Decomposition Yield Research Articles

Treatment of water contaminated with diphenolic acid by gamma radiation in the presence of different compounds

The elimination of diphenolic acid (DPA) from contaminated water is an urgent challenge. The aim of this study was to investigate DPA degradation by gamma radiation, studying the influence of the dose rate, initial DPA concentration, solution pH, the presence of O2, and the presence of different additives (e.g., Br−, Cl−, CO32-,NO2-,NO3-,andSO42-). A further objective was to study the effect of the water matrix (ultrapure water, surface water, and wastewater) and the variation in total organic carbon and toxicity as a function of absorbed dose. Results obtained showed that: gamma radiation was effective to remove DPA from aqueous solution; the dose constant was slightly dependent on the dose rate; and the solution pH had a major influence on DPA degradation, which was highest at pH 7. DPA degradation was reduced in the presence of Br−, Cl−, CO32-,NO2-,NO3-,andSO42- and was lower with higher concentrations of these species, largely due to their competition with DPA for the reactive radicals generated, especially HO. Lower yield of DPA decomposition were obtained with wastewater and surface water than with ultrapure water due to the presence of organic matter and HCO3-,Cl-,SO42-,andNO3- ions, which react with the reactive radical species (HO, H and eaq-). The TOC and toxicity of the medium decreased during DPA degradation in all water types studied.

Synthesis of hybrid carbon nanotubes using Brassica juncea L. application to photodegradation of bisphenol A

Hyperaccumulators contain tubular cellulose and heavy metals, which can be used as the sources of carbon and metals to synthesize nanomaterials. In this paper, carbon nanotubes (CNTs), Cu(0.05)Zn(0.95)O nanoparticles, and CNTs/Cu(0.05)Zn(0.95)O nanocomposites were synthesized using Brassica juncea L. plants, and the ultraviolet (UV)-light-driven photocatalytic degradations of bisphenol A (BPA) using them as photocatalysts were studied. It was found that the outer diameter of CNTs was around 50 nm and there were a few defects in the crystal lattice. The synthesized Cu(0.05)Zn(0.95)O nanocomposites had a diameter of around 40 nm. Cu(0.05)Zn(0.95)O nanocomposites have grown on the surface of the CNTs and the outer diameter of them was around 100 nm. The synthesized hybrid carbon nanotubes using B. juncea could enhance the efficiency of photocatalytic degradation on BPA. The complete equilibration time of adsorption/desorption of BPA onto the surface of CNTs, Cu(0.05)Zn(0.95)O nanoparticles, and CNTs/Cu(0.05)Zn(0.95)O nanocomposites was within 30, 20, and 30 min, and approximately 14.9, 8.7, and 17.4 % BPA was adsorbed by them, respectively. The combination of UV light irradiation (90 min) with CNTs, Cu(0.05)Zn(0.95)O nanoparticles, and CNTs/Cu(0.05)Zn(0.95)O nanocomposites could lead to 48.3, 75.7, and 92.6 % decomposition yields of BPA, respectively. These findings constitute a new insight for synthesizing nanocatalyst by reusing hyperaccumulators.

New insights into the methanol oxidation mechanism over Au/CeO2 catalyst through complementary kinetic and FTIR operando SSITKA approaches

The mechanism of methanol full oxidation over Au/CeO2 in the low temperature range has been clarified combining FT-IR spectroscopic results with kinetic calculations. A clear thermal effect of the infrared beam on the catalytic reaction was remarked and quantified. A global mechanistic model was proposed, providing the reaction order, the kinetic constants and the activation energy for the process, as well as valuable information on selected elemental steps. SSITKA experiments gave additional evidences on the formate decomposition as the rate determining step (RDS) of the reaction and proved the strict correlation between formate decomposition and CO2 yield, at different temperatures, further validating the kinetic model and differentiating the activation energy of the RDS from the apparent activation energy of the process as a whole.

