Palladium and silver extraction with thiacalix[4]arenes and their acyclic analogs from carbonate and ammonia-carbonate solutions

A quantitative comparison of palladium and silver extraction with p - tert -butylthiacalix[4]arene (TCA) from nitric acid, carbonate, ammonia-carbonate, and ammonia solutions was carried out. It was shown that TCA under optimal conditions can be used for concurrent extraction of palladium and silver from carbonate systems of CARBEX process, selective recovery of palladium from nitric acid solutions, and selective silver extraction from ammonia-carbonate solutions. Metal distribution ratios and effective extraction constants decrease when the complex-forming ability of aqueous phase rises (Na 2 CO 3 > NH 4 HCO 3 ). The ammonia complexation of Ag + is determining factor for silver, solution pH plays a certain role for palladium due to formation of hydroxo complexes.