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ChemSusChem Dec 2022Hydrogen peroxide (H O ) is an important green oxidizing agent for environmental protection and chemical production. In comparison to the traditional anthraquinone... (Review)
Review
Hydrogen peroxide (H O ) is an important green oxidizing agent for environmental protection and chemical production. In comparison to the traditional anthraquinone method, photosynthesis is a green and energy-saving process for H O production. To improve the stability and practical application value of the H O synthesized by photocatalysis, the H O photosynthesis should be conducted in pure water without involving any sacrificial reagents. In this regard, organic semiconducting catalysts pose as a suitable candidate for photocatalytic H O synthesis owing to their metal-free nature to prevent H O decomposition by the metal ions. In this Perspective, the H O photosynthesis history is firstly introduced, followed by a review of the organic semiconductor photocatalysts reported to date. Finally, the main problems to thwart the advances of current pure H O-to-H O photosynthesis are discussed, followed by proposed solutions to address these issues in order to pave new ways for the development of highly efficient metal-free organic photocatalysts for sustainable pure H O-to-H O conversion.
Topics: Hydrogen Peroxide
PubMed: 36177848
DOI: 10.1002/cssc.202201514 -
Chemical Reviews Apr 2021Dissolution of metals in organic solvents is relevant to various application fields, such as metal extraction from ores or secondary resources, surface etching or...
Dissolution of metals in organic solvents is relevant to various application fields, such as metal extraction from ores or secondary resources, surface etching or polishing of metals, direct synthesis of organometallic compounds, and separation of metals from other compounds. Organic solvents for dissolution of metals can offer a solution when aqueous systems fail, such as separation of metals from metal oxides, because both the metal and metal oxide could codissolve in aqueous acidic solutions. This review critically discusses organic media (conventional molecular organic solvents, ionic liquids, deep-eutectic solvents and supercritical carbon dioxide) for oxidative dissolution of metals in different application areas. The reaction mechanisms of dissolution processes are discussed for various lixiviant systems which generally consist of oxidizing agents, chelating agents, and solvents. Different oxidizing agents for dissolution of metals are reviewed such as halogens, halogenated organics, donor-acceptor electron-transfer systems, polyhalide ionic liquids, and others. Both chemical and electrochemical processes are included. The review can guide researchers to develop more efficient, economic, and environmentally friendly processes for dissolution of metals in their elemental state.
PubMed: 33724831
DOI: 10.1021/acs.chemrev.0c00917 -
Molecules (Basel, Switzerland) Dec 2022A rapid, cheap and feasible new approach was used to synthesize the Mg0.375Fe0.375Al0.25-LDH in the presence of tetramethylammonium hydroxide (TMAH), as a nontraditional...
A rapid, cheap and feasible new approach was used to synthesize the Mg0.375Fe0.375Al0.25-LDH in the presence of tetramethylammonium hydroxide (TMAH), as a nontraditional hydrolysis agent, applying both mechano-chemical (MC) and co-precipitation methods (CP). For comparison, these catalysts were also synthesized using traditional inorganic alkalis. The mechano-chemical method brings several advantages since the number of steps and the energy involved are smaller than in the co-precipitation method, while the use of organic alkalis eliminates the possibility of contaminating the final solid with alkaline cations. The memory effect was also investigated. XRD studies showed Fe3O4 as stable phase in all solids. Regardless of the alkalis and synthesis methods used, the basicity of catalysts followed the trend: mixed oxides > parent LDH > hydrated LDH. The catalytic activity of the catalysts in the Claisen−Schmidt condensation between benzaldehyde and cyclohexanone showed a linear dependence to the basicity values. After 2 h, the calcined sample cLDH-CO32−/OH−-CP provided a conversion value of 93% with a total selectivity toward 2,6-dibenzylidenecyclohexanone. The presence of these catalysts in the reaction media inhibited the oxidation of benzaldehyde to benzoic acid. Meanwhile, for the self-condensation of cyclohexanone, the conversions to mono- and di-condensed compounds did not exceed 3.8%.
Topics: Catalysis; Oxidation-Reduction; Oxides
PubMed: 36500481
DOI: 10.3390/molecules27238391 -
Journal of Colloid and Interface Science Jan 2023The migration of supercritical CO (scCO) injected into underground reservoirs as part of carbon capture and storage is influenced by organic contamination affecting...
HYPOTHESIS
The migration of supercritical CO (scCO) injected into underground reservoirs as part of carbon capture and storage is influenced by organic contamination affecting mineral wettability. Molecular dynamics (MD) simulations of relevant systems that incorporate representative organic solutes allow detailed investigation of changes in fundamental interfacial and capillary properties.
