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La(Ⅲ)-loaded bentonite/chitosan beads for defluoridation from aqueous solution
Pages: 458-466
Year: Issue:  5
Journal: Journal of Rare Earths

Keyword:  La(Ⅲ)bentonitechitosan beadsdefluoridationadsorptionfluoriderare earths;
Abstract: Developing low-cost and effective materials for excess fluoride removal is important for providing safe water. A novel adsorbent, La(Ⅲ)-loaded bentonite/chitosan beads(La-BCB) was prepared for defluoridation from aqueous solution. The effects of various parameters such as dosage of La(Ⅲ), pH, temperature, contact time, initial fluoride concentration and presence of co-existing anions were investigated to examine the defluoridation behavior. The maximum defluoridation capacity of La-BCB was 2.87 mg/g at pH 5, 30 °C. Scanning electron microscopy(SEM), energy dispersive spectroscopy(EDX) and Fourier transform infrared spectroscopy(FTIR) were employed to analyze the characteristics of La-BCB. The equilibrium fluoride adsorption data fitted well with both Langmuir and Freundlich isotherm models. The RL value revealed that the defluoridation process using La-BCB was favorable. The adsorption kinetics followed pseudo-second order kinetic as well as particle and intraparticle diffusion models. The presence of carbonate and bicarbonate reduced defluoridation capacity of La-BCB while sulphate, nitrate and chloride showed slight effect. The exhausted La-BCB was regenerated using sodium hydroxide with only 17% loss. The reasonable defluoridation mechanism could be interpreted as adsorption and ion exchange.
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