Partner und Internationale Organisationen
(Englisch)
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Universidade do Porto, Departamento de Quimica, Porto (P), University of Liverpool, Chemistry Department, Liverpool (UK),Consiglio Nazionale delle Ricerche, Istituto di Chimica E Tecnologie inorganiche E dei Materiali Avanzati, Padova (I),Asociacion de Investigacion Metalurgica del Pais Vasco, Department of Chemical Technology, San Sebastian (E),EA Technology Ltd, Chester (UK), Enirisorse S.p.A, Centro Ricerche Venezia, Venezia (I), EPFL, Lab. d'Electrochimie, Lausanne (CH)
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Abstract
(Englisch)
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In the first part of this project, we have investigated the fundamental aspects of voltammetry for ion transfer across supported liquid membranes. We have in particular designed a methodology to investigate assisted ion transfer reactions.
In the second part, we have built and tested electrochemical reactors for the separation of trace quantities of metal ion impurities from concentrated solutions.
The transfer of trace quantities of metal ions from one aqueous solution to another through a supported liquid membrane has been achieved using two types of electrochemical reactor designs.
The first approach is based on the use of porous membranes coated by a polyethylene terephthalate micro-perforated by a UV excimer laser photo-ablation process. These membranes are used to support an organic solvent (nitrophenyloctylether) containing a supporting electrolyte (tetrabutylammonium tetraphenylborate) and a macrocyclic ligand.
By this approach, we have obtained very selective separation of traces of copper from rhodium solutions, and of copper from lead solutions.
These micro-machined membranes could be used for period of two weeks without showing any sign of deterioration.
The second approach consist in supporting not the organic phase but the adjacent aqueous phase using classical dialysis membranes (cellulose acetate). Different electrode configurations have been tested controlling either the potential difference between the feed aqueous solution and the organic phase, or by directly controlling the potential difference between the feed and the stripping solutions. In the latter case, the selectivity was shown not to be as good as in the former.
This second approach allows to pass higher currents and to process larger quantities of feed solutions. However, the long-term stability of the dialysis membranes becomes the limiting factor when passing too high a current.
All in all, we have demonstrated the feasibility of electrochemical solvent extraction.
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