Cl Pretreatment Research Articles

Efficacy and Functional Mechanisms of a Two-Stage Pretreatment Approach Based on Alkali and Ionic Liquid for Bioconversion of Waste Medium-Density Fiberboard.

A novel pretreatment strategy utilizing a combination of NaOH and 1-Butyl-3-methylimidazolium chloride ([Bmim]Cl) was proposed to enhance the enzymatic hydrolysis of abandoned Medium-density fiberboard (MDF). The synergistic effect of NaOH and [Bmim]Cl pretreatment significantly improved the glucose yield, reaching 445.8 mg/g within 72 h, which was 5.04 times higher than that of the untreated samples. The working mechanism was elucidated according to chemical composition, as well as FTIR, 13C NMR, XRD, and SEM analyses. The combined effects of NaOH and [Bmim]Cl led to lignin degradation, hemicellulose removal, the destruction and erosion of crystalline regions, pores, and an irregular microscopic morphology. In addition, by comparing the enzymatic hydrolysis sugar yield and elemental nitrogen content of untreated MDF samples, eucalyptus, and hot mill fibers (HMF), it was demonstrated that the presence of adhesives and additives in waste MDF significantly influences its hydrolysis process. The sugar yield of untreated MDF samples (88.5 mg/g) was compared with those subjected to hydrothermal pretreatment (183.2 mg/g), Ionic liquid (IL) pretreatment (406.1 mg/g), and microwave-assisted ionic liquid pretreatment (MWI) (281.3 mg/g). A long water bath pretreatment can reduce the effect of adhesives and additives on the enzymatic hydrolysis of waste MDF. The sugar yield produced by the combined pretreatment proposed in this study and the removal ability of adhesives and additives highlight the great potential of our pretreatment technology in the recycling of waste fiberboard.

Structural and functional properties of collagen from tilapia scales pretreated by heat‐assisted ionic liquids

AbstractThis paper explores the structural and functional properties of collagen from tilapia scales pretreated by heat‐assisted ionic liquids (ILs). Results show that the solubility of collagen was significantly influenced by the type and concentration of ILs. With the increase of IL concentration, a remarkable decrease in solubility of collagen was seen. Fluorescence spectra show that heat and IL pretreatments induced the exposure of chromophores. Changes in sodium dodecyl sulfate–polyacrylamide gel electrophoresis indicated that subunits of collagen regenerated from most of the IL solvent systems were not destroyed. The functional properties of regenerated collagen were evaluated by gel strength, viscosity, water‐binding capacity, and emulsifying capacity. Results show that all heat‐assisted ILs pretreatments improved the gel strength and viscosity, and the highest gel strength and viscosity were both obtained in the collagen pretreated by heat‐assisted [EMIM]Cl. Heat‐assisted [BMIM]BF4 pretreatment exhibited the lowest water‐binding capacity. Heat‐assisted [BDMIM]Cl pretreatment indicated superior effect on improving emulsifying capacity than other pretreatments due to its ability to break most of the hydrogen bonds in collagen molecules, resulting in the formation of new re‐aggregates with higher solubility and more hydrophobic groups.

Solubility and aggregation of soy protein isolate induced by different ionic liquids with the assistance of ultrasound

The aim of this study was to evaluate the effects of ionic liquids (ILs) and ultrasound on the solubility and aggregation behavior of soy protein isolate (SPI). A variety of ILs were tested. Results showed that changes in cation or anion altered the physicochemical properties of ionic liquids, which in turn influenced the solubility of SPI. High concentration of ILs resulted in the formation of insoluble aggregates, which lead to the decrease of solubility. In most of the cases, ultrasound pretreatment had a considerable impact on the solubility and aggregation of SPI. The solubility of SPI processed by combination of 1 mg/mL 1-butyl-2,3-dimethyl imidazolium chloride ([BDMIM]Cl) and ultrasound changed remarkably compared with single ultrasound and single [BDMIM]Cl processing, which was increased by 71.8% compared with that of control (P < .05). Changes in particle size, intrinsic fluorescence spectra and free sulfhydryl (SH) groups indicated that the structure of SPI refolded and reaggregated after the ultrasound and ILs pretreatments. Combined ultrasound and 1 mg/mL [BDMIM]Cl pretreatment showed a synergistic effect on changing the SPI microstructure. In conclusion, ultrasound-assisted ILs could be an effective modification method for the globular proteins.

