Extraction and aggregation behaviour of Zr(IV) in diglycolamide solvents during the treatment of high-level liquid waste solution arising from metallic fuel reprocessing

• Published in: Journal of molecular liquids 2021-10, Vol.340, p.117236, Article 117236
• Main Authors: Prathibha, T., Rama Swami, K., Suneesh, A.S., Robert Selvan, B., Sriram, S., Venkatesan, K.A.
• Format: Article
• Language: English
• Subjects: Aggregation; Carbonyl ligands; Dynamic light scattering; High-level liquid waste; Metallic Fuel; Phosphoric acid; Zirconium
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2021.117236

[Display omitted] •Extraction of Zr(IV)from nitric acid in diglycolamide solvents.•Comparison of different phase modifiers for TODGA.•Minimizing the aggregation in TODGA maximizes Zr(IV) extraction.•Masking of Zr(IV) extraction using CyDTA.•Extraction from simulated HLLW solution. Zirconium was identified as a troublesome fission product interfering with the separation of trivalent actinides from high-level liquid waste (HLLW) solution. Since zirconium was used as a fuel component in metallic fuels, the amount of Zr(IV) present in HLLW arising from reprocessing of metallic fuel was nearly ten times higher than the conventional HLLW solutions. In the present study, the diglycolamide extractants proposed for the separation of trivalent actinides from HLLW were employed for the extraction of metal ions from nitric acid medium and fast reactor simulated high level liquid waste (FR-SHLLW) having the Zr(IV) concentrations varied from 0.006 M to 0.09 M. Dynamic light scattering study was performed on the organic phase obtained after extraction of zirconium to analyze the aggregation of extractants. The solvent system consisting of 0.1 M TODGA (N,N,N’,N’-tetraoctyldiglycolamide) along with 0.25 M HDEHP (bis(-2-ethylhexyl)phosphoric acid) in n-dodecane showed minimal aggregation tendency and higher loading capacity of Zr(IV) and was selected for further extraction of trivalent metal ions from FR-SHLLW. To minimize the extraction of Zr(IV) in organic phase, the effect of aqueous soluble complexing agent namely trans-1,2-diaminocyclo-hexane-N,N,N’N’-tetraaceticacid (CyDTA) was also studied during the extraction of trivalent lanthanides.