Choline Chloride-oxalic Acid Research Articles

One-pot levulinic acid production from rice straw by acid hydrolysis in deep eutectic solvent

Levulinic acid is a useful chemical platform derived from lignocellulose, which is applied in many applications such as solvents, fuels and pharmaceuticals. The natural structure of lignocellulose is recalcitrant to access cellulose and upgrade to levulinic acid. Here we showed that a combination of rice straw dissolution in carboxylic acid-based deep eutectic solvent (DES) and acid hydrolysis enabled rice straw conversion into levulinic acid. Among carboxylic acid-based DESs (choline chloride-acetic acid, choline chloride-oxalic acid, choline chloride-malonic acid and choline chloride-succinic acid), choline chloride-Oxalic acid DES potentially dissolved rice straw (100 °C for 2 h) and converted the dissolved cellulose to levulinic acid (52%) by HCl at mild condition (120 °C at 10 h and atmospheric pressure). Our approach is superior to conventional processes for levulinic acid production, such as no separation of intermediates (glucose and HMF), mild condition and inexpensive DES cost, making the one-pot process efficient and economically.

Natural deep eutectic solvent-based microwave-assisted extraction in the medicinal herb sample preparation and elemental determination by ICP OES

In this study, a microwave-assisted extraction (MAE) method based on the natural deep eutectic solvent (NADES) was developed for the Cd, Cu, Fe, Mn, and Zn determination in medicinal herb samples. The experimental conditions were optimized and the method parameters were evaluated using certified reference material. The NADES composed of choline chloride-oxalic acid prepared in a microwave system showed better extraction rates and low-energy consumption. Optimal conditions in the MAE were obtained using 35 s of extraction time, 90% of microwave power, and a 50 mg/mL sample-solvent ratio. Recoveries in the range of 87–109% and relative standard deviation < 8.45% were obtained. The limits of quantification (mg kg-1) were: 0.0233 (Cd), 0.0229 (Cu), 1.10 (Fe), 0.06 (Mn), and 0.67 (Zn). The medicinal herbs were analyzed and daily intake values were estimated for Cu (<0.20%), Fe (<18.1%), Mn (<13.8%), and Zn (<0.64%); concentrations above threshold values for Cd were found. The optimization of experimental conditions combined and the use of an eco-friendly solvent provided excellent analytical parameters in the proposed method.

Investigation into Lewis and Brønsted acid interactions between metal chloride and aqueous choline chloride-oxalic acid for enhanced furfural production from lignocellulosic biomass

Furfural has been identified as a valuable biobased platform chemical that can be further converted into bioenergy and biochemicals. Furfural is derived from lignocellulosic biomass and can also be regarded as a sustainable alternative to petrochemical products. Herein, the performance of trivalent metal chlorides (FeCl3, AlCl3) and tetravalent metal chlorides (SnCl4, TeCl4) as Lewis acidic cocatalysts was investigated in an aqueous choline chloride-oxalic acid (16.4 wt% H2O) deep eutectic solvent (DES) system for producing furfural from oil palm fronds (OPFs). The metal chlorides with greater electrical field gradients were stronger Lewis acids that enhanced both furfural production and degradation reactions. The main degradation product in this reaction system was humin, and this result was confirmed by FTIR analysis. By subjecting OPFs to an aqueous DES reaction (120 °C, 45 min) with SnCl4 (2.50 wt%), a furfural yield of 59.4% was obtained; without incorporated metal chlorides, the furfural yield was 46.1%. Characterization studies showed synergistic Lewis and Brønsted acid interactions between metal chlorides and DES components. Overall, the residual OPFs showed high glucan content, which led to the production of glucose (71.4%) as a byproduct via enzymatic hydrolysis. Additionally, the aqueous DES system was recycled and reused for several additional runs. The proposed aqueous DES system presents a promising biorefinery approach for the conversion of OPFs to biochemicals.

