H2O Mixtures Research Articles

Tetraphenylethylene[3]arene: synthesis, structure, and sensing of I−

Tetraphenylethylene[3]arene 1 was synthesized using 1,1′,4,4′-tetramethoxytetraphenylethylene and paraformaldehyde in dichloromethane. Host 1 exhibited strong bright blue fluorescence both in the solid state and THF–H2O mixtures with water fw ≥ 60%.

Two- and three-body attachment, electron transport and ionisation in water-air mixtures

Three-body electron attachment in the mixtures of H2O and dry air have been measured over a wide range of the density-reduced electric field, E/N, from 3–130 Td and gas pressures, for mixture combinations ranging from 1% to 50% of H2O. We have measured the regions of three-body attachment (3–30 Td) and two-body dissociative attachment (40–130 Td). Besides, the increasing amount of H2O in the mixture causes an increase in the three-body reaction rates of up to two orders of magnitude in comparison with that measured for dry air. On the other hand, the three-body attachment coefficients exceed the two-body ones (dissociative attachment) at high pressures. Good agreement has been found with previous measurements of H2O-dry air mixtures with H2O concentrations of up to 2%. We know of no previous work for higher H2O concentrations. Values of the effective ionisation coefficients and longitudinal diffusion coefficients derived from the same measurements are also presented.

Determination of technology-critical elements in seafood reference materials by inductively coupled plasma-tandem mass spectrometry

The certified reference materials (CRMs) BCR-668 (mussel tissue), NCS ZC73034 (prawn), NIST SRM 1566a (oyster tissue) and NIST SRM 2976 (mussel tissue) were analyzed for their mass fractions of 23 elements using inductively coupled plasma tandem-mass spectrometry (ICP-MS/MS). This study focused on the quantification of selected technology-critical elements (TCEs), specifically rare earth elements (REE) and the less studied TCEs Ga, Ge, Nb, In and Ta. Microwave assisted closed vessel digestion using an acid mixture of HNO3, HCl and H2O2 was applied to varying sample masses and two different microwave systems. Recoveries of 76% (Gd, NCS ZC73034) to 129% (Lu, BCR-668) were obtained for the REE and 83% (Ge, NCS ZC73034) to 127% (Nb, NCS ZC73034) for the less studied TCEs across all analyzed CRMs (compared to certified values) using the best-performing parameters. Mass fractions for all analyzed, non-certified elements are suggested and given with a combined uncertainty U (k = 2), including mass fractions for Ga (11 µg kg-1 ± 9 µg kg-1 to 67 µg kg-1 ± 8 µg kg-1) and In (0.4 µg kg-1 ± 0.3 µg kg-1 to 0.8 µg kg-1 ± 0.7 µg kg-1). This study provides mass fractions of possible new emerging contaminants and addresses the relevant challenges in quantification of less studied TCEs, thus allowing the application of existing CRMs for method validation in studies dealing with the determination of TCEs in seafood or other biota.Graphical abstract

Utilization of catfish fat by-products for the biological base oils synthesis

In this work, catfish fat by-product was utilized as feedstock in the synthesis of biological base oils. The study performs the effect of parameters on the reaction yield. 91.2% in (H2O2/CH3COOH/C=C) molar ratio of 4.5/1.5/1.0, the temperature of 50 oC, and 3 hours reaction time. The yield of the ring-opening reaction of epoxy with acetic anhydride reached at 90.2% in (acetic anhydride/epoxy) molar ratio of 1.5/1.0, the temperature of 95 oC, and 4.5 hours reaction time. The main functional groups of catfish oil starting material, epoxy catfish oil, and polyester catfish oil final product were identified by FT-IR and 1H-NMR spectral analysis methods. The observed results show that the catfish oil epoxidation reaction with a mixture of H2O2 and CH3COOH and the ring-opening reaction of epoxy with (CH3CO)2O, H2SO4 catalyst has occurred strongly and obtained product of catfish polyester oil could use as an alternative to mineral base oils and an environmentally friendly product.

