Submitted to: Desalination
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2008
Publication Date: 10/15/2009
Citation: Liu, S.X., Kim, J. 2009. Study of Asorption Kinetics of Surfactants onto Polyethersulfone Membrane Surface Using QCM-D. Desalination. 247(1):355-361.
Interpretive Summary: The membrane fouling problem (reduction of filtered volume over time) in processes of protein concentration and fractionation is often dealt with using periodic backwashing steps with soapy water that contains surfactant molecules; these cleaning procedures are set up based on the vendors’ recommendations. These recommendations are appropriate for new membranes with a particular model colloid that a vendor uses, which is quite different from any type of food protein. These procedures tend to become inadequate over time as the membranes get old and worn and covered with some stubborn surfactant molecules that survive repeated washing. Over time surfactants accumulated will foul the membrane surface by permanently attaching themselves in large quantity to the membrane surface and the walls of the inner pores of the membrane. The study described in this paper probes membrane fouling problem by surfactants with a new approach. We have been able to use Quartz Crystal Microbalance with Dissipation (QCM-D) instrument to establish parameters of adsorption of surfactants on the membrane surface and the viscoelastic properties of the adsorbed layer on the membrane, which has important implication on the extent of blockage caused by the adsorbed surfactant layer on the membrane surface and in the pores. The information from this study helped us to set up recommendations of optimal washing and other maintenance procedures of membranes, ensuring optimal membrane performance for separating food proteins in food and pharmaceutical industries.
Technical Abstract: The adsorption kinetics of surfactants onto the crystal surface spin-coated with a thin layer of a model membrane material, polyethersulfone was monitored through measurements of frequency and dissipation shifts simultaneously using a quartz crystal microbalance with dissipation (QCM-D) device. In this study, the viscoelastic behaviors of the adsorbed surfactant layers of sodium laureth sulfate, cocamidopropyl betaine and their mixed solution (1:1) expressed through the dissipation parameters from the QCM-D measurements were used to deduce the structures of the adsorbed layers of the surfactants as a combinative result of characteristics of the surfactant and the hydrophobicity of the membrane surface.