A Critical Review on Occurrence of Fluoride and Its Removal through Adsorption with an Emphasis on Natural Minerals

Thivya C, Chidambaram S, Rao MS, Thilagavathi R, Prasanna MV, Manikandan S. Assessment of fluoride contaminations in groundwater of hard rock aquifers in Madurai district, Tamil Nadu (India). Appl Water Sci. 2015; doi:10.1007/s13201-015-0312-0. Cotton FA, Wilkinson G, Murillo CA, Bochmann M. Advanced inorganic chemistry. 6th ed. New York: John Wiley & Sons; 2004. Darwen B. Bond dissociation energies in simple molecules. National Standard Reference Data Series, National Bureau of Standards, No. 31. Washington; 1970. Miessler GL, Tarr DA. Inorganic chemistry. 3rd ed. Sydney: Pearson Education; 2004. Pagaria SK, Pagaria RF. High fluoride content in the ground water of belora union:a comparative study. Rasayan J Chem. 2013; 6: 288-91. Sujatha D. Fluoride levels in the groundwater of the south-eastern part of Ranga Reddy district, Andhra Pradesh. India Environ Geol. 2013;44:587–91. Health Canada : Guidelines for Canadian Drinking Water Quality: Guideline Technical Document —Fluoride. 2010. Water, Air and Climate Change. Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario. (Catalogue No. H128-1/11-647E-PDF). Fawell JK, Ohanian E, Giddings M, Toft P, Magara Y, Jackson P. Fluoride in drinking-water, Background document for development of WHO guidelines for drinking-water quality.2006. http://www.who.int/water_sanitation_health/publications/fluoride_drinking_water_full.pdf. Accessed 26 Oct 2016. Weinstein LH, Davison A. Fluorides in the environment: effects on plants an d animal. London: CABI publishing; 2004. doi:10.1079/9780851996837.0000. Appelo CAJ, Postma D. Geochemistry, Groundwater and Pollution. A. A. Balkema Publishers, second ed. Chapter: Minerals and Water. London. 2005; 119–174. Dove P, Rimstidt JD. Silica water interactions. Rev Mineral. 1993;29:259–308. Rafique T, Shahid N, David O, Riaz H, Muhammad IB, Tanzil HU. Geochemical controls of high fluoride groundwater in Umarkot Sub-District, Thar Desert. Pakistan Sci Total Env. 2015;530–531:271–8. Bureau of Indian Standard (BIS). Indian standard specification for drinking water. IS 10500. 2012. https://archive.org/stream/gov.in.is.10500.2012/is.10500.2012#page/n3/mode/2up. Accessed 26 Oct 2016. Patil SS, Ingole NW. Studies on defluoridation- a critical review. J Engg Res Stud. 2011;3:111–9. E-ISSN0976–7916 Upadhyay M, Kumari K. Analytical study of fluoride ion in drinking water around Ambikapur, Sarguja District, Chhattisgarh, India. Int J of Engg Research Dev. 2013;5:14–21. Liteplo R, Gomes R, Howe P, Malcolm H. Environmental health criteria 227. World Health Organization, Geneva: Fluorides; 2002. Tomar V, Kumar D. A critical study on efficiency of different materials for fluoride removal from aqueous media. Chemistry Central Journal. 2013;7:1–15. Rao CRN. Fluoride and environment - a review, Proceedings of the Third International Conference on environment and health, Chennai, India. Chennai: Department of Geography, University of Madras and Faculty of Environmental Studies, York University. 2003. pp 386–99. Teotia SPS, Teotia M, Kishna S. Nutrition and bone health. Nutritional and metabolic bone and stone disease: Asian perspective. 1st Ed. New Delhi: CBS Publishers; 2008. Peterson PJ. Assessment of exposure to chemical contaminants in water and food. Sci Total Environ. 1995;168:123–9. Du J, Sabatini DA, Butler EC. Synthesis, characterization, and evaluation of simple aluminum-based adsorbents for fluoride removal from drinking water. Chemosphere. 2014;101:21–7. Lakshmaiah N, Srikantia SG. Fluoride retention in humans on sorghum and rice based diets. Indian J Med Res. 1977;65:543–8. Gwala P, Andey S, Nagarnaik P, Ghosh SP, Pal P, Deshmukh P, Labhasetwar P. Design and development of sustainable remediation process for mitigation of fluoride contamination in ground water and field application for domestic use. Sci of the Total Environ. 