Guanwei Peng,Yanyu Xie,Hui Chen,Jin Zou,Li Li,Chuanfa Luo,Limin Lu,Guojiang Mao
Photo-Fenton-like technology based on H 2 O 2 is considered as an ideal strategy to generate reactive oxygen species (ROS) for antibiotic degradation, but O 2 overflow in the process severely limits the utilization efficiency of H 2 O 2 . Herein, we fabricate Bi 2 MoO 6 (BMO) photocatalyst modified with Frustrated Lewis pairs (FLPs) as a Fenton catalyst model for enhancing reuse of spilled O 2 . The FLPs created by the introduction of cerium and oxygen vacancy were found to contribute to regulate the electronic structure of BMO and further improve the acidic and basic properties of photocatalyst surface. More importantly, the frustrated acid and base sites can enhance the H 2 O 2 and O 2 interfacial adsorption process and provide an Ce 4+ -O v -O 2− active site on the surface of Ce-BMO nanosheets, which can promote O 2 /•O 2 − / 1 O 2 /H 2 O 2 redox cycles to achieve high H 2 O 2 utilization efficiency. Specifically, in the experiment using tetracycline as a photocatalytic degradation object, the degradation activity of Ce-BMO was 2.15 times higher than that of BMO pure phase. Quenching experiments and EPR assays also confirmed that 1 O 2 and •O 2 − were the dominant oxidative species. This study systematically reveals the design of Fenton photocatalytic active sites at the atomic scale and provides new insights into constructing FLPs photocatalysts with high H 2 O 2 utilization efficiency.
Low H2O2 utilization efficiency is the main problem when Fenton system was used to oxidize NO in flue gas. To understand the behaviour of the free radicals during NO oxidation process in Fenton system is crucial to solving this problem. The oxidation capacity of ⋅OH and HO2⋅ on NO in Fenton system was compared and the useless consumption path of ⋅OH and HO2⋅ that caused the low utilization efficiency of H2O2 were studied. A method to enhance the oxidation ability and H2O2 utilization efficiency by adding reducing additives in Fenton system was proposed. The results showed that both of ⋅OH and HO2⋅ were active substances that oxidize NO. However, the oxidation ability of ⋅OH radicals was stronger. The vast majority of ⋅OH and HO2⋅ was consumed by rapid reaction ⋅OH + HO2⋅→H2O + O2 , which was the primary reason for the low utilization efficiency of H2O2 in Fenton system. Hydroxylamine hydrochloride and ascorbic acid could accelerate the conversion of Fe3+ to Fe2+, thereby increase the generation rate of ·OH and decrease the generation rate of HO2⋅. As a result, the oxidation ability and H2O2 utilization efficiency were enhanced.
Heterogeneous catalysis is a promising approach to achieve efficient As(III) oxidation by H 2 O 2 at circumneutral pH. However, radical-attack pathways dominated catalytic As(III) oxidation over most metal oxides is undesirably associated with low utilization of H 2 O 2 induced by rapid self-quenching of radicals. In this study, we developed a non-radical catalytic route to improve H 2 O 2 utilization efficiency for catalytic As(III) oxidation based on nanoceria. The performance and mechanism of As(III) oxidation by H 2 O 2 was investigated by employing four types of nanoceria with different crystallite sizes (9.1–80.6 nm). At the H 2 O 2 /As(III) molar ratio of 2.0, nanoceria exhibited crystallite size-dependent catalytic activity for oxidation of As(III) over a wide pH range (5–9). Based on comprehensive study including scavenging, enzymatic, and pretreatment experiments and miscellaneous spectroscopy techniques, the catalytic As(III) oxidation over nanoceria was proved to be mainly mediated by the non-radical Ce-hydroperoxo surface complexes, whilst the surface hydroperoxyl radical served as a minor oxidant. In contrast, the roles of dissolved oxygen, homogeneous H 2 O 2 , and OH radical were all negligible. No obvious interconversion of Ce(III)/Ce(IV) was observed by XPS for the catalytic process. Such non-radical pathway enabled a stoichiometric reaction with high H 2 O 2 utilization efficiency (90.5%–122%). Moreover, nanoceria could be recycled for five consecutive runs without desorption/regeneration treatment. This study sheds new light on the development of nanoceria-based catalytic processes for efficient oxidation of As(III).
Zhuangpeng Huang,Zhiping Chen,Yuancai Chen,Yongyou Hu
Iron-copper bimetal supported on mesoporous γ-Al 2 O 3 with different Fe/Cu ratios was prepared via a modified evaporation-induced self-assembly method and employed to degrade 4-chlorophenol (4-CP) in a Fenton-like process. The X-ray photoelectron spectroscopy, X-ray diffraction spectrum and UV–vis diffuse reflectance spectroscopy results confirmed the co-doping of Fe 2+ /Fe 3+ and Cu + /Cu 2+ into the lattice of γ-Al 2 O 3 through the bonds of Al O Fe and Al O Cu. With the iron and copper co-doped in γ-Al 2 O 3 , three-fold oxygen vacancies (V 0 ) could be achieved compared with that of non-metal catalysts, which was favorable for the reduction of iron and copper species. The 1Fe3Cu-γ-Al 2 O 3 with a Fe/Cu mass ratio of 1:3 exhibited the highest activity on Fenton-like degradation of 4-CP due to the synergistic effects of Fe and Cu by facilitating the electron transfer in the recycles of Cu + /Cu 2+ and Fe 2+ /Fe 3+ based on the results of X-ray photoelectron spectroscopy, cyclic voltammetry and electro paramagnetic resonance analysis. The utilization efficiency of H 2 O 2 was as high as 86.0% when 4-CP almost disappeared (i.e., 99.7 percent of 0.78 mM 4-CP) at 240 min and pH 7.0, additionally, their dechlorination and TOC removal efficiencies were 92.0% and 81.6%, respectively. The catalyst also displayed a good performance after 5th cycles. Furthermore, a possible mechanism for activation of OH on the catalyst surface was also proposed.
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