【作者】 李望；

【导师】 张一敏；

【作者基本信息】 武汉科技大学 ， 化学工艺， 2013， 博士

【摘要】 强酸浸出作业因其钒回收率高、原料适应性广等特点而广泛应用于石煤提钒工艺。但强酸浸出机制下，固然钒浸出率大幅度提高，亦造成多种杂质元素如Fe、Al、Mg、K、Na等大量进入酸浸液，且残余氢离子浓度较高，从而形成高酸多杂质含钒溶液。此类含钒溶液具有杂质离子种类多、浓度高，pH值极低，钒浓度不能直接沉钒等特征，其杂质离子的去除、酸的回收和钒的富集是强酸提钒工艺的关键环节。本文系统研究了高酸多杂质含钒溶液的膜分离预处理方法、对比酸性体系中钒及各杂质离子的离子交换及萃取行为特性，结合钒及杂质离子在离子交换及萃取过程中的热力学和动力学分析，提出膜分离回收酸—溶剂萃取去除杂质离子富集钒的高酸多杂质含钒溶液分离纯化工艺；研制出酸分离及钒截留效果良好的新型阴离子交换膜，并通过红外光谱、核磁共振等检测手段对阴离子交换膜进行了表征。湖北某地石煤经焙烧—硫酸浸出后，得pH为-1.08的多杂质酸浸液，利用市售DF120型阴离子交换膜对该高酸多杂质酸浸液进行预处理以分离回收硫酸。研究表明：在料液流速为0.21×10^-3m³/（h·m²），水料流速比为1.1～1.3的条件下，硫酸的回收率可达84%，钒、铝和铁的截留率分别为93%、92%和85%，证实阴离子交换膜预处理高浓度酸浸液具有酸回收率高和钒的截留效果良好的特点。阴离子交换膜预处理酸浸液的过程中，钒、铝和铁离子的截留率随料液流速的增加而增加，随水料流速比的增加而减小；硫酸回收率和金属截留率（Ⅴ，Al和Fe）均随金属离子浓度的增加而增加。处理后酸浸液的pH值由-1.08升至0.8，满足后续净化富集要求。但DF120型阴离子交换膜在长时间使用后易出现水反渗透现象。对经DF120型阴离子交换膜预处理后pH值升至0.8的含钒酸浸液进行离子交换和溶剂萃取的净化富集对比研究。离子交换试验结果表明：ZGA414树脂具有最优的吸附Ⅴ（Ⅴ）的性能，而树脂对Ⅴ（Ⅳ）的吸附能力较低；酸浸液中Fe（Ⅲ）杂质对树脂吸附Ⅴ（Ⅴ）的负面影响最为显著，Fe（Ⅲ）会导致树脂中毒；其他杂质离子如Al、Mg和K对树脂吸附Ⅴ（Ⅴ）无明显影响。ZGA414树脂吸附Ⅴ（Ⅴ）的热力学研究结果表明Ⅴ（Ⅴ）在树脂上的吸附过程是吸热过程，符合Freundlich等温吸附方程，吸附热力学参数△H=3.97kJ/mol，△S=47.83J/（mol/K），△G298.15=－10.29kJ/mol；ZGA414树脂对Ⅴ（Ⅴ）的吸附动力学研究表明该过程符合拟二级吸附交换动力学过程，pH为2.0时Ⅴ（Ⅴ）理论吸附量为217.39mg/g，吸附速率常数k298.15=0.0011g/（mg·h），同时该吸附过程主要受颗粒扩散控制。萃取试验结果表明：在15%D2EHPA为萃取剂、5%TBP为相调节剂、O/A为1:1条件下，Ⅴ（Ⅳ）的萃取率显著高于Ⅴ（Ⅴ），而Fe（Ⅲ）浓度大于5g/L时将严重影响Ⅴ（Ⅳ）的萃取；Fe（Ⅱ）、Al、Mg、Na和K等杂质离子对钒的萃取影响较小。该体系下Ⅴ（Ⅳ）的萃取热力学表明萃取反应的表观平衡常数K=0.9152，△H=9.367kJ/mol，△S=0.031J/（mol/K），△G298.15=0.22kJ/mol；Ⅴ（Ⅳ）的萃取机理研究表明D2EHPA对Ⅴ（Ⅳ）的萃取在溶液pH较低（<1.0）时生成VOR₂（HR）2，而在高pH值（>1.5）条件下生成VOR2；在pH值为1.5时，硫酸介质中Ⅴ（Ⅳ）对Fe（Ⅲ）和对Fe（Ⅱ）的分离系数分别为1.6和102，D2EHPA对三种离子萃取顺序为：Ⅴ（Ⅳ）>Fe（Ⅲ）>Fe（Ⅱ）。通过离子交换和溶剂萃取的净化富集对比研究确定：溶剂萃取法更适合于酸性体系多杂质含钒溶液的杂质离子去除和钒富集，实际含钒酸浸液进行五级萃取八级反萃试验，钒回收率可达99%。为克服市售DF120型阴离子交换膜易出现水反渗透现象的缺陷，采用聚苯醚（PPO）为基底膜材料，以PPO:Br2<1.42质量比加入溴水25°C反应3h，再150°C溴化改性8h后，PPO苯环及苯甲基位置被溴化总量为96%，通过控制PPO苯环和苯甲基位置的溴化取代度控制成膜的亲水性。采用平板刮膜的制膜方式，制得均质无孔溴化聚苯醚（BPPO）基膜；BPPO基膜与氨水交联后，再用三甲胺和乙二胺混合溶液（TMA:EDA=2:1）于45°C左右胺化16h，研制出机械性能良好的新型阴离子交换膜。通过静态扩散渗析试验，确定新型阴离子交换膜的酸分离及钒截留效果良好，同时膜的水反渗透现象得到缓解；通过红外光谱、核磁共振、电镜扫描以及接触角测定等手段对该阴离子交换膜进行表征，表明膜制备过程中溴化反应是影响后续胺化反应及阴离子交换膜制备效果的关键步骤，同时适当提高聚苯醚苯环位置溴化取代度和在一定范围内提高膜交联度可降低膜的水反渗透现象。更多还原

【Abstract】 The sulfuric acid leaching is broadly employed in vanadium extraction from stone coal, which is characterized by high vanadium recovery and wide adaptability for raw ore. However, as the vanadium recovery increases significantly with this strong acid leaching method, many impurities including Fe, Al, Mg, K, Na etc. are leached with vanadium at the same time. And also the residual H+concentration is too high in acid leaching solution. The above vanadium solution is characterized by variety of impurities and their high content, super low pH value and low vanadium concentration for precipitation recovery. So the key steps for vanadium recovery after this strong acid leaching process are separating impurities, recovering acid and concentrating vanadium.The methods for pre-treating acid leaching solution