Effect Of Ionic Liquid Concentration Research Articles

Optimised phycoerythrin extraction method from Porphyridium sp. combining imidazolium-based ionic liquids

Phycoerythrin (PE) extraction from Porphyridium sp. was studied employing ultrasound-assisted extraction combined with aqueous mixtures of two imidazolium-based ionic liquids (ILs) simultaneously, marking a significant novelty. A face-centred central composite design and response surface optimised PE yield (EPE), considering the effects of ionic liquid concentration (IL), [Emim][EtSO4]/[Bmim][EtSO4] mass ratio (E/B), biomass concentration (BM), and time (t). Improvements in EPE by 300 % and 115 % were achieved compared to a phosphate buffer solution and the freeze-thaw method, respectively. Temperature and pH effects were examined independently, leading to the determination of optimal operating conditions: BM = 10 mg mL−1, IL = 18.6 wt%, E/B = 0.78/0.22, t = 10 min, T = 35 °C, and pH = 7.5. Results indicated the potential for reusing the ILs for at least five consecutive extraction cycles, maintaining an EPE of 94.2 % compared to fresh ones. This underscores the success and innovation of the developed technology in enhancing PE extraction from Porphyridium sp.

Ionic liquid-based ultrasonic-assisted extraction coupled with HPLC to analyze isoquercitrin, trifolin and afzelin in Amygdalus persica L. flowers

This study aimed to establish a method for the simultaneous determination of isoquercitrin, trifolin and afzelin in A. persica flowers by high performance liquid chromatography (HPLC) with ionic liquid as extractant and ultrasonic-assisted extraction. The effects of ionic liquid concentration, solid–liquid ratio, number of crushing mesh, ultrasonic time, extraction temperature, and ultrasonic power on the extraction yield of three target compounds were investigated using the extraction yield of target analytes as the index. According to the results of single factor experiment, the Box-Behnken design-response surface methodology (BBD) was used to optimize the extraction method and compared with the traditional extraction method. The results showed that, calibration curves had excellent linearity (R2 > 0.9990) within the test ranges. In combination with other validation data, this method demonstrated good reliability and sensitivity, and can be conveniently used for the quantification of isoquercitrin, trifolin and afzelinin A. persica flowers. And the contents of isoquercitrin, trifolin and afzelin were 64.08, 20.55 and 75.63 μg/g, respectively. The optimal process obtained by BBD was as follows: ionic liquid concentration was 1.0 mol/L, solid–liquid ratio was 1:40 g/ml, mesh sieve was 50 mesh, ultrasonic time was 40 min, extraction temperature was 50 °C, and ultrasonic power was 400 W. Under the optimal conditions, the theoretical predicted total extraction yield of the three target compounds was 159.77 μg/g, which was close to the actual extraction value (160.26 μg/g, n = 3), this result indicating that the optimal process parameters obtained by response surface methodology analysis were accurate and reliable. The method was simple, accurate and rapid for determination the contents of three active ingredients in A. persica flowers.

Mass Transfer Characteristics of CO2 and Blended Aqueous Solutions of [C2OHmim][Lys]/MDEA in a Microchannel

In this paper, the two-phase flow and mass transfer process of CO2 and [C2OHmim][Lys]/MDEA mixed aqueous solution in a T-shaped microchannel were investigated systematically. By using a high-speed camera connected to a computer, the two-phase flow patterns were recorded online, including the Taylor flow and a small amount of Taylor-bubbly flow. And the effects of ionic liquid concentration and two-phase flow ratio (QG/QL) on bubble length, specific surface area, gas holdup, and mass transfer coefficient were studied experimentally. The results indicate that the blended solution of [C2OHmim][Lys]/MDEA could significantly enhance two-phase mass transfer compared to single N-methyldiethanolamine aqueous solution. The reaction mechanism between CO2 and ionic liquid/amine mixed aqueous solution was also analyzed. On the basis of experimental data, some new correlations for predicting the bubble initial length and the volumetric mass transfer coefficient were proposed, which matched well with the experimental data. This work is helpful to provide new ideas for the design of CO2 absorbents and further improve the data of gas–liquid mass transfer in microchannels.

