Air sparging: Prediction of air-water mass transfer coefficients
One of the difficulties with the application of air sparging as a remedial technology is that not much is known about the physical-chemical processes during air sparging. This study presents information on the air-water mass transfer of volatile organic compounds (VOCs) under air sparged conditions. The mass transfer coefficients were estimated using a single air channel experimental setup, where a thin channel of air (approx. 1.5 mm) was allowed to flow over saturated VOC-contaminated soil. The experimental setup allowed VOC concentrations in both liquid and gas phases to be measured. Eleven VOCs and three different porous media with mean particle size 0.168 mm, 0.190 mm, and 0.305 mm were used in the experiments. Air velocities ranged between 0.2 cm/s and 2.5 cm/s. Air-water mass transfer coefficients were estimated by fitting experimental data with an advection-diffusion model. The model assumed the existence of an aqueous phase influence zone (called the mass transfer zone (MTZ)) surrounding the air channel in which VOCs present were directly impacted by the air flow. The size of the influence zone was found to be a function of the physical-chemical characteristics of the porous media and the VOCs. The estimated liquid side lumped air-water mass transfer coefficients (K{sub L}a) were found to range from 2.6 x 10{sup {minus}5} to 2.4 x 10{sup {minus}4} min{sup {minus}1}. An empirical model was developed by correlating the modified Sherwood number with the air phase Peclet number. Henry's law constant, normalized particle size, and uniformity coefficient of the porous media.
- Research Organization:
- Iowa State Univ., Ames, IA (US)
- OSTI ID:
- 20014925
- Country of Publication:
- United States
- Language:
- English
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