Binary Extraction in Hydrometallurgy

Abstract

Results obtained during technological application of binary extraction (extraction by salts of organic acids and organic bases) for recovery and separation of non-ferrous, rare, noble and associated metals are presented in the paper. The method of extraction of copper, especially from leaching solutions of oxidised ores, with the use of tertraoc-tylammonium dialkyldithiophosphate has been developed- The binary extractant is characterized by high separation coefficients of copper and iron, large capacity according to copper and high rate of its extraction and stripping by solutions of ammonia. The technology has also been tested in the sorption-extraction mode. Possibilities of the use of binary extractants for the purification of sulphate solutions containing copper and iron, and also chloride solutions containing iron, have been discussed. The technological scheme developed for the purification of aluminium from iron in chloride solutions with the application of carboxylate of trialkylamine is characterized by a more concentrated strip solution obtained in comparison with the system based on trialkylamine. The technology of the extraction of indium from Zn-containing sulphate solutions with the use of binary extraction by dialkylphosphate of trioctylamine has been developed and adopted at the Chetaybinsk zinc factory. The use of hydrochloric acid has been avoided in the stripping stage by the application of binary extractant. The technological scheme worked out for the extraction of cadmium from Zn-containing sulphate solutions with the use of carboxylate of trialkylamine allows one to achieve objectives of cadmium recovery in the form of chloride anion, cadmium concentration and conversion with the generation of cadmium sulphate solution suitable for cementation and also simultaneous purification of zinc sulphate solution from chloride ion with the production of concentrated solution of natrium chloride. Possible uses of binary extractants for the recovery of molybdenum as well as extraction and separation of platinum metals are also discussed. In hydrometallurgy the extraction processes are most effectively applied to solve the following tasks: •extraction (and usually simultaneous concentration) of valuable components in processing solutions with complex composition; - separation of elements with similar properties and their isolation into corresponding products; •purification of aqueous technological solutions from elements - impurities; synthesis of inorganic compounds using, stripped solutions with definite element composition; •purification of industrial sewage. Obviously, an extractant is selected depending on the objectives. A search of extractants is a continuing process and a wide circle of specialists in the field of extraction chemistry and technology, organic synthesis, physical chemistry, and others take part inthis process. Recently processes of the so-called binary extraction have attracted re- searcher's attention considerably. A review of results obtained by us on the use of binary extraction for technological applications is given in the present paper.