A model to describe the retention of solute could reduce the need of repeated testing for each new application and be useful for understanding the separation mechanisms of nanofiltration.For uncharged solutes, the separation is achieved by sieving effect, and steric-hindrance pore(SHP)model is appropriate.But obtaining membrane pore radius (rp) from SHP model needs permeation experiments of uncharged solutes, which are difficult and burdensome.On the other hand, the molecular weight cut-off (MWC) is a concept that is strongly established in membrane field.By introducing the MWC in SHP model, the existing information about the membrane can be used, which can simplify the implementation of model.In this paper, the correlation between the Stokes radius (rs) and molecular weight (MW) was established.Then based on the assumption that the membrane pore radius equals the Stokes radius of uncharged solute with molecular weight equal to MWC, rp and rs can be expressed as functions of MWC and MW respectively.On the basis of SHP model and Spiegler-Kedem model, a model named as MWC parameters steric-hindrance pore model (MWC-SHP) was established.Permeation experiments of aqueous solution of glucose and sucrose with spiral membrane (NF270) were conducted and the structural parameters (rp and the ratio of membrane porosity to membrane thickness) were estimated by using MWC-SHP model and SHP model respectively.The results estimated from MWC-SHP model were in agreement with SHP model.Moreover, rejection prediction of uncharged solutes by nanofiltration with MWC-SHP model was in agreement with experimental data, which showed MWC-SHP model could be applicable to the evaluation of the structure of nanofiltration membrane and rejection prediction of uncharged solutes.
