P_(204)-HCl-H_3AOH体系萃取Ce(Ⅲ)的机理与萃取平衡常数

Extraction Mechanism of Ce(Ⅲ) in P_(204)-HCl-H_3AOH System and the Extraction Equilibrium Constant

在pH>1和0<pH≤1两种不同pH条件下,采用原子吸收光谱测定P204-HCl-H3AOH体系萃取Ce(Ⅲ)过程两相中的Ce浓度分别考察酸度和萃取剂浓度对Ce的分配比的影响,通过对P204+煤油体系以及P204-HCl-H3AOH体系负载Ce有机相进行红外光谱测试分析,研究P204-HCl-H3AOH体系萃取Ce的机理,并确定萃取平衡常数。研究结果表明,当pH>1时,萃取过程的实质是Ce离子与P—OH置换,遵循阳离子交换机制。其萃取平衡常数KCe为10-1.63;当0<pH≤1时,萃取过程较为复杂,柠檬酸的存在阻碍了P204二聚体的形成,萃取过程是由P O基团与P—OH基团同时参与与Ce的配合作用,其配合机制为阳离子交换机制和溶剂化配合双重机制,该机制增强了对Ce的萃取能力,使萃取容量提高。其萃取平衡常数KCe为100.13。

In the conditions of pH1 and 0pH≤1,Ce concentration is measured by the method of atomic absorption spectroscopy in the two phase of P204-HCl-H3AOH extraction system to study the effect of acidy and extractant concentration on distribution ratio of Ce.Through infrared spectrum testing and analysis of P204＋kerosene system and the organic phase loading Ce in the P204-HCl-H3AOH extraction system,the effect on extraction mechanism of Ce in P204-HCl-H3AOH extraction system by acidy is also studied.Whereby,the extraction equilibrium constant is calculated.The results show that displacement reaction between Ce and P—OH happens and the extraction process abide by the cation exchange mechanism under the condition of pH1,and the extraction equilibrium constant KCe is 10-1.63.Then both the group of P=O and the group of P—OH can do complex reaction with Ce and the extraction mechanism is the dual mechanism theory of cation exchange mechanism and salvation complex mechanism,which can increase the extraction capacity of Ce,and the extraction equilibrium constant KCe is 100.13.