EXPERIMENTAL STUDIES ON THE ENRICHMENT OF CARBOXYLIC-ACIDS WITH TRI-N-OCTYLPHOSPHINE OXIDE AS EXTRACTANT IN A SUPPORTED LIQUID MEMBRANE

The enrichment of carboxylic acids using a supported liquid membrane w as experimentally studied. A supported PTFE membrane was impregnated w ith a solution of tri-n-octylphosphine oxide (TOPO) dissolved in di-n- hexyl ether (DHE). TOPO was found to be an effective extractant, espec ially for highly polar acids. The extraction efficiency and the memory effects of the acids were investigated under various conditions of TO PO content and pH of the acceptor phase. It was observed that the pH o f the acceptor phase had a great influence on the memory effect and ex traction efficiency when using the TOPO-containing membrane; these eff ects were more pronounced for highly polar acids. The mechanisms of th e extraction and the memory effects of carboxylic acids and also the i nfluence of the co-diffusion of carbonic acid on the extraction are di scussed.