Journal of Food, Agriculture and Environment

Surface properties and adsorption characteristics for fluoride of kaolinite, ferrihydrite and kaolinite-ferrihydrite association

Author(s):

Shiyong Wei ^1*, Wenjun Xiang ²

Recieved Date: 2011-11-18, Accepted Date: 2012-01-03

Abstract:

Kaolinite (K), ferrihydrite (F) and kaolinite-ferrihydrite association (KF) were characterized using X-ray diffraction, potentiometric titrations and surface and pore structures analysis. Moreover, the adsorption characteristics for fluoride by the three samples were studied. Compared to the average values of the K and F samples, the BET surface area, external surface area, total pore volume and surface fractal dimension of the KF increased; however, the hydroxyl density and proton charge of the KF decreased. The pH of point of zero net proton charge (pHpznpc) of the K, F and KF appeared at pH 3.6-4.3, 8.0 and 6.2-7.2, respectively. The adsorption capacities (q_e) for fluoride by the three samples followed the order of F>KF>K, and the maximum adsorption capacity (q_max) of the KF was much higher than the average value of the K and F samples. The adsorption data for fluoride by the three samples could be well fitted by one-site Langmuir and two-site Langmuir models (R² = 0.981-0.992), but the Freundlich model can only describe the adsorption for fluoride by the KF sample (R² = 0.975). 

Keywords:

Ferrihydrite, kaolinite, kaolinite-ferrihydrite association, surface properties, adsorption, fluoride

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Journal: Journal of Food, Agriculture and Environment
Year: 2012
Volume: 10
Issue: 1
Category: Environment
Pages: 923-929

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