Extraction-Stripping Patterns during Co-Extraction of Copper and Nickel from Ammoniacal Solutions into Emulsion Liquid Membranes Using LIX 84I®

Extraction of nickel and its co-extraction with copper from ammoniacal media into emulsion liquid membrane systems (ELMs) was investigated using LIX 84I as the carrier. Measurement of the solute stripped in the internal phase of emulsion opened a new dimension in the study of the ELM extraction processes. The effect of operating parameters such as feed pH, initial feed concentration, and treat ratio of emulsion to feed and the effect of emulsion parameters such as internal phase stripping acid concentration, carrier concentration, and internal phase volume fraction were investigated. The optimal pH for extraction was 8.1. The overall extraction process was strongly favored by the factors that lead to enhancement of uptake of metal ions such as increase in the carrier concentration and the treat ratio. Investigations on the stripping patterns in W/O emulsions revealed that sulfuric acid of 1.0 M concentration was optimal for nickel stripping in ELMs but the process was slow. Stripping of copper was relatively fast and was favored by higher acid concentrations. The amount of nickel extracted declined in the presence of copper during co-extraction of copper and nickel and the amount of copper stripped in the internal phase of the emulsion was equivalent to the amount of nickel loaded by the emulsion. In general, almost 55% of the metal loaded in the emulsion was found to get stripped in the duration of the runs. Hence, there is scope to formulate emulsions and tune other operating parameters to achieve selective separation of one of the two metals co-extracted in the internal phase of the emulsion.