Carbon-supported ionic liquids as innovative adsorbents for CO2 separation from synthetic flue-gas

Development of ionic-liquid-impregnated activated carbon for sorptive removal of PFAS in drinking water treatment

Adsorption of per- and poly-fluoroalkyl substances (PFAS) on activated carbon (AC) is considerably hindered by the surface water constituents, degrading the ability of the AC adsorption process to remove PFAS in drinking water treatment. Herein, we developed ionic-liquid-impregnated AC (IL/AC) as an alternative to AC for PFAS sorption and demonstrated its performance with real surface water for the first time. Ionic liquids (ILs) of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (IL(C2)) and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (IL(C6)) were selected from among 272 different ILs using the conductor-like screening model for realistic solvents (COSMO-RS) simulation. Impregnation of the ILs in AC was verified using various analytical techniques. Although the synthesized IL/ACs were less effective than pristine AC in treating PFAS in deionized water, their performances were less impacted by the surface water constituents, resulting in comparable or sometimes better performances than pristine AC for treating PFAS in surface water. The removal efficiencies of 10 wt% IL(C6)/AC for six PFAS were 1.40-1.96 times higher than those of pristine AC in a surface water sample containing 2.6 mg/L dissolved organic carbon and millimolar-level divalent cation concentration. PFAS partitioning from the surface water to ILs was not hindered by dissolved organic matter and was enhanced by the divalent cations, indicating the advantages of IL/ACs for treating significant amounts of PFAS in water. The synthesized IL/ACs were effective at treating coexisting pharmaceutical and personal-care products in surface water, showcasing their versatility for treating a broad range of water micropollutants.

Enhanced CO2 Capture through SAPO-34 Impregnated with Ionic Liquid

The concurrent utilization of an adsorbent and absorbent for carbon dioxide (CO2) adsorption with synergistic effects presents a promising technique for CO2 capture. Here, 1-butyl-3-methylimidazole acetate ([Bmim][Ac]), with a high affinity for CO2, and the molecular sieve SAPO-34 were selected. The impregnation method was used to composite the hybrid samples of [Bmim][Ac]/SAPO-34, and the pore structure and surface property of prepared samples were characterized. The quantity and kinetics of the sorbed CO2 for loaded samples were measured using thermogravimetric analysis. The study revealed that SAPO-34 could retain its pristine structure after [Bmim][Ac] loading. The CO2 uptake of the loaded sample was 1.879 mmol g-1 at 303 K and 1 bar, exhibiting a 20.6% rise compared to that of the pristine SAPO-34 recording 1.558 mmol g-1. The CO2 uptake kinetics of the loaded samples were also accelerated, and the apparent mass transfer resistance for CO2 sorption was significantly reduced by 11.2% compared with that of the pure [Bmim][Ac]. The differential scanning calorimetry method revealed that the loaded sample had a lower CO2 desorption heat than that of the pure [Bmim][Ac], and the CO2 desorption heat of the loaded samples was between 30.6 and 40.8 kJ mol-1. The samples exhibited good cyclic stability. This material displays great potential for CO2 capture applications, facilitating the reduction of greenhouse gas emissions.

Greenhouse gases capture applying impregnated silica with ionic liquids, deep eutectic solvents, and natural deep eutectic solvents

The development of technologies to capture greenhouse gases (GHGs) like carbon dioxide (CO2) and nitrous oxide (N2O) is vital for climate change mitigation. Ionic liquids (ILs), deep eutectic solvents (DES), and natural deep eutectic solvents (NADES) are promising absorbents to abate GHGs emissions. However, their high viscosity limits the gas-liquid contact, as consequence of the mass transfer. To overcome this, their impregnation onto porous silica gel has been carried out, increasing the gas-liquid contact area. The present study analyzes the effect of size particle of silica gel impregnated with ILs, DES, and NADES over the CO2 and N2O capture at atmospheric conditions. The degree of impregnation of silica particles was determined by thermogravimetric analysis (TGA). The identification of functional groups present on the surface of silica, ILs, DES, and NADES was performed using Fourier-transform infrared spectroscopy (FTIR), and their crystalline structure was determined by X-ray diffraction (XRD). The partition coefficient of CO2 and N2O between gas and ILs, DES, and NADES was determined by a static headspace method. Results show that the degree of solvent impregnation on silica gel ranged from 36.8 to 43.0% w/w, the partition coefficient of CO2 in the impregnated silica varied from 0.005 to 0.067, and for N2O, from 0.005 to 0.032. This suggests that impregnated particles have a greater affinity for N2O compared to CO2. Using impregnated particles requires only 40% of the bulk solvent to achieve a similar GHG capture capacity compared to using bulk solvents.

