A Review of Metal oxide Nanomaterials for Fluoride decontamination from Water Environment

Fluoride pollution in water emerges a challenging problem to environmental researchers especially in regions where people depend on groundwater for drinking. Natural water bodies are experienced Fluoride impurities from geogenic and anthropogenic sources. Fluoride contamination in drinking water sources has been recognized as a major problem in many countries worldwide especially in several parts of India, China, Sri Lanka, South Africa, Tanzania, Argentina, East Africa, part of South Africa, Turkey and some part of South America. Intrusion of Fluoride with drinking water manifests several health effects such as dental caries and teeth mottling besides skeletal fluorosis. Due to clinical manifestations caused by drinking Fluoride contaminated water, the World Health Organization (WHO) has recommended 1.5 mg L-1. Hence, it is very much needed to supply water with safe F-. Various physico-chemical methods are available for defluoridation of water, out of which adsorption method is common and widely be used. to remove fluoride from water. Till date, activated alumina is most conventional adsorbing material that are conveniently being used for this purpose. However, activated alumina performed well in acidic environment and regeneration issue poses a complex problem. Other traditional adsorbents though are able to uptake Fluoride from water environment the low sorption capacities and efficiencies restricted their wide application. A major breakthrough took place in recent years due to application of nanomaterial in water purification. As compared with traditional materials used, nanostructure based adsorbents exhibited much higher performance and efficiency of water decontamination as well as providing a sustainable approach to safe water supply. Nonmaterial is being used throughout the globe as possible solution for removal of fluoride from water as an engineering tool. In the past ten years, many researchers have dealt with low cost and effective adsorbent nanomaterials for the removal of fluoride from aqueous solution and contaminated water. Among them Iron, Magnesia, Alumina, Cerium and calcium, Titania, Silica and Zirconium based metal oxide nanomaterials and composites have proven themselves as excellent adsorbents due to their unique features. The increased surface area of the metal oxide nanoparticles highly favours fluoride adsorption. Their high adsorption capacity, non-toxic nature, limited solubility in water and good desorption potential makes metal oxides a material of choice. The present paper discusses use of nanomaterial and composite nanomaterials for enhanced removal of fluoride contaminated water. The present study also highlights the various key factors (pH, agitation time, initial fluoride concentration, temperature, particle size, surface area, etc) which governs efficacy of different materials in the removal of fluoride from water. (C) 2019 Elsevier Ltd. All rights reserved.