Screening of commercial sorbents for removal of fluoride in synthetic and groundwater.
Numerous methods have been described employing various materials for fluoride removal due to the risk of high fluoride dosing for human health. There is a broad collection of commercial products for adsorption applications. The materials most recommended are activated alumina and bone char. Nineteen commercial sorbents were screened for fluoride removal in static experiments, with synthetic water and groundwater from the city of Aguascalientes (México), where some wells contain up to 15 mg l(-1) of fluoride. Removal efficiency of aluminas and activated carbons with a uniform particle diameter of 0.63 mm was compared. Four materials leading to a final concentration of 1 mg F- l(-1) were selected, pretreated, and characterized (X-ray diffractometry, infrared spectroscopy, titration, methylene blue and nitrogen adsorption) for further investigation. Adsorption rate constant was determined and obeyed a pseudo-first order equation. Fluoride removal was clearly improved after the conditioning procedure and was higher for aluminas than for bone carbons. The pretreated sample A5 adsorbed 5 mg g(-1) at 25 degrees C and pH 6 from a 20 mg F- l(-1) synthetic water solution after 7 hours by using a sorbent dose of 4 mg ml(-1). The specific saturation capacity with fluoride was aluminas - carbons for determined samples (10 mg g(-1), but the superficial capability was higher for the pretreated bone carbon sample CH5 (50 microg m(-2)) because of its higher acidity. At wells 4 and 5 (7.1 mg F- l(-1)) the reached efficiency was 91% for aluminas and 70% with bone carbon.
Hernández-Montoya
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Departamento de Ing. Química, Instituto Tecnológico de Aguascalientes, Apdo. Postal 616-1, Aguascalientes, Ags. 20360, Mexico.
Elizalde-González
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Trejo-Vázquez
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D000327:Adsorption; D019149:Bioreactors; D004058:Diffusion; D005459:Fluorides / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010100:Oxygen / Q000032:analysis; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D014961:X-Ray Diffraction
D014874:Water Pollutants, Chemical; D005459:Fluorides; D010100:Oxygen