The possibility of Pd (II), Pt (IV), and Rh (III) separation from chloride solutions by solvent extraction in rotating coiled columns (RCC) is demonstrated. The reagents most frequently used in extraction of platinum metals were selected as extractants: trioctylamine (TOA), methyltrialkylammonium chloride (MTAA), tributylphosphate (TBP), N, N, N',N'-tetra-re-octyldiglyTOlamide (TODGA). The completeness of extraction of the platinum group metals from individual and mixed hydrochloric acidic and chloride solutions was studied depending on the nature and concentration of the extractant, acidity of the test solutions and other factors. Optimal conditions for the quantitative extraction of metals from model hydrochloric acidic and chloride solutions and subsequent selective separation at the stripping stage are specified. A scheme of multistaged extraction separation of Pd (II), Pt (IV), and Rh (III) from chloride solutions using a 0.05 M solution of MTAA in toluene as a stationary phase in RCC is proposed. The scheme includes extraction of Pd (II) and Pt (IV) ions from a chloride solution (0, 1 M HCl + 30 g/liter NT) into the organic phase with simultaneous separation of Rh(III) remaining in the aqueous phase, and sequential stripping of Pd (II) and Pt (IV) from the organic phase with a 0.01 M solution of thiourea in 0.1 M HCl and a 1 M solution of thiourea in 0.5 M HCl, respectively. The scheme was tested in separation of the platinum group metals from the technological solution of a given composition. The degree of metal extraction with a 0.05 M MTAA solution in toluene and sequential stripping with thiourea solutions is 99.5% for Rh (III), 99.9% for Pd (II), and 97.4% for Pt (IV). The separated water fractions of rhodium and platinum after leaving the column did not contain impurities of other platinum metals whereas the water fraction of palladium contained 0.5% Pt.
Extraction of Platinum Group Metals under Low Chloride Concentration with Quaternary Ammonium Salt and Tributyl Phosphate