Monitoring of Membrane Fouling with Zeta Potential
Zeta potential measurements elucidate the fouling behavior of membranes and contribute to the optimization of membrane performance.
Nanofiltration membranes have attracted much attention lately for their distinctive separation perfor-mance. They have nominal nano-scale pores with an estimated pore size of 0.5 - 2 nm on their active surface. Nanofiltration is used in many industrial sectors for both the removal of organic and inorganic components.
The interaction of dissolved compounds in the feed solution with the membrane surface is responsible for membrane contamination (membrane fouling). Because of this effect the filtration resistance increases and the permeate flux through the membrane decreases with time. Fouling thus causes a higher energy consumption for membrane operation, a higher cleaning frequency and a shorter lifetime of the membrane. Studies on membrane fouling help to optimize the membrane surface and to extend its usage time, thus reducing process costs.
The measurement of streaming current reveals the changes on the membrane surface by fouling during the filtration process.
Clean thin-film composite polymer membranes typically show a high negative zeta potential. The decrease in the negative zeta potential after filtration indicates the deposition of a foulant layer on the membrane surface.
The zeta potential helps to monitor fouling during filtration and to optimize the efficiency of membrane cleaning.