Study of the MS response by TG-MS in an acid mine drainage efflorescence

The aim of this study is to employ a thermogravimetric analyzer coupled to a mass spectrometer to research into the influence of heating rate and sample mass on the response of the detector. That response is examined by means of a particular efflorescence taken from an acid mine drainage environment. This mixture of weathered products is mainly composed by secondary sulfate minerals, which are formed in evaporation conditions, appearing as efflorescence salts. Thermogravimetry coupled to mass spectrometry has been used to analyze the three main loss steps that happen when this combination of minerals is heated from 30 to 1,100 A degrees C. This inorganic material is based on a mixture of hexahydrite, zinc sulfate hexahydrate, apjonite, gypsum, plumbojarosite, calcite, quartz, and magnetite. While heating, three main effluent gases evolved from this efflorescence. At a standard heating rate of 10 A degrees C/min, loss of water (dehydration) occurred over 30-500 A degrees C in four major steps, loss of carbon dioxide (decarbonisation) occurred over 200-800 A degrees C in three steps, and loss of sulfur trioxide (desulfation) occurred over 400-1,100 A degrees C in three steps. According to the results, thermal analysis is an excellent technique for the study of decomposition in these systems.