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This study was conducted to determine the lignin substructures, hydroxyl (phenolic + aliphatic) contents, and carboxyl contents in kraft lignin (KL) prepared from mixed hardwoods by using 2D Heteronuclear Multiple Quantum Coherence Nuclear Magnetic Resonance (HMQC NMR) and 31P NMR techniques. Based on 2D HMQC NMR analysis of KL, stilbene and vanillin substructures were present in the aromatic region, while trace amounts of β-O-4 and β-β moieties were detected in the oxygenated aliphatic region. The total hydroxyl content calculated from 31P NMR was 5.24 mmol/g KL. The aliphatic hydroxyl content was 1.04 mmol/g KL, and phenolic hydroxyl content was 4.20 mmol/g KL. Of the phenolic hydroxyl groups, the contribution of syringyl (S) and guaiacyl (G) was 1.02 and 0.97 mmol/g KL, respectively. The S/G molar ratio of KL calculated from 31P NMR was 1.05. The carboxyl content was 0.44 mmol/g KL.

This study was conducted to determine the lignin substructures, hydroxyl (phenolic + aliphatic) contents, and carboxyl contents in kraft lignin (KL) prepared from mixed hardwoods by using 2D Heteronuclear Multiple Quantum Coherence Nuclear Magnetic Resonance (HMQC NMR) and 31P NMR techniques. Based on 2D HMQC NMR analysis of KL, stilbene and vanillin substructures were present in the aromatic region, while trace amounts of β-O-4 and β-β moieties were detected in the oxygenated aliphatic region. The total hydroxyl content calculated from 31P NMR was 5.24 mmol/g KL. The aliphatic hydroxyl content was 1.04 mmol/g KL, and phenolic hydroxyl content was 4.20 mmol/g KL. Of the phenolic hydroxyl groups, the contribution of syringyl (S) and guaiacyl (G) was 1.02 and 0.97 mmol/g KL, respectively. The S/G molar ratio of KL calculated from 31P NMR was 1.05. The carboxyl content was 0.44 mmol/g KL. [ABSTRACT FROM AUTHOR]

Boron selective resin is a crucial material used for extracting boron from salt lake brine, but the adsorption capacity of resin remains to be improved. In this work, a boron selective resin with high adsorption capacity was created by modifying branched poly (ethylene imine) (PEI) on chloromethyl polystyrene resin, followed by reacting with D-(+)-gluconic acid δ-lactone. The influence of surface hydroxyl content on adsorption capacity of the resin was investigated by varying molecular weights of PEI during modification. The adsorption mechanism of boric acid was explored by changing pH and composition of solution, and by analyzing the adsorption thermodynamic and kinetic behaviors. Furthermore, the selectivity of resin was assessed by the effects of coexisting ions on the adsorption rate of boric acid. The results show that PEI modification effectively increases the content of hydroxyl on the surface of the resin so as to enhance the adsorption capacity of the resin towards boric acid up to 39.4 mg/g. Also, the adsorption rate can still reach up to 75 % even in the presence of 400 times coexisting ion, showing a good selectivity. Furthermore, the adsorption of boric acid is primarily driven by boronate affinity rather than an anion exchange in alkaline solution. Finally, the dynamic extraction of boric acid was carried out, and gives an enrichment factor of up to 39.6 on fixed bed, demonstrating a potential of the resin in the field of boron extraction. [Display omitted] • PEI-mediated dihydroxy-functionalized resin possesses much higher adsorption capacity to boric acid. • Adsorption of boric acid is driven by boronate affinity rather than an anion exchange. • Relationship between adsorption capacity and molecular weight of PEI is explored. • The resin exhibits excellent selectivity and dynamic extraction ability. [ABSTRACT FROM AUTHOR]

Six Al- and Li-bearing tourmaline crystals from pegmatites were structurally and chemically characterized. These samples can be assigned to elbaite, fluor-elbaite and rossmanite. Quantitative analyses of light elements such as Li, B and H are not always easily accessible. Therefore a method for the calculation of Li and OH would be of a general interest for the Geosciences. In the present work we test whether relatively accurate Li and OH estimations are possible based on the deconvolution of the O–H stretching vibration modes in a Raman spectrum on common (Al, Li)-rich tourmalines. We use the short-range arrangement model in our band interpretation as this model, in contrast to other models, provides the ability to evaluate an additional parameter by analyzing the OH stretching modes that can be used in the formula calculation process, which ultimately leads to the estimation of Li and OH with high accuracy. We also compare microprobe and Raman spectroscopy results, which we combine, with optimized data derived from microprobe and single-crystal structure refinement by using the same crystals. Based on our investigations, where the Raman spectra were recorded on non-oriented crystal sections, we conclude that we produce more accurate estimations, when the effects of the section orientation are considered. Therefore, we also propose a new method to correct the influence of the orientation of the crystal section. [ABSTRACT FROM AUTHOR]

