Thermogravimetric analysis has been used to determine the thermal stability of the mineral stercorite H(NH4)Na(PO4)·4H2O. The mineral stercorite originated from the Petrogale Cave, Madura, Eucla, Western Australia. This cave is one of many caves in the Nullarbor Plain in the South of Western Australia. The mineral is formed by the reaction of bat guano chemicals on calcite substrates. Upon thermal treatment the mineral shows a strong decomposition at 191°C with loss of water and ammonia. Other mass loss steps are observed at 158, 317 and 477°C. Ion current curves indicate a gain of CO2 at higher temperature and are attributed to the thermal decomposition of calcite impurity

H Cheng

J Yang

KH Bakon

L-M Grand

PJ Bridge

Ray L. Frost

RF Platford

RL Frost

Sara J. Palmer

SJ Palmer

English

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Journal of Thermal Analysis and Calorimetry

Thermal stability of stercorite H(NH4)Na(PO4)·4H2O

Thermogravimetric analysis has been used to determine the thermal stability of the mineral stercorite H(NH4)Na(PO4)·4H2O. The mineral stercorite originated from the Petrogale Cave, Madura, Eucla, Western Australia.  This cave is one of many caves in the Nullarbor Plain in the South of Western Australia.  The mineral is formed by the reaction of bat guano chemicals on calcite substrates.  Upon thermal treatment the mineral shows a strong decomposition at 191°C with loss of water and ammonia. Other mass loss steps are observed at 158, 317 and 477°C.  Ion current curves indicate a gain of CO2 at higher temperature and are attributed to the thermal decomposition of calcite impurity

Frost, Ray L.

Palmer, Sara J.

Name not available

Thermal stability of stercorite H(NH4)Na(PO4)·4H2O – a cave mineral from Petrogale Cave, Madura, Eucla, Western Australia

