Efficient Catalytic Ozonation over Reduced Graphene Oxide for p-Hydroxylbenzoic Acid (PHBA) Destruction: Active Site and Mechanism

Abstract

Nanocarbons have been demonstrated as promising environmentally benign catalysts for advanced oxidation processes (AOPs) upgrading metal-based materials. In this study, reduced graphene oxide (rGO) with a low level of structural defects was synthesized via a scalable method for catalytic ozonation of p-hydroxylbenzoic acid (PHBA). Metal-free rGO materials were found to exhibit a superior activity in activating ozone for catalytic oxidation of organic phenolics. The electron-rich carbonyl groups were identified as the active sites for the catalytic reaction. Electron spin resonance (ESR) and radical competition tests revealed that superoxide radical ((•)O2(-)) and singlet oxygen ((1)O2) were the reactive oxygen species (ROS) for PHBA degradation. The intermediates and the degradation pathways were illustrated from mass spectroscopy. It was interesting to observe that addition of NaCl could enhance both ozonation and catalytic ozonation efficiencies and make ·O2(-) as the dominant ROS. Stability of the catalysts was also evaluated by the successive tests. Loss of specific surface area and changes in the surface chemistry were suggested to be responsible for catalyst deactivation.

Heterogeneous degradation of refractory pollutants by peroxymonosulfate activated by CoOx-doped ordered mesoporous carbon

“…4-oxo-TEMP was employed to trap 1 O 2 with the formation of 4-oxo-TEMPO, which was quite stable and could be detected easily from its characteristic three-line ESR spectrum with equal intensities (a N = 1.69 mT, g = 2.0054) [62]. The characteristic triplet of 4-oxo-TEMPO was observed in Fig.…”

Tailored synthesis of active reduced graphene oxides from waste graphite: Structural defects and pollutant-dependent reactive radicals in aqueous organics decontamination

“…Defects, surface oxygen containing groups have been speculated to be the potential active sites. Our previous work revealed that surface oxygen containing groups, especially the carbonyl groups would contribute to the catalytic efficiency [8]. However, the in-depth insights into the contribution of these potential active sites within rGO to the catalytic ozonation still remain unveiled.…”

“…Compared with ozonation process, catalytic ozonation is a more efficient AOP for non-selective mineralization of aqueous organic pollutants, relying on the generated reactive oxygen species (ROS) as well as the ozone molecules [8,9].…”

“…To construct a sustainable future, the emerging carbon-based materials, especially nanocarbons, have been developed as the state-of-the-art alternatives to the metal-based materials for environmental catalysis due to their exceptional physico-chemical properties, no heavy metal leaching and environmental friendliness [5,[11][12][13][14][15]. Studies revealed that graphene oxide (GO) and reduced graphene oxide (rGO) materials demonstrated excellent catalytic ozonation activities in destruction of POPs [8,16]. Defects, surface oxygen containing groups have been speculated to be the potential active sites.…”

Influence of the organic linker substituent on the catalytic activity of MIL-101(Cr) for the oxidative coupling of benzylamines to imines

“…NaN3 is a selective 1 O2 quencher. 56 The results of these quenching studies are shown in Figure 8 that plots the temporal profiles of a series of four reactions, in three of them the quencher was added at 5 h of reaction time, while no quenchers were added in the fourth experiment. It should be noted that none of the quenchers was able to stop completely the reaction, a fact that can be understood considering that activation of oxygen by MIL-101(Cr) takes place continuously, regardless the presence of quencher, inside the cavities of the material and, due to diffusion restrictions, complete quenching cannot be expected under continuous ROS generation.…”