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 non-hazardous waste) was observed at natural pH (7.9–9.0) for all the studied slag samples. In contrast, Al solubility from the Ausmelt slag was significantly higher (exceeding the EU limit for hazardous waste by 1.7×). However, geochemical modeling and scanning electron microscopy indicated that formation of stable Ca–Cu–Pb phases and the binding of As to newly formed Fe (oxy)hydroxides play an important role in efficient immobilization at the slag-water interface. In contrast, no controls were predicted for Sb, whose leaching was pH-independent. Nevertheless, Sb leached concentrations at natural pH were below EU limit for hazardous waste. The processing of primary Cu slags for metal recovery, and subsequent co-disposal of the resulting slag tailing with dolomite-rich mine tailing and local laterites is suitable for stabilizing the most hazardous co.