2014;488–489:588–94. Saxena VK, Ahmed S. Inferring the chemical parameters for the dissolution of fluoride in groundwater. Environ Geol. 2003;43:731–6. Jadhav SV, Bringas E, Yadav GD, Rathod VK, Ortiz I, Marathe KV. Arsenic and fluoride contaminated ground waters: a review of current technologies for contaminants removal. J Environ Manag. 2015;162:306–25. Reardon EJ, Wang Y. A limestone reactor for fluoride removal from wastewaters. Environ Sci Technol. 2000;34:3247–53. Loganathan P, Vigneswaran S, Kandasamy J, Naidu R. 943 Defluoridation of drinking water using adsorption processes. J 944 Hazard Mat. 2013;248-249:1–19. Mohapatra M, Anand S, Mishra BK, Giles DE, Singh P. Review of fluoride removal from drinking water. J Env Manage. 2009;91:67–77. Alarcon-Herrera MT, Bundschuh J, Nath B, Nicolli HB, Gutierrez M, ReyesGomez VM, Nunez D, Martin-Dominguez IR, Sracek O. Co-occurrence of arsenic and fluoride in groundwater of semi-arid regions in Latin America: genesis, mobility and remediation. J Hazard Mater. 2013;262:960–9. Malik AH, Khan ZM, Mahmood Q, Nasreen S, Bhatti ZA. Perspectives of low cost arsenic remediation of drinking water in Pakistan and other countries. J Hazard Mater. 2009;168:1–12. Malcuit E, Atteia O, Larroque F, Franceschi M, Pryet A. On the role of low permeability beds in the acquisition of F and SO4 concentrations in a multilayer aquifer. South-West France J Contam Hydrol. 2014;169:37–49. Kim SH, Kim K, Ko KS, Kim Y, Lee KS. Co-contamination of arsenic and fluoride in the groundwater of unconsolidated aquifers under reducing environments. Chemosphere. 2012;87:851–6. Brahman KD, Kazi TG, Afridi HI, Naseem S, Arain SS, Ullah N. Evaluation of high levels of fluoride, arsenic species and other physicochemical parameters in underground water of two sub districts of Tharparkar, Pakistan: a multivariate study. Water Res. 2013;47:1005–20. Su C, Wang Y, Xie X, Li J. Aqueous geochemistry of high-fluoride groundwater in Datong Basin. Northern China J Geochem Explor. 2013;135:79–92. Currell M, Cartwright I, Raveggi M, Han D. Controls on elevated fluoride and arsenic concentrations in groundwater from the Yuncheng Basin. China Appl Geochem. 2011;26:540–52. Kut KMK, Sarswat A, Srivastava A, Pittman CUJ, Mohan D. A review of fluoride in african groundwater and local remediation methods. Groundwater Sust Develop. 2016;2:190–212. Jha SK, Nayak AK, Sharma YK. Response of spinach (Spinacea oleracea) to the added fluoride in an alkaline soil. Food Chem Toxicol. 2008;46:2968–71. Choubey ON, Agrawal GD. A study of fluoride and their removal through adsorption from ground water of Rajgarh (block) M. P. India. J Chem Biol Phys Sci. 2011;2:49–53. Hussain I, Arif M, Hussain J. Fluoride contamination in drinking water in rural habitations of Central Rajasthan. India Environ Mont and Assess. 2012;184:5151–8. Yadav RK, Gautam R, Saini Y, Singh A. Determination of fluoride content in drinking water invicinity areas of Dausa district, Rajasthan. India Int J Sci Nat. 2012;3:176–9. Saxena S, Saxena U. Study of fluoride contamination status of ground water in Bassi tehsil of district Jaipur, Rajasthan. India Int J of Environ Sc. 2013;3:2251–60. Sim JM, Leong KM. Feasibility study on fluoride removal in drinking water in Mehsana. India Int NGO J. 2011;6:224–8. Duraiswami RA, Patankar UJ. Occurrence of fluoride in the drinking water sources from Gad River basin. Maharashtra Geol Soc India. 2011;77:167–74. Reddy AGS, Reddy DV, Rao PN, Prasad KM. Hydro geochemical characterization of fluoride rich groundwater of Wailapalli watershed, Nalgonda district, Andhra Pradesh. India Environ Monit Assess. 