Secondary Oxidation Research Articles

Study on the secondary oxidation behavior and microscopic characteristics of oxidized coal gangue.

Spontaneous combustion of coal gangue (CG) hills has caused varieties of secondary disasters that seriously endanger the ecological environment of the world. The emission law of index gases and their oxidation kinetics during the secondary oxidation process of CG with different ranks of oxidation were studied by using the temperature programmed device and online mass spectrometer (MS). Fourier transform infrared spectroscopy (FTIR) was used to reveal the changes of the CG internal active functional groups. The results showed that the energy required for the combustion of CG with low rank of pre-oxidation was significantly lower than that of the raw sample. However, as the oxidation rank increased, due to amounts of volatile components were released in the process of oxidation reaction, the CG in the combustion process of the emission of index gases and its oxygen consumption rate gradually reduced; the rapid oxidation stage shifted to the direction of the high temperature. In this study, the risk of spontaneous combustion of CG after oxidation at 80℃ under 3% oxygen concentration was the strongest. The results of this paper are of great guiding significance for exploring the spontaneous combustion characteristics of CG hills and their prevention by traditional covering method.

Exploring the potential of selective oxidation in bioconjugation of collagen with xyloglucan carboxylates

Xyloglucan (XG), as a natural biopolymer, possesses a sound biocompatibility and an impressive biodegradability, which are usually featured with abundant hydroxyl groups available for the bioconjugation with a bioactive moiety, suggesting a promising or unique value possibly applied in the field of biomedicine. In this study, XG was extracted from Tamarind seeds and subjected to four regioselective oxidation methods to introduce carboxyl groups onto the XG molecules for a bioconjugation with collagen. Galactose oxidase and reducing end aldehyde group oxidation mainly resulted in a low carboxylate content at ∼0.34 mmol/g, whereas the primary and secondary hydroxyl group oxidations would lead to a high carboxyl content at ∼0.84 mmol/g. The number-average molar mass (Mn) and weight-average molar mass (Mw) of XG were 8.8 × 105 g/mol and 1.1 × 106 g/mol, respectively. The oxidized XGs were then subjected to a further biofunctionalization with the collagen through EDC/NHS coupling, which exhibited a degree of conjugation rate, ranged from 50 % to 72 %. The collagen-conjugated at the C6 position of XGs exhibited the highest cell viability recorded at 168 % in promoting cell growth and proliferation after 72 h of culture, surpassing that of pure collagen recorded at 138 %, which may indeed suggest a promising value in a biomedical application.

Synergistic rosemary extract with TBHQ and citric acid improves oxidative stability and shelf life of peanut.

Lipid oxidation often accompanies the processing and storage of peanuts, which causes a serious waste of peanut resources. To solve the problem of being prone to oxidation in peanut processing, a ternary complex antioxidant based on rosemary extract (RE) was constructed to investigate its effect on the oxidative and thermal stability of peanuts, and the inhibition of peanut oxidation by compound antioxidants was revealed by dynamic Arrhenius formula and complexation theory. The results showed that there was a synergistic effect between RE and Tert-butyl hydroquinone (TBHQ), and the antioxidant effects of RE and TBHQ were 4.86 and 1.45 times higher when used in combination than when used alone, respectively. In addition, RE-TBHQ-CA (citric acid) effectively inhibited primary and secondary oxidation of peanuts with a shelf life 8.7 times longer than that of control peanuts. This study provides a novel antioxidant compounding idea, which has a positive effect on improving the quality of peanut and other nut products, prolonging the shelf life and reducing the waste of resources. PRACTICAL APPLICATION: Compounding a complex antioxidant that permits its use in peanuts. It was found that rosemary and TBHQ might have synergistic antioxidant effects. Meanwhile, this combination of RE-TBHQ-CA effectively inhibited the oxidation of peanut oils and prolonged the shelf life of peanuts. RE-TBHQ-CA is a highly efficient complex antioxidant that can reduce the amounts of antioxidants added while maintaining high antioxidant efficiency, which may be useful for the future preservation and storage of nut products as it positively affects the quality and shelf life of the product.

