Membrane selective recovery of HCl, zinc and iron from simulated mining effluents

This work proposes a flowsheet based on the combination of membrane processes for the effective recovery of value-added components contained in mining effluents with high concentration of hydrochloric acid and metal anionic and cationic chloro-complexes. A representative case of study has been selected consisting of a solution of zinc and iron that under the studied conditions were solubilized forming anionic and cationic chloro-complexes. The high complexity of the system requires of a selective membrane-based solvent extraction step to successfully achieve the separation of cationic iron from a solution containing the acid together with anionic species of zinc followed by a diffusion process through ion conductive membranes for acid recovery; in this step electrodialysis was selected searching for the optimum trade-off between process kinetics and separation selectivity. Although the quantitative results are case-dependent, the methodology can be well extended to any mining leaching effluent coming from the use of HCl as leaching agent and containing metal chloro-complexes.