Electrochemical Production of 70 wt ppm Ozone Water

The effects of water flow rate and current density on the ozone concentration in anode water were investigated using a new electrochemical ozone production (EOP) system. The absorption coefficient of O3 at 290 nm in water was found to be 720 L mol−1cm−1, about twice as large as that in the gas phase, 374 L mol−1 cm−1. The O3 concentration increased with increasing current density and decreasing anode water flow rate. The highest O3 concentration of 70 wt ppm was observed when the water flow rate was 100 mL/min, the current density was 2.13 A/cm2, and the cell pressure was 0.2 MPa. This concentration is the highest reported for a once-through EOP system. As the anode water flow rate decreased, the current efficiency of O3 production also decreased owing to the formation of O3 and O2 gases, which reduce the catalytically active area of the Pt anode. The high current efficiency of 29.1% at a water flow rate of 820 mL/min decreased to as low as 6.7% at 92 mL/min. The results of pressure dependence measurements of the current efficiency of O3 production and the O3 concentration in anode water suggest that high-pressure operation has a slightly positive effect on them.