Azzeddine Elmidaoui

Optimization of fluoride removal from brackish water by electrodialysis

The study showed that desired potable water can be easily obtained by electrodialysis from fluoride-rich brackish water. Studies have been performed to defluoridate brackish water containing 3000 ppm of total dissolved solids (TDS) and 3 ppm of fluoride using electrodialysis. The behaviour of water parameters (ion contents, TDS, pH, total hardness) with electrodialysis parameters (duration, flow rate, temperature, voltages) is followed. Optimal operational conditions for obtaining desired potable water have been proposed.

Competitive diffusion of hydrochloric acid and sodium chloride through an acid dialysis membrane

Abstract Competition between HCl and NaCl in dialysis across the anion exchange membrane Neosepta AFN was studied by measuring the diffusion flux of each electrolyte from aqueous solutions containing the two electrolytes. The acid flux was in all cases higher than the salt flux. These results are analyzed on the basis of the Nernst-Planck equation and the Teorell-Meyer-Sievers (TMS) theory. Measurements of the amounts of acid and salt in the membrane at sorption equilibrium were performed by using radioactive tracers. The results of such measurements, in conjunction with the results for the membrane electrical resistance, enabled us to obtain calculated values of the flux. These values were in satisfactory agreement with the experimental values. The two factors forming the basis of the greater diffusion flux for the acid than for the salt are, on the one hand, the higher mobility in the membrane phase of protons with respect to the other cations and, on the other hand, the higher degree of sorption of the acid in the membrane.

Preparation of perfluorinated ion exchange membranes and their application in acid recovery

Abstract The preirradiation grafting of crosslinked sulphonated styrene monomer (CSS) and a crosslinked aromatic monomer (ARM) onto ethylene-tetrafluoroethylene (ETFE) film was studied. The dependence of the grafting reaction on temperature, concentration of monomer, crosslinking agent, concentration of inhibitor and on the preirradiation dose was investigated. Interaction between monomer diffusibility and the viscosity of the monomer bath controls the grafting reaction. Other factors such as the mutual reactivity of monomer and crosslinking agent contribute to explaining the results of the grafting reaction. The properties of some membranes were also determined. The application of these membranes to acid recovery by dialysis, electrodialysis and electro-electrodialysis (EED) showed their excellent performance.

Chronopotentiometric response of a cation exchange membrane in contact with chromium(III) solutions

Abstract The paper deals with the transfer of ionic species containing Cr III through a CMV cation-exchange membrane. Two electrochemical techniques are used: the chronopotentiometric response and the transport number measurements. According to the composition of the anodic solution containing CrCl 3 , hydroxyl ion-chromium III complex forms enter into the membrane and water splitting occurs. This phenomenon is attributed to a poisoning of the membrane by these multivalent complex forms which change locally the selectivity of the cation-exchange membrane.

Transfer of H2SO4, Na2SO4 and ZnSO4 by dialysis through an anion exchange membrane

Abstract Competitive diffusion between H2SO4 and its salts (Na2SO4 and ZnSO4) was performed using a Neosepta AFN anion exchange membrane. The stronger affinity of sulfuric acid and the higher mobility of protons in the membrane with respect to sodium and zinc cations explain the great difference in the diffusivity between acid and salts through this membrane. Coexisting sodium and zinc sulfates have no significant effect on H2SO4 diffusion flux, ion content and electrical resistance. The results are analyzed with acid sulfuric solutions on the basis of the Nernst-Planck equation and Goldman hypothesis. Calculated values are compared with experimental values. This work shows that diffusion dialysis allows one to recover sulfuric acid from effluents containing sodium and zinc ions.

Synthesis of perfluorinated cation exchange membranes by preirradiation grafting of acrylic acid onto ethylene‐tetrafluoroethylene films

Hydrophilic carboxyl-containing fluoromembranes were obtained by preirradiation grafting of acrylic acid onto ethylene-tetrafluoroethylene film. The dependence of the grafting reaction on temperature, monomer concentration, nature and concentration of inhibitor, crosslinking agent, solvent, and on the preirradiation dose was investigated. The grafting rates increase with temperature, whereas the saturation degree of grafting (SDG) decreases. Addition of inhibitor minimizes homopolymerization and at the same time hinders the grafting reaction. The SDG increases markedly with monomer concentration until it reaches a maximum and thereafter decreases. The grafting rates increase with preirradiation dose. Addition of crosslinking agent initially decreases the SDG, and thereafter increases. The highest grafting rates are obtained using water as solvent followed by methanol and ethanol. The results are discussed on the basis of various parameters : interaction between monomer diffusibility and the viscosity of the monomer bath, the mutual reactivity of monomer, and the crosslinking agent. An agreement is observed between the values of the electrical resistance and the saturation degree of grafting.

NaCl diffusion across an amphoteric ion exchange membrane

Abstract The diffusion of NaCl across an amphoteric ion exchange membrane has been studied by measuring the diffusion flux of NaCl and the self-diffusion fluxes of Na+ and Cl− ions through this membrane. The NaCl fluxes through the amphoteric membrane are analysed on the basis of the Nernst-Planck equation and the TMS theory. The self-diffusion measurements make possible calculations of the individual difusion coefficients. The effects of the external pH on the physicochemical properties of the membrane are discussed. The measurement of the NaCl content in the membrane combined with the result of the membrane potential and with the result of the self diffusion measurements make it possible to obtain the theoretical values of the NaCl flux. These values are in satisfactory agreement with the experimental values.