Hydroxyl Content Research Articles

Influence of Soot Particles on the Gas-Phase Methane Conversion into Synthesis-Gas. The Role of H<sub>2</sub>O and CO<sub>2</sub> Additives

The influence of the formation of microheterogeneous soot particles on the gas-phase conversion of rich mixtures of methane with oxygen into synthesis gas in the temperature range from 1500 to 1800 K under the conditions of an adiabatic reactor was studied by kinetic modeling. The effect of CO2 and H2O additives on this process was studied. The appearance of soot particles is observed in rich mixtures, starting from the fuel excess factor ϕ = 3.33. At relatively low temperatures ~1500 K, a small amount of microheterogeneous soot particles is formed, which do not significantly affect the other components of the reacting system. A noticeable effect of soot particles at this temperature is observed at a higher value of ϕ = 8.0. This is most clearly manifested in the temperature profile of the process, in which, with the addition of water, two maxima are observed at times of the order of 0.01 and 0.1 s. In the case of CO2 additions, the second maximum on the temperature profile is almost not pronounced. A complex temperature profile leads to the appearance of the second maximum concentration of OH hydroxyl radicals at times of ~0.1 s. The addition of H2O and CO2 makes it possible to vary the H2/CO ratio in the synthesis gas over a wide range, which is necessary for the synthesis of various products. Since the added CO2 under these conditions is actually involved in the chemical process of obtaining synthesis gas, its partial recirculation from the conversion products makes it possible to reduce its emission during the production of synthesis gas.

Creating high-affinity binding sites for efficient CO2 and iodine vapor uptake through direct synthesis of novel triazine-based covalent organic polymers

Two types of triazine-based covalent organic polymers were successfully constructed through a one-pot and catalyst-free polycondensation approach. More specifically, two kinds of aromatic aldehyde containing different hydroxyl content named terephthalaldehyde and 2, 4, 6-trihydroxyisophthalaldehyde were selected and the derived polymers (denoted as POPs-1 and POPs-2) with large Brunauer-Emmett-Teller (BET) surface areas (> 360 m2/g), high total pore volume (> 0.47 m3/g), good stability and different heteroatoms (such as N and O) contents were prepared. Interestingly, POPs-1 featuring high BET surface area and N content (up to 34.83 %) exhibited excellent iodine vapor uptake of 441 wt% at 348 K/1.0 bar, POPs-2 with high O content (up to 25.83 %) showed better CO2 adsorption capacity (91.8 mg/g) at 273 K/1.0 bar and higher isosteric heat of adsorption (up to 85.0 kJ/mol) than that of POPs-1. This value of the isosteric heat is the highest value reported to date for porous organic polymers. This excellent adsorption performance was resulted either from the large BET surface area or high heteroatoms (N and O) contents of the porous adsorbents. The study offer an alternative route to develop high-performance porous adsorbents to capture carbon dioxide and iodine.

Demethylation of ethanol organosolv lignin by Na2SO3 for enhancing antioxidant performance

Natural polyphenol antioxidants have excellent antioxidant activity and degradability which are considered as one of the possible alternatives to chemical synthetic antioxidants. Here, lignin-based polyphenols were prepared from poplar lignin, pine lignin and rice husk lignin by demethylation, and no toxic reagents were used in the preparation process. The phenolic hydroxyl groups of all three lignin were increased and the methoxyl content was significantly reduced after the demethylation without degradation or structural changes in the lignin as shown by GPC and 2D HSQC analyses. Furthermore, the antioxidant activity of the modified lignin was significantly increased. In this paper, a green and efficient strategy was developed to prepare lignin-based polyphenols with high phenolic hydroxyl content, low molecular weight, strong antioxidant activity and low cytotoxicity, which have a promising future in the field of antioxidant applications.

