Treatment of copper (II)-loaded aqueous nitrate solutions by polymer enhanced ultrafiltration and electrodeposition

In this investigation the main design parameters of a process for the recovery of copper (II) ions from synthetic aqueous solutions have been obtained. The proposed process comprises the following stages: metal ion retention, polymer regeneration and metal recovery. Metal ion retention was performed by a batch polymer enhanced ultrafiltration (PEUF) process. For this, a bench-scale plant configured in closed-loop has been used. Selected water-soluble polymer was an industrial grade antiscalant called Colloid 208® (poly(acrylic acid) sodium salt, Mw 50,000 g mol−1). This polymer is responsible to sequester metal ion and to form macromolecular metallic complexes that can be rejected by an UF ceramic membrane (Carbosep M5; 10,000 Da). Temporal decrease of permeate fluxes has been reproduced with an empirical fouling model and evolution of metal rejection coefficients was estimated with a model taking into account chemical equilibriums in solution and mass conservation equations. Polymer regeneration and metal recovery stages have been tackled by both chemical (diafiltration) and electrochemical (electrodeposition) points of view. Electrodeposition showed more advantages, namely null water consumption, recovery of copper in its most valuable form and absence of regeneration solutions to be treated or reused. Moreover, it has been checked that polymer did not suffer oxidation or reduction reactions because of the electrochemical stage.