Separation of Co(II)/Ni(II) with Cyanex 272 using a flat membrane microcontactor: Stripping kinetics study, upscaling and continuous operation

In the present paper, the impact of the acid concentration, Cyanex 272 concentration, and membrane wetting properties on the stripping kinetics of loaded Cyanex 272 with cobalt is studied in a flat membrane microcontactor. To reduce the environmental impact and to be ever economically viable, the extractant needs to be regenerated. From the observed results, a model was derived to describe the stripping kinetics, enabling to maximize throughput. Like for the extraction of cobalt, also for the reversed reaction (stripping of loaded Cyanex 272 with cobalt), pseudo-first order kinetics could be assumed. However, unlike the extraction of cobalt, the reaction kinetics for the stripping of loaded Cyanex 272 had to be taken into account. As a consequence, the concentration of sulphuric acid influences the stripping kinetics and consequently throughput as well. Furthermore, it was also shown that the concentration of Cyanex 272 affected the stripping rate, in contrast to the extraction of cobalt. While for extraction diffusion in the organic phase can be neglected, this was no longer the case for stripping. When the concentration of Cyanex 272 was increased, the stripping rate decreased severely. To increase throughput, a scale-up strategy was proposed, that could realize without inducing a loss of efficiency. This was demonstrated by increasing throughput by a tenfold. Moreover, also the separation efficiency is studied in a continuous operation set-up over a span of 5 h. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.