Biopolymer modified transition metal spinel ferrites for removal of fluoride ions from water

Abstract

In present study different nano metal ferrites such as zinc ferrite (ZnFN), nickel ferrite (NiFN) and cobalt ferrite (CoFN) were modified with chitosan (CS) biopolymer to prepare recyclable magnetic chitosan composites and used as adsorbents to remove fluoride ions from aqueous solution. Various techniques like Fourier Transform Infra-Red (FT-IR), X-Ray Diffraction (XRD), Transmission Electron Microscope (TEM), BET analysis, Thermal Gravimetric Analysis (TG-DTA) and pH of point zero charges (pHzpc) were used to study the surface characterization and morphology of different magnetic chitosan composites. Thermal studies results reveal that the different chitosan composites are thermally stable up to 400 °C. The adsorption kinetics data obtained from different magnetic composites were best fitted in Lagergren Pseudo-second-order model. Among different isotherm models, the adsorption equilibrium data were best fitted in the Langmuir isotherm model. The calculated maximum adsorption capacities of ZnFN-CS, NiFN-CS, and CoFN-CS composites were 6.9, 8.3 and 6.7 mg/g, respectively. The calculated adsorption thermodynamic parameters values confirmed that the adsorption of fluoride ions is spontaneous and exothermic in nature. The regeneration efficiency of different magnetic composites was studied up to five successive cycles. The results revealed that the regeneration efficiencies of ZnFN-CS, NiFN-CS and CoFN-CS composites toward fluoride ions were reduced to 84%, 79%, and 76%, respectively.