Increasing Degree Of Oxidation Research Articles

Dual-Self-Crosslinking Effect of Alginate-Di-Aldehyde with Natural and Synthetic Co-Polymers as Injectable In Situ-Forming Biodegradable Hydrogel.

Injectable, in situ-forming hydrogels, both biocompatible and biodegradable, have garnered significant attention in tissue engineering due to their potential for creating adaptable scaffolds. The adaptability of these hydrogels, made from natural proteins and polysaccharides, opens up a world of possibilities. In this study, sodium alginate was used to synthesize alginate di-aldehyde (ADA) through periodate oxidation, resulting in a lower molecular weight and reduced viscosity, with different degrees of oxidation (54% and 70%). The dual-crosslinking mechanism produced an injectable in situ hydrogel. Initially, physical crosslinking occurred between ADA and borax via borax complexation, followed by chemical crosslinking with gelatin through a Schiff's base reaction, which takes place between the amino groups of gelatin and the aldehyde groups of ADA, without requiring an external crosslinking agent. The formation of Schiff's base was confirmed by Fourier-transform infrared (FT-IR) spectroscopy. At the same time, the aldehyde groups in ADA were characterized using FT-IR, proton nuclear magnetic resonance (¹H NMR), and gel permeation chromatography (GPC), which determined its molecular weight. Furthermore, borax complexation was validated through boron-11 nuclear magnetic resonance (¹¹B NMR). The hydrogel formulation containing 70% ADA, polyethylene glycol (PEG), and 9% gelatin exhibited a decreased gelation time at physiological temperature, attributed to the increased gelatin content and higher degree of oxidation. Rheological analysis mirrored these findings, showing a correlation with gelation time. The swelling capacity was also enhanced due to the increased oxidation degree of PEG and the system's elevated gelatin content and hydrophilicity. The hydrogel demonstrated an average pore size of 40-60 µm and a compressive strength of 376.80 kPa. The lower molecular weight and varied pH conditions influenced its degradation behavior. Notably, the hydrogel's syringeability was deemed sufficient for practical applications, further enhancing its potential in tissue engineering. Given these properties, the 70% ADA/gelatin/PEG hydrogel is a promising candidate and a potential game-changer for injectable, self-crosslinking applications in tissue engineering. Its potential to revolutionize the field is inspiring and should motivate further exploration.

Enhancement of interaction between Shenhua coal and GON-based dispersant with “surface-to-surface” adsorption by regulating the oxidation degree of GON: Experiments and simulations

The present study focuses on the synthesis of several graphene oxide nanosheet (GON)-based dispersants with an adsorption mode of “surface-to-surface” for the preparation of Shenhua coal (SC) water slurry (SCWS), achieved by grafting allyl polyoxyethylene ether (APEG) onto GON edges with varying degrees of oxidation using emulsion polymerization and esterification techniques. The impacts of the oxidation degree of GON on its structural characteristics and the performance of GON-based dispersants in SCWS were comprehensively assessed through a range of experimental techniques, alongside molecular dynamics (MD) simulations. Results demonstrated that with the increase in oxidation degree, there was an elevation of oxygen-containing groups, in which the content of COH decreased while the content of COC increased. Among all dispersants, GA-2, which was synthesized using GON-2 as the raw material with a graphite-to-KMnO4 mass ratio of 1:2.5, exhibited superior viscosity-reducing and stabilizing abilities compared to other dispersants. All SCWSs demonstrated pseudoplastic fluid behavior and showed good agreement with the Herschel-Bulkley model. After the adsorption of dispersants in SC, both the Zeta potential and surface wettability of SC significantly improved, especially with GA-2. The interaction mechanism between the dispersant and SC was analyzed by establishing and employing three adsorption models (M-1, M-2, and M-3). The interfacial adsorption structure confirmed that the dispersant exhibited “surface-to-surface” mode on coal through hydrophobic interaction, hydrogen bonding, and π–π interaction. Energy studies revealed that M-2 with the highest Eads (−105.31 kcal/mol) demonstrated superior adsorption strength compared to M-1 and M-3. Investigations into water molecule mobility revealed that the interaction between the GON-based dispersant and SC resulted in a reduction of water molecule mobility, thereby promoting water molecule aggregation to facilitate the formation of hydration films and enhance SCWS stability. In summary, an optimal oxidation degree of GON was found to be crucial for enhancing the performance of GON-based dispersants; higher oxidation levels may hinder dispersant adsorption on coal surfaces by converting hydroxyl and carboxyl groups into epoxide groups, thus impairing the conjugated structure.

