Ultrasonic regeneration studies on activated carbon loaded with isopropyl alcohol

Abstract

Ultrasonic regeneration of activated carbon loaded with isopropyl alcohol (IPA) was studied. IPA adsorption was performed batchwise at varying solution pH. Adsorption was optimal at solution pH 7, which was closest to the point of zero charge of the activated carbon (6.7). Ultrasonic regeneration was performed on IPA-loaded activated carbon with three factors being tested: ultrasonic intensity, solution temperature and ethanol addition. Regeneration efficiency increased with ultrasonic intensity up to 32.4 W/cm2 . A higher intensity led to a higher desorption but damaged the activated carbon, shown by a decrease in the particle size of activated carbon. The regeneration efficiency increased with solution temperature primarily because desorption is endothermic and because the surface tension and viscosity of a solution are reduced with increasing temperature, promoting cavitation bubble production. Ethanol addition increased regeneration efficiency up to 10%, as ethanol reduces tensile stress, facilitating cavitation bubble generation. At 15% and above, regeneration decreases, possibly due to coalescence of bubbles into larger, more stable bubbles. Under optimal parameters, the regeneration efficiency was 83%, which dropped to 64% after four regeneration cycles.