Integration of selectrodialysis and solvent-impregnated resins for Zn(II) and Cu(II) recovery from hydrometallurgy effluents containing As(V)

The main challenge for copper smelters is to ensure product quality under the constant increase in impurities (As, Se, Mo, Co, Zn, Sb, and Pb) in copper ores that has occurred over the years. The presence of toxic elements, such as As(V), in acidic streams rich Cu(II) and Zn(II) (pH 2.0-2.5) limits the valorisation of both metals. In this study, a novel combination of the following two ion-exchange-based processes were proposed: i) membrane selectrodialysis (SED) for the selective separation of Zn(II)/Cu(II) from As(V) and ii) solvent-impregnated ion exchange (IX) resins for the selective separation of Zn(II) from Cu(II). The selective separation of As(V), which is present in solution as H3AsO4/H2AsO4-, is achieved using a combination of monocharge and non-monocharge selective cation-exchange membranes to avoid the co-precipitation of As(V) when IX resins are used for Cu(II)/Zn(II) recovery. This combination of processes represents the novelty of the present study since it could be used in hydrometallurgical industries to remove As(V) and, at the same time, to valorize two value-added metals [Cu (II) and Zn(II)]. At the moment, only single-stage processes have been proposed. Using SED, a Cu(II)/Zn(II)-rich stream [97 +/- 2% Cu(II) and 82 +/- 3% Zn(II)) was obtained, and 60 +/- 4% of As(V) was removed from the initial feed stream. Then, the separation of Zn(II) from Cu(II) was proposed using Lewatit VP OC 1026 resin at pH = 2.2 and 4.3, respectively. In this IX resin process, it was possible to recover 70 +/- 3% of Zn(II) and 98 +/- 2% of Cu(II) and to concentrate Zn(II) and Cu(II) around 30- and 23-times, respectively.