Sewage sludge can provide a washing agent for remediation of soil from a metallurgical area

The search for washing agents recovered from waste is a new trend in the washing of soils contaminated with heavy metals (HMs). In the present study, dissolved organic matter (DOM) recovered from sewage sludge was used to remediate soil that originated from a metallurgical area and was contaminated with Cu (8109 mg kg−1), Pb (1473 mg kg−1) and Zn (531 mg kg−1). At pH 4 and a washing agent concentration of 4 g TOC dm−3, HMs removal proceeded according to pseudo-second-order kinetics with a relatively short equilibrium time (120 min). DOM was especially effective for removing Cu; in double washing, Cu removal was 5854 mg kg−1 (process effectiveness 72%), Zn removal was 258 mg kg−1 (process effectiveness 50.5%), but Pb removal was low (131 mg kg−1; 8.7%). DOM effectively removed metals from the exchangeable and acid soluble fraction. Based on the reduced partition index (IR), the intensity of Cu and Zn bonding in soil washed with DOM was twice as high as that in unwashed soil. Thus, DOM can serve as an effective washing agent for remediating soils contaminated with Cu and Zn, but it is not useful for removing Pb.