Effect of roasting parameters on arsenic removal from copper smelting dust

Abstract

In this study, we develop a roasting method for removing arsenic from sulfide copper-arsenic-containing materials. The object of the study was fine dust from copper smelting production of the following composition (wt%): 34.89 – Zn; 20.02 – Cu; 17.74 – Pb; 17.07 – Fe; 7.12 – As; 0.92 – Sb; 0.69 – Sn; 0.63 – Ca; 0.42 – Mo; and 0.34 – K. The chemical composition of the materials was analyzed using an SHIMADZU EDX-7000 energy dispersive X-ray fluorescence spectrometer and a Bruker D8 Advance diffractometer. The roasting process was carried out in a laboratory tube furnace at a temperature of 550–800°C for 60–120 minutes with the addition of 25–50% of FeS2 to the charge. Optimal conditions for reducing residual arsenic in the calcine to less than 0.3 wt% were identified: a temperature of 750–800°C, a duration of 1.5–2.0 h (in an inert atmosphere), and the use of 30 wt% of pyrite concentrate in the charge. Arsenic removal to the gas phase reached 91–96%. It is shown that in order to reduce the processing temperature to 600°C, it is necessary to add a reducing agent (coke fines) to the mixture of copper smelting dust with pyrite or increase the proportion of pyrite in the test charge to 50 wt% and hold the mixture for 1.5–2.0 h under inert atmosphere (argon and nitrogen) or low-oxygen blast. Arsenic removal to the gas phase reached 97%. X-ray spectral analysis of the residue deposited on the cooled ends of quartz tubes following the release of gases formed during roasting revealed that this material is predominantly (up to 93%) composed of arsenic. The resulting calcine contained 94 wt% of iron, zinc, copper and lead compounds. Therefore, the calcine obtained during the roasting of fine dust from copper smelting production is suitable for returning to the copper production process.