Polymer Membranes
Membrane sciences and technologies are now seen as an important tool for addressing some important global issues such as drinking water shortages, eliminating environmental burdens, etc. The main advantages of membrane technologies over the traditional processes (such as distillation, absorption, etc.) are: up to 10 times lower energy consumption, low investment and operating costs, easy scalability, small footprint, minimal environmental impact. The most widespread membrane technologies include sea water desalination utilizing the reverse osmosis process, drinking water and wastewater treatment with microfiltering, ultrafiltration, electrodialysis. In medicine the haemodialysis cleansing is a significant practice. In recent years the membrane gas separation technologies are developing rapidly.
The research is focused on a preparation of different types of membranes based on new polymer and composite materials for the use in membrane technologies such as membrane gas separation, electrodialysis, alkaline water electrolysis, fuel cells and enantio-selective separation of optically active substances. The research further focuses on the characterisation of newly prepared materials, both in terms of internal structure, thermal and mechanical properties, as well as transport (separation) properties.
Membrane gas separation
Membrane gas separation is a relatively young membrane technology whose current dynamic development is influenced by the results of intensive material research. Polymeric materials occupy an important role in membrane gas separations. Due to the presence of free volume between the macromolecules, these materials are able to separate gases at the molecular level (smaller molecules penetrate the free volume more easily than larger molecules). Also, the molecular force interaction of gases with the macromolecules of the polymer can have a significant impact on the permeability and separation efficiency of membranes. Such membranes then have the ability to divide gases based on their different solubility in the polymer material.
In our department, we are dedicated to synthesizing new polymer based materials and (nano)composites suitable for efficient gas separation. Significant attention is paid to the synthesis of new types of aromatic polymers such as polyimides (belonging to the group of so-called "high-performance" polymers) which are characterised not only by the excellent gas transport properties but also by excellent mechanical, chemical and thermal resistance. For newly prepared materials, structural parameters, thermal, mechanical and chemical stability, morphology and transport properties for selected gases are characterized.
Selected materials that meet certain conditions necessary for other possible applications are prepared in ultra-thin layers that are mechanically supported by special porous supports. Such formed composite membranes are characterisitc by the orders of magnitude increased permeance for gases, as the thickness of the functional layer (barrier) is small enough to be easily overcome by gases. Because ultra-thin layers are prone to creation of defects, the preparation process needs to be properly optimised. If these composite membranes do not contain any defects and their separation efficiencies are more than acceptable, such membranes can be applied into a membrane module. Membrane moduels can allow larger volumes of gaseous mixtures can be separated through. Typical gas-separation processes include nitrogen production from the air or reciprocally oxygen enrichment (Oxygenerator project ÚMCH-MemBrain), biogas processing (CH4/CO2 separation under MEMOSEP project), (bio)hydrogen separation (i-AlgMemB project) or CO2 capture from the thermall powerplants, heating plants and other sources (MEMSEP project).
An example of the utilization of the membrane separaration within complex fermentor - photobioreactor system in the framework of the project "Towards the sustainable production of valuable chemicals from microalgae based on the sequestration of refused-CO2 in a novel, circular-loop gas separation membrane bioreactor system" (i-AlgMemB)
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Bakoniy P. et al.; Feasibility study of polyetherimide membrane for enrichment of carbon dioxide from synthetic biohydrogen mixture and subsequent utilization scenario using microalgae. Int. J. Energy Res. 2020, 1–8. |
Membranes for electrolyzers fuel cells and for lithium ion batteries
Polymer membranes are also a key component of devices for alternative electric energy production (fuel cells) and electric energy storage (lithium ion batteries, water electrolyzers). Membranes, serving in those devices as an electrolyte, are ion-conductive, while for gases impermeable and for electrons resistive.
A series of ion exchange polymers were developed and used for preparation of membranes and catalyst binders. Contrary to currently used diaphragms for water electrolysis (AEM WE) that use binder and membranes as hydroxide conducting material, we used a different approach, in which new materials based on quaternised poly(phenylene oxide), PPO,(Fig.1) were used as a binder and solid electrolyte. We discovered that the cells assembled with membranes made of such material show higher efficiency than common commercial alkaline electrolysers
Nahoře —poly(2,6-dimethyl-1,4-phenylene oxide); dole — blokový kopolymer polystyrene-block-poly(5 ethylene-ran-butylene)-block-polystyrene (PSEBS) kvarternizované trimethylaminem a 1,4-diazabicyklo[2.2.2]oktanem.
