Mineralization of phenol by ozone combined with activated carbon: Performance and mechanism under different pH levels

Abstract

The degradation of phenol using ozone with activated carbon (O3/AC system) was investigated in this study. The O3/AC system was also compared with the single O3 and AC systems. The total organic carbon (TOC) removal efficiency in the O3/AC system was roughly 26% and 30% higher than the single AC and O3 systems, respectively. It was demonstrated that the phenol degradation rate and TOC removal efficiency were significantly affected by the ozone concentration, AC dosage, and solution pH. The pseudo-first-order and pseudo-second-order kinetic models were fitted to identify the mechanisms of the phenol removal process. The results of Scanning Electron Microscopy, Brunauer-Emmett-Teller, and Fourier-transform infrared spectroscopy of raw and used AC indicated that the surface morphology, microstructure, and functional group properties had been changed during the reaction process. The possible O3/AC system mineralization mechanism for phenol removal was tentatively proposed using scavenging active species such as ·OH, O2⋅−, and H2O2. The transformation byproducts generated during the application of the O3/AC system were identified by High Performance Liquid Chromatography and Gas Chromatography–Mass Spectrometry analyses. Therefore, the mineralization pathway of phenol in detail was proposed in acidic (pH 3.0) and alkaline (pH 11.0) conditions. This study provided a more systematic explanation of the mineralization mechanism for phenol in the O3/AC system.