Oxygen-limited Conditions Research Articles

CFD and LP code benchmark evaluating the onset of par operation in case of extremely low oxygen concentration

In many reactor containments Passive Autocatalytic Recombiners (PAR) are installed to mitigate the hydrogen threat in case of a severe nuclear reactor accident. PARs oxidize hydrogen catalytically into water vapor. The heat of catalytic reaction drives flow through the PAR unit by natural convection, which continuously brings “fresh” hydrogen-air mixtures to the PAR unit, thereby developing a self-sustained process until either hydrogen or oxygen falls below a minimum concentration.The test series (HR-33 to HR-35) of the OECD/NEA THAI-2 program investigated the influence of temperature, pressure and steam on the onset of hydrogen recombination in case of low or extremely low oxygen concentrations. These conditions with oxygen concentrations below 1 vol–% can occur in accident scenarios (e.g. late accident phase with molten core concrete interaction). A better understanding of the PAR performance in oxygen-limited conditions is important for hydrogen management in severe accidents.The test data of HR-35 was used for a blind benchmark exercise within the OECD/NEA joint project. Lumped parameter codes (MELCOR and COCOSYS) have been used as well as 3D/CFD codes (GASFLOW, GOTHIC and CFX). A variety of PAR models were used, including models based on engineering correlations, models with a detailed nodalization of the PAR unit, and a model with detailed heat and mass transfer process (REKO-DIREKT). Consequently, the benchmark provided a good opportunity to assess the PAR models that are deployed in the state of the art safety analysis tools, especially under conditions representative for the late phase of a severe accident.

Assessing oxygen limiting fermentation conditions for 2,3-butanediol production from Paenibacillus polymyxa

2,3-butanediol (2,3-BDO) is a platform chemical that can be converted to a wide array of products ranging from bio-based materials to sustainable aviation fuel. This chemical can be produced by a variety of microorganisms in fermentation processes. Challenges remain for high titer 2,3-BDO production during fermentation due to several parameters, but controlling oxygen is one of the most relevant processing parameters to ensure viable product output. This work investigated the fermentation of plant biomass sugars by the 2,3-BDO producer Paenibacillus polymyxa. Aerobic and oxygen limited fermentation conditions were initially evaluated using molasses-based media to determine cell growth and 2,3-BDO output. Similar conditions were then evaluated on hydrolysate from pretreated sweet sorghum bagasse (SSB) that contained fermentable sugars from structural polysaccharides. Fermentations in molasses media under aerobic conditions found that 2,3-BDO could be generated, but over time the amount of 2,3-BDO decreased due to conversion back into acetoin. Oxygen limited fermentation conditions exhibited improved biomass growth, but only limited suppression of 2,3-BDO conversion to acetoin occurred. Glucose depletion appeared to have a greater role influencing 2,3-BDO conversion back into acetoin. Further improvements in 2,3-BDO yields were found by utilizing detoxified SSB hydrolysate.

Countercurrent flame propagation inside vertical PMMA cylinders against pure oxygen flow

The countercurrent flame propagation against pure oxygen flow inside a vertical polymethyl methacrylate (PMMA) cylinder under oxygen-limited conditions was systematically investigated experimentally and numerically, with a particular attention given to the effect of the inner diameter (di = 6, 5, and 4 mm) of the cylinder. Metered pure oxygen was flowed through the cylinder from the bottom and, when ignition was initiated at the top, a blue flame was formed and propagated downwards in a quasi-steady state. The flame propagation velocity (Sf) was determined by analysing the digital video record of the entire flame propagation process. The flame was apparently fuelled by the volatiles from the pyrolysis of the inner surface the PMMA cylinder. The rate of pyrolysis (mpy) was estimated by measuring the initial and remaining masses of the PMMA cylinder. A transient two-dimensional axisymmetric numerical model considering one-step finite-rate PMMA pyrolysis and gaseous phase oxidation reactions was developed and applied to simulate the flame structure and propagation process. By comparing the measured and predicted Sf and mpy, the validity of the numerical model was confirmed. The flame structure was depicted and the role of the gas – solid heat transfer was quantified. A decrease in di leads to an increase in the heat flux that preheats the unburnt PMMA ahead of the flame front. This results in a greater pyrolysis rate of the unburnt PMMA and a faster flame propagation velocity. Effects of thickness of the PMMA cylinder and radiative heat transfer from the flame to the inner PMMA surface were also discussed.

