⿢Highly CO2-soluble polyethylene glycol diphosphates were designed and synthesized.⿢Solubility data for these compounds were determined and correlated.⿢Complexation mechanism was studied by characterization of IR, 1H NMR and ESI-MS.⿢Extraction experiment toward lanthanides was investigated.⿢All showed high efficiency and selectivity toward middle and heavy lanthanides.Three new CO2-philic open-chain organophosphorous chelating ligands, i.e. ethylene glycol bis(2-isopropoxyethyl) dimethyl diphosphate (EG2IPE), triethylene glycol bis(2-isopropoxyethyl) dimethyl diphosphate (EG3IPE), and tetraethylene glycol bis(2-isopropoxyethyl) dimethyl diphosphate (EG4IPE), were synthesized and characterized. Solubilities of these ligands in scCO2 were determined at different combinations of temperature (313.15⿿333.15 K) and pressure (9⿿20 MPa), which generally showed considerable solubility in each case. These experimental data are in agreement with computed data via a semi-empirical model, in which the average absolute relative deviations lie in the range of 4.09⿿4.95%. The effect of these ligands on supercritical fluid extraction of selected rare earth metals (La3+, Ce3+, Pr3+, Nd3+, Sm3+, Gd3+, Er3+, and Yb3+) was investigated at 313.15 K and 20 MPa. The extraction efficiency of this system was found to increase in the order EG4IPE < EG3IPE < EG2IPE with a range from 55% to 79%. The rationale behind different selectivities toward these metals was also discussed in comparison to other traditional organophosphorous agents. A detailed experimental analysis of the complexation patterns by means of a combination of IR, 1H NMR and ESI-MS has revealed that the interaction of ether oxygen group in EG4IPE with metals and the corresponding extraction mechanism.

•We determined the diffusion coefficients in 10 mol% ethanol modified CO2.•Four C18 unsaturated fatty acid methyl esters were selected as solutes.•The diffusion coefficient decreased with increasing the number of C-C double bonds.•We investigated several available models for pure CO2 with the experimental data.•The free volume model of Dymond gave the least average absolute deviations.To determine the molecular diffusion coefficients of C18 unsaturated fatty acid methyl esters in supercritical carbon dioxide (scCO2) containing 10 mol% ethanol as a modifier, four methyl esters of C18 fatty acids, i.e., methyl oleate, methyl ricinoleate, methyl linoleate and methyl linolenate were selected as the typical solutes. The diffusion coefficients were measured at temperatures from 313.15 to 333.15 K and pressures from 15 to 27 MPa using the Taylor–Aris chromatographic peak broadening (CPB) technique. The influences of temperature, pressure, density and viscosity of the solvent mixture on the diffusion coefficients were examined. The results show that methyl oleate always diffuses faster than methyl ricinoleate at the same operating condition. Moreover, the D12 values in ethanol-modified scCO2 decrease with the increase of the number of C-C double bonds in C18-methyl ester, which is consistent with the trend reported in pure scCO2. The diffusivity data are compared with the estimation of eleven predictive models. The modified Wilke–Chang equation is the best purely predictive model and the free volume model of Dymond with two adjustable parameter gives the least errors with average absolute deviations lower than 2.5%.

Wall-coated open-tubular (WCOT) columns provide higher column efficiency and lower solute interfacial adsorption effect than packed columns. However, previous efforts used to measure the infinite dilution activity coefficient (γ∞) via a chromatographic technique have used packed columns, because the low carrier gas flow rate (U) and the small stationary phase amount (n2) in WCOT columns raise large errors. By rationally revising the γ∞-calculation equation for static-wall-coated open-tubular column, we observed that U and n2 are not necessarily needed and the resulting error could be reduced, and WCOT column gas chromatography subsequently became a superior method for the accurate γ∞ determination. In this study, we validate our revised γ∞-calculation equation by measuring γ∞ in an ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate system, in which 55 organic compounds covering a wide range of functional groups were used as probe solutes and their γ∞ values in the ionic liquid were determined at 40.0, 50.0, and 60.0 °C. Experimental error analysis shows that our revised equation remarkably reduces the error compared to the common γ∞-calculation equation. Our data is consistent with previously reported values obtained via other techniques, which further proves the credibility of our revised equation. The accurately determined γ∞ values can be directly used to calculate the partial molar excess enthalpy, selectivity, and capacity, which will benefit for the rapid screening of solvents (especially ionic liquids) in separation approaches.