Extraction of Keratin from Poultry Feathers with Choline Chloride-Oxalic Acid Deep Eutectic Solvent

Extraction of Keratin from Poultry Feathers with Choline Chloride-Oxalic Acid Deep Eutectic Solvent

Beneficial and detrimental effects of choline chloride-oxalic acid deep eutectic solvent on biogas production.

Deep eutectic solvents (DES), a new class of alternative solvents, have recently been used in the pre-treatment of lignocellulosic biomass. Due to the ability to dissolve phenolic compounds, they have been efficiently applied as delignification agents. However, to extend DES application to bioprocesses, such as Anaerobic Digestion (AD), their toxicity to microbial consortia must be evaluated. In this work, an effective delignifying DES, composed of choline chloride (ChCl) and oxalic acid (OA) (1:1) was prepared and its effect evaluated, for the first time, in biogas production. Results show that the presence of DES had both beneficial and detrimental effects on the anaerobic consortium, depending on its concentration. In the concentration range of 0.3-12.5g/L, the presence of DES led to a lag-phase of 1 to 8 d as the DES concentration increased. However, after the lag-phase has been surpassed, DES up to a concentration of 12.5g/L improved the biogas production, reaching an accumulated biogas volume three times higher than the control assay for the concentration of 12.5g/L. For the highest DES concentrations (19.8-78.1g/L), the biogas production was inhibited. The assays performed with DES components alone have indicated that OA at 3.2g/L was the main responsible for the inhibition of biogas production (50% less biogas produced than the control). ChCl at 4.9g/L has not presented a lag-phase and produced an accumulated biogas volume like the control assay (1200mL for 30 d incubation). This work points out that ChCl:OA DES may be used in the delignification of biomass further submitted to AD, provided the inhibitory concentrations of OA are not achieved.

Supported liquid membranes comprising of choline chloride based deep eutectic solvents for CO2 capture: Influence of organic acids as hydrogen bond donor

This study focuses on a forward looking approach in which deep eutectic solvents (DESs), a new class of designer solvents, were impregnated into micro porous polyvinylidene fluoride (PVDF) membrane for the separation of CO2 from CH4. Three types of DESs were prepared by mixing and heating of hydrogen bond acceptor (choline chloride) with either malic acid, tartaric acid or oxalic acid as hydrogen bond donor. The Fourier transform infrared spectroscopy confirmed the hydrogen bond interactions in the resulting DES. Thermal gravimetric analysis (TGA) was used to evaluate the thermal stability of the prepared membranes. The DES based supported liquid membranes were investigated systematically to determine the permeability and selectivity for the mixture of gases at both ambient and elevated temperatures. The results showed that Choline Chloride-Malic acid, Choline Chloride-Tartaric acid and Choline Chloride-Oxalic acid DES-SLMs exhibited CO2 permeability of 30.32 Barrer, 34.00 Barrer and 37.30 Barrer, respectively while ideal selectivity of these membranes was found 51.39, 55.74 and 60.16 for CO2/CH4, respectively. The fabricated membranes were compared with some of the imidazolium supported ionic liquid membranes (SILMs) on the Robeson upper bound plot. The current study on DES-SLMs is expected to open new pathways for the exploitation of DESs for CO2 capture.

Use of Microwave-Assisted Deep Eutectic Solvents to Recycle Lithium Manganese Oxide from Li-Ion Batteries

To realize efficient recycling of lithium manganese oxide (LMO) from spent Li-ion batteries, microwave-assisted deep-eutectic solvent (DES) treatment is proposed. The effects of the DES, temperature, time, and liquid/solid (L/S) ratio on the leaching efficiency were studied by orthogonal and single-factor experiments. The results of the orthogonal experiments indicated that the effects of each factor on the leaching of Li and Mn ions lay in the following order: DES > L/S ratio > temperature > time. The results of the single-factor experiments indicated that the leaching efficiencies of both Li and Mn ions reached 96% under the condition of choline chloride–oxalic acid (ChCl–OA), 15 min, 75°C, and L/S ratio of 6 g/0.1 g. Microwave-assisted DES treatment is highly efficient for recycling LMO from Li-ion batteries, greatly decreasing the leaching time from several days to less than 1 h even at 75°C in comparison with the traditional heating method.

