Defluoridation of the Algerian north Sahara waters by adsorption onto local bentonites

• Published in: International journal of environmental studies 2009-04, Vol.66 (2), p.153-167
• Main Authors: Achour, Samia, Youcef, Leila
• Format: Article
• Language: English
• ISSN: 0020-7233; 1029-0400
• DOI: 10.1080/00207230902859747

Dans la zone orientale du Sahara septentrional, plusieurs enquetes epidemiologiques ont mis en evidence l'existence d'un probleme de fluorose endemique qui se traduit par des deformations dentaires et osseuses. Nous avons donc tente d'evaluer les possibilites de defluoruration d'eaux souterraines du sud algerien par adsorption sur des bentonites brutes et activees chimiquement. Dans un premier temps, nous avons realise des analyses d'eaux des forages les plus exploites dans les regions de Biskra, Ouargla, El Oued et Touggourt. Les resultats ont donne une idee eloquente de la presence excessive du fluor associee a une durete et une mineralisation elevees. Dans un second temps, nous avons determine les conditions optimales d'utilisation de deux bentonites (Mostaghanem et Maghnia) a l'etat brut puis traitees chimiquement sur des solutions synthetiques de fluorure de sodium. Les meilleurs resultats ont ete obtenus avec la bentonite activee de Maghnia a un rapport massique acide sulfurique/bentonite = 0,20, pour un temps d'activation de trois heures. L'efficacite du procede d'adsorption du fluor sur les deux bentonites a ensuite ete testee sur des eaux de boisson de la region de Biskra, naturellement chargees en fluor. Mots-cles: 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