Hydroxyl Content Research Articles

Stimuli-Chromic Oxazolidine Latex Nanoparticles for Dual-Responsive pH-Sensors and Rewritable Halochromic Papers: A Physicochemical Study on Colorimetric and Fluorimetric Signals.

Oxazolidine is a new category of stimuli-chromic compounds that has unique intelligent behaviors such as halochromism, hydrochromism, solvatochromism, and ionochromism, all of which have potential applications for designing and constructing chemosensors by using functionalized-polymer nanocarriers. Here, the poly(MMA-co-HEMA) based nanoparticles were synthesized by emulsion copolymerizing methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) in different copolymer compositions. The poly(MMA-co-HEMA) based nanoparticles were modified physically with tertiary amine-functionalized oxazolidine (as an intelligent pH-responsive organic dye) to prepare halochromic latex nanoparticles. Investigation of optical properties including absorbance and emission by spectroscopic methods indicates that the halochromic behavior of the oxazolidine in nanoparticles is influenced significantly by the particle size, morphology, and concentration of hydroxyl groups. To develop optical chemosensors for the detection of pH, the pH-responsivity of halochromic latex nanoparticles in aqueous solutions with different pHs in the wide range of 1-14 were studied by UV-vis and fluorescence spectroscopies, and these results confirmed the successful photodetection of pH in a fast and facile manner. The investigation of the solid-state optical properties and pH-responsivity of halochromic nanoparticles by impregnation of latex-coated cellulosic papers with solutions having different pHs indicates the halochromic nanoparticles maintained their optical properties after incorporation to cellulose matrix and displayed notable colorimetric and fluorimetric pH-responsivity. Hence, the paper-based pH-sensors were prepared from halochromic papers and the investigation of their pH-responsivities showed the halochromic papers constructed from halochromic nanoparticles with HEMA concentration above 20 wt % have the best pH-responsivity with high resolution, high contrast, and high-intensity color change and fluorescence emission change. In addition, the halochromic papers were used as rewritable hydrochromic papers for hand-writing and stamp-printing by using acid and base solutions as inks, in which papers based on halochromic nanoparticles with a HEMA concentration above 20 wt % have maximum printability, resolution, and intensity. This study proposed the significant effects of polarity and concentration of functional groups on the halochromic properties of oxazolidine molecules and the unique role of functionalized polymer nanoparticles as a carrier of oxazolidine for its protection toward environmental degradations. These parameters should be considered in future studies on the development of halochromic papers for intelligent pH-sensor and rewritable papers.

A ternary deep eutectic solvent for efficient biomass fractionation and lignin stabilization.

The efficient isolation and lignin stabilization are critical to the fractionation process of lignocellulosic biomass, enabling the subsequent valorization of both carbohydrates and lignin. In this study, a ternary deep eutectic solvent pretreatment system with outstanding reusability has been developed. Under optimal conditions (ChCl: MT: p-TsOH=1:1:0.5, 120°C, 60min), the system efficiently removed 94.66% of hemicellulose and 95.74% of lignin while retaining 84.50% of cellulose. Glucose was obtained from the cellulose-rich solid residue via enzymatic hydrolysis, achieving an 87.12% yield. This DES system inhibits lignin condensation through a dual mechanism of α-etherification and intermolecular forces (π-π stacking and hydrophobic interaction). The recovered lignin exhibits a low molecular weight (922-1049g/mol), high phenolic hydroxyl content (2.57-3.37mmol/g), low polydispersity (1.54-1.61), and high purity (93.02%). Combined with its superior antioxidant activity and UV shielding properties, this lignin represents a promising new resource with potential applications.

