Virus Inactivation by Homogeneous and Heterogeneous Fenton-like Processes
Human enteric viruses in water sources cause a great public health risk. Conventional disinfection treatments are not able to completely inactive viruses. However, advanced oxidation processes (AOPs) have recently been shown to effectively inactivate pathogens. One of the most promising AOPs is the Fenton process.
In the framework of this work, the main objective was to characterize the fate of viruses upon inactivation by homogeneous and heterogeneous Fenton and Fenton-like processes, as well as to elucidate the mechanisms governing virus inactivation by these processes. MS2 coliphage, a commonly used surrogate for human enteric viruses, was used as the model organism.
Virus inactivation by homogeneous, Cu- or Fe-catalyzed Fenton(-like) reactions, were studied at neutral pH. The effect of the metal (1-10 µM) and H2O2 (3-50 µM) concentrations, HO• production and sunlight on virus inactivation was investigated.
Virus inactivation followed first-order kinetic with respect to the H2O2 concentration for both treatments. The influence of the metal concentrations was more complex. For the Cu/H2O2 system, it was found that inactivation was governed by soluble Cu. In contrast, for the Fe/H2O2 system, the colloidal Fe was involved in inactivation rather than dissolved iron.
Sunlight only affected the Fe/H2O2 system. HO• production rates measured by electron spin resonance (ESR), could not account for the observed inactivation in Fe/H2O2 system. Other oxidants, such as ferryl species, must therefore play a role.
Overall, our results have shown that virus inactivation by Cu- and Fe- catalyzed Fenton reaction may serve as an efficient disinfection method. Virus inactivation by the heterogeneous Fenton process was carried out via iron(hydr-)oxide particles, such as hematite (α-Fe2O3), goethite (α-FeOOH), magnetite (Fe3O4) and amorphous iron (Fe(OH)3), in batch reactors at circumneutral pH.
The influence of adsorption and sunlight exposure on the survival of MS2 was investigated. Both mass-based and surface-area normalized pseudo-second order adsorption rate constants followed the same trend of α-FeOOH > α-Fe2O3 > Fe3O4 ≈ Fe(OH)3. Virus adsorption onto all particles was only partly reversible. In addition to irreversible adsorption, adsorption to three of the particles studied (α-FeOOH, Fe3O4, Fe(OH)3) caused slight virus inactivation (85%, 77%, 97%, respectively). Exposure of particle-adsorbed viruses to sunlight and H2O2 resulted in efficient inactivation, whereas inactivation was negligible for suspended viruses.
The observed first-order inactivation rate constants were 1.44×10-3, 1.09×10-3, 0,58, 1.48 min-1 for α-Fe2O3, α-FeOOH, Fe3O4 and Fe(OH)3, respectively.
Our results showed that in the heterogeneous Fenton system, inactivation was mainly attributed to a particle-mediated photo-Fenton-like reaction. Finally, the extent of genome and protein damage of MS2 coliphage during inactivation by the homogeneous Cu/H2O2 and Fe/H2O2 /sunlight systems were studied. The results showed that both damage to the genome and the capsid protein may contribute on virus inactivation by both treatments.
The patterns of damage were different, even though the same oxidant (HO•) was present in both systems, indicating the source of the oxidant is important. For the Cu system, the extent of genome damage was similar to that of inactivation, indicating that inactivation may occur via single-hit kinetics.
In contrast, for the Fe system, genome damage was very extensive in comparison to inactivation, consistent with multi-hit inactivation kinetics.
For both systems, the most susceptible region of the capsid protein was peptide segment 84-106, which is located on the capsid outer surface. The other regions of the protein are not likely to be involved in inactivation.
Overall, our findings suggested that both genome and protein oxidation by Cu and Fe systems may play a role in inactivation, and that the determination of molecular-level mechanisms governing inactivation can be assessed by MALDI-TOF-MS and qPCR.
Nieto Juarez, Jessica Ivana;科恩,他玛
Virus Inactivation by Homogeneous and Heterogeneous Fenton-like Processes
Nieto Juarez, Jessica Ivana ; Kohn, Tamar
Virus Inactivation by Homogeneous and Heterogeneous Fenton-like Processes - Infoscience https://infoscience.epfl.ch/record/174665
Analogies and differences among bacterial and viral disinfection by the photo-Fenton process at neutral pH: a mini review.
Over the last years, the photo-Fenton process has been established as an effective, green alternative to chemical disinfection of waters and wastewaters. Microorganisms' inactivation is the latest success story in the application of this process at near-neutral pH, albeit without clearly elucidated inactivation mechanisms. In this review, the main pathways of the combined photo-Fenton process against the most frequent pathogen models (Escherichia coli for bacteria and MS2 bacteriophage for viruses) are analyzed. Firstly, the action of solar light is described and the specific inactivation mechanisms in bacteria (internal photo-Fenton) and viruses (genome damage) are presented. The contribution of the external pathways due to the potential presence of organic matter in generating reactive oxygen species (ROS) and their effects on microorganism inactivation are discussed. Afterwards, the effects of the gradual addition of Fe and H2O2 are assessed and the differences among bacterial and viral inactivation are highlighted. As a final step, the simultaneous addition of both reagents induces the photo-Fenton in the bulk, focusing on the differences induced by the homogeneous or heterogeneous fraction of the process and the variation among the two respective targets. This work exploits the accumulated evidence on the mechanisms of bacterial inactivation and the scarce ones towards viral targets, aiming to bridge this knowledge gap and make possible the further application of the photo-Fenton process in the field of water/wastewater treatment.
