Green Pretreatment Method Research Articles

Superparamagnetic nanofluid based on target-specific deep eutectic solvent for determination of multiple perfluoroalkyl substances in edible oils

Deep eutectic solvents (DESs) are recognized as sustainable mediums, and DES-related materials have been used for the detection of perfluoroalkyl substances (PFASs). However, such studies were usually limited to only one category of PFASs among the massive target PFASs compounds. Additionally, the selectivity of the related detection method still needs improvement. In this study, a convenient and effective method for the direct selective microextraction of multiple PFASs was developed based on a target-specific DES-based superparamagnetic nanofluid. Parameters such as DES compositions, amount of DES-based nanofluid, and microextraction time were systematically investigated to establish a straightforward, rapid, sensitive, and efficient green pretreatment method. Under optimal conditions, the method demonstrated high sensitivity, good precision, a detection limit of 0.04–8.71 ng kg−1, a spike recovery of 80.49–119.95%, and low matrix effects (<20%). The potential mechanism was elucidated by ab initio molecular dynamics (AIMD) simulations. The solvent system exhibited diverse interaction modes with analytes of varying types, including hydrogen bond acceptors (HBA)···PFASs, HBA···FAAs···hydrogen bond donors (HBD), and hetero-halogen interactions. Finally, this method was applied to the monitoring of 13 PFASs compounds in 17 edible oil samples, and targets were detected in the range of 0.05–10.04 ng kg−1.

Deep eutectic solvent-functionalized amorphous UiO-66 for efficient extraction and ultrasensitive analysis of perfluoroalkyl substances in infant milk powder

In this study, a convenient and effective method for determination of perfluoroalkyl substances (PFASs) in infant formula was developed based on a novel dispersive solid-phase extraction using deep eutectic solvent-functionalized amorphous UiO-66 (DES/aUiO-66) as sorbent. The synthesis of materials could be achieved without the use of complex and environmentally unfriendly procedures. Parameters were systematically investigated to establish a simple, fast, and efficient green pretreatment method. The method demonstrated high sensitivity, good precision, a detection limit of 0.330–0.529 ng·kg−1, and low matrix effects (< 12.8%). The mechanism for this material was elucidated by ab initio molecular dynamics (AIMD) simulations and quantum chemistry calculations. The presence of massive pore structures and collectively synergistic binding sites facilitated affinity adsorption toward PFASs. Finally, this method was applied to the monitoring of PFASs in 10 actual milk powder samples. This groundbreaking approach opens new possibilities for the advancement of analytical techniques and food safety monitoring.

Ionic liquid pretreatment of lignocellulose for complete hemicellulose removal to produce high-purity cellulose mixed esters

Strategic valorization of agricultural waste can serve as waste management and promote sustainable biorefineries. Sugarcane bagasse is a readily available lignocellulosic biomass and can be converted into valuable cellulose-based thermoplastics. However, the cellulose purity significantly influences the material properties of the resulting thermoplastics, potentially limiting their applications. Therefore, conventional production necessitates harsh pretreatment of lignocellulose to isolate high-purity cellulose, followed by chemical modification. Here, we demonstrate a facile and green pretreatment method for complete removal of hemicellulose by incubating bagasse in a mixed system of an ionic liquid, 1-ethyl-3-methylimidazolium acetate (EmimOAc), and dimethyl sulfoxide (DMSO) at 140 °C, followed by precipitation in water, achieving >99 % hemicellulose removal. The pretreated bagasse, containing 71 % cellulose and 28 % lignin, underwent homogeneous transesterification with vinyl decanoate and isopropenyl acetate, using EmimOAc as both the solvent and catalyst, assisted by a co-solvent of DMSO. The polysaccharide derivative in the resulting acylated bagasse was separated from the lignin derivative by precipitation in methanol. The obtained polysaccharide derivative with high cellulose purity displayed a high weight-average molar mass of 1.5×106 g mol−1 and a polydispersity of 4. It also exhibited superior thermal stability (thermal degradation temperature, Td−5 %: 359 °C; glass transition temperature, Tg: 144 °C) compared to pulp-derived cellulose acetate decanoate (Td−5 %: 349 °C; Tg: 129 °C).

