Meeting with Prof. Bill

Today the whole FYP team met up with Prof. Bill.

Presentation & ROSA:

From ROSA, we can see the trend of the % recovery and salt rejection.

Increase of pressure will cause an increase in permeate flow rate, decrease in permeate concentration etc.

Suggestions from Prof. Bill:

• type of membrane used for the experiment need to be found out
• conductivity VS concentration at each temperature should be compared with those in the handbooks
• the built up of salt on the membrane will cause the water molecule to have difficulty to pass through the membrane (salt built up will diffuse back to the main feed stream)
• increase in flow rate (keeping the other variables constant) will increase in shear; decreasing the thickness of the concentration boundary
• Material Balance must be performed to compare with our experimental results

Membrane Characterization System:

We are told that the membrane that we used are for microfiltration.

The pore size of the membranes are too big. Salt particles can pass through it.

Hence, osmosis is not achieved.

• Chemical Potential Difference causes mass transfer between the DI water and concentrate.
• Both the water and the concentrate level need not cover the whole membrane.

We concluded that we would use a RO membrane (which we will get from Dr. Chong) to test it out again.

Vendor's P&ID:

• 1 low pressure feed pump
• 1 high pressure booster pump
• Pressure Reducing Valve between RO and NF1 (cheap and easily available)

Membrane Characterization System Experiment

Today, some of us conducted the experiment on theMembrane Characterization System Experiment in W314 lab.

The objective of this experiment is to study the osmotic pressure and resistance of different types of membranes.

Theoretically, we can calculate the osmotic pressure using this formula:

π = MRT

π- Osmotic Pressure

M- Concentration

R- Universal Gas Constant

T- Temperature

We want to prove that the experimental results would tally with theoretical value that we have calculated.

However, we couldn't get any results due to the following problems:

• we couldn't measure any voltage because there wasn't any point for us to connect the multimeter to the electrode
• there isn't any significant change in the water level, hence we couldn't calculate the osmotic pressure
• we cannot measure the conductivity because the conductivity was out of range for the conductivity meter

These are the possible causes which might have caused the problems to occur:

• the membrane; wrong placing of the membrane
• the salt solution is too concentrated for the osmosis phenomena to occur