As research on ROS advances, most radicals turn out to form inside the body itself. Since highly reactive species are unlikely to form in a reducing environment such as blood, a catalytic effect must be the cause.
HomeApplicationsLife SciencesReactive oxygen species (ROS)Fenton Reaction
Oxygen derived species have a degradative effect due to their high oxidation potential. Within a reducing environment like human blood (à antioxidants) such highly energetical molecules are expected to exist rather shortly. Yet, they tend to occur in measurable concentrations which indicates a helping hand working on their formation (Beresevicz 2000).
Iron's catalytic effect
Iron is suspected to be the driving force by catalysing the formation of oxygen derived radicals. The mechanism of a direct reaction with oxygen would be:
Beresevicz (2000) finds three point that speak in this thesis‘ favour:
I. In biological systems, O2 concentration is usually much greater than that of H2O2.
II. The rate constants for Fe2+-O2 and Fe2+-H2O2 are similar.
III. An unbound catalytic metal may be mainly present in reduced form, thereby favoring ist direct
interaction with O2 rahter than H2O2.
Fenton Reaction - Magnettech - ESR spectrometer http://www.magnettech.de/applications/life-sciences/reactive-oxygen-species-ros/fenton-reaction.html
Ascorbic acid/Fe@Fe2O3: A highly efficient combined Fenton reagent to remove organic contaminants
Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Institute of Environmental Chemistry, College of Chemistry, Central China Normal University, Wuhan 430079, PR China
The combination of ascorbic acid and Fe@Fe2O3 offers a highly efficient Fenton reagent.
Contaminant degradation constants were 38–53 times higher than those in the conventional Fenton systems.
The high activity was attributed to the effective Fe(III)/Fe(II) cycle and the iron-ascorbate complex formation.
In this study, we demonstrate that the combination of ascorbic acid and Fe@Fe2O3 core–shell nanowires (AA/Fe@Fe2O3) offers a highly efficient Fenton reagent. This combined Fenton reagent exhibited extremely high activity on the decomposition of H2O2 to produce OH for the degradation of various organic contaminants, including rhodamine B, methylene blue, alachlor, atrazine, siduron, lincomycin, and chloroamphenicol. The contaminant degradation constants in the AA/Fe@Fe2O3/H2O2 Fenton systems were 38–53 times higher than those in the conventional homogeneous Fenton system (Fe(II)/H2O2) at pH 3.8. Moreover, the OH generation rate constant in the AA/Fe@Fe2O3/H2O2 Fenton system was 1–3 orders of magnitudes greater than those of heterogeneous Fenton systems developed with other iron-containing materials (α-FeOOH, α-Fe2O3, FeOCl, and so on). The high activity of AA/Fe@Fe2O3 was attributed to the effective Fe(III)/Fe(II) cycle and the iron-ascorbate complex formation to stabilize ferrous ions with desirable and steady concentrations. During the AA/Fe@Fe2O3/H2O2 Fenton process, ascorbic acid served as a reducing and complexing reagent, enabling the reuse of Fe@Fe2O3 nanowires. We systematically investigated the alachlor and ascorbic acid degradation and found that they could be effectively degraded in the AA/Fe@Fe2O3/H2O2 system, accompanying with 100% of dechlorination and 92% of denitrification. This study sheds light on the importance of Fe(III)/Fe(II) cycle for the design of high efficient Fenton system and provides an alternative pathway for the organic contaminants removal.
Ascorbic acid/Fe@Fe2O3: A highly efficient combined Fenton reagent to remove organic contaminants - ScienceDirect
•SO4radical dot -和HOradical dot氧化起主导作用，Fe(IV)氧化起主导作用。
Fe(II)催化过氧一硫酸酯(PMS)活化过程能够降解持久性有机污染物，如多溴联苯醚(PBDEs)，但生成的Fe(III)向Fe(II)的转化速度较慢，限制了该过程的效率。在这项研究中,我们发现,添加少量的没食子酸(GA),模型化合物的天然多酚类物质,在铁(III) / PMS过程(即GA /铁(III) / PMS过程)可能产生的长期影响铁(II)回收和加速退化的2,2’,4,4’-tetrabromodiphenyl醚(BDE47)超过72 h。 条件下20.3µM GA, 13.6µM铁(III)和400 µM PMS, BDE47的降解效率达到85%,9.4倍的铁(III) / PMS的过程。降解动力学可分为初始“快速阶段”(kobs1 = 0.298 h−1)和第二个“缓慢阶段”(kobs2 = 0.021 h−1)。芳香自由基如hydroxycyclohexadienyl激进(poly-HCDradical点)由SO4radical点−/ HOradical点的攻击提出了GA负责铁(II)回收在第一阶段,尽管ring-opened产品SO4radical点−/ HOradical点攻击后GA-quinone主要发起铁(III)第二阶段。由于存在多种Fe(III)还原途径，PMS会被Fe(II)持续激活，形成so4自由基点−和HOradical点，它们是BDE47降解的主要反应物种。最后，从绿茶中提取的天然多酚对Fe(III)/PMS工艺降解BDE47具有明显的促进作用。本研究不仅为Fe(II)活化过硫酸盐链反应降解多溴二苯醚等难降解有机污染物提供了一种新的途径，而且为有机副产物对pmbased氧化体系中Fe的反应性提供了新的认识。
Gallic acid accelerated BDE47 degradation in PMS/Fe(III) system: Oxidation intermediates autocatalyzed redox cycling of iron - ScienceDirect