Role of O₃ in the removal of HCHO using a DC streamer plasma

Abstract

Formaldehyde is one of the most common volatile organic compounds and indoor contaminant, and one known to cause a variety of health problems. This paper proposes a streamer discharge reactor with negative or positive discharge for formaldehyde removal. The removal of HCHO and the simultaneous production of O 3 in a DC streamer plasma were investigated. The performances of the positive and negative discharges were compared. The electrical characteristics such as U-I characteristics, discharge pattern, and power source efficiency were studied, and the reaction results were evaluated by O 3 production, HCHO removal, and energy yield. Optical emission spectra were used to characterize the streamer and reactive species produced. A maximum HCHO removal rate of 78% was achieved at a specific energy density of 1700 J l −1 . Results suggest that the positive streamer is better at producing O 3 and oxidizing HCHO, compared to the negative counterpart. For the positive streamer plasma, the G-values of ozone production and formaldehyde decomposition are 0.59 molecules per 100 eV and 0.035 molecules per 100 eV, respectively. Interestingly, the production of O 3 and degradation of HCHO were found to be simultaneous but quasiindividual processes. Both reactions were controlled by the generation of O atoms, however they consumed O atoms independently. The active species of OH, H and O radicals were observed, which had contribution to the degradation of formaldehyde. Finally, the reaction mechanism and most possible reaction pathways for the two processes were discussed.

Noble-Metal-Based Catalysts on a Scale from Nanoparticles to Subnanoclusters and Single Atoms for Formaldehyde Oxidation at Room Temperature: A Review

“…157 Nonthermal plasma, including the forms of dielectric barrier discharge, streamer discharge, corona discharge, and microwave discharge, can produce oxidizing species ( • OH) to further oxidize HCHO into CO 2 and H 2 O. 158 Therefore, it can be considered as an excellent technology for pollution control. In addition, a photoassisted method can help to excite the activation of O 2 for semiconductors (such as MnO 2 , 159 TiO 2 , 160 etc.)…”

“…Ozone (O 3 ) is a good alternative for O 2 due to its stronger oxidizing capability as an oxidant, resulting in a shorter elimination time, such as in the system of MnO x /Al 2 O 3 . Nonthermal plasma, including the forms of dielectric barrier discharge, streamer discharge, corona discharge, and microwave discharge, can produce oxidizing species ( • OH) to further oxidize HCHO into CO 2 and H 2 O . Therefore, it can be considered as an excellent technology for pollution control.…”

Temporal evolution and mechanism of secondary streamers in N2/O2 mixtures at atmospheric pressure under DC voltage

“…Streamer discharges in N 2 /O 2 mixtures at atmospheric pressure have been widely used in various fields [1], including surface treatment [2,3], plasma-assisted combustion [4], plasma biomedicine [5,6], and air purification [7,8]. Most of these applications rely on chemically active species, mostly generated through energetic electron collisions with * Author to whom any correspondence should be addressed.…”

The Assessment of Indoor Formaldehyde and Bioaerosol Removal by Using Negative Discharge Electrostatic Air Cleaners

“…Yuan et al (2020) [ 17 ] reported that corona discharge could reduce the concentration of HCHO from 0.8 ppm to 0 ppm in 13 min. An ESP is commonly paired with a downstream catalyst to increase the HCHO removal rate and to reduce the amount of O 3 generated [ 18 , 19 ].…”