Atmospheric Oxidation of Pyrite in the Presence of Lewatit~R AF 5: A Parameters Study

摘要

Previous testwork conducted by the authors indicated the effectiveness of Lewatit~R AF 5, a micro/mesoporous carbonaceous bead, as a catalyst and sulfur sorbent in the atmospheric oxidation of pyrite. A study has been conducted in order to deduce the beneficial parameters of the atmospheric oxidation of pyrite assisted by AF 5, promoting maximum pyrite oxidation and elemental sulfur generation. Tests were conducted in 2 L jacketed reactors fitted with temperature controllers, oxygen spargers and flow metres, reflux condensers and mechanical mixers. The study consisted of multiple tests investigating the effect of temperature (75, 80, 85 and 90 oC), sulphuric acid concentration (0.25, 0.5 and 1.0 M), initial ferric concentration (0, 1, 5 and 10 g/L), pyrite concentrate to carbon catalyst ratio (4:1, 2:1, 1:1 and 1:2), pulp density (5, 10 and 20 %) and the impact of higher oxygen sparging rates (1.0 vs 0.2 L/min) on the atmospheric leaching of a pyrite concentrate assisted by AF 5. Testwork indicated that once AF 5 is added to the system, the above parameters have only a small impact on the oxidation results with two exceptions, temperature and concentrate to catalyst ratio. The best tests in terms of overall pyrite oxidation and elemental sulfur production were experienced by tests incorporating a 1:2 concentrate to catalyst ratio at 90 oC. These tests had an average of 98.1 % overall pyrite oxidation and more importantly, an elemental sulfur yield on average of 62.5 %. Increasing temperature from 75 to 90 oC improved overall pyrite oxidation from 71.9 to 93.6 %, however elemental sulfur yields of approximately 53.1 % were experienced at temperatures below 90 oC versus 49.1 % at 90 oC. Other trends experienced in the investigation of the various parameters will be further discussed.