Special Review on “Geological and Environmental Sciences for Sustainable Nuclear Energy”

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Econ. Environ. Geol. 2023; 56(5): 515-532

Published online October 30, 2023

https://doi.org/10.9719/EEG.2023.56.5.515

© THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY

Review of Thermodynamic Sorption Model for Radionuclides on Bentonite Clay

Jeonghwan Hwang1,*, Jung-Woo Kim1, Weon Shik Han2, Won Woo Yoon2, Jiyong Lee2, Seonggyu Choi3

1Disposal Safety Evaluation Research Division, Korea Atomic Energy Research Institute (KAERI)
2Department of Earth System Sciences, Yonsei University
3Disposal Performance Demonstration R&D Division, Korea Atomic Energy Research Institute (KAERI)

Correspondence to : *hwangjh@kaeri.re.kr

Received: September 22, 2023; Revised: October 13, 2023; Accepted: October 16, 2023

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided original work is properly cited.

Abstract

Bentonite, predominantly consists of expandable clay minerals, is considered to be the suitable buffering material in high-level radioactive waste disposal repository due to its large swelling property and low permeability. Additionally, the bentonite has large cation exchange capacity and specific surface area, and thus, it effectively retards the transport of leaked radionuclides to surrounding environments. This study aims to review the thermodynamic sorption models for four radionuclides (U, Am, Se, and Eu) and eight bentonites. Then, the thermodynamic sorption models and optimized sorption parameters were precisely analyzed by considering the experimental conditions in previous study. Here, the optimized sorption parameters showed that thermodynamic sorption models were related to experimental conditions such as types and concentrations of radionuclides, ionic strength, major competing cation, temperature, solid-to-liquid ratio, carbonate species, and mineralogical properties of bentonite. These results implied that the thermodynamic sorption models suggested by the optimization at specific experimental conditions had large uncertainty for application to various environmental conditions.

Keywords bentonite, radionuclide, thermodynamic sorption model, deep geological disposal repository, engineered barrier system

벤토나이트와 방사성 핵종의 열역학적 수착 모델 연구

황정환1,* · 김정우1 · 한원식2 · 윤원우2 · 이지용2 · 최승규3

1한국원자력연구원 저장처분기술개발부
2연세대학교 지구시스템과학과
3한국원자력연구원 저장처분성능검증부

요 약

벤토나이트는 고준위 방사성폐기물 처분을 위한 심층처분 시스템에서 처분용기와 암반 사이를 메우는 완충재로 고려되는 팽창성 점토이다. 벤토나이트는 높은 양이온교환능과 비표면적을 가지고 있기 때문에, 처분용기로부터 핵종이 누출될 경우, 수착하여 암반으로의 유출을 지연시키는 역할을 한다. 본 연구에서는 여러 선행연구에서 8종류의 벤토나이트를 사용하여 수행된 U, Am, Se, Eu 핵종의 수착실험 및 모델 자료를 취합하고, 각 연구에서 설정된 실험 조건들을 기반으로 열역학적 수착모델의 특성을 평가하였다. 핵종과 벤토나이트 간의 수착 거동 해석에 중요한 역할을 하는 열역학적 수착모델은 벤토나이트의 광물학적 특성뿐만 아니라 핵종 농도, 용액의 이온강도, 주 양이온, 온도, 고액비, 용존 탄산 농도 등 세부적인 실험 조건과 밀접하게 연관되어 있는 것으로 확인되었다. 이러한 결과는 특정 실험 조건에서 수행된 수착실험 및 모델의 최적화로 제안되는 수착 반응식과 반응상수가 다양한 환경 조건에 적용하기에 불확실성이 크다는 것을 의미한다. 따라서, 심층처분 시스템에 적용가능한 열역학적 수착모델을 구축하기 위해서는 현장 조사 및 실험이 함께 수행되어야 한다.

주요어 벤토나이트, 방사성핵종, 열역학적 수착모델, 심층처분 시설, 공학적방벽

Article

Special Review on “Geological and Environmental Sciences for Sustainable Nuclear Energy”

Econ. Environ. Geol. 2023; 56(5): 515-532

Published online October 30, 2023 https://doi.org/10.9719/EEG.2023.56.5.515

Copyright © THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY.