Nonsevere furfural production using ultrasonicated oil palm fronds and aqueous choline chloride-oxalic acid

Furfural is a versatile platform chemical that can be employed to produce green fuel and chemical intermediates. In this study, oil palm fronds were first subjected to ultrasonic pretreatment using an ultrasonic probe in water, which was followed by reaction in an aqueous choline chloride-oxalic acid (16.4 wt% H2O) deep eutectic solvent. The focus of this study was to investigate whether the duration and amplitude of ultrasonic pretreatment improve the furfural yield from oil palm fronds. Mechanoacoustic and sonochemical effects induced by ultrasound waves disrupted the lignin carbohydrate complex in biomass, which increased the hemicellulose availability in the oil palm fronds for furfural production in the subsequent aqueous choline chloride-oxalic acid reaction. By employing ultrasonic pretreatment at 80 % amplitude for 3 min and then an aqueous choline chloride-oxalic acid reaction at 120 °C for 60 min, a furfural yield of 56.5 % was obtained. Characterization studies (e.g., Fourier transform infrared spectroscopy, Brunauer-Emmet-Teller, X-ray diffraction, and field emission scanning electron microscopy) on the oil palm fronds yielded insights into the reaction. Additionally, the reacted oil palm frond residues had a high glucan content, which could be considered a valuable byproduct.

Natural deep eutectic solvent enhanced pulse-ultrasonication assisted extraction as a multi-stability protective and efficient green strategy to extract anthocyanin from blueberry pomace

A deep understanding upon the relation between anthocyanin extraction performance and physicochemical properties of natural deep eutectic solvents (NADESs) was obtained, and a high-efficiency NADES (Choline chloride-Oxalic acid (ChOa)) was selected and coupled with pulse-ultrasonication for anthocyanin extraction from blueberry pomace. Response surface methodology was adopted to analyzed the significant factors’ influence, interactive effects on extraction yield and optimize the extraction conditions. The theoretical optimal conditions with highest yield of total anthocyanins content (TAC) were 3.2 min of ultrasonic time, 325 W of ultrasonic power, 349.15 K of temperature, 60 mL/g of solvent to solid ratio, under which the experimental TAC value (24.27 ± 0.05 mg C3GE/g DW) was highly correlated with theoretical result (24.28 mg C3GE/g DW). Multi-stability protective effect of ChOa on anthocyanin over acidified ethanol was revealed by stability assays in high temperature, varying pH and light exposure conditions. FT-IR and DSC analysis further characterized the influence of ChOa over acidic ethanol on typical anthocyanins functional groups and thermal behavior of anthocyanin extracts. UPLC-Triple-TOF/MS analysis identified 10 anthocyanins that mainly consisted of delphinidin, petunidin, and malvidin compounds. Overall, this study provided a green, high-efficiency and multi-stability protective strategy for the recovery of anthocyanins from plant source by-products.

Effect of Choline-Based Deep Eutectic Solvent Pretreatment on the Structure of Cellulose and Lignin in Bagasse

Deep eutectic solvents (DESs) is a newly developed green solvent with low cost, easy preparation and regeneration. Because of its excellent solubility and swelling effect in lignocellulose, it has received widespread attention and recognition. In this study, choline-based deep eutectic solvents (DESs)—choline chloride-urea (CC-U), choline chloride-ethylene glycol (CC-EG), choline chloride-glycerol (CC-G), choline chloride-lactic acid (CC-LA), and choline chloride-oxalic acid (CC-OA)—were used to extract and separate bagasse. The effects of hydrogen bond donors on lignin separation and the fiber and lignin structure were investigated. All five DESs could dissolve lignin from bagasse; acidic DESs exhibited higher solubility than basic DESs. CC-OA effectively separated lignin and hemicellulose. CC-LA showed weaker lignin separation ability than CC-OA. CC-G, CC-EG, and CC-U were more inclined to selectively separate lignin than hemicellulose. The crystalline cellulose II structure was retained after DES pretreatment. Acidic DESs effectively improved the crystallinity of bagasse fiber; the crystallinities for CC-OA and CC-LA pretreatment were 62.26% and 61.65%, respectively. The lignin dissolved in DES was mainly syringyl lignin. The lignin dissolved in CC-U, CC-LA, and CC-OA contained a small amount of guaiacyl lignin.