L-2-Hydroxyglutarate Protects Against Cardiac Injury via Metabolic Remodeling.

L-2-hydroxyglutarate (L2HG) couples mitochondrial and cytoplasmic energy metabolism to support cellular redox homeostasis. Under oxygen-limiting conditions, mammalian cells generate L2HG to counteract the adverse effects of reductive stress induced by hypoxia. Very little is known, however, about whether and how L2HG provides tissue protection from redox stress during low-flow ischemia (LFI) and ischemia-reperfusion injury. We examined the cardioprotective effects of L2HG accumulation against LFI and ischemia-reperfusion injury and its underlying mechanism using genetic mouse models. L2HG accumulation was induced by homozygous (L2HGDH [L-2-hydroxyglutarate dehydrogenase]-/-) or heterozygous (L2HGDH+/-) deletion of the L2HGDH gene in mice. Hearts isolated from these mice and their wild-type littermates (L2HGDH+/+) were subjected to baseline perfusion and 90-minute LFI or 30-minute no-flow ischemia followed by 60- or 120-minute reperfusion. Using [13C]- and [31P]-NMR (nuclear magnetic resonance) spectroscopy, high-performance liquid chromatography, reverse transcription quantitative reverse transcription polymerase chain reaction, ELISA, triphenyltetrazolium staining, colorimetric/fluorometric spectroscopy, and echocardiography, we found that L2HGDH deletion induces L2HG accumulation at baseline and under stress conditions with significant functional consequences. In response to LFI or ischemia-reperfusion, L2HG accumulation shifts glucose flux from glycolysis towards the pentose phosphate pathway. These key metabolic changes were accompanied by enhanced cellular reducing potential, increased elimination of reactive oxygen species, attenuated oxidative injury and myocardial infarction, preserved cellular energy state, and improved cardiac function in both L2HGDH-/- and L2HGDH+/- hearts compared with L2HGDH+/+ hearts under ischemic stress conditions. L2HGDH deletion-induced L2HG accumulation protects against myocardial injury during LFI and ischemia-reperfusion through a metabolic shift of glucose flux from glycolysis towards the pentose phosphate pathway. L2HG offers a novel mechanism for eliminating reactive oxygen species from myocardial tissue, mitigating redox stress, reducing myocardial infarct size, and preserving high-energy phosphates and cardiac function. Targeting L2HG levels through L2HGDH activity may serve as a new therapeutic strategy for cardiovascular diseases related to oxidative injury.

Successful Application of Anammox Using the Hybrid Autotrophic-Heterotrophic Denitrification Process for Low-Strength Wastewater Treatment.

Directly integrating anammox into sewage treatment is attractive, but anammox bacteria (AnAOB) enrichment is complex due to vicious competition from heterotrophic bacteria (HB). A novel strategy of optimal organics management using a preanaerobic stage and subsequent limited-oxygen conditions (0.32 ± 0.15 mg-O2/L) is applied, and a hybrid autotrophic-heterotrophic denitrification process is developed to treat sewage-like wastewater with a COD/N ratio of 3.1 for 420 days. The stable process was achieved, and a high total nitrogen removal rate of 0.53 kg-N/(m3·d) was obtained compared to conventional nitrification/denitrification. The 16S rRNA high-throughput sequencing analysis suggested that the relative abundance of the nonendogenous HB (Denitratisoma and Thauera) was drastically reduced (P ≤ 0.001), whereas the endogenous denitrifying HB (Candidatus (Ca.) Competibacter) was significantly enriched in the anammox granules (9.98%, P ≤ 0.001). Moreover, Ca. Competibacter as an inner core and Nitrospira and Ca. Brocadia as an outside coating of the anammox granules indicated the cooperation of AnAOB with HB as revealed by laser-scanning confocal microscopy and qPCR. In situ tests further confirmed nitrite from two pathways (partial nitritation and endogenous partial denitritation) that favored AnAOB enrichment. Optimal organics management can mitigate the competition of HB with AnAOB by redirecting the metabolic pathways and microbial community, which is critical to directly integrating anammox into sewage treatment.

