Evaluation of a microfluidic atmospheric-pressure plasma reactor for water treatment

Patinglag, Laila, Sawtell, David, Iles, A, Melling, Louise, Whitehead, Kathryn and Shaw, Kirsty (2018) Evaluation of a microfluidic atmospheric-pressure plasma reactor for water treatment. In: International Symposium on Non-Thermal/Thermal Plasma Pollution Control Technology and Sustainable Energy (ISNTP-11), 01 July 2018 - 05 July 2018, Padova, Italy.

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Abstract

A dielectric barrier discharge (DBD) microfluidic plasma reactor, operated at atmospheric pressure, was studied for its potential to treat organic contaminants in water. The proposed microfluidic plasma reactor (MPR) allows in situ production of plasma in a continuous flow, operated under atmospheric pressure, for plasma-based water treatment. The MPR operates with glass as the dielectric barrier, where plasma is generated in the continuous gas flow stream of a gas-liquid two-phase annular flow regime in the microchannels. The microchannels have dimensions of 100 µm depth, 250 µm width and the plasma is generated in an approximately 21 cm length of microchannel arranged in a serpentine pattern. Methylene blue (MB) in solution was used as a model organic to investigate its degradation by plasma generated in the microchannels. The influence of discharge time, residence time and gas sources, i.e. air, argon and oxygen, on MB degradation was studied. The percentage degradation increased with lower liquid flow rates, with maximum degradation of MB achieved at a liquid flow rate of 35 µL/min and inlet gas pressure of 1 bar using oxygen as the working gas. Liquid chromatography/mass spectrometry analysis of the MB solution after treatment suggests degradation through fragmentation of MB. It is intended that the device will be used as proof of concept to introduce plasma technology as an advanced oxidation process for water treatment, with the potential to achieve total mineralization of dissolved organic materials and microbial inactivation, replacing water treatment chemicals and consumables.