An experimental study on the effect of spacer on concentration polarization in a long channel reverse osmosis membrane cell

Abstract

This study was to experimentally investigate the performance and organic fouling behaviour in a 1-m long RO membrane channel with or without spacer for desalting. It was found that local permeate flux distributed heterogeneously along the long membrane channel without a spacer inserted due to exponential growth of concentration polarization, which also resulted in decreasing salt rejection and increasing organic fouling along the membrane channel in the downstream direction. This heterogeneity could be lessened by inserting a spacer into the channel, which mitigated concentration polarization due to the enhanced turbulence caused by a spacer, especially at the downstream portion of the channel. However, in the upstream of the channel, inserting a spacer exerted an additional vertical resistance which might counteract the effect of concentration polarization mitigation by a spacer and caused a lower permeate flux. This suggests that it is necessary to consider the integral effect of spacer for designing an RO membrane module and an overall RO system in order to prevent extra resistance, reduce concentration polarization and membrane fouling.

Membrane Processes

“…NaOH-SDS) followed by an acid was the most effective combination for flux recovery; cleaning solely with an acid was the least effective. Mo and Ng (2010) investigated the effect of a feed spacer on concentration polarization and organic fouling using a narrow, 1 meter long membrane cell with the ability to measure local permeate fluxes (10 locations) along the length of the membrane. It was discovered that the flow did not distribute evenly along the membrane in the absence of the spacer, this resulted in exponential growth of concentration polarization as well as decreasing salt rejection and increasing organic fouling along the membrane channel; insertion of the spacer mitigated these effects.…”

Construction and validation of a long-channel membrane test cell for representative monitoring of performance and characterization of fouling over the length of spiral-wound membrane modules

“…In the feed channel of membrane system spacers influence the flow regime by imposing mixing and increased back diffusion of solutes from the membrane surface into the bulk solution. The use of feed spacers increases mass transfer [11] by reducing the CP [12], but also enhances the development of fouling in the feed channel [13][14][15][16].…”

“…However, in their long flat sheet membrane simulator the hydrodynamics differed from those in the SWM. Mo and Ng [12] pointed out the importance of undisturbed flow over the full length of the membrane element. They developed a 1-m long RO membrane test cell with pressure sensors along its length and permeate collectors for differential permeate analysis.…”

Optimum design of reverse osmosis systems for hydrogen peroxide ultrapurification

“…14 The requirements for hydrogen peroxide listed in Table 1 define five different electronic grades (Grades 1-5). The performance of individual reverse osmosis modules in terms of particular module geometry and design and operational conditions has been widely analyzed, [25][26][27][28][29][30] so suitable transport equations to describe the behavior of membrane modules are available to be applied to module optimization. for reducing impurity levels, the very low content of contaminants demanded by the semiconductor industry requires of further ultrapurification treatment.…”

“…[21][22][23][24] The complete optimization of a reverse osmosis network has to include the optimal design of both individual modules and the network configuration. The performance of individual reverse osmosis modules in terms of particular module geometry and design and operational conditions has been widely analyzed, [25][26][27][28][29][30] so suitable transport equations to describe the behavior of membrane modules are available to be applied to module optimization. The optimal configuration of reverse osmosis networks themselves had been less investigated, 31 but recently, several research groups have focused their efforts on the research of optimum design of reverse osmosis systems based on the previous pioneer works.…”