Air sparging: Air-water mass transfer coefficients

Experiments investigating the mass transfer of several dissolved volatile o rganic compounds (VOCs) across the air-water interface were conducted using a single-air-channel air-sparging system. Three different porous media wer e used in the study. Air velocities ranged from 0.2 cm s(-1) to 2.5 cm s(-1 ). The tortuosity factor for each porous medium and the air-water mass tran sfer coefficients were estimated by fitting experimental data to a one-dime nsional diffusion model. The estimated mass transfer coefficients K-G range d from 1.79 x 10(-3) cm min(-1) to 3.85 x 10(-2) cm min(-1). The estimated lumped gas phase mass transfer coefficients K(G)a were found to be directly related to the air diffusivity of the vee, air velocity, and particle size , and inversely related to the Henry's law constant of the VOCs. Of the fou r parameters investigated, the parameter that controlled or had a dominant effect on the lumped gas phase mass transfer coefficient was the air diffus ivity of the VOC. Two empirical models were developed by correlating the Da mkohler and the modified air phase Sherwood numbers with the air phase Pecl et number, Henry's law constant, and the reduced mean particle size of poro us media. The correlation developed in this study may be used to obtain bet ter predictions of mass transfer Auras for field conditions.