The objective of this work is to study the phosphate adsorption from natural waters by using a granular activated carbon (GAC). Experiments were carried out with synthetic solutions of phosphate prepared using groundwater (mineralized drinking water). Batch tests were carried out in order to study different operating parameters such as the effect of contact time, pH, initial phosphate concentration and adsorbent dosage. In addition, the adsorption kinetic data were simulated using the pseudo first order, the pseudo second-order and the intra-particle diffusion model. The sorption equilibrium was analyzed by Langmuir, Freundlich and Dubinin–Radushkevich isotherms model. Results show that the phosphate adsorption was reversible and the quantity adsorbed reached its maximum value (2.82 mg/g) after 30 min. It was also found that phosphate uptake was affected by variation of pH, initial concentration of phosphate and granular activated carbon dosage. The adsorption improved with increase in pH values, initial concentration and adsorbent dosage. The results of kinetic studies revealed that pseudo-second-order model adequately described the adsorption phosphate on GAC and the intra-particle diffusion involved in the adsorption mechanism. Also, isotherm study showed that Langmuir isotherm best fit the data and the adsorption was a physical type.

Dans la zone orientale du Sahara septentrional, plusieurs enquêtes épidémiologiques ont mis en évidence l’existence d’un problème de fluorose endémique qui se traduit par des déformations dentaires et osseuses. Nous avons donc tenté d’évaluer les possibilités de défluoruration d’eaux souterraines du sud algérien par adsorption sur des bentonites brutes et activées chimiquement. Dans un premier temps, nous avons réalisé des analyses d’eaux des forages les plus exploités dans les régions de Biskra, Ouargla, El Oued et Touggourt. Les résultats ont donné une idée éloquente de la présence excessive du fluor associée à une dureté et une minéralisation élevées. Dans un second temps, nous avons déterminé les conditions optimales d’utilisation de deux bentonites (Mostaghanem et Maghnia) à l’état brut puis traitées chimiquement sur des solutions synthétiques de fluorure de sodium. Les meilleurs résultats ont été obtenus avec la bentonite activée de Maghnia à un rapport massique acide sulfurique/bentonite = 0,20, pour un temps d’activation de trois heures. L’efficacité du procédé d’adsorption du fluor sur les deux bentonites a ensuite été testée sur des eaux de boisson de la région de Biskra, naturellement chargées en fluor. Mots‐clés: Fluor; Sahara; Adsorption; Bentonite In the eastern zone of northern Sahara, several epidemiological investigations have revealed the existence of an endemic fluorosis problem, which results in dental and bone deformities. The main cause of this is attributed to ingestion, for a relatively long time, of drinking water with high fluoride content. The adoption of a defluoridation process remains conditional on the physico‐chemical water quality, the simplicity of the process and the availability of reagents. We have therefore focused our study on the possible use of a clay widely available in the west of Algeria, bentonite. We have tried to assess the possibilities of groundwater defluoridation of southern Algerian by adsorption on raw bentonites and chemically activation. As a first step, we have carried out analyses of waters which are those most exploited in the regions of Biskra, Ouargla, El Oued and Touggourt. The results gave an eloquent idea of the excessive presence of fluoride. Our results also showed that these waters were characterized by a significant mineralization and an excessive hardness. As a second step, we determined the optimal conditions for use of two bentonites (Mostaghanem and Maghnia) in their raw state and then chemically treated. Trials were conducted with synthetic solutions of sodium fluoride. The best results were obtained with bentonite of Maghnia for a mass ratio acid/bentonite equal to 0.2 and an activation time of three hours. The effectiveness of the process of fluoride adsorption on both bentonites was then tested on drinking waters in the region of Biskra, naturally laden with fluoride.

The aim of this work is to contribute to the understanding of the conditions of formation of volatile and non volatile halogenated organic compounds during the chlorination of algerian surface waters leading to drinking waters. The presence of humic substances in these waters leads to a considerable consumption of chlorine and to important formation potentials of halogenated compounds. These potentially toxic compounds can be found in finished waters when their treatment is not optimized.

L’objectif de la présente étude est d’observer l’efficacité de la coagulation-floculation par le sulfate d’aluminium sur l’élimination des composés organiques à fonctions phénoliques (phénol et pyrogallol). L’intérêt s’est porté plus particulièrement sur l’incidence de sels minéraux constitutifs de la dureté « calcium et magnésium » et souvent présents dans la matrice minérale des eaux algériennes. Des essais de Jar-Test ont été réalisés sur les deux composés phénoliques dissous dans l’eau distillée seule, puis enrichie en sels minéraux. Ces essais ont été réalisés sur des solutions synthétiques d’eau distillée enrichies par les ions de calcium et de magnésium introduits sous différentes formes (CaCl2•2H2O; CaSO4•2H2O; CaCO3; MgCl2•6H2O; MgSO4•7H2O) et, enfin, avec les eaux souterraines de la région. Différents paramètres réactionnels ont été variés (ex. : l’effet du pH et l’influence de la teneur en sels) et cette approche a permis une meilleure compréhension des mécanismes d’interactions composés phénoliques / sels calciques et magnésiens. Les résultats obtenus indiquent que l’efficacité du procédé dépend du nombre et de la position des groupements phénoliques sur les molécules. Les principaux mécanismes seraient soit une adsorption physique, soit un échange de ligand ou une complexation à la surface des flocs d’hydroxydes d’aluminium. L’ajout de sels minéraux semble améliorer les rendements d’élimination de composés phénoliques testés et avoir un effet sur la gamme optimale de pH de coagulation. Une application de ce procédé à des eaux minéralisées (eaux de forage) de la région de Biskra, située au sud-est de l’Algérie, a abouti à une amélioration des rendements comparés à ceux dans de l'eau distillée. The objective of this study was to observe the effectiveness of coagulation-flocculation by aluminum sulfate on the removal of organic compounds with phenolic functional groups (phenol and pyrogallol). The work focused on the impact of the inorganic components of water hardness, calcium and magnesium, which are often present in the inorganic matrix of Algerian waters. Jar-test trials were conducted on the two phenolic compounds dissolved in distilled water only and then in water enriched with mineral salts. The tests were performed on synthetic solutions of distilled water enriched with calcium and magnesium ions, introduced in various forms (CaCl2•2H2O; CaSO4•2H2O; CaCO3; MgCl2•6H2O; MgSO4•7H2O). Several reaction parameters were varied, notably the pH and the salt content, and this approach yielded a better understanding of the mechanisms of interaction between phenolic compounds and calcium/magnesium salts. The obtained results indicate that the process efficiency depends on the number and position of phenolic groups on the organic molecules. The main mechanisms could be a physical adsorption, a ligand-exchange reaction or surface complexation on the aluminum hydroxide floc. The addition of inorganic salts appears to improve removal efficiencies for the tested phenolic compounds and affects the optimal pH range for coagulation. The application of this method to mineralized waters (well water), collected in the region of Biskra located in the southeastern Algeria, resulted in improvement of yields, compared to those obtained in distilled water.