Ionic Liquids Hybridization for Carbon Dioxide Capture: A Review

CO2 absorption has been driven by the need for efficient and environmentally sustainable CO2 capture technologies. The development in the synthesis of ionic liquids (ILs) has attracted immense attention due to the possibility of obtaining compounds with designated properties. This allows ILs to be used in various applications including, but not limited to, biomass pretreatment, catalysis, additive in lubricants and dye-sensitive solar cell (DSSC). The utilization of ILs to capture carbon dioxide (CO2) is one of the most well-known processes in an effort to improve the quality of natural gas and to reduce the green gases emission. One of the key advantages of ILs relies on their low vapor pressure and high thermal stability properties. Unlike any other traditional solvents, ILs exhibit high solubility and selectivity towards CO2. Frequently studied ILs for CO2 absorption include imidazolium-based ILs such as [HMIM][Tf2N] and [BMIM][OAc], as well as ILs containing amine groups such as [Cho][Gly] and [C1ImPA][Gly]. Though ILs are being considered as alternative solvents for CO2 capture, their full potential is limited by their main drawback, namely, high viscosity. Therefore, the hybridization of ILs has been introduced as a means of optimizing the performance of ILs, given their promising potential in capturing CO2. The resulting hybrid materials are expected to exhibit various ranges of chemical and physical characteristics. This review presents the works on the hybridization of ILs with numerous materials including activated carbon (AC), cellulose, metal-organic framework (MOF) and commercial amines. The primary focus of this review is to present the latest innovative solutions aimed at tackling the challenges associated with IL viscosity and to explore the influences of ILs hybridization toward CO2 capture. In addition, the development and performance of ILs for CO2 capture were explored and discussed. Lastly, the challenges in ILs hybridization were also being addressed.

Porous Polymer Supported Amino Functionalized Ionic Liquid for Effective CO2 Capture

A decrease in CO₂ emissions is urgently required in the present situation due to the fast growth of carbon dioxide (CO₂) in the atmosphere, which has caused a series of global climate issues. This study used an impregnation-evaporation method to immobilize an amino functionalized ionic liquid [C₂OHmim][Lys] on a chromatographic column filler GDX-103 and create a novel supported ionic liquid. The results showed that the supported ionic liquid with 60 wt % ionic liquid content had the best adsorption performance at 40 °C, and the CO₂ adsorption isotherm showed that the adsorption capacity at 0.1 MPa was 1.29 mmol CO₂/g sorbent, which was 6 times greater than the adsorption capacity of the pure carrier. The sample with 60% ionic liquid content has an adsorption capacity of 1.02 mmol CO₂/g sorbent under the condition of CO₂/N₂ mixed gas with 10% CO₂ content. This is 43 times greater than the adsorption capacity of the pure carrier, and its adsorption performance is stable after three adsorption and desorption cycles. Through the rich porous structure of GDX-103, the ionic liquid is effectively supported and dispersed, which expands the contact area between CO₂ and ionic liquid and enhances the mass transfer of CO₂. At the same time, CO₂ can be chemically bound to the groups on the anion of ionic liquid and be immobilized, so it has a high selective adsorption capacity of CO₂, which makes it a great alternative to traditional CO₂ adsorbents.

