Fluoride removal from drinking water by zirconium-impregnated fibrous protein

Zirconium-impregnated fibrous protein (ZrFP) adsorbent was synthesized by recovering fibrous protein (FP) with zirconium sulfate with immobilization reaction at pH 3.0–4.0. The adsorbent was characterized, and its performance for fluoride removal in drinking water was evaluated. Zirconium was well dispersed and impregnated on FP surface from SEM photos. Fourier transform infrared showed that the hydroxyl group of hydrous metal oxide (Zr-OH) appeared at 1,130 cm−1 after impregnation. ZrFP showed an alkaline surface charge property and exhibited the best efficiency at pH 5.0 with a fluoride sorption capacity of 12.6 mg/g at equilibrium concentration of 1.0 mg/L. Fluoride sorption kinetics was well described by the pseudo-second-order model, and sorption equilibrium was suitable to the Langmuir isotherm equation. It was found that the release of Zr(IV) in residual solution was below 0.3 mg/L, and column sorption experiment indicated the drinking water quality was improved by fluoride adsorption.