Arsenic extraction from copper concentrate using controlled oxidative roasting and filtration process

Abstract

For more efficient treatment of arsenic-bearing copper concentrates, arsenic can be extracted in two steps: high-temperature filtration of dust and low-temperature separation of condensed arsenic oxide. The oxygen content in the roasting environment has an important effect on the residual arsenic content in the concentrate. When the oxygen content is high, the arsenate formed remains in the concentrate. When the oxygen content is low, the formation of arsenic sulphide can clog the filter cake residue. Roasting at 700 °C with an oxygen content of 4 vol.% results in the lowest residual arsenic content in the concentrate, from 11.8 to 0.34 wt.%. In the pilot experiment, the oxygen content was indirectly controlled by controlling the feed rate. The residual arsenic content is reduced to 0.48 wt.% and the purity of the recovered As2O3 reaches 99.17 wt.%. Based on the study of the mechanism of arsenic change with different oxygen contents, a new process of oxygen-controlled roasting is proposed and successfully applied in the pilot test, so that the residual arsenic content in copper concentrates is lower than the standard of arsenic content in imported minerals from China (0.5 wt.%).