Switchable Hydrophilicity Solvents Research Articles

Use of switchable hydrophilicity solvents for the homogeneous liquid-liquid microextraction of triazine herbicides from environmental water samples.

A homogeneous liquid-liquid microextraction alternative, based on the use of switchable hydrophilicity solvents, is presented. The extraction technique makes use of 125 μL of a water-immiscible solvent (N,N-dimethylcyclohexylamine) that can be solubilized in the aqueous phase in 1:1 ratio using CO2 as a reagent. After the extraction, phase separation is induced by the addition of sodium hydroxide that produces a change on the ionization state of the amine, and centrifugation was not necessary. The extraction technique has been optimized and characterized using the determination of triazine herbicides by gas chromatography with mass spectrometry in water samples. The presence of metallic ions in environmental waters as interferents is easily avoided by the addition of ethylenediaminetetraacetic acid before the microextraction procedure. The proposed method allows the determination of the target analytes at the low microgram per liter range with good precision (relative standard deviation lower than 12.5%).

Extending the range of switchable-hydrophilicity solvents

A switchable-hydrophilicity solvent (SHS) is a solvent that in one state forms a biphasic mixture with water but can be reversibly switched to another state that is miscible with water. All of the amine SHSs that we have reported previously lie within a particular basicity and hydrophilicity range (9.5 < pKaH < 11 and 1.0 < log Kow < 2.5, respectively). We report an extension of this range by altering the pressure of CO2 as well as the water : SHS volume ratio used in the process. Increasing the pressure of CO2 and/or the water : amine volume ratio allows some amines with pKaH < 9.5 or log Kow > 2.5 to function as SHSs.

A virtual screening approach to identifying the greenest compound for a task: application to switchable-hydrophilicity solvents

QSAR-based virtual screening makes it easier to identify lead structures that could simultaneously satisfy several performance criteria and several green criteria.

Use of switchable solvents in the microextraction context

In this article, a new homogeneous liquid-liquid microextraction alternative, based on the use of switchable hydrophilicity solvents (SHS), is presented for the first time. The extraction technique makes use of a water-immiscible solvent (N,N-Dimethylcyclohexylamine) that can be solubilised in 1:1 ratio using CO2 as reagent. After the extraction, phases׳ separation is induced by the addition of sodium hydroxide, which produces a change on the ionisation state of the amine, centrifugation not being necessary. The extraction technique has been optimised and characterised using the determination of benz[a]anthracene by fluorimetric measurements in water samples as model analytical problem. Although the native fluorescence of the compound is quenched in the organic phase, this attenuation is reduced by diluting the extractant (1:1) in acetic acid. The fluorescence intensity is 35% higher in the SHS-acetic acid mixture than that obtained in pure methanol. The proposed method allows the determination of the target analyte with limit of detection of 0.08μg/L and good precision (relative standard deviation of 6.7% at the limit of quantification level). The recoveries were in the range of 72–100% fulfilling the Environmental Protection Agency criterion. Finally, the potential use of this microextraction technique in combination with gas chromatography is shown for several polycyclic aromatic hydrocarbons.

Extraction of phenolic compounds from crude pyrolysis oil

Due to serious environmental problem and strict regulations to control pollution, researchers across the globe are putting their effort to find clean, renewable, greener and cost effective method to produce biochemical from biomass. The aim of this article was to highlight the method to extract phenolic compounds from crude pyrolysis oil using switchable hydrophilicity solvents (SHS). The pyrolysis oil was produced from softwood Kraft lignin through novel microwave pyrolysis process. The extraction efficiency of the method discussed in this article was about 95%. However, it was applied to small batch of pyrolysis oil (10 g). The highlight also presents the advantage and disadvantage of phenolic compound extraction methods including the recent proposed by Fu et al., 2013.

Design and evaluation of switchable-hydrophilicity solvents

Switchable-hydrophilicity solvents (SHS) can switch reversibly between one form that is miscible with water and another that forms a biphasic mixture with water. New examples are reported and compared in terms of safety and environmental impact.

Modelling the behaviour of switchable-hydrophilicity solvents

A switchable-hydrophilicity solvent (SHS) is a solvent that in one state forms a biphasic mixture with water but can be reversibly switched to another state that is miscible with water. We describe a mathematical model of the behaviour of CO2-triggered SHS that narrows the search field for these solvents in terms of their basicity and hydrophilicity. By its predictive power, the mathematical model can assist in the optimization of processes using SHSs in terms of extrinsic parameters such as pressure and the relative volumes of solvent and water used. Models are presented for both a two-liquid system (consisting of the amine solvent and water) and a three-liquid system (consisting of the amine solvent, water, and 1-octanol). Partitioning data with toluene as the third component is also shown for comparison with 1-octanol.