Direct pretreatment of raw ramie fibers using an acidic deep eutectic solvent to produce cellulose nanofibrils in high purity

Due to biomass recalcitrance, the pulping and bleaching processes are usually needed to break down the resistance of the lignocellulosic matrix for nanocellulose extraction. In this study, an acidic deep eutectic solvent (DES) based on choline chloride-oxalic acid dihydrate was used to directly pretreat raw ramie fibers (RFs) without further bleaching/purification steps for producing cellulose nanomaterials. Raw RFs, DES pretreated RFs, and degummed RFs were comparatively studied as starting materials for the preparation of cellulose nanofibrils (CNFs) by ball milling. There was no significant difference between CNF samples prepared from the DES pretreated RFs after 6 h of ball milling and those from the degummed RFs after 12 h of ball milling. After 4 h DES pretreatment at 100 °C, the obtained CNFs had a high purity of glucan up to 90.31% and an average width of 14.29 nm. They also showed high crystallinity (79.17%) and high thermal stability (> 316.7 °C). The tensile strength and elastic modulus for the CNF films were 98.071 MPa and 2.749 GPa, respectively. Overall, with the choline chloride-oxalic acid dihydrate DES pretreatment, no additional pulping/bleaching processes were required for the preparation of nanocellulose from raw cellulosic fibers while the properties of the as-prepared nanocellulose were preserved.

Deep eutectic solvent-based headspace single-drop microextraction of polycyclic aromatic hydrocarbons in aqueous samples

An improved deep eutectic solvent (DES)-based headspace single-drop microextraction procedure has been developed as a green procedure for gas chromatography-mass spectrometric analysis of polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. The stability of the micro-drop was significantly improved using a DES as an extraction phase and a bell-shaped tube as a supporter. These strategies helped to perform the extraction process in higher temperatures and stirring rates. Finally, the back-extraction of the analytes into a proper solvent that is compatible with the chromatography system was applied. The efficacy of the independent variables on the extraction efficiency was evaluated via chemometric methods in two steps. The best result was obtained with choline chloride-oxalic acid at the molar ratio of 1:2, a stirring speed of 2000 rpm for 10 min as well as a sample temperature of 50 °C and with ionic strength prepared by using a 10% (w/v) NaCl. The method indicated a good linearity for the analytes (R2≥0.9989). Under optimal conditions, the analytical signal was linear in the range of 0.01–50 μg L−1. Limit of detection (LOD) and limit of quantification (LOQ) were evaluated at the concentration levels of 0.003–0.012 and 0.009–0.049 μg L−1, respectively. Intraday and interday precision for all targeted compounds was less than 7.2% and 11.3%, respectively. Consequently, the proposed procedure was efficiently applied to extract and analyze the 16 target compounds in real aqueous samples representing satisfactory recoveries (94.40–105.98%).

Comprehensive utilization of corncob for furfuryl alcohol production by chemo-enzymatic sequential catalysis in a biphasic system

A new process for the production of furfuryl alcohol from corncob was constructed by using deep eutectic solvents and whole cell catalysis in this paper. Firstly, the corncob was treated with deep eutectic solvents to convert the xylan into furfural, and then the pretreated corncob residue was enzymatically hydrolyzed to obtain a glucose-rich enzymatic hydrolysate, which was used to provide NADH for Bacillus coagulans NL01 during the process of furfural reduction. The furfural yield could reach 46% using the selected choline chloride-oxalic acid as catalysts and corncob as substrate under the optimized catalytic condition at 120 °C for 30 min. The final furfuryl alcohol yield of 20.7% was achieved with corncob as substrate. Moreover, this catalytic system realized the recycling of deep eutectic solvents three times, the high-value production of furfuryl alcohol, and the comprehensive utilization of corncob.