Ultrasound-Ionic Liquid Pretreatment Enhanced Conversion of the Sugary Food Waste to 5-Hydroxymethylfurfural in Ionic Liquid/Solid Acid Catalyst System

The purpose of this study was to efficiently convert the sugary food waste (SFW) to 5-hydroxymethylfurfural (5-HMF) by ultrasound-[Bmim]Cl pretreatment in ionic liquids (ILs)-ion exchange resin system. The effect of ultrasonic pretreatment on SFW and the effect of ultrasonic frequency, ILs, acid resin and catalyst load on SFW conversion were studied. The kinetic curve and the relationship between products and intermediates were studied. In addition, the structure of SFW was also studied by FT-IR and SEM. The results indicated ultrasound-[Bmim]Cl pretreatment can significantly promote the dissolution of cellulose in SFW, and the optimal ultrasonic frequency, solvent and catalyst were 20 + 40 + 60 kHz, [Bmim]Cl and D001-cc resin, respectively; under the best reaction conditions, the maximum 5-HMF yields from the orange and apple wastes were 42.15 and 44.66 mol%, respectively. The kinetic studies showed that the early stage of 100 and 120 °C was mainly the hydrolysis reaction, and late stage was mainly isomerization and dehydration reaction; the early stage of 140 and 160 °C was a rapid hydrolysis and dehydration reaction, and the late stage was mainly the rehydration reaction of 5-HMF. The relationship between the intermediate precursors and 5-HMF showed that the rates of formation and rehydration of 5-HMF increased with the increase in temperature, and the formation reaction was mainly concentrated in zone II. The FT-IR and SEM results of degradation products showed that cellulose in SFW was more easily hydrolyzed at high temperature and long time.

Pretreatment of quinoa straw with 1-butyl-3-methylimidazolium chloride and physiochemical characterization of biomass

Quinoa straw was pretreated with 1-butyl-3-methylimidazolium chloride ([Bmim]Cl). The levels of pretreatment temperature, duration, and liquid/solid ratio were optimized using orthogonal design to enhance the reducing sugar yield of treated sample. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction were used to assess structural changes in native and pretreated biomass. The effect of [Bmim]Cl pretreatment on the structure and properties of quinoa straw was significant. The optimum pretreatment conditions were liquid/solid ratio of 15:1, temperature of 100 °C, and duration of 5 h. The maximum reducing sugar yield of 33.22% was obtained, which was significantly higher than that of native quinoa straw. Unlike the untreated one, the pretreated quinoa straw showed clear pores and cracks and incomplete structure. Significant differences in the reducing sugar yield and structural characterization between [Bmim]Cl pretreated and untreated biomass demonstrated that [Bmim]Cl pretreatment of quinoa straw was effective for enzymatic hydrolysis.

1-Butyl-3-methylimidazolium chloride pretreatment of cotton stalk and structure characterization

Abstract Cotton stalk was pretreated with 1-butyl-3-methyimidazolium chloride ([Bmim]Cl) and the effect of pretreatment factors, including liquid/solid ratio, temperature, and pretreatment duration on cotton stalk was investigated. Scanning electronic microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction were used to identify structural changes in native and pretreated biomass. The optimum pretreatment conditions were as follows: liquid/solid ratio of 10:1, reaction temperature of 120 °C and duration of 5 h.The reducing sugar yield was 29.72%, which was significantly higher than that of native cotton stalk. The differences in the reducing sugar yields between [Bmim]Cl-pretreated and untreated biomass suggested that [Bmim]Cl pretreatment was effective to produce reducing sugars. The pretreated cotton stalk showed clear pores and cracks, low crystallinity, and incomplete crystal structure compared with untreated one. [Bmim]Cl could be reused at least four times without significant reduction in the reducing sugar yield.

