This paper presents a method of studying uranium speciation from in-situ leaching sandstone-type uranium deposits by a sequential extraction procedure and demonstrates its application to sandstone uranium exploration. The chemical extraction procedure was modified from Tessier. Uranium in samples was classified into five speciations: exchangeable ions, bound to carbonates, bound to Fe-Mn oxides, bound to sulfide-organic matter and residual speciation. The first four phases consisted of active uranium with the residual uranium being stable uranium. The results show that the uranium distribution characteristics were significantly different whether they were in different samples or in the same sample. The average amounts of residual speciation, carbonates speciation, exchangeable speciation, sulfide-organic matter speciation and Fe-Mn speciation decreased in order as 37. 75% (RSD = 1. 80% ), 20. 56% (RSD = 2. 72%), 15. 51% ( RSD = 1. 85% ), 14. 26% ( RSD = 2. 08% ) and 11.91% ( RSD = 1.75% ) , respectively. According to the present technology of acid dipped processing, the active uranium was teachable and the inert uranium was unleachable. This study indicates that residual speciation is the primary component. The uranium extraction rate for uranium ore with a high proportion of residual uranium ( such as the No.4 sample with 57.17% residual uranium in this paper) is lower and the extraction rale does not increase significantly by improving the dissolve acidity and oxidants.%以新疆某地浸砂岩型铀矿为研究对象,参考Tessier逐级化学提取方法,对10件矿芯试样进行铀赋存形态的研究.将铀赋存形态分为可交换离子态、碳酸盐结合态、铁锰氧化物结合态、硫化物及有机物结合态和残渣态,其中前4种形态铀为活性铀,残渣态铀为惰性铀.研究结果显示,无论是试样间还是同一试样内,铀的形态分布特征都存在明显的差异.各形态铀的含量(平均值)占总量铀的比例为:残渣态(37.75％,RSD为1.80％)＞碳酸盐结合态(20.56％,RSD为2.72％)＞可交换离子态(15.51％,RSD为1.85％)＞硫化物及有机物结合态(14.26％,RSD为2.08％)＞铁锰氧化物结合态(11.91％,RSD为1.75％),表明残渣态铀是砂岩型铀矿石中铀的重要赋存形式.针对目前酸法地浸工艺,活性铀是可被浸出的部分,而惰性铀对资源回收是无效的,对于残渣态铀所占比例较高的铀矿石,铀的浸出值较低,在地浸过程中依靠提高溶浸剂的酸度和增加氧化剂对提高浸出率是无益的.
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