EXTRACTION BEHAVIOUR OF PLATINUM(Ⅳ) IN CHLOROFORM WITH A CROWN ETHER FROM ACIDIC MEDIA

摘要

A new method for the extraction of platinum from hydrochloric acid media has been established based on the formation of ion-pair complex of platinum hexachloro anion with dicyclohexyl-18-crown-6 (DC18C6) oxonium cation in chloroform by means of liquid-liquid extraction and back-extraction combined with inductively coupled plasma atomic emission spectrometry (ICP-AES). The effect of various factors (solvent, crown ether, reagent concentration, acid concentration, shaking time, and foreign ions etc.) on the extraction and back-extraction of platinum has been investigated in detail. The platinum hexachloro anion in 8 mol/L hydrochloric acid forms a stable ion-association complex with protonated DC18C6 (0.05 mol/L DC18C6) as [H_3O·DC18C6~+]_2[PtCl_6~(2-)], and can be extracted quantitatively (97%) in chloroform within 5 min. Stripping of the extracted platinum was achieved with 0.1 mol/L hydrochloric acid. No extraction was observed when extracting palladium and rhodium under the same analytical conditions for platinum extraction. The content of platinum in palladium chloride and rhodium chloride of guaranteed reagent grade was determined after its separation by DC18C6 extraction at 8 mol/L hydrochloric acid and it was found to be 16.39 ug/g and 8.94 ug/g, respectively.