Removal of radioactive iodine from water using Ag2O grafted titanate nanolamina as efficient adsorbent

Efficient Removal of Cationic and Anionic Radioactive Pollutants from Water Using Hydrotalcite-Based Getters

Hydrotalcite (HT)-based materials are usually applied to capture anionic pollutants in aqueous solutions. Generally considered anion exchangers, their ability to capture radioactive cations is rarely exploited. In the present work, we explored the ability of pristine and calcined HT getters to effectively capture radioactive cations (Sr(2+) and Ba(2+)) which can be securely stabilized at the getter surface. It is found that calcined HT outperforms its pristine counterpart in cation removal ability. Meanwhile, a novel anion removal mechanism targeting radioactive I(-) is demonstrated. This approach involves HT surface modification with silver species, namely, Ag2CO3 nanoparticles, which can attach firmly on HT surface by forming coherent interface. This HT-based anion getter can be further used to capture I(-) in aqueous solution. The observed I(-) uptake mechanism is distinctly different from the widely reported ion exchange mechanism of HT and much more efficient. As a result of the high local concentrations of precipitants on the getters, radioactive ions in water can be readily immobilized onto the getter surface by forming precipitates. The secured ionic pollutants can be subsequently removed from water by filtration or sedimentation for safe disposal. Overall, these stable, inexpensive getters are the materials of choice for removal of trace ionic pollutants from bulk radioactive liquids, especially during episodic environmental crisis.

An investigation into the use of cuprous chloride for the removal of radioactive iodide from aqueous solutions

Cuprous chloride (CuCl) was examined as a precipitant to remove iodide (I(-)) from aqueous solutions. The effects of the dosage of CuCl, reaction time, initial concentrations of I(-) and bicarbonate (HCO3(-)) on I(-) removal were investigated. The results showed that the optimized removal efficiency of I(-) reached approximately 95.8% when the dosage was 150 mg/L, the initial I(-) concentration ranged from 5 to 40 mg/L and the reaction time was 15 min. The removal efficiency decreased from 95.8% to 76.0% with the addition of HCO3(-) at a concentration in the range of 0-107 mg/L. Furthermore, the dissociation of CuCl, the disproportionation reaction of Cu(+), the precipitation of cuprous iodide (CuI) and cuprous oxide (Cu2O), and the formations of copper sulfide (CuxS, 1≤x<2) were identified as the primary reactions using the PHREEQC software and the measurements of water quality parameters under various conditions. X-rays photoelectron spectroscopy (XPS) analysis was performed before and after the reaction, helping to elucidate the reaction mechanism. This study can provide a promising method to address radioactive I(-) pollution in water.

Adsorption of radioactive iodine on surfactant-modified sodium niobate

To capture radioactive iodine from wastewater, nanofibers and cubes of Ag₂O anchored to sodium niobate composites were prepared as absorbents.

Dragon's blood-aided synthesis of Ag/Ag2O core/shell nanostructures and Ag/Ag2O decked multi-layered graphene for efficient As(iii) uptake from water and antibacterial activity

Excellent As(iii) uptake and antibacterial activities of Ag/Ag₂O core/shell and multi-layered graphene nanostructures obtained with the aid of Dragon's blood.

Sorption and desorption studies of radioiodine onto silver chloride via batch equilibration with its aqueous media

The uncontrolled spread out of radioiodine (especially (1)(3)(1)I) produced from nuclear activities or accidents, due to its high volatility, to the biosphere represents an environmental impact because of its concentration in the thyroid gland and accumulation on soil surface. This work represents a simple method for isolation of radioiodine from aqueous solution in the form of insoluble solid compound and further recovery of it in aqueous phase for any further controlled use. Crystalline silver chloride was prepared and characterized. Batch sorption of (131)I onto the prepared AgCl was studied from different aqueous media (H2O and NaOH of different concentrations) and at different I(-):Ag molar ratios (from alkaline media) for different times at 25 °C. It was found that the sorption yield of (131)I from 2.5 M NaOH solution (at I(-):Ag and S2O3(2-):I(-) molar ratios of 0.025 and 2, respectively) reached 97.7% after 6 h and only slightly increased to 98.6% after 16 h of contact time. The presence of H2O2 adversely affected the batch sorption process. The included REDOX and precipitation reactions were discussed. Batch desorption of the sorbed (131)I from AgCl into aqueous phase was studied with NaOCl solutions of different concentrations and different contact times at 25 °C. Desorption yield of (131)I was found to be 94.5% with 10 mL of 0.5 M NaOCl solution after contact time of 16 h. Kinetic analysis has been performed for both batch sorption and desorption processes.

Efficient removal of radioactive iodide ions from water by three-dimensional Ag2O-Ag/TiO2 composites under visible light irradiation

Three-dimensional Ag2O and Ag co-loaded TiO2 (3D Ag2O-Ag/TiO2) composites have been synthesized through a facile method, characterized using SEM, EDX, TEM, XRD, XPS, UV-vis DRS, BET techniques, and applied to remove radioactive iodide ions (I(-)). The photocatalytic adsorption capacity (207.6 mg/g) of the 3D Ag2O-Ag/TiO2 spheres under visible light is four times higher than that in the dark, which is barely affected by other ions, even in simulated salt lake water where the concentration of Cl(-) is up to 590 times that of I(-). The capability of the composites to remove even trace amounts of I(-) from different types of water, e.g., deionized or salt lake water, is demonstrated. The composites also feature good reusability, as they were separated after photocatalytic adsorption and still performed well after a simple regeneration. Furthermore, a mechanism explaining the highly efficient removal of radioactive I(-) has been proposed according to characterization analyses of the composites after adsorption and subsequently been verified by adsorption and desorption experiments. The proposed cooperative effects mechanism considers the interplay of three different phenomena, namely, the adsorption performance of Ag2O for I(-), the photocatalytic ability of Ag/TiO2 for oxidation of I(-), and the readsorption performance of AgI for I2.

Selective capture of iodide from solutions by microrosette-like δ-Bi₂O₃

Radioactive iodine isotopes that are produced in nuclear power plants and used in medical research institutes could be a serious threat to the health of many people if accidentally released to the environment because the thyroid gland can absorb and concentrate them from a liquid. For this reason, uptake of iodide anions was investigated on microrosette-like δ-Bi2O3 (MR-δ-Bi2O3). The MR-δ-Bi2O3 adsorbent showed a very high uptake capacity of 1.44 mmol g(-1) by forming insoluble Bi4I2O5 phase. The MR-δ-Bi2O3 also displayed fast uptake kinetics and could be easily separated from a liquid after use because of its novel morphology. In addition, the adsorbent showed excellent selectivity for I(-) anions in the presence of large concentrations of competitive anions such as Cl(-) and CO3(2-), and could work in a wide pH range of 4-11. This study led to a new and highly efficient Bi-based adsorbent for iodide capture from solutions.

The dynamic process of radioactive iodine removal by ionic liquid 1-butyl-3-methyl-imidazolium acetate: discriminating and quantifying halogen bonds versus induced force

The halogen bonds vs. induced force of the dynamic process of iodine removal by ionic liquid is discriminated and quantified.