钨、钼过氧配合物溶液中的物种结构表征及稳定性研究

The new process of solvent extraction separation of Mo and W by H2O2-cmplexation is suitable for removing Mo from tungstate solution containing high content of Mo. It has a broad prospect in industrial application, which provided obvious advantages including deep removal of Mo, high recovery of W, low cost, clean and environment friendliness. However, the problems such as instability of the aqueous solution and third phase in extraction which exposed by industrial test are hard to optimize for the complexation of solution chemistry and lack of related theoretical research. Aiming at the problems, the structure characterization and stability of the tungstate and molybdenum peroxide complex solution will be investigated in this proposal. By the research, an in situ characterization and analysis method which sutable for solution state will be bulid, the application of flow Injection-ultraviolet spectrophotometry in the dynamics study of separation of Mo and W will be carried out, the dominant component and mutual transformation in the solution will be determined. The effect of various factor on the thermodynamic stability will be investigated by using the standard free enthalpy as an important index. By the dynamics research, the effect of various factor on the dynamic stability will be investigated and the mechanism will be revealed, the reaction rate equation will be determined, the math model will be bulid and the reaction mechanism will be conjectured. Based on the results of the theoretical research, the effective measures for improving the new procee will be proposed. This proposal aims to establish a good foundation for the theoretical study, and to provide a scientific evidence for the industrial application of the process of solvent extraction separation of Mo and W by H2O2-complexation.

双氧水配合法萃取分离钨钼新工艺适用于从高钼含钨溶液中除钼。它具有除钼彻底、钨收率高、成本低和清洁环保等优势，工业应用前景广阔。但该体系水溶液化学复杂，相关理论研究缺乏，导致工业试验中暴露的料液稳定性不佳、萃取第三相等问题难以有效优化。本项目针对工艺存在的问题，提出对钨、钼过氧配合物溶液展开物种结构表征和稳定性研究，具体包括：建立适用于溶液态的物种结构原位表征分析方法，实现流动注射-紫外分光光法在钨钼分离动力学研究中的应用，明确溶液中存在的优势组分及相互转化；通过热力学计算，以标准自由焓变为重要指标，揭示各因素对溶液热力学稳定性的影响规律；通过动力学研究，揭示影响溶液动力学稳定性的关键因素，获得反应速率方程，建立数学模型，推测反应机理；在此基础上提出工艺的改进方向。本项目旨在为双氧水配合萃取分离钨钼系列理论研究的开展奠定良好基础，并为该工艺成功应用于工业实践提供理论基础与科学依据。

针对双氧水配合法萃取分离钨钼工艺在工业化实验中显现出的料液稳定性差、生成萃取第三相等不足，本项目从钨、钼过氧配合物水溶液化学入手，展开了物种结构表征和稳定性研究，建立了适用于钨、钼过氧配合物溶液态物种结构原位表征的拉曼光谱-高斯拟合分析方法和紫外可见光光谱定量分析方法，实现了流动注射-紫外可见光光谱法在钨钼分离动力学研究中的应用，采用二元函数牛顿迭代法求解热力学模型，开发了基于Web的Mo-H2O2-H2O水系热力学在线计算平台。采用上述方法进行钨、钼过氧配合物溶液物种结构表征、热力学平衡和动力学稳定性研究，并提出工艺改进措施。结果表明：pH值、H2O2用量、浓度、放置时间等因素对钨、钼过氧配合物溶液中优势物种转化及分配影响显著，在强碱性条件下，过氧钨、钼酸根会迅速分解为MO42-；随着pH值的降低，过氧钼酸根向七聚体和二聚体转化，pH值降低至2.28时，[Mo7O22(O2)2]6- 和 [Mo2O3(O2)4(H2O)2]2-的相对丰度分别达到了29.64% 和51.19%；H2O2浓度的增加，会促进过氧钼配合物由七聚体向二聚体转变，当H2O2用量由η=0.5增加至η=2.5， [Mo7O22(O2)2]6-的相对丰度由36.46% 下降至6.29%，[Mo2O3(O2)4(H2O)2]2-的相对丰度由38.27% 提高至 83.18%；pH值、H2O2用量、浓度、放置时间等因素对料液的稳定性影响显著，析出的沉淀为过氧钨酸根分解产生的钨酸或无定形中间产物；随着静置时间的延长，[Mo2O3(O2)4(H2O)2]2-逐渐转化为[Mo7O22(O2)2]6-；选择pH值1.5-2.0、低温、低钨浓度、密封、避光等措施均有助于提高钨钼过氧配合料液的稳定性，减少沉淀析出；延长放置时间有利于提高除钼深度。本项目研究结果为双氧水配合萃取分离钨钼系列理论研究的开展奠定了良好基础，并为该工艺成功应用于工业实践提供了理论基础与科学依据。