Application of ionic liquids in organic pollutants control

Performance on adsorption of toluene by ionic liquid-modified AC in high-humidity exhaust gas

Volatile organic compounds (VOCs) frequently pose a threat to the biosphere, impacting ecosystems, flora, fauna, and the surrounding environment. Industrial emissions of VOCs often include the presence of water vapor, which, in turn, diminishes the adsorption capacity and efficacy of adsorbents. This occurs due to the competitive adsorption of water vapor, which competes with target pollutants for adsorption sites on the adsorbent material. In this study, hydrophobic activated carbons (BMIMPF6-AC (L), BMIMPF6-AC (g), and BMIMPF6-AC-H) were successfully prepared using 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) to adsorb toluene under humidity environment. The adsorption performance and mechanism of the resulting ionic liquid-modified activated carbon for toluene in a high-humidity environment were evaluated to explore the potential application of ionic liquids as hydrophobic modifiers. The results indicated that BMIMPF6-AC-H exhibited superior hydrophobicity. The toluene adsorption capacity of BMIMPF6-AC-H was 1.53 times higher than that of original activated carbon, while the adsorption capacity for water vapor was only 37.30% of it at 27 °C and 77% RH. The Y-N model well-fitted the dynamic adsorption experiments. To elucidate the microscopic mechanism of hydrophobic modification, the Independent Gradient Model (IGM) method was employed to characterize the intermolecular interactions between BMIMPF6 and toluene. Overall, this study introduces a new modifier for hydrophobic modification of activated carbon, which could enhance the efficiency of activated carbon in treating industrial VOCs.

1-Butyl-3-methylimidazolium Chloride Affects Anaerobic Digestion through Altering Organics Transformation, Cell Viability, and Microbial Community

1-Butyl-3-methylimidazolium chloride (BmimCl), an imidazolium-based ionic liquid, is considered the representative emerging persistent aquatic pollutant, and its environmental toxicity has attracted a growing concern. However, most of the investigations focused on monocultures or a single organism, with little information available on the complex syntrophic consortium that dominates the complex and successional biochemical processes, such as anaerobic digestion. In this study, the effect of BmimCl at environmentally relevant levels on glucose anaerobic digestion was therefore investigated in several laboratory-scale mesophilic anaerobic digesters to provide such support. Experimental results showed that BmimCl at 1-20 mg/L inhibited the methane production rate by 3.50-31.03%, and 20 mg/L BmimCl inhibited butyrate, hydrogen, and acetate biotransformation by 14.29%, 36.36%, and 11.57%, respectively. Toxicological mechanism studies revealed that extracellular polymeric substances (EPSs) adsorbed and accumulated BmimCl through carboxyl, amino, and hydroxyl groups, which destroyed the EPSs' conformational structure, thereby leading to the inactivation of microbial cells. MiSeq sequencing data indicated that the abundance of Clostridium_sensu_stricto_1, Bacteroides, and Methanothrix decreased by 6.01%, 7.02%, and 18.45%, respectively, in response to 20 mg/L BmimCl. Molecular ecological network analysis showed that compared with the control, the lower network complexity, fewer keystone taxa, and fewer associations among microbial taxa were found in the BmimCl-present digester, indicating the reduced stability of the microbial community.

Ionic liquids as alternative solvents for energy conservation and environmental engineering

Because of industrialization and modernization, phenomenal changes have taken place in almost all spheres of life. Consequently, the consumption of energy resources and the cases of environmental hazards have risen to an unprecedentedly high level. A development model with due consideration to nature and an efficient utilization of energy sources has become the need of the hour, in order to ensure a sustainable balance between the environmental and technological needs. Recent studies have identified the suitability of ionic liquids (ILs), often labeled as ‘green solvents’, in the efficient utilization of energy resources and activities such as bio-extraction, pollution control, CO2 capture, waste management etc. in an environmentally friendly manner. The advent of magnetic ionic liquids (MILs) and deep eutectic solvents (DESs) have opened possibilities for a circular economic approach in this filed. This review intends to analyze the environmental and energy wise consumption of a wide variety of ionic liquids and their potential towards future.

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.

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.

