Solvent Extraction/ion Exchange for Metal Separation and Recovery

Abstract

In the hydrometallurgical processing of complex ores/ concentrates/ secondaries/ wastes, the solutions containing different non-ferrous metals are obtained during leaching the materials in acidic, ammoniacal or alkaline lixiviants. The spent solutions & effluents are also generated in different process industries and contain metallic values. Their discharge in the sewage or river is major concern for environment. In order to meet the strict environmental regulation and conserve the natural resources, metallic values are to be reco-vered. The leach solutions, spent solution and effluents are usually processed to recover metallic values following precipitation, solvent extraction, ion exchange, electrolysis, evaporation, crystallization, electrodialysis etc. Solvent extraction (SX) is one such proven technique in the hydrometallurgical processing for selective extrac-tion and separation of metals due to the ease of applica-bility, versatility and ability to produce high value products. It is used on commercial scale for the recovery of different metals from different solutions viz. copper, nickel, cobalt, zinc, tungsten molybdenum, uranium, rare earths etc. The effluents from waste streams are also processed to recover metals using organic extractants. With the development of improved design of SX equipment and material of construction and newer organic extract-ants, it is possible to recover metals as value added products even from the complex solutions containing various ionic species. The process has been used first time in USA for nuclear application for extraction of uranium from nitrate solution using ether. Subsequently, developments were made for efficient extraction of uranium from other complex solutions.