2010;171:561–77. Jaganmohan P, Rao SVLN, Rao KRSS. Prevalence of high fluoride concentration in drinking water in Nellore district Andhra Pradesh, India: a biochemical study to develop the relation to renal failures. World J Med Sci. 2010;5:45–8. Karthikeyan K, Nanthakumar K, Velmurugan P, Tamilarasi S, Lakshmanaperumalsamy P. Prevalence of certain inorganic constituents in groundwater samples of erode district, Tamilnadu, India, with special emphasis on fluoride, fluorosis and its remedial measures. Environ Monit Assess. 2010;160:141–55. Srinivasamoorthy K, Vijayaraghavan K, Vsanthavigar M, Sarma S, Chidambaram S, Anandhan P, Manivannan R. Assessment of groundwater quality with special emphasis on fluoride contamination in crystalline bed rock aquifers of Mettur region, Tamilnadu. India Arab J Geosci. 2012;5:83–94. Beg MK. Geospatial analysis of fluoride contamination in ground water of Tamnar area. Chhattisgrh State: Raigarh District; 2009. Gupta S, Banerjee S, Saha R, Datta JK, Mondal N. Fluoride geochemistry of groundwater in Nalhati-1 block of the Birbhum District, West Bengal. India Fluoride. 2006;39:318–20. Mondal D, Gupta S, Reddy DV, Nagabhushanam P. Geochemical controls on fluoride concentrations in groundwater from alluvial aquifers of the Birbhum district, West Bengal. India J Geochem Explor. 2014;145:190–206. Kundu MC, Mandal B. Agricultural activities influence nitrate and fluoride contamination in drinking groundwater of an intensively cultivated district in India. Water Air Soil Pollut. 2009;198:243–52. Gupta S, Mondal D, Bardhan A. Geochemical provenance and spatial distribution of fluoride in groundwater in parts of Raniganj coal field, West Bengal. India Arch Appl Sci Res. 2012;4:292–306. Feenstra L, Vasak L, Griffioen J. Fluoride in groundwater: Overview and evaluation of removal methods, International Groundwater Resources Assessment Centre. Report nr. SP. 2007–1; pp 1–25. https://www.un-igrac.org/download/file/fid/275+&cd=1&hl=en&ct=clnk&gl=in. Accessed 30 Oct 2016. Simons R. Trace element removal from ash dam waters by nanofiltration and diffusion dialysis. Desalination. 1993;89:325–41. Sehn P. Fluoride removal with extra low energy reverse osmosis membranes: three years of large scale field experience in Finland. Desalination. 2008;223:73–84. Gong WX, Qu JH, Liu RP, Lan HC. Effect of aluminum fluoride complexation on fluoride removal by coagulation. Colloid Surf A. 2012a;395:88–93. Hu CY, Lo SL, Kuan WH. Effects of co-exiting anions on fluoride removal in electrocoagulation (EC) process using aluminium electrodes. Water Res. 2003;37:4513–23. Tembhurkar AR, Dongre S. Studies on fluoride removal using adsorption process. J Environ Sci Eng. 2006;48:151–6. Chunlu L, Nan C, Yanan Z, Rui L, Chuanping F. Polypyrrole-grafted peanut shell biological carbon as a potential sorbent for fluoride removal: sorption capability and mechanism. Chemosphere. 2016;163:81–9. Kumar GPK, Shambavi Kamath M, Mallapur PS. Defluoridation of water by using low cost activated carbon prepared from lemon peels. J Basic Appl Engg Res. 2016;3:658–60. (http://www.krishisanskriti.org/vol_image/13Jun201611061003%20%20%20%20%20%20%20%20Kiran%20Kumar%20G%20R%20%20%20%20%20%20%20%20%20%20%20658-660.pdf ) Fan X, Parker DJ, Smith MD. Adsorption kinetics of fluoride on low cost materials. Water Res. 2003;37:4929–37. Vinati A, Mahanty B, Behera SK. Clay and clay minerals for fluoride removal from water: a state-of-the-art review. Appl Clay Sci. 2015;114:340–8. Maliyekkal SM, Sharma AK, Philip L. Manganese-oxide-coated alumina: a promising sorbent for defluoridation of water. Water Res. 2006;40:3497–506. Bulusu KP, Nawalakhe WG. Defluoridation of water with activated alumina: batch operations. Indian J Environ Health. 1988;30:262–99. Wasay SA, Tokunaga S, Park SW. Removal of hazardous anions from aqueous solutions by La (III) - and Y (III)-impregnated alumina. Sep Sci Technol. 