Recovery of Cu-Fe-S matte from electroplating sludge via the sulfurization-smelting method

Abstract

In this work, Cu-Fe-S matte was prepared from the electroplating sludge (ES) via the sulfurization-smelting process. The recovery extents of Cu and Fe are 99.60% and 10.07%, respectively, demonstrating that the selective recovery of Cu was achieved using this process. The recovered matte (70%Cu-11%Fe-S) can be utilized as the raw material to produce pure Cu. Two kinds of ES (sulfur-containing electroplating sludge and phosphorus-containing electroplating sludge), with the main compositions of CaSO4-CuO-Fe2O3 (SES) and CuO-CaF2-CaO-P2O5 (PES), were mixed and co-reduced by carbon at 1000 ℃. At this stage, the CaSO4 in SES was utilized as the sulfurization agent to sulfurize the CuO to Cu5FeS4. The generated Cu5FeS4 was then separated from slag via smelting at 1500 ℃. During the smelting process, SiO2 was added as flux, and two immiscible phases, liquid Cu-Fe-S matte and molten slag, were formed. After cooling, the Cu-Fe-S matte with the main phase of Cu5FeS4, as well as the vitrified slag, was obtained. The leaching concentrations of toxic elements Cu, P, and F of slag were lower than the thresholds, and thereby, this slag can be safely used as the construction material.