Physical properties and chemical efficiency of an underwater dc discharge generated in He, Ar, N₂and air bubbles

Abstract

A dc excited discharge generated in bubbles (He, Ar, Air, N 2 ) in liquid phase is investigated in this work. Voltage/current characteristics and emission spectra of the discharge are recorded in the current range 10-30 mA. Electron density in the discharge is measured from Stark broadening of the H β line and is of the order of 2-6 × 10 20 m −3 , depending on the feed gas. Estimation of electron temperature is carried out based on the balance of charged particles. Gas temperature is estimated by the slope of the Boltzmann plot and by the simulation of the OH band with different T 1 rot , T 2 rot and T vib . Rotation temperature in the He discharge is 1200 K at I = 10 mA and linearly increases with current up to 1600 K. In the plasma of molecular gases the temperature is higher and almost constant at different currents. Chemical efficiency of the plasma is measured by the production of H 2 O 2 and by the destruction of Direct Blue 106 dye. The highest energy consumption of H 2 O 2 generation is achieved in the air discharge and it decreases up to 50% in the He plasma. Maximal efficiency of dye destruction is observed in the N 2 plasma characterized by an energy consumption of dye decomposition of 0.86 g kWh −1 .

State-by-state emission spectra fitting for non-equilibrium plasmas: OH spectra of surface barrier discharge at argon/water interface

“…A typical example of Boltzmann plot is shown in figure 10. This result at first sight resembles similar results obtained in works of others [1,34,35]. It should be noted, that in this case the Boltzmann plot was obtained using not a single rotational line, but using all lines from the respective upper state at once, even the overlapping ones.…”

“…This facilitates the inspection of the fit and the reliability can be judged easily. + This applies to discharges in contact with liquid water [34,35] and with excessive abundance of water vapour. There are also discharges with equilibriated distribution of OH(A) rotatinal levels [19].…”

Detailed Investigation of the Electric Discharge Plasma between Copper Electrodes Immersed into Water

“…Van der Waals broadening causes a red wavelength shift which is two-third of the size of the width w VdW . In our case, we consider that discharge occurs at atmospheric pressure (or higher) in air with 1-2% of the hydrogen, similar to [30]. Therefore, value of α presents a sum of atomic polarizabilities of air components (O, N, O 2 , N 2 , NO), and it was not taken from [29], but was calculated using Equation (A8).…”

Hydrogen Peroxide Generation by DC and Pulsed Underwater Discharge in Air Bubbles

“…The plasma is formed in the pathway by AC or DC high voltage across the reservoirs. The third group is electrical discharges in gas or vapor bubbles or on the water surface (18,41,42). Different kinds of experimental setups developed for discharge in gas or vapor bubbles were summarized in a recently published *Corresponding author; E-mail: Ranhua.Xiong@UGent.be review article (9).…”