Rational design of OH-functionalized Ti2CTx nanosheets and composite aerogel spheres: A highly efficient approach for U(VI) removal from simulated seawater

MXenes have demonstrated exceptional potential in the adsorption of uranium (U(VI)) from wastewater. However, significant challenges remain in the investigation of its adsorption capacity and mechanism. To enhance the adsorption capacity of Ti2CTx, this study conducted alkalization experiments on Ti2CTx and subsequently prepared Ti2C(OH)(0.13)@SA aerogel spheres by combining alkalized Ti2C(OH)(0.13) with sodium alginate (SA). The results indicated that alkalization effectively increased the proportion of OH functional groups. After alkalization treatment, Ti2C(OH)(0.13) exhibits a significantly enhanced adsorption capacity, reaching up to 951 mg g(- 1), which represents more than a twofold increase compared with untreated Ti2CTx. The adsorption follows pseudo-second-order kinetics and the Langmuir isotherm model, suggesting chemical and monolayer adsorption, respectively. Thermodynamic studies reveal an endothermic adsorption process. DFT calculations demonstrate that the OH functional group forms chemical bonds with U(VI), promoting reductive adsorption. Aside from electrostatic adsorption, XPS analysis confirms Ti(II) oxidation and U(VI) reduction. This study further investigates the adsorption capacity of Ti2C(OH)(0.13)@SA aerogel spheres in simulated seawater environments. It is found that even at an ultra-low concentration of U(VI) as low as 3.3 mu g/L, these aerogel spheres still exhibit significant adsorption performance, with an adsorption capacity reaching up to 3.21 mg g(-1), highlighting their substantial potential for applications.