TY - JOUR
T1 - Adsorption and Desorption Behaviors of Sr on Montmorillonite
T2 - A Triple Sr Isotope Perspective
AU - Liu, Hou Chun
AU - Hsieh, Jia You
AU - Chen, Yen Hong
AU - You, Chen Feng
AU - Jiang, Wei Teh
AU - Wen, Hsin Yi
N1 - Publisher Copyright:
© 2022 American Chemical Society.
PY - 2022/9/15
Y1 - 2022/9/15
N2 - 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 (87Sr/86Sr and δ88/86Sr) 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 Δ88/86Srmineral-water (a value independent from the clay type) was -0.17‰. Consequently, water δ88/86Sr 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.
AB - 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 (87Sr/86Sr and δ88/86Sr) 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 Δ88/86Srmineral-water (a value independent from the clay type) was -0.17‰. Consequently, water δ88/86Sr 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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U2 - 10.1021/acsearthspacechem.2c00222
DO - 10.1021/acsearthspacechem.2c00222
M3 - Article
AN - SCOPUS:85136656304
SN - 2472-3452
VL - 6
SP - 2250
EP - 2260
JO - ACS Earth and Space Chemistry
JF - ACS Earth and Space Chemistry
IS - 9
ER -