Oxidation Processes Of Organic Compounds Research Articles

ПЕРЕДОВІ ПРОЦЕСИ ОКИСНЕННЯ НА ОСНОВІ НАТРІЮ ПЕРКАРБОНАТУ. ОГЛЯД

The advantages of sodium percarbonate as a carrier of “solid hydrogen peroxide” compared to hydrogen peroxide in the liquid phase are considered. Methods of homogeneous (activation by ultraviolet radiation, electrodischarge plasma, in ultrasonic field, by metal ions) and heterogeneous (by natural and artificially synthesized minerals, iron nanoparticles that are immobilized on support materials, nanoparticles of iron compounds, bimetallic nanocomposite, ferrocene) activation of sodium percarbonate and their application in advanced oxidation processes of organic compounds based on it are presented. It was found that the acidic environment is more effective for homogeneous activation of sodium percarbonate by metal ions (in particular Fe2+), and a neutral or alkaline environment is more suitable for heterogeneous activation of sodium percarbonate.

QSAR Assessing the Efficiency of Antioxidants in the Termination of Radical-Chain Oxidation Processes of Organic Compounds.

Using the GUSAR 2013 program, the quantitative structure–antioxidant activity relationship has been studied for 74 phenols, aminophenols, aromatic amines and uracils having lgk7 = 0.01–6.65 (where k7 is the rate constant for the reaction of antioxidants with peroxyl radicals generated upon oxidation). Based on the atomic descriptors (Quantitative Neighborhood of Atoms (QNA) and Multilevel Neighborhoods of Atoms (MNA)) and molecular (topological length, topological volume and lipophilicity) descriptors, we have developed 9 statistically significant QSAR consensus models that demonstrate high accuracy in predicting the lgk7 values for the compounds of training sets and appropriately predict lgk7 for the test samples. Moderate predictive power of these models is demonstrated using metrics of two categories: (1) based on the determination coefficients R2 (R2TSi, R20, Q2(F1), Q2(F2), ) and based on the concordance correlation coefficient (CCC)); or (2) based on the prediction lgk7 errors (root mean square error (RMSEP), mean absolute error (MAE) and standard deviation (S.D.)) The RBF-SCR method has been used for selecting the descriptors. Our theoretical prognosis of the lgk7 for 8-PPDA, a known antioxidant, based on the consensus models well agrees with the experimental value measure in the present work. Thus, the algorithms for calculating the descriptors implemented in the GUSAR 2013 program allow simulating kinetic parameters of the reactions underling the liquid-phase oxidation of hydrocarbons.

COD/DOC balanced models for the oxidation process of organic compounds

Nowadays, several advanced oxidation and enzymatic processes are available for the removal of organic compounds. Mathematical models are crucial to optimize the operating conditions and to reduce the costs associated with the studied oxidation process. The present work deals with a procedure to develop COD/DOC balanced models to represent the oxidation process of organic compounds. The procedure is of general nature since no hypothesis is made regarding the identity of the organic compounds or the oxidant employed. Using the developed procedure, proposed oxidation pathways always fulfill elemental and electron balances. Several examples of oxidation pathways were studied to demonstrate the usefulness of the procedure. From the analysis of a particular pathway, several restrictions regarding the range of possible values of the model coefficients can be found. These restrictions can be used to enhance the robustness of the fitting procedure of the model by using different types of data, such as COD, DOC and/or the actual concentration of some relevant species. This work will help researchers in areas related to the removal of organic compounds using any oxidation process.

Benthic fluxes and nitrate reduction activity in a marine park (Northern San Jorge Gulf) from Patagonia Argentina

