Study on Factors Affecting Heavy Metal Sorption Characteristics of Two Geomaterials

Abstract

This study investigates effect of liquid to solid ratio, initial concentration of heavy metals, pH and composite heavy metal solution and nature of sorbent on sorption capacity of two different geomaterials such as clayey soil and moorum. The batch sorption experiments were carried out with the selected geomaterials using different heavy metal solutions such as Copper, Manganese, Zinc, Lead and Chromium. Based on the experimental results, the following conclusions are drawn i) increasing liquid to solid ratio decreases the removal rate of heavy metal, however heavy metal sorbed on unit mass of the sorbent increased at equilibrium ii) increase in pH and the initial heavy metal concentration leads to an increase in the heavy metal uptake by the geomaterials iii) nature of the clay mineral present in the geomaterials plays significant role in controlling the sorption characteristics of the geomaterials compared to amount of clay content present in the geomaterials iv) observed order of selectivity of heavy metals is Cr >Pb >Cu >Mn ∼Zn.

Full text

Geotechnical Engineering Journal of the SEAGS & AGSSEA Vol. 46 No.4 December 2015 ISSN 0046-5828
16
Study on Factors Affecting Heavy Metal Sorption Characteristics
of Two Geomaterials
K. M. Nithya
1
, D. N. Arnepalli
2
and S. R. Gandhi
3
1
Former research scholar, Department of Civil Engineering, Indian Institute of Technology Madras, Chennai, India
2
Assistant Professor, Department of Civil Engineering, Indian Institute of Technology Madras, Chennai, India
3
Professor, Department of Civil Engineering, Indian Institute of Technology Madras, Chennai, India
E-mail: kmnithya@gmail.com
ABSTRACT: This study investigates effect of liquid to solid ratio, initial concentration of heavy metals, pH and composite heavy metal
solution and nature of sorbent on sorption capacity of two different geomaterials such as clayey soil and moorum. The batch sorption
experiments were carried out with the selected geomaterials using different heavy metal solutions such as Copper, Manganese, Zinc, Lead
and Chromium. Based on the experimental results, the following conclusions are drawn i) increasing liquid to solid ratio decreases the
removal rate of heavy metal, however heavy metal sorbed on unit mass of the sorbent increased at equilibrium ii) increase in pH and the
initial heavy metal concentration leads to an increase in the heavy metal uptake by the geomaterials iii) nature of the clay mineral present in
the geomaterials plays significant role in controlling the sorption characteristics of the geomaterials compared to amount of clay content
present in the geomaterials iv) observed order of selectivity of heavy metals is Cr >Pb >Cu >Mn ~Zn.
KEYWORDS: Heavy metal, Geomaterials, Sorption capacity, Landfills, Clay liner
1. INTRODUCTION
The increasing problem of mobility of heavy metals into the
environment as a result of mining, industrial and agricultural
activities reveal that the removal of heavy metal ions from the waste
solutions is essential due to its toxic nature (Gulec et al. 2001). The
most common heavy metals in leachate solution are copper (Cu),
chromium (Cr), cadmium (Cd), lead (Pb), manganese (Mn), nickel
(Ni) and zinc (Zn). The concentration of these heavy metals varies
from 0 to 100 ppm in municipal solid waste leachate and 100 to
10000 ppm in mining wastes, sewage sludge and various industrial
wastes (Yong and Diperno, 1991).
Clay liners have been conventionally used as barriers in landfills
to prevent contamination of groundwater and subsoil by leachate.
Among the various available natural liner materials, compacted clay
liners are popularly used because of their low cost with reasonable
low hydraulic conductivity, high sorption capacity and resistance to
damage and puncture (Daniel and Benson, 1990; Guney et al. 2008;
Kang and Shackelford, 2010; Cossu, 2013). If natural clay or clayey
soils are not abundantly available, locally available geomaterial
which satisfies liner requirements can be used to construct the
landfill liners (Kaya and Durukan, 2004; Lakshmikantha and
Sivapulliah, 2006). The primary function of a liner system is to
prevent movement of leachate into the subsoil and ground water.
Thus, the sorption characteristics of geomaterial play a significant
role in evaluating their potential use as landfill liner material
(Wagner, 2013).
Batch sorption experiments are commonly employed to assess
sorption characteristics of geomaterials (McBride, 1994; ASTM D
4646-04, 2008; Arnepalli et al. 2010). Batch test results from the
literature studies showed that the solution composition, liquid to
solid ratio, initial concentration of the heavy metal solution, pH of
solution and the soil nature (e.g., soil constituent) had considerable
effect on sorption of heavy metals on clays (Roy et al. 1991; Chang
and Wang, 2002; Arnepalli et al. 2010; Allen et al. 1995; Kumar et
al. 2006; Degryse et al. 2009; Liu and Lu, 2011). However, no
study has been reported on effect of these variables on the sorption
characteristics of clayey soil and moorum for heavy metals such as
Copper, Manganese, Zinc, Lead and Chromium.
With this in view, the main objective of the present study is to
evaluate the effect of these parameters on sorption of selected heavy
metals on locally available soils such as clayey soil and moorum.
The objective was achieved by conducting batch sorption
experiments with varying liquid to solid ratios (L/S), initial
concentration of heavy metal solution, pH of solution and composite
heavy metal solution. The effect of composite heavy metal on
sorption capacity was assessed under fixed environmental
conditions such as initial concentration, pH and liquid to solid ratio.
