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钨钼在自然资源中常常伴生共存，并且在水溶液中的化学性质十分相近，因而钨钼分离引起了广泛的关注。目前，钨钼分离的研究主要集中在改变操作参数、优化工艺流程、开发新型沉淀剂和萃取剂等方面，而忽略了离子形态对钨钼回收和分离过程的影响。因此，为了探究离子形态在钨钼回收和分离过程中的作用，本文搭建了二级串联环隙式离心萃取器耦合电喷雾-飞行时间-质谱（ESI-TOF-MS）的在线监测平台，首先对酸性水溶液中钨钼离子形态聚合转化规律进行了研究，其次探究了伯胺N1923萃取回收钨钼过程中离子形态转化路径与宏观萃取反应之间的关系，最后探讨了钨钼离子形态对钨钼混合体系中钨去除效果及钼酸钠溶液净化程度的影响，取得的创新性结果如下：（1）采用ESI-TOF-MS表征方法研究了酸性水溶液中钨、钼离子形态分布，监测到了W1、W2、W4、W6、W10、W12等多种钨形态及Mo1、Mo2、Mo3、Mo4等多种钼形态，与拉曼方法相比具有优越性。同时，考察了监测过程中样品锥电压和源温对钨、钼离子形态分布的影响，确定最优锥电压和源温分别为20 V，60 °C。并进一步研究了酸种类、初始溶液浓度、溶液pH对钨、钼离子形态聚合转化的影响，结果表明，不同酸种类和初始溶液浓度在一定程度上影响钨、钼酸离子形态的聚合转化；钨、钼离子形态分布主要取决于溶液pH；钼形态更容易与溶液中酸根阴离子杂化。最后，总结了酸性水溶液中钨、钼离子形态聚合转化示意图。（2）基于环隙式离心萃取器耦合ESI-TOF-MS在线监测平台，对伯胺N1923回收钨、钼过程中宏观萃取反应和微观离子形态转化路径进行了研究。结果表明：伯胺N1923是一种高效萃取钨、钼的萃取剂，并且钼萃取反应比钨萃取反应更加迅速；钨萃取反应过程中，W1是非活性形态，仅参与钨离子平衡反应而不参与萃取反应，W10较其他形态更活泼并且更容易被萃取到有机相中；钼萃取反应过程中，当初始溶液中出现MoO3Xn-（X为酸介质阴离子）后，它会取代Mo4成为活性形态被优先萃取到有机相中。（3）利用在线监测平台对伯胺N1923分离钨钼混合体系中萃取反应及离子形态对钨去除效果、钼酸钠溶液净化效果的作用关系进行了研究。结果表明，在竞争萃取过程中，钨优先于钼被萃取，并且随着钨钼比的降低，钨的优势会越来越明显；监测到Mo1-Mo5、HWO4-及钨钼杂化离子形态NaMoWO7-、NaMo2WO10-和NaMo3WO13-，杂化离子会优先与伯胺N1923结合被萃取到有机相中，钨形态中杂化离子的相对含量越高越有利于钨的去除，此外，初始溶液中杂化离子的相对含量越高，得到钼酸钠溶液的纯度越高。;Tungsten and molybdenum often co-exist in natural resources, and the chemical properties in aqueous solution are very similar, so tungsten-molybdenum separation has always been the focus of attention. Most of the previous studies focused on changing operational parameters, technological process or developing new precipitants and extractants to optimize the separation of tungsten and molybdenum. However, the relationship between speciation and tungsten-molybdenum recovery/separation process has not been considered. To this end, this paper set up two-stage annular centrifugal contactors (ACCs) coupled electrospray-time of flight-mass spectrometry (ESI-TOF-MS) on-line monitoring platform to (1) investigate the polymerization and conversion rules of tungsten and molybdenum speciation in acidic aqueous solution, (2) study the relationship between microscopic tungsten/molybdenum species transformation pathways and macroscopic extraction during recovery process on the basis of primary amine N1923, (3) probe into the effect of tungsten and molybdenum speciation on the removal efficiency of tungsten as well as purification of sodium molybdate solution in tungsten-molybdenum mixture system. The results are as follows: (1) The speciation distribution of tungsten and molybdenum species in acidic aqueous solution was studied by ESI-TOF-MS characterization method, which was superior to Raman method. A variety of tungsten species such as W1, W2, W4, W6, W10, W12 and various molybdenum species such as Mo1, Mo2, Mo3, Mo4 were monitored. At the same time, the effects of sample cone voltage and source temperature on the speciation distribution of tungsten and molybdenum species were investigated. Optimum cone voltage and source temperature were 20 V, 60 °C. In addition, the effects of acid type, initial solution concentration, solution pH on the morphological polymerization of tungsten and molybdenum species were further studied. The results showed that the distribution of tungsten and molybdenum species mainly depended on the pH of solution. Different acid types and initial solution concentration affected the polymerization and transformation of tungsten and molybdenum species to some extent. Molybdenum species were easier to hybridize with acid anions in solution. The schematic diagrams of the morphological polymerization of tungsten and molybdenum species in acidic aqueous solution were summarized.(2) Based on the ESI-TOF-MS coupled with two-stage ACCs on-line monitoring platform, the macroscopic extraction and microscopic tungsten/molybdenum species transformation pathways in the recovery process by primary amine N1923 were studied. The results showed that primary amine N1923 was an efficient extractant for tungsten and molybdenum extraction, and the molybdenum extraction reaction was more rapid than tungsten extraction. During the tungsten extraction process, W1 was an inactive form, which only participated in the tungsten speciation equilibrium reaction rather than the extraction reaction, and W10 was more active and easier to be extracted into the organic phase than other species. During the molybdenum extraction process, when MoO3Xn- (X is an acid medium anion) appeared in the initial solution, it would replace Mo4 as the active form and be preferentially extracted into the organic phase.(3) The extraction process of tungsten-molybdenum separation and the effect of speciation on tungsten removal as well as sodium molybdate solution purification were studied by the on-line monitoring platform. The results showed that tungsten was extracted preferentially over molybdenum in the competitive extraction process, and with the decrease of tungsten-molybdenum ratio, the advantages of tungsten would become more and more obvious. Various species such as Mo1-Mo5, HWO4- as well as tungsten-molybdenum hybrid species NaMoWO7-、NaMo2WO10- and NaMo3WO13- were monitored. The hybrid species would be preferentially combined with the primary amine N1923 to be extracted into the organic phase. The higher relative content of the hybrid species in tungsten speciation, the better tungsten removal. In addition, the higher relative content of hybrid species in initial solution, the higher purity of the sodium molybdate solution.
|蔺淑洁. 基于含氧酸根形态监测的钨钼分离基础研究[D]. 中国科学院大学,2019.|
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