Adsorption behavior and mechanism of U(VI) onto phytic Acid-modified Biochar/MoS2 heterojunction materials

Using a low-cost, pollution-free and efficient adsorbents to adsorb uranium in radioactive wastewater is of great significance to protect the environment. In this study, bamboo powder-derived biomass charcoal (BDC) was first composited with MoS2, and then the composites were surface-modified with phytic acid to obtain BDC/MoS2-PO4. The microstructure of the adsorbents was analyzed by various characterization techniques. The adsorption kinetics results showed that the U(VI) adsorption by BDC/MoS2-PO4 was more in line with the pseudo-second-order kinetic model, suggesting that the process is mainly chemical adsorption. The adsorption isotherm model confirmed that the U(VI) adsorption by BDC/MoS2-PO4 conformed to the Langmuir isotherm model, which was mainly surface monolayer adsorption with a maximum adsorption capacity of 161.29 mg/g. Furthermore, the adsorption performance of the adsorbent for U(VI) was significantly enhanced after H2 plasma treatment (204.08 mg/g), indicating that the increase in sulfur vacancies favors the U(VI) adsorption. The EPR, XPS and FT-IR results suggested that the interaction mechanism could be explained in that the S vacancies, S, C-O and P-O of the BDC/MoS2-PO4 were bonded to [O = U = O]2+ in the solution. This study provides a theoretical and experimental basis for the design and synthesis of biochar-based materials, and also provides a reference for radioactive wastewater treatment.