Fenton Reaction Mechanism Research Articles

Surface boric acid modification promoted Fe3+/Fe2+ cycle and H2O2 activation for facilitating Fenton degradation performance of Bi2Fe4O9

Boric acid (H3BO3) modified Bi2Fe4O9 (H3BO3@Bi2Fe4O9, BBFO) materials were prepared by surface H3BO3 treatment on Bi2Fe4O9 (BFO) employing mechanical ball milling method. XPS analysis and FT-IR spectra demonstrates that H3BO3 was successfully fastened on BFO surface through intense friction and collision between mixed powder (H3BO3 and BFO) and abrasive. And EPR result illustrates that the more abundant oxygen vacancy (OVs) has been introduced into BFO surface in H3BO3 modification process. The Fenton degradation rate for oxytetracycline (OTC) of BBFO-2 materials reaches 75.0 % within 60 min, which is 21.8 % higher than that of BFO treated by ball milling process without H3BO3 modification (HBFO). And the H2O2 utilization rate (23.4 %) of BBFO-2 materials is higher than that of HBFO (7.6 %), which ascribes to the H3BO3 modification and the introduction of abundant OVs by the surface electrons accumulation and transfer for strengthening the Fe3+/Fe2+ cycle and H2O2 decomposition. The possible degradation pathways and Fenton reaction mechanism was speculated by ESR and HPLC-MS analysis. The manuscript provides a scientific reference and theoretical basis for investigating the preparation and enhancement mechanism of surface modification strategy for Fe-based Fenton catalysts.

Homogenous Sono-Fenton reaction can trigger long term bactericidal effect against Acinetobacter baumannii due to residual stress induced by reactive oxygen species

Gastrointestinal diseases caused by microbial contamination of water has been one of the enduring public health challenges of the mankind, wherefore demands continual innovation in the contemporary water treatment techniques. Here, a systematic study was carried out to elucidate the bactericidal mechanism of ultrasound assisted Fenton reaction (Sono-Fenton: SF) against multidrug resistant Acinetobacter baumannii. Inactivation of ≈5 × 106 CFU/mL of A. baumannii was achieved within 90 min of SF under weak acidic conditions using 20 mg L-1 of H2O2 and 2 mg L-1 of Fe2+. Having more than 99 % inactivation efficiency, no reactivation of the bacteria was observed for 96 h. After SF, a combination of ultrasound and H2O2 was found to be more efficient although complete inactivation was not achieved within the same time frame. Experimental evidence suggests the generation of multiple reactive oxygen species (ROS) such as H2O2, •OH and O2•–. The synergistic effect of ROS and ultrasound may have resulted in the membrane damage of the bacteria as evident from the electron microscopy analysis. Interestingly, our data also suggests that the residual stress associated with SF could have long term bactericidal effect and is influenced by incubation temperature. Comparative transcriptomic analysis showed that NirD/YgiW/YdeI family stress tolerance protein, KGG domain containing proteins, and PspC domain containing proteins, all known to control the stress induced responses in bacteria was significantly upregulated after SF treatment. Additionally, genes regulating transcription (GntR) and translation (rpsQ) have been downregulated which may induce a nutrient and metabolite limiting conditions in the bacterial cell. The bacterial inactivation ability of SF process was further validated with real water samples collected from natural systems and therefore, advocate the possible real-world applications.

The Fe3O4@UiO-66-NH2/PVDF-co-CTFE mixed matrix membrane with enhanced anti-fouling and self-cleaning performances for effectively removing dyes by Fenton reaction

