temperature in Kelvin; qe in mg/g,
is the equilibrium amount of Pb (II) adsorbed per specified amount of adsorbent
obtained by calculation from the second order kinetics model; qex
is the experimental equilibrium amount of Pb (II) adsorbed per specified
amount of adsorbent; RL is the Langmuir dimensionless factor;
R2 is the correlation coefficient; k2 is rate constant
The good agreement between calculated qe and experimental qex
(amounts of Pb (II) ions adsorbed), demonstrates that the adsorption kinetics
of Pb (II) onto clay follows very accurately the pseudo second order model according
to Ho and McKay (2000). Other researchers have found
results in agreement with those obtained in the present work. Pseudo-second-order
kinetic model was applied during the adsorption of lead (II) ions on bentonite
clay and parameters values such as: rate constant, amount of metal ions adsorbed
and correlation coefficient have been obtained and equal respectively to 0.0297g/mg/min,
36.71 mg g-1 and 0.99 (Zhu et al., 2008).
Gupta and Bhattacharyya (2008) found Pb (II) ions adsorption
kinetics on kaolinite and montmorillonite, to follow the pseudo-second-order
with rate constant varying between 0.035 and 0.0804g/mg/min, amount of metal
ions adsorbed ranged from 6.4 to 22.3 mg g-1 and correlation coefficient
equal to 0.99. It is to be noted that although the adsorption of ions Pb (II)
ions on bentonite, kaolinite, montmorillonite and clay from Bikougou follows
the kinetics of the pseudo-second order kinetic parameter values are not identical
because of differences in the nature, structure and composition between the
This study shows that clay from Bikougou has a great potential as adsorbent usable for the removal of Pb (II) ions from aqueous solutions. The amount of Pb (II) ions adsorbed on clay is pH, initial concentration of Pb (II) ions solution and temperature dependent. Langmuir and DKR models describe the adsorption isotherm but the best fit (R2 = 0.99) of experimental data is obtained with Langmuir isotherm. The adsorption process is spontaneous because of negative Gibbs free energy values given. It is accompanied by an endothermic interaction and a positive value of ΔS0 change. The adsorption obeys to kinetics of pseudo-second-order model and is controlled by a chemical mechanism.
1: Ahmad, A., M. Rafatullah, O. Sulaiman, M.H. Ibrahim, Y. Chii and B.M. Siddique, 2009. Removal of Cu (II) and Pb (II) ions from aqueous solutions by adsorption on Sawdust of Meranti Wood. Desalination, 247: 636-646.
2: Al-Futaisi, A., A. Jamrah and R. Al-Hanai, 2007. Aspects of cationic dye molecule adsorption to palygorskite. Desalination, 214: 327-342.
3: Garcia, T.A. and L. Corredor, 2004. Biochemical changes in the kidneys after perinatal intoxication with lead and./or cadmium and their antagonistic effects when coadministered. Ecotoxicol. Environ. Saf., 57: 184-189.
Direct Link |
4: Appel, C., L.Q. Ma, R.D. Rhue and E. Kennelley, 2003. Point of zero charge determination in soils and minerals via traditional methods and detection of electroacoustic mobility. Geoderma, 113: 77-93.
5: Ayari, F., E. Srasra and M. Trabelsi-Ayadi, 2007. Retention of lead from an aqueous solution by use of bentonite as adsorbent for a reducing leaching from industrial effluents. Desalination, 206: 270-278.
6: Babel, S. and T.A. Kurniawan, 2003. Low-cost adsorbents for heavy metals uptake from contaminated water: A review. J. Hazard. Mater., 97: 219-243.
CrossRef | PubMed | Direct Link |
7: Baker, L.A., P.L. Brezonik, E.S. Edgerton and R.W. Ogburn, 1985. Sediments acid neutralization in softwater lakes. Water Air Soil Pollution, 25: 215-230.
8: Baeyens, B. and M.H. Bradbury, 2004. Cation exchange capacity measurements on illite using the sodium and caesium isotope dilution technique: Effects of the index cation, electrolyte concentration and competition: Modelling. Clays Clay Minerals, 52: 421-431.
