Decomposition Of Organic Compounds Research Articles

Comparison of Different Carbon Sources on Biomethane Production with Clostridium cellulovorans and Methanogens

Methane (CH4) has attracted attention as not only one of the hydrogen carriers in terms of energy density, but also synthetic natural gas. In nature, the decomposition of organic compounds is performed with bacterial ecosystems that can produce CH4. Clostridium cellulovorans as a decomposer was cultivated with pig manure (PM) as an unused biomass in this study. As a result of high-performance liquid chromatography (HPLC) analysis, while formate and lactate were decreased in the C. cellulovorans medium containing 0.5% PM, acetate and butyrate were increased in it. Accordingly, in order to compare with the effect of carbon sources for methane production, the cocultivation of C. cellulovorans and the methanogenesis of Methanosarcina mazei or microbial flora of methane production (MFMP) was carried out in the C. cellulovorans medium. As a result, only the cocultivation with C. cellulovorans and MFMP showed methane production in 0.5% acetate medium. Moreover, in comparison with a carbon source in either 1% acetate or 1% methanol medium, MFMP was only cultivated after being precultivated with 0.5% glucose medium for 12 h. The results revealed that MFMP with a 1% methanol medium produced methane approximately eight times higher than with 1% acetate medium. After cultivation with 1% acetate or 1% methanol, next-generation sequencing (NGS) analysis of MFMP was carried out. Interestingly, Methanofollis (0.211%), belonging to methanogens through the CO2 reduction pathway, was dominant in the 1% acetate medium for 72 h cultivation, while Methanosarcina siciliae (1.178%), M. barkeri (0.571%), and Methanofollis (0.490%) were major species in 1% methanol medium for 72 h cultivation. Since Methanosarcina spp. belong to acetoclasts (acetoclastic pathway), methanol could promote the growth of Methanosarcina spp., rather than acetate. Therefore, it seems that Methanosarcina spp. may play a key methanogenesis role in MFMP. Thus, these results will provide important information for low-cost biomethane production.

Hierarchical Co-Fe layered double hydroxides (LDH)/Ni foam composite as a recyclable peroxymonosulfate activator towards monomethylhydrazine degradation: Enhanced electron transfer and 1O2 dominated non-radical pathway

The growing application of rocket propellants (e.g., monomethylhydrazine (MMH)) leads to awful water pollution, and thus it is urgent to develop efficient remediation methods to remove it from wastewater. Although persulfate-based catalytic technologies are promising for refractory organic compounds decomposition, the undesired aggregations, high cost and troublesome separation of powder catalysts still limit their wide-applications. To address these issues, we prepared Co-Fe layered double hydroxides (CoFe-LDH)/Ni foam (NF) composite as a recyclable peroxymonosulfate (PMS) activator to decontaminate MMH with high robustness to the high-strength co-existing pollutants within a wide pH range. The interfacial synergism between CoFe-LDH and NF could promote the charge transfer in the catalysis. DFT and XPS analysis elucidated the introduction of Ni and Co greatly facilitate charge transfer from LDH/NF to PMS. This work offers profound insights propellant-containing wastewater via non-radical (1O2 and electron transfer) pathway in the presence of PMS with reclamation of cost-effective heterogeneous catalysts.

Synthesis of Hydroxyapatites via Wet Mechanochemical Process for Enhanced Catalytic Decomposition of Volatile Organic Compounds

Synthesis of Hydroxyapatites via Wet Mechanochemical Process for Enhanced Catalytic Decomposition of Volatile Organic Compounds

Study on organic matter decomposition and siderophore production of rhizobacteria isolated from black pepper grown in Loc Ninh, Binh Phuoc province, Vietnam

This study was carried out determining capability of organic compound decomposition and siderophore synthesis of 39 plant growth promotion rhizobacteria strains isolated from rhizosphere of black pepper (Piper nigrum L.) in a previous study. The ability to degrade organic compounds including proteins, lipids, cellulose and chitin was investigated by agar well diffusion method. The ability to produce siderophore was qualified by liquid CAS method and strains with good results were further investigated by PS-CAS agar plate method. The results showed that the number of bacterial strains capable of degrading protein, cellulose, chitin and lipid were 37, 27, 16 and 6, respectively. Twenty-two strains changed color of CAS agar, of which 6 strains had a band width of 4.5 cm. The seven best strains identified were Proteus mirabilis (LD2), Bacillus megaterium (LT4), B. subtilis (LT2), B. cereus (LD7, LD8, LD16, LT19) by Matrix Assisted Laser Desorption/Ionization-Time of Flight method. These were plant growth-promoting rhizobacteria that had been reported on potential applications in agriculture.

