Mechanistic and thermodynamic aspects of Cs(I) and Sr(II) interactions with smectite-rich natural clay

Kasar, Sharayu; Kumar, Sumit; Saha, Abhijit; Tomar, B. S.; Bajpai, R.

doi:10.1007/s12665-017-6595-8

Cited by 13 publications

(8 citation statements)

References 40 publications

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“…An extended X-ray absorption fine structure (EXAFS) analysis confirmed that Sr forms mononuclear, outer-sphere complexes at the water/clay interface during adsorption at pH < 11. ,− This is regardless of the clay type and even after laboratory incubation for 1 year . The distribution coefficient ( K d ) of Sr 2+ adsorption by minerals increases linearly with pH (if pH ≤ 5). , Various environmental factors can affect the adsorption of Sr, including water ionic strength, ,,, temperature, , Sr 2+ concentration, , and humic acid content . Sr 2+ is found in the form of weakly bound outer-sphere complexes at the water/mineral interface and readily competes with other monovalent and divalent cations coexisting in waters: ,, Sr adsorption decreases with increasing water ionic strength.…”

Section: Introductionmentioning

confidence: 94%

Adsorption and Desorption Behaviors of Sr on Montmorillonite: A Triple Sr Isotope Perspective

Liu

Hsieh

Chen

et al. 2022

ACS Earth Space Chem.

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Montmorillonite is a widespread mineral, which affects the migration of Sr in the critical zone. Hydrochemical factors influencing Sr adsorption have been evaluated in the literature through laboratory batch experiments. Since those experiments were conducted using high-concentration and high-purity standard solutions, the influences of chemical matrices or element relative concentrations in water remain unclear. Here, we reassessed the adsorption and desorption behaviors of Sr on montmorillonite using natural waters with various chemical matrices and ionic strengths. Triple Sr isotopes ( 87 Sr/ 86 Sr and δ 88/86 Sr) were used to trace the exchange processes between the minerals and the waters. Adsorption and desorption occurred in all processed samples, but to varying degrees. These phenomena (especially desorption) were principally controlled by the ionic competition of divalent ions (i.e., Ca and Mg), rather than by ionic strength. Sr isotope fractionation occurred during adsorption. Isotopically lighter Sr was preferentially adsorbed: the mean Δ 88/86 Sr mineral−water (a value independent from the clay type) was −0.17‰. Consequently, water δ 88/86 Sr depended on both the mixing of mineral-bound and initial water Sr and on the degree of Sr adsorption; moreover, the exchange process was a reversible reaction and reached its chemical and isotopic equilibrium within a short time.

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Section: Introductionmentioning

confidence: 94%

Adsorption and Desorption Behaviors of Sr on Montmorillonite: A Triple Sr Isotope Perspective

Liu

Hsieh

Chen

et al. 2022

ACS Earth Space Chem.

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“…The equilibrium experiments with bentonites of western India, carried out in the concentration of 10 −9 -10 −2 mol/L at pH 5.6 ± 0.2 in 0.1 and 0.01 M NaCl, revealed two types of sorption centers for Cs + and only one type for Sr 2+ [30,33]. In addition, Putilina et al [49] showed that formation of surface Sr(II) complexes on the side surfaces of (010) 2:1 clay minerals makes a significant contribution to the total sorption at pH > 8.…”

Section: Heterogeneity Of Sorption Centersmentioning

confidence: 97%

“…As shown by numerous studies, the main sorption mechanism of Cs(I) and Sr(II) on montmorillonite is ion exchange [20,24,33,55], which occurs regardless of pH.…”

Section: Adsorption Mechanisms Of Cs(i) and Sr(ii)mentioning

confidence: 99%

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Adsorption of Cs(I) and Sr(II) on Bentonites with Different Compositions at Different pH

