Jacqueline Sandeaux

Salicylic acid production by electrodialysis with bipolar membranes

Abstract Production of salicylic acid from sodium salicylate was carried out by electrodialysis (ED) using bipolar membranes (BPM). The process feasibility was tested using a laboratory ED-cell with a membrane area of 40 cm 2 . The performances of two commercial bipolar membranes (Tokuyama Soda and Stantech membranes) are compared. Current efficiencies for salicylic acid and caustic soda production are close for both bioolar membranes (80–90%), but differences are observed with respect to energy consumption which are related to the electrical characteristics of the membranes.

Elimination of nitrate from drinking water by electrochemical membrane processes

The performance of three membrane processes (Donnan dialysis, electrodialysis, electrodeionization) using an ADS-Morgane anion-exchange membrane, was compared to remove nitrate from drinking water. The influence of concentration, current density and flow rate was studied with a 3.10−3 M nitrate solution to determine the best experimental conditions. Then the membrane processes were applied for the treatment of Montpellier drinking water where the nitrate concentration was increased up to a concentration of 80–100 ppm. In all cases the results showed extraction ratios higher than 80%. With the electrodialysis and electrodeionization techniques, the extraction rate of nitrate was faster than with Donnan dialysis, and a deionized water of high purity was obtained. A nitrate elimination ratio of 99% has been reached with electrodeionization.

Continuous electropermutation with ion-exchange textiles

Abstract A continuous electropermutation process using ion-exchange textiles has been developed in order to eliminate cations from low concentration solutions. The applied voltage was used simultaneously as the driving force for extracting the cations and regenerating the ion-exchange textiles. Due to their sheet form and swelling in aqueous solutions, these ion-exchange materials provide a good contact with ion-exchange membranes. This process was tested with NaCl solutions under various experimental conditions; then it was applied to treate a solution containing metal ions such as Zn2+. The study carried out with a laboratory pilot developing an active membrane area of 20 cm2 showed that the process is able to achieve high levels of removal (>95%) and to concentrate cations in small volumes of the receiving compartment. The presence of ion-exchange textiles in the feed compartment of the ED stack allows a lower power consumption than with conventional electrodialysis.

Production of High Resistivity Water by Electrodialysis. Influence of Ion-Exchange Textiles as Conducting Spacers

Production of high resistivity water was investigated by electrodialysis (ED) using either inert or conducting spacers. Ion-exchange textiles were used as conducting spacers. Experiments were performed on a preindustrial scale with a pilot consisting of nine two-compartment cells, each membrane having an effective area of 176 cm2. Three configurations of the ED stack were investigated for the dilution compartment: EDIT-(2) with a 2-mm thick ion-exchange textile, and ED-(2) or ED-(0.4), with a 0.4-mm thick inert spacer inserted between 2 or 0.4 mm thick dilution compartments, respectively. The textile induces a moderate increase in the pressure drop between the inlet and outlet of the stack. The performances of the different processes were compared under various experimental conditions of pH, nitrogen bubbling throughout the feed solution, flow rate, and current density. The results show that for an inlet conductivity of 10–15 μS·cm−1, a flow rate of of 2.2 × 10−5 m3·s−1, and an applied voltage of 80 V, an...

Electrotransport of alanine through ion-exchange membranes

Abstract The extraction of alanine by electrodialysis was studied taking into consideration the competition of protons or hydroxyl ions in the membrane transport process. The diffusion and electrodiffusion of alanine from solutions (1M) were examined at different pH varying from 1.4 to 11, by measuring, under different current densities in the range 0–30 mA-cm2, the alanine fluxes through an anion exchange membrane as well through a cation exchange membrane. The best value of the acid pH for extraction of alanine into the cationic form is around 2.1. At lower pH the competition of protons is too strong. For extraction of alanine into the anionic form the best value of the basic pH is 11 where the current efficiency is near 100%. In the electrotransport of alanine, concentration polarization and water splitting in the anion exchange membrane have an influence on the alanine extraction rate.

