TODGA-DHOA体系萃取金属离子Ⅱ.对Pu(Ⅲ,Ⅳ,Ⅵ)的萃取
Extraction of Metal Ions From Aqueous Nitric Acid Solutions With TODGA and DHOA Ⅱ. Extraction of Pu(Ⅲ,Ⅳ,Ⅵ) Ions
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摘要: 研究了以N,N,N′,N′-四辛基-3-氧戊二酰胺(TODGA)和N,N-二己基辛酰胺(DHOA)为萃取剂，正十二烷为稀释剂体系对Pu(Ⅲ)、Pu(Ⅳ)和Pu(Ⅵ)的萃取行为，主要考察了萃取剂浓度、HNO3浓度和NaNO3浓度的影响。结果表明：TODGA和DHOA对Pu(Ⅲ)、Pu(Ⅳ)和Pu(Ⅵ)的萃取分配比大小顺序均为：D(Pu(Ⅲ))＞D(Pu(Ⅳ))＞D(Pu(Ⅵ))，TODGA/正十二烷体系中加入DHOA时，对Pu(Ⅲ,Ⅳ,Ⅵ)萃取具有一定抑制作用，但在较高酸度范围内(≥3.0 mol/L HNO3)，不论体系中Pu的价态为何种形式，TODGA均能对其进行有效的回收。TODGA萃取Pu(Ⅲ,Ⅳ,Ⅵ)的方程式分别为：
Pu3++3NO-
Pu4+a+4NO-3a+3TODGAo→Pu(NO3)4·3TODGAo
PuO2+Abstract: The recovery of uranium and plutonium from the spent nuclear fuel by Purex reprocess is a well-established technology on an industrial scale. However, about 0.5%Pu enter the raffinate flows(high-level liquid waste). From the disposal of waste and environmental concern, this fraction of Pu must be separated and recovered from HLLW. Recently developed N,N,N′,N′-tetraoctyl diglycolamide (TODGA) has been identified as one of the most promising extractants being considered for the partitioning of trivalent actinides and lanthanides from HLLW solutions. In the present paper, extraction characteristics of TODGA and N, N-dihexyl octanamide(DHOA), for Pu(Ⅲ), Pu(Ⅳ) and Pu(Ⅵ), from nitric acid solutions were studied. The effects of concentration of the nitric acid, salting-out agents in aqueous phase and the extractant in organic phase on distribution ratios were examined. The results show that Pu(Ⅲ), Pu(Ⅳ) and Pu(Ⅵ) are well extracted by TODGA. The order of distribution ratios of Pu(Ⅲ), Pu(Ⅳ) and Pu(Ⅵ) ions by TODGA is D(Pu(Ⅲ))＞D(Pu(Ⅳ))＞D(Pu(Ⅵ)). After adding DHOA to TODGA/dodecane system, the distribution ratios of Pu(Ⅲ), Pu(Ⅳ) and Pu(Ⅵ) decrease with increasing of the concentration of DHOA, but the distribution ratios are large enough for recovery of them from aqueous HNO3 solution. The extraction equations of Pu(Ⅲ,Ⅳ,Ⅵ) ions by TODGA are deduced as follows:
Pu3++3NO
Pu4+a+4NO
PuO2+
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