Recovery of tungstate from aqueous solutions by ion exchange

A commercial anionic resin has been tested to evaluate its suitability for tungsten recovery from aqueous solutions. Equilibrium runs at fixed temperature have been carried out at different pH levels, showing a higher exchange capacity at acid pH. Kinetics studies consist of the analysis of the breakthrough curves at different tungsten concentrations, flow rates, pHs, and bed depths. At basic pH, the breakpoint and the saturation times of the system are almost constant with pH whatever the flow rates and the tungsten concentrations are. Moreover, the length of the mass transfer zone remains almost unchanged with bed depth, feed flow rate and concentration. At acid pH a critical working condition appears, as the breakpoint time progressively decreases and the saturation time strongly increases. The different behaviors of the exchange resin at acid and basic pHs can be connected to the different forms of tungsten present in solution.