Synthesis and spark plasma sintering of solid-state matrices based on calcium silicate for 60Co immobilization

An effective sorption material for the immobilization of cobalt radionuclides into highly safe and reliable solid-state matrices is proposed. The resulting silicate sorbent СaSiO ₃ had an amorphous mesoporous structure (A _BET 53 m ² /g) and a sorption capacity Co ions of 3.32 mmol/g. The physico-chemical characteristics of the СaCoSi ₂O ₆ sample obtained after Co ²⁺ ions sorption were studied using XRD, N ₂ and Ar adsorption-desorption, SEM-EDX and TG/DTA methods. Solid-state silicate matrices characterized by high density values (2.86–3.16 g/cm ³ ), compressive strength (150–637 MPa) and Vickers microhardness (1.80–5.25 GPa) were obtained by spark plasma sintering (SPS). The sample obtained at 1000 °C had the lowest values of Co ²⁺ ions leaching (R _Co ~10 ⁻⁷ g/(cm ² ×day)) and diffusion coefficient (De 1.73 ×10 ⁻¹⁷ cm ²/s) from silicate matrices. Thus, the obtained СaCoSi ₂O ₆ silicate matrices saturated with Co ions comply with the regulatory requirements of GOST R 50926–96 and ANSI/ANS 16.1 for ⁶⁰Co immobilization.