Decomposition Of Oxalic Acid Research Articles

Coproduction of hydrogen peroxide and formic acid as potential hydrogen-carrier through photocatalytic reformation of sacrificial chemical

This study explores the challenges to photo-reforming sacrificial chemicals into beneficial by-products while improving photocatalytic activity in H2O2 production by addressing several issues. The resorcinol-formaldehyde/graphitic carbon nitride composite (RF0.2GCN) with nanosheet-like RF morphology achieved a higher degree of surface-to-surface contact through -C-NH-CH2- and -NH-CH-OH than the nanosphere (RF0.8GCN). The RF0.2GCN produced H2O2 at 325.2 µg g−1 s−1 in the presence of oxalic acid (OA) at pH 2.1 with apparent quantum yield (AQY) of 12.7 %. The conduction band position potential was +0.54 VNHE, which is thermodynamically unfavorable for H+/H2 (E°: 0.00 VNHE) and O2/·O2- (E°: −0.046 VNHE) reaction and also inhibits the decomposition of H2O2 (H2O2/·OH, E°: +0.39 VNHE). Furthermore, the decomposition of OA formed formic acid (FA) at 82 % selectivity and concurrent CO2·- formation could promote electron density in the conduction band via its electron-donating ability·H2O2 was purified by isolating FA using anion exchange resin, and FA was recovered by desorption from the resin using HCl (pH 3).

Unrecognized Role of Organic Acid in Natural Attenuation of Pollutants by Mackinawite (FeS): The Significance of Carbon-Center Free Radicals.

Organic acid is prevalent in underground environments and, against the backdrop of biogeochemical cycles on Earth, holds significant importance in the degradation of contaminants by redox-active minerals. While earlier studies on the role of organic acid in the generation of reactive oxygen species (ROS) primarily concentrated on electron shuttle or ligand effects, this study delves into the combined impacts of organic acid decomposition and Mackinawite (FeS) oxidation in contaminant transformation under dark aerobic conditions. Using bisphenol A (BPA) as a model, our findings showed that oxalic acid (OA) notably outperforms other acids in enhancing BPA removal, attaining a rate constant of 0.69 h-1. Mass spectrometry characterizations, coupled with anaerobic treatments, advocate for molecule-O2 activation as the principal mechanism behind pollutant transformation. Comprehensive results unveiled that carbon center radicals, initiated by hydroxyl radical (•OH) attack, serve as the primary agents in pollutant oxidation, accounting for at least 93.6% of the total •OH generation. This dynamic, driven by the decomposition of organic acids and the concurrent formation of carbon-centered radicals, ensures a steady supply of electrons for ROS generation. The obtained information highlights the importance of OA decomposition in the natural attenuation of pollutants and offers innovative strategies for FeS and organic acid-coupled decontamination.

Estimation of vanadium removal from calcification roasting-acid leaching tailings using ultrasonic-H2C2O4 synergistic technology

Metal vanadium smelting produces roasting-acid leaching tailings containing approximately 1% vanadium residue, making it challenging to store and recycle these waste tailings in an environmentally friendly manner. To address this issue, a clean method called ultrasonic-enhanced oxalic acid complexation was proposed in this study for efficient removal of residual vanadium. Under the optimal conditions, the removal rate of vanadium and the decomposition rate of oxalic acid reached 86.88% and 23.6%. An in-depth analysis on the experimental results in combination with thermodynamics found a virtuous cycle chain induced by ultrasonic cavitation. Ultrasonic waves facilitated the decomposition of oxalic acid, producing more CO2 to supplement the limited cavitation bubble nucleuses. Consequently, the cavitation effect was strengthened, leading to an increased yield of OH radicals. This resulted in a continuous improvement in the oxidation environment. Furthermore, the enhanced virtuous cycle generated by ultrasonic cavitation produced powerful microjets that facilitated the stripping and dispersion of mineral particles. Overall, the oxalic acid-ultrasonic leaching technique offers a clean and efficient technology for separating vanadium.