2. MATERIALS CHARACTERIZATION
2.1 Materials
Samples of clayey soil and moorum were chosen in this study. The
geomaterials were processed by removing the gravel size particles;
further the processed samples were tested for their physical,
geotechnical, chemical and mineralogical, and sorption
characteristics and the details are presented in the following section.
Heavy metals such as copper, Cu
2+
, in its sulphate form; zinc, Zn
2+
,
and lead, Pb
2+
, in their nitrate form and manganese, Mn
2+
, and
chromium, Cr
3+
in their chloride form were used as model
contaminants.
The heavy metals were chosen to simulate landfill
leachate collected from hazardous waste disposal facility, i.e.,
engineered landfill, developed and operated by M/S Ramkey, at
Hyderabad, Andhra Pradesh, India The concentration of the heavy
metals presents in the solution is determined using an Atomic
Absorption Spectrometer, AAS (Perkin Elmer, USA).
2.2 Physical and Geotechnical characteristics
The specific gravity of the geomaterials was obtained using a water
pycnometer, by following the guidelines presented in ASTM D854-
06. The particle size distribution of the geomaterials were assessed
as per ASTM D422-94. The consistency limits such as liquid limit,
LL, plastic limit, PL and shrinkage limit, SL, along with differential
free swell index, FSI were determined by following the guidelines
presented in ASTM D4318-94 and ASTM D427-94 respectively,
and the results obtained are presented in Table 1. Based on the
particle size distribution and consistency limits, the geomaterials
were classified according to Unified Soil Classification System,
USCS (ASTM D2487-94), as depicted in Table 1. The compaction
characteristics of the geomaterial such as maximum dry density,
γ
dmax
and optimum moisture content, OMC, were determined as per
the guidelines presented in ASTM D698-04 and results are
presented in Table 1. The coefficient of permeability, k, of the
selected geomaterials is evaluated using the flexible wall
permeameter, and by following the guidelines presented in ASTM
D5084 (2010) and results obtained are illustrated in Table 1.

Geotechnical Engineering Journal of the SEAGS & AGSSEA Vol. 46 No.4 December 2015 ISSN 0046-5828
17
2.3 Chemical and Mineralogical characteristics
As depicted in Table 2, the chemical characteristics of the
geomaterials such as cation exchange capacity, CEC, as per IS 2720
Part XXIV-76, carbonates (Hesse et al 1972), organic matter
(ASTM D2974-07) and pH (ASTM D4972-01) were determined.
The specific surface area, SSA, of these samples was obtained by
employing the nitrogen gas adsorption technique with the help of
BET surface area analyser.
Table 1 Physical and geotechnical characteristics of the geomaterials
Property Value
CS MO
G 2.7 2.71
Particle size distribution characteristics
Size Percent fraction (%)
Gravel 0 2.7
Sand 24 59.2
Silt 42 21.5
Clay 34 16.6
Consistency limits (%)
Liquid limit 49 49
Plastic limit 20 21
Shrinkage limit 13 14
Plasticity Index 29 28
USCS* Classification CL SC
Geotechnical characteristics
γ
dmax
(g/cc) 1.7 1.4
OMC (%) 18 24
FSI (%) 40 30
k (×10
-
10
m/s) 0.71 4.8
*
Unified soil classification system (ASTM D2487, 1994)
Table 2 Chemical and mineralogical characteristics of the
geomaterial
Property Materials
CS MO
Chemical characteristics
pH 6.5 8.9
CEC (meq./100g) 18.1 24.2
SSA (m2/g) 53.7 65.9
Carbonates (%) 9 9.3
Organic matter (%) 8.6 9.8
Major Oxides (%)
SiO
2
44.2 44.2
Al
2
O
3
13.2 13.2
Fe
2
O
3
31.6 31.6
TiO
2
5.9 5.9
SO
3
--- ---
CaO 2.3 2.3
K
2
O 0.5 0.5
MgO 0.4 0.4
P
2
O
5
0.8 0.8
MnO 0.7 0.7
Cl --- 0.1
Mineral present
Mineral Name
Kaolinite,
Illite, Quartz,
Feldspar
Chlorite, Illite, Illite-
Montmorillonite,
Hematite, Muscovite
-- less than detectable limit of the instrument (0.001%)
Further the chemical compositions of the geomaterials were
obtained using an X-ray Fluorescence setup, XRF (Phillips 1410,
Holland). Four grams of finely ground sample, 1 g of
microcrystalline cellulose and isopropyl alcohol were mixed
thoroughly, using mortar and pestle and the mixture was kept below
an infrared lamp for slow drying. A small aluminum dish of inner
diameter 33 mm and height of 12 mm was taken and two third of
this dish was filled with mixture of 70 percent methylcellulose and
30 percent paraffin wax, followed by filling up the container by the
dried sample. In order to make a sample pellet, the filled aluminum
dish was compressed with the help of a hydraulic jack by applying a
load of approximately 15 tons. Further the chemical composition of
the geomaterial was determined by mounting the compressed
sample pellet in the sample holder of the XRF test setup, and the
obtained results are presented in Table 2 in their major oxide form.
In addition to this the mineralogical characteristics of the
material was determined with the help of an X-ray Diffraction
Spectrometer, XRD, (Phillips 2400, Holland), using a graphite
monochromator and Cu-Kα radiation. Minerals present in these
samples were identified by using the database “Joint Committee on
Powder Diffraction Standards” (JCPDS-94) search files, and the
results are presented in Table 2.