1996;31:1501–14. Shimelis B, Zewge F, Chandravanshi BS. Removal of excess fluoride from water by aluminum hydroxide. Bull Chem Soc Ethiopia. 2006;20:17–34. Ku Y, Chiou H. The adsorption of fluoride ion from aqueous solution by activated alumina. Water Air Soil Pollut. 2002;133:349–61. Ghorai S, Pant KK. Investigations on the column performance of fluoride adsorption by activated alumina in a fixed-bed. Chem Eng J. 2004;98:165–73. Ghorai S, Pant KK. Equilibrium, kinetics and breakthrough studies for adsorption of fluoride on activated alumina. Sep Purif Technol. 2005;42:265–71. Sajidu S, Kayira Masamba C, Mwatseteza J. Defluoridation of groundwater using raw bauxite: rural domestic defluoridation technology. Environ Nat Resour Res. 2012;2:1–9. Goswami A, Purkait MK. The defluoridation of water by acidic alumina. Chem Eng Res Des. 2012;90:2316–24. Puri BK, Balani S. Trace determination of fluoride using lanthanum hydroxide supported on alumina. J environ Sci health. Part A: Toxic/Hazardous Subst Environ Eng. 2000;35:109–21. Teng SX, Wang SG, Gong WX, Liu XW, Gao BY. Removal of fluoride by hydrous manganese oxide-coated alumina: performance and mechanism. J Hazard Mater. 2009;168:1004–11. Das N, Pattanaik P, Das R. Defluoridation of drinking water using activated titanium rich bauxite. J Colloid Interface Sci. 2005;292:1–10. Tripathy SS, Raichur AM. Abatement of fluoride from water using manganese dioxide-coated activated alumina. J Hazard Mater. 2008;153:1043–51. Ayoob S, Gupta AK. Performance evaluations of alumina cement granules in removing fluoride from natural and synthetic waters. Chem Eng J. 2009;150:485–91. Bansiwal A, Pillewan P, Biniwale RB, Rayalu SS. Copper oxide incorporated mesoporous alumina for defluoridation of drinking water. Microporous Mesoporous Mater. 2010;129:54–61. Jagtap S, Yenkie MKN, Labhsetwar N, Rayalu S. Defluoridation of drinking water using chitosan based mesoporous alumina. Microporous Mesoporous Mater. 2011;142:454–63. Sujana MG, Soma G, Vasumathi N, Anand S. Studies on fluoride adsorption capacities of amorphous Fe/Al mixed hydroxides from aqueous solutions. J Fluor Chem. 2009;130:749–54. Camacho LM, Torres A, Saha D, Deng S. Adsorption equilibrium and kinetics of fluoride on sol-gel derived activated alumina adsorbents. J Colloid Interface Sci. 2010;349:307–13. Cheng J, Meng X, Jing C, Hao J. La3+−modified activated alumina for fluoride removal from water. J Hazard Mater. 2014;278:343–9. Chibi C, Haarhoff J. A promising approach to fluoride removal in rural drinking water supplies. Proceedings of WISA. Biennial Conference, Sun City, South Africa. 2000. Chaturvedi AK, Pathak KC, Singh VN. Fluoride removal from water by adsorption on China clay. Appl Clay Sci. 1988;3:337–46. Moges F. Zewge, Socher. Preliminary investigations on the defluoridation of water using fired clay chips. J African Earth Sci. 1996;22:479–82. Coetzee PP, Coetzee LL, Puka R, Mubenga S. Characterisation of selected south African clays for defluoridation of natural waters. Water SA. 2003;29:331–8. Hamdi N, Srasra E. Retention of fluoride from industrial acidic wastewater and NaF solution by three Tunisian clayey soils: research report. Fluoride. 2009;42:39–45. Sarkar M, Banerjee A, Pramanick PP, Sarkar AR. Use of laterite for the removal of fluoride from contaminated drinking water. J Colloid Interface Sci. 2006;302:432–41. Wang Y, Reardon EJ. Activation and regeneration of a soil sorbent for defluoridation of drinking water. Appl Geo chem. 2001;16:531–9. Chen N, Zhang Z, Feng C, Sugiura N, Li M, Chen R. Studies on fluoride adsorption of iron-impregnated granular ceramics from aqueous solution. Mat Chem Phys. 2011;125:293–8. Wambu EW, Onindo CO, Ambusso WJ, Muthakia GK. Fluoride adsorption onto an acid treated lateritic mineral from Kenya: equilibrium studies. Afr J Environ Sci Technol. 