Ionic Liquid Treatment Research Articles

Repeated Utilization of Ionic Liquid to Extract Lipid from Algal Biomass

In this work, different kinds of ionic liquids and reaction conditions for the extraction of lipid from microalgae biomass were optimized and repeated use of ionic liquids for microalgal lipid extraction was evaluated. Morphological changes of microalgae cells were compared in terms of pre- and post-treatment to understand the mechanisms of ionic liquid treatment. Ionic liquid [BMIM][MeSO4] showed the best lipid extraction efficiency at 70°C and with reaction time of 2 hours. The ratios (ILs : methanol) of 1 : 7 and 1 : 3 were the optimum ratios to complete the extraction of the lipids from microalgae. The initial 50% volume fraction of [BMIM][MeSO4] was 16.04% of dry weight, which showed the highest five average extraction rates. The loss of ionic liquid in the reaction system and the increase in water content of ionic liquids were considered as the main reasons for the decrease in the extraction rate. It is suggested that the potential of lipid extraction in this IL-methanol co-solvent system is promising due to the high efficiency, low cost, safety, environmental protection, and other characteristics.

A NOVEL THIN FILM COMPOSITE REVERSE OSMOSIS MEMBRANE MODIFIED BY IONIC LIQUID

ABSTRACT Thin Film Composite Reverse Osmosis (TFC RO) membranes have undergone significant changes since inception; particularly the top polyamide layer has been tuned for optimal performance. The present paper demonstrates the novel approach to alter the polyamide membrane performance by subjecting it to ionic liquids. Ionic liquids 1-Butyl-3-Methylimidazolium Chloride [BMIM][Cl], 1-Methyl-3-Octylimidazolium Chloride [C8MIM][Cl] and 1-Butyl-3-Methylimidazolium Bromide [BMIM][Br] were used to alter the membrane performance. About a 6.5% increase in MgSO4 rejection and about an 87% increase in water-flux were noted when the membrane was subjected to 3000 mg/L [BMIM][Cl] after 2000 mg/L sodium hypochlorite each for 2 hours. Also, the decline in contact angle from 52.86o to 43.12o by this treatment demonstrated higher hydrophilicity. Atomic force microscope images showed a decline in surface roughness with the treatment. Scanning electron micrographs were taken to understand the changes in morphology of thin film composite reverse osmosis membranes with ionic liquid treatment. Attenuated total reflectance, infrared spectroscopy and nuclear magnetic resonance analysis were done to evaluate the changes in chemical structure and it was found that the treatment resulted in chemical structural modification of thin film composite reverse osmosis membranes with ionic liquid treatment.

Behavior of oxygen-containing groups in grass lignin during dissolution in basic ionic liquids

Three basic ionic liquids(BILs), 1-amyl-3methylimidazolium acetate (C5mim][Ac]), 1-butyl-3methylimidazolium acetate ([Bmim][Ac]) and 1-ethyl-3-methylimidazolium acetate ([Emim][Ac]), have been applied for the dissolution of lignin from wheat grass under microwave conditions with the decreased alkalinity order of [Emim][Ac]>[Bmim][Ac]>[C5mim][Ac]. Also the behavior of oxygen-containing groups within lignin in the dissolution of ionic liquids was investigated by elemental analysis, analytical pyrolysis, 2D-HSQC spectra, GPC, TG and FTIR analysis. Results revealed that [Emim][Ac] showed a higher dissolution capacity (≥ 330 g/kg) at 80°C within 30 min under microwave condition with higher alkalinity. In the process of dissolution, ionic liquids mainly attack the oxygen-containing groups and the aryl ether bond in the lignin side chain. The methoxy content reduction, the cleavage of β-O-4’ linkages and the degradation of β–β linkages obviously happened in the dissolution process, resulting in the decrease of the molecular weights. Ionic liquids treatment selectively degraded the G-type lignin fragments with demethoxylation and dehydration reactions occurring during dissolution. The results also indicate that the shorter the alkyl chain of the ionic liquids, the stronger the alkalinity is, the more destructive the oxygen-containing groups in the lignin side chain.

