The scheme of the reactor is shown in Fig. 1. The reactor chamber is a cylindrical vessel with a diameter of 100 mm and height of 150 mm. The DC discharge system consists of a high voltage power supply connected through a ballast resistor to the reactor chamber. The power supply can provide a voltage of 15 kV and current at the range of 0-100 mA. The polarity of the HV electrode is positive through all the experiments. A cone-shaped stainless steel metal electrode with a top angle of approximately 40° and a rounded, polished tip is attached to a micrometer screw above the liquid reservoir. The distance between the electrode and the water surface can be adjusted with the micrometer screw with a precision of 0.1 mm. In all experiments, this distance is fixed to 10 mm and treatment is carried out for 2 hours. The glow discharge degradation of AB25 is studied in the reactor for a constant solution volume of 500 mL, while stirring the liquid medium in order to achieve a uniform treatment of the whole volume. The efficiency of the discharge has been examined by measuring the decolorization of the dye solution with a
UV/VIS spectrophotometer UV mini-1240 “SHIMADZU”, (SBN –SPEC-91). The concentration of the dye was determined from the measured UV–VIS spectrum, using the maximum of AB25 absorption at 602 nm.