Twente has always been a pioneer in membrane technology. About 50 years ago, with the arrival of Kees Smolders, research on membranes started at the Technische Hogeschool Twente, later University of Twente. And some 10 years later, Ton Burggraaf and his group started developing ceramic membranes. The history book ’50 years of membrane research in … Continue reading 50 years of membrane research in Twente
Selectivity and permeability are key properties to characterise a membrane. The selectivity indicates how well a membrane can separate. Comparing the composition of a mixture before the membrane and after it has passed the membrane gives an impression of the selectivity of the membrane for that mixture. If one component of the mixture does pass … Continue reading Selectivity and permeability
Polystyrene foam, filters, porous asphalt, aerogel … They all have one thing in common: besides ‘real material’ they also consist of empty space: small cavities or continuous channels – sometimes even from one side of the material to the other. In other words: they are porous. The presence of pores influences the materials properties to … Continue reading Porous materials
The Swedish mineralog Axel Fredrik Cronstedt was rather surprised in the middle of the 18th century when he heated a piece of stone with a burner. What happened? The stone started to bubble and hiss. Water adsorbed inside these stones was released as steam. He called these stones zeolites, after the ancient Greek words zeos … Continue reading Zeolites as water softeners in detergents
A membrane is a selectively permeable separation wall. Some substances can pass and others cannot, allowing to separate the ‘some’ from the ‘others’. Its simplicity, and therefore its versatility, is the great strength of this type of filter. Today, they are widely used to convert salt water into fresh water and in kidney dialysis. But … Continue reading Membrane technology in a nutshell
Exhaust gases from diesel cars contain soot particles, which are the result of combustion (pyrolysis) in the diesel engine. Soot particles in the (sub)micron range appear to have such a detrimental effect on human health that the European Commission decided to restrict their emission. For example, the Euro V standard came into effect as of … Continue reading How does a soot filter capture particulate matter in diesel cars?
It becomes more and more common: rainwear or sportswear that is waterproof and breathable at the same time. Porous materials that allow water vapour (perspiration) to pass while rejecting liquid (rain) water form the basis. The secret lies in the combination of the open structure and the water repellence of tissues. In fact, any tissue … Continue reading Breathable rainwear
They treat 180 liters of blood daily, which they process to remove waste products: our kidneys. These two complex organs filter breakdown products of protein and amino acid metabolism – especially urea – from the blood, and these waste products leave the body with the urine. When the kidneys stop doing their job, the waste … Continue reading Membranes and renal dialysis
The porosity of a material indicates what is the volume of empty space with respect to the total volume. So if you know that a material is 25% porous, then it consists for 75% of ‘real material’, and the remaining quarter is ‘nothing’ or air. But in addition to this absolute value for the porosity, … Continue reading Membrane characterisation by permporometry
