Cadmium(II) recovery from hydrochloric acid solutions using Amberlite XAD-7 impregnated with a tetraalkyl phosphonium ionic liquid

Cyphos® IL-101 (tetraalkyl phosphonium ionic liquid, IL) was immobilized in a synthetic resin (Amberlite XAD-7) for preparing an solvent impregnated resin (SIR). This SIR was tested for Cd(II) sorption in HCl solutions. Optimum sorption occurs for HCl concentrations close to 3-4 M through an ion exchange mechanism involving phosphonium cation and CdCl42-. Sorption capacity increased with IL loading, though a fraction of the IL remained inactive, being bound to the polymer support. Sorption capacity is poorly influenced by metal ions that do not form chloroanionic species. Uptake kinetics are controlled by the resistance to intraparticle diffusion. The intraparticle diffusivity coefficient increased with temperature, initial metal concentration but decreased with increasing IL loading (probably due to a decrease of the interfacial area and a slow diffusion of metal ions in the organic phase that fills the porous network). Metal desorption and resin recycling can be performed using nitric acid (0.1 M) with sorption and desorption performances maintained for at least five cycles.