Synthesis and characterization of Ag@Cu-based MOFs as efficient adsorbents for iodine anions removal from aqueous solutions

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.

Recent Advances in Metal-Organic Frameworks and Their Derivatives for Adsorption of Radioactive Iodine

Radioactive iodine (131I) with a short half-life of ~8.02 days is one of the most commonly used nuclides in nuclear medicine. However, 131I easily poses a significant risk to human health and ecological environment. Therefore, there is an urgent need to develop a secure and efficient strategy to capture and store radioactive iodine. Metal-organic frameworks (MOFs) are a new generation of sorbents with outstanding physical and chemical properties, rendering them attractive candidates for the adsorption and immobilization of iodine. This review focuses on recent research advancements in mechanisms underlying iodine adsorption over MOFs and their derivatives, including van der Waals interactions, complexing interactions, and chemical precipitation. Furthermore, this review concludes by outlining the challenges and opportunities for the safe disposal of radioactive iodine from the perspective of the material design and system evaluation based on our knowledge. Thus, this paper aims to offer necessary information regarding the large-scale production of MOFs for iodine adsorption.

Fluorescent cellulose nanofibrils-based hydrogel incorporating MIL-125-NH2 for effective adsorption and detection of iodide ion

To remove iodine ion (I-) from wastewater, a novel hydrogel, the fluorescent cellulose nanofibrils-based hydrogel (FCNH), was synthesized to enable both detection and adsorption of I-. The FCNH comprised cellulose nanofibrils (CNs), silver nanoclusters (AgNCs), and MIL-125-NH2. It exhibited an excellent adsorption capacity for I-, with a maximum adsorption capacity of 373.7 mg/g, fitting both the Langmuir and pseudo-second-order models. Additionally, FCNH displayed excellent regeneration properties, retaining 88.0 % of its initial adsorption capacity after six adsorption-desorption cycles. Functioning as a fluorescent sensor, the synthesized FCNH enabled the detection of I- through dynamic quenching, with linear ranges of 5 to 200 mg/L and 0.2 to 1.0 μg/L, and a determination limit of 0.11 μg/L. Analysis of the adsorption and detection mechanisms revealed that FCNH's outstanding performance arose from its 3D porous structure comprising CNs, AgNCs, and MIL-125-NH2. Economic analysis indicated that FCNH was inexpensive compared to commercially available activated carbon. Thus, FCNH demonstrated significant potential as an economical and reusable adsorbent for iodine ion removal.

Impact of (nano ZnO/multi-wall CNTs) prepared by arc discharge method on the removal efficiency of stable iodine 127I and radioactive iodine 131I from water

Radioactive iodine isotopes especially 131I are used for diagnosis and treatment of different types of cancer diseases. Due to the leak of radioactive iodine into the patient's urine in turn, the wastewater would be contaminated, so it is worth preparing a novel adsorption green material to remove the radioactive iodine from wastewater efficiently. The removal of 127I and 131I contaminants from aqueous solution is a problem of interest. Therefore, this work presents a new study for removing the stable iodine 127I- and radioactive iodine 131I from aqueous solutions by using the novel nano adsorbent (Nano ZnO/MWCNTs) which is synthesized by the arc discharge method. It is an economic method for treating contaminated water from undesired dissolved iodine isotopes. The optimal conditions for maximum removal are (5 mg/100 ml) as optimum dose with shacking (200 rpm) for contact time of (60 min), at (25 °C) in an acidic medium of (pH = 5). After the adsorption process, the solution is filtrated and the residual iodide (127I-) is measured at a maximum UV wavelength absorbance of 225 nm. The maximum adsorption capacity is (15.25 mg/g); therefore the prepared nano adsorbent (Nano ZnO/MWCNTs) is suitable for treating polluted water from low iodide concentrations. The adsorption mechanism of 127I- on to the surface of (Nano ZnO/MWCNTs) is multilayer physical adsorption according to Freundlich isotherm model and obeys the Pseudo-first order kinetic model. According to Temkin isotherm model the adsorption is exothermic. The removal efficiency of Nano ZnO/MWCNTs for stable iodine (127I-) from aqueous solutions has reached 97.23%, 89.75%, and 64.78% in case of initial concentrations; 0.1843 ppm, 0.5014 ppm and 1.0331 ppm, respectively. For the prepared radio iodine (131I-) solution of radioactivity (20 µCi), the dose of nano adsorbent was (10 mg/100 ml) and the contact time was (60 min) at (pH = 5) with shacking (200 rpm) at (25 °C). The filtration process was done by using a syringe filter of a pore size (450 nm) after 2 days to equilibrate. The removal efficiency reached (34.16%) after the first cycle of treatment and the percentage of residual radio iodine was (65.86%). The removal efficiency reached (94.76%) after five cycles of treatment and the percentage of residual radio iodine was (5.24%). This last percentage was less than (42.15%) which produces due to the natural decay during 10 days.