AROMATIC COMPOUND DEGRADATION IN WATER USING A COMBINATION OF SONOLYSIS AND OZONOLYSIS

The combination of sonolysis and ozonolysis as an advanced oxidation p rocess was investigated to gain insight into factors affecting enhance ment of the combined system. Sonolysis, ozonolysis, and a combination of the two were used to facilitate the degradation of three known orga nic contaminants, nitrobenzene (NB), 4-nitrophenol (4-NP), and C-chlor ophenol (4-CP), in water. Experiments were performed at frequencies of 20 and 500 kHz. At 20 kHz, there appeared to be an enhancement due to sonolytic ozonation, while at 500 kHz, an apparent retardation was se en. The catalytic effects of NB, 4-NP, and 4-CP degradation at 20 kHz increased with decreasing k(O3), of the compounds, whereas retardation at 500 kHz was correlated with increasing k(O3). The correlation of a ppa rent rate enhancement at 20 kHz and retardation at 500 kHz with k (O3) is consistent with a pathway involving the thermolytic destructio n of ozone to form atomic oxygen. Atomic oxygen then reacts with water vapor in cavitation bubbles, yielding gasphase hydroxyl radical. Enha ncement in loss of total organic carbon (TOC) by sonolytic ozonation w as considerable at both 20 and 500 kHz with all three compounds. In ad dition, intermediate product formation was observed.