Enhanced performance and stability of Cu/ZnO catalyst by hydrophobic treatment for low-temperature methanol synthesis from CO2

CO2 hydrogenation to methanol is an efficient way to utilize CO2 and store hydrogen. However, realizing high activity and methanol selectivity as well as excellent stability are still challenges due to the competitive reverse water-gas shift (RWGS) reaction and the accumulation of water on the catalyst surface. Herein, Cu/ZnO catalyst was prepared by oxalic acid-assisted solid-state grinding method and then was subjected to hydrophobic treatment using stearic acid as a functionalization agent. The effect of stearic acid concentration on the physicochemical properties of Cu/ZnO catalysts and the catalytic activity for low-temperature CO2 hydrogenation to methanol was investigated and discussed in detail. Detailed catalyst characterizations disclosed that hydrophobic treatment using suitable concentration of stearic acid removed residues from the decomposition of oxalic acid and also increased specific surface area, surface basicity, reducibility and hydrogen adsorption strength on Cu/ZnO catalysts, leading to the enhanced catalytic performance and methanol selectivity. Among all the catalysts, Cu/Zn-2 mM catalyst exhibited methanol selectivity and methanol space time yield (STY) of 78.8% and 87.17 g/kg·h−1 at 200 ℃, much higher than those of untreated Cu/ZnO catalyst (71.7% and 68.93 g/kg·h−1). The hydrophobic Cu/Zn-2 mM catalyst also exhibited outstanding stability for low-temperature CO2 hydrogenation to methanol, keeping its activity for 100 h without obvious deactivation when compared to untreated Cu/ZnO catalyst. This facile hydrophobic treatment using stearic acid not also enhanced catalytic activity, methanol selectivity and stability of Cu/ZnO catalysts for low-temperature methanol synthesis, but also enlightened the invention of more hydrophobic materials in the near future.

Magnetic nano-size normal spinel-ZnFe2O4 and inverse spinel-MnFe2O4 for catalytic ozonation: Performance and mechanism

Spinel nanomaterials, as magnetic catalysts for catalytic ozonation, have gradually attracted the attention of researchers due to the easy-to-separate and recyclable properties. However, few studies have systematically studied the catalytic mechanism. Hence, normal spinel-ZnFe2O4 and inverse spinel-MnFe2O4 were prepared and applied to catalyze the ozonation of oxalic acid (OA) and phenol in this study. ZnFe2O4 and MnFe2O4 showed opposite catalytic abilities: MnFe2O4 performed better than ZnFe2O4 in OA decomposition and the TOC (total organic carbon) removal efficiency reached 92.1%; ZnFe2O4 performed better than MnFe2O4 in phenol decomposition and the TOC removal efficiency reached 60.3%. Radical quantitative results showed •OH and •O2– were the main radicals with MnFe2O4 during the catalytic ozonation, and •OH was the main radical for the ZnFe2O4. DFT (density functional theory) calculation and catalysts characterization indicated a smaller band gap endowed MnFe2O4 with higher electron transport capacity than ZnFe2O4, which catalyze ozone decomposition into •O2–; ZnFe2O4 possessed more abundant surface hydroxyl groups than MnFe2O4, which catalyze ozone decomposition into •OH. Conclusively, this study systematically revealed the different catalytic mechanisms of normal spinel-ZnFe2O4 and inverse spinel-MnFe2O4, and showed a positive effect on the application of spinel catalysts.

Green and facile production of high-quality graphene from graphite by the intercalation and decomposition of oxalic acid

• A green and environmentally friendly chemical exfoliation method was developed. • Oxalic acid is used for the first time alone for chemical intercalation exfoliation of natural flake graphite. • No water-washing and effluent-treatment are involved during the whole chemical exfoliation process. • The 9-μm-thick-graphene film exhibits excellent electrical conductivity (5.05 × 10 5 S/m) and EMI shielding property (53.9 dB). The environmentally friendly preparation of graphene remains a great challenge. Herein, a novel and green preparation method for graphene has been developed. Graphene sheets were successfully exfoliated from graphite by intercalation and decomposition of oxalic acid for the first time. The whole chemical exfoliation process does not involve any waste liquid disposal, and, more importantly, the decomposed products by oxalic acid are CO 2 and H 2 O, respectively, demonstrating that the exfoliation method is environmentally friendly. The obtained graphene sheets exhibit high-quality and large-size with a yield of about ∼ 100%. The prepared graphene film exhibits excellent electrical conductivity (5.05 × 10 5 S/m) and EMI shielding property (53.9 dB with a thickness of 9.0 μm), suggesting a great prospect for miniaturized electronic devices and flexible wearable applications.

