Simulated Radioactive Wastewater Research Articles

TFN nanofiltration membrane incorporating ZIF-8@MXene for efficient removal ReO4- from simulated nuclear-contaminated wastewater

In an effort to explore the potential application prospects of membrane separation technology in treating nuclear-contaminated wastewater, a TFN nanofiltration membrane incorporating the ZIF-8@Ti3C2Tx nanocomposite was successfully synthesized using the interfacial polymerization method. This involved doping the microemulsion of ZIF-8@Ti3C2Tx into the aqueous (organic) phase. The morphology and structure of ZIF-8@MXene nanocomposites and TFN nanofiltration membranes were characterized. The selective removal of ReO4- from simulated radioactive wastewater using the TFN nanofiltration membrane was evaluated. The results indicated that the ZIF-8@Ti3C2Tx composite, uniformly dispersed in the polymer, effectively enhanced the pore structure and polarity of the nanofiltration membrane, thereby improving its permeability. The electronegativity of ZIF-8@Ti3C2Tx also enhanced the negative charge on the surface of the polymer membrane, significantly improving the membrane’s performance in rejecting ReO4- while maintaining a low retention rate for Na+. This design facilitates the efficient selection of ReO4- from high-salinity wastewater. In addition, the layer spacing of Ti3C2Tx further improved the screening of ReO4- and Na+. However, when 0.75 g·L−1 of microemulsion was added, it became challenging to disperse the microemulsion completely in the organic phase. This led to the agglomeration of composites in the nanofiltration membrane, weakening both flux and selectivity. Optimal performance was achieved with a microemulsion doping amount of 0.5 g·L−1, resulting in the nanofiltration membrane M-O-1 exhibiting the best performance (Jp = 41.92 L·m2·h−1 and R(ReO4-) = 65.81%). Even at a high salt concentration (20 g·L−1), the M-O-1 membrane retained approximately 55% of pollutants after continuous operation for 5 h, indicating that the TFN nanofiltration membrane containing ZIF-8@Ti3C2Tx holds significant promise for selectively extracting 99Tc from wastewater with a high salt content.

Facile preparation of UiO-66-Lys/PAN nanofiber membrane by electrospinning for the removal of Co(II) from simulated radioactive wastewater

In this study, metal-organic framework (MOF) nanofiber membranes (NFMs) UiO-66-Lys/PAN were prepared by electrospinning using polyacrylonitrile (PAN) as the matrix, UiO-66-NH2 as the filler, and lysine (Lys) as the functional monomer. The membranes were subsequently employed to extract cobalt ions from simulated radioactive wastewater. The findings showed that the best performance of the membrane was obtained with a 3 % MOF content (3%UiO-66-Lys/PAN). Specifically, the pure water flux (PWF) of the 3 % UiO-66-Lys/PAN membrane reached 872 L m−2 h−1 with a cobalt ion retention of 45.4 %. In addition, adsorption experiments indicated that the NFMs had a theoretical maximum adsorption capacity of 41.4 mg/g for cobalt ions. The Langmuir isotherm model and the pseudo-second-order kinetic model were observed in the adsorption process, suggesting that the membrane material showed uniform adsorption of cobalt ions on a monolayer level, with an endothermic absorption process. XPS analysis confirmed that 3%UiO-66-Lys/PAN facilitated the adsorption of cobalt ions through a coordination effect, with the N and O atoms serving as coordinating atoms. Moreover, the material displayed excellent radiation stability even when exposed to doses ranging from 20 to 200 kGy. This study validated the stability of the MOF NFMs under real irradiation with radioactive nuclides (60Co) and demonstrated efficient cobalt ion separation. This study has important practical implications for the treatment and disposal of small volumes of 60Co-containing radioactive wastewater for engineering applications.