Properties of an anion exchange membrane in contact with aqueous solutions of sodium chloride and sodium benzenecarboxylate or benzenesulfonate

Abstract Some properties of an anion-exchange membrane, ADS (Morgane-Solvay), were studied in aqueous solutions containing both sodium chloride and sodium benzenecarboxylate or benzenesulfonate. Measurements of electric resistance, water content, ion-exchange aqueself-diffusion flux were performed as a function of the organic salt concentration (10 −3 to 10 −1 M) in the external aqueous solution. The membrane affinity is greater for benzenesulfonate than benzenecarboxylate ion. The electric resistance decreases when the Cl − counter-ions are substituted by these organic ions more hydrophobic and less mobile. The self-diffusion flux of the Cl − ion through the membrane are strongly dependent on the water content and the concentration of this inorganic anion inside the membrane.

Potential use of Cu2+, K+ and Na+ for the destruction of Caulerpa taxifolia: differential effects on photosynthetic parameters.

Chemical techniques were investigated in order to eradicate Caulerpa taxifolia, a green alga spreading at a remarkable rate in the Mediterranean Sea. The action of copper, potassium and sodium ions on survival rates and photosynthetic parameters was compared, in order to optimise the conditions of further in situ treatments. The lethal doses were determined and the impact of the studied cations on photosynthesis and respiration rates and PSII photochemistry was analysed from measurements of net oxygen exchanges and chlorophyll fluorescence. The Cu2+ concentrations required to obtain 100% mortality were 15 × 102 to 104 times lower than those of K+ and Na+. Respiration was slightly affected whatever the salt concentration,while photosynthesis could be totally inhibited depending on the applied treatment. Changes in the structure of the Ribulose-1,5-biphosphate carboxylase/oxygenase (RubisCO, EC: 4.1.1.39) were also detected when C. taxifolia under went cation treatments (10 mg L-1 Cu2+, 1h; 20 gL-1 K+, 3 h; 20 g L-1 Na+, 1 h). Given the high concentration and long incubation periods required with K+ and Na+ ions, these cations are not suitable to be used in situ. Our results make possible the utilisation of copper cations following technical approaches such asion-exchange textile covers, which allows a controlled release of cupric ions without dissemination in the marine environment.

Physico-chemical characterization of the ionic permeability of an enteric coating polymer

Cellulose acetate phthalate (CAP) is widely used as an enteric coating polymer. In this work, radiotracer and impedance measurements were performed in order to study the evolution in time of CAP films immersed in different solutions including artificial gastric juice. The membrane permeabilities demonstrate a strong dependence on the pH value, suggesting our film to behave like a cation-exchange membrane. A two-step transport mechanism is proposed to explain the variation of the experimental data with time. The effects of different plasticizers and solvents were also investigated, our observations showing the importance of using a hydrophobic plasticizer to improve the gastroresistance of the polymer.

Sorption equilibrium of aromatic anions in an anion exchange membrane

Abstract Ion exchange and water content measurements were performed with an anion exchange membrane, ADS XL 10 (Solvay), equilibrated in aqueous solutions containing mineral electrolyte as NaCl, and/or organic electrolyte as sodium benzene carboxylate (ΦCO2Na) and sodium 4-hydroxy-1-naphthalenesulfonate (ΦΦOHSO3Na). By using radiotracers, it was possible to determine the amount of the total mineral and organic ionic species present inside the membrane. The fixation of big organic ions balancing the exchanging sites of the membrane can modify the membrane structure, creating micropores able to sorb more electrolytes. It was established that the sorption of hydrophobic organic ions corresponds to a ‘micelle mechanism’, The penetration of hydrophobic ions into the membrane induces a change in the molar volume of the wet membrane in relation to the variation of the water content.

Desorption of counter-ions followed with labelled ions and water dissociation in perfluorinated quaternary ammonium membranes and Nafion 125 membranes

Abstract Desorption and exchange phenomena have been studied in perfluorinated quaternary ammonium membranes (QAM) by means of radiotracers. In these anion exchange membranes, counter-ion desorption followed with 36 Cl gave higher results than co-ion desorption followed with 22 Na. The cation exchange Nafion 125 membrane gave similar results. When these two kinds of membranes, equilibrated in 0.1 M NaCl at pH 7, are desorbed in water at this pH, pH decreases with QAM and increases with Nafion 125. These shifts in pH values are observed over a wide range of pH around 7. These results can be explained by a larger water dissociation due to the catalyzing action of the exchange sites.