In this work, selenate removal from water was studied using a material from the layered double hydroxide family. This material is a mixture of two hydrocalumite phases, chloro-hydrocalumite [Ca₄Al₂(OH)₁₂]·[Cl₂·4H₂O] and chloro-carboaluminate hydrocalumite [Ca₄Al₂(OH)₁₂]·[Cl(CO₃)₀.₅·10.8H₂O]. This material is called aged-FS in this thesis. Aged-FS was obtained by the co-precipitation method followed by an aging process. The aging condition was initial pH 12.0, liquid/solid ratio 20, 65 °C, for 7

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... days. During aging, a phase transformation from chloro-hydrocalumite in the hexagonal crystal system to chloro-carboaluminate hydrocalumite in the monoclinic crystal system was observed. The aluminum hydroxide impurity was removed and katoite (Ca3Al2(OH)12) was formed. The formation of well-shaped hexagon crystallites and agglomeration of particles were observed by morphology and particle size studies, respectively. The carbonate content increased during aging from 1.15 to 3.00 wt.%. By aging, ~50% reduction in FS dissolution was recorded. By some modifications in nitrogen purging of the synthesis process, the carbonate content was reduced from 1.15 to 1.01 wt.%. For selenate removal studies, the effect of initial pH, liquid/solid ratio, time, temperature, agitation, selenate concentration, sulfate and carbonate interference, and container type were studied. The highest loading percentage of selenate and the lowest dissolution of aged-FS was achieved at initial pH 12.0, liquid/solid ratio 200, 30 °C, 24 h, and 150 RPM. A selenate loading isotherm was fitted to the Langmuir model with maximum loading of 71.1 mg Se/g. The intercalated carbonate in aged-FS did not interfere with selenate removal while significant interference was observed from carbonate in solution. The sulfate anion did not interfere with selenate adsorption. The Al dissolution from aged-FS in an adsorption test was suppressed using calcium hydroxide solution. The Al concentration reached to 0.07 ppm; a value lower than the maximum instantaneous value set by [...]