Removal of chromium(III) from acidic aqueous solution by polymer inclusion membranes with D2EHPA and Aliquat 336

A facilitated transport of chromium(III) through polymer inclusion membrane (PIM) containing 2-ethylhexylphosphonic acid (D2EHPA) as an ion carrier and tricaprylylmethylammonium chloride (Aliquat 336) as a plasticizer was investigated. In order to optimize conditions of the membrane transport, the initial flux of chromium(III) ions was considered as a function of acidity and temperature of source phase, membrane thickness and amount of plasticizer in the membrane. The highest values of initial flux of chromium(III) ions were obtained for source phase pH equal to 4.0 and for 1.5 cm3 Aliquat 336 per 1.0 g cellulose triacetate (CTA) in the membrane phase. The activation energy value found from Arrhenius plot to be equal 110 kJ/mol suggests that the transport process is controllable by chemical reaction. The competitive transport of Cr(III) and Cr(VI) across PIMs consisting of 29% CTA, 19% D2EHPA and 52% Aliquat 336 from aqueous source phase with two different pH values 1.0 and 4.0 was also carried out. It was found that at pH 1.0 the removal of Cr(VI) ions is more efficient in comparison with Cr(III), while at pH 4.0 the reverse selectivity was observed.