Citation:

Wallace, A., C. Su, AND W. Sun. Adsorptive Removal of Fluoride from Water Using Nanomaterials of Ferrihydrite, Apatite, and Brucite: Batch and Column Studies. ENVIRONMENTAL ENGINEERING SCIENCE. Mary Ann Liebert, Inc., Larchmont, NY, 36(5):634-642, (2019). https://doi.org/10.1089/ees.2018.0438

Impact/Purpose:

Exposure to fluoride at concentrations exceeding the allowable concentration, such as 1.5 to 2 mg L−1, can be detrimental to humans causing dental and/or skeletal fluorosis (Gao et al. 2009). This study investigated the adsorptive removal of fluoride from simulated water pollution using various (hydro)oxide nanomaterials. Among eleven (hydro)oxide nanomaterials tested in this study, ferrihydrite, HAP, and brucite showed 2-5 times higher removal of fluoride than other nanomaterials from synthetic fluoride solutions. The Freundlich and Redlich–Peterson adsorption isotherms described the adsorptive capacity and mechanism based on higher R2 values. Additionally, the adsorption kinetics were well described by the intra-particle diffusion model. Column studies in a fixed bed continuous flow through column showed that experimental results fitted well with the Thomas model with R2 values at least 0.885 or higher. The study implicated that (hydro)oxide nanomaterials of iron calcium and magnesium could be effective sorptive materials incorporated into filtration systems for the remediation of fluoride polluted water.

Description:

This study investigated the adsorptive removal of fluoride from simulated water pollution using various (hydro)oxide nanomaterials, which have the potential to be used as sorbents for surface water and groundwater remediation. The tested nanomaterials include hematite, magnetite, ferrihydrite, goethite, hematite-alpha, hydroxyapatite (HAP), brucite, and four titanium dioxides (TiO2-A (anatase), TiO2-B (rutile), TiO2-C (rutile), and TiO2-D (anatase)). Among eleven (hydro)oxide nanomaterials tested in this study, ferrihydrite, HAP, and brucite showed 2-5 times higher removal of fluoride than other nanomaterials from synthetic fluoride solutions. The Freundlich and Redlich–Peterson adsorption isotherms better described the adsorptive capacity and mechanism than the Langmuir isotherm based on higher R2 values, indicating better fit of the regression predictions. Additionally, the adsorption kinetics were well described by the intra-particle diffusion model. Column studies in a fixed bed continuous flow through system were conducted to illustrate the adsorption and desorption behavior of fluoride on ferrihydrite, HAP, or brucite. The experimental results fitted well with the Thomas model because of the R2 values at least 0.885 or higher. By comparisons of the adsorption capacity and the rate constant, columns packed with ferrihydrite exhibited not only faster rates, but also higher sorption capacity than those packed with HAP or brucite. The desorption tests in deionized water showed that the adsorbed fluoride could be desorbed at a lower efficiency, ranging from 4.0% to 8.9%. The study implicated that (hydro)oxide nanomaterials of iron calcium and magnesium could be effective sorptive materials incorporated into filtration systems for the remediation of fluoride polluted water.

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