A comprehensive study for the potential removal of 152+154Eu radionuclides using a promising modified strontium-based MOF.

A facile modification of a strontium-based MOF using oxalic acid was carried out to prepare MTSr-OX MOF, which was used as a potential substance for eliminating 152+154Eu radioisotopes. Various analytical techniques were used to characterize MTSr-OX-MOF. The prepared MOF had a rod-like structure with a BET surface area of 101.55 m2 g-1. Batch sorption experiments were used to investigate the sorption performance of MTSr-OX-MOF towards 152+154Eu radionuclides where different parameters like pH, contact time, initial 152+154Eu concentration, ionic strength, and temperature were scrutinized to determine the optimum conditions for 152+154Eu removal. MTSr-OX-MOF showed superior effectiveness in the elimination of 152+154Eu with a maximum sorption capacity of 234.72 mg g-1 at pH 3.5. Kinetics fitted with the pseudo-second-order model and the Langmuir model correctly described the sorption mechanism. The thermodynamic variables were carefully examined, demonstrating that the 152+154Eu sorption was endothermic as well as spontaneous. The MTSr-OX-MOF has been found to be a significantly more effective sorbent towards 152+154Eu than that of many other adsorbents. When applied to real active waste, MTSr-OX-MOF demonstrated excellent removal performance for a wide range of radionuclides. As a result, the MTSr-OX-MOF can be recognized as an attractive solution for the 152+154Eu purification from active waste.

Recent progress in high-performance environmental impacts of the removal of radionuclides from wastewater based on metal-organic frameworks: a review.

The nuclear industry is rapidly developing and the effective management of nuclear waste and monitoring the nuclear fuel cycle are crucial. The presence of various radionuclides such as uranium (U), europium (Eu), technetium (Tc), iodine (I), thorium (Th), cesium (Cs), and strontium (Sr) in the environment is a major concern, and the development of materials with high adsorption capacity and selectivity is essential for their effective removal. Metal-organic frameworks (MOFs) have recently emerged as promising materials for removing radioactive elements from water resources due to their unique properties such as tunable pore size, high surface area, and chemical structure. This review provides an extensive analysis of the potential of MOFs as adsorbents for purifying various radionuclides rather than using different techniques such as precipitation, filtration, ion exchange, electrolysis, solvent extraction, and flotation. This review discusses various MOF fabrication methods, focusing on minimizing environmental impacts when using organic solvents and solvent-free methods, and covers the mechanism of MOF adsorption towards radionuclides, including macroscopic and microscopic views. It also examines the effectiveness of MOFs in removing radionuclides from wastewater, their behavior on exposure to high radiation, and their renewability and reusability. We conclude by emphasizing the need for further research to optimize the performance of MOFs and expand their use in real-world applications. Overall, this review provides valuable insights into the potential of MOFs as efficient and durable materials for removing radioactive elements from water resources, addressing a critical issue in the nuclear industry.

Sorption and transport characteristics of europium on sandy soils.

Radioactive europium can be released as a fission product during nuclear incidents and pose a threat to the human and surrounding environment because of its biological activity and long decay half-lives. For safe design issues and human health protection demands in construction of the planned nuclear power plants (NPPs) at Al-Dabaa site, it is necessary to study the sorption and transport of different radionuclides as europium within the selected area for predicting their fate at any crisis. Many soil samples were collected from different locations at the area selected along the northwestern coast of Egypt. The samples were transported to the laboratory, preserved, and characterized using X-Ray fluorescence (XRF), Fourier transform infrared spectroscopy (FT-IR), and X-Ray diffraction (XRD). Experiments were performed to study the sorption and transport kinetics of Eu(III) ions on two sandy soil samples from the collected ones. The effect of different parameters (e.g. contact time, pH, initial europium concentration, and temperature) on the sorption behavior europium was explored in a static condition. The maximum sorption capacity was determined and found to be 3.4 and 7.0 mg g-1 for sorption of Eu(III) ions onto soil-1 and soil-2, respectively. Different models were applied to assess the sorption of europium onto the surface of the investigated soils. Data confirmed that Eu retention was attained through a chemisorption process. Further, the thermodynamic parameters were determined and their values confirmed the endothermic nature of the sorption process. The transport of europium radionuclides, with groundwater, through homogeneous porous media with uniform one-dimensional flow in the geosphere was processed and the relative migration velocity was determined in presence of both distilled and seawater media. The transport of Eu(III) radionuclides was higher in presence of seawater than that in presence of distilled water by about two order of magnitude. This obviously clarified the effect of seawater in accelerating the transport of radionuclides with groundwater in the geosphere of studied area. The role of different competing ions have various valances on the relative migration velocity was explored. Further, the time required for studied radionuclides to reach Mediterranean Sea was determined.

