Fluoride Ions Sequestration From Contaminated Water Using PVA-Agar-Based Green Anion-Exchanger

Abstract

The current work is focused on the designing of a green interpenetrating polymer network (IPN) PA@polyAAm:AN using polyvinyl alcohol-agar hybrid backbone and its subsequent conversion into an anion-exchanger PA@polyAAm:AN-AE through reduction of nitrile group in presence of LiAlH₄. Further, the reduced form of IPN was quaternized using methyl iodide so that anion to anion exchange could take place between F⁻ and I⁻ anions. The primary objective of synthesizing an anion-exchanger was to eliminate F⁻ ions from contaminated water through the utilization of a prepared device. During the optimization of different experimental parameters for getting the optimal anion-exchange capacity (AEC), the favorable conditions found were: pH, 9.0; contact period, 120 min; adsorbent dosage, 30 mg and initial F⁻ ion concentration, 8.0 mg L⁻¹. The pseudo-second order kinetic model best described the F⁻ ions adsorption kinetics, with a 0.97 R² value. The rate constant (K_F) was found to be 2.3, which further supported the validity of the Freundlich isotherm. Thus, the current study has remarkable potential with a 79.99% adsorption capacity for eliminating F⁻ ions. Moreover, the ecofriendly anion-exchanger prepared was found effective in the removal of F⁻ ions from aqueous medium up to four cycles during reusability analysis.