Destruction Technology During VOCs Treatment-3

Destruction Technology

Photocatalytic degradation

Photolysis refers to the oxidation of target pollutants adsorbed on the surface of photocatalysts under light conditions, and the oxidation and decomposition of them into CO2 and H2O to achieve the degradation of VOCs.

When the photocatalyst is illuminated, electron (e-) transition occurs, and electron (e-) transitions from the low-energy valence band (VB) to the high-energy conduction band (CB), and the low-energy valence band (VB) forms electron holes due to the lack of electrons. (h+).

When O2 and H2O are adsorbed on the surface of the photocatalyst, the electron holes will react with H2O on the surface of the photocatalyst to form hydroxyl radicals ( OH), and also combine with hydroxide ions (OH-) to form hydroxyl radicals ( OH).

The photo generated electrons will react with O2 to generate superoxide anion radicals (·O-2), superoxide anion radicals (·O-2) combine with hydrogen ions (H+) to form superoxide radicals (HO2·), and superoxide anion radicals (·O-2) combine with hydrogen ions (H+) to form superoxide radicals (HO2·). Hydrogen oxide radicals (HO2·) then undergo a series of reactions to generate O2, hydroxide ions (OH-), and hydroxyl radicals (·OH). VOCs will react with the free radicals generated in the above reactions.

TiO2, Fe2O3, ZnO, CdS, WO3, SnO2, ZrO2 are several common photocatalysts in the current industrial field. Among them, TiO2 has the advantages of high activity, low price, stable reaction conditions, non-toxic and harmless, etc. It also has disadvantages such as low utilization of visible light.

Therefore, scientific researchers often modify it. Common modification methods include metal doping, non-metal doping, noble metal deposition, compound semiconductor, surface photosensitization, and TiO2 immobilization.

Low temperature plasma method

Low-temperature plasma method is a process in which high-energy electrons or free radicals react with organic waste gas to generate CO2 and H2O. base, and react with VOCs molecules, thereby degrading and removing VOCs.

This method has a good treatment effect and is suitable for the treatment of medium and low concentration waste gas, but the energy consumption is high, and secondary pollution is easily caused during the degradation process.

When choosing a VOCs treatment technology, it is necessary to consider its own properties, and select an appropriate purification technology according to factors such as VOCs concentration, gas flow, and purification requirements.