Design and preparation of zirconium-induced bio-foam for the removal of fluoride, chromate, and other emerging pollutants: A scale-up approach

Abstract

About 1.5 billion people are exposed to fluoride-contaminated water worldwide, and prolonged exposure (>3 ppm) can cause a number of health issues. In this study, zirconium(IV)-chitosan@agar (Zr-CA) biofoam was synthesized with improved stability in a simple two-step reaction using chitosan and agar biopolymers with in-situ generated zirconia (ZrO2) for Fluoride (F-), Chromium (Cr(VI)), Diclofenac (Df) and Ciprofloxacin (Cf) removal. The Zr-CA biofoam was confirmed by a series of physico-chemical techniques such as FE-SEM, EDAX, XPS, XRD, FTIR and BET analysis, where a surface area of the biofoams was about 2 m2/g. The adsorption efficiency of the biofoams was studied by kinetic, isotherm, pH and thermodynamic investigations as well as interference of co-existing ions. The adsorption studies were well-agreed with the Langmuir isotherm and pseudo-second order kinetics. From the Langmuir calculations, the adsorption capacity (qmax) of the 2-Zr-CA biofoam for F- and Cr (VI) was 114.94 and 340.13 mg/g, respectively. The 2-Zr-CA biofoam was also utilized in the filtration model as a dynamic flow method to remove F-, Cr (VI), Df and Cf from the aqueous solution in which the rejection was 97.82 %, 98.12%, 96.86% and 94.17% and the flux rates were 881.03, 967.87, 979.54 and 988 Lm-2h−1, respectively. For real fluoride water purification 2-Zr-CA biofoam (30 gm with 8 cm height and 6.5 cm diameter) based purification device for fluoride contaminated water (18 L) was purified from its initial concentration of 4.83 ppm to equilibrium concentration of 1.78 ppm.