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Taking the analytical results of nuclear magnetic resonance as the standard, the hydroxyl content in hydroxyl silicone oil with different specifications were compared by infrared spectroscopy and reaction gas volume method. The results show that both methods can measure the hydroxyl content accurately, are also suitable for testing the hydroxyl content of low-viscosity hydroxyl-terminated vinyl silicone oil and hydroxyl fluorosilicone oil. The dispersion degree of infrared spectroscopy is smaller than that of reactant by gas volume method. [ABSTRACT FROM AUTHOR]

Industrial wood is typically dried artificially after felling. The drying process is often very lengthy and consumes a large amount of energy, however, and inappropriate drying schedule can cause defects in the wood. Pretreatments such as ultrasound show the potential to reduce wood drying time without impacting quality. This study investigated the influence of ultrasound pretreatment on vacuum drying behavior, hydroxyl content, and microstructural properties of fast-growing wood samples. Pretreatments were performed at ultrasound intensity of 10 W cm−2and frequencies of 28 and 40 kHz, respectively, for 30, 60, and 90 min, respectively, then pretreated samples were dried at 40°C temperature under absolute pressure of 0.08 MPa. Results showed that ultrasound pretreatment did shorten the wood vacuum drying time, increase effective water diffusivity, open water channels, decompose wood extractives, and decrease hydroxyl content. In effect, ultrasound pretreatment can be applied to successful reduce wood drying time. [ABSTRACT FROM AUTHOR]

Highlights: [•] FFA of Pongamia pinnata oil was used to transesterify into FAME. [•] The hydroxyl content and GC–MS analysis were carried out. [•] The data from the hydroxyl content and GC–MS analyses were compared. [•] The calibration curve was plotted with respect to the hydroxyl content and percentage conversion. [ABSTRACT FROM AUTHOR]

Abstract: The surface hydroxyl content and surface structure of silica and other oxides with and without surface modification were systematically studied by solid state 29Si NMR, thermogravimetric analysis, and the lithium alanate method. Aerosil 90 as a well described reference system and functionalized zirconia–silica particles were used in the validation of the lithium alanate method. 3-Methacryloxypropyltrimethoxysilane and dodecylphosphonic acid were applied as surface modifiers. The determination of silanol content of Aerosil 90 by 29Si NMR and TGA confirms the results obtained by the lithium alanate method, which also allows for the determination of the remaining surface hydroxyl content after surface modification. For both silane coupling agents, the residual hydroxyl content of modified zirconia–silica is decreased by a factor of approximately 2 compared with that of the unmodified mixed oxide, whereas after modification with dodecylphosphonic acid, the hydroxyl content is slightly higher. These results are again in good agreement with those by 29Si NMR confirming that the lithium alanate method is a reliable and easily practicable method for surface hydroxyl determination. [Copyright &y& Elsevier]

The thermal decomposition behavior of poly(vinyl alcohol) (PVA) with two different hydroxyl contents, 88 and 99%, was investigated. UV-Vis spectroscopy, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and TGA-FTIR were used to detect the volatile and nonvolatile products of the thermal decomposition of PVA. The results suggest that the PVA, after thermal treatment, can form chromophoric polyene structure, as well as carbonyl groups. The PVA with 88% hydroxyl content underwent slower decomposition below 280°C and generated water and carboxyl acid as the dominant volatile products, however, as for the PVA with 99% hydroxyl content, the dominant volatile products were water, unsaturated aldehydes, and other unsaturated compounds. [ABSTRACT FROM AUTHOR]

We present a study on the effect of high dose (kGy) electron beams on pure silica core fibers through examining the following phenomena within the fibers: radioluminescence (RL), radiation induced attenuation (RIA), and recovery. The objective is to identify the relevant characteristics of these fibers having favourable radiation response, that can be utilized in the development of dose measurement systems for high dose (kGy) environments. Two types of 20 m long pure silica optical fiber samples have been used, differing in their concentrations of hydroxyl (OH) content. Segments of 3.5 m length from each fiber were wound into coils of radius ~25 cm and exposed to consecutive irradiation doses, in the order of tens of kGy (10 kGy through 70 kGy in individual exposures), leading to a cumulative dose of some 300 kGy. The low-OH fiber showed saturation of response at the shorter wavelengths of the RL spectrum for doses of 30 kGy and above, resulting from presence of Oxygen Defect Centers (ODC). At the longer wavelengths the RL response of the low-OH optical fibers is observed to increase with dose, attributed to various bonding structural defects of silica nanoclusters. The saturation effect at shorter wavelengths is less prominent in the high-OH samples, where a monotonic increase is observed up to ~60 kGy indicating the formation of radiation induced ODC beyond this point. For cumulative dose of ~70 kGy, the highest RIA losses were registered at 550 nm (12.74 dB/m) for low-OH sample, and at 460 nm (4.75 dB/m) for high-OH sample. The high-OH sample showed much faster recovery post-irradiation, making it more suitable for repeated usage. Both the RL and RIA phenomena observed herein show the feasibility of pure silica optical fibers for dose measurement in high dose (kGy) environments up to individual dose of ~70 kGy. • Electron beam induces luminescence of different peak in vary hydroxyl fiber. • Intensity of the emissions peak vary in accordance to the dose. • Radiative induced effects of the optical fiber may occur simultaneously. • Recovery in the silica fiber varies at different emission peak wavelength. [ABSTRACT FROM AUTHOR]

