Tungsten removal from molybdate solutions using ion exchange

Abstract

The selective adsorption of tungsten (W) onto the polyhydroxy chelating resin D403 by ion exchange from molybdate solutions was studied by batch and column experiments. The batch experiments indicated that W could be preferentially adsorbed onto the D403 resin under weakly basic conditions of pH>8, above which both tungsten and molybdenum (Mo) exist as monoions, WO42− and MoO42−. The separation factors for W over Mo were above 22 for solutions containing Mo from 30 to 100g/L, with mass ratios of Mo/W>50. This finding means that the D403 resin has a much stronger affinity toward WO42− than MoO42−, although their properties are similar. A comparison experiment with the D301 resin indicated that the selective adsorption of WO42− over MoO42− at pH>8.0 could be attributed to the effect of hydroxyl groups (−OH) in the D403 resin. The elution tests demonstrated that both metals could be easily eluted with 1mol/dm3 NaOH for only 1h. The column experiments further confirmed the applicability of the D403 resin in the industrial production of sodium molybdate or ammonium molybdate systems with W removal ratios from 93.35% to 97.56%.