Structure-property relationship of native-like lignin nanoparticles from softwood and hardwood

Renewable resources such as wood are an important candidate towards the replacement of fossil-based materials with bio-based materials. Lignin, comprising up to 40% of woody biomass, has shown great potential in the preparation of nanoparticles (LNPs), which can be used in diverse material applications. Typically, LNPs are prepared from technical lignins, deriving from pulping processes. Their formation is thought to be driven by the hydroxyl content and molecular weight of lignin. However, other equally important parameters are the monolignol composition and the concentration of lignin used. In this study, we used native-like lignin fractions from hardwood and softwood to investigate the impact of lignin structure on LNP formation. We identified a synergistic effect between π-π stacking and hydroxyl group content in nanoparticle formation. Our LNPs exhibited different morphologies, including compact, collapsed spheres, and ‘snowman’ aggregates. The results described herein provide an in-depth perspective on the formation and structure-property relationship of LNPs from native-like lignin fractions. With this study we aim to promote biorefinery concepts, in which the lignin structure is preserved during extraction.

SiO2 soot preform sintering process for the synthesis of large-size and high-purity silica glass

The indirect chemical vapor deposition (CVD) method is a promising method to synthesize high-purity silica glass. As a critical procedure of this method, the sintering process is rather complex due to the interactive physical phenomena, and an in-depth understanding is therefore required. In this paper, a comprehensive multiphase porous medium model is developed by introducing the shrinkage mechanism, which agrees well with the experimental results. With this model, the dynamic characteristics during the sintering process, including temperature distribution, volumetric deformation, hydroxyl content evolution, and internal stress development, are well predicted. A parametric sensitivity analysis is conducted then, which shows that the average porosity and hydroxyl concentration are mainly affected by the average particle radius, while the maximum effective stress is sensitive to both Young's modulus and the average particle radius. Finally, the effects of key operating parameters are explored, and it is found that a lower working pressure, an appropriate sintering temperature such as 1450 °C, or a proper initial porosity such as 80.0%, is more desirable for a sintered product with high optical performance. This study can deepen the understanding of the SiO2 soot preform sintering process, and provide a good basis for further optimization.

Effect of Graphene Oxide-Modified CaAl-Layered Double Hydroxides on the Carbon Dioxide Permeation Properties of Fluoroelastomers.

This work aimed to investigate the CO2 gas barrier and mechanical properties of fluorine rubber nanocomposites filled with Ca/Al layered hydroxide (graphene oxide [GO]/LDH-Ca2Al) modified by GO. GO/LDH-Ca2Al nanocomposite fillers were prepared by depositing Ca/Al layered hydroxide (LDH-Ca2Al) into the surface of alkalized GO (Al-GO). The prepared GO/LDH-Ca2Al nanocomposite fillers and complexes were characterized by Fourier infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) for structural and micromorphological characterization. The results showed that GO/LDH-Ca2Al was successfully prepared with strong interactions between Al-GO and LDH, and the compatibility of GO/LDH-Ca2Al nanocomposite fillers with the polymer was significantly improved compared with that of LDH-Ca2Al. Consequently, both the fracture strength (σb) and strain (εb) of GO/LDH-Ca2Al nanocomplexes remarkably increased, and they exhibited excellent mechanical properties. Differential scanning calorimetry and thermogravimetric analysis were used to characterize the thermal stability of GO/LDH-Ca2Al nanocomposite fillers, and GO/LDH-Ca2Al nanocomposite fillers have better thermal stability than LDH-Ca2Al. The reaction products (S-LDH-Ca2Al and S-GO-Ca2Al) of LDH-Ca2Al and GO/LDH-Ca2Al with CO2 were characterized using XRD and TGA, respectively, and the results show that LDH-Ca2Al reacts readily and chemically with CO2, resulting in a lower diffusion coefficient of CO2 in the LDH-Ca2Al nanocomplexes than that of the GO/LDH-Ca2Al nanocomplexes and leading to the destruction of the laminar structure of LDH-Ca2Al, while GO/LDH-Ca2Al has better CO2 resistance stability. GO/LDH-Ca2Al nanocomplexes exhibited a reduced content of hydroxyl groups with pro-CO2 nature exposed on the surface of LDH-Ca2Al, improving the interfacial interaction between the nanofillers and the rubber matrix and enhancing the dispersion of GO/LDH-Ca2Al in the polymers. Moreover, CO2 in the soluble GO/LDH-Ca2Al nanocomposites was significantly reduced, while the diffusion properties demonstrated weak temperature dependence on solubility. The mechanism of the CO2 gas barrier of polymers filled with GO/LDH-Ca2Al was proposed on the basis of the Arrhenius equation.

