Simultaneous extraction and stripping of EDTA-chelated metallic anions with Aliquat 336 in hollow fiber contactors

The extraction of Cu2+ from an equimolar EDTA (ethylenediaminetetraacetic acid) feed solution through microporous hollow fibers to a kerosene phase containing Aliquat 336 (a quaternary amine) was examined, in which Cu(II) was then stripped to an aqueous phase containing HCI. Experiments were conducted as functions of the initial feed Cu2+ concentration (1-10 mol/m(3)), amine concentration (0.1-0.3 mol/dm(3)), and stripping HCl concentration (0.2-4 mol/dm(3)). A mass-transfer model was proposed to predict the time profiles of Cu2+ during a simultaneous extraction-stripping process in two hollow-fiber contactors. The calculated results well agreed with the measured data (standard deviation 10% in both extraction and stripping modules). The mass-transfer mechanism of such an extraction process could be identified by comparing the fractional resistance of each step. Under the conditions studied, it was shown that the extraction process was governed by combined aqueous-layer and membrane diffusions at the early stage of process, whereas the stripping process was dominantly controlled by membrane diffusion. (C) 2002 Elsevier Science Ltd. All rights reserved.