Effect of Antisolvent Used to Regenerate Cellulose Treated with Ionic Liquid on Its Properties.

The solvolysis reaction with ionic liquids is one of the most frequently used methods for producing nanometer-sized cellulose. In this study, the nanocellulose was obtained by reacting microcrystalline cellulose with 1-ethyl-3-methylimidazolium acetate (EmimOAc). The aim of this research was to determine the influence of various antisolvents used in the regeneration of cellulose after treatment with ionic liquid on its properties. The following antisolvents were used in this research: acetone, acetonitrile, water, ethanol and a mixture of acetone and water in a 1:1 v/v ratio. The nanocellulose was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), dynamic light scattering (DLS), scanning electron microscopy (SEM) and elemental analysis (EA). The results show that the antisolvent used to regenerate cellulose after the solvolysis reaction with EmimOAc affects its properties. Water, ethanol and a mixture of acetone and water successfully removed the used ionic liquid from the cellulose structure, while acetone and acetonitrile were unable to completely remove EmimOAc from the cellulosic material. The results of the XRD analysis indicate that there is a correlation between the ionic liquid content in the regenerated cellulose and its degree of crystallinity. Among the tested solvents, water leads to the effective removal of EmimOAc from the cellulose structure, which is additionally characterized by the smallest particle size and non-formation of agglomerates.

Fabrication of chitosan@activated carbon composites in EmimAc for Cd(II) adsorption from aqueous solution: Experimental, optimization and DFT study.

Adsorption efficiency of a duo-material blend featuring the fabrication of modified chitosan adsorbents (powder (C-emimAc), bead (CB-emimAc) and sponge (CS-emimAc)) for the removal of Cd(II) from aqueous solution was investigated. The chitosan@activated carbon (Ch/AC) blend was developed in a green ionic solvent, 1-ethyl-3-methyl imidazolium acetate (EmimAc) and its characteristics was examined using FTIR, SEM, EDX, BET and TGA. The possible mechanism of interaction between the composites and Cd(II) was also predicted using the density functional theory (DFT) analysis. The interactions of various blend forms (C-emimAc, CB-emimAc and CS-emimAc) with Cd(II) gave better adsorption at pH 6. The composites also present excellent chemical stability in both acidic and basic conditions. The monolayer adsorption capacities obtained (under the condition 20 mg/L [Cd], adsorbent dosage 5 mg, contact time 1 h) for the CB-emimAc (84.75 mg/g) > C-emimAc (72.99 mg/g) > CS-emimAc (55.25 mg/g), as this was supported by their order of increasing BET surface area (CB-emimAc (120.1 m2/g) > C-emimAc (67.4 m2/g) > CS-emimAc (35.3 m2/g)). The feasible adsorption interactions between Cd(II) and Ch/AC occurs through the O-H and N-H groups of the composites, as supported by DFT analysis in which an electrostatic interactions was predicted as the dominant force. The interaction energy (-1309.35 eV) calculated via DFT shows that the Ch/AC with amino (-NH) and hydroxyl (-OH) groups are more effective with four significant electrostatic interactions with the Cd(II) ion. The various form of Ch/AC composites developed in EmimAc possess good adsorption capacity and stability for the adsorption Cd(II).

Study of the Plasticization Effect of 1-Ethyl-3-methylimidazolium Acetate in TPS/PVA Biodegradable Blends Produced by Melt-Mixing.

The first step towards the production and marketing of bioplastics based on renewable and sustainable materials is to know their behavior at a semi-industrial scale. For this reason, in this work, the properties of thermoplastic starch (TPS)/polyvinyl alcohol (PVA) films plasticized by a green solvent, as the 1-ethyl-3-methylimidazolium acetate ([Emim+][Ac-]) ionic liquid, produced by melt-mixing were studied. These blends were prepared with a different content of [Emim+][Ac-] (27.5-42.5 %wt.) as a unique plasticizer. According to the results, this ionic liquid is an excellent plasticizer due to the transformation of the crystalline structure of the starch to an amorphous state, the increase in flexibility, and the drop in Tg, as the [Emim+][Ac-] amount increases. These findings show that the properties of these biomaterials could be modified in the function of [Emim+][Ac-] content in the formulations of TPS, depending on their final use, thus becoming a functional alternative to conventional polymers.

