Purification Technology Of Vanadium Pentoxide By Low Temperature Chlorination With Anhydrous Aluminum Chloride

With the development of modern industry and technology,high-purity vanadium pentoxide finds more and more applications in many fields including vanadium redox flow battery(VRB),vanadium-aluminum alloy,lithium battery and catalyst.Due to the high cost,long flow sheet,heavy pollution and low purity,most of the conventional methods for preparing V2O5 are still in the laboratory stage.The investigations on preparing high-purity V2O5 with a lower cost,shorter and cleaner process has been attracted increasing attention.In this paper,a novel low temperature chlorination method with anhydrous aluminum chloride was proposed.Vanadium can be separated alone from Fe,Al,Si and other impurities,and high-purity vanadium pentoxide can be obtained.Firstly,the technological process was determined on the basis of theoretical analysis and probe test.Then,the conditions and mechanism of chlorination reaction process were systematically studied.In addition,with VOCl3 as the raw material of hydrolysis reaction,the effects of hydrolysis conditions on precipitation rate and product purity were also discussed.High-purity V2O5 was finally obtained.And with three kinds of raw materials,the whole process of preparing high-purity V2O5 was confirmed.The main innovative results of this paper can be summarized as follows:(1)Based on thermodynamic analysis,property analysis and probe test,the whole process to prepare high-purity V2O5 was confirmed.The chlorination reaction between AICl3 and V2O5 is thermodynamically possible.By combination with the boiling points of the different metal chlorides,it is speculated that using AICl3 as the chlorination agent could achieve an effective vanadium separation from other impurities at low temperature.The chlorination process of V2O5 with AICl3 produced intermediate VOCl3 at the temperature of 160℃.Then,after hydrolysis and calcination of intermediate,high-purity V2O5 was obtained.(2)The effects of reaction temperature,raw material ratio,the dosage of additive and others were systematically studied.The optimal conditions of chlorination reaction were determined,and in combination with the analysis of TG-DSC,SEM,EDS,the chlorination reaction mechanism was researched.The optimal conditions are determined as follows:the reaction temperature is at 170℃,the a mole ratio of V2O5:AlCl3 is at 1:6,the dosage of sodium chloride of x=nAlCl3/(nAlCl3 + nNaCl)=0.6.Under the optimal conditions,the reaction time is decreased to 1 h,the extraction of vanadium is 83.35%,and the purity of VOCl3 is achieved as high as 99.95%.The intermediate AlOCl is produced in the process of chlorination reaction.Finally,AlCl3 is all transformed into Al2O3(3)The effects of hydrolysis conditions on precipitation rate and the product purity were investigated.The optimal hydrolysis conditions are determined as a vanadium concentration of 13.4 to 68.8(V2O5)g/L,an ammonium adding coefficient of 0.8 to 1.0,a temperature of 35℃,and a stirring intensity of 15 r/s.Under these conditions,the precipitation rate reaches the maximum value.The purity and the surface information of the obtained product V2O5 are carefully identified by using the analysis of ICP,XRD,XRF and XPS.V2O5 with a purity of 99.97%at least is obtained.(4)Three kinds of V2O5 raw materials,extracted from vanadium titano-magnetite,stone coal and vanadium slag,with an original purity of 96.487%,96.675%,and 25.46%,respectively,were employed to purify and prepare high-purity V2O5.The purities of the obtained V2O5 products were found to be higher than 99.84%,99.97%,and 99.70%respectively.It was confirmed that,the method proposed in this paper provides a new idea for purifying and preparing high-purity V2O5.