Degradation of AB25 dye in liquid medium by atmospheric pressure non-thermal plasma and plasma combination with photocatalyst TiO2

In this work, degradation of the anthraquinonic dye Acid Blue 25 by non-thermal plasma at atmospheric pressure with and without photocatalyst is investigated. Titanium dioxide (TiO2) is used as a photocatalyst. The dye degradation by plasma in the presence of TiO2 is investigated as a function of TiO2 concentration, dye concentration and pH. The degradation rate is higher in acidic solutions with pH of 2 to 4.3, especially at pH 2, and decreases to 0.38 mg L-1 min(-1) with the increase of pH from 2 to 5.65. A similar effect is observed in basic media, where a higher degradation rate is found at pH = 10.3. The degradation rate increases in the presence of TiO2 compared to the discharge without photocatalysis. The results show that the degradation of the dye increases in the presence of TiO2 until the catalyst load reaches 0.5 g L-1 after which the suppression of AB25 degradation is observed. The results indicate that the tested advanced oxidation processes are very effective for the degradation of AB25 in aqueous solutions

Variation in guided streamer propagation along a DBD plasma jet by tailoring the applied voltage waveform

Experimental data on the evolution of a helium atmospheric pressure plasma jet driven by two different voltage waveforms are presented. The characteristics of directed ionization waves (guided streamers) were compared for a sinusoidal voltage waveform with a frequency of 52 kHz and a voltage waveform that was formed via the superposition of 41.6 kHz bipolar square pulses and 300 kHz oscillations. With the sinusoidal voltage, two consecutive ionization waves were observed. With a special tailoring voltage, control of the guided streamer propagation in a stepwise mode was achieved. The observed second streamer and the second step of propagation could be regarded as a secondary ionization wave for both voltages. A change in the voltage waveform led to significant variations in the secondary ionization wave formation and streamer parameters. The voltage waveform enabled the number of ionization waves and their propagation to change, which provided the possibility of controlling the plasma parameters of the jet