Solidification of ettringite after uptaking selenate as a surrogate of radionuclide in glass-ceramics by using industrial by-products

After accumulation of toxic ions from a contaminated source, spent absorbents and coprecipitation sludge should be stabilized before landfilling for long time storage, especially in the case of absorbed radionuclides. Therefore, development of novel and efficient method to stabilize spent absorbents that contain highly toxic ions is urgently needed. In the present work, the use of industrial by-products as raw materials to produce ceramics to treat toxic waste was investigated. As a typical oxoanion absorbent, selenate-doped ettringite was mixed with granulated blast furnace slag and silica fume 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 test. The synthesized ceramics exhibited excellent behavior for immobilization of selenate, and only 0.1 mg/L of selenate was leached out. However, the total concentration of selenate in the mixture was not reduced during calcination. The X-ray photoelectron spectroscopy revealed the stabilization mechanism is based on encapsulation. In addition, the ceramic materials exhibited excellent chemical stability at pH 2–12. These results showed that industrial by-products can be successfully applied to produce ceramics for immobilization and storage of hazardous wastes.