Supported liquid membranes using ionic liquids: study of stability and transport mechanisms

Determination of catechol in water with deep eutectic supramolecular solvents-assisted magnetic κ-carrageenan nanoparticles

A combination of magnetic κ-carrageenan nanoparticles and deep eutectic supramolecular solvents used for extraction of catechol from water was evaluated by the magnetic dispersion solid phase extraction method. The magnetic κ-carrageenan nanoparticles (KC@Fe3O4MNPs) and the deep eutectic supramolecular solvent (DESP) were characterised by 1H NMR, FT-IR, XRD, SEM, VSM, TG, and BET. The adsorption kinetics, adsorption isothermal model, adsorption thermodynamics and effects of pH and salt concentration were investigated. Additionally, the factors used in the desorption process, such as the type, dosage, concentration and time, were analysed. Under the optimised conditions, the analytes were linear over the range 5-5000 ng mL-1, with a correlation coefficient greater than 0.999 and detection and quantitation limits of 1.6 and 4.7 ng mL-1, respectively. The procedure was successfully applied to determinations of the analytes of interest in spiked water samples with relative average recoveries ranging from 94.3% to 101.5%. These results indicated that the combination of functionalized magnetic nanoparticles and DESP had high specificity and extraction efficiency for catechol and will be a feasible alternative to conventional analyses of organic phenolic pollutants in water.

An Ionic Supported Liquid Membrane for the Recovery of Bisphenol A from Aqueous Solution

In this work, a flat supported liquid membrane (FSLM) was applied for the extraction of bisphenol A (BPA) from aqueous solutions, using an ionic liquid as a carrier. The liquid membrane consists of tricaprylmethylammonium chloride (aliquat 336^®) diluted in 2-octanol. Furthermore, to obtain the best transport efficiency, the impacts of various experimental parameters were investigated. These parameters included aliquat 336^® concentration, the concentration of BPA in the feed phase, the pH of the feed phase, the concentration of NaOH in the receiving phase, the polymeric support nature, the percentage of extractant in the organic phase, and the solvent nature. The optimum conditions of the experiment were 50% (v/v) aliquat 336^®/2-octanol as the organic phase, a transport time of 8 h, and 1 × 10^-2 mol L^-1 NaOH as the receiving phase. The BPA was successfully recovered (the recovery percentage was about 89%). Supported liquid membrane-based aliquat 336^®/2-octanol displayed an acceptable stability with re-impregnation after 5 days of operation.

Determination of nerve agent biomarkers in human urine by a natural hydrophobic deep eutectic solvent-parallel artificial liquid membrane extraction technique

Alkyl methyl phosphonic acids (AMPAs) are the major metabolites of organophosphorus nerve agents. A method based on the use of natural hydrophobic deep eutectic solvents as supported liquid membrane in parallel artificial liquid microextraction (PALME) combined with LC-MS/MS analysis was developed and applied to their extraction from urine samples. PALME is a miniaturized liquid-phase extraction method performed in a multiwell plate format where the aqueous sample and the aqueous acceptor phase are separated by a flat membrane impregnated with an organic solvent. In this study, we investigated the possibility of replacing the harmful conventional organic solvent by an emerging green solvent, a coumarin/thymol-based deep eutectic solvent, in ordered to raise the greenness of the sample preparation method. Linear response was obtained in an interval of 0.5, 5 or 10-100 ng/ml depending on the AMPAs with a determination coefficients (R²s) ranging from 0.9751 to 0.9989 for their determination in not treated urine samples. Enrichment factors (EFs) up to 12.65 were obtained, and repeatability was within 8.90-16.28% RSD (n = 12). The limit of quantifications (LOQs: S/N ≥ 10) of the whole analytical procedure were in the range from 0.04 to 5.35 ng/ml. In addition to its good sensitivity, the presented method permitted the treatment of 192 samples in 120 min (equivalent to 37.5 s/sample), which places it as one of the most powerful preparation technique for biomonitoring of civilian or military people exposed to nerve agents in case of public health emergency. Indeed, the developed procedure combined sensitivity, high-throughput, greenness, simplicity and practicality for the determination of five acidic polar AMPAs in urine samples.

