Modeling of effect of pH on mass transfer of copper(II) extraction by hollow fiber renewal liquid membrane

In this paper, the effects of pH on the mass transfer of copper extraction with hollow fiber renewal liquid membrane (HFRLM), which is a new type of liquid membrane system based on the surface renewal theory, were investigated. The system of CuSO4 in acetate buffer solution + D2EHPA in kerosene + acidic aqueous solutions was used to study the effects of pH and acetate ion concentration in the feed phase and type and acidity of the stripping phase on the mass transfer performance of the HFRLM process. Results showed that the mass transfer flux and removal efficiency of copper increase with increasing pH in the feed phase, reach a maximum value at pH of 4.44, and then decrease; an addition of acetate buffer solution at a low acetate ion concentration in the feed phase is enough for maintaining the higher mass transfer flux and removal efficiency in the HFRLM process. The influence of the stripping phase on the mass transfer performance of the HFRLM process is weak in our ranges studied. The stripping phase at a low hydrogen concentration is enough for the extraction of copper by HFRLM. The mass transfer fluxes of copper ions from feed solutions with different stripping acids followed the order: Cl- > PO43- > SO42- > NO3-. And, a detailed mathematical model was developed based on the surface renewal theory. The calculated results have good agreement with experimental results.