Distribution of elements between copper and FeOx–CaO–SiO2 slags during pyroprocessing of WEEE: Part 2 – indium

Abstract

Electronic waste (WEEE) is being generated at a rapidly increasing rate and leading to the removal of scarce and valuable metals from the materials cycle. The search for efficient WEEE reprocessing methods requires reliable data on the distribution of these valuable metals during smelting. In this work the distribution ratio of indium between FeOx–CaO–SiO2 slags and copper was examined at an oxygen partial pressure of 10−8 MPa (10−7 atm) and at 1300°C. The indium distribution ratio was strongly dependant on the CaO content, decreasing as the CaO content increased, but relatively unaffected by the Fe/SiO2 ratio of the slag over the range examined. Indium was inferred to be present in slag as InO1·5. The activity coefficient of InO1·5 was calculated and presented as iso-activity coefficient curves on the copper-saturated FeOx–CaO–SiO2 phase diagram. Volatilisation of indium under the oxidising conditions used in this work was insignificant, and it was shown that this is consistent with theoretical expectations. Only in much lower oxygen partial pressure environments can indium volatilisation be expected.