Growth Mechanism of Spiky Nb2O5 Nanoparticles and their Electrochemical Property

Spiky nanoarchitecture composed of numerous nanorods and a spherical core has applications in various fields because of its high performance and durability. However, controlling the spiky structure is challenging because of an unclear formation mechanism. This study investigates the growth mechanism of spiky nanostructure by hydrothermally synthesizing Nb2O5 with various conditions and additives, and it is shown that adsorption and gradual decomposition of ligands promote the formation of the spiky shape. Using oxalic acid as an additive and synthesizing at 160 °C, which is below oxalic acid's decomposition temperature, spherical Nb2O5 with a rough surface that consists of a nanostructure with less than 5 nm size forms, and its surface is protected by oxalate ions. When the synthesis temperature increases to 180 °C, oxalate ions are decomposed, and nanorods grow on the spherical particles. The results show that oxalate ions suppress particle growth, promote self‐assembly, and control subsequent particle growth, resulting in complex nanostructures. When used as anode material in lithium‐ion batteries, the spiky Nb2O5 nanoparticles show a higher capacity (143 mAh g−1) than collapsed spiky particles (92 mAh g−1) and nanorods (37 mAh g−1) because of fast lithium‐ion diffusion on the surface nanostructure and high dispersibility.

Experimental study of the hydrothermal reactivity of oxalic acid under high pressure

The thermal stability of organic acids has a close relationship with the formation mechanism of secondary pores in deep reservoirs. Experiments were conducted to investigate the thermal stability of oxalic acid under high pressure and the influence of K-feldspar on oxalic acid decomposition. The experiment temperatures were set in the range of 130-330°C and each experiment was performed for 72h under 60MPa. Results show that both temperature and K-feldspar have significant influence on the decomposition of oxalic acid. The oxalic acid decomposed slowly at temperatures less than 180°C, and most of the oxalic acid decomposed at temperatures between 180°C and 230°C. Besides, the decarboxylation reaction proceeded more slowly in the presence of K-feldspar than the mineral-free experiments, which is most likely attributed to the increasing pH caused by dissolution. In addition, because the decomposition rate of oxalic acid was low, the K-feldspar dissolution was not affected at temperatures lower than 230°C.

Synthesis of Ti3+ self-doped mesoporous TiO2 cube with enhanced visible-light photoactivity by a simple reduction method

Through a simple reduction method, mesoporous anatase TiO2 cube was synthesized and the Ti3+ species and oxygen vacancies were successfully introduced into the anatase TiO2. CO2 and CO gases were produced by the thermal decomposition of oxalic acid and acted as a soft template to form the mesoporous structure, wherein CO acted as a reducing agent for reducing Ti4+ to Ti3+. The X-ray photoelectron spectroscopy spectra confirmed the presence of Ti3+ and oxygen vacancies in the samples. The UV–vis diffuse reflection spectra showed that the Ti3+ and oxygen vacancies shift the absorption edges of TiO2 from UV to the visible light region, which leaded to the enhanced photocatalytic activity. The charge carrier recombination rates of as-prepared samples were monitored by PL spectroscopy. The results showed that the trend was TiO2-3.70 < TiO2-1.85 < TiO2-0 < TiO2-7.41 < TiO2-11.11 (The X in the sample number TiO2-X refers to the ratio of the amount of H2C2O4 to Ti(SO4)2 (mole ratio)), implying that the charge carrier recombination rate of TiO2-3.70 was the lowest, which was responsible for enhancing the photocatalytic activity in the degradation of methylene orange under visible light irradiation. The Ti3+ and oxygen vacancies content, crystal size, specific area were strongly affected by the amount of oxalic acid. The oxalic acid content had an optimum value for the highest photocatalytic activity. It was worth noting that the sample exhibits excellent photocatalytic stability even after five recycles. This work demonstrates a new way to fabricate Ti3+ self-doped mesoporous TiO2 cube that have multiple channel structure and has potential to be used as in environmental photocatalysis.

