Post-decontamination treatment of MXene after adsorbing Cs from contaminated water with the enhanced thermal stability to form a stable radioactive waste matrix

• Published in: Journal of nuclear materials 2021-01, Vol.543, p.152566, Article 152566
• Main Authors: Hassan, Muhmood ul, Lee, Sujeong, Mehran, Muhammad Taqi, Shahzad, Faisal, Husnain, Syed M., Ryu, Ho Jin
• Format: Article
• Language: English
• Subjects: Adsorbents; Adsorption; Ceramic powders; Ceramics; Cesium; Chemical degradation; Cold pressing; Cold sintering; Composite; Composite materials; Decontamination; Hydroxyapatite; Immobilization; Leaching; Leaching rate; Low temperature; Matrix materials; Microhardness; MXenes; Oxidation; Radioactive waste disposal; Radioactive wastes; Radioisotopes; Simulation; Sintering (powder metallurgy); Stable; Stoichiometry; Thermal stability; Volatilization; Waste management; Water pollution; Water purification
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2020.152566

•Cs adsorbed MXene was thermally stable when mixed with hydroxyapatite and cold sintered at 200 °C.•Hydroxyapatite significantly enhanced the oxidation resistance of MXene by reacting with its terminal group.•MXene-ceramic composite exhibited a > 65 °C increase in oxidation temperature compared to pure MXene in an air environment.•Dried MXene-ceramic composite was cold sintered (200 °C, 10 min) without using any transient phase.•The sintered matrix was highly dense with good micro hardness of 2.2 ± 0.2 GPa and low leaching rates of 10−4 g•m−2•d−1. Safe and stable immobilization of spent adsorbents is a crucial step in nuclear and radioactive waste management. This study provides the first example of the green immobilization of simulated radioactive cesium-adsorbing MXene (Ti3C2Tx) by using hydroxyapatite (HAp) ceramic as a host matrix. The MXene-HAp (MX-HAp) composite exhibited a significantly enhanced thermal stability than that of the pure Cs-adsorbing MXene. The immobilization process was carried out by cold sintering at a low temperature (200 °C), which prevented the possible oxidation and chemical degradation of the spent adsorbent. The developed composite ceramic matrix was highly dense (3 ± 0.01 g·cm−3), mechanically strong (microhardness 2.2 ± 0.2 GPa), and chemically stable. The normalized leaching rate of simulated radioactive cesium was calculated to be 2.02 (±0.09) × 10−4 g·m−2·d−1. Thus, the thermal stability of MXene was enhanced using the HAp dried ceramic powder and non-volatile immobilization of the dried MX-HAp composite was achieved by cold sintering. The reported immobilization process showed no adverse effects on the stoichiometry of the composite matrix materials and no volatilization loss of the adsorbed simulated radionuclide was observed. This study is set to take the green immobilization process for spent adsorbents to the next level by combining MXenes and HAp to develop different types of composite materials. [Display omitted]