Sonochemical Degradation of Chlorinated Phenolic Compounds in Water: Effects of Physicochemical Properties of the Compounds on Degradation

This study examined a comparative degradation of various chlorinated phenolic compounds including phenol, 4-chlorophenol (4-CP), 2,6-dichlorophenol (2,6-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP), and pentachlorophenol (PCP) using 28, 580, and 1,000 kHz ultrasonic reactors. The concentration of hydrogen peroxide was also determined in order to investigate the efficacy of different sonochemical reactors for hydroxyl radical production. Clearly, it was observed that the 580 kHz sonochemical reactor had maximum efficacy for hydroxyl radical production. The degradation of all the compounds followed the order; 580 kHz (91–93%) > 1,000 kHz (84–86%) > 28 kHz (17–34%) with an initial concentration of 2.5 mg L−1 at a reaction time of 40 min with ultrasonic power of 200 ± 3 W and aqueous temperature of 20 ± 1°C in each experiment. Overall, the degradation of those phenolic compounds followed the order, PCP > 2,3,4,6-TeCP > 2,4,6-TCP > 2,6-DCP > 4-CP > phenol at various frequencies in the presence/absence of a radical scavenger (tert-butyl alcohol). It was revealed that the correlations between the compound degradation rates and the physicochemical parameters, R2 = 0.99 for octanol–water partition coefficient, R2 = 0.95 for water solubility, R2 = 0.94 for vapor pressure, and R2 = 0.88 for Henry’s law constant, excluding PCP, were very good in the entire range of each parameter.