Effect of Low Concentrations of Lithium Chloride Additive on Cellulose-Rich Ultrafiltration Membrane Performance.

Various water treatment processes make extensive use of porous polymeric membranes. A key objective in membrane fabrication is to improve membrane selectivity without sacrificing other properties such as permeability. Herein, LiCl (0-2 wt.%) was utilised as a preforming agent in fabricating biomass-derived cellulosic membranes. The fabricated membranes were characterised by dope solution viscosity, surface and cross-sectional morphology, pure water flux, relative molecular mass cut-off (MWCO, 35 kDa), membrane chemistry, and hydrophilicity. The results demonstrated that at the optimum LiCl concentration (0.4 wt.%), there is an interplay of thermodynamic instability and kinetic effects during membrane formation, wherein the membrane morphology and hydrophilicity can be preferably altered and thus lead to the formation of the membrane with better rejection at no detriment to its permeability.

A caffeic acid electrochemical sensor amplified with GNR/CoFe2O4@NiO and 1-Ethyl-3-methylimidazolium acetate; a new perspective for food analysis.

Determining Caffeic acid is important as an antioxidant compound in food. In this study, caffeic acid (CA) was measured using a carbon paste electrode modified with GNR/CoFe2O4@NiO and 1-Ethyl-3-methylimidazolium acetate (EMIM Ac) as ion liquid. A simple sensor showed a higher current than a bare carbon paste; thus, it can be said that the modified electrode has a higher sensitivity for detecting CA. The linear range of this sensor and its detection limit was equal to 0.01-100.0 µM and 0.01 µM, respectively. Moreover, the developed electrode indicated outstanding selectivity in the presence of several interferences, high sensitivity, reproducibility, and long-term stability. The percentage recovery of CA obtained with the developed sensor affirmed its reliability for CA determination in real samples. The modified sensor's accuracy was confirmed to identify this analyte according to the results.

Wood-Based Cellulose-Rich Ultrafiltration Membranes: Alkaline Coagulation Bath Introduction and Investigation of Its Effect over Membranes' Performance.

In this study, wood-based cellulose-rich membranes were produced with a novel approach to casting procedure. Flat-sheet membranes were prepared from birch biomass pretreated with deep eutectic solvent and dissolved in ionic liquid-dimethylsulfoxide system via phase inversion method. Alkaline coagulation bath filled with sodium hydroxide solution was added to the process before a water coagulation bath and aimed to improve membranes' performance. The effect of NaOH coagulation bath on the membrane was studied based on two NaOH concentrations and two different treatment times. The characterisation methods included measuring pure water permeabilities, polyethylene glycol 35 kDa model solution retentions, hydrophilicity, zeta potential, and chemical structure. Additionally, suitability of the membranes for removing residual phosphorous from a municipal wastewater treatment plant's effluent was studied. The study revealed that introduction of the alkaline coagulation bath led to additional removal of lignin from membrane matrix and increase in the filtration capacity up to eight times. The resulting membranes can be characterised as very hydrophilic, with contact angle values 11.9-18.2°, negatively charged over a wide pH range. The membranes with the highest permeability, 380-450 L/m2·h·bar, showed approximately 70% phosphorus removal from purified wastewater, good removal of suspended solids, and low irreversible fouling tendency.

Green synthesis of acetylated maize starch in different imidazolium carboxylate and choline carboxylate ionic liquids.

This work demonstrates that acetylated maize starches (AMS) with varied degree of substitution (DS, 0.26-2.63) was synthesized in ionic liquids (ILs) (imidazolium chloride, imidazolium carboxylate and choline carboxylate) at 85 °C without catalyst. The DS of AMS and reaction efficiency increased with decreasing alkyl chain length of cations or anions, while decreased as the choline cation replaced the imidazolium cation and the chloride anion replaced the acetate anion. The AMS synthesized in imidazolium-based ILs exhibited much higher hydrophobicity and thermal stability than the native starch. Rheological properties of ILs and ATR-FTIR analysis of acetic anhydride/ILs mixtures indicated that a shorter alkyl side chain or the combination of an imidazolium cation and an acetate anion gave ILs lower viscosities and weaker interactions between acetic anhydride molecules, which favored the acetylation of starch. These findings provide insights into the design of green processes to modify starch and the application of acetylated starch.