Review of Thermodynamic Sorption Model for Radionuclides on Bentonite Clay

Jeonghwan Hwang1,*, Jung-Woo Kim1, Weon Shik Han2, Won Woo Yoon2, Jiyong Lee2, Seonggyu Choi3

1Disposal Safety Evaluation Research Division, Korea Atomic Energy Research Institute (KAERI)
2Department of Earth System Sciences, Yonsei University
3Disposal Performance Demonstration R&D Division, Korea Atomic Energy Research Institute (KAERI)

Correspondence to:*hwangjh@kaeri.re.kr

Received: September 22, 2023; Revised: October 13, 2023; Accepted: October 16, 2023

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided original work is properly cited.

Abstract

Bentonite, predominantly consists of expandable clay minerals, is considered to be the suitable buffering material in high-level radioactive waste disposal repository due to its large swelling property and low permeability. Additionally, the bentonite has large cation exchange capacity and specific surface area, and thus, it effectively retards the transport of leaked radionuclides to surrounding environments. This study aims to review the thermodynamic sorption models for four radionuclides (U, Am, Se, and Eu) and eight bentonites. Then, the thermodynamic sorption models and optimized sorption parameters were precisely analyzed by considering the experimental conditions in previous study. Here, the optimized sorption parameters showed that thermodynamic sorption models were related to experimental conditions such as types and concentrations of radionuclides, ionic strength, major competing cation, temperature, solid-to-liquid ratio, carbonate species, and mineralogical properties of bentonite. These results implied that the thermodynamic sorption models suggested by the optimization at specific experimental conditions had large uncertainty for application to various environmental conditions.

Keywords bentonite, radionuclide, thermodynamic sorption model, deep geological disposal repository, engineered barrier system

벤토나이트와 방사성 핵종의 열역학적 수착 모델 연구

황정환1,* · 김정우1 · 한원식2 · 윤원우2 · 이지용2 · 최승규3

1한국원자력연구원 저장처분기술개발부
2연세대학교 지구시스템과학과
3한국원자력연구원 저장처분성능검증부

Received: September 22, 2023; Revised: October 13, 2023; Accepted: October 16, 2023

요 약

벤토나이트는 고준위 방사성폐기물 처분을 위한 심층처분 시스템에서 처분용기와 암반 사이를 메우는 완충재로 고려되는 팽창성 점토이다. 벤토나이트는 높은 양이온교환능과 비표면적을 가지고 있기 때문에, 처분용기로부터 핵종이 누출될 경우, 수착하여 암반으로의 유출을 지연시키는 역할을 한다. 본 연구에서는 여러 선행연구에서 8종류의 벤토나이트를 사용하여 수행된 U, Am, Se, Eu 핵종의 수착실험 및 모델 자료를 취합하고, 각 연구에서 설정된 실험 조건들을 기반으로 열역학적 수착모델의 특성을 평가하였다. 핵종과 벤토나이트 간의 수착 거동 해석에 중요한 역할을 하는 열역학적 수착모델은 벤토나이트의 광물학적 특성뿐만 아니라 핵종 농도, 용액의 이온강도, 주 양이온, 온도, 고액비, 용존 탄산 농도 등 세부적인 실험 조건과 밀접하게 연관되어 있는 것으로 확인되었다. 이러한 결과는 특정 실험 조건에서 수행된 수착실험 및 모델의 최적화로 제안되는 수착 반응식과 반응상수가 다양한 환경 조건에 적용하기에 불확실성이 크다는 것을 의미한다. 따라서, 심층처분 시스템에 적용가능한 열역학적 수착모델을 구축하기 위해서는 현장 조사 및 실험이 함께 수행되어야 한다.

주요어 벤토나이트, 방사성핵종, 열역학적 수착모델, 심층처분 시설, 공학적방벽


    List of previous studies, together with utilized bentonite samples, sorption models, and target radionuclides.