et al. 2022

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This paper deals with adsorption regularities and mechanisms of nonradioactive Cs(I) and Sr(II) analogs on bentonites of different chemical and mineral composition from solutions of Cs and Sr nitrates with pH 3, 7, and 10 units at constant ionic strength. The bentonites were taken from the deposits Taganskoe (T), Dash-Salakhlinskoe (DS), Zyryanskoe (Z), and 10th Khutor (10H). The pH of bentonite aqueous suspensions, T and DS, exceeded 9 units. A less alkaline reaction was observed in bentonite suspensions Z and T with pH 8.94 and 7.70, respectively. Bentonites T and DS contained significant amounts of nonsilicate iron compounds, 1.0 and 0.5%, respectively. The recovery rate of the studied clays from aqueous solutions of Cs(I) and Sr(II) ions in concentrations from 0.25 to 5 mmol/L varied from 50% to 90% and decreased in the following order: “Ta-ganskoe” > “Dash-Salakhlinskoe” > “Zyryanskoe” > “10th Khutor” in the studied pH range. The main mechanism of Cs(I) and Sr(II) sorption in the studied pH range was cation fixation in the form of outer-sphere complexes on planar surfaces resulting from ion exchange. Increasing pH (pH > 6) enhanced pH-dependent positions, which allowed Cs(I) and especially Sr(II) ions to fix on them more firmly as inner-sphere complexes. At pH 9–10, Sr(II) could precipitate in the form of carbonates. The sorption of Cs(I) + and Sr(II) was accompanied by competitive interactions with proton at pH < 6 and Na+, Ca2+, Mg2+, and K+ cations at higher pH values. This competition was more apparent at concentrations of Cs(I)and Sr(II) in initial solutions < 0.5 mmol/L. The ability of bentonite T to sorb Cs(I) and Sr(II) in large amounts compared to the other bentonites was determined by high CEC values and charge of smectite T.

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“…Sr can also react with clinoptilolite in complex reactions and ion exchange reactions, and the sorption process is affected by intraparticle and surface film diffusion [ 18 ]. In addition, batch experiments show that the sorption behavior of Sr can be influenced by many factors, such as temperature [ 19 ], pH [ 20 ], colloids [ 21 , 22 ], solid amount [ 23 , 24 ], initial concentration [ 25 ], and ionic strength [ 26 ]. From the above research, it can be recognized that the adsorption behavior of Sr in the claystone of geological disposal repositories is complex and affected by many factors.…”

Section: Introductionmentioning

confidence: 99%

A Study of Sr Sorption Behavior in Claystone from a Candidate High-Level Radioactive Waste Geological Disposal Site under the Action of FeOOH Colloids

Wang

Cai

Zuo

et al. 2022

IJERPH

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Colloids have a significant influence on the migration of nuclides in claystone, which is an important geological barrier. The sorption of strontium on claystone in the presence of FeOOH colloids was investigated in samples from the Suhongtu site, a candidate high-level radioactive waste disposal site in China. The effects of colloid amount, solid content, and pH were investigated by batch tests, and the sorption reaction mechanism was analyzed by kinetic modeling and microscopic characterization techniques. The results indicate that the sorption of Sr by claystone increased with the solids content, and the claystone had a stronger Sr sorption capacity under alkaline conditions. The Sr sorption kinetics were best described by the pseudo-first-order and pseudo-second-order models, which revealed that the progress is affected by physical diffusion and chemical sorption. Furthermore, the microscopic characterization results demonstrate that cation exchange reactions and surface complex reactions are the main sorption mechanisms for Sr sorption on claystone. Ca and Mg plasmas in claystone minerals can have cation replacement reactions with Sr, and functional groups such as -OH and [CO3]2− can have complexation reactions with Sr to adsorb Sr on the surface of the claystone. Additionally, the presence of the FeOOH colloid inhibited the sorption effect of claystone slightly. The FeOOH colloid could occupy sorption sites on the claystone surface, which reduces the activity of the functional groups and inhibits the sorption of Sr on claystone.

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Mechanistic and thermodynamic aspects of Cs(I) and Sr(II) interactions with smectite-rich natural clay

Cited by 13 publications

References 40 publications

Adsorption and Desorption Behaviors of Sr on Montmorillonite: A Triple Sr Isotope Perspective

Adsorption and Desorption Behaviors of Sr on Montmorillonite: A Triple Sr Isotope Perspective

Adsorption of Cs(I) and Sr(II) on Bentonites with Different Compositions at Different pH

A Study of Sr Sorption Behavior in Claystone from a Candidate High-Level Radioactive Waste Geological Disposal Site under the Action of FeOOH Colloids

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