Intensification of membrane processes. Remediation of groundwaters by emulsion pertraction as a case study

Abstract

Membrane technology is strongly related tothe process intensification strategy, being thedesign of new operating modes one of the objec-tives, with the focus in the replacement of large,expensive and energy-intensive equipment withones that are less costly, more efficient or thatcombines multiple operations into a single appa-ratus [1]. Membrane contactors are expected toplay a decisive role in this scenario, based intwo principal characteristics: the ability to createa large exchange area for mass transfer and/orreaction and the independent fluid dynamics thatallow an easily controlled operation. Moreover,for the multiscale implementation of membranecontactors, effective computer aid processengineering is required [2]. The case study presented in this work is theremediation of polluted groundwaters containinghexavalent chromium coming from industrialeffluents leakages where other competitivespecies such as sulphate and chloride anions arealso present due to the reservoir location. Thedevelopment and implementation of the sustain-able technology that permits the recovery of thevaluable compounds and the effluent purifica-tion with minimum energy cost is of interest dueto the economical, environm ental and social bene-fits [3]. Membrane based solvent extractiontechnologies and in particular Emulsion Per-traction Technology (EPT) using hollow fibermodules, was the selected technology. In EPT,the aqueous phase with the target species is con-tacted in one hollow fiber module with an emul-sion formed by stripping phase dispersion intothe organic phase that contains a selectiveextractant. The chromium is transferred fromthe aqueous feed solution to the organic phase,and then it is transported to the internal back-extraction solution [4]. Thus, in the EPT technol-ogy, extraction and back-extraction operationsare efficiently combined in a single membranecontactor unit. The optimal emulsion pertraction processmust be able, with minimum cost, to obtaintreated effluent streams suitable of being dis-posed into the environment, and at the sametime a concentrated chromium stream that couldbe re-used in some industrial application. Thecosts evaluation in membrane processes can be