I have been learning about water coagulation in my chemistry textbook. Apparently, before being treated, water has clay particles, primarily silicates and aluminosilicates, which apparently have a negative charge. These particles repel each other, forming a colloidal mixture.
My question is: how exactly do the silicates and aluminosilicates have a negative charge? I understand that silicates and aluminosilicates have a negative silicate/aluminosilicate anion, but wouldn't that negative charge be counteracted by their bonding to a positive cation, causing the silicate/aluminosilicate to have an overall neutral charge?
My current conjecture is that, in water, the silicate/aluminosilicates particles dissociate, and the cations are solvated by water however the silicate/aluminosilicate anions are too large to be solvated, thus they remain in the water and repel each other. This is the only way that it currently makes sense to me because other ionic compounds like sodium chloride do not form colloids in water despite obviously having cations and anions; likely because both the cations and anions are solvated by the water particles because they are both small enough.
If anyone can correct my conjecture/explain to me how this works, I would really appreciate it.