Transmission Spectrum of Nanoporous Aerogel Filled with SO2 and a Mixture of H2O and SO2 Vapors

Transmission Spectrum of Nanoporous Aerogel Filled with SO2 and a Mixture of H2O and SO2 Vapors

Extractive distillation for separation of isopropanol-n-propanol-water ternary system: Mechanism analysis and process design

In the process of producing isopropanol (IPA) by direct hydration of propylene, a mixture of IPA, n-propanol (NPA) and H2O is formed. In order to obtain high purity IPA and NPA, extractive distillation technology can be used to separate these three components. In this paper, Based on the COSMO-RS model, 1-ethyl-3-methylimidazolium dicyandiamide ([EMIM][DCA]) was selected as the extractant for extractive distillation in ionic liquids. The extractive distillation process for the separation of IPA-NPA-H2O system with ethylene glycol (EG) or [EMIM][DCA] as extractant was designed and optimized by multi-objective genetic algorithm. Process simulation results show that the process using [EMIM][DCA] can reduce total annual cost by 44.635% and total gas emission by 29.873% compared with the traditional organic solvent EG as extractant. These results show that [EMIM][DCA] is a good extractant, which can reduce the gas emission and energy consumption of the distillation process. In addition, we further explored the separation mechanism of the system at the molecular level by analyzing the σ-curve and the intermolecular interaction energy.

High-pressure adsorption phenomena in natural and synthetic zeolites with EAB topology

The high-pressure behaviour and the crystal-fluid interaction of zeolites with EAB topology were investigated by in-situ single-crystal and powder synchrotron X-ray diffraction, both on synthetic and natural samples. The experiments were conducted using a diamond anvil cell and different pressure transmitting fluids, including: the non-penetrating silicone oil and the potentially penetrating methanol:ethanol:H2O = 16:3:1 mixture, methanol and distilled H2O. The zeolites intrinsic compressional behaviour investigated with a non-penetrating fluid showed the significant role of the extra framework population on the bulk compressibility. Notably, within the first ∼0.5 GPa of the silicone oil ramp, the bulk modulus (KV0 = βV0−1) resulted to be KV0 = 62(1) GPa for the natural bellbergite and KV0 = 16(4) GPa for the synthetic K-analogue. The synthetic EAB zeolites demonstrated a high host capacity for methanol molecules, which were not able to penetrate the natural bellbergite cavities. A comparative analysis between the behaviour of zeolites with EAB topology and structurally similar zeolites, such as erionite (ERI topology) and offretite (OFF), is provided.

Novel force field for the ionic liquid [Bmim][Nf2T] and its transferability in a mixture with water

In this work, a new force field is presented for the ionic liquid 1-butyl-3-methylimidazolium - bis(trifluoromethylsulfonyl)imide, [Bmim][Nf2T]. As a part of the ϵ force field, the acronym IL/ϵ is used to refer to this ionic liquid. This new force field reproduces the dielectric constant, the density, and the enthalpy of vaporization, with an error of less than 3%, being possible to generate new force fields for ionic liquids, based on the flexibility of the molecule. In addition, a study of the [Bmim][Nf2T]-H2O mixture is performed from pure IL to pure water, passing through various concentrations.

Enhancement of selective SiGe dissolution through facilitated surface oxidation by formation of hydroxyl radicals in peracetic acid solution

Herein, we investigate the selective oxidation and dissolution behavior of SiGe over Si using mixtures of HF, H2O2, CH3COOH, and CH3COOOH (peracetic acid, PAA). We observe a significantly higher dissolution rate for SiGe compared to Si in the PAA solution. This difference can be attributed to more rapid and vigorous oxidation of the SiGe surface compared to that of the Si surface. We introduce a novel method to further enhance the selective dissolution of SiGe by controlling the formation of hydroxyl radicals in the PAA solution. When the formation of hydroxyl radicals is enhanced, the SiGe dissolution rate and selectivity significantly increase from 212 nm/min and 111 to 793 nm/min and 225, respectively. The selective etching of the SiGe layers is also achieved on vertically stacked multilayer SiGe/Si trench structures at an etching factor of 95:1. The increase in the SiGe dissolution rate and selectivity over Si can be attributed to the effective oxidation of the SiGe surface by hydroxyl radicals without causing surface roughening in either SiGe or Si. Based on the results, we propose a mechanism for the selective oxidation and dissolution of SiGe in PAA solution, with and without the enhancement of hydroxyl radicals.