It is a major obstacle to further development of membrane technology that membrane fouling occurs. In this study, a novel Fe3O4@UiO-66-NH2/PVDF-co-CTFE mixed matrix membrane was successfully developed by mixing Fe3O4@UiO-66-NH2 nanoparticles (NPs) into PVDF-co-CTFE membrane through a simple non-solvent-induced phase separation (NIPS) method, and was used for degradation of organic wastewater. The results of the incorporated Fe3O4@UiO-66-NH2 NPs content on the morphology, pore structure and physicochemical structure of samples were investigated systematically. The results indicated that the Fe3O4@UiO-66-NH2 NPs addition in membrane matrix improved the permeability and significantly enhanced the anti-fouling performance. When 2 wt% Fe3O4@UiO-66-NH2 NPs was added, the mixed matrix membrane had excellent comprehensive performance, maintaining a high pure water flux of 226.8 L m−2 h−1, the BSA rejection rate reached 95.9%, and the flux recovery rate was 71.38%. Importantly, the membrane possessed high catalytic performance based on the Fenton reaction mechanism, and the removal rate of 20 mg L−1 MB solution (400 mL) was up to 99.04%, and showed excellent self-cleaning characteristics and long-term stability. In conclusion, this study provided a new idea for the development of Fenton catalytic membranes with excellent anti-fouling performance for wastewater treatment in complex environments.

Usnea antarctica (James Ross Island, Antarctica) and Usnea subfloridana (Uludağ, Turkey) Incorporated Hybrid Nanoflowers with Their Intrinsic Catalytic and Antimicrobial Activities

AbstractHerein, we used lichen extracts, for the first time, in formation of organic‐inorganic nanoflowers and we utilized them as novel nanobiocatalyst and antimicrobial agents. Two lichen species, Usnea Antarctica (U. Antarctica) and Usnea subfloridana (U. subfloridana) were collected from James Ross Island (Artarctica Peninsula, Antarctica) and from Uludağ National park (Bursa, Turkey), respectively and both species were separately extracted in methanol and water. In terms of nanoflower synthesis, the extracts were used as organic components and copper (II) ions (Cu2+) acted as inorganic components for formation of U. antarctica and U. subfloridana based hybrid nanoflowers (hNFs). The peroxidase mimic catalytic and antibacterial activities of the hNFs were systematically examined towards model substrate and bacteria strains, respectively via Fenton reaction mechanism. We demonstrated how the types of lichens and their extracts prepared in methanol and water influence morphologies, catalytic and antibacterial activities of the hNFs. We found that no 2 hNFs formed from U. subfloridana extract prepared in water exhibited highly enhanced catalytic activity owing to its uniform, more compact and porous flower‐like structures with high surface‐to‐volume ratio. We expect that lichens extracts based hNFs with great catalytic activities can be promisingly alternative against enzymes and used in various scientific and technical fields.

The degradation of dissolved organic matter in black and odorous water by humic substance-mediated Fe(II)/Fe(III) cycle under redox fluctuation

In nature, the hydroxyl radical (•OH) is produced during the anaerobic-aerobic transition when groundwater level fluctuates. In addition, the •OH is also detected in iron-bearing clay minerals and iron oxides during the redox process. Goethite is one of the most stable iron oxides involved in biogeochemical cycles. In this study, the coexisting humic acid (HA) enhanced the generation of Fe(II) during the iron reduction process and accelerated the generation of •OH in the redox process of goethite. The organic contaminants in black and odorous water were decomposed by constructing an iron-reducing bacteria-HA-Fe(II)/Fe(III) reaction system under anaerobic-aerobic alternation. The results demonstrated that in the anaerobic stage, HA could promote the reduction and dissolution of goethite through the complexation effect and electron shuttle mechanism, as well as significantly strengthening the iron reduction process in water. Under aerobic conditions, Fe(II) in the reaction system would activate O2 to generate •O2−. The •OH, formed by Fe (II) and •O2− via Fenton reaction and Haber-Weiss mechanism, oxidized dissolved organic matter (DOM) in water. The characterization of DOM by three-dimensional fluorescence spectroscopy (3DEEM) indicated that after four redox fluctuations, the organic contaminants in water samples were effectively degraded. Generally, this study provides new approaches and insights into the biogeochemical cycling of Fe and C elements and water pollution remediation at the anoxic-anoxic interface.