Evolution of macromolecular structure during coal oxidation via FTIR, XRD and Raman

The analysis of the macromolecular structure and morphology in coal during oxidation is the basis to explore the mechanism of spontaneous combustion. To explore the evolutionary rules of coal macromolecular structure during oxidation, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Raman Spectroscopy (Raman) were employed to analyze the coal samples with different oxidation degrees. The results revealed that the oxidation action led to the decrease of the aliphatic structures and aromatic hydroxyl groups in coal, while promoting the formation of oxygen-containing functional groups and aromatic structures. It also led to a relative increase of free hydroxyl groups linked to hydrogen bonds. The aromatic layer spacing (d002) decreased with increasing oxidation degree, while the microcrystal stacking height (Lc), the aromatic layer diameter (La), the average number of crystal stacking layers (n) generally increased. It indicated that small aromatic ring molecules in coal could undergo continuous polymerization during oxidation to form a single aromatic layer structure. The variation of Raman spectrum parameters exhibited a consistent decreasing trend in WD/WG, ID/IG, AD/AG, and A(GR+SL)/AG value, indicating an increase in the vibration of sp2 hybridization carbon atoms within the lattice structure of coal. Conversely, PG-D, AS/AD and A(GR+VL+VR)/AD value increased overall, suggesting that small aromatic rings decreased in content during oxidation while polymerizing into larger aromatic rings. The coal structure underwent a brief stage of disordered evolution during oxidation, followed by removal of impurity structures and condensation of aromatic structures due to increasing oxidation temperatures, ultimately leading to a highly ordered crystalline state. The oxidation process significantly influenced the development of coal's aromatic structure, particularly in less metamorphic coal. The research findings provide a theoretical basis for analyzing the underlying mechanism behind spontaneous combustion induced by coal oxidation.

Oxidation-alkaline-enhanced abiotic humification valorizes lignin-rich biogas digestate into artificial humic acids

This study introduces a cost-effective, mild thermal abiotic humification method for producing highly humified artificial humic acids (AHAs) from lignin-rich biogas digestate. Derived from the anaerobic digestion of cattle manure, the digestate slurry undergoes an MnO2-KOH-urea-enhanced humification reaction. Key process variables, such as MnO2 dose (0–15 mg/L), KOH dose (0–1 mol/L), urea dose (0–1.2 mol/L), reaction time (30–150 min), and temperature (25–85 °C), were systematically explored to optimize AHA yield, carboxylic acid content, and lignin removal. Optimal conditions, employing 7.69 mg/L of MnO2, 0.57 mol/L of KOH, and 0.63 mol/L of urea at 85 °C for 106 min, resulted in an impressive AHA yield of 32.15%, featuring a significant carboxylic acid content of 3.325 mmol/g. Under these conditions, up to 65% of lignin was effectively removed, accompanied by the release of orthophosphate up to 258 mg/L. The produced AHAs exhibited reduced toxicity, as demonstrated by substantial reductions of 54.13%, 57.14%, and 42.50% in phenols, furfural, and hydroxymethylfurfural, respectively. Notably, the AHAs displayed favorable characteristics, including a lower molecular weight (760.49 g/mol), diminished aromaticity (66.25% reduction), higher humification degree (lower C/N ratio of 8.79), increased oxidation degree (higher O/C ratio of 0.6), and elevated spectral index of humification (higher E4/E6 of 4.58). Analytical techniques, such as FT-IR, XPS, and TGA-MS, revealed chemical resemblance and enhanced functionality of AHAs compared to natural counterparts. Differentiation between AHA, lignin, and humification residues was confirmed through SEM-EDX, ICP-OES, and organic/inorganic carbon analyses. The obtained AHAs exhibit promising characteristics suitable for diverse applications in sustainable agriculture and environmental management.

