Fundamental studies on arsenic removal from copper concentrate by heat treatment

The arsenic content of copper ore for smelting is increasing in recent years. But high arsenic-containing copper ore or concentrate has disadvantage environmentally and economically because arsenic is harmful and should be treated decently in metallurgical process. In this paper, the fundamental experiment for the elimination of arsenic from copper concentrate by volatilization process as sulfide using heat treatment is discussed. A copper concentrate sample was used in this study. The sample was heat-dried for 24 hours, ground under 150 urn, and provided following analysis and experiments. The mineral composition was analyzed by XRD analysis, resulted in Chalcopyrite (CuFeS₂) and Pyrite (FeS₂). The semiquantitative analysis was performed by XRF, resulted in 0.2 wt% for arsenic, 33.4 wt% for copper, 25.1 wt% for sulfur, 19.1 wt% for iron, 9.9 wt% for oxgen, 4.9 wt% for silicon, and 3.0 wt% for aluminum. For removing arsenic, the sample was heated for 10 to 180 minutes to the temperature range of 673 K to 1173 K in silica furnance tube in inert atmosphere (Ar gas). The residue was dissolved in aqua regia, analyzed by ICP-AES in order to determine the quantity of residual arsenic. XAFS (X-ray adsorption fine structure) analysis was also conducted to find the chemical form of copper and arsenic in the ore and arsenic sulfide in the dust. The decomposition of the sample and volatilization of arsenic were observed above 773 K. A sharp decrease of residual arsenic in the sample was observed around 873 to 923 K and almost all arsenic was removed by volatilization from the sample over 973 K. Residual arsenic content in the sample was 0.019 wt% at 973 K and 0.004 wt% at 1173 K. XAFS analysis revealed that the main chemical form of arsenic in the dust was combintation of arsenic sulfide (AS2S3 and AS4S4).