Removal of Toluene from Air Using PAC/Water Slurry Reactor

A bench‐scale, continuous, stirred‐tank reactor is used to study the removal of a volatile organic compound, toluene, from air through absorption into water and subsequent adsorption onto powdered activated carbon in the reactor. Both steady and unsteady state data are used to calibrate and test a mathematical model, which is based on gas transfer at the gas/liquid interface, diffusional resistance in the boundary layer around activated carbon particles, and diffusional resistance through activated carbon pores. The model is solved numerically using the orthogonal collocation method on finite elements. Both the steady and unsteady state data are described well with the model. The experimental and modeling results show that the removal of toluene from air is greatly enhanced by adding activated carbon to the scrubbing water. The presence of activated carbon lowers dissolved toluene concentrations and thus maintains a high driving force for toluene absorption into water. The effect of carbon pore diffusion is found to be appreciable. The value of the effective diffusivity that gives the best fit for both steady state and unsteady state data is $0.001{\mathrm{cm}}^2/\min \text{,}$ which is on the same order of magnitude with the bulk diffusivity.