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1.
Environ Sci Pollut Res Int ; 31(23): 34112-34123, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38696009

RESUMO

Cesium removal from aqueous solutions of radioactive waste streams is a challenge in the field of radioactive waste management; this is due to the small atomic radii of Cs+ metal ions and their high migration ability. So, the development of a withstand system for the removal of Cs+ is crucial. In the current study, the removal of radioactive cesium from aqueous solutions using an RO-TLC membrane was studied. Two modifications were conducted; the first is to enlarge the cesium metal ion radii by interacting with mono- and dibasic acids, namely, stearic acid, tartaric acid, citric acid, and EDTA, and the second is the modification of the RO membrane pore size via reaction with the same acids. The modification was confirmed using SEM, FTIR, and EDX analysis techniques. The Cs+ and K+ rejection capacities and water permeability across the membrane at 1.5 bars were evaluated. Along with using the above-mentioned acids, the Cs+ metal ion retention index (RCs) was also obtained. It was found that employing EDTA as a chelating agent in an amount of 1.5 g/L in conjunction with the variation of feed content since it provided the highest value of RCs ~ 98% when used. Moreover, the elution of Cs+ using water, EDTA, ammonia, and HCl is also investigated. The optimal value of the eluent concentration was (0.25 M) HCl. Finally, Langmuir and Freundlich isotherm models were applied for a better understanding of the sorption process. The results of the present work more closely match the Langmuir isotherm model to determine the dominance of the chemical sorption mechanism.


Assuntos
Radioisótopos de Césio , Osmose , Resíduos Radioativos , Membranas Artificiais , Poluentes Radioativos da Água
2.
Environ Sci Technol ; 58(20): 8909-8918, 2024 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-38728532

RESUMO

Over 4 million liters of mixed acidic (∼pH 2.5), high ionic strength (∼5 M nitrate) plutonium (Pu) processing waste were released into the 216-Z-9 (Z-9) trench at the Hanford Site, USA, and trace Pu has migrated 37 m below the trench. In this study, we used flowthrough columns to investigate Pu transport in simplified processing waste through uncontaminated Hanford sediments to determine the conditions that led to Pu migration. In low pH aqueous fluids, some Pu breakthrough is observed at pH < 4, and increased Pu transport (14% total Pu breakthrough) is observed at pH < 2. However, Pu migrates in organic processing solvents through low pH sediments virtually uninhibited with approximately 94 and 86% total Pu breakthrough observed at pH 1 and pH 3, respectively. This study demonstrates that Pu migration can occur both with and without organic solvents at pH < 4, but significantly more Pu can be transported when partitioned into organic processing solvents. Our data suggest that under acidic conditions (pH < 4) in the vadose zone beneath the Z-9 trench, Pu present in organic processing solvents moved relatively unhindered and may explain the historical downward migration of Pu tens of meters below the Z-9 trench.


Assuntos
Plutônio , Concentração de Íons de Hidrogênio , Poluentes Radioativos da Água , Sedimentos Geológicos/química , Resíduos Radioativos , Solventes/química
3.
J Environ Manage ; 357: 120851, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38581894

RESUMO

Conventional liquid treatments for large-scale, low-level radioactive wastewater, such as ion exchange and waste solidification, face challenges due to the large amounts of secondary waste and high disposal costs. A new large-scale decontamination method is proposed that uses kapok fiber composites for rapid radionuclide adsorption and high volume reduction to minimize secondary waste. The composite consists of natural zeolite and kapok holocellulose, which has high water-soaking ability and low-temperature pyrolysis. The kapok composites, fabricated using a commercial wet-laid nonwoven manufacturing process, absorbs 99% of low-level radioactive cesium in 20 min, reducing the volume by 98% and the weight by 47% at 300 °C. The low-temperature pyrolysis process below 300 °C prevents cesium desorption and gasification by avoiding zeolite destruction. The mass-producible kapok composites can be used for adsorbing various radionuclides in large-scale wastewater by attaching specific adsorbents for target isotopes to the composites.


