Synthesis of Graphene Oxide and Its Application for Efficient Removal of Fluoride from Water.

Excess of fluoride (F-) in drinking water is a serious worldwide problem because more than 20 countries from all over the world including India are suffering from F- toxicity. Herein an attempt has been made for removal of F- from water using Graphene Oxide (GO) as a nanoadsorbent. GO has proven better nanoadsorbent because of easy mass production, presence of plentiful oxygen containing functional group on its surface, water dispersibility and sheet like structure. Adsorption experiments were conducted in batch reactor at different pH, GO dose, initial [F-], contact time and temperature by optimizing one variables at a time approach. Optimization experiment results showed that uptake capacity of GO was 28.26 mg/g and it is capable to remove nearly 94.2% of fluoride at pH 2, GO dose 0.5 g/L, temperature 35°C, and initial [F-] 15 mg/L. For further optimization of adsorption variables Response Surface Methodology (RSM) was also employed and maximum 98.2% removal was achieved at RSM predicted conditions viz. pH 2.5, GO dose 0.5 g/L, temperature 36.7°C, and initial [F-] 15 mg/L. UV-visible, FTIR and SEM analysis were conducted before and after the adsorption which confirmed the presence of F- at the surface of GO. Under optimum conditions the isothermic studies have been conducted and it was found that the experimental data fit well to the Langmuir isotherm model illustrating monolayer pattern of the adsorption. Thermodynamic studies were also investigated for the current adsorption system which revealed the spontaneous and endothermic nature of the process while kinetic study indicated that the present adsorption system is best explained by pseudo-second order kinetic pathway. GO was regenerated by 0.5 M NaOH and it was reused many times although its uptake capacity decreases slightly after every adsorption-desorption cycle. [ABSTRACT FROM AUTHOR]