Effects of water content on the dissolution behavior of wool keratin using 1-ethyl-3-methylimidazolium dimethylphosphate

Ionic liquids(ILs) are eco-friend and recyclable solvents for dissolution of wool keratin, and water is often used as antisolvent to regenerate keratin from IL solution. To recycle the ILs, removing water is the necessary step. However, complete removal of the water is energy-intensive and costly. The water in ionic liquids would change the physicochemical properties and cluster structures of the IL and further affect its dissolution behavior on keratin. Here, 1-ethyl-3-methylimidazolium dimethylphosphate([Emim]DMP) was used for experiments due to its good performance on dissolving keratin. The experimental and simulation results showed that the dissolving capability of [Emim]DMP was decreased and the interactions between cation and anion became weaker with water concentration increasing. Furthermore, the dissolution time of wool keratin in [Emim]DMP increased with water content rising. At the same time, the effect of water in ILs on the secondary structure distribution and thermal stability of regenerated keratin was not obvious. In this work, by taking the structures of [Emim]DMP, keratin dissolution time and properties of the regenerated keratin into consideration, a balanced range of water content in [Emim]DMP was determined, which could not only reduce recycling cost but also not affect the dissolution behavior of the IL.     

Liquid–Liquid Equilibrium of Water + 1-Propanol or 1-Butanol + Dibutyl Ether Ternary Systems: Measurements and Correlation at Three Temperatures

Liquid–liquid equilibrium (LLE) date for the ternary systems of {water?+?1-propanol?+?dibutyl ether (DBE)} and (water?+?1-butanol?+?DBE) were determined at T?=?(293.15, 303.15, 308.15) K under atmospheric pressure. Distribution coefficients and separation factors of 1-propanol in the mixtures were calculated and are discussed. The influence of temperature on the liquid phase regions was analyzed. In addition, the experimental values were correlated well with the modified and extended UNIQUAC models; the modified UNIQUAC model represents the data better than the extended UNIQUAC model.     

Modeling gradient elution in countercurrent chromatography: efficient separation of tanshinones from Salvia miltiorrhiza Bunge

Countercurrent chromatography (CCC) is a support-free liquid-liquid chromatography using centrifugal fields to hold the liquid stationary phase. CCC has been widely applied in the separation of various natural and synthetic components using a variety of biphasic liquid systems. The related hexane or heptane/ethyl acetate/methanol or ethanol/water biphasic liquid systems demonstrated their significance in CCC. Gradient is difficult in CCC since any composition change in one phase induces a composition change of the other phase to maintain phase equilibrium. This work provides a new insight into linear gradient elution in CCC that is feasible with some biphasic liquid systems such as selected compositions of the hexane/ethyl acetate/ethanol/water systems. The equations modeling solute motion inside the CCC column are proposed. Particular compositions of the liquid system, namely the hexane/ethyl acetate/ethanol/water 8:2:E:W compositions with E + W = 10, were studied from W = 1 to 9. They showed moderate changes in the upper organic phase compositions. The model is tested with the separation of tanshinones from the rhizome of Salvia miltiorrhiza Bunge. Different linear solvent gradient profiles were experimentally performed between 8:2:5:5 and 8:2:3:7 compositions and the results were evaluated using the proposed model. Five tanshinones including dihydrotanshinone I, cryptotanshinone, tanshinone I, 1,2-dihydrotanshinquinone, and tanshinone IIA have been successfully separated (>95% purities) using a gradient profile optimized by the developed model. The gradient model can be used only with biphasic liquid systems in which one phase shows minimum composition changes when the other phase composition changes notably. This case is not the general case for biphasic liquid systems but can be applied with specific compositions of the quaternary hexane or heptane/ethyl acetate/methanol or ethanol/water most useful CCC liquid systems.     

