Abstract: Toxicity characteristic leaching procedure (TCLP) of zinc plating
sludge was carried out to assess the leaching potential of the sludge and the
leachates were analyzed for heavy metals. The concentration of zinc, chromium,
and lead in the leachate were 371.5 mg/L, 1.95 mg/L and 1.99 mg/L respectively.
Solidification of zinc sludge was carried out using four different binder
systems consisting of cement mortar, fly ash, clay and lime and cured for 28 d.
The ratio of sludge added varied from 60% to 80% by volume. The solidified
products were tested for metal fixing efficiency and physical strength. It was
observed that the volume of sludge added that resulted in maximum metal
stabilization was 60% for all the combinations, above which the metal fixation
efficiency decreased resulting in high values of zinc in the leachate. Addition
of 5% sodium silicate enhanced the chemical fixation of metals in all the
binder systems. Among the four fixing agents studied, mixture of fly ash: lime,
and cement mortar: lime stabilized zinc and other metals in the sludge
effectively than other combinations. Addition of lime increased the
stabilization of zinc whereas cement mortar increased the strength of the