Dual network nano-Zr@chitosan-?-carrageenan hydrogel beads as an adsorbent for fluoride removal from aqueous solution: equilibrium, kinetic and thermodynamic studies

The occurrence of a high concentration of fluoride ions in drinking possess serious issues related to human health. The present study aims to develop a potent adsorbent from the nano-zirconium prepared from the leaf extract of Azolla pinnata. Nanoparticles were embedded into chitosan-kappa-carrageenan beads and used for defluoridation from an aqueous solution. The prepared adsorbent was characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), selected area electron diffraction, and Fourier-transform infrared spectroscopy (FTIR) analysis. Various parameters, for example, adsorbent dosages, pH, contact time, and temperature affecting adsorption of fluoride were examined. The results of the batch adsorption study for the designed dual network, Zr@chitosan-kappa-carrageenan beads showed the highest removal efficiency of 97.5% at 6.5. The Langmuir model yielded a better representation of the experimental results where the maximum removal capacity was reported to be 22.9 mgg-1. Thus, prepared hydrogel beads can be considered a good defluoridating agent.