Catalytic activation of peracetic acid for capsaicin degradation by Co3O4 nanoparticles in-situ anchored carbon-coated MXene nanosheets: Performance and mechanism insight

Pelargonic acid vanillylamide (PAVA), a capsaicin-type dacryagogue agent utilized for anti-terrorism and riot control, possesses a low stimulus threshold. This characteristic can lead to environmental contamination following its application and may easily result in secondary stimulation to personnel. The synthesized cobalt-doped Co3O4/Ti3C2@C nanocomposite is applied to activate peracetic acid (PAA) and degrade PAVA. A carbon layer was coated on the surface of Ti3C2-MXene nanosheets to solve the problem of poor oxygen resistance in MXenes; thus, preventing a remarkable loss of surface reactivity. The BET surface area of Co3O4/Ti3C2@C was enlarged to 149.6 m2/g, substantially larger than that of Ti3C2 (13.0 m2/g) and Co3O4 (56.4 m2/g). The enhanced BET surface area and more active sites confer remarkable PAA activation and catalytic degradation properties toward PAVA. With 0.5 mg/mL of Co3O4/Ti3C2@C and 0.35 mM of PAA, 100 mg/L of PAVA was completely degraded in 60 min. Factors such as initial pH, PAVA concentration, catalyst dosage, and PAA concentration on PAVA degradation were systematically evaluated. Additionally, the nanocomposite's reusability and stability were confirmed through recycling tests. Radical quenching experiments and electron paramagnetic resonance analysis demonstrated that the acetylperoxy radical (CH3CO3) was the primary species responsible for PAVA degradation. This study offers an example of the application of MXene and transition metal-activated PAA in wastewater treatment.