9: Bayat, B., 2002. Compatative study of adsorption properties of Turkish fly ashes: I. The case of nickel (II), copper (II) and zinc (II). J. Hazardous Mater., 95: 251-273.
10: Boehm, H.P., 1994. Some aspects of the surface chemistry of carbon blacks and other carbons. Carbon, 32: 759-769.
CrossRef | Direct Link |
11: Brunauer, S., 2007. The Adsorption of Gases Ans Vapors, Vol I-Physical Adsorption. Oxford University Press, London, pp: 03.
12: Eba, F., S. Gueu, A.E. Mvongbote, J.A. Ondo, B.K. Yao, J.N. Nlo and R.K. Biboutou, 2010. Evaluation of the adsorption capacity of the natural clay from Bikougou (Gabon) to remove Mn (II) from aqueous solution. Int. J. Eng. Sci. Technol., 2: 5001-5016.
Direct Link |
13: Erdem, E., N. Karapinar and R. Donat, 2004. The removal of heavy metal cations by natural zeolites. J. Colloid Interface Sci., 280: 309-314.
CrossRef | Direct Link |
14: Frisbie, S.H., R. Ortega, D.M. Maynard and B. Sarkar, 2002. The concentration of arsenic and other toxic elements in Bangladesh`s drinking water. Environ. Health Prospect, 110: 1147-1153.
Direct Link |
15: Gueu, S., B. Yao, K. Adouby and G. Ado, 2006. Heavy metals removal in aqueous solution by activated carbons prepared from coconut shell and seed shell of the palm tree. J. Applied Sci., 6: 2789-2793.
CrossRef | Direct Link |
16: Gueu, S., B. Yao, K. Adouby and G. Ado, 2007. Kinetics and thermodynamics study of lead adsorption on to activated carbons from coconut and seed hull of the palm tree. Int. J. Environ. Sci. Technol., 4: 11-17.
CrossRef | Direct Link |
17: Ho, Y.S. and G. McKay, 1999. The sorption of lead(II) ions on peat. Water Res., 33: 578-584.
CrossRef | Direct Link |
18: Hellferich, F., 1962. Ion Exchange. Mc Graw-Hill, New York, pp: 166.
19: Ho, Y.S. and G. McKay, 1999. Batch lead (II) removal from aqueous solution by peat: Equilibrium and kinetics. Process Safety Environ. Protec., 77: 165-173.
20: Ho, Y.S., J.C.Y. Ng and G. McKay, 2001. Removal of Lead (II) from effluents by sorption on peat using second-order kinetics. Separ. Sci. Technol., 36: 241-261.
21: Ho, Y.S. and G. McKay, 2000. The kinetics of sorption divalent metal ion onto sphagnum mass peat. Water Res., 34: 735-742.
Direct Link |
22: Ho, Y.S. and G. McKay, 1999. Pseudo-second order model for sorption processes. Proces. Biochem., 34: 451-465.
CrossRef | Direct Link |
23: Ijagbemi, C.O., M.H. Baek and D.S. Kim, 2009. Montmorillonite surface properties and sorption characteristics for heavy metal removal from aqueous solutions. J. Hazard. Mater., 166: 538-546.
24: Juang, R.S., F.C. Wu and R.L. Tseng, 1997. The ability of activated clay for the adsorption of dyes from aqueous solutions. Environ. Technol., 18: 525-531.
CrossRef | Direct Link |
25: Kadirvelu, K. and C. Namasivayam, 2003. Activated carbon from coconut coitpith as metal adsorbent: Adsorption of Cd (II) from aqueous solution. Adv. Environ. Res., 7: 471-478.
Direct Link |
26: Karapinar, N. and R. Donat, 2009. Adsorption behavior of Cu2+ and Cd2+ on to natural bentonite. Desalination, 249: 123-129.
27: Kwon, S.C., D.I. Song and Y.W. Jeon, 1998. Adsorption of phenol and nitrophenol isomers onto montmorillonite modified with hexadecyltrimethylammonium cation. Sep. Sci. Technol., 33: 1981-1998.