Overview of Membrane Science and Technology in Portugal

Membrane research in Portugal is aligned with global concerns and expectations for sustainable social development, thus progressively focusing on the use of natural resources and renewable energy. This review begins by addressing the pioneer work on membrane science and technology in Portugal by the research groups of Instituto Superior Técnico-Universidade de Lisboa (IST), NOVA School of Science and Technology-Universidade Nova de Lisboa (FCT NOVA) and Faculdade de Engenharia-Universidade do Porto (FEUP) aiming to provide an historical perspective on the topic. Then, an overview of the trends and challenges in membrane processes and materials, mostly in the last five years, involving Portuguese researchers, is presented as a contribution to a more sustainable water-energy-material-food nexus.

Comparison of CO2 Separation Efficiency from Flue Gases Based on Commonly Used Methods and Materials

The comparison study of CO₂ removal efficiency from flue gases at low pressures and temperatures is presented, based on commonly used methods and materials. Our own experimental results were compared and analyzed for different methods of CO₂ removal from flue gases: absorption in a packed column, adsorption in a packed column and membrane separation on polymeric and ceramic membranes, as well as on the developed supported ionic liquid membranes (SILMs). The efficiency and competitiveness comparison of the investigated methods showed that SILMs obtained by coating of the polydimethylsiloxane (PDMS) membrane with 1-ethyl-3-methylimidazolium acetate ([Emim][Ac]) exhibit a high ideal CO₂/N₂ selectivity of 152, permeability of 2400 barrer and long term stability. Inexpensive and selective SILMs were prepared applying commercial membranes. Under similar experimental conditions, the absorption in aqueous Monoethanolamine (MEA) solutions is much faster than in ionic liquids (ILs), but gas and liquid flow rates in packed column sprayed with IL are limited due to the much higher viscosity and lower diffusion coefficient of IL. For CO₂ adsorption on activated carbons impregnated with amine or IL, only a small improvement in the adsorption properties was achieved. The experimental research was compared with the literature data to find a feasible solution based on commercially available methods and materials.

Novel Poly(ionic liquid) Augmented Membranes for Unconventional Aqueous Phase Applications in Fractionation of Dyes and Sugar

Poly(ionic) liquid (PIL) augmented membranes were fabricated through self-polymerization of 2-vinyl pyridine and 4-vinyl pyridine followed by dopamine triggered polymerization and bridging with inert polyamide support. The resulting membranes acquired a positive surface charge with a high degree of hydrophilicity. Fourier transformed Infra-red (FTIR) and Energy dispersive X-ray (EDX) spectroscopic investigation revealed the successful augmentation of PIL surface layer, whereas surface morphology was investigated through scanning electron microscopy (SEM) imaging. This manuscript demonstrates pi electron-induced separation of dyes with the trend in permeability: Coomassie Brilliant Blue G (CBBHG) > Remazol Brilliant Blue R (RBBR) > Eichrome Black T (EBT) > Congo Red (CR). CBBG exhibited extended conjugation over large aromatic domain. RBBR and EBT were associated withtheelectron-donating -NH2 group and electron-withdrawing -NO2 group, respectively, hence pi electron density on aromatic ring varied. The steric repulsion between two pairs of ortho hydrogens (Hs) in biphenyl moieties of CR resulted in deviation of planarity and hence aromaticity leading to the lowest permeability. The sugar fractionation followed the trend: Galactose > Mannose > Fructose > Glucose > Xylose. More hydroxyl (-OH) groups in sugars and their conformational alignment in the same direction, exhibited more lone pair of electrons leading to more interaction with PIL and hence better permeability. Pentose showed poorer permeation than hexose, whereas aldose showed better permeation than ketose.

Investigating the Proton and Ion Transfer Properties of Supported Ionic Liquid Membranes Prepared for Bioelectrochemical Applications Using Hydrophobic Imidazolium-Type Ionic Liquids

Hydrophobic ionic liquids (IL) may offer a special electrolyte in the form of supported ionic liquid membranes (SILM) for microbial fuel cells (MFC) due to their advantageous mass transfer characteristics. In this work, the proton and ion transfer properties of SILMs made with IL containing imidazolium cation and [PF₆]⁻ and [NTf₂]⁻ anions were studied and compared to Nafion. It resulted that both ILs show better proton mass transfer and diffusion coefficient than Nafion. The data implied the presence of water microclusters permeating through [hmim][PF₆]-SILM to assist the proton transfer. This mechanism could not be assumed in the case of [NTf₂]⁻ containing IL. Ion transport numbers of K⁺, Na⁺, and H⁺ showed that the IL with [PF₆]⁻ anion could be beneficial in terms of reducing ion transfer losses in MFCs. Moreover, the conductivity of [bmim][PF₆]-SILM at low electrolyte concentration (such as in MFCs) was comparable to Nafion.

