Review
Review of fluoride removal from drinking water

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Abstract

Fluoride in drinking water has a profound effect on teeth and bones. Up to a small level (1–1.5 mg/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 (4–10 mg/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.

Introduction

The fluoride occurs mainly as sellaite (MgF2), fluorspar (CaF2), cryolite (Na3AlF6) and fluorapatite [3Ca3(PO4)2 Ca(F,Cl2)]. As fluorspar it is found in sedimentary rocks and as cryolite in igneous rocks. These fluoride minerals are nearly insoluble in water. Hence fluorides will be present in groundwater only when conditions favour their dissolution or high fluoride containing effluents are discharged to the water bodies from industries.

Fluoride in drinking water has a profound effect on teeth and bones. Fluoride displaces hydroxide ions from hydroxyapatite, Ca5(PO4)3OH, the principal mineral constituent of teeth (in particular the enamel) and bones, to form the harder and tougher fluoroapatite, Ca5(PO4)3F. Up to a small level this strengthens the enamel. However, fluoroapatite is an order of magnitude less soluble than hydroxyapatite, and at high fluoride concentration the conversion of a large amount of the hydroxyapatite into fluoroapatite makes the teeth and (after prolonged exposure) the bones denser, harder and more brittle. In the teeth this causes mottling and embrittlement, a condition known as dental fluorosis. With prolonged exposure (Dissanayake, 1991) at higher fluoride concentrations dental fluorosis progresses to skeletal fluorosis (Table 1). Fluoride is thus considered beneficial in drinking water at levels of about 0.7 mg/L but harmful once it exceeds 1.5 mg/L which is the World Health Organisation limit being followed in most of the nations (WHO, 1985, Smet, 1990) and is also the Australian recommended limit (NHMRC, 2004). The difference between desirable doses and toxic doses of fluoride is ill-defined, and fluoride may therefore be considered as an essential mineral with a narrow margin of safety (WHO, 1984).

With the increase in industrial activities water bodies with excess levels of fluoride are becoming a matter of great concern. High fluoride concentrations in groundwater, up to more than 30 mg/L, occur widely, notably in the United States of America, Africa and Asia (Czarnowski et al., 1996, Azbar and Turkman, 2000, Wang et al., 2002, Agarwal et al., 2003, Moges et al., 1996, Gaciri and Davies, 1992, Chernet et al., 2002, Mjengera and Mkongo, 2002, Moturi et al., 2002, Apambire et al., 1997). Long back it was estimated (WHO, 1984) that more than 260 million people worldwide consume drinking water with a fluoride content of >1.0 mg/L. The majority of these people live in tropical countries where the problem is exacerbated by the need to drink more water because of the heat. It is thus absolutely essential to bring down the fluoride levels to acceptable limits for which tremendous research and development efforts are being put all over the world. The present paper reviews the techniques available and ongoing efforts for fluoride removal from drinking water.

Section snippets

Methods of defluoridation from aqueous solutions

The objective in fluoride removal is to treat the contaminated water so as to bring down fluoride concentration to acceptable limits. The defluoridation techniques can be broadly classified into two categories, namely membrane and adsorption techniques. (High concentrations of fluoride in industrial effluents are usually brought down to ∼ 30 mg/L following precipitation method making use of calcium/magnesium/barium hydroxide slurry to reject fluoride as CaF2, MgF2 or BaF. This method is not

Conclusion

A brief review on fluoride removal for drinking water has been presented. The fluoride removal methods have been broadly divided in two sections dealing with membrane and adsorption techniques. Reverse osmosis, nanofiltration, dialysis and electro-dialysis have been discussed under membrane techniques. 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

Acknowledgements

The authors are thankful to Prof. B.K. Mishra, Director, Institute of Minerals and Materials Technology for his kind permission to publish this paper. The authors are thankful to Department of Science and Technology, India and DEST, Australia for financial support under INDO-AUS Strategic Research Fund Scheme.

References (144)

  • W. Czarnowski et al.

    Fluoride in drinking water and human urine in Northern and Central Poland

    Sci. of the Total Environ.

    (1996)
  • D.P. Das et al.

    Physicochemical characterization and adsorption behavior of calcined Zn/Al hydrotalcite-like compound (HTlc) towards removal of fluoride from aqueous solution

    J. Colloid Interface Sci.

    (2003)
  • N. Das et al.

    Defluoridation of drinking water using activated titanium rich bauxite

    J. Colloid Interface Sci.

    (2005)
  • A.A.M. Daifullah et al.

    Adsorption of fluoride in aqueous solutions using KMnO4-modified activated carbon derived from steam pyrolysis of rice straw

    J. Hazard. Mater.

    (2007)
  • E. Drioli et al.

    Integrated membrane operations in desalination processes

    Desalination

    (1999)
  • F. Durmaz et al.

    Fluoride removal by Donnan dialysis with anion exchange membranes

    Desalination

    (2005)
  • X. Fan et al.

    Adsorption kinetics of fluoride on low cost materials

    Water Res.

