Waste management strategies to mitigate the effects of fluorinated greenhouse gases on climate change

Funding Information: Funding: This work was funded by FCT/MCTES (Portugal), project PTDC/EQU-EQU/29737/2017, and was supported by the Associate Laboratory for Green Chemistry—LAQV, which is financed by national funds from FCT/MCTES (UIDB/50006/2020) and by Marine and Environmental Sciences Centre—MARE, which is financed by national funds from FCT/MCTES (UIDB/04292/2020). Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.Fluorinated greenhouse gases (F-gases) are used for various applications, such as in refrigeration and air conditioning, as substitutes of the ozone-depleting substances. Their utilization has increased drastically over the last few decades, with serious consequences for global warming. The Kigali Amendment to the Montreal Protocol and several national and international legislations, such as the 2014 EU F-gas Regulation, aim to control the utilization and emissions of these gases. In the EU, the phase-down of hydrofluorocarbons (HFCs) is underway, with successive reductions in quotas up to 2050. Under this scenario, efficient strategies for managing the produced and already existing F-gases are of vital importance to guarantee that their effect on the environment is mitigated. Up to now, most of the F-gases recovered from end-of-life equipment or when retrofitting systems are either released into the atmosphere or destroyed. However, in order to put forward a cost-efficient adaptation to the F-gas phase-down, increasing separation and recycling efforts must be made. This critical review aims at providing a revision of the current F-gas management problems and strategies and providing an overview on the innovative strategies that can be applied to contribute to build a sustainable market under circular economy principles.publishersversionpublishe

Understanding the Absorption of Fluorinated Gases in Fluorinated Ionic Liquids for Recovering Purposes Using Soft-SAFT

2020.00835.CEEIND 2021.01432.CEECIND RC2-2019-007It is proven that fluorinated gases (F-gases) have a vast impact on climate change due to their high global warming potential. Hence, it is imperative to search for new molecules to replace them in current applications, as well as technologies to capture, recover, and recycle F-gases to avoid their emissions to the atmosphere. One of the attractive technologies for this purpose is to absorb them in fluorinated ionic liquids (FILs), given their solubilization power. However, the complexity of FILs and the time-consuming experimental methodologies to fully characterize them hinder their prompt usage in this urgent field. In this work, the soft-Statistical Associating Fluid Theory (soft-SAFT) Equation of State is used as a tool to investigate the solubility of six different F-gases (R-32, R-125, R-134a, R-14, R-116, R-218) in five FILs ([C2C1Im][C4F9SO3], [C2C1Im][C4F9CO2], [C2C1py][C4F9SO3], [C2(C6F13)C1Im][N(CF3SO2)2], and [C2(C6F13)C1Im][N(C2F5SO2)2]). The robustness of the soft-SAFT approach allowed the establishment of new FIL models in a simple and fast way, and the calculation of F-gases solubility in them, in excellent agreement with existing experimental data. Once the models were assessed, a systematic study was performed regarding the structural features of FILs favoring their performance to absorb F-gases by using the soft-SAFT approach as a screening tool. It has been obtained that the solubility is favored by the presence of a perfluoroalkyl chain in the imidazolium cation, together with a bulkier anion. In all cases, [C2(C6F13)C1Im][N(C2F5SO2)2] shows a superior solubility of F-gases than the [C2(C6F13)C1Im][N(CF3SO2)2], also indicating that the addition of one carbon to the two anionic symmetric fluorinated chains contributes to the gas-philicity of the FILs. This work proves the relevance of using the soft-SAFT framework to obtain insights into the behavior of such complex systems and key trends, even when experimental data are scarce, as a step forward in assessing systems for separating and recovering F-gases.publishersversioninpres

Separation of azeotropic mixtures using protic ionic liquids as extraction solvents

IF/00190/2014; IF/00210/2014; PTDC/EQU-EQU/29737/2017; PTDC/QEQ-FTT/3289/2014; IF/00210/2014/CP1244/CT0003; UID/QUI/50006/2019; POCI-01-0145-FEDER-007265; University of Pamplona, Internal Project 2-2017.The aim of this work is to evaluate the separation of hydrocarbons (hexane and heptane) from their azeotropic mixtures with ethanol using protic ionic liquid (PIL) as extraction solvents. With this goal in mind, PILs were synthesized and their thermal and physical characterization were carried out. Experimental determination of the phase equilibrium for the ternary systems hydrocarbons + ethanol + PIL at 298.15 K and 101.2 kPa were also carried out in order to evaluate the feasibility of this application. The solute distribution ratio and the selectivity were also determined to compare the solvent capacity of these PILs. The NRTL equation was used to correlate the experimental data. Furthermore, this paper provides a comparison of the solvent capacity of these PILs with different extraction solvents (ionic liquids (ILs), ILs mixtures and deep eutectic solvents) available in the literature. Then, a critical review for the separation of these azeotropic mixtures was carried out using the extraction processes data obtained through the simulation using a conventional software.preprintpublishe