The Effect of Temperature on Molecular Structure of Medium-Rank Coal via Fourier Transform Infrared Spectroscopy.

Fourier transform infrared spectroscopy (FTIR) was used to study the molecular structure of four medium- and low-temperature heat-treated medium-rank coals. The FTIR spectral parameters, which consist of CH2/CH3, aromaticity (fa), aromatic carbon rate (fC), aromatic hydrogen rate (fH), oxygen-containing (C-O) rate (IR), organic matter maturity (M), and the degree of aromatic condensation (Dc), indicate different characteristics, including changes in the aromatic hydrocarbon structure, fatty hydrocarbon structure, hydroxyl structure, and oxygen-containing functional groups of medium-rank coal. The results show that with the increase in heat treatment temperature, the sulfur content in coal gradually decreases, but the C/H ratio gradually increases. Meanwhile, the content of kaolinite and pyrite in coal gradually decreases, whereas the content of dolomite and hematite gradually increases. With the increase in heat treatment temperature, the relative content of ether oxygen hydroxyl groups in the hydroxyl structure significantly decreases, but the relative content of self-associated hydroxyl groups increases. The relative content of alkyl ether (C-O) in oxygen-containing functional groups gradually increases, whereas the relative content of aromatic nucleus C=C vibration presents a trend of first increasing and then decreasing. In addition, -CH2- is the majority in the structure of fatty hydrocarbons, and the absorption peak intensity of asymmetric -CH3 stretching vibration increases with the increase in heat-treated temperature. The structure of aromatic hydrocarbons mainly consists of four substituted benzene rings (except for R-303.15 K), in which the relative content of the trisubstituted benzene ring decreases with the increase in heat treatment temperature. With the increase in the heat-treated temperature of medium-rank coal, Dc, fH, fC, and fa show a trend of first increasing and then decreasing, M and IR reveal a trend of first decreasing and then increasing, and CH2/CH3 present a gradually decreasing trend. In conclusion, during the increase in the heat treatment temperature of medium-rank coal, the length of the fatty side chains in the fatty hydrocarbon structure becomes shorter, the number of branch chains continuously increases, and the maturity and condensation degree of organic matter first increases and then decreases. On this basis, further research on the effect of coal gasification suggests combining various technologies such as 13C NMR, XRD, and TG-MS to obtain semi-quantitative structural information of molecules in coal from different perspectives.

Flexibility and abrasion tolerance of superamphiphobic coatings with rigid core–shell particles

