Measurement of Ozone Concentration in Atmospheric Pressure Air Barrier Discharge by Optical Absorption Spectroscopy

As a strong oxidant and bactericide, oxygen has great potentials in various applications, such as pollutant degradation, food processing, sterilization, and medical services. Atmospheric pressure dielectric barrier discharge (DBD) is an extremely efficient method of generating ozone. DBD is generated in atmospheric pressure air between two parallel-plate electrodes excited by alternating current voltage. Waveforms of applied voltage and light emission are measured by optical and electrical methods. It can be found that the light emission presents lots of narrow pulses, which distribute stochastically in every half cycle of applied voltage. These narrow pulses only sustain about several tens ns to several hundred ns, which indicates that barrier discharge in atmospheric pressure air belongs to a streamer regime. Based on 200 and 900 nm scanned optical spectrum emitted from the discharge, the emissions mainly include those from the second positive system of the nitrogen molecule (C-3 Pi-B-3 Pi) the first negative system of the nitrogen molecular ion (B-2 Sigma-X-2 Sigma) , the first positive system of the nitrogen molecule (B-3 Pi-A(3)Pi) , and oxygen atomic (OI : 715. 7 nm, 799. 5 nm). Moreover, no emission line is observed between 200 nm and 300 nm (ultraviolet (UV) region). Due to a strong absorption peak in this UV region, absorption spectrum in UV region between 230 and 300 nm can be used to obtain the ozone density. In doing so, UV lamp irradiates the plasma area from one side of the discharge region, and transmitted light is received by the spectrometer on the other side. Absorption spectra are measured when DBD is on and off. Absorption spectroscopy can effectively monitor the change of ozone concentration. Its advantages are simple operation, low requirements on the experimental environment, being able to be used under discharge conditions, and continuous monitoring of ozone concentration changes. Ozone concentration is calculated as a function of peak voltage and driving frequency based on Beer-Lambert' s law. It is found that ozone concentration increases with increasing peak voltage or driving frequency. These results are of great significance to industrial application of dielectric barrier discharge at atmospheric pressure.