Bulk Mass Transport
This chapter examines the effects of concentration polarization. In order to evaluate the solute concentration profiles, it is necessary to solve the governing equations describing solute mass transfer in the feed (bulk) solution for the particular membrane device. The chapter examines the concentration polarization phenomenon during particle microfiltration due to the unique behavior of particulate systems. One of the critical factors determining the overall performance of any membrane device is the rate of solute or particle transport in the bulk solution adjacent to the membrane. In the osmotic pressure model, the filtrate flux is assumed to be determined entirely by the difference between the applied transmembrane pressure and the osmotic pressure difference associated with the retained solutes. The gel polarization model provides an alternative description of the filtrate flux during macrosolute ultrafiltration. The mesh spacer in the spiral wound module causes a significant increase in the mass transfer coefficient compared to that for an open-channel plate-and-frame system.