CHAPTER -5
SPECIATION OF HEAVY METALS IN STABILIZED
MSW SAMPLE AND SBA: AN ASSESSMENT
5.1. Introduction
Measurement of the total concentration of the metals provides inadequate
information to assess the bioavailability, mobility and related toxicity of the heavy
metals. An evaluation of total metals levels following a strong acid digestion of the
sample may be useful as a global index of contamination in recent years interests in
determining the speciation of metals in environment samples has increased. The
application of this method has been used for atmospheric particulars by walter et al.,
(1989), sediments by Gonzalez et al., (1995).
In this study, sequential extraction procedure of Tessier et al., (1979) has been
used. The chemical partitioning of heavy metals in this method are represented by five
fractions of chemical phases like a) exchangeable metals b) bound to carbonates c)
bound to Fe-Mn oxides d) bond to sulphides and organic matter and e) residual
fraction.
a) Fraction 1- Exchangeable Fraction.
Metals extracted in the exchangeable fraction include weakly adsorbed metals
and can be released by ion-exchange process. Changes in the ionic
composition of the water would strongly influence the ionic exchange process
of the metal ions with the major constituents of the samples like clays,
hydrated oxides of iron and manganese.
b) Fraction 2- Bound to carbonates
The metals bound to carbonate phases are affected by ion exchange and
changes of pH. Significant amount of trace metals can be co-precipitated with
carbonates at the appropriate pH.
c) Fraction 3- Bond to oxides of Iron and manganese
Fraction 3 represents the presence of oxides between particles or coatings on
particles with large surface areas for absorbing trace metals. Under reducing
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conditions Fe(III) and Mn(IV) could release adsorbed trace metals .
d) Fraction 4-Bond to organic matter
Trace metals may be bound by various forms of organic matter, living
organisms
and
coating
on
mineral
particles
through
complex
or
bioaccumulation. These substances may be degraded by oxidation leading to a
release of soluble metals.
e) Fraction 5-Residual or Inert Fraction
Fraction largely consists of mineral compounds, where metals are firmly
bonded within crystal structure of the minerals.
In the present study chemical fractionation of metals like Chromium, copper,
lead, Cadmium and Mercury was carried out to evaluate their geochemical behaviour
like mobility and bioavailability.
The results obtained shows that the amounts of heavy metals extracted from
each fraction vary widely. The order of mobility of the metals considering their
abundance in the fractions is exchangeable>bound to carbonate>bound to
oxides>bound to organics> residual (Tessier et al., 1979). Oxides exists as nodules
and cement between particles. These oxides hold trace metals and can be mobilized
under reducing and acidic conditions. The organic phase is relatively stable in nature
but can be mobilized under strong oxidizing conditions due to degradation of organic
matter (Tessier et al., 1979; J.Haung et al., 2007).
5.2. Speciation of Heavy metals in Stabilized Municipal Solid waste
sample (SMSW) and Stabilized Bottom ash (SBA).
Industrial activities and disposing of materials like batteries, scrap metals etc.
leads to generation of large quantities of pollutants, especially heavy metals.
Sequential extractions are ideally used to dissolve different phases in a sample one
after one. This implies that any associated metals dissolve with their host phase
(Tessier et al., 1979; Trolard et al., 1995).in the present study an attempt has been
made to study the heavy metal speciation in stabilized MSW and Stabilized Bottom
ash collected from the previous experimentation of this work.
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5.2.1. Speciation of Heavy metals in Fe2O3 stabilized MSW sample and BA
sample
The concentrations of the heavy metals in Stabilized MSW sample and
Stabilized Bottom ash sample using Fe2O3 nano particle are shown in Table 5.1. and
Table 5.2. respectively.

The concentration of Cadmium and Mercury metal in stabilized MSW sample
was in BDL in all the fractions. (Table 5.1.)

Copper was less in Bound to oxides of iron and manganese form (F3) and inert
in bound to carbonates form (F2). (Table 5.1.)

Lead was present in smaller fraction to Bond to organic matter (F4) and inert
in Residual fraction (F5). (Table 5.1.)