Conjugated safflower seed oil and its oleogels stabilization properties: Thermodynamic properties, rheology, oxidative stability

Conjugated safflower seed oil (CSSO) was used as the base oil, and beeswax (BW) was used as the gelling agent to prepare BW-CSSO oleogel. The effects of different additions of wax on the properties of BW-CSSO oleogel, as well as their oxidative stability, were investigated. The results indicated that an oleogel could be formed with CSSO at a BW concentration of 5 wt% at 25 °C, and the oil-holding capacity and hardness of the oleogel increased significantly as the BW concentration increased from 5 wt% to 11 wt%. Differential scanning calorimetry results showed that the peak crystallization and melting temperatures of the oleogel generally increased with the increase of wax addition, and both the crystallization and melting peaks became clearer and sharper. The rheological results indicated that all the samples showed shear-thinning behavior and higher concentrations of BW-CSSO oleogel were more capable of forming robust structures with lower frequency dependence. The free fatty acid release rate from BW-CSSO oleogel decreased with increasing BW concentration because the oleogel was stronger due to the formation of a more robust network, and the network of strong crystals influences the contact between lipase and oil, slowing down the release of oil from the interior of the oleogel structure and affecting the hydrolysis of oil. The network structure of the oleogel could inhibit the generation of CSSO secondary oxidation products and improve the oxidative stability of CSSO. This study provides the relevant parameters of the BW-CSSO oleogel and lays the foundation for subsequent studies.

Thermal oxidation mechanism of palmitic aicd

The oxidation and degradation of fats lead to a decrease in the nutritional value of food and pose safety concerns. Saturated fatty acids also hold a significant position in the field of lipid oxidation. In this study, the oxidation products of methyl palmitate were investigated by using gas chromatography mass spectrometry (GC–MS). Seven monohydroperoxides and 72 secondary oxidation products were detected. Combined with density functional theory (DFT) calculations, the formation mechanisms of oxidation products can be summarized into four stages. The initial stage involved the formation of monohydroperoxides and alkanes, followed by the subsequent stage involving methyl x-oxo(hydroxy)hexadecanoates. The third stage involved the formation of methyl ketones, carboxylic acids, and aldehydes, while the final stage involved lactones. Meanwhile, methyl ketones were the most abundant oxidation product, approximately 25 times more abundant than aldehydes; the calculated results agreed well with the experimental results. The establishment of a comprehensive thermal oxidation mechanism for palmitic acid provided a new foundation for future lipid oxidation analyses.

Use of mushrooms as antioxidants in a lipid oxidation model under indirect and direct oxidation tests: ethanolic extracts of Ganoderma resinaceum and Phlebopus bruchii.

Foods contain lipids that are easily susceptible to oxidation, which can modify their sensory properties. Although these compounds provide characteristic flavours and odours, there are also unwanted compounds, such as volatile secondary oxidation products, representing a recurring problem for both the industry and consumers. Synthetic antioxidants are often employed to prevent this but their chronic consumption can be detrimental to human health. The present study evaluates the antioxidant potential of ethanolic extracts from Ganoderma resinaceum and Phlebopus bruchii using an accelerated oxidation test. The composition profile of the extracts was investigated, identifying the presence of tryptophan, quinic acid, caffeic acid and 3,4-dihydroxyphenylglycol-phenolic acid. The antioxidant capacity of the extracts was compared with that of butylated hydroxytoluene (BHT) in sunflower oil that was oven-heated at 60 °C. Chemical (peroxide value, p-anisidine value and conjugated dienes) and volatile (2-octenal, 2-heptenal and 2,4-decadienal) indicators were measured over 28 days. The peroxide value decreased for both extracts at a similar level to that of BHT 0.02% w/w, and conjugate dienes decreased in the presence of G. resinaceum 0.1% w/w. Meanwhile, p-anisidine exhibited a slightly greater decrease for P. bruchii 0.1% w/w than for BHT. The sample with 0.1% w/w of extracts showed a reduction in volatile secondary oxidation compounds, indicating significant antioxidant activity. Based on these results, both extracts could be proposed as potential antioxidants in foods with a high lipid content. © 2024 Society of Chemical Industry.

