Extraction of Phenols from Water with Functionalized Ionic Liquids

Ionic liquid-based dispersive liquid-liquid microextraction of succinic acid from aqueous streams: COSMO-RS screening and experimental verification

In the present investigation, a total of 108 combinations of ionic liquids (ILs) were screened using the conductor-like screening model for real solvents (COSMO-RS) with the aid of six cations and eighteen anions for the extraction of succinic acid (SA) from aqueous streams through dispersive liquid-liquid microextraction (DLLME). Using the screened ILs, an ionic liquid-based DLLME (IL-DLLME) was developed to extract SA and the role of different reaction parameters in the effectiveness of IL-DLLME approach was investigated. COSMO-RS results suggested that, quaternary ammonium and choline cations form effective IL combinations with [OH¯], [F¯], and [SO42¯] anions due to hydrogen bonding. In view of these results, one of the screened ILs, tetramethylammonium hydroxide [TMAm][OH] was chosen as the extractant in IL-DLLME process and acetonitrile was adopted as the dispersive solvent. The highest SA removal efficiency of 97.8% was achieved using 25 μL of IL [TMAm][OH] as a carrier and 500 μL of acetonitrile as dispersive solvent. The highest amount of SA was extracted with a stir time of 20 min at 300 rpm, followed by centrifugation for 5 min at 4500 rpm. Overall, the findings showed that IL-DLLME is efficient in extracting succinic acid from aqueous environments while adhering to the first-order kinetics.

Molecular insights into dicationic versus monocationic ionic liquids as a high hydrophobic alternative for the separation of phenol from waters

The hydrophobic nature of an extractant is particularly critical in the treatment of wastewater. Considering that dicationic ionic liquids (DILs) are likely to be more hydrophobic, a comparative study of the separation of phenol from waters using [NTf2]- based monocationic ionic liquids (MILs) and DILs is carried out both from experimental and theoretical analysis perspectives. Experimental results revealed that DILs exhibited superior extraction ability compared to MILs, with extraction efficiencies of 93.7% and 97.4% using [BMIM][NTf2] and [C6(MIM)2][NTf2]2 as extractants, respectively. The microscopic examination through theoretical calculations elucidated the higher hydrophobicity and extraction efficiency of DILs over MILs. The results indicated that the DIL showed stronger hydrophobicity than the MIL because the hydrogen bond strength between the DIL and water was lower than that of the MIL. Although the hydrogen bond strength between the DIL and phenol was lower than that of the MIL, the stronger van der Waals forces existed between DIL and phenol, so DIL was more efficient in extracting phenol. In addition, the experimental parameters were optimized to provide basic data for application, such as mass ratio of ILs to water, extraction time and temperature, pH, and initial phenol content. Finally, the DILs were recovered using rotary evaporation apparatus, and the results demonstrated that DILs had good recovery and reuse performance. In brief, this work could provide an effective method for the treatment of phenol-containing wastewater. And the revelation of molecular mechanism is expected to positively impact the design of high-performance task-specific ILs.

Performance of ionic liquid functionalized metal organic frameworks in the adsorption process of phenol derivatives

