Separation of palladium and europium upon extraction with phosphorylated calix[4]- and thiacalix[4]arenes from nitric acid and carbonate solutions

Separate and concurrent extraction of palladium and europium from nitric acid and carbonate solutions with calix[4]- and thiacalix[4]arenes, their phosphorylated derivatives, and mixtures have been carried out. Charge state of sulfur and oxygen donor atoms in the extractants have been studied by XPS, XES, and quantum chemical calculations. It has been experimentally confirmed that the electronic structure of substituents at PO group has no effect of on the charge state of sulfur atoms in phosphorylated thiacalixarenes and assumption on the possible electronic effect of bridging sulfur atoms on the charge state of phosphoryl oxygen in bifunctional extractants has been made. These results substantiate the method of combined extraction of Pd and Eu from nitric acid solutions and their separation with factor 2 × 103 upon carbonate back extraction of europium and are of interest for simplified (Purex) and promising (Carbex) processes.