Showing papers on "Oxalic acid published in 2009"
TL;DR: In this paper, the degradation of a 41 mg dm -3 ibuprofen (2-(4-isobylphenyl)propionic acid) solution of pH 3.0 has been comparatively studied by electrochemical advanced oxidation processes (EAOPs) like electro-Fenton, UVA photo-electro-fenton and solar photoelectrofenton at constant current density, and experiments were performed in a one-compartment cell with a Pt or boron-doped diamond (BDD) anode and an O 2 -diffusion cath
222 citations
TL;DR: The effect of reaction conditions including the initial pH value, and the dosages of ferrous ions and hydrogen peroxide on 2,6-dimethylaniline and COD removal were investigated and an oxidation pathway of the target organic was proposed.
Abstract: 2,6-Dimethylaniline degradation by Fenton process has been studied in depth for the purpose of learning more about the reactions involved in the oxidation of 2,6-dimethylaniline under various reaction conditions. The effect of reaction conditions including the initial pH value, and the dosages of ferrous ions and hydrogen peroxide on 2,6-dimethylaniline and COD removal were investigated. 2,6-Dimethylaniline removal efficiency of 70% was achieved under optimal reaction conditions of pH value of 2, dosage of 2 mM of ferrous ion, and 20 mM of hydrogen peroxide after 3 h. A series of intermediates were identified, corresponding to ring compounds and short-chain organic acids. The intermediates were 2,6-dimethylphenol, 2,6-dimethylnitrobenzene, 2,6-dimethylbenzoquinone, 3-hexanone, maleic acid, acetic acid, formic acid, and oxalic acid. An oxidation pathway of the target organic was also proposed in this study.
212 citations
TL;DR: The results suggest that cloud processing of glyoxal could be an important source of SOA, and validate for the first time the accuracy of model predictions at cloud-relevant concentrations.
Abstract: Previous experiments demonstrated that aqueous OH radical oxidation of glyoxal yields low-volatility compounds. When this chemistry takes place in clouds and fogs, followed by droplet evaporation (or if it occurs in aerosol water), the products are expected to remain partially in the particle phase, forming secondary organic aerosol (SOA). Acidic sulfate exists ubiquitously in atmospheric water and has been shown to enhance SOA formation through aerosol phase reactions. In this work, we investigate how starting concentrations of glyoxal (30-3000 microM) and the presence of acidic sulfate (0-840 microM) affect product formation in the aqueous reaction between glyoxal and OH radical. The oxalic acid yield decreased with increasing precursor concentrations, and the presence of sulfuric acid did not alter oxalic acid concentrations significantly. A dilute aqueous chemistry model successfully reproduced oxalic acid concentrations, when the experiment was performed at cloud-relevant concentrations (glyoxal <300 microM), but predictions deviated from measurements at increasing concentrations. Results elucidate similarities and differences in aqueous glyoxal chemistry in clouds and in wet aerosols. They validate for the first time the accuracy of model predictions at cloud-relevant concentrations. These results suggest that cloud processing of glyoxal could be an important source of SOA.
196 citations
TL;DR: The photocatalytic degradation of Rhodamine B (RhB) was carried out using TiO2 supported on activated carbon (TiO2-AC) under microwave irradiation and the intermediates transformed to acid molecules which were mineralized to water and carbon dioxide.
Abstract: The photocatalytic degradation of Rhodamine B (RhB) was carried out using TiO2 supported on activated carbon (TiO2-AC) under microwave irradiation Composite catalyst TiO2-AC was prepared and characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) In the process of microwave-enhanced photocatalysis (MPC), RhB (30 mg/L) was almost completely decoloured in 10 min, and the mineralization efficiency was 960% in 20 min The reaction rate constant of RhB in MPC using TiO2-AC by pseudo first-order reaction kinetics was 416 times of that using Degussa P25 Additionally, according to gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS) identification, the major intermediates of RhB in MPC included two kinds of N-de-ethylation intermediates (N, N-diethyl-N'-ethyl-rhodamine (DER)), oxalic acid, malonic acid, succinic acid, and phthalic acid, maleic acid, 3-nitrobenzoic acid, and so on The degradation of RhB in MPC was mainly attributed to the destruction of the conjugated structure, and then the intermediates transformed to acid molecules which were mineralized to water and carbon dioxide
194 citations
TL;DR: In this paper, it was shown that inulin is soluble in ionic liquids (ILs) choline chloride (ChoCl)/oxalic acid and ChoCl/citric acid, which are prepared entirely from cheap and renewable materials.
