Kaolin and other clays are partly soluble in acidic solutions (organic or inorganic acids in water) but the behaviour is complex and the solubility is never complete.  Increasing the acid content doesn't necessarily increase the solubility.

Dear Dr. Krishna,

I don't think there is a solvent existed to dissolve kaolin completely. But you can refer to the protocal of digestion during soil analysis. After the completion of digestion, the solution can be miscible with water. I'm not sure it's reasonable for your needs, because during digestion, the temperature could reach 200 degree celcius. Good luck.

Regards,

Ping

Kaolin and other clays are partly soluble in acidic solutions (organic or inorganic acids in water) but the behaviour is complex and the solubility is never complete.  Increasing the acid content doesn't necessarily increase the solubility.

Keep in mind that any " dissolution of minerals" like kaolin are really reactions breaking silicate bonds irreversibly. Thus the geochemist wishing to do ICP or AA analysis uses acids such as nitric, and then follows with hydrofluoric  acids. These digests can render water soluble simple anion and cation solutions in water.

Be aware that you won't ever get back the kaolin mineral by neutralizing the acid solutions.

Why one uses the nitric first, to completely destroy organics and remove the polyvalent cations like Ca as nitrate aqueous solutions. It obviously means separate analysis, since the two solutions won't be combined.