Preparation of acid-modified waste mask-based activated carbon grafted chitosan composites and their efficient removal of uranyl ions

Resource utilization of waste masks is of great significance for environmental protection. In this study, acid-modified waste mask-based activated carbon grafted chitosan composites (CSMA) were prepared using waste masks as a carbon source, chemically modified by introducing sulphonic acid groups through sulfuric acid treatment and further loaded with chitosan, and used for the efficient removal of U(VI) from aqueous solutions. Various characterization techniques, including SEM, FTIR, BET, and XPS, were utilized to investigate the microstructure and surface chemistry of CSMA. The experimental data indicate that optimal adsorption efficiency for CSMA about U(VI) is achieved at a pH of 7, utilizing an adsorbent dosage(m/V) of 0.1 g·L^-1, a reaction duration of 6 h, and a temperature of 303 K. Under these conditions, the maximum adsorption capacity reaches 467.93 mg/g. From the kinetic and thermodynamic results of adsorption, it can be seen that the process of CSMA adsorption on uranyl ions was more in line with the Langmuir isotherm model and pseudo-second-order model. Thermodynamic analysis further confirms that this adsorption process is spontaneous and endothermic. In complex aqueous environments containing various co-existing ions, CSMA demonstrates good selective adsorption capabilities. After several testing cycles, CSMA still maintains a high adsorption efficiency for U(VI). Mechanistic studies using XPS/FTIR suggested that U(VI) capture was governed by coordination/chelation with surface functional groups (-NH₂, -OH, -SO₃H). This study not only presents an innovative approach for resource utilization from discarded masks but also offers an efficient and cost-effective solution for removing radioactive nuclides and facilitating environmental remediation.