Cellulose transformation into methyl glucosides catalyzed by H3PW12O40: Enhancement of ionic liquid pretreatment

AbstractThe efficient alcoholysis of cellulose to monosaccharide is of great importance to produce fuels and fine chemicals from renewable feedstocks. In this work, the conversion of cellulose into methyl glucosides was investigated by combining the pretreatment process of the ionic liquid 1‐allyl‐3‐methylimidazolium chloride ([Amim]Cl) and the subsequent alcoholysis catalyzed by the heteropolyacid H3PW12O40. The X‐ray diffraction characterization of [Amim]Cl‐pretreated cellulose shows that the pretreatment process could transform cellulose I to cellulose II resulting in the loss of crystalline structure. The subsequent alcoholysis of the pretreated cellulose catalyzed by H3PW12O40 proves to be a highly efficient way to convert cellulose to methyl glucosides in the medium of methanol. Under the optimized conditions of the [Amim]Cl pretreatment and alcoholysis reaction, the highest yield of methyl glucosides reaches up to 70.2 mass%, which is much higher than those previously published without pretreatment process.

Structural Changes of Lignin after Ionic Liquid Pretreatment

Changes of lignin’s structure were investigated resulting from an ionic liquid ([Bmim]Cl,1-butyl-3-methylimidazolium chloride salt) pretreatment. The purified lignin was pretreated by [Bmim]Cl under the following conditions: the ionic liquid to lignin mass ratio was 10:1, the temperature was 85 °C, and the processing time was 2 h and 4 h. The chemical structure of lignin was studied via Ultraviolet (UV) spectra, Fourier Transform infrared (FT-IR) spectra, Nuclear Magnetic Resonance Spectroscopy (13C-NMR), Gel Permeation Chromatography (GPC), X-ray photoelectron spectroscopy (XPS), and Thermogravimetric Analysis (TG). The total content of phenolic hydroxyl increased with increased time. Moreover, the contents of [OHI] and [OHII] (types of phenolic hydroxyl groups) groups were disproportionately increased. The main structure of lignin still was present after the [Bmim]Cl pretreatment. The β-O-4 linkages were broken apart. The degree of lignin degeneration increased with increased time, after being pre-treated with [Bmim]Cl. Simultaneously, a condensation reaction also took place during the pretreatment. Understanding the chemical changes to wheat straw lignin during an ionic liquid pretreatment provides an important theoretical basis for its further industrial use.

Microstructure Properties and Cellulase Hydrolysis Efficiency of Hybrid Pennisetum with [Amim]Cl Pretreatment

The complex microstructure of lignocellulosic biomass restricts its conversion into bio-ethanol. In this study, the effects of an ionic liquid (IL) 1-allyl-3-methylimidazolium chloride ([Amim]Cl) pretreatment on the microstructure properties and cellulase hydrolysis efficiency of hybrid Pennisetum (P. americanum × P. purpureum, lignocellulosic biomass) were investigated. After the [Amim]Cl pretreatment, the bonds of lignin-carbohydrate complex (LCC) and C=O in xylan were destroyed and the content of inter-molecular H-bonds O(6)H…O(3’) decreased by 47.2%, while the content of intra-molecular H-bonds of O(2)H…O(6) and O(3)H…O(5) increased by 9.5% and 47.0%, respectively. The crystallinity and the crystallite size decreased by 20.8% and 42.22%, respectively, and the cellulose crystalline structure changed from cellulose crystalline I to cellulose crystalline II. The specific surface area increased from 0.15 to 10.11 m2/g after the [Amim]Cl pretreatment. The glucose recovery increased by 10.3 times after being pretreated with [Amim]Cl, compared with the unpretreated sample.

