Adsorption Behavior of Platinum Group Metals onto a Silica-based (Crea+Dodec)/SiO2-P Extraction Resin from Simulated High Level Liquid Waste

Basic properties of a silica-based macroporous N’,N’-di-n-hexyl-thiodiglycolamide (Crea) extraction resin, (Crea+Dodec)/SiO₂-P were examined. This extraction resin was synthesized by impregnating Crea and its modifier, n-Dodecyl alcohol (Dodec) into the macroporous SiO₂-P support with a mean diameter of 50 μm. Adsorption behavior of platinum group metals (PGMs) and some fission product elements from simulated high level liquid waste onto the resin was investigated by batch experiment. It was found that (Crea+Dodec)/SiO₂-P extraction resin exhibited good adsorption selectivity for PGMs over other tested elements in 0.1-5.0 M HNO₃ solution. This resin showed strong affinity to Pd(II) especially in a short contact time but almost no adsorption for rare earth elements. Adsorption behavior of PGMs in experiment could be expressed by the Langmuir monomolecular layer adsorption mode. Meanwhile, adsorption results were fitted well with the pseudo-second order model and the rate-controlling step of this adsorption process was governed by the chemisorption process. In addition, the adsorption isotherms and thermodynamic parameters of tested elements were calculated by the Langmuir, Freundlich, and van’t Hoff equations, respectively.     

Synthesis of a Novel Macroporous Silica-Calix[4]arene-Crown Supramolecular Recognition Material and its Adsorption for Cesium and some Typical Metals in Highly Active Liquid Waste

Abstract

A novel macroporous silica-based 25,27-bis(iso-propyloxy)calix[4]arene-26,28-crown-6 (BiPCalix[4]C6) supramolecular recognition material, BiPCalix[4]C6/SiO₂-P, was synthesized. It was prepared by impregnation and the immobilization of the BiPCalix[4]C6 molecule into the pores of the macroporous SiO₂-P particles. The adsorption of Cs(I) and some typical elements Na(I), K(I), Rb(I), Sr(II), Ba(II), Ru(III), Mo(VI), La(III), and Y(III) onto the BiPCalix[4]C6/SiO₂-P material was investigated. The effects of the HNO₃ concentration, contact time, and temperature on the adsorption of the tested metals were studied. It was found that at the optimum concentration of 3.0 M HNO₃, BiPCalix[4]C6/SiO₂-P exhibited excellent adsorption ability and high selectivity for Cs(I) over all the tested elements, which showed weak or almost no adsorption except Rb(I). A pseudo-second-order model was found to be able to describe the adsorption kinetics of Cs(I). The chemical complexation of Cs(I) with BiPCalix[4]C6/SiO₂-P was considered to be the rate-controlling step. Meanwhile, the thermodynamic parameters of the Cs(I) adsorption, ΔH?, ΔG?, and ΔS? were determined. The adsorption of Cs(I) onto BiPCalix[4]C6/SiO₂-P was exothermic. It was demonstrated that in 3.0 M HNO₃, the novel macroporous BiPCalix[4]C6/SiO₂-P material shows promise for the partitioning of Cs(I) from highly active liquid waste.     

碱土金属氧化物含量对模拟高放废液玻璃固化体析晶行为的影响

以硼硅酸盐玻璃作为基础玻璃基材,通过熔融法制备了含16%(质量分数)模拟高放废液的玻璃固化体,探究了碱土金属氧化物含量对玻璃固化体析晶行为的影响,以期在保证玻璃固化体性能要求的前提下,通过控制碱土金属氧化物的含量抑制玻璃固化体的析晶倾向。结果显示:碱土金属氧化物(CaO+MgO+BaO)含量在7%~19%(质量分数)时,玻璃固化体析晶上限温度和析晶率随碱土金属氧化物含量的降低而逐渐降低;玻璃网络聚合度的增加能够显著增强玻璃固化体的抗析晶性能,当碱土金属氧化物含量低于11%(质量分数)时玻璃固化体中硫酸盐的溶解度明显下降。基于包容0.7%(质量分数)SO₃的要求,碱土金属氧化物含量适宜组成应控制在11%(质量分数)以上。     

Demonstration of an Improved Total Partitioning Process for High Level Liquid Waste Using Annular Centrifugal Contactors

High level liquid waste (HLLW) produced from the reprocessing of the spent nuclear fuel still contains moderate amounts of uranium, transuranium (TRU) actinides, ⁹⁰Sr, ¹³⁷Cs, etc., and thus constitutes a permanent hazard to the environment. The partitioning and transmutation (P&T) strategy has increasingly attracted interest for the safe treatment and disposal of HLLW, in which the partitioning of HLLW is one of the critical technical issues. An improved total partitioning process, including a TRPO (tri-alkylphosphine oxide) process for the removal of actinides, a CESE (crown ether strontium extraction) process for the removal of Sr, and a calixcrown ether extraction process for the removal of Cs, has been developed to treat Chinese HLLW at the Institute of Nuclear and New Energy Technology (INET), Tsinghua University, China. A demonstration test of the improved total partitioning process was carried out using 74-stage 10-mm-dia annular centrifugal contactors and simulated HLLW. The test results showed that the decontamination factors were >1.2 × 10⁶, 4600, and 7500 for Nd, Sr, and Cs, respectively. In the test, Nd was used to simulate Am. During the test, 74-stage 10-mm-dia annular centrifugal contactors worked stable continuously with no stage failing or interruption of the operation.     

Adsorption behavior and radiation effects of a silica-based (Calix(4)+Dodecanol)/SiO2-P adsorbent for selective separation of Cs(I) from high level liquid waste

A macroporous silica-based (Calix[4]+Dodecanol)/SiO₂-P absorbent for separation of Cs(I) from HNO₃ solution was prepared by impregnating the 1,3-[(2,4-Diethylheptylethoxy)oxy]-2,4-crown-6-calix[4]arene and its molecule modifier 1-dodecanol into a macroporous silica/polymer composite support. To establish its application into partitioning of Cs(I) from High Level Liquid Waste (HLLW), the adsorption properties and radiation effects on the adsorbent were investigated. The adsorbent showed a relatively large distribution coefficient of Cs(I) and fast equilibrium time in simulated HLLW. Additionally, the adsorbent under the gamma-ray field was found to be able to selectively adsorb Cs(I) with similar behavior to the adsorption without irradiation up to at least 170 kGy.