The pH dependent leaching behavior of sl

The leaching behaviors of primary copper (Cu) slags originating from Ausmelt, reverberatory, and converter furnaces operating under a single technological process were compared to a residual slag tailing obtained by slag re-processing via flotation and metal recovery. The EN 12457-2 leaching test, used for assessment of the hazardous properties, was followed by the CEN/TS 1497 pH-static leaching test (pH range 3–12). Both leaching experiments were coupled with a mineralogical investigation of the primary and secondary phases as well as geochemical modeling. Metals (Cd, Cu, Pb, Zn) exhibit the highest leaching at low pH. Under acidic conditions (pH 3–6), Ausmelt slag and slag tailing exhibited higher metal leaching compared to other slag types. Very low leaching of metals (far below EU limits for nonhazardous waste) was observed at natural pH (7.99–0.90 for all the studied slag samples). Electron microscopy indicated that formation of stable Ca–Cu–Pb phases plays an important role in efficient immobilization at the slag-water interface. The geochemical modeling suggested differing metal speciation based on pH levels, indicating the importance of understanding these behaviors for environmental implications.