Niobium-based single-atom catalyst promoted fractionation of lignocellulose in choline chloride-lactic acid deep eutectic solvent

Pretreatment is the key step to convert lignocelluloses to sustainable biofuels, biochemicals or biomaterials. In this study, a green pretreatment method based on choline chloride-lactic acid deep eutectic solvent (ChCl-LA) and niobium-based single-atom catalyst (Nb/CN) was developed for the fractionation of corn straw and further enzymatic hydrolysis of cellulose. With this strategy, significant lignin removal of 96.5 % could be achieved when corn straw was pretreated by ChCl-LA (1:2) DES over Nb/CN under 120 °C for 6 h. Enzymatic hydrolysis of the cellulose-enriched fraction (CEF) presented high glucose yield of 92.7 % and xylose yield of 67.5 %. In-depth investigations verified that the high yields of fractions and monosaccharides was attributed to the preliminary fractionation by DES and the deep fractionation by Nb/CN. Significantly, compared to other reported soluble catalysts, the synthesized single-atom catalyst displayed excellent reusability by simple filtration and enzymatic hydrolysis. The recyclability experiments showed that the combination of ChCl-LA DES and Nb/CN could be repeated at least three times for corn straw fractionation, moreover, the combination displayed remarkable feedstock adaptability.

A hydrophobic deep eutectic solvent-based vortex-assisted liquid-liquid microextraction applied for doping control of aromatase inhibitors from equine urine

Aromatase inhibitors (AIs) can indirectly cause increased testosterone in animals, which leads to the improvement of the athletic ability of horses. For the protection of horses and the consideration of fair competition, AIs were listed as prohibited drugs by the Federation Equestre Internationale (FEI). There were several disadvantages using traditional pretreatment methods before analyzing these drugs from biological samples. A rapid and green pretreatment method has been developed by utilizing the hydrophobic deep eutectic solvent (DES)-based vortex-assisted liquid-liquid microextraction (DES-VALLME) followed by ultra-high performance liquid chromatography tandem triple-quadrupole mass spectrometry (UHPLC-MS/MS) technique for the efficient extraction and sensitive detection of AIs in equine urine samples. The combination of menthol and 4-fluorophenol in a molar ratio 1:4 was chosen as the optimum composition of DES for extracting AIs. Under the optimum conditions, only 80 μL of DES, 1 mL equine urine and 2 min were expended. An external standard calibration method was utilized for determination, and a linear relationship was achieved with a concentration range of 0.02–4000 ng mL−1 (r2 ≥ 0.9983). The limits of detection of the method based on a signal-to-noise ratio of 3 were 0.01–4 ng mL−1. The accuracy recoveries ranged from 94.9% to 113.4% within the intra-day and inter-day relative standard deviations of less than 9.1%. Compared with traditional extraction methods, the DES-VALLME method had the advantages of rapidity, simplicity, efficiency, low toxicity, and low cost. This method has potential and possessed brilliant prospects for doping control.

PH-responsive switchable deep eutectic solvents to mediate pretreatment method for trace analysis of triazole fungicides in peel wastes

The existing QuEChERS-combined analytical pretreatment methods are limited by large reagent consumption, high environmental burden, and mediocre effects. To provide an efficient and green pretreatment method, this study developed pH-responsive switchable deep eutectic solvents (SDESs) to extract triazole fungicides (TFs) from fruit peel wastes, which could enhance the preconcentration effect of target compounds in food waste samples with complex matrices. The mechanisms of pH-induced phase transition and hydrophobicity-hydrophilicity conversion of pH-responsive SDESs were investigated by pH phase diagrams and chemical characterization techniques, respectively. We validated the established method by high-performance liquid chromatography-diode array detector (HPLC-DAD), and lower LOD (0.089–0.351 ng mL−1), LOQ (0.297–1.172 ng mL−1), RSD (≤8.8 %) and satisfactory recoveries (90.6 %-110.9 %) and preconcentration factors (389–512) were obtained in rotting grape peel, watermelon peel, and orange peel samples. Our findings highlight the potential of pH-responsive SDESs in the extraction and analysis of various natural food products.

