Abstract
This work communicates an exploration for investigating the extraction of cerium(III) ions from dilute aqueous feed solutions by emulsion liquid membrane (ELM). The ELM contains di(2-ethylhexyl)phosphoric acid (D2EHPA) as extractant, Span 80 as surfactant and kerosene as diluent. Nitric acid was used as internal stripping aqueous phase. Influence of operating parameters that affect the permeation of Ce(III) such as surfactant concentration, carrier concentration, external phase pH, internal phase concentration, type of internal phase, stirring speed, volume ratio of internal phase to membrane phase, treatment ratio, diluent type and Ce(III) concentration was examined. Additionally, the effect of salts (Na2SO4 and NaCl) concentration on the extraction of Ce(III) was studied. The obtained results show that it was possible to completely extract the Ce(III) ions from the external feed solution under the most favorable conditions. Best experimental parameters for higher extraction efficiency are: emulsion volume: 20 mL; external phase (Ce(III) solution) volume: 250 mL; surfactant concentration: 3% (w/w); D2EHPA concentration: 0.4% (w/w); volume ratio of internal phase to organic phase: 1/1; stirring speed: 200 rpm; volume ratio of water-in-oil emulsion to external phase: 20/250; internal stripping phase concentration (HNO3): 0.2 N; pH of the feed phase: 5.1 (natural); diluent: kerosene. Both the rate and efficiency of Ce(III) extraction were not meaningfully affected by the augmentation in NaCl concentration in the interval 0.5-5 g L-1 and the increase of Na2SO4 concentration in the range 0.1-20 g L-1. Besides, the effectiveness of the ELM method to remove Ce(III) from real environmental matrices such as natural mineral water (Zamzam) and seawater was proven. ELM process is a promising alternative to conventional methods and should increase awareness of the potential for recovery of Ce(III) ions from dilute aqueous solutions.