Influence of hydrogen peroxide on the simultaneous removal of Cr(VI) and methylene blue from aqueous medium under atmospheric pressure plasma jet

An efficient reduction of Cr(VI) to Cr(III) was carried out under argon plasma jet operating in aqueous medium. The effect of gas flow, pH and addition of a buffer were examined. Typical results indicated that argon plasma favored the formation of the highest amount of hydrogen peroxide that reduces Cr(VI) to Cr(III), especially under acidic medium. Quantification of hydroxyl radicals and the effect of various hydroxyl scavengers were studied. It was observed that simultaneous mitigation of Cr(VI) and methylene blue is more beneficial than removal of the individual pollutant. Methylene blue promoted the Cr(VI) reduction, whereas addition of catalytic amounts of iron(II) salt favored methylene blue oxidation via Fenton reactions. During the present study, a maximum energy yield of around 24 g/kWh was obtained at 16 kV and 50 ppm of Cr(VI) concentration