The growth of industrial activities has produced a significant increase in the release of toxic organic pollutants (OPs) to the environment from industrial wastewater. On this premise, this study reports the use of metal organic frameworks (MOFs) impregnated with various ionic liquids (ILs) in the adsorption of phenol derivatives, i.e., 2,6-dimethylphenol and 4,4'-dihydroxybiphenyl. MOFs were prepared starting from 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) with divalent (Co, Ni, Cu) and trivalent (Ce) metal salts in mild hydrothermal conditions using water as a green solvent. Imidazolium base ionic liquids, namely 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium nitrate, 1-butyl-3-methylimidazolium chloride, and 1-hexyl-3-methyl-imidazolium chloride, were used to modify MOFs, leading to composite materials (IL@MOF), which show the structural characteristics of MOFs, and complement the advantages of ILs. SEM, EDX images, and TG data indicate that the IL is just attached on the surface of the adsorbent material, with no changes in crystal size or morphology, but with slightly altered thermal stabilities of IL@MOF composites compared to the original ILs and MOFs, pointing to some interionic interaction between IL and MOF. This research consists of equilibrium experiments, studying the effect of the initial concentration of OPs on the adsorption efficiency of the as-prepared MOFs and IL@MOF, in order to determine the influence of the nature of the adsorbent on its developed adsorption capacity and to investigate the performance of both ILs and MOFs. To determine the maximum adsorption capacity, several empirical isotherms were used: Langmuir, Freundlich, Redlich-Peterson, and Dubinin-Radushkevich. The characteristic parameters for each isotherm and the correlation coefficient (R2) were identified. The IL modification of MOFs increased the adsorption capacity of IL@MOF for the removal of phenol derivatives from aqueous solution. The adsorption capacity function of the MOF structure follows the trend CeHEDP > CoHEDP > NiHEDP > CuHEDP. The best performance was achieved by adsorbent materials based on Ce.

A green hydrophobic deep eutectic solvent for extraction of phenol from aqueous phase

Deep eutectic solvents (DESs), have been recognized as effective materials for the extraction of different compounds. In this study, the performance of a novel hydrophobic DES was evaluated for the extraction of phenol from aqueous solutions. Octanoic and dodecanoic fatty acid precursors with a definite molar ratio of 3:1, respectively, were used for the DES having a low melting point of 8.3 °C. The purity and stability of the product were confirmed via characterizing by FTIR, 1H and 13C NMR methods. The liquid-liquid equilibrium of the water + phenol + DES ternary system at different temperatures of 293.2, 298.2 and 308.2 K was accordingly studied through cloud point titration method and refractive index measurement. Interestingly, the important parameters of the solute distribution coefficient and the separation factor were, respectively, within the high levels of (6.8321-9.7787) and (895.76-2770.17), indicating the amazing capability of the DES. Reasonably, both of these parameters decreased with temperature. The NRTL and UNIQUAC thermodynamic models were employed to reproduce the obtained tie-lines and to determine the interaction parameters at each temperature. The low level root mean square deviations for the mentioned models were, respectively, within (0.0014-0.0027) and (0.0045-0.0063); confirming satisfactorily agreement with the experimental data.

Evaluating ionic liquids for its potential as eco-friendly solvents for naproxen removal from water sources using COSMO-RS: Computational and experimental validation

An emerging contaminant of concern in aqueous streams is naproxen. Due to its poor solubility, non-biodegradability, and pharmaceutically active nature, the separation is challenging. Conventional solvents employed for naproxen are toxic and harmful. Ionic liquids (ILs) have attracted great attention as greener solubilizing and separating agent for various pharmaceuticals. ILs have found extensive usage as solvents in nanotechnological processes involving enzymatic reactions and whole cells. The employment of ILs can enhance the effectiveness and productivity of such bioprocesses. To avoid cumbersome experimental screening, in this study, conductor like screening model for real solvents (COSMO-RS) was used to screen ILs. Thirty anions and eight cations from various families were chosen. Activity coefficient at infinite dilution, capacity, selectivity, performance index, molecular interactions using σ-profiles and interaction energies were used to make predictions about solubility. According to the findings, quaternary ammonium cations, highly electronegative, and food-grade anions will form excellent ionic liquid combinations for solubilizing naproxen and hence will be better separating agents. This research will contribute easy designing of ionic liquid-based separation technologies for naproxen. In different separation technologies, ionic liquids can be employed as extractants, carriers, adsorbents, and absorbents.

