助溶剂对铝合金表面硅烷化预处理的影响

为了了解3-缩水甘油醚丙基三甲氧基硅烷(γ-GPTMS)溶液中助溶剂对水解的γ-GPTMS在铝合金表面的沉积特性的影响,用X射线光电子衍射(XPS)测定了不同助溶剂含量,不同γ-GPTMS浓度的溶液沉积在铝合金表面的硅含量,同时用反射吸收红外光谱(RAIRS)对铝合金表面膜层进行了表征,结果表明,助溶剂对γ-GPTMS在铝合金表面沉积有显著影晌,γ-GPTMS的纯水溶液在铝合金表面所形成硅烷化膜层的硅元素量最高,沉积量随溶液中γ-GPTMS浓度的增加而增加。另外,膜层与氧化的铝合金表面之间形成铝硅氧烷(Al-O-Si)共价键,而且γ-GPTMS分子中的烷氧乙基分布在膜层的外表面,具有较大的反应活性。     

Co-nonsolvency effects in the thermoprecipitation of oligomeric polyacrylamides from hydro-organic solutions

Co-solutes and co-solvents influence the thermoprecipitation of stimulus-responsive polymers from aqueous solution. Taking the behavior of oligomeric poly-(N-isopropylacrylamide) prepared by chain transfer polymerization as reference, the influence of organic solvents (concentration <2 M) on the thermoprecipitation of polyacrylamides with critical solution temperatures (CST) in pure water between 30 and 75 °C is investigated using turbidity and differential scanning calorimetry. Depending on the system, both increase and decrease but also the disappearance of the CST is observed. The strength of the observed effect is related not only to the size but also the structure of the hydrophobic domain of the solvent molecule. Contrary to the effects observed upon the addition of simple salts as additives, the chemistry of the investigated polyacrylamide is of direct consequence for the effect of a given solvent. Certain parallels can hence be drawn to the behavior previously observed for additives such as anionic surfactants and alkylamines.     

Reversible phase transfer of graphene oxide and its use in the synthesis of graphene-based hybrid materials

A phase transfer protocol for graphene oxide (GO) was demonstrated with a long chain alkylamine–dodecylamine (DDA) as phase transfer agent. By this method, GO sheets can be easily transferred from water to various low polar organic solvents such as cyclohexane, petroleum ether, kerosene, toluene, carbon tetrachloride, etc. through forming noncovalent DDA–GO hybrids. The reversible phase transfer of GO between aqueous phase and organic phase was also realized through the formation and destruction of a DDA–GO micelle. It was found that ethanol plays a critical role in the phase transfer process, while other experimental parameters, such as pH value and the concentration of GO, do not have an obvious influence on the transfer efficiency over a wide range. A detailed mechanism for the phase transfer is proposed on the basis of experimental observation. With this phase transfer technique, a simple, efficient, and versatile approach is also developed to synthesize a variety of graphene-based metal and alloy hybrids in low-polar organic solvents.     

Kinetics of facilitated proton transfer by hydrophobic aromatic amines across the water/1,2-dichloroethane interface

The kinetics of proton transfer facilitated by 4-octylaniline, 4-dodecylaniline and 4-hexadecylaniline across the water/1,2-dichloroethane interface has been investigated by cyclic voltammetry and ac impedance. It was found that their electrochemical behaviour is very similar and the three amines assist proton transfer from the aqueous to the organic phase. The formal Gibbs energy of proton transfer and the formal rate constant were evaluated. It is concluded that interfacial organisation of these molecules is an important factor in the kinetics of facilitated proton transfer and that the aromatic ring is able to penetrate the interface whilst the long hydrophobic chain contributes to the stability of the amine in the organic phase.     

