A newly proposed isotherm model to predict Cs exchange with crystalline silicotitanate in tank waste simulants

Journal Article · 25 December 2021 · Separation Science and Technology

DOI: https://doi.org/10.1080/01496395.2021.2010095 · OSTI ID:2566217

Campbell, Emily L.  ^[1]; Westesen, Amy M.  ^[1]; Fiskum, Sandra K. ^[1]; Lumetta, Gregg J.  ^[1]; Peterson, Reid A.  ^[1]

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1. Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

The Zheng Anthony Miller (ZAM) computer model, a multicomponent ion exchange model used to predict the exchange of Group I metals onto crystalline silicotitanate (CST), has historically been used to predict Cs distribution coefficients from Hanford and Savannah River Site (SRS) tank waste simulants. Comparison of experimentally determined Cs distribution coefficients from tank waste simulants with ZAM isotherm model predictions indicate overprediction of Cs and K distribution coefficients for simple and complex simulants with the engineered form of CST. Additionally, recent changes in chemical composition/manufacturing of IONSIV ^TM R9140-B have resulted in increased Cs capacity from high-salt, highly alkaline solutions. Here, this work served to assess different isotherm models and refine equilibrium parameters to develop a model that can be applied to Hanford and SRS tank waste Cs removal efforts. Toward this goal, the Campbell Westesen Peterson (CWP) model was developed. This model utilized the experimentally determined Cs capacity, and simplified ZAM equilibria expressions to include only the binary substitution of Cs⁺ or K⁺ on the Na⁺ sites. Equilibrium constants for these equations were refined using experimentally determined distribution coefficients. Overall, the CWP model significantly improved our ability to predict both Cs and K loading capacity from complex matrices.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC05-76RL01830
• OSTI ID: 2566217
• Report Number(s): PNNL-SA-164908
• Journal Information: Separation Science and Technology, Journal Name: Separation Science and Technology Journal Issue: 11 Vol. 57; ISSN 0149-6395
• Publisher: Taylor & FrancisCopyright Statement
• Country of Publication: United States
• Language: English