Water and Air Pollution Removal by Photocatalytic processes

Since now three decades, advanced oxidation technologies “in particular photocatalysis” gained much attention by Scientifics. In their point of view, to counter environmental pollutions, a simple and comprehensive photonic reaction system which converts the photon energy into the chemical energy of a redox system such as photocatalysis, would be helpful for the detoxification processes.

The activity of the group has started on the physical chemistry line, and then more interest has been given to transfer phenomena of matter and light in the view of the design of photocatalytic reactors.

The activity of the team is summarized here after:

Photocatalysis with suspended photocatalyst.

As the photocatalyst is usually found in powder, it can be used in suspension in the water to be treated, which allows a large interface area. Thus work has been done by using 1,2-dichloroethane as a model pollutant. Much attention has been given to the adsorption process. Both the kinetics and the equilibrium have been studied as well as the inhibiting effect of inorganic ions.

Immobilised photocatalyst.

Immobilised catalyst permits to avoid the separation process inherent to the use of suspended catalyst. In this second study, different types of immobilised catalysts have been prepared and studied: either by direct deposition of TiO 2 or by the “sol-gel” method with a precursor.

Light collection.

Most deposits scatter light on the one hand and are more efficient as a thin layer on the other hand. Then, a photocatalytic reactor has to be designed with a 3-dimensional geometry, taking into account the absorption and scattering.

Solar detoxification.

As the photocatalyst can be excited by near UV light, a solar process is feasible. Works has been carried in the laboratory using fluorescent UV lamps emitting at λ 400 nm.

Air treatment.

The work carried out on water treatment is being extended in the field of air treatment (VOCs, odours) using deposited photocatalyst either in tubular or annular reactor. Removal of low-ppm concentrations of acetaldehyde, a common indoor air pollutant, by photocatalysis is investigated in an annular photoreactor. Reactor design is performed with the dispersion model and residence time distribution simulation by CFD. No by-products are detected and complete carbon balance is achieved allowing assumption that removed acetaldehyde is well converted into carbon dioxide and water. Dependence of reaction rate on light intensity is studied; showing a first order tendency in the experimental conditions.

Photocatalytic reactor design.

The purpose of this task is to design more or less complex monolithic supports and coat them with TiO 2 Degussa P25 to be at the maximum of absorption. Several supports with different arrangement in space were first designed by stereolithography.

Since now three decades, advanced oxidation technologies “in particular photocatalysis” gained much attention by Scientifics. In their point of view, to counter environmental pollutions, a simple and comprehensive photonic reaction system which converts the photon energy into the chemical energy of a redox system such as photocatalysis, would be helpful for the detoxification processes.

The activity of the group has started on the physical chemistry line, and then more interest has been given to transfer phenomena of matter and light in the view of the design of photocatalytic reactors.

The activity of the team is summarized here after:

Photocatalysis with suspended photocatalyst.

As the photocatalyst is usually found in powder, it can be used in suspension in the water to be treated, which allows a large interface area. Thus work has been done by using 1,2-dichloroethane as a model pollutant. Much attention has been given to the adsorption process. Both the kinetics and the equilibrium have been studied as well as the inhibiting effect of inorganic ions.

Immobilised photocatalyst.

Immobilised catalyst permits to avoid the separation process inherent to the use of suspended catalyst. In this second study, different types of immobilised catalysts have been prepared and studied: either by direct deposition of TiO 2 or by the “sol-gel” method with a precursor.

Light collection.

Most deposits scatter light on the one hand and are more efficient as a thin layer on the other hand. Then, a photocatalytic reactor has to be designed with a 3-dimensional geometry, taking into account the absorption and scattering.

Solar detoxification.

As the photocatalyst can be excited by near UV light, a solar process is feasible. Works has been carried in the laboratory using fluorescent UV lamps emitting at λ 400 nm.

Air treatment.

The work carried out on water treatment is being extended in the field of air treatment (VOCs, odours) using deposited photocatalyst either in tubular or annular reactor. Removal of low-ppm concentrations of acetaldehyde, a common indoor air pollutant, by photocatalysis is investigated in an annular photoreactor. Reactor design is performed with the dispersion model and residence time distribution simulation by CFD. No by-products are detected and complete carbon balance is achieved allowing assumption that removed acetaldehyde is well converted into carbon dioxide and water. Dependence of reaction rate on light intensity is studied; showing a first order tendency in the experimental conditions.

Photocatalytic reactor design.

The purpose of this task is to design more or less complex monolithic supports and coat them with TiO 2 Degussa P25 to be at the maximum of absorption. Several supports with different arrangement in space were first designed by stereolithography.

Further reading

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