Study on the Effect of Gamma-Ray Irradiation on the Adsorption of ⁹⁹Tc and Re by a Silica-Based Pyridine Resin

A silica-based anion exchange resin was synthesized and used to remove 99Tc from real radioactive liquid waste. The adsorbent had a uniform particle size and exhibited good thermal stability up to 100 °C, which is promising for large-scale column experiments. In accordance with the chemical similarity with Tc, Re was used as a surrogate in this study. The N 1s high-resolution XPS spectra of the adsorbent before and after the adsorption of Re indicated that the ion exchange reaction was the controlling mechanism in the process. After γ-ray irradiation, the changing trend of the Kd was consistent, which showed that the competitive adsorption of NO3− led to a decrease in Kd. The adsorption capacity for the Re decreased slightly from 35.8 to 31.9 mg/g with the increase in the absorbed dose from 0 to 50 kGy. The separation and recovery of Re and the coexisting ions were achieved by chromatographic separation experiments, and the recovery percentage of Re was 86%. In real radioactive liquid waste, N3/SiO2 exhibited good selectivity toward 99Tc over the coexisting metals, namely, 90Sr, 137Cs, 241Am, and U, and the decontamination efficiency of 99Tc attained 65%