Surface wettability of supercritical CO2 - ionic liquid processed aromatic polyamides

Abstract Wettability of aromatic polyamides (aramids) was investigated after exposed to the binary system of 1-Butyl-3-methylimidazolium hexafluorophosphate and supercritical CO2, which was performed at a pressure of 30 MPa for 60 min by varying the treatment temperature between 80 °C and 120 °C. Dynamic contact angle analysis for the original and treated aramids was conducted to determine the correlation between the surface treatment and the polymer wettability. It is confirmed that the water contact angles for aramids were reduced significantly from 139.8° to 83.0° in the supercritical CO2-ionic liquid systems, and the hydrogen bonding structure between the amide linkages in aramids and the PF¯6 in [BMIM][PF6] was proved to form, which is conducive to the improvement of wettability. SEM observations revealed more and more pleat-like wrinkles appeared on the surface of aramid, accompanied by the notable fiber swelling in the supercritical CO2-ionic liquid systems. In addition, XRD and TG analysis indicated that the crystallinity and the maximum decomposition temperatures of aramids were decreased gradually with ionic liquid treatment while those of aramids were increased with the temperature rising by adding ionic liquid in supercritical CO2. Overall, this proves to be an more effective and ecofriendly approach for aramid modification by supercritical CO2-ionic liquid systems.

Recyclable One-Step Extraction and Characterization of Intact Melanin from Alpaca Fibers

Melanin, a ubiquitous natural pigment, has attracted much attention in energy and nanotechnology areas in recent years. With the increasing demand for high-quality melanin materials and sustainable experimental environment, this study was conducted to achieve melanin with intact structure through recyclable extraction method using ionic liquid (IL). Melanin extracted from base dissolution and acid isolation (BA) method and acid hydrolysis (AH) method were also used for comparison. SEM and 13C-NMR characterizations indicated that IL treatment has retained the original structure of melanin while other methods caused particle damage to various degrees. In addition, the recycled IL (up to five times) showed good reproducibility, and the performance of extracted melanin at the 5th cycle was well-maintained.

Extraction of lignin, structural characterization and bioconversion of sugarcane bagasse after ionic liquid assisted pretreatment.

The primary focus of this work was to recover lignin and investigate the structural changes in sugarcane bagasse after pretreatment with ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM]oAc). 90% lignin recovery was achieved while bagasse was treated with [EMIM]oAc at 140°C, 120min reaction time and 1:20 bagasse to the ionic liquid ratio (w/w). The impact of ionic liquid pretreatment on bagasse was confirmed by qualitative analysis of untreated and pretreated bagasse. Scanning electron microscopy analysis exhibited the porous and irregular structure of bagasse after pretreatment. X-ray powder diffraction analysis verified a decrease in crystallinity as a result of the pretreatment process by showing a 14.7% reduction of Crystallinity index after ionic liquid treatment. The efficacy of [EMIM]oAc on bagasse treatment was also examined by enzymatic hydrolysis which manifested an increase in reducing sugar yield as a result of pretreatment. Maximum yield of 54.3% reducing sugar was obtained after 72h enzymatic hydrolysis of pretreated bagasse. Recovered lignin was analyzed qualitatively. 1D NMR spectroscopy of lignin revealed the presence of essential functional groups whereas 2D NMR spectroscopy showed the dominance of etherified syringyl unit. Further ionic liquid recovery and reuse were substantiated by Gel permeation chromatography analysis of lignin. Weight average molecular weight (Mw) of lignin extracted by fresh [EMIM]oAc was obtained as 1769g/mol (in the previous study) while lignin recovered by recycled [EMIM]oAc showed almost equal Mw 1765g/mol in this study. Thus, the current investigation corroborated satisfactory performance of [EMIM]oAc in lignocellulose processing which further enhanced enzymatic hydrolysis in the subsequent step.