Effects of three polyphenols with different numbers of phenolic hydroxyls on the structural and interfacial properties and lipid-protein co-oxidation of oil body emulsions

Oil bodies (OBs) are organelles for storing lipids, and they are composed of lipid cores and monolayer phospholipid protein membranes. During storage, membrane proteins anchored in the lipid core are often damaged by lipid oxidation products, leading to oxidative damage and a decreased quality of emulsified foods. Here, three natural antioxidants (gallic acid (GA), epigallocatechin gallate (EGCG), and tannic acid (TA)) were added to OB emulsions to study the effects of polyphenols on protein interfacial properties during oxidation and the lipid-protein co-oxidation behavior. Compared to GA, EGCG and TA with higher molecular weights and hydroxyl substitution showed better antioxidant activity, metal chelating activity, iron reduction ability, and affinity for OB. The polyphenols significantly reduced the contents of free amino and sulfhydryl groups in OB. Infrared spectroscopy analysis indicate that hydrogen bonding and hydrophobic interactions may exist between the polyphenols and OB. During storage, polyphenols inhibited >23% of the primary and secondary lipid oxidation products in the emulsions, whereas the formation of carbonyl groups and disappearance of sulfhydryl groups were only inhibited by 10.7% and 7.4%, respectively, indicating that polyphenols preferentially inhibited lipid oxidation over protein oxidation. Electrophoresis results showed that moderate oxidation (3 days of storage) disrupted the disulfide bonds of proteins. Note that moderate oxidation enhanced the interfacial properties of OB proteins, whereas excessive oxidation led to protein aggregation. This study offers new perspectives on using polyphenols to regulate the lipid-protein co-oxidation in OB, as well as the different properties of OB proteins after oxidation.

The Effect of Low Temperature Storage on the Lipid Quality of Fish, Either Alone or Combined with Alternative Preservation Technologies.

Marine foods are highly perishable products due to their high content of polyunsaturated fatty acids, which can be readily oxidized to form peroxides and secondary oxidation products, thus conferring such foods undesirable organoleptic characteristics and generating harmful compounds that are detrimental to the health of consumers. The use of preservation methods that minimize lipid oxidation is required in the fishing and aquaculture industries. Low temperature storage (chilling or freezing) is one of the most commonly used preservation methods for fish and seafood, although it has been shown that the oxidation of the lipid fraction of such products is partially but not completely inhibited at low temperatures. The extent of lipid oxidation depends on the species and the storage temperature and time, among other factors. This paper reviews the effect of low temperature storage on the lipid quality of fish, either alone or in combination with other preservation techniques. The use of antioxidant additives, high hydrostatic pressure, irradiation, ozonation, ultrasounds, pulsed electric fields, and the design of novel packaging can help preserve chilled or frozen fish products, although further research is needed to develop more efficient fish preservation processes from an economic, nutritional, sensory, and sustainable standpoint.

Antioxidant Activity of Humulus lupulus Phenolic Hop Extracts in Creating a New Pâté: An Element Affecting Fat Stability and Microbiological Quality during Storage.

