(35a) Eddy Diffusivity Spiegler-Kedem (EDSK) Model for Reverse Osmosis Membrane

An Eddy Diffusivity Spiegler-Kedem (EDSK) model is developed for estimating the permeate flux and concentration at high flux mass transfer in membranes. In this model, the mass transport in membrane and concentration polarization layer was described by Spiegler-Kedem model and Eddy diffusivity model respectively. The experiment is carried for both high and low permeate flux regions in reverse osmosis membrane cell for the separation of single solute of NaCl and CaCl2 aqueous solution. The rejection of both NaCl and CaCl2 first increases and then decreases with increasing feed pressure. However, the observed rejection of CaCl2 is found to be higher than the observed rejection of NaCl. The separation data of NaCl and CaCl2 is analyzed by both EDSK model and Combined Film Spiegler-Kedem (CFSK) model. The model parameters of both the models were estimated by using error minimization-simplex search. The maximum error between the experimental and theoretical values of both permute flux and permeate concentration are calculated for both EDSK and CFSK models and were found to be 17% and 20%, 45 % and 56 % respectively. Finally the EDSK model prediction compared with prediction of Extended Nernst Planck (ENP) equation model using literature data of MgCl2, MgSO4 and Na2SO4 ? water system. The above analysis concludes that the EDSK model predicts slightly better than the ENP model and the CFSK model fails to predict the permeate flux when flux across the membrane is high