OH Number Research Articles

Synthesis of d-Gluconic Acetal Surfactants and Their Foaming Behaviors.

Sugars are natural and environmentally benign substances, which can offer various hydroxyl groups. The understanding of details of the hydroxyl interactions in the hydrophilic groups of sugar-based surfactants, as well as the related properties, is still indistinct. Here, novel d-gluconic acetal surfactants with bicyclic and monocyclic structures in the head group were designed and synthesized. The obtained surfactant with a bicyclic architecture exhibited excellent foamability and a multistimulus-responsive behavior toward foam stabilization. In addition, the control of foamability from defoaming and foaming could be achieved by changing pH values or bubbling gas of CO2/N2. To explore the structural effects such as hydroxyl groups and rigidity of the head group on the properties of sugar-based surfactants, another kind of amphiphilic molecule with various OH- groups and a monocycle in the head group was designed for comparison. These two series of amphiphilic molecules both exhibited good surface activity. However, only the d-gluconic acetal surfactant with a bicyclic structure and a smaller number of OH- groups exhibited excellent foamability. Further studies showed that the foam behaviors were attributed to the conformation and arrangement of the surfactant molecule at the surface layer with the assistance of hydrogen bonds formed by hydroxyl groups and H2O molecules. In addition, the surfactant could provide an environmentally friendly foamer in many potential applications.

Characterisation of ethylene flames under a range of low-oxygen concentrations

New understanding of turbulent ethylene (C2H4) jet flames, issuing into a range of preheated coflowing oxidisers with reduced oxygen (O2) concentrations are reported. These conditions emulate moderate or intense low-oxygen dilution (MILD) combustion. To resolve previously reported non-monotonic trends, comparisons are made for coflow O2 concentrations of 3%, 4%, 5%, 6%, 9% and 11% and coflow temperatures of 1250K, 1315K and 1385K. Instantaneous and simultaneously planar imaging measurements of temperature, hydroxyl radicals (OH) and formaldehyde (CH2O) were taken at eight downstream locations ranging from 9mm to 75mm. The new data reveal non-monotonic lift-off trends in the OH and CH2O formation heights at all three temperatures. Compared with extant measurements, the higher resolution and greater control of coflow composition provide a detailed exploration of the transitional behaviour that occurs when MILD combustion conditions are achieved. The results experimentally demonstrate non-monotonic variation in lift-off height, and show that the same behaviour is present in both the OH and CH2O formation heights, and occurs at all three temperatures, which is due to the movement of the location of the stoichiometric and most reactive mixture fractions to the coflow side of the jet shear layer. The results also show that increasing the oxidiser temperature does not have a significant effect on the OH number density for a given temperature but does result in a significant decrease in lift-off height and CH2O concentration.

Direct Determination of the Activation Energy for Diffusion of OH Radicals on Water Ice

Using a combination of photostimulated desorption and resonance-enhanced multiphoton ionization methods, the behaviors of OH radicals on the surface of an interstellar ice analog were monitored at temperatures between 54 and 80 K. The OH number density on the surface of ultraviolet-irradiated compact amorphous solid water gradually decreased at temperatures above 60 K. Analyzing the temperature dependence of OH intensities with the Arrhenius equation, the decrease can be explained by the recombination of two OH radicals, which is rate-limited by thermal diffusion of OH. The activation energy for surface diffusion was experimentally determined for the first time to be 0.14 ± 0.01 eV, which is larger than or equivalent to those assumed in theoretical models. This value implies that the diffusive reaction of OH radicals starts to be activated at approximately 36 K on interstellar ice.

The removal efficiency and reaction mechanism of the aluminum coagulant on phenolic compounds in the presence of hardness salts

This study is the evaluation of the coagulation efficiency of the aluminum sulfate on the removal of catechol and pyrogallol. The study has focused on the impact of inorganic components of hardness Algerian waters. Jar-test trials were conducted on the two phenolic compounds dissolved in distilled water only, which was later enriched with minerals. Several reaction parameters varied, including the effect of pH and the influence of the salt content, and this approach yielded a better understanding of interaction between phenolic compounds and calcium/magnesium salts. The results indicate that the process efficiency depends on the number and position of OH in molecules. The main mechanisms would be either a physical adsorption, an exchange of ligand, or complexation on the floc surface of aluminum hydroxide. Moreover, the addition of inorganic salts appears to improve removal efficiency of tested phenolic compounds and have an effect on the optimal pH range for coagulation.

