Facilitating Ulvan Extraction from Ulva lactuca via Deep Eutectic Solvent and Peracetic Acid Treatment

Deep eutectic solvents (DESs) consist of a mixture of two or more solid components, which gives rise to a lower melting point compared to the starting materials. Until recently only hydrophilic DESs were available, and despite their revolutionary role in the alternative-solvents field, important issues in chemistry, and chemical engineering (such as water-related problems and the replacement of toxic volatile organic compounds) could not be tackled. Hydrophobic (deep)-here in parenthesis due to the different depths of the eutectic melting points-eutectic solvents are a subclass of DESs where both components are hydrophobic. The low toxicity, high biodegradability, and straightforward preparation without further purification steps of naturally occurring low-cost compounds are among the key advantages. Although research on hydrophobic DESs is scarce (the first report was only published in 2015), some interesting features and applications have been reported and deserve to be evaluated and comparisons established. This Minireview is divided into two parts: The first part provides a brief general introduction to DESs and the second part discusses the nomenclature using solid-liquid phase diagram analysis, chemical stability, thermophysical properties comparison, and finally the most important emerging fields of application.

Lignocellulosic biomass, particularly agricultural residues, represents an abundant, renewable, and underutilized resource for the sustainable production of cellulose-based materials. It is mainly composed of cellulose, hemicelluloses, and lignin, which together form a complex, recalcitrant structure. These components can be selectively separated and transformed into value-added products through appropriate pre-treatment strategies. Among different agricultural by-products, corn stalks – an inevitable residue of large-scale maize cultivation – are of particular interest due to their high polysaccharide content, favorable fiber morphology, and constant availability. Their low economic value and lack of competition with food crops make them an attractive and sustainable feedstock. Valorizing corn stalks not only reduces agricultural waste but also supports circular economy principles, offering a renewable alternative to fossil-derived raw materials in the production of bio-based coatings, packaging, and composites. This study explores various methods of processing corn stalks to extract cellulosic fibers for potential use in bio-based coatings. The focus was on removing non-cellulosic components and their impact on the structure of the final product. Processing methods investigated include ethanol (ET), ethanol-benzene mixture (SB), hot water (HW), 1 % alkali solution (AT), deep eutectic solvents (DES) in various combinations, and peracetic acid. ET and SB provided the highest yields - 98.5 % and 96.4 % respectively, primarily removing extractive substances without significant structural changes. HW processing also yielded high at 91 %, removing only water-soluble components. Conversely, 1 % alkali solution reduced the yield to 83.5 % due to removal of low-molecular-weight hemicelluloses. The impact of DES was unexpected: it acted as an extractor rather than a delignifying agent (yielding 89.5 % for DES and 90.8 % for SB+DES). However, addition of hydrogen peroxide to DES significantly enhanced delignification by generating peracetic acid, resulting in product bleaching and enrichment with polysaccharides. The most profound delignifying effect was observed with peracetic acid treatment, producing a white, fine-fibrous product with minimal lignin content at 3 %. The findings provide valuable insights into tailoring pre-treatment strategies for lignocellulosic biomass, highlighting the potential of optimized processing routes for producing high-purity cellulose suitable for sustainable, bio-based coating applications.

Marine algae are the most important source of non-animal sulphated polysaccharides which possess important pharmacological activities such as anticoagulant, antioxidant, anti-inflammatory, antiviral, antibacterial agents. Therefore, marine algae derived sulphated polysaccharides have great potential to be further developed as medicinal products. Marine macroalgae were collected seasonally for one year (September 2013 to August 2014) from the intertidal zone of site I: Ras El-Adabiya whichlocated on the western shore of Suez Bay and site II: Ras Sedr which located north–east of the Gulf of Suez. The purpose of this study was to extract sulphated polysaccharides from marine macroalgae (Ulva lactuca, Codium dwarkense, Hypnea cornuta, Hormophysa triquetra, Sargassum denticulatum and Cystoseira myrica) by two different methods (hot and cold water extracts) and chemical analysis also done ( protein content, total sugar , sulphate content , sulfer and nitrogen and uronic acid). The results of thephysico-chemical parameters for sea water samples showed that temp ranged between 15-30 °C, pH 7.8-8.7, salinity 38-42 ‰ , DO 6-7 mg/L, NO3 0.021-4.6 mg/L,NO2 0.004 -0.032 mg/L, NH4 0.019-0.3mg/L and PO4 0.005-0.015 mg/L. The potential of use sulphated polysaccharides as natural anticoagulant was tested by the activated partial thromboplastin time (APTT) and the prothrombin time (PT) tests. The results showed that higher blood anticoagulant activity of SPs is proportional to the carbohydrate and sulphate contents and inversely proportional to the protein and uronic acid contents. So, The significant highest value of prothrombin time was 26.50±0.10 sec at conc. of 20% SPs cold extract from the brown alga Hormophysa triquetra, while the lowest value was 1.13±0.06 sec at conc. of 5% SPs hot extract of the red alga Hypnea cornuta. Also, the results indicated that the highest value of activated partial thromboplastintime 42.20±0.10 sec was recorded atconc. of 20% SPs cold extract from the brown alga Hormophysa triquetra, On the other hand, the lowest value 5.63±0.25 sec was recorded at conc. of 5% SPs hot extract from the red alga Hypnea cornuta .