Limonene in Arizona liquid systems used in countercurrent chromatography. I Physicochemical properties

Limonene is a biorenewable cycloterpene solvent derived from orange peel waste. Its potential as a “green” solvent to replace heptane was recently evaluated. Countercurrent chromatography (CCC) is a preparative separation technique using biphasic liquid systems. One liquid phase is the mobile phase; the other liquid phase is the stationary phase held in place by centrifugal fields. A particular range of special proportions of the heptane/ethyl acetate/methanol/water system is called the Arizona (AZ) liquid system when the heptane/ethyl acetate ratio is exactly the same as the methanol/water ratio. A continuous polarity decrease is obtained between the most polar A composition (ethyl acetate/water or 0/1/0/1 v/v) and the least polar Z composition (heptane/methanol or 1/0/1/0 v/v), replacing heptane by limonene and methanol by ethanol produce biphasic liquid systems much more environmentallyfriendly than the original AZ compositions. The chemical compositions of the two liquid phases of 12 AZ limonene/ethyl acetate/ethanol/water proportions were fully determined by Karl-Fisher titration of water and by gas chromatography for the organic solvents. The results were compared with the compositions of the corresponding AZ mixtures containing heptane and methanol. Significant differences in ethyl acetate and ethanol distribution between phases of the two systems with identical volume proportions were established. The ratio of the upper phase over the lower phase volumes and the phase density difference are important in CCC, there are also significant differences between the classic and “green” AZ systems that are discussed.     

Excess molar volume measurements of ternary mixtures [2-propanol+ethyl acetate+n-hexane] and their binary constituents at 298.15, 308.15 and 313.15 K

The excess molar volume of the ternary mixture [2-propanol?+?ethyl acetate?+?n-hexane], and its binary constituents; [2-propanol?+?ethyl acetate], [2-propanol?+?n-hexane] and [ethyl acetate?+?n-hexane] were evaluated by the mixtures density measurements over the whole concentration range at three temperatures 298.15, 308.15 and 313.15?K. The excess molar volumes data were fitted to the Redlich–Kister (RK) type equation and the parameters of this equation have been calculated and presented for the studied mixtures.     

Vapor pressure measurement for water,methanol, ethanol,and their binary mixtures in the presence of an ionic liquid 1-ethyl-3-methylimidazolium dimethylphosphate

Vapor pressure data were measured for water, methanol and ethanol as well as their binary mixtures with an ionic liquid (IL) 1-ethyl-3-methylimidazolium dimethylphosphate ([EMIM][DMP]) at varying temperature and IL-content ranging from mass fraction of 0.10–0.70 by a quasi-static method. The vapor pressure data for the IL-containing binary systems were correlated using NRTL equation with average absolute relative deviation (ARD) within 0.0076, and the binary NRTL parameters was used for predicting the vapor pressure of the IL-containing ternary systems with reasonable accuracy. In addition, the infinite activity coefficients of solvents in [EMIM][DMP] and isobaric vapor–liquid equilibrium for IL-containing ternary systems at 101.325 kPa and mass fraction of IL being 0.5 were predicted with the regressed NRTL parameters. The results indicate that ionic liquid [EMIM][DMP] can depress the volatility of the solvents of water, methanol and ethanol but to a varying degree, leading to the variation of relative volatility of a solvent and even removal of azeotrope for water–ethanol mixture.     

Binodal curve of two liquid phases and solid-liquid equilibrium for water + fatty acid + ethanol systems and water + fatty acid + acetone systems

To determine the liquid-liquid-solid three-phase equilibrium (LLSE), binodal data of the liquid-liquid equilibrium (LLE) and the solid-liquid equilibrium (SLE) have been measured for the ternary water + acetone or ethanol + lauric acid, myristic acid or palmitic acid systems. The binodal region for two liquid phases increases successively in the following order of the third component: lauric acid < myristic acid < palmitic acid. The binodal regions of the ternary systems with acetone as the second component are larger than those for ethanol. These binodal curves are not highly sensitive to temperature. The isothermal solubility of these fatty acids is considerably reduced when the water content in the aqueous phase increases. The solubility of fatty acids is successively reduced in the following order: lauric acid > myristic acid > palmitic acid. The solubility of fatty acids in aqueous solutions containing acetone is smaller than in those containing ethanol. Predictions of both the binodal curve for LLE and the SLE curve by the UNIFAC method and the NRTL equation do not represent the experimental data. However, data of the binodal curve and solubility are well correlated by the NRTL equation, and also the LLSE relationship could be represented.     

