Immobilization of novel bifunctional polymer with amide and amidoxime groups in biochar-chitosan composite gels for enhancing uranium(VI) uptake

Abstract

This work synthesized poly ethanolamine amidoxime modified winter melon and chitosan-derived biochar (PEA-CTS@WBC) using chemical crosslinking method for uranium(VI) removal. The factors influencing uranium(VI) adsorption by PEA-CTS@WBC, including pH, adsorbent dosage, time, temperature, and initial U(VI) concentration were explored. The material’s performance was characterized, and the underlying mechanism of U(VI) removal was analyzed using various techniques. The characterization results indicated that the PEA-CTS@WBC took on a membrane shape with numerous pores and wrinkles distributed on the surface, providing more active sites that can effectively promote the complexation and adsorption of U(VI). The results demonstrated that PEA-CTS@WBC effectively removed U(VI), achieving a maximum adsorption capacity of 485.89 mg/g at the pH of 5.0. The process suggested a dominant role for chemical adsorption. The Freundlich isotherm model demonstrated a high degree of alignment with the observed adsorption behavior, indicating a predominantly multilayer adsorption process. Thermodynamic studies indicated that adsorption was a spontaneous endothermic process. The XPS analysis demonstrated that the adsorption process was primarily due to the formation of stable complexes with NH3+-C(O), N–C, C–N, C=C, O–H and C=O. This research showed that the introduction of amide and amidoxime groups significantly improved the adsorption effect of biochar-chitosan gels on U(VI). PEA-CTS@WBC had a high selective adsorption characteristics and good reusability for U(VI) in aqueous solutions. PEA-CTS@WBC was an economical, efficient and stable composite material. These findings provided a theoretical basis for the treatment of wastewater contaminated with U(VI).