| Vanadium-bearing shale is an important vanadium-containing resource,its reserves are huge and widely distributed in China.In recent years,a lot of scholars have paid attention and researched it.At present,there are some key problems in the vanadium extraction process of vanadium-bearing shales,such as acid consumption and high energy consumption,which restrict the green sustainable development of the vanadium-bearing shale extraction industry.Compared to the conventional techniques,biotechnological is gradually used in many fields such as more and more mineral extraction and secondary resource recycling with its advantages of environmental protection and low cost.According to the current research on the biological extraction of vanadium-containing shales,biological extraction is feasible,but there are relatively few studies.Therefore,based on previous studies,this study took the vanadium-bearing shale in Hubei as the raw material,and the best process parameters in the leaching process on vanadium efficiency has been investigated by Acidithiobacillus ferrooxidans(A.ferrooxidans).In order to improve the leaching effect,the decarbonization of the raw ore and the change of the energy sources of the growth of bacteria were conducted to explore the impact of the leaching process and the leaching mechanism.The results showed that the vanadium efficiency was 27.17% under the conditions of initial pH 2.0,pulp concentration 30 g/L and inoculation amount 10%.When adding 12 g/L pyrite,the vanadium efficiency was 49.45%.In order to further improve the leaching rate of vanadium,the effects of different energy materials on the leaching of vanadium-bearing shale raw ore and decarbonized samples were studied.The promoting effect of energy source on vanadium leaching efficiency is: sulfur> mixed energy substances> ferrous ions.The vanadium bioleaching efficiency of decarbonized samples using sulfur as sole energy and its mixture were 15.36% and 4.71% higher than raw ore,respectively.When ferrous ions were used as sole energy substances,the leaching efficiency of decarburized samples is lower than that of raw ore by 10.28%.The results show that after 20 days leaching with sulfur as the sole energy source,the leaching efficiency of vanadium-bearing shale can respectively reach 47.86% and 63.32%.Finally,in order to improve the leaching efficiency,the leaching process of decarburized samples with sulfur was conducted.At an initial inoculum of 20%,pulp concentration 20 g/L,initial pH 1.8,8 g/L of sulfur powder was added into 250 mL Erlenmeyer flasks in an orbital shaker at 30 °C and 160 rpm.for 30 days,and the vanadium leaching rate reached 74.22%.According to the abnormal phenomenon that the leaching rate decreases after decarbonization,the bioleaching mechanism of raw ore and decarbonized sample with ferrous as sole energy source is explored.The results showed that jarosite is an important factor in the bioleaching process of vanadium-bearing shale,which is also the main problem of the difference between the vanadium-bearing shale raw ore and decarbonized sample.Due to the difference of the composition between the raw ore and the decarburized ore,the formation rate of the jarosite is different during the leaching process.The quickly production of jarosite in the decarburized sample covers the surface of vanadium-contain minerals,resulting in a lower leaching efficiency than the raw ore.Therefore,the energy of sulfur avoids the influence of jarosite,and provides a more stable high acidity atmosphere,which is the key factor to improve the vanadium leaching efficiency from vanadium-bearing shale. |