A novel strontium-based MOF: synthesis, characterization, and promising application in removal of 152+154Eu from active waste.

Removal of hazardous radioactive materials such as 152+154Eu from active waste using the batch approach has attracted attention nowadays. In this work, a novel melamine-terephthalic strontium metal-organic framework (MTSr-MOF) was prepared via a hydrothermal method. The MTSr-MOF was characterized by various analytical techniques such as FT-IR, 1H/13C-NMR, mass spectroscopy, XPS, XRD, TGA, BET, FE-SEM/EDX, TEM, and UV. The obtained data revealed that MTSr-MOF exhibited brick-like building blocks that were bridged together by the linkers, and each block had a thickness of ∼120 nm. The BET surface area was 74.04 m2 g-1. MTSr-MOF was used for the removal of 152+154Eu radionuclides from active waste. Further functionalization using various modifiers, including oxalic acid, EDTA, sulfuric acid, and sodium hydroxide was carried out to improve the sorption efficiency of MTSr-MOF towards 152+154Eu radionuclides. Among them, MTSr-MOF modified with oxalic acid (MTSr-OX-MOF) demonstrated a superior removal efficiency toward 152+154Eu radionuclides when compared to MTSr-MOF or other published reports, with a removal efficiency of more than 96%. The higher sorption efficiency of the MTSr-OX-MOF indicates that it could be a promising candidate for the removal of 152+154Eu radionuclides from radioactive waste.

Hydroxyapatite/NiFe2O4 superparamagnetic composite: Facile synthesis and adsorption of rare elements.

A magnetic hydroxyapatite composite (CaHAP/NF) derived from calcium hydroxyapatite [Ca10(PO4)6(OH)2] and nickel ferrite [NiFe2O4] was successfully synthesized by a coprecipitation method. The synthesized composite was characterized using Fourier transform infrared spectroscopy (FT-IR), X-Ray diffractometer (XRD), thermogravimetric differential thermal analysis (TG-DTA), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). Results clarify that the composite is a crystalline in nature, thermally stable up to 800 °C and possesses a high porous structure. The synthesized CaHAP/NF composite is a superparamagnetic material easily separated from aqueous solutions and would dissociate to some extent in strongly acidic conditions. The synthesized material was successfully applied as a solid phase for separation of Eu(III) and Tb(III) ions from aqueous solutions. The effect of various parameters (e.g. solution pH, equilibrium time and ionic strength) on sorption process was studied in static conditions. The synthesized sorbent could be considered as an efficient candidate for separation and recovery of Eu(III) and Tb(III). The sorption process was very fast initially, reached equilibrium within 6 h of contact and independent of ionic strength. The maximum sorption capacity values were 137.35 and 130.43 mg g-1 for Eu(III) and Tb(III), respectively. Desorption of Eu(III) and Tb(III) from loaded sample was studied using various eluents and maximum recovery was obtained using FeCl3 and EDTA solutions. More importantly, both FeCl3 and EDTA were individually applied as eluents in chromatographic separation of Eu(III) and Tb(III) in CaHAP/NF packed column and the best separation results were obtained by EDTA.

Synthesis and characterization of magnetic hexacyanoferrate (II) polymeric nanocomposite for separation of cesium from radioactive waste solutions.

Nanocrystalline potassium zinc hexacyanoferrate loaded on nanoscale magnetite substrate was successfully synthesized for significantly enhanced removal of cesium from low-level radioactive wastes. A description was given for preparation and properties of these precursors. The physicochemical properties of these nanocomposites were determined using different techniques including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Data clarified that supporting potassium zinc hexacyanoferrates on iron ferrite nanoparticles increased their thermal stability. Further, Fourier transform infrared spectra confirmed that the nanocomposites were well coordinated and incorporated in the polymer matrix. The average particle sizes, of these nanoparticles, determined by SEM had a good agreement with XRD results. Based on characterization data, the prepared zinc hexacyanoferrates were proposed to have a zeolitic rhombohedral structure with cavities can host alkali metal ions and water molecules. The magnetic analysis showed a super-paramagnetic behavior. Batch technique was applied to evaluate the influences of initial pH value, contact time, and competing cations on the efficiency of cesium removal. The sorption process was fast initially, and maximum separation was attained within 2h of contact. Cesium exchange was independent from pH value and deviate from ideal exchange phenomena. In neutral solutions, Cs(+) was retained through exchange with K(+); however, in acidic solution, phase transformation was proposed. Sorption capacity of these materials attained values amounted 1965 mg g(-1). The synthesized nanocomposites exhibited different affinities toward Cs(I), Co(II), and Eu(III) elements and showed a good ability to separate them from each other.