Electrodeposition of Copper and Brass Coatings with Olive-Like Structure.

One method of creating a brass coating is through electrodeposition, which is most often completed in cyanide galvanic baths. Due to their toxicity, many investigations focused on the development of more environmentally friendly alternatives. The purpose of the study was to explore a new generation of non-aqueous cyanide-free baths based on 1-ethyl-3-methylimidazolium acetate ionic liquids. The study involved the formation of copper, zinc, and brass coatings. The influence of the bath composition, cathodic current density, and temperature was determined. The obtained coatings were characterized in terms of their morphology, chemical composition, phase composition, roughness, and corrosion resistance. It was found that the structure of the obtained coatings is strongly dependent on the process parameters. The three main structure types observed were as follows: fine-grained, porous, and olive-like. To the best knowledge of the authors, it is the first time the olive-like structure was observed in the case of an electrodeposited coating. The Cu-Zn coatings consisted of 19-96 at. % copper and exhibited relatively good corrosion resistance. A significant improvement of corrosion properties was found in the case of copper and brass coatings with the olive-like structure.

Graphene oxide enhanced ionic liquid plasticisation of chitosan/alginate bionanocomposites.

The effect of graphene oxide (GO) or reduced GO (rGO) on the structure and properties of polyelectrolyte-complexed chitosan/alginate bionanocomposites is highly dependent on plasticiser type (glycerol or 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc])) due to the competing interactions between the components. For the glycerol-plasticised chitosan/alginate matrix, inclusion of GO/rGO enhanced the chitosan crystallinity and increased matrix ductility. While the chitosan/alginate matrix plasticised by [C2mim][OAc] showed dramatically weakened interactions between the two biopolymers, GO was highly effective at counteracting the effect of [C2mim][OAc] by interacting with the biopolymers and the ionic liquid ions, resulting in enhanced mechanical properties and decreased surface hydrophilicity. Compared with GO, rGO was much less effective at promoting chitosan-alginate interactions and even resulted in higher surface hydrophilicity. However, irrespective of the plasticiser type, inclusion of rGO resulted in reduced crystallinity by restricting the interactions between [C2mim][OAc] and the biopolymers, and higher ionic conductivity.

One-pot production of lactic acid from rice straw pretreated with ionic liquid.

Production of platform chemicals has been advocated as a sustainable option to tackle the problems associated with agro-waste management. In this report, for the first time, efforts were made to effectively produce second-generation lactic acid from rice straw pretreated with imidazolium ionic liquid [EMIM][OAc] and subsequently fermented with a promising Lactobacillus plantarum SKL-22 strain saccharified with a commercial cellulase enzyme. Medium optimization was carried out to enhance the lactic acid (LA) yield by response surface methodology. In a 5 L bioreactor, the process was further upscale, and a yield increment of 1.11% was observed. The process using rice straw as substrate led to a LA yield of 36.75 g/L from L. plantarum SKL-22 in a single pot bioprocess. Overall, the above finding has shown the ability of L. plantarum SKL-22 to produce LA from the hydrolysate of rice straw. This study presented a novel environmental-friendly method for LA production.

Regeneration behavior of chitosan from ionic liquid using water and alcohols as anti-solvents.

While ionic liquids (ILs) have been considered as effective and "green" solvents for biopolymer processing, regeneration of IL-dissolved biopolymers could largely impact biopolymer structure and properties. This study indicates that the reconstitution of chitosan structure during regeneration from 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) depends on anti-solvent (water, methanol or ethanol) largely. Irrespective of anti-solvent, the chitosan chemical structure was not varied by dissolution or regeneration. With water, the regenerated chitosan had the highest crystallinity index of 54.18%, followed by those with methanol (35.07%) and ethanol (25.65%). Water as an anti-solvent could promote chitosan chain rearrangement, leading to the formation of an ordered aggregated structure and crystallites. Density functional theory (DFT) simulation indicates that the number of hydrogen bonds formed between anti-solvents and [Emim][OAc] was in the order of water > methanol > ethanol. With water used for regeneration, the aggregation and rearrangement of chitosan chains occurred more easily.