Deep eutectic solvents (DESs) have emerged as an alternative to both common organic solvents and ionic liquids (ILs). DESs share physicochemical properties with ILs such as low vapor pressure, high thermal stability, high viscosity while offering advantages such as low toxicity, lower cost, and ease of preparation. Moreover, DESs are attractive candidates for electrochemical applications due to their large voltage windows and solubility properties. DESs as a solvent class share a general composition of a hydrogen bond donor (HBD), typically a polyol, amide, or acid, and a hydrogen box acceptor (HBA), usually a quaternary ammonium or phosphonium salt. At a specific molar composition of a HBD and HBD, the DES forms a eutectic mixture resulting in a large melting point depression due to extensive hydrogen bonding between the components.Despite being widely studied, the microscopic structures of DESs have remained largely uncharacterized. Herein, we present a multitechnique NMR study of two DESs: glyceline (glycerol + choline chloride) and ethaline (ethylene glycol + choline chloride). Fast-field cycling 1H relaxometry, pulsed field gradient diffusion, nuclear Overhauser effect spectroscopy (NOESY), 13C NMR relaxation, and pressure-dependent NMR experiments are deployed to sample a range of frequencies and modes of motion of the polyol and choline components of the DES. Generally, translational and rotational diffusion of polyols are more rapid than those of choline while short-range rotational motions observed from 13C relaxation indicate slow local motion of glycerol at low choline chloride (ChCl) content. We show how the additional hydroxyl group present in glycerol contributes to not only higher viscosities, but a larger perturbation of the hydrogen bonding network by the addition of ChCl.Additionally, we have investigated the solubility properties of several lithium salts (LiTFSI, LiFSI, LiPF6, LiBF4, and LiOAc) in these DESs and utilized the same suite of NMR techniques to understand how they act as solvents. We observe that due to anion effects, the heterogeneities present in DES result in differential solvation for some species where there is a distinction of lithium salts co-existing in these holes as well as the bulk. The large changes in the structural organization of DESs that result from the presence of lithium salts will serve as a guide to the design of a new class of electrolytes for lithium-ion batteries.

Gallic acid (GA) (3,4,5-trihydroxybenzoic acid), which is a natural secondary metabolite and widely isolated from various plants, is for the first time employed as a hydrogen bond donor (HBD) for preparing a deep eutectic solvent (DES) with choline chloride (ChCl) as a hydrogen bond acceptor (HBA). This DES has been applied as an extractant to separate gycerol from biodiesel. The finding indicates that a DES could be formed at a molar ratio of ChCl to GA of 5 : 1, 6 : 1, and 7 : 1. The characterization of the synthesized DES shows its acidic polar property with a pH of lower than its constituents, density of lower than biodiesel, and the viscosity within the range reported for previously prepared DES. Functional groups analysis using FTIR indicated the presence of all functional groups from GA and ChCl in the DES structure, along with the absence of any new spectral peaks, suggesting that there was no chemical reaction involved in the DES formation. Its ability to reduce the glycerol concentration in the biodiesel in the range of 74.6 to 99.8 % denotes its capability as a potential extractant for separation of glycerol from biodiesel.

