Exploration of heavy metal ions transmembrane flux enhancement across a supported liquid membrane by appropriate carrier selection

Extraction capabilities of three kinds of carriers, Aliquat 336, Kelex 100 and LIX 54, for cadmium removal have been investigated in supported liquid membrane (SLM) systems. The maximum fluxes obtained using Aliquat 336, Kelex 100 and LIX 54 are 1.12 x 10(-9), 1.5 x 10(-10) and 7.9 x 10(-11) mol/(cm(2) s), respectively. Theoretical calculation of these three carriers' extraction capabilities for cadmium in SLM systems using the quantum chemical computation method has also been carried out. The single point energy calculation results show that the energy changes in the complex formation process are in the order of Aliquat 336/Cd(II) > Kelex 100/Cd(II) > LIX 54/Cd(II), with energy changes of -657.79, -329.19 and 96.32kcal/mol, respectively. This indicates the quantum chemical computation supports the experimental results well and can be proposed as an effective tool for carrier selection in the SLM system. FTIR results also agree with the computational results quite well. Investigation on the influence of stirring rate and strippant on the cadmium flux reveals that a stirring rate of 400 rpm and the use of 1 mM EDTA as the strippant constitute the optimal experimental conditions. It was also found that cadmium flux is a function of feed concentration at the low concentration stage and the cadmium flux is enhanced by appropriate addition of certain anion into the feed. (C) 2007 Elsevier Ltd. All rights reserved.