The Effect of Different Sulphur Sources Applied at Various Rates on Soil pH

Soil pH, governed by the relative concentrations of hydrogen () and hydroxyl () ions, is a key factor affecting the chemical, physical, and biological properties of soils. Most soils in Türkiye are alkaline due to calcareous parent material and climatic influences, which restricts the availability of essential nutrients to plants. Sulphur applications are widely employed to reduce soil pH and increase nutrient bioavailability. The use of Sulphur for the amelioration of alkaline soils will continue to be a crucial strategy for enhancing agricultural sustainability in the future. This study investigates the effects of different Sulphur sources on the pH of sandy and clay-loam texture soils. This study investigates the effects of different Sulphur sources on the pH of sandy and clay loam textured soils. The soil samples used in the research were taken from Pınarbaşı and Melikgazi districts of Kayseri province, and soil samples were taken from both regions from a depth of 30 cm and from 20 randomly determined different points. Sulphur applications were applied at rates of (0, 0.02, 0.04 g 100 g-1) (X: powdered Sulphur ) and (0, 0.044, 0.088 g 100 g-1) (Y: granular Sulphur ) based on weight for clay-loam and sandy textured soils, respectively. Samples taken on days 0, 15, 30, 60, 90, 180, and 360 post-applications showed that the impact of Sulphur applications on soil pH change was significant across all treatments (p<0.01). The lowest pH measurement, 6.92, was observed in sandy textured soils with an application from granular Sulphur at 0.088 g 100 g-1. The pH change in clay-loam textured soils was found to range from 8.13 to 7.79, and in sandy textured soils from 7.69 to 6.92. These changes suggest that the acidifying effect of Sulphur oxidation on soil pH varies depending on the soil’s buffering capacity, particle size ratio, application rate, and incubation day. Consequently, the granular Sulphur was found to be more effective compared to the control and powdered Sulphur , and an application rate of 0.088 g 100 g-1 might be effective for both clay-loam and sandy soils. However, due to its lack of economic feasibility, 0.044 g dose or the doses from powdered Sulphur might be more appropriate.

Nanoconfinement-Enabled Resistance to Water Matrix Components for Selective Degradation of Micropollutants.

Despite recent substantial advances in water treatment, the ability to selectively degrade trace micropollutants in real waters with complex matrix components remains a grand challenge. Here we report rational crafting of graphene oxide (GO)-wrapped defective TiO2 composite catalysts that creates nanoscopic confinement over the TiO2 surface within GO, thereby enabling the selective degradation of micropollutants through effectively excluding natural organic matter (NOM) and anions from the nanoconfined catalytic sites. In contrast to unconfined counterparts, the nanoconfined composite catalysts retain high degradation efficiency when exposed to various concentrations of NOM and anions, even in real water samples. Oxygen vacancies in TiO2 promote electron separation and oxygen adsorption, leading to a 4.9-fold increase in hydroxyl radical concentration within the nanoconfined space compared to the bulk solution. In-situ X-ray photoemission spectroscopy and Raman spectroscopy unveil the nanoconfined catalytic sites on the TiO2 surface, where micropollutants smaller than the pores of GO are effectively degraded, while NOM with a larger size is excluded by GO. Furthermore, the formation of toxic disinfection byproducts is well controlled due to the exclusion of NOM. This work provides a simple yet viable strategy for designing 2D material-wrapped catalysts to selectively degrade target micropollutants in complex real waters.

A Systematic Study of the Structural Properties of Technical Lignins.

Technical lignins are globally available and a sustainable feedstock. The unique properties of technical lignins suggest that these materials should have several industrial applications. The main proposal of this study is to evaluate the relationship between the structure and properties of two technical lignins. Morphological, chemical, physical, and thermal properties of sodium lignosulfonate (LGNa) and magnesium lignosulfonate (LGMg) were investigated. The results showed that a higher formation of intramolecular hydrogen bonds may occur in lignins with a higher content of phenolic hydroxyl groups, such as LGMg. As a result, an increase in the energy of hydrogen bonds in the lignosulfonate structure was observed, without significant change in the hydrogen bond distances. In addition, higher content of phenolic hydroxyl groups might also reduce lignosulfonates thermal stability. The combustion index value was three times higher for LGMg than for LGNa. The characterization study also revealed that phenolic hydroxyl groups influence the main properties of technical lignins and can be a determining factor when these lignosulfonates are used in industrial applications.

