Layered V₄AlC₃ MAX phase for degradation of pharmaceutics through sonocatalytic activation of peroxymonosulfate: Synergistic effect, degradation pathways, and toxicity assessment

The V₄AlC₃ MAX phase, as the precursor of MXene, was developed for levofloxacin degradation through sonocatalytic activation of peroxymonosulfate (PMS). The reactive sintering method was used to synthesize V₄AlC₃ MAX phase. Vanadium, aluminium and graphite, with molar ratios 4:1.2:3, were mixed in ball milled (ball-to-material ratio of 3:1, 12 h, 350 rpm), compressed into a disc and placed in a tubular furnace (1600 ℃ for 2 h). The stacked layered morphology of the MAX phase was confirmed by SEM and TEM images. With an average crystal size of 48.5 nm and a narrow band gap (1.92 eV), the V₄AlC₃ MAX phase exhibited remarkable sonocatalytic activity. Under optimum conditions, US/V₄ALC₃ MAX phase/PMS process exhibited 88.4 % levofloxacin degradation efficiency in 60 min. First order rate constant (k_app) of the US/V₄AlC₃ MAX phase/PMS process was 10.22, 7.43, and 4.78 times higher than that of US/V₄AlC₃ MAX phase, US/PMS, and V₄AlC₃ MAX phase/PMS processes, respectively. V₄AlC₃ MAX phase showed remarkable reusability after 5 cycles. It was proved that superoxide radical was the main active substance in the degradation process. The possible intermediates were identified through LC-MS analysis, and four main degradation pathways were proposed. The mechanism of PMS-assisted sonocatalytic degradation of levofloxacin was described.