Copper slag: The leaching behavior of heavy metals and its applicability as a supplementary cementitious material

Abstract

In this study, copper slag (CS) was investigated in detail. The leaching mechanisms of the heavy metals in CS were identified via a pH-dependent leaching test combined with a sequential extraction procedure. Further, the applicability of CS as a supplementary cementitious material (SCM) was evaluated. The highest leaching concentration of the target heavy metals was observed under acidic conditions and decreased with the increasing pH. However, Ni, Pb, and Zn exhibited an upward leaching trend under alkaline conditions. Sequential extraction showed that Cd, which was considered to be the most mobile heavy metal, mainly existed in the exchangeable state. CS exhibited great potential with respect to usage as an SCM. The overall compressive strength of ordinary Portland cement (OPC)-based composites decreased with the incorporation of CS. When considering a CS content of 50 wt%, the overall compressive strengths of such composites were approximately 2.56 and 27.37 MPa after being cured for 3 and 28 days, respectively. Furthermore, the encapsulation effect associated with the OPC promoted the immobilization of the heavy metals in CS. Thus, the usage of CS as an SCM can meet the requisites for green construction.