Changes In Chemical Species Research Articles

Overlooked Impacts of Alcohols in Electro-H2O2 and Fenton Chemistry.

Alcohols are promising fuels for direct alcohol fuel cells and are common scavengers to identify reactive oxygen species (ROS) in electro-Fenton (EF) systems. However, the side impacts of alcohols on oxygen reduction reactions and ROS generation are controversial due to the complex interactions between electrodes and alcohol-containing electrolytes. Herein, we employed synchrotron-Fourier-transform infrared spectroscopy and electron paramagnetic resonance technologies to directly observe the changes of chemical species and electrochemical properties on the electrode surface. Our studies suggested that alcohols exhibited different limiting degrees on proton (H+) mass transfer toward the catalytic surface, following an order of methanol < ethanol < isopropanol < tert-butyl alcohol (TBA). In addition, the formation of hydrophobic TBA clusters at high concentrations (>400 mM) resulted in a significant reduction in ionic conductivity and an elevation in charge transfer resistance, which impedes H+ mass transfer and raises the energy barrier for 2e- oxygen reduction reaction processes. Moreover, the organic radical •CH2(CH3)2CH2OH produced by the interaction of Fe3+ and •OH with the alcohol in the EF system serves as a crucial intermediate in facilitating H2O2 regeneration, which complicates the quenching effect of alcohols on •OH identification. Therefore, it is recommended that methanol should be used as the scavenger instead of TBA and the concentration should be less than 400 mM in EF systems.

Key Principles of Advanced Oxidation Processes: A Systematic Analysis of Current and Future Perspectives of the Removal of Antibiotics from Wastewater

In line with the development of industrial society, wastewater has caused multiple environmental problems. Contaminants of emerging concern (CECs) in water and wastewater are persistent, and for this reason they can cause serious problems for human health, animal health, and the whole environment. Therefore, it is absolutely necessary to apply efficient methods for the treatment of wastewater that has a high concentration of organic compounds. Over recent years, the prescribed and non-prescribed consumption of antibiotics has increased significantly worldwide. Large quantities of antibiotics are discharged into wastewater because of their incomplete absorption by living organisms. However, even small concentrations present in aquatic environments represent a major risk to human health and environment protection. This paper presents the main advantages and disadvantages of advanced oxidation processes, and the current state and new perspectives in the field of environment protection. This study summarizes data from the most recent specialized scientific literature that focuses on the topic of advanced oxidation processes, thus bringing all these aspects to the attention of researchers in a single work that adds comments and interpretations related to the presented processes. Advanced oxidation processes (AOPs) are often used in the treatment of different types of wastewater. AOPs are based on physicochemical processes that create significant structural changes in chemical species. The majority of antibiotics may be eliminated using physicochemical processes, such as photo-Fenton oxidation, photolysis, ozonation, electrooxidation, heterogeneous catalysis, and other bioprocesses. In comparison to conventional chemical processes, AOPs provide superior oxidation efficiency, ideal operating costs, and zero secondary pollutants.

A modified gas-phase scheme for advanced regional climate modelling with RegCM4

Climate models in the past decades have been developed to such an extent to include atmospheric chemistry as part of their climate simulations. This is necessary for providing policy-makers and other stakeholders with reliable atmospheric projections as well as information about changes in chemical species as a consequence of climate change. The regional climate model (RCM), RegCM4 is a community model which contains only one gas-phase mechanism module (CBM-Z) that includes the formation, deposition, and transport of a number of volatile organic compounds (VOCs). In this paper, the CB6-C, a new gas-phase mechanism module, is combined with RegCM4 to produce a larger suite of VOCs and chemical mechanisms for important anthropogenic and biogenic species, most notably benzene, terpenes, acetylene and their corresponding oxidation products. In order to evaluate this new module, climatologies of the CB6-C and CBM-Z simulations are compared to gridded and station data. The results reveal the two schemes to be similar with some improvement of surface carbon monoxide and tropospheric ozone in the CB6-C. However, organic products were found to be under-predicted for both schemes, suggesting the need of more development in the implementation of atmospheric chemistry in RegCM4. Despite its limitations, the input conditions (emissions and boundary conditions) are easy to modify, making the new gas-phase scheme an important advancement in the modelling of atmospheric chemistry within a RCM, as it provides a pathway for new research that may eventually help health studies.