Inhibiting effect of [HOEmim][BF4] and [Amim]Cl ionic liquids on the cross-linking reaction of bituminous coal

In order to reduce the hazard of coal spontaneous combustion, the cross-linking reaction between O-containing functional groups of coal should be inhibited. So the inhibitory effect of an ionic liquid (IL) on the cross-linking reaction was studied. The O-containing functional groups change the weight loss and H2O, CO2, CO yields of bituminous coal before and after [HOEmim][BF4] and [Amim]Cl pre-treatment and were detected by Fourier Transform Infrared spectroscopy (FTIR) and Thermo Gravimetric (TG) analysis. The results show that [Amim]Cl has a weaker ability to inhibit the cross-linking reaction of bituminous coal compared to [HOEmim][BF4]. Besides, based on Quantum Chemistry calculation, it was found that the different inhibiting effects of [HOEmim][BF4] and [Amim]Cl are greatly related to their anions and the H linked with C2 atom on the imidazole ring. The H-donor ability of coal will be enhanced by [HOEmim][BF4] leading to a weaker cross-linking reaction of coal.

Pyrolysis of lignite following low temperature ionic liquid pretreatment

A new and effective method, lignite pyrolysis with pretreatment with ionic liquid 1-butyl-3-methyl-imidazolium chloride ([Bmim]Cl) at low temperature, was studied. It is found that [Bmim]Cl pretreatment increased the total yield of liquid products and oil fractions compared to original lignite. The pretreatment temperature and the ratio of [Bmim]Cl to lignite play key roles on the increase of total liquid yield and the change of tar composition. The increases of liquid products yield and oil fractions content are found to be caused by the changes of composition of oxygen-containing functional groups in lignite through [Bmim]Cl pretreatment. It is also found that [Bmim]Cl can be efficiently recovered and the pretreatment performance of regenerated [Bmim]Cl is slightly lower than that of fresh [Bmim]Cl.

Optimization of [Amim]Cl Pretreatment Conditions for Maximum Glucose Recovery from Hybrid Pennisetum by Response Surface Methodology

Because of a complex chemical ultra-structure of lignocellulosic biomass, pretreatment is a necessary step for its conversion into bio-ethanol. In the present study, pretreatment conditions using the ionic liquid (IL) 1-allyl-3-methylimidazolium chloride ([Amim]Cl) were optimized for a relatively new model energy crop, hybrid Pennisetum (P. americanum × P. purpureum) to maximize the yield of fermentable sugars (glucose). The design of experiment programs employed a central composite design (CCD), with variables of temperature (102 to 187 °C), retention time (0.5 to 5.5 h), and solids loading (2 to 15 wt%). These factors were further optimized using response surface methodology (RSM). The proposed quadratic model to predict the glucose recovery from hybrid Pennisetum was verified by variance analysis (ANOVA). The model displayed high F and R2 values, indicating that it could be successfully used to identify the relationship among the independent variables studied. A maximum glucose recovery of 72.2% was found with temperature conditions of 139 °C, 2.97 h retention time, and 9.1 wt% solids loading.

Histological studies of neuroprotective effects of Curcuma longa Linn. on neuronal loss induced by dexamethasone treatment in the rat hippocampus

Long term exposure to dexamethasone (Dx) is associated with brain damage especially in the hippocampus via the oxidative stress pathway. Previously, an ethanolic extract from Curcuma longa Linn. (CL) containing the curcumin constituent has been reported to produce antioxidant effects. However, its neuroprotective property on brain histology has remained unexplored. This study has examined the effects of a CL extract on the densities of cresyl violet positive neurons and glial fibrillary acidic protein immunoreactive (GFAP-ir) astrocytes in the hippocampus of Dx treated male rats. It showed that 21days of Dx treatment (0.5mg/kg, i.p. once daily) significantly reduced the densities of cresyl violet positive neurons in the sub-areas CA1, CA3 and the dentate gyrus, but not in the CA2 area. However, CL pretreatment (100mg/kg, p.o.) was found to significantly restore neuronal densities in the CA1 and dentate gyrus. In addition, Dx treatment also significantly decreased the densities of the GFAP-ir astrocytes in the sub-areas CA1, CA3 and the dentate gyrus. However, CL pretreatment (100mg/kg, p.o.) failed to protect the loss of astrocytes in these sub-areas. These findings confirm the neuroprotective effects of the CL extract and indicate that the cause of astrocyte loss might be partially reduced by a non-oxidative mechanism. Moreover, the detection of neuronal and glial densities was suitable method to study brain damage and the effects of treatment.