Synthesis of new polyethoxylated tertiary amines and their use as Switchable Hydrophilicity Solvents

New polyethoxylated tertiary amines were synthesised and applied as Switchable Hydrophilicity Solvents (SHS) in the extraction and recovery of lipids from algal cultures, bypassing harvesting and de-watering steps. The eco-toxicological profile of the new amines was explored by evaluating their potential in inhibiting algal growth, and deepened by measuring the acute toxicity towards the crustacean Daphnia magna and the ready biodegradability in water. Among the synthesised amines, the one bearing two ethoxy units, named amine 2, showed the best combination in terms of lipids' extractive performances and toxicity; therefore it could be considered as a good alternative to N,N-dimethylcyclohexylamine (DMCHA), at the moment the most studied and effective SHS.

Extraction of phenols from lignin microwave-pyrolysis oil using a switchable hydrophilicity solvent

Microwave pyrolysis of lignin, an aromatic polymer byproduct from paper-pulping industry, produces char, gases, and lignin pyrolysis oil. Within the oil are valuable phenolic compounds such as phenol, guaiacol and catechol. In this work, we describe a method using switchable hydrophilicity solvents (SHS) to extract phenols as a mixture from lignin microwave-pyrolysis oil at the scale of 10 g of bio-oil. Even at this small scale, losses are small; 96% of the bio-oil was recovered in its three fractions, 72% of guaiacol and 70% of 4-methylguaiacol, the most abundant phenols in the bio-oil, were extracted and 91% of the solvent SHS was recovered after extraction. The starting material (lignin microwave-pyrolysis oil) and the three fractions resulted from SHS extraction were characterized by GC-MS and quantitative (13)C{(1)H} and (31)P{(1)H} NMR spectroscopy.

Switchable hydrophilicity solvents for lipid extraction from microalgae for biofuel production

A switchable hydrophilicity solvent (SHS) was studied for its effectiveness at extracting lipids from freeze-dried samples of Botryococcus braunii microalgae. The SHS N,N-dimethylcyclohexylamine extracted up to 22wt.% crude lipid relative to the freeze-dried cell weight. The solvent was removed from the extract with water saturated with carbon dioxide at atmospheric pressure and recovered from the water upon de-carbonation of the mixture. Liquid chromatography–mass spectrometry (LC–MS) showed that the extracted lipids contained high concentrations of long chain tri-, di- and mono-acylglycerols, no phospholipids, and only 4–8% of residual solvent. Unlike extractions with conventional organic solvents, this new method requires neither distillation nor the use of volatile, flammable or chlorinated organic solvents.

Tertiary amine solvents having switchable hydrophilicity

Several tertiary amines serve as switchable-hydrophilicity solvents, meaning that they are hydrophobic solvents having very low miscibility with water when under air but hydrophilic solvents having complete miscibility with water when under an atmosphere of CO2. Unlike the only previously reported switchable-hydrophilicity solvent, these amines are easily prepared and, in some cases, commercially available. The effect of temperature, gas flow rates, choice of amine and additives on the switching process is described. These solvents can be applied to the recycling of polystyrene foam.

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Separation is widely involved in many fields, such as materials synthesis, gas purification or removal, water treatment, petroleum exploitation, soil remediation, food and medicine production, etc. Compared with the physical separation, the chemical separation has unique advantages when the functionalized process aids are added in systems. The CO2-responsive materials are considered as promising separating mediums due to their relatively green and easily recyclable properties, which realize the resource utilization of CO2. Up to date, the reported CO2-responsive materials are mainly referred to switchable-hydrophilicity solvents, switchable surfactants, switchable water additives, switchable ionic liquids and CO2-responsive polymers. These CO2-responsive materials can be switched by CO2 trigger at moderate conditions, showing switchable properties, such as hydrophilicity-hydrophobicity conversion, switching “on” or “off” surface-activity and switchable change in ionic strength. These switchable properties can be applied in separations, especially in oil-solid separation, oil-water separation, wastewater treatment and acid gas capture. In this review, the recent advances of CO2-responsive materials in separation fields above have been overviewed. Additionally, the present challenges and future engineering considerations have been touched to provide potential insights and theoretical fundamentals for developing CO2-responsive materials.