    NoReferenceBentoniteSorption ModelRadionuclides
    1Bradbury and Baeyens (2002)SWy-12SP-NE-SC/CEEu
    2Bradbury and Baeyens (2005)SWy-12SP-NE-SC/CEU, Am, Eu
    3Bradbury and Baeyens (2006)SWy-12SP-NE-SC/CEAm, Eu
    4Fernandes et al. (2008)SWy-12SP-NE-SC/CEEu
    5Fernandes et al. (2012)SWy-12SP-NE-SC/CEU
    6Schnurr et al. (2015)SWy-12SP-NE-SC/CEEu
    7Kowal-Fouchard et al. (2004)Volclay2SP-CC-SC/CEU
    8Bradbury and Baeyens (2011)MX-802SP-NE-SC/CEU, Eu
    9Tertre et al. (2006)MX-802SP-DL-SC/CEEu
    10Yang et al. (2010)Jinchuan2SP-DL-SC/CEU
    11Guo et al. (2009)Jinchuan2SP-DL-SC/CEEu
    12Missana et al. (2021)FEBEX2SP-NE-SC/CEEu
    13Missana et al. (2009)FEBEX2SP-NE-SC/CESe
    14Kumar et al. (2013)Western India2SP-NE-SC/CEAm, Eu
    15Gao et al. (2021)GMZ2SP-NE-SC/CEAm
    16Shi et al. (2014)GMZ2SP-DL-SC/CESe, Eu
    17Pablan and Turner (1996)SAz-12SP-DL-SC/CEU


    List of bentonite samples considered in this study, together with the experimental conditions used in reference studies from 1–10 (details were provided in Table 1). [R]initial represented the concentration of radionuclides, Major Cat. represented the predominant cations, S:L Ratio represented for the solid to liquid ratio, and [CO3]total represented the carbonate concentration.


    Bentonite [Ref]Radio nuclide[R]initial (mol L–1)pHTemp (℃)Major Cat.Ionic Strength (mol L–1)S:L Ratio (g L–1)[CO3]total (mol L–1)
    SWy-1 [1]Eu9.5×10–93–1025Ca0.0661-
    10–9–10–36.925Ca0.0661-
    10–9–10–36.025Ca0.0661-
    1.3×10–74–925Na+0.11.5-
    10–9–10–36.0, 7.225Na+0.10.5-
    10–9–10–36.025Na+0.10.5-
    SWy-1 [2]U1.4×10–73–1025Na+0.011.2-
    1.4×10–73–1025Na+0.11.2-
    Am3×10–83–1025Na+0.14-
    3×10–83–1025Na+14-
    Eu1.3×10–73–1025Na+0.11.5-
    9.5×10–94–925Ca0.0661-
    SWy-1 [3]Am1.5×10–103–1025Na+0.10.62-
    6.2×10–83–925Ca0.0660.86–2-
    SWy-1 [4]Eu2×10–94–925Na+0.11-
    2×10–96–1025Na+0.1110–3.5 atm
    2×10–97–925Na+0.112×10–2
    SWy-1 [5]U10–73–925Na+0.10.9-
    10–74–1025Na+0.12.510–3.5 atm
    10–77–925Na+0.14.310–3, 3×10–3, 5×10–3
    10–8–10–45, 6.8, 825Na+0.10.9-
    10–8–10–45, 6.8, 825Na+0.11.510–3.5 atm
    SWy-1 [6]Eu2×10–73–1225Na+0.12-
    2×10–73–1225Na+0.92-
    2×10–73–1225Na+3.92-
    Volclay [7]U10–62–725Na+0.110-
    10–32–725Na+0.510-
    10–42–725Na+0.1, 0.510-
    MX-80 [8]U3×10–8–10–67.625Na+0.60.32–13.5-
    Eu3.2×10–11–1.6×10–67.525Na+0.61.56-
    MX-80 [9]Eu10–63–1025Na+0.52.5-
    10–64–840Na+0.52.5-
    10–62–780Na+0.52.5-
    10–62–4150Na+0.52.5-
    Jinchuan [10]U8×10–53–1025Na+0.11-
    4×10–54–1025Na+0.11-
    10–5–10–34.825Na+0.11-
    10–5–10–35.825Na+0.11-
    8×10–5525Na+0.10.1–5-
    8×10–53–1025Na+0.1110–3.58 atm
    8×10–53–1060Na+0.11-
    8×10–53–780Na+0.11-


    List of bentonite samples considered in this study, together with the experimental conditions used in reference studies from 11–17 (details were provided in Table 1). [R]initial represented the concentration of radionuclides, Major Cat. represented the predominant cations, S:L Ratio represented for the solid to liquid ratio, and [CO3]total represented the carbonate concentration.


