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使用单级萃取-反萃取工艺,从湿法磷酸(WPA)中回收铀和稀土的新工艺,既简单又易于控制,因为它只涉及酸性介质。该工艺是基于用二(2-乙基己基)磷酸(DEPA)和磷酸三丁酯(TBP),从湿法磷酸中萃取铀和稀土。发现DEPA是唯一有效的,它稳定并且易于反萃取。其它的有机磷酸酯易水解,并且很难反萃取。用含有酸性氟化物的介质,对稀土和铀进行反萃取。对于铀来说,以六价(U~(6+))形成被萃取,铀由于Fe~(2+)还原成4价(U~(4+))不萃取状态,而进入到反萃取液中。稀土和铀(U~(4+))以氟化物形式立刻沉淀下来。铀以UF_42.5H_2O或一种四价化合物沉淀,这与反萃取液有关。这种沉淀物是一种“绿色的饼”。将“绿色的饼”先在氮气中400℃下脱水后,用F_2氧化成高纯六氟化铀。稀土部份由钇族组成,其中钇是主要元素。 上述工艺比两级萃取-反萃取投资费用低,对于绿色湿法磷酸,其运行成本大约是30美元/kg。
The new process for the recovery of uranium and rare earths from wet-process phosphoric acid (WPA) using a single stage extraction-stripping process is simple and easy to control because it involves only acidic media. The process is based on the extraction of uranium and rare earths from wet process phosphoric acid using di (2-ethylhexyl) phosphoric acid (DEPA) and tributyl phosphate (TBP). DEPA was found to be the only effective, stable and easily stripped. Other organophosphates are readily hydrolyzed and difficult to back-extract. With acidic fluoride containing medium, the rare earth and uranium were back-extracted. For uranium, it is extracted by hexavalent (U ~ (6+)) formation and uranium is not extracted due to Fe ~ (2+) reduction to tetravalent (U ~ (4+) in. Rare earths and uranium (U ~ (4+)) precipitated as fluoride immediately. Uranium precipitates with UF_42.5H_2O or a tetravalent compound, which is related to the stripping solution. This deposit is a “green cake.” The “green cake” was first dehydrated at 400 ° C in nitrogen and then oxidized with F_2 to high-purity uranium hexafluoride. Rare earth part of the composition of the yttrium, yttrium is the main element. The above process is less expensive to invest than two-stage extraction-back-extraction and costs about $ 30 / kg for green wet-process phosphoric acid.