Molecular simulation study of microstructural evolution during low-temperature oxidation of coal

In this study, industrial analysis, 13C NMR spectroscopy, X-ray photoelectron spectroscopy (XPS), and in-situ infrared spectroscopy were employed to determine the elemental composition and structure of Tingnan coal. The peak area, pore volume, and specific surface area were used as the main parameters to investigate the structural changes of coal molecules and pore evolution during low-temperature coal oxidation, using an automated surface area and pore size analyzer. The analysis revealed that with increasing oxidation degree, the CH groups in the aromatic structure gradually decreased, while the total content of oxygen-containing functional groups such as alcohols, phenols, carboxyls, and carbonyls remained relatively constant. However, the relative content of hydroxyl groups and ether linkages increased with increasing oxidation temperature. Additionally, coals with different oxidation degrees exhibited well-developed micropores, and the specific surface area gradually decreased while the pore size increased with temperature. Molecular models of Tingnan coal in its original state and oxidized at temperatures of 50 °C, 70 °C, and 110 °C were constructed using Materials Studio software. Based on these models, pores with diameters of 2.79 nm, 3.07 nm, 3.07 nm, and 3.11 nm and a length of 4.5 nm were constructed using the coal molecular structure as the pore walls.

Effect of oxidation on the combustion flame characteristics of Jatropha biodiesel

This study investigated the effect of oxidation on the pyrolysis and combustion flame performance of Jatropha biodiesel. To analyze the escape characteristics of multi-component gas products during the pyrolysis and high-temperature oxidation processes of fresh and oxidized Jatropha biodiesel, the TG-FTIR-MS combined system was employed. In addition, various analytical equipment such as an OH-PLIF system, a flue gas analyzer, a spectral analyzer, and a transmission electron microscope were employed to examine the laminar premixed combustion flame and pollutant emissions of Jatropha biodiesel before and after oxidation. The results demonstrate that oxidation exhibits a nonlinear effect on the thermal decomposition of Jatropha biodiesel. Notably, the reaction activation energy exhibits an initial increase and followed by a decrease. Moreover, an increased oxidation degree led to a reduction in the activation energy of the high-temperature oxidation reaction of Jatropha biodiesel, without considerably affecting the total weight loss temperature. Furthermore, the peak temperatures of DTG and DSC exhibited a minor decrease. The production of C2, CH, and OH free radicals in the combustion flame of oxidized Jatropha biodiesel increased, along with an elevation in the spectral intensity of carbon smoke. With an increase in the degree of oxidation, the CO emission concentration from the combustion of Jatropha biodiesel decreased gradually from 75 mg/m3 to 36 mg/m3 after 6 h of oxidation. Additionally, NOx emissions gradually increased from 131 mg/m3 to 186 mg/m3 after 6 h of oxidation, and the particle size of carbon smoke exhibited a reduction of 28%.

Systematic assessment of the silk deterioration behaviors for silk aging prediction

The silk cultural artifacts have suffered significant deterioration since their discovery, and the unsuitable conditions in the storage environment will further exacerbate this degradation. Systematically and quantitatively assessing the degree of deterioration of silk fabrics with multiple indexes is imperative. In this study, color difference, oxidation degree, crystallinity, and amino acid contents were employed to investigate the aging degradation process of silk fabrics. The results illustrated that both thermal and ultraviolet aging processes were accompanied by discoloration, increasing oxidation degree, decreasing crystalline degree, and amino acid contents reduction. Moreover, the aging level of silk fabrics deterioration behaviors varied across three different stages: (i) the initial stage was primarily marked by color changes, (ii) while oxidation degree and crystallinity alterations dominated in the intermediate phase, (iii) and a substantial reduction in amino acid contents prevailed during the final stage of aging. Therefore, the color difference could be identified as the early safety warning indicator for cultural relics preservation. The GM (1, 1) and GNNM (1, 1) forecasting models were utilized and the results suggested that GNNM (1, 1) outperformed GM (1, 1) in predicting the color properties of silk fabrics, indicating its potential for widespread use in predicting the deterioration of silk artifacts within collections. Collectively, this work comprehensively investigated the degradation process of silk fabrics and further achieved the prediction of color property changes during the simulated aging process, thereby providing a theoretical foundation for the conservation and protection of silk fabrics.