Improvement on the extraction efficiency of low density lipoprotein in an ionic liquid microemulsion

A novel microemulsion is developed at room temperature with 30 µL of sodium alginate sulfate (SAS, 0.02 mol/L), 0.005 g bis (2-ethylhexyl) succinate sulfonate (AOT) and 270 µL of 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF₆) ionic liquid as aqueous phase, surfactant and IL phase, respectively. The SAS/AOT/BmimPF₆ microemulsion significantly improves the extraction efficiency for low density lipoprotein (LDL). 96% LDL in a 300 µL of PBS is selectively extracted into a same volume of microemulsion, with respect to those of 67%, 76% and 85% by BmimPF₆, H₂O/AOT/BmimPF₆ microemulsion and sodium alginate (SA)/AOT/BmimPF₆ microemulsion. LDL in the SAS/AOT/BmimPF₆ microemulsion is distributed both in BmimPF₆ via hydrophobic interaction and in the "pools" of the microemulsion via electrostatic interaction with AOT and specific interaction between LDL with SAS. 83% of LDL in the microemulsion can be readily back extracted into an aqueous phase with 0.8% (m/v) of sodium dodecyl sulfate (SDS) as stripping reagent. For practical applications, LDL in human serum is selectively extracted with the microemulsion, as demonstrated by enzyme linked immunosorbent assay (ELISA) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).

Effects of soil components and solution inorganic cations on interactions of imidazolium-based ionic liquid with soils

Effects of alkyl chain length of ionic liquid (IL), soil components and solution inorganic cations on a selected IL (1-methyl-3-octylimidazolium chloride, [OMIM]Cl) interaction with Chinese soils were investigated using batch sorption experiments. The results indicated that sorption energy was mainly controlled by chain length of [OMIM]Cl and contents of soil organic matter (SOM). [OMIM]Cl sorption on soils was mainly controlled by cation exchange process. Contributions of SOM and clay minerals (CMs) to [OMIM]Cl sorption were 7.3%-53.8% and 46.2%-92.7%, respectively. SOM possessed higher energy cation-exchange binding sites than CMs. To predict the sorption of [OMIM]Cl on soils, a model for the relationship between sorption coefficient (K_d) and cation exchange capacity (CEC) from soil components (SOM and CMs, i.e., CEC_SOM and CEC_CMs) as well as solution concentration (C_e) was established: LogK_d = Log(1.67*CEC_SOM + 3.22*CEC_CMs) - 0.58LogC_e. This model could provide a good prediction for sorption coefficients and the prediction errors were within 0.48 log unit. Competitive effects caused by inorganic cations followed the order of Ca²⁺ = Mg²⁺ > K⁺ > Na⁺. Concentrations and valence of coexisting ions both affect their competitive capability on [OMIM]Cl sorption. The finding of this study provided valuable information for evaluating the fate of [OMIM]Cl in soils.

Current status and future challenges in ionic liquids, functionalized ionic liquids and deep eutectic solvent-mediated synthesis of nanostructured TiO2: a review

This review is on current advancements in IL-mediated synthesis of TiO₂, and the potential for future research in this area.

Environmental Application, Fate, Effects, and Concerns of Ionic Liquids: A Review

Ionic liquids (ILs) comprise mostly of organic salts with negligible vapor pressure and low flammability that are proposed as replacements for volatile solvents. ILs have been promoted as "green" solvents and widely investigated for their various applications. Although the utility of these chemicals is unquestionable, their toxic effects have attracted great attention. In order to manage their potential hazards and design environmentally benign ILs, understanding their environmental behavior, fate and effects is important. In this review, environmentally relevant issues of ILs, including their environmental application, environmental behavior and toxicity are addressed. In addition, also presented are the influence of ILs on the environmental fate and toxicity of other coexisting contaminants, important routes for designing nontoxic ILs and the techniques that might be adopted for the removal of ILs.

The electrochemical oxidation of toluene catalysed by Co(ii) in N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide

Co(ii) catalysed electro-oxidation of toluene in room temperature ionic liquid.

Very fast catalytic reduction of 4-nitrophenol, methylene blue and eosin Y in natural waters using green chemistry: p(tannic acid)–Cu ionic liquid composites

Using tannic acid (TA) as a biopolymer, poly(tannic Acid) (p(TA)) microgels were obtained by cross-linking TA with trimethylolpropane triglycidyl ether (TMPGDE) as cross-linker in a water-in-oil micro emulsion system.

Ionic liquid poly(3-n-dodecyl-1-vinylimidazolium) bromide as an adsorbent for the sorption of hemoglobin

A novel polymeric ionic liquid, poly(1-vinylimidazolium-3-n-dodecyl) bromide, exhibits selective adsorption of hemoglobin from human whole blood.