The triethylene glycol and tripropylene glycol derivatives terminated with the CO2-philic phosphoryl groups, named 2-(2-(2-((2-ethylhexoxy(methoxy)phosphoryl)oxy)ethoxy)ethoxy)ethyl 2-ethylhexyl methyl phosphate (EG3EH) and 2-(2-(2-((2-ethylhexoxy(methoxy)phosphoryl)oxy)propoxy)propoxy)propyl 2-ethylhexyl methyl phosphate (PG3EH), were synthesized and characterized. The solubilities of EG3EH and PG3EH in scCO2 were determined by a static method at temperatures from (313 to 333) K and over a pressure range of (10 to 19) MPa. The values calculated by the Bartle semiempirical model exhibited good agreement with the experimental data.

A study was carried out concerning the effects of an ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4) on the properties of nonionic surfactant-based H2O + Triton X-100 (TX-100) + hexanol + cyclohexane microemulsions. Several properties of microemulsions, such as polarity, conductivity, viscosity, and droplet size, were investigated with the mass ratio of TX-100/hexanol/cyclohexane = 3:2:7. With the addition of IL, the polarity of the microemulsions increases. Conductivity results reveal that the onset water content of electrical percolation decreases with the presence of IL and continues to decrease as the amount of IL increases. The viscosity of microemulsions increases with the increasing amount of IL. Dynamic light scattering (DLS) measurements indicate that the droplet sizes of microemulsions increase with the addition of IL. All results presented in this study suggest that the IL is solubilized into the polar core of microemulsions.

The effect of ionic liquids (ILs) on temperature-induced percolation of water/sodium bis-(2-ethylhexyl) sulfosuccinate (AOT)/isooctane microemulsions was investigated. Several properties of microemulsions, including percolation temperature threshold (Tp), viscosity, and droplet size were used to demonstrate the effect of the structure of ILs on percolation phenomena. Percolation phenomena of microemulsions were clearly observed after the addition of IL, and the Tp of microemulsions increased with increases in the ILs concentration. In addition, Tp was greatly affected by the alkyl side-chain length of imidazolium cation and increased with increases in chain length. However, Tp was slightly affected by the ILs anions due to the charge exclusion caused by the head group of surfactant. Additionally, the viscosity and droplet size of microemulsions decreased with the addition of ILs, and the observed decrease correlated roughly with an increase in Tp. These results also confirm the influence of ILs on percolation phenomena of the microemulsions.Graphical abstractHighlights► Temperature-induced percolation of microemulsions with ionic liquid (IL) was studied. ► Percolation temperature (Tp) of microemulsions increases with the addition of IL. ► Tp is greatly affected by the alkyl side-chain length of imidazolium cation of IL. ► The viscosity and droplet size of microemulsions decrease with the addition of IL. ► The decrease of viscosity and droplet size correlate roughly with an increase in Tp.

The solution of ionic liquid (IL) bmimCl and polar organic solvent formamide (FA) were used to form nonaqueous microemulsions in cyclohexane by the aid of surfactant Triton X-100 (TX-100). The phase behavior of the bmimCl–FA/TX-100/cyclohexane system at 25 ± 0.1 °C was studied. Electrical conductivity measurement was used to identify the microstructures of the nonaqueous microemulsions. Based on the phase diagram, the reverse microemulsions containing bmimCl–FA as the internal phase were investigated by the dynamic light scattering (DLS) and UV–vis spectroscopy. The result of DLS experiments confirmed the formation of reverse microemulsions of bmimCl–FA in cyclohexane. The UV–vis studies with methyl orange (MO) and methylene blue (MB) as absorption probes further confirmed the existence of reverse microemulsions. UV–vis studies using CoCl2 as probe also indicated that the reverse microemulsions could dissolve metal salt.Graphical abstractHighlights► Microemulsions with ionic liquid and a nonaqueous polar solvent as the polar phase. ► Characterization by means of conductivity, DLS and UV–vis spectroscopy. ► Linear increase of the microemulsions droplet size by adding the polar phase. ► These nonaqueous microemulsions can dissolve metal salt.