Phenolic Hydroxyl‐Activated Lignin for Preparation of Extreme Environments Adaptive Adhesives

ABSTRACTEpoxy resins is widely applied in various industrial production. Lignin exhibits enormous potential as an alternate for health‐risk compound, bisphenol A, in the preparation of epoxy resin adhesives. However, the complicated structures and low reactivity limit the further utilization of lignin. In this study, a green deep eutectic solvent (DES) was utilized to enhance the phenolic hydroxyl content of hard wood organic lignin, from 3.63 to 5.63 mmol/g, to promote the reactivity of lignin during the preparation process of epoxy resin adhesives. Enabling by the DES induced lignin activation, the prepared lignin‐based epoxy resin exhibited excellent epoxy‐value (0.41 mol/100 g) and the as‐prepared adhesives possessed remarkable mechanical properties (tensile stress up to 50.86 MPa). Even after exposure to extreme conditions (freezing or soaking for 48 h), the adhesives maintained over 70% mechanical strength. This work contributes to the broader effort towards sustainable lignin‐based adhesives in industrial applications.

Enhancing the water resistance properties of bamboo particleboard by reconstructing lignocellulose through carbonization treatment

Bamboo particleboards are recognized as a highly promising alternative to traditional wood particleboards owing to their short growth cycle, abundant availability, and exceptional mechanical properties. However, bamboo particleboards frequently exhibit undesirable hygroscopicity, which limits their broader applications. This study introduces a straightforward and inhibitor-free carbonization treatment method to enhance the water resistance properties of bamboo particleboards. During the carbonization process, the degradation of hemicelluloses and amorphous cellulose, combined with the condensation reactions among lignin molecules, leads to a significant reduction in the hydrophilic hydroxyl and carbonyl group content, resulting in a more compact micro-fibril structure. Concurrently, the degradation of specific macromolecules within the cell wall facilitates the crushing of bamboo during particleboard pressing, thereby reducing the macroscopic pore size between the particles in the board. When compared to the original bamboo particleboard, the moisture absorption, 24-h water absorption (at a relative humidity of 50 %), 24-h thickness swelling, and bound water content of the deep carbon bamboo particleboard decreased by 32.28 %, 81.57 %, 67.16 %, and 66.7 %, respectively, while the water contact angle increased by 88.89 %.

Oxidant concentrations and photochemistry in a vehicle cabin.

Indoor air quality (IAQ) in vehicles can be important to people's health, especially for those whose occupations require them to spend extensive time in vehicles. To date, research on vehicle IAQ has primarily focused on direct emissions as opposed to chemistry happening in vehicle cabins. In this work, we conducted time-resolved measurements of the oxidants and oxidant precursors ozone (O3), nitric oxide (NO), nitrogen dioxide (NO2), and nitrous acid (HONO) inside the cabin of a 2012 Toyota Rav4 under varying ventilation conditions (i.e., car off, car on with passive ventilation, car on with mechanical ventilation via the recirculating fan, and car on with mechanical ventilation via the direct fan). Ozone levels inside the vehicle were significantly lower than outdoors under most conditions, and were approximately half the outdoor levels when the direct fan was in operation. Nitric oxide and NO2 concentrations were very low both inside the vehicle and outdoors. Nitrous acid levels in the vehicle were lower than reported values in other indoor environments, though much higher than expected outdoor levels. We also investigated the potential for photochemical production of radicals in the vehicle. Time- and wavelength-resolved solar irradiance spectra were collected, and steady state hydroxyl radical (OH) and nitrate radical (NO3) concentrations were calculated. Steady state OH concentrations were predicted to be similar to those in air masses in residences illuminated by sunlight, suggesting the importance of HONO photolysis in vehicles. Conversely, nitrate radicals (NO3) were not considered significant indoor oxidants in our study due to rapid titration by NO. Overall, our findings emphasize the importance of both air exchange and photochemistry in shaping the composition of air inside vehicles.

