In aqueous solutions, Si4+ ions cannot exist. In this sense, silicon is similar to sulfur, the ions of which also do not exist in aqueous solutions. For sulfur, you use sulfate ions SO42-, and for silicon, the easiest way is to use silicate ions: SiO32-.

https://www.alsenvironmental.co.uk/media-uk/pdf/datasheets/waste-water/als_ww_ionic_balance_v3.pdf

Dear Denisa Macková

Thank you very much for your interesting question. I think your question is about balancing the silicate anions with counter positive ions. Please have an understanding about the classification and structure of silicate anions. Following links may help you a lot.

https://www.adichemistry.com/inorganic/p-block/group-14/silicates/silicates-1.html

https://en.wikipedia.org/wiki/Silicate

Good luck !

Hi,

I'm still a bit confused of the Si ion balance. It is still true when I incorporate Si at any form the balance is bad.

But I have found two sources which says I should not integrate Si.

Study and interpretation of the Chemical Characteristics of Natural Water, 1986

"The convention of representing dissolved silica as the oxide SiO2 has been followed by all water analysts. Some of the older literature implied that the material was present in colloidal form, but occasionally a charged ionic species, SiO32-, was specified. In most waters, it is fully evident that the dissolved silicon does not behave like a charged ion."

L. J. Zeman and Olav Slaymaker, 2009

"In the present mass balance model, the major cations, anions and silica were budgeted"..."Implications of the model were related to discharge control of silica load"...

What do you think about that?

Thank you very much