Abstract
The present work reports an investigation for examining the use of low-frequency ultrasound (20 kHz) as an inventive technique for the regeneration of granular activated carbon (GAC) saturated by 4-chlorophenol (4-CP) in batch-loop reactor. The effects of experimental conditions such as the amount of adsorbent (0.05-0.4 g), intensity of ultrasound irradiation (20-35%), temperature (25-55 degrees C), flow rate (3-30 mL/min) and total volume of regenerating solution (200-300 mL), NaOH (0.01-0.1 N), ethyl alcohol (10-60%) and mixture of NaOH, and ethanol on the regeneration process were examined. The obtained results show that the amount of 4-CP desorption decreased with increasing the amount of adsorbent and intensity of ultrasonic irradiation. The desorption gradually increased with the increase in temperature and flow rate and total volume of regenerating solution. Using NaOH or/and ethyl alcohol as regenerating solutions causes an improvement in the desorption of 4-CP from GAC. The regeneration of spent GAC by ultrasonic irradiation is due to the generation of physical and thermal effects of ultrasound. It can be concluded that desorption by ultrasound can be an alternative technique to classical methods used for the regeneration of exhausted GAC.