Fibrous adsorbents derived from polyphenolic chemistry for remediation of fluoride contamination at low concentrations

Abstract

Fluoride contamination in drinking water is one of the most concerned environmental issues. Herein, a new type of fibrous adsorbent was prepared by polyphenolic chemistry enabled facile synthesis approach that was dependent on the surface modification of chitosan fibers (CF) with plant polyphenols, followed by the chelation with Zr(IV) (CF-Zr). The presence of plant polyphenols allow for a facile and stable anchoring of Zr(IV) onto the CF, which provided sufficient active sites for the adsorption of fluoride at low concentrations. Notably, at low concentration of 2.0 mg/L, the CF-Zr was capable of removing 97.59 % of fluoride, which was considerably higher than commercial activated carbon (3.58 %). The outstanding adsorption performances of CF-Zr to fluoride was attributed to the Zr(IV), which provided high affinity to fluoride by the formation of Zr-oxyfluoride species. The fibrous morphology of the CF-Zr guaranteed a fast adsorption process, with ∼ 30 min to reach the adsorption equilibrium. The Langmuir model well fitted the adsorption isotherms, and the corresponding equilibrium adsorption capacity was determined to be 74.52 mg g−1, close to the experimentally determined maximum adsorption capacity (77.04 mg g−1). The fluoride adsorbed onto the CF-Zr was desorbed by NaOH solution, with the desorption percentage of 90.22 %.