CO2 Adsorption Performance on Surface-Functionalized Activated Carbon Impregnated with Pyrrolidinium-Based Ionic Liquid

The serious environmental issues associated with CO2 emissions have triggered the search for energy efficient processes and CO2 capture technologies to control the amount of gas released into the atmosphere. One of the suitable techniques is CO2 adsorption using functionalized sorbents. In this study, a functionalized activated carbon (AC) material was developed via the wet impregnation technique. The AC was synthesized from a rubber seed shell (RSS) precursor using chemical activation and was later impregnated with different ratios of [bmpy][Tf2N] ionic liquid (IL). The AC was successfully functionalized with IL as confirmed by FTIR and Raman spectroscopy analyses. Incorporation of IL resulted in a reduction in the surface area and total pore volume of the parent adsorbent. Bare AC showed the largest SBET value of 683 m2/g, while AC functionalized with the maximum amount of IL showed 14 m2/g. A comparative analysis of CO2 adsorption data revealed that CO2 adsorption performance of AC is majorly affected by surface area and a pore-clogging effect. Temperature has a positive impact on the CO2 adsorption capacity of functionalized AC due to better dispersion of IL at higher temperatures. The CO2 adsorption capacity of AC (30) increased from 1.124 mmol/g at 25 °C to 1.714 mmol/g at 40 °C.

IL-Functionalized Mg3Al-LDH as New Efficient Adsorbent for Pd Recovery from Aqueous Solutions

Palladium is a noble metal of the platinum group metals (PGMs) with a high value and major industrial applications. Due to the scarce palladium resources, researchers' attention is currently focused on Pd ions recovery from secondary sources. Regarding the recovery process from aqueous solutions, many methods were studied, amongst which adsorption process gained a special attention due to its clear advantages. Moreover, the efficiency and the selectivity of an adsorbent material can be further improved by functionalization of various solid supports. In this context, the present work aims at the synthesis and characterization of Mg₃Al-LDH and its functionalization with ionic liquid (IL) (Methyltrialkylammonium chloride) to obtain adsorbent materials with high efficiency in Pd removal from aqueous solutions. The maximum adsorption capacity developed by Mg₃Al-LDH is 142.9 mg Pd., and depending on the functionalization method used (sonication and co-synthesis, respectively) the maximum adsorption capacity increases considerably, q_max-Mg₃Al IL-US = 227.3 mg/g and q_max-Mg₃Al IL-COS = 277.8 mg/g.

A Systematic Review of Amino Acid-Based Adsorbents for CO2 Capture

The rise of carbon dioxide (CO2) levels in the atmosphere emphasises the need for improving the current carbon capture and storage (CCS) technology. A conventional absorption method that utilises amine-based solvent is known to cause corrosion to process equipment. The solvent is easily degraded and has high energy requirement for regeneration. Amino acids are suitable candidates to replace traditional alkanolamines attributed to their identical amino functional group. In addition, amino acid salt is a green material due to its extremely low toxicity, low volatility, less corrosive, and high efficiency to capture CO2. Previous studies have shown promising results in CO2 capture using amino acids salts solutions and amino acid ionic liquids. Currently, amino acid solvents are also utilised to enhance the adsorption capacity of solid sorbents. This systematic review is the first to summarise the currently available amino acid-based adsorbents for CO2 capture using PRISMA method. Physical and chemical properties of the adsorbents that contribute to effective CO2 capture are thoroughly discussed. A total of four categories of amino acid-based adsorbents are evaluated for their CO2 adsorption capacities. The regeneration studies are briefly discussed and several limitations associated with amino acid-based adsorbents for CO2 capture are presented before the conclusion.

Engineering encapsulated ionic liquids for next-generation applications

Ionic liquids (ILs) have attracted considerable attention in several sectors (from energy storage to catalysis, from drug delivery to separation media) owing to their attractive properties, such as high thermal stability, wide electrochemical window, and high ionic conductivity. However, their high viscosity and surface tension compared to conventional organic solvents can lead to unfavorable transport properties. To circumvent undesired kinetics effects limiting mass transfer, the discretization of ILs into small droplets has been proposed as a method to increase the effective surface area and the rates of mass transfer. In the present review paper, we summarize the different methods developed so far for encapsulating ILs in organic or inorganic shells and highlight characteristic features of each approach, while outlining potential applications. The remarkable tunability of ILs, which derives from the high number of anions and cations currently available as well as their permutations, combines with the possibility of tailoring the composition, size, dispersity, and properties (e.g., mechanical, transport) of the shell to provide a toolbox for rationally designing encapsulated ILs for next-generation applications, including carbon capture, energy storage devices, waste handling, and microreactors. We conclude this review with an outlook on potential applications that could benefit from the possibility of encapsulating ILs in organic and inorganic shells.