Facile construction of a core-shell structured metal-organic frameworks nanofiber membrane for removing Co(II) from simulated radioactive wastewater

A novel core–shell structured composite of UiO-66-Tu/PAN nanofiber membranes (NFMs) functionalized with thiourea (Tu) was developed for the efficient separation of Co(II) from simulated radioactive wastewater. Various analytical techniques were employed to characterize the structure and properties of the NFMs. The filtration performance, flux, and hydrophilicity of the membrane were evaluated using a membrane flux tester and contact angle (CA) measurements, respectively. The adsorption performance of UiO-66-Tu/PAN for Co(II) was investigated through batch adsorption experiments. The results indicate that at a UiO-66-Tu/PAN content of 7 %, the UiO-66-Tu/PAN NFMs exhibit better hydrophilicity (CA of 37.8°) and a higher cobalt ion retention rate (77.41 %). Under optimal conditions, the theoretical maximum adsorption capacity for cobalt ions is 51.2 mg/g. X-ray photoelectron spectroscopy (XPS) analysis was utilized to clarify the adsorption mechanism of Co(II) by the 7 %UiO-66-Tu/PAN composite, showing a coordination mechanism that involves the participation of oxygen, nitrogen, and sulfur atoms in the ligand. In addition, the material also demonstrates excellent radiation stability (50–100 kGy). It should be pointed out that this is the first time that metal–organic frameworks (MOFs) core–shell nanofibers membranes have been used for cobalt ion separation. The development of this new material effectively addresses the challenges associated with using MOFs as powdered adsorbents, achieving efficient purification of wastewater and providing important engineering significance for the treatment and disposal of trace amounts of 60Co radioactive wastewater.

Fabrication of highly efficient hydroxyapatite microtubes for uranium sequestration and immobilization

Uranium-containing wastewater is a common by-product of uranium mining. Phosphate and phosphate minerals can interact with uranyl ions [U(VI)], impeding the migration of these ions by forming relatively stable uranium-containing crystalline phase(s). In this study, hydroxyapatite microtubes (HAP-T) were fabricated to sequester uranyl ions from simulated radioactive wastewater. HAP-T had excellent adsorption and stability properties; over 98.76% of U(VI) could be sequestrated by 0.25 g/L HAP-T within 5 min at pH = 4.0. The isotherms and kinetics data could be suitably reflected by the Freundlich and the pseudo second-order kinetic models, respectively. The maximum adsorption capacity of HAP-T was 356.42 mg/g. The adsorption ability of HAP-T for U(VI) was inhibited when Mg2+ or SO42− ions or fulvic acid (FA) substances existed in the simulated radioactive wastewater. The inhibition by FA was attributed to its negative charges, which caused competition between FA and HAP-T for uranium sequestration. The primary mechanisms of U(VI) sequestration by HAP-T were electrostatic interactions and surface complexation. The effectiveness of HAP-T, HAP-B (bio-hydroxyapatite synthesized from fish bone), and HAP-C (commercially available synthesized hydroxyapatite) for uranium immobilization was compared; HAP-T was more effective than HAP-B or HAP-C in immobilizing uranium. HAP-T, which has a micron-sized tubular structure, is likely less mobile in groundwater than are HAP-B and HAP-C, which have nanoscale granular structures. In conclusion, HAP-T can be used to sequester and immobilize uranyl ions.

Gamma radiation-induced synthesis of TiO2 immobilized on polyacrylonitrile nanocomposite for gallium, strontium and rubidium ions separation from aqueous solutions

In this study, polyacrylonitrile-titanium oxide (PAN@TiO2) nanocomposite was synthesized using gamma radiation to immobilize TiO2 on polyacrylonitrile (PAN) for effective adsorption of gallium, strontium and rubidium ions from simulated radioactive wastewater. The nanocomposite material was characterized using various techniques such as FT-IR, XRD, EDX, SEM, thermal analysis and particle size distribution. In addition, the performance of PAN@TiO2 nanocomposite was evaluated under different conditions such as the initial concentration of Ga3+, Sr2+ and Rb+, shaking time and temperature. The findings indicated that the isotherm as well as kinetic data for adsorption, respectively, fitted to Langmuir model and pseudo-second order model. The monolayer sorption capacity values for Ga3+, Sr2+ and Rb+ were 18.01, 16.90 and 3.79 mg.g−1, respectively. The adsorbent was also tested for real groundwater sample collected from Marsa Alam, Egypt, which contained various cations and anions such as Mg2+, Na+, K+, HCO3−, Cl−, SO42−, Ga3+, Rb+, Sr2+, Pb2+, Zn2+ and Cu2+. The results revealed that PAN@TiO2 nanocomposite has great potential for the treatment of real groundwater sample contaminated with the studied ions; Ga3+, Sr2+ and Rb+, making it suitable for use in a variety of industrial and environmental applications.

