Methods of defluoridation: Adsorption and regeneration of adsorbents

Abstract

This chapter begins with an overview of operational defluoridation methods. Main methods in operational plants are adsorption on activated alumina, separation by reverse osmosis or nanofiltration, and electrocoagulation using soluble aluminum anode. Exhausted alumina can be regenerated by washing with alkali solution followed by an acid activation. Domestic defluoridations work with small equipment using adsorption on activated alumina or separation with reverse osmosis. Adsorption on alumina and regeneration of exhausted adsorbent is a model in the research of new fluoride adsorbents. In the second part, the chapter gives recent results of research about defluoridation methods. The research of new fluoride adsorbents explores the use of fluorophilic elements dispersed in insoluble materials. These new fluoride adsorbents are characterized by the presence of double or triple oxides or nanomaterials or show composite structures. In the field of fluoride removal, there are a lot of researches of low-cost adsorbents made from renewable biomass or made from geological materials and about electrochemical and membrane processes.