N. Mameri

Defluoridation of septentrional Sahara water of north Africa by electrocoagulation process using bipolar aluminium electrodes

Abstract The purpose of this paper is to suggest an efficient defluorination process which does not require a big investment. For this, the electrocoagulation process with aluminium bipolar electrodes was used. In the first step, the influence of parameters such as inter-electrode distance, fluoride concentration, temperature and the pH of the solution, were investigated and optimized with synthetic water in batch mode. In the second step, the optimization process was continued with Oued Souf water (south Algeria) where the influence of the current density and the area/volume ratio on the defluorination process was evaluated. The electrocoagulation process with aluminium bipolar electrodes permitted the defluorination of Sahara water without adding soluble salts to the treated water. The aluminium–fluoride weight ratio attained 17/1.

Study of a new technique for fluoride removal from water

Abstract A new technique based on the combination of an activated alumina column and an electrochemical system for fluoride removal from water is reported in this study. In the first step, the optimization of the process was achieved under various experimental parameters (volumetric flow, temperature, pH, initial fluoride concentration and hardness) with a synthetic solution. The comparison of the performance of the current activated alumina process and the electrosorption system proved to be more efficienct than the latter in removing fluoride from water. Thus, the fluoride sorption capacity at the breakthrough point of the activated alumina column reached 3.8 mg F − /L. It was increased by about 60% by means of the electrochemical process than the results obtained in current mode. Moreover, it was found that the electrosorption system could be utilized to regenerate the saturated activated alumina. In the second step, the electrosorption process was utilized to treat Sahara drinking water naturally contaminated with fluoride (3 mg/L) under optimum conditions previously determined. The electrosorption process coupled with activated alumina column has been successfully applied for fluoride removal from drinking water.

DEFLUORIDATION OF SAHARA WATER BY SMALL PLANT ELECTROCOAGULATION USING BIPOLAR ALUMINIUM ELECTRODES

The purpose of this paper is to propose an efficient and low cost defluoridation process based on electrocoagulation with aluminium bipolar electrodes. The performance of a pilot scale electrochemical reactor equipped with aluminium bipolar electrodes with an anode active area surface of about 1.6 m2 was studied. The pilot study yielded promising results, suggesting that further in-depth development studies are justified.

Anticancer activity of chemically prepared shrimp low molecular weight chitin evaluation with the human monocyte leukaemia cell line, THP-1

In the present study, anticancer activities of chitin, chitosan and low molecular weight chitin were evaluated using a human tumour cell line, THP-1. A molecular weight-activity relationship and an electrostatic interaction-activity relationship were determined. The cytotoxic effects of chitin and derivatives were also evaluated using a normal human foetal lung fibroblastic cell line, MRC-5 and the specific cytotoxicity of chitin and derivatives to tumour cell lines was demonstrated. The high antitumour effect of low molecular weight of chitin was established.

Equilibrium, kinetic and thermodynamic studies on aluminum biosorption by a mycelial biomass (Streptomyces rimosus).

This work focused on kinetic, equilibrium and thermodynamic studies on aluminum biosorption by Streptomyces rimosus biomass. Infrared spectroscopy analysis shows that S. rimosus present some groups: hydroxyl, methyl, carboxyl, amine, thiol and phosphate. The maximum biosorption capacity of S. rimosus biomass was found to be 11.76 mg g(-1) for the following optimum conditions: particle size, [250-560] μm, pH 4-4.25, biomass content of 25 g L(-1), agitation of 250 rpm and temperature of 25 °C. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models were applied to describe the biosorption isotherms at free pH (pH(i) 4) and fixed pH (pH(f) 4). Langmuir model is the most adequate. With fixed pH, the maximum biosorption capacity is enhanced from 6.62 mg g(-1) to 11.76 mg g(-1). The thermodynamic parameters (ΔG°, ΔH° and ΔS°) showed the feasibility, endothermic and spontaneous nature of the biosorption at 10-80 °C. The activation energy (Ea) was determined as 52.18 kJ mol(-1) using the Arrhenius equation and the rate constant of pseudo-second-order model (the most adequate kinetic model). The mean free energy was calculated as 12.91 kJ mol(-1) using the D-R isotherm model. The mechanism of Al(III) biosorption on S. rimosus could be a chemical ion exchange and carboxyl groups are mainly involved in this mechanism.

The Influence of Parameters Affecting Boron Removal by Electrocoagulation Process

Boron removal in seawater desalination presents a particular challenge. In seawater reverse osmosis (SWRO) systems boron removal at low concentration (<0.5 mg/L) is usually achieved by a second pass using brackish water RO membranes. However, this process requires chemical addition and important additional investment, operation and maintenance, and energy costs. Electrocoagulation (EC) process can be used to achieve such low boron concentration. In this work, the removal of boron from aqueous solution was carried out by EC process using aluminum and iron electrodes. Several operating parameters on the removal efficiency such as initial pH, current density, initial boron ion concentration, feed concentration, gap between electrodes, and electrode material, were investigated. In the case of bipolar electrocoagulation (BEC), an optimum removal efficiency of 96% corresponding to a final boron concentration of 0.4 mg/L was achieved at a current density of 6 mA/cm² and pH = 8 using aluminum electrodes. The concentration of NaCl was 2,500 mg/L and the gap between the electrodes of 0.5 cm. Furthermore, a comparison between monopolar electrocoagulation (MEC) and BEC using both aluminum and iron electrodes was carried out. Results showed that the BEC process has reduced the current density applied to obtain high level of boron removal in a short reaction time compared to MEC process. The high performance of the EC showed that the process could be used to reduce boron concentration to acceptable levels at low-cost and more environmentally friendly.