Protic acid resin enhanced 1-butyl-3-methylimidazolium chloride pretreatment of Arundo donax Linn.

To improve the cellulose digestibility of energy crop Arudo donax Linn. with cost-efficient, a novel pretreatment of protic acid resin Amberlyst 35DRY catalyzed inexpensive ionic liquid (IL) 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) was developed in this work. The pretreatment was performed at 160°C with [C4mim]Cl for 1.5h, followed by Amberlyst 35DRY catalyzed at 90°C for 1h. The IL-Amberlyst pretreatment was demonstrated to be effective, evidenced by the reduction in cellulose crystallinity (31.4%) and increased porosity caused by extensive swelling the undissolved biomass and partial depolymerization of the longer cellulose chain of the dissolved biomass by Amberlyst. Consequently, a higher glucose yield (92.8%) was obtained than for the single [C4mim]Cl pretreatment (42.8%) at an enzyme loading of 20FPU/g substrate. Overall, the enhanced pretreatment was competitive by using inexpensive and recyclable IL-Amberlyst 35DRY pretreated system with shorter processing time and reduced enzyme usage.

Comparison Study of Different Ionic Liquid Pretreatments in Maximizing Total Reducing Sugars Recovery

A process scheme combining the most suitable ionic liquid pretreatment, followed by solid acid and enzymatic saccharification was used to maximize the reducing sugars recovery from sago waste. Three types of ionic liquids, i.e. 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]) and 1-ethyl-3-methylimidazolium diethyl phosphate ([EMIM][(EtO)2PO2]) were evaluated based on their performance in terms of the total reducing sugars recovery, chemical cost, and pretreatment energy requirement. The results showed that all the ionic liquids assisted the saccharification processes by dissolving and depolymerizing the carbohydrates of the sago waste into shorter chain soluble oligosaccharides, as well as disrupting the biomass structure to produce an amorphous pretreated solid residue. The solid acid saccharifications of the prehydrolysates obtained from the [BMIM]Cl pretreatment gave the highest reducing sugars recovery (61-63%) irrespective of the solid acid catalyst employed. On the other hand, enzymatic saccharification of [EMIM][OAc] pretreated solid residues showed the highest reducing sugars recovery (29%). A maximum recovery of 90% reducing sugars was achieved via incorporation of the ionic liquid pretreatment, solid acid and enzymatic saccharifications using [BMIM]Cl, Amberlyst 15 (A15) and Trichoderma viride cellulase respectively. This study suggests that the combined sequential process can maximize the reducing sugars recovery from sago waste effectively.

Effect of Ionic Liquid Pretreatment on the Structure and Enzymatic Saccharification of Cassava Stillage Residues

Cassava stillage residue (CSR), the solid wastes generated from cassava-based bio-ethanol production, can be used to produce ethanol because of its high contents of cellulose. This study has focused on the pretreatment of CSR using the ionic liquid (IL) of 1-butyl-3-methyl imidazolium chloride ([Bmim]Cl). The changes in surface morphology, particle size and functional groups of pretreated CSR were examined by scanning electron microscopy (SEM), laser diffraction instrument and Fourier transform infrared (FTIR) spectroscopy. The results showed that [Bmim]Cl pretreatment could significantly damage the structure of cassava cellulose and increase the enzymatic saccharification rate.