Enhancing α-etherification of lignin in Eucalyptus diol pretreatment to improve lignin monomer production

In this work, α-etherification of lignin in diol pretreatment was selectively enhanced at mild temperature for lignin isolation and subsequent valorisation. More than 90 % of lignin was removed from Eucalyptus at 120 °C in diol (ethylene glycol and 1,4-butanediol) pretreatment, resulting in >90 % cellulose conversion in 24 h at 7.5 FPU/g glucan cellulase loading. Subsequent catalytic transfer hydrogenolysis of the isolated lignins with Ru/C in ethanol gave 15 % monomer yield on native lignin basis, 5 times of that from the technical ethanol process (170 °C). HSQC NMR analysis revealed that diol pretreated lignin (120 °C) contained ∼23 % α-etherified β–O–4 interunit bonds, indicating that lignin degradation (i.e. cleavage of β–O–4 bonds) was suppressed via etherification by grafting a hydroxyl group at the α position of lignin. This finding was consistent with the isolated lignin (120 °C) had less number of phenolic OH and higher molecular weight via31P NMR and GPC analysis. 31P NMR analysis also revealed that diol isolated lignin contained more number of aliphatic OH than ethanol-isolated lignin, which increased lignin solubility and maintained the high yield (>80 %) of isolated lignin from Eucalyptus at 120 °C as expected. In summary, diol pretreatment of woody biomass can effectively isolate more lignin for hydrogenolysis to valued-added monomers without compromising the isolated yield of lignin and hydrolysis yield of remained cellulose.

Femtosecond ultraviolet laser absorption spectroscopy for simultaneous measurements of temperature and OH concentration

This Letter reports a femtosecond ultraviolet laser absorption spectroscopy (fs-UV-LAS) for simultaneous in situ measurements of temperature and species. This fs-UV-LAS technique was demonstrated based on X2Π-A2Σ+ transitions of OH radicals near 308 nm generated in low temperature plasmas and flames. The fs-UV-LAS technique has revealed three major diagnostic benefits. First, a series of absorption features within a spectral bandwidth of ∼3.2 nm near 308 nm were simultaneously measured and then enabled simultaneous multi-parameter measurements with enhanced accuracy. The results show that the temperature and OH concentration could be measured with accuracy enhanced by 29–88% and 58–91%, respectively, compared to those obtained with past two-narrow-line absorption methods. Second, an ultrafast time resolution of ∼120 picoseconds was accomplished for the measurements. Third, due to the large OH X2Π-A2Σ+ transitions in the UV range, a simple single-pass absorption with a 3-cm path length was allowed for measurements in plasmas with low OH number density down to ∼2 × 1013 cm−3. Also due to the large OH UV transitions, single-shot fs absorption measurements were accomplished in flames, which was expected to offer more insights into chemically reactive flow dynamics.

High-efficient degradation of sulfamethazine by electro-enhanced peroxymonosulfate activation with bimetallic modified Mud sphere catalyst

Electrocatalytic oxidation and persulfate (PMS) advanced oxidation were widely favored by researchers, but their wide application has been limited due to poor mass transfer efficiency and poor mineralization rate. In this study, the codoping of rural mud and bimetallic oxides (copper and nickel) (Md-Cu-Ni) was prepared. Then, Md-Cu-Ni was used as a catalyst for electrocatalytic oxidation and PMS advanced oxidation to degrade sulfamethazine (SMT). The structure, surface morphology and catalytic performance of the Md-Cu-Ni were characterized by a series of instruments. The electron spin resonance spectroscopy test results confirmed that Md-Cu-Ni produced a large number of OH and SO4−. The electrochemical workstation confirmed that Md-Cu-Ni had strong electrocatalytic activity and repolarization ability. Then, the result shows that the removal efficiency and mineralization rate by three-dimensional electrocatalytic coupled PMS advanced oxidation technology were 99.56% and 88.63% in 90 min. The effect of the pH, voltage, aeration flow rate, plate spacing, Na2SO4 dosage, potassium peroxymonosulfate sulfate complex salt dosage on SMT degradation was investigated. Moreover, this method also has high degradation efficiency for other 13 organic pollutants. Cycling experiments demonstrated the good stability of Md-Cu-Ni. It was found that 16 intermediates appeared in the degradation process by LC-MS. It was believed that this work provides a new vision for water treatment.

