Composition of phosphates formed by the interaction of liquid glass with orthophosphoric acid solutions

Abstract

The chemical and phase composition of products formed by interaction of liquid glass with 20– 80% H3PO4is investigated. It is shown that the products of the synthesis include hydrated silicon and phosphorus containing phases. The silicon containing phase is a mixture of amorphous silica gel and nonstoichiometric sodium silicates. The phosphorus containing phase is sodium hydrophosphate Na2HPO4· 12H2O. It is established that the crystalline phase is formed irrespective of a mixing method and acid concentration. It is suggested that the cause of formation of acid salt of phosphoric acid even at a large excess of water glass is replacement of protons H + of silanol ?Si-OH-groups of silicic acid by cations of Na + and formation of sodium silicates which act as a connecting bridge between adjacent globules of the formed hydrogel.