Study On The Effect And Mechanism Of Calcium Roasting Additive On Extracting Vanadium From Vanadium-bearing Black Shale

Most of the vanadium in the mica type vanadium shale is stable in the mica octahedral stable structure,and the structure is difficult to destroy.It is very important to destroy the aluminosilicate mineral structure in the mica type vanadium shale under the action of additive and high temperature,and release vanadium from the target element into the solution.In order to improve the vanadium leaching rate,while reducing the pollution of the environment.In this paper,vanadium was leached by acid after adding calcium additive and roasting vanadium-bearing black shale under high temperature conditions.The roasting mechanism of calcium roasting additive and the effect on the extraction process of vanadium were discussed.The results of this study showed that roasted clinker can be obtained under the conditions of adding 6% CaO,4% CaF₂,roasting temperature 850? and roasting time 90 min.the leaching rate of vanadium can reach 86.74% in the calcified roasting under the conditions including leaching temperature of 95?,the sulfuric acid concentration of 15%?v/v?,leaching time of 2 h,and ratio of liquid to solid of 3 mL/g.At the same roasting temperature and roasting time,the calcified clinker obtained by adding the additive can obtain higher vanadium leaching rate and the leaching rate of vanadium is higher than that of the blank roasting clinker under the same leaching conditions.CaO and V₂O₅ in the calcium calcination additive react with each other to produce calcium metavanadate,calcium vanadate,in which the reaction ?G^? of the calcium metavanadate is minimized.CaO in calcium calcination additive has a good affinity for V₂O₅.Roasting can promote the reaction of CaO with vanadium oxides to produce calcium vanadate which is insoluble in water but soluble in acid.F-in the CaF₂ has a strong diffusivity,the mica structure Si-O tetrahedron,Al-O octahedral oxygen bond breakage,low-valent vanadium exposed,is conducive to the oxidation of vanadium into soluble high valence vanadium.And the addition of the roasting additive causes the calcination method to have a certain desulfurization effect.The sulfur content in the roasted clinker was 0.94% at the time of blank roasting to 1.94% of calcified roasting.The sulfur element in the Vanadium-bearing black shale is fixed in the form of gypsum during the calcination process,reducing the pollution to the atmosphere and realizing the cleaner production.The kinetic study showed that the activation energy of acid leaching reaction decreased from 42.50 kJ/mol in the blank roasting to 22.56 kJ/mol in the activation roasting,and the reaction order decreased from 1.15 to 0.85.Activated roasting has a good mineral activation,which can accelerate the leaching of vanadium and reduce the dependence on high temperature and high acid in leaching process.