title: Factors Governing the Performance of Bauxite for Fluoride Remediation of Groundwater.
abstract: Globally, 200 million people drink groundwater contaminated with fluoride concentrations exceeding the World Health Organization's recommended level (WHO-MCL = 1.5 mg F-/L). This study investigates the use of minimally processed (dried/milled) bauxite ore as an inexpensive adsorbent for remediating fluoride-contaminated groundwater in resource-constrained areas. Adsorption experiments in synthetic groundwater using bauxites from Guinea, Ghana, U.S., and India as single-use batch dispersive media demonstrated that doses of ∼10-23 g/L could effectively remediate 10 mg F-/L. To elucidate factors governing fluoride removal, bauxites were characterized using X-ray fluorescence, X-ray diffraction, gas-sorption analysis, and adsorption isotherms/envelopes. All ores contained gibbsite, had comparable surface areas (∼14-17 m2/g), had similar intrinsic affinities and capacities for fluoride, and did not leach harmful ions into product water. Fluoride uptake on bauxite -primarily through ion-exchange- was strongly pH-dependent, with highest removal occurring at pH 5.0-6.0. Dissolution of CaCO3, present in trace amounts in India bauxite, significantly hindered fluoride removal by increasing solution pH. We also showed that fluoride remediation with the best-performing Guinea bauxite was ∼23-33 times less expensive than with activated alumina. Overall, our results suggest that bauxite could be an affordable fluoride-remediation adsorbent with the potential to improve access to drinking water for millions living in developing countries.
authors.affiliation: Department of Civil and Environmental Engineering, University of California , Berkeley, California 94720-1710, United States.
authors.forename: Katya
authors.identifier: 0000-0002-8606-1845
authors.initials: K
authors.lastname: Cherukumilli
authors.affiliation: Department of Civil and Environmental Engineering, University of California , Berkeley, California 94720-1710, United States.
authors.forename: Caroline
authors.initials: C
authors.lastname: Delaire
authors.affiliation: Department of Civil and Environmental Engineering, University of California , Berkeley, California 94720-1710, United States.
authors.forename: Susan
authors.initials: S
authors.lastname: Amrose
authors.affiliation: Department of Civil and Environmental Engineering, University of California , Berkeley, California 94720-1710, United States.|Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Ashok J
authors.initials: AJ
authors.lastname: Gadgil
mesh_terms: D000327:Adsorption; D000537:Aluminum Oxide / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry*; D060587:Groundwater / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D014874:Water Pollutants, Chemical; D018508:Water Purification
chemical_list: D014874:Water Pollutants, Chemical; D000537:Aluminum Oxide; D005459:Fluorides