Fundamental Insights in Alcoholic Ammoniacal Systems for Selective Solvometallurgical Extraction of Cu, Zn, and Pb from Tailings

摘要

This study investigates the use of novel alcoholic ammoniacal systems for the extraction of Cu, Zn, and Pb from Fe-rich residue materials as an alternative technology to traditional aqueous ammoniacal extraction. To this purpose, methanol- and ethanol-based ammoniacal solutions were prepared with several ammonium salts (ammonium chloride, -acetate, -carbonate, and -sulfate) and tested for their metal extraction potential (i.e., metal solubility and selectivity) in synthetic systems with metal sulfate salts of Cu, Zn, Pb, and Fe. The obtained metal solubility results were interpreted by modeling the conditions of the different alcoholic ammoniacal systems (NH3 concentration, pH), and used to select the most promising extraction systems. Furthermore, the initial alkalinity of these selected ammoniacal systems was adapted with stoichiometric NaOH additions, which proved to be a determining factor for the NH3 concentration and the pH and, thus, also for the metal solubility and selectivity. Finally, in a case study on the extraction of Cu, Zn, and Pb from a roasted sulfidic tailing, the ammonium acetate NaOH methanol solution and the ammonium chloride methanol solution showed promising metal extraction efficiencies for Zn (>40) and Cu (>27), while a very low Fe concentration in the extraction solution was assured (<0.3 mM). These results warrant further research to reveal the full potential of non-aqueous ammoniacal metal extraction.