Superamphiphobic coatings maintain surfaces clean even facing severe oil contamination, which is crucial for ensuring the lifespan of materials in highly polluted environments. Achieving excellent wear resistance and flexibility individually on superamphiphobic surfaces is relatively simple, but simultaneously obtaining both properties is challenging and often requires compromises. In this study, we develop an innovative approach inspired by “overcoming firmness by gentleness” to create superamphiphobic composite coatings with flexibility and abrasion tolerance. This innovative strategy combines a soft polyurethane resin with rigid diatomite/aluminum hydroxide (core–shell) particles, resulting in a coating structure resembling karst topography. Depositing aluminum hydroxide enhances the reactivity and content of hydroxyl groups on diatomite particles, simultaneously improving the hardness and 1H,1H,2H,2H-Perfluorodecyltrichlorosilane (FDTS) grafting degree of the core–shell particles. Residual hydroxyl groups on the semi-fluorination core–shell particles chemically bond with the isocyanate groups in the waterborne polyurethane resin, leading to enhanced crosslinking density and improved wear resistance of the coating. The top coating of F-SiO2 particles leads to a reduction in the surface energy of the core–shell coating. The obtained core–shell coating demonstrates excellent oil resistance even after 800 cycles of Taber abrasion under a load of 250 g and 1000 cycles of 360° bending, demonstrating remarkable wear resistance and flexibility simultaneously. This approach provides valuable insights for developing superamphiphobic composite coatings with flexibility and abrasion tolerance and opens new possibilities for their applications in flexible electronics and droplet manipulation.

Production of reactive oxygen species and its role in mediating the abiotic transformation of organic carbon in sandy soil under vegetation restoration

The significant impact of vegetation restoration on the turnover of organic carbon (OC) is mainly attributed to biological processes. However, the contribution of abiotic processes associated with reactive oxygen species (ROS) during vegetation restoration has remained largely overlooked. Therefore, we systematically explored ROS distribution and production mechanisms in sandy soil and their corresponding effects on OC oxidation through field monitoring and incubation experiments. The cumulative concentrations of hydroxyl radicals (•OH) produced within 24 h varied in different soils undergoing vegetation restoration, ranging from 2.36 to 22.05 μmol kg‒1, which were derived from the Fenton-like reaction of hydrogen peroxide (H2O2) and biotic-induced Fe(II). In addition, during the oxidation of reductive SOC, H2O2 can be formed and react with Fe(II) to generate •OH. Further, •OH significantly induced the abiotic transformation of OC, accounting for 15.93%‒25.80% of carbon dioxide (CO2) efflux. Specifically, 1 mol •OH can induce the production of 0.01–0.02 mol CO2 for particulate organic carbon (POC) and 0.03‒0.23 mol CO2 for mineral-associated organic carbon (MOC), as demonstrated by chemical quenching and sterilisation experiments. This indicated that MOC was more sensitive to •OH attacks. Collectively, our findings provide insights into the accumulation of ROS in sandy soils during vegetation restoration, with •OH playing a key role in SOC oxidation, as well as the patterns of SOC turnover and its response to changes in the soil environment.Graphical

Controllable Synthesis of Defective UiO-66 for Efficient Degradation and Detection of Ozone.

Metal-organic framework (MOF) structures have gained significant attention for their exceptional catalytic performance in ozone degradation, even under high humidity conditions, which is attributed to the presence of unsaturated metal sites (MOF defects). However, the correlation between MOF defects and catalytic ozone remains ambiguous, and a general approach for the controllable synthesis of high-performance MOF structures is currently lacking. Herein, different defective UiO-66 materials with cluster or ligand defects were obtained by precisely controlling small molecular acid modulators. Their catalytic performance can be analyzed in real time through the specific cataluminescence (CTL) signal of ozone at the interface. The presence of ligand defects was found to be crucial for both catalytic degradation and luminescence of ozone, and the CTL signal exhibited a positive correlation with the endogenous hydroxyl group content in the material (R2 = 0.982), while external humidity further supplemented internal water molecules within the material. Furthermore, theoretical calculations were conducted to compare the adsorption behaviors of ozone on the defective UiO-66 under dry/wet conditions, leading to the proposal of two potential reaction pathways. Subsequently, UiO-66-DA with superior catalytic performance was employed to develop a highly efficient CTL sensor capable of accurately detecting ozone (LOD = 23.3 ppb). This study held significant value in elucidating the reaction site of ozone on MOFs and achieving optimal catalytic effects through the careful selection of modulators and humidity levels.

