Roger 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.

Recovery of spent acid by electrodialysis in the zinc hydrometallurgy industry: Performance study of different cation-exchange membranes

Abstract A performance study of four different cation-exchange membranes was conducted on laboratory and pilot scale (172 cm 2 /membrane, model CS-0 from Asahi Glass Co.) electrodialysis cells, using Neosepta CMS from Tokuyama Soda Co.; Morgane CRA from Solvay; Selemion CHV from Asahi Glass Co. and Nafion 117 from DuPont, coupled with a Morgane ARA 17-10 anion-exchange membrane. Comparisons were made of the sulphuric acid recovery rate, water transport, metal leakage and energy intake for these membranes. Proton permselectivity and metal leakage, co- and counter-ion transport numbers of the CMS membrane were investigated using Hittorfs method and radiotracer methods. This study shows that electrodialysis is suitable for the treatment of zinc hydrometallurgy effluents. However, R & D work must still be done in order to improve and optimize the technology for its use in future industrial applications. In particular, research efforts must concentrate on the synthesis of affordable and stable cation-exchange membranes showing high selectivity towards protons.

Transport of Na+ by monensin across bimolecular lipid membranes

Transmembrane 22Na fluxes across bimolecular lipid membranes are measured under two different experimental conditions: (a) the pH is the same in the two bulk aqueous solutions on either side of the membrane while the concentrations of Na+ are different; (b) the concentration of Na+ are identical but pH of the two solutions are different. In this latter case, the transport of Na+ occurs in the opposite direction to the difference of the proton concentration. In both cases, the electrical charge flux in negligible. A transport model is proposed to account for the experimental data.

Denitrification of drinking water by the association of an electrodialysis process and a membrane bioreactor: feasibility and application

Abstract A hybrid process combining electrodialysis and a membrane bioreactor was investigated to treat ground waters with excessive nitrate concentrations. Electrodialysis (ED) allowed the nitrate separation producing, on one hand, partially demineralized waters whose ion concentrations were in agreement with the norm, and on the other hand, brines that were treated by a membrane bioreactor. Experiments performed at laboratory scale with synthetic solutions and pre-industrial scale to treat a ground water contaminated by nitrates showed high efficiency of the hybrid process. The nitrate concentration of the treated water remained below the acceptable value (50 mg/l−1) and even below the recommended value (25 mg/l−1) for drinking water. Moreover, the ED treatment induced a softening of the treated water. The biological denitrification allowed the almost total removal of nitrates (99%) with kinetics close to 0.3kgN NO3/kg MVS/d and a limited sludge production of 0.5 gV.S.S./gN NO3.

Treatment of fishery washing water by ultrafiltration

The recovery and concentration of proteins from the waste water of a fish plant was achieved by ultrafiltration. Two UF modules equipped with Ceraver and Patterson Candy International (PCI) membranes were tested. Despite different cut-off values, similar apparent rejection coefficients (70% and 80% respectively) were obtained. Optimum economic conditions were established, corresponding to average transmembrane pressures of 2.2 x10 5 and 3.8 x 10 5 Pa and tangential flow rates of 6.0 and 0.47 m s -1 for Ceraver and PCI membranes, respectively. The protein concentration in the feed solution was increased from 5 to 35 g dm -3 . The study showed that the method could reduce pollution due to organic matter by decreasing the value of the Biological Oxygen Demand after 5 days (BOD 5 ) by about 80%.

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.

Extraction of amphoteric amino acids by an electromembrane process. pH and electrical state control by electrodialysis with bipolar membranes

Electrodialysis (ED) with bipolar membranes (BPM) was applied for the extraction of amino acids in an electrically neutral form. Under voltage, BPM split water, generating hydroxyl ions at the anodic side and protons at the cathodic side. The use of these membranes represents a newer method to convert neutral species into electrically charged species that are able to cross homopolar ED membranes. The ED operations were performed using a laboratory cell with a membrane area of 50 cm2. A mixture containing five amino acids (Gly, Ser, Ala, Val, Phe) was examined. The concentration of each amino acid was 100 mmol dm−3. The current density and pH in the feed and receiver compartments were varied. Extraction degrees and current efficiencies were calculated and compared under different experimental conditions.

Use of a membrane bioreactor for denitrification of brine from an electrodialysis process

Electrodialysis (ED) is an efficient process for the treatment of drinking water with high nitrate concentration. However it achieves only a transfer of pollution by producing concentrated brines. This study demonstrated the feasibility of ED brine denitrification in a membrane bioreactor (MBR). The results showed the high efficiency of the MBR despite the drastic conditions of nitrate concentration, pH and salinity of the ED concentrates. The denitrification kinetics close to 0.01 mgNO 3 – -N mgVSS –1 h –1 were in agreement with the literature values obtained with usual conditions. Next, the efficiency and performance of the hybrid process to treat ground water contaminated by nitrate was demonstrated in situ at Rodilhan (France). After ED treatment, the nitrate concentration of the treated water remained below the acceptable value (50 mg l –1 ) and a softening of the treated water was obtained. The membrane bioreactor allowed the almost total destruction of ED concentrate nitrate (99 %) with kinetics close to 0.3 kgNO 3 – -N kgVSS –1 d –1 and a sludge production of 0.5 gVSS gNO 3 – .

Extraction of amino acids from protein hydrolysates by electrodialysis

Protein hydrolysates were obtained by acid hydrolysis from animal or human residues, such as poultry feathers, ox blood and human hair. After neutralization and discolouration with active charcoal, the hydrolysates were treated by successive electrodialysis (ED) in order to extract amino acids into several fractions. The current density and pH were optimized for each ED operation performed with preindustrial pilot scale equipment. The first step was the demineralization of amino acid mixtures using an ED stack with two compartments. The salt removal was achieved with extraction degrees higher than 90% and current efficiencies of about 80%. In the most favourable case, the amino acid losses did not exceed 10%. The second step was the extraction of the charged amino acids using an ED stack with four compartments. Three fractions were obtained, corresponding to the acidic, basic and neutral amino acids. The extraction degrees varied from 80% to 100%. In the third step, the fractionation of basic amino acids on the one hand, and neutral amino acids on the other hand, was carried out with enrichment degrees varying from 50% to 80%.

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.