EXPERIMENTS
We use MD simulations to explore the effects of four organic solutes (quinoline, decanoic acid, coronene, sorgoleone) on the wettability of quartz by water in the presence of scCO. We examine the impacts of polar, alkyl, and aromatic moieties as well as fluid flow velocity at elevated temperatures and pressures.
FINDINGS
Organic molecules accumulate at the water-CO interface, where they distribute according to their size and functional groups. Certain organics penetrate the adsorbed water film at the quartz-CO interface, revealing two modes of hydrogen bonding between polar organic functional group, water, and quartz surface -OH groups. Interfacial energies and contact angles are minimally impacted by organic adsorption at the water-CO interface, possibly due to simultaneous CO desorption. Non-equilibrium MD simulations reveal that flow-induced redistribution of organic compounds modulates the radii of curvature of the advancing and receding water-CO interfaces. Our results indicate that organic adsorption on water surfaces is likely ubiquitous during multi-phase flow in soils and sedimentary rocks, with implications for the mobilization and transport of organic compounds.
Topics: Quartz; Water; Carbon Dioxide; Solutions; Minerals; Soil; Carbon; Quinolines
PubMed: 36081206
DOI: 10.1016/j.jcis.2022.08.124 -
The Science of the Total Environment Feb 2020Epidemiology studies over the past five decades have provided convincing evidence that exposure to air pollution is associated with multiple adverse health outcomes,... (Review)
Review
Epidemiology studies over the past five decades have provided convincing evidence that exposure to air pollution is associated with multiple adverse health outcomes, including increased mortality. Air pollution is a complex mixture of particles, vapors and gases emitted from natural and anthropogenic sources as well as formed through photochemical transformation processes. In metropolitan areas, air pollutants from combustion emissions feature a blend of emitted particles, oxides of carbon, sulfur and nitrogen, volatile organic compounds, and secondary reaction products, such as ozone, nitrogen dioxide, and secondary organic aerosols. Because many of the primary and transformed pollutants track together, their relative contributions to health outcomes are difficult to disentangle. Aside from the criteria pollutants ozone and nitrogen dioxide and some of the simpler aldehydes (e.g. formaldehyde and acrolein), other products from photochemical processes are a particularly vexing class of chemicals to investigate since they comprise a dynamic ill-defined complex mixture in both particulate and gas phases. The purpose of this review was to describe and compare health effects of freshly emitted versus oxidatively or photochemically aged air pollutants. In some cases, (e.g. single volatile organic compounds) photochemical transformation resulted in marked enhancements in toxicity through formation of both known and unidentified reaction products, while in other examples (e.g. aging of automobile emissions) the potentiation of effect was variable. The variation in experimental design, aging system employed, concentration and type of starting agent, and toxicity endpoints make comparisons between different studies exceedingly difficult. A more systematic approach with a greater emphasis on higher throughput screening and computational toxicology is needed to fully answer under what conditions oxidatively- or photochemically-transformed pollutants elicit greater health effects than primary emissions.
Topics: Air Pollutants; Air Pollution; Aldehydes; Environmental Exposure; Humans; Nitrogen Dioxide; Ozone; Particulate Matter; Volatile Organic Compounds
PubMed: 31838301
DOI: 10.1016/j.scitotenv.2019.135772 -
RSC Advances Sep 20212,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) is the most widely used quinone with a high reduction potential, and it commonly mediates hydride transfer reactions and... (Review)
Review
2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) is the most widely used quinone with a high reduction potential, and it commonly mediates hydride transfer reactions and shows three accessible oxidation states: quinone (oxidized), semiquinone (one-electron-reduced), and hydroquinone (two-electron-reduced). DDQ has found broad utility as a stoichiometric oxidant in the functionalization of activated C-H bonds and the dehydrogenation of saturated C-C, C-O, and C-N bonds. The cost and toxicity of DDQ triggered recent efforts to develop methods that employ catalytic quantities of DDQ in combination with alternative stoichiometric oxidants. The aerobic catalytic approach was established for the selective oxidation of non-sterically hindered electron-rich benzyl methyl ethers and benzylic alcohols, and effectively extended to the oxidative deprotection of -methoxybenzyl ethers to generate the alcohols in high selectivity. A combination of DDQ and protic acid is known to oxidize several aromatic donors to the corresponding cation radicals. The excited-state DDQ converts benzyls, heteroarenes, fluoroarenes, benzene, and olefins into their radical cation forms as well as chloride and other anions into their respective radicals. These reactive intermediates have been employed for the generation of C-C and C-X (N, O, or Cl) bonds in the synthesis of valuable natural products and organic compounds. To the best of our knowledge, however, there is still no review article exclusively describing the applications of DDQ in organic synthesis. Therefore, in the present review, we provide an overview of DDQ-induced organic transformations with their scope, limitations and the proposed reaction mechanisms.