Oxalic acid-mediated catalytic transfer hydrodeoxygenation of waste cooking oil

Oxalic acid was employed for the catalytic transfer hydrogenation of used vegetable cooking oil. Hydrogen production was achieved upon the decomposition of oxalic acid using a commercial industrially sulfided NiW/SiO2-Al2O3 catalyst. Products were analysed by attenuated infrared spectroscopy, simulated distillation and gas chromatography-flame ionisation detection/thermal conductivity detection for the produced gases. No hydrogen gas was added for these tests, which were performed in a nitrogen atmosphere at an initial pressure of 0 bar in an autoclave. Unprecedented results were obtained, with a high yield of deoxygenated hydrotreated vegetable oil hydrocarbons being achieved while avoiding the use of formic acid, which is both toxic and irritant.

Hybrid reactor based on hydrodynamic cavitation, ozonation, and persulfate oxidation for oxalic acid decomposition during rare-earth extraction processes

A cost-effective method for treating oxalic acid (OA) during rare-earth extraction was developed using hydrodynamic cavitation (HC), ozone (O3), and persulfate (PS) (HC@PS@O3 process). The results showed that the optimal inlet pressure during HC was 5.10 kg cm−2 with an orifice plate diameter of 2 mm. Moreover, HC was shown to activate PS, providing an alternative activation method to base or heat as an ultrasound activation method for chemical oxidation. O3 was also shown to activate PS. For OA oxidation using the HC@PS@O3 process, the optimum pH was 3 and the reaction rate increased with increasing temperature. Further, the activation energy was 36.69 kJ mol−1. The mechanisms unveiled in this study will allow optimization of the HC@PS@O3 process as a chemical oxidation technology. The kinetic investigation and economic evaluation of the HC@PS@O3 process can be used as the basis for real wastewater treatment processes in the future.

Kinetic Monte Carlo Simulation of Oxalic Acid Ozonationover Lanthanum-based Perovskitesas Catalysts

Kinetic Monte Carlo simulation was applied to investigation of kinetics and mechanism of oxalic acid degradation by direct and heterogeneous catalytic ozonation. La-containing perovskites including LaFeO3, LaNiO3, LaCoO3 and LaMnO3 was studied as catalyst for oxalic acid ozonation. The reaction kinetic mechanisms of each abovementioned catalytic systems has been achieved. The rate constants values for the each step of the reaction mechanisms were obtained as adjustable parameters by kinetic Monte Carlo simulation. Comparison of the direct and catalytic ozonation simulated results proves the lanthanum-based perovskites catalysts displays significant roles during oxalic acid ozonation by increasing reactivity of ozone and oxalic acid on the surface of catalyst. Also the effect of inlet ozone concentration and initial amount of LaMO3 (M= Fe, Ni, Co, Mn) on the rate of oxalic acid decomposition has been studied. The kinetic Monte Carlo simulation results of this research have satisfactorily agreement with the existing experimental data for the oxalic acid ozonation.

DFT Investigation of the Kinetics and Mechanism of the Thermal Decomposition of Oxalic Acid

Density functional theory calculations with different functionals have been performed to investigate the kinetics and mechanism of the thermal decomposition of oxalic acid in the gas phase and in solution in aniline, N-methylaniline, quinoline and DMSO. Five major possible mechanisms for this reaction have been proposed. Comparison between the theoretical data and experimental results shows that in the most probable path of this reaction CO, CO2 and H2O are produced. Moreover, this reaction is a little faster in the gas phase than in solvents. Quantum theory of atoms in molecules analysis indicates that C–C and O–H bond formations in the transition states have a covalent nature, because the ratios of kinetic energy density to potential energy density at the corresponding bond critical points are smaller than 0.5. Based on natural bond orbital analysis, during transition state formation, the interaction energy between the lone pair of electrons of the oxygen atom and the π* molecular orbital of the critical C–O bond is reduced and solvents affect the charge transfer process.