Insight into enhanced Fenton-like degradation of antibiotics over CuFeO2 based nanocomposite: To improve the utilization efficiency of [rad]OH/O2[rad]- via minimizing its migration distance

In Fenton or Fenton-like processes, the key step is to catalyze H2O2 and produce highly reactive OH radicals. More efforts are then focus on designing efficient heterogeneous Fenton catalysts by activating H2O2 to generate OH at the highest possible steady state concentration. In this study, using the antibiotic ofloxacin as target organic pollutant, we firstly demonstrate a point of view for improving OH utilization efficiency by regulating surface chemical reactions to minimizing its migration distance to the target pollutant. C doped g-C3N4 incorporated CuFeO2 (CCN/CuFeO2) exhibited almost ten times higher ofloxacin degradation rate constant than our previously reported CuFeO2 {012} catalyst (0.1634 vs 0.0179 min−1). Since similar amount of OH was generated, the different inhibition effect of tert-butyl alcohol and nitrobenzene on the ofloxacin degradation confirmed that the much-enhanced ofloxacin degradation was attributed to the surface Fenton reaction process. According to XPS and EXAFS characterization, the C–O–Cu bond between g-C3N4 and CuFeO2 established a closed-circuit surface Fenton reaction mechanism. H2O2 was adsorbed and decomposed into OH/O2- over ≡Cu + site in CuFeO2. The successful construction of CCN/CuFeO2 creates a negative surface potential and benefits the enrichment of target antibiotics from water, which greatly reduces the migration distance of OH/O2•- to adjacent pollutant and then increases the OH/O2- utilization efficiency by avoiding the unwanted quenching. Hence, CCN/CuFeO2 possesses superior Fenton catalytic activity and long-term stability.

Simulation study of phenol degradation by Fenton process using ASPEN-Plus

Present study deals with the simulation of the Fenton’s process for the removal of phenol using ASPEN-Plus. The effect of phenol concentration, catalyst loading, mole ratio of H2O2 to iron ion, and temperature on the phenol degradation rate has been studied using the developed process flow diagram. The result shows higher flow rate of hydrogen peroxide (4.2 kmol/h) favours phenol degradation (98%) since the hydroxyl radical availability rises. Increase in catalyst loading (186 g) and rise in mole ratio of hydrogen peroxide to iron ion (~1) improves the removal of phenol (~97%) from wastewater since the hydroxyl radical formation improves and thus affect the mechanism and chemical kinetics of Fenton reaction. Increase in temperature improves the degradation, however high temperature above optimum condition (32.5C) does not favour the degradation of phenol.

Self-amplification of oxidative stress with tumour microenvironment-activatable iron-doped nanoplatform for targeting hepatocellular carcinoma synergistic cascade therapy and diagnosis

BackgroundHepatocellular carcinoma is insensitive to many chemotherapeutic agents. Ferroptosis is a form of programmed cell death with a Fenton reaction mechanism. It converts endogenous hydrogen peroxide into highly toxic hydroxyl radicals, which inhibit hepatocellular carcinoma progression.MethodsThe morphology, elemental composition, and tumour microenvironment responses of various organic/inorganic nanoplatforms were characterised by different analytical methods. Their in vivo and in vitro tumour-targeting efficacy and imaging capability were analysed by magnetic resonance imaging. Confocal microscopy, flow cytometry, and western blotting were used to investigate the therapeutic efficacy and mechanisms of complementary ferroptosis/apoptosis mediated by the nanoplatforms.ResultsThe nanoplatform consisted of a silica shell doped with iron and disulphide bonds and an etched core loaded with doxorubicin that generates hydrogen peroxide in situ and enhances ferroptosis. It relied upon transferrin for targeted drug delivery and could be activated by the tumour microenvironment. Glutathione-responsive biodegradability could operate synergistically with the therapeutic interaction between doxorubicin and iron and induce tumour cell death through complementary ferroptosis and apoptosis. The nanoplatform also has a superparamagnetic framework that could serve to guide and monitor treatment under T2-weighted magnetic resonance imaging.ConclusionThis rationally designed nanoplatform is expected to integrate cancer diagnosis, treatment, and monitoring and provide a novel clinical antitumour therapeutic strategy.Graphical

Using circular economy principles to recycle materials in guiding the design of a wet scrubber-reactor for indoor air disinfection from coronavirus and other pathogens.