The impact of redox annealing on intrinsic properties and fluoride adsorption performance of CeO2 nanomaterials

The presence of excess fluoride ions in drinking water has raised widespread concerns, necessitating the development of effective methods for its removal. Cerium dioxide (CeO2) holds promise as a selective adsorbent for fluoride ions, due to its exceptional affinity for fluoride and stability across a wide pH range. However, the impact of intrinsic properties of CeO2 on its adsorption characteristics and mechanisms remains unclear. In this study, we prepared a range of CeO2 materials with diverse intrinsic properties by adjusting the annealing temperature and atmosphere. Through a series of characterization techniques, we discovered a correlation between the content of oxygen vacancies, Ce(III) species, and surface hydroxyl groups (–OH), all of which decreased simultaneously with increasing air annealing temperature. With respect to the adsorption performance, the highest fluoride adsorption capacity of 111.1 mg g−1 was observed in un-CeO2, representing the nanomaterials with the highest oxygen vacancies. This capacity gradually decreased to 29.1 mg g−1 in 800-CeO2. Following fluoride adsorption, the oxygen vacancy density, Ce(III) content, and surface –OH content of all CeO2 materials decreased. When CeO2 materials were annealed in H2 for 1 h, the F− adsorption density increased due to the formation of more oxygen vacancies and surface –OH. Based on our findings, we conclude that oxygen vacancies play a critical role in determining whether fluoride ions can successfully exchange with surface –OH groups and enter the crystal lattice of CeO2, which significantly affects the adsorption performance. The pivotal role of oxygen vacancies, as proposed in this study, provides a valuable direction for future research aimed at enhancing the fluoride adsorption performance of CeO2.

Dissolved carbon in biochar: Exploring its chemistry, iron complexing capability, toxicity in natural redox environment

Dissolved black carbon (DBC) plays a crucial role in the migration and bioavailability of iron in water. However, the properties of DBC releasing under diverse pyrolysis conditions and dissolving processes have not been systematically studied. Here, the compositions of DBC released from biochar through redox processes dominated by bacteria and light were thoroughly studied. It was found that the DBC released from straw biochar possess more oxygen-containing functional groups and aromatic substances. The content of phenolic and carboxylic groups in DBC was increased under influence of microorganisms and light, respectively. The concentration of phenolic hydroxyl groups increased from 10.0∼57.5 mmol/gC to 6.6 ∼65.2 mmol/gC, and the concentration of carboxyl groups increased from 49.7∼97.5 mmol/gC to 62.1 ∼113.3 mmol/gC. Then the impacts of DBC on pyrite dissolution and microalgae growth were also investigated. The complexing Fe3+ was proved to play a predominant role in the dissolution of ferrous mineral in DBC solution. Due to complexing between iron ion and DBC, the amount of dissolved Fe in aquatic water may rise as a result of elevated number of aromatic components with oxygen containing groups and low molecular weight generated under light conditions. Fe-DBC complexations in solution significantly promoted microalga growth, which might be attributed to the stimulating effect of dissolved Fe on the chlorophyll synthesis. The results of study will deepen our understanding of the behavior and ultimate destiny of DBC released into an iron-rich environment under redox conditions.