Revealing charge-transfer effects in gas-phase water chemistry

An understanding of the interactions involving water and other small hydrogenated molecules such as H(2)S and NH(3) at the molecular level is an important and elusive scientific goal with potential implications for fields ranging from biochemistry to astrochemistry. One longstanding question about water's intermolecular interactions, and notably hydrogen bonding, is the extent and importance of charge transfer (CT) , which can have important implications for the development of reliable model potentials for water chemistry, among other applications. The weakly bound adducts, commonly regarded as pure van der Waals systems, formed by H(2)O, H(2)S, and NH(3) with noble gases or simple molecules such as H(2), provide an interesting case study for these interactions. Their binding energies are approximately 1 or 2 kJ/mol at most, and CT effects in these systems are thought to be negligible. Our laboratory has performed high-resolution molecular-beam scattering experiments that probe the (absolute scale) intermolecular potential of various types of these gas-phase binary complexes with extreme sensitivity. These experiments have yielded surprising and intriguing quantitative results. The key experimental measurable is the "glory" quantum interference shift that shows a systematic, anomalous energy stabilization for the water complexes and clearly points to a significant role for CT effects. To investigate these findings, we have performed very accurate theoretical calculations and devised a simple approach to study the electron displacement that accompanies gas-phase binary intermolecular interactions in extreme detail. These calculations are based on a partial progressive integration of the electron density changes. The results unambiguously show that water's intermolecular interactions are not typical van der Waals complexes. Instead, these interactions possess a definite, strongly stereospecific CT component, even when very weak, where a water molecule may act as electron donor or acceptor depending on its orientation. CT is mediated by an asymmetric role played by the two hydrogen atoms, which causes strong orientation effects. The careful comparison of these calculations with the experimental results shows that the stabilization energy associated to CT is approximately 2-3 eV per electron transferred and may make up for a large portion of the total interaction energy. A simple electron delocalization model helps to validate and explain these findings.     

Effect of swelling on mass transfer performance in membrane extraction

The membrane extraction experiments were performed with tributyl phosphate/acetic acid (HAc)/water, n-butanol/HAc/water and 20% Alamine (in kerosene); HAc; and water as working systems. HAc was transferred from the aqueous phase to the organic phase. The effect of flat membranes swelling on mass transfer was studied. The membranes were microporous polysulfone and microporous polytetrafluoroethylene. The overall mass transfer coefficients based on the water phase were calculated and compared between nonswollen and swollen membranes. The experimental results show that the physical structure of the flat membranes used in our experiments was changed if soaked by organic solvents; however, change in thickness was not found. The overall mass transfer coefficients clearly were decreased after the flat membranes were swollen. The most likely reason is that the mass transfer resistance was increased because of the change of the membrane structure. The results also show that it is better to choose a hydrophilic membrane to reach high mass transfer performance when the equilibrium constant is very low. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1555–1561, 1999     

Binary mixtures of HMIMPF6 ionic liquid and n-butyl acetate cosolvent in the extraction of acetone from aqueous solutions

A remarkable disadvantage of pure ionic liquids, to be used as a solvent in different processes, is their high viscosity and density. Here, n-butyl acetate was used as a cosolvent in the liquid–liquid system of {water?+?acetone?+?1-hexyl-3-methylimidazolium hexafluorophosphate (HMIMPF₆) ionic liquid}. Mixtures of the ionic liquid and the cosolvent were used as the organic phase to extract acetone from aqueous phase. A drastic decrease in viscosity and a significant decrease in density of the ionic liquid were achieved in the presence of cosolvent. Accordingly, the liquid–liquid equilibrium of different provided systems was studied under temperature of 298.2?K and atmospheric pressure of 81.5?kPa. Binary phase regions and corresponding tie-lines and binodal curves were obtained for ternary and quaternary systems. Results show the extension of the binodal solubility region as well as enhancements up to 41.8% in the acetone separation factor. The tie-line data consistency was confirmed by the Othmer–Tobias and the Hand equations. Moreover, the nonrandom two-liquid model of activity coefficient was applied satisfactorily to reproduce the equilibrium data with a root-mean-square deviation of only 1.95%.     

Cosolvent effects on the diffusions of 1,3-dichlorobenzene, l-carvone, geraniol and 3-fluorophenol in supercritical carbon dioxide

