Nitrogen-rich carbon nitrogen polymers for enhancing the sorption of uranyl

摘要

Nitrogen enrichment and increased nitrogen content is an effective strategy for enhancing adsorption of uranium by carbon nitride polymers.Herein,we reported the uranium absorption by using a structurally well-defined and nitrogen-rich carbon nitride polymer with C_(3)N_(5) stoichiometry for the first time.In comparison with the adsorption performance of g-C_(3)N_(4) for U(Ⅵ),the conjugation system of the material was increased by connecting the heptazine unit through the azo bridge in the structure of C_(3)N_(5),so that C_(3)N_(5) exhibited several times higher adsorption performance than that of g-C_(3)N_(4).The C_(3)N_(5) has high kinetics for uranyl ions,which can adsorb100 mg/g U(Ⅵ)in only 10 min and reach complete adsorption equilibrium in 60 min;the theoretical maximum adsorption capacity is 207 mg/g,meanwhile,the material exhibits high selectivity.The results of spectral analysis and theoretical calculations indicate that the process of uranyl ion capture by C3N5is a combination of physical and chemical adsorption,and its higher density of electronic states makes the electrostatic binding ability enhanced,which is favorable to the adsorption of uranyl ions by C_(3)N_(5).This work indicates that C_(3)N_(5) has great promise and application in the separation and enrichment of uranyl ions,and also provides a reference for the systematic investigation of the adsorption ability of nitrogenrich carbon nitrogen polymers on uranyl ions.