Showing papers on "Oxalic acid published in 2010"

Facile synthesized nanorod structured vanadium pentoxide for high-rate lithium batteries

Abstract: Nano-structured vanadium oxide (V2O5) is fabricated via a facile thermal-decomposition of vanadium precursor, vanadyl oxalate, which is produced by reacting micro-sized V2O5 with oxalic acid. The V2O5 nanoparticles produced by this method exhibit much better electrochemical performance than commercial micro-sized V2O5. The optimized-nanorod electrodes give the best specific discharge capacities of 270 mAh g−1 at C/2 (147 mA g−1) coupled with good cycle stability with only 0.32% fading per cycle. Even at a high rate of 4C (1176 mA g−1), the nanorod electrode still delivers 198 mAh g−1. These results suggest that the well-separated V2O5 nanorod is a good cathode material for high-rate lithium battery applications.

FeOOH catalytic ozonation of oxalic acid and the effect of phosphate binding on its catalytic activity

Abstract: The catalytic activity of FeOOH on ozonation of oxalic acid at pH 4.0 and 7.0 conditions was investigated in a semi-continuous experimental mode. The results indicate that FeOOH can effectively promote the generation of hydroxyl radicals ( OH) under acidic and neutral pH conditions, resulting in the enhancement of the degradation efficiency of oxalic acid by ozone. It is deduced that the hydroxyl groups both of in neutral state (Me-OH) and positive charge state (Me-OH2+) can perform as the active sites for ozone decomposition into hydroxyl radicals generation. The ligand exchange of hydroxyl groups by phosphate adsorption deteriorates the catalytic activity of FeOOH on ozonation, but the phosphate is found to desorb from FeOOH during the catalytic ozonation process, resulting in the reactivation of the catalytic activity of FeOOH.

Molecular distributions of dicarboxylic acids, ketocarboxylic acids and α-dicarbonyls in biomass burning aerosols : implications for photochemical production and degradation in smoke layers

Abstract: Aerosols in the size class 2 –C 11 ) and related compounds (ketocarboxylic acids and α-dicarbonyls) were identified using gas chromatography (GC) and GC/mass spectrometry (GC/MS). Among the species detected, oxalic acid was found to be the most abundant, followed by succinic, malonic and glyoxylic acids. Average concentrations of total dicarboxylic acids, ketocarboxylic acids and α-dicarbonyls in the aerosol samples were 2180, 167 and 56 ng m −3 , respectively. These are 2–8, 3–11 and 2–16 times higher, respectively, than those reported in urban aerosols, such as in 14 Chinese megacities. Higher ratios of dicarboxylic acids and related compounds to biomass burning tracers (levoglucosan and K + ) were found in the daytime than in the nighttime, suggesting the importance of photochemical production. On the other hand, higher ratios of oxalic acid to other dicarboxylic acids and related compounds normalized to biomass burning tracers (levoglucosan and K + ) in the daytime provide evidence for the possible degradation of dicarboxylic acids (≥C 3 ) in this smoke-polluted environment. Assuming that these and related compounds are photo-chemically oxidized to oxalic acid in the daytime, and given their linear relationship, they could account for, on average, 77% of the formation of oxalic acid. The remaining portion of oxalic acid may have been directly emitted from biomass burning as suggested by a good correlation with the biomass burning tracers (K + , CO and EC a ) and organic carbon (OC). However, photochemical production from other precursors could not be excluded.

C2H5OH sensing characteristics of various Co3O4 nanostructures prepared by solvothermal reaction

Abstract: Various morphologies of Co-containing precursors such as nanorods, nanosheets, and nanocubes were prepared by controlling the solvothermal reaction using cobalt acetate, L(+)-lysine, and oxalic acid, all of which were successfully converted into Co 3 O 4 nanostructures without morphological variation. The gas responses of these Co 3 O 4 nanosheets, nanorods, and nanocubes to 100 ppm C 2 H 5 OH at 300 °C were 10.5, 4.7, and 4.5 times higher than those of the Co 3 O 4 agglomerated nanopowders, respectively. In addition, the selectivity to C 2 H 5 OH over CO and H 2 , as well as the response/recovery kinetics, were significantly improved. These enhanced gas-sensing characteristics were attributed to the less agglomerated nanostructures of the sensing materials.

Enhancement of photocatalytic oxidation of oxalic acid by gold modified WO3/TiO2 photocatalysts under UV and visible light irradiation

Abstract: The photooxidation of oxalic acid, catalyzed by nanosized TiO2 or WO3 and composite photocatalysts: Au/TiO2, Au/WO3, WO3/TiO2, Au/WO3/TiO2 was studied under irradiation with UV, visible and combined UV–visible light. The catalysts were characterized by the XRD, XPS, SEM and TEM methods. The photocatalytic mineralization of oxalic acid, catalyzed by WO3/TiO2 or Au/WO3/TiO2, proceeded at a significantly higher rate under UV-A irradiation than that under visible light. This is due to the lower specific surface area of the WO3 and its small amount in the composite catalyst. Doping of the semiconductor materials with gold nanoparticles more than doubles the rates of mineralization of oxalic acid, compared to the un-doped samples, and more significantly in the case of Au/WO3/TiO2. The higher rate constants of oxalic acid decomposition under UV, visible or UV–visible light irradiation with the WO3/TiO2 and Au/WO3/TiO2 catalysts, compared with those measured with the individual oxide photocatalysts, are due to the more efficient separation of the electron–hole charges generated upon irradiation. Especially efficient is the charge separation in the case of the Au/WO3/TiO2 photocatalyst under irradiation with UV or combined UV–visible light, when the rate constants of oxalic acid destruction are approximately 1.7 times higher than that of the process catalyzed by Au/TiO2 and 3 times higher than that catalyzed by pure TiO2.

