The contribution gives results of hydrogen peroxide generation obtained in the DC diaphragm discharge in water solutions. Chemical active species, such as hydroxyl radicals and hydrogen peroxide are produced by the discharge. The dependencies of hydrogen peroxide concentration on high voltage (magnitude and polarity), material of electrodes and dielectric diaphragm are studied for one electrolyte (NaCl) used for initial solution conductivity. The used dielectric diaphragms differ in material and they have various thickness.PACS: 52.80.Wq

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Paper describes results of our research on DC diaphragm discharge creation in water solutions of electrolytes from the viewpoint of its principles, properties and applications. The thermal theory of discharge ignition in bubbles of evaporated solution has been confirmed by both high speed camera and sound records. Static current-voltage characteristics revealed a significant dependence of discharge breakdown on the solution conductivity. Determined breakdown parameters lay in the range of 900-1300 V and 40-100 mA, respectively, for NaCl solution conductivity varying from 150 to 1300 µS•cm-1. Time resolved electrical characteristics showed a simultaneous appearance of current, voltage and sound oscillations as well as a light emission. Plasma diagnostics by optical emission spectroscopy confirmed formation of reactive species (hydroxyl, hydrogen and oxygen radicals) and excitation of metallic atoms presented in the solution. Moreover, rotational temperature was calculated from the obtained OH spectrum. Experiments focused on the diaphragm discharge applications are outlined in the paper. Results of hydrogen peroxide production, organic dye decomposition and treatment of humic acid solutions are compared from the viewpoint of experimental conditions.

This work is focused on optical emission spectroscopy observations of DC non-pulsed diaphragm discharge in various water solutions of sodium and potassium salts. The emission intensity dependencies of hydrogen, oxygen, and alkaline metal lines on the salt kind are studied and compared also with respect to the initial solution conductivity. The hydrogen and oxygen intensities increase more or less linearly with the increasing solution conductivity. The sodium intensity behaves identically, but the potassium intensity decreases with the conductivity increase. The hydrogen intensity is higher in the case of salts containing potassium. The dependence of the H α line intensity on the salt kind is lower than if a sodium salt is used. The oxygen emission is more or less independent on the used salt. In addition, the rotational temperature from the OH radical spectrum is calculated for the investigated electrolytes and it is in the range from 500 to 900 K, according to the initial solution conductivity. The dependence of the rotational temperature on the salt kind is not clear so far.

This paper presents results obtained from a preliminary investigation of humic acids solutions treated by the DC non-pulsed diaphragm discharge. The first attempts at the removal of humic acids from water by the diaphragm discharge were carried out in a batch discharge reactor. The UV-VIS absorption spectroscopy and the fluorescence spectroscopy were used as fast analytical methods for the determination of changes in humic acids chemical structure. From the obtained fluorescence spectra of the treated solutions, the index of humification was calculated as a ratio of the emission intensities at 470 and 400 nm. The index value points to the ratio of aromatic and aliphatic components in the humic acids mixture. The decrease of the index indicates the increasing aliphatic character of the mixture. Results obtained from the discharge treatment of humic acids solutions are compared to those obtained from experiments with organic dyes dissolved in water and their decomposition by the diaphragm discharge.PACS : 52.80.Wq

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The process of organic dye removal from various water solutions containing organic dyes and inorganic additives by the DC diaphragm discharge has been studied in so called “negative part” of this. The concentration of treated dye decreases almost exponentially to constant residual value. The final dye concentration reached approximately 20% of the initial value after 10 minutes of the treatment of the Direct Red 79 dye solution. The dye de-coloration was affected by the dye structure. The azo and diazo compounds have been degraded significantly faster to be compared to thiazine compounds. The degradation process requires an optimal adjustment of the initial solution conductivity. The optimum conductivity of approximately 600 μS⋅cm