A new bench-top reactor employing a streamer discharge in air was developed and tested for potential use in an advanced oxidation stage in water treatment processes. The complex heterogeneous system and the ensuing chemical processes were characterized using an integrated approach to map the morphology of the plasma/gas/ liquid interface, identify the plasma short-lived excited species, determine the oxidants in solution and monitor the organic pollutants degradation. Three model pollutants were used in these experiments, rhodamine B, phenol and metolachlor. The first two are common standards used to evaluate the performance of advanced oxidation processes. Metolachlor is a widely used herbicide listed among the most important recalcitrant emerging organic pollutants. Energy efficiency, kinetics and products of our tests show a good performance of the reactor. Specifically, mineralization appears feasible also in the case of metolachlor.metolachlor, phenol, reactive oxygen species, streamer discharge, water treatment

A thermionic plasma source apparatus has been developed and characterised for high-density gaseous plasma antenna (GPA) applications. The system produces a cylindrical plasma column which is 100 mm long with a diameter of 8 mm and operates with a total plasma power consumption of 70 to 200 W, depending mainly on the DC discharge current. The plasma column electron density and temperature is measured via microwave interferometry and optical emission spectroscopy. The plasma properties are investigated for Ar, Kr and Xe at pressures from 1 to 4 mbar. The system has demonstrated higher electron densities (>1019 m−3) at low pressures (<2 mbar) than has been experimentally achieved before for GPA applications. This could allow for high gain GPA operation comparable to that of conventional metallic antennas. Additionally, the source has demonstrated operation over a wide range of electron densities, from 2 × 1018 to 1 × 1019 m−3, which can allow for frequency hopping. The plasma columns electron temperature remains around 1.5 eV for argon, largely uninfluenced by the pressure or discharge current. These plasma column measurements obtained are used to analyse the plasma properties influence on GPA performance. This analysis indicates that at high density operation, a gain is achieved which is only 22% lower than that of the conventional metallic antenna. Furthermore, the density ranges demonstrated could enable wide-range frequency hopping of over 100 MHz, with a gain greater than 1.3 dBi.

A reactor with two interchangeable plasma sources was developed and tested in water decontamination experiments using phenol as model organic pollutant. The two configurations were characterized and compared by determining the reactive species produced in the aqueous phase (concentration of ozone and of hydrogen peroxide as a function of input energy and rate of OH radical production) and the efficiency in phenol degradation. The streamer discharge performed significantly better than the dielectric barrier discharge: the rate of OH radicals production was ten times faster and the efficiency of phenol degradation, as measured by the G50 parameter, was more than twice as large. Moreover, the streamer discharge induced process was kinetically faster and achieved better mineralization yields in shorter times.