Synthesis of tobermorite from the ash after treatment of asbesto-containing disaster waste, and its removal ability of Cs(I) from aqueous solution

Abstract

Tobermorite was synthesized successfully from the ash, which was produced and detoxified from asbesto-containing disaster waste in great east Japan earth quake, by alkali hydrothermal treatment. Tobermorite synthesis was examined as a function of reaction temperature and NaOH concentration. The formation of tobermorite was identified in the product treated with 1-4 M NaOH solution at 130 and 180o C, while no product phases was identified at 80o C. With increasing reaction temperature, intensity of tobermorite phase in the product and Cs+ removal ability of the product increase. The product, which was treated with 4 M NaOH at 180o C for 20 h, revealed the high selective uptake for Cs+ in saline water. The Cs+ uptake of the product was extrapolated using Langmuir and Freundlich isotherm models, experimental data are found to fit Langmuir than Freundlich, and the calculated uptake amount was 0.51 mmol/g. The kinetics for Cs+ uptake was tested for pseudo-second order reactions, and the rate constants of uptake were calculated. With increasing temperature of aqueous solution, the kinetics of uptake is almost same and the uptake amount of Cs+ decreases. The product is expected to be used for Cs+ removal from wastewater.