Recovery and immobilization of cesium from aqueous solution after hydrothermal treatment using functional porous glass

Fukushima Daiichi Nuclear Power Station accident caused a large amount of waste contaminated with radioactive Cs. Decontamination of radioactive Cs from soil and its safe disposal are required. Functional porous glass (FPG) is effective for removal of Cs from aqueous solution, and vitrification can subsequently be done in a stepwise process. To demonstrate the validity of this proposed decontamination process, adsorption, elution, and vitrification experiments were carried out. First, the adsorption of Cs on FPG was governed by a pseudo second-order kinetic model and the adsorption isotherm was in accord with the Langmuir model. The adsorption experiments targeted 11 elements, which represent the components after hydrothermal treatment of contaminated soil; Cs showed the highest adsorption selectivity. Second, the vitrification tests of the FPG with CsCl revealed that no loss of Cs was observed at temperatures up to 1200°C The elution experiments showed the lowest normalized leaching (NLCs) values at a low temperature of 800°C without Na addition, or at 1200°C with Na addition, indicating that the melting of the pores and glass matrix, retention within the aluminosilicate structure were the key experimental factors. The feasibility of removal and vitrification of Cs via FPG was demonstrated.