The pH-dependent leaching behavior of slags from various stages of a copper smelting process: Environmental implications. (1st February 2017)

• Record Type: Journal Article
• Authors: Jarošíková, Alice; Ettler, Vojtěch; Mihaljevič, Martin; Kříbek, Bohdan; Mapani, Ben
• Is Part Of: Journal of environmental management. Volume 187(2017)
• Page Start: 178
• Page End: 186
• Publication Date: 2017-02-01
• Subjects: Copper slag -- pH-dependent leaching -- Solubility controls -- Slag re-processing -- Modeling; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2016.11.037
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: The leaching behaviors of primary copper (Cu) slags originating from Ausmelt, reverbatory, 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 14997 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, relatively high leaching of As was observed over the entire pH range, especially for Ausmelt slag (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 arsenates and the binding of As to newly formed Fe (oxyhydr)oxides play an important role in efficient As immobilization at the slag-water interface. In contrast, no controls were predicted for Sb, whose leaching was almost pH-independent. Nevertheless Sb leached concentrations at natural pH were below EU limit for hazardous waste. Re-processing of primary Cu slags for metal recovery, and subsequent co-disposal of the resulting slag tailing with dolomite-rich mine tailing and local laterite is suitable for stabilizing the remaining contaminants (except Sb) and limiting their leaching into the environment. Graphical abstract: Highlights: Metal(loid) leaching from Cu smelting slags is pH-dependent. High leaching of Cu, Cd, Pb and Zn under acidic conditions at pH < 5. Slags classified as inert wastes due to low metal leaching at natural pH (7.9–9.0). Insoluble Ca-Cu-Pb arsenates efficiently control As leaching from slags. Slag co-disposal with mine tailing and laterite helps to lower metal(loid) leaching.