The aim of the present study was to devise and validate an appropriate treatment process for disposal of
hazardous barium and cyanide waste into a landfill at a Common Hazardous Waste Treatment Storage
Disposal Facility (CHWTSDF). The waste was generated during the process of hardening of steel
components and contains cyanide (reactive) and barium (toxic) as major contaminants. In the present
study chemical fixation of the contaminants was carried out. The cyanide was treated by alkali chlorination
with calcium hypochlorite and barium by precipitation with sodium sulfate as barium sulfate. The
pretreated mixture was then solidified and stabilized by binding with a combination of slag cement,
ordinary Portland cement and fly ash, molded into blocks (5 5 5 cm) and cured for a period of 3, 7
and 28 days. The final experiments were conducted with 18 recipe mixtures of waste þ additive:binder
(W:B) ratios. The W:B ratios were taken as 80:20, 70:30 and 50:50. The optimum proportions of additives
and binders were finalized on the basis of the criteria of unconfined compressive strength and leachability.
The leachability studies were conducted using the Toxicity Characteristic Leaching Procedure. The
blocks were analyzed for various physical and leachable chemical parameters at the end of each curing
period. Based on the results of the analysis, two recipe mixtures, with compositions e 50% of
[waste þ (120 g Ca(OCl)2 þ 290 g Na2SO4) kg1 of waste] þ 50% of binders, were validated for in situ
stabilization into a secured landfill of CHWTSDF