The water solubilization capacity of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in isooctane microemulsions in the presence of chloride anion-based ionic liquids (ILs), such as 1-ethyl-3-methylimidazolium chloride (emimCl), 1-butyl-3-methylimidazolium chloride (bmimCl), and 1-octyl-3-methylimidazolium chloride (omimCl), was investigated. The water solubilization capacity is enhanced at low IL concentrations but decreases at high concentrations of IL. Meanwhile, the water solubilization capacity increases with the increase of chain length of ILs at low IL concentrations. The effect of ILs on the volume-induced percolation of AOT microemulsions was also studied. For the microemulsions, with an increasing volume fraction of dispersed phase (Φ), no percolation phenomena can be observed at high concentrations of IL, whereas the percolation conductance occurs at low IL concentrations and the percolation threshold (Φp) increases with the increase of IL concentrations. For the IL-containing microemulsions, the Φp increases with increasing IL chain length under the same conditions.

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.Graphical abstractHighlights• The molecular diffusion coefficients of 1,3-dichlorobenzene, 3-fluorophenol, geraniol, and l-carvone in supercritical carbon dioxide and CO2 with n-hexane, tetrahydrofuran, methanol, isopropanol, and acetonitrile as cosolvents were measured by the Taylor–Aris chromatographic peak broadening method. • Cosolvent effect parameter was introduced to quantitatively compare the strength of interaction between solute and cosolvent. • For cosolvent without hydrogen-bond ability, the cosolvent effect parameter decreases with the increase of molecular volume and mass of the solutes. • For cosolvent with only HBA basicity, the solute with higher HBD acidity has smaller cosolvent effect parameter. • For amphiprotic cosolvent, the solute with higher HBD acidity has smaller cosolvent effect parameter, implying HBD acidity rather than HBA basicity of the solute makes a major contribution to the hydrogen-bond interaction between solute and cosolvent.

Chromatograms of tocopherol homologues were obtained by a column of analytical size (inner diameter (ID) 0.46 cm cm×10 cm) packed with silica gel. Adsorption isotherms and film mass-transfer coefficient were estimated from the chromatograms by using a general rate model, which considers axial dispersion, external mass-transfer and intraparticle diffusion. Based on the obtained isotherms and mass-transfer coefficient, the separation process of tocopherol homologues on simulated moving bed (SMB) was simulated using the same model. According to the simulated results, a mixture of α-, γ-, δ-tocopherols and other impurities was separated on an SMB equipment. The SMB equipment was composed of 8 columns of ID 2 cm×10 cm, with 2 columns in each section. The solid phase was silica gel, and the mobile phase was n-hexane/2-propanol (99/1 by volume). γ- and δ-tocopherols of purity greater than 98% were obtained with recovery greater than 98%. The effects of operating conditions (flow rates and switching time) on the performance of SMB were studied by both simulation and experiments. It was found that all the simulation results were quite close to the experimental results. We conclude that process development and optimization of operating conditions of SMB by simulation are feasible.

The adsorption of penicillin G sodium (PGS) on a hydrophilic gel, Toyopearl HW-40F, was investigated by the frontal analysis method. Effects of media, buffer concentration, and temperature on the adsorption equilibrium were examined in the buffer concentration range of (0.005 to 0.05) mol·L−1 and temperature range of (278.15 to 308.15) K. At the same pH value, the ionic strength of the mobile phase greatly influences the adsorption of PGS. The adsorption isotherms of PGS are comparable at different temperatures. The equilibrium data were modeled by the Freundlich equation with AARD in the range of (0.86 to 7.15) %.

The solubility of oxymatrine in supercritical carbon dioxide over the pressures ranging from (11 to 21) MPa and at the temperatures of (308.15, 318.15, and 328.15) K was measured using a continuous flow-type apparatus. The measured solubilities were correlated using a semiempirical model proposed by Bartle.