-
Environment International Dec 2019Sulfate radical-based advanced oxidation processes (AOPs) have drawn increasing attention during the past two decades, and Mn-based materials have been proven to be... (Review)
Review
Sulfate radical-based advanced oxidation processes (AOPs) have drawn increasing attention during the past two decades, and Mn-based materials have been proven to be effective catalysts for activating peroxymonosulfate (PMS) and peroxydisulfate (PDS) to degrade many contaminants. This article presents a comprehensive review of various Mn-based materials to activate PMS and PDS. The activation mechanisms of different Mn-based catalysts (i.e., Mn oxides MnO, MnO hybrids, and MnO‑carbonaceous material composites) were first summarized and discussed in detail. Besides the commonly reported free radicals (SO and OH), non-radical mechanisms such as singlet oxygen and direct electron transfer have also been discovered for selected materials. The effects of pH, inorganic ions, natural organic matter (NOM), dissolved oxygen content, temperature, and the crystallinity of the materials on the catalytic reactivity were also discussed. Then, important instrumentations and technologies employed to characterize Mn-based materials and to understand the reaction mechanisms were concisely summarized. Three common overlooks in the experimental designs for examining the PMS/PDS-MnO systems were also discussed. Finally, future research directions were suggested to further improve the technology and to provide a guidance to develop cost-effective Mn-based materials to activate PMS/PDS.
Topics: Catalysis; Manganese; Oxidation-Reduction; Peroxides; Sulfates; Water Pollutants, Chemical
PubMed: 31520961
DOI: 10.1016/j.envint.2019.105141 -
Redox Biology 2015Superoxide ( [Formula: see text] ) has been implicated in the pathogenesis of many human diseases including hypertension. Mitochondria-targeted superoxide scavenger...
Superoxide ( [Formula: see text] ) has been implicated in the pathogenesis of many human diseases including hypertension. Mitochondria-targeted superoxide scavenger mitoTEMPO reduces blood pressure; however, the structure-functional relationships in antihypertensive effect of mitochondria-targeted nitroxides remain unclear. The nitroxides are known to undergo bioreduction into hydroxylamine derivatives which reacts with [Formula: see text] with much lower rate. The nitroxides of pyrrolidine series (proxyls) are much more resistant to bioreduction compared to TEMPOL derivatives suggesting that mitochondria-targeted proxyls can be effective antioxidants with antihypertensive activity. In this work we have designed and studied two new pyrrolidine mitochondria targeted nitroxides: 3-[2-(triphenyphosphonio)acetamido]- and 3-[2-(triphenyphosphonio) acetamidomethyl]-2,2,5,5-tetramethylpyrrolidine-1-oxyl (mCP2) and (mCP1). These new mitochondria targeted nitroxides have 3- to 7-fold lower rate constants of the reaction with O2(-•) compared with mitoTEMPO; however, the cellular bioreduction of mCP1 and mCP2 was 3- and 2-fold slower. As a consequence incubation with cells afforded much higher intracellular concentration of mCP1 and mCP2 nitroxides compared to mitoTEMPO nitroxide. This has compensated for the difference in the rate of O2(-•) scavenging and all nitroxides similarly protected mitochondrial respiration in H2O2 treated endothelial cells. Treatment of hypertensive mice with mCP1 and mCP2 (1.4mg/kg/day) after onset of angiotensin II-induced hypertension significantly reduced blood pressure to 133±5mmHg and 129±6mmHg compared to 163±5mmHg in mice infused with angiotensin II alone. mCP1 and mCP2 reduced vascular O2(-•) and prevented decrease of endothelial nitric oxide production. These data indicate that resistance to bioreduction play significant role in antioxidant activity of nitroxides. Studies of nitroxide analogs such as mCP1 and mCP2 may help in optimization of chemical structure of mitochondria-targeted nitroxides for improved efficacy and pharmacokinetics of these drugs in treatment of hypertension and many other conditions including atherosclerosis, diabetes and degenerative neurological disorders in which mitochondrial oxidative stress seems to play a role.
Topics: Angiotensin II; Animals; Antihypertensive Agents; Antioxidants; Aorta; Blood Pressure; Cell Line; Cyclic N-Oxides; Endothelial Cells; Humans; Hydrogen Peroxide; Hypertension; Infusion Pumps, Implantable; Male; Mice; Mice, Inbred C57BL; Mitochondria; Molecular Targeted Therapy; Organophosphorus Compounds; Piperidines; Superoxides
PubMed: 25677087
DOI: 10.1016/j.redox.2014.12.012 -
Environmental Science & Technology Nov 2022Abundant substituted catechols are emitted to, and created in, the atmosphere during wildfires and anthropogenic combustion and agro-industrial processes. While ozone...