High temperature oxygen separation for the sulphur family of thermochemical cycles - part I: Membrane selection and flux testing

This work investigates the feasibility of applying high temperature oxygen separation to the sulphuric acid decomposition process, a common step in the Sulphur Iodine and Hybrid Sulphur thermochemical cycles for massive scale hydrogen production. Process simulations indicate that the decomposition yield can be increased from 62.3% to 90.1% by using a catalytic membrane reactor. Equilibrium calculations show yttria-stabilised zirconia (YSZ), combined with platinum electrodes, to be a candidate membrane for the separation process. Bespoke experimental apparatus was designed and commissioned in order to investigate the oxygen flux through YSZ membranes in the presence of sulphur dioxide, during external voltage application. Results from an experiment at 900 °C show that oxygen permeation through YSZ membranes occurs under these conditions. X-ray diffraction and impedance spectroscopy are used to investigate the reason for the oxygen flux decrease with time.

Quantum yields of decomposition and homo-dimerization of solid L-alanine induced by 7.2 eV Vacuum ultraviolet light irradiation: an estimate of the half-life of L-alanine on the surface of space objects.

One of the leading hypotheses regarding the origin of prebiotic molecules on primitive Earth is that they formed from inorganic molecules in extraterrestrial environments and were delivered by meteorites, space dust and comets. To evaluate the availability of extraterrestrial amino acids, it is necessary to examine their decomposition and oligomerization rates as induced by extraterrestrial energy sources, such as vacuum ultraviolet (VUV) and X-ray photons and high energy particles. This paper reports the quantum yields of decomposition ((8.2 ± 0.7) × 10(-2) photon(-1)) and homo-dimerization ((1.2 ± 0.3) × 10(-3) photon(-1)) and decomposition of the dimer (0.24 ± 0.06 photon(-1)) of solid L-alanine (Ala) induced by VUV light with an energy of 7.2 eV. Using these quantum yields, the half-life of L-Ala on the surface of a space object in the present earth orbit was estimated to be about 52 days, even when only photons with an energy of 7.2 eV emitted from the present Sun were considered. The actual half-life of solid L-Ala on the surface of a space object orbit around the present day Earth would certainly be much shorter than our estimate, because of the added effect of photons and particles of other energies. Thus, we propose that L-Ala needs to be shielded from solar VUV in protected environments, such as the interior of a meteorite, within a time scale of days after synthesis to ensure its arrival on the primitive Earth.

Adsorption of Organophosphates into Microporous and Mesoporous NaX Zeolites and Subsequent Chemistry

Due to the neurotoxicity of organophosphate (OP) pesticides and nerve agents synthesized as military or terror agents, their safe destruction and disposal is of considerable current importance. A representative OP, trimethyl phosphate (TMP), was adsorbed onto NaX zeolite, two mesoporous modifications, and a low-silica X zeolite. The nucleophilic chemical reactions of TMP with the zeolites were investigated by solid-state 13C and 31P nuclear magnetic resonance (NMR) and the solvent extracts by 1H, 13C, and 31P NMR. Nucleophilic substitution and subsequent hydrolysis reaction schemes are proposed. All of the zeolites have similar TMP decomposition yields, supporting the hypothesis that slow or incomplete diffusion of TMP in the microporous zeolite regions limits TMP decomposition.

Decomposição e dinâmica de liberação de nitrogênio e fósforo de frações vegetais de Salvinia auriculata Aubl. em um reservatório da Amazônia legal

This study aimed to determine the decomposition coefficients of the submerged (SP) and aerial part (AP) of S. auriculata at two different depths within water column (surface and sediment). It also quantified the decomposition yield of S. auriculata and the temporal changes of nitrogen and phosphorous content of the remaining biomass. The macrophytes were fractionated in parts and were dried in sequence until attaining constant weight. The litterbags with plant material were incubated in the reservoir of UHE Lajeado. The results of mass loss showed that there were no significant differences among the AP-sed and AP-sur (p > 0.05). However, the AP-sed was significantly different from SP-sed (p -1 and AP-sur a k of 0.0067 day -1 . The SP-sed presented a k of 0.0027 day -1 and the SP-sur 0.0040 day -1 . It was also noticed that during the first days of decomposition great amounts of nitrogen and phosphorous were solubilized. This event was related to the leachate process; from the 14th day of decomposition, an increasing trend was observed in nitrogen concentrations. This fact was probably related to detritus enrichment by microbial colonization.

