Formation mechanism of zinc-doped fayalite (Fe2-xZnxSiO4) slag during copper smelting

[Display omitted] •The occurrence state of zinc in the copper slag is obtained theoretically.•Zn(II) substitutes for the iron sites in the internal SiOFe(II) (M2) bond to form Fe2-xZnxSiO4.•Formation mechanism is actually an ion exchange process between Zn(II) and Fe(II).•The priority of the substituting for the iron site in the fayalite structure is proved by MS software calculation. The interactions between Fe2SiO4 and ZnO play an essential role in the recovery of zinc from copper slag. The dissolution and substitution mechanism of ZnO in fayalite were investigated by using TG-DSC, XRD, PPMS DynaCool, XPS, Mossbauer and SEM-EDS analyses and compared with MS calculation results. The results indicate that the dissolution and substitution are actually processes of the penetrating dissolution of Zn(II) ions that can be divided into three steps: 1) ZnO dissociates into Zn1-yO and Zn(II) ions; 2) Zn(II) penetrates the gap of the octahedron outer layer to substitute Fe(II) sites in the internal structure of SiOFe(II) (M2) to form (Fe2-x, Znx)SiO4; 3) Fe(II) is forced to migrate to the surface of (Fe2-x, Znx)SiO4 to form (Zn1-y, Fe(II)y)O. These findings can be derived the occurrence state and distribution of zinc in copper slag theoretically.