Study On The Extraction Of Vanadium Pentoxide From Low-grade Stone Coal Vanadium Ore

Stone coal is a unique and abundant vanadium-bearing resource in China.However,due to its low grade of vanadium,as well as occurrence state of vanadium and mineral composition are complicated,which result in low level of resource utilization,and a large number of stone coal resources are ready for development.Although there are many vanadium extraction processes and their characteristics are different,problems such as heavy pollution,large energy consumption,long operation cycle,low recovery and purity of products are common.In view of the existing problems in vanadium extraction process and according to the mineralogy characteristics of stone coal vanadium ore,a process of"low-temperature sulfation roasting-water leaching-solvent extraction"is proposed in this paper,and systematic experiments and mechanism studies are carried out for the process.Firstly,from the point of mineralogy,the mineralogical characteristics of the sample are ascertained.Taking the stone coal in Jiangkou County of Guizhou Province as the object of experiment,the grade of V₂O₅ is very low,only 0.62%.And its vanadium occurs in the lattice of aluminosilicate minerals?mica,illite,etc.?in the form of V???as isomorphic phase instead of Al???,which belongs to a low-grade refractory ore.According to the mineralogical characteristics of stone coal vanadium ore,vanadium extraction process of"low-temperature sulphation roasting-water leaching"was determined,and the influence of main factors and internal causes were investigated.The optimum conditions for roasting are as follows:60%of roasting particle size-0.074mm,20%of H₂SO₄ dosage and250?of temperature for 2h.Through valence comparison and mineral changes analysis,it is known that V³⁺in the sample has been converted to higher valence of V⁴⁺and V⁵⁺,meanwhile,the characteristic diffraction peaks of vanadium-bearing aluminosilicate minerals are obviously weakened,which indicate the crystal lattice could be effectively destroyed.The vanadium leaching rate in leaching solution were 80.32%,when the roasting sample was leached for 1.5h at leaching temperature of 90?,liquid-solid ratio of 1.5:1,and agitation speed of 300r/min.The purification and enrichment of leaching solution is determined by the process of solvent extraction.On the basis of optimization of extraction system and pretreatment before extraction,the effects of main factors on extraction and stripping were investigated.Results show that extraction of vanadium with organic phase of"10%P204+5%TBP+85%sulfonated kerosene"has the advantages of good selectivity,fast extraction speed and high extraction rate.Under the conditions of room temperature,O:A=1:4,pH=3.0,extraction time of 5min.Through five-stage countercurrent extraction,the extraction rate of vanadium and iron were over 96%and 6.77%,respectively.A good separation effect of vanadium and iron has been obtained.H₂SO₄ was used as stripping agent in the loaded organic phase,which phase separation speed is fast,the interface is clear and the stripping rate is high.Five-stage countercurrent stripping were carried out at room temperature,H₂SO₄ concentration of 2.0mol/L,stripping time of 15min and phase ratio of O:A=4:l.The stripping rate of vanadium is over 99%,while that of iron is only 4.68%.After extraction-stripping,vanadium can be effectively enriched and most of impurities are removed.The stripping solution can be directly used for vanadium precipitation.Meanwhile,The analysis of chemical behavior of solution extracted by P204 shows that in order to ensure that VO²⁺is the main form of vanadium and reduce hydrolysis of Fe³⁺,the concentration of H⁺should be lowered as far as possible in the range of pH<4.03 to obtain higher extraction rate,and the relationship between extraction and vanadium loss in hydrolysis should be balanced.Vanadium precipitation from stripping solution with acid ammonium salt after oxidation,the influence of main factors and internal causes was studied.Under the optimum conditions,the orange ammonium polyvanadate precipitation?red cake,APV?is crystallized.Finally,High-quality vanadium products can be obtained by calcining.The calculation shows that the recovery rate of purification and enrichment is 94.19%.The total recovery rate of vanadium is 75.65%.Compared with the conventional and traditional vanadium extraction process?recovery rate of vanadium is less than 60%?,the index is greatly improved.The new vanadium extraction process has advantages of low energy consumption,short operation cycle,high recovery and good product purity.The hazards,treatment and recovery methods of pollutants such as dust,gas,residue and waste water was produced in the process of roasting,water leaching,purification and enrichment are analyzed,which gives a basis for clean production of stone coal vanadium ore.