In order to get an insight into solute-cosolvent interactions and to predict the cosolvent effects on diffusions, several cosolvents and solutes with different size, hydrogen-bond donor (HBD) acidity, and hydrogen-bond acceptor (HBA) basicity were chosen, and the molecular diffusion coefficients of the solutes in pure and modified supercritical carbon dioxide were measured by the Taylor-Aris chromatographic peak broadening method. Cosolvent effect parameter, which is defined as the ratio of diffusion coefficient with and without cosolvent, respectively, is introduced to quantitatively compare the strength of different types of interaction between solute and cosolvent, especially hydrogen bonding. For cosolvent without hydrogen-bond ability, the cosolvent effect parameter decreases with the increase of molecular volume and weight of the solutes, in that the strength of dispersion force with cosolvent increases with their size. For cosolvent with only HBA basicity, the solute with higher HBD acidity has smaller cosolvent effect parameter, due to the fact that the strength of hydrogen-bond interaction between the solute and cosolvent only depends on and increases with the HBD acidity of the solute. For amphiprotic cosolvent, the solute with higher HBD acidity has smaller cosolvent effect parameter, it can be inferred from which that HBD acidity rather than HBA basicity of the solute makes a major contribution to the hydrogen-bond interaction between solute and cosolvent. These results are consistent with the interpretation by the Kamlet-Taft solvatochromic parameters (HBD acidity and HBA basicity). Moreover, a nonlinear decrease in diffusion coefficient with the increase of cosolvent concentration is observed, which is typical of the behavior of the system with strong interaction.     

THE VAPOR-LIQUID EQUILIBRIUM OF ETHANOL-WATER MIXTURE IN THE PRESENCE OF BENZYLTRIETHYLAMMONIUM CHLORIDE SALT AT ATMOSPHERIC PRESSURE

The phase transfer catalysis reaction is gaining more and more attention in chemical industry. Usually, the chemicals used as phase transfer catalyst are organic salts. Unfortunately, the effect of an organic salt on the vapor-liquid equilibrium (VLE) of a mixture has hardly been reported in literature. In this study, the effect of the benzyltriethylammonium chloride organic salt on the VLE of ethanol-water mixture was obtained experimentally. It is observed that this organic salt can shift and even break away the azeotrope of ethanol -water mixture as an inorganic salt does. The experimental data were correlated with the models or Tan (1987, 1990) and Ohe (1991). The results were not satisfactory probably due to the complicated interactions among ions and molecules and the big different particle sizes or ion, solvent molecule, and salt molecule.

The vapor pressures of benzyltriethylammonium chloride-ethanol mixtures needed in this study for determining solvent-salt interaction parameters in the correlation model were also measured and regressed by the Patil model (1990).     

滴外传质系数的研究

作者采用四个体系,测定有机溶剂液滴在水相中自由下降时溶质的传递速率。所选择的溶质,其分配系数均极有利于有机相,故滴内阻力可以略而不计。 实验中竭力防止系统的沾染,获得了重现性好的实验数据。作者比较了计算滴外系数的各种关系式的适用性,发现各式仅在一定的范围内适合。并提出了纯物系和实际萃取过程中沾染物系的滴外传质系数的一般关联方法。 在所选择的体系的浓度范围内,以光纹技术进行观察,当液滴悬垂于静止的水溶液中,未发现可察觉的介面骚动现象,故作者提出的一般关联方法仅能适用于无介面骚动现象的传质过程。     

Use of the microchannel dimensions for studying assisted ion transfers at liquid-liquid supported microinterface

This paper confirms that, in the case of a more complex system like an assisted transfer of a metallic cation, the supported liquid-liquid microinterface behaves like a recessed or inlaid electrode depending on the transfer direction. This asymmetrical situation is a great advantage when studying the interfacial mechanism. We can thus determine in which phase the formation of the complex takes place. In this way, a well-known system, extraction of Zn(II) ions by 8-hydroxyquinoline, was studied. Three microchannels with various lengths but with an identical diameter were used to increase the asymmetrical situation. Voltammetric curves at various scan speeds give information on the diffusion pattern of complex transfer depending on the length of the microchannels. The complex is formed in the aqueous solution and so it is transferred into the organic solution. The stability constants of Zn(II)-HQ complex in water and in dichloroethane were evaluated. The transfer potential was also evaluated independently of the experimental apparatus. These results clearly show that this experimental device is a very well-adapted tool for studying systems, which present transfers of species across liquid-liquid interfaces.     