Synthesis and Application of a Novel Metal-Organic Frameworks-Based Ion-Imprinted Polymer for Effective Removal of Co(II) from Simulated Radioactive Wastewater.

In this work, a novel metal-organic frameworks (MOFs)-based ion-imprinted polymer (MIIP) was prepared to remove Co(II) from simulated radioactive wastewater. The batch experiments indicated that the sorption was well described by the pseudo-second-order kinetic and Langmuir models, and it is monolayer chemisorption. The theoretical maximum sorption capacity was estimated to be 181.5 mg∙g-1, which is by far the reported maximum value of Co(II) sorption by the imprinted materials. The MIIP presented an excellent selectivity for Co(II) in the presence of common monovalent and divalent metal ions, and the selectivity coefficients were 44.31, 33.19, 10.84, 27.71, 9.45, 16.25, and 7.60 to Li(I), K(I), Mg(II), Ca(II), Mn(II), Ba(II), and Cd(II), respectively. The sorption mechanism was explored by X-ray photoelectron spectroscopy (XPS) technology and density functional theory (DFT) calculations, suggesting that Co(II) was adsorbed by the MIIP via the chelation of 4-vinylpyridine (VP) ligands with Co(II), which was a spontaneous process, and the optimal coordination ratio of VP to Co(II) was 6. This work suggested that the MIIP has a high sorption capacity and excellent selectivity for Co(II), which is of great significance for the selective separation of Co-60 from radioactive wastewater.

Radiation synthesis of binary poly(ionic liquid) functionalized silica-based materials for selective adsorption of ReO4− as analogue of TcO4− from simulated radioactive wastewater

Binary ionic liquid functionalized silica-based adsorbents for the treatment of TcO4− in radioactive wastewater was synthesized and evaluated. The column adsorption capacity of adsorbents increased with increasing hydrophobicity of the ionic liquid.

Layered metal sulfide NMTS for rapid removal of radioactive strontium ions from aqueous solution

A one-step hydrothermal method was used to synthesize a quaternary metal sulfide material, NMTS, to remove strontium ions from simulated radioactive wastewater, in which metal tin was replaced by tin and magnesium salts to reduce the cost of the raw materials. The adsorption characteristics and behavior of Sr2+ were studied using batch experiments. NMTS has a layered structure, and the approximate molar ratio of Na:Mg:Sn:S is 4:1:10:23, with an approximate 61% reduction in the raw material cost compared to NaTS. NMTS exhibited ultrafast kinetics for Sr2+ with rapid adsorption of 97.1% in 0.5 min and 99.8% at an equilibrium time of 3 min, followed by the pseudo-second-order model and Langmuir model with a maximum adsorption amount of 52.6 mg/g at 298 K. NMTS had a high affinity for Sr2+ with Kd values of >106 at pH values ranging from 4 to 11. The adsorption of Sr2+ mainly involves ion exchange and surface adsorption. Ion exchange Na+ for Sr2+ was predominant with initial Sr2+ concentrations ranging from 5 to 20 mg/L, and both ion exchange and surface SrS bonding interactions occurred with initial Sr2+ concentrations higher than 20 mg/L. Sodium and potassium ions had little effect on the adsorption of Sr2+, whereas the presence of calcium and magnesium ions greatly affected it. In addition, NMTS also exhibited high selectivity for the adsorption of cobalt, nickel, and manganese, followed by Ni2+ > Sr2+ > Mn2+ > Co2+. NMTS is a promising adsorbent for removing Sr ions from aqueous solutions.

Study on the migration performance of Cs(I) in the treatment of simulated radioactive wastewater by electrodialysis.