α-MoO3 with inhibitive properties in Fenton reactions and insights on its general impact on OH radical based advanced oxidation processes

MoO3 is an intensively researched metal oxide, and it is considered a promising visible light driven photocatalyst and an excellent adsorbent of cationic dyes. In the present work orthorhombic α-MoO3 was obtained via calcination of ammonium heptamolybdate where structural modifications were induced by changing the applied calcination temperature (400–750 °C). Further subtle structural (crystallographic plane ratio) and morphological modifications were achieved via hydrothermal recrystallization. Differences between samples were clearly evidenced by various characterization techniques, especially in the case of the crystalline facet ratio and the morphology. The differently structured α-MoO3 samples were investigated as an inhibitor for Fenton reactions where the organic compounds decomposition relies on the generation of OH radicals. It was found that α-MoO3 strongly inhibits the rate of methyl orange (MO) decolorization. This might imply that MoO3 could be a OH radical scavenger since Fenton reactions’ effectivity relies on the presence of OH and O2– radicals. We demonstrated that the inhibition efficiency of α-MoO3 correlates strongly with the acidification rate of the aqueous solution in the presence of α-MoO3. However, this pH decline was consistent with crystalline facet ratio within a sample series, while the recrystallized samples disprove this structural connection showing a more complex relationship between the structural characteristics of α-MoO3 and its inhibitive properties of Fenton reactions. The present work pointed out that MoO3 can inhibit reactions which are based on intensive OH radical generation processes such as photocatalysis.

Investigation of BiVO4-based advanced oxidation system for decomposition of organic compounds and production of reactive sulfate species

Growth of population and expansion of industries lead to increasing contamination of environment with various organic pollutants. If not properly cleaned, wastewater contaminates freshwater resources, aquatic environment and has huge negative impact on ecosystems, quality of drinking water and human health, therefore new and effective purification systems are in demand. In this work bismuth vanadate-based advanced oxidation system (AOS) for the decomposition of organic compounds and production of reactive sulfate species (RSS) was investigated. Pure and Mo-doped BiVO4 coatings were synthesized using sol-gel process. Composition and morphology of coatings were characterized using X-ray diffraction and scanning electron microscopy techniques. Optical properties were analyzed using UV–vis spectrometry. Photoelectrochemical performance was studied using linear sweep voltammetry, chronoamperometry and electrochemical impedance spectroscopy. It was shown that increase in Mo content affects the morphology of BiVO4 films, reduces charge transfer resistance and enhances the photocurrent in the solutions of sodium borate buffer (with and without glucose) and Na2SO4. Mo-doping of 5–10 at.% leads to 2- to 3-fold increase in photocurrents. Faradaic efficiencies of RSS formation ranged between 70 and 90 % for all samples irrespective of Mo content. All studied coatings demonstrated high stability in long-lasting photoelectrolysis. In addition, effective light-assisted bactericidal performance of the films in deactivation of Gram positive Bacillus sp. bacteria was demonstrated. Advanced oxidation system designed in this work can be applied in sustainable and environmentally friendly water purification systems.

Solubility and Decomposition of Organic Compounds in Subcritical Water.

In this article, studies on organic solubility and stability in subcritical water reported during the past 25 years have been reviewed. Data on the solubility and decomposition of organic compounds in subcritical water, a green solvent, are needed in environmental remediation, chemistry, chemical engineering, medicine, polymer, food, agriculture, and many other fields. For solubility studies, the experimental systems used to measure solubility, mathematical equations derived and applied for the modeling of the experimentally determined solubility data, and the correlation between the predicated and experimental data have been summarized and discussed. This paper also reviewed organic decomposition under subcritical water conditions. In general, the solubility of organics is significantly enhanced with increasing water temperature. Likewise, the percentage of organic decomposition also increases with higher temperature.

