Cleaner Extraction Of Vanadium From Vanadium-bearing Stone Coal By Hydrometallurgical Method Of Sulfuric Acid Leaching Under Atomospheric Pressure

China is one of the greatest vanadium industry countries in the world,and has an abundant vanadium-bearing resources.Both the production and consumption of vanadium products occupy the first place in the world.As a characteristic vanadium-bearing mineral resources in China,stone coal is one of the important raw materials for producing vanadium products due to its broad distributions and rich reserves.High temperature roasting-acid leaching process is the traditional method of extracting vanadium from stone coal.The method is of short flowsheet,and the process technology is mature.However,the recovery rate of vanadium is low.Moreover,the disposal of industrial wastes cannot meet the standards of national environmental emission.Aiming at the urgent need of the clean production technology upgrading for vanadium extraction from stone coal in China,a suitable technological route of extracting vanadium was proposed based on the process of clean vanadium extraction from vanadium-bearing stone coal by hydrometallurgical method.Firstly,the occurrence state of vanadium and mineral types of stone coal,the process mineralogy of vanadium-bearing stone coal from different regions was characterized to determine the mineral structure.Subsequently,the effect of acid leaching process on the leaching behaviors of vanadium and associated elements were investigated.The key control factors that affected leaching rate of vanadium were discussed to obtain the optimum technology parameters.The experimental results can provide the theoretical and design basis for industrial applications.The main innovative progress is summarized as follows:?1?The process mineralogy of vanadium-bearing stone coal from Shangluo,Shaanxi Province,Huaihua,Hunan Province and Dunhuang,Gansu Province was investigated to ascertain the mineral structure,occurrence state of vanadium and mineral types of stone coal.The results showed that quartz,orthoclase,muscovite and phlogopite were the primary phases in vanadium-bearing stone coal from Shangluo,Shaanxi Province.Furthermore,the distribution rates of vanadium in iron oxides.adsorbed and free vanadium oxides,silicate minerals and organic matter were 27.71%,25.80%,25.05%and 13.35%,respectively.The distribution rate of vanadium in aluminosilicate minerals was low.Thus,it is easy to extract vanadium from this kind of stone coal,which is considered as a typical weathering type stone coal.The phase composition of stone coal from Huaihua,Hunan Province was consistent with that from Shangluo,Shaanxi Province.Nevertheless,it belongs to a semi-weathering type stone coal.Muscovite,vanadium and titanium oxides were the major vanadium-bearing minerals.The diffraction peak intensity of mica minerals in vanadium-bearing stone coal from Dunhuang,Gansu Province was strong.Vanadium was mostly found in silicate minerals.Particularly,the distribution rates of vanadium in silicate minerals and iron oxides were 92.44%and 5.63%,respectively.The distribution rate of vanadium in other minerals was less than 1%.As a result,it was a kind of primary stone coal.?2?The most suitable processing technology for vanadium extraction from different kinds of vanadium-bearing stone coal was proposed,and the optimum technological conditions were obtained.For the vanadium-bearing stone coal from Shangluo,Shaanxi Province and Huaihua,Hunan Province,a high extraction rate could be obtained by simple acid leaching method.92.8%and 80.6%of the vanadium leaching efficiency could be achieved under the following conditions:the H2SO4 concentration of 30%,the liquid-solid ratio of 2 mL/g,the leaching time period of 12 h.For the vanadium-bearing stone coal from Dunhuang,Gansu Province,an excellent leaching efficiency of vanadium could be reached via sulfuric acid baking followed by acid leaching.Under optimized conditions?mineral particle size of-150 ?m,sulfuric acid addition of 73.6%,baking temperature of 250 ?,baking time period of 30 min,acid leaching at 80 ? for 60 min,and liquid/solid ratio of 2 mL/g?,the leaching rate of vanadium reached 94.3%.?3?Leaching behaviors of associated elements of vanadium in stone coal minerals during sulfuric acid baking followed by acid leaching was investigated.The results indicated that Fe and Ca were leached preferentially from Fe and Ca bearing minerals,and V,Al,Mg,K,etc were leached synchronously from mica.The key factors that influenced the baking process were baking temperature,sulfuric acid dosage and baking time.The effects of the three factors on the baking process were same.Firstly,mica decomposed at the presence of sulfuric acid,and KAl?SO4?2 and KV?SO4?2 were generated.Then,Al₂?SO₄?₃ and VOSO₄ were formed under the function of sulfuric acid.