Choline chloride-based deep eutectic solvents for efficient delignification of Bambusa bambos in bio-refinery applications

The use of choline chloride–oxalic acid (CO) and choline chloride–urea (CU) green solvents as mediator for delignification of Bambusa bambos stem (BS) has been studied. The optimal delignification of BS obtained at 120 °C and 4 h of DESs (deep eutectic solvents) treatment process. The morphological structure of raw BS and treated BS was analyzed by SEM, XRD, and FTIR. The results showed that the crystallinity index increased from 43.8 in raw BS, to 44.3%, and CUT-BS and 46.4 in COT-BS. The surface elemental composition of BS was estimated by photoelectron spectroscopy (XPS). The carbon and oxygen elemental contents in the biomass surface were determined by XPS survey, C1s, and O1s spectra. The delignification using CO system (25.4%) more easily digested the BS biomass compared to CU system (19.4%). The use of acid DES can be an effective pretreatment process compared to basic treatment processes for biomass fractionation in bio-refinery applications.

Palladium Electrodeposition from Deep Eutectic Solvents

Palladium is a platinum group metal that has been reported to be useful as electrocatalyst for several important reactions such as formic acid oxidation, alcohol oxidation and oxygen reduction. In this context the electrodeposition of Pd is of particular interest.Palladium electrodeposition in aqueous media requires potentials close to the decomposition of water, leading to low faradaic yields and embrittlement of electrodeposited palladium. The use of unconventional solvents such as deep eutectic solvents (DESs) is expending as a promising alternative for the electrochemical deposition of metals. These are obtained by mixing a quaternary ammonium salt and a hydrogen-bond donor, leading to a melting point much lower than the pure components. These eutectics are easy to prepare, inexpensive and offer a high electrical conductivity. Owing to their thermal stability and wide electrochemical window, these media become more widespread in the field of metal electrodeposition, though fundamental studies are relatively scarce.The present work focuses on the electrodeposition of palladium from deep eutectic solvents based on choline chloride.The electrochemical behaviour of Pd(II) has been investigated at 60°C in choline chloride–urea (ChCl-U) and choline chloride–oxalic acid (ChCl-Ox). Cyclic voltammetry (CV) and potentiostatic measurements performed in the presence of Pd(II) at a glassy carbon electrode (GC) are compared with data obtained at a gold electrode.Peaks in the CV curves are assigned to the Pd deposition and its dissolution but also to the formation of palladium hydride (PdHx). The Pd(II) electrochemistry is significantly different in the two DESs, owing to their differing proton donating properties and Pd speciation.By selecting appropriate potentials, Pd electrodeposits were formed and analysed. The kinetics of Pd electrodeposition was followed by chronoamperometry. The i-t curves obtained at a glassy carbon electrode clearly revealed that the metal deposition is controlled by a nucleation and growth process. The current transients, discussed on the basis of existing models, indicate that the deposition occurs via 3D nucleation with diffusion controlled growth.

APPLICATION OF GREEN EXTRACTION METHODS TO RESVERATROL EXTRACTION FROM PEANUT (ARACHIS HYPOGAEA L.) SKIN

Objective: This study compared the maceration extraction method with non-conventional extraction methods such as ultrasound-assisted extraction(UAE) and microwave-assisted extraction (MAE).Methods: To obtain resveratrol, various conditions were optimized: Solvent types (organic solvent [i.e. 70% ethanol] and green solvents [i.e. naturaldeep eutectic solvent (NADES) and ionic liquid (IL)]) and extraction methods. The resveratrol content in the extracts was analyzed by high-performanceliquid chromatography.Results: It was determined that resveratrol extracted by UAE with NADES was composed of choline chloride–oxalic acid when the followingconditions were used: The solid/liquid ratio of 1:20 (g/mL) and the extraction time of 15 min. These conditions produced higher resveratrol content(0.049 mg/g dry weight) than that using MAE with 70% ethanol (0.011 mg/g dry weight). However, the maceration method yielded the highestamount of resveratrol (0.221 mg/g dry weight), and MAE with IL produced the smallest amount of resveratrol (0.157 × 10−3 mg/g dry weight).Conclusion: Peanut skin extracted using the maceration method produced the highest amount of resveratrol compared to that using other methods.