Encapsulated ionic liquids (ILs) are candidate materials for several applications owing to the attractive properties of ILs combined with the enhanced mass transfer rate obtained through the discretization of ILs in small capsules.

Adsorption of CO2 on Activated Carbons Prepared by Chemical Activation with Cupric Nitrate

Activated carbons were prepared from a lignocellulosic material, African palm shells (Elaeis guineensis), by chemical impregnation of the precursor with solutions of 1-7% w/v Cu(NO₃)₂ at five different concentrations. These were carbonized in a carbon dioxide atmosphere at 1073 K to obtain different carbons. Their textural properties were characterized by nitrogen and carbon dioxide adsorption isotherms in order to evaluate the pore-size distribution. The immersion enthalpies of the activated carbons in benzene, dichloromethane, and water were determined. The CO₂ adsorption capacities of the materials at 273 K under low-pressure conditions were also determined. Chemical characterization was performed by mass spectrometry, Fourier transform infrared spectroscopy, and temperature-programmed reduction. With this method of preparation under the concentrations described, activated micro-mesoporous carbons were obtained, with the formation of highly mesoporous solids that favored the process of diffusion of molecules of CO₂ into the material. Here, we show that activated carbons were obtained with different textural characteristics: surface Brunauer-Emmett-Teller areas varied between 473 and 1361 m² g^-1 and micropore volume between 0.18 and 0.51 cm³ g^-1. The activated carbon with the highest values of textural parameters was ACCu5-1073. Micro-mesoporous solids were obtained with the methodology used. This is important as it may help the entry of CO₂ molecules into the pores. The adsorption of CO₂ in the materials prepared presented values between 103 and 217 mg CO₂ g^-1; the values of volume of narrow microporosity obtained were between 0.16 and 0.45 cm³ g^-1. The solid with the greatest capacity for adsorption of CO₂ and volume of narrow microporosity was ACCu3-1073. The use of these solids is of importance for future practical and industrial applications. The adsorption kinetic of CO₂ in the activated carbons prepared with metallic salt of copper is in good accordance with the intraparticle diffusion model, for which diffusion is the rate-limiting step. The adsorption of CO₂ in the prepared activated carbons is favorable from the energy and kinetic point of view, as these accompanied by the presence of wide micro-mesoporosity favor the entry of CO₂ into the micropores.

Capsules of Reactive Ionic Liquids for Selective Capture of Carbon Dioxide at Low Concentrations

The task-specific ionic liquid (IL), 1-ethyl-3-methylimidazolium 2-cyanopyrolide ([EMIM][2-CNpyr]), was encapsulated with polyurea (PU) and graphene oxide (GO) sheets via a one-pot Pickering emulsion, and these capsules were used to scrub CO₂ (0-5000 ppm) from moist air. Up to 60 wt % of IL was achieved in the synthesized capsules, and we demonstrated comparable gravimetric CO₂ capacities to zeolites and enhanced absorption rates compared to those of bulk IL due to the increased gas/liquid surface-to-volume area. The reactive IL capsules show recyclability upon mild temperature increase compared to zeolites that are the conventional absorber materials for CO₂ scrubbing. The measured breakthrough curves in a fixed bed under 100% relative humidity establish the utility of reactive IL capsules as moisture-stable scrubber materials to separate CO₂ from air, outperforming zeolites owing to their higher selectivity. It is shown that thermal stability, CO₂ absorption capacity, and rate of uptake by IL capsules can be further modulated by incorporating low-viscosity and nonreactive ILs to the capsule core. This study demonstrates an alternative and facile approach for CO₂ scrubbing, where separation from gas mixtures with extremely low partial pressures of CO₂ is required.

The effect of nanoscale friction of mesoporous carbon supported ionic liquids on the mass transfer of CO2 adsorption

The nanofriction was linked with CO₂ mass transfer at ionic liquid–solid interfaces, where the smaller nanofriction accelerates the CO₂ adsorption.

