Characteristics and chemical speciation of waste copper slag.

Waste copper slag contains abundant valuable metal element Fe, and residual elements such as Cu, As, Pb, Zn, and Mo. Simply stockpiling or landfilling would waste valuable metal resources and cause contamination due to the leachable harmful elements. In this paper, the HJ/T299-2007 test and TCLP test have been utilized to evaluate the leaching toxicity of waste copper slag, while the sequential extraction procedure was carried out to investigate the different chemical speciation and the bioavailability of the residual metal elements in the waste copper slag. The results show that Pb in the waste copper slag exceeds the regulatory value of TCLP in the leaching tests, which means that the waste copper slag may contaminate the surrounding environment. According to the characteristics of the waste copper slag, the residual metal elements are mainly wrapped by the fayalite or silicate matrix. Cu and Fe are mainly in the form of crystalline iron-manganese oxide by the sequential extraction procedure, while Mo, As, and Zn are mainly in the residual form. Pb mainly exists in the form of carbonate, which is easy to be extracted. The orders of the apparent mobility and potential metal bioavailability of the selected residual metals are Pb>Cu>Zn>As>Mo>Fe.