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Abstract
Fluoride in drinking water has a profound effect on teeth and bones. Up to a small
level (1-1.5mg/L) this strengthens the enamel. Concentrations in the range of 1.5-4
mg/L result in dental fluorosis whereas with prolonged exposure at still higher fluoride
concentrations (4-10mg/L) dental fluorosis progresses to skeletal fluorosis. High
fluoride concentrations in groundwater, up to more than 30 mg/L, occur widely, in
many parts of the world. This review article is aimed at providing precise information
on efforts made by various researchers in the field of fluoride removal for drinking
water. The fluoride removal has been broadly divided in two sections dealing with
membrane and adsorption techniques. Under the membrane techniques reverse osmosis,
nanofiltration, dialysis and electro-dialysis have been discussed. Adsorption, which
is a conventional technique, deals with adsorbents such as: alumina/aluminium based
materials, clays and soils, calcium based minerals, synthetic compounds and carbon
based materials. Studies on fluoride removal from aqueous solutions using various
reversed zeolites, modified zeolites and ion exchange resins based on cross-linked
polystyrene are reviewed. During the last few years, layered double oxides have been
of interest as adsorbents for fluoride removal. Such recent developments have been
briefly discussed.