Seaweed Polysaccharide Based Products and Materials: An Assessment on Their Production from a Sustainability Point of View

Among the various natural polymers, polysaccharides are one of the oldest biopolymers present on the Earth. They play a very crucial role in the survival of both animals and plants. Due to the presence of hydroxyl functional groups in most of the polysaccharides, it is easy to prepare their chemical derivatives. Several polysaccharide derivatives are widely used in a number of industrial applications. The polysaccharides such as cellulose, starch, chitosan, etc., have several applications but due to some distinguished characteristic properties, seaweed polysaccharides are preferred in a number of applications. This review covers published literature on the seaweed polysaccharides, their origin, and extraction from seaweeds, application, and chemical modification. Derivatization of the polysaccharides to impart new functionalities by chemical modification such as esterification, amidation, amination, C-N bond formation, sulphation, acetylation, phosphorylation, and graft copolymerization is discussed. The suitability of extraction of seaweed polysaccharides such as agar, carrageenan, and alginate using ionic solvent systems from a sustainability point of view and future prospects for efficient extraction and functionalization of seaweed polysaccharides is also included in this review article.

Deep eutectic solvents: alternative reaction media for organic oxidation reactions

Deep eutectic solvents (DESs) are a valid alternative to common organic solvents and ionic liquids (ILs) as solvent media for organic oxidation reactions.

Development and Application of Supported Ionic Liquid Membranes in Microbial Fuel Cell Technology: A Concise Overview

Membrane separators are key elements of microbial fuel cells (MFCs), especially of those constructed in a dual-chamber configuration. Until now, membranes made of Nafion have been applied the most widely to set-up MFCs. However, there is a broader agreement in the literature that Nafion is expensive and in many cases, does not meet the actual (mainly mass transfer-specific) requirements demanded by the process and users. Driven by these issues, there has been notable progress in the development of alternative materials for membrane fabrication, among which those relying on the deployment of ionic liquids are emerging. In this review, the background of and recent advances in ionic liquid-containing separators, particularly supported ionic liquid membranes (SILMs), designed for MFC applications are addressed and evaluated. After an assessment of the basic criteria to be fulfilled by membranes in MFCs, experiences with SILMs will be outlined, along with important aspects of transport processes. Finally, a comparison with the literature is presented to elaborate on how MFCs installed with SILM perform relative to similar systems assembled with other, e.g., Nafion, membranes.

Ionic liquid-based water treatment technologies for organic pollutants: Current status and future prospects of ionic liquid mediated technologies

Water scarcity motivated the scientific researcher to develop efficient technologies for the wastewater treatment for its reuse. Ionic liquids have been applied to many industrial and analytical separation processes, but their applications in the wastewater treatment, especially in the removal of organic pollutants, are still not well explored. Potential applications of ionic liquids include solvent extraction, solvent membrane technologies and ionic liquid-modified materials that are mainly used as adsorbents. Aforementioned technologies have been examined for the abatement of phenol, chloro- and nitrophenols, toluene, bisphenol A, phthalates, pesticides, dyes, and pharmaceuticals etc. Present review enlightens the application of different ionic liquids in wastewater treatment and suggests the versatility of ionic liquids in the development of rapid, effective and selective removal processes for the variety of organic pollutants. Implementation of ionic liquid based technologies for wastewater treatment have lots of challenges including the selection of non-hazardous ionic liquids, technological applications, high testing requirements for individual uses and scaling-up of the entire pollutant removal, disposal, and ionic liquid regeneration process. Toxicity assessment of water soluble ionic liquids (ILs) is the major issue due to the widespread application of ILs and hence more exposure of environment by ILs. The development of effective technologies for the recovery/treatment of wastewater contaminated with ILs is necessary from the environmental point of view. Furthermore, the cost factor is the major challenge associated with ionic liquid-based technologies.

Pore Scale Visualization of Drainage in 3D Porous Media by Confocal Microscopy

We visualize the dynamics of immiscible displacement of a high viscosity wetting phase by a low viscosity non-wetting phase in a three-dimensional (3D) glass bead packing using confocal microscopy. Both phases were doped with two different fluorescent dyes, which enabled visualization of both phases simultaneously and quantification of the phase volumes without the need of image subtraction operations. The transient results show details of the displacement process and how pores are invaded by the non-wetting displacing phase. The static images at the end of the displacement process reveal how the trapped ganglia volume and morphology change with capillary number. The wetting phase is trapped as pendular rings spanning one to multiple pore necks. Details of the pore scale flow of oil wet media revealed with the experimental methods presented here can lead to better fundamental understanding of the physical processes and optimized enhanced oil recovery methods, CO₂ sequestration and aquifer remediation.

