Reverse Osmosis
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This Demonstration models a reverse osmosis process in which salt water at high pressure is fed to a chamber with a membrane that is only permeable to water. The outlet permeate stream is pure water at low pressure, and the retentate stream is water enriched in salt. 

Use the sliders to set the pressure drop across the membrane, the inlet salt mass fraction and the stirring bar speed. Increasing the stirring speed decreases concentration polarization on the feed side of the membrane and increases water flux through the membrane. The inlet mass flow rate is fixed and the process is isothermal. 

The water flux through the membrane is plotted versus the pressure drop across the membrane. The blue line represents the water flux when pure water is fed to the system. The green line represents the water flux when salt water is fed to the system. The dashed black line indicates the maximum water flux through the membrane. The values in the diagram on the right correspond to the conditions represented by the black dot, whose location is selected by the pressure drop slider. If the pressure drop is less than the osmotic pressure (orange dot on the x-axis), the system exhibits osmosis, and pure water permeates into the salt water feed. 

Uncheck the "show diagram" box to remove the flow diagram on the right and display a larger graph of flux versus pressure drop.