Quantification and risk assessment of organic products resulting from non-thermal plasma removal of toluene in nitrogen

Real-time analysis of intermediate products from non-thermal plasma degradation of ethyl acetate in air using PTR-MS: Performance evaluation and mechanism study

Non-thermal plasma (NTP) has developed into an emerging end-of-pipe technology for treating volatile organic compounds (VOCs) present in unhygienic point source of air streams. In this work, NTP oxidation of low-concentration ethyl acetate was performed in a coaxial double dielectric barrier discharge reactor. The effects of initial ethyl acetate concentration, gas flow rate, and external electrode length on ethyl acetate degradation were systematically investigated as a function of discharge power. In addition, detailed real-time and online proton transfer reaction mass spectrometry analysis was used to identify the transient species formation and transition in the various NTP oxidation periods of ethyl acetate. Based on the analysis of organic by-products, the degradation mechanism was speculated and the major reaction channels were presented. This study would deepen the understanding of plasma degradation of VOCs and reveal the plasma-chemical mechanism.

Application of proton transfer reaction mass spectrometry for the assessment of toluene removal in a nonthermal plasma reactor

Proton transfer reaction mass spectrometry (PTR-MS) is a mature technique for the real-time measurement and monitoring of volatile organic compounds in the atmosphere. In this paper, a modified quantification method for PTR-MS was used to assess the performance of nonthermal plasma (NTP) reactor for the removal of toluene which was widely used in industrial production processes. Toluene and 11 corresponding organic by-products were tentatively identified and quantified by a proton transfer reaction time-of-flight mass spectrometer. The degradation dynamics of toluene and the formation of organic by-products were monitored in real-time (resolution = 1 second) under "plasma off" and "plasma on" conditions. We conclude that initial concentration and gas flow rate were the key parameters in the health risk assessment of NTP for the removal of toluene. The toluene removal efficiency and CO₂ selectivity decreased with increasing upstream toluene concentration or gas flow rate, whereas the health risk influence index increased with increasing upstream toluene concentration or gas flow rate. The highest removal efficiency of toluene (100%), CO₂ selectivity (53.2%), and the best health risk influence index for organic by-products (0.11) were achieved when the toluene concentration was kept at 105 ppmv and flow rate at 0.4 L/minute. The results demonstrate that PTR-MS is a promising tool to improve the practical applications of volatile organic compound removal by NTP because it can be used to optimize the NTP working conditions by providing a precise, fast, and clear health risk assessment for organic by-products based on their real-time analysis.