Abundant substituted catechols are emitted to, and created in, the atmosphere during wildfires and anthropogenic combustion and agro-industrial processes. While ozone (O) and hydroxyl radicals (HO) efficiently react in a 1 μs contact time with catechols at the air-water interface, the nighttime reactivity dominated by nitrate radicals (NO) remains unexplored. Herein, online electrospray ionization mass spectrometry (OESI-MS) is used to explore the reaction of NO(g) with a series of representative catechols (catechol, pyrogallol, 3-methylcatechol, 4-methylcatechol, and 3-methoxycatechol) on the surface of aqueous microdroplets. The work detects the ultrafast generation of nitrocatechol (aromatic) compounds, which are major constituents of atmospheric brown carbon. Two mechanisms are proposed to produce nitrocatechols, one (equivalent to H atom abstraction) following fast electron transfer from the catechols (QH) to NO, forming NO and QH that quickly deprotonates into a semiquinone radical (QH). The second mechanism proceeds via cyclohexadienyl radical intermediates from NO attack to the ring. Experiments in the pH range from 4 to 8 showed that the production of nitrocatechols was favored under the most acidic conditions. Mechanistically, the results explain the interfacial production of chromophoric nitrocatechols that modify the absorption properties of tropospheric particles, making them more susceptible to photooxidation, and alter the Earth's radiative forcing.
Topics: Nitrates; Water; Nitrogen Oxides; Oxidation-Reduction; Catechols
PubMed: 36318667
DOI: 10.1021/acs.est.2c05640 -
Nature Chemistry Mar 2019Despite significant progress in the development of site-selective aliphatic C-H oxidations over the past decade, the ability to oxidize strong methylene C-H bonds in the...
Despite significant progress in the development of site-selective aliphatic C-H oxidations over the past decade, the ability to oxidize strong methylene C-H bonds in the presence of more oxidatively labile aromatic functionalities remains a major unsolved problem. Such chemoselective reactivity is highly desirable for enabling late-stage oxidative derivatizations of pharmaceuticals and medicinally important natural products that often contain such functionality. Here, we report a simple manganese small-molecule catalyst Mn(CF-PDP) system that achieves such chemoselectivity via an unexpected synergy of catalyst design and acid additive. Preparative remote methylene oxidation is obtained in 50 aromatic compounds housing medicinally relevant halogen, oxygen, heterocyclic and biaryl moieties. Late-stage methylene oxidation is demonstrated on four drug scaffolds, including the ethinylestradiol scaffold where other non-directed C-H oxidants that tolerate aromatic groups effect oxidation at only activated tertiary benzylic sites. Rapid generation of a known metabolite (piragliatin) from an advanced intermediate is demonstrated.
Topics: Chemical Phenomena; Chemistry, Organic; Hydrocarbons, Aromatic; Oxidation-Reduction
PubMed: 30559371
DOI: 10.1038/s41557-018-0175-8 -
Ecotoxicology and Environmental Safety May 2022The frequent use of antibiotics allows them to enter aqueous environments via wastewater, and many types of antibiotics accumulate in the environment due to difficult... (Review)
Review
The frequent use of antibiotics allows them to enter aqueous environments via wastewater, and many types of antibiotics accumulate in the environment due to difficult degradation, causing a threat to environmental health. It is crucial to adopt effective technical means to remove antibiotics in aqueous environments. The Fenton reaction, as an effective organic pollution treatment technology, is particularly suitable for the treatment of antibiotics, and at present, it is one of the most promising advanced oxidation technologies. Specifically, rapid Fenton oxidation, which features high removal efficiency, thorough reactions, negligible secondary pollution, etc., has led to many studies on using the Fenton reaction to degrade antibiotics. This paper summarizes recent progress on the removal of antibiotics in aqueous environments by Fenton and Fenton-like reactions. First, the applications of various Fenton and Fenton-like oxidation technologies to the removal of antibiotics are summarized; then, the advantages and disadvantages of these technologies are further summarized. Compared with Fenton oxidation, Fenton-like oxidations exhibit milder reaction conditions, wider application ranges, great reduction in economic costs, and great improved cycle times, in addition to simple and easy recycling of the catalyst. Finally, based on the above analysis, we discuss the potential for the removal of antibiotics under different application scenarios. This review will enable the selection of a suitable Fenton system to treat antibiotics according to practical conditions and will also aid the development of more advanced Fenton technologies for removing antibiotics and other organic pollutants.