A novel approach based on detailed structural and molar free volume analyses to characteristics of deep eutectic solvents specialized for CO2 absorption

Deep eutectic solvents (DES), a class of novel green solvents, offer a promising alternative for the extraction of bioactive compounds from traditional Chinese medicinal herbs, addressing both environmental and efficiency limitations associated with conventional organic solvents. Their advantages include straightforward synthesis, low toxicity, biodegradability, and tunable physicochemical properties. This article systematically summarizes recent advances in the application of DES for extracting various active ingredients of traditional Chinese medicine, including flavonoids, saponins, alkaloids, polysaccharides, polyphenols, and volatile oils. It focuses on analyzing the structural characteristics of these compound classes and the underlying principles guiding DES selection, categorizes DES systems suitable for each class of active ingredient, and outlines the corresponding optimized process conditions. Building upon this foundation, the extraction mechanisms—particularly hydrogen bonding interactions and polarity matching between DES and target components—were investigated, and the influencing factors and underlying patterns governing DES extraction efficiency were systematically summarized. In response to current research challenges—including high viscosity, difficult separation and recovery, and the absence of a targeted design theory—future research directions were proposed to support the continued advancement of green extraction processes for traditional Chinese medicine.

Sugar cane bagasse was delignified in a two-step process with peracetic acid and alkali. Peracetic acid pre-treatment with concentration of 25% based on oven-dry fiber at 60 min, with a liquor to wood (L/W) ratio of 9:1 and a temperature of 50 °C improved the second stage delignification, compared with soda pulping. The second stage was carried out at three levels of temperatures, times, and 20% sodium hydroxide based on oven-dry fiber. Soda pulping at 165 °C, 120 min, 20% sodium hydroxide based on oven-dry fiber, and L/W 10:1 was selected to compare with two-step delignification. The two-step delignification reduces the severity of pulping conditions, including temperature and pressure, and subsequent imposes less risks compared with the soda pulping at 165 °C. The advantages of this method are high delignification and reduction of kappa number with respect to lower temperature and pressure compared with soda pulping. The total time in two-step was increased from soda pulping. Two optimum conditions for alkali step were obtained at 120 °C and 140 °C and 90 min for pretreated bagasse pulping, and similar properties were achieved with soda pulping at 165 °C and 120 min. The yield of fibers, Kappa number, and data analysis using Duncan method were measured and recorded.

Deep eutectic solvents (DES) are defined as combinations of two or three components which are able to establish hydrogen bond interactions with each other to form an eutectic mixture, that have a melting point lower than that of the each individual component. This study aims to determine the characteristics of DES based on choline chloride (ChCl) as quaternary ammonium salts and p-toluenasulfonic acid (PTSA) as hydrogen bond donors and to investigate their selectivity for dissolving metals in tin tailings. Synthesis of DES was carried out by mixing ChCl and PTSA with variations of the mole fraction, then stirring at 80 oC for 15 minutes. Resulted products were characterized their freezing point, density, viscosity, conductivity and functional groups. Mixture with a mole fraction of ChCl 0.6 formed homogeny clear liquid. It has a freezing point of 8 oC, density of 1.207 g/mL, viscosity of 4.663 cP, and conductivity of 182.4 mS/cm. Based on fourier transform infrared (FTIR) analysis, the interaction between ChCl and PTSA was due to the formation of hydrogen bonds between the O atoms of PTSA and the H atoms of ChCl. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis showed the presence of 1962 ppm of Fe metal dissolved in DES. This value was significant greater than the presence of other metals in the DES.

Ultrasound-enhanced peracetic acid oxidation improves short-chain fatty acids production from waste activated sludge

Deep eutectic solvents (DESs), a new class of green solvents, have attracted considerable attention for CO2 capture. In this study, we synthesised DESs using a superbase, 1,5-diazabicyclo [4.3.0] non-5-ene (DBN), as the hydrogen bond acceptor and a weak acid, diethylene glycol (DEG), as the hydrogen bond donor in different molar ratios to achieve efficient and reversible CO2 absorption. Experimental results indicate that DES2 (DBN:DEG = 1:2) exhibits optimal CO2 absorption performance (a maximum absorption capacity of 0.275 gCO2/gDES. Deep eutectic solvents at 30°C and flow rate of 30 mL/min). Nuclear magnetic resonance (NMR) spectroscopy reveals that DEG activated by DBN in DESs can react with CO2 to form carbonates, thereby enabling CO2 capture. In addition, monoethanolamine was added to the DESs as a promoter, thereby enhancing the CO2 absorption performance, with a maximum absorption capacity of 0.316 gCO2/gDES. 13C NMR and Fourier transform infrared analyses revealed that the amino and hydroxyl groups in the DESs can simultaneously react with CO2 to form carbamate and carbonate, achieving synergistic absorption.

