Water defluoridation with special emphasis on adsorbents-containing metal oxides and/or hydroxides: A review

Abstract

Fluoride contamination in drinking water has been recognized as one of the major worldwide problems since this represents a serious threat to human health. The World Health Organization (WHO) recommends the guideline value (maximum permissible limit) of 1.5mgL−1 for fluoride in drinking water. Unfortunately, many countries have high fluoride concentrations (up to 30mgL−1) in water supplies that may cause widespread fluorosis and skeletal illnesses among the population. Many methods have been developed for fluoride removal from water including adsorption, ion exchange, electrodialysis and precipitation. Nevertheless, more efficient and cost-effective processes and materials are needed to comply with the fluoride maximum permissible limit. Adsorption has been widely used because it is the most cost-effective methodology for the removal of ionic contaminants from aqueous solutions. Various adsorbent materials have been used to remove fluoride from water, for instance activated alumina, activated carbon, bone char, minerals, among others, but unfortunately their chemical stability and/or selectivity and adsorption capacity is something that still has to improve substantially. During the last decade, metal oxyhydroxides in powder form and supported on different matrixes have been of great interest for fluoride removal. This review condenses the advances on this last topic that is still under study.