DEVELOPMENT OF QUALITY INDICATORS OF A NEW BIOSTIMULANT FROM PARACETAMOL WASTE

Introduction. In recent years, there has been a substantial rise in the utilization of biostimulants in agricultural crop production. The authors’ exten-sive research over the years has revealed that the byproduct of bacterial degradation of paracetamol exhibits a notable stimulatory effect on various medicinal and agricultural plants from different families. It serves as an inducer for the accumulation of biologically active substances in these plants, thereby making it a promising and efficient biostimulant. The purpose of this study is to establish a comprehensive set of indicators and create a preliminary specification for the quality control of the bacte-rial degradation product of paracetamol, which serves as a new biostimulant for medicinal and agricultural plants. Material and methods. For this study, we utilized the bacterial degradation product of paracetamol, derived from a pharmaceutical substance with an expired shelf life. The product was obtained from the Laboratory of Alkanotrophic Microorganisms, Perm Federal Research Center UB RAS (Perm). We employed various methods to analyze the product, including determining the melting point through the capillary method, assessing lead, cadmium, and arsenic content using an atomic absorption spectrometer with electrothermal atomization (MGA-915M, Lumex, Russia) and the Mga software on a personal computer running the Windows®-2000/XP operating system. Additionally, we recorded the IR spectrum using a Specord M80 IR spectrometer (Carl Zeiss Industrielle Messtechnik GmbH, Germany), and the electronic spectra were obtained with a Lambda EZ 201 spectrophotometer (Perki-nElmer, USA). The quantification of phenolic hydroxyl and carboxyl groups was performed through back acid-base potentiometric titration. Results: The product of bacterial degradation of paracetamol is practically insoluble in water, ether, very slightly soluble in chloroform, slightly soluble in hexane and acetonitrile, soluble in acetone and ethyl acetate, freely soluble in methyl alcohol, 95% ethyl alcohol and dimethyl sulfoxide. The melting point ranged from 150 to 206 °C, with decomposition. The heavy metal and arsenic content in samples of the product with varying shelf life complied with the standards outlined in general pharmacopoeia monograph 1.5.3.0009.15. The IR spectrum exhibited characteristic absorption bands of func-tional groups, including C–H aromatic (3042 cm1), –OH phenolic (3425 cm1), –NH– (3200 cm1), and C= N (1609 cm1). The electronic spectra of product solutions, in the concentration range of 5·106 to 2.5·105 g/cm3, displayed absorption maxima at λ=218 and λ=318 nm. The content of phenolic hydroxyls in the product composition ranged from 4.22 to 5.16 mmol-eq/g, while carboxyl groups ranged from 1.76 to 3.05 mmol-eq/g, comparable to the quantities found in humic acids. Conclusions. We have established a comprehensive list of indicators and developed a preliminary specification for the quality control of the bacterial degradation product of paracetamol as a biostimulant for medicinal and agricultural plants.

Inhibition of growth for Microcystis aeruginosa by insertion of iron ion into biochar modified copper metal organic framework (Fe3O4-BC@Cu-MOF-74) under visible light

Microcystis aeruginosa (M. aeruginosa) was a kind of harmful algae in various aquatic ecosystems, which has caused much public concern. The existing algae removal methods showed disadvantages such as incomplete algae removal and excessive capital investment. Based on the specificity of algal cells, insertion of iron ion into biochar-modified copper metal organic framework (Fe3O4-BC@Cu-MOF-74) was synthesized by biochar and MOF with the introduction of Fe3O4. Fe3O4-BC@Cu-MOF-74 was thin, porous and stable. C, O, Fe, and Cu were mainly contained, and it was characterized by peaks (111), (220), (331), (111), (400), (331) and (024) in crystal planes and C–O bonds, Cu–O bonds and O–H bonds were contained. Algal cell growth was significantly inhibited, with a growth inhibition efficiency of 32.21 % by Fe3O4-BC@Cu-MOF-74 under visible light. Chlorophyll-a was reduced by nearly 60 %. The high concentration of oxygen and hydroxyl radicals in the complex accelerated the oxidative process in cells, leading to oxidative stress, which triggered an increase in the concentration of relevant antioxidant enzymes, leading to an increase in soluble protein content. The presence of Cu2+, Fe2+ and Fe3+ could also attack and damage the cell membrane surface, leading to cell rupture and death. Fe3O4-BC@Cu-MOF-74 showed a promising application in the problem of inhibiting the growth of M. aeruginosa under visible light.