Biodegradation of Gramineous Lignocellulose by Locusta migratoria manilensis (Orthoptera: Acridoidea)

Exploring an efficient and green pretreatment method is an important prerequisite for the development of biorefinery. It is well known that locusts can degrade gramineous lignocellulose efficiently. Locusts can be used as a potential resource for studying plant cell wall degradation, but there are few relative studies about locusts so far. Herein, some new discoveries were revealed about elucidating the process of biodegradation of gramineous lignocellulose in Locusta migratoria manilensis. The enzyme activity related to lignocellulose degradation and the content of cellulose, hemicellulose, and lignin in the different gut segments of locusts fed corn leaves were measured in this study. A series of characterization analyses were conducted on corn leaves and locust feces, which included field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction pattern (XRD), and thermogravimetric (TG) analysis. These results showed that the highest activities of carboxymethyl cellulase (CMCase), filter paper cellulase (FPA), and xylanase were obtained in the foregut of locusts, which strongly indicated that the foregut was the main lignocellulose degradation segment in locusts; furthermore, the majority of nutritional components were absorbed in the midgut of locusts. The activity of CMCase was significantly higher than that of xylanase, and manganese peroxidase (MnPase) activity was lowest, which might be due to the basic nutrition of locusts being cellulose and hemicellulose and not lignin based on the results of FE-SEM, FTIR, XRD, and TG analysis. Overall, these results provided a valuable insight into lignocellulosic degradation mechanisms for understanding gramineous plant cell wall deconstruction and recalcitrance in locusts, which could be useful in the development of new enzymatic pretreatment processes mimicking the locust digestive system for the biochemical conversion of lignocellulosic biomass to fuels and chemicals.

Rice straw structure changes following green pretreatment with petha wastewater for economically viable bioethanol production

Energy efficient and environment friendly pretreatment processes for the production of biofuel have remained elusive and the research is further compounded by the high cost of processing lignocellulosic biomass—an essential factor for producing sustainable biofuels. In the last few decades, a number of pretreatment methods have been proposed, specifically chemical pretreatments but are either expensive or harmful to the environment. To address this urgent need, we propose a green pretreatment method that utilises the highly alkaline by-product, petha wastewater to pretreat the lignocellulosic waste rice straw (RS). The effectiveness of the pretreatment was analysed by monitoring both enhanced cellulose content and reducing sugar yield along with removal of hemicellulose and lignin. We found that PWW pretreatment yielded five times more reducing sugar than native RS with 10.12% increment in cellulose content. SEM and EDX studies further revealed that our process enhanced surface roughness and carbon content (from 32.19% increased to 41.59% and 41.66% for A and D, respectively) along with reduction in silica content (from 8.68% in RS to 4.30% and 7.72% for A and D, respectively). XRD and FTIR analyses indicate crystallinity index (CI) and alteration in lignocellulosic structure of RS, respectively. Decrease in CI was about 43.4% in A whereas only 4.5% in D as compared to native RS (CI 54.55%). Thereby we found PWW to be better substitute of an alkali for pretreatment of RS with negligible environmental impacts.

Dispersive liquid-liquid microextraction based on deep eutectic solvent for elemental impurities determination in oral and parenteral drugs by inductively coupled plasma optical emission spectrometry

A simple, fast, sensitive and green pretreatment method for determination of Cd, Co, Hg, Ni, Pb and V in oral and parenteral drug samples using inductively coupled plasma optical emission spectrometry (ICP OES) has been developed. According to United States Pharmacopoeia (USP), those metals must be reported in all pharmaceutical products for quality control evaluation (i.e., elemental impurities from classes 1 and 2A of USP Chapter 232). To improve the analytical capabilities of ICP OES, a dispersive liquid-liquid microextraction (DLLME) has performed using a safe, cheap and biodegradable deep eutectic solvent (DES) as extractant solvent (a mixture of 2:1 M ratio of DL-menthol and decanoic acid). Seven parameters affecting the microextraction efficiency have carefully optimized by multivariate analysis. Under optimized conditions, the DES-based DLLME-ICP OES procedure improved limit of quantitation (LOQ) values on range from 12 to 85-fold and afforded an enrichment factor on average 60-times higher than those obtained to direct ICP OES analysis. Consequently, LOQ values for Cd, Co, Hg, Ni, Pb and V have been on average 10-times lower than target limits recommended for drugs from parenteral route of administration. Trueness has evaluated by addition and recovery experiments following USP recommendations for three oral drug samples in liquid dosage form and three parenteral drugs. Recovery and RSD values have been within the range of 90–109% and 1–6%, respectively. All analytes were below the respectives LOQ values, hence, lower than the limits proposed by USP Chapter 232.