Fuel cell is an electrochemical device that directly converts chemical energy into electrical power. On the catalyst, a fuel, most often hydrogen, is split into protons ans electrons. The electrons flow the the external circuit and produce electrical power. The protons permeate through the membrane. At the other side of the membrane electrons, protons and oxygen coming from outside combine to form water. Fuel cells can operate permanently until the supply of hydrogen and oxygen is stopped. Our research deals with the preparation of homogeneous ion-exchange membranes based both on aromatic and aliphatic polymers. The current research is also focused on the preparation of membranes whose active component is a phosphonic acid group, e.i.the membranes with enhanced stability.
Separation of enantiomers by chiral membranes
Preparation of enantiopure compounds still represents a challenging task, despite the great progress in asymmetric syntheses and enantioseparation techniques. Nowadays, there is a strong tendency to use enantiopure drugs instead of racemates so that to reduce the unnecessary burden of the undesirable enantiomer in human organism. Therefore, a number of the racemic drugs have been reformulated as single enantiomers. During more than a half century of experience with industrial enantioseparation, various effective techniques have been developed. However, their use is often limited by a high manufacturing cost. A way to get around the problem consists in introducing new methods of chiral separation with a potential industrial use. One of the very promising techniques is an enantioseparation on polymer membranes. Its main advantage is that the use of membrane technologies has, in general, a positive impact on the cost of the manufacturing processes.
Recently, we published a paper on the synthesis and chiral recognition properties of polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (PSEBS) membranes bearing covalently anchored (S)-(−)-α-methylbenzylamine as a chiral selector, which exhibited an ability to separate racemic tryptophan and ibuprofen in preferential soption experiments.
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Otmar, M. et al.; Preparation of PSEBS membranes bearing (S)-(–)-methylbenzylamine as chiral selector. Eur. Polym. J. 2020, 122, 109381. |
We also described chiral templating of polycarbonate membranes with (−)-α-pinene using the modified atomic layer deposition (ALD) approach. During the research a functional protocol for enantioselective membranes was developed. The key, enantioselectivity-promoting, factor consists in a deposition of aluminum oxide layer before the templating process. These membranes exhibited a significantly higher sorption of (−)-α-pinene compared to (+)-α-pinene and racemate.
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Brožová, L. et al.; Chiral Templating of Polycarbonate Membranes by Pinene Using the Modified Atomic Layer Deposition Approach. Langmuir 2020, 36, 12723–12734. |
Fundings:
- Advanced materials for batteries (MAT4BAT) EU FP7, NMP3-LA-2013-608931
- Next Generation Alkaline Membrane Water Electrolysers with Improved Components and Materials (NEWELY), HORIZON 2020 , H2020-JTI-FCH-2019-1-875118
- Membrane separation of carbon dioxide from flue gas and its subsequent use (MEMSEP), TAČR TK02030155
- Separation of Enantiomers by Chiral Membranes GAČR 20-06264S
- Advanced nanostructured membrane-electrode assembly with the improved mass and charge and chargé transport for PEM water electrolysis, GAČR 20-06422J
- Towards the sustainable production of valuable chemicals from microalgae, MŠMT (program V4-Korea Joint Research Projects) 8F17005
- Polymers for Power engineering – Energolab, was cofinanced from the European Regional Development Fund through the Operational Programme Prague – Competitiveness (OPPK), CZ.2.16/3.1.00/24504.
Cooperation:
- University of Chemistry and Technology, Prague
New conductive polymer membranes for fuel cells and water electrolysis are being developed and studied in the framework of EU and Czech projects.
- Institute of Chemical Process Fundamentals of the CAS, Prague
New polymer membranes for enantiomers separation are prepared and characterized
- University of Pannonia, Veszprém, Hungary
Common research on biohydrogen production and purification by membrane processes, including microbial electrolysis cells.
- HZG, Geesthacht, Germany
Cooperation in the field of composite membranes for gas separation
Cooperation with industry in research and development of new membranes with required properties as well as in implementation of new methods of membrane preparation:
- MemBrain Inc., Stráž pod Ralskem, Czech Republic
is our strategic partner in the membrane research with the focus on membranes for gas separation, biogas upgrading, ion-exchange membranes and many other research activities.
- Mega Inc., Stráž pod Ralskem, Czech Republic
is the producer of heterogeneous ion-exchange membranes RALEX for electrodialysis, electrophoresis and membrane electrolysis. Common projects in material research and membrane production technology are the subject of the cooperation.