Unveiling the Influence of Non-Toxic Fluorinated Ionic Liquids Aqueous Solutions in the Encapsulation and Stability of Lysozyme

Proteins are bioactive compounds with high potential to be applied in the biopharmaceutical industry, food science and as biocatalysts. However, protein stability is very difficult to maintain outside of the native environment, which hinders their applications. Fluorinated ionic liquids (FILs) are a promising family of surface-active ionic liquids (SAILs) that have an amphiphilic behavior and the ability to self-aggregate in aqueous solutions by the formation of colloidal systems. In this work, the protein lysozyme was selected to infer on the influence of FILs in its stability and activity. Then, the cytotoxicity of FILs was determined to evaluate their biocompatibility, concluding that the selected compounds have neglected cytotoxicity. Therefore, UV–visible spectroscopy was used to infer the FIL-lysozyme interactions, concluding that the predominant interaction is the encapsulation of the lysozyme by FILs. The encapsulation efficiency was also tested, which highly depends on the concentration and anion of FIL. Finally, the bioactivity and thermal stability of lysozyme were evaluated, and the encapsulated lysozyme keeps its activity and thermal stability, concluding that FILs can be a potential stabilizer to be used in protein-based delivery systems.publishersversionpublishe

Ecotoxicity and Hemolytic Activity of Fluorinated Ionic Liquids

The task-specific design of ionic liquids (ILs) has emerged in several industrial and pharmaceutical applications. The family of ILs with fluorine tags equal to or longer than four carbon atoms, the fluorinated ionic liquids (FILs), combine the best properties of ILs with the ones of perfluorinated compounds, and are being designed for several specific purposes. In the pharmaceutical field, there is an urgency to search for novel antibacterial agents to overcome problems associated to antimicrobial resistances. Then, the main purpose of this work is to evaluate the environmental impact and the ability of FILs to be used as antibacterial agents against Pseudomonas stutzeri bacteria. Beyond its rare pathogenicity, these bacteria are also used as a bioremediation agent to treat several contamination sites. Then, it is important to determine which FILs have antibacterial properties, and which do not impact the bacterial growth. The biocompatibility of FILs was also evaluated through their hemolytic activity and represent a step forward the application of FILs in pharmaceutical applications. The results proved that high concentrations of FILs can have a reduced ecotoxicity and a high biocompatibility. [C8C1Im][CF3SO3] was identified as the most promising compound to be used as an antibacterial agent since it prevents the growth of bacteria at concentrations compatible with the red blood cells’ viability.publishersversionpublishe

Functionalization of fluorinated ionic liquids: A combined experimental-theoretical study

FCT/MCTES (Portugal), through: grant SFRH/BD/130965/2017 (M.LF.); Investigador FCT 2014 (IF/00190/2014 to A.B.P. and IF/00210/2014 to J.M.M.A.); projects PTDC/EQU-EQU/29737/2017, PTDC/QEQ-FTT/3289/2014 and IF/00210/2014/CP1244/CT0003. Associate Laboratory for Green Chemistry-LAQV, financed by national funds from FCT/MCTES (UID/QUI/50006/2019). projects 2018-LC-01 and 2019-URL-IR1rQ-011, from Obra Social "la Caixa" and by Khalifa University through project RCII-2018-0024.We present new experimental and modelling data concerning imidazolium based-FILs synthesized with a hydroxyl group in the end of the cationic hydrogenated side chain and compared them with the analogous non-functionalized FILs in order to verify their suitability in the biomedical field. The thermophysical and thermodynamic properties of the neat compounds and the self-aggregation behaviour of FILs in aqueous solutions were measured and compared with theoretical results from the soft-SAFT equation of state, in good agreement with each other. Results showed that the presence of the hydroxyl group increases the density and viscosity of pure compounds and aqueous mixtures, whereas the thermal stability, melting, free volume, ionicity and self-aggregation behaviour decrease. These properties are improved with respect to the conventional perfluorosurfactants for the desired application, due to the full miscibility in water and the promising improved biocompatibility.authorsversionpublishe

