Serious concerns have been raised from the solid waste processing field about minimizing the environmental footprint of electroplating sludge (ES), not only because of its hazardousness but also due to the rising demand for recycling non-renewable metal resources. A low-temperature alkaline matte smelting process is proposed in the present study. Na₂CO₃ was used as a flux reagent for smelting ES at 1250 °C, which is 100–250 °C lower than those previously reported. XRD and SEM–EDS revealed that the presence of Na species in the matte and slag phases was conducive to reducing the smelting temperature. The relationship between the processing parameters, i.e., Na₂CO₃, coal powder, and sulfur dosages, and the partitioning of Cu, Ni, and Cr were investigated for optimal metal recovery. A copper–nickel matte (Cu + Ni = 46.9 wt%) was produced. Cu and Ni recovery achieved 95% and 90%, respectively, while over 99% Cr was concentrated in the slag. The TCLP test indicated that heavy metal leaching toxicities of the slag were below the Chinese national identification standards (GB5085.3-2007) due to the formation of stable spinel phases and embedment of heavy metals in the glassy slag matrix.

Graphical Abstract