Photolysis of gaseous butyl acetate using built-in microwave discharge electrodeless lamps

This paper examined the photolysis of gaseous butyl acetate by built-in microwave discharge electrodeless lamps. Bromine and iodine lamps were used to investigate the effects of microwave input power, inlet concentration, gas residence time, and different filling materials on butyl acetate decomposition and energy yield. Water vapor and ammonia were utilized as additional chemicals to determine if they can improve removal efficiency. Built-in structure and external structure were also compared. When the gas flow velocity is 0.025m/s, and the inlet concentration is 1.5mg/m3, the removal efficiency of butyl acetate can reach over 78%, which is the highest in this study. Additional water vapor and ammonia can hardly improve the degradation. To some extent, built-in MDELs are better than external MDELs. The results will help promote the study of microwave discharge electrodeless lamps and their effect on the degradation of gaseous pollutants. Maybe, as the research goes on, it could realize the span from laboratory scale to practical application, and will become an advanced technology for the gaseous pollutants control.

Review and model-based analysis of factors influencing soil carbon sequestration under hybrid poplar

The potential for soil carbon (C) sequestration under short-rotation woody crops, like hybrid poplar (Populus spp.), is a significant uncertainty in our understanding of how managed tree plantations might be used to partially offset increasing atmospheric CO2 concentrations. Through development of a multi-compartment model, we reviewed information from studies on hybrid poplar and analyzed the potential impact of changes in plant traits and nitrogen (N) fertilization on soil C storage. For a hypothetical setting in the southeastern U.S.A., and starting from soils that are relatively depleted in organic matter (2.5 kg C m−2), the model predicted an increase in mineral soil C stocks (1.7 kg C m−2) over four 7-year rotations of hybrid poplar. However, at the end of the fourth rotation, both cumulative soil C gains and annual rates of soil C accrual (23–93 g C m−2 yr−1) varied widely depending on fertilization rate, biomass yield, and rates of dead root decomposition (three factors that were examined in a factorial model-based experiment). Our analysis indicated that processes linked to genetically modifiable poplar traits (aboveground biomass production, belowground C allocation, root decomposition) are potential controls on soil C sequestration. Key measures of model performance were sensitive to how aboveground biomass production responded to N fertilization. Site specific properties that were independent of plant traits were also important to predicted soil C accumulation and point to possible genotype x site interactions that may explain contradictory data from both empirical and theoretical studies of C sequestration under hybrid poplar plantations.

ChemInform Abstract: Regioselective Fischer Indole Route to 3-Unsubstituted Indoles.

Use of Eaton's reagent (P 2 O 5 /MeSO 3 H) as acide catalyst in the Fischer indole reaction using methyl ketones provides unprecedented regiocontrol to form the 3-unsubstituted indoles. In several instances where the harshness of the reagent causes decomposition and low yields, dilution in sulfolane or dichloromethane results in far less degradation and higher yields of indoles. Steric effects and the acidity of the medium are the two major factors that control the regioselectivity. The role of the P 2 O 5 in the reagent mixture P 2 O 5 /MeSO 3 H is simply as a drying agent when used as catalyst for the Fischer indole reaction

Decomposition of halophenols in room-temperature ionic liquids by ionizing radiation

