基于微乳液的含铬钒渣钠化焙烧熟料中钒铬的浸提与原位分离方法及调控机制

Extraction of vanadium and chromium from the chromium-bearing vanadium slag is the key point to increase the comprehensive utilization extent of the high chromic vanadium titanomagnetite ore. All the present extraction methods of them are limited by the difficulty in separation of sodium vanadates and sodium chromates in aqueous solution. The W/O microemulsion is a thermodynamically stable and uniform dispersion system in which nano scaled water drops disperse in hydrophobic solvents, which can extract metal ions at high efficiency. Preliminary research results show that microemulsion can selectively reduce sodium chromate, in the mixture with sodium vanadates, to Cr3+ cations that can be separated from vanadate anions more easily. Based on this discovery, the novel idea of microemulsion leaching and in-situ separation has been proposed to extract vanadium and chromium in the sodium roasted chromium-bearing vanadium slag. Using microemulsion system as leaching reagent, sodium vanadates and sodium chromates could be extracted, during which sodium chromates will be selectively reduced and thus separated from vanadates by emulsion extraction, which is “in-situ separation”. Combing microstructure characterization technique such as FFTEM-EELS and analytical chemistry determination methods such as SPR, the phase transfer rules of vanadium-bearing phases and chromium-bearing phases and their separation mechanism at molecular level will be revealed. By this way, the method of microemulsion leaching and in-situ separation can be thus established, together with the regulating mechanism of leaching and in-situ separating vanadium and chromium. Research results from this project will promote developing the green and efficient technology process of comprehensive utilization for the high chromic vanadium titanomagnetite ore in China.

含铬钒渣中钒、铬的提取是决定高铬型钒钛磁铁矿资源综合利用度的关键。当前各种钒铬提取技术都难以绿色、经济地分离含钒物相与含铬物相。油包水型微乳相是纳米级水滴均匀分散在油性溶剂中的稳定分散体系，能高效萃取金属离子；且我们前期研究发现，该型微乳相能选择性还原钒酸钠与铬酸钠混合物中的铬酸钠为Cr3+阳离子而使铬易于与含钒阴离子分离。基于此，本项目提出“微乳液浸提与原位分离钒铬”的构想。以微乳液体系为浸提剂，浸提含铬钒渣钠化焙烧熟料中钒酸钠与铬酸钠的同时选择性还原铬酸钠并萃取分离钒、铬（即“原位分离”）。联用FFTEM-EELS等材料微观结构表征技术与SPR等分析化学表征方法，探明含钒物相与含铬物相在微乳液浸提与原位分离过程中的相转移规律与分子尺度分离机理，建立“微乳液浸提与原位分离法”，获得浸提与原位分离钒、铬的调控机制。该项目的研究将推动我国高铬型钒钛磁铁矿资源绿色高效综合利用新工艺技术的发展。

在高铬型钒钛磁铁矿资源即将战略开采的时代背景下，针对其冶炼产生的高铬型钒渣中钒、铬资源的分离与提取难题，本项目利用微乳液的高容量特性开展了钒、铬分离方法及微乳液浸提钒方法的研究，解决了钒、铬高效分离的难题。首先建立了稳定、高效、选择性萃钒的微乳液体系。利用第一性原理理论计算与实验研究相结合，深入研究了萃取剂分子与钒多酸分子的相互作用机理，揭示了钒多酸分子的自适应性结构转变机制：在季铵盐阳离子诱导下，钒多酸分子由V-O八面体配位的V10O28^6-结构转变为V-O四面体配位的V10O26^2-结构，其原子堆积密度更加松散。基于微乳液选择性萃钒，建立了溶液中钒、铬的微乳液高效分离方法，以解决提钒浸出液及钒产业废弃物（危废）中钒、铬的分离回收难题。将该法应用于沉钒废水处理，可成功分别回收其中96.29%的钒、95.56%的铬元素。基于该法处理钒铬还原渣，钒回收率为96.32%、所得V2O5产品纯度为99.60%，铬回收率为92.68%、所得Cr2O3产品纯度为98.83%。当用该法处理铬泥时，钒回收率为95.53%、产品V2O5纯度99.34%，铬回收率92.68%、产品Cr2O3纯度98.25%，铁回收率98.25%、产品FeC2O4纯度99.12%。基于萃取剂分子对钒多酸形态的调控机理，建立了基于微乳液萃取的溶液态钒、磷分离方法，分离系数高达22000。将该法用于高磷钒渣中钒、磷的分离，钒回收率为87.3%、产品V2O5纯度为99.7%。在上述研究基础上，考虑增溶水量问题，采用以二乙基己基磷酸为萃取剂的微乳液体系直接浸提钒渣钠化焙烧熟料中的钒，建立了钒渣熟料的微乳液浸提法。该法将钒提取与纯化同步完成，在保证钒回收率达79.57%的前提下，缩短了高纯钒制品的制备流程。本项目的研究成果完善了钒多酸化学理论，推动了我国高铬型钒钛磁铁矿资源绿色高效综合利用技术的发展。