    Bentonite [Ref]Radio nuclide[R]initial (mol L–1)pHTemp (℃)Major Cat.Ionic Strength (mol L–1)S:L Ratio (g L–1)[CO3]total (mol L–1)
    Jinchuan [11]Eu6.7×10–82–1025Na+0.10.5-
    3.3×10–62–1025Na+0.10.5-
    6.7×10–83–1025Na+0.10.510–3.58 atm
    3.8×10–73–1025Na+0.10.510–3.58 atm
    3.3×10–63–1025Na+0.10.510–3.58 atm
    10–9–10–34, 625Na+0.11-
    10–9–10–36.525Na+0.10.5-
    10–9–10–37.525Na+0.10.25-
    FEBEX [12]Eu10–83–1125Na+0.001–0.20.5-
    10–8–10–34.125Na+0.20.5-
    10–9–10–33.825Na+0.10.5-
    10–9–10–33.925Na+0.050.5-
    FEBEX [13]Se4×10–103–1125Na+0.001–0.50.5-
    10–10–10–44.325Na+0.1, 0.50.5–1-
    10–10–10–47.225Na+0.010.5–1-
    Western India [14]Am6×10–92–1025Na+0.10.5-
    6×10–92–1025Na+0.050.5-
    6×10–92–1025Na+0.010.5-
    6×10–92–1025Ca0.0340.5-
    Eu10–7–10–36.025Na+0.10.5-
    GMZ [15]Am6×10–103–1025, 50, 80Na+0.10.5-
    6×10–103–1025Ca0.10.5-
    6×10–104.1, 6.625Na+0−0.30.5-
    10–10–10–84.025Na+0.10.5-
    10–11–10–96.525Na+0.10.5-
    10–10–10–83.725Ca0.10.5-
    GMZ [16]Se1.2×10–53–925Na+0.120-
    10–6–10–34.125Na+0.120-
    Eu3.3×10–54–925Na+0.11-
    Se1.2×10–53–925Na+0.120-
    Eu3.3×10–5
    Se3.3×10–54–925Na+0.11-
    Eu3.3×10–5
    Se3.3×10–34–925Na+0.11-
    Eu3.3×10–5
    SAz-1 [17]U2×10–72–925Na+0.10.03–310–3.5 atm
    2×10–62–925Na+0.10.310–3.5 atm


    Summary of the site types, site capacities of sorption models for various bentonite samples. Here, Ss-OH, Sw1-OH, Sw2-OH, Al-OH, Si-OH, Sw-OH, S-OH, and Y-OH represented surface complexation sites, and X represented cation exchange sites.


    BentoniteSorption ModelSite TypesSite CapacitiesReference
    SWy-12SP-NE-SC/CESs-OH2.0 × 10−3 mol kg−11–6
    Sw1, w2-OH4.0 × 10−2 mol kg−1
    X0.87 eq kg−1
    Volclay2SP-CC-SC/CEAl-OH1.75 × 10−2 mol kg−17
    Si-OH2.5 × 10−1 mol kg−1
    X5.75 × 10−1 mol kg−1
    MX-802SP-NE-SC/CESs-OH2.0 × 10−3 mol kg−18
    Sw1, w2-OH4.0 × 10−2 mol kg−1
    X0.787 eq kg−1
    2SP-DL-SC/CEAl-OH1.7 × 10−3 mol m−29
    Si-OH3.4 × 10−3 mol m−2
    X3.63 × 10−5 mol m−2
    Jinchuan2SP-DL-SC/CES-OH5.88 × 10−7 mol m−210
    Y-OH1.18 × 10−6 mol m−2
    X1.16 × 10−5 mol m−2
    2SP-DL-SC/CESs-OH1.88 × 10−8 mol m−211
    Sw-OH5.69 × 10−7 mol m−2
    Y-OH1.18 × 10−6 mol m−2
    X1.16 × 10−5 mol m−2
    FEBEX2SP-NE-SC/CESs-OH2.01 × 10−3 mol kg−112
    Sw-OH6.01 × 10−2 mol kg−1
    X1.02 eq kg−1
    2SP-NE-SC/CESs-OH2.01 × 10−3 mol kg−113
    Sw-OH6.01 × 10−2 mol kg−1
    Western India2SP-NE-SC/CESs-OH1.8 × 10−3 mol kg−114
    Sw-OH3.6 × 10−2 mol kg−1
    X0.76 eq kg−1
    GMZ2SP-NE-SC/CESs-OH1.04 × 10−8 mol m−215
    Sw-OH1.03 × 10−6 mol m−2
    Y-OH2.08 × 10−6 mol m−2
    X1.35 × 10−5 mol m−2
    2SP-DL-SC/CES-OH9.39 × 10−7 mol m−216
    Y-OH1.18 × 10−6 mol m−2
    X1.35 × 10−5 mol m−2
    SAz-12SP-DL-SC/CEAl-OH4.73 × 10−5 mol L−117
    Si-OH5.69 × 10−5 mol L−1


    Summary of the protolysis reactions and their constants of sorption models for various bentonite samples. Here, Ss-OH, Sw1-OH, Sw2-OH, Al-OH, Si-OH, Sw-OH, S-OH, and Y-OH represented surface complexation sites, respectively.


