Pyrometallurgical elimination of arsenic from copper with a calcium flux

摘要

This paper presents the results from research work carried out on the thermal properties of copper thioarsenites under neutral and oxidizing conditions. The experimental work led to the determination of thermodynamic properties of synthetic copper thiosalts, analogs of the natural minerals tennantite and enargite. The mechanism for arsenic elimination from mattes into a slag and a gaseous phase was determined in laboratory tests. Addition of calcium containing industrial residues to arsenic contaminated copper matte led to a twofold reduction of arsenic in the matte. The elimination of arsenic during the fire refining of copper was also evaluated. Results show that in the current practice, this is achieved by over oxidation of copper and by the dissolution of fluxes in a copper oxide rich slag. This work proposes to achieve this effect by using low melting borax containing slags. In this case, copper overoxidation can be reduced by a factor of 4 to 5 times while also attaining a high degree of arsenic elimination (96-98%). The process of arsenic elimination in weakly-oxidizing conditions is more economical than the present practice as a result of the much lower use of hydrocarbons for back reduction of the copper oxides.