An insight into the thermal properties of struvite-k by Rietveld refinement method

Abstract

This work investigated the thermal properties of struvite-k (a main binding phase and a strength-giving mineral from the magnesium potassium phosphate cements) exposed to different conditions by Rietveld Refinement Method coupled with X-ray diffraction analysis (XRD) identification, thermogravimetry/differential scanning calorimetry (TG/DSC) and Fourier-transform infrared spectroscopy (FTIR) method. The struvite-k presented significant vulnerability when exposed to above 70 °C, and destabilized to MgKPO4⋅H2O instead of MgKPO4, where, the remaining (0 3 1) and (2 1 2) planes were attributed to magnesium potassium phosphate monohydrate (MgKPO4·H2O). Coordinate a and c of the struvite-k crystal demonstrated significant responses to the heating temperature in comparison with coordinate b. Increasing the temperature up to 90 °C could decrease the length c of the struvite-k from 11.1022 Å to 9.8493 Å, and decrease its crystal size from 119.9 nm to 6.7 nm. The present work could provide fundamental knowledge on practical applications of MKPCs, such as construction, nuclear waste management, and phosphate recovery.