Rates and Dynamics of Mercury Isotope Exchange between Dissolved Elemental Hg(0) and Hg(II) Bound to Organic and Inorganic Ligands.

Mercury (Hg) isotope exchange is a common process in biogeochemical transformations of Hg in the environment, but it is unclear whether and at what rates dissolved elemental Hg(0)aq may exchange with divalent Hg(II) bound to various organic and inorganic ligands in water. Using enriched stable isotopes, we investigated the rates and dynamics of isotope exchange between 202Hg(0)aq and 201Hg(II) bound to organic and inorganic ligands with varying chemical structures and binding affinities. Time-dependent exchange reactions were followed by isotope compositional changes using both inductively coupled plasma mass spectrometry and Zeeman cold vapor atomic absorption spectrometry. Rapid, spontaneous isotope exchange (<1 h) was observed between 202Hg(0)aq and 201Hg(II) bound to chloride (Cl-), ethylenediaminetetraacetate (EDTA), and thiols, such as cysteine (CYS), glutathione (GSH), and 2,3-dimercaptopropanesulfonic acid (DMPS) at a thiol ligand-to-Hg(II) molar ratio of 1:1. Without external reductants or oxidants, the exchange resulted in transfer of two electrons and redistribution of Hg isotopes bound to the ligand but no net changes of chemical species in the system. However, an increase in the ligand-to-Hg(II) ratio decreased the exchange rates due to the formation of 2:1 or higher thiol:Hg(II) chelated complexes, but had no effects on exchange rates with 201Hg(II) bound to EDTA or Cl-. The exchange between 202Hg(0)aq and 201Hg(II) bound to dissolved organic matter (DOM) showed an initially rapid followed by a slower exchange rate, likely resulting from Hg(II) complexation with both low- and high-affinity binding functional groups on DOM (e.g., carboxylates vs bidentate thiolates). These results demonstrate that Hg(0)aq readily exchanges with Hg(II) bound to various ligands and highlight the importance of considering exchange reactions in experimental enriched Hg isotope tracer studies or in natural abundance Hg isotope studies in environmental matrices.

Operando MAS NMR Reaction Studies at High Temperatures and Pressures

Operando MAS NMR studies provide unique insights into the details of chemical reactions; comprehensive information about temperature- and time-dependent changes in chemical species is accompanied by similarly rich information about changes in phase and chemical environment. Here we describe a new MAS NMR rotor (the WHiMS rotor) capable of achieving internal pressures up to 400 bar at 20 °C or 225 bar at 250 °C, a range that includes many reactions of interest. The MAS NMR spectroscopy enabled by these rotors is ideal for studying the behavior of mixed-phase systems, such as reactions involving solid catalysts and volatile liquids, with the potential to add gases at high pressure. The versatile operation of the new rotors is demonstrated by collecting operando 1H and 13C spectra during the hydrogenolysis of benzyl phenyl ether, catalyzed by Ni/γ-Al2O3 at ca. 250 °C, both with and without H2 (g) supplied to the rotor. The 2-propanol solvent, which exists in the supercritical phase under these reaction condi...

Influence of the shielding gas composition on the passive film and erosion corrosion of tube-to-tube sheet welds of hyper duplex stainless steel

Resistance to erosion corrosion was determined by degree of repair of passive film under flowing conditions combined corrosive solution. To examine effects of nitrogen addition to argon shielding gas on erosion corrosion of hyper duplex stainless steel welds, stability of oxide film passivity of hyper duplex stainless steel welds was measured through electrochemical tests and X-ray photoelectron spectroscopy analyses. The results indicated the resistance to erosion corrosion was improved due to the increase of austenite phase and the stability of the passive film resulting in change of chemical species as supplemented with the nitrogen gas in the argon shielding gas.