Biomass Valorization of Walnut Shell for Liquefaction Efficiency

Globally, lignocellulosic biomass has great potential for industrial production of materials and products, but this resource must be used in an environmentally friendly, socially acceptable and sustainable manner. Wood and agricultural residues such as walnut shells as lignocellulosic biomass are one of the most affordable and important renewable resources in the world, which can partially replace fossil resources. The overall objective of the research is to provide background information that supports new applications of walnut shells in a biorefinery context and to increase the economic value of these non-wood forest products. This paper presents the properties characterization of liquefied biomass according to their chemical composition. All results were compared to liquefied wood. In this study, the liquefaction properties of five different walnut shell particle sizes were determined using glycerol as the liquefaction reagent under defined reaction conditions. The liquefied biomass was characterized for properties such as percentage residue, degree of liquefaction, and hydroxyl OH numbers. The chemical composition of the same biomass was investigated for its influence on the liquefaction properties. Accordingly, the main objective of this study was to determine the liquefaction properties of different particle sizes as a function of their chemical composition, also in comparison with the chemical composition of wood. The study revealed that walnut shell biomass can be effectively liquefied into glycerol using H2SO4 as the catalyst, with liquefaction efficiency ranging from 89.21 to 90.98%.

Composition and Structure of Ethanol-Lignins of Coniferous and Deciduous Wood and Products of their Catalytic Telomerization with 1,3-Butadiene

The composition and structure of ethanol-lignins of coniferous (abies, pine) and deciduous (aspen, birch) wood and products of their catalytic telomerization with 1,3-butadiene has been studied with use of the methods 31P-NMR, gel-permeation chromatography, scanning electron microscopy and elemental analysis. Data on the nature and content of hydroxyl groups in ethanol-lignins were obtained using phosphorylation of lignins with 2-chloro‑4,4,5,5,-tetramethyl‑1,3,2-dioxaphospholane.The studied lignins differ from each other in the content of aliphatic, phenolic and carboxyl groups. The total content of hydroxyl groups increases in the series of ethanol-lignins: birch < aspen < pine < abies. For the modification of ethanol-lignins, the reaction of catalytic telomerization with 1,3-butadiene was used at 70 °C and 90 °C in the presence of a complex of palladium (II) diacetate with the sodium salt of triphenylphosphine trisulfate. By comparing the number of aliphatic, phenolic and carboxyl OH- groups in the initial and telomerized ethanol-lignins, it was found that only aliphatic and phenolic hydroxyl groups participate in the telomerization reaction. Telomerization of ethanol-lignins with 1,3-butadiene increases their average molecular weight and reduces polydispersity. The morphology of telomerized and initial samples of ethanol-lignins varies significantly

Dimensionless parameters controlling the spreading behaviors of free-falling molten metal on dry surface

Understanding the spreading behavior of a molten core is important for predicting the progression of severe accidents and ensuring the smooth decommissioning of severe accident-experienced nuclear power plants. In the current study, molten-metal drop experiments were performed using tin and copper. These experiments were conducted to expand the fundamental knowledge on spreading and deposition behaviors to verify the analysis model. In the case of a nozzle diameter of 4 mm, the deposited metal was uniformly relocated; however, the center was extremely thin and Sn demonstrated a circular shape for a nozzle diameter of 10 mm, while Cu spread non-uniformly. The unevenness ratios for Cu were much higher than that of the Sn independent of the dropped height and the nozzle diameters. The effects of hydraulic and thermal dimensionless numbers on the deposition and spreading behaviors were analyzed. A correlation between the spreading and deposition behaviors and the dimensionless numbers of Re, We, Pe, Oh, and Bo was observed. In particular, the Oh and Bo numbers had significantly high correlation coefficients with the dimensionless spreading area, where effects of inertial force on the spreading process were relatively low. The experimental correlation of the dimensionless spreading area was proposed using the Re and Bo numbers. The prediction capability was improved, in which the predicted values were within 28% for the current experiments.

