Zirconium–Cerium and Zirconium–Lanthanum complexed polyvinyl alcohol films for efficient fluoride removal from aqueous solution
In the current work, user-friendly, biodegradable, Zirconium-Lanthanum (ZLPC) and Zirconium-Cerium (ZCPC) complexed Polyvinyl alcohol (PVA) films were solvent casted for effective defluoridation of water. The films were characterised using SEM coupled EDS, XPS, TGA, XRD and FT-IR. These films adsorbed 95−97% fluoride from water at pH 7, with 85% removal by ZLPC and 93% removal by ZCPC within the first 45 minutes of the adsorption process. A maximum adsorption capacity of 11.57 mg/g and 12.88 mg/g, corresponding to ZLPC and ZCPC respectively, was obtained using Langmuir adsorption isotherm. The films followed pseudo-second-order kinetics (R2≤0.99) in both the cases, which was further established by low values of chi-square and root mean square error (RMSE). The ICP-AES analysis confirmed no leaching of the metal ions from the polymer films into the treated water. The films were found to be stable in both acidic and basic medium. No interference to fluoride adsorption was detected even at 100 mg/L of Cl−, NO3− and SO42− while some interference was observed in the presence of PO43− and HCO3−. The change in Gibbs free energy for fluoride adsorption using the ab-initio method was found to be −330.05 kJ/mol, which indicated spontaneity of the process. This was further reinforced by the thermodynamic data obtained from adsorption studies. The films were reusable and showed ∼85% removal of fluoride even after the fifth regeneration cycle. Thus, these handy films have a scope to be developed into a prototype for defluoridation of ground water.