Strategies to increase selectivity of analytical methods for As, Cr and Se speciation in biological samples: A review

AbstractThis review provides an overview and discusses different analytical strategies that minimize or eliminate the preparation of samples for speciation of organic and inorganic species of As, Cr and Se in samples of biological interest. These metals are important for the human body and the presence of various chemical forms of metals determines its essentiality and toxicity, thus speciation comes as an important tool for the study of biological samples. However, speciation requires a reduction in the steps of sample preparation, allowing a sample investigation in its most native form in order to reduce the changes in chemical species. The strategies proposed for speciation of these metals include: solid phase extraction, point cloud extraction, suspension and direct analysis. Selected methods proposed for the speciation of organic and inorganic species of As, Cr and Se were reviewed including their main figures of merit, advantages and disadvantages

A History Matching Study of Nagaoka Site for Geochemical Model Calibration in Reactive Transport Model: Using Concentration Changes of Chemical Species from Post-Injection Water Sampling Data

Abstract Although it is necessary to conduct reactive transport simulation for CO2 mineralization prediction, some data in geochemical calculation have high uncertainty. We attempted to revise reactive surface area (RSA) data by matching the simulation results from TOUGHREACT ver.1 with the sampled formation water composition data of Nagaoka site. First, we used 1-D radial model to revise RSA and then applied it to 2-D radial model to verify the reliability under the more realistic condition. The procedure introduced in this paper could reduce the time to work on history matching study which contains time-consuming geochemical calculation.

Construction of Microbial Kinetics Database for PA of HLW disposal

ABSTRACTTo evaluate a change of chemical species of groundwater composition by the metabolism of microbes, which will be introduced to deep underground from the surface and be in a deep underground, is important for the discussion of the microbial effects on the performance assessment of the high-level radioactive waste repository. The purpose of this study is to develop of a microbial kinetics database to evaluate their activities in the deep underground environment.Some microbial metabolism data were collected and constructed their kinetics database for aerobic, denitrifying, manganese reducing, iron reducing, sulfate reducing, methanogenic and acetogenic bacteria to evaluate above groundwater chemistry. About 1260 data were selected by literature survey for some journals and books published from 1960s and summarized in this microbial kinetics database. Some sensitivity analyses were performed for some parameter of metabolism of microbes.

13C-NMR Spectroscopic Study on Chemical Species in Piperazine−Amine−CO2−H2O System before and after Heating

Chemical reactions associated with the absorption of CO2 into aqueous solutions of blends of piperazine (PZ) with N- methyldiethanolamine (MDEA), etc. were studied by 13C-NMR spectroscopy. The coexistence of PZ and MDEA enhanced the initial apparent rate of HCO3−/CO2−3 formation. This result can be explained by considering that PZ−monocarbamate rapidly formed works as an organocatalyst in the formation reaction of HCO−3. Concentration changes of chemical species in CO2-absorbed aqueous amine solutions upon heating (80°C, 30min) were studied by 13C-NMR spectroscopy. Carbon dioxide regeneration originates mainly from HCO3−/CO3, and not form carbamate and carbonate.

Formation of a solid electrolyte interface on single wall carbon nanotube electrodes in lithium ion batteries

The formation of a solid electrolyte interface (SEI) at the surface of a SWNT electrode was investigated by SEM, TEM, XRD, and Raman spectroscopy. These analyses were carried out at different charge-discharge cycles, showing the cycle dependent character of the SEI formation. The changes in chemical species of SEI with increased number of cycles have been examined. This study shows by XRD, that inorganic species of SEI are LiF and Li2CO3, and that the SEI formation depends on the number of discharge-charge cycles.

Macronutrient (N, P, K) and Redoximorphic Metal (Fe, Mn) Allocation in Leersia oryzoides (Rice Cutgrass) Grown Under Different Flood Regimes

