J. Sarrazin

Rejection of mineral salts on a gamma alumina nanofiltration membrane application to environmental process

Abstract Nanofiltration of salt solutions through an alumina membrane prepared by a sol gel process was investigated: rejections depend on the charge of the ions and decrease in the order: (divalent cation, monoanion) > (monocation, monoanion) or (dication, dianion) > (monocation, dianion). The surface charge of the membrane in the investigated solutions was shown to be positive over a very large pH range. The rejection of ionic species can be rationalised by taking into account the low pore diameters of the membrane and its surface charge: as in the case of organic nanofiltration membranes, the rejection mechanism depends on the relative ratio of the coulombic, dielectric and hydration interactions between the membrane material and the ionic species. The use of nanofiltration through the alumina nanofiltration membrane for denitration of water is also presented.

Methanol removal from organic mixtures by pervaporation using polypyrrole membranes

Abstract Conducting polymer composite membranes with a separation layer of polypyrrole doped with hexafluorophosphate (PF6−) and p-toluenesulfonate (CH3C6H4SO3−), were examined for the removal of methanol from organic solvents (toluene, IPA, MTBE and acetonitrile) by pervaporation. In all the cases, both membranes displayed preferential permeation of methanol. Selectivities and permeation rates as functions of methanol content were studied. The highest selectivity to methanol over toluene, accompanying an acceptable methanol flux, was obtained with the membrane doped by PF6−.

Salt filtration on gamma alumina nanofiltration membranes fired at two different temperatures

The performance towards filtration of different salts of two gamma alumina nanofiltration membranes, fired at 450°C and 650°C, were compared in terms of flux and rejection. The phenomenological parameters (reflection coefficient σ and overall solute permeability P) were determined for some salts.

Treatment of nickel containing industrial effluents with a hybrid process comprising of polymer complexation–ultrafiltration–electrolysis

A process was studied at the laboratory level and on a pre-industrial pilot for pollutant removal from industrial waste waters containing nickel cations. Five successive steps are involved: (1) complexation of the metal by means of polymeric ligands; (2) ultrafiltration of the complex, which produced a purified effluent and a concentrated metal complex solution; (3) decomplexation by acidification; (4) ultrafiltration of the concentrate after acidification allowing the recycling of the complexing agent; (5) electrolysis of the concentrated nickel solution (filtrate). A polycarboxylate and a polyethylenimine were investigated as complexing agents in a laboratory pilot, which lead to high rejection of nickel, even in the presence of salts such as NaCl or NaNO3. The decomplexation of polyethylenimine appeared to be too slow to be of practical interest for industrial use. The performances of several different membranes with polycarboxylate–nickel complexes were compared in a pre-industrial pilot and the operating parameters (temperature, pressures, liquid rate) were optimised. Starting from nickel at 60 mg l−1, volume concentration factors up to 20 were shown to be of practical interest. Acidification and diafiltration of the concentrate afforded Ni(II) solutions which could be easily electrolysed while the complexing agent could be recycled to the beginning of the process.

Grafting γ alumina microporous membranes by organosilanes:: Characterisation by pervaporation

Abstract γ alumina microporous membranes, produced from a sol–gel process, were grafted by means of chloro-, methoxy- or ethoxy-organosilanes. The grafting conditions were first tested on γ alumina powders which were characterised by means of thermogravimetric analysis and nitrogen adsorption. The membrane material was studied by means of infrared spectrometry, nitrogen adsorption and nitrogen permeation. The performances of grafted and ungrafted membranes were examined for the separation by pervaporation of binary mixtures such as water/ethanol, cyclohexane/toluene, ethanol/cyclohexane and methylethylketone/cyclohexane.

GAMMA ALUMINA NANOFILTRATION MEMBRANE APPLICATION TO THE REJECTION OF METALLIC CATIONS

Abstract A gamma alumina nanofiltration membrane, prepared by a sol-gel process, exhibits interesting properties for the filtration of metallic complexes. Experimental rejection and fluxes depend on the pH of the solution. Comparison of the distribution diagrams of the species in solution as a function of pH, established for several metallic complexes using equilibrium constants, shows that rejections and fluxes are affected by the size and the charge of the complex. High rejection ( > 95%) can be reached if the molecular weight of the complex is higher than 400. For positively charged complexes, the flux of the permeate is almost independent of the pH of the solution, whereas for negatively charged ones, the flux increases with increasing pH.

Electrochemical preparation of polypyrrole membranes and their application in ethanol-cyclohexane separation by pervaporation

Abstract Polypyrrole films were deposited on stainless steel meshes by anodic electropolymerization of pyrrole dissolved in acetonitrile. Established on the electrochemical and morphological studies on the growth of polypyrrole film, both the oxidized, with PF6− as counter-ion, and neutral polypyrrole membranes were obtained. The performances of these membranes towards ethanol-cyclohexane separation by pervaporation were investigated. Results indicate preferentian permeation of ethanol and clearly show a feasibilily of exploiting conducting polymers in the pervaporation process.

Investigations on Ozone Contacting by Ceramic Membranes

Abstract Ozone transfer was investigated using various oxide ceramic membranes and different process parameters. The ozone mass transfer per contactor volume through hydrophilic membranes was in the same order of magnitude as conventional bubble contacting. The pressure differential between the gaseous and aqueous phase as well as the membrane materials microstructure was found to widely determine the transfer rate. A hydrophobic coating of the membrane surface led to a considerable increase in transfer. Bubble free ozone contacting with porous ceramic is a possible approach for the ozonation of problematic wastewaters susceptible of excessive foam formation.

Bubble‐free Ozone Contacting with Ceramic Membranes for Wet Oxidative Treatment

A bubble-free ozone contacting process by means of porous ceramic membrane was investigated and found to be an auspicious approach for the ozonation of highly polluted organic waste water displaying excessive foam formation with conventional contacting methods. Ozone transfer was measured with several membranes and at different process parameters. The ozone mass transfer per contactor volume was found to be on the same order of magnitude as conventional bubble contacting. The pressure difference between the gaseous and aqueous phase as well as the membrane materials microstructure was identified to widely determine the transfer efficiency.

Behaviour of copper and silver in complexing medium in the course of nanofiltration on both mineral and organic membrane

The recent development of new mineral and organomineral membranes induced an increasing interest in the nanofiltration process. Their better mechanical as well as chemical properties allow them to challenge widely commercialised organic membranes. In this work, the behaviour of both copper and silver in the course of nanofiltration is studied in presence of nitriloacetic acid (NTA) and sodium thiosulphate. Filtrations were performed using two different types of membrane: a mineral gamma alumina membrane with a point of zero charge equal to 8.2, and an organic membrane (MT34). Effects of the nature of ligand, pressure, pH and metal concentration were examined on each studied membrane. Filtrations on organic membrane showed that only the molecular weight can be considered as an preponderant parameter in relation with the rejection yield. On the other hand, based on both electric interaction and molecule size, the mineral amphoteric membrane allowed various possibilities of separation between the two metals according to the pH value.