An investigation on reuse of Cr-contaminated sediment: Cr removal and interaction between Cr and organic matter

Sewage sludge, mine tailing and dredged sediment, as well as wastewater rich in heavy metal, pose threats to biota life and their treatments are thorny issues. A novel strategy using Cr-contaminated sediment to treat wastewater containing heavy metals is proposed in this study. The Cr-contaminated sediment (Cr-CS) is used to remove hexavalent chromium (Cr(VI)) from wastewater. Experimental results show that the background Cr concentration in the sediment has little influence on the removal efficiency of total Cr under the examined conditions (300–1,000 mg kg−1). The existence of organic matter favors the reduction of Cr(VI), but has limited effect on the removal of Cr(III). The total Cr removal process involves reduction, adsorption and precipitation, and is highly pH-dependent. The optimum pH values for Cr(VI) reduction and Cr(III) removal are determined as 1.0 and 4.0, respectively. The removal efficiency of total Cr under optimum conditions reaches 95.8%. The results also suggested co-existent heavy metals (Cd, Cu, Pb, and Ni) were hard to release to the water under experimental conditions (i.e., the release amounts are ranged from 0.0035 to 0.055 mg L−1 for Cd, Cu, Pb, and Ni, respectively, which can achieve the comprehensive sewage discharge standard). This work demonstrated that use of some heavy-metal-contaminated sediments to treat wastewater containing the same heavy metal could be a feasible approach.

The treatment of sediments containing excess heavy metals requires high overall cost. We proposed a feasible strategy to reuse the Cr contaminated sediment to treat wastewater containing Cr, and the enriched heavy metal may be recycled.Figure optionsDownload as PowerPoint slideHighlights
► A strategy using the Cr-contaminated sediment to treat Cr wastewater was proposed.
► The parameters influencing the removal efficiencies of total Cr were obtained.
► The release of co-existent heavy metals and Cr removal mechanism were studied.