Selective uptake and recovery of palladium by biopolymer microcapsules enclosing cyanex 302 extractant

Selective uptake and recovery of platinum group metals are an important subject in the high level liquid waste treatment. An extractant having a strong affinity for palladium, bis(2,4,4-trimethylpentyl) monothiophosphinic acid (Cyanex 302, HA), was enclosed into microcapsules by utilizing highly immobilizing ability of biopolymer (alginate and alginic acid gel polymers). The uptake of Pd^2plus, Ru(NO)³⁺ and Rh³⁺ for granular microcapsules has been studied by batch and column methods. A relatively large distribution coefficient of Pd^2plus, K_{d, Pd}, of above 10⁴ cm³/g was obtained in the presence of 0.2–0.5 M HNO₃ and the separation factors of Pd/Ru and Pd/Rh were estimated to be above 10². The uptake of Pd²⁺ on microcapsules followed a Langmuir-type uptake isotherm and the maximum uptake capacity was estimated to be 0.72–0.96 mmol/g. These metal cations were chromatographically separated through the column packed with HA-alginate microcapsules.