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

Magnesium potassium phosphate hexahydrate (MgKPO4·6H2O) was used as solidification matrix to immobilize some radioactive element and some heavy metal ions, the stability of MgKPO4·6H2O under different conditions had become the focus. This work gives new insights on the stability of synthesized MgKPO4·6H2O in the different temperatures and pH values solutions. The solid phase transformed from synthesized MgKPO4·6H2O 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 MgKPO4·6H2O had almost no phase transition at the temperature of 50°C and 60°C. Mg3(PO4)2·22H2O appears with the increase of solution temperature. The main phase is MgKPO4·6H2O at the pH of 9 and 12, minor MgHPO4·3H2O formed at the pH of 6, next Mg3(PO4)2·22H2O formed at the pH of 3 and 6. High pH value environment is beneficial for the maintenance of MgKPO4·6H2O. This study is an important guidance for the application of MgKPO4·6H2O crystal. [ABSTRACT FROM AUTHOR]