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Factors Governing the Performance of Bauxite for Fluoride Remediation of Groundwater Aruna Kirani Katyayani Cherukumilli, Caroline Delaire, Susan E. Amrose, and Ashok J. Gadgil Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b04601 • Publication Date (Web): 20 Jan 2017 Downloaded from http://pubs.acs.org on January 21, 2017
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Environmental Science & Technology
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Factors Governing the Performance of Bauxite for Fluoride
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Remediation of Groundwater
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Katya Cherukumilli *,†, Caroline Delaire†, Susan Amrose†, Ashok J. Gadgil†,Ψ
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†
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94720-1710, United States
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Ψ
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United States
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Corresponding Author. *Katya Cherukumilli, E-mail:
[email protected]; phone: 407-
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529-9943; address: 410 O’Brien Hall, Berkeley, CA 94720.
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Department of Civil and Environmental Engineering, University of California, Berkeley, California
Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, California 94720,
ABSTRACT
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Globally, 200 million people drink groundwater contaminated with fluoride concentrations
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exceeding the World Health Organization’s recommended level (WHO-MCL =1.5 mg F-/L). This
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study investigates the use of minimally-processed (dried/milled) bauxite ore as an inexpensive
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adsorbent for remediating fluoride-contaminated groundwater in resource-constrained areas.
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Adsorption experiments in synthetic groundwater using bauxites from Guinea, Ghana, USA, and
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India as single-use batch dispersive media demonstrated that doses of ~10-23 g/L could effectively
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remediate 10 mg F-/L. To elucidate factors governing fluoride removal, bauxites were characterized
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using
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isotherms/envelopes. All ores contained gibbsite, had comparable surface areas (~14-17 m2/g), had
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similar intrinsic affinities and capacities for fluoride, and did not leach harmful ions into product
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water. Fluoride uptake on bauxite -primarily through ion-exchange- was strongly pH-dependent,
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with highest removal occurring at pH 5.0-6.0. Dissolution of CaCO3, present in trace amounts in
X-ray
fluorescence,
X-ray
diffraction,
gas-sorption
analysis,
and
adsorption
1 ACS Paragon Plus Environment
Environmental Science & Technology
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India bauxite, significantly hindered fluoride removal by increasing solution pH. We also showed
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that fluoride remediation with the best-performing Guinea bauxite was ~23-33 times less expensive
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than with activated alumina. Overall, our results suggest that bauxite could be an affordable fluoride-
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remediation adsorbent with the potential to improve access to drinking water for millions living in
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developing countries.
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1. INTRODUCTION
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Over 200 million people worldwide drink groundwater containing naturally-occurring1 fluoride
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concentrations2 surpassing the World Health Organization’s maximum recommended contaminant
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level (WHO-MCL) of 1.5 mg F-/L.3 Although fluoride at low concentrations (
