how to set up the ions in water dans my nano-fluidics

hi everyone,

I'm trying to simulate the nanofluidics covered by a layer of SiO2 of which the thickness is about 50nm. In the nanofluidicsm there is water or other liquid. First of all, I set the relative permittivity of water 80 to get a general idea. But in reality, there are ions in the water and I do not know how to deal with it.

Can anyone help me with this problem. Thank you in avance.

WANG Fei