An arduous need exists to discover rapid solutions to avoid the accelerated spread of coronavirus especially through the indoor environments like offices, hospitals, and airports. One such measure could be to disinfect the air, especially in indoor environments. The goal of this work is to propose a novel design of a wet scrubber-reactor to deactivate airborne microbes using circular economy principles. Based on Fenton’s reaction mechanism, the system proposed here will deactivate airborne microbes (bioaerosols) such as SARS-CoV-2. The proposed design relies on using a highly porous clay–glass open-cell structure as an easily reproducible and cheap material. The principle behind this technique is an in-situ decomposition of hydrogen peroxide into highly reactive oxygen species and free radicals. The high porosity of a tailored ceramic structure provides a high contact area between atomized oxygen, free radicals and supplied polluted air. The design is shown to comply with the needs of achieving sustainable development goals.

Role of The Concentration of Fe/C Catalysts on Heterogeneous Fenton Degradation Remazol Yellow FG

Remazol Yellow FG is a thiazine dye widely used in textile industries. This compound is difficult to degrade naturally. One method that can be used for wastewater treatment is the Advanced Oxidation Process with heterogeneous Fenton reaction. The heterogeneous Fenton reaction mechanism uses H2O2 as an oxidizer and iron nanoparticles as a catalyst. One material that can be used as catalyst support for iron nanoparticles is activated carbon. Activated carbon can be modified as a catalyst support because it has a large surface area. Iron oxide (Fe2O3) is embedded in activated carbon through the process of impregnation and calcination at a temperature of 300°C. Fe2O3 loading varies 2%, 4%, and 6% of the total carbon mass. Fe/C catalysts were characterized by SEM and BET-BJH. The catalytic degradation reaction of Remazol Yellow FG was carried out by dissolving 200ml of Remazol Yellow FG at a concentration of 20ppm and adding 5ml of H2O2.The degradation results using 96 hours Fe/C catalyst for variations of concentration were analyzed using a UV-VIS spectrophotometer. Then the measurement of degradation for Fe2O3 concentration of 2%, 4%, 6% using the heterogeneous Fenton method resulted in the percent removal of 16.82%, 40.46%, 38.32%. Whereas using physical adsorption on each variable Fe2O3 concentration did not result in percent removal. Data shows that the degradation capacity of Remazol Yellow FG using heterogeneous Fenton reaction increases with increasing Fe2O3 concentration. This also proves that the heterogeneous Fenton method using the Fe/C catalyst is effective for the degradation of Remazol Yellow FG.

Nanoscale Fe0/Cu0 bimetallic catalysts for Fenton-like oxidation of the mixture of nuclear-grade cationic and anionic exchange resins

Spent resins generated from the nuclear industrial processes are still difficult to be treated and disposed. Fenton-like processes have great application potential in the treatment of spent resins, but the Fenton reaction mechanisms and resin degradation pathways remain challenging. In this study, nanoscale Fe0/Cu0 bimetallic catalysts were prepared and characterized for the Fenton-like degradation of the mixture of cationic and anionic resins. High catalytic property of Fe0/Cu0 bimetallic nanoparticles activated by H2O2 was evaluated, according to the effects of various nanoparticles, temperature, catalyst amount, H2O2 concentration and the mixing ratio of cationic and anionic resins. Combined the shape and color changes of mixed resins with the experimental and calculated characterization results, different degradation difficulty of cationic and anionic resins and their degradation mechanisms were studied. According to the density functional theory calculations of the optimized resin molecules with the Fe0/Cu0 catalyst, the mechanisms of Fenton-like reactions and the degradation of mixed resins through the synergistic effect of Fe and Cu species were proposed. The comprehensive Fenton-like reactions and degradation mechanisms provide new insights to advance the treatment of spent resins and organic polymers by Fenton-like processes.

