Development of multi-stage plasma and photocatalytic system for removing air pollutants

Abstract

A number of techniques for air pollutant removals are available such as adsorption, biofiltration and incineration. However, these techniques require further treatment and/or are energy-intensive leading to high treatment costs. Both plasma and photocatalysis are promising alternatives since these two techniques can be operated at ambient conditions resulting in low energy consumption as compared to the conventional methods. The main objective of this work was to develop a combined plasma and photocatalytic system for VOC removals. A four-stage plasma and photocatalytic reactor system was setup to study the oxidation of ethylene as a model pollutant. An increase in either applied voltage or stage number of plasma reactors enhanced C[subscript 2]H[subscript 4] conversion and CO[subscript 2] selectivity which is in contrast with the effects of frequency and feed flow rate. The commercial TiO[subscript 2] (Degussa P25), sol-gel TiO[subscript 2], and 1% Pt/sol-gel TiO[subscript 2] were used as photocatalysts. The presence of all studied photocatalysts increased the C[subscript 2]H[subscript 4] and O[subscript 2] conversions as well as CO[subscript 2] selectivity in the following order: 1% Pt/TiO[subscript 2]>TiO[subscript 2]>Degussa P25. The synergistic effect of photocatalysts presented in the plasma reactor is resulted from the activation of TiO[subscript 2] by the energy generated from the plasma.