Frost, Ray

Palmer, Sara

Queensland University of Technology ePrints Archive

1  Thermal stability of stercorite H(NH4)Na(PO4)·4H2O – a cave mineral from Petrogale 1 Cave, Madura, Eucla, Western Australia 2 Ray L. Frost  and Sara J. Palmer  3 Chemistry Discipline, Faculty of Science and Technology, Queensland University of 4 Technology, GPO Box 2434, Brisbane Queensland 4001, Australia. 5  6 ABSTRACT 7 Thermogravimetric analysis has been used to determine the thermal stability of the mineral 8 stercorite H(NH4)Na(PO4)·4H2O. The mineral stercorite originated from the Petrogale Cave, 9 Madura, Eucla, Western Australia.  This cave is one of many caves in the Nullarbor Plain in 10 the South of Western Australia.  The mineral is formed by the reaction of bat guano 11 chemicals on calcite substrates.  Upon thermal treatment the mineral shows a strong 12 decomposition at 191°C with loss of water and ammonia. Other mass loss steps are observed 13 at 158, 317 and 477°C.  Ion current curves indicate a gain of CO2 at higher temperature and 14 are attributed to the thermal decomposition of calcite impurity.  15 KEYWORDS: thermogravimetric analysis, stercorite, ‘cave’ mineral, brushite, 16 mundrabillaite, archerite. 17  18  19  20  21  22 23                                                   Author to whom correspondence should be addressed (r.frost@qut.edu.au) 2  Introduction 24  The mineral stercorite originated from the Petrogale Cave, Madura , Eucla, Western 25 Australia.  Many minerals may form in these caves, some of which include archerite 26 (K,NH4)(H2PO4) [1], and mundrabillaite (NH4)2Ca(HPO4)2·H2O  [2]. These minerals occur as 27 stalactites and as crusts on the walls and floors of the caves.  Other minerals found in the 28 Petrogale cave include aphthitalite (K,Na)3Na(SO4)2, halite NaCl, syngenite 29 (K,Na)3Na(SO4)2, oxammite (NH4)2(C2O4) · H2O, weddellite Ca(C2O4)·2H2O, whitlockite 30 Ca9Mg(PO4)6(HPO4), guanine C5H5N5O, newberyite Mg(HPO4)·3H2O and calcite CaCO3.  31 These minerals are formed through the chemical reactions of calcite with bat guano or with 32 chemicals from bat guano which are water soluble and crystallise out on the calcite surfaces.  33 The mineral stercorite is water soluble and may translocate through the Petrogale cave 34 network[3]. 35 Thermal analysis offers an important technique for the determination of the thermal stability 36 of minerals [4-13]. Importantly the decomposition steps [13-15] can be obtained and 37 mechanisms of decomposition of the mineral ascertained. There have been almost no studies 38 of the thermal analysis of ‘cave’ minerals. In this research, we report the thermal 39 decomposition of the mineral stercorite, a mineral common to caves worldwide.   40 Experimental 41 Minerals 42 The mineral stercorite was supplied by The Australian Museum and originated from 43 Petrogale Cave, Madura, Western Australia.  Details of the mineral have been published 44 (page 561) [16].   45 Thermogravimetric analysis 46 Thermal decomposition of stercorite was carried out in a TA® Instruments incorporated 47 high-resolution thermogravimetric analyser (series Q500) in a flowing nitrogen 48 atmosphere (80 cm3/min). Approximately 28 mg of sample was heated in an open 49 platinum crucible at a rate of 5.0 °C/min up to 1000°C at high resolution. With the quasi-50 isothermal, quasi-isobaric heating program of the instrument the furnace temperature was 51 regulated precisely to provide a uniform rate of decomposition in the main decomposition 52 3  stage. The TGA instrument was coupled to a Balzers (Pfeiffer) mass spectrometer for gas 53 analysis. Only selected gases such as water and sulphur dioxide were analysed. X-Ray 54 diffraction patterns were collected using a Philips X'pert wide angle X-Ray 55 diffractometer, operating in step scan mode, with Cu K radiation (1.54052 Å). 56 Results and Discussion 57 The thermogravimetric and differential thermogravimetric analyses of stercorite are displayed 58 in Figure 1. The ion current curves of the evolved gases are shown in Figure 2.  The dTG 59 curve shows maxima at 158 and 191, 317, 477 and 567°C with measured mass losses of 60 21.75, 14.92, 5.17 and 1.11%. A small mass loss of 1.17% is found at temperatures from 61 ambient up to 83°C and is attributed to the loss of adsorbed water.  The ion current curves 62 clearly show that water is the evolved gas at 170, ~190 and 305°C. The theoretical mass loss 63 for water based upon the formula is 34.44%.  The total mass loss over the 83 to 405°C 64 temperature range is 14.92 + 21.75% = 36.67%, which is higher than the calculated figure. It 65 is considered that NH3 is lost at the same time as the water. If this is the case, then this mass 66 should be included in the calculation. The calculated mass for NH3 is 8.61%. This makes the 67 total mass for evolved NH3 and water as ~43% which is too high. The thermal stability of 68 stercorite is determined by the temperature of the first mass loss at 191°C. It is proposed that 69 water and ammonia is lost at this temperature. The total theoretical mass loss for stercorite is 70 43.05%. The measured mass loss for stercorite is 41.84% which is close to the calculated 71 value. Stercorite is found on calcite stalactites and thus CaCO3 may be an impurity in the 72 mineral.  The higher temperature mass losses as is indicated by the ion current curves appear 73 to be due to the decomposition of calcite.  74  75 Mechanism of formation of stercorite H(NH4)Na(PO4)·4H2O 76 In the laboratory, the mineral is readily synthesised by mixing aqueous solutions of sodium 77 hydrogen phosphate Na2HPO4 and ammonium hydrogen phosphate (NH4)2HPO4  [3].  