Gliding arc plasma assisted photocatalytic degradation of anthraquinonic acid green 25 in solution with TiO2

Abstract

Anthraquinonic acid green 25 (AG 25) removal was investigated by plasmachemistry using non-thermal gliding arc at atmospheric pressure.The gaseous species formed in the discharge, and especially OH radicals, induce strong oxidizing effects in the target solution. The removal of thedye was carried out in the absence and presence of TiO2as photocatalyst. The decolourization of AG 25 was followed by UV–vis spectrometry (at643 nm), while the degradation was followed by COD measurements. The effects of operating variables such as initial concentration of AG 25 andcatalyst concentration were investigated. Experiments were carried out to optimise the amount of TiO2. The results showed that maximumdegradation was attained for 2 g L 1TiO2concentration. At this optimum concentration, the dye (80mM) was totally decolourized within 15 minof plasma-treatment time, and 93% removal of initial COD was attained after a 180-min plasma-treatment time. In the absence of catalyst, colourremoval was 46% after 15 min, while COD abatement reached 84% after 180 min. The extent of degradation decreased with initial concentrationand the time required for complete degradation increased. In all cases, the plasma-treated samples in the presence or absence of catalyst were foundto follow pseudo-first order reaction kinetics. The TiO2-mediated plasmachemical process showed potential application for the treatment of dyesolutions, resulting in the mineralization of the dye confirmed by sulfate ion formation.#2006 Elsevier B.V. All rights reserved.