Decomposition Of Organic Acids Research Articles

Metabolic mechanisms of carbon and nitrogen interactions during anaerobic digestion of coal

There was limited research on the impact of nitrogen metabolism in the process of methane production with coal, even if carbon and nitrogen metabolism were closely interconnected. Lignite was the source of carbon and nitrogen in anaerobic digestion system. The relationship between carbon and nitrogen metabolism was systematically discussed during the anaerobic digestion process. The results showed that phenolic carbon or ether carbon (C-O), pyridine-type nitrogen (N-6) and nitrogen oxide compound (N-X) in coal were decomposed under the action of Macellibacteroides, Sphaerochaeta and Trichococcus in the hydrolysis stage, respectively. In the acidogenesis stage, the stress of volatile fatty acids and ammonia produced by dissolved organic matter under the action of Syner-01 and Sphaerochaeta on hydrogenotrophic and acetoclastic methanogens was alleviated during the nitrogen cycle. In the acetogenesis stage, acetic acid produced from the decomposition of organic acids and alcohols by Synergistaceae and Sedimentibacter was competed by denitrifying bacteria and acetogenic methanogens. In the methanogenesis stage, CO2 was reduced by Methanobacterium and Methanoculleus to produce CH4, while acetic acid was decomposed by Methanosaeta to produce CH4. And methyl substances were generated into CH4 by Methanosarcina and Methanofastidiosum. This understanding will provide a basis for strengthening the favorable factors in biomethane production.

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.

Study of two-phase anaerobic digestion of corn stover: Focusing on the conversion of volatile fatty acids and microbial characteristics in UASB reactor

Methanogenic performance and microbial communities including both bacteria and archaea in UASB reactor treating acidogenic metabolites from acidification of ensiled corn stover (ECS) were investigated. Gradient organic loading rates (OLRs) were adopted to study the conversion of volatile fatty acids (VFAs) characterized by high concentration of acetic acid and propionic acid. The removal rate of chemical oxygen demand (COD) reached above 80.0 % at OLR of 8 g/L·d and volumetric methane production rate improved significantly as the OLR increased. When OLR was 10 g COD/L·d, acetic and propionic acids in effluent were accumulated and failure of methane production occurred. Compared with the control, the methanogenic inhibition was caused by the presence of high concentration of propionic acid. The profile of conversion of individual VFAs in UASB reactors was investigated at different OLRs. Furthermore, microbial communities in anaerobic sludge at OLR of 8 g COD/L·d were compared with those in inoculum and the shift of bacteria and archaea were analyzed. The abundances of some representative acetogenic bacteria such as Proteobacteria (14.18 %) and Bacteroidetes (11.16 %) increased obviously, which contributed to the oxidation and decomposition of organic acids. Acetotrophic methanogen (Methanosaeta) and hydrogenotrophic methanogen (Methanobacterium) played synergistic roles with acetogens to efficiently complete the VFAs conversion. This study will be of great importance to guide the application of two-phase AD of agricultural waste in full-scale plant.

Degradation of root exudates in closed hydroponic systems using UV/H2O2: Kinetic investigation, reaction pathways and cost analysis

Qualitative screening of reused nutrient solution (RNS) displays the presence of several organic acids. In this study, the degradation by UV/H2O2 of three of those organic acids (benzoic (BA), phthalic acid (PhA) and succinic acid (SA)) present in RNS was investigated. The results indicated that (i) the degradation rate of BA was faster than that of PhA and SA and (ii) by increasing the contact time the degradation of all acids was improved. For example, the removal of BA increased from 83% and 91% when increasing the contact time from 90 min to 270 min in the presence of 50 mg L−1 and UV. A maximum COD (30%) and UV254 (68%) removal were obtained when 200 mg L−1 H2O2 was applied for 90 min. No significant change was observed in terms of parameters such as PO43− and NO3− while electrical conductivity (EC) and pH were slightly changed during the oxidation process. Pseudo- first -order represented well the experimental data for the degradation of the selected organic acids in RNS (particularly for BA and PhA), exhibiting high linear correlation coefficients (R2 ≥ 0.96). Moreover, the results showed that the decomposition of organic acids was significantly influenced in the presence of inorganic ions in RNS. GC–MS analysis revealed the presence of several intermediate products during the oxidation process and the primary reaction pathway of benzoic acid was accordingly proposed. Finally, a bench scale cost investigation showed that low concentration H2O2 (50 mg L−1) in longer time (270 min) is more cost effective than high concentration H2O2 (200 mg L−1) in a shorter time (90 min).

