atech innovations gmbh

Ceramic membranes with higher abrasion resistance


Courtesy of atech innovations gmbh

High flux rates, combined with a very high chemical and thermal resistance and the resulting operational reliability - these are the reasons why users worldwide opt for ceramic membranes.

Up to now, the only parameter where ceramic membranes performed well but not excellent was abrasion resistance.

Therefore, filtering of abrasive matter required pre-treatment stages such as prefiltration, centrifuging, or sedimentation in order to protect the membrane.

Ceramic membranes (without binding agents) lost their screening characteristics not because of corrosion but mostly because of abrasion.

This damage to the membrane is due to the fact that the highly porous structure is only supported by small “sinter necks” between the particles of the membrane layer.

Therefore, abrasion resistance is significantly lower than that of a “more densely structured” layer.

atech innovations gmbh has succeeded in improving the abrasion resistance of membranes. Their new product line DURatech is manufactured using an innovative coating process (pictures 1 and 2).

Diagrams 1 and 2 show the results of standardized scratch test measurements on membrane surfaces performed under defined conditions. In a scratch test, a needle is drawn over the surface while the force acting vertically is steadily increased, and the penetration depth is measured.

At an identical force, the needle penetrates a standard membrane to approximately double the depth than a DURatech membrane or, respectively, approximately twice as much force is needed to achieve the same penetration depth for a DURatech membrane (diagram 1).

It is true for DURatech membranes as well that with reducing pore sizes their abrasion resistance declines as well, i.e. if an identical force is applied the penetration depth of the needle increases (diagram 2).

At present, test filtration runs are performed using model liquids containing highly abrasive components to determine the limits of abrasion resistance.

The improvement of abrasion resistance has already been proven by long-term operation in an industrial membrane filter installation.

A mixture which, as a result of pollution, permanently contains a portion of silica sand was filtered using DURatech membranes (0.05 μm) and the results were compared to filtering by means of standard membranes of identical pore size.

After 6 months of continuous operation, the membranes were compared under a scanning electron microscope (pictures 3 and 4). It can be seen that the DURatech membrane is complete and does not show any scratches, while the standard membrane has lost its active screening layer and the supporting structure on the surface becomes visible.

A particularly remarkable feature of this new development is that the flux rates of the membranes (standard and DURatech) are absolutely comparable. This means that the researchers of atech innovations gmbh did not reduce the open porosity (directed towards the “more densely structured” layer), accepting the inevitable reduction of flux rates, but instead used an innovative coating process in order to optimize ceramic membranes.

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