LIX®-loaded polymer inclusion membrane for copper(II) transport: 1. Composition–performance relationships through membrane characterization and solubility diagrams

The effects of different components on the performance of a selected polymer inclusion membrane (PIM) system developed for copper transport were assessed by means of different analytical techniques. Copper(II) transport data, thermal analysis, transmission infrared mapping microspectroscopy (TIMM) and AFM were used to characterize chemical and physical behavior of PIMs with different compositions. The prepared membranes, made using cellulose triacetate (CTA) as support, tris(2-n-butoxyethyl) phosphate (TBEP) as plasticizer, together with an additive (ethanol), and LIX® 84-I, LIX® 984 or LIX® 54-100 as carrier, showed increasing copper(II) permeabilities in the order LIX® 54-100 < LIX® 984 < LIX® 84-I. Membrane permeabilities increased up to 2.6-fold in the strip solution side for LIX® 84-I PIMs cast with ethanol, and Cu(II) accumulation within the membrane was observed to vary with the amount of additive. The modifications of the transport properties of the PIMs were satisfactorily correlated with the distribution profiles of the membrane components (obtained by TIMM), glass transition temperatures, casting method and topographic structure of the films with the aid of a Teas graph implemented for PIM applications. From this graph it was possible to interpret the interactions between the different membrane components in a phenomenological way, thus contributing to improve the understanding of the role played by each one in the development of a more efficient PIM system for copper transport when using LIX® reagents as carriers.