Extracting heavy metals from municipal and industrial sludges

Abstract This study used acidity, ethylenediaminetetracetic (EDTA) and nitrilotriacetic (NTA) acids treatment processes to explore the removal efficiencies of heavy metals from urban and industrial sludges. The results indicate that the optimum treatment efficiencies of heavy metals extraction from sludge are related to the species of heavy metals in sludge, dosage of extractants and the reaction time. The removal efficiency of a three-stage countercurrent process was higher than those of single-stage processes. The reaction kinetics can be expressed by the equation d C /d t = − KC . The cost of the acid treatment process per unit weight of heavy metal extracted was lowest in conditions of high heavy metal concentrations, but the EDTA process was the cheapest with low heavy metal concentrations.