Effect of burial processes on the evolution of organic acids and implications for acidic dissolution from a case study of the Nanpu Sag, Bohai Bay Basin, China

Based on previous research examining the controlling factors of the generation and decomposition of organic acids, our study discusses the effect of burial processes on the evolution of organic acids and the development of secondary pores related to acidic dissolution using a case study of the Nanpu Sag, Bohai Bay Basin, China. The depth range of the present distribution of organic acids was determined from the measured data for vitrinite reflectance (Ro) and formation temperature to be approximately 2000–3500 m. This range corresponds to the vertical distribution of feldspar dissolution pores, except for the No. 3 structural belt, a risk exploration area, where feldspar dissolution can be observed in a deeper interval corresponding to the Es1 Formation. This finding indicates that feldspar was dissolved in the early burial stage of the Es1 Formation of the No. 3 structural belt, unlike in the other structural belts. During the Shahejie depositional period, the subsidence rate was lower than it was during the Dongying depositional period, except at the No. 3 structural belt. The subsidence rate at the No. 3 structural belt was higher during the Shahejie depositional period because this structural belt is adjacent to the east section of the Shabei Fault. Simulations of the organic matter evolution for two types of burial history were processed to clarify the effect of burial history on organic acids evolution. Consequently, we suggest that the different burial histories result in different situations of secondary pore development. A slow-to-fast process leads to delayed generation of organic acids and high formation temperature, which results in the decomposition of organic acids, and hence weakened dissolution. Conversely, a fast-to-slow process preserves organic acids well and strengthens dissolution in the early burial stage.

Role of Low-Molecule-Weight Organic Acids and Their Salts in Regulating Soil pH

The process of organic materials increasing soil pH has not yet been fully understood. This study examined the role of cations and organic anions in regulating soil pH using organic compounds. Calcareous soil, acid soil, and paddy soil were incubated with different simple organic compounds. pH was determined periodically and CO 2 emission was also measured. Mixing organic acids with the soil caused an instant decrease of soil pH. The magnitude of pH decrease depended on the initial soil acidity and dissociation degree of the acids. Decomposition of organic acids could only recover the soil pH to about its original level. Mixing organic salts with soil caused an instant increase of soil pH. Decomposition of organic salts of sodium resulted in a steady increase of soil pH, with final soil pH being about 2.7–3.2 pH units over the control. Organic salts with the same anions (citrate) but different cations led to different magnitudes of pH increase, while those having the same cations but different anions led to very similar pH increases. Organic salts of sodium and sodium carbonate caused very similar pH increases of soil when they were added to the acid soil at equimolar concentrations of Na +. The results suggested that cations played a central role in regulating soil pH. Decarboxylation might only consume a limited number of protons. Conversion of organic salts into inorganic salts (carbonate) was possibly responsible for pH increase during their decomposition, suggesting that only those plant residues containing high excess base cations could actually increase soil pH.

Contribution of different proton sources to pedogenetic soil acidification in forested ecosystems in Japan

The contribution of different proton sources to pedogenetic soil acidification was evaluated for three Japanese forest soils, i.e. ando soil, podzolic soil and brown forest soil in relation to the respective soil forming processes. Soil acidification rate and net proton generation were quantified based on the theory of proton budget for the respective soil horizon compartments (mainly the O, A and B horizons) by measuring fluxes of solutes entering and leaving the soil horizon compartment and vegetation uptake. Protons were produced by the dissociation of organic acids and nitrification in the O horizon and then consumed by adsorption and decomposition of organic acids and nitrate uptake by vegetation in deeper soil horizons at all plots. Excess uptake of cation over anion by vegetation was highest among proton sources in the whole soil compartment at all plots. Pedogenetic soil acidification was considered to include cation leaching from surface soil horizons due to proton generation by the dissociation of organic acids and nitrification and subsequent cation excess accumulation in wood in the growth stage of forests. In ando soil, andosolization resulted from the low contribution of net proton generation by the dissociation of organic acids as well as a lower soil acidification rate and complete acid neutralization. Dissolved organic carbon (DOC) fluxes in ando soil were lower than those in podzolic soil and brown forest soil due to high adsorption capacity of amorphous materials. In podzolic soil, podzolization resulted from intensive acidification in the O horizon, which derived from net proton generation by the dissociation of organic acids and nitrification as well as cation excess uptake by vegetation due to concentrated fine root biomass in the O horizon, and subsequent high proton efflux to subsoil. The high fluxes of DOC and Al leached from surface soil horizons were considered to contribute to eluviation of Al from surface soil and illuviation in subsoil in podzolic soil. In brown forest soil, brunification resulted from a lower DOC flux from the O horizon due to high decomposition and adsorption by oxides, where podzolization was weakened by high acid neutralization. Thus, the three representative processes involved in the pedogenesis of Japanese forest soils were well characterized by quantification of the respective proton-generating and consuming processes in each soil horizon.