193 citations
TL;DR: In this paper, the photocatalytic activity of the as-obtained CuFe2O4 nanoparticles has been evaluated based on the H2 evolution from aqueous oxalic acid solution under visible light irradiation.
172 citations
TL;DR: In this article, the authors investigated the potential for aqueous glycolaldehyde oxidation to produce low volatility products that contribute SOA mass, including malonic acid, succinic acid, and higher molecular weight compounds, including oligomers.
161 citations
TL;DR: Different activated carbon-supported Fe catalysts have been prepared and tested in CWPO of phenol and three well characterized activated carbons and two iron precursors (iron nitrate and iron pentacarbonyl) have been used as discussed by the authors.
Abstract: Different activated carbon-supported Fe catalysts have been prepared and tested in CWPO of phenol Three well characterized activated carbons and two iron precursors (iron nitrate and iron pentacarbonyl) have been used The behavior of these catalysts in CWPO has been related with their porous structure, surface composition, in terms of oxygen groups and Fe distribution onto the catalyst particles The catalysts with a more uniform distribution of Fe showed a higher oxidation activity than the ones with an internal (egg-yolk type) or external (egg-shell type) distribution These last provoke a faster decomposition of H 2 O 2 mainly to O 2 , non-reactive at the mild reaction temperature used (50 °C) No significant differences were observed from the iron precursors Complete conversion of phenol and almost 80% mineralization were obtained in less than 2 h with the best catalyst The residual by-products consisted in short-chain organic acids without significance in terms of toxicity Fe leaching was observed in all the cases which can be mainly attributed to the presence of oxalic acid as oxidation by-product, refractory to the CWPO process investigated The intensity of Fe leaching was related with the concentration of oxalic acid
158 citations
TL;DR: In this paper, the effect of ozonation pretreatment on the catalytic activity of multilwalled carbon nanotube (MWCNT) and the oxalic acid oxonation mechanism was investigated.
Abstract: Multi-walled carbon nanotube (MWCNT) has been used in the catalytic ozonation of oxalic acid in aqueous solution, which was pretreated using ozone and was characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption and Boehm titration. The effect of ozonation pretreatment on the catalytic activity of MWCNT and the ozonation mechanism of oxalic acid in the presence of MWCNT were investigated. The results indicate that with the increasing pretreatment time, the atom ratio of oxygen to carbon and the number of surface acid groups on MWCNT increase, while the catalytic activity of MWCNT on ozonation of oxalic acid decreases, suggesting that the chemical characteristics of MWCNT mainly determine its catalytic activity on oxalic acid mineralization. The inhibition of tert-butyl alcohol on the degradation of oxalic acid is slight for pristine MWCNT catalytic ozonation and this inhibition trend becomes more obvious when MWCNT was pretreated by ozone. A free radical mechanism was proposed which involves both surface reactions and bulk reactions between the oxalic acid and active species.
123 citations
TL;DR: From these oxidation by-products, a plausible reaction sequence for m-cresol mineralization on both anodes is proposed and the energy consumption for the corresponding electrochemical process is calculated.
116 citations
TL;DR: In this article, the electrochemical behavior of pure Ti and Ti-6Al-4V alloy was investigated in oxalic acid solution using various electrochemical techniques, i.e., open circuit potential (OCP), potentiodynamic polarization, electrochemical impedance measurements (EIS), and surface examination via scanning electron microscope (SEM) technique.
TL;DR: In this paper, phenol as surrogate compound for NOM was ozonated while suppressing reactions of ·OH radicals by addition of tert-butanol, and batch experiments showed benzoquinone (40 and 18%), catechol (33 and 1%), cis,cis-muconic acid (6 and 3%), and hydroquinone(2 and 7%) to be the most abundant primary products at pH 7 and 3.