    BentoniteSorption ModelProtolysis Reactionslog Ksite
    SWy-12SP-NE-SC/CESs/w1-OH + H+ ↔ Ss/w1-OH2+4.5
    Ss/w1-OH ↔ Ss/w1-O + H+−7.9
    Sw2-OH + H+ ↔ Sw2-OH2+6.0
    Sw2-OH ↔ Sw2-O + H+−10.5
    Volclay2SP-CC-SC/CEAl-OH + H+ ↔ Al-OH2+7.9
    Al-OH ↔ Al-O + H+−9.4
    Si-OH ↔ Si-O + H+−7.8
    MX-802SP-NE-SC/CESs/w1-OH + H+ ↔ Ss/w1-OH2+4.5
    Ss/w1-OH ↔ Ss/w1-O + H+−7.9
    Sw2-OH + H+ ↔ Sw2-OH2+6.0
    Sw2-OH ↔ Sw2-O + H+−10.5
    2SP-DL-SC/CEAl-OH + H+ ↔ Al-OH2+5.1
    Al-OH ↔ Al-O + H+−8.5
    Si-OH ↔ Si-O + H+−7.9
    Jinchuan2SP-DL-SC/CES-OH + H+ ↔ S-OH2+3.23
    S-OH ↔ S-O + H+−3.89
    Y-OH ↔ Y-O + H+−6.57
    2SP-DL-SC/CESs, w-OH + H+ ↔ Ss, w-OH2+3.23
    Ss, w-OH ↔ Ss, w-O + H+−3.89
    Y-OH ↔ Y-O + H+−6.57
    FEBEX2SP-NE-SC/CESs-OH + H+ ↔ Ss-OH2+4.8
    Ss-OH ↔ Ss-O + H+−9.9
    Sw-OH + H+ ↔ Sw-OH2+5.3
    Sw-OH ↔ Sw-O + H+−8.4
    Western India2SP-NE-SC/CESs-OH + H+ ↔ Ss-OH2+4.5
    Ss-OH ↔ Ss-O + H+−7.9
    Sw-OH + H+ ↔ Sw-OH2+4.5
    Sw-OH ↔ Sw-O + H+−7.9
    GMZ2SP-NE-SC/CESs, w-OH + H+ ↔ Ss, w-OH2+5.83
    Ss, w-OH ↔ Ss, w-O + H+−7.02
    Y-OH ↔ Y-O + H+−8.75
    2SP-DL-SC/CES-OH + H+ ↔ S-OH2+6.15
    S-OH ↔ S-O + H+−9.27
    Y-OH ↔ Y-O + H+−9.06
    SAz-12SP-DL-SC/CEAl-OH + H+ ↔ Al-OH2+8.33
    Al-OH ↔ Al-O + H+−9.73
    Si-OH ↔ Si-O + H+−7.20


    Surface complexation constants and selectivity coefficients on surface complexation sites (Ss-OH, Sw1-OH, Al-OH, Si-OH) and cation exchange sites (X) for uranium (U) sorption on various bentonites.


