Environmental risk assessment and stabilization/solidification of zinc extraction residue: II. Stabilization/solidification

Heavy metal contamination is an important problem that is encountered at many metallurgical sites. Solidification/stabilization is a widely applied remediation technology for heavy metal contamination. In the study, solidification and stabilization of zinc extraction residue containing some heavy metals (e.g. Pb, Zn, Cd, Mn) which can leach using Portland cement, fly ash and lime was examined. Zinc extraction residue was solidified and stabilized with different amounts of Portland cement, fly ash and lime for heavy metal immobilization. Leaching behavior of all solidified/stabilized products was tested by pH dependent batch leaching test, Toxicity Characteristic Leaching Procedure (TCLP) and Synthetic Precipitation Leaching Procedure (SPLP). The results were evaluated in order to determine if the solidified/stabilized products can be disposed of at a landfill site with domestic waste or at a segregated landfill. Mechanical strength decreases with increase in the waste content. Heavy metals in the waste could be considerably immobilized by the solidification/stabilization process.

Research Highlights
► A monolithic solid of high structural integrity is obtained with mixing of Portland cement (40%) and the zinc extraction residue. Extractable heavy metals in the waste can be successfully immobilized with Portland cement and fly ash. Lead in the form of anglesite found in the waste is transformed into susannite and cerrusite minerals by solidification/stabilization treatments.