Wettability of coal by room temperature ionic liquids

ABSTRACT The wettability of room temperature ionic liquids (ILs) on coal structure was studied by measuring contact angle, water-retaining property, and FTIR spectra. The eight ILs utilized were [EMIm][BF4], [EMIm][NTf2], [PMIm][BF4], [BMIm][BF4], [HOEtMIm][BF4], [HOEtMIm][NTf2], [P4,4,4,1][MeSO4] and [P4,4,4,2][DEP]. The contact angle results showed that compared with distilled water, the contact angles of ILs decreased, indicating good wetting effect. However, different ILs showed different wetting effects. Among of them, the [HOEtMIm][NTf2] had the best wetting effect, the [P4,4,4,2][DEP] and [P4,4,4,1][MeSO4] were in the second place, and the worst one was [HOEtMIm][BF4]. The water-retaining experiments showed that the evaporation rate of coal containing ILs was slower and the water-retaining time was longer, indicating that the coal containing ILs had stronger resistance to moisture evaporation. The water-retaining property of [EMIm][BF4] was the best. The FTIR experiments showed that the main structure of coal was not changed but some structures changed by ILs treatment. The significant changes were the aliphatic hydrogen groups (1435 and 1371 cm−1), the C-O bond (1300–1000 cm−1) and the mineral structures (1032 and 472 cm−1). This study will provide a new development platform for the ILs used for coal dust prevention.

The effect of chemical modification of wood in ionic liquids on the supermolecular structure and mechanical properties of wood/polypropylene composites

Effects of chemical modification of wood with innovative ionic liquid on the supermolecular and morphology of wood/polypropylene composites were investigated using X-ray diffraction, hot stage optical microscopy, and differential scanning calorimetry. For the first time the chemical treatment of wood was conducted solely with newly synthesized ionic liquid, didecyldimethylammonium bis(trifluoromethylsulfonyl)imide. The modification was found to be responsible for significant changes in nucleating abilities of wood in polypropylene matrix. These findings were confirmed by crystallization temperature, crystal conversion, crystallization half-time parameters, as well as observation of transcrystalline structures. Ionic liquid treatment of wood influenced also formation of polymorphic forms of polymer matrix. In contrast to composites with untreated wood, in composites with modified wood filler formation of β-phase of polypropylene was observed. This fact was discussed in view of differences in nucleating activity of lignocellulosic filler, resulting from chemical treatment with ionic liquid. Moreover, a relationship between mechanical properties of composites and the phenomena taking place at the polymer-filler interface, controlled by chemical modifications of lignocellulosic components, was evaluated.

Enhancement of Electrical Conductivity of Polyethylene Terephthalate (PET) Fabrics via Ionic Liquids

ABSTRACTIn this study, polyethylene terephtalate (PET) fabrics were treated with two types of ionic liquids, 1-ethyl-2,3-dimethylimidazolium ethyl sulfate (EIL) and methyl-tri-n-butylammonium methyl sulfate (BIL), resulting in noticeably better long-term electrical conductivity of treated PET fabrics. Thermal conductivity, thermal stability, surface morphology and chemical structure were also explored. The effects of concentration of EIL (2, 6, 10 w/v %) and BIL (10, 15, 20 w/v %) ionic liquids were discussed. With the given set up, surface resistivities of the PET fabrics decreased with treatment application of the ionic liquids. Besides, BIL treatment provided higher electrical conductivity as compared with EIL. Moreover, surface resistivity presented diminishing tendency with increasing the concentration. It is also found that thermal degradation temperatures of the PET fabrics decreased with ionic liquids treatment. A coating layer was observable on surface of the fabric and in the gaps of the yarns with the ionic liquids treatment. This work provided a novel method for obtaining enhanced electrically conductive PET fabrics for textile industry.

