Conversion of Debris-Treated Ash into a Cesium-Adsorbent Using Alkali Reaction

抄録

A Cs-adsorbent including tobermorite was successfully synthesized from debris-treated ash via an alkali treatment. Tobermorite synthesis was examined as a function of the reaction temperature, time, solid/liquid ratio, and NaOH concentration. The formation of tobermorite was identified in the product treated with a 2–5-M NaOH solution, with a solid/liquid ratio of 50–250 g/L, at 180°C after a 24-h reaction. As the reaction temperature increased, tobermorite was rapidly synthesized owing to the rapid dissolution of Si and Al from the ash. The product, which was treated with 2.0-M NaOH solution (250 g/L) at 180°C for 24 h, indicated the high selective uptake ability for Cs⁺ in saline water. On increasing the solution pH, the adsorption of Cs⁺ increased and remained almost constant above a pH of 6. The Cs⁺ uptake ability of the product was extrapolated using the Langmuir and Freundlich isotherm models, was found to fit the Langmuir model better than the Freundlich model, and the calculated uptake ability was 0.36 mmol/g. The kinetics for the Cs⁺ uptake ability was tested for pseudo-second-order reactions, and the rate constants of the uptake were calculated. Regardless of the temperature of the aqueous solution, the kinetics of the uptake and the uptake of Cs⁺ were almost the same.