Production of magnetic biocomposite beads incorporated with walnutshell and their use in removal of cationic dye from aqueous solutions

Due to the scarcity of usable water resources in the world, efficient use of water is of great importance. For this reason, researchers are carried out on different methods to make reusable the water polluted by many factors. In this study, an environmentally friendly magnetic (m) biocomposite adsorbent was prepared for the removal of cationic dye brilliant green (BY), which is known to have toxic effects, from aqueous solutions by adsorption method. Alginate (AL), xanthan gum (KS) and walnut shell powder (C) were used in the preparation of magnetic biocomposite beads. In order to effectively remove the dye from water, the optimum magnetic biocomposite bead preparation ratio was determined as 1.5%AL/0.5%KS/1%C. The synthesized magnetic biocomposite beads were characterized by FTIR, SEM and TGA/DTG. In the FTIR and SEM analyzes, it was determined that the dye was adsorbed on the magnetic biocomposite, while the degradation took place in three stages in the TGA/DTG analysis. The effective adsorption parameters of the synthesized magnetic biocomposite beads in removing the dye from the water were optimized. Optimum pH in adsorption studies: 8, duration: 120 min. has been determined. It was determined that while temperature increased the adsorption efficiency, salt (NaCl) decreased it. In the adsorption studies, the maximum adsorption capacity of the magnetic biocomposite was found to be 380±17,25 mg/g. Langmuir, Freundlich, Temkin and Dubinin-Radushkevich adsorption isotherms were investigated and it was determined that the adsorption fit the Freundlich isotherm model with higher accuracy (R2 = 0.9983) and low mean square error (RSME = 9,29). In the kinetic studies, it was concluded that the adsorption capacity increased with temperature and the pseudo second-order kinetic model and the intraparticle diffusion process operated simultaneously in the adsorption of BY to the magnetic biocomposite beads. Thermodynamic calculations showed that physical forces are effective in adsorption and the adsorption process proceeds endothermically (ΔH=79.90 kJ/mol). Also, the negative values of ΔG° indicated the possibility of the adsorption process and that it was spontaneous.