Topics: Anti-Bacterial Agents; Catalysis; Hydrogen Peroxide; Oxidation-Reduction; Wastewater; Water; Water Pollutants, Chemical; Water Purification
PubMed: 35395600
DOI: 10.1016/j.ecoenv.2022.113464 -
International Journal of Environmental... Mar 2022Cadmium (Cd)-contaminated paddy soils are a big concern. However, the effect of irrigation with acid water on the migration and transformation of Cd and the effect of...
Cadmium (Cd)-contaminated paddy soils are a big concern. However, the effect of irrigation with acid water on the migration and transformation of Cd and the effect of alternating redox conditions caused by intermittent irrigation on Cd aging processes in different depths of paddy soils are unclear. This study revealed Cd fractionation and aging in a Cd-contaminated paddy soil under four irrigation periods with acid water and four drainage periods, by applying a soil columns experiment and a sequential extraction procedure. The results showed that the dynamic changes of soil pH, oxidation reduction potential (ORP), iron (Fe) oxides and dissolved organic carbon (DOC) throughout the intermittent irrigation affected the transformation of Cd fractions. After 32 days, the proportion of exchangeable Cd (F1) to the total Cd decreased with a reduction of 24.4% and 20.1% at the topsoil and the subsoil, respectively. The labile fractions of Cd decreased, and the more immobilizable fractions of Cd increased in the different depths of soils due to the aging process. Additionally, the redistribution of the Fe and Mn oxide-bound Cd (F3) and organic matter and secondary-sulfide-bound Cd (F4) occurred at different depths of soils during the incubation time. Overall, the bioaccessibility of Cd in the subsoil was higher than that in the topsoil, which was likely due to the leaching and accumulation of soluble Cd in the deep soil. In addition, the aging processes in different depths of soils were divided into three stages, which can be mainly described as the transformation of F1 into F3 and F4.
Topics: Cadmium; Environmental Pollution; Oryza; Oxides; Soil; Soil Pollutants; Water
PubMed: 35329022
DOI: 10.3390/ijerph19063339 -
Angewandte Chemie (International Ed. in... May 2022This work reports an aqueous dye-sensitized photoelectrochemical cell (DSPEC) capable of oxidizing glycerol (an archetypical biobased compound) coupled with H...
This work reports an aqueous dye-sensitized photoelectrochemical cell (DSPEC) capable of oxidizing glycerol (an archetypical biobased compound) coupled with H production. We employed a mesoporous TiO photoanode sensitized with the high potential thienopyrroledione-based dye AP11, encased in an acetonitrile-based redox-gel that protects the photoanode from degradation by aqueous electrolytes. The use of the gel creates a biphasic system with an interface at the organic (gel) electrode and aqueous anolyte. Embedded in the acetonitrile gel is 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), acting as both a redox-mediator and a catalyst for oxidative transformations. Upon oxidation of TEMPO by the photoexcited dye, the in situ generated TEMPO shuttles through the gel to the acetonitrile-aqueous interface, where it acts as an oxidant for the selective conversion of glycerol to glyceraldehyde. The introduction of the redox-gel layer affords a 10-fold increase in the conversion of glycerol compared to the purely aqueous system. Our redox-gel protected photoanode yielded a stable photocurrent over 48 hours of continuous operation, demonstrating that this DSPEC is compatible with alkaline aqueous reactions.
Topics: Acetonitriles; Coloring Agents; Cyclic N-Oxides; Glycerol; Oxidation-Reduction; Photosynthesis; Solar Energy; Water
PubMed: 35266261
DOI: 10.1002/anie.202200175 -
Antioxidants & Redox Signaling May 2023Cardiovascular disease and drug-induced health side effects are frequently associated with-or even caused by-an imbalance between the concentrations of reactive oxygen... (Review)
Review
Vascular Redox Signaling, Endothelial Nitric Oxide Synthase Uncoupling, and Endothelial Dysfunction in the Setting of Transportation Noise Exposure or Chronic Treatment with Organic Nitrates.