In this article, we report the reaction of halophenols with solvated electrons in room-temperature ionic liquids (RTILs) initiated by γ-ray and pulsed electron radiolyses. The decomposition G-values of ortho-chlorophenol (CP) in N-methyl- N-propylpyrrolidinium–bis(trifluoromethanesulfonyl)imide (TFSI), N-butyl- N-methylpyrrolidinium–TFSI and N-methyl- N-propylpiperidinium–TFSI were estimated to be 1.4, 1.6, and 1.7 molecules 10 −2 eV −1 under γ-ray irradiation; these values were almost the same as the yield of solvated electron formation. The second-order rate constant for the reaction of CP with solvated electrons in diethylmethyl(2-methoxyethyl)ammonium (DEMMA)–tetrafluoroborate (BF 4) was one order of magnitude lower than that in DEMMA–TFSI although the G-values of CP decomposition and phenol formation in DEMMA-BF 4 were higher. The decomposition yield of ortho-iodophenol in DEMMA–TFSI was slightly higher than that of the other halophenol ( ortho-fluorophenol, CP, and ortho-bromophenol), and the formation yield of phenol for the decomposition of only ortho-fluorophenol was lower.

Catalytic decomposition of liquid hydrocarbons in an aerosol reactor: A potential solar route to hydrogen production

Catalytic decomposition of liquid fuels (n-octane, iso-octane, 1-octene, toluene and methylcyclohexane) is achieved in a continuous tubular aerosol reactor as a model for the solar initiated production of hydrogen, and easily separable CO free carbonaceous aerosol product. The effects of fuel molecular structure and catalyst concentration on the overall hydrogen yield were studied. Iron aerosol particles used as the catalysts, were produced on-the-fly by thermal decomposition of iron pentacarbonyl. The addition of iron catalyst significantly decreases the onset temperature of hydrogen generation as well as improves the reaction kinetics by lowering the reaction activation energy. The activation energy without and with iron addition was 260 and 100 kJ/mol, respectively representing a decrease of over 60%. We find that with the addition of iron, toluene exhibits the highest hydrogen yield enhancement at 900 °C, with a 6 times yield increase over thermal decomposition. The highest H 2 yield obtained was 81% of the theoretical possible, for n-octane at 1050 °C. The general trend in hydrogen yield enhancement is that the higher the non-catalytic thermal decomposition yield, the weaker the catalytic enhancement. The gaseous decomposition products were characterized using a mass spectrometer. An XRD analysis was conducted on the wall deposit to determine the product composition and samples for electron-microscopic analysis were collected exiting the furnace by electrostatically precipitating the aerosol onto a TEM grid.

Degradation of pharmaceutical compound pentoxifylline in water by non-thermal plasma treatment

The decomposition of a model pharmaceutical compound, pentoxifylline, in aqueous solution was investigated using a dielectric barrier discharge (DBD) in coaxial configuration, operated in pulsed regime, at atmospheric pressure and room temperature. The solution was made to flow as a film over the surface of the inner electrode of the plasma reactor, so the discharge was generated at the gas–liquid interface. Oxygen was introduced with a flow rate of 600 sccm. After 60 min plasma treatment 92.5% removal of pentoxifylline was achieved and the corresponding decomposition yield was 16 g/kWh. It was found that pentoxifylline degradation depended on the initial concentration of the compound, being faster for lower concentrations. Faster decomposition of pentoxifylline could be also achieved by increasing the pulse repetition rate, and implicitly the power introduced in the discharge, however, this had little effect on the decomposition yield. The degradation products were investigated by liquid chromatography–mass spectrometry technique (LC–MS). The evolution of the intermediates during plasma treatment showed a fast increase in the first 30 min, followed by a slower decrease, so that these products are almost completely removed after 120 min treatment time.

