Research on Oxidization in Cerium Separation Process and amelioration of technics

针对Cyanex 923萃取分离铈、钍、稀土过程中Ce(IV)在萃取过程中被有机相中的还原性物质还原的问题，提出采用高锰酸钾氧化萃余水相中的Ce(III)。研究结果表明，在酸性条件下，高锰酸钾能有效的氧化水相中的Ce(III)，但在萃取过程中，高锰酸根会先于Ce（IV）被萃入到有机相中，从而失去氧化Ce(III)的能力，由此提出氧化过程必须无含Cyanex 923有机相存在并参与设计了一套油水分离氧化装置。经过高锰酸钾氧化后，萃余水相中铈可低于0.5g/L，铈收率达到98%。 针对攀西氟碳铈矿新流程中直接制备的纳米级氟化铈，考察了氟化铈的紫外吸收性能，发现其在254nm处有特征吸收峰，还考察了分散剂的极性强弱、分散物浓度、粒径、温度及表面包覆等因素对紫外吸收性能的影响；发现随着粒径的减小，紫外吸收峰发生明显的红移；经TiO2包覆后CeF3的紫外吸光域范围扩展。 研究了Cyanex 923与P204组成的双溶剂萃取体系及其单独体系萃取Ce(IV)、F及Ce(IV)-F混液的热力学性质，得出了协同萃取机理，获得了萃取平衡方程式以及协萃物的组成。研究发现混合体系对Ce(IV)及Ce(IV)-F混液中的Ce、F均有明显的协萃作用，这为该萃取体系应用于现实分离中提供了可靠的保证。 在上述工作的基础上，提出了Cyanex 923与P204组成的双溶剂萃取体系分离攀西氟碳铈矿的新清洁冶金流程。对影响这一流程的化学因素进行了系统研究，并给出了工艺运行参数。In order to raising the recovery of Ce(IV) which can be reduced by the organic phase, KMnO4 was adopt to oxidize Ce(III) aqueous phase in the process of recovering Ce, Th and rare earths with Cyanex 923. The results showed that, Ce(III) could be effectively oxidized to Ce(IV) by KMnO4 in aqueous phase under acidity condition, However, MnO4- was easier to be extracted into organic phase than Ce(IV), and lost it oxidizingd property. A new online oxidization process in the aqueous phase was proposed. A new oil-water separator had been designed. High yield of Ce was obtained. UV-absorption properties of nano-sized CeF3 which were obtained in the solvent extraction process to deal with Panxi Bastnasite leaching solution had been studied with different factors such as the size of particles, the dispersal solvents, temperature and other coated metals, etc. It was found that absorption spectra of CeF3 appeared at 254nm and which is shifted to the longer wavelength with the size decreased. UV-absorption range of CeF3 coated with TiO2 become broad. The extraction and recovery of Ce(IV), F and Ce(IV)-F solutions using Cyanex 923, P204 or them together had been investigated. The synergistic effect, extraction mechanism and thermodynamic parameters were investigated. Both Ce(IV) and F could be effectively extracted by two extractants from Ce(IV) and Ce(IV)-F mixture solution. The possibility to separate Ce(IV) and F from bastnasite leaching solution and the potential application of this extraction process had been discussed. A new clean hydrometallurgy process using dual-solvent of Cyanex 923 and P204 to deal with Panxi bastnasite leaching solution was proposed. Based on above results, the technical parameters were obtained from studying on chemical influence factors of the process