Use of atmospheric pressure plasmas for decontamination of water containing organophosphates

Abstract

Non-equilibrium atmospheric pressure plasmas (APP) are chemically active media with properties adjustable to comply with various application demands. ln biomedical field, so far APP have demonstrated excellent applicability in sterilization and cleaning, i.e. for treatment of organic materials and microorganisms. Atmospheric pressure plasma jets (APPJ) proved to be technically simple and efficient sources of cold APP which are suitable for different application setups. Recently, a new research field-plasmas in agriculture emerged, widening number of applications. Since APPJs can also operate in contact with liquids, they are suitable for new applications in plasma agriculture. Initial investigations show that chemically reactive environment produced by these sources can influence and modify physical and chemical properties of liquids. As one of the main surface water contaminants are pesticides used in agriculture our idea is to use APP for water detoxification. Namely, we conducted a study on decontamination of water samples polluted with different pesticides, i.e. organophosphate compounds, by using APPJs. We used two different jet configurations powered by a kHz signal source with He as working gas and treated liquid samples at different distances between the jet and the sample surface, for different duration times and for different liquid sample volumes. Optical and electrical characterization of the APPJs is performed in order to obtain information about the plasma properties and stability of the treatment conditions. Liquid sample analysis before and after the treatment are executed by using high performance liquid chromatography (HPLC) and liquid chromatography coupled with mass spectrometry (LC-MS) in order to follow degradation of organophosphates. Significant and efficient degradation of both pesticides is noticed and appearance of degradation products is observed in the liquid sample. Dependence of the decontamination efficiency on treatment time is determined. We also investigated toxicity of degradation products. Thus, from the data obtained we could assess the decontamination efficiency for different APPJ types and also to provide information about mechanisms governing the plasma destruction of organophosphates.