Effect of annealing treatment on crystalline and dielectric properties of PVDF/PEG-containing ionic liquid composites

To investigate the effect of poly(ethylene glycol)-containing ionic liquid (IL) and thermal annealing treatment on crystallization and dielectric relaxation behavior of poly(vinylidene fluoride) (PVDF), a series of PVDF/IL composites have been prepared using a solution-cast method. The interaction between imidazolium cation of ILs and >CF2 groups of PVDF can transfer nonpolar α phase to polar β and γ phase as a template at the primary crystallization, and then the interaction between PEG of ILs and >CF2 groups of PVDF can facilitate the PVDF chains in amorphous region to bring more polar phase and decrease the degree of crystallization for PVDF composites according to the template under thermal annealing treatment. The experimental dielectric data were analyzed within the formalisms of complex permittivity and electric modulus. In the frequency spectra of PVDF composites, dc conductivity, electrode and Maxwell-Wagner-Sillars (MWS) interfacial polarization resulted in high values of dielectric permittivity. The incorporation of ILs into the matrix and thermal annealing treatment can accelerate dc conductivity. The temperature dependence of relaxation time of dc conductivity follows the Arrhenius equation. The effect of annealing treatment on charge carrier movement mechanism was resulted from the increase of ion mobility induced by polymer chain segmental motion and polar phase crystals.

Influence of imidazolium-based ionic liquids on coal oxidation

In order to find the ionic liquids (ILs) which can significantly suppress coal oxidation, nine imidazolium-based ILs, [EMIm][BF4], [EMIm]Ac, [BMIm][BF4], [BMIm]Ac, [AMIm][BF4], [HOEtMIm][BF4], [HOEtMIm][NTf2], [AOEMIm][BF4] and [EOMIm][BF4], were used to treat lignite sample to reveal the inhibitory effect of ILs on coal oxidation activity. The TGA results showed that the ILs can reduce the mass loss of coal, of which the ILs [HOEtMIm][BF4] and [HOEtMIm][NTf2] showed the strongest reducing effect, while the IL [AMIm][BF4] showed the weakest reducing effect. Differential thermal analysis (DTA) results indicated that the heat release of [HOEtMIm][BF4] and [HOEtMIm][NTf2]-treated coal were very less. At the same time, the oxidation reactions of the two coals were delayed. IR results showed that ILs treatment can effectively destroy the associated hydroxyl in coal and change the content of carbonyl and ether bonds. In the process of coal oxidation, the oxidation activity of hydrogen bonding, ether bonds in [HOEtMIm][BF4] and [HOEtMIm][NTf2]-treated coal were weakened significantly at the initial oxidation process. With the oxidation processing, the content of generated carbonyl was reduced. The micro mechanism of the reduced coal oxidation activity was ascribed to the weaker oxidation activity of the ether bonds and the inhibited formation of the carbonyl groups.

Preparation and structural characterization of lignin micro/nano-particles with ionic liquid treatment by self-assembly

Preparation and structural characterization of lignin micro/nano-particles with ionic liquid treatment by self-assembly

Effects of imidazolium-based ionic liquids with different anions on wheat seedlings

The effects of five imidazolium ionic liquids with different anions were studied in hydroponically grown wheat seedlings at concentrations of 50, 100, 150, 200, 250, and 300 mg L−1. The results showed that shoots and roots grew shorter and dry weight decreased with increasing concentrations of ionic liquids. Moreover, the antioxidant enzyme activities decreased and malondialdehyde (MDA) content was greater in the leaves of wheat seedlings subjected to ionic liquid (IL) treatments. The order of influence of ionic liquids on these indexes was [C4mim][TfO]> [C4mim][Cl]> [C4mim][BF4]> [C4mim][Lact]> [C4mim][Ala]. A transmission electron microscope (TEM) was used to observe leaf and root cellular structures, such as chloroplast, nucleus, mitochondria, and rough endoplasmic reticulum, in wheat exposed to ionic liquids at a concentration of 150 mg L−1. The results showed that the cellular structures of wheat were affected, and the degree of the effect of five ILs was consistent with the general trend of the measured indexes in this study. Ionic liquids influence the growth of plants by impeding growth, disrupting metabolic physiology and changing cellular structures. The degree of toxicity of imidazolium-based ionic liquids with different anions varies.