The nitrogen-doped graphene-like carbon nanosheets: Confined construction and oxygen-limited oxidation for higher removal efficiency toward organic contaminants

Due to the excellent properties, including large specific surface area, stable structure, and strong adsorbability, mesoporous carbon material has captured a lot of attention and applied to various fields. Here, we proposed a facile approach to synthesize nitrogen-doped graphene-like carbon (NGLC) nanosheets and investigated the performance in wastewater decontamination. In this work, NGLC nanosheets were obtained via the combination of confined synthesis and low-temperature calcination in oxygen-limited condition. Such NGLC nanosheets were composed of several carbon layers with porous structure, which provided a large specific surface area (421.85 m2 g−1). Meanwhile, the NGLC was endowed with abundant active sites, including oxygen-contained groups and nitrogen species, via low-temperature calcination in oxygen-limited conditions. These properties allow the NGLC to be an excellent adsorbent for organic pollution treatment. The maximum adsorption capacities toward cationic dyes, the rhodamine B (RhB) and methylene blue (MB), reached as high as 1272.74 mg g−1 and 679.55 mg g−1, respectively, indicating the promising potential for the cationic contaminants treatment. The excellent reusability and wide pH suitability (2–10) were observed by batch adsorption experiments. The kinetic adsorption test showed that 98.97% of RhB could be adsorbed by NGLC-450 after 150 min contact time at 25 °C, while the RhB removal efficiencies from bulk polydopamine derived carbon material (denoted as PDA carbon) and NGLC-450-Ar (generated at argon atmosphere) were only 17.56% and 62.03%, respectively. The significant difference in adsorption performance implied the importance of confined synthesis with template-assistance and oxygen-limited oxidation. The adsorption process involved the pore filling & adsorption, electrostatic interaction, and π-π interaction, as well as the hydrogen bonding, which was demonstrated by experiment and Fourier transform infrared (FT-IR) & X-ray photoelectron spectroscopy (XPS) analysis.

Inhibition of polycyclic aromatic hydrocarbon (PAHs) release from sediments in an integrated rice and crab coculture system by rice straw biochar

As persistent organic pollutants that are widely present in the environment and that pose substantial threats to human health, polycyclic aromatic hydrocarbons (PAHs) have received much attention from researchers around the world, but few studies have investigated the PAHs contamination of sediments in rice and crab coculture farming systems. In this study, rice straw biochar was prepared from rice straw, an abundant agricultural waste product, under oxygen-limited conditions at 500 °C. The rice straw biochar was characterized by scanning electron microscopy (SEM), specific surface and pore size analysis (BET), Fourier transform infrared spectroscopy (FTIR), and Raman Spectroscopy. The effect of using rice stalk biochar as a sorbent on the inhibition of the release and migration of PAHs from sediments in a rice and crab coculture system and the biological effects of PAHs within the system were studied for the first time. The results showed that rice straw biochar has a rich pore structure and high specific surface area, and the high-temperature charring method utilized in this study improved the charring and aromaticity of rice straw. The addition of rice straw biochar increased the immobilization of PAHs in sediments by 40.41%–119.62% and inhibited the migration of PAHs from the sediments to the overlying water, which reduced the PAHs content of the pore water at the sediment-water interface by 11.41%–58.73% and reduced the PAHs content of the overlying water in the dissolved and particulate forms by 54.67%–81.03% and 5.08%–55.20%, respectively. The addition of rice straw biochar reduced the biological effectiveness of PAHs in the system, and the enrichment of PAHs in crabs and rice decreased by 38.17–69.53% and 32.12%–97.63%, respectively. In addition, rice straw biochar changed the distribution of PAHs in rice, increasing the PAHs content of the stalks and leaves of rice by 2%–15% and 4%–17%, respectively, while the PAHs content of the roots was reduced by 8%–20%. These results confirm that rice straw biochar can effectively inhibit the migration and release of PAHs from sediments and reduce the bioavailability of phenanthrene (PHE) in integrated farming systems. The results provide theoretical and technical support for the study of straw waste utilization and remediation of PAHs pollution.

The Orphan Response Regulator Rv3143 Modulates the Activity of the NADH Dehydrogenase Complex (Nuo) in Mycobacterium tuberculosisvia Protein-Protein Interactions.

