Conventional and Membrane Techniques of Fluoride Removal from Aqueous Environment.

Fluoride contamination of surface and ground waters is frequently observed around the world. Fluorides may originate from both anthropogenic and the natural sources. In small amounts, they are beneficial for bone and teeth development. However, higher concentrations in drinking water are harmful to human health. According to WHO guidelines, the fluoride content in drinking water cannot exceed 1.5gF(-)/m(3). Therefore, more effective and economic defluoridation methods are sought. Fluorides can be removed from water environment by various physico-chemical methods such as adsorption, coagulation, precipitation, ion-exchange as well as the membrane processes. Examples of fluoride elimination processes and techniques are discussed, taking account of their limitations affecting the efficacy of fluoride removal from water solutions. It was demonstrated that the extent of fluoride removal in different technological processes primarily depends on solution pH, the initial F- ion concentration, presence of coexisting ions, adsorbent type and membrane properties. The study results indicate that under optimal operational conditions the fluoride removal efficacy may exceed 90%.