Plasma-catalytic degradation of anthraquinonic dye in aqueous solution by gliding arc discharge

Anthraquinonic Acid Green 25 (AG25) removal was investigated by plasma-chemistry using non-thermal gliding arc at atmospheric pressure. The gaseous species formed in the discharge, and especially OH degrees radicals, induce strong oxidizing effects in the target solution. The removal of the dye was carried out in the absence and presence of TiO2 as photocatalyst. The decolourization of AG25 was followed by UV-Vis spectrometry (at 643 nm), while the degradation was followed by COD measurements. The effects of operating variables such as initial concentration of AG25 and catalyst concentration were investigated. Experiments were carried out to optimise the amount of TiO2. The results showed that maximum degradation was attained for 2 g.L-1 TiO2 concentration. At this optimum concentration, the dye (80 mu M) was totally decolourized within 15min of plasma-treatment time, and 93% removal of initial COD was attained after a 180min plasma-treatment time. In the absence of catalyst, colour removal was 46% after 15min, while COD abatement reached 84% after 180min. The extent of degradation decreased. with initial concentration and the time required for complete degradation 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 TiO2 mediated plasma-chemical process showed potential application for the treatment of dye solutions, resulting in the mineralization of the dye confirmed by sulphate ion formation.