The huge quantity of coal ash produced in
Indian thermal power plants is disposed of in ash landfills
or ash ponds. The deposition of ash in ash ponds through
conventional lean slurry form is viewed as a major
potential release of many environmentally sensitive heavy
metals due to possible contamination with ground water.
An attempt has been made in this paper to assess the
leachability of the heavy metals such as Cu, Pb, Ni, Co, Zn,
Cd, Hg and As from two Indian power plant ash samples in
the presence of some selective low-cost additives. The
additives used for the study were sodium silicate (Na
2-
SiO
3∙5H
2O), Reetha fruit (botanical name:
Sapindus Mukorossi
) extract, banana leaf extract, Aloe vera juice and
active carbon. By adopting short duration (7 days) batch
leaching test and toxicity characteristics leaching procedure
(TCLP), the behaviour of various heavy metal ions
released in water influenced by small dosage of these
selective additives has been analysed. By introducing the
same additives, the rheological behaviour of the two fly ash
samples at high solids concentration (
CW = 55–67.5 % by
weight) was carried out using a HAAKE rotational
rheometer (model: RheoStress 1, Thermo Fisher Scientific).
The influence of small dosage of these additives on
rheological parameters of the ash-water slurry has been
discussed.