Ionic liquid pretreatment to enhance the anaerobic digestion of lignocellulosic biomass

Four lignocellulosic biomasses, water hyacinth, rice straw, mango leaves and spruce were pretreated by ionic liquid (IL) to enhance anaerobic digestion. The effect of pretreatment conditions, such as alkyl chain length of IL, temperature, time and operation cycle on lignocellulosic composition, structure and biogas production was evaluated. The enhancement of biogas production by [C4mim]Cl pretreatment at 120°C for 2 h decreases in the order of water hyacinth>spruce>rice straw>mango leaves. Higher methane production of regenerated rice straw and mango leaves could reach 233 and 125 mL/g carbohydrates under 140°C or 2 h and 140°C for 8, respectively. Furthermore, the technology of aqueous biphasic systems was developed to recovery IL, and the recovery rate of ILs was in the range of 54.3-94.6%.

Task-specific ionic liquid [SBMIM]Cl in one-step dissolution and hydrolysis of fibre sludge

Fibre sludge is a cellulose-rich by-product obtained from the chemical pulping process of wood chips. In this study, a one-step pretreatment procedure is considered in which fibre sludge can be simultaneously dissolved and depolymerised in an ionic liquid media. Task-specific ionic liquid (TSIL), i.e. 1-(4-sulfonylbutyl)-3-methylimidazolium chloride [SBMIM]Cl, is used as an ionic liquid media.Based on the results, [SBMIM]Cl has the ability to dissolve and hydrolyse fibre sludge in a one-step reaction. Yields of total reducing sugars (TRS) after [SBMIM]Cl pretreatment were not high (a mass fraction around 4–5%), but still comparable to yields of TRS after acid hydrolysis (a mass fraction between 2 and 8%). Furthermore, [SBMIM]Cl is able to dissolve and depolymerise both dry and wet material even up to a moisture mass fraction of 50%, which is a significant advantage when wet fibre sludge is used as a raw material.

Enzyme-catalyzed hydrolysis of fibre sludge into reducing sugars

The main goal of this research is the enzyme-catalyzed conversion of fibre sludge into reducing sugars, which can further be transformed into higher alcohol biofuels by fermentation. Enzymatic hydrolysis of 1-allyl-3-methylimidazolium chloride ([AMIM]Cl) pretreated fibre sludge demonstrated that this cellulose-rich waste fraction can be successfully converted into reducing sugars. The organic material content of this fibre sludge was determined to be about 80 %. The relative yields of total reducing sugars (glucose) in this study were higher (maximum >95 %) compared with our earlier studies (34 %) of the same pretreatment procedure followed by acid hydrolysis and enzymatic hydrolysis. Due to the ionic liquid used in this study, we were able to recover 85 % (compared with 50 %) of the initial dry fibre sludge with [AMIM]Cl pretreatment.

Hydrolysis of cellulose to glucose at the low temperature of 423 K with CaFe2O4-based solid catalyst

Weakly magnetic CaFe2O4 was synthesized by calcination of the hydroxides co-precipitated from aqueous Ca(NO3)2·6H2O and Fe(NO3)3·9H2O solutions in the presence of urea. Microcrystalline cellulose was treated with ionic liquid (IL) [AMIM]Cl (1-allyl-3-methylimidazolium chloride) and hydrolyzed in the presence of the catalyst at 423K. No IL contamination was detected in the treated cellulose by energy-dispersive X-ray spectrometry (EDX). A maximum hydrolysis yield of 49.8% and glucose selectivity of 74.1% was obtained. The catalyst was separated and reused four times, showing only a slight decrease in activity. The catalyst was stable and only minor leaching into water occurred as indicated by inductively coupled plasma atomic emission spectrometry (ICP), X-ray diffraction (XRD), and temperature programmed desorption (TPD) measurements and a neutral pH after reactions. Hydrolysis of cellulose with CaFe2O4 catalyst combined with [AMIM]Cl pretreatment is a green, energy-saving and efficient process.