Effects of salt and alkali stress on growth, accumulation of oxalic acid, and activity of oxalic acid-metabolizing enzymes in Kochia sieversiana

Kochia sieversiana (Pall.) C.A. Mey. is a forage plant that can grow in extremely alkalinized grasslands at pH 10 or higher. Accumulation of a large amount of oxalic acid (OxA) is a primary characteristic of K. sieversiana. In our study, seedlings of K. sieversiana were exposed to the following conditions: non-stress, salinity (200 mM, a molar ratio of NaCl and Na2SO4 1:1), and alkali stress (200 mM, a molar ratio of NaHCO3 and Na2CO3 1:1). Growth, water content, content of organic acids (including OxA), Na+, and K+, and activities of some OxA metabolism-related enzymes were determined. Results show that glycolate oxidase was the key enzyme for OxA synthesis; however, the carboxylation of phosphoenolpyruvate (PEP) by PEP carboxylase (PEPC) probably played a minor role in the OxA-synthetic pathway. The pathway of L-ascorbic acid catabolism was not the main source of OxA accumulation, and the activity of oxalate oxidase (OxO) involved in OxA decomposition was not a limiting factor for inner OxA accumulation. Taken together, accumulation of a large amount of OxA are not related to the degradation and secretion function of OxO but largely depend upon its synthetic function.

Radiolytic decomposition of oxalic acid in water solutions

Radiolytic decomposition of oxalic acid in water solutions

The Decomposition of Oxalic Acid in Nitric Acid

The rate of decomposition of oxalic acid in strong nitric acid solutions increases with increasing acidity and temperature with the rate of reaction following pseudo-first-order kinetics with respect to oxalic acid. The order of nitric acid on the overall reaction has been shown to be 2.7, although this result should be treated with some caution due to scatter in the results at different temperatures. The activation energy was determined to be 116 ± 7 kJ·mol−1.

Promoting the oxidative removal rate of oxalic acid on gold-doped CeO2/TiO2 photocatalysts under UV and visible light irradiation

Abstract The photooxidation of oxalic acid, catalyzed by nanosized TiO 2 , CeO 2 , CeO 2 /TiO 2 and the respective gold-doped samples has been studied under irradiation with UV and visible light. UV–vis DRS, XRD, TEM, SEM, XPS techniques have been applied to the characterization of prepared photocatalysts. The photocatalytic mineralization of oxalic acid, catalyzed by CeO 2 /TiO 2 or Au/CeO 2 /TiO 2 , proceeded at a significantly higher rate under UV-A light irradiation than that under visible light. This is due to the low content of the CeO 2 (5 wt.%) in the composite catalyst. Doping the semiconductor materials with gold nanoparticles increases more than twice the rates of mineralization of oxalic acid, compared to non-doped samples. The higher rate constants of oxalic acid decomposition under UV or visible light irradiation over the CeO 2 /TiO 2 and Au/CeO 2 /TiO 2 catalysts, in comparison to those measured over the individual oxides, are due to the more efficient separation of the electron–hole pairs generated under irradiation. Especially efficient is the charge separation in the case of the Au/CeO 2 /TiO 2 photocatalyst under irradiation with UV light, when the rate constants of oxalic acid oxidation are approximately 1.6 times higher than the values when the process is catalyzed by Au/TiO 2 and 3.1 times higher than that over pure TiO 2 .

Reactive intermediates in (4)He nanodroplets: infrared laser Stark spectroscopy of dihydroxycarbene.

Singlet dihydroxycarbene (HOC̈OH) is produced via pyrolytic decomposition of oxalic acid, captured by helium nanodroplets, and probed with infrared laser Stark spectroscopy. Rovibrational bands in the OH stretch region are assigned to either trans,trans- or trans,cis-rotamers on the basis of symmetry type, nuclear spin statistical weights, and comparisons to electronic structure theory calculations. Stark spectroscopy provides the inertial components of the permanent electric dipole moments for these rotamers. The dipole components for trans, trans- and trans, cis-rotamers are (μa, μb) = (0.00, 0.68(6)) and (1.63(3), 1.50(5)), respectively. The infrared spectra lack evidence for the higher energy cis,cis-rotamer, which is consistent with a previously proposed pyrolytic decomposition mechanism of oxalic acid and computations of HOC̈OH torsional interconversion and tautomerization barriers.