Alkane effect in the Arizona liquid systems used in countercurrent chromatography

Countercurrent chromatography (CCC) is a separation technique that uses a biphasic liquid system; one liquid phase is the mobile phase, the other liquid phase is the stationary phase. Selection of the appropriate liquid system can be a problem in CCC, since it is necessary to select both the “column” and the mobile phase at the same time as the first is completely dependent on the second. A range of systems with various proportions of solvents were developed to ease this choice; 23 variations of the heptane/ethyl acetate/methanol/water biphasic liquid system were labeled A to Z. This range proved to be extremely useful and became the popular Arizona (AZ) liquid system. However, authors often replace the heptane with hexane. In this work, the chemical compositions of the upper phases and the lower phases of 55 Arizona systems made with various alkanes (pentane, hexane, heptane, isooctane and cyclohexane) were determined by gas chromatography and Karl Fischer titration. The test mixture separated consisted of five steroid compounds. The lower phases were found to have similar compositions when different alkanes were used, but the upper phases were found to change. Exchanging heptane for hexane or isooctane produced minimal changes in the CCC chromatogram, while changing the proportions of the solvents resulted in an exponential change in the retention volumes. The high density of cyclohexane made liquid stationary phase retention difficult. All Arizona systems equilibrated within 30 min, but were not stable: water slowly hydrolyzed the ethyl acetate (as shown by a continuous decrease in the pH of the lower aqueous phase), especially in the water-rich systems (early alphabet letters).     

Liquid–Liquid Equilibrium Data for 1-Ethyl-3-methylimidazolium Acetate–Thiophene–Diesel Compound: Experiments and Correlations

Extraction of thiophene from cyclohexane, isooctane and toluene were performed using the ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]) at T=298.15 K. The liquid?Cliquid equilibrium (LLE) experiments were performed on three systems, namely: [EMIM][OAc]?Cthiophene?Ccyclohexane, [EMIM][OAc]?Cthiophene?Cisooctane and [EMIM][OAc]?Cthiophene?Ctoluene. The LLE data showed that [EMIM][OAc] has a higher selectivity at low concentration of thiophene and also showed that the hydrocarbon-rich phase is free of ionic liquid. This implies that there will be no cross contamination and the ionic liquid will be a non-pollutant in fuel after extraction. Further, the amount of hydrocarbon in the ionic-liquid-rich phase is very small. This implies that ionic liquid can be regenerated with negligible loss of fuel. LLE data was then correlated using the NRTL and UNIQUAC models. These showed root mean square deviation (RMSD) values of 0.82?% and 1.46?% for the isooctane system, 1.37?% and 1.57?% for the cyclohexane system and 1.39?% and 1.53?% for the toluene system.     

293.15K时咪唑醋酸盐-乙醇二元体系的体积性质及分子间相互作用简

用比重瓶法测定了293.15 K时1-甲基咪唑醋酸盐([Mim]Ac)/1,3-二甲基咪唑醋酸盐([Mmim]Ac)/1-乙基-3-甲基咪唑醋酸盐([Emim]Ac)-乙醇(EtOH)二元体系在全组成范围内的密度. 计算出[Mim]Ac/[Mmim]Ac/[Emim]Ac和EtOH的表观摩尔体积和体系的超额摩尔体积. 用三参数多项式关联拟合了表观摩尔体积与摩尔分数的关系,外推出组分的极限偏摩尔体积和摩尔体积. [Mim]Ac/[Mmim]Ac/[Emim]Ac和EtOH的摩尔体积的外推值与实验值分别在±0.07和±0.04 cm3/mol范围内相一致. 计算出了[Mim]Ac/[Mmim]Ac/[Emim]Ac和EtOH分别在无限稀溶液中的溶剂化系数. 用Redlich-Kister 方程关联拟合了超额摩尔体积与摩尔分数的关系. 分别根据极限偏摩尔体积、摩尔体积与极限偏摩尔体积的差值、溶剂化系数和超额摩尔体积对照讨论了分子间相互作用的强弱. 结果显示,在[Mim]Ac/[Mmim]Ac/[Emim]Ac的浓度无限稀溶液中,[Mim]Ac/[Mmim]Ac/[Emim]Ac-EtOH分子对间相互作用的强弱顺序为[Mim]Ac-EtOH>[Mmim]Ac-EtOH >[Emim]Ac-EtOH;在EtOH的浓度无限稀溶液中,以及体系中[Mim]Ac/[Mmim]Ac/[Emim]Ac的摩尔分数在0.15～0.95间时,[Mim]Ac/[Mmim]Ac/[Emim]Ac-EtOH分子对间相互作用的强弱顺序都为[Emim]Ac-EtOH>[Mmim]Ac-EtOH>[Mim]Ac-EtOH.     