Two-component signal transduction systems enable mycobacterial cells to quickly adapt and adequately respond to adverse environmental conditions encountered at various stages of host infection. We attempted to determine the role of the Rv3143 “orphan” response regulator in the physiology of Mycobacterium tuberculosis and its orthologue Msmeg_2064 in Mycobacterium smegmatis. We identified the Rv3143 protein as an interaction partner for NuoD, a member of the type I NADH dehydrogenase complex involved in oxidative phosphorylation. The mutants Δrv3143 and Δmsmeg_2064 were engineered in M. tuberculosis and M. smegmatis cells, respectively. The Δmsmeg_2064 strain exhibited a significant reduction in growth and viability in the presence of reactive nitrogen species. The Rv3143-deficient strain was sensitive to valinomycin, which is known to reduce the electrochemical potential of the cell and overexpressed genes required for nitrate respiration. An increased level of reduction of the 2,3,5-triphenyltetrazolium chloride (TTC) electron acceptor in Δrv3143 and Δmsmeg_2064 cells was also evident. The silencing of ndh expression using CRISPRi/dCas9 affected cell survival under limited oxygen conditions. Oxygen consumption during entry to hypoxia was most severely affected in the double-mutant Δmsmeg_2064 ndhCRISPRi/dCas9 . We propose that the regulatory protein Rv3143 is a component of the Nuo complex and modulates its activity.

The Mechanism of Cu2+ Sorption by Rice Straw Biochar and Its Sorption-Desorption Capacity to Cu2+ in Soil.

Copper (Cu) pollution in soils has received considerable research attention globally, and biochar has been widely used as an adsorbent for soil pollution of Cu. However, most of the studies focused on the adsorption capacity of biochar, the bioavailability of Cu absorbed by biochar remains unclear. In this work, rice straw biomass was pyrolyzed under oxygen-limited conditions at 400°C (BC400) and 600°C (BC600), their apparent structure, group characteristics, and basic physical and chemical properties were determined. The isothermal and kinetics adsorption of Cu by BC400 and BC600 were analyzed. A pot experiment was used to evaluate the passivation of Cu in the soil by biochar and the bioavailability of Cu adsorbed by biochar in the soil. The smooth surfaces of BC400 evolved into more rough surfaces for BC600, and both types of surfaces may give active sorption sites for Cu, according to SEM pictures. FTIR analysis suggested that BC600 is endowed with more condensed aromatic carbon structures and more available polar functional groups. The adsorption processes of Cu2+ by biochar were better fitted Langmuir equation and pseudo-second-order kinetic model. The adsorption isotherms showed monolayer adsorption of Cu2+ on biochar. The maximum adsorption capacities of BC600 and BC400 on Cu2+ were 43.75 and 30.70mg g-1, respectively. Moreover, the pot experiment showed that BC400 and BC600 not only have a strong "passivation" effect on Cu in soil but also prevent the release of adsorbed Cu. Overall, more aromatic carbon structure, more polar functional groups, and higher pH are associated with BC600's increased Cu immobilization ability in soil.

Vitreoscilla hemoglobin enhances the catalytic performance of industrial oxidases in vitro.

Oxidases are a group of oxidoreductases and need molecular oxygen in the catalytic process. Vitreoscilla hemoglobin (VHb) can improve the growth and productivity of host cells under hypoxic conditions, rendering it attractive for industrial application. In this work, we demonstrated the addition of immobilized VHb increased the catalytic activity of immobilized D-amino acid oxidase of Trigonopsis variabilis by two-fold when catalyzing cephalosporin C under oxygen-limited conditions. A similar increase of activities was observed in glucose oxidase, alcohol oxidase, and p-hydroxymandelate synthase by adding free VHb or immobilized VHb under hypoxic conditions. When L-glutamate oxidase was used to catalyze L-glutamate to produce α-ketoglutarate, the yield increased from 80.6 to 96.9% by fusing VHb with L-glutamate oxidase. Results demonstrated that the addition of free VHb, immobilized VHb, or fused VHb could increase the catalytic efficiency of oxidases, which was considered by increasing the concentration of the microenvironmental oxygen. Thus, VHb may become a potential additive agent to promote the efficiency of oxidases on industrial scale . KEY POINTS: • First time confirmation of facilitation of VHb on several industrial oxidases in vitro • VHb functions under hypoxic conditions rather than oxygen-enriched conditions • VHb functions in vitro in the form of free, immobilized protein and fusion enzyme.

