| 题名 | 钒渣液相氧化钒铬高效提取及钒氧化物制备应用基础研究 |
| 作者 | 刘彪 |
| 学位类别 | 博士 |
| 答辩日期 | 2014-05 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 张懿 |
| 关键词 | 钒渣 NaOH-NaNO3 钒铬共提 电解还原 清洁生产 |
| 其他题名 | Applied Fundamental Research on the Effective Extraction of Vanadium and Chromium from Vanadium Slag by Liquid Phase Oxidation and Synthesis of Vanadium Oxides |
| 学位专业 | 化学工艺 |
| 中文摘要 | 钒、铬是我国重要的战略金属资源，在钢铁、化工、航空航天等领域有广泛的应用。我国的钒资源相对较为丰富，但是铬资源极度匮乏，对外依存度高达90%以上。我国钒钛磁铁矿储量巨大，并且含有丰富的钒、钛、铬资源，如何充分利用钒钛磁铁矿中的铬资源，对于应对我国铬资源紧缺的问题具有重要意义。传统的五氧化二钒生产工艺中存在着钒铬转化率低、废气污染环境、产生大量氨氮废水以及钠盐无法回收等问题，本论文以实现钒渣中钒铬的高效同步提取以及钒产品的清洁转化为目的，从改变反应途径着手，提出了钒渣液相氧化及电解还原制备钒氧化物的新方法，并开展了系统的应用基础研究，为钒渣的清洁、高效生产提供理论依据。本论文取得如下创新性进展： (1) 首次将NaOH-NaNO3液相氧化技术应用于钒渣中钒铬的同步提取，研究了钒铬尖晶石在NaOH-NaNO3熔盐体系中的动力学，发现钒铬尖晶石在NaOH-NaNO3体系中的浸出过程符合未反应收缩核模型，钒铬溶出的控制步骤为表面化学反应控制。通过考察不同动力学因素的影响，获得了钒渣分解的最优反应条件：反应温度400 oC，液固比4:1，碱盐比1:1，搅拌转速700 rpm，氧气流量0.4 L/min，反应时间为180 min，钒铬的溶出率分别达到93.7%和81.0%。该工艺实现了钒渣中钒铬的同步提取，并从根本上解决了传统钠化焙烧工艺的废气污染问题。 (2) 系统研究了NaOH-NaNO3二元熔盐体系中NaNO3的稳定性以及氧化性，探讨了NaNO3分解产生活性氧的机制。NaOH可以促进NaNO3分解产生NaNO2和O2，同时抑制NaNO2分解产生氮氧化物(NO、NO2)。在NaNO3分解产生NaNO2的过程中会生成O，O可以与NaOH熔盐体系中存在的O2-结合，生成高活性的过氧根O22-和超氧根O2-，这些活性氧负离子可能是该二元体系具有强氧化性的根本原因。不同熔盐体系的氧化性顺序为：NaOH-NaNO3>NaOH-O2>NaNO3。 (3) 深入阐述了钒渣在NaOH-NaNO3熔盐体系中的氧化分解机理，明确了钒渣氧化过程的活性氧量化调控机制。钒渣中的钒铬尖晶石和橄榄石都是酸性、还原性的氧化物，在NaOH-NaNO3二元熔盐体系中，NaNO3为氧化剂，可以迅速分解产生大量的活性氧，将钒渣中低价态的氧化物氧化为高价态。而NaOH提供碱，与酸性的高价态氧化物反应生成可溶性盐，从而实现钒渣的分解。NaOH-NaNO3为钒渣的分解提供了理想的反应条件，钒铬实现了高效、同步提取。 (4) 应用循环伏安法首次系统研究了碱性溶液中钒的氧化还原特性，发现碱性溶液中的钒酸根有一个还原峰和两个氧化峰，还原峰对应VO43-到V(OH)2的还原反应，两个氧化峰分别对应V(OH)2到V(OH)3和V(OH)3到VO43-的氧化反应。通过研究钒在阴极的还原机理，发现钒酸根的还原反应是一个不可逆的三电子转移过程，第一个电子的转移过程是整个还原反应的控制步骤。 (5) 提出了一种碱溶液中电解还原制备钒氧化物的新方法，通过考察电流密度、温度、钒浓度、碱浓度对电解的电流效率和直流电耗的影响，获得了电解制备钒氧化物的最优条件：电解温度60 oC，钒浓度0.2 M，电解液碱浓度0.4 M，电流密度267 A/m2。最优电解条件下的电流效率为27%，直流电耗为3100 kWh/t。低温电解有利于制得低钠含量的电解产物，20 oC下电解所得到的电解产物的Na2O含量仅为0.53%。该方法可以同步实现钒氧化物的制备和碱的富集，是一种清洁的钒氧化物制备方法。 |
| 英文摘要 | Vanadium and chromium are the strategic metals in China. They play an import role in iron and steel, chemical engineering and aerospace. Vanadium resources are abundant in China. But the chromium resources are extremely scarce and over 90% of the chromium resources are depended on import. In China, they are massive vanadium titano-magnetite deposits which contain abundant vanadium, titanium and chromium. Fully utilizing the the chromium resources in vanadium slag has fundamental significance for the shortage of chromium in China. There are many problems in traditional vanadium pentoxide production, such as the low conversion of vanadium and chromium, the exhaust pollution, the generation of ammoniated waste water and unrecoverable sodium salt. This thesis aimed at the synchronous extraction of vanadium and chromium and cleaner conversion of vanadium products. By altering the reaction pathway, a new synthesis method of vanadium oxides by liquid phase oxidation-electrolysis reduction was proposed, and applied fundamental research was systematically developed. It provided theory basis for the cleaner and effective conversion of vanadium slag. In this thesis, the following