Fenton reaction mechanism generating no OH radicals in Nafion membrane decomposition

Mechanism of Fenton reaction, which is a most widely-used degradation test for organic materials using hydrogen peroxide (H_2O_2) and iron (Fe) cations, is revealed for the decomposition of hydrated Nafion membrane. This reaction mechanism has been assumed to generate OH radicals. For a doubly-hydrated Nafion membrane model, Fenton reaction with divalent and monovalent Fe (Fe^{2+} and Fe^+) cation hydration complexes is explored for experimentally-supported hydration numbers using long-range correction for density functional theory. As a result, it is found that H_2O_2 coordinating to the Fe^{2+} hydration complexes first approaches Nafion side chains in high humidity, then leads to the C–S bond dissociation of the side chain to produce carbonic acid group and sulfonic acid ion. On the other hand, once electron transfer proceeds between iron ions, the O–O bond of the coordinating H_2O_2 is extended, then the C–S bond is dissociated to produce trihydroxymethyl group and sulfur trioxide, which are rapidly transformed to carboxyl group and sulfonic acid ion in aquo. This mechanism is confirmed by the vibrational spectrum analysis of the decomposed product. Collective Nafion decomposition mechanisms also suggest that the decomposition reaction uses the recycle of generated Fe cation hydration complexes under acidic condition near membrane surface.

Self-Amplification of Tumor Oxidative Stress with Degradable Metallic Complexes for Synergistic Cascade Tumor Therapy.

The ferroptosis effect has been illuminated with a clear Fenton reaction mechanism that converts endogenous hydrogen peroxide (H2O2) into highly oxidative hydroxyl radicals (·OH) in ROS-amplified tumor therapy. This ferroptosis-related oxidation effect was then further enhanced by the enzyme-like roles of cisplatin (CDDP). This CDDP-induced apoptosis was promoted in reverse by ferroptosis via the depletion of glutathione (GSH) and prevention of DNA damage repair. Here, we have developed degradable metallic complexes (PtH@FeP) containing an Fe(III)-polydopamine (FeP) core and HA-cross-linked CDDP (PtH) shell, exaggerating in situ toxic ROS production via the synergistic effect of CDDP and Fe(III). Taken together, the rationally designed PtH@FeP provided a new strategy for self-amplified synergistic chemotherapy/ferroptosis/photothermal therapy (PTT) antitumor effects with a reduced dosage that facilitates clinical safety.

The mechanism of Fenton reaction of hydrogen peroxide with single crystal 6H-SiC substrate

The strong oxidant hydroxyl radical (*OH) generated during Fenton reactions can be used for the chemical mechanical polishing (CMP) of single-crystal silicon carbide (SiC). In this study, we first determine the optimal concentration of the ferrosoferric oxide (Fe3O4) catalyst for the Fenton reaction. Then, we performed Fenton oxidation experiments on 6H-SiC substrates using five groups of reaction solution: hydrogen peroxide (H2O2) solution with four different initial concentrations (5.0, 7.5, 10.0, and 15.0 wt%) and with 1.0 wt% Fe3O4 catalyst and a solution containing 7.5 wt% H2O2 without a catalyst. The concentrations of H2O2, ferrous ions (Fe2+), iron ions (Fe3+), and *OH were monitored during the reaction. Moreover, the surface morphologies and elemental compositions of the SiC substrate before and after oxidation were analysed by scanning electron microscopy and energy dispersive spectroscopy. Finally, the specific components of the oxidation products were analysed by X-ray photoelectron spectroscopy to reveal the reaction mechanism of H2O2 with 6H-SiC. As the reaction proceeded, all the H2O2 concentrations decreased continuously, while the Fe3+ and Fe2+ concentrations increased. After the first 90 min, the H2O2 concentration decreased by approximately 50%–60%, while the Fe2+ concentration increased by approximately 50%–60%. Moreover, the *OH concentration initially increased and then decreased, and the *OH concentration reached its maximum within 100–120 min. At an initial H2O2 concentration of 7.5 wt% with 1.0 wt% Fe3O4, the maximum *OH concentration was approximately 54.4%, 11.8%, 42.5%, and 478% higher than those reached at an initial H2O2 concentration of 5.0, 10.0, and 15.0 wt% with 1.0 wt% Fe3O4 catalyst and in the solution containing 7.5 wt% H2O2 without catalyst, respectively. Surface oxide layers with different thicknesses were found on the SiC substrates oxidised with the different reaction solutions; the layers on the SiC substrates oxidised with 7.5 wt% H2O2 and 1.0 wt% Fe3O4 exhibited a favourable oxidation effect. The initial H2O2 concentration influenced the change in Fe3+, Fe2+, and *OH concentrations. This indicated that further affecting the oxidation effect on the SiC by generating more *OH leads to a greater oxidation effect. The *OH produced damaged the C-Si and C-C bonds on the SiC so that C and Si atoms were separately combined with O atoms to generate CO2 gaseous and SiO2 oxide layers. In this way, SiC substrates were oxidised and corroded, realising the CMP of the SiC with a high removal rate and low roughness.

