Search Results (80)

Biosorption is an impurity-free application developed from the use of nuclear technology for peaceful purposes in everyday life and can be used to treat wastewater streams contaminated with various radionuclides. In this study, a laboratory decontamination experimental approach was developed to apply commercial chitosan as a biosorbent applied for removing radiocesium (Cs-137) and/or radiocobalt (Co-60) from spiked aqueous media. The factors assumed to affect the biosorption of both radionuclides included contact time, pH, and initial radioactivity content. In addition, the biosorbent dose and temperature of the process were studied. Both the biosorption capacity and the biosorption efficiency of the treatment process were calculated. According to FT-IR analysis, it can be assumed that the chitosan amine group (-NH₂) is almost accountable for the biosorption of both radionuclides from waste solution simulates. Based on the data obtained, commercial chitosan can be considered an economical and efficient biosorbent for handling low- and medium-level radioactive wastewater streams containing cesium and/or cobalt radionuclides. The acquired data showed that 144 h is an adequate time to remove more than 94% of radiocobalt and about 93% of radiocesium, from a separate solution for each, at pH ~6.5 and using 0.5 g of commercial chitosan. Full article

(1) Background: The frequency and intensity of war-like activities (war, military training, and shooting ranges) worldwide cause soil pollution by metals, metalloids, explosives, radionuclides, and herbicides. Despite this environmentally worrying scenario, soil decontamination in former war zones almost always involves incineration. Nevertheless, this practice is expensive, and its efficiency is suitable only for organic pollutants. Therefore, treating soils polluted by wars requires efficient and economically viable alternatives. In this sense, this manuscript reviews the status and knowledge gaps of mycoremediation. (2) Methods: The literature review consisted of searches on ScienceDirect and Web of Science for articles (1980 to 2023) on the mycoremediation of soils containing pollutants derived from war-like activities. (3) Results: This review highlighted that mycoremediation has many successful applications for removing all pollutants of war-like activities. However, the mycoremediation of soils in former war zones and those impacted by military training and shooting ranges is still very incipient, with most applications emphasizing explosives. (4) Conclusion: The mycoremediation of soils from conflict zones is an entirely open field of research, and the main challenge is to optimize experimental conditions on a field scale. Full article

Although the potential of natural minerals for purification of liquid radioactive wastes (LRW) from radionuclides has been widely studied, the use of hybrid polymer composites made of zeolite is still rather scarce. This article reports on the preparation of zeolite-based hybrid polymer composites using the in situ polymerization technique in the body of mineral matrix and its intercalated with copper ferrocyanide (CuFC) forms. This hybrid polymer composites have shown unique and enhanced properties for the removal of micropollutants from wasted water as compared to the individual mineral. The change in conventional properties of two mixed minerals, such as zeolite and bentonite, and their intercalated with CuFC forms were probed using techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Mössbauer spectroscopy (MS) and FT-IR analysis. The totality of analysis showed a coexistence of intercalated and percolated zeolite phases. The hybrid polymer composites exhibited both adsorption and ion-exchange properties in the removal of ^134,137Cs⁺, ^57,60Co²⁺ and ⁸⁵Sr²⁺ radionuclides from LRW. Full article

Identifying potential sources of suspended sediment (SS) in headwater catchments is crucial for water quality management. To differentiate these potential SS sources, we investigated the distribution of two fallout radionuclides (FRNs), ¹³⁷Cs and ²¹⁰Pb_ex, using gamma spectrometry along with soil organic matter (SOM) analysis in a headwater catchment with five potential SS sources: cultivated land, non-harvested forest floor, eroded hillslope, harvested forest floor, and stream bank. The ¹³⁷Cs and ²¹⁰Pb_ex concentrations and the SOM content were considerably higher in the harvested forest floor materials than in the other four potential SS source materials. FRN concentrations revealed distinct properties according to the type of potential SS sources. Specifically, the combination of FRNs (with the effect of SOM content removed) associated with the mineral fraction and SOM showed distinguishable differences among the potential SS sources, except for no difference between cultivated land and eroded hillslope. Therefore, SOM and FRNs, or their combination, can be effective indices to differentiate or trace potential SS sources on various land use/land cover types within a catchment. Further field tests will allow the tracing techniques that bind FRNs with SOM to contribute to understanding SS transport from non-point sources within a catchment. Full article