Effect of step-by-step depolarization on electret performance of OH defect-controlled ceramic hydroxyapatite

Ceramics electrets of hydroxyapatite (HAp) have been developed for both power generators and artificial bones. However, the formation mechanisms of the HAp electrets have not yet been completely understood. In particular, it is unclear how the OH− ion-dipoles in HAp lattices contribute to electret performance. Herein, we show that HAp with controlled OH− ion content exhibits excellent performance as an electret. We prepare OH−-defect-controlled HAp samples either by restricted dehydration during thermal process or by valence control through the substitution of Ca2+ with Nd3+. The experimental results prove that the electrets prepared by partially dehydrated HAp and Nd-substituted HAp with a small number of OH− ions showed better performance. Our results suggest that the OH− ion-dipole polarization contributes negatively to the electret performance.

An improved collision - radiation model of the OH spectrum in the ultraviolet band

In order to calculate the spectral radiation characteristics of OH(A2∑) molecules more accurately, an improved collision-radiation (C-R) model is proposed to determine the excited states OH(A) number density. The six-components air model (CO, CO2, H2, H2O, N2, and O2) instead of the two-components air model (N2 and O2) are used as other plume products in the excitation/de-excitation radiation reaction, and the rate of the four reactions are modified to improve the accuracy and applicability of the number density. Effects of temperature and other plume products on the number density of excited states are analyzed in the experiment, and the spectral radiation characteristics of OH(A) can be obtained by using this improved C-R model. Results of these calculations are then compared with other series of experimental data of exhaust plume and shock layer, the results show that both the original model and the improved model can be used to calculate the radiation characteristics in shock layer, however, due to the great error, the original model not apply to calculation of the OH(A) number density in exhaust plume, and the result of the improved model is in good agreement with the Atlas experimental data. As the vibrational-rotational level distribution number density has a close relationship with radiative spectral characteristics, a more focused OH(A) particle number density model will be more helpful to the hypersonic target detection and recognition.

Shaping Magnetite by Hydroxyl Group Numbers of Small Molecules.

Despite numerous reports on magnetite formation with the assistance of various additives, the role of hydroxyl group (-OH) numbers in small polyol molecules has not yet been understood well. We selected small molecules containing different -OH numbers, such as ethanol, ethylene glycol, propanetriol, butanetetrol, pentitol, hexanehexol, and cyclohexanehexol, as additives in coprecipitation. By increasing the -OH number in these small polyol molecules, the formation of crystallization was slowed, and the size and shape of magnetite were regulated as well possibly due to the changed complexation strength and the stability of the precursor. The increase in temperature and the Fe2+/Fe3+ ratio can reduce the complexation strength. The nucleation and growth of magnetite proceed possibly through the aggregation of polyol-stabilized amorphous complexes and two-line ferrihydrite with low crystallinity based on the -OH numbers, suggesting a nonclassical pathway. The as-prepared magnetite showed a r2/r1 ratio after in vitro MRI measurement as follows: Fe3O4@He-6OH rod < Fe3O4@Pr-3OH sheet < Fe3O4@Pe-5OH cube. The Fe3O4@He-6OH rod and Fe3O4@Pr-3OH sheet displayed T1-T2 dual modal contrast ability, while the Fe3O4@Pe-5OH cube can be T2-dominated. This research provides a simple but an essential approach for designing MRI contrast agents.