The aim of this study was to evaluate the effect of hop extracts on changes in the primary and secondary fat oxidation products, physicochemical properties, and microbiological quality of pâté-type offal sausages obtained through the partial replacement of animal fat with vegetable fat. This study demonstrated that the extraction efficiency varied among hop cone varieties, with the highest efficiency observed for the Lubelski variety and the lowest for the Magnum variety. The phenolic compound content was higher in the Magnum cones (2.74 ± 0.11 mg/g dry matter) compared to the Lubelska cones (2.27 ± 0.05 mg/g of product). Additionally, the DPPH radical scavenging activity was greater in the extract from the Magnum cones (4.21 ± 0.09 mg TE/g d.w.) than in the extract from the Lublelski cones (3.87 ± 0.05 mg TE/ g d.w.). Similarly, the extracts from the Lubelski cones exhibited a higher antiradical activity against the ABTS radical compared to the extract from Magnum cones. Throughout storage, a significant increase in the pH value was observed in the control sample and in the samples with a 20% replacement of animal fat with rapeseed oil and Magnum hop extract. However, the addition of Lubelski hop extract resulted in a decrease in the pH value during the 15-day storage period. The samples with a 20% replacement of animal fat with rapeseed oil and 0.1% Lubelski hop extract showed the least changes in water activity during storage. The samples with a 20% replacement of animal fat with rapeseed oil and the addition of 0.2% Lubelski hop extract had the lowest peroxide value and TBARS index throughout the storage period. The addition of hop extract inhibited the growth of the total number of microorganisms in the tested sausages. In the samples with a 20% replacement of animal fat with rapeseed oil, the content of aerobic microorganisms, compared to the control sample, was statistically significantly lower.

Nickel-Catalyzed Atroposelective C-H Alkylation Enabled by Bimetallic Catalysis with Air-Stable Heteroatom-Substituted Secondary Phosphine Oxide Preligands.

The catalytic asymmetric construction of axially chiral C-N atropisomers remains a formidable challenge due to their low rotational barriers and is largely reliant on toxic, cost-intensive, and precious metal catalysts. In sharp contrast, we herein describe the first nickel-catalyzed atroposelective C-H alkylation for the construction of C-N axially chiral compounds with the aid of a chiral heteroatom-substituted secondary phosphine oxide (HASPO)-ligated Ni-Al bimetallic catalyst. A wide range of alkenes, including terminal and internal alkenes, were well compatible with the reaction, providing a variety of benzimidazole derivatives in high yields and enantioselectivities (up to 97:3 e.r.). The key to success was the identification of novel HASPOs as highly effective chiral preligands. Mechanistic studies revealed the catalyst mode of action, and in-depth data science analysis elucidated the key features of the responsible chiral preligands in controlling the enantioselectivity.

Lipidomics analysis unveils the dynamic alterations of lipid degradation in rice bran during storage

Recent explorations into rice bran oil (RBO) have highlighted its potential, owing to an advantageous fatty acid profile in the context of health and nutrition. Despite this, the susceptibility of rice bran lipids to oxidative degradation during storage remains a critical concern. This study focuses on the evolution of lipid degradation in RBO during storage, examining the increase in free fatty acids (FFAs), the formation of oxylipids, and the generation of volatile secondary oxidation products. Our findings reveal a substantial rise in FFA levels, from 109.55 to 354.06 mg/g, after 14 days of storage, highlighting significant lipid deterioration. Notably, key oxylipids, including 9,10-EpOME, 12,13(9,10)-DiHOME, and 13-oxoODE, were identified, with a demonstrated positive correlation between total oxylipids and free polyunsaturated fatty acids (PUFAs), specifically linoleic acid (LA) and α-linolenic acid (ALA). Furthermore, the study provides a detailed analysis of primary volatile secondary oxidation products. The insights gained from this study not only sheds light on the underlying mechanisms of lipid rancidity in rice bran but also offers significant implications for extending the shelf life and preserving the nutritional quality of RBO, aligning with the increasing global interest in this high-quality oil.

Reductive Coupling of P(O)-H Compounds and Aldehydes for the General Synthesis of Phosphines and Phosphine Oxides.

A novel strategy for the selective construction of a C(sp3)-P(III) or -P(V) bond from >P(O)-H compounds and aldehydes is disclosed. By using the H3PO3/I2 system, various secondary phosphine oxides could react with both aromatic and aliphatic aldehydes to afford valuable phosphines (isolated as sulfides) and phosphine oxides in good yields. This method features a wide substrate scope and simple reaction conditions and avoids the use of toxic halides and metals.