Emerging boron nitride nanosheets: A review on synthesis, corrosion resistance coatings, and their impacts on the environment and health

Abstract The aim of this study is to assess the effectiveness of hexagonal boron nitride (hBN) coatings to enhance the corrosion resistance of metals as well as evaluate their crucial toxicological impacts on both the environment and human health. Organic coatings are extensively applied in the field of protecting metals against corrosion. They are preferred as corrosion inhibitors due to their carbonyl and hydroxyl group content, but they have drawbacks regarding brittleness, porosity, and oxidation susceptibility. In this review, we mainly focused on the synthesis, properties, and applications of hBN coatings and emphasized the way to improve corrosion resistance in metals and alloys. Furthermore, our discussion demonstrated that the boron nitride nanosheet (BNNS) coatings significantly improve corrosion resistance, hydrophobicity, and crack mitigation properties. The researchers achieved reduced coating porosity and enhanced protection against corrosive media by effectively dispersing BNNS in organic resin. This study also determines the protective mechanism of BNNS composite coatings against corrosion. Moreover, we addressed the impact of BBNS synthesis and its physicochemical properties on the environment and organisms. Finally, suggestions are made for future research and the sustainability of industrial use to broaden the scope of applications for BNNS composite coating.

Narrative Review of Free Radicals and Reactive Oxygen Species in Otitis Media.

Many studies have evaluated the roles of free radicals and reactive oxygen species (ROS) in various diseases. To date, however, no systematic review has specifically investigated the involvement of free radicals and ROS in acute otitis media (OM), OM with effusion, and chronic OM. The present study therefore assessed the roles of free radicals and ROS in OM. SCOPUS, PubMed, Cochrane Library, EMBASE, and Google Scholar were comprehensively searched to identify studies assessing the roles of free radicals and ROS in OM. Relevant studies were identified and their findings summarized. The literature search identified 21 studies. A review of their findings showed that the concentrations of hydrogen peroxide (H2O2), lipid hydroperoxide (LPO), and myeloperoxidase (MPO) were elevated in patients with acute OM; that the concentrations of H2O2, LPO, MPO, xanthine oxidase (XO), superoxide dismutase (SOD), glutathione peroxidase (GPX), malondialdehyde (MDA), hydroxyl radical (·OH), and nitrotyrosine were elevated in patients with OM with effusion; and that the levels of nitric oxide (NO), MPO, 4-hydroxynonenal (4-HNE), and malondialdehyde (MDA) were elevated in patients with chronic OM. Although some studies reported that SOD levels were increased in patients with OM with effusion, decreases in antioxidants such as SOD and catalase, as well as total antioxidant capacity, were observed across all types of OM. Although the levels of free radicals and ROS varied by type of OM, study design, control group selection, sample type, ROS and free radical markers, and antioxidant types, most studies showed increased ROS and decreased antioxidants in OM patients. These findings suggest that levels of free radicals and ROS are strongly associated with the pathophysiology of OM.

Efficient Separation of Poplar Lignin Using a New Carboxylic Acid-Based Deep Eutectic Solvents - Choline Chloride/Malonic Acid.

Separation of lignin by pretreatment is an important step in biomass refining. This study investigated how a novel dicarboxylic acid-based deep eutectic solvent (DES) - choline chloride (ChCl)/malonic acid (MA) - affected the process of separating lignin from poplar. At 140 °C for 3.0 h, with a ChCl: MA molar ratio of 1: 3.5, the ideal pretreatment conditions were met, and 91.8 % lignin was obtained. Even after five DES reuses, the consistent and effective separation efficiency of 77.9 % remains unchanged. The hydrolysate contained 92.4 % of the recovered lignin, with a purity of 94.6 %. Moreover, the regenerated lignin obtained through the new DES pretreatment exhibited a high phenolic hydroxyl content of 1.9 mmol g-1 and a low polydispersity index of 1.4. The results showed efficient and selective separation of lignin using the new binary carboxylic acid-based DES pretreatment was achieved. This research offers a novel approach to effectively separate wood fiber biomass and extract valuable lignin.

Inhibitory Effect and Mechanism of Dancong Tea from Different Harvesting Season on the α-Glucosidase Inhibition In Vivo and In Vitro.