    Surface complexation / Cation exchange reactionlog K
    SWy-1 + 2SP-NE-SC/CE
    Ss-OH + UO22+ ↔ Ss-OUO2+ + H+3.1a,b
    Ss-OH + UO22+ + H2O ↔ Ss-OUO2OH + 2H+−3.4a, −4.6b
    Ss-OH + UO22+ + 2H2O ↔ Ss-OUO2(OH)2 + 3H+−11a, −12.6b
    Ss-OH + UO22+ + 3H2O ↔ Ss-OUO2(OH)32− + 4H+−20.5a, −20.9b
    Ss-OH + UO22+ + CO32− ↔ Ss-OUO2CO3 + H+9.8b
    Ss-OH + UO22+ + 2CO32− ↔ Ss-OUO2(CO3)23− + H+15.5b
    Sw1-OH + UO22+ ↔ Sw1-OUO2+ + H+0.7a, 0.5b
    Sw1-OH + UO22+ + H2O ↔ Sw1-OUO2OH + 2H+−5.7a,b
    Sw1-OH + UO22+ + CO32− ↔ Sw1-OUO2CO3 + H+9.3b
    2Na-X + UO22+ ↔ UO2-X2 + 2Na+0.7a, 1.4a, 0.45b
    MX-80 + 2SP-NE-SC/CE
    Ss-OH + UO22+ ↔ Ss-OUO2+ + H+3.1c
    Ss-OH + UO22+ + H2O ↔ Ss-OUO2OH + 2H+−3.4c
    Ss-OH + UO22+ + 2H2O ↔ Ss-OUO2(OH)2 + 3H+−11c
    Ss-OH + UO22+ + 3H2O ↔ Ss-OUO2(OH)32− + 4H+−20.5c
    Sw1-OH + UO22+ ↔ Sw1-OUO2+ + H+0.7c
    Sw1-OH + UO22+ + H2O ↔ Sw1-OUO2OH + 2H+−5.7c
    Sw1-OH + UO22+ + CO32− ↔ Sw1-OUO2CO3 + H+9.3c
    2Na-X + UO22+ ↔ UO2-X2 + 2Na+0.15c
    Volclay + 2SP-CC-SC/CE
    Al-(OH)2 + UO22+ ↔ Al-(OH)2UO22+14.9d
    Si-(OH)2 + UO22+ ↔ Si-O2UO2 + 2H+−3.8d
    Si-(OH)2 + 3UO22+ + 5H2O ↔ Si-O2(UO2)3(OH)5− + 7H+−20.0d
    2Na-X + UO22+ ↔ UO2-X2 + 2Na+3.0d
    SAz-1 + 2SP-DL-SC/CE
    Al-OH + UO22+ ↔ Al-OUO2+ + H+2.7e
    Al-OH + 3UO22+ + 5H2O ↔ Al-O(UO2)3(OH)5 + 6H+−14.95e
    Si-OH + UO22+ ↔ Si-OUO2+ + H+2.6e
    Si-OH + 3UO22+ + 5H2O ↔ Si-O(UO2)3(OH)5 + 6H+−15.29e

    aBradbury and Baeyens, 2005.

    bFernandes et al., 2012.

    cBradbury and Baeyens, 2011.

    dKowal-Fouchard et al., 2004.

    ePabalan and Turner, 1996.



    Surface complexation constants and selectivity coefficients on surface complexation site (S-OH) and cation exchange site (X) for uranium (U) sorption on Jinchuan bentonite at elevated temperature condition (Yang et al., 2010).


    Surface complexation / Cation exchange reactionlog K
    Jinchuan + 2SP-DL-SC/CE
    S-OH + UO22+ ↔ S-OUO2+ + H+−0.9a, 0.1b, 0.5c
    S-OH + 3UO22+ + 5H2O ↔ S-O(UO2)3(OH)5 + 6H+−15.7a, −13.1b, −11.3c
    S-OH + 3UO22+ + 7H2O ↔ S-O(UO2)3(OH)72− + 8H+−26.2a, −23.0b, −21.0c
    2Na-X + UO22+ ↔ UO2-X2 + 2Na+0.6a, b, c

    aT = 25℃.

    bT = 60℃.

    cT = 80℃.



    Surface complexation constants and selectivity coefficients on surface complexation sites (Ss-OH, Sw-OH) and cation exchange sites (X) for americium (Am) sorption on various bentonite samples.


    Surface complexation / Cation exchange reactionlog K
    SWy-1 + 2SP-NE-SC/CE
    Ss-OH + Am3+ ↔ Ss-OAm2+ + H+1.6a,b
    Ss-OH + Am3+ + H2O ↔ Ss-OAmOH+ + 2H+−6.8a,b
    Ss-OH + Am3+ + 2H2O ↔ Ss-OAm(OH)2 + 3H+−15a, −14.8b
    Ss-OH + Am3+ + 3H2O ↔ Ss-OAm(OH)3− + 4H+−25.6a
    3Na-X + Am3+ ↔ Am-X3 + 3Na+1.67a, 1.46b
    3Ca-X2 + 2Am3+ ↔ 2Am-X3 + 3Ca2+1.66b
    GMZ + 2SP-NE-SC/CE
    Ss-OH + Am3+ ↔ SsO-Am2+ + H+2.7c
    Ss-OH + Am3+ + H2O ↔ Ss-OAmOH+ + 2H+−5.5c
    Ss-OH + Am3+ + 2H2O ↔ Ss-OAm(OH)2 + 3H+−13.5c
    Ss-OH + Am3+ + 3H2O ↔ Ss-OAm(OH)3− + 4H+−25.1c
    3Na-X + Am3+ ↔ Am-X3 + 3Na+2.0c
    Na-X + 0.5Ca2+ ↔ Ca0.5-X + Na+0.4c
    Western India + 2SP-NE-SC/CE
    Ss-OH + Am3+ ↔ Ss-O Am2+ + H+1.87d
    Ss-OH + Am3+ + H2O ↔ Ss-OAmOH+ + 2H+−5.4d
    Ss-OH + Am 3+ + 2H2O ↔ Ss-OAm(OH)2 + 3H+−20.2d
    Sw-OH + Am 3+ ↔ Sw-OAm2+ + H+−0.3d
    3Na-X + Am3+ ↔ Am-X3 + 3Na+1.3d