Liquid-liquid phase equilibrium of (piperidinium-based ionic liquid + an alcohol) binary systems and modelling with NRHB and PCP-SAFT

The phase diagrams for binary systems of {1-propyl-1-methylpiperidinium bis{(trifluoromethyl)sulfonyl}imide [PMPIP][NTf₂] + an alcohol (butan-1-ol, pentan-1-ol hexan-1-ol, heptan-1-ol, octan-1-ol, decan-1-ol and undecan-1-ol} have been determined at atmospheric pressure using a dynamic method. The influence of an alcohol chain length is discussed for this ionic liquid (IL). A systematic decrease in the solubility is observed with an increase of the alkyl chain length of an alcohol. Liquid + liquid phase equilibrium (LLE) with an upper critical solution temperature was observed. The phase diagrams reported are compared to systems published earlier with the 1-alkyl-1-methylpiperidinium-based ionic liquid. The basic thermal properties of the pure IL, i.e. melting temperature and the enthalpy of fusion, the glass transition temperature and heat capacity at melting temperature have been measured using a differential scanning microcalorimetry technique. The density of [PMPIP][NTf₂] as a function of temperature was measured. The results of the LLE correlation with two models viz. the lattice theory based on non-random hydrogen bonding (NRHB) and the Perturbed-Chain Polar Statistical Associating Fluid Theory (PCP-SAFT) are presented. Both models are capable of describing pure fluid properties of IL (densities and solubility parameters) by using one set of parameters and the LLE in binary systems. This is to our knowledge the first paper presenting the SAFT modelling of binary LLE in ionic liquid systems.     

Vapor pressures,excess enthalpies,and specific heat capacities of the binary working pairs containing the ionic liquid 1-ethyl-3-methylimidazolium dimethylphosphate

In present research the binary solutions containing ionic liquid (IL), 1-ethyl-3-methylimidazolium dimethylphosphate ([EMIM] [DMP]), are considered as new working pairs for absorption heat pumps or absorption refrigerators. The IL was synthesized in the lab and mixed with water, ethanol, or methanol. Experimental (vapor + liquid) equilibrium (VLE) of these binary systems was measured at different mole fractions ranging from 0.1 to 0.5 and was correlated by the NRTL equation within the average relative deviation of 2%, which means that the (vapor + liquid) equilibrium of these binary solutions containing ionic liquid can be predicted by traditional non-electrolyte solution model. Meanwhile these binary solutions are a negative deviation from Raoult’s law. Excess enthalpy of these binary systems was measured at the temperature of T = 298.15 K and at the pressure of 1 atm. The results indicate that the mixing processes of [EMIM] [DMP] with water, ethanol, or methanol are exothermal, which is a very important characteristic for working pairs used in absorption heat pumps or in absorption refrigerators.     

反气相色谱法测定离子液体1-己基-3-甲基咪唑三氟甲磺酸盐的热力学参数

采用反气相色谱法研究了343.15~373.15 K温度范围内离子液体1-己基-3-甲基咪唑三氟甲磺酸盐([HMIM]OTF)的热力学参数。根据18种探针溶剂的保留时间计算出探针溶剂与[HMIM]OTF之间的摩尔吸附焓、无限稀释的摩尔混合焓、摩尔蒸发焓、质量部分活度系数、Flory-Huggins相互作用参数及[HMIM]OTF的溶解度参数。结果表明,所选溶剂中正构烷烃、四氢呋喃、乙醚、环己烷和苯为[HMIM]OTF的不良溶剂;二氯甲烷、丙酮、氯仿、乙酸乙酯、四氯化碳、乙酸甲酯、甲苯和甲醇为[HMIM]OTF的良溶剂;运用外推法得到了室温(298.15 K)时[HMIM]OTF的溶解度参数为20.74 (J/cm³)^0.5。本研究为离子液体的应用及相关工作提供了参考。     

Numerical study on the convective heat transfer performance of a developed MXene IoNanofluid in a horizontal tube by considering temperature-dependent properties

Journal of Thermal Analysis and Calorimetry - In this study, the heat transfer performance of [MMI][DMP] ionic liquid solution (20 vol% IL?+?80 vol% deionized water) in the presence of...     

