Removal of uranium(VI) from aqueous solution using nanoscale zero-valent iron supported on activated charcoal

Cost-effective core@shell structured zero-valent iron nanoparticles @ magnetic (nZVI@Fe3O4) for Cr(vi) removal from aqueous solutions: preparation by disproportionation of Fe(ii)

Nanoscale zero-valent iron (nZVI) and its composites are known for their excellent ability to remove Cr(vi), but their preparation can be expensive due to the reduction processes. This study presents a cost-effective method to prepare core@shell structured nZVI@Fe3O4 nanocomposites using a novel Fe(ii) disproportionation reaction. The nZVI@Fe3O4 was thoroughly characterized using various techniques, including FESEM, HRTEM, EDS, XPS, XRD, FTIR, and VSM. Batch experiments were performed to evaluate the removal efficiency of nZVI@Fe3O4 in eliminating Cr(vi) ions from aqueous solutions, while classical models were employed to investigate the influencing factors associated with the removal process. The results showed that a 0.7 mg per ml NaOH solution reacted with Fe(ii) at 150 °C for 0.5 h could be used to prepare nZVI@Fe3O4 composites efficiently and inexpensively. nZVI@Fe3O4 was able to remove more than 99% of Cr(vi) from both simulated Cr(vi) solutions and real electroplating wastewater, and the recovery and preparation could be easily performed using external magnets to separate it from the solution. At pH 6.0, the maximum adsorption capacity (qmax) for Cr(vi) reached 58.67 mg g-1. The reaction mechanism was discussed from the perspective of electron transfer. Overall, the results suggest that nZVI@Fe3O4, an efficient adsorbent prepared using an environmentally friendly and inexpensive Fe(ii) disproportionation reaction, is a promising option for the treatment of Cr(vi) from industrial wastewater and other contaminated water sources.

Uranium and Thorium water decontamination via novel coated Cu-based nanoparticles; the role of chemistry and environmental implications

The removal of radioactive contaminants from aquifers is a matter of great concern. In this paper, coated copper-based nanoparticles (Cu-based NPs) were investigated as sorbent materials to remove uranium and thorium from low-level wastes, and especially from water, considering the influences of temperature, time, concentration, and pH. Cu-based NPs were derived through a hydrothermal synthesis from copper nitrate degradation in the presence of the bifunctional with COOH-terminated PEG, TEG as well as PEG 8000. The characterization was undertaken using XRD, TEM, TG/DTG, FTIR, and SEM-EDS. Isotherm models such as Langmuir and Freundlich were applied, while kinetic data were successfully reproduced by the pseudo-second-order equation and thermodynamic parameters were calculated. To investigate the removal mechanisms, UV-fluorescence and X-ray photoelectron spectroscopy were used. In the case of uranium, the predominant mechanism includes the formation of surface complexes, followed by extensive reduction (65%) of U(VI) to less soluble U(IV) while in the case of thorium, surface precipitation dominates. Copper nanoparticles exhibited significant U(VI) uptake capacity resulting in a decrease of the U-concentration below the acceptable limit of 30 μg/L and can be successfully applied in water treatment technology.

Graphene-based materials for the adsorptive removal of uranium in aqueous solutions

Ground water contamination by radioactive elements has become a critical issue that can pose significant threats to human health. Adsorption is the most promising approach for the removal of radioactive elements owing to its simplicity, effectiveness, and easy operation. Among the plethora of functional adsorbents, graphene oxide and its derivatives are recognized for their excellent potential as adsorbent with the unique 2D structure, high surface area, and intercalated functional groups. To learn more about their practical applicability, the procedures involved in their preparation and functionalization are described with the microscopic removal mechanism by GO functionalities across varying solution pH. The performance of these adsorbents is assessed further in terms of the basic performance metrics such as partition coefficient. Overall, this article is expected to provide valuable insights into the current status of graphene-based adsorbents developed for uranium removal with a guidance for the future directions in this research field.

Synthesis of FC-supported Fe through a carbothermal process for immobilizing uranium

The abundant generation of uranium (U), a radioactive nuclide, engenders a severe hazard to the environment. Iron based materials were used to immobilize U from water, however, the immobilization is limited by the agglomeration of nanoparticle Fe. In this study, a novel carbothermal process was proposed to synthesize flour carbon (FC) supported nano-flake Fe (Fe-FC). Scanning electron microscopy (SEM) and nitrogen isotherm adsorption-desorption analysis were conducted to characterize Fe-FC. The immobilization characteristics were investigated through batch sorption experiments. Results indicated that nano-flake was appropriately dispersed on the surface. The sorption capacity reached 19.12 mg/g when the initial concentration of U and the dosage of Fe-FC were 20 mg/L and 1 g/L, respectively. Langmuir isotherm sorption and pseudo-second-order models were fitted well to sorption experimental data. The sorption mechanism is ascribed to surface chemisorptions between U(VI) and Fe-FC. Subsequently, X-ray diffraction (XRD) analysis validated that formation of Fe₂UO₃ contributed to the favorable immobilization of U and that Fe₂UO₃ was the fate of U.