Study of potentialities of micellar enhanced ultrafiltration for the decontamination of aqueous effluents containing heavy metals

This work deals with the extraction of thorium, ruthenium and uranium by ultrafiltration using different micellar systems. These extractions are carried out in media which are strongly charged in salts (nitrates and carbonates). In the first part of this work has been studied the behaviour of micellar solutions. The type of used ultrafiltration (frontal or tangential), the pH, the initial concentration of surfactant, the salt type, the pressure, the recirculation rate, the surfactant type, the nature of the membrane (organic or mineral), the membrane support (aluminium oxide or carbon), the membrane cut threshold are factors able to affect the behaviour of micellar solutions, so their influences have been studied. This preliminary study has allowed to determine the ultrafiltration experimental conditions required to obtain the best possible flux for a minimal loss of surfactant in the permeate. The second part of this work deals with the metals extraction. The presence of strong salts concentrations is prejudicial to the process for the extractions carried out with SDC, CPC, or CTAB alone. The author has then studied micellar systems solubilizing an extractant agent (systems: Triton-X-100/Kelex-100, Triton-X-100/HS-21 and Brij 35/HS-21). The study of the different parameters affecting the extraction yields has allowed in this case to improve the results for reaching yields sometimes superior to 99.9% as well as for some metals taken separately than for the three metals treated simultaneously. The results of this work have shown the evident potentialities of the use of a surfactant/extractant system for the decontamination of effluents containing heavy metals and metals strongly charged in nitrates. (O.M.)