Assuntos
Resíduos Radioativos , Zeolitas , Águas Residuárias , Césio , Radioisótopos , Adsorção , Resíduos Radioativos/prevenção & controle
4.
Chemosphere ; 358: 141761, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38531499

RESUMO

Low-level radioactive wastes were disposed at the Little Forest Legacy Site (LFLS) near Sydney, Australia between 1960 and 1968. According to the disposal records, 233U contributes a significant portion of the inventory of actinide activity buried in the LFLS trenches. Although the presence of 233U in environmental samples from LFLS has been previously inferred from alpha-spectrometry measurements, it has been difficult to quantify because the 233U and 234U α-peaks are superimposed. Therefore, the amounts of 233U in groundwaters, soils and vegetation from the vicinity of the LFLS were measured using accelerator mass spectrometry (AMS). The AMS results show the presence of 233U in numerous environmental samples, particularly those obtained within, and in the immediate vicinity of, the trenched area. There is evidence for dispersion of 233U in groundwater (possibly mobilised by co-disposed organic liquids), and the data also suggest other sources of 233U contamination in addition to the trench wastes. These may include leakages and spills from waste drums as well as waste burnings, which also occurred at the site. The AMS results confirm the historic information regarding disposal of 233U in the LFLS trenches. The AMS technique has been valuable to ascertain the distribution and environmental behaviour of 233U at the LFLS and the results demonstrate the applicability of AMS for evaluating contamination of 233U at other radioactive waste sites.


Assuntos
Água Subterrânea , Espectrometria de Massas , Monitoramento de Radiação , Resíduos Radioativos , Poluentes Radioativos do Solo , Solo , Urânio , Poluentes Radioativos da Água , Resíduos Radioativos/análise , Água Subterrânea/química , Água Subterrânea/análise , Monitoramento de Radiação/métodos , Urânio/análise , Poluentes Radioativos da Água/análise , Solo/química , Poluentes Radioativos do Solo/análise , Austrália , Plantas/química
5.
Curr Environ Health Rep ; 11(2): 318-328, 2024 06.
Artigo em Inglês | MEDLINE | ID: mdl-38538904

RESUMO

PURPOSE OF REVIEW: This review provides insights into resolving intergenerational issues related to the disposal of waste containing high amounts of uranium (uranium waste), from which distant future generations will have higher health risks than the current generation. RECENT FINDINGS: Uranium (half-life: 4.5 billion years) produces various progeny radionuclides through radioactive decay over the long term, and its radioactivity, as the sum of its contributions, continues to increase for more than 100,000 years. In contrast to high-level radioactive wastes, protective measures, such as attenuation of radiation and confinement of radionuclides from the disposal facility, cannot work effectively for uranium waste. Thus, additional considerations from the perspective of intergenerational ethics are needed in the strategy for uranium waste disposal. The current generation, which has benefited from the use and disposal of uranium waste, is responsible for protecting future generations from the potential risk of buried uranium beyond the lifetime of a disposal facility. Fulfilling this responsibility means making more creative efforts to convey critical information on buried materials to the distant future to ensure that future generations can properly take measures to reduce the harm by themselves in response to changing circumstances including people's values.


Assuntos
Resíduos Radioativos , Urânio , Humanos , Eliminação de Resíduos
6.
J Appl Microbiol ; 135(3)2024 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-38458234

RESUMO

AIMS: Many countries are in the process of designing a deep geological repository (DGR) for long-term storage of used nuclear fuel. For several designs, used fuel containers will be placed belowground, with emplacement tunnels being backfilled using a combination of highly compacted powdered bentonite clay buffer boxes surrounded by a granulated "gapfill" bentonite. To limit the potential for microbiologically influenced corrosion of used fuel containers, identifying conditions that suppress microbial growth is critical for sustainable DGR design. This study investigated microbial communities in powdered and gapfill bentonite clay incubated in oxic pressure vessels at dry densities between 1.1 g cm-3 (i.e. below repository target) and 1.6 g cm-3 (i.e. at or above repository target) as a 1-year time series. RESULTS: Our results showed an initial (i.e. 1 month) increase in the abundance of culturable heterotrophs associated with all dry densities <1.6 g cm-3, which reveals growth during transient low-pressure conditions associated with the bentonite saturation process. Following saturation, culturable heterotroph abundances decreased to those of starting material by the 6-month time point for all 1.4 and 1.6 g cm-3 pressure vessels, and the most probable numbers of culturable sulfate-reducing bacteria (SRB) remained constant for all vessels and time points. The 16S rRNA gene sequencing results showed a change in microbial community composition from the starting material to the 1-month time point, after which time most samples were dominated by sequences associated with Pseudomonas, Bacillus, Cupriavidus, and Streptomyces. Similar taxa were identified as dominant members of the culture-based community composition, demonstrating that the dominant members of the clay microbial communities are viable. Members of the spore-forming Desulfosporosinus genus were the dominant SRB for both clay and culture profiles. CONCLUSIONS: After initial microbial growth while bentonite was below target pressure in the early phases of saturation, microbial growth in pressure vessels with dry densities of at least 1.4 g cm-3 was eventually suppressed as bentonite neared saturation.