Vegetated drainages are an effective method for removal of pollutants associated with agricultural runoff. Leersia oryzoides, a plant common to agricultural ditches, may be particularly effective in remediation; however, research characterizing responses of L. oryzoides to flooding are limited. Soil reduction resulting from flooding can change availability of nutrients to plants via changes in chemical species (e.g., increasing solubility of Fe). Additionally, plant metabolic stresses resulting from reduced soils can decrease nutrient uptake and translocation. The objective of this study was to characterize belowground and aboveground nutrient allocation of L. oryzoides subjected to various soil moisture regimes. Treatments included: a well-watered and well-drained control; a continuously saturated treatment; a 48-h pulse-flood treatment; and a partially flooded treatment in which water level was maintained at 15 cm below the soil surface and flooded to the soil surface for 48 h once a week. Soil redox potential (Eh, mV) was measured periodically over the course of the 8-week experiment. At experiment termination, concentrations of Kjeldahl nitrogen, phosphorus (P), potassium (K), iron (Fe), and manganese (Mn) were measured in plant tissues. All flooded treatments demonstrated moderately reduced soil conditions (Eh < 350 mV). Plant Kjeldahl nitrogen concentrations demonstrated no treatment effect, whereas P and K concentrations decreased in aboveground portions of the plant. Belowground concentrations of P, Mn, and Fe were significantly higher in flooded plants, likely due to the increased solubility of these nutrients resulting from the reductive decomposition of metal–phosphate complexes in the soil and subsequent precipitation in the rhizosphere. These results indicate that wetland plants may indirectly affect P, Mn, and Fe concentrations in surface waters by altering local trends in soil oxidation–reduction chemistry.

Changes in Chemical Species of Copper Added to Brown Forest Soil in Japan

Heavy metals are present as various chemical species in soil environments. Chemical species of heavy metals determinate their behavior in soil, so they must be more important concern than total contents in treating problems about heavy metal polluted soil. Microbial activity is thought to be one of the factors that affect chemical speciation of heavy metals. Although some possible microbial mechanisms have been suggested, their effects on heavy metals have not previously been thoroughly studied. In this study, we investigated whether microorganisms contribute to the fractionation of Cu in a forest soil. Copper-enriched, sterilized forest soil samples were buried at their places of origin, and subsamples were collected for analysis 3, 10, 17, 30, 60, and 90 days after burial. Tessier’s sequential extraction was employed to analyse Cu fractionation. Until two months after burial, the added Cu remained nearly unchanged. But a dramatic change was found in soil subsamples after three months. In both the A and B horizons, the carbonate fraction of Cu increased and the residual fraction decreased. We also found that clay minerals and persistent organic matter are important binding substances of Cu in the residual fraction. The change from residual to carbonate fraction could be caused by microbial activity.

Electroporation of biological membranes from multicellular to nano scales

Electroporation, widely used in research and applications, is briefly reviewed. Both cell and artificial planar bilayer membranes exhibit dramatic changes if the transmembrane voltage is raised to /spl sim/0.2 to 1 V by various electric field pulses. Ionic and molecular transport increases by orders of magnitude, with both reversible and irreversible outcomes. Initially the term breakdown was used, but ion pair generation of classic dielectric breakdown was ruled out. Instead, a stochastic pore hypothesis is consistent with features of electroporation in planar lipid membranes. There is a rapid, nonlinear conduction increase through a rapidly evolving pore population, and this causes the fast membrane discharge previously termed "breakdown". Phenomena due to primary aqueous pores and secondary processes such as heating and chemical exchange have been observed in planar bilayers, cell single systems encountered mainly in vitro, multicellular systems relevant to in vivo applications, and possibly subcellular structures such as mitochondria. For membrane systems that approach nanoscales, modified behavior should occur because of conformational constraints, and deterministic processes may become more important. Understanding electroporation is a subset of a general problem: obtaining a quantitative description of how electromagnetic field-altered changes in chemical species within a biological system govern observed effects.

Caution against using propylene glycol as a solvent in epilepsy drug research

Anticonvulsive effects and changes in chemical species reflecting nitric oxide production (NOx levels) were induced in the EL mouse by a solvent mixture commonly used to dissolve antiepileptic drugs. The mixture consisted of porpylene glycol (PG) and ethanol in saline (PES), and included 10.5% ethanol plus 20, 40, or 60% PG. PES mixtures suppressed seizures in EL mice in proportion to concentrations of PG. NOx levels in the brains of mice treated with PES mixtures including 40 or 60% PG were significantly lower than in control mouse brain. These results suggested that anticonvulsive effects of PES mixtures were related to reduction of NOx levels in brain. PG should not be used as a drug solvent in epilepsy research.

