Tungsten removal from molybdate solutions using ion exchange

• The polyhydroxy chelating resin D403 has much stronger affinity towards WO42 − than MoO42 −.
• The D403 resin can directly separate WO42 − from MoO42 − at pH > 8.
• The separation factors are above 22 for solutions of 30 g/dm3 Mo with Mo/W mass ratios over 50.
• The deep removal ratios of W from molybdate are up to 97.56% by column tests.

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 100 g/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 1 mol/dm3 NaOH for only 1 h. 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%.