Regulating the Superficial Vacancies and OH− Orientations on Polarized Hydroxyapatite Electrocatalysts

AbstractSmart designs of hydroxyapatite (HAp) materials with customized electrical properties are drawing increasing attention for their wide range of potential applications. Such enhanced electrical properties directly arise from the number and orientation of OH− groups in the HAp lattice. Although different polarization treatments have been proposed to enhance the final conductivity by generating vacancies at high temperatures and imposing specific OH− orientations through electric voltages, no direct measurement showing the evolution that OH− groups undergo has been described yet. In this article, the first direct empirical observation that allows the characterization of both the generation of vacancies and the polarization of OH− groups is reported. The mechanisms behind the electrical enhancement are elucidated allowing to distinguish between charge accumulation at the crystal grains, which is due to the formed vacancies, and charge accumulation in the boundaries of particles. In addition, a linear dependence between the number of vacancies and the superficial charge is observed. Therefore, it is demonstrated that the charge accumulation at the micrometric grain boundaries has a great impact on the catalytic properties of the thermally stimulated polarized HAp. These results will be used for further optimization of the catalyst properties.

Computational study of Fe3O4 adsorption behaviour on the secondary side of the heat exchange tube in the steam generator

Based on the scaling problem on the outer surface of the steam generator tube in the secondary circuit condition of pressurizedwaterreactor, the molecular dynamic was used to calculate the adsorption characteristics of Fe3O4. The trajectory, mean squared displacement, radial distribution function and adsorption energy of Fe3O4 agglomeration and deposition process were further analyzed through variation of temperature and concentration. When the temperature was between 510 K and 530 K, the diffusion coefficient of Fe2+ and OH− could reach the minimum value of 2.255 × 10-5 cm2/s and 2.638 × 10-5 cm2/s, respectively. During variation of Fe2+ concentration, the size of agglomerate particles increased continuously, and the diffusion coefficient of H2O can reach the minimum value of 3.78 × 10-5 cm2/s. Fe2+ with positive charges can effectively agglomerate with H2O and OH−, forming the tetrahedral and octahedral structures of Fe3O4 crystal. At this time, a small number of OH− were adsorbed at the interface of the matrix, forming the double electrical layer and affecting the deposition of agglomerated Fe3O4. Apart from this, high temperature is beneficial to inhibit scaling deposition in part. Likewise, low concentration of the dissolved Fe2+ and OH− can also lead to weaker deposition of agglomerated Fe3O4 on the outer scaling layer of the secondary side in the steam generator.

Chemical and Thermo-Mechanical Properties of Waterborne Polyurethane Dispersion Derived from Jatropha Oil.

Nowadays, there is a significant trend away from solvent-based polyurethane systems towards waterborne polyurethane dispersions due to government regulations requiring manufacturers to lower total volatile organic compounds, as well as consumer preference for more environmentally friendly products. In this work, a renewable vegetable oil-based polyol derived from jatropha oil was polymerized with isophorone diisocyanate and dimethylol propionic acid to produce anionic waterborne polyurethane dispersion. Free standing films with up to 62 wt.% bio-based content were successfully produced after evaporation of water from the jatropha oil-based waterborne polyurethane (JPU) dispersion, which indicated good film formation. The chemical and thermo-mechanical properties of the JPU films were characterized. By increasing the OH numbers of polyol from 161 mgKOH/g to 217 mgKOH/g, the crosslinking density of the JPU was significantly increased, which lead to a better storage modulus and improved hydrophobicity. Overall, JPU produced from polyol having OH number of 217 mgKOH/g appears to be a promising product for application as a binder for wood and decorative coatings.

Preparation and performance study of hydrotalcites /PLA composites

3D printing technology is known as the core technology of “the third industrial revolution”. Poly (lactic acid) (PLA) is a new type of biodegradable thermoplastic resin, which is renewable. It has a wide range of raw materials. It also has the properties of high strength, good biocompatibility, excellent mechanical properties, thermoplastic and transparency. Hydrotalcite (HT) was synthesized by coprecipitation method and modified to prepare the HT/PLA composites. The results show that the structure of HT is good. After KH550 surface modification, a large number of OH and Si-O groups are introduced into PLA surface. TG results show that the HT sample has good thermal stability. Compared with pure PLA, the glass transition temperature and crystallization temperature of HT / PLA composites decreases, while the melting temperature increases.