2.4 Sorption characteristics
The processed material, i.e., the material passing through 2 mm
sieve was employed to perform batch sorption experiments
(Grolimund et al. 1995). Two grams of sample was mixed with 100
ml of the corresponding heavy metal solution with different initial
concentration in the air tight polypropylene sample bottles. The
sample bottles were kept on a mechanical shaker and shaken for an
equilibration sorption period of 24 hours (ASTM D4646-04). Later
these bottles were removed from the shaker and their contents were
centrifuged, which helps in separating solid particles from the
solution. The clear solution was transferred from these bottles and
was filtered using a 45 μm filter paper. The filtrate was analyzed for
various heavy metals using AAS.
Furthermore, blank tests i.e., sampling bottles filled with a
certain concentration of heavy metal without the geomaterial and
control experiments i.e., sampling bottles filled with the
geomaterials and the distilled water were performed to establish the
sorption capacity of the sample bottle and the trace level
concentrations of the concerned heavy metal residual present in the
geomaterial (Grolimud et al. 1995; Gao et al. 1997; ASTM D4646-
04). The obtained sorption capacity of the sample bottle and trace
level residual concentrations present in the geomaterial were used to
compute the corrected initial concentration of the solution, C
i
and
equilibrium solution concentration, C
e
, i.e., the concentration of
heavy metal present in the solution after equilibration time. Later,
the normalized mass of the heavy metal sorbed on the geomaterial,
C
s
, was computed using Eq. (1).
ܿ
௦
=ሺܿ
௜
− ܿ
௘
ሻ×ሺܮ/ܵሻ
(1)
3. RESULTS AND DISCUSSION
3.1 Effect of liquid to solid ratio (L/S)
To demonstrate the effect of liquid to solid ratio on mass of the
contaminant removed by the geomaterial, C
s
, the variation of C
s
with L/S was developed as shown in Figures 1 and 2. Furthermore,
the percent removal of concentration from 100 ml solution, PR, of
various heavy metals over a wide range of concentration values and
L/S were obtained using Eq. (2). The obtained results are presented
in Tables 3 to 4.
ܴܲ =
ሺ௖
೔
ି௖
೐
ሻ
௖
೔
× 100
(2)
It can be observed from the Figures 1 and 2 that, the amount of
heavy metal sorbed by the geomaterial varies nonlinearly with L/S
and its variation becomes insignificant at high L/S values. This may
be due to the mass of the contaminant present in the solution is
significantly high at large L/S values, as compared to the affinity of

Geotechnical Engineering Journal of the SEAGS & AGSSEA Vol. 46 No.4 December 2015 ISSN 0046-5828
18
the potential sorption sites available (Vengris et al. 2001; Bordas
and Bourg, 2001; Arnepalli et al. 2010). In addition, at high L/S
values dispersion of particles increases available sorption sites
between the particles, whereas at low L/S values aggregation and
flocculation decreases available sorption sites.
0 50 100 150 200 250
0
3x10
3
6x10
3
9x10
3
1x10
4
2x10
4
C
i
=100mg/l
Cr
Pb
Cu
Mn
Zn
Sorbed amount (mg/kg)
L/S
Figure 1 Variation of mass of the heavy metals sorbed by the clayey
soil with liquid to solid ratio
0 50 100 150 200 250
0
4x10
3
8x10
3
1x10
4
2x10
4
2x10
4
Sorbed amount (mg/kg)
L/S
C
i
=100mg/l
Cr
Pb
Cu
Mn
Zn
Figure 2 Variation of mass of the heavy metals sorbed by the
moorum with liquid to solid ratio
It can also be observed from the data presented in Tables 3 and 4
that, percent removal of heavy metal present in a 100 ml solution,
PR, decreases as L/S value increases, this is mainly because, at high
L/S values the mass of the geomaterial available for removal of
heavy metal from the constant volume of the solution, is quite low.
On the other hand for low L/S values, the number of sorption sites
available is significantly high when compared to the mass of the
contaminant present in the solution, which in turn increases the
sorption of heavy metals. Though the available sorption sites for
removal of heavy metals is high at a low L/S value, this scenario
may impose significant competition between the heavy metals and
desorbed cations such as Mg
2+
and Ca
2+
(Bittel and Miller, 1974).
This demonstrates the fact that, the efficiency of the geomaterial to
retain heavy metal increases with the increase of L/S, for a given
concentration value. It can also be noticed that, the rate of increase
in sorption due to increase in L/S value, is almost constant for all the
initial concentration of the different heavy metals considered in this
study. In view of the above mentioned facts, it is essential to
consider the effect of L/S while assessing the long term performance
of landfill liners.