Food waste decomposition in leachbed reactor: Role of neutralizing solutions on the leachate quality

The neutralization effects of 0.1 M NaHCO 3, KPO 4-buffer (pH 7.0) and sodium acetate (NaOAc) solutions (500 ml/kg food waste/day) on controlling the pH and leachate quality in an acidogenic reactor of food waste anaerobic digestion was investigated. pH of leachate from the reactor was low and ranged from 3.24 to 4.15. Although differences in chemical oxygen demand (COD) were observed, the cumulative COD yields were almost similar. Ammonia concentrations gradually decreased from 26 to 3 mg/l after 15 days. Acetic acid was the major fraction and the total VFAs decreased gradually for a week and increased thereafter, with a sharp increase in NaOAc treatment. VFAs yield and acetate/propionate ratio were the highest in NaOAc treatment, followed by NaHCO 3 and KPO 4 treatments. Volatile solids reduction was the lowest in NaOAc treatment (47.5%) and highest in NaHCO 3 treatment (67.0%). With lower decomposition and higher yield of VFA and COD, NaOAc could be used as a neutralizing agent in acidogenic reactors to improve the efficiency of the acidogenesis process.

Quantitative image‐based spectral reconstruction for computed tomography

Computed tomography (CT) devices are routinely employed to obtain three-dimensional images of the human body. The reconstructed CT numbers represent weighted x-ray attenuation coefficients. Their spectral weighting is influenced by the selected x-ray source spectrum, the detector characteristics, and the attenuating object itself. The quantitative ground truth of the scanned object is given by the spectral attenuation coefficient. It is not directly measurable in standard CT. For spectral CT measurements, algorithms like the basis material decomposition yield parametrized representations of the spectral mass attenuation coefficient. In practical applications, image-based formulations are commonly used. They are affected by both the CT system characteristics and the object self-attenuation effects. In this article the authors introduce an image-based spectral CT method. It expresses measured CT data as a spectral integration of the spectral attenuation coefficient multiplied by a local weighting function (LWF). The LWF represents the local energy weighting in the image domain, taking into account the system and reconstruction properties and the object self-attenuation. A generalized image-based formulation of spectral CT algorithms is obtained, with no need for additional corrections of, e.g., beam hardening. The iterative procedure called local spectral reconstruction yields both the mass attenuation coefficients of the object and a representation of the LWF. The quantitative accuracy and precision of the method are investigated in several applications: First, beam hardening corrections to various target energy weightings and attenuation correction maps for SPECT/CT and PET/CT are calculated. Second, an iodine density evaluation is performed. Finally, a direct identification of spectral attenuation functions using the LWF result is demonstrated. In all applications, the ground truth of the objects is reproduced with a quantitative accuracy in the subpercent to 2% range. An exponential convergence behavior of the iterative procedure is observed, with one to two iteration steps as a good compromise between quantitative accuracy and precision. The authors conclude that the method can be used to perform image-based spectral CT reconstructions with quantitative accuracy. Existing algorithms benefit from the intrinsic treatment of beam hardening and system properties. Novel algorithms are enabled to directly compare material model functions to spectral measurement data.

Ultrafast time‐resolved studies of the photochemistry of diazo carbonyl compounds

AbstractThe rich photochemistry of diazo carbonyl compounds in solution has been extensively studied by ultrafast transient absorption spectroscopy with UV–Vis and mid‐IR detection. Both, stepwise (carbene mediated) and concerted Wolff rearrangement (WR) mechanisms have been confirmed for cyclic and acyclic diazo carbonyl precursors. Cyclic diazo‐carbonyl compounds are structurally locked in a syn conformation and mainly follow the concerted mechanism, however, a stepwise pathway does slightly contribute to the overall WR process, contrary to Kaplan's rule. With acyclic diazo ester carbonyl compounds, the WR process is dominated by the stepwise mechanism. A carbene–carbene interconversion process and singlet to triplet carbene intersystem crossing (ISC) processes are discussed in this review. The growth of secondary species (cations, ylides, OH insertion product) emerging from an interaction between a singlet carbene and solvent molecules has been characterized by picosecond time‐resolved UV–Vis transient absorption spectroscopy. Carbene reactivity results in shortening of the singlet carbene lifetime relative to more inert solvents. The quantum yield of diazo decomposition can be deduced from partial ground state bleach recovery using ultrafast time‐resolved IR spectroscopy. Copyright © 2009 John Wiley & Sons, Ltd.