Enhancing ammonia oxidation mediated using different crystalline Mn-oxides in an anoxic environment

A recent study found that the nitrogen cycle in marine sediments can occur under oxygen-limited conditions, and this is associated with a reduction of Mn (IV). However, the effect of MnO2 mediated anoxic ammonia oxidation in different sediments field test results are controversial. In this study, based on the fact that the crystal form and morphology of MnO2 in marine sediments are affected by geochemistry, α-, β-, γ-MnO2 and amorphous MnO2 were prepared to explore the effect of the different MnO2 crystals on nitrogen removal under oxygen-limited conditions. The experimental results showed that the anoxic ammonia oxidation process was mediated by microorganisms, and the reaction was affected by pH and temperature. The optimal pH was 7 in the range of pH 4–9 and the optimal temperature was 25 °C in the range of 10 °C–40 °C. When the initial concentration of NH4+-N was 50 mg/L, the removal amounts of NH4+-N under an anoxic condition by α-, β-, γ-MnO2 and amorphous MnO2 were 18.97 mg/L/d, 6.12 mg/L/d, 10.68 mg/L/d and 24.89 mg/L/d, respectively. During the anoxic oxidation between MnO2 and NH4+-N, the adsorption process occurred. In addition, the oxidation process produced both NOx−-N (nitrification reaction) and gaseous nitrogen (ammonia oxidation reaction). The kinetic study showed that the NH4+-N removal process conformed to the pseudo-second-order rate model, and the removal rates were ranked as amorphous MnO2 > α- > γ- > β-MnO2. Together, these results showed that the amorphous MnO2 crystal structure was conducive to improve anoxic ammonia oxidation and nitrogen removal under oxygen-limited conditions.

Ammonium Removal and Potential Microbial Interactions under Oxygen-Limited Conditions

Ammonium Removal and Potential Microbial Interactions under Oxygen-Limited Conditions

Degradation Behavior of Biodegradable Plastics in Thermophilic Landfill Soil and Wastewater Sludge Conditions

In this study, three common biodegradable plastics, namely, poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), poly(butylene succinate) (PBS) and poly(butylene adipate-co-terephthalate) (PBAT) were all buried in a mixture of landfill soil and wastewater sludge and incubated under thermophilic (61°C) oxygen-limited conditions. At the end of the 90-day test, the degradation ranking order was PHBV > PBS > PBAT. Only PHBV was completely degraded over the 60 days, while PBS and PBAT displayed 24.04% ± 3.37% and 18.26% ± 3.77% weight loss, respectively. The differences in the degradation and disintegration profiles among these materials were observed. The results showed that PHBV lost its thickness and degraded from the edges of the specimens. Both PBS and PBAT were reduced into small fragile fragments during the degradation process. SEM micrographs revealed that irregular roughness with many holes and cracks was characteristic of PHBV, while slightly smooth surfaces were found on PBS and PBAT. All the materials showed continuous decreases in the thermal stability and the percentage of carbon content in the molecular structures after the degradation test. Fourier transform infrared (FTIR) spectroscopy revealed that the chemical structure of PHBV was changed during the biodegradation test, while both PBS and PBAT were unchanged under the same test conditions. However, the peak for carboxylate ions was found after the degradation of all the samples. Having a deep understanding of the degradability behavior can contribute to the development of biodegradable plastic waste management in the future.

Comparative metabolome and transcriptome analyses of the properties of Kluyveromyces marxianus and Saccharomyces yeasts in apple cider fermentation

This study explored the application of Kluyveromyces marxianus and Saccharomyces cerevisiae (commercial and wild type) in the alcoholic fermentation of Fuji apple juice under static conditions. Metabolome analyses revealed that ethyl esters, including ethyl hexanoate, ethyl decanoate, ethyl octanoate, octanoic acid and decanoic acid, were the dominant components in ciders fermented by the Saccharomyces yeasts. In the K. marxianus ciders, ethyl acetate, hexyl acetate, propyl acetate and acetic acid were the most abundant volatiles, suggesting that the cider fermented by K. marxianus might have a fruitier smell. Transcriptome analyses were adapted to gain insight into the differential metabolite patterns between K. marxianus and S. cerevisiae during cider fermentation. GO and KEGG enrichments revealed that the metabolic pathways of glucose, organic acids and amino acids during cider fermentation were quite different between these two yeasts. The K. marxianus strain exhibited a higher rate of glycolysis and ethanol fermentation than did Saccharomyces yeasts under oxygen-limited conditions. It also reduced the metabolic flux of acetate into acetyl-CoA and then into the TCA cycle, increasing the syntheses of ethyl acetate and relevant esters, which may affect its cell growth under anaerobic conditions but enriched the taste and variety of aromas in apple cider.