results and progresses were achieved: (1) The liquid phase oxidation of NaOH-NaNO3 was firstly introduced in the synchronous extraction of vanadium and chromium from vanadium slag. The decomposition kinetics of vanadium and chromium spinels was studied. It was found that the leaching of vanadium and chromium spinels in NaOH-NaNO3 could be described by unreacted shrinking core model and it was controlled by surface chemical reaction. By investigating various kinetic factors, the optimal reaction conditions were obtained. Under the optimal reaction conditions of decomposition temperature 400 oC, liquid-to-solid ratio 4:1, alkali-to-salt ratio 1:1, agitation speed 700 rpm, oxygen flow rate 0.4 L/min, and reaction time 180 min, the recoveries of vanadium and chromium reach up to 93.7% and 81.0%, respectively. This technology realized the the synchronous extraction of vanadium and chromium. The exhaust pollution problem in traditional soadium roasting was resolved. (2) The stability and oxidation of NaNO3 in the NaOH-NaNO3 binary system was systematically investigated. The generation mechanism of active oxygen species from NaNO3 was studied. The results showed that NaOH could accelerate the decomposition of NaNO3 to produce NaNO2 and O2, but depress the further decomposition of NaNO2 to produce nitric oxides (NO or NO2). In the decomposition process of NaNO3, oxygen atom may be produced and could react with O2- in molten NaOH to produce highly active O22- and O2-, which may explain why the binary molten salts system possessed strong oxidizing. The oxidizing order of molten salts systems were: NaOH-NaNO3>NaOH-O2>NaNO3. (3) The decomposition mechanism of vanadium slag in NaOH-NaNO3 was well described in this work. It cleared the regulatory mechanism of active oxygen during the decomposition of vanadium slag. The spinels and fayalite were acidic and reductive oxides. In the binary molten salts system of NaOH-NaNO3, NaNO3 played a role of oxidant and was quickly decomposed to produce lots of active oxygen, which oxidized reductive oxides to high state. While NaOH worked as a base and could react with high state acidic oxides to form salt. The vanadium slag was well decomposed by NaOH and NaNO3. NaOH-NaNO3 provided an ideal reaction medium for the decomposition of vanadium slag. Thus vanadium and chromium were synchronously and effectively extracted. (4) The redox feature of vanadium in alkaline solutions was firstly systematically investigated by cyclic voltammetry. The cyclic voltammetry of vanadium in alkaline solutions showed a reduction wave and two oxidation waves The cathodic reduction wave was attributed to an three-electron transfer reaction to produce V(OH)2. The two oxidation waves corresponded to the oxidation of V(OH)2 to V(OH)3 and V(OH)3 to VO43- |
| 语种 | 中文 |
| 公开日期 | 2015-07-08 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/15542]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 刘彪. 钒渣液相氧化钒铬高效提取及钒氧化物制备应用基础研究[D]. 中国科学院研究生院. 2014. |
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