    aBradbury and Baeyens, 2005.

    bBradbury and Baeyens, 2006.

    cGao et al., 2021.

    dKumar et al., 2013.



    Surface complexation constants on surface complexation sites (Ss-OH, Sw-OH, and S-OH) for selenium (Se) sorption on various bentonite samples.


    Surface complexation / Cation exchange reactionlog K
    FEBEX + 2SP-NE-SC
    Ss-OH2+ + SeO32− ↔ Ss-OH2SeO3−12.0a
    Sw-OH2+ + SeO32− ↔ Sw-OH2SeO3−11.95a
    Ss-OH2+ + HSeO3 ↔ Ss-OH2SeO317.9a
    Sw-OH2+ + HSeO3 ↔ Sw-OH2SeO317.65a
    GMZ +2SP-DL-SC/CE
    S-OH2+ + HSeO3 ↔ S-SeO3+ H2O3.3b
    2S-OH + HSeO3 ↔ (S)2-SeO3 + H2O + OH−15.8b
    2S-OH + Eu3+ + HSeO3 ↔ (SO)2-EuSeO3 + 3H+−1.1b

    aMissana et al., 2009.

    bShi et al., 2014.



    Surface complexation constants and selectivity coefficients on surface complexation sites (Ss-OH, Sw-OH, S-OH) and cation exchange sites (X) for europium (Eu) sorption on various bentonite samples.


    Surface complexation / Cation exchange reactionlog K
    SWy-1 + 2SP-NE-SC/CE
    Ss-OH + Eu3+ ↔ Ss-OEu2+ + H+1.6a, b, 2.3c
    Ss-OH + Eu3+ + H2O ↔ Ss-OEuOH+ + 2H+−6.4a, −5.9b, c
    Ss-OH + Eu3+ + 2H2O ↔ Ss-OEu(OH)2 + 3H+−15.7a, −14.2b, −13.9c
    Ss-OH + Eu3+ + 3H2O ↔ Ss-OEu(OH)3− + 4H+−25.8c
    Ss-OH + Eu3+ + CO32− ↔ Ss-OEuCO3 + H+8.3b
    Ss-OH + Eu3+ + CO32− + H2O ↔ Ss-OEuOHCO3 + 2H+−0.25b
    3Na-X + Eu3+ ↔ Eu-X3 + 3Na+1.47a, 1.46b, 1.5c
    MX-80 + 2SP-NE-SC/CE
    Ss-OH + Eu3+ ↔ Ss-OEu2+ + H+1.6d
    Ss-OH + Eu3+ + H2O ↔ Ss-OEuOH+ + 2H+−16.4d
    Ss-OH + Eu3+ + 2H2O ↔ Ss-OEu(OH)2 + 3H+−15.7d
    3Na-X + Eu3+ ↔ Eu-X3 + 3Na+1.5d
    Jinchuan + 2SP-DL-SC/CE
    Ss-OH + Eu3+ ↔ Ss-OEu2+ + H+1.3e, f
    Sw-OH + Eu3+ ↔ Sw-OEu2+ + H+−2.0e, f
    Sw-OH + Eu3+ + H2O↔ Sw-OEuOH+ + 2H+−6.8e, f
    Sw-OH + Eu3+ + 3H2O ↔ Sw-OEu(OH)3− + 4H+−20.6e, f
    Sw-OH + Eu3+ + CO32− ↔ Sw-OEuCO3+ H+8.2e
    3Na-X + Eu3+ ↔ Eu-X3 + 3Na+1.3e, f
    GMZ + 2SP-DL-SC/CE
    S-OH + Eu3+ + H2O ↔ Ss-OEuOH+ + 2H+−7.7g
    2S-OH + Eu3+ + HSeO3 ↔ (SO)2-EuSeO3 + 3H+−1.1g
    3Na-X + Eu3+ ↔ Eu-X3 + 3Na+2.0g
    Western India + 2SP-NE-SC/CE
    Ss-OH + Eu3+ ↔ Ss-OEu2+ + H+1.87h
    Ss-OH + Eu3+ + H2O ↔ Ss-OEuOH+ + 2H+−5.4h
    Ss-OH + Eu3+ + 2H2O ↔ Ss-OEu(OH)2 + 3H+−20.2h
    Sw-OH + Eu3+ ↔ Sw-OEu2+ + H+−0.3h
    3Na-X + Eu3+ ↔ Eu-X3 + 3Na+1.3h

