The influence of the substituent on the phenol oxidation rate and reactive species in cubic MnO₂catalytic ozonation

Abstract

Shape-controlled MnO 2 , Mn 2 O 3 and Mn 3 O 4 were prepared and applied in catalytic ozonation of phenol (Ph), p-cresol (Ph-CH 3 ) and p-chlorophenol (Ph-Cl). Their textural properties were characterized by XRD, SEM, TEM, nitrogen physical adsorption and CV. MnO 2 was found to be more active than Mn 2 O 3 and Mn 3 O 4 for its higher electron transfer ability and higher amount of oxygen defects or surface hydroxyl groups. The degradation order was Ph-Cl > Ph-CH 3 > Ph in the mixed solution, while the trend became Ph-CH 3 > Ph-Cl > Ph in the single component solution, indicating that an electron donating group (EDG) and an electron withdrawing group (EWG) both benefit phenol degradation. The co-existing phenol had a different effect on the degradation of the other in the ozonation and catalytic ozonation of the mixed solution, but their influence on each other was universally opposite. Superoxide radical, singlet oxygen and molecular ozone were mainly responsible for phenol degradation in bulk solution. The contribution of ozone and singlet oxygen to the phenol degradation follows the order Ph-CH 3 > Ph > Ph-Cl, indicating an electrophilic attack reaction, while the trend is opposite for superoxide radical oxidation, possibly due to a nucleophilic reaction pattern.

Catalytic performance of MnFeSi composite in selective oxidation of styrene, ethylbenzene and benzyl alcohol

“…9c, included). The weak signal with g value close to 2 has steps, being ascribed to Mn 4+ /Mn 3+ ion from MnO 2 phase [32,33]. All samples tested in distinct reaction conditions show similar features to those of MnFeSi tested at 50 • C using a catalyst mass of 100 mg and H 2 O 2 to styrene molar ratio of 1 during 6 h of reaction.…”

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

“…The surface hydroxyl groups acting as the Lewis acid sites are favorable for ozone adsorption and decomposition, while the carbonyl groups accelerate the electron transfer process within the ozone activation. Previously, we found that the main ROS in catalytic ozonation of phenolics varied with the substituted groups [45]. To further probe the determination of target pollutants on the dominant ROS in catalytic ozonation, three aliphatic organics (OA, AA and FA) and three phenolic pollutants (4-NP, PHBA and ASA) were selected as the degradation targets for the radical scavenging tests (Fig.…”

Catalytic Ozonation of Melanoidin in Aqueous Solution over CoFe2O4 Catalyst

“…In the catalytic ozonation of organic compounds, ozone is firstly adsorbed onto the catalyst surface, and then decomposed to produce hydroxyl radicals (•OH) on the solid surface, where the organic pollutants may (or not) be adsorbed 19,20 . The adsorption of O 3 and/or the organic molecule on the catalyst surface is a fundamental step in the catalytic ozonation [21][22][23] . Although there is experimental evidence to assume that heterogeneous catalytic ozonation involves the generation of hydroxyl radicals (•OH), some researchers reported the occurrence of direct reactions between molecular ozone and organic compounds adsorbed on the solid surface of the catalyst 24 .…”