Surface Functionalization of Activated Carbon with Phosphonium Ionic Liquid for CO2 Adsorption

Immobilization of phosphonium ionic liquid (IL) onto activated carbon (AC) was synthesized via grafting and impregnated methods, and the modified materials were analyzed via Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction, thermal gravity analysis, scanning electron microscope, pore structure and CO2/N2 adsorption selectivity. The effect of the gas flow rate (100–500 mL/min) and adsorption pressure (0.2–0.6 MPa) on the dynamic adsorption behavior of mixture gas containing 15 vol.% CO2 and 85 vol.% N2 was explained using a breakthrough method. By analyzing the breakthrough curves, the adsorption capacity was determined. The results show that surface functionalization of activated carbon with phosphonium ionic liquid is conducive to improving CO2/N2 selectivity, especially ionic liquid-impregnated film. The different adsorption behaviors of impregnated and grafted adsorbents are observed under various conditions. The grafted AC had better CO2 adsorption and mass transfer due to a lower blockage of pores by ionic liquid.

Encapsulation of Ionic Liquids with an Aprotic Heterocyclic Anion (AHA-IL) for CO2 Capture: Preserving the Favorable Thermodynamics and Enhancing the Kinetics of Absorption

The performance of an ionic liquid with an aprotic heterocyclic anion (AHA-IL), trihexyl(tetradecyl)phosphonium 2-cyanopyrrolide ([P₆₆₆₁₄][2-CNPyr]), for CO₂ capture has been evaluated considering both the thermodynamics and the kinetics of the phenomena. Absorption gravimetric measurements of the gas-liquid equilibrium isotherms of CO₂-AHA-IL systems were carried out from 298 to 333 K and at pressures up to 15 bar, analyzing the role of both chemical and physical absorption phenomena in the overall CO₂ solubility in the AHA-IL, as has been done previously. In addition, the kinetics of the CO₂ chemical absorption process was evaluated by in situ Fourier transform infrared spectroscopy-attenuated total reflection, following the characteristic vibrational signals of the reactants and products over the reaction time. A chemical absorption model was used to describe the time-dependent concentration of species involved in the reactive absorption, obtaining kinetic parameters (such as chemical reaction kinetic constants and diffusion coefficients) as a function of temperatures and pressures. As expected, the results demonstrate that the CO₂ absorption rate is mass-transfer-controlled because of the relatively high viscosity of AHA-IL. The AHA-IL was encapsulated in a porous carbon sphere (Encapsulated Ionic Liquid, ENIL) to improve the kinetic performance of the AHA-IL for CO₂ capture. The newly synthesized AHA-ENIL material was evaluated as a CO₂ sorbent with gravimetric absorption measurements. AHA-ENIL systems preserve the good CO₂ absorption capacity of the AHA-IL but drastically enhance the CO₂ absorption rate because of the increased gas-liquid surface contact area achieved by solvent encapsulation.

Adsorption of CO2 onto Activated Carbons Prepared by Chemical Activation with Metallic Salts

Activated carbons are obtained by chemical activation of African Palm shells (Elaeis guineensis) with different impregnating agents, i. e. magnesium chloride (MgCl2) and calcium chloride (CaCl2) aqueous solutions at different concentrations (3, 5 and 7 % w/v) and temperatures (between 773 and 1073 K), in order to assess their influence on the development of the porosity. The activated carbons prepared are characterized in terms of both textural and chemical properties. The activated carbons have a surface area and a pore volume ranging between 19 and 501 m2.g−1 and 0.03–0.29 cm3.g−1, respectively. Based on the obtained results, the samples with higher surface area and pore volume (i. e. those impregnated with MgCl2 and CaCl2 solutions and thermally treated at 1073 K) are selected to evaluate the adsorption capacity and affinity for CO2. CO2 adsorption capacity varies between 1.78 and 2.95 mmolCO2.g−1 at 273 K and low pressure, and the activated carbon impregnated with the solution of MgCl2 3% and activated at 1073 K (i. e. ACMg3-1073) showed the best performances. Finally, the kinetic results show that adsorption rate for sample ACMg3-1073 is enhanced by its micro-mesoporous nature, being the access routes to the micropores larger.

Adsorption of CO2 onto Activated Carbons Prepared by Chemical Activation with Metallic Salts

This article has been retracted due to honest error by the author. For further information, please see https://doi.org/10.1515/ijcre-2017-9198.