Formation pathways of organic aerosols over a tropical coastal atmosphere

The characteristics of non-refractory submicron aerosols (NR-PM1), focusing on organic aerosols, are examined over a tropical coastal location, Thumba, in southern peninsular India. The measurements were carried out using an aerosol chemical speciation monitor during 2017–2021. The results indicated organic aerosols as the major component (67–85%) in the NR-PM1 mass loading during all seasons. Positive matrix factorization (PMF) analysis on the OA mass spectra yielded two factors resolving Hydrocarbon-like organic aerosols (HOA) and Oxygenated organic aerosols (OOA), with the major contribution to OA coming from OOA (mass fraction >50%) during all the seasons. Examination of the diurnal variations revealed the daytime enhancement in OOA and sulfate mass fractions, indicating photochemical production overwhelming the dilution at the surface due to local atmospheric boundary layer expansion. The OOA mass concentration showed a good correlation (R > 0.5) with odd oxygen (O3+NO2) and with an increase in oxygen-to-carbon ratio (ΔO:C = 0.11 to 0.35 with Δodd oxygen = 60 μg m−3 for different seasons) (i.e., increased oxidation degree of OA) signifying the dominance of photochemistry and subsequent enhanced atmospheric oxidative capacity in OOA formation. Interestingly, the aerosol liquid water content (ALWC) doubled during the nighttime (>40 μg m−3) compared to the daytime (<20 μg m−3) in different seasons, indicating the combined impact of varying submicron aerosol composition and ambient relative humidity. Since highly humid (relative humidity >85%) conditions prevail over this tropical coastal station, especially during the nighttime, the role of aqueous-phase formation of OA is also examined. It was found that less oxidized/less-hygroscopic OA were prevalent during the nighttime, resulting in lower aqueous-phase OA processing. During all the seasons, the hygroscopicity of organics (кorganics) reached as high as > 0.22 and was mainly driven by photochemical processing rather than aqueous-phase chemistry. These results highlight the importance of the OA formation pathways in affecting their hygroscopic properties over the tropical atmosphere.

Tuning the properties of pineapple peel cellulose nanofibrils by TEMPO-mediated oxidation and ball milling

In this study, the oxidized cellulose nanofibrils from pineapple peel (PP-TOCNF) were prepared by TEMPO-mediated oxidation followed by ball milling. The influence of oxidation degree on the structure and properties of PP-TOCNF were investigated, including Fourier transform infrared spectroscopy , X-ray diffraction, atomic force microscope (AFM), X-ray photoelectron spectroscopy and thermogravimetry, as well as the potential application in aerogels. The results suggested that TEMPO oxidation facilitated the dispersion of PP-TOCNF due to the strong electrostatic repulsion between –COO− groups. Regulating oxidation degree by varying NaClO concentration could effectively adjust the –COO− content (0.167–0.550 mmol/g), zeta potential (− 18 to − 34 mV) and rheological properties. The obtained PP-TOCNF showed a long fibrillar structure, whose average diameter and CrI values gradually decreased with the increase of oxidation degree. The PP-TOCNF-based aerogels exhibited a light weight, good porosity, water absorption, and mechanical properties, which also can be easily adjusted by oxidation degree of PP-TOCNF. Furthermore, TEMPO oxidation improved the stability and shape recovery ability of aerogels in water.Graphical abstract

Molecular insights into gas hydrate formation in the presence of graphene oxide solid surfaces

• Molecular dynamics simulations of hydrate homogeneous nucleation and growth influenced by graphene oxide (GO) surfaces are performed. • The methane attraction of hydrates formation competes with the attraction of GO surface which may lead to the hydrate composition. • The increase of oxidation degree increases the instability of the hydrate structure. Different organic or inorganic materials have been used to control the nucleation and growth of hydrate in oil and gas transportation or storage fields and so on. In this study, the molecular dynamics simulations method is used to study the effect of graphene oxide(GO) on nucleation and growth of methane hydrate. The mirror, rotation and random systems for different spatial distributions of oxidized functional groups on GO layers and the different oxidation degree systems are constructed to study the effect on methane hydrate formation. It is found that the spatial distribution has little effect on hydrate formation with the same oxidation degree conditions. Most of the hydrate is normal growth but a few cases produce the hydrate decomposition phenomenon which is caused by the nucleation of randomness and surface adsorption of methane. The GO surfaces compete with the formed cages for solvated methane, which decreases the concentration of solvated methane and is not conducive to hydrate formation. Increasing the degree of oxidation will cause more instability for the hydrate growth state because of the thicker water adsorption layer and more H-bonds formed between GO and water. The adsorption layer of water and methane and their relative positions are displayed clearly for the first time. Our results provide a possible microscopic explanation of the GO influence on methane hydrate formation and provide new insights for using GO surface material as an inhibitor for hydrate formation.

