EFFECT OF BUBBLE HYDRODYNAMIC AND LIQUID PHASE ON MASS TRANSFER MECHANISM IN BUBBLE COLUMN.

Abstract

The absorption mechanism of aeration and hydrophobic Volatile Organic Compounds (benzene) was investigated in a bubble column. The diffusers used in this study were rigid and flexible orifices. Tap water, and aqueous solution of commercial surfactants: cationic (DTAB), anionic (SES) and non-ionic (Dehydol LS 5 TH and Tween 80) were used as absorbents in this experiment. Moreover, the range of surfactant concentrations for aeration and benzene are 0.01, 0.1 CMC, and 0.1, 1, 3 CMC, respectively. Those were analyzed with the superficial gas velocity applied. The bubble hydrodynamic parameters were determined by using a high speed camera (340 frames/sec) and an image analysis program. The results showed the rigid orifice provides the highest mass transfer rate due to the small bubble size generated and thus the increase of interfacial area (a). The values of interfacial area and volumetric mass transfer coefficients (kLa) increased roughly linearly with the superficial gas velocity. Moreover, the kL coefficients obtained with surfactant solutions were less than those obtained with tap water: these results compensates with the increase of interfacial area. Furthermore, the parameters such as the type of surfactants, molecular weight, CMC, and surface tension were proven for significantly altering mass transfer and bubble hydrodynamic parameters in this research. Due to the application and improvement of benzene absorption in bubble column, the granular activated carbon (GAC) was filled into a bubble column reactor. It can be noted that the addition of (GAC) into the reactor with tap water can provide the highest benzene removal efficiency (up to 74.45%) compared with the non-ionic surfactant as absorbent. Moreover, the presence of non-ionic surfactant molecules can cause the negative effect onto the GAC adsorption capacity due to their attachment mechanism. Finally, it has been suggested that rigid diffuser applied with the superficial gas velocity at 0.0032 m.s-1, and water combined with granular activated carbon are the optimal design and operation for hydrophobic VOCs absorption in the bubble column used in this study.