The thermal decomposition of thaumasite from Mothae kimberlite pipe,Lesotho, Southern Africa |
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Authors: | P Kresten G Berggren |
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Institution: | (1) Section for Fuel Technology, Studsvik AB Atomenergi Sweden, S-61101 Nyköping 1, Sweden |
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Abstract: | The endothermic decomposition of thaumasite from Mothae which has been investigated by DTA and TG shows a peak temperature of 138–203°, and reaction orders of 0.45–1.00, depending on the heating rate employed. The activation energy of the reaction was found to be about 19 kcal/mole; the enthalpy is 246 cal/g.The decomposition seems to be divided into one reaction withn=0.90, immediately followed by one withn=1.59. The first reaction is attributed to the loss of H2O, the second one to the (partial) release of OH and CO2.
Zusammenfassung Die durch DTA und TG überprüfte endothermische Zersetzung von Thaumasit aus Mothae zeigt in Abhängigkeit der angewandten Aufheizgeschwindigkeiten Spitzentemperaturen zwischen 138 und 203° C, sowie Reaktionsordnungen von 0.45 bis 1.00. Die Aktivierungsenergie der Reaktion ergab sich zu 19 Kcal/Mol, die Enthalpie zu 246 cal/g.Die Zersetzung scheint in eine Reaktion vonn=0.90 und eine sofort darauffolgende vonn=1.59 geteilt zu sein. Die erste Reaktion wird dem Verlust von H2O, die zweite der (teilweisen) Freisetzung von OH und CO2 zugeschrieben.
Résumé La décomposition endothermique de la thaumasite de Mothae a été étudiée par ATD et TG. Suivant la vitesse de chauffage utilisée la température au sommet du pic varie de 138 à 203° C et l'ordre de réaction de 0.45 à 1.00. On a trouvé que l'énergie d'activation s'élevait à 19 kcal, mol–1 et l'enthalpie à 246 cal. g–1.Il semble que la décomposition s'effectue suivant une réaction d'ordren=0.90, immédiatement suivie par une autre oùn=1.59. On attribue la première réaction à la perte d'eau et la seconde à la libération (partielle) d'hydroxyles OH et d'anhydride carbonique CO2.
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![tscy](/content/t48p75u7x430j691/xxlarge1094.gif) ![icy](/content/t48p75u7x430j691/xxlarge1080.gif) 0,45–1,00 ![zcy](/content/t48p75u7x430j691/xxlarge1079.gif) ![acy](/content/t48p75u7x430j691/xxlarge1072.gif) ![vcy](/content/t48p75u7x430j691/xxlarge1074.gif) ![icy](/content/t48p75u7x430j691/xxlarge1080.gif) ![scy](/content/t48p75u7x430j691/xxlarge1089.gif) ![icy](/content/t48p75u7x430j691/xxlarge1080.gif) ![mcy](/content/t48p75u7x430j691/xxlarge1084.gif) ![ocy](/content/t48p75u7x430j691/xxlarge1086.gif) ![scy](/content/t48p75u7x430j691/xxlarge1089.gif) ![tcy](/content/t48p75u7x430j691/xxlarge1090.gif) ![ocy](/content/t48p75u7x430j691/xxlarge1086.gif) ![scy](/content/t48p75u7x430j691/xxlarge1089.gif) ![kcy](/content/t48p75u7x430j691/xxlarge1082.gif) ![ocy](/content/t48p75u7x430j691/xxlarge1086.gif) ![ocy](/content/t48p75u7x430j691/xxlarge1086.gif) ![scy](/content/t48p75u7x430j691/xxlarge1089.gif) ![tcy](/content/t48p75u7x430j691/xxlarge1090.gif) 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![kcy](/content/t48p75u7x430j691/xxlarge1082.gif) ![ocy](/content/t48p75u7x430j691/xxlarge1086.gif) ![lcy](/content/t48p75u7x430j691/xxlarge1083.gif) 