    (2003)
  • J. Fan et al.

    Comment on “Factors influencing the removal of fluoride from aqueous solution by calcined Mg–Al–CO3 layered double hydroxides”

    J. Hazard. Mater.

    (2007)
  • P. Fu et al.

    A pilot study on groundwater natural organics removal by low-pressure membranes

    Desalination

    (1995)
  • H. Garmes et al.

    Defluoridation of groundwater by a hybrid process combining adsorption and Donnan dialysis

    Desalination

    (2002)
  • V.K. Gupta et al.

    Defluoridation of wastewaters using waste carbon slurry

    Water Res.

    (2007)
  • M. Hichour et al.

    Fluoride removal from diluted solutions by Donnan dialysis with anion-exchange membranes

    Desalination

    (1999)
  • K. Hu et al.

    Nanofiltration membrane performance on fluoride removal from water

    J. Membr. Sci.

    (2006)
  • S. Jagtap et al.

    New modified chitosan-based adsorbent for defluoridation of water

    J. Colloid Interface Sci.

    (2009)
  • N. Kabay et al.

    Separation of fluoride from aqueous solution by electrodialysis: effect of process parameters and other ionic species

    J. Hazard. Mater.

    (2008)
  • P.M.H. Kau et al.

    Fluoride retention by kaolin clay

    J. Contam. Hydrol.

    (1997)
  • S. Lahnid et al.

    Economic evaluation of fluoride removal by electrodialysis

    Desalination

    (2008)
  • A. Lhassani et al.

    Selective demineralization of water by nanofiltration: application to the defluorination of brackish water

    Water Res.

    (2001)
  • Y.H. Li et al.

    Adsorption of fluoride from water by amorphous alumina supported on carbon nanotubes

    Chem. Phys. Lett.

    (2001)
  • Y.H. Li et al.

    Adsorption of fluoride from water by aligned carbon nanotubes

    Mater. Res. Bull.

    (2003)
  • H. Lounici et al.

    Study of a new technique for fluoride removal from water

    Desalination

    (1997)
  • L. Lv et al.

    Factors influencing the removal of fluoride from aqueous solution by calcined Mg–Al–CO3 layered double hydroxides

    J. Hazard. Mater.

    (2006)
  • L. Lv et al.

    Treatment of high fluoride concentration water by MgAl–CO3 layered double hydroxides: kinetic and equilibrium studies

    Water Res.

    (2007)
  • S. Mandal et al.

    Adsorption of fluoride ions by Zn–Al layered double hydroxides

    Appl. Clay Sci.

    (2008)
  • S. Mandal et al.

    Cellulose supported layered double hydroxides for the adsorption of fluoride from aqueous solution

    Chemosphere

    (2008)
  • S.M. Maliyekkal et al.

    Manganese-oxide-coated alumina: a promising sorbent for defluoridation of water

    Water Res.

    (2006)
  • S.M. Maliyekkal et al.

    Enhanced fluoride removal from drinking water by magnesia-amended activated alumina granules

    Chem. Eng. J.

    (2008)
  • Meenakshi et al.

    Fluoride in drinking water and its removal

    J. Hazard. Mater.

    (2006)
  • G. Moges et al.

    Preliminary investigations on the defluoridation of water using fired clay chips

    J. Afr. Earth Sci.

    (1996)
  • D. Mohan et al.

    Arsenic removal from water/waste water using adsorbents – a critical review

    J. Hazard. Mater.

    (2007)
  • D. Mohapatra et al.

    Use of oxide minerals to abate fluoride from water

    J. Colloid Interface Sci.

    (2004)
  • P. Nayak

    Review aluminium: impacts and disease

    Environ. Res. Sec. A

    (2002)
  • P.I. Ndiaye et al.

    Removal of fluoride from electronic industrial effluent by RO membrane separation

    Desalination

    (2005)
  • M.S. Onyango et al.

    Adsorption equilibrium modeling and solution chemistry dependence of fluoride removal from water by trivalent-cation-exchanged zeolite F-9

    J. Colloid Interface Sci.

    (2004)
  • J. Palmeri et al.

    Theory of pressure-driven transport of neutral solutes and ions in porous ceramic nanofiltration membranes

    J. Membr. Sci.

    (1999)
  • L. Paugam et al.

    Transfer of monovalent anions and nitrates especially through nanofiltration membranes in brackish water conditions

    Sep. Purif. Technol.

    (2004)
  • P.C. Pavan et al.

    Sorption of anionic surfactants on layered double hydroxides

    J. Colloid Interface Sci.

    (2000)
  • S. Annouar et al.

    Defluoridation of underground water by adsorption on the chitosan and by electrodialysis

    Desalination

    (2004)
  • W.B. Apambire et al.

    Geochemistry, genesis and health implications of fluoriferous groundwaters in the upper regions of Ghana

    Environ. Geol.

    (1997)
  • B.V. Apparao et al.

    Permissible limits of fluoride on in drinking water in India in rural environment

    Ind. J. Environ. Protec.

    (1986)
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