Physicochemical characterization of the retardation of aqueous Cs+ ions by natural kaolinite and clinoptilolite minerals

Abstract

The aim of this study was to carry out kinetic, thermodynamic, and surface characterization of the sorption of Cs + ions on natural minerals of kaolinite and clinoptilolite. The results showed that sorption followed pseudo-second-order kinetics. The activation energies were 9.5 and 13.9 kJ/mol for Cs + sorption on kaolinite and clinoptilolite, respectively. Experiments performed at four different initial concentrations of the ion revealed that the percentage sorption of Cs + on clinoptilolite ranged from 90 to 95, compared to 28 to 40 for the kaolinite case. At the end of a 1 week period, the percentage of Cs + desorption from clinoptilolite did not exceed 7%, while it amounted to more than 30% in kaolinite, indicating more stable fixation by clinoptilolite. The sorption data were best described using Freundlich and D-R isotherm models. Sorption showed spontaneous and exothermic behavior on both minerals, with H 0 being −6.3 and −11.4 kJ/mol for Cs + uptake by kaolinite and clinoptilolite, respectively. Expanding the kaolinite interlayer space from 0.71 to 1.12 nm using DMSO intercalation, did not yield a significant enhancement in the sorption capacity of kaolinite, indicating that the surface and edge sites of the clay are more energetically favored. EDS mapping and elemental analysis of the surface of kaolinite and clinoptilolite revealed more intense signals on the surface of the latter with an even distribution of sorbed Cs + onto the surfaces of both minerals.

Kinetic and thermodynamic investigations of strontium ions retention by natural kaolinite and clinoptilolite minerals

“…This behavior differs from the one reported for Cs + in our earlier study, which showed exothermic behavior [1]. The difference can probably be attributed to the large difference in hydration enthalpies, being −276 and −1443 kJ/mol for Cs + and Sr 2+ ions, respectively.…”

“…This behavior is similar to the one reported earlier for Cs + [1], which could be indicating that such a trend stems from the sorption characteristics of the clay. As was reported for Cs + , the extent of fixation of Sr 2+ by clinoptilolite at the highest studied loading is showing a progressive increase leading to equilibrium attainment within the second day of contact.…”

“…• C. smaller than the ones reported earlier for Cs + sorption on both minerals under the same experimental conditions [1]. As was mentioned in the experimental part, the solutions were prepared using tapwater which contained high concentration of Ca (200 mg/L).…”

“…The results were compared with those of an earlier study in which the same parameters were investigated for Cs + sorption on the same minerals [1]. Strontium, Sr, is an alkali-earth element found in rocks, soil, coal, and oil.…”

Adsorption of Methylene Blue from Aqueous Solution on High Lime Fly Ash: Kinetic, Equilibrium, and Thermodynamic Studies

“…The distribution coefficient is an empirical equilibrium constant and it is valid at particular initial concentration and reaction conditions. [37] The calculated values of DH , DS , and DG at different concentration of the MB adsorption on the high lime fly ash were given in Table 4. The positive value of DH indicates the endothermic nature of the adsorption process of MB on the high lime fly ash.…”