Table 3 Percent removal of various heavy metals by clayey
soil over wide range of liquid to solid ratio
Heavy
Metal L/S Initial Concentration (mg/l)
≤ 100 ≤ 200 ≤ 300
≤ 600
Cu
10 99 96.5 87.5 73
20 94 89.5 79 64
50 76 68.5 56 45
100 59 51.5 35 22.5
200 22 19.5 16 13.5
Mn
10 92 86.6 75.5 64
20 83 75.5 62 48
50 58 47 30.5 20.5
100 25 20.5 14.5 11.5
200 19 15 9.5 6
Zn
10 96 85.5 71 58.5
20 90 76.5 53.5 36
50 47 37 23 15
100 25 19.5 12 8
200 14 11 6.5 5-3
Pb
10 98 97.5 96 94.5
20 95 94 91.5 88.5
50 87 85 80.5 72.5
100 52 45.5 35 25.5
200 33 30.5 25 20
Cr
10 99.5 98.8 97.5 96.5
20 99 98.5 97 93.5
50 98 94.5 87 75
100 96 83 62 44.5
200 65 52 34 23
Table 4 Percent removal of various heavy metals by moorum over
wide range of liquid to solid ratio
Heavy
Metal L/S Initial Concentration (mg/l)
≤ 100 ≤ 200 ≤ 300
≤ 600
Cu
10 99 98.5 97.5 96.5
20 99 98.0 95.0 87.5
50 94 88.0 78.0 66.5
100 80 70.0 55.0 42.5
200 41 34.5 26.0 20.0
Mn
10 99 98.0 95.5 85.0
20 97 90.5 78.5 57.5
50 90 73.0 49.0 31.5
100 46 37.5 25.5 18.0
200 26 22.0 15.5 10.5
Zn
10 99 98.5 97.0 88.5
20 97 92.0 81.5 63.5
50 86 73.0 52.5 35.5
100 52 41.0 25.5 17.5
200 28 22.0 13.5 9.0
Pb
10 99 98.5 97.5 97.0
20 98 97.0 95.5 94.5
50 92 90.0 85.5 76.5
100 82 74.5 62.0 50.5
200 58 51.5 41.5 33.0
Cr
10 100 99.0 98.5 98.0
20 99 98.5 98.0 97.5
50 99 97.0 92.5 80.5
100 98 89.0 73.0 55.5
200 75 64.5 49.0 39.0

Geotechnical Engineering Journal of the SEAGS & AGSSEA Vol. 46 No.4 December 2015 ISSN 0046-5828
19
3.2 Effect of Initial Concentration
In order to evaluate the effect of initial concentration of heavy metal
ions present in the solution on sorption characteristics of the
geomaterials, batch sorption experiments were carried out with
different initial metal ion concentrations. The obtained results are
graphically represented in the form of “variation of mass of heavy
metal sorbed by the geomaterial, C
s
, with initial concentration, C
i
”
and “variation of percent removal, PR, of heavy metals with initial
concentration C
i
,” for a L/S of 50 for the geomaterials and heavy
metals considered in this study, as depicted in Figures 3 and 4. It can
be observed from Figures 3 and 4 that the increase in initial
concentration of heavy metal results in an increase and decrease of
the amount of heavy metal uptake per unit weight of the sorbent and
percent removal rate of heavy metal, respectively. This may be
because at the high initial concentrations, the ratio of number of
moles of heavy metal to the available sorption sites is high as
compared to that of low initial concentration.
Furthermore, it can be observed from Figures 3 and 4 that the
removal of heavy metal chromium and lead are greater than 70
percent over a range of initial concentration (100-600 mg/l). In case
of copper there is slight drop in the removal rate at higher initial
concentrations, whereas for the manganese and zinc the removal rate
was reduced significantly as the initial concentration increases. The
difference in percent removal rate of different heavy metal ions at
the same initial concentration may be attributed due to the difference
in their chemical affinity and cation exchange capacity. In view of
the above facts, it can be concluded that the influence of initial
concentration of heavy metals on removal rate is highly depends on
the nature of the geomaterial and heavy metals (Ayala et al. 2008;
Shu-li et al. 2009).
0 300 600 900
0.0
4.0x10
3
8.0x10
3
1.2x10
4
1.6x10
4
2.0x10
4
0 300 600 900
0
20
40
60
80
100
120
Ci
(mg/l)
Ci
(mg/l)
Cs
(mg/kg)
Heavy metal
Cr Pb Cu Mn Zn
PR (%)
Figure 3 Effect of initial concentration on mass of heavy metal
sorbed and percent removal by the clayey soil
0 200 400 600 800
0.0
4.0x10
3
8.0x10
3
1.2x10
4
1.6x10
4
2.0x10
4
2.4x10
4
0 200 400 600 800
0
20
40
60
80
100
120
Ci (mg/l)
Cs
(mg/kg)
Heavy metal
Cr Pb Cu Mn Zn
C
i
(mg/l)
PR (%)
Figure 4 Effect of initial concentration on mass of heavy metal
sorbed and percent removal by the moorum
3.3 Effect of Sorbent
To demonstrate the influence of the sorbent/geomaterial nature on
sorption behaviour of heavy metals, the variation of mass of heavy
metals sorbed by geomaterials with initial concentration were
obtained. For the sake of briefness, the results corresponding to
copper is only presented in the form of Figure 5.
0 200 400 600 800
0.0
5.0x10
3
1.0x10
4
1.5x10
4
2.0x10
4
Geomaterial
CS
MO
C
s
(mg/kg)
Ci (mg/l)
Figure 5 Effect of sorbent on sorption behaviour of copper
It can be noticed from Figure 5 that moorum exhibited a higher
sorption affinity towards all heavy metals compared to that of the
clayey soil. Though the clayey soil contains a reasonably high clay
content as compared to that of moorum, still it exhibits a low
retention capacity for all the heavy metals considered in this study.
