Activation of peracetic acid by thermally modified carbon nanotubes: Organic radicals contribution and active sites identification

Peracetic acid (PAA) activated by carbon materials as an environmentally friendly technology has attracted rising attention for compounds degradation. In this work, thermally modified carbon nanotubes were applied to efficiently activate PAA for phenol (PE) degradation. The identification of active sites involved in PAA activation and the contributions of different reactive radicals to the PE degradation were systematically investigated. Excellent removal efficiency of PE was obtained in the CNTs/PAA system within 30 min at neutral conditions. Electron paramagnetic resonance (EPR) technique and radical quenching studies confirmed that organic radicals were the dominant reactive species in the reaction process, while •OH made limited contribution to PE degradation. The material characterization proved that the lattice defects rate of modified CNTs was positively correlated with the catalytic activity. The adsorption models verified that the double-vacancy defects (CNTs-DV) played a major role on the adsorption of PAA and activation process. In contrast to the influence of chlorine and carbonate ions, the PE degradation in CNTs/PAA system was strongly affected by the initial pH and the presence of humic acid. Moreover, modified CNTs could still maintain good catalytic activity after five-cycle runs. Overall, this work not only provides valuable insights for the rational design and directional synthesis of high-performance nano-carbon catalysts, but also proposes a very meaningful oxidation system for wastewater treatment.