Recovery of tungstate from aqueous solutions by ion exchange resins

An 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. Kinetic studies consist of the analysis of the breakthrough curves at different tungsten concentrations, flow rates, pH and bed heights. At basic pH, for a given flow rate and concentration, the breakpoint and the saturation times of the system are almost constant with pH. Moreover the length of the mass transfer zone remains almost unchanged with bed height, 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 behaviour of the exchange resin at acid and basic pH can be connected to the different forms of tungsten present in solution