Transport behavior of thorium(IV) in a continuous-flow liquid membrane containing Di-(2-ethylhexyl) phosphonic acid

As a step towards the development of liquid membrane technology for the recovery of thorium from dilute solutions, the article investigates transport behavior of Th(IV)‏ from a feed (solution) phase containing 0.0001M hydrochloric acid (HCl) into a recovery phase containing 1.5M sulfuric acid (H2SO4) in a continuous flow liquid membrane (CFLM) containing 0.2 M Di-(2-ethylhexyl) phosphoric acid (D2EHPA) as the ion carrier. The assessment of the transport process was performed by determining the kinetic parameters—mass transfer coefficient, and entrance and exit flow in and out of the chloroform membrane. The ability of the CFLM for thorium(IV) recovery from aqueous solutions was confirmed with transport experiments. In addition, transport experiments also show the extraction and back-extraction steps to proceed simultaneously and in a continuous fashion. The obtained results showed that with an increasing flow rate of the membrane and recovery phases the transport rate of thorium ions will increase, while feed flow rate had no significant effect on the transport of thorium(IV). At the flow rates higher than 300 mL min-1 for the recovery phase, the mass transfer resistance in this phase decreases to its lowest value. According to the kinetic studies, extraction of metal ions from the feed solution provides faster kinetics than their back extraction into the recovery aqueous phase.