Modelling Cell Growth and Polyhydroxyalkanoate (PHA) Polymer Synthesis by Pseudomonas Putida LS46 under Oxygen-Limiting Conditions

Background: Polyhydroxyalkanoates (PHAs) are biodegradable, biocompatible, and non-toxic polymers synthesized by bacteria that may be used to displace some petroleum-based plastic materials. One of the major barriers to the commercialization of PHA biosynthesis is the high cost of production. Objective: Oxygen-limitation is known to greatly influence bacterial cell growth and PHA production. In this study, the growth and synthesis of medium chain length PHAs (mcl-PHAs) by Pseudomonas putida LS46, cultured in batch-mode with octanoic acid, under oxygen-limited conditions, was modeled. Methods: Four models, including the Monod model, incorporated Leudeking-Piret (MLP), the Moser model incorporated Leudeking-Piret (Moser-LP), the Logistic model incorporated Leudeking- Piret (LLP), and the Modified Logistic model incorporated Leudeking-Piret (MLLP) were investigated. Kinetic parameters of each model were calibrated using the multi-objective optimization algorithm, Pareto Archived Dynamically Dimensioned Search (PA-DDS), by minimizing the sum of absolute error (SAE) for PHA production and growth simultaneously. Results and Conclusions: Among the four models, MLP and Moser-LP models adequately represented the experimental data for oxygen-limited conditions. However, the MLP and Moser-LP models could not adequately simulate PHA production under oxygen-excess conditions. Modeling cell growth and PHA will assist in the development of a strategy for industrial-scale production.

Characterization of organophosphate pesticide sorption of potato peel biochar as low cost adsorbent for chlorpyrifos removal

There has been a growing interest in the scientific world in the production of biochar from natural organic wastes as potential sustainable precursors for bioremediation. Potato peel biochar was produced by slow pyrolysis method under oxygen-limited conditions and used as bio adsorbent in bioremediation of commercial pesticide having Chlorpyrifos as an active component. Chlorpyrifos is an organophosphate pesticide, highly neurotoxic, and primarily targets the central nervous system of pests and insects. The excess residues of chlorpyrifos are hazardous to environmental flora and fauna. Chlorpyrifos was treated against biochar at varying physical parameters and further optimized by using response surface methodology through Box-Behnken design (BBD). 72.06% of pesticide removal was observed post 24 h of treatment against a pesticide concentration of 1346.85 μg/ml with a biochar concentration of 1.04 mg/ml under room temperature at pH 5.04. Biochar was characterized by proximate and ultimate analysis, FTIR, and SEM-EDX. Characterization by SEM-EDX showed the surface morphology and minerals on the peel and biochar. Microgram of potato peel shows pores of larger size than biochar having many cavities with different dimensions. In the plant system, growth morphology, nutritional status, polyphenols, total antioxidant content, and free radical scavenging activity were assessed. Enhancement in presence of biochar was recorded in growth morphology and plant biomolecules including photosynthetic pigments. Better translocation of the nutrient is recorded in biochar treated plants, as evidenced by the low amount of carbohydrate and protein in treated leaves. Biocompatibility assessment of chlorpyriphos in fish erythrocytes showed 43.26% hemolysis by pesticide-treated biochar. The practical use of this approach can also be best utilized if applied to those geographical regions where the soil pH is acidic. Biochar is a marketable bio-product, which can have a positive impact in agriculture, industries, and the energy sector creating a bio-based economy with reduced environmental pollution.

