Adsorption characteristics of used granular activated carbon regenerated by ultrasonic backwashing

Activated carbon is used in water-treatment processes owing to its strong adsorption capacity. Ultrasonic-backwash regeneration of particulate activated carbon in an ozone activated carbon filter was investigated with sodium benzoate as the model pollutant, and the effects of regeneration parameters (ultrasonic frequency, power, regeneration time, and backwashing intensity) on the regeneration efficiency of the activated carbon were studied. The regenerated carbon was characterized by BET, SEM, XPS, and strength, and compared with used activated carbon. The ideal regeneration parameters were determined to be 120 kHz ultrasonic frequency, 360 W ultrasonic power, 1 L/min backwashing intensity, and 10 min regeneration time. The results showed that ultrasonic treatment changes part of the pore structure of the activated carbon; that the high-speed microjets generated by cavitation as well as the high-pressure microbubbles play important roles in the regeneration of the activated carbon; and that backwashing facilitates a range of ultrasonic action on the activated carbon, positively affecting the regeneration process.