Monitoring of nonthermal plasma degradation of phthalates by ion mobility spectrometry

Abstract

Ion mobility spectrometry was used to monitor the degradation of phthalate vapors by corona discharge. Three different phthalates (dimethyl [DMP], diethyl [DEP], and dipropyl [DPP]) were examined in a corona discharge reactor (wire-to-cylinder geometry) at direct current positive polarity in ambient air. The relative removal efficiencies up to 96% and energetical degradation efficiencies of 229.27, 216.12, and 198.84 kJ mg−1 were achieved for DMP, DEP, and DPP, respectively. Byproducts such as methanol, ethanol, and 1- and 2-propanol at extremely low densities were also detected. The identified degradation processes involved two steps: (i) An electron-impact dissociation of phthalates into alkoxyl radicals and (ii) reactions of alkoxy radicals with water molecules to form alcohols.