Study of a Hydrophilic Healing-Promoting Porcine Acellular Dermal Matrix

Sodium hyaluronate (SH) is recognized as the strongest natural humectant, since it contains a large number of hydroxyl and carboxyl groups in its structure, and can absorb 1000 times its own weight of water. The porcine acellular dermal matrix (pADM) has been widely used in biological materials for its biological activities, such as promoting cell proliferation and promoting wound healing. Enhancing the hydrophilic and moisturizing properties of the pADM is expected to further improve its ability to promote wound healing. However, there are no strong chemical bonds between SH and pADM. Therefore, SH was oxidized by sodium periodate in this study, and was further used to cross-link it with pADM. The microstructure, hydrophilicity, moisture retention, degradation and cytotoxicity of pADM cross-linked with different oxidation degrees of oxidized sodium hyaluronate (OSH) were studied. The results show that OSH-pADM maintained the secondary structure of natural collagen, as well as the good microporous structure of native pADM after cross-linking. With increasing oxidation degree, the surface hydrophilicity and moisture retention capacities of OSH-pADM increased; among them, OSH-pADM cross-linked with 40% oxidation degree of OSH was found to have the strongest moisture retention capacity. The hygroscopic kinetics at 93% RH were conformed to the second-order hygroscopic kinetics equation, indicating that the hygroscopic process was controlled by chemical factors. The degradation resistance of OSH-pADM also increased with increasing oxidation degree, and the cytotoxicity of OSH-pADM was acceptable. The in vivo full-thickness wound healing experiments showed that OSH-pADM had an obvious ability to promote wound healing. It can be speculated that OSH-pADM, with its good hydrophilic and moisturizing properties, physicochemical properties and biocompatibility, has great potential for facilitating wound repair.

Effects of interlayer spacing and oxidation degree of graphene oxide nanosheets on water permeation: a molecular dynamics study.

Graphene oxide (GO) membranes have shown great potential in the applications of water filtration and desalination. The flow behavior and structural properties of water molecules through GO nanochannels are still under debate. In this work, molecular dynamics simulations were performed to explore the effects of interlayer spacing and oxidation degree of GO nanochannels on water transport. The results show that GO nanosheets have strong adsorption capacity. The adsorbed layer of water molecules on GO surface is thermodynamically stable and not easy to flow. When the interlayer spacing falls into the range of 0.6 ~ 1.0nm, water molecules form into single or double adsorbed layers between two GO nanosheets. When the interlayer spacing is bigger than 1.2nm, the other water layers in the middle of nanochannel become disordered. Taking the separation performance based on size exclusion into consideration, the most suitable interlayer spacing for water nanofiltration is approximate 1.2nm, which has one flowing layer of water molecules. Oxygen-containing groups are unfavorable for water permeation, as more and more hydrogen bonds prevent water flowing on GO surface with the increasing oxidation degree. Our simulation results may help to improve the design of GO nanofiltration membranes for water treatment.

Operation of Diamond Solution-Gated Field-Effect Transistor in the Frequency Domain

Here, the effect of frequency-domain sensing with diamond solution-gated field-effect transistors (SGFET) was investigated, where a sine wave with different frequencies (3, 30, 300, and 3 kHz) was applied at the gate. Variation of the power spectral density (PSD) amplitudes of the drain-source current was examined by using the NaCl gate electrolyte with various concentrations. With the increase of NaCl concentration, the PSD amplitudes basically increase for hydrogen-terminal diamond SGFET, however, the change of PSD amplitudes is not so obvious. When the diamond surface is partially oxidized by the UV radiation in the atmosphere, the PSD amplitudes increase first and then decrease with the concentration of NaCl aqueous solution. And the sensitivity of oxidized diamond SGFET is higher than that of hydrogen-terminated and increases with the increase of oxidation degree.

