Evaluation of fluoride removal from water by hydrotalcite-like compounds synthesized from the kaolinic clay

Abstract

The present study investigates the fluoride sorption by Mg-Al-CO3 prepared from a kaolinite as natural source of aluminium using two simple methods. The first method uses the kaolinite in natural solid state; the second method uses the filtrate of the kaolinite after dissolution by acidic solutions. The adsorption characteristics of the fluoride from synthetic wastewater on calcined LDH samples were evaluated under laboratory conditions. The anionic clays tested were [Ksd3P10-T150] synthesized by method (1) using kaolinitic clay in solid state and [Kliq3P10] synthesized by method (2). The equilibrium isotherm showed that the uptake of fluoride ion was consistent with the Langmuir and Freundlich equations and that the Freundlich model gave a better fit to the experimental data than the Langmuir model. The maximum adsorption capacity is 238 and 175 mg/g for KliqP10-(500)-LDH and KsdP10-(500)-LDH, respectively, higher than that reported on other adsorbents for fluoride removal A mechanism for removal of fluoride ion has been confirmed by X-ray diffraction. Overall, the results demonstrate the convenient synthesis of the hydrotalcite from the kaolinite and the high efficiency of fluoride removal that is promising for potential applications of calcined KliqP10 and KsdP10-LDH in the environmental clean-up and remediation of contaminated water.