As a competitive radioactive wastewater treatment technology, electrodialysis (ED) has the advantages of low operating pressure and high cycles of concentration. In order to analyze the migration performance of radionuclides during the treatment of radioactive wastewater by ED, a radionuclide migration model was constructed based on the mass conservation law and Faraday's law with the typical radionuclide cesium as the research object. Experiments were carried out for the treatment of simulated radioactive wastewater in a small-scale ED system, and the average migration rate of radionuclides under different operating conditions was predicted by the model. The results showed that the experimental values of concentration and average migration rate of Cs(I) were significantly correlated with the calculated values of the model, in which the relative error of the average migration rate was 4.54%. The variation characteristics of Cs(I) concentration in diluted solution under different current and volume ratio conditions can be predicted by the model. The average variation rate of Cs(I) concentration decreases significantly with the increase of current and volume ratio.

Treatment of Simulated Radioactive Wastewater Using Reverse Osmosis and Membrane Distillation

With the rapid development of nuclear power, increasing attention has been paid to the treatment of low-level radioactive wastewater (LLRW). In this study, reverse osmosis (RO) and membrane distillation (MD) are used to treat LLRW containing Ce(III), U(VI), and Co(II). RO was used for the purification of LLRW. MD was used for further concentration of RO concentrate. The effect of the operating parameters, including operating pressure (0.6 to 1.4 MPa), feed pH (7 to 9), feed concentration (2 to 10 mg/L), feed temperature (50°C to 90°C), and feed flow rate (80 to 160 L/h) on the permeate flux and the rejection rate of the RO process and MD process was studied. The results demonstrate that it is very effective to use the RO process to treat LLRW containing Ce(III), U(VI), and Co(II), with the rejection rates of Ce(III), U(VI), and Co(II) higher than 99.97%, 99.98%, and 99.35%, respectively. The operating pressure has a significant effect on the permeate flux in the RO process. The permeate flux increases from 9.84 to 23.03 L/m2·h when the operating pressure increases from 0.6 to 1.4 MPa. The feed pH has an apparent influence on nuclide rejection. At the feed pH = 9, the rejection rates of Ce(III), U(VI), and Co(II) by the RO process can reach 99.99%, 99.99%, and 99.79%, respectively. MD can reject almost all the nuclides in the RO concentrate, with rejection rates consistently higher than 99.98%. Increasing the feed temperature and feed flow rate can result in a significant increase in the permeate flux, but has almost no effect on nuclide rejection in the MD process.

A Sustainable Green Approach for Efficient Capture of Strontium from Simulated Radioactive Wastewater Using Modified Biochar

A Sustainable Green Approach for Efficient Capture of Strontium from Simulated Radioactive Wastewater Using Modified Biochar

Magnetic amidoxime-functionalized MXenes for efficient adsorption and immobilization of U(VI) and Th(IV) from aqueous solution

Herein, Fe3O4 nano-particles were integrated into the interlamellarspacing of amidoxime-functionalized Ti3C2 to construct a novel magnetic MXenes based composites (Fe3O4@Ti3C2-PDA/OA), and applied to removal radionuclides from the simulated radioactive wastewater. The physico-chemical properties of the surface functionalized MXenes were probed using advanced spectroscopy techniques, while batch experiments were conducted to investigate the influence of pH value, contact time and coexisting pollutants on enrichment of U(VI)/Th(IV). The experimentally determined the maximum adsorption amounts for U(VI) (pH = 5.0) and Th(IV) (pH = 3.0) on Fe3O4@Ti3C2-PDA/OA were 165.9 mg/g and 202.7 mg/g, which were much larger than the traditional adsorption materials. Meanwhile, the well-modeled results of isotherm and kinetics data demonstrated that elimination of the two radionuclides were a monolayer and chemisorption process, whereas the calculation of thermodynamic data indicated that the adsorption was a spontaneous and endothermic process. The spectral analysis results revealed that the elimination mechanism was achieved through the complexation of hydroxyls and amidoxime groups anchored onto the skeleton of Fe3O4@Ti3C2-PDA/OA with U(VI)/Th(IV). This work provided a bright future for MXenes based composites in the application of remediation of radioactive ions.