Bi/SnO2/TiO2-graphene nanocomposite photocatalyst for solar visible light-induced photodegradation of pentachlorophenol.

In this study, for the first time, a TiO2/graphene (G) heterostructure was synthesized and doped by Bi and SnO2 nanoparticles through a hydrothermal treatment. The as-synthesized nanocomposite was employed for photocatalytic degradation of pentachlorophenol (PCP) under visible light irradiation. Structural characterizations such as X-ray photoelectron spectroscopy (XPS) and X-ray diffraction spectroscopy (XRD) proved the valence band alignment at Bi/SnO2/TiO2-G interfaces and crystallinity of the nanocomposite, respectively. The as-developed nanocomposite photocatalyst was able to decompose 84% PCP, thanks to the generation of a large number of active OH•- and O2•- radicals. To achieve this optimum photodegradation efficiency, various parameters such as pH, catalyst dosage, and PCP concentration were optimized. The results showed that the PCP photodegradation process followed the first-order kinetic model and the reaction rate constant rose from 0.007min-1 (Bi) to 0.0149min-1 (Bi/SnO2/TiO2-G). The PCP photodegradation efficiency did not decrease significantly after 5cycles, and the nanocomposite photocatalyst still showed a high efficiency of 68% in the last cycle. The excellent photocatalytic activity of Bi/SnO2/TiO2-G is ascribed as well as the heterostructure of the nanocomposite photocatalyst.

Hexadecyltrimethylammonium hydroxide promotes electrocatalytic activity for the oxygen evolution reaction

The oxygen evolution reaction is an essential factor in many renewable energy technologies, such as water splitting, fuel cells, and metal–air batteries. Here we show a unique solution to improve the oxygen evolution reaction rate by adjusting the electrolyte composition via the introduction of hexadecyltrimethylammonium hydroxide into an alkaline electrolyte. The strong adsorption of hexadecyltrimethylammonium cations on the surface of electrocatalysts provides the increased absolute number of OH− ions near the electrocatalyst surface, which effectively promotes the oxygen evolution reaction performance of electrocatalysts, such as Fe1−yNiyS2@Fe1−xNixOOH microplatelets and SrBaNi2Fe12O22 powders. Meanwhile, we present an electrochemical conditioning approach to engineering the electrochemically active surface area of electrocatalysts, by which the resultant Fe1−yNiyS2@Fe1−xNixOOH microplatelets have a larger electrochemically active surface area after the electrochemical conditioning of the as-synthesized Fe1−yNiyS2 microplatelets using ammonia borane than those obtained after the conventional electrochemical conditioning without ammonia borane, presumably due to the appropriate conversion rate of Fe1−xNixOOH shells.

Fabrication of monodispersed plasmonic photocatalysts on activated carbon with the carbon source and reduction property of sewage sludge

Fabrication of porous carbon supported plasmonic photocatalysts with the low-cost carbon waste is a promising strategy for resource utilization. Herein, a sewage sludge was chosen for the synthesis of the sewage sludge activated carbon (SSC) supported Bi3+-doped TiO2 and Bi0 (SSCTB) photocatalysts. Through the pyrolytic carbonization, the sewage sludge was simultaneously displayed as the carbon precursor and reduction agent for the formation of SSC and Bi0, respectively. The results showed that the monodispersed Bi3+-doped TiO2 nanoparticles embedded with Bi0 were in-situ formed on the porous SSC. The synergistic effect of the localized surface plasmon resonance (LSPR) of Bi0, Bi3+ doping in TiO2, and the carbon of SSC greatly improved the light response ability and charge separation efficiency of the SSCTB samples. Under UV–Vis-NIR light irradiation for 60 min, the SSCTB sample with 5% of Bi (SSCTB5) possessed higher degradation rate of 47% for methyl orange compared with those of other samples. The photocatalytic mechanism was proposed based on the LSPR effect and the charge transfer process, where SSCTB5 was able to yield the highest numbers of OH and O2− radicals. The fabrication of the SSC supported plasmonic photocatalysts provides a cost-efficient strategy for the resource utilization of sewage sludge.