EDAC-modified chitosan/imidazolium-polysulfone composite beads for removal of Cr(VI) from aqueous solution

To enhance the stability and adsorption performance of chitosan in Cr(VI)-contaminated acidic wastewater, a novel EDAC-modified-EDTA-crosslinked chitosan derivative (CSEC) was synthesized via a one-pot method with chitosan, 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC), and Na₂EDTA as raw materials. To further improve the mechanical strength and separation performance of CSEC, a novel composite bead (CSEP) of CSEC and imidazolium-functionalized polysulfone (IMPSF) was prepared through a phase inversion method. The chemical composition and microstructure of CSEC and CSEP were characterized by FESEM, FTIR, NMR and XPS techniques. The maximum adsorption capacities of CSEC and CSEP for Cr(VI) were 145.96 and 135.82 mg g^-1 at pH 3, respectively, and the equilibrium time for Cr(VI) adsorption by CSEC and CSEP was 5 min and 8 h, respectively. The adsorption process of Cr(VI) by both CSEC and CSEP was exothermic and spontaneous. Compared to CSEC, CSEP has significantly enhanced resistance to interference from coexisting anions. The removal mechanism of Cr(VI) by CSEP might involve redox reaction as well as electrostatic attraction between Cr(VI) oxyanions and various nitrogen cations, including protonated amino groups, guanidinium groups, protonated tertiary amine groups, and imidazolium cations. The CSEP beads have potential application value in the treatment of acidic wastewater containing Cr(VI).