Post-discharge DBD plasma treatment for degradation of organic dye in water: A comparison with different plasma operation methods

Dielectric barrier discharge (DBD) plasma reactor is an innovative advanced oxidation technology for degradation of organic dye in water. In this study, the crystal violet (CV) solution was exposed to a post-discharge DBD plasma in which O-2 was used as the feed gas. In this mode, the liquid target is isolated from the plasma medium and the plasma effluent gas is bubbled across the liquid target to increase mass transfer between reactive species and the solution. The influence of operating parameters including applied power and gas flow rate was studied. It was shown that increasing reactor temperature resulted in the reduction of CV removal. Dilution of the plasma forming gas (pure O-2) with Ar enhanced the CV removal up to 44%. The kinetic model of CV bleaching was shown to follow a first-order reaction. In the most suitable experimental condition after one minute treatment, the CV decolorization of 100% was achieved, and the total organic carbon (TOC) dropped to zero. Preliminary investigation into the byproducts through UV-VIS, TOC and GC-MS were done which showed the disappearance of the aromatic rings. This work also outlines current operation methods for plasma treatment of organic dyes in water and compares their performance in terms of energy efficiency, degradation rate constant and formation of main reactive species. The interesting results of post discharge treatment which can be compared quite favorably with those achieved by other operation methods, are the degradation rate constant of 4.37 (1/min) and energy efficiency of 12.2 (g/kWh).