Comparative study on phase transition and morphology of starch from maize and potato in ionic liquid/water mixtures: Effects of the different ratio.

"Green" solvent ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([Emim]Ac) was used as a solvent for maize starch (MS) and potato starch (PS). Different scanning calorimetry (DSC), microscopy, rapid visco analysis, X-ray diffractometry and scanning electron microscopy were carried out to systematically investigate the phase transition, viscosity, crystalline structure and morphology of the two typical starches. The effect of [Emim]Ac/H2O ratio on the behaviors of starch was explored and the difference between native MS and PS in [Emim]Ac/H2O mixtures was compared. The effects of IL were closely related to the starch source and structure. With the increase of [Emim]Ac/H2O ratio, the gelatinization and dissolution of starch occurred competitively and synergistically. DSC results demonstrated that the transition of starch was from a single endotherm to an exotherm/endotherm, and then to a single exotherm with the increase of IL. The gelatinization temperature of MS was as low as 44.4 °C in IL/H2O mixture, which provided a wonderful solvent for MS. RVA, microscopy, XRD and SEM results provided forceful evidence for the effect of [Emim]Ac. This study provided experimental supports and theoretical foundation for understanding the starch behaviors in "green" solvents and expanding industrial applications of starch-based degradable materials in more appropriate solvents.

Electroconductive starch/multi-walled carbon nanotube films plasticized by 1-ethyl-3-methylimidazolium acetate.

Starch/multi-walled carbon nanotube (MWCNT) films were prepared by casting using an ionic liquid (1-ethyl-3-methylimidazolium acetate, [emim+][Ac-]) as plasticizer for the first time. The effect of the MWCNT content (0.25-5 wt.%, with respect to the sum of starch and plasticizer mass) on thermal, mechanical and electroconductive behavior of the films was studied. Films containing 0.5 wt.% MWCNT showed increases of 327 % in maximum tensile strength, 2484 % in Young's modulus and 82 % in elongation at break. The significant improvements are explained by the good MWCNT dispersion in the matrix and by the effect of [emim+][Ac-] as an efficient plasticizer, which leads to higher extensibility. The MWCNT/[emim+][Ac-] combination have a synergistic effect on film electrical conductivity, increasing a 130% (3 wt.% MWCNT). These films, easily prepared by a "green" process, have potential applications in the packaging industry but also in the field of lithium batteries, fuel cells and dye-sensitized solar cells.

Comparative study on properties of starch films obtained from potato, corn and wheat using 1-ethyl-3-methylimidazolium acetate as plasticizer.

Starch films are gaining attention as substitutes of synthetic polymers due to their biodegradability and low cost. Some ionic liquids have been postulated as alternatives to glycerol, one of the best starch plasticizers, due to their great capacity to form hydrogen bonds with starch and hence great ability of preventing starch retrogradation and increasing film stability. In this work, [emim+][Ac-]-plasticized starch films were prepared from potato, corn and wheat starch. The effect of starch molecular structure in terms of granular composition (amylose and phosphate monoester contents) and molecular weight (Mw) on film properties was evaluated. Potato starch films were the most amorphous because of the higher Mw and phosphate monoester content of potato starch, both contributing to a lower rearrangement of the starch chains making the crystallization process difficult. In contrast, corn and wheat starches lead to more crystalline films because of their lower Mw, which may imply higher mobility and crystal growth rate, and lower phosphate monoester content. This more crystalline structure could be the responsible of their better mechanical properties. [emim+][Ac-] can be considered suitable for manufacturing starch films showing corn and wheat starch films similar properties to synthetic low-density polyethylene, but involving a simple and environmentally-friendly process.

Smart Collagen Hydrogels Based on 1-Ethyl-3-methylimidazolium Acetate and Microbial Transglutaminase for Potential Applications in Tissue Engineering and Cancer Therapy.

