Relationship between mineralogical phase and bound heavy metals in copper smelting slags

The migration and transformation of hazardous metals in copper smelting slags (CSS) threats the environment. However, the unclear relationship between phases and heavy metals in CSS hinders the development of harmless technology. In this work, we investigated the mineralogical composition of CSS and the corresponding heavy metal distribution, and explored the relationship between mineral phases and bound heavy metals. Fayalite (47.4%) was identified as the main phase in CSS by XRD refinement along with other phases of hedenbergite (38.7%), magnetite (11.0%) and iron (2.9%). Heavy metals mainly distributed in fayalite and less in hedenbergite and other phases. The specific sequential extraction showed fayalite was difficult to extract since 89.7% arsenic, 85.0% lead and 76.9% copper were tightly bound with these minerals. It meant that fayalite had a much stronger binding ability with heavy metals than that of other phases. Fayalite could transform into magnetite during alkali disaggregation resulting in the changing of heavy metal binding from strong to weak. This work is an approximation to break through the bottleneck of phase identification and binding relationship of heavy metals in CSS, and provides novel approaches and theoretical evidence for the CSS and similar smelting slags harmfulness treatment.