Kinetic modeling of simultaneous recovery of metallic cations and anions with a mixture of extractants in hollow-fiber modules

The simultaneous extraction recovery of free Cu2+ ions and ethylenediaminetetraacetic acid (EDTA)-chelated anions from chloride solutions into a stripping HCl solution with a mixture of LIX64N and Aliquat 336 was studied in two hollow-fiber modules. A kinetic model is presented that considers possible mass transfer steps, including aqueous-layer diffusion, interfacial chemical reaction, membrane diffusion, and organic-layer diffusion. In particular, the effects of the preferential extraction of one metallic species and the mutual interaction of the two extractants were also corrected in this model on the basis of the results for individual, extraction systems. The calculated time profiles of the total CuII) concentrations were in reasonable agreement with the experimental data (standard deviations of 11% in both the extraction and back-extraction modules). Finally, the rate-controlling mechanisms of such nondispersive extraction processes were quantitatively identified and are discussed in terms of a comparison of the resistance of each mass transfer step.