三种中性磷萃取剂萃取分离铀(Ⅵ)与钍(Ⅳ)的研究  

Extraction of U(Ⅵ) and Th( Ⅳ) with three neutral extractants containing phosphorus

作　　者：李诗萌 谈梦玲 丁颂东[1] 李方[1] 李晴暖[2] 张岚[2] 刘春霞[2] 

机构地区：[1]四川大学化学学院,四川成都610064 [2]中国科学院上海应用物理研究所,上海201800

出　　处：《化学研究与应用》2016年第3期307-315,共9页Chemical Research and Application

基　　金：国家自然科学基金项目(91126016;91426302;J1210004)资助;中国科学院战略性先导科技专项项目(XDA02030000)资助

摘　　要：以磺化煤油作稀释剂,比较研究了三种中性磷萃取剂甲基膦酸二甲庚酯(P350)、磷酸三异戊酯(TiAP)和磷酸三丁酯(TBP)在HNO3溶液中对U(Ⅵ)、Th(Ⅳ)及自身对HNO_3的萃取行为。分别考察了两相接触时间、酸度、萃取剂浓度和温度对U(Ⅵ)、Th(Ⅳ)萃取分配比的影响。结果表明它们萃取HNO_3均形成1∶1型萃合物。随HNO_3浓度增加,U(Ⅵ)和Th(Ⅳ)的萃取分配比先增大后减小。相同条件下,P350对U(Ⅵ)、Th(Ⅳ)的萃取能力及铀/钍分离选择性显著大于TiAP和TBP。当被萃水相存在大量Th(Ⅳ)时,Th(Ⅳ)对U(Ⅵ)的萃取有盐析作用,U(Ⅵ)的分配比增加;Th(Ⅳ)的分配比下降。斜率分析表明三种萃取剂与U(Ⅵ)和Th(Ⅳ)分别形成2∶1和3∶1型萃合物。同时,给出了表观萃取平衡常数Kex和萃取反应热力学函数ΔH、ΔS和ΔG的值。用ICP-AES分析方法,还对三种萃取剂在不同浓度的HNO_3溶液中的溶解度进行了测定。此外,还测定了三者萃取Th(Ⅳ)的极限有机相浓度(LOC)。For the first time,the extraction behaviors of U（ Ⅵ） and Th（ Ⅳ）,as well as the extraction of nitric acid were comparatively investigated by using di（ 1-methyl-heptyl） methyl phosphonate（ P350）,triisoamyl phosphate（ Ti AP） or tributyl phosphate（ TBP） as an extractant and sulfonated kerosene as a diluent.Effects of contact time,acidity,concentration of extractant and temperature on the distribution ratio of U（ Ⅵ） and Th（ Ⅳ） were evaluated.In the examination of acidity range from 0. 01 to 6. 0 mol·L^-1,the distribution ratios of U（ Ⅵ） and Th（ Ⅳ） increased at first and then decreased with the increase of nitric acid concentration.P350 exhibited higher selectivity for U（ Ⅵ） than for Th（ Ⅳ） with the separation factor SFU / Thvalues of 25. 3-121. Whereas under the same conditions,SFU / Thvalues of Ti AP and TBP were only 4. 47-27. 1 and 1. 40-27. 2,separately.Slope analyses showed that U（ Ⅵ） and Th（ Ⅳ） were extracted as di-solvated and tri-solvated species by three extractants,severally.The thermodynamic parameters（ ΔH,ΔS and ΔG） were presented.In addition,solubility of the extractants in various HNO3 solution was firstly determined through the analysis of phosphorus content using ICP-AES.The limiting organic concentration（ LOC） values of Th（ Ⅳ） were also measured.

关 键 词：甲基膦酸二甲庚酯 磷酸三异戊酯 磷酸三丁酯 铀(VI) 钍(IV) 萃取 

分 类 号：O615.11[理学—无机化学]