CO2 hydrates phase behaviour and onset nucleation temperatures in mixtures of H2O and D2O: Isotopic effects

In this work, we report the CO2 hydrate phase equilibria in water (H2O), heavy water (D2O), and their binary mixtures following the isochoric pressure search method using a rocking cell apparatus. The phase behaviour was mapped within the temperature and pressure range of 276.32 – 284.80 K and 1.59 – 3.78 MPa, respectively. It was found that there is a difference of ∼ 2 K in the equilibrium line of CO2 hydrates formed in H2O and in D2O, respectively. The hydrate dissociation enthalpies obtained using the Clausius-Clapeyron equation indicate almost similar values formed either in D2O, H2O or their mixtures. These shifts in this equilibrium temperature were compared with the triphasic equilibrium temperature variation estimation obtained using Molecular Dynamics Simulations and a very good agreement with the experimentally obtained values was observed. Further, a constant cooling method was used to obtain the onset temperature of hydrate nucleation for these systems at 3.6 MPa. It has been found that during the cooling ramps, the nucleation always occurred in the vicinity of the temperature of maximum density (TMD) of the systems where water still retains some structuredness. The nucleation experiments also give information about the metastable zone width (MSZW) of the studied systems. The results reported in this work indicate the magnitude of the isotopic effect on CO2 hydrate formation and dissociation that may have implications towards the application of hydrate technology for separation and purification processes.

Alumina layers deposited by atomic layer deposition with different precursors: Surface photovoltage measurements

The electrical and passivation properties of alumina layers deposited by the atomic layer deposition (ALD) technique with trimethylaluminium (TMA) and two different oxidants (ozone and water) and their mixture under different deposition conditions were investigated by using surface photovoltage. In all alumina layers negatively charged defects were observed after the ALD deposition. The density of interface states (Dit) and the density of negative charge (CFix) in as-deposited alumina layers prepared with water was found to be lower in comparison to wafers prepared with O3 or with a mixture of H2O and O3. The minority carrier diffusion length was also larger in wafers prepared with H2O and TMA. By comparing the deposition conditions of different alumina layers we concluded that interstitial oxygen could be responsible for the appearance of the negatively charged defects. After the broadband illumination we also observed a significant increase of CFix in all alumina layers independent of the precursors used for the deposition and only small changes of Dit were detected. O-related defects could also lead to such changes of CFix after the illumination.

Are NH3 and CO2 Ice Present on Miranda?

Published near-IR spectra of the four largest classical Uranian satellites display the presence of discrete deposits of CO2 ice, along with subtle absorption features around 2.2 μm. The two innermost satellites, Miranda and Ariel, also possess surfaces heavily modified by past endogenic activity. Previous observations of the smallest satellite, Miranda, have not detected the presence of CO2 ice, and a report of an absorption feature at 2.2 μm has not been confirmed. An absorption feature at 2.2 μm could result from exposed or emplaced NH3- or NH4-bearing species, which have a limited lifetime on Miranda’s surface, and therefore may imply that Miranda’s internal activity was relatively recent. In this work, we analyzed near-IR spectra of Miranda to determine whether CO2 ice and the 2.2 μm feature are present. We measured the band area and depth of the CO2 ice triplet (1.966, 2.012, and 2.070 μm), a weak 2.13 μm band attributed to CO2 ice mixed with H2O ice, and the 2.2 μm band. We confirmed a prior detection of a 2.2 μm band on Miranda, but we found no evidence for CO2 ice, either as discrete deposits or mixed with H2O ice. We compared a high signal-to-noise-ratio spectrum of Miranda to synthetic and laboratory spectra of various candidate compounds to shed light on what species may be responsible for the 2.2 μm band. We conclude that the 2.2 μm absorption is best matched by a combination of NH3 ice with NH3 hydrates or NH3–H2O mixtures. NH4-bearing salts like NH4Cl are also promising candidates that warrant further investigation.

Syngas production from NH3 and CO2 through chemical looping ammonia cracking - reverse water gas shift

Ammonia (NH3) offers benefits over molecular hydrogen as an energy vector because it can be liquefied, transported, and stored more easily using the existing infrastructure. NH3 can react with CO2 to produce syngas (H2 +CO) as a feedstock for circular chemical production. In the conventional process design, this involves: 1) cracking of NH3 to N2 and H2, 2) subsequent product gas separation, and 3) CO production through the reverse water gas shift (RWGS) reaction. Herein, a novel approach referred to as “NH3-RWGS” is presented, which integrates these three steps into a two-reactor process utilizing the chemical-looping principle. In the first reactor, NH3 is cracked over a catalytically active bed material, and H2 reacts further with the metal oxide bed material, producing H2O and N2 as gaseous products and reduced metal oxide/metal. This reduced metal oxide is then moved to the second reactor, where it reacts with CO2 or a mixture of CO2 and H2O, forming CO and H2 as the desired product gas and the re-oxidized metal oxide, which is returned to the first reactor. This process can be favorably implemented in two gas–solid countercurrent flow moving beds. Herein, the underlying design principles are developed, and the maximum achievable gas conversion with an iron-based bed material is established. The feasibility of the underlying chemistry was demonstrated using a supported Fe/MgAl2O4 bed material that exhibited fast kinetics and cyclic stability for the relevant reactions.

