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Activated Sericite: An Efficient and Effective Natural Clay Material for Attenuation of Cesium from Aquatic Environment

Pedosphere 2014 v.24 no.6 pp. 731-742
aquatic environment, cesium, clay, data collection, electrolytes, equations, hydrochloric acid, mica, models, pH, soil erosion, sorption, sorption isotherms, surface area
Sericite is mica-based natural clay that is annealed at 800 °C for 4 h, followed by acid activation using 3.0 mol L−1 HCl at 100 °C. The interaction of cesium (I), Cs(I), with sericite could provide useful data for the study of soil erosion or mass water movement utilizing the natural radioactive Cs. In this study sericite and activated sericite were used to assess their suitability in the attenuation of Cs from the aquatic environment under both batch and column experiments. The surface morphological studies indicated that a disordered and heterogeneous surface structure was exhibited by the activated sericite, whereas the native sericite exhibited a compact and layered structure. The Brunauer-Emmett-Teller (BET) specific surface area results indicated a significant increase in the surface area due to the activation of sericite. The batch reactor data collected for various parametric studies revealed that an increase in pH (from 2.0 to 8.0) and sorbate concentration (from 10.0 to 100.0 mg L−1) apparently favored the attenuation of Cs(I). The timedependent sorption data revealed that Cs(I) uptake was very rapid, and it achieved its saturation value within just 50 min of contact. The kinetic modeling studies indicated that the uptake of Cs(I) followed a pseudo-second-order rate equation; hence, the attenuation capacity of these solids for Cs(I) was estimated to be 0.858 and 4.353 mg g−1 for sericite and activated sericite solids, respectively. The adsorption isotherm modeling data showed a reasonably good applicability of the Freundlich model than the Langmuir model. The effect of background electrolyte concentrations (0.001 to 0.1 mol L−1) of Mg(NO3)2 indicated that the presence of this electrolyte could not significantly affect the percent removal of Cs(I) by activated sericite. Furthermore, the fixed-bed column reactor operations were performed to obtain the breakthrough data, which were fitted well to the Thomas non-linear equation. Therefore, the loading capacity of Cs(I) was estimated to be 1.585 mg g−1 at the initial influent Cs(I) concentration of 30.0 mg L−1 at pH 5.0.