Flash co-pyrolysis of biomass with polyhydroxybutyrate: Part 1. Influence on bio-oil yield, water content, heating value and the production of chemicals

Bio-oil obtained via flash pyrolysis shows potential to be applied as a renewable fuel. However, bio-oil often contains high amounts of water, which is a major drawback for its application. The influence of a biopolymer - polyhydroxybutyrate (PHB) on the pyrolysis of willow is investigated using a semi-continuous home-built pyrolysis reactor. The flash co-pyrolysis of willow/PHB blends (w/w ratio 7:1, 3:1, 2:1 and 1:1) clearly shows particular merits: a synergetic increase in pyrolysis yield, a synergetic reduction of the water content in bio-oil, an increase in heating value, and a production of easily separable chemicals. The occurrence of synergetic interactions is observed based on a comparison between the actual pyrolysis results of the willow/PHB blends, the theoretical pyrolysis results calculated from the reference pyrolysis experiments (pure willow and pure PHB) and their respective w/w ratio. The co-pyrolysis of 1:1 willow/PHB shows the best overall results.     

Complex stability of sugars and sugar alcohols with NA + , CA 2+ , and LA 3+ in chromatographic separations using poly(styrene- CO -divinylbenzene) resins and aqueous organic eluents

The complex formation between metal ions and carbohydrates in solvent mixtures has been studied by chromatographic measurements. The effect of noncomplexing partition was decreased by attaching the active groups only on the shell of the stationary phase particles. Poly(styrene- co -divinylbenzene) resin beads were surface-sulfonated for that purpose. Thus the inner part of the sulfonated bead remained inactive and nonswellable. The counter-ions examined were Na + , Ca 2+ , and La 3+ , and the organic cosolvents were ethanol and acetonitrile. The stability constants of the very weakly complexing D -glucose, D -xylose, and L -rhamnose, the weakly complexing D -fructose and L -arabinose, and the strongly complexing xylitol and D -sorbitol were determined. The increasing organic cosolvent content increased the retention times, which is explained by the increased complex stability between the complexing solute and the counter-ion. The effect was greatest for the complex-forming sugars in the Ca 2+ form and for the sugar alcohols in the La 3+ form. The organic cosolvent had only a minor effect on the weakly complexing components, whereas the complex stability of the strongly complexing xylitol and sorbitol in 50 wt% ethanol solution in the La 3+ resin was more than five times higher compared to the stability measured in pure water.     

COMPLEX STABILITY OF SUGARS AND SUGAR ALCOHOLS WITH Na + , Ca 2+ , and La 3+ IN CHROMATOGRAPHIC SEPARATIONS USING POLY(STYRENE- CO -DIVINYLBENZENE) RESINS AND AQUEOUS ORGANIC ELUENTS

The complex formation between metal ions and carbohydrates in solvent mixtures has been studied by chromatographic measurements. The effect of noncomplexing partition was decreased by attaching the active groups only on the shell of the stationary phase particles. Poly(styrene- co -divinylbenzene) resin beads were surface-sulfonated for that purpose. Thus the inner part of the sulfonated bead remained inactive and nonswellable. The counter-ions examined were Na + , Ca 2+ , and La 3+ , and the organic cosolvents were ethanol and acetonitrile. The stability constants of the very weakly complexing D -glucose, D -xylose, and L -rhamnose, the weakly complexing D -fructose and L -arabinose, and the strongly complexing xylitol and D -sorbitol were determined. The increasing organic cosolvent content increased the retention times, which is explained by the increased complex stability between the complexing solute and the counter-ion. The effect was greatest for the complex-forming sugars in the Ca 2+ form and for the sugar alcohols in the La 3+ form. The organic cosolvent had only a minor effect on the weakly complexing components, whereas the complex stability of the strongly complexing xylitol and sorbitol in 50 wt% ethanol solution in the La 3+ resin was more than five times higher compared to the stability measured in pure water.     

Concerted Electron/Proton Transfer Mechanism in the Oxidation of Phenols by Laccase

This study aimed to assess structural requirements in the enzyme/substrate interactions that are responsible for tuning the enzymatic reactivity. To better assess the role of the aspartic residue in the substrate‐binding pocket of basidiomycete‐type laccases, we compared the catalytic efficiency of wild‐type enzymes to that of a mutant in which carboxylic acid residue Asp206 was changed to alanine. Oxidation efficiency towards phenolic substrates by laccases of Trametes villosa, Trametes versicolor and a T. versicolor D206A mutant was studied at two pH values. By the Hammett approach and Marcus analysis, we obtained unambiguous evidence that the oxidation takes place by a concerted electron/proton transfer (EPT) mechanism, and that at pH 5 (optimum pH for enzyme activity) the phenolic proton is transferred to Asp206 during the concerted electron/proton transfer process.     

