Short-term interaction of Fe(II)–GMZ bentonite under hydro-thermo-mechanical conditions

The interface reaction between the bentonite buffer barrier and the metal disposal canister is one of the key factors affecting the long-term safety of high-level radioactive waste geological disposal repository. To investigate the short-term interactions between Fe(II) corrosion products and Gaomiaozi(GMZ) bentonite under low-to-moderate temperature and confining pressure, GMZ bentonite is selected as the test material. An independently developed THCM reaction platform is used to conduct Fe(II)-bentonite contact reaction experiments under different Fe(II) concentrations, temperatures, confining pressures and solution conditions. The ion composition of the suspension after the reaction and the changes in the solid-phase mineral structure are analyzed by atomic absorption spectroscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The results showed that contact with Fe(II) caused a rapid redistribution of aqueous cations, including an increase in the Na⁺ concentration, which is consistent with cation exchange involving the montmorillonite. Increasing the reaction time and temperature affected the aqueous ion composition and the local hydration and bonding environments of the solid phase. However, the XRD and FTIR results don’t provide conclusive evidence for structural Fe incorporation or montmorillonite-to-illite transformation. These findings provide laboratory-scale information on the short-term interaction between Fe(II)-bearing solutions and GMZ bentonite powder, while further validation using highly compacted bentonite is required before extrapolation to repository buffer conditions.