28: Langmuir, I., 1918. The adsorption of gases on plane surfaces of glass, mica and platinum. J. Am. Chem. Soc., 40: 1361-1403.
CrossRef | Direct Link |
29: Ma, C. and R.A. Eggleton, 1999. Cation exchange capacity of kaolinite. Clays Clay Minerals, 47: 174-180.
Direct Link |
30: Maes, A., M.S. Stul and A. Cremers, 1979. Layer charge – cation-exchange capacity relationship in montmorillonite. Clays Clay Minerals, 27: 387-392.
Direct Link |
31: Mukana, W.M. and K.M. Kifuani, 2000. Preparation of active carbon from sawdust of sugar cane bagasse, wood of Ntola and Lifaki soaked in sodium hydroxide caustic solution Congolese. J. Nucl. Sci., 16: 84-92(Original article in French).
32: Njopwouo, D., 1984. Mineralogy and physical chemistry of clays from bomkoul and balengou (cameroon). Use in the polymerization of styrene and strengthening of natural rubber. Ph.D. Thesis, University of Yaounde (Cameroon).
33: Hang, P.T. and G.W. Brindley, 1970. Methylene blue absorption by clay minerals. Determination of surface area and cation exchange capacities (Clay-Organic Studies XVIII). Clays Clays Miner., 18: 203-212.
Direct Link |
34: Potgieter, J.H., S.S. Potgieter-Vermaak and P.D. Kalibantong, 2006. Heavy metals removal from solution by palygorskite clay. Miner. Eng., 19: 463-470.
CrossRef | Direct Link |
35: Remi, J.C. and L. Orsini, 1976. Using chloride cobalthexamine for the simultaneous determination of exchange capacity and exchangeable bases in soils. Soil Sci., 4: 269-275.
36: Saeed, M.M., M.H. Chaudhary and M. Ahmed, 2003. Adsorption profile of preheated Cr (III)-SCN complexes on polyurethane foam. J. Radioanal. Nucl. Chem., 258: 151-156.
37: Santamarina, J.C., K.A. Klein, Y.H. Wang and E. Prencke, 2002. Specific surface: Determination and relevance. Can. Geotech. J., 39: 233-241.
CrossRef | Direct Link |
38: Gupta, S.S. and K.G. Bhattacharyya, 2008. Immobilization of Pb (II), Cd (II) and Ni (II) ions on kaolinite and montmorillonite surfaces from aqueous medium. J. Environ. Manage., 87: 46-58.
CrossRef | PubMed |
39: Gupta, S.S. and K.G. Bhattacharyya, 2005. Interaction of metal ions with clays: A case study with Pb (II). Applied Clay Sci., 30: 199-208.
40: Wang, S.G., W.X. Gong, X.W. Liu, Y.W. Yao, B.Y. Gao and Q.Y. Yue, 2007. Removal of lead (II) from aqueous solution by adsorption onto manganese oxide-coated carbon nanotubes. Separat. Purificat. Technol., 8: 17-23.
41: Lin, S.H. and R.S. Juang, 2002. Heavy metal removal from water by sorption using surfactange modified montmorillonite. J. Hazard. Mater., 92: 315-326.
42: Tien, C.T. and C.P. Huang, 1991. Kinetics of Heavy Metal Adsorption on Sludge Particulate. In: Heavy Metal in the Environment, Vernet, J.P. (Ed.). Elesvier Science Publishers, USA., pp: 313-328.
43: Yvon, J., J. Banduacco, J.M. Cases and J. Weiss, 1990. Elements of Mineralogy Quantitative Microanalysis Clays. In: Clay Materials, Structures, Properties and Applications, Decarream, A. (Ed.). SFMC-GFA, Paris, pp: 473-489.
44: Zhu, S., H. Hou and Y. Xue, 2008. RETRACTED: Kinetic and isothermal studies of lead ion adsorption onto bentonite. Applied Clay Sci., 40: 171-178.
45: Jain, C.K. and D. Ram, 1997. Adsorption of lead and zinc on bed sediments of the river Kali. Water Res., 31: 154-162.