Characterization of Quaternary-Ammonium-Based Ionogel Membranes for Application in Proton Exchange Membrane Fuel Cells.

In recent years, the quest to advance fuel cell technologies has intensified, driven by the imperative to reduce reliance on hydrocarbon-derived fuels and mitigate pollutant emissions. Proton exchange membranes are a critical material of fuel cell technologies. The potential of ionic liquid-based polymer inclusion membranes or ionogels for proton exchange membrane fuel cells (PEMFCs) has recently appeared. Thermal stability, SEM-EDX characterization, NMR and IR characterization, thermogravimetric analysis, ion exchange capacity, and water uptake are key properties of these membranes which need to be investigated. In this work, ionogel based on quaternary ammonium salts, such as [N8,8,8,1+][Cl-], [N8,8,8,1+][Br-], and [N8-10,8-10,8-10,1+][Cl-] in various compositions with poly(vinyl chloride) are extensively studied and characterized based on those key properties. The best properties were obtained when a quaternary ammonium cation was combined with a bromide anion. Finally, ionogels are tested in microbial fuel cells. Microbial fuel cells based on the ionogel reach a maximum of 147 mW/m2, which represents 55% of the reference membrane (Nafion 212). These results indicate that we still have the possibility of improvement through the appropriate selection of the cation and anion of the ionic liquid. Overall, the promise of ionogel membranes as a viable alternative in fuel cell applications has been demonstrated.

Polymeric Inclusion Membranes Based on Ionic Liquids for Selective Separation of Metal Ions.

In this work, poly(vinyl chloride)-based polymeric ionic liquid inclusion membranes were used in the selective separation of Fe(III), Zn(II), Cd(II), and Cu(II) from hydrochloride aqueous solutions. The ionic liquids under study were 1-octyl-3-methylimidazolium hexafluorophosphate, [omim+][PF6-] and methyl trioctyl ammonium chloride, [MTOA+][Cl-]. For this purpose, stability studies of different IL/base polymer compositions against aqueous phases were carried out. Among all polymer inclusion membranes studied, [omim+][PF6-]/PVC membranes at a ratio of 30/70 and [MTOA+][Cl-]/PVC membranes at a ratio of 70/30 were able to retain up to 82% and 48% of the weight of the initial ionic liquid, respectively, after being exposed to a solution of metal ions in 1 M HCl for 2048 h (85 days). It was found that polymer inclusion membranes based on the ionic liquid methyl trioctyl ammonium chloride allowed the selective separation of Zn(II)/Cu(II) and Zn(II)/Fe(III) mixtures with separation factors of 1996, 606 and, to a lesser extent but also satisfactorily, Cd(II)/Cu(II) mixtures, with a separation factor of 112. Therefore, selecting the appropriate ionic liquid/base polymer mixture makes it possible to create polymeric inclusion membranes capable of selectively separating target metal ions.

Immobilization in Ionogel: A New Way to Improve the Activity and Stability of Candida antarctica Lipase B.

New Candida antarctica lipase B derivatives with higher activity than the free enzyme were obtained by occlusion in an organogel of an ionic liquid (ionogel) based on the ionic liquid [Omim][PF6] and polyvinyl chloride. The inclusion of glutaraldehyde as a crosslinker improved the properties of the ionogel, allowing the enzymatic derivative to reach 5-fold higher activity than the free enzyme and also allowing it to be reused at 70 °C. The new methodology allows enzymatic derivatives to be designed by changing the ionic liquid, thus providing a suitable microenvironment for the enzyme. The ionic liquid may act on substrates to increase their local concentration, while reducing water activity in the enzyme's microenvironment. All this allows the activity and selectivity of the enzyme to be improved and greener processes to be developed. The chemical composition and morphology of the ionogel were also studied by scanning electron microscopy-energy dispersive X-ray spectroscopy, finding that porosity, which was related with the chemical composition, was a key factor for the enzyme activity.

Bioreactor Membranes for Laccase Immobilization Optimized by Ionic Liquids and Cross-Linking Agents.

A novel concept of membrane bioreactor based on polymeric ionic liquids laccase membrane has been implemented in batch process for decolorization of the anthraquinonic dye Remazol Brillant Blue R (RBBR). New laccase immobilization strategy has been optimized by casting the enzyme into a polymeric inclusion membrane (PIM) using ionic liquids (ILs) and polyvinyl chloride (PVC) leading to laccase polymeric IL membrane (PILM). Four different ILs (1-octyl-3-metylimidazolium bis(trifluoromethylsulfonyl)imide, [OMIM][NTF2]; cholinium bis(trifluoromethylsulfonyl)imide, [Ch ol][NTF2]; cholinium dihydrogenphosphate, [Chol][H2PO4] and hydroxyethylammonium formate, [HEA][Fo]) have been screened and mixed to constitute the active phase of the support of PIM. This strategy has been fully succeeded since high laccase immobilization rates were recorded (about 98%) when using the optimal mixture containing three ILs (45% [OMIM][NTf2]/5% [Chol][NTf2]/2.5% [HEA][Fo]) and supplemented by 0.5% glutaraldehyde. It was found that such mixture contributes to increase the stability and reusability of laccase-PILM during eight successive assays in a batch discontinued stirred reactor. Decolorization rate of 75% has been reached in the batch decolorization process of RBBR with high reusability yield. Graphical Abstract Decolorization of RBBR by PILM_laccase.