Acid/base separation in nanofiltration

How do semi-permiable membranes handle salts that can separate into an acid and a base based on the "rules" of the membrane? 


For example, say I have a nanofiltration membrane that rejects multivalent ions (eg $SO\_4^{-2}$) but passes monovalent ones (eg $Na^+$) ([common in nanofiltration membranes](https://dowac.custhelp.com/app/answers/detail/a_id/4925/~/filmtec-membranes---nanofiltration---mwco)). If I supply a pressurized feed of an aqueous mixed-valency salt solution, say $Na\_2SO\_4$, what happens?


I can't find any literature that describes what happens in a simple case like this without other ions around. I can imagine two options are most likely:


1. The salt gets rejected. This is implied by lots of literature, but I can't find it explicitly stated.
2. The monovalent ion passes, in the above example creating $NaOH$ solution permeate and $H\_2SO\_4$ solution retentate. Evaluating the osmotic pressure in this case would be very odd as I guess you would have to include the disassociation energy of water.


What happens in this type of situation?