The adsorption of actinide ions (Am(III) and U(VI)) from aqueous solutions using pristine and oxidized carbon fabrics was investigated by means of batch experiments at different pH values (pH 4, 7 and 9) and temperatures (25, 35 and 45 °C) under ambient atmospheric conditions. The experimental results indicated that both the pH and the fabric texture affected the adsorption rate and the relative removal efficiency, which was 70% and 100% for Am(III) and U(VI), respectively. The K_d (L/kg) values for U(VI) were generally found to be higher (2 < log₁₀(K_d)< 3) than the corresponding values for Am(III) adsorption (1.5 < log₁₀(K_d) < 2). The data obtained from the experiments regarding the temperature effect implied that the relative adsorption for both actinides increases with temperature and that adsorption is an endothermic and entropy-driven reaction. The application of the fabrics to remove the two actinides from contaminated seawater samples showed that both the relative removal efficiency and the K_d values decreased significantly due to the presence of competitive cations (e.g., Ca²⁺ and Fe³⁺) and complexing anions (CO₃²⁻) in the respective waters. Nevertheless, the removal efficiency was still remarkable (50% and 90% for Am(III) and U(VI), respectively), demonstrating that these materials could be attractive candidates for the treatment of radionuclide/actinide-contaminated waters. Full article

Adsorption is one of the main methods of water purification. Novel advanced, eco-friendly, cost-effective adsorbents with high adsorption capacity and selectivity are required to remove pollutants from aqueous solutions. Plant polymers are viewed as both prospective adsorbents and as raw materials to produce them instead of conventional adsorption materials. There is widespread interest in using rice husk as a universal sorbent to remove different contaminants from aqueous media because of its surplus availability, low cost, and high content of oxygen containing functional and silanol groups as active sites for adsorptive extraction. Different methods of heat and chemical treatments have been developed to improve the sorption properties of raw rice husk. Unmodified rice husk and rice-husk-based sorbents have been tested to uptake non-ferrous, ferrous, minor, precious, rare, and rare-earth metals and radionuclides from artificial and industrial solutions, natural contaminated water, and industrial wastewater. This review summarizes the results of numerous studies and characterizes the current state of work in this area, with recommendations for further development. Full article

Clay minerals are widely used to treat groundwater and surface water containing radionuclides. In our study, the method of mechanochemical activation for increasing the sorption capacity of the natural clay mineral montmorillonite was used. By adjusting the grinding time, the increasing sorption parameters of mechanochemically activated montmorillonite were determined. X-ray diffraction method, scanning electron microscopy, and the determination of the specific surface by low-temperature adsorption–desorption of nitrogen to characterize the natural and mechanochemical-activated montmorillonites were used. It was established that the maximal sorption of uranium, strontium, and cesium is found for montmorillonite after mechanochemical treatment for 2 h. It is shown that the filling of the surface of montmorillonite with ions of different natures occurs in various ways during different times of mechanochemical treatment. The appropriateness of the Langmuir and Freundlich models for the sorption parameters of uranium, strontium, and cesium ions on montmorillonite after its mechanochemical activation was established. The effect of natural organic substances—humic acids—on the efficiency of water purification from uranium on mechanoactivated montmorillonite was studied. The obtained sorbents can be effectively used for the removal of trace amounts of radionuclides of different chemical natures (uranium, cesium, and strontium) from polluted surface and ground waters. Full article

For innovative application in wastewater treatment techniques, MnO-Fe₂O₃ nanocomposites were successfully synthesized using the sol–gel auto-combustion method at different temperatures for the adsorption of ¹³⁷Cs and ⁶⁰Co radionuclides from aqueous solution. The characterization of these nanocomposites was carried out through FT-IR, SEM-EDX, and X-ray diffraction. These nanocomposites were employed as adsorbent materials for the removal of ¹³⁷Cs and ⁶⁰Co radionuclides from simulated radioactive waste solutions. The study involved a series of experiments aiming to demonstrate the MnO-Fe₂O₃ nanoparticles’ exceptional adsorption potential concerning ¹³⁷Cs and ⁶⁰Co. Additionally, the investigation delved into how variations in temperature, dose amount, contact time, and pH value influence the adsorption dynamics. Due to their high specific surface area, the synthesized MnO-Fe₂O₃ nanoparticles had high adsorption capacity of more than 60% and 90% for ¹³⁷Cs and ⁶⁰Co, respectively. By investigation of kinetics and adsorption isotherms, pseudo-second-order reaction and the Langmuir model turned out to fit well for the adsorption of ¹³⁷Cs and ⁶⁰Co onto the MnO-Fe₂O₃ nanocomposites. Moreover, a thermodynamic analysis revealed that the adsorption process was spontaneous for both target metals and the adsorption of ⁶⁰Co was endothermic, whereas the adsorption of ¹³⁷Cs was exothermic. Full article

