Fluoride Adsorption from Water on Waste Materials

Abstract

The occurrence and concentrations of fluoride in surface and groundwater depend on pH, total dissolved solids, alkalinity, hardness, and geochemical composition of aquifers. However, in many countries, elevated fluoride concentration values are the result of fluoride-contaminated wastewater discharges. Because of fluoride pollution and the health problems that it causes, the World Health Organization (WHO) has set a maximum permissible fluoride content in drinking water of 1.5 mg l −1 . There are different ways of removing elevated concentrations of fluoride from water, such as coagulation and precipitation, membrane processes, electrochemical treatments, ion-exchange and its modification, but the adsorption process is generally accepted as the cheapest and most effective method for removing fluoride from water. Organic waste is increasing every day, especially in developed countries, and is generated in both industries and households. One of the ways to reduce such waste is the production of adsorbents for water defluorination. Adsorbents, most often pre - pared as activated carbon, can be obtained from various materials such as egg shells, fruit and vegetable peel, various leaves, stems, trunk bark, grain shells, legume shells, and many others. The aim of this paper is to provide an overview of the latest research on the use of adsorbents obtained from organic waste materials in order to remove elevated concentrations of fluoride from water.