Environmental Engineering Reference
In-Depth Information
Response Surface Methodology followed in the present study showed a
significant improvement in the quality of jarosite waste composite bricks to
meet both the satisfactory condition to meet the engineering properties for use
in construction application as well as the toxic elements leachate concen-
trations were below the recommended values for its utility.
From the present study, jarosite waste seems to be a potential resource,
which has to be recycled in a technically feasible and environment friendly
manner. Response Surface Methodology model employed in this study showed
that application of 36.5% Jarosite waste, 40.5% Clay and 23% CCRs is the
optimum mix design, as an intermediate condition, to achieve desirable
compressive strength (62.92 kg/cm
2
), water absorption (18%); shrikage (14 %)
and density (1.7 gm/cm
3
) together with the low leachate concentration of lead
(< 5 ppm)
.
and cadmium (< 1ppm) and other toxic elements in the jarosite
waste composites for the efective utilisation. The model predictions for brick
properties at a given set of brick and the overall desirability value for these
brick mixtures is 0.973 and 0.887. The
predicted results were compared with
the experimental data and confirmed that the response characteristics are
identical and also which meet the quality standard (BIS 2248:1992) for
construction applications. It is evident from the present study that during
sintering process under solid-state reaction, toxic substances/elements in
jarosite waste were detoxified / immobilized through complexing in the
silicate matrix. In the present study, this was achieved through sintering
solidified products at 960
0
C 2
0
C. During firing of jarosite waste s/s jarosite
waste composite bricks, a considerable amount of liquid phase was expected to
be formed, which might have reduced the porosity and specific surface area
under the capillary tension forces in the fine pores of the s/s jarosite waste
sintered products resulting less water absorption and higher compressive
strength and this was further confirmed from the SEM microstructure of the
fracture surface of the composite bricks. Due to the above mechanism, the
leaching potentials of toxic elements such as Pb, Cd,Cr, As, Se, Ag, Ni, Zn in
the s/s products were found lower concentration than that of the permissible
limits reported in the USEPA-TCLP standard for non hazardous category and
extended the scope for the utility of the jarosite waste and other mineral wastes
for value added applications.
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