| Vanadium-a significant strategic resource has been widely used in steel,chemical and other industries,its development and utilization are particularly important.However,there are some problems in the traditional vanadium extraction process,such as serious environmental pollution and low recovery rate of vanadium.So,in this paper,a new process of low temperature sulfating in situ activation roasting-water leaching was proposed to treat bauxitetype vanadium ore.The investigation of process mineralogy characteristics revealed the interaction between vanadium and gangue minerals,which provided the mineralogy separation basis for vanadium extraction.In addition,to identify the optimal technological parameters,the impacts of various factors have been comprehensively explored,which affected the vanadium leaching recovery in the process of low temperature sulphating roasting and water leaching.This paper focused on the study of mineral phase evolution in the process of low temperature sulfating roasting-water leaching,mastered the action mechanism affecting vanadium extraction and laws of thermodynamic change,and established the corresponding kinetic model through the study of vanadium leaching process.All the above research categories could provide a new technical scheme for efficient vanadium extraction from bauxite-type vanadium ore;besides,they were of important practical significance for promoting the development of complex refractory vanadium ore resources.(1)The results of process mineralogy of bauxite type vanadium ore showed that:In bauxitevanadium ore,the vanadium mainly occurs in aluminosilicate minerals with two forms of V3+and V4+,vanadium elements are closely associated with aluminum,and usually in the form of isotropy to replace Al3+,Fe3+ in the mineral lattice.The size of mineral particles varied widely with most particle diameters in 0～10 μm,and very few particles’ diameters were larger than 100 μm.The particle shape was mainly irregular flakes and fine grain.(2)Based on the study of process mineralogy,experiments have been carried out to research affecting factors on separation of vanadium from the bauxite-vanadium ore by the new process of low temperature sulfating in situ activation roasting-water leaching.It achieved a high vanadium leaching recovery of 90.57%,vanadium was separated and enriched under the following conditions:mixing the-0.096 mm raw ore with 40 wt.%sulfuric acid,roasting for 120 minutes at 250℃ to obtain the roasted product,leaching the roasted product at 60℃ with an L/S ratio of 3:1 mL/g and added 6 wt.%ammonium molybdate as an aid,leaching for 120 minutes.In the end,the vanadium content in the leaching residue was only 0.098%.(3)Research on the mechanism of roasting and leaching processes showed that:Under the synergistic action of sulfuric acid and rising temperature,the major vanadium-bearing mineral illite was degraded and reacted to generate munirite and misenite during the roasting process.V3+was liberated from aluminosilicate mineral crystals to participate in the oxidation reaction and converted to V5+.Gypsum was formed when calcite combines with sulfuric acid.During the water leaching process,leftover sulfuric acid in calcine decomposed H+to generate an acidic environment that promoted munirite decomposition in an aqueous solution,and vanadium elements enter the leaching solution as VO3-or H2VO4-to form vanadium-rich solution.(4)Under the experimental temperature conditions,the reaction of metal oxides such as V2O3,K2O,CaO,Al2O3,and MgO with sulfuric acid could be spontaneous,and the rising of temperature promoted the formation of water-soluble NaVO3,which created favorable conditions for vanadium extraction via water leaching.At room temperature,the hydrolysis reactions of NaVO3 and K2SO4 could not occur spontaneously,although the hydrolysis reactions of Al2(SO4)3 and MgSO4 might occur spontaneously at a lower temperature,increasing the temperature would impede the reaction.The thermodynamic analysis validated the thermodynamic viability of the low temperature sulfating roasting-water leaching vanadium extraction process and gave theoretical support for optimizing roasting and leaching parameters.(5)The leaching process of bauxite calcined vanadium ore conformed to the mixed control model of the unreacted shrinkage core model,which means that the leaching process was controlled by diffusion and chemical reaction at the same time.The leaching process had an apparent activation energy E=32.74 kJ/mol,a frequency factor A=8.414 s-1,a vanadium leaching reaction recovery constant k(v)and the functional relationship between the temperature T fork k(V)=8.414exp(-3.94×103/T). |
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