Synthesis of a chitosan@hydroxyapatite composite hybrid using a new approach for high-performance removal of crystal violet dye in aqueous solution, equilibrium isotherms and process optimization

Background: Novel chitosan and hydroxyapatite-based bio composites were studied as potential adsorbents for the removal of crystal violet, a cationic dye, present in an aqueous solution employing various experimental metrics such as initial concentration, pH, adsorbent mass, contact time, temperature, and effect of agitation. Methods: The biosorbent was analyzed by several techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface by BET theory, thermal analysis ATG and X-ray energy dispersal (EDS). Significant Findings: The present study focuses on the synthesis of chitosan, a polymer extracted from shrimp shells, and its association with synthesized hydroxyapatite to form a Cs@Hap composite effective for the adsorption of a cationic dye, crystal violet. The physical and functional properties of the composite were studied using several techniques. X-ray diffraction confirmed the formation of the composite by its crystalline structure, infrared analysis revealed the presence of NH, OH and PO functional groups responsible for the adsorption, SEM coupled with EDS as well as BET and ATG allowed to characterize the surface of the composite as porous, rough and heterogeneous, with an SSA of 138.47 m2g  1, perfect for the adsorption of the given dye. The resulting adsorption efficiency is high and was able to reach a maximum of 93.21% through the optimization of the parameters affecting the adsorption, namely an adsorbent mass of 0.1 g at a pH value equal to 6.5. The kinetic, isothermal and thermodynamic study showed that the adsorption was endothermic and follows the pseudosecond order and Redlich-Peterson models. The regression coefficient R2= 0.9219 showed the validity of the response surface methodology coupled to the Box Behnken design (RSM-BBD) in predicting the percent removal of CV by adsorption.

Automated summary

Novel chitosan and hydroxyapatite-based bio composites were synthesized and studied as effective adsorbents for the removal of crystal violet. The physical and functional properties of the composite were analyzed using various techniques, confirming its suitability for dye adsorption. The optimization of adsorption parameters resulted in a high adsorption efficiency of 93.21%.