Comparison of Deep Eutectic Solvents on Pretreatment of Raw Ramie Fibers for Cellulose Nanofibril Production.

Deep eutectic solvents (DESs), featured as promising green solvents, were applied to examine their effectiveness in pretreating raw ramie fibers (RFs) for cellulose nanofibril (CNF) production. The pretreatment performance of three DESs, i.e., choline chloride–urea (CU), choline chloride–oxalic acid dihydrate (CO), and choline chloride–glycerol (CG), was evaluated based on chemical composition analysis and structural and morphological changes. CO attained the most dramatic morphological changes of RFs, followed by CG and CU. Its high structural disruption of RFs during the pretreatment process, shown in the results from scanning electron microscopy and atomic force microscopy, could be due to an outstanding ability to remove amorphous cellulose and noncellulosic components from raw RFs, confirmed by the results of chemical composition analysis, Fourier transform infrared spectroscopy, and X-ray diffractometry. Overall, this study provided an innovative and effective pretreatment process for fractionating raw cellulosic fibers, so as to promote the subsequent preparation of CNFs.

One-pot multi-component process for the synthesis of 4-azaphenanthrene-3,10-dione, 1,8-dioxo-octahydroxanthene and tetrahydrobenzo[b]pyran derivatives catalyzed by the deep eutectic solvent choline chloride-oxalic acid

Abstract An effective method based on choline chloride (ChCl)-oxalic acid (Ox) deep eutectic solvent was proposed for the synthesis of 4-azaphenanthrene-3,10-dione, 1,8-dioxo-octahydroxanthene and tetrahydrobenzo[b]pyran derivatives. The eutectic mixture worked as both the solvent and acidic catalyst for conversion. The impacts of different variables, including the composition and volume of ChCl-Ox, and temperature, on reaction yield were studied for optimization. The crucial advantages of this process are simplicity of the experimental procedure, high yields, short reaction times, high recyclability, and the use of safe and inexpensive components.

Preparation of cellulose nanofibrils from okara by high pressure homogenization method using deep eutectic solvents

The interest in the application of deep eutectic solvents (DES) as a green solvent has increased rapidly. The application of DES in agro-industrial okara treatment can be developed into industrialization. In order to simplify the degreasing, deproteinization and cellulose extraction steps in the process of pretreating okara cellulose, a new approach to cellulose extraction from okara via one-pot DES treatment is established. Three different complexing agents, choline salts in oxalic acid, in glycerol and in urea are studied in this work. The structure and properties of cellulose nanofibers (CNFs) prepared by high pressure homogenization following pretreatment of okara with anionic systhesized DES are investigated. The effects of different systems on the degree of microfibrillation of okara are analyzed using techniques such as SEM, FTIR, TD and DTG. The results indicate that by pretreating okara with choline chloride–oxalic acid type solvent, CNFs with average diameter of 27 nm are obtained using high pressure homogenization.

Corrosion Processes of Uranus B6 and Monel 400 Special Alloys in Deep Eutectic Solvents

The corrosion behaviour of special alloys (Uranus B6 steel and Monel 400) exposed to chlorine chloride-deep eutectic solvents (DES) at 353 K has been investigated by polarization curves method. The corresponding corrosion parameters in choline chloride-oxalic acid and choline chloride-malonic acid were calculated. Micrographic images before and after immersion in the corrosive medium were obtained. Measurements of the influence of the corrosion process on the crystal structure and specific magnetization of the studied steels was carried out by using X-ray diffraction and respectivelly ponderomotive methods.