Abstract: Organic acids are part of assimilable organic carbon (AOC) formed from natural organic matter (NOM) during ozonation for drinking water production. To elucidate the formation of organic acids, phenol as surrogate compound for NOM was ozonated while suppressing reactions of ·OH radicals by addition of tert-butanol. Batch experiments show benzoquinone (40 and 18%), catechol (33 and 1%), cis,cis-muconic acid (6 and 3%), and hydroquinone (2 and 7%) to be the most abundant primary products at pH 7 and 3, respectively. The tertiary product oxalic acid was obtained in similar yields from phenol ozonation (0.8%) as during ozonation of lake water (1.6%). Together with other low molecular weight organic acids it was formed upon small ozone exposures, as was shown by time-dependent experiments in time ranges of 0.4–23 and 0.07–1.0 seconds for pH 3 and 7.25, respectively.
TL;DR: Kinetic results show evidence of pseudo-first-order degradation and a new approach for promoting ferric reduction efficiency using a different electrochemical cell and the photoelectro-Fenton process has been developed to degrade organic toxic contaminants.
TL;DR: In this paper, the authors measured oxalic acid in individual aerosol particles using single particle aerosol time-of-flight mass spectrometry (ATOFMS) in the summer of 2007 in Shanghai, China.
TL;DR: The role of iron on the degradation of different organic compounds, differing in their structure (aliphatic versus aromatic) and iron complex formation capacity, by conventional and photo-Fenton processes was investigated in this paper.
TL;DR: In this paper, the effect of pH, organic ligand concentration and disk rotation velocity on the partial current density of chromium electroplating was demonstrated and compared with the experimental data.
TL;DR: Ethanol production was affected by reaction temperature more than by oxalic acid and reaction time over the ranges examined, while the ethanol yield after SSF with P. stipitis was significantly higher than predicted by sequential saccharification and fermentation of substrate pretreated under the same condition.
TL;DR: In this article, the authors investigated the influence of the operative parameters on the performances of the electrochemical incineration of oxalic acid (OA) at Ti/IrO2-Ta2O5 (DSA-O2) anode.
TL;DR: In this paper, a facile citric acid (CA)-assisted sol-gel method was used to synthesize a nanocomposite of CuCr2O4/TiO2 heterojunction.
TL;DR: Barling et al. as mentioned in this paper analyzed the isotope fractionation mechanisms during the transport of iron (Fe) within hydrothermal and soil environments by leaching of complex, polyminerallic rocks.
TL;DR: In this paper, stable carbon isotope ratio (δ13C) data were collected from Zurich city in 2002 and 2003 in the gas and aerosol phase, and the corresponding analysis was performed using a wet oxidation method followed by isotope-ratio mass spectrometry.
TL;DR: In this paper, the effects of four carboxylic acids: malic, citric, tartaric and oxalic acids on the leaching of iron from two commercial iron oxides (hematite, α-Fe2O3, and magnetite, Fe3O4) have been investigated.
Abstract: The effects of four carboxylic acids: malic, citric, tartaric and oxalic acids on the leaching of iron from two commercial iron oxides (hematite, α-Fe2O3, and magnetite, Fe3O4) have been investigated. The variables studied were the doses of iron oxides and carboxylic acids used as well as aqueous pH, temperature and the presence of hydrogen peroxide and/or UV-A radiation. On the whole, Fe3O4 led to higher amounts of leached iron than α-Fe2O3, and oxalic acid was the most effective carboxylic acid used. The importance of iron leaching has been considered to explain the photodegradation of bisphenol A (BPA) by UV-A/iron oxides systems. The influence of the presence of hydrogen peroxide and/or titania on the efficiency of these oxidation systems was also investigated. At the conditions tested, advanced oxidation with the UV-A/iron oxide/oxalic acid/H2O2/TiO2 system led to the lowest BPA half life (<15 min) among those processes studied.
TL;DR: In this article, the effect of oxalic acid and pH on iron reduction by a biomimetic fungal chelator and on the adsorption/desorption of iron to/from wood was investigated.
TL;DR: In this paper, the photoresponse of PbO 2 -TiO 2 nanoparticles to illumination at λ ǫ>-320nm was shown. And the life service of these electrodes increases by a factor of about 3 with respect to traditional Pb O 2 -based anodes.
TL;DR: In this article, a monoclinic-type Li 3 V 2 (PO 4 ) 3 cathode material was synthesized via calcining amorphous Li 3V 2(PO 4 ), obtained by chemical reduction and lithiation of V 2 O 5 using oxalic acid as reducer and lithium carbonate as lithium source in alcohol solution.
TL;DR: Measurement of adsorption and desorption kinetics by ATR-IR spectroscopy is expected to provide a relatively rapid means of assessing the presence of species of different adsorptive affinities in systems in which their spectra are not well differentiated.
