Performance and mechanism of Cr(VI) removal from aqueous solution by polydopamine/Ce-UIO-66 co-modified...

In this study, polydopamine/Ce-UIO-66 co-modified glutaraldehyde crosslinked chitosan (CGCP) composite was prepared by chemical cross-linking and oxidative polymerization methods and used to remove Cr(VI) from aqueous solution. The removal efficiency of Cr(VI) by CGCP gradually decreased with increasing pH, and the highest removal efficiency of 94.18 % was achieved at pH = 2.0, C₀, _Cr(VI) = 100 mg L^-1 and CGCP dosage = 0.03 g. The adsorption capacity reached a maximum of 398.86 mg g^-1. The negative influence of coexisting ions (Na⁺, Ca²⁺, Mg²⁺, Cl^-, SO₄^2-, PO₄^3- and CO₃^2-) increased with the increase of the concentration, among which CO₃^2- had the greatest negative influence since OH^- formed by its hydrolysis affected the protonation of the surface functional groups of CGCP. The removal process of Cr(VI) by CGCP is a spontaneous endothermic process, which follows the pseudo-second-order kinetic model and the Freundlich isotherm model. Glutaraldehyde cross-linking increased the mechanical strength and acid resistance of chitosan, the incorporation of Ce-UIO-66 increased the active sites of the composite, and the incorporation of polydopamine further increased the stability. The removal of Cr(VI) by CGCP composite involved electrostatic adsorption, ion exchange, reduction and complexation. Therefore, CGCP composite can remove Cr(VI) from wastewater stably and efficiently, and has a good application prospect.