Steady state modeling of concentration polarization including adsorption during nanofiltration of dye solution

Steady state modeling of nanofiltration of a dye (eosin as model dye) solution was carried out. The model was based on simultaneous solution of solution-diffusion model, film theory and osmotic pressure model. The osmotic pressure model was modified by incorporating adsorption of dyes onto the membrane surface. The model parameters were estimated by comparing the calculated and experimental data of permeate flux and permeate concentration. It was observed that although membrane hydraulic resistance was the dominant one, adsorption resistance becomes more significant with increase in feed dye concentration and transmembrane pressure drop and decrease in crossflow velocity. For example, for eosin feed concentration of 0.2 kg/m3 and crossflow velocity of 0.46 m/s and transmembrane pressure of 828 kPa, the resistance offered by adsorbed solutes was found to be as high as 21% of the total resistance. The combined model successfully simulates the system performance in terms of permeate flux and permeate concentration.