Abstract: Adsorption and desorption kinetics at the solid/solution interface have been monitored using attenuated total reflection infrared (ATR-IR) spectroscopy to evaluate this approach as an alternative to equilibrium (adsorption isotherm) measurements of adsorption affinity. The adsorption and desorption kinetics of oxalate ion to anatase TiO2 have been measured by using aqueous 1 × 10−4 mol L−1 oxalic acid solutions at pH 4 and thin films of TiO2 particles deposited on an internal reflection prism. The adsorption kinetics were obtained from the absorbance versus time behavior of major adsorbed oxalate infrared absorptions with flow of oxalic acid solution followed by flow of solution not containing oxalic acid to measure the desorption kinetics. Regression analysis of the desorption data based on Langmuir kinetics yielded three distinct pseudo-first-order rate constants with desorption half-lives of 300, 14, and 2 min, indicating the presence of three adsorbed oxalate species of different adsorption affinities...
TL;DR: Pt-, Au-and Ag-deposited Degussa P25 photocatalysts [at 1% (m/m) noble metal loading] were prepared in which the noble metals are most likely to be very finely dispersed on the surface of the TiO2 nanocrystals.
Abstract: Pt-, Au- and Ag-deposited Degussa P25 photocatalysts [at 1% (m/m) noble metal loading] were prepared in which the noble metals are most likely to be very finely dispersed on the surface of the TiO2 nanocrystals. Deposition of noble metals increased the photocatalytic efficiency (relative to the bare photocatalyst) in the decomposition of oxalic- and formic acid, while decreased it in phenol containing systems. In H2-production, a very high quantum yield has been found for the Pt–TiO2 photocatalyst in the presence of oxalic and formic acids as sacrificial reagents, which opens the possibility for the economic use of industrial side products (e.g., oxalic- and formic acid) for photocatalytic H2-production.
TL;DR: In this article, needle-shaped and rod-shaped SrFe 12 O 19 nanoparticles have been synthesized using the sol-gel method, in combination with the self-propagating combustion technique, by adding a little organic template (EDTA, molten stearic acid, or oxalic acid) as dispersant during citric acid addition.
TL;DR: In this paper, a mixture of acidic solutions containing cations and oxalic acid was introduced in an open vessel, leading to a poorly-crystallized precipitate, then the starting mixture was placed in an acid digestion bomb then set in an oven in order to reach hydrothermal conditions.
TL;DR: In this article, an experimental study based on ferrioxalate-assisted solar photo-Fenton (SPFox) process shows how non-biodegradable azo dye Orange II (OII) solutions degradation can be enhanced or slowed down by continuous addition of hydrogen peroxide and air injection depending on operation conditions.
Abstract: An experimental study based on ferrioxalate-assisted solar photo-Fenton (SPFox) process shows how non-biodegradable azo dye Orange II (OII) solutions degradation can be enhanced or slowed down by continuous addition of hydrogen peroxide and air injection depending on operation conditions. The decoloration and mineralization of dye solution has been carried out in a solar Compound Parabolic Collector (CPC). An optimization study was done by using Multivariate Experimental Design including the following variables: flow rate of H2O2, air flow rate, pH and initial concentrations of Fe(II) and oxalic acid. The efficiency of photocatalytic degradation was determined from the analysis of color and Total Organic Carbon (TOC). Experimental data were fitted using neural networks (NNs) which allow the simulation of the process for any value of variables in the studied experimental range. The results reveal that the continuous addition of H2O2 improves the photocatalytic efficiency since the scavenger effect of peroxide is minimized. On the other hand, this system permits the use of a ferrous concentration below the discharge legal limit (2 ppm) being bubbling of air not necessary in that conditions. In addition, oxalic acid can be used to pH adjustment, reducing the operation costs of Fe removal, chemicals and electric power. Under the optimal conditions, 100% decoloration of dye solution can be reached by using both processes (SPFox with H2O2 addition at the beginning or along the reaction) but with different reaction rates. However, the efficiency of TOC removal was higher in the SPFox process with continuous addition of H2O2 (95% TOC removal in SPFox system with continuous addition of peroxide versus 80% TOC removal in SPFox system when peroxide is added at the beginning of the reaction). Molecular and/or radical reaction pathway was studied by conducting the reaction in the presence and absence of tert-butylalcohol.