PubMed: 35479576
DOI: 10.1039/d1ra04575j -
Frontiers in Microbiology 2021Large amounts of methane, a potent greenhouse gas, are produced in anoxic sediments by methanogenic archaea. Nonetheless, over 90% of the produced methane is oxidized... (Review)
Review
Large amounts of methane, a potent greenhouse gas, are produced in anoxic sediments by methanogenic archaea. Nonetheless, over 90% of the produced methane is oxidized via sulfate-dependent anaerobic oxidation of methane (S-AOM) in the sulfate-methane transition zone (SMTZ) by consortia of anaerobic methane-oxidizing archaea (ANME) and sulfate-reducing bacteria (SRB). Coastal systems account for the majority of total marine methane emissions and typically have lower sulfate concentrations, hence S-AOM is less significant. However, alternative electron acceptors such as metal oxides or nitrate could be used for AOM instead of sulfate. The availability of electron acceptors is determined by the redox zonation in the sediment, which may vary due to changes in oxygen availability and the type and rate of organic matter inputs. Additionally, eutrophication and climate change can affect the microbiome, biogeochemical zonation, and methane cycling in coastal sediments. This review summarizes the current knowledge on the processes and microorganisms involved in methane cycling in coastal sediments and the factors influencing methane emissions from these systems. In eutrophic coastal areas, organic matter inputs are a key driver of bottom water hypoxia. Global warming can reduce the solubility of oxygen in surface waters, enhancing water column stratification, increasing primary production, and favoring methanogenesis. ANME are notoriously slow growers and may not be able to effectively oxidize methane upon rapid sedimentation and shoaling of the SMTZ. In such settings, ANME-2d () and ANME-2a may couple iron- and/or manganese reduction to AOM, while ANME-2d and NC10 bacteria () could couple AOM to nitrate or nitrite reduction. Ultimately, methane may be oxidized by aerobic methanotrophs in the upper millimeters of the sediment or in the water column. The role of these processes in mitigating methane emissions from eutrophic coastal sediments, including the exact pathways and microorganisms involved, are still underexplored, and factors controlling these processes are unclear. Further studies are needed in order to understand the factors driving methane-cycling pathways and to identify the responsible microorganisms. Integration of the knowledge on microbial pathways and geochemical processes is expected to lead to more accurate predictions of methane emissions from coastal zones in the future.
PubMed: 33679659
DOI: 10.3389/fmicb.2021.631621 -
Journal of Environmental Management Aug 2023Landfill leachate (LL) represents a very complex effluent difficult to treat and to manage which usually requires a chemical pre-treatment. In this study, response...
Improving organic matter and nutrients removal and minimizing sludge production in landfill leachate pre-treatment by Fenton process through a comprehensive response surface methodology approach.
Landfill leachate (LL) represents a very complex effluent difficult to treat and to manage which usually requires a chemical pre-treatment. In this study, response surface methodology (RSM) was used to identify the optimum operating conditions of the Fenton process as a pre-treatment of LL in order to reduce the high organic content and simultaneously optimize the BOD:TN:TP ratio. The dosages of Fenton process reagents, namely Fe and HO, were used as variables for the implementation of RSM. Chemical oxygen demand (COD), five-days biochemical oxygen demand (BOD), total nitrogen (TN), total phosphorus (TP) removals (and simultaneously BOD:TN:TP ratio), sludge-to-iron ratio (SIR) and organic removal-to-sludge ratio (ORSR) were selected as target responses. This approach considered the SIR and ORSR parameters which are a useful tool for assessing sludge formation during the process along with organic matter removal. The variables (HO and Fe concentrations) significantly affected the responses, as the role of oxidation mechanism is dominant with respect to coagulation one. The pH for the process was fixed to 2.8 while the treatment time was set to 2 h. The optimum operational conditions obtained by perturbation and 3D surface plot, were found to be 4262 mg/L and 5104 mg/L for Fe and HO, respectively (HO/Fe molar ratio = 2) with COD, BOD, TN and TP removals of 70%, 67%, 84% and 96% respectively, while SIR and ORSR final values were 1.15 L/mol and 33.79 g/L respectively, in accordance with models-predicted values. Moreover, the initial unbalanced BOD:TN:TP ratio (9:1:1) was significantly improved (100:6:1), making the effluent suitable for a subsequent biological treatment. The investigated approach allowed to optimize the removal of organic load and nutrients as well as to minimize the sludge formation in Fenton process, providing a useful tool for the operation and management of LL pre-treatment.