伴随传质的液液体系微分散流型图的实验研究(英文)

This paper presents the experimental results of liquid-liquid microflows in a coaxial microfluidic device with mass transfer.Three working systems were n-butanol + phosphoric acid(PA) + water,methyl isobutyl ketone(MIBK) + PA + water,30% kerosene in tri-n-butylphosphate(TBP) + PA + water.The direction and intensity of mass transfer were adjusted by adding PA in one of two phases mutual saturated in advance.When PA transferred from the organic phase to the aqueous phase,tiny aqueous droplets may generate inside the organic phase by mass transfer inducement to form a new W/O/W flow pattern directly on some special cases.Once the PA concentration was very high,violent Marangoni effect could be observed to throw part of organic phase out of droplets as tail.The interphase transfer of PA could expand the jetting flow region,in particular for systems with low or medium inter-facial tension and when the mass transfer direction was from the aqueous phase to the organic phase.     

The influence of molecular diffusion on mass transfer between turbulent liquids

The influence of molecular diffusion on liquid—liquid mass transfer in a stirred transfer cell has been found by measuring the rates transfer of helium and iso-butane from water to toluene and dekalin. These solutes have very different diffusion coefficients, their presence does not alter the physical properties of the liquids and, because their equilibrium distributions strongly favour the organic phases, the water phase mass transfer coefficient could be determined and was found to depend on the square root of the diffusion coefficient.The results are compared with the predictions of a model for liquid—liquid mass transfer under turbulent conditions, based on the approach of an eddy to the interface being restrained by interfacial tension and gravitational forces and taking into account eddy pressure fluctuations in both phases. This model provides a correlation for these results, as well as water phase mass transfer coefficients for the transfer of iso-butane from water to n-octanol, and previous stirred transfer cell results.     

Thermodynamics of organic compound transfer from the gas phase to environmentally important sorbents

Linear Free Energy Relationships (LFERs) based on distribution coefficients between the aqueous phase and the sorbent are often unsuccessful for interpreting sorption mechanisms in environmentally important sorbents because they comprise contributions not only from solute interactions with the sorbent, but also from hydration of the solute in bulk water. To avoid this problem, we suggest an approach for studying interactions between organic sorbates and environmentally important sorbents using a thermodynamic cycle to eliminate interactions between the solute and bulk water. In this approach, aqueous distribution coefficients are converted to gas phase distribution coefficients that are related to the free energy of transfer from the gas phase to the hydrated sorbent, and include contributions from all interactions occurring during the transfer. Gas phase distribution coefficients are compared for different compounds with similar molar refraction values to give insights into the nature of specific and nonspecific interactions of organic molecules with environmental sorbents. This methodology is illustrated for sorption of organic molecules in soil organic carbon and at mineral surfaces, and examples of insights obtainable from this methodology are given.     

冷冻干燥过程强化中冷冻阶段优化的研究进展

冷冻干燥产品质量高,但时间长、能耗高。本文综述了冷冻干燥过程强化中冷冻阶段的优化方法,控制冷冻速率、调节冰晶成核和退火处理可以获得大而均匀的冰晶从而提高升华干燥阶段速率,但物料内部比表面积的减小会降低解吸干燥阶段速率,这类常规的冷冻阶段优化方法对弱吸湿性的物料有一定的强化效果。有机溶剂具有较高的蒸气压,作为共溶剂时可以增加传质推动力,但较低的有机溶剂残留量要求阻碍了其进一步应用。“初始非饱和多孔介质冷冻干燥”的技术思想是将液体物料首先制备成具有一定初始孔隙的冷冻物料,然后再进行冷冻干燥。物料具有的初始孔隙为水蒸气的迁移提供了便捷的通道,而且纤薄的固体基质也有利于结合水的解吸,可以同时强化升华干燥阶段和解吸干燥阶段。该技术思想是过程低消耗和产品高质量的完美结合,为解决冷冻干燥过程速率低的问题提供了新的方案。