Possibilities of chromium (III) separation from acid solution using the double-carrier supported liquid membrane (DCSLM)

This paper describes the problem of recovery and reusing chromium from aqueous solutions. The authors studied a novel double-carrier supported liquid membrane system (DCSLM) with di(2-ethylhexyl) phosphoric acid (D2EHPA) and bis(2,4,4-trimethyl) phosphinic acid (Cyanex272) as a carrier of Cr(III) ions as a method to separate chromium (III) from acid solutions. As a result, they confirmed that the presence of two carriers in the DCSLM with the most effective carrier concentration ratios, leads to approximately three times shorter pertraction, compared to a process conducted with the D2EHPA only. It was found that synergistic effect is independent of the initial concentration of chromium in the feed solution. Higher initial concentrations of Cr(III) ≥ 0.01 mol dm⁻³ cause high ‘exhaustion’ of active carrier molecules at the interface. Moreover, the authors observed the increase in viscosity in the membrane phase and process inhibition. It was found that efficiency of separation of chromium ions from aqueous solutions using a liquid membrane depends on the transport rate for these ions in the membrane (ions pertraction). Therefore, it was concluded that the pertraction stage of the Cr(III) ions limits the efficiency of the whole separation process.