This may be attributed to the relatively low pH of the clayey soil
and presence of less reactive clay minerals in it (Kookana and
Naidu, 1998; Ouhadi et al. 2001). On the other hand moorum
exhibited high retention capacity, as its specific surface area and pH
is high and it also contains clay minerals such as illite and
montmorillonite in it.
3.3 Effect of pH
The solution pH plays a predominant role in determining the
sorption behaviour of heavy metals as the solubility of the heavy
metal, carbonates and phosphates depends on the pH of the solution
(Bruemmer et al. 1986). The pH of the solution also affects metal
hydrolysis; ion pair formation; organic matter solubility and surface
charge of iron and aluminum oxides and organic matter (Bruemmer
et al. 1986; McBride, 1994; Sauve et al. 1988).
In view of the above facts the present study attempts to evaluate
the influence of pH of the solution on the sorption behaviour of
various heavy metals on the selected geomaterials corresponding to
the L/S value of 50. It can be noticed that, the majority of the heavy
metals considered in this study may get precipitated at pH value 6
and above, hence pH of the model contaminant is maintained less
than 6 by adding 0.1M HNO
3
and
NaOH. The batch sorption
experiments were conducted by varying the solution pH from 2 to 5.
The results obtained for clayey soil and moorum are presented in
Figure 6 to 10.
It can be observed from Figures 6 to 10 that sorption of heavy
metal increases with increase in the pore solution pH of heavy metal
solution. It is conceivable that at low solution pH values, the higher
number of protons H
+
available in the solution and competes with
the positively charged heavy metal ions to get sorbed more on the
geomaterial. Further, as the pH increases and the balance between
protons, H
+
, and hydroxide ions, OH
-
, is predominant and only
positively charged metal ions get sorbed on the geomaterials (Forbes
et al. 1974; Farrah and Pickering, 1977) which results in an increase
in sorption capacity of the geomaterial.

Geotechnical Engineering Journal of the SEAGS & AGSSEA Vol. 46 No.4 December 2015 ISSN 0046-5828
20
0 200 400 600 800
0.0
5.0x10
3
1.0x10
4
1.5x10
4
2.0x10
4
0 200 400 600 800
0.0
5.0x10
3
1.0x10
4
1.5x10
4
2.0x10
4
CS
Cs (mg/kg)
Ce (mg/l)
pH
2 3 4 5
MO
Ce (mg/l)
Figure 6 Effect of solution pH on the sorption capacity of clayey
soil and moorum for heavy metal copper
0 200 400 600 800
0.0
2.0x10
3
4.0x10
3
6.0x10
3
8.0x10
3
0 200 400 600 800
0.0
2.0x10
3
4.0x10
3
6.0x10
3
8.0x10
3
CS
Cs (mg/kg)
Ce (mg/l)
pH
2 3 4 5
MO
Ce (mg/l)
Figure 7 Effect of solution pH on the sorption capacity of clayey soil
and moorum for heavy metal manganese
0 200 400 600 800
0.0
2.0x10
3
4.0x10
3
6.0x10
3
8.0x10
3
1.0x10
4
0 200 400 600 800
0.0
2.0x10
3
4.0x10
3
6.0x10
3
8.0x10
3
1.0x10
4
CS
Cs (mg/kg)
Ce (mg/l)
pH
2 3 4 5
MO
Ce (mg/l)
Figure 8 Effect of solution pH on the sorption capacity of clayey
soil and moorum for heavy metal zinc
Furthermore it has been noticed that the solution pH effect is
strongly evident for copper and lead when compared to other heavy
metals considered in this study. The reason for this behaviour is that
the surface complexation reactions associated with the lead and
copper are influenced by the electrostatic attraction between the
surface charge and the dissolved ions. Since the hydrated lead ion
have greater ionic radius (1.2 Å), it has lower charge density and
therefore, are more affected by the protonation of the surface groups
that limits the number of sorption sites on geomaterial. In addition to
this, the reduction in sorption affinity of heavy metal copper as
result of decrease in pH is probably due to the formation of ion
structure upon aquation (Farrah and Pickering, 1977). That is [Cu
(H
2
O)
6
]
2+
has tetragonal distortion due to the Jahn-Teller effect in
which the octahedral structure has been contracted along the x and y
axes (Nicholls, 1974). This contraction along the x
and y
axis results
in a structure having
four shorter bonds and two longer bonds which
lowers the energy of the ion structure and this hinders the binding of
the heavy metal copper with surface groups of the geomaterial and
this effect is more prominent when these groups are more protonated
(Charlet et al. 1993; Wanner et al. 1994).
0 200 400 600 800
0
1x10
4
2x10
4
3x10
4
4x10
4
0 200 400 600 800
0
1x10
4
2x10
4
3x10
4
4x10
4
CS
Cs (mg/kg)
Ce (mg/l)
pH
2 3 4 5
MO
Ce (mg/l)
Figure 9 Effect of solution pH on the sorption capacity of clayey
soil and moorum for heavy metal lead
0 100 200 300 400
0.0
5.0x10
3
1.0x10
4
1.5x10
4
2.0x10
4
2.5x10
4
0 100 200 300 400
0.0
5.0x10
3
1.0x10
4
1.5x10
4
2.0x10
4
2.5x10
4
CS
Cs (mg/kg)
Ce (mg/l)
pH
2 3 4 5
MO
Ce (mg/l)
Figure 10 Effect of solution pH on the sorption capacity of
clayey soil and moorum for heavy metal chromium
3.4 Competition and Selectivity Order of the Heavy Metals
To study the influence of solution composition on the sorption
characteristics of the geomaterials, batch sorption experiments were
conducted corresponding to L/S of 50 with single and composite
heavy metal solutions which contain different heavy metals such as
chromium, lead, copper, zinc and manganese. The results pertaining
to both single and composite heavy metal solutions are presented in
Figures 11 and 12.