For the first time, collagen-based hydrogels were fabricated in the presence of a biocompatible ionic liquid, 1-ethyl-3-methylimidazolium acetate ([EMIM] [Ac]), by a simple biopolymer cross-linking process facilitated by the strong catalytic hydrolysis of microbial transglutaminase (MTGase). Phosphate buffer solution (PBS)-encapsulated human-like collagen (HLC) or fish bone collagen (FBC) for the composite hydrogels was simply prepared by the codissolution of biopolymers in [EMIM] [Ac] or, in the absence of the ionic liquid, by the dispersion of MTGase in the biopolymer solution, leading to the formation of MTGase-aided hydrogels (Gel1 and Gel4) and [EMIM] [Ac]/MTGase-aided hydrogels (Gel2, Gel3, and Gel5). The effects of different contents of [EMIM] [Ac] and collagens of different origins (HLC and FBC) during fabrication on a range of structural and material characteristics, including the synthesis mechanism, three-dimensional structure, swelling behavior, mechanical strength, enzymatic hydrolysis rate, cytotoxicity, fibroblast cell proliferation rate, in vitro inhibition of cancer cells and cell adhesion, and in vivo histocompatibility, were investigated. Surprisingly, fabrication with [EMIM] [Ac] had significant effects on the structure and properties of the collagen/MTGase-based hydrogels. In other words, [EMIM] [Ac] changed the underlying mechanism responsible for the advantageous properties of the hydrogels by changing the three-dimensional structure of HLC or FBC, which improved their effects on fibroblast proliferation (3T3-L1 and L929 cells) and their in vitro inhibition of cancer cells (HepG2 and MKN45 cells). The use of the ionic liquid also imbued the hydrogels with degradation resistance and anti-inflammatory properties after subcutaneous injection into mice (in vivo). The catalytic hydrolysis by MTGase and the [EMIM] [Ac] content were the major factors that influenced the properties of the collagen. This result suggests the potential application of ionic liquid-enzymatic hydrolysis in the fabrication of collagen hydrogels in circumstances where the control of the properties by an ionic liquid is desirable. Therefore, [EMIM] [Ac] could be a promising solvent for the development of collagen into smart biomaterials with controlled biodegradation rates that can meet the needs of specific potential applications, such as tissue engineering and cancer therapy.

Effect of anti-solvents on the characteristics of regenerated cellulose from 1-ethyl-3-methylimidazolium acetate ionic liquid.

This work investigates the effect of different anti-solvents (water, ethanol, or both water and ethanol) on the characteristics of cellulose dissolved and then generated from 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]). Compared with original microcrystalline cellulose (MCC) granules, all regenerated celluloses showed a homogeneous, agglomerated macromorphology and had its crystalline structure transformed from original cellulose I to cellulose II. The regenerated cellulose using water (43.3%) had a higher degree of crystallinity than that using ethanol (13.5%), and a degree of crystallinity of 21.3% was obtained when an ethanol-water-ethanol treatment method was used. SAXS and FTIR results indicate that water as an anti-solvent could promote the rearrangement of cellulose molecular chains and the rebuilding of an ordered aggregated structure. Moreover, the regenerated cellulose with water showed better thermal stability than that of the samples regenerated using ethanol. Thus, our results suggest that the reconstitution of cellulose molecules during regeneration with various anti-solvents can affect the multiscale structures and properties of cellulose.

Enzymatic hydrolysis of ionic liquid-extracted chitin.

Chitin, one of Nature's most abundant biopolymers, can be obtained by either traditional chemical pulping or by extraction using the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate. The IL extraction and coagulation process provides access to a unique chitin, with an open hydrated gel-like structure. Here, enzymatic hydrolysis of this chitin hydrogel, dried shrimp shell, chitin extracted from shrimp shells using IL and then dried, and commercial chitin was carried out using chitinase from Streptomyces griseus. The enzymatic hydrolysis of shrimp shells resulted only in the monomer N-acetylglucosamine, while much higher amounts of the dimer (N,N'-diacetylchitobiose) compared to the monomer were detected when using all forms of 'pure' chitin. Interestingly, small amounts of the trimer (N,N',N''-triacetylchitotriose) were also detected when the IL-chitin hydrogel was used as substrate. Altogether, our findings indicate that the product distribution and yield are highly dependent on the substrate selected for the reaction and its hydrated state.