Here, the hydroxyl content of reduced graphene oxide (rGO) is controlled by adjusting reduction time with l -ascorbic acid as reduction agent to study the effect on cathode performance of lithium sulfur batteries (LSBs). The results indicate that the hydroxyl content decreases from 35.8% to 17.9% with prolonging reduction time from 6 h to 48 h, and the C/O ratio increases. More importantly, it is demonstrated that the rGO with relatively low hydroxyl content within 36 h of reduction is more beneficial to enhance both the initial capacity and capacity retention as well as rate performance of LSBs, which is ascribed to the higher conductivity, stronger adsorption and relatively few reaction by-products with the decrease of hydroxyl content. However, when the reduction time is further prolonged to 48 h, the cathode performance deteriorates. As a result, rGO-36h/S electrode with the optimum hydroxyl content (19.2%) achieves an initial discharge capacity of 1340.9 mAh g−1, which still maintains 707.8 mAh g−1 over 100 cycles at 0.1C. This work may provide a guide for reducing GO when used as sulfur host material or matrix material of LSBs. [ABSTRACT FROM AUTHOR]

Zinc-rich fluor-elbaite from Piława Górna, Poland, was studied by electron microprobe (EPMA), single-crystal X‑ray diffraction (SREF), and Raman spectroscopy (RS) to check the possibility of the application of RS to draw crystal-chemical conclusions for Al-rich and Li-bearing tourmalines on basis of the O-H stretching vibrations in the spectral range 3400-3800 cm-1. This tourmaline, forming a thin metasomatic zone around gahnite, features varying compositions with a ZnO content reaching in the studied fragment of 5.70(12) wt%. The crystal structure of this Zn-rich fluor-elbaite [a = 15.921(1), c = 7.127(1) Å] was refined with a R1 value of 1.67%. Its formula was determined on the basis of electron-microprobe and structure refinement as X(Na0.84o0.14Ca0.01)Σ1.00 Y(Al1.06Li0.84Zn0.69Fe2+0.32Mn0.09)Σ3.00ZAl6(BO3)3(TSi6O18)V(OH)3 W(F0.65OH0.26O0.09). The deconvolution of the O-H stretching vibration bands, performed by fitting of an input model of component bands with Gaussian function shapes for the empirical spectrum, indicates that each of the three maxima assigned for VOH bonded to YAl3+, Y2+, and YLi+ and with the total integral intensity of at least 75% of the total OH content could be resolved into 1 to 3 bands, depending on the X-site occupation (vacancies, Na+, and Ca2+). The deconvolution indicates further that several low intense bands of WO-H modes above a Raman shift of 3600 cm-1, totally reaching ≤25%, are dependent on the occupation of triplets of YYY cations bonded to the hydroxyl. These WO-H modes are also influenced by the X-site occupation. Due to ordering of all octahedral cations (except Al) at the Y site and a complete occupation of the Z site by Al and the V site by OH, it seems possible to evaluate the Li and OH contents in a Al-rich and Li-bearing tourmaline directly from the Raman spectrum. By using the ratio VOHIYAlZAlZAl/(VOHIYZZ + WOHIYYY) as evaluated from RS, corresponding to the ratio YAl/V+WOH in the crystal, the formula of the Zn-rich fluor-elbaite can be calculated as X(Na0.85o0.14Ca0.01)Σ1.00Y(Al1.11Y2+1.11Li0.78)Σ3.00 ZAl6(BO3)3(Si6O18)(OH)3(F0.65OH0.13O0.22), where Y2+ = Zn + Fe + Mn. The formula, determined only on basis of EPMA and deconvolution of RS in the O-H stretching bands, corresponds very well (≤1 SD range of EPMA) to the formula determined on basis of EPMA and SREF. This result implicates that the O-H stretching vibrations, measured by Raman spectroscopy, could be applied for Al-rich and Li-bearing tourmalines as a useful tool for providing additional information for determining the crystal-chemical formula. It is also very helpful when crystal structural data are not available. [ABSTRACT FROM AUTHOR]