It can be noted from Figures 11 and 12 that the percent removal
of heavy metal by the geomaterial corresponding to composite
solution is lower when compared to that of the single heavy metal
solution. This may be attributed to the competition among the heavy
metals not only for the potential sorption sites but also for
precipitation onto the geomaterial surface (Elliott et al. 1986).
When the single heavy metal solution is allowed to interact with
the geomaterial, only that particular heavy metal is involved with
the formation of the metal complex with the available hydroxyl

Geotechnical Engineering Journal of the SEAGS & AGSSEA Vol. 46 No.4 December 2015 ISSN 0046-5828
21
group. However if the metal solution contains more than one heavy
metal, there is a possibility of competition among the heavy metals
present in the solution to form metal complexes with that available
hydroxyl group, which leads to reduction of the sorption affinity of
the geomaterials towards the composite heavy metal solution.
0 200 400 600 800
0
20
40
60
80
100
0 200 400 600
0
20
40
60
80
100
C
i
(mg/l)
PR (%)
C
i
(mg/l)
Heavy metal
Cr Pb Cu Mn Zn
(a) single heavy metal (b) composite heavy metals
Figure 11 Percent removal of heavy metal by clayey soil
0 200 400 600
0
20
40
60
80
100
0 200 400 600
0
20
40
60
80
100
C
i
(mg/l)
PR (%)
C
i
(mg/l)
Heavy metal
Cr Pb Cu Mn Zn
(a) single heavy metal (b) composite heavy metals
Figure 12 Percent removal of heavy metal by morum
It can be noticed from Figures 11 and 12 that selectivity order of
heavy metals for both single and composite solutions seems to be
same and the observed order of selectivity is Cr >Pb >Cu >Mn ~Zn.
This order of selectivity of heavy metals can be substantiated by
considering chemical characteristics of heavy metals which are
adopted from the literature as presented in Table 5 (Wiklander and
Nilsson, 1954; Evans, 1966; Hsu, 1989; Schwertmann and Taylor,
1989; Sposito, 1986).
It can be noted that the selected geomaterials have shown higher
affinity towards the heavy metal chromium even its electro
negativity value is smaller than copper and lead, as depicted
Table 5. This anomaly may be due to the higher valence of the
heavy metal chromium (Smith and McGrath, 1990). It is also
observed that lead is the second most preferentially sorbed heavy
metal by both clayey soil and moorum geomaterials when compared
to the heavy metal copper. This finding may be substantiated by
considering the misono softness parameter of heavy metals which
determines the relative tendency of the metal to form covalent bonds
based on the ionic radius and the ionization potential (Sposito,
1989). Furthermore, the heavy metal zinc is preferentially sorbed
over manganese for the geomaterial moorum whereas in the case of
clayey soil, manganese is preferentially sorbed over zinc. Based on
the above facts it is concluded that, the selectivity of heavy metals
of similar valence can be determined approximately by considering
the misono softness parameter of heavy metals.
Table 5 Chemical characteristics of the heavy metals considered in
this study (Sposito, 1986)
Heavy
metal Valence Electro
negativity
Misono softness
parameter (nm)
Chromium 3 1.66 0.226
Lead 2 1.8 0.393
Copper 2 1.9 0.284
Zinc 2 1.6 0.240
Manganese 2 1.55 0.273
4. CONCLUSION
This study presents an investigation on the effects of the liquid to
solid ratio, initial concentration of heavy metals, nature of sorbent,
pH of solution and solution composition on the sorption of heavy
metals onto two types of geomaterials. Based on this study, the
following conclusions can be drawn.
 With the increase of liquid to solid ratio results decrease
of removal rate of heavy metal, however sorbed heavy
metal on unit mass (C
s
) of the sorbent increased at
equilibrium for both the geomaterials. Further, increasing
the initial heavy metal ion concentration leads to an
increase in the heavy metal uptake in the geomaterials.
 The nature of clay mineral present in the geomaterials
plays significant role in controlling the sorption
characteristics of the geomaterials compared to that of
amount of clay content present in the geomaterials.
 A unit change in the soil solution pH results in a
significant change in its retention capacity and hence the
sorption mechanism of heavy metals in the soils. The
decrease of solution acidity increases the amount of
sorbed ion on the sorbent.
 Both the geomaterials sorbed larger amounts of heavy
metals under the single component condition, indicating
the influence of solution composition on geomaterial
sorption performance.
 The higher valence heavy metals are preferentially sorbed
by geomaterials when compared to the lower valence
heavy metals.
 The selectivity of heavy metals of the same valence can be
approximately determined by considering the misono
softness parameter of heavy metals
The sorption capacity of geomaterials is significantly affected by
various parameters which should be considered while assessing the
long term performance of a landfill liner.
5. REFERENCES
Allen, H.E., Chen, Y.T., Li, Y. and Huang, C.P. (1995) “Soil
partition coefficients for Cd by column desorption and
comparison to batch adsorption measurements”.