HPLC organic acid analysis in different citrus juices under reversed phase conditions.

Abstract: A reversed phase HPLC method for separation and quantification of organic acids (oxalic, citric, tartaric, malic, ascorbic and lactic acids) in fruit juices was developed. The chromatographic separation was performed with a Surveyor Thermo Electron system at 10C by using potassium dihydrogen orthophosphate buffer (pH 2.8) as mobile phase, an Hypersil Gold aQ Analytical Column and diode array detection at ?=254 nm for ascorbic acid and ?=214 nm for the other organic acids. Organic acid profiles of ten species of Citrus: sweet orange, minneola, clementine, mandarin orange, pomelo, lemon, lime, sweetie, white and pink grapefruit were established. Species significantly affect the organic acid distribution of citrus fruit juices. In all citrus juices, the most abundant organic acid was citric acid, ranging from 6.88 to 73.93 g/l. Citrus juices are good sources of ascorbic acid (0.215-0.718 g/l). Average ascorbic acid was the highest in lemon juice followed by sweet orange juice, sweetie and white grapefruit.

In situ 2,5-pyrazinedicarboxylate and oxalate ligands synthesis leading to a microporous europium–organic framework capable of selective sensing of small molecules

Abstract: A new microporous europium-containing metal–organic framework [Eu2(μ2-pzdc)(μ4-pzdc)(μ2-ox)(H2O)4]·8H2O (1) (H2pzdc = 2,5-pyrazinedicarboxylic acid, H2ox = oxalic acid) has been hydrothermally synthesized via an unprecedented in situ formation of 2,5-pyrazinedicarboxylate (pzdc) and oxalate (ox) ligands. Structure 1 was characterized by both single-crystal and powder X-ray diffraction analysis. It can be described as a 4-connected binodal Moganite network with the Schlafli symbol of (4·64·8)2(42·62·82), which exhibits a reversible and highly selective sensing function with respect to acetone.

Synthesis, Crystal Structure, and Photoluminescence of a Series of Zinc(II) Coordination Polymers with 1,4-Di(1H imidazol-4-yl)benzene and Varied Carboxylate Ligands

Abstract: Six new coordination polymers [Zn2(L)(OX)2] (1), [Zn2(L)(1,2-BDC)2]·2H2O (2), [Zn2(L)(1,3-BDC)2(H2O)] (3), [Zn(L)(1,4-BDC)] (4), [Zn2(L)(BPDA)2]·2.68H2O (5), and [Zn3(L)2(BTC)2(H2O)2]·3H2O (6) were obtained by hydrothermal reactions of zinc(II) sulfate heptahydrate with rigid ditopic ligand 1,4-di(1H-imidazol-4-yl)benzene (L), sodium hydroxide, or tetrabutylammonium hydroxide and the corresponding carboxylic acid, namely, oxalic acid, 1,2-benzenedicarboxylic acid, 1,3-benzenedicarboxylic acid, 1,4-benzenedicarboxylic acid, 4,4′-biphenyldicarboxylic acid, or 1,3,5-benzenetricarboxylic acid, respectively. The complexes were characterized by single-crystal X-ray diffraction, IR, thermogravimetric, and elemental analyses. Complexes 1 and 2 are three-dimensional (3D) frameworks with infinite two-dimensional (2D) networks pillared by L ligands, and 1 possesses rare self-penetrating mab topology, while 2 shows ins topology. Complex 3 is a 2D bilayer network with infinite one-dimensional double Zn(II)-1,3-BDC2− c...

Reduction of Energy Requirement of CO2 Desorption by Adding Acid into CO2-Loaded Solvent†

Abstract: The effect of the addition of weak acids into CO2-loaded solvents or rich solvents on the energy requirement of CO2 desorption was investigated experimentally. The commercially available CO2 solvent monoethanolamine (MEA) was used to absorb different amounts of CO2. Subsequently, a few weak acids such as suberic acid, phthalic acid, and oxalic acid were added into the solvents to study the effect of acid amount on the rate of CO2 release. It was found that CO2 could be released much faster and in much larger quantity with the addition of weak acids while the other desorption conditions were maintained the same. The amount of CO2 released was found to be proportional to the amount of acid added. Acid addition could be potentially used to reduce the energy requirement for CO2 desorption from solvent.