Sorption of fluorinated greenhouse gases in silica-supported fluorinated ionic liquids

the contracts of Individual Call to Scientific Employment Stimulus 2020.00835.CEECIND (J.M.M.A.) / 2021.01432.CEECIND (A.B.P.), the Norma Transitória DL 57/2016. Publisher Copyright: © 2022 The Authors.The Kigali Amendment to the Montreal Protocol limits the global use of fluorinated greenhouse gases (F-gases) and encourages the development of a new generation of refrigerants with lower global warming potential. Therefore, there is a need to develop efficient and sustainable technologies to selectively capture and recycle the F-gases as new environmentally sustainable refrigerants. Here, ionic liquids (ILs) with high F-gas uptake capacity and selectivity were supported on silica and their potential as media for selective F-gas sorption was studied. For this purpose single-component sorption equilibria of difluoromethane (R-32), pentafluoroethane (R-125), and 1,1,1,2-tetrafluoroethane (R-134a) were measured at 303.15 K by gravimetry. The sorption data were successfully correlated using classical models of sorption thermodynamics. The results show that the IL supported in the porous volume and on the external surface of the porous silica controls the F-gas uptake in the composites and that changing the IL's cations and anions allows fine-tuning the selectivity of the sorption process. This work brings crucial knowledge for the development of new materials based on ILs for the selective sorption of F-gases.publishersversionpublishe

Absorption of Fluorinated Greenhouse Gases Using Fluorinated Ionic Liquids

funding of the KET4F-Gas project, SOE2/P1/P0823, co -funded by the Interreg Sudoe Programme through the European Regional Development Fund (ERDF). FCT/MCTES for financial support through IF/00190/2014 , IF/00210/2014 financial support through the Norma TransitOria DL 57/2016 Program Contract (FCT/MCTES). FCT/MCTES (UID/QUI/50006/2019).The increasing awareness of the environmental impact of fluorinated gases (F-gases) used in refrigeration is instigating the development of technologies to recover and recycle them. With this goal in mind, single-component absorption equilibrium isotherms at 303.15 K of F-gases in different ionic liquids (ILs) were determined using a gravimetric method. The selected F-gases are the most used in domestic refrigeration (R-32: difluoromethane, R-125: pentafluoroethane, and R-134a: 1,1,1,2-tetrafluoroethane). The results show that ILs containing a fluorinated alkyl side chain with four carbon atoms, that is, fluorinated ILs (FILs), have higher gas absorption capacity than conventional fluoro-containing ILs. All studied ILs showed ideal selectivity toward R-134a. Conventional fluoro-containing ILs showed better selectivities for the separation of the binary mixtures R-134a/R-125 and R-32/R-125, and FILs showed better selectivities for the R-134a/R-32 mixture. These results provide fundamental knowledge of the behavior of these new alternative solvents and key information for their application in the separation of F-gas mixtures of commercial refrigerants.authorsversionpublishe

Understanding the phase and solvation behavior of fluorinated ionic liquids

the contract of Individual Call to Scientific Employment Stimulus 2021.01432.CEECIND (A.B.P.) Additional partial support has been provided by Khalifa University of Science and Technology through project RC2-2019-007. Publisher Copyright: © 2022 The AuthorsFluorinated ionic liquids (FILs) are defined as molecules having fluorinated tags equal to or longer than 4 carbon atoms in the anion and/or cation structures. They present nanosegregated domains making them 3-in-1 solvents with exceptional properties, including an attractive solubility power. This work is an important contribution towards understanding the current research on the phase behavior of FILs, which may be used as task-specific materials for industrial applications. An overview of the main works published in the last two decades is presented, concerning gas solubility in FILs, the application of membranes to improve the gas absorption in FILs, and the use of modeling approaches to ease the application of FILs in gas capture and separation processes, with emphasis on the relationship between the structural properties and their performance. Contributions concerning the liquid-liquid and solid-liquid equilibria behavior of FILs, including the liquid-liquid equilibria (LLE) of FILs in water and perfluoroalkanes, and the solid-liquid equilibria (SLE) of solid FILs in water and mixtures of FILs are also presented. Regarding the absorption of gases in FILs, a careful analysis of the published works reveals that: (1) an optimal density of fluorine atoms in FILs structure is required to positively impact the absorption of different gases, (2) the functionalization of membranes can be also a useful method to improve the performance in separation processes, and (3) modeling tools can ease the screening of the features that promote the absorption of gases by FILs. The study of FILs LLE showed a rich phase behavior with water and perfluoroalkanes and the enhanced surfactant power of FILs, which is highly dependent on the length of the hydrogenated and fluorinated side chains. Finally, studying the SLE of FILs mixtures allowed the formation of deep eutectic systems that enlarges the applicability of FILs.publishersversionpublishe