Water permeability in polymeric membranes, Part II

Abstract

This study is a combination of experimental and theoretical works in an attempt to produce a new useful empirical model for the mass transfer in pressure-driven membrane separation processes. Following on from our previous work in Part I, this part II paper introduces three new permeability models when using aqueous solutions as feed. The Solution-Diffusion Pore-Flow Concentration-Polarization (SDPFCP) model, which is a combination between the Solution-Diffusion Pore-Flow (SDPF) model [1] and the Concentration Polarization (CP) model, is presented. The SDPFCP model examines the CP model to represent the transfer phenomena outside the membrane by merging its effect within the water permeability coefficient. A further development for this model, the SDPFCP+, is obtained by adding an additional resistance to the system in series with the membrane resistance and the CP. The second model shows fair representation of the experimental results. The Solution-Diffusion Pore-Flow Fluid-Resistance (SDPFFR) model is then proposed to provide better representation for the system. The feed solution resistance to water flux, the Fluid Resistance (FR), is suggested to replace the CP and the additional resistance. The latter model shows excellent fitting to the experimental results; it may be useful for development and design applications, when based on experimental data. Crown Copyright (C) 2010 Published by Elsevier By. All rights reserved

Inefficacy of osmotic backwash induced by sodium chloride salt solution in controlling SWRO membrane fouling

“…After deducting the feed pressure of about 70 bar, a net osmotic pressure of about 125 bar is theoretically available to induce a high osmotic backwash flow, but this did not happen in practice. The tight configuration of spiral wound membrane as well as the inherent properties of SWRO membranes could have prevented the smooth osmotic backwash flow from the permeate side to the feed side of the membrane (Qin et al 2009;Merdaw et al 2010). Moreover, the osmotic backwash flow is diffusive in nature rather than convective flow.…”

Experimental approaches to feed solution permeability in pressure-driven membrane separation processes

“…where A w is the overall water permeability for the system (the membrane permeability, for short), A wm is the membrane material permeability to water (the pure water permeability, for short), and A f is the feed solution permeability to water (the fluid permeability, for short), which is suggested to be dependent on P according to the following empirical relationship [2]:…”

“…Some of those models rely on relatively simple concepts while others are far more complex and need sophisticated mathematical techniques [1]. The mass transfer outside the membrane, normally in the feed side, is usually described by the concentration polarization model, which has been criticised by many experimental studies [2,3].…”

“…By incorporating the feed fluid resistance (FR) to the SDPF model, the final model, the solution-diffusion pore-flow fluid-resistance (SDPFFR) model, is proposed to cover the whole membrane separation system, as shown in Fig. 1 [2]. This model replaces the concentration polarization (CP) model by an empirical representation for the FR.…”

Harvesting of microalgal biomass using MF membrane: Kinetic model, CDE model and extended DLVO theory

“…Another advantage, primarily important in certain applications where temperature-sensitive substances are involved, is that membrane separation occurs essentially at ambient temperature with no phase change [2].…”