New capabilities in extraction of platinum metal chloride complexes with oxygen-containing extractants

Abstract

The efficiency of extraction of platinum metal chloride complexes with oxygen-containing extractants can be increased in going from acid chloride solutions to mixed acid sulfate-chloride solutions.In the initial stage of the development of extraction methods for the isolation of platinum metals attention was given mainly to extraction of their halide complexes with neutral oxygen-containing extractants [1]. Later on emphasis was transferred toward nitrogen-and sulfur-containing extractants [2,3]. Taking into account the importance of reversibility of transitions between aqueous and organic phases for extraction methods, this tendency restricted their application for both analytical and technological purposes. The formation of stable complexes by platinum metals with sulfur-and nitrogen-containing extractant molecules makes the extraction process with such compounds (including chelating extractants with the same donor atoms) irreversible, so that platinum metals are transferred from aqueous solution into organic phase without a possibility for re-extraction. The potential for further improvement of extraction methods for isolation of platinum metals following traditional way of searching for new extractants was largely exhausted [4].

Determination of trace amounts of Pd(II), Pt(IV), and Ir(IV) chlorocomplexes by capillary electrophoresis with extraction-chromatographic preconcentration

“…The high est partition coefficients and coefficients of selectivity with respect to Fe(III), Cu(II), and ions of base metals were obtained in the extraction of Pd(II) and Pt(IV) with tributyl phosphate as chlorocomplexes from mixed solutions of hydrochloric and sulfuric acids with the minimum concentrations 0.01-0.1 M of HCl and 4-8 M of H 2 SO 4 [2]. To retain platinum metal as their chlorocomplexes, a mixed solution of 0.1 M HCl + 4 M H 2 SO 4 was selected for the prepara tion and storage of stock solutions.…”

“…For example, in the determination of platinum metals in their most typical form of chloride complexes, such conditions of preconcentration and separation from related impurities are required that preclude the transformation of chloride complexes into other species of platinum metals in solution. Among the currently known methods for the precon centration and separation of platinum metals as chlo ride complexes, ensuring the complete reversibility of the separation process and the greatest preconcentra tion ratios in combination with the possibility of the separation of base metal impurities offers extraction with tributyl phosphate from mixed solutions of hydrochloric and sulfuric acids with a minimum con centration of hydrochloric acid, sufficient to preserve platinum metals in the form of chloride complexes [2]. An additional advantage of this extraction system is the possibility of its adaptation to the conditions of extraction-chromatographic separation of platinum metals in the form of chloride complexes.…”