Effect of temperature and pH value on the stability of magnesium potassium phosphate hexahydrate

Magnesium potassium phosphate hexahydrate (MgKPO 4 ·6H 2 O) was used as solidification matrix to immobilize some radioactive element and some heavy metal ions, the stability of MgKPO 4 ·6H 2 O under different conditions had become the focus. This work gives new insights on the stability of synthesized MgKPO 4 ·6H 2 O in the different temperatures and pH values solutions. The solid phase transformed from synthesized MgKPO 4 ·6H 2 O was characterized by X‐ray diffractometer (XRD), thermal gravity analysis (TG/DSC), Fourier‐transform infrared spectrum (FTIR) and scanning electron microscope (SEM) at different temperature and pH values solution. Results indicated MgKPO 4 ·6H 2 O had almost no phase transition at the temperature of 50°C and 60°C. Mg 3 (PO 4 ) 2 ·22H 2 O appears with the increase of solution temperature. The main phase is MgKPO 4 ·6H 2 O at the pH of 9 and 12, minor MgHPO 4 ·3H 2 O formed at the pH of 6, next Mg 3 (PO 4 ) 2 ·22H 2 O formed at the pH of 3 and 6. High pH value environment is beneficial for the maintenance of MgKPO 4 ·6H 2 O. This study is an important guidance for the application of MgKPO 4 ·6H 2 O crystal.