Application of a phosphonium-based ionic liquid for reactive textile dye removal: Extraction study and toxicological evaluation

Textile dyeing processes are known for their negative environmental impacts due to the production of aqueous effluents containing toxic dyes. Therefore, new wastewater treatment processes need to be developed to treat such effluents, including Liquid-Liquid Extraction (LLE) process using Ionic Liquids (IL). This work aimed to evaluate the application of the hydrophobic IL trihexyltetradecylphosphonium decanoate to extract black, navy, and royal reactive dyes from water and evaluate the toxicological aspects of the resulting water stream. We investigated the effect of selected parameters, such as pH (2-12), temperature (20-50 °C), salt effects, dye concentration (0.5-50 mg/L), and phase volume ratio (900-9000) on the dye extraction. The results showed extraction yields as high as 97% for the three dyes and an extraction capacity of approximately 300 mg/g for black and navy dyes and 400 mg/g for royal. The toxicity tests involved Lactuca sativa, Triticum aestivium L, and Daphnia magna as bioindicators. The difference between the toxicity of the dye solutions before and after extraction was not statistically significant when L. sativa and Triticum aestivum L were used as bioindicators. However, the extracted solution showed increased toxicity towards D. magna due to traces of IL. Overall, the IL has a high extraction capacity for the black, navy, and royal dyes. Nevertheless, further studies on LLE associated with other processes must be carried out to reduce the risk linked to the toxicity of IL transferred to the water.

Ionic liquids and deep eutectic solvents for the recovery of phenolic compounds: effect of ionic liquids structure and process parameters

Water pollution is a severe and challenging issue threatening the sustainable development of human civilization. Besides other pollutants, waste fluid streams contain phenolic compounds. These have an adverse effect on the human health and marine ecosystem due to their toxic, mutagenic, and carcinogenic nature. Therefore, it is necessary to remove such phenolic pollutants from waste stream fluids prior to discharging to the environment. Different methods have been proposed to remove phenolic compounds from wastewater, including extraction using ionic liquids (ILs) and deep eutectic solvent (DES), a class of organic salts having melting point below 100 °C and tunable physicochemical properties. The purpose of this review is to present the progress in utilizing ILs and DES for phenolic compound extraction from waste fluid streams. The effects of IL structural characteristics, such as anion type, cation type, alkyl chain length, and functional groups will be discussed. In addition, the impact of key process parameters such as pH, phenol concentration, phase ratio, and temperature will be also described. More importantly, several ideas for addressing the limitations of the treatment process and improving its efficiency and industrial viability will be presented. These ideas may form the basis for future studies on developing more effective IL-based processes for treating wastewaters contaminated with phenolic pollutants, to address a growing worldwide environmental problem.

Enhanced extraction of phenol from model oils using ionic liquids elucidated with neutron diffraction

Aromatic cation ionic liquids (ILs) based on alkylpyridiniums are shown to be good phenol extractants from model oils (hexane/toluene). ILs with hard basic anions are found to have best extraction efficiency consistent with tetraalkylammonium salts ([NR4]X). Key extraction interactions were analysed using small angle neutron diffraction. Trifluoromethanesulphonate ([OTf]- or triflate) anions provide the synergistic effects of reduced cation-phenol centre of mass (COM) distances and increased hydrogen bonding that are linked to the improved extraction efficiency. Increases in cation electron density (methylpyridinium ([Me-Py]+) vs. methylpicolinium ([Me-3-Pic]+)) also reduce cation-phenol COM interaction lengths consistent with small increases in extraction efficiency for the same ionic liquids.

Encapsulation of Ionic Liquids for Tailored Applications

This spotlight article highlights the favorable impact encapsulation of ionic liquids (ILs) has on multiple advanced applications. ILs are molten salts with many attractive properties such as negligible vapor pressure, good thermal stability, and high ionic conductivity; however, their widespread implementation in advanced applications is hampered by their relatively high viscosity, which makes them difficult to handle and results in slow mass transfer rates. The ability to encapsulate IL in a shell holds potential to impact many applications, including separations, gas sequestration, and energy storage and management, given that the capsule structure provides high surface area compared to that of bulk IL and also allows handling of the IL as a solid. Herein, we discuss encapsulation of ILs using different approaches and highlight the contributions from our lab in both capsule preparation and application. Specifically, we have developed the ability to use 2D carbon nanoparticle surfactants and interfacial polymerization to prepare capsules of IL using both IL-in-water and IL-in-oil Pickering emulsions as templates. This facile, one-step method to encapsulate ILs gives structures with beneficial performance in supercapacitors, separations, and CO₂ sequestration, as discussed herein. We conclude this spotlight with an outlook on how to improve upon these systems for next-generation applications.

