基于电化学机理的含钒云母中V(Ⅲ)浸出过程研究

The main occurrence state of vanadium in stone coal is V(III) (trivalent vanadium), and it is difficult to be extracted as the V(III) is embedded in the crystal lattice of the vanadium-containing mica minerals. And for this reason,vanadium leaching rate is low, which is one of the main problems of vanadium extraction from stone coal. It is very difficult to extract this part of the V(III) unless crystal lattice of the vanadium-containing mica is destroyed and V(III) is oxidized to V(IV) or V(V). Because of the lack of knowledge regarding the theory of this process, the relevant scientific issues need further study.Lattice evolution and damage mechanism of synthetic vanadium-containing mica are studied via 27Al MAS NMR，XRD，FTIR and XPS analysis，and the dissolution kinetics of V (III) oxide is studied by means of the dissolution experiments.The electrochemical behavior of V (III) in the presence of oxidizing agent are studied by means of dynamic potential scanning and cyclic voltammetry in the three electrode system. And on this basis, effects of pulp potential on V (Ⅲ) oxidation and vanadium extraction are investigated. Through the above research, dissolution and oxidation mechanism model of V (III) will be established. Research results of this project can provide theoretical foundation for strengthening the leaching process, and can enrich and improve the theory of stone coal leaching process.

石煤中约70%的钒通过取代Al(Ⅲ) 以V (Ⅲ)形式赋存于云母矿物八面体晶格中，常规方法难以将其浸出，导致钒浸出率低，这是石煤提钒亟待解决的主要问题之一。要浸出这部分钒，须破坏云母矿物晶体结构并使V (Ⅲ)氧化。目前，对于这一过程机理认识不够清楚，相关科学问题急需深入研究。本项目从石煤矿石中分离出含钒云母矿物，采用27Al魔角旋转核磁共振、XRD、FTIR、XPS等手段研究含钒云母晶格演变、破坏机制；通过溶解试验，研究V (Ⅲ)氧化溶解动力学；采用三电极体系，通过动电位扫描、循环伏安等手段，研究氧化剂存在条件下V (Ⅲ)电化学行为；在此基础上，研究矿浆电位对V(Ⅲ)氧化及浸出的影响规律。通过上述研究，建立V(Ⅲ)溶出—氧化机理模型，深入揭示含钒云母中V(Ⅲ)溶出机制及浸出过程电化学机理，为石煤酸浸过程强化提供理论支持，拓展和完善石煤浸出理论。

含钒矿物晶体结构破坏和V(Ⅲ)氧化是石煤浸出的关键问题，对这一过程机理一直以来认识不足，相关科学问题亟需深入研究。本项目通过元素溶出试验结合XRD、FTIR、XPS等手段研究了含钒云母晶格演变、破坏机制，研究结果表明，酸浸过程中，含钒云母晶体结构四面体、八面体的结构发生相应调整，破坏的晶面主要是（137）、（208）晶面，晶面间距也发生相应的变化，从而使这些离子赋存状态发生变化，有利于其溶出。含钒云母中元素的溶出与晶体内部晶面间距有关，晶面间距越大，特定元素越易溶出。V (Ⅲ)氧化溶解研究表明，V2O3在硫酸溶液中溶解率随硫酸浓度、时间和温度增加而增加，但其溶解率低。添加 KMnO4、NaClO3、NH4S2O8、Fe2(SO4)3等氧化剂对V2O3的溶解率影响较小。还原剂NaNO2、Na2SO3、FeSO4·7H2O等对V2O5在硫酸中的溶解率有明显影响；还原剂存在时，V(V)被还原成V(IV)，可提高V2O5溶解率。电化学研究结果表明，VOSO4硫酸溶液体系循环伏安曲线中均有很明显的VO2+/VO2+特征峰，FeSO4·7H2O、MnO2、Fe2(SO4)3、NaClO3、NaClO、H2O2、KMnO4、C₆H₈O₇等添加剂对VOSO4电化学行为有不同程度的影响，部分添加剂可以提高溶液的活性。分别以石煤原矿和石煤焙烧料为浸出对象，施加电场，电场对前者钒浸出率影响小，对后者钒浸出率影响大。焙烧过程中低价钒氧化为五价钒，焙烧料施加电场浸出体系中，出现VO2+/VO2+价态转化，钒溶解率增加，钒浸出率提高。通过上述研究，揭示了含钒矿物晶体结构破坏规律极其结构演变历程以及V(Ⅲ)氧化机理，查明了V2O3、V2O5溶解过程中氧化剂、还原剂分别对二者溶解性能影响规律；阐明了V(Ⅲ)在硫酸溶液体系中电化学行为和反应机理；探讨揭示了矿浆电位对V(Ⅲ)氧化及浸出行为的影响。研究成果拓展和完善了石煤浸出过程理论，可为石煤酸浸过程强化提供理论依据。