Study on the treatment of radioactive wastewater by non-contact membrane distillation

Conventional contact membrane distillation technology has some problems, such as membrane fouling and wetting, resulting in short membrane life, low permeate flux, and instability, which limit its industrial application. Here, a non-contact membrane distillation method is proposed for radioactive wastewater treatment. The effects of hot-side inlet temperature, hot-side flow rate, sweeping gas temperature, and cold-side flow rate on permeate flux are examined. The purification ability of this method for strontium ion in simulated radioactive wastewater and actual radioactive wastewater from uranium-containing hydrometallurgical purification plant was investigated. Under the optimized conditions, the permeate flux of non-contact membrane distillation unit reaches 24.87 kg/(m2·h), the rejection rate of Sr2+ in simulated radioactive wastewater is more than 99.99%, and the decontamination factor can reach more than 4.5 × 106. The total α and β activity concentrations in the radioactive wastewater are 21279.7 Bq/L and 17811.9 Bq/L, respectively, while the actual α and β activity concentrations of the distillate produced by the membrane distillation device are 0.205 Bq/L and 0.877 Bq/L, respectively. Overall, the proposed method has the advantages of long membrane service life, high and stable permeate flux, which can facilitate its large-scale industrial application in volume reduction and deep purification of radioactive wastewater.

The synthesis of a novel conjugated microporous polymer and application on photocatalytic removal of uranium(Ⅵ) from wastewater under visible light

• A novel porphyrin-based CMP(TT-TPP) showed wide visible light adsorption. • The U(Ⅵ) removal capacity of TT-TPP was 3571.2 mg g −1 . • 80% uranium removal was achieved under solar irradiation. • Good removal rates were reached on high acidity and high salt condition. • TT-TPP displayed a fine selectivity for U(Ⅵ) from simulated radioactive wastewater. Photocatalytic reduction of uranium(Ⅵ) is an efficient and non-pollutant strategy for removal of uranium(Ⅵ) from waste water. However, most current photocatalysts are limited in practical application due to low visible light utilization and low activity on acidic condition. In this work, a new conjugated microporous polymer (CMP) named TT-TPP has been synthesized by C–H arylation between 5, 10, 15, 20-tetrakis(4-bromophenyl)-porphyrin and thieno[3,2-b]thiophene. TT-TPP exhibits excellent chemical stability and photochemical property. It can be used for visible light driven photocatalytic reduction of U(VI) on highly acidic condition (pH = 2–5) with high uranium removal capacity (3571.2 mg g −1 ). Even in 3 M NaNO 3 solution, the removal rate of U(Ⅳ) could reach to 89.9%. TT-TPP still exhibits an excellent uranium selectivity over these competing metal cations, and 97.6% U(Ⅳ) in simulated radioactive wastewater is removed. The X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and the fourier transform infrared spectroscopy (FT-IR) confirmed the reduced uranium was in the form of UO 2 ⋅nH 2 O. In addition, TT-TPP also shows excellent photocatalytic U(VI) reduction performance under natural sunlight irradiation.

Pilot-scale vacuum membrane distillation for decontamination of simulated radioactive wastewater: System design and performance evaluation

• Pilot-scale VMD plant with 8.0 m 3 /d production was developed. • Design scheme and schematic of VMD pilot plant were detailed. • High DF of 10 4.85 for Cs and high CF of 110.3 were achieved. • Detailed evaluation of energy efficiency through STEC and GOR was conducted. • Heat loss of pilot-scale membrane module as heat pinch effect was analyzed. A pilot-scale vacuum membrane distillation (VMD) demonstration plant for decontamination of radioactive wastewater with 8.0 m 3 /d water production was developed. The design scheme, main components and functions of VMD pilot plant were detailed. Effects of operational parameters on permeate flux, gain output ratio (GOR) and decontamination factor (DF) of simulated radioactive wastewater were analyzed. As feed temperature increased from 70℃ to 90℃, permeate flux grew exponentially from 1.59 kg/(m 2 ·h) to 6.82 kg/(m 2 ·h). High DF 10 4.85 of Cs + and high concentration factor (CF) 110.3 of simulated radioactive wastewater were reached with stable permeate flux in pilot-plant-scale. DF of Cs + and GOR were relatively stable under various operation conditions. The outlet temperature of membrane modules increased with the growth of flow rate, bringing about 9 °C temperature difference between 2 m 3 /h and 14 m 3 /h at the same inlet temperature of 70 °C. The significant heat loss in radial direction as temperature polarization and in axial direction as the heat pinch effect in hollow fiber membrane modules are the main issues for large-scale MD plant. This study demonstrates a remarkable potential of VMD for decontamination of radioactive wastewater and provides an integrated design of VMD pilot-scale plant.