Photocatalysis: A Possible Vital Contributor to the Evolution of the Prebiotic Atmosphere and the Warming of the Early Earth

The evolution of the early atmosphere was driven by changes in its chemical composition, which involved the formation of some critical gases. In this study, we demonstrate that nitrous oxide (N2O) can be produced from Miller’s early atmosphere (a mixture of CH4, NH3, H2, and H2O) by way of photocatalysis. Both NH3 and H2O were indispensable for the production of N2O by photocatalysis. Different conditions related to seawater and reaction temperature are also explored. N2O has a strong greenhouse gas effect, which is more able to warm the Earth than other gases and offers a reasonable explanation for the faint young Sun paradox on the early Earth. Moreover, the decomposition of N2O into N2 and O2 can be boosted by soft irradiation, providing a possible and important origin of atmospheric O2 and N2. The occurrence of O2 propelled the evolution of the atmosphere from being fundamentally reducing to oxidizing. This work describes a possible vital contribution of photocatalysis to the evolution of the early atmosphere.

Quartz-Enhanced Photoacoustic Spectroscopy Assisted by Partial Least-Squares Regression for Multi-Gas Measurements.

We report on the use of quartz-enhanced photoacoustic spectroscopy (QEPAS) for multi-gas detection. Photoacoustic (PA) spectra of mixtures of water (H2O), ammonia (NH3), and methane (CH4) were measured in the mid-infrared (MIR) wavelength range using a mid-infrared (MIR) optical parametric oscillator (OPO) light source. Highly overlapping absorption spectra are a common challenge for gas spectroscopy. To mitigate this, we used a partial least-squares regression (PLS) method to estimate the mixing ratio and concentrations of the individual gasses. The concentration range explored in the analysis varies from a few parts per million (ppm) to thousands of ppm. Spectra obtained from HITRAN and experimental single-molecule reference spectra of each of the molecular species were acquired and used as training data sets. These spectra were used to generate simulated spectra of the gas mixtures (linear combinations of the reference spectra). Here, in this proof-of-concept experiment, we demonstrate that after an absolute calibration of the QEPAS cell, the PLS analyses could be used to determine concentrations of single molecular species with a relative accuracy within a few % for mixtures of H2O, NH3, and CH4 and with an absolute sensitivity of approximately 300 (±50) ppm/V, 50 (±5) ppm/V, and 5 (±2) ppm/V for water, ammonia, and methane, respectively. This demonstrates that QEPAS assisted by PLS is a powerful approach to estimate concentrations of individual gas components with considerable spectral overlap, which is a typical scenario for real-life adoptions and applications.

Water vapor effects on the oxidation resistance of modified potassium silicate coating at high temperature

An inorganic potassium silicate coating with pigments of alumina, aluminum phosphate, NiCrAlY and copper chromite black was prepared on CB2 stainless steel. Oxidation behavior in either ambient air or O2+H2O mixture at 630 °C for 2000 h was comparatively studied, and the coating exhibited excellent resistance under both test conditions. The water vapor considerably accelerated the oxidation of the uncoated CB2 steel, as the hydroxide, the main constituent of the coating, had a negligible evaporation rate at test temperature, while it had a limited effect on the coated sample. Meanwhile, the existence of coating may prolong or eliminate the incubation period in the O2+H2O mixture at 630 °C. After oxidation, the coating matrix is in an amorphous state and fillers as alumina and copper chromite black are stable in the coating. Leucite (KAlSi2O6) formed by Al from NiCrAlY and potassium silicate in the coatings was detected after tests either in O2 or O2+H2O mixture.

