Solidification process with enhancement of heavy metals insolubilization

Abstract

The process for immobilizing a hazardous waste containing heavy metals comprises the steps of pretreating the waste by adding a sulfide to the hazardous waste so as to generate the sulfides of the heavy metals from the hazardous waste, mixing a chemical reagent with the pretreated waste, and blending the mixture of the chemical reagent and the pretreated waste with a pozzolanic material. The chemical reagent contains a mixture of a retarder and an accelerator. This process further comprises the step of mixing a neutralizing reagent with the hazardous waste so as to cause the hazardous waste to have a pH of between 5 and 14. The neutralizing reagent is an alkaline material, preferably lime, hydrated lime, or calcium hydroxide. The sulfide is either sodium hydrosulfide or sodium sulfide. The process further includes the step of separating the pretreated waste containing the generated sulfides of the heavy metals from the supernatant portion of the liquid hazardous waste prior to the step of mixing the chemical reagent. The retarder of the chemical reagent is a monomeric polyalcohol. The accelerator is calcium chloride.