2012;6:160–9. Maiti A, Basu JK, De S. Chemical treated laterite as promising fluoride adsorbent for aqueous system and kinetic modelling. Desal. 2011;265:28–36. Gogoi PK, Baruah R. Fluoride removal from water by adsorption on acid activated kaolinite clay. Indian J Chem Technol. 2008;15:500–3. Kamble SP, Dixit P, Rayalu SS, Labhsetwar NK. Defluoridation of drinking water using chemically modified bentonite clay. Desal. 2009;249:687–93. Ma J, Qi J, Yao C, Cui B, Zhang T, Li D. A novel bentonite-based adsorbent for anionic pollutant removal from water. Chem Eng J. 2012;200-202:97–103. Togarepi E, Mahamadi C, Mangombe A. Defluoridation of water using physico-chemically treated sand as a low cost adsorbent: an equilibrium study. Afr J Environ Sci Technol. 2012;6:176–81. Ma Y, Shi F, Zheng X, Ma J, Gao C. Removal of fluoride from aqueous solution using granular acid-treated bentonite (GHB): batch and column studies. J Hazard Mater. 2011;185:1073–80. Kim JH, Lee CG, Park JA, Kang JK, Choi NC, Kim SB. Use of pyrophyllite clay for fluoride removal from aqueous solution. Desalin Water Treat. 2013;51:3408–16. Gitari WM, Ngulube T, Masindi V, Gumbo JR. Defluoridation of groundwater using Fe3+ modified bentonite clay: optimization of adsorption conditions. Desalin Water Treat. 2015;53:1578–90. Osei J, Gawu SKY, Schafer AI, Atipoka FA, Momade FWY. Impact of laterite characteristics on fluoride removal from water. J Chem Tech Biotech. 2016;91:911–20. Shan Y, Guo H. Fluoride adsorption on modified natural siderite: optimization and performance. Chem Eng J. 2013;223:183–91. Asgari G, Roshani B, Ghanizadeh G. The investigation of kinetic and isotherm of fluoride adsorption onto functionalize pumice stone. J Hazard Mater. 2012;217-218:123–32. Malakootian M, Moosazadeh M, Yousefi N, Fatehizadeh A. Fluoride removal from aqueous solution by pumice: case study on Kuhbonan water. Afr J Environ Sci Technol. 2011;5:299–306. Salifu A, Petrusevski B, Ghebremichael K, Modestus L, Buamah R, Aubry C, Am GL. Aluminum (hydr)oxide coated pumice for fluoride removal from drinking water: synthesis, equilibrium, kinetics and mechanism. Chem Eng J. 2013;228:63–74. Nath SK, Dutta RK. Fluoride removal from water using crushed limestone. Indian J Chem Technol. 2010;17:120–5. Tang Y, Wang J, Gao N. Characteristics and model studies for fluoride and arsenic adsorption on goethite. Environ Sci. 2010;22:1689–94. Teutli-Sequeira A, Solache-Ríos M, Balderas-Hernández P. Modification effects of hematite with aluminium hydroxide on the removal of fluoride ions from water. Water Air Soil Poll. 2012;223:319–27. Teutli-Sequeira A, Solache-Ríos M, Martínez-Miranda V, Linares-Hernández I. Comparison of aluminium modified natural materials in the removal of fluoride ions. J Colloid Interface Sci. 2014;418:254–60. Chidambaram C, Ramanathan AL, Vasudevan S. Fluoride removal studies in water using natural materials. Water SA. 2003;29:339–43. Zhang S, Lu Y, Lin X, Su X, Zhang Y. Removal of fluoride from groundwater by adsorption onto La (III) – Al (III) loaded scoria adsorbent. Appl Surface Sci. 2014;303:1–5. Mohapatra M, Hariprasad D, Mohapatra L, Anand S, Mishra BK. Mg-doped nano ferrihydrite—a new adsorbent for fluoride removal from aqueous solutions. Appl Surf Sci. 2012;258:4228–36. Eskandarpour A, Onyango MS, Ochieng A, Asai S. Removal of fluoride ions from aqueous solution at low pH using schwertmannite. J Hazard Mater. 2008;152:571–9. Guo Q, Reardon EJ. Fluoride removal from water by meixnerite and its calcination product. Appl Clay Sci. 2012;56:7–15. Jiménez-Reyes M, Solache-Ríos M. Sorption behavior of fluoride ions from aqueous solutions by hydroxyapatite. J Hazard Mater. 2010;180:297–302. Sun Y, Fang Q, Dong J, Cheng X, Xu J. Removal of fluoride from drinking water by natural stilbite zeolite modified with Fe (III). Desal. 