Dear Foroogh,

It strongly depends on your tested system. While using fresh membranes, maldistribution can occur due to inhomogeneous pore size distributions. With dirty membranes, it is hard to handle optimal cleaning strategies in order to reach water permeability.

Can you give any further information about your system?

Tobias

Dear Mohammad and Tobias,

Thank you for your response. I test UF PVDF membrane with out any coating. Because the pore size distribution is not same for all parts of the flat sheet UF PVDF membrane, we have different properties in different parts. So we have to test different parts and then make an average for every property like pure water flux, porosity, BSA rejection, ... .

Actually all researchers have to do this. But, What is the reason of this pore size maldistribution?

I think pore size maldistributions can be attributed to the manufacturing process. Actually, the difference should be small (< 5%). Initially, you should clean the membrane with deionized water to remove glycerine or other humidifying substances. This could have an effect on your water flux.

Kind regards