Activation of Peracetic Acid by Thermally Modified Carbon Nanotubes: Organic Radicals Contribution and Active Sites Identification

Abstract

Carbon materials activated peracetic acid (PAA) as an environmentally friendly technology has attracted wide attention for pollutants degradation. In this work, thermally modified carbon nanotubes (CNT-t) 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 CNT−800/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 oxygen species (ROS) in the reaction process, while •OH made limited contribution to PE degradation. The material characterization proved that the lattice defects rate of CNT is 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 CNT/PAA system was strongly affected by the initial pH and the presence of humic acid. Moreover, CNT-800 can 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.

Keywords: peracetic acid, Carbon nanotube, organic radicals, double-vacancy defects