Shih-Chin Tsai

Cesium adsorption and distribution onto crushed granite under different physicochemical conditions

The adsorption of cesium onto crushed granite was investigated under different physicochemical conditions including contact time, Cs loading, ionic strength and temperature. In addition, the distribution of adsorbed Cs was examined by X-ray diffraction (XRD) and EDS mapping techniques. The results showed that Cs adsorption to crushed granite behaved as a first-order reaction with nice regression coefficients (R(2) > or = 0.971). Both Freundlich and Langmuir models were applicable to describe the adsorption. The maximum sorption capacity determined by Langmuir model was 80 micromol g(-1) at 25 degrees C and 10 micromol g(-1) at 55 degrees C. The reduced sorption capacity at high temperature was related to the partial enhancement of desorption from granite surface. In general, Cs adsorption was exothermic (DeltaH<0, with median of -12 kJ mol(-1)) and spontaneous (DeltaG<0, with median of -6.1 at 25 degrees C and -5.0 kJ mol(-1) at 55 degrees C). The presence of competing cations such as sodium and potassium ions in synthetic groundwater significantly reduces the Cs adsorption onto granite. The scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM/EDS) mapping method provided substantial evidences that micaceous minerals (biotite in this case) dominate Cs adsorption. These adsorbed Cs ions were notably distributed onto the frayed edges of biotite minerals. More importantly, the locations of these adsorbed Cs were coincided with the potassium depletion area, implying the displacement of K by Cs adsorption. Further XRD patterns displayed a decreased intensity of signal of biotite as the Cs loading increased, revealing that the interlayer space of biotite was affected by Cs adsorption.

Determination of sorption and diffusion parameters of 99Tc in crushed granite using through-diffusion experiments

Diffusion and sorption are important processes associated with radionuclides migration in crystalline rock. These processes are studied in the laboratory using borehole core samples. In this study, we obtained distribution coefficients (Kd), apparent diffusion coefficients (Da) and retardation factor (Rf) using batch and through-diffusion experiments. The

Determination of sorption and diffusion parameters of Se(IV) on crushed granite

R_{\text{f}}^{\text{H/Tc}}

Investigation into bentonite colloid sorption behavior of cesium using batch tests

RfH/Tc and

Numerical analysis for characterizing the sorption/desorption of cesium in crushed granite

K_{\text{d}}^{\text{H/Tc}}

Sorption and diffusion of HTO and cesium in crushed granite compacted to different lengths

KdH/Tc values obtained using the accumulative concentration method were lower than those derived in the batch experiments. These findings demonstrate that reliable Rf and Kd values of 99Tc can be obtained using through-diffusion experiments with a non-reactive radiotracer, thereby bolstering confidence in the assessment of the long-term performance of disposal repositories.