Coprecipitation of As, Zn, Cu and Pb into secondary iron minerals from sulfide wastes of Berikul mine (Russia)

摘要

Accumulation of As, Zn, Cu, and Pb in different secondary phases during supergenic weathering of high-sulfide wastes (40-45 wt% of sulfides) is considered. Sulfide oxidation leads to generation of acid pore solutions (pH=1.6-1.9) containing high concentration of SO_4~(2-)(160-200 g/L), Fe (30-75 g/L), As (11-50 g/L), Zn (0.4-4 g/L), Cu (0.2-0.6 g/L), and Pb (0.03-0.04 g/L). From these solutions As is precipitated as amorphous mixture of iron arsenates and sulfoarsenates in a deep horizons of wastes. Zn and Cu are incorporated into sulfates of divalent iron: melanterite (Zn - 0.34 wt%, Cu - 0.24 wt. %) and rozenite (Zn -1.0 wt%, Cu - 0.16 wt%). Pb, mainly, is coprecipitated with minerals of jarosite group. In jarosite the Pb content reach up to 4.3 wt%. Coprecipitation of toxic elements with sulfates and sulfoarsenates of iron is shown to be a very important mechanism controlling concentration of heavy metals in pore solution of high-sulfide mine wastes.