Extraction of cadmium from phosphoric acid using resins impregnated with organophosphorus extractants

In the first part of this work, Amberlite XAD-7, impregnated with Cyanex 301, is selected among several supports and organophosphorus extractants for its high affinity for cadmium in phosphoric acid solutions. Initially, the work focuses on the study of cadmium extraction and stripping, in both batch and column systems, using synthetic solutions. This extraction system can be efficiently used for the recovery of cadmium from concentrated phosphoric acid solutions (up to 12 M). Cadmium can be removed from loaded resins using hydrochloric acid (5 M.), and the resin can be reused without additional treatment. The second part of the study focuses on the recovery of cadmium from industrial phosphoric acid solutions. The presence of iron(III) and copper(II) in large concentrations has a significantly negative effect on extraction properties. A pretreatment consisting in the reduction of ferric and cupric ions using Na2S2O4 or iron powder was used. The extraction efficiency was thereby increased, but it remained lower than that obtained with synthetic solutions. Recycling was also strongly limited: the presence of other competitor ions can explain this decrease in extraction efficiency.