Oil crystallization properties as an index for monitoring early stage curing of oil-based paints: DSC analysis on linseed oil systems

In this work, we propose to follow the crystallization capability of oils in oil-based paints, during curing, as an indirect index of the matrix status in the early stages of paint film formation that usually are indicative and crucial to understand the process evolution. To proof the concept, the oil crystallization properties were investigated through DSC measurements on samples of both unpigmented linseed oil and two model paints, composed by lead white + linseed oil (LWLO) and ultramarine blue + linseed oil (UBLO), at different ageing time at room and oxygen-limiting conditions. The results indicate that the curing process strongly affects the oil’s ability of forming crystals in the paint layers, and the proposed experimental approach is rather suitable and sensitive enough to discriminate differences between the action of pigments and environmental conditions. On the other hand, despite the simplicity and the potentiality, this approach is limited at the early stages of paint curing offering an index of the overall matrix status and therefore must be intended as a complementary method that has to be integrated with other approaches if the aim is to explore in detail the chemical and physical aspects of the curing process.

Pyrolysis of rice husk using CO2 for enhanced energy production and soil amendment

Anthropogenic CO2 generations from use of fossil resources has led to catastrophic climate problems. Biochar is a promising material for CO2 capture and storage in soil, because it does not require additional storage space. To produce biochar, pyrolysis is required in an oxygen-limited condition. In an attempt to offer more environmentally benign route for biochar formation, this study introduced CO2 as a reaction agent. Using rice husk as a model compound, biochars were produced under CO2 and N2 condition. Porosity of rice husk biochars (RHBs) were enhanced under CO2 condition, because CO2 affected to formation of nano-sized pores. pH and moisture retention capacity of garden soil was controlled with an addition of RHBs. Mixtures of garden soil and RHB were also used as cultivation media for growth of barley grass, and plant growth in the mixtures was improved by 20% comparing to garden soil. Moreover, CO2 contributed to enhanced syngas generation during biochar production through gas phase reactions between CO2 and volatile compounds. Thus, this study proved that CO2 is a useful reactant for pyrolysis of biomass waste.

Opportunities and challenges of applying biochar to boost agricultural output and repair salt-damaged soils

Soil salinization is recognized as a serious form of soil degradation, affecting crop production and compromising food security. It is crucial to remediate the negative impacts of soil salinization to improve the associated soil functions. Biochar amendments are used to reclaim the salt-affected lands. Therefore, the main objective of the present paper was to review and discuss the recent studies investigating a role of biochar in improving soil properties and plant growth in salt-affected soils. Recently, biochar (solid carbonaceous residue, produced under oxygen-free or oxygen-limited conditions at temperatures ranging from 300 to 1000 C) has attracted considerable attention as a soil amendment. An emerging pool of knowledge shows that biochar addition is effective in improving physical, chemical and biological properties of salt-affected soils. Biochar amendments improve not soil properties but also support plant growth and ameliorate soil problems. However, some studies have also found an increase in soil salinity with biochar application at high rates. Further, the high cost associated with production of biochar and high application rates remains a significant challenge to its widespread use in areas affected by salinity. Therefore, the underlying mechanisms of such beneficial effects provided by biochar amendment of soils are highly complex. Therefore, more in-depth studies are needed to understand biochar interactions with soil organisms under extreme environments, which would help achieve maximum benefits of biochar under saline soil conditions.

Pyrite effects on the oxidation of in situ crude oil

As an enhanced oil recovery method, the air injection process (AIP) has been applied for decades. However, deviations are still being identified between laboratory tests and field applications. One possible reason for such deviations is the formation minerals of the crude oil reservoir. Some natural minerals are beneficial for the oxidation of hydrocarbons and may affect the AIP behavior. Herein, the accelerated-rate calorimetry (ARC) was adopted to study the crude oil oxidation when containing pyrite or iron oxide under adiabatic and high-pressure conditions. The temperature profiles and detailed kinetic data from the ARC tests were compared for the crude oil oxidation traits, with different ground mineral particles presented in the ARC vessel, to figure out the catalytic effects of iron minerals on the crude oil oxidation. Results indicate that iron oxide showed a catalytic effect on the high-temperature oxidation period of crude oil, whereas the pyrite could not generate enough iron oxides to catalyze crude oil oxidation under limited oxygen conditions. During the test, since pyrite oxidizes before the crude oil, the enthalpy from pyrite oxidation could benefit the onset of crude oil oxidation. Hence, this study could be beneficial for future AIP engineering design and AIP candidate reservoir screening.