Minor elements distribution during the smelting of WEEE with copper scrap

The disposal of waste electrical and electronic equipment (WEEE) into landfill is no longer acceptable in most countries. WEEE contains toxic materials which cause environmental damage when they leach from landfill, but it also contains significant amounts of valuable metals and thus represents a potential resource for these metals. Reprocessing WEEE presents many technical challenges. The combination of metals found in WEEE is not the same as that found in ores, so the smelting techniques and slag systems that produce good recoveries of valuable metals from concentrates may not also produce high recoveries from WEEE. One attractive option for reprocessing WEEE is to add it to the feed to a secondary copper smelter using the traditional black copper route. Good examples of valuable minor elements in WEEE are tin and indium. The distribution behaviour of tin in common slags in copper smelting, calcium ferrite slag and ferrous silicate slag, is known but the behaviour of tin in ferrous calcium silicate slag is unknown. The way in which indium distributes in such a smelting circuit is also unknown because it is not a significant impurity in most copper ores. In this work the distribution of tin and indium between molten copper and slags whose compositions lie within the CaO-SiO2-FeOx (FCS) slag system has been reviewed. The results of experimental determinations of the tin and indium distribution at 1300oC have been reported and were used to calculate the activity coefficient of tin oxide and indium oxide in the slags. The activity coefficient data was utilised in a thermodynamic model of a secondary copper smelter to predict the way in which tin and indium deports to the various phases during the major processing stages.<br>