Tea polyphenols have been reported to decrease the rate of starch hydrolysis by inhibiting α-glucosidase. However, the effect of the tea harvesting season and the structure of catechin monomers on the inhibitory activity of α-glucosidase is not understood. In this study, the inhibitory effect and underlying mechanism of four seasons of Dancong tea against α-glucosidase were investigated by in vivo and in vitro experiments, multi-spectroscope and molecular dynamic. The Dancong tea harvested in spring and winter showed a stronger inhibitory effect on α-glucosidase due to a higher content of catechin, especially EGCG ((-)-epigallocatechin-3-gallate). The results of in vivo and in vitro experiments showed that EGCG and ECG ((-)-epicatechin-3-gallate) with a higher content of gallate and hydroxyl groups exhibited a stronger inhibitory effect on starch hydrolysis, rise of postprandial blood glucose and activities of α-glucosidase compared to EGC ((-)-epigallocatechin) and EC ((-)-epicatechin). These gallate and hydroxy groups were more effective in interacting with the amino acid residues in the active site of α-glucosidase, leading to structural changes in the enzyme. Certainly, the inhibitory effect of Dancong tea on α-glucosidase explains one of the mechanisms by which it helps alleviate diabetes; the other hypoglycaemic mechanisms of Dancong tea will be further explored.

Preparation of aminated hardwood kraft lignin by Mannich reaction and its structural and thermal characterization

This study investigated the characteristics of aminated kraft lignin (AKL) prepared from the Mannich reaction of hardwood kraft lignin (KL) and diethylenetriamine (DETA) for future application in dye removal. Three aminated samples—AKL-3.5, AKL-7.5, and AKL-15—were prepared using different amounts of DETA (3.5, 7.5, and 15 mmol). The morphology, chemical, and thermal properties of AKLs were investigated through various instrumental analyses and compared with KL. Elemental analysis showed that AKL-15 contained the highest nitrogen content (8%). Based on scanning electron microscopy (SEM), AKLs exhibited a smoother surface compared to KL and aggregated into clusters. Infrared, X-ray photoelectron and 2D heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy confirmed the successful introduction of primary and secondary amines, and C = N functionality into the lignin structure.31P NMR indicated a decrease in hydroxyl group contents of guaiacyl and p-hydroxyphenyl units and an increase in C5 amine-substituted units for AKL-15. Thermal analyses (TGA and DSC) indicated that AKLs were thermally less stable and reduced glass transition temperature (Tg) than KL. These findings contribute to the limited literature on the amination of hardwood lignin, as most amination studies focus on softwood and grass lignins.

Switchable Solvent for Separation and Extraction of Lignin from Lignocellulose Biomass: An Investigation of Chemical Structure and Molecular Weight.

Lignin, the most abundant natural aromatic polymer, holds considerable promise for applications in various industries. The primary obstacle to the valorization of lignin into useful materials is its low molecular weight and diminished chemical reactivity, attributable to its intricate structure. This study aimed to treat lignocellulosic biomass using a switchable solvent (DBU-HexOH/H2O) derived from the non-nucleophilic superbase 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU), which efficiently separates and extracts lignin from poplar wood. Additionally, it sought to characterize fundamental properties of the extracted switchable solvent lignin (SSL) and propose a mechanism for its separation. In comparison to milled wood lignin, SSL exhibits a greater molecular weight, superior homogeneity, and enhanced stability. The SSL sample was analyzed using spectroscopies including infrared spectroscopy, nuclear magnetic resonance, and X-ray photoelectron spectroscopy. The findings indicated that the structure of SSL was preserved, with the switchable solvent primarily cleaving the C-C and α-O-4 bonds, resulting in a low hydroxyl content, an elevated H/C ratio, and a reduced O/C ratio. The SSL was successfully prepared to lignin nanoparticles (LNPs) with size range of 531-955 nm. This paper presents a technique for processing lignocellulosic biomass using a switchable solvent, highlighting advancements in lignin's structure and enhancing its use in the chemical sector.

Molecular Dynamics Simulation of the Effect of Shale Wettability on CO2 Enhanced Oil Recovery.

