Sonochemical Degradation of Aqueous Phenol in a 35 kHz Sonoreactor

Abstract

The sonochemical degradation of phenol at 35 kHz frequency was investigated. The results showed that an increase in the initial phenol concentration reduced the degradation rate, but the pH did not seem to have a strong effect on the reaction. The addition of salt, NaCl, was able to accelerate the rate of phenol decomposition. However, the extent of the effect differed with respect to the initial salt concentrations. With 50 mg/L of phenol, the rates of decomposition were 1.08 and 1.23 times higher on the addition of 0.5 and 1 M NaCl, while those for 200 mg/L were 1.86 and 2.16 times, respectively. In the presence of SDS (sodium dodecyl sulfate), the degradation dropped with increases amount of surfactant. At the cmc (critical micelle concentration), the amount of phenol remained unchanged after 5 hour of sonication. However, when SDS was introduced at concentrations where the cmc was exceeded, the degradation increased slightly. Phenol degradation was depressed on the addition of CO32-, because CO32- is a radical scavenger in bulk solution. When the ratio of CO32- to phenol was increased from 10: 1 (mol CO32- : mol phenol) to 100: 1, the degradation rate reached the value that under the control conditions (without CO32-). In the present of 15 mol tert-butanol: 1 mol phenol, the amount of phenol remained unchanged after 5 h of sonication.