钒渣钙化酸浸液制备高纯V_(2)O_(5)的工艺研究

Preparation of High-Purity V_(2)O_(5) using an Acidic Vanadium Slag Leaching Solution from Calcification Roasting

钒电解液是钒电池储能系统的关键材料,钒电解液中Mn,Cr,Ti等杂质元素含量对钒电池性能影响很大。高纯V_(2)O_(5)作为钒电解液的重要原料,主要从钒渣钠化焙烧-水浸或者钙化焙烧-酸浸两种工艺获得。本文选取钙化焙烧-酸浸含钒浸出液进行研究,针对其中Mn,Cr,Ti等杂质离子的除杂,形成浸出液水解沉钒—碱溶和净化—铵盐沉钒—煅烧的工艺流程,制备高纯V_(2)O_(5)。确定优化的钒浸出液水解沉钒制备粗V_(2)O_(5)条件为:反应时间为2.0 h,反应pH值为2.2,反应温度为80℃;将获得的粗V_(2)O_(5)进行碱溶二次净化,在优化条件为:NaOH浓度为1%,碱溶终点pH值为8.0,加入阴离子型絮凝剂,温度为60℃时,Mn,Cr,Ti等杂质均得到进一步去除;以经过二次净化后的钒浸出液为原料,在条件为反应时间为60 min,pH值为2.0,温度为90℃,加铵系数(K)为1.2时制备多钒酸铵,再得到高纯V_(2)O_(5),Mn,Cr,Ti等杂质离子都得到了有效去除。

High-purity V_(2)O_(5) is one of the key raw materials of vanadium battery energy storage system,and its demand is increasing withthe development of vanadium battery energy storage technology.At present,China mainly uses converter vanadium slag as the raw materi-al to obtain vanadium-containing leachate through two processes of sodiumization roasting-water leaching or calcification roasting-acidleaching,and then prepare V_(2)O_(5),and then remove impurities to prepare high-purity V_(2)O_(5).Because there are many associated elements inthe vanadium slag,they will be enriched in the leaching solution with vanadium,which will reduce the purity of the vanadium pentoxideproduct,and then affect the performance of the vanadium electrolyte.Theoretically,depending on the vanadium extraction process,thecomposition of the vanadium leaching solution will be different.The metal ions contained in the vanadium leaching solution may includeV,Fe,Mn,Cr,Ti,Na and Ca,and the non-metal ions may include Si,P,S,etc.,these elements not only have variable valence,but alsomay form complex heteropolyacid ions with other ions or ion groups.Using a suitable extractant or exchange resin could recover vanadiumand obtain its high-purity product,but the large amount of extraction method and ion exchange reagent and the long process could not meetthe large-scale production of high-purity V_(2)O_(5) products.At present,the impurity removal of vanadium leaching solution was only a onestep impurity removal,that was,to remove a specific impurity by adjusting the p H or adding a coprecipitation agent,but the impurities ofMn,Cr,and Ti were still high,and the V_(2)O_(5) produced was not suitable for preparing vanadium electrolysis.The main content of this exper-iment included three parts:hydrolysis precipitation of vanadium leaching solution,dissolution and purification of crude vanadium pentox-ide,and vanadium precipitation by ammonium salt.Firstly,the raw materials of the leachate were hydrolyzed to precipitate vanadium toobtain crude vanadium pentoxide product,and part of Mn,Cr,Fe,Mg,etc.were removed.Secondly,the crude vanadium pentoxide wasalkali-dissolved by adding a flocculant to obtain a vanadium purification solution.The resulting waste residue contained the removed impu-rities such as Mn,Mg,Si,and Ti.Finally,the vanadium purification solution was subjected to ammonium salt precipitation by adding am-monium sulfate to obtain ammonium polyvanadate,which was then calcined to prepare high-purity vanadium pentoxide.The effects of hy-drolysis time,hydrolysis temperature and hydrolysis p H on the preparation of crude vanadium pentoxide were studied.The optimal condi-tions for preparing crude V_(2)O_(5) by hydrolysis of vanadium precipitation were as follows:reaction time of 2.0 h,reaction pH value of 2.2,re-action temperature of 80 ℃.Under this experimental condition,the vanadium precipitation rate was 97.9%,the manganese removal ratewas 99.7%,and the chromium removal rate was 61.8%.This process could not remove Ti.According to the scanning electron microscope(SEM)and X-ray diffraction(XRD)analysis of the crude V_(2)O_(5),it could be seen that the crude vanadium pentoxide obtained by the experi-ment had a lamellar structure,mainly composed of V_(2)O_(5)·H_(2)O,and also contained impurities such as MgSO_(4),Mg SiO_(3),K_(3)MnO_(4)CrO_(4),andfurther purification was required.By studying the effect of alkali dissolving endpoint p H and flocculant on the purification of crude vanadi-um pentoxide,and analyzing the influence of ammonium addition coefficient on the rate of vanadium precipitation,the optimal processconditions for crude V_(2)O_(5) purification were determined as follows:Na OH concentration of 1%,final pH value of alkali solution was 8.0.Add an anionic flocculant at a temperature of 60 ℃,and the mass ratio of impurity elements to vanadium in the vanadium purification solu-tion was Mn/V=0.021×10^(-4),Ti/V=0.067×10^(-4),Cr/V=0.13×10^(-4).Under the conditions of a reaction time of 60 min,a pH value of 2.0,a tem-perature of 90 ℃,and an ammonium addition coefficient(K)of 1.2,the obtained vanadium purification solution was prepared into highpurity V_(2)O_(5),and the vanadium precipitation rate could reach 99.2%,which could effectively remove impurities Mn and Ti,Cr.The ammo-nium polyvanadate product was prepared according to the optimal conditions obtained by hydrolysis and precipitation of vanadium,alkalisolution and purification,and ammonium salt precipitation of vanadium.According to XRD pattern of ammonium polyvanadate,it couldbe known that all the characteristic peaks of ammonium polyvanadate were in the pattern,and there were no other impurity peaks.The am-monium polyvanadate product obtained in the experiment was relatively pure.After drying the ammonium polyvanadate,it was calcined ina muffle furnace at 550 ℃ in an oxidizing environment for 2 h to obtain the final powdered V_(2)O_(5) product.According to the SEM image of V_(2)O_(5),it could be seen that it was mainly a sheet structure.It could be seen from XRD pattern that the main component of the product was V_(2)O_(5),and no characteristic peaks of other substances were found,and the main impurities had been effectively removed.Chemical analy-sis showed that the purity of high-purity V_(2)O_(5) products was greater than 99.9%.In this paper,a multi-step impurity removal method wasused to study the purification of vanadium leaching solution,and a high-purity vanadium pentoxide product with a purity greater than 99.9% was prepared.This method may have a certain enlightenment for the preparation of industrial high-purity vanadium pentoxide.