Ecology, Environment and Conservation Paper

A REVIEW ON ADSORPTION EFFICIENCY OF WIDELY ADOPTEDADSORBENTS USED IN DEFLUORIDATION OF AQUEOUS MEDIA

Rosalin Das

Abstract

The review article provides an insight on various adsorbents and their efficiency in fluorideremoval fromdrinking and waste water. The capacity of fluoride removal of adsorbent is dependent on pH, contact time,temperature, surface area of adsorbent and initial concentration of fluoride solution etc. In comparison tothe traditional natural methods, the synthetic and nanostructure-based adsorbents, exhibited higherperformance and efficiency of defluorination which provides a sustainable approach to safe drinking waterquality. The present paper deals with some widely adopted natural adsorbent, synthetic and nanostructurebasedadsorbents. The natural adsorbent includes, thermally treated lateritic soil, modified natural magnetiteore (Fe3O4) with aluminum and lanthanum ions, lateritic soils, Titanium hydroxide, limestone (LS) andaluminium hydroxide, sedimentation with calcium and aluminium. The Synthetic adsorbent includes,Surface-functionalized polyurethane foam (SPUF); Schwertmannite; Carbonaceous material from pyrolysisof sewage sludge; Chitosan. And the effective adsorbent nano scale structure includes, nanoscale aluminiumoxide hydroxide (AlOOH), Magnetic iron oxide/aluminium hydroxide composite, sulfatedoped Fe3O4/Al2O3 nanoparticles, nano-scale aluminum oxide hydroxide (nano-AlOOH), Graphene Nanoparticlesadsorbent, Al2O3/Bio-TiO2 nano composite (ABN), Green synthesized Fe3O4/Al2O3nanoparticles with coatedpolyurethane foams etc. The activated alumina is most conventional fluoride adsorbing material. However,activated alumina performs well in acidic environment with complex regeneration issue. Although othertraditional adsorbents remove fluoride from water but they have lower efficiency, which restrict theirapplication. In case of synthetic and nano structured based adsorbents, due to increased surface area, nontoxicnature, limited solubility in water and high adsorption efficiency, these methods are widely accepted andproven environmentally suitable.