Surface-Functionalized Nanocelluloses as Viscosity-Modifying Agents in Engineered Cementitious Composites

This study investigated the feasibility of using nanofibrilliated celluloses (CNF) (0.1% by weight of binder materials) with three oxidation degrees, no oxidation (NCNF), low oxidation (LCNF), and high oxidation (HCNF), as a viscosity-modifying agent (VMA) to develop polyethylene fiber (PE)-engineered cementitious composites (ECC). Attenuated total reflection-Fourier transform infrared (ATR-FTIR), dynamic light scattering (DLS), and zeta potential were performed to characterize the properties of the CNF with different oxidation degrees. More stable CNF suspensions could be obtained due to the increasing oxidation degree. Rheology tests showed that CNF replacing VMA could modify the plastic viscosity and yield stress of the fresh matrices. With increasing the oxidation degree of CNF, a significant enhancement was seen for the rheological parameters. It was conducted that CNF could increase the compressive strength, the tensile stress, the nominal flexural strength, and the fracture toughness compared with ECC using VMA, and much higher oxidation degrees yielded higher enhancements (HCNF &amp;gt; LCNF &amp;gt; NCNF). ECC using CNF to replace VMA also achieved ultra-high ductility behavior with the tensile strain of over 8% and the saturated multiple cracking pattern. These finds were supplemented by thermal gravimetric analysis (TGA), which showed that the degree of hydration increased with increasing CNF surface oxidation degree. Additionally, the morphology images of PE fibers were observed by scanning electron microscope (SEM).

Stoichiometry Dependence of Physical and Electrochemical Properties of the SnOx Film Anodes Deposited by Pulse DC Magnetron Sputtering.

A batch of Sn oxides was fabricated by pulse direct current reactive magnetron sputtering (pDC−RMS) using different Ar/O2 flow ratios at 0.3 Pa; the influence of stoichiometry on the physical and electrochemical properties of the films was evaluated by the characterization of scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray reflection (XRR), X-ray photoelectron spectroscopy (XPS) and more. The results were as follows. First, the film surface transitioned from a particle morphology (roughness of 50.0 nm) to a smooth state (roughness of 3.7 nm) when Ar/O2 flow ratios changed from 30/0 to 23/7; second, all SnOx films were in an amorphous state, some samples deposited with low O2 flow ratios (≤2 sccm) still included metallic Sn grains. Therefore, the stoichiometry of SnOx calculated by XPS spectra increased linearly from SnO0.0.08 to SnO1.71 as the O2 flow ratios increased, and the oxidation degree was further calibrated by the average valence method and SnO2 standard material. Finally, the electrochemical performance was confirmed to be improved with the increase in oxidation degree (x) in SnOx, and the SnO1.71 film deposited with Ar/O2 = 23/7 possessed the best cycle performance, reversible capacity of 396.1 mAh/g and a capacity retention ratio of 75.4% after 50 cycles at a constant current density of 44 μA/cm2.

Tribological mechanism of (Cr, V)N coating in the temperature range of 500–900 °C

Aiming to study the influence of temperature on the wear mechanism, we fabricated (Cr, V)N coating by cathodic arc ion-plated and conducted tribological experiments at 500–900 °C. The results indicated that there were two tribological behaviors, depending on the temperature. Below 600 °C, the (Cr, V)N coatings exhibited a high friction coefficient, but generated a mild wear because of the slight oxidation. Above 700 °C, the increased oxidation degree reduced adhesion of asperity contacts. However, the wear rate enhanced significantly with the temperature increasing from 700 to 900 °C due to the fast oxidation accompanied by the decrease in both hardness and adhesion strength.