Effects of the Combined Utilization of Ultrasonic/Hydrogen Peroxide on Excess Sludge Destruction

Excess sludge reduction has been a research hotspot for a long time. Ultrasonic treatment of excess sludge was an efficient and green pretreatment method, and also can be combined with the addition of oxidants. To improve the effect of ultrasound treatment on sludge destruction, hydrogen peroxide (H2O2) was added to examine the combined results in the current study. The effects of the ultrasound/hydrogen peroxide system on the release of sludge organic matter during the destruction process were studied. Single-factor experiments were carried out to determine the optimal operating conditions. With the initial pH of 11.0, H2O2 concentration of 0.5 mmol/L, initial sludge concentration of 17 g/L, and 15 min ultrasonic treatment, the maximum soluble chemical oxygen demand (ΔSCOD) in the sludge supernatant after destruction was achieved at 3662.78 ± 239.21 mg/L, with a disintegration degree of 28.61 ± 2.14%, sludge reduction rate of 19.47 ± 0.82%, and the change of mixture sludge concentration (ΔMLSS) of 3.31 ± 0.06 g/L. Meanwhile, the release of nitrogen and phosphorus were greatly improved. Under the optimal conditions, the release of total nitrogen (TN), ammonia nitrogen (NH3-N) and total phosphorus (TP) were 282.30 ± 24.06 mg/L, 25.68 ± 2.09 mg/L, and 105.69 ± 7.84 mg/L, respectively. The current work had provided solid evidence showing the addition of hydrogen peroxide can effectively strengthen the treatment effects of ultrasound on sludge destruction.

Overcoming biomass recalcitrance by synergistic pretreatment of mechanical activation and metal salt for enhancing enzymatic conversion of lignocellulose

BackgroundDue to biomass recalcitrance, including complexity of lignocellulosic matrix, crystallinity of cellulose, and inhibition of lignin, the bioconversion of lignocellulosic biomass is difficult and inefficient. The aim of this study is to investigate an effective and green pretreatment method for overcoming biomass recalcitrance of lignocellulose.ResultsAn effective mechanical activation (MA) + metal salt (MAMS) technology was applied to pretreat sugarcane bagasse (SCB), a typical kind of lignocellulosic biomass, in a stirring ball mill. Chlorides and nitrates of Al and Fe showed better synergistic effect with MA, especially AlCl3, ascribing to the interaction between metal salt and oxygen-containing groups induced by MA. Comparative studies showed that MAMS pretreatment effectively changed the recalcitrant structural characteristics of lignocellulosic matrix and reduced the inhibitory action of lignin on enzymatic conversion of SCB. The increase in hydroxyl and carboxyl groups of lignin induced by MAMS pretreatment led to the increase of its hydrophilicity, which could weaken the binding force between cellulase and lignin and reduce the nonproductive binding of cellulase enzymes to lignin.ConclusionsMAMS pretreatment significantly enhanced the enzymatic digestibility of polysaccharides substrate by overcoming biomass recalcitrance without the removal of lignin from enzymatic hydrolysis system.

