Abstract
The removal performance of chlorinated organic compounds from porous materials under ultrasound irradiation was experimentally investigated. o-dichlorobenzene and hexane were used as the model PCB and the solvent. Wood chips were impregnated with o-dichlorobenzene at 200 Pa for 24 hours and they were used as the sample. The apparatus consisted of a water bath, a glass vessel and an ultrasonic oscillator. The o-dichlorobenzene concentration in solvent was measured by using a UV spectrometer and the removal ratio of o-dichlorobenzene was calculated. The ultrasonic intensity at the center of vessel bottom was measured by using a hydrophone. The sample size, solvent temperature, ultrasonic intensity and frequency were varied, and the removal ratio of o-dichlorobenzene from sample was measured. For a comparison, the shaking cleaning was also conducted.In the case of shaking, the removal ratio increased with time for the different-size samples. For the ultrasonic irradiation, the removal ratio rapidly increased and became almost unity after 100 minutes when the sample lengths were 5 and 10 mm. At the same length of sample, the removal rate for ultrasonic irradiation was much higher than that for shaking. The difference of removal ratio between the ultrasonic irradiation and the shaking became larger as the sample was longer. The removal ratio increased with increasing ultrasonic intensity and became constant beyond a certain ultrasonic intensity. The removal ratio depended hardly on the frequency and temperature, but was strongly controlled by the ultrasonic intensity. Under ultrasonic irradiation, o-dichlorobenzene was removed from the sample mainly by the longitudinal vibration.
