TFN nanofiltration membrane incorporating ZIF-8@MXene for efficient removal ReO4- from simulated nuclear-contaminated wastewater

Abstract

In an effort to explore the potential application prospects of membrane separation technology in treating nuclear-contaminated wastewater, a TFN nanofiltration membrane incorporating the ZIF-8@Ti3C2Tx nanocomposite was successfully synthesized using the interfacial polymerization method. This involved doping the microemulsion of ZIF-8@Ti3C2Tx into the aqueous (organic) phase. The morphology and structure of ZIF-8@MXene nanocomposites and TFN nanofiltration membranes were characterized. The selective removal of ReO4- from simulated radioactive wastewater using the TFN nanofiltration membrane was evaluated. The results indicated that the ZIF-8@Ti3C2Tx composite, uniformly dispersed in the polymer, effectively enhanced the pore structure and polarity of the nanofiltration membrane, thereby improving its permeability. The electronegativity of ZIF-8@Ti3C2Tx also enhanced the negative charge on the surface of the polymer membrane, significantly improving the membrane’s performance in rejecting ReO4- while maintaining a low retention rate for Na+. This design facilitates the efficient selection of ReO4- from high-salinity wastewater. In addition, the layer spacing of Ti3C2Tx further improved the screening of ReO4- and Na+. However, when 0.75 g·L−1 of microemulsion was added, it became challenging to disperse the microemulsion completely in the organic phase. This led to the agglomeration of composites in the nanofiltration membrane, weakening both flux and selectivity. Optimal performance was achieved with a microemulsion doping amount of 0.5 g·L−1, resulting in the nanofiltration membrane M-O-1 exhibiting the best performance (Jp = 41.92 L·m2·h−1 and R(ReO4-) = 65.81%). Even at a high salt concentration (20 g·L−1), the M-O-1 membrane retained approximately 55% of pollutants after continuous operation for 5 h, indicating that the TFN nanofiltration membrane containing ZIF-8@Ti3C2Tx holds significant promise for selectively extracting 99Tc from wastewater with a high salt content.