Swelling and microwave-assisted hydrolysis of animal keratin in ionic liquids

Four kinds of acidic ionic liquids (ILs) were synthesized to hydrolyze keratin with microwave radiation for the first time, among which 1-propylsulfonic-3-methylimidazolium hydrogensulfate ([PSmim]HSO4) presented the best performance for the sample of wool. Then the effects of ionic liquid concentration, solid–liquid ratio, duration, and microwave power on the hydrolysis rate of wool were investigated. After that, the optimum hydrolysis conditions for keratin were determined as: 2 mol/L [PSmim]HSO4, radiation time of 3 h, solid–liquid ratio of wool to ionic liquid at 1:10, microwave power of 300 W, and the final hydrolysis rate of wool was more than 98%; besides that, the swelling effect and kinetics of related processes were also explored, and the hydrolysates were characterized by infrared spectra (IR) and thermalgravimetric analysis (TGA), which were further compared with the product hydrolyzed by traditional volatile strong acid. Furthermore, this IL-catalyzed microwave-assisted method was also applied to hydrolyze a series of feathers and hairs with the comprehensive comparison on the antioxidant activity, free amino acid concentration, and molecular distribution of hydrolysates. The recovered ionic liquid by resin was not changed from its original status obviously, which could be reused and improve the economy of the whole process. Compared with conventional ways, higher hydrolysis degree can be obtained by the developed method, which was a high-efficient, low consumption and environmentally friendly technique.

Molecular structure characterization of lignite treated with ionic liquid via FTIR and XRD spectroscopy

In order to characterize the effect of ionic liquid concentration on the molecular structure of lignite, the X-ray diffraction (XRD) and Fourier transform infrared (FTIR) experiments were performed on lignite coal samples treated with different concentrations of ionic liquids. The results show that with the increase of IL concentrations, the apparent aromaticity fa increases gradually. The chemical bonds on both sides of the alkyl groups are destroyed, the alkyl chains become shorter, and the molecular structure become more compact. The C-O groups such as alcohol, phenol and ether groups are converted to CO groups such as carbonyl, aldehyde and carboxy groups. The inter-layer spacing (d002) ranges from 0.374 to 0.379, which is slightly higher than that in pure graphite. It indicates that the crystalline order in coal samples is in a lower degree. The La ranges from 3.05 to 4.05 nm and Lc ranges from 0.98 to 1.11 nm, which indicates the crystallite size increases further and the order degree of coal samples gradually approaches graphitization. The results of this paper can provide some reference for studying the characteristics of molecular structure change of coal.

Effects of ionic liquid concentration on coal low‐temperature oxidation

AbstractIn order to find out the optimal concentration of ionic liquid to lower the cost of inhibiting coal spontaneous combustion, effects of aliphatic hydrocarbons, hydrogen bonds, and some structural parameters of coal samples treated with low‐concentration ionic liquids were analyzed through Fourier‐transform infrared spectroscopy (FTIR) and temperature‐programmed experiments. Meanwhile, the changes of index gases in the heating process were observed by the temperature‐programmed method. The results show that the contents of aliphatic hydrocarbons in the treated coal samples decrease remarkably, so does the length of aliphatic chain CH2/CH3; besides, the amount of CO produced also decreases to some extent. When the mass concentration ratio is 1:10, HB‐tc, BB‐tc, AC‐tc, and BN‐tc can reduce the spatial structure and enhance the structural stability of aromatic clusters in coal. The CO concentrations of 1:2 HB‐tc and 1:10 AC‐tc are obviously lower than that of raw coal, indicating their better inhibitory effects. The inhibitory effect of HB‐tc decreases with the decrease in concentration. With the rise of temperature, the effect of concentration on the inhibition of CO production gradually weakens at 180°C and 200°C. AC‐tc achieves the optimum inhibitory effect near 1:10 mass concentration ratio.

