Photocatalytic materials and technologies
Responsible worker |
Expert adviser |
Department of UCT Prague |
1. Offered services |
2. Research and development activities | 3. Equipment |
determination of photocatalytic activity in gas phase using ISO standard methods |
development of new photocatalytic materials, pigments and paints |
apparatus for determination of photocatalytic activity in the gas phase according to the ISO methodology (including NOx analyzer. GC-FID chromatograph) |
determination of photocatalytic activity using smart inks
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development of new methods of photocatalytic activity assessment |
equipment for the preparation of photocatalytic coatings, dispersions and active surfaces (dissolver, Turrax homogenizer, ultrasonic bath,) |
equipment for application of photocatalytic active layers (dryer, set of round wound rot K-bars) |
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consultation in the field of photocatalytic materials |
standardization |
colorimeter for objective color measurement |
The specialization of the group is focused on evaluation of photocatalytically active surface such as glass, ceramics, paints, concrete, textiles etc. Semiconductor photocatalysis represents promising method for removing pollutants from the environment, whether it is a degradation of toxic substances dissolved in water (pesticides, dyes, pharmaceuticals), in air (VOCs, NOx) or solid phase (fats). Another application is based on the ability to inactivate growth of the microorganism.
Application of photocatalysis can be divided in two main areas:
- self-cleaning surfaces – the current application of such surface is mainly with regard to exterior facade paints which, via the photocatalytic processes are not susceptible to soiling and so help exterior of the building clean
- air or water treatment- -based on the ability of photoactive material to oxidative decompose of specific undesirable substances present in the polluted air or water. This makes it possible to suppress some of the adverse effects of human activities, eg. air pollution in densely populated areas. Application of such methods it is possible to suppress some of the adverse effects of human activities. (air pollution in densely populated areas.)
Cooperation:
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Faculty of Civil Engineering. CTU Prague
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Determination of photocatalytic activity in gas phase using ISO standard methods
These ISO standard methods are suitable for testing of photocatalytic products (paints, tiles, etc.) in terms of their ability to degrade of pollutants in the air.
Standard ISO methods of photocatalytic activity assessment in gas phase are based on photocatalytic degradation of pollutant such as NOx, formaldehyde in air during irradiation of sample by UV light in trough-flow photoreactor. Photocatalytic activity is than expressed as an amount of degraded pollutant during test.
Apparatus for photocatalytic activity assessment in gas phase using ISO methodology
standard |
ISO 22197-1 |
ISO 22197-2 |
ISO 22197-3 |
ISO 22197-4 |
pollutant |
NO |
acetaldehyde |
toluene |
formaldehyde |
Overview of the installed ISO methods, ISO 22197-3 (removal of toluene) is realized in cooperation with the Department of Inorganic Technology
Dimensions of sample:
The standard sample size is 5x10 cm (thickness 4 and 8 mm).
Determination of photocatalytic activity using new rapid method based on smart inks
This method is suitable for rapid testing of various photocatalytic materials such as self-cleaning glass, paints, and tiles. The principle of method is based on color change of dye in ink which occurs on photocatalytic surface. Currently, this method is in preliminary proceedings for the ISO standard.
Smart inks contain besides dye also glycerol which act as a sacrificial electron donor. Photogenerated holes oxidized glycerol to glyceraldehyde or to other intermediates, excited electrons reduce irreversible dye and this reduction is connected with change of the color. Due to the presence of glycerol, it comes to good charge separation and the reduction of dye is comparing to oxidative reaction (e.g. oxidation of azodye in aqueous solution) very quick and takes few seconds.
The assessment of photocatalytic activity is based on graphical analysis of sample cover with thin film of ink. Photocatalytic activity is than expressed as a time needed for 90% of overall color change of ink film.
Dimension of sample:
At least 8 samples (2,5x 2,5 cm) thickness 3 mm.
On the bottom there is illustrated an example of reduction of Resazurin on commercial self -cleaning glass and on reference sample without active layer. On the self-cleaning glass it comes to reduction of Resazurin to Resorufin which is connected with the color change form blue to pink. On the reference sample without active layer the photocatalytic reduction of Resazurin does not occur.
Color change of Resazurin on commercial self- cleaning glass (up) and reference inactive sample (bottom).