Fluoride removal with electro-activated alumina

“Ecole Nationale Polytechnique dillger, B.P. 182-16200, El Harrach, Alger, Algeria “DPpartement GEnie chimique, University of Technology of Compiggne, B.P. 20.509, 60205 CompiGgne cedex, France Tel. +33 (3) 44 23 44 57; Fox: +33 (3) 44 23 52 16; email: nabil.mameri@utc.j? Received 15 November 2002; accepted 10 February 2003 Abstract A new activation technique using alumina was developed for the removal of fluoride from water. This technique is based on an electro-activation by means of an electrical field. The optimum activation parameters (potential and contact time) were determined, and an activation time of about 120 min and a potential of +lOO mV/SCE were then selected. The effect of various experimental parameters - ionic strength, pH hardness, and fluoride-alumina concentration ratio GGb- was determined for the adsorption capacities ofthe electro-activated alumina. The effect ofthese parameters on the fluoride adsorption capacities of both electro-activated adsorbent and conventional alumina was essentially the same, except for the ionic strength parameter. Indeed, ionic strength did not have a considerable effect on the performance of the conventional alumina. However, for the electro-activated alumina, an increase in ionic strength induced a slight increase in the fluoride adsorption capacity ofthe electro-activated adsorbent. The optimum conditions, determined in the batch mode, gave an optimal pH ranging from 3.5 to 5 and a C,,/C, ratio of about 4. At a NaCl concentration of 800 mg dm3, the fluoride adsorption capacity of the electro-activated alumina was about 55% better than that of conventional alumina. Keywordrs: Adsorbent activation; Electrochemical technique; Fluorine; Alumina

Purification, characterization, and molecular cloning of an extracellular chitinase from Bacillus licheniformis stain LHH100 isolated from wastewater samples in Algeria.

An extracellular chitinase (ChiA-65) was produced and purified from a newly isolated Bacillus licheniformis LHH100. Pure protein was obtained after heat treatment and ammonium sulphate precipitation followed by Sephacryl S-200 chromatography. Based on matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF/MS) analysis, the purified enzyme is a monomer with a molecular mass of 65,195.13 Da. The sequence of the 27 N-terminal residues of the mature ChiA-65 showed high homology with family-18 chitinases. Optimal activity was achieved at pH 4 and 75 °C. Among the inhibitors and metals tested, p-chloromercuribenzoic acid, N-ethylmaleimide, Hg(2+), and Hg(+) completely inhibited enzyme activity. Chitinase activity was high on colloidal chitin, glycol chitin, glycol chitosane, chitotriose, and chitooligosaccharide. Chitinase activity towards synthetic substrates in the order of p-NP-(GlcNAc)n (n = 2-4) was p-NP-(GlcNAc)2 > p-NP-(GlcNAc)4 > p-NP-(GlcNAc)3. Our results suggest that ChiA-65 preferentially hydrolyzed the second glycosidic link from the non-reducing end of (GlcNAc)n. ChiA-65 obeyed Michaelis-Menten kinetics, the Km and kcat values being 0.385 mg, colloidal chitin/ml and 5000 s(-1), respectively. The chiA-65 gene encoding ChiA-65 was cloned in Escherichia coli and its sequence was determined. Above all, ChiA-65 exhibited remarkable biochemical properties suggesting that this enzyme is suitable for bioconversion of chitin waste.

Application of the electrosorption technique to remove Metribuzin pesticide.

The present work deals with the removal of Metribuzin from aqueous solutions in a batch and continuous mode using electrosorption technique. This technique is based on the combination of two processes: the adsorption of Metribuzin into activated granular carbon (GAC) column and the application of the electrochemical potential. The effects of various experimental parameters (electrochemical potential, volumetric flow rate and initial Metribuzin concentration) on the removal efficiency were investigated. The pesticide sorption capacity at the breakthrough point of the GAC column reached 22 mg(pesticide)g(GAC)(-1). It was increased by more than 100% when the desired electrical potential (-50 mV/SCE) was applied in comparison with the conventional GAC column in similar experimental conditions without electrical potential. Evenmore, the electrosorption technique reduced considerably the drastic decrease encountered when passing from batch mode to continuous column mode.

Electrodialysis with bipolar membrane for regeneration of a spent activated carbon

The main purpose of the present work was to develop a treatment method to regenerate granular adsorbent beds saturated with H(2)S by utilizing three electrodialysis compartments equipped with a cation or an anion exchange membrane or a bipolar membrane. Three electrodialysis compartments were utilized under various experimental parameters to determine the optimum conditions for the recovery of column particles saturated by H(2)S. The desulphurization operation is achieved with the extent of extraction close to 90% and an electric current density of about 30%. Use of the bipolar membrane makes it possible to regenerate the saturated adsorbent granules without adding chemical products. Since the only reagent was electricity, the projected economics are very attractive.