The quality of outdoor air is a much discussed topic in media and politics, while indoor air quality (IAQ) is often overlooked. Despite the fact that people spend the largest fraction of their time (85%) indoors, poor IAQ is still an underestimated problem. In fact, indoor air is often of worse quality than outdoor air. So it is definitely time to focus on indoor air quality as well.
This research deals with air purification with specific focus on the development of a sustainable indoor air purification technology. Air purification technology on the market is commonly based on electrostatic precipitation (ESP) with corona discharge as plasma source. This technique has, however, some disadvantages. For example, formation of by-products (e.g. ozone) that are powerful oxidants; displacement instead of degradation of the pollutants to another phase and occurrence of irreversible deposition on the collector electrode. The latter results in a decline of the efficiency of the ESP.
Implementing a photocatalytic nano-coating offers an innovative and sustainable solution to eliminate these drawbacks. This solution includes several different opportunities: For one, the nano-coating ensures the conversion of harmful intermediates and end-products to harmless products. Secondly, due to the photocatalytic activity complete mineralisation of the pollutants can be achieved. Furthermore, the occurrence of irreversible deposition and, consequently the additional wash step, is avoided.
The aim of this project is thus to develop an integrated air purification technology, using electrostatic precipitation and photocatalytic degradation of trapped particles, also called plasma assisted catalysis.
The research itself is divided into three work packages.
First, it is needed to study the decomposition processes in plasma of individual pollutants like formaldehyde and particulate matter (PM). These experiments will be conducted in an electrostatic precipitator on lab scale. After studying the individual pollutants, the abatement of a realistic indoor air composition, for example environmental tobacco smoke (ETS), will be investigated as well.
During the second phase, a selected photocatalytic nano-coating will be optimised. This optimisation is done in function of the maximum photocatalytic activity in the gas phase. It is, however, very important that other properties, necessary for the implementation in a plasma assisted catalysis set-up, are also investigated. These features include excellent adhesion on the substrate, good conductivity, optimal amount of deposited material, large specific surface area, open porosity and the required crystal structure. This work package results in a sustainable coating that has all the specific requirements needed to work in a plasma reactor.
The third phase of this project includes the same experiments as performed in the first phase but this time with a coating applied on the collector electrode. Comparing the decomposition processes with and without coating enables to determine the influence of the coating on the working of the ESP. Hence, the synergetic effect of the plasma assisted catalytic system will be investigated. The coating can be further improved after obtaining the results of this phase. Obviously, the three different work packages are in close collaboration with each other.