In-situ characterization of oxalic acid breakdown at elevated P and T: Implications for organic C-O-H fluid sources in petrologic experiments

Decomposition of oxalic acid in the presence of water was examined in a hydrothermal diamondanvil cell up to 800 °C and 970-1480 MPa as a function of oxygen fugacity to assess its usefulness as a C-O-H fluid source in petrologic experiments. Fluid, vapor, and solid species were identified in situ at elevated temperature and pressure with Raman spectroscopy and optical microscopy. Under oxidizing conditions (buffered by the reaction NiO ↔ Ni+½O2), oxalic acid decomposes to carbon dioxide and water. Under reducing conditions (buffered by the reaction Mo+O2 ↔ MoO2), oxalic acid decomposes to methane and hydrogen. Under unbuffered conditions, at intermediate oxygen fugacity (~0 to 1 log units below the fayalite-quartz-magnetite buffer), oxalic acid disproportionates to graphite and minor methane and carbon dioxide. The results from the Ni-NiO-buffered and Mo-MoO2-buffered experiments result in observed fluid species that are similar to those predicted by previous investigations. However, there are substantial differences between our results and previous studies of oxalic acid decomposition in the unbuffered experiment that was within a log unit of the fayalite-magnetite-quartz (FMQ) buffer. These include the detection of aqueous C-H species at temperatures as low as 400 °C and a solid graphite-like phase at 800 °C. These differences can be explained if we consider that aqueous H2 in our experiment reacted to form the C-H species, instead of being lost via diffusion through the H2-permeable capsules used in previous studies. Consequently, for experiments within about 1 log unit of the FMQ buffer curve, oxalic acid is likely a poor choice for a C-O-H fluid source because the formation of graphitic carbon would result in significant deviations from the expected C-O-H fluid composition and concentration (i.e., CO2+H2O). At oxygen fugacities outside a log unit of FMQ, the observed fluid species are similar to those predicted by previous investigations and the use of oxalic acid as a C-O-H fluid source is permissible from the perspective of oxygen fugacity, although other system parameters (e.g., sample geometries, capsule thickness, capsule materials, gasket materials, wall thickness) must still be considered.

Stable carbon isotopic compositions of low-molecular-weight dicarboxylic acids, glyoxylic acid and glyoxal in tropical aerosols: implications for photochemical processes of organic aerosols

Tropical aerosols of PM2.5 and PM10 were collected at a rural site in Morogoro, Tanzania (East Africa), and analysed for stable carbon isotopic composition (δ13C) of dicarboxylic acids (C2–C9), glyoxylic acid (ωC2) and glyoxal (Gly) using gas chromatography/isotope ratio mass spectrometer. PM2.5 samples showed that δ13C of oxalic (C2) acid are largest (mean, −18.3±1.7‰) followed by malonic (C3, −19.6±1.0‰) and succinic (C4, −21.8±2.2‰) acids, whereas those in PM10 are a little smaller: −19.9±3.1‰ (C2), −20.2±2.7‰ (C3) and −23.3±3.2‰ (C4). The δ13C of C2–C4 diacids showed a decreasing trend with an increase in carbon numbers. The higher δ13C values of oxalic acid can be explained by isotopic enrichment of 13C in the remaining C2 due to the atmospheric decomposition of oxalic acid or its precursors. δ13C of ωC2 and Gly that are precursors of oxalic acid also showed larger values (mean, −22.5‰ and −20.2‰, respectively) in PM2.5 than those (−26.7‰ and −23.7‰) in PM10. The δ13C values of ωC2 and Gly are smaller than those of C2 in both PM2.5 and PM10. On the other hand, azelaic acid (C9; mean, −28.5‰) is more depleted in 13C, which is consistent with the previous knowledge; that is, C9 is produced by the oxidation of unsaturated fatty acids emitted from terrestrial higher plants. A significant enrichment of 13C in oxalic acid together with its negative correlations with relative abundance of C2 in total diacids and ratios of water-soluble organic carbon and organic carbon further support that a photochemical degradation of oxalic acid occurs during long-range transport from source regions.