Measurement of water permeation kinetics across reverse osmosis and nanofiltration membranes: apparatus development
Katie Benko, J J. Pellegrino, Larry W. Mason, Kevin Price
An apparatus has been developed to accurately measure the unsteady permeation of pure water through permselective reverse osmosis (RO) and nanofiltration membranes under an osmotic pressure gradient. The key component of the apparatus is a capacitance-based level sensor with a flow rate resolution of 30 to 50 nL/s. The measurement protocol is an application of the familiar time-Iead analysis that assumes the membrane is presaturated with water, thus two membrane parameters could ultimately be extracted: one which relates to water mobility and another related to water solubility. This paper presents the details of the apparatus design and operation including control measurements to define the experimental uncertainties. To illustrate the technique, data is presented for a thin film composite seawater desalination membrane. These initial measurements of the water back-diffusion through a seawater RO membrane, which was exposed to varying levels of free chlorine, illustrate the utility of the apparatus for monitoring subtle changes in a membrane's material properties. In the cases presented, only a simple, steady diffusion model was used to quantify the results in terms of the permeance. Of course, "gross" damage to the membrane removes its capability of supporting the osmotic pressure gradient and this case is easily detected with this measurement technique.
diffusion, integrity test, kinetics, nanofiltration, osmotic pressure, reverse osmosis, water
, Pellegrino, J.
, Mason, L.
and Price, K.
Measurement of water permeation kinetics across reverse osmosis and nanofiltration membranes: apparatus development, Journal of Membrane Science, [online], https://doi.org/10.1016/j.memsci.2005.07.001
(Accessed December 10, 2023)