Modeling fouling kinetics for experiments with transmission varying during filtration

Abstract

Analyzing fouling mechanisms during membrane filtration using modeling approaches is often essential to identify ways to reduce the impact of fouling. However, in some cases, fouling modeling is made difficult because the progressive formation of a deposit modifies the transmission of species across the membrane (membrane selectivity) and therefore the flux of species accumulated on the membrane (fouling kinetics). A model is developed to describe the kinetics of fouling coupled with the change in selectivity induced by fouling. The originality of this model lies in the fact that it considers that the transmission of species changes as a result of the formation of deposits, where classic models consider transmission as constant. The model is compared with filtration experiments performed using a mixture of latex particles of different diameters on microfiltration membranes in the case where some of particles are smaller than the membrane pore size. It proves capable of describing both the fouling kinetics of and the time evolution of particle transmission. In addition, the model describes the variations frequently obtained when plotting the second derivative against the first derivative of filtration kinetics. Applying the model to different membranes (same announced pore size, different materials) reveals that variations in fouling behavior can be linked to differences in their internal porous structures, which influence their capacity for in depth accumulation prior to deposit formation.