Fluoride Removal from Groundwater by Mineral-based Materials at Environmentally-relevant Concentrations

Excessive fluoride (F¯) in drinking water due to natural and anthropogenic activities is a serious health hazard affecting humans worldwide. Groundwater is the major and preferred source of drinking water, also in developing countries. The removal of the excess F^- from groundwater prior to drinking is important in terms of protection of public health. Current defluoridation techniques can be generally grouped into precipitation, coagulation, membrane processes, electrochemical processes, and adsorption/ion exchange. Although considerable advancement has been made in defluoridation research, a universal and sustainable solution to this ongoing crisis still appears intangible. By means of comparison to over 100 different materials, it can be concluded that mineral based materials are among the most promising for F^- removal for drinking water production. Therefore, this thesis focused on investigating F^- removal from groundwater by layered double hydroxides (LDHs), geopolymers, softening pellets and struvite. Alike various clays and rocks, these materials are composed primarily of minerals, (naturally) crystallized and have a periodic structure. These materials were selected, apart for their affinity for F^- removal, because of their low cost and local availability, for example due to being waste or by products from industrial operations.