Prediction of boron transport through seawater reverse osmosis membranes using solution–diffusion model

One of the key transport parameter—permeability, is being used as an intrinsic characteristic of membrane for reverse osmosis process prediction. In this study, the prediction of reverse osmosis process in terms of boron rejection was carried out in two steps. First, the permeability of boron existing as boric acid − B(OH)3 and as metaborate ion B(OH)4 through seawater reverse osmosis membranes was estimated in three types of feed matrix: DI water, NaCl and artificial seawater. The second step was to develop a computer program using boric and borate permeabilities as inputs to predict the boron rejection at different operating conditions. The governing equations were derived from the solution–diffusion model. The effect of temperature was quantitatively determined employing a representative constant and incorporated with the program. The prediction showed good agreement with experimental data obtained from a lab-scale plate-frame type reverse osmosis system.

The prediction of boron transport through SWRO membranes was conducted with SR and SHN membrane using a lab-scale plateframe RO system. The effects of pH and temperature on boron rejection were found to be consistent with previous study. Further, boric and borate permeabilities were investigated separately and simultaneously using a simplified solution–diffusion model and nonlinear regression. Temperature effect was also quantitatively determined through an empirical temperature effect constant. The prediction by FORTRAN program well matched with experimental observation. This study can be easily incorporated in the complete prediction of RO process performance and applied to a pilot or large-scale system with some correction factors.