Green and sustainable production of high-purity lignin microparticles with well-preserved substructure and enhanced anti-UV/oxidant activity using peroxide-promoted alkaline deep eutectic solvent

Deep eutectic solvents (DESs) have emerged as promising and eco-friendly solvents for the efficient extraction of lignin from biomass due to their low cost and environmental benefits. Nevertheless, the prevalent use of acidic DESs in lignin extraction often results in excessive depolymerization and recondensation of lignin, thereby impeding its downstream applications. In this study, we developed a range of alkaline DESs (ADESs), both pure and peroxide-containing, for the extraction of high-quality lignin from bamboo. Moreover, carbon dioxide (CO2) was employed for the precipitation and regeneration of the extracted lignin. The obtained lignin fractions were comprehensively characterized in terms of yield, purity, morphology, solubility, structural features, and anti-UV/oxidant activity. The results showed that the monoethanolamine-based ADES demonstrated superior performance among the pure ADESs. Structural analysis confirmed the well-preserved substructures of lignin fractions obtained using ADESs, with β-O-4 bond retention ranging from 49.8 % to 68.4 %. The incorporation of a suitable amount of peroxide improved lignin yield, morphology, solubility, and anti-UV/oxidant activity. Additionally, the anti-UV/oxidant activity of lignin exhibited a positive correlation with its phenolic hydroxyl content. This study provides a valuable reference for the green and sustainable production and valorization of lignin within the existing biorefinery framework.

Preparation and performance of TiO2/ZnO humidity sensor based on TiO2

In this study, TiO2 was selected as the primary material to prepare a humidity sensor. To enhance its sensing performance, it was doped with ZnO, and a TiO2/ZnO composite was synthesized via the hydrothermal method. Based on this composite material, a TiO2/ZnO humidity sensor was designed and fabricated. The sensor properties were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) techniques. The increase in hydroxyl and oxygen vacancy content on the surface of composite materials enhances their sensitivity to water molecules, leading to improved sensor response. The construction of ZTO3 heterojunction promotes the migration of electrons on the sensor surface to improves the performance of the sensor. Humidity sensor based on the TiO2/ZnO composite material exhibits excellent performance, with high response to water molecules, a fast response/recovery time (18/22 s), low humidity hysteresis (1.55 %), and low interference from monochromatic light. Thus, the TiO2-based humidity sensor doped with ZnO shows great potential for practical applications.

Unveiling the mechanistic aspects of methylene blue adsorption onto a novel phosphate-decorated coconut fiber lignin

The aim of this work was to evaluate the adsorptive performance of the phosphorylated coconut fiber lignin (PCFL) obtained through an innovative biorefinery process for removing methylene blue (MB). PCFL was obtained using coconut fiber mixed with 85 % wt. H3PO4 at 70 °C for 1 h. Milled wood lignin (MWL) and PCFL were characterized by FTIR, CP-MAS 31P NMR, phosphorous and hydroxyl contents, pHPZC, and BET analyses. The batch adsorption tests evaluated the effects of the biosorbent (0.25 – 4 g L-1) and adsorbate dosages (2.5 – 7.5 mg L-1), contact time (0 – 60 min), pH (4 – 8), ionic strength (0.001 – 0.1 mol L-1) and temperature (298.15 – 318.15 K) on MB adsorption. Kinetic, equilibrium, and thermodynamic modeling were used. The phosphorous content on PCFL was 2.5 times higher than that of MWL. PCFL presented an enhanced adsorptive performance for removing MB, which was spontaneous (ΔG0 < 0), endothermic (ΔH0 > 0), with affinity between the biosorbent and adsorbate (ΔS0 > 0), and driven by physisorption (Ea > 40 kJ mol-1). The adsorptive performance of PCFL was enhanced due to the grafting of new active sites by using an innovative biorefinery process, showing its potential to be used for textile effluent remediation.

