Optimization of Cr(III) transport in a polymer inclusion membrane system through experimental design strategies

A polymeric inclusion membrane using di-(2-ethylhexyl)phosphoric acid (D2EHPA) as carrier, 2-nitrophenyl octyl ether (2NPOE) as plasticizer, and cellulose triacetate (CTA) as base polymer was employed to evaluate the facilitated transport of Cr(III) in aqueous medium. An experimental design strategy based on a Doehlert matrix was used to optimize the membrane composition, using two normalized functions as response variables ( G feed , G strip ). The amounts of D2EHPA, NPOE, and CTA used in the experimental design varied within the range 0.03–0.075 g; the concentration of the feed phase used was 6 mg/L Cr(III) at pH 4.0 adjusted with 0.01 mol/L AcOH/AcONa buffer solution; and 1 mol/L HCl was used as the strip phase. The optimal membrane reached a maximum recovery of (96.0 ± 0.6)% after 8 h of pertraction. The effects of pH of the feed phase and the presence of different interfering ions ( SO 4 2 - , Cl - , Na + , K + , and Ca 2 + ) were evaluated as well. Based on liquid–solid extraction experiments, the extraction and transport mechanisms for the system were proposed. Graphical abstract