Efficient removal and recovery of arsenic from copper smelting flue dust by a roasting method: Process optimization, phase transformation and mechanism investigation

The efficient removal and recovery of arsenic from copper smelting flue dust have received widespread attention due to its extremely high toxicity and carcinogenicity. In this research, a roasting method used for treating the dust at a relatively low temperature (300–400 ℃), with adding sulfuric acid and bitumite, was proposed, in which the reduction of As(Ⅴ) and oxidation of arsenic sulfides were achieved simultaneously. It was proved by thermodynamic analysis and experiments that adding sulfuric acid was favorable for the removal of arsenic, through enhancing the thermodynamic driving force and promoting the transformation of arsenate and arsenic sulfides to As2O3. The phase transformation of arsenic was analyzed using XRD, SEM-EDS and XPS, which indicated that coal addition, roasting temperature and H2SO4 dosage play essential roles in arsenic removal. Based on the lab-scale experiments, the optimal conditions for arsenic removal were found to be at the roasting temperature of 300–400 °C, roasting time of 2–3 h, coal addition of 5% and H2SO4 dosage of 0.2–0.3 mL/g. Around 98% of arsenic was volatilized from the dust, while arsenic content in the residue was decreased to 0.57%. Eventually, arsenic was recovered as As2O3 with a high purity of 99.05%.