A facile and green pretreatment method for nonionic total organic halogen (NTOX) analysis in water – Step I. Using electrodialysis to separate NTOX and halides

Adsorbable organic halogen (AOX) is a bulk organic parameter conventionally used to indicate all adsorbable halogenated organic disinfection byproducts formed in disinfected water. Analytically, AOX is determined by three sequential steps: 1) concentration and separation of AOX from halides with activated carbon, 2) conversion of AOX into halides with pyrolysis, and 3) quantification of halides via microcoulometry or ion chromatography (IC). Because the approach is relatively costly and cannot effectively recover non-adsorbable compounds, we herein proposed a facile and green pretreatment tool to measure the nonionic portion of total organic halogen (NTOX) with a new three-step approach: 1) separation of NTOX and halides with electrodialysis (ED), 2) conversion of NTOX into halides with ultraviolet, and 3) analysis of halides with IC. To verify this proposal, this study presented the efficiency of ED in separating halides and NTOX under a variety of operational and environmental conditions. The results showed that ED removed ≥98.5% of fluoride, chloride, bromide, and iodide from all tested waters (up to 1000 mg-X/L) within 1.5 h. Meanwhile, ED recovered an average of 87.9% of fourteen small molecular weight model compounds with each at 100 μg/L. By using electrospray ionization-triple quadrupole mass spectrometry, the whole pictures of high molecular weight compounds in a chlorinated drinking water before and after ED pretreatment were compared, which revealed 79.7% and 83.6% recoveries of overall polar chlorinated and brominated compounds, respectively. In addition, the quantity and property of the dissolved organic matter were largely maintained by ED, and the retained organics may be used for later characterization. The study hence presents a novel use of ED as a pretreatment tool to enable subsequent NTOX measurement.

A facile and green pretreatment method for nonionic total organic halogen (NTOX) analysis in water – Step II. Using photolysis to convert NTOX completely into halides

Adsorbable organic halogen (AOX) is a parameter conventionally used to indicate the sum of organic halogenated disinfection byproducts (DBPs), which are formed from the reactions of disinfectants with dissolved organic matter, bromide and iodide in water. To overcome the issues of the AOX analytical method, we proposed a new facile and green pretreatment method to enable the analysis of nonionic total organic halogen (NTOX) via the following three steps: 1) separation of NTOX and halides with electrodialysis, 2) conversion of NTOX with ultraviolet (UV) photolysis, and 3) analysis of halides with ion chromatography. To verify this proposal, we mainly evaluated the efficiency of vacuum ultraviolet (VUV) coupled with UV photolysis (VUV−UV) in converting NTOX into halides. Results showed that by applying VUV irradiation for 60 min and UV irradiation at pH 10–11 for another 30 min, over 85.5% of each halide from 20 representative small molecular weight DBPs (each at 100 μg-X/L level) was recovered. The purpose of UV photolysis under alkaline conditions was to reduce oxyhalides (such as bromate and iodate) formed in the VUV process back to halides. With the aid of electrospray ionization-triple quadrupole mass spectrometry, we captured the whole pictures of high molecular weight polar DBPs in a chlorinated drinking water before and after VUV−UV, through which averagely 96.4% of dehalogenation with the VUV−UV treatment was observed. An illustrative comparison of the conventional AOX method and the proposed NTOX method indicates that although the detected NTOX was lower (by 2.3–30.6%) than AOX, the results of the two methods were highly correlated (R2 > 0.97). All these hence verified the photolysis as a mature yet novel tool for sample pretreatment in environmental analytical chemistry.

Medium-assisted non-polar solvent dynamic microwave extraction for determination of organophosphorus pesticides in cereals using gas chromatography-mass spectrometry

A fast and green pretreatment method, medium-assisted non-polar solvent dynamic microwave extraction, was first applied to extract ten of organophosphorus pesticides (OPPs) from five cereal samples. Without adding any polar solvent, graphite powders (GP) were used as microwave absorption medium to transform microwave energy into heat energy. For recycling GP, an extractor was made by sealing GP inside the exterior tube of a glass sleeve. By dynamic microwave extraction using hexane as extraction solvent, ten OPPs could be extracted completely within 200s, and the extract was directly analysed by GC–MS without any clean-up process. The effects of some experimental parameters on extraction efficiency were investigated and optimised. Relative standard deviations of intra- and inter-day ranging from 1.02% to 5.32% were obtained. Five real samples were analysed, and the recoveries obtained were in the range of 73.2–99.8%, and the relative standard deviations were lower than 6.63%.