Co-treatment of electroplating sludge, copper slag, and spent cathode carbon for recovering and solidifying heavy metals

Abstract Electroplating sludge, a hazardous solid waste product of the electroplating industry, presents a serious environmental pollution risk. In this study, an environmentally friendly process for solidifying and recovering heavy metals from electroplating sludge using copper slag and spent cathode carbon is proposed. Combining the results of toxicity characteristic leaching procedure tests, thermodynamic analysis, chemical analysis, X-ray diffraction analysis, and electron probe microanalysis, the Cr, Ni, Cu, Fe, and F transformation mechanisms were first probed during vitrification. Under optimal experimental conditions, the Cr, Ni, and Cu recovery ratios reached 75.56 wt%, 98.41 wt%, and 99.25 wt%, and they increased by 40%, 5%, and 5%, respectively compared with the currently utilized technique. Moreover, the toxicity leaching results of the slag indicate that the Cr, F, and Cu are stable, while Ni is easily leached from the (Fe,Ni)(Fe,Cr)2O4 and alloy phases. Under the optimal metal recovery conditions, the leaching concentrations of Cr, Cu, F, and Ni were 0.57 mg/L, 4.45 mg/L, 1.52 mg/L, and 1.85 mg/L, respectively, which can be reused in other materials, minimizing the environmental risk. The electroplating sludge, copper slag, and spent cathode carbon co-treatment process achieves waste disposal with waste and significantly reduces electroplating sludge processing costs.