Environmental Science and Technology, 29, pp1887-1891.
Arnepalli, D.N., Rao, B.H., Shanthakumar, S. and Singh, D.N.
(2010) “Determination of Distribution Coefficient of
Geomaterials and Immobilizing Agents”. Canadian
Geotechnical Journal, 47, pp1139-1148.

Geotechnical Engineering Journal of the SEAGS & AGSSEA Vol. 46 No.4 December 2015 ISSN 0046-5828
22
ASTM Standard D422 (1994) Standard test method for particle size
analysis of soils, Annual Book of ASTM Standards, 04.08,
ASTM International, West Conshohocken, PA, USA.
ASTM Standard D427 (1994) Standard test method for shrinkage
factors of soils by mercury method, Annual Book of ASTM
Standards, 04.08, ASTM International, West Conshohocken,
PA, USA.
ASTM Standard D4318 (1994) Standard test method for liquid limit,
plastic limit and plasticity index of soils, Annual Book of
ASTM Standards, 04.08, ASTM International, West
Conshohocken, PA, USA.
ASTM Standard D2487 (1994) Standard classification of soils for
engineering purposes (Unified Soil Classification System),
Annual Book of ASTM Standards, 04.08, ASTM
International, West Conshohocken, PA, USA.
ASTM Standard D4972 (2001) Standard test method pH of soils,
Annual Book of ASTM Standards, 04.08, ASTM
International, West Conshohocken, PA, USA.
ASTM Standard D4646 (2004) Standard test method for 24-h batch-
type measurement of contaminant sorption by soils and
sediments, Annual Book of ASTM Standards, 04.11, ASTM
International, West Conshohocken, PA, USA.
ASTM Standard D854 (2006) Standard test methods for specific
gravity of soil solids by water pycnometer method, Annual
Book of ASTM Standards, 04.08, ASTM International, West
Conshohocken, PA, USA.
ASTM Standard D698 (2007) Standard test method for laboratory
compaction characteristics of soils using light effort, Annual
Book of ASTM Standards, 04.08, ASTM International, West
Conshohocken, PA, USA.
ASTM Standard D2974 (2007) Standard test methods for moisture,
ash, and organic matter of peat and other organic soils,
Annual Book of ASTM Standards, 04.08, ASTM
International, West Conshohocken, PA, USA.
ASTM D5084 (2010). Standard test methods for measurement of
hydraulic conductivity of saturated porous materials using a
flexible wall permeameter. Annual Book of ASTM
Standards, 04.08, ASTM International, West Conshohocken,
PA, USA.
Ayala, A., Vega, J.L., Alvarez, R and Loredo, J. (2008) “Retention
of heavy metal ions in bentonites from Grau Region”.
Environmental Geology, 53, pp1323-1330.
Bittel, J.E. and Miller, R.J. (1974) “Lead, cadmium and calcium
selectivity coefficients on montmorillonite, illite and
kaolinite”. Journal of Environmental Quality, 3, Issue 3, pp
250-253.
Bordas, F.and Bourg, A. (2001) “Effect of solid–liquid ratio on the
mobilization of cu, Pb, Cd and Zn from polluted river
sediment, Water Air Soil Pollution, pp128, 391–400.
Bruemmer, G.W., Gerth, J. and Herms, U. (1986) “Heavy metal
species, mobility and availability in soils” Journal of Plant
Nutrition and soil Science, 149, pp382-398.
Cossu, R (2013) “Groundwater contamination from landfill
leachate: when appearances are deceiving!”. Waste
Management, 33, pp1793–1794.
Chang, T. W. and Wang, M. K. (2002) “Assessment of
sorbent/water ratio effect on adsorption using dimensional
analysis and batch experiments”. Chemosphere, 48, pp 419-
426.
Charlet, L., Schindler, P.W., Spadini, L., Furrer, G., and Zysset, M.
(1993) “Cation adsorption on oxides and clays: the aluminum
case”. Aquatic Science, 55, Issue 4, pp1015–1621.
Daniel, D.E., and Benson, C.H. (1990) “Water content-density
criteria for compacted soil liners”. Journal of Geotechnical
Engineering, 119, Issues 2, pp. 223–237.
Degryse, F., Smolders, E. and Parker, D. R. (2009) “Partitioning of
metals (Cd, Co, Cu, Ni, Pb, Zn) in soils: concepts,
methodologies, prediction and applications - a review”,
European Journal of Soil Science, 60, pp590-612.
Elliott, H.A., Linerati, M.R. and Huang, C.P. (1986) “Competitive
adsorption of heavy metals by soils”. Journal of
Environmental Quality, 15, pp214-219
Evans, R.C.(1966) An introduction to crystal chemistry. Cambridge
University Press, London.
Farrah, H. and Pickering, W.F. (1977) “The sorption of Lead and
Cadmium species by clay minerals”. Australian Journal of
Chemistry, 30, pp1417-1422.
Forbes, E.A., Posner, A.M. and Quirk, J.P. (1974) “The specific
adsorption of inorganic Hg (II) species and Co (III) complex
ions on goethite”. Journal of Colloid and Interface Science,
49, pp403-409.
Gao, S., Walker, W.j., Dahlgren, R., and Bold, J. (1997)
“Simultaneous sorption of Cd, Cu, Ni, Pb and Cr on soil
treatment with sewage sludge supernatant”. Water, Air and
Soil Pollution, 93, pp331-345.
