Comparative study on the degradation of phenol by a high-voltage pulsed discharge above a liquid surface and under a liquid surface

The degradation of phenol by pulsed discharge plasma above a liquid surface (APDP) and under a liquid surface (UPDP) was compared. The effects of discharge voltage, discharge distance, initial solution conductivity and initial pH on the removal of phenol were studied. It was concluded that the removal of phenol increases with increasing discharge voltage and with decreasing discharge distance in both APDP and UPDP systems. An increase in the initial solution's conductivity has a positive effect in the APDP system but a negative effect in the UPDP system. In addition, alkaline conditions are conducive to the degradation of phenol in the APDP system, while acidic conditions are conducive in the UPDP system. Free radical quenching experiments revealed that ·O₂^- has an important influence on the degradation of phenol in the APDP system, while ·OH plays a key role in the UPDP system. This paper verifies the differences in the two discharge methods in terms of phenol removal.