Chloroacetyl-Mediated Modification of Chitosan by Tannic Acid to Synthesize Economical Tanninate-Chitosan and Its Use in Fluoride Ions Adsorption from Aqueous Solution

The multi-functional, green and environmental acceptable adsorbents were synthesized from activated chitosan for fluoride ions via mild-strategies. Chloroacetylation reaction was performed to integrate an active group to the chitosan structural unit. Subsequently, the integrated active group was derivatized with tannin acid, an environmental-friendly natural polyphenol via a simple reaction. The synthesized products were evaluated for their structures via FTIR, H-1-NMR, UV, SEM-EDS, elemental mapping, BET surface analysis, and XPS. The capability of the synthesized green products was appraised for fluoride ions sorption in circumneutral conditions. The results confirmed the maximum sorption capability of >= 97 % even at trace level and also proved remarkable results in competition with competitive ions. The equilibrium sorption data supported the maximum adsorption capacity of 28.57 mg g(-1) by the Langmuir model within 60 min at pH 7.0, which is nearly analogous to the experimental data of 22.02 mg g(-1) at 10 ppm. Therefore, in conclusion, the proposed green adsorbent is economical, and is even appropriate at almost neutral pH, which designates its applicability for treating drinking water.