Ionic pumping in a cadmium, ortho phosphoric acid-phosphate tributyl-ammonium carbonate system: Chemical study of compartments Presented at the EuroMed 2006 conference on Desalination Strategies in South Mediterranean Countries: Cooperation between Mediterranean Countries of Europe and the Southern Rim of the Mediterranean. Sponsored by the European Desalination Society and the University of Montpellier II, Montpellier, France, 21-25 May 2006

An ionic pump has been devised thanks to liquid-liquid extraction/reextraction where the extraction compartment and the reextraction compartment are put in contact with one another through the membrane composed of a mediator diluted in kerosene. We have applied this process to a system of cadmium, ortho phosphoric acid-phosphate tributyl, kerosene-ammonium carbonate. Interesting performances have been realized for diluted solutions (100 ppm). The study chemical parameters allowed to obtain the variables giving the extraction and reextraction efficiencies optimum. For the extraction compartment, the competition of orthophosphoric acid has been found. The study of the chemical variables of the reextraction compartment has demonstred that the nature and the concentration of a desactivation cosolute is very important and determinant for the formation of the non extractibles species. A chemical modelization has allowed to identify the extraction mecanisms. The classical behaviour obtained in agitated surroungings has been found again. The membrane can work thanks to the "activation" by the cosolute of the transportor at one interface and to the "deactivation" at other interface, both of these mechanisms of the active transport creating real ionic pumping.