Effect of ionic liquid concentration on the photovoltaic performance of dye-sensitized solar cell

Abstract Quasi-solid-state electrolytes based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVdf-HFP), propylene carbonate (PC), 1,2-dimethoxyethane (DME) and different concentrations of 1-methyl-3-propylimidazolium iodide (MPII) salt were prepared. The highest room temperature conductivity of 4.6 x 10-3 S cm-1 was achieved with 1.0M MPII. The effect of MPII on the conductivity was discussed on the basis of number free ions. The number of free ions were estimated by impedance spectroscopy method. DSSC at 1.0M MPII shows the conversion efficiency, η of 3.70% with short-circuit current density, Jsc of 8.65 mA cm-2, open circuit voltage, Voc of 641 mV and a fill factor, FF of 66%.

Three-component mixed matrix membrane containing [Hmim][PF6] ionic liquid and ZSM-5 nanoparticles based on poly (ether-block-amide) for the pervaporation process

Three-component mixed matrix membranes based on poly (ether-block-amide) (PEBA) were prepared by incorporation of ZSM-5 zeolite nanoparticles and [Hmim][PF6] ionic liquid for the separation of ethyl acetate (EAc) from EAc/water mixtures using the pervaporation process. At first, the dual-layer PEBA/polyethersulfone (PES) membranes containing [Hmim][PF6] in the active layer were prepared and employed in the pervaporation process. It was found that the ionic liquid leached out from the membrane during the pervaporation experiments and decreased the membrane selectivity. In order to avoid leaching out of the ionic liquid, triple-layer membranes consisting of a ZSM-5/PEBA as the top layer on a [Hmim][PF6]/PEBA as the intermediate layer and PES as the support layer were developed. The effect of ionic liquid concentration in the intermediate layer on the membrane separation performance was investigated and the results indicated that the membrane containing 2.5%wt. [Hmim][PF6] had the best separation performance in terms of the pervaporation separation index (PSI). Moreover, the ZSM-5 nanoparticles were added to the intermediate layer of the triple-layer membranes to improve the performance of the membranes. It was found that simultaneous loading of the ZSM-5 and [Hmim][PF6] in the PEBA matrix significantly improved the separation performance of the membrane as the PSI of the prepared three-component mixed matrix membrane was 1.5 times the PSI of the neat PEBA membrane.

Influence of ultrasonic assisted ionic liquid on heavy oil structure

The effect of ionic liquid concentration on the content of four components and structural composition of heavy oil was studied by using ultrasonic-assisted nickel based ionic liquid. The results reveals that compared with crude oil and individual ultrasonic crude oil, the combination of ultrasonic wave and ionic liquid can achieve synergistic effect. Saturate increased and aromatic decreased gradually as the increase of the concentration of ionic liquid. The structure of resin and asphaltene has been characterized by infrared and nuclear magnetic resonance spectroscopy. It has been indicated that the structure of polyaromatic compounds can be obviously changed and mainly occurrence in alkyl side chain cleavage and cycloalkanes ring-opening reaction.

Destabilizing sodium borohydride with an ionic liquid

Sodium borohydride (NaBH4) is a complex hydride containing 10.5% of its mass as hydrogen; however, it is too stable to desorb hydrogen at room temperature. An ionic liquid (IL), vinylbenzyl trimethylammonium chloride, was applied to modify the charge distribution in BH4− and promote the dehydrogenation of NaBH4. The effect of IL concentration as well as particle size on the amount of desorbed hydrogen was investigated. The dehydrogenation reaction of the IL–NaBH4 complex was exothermic (negative enthalpy), which is in contrast to the endothermic hydrogen desorption reaction for pure NaBH4 (positive enthalpy). The enthalpy of the IL–NaBH4 complex for dehydrogenation was lower than NaBH4 due to the interactions of the cation, the IL, and the borohydride. Dehydrogenation of the mixture (mass ratio of NaBH4:IL = 1:2) started below 160 °C, with a maximum hydrogen desorption capacity of 2.1 wt%. The strong amine cation in the IL led to destabilization of the borohydride by polarization, thus resulting in improved dehydrogenation of the complex hydride. The enthalpy of the dehydrogenation reaction was −4.8 kJ mol−1 of hydrogen. The exothermic nature of the reaction was caused by deformation of the lattice and destabilization from the IL.

