Novel combination of high voltage nanopulses and in-soil generated plasma micro-discharges applied for the highly efficient degradation of trifluralin

Cold plasma is considered a highly competitive advanced oxidation process for the removal of organic pollutants from soil. Herein, we describe for the first time the combination of in-soil generated plasma micro-discharges with the advantageous high voltage nanosecond pulses (NSP) towards the high-efficient degradation of trifluralin in soil. We performed a detailed parametric analysis (pulse frequency, pulse voltage, soil thickness, soil type, energy efficiency) to determine the optimum operational conditions. High trifluralin degradation was achieved even at the higher soil thickness, indicating that the production of plasma discharges directly inside the soil pores enhanced the mass transfer of plasma reactive oxygen and nitrogen species (RONS) in soil. The energy efficiency achieved was outstanding, being up to 2-3 orders of magnitude higher than those reported for other plasma systems. We identified the intermediate degradants and proposed the most dominant degradation pathways whereas a thorough exhaust gases analysis, optical emission spectroscopy (OES) and active species inhibition by using trapping agents revealed the main RONS involved. This effort constitutes a significant advancement in the "green" credentials and application of plasma-induced degradation of pollutants as it describes for the first time the removal of the highly harmful and toxic pesticide trifluralin from soil and provides a novel perspective towards the future development of cold plasma-based soil remediation technologies.