Degradation of methylene blue through atmospheric pressure glow discharge plasma treatment

Abstract The degradation of Methylene Blue (MB) dye through treatment with an atmospheric pressure glow discharge plasma is presented in this work. The set-up used in this work has the advantage of being very simple without any gas supply. Plasma was diagnosed using optical emission spectroscopy, and rotational temperature of the hydroxyl radicals was measured. The effects of plasma current, treatment time, polarity and material of the electrodes on degradation of MB dye were studied. Experimental results showed that the degradation of dye increased with plasma current and treatment time. Polarity of the electrodes also have an effect in that the liquid cathode mode has about 14% higher degradation efficiency than liquid anode mode. Interestingly, it was found that anodic dissolution of copper electrode aids in degradation of MB dye by initiating Fenton like reactions involving copper ions, which was absent in the case of stainless steel electrode. After 40 min of treatment, the maximum degradation efficiency and COD removal rate achieved was 77% and 74% respectively, while the degradation yield obtained was 0.32 g.kW –1 .h –1 .