Synthesis of magnetic nanoparticles-containing nanocomposite hydrogel and its potential application for simulated radioactive wastewater treatment

Nanocomposite hydrogels, bearing different functional groups, are potential materials for removing contaminants from water with high capacity and selectivity. A novel polyfunctional nanocomposite hydrogel (NCHG) was developed for the treatment of radioactive waste. It is based on magnetic composite nanoparticles (MCNPs) formed by encapsulating magnetite in polystyrene-co-polymethacrylic acid (PS-co-PMAA) miniemulsion. The MCNPs were then used as a physical crosslinker for the graft polymerization of sodium styrene sulfonate SSS and acrylic acid AA in the presence of polyacrylamide PAM to form an interconnected NCHG bearing different functional groups. The NCHG was characterized by FTIR, DLS, and TEM. The results indicated that a successful encapsulation of magnetite NPs took place and the MCNPs were ~100 nm in size. The presence of the MCNPs in the graft polymerization system greatly enhanced the conversion %. The optimum ultrasound homogenization of the polymerization reaction was found to be 11 min and the optimum gamma radiation dose for the initiation of polymerization reaction was 25 kGy. The NCHG was used for the removal of Cs+, Co2+, and Sr2+ ions from simulated radioactive waste. The initial concentration was studied from 50 to 600 mg/L, and the equilibrium adsorption capacities of Cs+, Co2+, and Sr2+ were found to increase from 8.49 to 53.37, 11.17–80.69, and 10.75–65.35 mg/g, respectively. The calculated thermodynamic parameters namely, Gibbs free energy (ΔG°), Enthalpy (ΔH°) and entropy (ΔS°) indicated an endothermic chemisorption process.

Removal of uranium(VI) from simulated wastewater by a novel porous membrane based on crosslinked chitosan, UiO-66-NH2 and polyvinyl alcohol

The development of highly efficient adsorbent presents an enticing prospect for U(VI)-containing radioactive wastewater treatment. In this work, a novel porous cCS/PVA/UiO-66-NH2 membrane absorbent comprising of crosslinked chitosan (cCS), polyvinyl alcohol (PVA) and UiO-66-NH2 is designed and prepared. The adsorption capacity of porous cCS/PVA/UiO-66-NH2 membrane achieves 316.50 mg g−1 under an optimal condition. Furthermore, the porous cCS/PVA/UiO-66-NH2 membrane exhibits a high selectivity for U(VI) adsorption in simulated radioactive wastewater treatment. The possible mechanism of U(VI) adsorption onto porous cCS/PVA/UiO-66-NH2 membrane mainly includes surface complexation and cation exchange processes. In addition, the porous cCS/PVA/UiO-66-NH2 membrane also exhibits excellent cycling adsorption-‍desorption performance. All these results demonstrate that the porous cCS/PVA/UiO-‍66-NH2 membrane is a promising candidate for application in U(VI) removal from radioactive wastewater.