    aBradbury and Baeyens, 2005.

    bFernandes et al., 2008.

    cSchnurr et al., 2015.

    dBradbury and Baeyens, 2011.

    eGuo et al., 2009.

    fChen et al., 2014.

    gShi et al., 2015.

    hKumar et al., 2013.



    Surface complexation constants and selectivity coefficients on surface complexation site (Al-OH) and cation exchange site (X) for europium (Eu) sorption on Jinchuan bentonite at elevated temperature condition (Tertre et al., 2006).


    Surface complexation / Cation exchange reactionlog K
    MX-80 + 2SP-DL-SC/CE
    Al-OH + Eu3+ ↔ Al-OEu2+ + H+−1.0a, 2.5b, 6.5c, 7.5d
    3Na-X + Eu3+ ↔ Eu-X3 + 3Na+5.4a, b, c, d

    aT = 25℃.

    bT = 40℃.

    cT = 80℃.

    dT = 150℃.



    Surface complexation constants and selectivity coefficients on surface complexation site (Ss-OH, Sw1-OH) and cation exchange site (X) for europium (Eu) sorption on Na- and Ca-bentonite (Bradbury and Baeyens, 2002).


    Surface complexation / Cation exchange reactionlog K
    SWy-1 + 2SP-NE-SC/CE
    Ss-OH + Eu3+ ↔ Ss-OEu2+ + H+1.8a, 0.8b
    Ss-OH + Eu3+ + H2O ↔ Ss-OEuOH+ + 2H+−5.4a, −5.7b
    Ss-OH + Eu3+ + 3H2O ↔ Ss-OEu(OH)3− + 4H+−22.1a, −22.6b
    Sw1-OH + Eu3+ ↔ Sw1-OEu2+ + H+−0.5a, −1.2b
    Ss-OH + Eu3+ ↔ Ss-OEu2+ + H+1.8a, 0.8b
    3Na-X + Eu3+ ↔ Eu-X3 + 3Na+1.47a, b
    3Ca-X2 + 2Eu3+ ↔ 2Eu-X3 + 3Ca2+1.11a, b

    aNa-montmorillonite.

    bCa-montmorillonite.



    Surface complexation constants on surface complexation sites (Ss-OH, Sw1-OH) for europium (Eu) sorption on FEBEX bentonite sample using different thermodynamic databases, EQ(3)/6 and ThermoChimie (Missana et al., 2021).


    Surface complexation / Cation exchange reactionlog K
    FEBEX+ 2SP-NE-SC/CE
    Ss-OH + Eu3+ ↔ Ss-OEu2+ + H+0.9a, 1.24b
    Ss-OH + Eu3+ + 2H2O ↔ Ss-OEu(OH)2 + 3H+−12.2a, −16.02b
    Sw1-OH + Eu3+ ↔ Sw1-OEu2+ + H+−0.05a, −0.32b
    Sw1-OH + Eu3+ + 2H2O ↔ Sw1-OEu(OH)2 + 3H+−13.62a, −17.16b
    Ss-OH + Eu3+ + CO32− ↔ Ss-OEuCO3+ H+−2.48a, 7.68b
    Sw1-OH + Eu3+ + CO32− ↔ Sw1-OEuCO3+ H+−3.36a, 5.7b

    aEQ(3)/6 (Delany and Lundeen, 1991).

    bThermoChimie (Guillaumont and Mompean, 2003).


    KSEEG
    Dec 29, 2023 Vol.56 No.6, pp. 629~909

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