19 ![kcy](/content/t48p75u7x430j691/xxlarge1082.gif) ![kcy](/content/t48p75u7x430j691/xxlarge1082.gif) ![acy](/content/t48p75u7x430j691/xxlarge1072.gif) /![mcy](/content/t48p75u7x430j691/xxlarge1084.gif) ![ocy](/content/t48p75u7x430j691/xxlarge1086.gif) ![lcy](/content/t48p75u7x430j691/xxlarge1083.gif) , ![ecy](/content/t48p75u7x430j691/xxlarge1101.gif) ![ncy](/content/t48p75u7x430j691/xxlarge1085.gif) ![acy](/content/t48p75u7x430j691/xxlarge1072.gif) ![softcy](/content/t48p75u7x430j691/xxlarge1100.gif) ![pcy](/content/t48p75u7x430j691/xxlarge1087.gif) ![icy](/content/t48p75u7x430j691/xxlarge1080.gif) - 246 ![kcy](/content/t48p75u7x430j691/xxlarge1082.gif) ![acy](/content/t48p75u7x430j691/xxlarge1072.gif) / . ![Kcy](/content/t48p75u7x430j691/xxlarge1050.gif) ![acy](/content/t48p75u7x430j691/xxlarge1072.gif) ![zhcy](/content/t48p75u7x430j691/xxlarge1078.gif) ![iecy](/content/t48p75u7x430j691/xxlarge1077.gif) ![tcy](/content/t48p75u7x430j691/xxlarge1090.gif) ![scy](/content/t48p75u7x430j691/xxlarge1089.gif) , ![chcy](/content/t48p75u7x430j691/xxlarge1095.gif) ![rcy](/content/t48p75u7x430j691/xxlarge1088.gif) ![acy](/content/t48p75u7x430j691/xxlarge1072.gif) ![zcy](/content/t48p75u7x430j691/xxlarge1079.gif) ![lcy](/content/t48p75u7x430j691/xxlarge1083.gif) ![ocy](/content/t48p75u7x430j691/xxlarge1086.gif) ![zhcy](/content/t48p75u7x430j691/xxlarge1078.gif) ![iecy](/content/t48p75u7x430j691/xxlarge1077.gif) ![ncy](/content/t48p75u7x430j691/xxlarge1085.gif) ![icy](/content/t48p75u7x430j691/xxlarge1080.gif) ![rcy](/content/t48p75u7x430j691/xxlarge1088.gif) ![acy](/content/t48p75u7x430j691/xxlarge1072.gif) ![zcy](/content/t48p75u7x430j691/xxlarge1079.gif) ![dcy](/content/t48p75u7x430j691/xxlarge1076.gif) ![iecy](/content/t48p75u7x430j691/xxlarge1077.gif) ![lcy](/content/t48p75u7x430j691/xxlarge1083.gif) ![yacy](/content/t48p75u7x430j691/xxlarge1103.gif) ![tcy](/content/t48p75u7x430j691/xxlarge1090.gif) ![scy](/content/t48p75u7x430j691/xxlarge1089.gif) ![ncy](/content/t48p75u7x430j691/xxlarge1085.gif) ![ocy](/content/t48p75u7x430j691/xxlarge1086.gif) ![dcy](/content/t48p75u7x430j691/xxlarge1076.gif) ![ncy](/content/t48p75u7x430j691/xxlarge1085.gif) ![rcy](/content/t48p75u7x430j691/xxlarge1088.gif) ![iecy](/content/t48p75u7x430j691/xxlarge1077.gif) ![acy](/content/t48p75u7x430j691/xxlarge1072.gif) ![kcy](/content/t48p75u7x430j691/xxlarge1082.gif) ![tscy](/content/t48p75u7x430j691/xxlarge1094.gif) ![icy](/content/t48p75u7x430j691/xxlarge1080.gif) n=0,90, ![zcy](/content/t48p75u7x430j691/xxlarge1079.gif) ![kcy](/content/t48p75u7x430j691/xxlarge1082.gif) ![ocy](/content/t48p75u7x430j691/xxlarge1086.gif) ![tcy](/content/t48p75u7x430j691/xxlarge1090.gif) ![ocy](/content/t48p75u7x430j691/xxlarge1086.gif) ![ocy](/content/t48p75u7x430j691/xxlarge1086.gif) ![ncy](/content/t48p75u7x430j691/xxlarge1085.gif) ![iecy](/content/t48p75u7x430j691/xxlarge1077.gif) ![mcy](/content/t48p75u7x430j691/xxlarge1084.gif) ![iecy](/content/t48p75u7x430j691/xxlarge1077.gif) ![dcy](/content/t48p75u7x430j691/xxlarge1076.gif) ![lcy](/content/t48p75u7x430j691/xxlarge1083.gif) ![iecy](/content/t48p75u7x430j691/xxlarge1077.gif) ![ncy](/content/t48p75u7x430j691/xxlarge1085.gif) ![ncy](/content/t48p75u7x430j691/xxlarge1085.gif) ![scy](/content/t48p75u7x430j691/xxlarge1089.gif) ![lcy](/content/t48p75u7x430j691/xxlarge1083.gif) ![iecy](/content/t48p75u7x430j691/xxlarge1077.gif) ![dcy](/content/t48p75u7x430j691/xxlarge1076.gif) ![ucy](/content/t48p75u7x430j691/xxlarge1091.gif) ![iecy](/content/t48p75u7x430j691/xxlarge1077.gif) ![iecy](/content/t48p75u7x430j691/xxlarge1077.gif) ![acy](/content/t48p75u7x430j691/xxlarge1072.gif) ![kcy](/content/t48p75u7x430j691/xxlarge1082.gif) ![tscy](/content/t48p75u7x430j691/xxlarge1094.gif) ![icy](/content/t48p75u7x430j691/xxlarge1080.gif) n=1,59. ![Pcy](/content/t48p75u7x430j691/xxlarge1055.gif) ![iecy](/content/t48p75u7x430j691/xxlarge1077.gif) ![rcy](/content/t48p75u7x430j691/xxlarge1088.gif) ![vcy](/content/t48p75u7x430j691/xxlarge1074.gif) ![acy](/content/t48p75u7x430j691/xxlarge1072.gif) ![rcy](/content/t48p75u7x430j691/xxlarge1088.gif) ![iecy](/content/t48p75u7x430j691/xxlarge1077.gif) ![acy](/content/t48p75u7x430j691/xxlarge1072.gif) ![kcy](/content/t48p75u7x430j691/xxlarge1082.gif) ![tscy](/content/t48p75u7x430j691/xxlarge1094.gif) ![icy](/content/t48p75u7x430j691/xxlarge1080.gif) ![pcy](/content/t48p75u7x430j691/xxlarge1087.gif) ![rcy](/content/t48p75u7x430j691/xxlarge1088.gif) ![icy](/content/t48p75u7x430j691/xxlarge1080.gif) ![pcy](/content/t48p75u7x430j691/xxlarge1087.gif) ![icy](/content/t48p75u7x430j691/xxlarge1080.gif) ![scy](/content/t48p75u7x430j691/xxlarge1089.gif) ![acy](/content/t48p75u7x430j691/xxlarge1072.gif) ![ncy](/content/t48p75u7x430j691/xxlarge1085.gif) ![pcy](/content/t48p75u7x430j691/xxlarge1087.gif) ![ocy](/content/t48p75u7x430j691/xxlarge1086.gif) ![tcy](/content/t48p75u7x430j691/xxlarge1090.gif) ![iecy](/content/t48p75u7x430j691/xxlarge1077.gif) ![rcy](/content/t48p75u7x430j691/xxlarge1088.gif) ![vcy](/content/t48p75u7x430j691/xxlarge1074.gif) ![ocy](/content/t48p75u7x430j691/xxlarge1086.gif) , ![vcy](/content/t48p75u7x430j691/xxlarge1074.gif) ![tcy](/content/t48p75u7x430j691/xxlarge1090.gif) ![ocy](/content/t48p75u7x430j691/xxlarge1086.gif) ![rcy](/content/t48p75u7x430j691/xxlarge1088.gif) ![acy](/content/t48p75u7x430j691/xxlarge1072.gif) - ![chcy](/content/t48p75u7x430j691/xxlarge1095.gif) ![acy](/content/t48p75u7x430j691/xxlarge1072.gif) ![scy](/content/t48p75u7x430j691/xxlarge1089.gif) ![tcy](/content/t48p75u7x430j691/xxlarge1090.gif) ![icy](/content/t48p75u7x430j691/xxlarge1080.gif) ![chcy](/content/t48p75u7x430j691/xxlarge1095.gif) ![ncy](/content/t48p75u7x430j691/xxlarge1085.gif) ![ocy](/content/t48p75u7x430j691/xxlarge1086.gif) ![mcy](/content/t48p75u7x430j691/xxlarge1084.gif) ![vcy](/content/t48p75u7x430j691/xxlarge1074.gif) ![ycy](/content/t48p75u7x430j691/xxlarge1099.gif) ![dcy](/content/t48p75u7x430j691/xxlarge1076.gif) ![iecy](/content/t48p75u7x430j691/xxlarge1077.gif) ![lcy](/content/t48p75u7x430j691/xxlarge1083.gif) ![iecy](/content/t48p75u7x430j691/xxlarge1077.gif) ![ncy](/content/t48p75u7x430j691/xxlarge1085.gif) ![icy](/content/t48p75u7x430j691/xxlarge1080.gif) OH CO2.
The material used for this study has been kindly supplied by Dr. P. H. Nixon, former chief geologist, Department of Mines, Maseru, Lesotho. |
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