Phosphogypsum (PG: CaSO₄·2H₂O) is a waste product (or by-product) from the production of phosphoric acid, the main component in the production of concentrated simple and complex fertilizers. The world production of phosphogypsum exceeds 200 million tons per year. PG discharged into water bodies (seas, rivers) or disposed of in land dumps may contain elements (including heavy metals and radionuclides) in forms and concentrations that are toxic to ecosystems and human health, which raises concerns about its impact on the environment. The concentrations of these elements vary depending on the region where the raw material is mined and the process used to produce phosphoric acid. Given the significant volumes of phosphogypsum formed, an urgent problem is not only the development of methods for its disposal, but also a special, specific control over its composition after the release of PG and during its use for removal, transportation, and storage in dumps and sludge storages. This article presents the results of comprehensive studies on the determination of the chemical and mineralogical composition of by-products from an experimental plant for the processing of phosphate raw materials of the designed chemical complex of the EuroChem-Karatau company (Republic of Kazakhstan). Based on the conducted studies, it was established that, in terms of the total toxicity index, the studied wastes belong to the fourth hazard class (low-hazardous) with the possibility of processing for the purpose of their further use. Full article

The binding of actinide ions (Am(III) and U(VI)) in aqueous solutions by hybrid silica–hyperbranched poly(ethylene imine) nanoparticles (NPs) and xerogels (XGs) has been studied by means of batch experiments at different pH values (4, 7, and 9) under ambient atmospheric conditions. Both materials present relatively high removal efficiency at pH 4 and pH 7 (>70%) for Am(III) and U(VI). The lower removal efficiency for the nanoparticles is basically associated with the compact structure of the nanoparticles and the lower permeability and access to active amine groups compared to xerogels, and the negative charge of the radionuclide species is formed under alkaline conditions (e.g., UO₂(CO₃)₃⁴⁻ and Am(CO₃)₂⁻). Generally, the adsorption process is relatively slow due to the very low radionuclide concentrations used in the study and is basically governed by the actinide diffusion from the aqueous phase to the solid surface. On the other hand, adsorption is favored with increasing temperature, assuming that the reaction is endothermic and entropy-driven, which is associated with increasing randomness at the solid–liquid interphase upon actinide adsorption. To the best of our knowledge, this is the first study on hybrid silica–hyperbranched poly(ethylene imine) nanoparticle and xerogel materials used as adsorbents for americium and uranium at ultra-trace levels. Compared to other adsorbent materials used for binding americium and uranium ions, both materials show far higher binding efficiency. Xerogels could remove both actinides even from seawater by almost 90%, whereas nanoparticles could remove uranium by 80% and americium by 70%. The above, along with their simple derivatization to increase the selectivity towards a specific radionuclide and their easy processing to be included in separation technologies, could make these materials attractive candidates for the treatment of radionuclide/actinide-contaminated water. Full article

The governance of uranium tailings aims to improve stability and reduce radionuclide uranium release. In order to achieve this goal, the uranium removal solution test and uranium tailings grouting test were successively carried out using microbially induced calcium carbonate precipitation (MICP) technology. The effect of MICP on the reinforcement of uranium tailings and the synchronous control of radionuclide uranium in the tailings were discussed. The solution test results show that Sporosarcina pasteurii could grow and reproduce rapidly in an acidic medium with an initial pH of 5. The uranium concentration decreased with the increase in MICP reaction time, and the removal efficiency reached 60.9% at 24 h. In the solidification test of tailings, the strength of tailings improved significantly after 12 days of reinforcement, with an increase in the cohesion of tailings by 2.937 times and an increased internal friction angle of 8.393°. The peak stress value of solidified tailings at the surrounding pressure of 50 kPa increased by 1.87 times, and the uranium concentration in the discharge fluid decreased by 76.91% compared to the blank group. This study provides valuable insights and references for safely disposing of uranium tailings. Full article

