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 30 1, 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 batc h and column systems, using synthetic solutions. This extraction system can be efficiently used for the recovery of cadmium from concentrated phosphor ic acid solutions (up to 12 M). Cadmium can be removed from loaded resins u sing hydrochloric acid (5 M.), and the resin can be reused without addition al treatment. The second part of the study focuses on the recovery of cadmi um 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 effi ciency 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.