Investigation of an alternative chemical agent to recover valuable metals from anode slime

Anode slime (AS) including high content of precious metals is a by-product obtained after the electro-refining stage in copper production. In this study, it is aimed to recover Cu, Au, and Ag from the AS by using 1-butyl-3-methyl-imidazolium hydrogen sulphate ([Bmim]HSO4) ionic liquid (IL) as a green solvent. The effects of IL concentration, temperature, reaction time and pulp density on recovery of valuable metals were statistically investigated. A high copper recovery of 87.52% was obtained under optimum condition as in 60% (v/v) [Bmim]HSO4 at 50 °C after 2 h, pulp density at 40 g/L (1/25 solid/liquid ratio). Also, a remarkable gold recovery as 97.32% has been achieved in 80% (v/v) [Bmim]HSO4 at 95 °C after 4 h, pulp density at 40 g/L. Temperature and IL concentration were detected as the most effective parameters for copper and gold recovery from AS, respectively. Silver could not be recovered from the AS due to the lower solubility in [Bmim]HSO4 IL media. According to experimental results, [Bmim]HSO4 could be offered as an alternative leaching agent, instead of conventional solvents, to recover valuable metals from copper anode slime.

Unique reversibility in extraction mechanism of U compared to solvent extraction for sorption of U(VI) and Pu(IV) by a novel solvent impregnated resin containing trialkyl phosphine oxide functionalized ionic liquid

Novel Solvent Impregnated Resin (SIR) material was prepared by impregnating a trialkyl phosphine oxide functionalized ionic liquid (IL) into an inert polymeric material XAD-7. A series of SIR materials were prepared by varying the IL quantity. Sorption of both U(VI) and Pu(IV) were found to increase with increasing IL concentration in SIR up to an optimum IL concentration of 435 mg g−1 of SIR beyond which no effect of IL concentration was observed. A change of mechanism of sorption for U(VI) by SIR was observed in comparison to solvent extraction. The dependency of U(VI) sorption with nitric acid concentration showed a reverse trend compared to solvent extraction studies while for Pu(IV) the trend remained same as observed with solvent extraction. Sorption of both the radionuclides was found to follow pseudo second order mechanism and Langmuir adsorption isotherm. Distribution co-efficient measurements on IL impregnated SIR showed highly selective sorption of U(VI) and Pu(IV) over other trivalent f-elements and fission products from nitric acid medium.

An Poly(vinylidene Fluoride) (PVDF) Membrane Preparation with an Ionic Liquid via Thermally Induced Phase Separation Melt Technology

Poly(vinylidene fluoride) (PVDF)/1-butylpyridinium hexafluorophosphate ([BPy]PF6) flat sheet membranes were successfully prepared via thermally induced phase separation (TIPS) melt technology. The effect of ionic liquid concentration on the morphology, permeability and strength of the fabricated membrane was studied.

Surface-active ionic liquids for palladium-catalysed cross coupling in water: effect of ionic liquid concentration on the catalytically active species.

We report the design and synthesis of surface-active ionic liquids for application in palladium-catalyzed cross coupling reactions. A series of dodecylimidazolium-based ionic liquids were applied as additives in the Heck reaction of ethyl acrylate and iodobenzene, and high yields of >90% could be obtained in water without the addition of further ligands. Our results indicate that the ionic liquid concentration in water is the key factor affecting the formation of the catalytically active species and hence the yield. Moreover, imidazolium-based ionic liquids that are able to form a carbene species differ significantly from conventional cationic surfactants, as a concentration dependent formation of the N-heterocyclic carbene complex was observed.

