Immobilization of heavy metals in a contaminated soil using organic sludge char and other binders

The applicability of tannery (TSC) and dye sludge char (DSC) as a binder to immobilize heavy metals (Zn, Cu and Ni) in soil was investigated. The toxicity characteristic leaching procedure (TCLP) was used to estimate the immobilization efficiency for single-binders (TSC and DSC) and binary-binders (TSC or DSC combined with tripostassium phosphate (K ₃PO ₄) diammonium phosphate (DAP), lime or ladle slag). The immobilization efficiencies of Zn, Cu and Ni by TSC amendment were 84.2, 100.0 and 40.0%, respectively, which were higher than 28.5, 100.0 and 54.9% by DSC amendment for a binder dose of 0.80 g char/g soil. The binary-binder enhanced Zn immobilization to 56.3 and 97.2% at 0.6 g-DSC/0.06 g-Ca(OH) ₂ and 0.4 g-TSC/0.08 g-Ca(OH) ₂, respectively per 1 g dried soil. The immobilization efficiencies of heavy metals increased with aging for the DSC-binary binders, but not for TSC-binary binders.