Scaling-Up Ionic Liquid-Based Technologies: How Much Do We Care About Their Toxicity? Prima Facie Information on 1-Ethyl-3-Methylimidazolium Acetate.

The potential of the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) to dissolve a variety of biopolymers such as cellulose and chitin, makes it an attractive candidate for scaled-up industrial utilization. In fact, the first steps towards its use at industrial scale have been taken. This increases the urgency to fill the knowledge gaps in its toxicity and environmental impact in order to predict and control its environmental fate. In this mini-review, we discuss the available literature surrounding this key IL. The literature (through the analysis of toxicity of the anion and the cation separately) suggests that [C2mim][OAc] is a relatively safe choice for industrial applications. However, because the IL should be considered as a compound, with unique properties arising from the interactions between the ions, comprehensive toxicity information for this particular IL is still required. To decide, prima facie, if this IL is toxic or not, evaluation of its influence on human health and ecotoxicity is needed prior to its large scale utilization. We chose in this mini-review to focus on toxicity surrounding this IL and evaluate what is known and what is not. Here with all the information in hand, we hope that the urgent need for [C2mim][OAc] toxicological assessment before it can be used in numerous technologies is highlighted. In the near future, we expect that the assessment of toxicity and environmental fate and impact can be integrated directly into any research into the industrial utilization of this IL and any others contemplated for industrial application.

1-Ethyl-3-methylimidazolium tolerance and intracellular lipid accumulation of 38 oleaginous yeast species.

Pretreatment with ionic liquids (IL) such as 1-ethyl-3-methylimidazolium chloride or acetate is an effective method for aiding deconstruction of lignocellulosic biomass; however, the residual IL remaining in hydrolysates can be inhibitory to growth of ethanologenic or oleaginous yeasts that have been examined in the literature. The aim of this study was to identify oleaginous yeasts that are tolerant of the IL [C2C1Im][OAc] and [C2C1Im]Cl using 45 strains belonging to 38 taxonomically diverse species within phyla Ascomycota and Basidiomycota. Yeasts were cultivated in laboratory medium supplemented with 0, 2, or 4% IL in 96-well plates. The eight most tolerant strains were then cultivated in 10-mL media with no IL, 242mM [C2C1Im][OAc], or 242mM [C2C1Im]Cl. The effects of [C2C1Im]+ exposure on cell mass production and lipid accumulation varied at the species and strain level. The acetate salt decreased cell biomass and lipid production more severely than did the chloride ion for six strains. Lipid output was not markedly different (2.1 vs. 2.3 g/L) in Yarrowia lipolytica UCDFST 51-30, but decreased from 5 to 65% in other yeasts. An equimolar concentration of the chloride salt resulted in much milder effects, from 25% decrease to 66% increase in lipid output. The highest lipid outputs in this media were 8.3 and 7.9 g/L produced by Vanrija humicola UCDFST 10-1004 and UCDFST 12-717, respectively. These results demonstrated substantial lipid production in the presence of [C2C1Im]Cl at concentrations found in lignocellulosic hydrolysates, and thus, these two strains are ideal candidates for further investigation.

Nanostructured cellulose-xyloglucan blends via ionic liquid/water processing.

In this work, the properties of cellulose (CE)/xyloglucan (XG) biopolymer blends are investigated, taking inspiration from the outstanding mechanical properties of plant cell walls. CE and XG were first co-solubilized in an ionic liquid, 1-ethyl-3-methylimidazolium acetate, in order to blend these biopolymers with a varying CE:XG ratio. The biopolymers were then regenerated together using water to produce solid blends in the form of films. Water-soluble XG persisted in the films following regeneration in water, indicating an attractive interaction between the CE and XG. The final CE:XG ratio of the blends was close to the initial value in solutions, further suggesting that intimate mixing takes place between CE and XG. The resulting CE/XG films were found to be free of ionic liquid, transparent and with no evidence of phase separation at the micron scale. The mechanical properties of the blend with a CE:XG ratio close to one revealed a synergistic effect for which a maximum in the elongation and stress at break was observed in combination with a high elastic modulus. Atomic force microscopy indicates a co-continuous nanostructure for this composition. It is proposed that the non-monotonous variation of the mechanical performance of the films with XG content is due to this observed nanostructuration.