Radiation-induced surface modification of silanized silica with n-alkyl-imidazolium ionic liquids and their applications for the removal of ReO4− as an analogue for TcO4−

As a radioactive fission product, 99Tc always existed in the combined extreme conditions of super acidity, high ionic strength, and strong radiation field, which made the efficient removal of Tc a challenge. Herein, for the first time, a series of n-alkyl-imidazolium ionic liquids were grafted onto silanized silica using radiation technique. The surface and structure properties of prepared adsorbents (SiO2-MPTS-[CnVIm]Br) were characterized by FT-IR, TGA, XPS, BET, and SEM-EDS. Subsequently, their adsorption properties for ReO4− (a nonradioactive surrogate of TcO4−) were studied in detail. These adsorbents exhibited an adsorption capacity of approximately 190 mg g−1 for ReO4−. It was found that adsorbents with longer alkyl chains showed better selectivity against ReO4− under the conditions of strong acids and a large excess of competitive ions. Column experiments indicated that these adsorbents could be recycled 10 times with negligible capacity loss. In addition, their adsorption performance remained unchanged after 800 kGy radiation. The column experiments of treating simulated radioactive wastewater proved that SiO2-MPTS-[CnVIm]Br was promising for selective separation of TcO4−/ReO4− from a variety of fission products. Lastly, XPS and FT-IR analysis confirmed that the adsorption mechanism was based on ion-exchange.

Silver-decorated ZIF-8 derived ZnO concave nanocubes for efficient photooxidation-adsorption of iodide anions: An in-depth experimental and theoretical investigation

Elimination of radioactive iodide (I-) from complex solution of used nuclear fuel directly is the optimum scheme in the remediation of iodide released into the environment. However, this assignment represents a tremendous challenge given the combined harsh conditions of strong acidity, high ionic strength, and strong ionizing radiation field. Here, we surmount the challenge by applying silver-decorated ZIF-8 derived ZnO concave nanocubes (CNCs) (denoted as AZ) as a potential photocatalyst and adsorbent for photooxidation-adsorption of I- from simulated radioactive wastewater. The as-synthesized product showed a prominent I- uptake capacity of 129.3 ​mg g-1 under visible light with relatively fast kinetic adsorption process as well as remarkable selectivity, strong acid resistance and excellent γ radiation resistance. The uptake process, with spontaneity and exothermic, followed the pseudo-second-order kinetics and Langmuir isotherm models. The mechanism explaining the excellent properties was investigated systematically and could be epitomized into the following: AZ nanocomposites possessed the cumulative effects of the uptake performance of Ag2O for I-, the photooxidation property of Ag(0)@ZnO CNCs for oxidation of I- to I2 under visible light. Density functional theory (DFT) calculations further revealed that I2 was more likely to bind to nearby Ag site yielding AgI, or be trapped readily by AgI to form AgI3. Overall, our work provides a facile and useful pathway toward radioactive iodine elimination.

Radiation synthesis of ionic liquid-functionalized silica-based adsorbents: a preliminary investigation on its application for removal of ReO4- as an analog for TcO4.

The decontamination of radioactive TcO4- from nuclear wastes is becoming increasingly crucial for spent nuclear fuel reprocessing and environmental remediation. In this work, a series of ionic liquid-immobilized silica-based adsorbents (SVIL-Cn, n = 1, 4, 8) were newly synthesized using the radiation-induced grafting of 4-vinylbenzyl chloride onto silanized silica and subsequent functionalization with 1-methylimidazole, 1-butylimidazole, or 1-octylimidazole. The synthesis conditions such as the solvent, absorbed dose, and monomer concentration were investigated in detail, and the resulting adsorbents were characterized by elemental analysis, FT-IR, SEM, and TGA. In batch experiments, the adsorbents exhibited a high ReO4- (a nonradioactive surrogate of TcO4-) removal efficiency over a wide pH range (3 ~ 8), and SVIL-C1 showed a maximum adsorption capacity of 70.62 mg g-1 towards ReO4-. In addition, their adsorption performance barely changed after 800 kGy radiation. The column experiments for treating simulated radioactive wastewater showed that the SVIL-Cn adsorbents could selectively separate TcO4-/ReO4- from a variety of fission products, and they could be recycled four times with negligible capacity loss. Lastly, XPS and FT-IR analysis confirmed that the adsorption proceeded via an ion-exchange mechanism. The results showed that these adsorbents are suitable for the efficient removal of TcO4-/ReO4- from radioactive wastewater with complex compositions.