Electrocatalytically enhanced Cu(II)/peroxymonosulfate (PMS) oxidation: Focus on electrically-induced sustained Cu(II)/Cu(I)/Cu(III) cycling and suppression of singlet oxygen (1O2) production

Numerous azo dyes are discharged into industrial wastewater annually, posing significant threats to ecology and human health. In this study, an applied electric field was implemented in a trace copper-activated peroxymonosulfate system (EC/Cu(II)/PMS), achieving high removal efficiency (95.40 %) of Congo red (CR). The electron-donating effect of the cathode greatly enhanced the redox cycling of Cu(II)/Cu(I). Almost complete activation of PMS occurred during the entire reaction with an electrical consumption of merely 0.85 kWh/m3. Using electron paramagnetic resonance (EPR), quenching experiments, and chemical probes, the reactive substance that dominate CR removal, including Cu(III), sulfate radical (SO4•−), hydroxyl radical (HO∙), and singlet oxygen (1O2), were investigated. Cu(III) was identified as the main reactive substance, contributing over 90 %, and was primarily formed through double electron transfer of Cu(I). HO∙ can emerge as a secondary oxide of Cu(III). SO4•− originated mainly from the electroactivation of PMS. It was noted that 1O2 can be physically quenched by water, and thus 1O2 was considered as a side reaction product of PMS. Applying an electric field lowered the overall production of 1O2 and markedly mitigated the inefficient consumption of PMS. Moreover, the degradation pathways proposed for CR, based on mass spectrometry analysis, were in agreement with the predictions made by density functional theory (DFT). The toxicological characteristics of both CR and its intermediates were comprehensively analyzed as well. The study presents a straightforward and efficient strategy for PMS activation with versatile application potential for dye wastewater treatment.

Evolution of pore structure and changes in oxidation characteristics of coal after heating freezing treatment

To study the spontaneous combustion characteristics of preheated coal treated by liquid nitrogen (LN2), surface structure test, thermal analysis experiment and chemical characteristic analysis experiment were used to study the change characteristics of surface structure, oxidation characteristic and chemical structure of coal under the action of LN2 quenching. The results showed that with the increase of preheating temperature, the fractal dimension, specific surface area, pore volume and average pore diameter of the LN2 treated coal (quenched-coal) increase. With the increase of preheating temperature, under the oxidation condition, the CO and CO2 produced at ST of 230 ℃ are 1.19 times and 1.21 times higher than those at ST of 70 ℃. The CO/CO2 emission of quenched-coal is significantly increased, and the secondary oxidation capacity is stronger. Due to the more developed pore cracks of coal under pyrolysis and quenching conditions, the natural characteristics of coal are stronger. The oxygen adsorption capacity and apparent activation energy of pyrolysis coal in the stageⅠ affected by LN2 are stronger. Oxidized coal shows stronger oxidation and heat release ability in the stageⅡ under the action of LN2, resulting in higher apparent activation energy in this endothermic stage. The addition of LN2 blocked the oxidation reaction of preheated coal and sealed the structure of -C = O, –COOH and –OH. The bridge bond –CH2- structure of pyrolysis coal is further destroyed, and the ratio of –CH2/–CH3 is reduced. The increase of alkyl free radicals in pyrolysis coal and alkyl oxygen free radicals in oxidation coal accelerates the spontaneous combustion oxidation of coal. The research results have important guiding significance for the occurrence and prevention of coal reignition disaster after LN2 fire quenching.

