SEPARATION OF TUNGSTATES FROM AQUEOUS MIXTURES CONTAINING IMPURITIES (ARSENATE, PHOSPHATE AND SILICATE ANIONS) USING ION FLOTATION

Ion flotation, using dodecylamine as surfactant and magnesium ions as depressant agents, was found to be an effective method for the selecti ve separation and recovery of tungstate from arsenate anions in dilute aqueous solutions. Arsenates represent the main impurity in tungsten- containing waste waters or leaching solutions of hydrometallurgical or igin; magnesium chloride is a relatively common precipitant, used in t ungsten hydrometallurgy. The main parameters affecting this process we re investigated, namely concentrations of reagents (Mg2+ ions, dodecyl amine, arsenate and tungstate), solution pH, co-existence and effectiv e separation from other impurities, such as phosphate and/or silicate anions, and the effectiveness of the separation process in solutions o f high ionic strength (using NaCl and Na2SO4 salts). It was found that at pH range between 2 and 5, tungstate anions can be quantitatively r ecovered from aqueous mixtures containing arsenates, phosphates and si licates, while the co-removal of the impurities was below 20%.