PHYSICO-CHEMICAL PROCESSES OF METHANOGENESIS UNDER THE INFLUENCE OF THE ELECTROMAGNETIC FIELD

Currently, waste disposal is strictly regulated by governments to reduce soil, water and air pollution caused by burial and direct discharge of waste into water. Anaerobic digestion has been touted as a means of dealing with organic waste while meeting humanity's energy needs. The process involves the production of biogas by microbial decomposition of organic compounds without oxygen, reducing the amount of organic matter to be removed. Anaerobic digestion produces a nutrient-rich digestate that can have agricultural value and produces methane-rich biogas that can be used as fuel directly or can be converted to compressed natural gas and liquefied natural gas. The purpose of the study is to determine the influence of magnetic fields on the physicochemical processes of methanogenesis and the output of biogas during the fermentation of pig manure. The work highlights the issue of the influence of a low-frequency electromagnetic field on the physicochemical processes of anaerobic fermentation of pig manure. The kinetics of chemical reactions in substrates under the influence of a magnetic field and its effect on the solubility of salts, acids and alkalis in solutions, as well as on the redox potential, pH value and electrophysical parameters of the substrate in the process of methanogenesis are considered. The yield of biogas under the influence of a low-frequency electromagnetic field on the process of anaerobic fermentation of the substrate and without influence was studied.

Comparison of the efficiency of organic compounds decomposition in sewage sludge using selected physical, chemical and biological methods

Comparison of the efficiency of organic compounds decomposition in sewage sludge using selected physical, chemical and biological methods

Synthesis of 2D/2D direct Z-scheme WO3/Bi5O7I heterojunctions for decomposition and detoxification of organic compounds under simulated sunlight

For this study, a WO3/Bi5O7I direct Z-scheme heterojunction material was successfully synthesized via a solvothermal-calcination method. The WO3/Bi5O7I heterostructure enhanced the absorption of light and accelerated the separation of charge carriers. Under simulated sunlight irradiation, the removal rate of rhodamine B (RhB) reached 99.6% over the optimal WB14 composite (mass ratio of WO3: Bi5O7I was 14%), which was 2.53 and 30 times that of pristine Bi5O7I and WO3, respectively. Experimental parameters including the WB14 dosage, initial RhB concentration, solution pH, and water sources were explored. Meanwhile, the WB14 exhibited excellent stability and reusability under simulated sunlight. The degradation pathway of RhB was speculated and the toxicity of intermediates was evaluated using the ECOSAR program. Moreover, tetracycline (TC) was employed as a common antibiotic to verify the universality of the catalysts. Capturing experiments and electron paramagnetic resonance (EPR) tests revealed that h+ served as the main active species in the photocatalysis, while OH and O2– played secondary roles. Finally, the formation of Z-scheme heterojunctions between the Bi5O7I and WO3 was inferred based on charge carrier migration and reactive species in the photocatalytic system. This study provides insights into the design of Z-scheme heterojunctions, which is helpful toward the development of Z-scheme heterojunction concepts.

Effects of volatile-char interaction on the product properties from municipal sludge pyrolysis

In order to realize the harmless treatment and resource utilization of municipal sludge, the effect of volatile-char interaction on the properties of sludge pyrolysis products was investigated using a two-stage pyrolysis reactor. The experimental results show that volatile-char interaction promotes the decomposition of organic compounds into small molecular gases, which increases the gas yield and reduces the liquid and oil yields. Under the experimental conditions, the volatile-char interaction increases the mass yields of H2, CO and CO2 to varying degrees, and the yield of H2 increases maximum by 55.7–114.5% compared to that without interaction. The effect of interaction on the composition of bio-oil occurs mainly at low temperature range of 400–600 ℃ by reducing the content of oxygen-containing compounds except for aldehydes/ketones. The physical and chemical structure of solid char changes dramatically with the interaction. The enhanced removal of O-containing groups occurs and the degree of aromaticity of the char is increased due to the strengthened dehydrogenation and polycondensation of hydrocarbons. Meanwhile, the transformation of non-hydroxyapatite phosphorus to hydroxyapatite phosphorus in solid phase products is greatly promoted at high temperature of 700–800 ℃, increasing the potential utilization of char as carbon-based phosphate fertilizer in agriculture.