Pickering Emulsion-Templated Encapsulation of Ionic Liquids for Contaminant Removal

Ionic liquids (ILs) have received attention for a diverse range of applications, but their liquid nature can make them difficult to handle and process and their high viscosities can lead to suboptimal performance. As such, encapsulated ILs are attractive for their ease of handling and high surface area and have potential for improved performance in energy storage, gas uptake, extractions, and so forth. Herein, we report a facile method to encapsulate a variety of ILs using Pickering emulsions as templates, graphene oxide (GO)-based nanosheets as particle surfactants, and interfacial polymerization for stabilization. The capsules contain up to 80% IL in the core, and the capsule shells are composed of polyurea and GO. We illustrate that capsules can be prepared from IL-in-water or IL-in-oil emulsions and explore the impact of monomer and IL identity, thereby accessing different compositions. The spherical, discrete capsules are characterized by optical microscopy, scanning electron microscopy, infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, and ¹H NMR spectroscopy. We illustrate the application of these IL capsules as a column material to remove phenol from oil, demonstrating ≥98% phenol removal after passage of >170 column volumes. This simple method to prepare capsules of IL will find widespread use across diverse applications.

Liquid-liquid extraction of phenolic compounds from water using ionic liquids: Literature review and new experimental data using [C2mim]FSI

In this work, the capability of the ionic liquid, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, [C₂mim]FSI, to extract o-cresol, 2-chlorophenol, resorcinol and phenol from water, reaching the legal limit of 1 mg L^-1 was analyzed. The extraction process was carried out for each one of these phenolic compounds varying the initial concentration in water from 3 mg L^-1 to 1000 mg L^-1, and for aqueous mixtures of the four phenolic compounds in the same concentration range. Because of the scarcity of physical properties of the [C₂mim]FSI, density, speed of sound, dynamic viscosity and refractive index were measured from 293.15 to 343.15 K at atmospheric pressure. From the experimental data, the thermal expansion coefficient and the isentropic compressibility for the pure ionic liquid were calculated. Even though [C₂mim]FSI is hydrophobic, it can solve small quantities of water that can hinder the recovery of the ionic liquid, consequently the solubility of water in the ionic liquid was determined at several temperatures and atmospheric pressure. In addition to experimental data, a literature review on the use of ionic liquids to extract phenolic compounds from water was performed.

Development of supramolecular solvent based microextraction prior to high performance liquid chromatography for simultaneous determination of phenols in environmental water

SUPRAS based microextraction for phenols.

Ultraviolet-Visible (UV-Vis) and Fluorescence Spectroscopic Investigation of the Interactions of Ionic Liquids and Catalase

The inhibitory effects of nine ionic liquids (ILs) on the catalase activity were investigated using fluorescence, absorption ultraviolet-visible spectroscopy. The interactions of ILs and catalase on the molecular level were studied. The experimental results indicated that ILs could inhibit the catalase activity and their inhibitory abilities depended on their chemical structures. Fluorescence experiments showed that hydrogen bonding played an important role in the interaction process. The inhibitory abilities of ILs on catalase activity could be simply described by their hydrophobicity and hydrogen bonding abilities. Unexpected less inhibitory effects of trifluoromethanesulfonate (TfO^-) might be ascribed to its larger size, which makes it difficult to go through the substrate channel of catalase to the active site.

