sedimentation SiO2

[Aksenova]

Hello!
The situation is as follows: I have a liquid composition (water - anions, cations), also the water contains quite a large amount of SiO2. The pH and temperature of the liquid are also known. I learned how to enter these data into the program, the program made calculations.
Question: how do I understand whether silicates or silica precipitate under the specified conditions?  I saw the calculated saturation indices, but how to interpret these data - I do not understand.
Question - how to indicate the pressure at which the investigated liquid is located?
I would be very grateful for your help in this matter.

[dlparkhurst]

If the SI for a mineral is less than zero, the mineral could dissolve, but it cannot precipitate. I the SI for a mineral is greater than zero, the mineral could precipitate, but cannot dissolve. If the SI is near zero, it could mean the mineral is reacting fast enough to maintain equilibrium.

The "could" means that reaction kinetics are involved. The rate at which the minerals dissolve or precipitate depends on other factors, so that minerals may not react, even if the SI indicates that a reaction is thermodynamically favored.

There are also many uncertainties, mostly related to the the appropriate log K for minerals. Log Ks vary depending on the composition of minerals and the treatment of thermodynamic data. Uncertainties in log Ks directly affect the uncertainty on the saturation index for a mineral.

[Aksenova]

Thank
Can you please tell me if I understand correctly that the pressure should be set in the wrong place to set the ions?

How can I specify the phase of the substance?

And where can I add information about the presence of arsenic in the ionic composition?

I will be very grateful for help in this question.