Exploiting Ion-Dipole and Ion-Exchange Interactions for the Removal of Aminopyridines from Aqueous Environments Using Polymer Inclusion Membranes

Aminopyridines, such as 4-amino-2-chloropyridine (ACP), are not only starting materials for many useful chemicals but also decomposition by-products that are extremely stable in an aqueous environment. Aliquat 336 has proved useful as a carrier in polymer inclusion membranes (PIMs) for the extraction and transport of small organic anions through ion-exchange processes. However, less attention has been paid to the use of the carrier for the extraction of neutral or cationic organic compounds like aminopyridines. The current study focuses on using PIMs containing Aliquat 336 to target ACP using ion-dipole interactions. The investigations were performed using both experimental methods and computational modelling. The findings indicated that ACP was transported through a combination of both passive and facilitated diffusion in the rate-determining steps. Significant facilitated transport occurred when PIMs contained 10 wt% or more Aliquat 336. The transport of ACP was fundamentally driven by pH but also benefited from a chloride gradient that resulted in the concurrent transport of orthophosphate. An optimal membrane composition delivered a reasonable flux of 413 (& PLUSMN; 9) x 10(-8) mol m(-2) s(-1) and good transport efficiency of 98% for ACP. Our findings provide more incentive for the continued development of PIM chemistry to target troublesome organic pollutants and recover useful chemicals from water sources.