Novel Prussian blue analogues@MXene nanocomposite as heterogeneous activator of peroxymonosulfate for the degradation of coumarin: The nonnegligible role of Lewis-acid sites on MXene

In this study, with two dimensional MXene as the substrate, Prussian blue [email protected] composite ([email protected]) was fabricated and utilized as a heterogeneous catalyst for the oxidative degradation of coumarin (COU) based on peroxymonosulfate activation. The initial pH strongly affected the degradation process, and the alkaline pH was beneficial to the COU degradation than the acidic pH. The kinetic rate constants were determined to be 0.030, 0.055, 0.121 and 0.246 min-1at pHs of 3.0, 5.0, 6.6 and 10.0, respectively. The TOC removal efficiency achieved at pH 10.0 was 70.9% in 20 min reaction time. Radical scavengers tests showed that in the presence of 500 mM tert-butyl alcohol (TBA), the rate constant was gradually enhanced from 0.004 to 0.040 min−1 with increasing the solution pH from 3.0 to 10.0; while with the addition of 500 mM Methanol (Me), the rate constants were determined to be 0.002, 0.001, 0.002, and 0.002 min−1 at pHs of 3.0, 5.0, 6.6, and 10.0, respectively. Mechanism study indicated that the differences in COU degradation at different pHs could be mainly ascribed to the unsaturated Ti-C-O (Lewis-acid site) and terminal F-Ti on the catalyst surface. This work not only demonstrated that [email protected] was a promisingly effective catalyst for PMS activation for COU degradation, but also clearly spelled out the role of Lewis-acid sites of MXene in MXene-based catalysts.