The Northern San Jorge Gulf (NSJG) was declared Coastal Marine Park in 2008 with the goal of preserving its biodiversity. In situ benthic fluxes experiments were performed using an opaque chamber in Sara Creek (SC) and Malaspina Creek (MC). Moreover, ex situ nitrate reduction activity was assessed using a continuous flow-through system. Benthic fluxes in MC, showed a consumption of oxygen (794 ± 196 mg m−2 h−1) and nitrate (103 ± 68 µmol m−2 h−1) by sediment and release of ammonium (175 ± 60 µmol m−2 h−1), phosphate (66 ± 10 µmol m−2 h−1) and silicate (116 ± 66 µmol m−2 h−1) towards the water column. In SC, the same pattern was observed and the fluxes values were 375 ± 132, 128 ± 1, 76 ± 12, 39 ± 24 and 133 ± 81, respectively. Only, ammonium and oxygen fluxes showed significant differences between sites, due to the highest organic matter content and the particular hydrodynamic conditions in MC. These are the first benthic flux measurements made within the protected area. Nitrate uptake rate, based on Michaelis–Menten kinetic, was K m : 155.3 µM and V max: 0.053 µM g−1 h−1 in SC and K m : 131.2 µM and V max: 0.039 µM g−1 h−1 in MC. Considering the nitrate dynamic we concluded that the sediments both SC and MC act as a sink of nitrate. This ion could be principally used as a terminal electron acceptor during the oxidation process of organic compounds in sediments of NSJG.

Oxidizer Demand in the Unsaturated Zone of a Surface‐Spreading Soil Aquifer Treatment System

Core Ideas We investigated the Shafdan SAT system, known for its good performance. We showed that oxidation of organic and nitrogen compounds occurs in the vadose zone. We calculated the oxidizer balance over the vadose zone and the overall system. The balance reveals 42.5 ± 12. mg/L of oxygen consumption in the vadose zone. Soil aquifer treatment (SAT) is increasingly considered to be a favorable polishing method before the use of secondary or tertiary wastewater effluents for unrestricted irrigation or disposal to the sea. Most of the oxidation processes of organic compounds as well as of nitrogen compounds take place in the unsaturated zone of the SAT. A material balance over the unsaturated zone of a high‐frequency SAT system reveals that 90% of the removal of organic matter and complete ammonium oxidative removal already occur within the unsaturated zone. This is observed, despite the short (less than 3 wk) water retention time in this zone, compared with the subsequent 6‐ to 36‐mo retention time within the aquifer. An oxidizer balance over the unsaturated zone reveals that 42.5 ± 12 mg/L of oxygen is consumed in the unsaturated zone. This consumption level is five times higher than the oxygen saturation level under the conditions prevailing in the effluent. The implications of this excessively high oxygen demand in the vadose zone on manganese mobilization in the aquifer are addressed.

Photocatalytic oxidation of ethanol and isopropanol vapors on cadmium sulfide

CdS-based catalysts preparation has been investigated, and the obtained photocatalysts were characterized and tested in photocatalytic oxidation of ethanol and isopropanol vapors under visible light irradiation (λ>420nm) with oxygen of air. The catalysts were prepared with a two-step method: (1) reaction between CdCl2 and NaOH and (2) exchange of hydroxide ions of Cd(OH)2 intermediate with S2− to form CdS. Influence of the reagents addition rate, stirring rate, temperature of the reaction mixture and the reagents’ ratio on the oxidation rate of alcohols on solids was investigated. It was found that the rate of photooxidation increases with the increase in the stirring rate and with the decrease in the reagents addition rate during the synthesis. The photocatalytic activity as a function of sulfur content reaches the highest value for the stoichiometric CdS, which is obtained at ≥2:1 S2− to Cd2+ molar ratio in precursors. Kinetic features of the isopropanol photocatalytic oxidation were studied. The Langmuir–Hinshelwood model describes satisfactorily the rate vs. concentration curve. The increase in the air relative humidity results in higher isopropanol oxidation rate. Partial deactivation of CdS catalyst was observed and described with exponential decay. Deactivation was less pronounced at high relative humidity. CdS deactivation took place due to the surface sulfur ions oxidation with formation of SO42- groups. The results show a potential of CdS photocatalysis for solar light–driven green oxidation processes of organic compounds.