Screening of glycoside hydrolases and ionic liquids for fibre modification

AbstractBACKGROUNDThis study elaborates the possibility to apply combined ionic liquid (IL) and enzyme treatments for pulp fibre modification. The approach involves swelling of fibre surfaces with IL followed by enzymatic modification of the disrupted fibre surface using carbohydrate active enzymes.RESULTSThe capacity of seven cellulose‐dissolving or cellulose‐swelling ionic liquids to swell pulp fibres was compared. In addition, thirteen cellulases and five xylanases were screened for their IL tolerance, which determines their applicability in combined or sequential IL–enzyme treatments of fibres. Among the studied ionic liquids, 1‐ethyl‐3‐methylimidazolium dimethylphosphate ([EMIM]DMP) and 1,3‐dimethylimidazolium dimethylphosphate ([DMIM]DMP) had the strongest effect on fibre swelling. These solvents were also found to be the least inactivating for the studied enzymes.CONCLUSIONEnzyme compatibility and cellulose‐dissolving capability are not two conflicting properties of an ionic liquid. © 2017 Society of Chemical Industry

Switchable ionic liquids enable efficient nanofibrillation of wood pulp

Use of switchable ionic liquid (SIL) pulp offers an efficient and greener technology to produce nanofibers via ultrafine grinding. In this study, we demonstrate that SIL pulp opens up a mechanically efficient route to the nanofibrillation of wood pulp, thus providing both a low cost and chemically benign route to the production of cellulose nanofibers. The degree of fibrillation during the process was evaluated by viscosity and optical microscopy of SIL treated, bleached SIL treated and a reference pulp. Furthermore, films were prepared from the fibrillated material for characterization and tensile testing. It was observed that substantially improved mechanical properties were attained as a result of the grinding process, thus signifying nanofibrillation. Both SIL treated and bleached SIL treated pulps were fibrillated into nanofibers with fiber diameters below 15 nm thus forming networks of hydrophilic nature with an intact crystalline structure. Notably, it was found that the SIL pulp could be fibrillated more efficiently than traditional pulp since nanofibers could be produced with more than 30% less energy when compared to the reference pulp. Additionally, bleaching reduced the energy demand by further 16%. The study demonstrated that this switchable ionic liquid treatment has considerable potential in the commercial production of nanofibers due to the increased efficiency in fibrillation.

Ionic liquid treatment for increasing the wet strength of cellulose paper

In this study, ionic liquid treatment for increasing the wet strength of cellulose paper was studied. The effects of treatment conditions with the ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) on the wet strength were investigated. First, the [BMIM]Cl (20 g) was melted at 80–100 °C and the paper was immersed in it for 5–60 s. Next, the paper was immersed in ethanol, and finally, it was washed with distilled water. The paper was dried in a hot press at 110 °C and 1.1 MPa for 5 min. The [BMIM]Cl treatment improved the wet strength of the paper. Disintegration of the papers was investigated by immersing them in distilled water, and the paper treated with [BMIM]Cl did not disintegrate. The minimum treatment time required for improvement of the wet strength of the paper was only 5 s. Excess [BMIM]Cl from the original treatment was recovered by vacuum distillation and dehydration was used to treat new paper. This recovered [BMIM]Cl enhanced the wet strength to a level similar to that obtained with the virgin [BMIM]Cl. Therefore, the [BMIM]Cl can be efficiently re-used in this method. The paper treated with [BMIM]Cl will be composed completely of cellulose. Therefore, this method is a viable alternative to treatment by adding chemical such as a polyamideamine epichlorohydrin (PAE).

