Decomposition/volatilization of enargite in Nitrogen - Oxygen atmosphere

Enargite (Cu₃AsS₄) occurs as impurity in most Chilean copper sulfide minerals. However, when enargite content in copper concentrates is high (>1.5%), smelting of such a concentrate produces pollution problems and contamination of the final copper with arsenic. Thus understanding the behavior of enargite at high temperatures is crucial. In this paper, research data is discussed on the decomposition/volatilization of natural enargite mineral in nitrogen and oxygen-containing atmospheres by thermogravimetry and DTA analyses. The results indicated that enargite decomposes in nitrogen through intermediate tenantite to form Cu₂S in the range 600-900°C. However, in the presence of oxygen, enargite reacts forming CuO as final product. Temperature affects significantly the arsenic volatilization rate in inert and oxidizing atmospheres. At 900°C in pure nitrogen, 95 % arsenic volatilized in 15 min, while in the presence of 10 % oxygen, 95% of arsenic volatilized in 6 min. At higher oxygen concentration, the rate is even faster.