Use of capacitive microsensors for concentration polarization characterization in pressure-driven crossflow membrane filtration

In membrane separation processes, the presence of the concentration polarization boundary layer (CPBL) can lead to a decline in the flux and an increased risk of membrane fouling. This paper describes the development of capacitive microsensors for real-time in-situ monitoring of CPBL growth in a nanofiltration membrane module using CaSO₄ solution as the feed. The sensors respond to changes in solute concentration as a function of distance from the membrane surface. Detection capability was determined in a series of comprehensive experiments with systematic changes in feed concentration and module operating parameters. The specially designed microcapacitor assembly provides a unique capability for real-time characterization of the transient and steady state concentration polarization behavior.