Reverse Osmosis

Safety Procedures

Please be aware of any potential hazards prior to operating any experiment. Only use salt water during this experiment and notify any lab personal if there are any major leaks. If and when you move the discharge streams, make sure they are secure to avoid spills.

Other Safety Concerns:

• Wear a lab coat and safety glasses at all times

• Never run pumps dry

• The system pressure may approach 100 psig, so keep an eye out for leaks.

• Never fully submerge the conductivity probe in the tank; submerge only the metal tip.

Programs, Equipment, and Instruments

• Desktop with DataLogger Software

• Pump

• Conductivity probe

• Stir plate

• Balance

Objectives

1. Create a calibration curve for the conductivity probe.

2. Determine equations to estimate values of the rejection coefficient r, the water permeability coefficient Aᵥᵥ (sometimes just called A), and the salt permeability coefficient B (see the first reference for more details).

Tips

1. Plan your experiments before coming to the lab.

2. Always use the lowest possible setting on the conductivity probe. For example, if your sample conductivity is about 150 uS/cm then your range should be set to 0-200 uS/cm and not 0-2000 uS/cm.

3. Each range setting on the probe requires its own unique calibration curve. 

4. Make sure the bypass valve is closed before adjusting the pressure on the system.

5. Never completely close the ball valve that controls the transmembrane pressure (there should always be a small amount of retentive flow).

References

1. Hung, L.Y.; Lue, S.J.; You, J.H., Mass-transfer modeling of reverse-osmosis performance on 0.5-2% salty water. Desalination 2011, 265, 67-73.

2. McCabe, W.L.; Smith, J.C.; Harriott, P., Unit Operations of Chemical Engineering, 7th ed.; McGraw Hill: New York, 2005, Ch. 26.

3. Prudich, M.E. et al, Alternative Separation Processes. In Chemical Engineers' Handbook, Perry, R., Chilton, C., Eds., 8th ed.; McGraw Hill: New York, 2008, S. 20.

4. Seader, J.D.; Henley, E.J.; Roper, D.K., Separation Process Principles: Chemical and Biochemical Operations, 3rd ed.; John Wiley and Sons: New Jersey, 2010, Ch. 14.

5. Alghoul, M.A.; Poovanaesvaran, P.; Sopian, K.; Sulaiman, M.Y., Review of brackish water reverse osmosis (BWRO) system designs. Renew. Sustain. Energy Rev. 2009, 13, 2661-2667.

6. Fritzmann, C.; Lowenberg, J.; Wintgens, T.; Melin, T., State-of-the-art of reverse osmosis desalination. Desalination 2007, 216, 1-76.

7. Malaeb, L.; Ayoub, G.M., Reverse osmosis technology for water treatment: State of the art review. Desalination 2011, 267, 1-8

8. Ma, S.; Kassinos, S.C.; Kassinos, D.F., Assessing the impact of concentration-dependent fluid properties on concentration polarization in crossflow membrane systems. Ind. Eng. Chem. Res. 2008, 47, 1636-1649