Ascorbate guided conversion of hydrogen peroxide to hydroxyl radical on goethite

In this study, we demonstrate that the addition of ascorbate can lower the conversion percentage of H2O2 to O2 from 71% to 11%, and thus increase the conversion percentage of H2O2 to OH from 11% to 82% on goethite within 3 h. This greatly enhanced production of OH could be attributed to the efficient Fe(III)/Fe(II) redox cycle accelerated by ascorbate, which produced abundant Fe(II) confined on the goethite surface, favoring the conversion of H2O2 to OH. Meanwhile, the decreased surface Fe(III) of goethite strongly inhibited the conversion of H2O2 to O2. These findings can clarify the quantitative influence of ascorbate on the H2O2 decomposition process over the iron mineral surface, and thus deepen the understanding of heterogeneous Fenton reaction mechanism during organic containment treatment.

Significant enhancement of photo-Fenton degradation of ofloxacin over Fe-Dis@Sep due to highly dispersed FeC6 with electron deficiency

An efficient strategy for enhancing iron efficiency in heterogeneous Fenton reaction via the pyrolysis of ferrocene chemically modified sepiolite (Sep) was proposed in this study. Highly dispersed FeC6 on sepiolite (Fe-Dis@Sep) was synthesized as an efficient photo-Fenton catalyst for the visible light degradation of ofloxacin (OFX). It exhibits an excellent Fenton activity and stability towards OFX degradation. The pseudo-first order reaction rate constant of Fe-Dis@Sep was 5.1-fold higher than that of the supported catalyst with aggregated iron oxides prepared by traditional impregnation method (Fe-Agg@Sep). Based on TEM images and density functional theory (DFT) calculation, the enhanced Fenton activity of Fe-Dis@Sep was attributed to the unique incorporation of FeC6 on Sep via Si-O-C-Fe bond which not only favor the high dispersion of FeC6 with an electron deficiency but also promote Fe(III) to Fe(II) cycle via the formation of surface Fe-H2O2 complex. OH and O2- were identified as active species for OFX degradation in Fe-Dis@Sep-H2O2-Vis system. 98.7% of F and 97.0% of N in OFX was converted into F− and NO3− with a TOC removal efficiency of 89.35%. The possible degradation pathway of OFX was also proposed according to HPLC-MS results. Finally, the Fenton reaction mechanism over Fe-Dis@Sep was discussed.