Influence of different heat treatments on the surface properties and catalytic performance of carbon nanotube in ozonation

Abstract: The influences of treatment conditions, gas atmosphere (N2 and H2) and temperature (450 °C and 950 °C), on the surface properties and catalytic performance of carbon nanotube (CNT) were investigated for the degradation of oxalic acid in aqueous solution by the process of catalytic ozonation. No obvious change on the textural properties of CNT is found after heat treatment, while the results of Boehm titration clearly indicate the reduction of acidic groups and the increase of basic groups on CNT surface after heat treatment under different conditions, and then a significant improvement on oxalic acid removal by CNT catalytic ozonation is obtained. The heat treatment of CNT under H2 atmosphere is more effective in eliminating acidic groups and increasing basic groups than the case of N2 atmosphere at the same temperature, which results in higher catalytic activity and lower total organic carbon (TOC) release in ozonation correspondingly. A linear relationship is observed between the pH at the point of zero charge (pHPZC) of CNT and the rate constant for ozonation of oxalic acid in the presence of CNT with different treatments. It is suggested that heat treatment can increase the basic property of CNT, which can enhance the contribution of surface reactions to the whole reactions for ozonation of oxalic acid.

Formation and properties of hydrogen-bonded complexes of common organic oxalic acid with atmospheric nucleation precursors

Abstract: Nucleation in the Earth’s atmosphere plays a vital role in the aerosol radiative forcing associated directly with the production of ultrafine particles responsible for adverse public health impacts and global climate changes. In the present work, the interaction of the common organic oxalic acid with the atmospheric nucleation precursors and trace ionic species has been investigated using the Density Functional Theory (DFT). A comprehensive study of the hydrogen-bonded complexes of oxalic acid with neutral monomers and ionic clusters of the sulfuric acid, water and ammonia, the key atmospheric nucleation precursors, has been carried out. We found that the bonding of the oxalic acid with the above-mentioned neutrals is moderately weak, and thus, the oxalic acid cannot stabilize the binary sulfuric acid–water and ternary sulfuric acid–ammonia clusters. The interaction of the oxalic acid with positive ionic species is, in contrast, strong and significantly enhances stability of the clusters formed over the ions. The hydration of positively charged (C2H2O4)(H3O+), ( C 2 H 2 O 4 ) ( NH 4 + ) and (C2H2O4)(H3O+)(H2SO4) clusters is also strong and close to that of the sulfuric acid, the key atmospheric nucleation precursor. These considerations lead us to a logical conclusion that the oxalic acid can catalyse the production of positively charged pre-nucleation clusters and, thus, its role in nucleation of positive ions in the Earth’s troposphere should be studied in further details.

The Key Physiological Response to Alkali Stress by the Alkali-Resistant Halophyte Puccinellia tenuiflora is the Accumulation of Large Quantities of Organic Acids and into the Rhyzosphere

Abstract: Eight-week-old seedlings of Puccinellia tenuiflora were stressed by exposure to 1: 1 molar ratio mixtures either of the two neutral salts NaCl and Na 2 SO 4 or of the two alkali salts, NaHCO 3 and Na 2 CO 3 . To identify the physiological mechanisms involved in this plant's resistance to alkali stress, the relative growth rates, the quantities and compositions of organic acids accumulated and secreted through the roots into the rhyzosphere, the concentrations of inorganic ions, proline and other solutes accumulating in the shoots were measured. The results show that the organic acid constituents in the shoots and roots were much the same. These were predominantly malic acid, oxalic acid, citric acid and succinic acid. The total concentration of organic acids in the shoots increased strongly with increasing alkali stress. However, these either did not increase or they decreased slightly with increasing salt stress. Of the four organic acids, the concentration difference between salt- and alkali-stressed plants was most striking for citric acid. This became the dominant organic acid component under alkali stress. Results show that proline is the main organic osmolyte, whereas the contribution of betaine to osmotic adjustment is insignificant under either salt or alkali stress. The main organic acid accumulated was not only an important organic osmotic regulator, but also an important negative charge contributor, playing important roles in ionic balance and pH adjustment. The concentrations of Na + , K + , Cl - and of organic acid were 80.7% of all solutes under salt stress. The concentrations of Na + , K + , Cl - and of organic acid were 85.4% of all solutes under alkali stresses. The ionic balance was disrupted by the strong increase in Na + content under alkali stress. This perhaps explains why large amounts of the organic acids were accumulated. The organic acid concentration in the roots was lower than in the shoots. The roots secreted citric acid into the rhyzosphere only under alkali stress, secretion of the other organic acids was not detected. Therefore, citric acid secreted from the roots probably plays an important role in pH adjustment in the rhyzosphere of P. tenuiflora.

Charge Density Analysis of Crystals of Nicotinamide with Salicylic Acid and Oxalic Acid: An Insight into the Salt to Cocrystal Continuum

Abstract: Charge density analysis from both experimental and theoretical points of view on two molecular complexes: one is formed between nicotinamide and salicylic acid, and the other formed between nicotinamide and oxalic acid brings out the quantitative topological features to distinguish a cocrystal from a salt.