砂岩铀矿不同铀组分活度比特征及其对地浸采铀的指示

ARS Characteristics of Different Uranium Fractions in Sandstone Uranium Deposit and Their Indication for in-situ Leaching of Uranium

为研究铀同位素^(234)U/^(238)U活度比(ARS)对地浸采铀过程的指示作用,采用逐级提取方法分离新疆某砂岩铀矿的铀化学组分,通过柱浸实验获取浸出液,用ICP-MS和TiCl_3还原-NH_4VO_3氧化滴定法分别测量其中的ARS值和铀浓度。结果表明,ARS在可离子交换态(F1)和酸易溶态(F2)中较高(1.293~1.348),在酸可溶态(F3)中略有下降(1.204~1.229),在可氧化态(F4)中降到最低(0.917~0.934),在难溶态(F5)中又升高至1.018~1.142;浸出过程可根据ARS变化分为3个阶段:第1阶段ARS较高,在1.217~1.318之间,主要是F1、F2和F3中的U(Ⅵ)浸出;第2阶段ARS下降直至1.016,主要是F3及F4中的U(Ⅳ)溶解;第3阶段ARS在1.070~1.118之间小幅波动,主要是F5中极少量难溶的铀浸出。

In order to study the indicative function of ^（234）U/238U activity ratios（ARS）to in-situ leaching of uranium,taking uranium ore from Xinjiang as an example,sequential extraction test was adopted to separate different uranium chemical fractions,and horizontal column leaching test was applied to obtain pregnant leach solution.ARS in the chemical fractions and the pregnant leach solution were measured by ICP-MS and thenuranium concentrations in leaching pregnant solution were measured by TiCl3 reduction NH4VO3 oxidation titration method.The results show that ARS are higher（1.293-1.348）in exchangeable fraction（F1）and easily acid soluble fraction（F2）,which decrease to 1.204-1.229 in acid soluble fraction（F3）and then reduce to the minimum 0.917-0.934 in oxidation fraction（F4）.After that ARS increase to 1.018-1.142 in hardly soluble fraction（F5）. Three phases of uranium leaching were identified according to the ARS.The first phase was characterized by the relatively high ARS in the range of 1.217-1.318,and the leaching uranium is mainly U（Ⅵ）in fraction F1,F2 and F3.The second phase was represented as the decrease of ARS,up to 1.016,and the leaching uranium is mainly U（Ⅳ）partly in F3 and primarily in F4.The third phase was characterized by the fluctuant ARS of 1.070-1.118,and the few leaching uranium is mainly the hardly soluble uranium in F5.