Preparation Of Vanadium Dioxide Powder By Separation And Purification Of Vanadium Leaching Solution

Vanadium dioxide(VO₂)has a phase transition at 68°C.At this time,the physical and chemical properties of VO₂ have a mutation,which is widely used in smart windows,photoelectric switches,supercapacitors and other fields.Because of the numerous valence states of vanadium,it is difficult to prepare pure phase VO₂.At present,it has become increasingly mature that the process of extracting vanadium from stone coal to prepare high-purity vanadium pentoxide(V₂O₅),but the preparation of low valence vanadium oxides from stone coal is rarely reported.In this paper,VO₂ powder was prepared from Xiangxi stone coal vanadium ore by acid leaching,separation and enrichment,and redox.A process method for direct preparation of VO₂ from stone coal vanadium ore,which provides a new way for the preparation of VO₂ powder.Xiangxi stone coal was used as raw material,and manganese dioxide(Mn O₂)was added as leaching aid.The effects of leaching aid dosage,leaching time,leaching temperature,liquid-solid ratio and sulfuric acid concentration(volume fraction)on leaching rate were investigated.The experimental results showed that the vanadium grade in stone coal vanadium ore is 1.2%.The vanadium leaching rate was 93.20%under the conditions of Mn O₂ dosage of 2%,leaching time of 10 h,leaching temperature of 90°C,liquid-solid ratio of 1:1,and sulfuric acid volume concentration of25%.The adsorption and desorption of simulated vanadium solution by ion exchange resin was conducted.The effects of resin type,adsorption p H value,adsorption temperature and flow rate on adsorption were investigated.Effects of type and flow rate of resolvent on resolution.Under the optimal conditions,the actual system adsorption and desorption of vanadium-containing leaching solution were carried out.The experimental results showed that SQD 816-3*resin had the best adsorption effect on vanadium.Under the optimal conditions,the maximum static and dynamic adsorption capacities of the actual system were 255.0 mg/g and 196.6 mg/g,respectively.The static and dynamic analysis rates were 90.48%and 91.15%,respectively.The experimental adsorption model and kinetic study showed that the adsorption process of SQD 816-3*resin conformed to the Langmuir isothermal adsorption model.The control step was the combined control of intraparticle diffusion and chemical reaction,and the reaction order was the pseudo-second-order reaction process.The vanadium leaching solution can be treated with ion exchange resin to achieve satisfactory separation and purification effect.VO₂ powder was prepared by hydrothermal method using sulfur powder as reducing agent,high purity V₂O₅ and vanadium eluent as vanadium sources respectively.When V₂O₅ was used as vanadium source,the optimal reaction conditions were as follows:reaction p H=6,n(S):n(V₂O₅)=0.7:1,reaction time 32 h,reaction temperature210°C,vanadium solution concentration 10 g/L.After calcination at 650°C for 3 h in argon atmosphere,the purity of VO₂ was 97.40%.When vanadium eluent was used as raw material,the purity of VO₂ was 95.40%.The advantage of this method is that the reducing agent is cheap and easy to obtain,the process is simple,and has certain economic benefits.VO₂ powder was prepared by chemical precipitation method with Fe powder as reducing agent,high-purity V₂O₅ and vanadium eluent as vanadium sources,respectively.The effects of p H value,reduction temperature,reduction time,dosage of reducing agent,precipitation temperature and precipitation time on the purity of VO₂were discussed when V₂O₅ was used as vanadium source.The purity of VO₂ was98.32%and 97.01%,respectively,using high-purity V₂O₅ and vanadium eluent as vanadium sources.DSC analysis showed that the phase transition temperatures were68.82°C and 63.67°C,respectively.Affected by size effect and purity,the phase transition temperature of VO₂ prepared with vanadium eluent as vanadium source was lower than the theoretical value of 68°C.XRD and SEM showed that the product had a single component and high purity.