In recent years, deep eutectic solvents (DESs) have experienced widespread growth due to their potential use as “green solvents” replacing traditional organic solvents. DESs present important advantages such as easy preparation, high affinity, low toxicity and accessibility of their components. Therefore, they have been applied as extracting agents in liquid phase microextraction techniques. Despite the DESs advantages, some limitations have been described related to their solubility, viscosity, selectivity and stability, consequently, an alternative described is binary DESs incorporation of a third component (ternary deep eutectic solvents) have been developed as an alternative. This new type of solvents improves some physical and chemical characteristics as well as extraction efficiency and selectivity, besides to exhibit good stability in polar or nonpolar matrices, high ratio dispersion and separation from extraction media, good selectivity and affinity toward various compounds. This review classifies ternary DESs based on the components used in their synthesis, as hydrophilic ternary DESs, hydrophobic ternary DESs, magnetic ternary DESs, supramolecular ternary DESs, and polymeric ternary DESs and their sub-classifications. Emerging trends in the development of ternary DES, including the interaction mechanisms for the extraction process, their application in various matrices, and the results obtained for different target compounds, are described and discussed.

Deep Eutectic Solvent (DES) are eutectic mixes of hydrogen bond acceptors (HBA) and donors (HBD) with melting points significantly lower than their constituents. Choline chloride (ChCl) and glycerol were chosen as HBA and HBD because they are simple to prepare, have low toxicity, are biodegradable, and are environmentally friendly. As a result, the study aims to determine the feasibility of extracting lignin from oil palm fronds (OPF) and empty fruit bunches (EFB) using DES. The molar ratios of DESs were investigated to determine their effect on OPF solubility and lignin yield. The reaction is carried out at a solid loading ratio of 1:10, 150°C, and 6 hours. Because the DES medium induces homogeneous swelling and breakdown of small fibre fragments but not dissolution, both OPF and EFB are insoluble in DES. Small fragment disintegration suggests rapid dissolution, which will be easily dissolved in the DESs. The lignin yield and solubility of EFB and OPF in DESs are significantly reduced when the molar concentration of glycerol is increased. The highest lignin yields, 27.6% (EFB) and 16.1% (OPF) were obtained with a ChCl/glycerol molar ratio of 1:3. The comparatively low lignin yield achieved for both OPF and EFB is ascribed to the poor hydrogen bonding between the chloride ion and the hydroxyl group of the DES due to the low acidity of the DES. Despite this, lignin is extracted successfully due to the presence of chloride ions in ChCl, which target β-O-4 bonds and successfully cleave the ether bonds present in the lignin-carbohydrate linkage.

Deep eutectic solvents (DESs) are novel solvent media that are currently under investigation as an alternative to ionic liquids and conventional solvents. The physical properties of DESs as well as their mild environmental footprint and potentially critical industrial application necessitate understanding the interaction of functional groups on both the salt and hydrogen bond donor (HBD). In this study, four DESs were prepared by mixing triethylenglycol, diethylenglycol, ethylenglycol, and glycerol as HBDs with methyltriphenyl phosphonium bromide as a salt at a molar ratio of 1:4. Fourier transform infrared spectroscopy was conducted to highlight the chemical structure and mechanism of the combination of the four DESs. New spectra illustrating the combination of the functional groups of the HBDs and salt were observed and interpreted. This study is the first to investigate the properties of neoteric FT-IR for phosphonium-based DESs in addition to (MTPB:TEG) which was reported previously.

After biomass fractionation using deep eutectic solvents (DES), solvent recovery is an essential step. Recovery of lignin from DES by liquid–liquid extraction (LLX) may provide large energy savings compared to cold water precipitation. Lignin that is dissolved in DES from biomass fractionation is inhomogeneous, meaning it has various fractions with different molar weights and possibly variations in functional group densities. Therefore, it is important to compare recoverability of every lignin fraction by LLX with cold-water precipitation. In this work, the recovery of lignin from a DES comprised of 30 wt% choline chloride and 70 wt% lactic acid was studied. Using as much as 30 wt% choline chloride is beneficial to limit leaching of lactic acid. Three cross-current extractions were performed using 2-MTHF. This method recovered 95% of the lignin fractions around 2000 g/mol and 85% of the lignin fractions around 10,000 g/mol. No inter-aromatic ether bonds were found in the lignin remaining in the DES raffinate by heteronuclear single quantum coherence spectroscopy (HSQC), indicating the remaining lignin in the DES has a highly condensed nature. Cold water precipitation could fully recover the lignin fractions above 4000 g/mol using 3.5 kg water per kg DES. However, only half of the lignin fraction of 1000 g/mol was recovered. Briefly, LLX is more suitable for the recovery of low molar weight fractions, while cold water precipitation is more suitable for the heavy molar weight fractions. For industrial applications, a combination of both approaches is essential for full lignin recovery.