Decolorization of azodyes using the atmospheric pressure plasma jet*

Atmospheric pressure plasma jet operated in air/argon mixture is tested for decolorization of Bezactiv Orange V-3R dye used in the textile industry. The decolorization efficiency is determined by spectrophotometric measurements at 493.7 nm which corresponds to the breaking of dye N$=$N bond. The initial concentration of 50~mg/L of dye is reduced 50 times after 120 minutes of treatment by plasma. The results are compared to the efficiency of the suspended TiO$_{2}$ powder and activated by an UV lamp (300~W). The radicals responsible for removal of the dye are OH and super-anion radical. It is found that efficiency of the plasma and TiO$_{2}+$ UV is quite similar for the treatment times up to 60 min. After that, TiO$_{2}$ shows higher decolorization rates (100 times reduction after 90 min). However, when plasma and TiO$_{2}$ (but without the UV lamp) are applied together, it is found that there are synergetic effects and that the efficiency is increased. Plasma (less than 2 W) is not expected to produce high amounts of UV light in the atmospheric pressure.