Ionic liquid-based hollow fiber-supported liquid-phase microextraction enhanced electrically for the determination of neutral red

A method of ionic liquid-based hollow fiber liquid-phase microextraction enhanced electrically was successfully developed and applied to the extraction and determination of neutral red (NR) dye, which was selected as the model analyte. A room temperature ionic liquid, 1-octyl-3-methylimidazolium hexafluorophosphate ([C₈mim][PF₆]), was placed in the pores of a polytetrafluoethylene hollow fiber, which acts as a liquid membrane and the acceptor solution. The extraction parameters affecting the enrichment factor of NR, such as pH, extraction time, elution time, stirring rate, and the voltage were optimized. In addition, UV–Visible (UV–Vis) or electrochemiluminescence spectra were also determined. The extraction rate and capacity of NR could be improved significantly by cathodic polarization. Under the optimized extraction conditions (organic liquid microextraction phase [C₈mim][PF₆], pH 7, stirring rate 300 rpm, extraction time 20 minutes, ultrasonic-assisted elution time 3 minutes, voltage −70 V), the detection limit of 0.38 μg/L and linear correlation coefficient of r > 0.99 were obtained. The established method was successfully applied to the analysis of three soft drink samples, which were spiked with NR standards at the concentrations of 0.1, 1.0, and 5.0 mg/L, and satisfactory results were obtained.

Hg⁰ removal from flue gas by ionic liquid/H₂O₂

1-Alkyl-3-methylimidazolium chloride ionic liquids ([Cnmim] Cl, n=4, 6, 8) were prepared. The ionic liquid was then mixed with hydrogen peroxide (H2O2) to form an absorbent. The Hg(0) removal performance of the absorbent was investigated in a gas/liquid scrubber using simulated flue gas. It was found that the ionic liquid/H2O2 mixture was an excellent absorbent and could be used to remove Hg(0) from flue gas. When the mass ratio of H2O2 to ionic liquid was 0.5, the absorbent showed high Hg(0) removal efficiency (up to 98%). The Hg(0) removal efficiency usually increased with the absorption temperature, while decreased with the increase of alkyl chain length in ionic liquid molecule. The Hg(0) removal mechanism involved with Hg(0) oxidation by H2O2 and Hg(2+) transfer from aqueous phase to ionic liquid phase.

Ionic liquids and deep eutectic mixtures: sustainable solvents for extraction processes

In recent years, ionic liquids and deep eutectic mixtures have demonstrated great potential in extraction processes relevant to several scientific and technological activities. This review focuses on the applicability of these sustainable solvents in a variety of extraction techniques, including but not limited to liquid- and solid-phase (micro) extraction, microwave-assisted extraction, ultrasound-assisted extraction and pressurized liquid extraction. Selected applications of ionic liquids and deep eutectic mixtures on analytical method development, removal of environmental pollutants, selective isolation, and recovery of target compounds, purification of fuels, and azeotrope breaking are described and discussed.

Novel optically active poly(amide-thioester-imide)s containing l-α-amino acids and thiadiazol anticorrosion group

Here, for the first time, we report the synthesis of a new class of optically active polymers, poly(amide-thioester-imide)s (PATEI)s, containing flexible and anticorrosion linkages. Step growth polymerization of a novel diamine with diacids containing amino acid and trimellitylimide groups in tetrabutylammonium bromide, in the molten state, which acts as a molten ionic salt medium, was carried out. The obtained polymeric materials were of the nanoscale size and were assembled by filamentary particles as shown by field-emission scanning electron microscopy micrographs, which were distributed uniformly and randomly, with an average nanosize diameter of about 40 nm. The polymeric samples were readily soluble in a variety of common organic solvents and formed low-colored and flexible thin films via solution casting. The values of absorption edge wavelength ( λ0) were determined by ultraviolet–visible spectroscopy, and all of the resulting PATEI films exhibited high-optical transparency. According to x-ray diffraction patterns, all the PATEIs were amorphous. The structure of PATEIs were also characterized by Fourier-transform infrared spectroscopy, Proton-nuclear magnetic resonance, elemental, and thermogravimetric analysis techniques. The effect of ultrasound on the morphology of polymers was also investigated. This study confirmed that the size of polymer particles decreased and there was a change in their morphology.