Degradation of Acid Orange 7 Solution by Air-liquid Gliding Arc Discharge in Combination with TiO2 Catalyst

The degradaiton of Acid Orange 7 (AO7) using the plasma-catalytic process, has been stdudied by non-thermal gliding arc technique coupled to P25 titanium dioxide (TiO2). Eperiments were carried out to optimise the amount of photo-catalyst. The results showed that maximum decolorization and degradation were attained 0.5 g l(-1) TiO2 concentration. At this optimum concentration, the dye (180 mu M) was totally decolorized within 75 min plasma/TiO2 treatment, and 92.5% removal of initial chemical oxygen demand (COD) was attained after a 125 min plasma/TiO2 treatment. The extent of degradation decreased with initial concentration and the absolute removal amount increased. In all cases, the plasma-treated samples in the presence or absence of catalyst were found to follow pseudo first-order reaction kinetics. The main intermediates of AO7 degradation were benzenesulfonic acid, hydroquinone, 1,4-benzoquinone, 1,2-naphthoquinone, ring cleavage products (oxalic acid, acetic acid, malonic acid and others). Furthermore, possible pathways of AO7 degradation in solution were proposed.