Preparation and adsorption properties for fluoride of kaolinite-magnetite association

Kaolinite-magnetite association (KMA) was prepared by co-precipitation and characterized using X-ray diffraction and surface structural analysis, and the adsorption characteristics for fluoride by KMA were studied. Compared to the average values of the pure kaolinite and magnetite, the BET surface area, external surface area and surface fractal dimension of KMA increased. The maximum adsorption capacities (qmax) for fluoride by the samples followed the order of Magnetite >; KMA >; Kaolinite, and that of KMA was much higher than the average value of kaolinite and magnetite. The adsorption data for fluoride by the three samples could be well fitted by one-site Langmuir and two-site Langmuir models (R2 =0.983-0.991), but Freundlich model can only describe the adsorption for fluoride by KMA (R2 =0.988).