The effective removal of Congo red dye via chitosan-layered double hydroxide composite and the deep insight into mechanism

Abstract

In this study, the chitosan microspheres (CSM) were successfully prepared by emulsion crosslinking method, and layered double hydroxides (LDH) was grown in situ on the surface of the chitosan microspheres to prepare chitosan-layered double hydroxide composites (CS@LDH). The properties of CS@LDH composites were characterized by means of SEM, XRD, FT-IR and EDS. The removal effect of the composite on Congo red (CR) dye was studied. The batch adsorption experiments indicated that chitosan intercalated LDH obtained better adsorption capacity for CR than CSM and LDH, the equilibrium adsorption capacity of CS@LDH, CSM and LDH was 745.8, 285.5 and 226.4mg g−1, respectively. The results of adsorption dynamics and isotherm models showed that the adsorption process was more consistent with Elovich nonlinear model and Temkin isotherm model. The characterization of CS@LDH after adsorption of CR implied that the affinity between CS@LDH and CR mainly involved electrostatic interaction was revealed via Independent Gradient Model based on the Hirshfeld partition of molecular density (IGMH) and Hirshfeld surface analysis. In addition, molecular dynamics (MD) simulations were conducted to analyze the influence of CS@LDH on the structure and properties of CR. The results indicate a significant adsorption effect of CS@LDH on CR.