Removal of a synthetic organic chemical by PAC-UF systems--I: Theory and modeling

Based on the age distributions of powdered activated carbon (PAC) in reactors, the competitive bi-solute isotherm and the pore-surface diffusion mechanism, a model was developed to predict the removal of a trace synthetic organic chemical (SOC) when PAC was applied to an ultrafiltration (UF) membrane system. Independent experiments evaluated the input parameters for the model. The pore diffusion in liquid-filled pore was the dominant internal mass transfer mechanism in a PAC particle and the surface diffusion mechanism was neglected in the model. Model prediction was compared with data from pilot plant experiments treating simazine in natural water. Due to the blending and the increasing PAC in the UF loop, a transient behavior of effluent simazine concentration was observed in the UF effluent. The model predicted successfully this periodical variation of the simazine concentration in the UF loop effluent, as well as the simazine concentration in the effluent from the PAC slurry contactor. The faithful model prediction required the modeling of the phenomenon of adsorption/desorption of an SOC on membrane itself.