Gamma irradiation of pharmaceutical compounds, nitroimidazoles, as a new alternative for water treatment

The main objectives of this study were: (1) to investigate the decomposition and mineralization of nitroimidazoles (Metronidazole [MNZ], Dimetridazole [DMZ], and Tinidazole [TNZ]) in waste and drinking water using gamma irradiation; (2) to study the decomposition kinetics of these nitroimidazoles; and (3) to evaluate the efficacy of nitroimidazole removal using radical promoters and scavengers. The results obtained showed that nitroimidazole concentrations decreased with increasing absorbed dose. No differences in irradiation kinetic constant were detected for any nitroimidazole studied (0.0014–0.0017 Gy −1). The decomposition yield was higher under acidic conditions than in neutral and alkaline media. Results obtained showed that, at appropriate concentrations, H 2O 2 accelerates MNZ degradation by generating additional HO ; however, when the dosage of H 2O 2 exceeds the optimal concentration, the efficacy of MNZ degradation is reduced. The presence of t-BuOH (HO radical scavenger) and thiourea (HO , H and e aq − scavenger) reduced the MNZ irradiation rate, indicating that degradation of this pollutant can take place via two pathways: oxidation by HO radicals and reduction by e aq − and H . MNZ removal rate was slightly lower in subterranean and surface waters than in ultrapure water and was markedly lower in wastewater. Regardless of the water chemical composition, MNZ gamma irradiation can achieve i) a decrease in the concentration of dissolved organic carbon, and ii) a reduction in the toxicity of the system with higher gamma absorbed dose.

Direct Observation of Acyl Azide Excited States and Their Decay Processes by Ultrafast Time Resolved Infrared Spectroscopy

The photochemistry of three carbonyl azides was studied by ultrafast time-resolved IR spectroscopy. Benzoyl, 2-naphthoyl, and pivavoyl azides are promoted to upper excited states S(n) with 270 nm excitation in chloroform. The S(n) states decay in 300 fs to form both the carbonylnitrenes and the S(1) excited states. The decay of the S(1) states of the carbonyl azides correlates with the growth of isocyanates. Formation of carbonylnitrene from S(1) is at most a minor process if it happens at all. The quantum yields of azide decomposition of these azides with 270 nm light are close to unity in chloroform.

Improvement of the Diluted Propane Efficiency Treatment Using a Non-thermal Plasma

The decomposition of propane diluted in air has been investigated using a pulsed high-voltage dielectric barrier discharges reactor. Effects of the temperature (from 300 to 800 K) and humidity in air on propane conversion and on produced species are studied. CO and CO2 are the two main carbon species produced but other carbon species can be also obtained as functions of electrical parameters or temperature. Total decomposition of inlet propane to CO2 is possible when propane is diluted in wet air from 600 K. Thermal energy is an important parameter to limit the energy density injected in the plasma reactor and to reduce the total energetic cost keeping a high propane decomposition yield.

Radiation-chemical removal of corrosion hydrogen from VVER first-loop coolant

Room-temperature γ radiolysis of water solutions of ammonia in the presence of hydrogen peroxide is studied. It is found that in de-aerated solutions the yield of hydrogen peroxide decomposition is 3.8–5.5 mol/100 eV depending on its initial concentration. In the absence of hydrogen peroxide, the yield of the decomposition of ammonia is 0.34–0.39 particles/100 eV; adding hydrogen peroxide to the solution increases the rate of decomposition of ammonia and saturation of the solution with hydrogen decreases it. The data obtained are used for mathematical simulation of the influence of hydrogen peroxide on the composition of the first-loop coolant of a hypothetical ship reactor facility with VVER where equipment corrodes with hydrogen being formed. It is shown that adding hydrogen peroxide to the coolant in molar concentration equal to that of corrosion hydrogen decreases the stationary concentration of hydrogen and ammonia to the level characteristic for the case where there is no equipment corrosion with hydrogen being formed in the loop.