Histidine-conjugated chitosan as efficient adsorbent for Congo red dye elimination from aqueous solution

A two-step procedure was employed to synthesize histidine-conjugated chitosan (His-Cs). Initially l-histidine (His) was reacted with epichlorohydrin in an alkaline medium, followed by reaction of the resultant product with chitosan (Cs) in the same medium, producing His-Cs (yield = 96.5%). The chemical structure of His-Cs was verified using suitable analytical methods, including FTIR, XRD, SEM, and EDS. His-Cs was utilized as an adsorbent and demonstrated exceptional capabilities for the adsorption of Congo Red (CR) dye. The equilibrium results aligned with the Temkin adsorption isotherm. The greatest removal efficiency of His-Cs for CR dye was 99.17%. The Elovich model precisely described the kinetics of adsorption. The adsorption process was endothermic at the applied temperatures. The results indicate that His-Cs may be effectively utilized for the extraction of CR dye from aqueous solutions.