Study the Effect of Dielectric Barrier Discharge (DBD) Plasma on the Decomposition of Volatile Organic Compounds

Recently, research has focused on non-thermal plasma (NTP) technologies as a way to remove volatile organic compounds from the air stream, due to its distinctive qualities, which include a quick reaction at room temperature. In this work, the properties of the plasma generated by the dielectric barrier discharge (DBD) system and by a glass insulator were studied. Plasma was generated at different voltages (3, 4, 6, 7, 8 kV ) with a fixed distance between the electrodes of 5 mm, and a constant argon gas flow rate of (2.5) I/min. DBD plasma emission spectra were recorded for each voltage. The Boltzmann plot method was used to calculate the electron temperature in the plasma ( ), and the Stark expansion method was used to calculate the electron density ( ). The decomposition of organic compounds (cyclohexane) was also studied using DBD plasma. The results showed that the potential difference between the two electrodes has a clear effect on the plasma parameters, as the temperature of the electrons and the density of electrons increase with the increase in the potential difference between the two electrodes. The DBD plasma system proved to be a good way to decompose volatile organic compounds, as the results proved the emission of hydrogen gas as one of the dissociation products of cyclohexane.

Microbial metabolic responses and CO2 emissions differentiated by soil water content variation in subarctic tundra soils.

Recent rapid air temperature increases across the northern-latitude tundra have prolonged permafrost thawing and snow melting periods, resulting in increased soil temperature (Ts) and volumetric soil water content (SWC). Under prolonged soil warming at 8°C, Alaskan tundra soils were incubated in a microcosm system and examined for the SWC differential influence on the microbial decomposition activity of large molecular weight (MW) humic substances (HS). When one microcosm soil (AKC1-1) was incubated at a constant SWC of 41% for 90 days (T = 90) and then SWC was gradually decreased from 41% to 29% for another T = 90, the initial HS was partly depolymerized. In contrast, in AKC1-2 incubated at a gradually decreasing SWC from the initial 32% to 10% for T = 90 and then increasing to 27% for another T = 90, HS depolymerization was undetected. Overall, the microbial communities in AKC1-1 could maintain metabolic activity at sufficient and constant SWC during the initial T = 90 incubation. In contrast, AKC1-2 microbes may have been damaged by drought stress during the drying SWC regimen, possibly resulting in the loss of HS decomposition activity, which did not recover even after re-wetting to an optimal SWC range (20-40%). After T = 90, the CO2 production in both treatments was attributed to the increased decomposition of small-MW organic compounds (including aerobic HS-degradative products) within an optimal SWC range. We expect this study to provide new insights into the early effects of warming- and topography-induced SWC variations on the microbial contribution to CO2 emissions via HS decomposition in northern-latitude tundra soil.

Insights into the different catalytic behavior between Ce and Cr modified MCM-41 catalysts: Cr2S3 as new active species for CH3SH decomposition

High sulfur resistance and high stability of catalysts are crucial for the catalytic decomposition of sulfur-containing volatile organic compounds. In this work, compared to 5Ce-MCM-41, the 5Cr-MCM-41 catalyst exhibited ultra-stability (no activity loss at 600 h) and higher sulfur resistance. The physical structure and chemical characteristics of the catalysts were analyzed by XRD, H2-TPR, NH3-TPD, CO2-TPD, XPS, and TEM. Combining the characterization results, we found that the 5Cr-MCM-41 catalyst presented outstanding catalytic performance due to superior reducibility and appropriate acidity, which results in the conversion of most of the C and S elements in the CH3SH to the gas-phase coke- and sulfur-containing products rather than accumulating on the catalyst surface. Meanwhile, the catalytic performance, reaction path, and deactivation mechanism of rare earth metal (Ce) and transition metal (Cr) modified MCM-41 catalysts were systematically investigated by in situ DRIFTS and DFT calculations. Additionally, a new active phase (sulfide state Cr2S3) was proposed and proved via accurately designed experiments, which plays a significant role in the collaborative removal of CH3SH with hexavalent chromium (Cr(VI)). These findings are beneficial for designing high sulfur resistance catalysts for the removal of CH3SH and other sulfur-containing products.

