Highly efficient removal of U(VI) in aqueous solutions by tea waste-derived biochar-supported iron-manganese oxide composite

Uranium-containing wastewater poses a major threat to human health because of its toxicity and radioactivity. To address this issue, tea waste-derived porous biochar supporting the Fe-Mn bimetallic composite (FMBC) was fabricated using impregnation-pyrolysis and applied for U(VI) removal from aqueous solution. Batch experiments and characterization analysis were performed to investigate the adsorption properties and interaction mechanisms. Results showed that FMBC exhibit a maximum U(VI) removal capacity of 510.8 mg/g at pH = 5, T = 303 k, and t = 25 min. The kinetic and isotherm date fitted well with the pseudo-second-order kinetic model and Langmuir isotherm model, respectively, indicating that uranium adsorption is dominated by chemical adsorption on FMBC. FTIR and XPS analyses further confirmed that the U(VI) adsorption mechanism by FMBC was attributed to surface complexation, pi-pi bonding, and reduction processes. In addition, the Cationic competitive adsorption experiment further highlighted the excellent selective performance of FMBC for U(VI) removal from aqueous solutions, which is important in radionuclides' pollution treatment.