Synergistic adsorption of U(VI) from seawater by MXene and amidoxime mixed matrix membrane with high efficiency

Abstract

Two-dimensional metal carbides (MXene) and amidoxime-based materials have attracted more and more attention in heavy metal adsorption. Herein, we prepared a mixed matrix membrane of amidoximized polyacrylonitrile with MXene particles by a simple phase separation method (M/PAO mixed matrix membrane). The M/PAO mixed matrix membrane had excellent U(VI) ion selectivity compared to vanadium. Under the synergistic adsorption of the two functional adsorption units, the maximum adsorption capacity can reach 10.31 g/m2 (364.46 mg/g) at pH = 6, while the adsorption capacity of U(VI) can reach 37.49 mg/m2 (1.3225 mg/g) in a seven-day natural seawater experiment, which was far more than that of single amidoxime-based adsorbent. Pseudo-second-order kinetics and Langmuir adsorption model were used to study the adsorption behavior. The results of various characterization methods showed the complexation mechanism between the M/PAO mixed matrix membrane and U(VI) ions. Considering its excellent adsorption capacity and facile preparation process, we believe that the M/PAO mixed matrix membrane is one of the most promising candidates for large-scale U(VI) extraction from seawater.