| Summary: | Irradiation resistance is important for adsorbents used in radioactive environments such as high-level liquid waste. In this work, a silica-based composite adsorbent (KAlFe(CN)<sub>6</sub>/SiO<sub>2</sub>) was synthesized and γ-irradiated from 10 to 1000 kGy. The angles of the main X-ray diffraction peaks slightly decreased with the increase in irradiation dose, and a minor decomposition of CN<sup>−</sup> occurred after irradiation to 1000 kGy, indicating that the KAlFe(CN)<sub>6</sub>/SiO<sub>2</sub> adsorbent could preserve structural integrity with a dose below 100 kGy. In 1 to 7 M HNO<sub>3</sub>, the adsorption ability of the irradiated KAlFe(CN)<sub>6</sub>/SiO<sub>2</sub> remained performant, with a higher <i>K</i><sub>d</sub> than 1625 cm<sup>3</sup> g<sup>−1</sup>. The adsorption equilibrium of Pd(II) in 3 M HNO<sub>3</sub> was attained within 45 min before and after irradiation. The maximal adsorption capacity <i>Q</i><sub>e</sub> of the irradiated KAlFe(CN)<sub>6</sub>/SiO<sub>2</sub> on Pd(II) ranged from 45.1 to 48.1 mg g<sup>−1</sup>. A 1.2% relative drop in <i>Q</i><sub>e</sub> was observed after 100 kGy irradiation, showing that γ-irradiation lower than 100 kGy insignificantly affected the adsorption capacity of KAlFe(CN)<sub>6</sub>/SiO<sub>2</sub>. Calculating and comparing the structures and free energies of different adsorption products via the density functional theory (DFT) method showed that KAlFe(CN)<sub>6</sub>/SiO<sub>2</sub> was more inclined to completely adsorb Pd(II) and spontaneously generate Pd[AlFe(CN)<sub>6</sub>]<sub>2</sub>.
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