Topics: Sewage; Water Pollutants, Chemical; Hydrogen Peroxide; Iron; Oxidation-Reduction
PubMed: 37094386
DOI: 10.1016/j.jenvman.2023.117950 -
Ecotoxicology and Environmental Safety Nov 2023The use of Advance Oxidation Process (AOPs) has been extensively examined in order to eradicate organic pollutants. This review assesses the efficacy of photolysis, O... (Review)
Review
The use of Advance Oxidation Process (AOPs) has been extensively examined in order to eradicate organic pollutants. This review assesses the efficacy of photolysis, O based (O/UV, O/HO, O/HO/UV, HO/UV, Fenton, Fenton-like, hetero-system) and sonochemical and electro-oxidative AOPs in this regard. The main purpose of this review and some suggestions for the advancement of AOPs is to facilitate the elimination of toxic organic pollutants. Initially proposed for the purification of drinking water in 1980, AOPs have since been employed for various wastewater treatments. AOPs technologies are essentially a process intensification through the use of hybrid methods for wastewater treatment, which generate large amounts of hydroxyl (•OH) and sulfate (SO4·-) radicals, the ultimate oxidants for the remediation of organic pollutants. This review covers the use of AOPs and ozone or UV treatment in combination to create a powerful method of wastewater treatment. This novel approach has been demonstrated to be highly effective, with the acceleration of the oxidation process through Fenton reaction and photocatalytic oxidation technologies. It is clear that Advance Oxidation Process are a helpful for the degradation of organic toxic compounds. Additionally, other processes such as •OH and SO4·- radical-based oxidation may also arise during AOPs treatment and contribute to the reduction of target organic pollutants. This review summarizes the current development of AOPs treatment of wastewater organic pollutants.
Topics: Hydroxyl Radical; Hydrogen Peroxide; Wastewater; Oxidation-Reduction; Environmental Pollutants
PubMed: 37890248
DOI: 10.1016/j.ecoenv.2023.115564 -
Journal of Animal Science Apr 2022Sperm are susceptible to excessive reactive oxygen species (ROS). Spermine and spermidine are secreted in large amounts by the prostate and potent natural free radical...
Sperm are susceptible to excessive reactive oxygen species (ROS). Spermine and spermidine are secreted in large amounts by the prostate and potent natural free radical scavengers and protect cells against redox disorder. Thus, we used boar sperm as a model to study the polyamines uptake and elucidate whether polyamines protected sperm from ROS stress. Seven mature and fertile Duroc boars (aged 15 to 30 mo) were used in this study. In experiment 1, spermine and spermidine (3.6 ± 0.3 and 3.3 ± 0.2 mmol/L, respectively) were abundant in seminal plasma, and the content of polyamine decreased (P < 0.05) after preservation at 17 °C for 7 d or incubation at 37 °C for 6 h. In experiment 2, using labeling of spermine or spermidine by conjugation with fluorescein isothiocyanate and ultra-high-performance liquid chromatography, we found that the accumulation of spermine or spermidine in sperm was inhibited by quinidine and dl-tetrahydropalmatine (THP, organic cation transporters [OCT] inhibitors, P < 0.05), but not mildronate and l-carnitine (organic cation/carnitine transporter [OCTN] inhibitors, P > 0.05). In experiment 3, the addition of spermine or spermidine (0.5 mmol/L) in the extender resulted in higher motility, plasma membrane and acrosome integrity, and lower ROS level after preservation in vitro at 17 °C for 7 d (P < 0.05). In experiment 4, in the condition of oxidative stress (treatment with H2O2 at 37 °C for 2 h), the addition of spermine (1 mmol/L) or spermidine (0.5 mmol/L) in extender increased activities of glutathione peroxidase, glutathione reductase, and glutathione S-transferase; reduced glutathione and oxidized glutathione ratio (P < 0.05); and alleviate oxidative stress-induced lipid peroxidation, DNA damage, mitochondrial membrane potential (ΔΨm) decline, adenosine triphosphate depletion, and intracellular calcium concentration ([Ca2+]i) overload (P < 0.05), thereby improving boar sperm motility, the integrity of plasma membrane and acrosome (P < 0.05) in vitro. These data suggest that spermine and spermidine alleviate oxidative stress via the antioxidant capacity, thereby improving the efficacy of boar semen preservation.
Topics: Animals; Hydrogen Peroxide; Male; Oxidative Stress; Polyamines; Semen Preservation; Sperm Motility; Spermatozoa; Swine
PubMed: 35247050
DOI: 10.1093/jas/skac069