Pressure oxidation kinetics of orpiment (As2S3) in sulfuric acid |
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| Affiliation: | 1. Department of Advanced Materials Science & Engineering, Institute of Rare Metal, Mokpo National University, Chonnam 534-729, Republic of Korea;2. Metallic Resources Technology Laboratory, LS-Nikko Copper Inc., Kyunggi 463-400, Republic of Korea;1. CSIRO Mineral Resources, P.O. Box 7229, Karawara, W.A. 6152, Australia;2. TSW Analytical Pty Ltd., P.O. Box 240, Como, W.A. 6952, Australia;1. Discipline of Chemistry and Physics, College of Science, Health, Engineering and Education, Murdoch University, Perth, WA 6150, Australia;2. John de Laeter Centre, Curtin University, Perth, WA 6845, Australia;3. The Njord Centre, PGP, Department of Geosciences, University of Oslo, Oslo, Norway;4. University Grenoble Alpes, University Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre, 38000 Grenoble, France;5. Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506, USA |
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| Abstract: | Pressure oxidation kinetics of a massive orpiment (As2S3) sample in sulfuric acid solution were systematically investigated. The effects of temperature (170 to 230 °C), mean particle size (48 to 125 μm diameter) and oxygen partial pressure (345 to 1035 kPa) were evaluated. Oxidation rates were found to be affected significantly by changes in temperature and particle size, but were relatively insensitive to changes in oxygen partial pressure. Kinetics appear to be controlled by product layer diffusion over the temperature range of 170 to 210 °C, due to the formation of elemental sulfur on particle surfaces. However, Arrhenius activation energies over this range are large (> 40 kJ/mol) and increase with decreasing temperature, perhaps reflecting the kinetics of sulfur oxidation rather than diffusion. Above 210 °C the rate-controlling step is a surface reaction with an activation energy of approximately 33.8 kJ/mol. The reaction order at 210 °C is approximately 0.2 with respect to oxygen partial pressure. |
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