| The Determination of the Stability Constants of Zr(Ⅳ) and U (Ⅵ) Complex by AHA and the Study of the Decontamination of Zr in Purex U-cycle With AHAAcetohydroxamic acid (AHA), which has -CONHOH radical, has excellent chelation with many metal ions. Due to its special property, AHA has been identified as a useful reagent for the Np, Pu separation from U in the Purex process.In this paper, the stability constants of AHA complexes with U(Ⅵ) and Zr(Ⅳ) have been determined.The decontamination of Zr using AHA in the U purification cycle was investigated by single-stage and counter current cascade experiments simulated to the 2D extractor.1. The first and second stability constants of AHA complexes with U(Ⅵ) have been determined by pH potentiometric method.The value of stability constantβ1 andβ2 are 8.6×107,3.8×1014, respectively.β1(Pu(Ⅳ))/β1(U(Ⅵ)) andβ1(Np(Ⅳ))/β1(U(Ⅵ)) are more than 103.2. The first, second and third stability constants of AHA complexes with Zr(Ⅳ) have been determined by solvent extraction method .The value of stability constantβ1,β2 andβ3 are 6.7×1013,1.8×1025 and 3.8×1035, respectively. AHA has strong ability to coordinate with Zr(Ⅳ), which means AHA may improve DF(Zr(Ⅳ)) in the U purification cycle.3. The results of single -stage experiments of Zr decontamination using AHA as washing agent show that:(1) Scrubbing section: With the growth of HNO3 concentration, the increase extent of D(Zr(Ⅳ)) in U system is larger than D(Zr(Ⅳ)) in U-absent system.In the range of experimental condition, the increase of D(Zr(Ⅳ)) in the U system is slow with the growth of HDBP concentration. When HDBP concentration is more than 0.001mol/L, the increase of D(Zr(Ⅳ)) in the U-absent system is rapid with the growth of HDBP concentration.(2) Scrubbing section: With the growth of AHA concentration, D(Zr(Ⅳ)) decreases rapidly compared with AHA-absent system.When c(AHA)＞0.2mol/L, D(Zr(Ⅳ)) decreases a little.(3) Scrubbing section: DF(Zr(Ⅳ)) could be improved by increasing the scrubbing times and decreasing the phase ratio.(4) Extraction section: D(Zr(Ⅳ)) increases while HNO3 concentration increases and AHA concentration decreases. When p(U(Ⅵ))＞50g/L, D(Zr(Ⅳ)) decreases a little.4. Two times counter current cascade experiments' result shows that DF(Zr(Ⅳ)) is 3.2×104,4.3×104, respectively.Material balance of Zr(Ⅳ) is 100%,98%, respectively. All the results indicate that the decontamination of Zr(Ⅳ) could be improved using AHA under the precondition of ensuring U recovering rate in the U purification cycle.
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