LLE of ternary mixtures of water/acetone/2-ethyl-1-hexanol at different temperatures

Experimental liquid–liquid equilibrium (LLE) data were determined for a ternary system water+acetone+2-ethyl-1-hexanol at various temperatures of 298.2, 303.2, 308.2, and 313.2 K and atmospheric pressure. The UNIQUAC model was used to correlate the experimental tie-line data. The LLE data were correlated fairly well with this solution model, indicating the reliability of the UNIQUAC equation for this ternary system. The average root mean square deviation between the observed and calculated mole fractions was 1.87%. The mutual solubility of 2-ethyl-1-hexanol and water was also investigated by the addition of acetone at different temperatures.     

Characterization of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][Tf2N])∕TX-100∕cyclohexane ternary microemulsion: investigation of photoinduced electron transfer in this RTIL containing microemulsion

In this study we have characterized a ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethyl- sulfonyl)imide containing ternary nonaqueous microemulsion ([Emim][Tf(2)N]∕∕TX-100∕cyclo- hexane). The phase behavior and dynamic light scattering study show that the [Emim][Tf(2)N]∕TX-100∕cyclohexane three component system can form microemulsion with [Emim][Tf(2)N] as polar core at suitable condition. We have investigated photoinduced electron transfer (PET) using dimethyl aniline as electron donor and several Coumarin dyes as electron acceptor molecules at two different R values (R = [ionic liquid]∕[surfactant]) to observe how the dynamics of the PET rate is affected in this type of confined microenvironment compared to that of the PET dynamics in neat ionic liquid and other pure solvent media. The plot of observed k(q) values with the free energy change (ΔG(0)) for electron transfer reaction shows an apparent inversion in the observed rate as predicted by the Marcus theory.     

反气相色谱法测定有机溶剂在离子液体1-丁基-3-甲基咪唑六氟磷酸盐中的热力学参数

在343.15~373.15 K温度范围内,采用反气相色谱法(IGC)测试了18种有机溶剂在离子液体1-丁基-3-甲基咪唑六氟磷酸盐([BMIM]PF₆)中的热力学参数。在测试温度范围内计算了有机溶剂与[BMIM]PF₆之间的摩尔吸收焓、质量分数活度系数、Flory-Huggins相互作用参数、偏摩尔混合焓和无限稀释活度系数等热力学参数。结果表明,所选的有机溶剂中,正构烷烃、环己烷、四氢呋喃、乙醚和四氯化碳为[BMIM]PF₆的不良溶剂。 相比之下,苯、甲苯、间二甲苯、二氯甲烷、丙酮、氯仿、乙酸乙酯、乙酸甲酯、乙醇和甲醇是[BMIM]PF₆的良溶剂。     

Determination of uracil in 5-fluorouracil substance by high-performance liquid chromatography

Separation of 5-fluorouracil and uracil in chromatographic systems consisting of a silica column as a stationary phase and ethyl acetate or ethyl acetate partially saturated with water as a mobile phase has been studied. The results indicated that when saturation of ethyl acetate with water was chosen to reach more than 60%, such mobile phases [e.g., 2.4% (v/v) water in ethyl acetate] are useful in determining uracil in 5-fluorouracil substances.     

Thermophysical properties of biodiesel and related systems: (Liquid + liquid) equilibrium data for soybean biodiesel

This work reports (liquid + liquid) equilibrium (LLE) data for the systems of interest in soybean biodiesel production. Numerical data for LLE were obtained for binary, ternary and quaternary systems comprising fatty acid methyl esters (FAME) and fatty acid ethyl esters (FAEE) from soybean oil, water, glycerol, methanol, and ethanol at temperatures of (303.15, 318.15, and 333.15) K. Quantification of compounds in equilibrium in both phases was determined by analytical methods whereas solubility curves (binodal) were obtained by the cloud-point method. For all systems investigated, good alignments were obtained between phase compositions and the initial as well as overall compositions hence indicating low deviations from the mass balance. Experimental results were correlated using the UNIQUAC model with satisfactory agreement between experiment and theory.