On the Selective Transport of Nutrients through Polymer Inclusion Membranes Based on Ionic Liquids

In the last few years, the use of ionic liquid-based membranes has gained importance in a wide variety of separation processes due to the unique properties of ionic liquids. The aim of this work is to analyze the transport of nutrients through polymer inclusion membranes based on different concentrations of methyltrioctylammonium chloride, in order to broaden the application range of these kinds of membranes. Calcium chloride (CaCl2) and sodium hydrogen phosphate (Na2HPO4) nutrients were used at the concentration of 1 g·L−1 in the feeding phase. The evolution of the concentration in the receiving phase over time (168 h) was monitored and the experimental data fitted to a diffusion-solution transport model. The results show very low permeation values for CaCl2. By contrast, in the case of Na2HPO4 the permeation values were higher and increase as the amount of ionic liquid in the membrane also increases. The surface of the membranes was characterized before and after being used in the separation process by scanning electron microscopy coupled to energy dispersive X-Ray spectroscopy (SEM–EDX) and elemental mapping analysis. The SEM–EDX images show that the polymer inclusion membranes studied are stable to aqueous solution contacting phases and therefore, they might be used for the selective transport of nutrients in separation processes.

Performance of butanol separation from ABE mixtures by pervaporation using silicone-coated ionic liquid gel membranes

This work aims at the separation of n-butanol from aqueous solutions by means of pervaporation using membranes based on gelled ionic liquids (IL).

Selective separation of furfural and hydroxymethylfurfural from an aqueous solution using a supported hydrophobic deep eutectic solvent liquid membrane

For the first time, 12 different supported deep eutectic solvent (DES) liquid membranes were prepared and characterized.

Novel generation of deep eutectic solvent as an acceptor phase in three-phase hollow fiber liquid phase microextraction for extraction and preconcentration of steroidal hormones from biological fluids

In this study, a novel generation of deep eutectic solvents (DESs) was used as an acceptor phase in three-phase hollow fiber liquid phase microextraction (HF-LPME) based on two immiscible organic phases. It was compared with other common DESs for extraction and preconcentration of dydrogesterone (DYD) and cyproterone acetate (CPA) from urine and plasma samples. The extracted analytes were analyzed by high performance liquid chromatography with UV-vis detector (HPLC-UV). This phosphonium based DES due to low volatility, low price and multifunctionality introduced itself as worthy next generation of acceptor phase in HF-LPME. The factors affected on extraction efficiency of the analytes were investigated and optimized. The performance of the proposed method was studied in terms of linear ranges (LRs from 1 to 500µgL^-1 with R² ≥ 0.9946), precision (RSD% ≤ 6.3) and limits of detection (LODs in the range of 0.5-2µgL^-1). Under the optimized conditions, preconcentration factors in the range of 187-428 were obtained. Finally, the method was applied to the analysis of DYD and CPA in human urine and plasma samples and desirable results were obtained.

Supramolecular nanosolvent-based hollow fiber liquid phase microextraction as a novel method for simultaneous preconcentration of acidic, basic and amphiprotic pollutants

In this study, for the first time, coextraction of acidic, basic and amphiprotic pollutants was performed using supramolecular nano solvent-based hollow fiber liquid phase microextraction.

The Effect of Microporous Polymeric Support Modification on Surface and Gas Transport Properties of Supported Ionic Liquid Membranes

Microporous polymers based on anionic macroinitiator and toluene 2,4-diisocyanate were used as a support for 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf₂N]) immobilization. The polymeric support was modified by using silica particles associated in oligomeric media, and the influence of the modifier used on the polymeric structure was studied. The supported ionic liquid membranes (SILMs) were tested for He, N₂, NH₃, H₂S, and CO₂ gas separation and ideal selectivities were calculated. The high values of ideal selectivity for ammonia-based systems with permanent gases were observed on polymer matrixes immobilized with [bmim][PF₆] and [emim][Tf₂N]. The modification of SILMs by nanosize silica particles leads to an increase of NH₃ separation relatively to CO₂ or H₂S.