Degradation of organic dye using plasma discharge: optimization, pH and energy

Decolorization of Acid Orange 142 (AO142) as important water pollutant was observed on the exposure of the dye solutions to an atmospheric non-thermal gas plasma. A response surface methodology (RSM) combined with a central composite design (CCD) was utilized to optimize the main factors (variables) affecting the degradation efficiency (response) of AO142, such as the applied voltage, the gap distance between the high voltage electrode and the surface of the solution. The regression analysis showed that a first-order polynomial model well fits the experimental data with a coefficient of determination R2 = 0.96. FT-IR, UV-vis, TOC and GC-MS measurements were used to investigate the decolorization of the dye on exposure to the plasma discharges. A possible degradation pathway was postulated. Additionally, the conductivity and pH changes during the treatment were also evaluated. The plasma treatment combined with Fe2+ (plasma Fenton reaction) exhibited a higher degradation efficiency, higher energy yield connected with lower energy consumption in comparison to the plasma treatment without Fe2+ addition.