An easy way for the removal of residual hydrocarbon fractions from crystallized cannabigerol and cannabidiol

In this study we set-up and validated a novel, easy to handle, chemically green, and efficient methodology for the removal of residual hydrocarbon fractions from crystallized cannabigerol and cannabidiol, in turn deriving from the purification and fractionation of hemp-based phytopreparations. The technique described herein is based on the azeotropic distillation of n-pentane, n-hexane and / or n-heptane with H2O in mixtures artificially created by incorporation of this latter to solid cannabidiol and cannabigerol in a fixed ratio (e.g. 10 g of cannabinoids / 0.5 mL distilled H2O), followed by intimate dispersion and mild heat treatment (40 °C) in a rotary evaporator for 30 min under vacuum (50 mmHg). Initial and final percentages of n-pentane, n-hexane, and n-heptane and original and final purity degree of cannabidiol and cannabigerol have been quantified by head space GC/MS and HPLC, respectively. Results from the present study revealed how the residual hydrocarbon fractions decreased by 97.4% (n-pentane), 99.2% (n-hexane), and 98.6% (n-heptane) (n = 6) for cannabidiol and 97.2% (n-pentane), 99.1% (n-hexane), and 99.0% (n-heptane) (n = 6) for cannabigerol. Thus, the method described herein could represent a novel, alternative, easy, and cheapest way for processing cannabinoids from raw hemp material in order to virtually remove all the hydrocarbon solvents used during manufacturing and fractionation procedures. This in turn leads to obtain semi-finished products with high purity and safely compliant with the legal limits regarding the residual content of hydrocarbons. The process set up herein can be considered as a chemically green one since it employs only H2O as the solvent to perform experimental operations and laboratory facilities, like a vacuum pump (even a cheap one like a water vacuum pump) and a rotary evaporator, that are easily accessible to a wide audience. To the best of our knowledge, such an approach is described herein for the first time in the literature.

Synthesis of Flavones through NaI‐Mediated Electrochemical Cyclization of Chalcones

AbstractA mild electrochemical oxidative cyclization for the synthesis of flavones from easy‐access 2’‐hydroxychalcones was developed using an inexpensive NaI as mediator and electrolyte under ambient temperature in a mixture of EtOH and H2O as solvent. This method was successfully applied to synthesize 26 examples of flavones from a variety of functionalized 2’‐hydroxychalcones. A gram‐scale formal synthesis of bioactive scutellarein was successfully demonstrated. Control experiments were conducted to disclose a possible indirect oxidation via in situ generation of iodine. The main advantages of this reaction include its broad substrate scope, scalability, ability to operate with benign solvent, and no requirement for strong oxidizing agents and external additives.

Densification mechanism of ZnO ceramics prepared by cold sintering with molten zinc acetate dihydrate as the transient liquid medium

The transportation of Zn2+ in acetic acid (HOAc) or Zn(OAc)2 water solution was considered crucial for the successful cold sintering of ZnO ceramics. However, our work shows that ZnO ceramics can even be densified by cold sintering with the aid of solid Zn(OAc)2·2 H2O without introducing extra free water. DSC-TG analysis reveals that pure Zn(OAc)2·2 H2O is dehydrated completely into solid Zn(OAc)2 during heating in an open environment, while it melts in ZnO-Zn(OAc)2·2 H2O mixture or a high-pressure and semi-closed circumstance due to the strongly suppressed dehydration. Consequently, molten Zn(OAc)2·2 H2O acts as the transient liquid medium for the dissolution-precipitation process at over 100 °C, and plays a dominant role in the densification, microstructural evolution, and mechanical robustness of the cold-sintered ZnO ceramics. The densification mechanism is confirmed by the pressure-time curves, and reveals a novel strategy for cold sintering of water-insoluble ceramics by introducing molten hydrated salt or alkali as the transient liquid medium.

Highly Selective Etching of SiGe to Si for GAAFET

Highly selective etching of SiGe over Si is required for the fabrication of gate-all-around field-effect transistors (GAAFET). A solution consisting of a mixture of H2O2, CH3COOH, and HF is known to etch SiGe with high selectivity over Si. The detailed etching mechanism of SiGe and Si in this solution was investigated in this study. The effect of each chemical species on the etching of SiGe and Si was investigated using various concentrations of H2O2, CH3COOH, and HF. It was found that the etching rate of SiGe was highly relevant to the concentration of peracetic acid (PAA) which was produced by the reaction between H2O2 and CH3COOH. In addition, various additives which can further increase the SiGe selectivity and their mechanisms were investigated.