Optimizing pre-reduction of vanadium–titanium magnetite through recycling and integrating of top gas from melting furnace and tail gas from rotary kiln

In this study, the pre-reduction impact of CO and H2 on vanadium–titanium magnetite (VTM) was examined considering the composition of the top gas of the melting furnace. Additionally, the recycled and upgraded tail gas from the rotary kiln was mixed with the top gas of the melting furnace to enhance the pre-reduction effect and meet the temperature requirements of the rotary kiln. By analyzing the variations in the tail gas composition, the possible reactions occurring during the VTM pre-reduction process were determined. The results demonstrate the crucial role of H2 in the reduction process. A 20% H2 concentration yields a reduction effect similar to that achieved with 55% CO, resulting in a complete reduction of magnetite. However, the presence of CO2 in the gas hinders the reduction reaction by decreasing the reduction capacity of CO or inducing a secondary oxidation of the reduction products. Furthermore, the introduction of half of the tail gas of the rotary kiln into the top gas of the melting furnace increases the metallization rate of VTM pellets from 37.84% to 57.2%. These findings provide valuable references for utilizing the high-temperature top gas of the melting furnace for VTM pre-reduction in rotary kilns.

Long‐Emission‐Wavelength Humic‐Like Component (L‐HULIS) as a Secondary Source Tracer of Brown Carbon in the Atmosphere

AbstractThe optical properties of secondary brown carbon (BrC) aerosols are poorly understood, hampering quantitative assessments of their impact. We propose a new method for estimating secondary source of BrC using excitation‐emission matrix (EEM) fluorescence spectroscopy, combined with parallel factor analysis (PARAFAC) and partial least squares regression (PLSR). Experiments were conducted on a collection of PM2.5 samples from urban areas in five Chinese cities during winter and summer. The humic‐like component with long‐emission wavelengths (L‐HULIS) was identified as a secondary source tracer of BrC. This was confirmed by correlating PARAFAC components with secondary organic aerosol tracers and molecular oxidation indices obtained from Fourier transform ion cyclotron resonance mass spectrometry analysis. Using L‐HULIS as a secondary tracer of BrC, it was determined that the contribution of secondary sources to water‐soluble BrC (WS‐BrC) in source emission samples is significantly smaller than in PM2.5 from five Chinese cities, supporting our method. In the five cities, secondary source derived via L‐HULIS contributes a dominant potion (80% ± 3.5%) of WS‐BrC at 365 nm during the summer, which is approximately twice as high as during the winter (45% ± 4.9%). Radiocarbon isotope (14C) analysis provides additional constraints to the sources of L‐HULIS‐derived secondary WS‐BrC in urban PM2.5, suggesting that aged biomass burning is the dominant contributor to secondary WS‐BrC in winter, and biogenic emission is dominant during summer. This study is the first report on identification of secondary sources of BrC using the fluorescence technique. It demonstrates the potential of this method in characterizing non‐fossil source secondary BrC in the atmosphere.

Influence of storage temperature and natural antioxidants addition on chia oil nutraceutical blends shelf life

AbstractThis study focuses on the influence of storage temperature and addition of commercial natural antioxidant‐rich sources on the shelf life of chia oil (CO) nutraceutical blends. CO is a valuable product for consumers due to its high ω‐3 content, but its susceptibility to oxidation comprises challenges for its shelf life and quality. Thereby, different chia oil‐antioxidant blends were prepared and stored at 4°C and 25°C to evaluate alternative shelf‐life conditions. Commercial antioxidant‐rich sources containing astaxanthin (ASX), β‐carotene (BC) and vitamin E (VE) were added either alone or combined to CO. To monitor blends oxidative stability during storage, primary and secondary oxidation compounds were assessed weekly using peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) as indicators. Results showed that storage temperature played a significant role on oxidative stability of CO. When stored under refrigeration at 4°C, the oil exhibited low and stable oxidation indicators over time, regardless of the antioxidants used. However, at room temperature (25°C), the use of antioxidants and some particular combinations of them became crucial to prevent oil oxidative deterioration. Nutraceutical blends of CO/BC and CO/ASX were the best options to preserve CO from oxidation after 8 weeks storage at room temperature (PV < 2 meq O2/kg oil).Practical Applications: This work provides evidence on enhancing oxidative stability of chia oil through addition of natural antioxidants and proper storage. We focused primarily on designing blends from edible ingredients that are currently available in the market, with the aim of ensuring easy accessibility and affordability. Our findings offer valuable insights for the development of chia oil and antioxidant‐enriched blends, that could potentially serve as nutraceuticals or pharmacy‐compounded supplements to manage specific chronic inflammatory diseases. Our study highlights the importance of considering storage temperature and antioxidant selection to enhance shelf life and quality. These results have significant implications for the food industry, nutrition, and health, by providing valuable information for the creation of healthier and more sustainable food products. Furthermore, this work underscores the need for companies and retailers handling and storing vegetable oils with high omega‐3 content to adopt improved storage practices to ensure the quality and longevity of their products.