Basic Study on Anaerobic Biological Filtration Using a Floating Filter Media

An experiment of anaerobic filtration using a floating media was carried out in this study. In the present system, a bench-scale column of 50 mm in diameter and of 1500 mm in height and a floating media consisting of S-shaped polystyrene pieces were employed. The purpose of this study was to collect the basic data of anaerobic biological filtration using a floating media. Under the laboratory conditions, it was found that the start-up of an anaerobic biological filter took about half month at 20°C and a lower BOD loading was favorable for this start-up. The BOD removal efficiency over 60% could be achieved at a BOD volumetric loading of the filter bed under 6 kg/m3/d. An effluent BOD concentration became high when the flow rate was high, especially with circulation of treated water, which afforded a large effect on an effluent BOD concentration. As for the mechanism of BOD removal by anaerobic filtration, it was evident that long retention time worked in favor for organic acid generation, and the circulation of treated water promoted decomposition of organic acids.

Mecanisme d'action des radicaux OH [rad] sur les acides glycolique, glyoxylique, acetique et oxalique en solution aqueuse: Incidence sur la consammation de peroxyde d'hydrogene dans les systemes [formula omitted] et [formula omitted

The aim of this work is to study the mechanism of the reaction of hydroxyl radicals with simple aliphatic acids (acetic, glycolic, glyoxylic and oxalic acids; see Table 1) in aqueous solution. The decomposition of organic acids by hydroxyl radicals has been studied using the photolysis of hydrogen peroxide and the ozone/hydrogen peroxide system.

The study of soil chemistry through quasi-steady-state models: II. Acidity of soil solution

The acidity of three hypothetical soil solutions was studied with a quasi-steady-state model. Processes were assigned to one of three time scales: fast (processes at equilibrium), slow (processes for which the kinetics are specified explicitly), or very slow (processes that have a negligible effect on the steady-state solution). Reactions among species in solution and precipitation/dissolution reactions of solid Al(OH) 3(s) were considered to be at equilibrium. The slow processes were uptake of nutrients by plants, root respiration, release of nutrients, production of CO 2 and organic acids during decomposition of organic matter, decomposition of organic acids, nitrification, atmospheric deposition, exchange of CO 2 with the atmosphere, and weathering. The relative importance of biological, chemical, and physical processes controlling the acidity and speciation of soil solution was examined; three cases illustrate high vs. low rates of weathering and absence vs. presence of organic acids. The sensitivity of the calculated solution pH to values of parameters in the model was examined through calculated sensitivity coefficients and an analysis of equations governing the system. Fluxes of acidity due to biological processes are larger than fluxes due to other processes, but because of internal feedback their effect on pH may not be as large as expected.

Decomposition of Organic Acids During Processing and Storage

Solutions (0.1 N) of organic acids as well as tissue concentration levels were processed at several temperatures with varyious F0 values. Analyses were done using an automatic organic acid analyzer and paper chromatography. Pyrrolidone-carboxylic acid was produced from glutamic acid, fumaric from maleic acid, itaconic and trans-aconitic from cis-aconitic acid, malonic acid decomposed to acetic acid, and oxalacetic to pyruvic acid. At tissue concentration level oxalacetic acid decomposed completely at all process temperatures to pyruvic acid and to a lesser degree during storage without processing. Decomposition of other organic acids increased with increasing process time. The decompositon of malonic to acetic acid was the only reaction which was decreased significantly by use of a High-temperature Short-time process. However, the amount of decomposition of all acids, except oxalacetic, was low both after processing and during storage.

Catalyzed thermal decomposition of organic acids. Part 2.—Catalyzed decomposition of cyclopentane- and cycloheptane-carboxylic acids by hydrogen bromide

Cyclopentane- and cycloheptane-carboxylic acids decompose by a molecular mechanism into carbon monoxide, water and the corresponding alkene on catalysis by HBr in a seasoned Pyrex vessel. The decomposition is homogeneous and first order in acid and catalyst, HBr. The second order rate constants, expressed by the Arrhenius equations are: k2= 1012.17e–29 550/RT cm3 mol–1 s–1 for cycloheptanecarboxylic acid and k2= 1013.49e–34 590/RT cm3 mol–1 s–1 for cyclopentanecarboxylic acid over the temperature range 369.0–434.0°C (R in cal mol–1).

The catalysed thermal decomposition of organic acids. Part I. The catalysed decomposition of cyclohexanecarboxylic acid by hydrogen bromide

Hydrogen bromide catalyses the thermal decomposition of cyclohexanecarboxylic acid into essentially cyclohexene, carbon monoxide, and water in the temperature range 642–703 K in a seasoned Pyrex reaction vessel. The first-order rate constants are proportional to the hydrogen bromide concentration. The reaction is homogeneous and predominantly molecular. The Arrhenius equation is k2/cm3 mol–1 s–1= 1013·562 exp (–34,480/RT).

Decomposition of Organic Acids and Gas Formation in Flooded Soil

Abstract Methane is formed by the specific bacteria which are strictly anaerobic. All of the methane bacteria can not decompose the more usual substrates for bacteria such as carbohydrates and amino acids. They can use only alcohol, volatile fatty acids, and gases such as CO2, CO and H2 as their substrates1).

The Decomposition of Organic Acids in the Presence of Lead Tetraacetate*

The Decomposition of Organic Acids in the Presence of Lead Tetraacetate^*