Spectroscopic studies on the inhibitory effects of ionic liquids on lipase activity

The effects of ionic liquids (ILs) on the lipase activity were studied by UV-Vis spectroscopy and the IL-lipase interaction mechanism at the molecular level was investigated by fluorescence technique. Experimental results indicated that the lipase activity was inhibited by ILs and the degree of inhibition highly depended on the chemical structures of ILs. The inhibitory ability of the Cl(-)- and Br(-)-based ILs increased with increasing the alkyl chain length in the IL cation. Thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS) were obtained by analyzing the fluorescence behavior of lipase with the addition of ILs. Both ΔH and ΔS were positive suggesting hydrophobicity was the major driven force for the Cl(-)- and Br(-)-based ILs. For the BF4(-)-, CF3SO3(-)-, ClO4(-)- and N(CN)2(-)-based ILs, hydrogen bonding was the main driven force. For a more comprehensive understanding of the effects of ILs on lipase activity, the roles of hydrophobicity and hydrogen bonding must be considered simultaneously. A regression-based equation was developed to describe the relationship of the inhibitory ability of ILs and their hydrophobicity and hydrogen bonding ability.

Evaluation of the toxicity of ionic liquids on trypsin: A mechanism study

The toxicity of ionic liquids (ILs) was evaluated by using trypsin as biomarker. Experimental results indicated that the trypsin activity was inhibited by ILs and the degree of inhibition highly depended on the chemical structures of ILs. Primary analysis illustrated that hydrophobicity of ILs was one of the driven forces ruling the ILs-trypsin interaction. Thermodynamic parameters, Gibbs free energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS) were obtained by analyzing the fluorescence behavior of trypsin in the presence of ILs. Both negative ΔH and ΔS suggested hydrogen bonding was the major driven force underlying the IL-trypsin interaction. To assess the toxicity of ILs, it should be considered the combination of the hydrogen bonding ability and hydrophobicity of ILs. A regression based model was established to correlate the relationship of the inhibitory ability, hydrophobicity and hydrogen bonding ability of ILs.

Inhibitory effects of ionic liquids on the lactic dehydrogenase activity

Ionic liquids (ILs) were widely used in scientific and industrial application and have been reported to possess potential toxicity to the environment and human health. The effects of six typical N-methylimidazolium-based ILs ([Cnmim]X, n=4, 6, 8; X=Br(-), Cl(-), BF4(-), CF3SO3(-)) on the lactic dehydrogenase (LDH) activity and the molecular interaction mechanism of ILs and the LDH were investigated with the aid of spectroscopic techniques. Experimental results showed that the LDH activity was inhibited in the presence of ILs. For the ILs with the same anion but different cations, their inhibitory ability on the LDH activity increased with increasing the alkyl chain length on the IL cation. Thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS) were obtained by analyzing the fluorescence behavior of LDH with the addition of ILs. Both positive ΔH and ΔS suggested that hydrophobicity was the major driven force in the interaction process as expected.

A novel cyano functionalized silica-titania oxide sol–gel based ionic liquid for the extraction of hazardous chlorophenols from aqueous environments

The extraction of chlorophenols on Si-Ti@CN/IL is highly pH dependent and significant percent extraction was achieved at pH = 2.

Recovery of tyrosol from aqueous streams using hydrophobic ionic liquids: a first step towards developing sustainable processes for olive mill wastewater (OMW) management

Hydrophobic ILs have been proposed as VOCs replacements for tyrosol recovery from aqueous solutions, revealing promising extraction efficiency and regeneration capacity. This will help developing sustainable processes for olive mill waste management.

Magnetic solid phase extraction of polycyclic aromatic hydrocarbons and chlorophenols based on cyano-ionic liquid functionalized magnetic nanoparticles and their determination by HPLC-DAD

The extraction of CPs & PAHs on MNP@CN/IL provides highly percent recovery with good precision and enrichment factor of i.e., 100 & 200 for CPs and PAHs respectively.