Study to Evaluate Photocatalytic Decomposition of Several Organic Compounds and Self-Cleaning Ability of Fabrics Containing ZnO

ZnO's ability to decompose organic substances is receiving much attention in multiple applications. ZnO has a broad spectrum of light absorption natural or synthetic, for a wide range of wavelengths, and is an important material with excellent properties, environmentally friendly, nontoxic, inexpensive, and high redox potential features with simple manufacturing methods. In this study, zinc oxide nanoparticles were synthesized by precipitation method with the participation of precursors (CH3COO)2Zn.2H2O and KOH. The surface morphology, chemical properties, and chemical composition of the ZnO catalyst were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy, and Energy-Dispersive X-ray Spectroscopy (SEM-EDS). The photocatalytic activity of ZnO was evaluated with the color change of methylene blue (MB), methylene orange (MO), and diluted coffee solutions. The results show that ZnO has a high photocatalytic activity with a decomposition ability of over 90% for MO and MB pigments, and over 40% for a coffee solution when irradiated under ultraviolet light. This study's cotton fabric impregnated with ZnO showed good self-cleaning effects against organic pigments, which are MB, MO, and coffee. The results were demonstrated by the color changes over a 19-h period of time.

Water trophy assessment of the cooling system of the “Dolna Odra” power plant on the basis of algae indicator organisms

The paper presents the results of water trophy assessment from various stations of the cooling system of the “Dolna Odra” (Poland) power plant. The assessment was made based on the indicator phytoplankton species collected four times at four sites located in different parts of the hydrological system cooling the technical infrastructure of the power plant. The sites were characterised by water with a natural temperature for individual seasons, as well as by thermals changed as a result of the discharge of cooling waters. For each site, the saprobic index was calculated based on indicator species.
 The analysis showed that the changes in trophic conditions, both in waters with changed thermals and in waters not subject to the influence of after-cool waters, are not subject to significant changes. The waters of all studied sites in the analysed periods of the year should be classified according to Sladeček and Sládečková (1996) to the waters of the β–mesosaprobic zone, with a saprobic index value ranging from 1.51 to 2.50 (average S = 2.0). This zone is characterised by the course of biochemical processes under aerobic conditions, as a result of which complete oxidation of the intermediate products of decomposition of organic compounds takes place.

Impact of biochar, fertilizers and cultivation type on environmentally persistent free radicals in agricultural soil

Environmentally persistent free radicals (EPFRs) have been considered as emerging contaminants due to their detrimental effects on human health. The adverse health impacts are attributed to oxidative stress induced by EPFRs through the formation of reactive oxygen species (ROS). In soils, it may also increase the degradation process of polymeric organic matter and/or undesired organic pollutants through hydroxyl radical activity. The biochar pyrolysis process entails the thermal decomposition of organic compounds in the biomass, with the carbonization conditions and feedstock type facilitating the formation of EPFRs. When biochar is used to amend soil, these radicals may promote the formation of ROS, and thus influence the transformation of organic and inorganic contaminants in soil and impact the rhizosphere. Agricultural soils are being amended with biochar to mainly increase carbon content and facilitate the plant growing conditions. Therefore, agricultural soils may become a source of EPFRs. However, the fate and transformations of EPFRs in soils after biochar amendment are not well understood or studied. This paper presents the first (to our knowledge) studies of EPFRs behaviour in agricultural soil with different input of biochar, cultivation types and residence time period. Different cultivation types, addition of fertilisers and variation in biochar input, on the one hand, and presence of metals in soil, biochar and fertilizers, on the other hand, provide different conditions for EPFRs formation, accumulation and fate in agricultural soils. Two significant factors have been found to determine the fate of EPFRs in soil: transition metal content (particularly those in reaction available form) and cultivation level of soil. Cultivation significantly decreased presence of EPFRs, both carbon-centered and oxygen-centered, in relatively short periods of time, while metal presence (and particularly through fertilizer supplementation) increases the half-life of radicals and transforms organic matter to more oxygen-centered EPFRs. The amount of biochar addition plays a secondary role as the EPFRs content in the soils is in a longer term primarily controlled by the other two factors. • Transition metal content and cultivation control fate of EPFRs from biochar to soil. • Transition metals addition with fertilizers increases O-centered EPFRs in soil. • Remediation or carbon supply determines the application method of biochar.

