Highly efficient adsorption and immobilization of U(VI) from aqueous solution by alkalized MXene-supported nanoscale zero-valent iron

A novel composite of zero-valent iron nanoparticles supported on alkalized Ti3C2Tx nanoflakes (nZVI/Alk-Ti3C2Tx) was constructed by an in-situ growth method for simultaneous adsorption and reduction U(VI) from aqueous solution in anoxic conditions. The effect of various factors such as adsorbent dose, pH, ionic strength, contact time, initial U(VI) concentration and environmental media were comprehensively investigated by batch experiments. Benefiting from the good dispersion uniformity of nZVI on MXene substrates, nZVI/Alk-Ti3C2Tx exhibited rapid removal kinetics, excellent selectivity, 100% removal efficiency and up to 1315 mg g−1 uptake capacity for U(VI) capture. In the presence of mimic groundwater, 1.0 mM NaHCO3 and 10 mg L−1 humic acid, the removal percentages of U(VI) by the composites could reach 95.1%, 88.9% and 69.5%, respectively. The reaction mechanism between U(VI) and nZVI/Alk-Ti3C2Tx has been clarified based on FTIR, XANES, XPS and XRD analysis. Depending on the consumption of reactive nZVI in the composites and the solution pH, the elimination of U(VI) could be realized by different pathways including reductive immobilization in the form of UO2, inner-sphere surface complexation and hydrolysis precipitation. The present study illustrates that the nZVI/Alk-Ti3C2Tx composite may be an efficient scavenger for radioactive wastewater purification in environmental remediation.