Effect of Ultrasound on Bisphenol A Adsorption on the Granular Activated Carbon Myunghee Lim, Younggyu Son, Mingcan Cui, and Jeehyeong Khim  School of Civil, Environmental and Architectural Engineering, Korea University, 5 ga, Anam-dong, Seongbuk-gu, Seoul 136-701, Korea Received November 24, 2009; accepted February 12, 2010; published online July 20, 2010 The aim of this study is to investigate the effects of ultrasound (power, frequency) on bisphenol A (BPA) adsorption on granular activated carbon (GAC). The result of adsorption isotherm in a BPA solution, using sonicated GAC (at 35 kHz) can more successfully adsorb BPA than sonicated GAC (at 300 kHz) and the original GAC. At low frequency GAC has a high cavitation effect. Therefore, the amount of adsorbed BPA at a low frequency was higher than at a high frequency. In isotherm experiments, ultrasound can enhance the adsorption process in GAC in both frequencies (35 and 300 kHz). These results agree with other previous researches. The effect of power intensity in the adsorption of BPA is increased the adsorption of BPA with increasing power. The optimum power exists and differs from frequencies because the cavitation effect is not the same with different frequencies. # 2010 The Japan Society of Applied Physics DOI: 10.1143/JJAP.49.07HE10 G ranular activated carbon (GAC) is one of the most effective adsorbents for organic compounds be- cause of its extended surface area, high adsorption capacity, micro porous structure and special surface reac- tivity. 1) Ultrasound has proven to be a very useful tool in intensifying the mass transfer process in the heterogeneous phase (soil, slurry, sludge). 2,3) The physical effects of ultrasound were explained by the cavitation event. The cavitation bubble was produced, and then expanded and collapsed. The implosion is asymmetric, producing a liquid jet at the surface of solids that can move up to 400 km/h. 2) Recently, the adsorption process with a combination of adsorbents (GAC, clay) and ultrasound has been investigated in many studies. These studies were conducted for pow- er, 1,2,4,5,9) temperature, 1,2,5,6,8) GAC particle size, 4) types of adsorbents, 6–9) frequency, 5) and pH. 6) However, previous results were not consistent with the effect of ultrasound on adsorption characteristics. The objective of the present work was to investigate the adsorption characteristics of bisphenol A (BPA) in an aqueous solution GAC in the absence/presence of ultra- sound for different ultrasonic powers and frequencies. Prior to use, the GAC was washed several times with deionized water at room temperature. These carbons were then dried overnight in an oven at 110  C. Used GAC was Filtrasorb 300 (Calgon Carbon), and its effective size was 0.8 –1.0 mm. The adsorption of the BPA solution in GAC was studied for an initial concentration of 10 mg/L. The amount of GAC was 1 g/L in an ultrasonic reactor. A constant temperature was maintained during adsorption experiments (120 min) by use of a cooling water system. Figure 1 shows the reactor scheme. The mixing rate was 300 rpm. For the isotherm experiments of the BPA solution, the original GAC, sonicated GAC 1 (35 kHz, 2 h), and sonicated GAC 2 (300 kHz, 2 h) were studied. Three adsorbents were placed in six different amounts (0.1, 0.2, 0.4, 0.8, 1, 3 g/L) in a 1 L flask with BPA solutions of 10 mg/L concentration. Fourty-eight hours was a sufficient time to allow for equilibrium. The suspension was then filtered with a syringe filter (0.45 mm, Whattman). The BPA concentration was analyzed by high performance liquid chromatography (HPLC; Dionex Ultimates 3000). 35, 300 kHz ultrasound was emitted from a cup-horn type transducer (Mirae Ultrasonic Tech.) which consisted of a single piezoelectric transducer (PZT; Tamura). The diameter of each transducer is 10 cm. The input powers were 20, 40, and 60 W. The delivered power in the reactor was measured by a power meter (METEX M-4660M) that indicated the power consumption of the ultrasonic controller. The values were 28.5, 55.8, and 62.3 W at 35 kHz and 27.6, 54.7, and 66 W at 300 kHz. Equilibrium isotherms were conducted for 48 h using three types of GAC (original, sonicated 35 and 300 kHz). The reason why three different types of GAC were chosen in our study was because the surface characteristics differed with various ultrasonic frequencies. Other investigations only conducted adsorption isotherms using different ultra- sonic powers, 1,10) temperatures, 2) and various activated carbons. 6–8) The physical effect of ultrasound differs from frequency. Therefore, we use two different types of GAC that were sonicated at 35 and 300 kHz for 2 h. The dosages of GAC were 0.1, 0.2, 0.4, 0.8, 1, and 3 g/L. The result of the Freundlich isotherm in the BPA solution is shown in Fig. 2. 11) BPA in solution was delivered more rapidly to the surface of GAC at a low frequency (35 kHz) than at a high frequency (300 kHz). A low frequency has a higher cavitation effect than a high frequency; therefore, adsorption results show that a low ultrasonic frequency can enhance the equilibrium arrival rate compared to a high frequency. For more than 1 g/L of AC, the amount adsorbed was almost the same. Therefore, 1 g/L of GAC was used in the adsorption tests. Figures 3 and 4 show the adsorption results of BPA solution in GAC at 35 and 300 kHz respectively. The concentration of BPA was the remained one in solution. Fig. 1. (Color online) Schematic diagram of sonoreactor: (1) ultrasonic controller, (2) mixing system, (3) cup-horn type transducer, (4) cooling water system.  E-mail address: hyeong@korea.ac.kr Japanese Journal of Applied Physics 49 (2010) 07HE10 BRIEF NOTE 07HE10-1 # 2010 The Japan Society of Applied Physics