with variety of impurities are discussed. The extraction and ion exchange behaviors of vanadium and various impurities in acid system are investigated contrastively. The extraction and ion exchange of thermodynamics and kinetics are theoretically analyzed. The suitable separation and purification process for vanadium extraction from above acid leaching liquid is determined, which is vanadium acid solution-sulfuric acid separated by membrane-purified by solvent extraction-vanadium precipitation. And a new anion exchange membrane (AEM) was made for high acid recovery and vanadium rejection. The Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear magnetic resonance (NMR) are employed for characterization of its function groups.The acid leaching solution with variety of impurities is obtained by roasting-sulfuric acid leaching process to the stone coal from Hubei area, of which the pH is-1.08. The commercial DF120AEM is used to recover sulfuric acid as a pre-treatment method from above acid solution. The results show that sulfuric acid recovery can reach to84%, and vanadium, iron and aluminum rejection can attain93%,92%and85%with the feed flow rate of0.21×10-3m3/(h·m2), flow rate ratio of water and feed of1.1-1.3. The AEM is proved to be characterized by high recovery of acid and well V rejection for pre-treating the strong acid solution. The rejection of V, Al and Fe ions are found to increase with the increase of feed flow rate and the decrease of the flow rate ratio of water to feed. Both the acid recovery and metal ions (V, Al and Fe) rejections are increased by raising the concentrations of these ions. The pH value of treated solution increases from-1.08to0.8, which meets the requirement of the next separation and concentration process. But the DF120AEM has a serious water osmosis problem after long term use.The comparison study of ion exchange and solvent extraction is conducted after the vanadium acid leaching solution is pre-treated by DF120AEM, where the pH increases to0.8. Ion exchange test results show that ZGA414resin has the optimal adsorption performance of V(V), and the resin has the lower adsorption capacity of V(IV). Fe(III) has the most serious negative influence on V(V) adsorption in the acid leaching solution, which leads to resin poisoning. Other impurity ions such as Al, Mg and K have no obvious effect on V(V) absorption. Thermodynamic research results show that the V(V) absorption on the ZGA414resin is endothermic process, which is in accordance with the Freundlich isothermal adsorption equation. The adsorption thermodynamics parameter ΔH=3.97kJ/mol, ΔS=47.83J/(mol/K), ΔG298.15=-10.29kJ/mol. Kinetics study of V(V) adsorption on ZGA414resin shows that the process is in line with the simulative secondary exchange kinetics of adsorption process. The theory maximum V(V) adsorption content is217.39mg/g at