Hessel Castricum from the University of Amsterdam has developed a versatile membrane that is capable of separating gas and liquid mixtures in an energy-efficient manner. He conducted his research with colleagues from the University of Twente and the Energy research Centre of the Netherlands. The new membrane can probably be employed under industrial conditions on a large scale in the future. This has not been possible until now, because virtually all membranes developed so far are insufficiently stable. What is also striking about this discovery is that the functionality of the membrane can be adjusted by varying the structure. This new membrane can lead to significant energy and cost savings.
The results were singled out as a research highlight in the journal Advanced Functional Materials.
Membranes are an inexpensive means of separation compared, for example, to distillation: easy and energy-efficient (and therefore relatively cheap). The separation of molecular mixtures with a membrane is, however, a method that is currently rarely used, especially for large processes. This is mainly due to the fact that little or no systems have been sufficiently tested to be applied reliably. The limited stability of most materials is the main cause.
Variable by organic bridge
The newly developed type of membrane can be used for many years at high (relevant) temperatures in mixtures in which a lot of water is present. It is therefore extremely stable. The material also allows much faster transport of molecules than, for example, polymers.
The membrane is made from a hybrid material that has both ceramic and polymeric properties. The scientists discovered that it is possible to alter the characteristic building block of this membrane: an organic bridge between two silicon atoms. Because of this variation, the membrane can be optimised for separation of different mixtures.
By using short bridges, it is possible to make the membrane selective for the smallest molecules, such as hydrogen and water. In contrast, slightly larger molecules such as CO2 or alcohols can pass more easily through the membrane by using larger bridges. Moreover, the material can actually be made water-repellent, by using, for example, long organic bridges. As a result, industry can decide to adopt membrane technology sooner and for more processes. Examples of potential applications include the dewatering of bio-fuels, CO2 sequestration and hydrogen production.
For these techniques to be used in practice, the reliability of the new membrane technology needs to be examined on a larger scale than in a lab. In this respect, it is perhaps interesting that a pilot plant has recently been opened at Plant One in the Botlek area of Rotterdam. The first material developed will be tested there on a larger scale.
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