2011;277:121–7. Gómez-Hortigüela L, Pérez-Pariente J, García R, Chebude Y, Díaz I. Natural zeolites from Ethiopia for elimination of fluoride from drinking water. Sep Purif Technol. 2013;120:224–9. He J, Chen JP. A zirconium-based nanoparticle: essential factors for sustainable application in treatment of fluoride containing water. J Coll Interface Sci. 2014;416:227–34. Dou X, Mohan D, Pittman Jr CU, Yang S. Remediating fluoride from water using hydrous zirconium oxide. Chem Eng J. 2012;198-199:236–45. Swain SK, Patnaik T, Patnaik PC, Jha U, Dey RK. Development of new alginate entrapped Fe(III)–Zr(IV) binary mixed oxide for removal of fluoride from water bodies. Chem Eng J. 2013;215–216:763–71. Poursaberi T, Hassanisadi M, Torkestani K, Zare M. Development of zirconium (IV) -metalloporphyrin grafted Fe3O4 nanoparticles for efficient fluoride removal. Chem Eng J. 2012;189–190:117–25. Swaina SK, Mishra S, Patnaik ST, Patel RK, Jha U, Dey RK. Fluoride removal performance of a new hybrid sorbent of Zr (IV) – ethylenediamine. Chem Eng J. 2012;184:72–81. Mahramanlioglu M, Kizilcikli I, Bicer IO. Adsorption of fluoride from aqueous solution by acid treated spent bleaching earth. J Fluor Chem. 2002;115:41–7. Malakootian M, Fatehizadeh A, Yousefi N, Ahmadian M, Moosazadeh M. Fluoride removal using regenerated spent bleaching earth (RSBE) from ground water: case study on Kuhbonan water. Desal. 2011;277:224–49. Cengeloĝlu Y, Kir E, Ersoz M. Removal of fluoride from aqueous solution by using red mud. Sep Purif Technol. 2002;28:81–6. Tor A, Danaoglu N, Arslan G, Cengeloglu Y. Removal of fluoride from water by using granular red mud: batch and column studies. J Hazard Mater. 2009;164:271–8. Liang W, Couperthwaite SJ, Kaur G, Yan C, Johnstone DW, Millar GJ. Effect of strong acids on red mud structural and fluoride adsorption properties. J Colld and Inter Sc. 2014;423:158–65. Gupta VK, Ali I, Saini VK. Defluoridation of wastewaters using waste carbon slurry. Water Res. 2007;41:3307–16. Kemer B, Ozdes D, Gundogdu A, Bulut VN, Duran C, Soylak M. Removal of fluoride ions from aqueous solution by waste mud. J Hazard Mater. 2009;168:888–94. Oh TK, Chikushi J, Saeki K. The adsorption of hydrogen fluoride and fluoride ion on water treatment sludge. J Fac Agr Kyushu Univ. 2009;54:205–8. Biswas G, Dutta M, Dutta S, Adhikari K. A comparative study of removal of fluoride from contaminated water using shale collected from different coal mines in India. Environ Sci Pollut Res. 2016;23:9418–31. Verberne AJP, Wouters JW. Membraanfiltratie voor de drinkwaterbereiding: economische optimalisatie van ontwerpparameters. H2O Abonnementen Administratie. 1993; 383. Ghosh D, Medhi CR, Purkait MK. Treatment of fluoride containing drinking water by electrocoagulation using monopolar and bipolar electrode connections. Chemosphere. 2008;73:1393–400. Mazighi A, Lounici H, Drouiche N, Leenaerts R, Abdi N, Grib H, Mameri N. Economic study of groundwater defluoridation of the north African Sahara. Desal Water Treat. 2015;54:2681–91. Lahnid S, Tahaikt M, Elaroui K, Idrissi I, Hafsi M, Laaziz I, Amor Z, Tiyal F, Elmidaoui A. Economic evaluation of fluoride removal by electrodialysis. Desal. 2008;230:213–9. Elazhar F, Tahaikt M, Zouahri A, Taky M, Hafsi M, Elmidaoui A. Defluoridation of Moroccan groundwater by nanofiltration and electrodialysis: performances and cost comparison. World Appl Sci J. 2013;22:844–50. Chakrabortty S, Pal M, Roy M, Pal P. Fluoride in groundwater: low-cost separation and stabilizationby response surface optimization. Int J Environ Sci Technol. 2016;13:813–24. Gupta VK, Carrott PJM, MML RC, Suhas. Low-cost adsorbents: growing approach to wastewater treatment—a review. Critical Reviews in Env Sci Tech. 2009;39:783–842.