In recent works, many industrial by-products were employed as solid precursors for the synthesis of alkali-activated binders and as alternatives to Portland cement for the immobilization of hazardous, toxic and nuclear wastes. Among industrial wastes, alkali-activated brick was found to be an interesting porous composite for removing very toxic heavy metals (Pb²⁺, Cd²⁺, Co²⁺) and radio-nuclides (Sr²⁺, Cs⁺, Rb⁺) from aqueous solutions. The starting material is very attractive due to the presence of metakaolinite as a geo-polymer precursor and silica for increasing material permeability and facilitating water filtration. The alkaline reaction gave rise to geo-polymerization followed by partial zeolitization. Elemental surface micro-analysis was performed by Scanning Electron Microscopy (SEM) equipped with an Energy-Dispersive X-ray Spectrometer (EDS). The formation of crystalline phases was corroborated by X-ray diffraction (XRD) analysis. Information about ²⁹Si, ²⁷Al and ¹H nuclei environments in crystallized and amorphous aluminosilicates was obtained by ²⁹Si, ²⁷Al and ¹H MAS NMR. ²⁷Al–¹H dipolar-mediated correlations were investigated by employing dipolar hetero-nuclear multiple quantum coherence (D-HMQC) NMR, highlighting Al–O–H bonds in bridging hydroxyl groups (Si–OH–Al) that are at the origin of adsorptive properties. Aqueous structural stability and cationic immobilization characteristics before and after material calcination were investigated from acid-leaching experiments. Full article

Low-cost sorption materials based on the clay mineral of the smectite group—montmorillonite—were used for the removal of radionuclides uranium (VI) and strontium (II) from contaminated water. A wide range of industrial methods such as thermal treatment, acid activation, and mechanochemical activation were applied. Complex methods, such as SEM microscopy analysis, X-ray powder diffraction (XRD), thermal analysis, and nitrogen adsorption–desorption at −196 °C, were used to assess the characteristics of the structure of the obtained materials. The thermal treatment, acid activation, and mechanochemical activation resulted in changes in the surface properties of the clay minerals: specific surface area, porosity, and distribution of active sites. It was established that the mechanochemical activation of montmorillonite significantly increases the sorption characteristics of the material for U(VI) and Sr(II) and the acid activation of montmorillonite increases it for U(VI). The appropriateness of the experimental adsorption values for U(VI) and Sr(II) on modified montmorillonite to Langmuir and Freundlich models was found. Independently of the changes induced by acid attack, calcinations, or milling, the sorption of U(VI) and Sr(II) ions on treated montmorillonite occurs on a homogeneous surface through monolayer adsorption in a similar fashion to natural montmorillonite. Water purification technologies and modern environmental protection technologies may successfully use the obtained clay-based sorbents. Full article

Microbial life can thrive in the most inhospitable places, such as nuclear facilities with high levels of ionizing radiation. Using direct meta-analyses, we have previously highlighted the presence of bacteria belonging to twenty-five different genera in the highly radioactive water of the cooling pool of an operating nuclear reactor core. In the present study, we further characterize this specific environment by isolating and identifying some of these microorganisms and assessing their radiotolerance and their ability to decontaminate uranium. This metal is one of the major radioactive contaminants of anthropogenic origin in the environment due to the nuclear and mining industries and agricultural practices. The microorganisms isolated when sampling was performed during the reactor operation consisted mainly of Actinobacteria and Firmicutes, whereas Proteobacteria were dominant when sampling was performed during the reactor shutdown. We investigated their tolerance to gamma radiation under different conditions. Most of the bacterial strains studied were able to survive 200 Gy irradiation. Some were even able to withstand 1 kGy, with four of them showing more than 10% survival at this dose. We also assessed their uranium uptake capacity. Seven strains were able to remove almost all the uranium from a 5 µM solution. Four strains displayed high efficiency in decontaminating a 50 µM uranium solution, demonstrating promising potential for use in bioremediation processes in environments contaminated by radionuclides. Full article

The paper deals with checking the possibility of using fly ash (FA) as a sorbent in the batch adsorption method of removing radionuclides from aqueous solutions. An adsorption-membrane filtration (AMF) hybrid process with a polyether sulfone ultrafiltration membrane with a pore size of 0.22 μm was also tested as an alternative to the commonly used column-mode technology. In the AMF method, metal ions are bound by the water-insoluble species prior to the membrane filtration of the purified water. Thanks to the easy separation of the metal-loaded sorbent, it is possible to improve water purification parameters using compact installations and reduce operating costs. This work evaluated the influence of such parameters on cationic radionuclide removal efficiency (EM): initial pH and composition of the solution, contact time of the phases, and the FA doses. A method for removing radionuclides, ordinarily present in an anionic form (e.g., TcO₄⁻), from water, has also been presented. The results show, that both batch adsorption of radionuclides and adsorption-membrane filtration (AMF) using the FA as an adsorbent can be effectively used for water purification and in the form of a solid directed to long-term storage. Full article