Metal recovery from spent lithium-ion batteries cathode materials: Comparative study of sugar-based reductants

Sugars and sugar-rich agricultural by-products are cheaper and eco-friendly alternatives to conventional reductants used in recovering metals from spent lithium-ion batteries. Still, they are rarely used due to a poor understanding of their performance and reaction chemistry. In this study, two hypotheses bearing on the role of chemistry and influence of non-sugary organic compounds (impurities) on the performance of sugars, namely: glucose, fructose and sucrose, and a parent sugar-rich agro-industrial by-product – molasses, as reductants in the leaching of Li, Co, Mn and Ni from spent lithium-ion battery cathode material were tested. Statistical analysis using ANOVA revealed that the performance of the sugars and molasses are similar with >85% Mn, >88% Ni, >88%Co and >98% Li leached at 90 °C and 60 min. This shows that the presence of non-sugar organic compounds does not hamper the performance of the sugars-based reductants. The performance of the sugars relies more on temperature than chemistry. Furthermore, evaluation of the oxidation pathway hints at a potential inhibition of secondary oxidation reactions at lower temperatures. This study provides statistically validated proof that the performance of sugarcane molasses, even at lower concentration, is equipollent to the pure sugars in the leaching of critical metals from spent lithium-ion batteries.

Particle phase state and aerosol liquid water greatly impact secondary aerosol formation: insights into phase transition and its role in haze events

Abstract. The particle phase state is crucial for reactive gas uptake, heterogeneous, and multiphase chemical reactions, thereby impacting secondary aerosol formation. This study provides valuable insights into the significance of particle-phase transition and aerosol liquid water (ALW) in particle mass growth during winter. Our findings reveal that particles predominantly exist in a semi-solid or solid state during clean winter days with ambient relative humidity (RH) below 30 %. However, a non-liquid to liquid phase transition occurs when the ALW mass fraction exceeds 15 % (dry mass) at transition RH thresholds of 40 %–60 %. During haze episodes, the transformation rates of sulfate and nitrate aerosols rapidly increase through phase transition and increased ALW by 48 % and 11 %, respectively, resulting in noticeable increases in secondary inorganic aerosols (SIA). The presence of abundant ALW, favored by elevated RH and higher proportion of SIA, facilitates the partitioning of water-soluble compounds from the gas to the particle phase, as well as heterogeneous and aqueous processes in liquid particles. This leads to a substantial increase in the formation of secondary organic aerosols and elevated aerosol oxidation. Consequently, the overall hygroscopicity parameters exhibit a substantial enhancement, with a mean value of 23 %. These results highlight phase transition as a key factor initiating the positive feedback loops between ALW and secondary aerosol formation during haze episodes over the North China Plain. Accurate predictions of secondary aerosol formation necessitate explicit consideration of the particle phase state in chemical transport models.

Regioselective One-Pot Synthesis of Vicinal Bisphosphine Derivatives from Nitroalkenes by Hydrophosphinylation/Elimination/Hydrophosphinylation.

Herein, a facile method is developed for the synthesis of vicinal bisphosphine derivatives based on a cascade of hydrophosphinylation, elimination, and hydrophosphinylation of secondary phosphine oxides with nitroalkenes. This cascade reaction provides step-economy access to a series of vicinal bisphosphine derivatives with high to excellent yields (up to 99%). This method was further extended to prepare, in one-pot, regioselective vicinal bisphosphine derivatives that incorporated two different phosphorus functional groups.