Cardiovascular disease and drug-induced health side effects are frequently associated with-or even caused by-an imbalance between the concentrations of reactive oxygen and nitrogen species (RONS) and antioxidants, respectively, determining the metabolism of these harmful oxidants. According to the "kindling radical" hypothesis, the initial formation of RONS may further trigger the additional activation of RONS formation under certain pathological conditions. The present review specifically focuses on a dysfunctional, uncoupled endothelial nitric oxide synthase (eNOS) caused by RONS in the setting of transportation noise exposure or chronic treatment with organic nitrates, especially nitroglycerin (GTN). We further describe the various "redox switches" that are proposed to be involved in the uncoupling process of eNOS. In particular, the oxidative depletion of tetrahydrobiopterin and S-glutathionylation of the eNOS reductase domain are highlighted as major pathways for eNOS uncoupling upon noise exposure or GTN treatment. In addition, oxidative disruption of the eNOS dimer, inhibitory phosphorylation of eNOS at the threonine or tyrosine residues, redox-triggered accumulation of asymmetric dimethylarginine, and l-arginine deficiency are discussed as alternative mechanisms of eNOS uncoupling. The clinical consequences of eNOS dysfunction due to uncoupling on cardiovascular disease are summarized also, providing a template for future clinical studies on endothelial dysfunction caused by pharmacological or environmental risk factors.
Topics: Humans; Nitric Oxide Synthase Type III; Nitrates; Cardiovascular Diseases; Noise, Transportation; Reactive Oxygen Species; Vascular Diseases; Oxidation-Reduction; Nitric Oxide; Endothelium, Vascular
PubMed: 36719770
DOI: 10.1089/ars.2023.0006 -
Water Research Aug 2023Dissolved organic matters (DOM) are widely present in different water sources, causing significant effects on water treatment processes. Herein, the molecular...
Dissolved organic matters (DOM) are widely present in different water sources, causing significant effects on water treatment processes. Herein, the molecular transformation behavior of DOM during peroxymonosulfate (PMS) activation by biochar for organic degradation in a secondary effluent were comprehensively analyzed. Evolution of DOM was identified and inhibition mechanisms to organic degradation were elucidated. DOM underwent oxidative decarbonization (e.g., -CHO, -CH, -CH and -CO), dehydrogenation (-2H) and dehydration reactions by OH and SO. N and S containing compounds witnessed deheteroatomisation (e.g., -NH, -NO+H, -SO, -SO, -SH), hydration (+HO) and N/S oxidation reactions. Among DOM, CHO-, CHON-, CHOS-, CHOP- and CHONP-containing molecules showed moderate inhibition while condensed aromatic compounds and aminosugars exhibited strong and moderate inhibition effects on contaminant degradation. The fundamental information could provide references for the rational regulation of ROS composition and DOM conversion process in a PMS system. This in turn offered theoretical guidance to minimize the interference of DOM conversion intermediates on PMS activation and degradation of target pollutants.
Topics: Dissolved Organic Matter; Environmental Pollutants; Peroxides; Organic Chemicals
PubMed: 37290196
DOI: 10.1016/j.watres.2023.120166 -
The Journal of Physical Chemistry. A Jun 2021The fates of organic hydroperoxides (ROOHs) in atmospheric condensed phases are key to understanding the oxidative and toxicological potentials of particulate matter....
The fates of organic hydroperoxides (ROOHs) in atmospheric condensed phases are key to understanding the oxidative and toxicological potentials of particulate matter. Recently, mass spectrometric detection of ROOHs as chloride anion adducts has revealed that liquid-phase α-hydroxyalkyl hydroperoxides, derived from hydration of carbonyl oxides (Criegee intermediates), decompose to geminal diols and HO over a time frame that is sensitively dependent on the water content, pH, and temperature of the reaction solution. Based on these findings, it has been proposed that H-catalyzed conversion of ROOHs to ROHs + HO is a key process for the decomposition of ROOHs that bypasses radical formation. In this perspective, we discuss our current understanding of the aqueous-phase decomposition of atmospherically relevant ROOHs, including ROOHs derived from reaction between Criegee intermediates and alcohols or carboxylic acids, and of highly oxygenated molecules (HOMs). Implications and future challenges are also discussed.
Topics: Atmosphere; Hydrogen-Ion Concentration; Mass Spectrometry; Peroxides; Thermodynamics; Water
PubMed: 33904735
DOI: 10.1021/acs.jpca.1c01513