The wettability of shale is an important factor affecting oil and gas extraction, and conventional experimental methods are difficult to study at the nanoscale. Moreover, most existing studies are qualitatively based on the wettability of rock surfaces with little consideration for their impact on the CO2-EOR. This study employs molecular dynamics simulation methods to conduct an in-depth analysis of the role of rock surface wettability in the CO2-enhanced oil recovery (EOR) process. The research findings indicate that as the surface hydroxyl content increases, the adsorption affinity for CO2 is enhanced, with the selectivity increasing exponentially from 0.74 in the strongly oleophilic wetting (SOW) pore to 3.62 in the strong hydrophilic wetting (SHW) pore. Additionally, variations in wettability result in different types of CO2 displacement. As oil wettability decreases, the contact interface between CO2 and oil changes from a convex to a concave shape. Moreover, different types of wettability result in different dynamic contact angle changes over time, which significantly impacts various displacement stages. A comprehensive comparison shows that pores exhibiting oil-wet characteristics reduce the efficiency of the CO2-EOR. Finally, the investigation explored the influence of pore structure on oil displacement efficiency. In double pores, when the larger pores exhibit hydrophobic characteristics, they further accelerate the displacement speed of the smaller pores. In connected pores, the presence of notch speeds up the displacement effect within the smaller pores, reducing the impact of wettability on displacement efficiency. This study deeply analyzes the role of shale surface wettability in the CO2-EOR process, revealing the impact of wettability on the CO2 adsorption affinity, fluid displacement, oil displacement efficiency, and flow characteristics of shale oil, providing an important theoretical basis for optimizing the CO2-EOR process by adjusting wettability.

Electric Field-Induced Synergetic Enhancement of Local Hydroxyl Concentration and Photogenerated Carrier Density for Removal of COads in Electrocatalytic Formic Acid Oxidation.

Direct formic acid fuel cell (DFAFC) is an efficient power generation device, due to its high energy density, low fuel crossover and low emission. However, the anodic reaction of DFAFC, formic acid oxidation (FAOR), inevitably proceeds through an indirect pathway, adsorbing carbon monoxide intermediate (COads), resulting in a rapid decline of activity for FAOR. Therefore, effectively removing COads is the key to the development of DFAFC. In this work, Pd/CeO2 catalyst is synthesized by in situ growth of Pd nanoparticles on the hollow CeO2. Due to the difference of work function between Pd and CeO2, a built-in electric field from Pd side to CeO2 side is formed, which induces a synergistic enhancement of the photogenerated carrier density and the local high hydroxyl concentration at the Pd/CeO2 interface, thus promoting the oxidative removal of COads and significantly improving the stability of FAOR. Therefore, in photo-assisted electrocatalytic FAOR, Pd/CeO2 not only possessed high mass activity (4161.72 mA mg-1 Pd), and its mass activity decreases by only 20.1% after 40000 s chronoamperometry test, which is superior to most Pd-based catalysts. This work provides a new strategy for efficient removal of COads in FAOR through constructing built-in electric fields, which promotes the DFAFC application.

The long-term impact of biogenic volatile organic compound emissions on urban ozone patterns over central Europe: contributions from urban and rural vegetation

Abstract. The paper evaluates the long-term (2007–2016) impact of biogenic volatile organic compound (BVOC) emissions on urban ozone patterns over central Europe, specifically focusing on the contribution of urban vegetation using a regional climate model coupled offline to a chemistry transport model. BVOCs are emitted by terrestrial ecosystems, and their impact is considered especially important over NOx-rich environments such as urban areas. The study evaluates the impact of BVOC emissions on ozone (O3), formaldehyde (HCHO), and hydroxyl radical (OH) near-surface concentrations, showing an increase in summer ozone by 6 %–10 % over large areas in central Europe due to their emissions. It also demonstrates a substantial increase in formaldehyde concentrations. Additionally, the impact of BVOC emissions on hydroxyl radical concentrations shows a decrease over most of the modeled region by 20 %–60 %, with some increases over urban areas. Impacts on peroxy radicals (HO2 and higher RO2) are shown too. Importantly, the study explores the partial role of urban vegetation in modulating ozone and evaluates its contribution to the overall ozone formation due to all BVOC emissions. The findings reveal that urban BVOC emissions contribute to around 10 % of the total impact on ozone and formaldehyde concentrations in urban areas, indicating their significant but localized influence. The study also conducts sensitivity analyses to assess the uncertainty arising from the calculation of the urban fraction of BVOC emissions. The results show that the impact of urban BVOC emissions responds to their magnitude nearly linearly, with variations up to 4-fold, emphasizing the importance of accurately quantifying the urban BVOC fluxes. Overall, the study sheds light on the intricate relationship between urban vegetation, BVOC emissions, and their impact on atmospheric chemistry, providing valuable insights into the regional chemistry of BVOC emissions over central Europe and the causes of urban ozone pollution.

