Ionic Reactions of Chlorinated Volatile Organic Compounds in Air Plasma at Atmospheric Pressure

Summary: Results of the ionic reactivity in air plasma at atmospheric pressure of several important chlorinated VOCs are reported and discussed. These VOCs include saturated (CH 2 Cl 2 , CHCl 3 , CCl 4 , CH 2 ClCH 2 Cl, CHCl 2 CH 3 ), unsaturated (trichloroethene, Cl 2 CCHCl) and aromatic (chlorobenzene, C 6 H 5 Cl) chloro‐substituted hydrocarbons. The experiments were conducted with a commercial mass spectrometer consisting of a quadrupolar mass analyzer interfaced to an APCI (Atmospheric Pressure Chemical Ionization) ionization source, which uses a corona discharge at atmospheric pressure for the production of a non‐thermal plasma. Some experiments were also conducted with a triple quadrupole mass analyzer in order to study the reactions of specific ions singled out from the plasma on the basis of their characteristic mass/charge ratio. The organic chlorides examined display a few common reactions, such as, most importantly, reductive dissociation to Cl − , but also some ionic reaction channels which are peculiar to the structural features of the specific VOC. Particularly interesting, among the various processes observed and studied, are ionic reactions which might play an important role in the plasma induced oxidative decomposition of VOCs in treatment applications and which involve water, either as the neutral or as the ionic reagent (H 3 O + ), and O . Positive APCI mass spectra of CCl 4 in synthetic air recorded at (a) 30 °C and Δ V = 1 V, (b) 30 °C and Δ V = 150 V and (c) 300 °C and Δ V = 150 V. magnified image Positive APCI mass spectra of CCl 4 in synthetic air recorded at (a) 30 °C and Δ V = 1 V, (b) 30 °C and Δ V = 150 V and (c) 300 °C and Δ V = 150 V.