Unveiling the interaction mechanism of renewably hydrophilic PVP/MOF-199@PEI/SA microsphere for enhanced removal of uranium and europium from wastewater

摘要: In recent years, the global nuclear industry has experienced rapid development, which has led to an increasing severity of water environment pollution caused by the accidental leakage of radioactive nuclides. Therefore, there is an urgent demand to develop a highly efficient and environmentally friendly adsorbent to resolve the pollution issue. In this study, the polyvinylpyrrolidone/MOF-199 of hydrophilic polyethyleneimine high-molecular polymer decorated sodium alginate (PVP/MOF-199@PEI/SA) microspheres were successfully synthesized, which was exhibited excellently chemical stability and physical structure stability, through containing abundant functional groups and chelation reaction with radionuclides. Macroscopic experiments were conducted to investigate the removal performance of PVP/MOF-199@PEI/SA toward Eu(III) and U(VI) from wastewater under different environmental factors. Experimental results showed that the maximum adsorption capacities of the PVP/MOF-199@PEI/SA for Eu(III) and U(VI) were 1.02×10-3 mol/g and 1.22×10-3 mol/g, which were higher than the average levels reported in recent years. Additionally, the adsorption isotherms of the microspheres for Eu(III) and U(VI) were fitted well with Langmuir model, indicating that adsorption process was entirely endothermic. The excellent adsorption performance of PVP/MOF-199@PEI/SA was verified through kinetic models, with adsorption equilibrium for both Eu(III) and U(VI) to achieve within 2 h. The adsorption results were closely aligned with pseudo-second-order kinetic model, suggesting that the adsorption processes were involved multi-step chemical adsorption. Based on XPS analysis results, it was inferred that the adsorption mechanisms of PVP/MOF-199@PEI/SA microsphere for Eu(III) and U(VI) were primarily involved surface complexation, chelation reaction and electrostatic interactions. Furthermore, the good reusability and excellent selectivity of PVP/MOF-199@PEI/SA were verified through cyclic adsorption tests and competition adsorption, respectively. Based on the above findings, the PVP/MOF-199@PEI/SA possess significant application prospect in effectively treating with Eu(III) and U(VI) in nuclear wastewater.