Abstract
Separation of Co(II) and Li(I) by non-dispersive solvent extraction using a hollow fiber supported liquid membrane has been investigated. Separation of both the metals by flat sheet supported liquid membrane and dispersive solvent extraction technique has also been investigated and compared. The parameters for the three processes were optimized to achieve quantitative separation of Co(II) over Li(I) with Cyanex 272 diluted with kerosene. The feasibility to produce pure metal salt solutions was established by controlling the process parameters like pH of the feed solution, extractant concentration, metal ion concentration and acid concentration for selective stripping. For both the hollow fiber and the flat sheet supported liquid membrane processes, the aqueous feed pH of 6.0 and 750mol/m3 of Cyanex 272 in the membrane phase were the best conditions for extraction, whereas the best stripping results were obtained with 100 and 25mol/m3 H2SO4, respectively. In the case of dispersive solvent extraction process, the quantitative separation of the metals was achieved by extraction at equilibrium pH of 5.50 using 100mol/m3 of Cyanex 272, and stripping with 10mol/m3 H2SO4 solution. Under the optimum conditions, the separation factor was found to be 18, 178 and 180 for hollow fiber supported liquid membrane, flat sheet supported liquid membrane, and dispersive solvent extraction, respectively. Suitable mathematical models for the quantitative extraction of the metal in dispersive solvent extraction and mass-transfer coefficient in non-dispersive solvent extraction were proposed and validity of the models was verified. Proposed models and the mathematical analyses revealed that both dispersive solvent extraction and non-dispersive solvent extraction process followed cation-exchange reaction mechanism with similar kind of stoichiometry.
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