Evaluation study on a macroporous silica-based isohexyl-BTP adsorbent for minor actinides separation from nitric acid medium

Abstract

Abstract To separate the long-lived minor actinides (MA = Am, Cm) from high level liquid waste (HLLW), we have been studying a partitioning technology named “MAREC” (Minor Actinides Recovery from HLLW by Extraction Chromatography) process which consists of two separation columns packed with silica-based adsorbents. In this work, we prepared the silica-based 2,6-bis(5,6-diisohexyl-1,2,4-triazin-3-yl)pyridine (isohexyl-BTP/SiO2-P) adsorbent used in the second column (0.01 ∼ 0.1 mol dm –3 HNO3) in the MAREC process for the separation of trivalent minor actinides (MA(III)) from trivalent rare earth elements (RE(III)) which are contained in HLLW. The content of extracting agent isohexyl-BTP in isohexyl-BTP/SiO2-P was as high as 33.3% of the total mass of the adsorbent. The adsorbent exhibited high affinity and selectivity for Am(III) over RE(III) not only in nitric acid solution but also in nitrate solution. Investigation showed that only a small part of isohexyl-BTP molecules inside isohexyl-BTP/SiO2-P leaked into 0.01 mol dm –3 HNO3 with or without γ-irradiation. The adsorption performance of isohexyl-BTP/SiO2-P did not evidently change after 120 d of contact with 0.01 mol dm –3 nitric acid. Furthermore, after γ-irradiated in 0.01 mol dm –3 HNO3 under the experimental conditions, isohexyl-BTP/SiO2-P exhibited higher adsorption for RE(III) than before γ-irradiation.