Abstract

The feasibility of fluoride adsorption from aqueous solutions using naturally available bentonite clay in both modified and unmodified forms is investigated in this report. SEM, EDX, XRD, and FT-IR analysis are applied to describe the structure and nature of unmodified and modified bentonite clay. The physicochemical characteristics of the adsorbent were also investigated by its moisture content, pH, apparent density, specific surface area, cation exchange capacity and its point of -zero charge determination. SEM image reveals particles are dispersed homogeneously and are irregular in shape. XRD and EDX analyses reveal that the bentonite is composed of seven materials: Calcite, Silica, Alumina, Hematite, bornite and Green cinnabar, and Chloride are considered as impurity. Raw bentonite (RB) clays have shown very low fluoride removal efficiency (47.19%). Modification of the clay surface with HCl (ATB) and aluminum oxide (AOMB), on the other hand, increased fluoride removal efficiency to 79.77% and 94.38%, respectively. At 5 mg/L initial fluoride concentration, 10 cm bed depth packed dose of adsorbent, and 180 min breakthrough time, a 2.88 mg/g of fluoride removal capacity was observed. As the result, aluminum oxide modified bentonite clay was chosen for further investigation and its result is not presented here.

Highlights

  • Clay minerals adsorption experimentation for low fluoride concentrations (5,10 and 12 mg/l) was successful.

  • Most of the experimentation done so far are in batch using clay-based minerals and leads to shorter reaction times thus far from equilibrium.

  • Column -experimentation using clay minerals was difficult but this study apply the clay as a filter media through surface modification of the adsorbent.

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