The 78 reaction is displayed below. Platford [3] showed that the two chemicals were in congruency 79 with their components. It is likely that low temperatures aid the formation of stercorite, as 80 might occur in caves on the Nullarbor Plains in Western Australia.  Whether or not the 81 mineral stercorite is formed by solubility effects from undersaturated solutions is open to 82 4  question, but it does seem likely. The presence of the calcite surface serves as a template 83 surface for the crystallisation of stercorite. 84 Na2HPO4   +   (NH4)2HPO4  +  4H2O →  2H(NH4)Na(PO4)·4H2O 85  86 CONCLUSIONS  87 The mineral stercorite is an ammoniated hydrogen sodium phosphate and is found in caves in 88 Western Australia and is especially known from the Petrogale Cave, near Madura, Western 89 Australia.  The mineral has also been found at Ichaboe Island, Namibia and Gua˜nape Island, 90 Peru. It is a mineral formed by the reaction of calcite with bat (or bird) guano. The mineral is 91 associated with other phosphate minerals including struvite, archerite, and brushite.  92 According to Platford [3], the mineral is formed from solution. Hence, the basic components 93 of the mineral can be translocated through a cave system. 94 The thermal stability of stercorite is determined by the temperature of the first mass loss at 95 191°C. It is proposed that water and ammonia is lost at this temperature. The total theoretical 96 mass loss for stercorite is 43.05%. The measured mass loss for stercorite is 41.84% which is 97 close to the calculated value.  In other words the ‘cave’ mineral stercorite would not be stable 98 if the temperature of the cave system was elevated.   99 Acknowledgements 100 The financial and infra-structure support of the Queensland University of Technology, 101 Chemistry discipline is gratefully acknowledged. The Australian Research Council (ARC) is 102 thanked for funding the instrumentation.   103 104 5  References 105 [1] Bridge, P. J., Archerite, (K,NH4)H2PO4, a new mineral from Madura, Western 106 Australia,Mineralogical Magazine 41 (1977) 33-35. 107 [2] Bridge, P. J., Clark, R. M., Mundrabillaite - a new cave mineral from Western 108 Australia,Mineralogical Magazine 47 (1983) 80-81. 109 [3] Platford, R. F., Thermodynamics of system water-disodium hydrogen phosphate-110 diammonium hydrogen phosphate at 25.deg,Journal of Chemical and Engineering Data 19 111 (1974) 166-168. 112 [4] Cheng, H., Yang, J., Frost, R. L., Liu, Q., Zhang, Z., Thermal analysis and Infrared 113 emission spectroscopic study of kaolinite-potassium acetate intercalate complex,J. Therm. 114 Anal. Calorim. 103 (2011) 507-513. 115 [5] Bakon, K. H., Palmer, S. J., Frost, R. L., Thermal analysis of synthetic reevesite and 116 cobalt substituted reevesite (Ni,Co)6Fe2(OH)16(CO3) Â· 4H2O,J. Therm. Anal. Calorim. 117 100 (2010) 125-131. 118 [6] Cheng, H., Liu, Q., Yang, J., Frost, R. L., Thermogravimetric analysis of selected 119 coal-bearing strata kaolinite,Thermochim. Acta 507-508 (2010) 84-90. 120 [7] Cheng, H., Liu, Q., Yang, J., Zhang, J., Frost, R. L., Thermal analysis and infrared 121 emission spectroscopic study of halloysite-potassium acetate intercalation 122 compound,Thermochim. Acta 511 (2010) 124-128. 123 [8] Cheng, H., Liu, Q., Yang, J., Zhang, Q., Frost, R. L., Thermal behavior and 124 decomposition of kaolinite-potassium acetate intercalation composite,Thermochim. Acta 125 503-504 (2010) 16-20. 126 [9] Frost, R. L., Palmer, S. J., Grand, L.-M., Synthesis and thermal analysis of indium-127 based hydrotalcites of formula Mg6In2(CO3)(OH)16·4H2O,J. Therm. Anal. Calorim. 101 128 (2010) 859-863. 129 [10] Frost, R. L., Palmer, S. J., Kristof, J., Horvath, E., Dynamic and controlled rate 130 thermal analysis of halotrichite,J. Therm. Anal. Calorim. 99 (2010) 501-507. 131 [11] Frost, R. L., Palmer, S. J., Kristof, J., Horvath, E., Thermoanalytical studies of silver 132 and lead jarosites and their solid solutions,J. Therm. Anal. Calorim. 101 (2010) 73-79. 133 [12] Grand, L.-M., Palmer, S. J., Frost, R. L., Synthesis and thermal stability of 134 hydrotalcites containing manganese,J. Therm. Anal. Calorim. 100 (2010) 981-985. 135 [13] Grand, L.-M., Palmer, S. J., Frost, R. L., Synthesis and thermal stability of 136 hydrotalcites based upon gallium,J. Therm. Anal. Calorim. 101 (2010) 195-198. 137 [14] Palmer, S. J., Frost, R. L., Thermal decomposition of Bayer precipitates formed at 138 varying temperatures,J. Therm. Anal. Calorim. 100 (2010) 27-32. 139 [15] Yang, J., Frost, R. L., Martens, W. N., Thermogravimetric analysis and hot-stage 140 Raman spectroscopy of cubic indium hydroxide,J. Therm. Anal. Calorim. 100 (2010) 109-141 116. 142 [16] Anthony, J. W., Bideaux, R. A., Bladh, K. W., Nichols, M. C., Handbook of 143 Mineralogy Vol.IV. Arsenates, phosphates, vanadates - Mineral Data Publishing, Tucson, 144 Arizona, Mineral data Publishing, Tucson, Arizona, 2000. 145  146  147 148 6  List of Figures 149 Figure 1 Thermogravimetric and differential thermogravimetric analysis of stercorite. 150 Figure 2 Selected ion current curves of the evolved gases resulting from the thermal 151 decomposition of stercorite152 7   153  154 Figure 1 155  156 157 8   158  159 Figure 2 160 

Thermal stability of stercorite H(NH4)Na(PO4).4H2O - A cave mineral from Petrogale Cave, Madura, Eucla, Western Australia

Thermal stability of stercorite H(NH4)Na(PO4).4H2O - A cave mineral from Petrogale Cave, Madura, Eucla, Western Australia

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