Chromium was lesser in Bound to carbonates fraction (F2) and mainly found
in Residual or inert fraction (F5) as inert metal. (Table 5.1.)

The Cadmium and Mercury metal concentration in Stabilized Bottom ash
sample was BDL at all the fractions. (Table 5.2.)

In the present study the concentration of Copper was lesser in Residual form
(F5) and inert in bound to organic matter (F4). (Table 5.2.)

During the study the Lead concentration was lesser in Residual form (F5) and
more in bound to organic matter (F4). (Table 5.2.)

Slightly lower concentration of Chromium metal was bound to Residual
fraction (F5) and bounded in higher concentration to oxides of iron and
manganese fraction (F3). (Table 5.2.)
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Table. 5.1. Speciation of Heavy metals from Stabilized MSW sample (mg/kg)
Sl.no
Heavy
F1
F2
F3
F4
F5
metals
1
Cadmium
BDL
BDL
BDL
BDL
BDL
2
Copper
BDL
0.460
0.210
0.370
0.11
3
Lead
BDL
BDL
BDL
0.080
0.169
4
Chromium
BDL
0.040
0.060
0.120
0.095
5
Mercury
BDL
BDL
BDL
BDL
BDL
Table. 5.2. Speciation of Heavy metals from Stabilized BA sample (mg/kg)
Sl.no
Heavy
F1
F2
F3
F4
F5
metals
1
Cadmium
BDL
BDL
BDL
BDL
BDL
2
Copper
BDL
BDL
BDL
0.165
0.086
3
Lead
BDL
BDL
BDL
0.016
0.025
4
Chromium
BDL
BDL
0.180
0.140
0.107
5
Mercury
BDL
BDL
BDL
BDL
BDL
5.2.2. Speciation of Heavy metals in FeOOH Stabilized MSW sample and BA
sample.
The concentrations of the heavy metals in Stabilized MSW sample and
Stabilized Bottom ash sample using FeOOH nanoparticle are shown in Table 5.3. and
Table 5.4. respectively.
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
The concentration of Cadmium and Mercury metal in stabilized MSW sample
was in BDL in all the fractions. (Table 5.3.)

Copper was less in Bound to organic matter (F4) and inert in bound oxides of
iron and manganese fraction (F3). (Table 5.3.)

Lead was present in smaller fraction to Bond to organic matter (F4) and inert
in oxides of iron and manganese fraction (F3). (Table 5.3.)

Chromium was lesser in oxides of iron and manganese fraction (F3) and
mainly found in Residual or inert fraction (F5) as inert metal. (Table 5.3.)

The Cadmium and Mercury metal concentration in Stabilized Bottom ash
sample was BDL at all the fractions. (Table 5.4.)

In the present study the concentration of Copper was lesser in Residual form
(F5) and inert in bound to organic matter (F4). (Table 5.4.)

During the study the Lead concentration was in Residual form (F5). (Table
5.4.)

Slightly lower concentration of Chromium metal was bound to oxides of iron
and manganese fraction (F3) and bounded in higher concentration to organic
matter (F4). (Table 5.4.)
Table. 5.3. Speciation of Heavy metals from Stabilized MSW sample (mg/kg)
Sl.no
Heavy
F1
F2
F3
F4
F5
metals
1
Cadmium
BDL
BDL
BDL
BDL
BDL
2
Copper
BDL
BDL
0.162
0.030
0.065
3
Lead
BDL
BDL
0.186
0.080
0.049
4
Chromium
BDL
BDL
0.148
0.360
0.065
5
Mercury
BDL
BDL
BDL
BDL
BDL
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Table. 5.4. Speciation of Heavy metals from Stabilized BA sample (mg/kg)
Sl.no
Heavy
F1
F2
F3
F4
F5
metals
1
Cadmium
BDL
BDL
BDL
BDL
BDL
2
Copper
BDL
BDL
0.100
0.120
0.030
3
Lead
BDL
BDL
BDL
BDL
0.040
4
Chromium
BDL
BDL
0.037
0.200
0.190
5
Mercury
BDL
BDL
BDL
BDL
BDL
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