Activated carbons are obtained by chemical activation of African Palm shells (Elaeis guineensis) with different impregnating agents, i. e. magnesium chloride (MgCl2) and calcium chloride (CaCl2) aqueous solutions at different concentrations (3, 5 and 7 % w/v) and temperatures (between 773 and 1073 K), in order to assess their influence on the development of the porosity. The activated carbons prepared are characterized in terms of both textural and chemical properties. The activated carbons have a surface area and a pore volume ranging between 19–501 m2.g−1 and 0.03–0.29 cm3.g−1, respectively. Based on the obtained results, the samples with higher surface area and pore volume (i. e. those impregnated with MgCl2 and CaCl2 solutions and thermally treated at 1073 K) are selected to evaluate the adsorption capacity and affinity for CO2.

CO2 adsorption capacity varies between 1.78 and 2.95 mmolCO2.g−1 at 273 K and low pressure, and the activated carbon impregnated with the solution of MgCl2 3 % and activated at 1073 K (i. e. ACMg3-1073) showed the best performances. Finally, the kinetic results show that adsorption rate for sample ACMg3-1073 is enhanced by its micro-mesoporous nature, being the access routes to the micropores larger.

Carbon Dioxide Adsorption Using High Surface Area Activated Carbons from Local Coals Modified by KOH, NaOH and ZnCl2 Agents

Activated carbons of various features were produced by the impregnation of local coal samples that were taken from Kilimli region of Zonguldak (Turkey) with chemical agents KOH, NaOH and ZnCl2 at different temperatures (600–800 °C) and concentrations (1:1–6:1 agent:coal), for their evaluation in CO2 adsorption studies. BET, DR, t-plot and DFT methods were used for the characterization of carbon samples based on N2 adsorption data obtained at 77 K. The pore sizes of activated carbons produced were generally observed to be in between 13–25 Å, containing highly micropores. Mesopore formations were higher in samples treated with ZnCl2. The highest value for the BET surface area was found as 2,599 m2 g−1 for the samples treated with KOH at 800 °C with a KOH to coal ratio of 4:1. It was observed that the CO2 adsorption capacities obtained at atmospheric pressure and 273 K were considerably affected by the micropore volume and surface area. The highest CO2 adsorption capacities were found as 9.09 mmol/g (28.57 % wt) and 8.25 mmol g−1 (26.65 % wt) for the samples obtained with KOH and NaOH treatments, respectively, at ratio of 4:1. The activated carbons produced were ordered as KOH>NaOH>ZnCl2, according to their surface areas, micropore volumes and CO2 adsorption capacities. The low-cost experimental methods developed by the utilization of local coals in this study enabled an effective capture of CO2 before its emission to atmosphere.

Encapsulated Ionic Liquids for CO2 Capture: Using 1-Butyl-methylimidazolium Acetate for Quick and Reversible CO2 Chemical Absorption

The potential advantages of applying encapsulated ionic liquid (ENIL) to CO₂ capture by chemical absorption with 1-butyl-3-methylimidazolium acetate [bmim][acetate] are evaluated. The [bmim][acetate]-ENIL is a particle material with solid appearance and 70 % w/w in ionic liquid (IL). The performance of this material as CO₂ sorbent was evaluated by gravimetric and fixed-bed sorption experiments at different temperatures and CO₂ partial pressures. ENIL maintains the favourable thermodynamic properties of the neat IL regarding CO₂ absorption. Remarkably, a drastic increase of CO₂ sorption rates was achieved using ENIL, related to much higher contact area after discretization. In addition, experiments demonstrate reversibility of the chemical reaction and the efficient ENIL regeneration, mainly hindered by the unfavourable transport properties. The common drawback of ILs as CO₂ chemical absorbents (low absorption rate and difficulties in solvent regeneration) are overcome by using ENIL systems.

Ammonia capture from the gas phase by encapsulated ionic liquids (ENILs)

Encapsulated ionic liquids (ENILs) based on carbonaceous submicrocapsules were designed, synthesized and applied to the sorption of NH₃ from gas streams.

An investigation of the textural properties of mesostructured silica-based adsorbents for predicting CO2 adsorption capacity

The CO₂ uptake of more than 30 physisorbents was found to correlate with their textural parameters, namely the product of the available surface area (S_BET) and the affinity of the surface toward adsorptives (C parameter).