Ionic liquid as a mobile phase additive in high-performance liquid chromatography for the simultaneous determination of eleven fluorescent whitening agents in paper materials.

In the present study, 11 4,4'-diaminostilbene-2,2'-disulfonic acid based fluorescent whitening agents with different numbers of sulfonic acid groups were separated by using an ionic liquid as a mobile phase additive in high-performance liquid chromatography with fluorescence detection. The effects of ionic liquid concentration, pH of mobile phase B, and composition of mobile phase A on the separation of fluorescent whitening agents were systematically investigated. The ionic liquid tetrabutylammonium tetrafluoroborate is superior to tetrabutylammomnium bromide for the separation of the fluorescent whitening agents. The optimal separation conditions were an ionic liquid concentration at 8 mM and the pH of mobile phase B at 8.5 with methanol as mobile phase A. The established method exhibited low limits of detection (0.04-0.07 ng/mL) and wide linearity ranges (0.30-20ng/mL) with high linear correlation coefficients from 0.9994 to 0.9998. The optimized procedure was applied to analyze target analytes in paper samples with satisfactory results. Eleven target analytes were quantified, and the recoveries of spiked paper samples were in the range of 85-105% with the relative standard deviations from 2.1 to 5.1%. The obtained results indicated that the method was efficient for detection of 11 fluorescent whitening agents.

Permeability of dilute ionic liquid solutions through a nanofiltration membrane – Effect of ionic liquid concentration, filtration pressure and temperature

Abstract Nanofiltration is studied to separate glucose from dilute ionic liquid [emim][OAc]–water solutions. The aim of the research is to evaluate the effect of filtration pressure, temperature and ionic liquid (IL) concentration on the separation of ionic liquid and glucose. This kind of separation challenge can be formed in the regeneration of cellulose fibres in a wet spinning bath. The separation tests are done with an NF270 nanofiltration membrane. The tolerance of the NF membrane in ionic liquid is also estimated. Effective osmotic pressures and viscosity were found to have a major role in the permeability of the membrane when filtration was done at dilute IL solutions. Temperature was found to have a significant effect on the flux due to reduced viscosity at higher temperatures. The flux was increased by about 50% when the temperature increased from 20 °C to 40 °C. The best possible separation factor values were achieved when the feed solution contained 1 wt% [emim][OAc] at 20 °C temperature and the filtration pressure was 6 bars. On the basis of the IL concentration and temperature test series, a good separation window for this kind of solution would be at permeate flux values from 50 L m−2 h−1 to 100 L m−2 h−1. After a test series in concentrations of IL from 0.5 wt% to 10 wt%, the pure water permeability (PWP) was reduced by 23% from the original. The decline of PWP during the temperature tests series was 33%.

Synthesis by an ionic liquid-assisted method and optical properties of nanoflower Y 2O 3

Flower-like Y 2O 3 nano-/microstructured phosphors without metal activators have successfully been fabricated by an ionic liquid (IL)-assisted method involving temperature (600 °C) annealing. In this paper, the effect of IL concentration on the morphology of the product has been investigated. The IL plays a crucial role in the formation of various morphologies of Y 2O 3. The structural and morphological features of the obtained samples have been characterized by means of X-ray powder diffraction (XRD) analysis, photoluminescence spectra (PL), Fourier-transform infrared (FT-IR) spectra and X-ray photoelectron spectra (XPS). The photoluminescence spectra of the products exhibit an intense bluish-white emission (ranging from 405 to 430 nm and centered at 418 nm). The luminescent mechanisms have been ascribed to the carbon impurities in the Y 2O 3 host. The effect of the ILs cation and the counter anions on the Y 2O 3 morphology of these nanostructures was studied experimentally. It was observed that Y 2O 3 morphology and PL of these nanostructures were strongly influenced by the type of cation and anion. As the length of the subsidiary chain of cation section of IL (imidaziole ione) reduces, the thickness of the nano-sheets increases. It is expected that the present method may easily be extended to similar nano-/microstructures of other oxide materials. Such investigations are currently underway.