Destabilization mechanism of acid aluminum phosphate solution: Effects of P/Al ratio, concentration and boron doping

The poor long-term stability of acid aluminum phosphate (AAP) solutions limits their industrial application. To understand its destabilization mechanism, the effects of phosphorus to aluminum ratio, concentration, and boron doping on the stability of the AAP solution are investigated. The destabilization mechanism involves polymerizing the aluminum phosphate species to form insoluble aluminum phosphate compounds. The solution concentration controls the polymerization kinetics, and reducing the concentration can improve the stability of the AAP solution. Boron introduction improves solution stability by reducing the number of active sites on the aluminum phosphate species available for polymerization and by increasing solution viscosity to restrict the movement of the aluminum phosphate species.