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- Title
An investigation of the thermal behavior of magnesium ammonium phosphate hexahydrate.
- Authors
Ramlogan, Marlon; Rouff, Ashaki
- Abstract
Struvite (MgNHPO·6HO) was heated to temperatures from 55 to 300 °C. X-ray diffraction analysis revealed struvite was stable at 55 °C, partially decomposed to dittmarite (MgNHPO·HO) at 100-200 °C, and formed an amorphous phase at 250-300 °C. Thermogravimetric analysis confirmed sample mass loss consistent with dittmarite formation at 100-200 °C and evolution of all volatiles at 250-300 °C. Fourier transform infrared (FTIR) spectroscopy detected the ν NH band in 55-200 °C solids, as expected for struvite and dittmarite. This band decreased in intensity at 250 °C, and was not evident at 300 °C, confirming loss of NH(s) at these temperatures. FTIR spectra also showed changes in the vibrations of the ν PO band. At 55 °C, splitting in the band indicated destabilization of the PO(s) group despite no change in mineralogy. Vibrations at 100-200 °C were associated with dittmarite and MgHPO, and at 250-300 °C, MgHPO and MgPO. Analysis of acid-digested solids indicated the presence of P other than P-PO at 200-250 °C, confirming MgPO formation. Overall, heat treatment of struvite produces several decomposition products, complete identification of which requires the use of multiple approaches. Temperature-induced phase transformations along with emission of NH(g) have implications for use of struvite in multiple applications.
- Subjects
MAGNESIUM alloys; AMMONIUM phosphates; X-ray diffraction; METAL formability; FOURIER transform infrared spectroscopy; CHEMICAL decomposition
- Publication
Journal of Thermal Analysis & Calorimetry, 2016, Vol 123, Issue 1, p145
- ISSN
1388-6150
- Publication type
Article
- DOI
10.1007/s10973-015-4860-1