Frontiers of positron and positronium chemistry in condensed media

Our work proves that positron annihilation spectroscopy is an excellent tool to follow the structural changes in chemical species. We present four examples to support the above statement. The sizes of defects in electrodeposited chromium layers were studied and estimated on the basis of positron lifetime spectra decomposed into two components. Vacancies, di-vacancies and vacancy-clusters could be identified in the electrodeposites. The changes of the size distribution of the free volume units in poly(methylmetacrylate) on the dependence of molecular weight and dispersity were described by the correlation between the lifetime ofortho-Ps and the free volume units in polymers. It was found that the free volume is affected by both the molecular weight and dispersity. The effect of dispersity was explained by the sample preparation technique, namely by the application of high pressure. The ortho-para conversion ofortho-Ps was used to follow the partial spin-crossover in [Fe(1-ethyl-1H-tetrazole)6](BF4)2. The spin-crossover temperature was identified to be 105 K. A conformal structural transformation was found in [Zn(1-propyl-1H-tetrazole)6](BF4)2 between 170 and 90 K by positronium lifetime measurement and the role of (BF4)2− anion, in this transformation, was proved by19F NMR spectroscopy.

Removal of Iodine and Methyl Iodide in Gas by Wetted-Wall Reactor Based on Selective Electron Attachment.

An electron attachment reaction, which produces a negative ion by the collision between an electron and a gas molecule, can be applied to gas purification because this reaction has a very high selectivity depending on the electron energy, the structure of the gas molecules and its electron affinity. In this study, a wetted-wall reactor using corona discharge was proposed and experiments involving removal of dilute iodine and methyl iodide from nitrogen were conducted. A deposition-type reactor using the discharge, which had been previously proposed by the authors, showed removal limitations of iodine and methyl iodide. On the other hand, in the removal of iodine by the wetted-wall reactor, negative ions produced by electron attachment were absorbed into the liquid film on the anode resulting in the change of chemical species in the liquid so that gas absorption increased to raise the removal efficiency. Since iodine produced by the dissociative electron attachment of methyl iodide inhibited the removal of methyl iodide, it was effective to prevent the formation of iodine in the reactor for pursuing high removal efficiency of methyl iodide. In the removal of methyl iodide by the wetted-wall reactor, the reaction byproduct, iodine, was not produced in the reactor, and the removal efficiency became high compared with the deposition-type reactor.

In-Situ and Ex-Situ Studies of Silicon Interfaces and Nanostructures by Ellipsometry and Rds

AbstractWe report surface-induced optical anisotropy (SIOA) spectra and dielectric function data of vicinal Si(001) surfaces using reflectance-difference spectroscopy (RDS) and spectroscopic ellipsometry (SE). To find the main contributions of the optical response we took data for clean and by hydrogen, oxygen, and arsenic modified surfaces. The SIOA lineshapes, as measured by reflectance-difference (RD) spectroscopy, can be either derivative-like or similar to the dielectric function as measured by SE. The derivative-like spectra appear to be associated with step contributions while the dielectric-function-like behavior appears to arise from terrace dimers and/or changes in chemical species bonded to the steps. In addition, we present SE data of silicon nanostructures formed by electrochemical etching and find that their behavior is dominated by interface properties.

Mössbauer Studies of Adsorption and Thermal Treatment of Fe3+ Ions on Silica-Gel, Al2O3 and Natrolite

Mossbauer studies of Fe 3+ ions on Si-gel, Al 2 O 3 and a natural zeolite mineral natrolite, treated with Fe(NO 3 ) 3 and FeCl 3 solutions and subsequently heated in steps upto 950°C, have been carried out to study the adsorption and change of chemical species caused by thermal treatment. It is inferred that iron ions exist as superparamagnetic particles of α-FeOOH on all the surfaces studied upto 200°C. Further heating to 400°C, transforms it partly into fine particles of α-Fe 2 O 3 , the conversion however, becoming complete by 600°C. At 800–950°C, Fe 3+ enters the Al 2 O 3 lattice substitutionally, while in the case of Si-gel, α-Fe 2 O 3 particles register an increase in crystallite size only. In the case of natrolite, there results particles of α-Fe 2 O 3 with size greater than 150 A, when heated to 800–950°C.