First principles study of Fenton reaction catalyzed by FeOCl: reaction mechanism and location of active site

Fe-based solid catalysts in promoting Fenton reaction to generate ·OH radical has drawn much attention, and interestingly, FeOCl was reported to have superior activity compared with the traditional Fe2O3 catalysts. However, the mechanism of Fenton reaction on FeOCl and the origin of high activity remain unclear. Herein, by virtue of DFT + U calculations, the H2O2 decomposition and conversion mechanism on FeOCl(100) surface were systematically investigated. It is found that on clean FeOCl(100) surface, the exposed [Fe3+–Fe3+] sites can hardly break O–O bond of H2O2 into OH groups, but instead H2O2 tends to dehydrogenate by the surface lattice O, resulting in a series of side reactions and final conversion into O2, while the left H atoms gradually saturate the surface lattice O and reduce Fe3+ into Fe2+. On fully H-covered FeOCl(100), H2O2 can efficiently dissociate at [Fe2+–Fe2+] sites into two OH, but OH binds with Fe2+ so strongly that it cannot desorb as ·OH radical as easily as that on Fe3+. Interestingly, FeOCl(100) tends to be partially protonated in the real acid solution, which, along with H2O2 dehydrogenation, results in the formation of active unit [Fe2+–Fe3+]. On [Fe2+–Fe3+] unit, H2O2 can easily break its O–O bond and OH at Fe3+ can desorb as ·OH radical, while the other OH at Fe2+ couples with the surface H into H2O and finish the catalytic cycle. By comparison, Fe2O3(012) cannot provide enough [Fe2+–Fe3+] active units due to the relative difficulty in H2O2 dehydrogenation, which accounts for its inferior catalytic efficiency for Fenton reaction.

Advancing Fenton and photo-Fenton water treatment through the catalyst design

The review is devoted to modern Fenton, photo-Fenton, as well as Fenton-like and photo-Fenton-like reactions with participation of iron species in liquid phase and as heterogeneous catalysts. Mechanisms of these reactions were considered that include hydroxyl radical and oxoferryl species as the reactive intermediates. The barriers in the way of application of these reactions to wastewater treatment were discussed. The following fundamental problems need further research efforts: inclusion of more mechanism steps and quantum calculations of all rate constants lacking in the literature, checking the outer sphere electron transfer contribution, determination of the causes for the key changes in the homogeneous Fenton reaction mechanism with a change in the reagents concentration. The key advances for Fenton reactions implementation for the water treatment are related to tremendous hydrodynamical effects on the catalytic activity, design of ligands for high rate and completeness of mineralization in short time, and design of highly active heterogeneous catalysts. While both homogeneous and heterogeneous Fenton and photo-Fenton systems are open for further improvements, heterogeneous photo-Fenton systems are most promising for practical applications because of the inherent higher catalyst stability. Modern methods of quantum chemistry are expected to play a continuously increasing role in development of such catalysts.

Progress in the Mechanism and Kinetics of Fenton Reaction

Progress in the Mechanism and Kinetics of Fenton Reaction

Heterogeneous Fenton-like degradation of ofloxacin over a wide pH range of 3.6–10.0 over modified mesoporous iron oxide

To develop an efficient heterogeneous Fenton catalyst over a wide pH range without any external energy input is still a challenging work. In this study, the Fenton activity of mesoporous iron oxide was firstly extended to pH of 3.6–10.0 by the carbon quantum dots (CQDs) and Cu modification (CQDs/Cu-MIO). The characterization studies indicated that CQDs/Cu-MIO had a typical mesoporous structure and CQDs was highly dispersed on the surface of catalyst. While Cu element with Cu (I) and Cu (II) was introduced in the framework of iron oxide by chemical binding of FeOCu. Without the aids of UV, CQDs/Cu-MIO exhibited an excellent efficiency and the ofloxacin (OFX) degradation followed the pseudo-first order kinetic model with a reaction constant of 0.1109min−1. Moreover, the catalyst can be reused for 6 times with good stability, in which the maximum concentration of leaching Fe and Cu ions were 0.085 and 0.015mmol/L. The optimum reaction condition was evaluated and the degradation process of OFX was further investigated by FT-IR spectrum. The reactive oxygen species involved in OFX degradation, the effects of mesoporous structure, Cu/Fe multivalent state and the excellent capability of electron transformation/energy exchange of CQDs on the enhancement of CQDs/Cu-MIO Fenton activity were also discussed. Finally, the heterogeneous Fenton reaction mechanism was proposed based on the experimental results.