Mohamed Taky

Fluoride removal from brackish water by electrodialysis

Studies have been conducted to reduce fluorine by electrodialysis from a brackish water containing 3000 ppm of total dissolved solids (TDS) and 3 ppm of fluoride. Two methods have been proposed and described to minimize the precipitation risks of the bivalent salts in the concentrate compartment. Measurements indicate that after electrodialysis, the targets concerning the quality of produced water were all achieved. The method without chemical pretreatment seems more simple to conduct and more adapted to environmental requirements than the method with pretreatment. From these studies it is demonstrated that electrodialysis is a reasonable process for removing fluoride from brackish water.

Polarization phenomena at the interfaces between an electrolyte solution and an ion exchange membrane. Part I : Ion transfer with a cation exchange membrane

Abstract Polarization phenomena occurring with ion exchange membranes have been investigated for the Selemion AMV anion exchange membrane in contact with NACl solutions. Recording of the current density—voltage responses combined with pH measurements and with individual ion flux measurements allow the determination of which phenomena are at the basis of the current transport. The concentration and potential profiles within the depleted unstirred layer have been calculated. Water splitting is indicated beyond the limiting current density. Analysis of the different overvoltages leads to a comparison between the interfacial transfer overvoltages of both the AMV anion exchange membrane and the CMV cation exchange membrane.

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.

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.

Transport properties of a commercial cation-exchange membrane in contact with divalent cations or proton-divalent cation solutions during electrodialysis

Abstract The ionic transport of divalent cations and the competitive transport between protons and divalent cations through a commercial cation-exchange membrane are investigated by means of both current- transmembrane potential difference responses and ionic flux measurements. The apparent rate constants of penetration of ions into the membrane are obtained from both electrodiffusion Nemst-Planck equations and Butler-Volmer relations. With protons-divalent cations mixed solutions (Zn 2+ , Ca 2+ , Mg 2+ ), this apparent rate constant is always greater for protons than for divalent cations, regardless of the applied current density. With divalent cations only, no water splitting occurs.

Removal of hardness from groundwater using two nanofiltration membranes: experimental study and modeling

Water hardness causes potentially costly nuisance problems in homes and in industry, such as disabling washing, formation of tartar carbonate and magnesium hydroxide in the pipe network of hot water. In this work, the ability of two commercial nanofiltration membranes (NF90, NF270) to remove hardness from the Maâmora groundwater (North of Morocco) was studied. Experiments were carried out in the pressure range of 5–40 bar and for different total hardness (TH) of the feed water. The effects of the trans-membrane pressure on the permeate flux and retention rate were investigated for each membrane. The results show that the nanofiltration membranes are capable of retaining the total hardness present in groundwater. Experiment results were correlated and analysed using Spiegler–Kedem model. Model parameters (the reflection coefficients and the solute permeability) have been determined for the two membranes using an adequate mathematical optimization procedure (Levenberg-Marquardt ś algorithm: LMA). Model predictions of Ca2+ and Mg2+ rejection were used to calculate rejection for Total Hardness. The modeling results were in good agreement with the experimental data for both NF90 and NF270 membrane. The correlation coefficient was greater than 0.9 in all cases. Also, statistical analysis of residual errors based on the root mean square error (RMSE), the normalized root mean square error (NRMSE) and the Nash-sutcliffe efficiency (NSE) coefficient demonstrates the good performance of the model and the optimization procedure. Results of this study are of great importance for local managers since waters of Maâmora groundwater are locally used in many areas and are part of several water management plans.