Bleached rice straw lignin: Thermal-chemical properties and its application in polyurethane-based paper coatings

Rice straw lignin (LRS) tends to be dark in color, which makes it less appealing for material applications. Therefore, a bleaching process involving lignin oxidation is of interest. This study aimed to investigate the mechanical and chemical properties of bleached LRS and explore its potential application in PU-based paper coatings. LRS and commercial lignin (LC) were subjected to bleaching using 29% H2O2 through oxidation treatment. The bleached lignin was then used to prepare PU-based paper coatings. The effects of bleaching treatment on the functional groups, structural, and thermal properties of lignin, as well as the water resistance of the PU composites were assessed. The oxidation treatment resulted in a reduction in the phenolic hydroxyl content, methoxy content, antioxidant activity, and equivalent weight of lignin. However, LRS exhibited greater thermal resistance than did LC. The bleached LRS was successfully integrated with toluene di-isocyanate (TDI) to produce transparent polyurethane. This polyurethane was then applied as a coating for paper containers, which successfully held cold water for over 4 h without leaking, indicating its outstanding water repellency.

Phase-Field Approach to Formation of Aluminum Oxyhydroxide Nanofibrils on a Liquid Aluminum Alloy Surface in Water-Containing Atmospheres

Formation of peculiar nanofibril structures on the surface of liquid aluminum alloys as a result of chemical reaction of aluminum with water vapors was well studied experimentally for various alloy components starting from mercury. However, the mechanism of nanofibril formation remains unclear to date, and the lack of an appropriate theoretical model does not allow evaluation of the structure parameters depending on the process conditions. We assume that the interface layer between the liquid metal phase and the atmosphere, containing the water vapor, develops certain inhomogeneities respect to the content of hydroxyl groups. That provides areas of suppressed and enhanced diffusion of the aluminum from the liquid phase toward the atmosphere contact. Phase-field modeling, taking into account their elastic interaction, demonstrates formation of the array of nano-islands, enriched with hydroxyl groups, which can be precursors for formation and growth of nanofibrils with elements of pre-boehmite structure.

The effect of heating rate on secondary oxidation of coal spontaneous combustion under hypoxic conditions

ABSTRACT Coal spontaneous combustion (CSC) presents significant safety risks in coal mining. This study investigates the causes through experiments on lignite from southwestern China. The coal samples underwent varying heating rates (HRs) in a programmed temperature furnace under 5% O2 to produce experimental samples. Custom-engineered heating apparatuses, gas chromatography (GC), and Fourier-transform infrared spectroscopy (FTIR) were enlisted to analyze the effects of HR on coal oxygen consumption, CO emissions, and functional group conversions under hypoxic circumstances.The principal discoveries indicate that HR significantly influences secondary oxidation and the transformation of functional groups, thereby affecting the CSC process. The optimal HR for secondary oxidation depends on the initial oxidation temperature. At an initial oxidation temperature of 80°C, coal samples subjected to a heating rate of 0.4 °C/min demonstrated an elevated rate of oxygen consumption, along with markedly higher levels of aromatic hydrocarbons and oxygen-containing functional groups in comparison to other samples. At HRs of 0.8 °C/min and 1.2 °C/min, the oxygen consumption rate increased with the initial oxidation temperature, ultimately exceeding the aliphatic hydrocarbon group content in samples treated at other temperatures. The hydroxyl content decreased with rising temperature but was maintained at lower HRs at lower temperatures.