Ultimate Localization

We report approaches to grow directly noble-metal-(NM)-decorated nanotubes by self-organized anodization. Key to obtain highly defined tubes is an optimized and controlled anodization of Ti-Pt (or other NM) alloys in fluoride containing solutions. In general, the morphology of porous TiO2 and of the tubular layers is affected strongly by the electrochemical growth parameters. NM-decorated titanium-dioxide is a highly functional material that has numerous interesting properties, for example, in solar energy conversion, catalysis of the decomposition of organic compounds (self-cleaning). Therefore this simple approach to produce this highly defined nanoscopic form of NM-TiO2 bears a high potential for technological exploitation. Over the years numerous efforts have been devoted to the shrinkage of the NM-particles to enhance the usage of the noble metal. Evidently the most extreme case of shrinkage is the use of an isolated single atoms of Pt. The use of single atoms as a co-catalyst in photocatalysis has in recent years attracted strong interest, not only because the single atom state represents a maximized surface to volume efficiency, but also because single atom reactivity allows for unprecedented reaction pathways.In the presentation we discuss the formation of Pt dispersed and anchored as single atoms on TiO2 nanotubes and the use of such tubes in highly effective photocatalysis.

Experimental Proof of a Transformation Product Trap Effect with a Membrane Photocatalytic Process for VOC Removal.

The decomposition of volatile organic compounds by photocatalytic oxidation (PCO) has been widely studied. However, the technological development of this oxidative technique has to address how to handle the formation of transformation products. The work presented here investigates the original combination of a dense membrane separation process and PCO to intensify the trapping and reduction of PCO transformation products. Specific monitoring of toluene PCO transformation products, such as benzene and formaldehyde, in the outflow of both permeate and retentate compartments was proposed. The influence of operating parameters on the process, i.e., light intensity, pressure, membrane type, and catalyst mass, was also studied. The results reveal that membrane separation-PCO hybridization is particularly effective for reducing the presence of benzene and formaldehyde in the effluent treated. The benzene concentration in the outflow of the hybrid module can be reduced by a factor of 120 compared to that observed during the PCO of toluene alone.

Inline imaging reveals evolution of the size distribution and the concentration of microbubbles in dissolved air flotation

Dissolved air flotation (DAF) is an efficient process to remove impurities from fresh or salt water. As the removal is based on the agglomeration of impurities on the generated microbubbles, the size distribution and concentration of air bubbles are key parameters in dissolved air flotation. However, the development of microbubbles in the whole flotation process remains unexplored. In this study, we show that state-of-the-art inline microscopy enables the image acquisition of bubbles in DAF. Based on image analysis, thousands of microbubbles (10-200 µm) were analyzed within 6-12 min experiments. Consequently, bubble size distributions and bubble concentrations can be determined with moderate effort. Bubble size distributions were measured in a lab-scale DAF comprising a saturation unit, a decompression valve in/after which the bubbles are formed, and the actual flotation tank. The state of the microbubbles is not only determined at different positions within the tank but also in the supply pipe from the decompression valve to the tank. All bubble size distributions were unimodal and can be described well with Burr XII distributions. For fresh water, bubble size increased while bubble concentration decreased along the supply pipe between the decompression valve and the inlet of the flotation tank, indicating bubble coalescence. Compared to freshwater, saltwater inhibited this bubble coalescence in the pipe. Within the flotation tank, the bubble size did not change drastically for neither salt- nor freshwater. However, the bubble concentration decreased for both waters, which could be explained by dilution effects. Our results demonstrate that the developed inline method is a promising tool to study the evolution of microbubbles in flotation systems. Further, it might also be applied to investigate microbubbles in other processes such as fermentation, decomposition of organic compounds, and fouling mitigation in membranes.