Grolimund, D., Bokkovec, M., Federer, P., and Sticher, H. (1995)
“Batch experiments for sorption capacity of porous media”.
Environmental Science and Technology, 29, pp2317-2321.
Guney,Y., Koparal, S., and Aydilek, A.H., (2008) “Sepiolite as an
alternative liner material in municipal solid waste landfills”.
Journal of Geotechnical and Geoenvironmental Engineering,
134, Issues 8, pp1166–1180.
Gulec,N., Gunal, B.C., and Erler, A. (2001) “Assessment of soil and
water contamination around an ash-disposal site: a case study
from the seyitomer coal-fired power plant in Western
Turkey”. Environmental Geology, 40, pp331–344
Hesse, P.R. (1972) A textbook of soil chemical analysis, Chemical
Publishing, New York.
Hsu, P.H.(1989) Aluminium oxides and oxyhydroxides. In J.B.
Dixon and S.B. Weed (eds.), Minerals in soil environments,
ASA and SSSA, Madison, WI, pp379-438.
IS 2720, Part XXIV (1976) Methods of test for soils: Determination
of cation exchange capacity, Indian Standards Institute, New
Delhi, India, pp3-10.
JCPDS, (1994) Powder diffraction file, 44, 7354-CD ROM (PDF 1-
44), International Centre for Diffraction Data, Pennsylvania,
USA.
Kang, J., and Shackelford, C. (2010) “Membrane Behavior of
Compacted Clay Liners”. Journal of Geotechnical and
Geoenvironmental Engineering, 136, Issues 10, pp1368–
1382.
Kaya, A., and Durukan, S. (2004) “Utilization of bentonite-
embedded zeolite as clay liner”. Applied Clay Science, 25,
pp83-91.
Kumar, M. and Philip, L. (2006) “Adsorption and desorption
characteristics of hydrophobic pesticide endosulfan in four
Indian soils”. Chemosphere, 62, pp1064- 586.
Kookana, R. S., and Naidu, R. (1998) “Effect of soil solution
composition on cadmium transport through variable charge
soils”. Geoderma, 84, pp235-248.
Lakshmikantha, H. and Sivapulliah, P.V. (2006) “Relative
performance of lime stabilized amended clay liners in
diffeent pore fluids”. Applied Clay Science, 24, pp1425-1448
Liu, X. and Lu, X. (2011) “Correlation between Bentonite’s Cation
Exchange Capacity 594 (CEC) activated clay quality indexes
and activation strength”. Applied Mechanics and Materials,
99-100, pp1031-1034.
Mcbride, M.B. (1994) Environmental Chemistry of Soils. Oxford
University, Newyork.
Nicholls, D. (1974) Complexes, first row transition elements,
London: Basingstoke, Macmillan.
Ouhadi V.R., and Yong, R.N., (2001) “The Role and Influence of
Clay Fraction of Marly Soils on their Geotechnical and Geo-
environmental Performance”. Proceedings of the 3
rd
BGS
Geo-environmental Engineering Conference, pp216 - 223.
Roy, W.R., Krapac,I.G., Chou, S.F.G., and Griffith, R.A. (1991)
“Batch type procedures for estimating soil adsorption of

Geotechnical Engineering Journal of the SEAGS & AGSSEA Vol. 46 No.4 December 2015 ISSN 0046-5828
23
chemicals”. EPA/530/SW-87/006-F, USEPA, Washington,
DC.
Sauve, S., McBride, M. and Hendersnot, W.H. (1988) “Soil solution
speciation of lead (II): Effects of organic matter and pH”. Soil
Science Society of America Journal, 62, pp618-621.
Schwertmann, U. and Taylor, R.M. (1989) Iron oxides. In J.B.
Dixon and S.B. Weed (eds.), Minerals in soil environments,
ASA and SSSA, Madison, WI.
Shu-li, D., Yu-Zhuang, S., Cui-na, Y., and Bo-hui, X. (2009)
“Removal of copper from aqueous solution by bentonites and
the factors affecting it”. Mining Science and Technology, 19,
489-492.
Smith, S., and McGrath, S.P. (1990) Chromium and nickel. In
Alloway, B.J. (eds.) Heavy metals in soil. Glasgow,
Academic & Professional, London, pp. 125-150.
Sposito, G. (1986). Distribution of potentially hazardous trace
metals. Metal Ions Biological Systems, 18, pp1-20.
Sposito, G. (1989) The chemistry of soils, Oxford University Press,
New York.
Vengris, T., Binkiene, R and Sveikauskite, A. (2001) “Nickel,
copper and zinc removal from waste water by a modified clay
sorbent”. Applied Clay Science, 18, pp183-190.
Wagner, J.F. (2013) “Developments in clay Science”. Chapter 5.3,
Handbook of clay science, 5, pp663-676.
Wanner, H., Albinson, Y., Karnland, O., Wieland, E., Wersin, P.,
and Charlet, L. (1994) “The acid/base chemistry of
montmorillonite”. Radiochimica Acta, 66–67, pp157–162.
Wiklander, L., and Nilsson, E. (1954) “Ion release as influenced by
the mode of exchange”. Journal of Colloid Science, 9, pp223-
232.
Yong, R.N., and Di Perno, N. (1991) “Sources and characteristics of
waste: with specific reference to Canada”. McGill University,
Geotechnical Research Center, Geoenvironmetal Series.