EARTH

[3812-23-05] Solidification of selenate-bearing ettringite in glass-ceramics by using industrial by-products

○Binglin Guo¹, Keiko Sasaki¹, Tsuyoshi Hirajima¹ (1. kyushu university)

Chairman: Jae-Young Jung （Kyungpook National University）, Liyuan Chai (Central South University)

Keywords:Calcination, Selenate, Glass ceramics, Radioactive waste, Solidification

After accumulation of radionuclides from contaminated sources, spent absorbents and co-precipitated sludge is classified into radioactive wastes and should be stabilized before landfilling for long term storage. Therefore, development of efficient technologies to stabilize spent absorbents bearing radionuclides is urgently needed. In the present work, the ultilization of industrial by-products as raw materials to produce ceramics to stabilize radioactive waste was investigated using a surrogate. Selenate-doped ettringite was mixed with granulated blast furnace slag (GBFS) and silica fume (SF) and then calcined at various temperatures to produce glass-ceramics. Above 800 °C, the amorphous mixture was converted to glass-ceramics, which were subjected to the toxicity characteristic leaching procedure (TCLP) test. The synthesized ceramics exhibited excellent results for immobilization of selenate in which less than 0.1 mg/L of selenate was leached out. Moreover, according to the digestion experiment, the quantity loss of selenate in the ceramics was not observed even after calcination. The X-ray photoelectron spectroscopy (XPS) revealed the stabilization mechanism is based on encapsulation. In addition, the ceramic materials exhibited excellent chemical stability in a wide range of pH from 2 to 12. These results showed that industrial by-products can be successfully applied to produce ceramics for not only immobilization but also storage of hazardous wastes.