High Removal Efficiency of Radioactive Iodine with In Situ-Synthesized Ag2O–Mg(OH)2 Plate Composites

To promote the capacity of adsorbing radioactive iodine (I^-) in acid and alkaline situations, a high-removal-efficiency adsorbent based on silver oxide (Ag₂O) and magnesium hydroxide (Mg(OH)₂) was synthesized by the in situ method. To determine the mechanism of this novel absorbent, batch experiments related to the temperature, pH, competitive ion (Cl^-), and kinetic analysis were carried out. The results showed that the Ag₂O-Mg(OH)₂ plate composites had high adsorption capacity and efficiency for I^- (409 mg/g, 25 °C) with a wide range of pH values (3-9). In addition, the adsorption time from the initial concentration to I^- removal (97.36%) was only 20 min. Competitive ion experiments depicted that Cl^- influenced the capacity of adsorbing I^-. The k value of the pseudo-second-order model and regression factor R ² were 7.86 × 10^-3g mg^-1 min^-1 and 0.999 at 25 °C, respectively. The kinetics and XPS results proved that the mechanism of adsorption was chemical adsorption. Compared with other commercial adsorbents, the Ag₂O-Mg(OH)₂ plate composites had potential for application in nuclear wastewater treatment with low cost and high efficiency.