Thermal and mechanical properties of chitosan nanocomposites with cellulose modified in ionic liquids

In this paper, ionic liquid treatment was applied to produce nanometric cellulose particles of two polymorphic forms. A complex characterization of nanofillers including wide-angle X-ray scattering, Fourier transform infrared spectroscopy, and particle size determination was performed. The evaluated ionic liquid treatment was effective in terms of nanocrystalline cellulose production, leaving chemical and supermolecular structure of the materials intact. However, nanocrystalline cellulose II was found to be more prone to ionic liquid hydrolysis leading to formation larger amount of small particles. Each nanocrystalline cellulose was subsequently mixed with a solution of chitosan, so that composite films containing 1, 3, and 5% mass/mass of nanometric filler were obtained. Reference samples of chitosan and chitosan with micrometric celluloses were also solvent casted. Thermal, mechanical, and morphological properties of films were tested and correlated with properties of filler used. The results of both, tensile tests and thermogravimetric analysis showed a significant discrepancy between composites filled with nanocrystalline cellulose I and nanocrystalline cellulose II.

An ionic liquid treatment and fractionation of cellulose, hemicellulose and lignin from oil palm empty fruit bunch

This work reports on a complete isolation and characterization of lignocellulosic compounds from oil palm empty fruit bunch (OPEFB) by ionic liquid (IL) treatment and alkaline treatment processes. The fractionated lignocellulosic compounds were confirmed by FTIR and CP/MAS 13CNMR analyses. The yield of the cellulose, hemicellulose and lignin fractions was 52.72±1.50% wt., 27.17±1.68% wt. and 16.82±1.15% wt. with molecular weight of 1869g/mol, 1736g/mol and 2695g/mol, and degradation temperature of 325.65°C, 236.25°C, and 201.40°C, respectively. The SEM image illustrates the bundle-like fiber of cellulose fraction and smaller particle size of hemicellulose and lignin fractions with inconsistent shape. The XRD patterns depict the crystalline cellulose, amorphous lignin and partially amorphous hemicellulose fractions property. The IL could be recovered and reused with an overall recovery of 48% wt. after the fourth cycle.

Preparation of high purity silica originated from rice husks by chemically removing metallic impurities

Abstract Chemical treatments were used to synthesize high-purity silica from rice husk. A comparative study was carried out by using four chemicals: sulfuric acid, hydrogen chloride, oxalic acid, and ionic liquid (1-butyl-3-methylimidazolium hydrogen sulfate). The ash content significantly increased in sulfuric-acid and the ionic liquid treatments with the removal of both cellulose and hemicellulose. Drastic increases of silica purity were observed in samples treated with sulfuric acid and the ionic liquid at 99.6% and 99.5%, respectively. Furthermore, the ionic liquid treatment increased the surface area and pore volume by 1.9 times and 2.4 times, respectively, with respect to the sample not subjected to chemical treatment.

Ultrasonic-assisted ionic liquid treatment of chemithermomechanical pulp fibers

Enhancing the swelling of chemithermomechanical pulp is essential for improving its physical properties and thus broadening its end-use applications. In this work, ionic liquid (IL) using 1-allyl-3-metheylimidazolium chloride ([Amim]Cl) was used for reducing hydrogen bonding within the fiber wall, and ultrasonic treatment was used for improving the performance of IL treatment. Mixing IL with pulp fibers at 5 ml/g concentration decreased the Canadian standard freeness (CSF) of pulp from 760 to 570 ml at room temperature, and the pretreatment with ultrasonic treatment for 20 min reduced its CSF to 545 ml. The ultrasonic-assisted IL treatment improved the tensile, tear and burst indices as well as the folding endurance of the cellulosic network by 41, 36, 12 and 150%, respectively. The surface charge density and area of fibers were improved, but the lignin and hemicellulose contents of the fibers were reduced via ultrasonic-assisted IL treatment.