Synergistic effect of pulsed corona discharges and ozonation on decolourization of methylene blue in water
The effect of O2 and O3 bubbling on decolourization of methylene blue by pulsed corona discharges in water was studied. The pulsed corona discharges were produced by charging an 80 pF capacitor with a 40 kV DC source, through a 100 MΩ resistor, and discharging it into a needle-plate type reactor at 60 Hz through a rotating spark gap switch. A 20 ml sample of 13.25 mg l-1 methylene blue in distilled water was decolourized in 120 min. Bubbling O2 at 10 ml min-1 through the discharge region reduced the decolourization time to 25 min. Bubbling O2 containing 1500 µmol O3 l-1 at 10 ml min-1 reduced the decolourization time to 8 min. The O3 was produced by fractionating input energy between a water treatment reactor and a O3 generator, i.e. no additional energy was consumed for O3 production. Under the same experimental conditions methylene blue solution in tap water was decolourized in >210 min by corona discharge in solution, in 30 min by corona discharge with O2 bubbling, and in 11 min by corona discharge with bubbling of O2 containing 1500 µmol O3 l-1.