Effect of 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) induced oxidation on the physicochemical properties, in vitro digestibility, and nutritional value of egg white protein

Protein oxidation can influence the quality of food during processing and storage. This study examined the changes in physicochemical properties and in vitro digestibility of egg white protein (EWP) oxidized with a peroxyl-radical-generating system (2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) simulating the oxidation environment of industrial processing. With the increasing AAPH concentration, all amino acid contents and protein solubility decreased, the carbonyl content almost doubled increased, free sulfhydryl content almost decreased by three quarters. The essential amino acids, such as phenylalanine, leucine, threonine, histidine was particularly sensitive towards oxidation, decreased by more than 10% after EWP oxidized by 5.0 mmol/L AAPH. Volume of larger soluble aggregates formed by AAPH increased, and the digestibility of EWP, decreased with the increase of oxidation degree. Molecular weight analysis showed that the content and antioxidant activity of low molecular weight peptides obtained by pepsin hydrolysis or trypsin hydrolysis was gradually reduced with the increase of the degree of oxidation, which indicated that the nutritional and biological activity of EWP was reduced by oxidation. These results may help to understand the changes in the functional and nutritional quality of egg-based foods that involve oxidation during processing.

Significant changes in autumn and winter aerosol composition and sources in Beijing from 2012 to 2018: Effects of clean air actions.

A seven-year long-term comprehensive measurement of non-refractory submicron particles (NR-PM1) in autumn and winter in Beijing from 2012 to 2018 was conducted to evaluate the effectiveness of the clean air actions implemented by the Chinese government in September 2013 on aerosols from different sources and chemical processes. Results showed that the NR-PM1 concentrations decreased by 44.1% in autumn and 73.2% in winter from 2012 to 2018. Sulfate showed a much larger reduction than nitrate and ammonium in both autumn (55%) and winter (86%) and that nitrate even slightly increased by 15.8% in autumn. As a result, aerosol pollution in winter gradually changed from sulfate-rich to nitrate-rich with a sudden change after 2016 and the dominant role of nitrate in autumn was also strengthened after 2016. Among primary organic aerosol (OA) types, biomass burning OA and coal combustion OA exhibited the largest decline in autumn and winter, with reductions of 87.5% and 77.3%, respectively, while hydrocarbon-like OA (HOA) exhibited the smallest decline in both autumn (24.4%) and winter (37.1%). These significant changes in aerosol compositions were highly consistent with the much faster reduction of SO2 (75-85%) than NOx (36-59%) and were mainly due to the clean air actions rather than the impact of meteorological conditions. What's more, the enhanced atmospheric oxidizing capacity, which was indicated by increased O3, altered the chemical processes of oxygenated OA (OOA), especially in autumn. Both of less-oxidized OOA (LO-OOA) and more-oxidized OOA showed elevated contributions in OA by 4% in autumn. The increased oxygen-to-carbon ratios of LO-OOA in autumn (from 0.42 to 0.58) and winter (from 0.44 to 0.52) indicated the enhanced atmospheric oxidizing capacity strengthened photochemical reactions and resulted in the increased oxidation degree of LO-OOA. This study demonstrates the effectiveness of the clean air actions for air quality improvement in Beijing.

Study on co-adsorption mechanisms of benzene and toluene on activated carbon via molecular simulation

In this paper, four-type activated carbon (AC) models are constructed and the co-adsorption processes of benzene and toluene on models under 303.15 K are studied by molecular simulation. The microscopic mechanisms in adsorption process including isotherms, energy changes, adsorption sites, and diffusion coefficients were discussed. The results indicate the small micropores less than 13 Å and larger micropores, smaller mesopores from 13 Å to 24 Å are favorable for benzene adsorption and toluene adsorption, respectively. Moreover, the adsorption amounts increase with the increase of oxidation degree in AC structure.

Insight into the effect of oxidation degree of graphene oxides on their removal from wastewater via froth flotation

The effect of oxidation degree of graphene oxides (GO) on their removal from wastewater via froth flotation was studied in this work. Four types of GO samples with different oxidation degrees were synthesized and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), atomic force spectroscopy (AFM) et al. The effects of cetyl trimethyl ammonium bromide (CTAB) concentration, pH, stirring time on the removal of GO by froth flotation had been discussed. It was found that the addition of CTAB could improve surface hydrophobicity of GO, endowing GO to be easily separated by froth flotation. The removal was dependent on CTAB dosage, pH and stirring time. Moreover, the removal first increased and then decreased with the increasing oxidation degree of GO, and less kinetic energy input was needed to overcome the energy barrier between GO flocs with the increase of oxidation degree. The removal mechanism was proven to be electrostatic attraction, and the different contents of oxgenous-containing functional groups in GOs with various oxidation degrees played a vital role in their removal via froth flotation.