Polymer inclusion membranes based on CTA/PBAT blend containing Aliquat 336 as extractant for removal of Cr(VI): Efficiency, stability and selectivity

Cellulose triacetate (CTA) and poly(butylene adipate-co-terephthalate) (PBAT)-based polymer inclusion membranes (PIMs) containing ionic liquid (tricaprylmethylammonium chloride (Aliquat 336)) as the carrier extractant were obtained for the facilitated and selective transport of Cr(VI) ions. The composition of PIMs was optimized in terms of the CTA/PBAT ratio. The obtained membranes were investigated using different techniques in order to show the influence of the membrane composition and the ionic liquid presence on the PIM resulting properties. The infrared analysis confirmed the presence of the intermolecular interactions of the hydroxyl groups of CTA with the carboxyl groups of PBAT and of the negatively charged carboxyl groups of CTA with the positively charged ammonium groups of Aliquat 336. The water contact angle measurements highlighted that the Aliquat 336 and PBAT presence modified the membrane hydrophobic/hydrophilic character. Moreover, it was shown that PIM containing the equivalent content of CTA and PBAT (35/35 wt%/wt%) with 30 wt% of Aliquat 336 revealed the optimized composition and was used for the Cr(VI) ions transport measurements. It was found that this PIM transported > 99% of Cr(VI) in only 6 h and accumulated < 5% of Cr(VI) ions with a high initial flux. For the first time it is shown that the selective Cr(VI) transport through blend PIM with reduced extractant content and without plasticizer is more efficient compared to common PIMs. Besides, the stability of obtained blend PIMs was confirmed by carrying out continuous transport studies over a long period of time (> 120 h).