you've asked two completely different questions in one poorly worded question. Re-submit your question in such a manner that it can be answered.

Thanks for your response Mark. 

1) what would be considered the best pore size to desalinate seawater using dialysis membrane tube

2) what are the other experimental conditions...  here a good article describing the methodology will be much appreciated 

A simple search on Google gave me multiple sources. Surely you can run a Google search? Part of investigation is learning to use your resources.