ChemInform Abstract: Initiation and Catalysis of Oxidation Processes of Organic Compounds in an Acoustic Field

ChemInform Abstract: Initiation and Catalysis of Oxidation Processes of Organic Compounds in an Acoustic Field

Photoinduced Charge-Transfer Processes on MOF-5 Nanoparticles: Elucidating Differences between Metal-Organic Frameworks and Semiconductor Metal Oxides

Metal-organic frameworks (MOFs), which exhibit large surface area and porosity retention upon solvent removal, have attracted considerable attention due to their elegant topology and potential applications in separation, gas storage, nonlinear optics, and catalysis. We report herein comprehensive studies on the nature of luminescence transitions in MOF-5 nanoparticles, which are referred to as MOF-5_n, and the interfacial charge transfer from the photoexcited MOF-5_n to various organic compounds. The time-resolved diffuse reflectance (TDR) and fluorescence spectroscopies were combined in order to clarify the photoinduced one-electron oxidation processes of organic compounds on the MOF-5_n. First, to identify the nature of the luminescence transitions in MOF-5, the temperature dependences of the spectral characteristics were elucidated and compared with those of ZnO nanoparticles. The quenching of MOF-5 emission by several substrates (S), such as aromatic sulfides and amines, was then investigated using steady-state and time-resolved fluorescence spectroscopies. The one-electron oxidation reaction of S during the 355 nm laser flash photolysis of MOF-5_n in acetonitrile was directly examined using TDR spectroscopy, and it was revealed that MOF-5 has a much higher oxidation reaction efficiency than that of P-25 TiO2 powder, which is the most common photocatalyst. The experimental data were rationalized in terms of the Marcus theory on the electron transfer reactions. Moreover, the influence of adsorbed water on the reaction processes was examined because the MOF crystal morphology is affected by exposure to water during synthesis or after evacuation. Consequently, the present study provides an excellent opportunity to understand the difference in the photoinduced charge-transfer processes between MOFs and semiconductors.

Phenol oxidation kinetics in water solution using iron(3)-oxide-based nano-catalysts

The influence of inorganic ions (HCO 3, PO 4/HPO 4/H 2PO 4, Cl, SO 4, Ca, Na and Mg) on the advanced chemical oxidation process of organic compounds dissolved in water is reported here. The catalytic behavior of iron(3)-oxide-based nano-particles was investigated together with inorganic ions and hydrogen peroxide concentrations, and pH level. Phenol was chosen as a typical organic contaminant for this study as a simulating pollutant. The limiting concentrations of radical scavengers making the oxidation process inefficient were identified. The strong effect of concentration of radical scavengers HCO 3, PO 4/HPO 4/H 2PO 4, the nano-catalyst and hydrogen peroxide concentrations, and pH on the phenol oxidation rate and lag time period before reaction starts was determined. It was shown that Cl, SO 4, Ca, Na and Mg ions had no significant effect on the kinetics of phenol oxidation.

Oxodicarboxylic acids in atmospheric aerosol particles

Fine mode aerosol was collected on quartz fiber filters at several sites across Europe. These samples were analyzed for carboxylic acids by liquid chromatography coupled to a hybrid (quadrupole and time-of-flight) mass spectrometer (LC/MS/MS-TOF). A series of oxodicarboxylic acids (C 7–C 11) was detected. Oxodicarboxylic acids are linear dicarboxylic acids with an additional carbonyl group. Previous measurements of these acids are scarce and their sources are largely unknown. Several structural isomers (different positions of the carbonyl group within the molecule) could be identified and differentiated by the combination of laboratory experiments and high mass accuracy measurements. The homologs with 9–11 carbon atoms were identified for the first time in atmospheric aerosol particles. The concentrations of oxodicarboxylic acids in ambient aerosol samples frequently exceeded those of the corresponding unsubstituted dicarboxylic acids. Oxodicarboxylic acids have been shown to be products of the reaction of dicarboxylic acids with OH radicals in chamber experiments and a reaction mechanism is proposed. Good correlation of oxodicarboxylic acid and hydroxyl radical concentrations was found at two measurement sites (Finland and Crete) of different geographic location and meteorological conditions. The ratios of individual isomers from the field samples are comparable to those of the laboratory experiments. The results of this study imply that the reaction of OH radicals and dicarboxylic acids is an important pathway for the production of oxodicarboxylic acids in the atmosphere. Oxodicarboxylic acids seem to be important intermediates in atmospheric oxidation processes of organic compounds.

Sunlight Induced Decoloration/Degradation of Non-Biodegradable Orange II Dye by Advanced Oxidation Technologies in Homogeneous and Heterogeneous Media

AbstractLight and dark oxidation processes of organic compounds involving H