Constructing coconut shell biochar/MXenes composites through self-assembly strategy to enhance U(VI) and Cs(I) immobilization capability

Highlights

•	A coconut shell  biochar-based composite was successfully constructed.
•	Modified biochar exhibited excellent adsorption ability for U(VI)/Cs(I).
•	Removal process of U(VI)/Cs(I) was mainly controlled by chemical adsorption.
•	Elimination mechanism was associated with ion exchange and chelation.

Abstract

Herein, a biochar-based composite (Ti₃C₂T_x@biochar-PDA/PEI) was constructed by decorating Ti₃C₂T_x and polydopamine on coconut shell biochar via electrostatic self-assembly method. Different characterization techniques were applied to explore the structure, morphology and composition of the sorbents. It was found that the higher porosity and diverse functional groups were conducive for Ti₃C₂T_x@biochar-PDA/PEI to capture radionuclides, and the water environmental conditions made a great contribution to the adsorption process. The process of removing U(VI)/Cs(I) well complied with the Langmuir isotherm and Pseudo-second-order equations, which indicated that the single layer chemical adsorption occurred on the solid liquid interface. Meanwhile, this produced composite exhibited superior removal performance under complex co-existing ion environment, and the maximum adsorption amounts of U(VI) and Cs(I) reached up to 239.7 and 40.3 mg g⁻¹. Impressively, this adsorbent still exhibited good adsorption performance after three cycles of regeneration. The spectral analysis and DFT calculation demonstrated that adsorption of U(VI) might be a chemical process, while the adsorption of Cs(I) should be ion exchange or electrostatic attraction. This study demonstrated the potential application of Ti₃C₂T_x@biochar-PDA/PEI as an effective remediation strategy for radioactive wastewater cleanup.

Funding

The China Postdoctoral Science Foundation(2021M702911); The Zhejiang Public Welfare Technology Application and Social Development Project(LGF21C030001)