Flame retardant, strong and tough, low dielectric epoxy thermoset enabled by a novel bi-DOPO type epoxy with aggregation-induced emission

Multifunctional epoxy resins with excellent flame retardancy, high strength, high toughness, low dielectric loss and strong fluorescence show great potentials in electrical/electronic applications; however, simultaneously achieving those goals are difficult. To address those challenges, an epoxy resin with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) pendant group and flexible aliphatic spacer (DOPOEP) was developed. V-0 rating in UL-94 test and LOI of 33.1% are achieved at only 0.45 wt% phosphorus loading, benefitting from the flame retardant mechanism in gas and condensed phase. Compared with neat DGEBA, the cured epoxy with 10 wt% DOPOEP shows 13.4% and 37.6% improvements in tensile strength and impact strength, respectively; in addition, the tensile strength of the cured epoxy with 20 wt% DOPOEP is as high as 102.2 MPa, a 35.3% increase, without compromising toughness. The strengthening effects of DOPOEP derive from π-π stacking and hydrogen bonding, and the improved toughness is due to the flexible aliphatic spacer and reduced crosslinking density. Meanwhile, free volume reduction was observed after introducing DOPOEP, which is responsible for the improved modulus. DOPOEP addition also lowers the hydroxyl group concentration, leading to lower dielectric constant and dielectric loss tangent. Moreover, the aggregation-induced emission behavior of DOPOEP was reported, and its application in anti-counterfeiting field was explored. In air, the fluorescence of DOPOEP-containing thermoset steadily diminishes with increasing temperature, however the fluorescence changing trend is complex in vacuum. Besides, the fluorescence of DOPOEP is effective in the visual detection of defects and flaws in cured products. This work provides a new direction for developing high-performance epoxy with multifunction.

Original synthesis of polyvinyl butyral with a green deep eutectic solvent and a weakly polyacrylic acid from polyvinyl alcohol and the impacts of the chains structures of polyvinyl alcohol

AbstractIn this work, an environmentally‐friendly deep eutectic solvent (DES) was employed as a catalyst to generate polyvinyl butyral (PVB) resins from polyvinyl alcohol (PVA) with a weakly acidic polymer (polyacrylic acid [PAA]) as an emulsifier. Finally, high viscosity PVB resins with molecular weight of 110,000–200,000 g · mol−1 and acetalization degree above 83% were successfully synthesized, which was found to satisfy the requirements for interlayer films between safety glass. Furthermore, it was well proved that the properties of PVB resins immensely depend on the molecular structures of the PVA. The molecular weight of the PVB, independent of alcoholic degrees of the PVA, indicated an upward trend with the increase of the molecular weight of the PVA. As for these four PVBs with high molecular weight, the Tg was sensitive to the content of hydroxyl and acetal groups rather than molecular weight, associated with the inter‐ or intra‐molecule hydrogen bond between OH. PVB‐1799 and PVB‐1797 had higher Ti and Tg than that of PVB‐1788 and PVB‐1795 because the former had low contents of vinyl acetate group (VAc) and alcohol hydroxyl group (VOH). The tensile strength of PVBs was all higher than 30 Mpa, and the elongation at break was about 300% due to their high molecular weights.

Constructing an oxygen vacancy- and hydroxyl-rich TiO2-supported Pd catalyst with improved Pd dispersion and catalytic stability.

Surface property modification of catalyst support is a straightforward approach to optimize the performance of supported noble metal catalysts. In particular, oxygen vacancies and hydroxyl groups play significant roles in promoting noble metal dispersion on catalysts as well as catalytic stability. In this study, we developed a nanoflower-like TiO2-supported Pd catalyst that has a higher concentration of oxygen vacancies and surface hydroxyl groups compared to that of commercial anatase and P25 support. Notably, due to the distinctive structure of the nanoflower-like TiO2, our catalyst exhibited improved dispersion and stabilization of Pd species and the formation of abundant reactive oxygen species, thereby facilitating the activation of CO and O2 molecules. As a result, the catalyst showed remarkable efficiency in catalyzing the low-temperature CO oxidation reaction with a complete CO conversion at 80 °C and stability for over 100h.