Thermal decomposition of peisleyite: a thermogravimetry and hot stage Raman spectroscopic study

Abstract

High resolution thermogravimetric analysis coupled with a gas evolution mass spectrometer was used to study the decomposition of peisleyite Na3 Al16(SO4)(PO4)10(OH)17•20H2O. Peisleyite, a hydrated hydroxylated multianion mineral, shows thermal decomposition in 5 stages, indicative of a loss of water, hydroxyl units and sulphate. Thermal analysis shows the loss of water and hydroxyl units occurs in 3 distinct stages; at 36 degrees Celsius, 105 degrees Celsius and 162 degrees Celsius. The high resolution thermogravimetry was complimented with hot stage Raman spectroscopy, which follows the dehydration of peisleyite. This dehydration can be followed by the decrease in intensity of the OH stretching vibrations which occur between 4000 and 2500cm-1 and by the shift in the sulphate and phosphate peaks which occur due to changes in the mineral structure.