Thermodynamic modeling of selenide matte converting

A by-product of the electrorefining of anode copper is a slime that contains significant amounts of silver, as well as selenium, copper, and other minor elements such as gold. Slimes are usually smelted to recover silver and gold. The thermodynamics of the smelting of such selenium-rich materials have received scant attention, and the little that has been done leads to erroneous predictions. In this work, a chemical potential diagram is developed that successfully explains previously published observations. The smelting of slimes was also modeled with a computational thermodynamics package. Despite the simplicity of the model, which assumed that the activity coefficients of all species remained constant throughout oxidation, it gave good agreement with experimental results published elsewhere for the compositions of all phases during smelting. The model was used to demonstrate that using air rather than pure oxygen significantly affected only the selenium content of the slag, reducing it to low levels. Smelting temperature in the range tested was shown not to be an important process variable.