Mechanistic insight into confined Fenton system in the MXene layer (MXene-Fe@PES) for enhanced aquatic contaminant removal

The confinement strategy was considered as an effective method for enhanced aquatic contaminant removal in catalytic systems, and the two-dimensional (2D) material displayed sufficient capacities for contaminant attenuation as compared to other materials due to the unique interlayer structures. However, information on the construction of confined catalytic systems using 2D materials is still lacked. Here, a novel 2D catalytic system in which Fe atoms were illustrated into MXene layers and polyether sulfone (PES) substrate (named MXene-Fe@PES) was established to explore its degradation potential toward typical aquatic contaminants e.g., phenol. Compared to the control (Fe@PES), higher electron densities and migration rates, but lower coordination numbers of Fe atoms were achieved in the MXene-Fe@PES system. This new system with 14.5 & Aring; channels (model phenol: 1.472 s(-1)) exhibited an ultrafast degradation rate, which was 60 similar to 1200 times higher than the common homogeneous and heterogeneous Fenton-like systems. Further analysis showed that enhanced reactive oxygen species generation, electron density of Fe site, H2O2 decomposition, electron interactions between Fe and H2O2, and O-O bond cleavage in H2O2 accounted for the improved contaminant removal. Moreover, the degradation pathway of phenol was changed from the kinetically favorable ring-opening pathway in Fe@PES system to the thermodynamically favorable oligomerization pathway in MXene-Fe@PES system. Application in actual water samples, including river waters, lake waters, and treated-wastewater effluents showed that the removal efficiencies were maintained at 69 similar to 97%, indicating high potential for water decontamination. Correlation analysis showed that phenol removal in actual waters was negatively correlated with the abundances and molecular weights of dissolved organic matters as well as the phosphorus concentrations. This study provides not only a paradigm for the delicate design of high-efficient confined Fenton reaction system, but also a theoretical reference for the construction and selection of catalytic systems in environment restoration of actual waters.