Adsorption performance and mechanism of g-C3N4/CS composite for U(VI) from aqueous solution

Aimed at the problem of environmental uranium pollution caused by uranium-containing wastewater generated in the process of nuclear energy development and application, by loading g-C3N4 on chitosan (CS) through the cross-linking method, g-C3N4/CS composite was synthesized and used to remove U(VI) from aqueous solutions. The surface properties and the interaction mechanism of g-C3N4/CS were analyzed. The results show that when the adsorbent dosage of g-C3N4/CS is 0.2 g/L, mass fraction of g-C3N4 is 20%, adsorption time is 120 min, adsorption temperature is 308 K, and pH is 6, the maximum adsorption capacity of g-C3N4/CS on U(VI) reaches 324.45 mg/g. The adsorption of U(VI) by g-C3N4/CS involves a spontaneous endothermic process that follows the Langmuir isotherm model and quasi-second-order kinetic model. The adsorption mechanism of U(VI)by g-C3N4/CS is primarily attributedto the coordinated complexation of functional groups such as -NH, -OH, C-O, C=O, and C-N. The results of the recycling experiments show that g-C3N4/CS has good reusability.