pH value of2.0, and the adsorption rate constant k298.15=0.0011g/(mg-h). At the same time, the adsorption process is mainly controlled by particle diffusion. Extraction test results show that the V(IV) extraction ratio is significantly higher than that of V(V) under the condition of the O/A1:1with15%D2EHPA as extraction agent and5%TBP as the phase modifier. The effect of Fe (II) on the V(IV) extraction is not obvious, but the V(IV) extraction is seriously affected while Fe(III) concentration is higher than5g/L. Al, Mg, Na and K have no obvious negative effect on vanadium extraction. V(IV) thermodynamics study in this system shows that the extraction reaction apparent equilibrium constant K=0.9152, ΔH=9.367kJ/mol, ΔS=0.031J/(mol/K), ΔG298.15=0.22kJ/mol. The extraction mechanism of V(IV) with D2EHPA studies have shown that VOR2(HR)2compound generated when pH value is low (<1.0), and VOR2compound generated under the condition of high pH value (>1.5). Separation factor of V(IV) to Fe(III) and Fe(II) in sulfuric acid medium is1.6and102respectively at pH value of1.5. Sequence of three kinds of ion extractions with D2EHPA is:V(IV)> Fe(III)> Fe(II). So solvent extraction is a more suitable separation and purification technology to separate impurities and concentrate vanadium from acid leaching solution with variety of impurities in this study. The vanadium recovery can reach to99%by a five-stage extraction and a eight-stage stripping process from the real acid leaching solution.The water-osmosis problem is easily found when the commercial DF120AEM is used. For overcoming this defect, the polyphenylene oxide (PPO) is used as a base membrane material. The bromination of PPO is operated with weight ratio of PPO:Br2<1.42first at25℃for3h and then at150℃for8h, and the total bromination degree of aryl and benzyl position of PPO is96%. The hydrophility of membrane can be controlled by changing the bromination degree in aryl and benzyl position of PPO. The homogeneous and nonporous brominated PPO (BPPO) is prepared by using casting film forming method. The base BPPO is cross-linked by ammonia solution and aminated with trimethylamine(TMA) and ethylenediamine(EDA) mixed solution (TMA:EDA=2:1, v/v) for16h at45℃. The novel AEM with well mechanical property is fabricated. Static diffusion dialysis experiment with this new membrane is carried out, the acid recovery and vanadium rejection is good and the water-osmosis problem is solved. FTIR, NMR, SEM and contact angle tests are used for this AEM characterization. It is certified that the film bromination reaction significantly is the key step for the followed amination reaction and the properties of the final film in the whole preparation process. The water-osmosis problem can be solved by properly increasing aryl bromination degree and amination cross-linking degree within a certain degree.更多还原