Assuntos
Bentonita , Resíduos Radioativos , Resíduos Radioativos/análise , Argila , RNA Ribossômico 16S/genética
7.
J Environ Manage ; 356: 120616, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38518493

RESUMO

Metakaolin-based geopolymers are very promising materials for improving the safety of low and intermediate level radioactive waste disposal, with respect to ordinary Portland cement, due to their excellent immobilization performance for Cs+ and superior chemical stability. However, their application is limited by the fact that the leaching behavior of Cs+ is susceptible to the presence of other ions in the environment. Here, we propose a way to modify a geopolymer using perfluorodecyltriethoxysilane (PDFS), successfully reducing the leaching rate of Cs+ in the presence of multiple competitive cations due to blocking the diffusion of water. The leachability index of the modified samples in deionized water and highly concentrated saline water reached 11.0 and 8.0, respectively. The reaction mechanism between PDFS and geopolymers was systematically investigated by characterizing the microstructure and chemical bonding of the material. This work provides a facile and successful approach to improve the immobilization of Cs ions by geopolymers in real complex environments, and it could be extended to further improve the reliability of geopolymers used in a range of applications.


Assuntos
Resíduos Radioativos , Eliminação de Resíduos , Reprodutibilidade dos Testes , Polímeros , Eliminação de Resíduos/métodos , Íons
8.
J Environ Manage ; 356: 120712, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38531127

RESUMO

This review paper provides a comprehensive analysis of cement-based solidification and immobilisation of nuclear waste. It covers various aspects including mechanisms, formulations, testing and regulatory considerations. The paper begins by emphasizing the importance of nuclear waste management and the associated challenges. It explores the mechanisms and principles in cement-based solidification, with a particular focus on the interaction between cement and nuclear waste components. Different formulation considerations are discussed, encompassing factors such as cement types, the role of additives and modifiers. The review paper also examines testing and characterisation methods used to assess the physical, chemical and mechanical properties of solidified waste forms. Then the paper addresses the regulatory considerations and compliance requirements for cement-based solidification. The paper concludes by critically elaborating on the current challenges, emerging trends and future research needs in the field. Overall, this review paper offers a comprehensive overview of cement-based solidification, providing valuable insights for researchers, practitioners and regulatory bodies involved in nuclear waste management.


Assuntos
Resíduos Radioativos , Gerenciamento de Resíduos , Gerenciamento de Resíduos/métodos , Resíduos Perigosos
9.
Chemosphere ; 352: 141462, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38364923

RESUMO

The migration and retention of radioactive contaminants such as 137Cesium (137Cs) in various environmental media pose significant long-term storage challenges for nuclear waste. The distribution coefficient (Kd) is a critical parameter for assessing the mobility of radioactive contaminants and is influenced by various environmental conditions. This study presents machine-learning models based on the Japan Atomic Energy Agency Sorption Database (JAEA-SDB) to predict the Kd values for Cs in solid phase groups. We used three different machine learning models: random forest (RF), artificial neural network (ANN), and convolutional neural network (CNN). The models were trained on 14 input variables from the JAEA-SDB, including factors such as the Cs concentration, solid-phase properties, and solution conditions, which were preprocessed by normalization and log-transformation. The performances of the models were evaluated using the coefficient of determination (R2) and root mean squared error (RMSE). The RF, ANN, and CNN models achieved R2 values greater than 0.97, 0.86, and 0.88, respectively. We also analyzed the variable importance of RF using an out-of-bag (OOB) and a CNN with an attention module. Our results showed that the environmental media, initial radionuclide concentration, solid phase properties, and solution conditions were significant variables for Kd prediction. Our models accurately predict Kd values for different environmental conditions and can assess the environmental risk by analyzing the behavior of radionuclides in solid phase groups. The results of this study can improve safety analyses and long-term risk assessments related to waste disposal and prevent potential hazards and sources of contamination in the surrounding environment.


Assuntos
Césio , Resíduos Radioativos , Césio/análise , Radioisótopos de Césio/análise , Resíduos Radioativos/análise , Japão
10.
Radiat Environ Biophys ; 63(1): 1-6, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38367061

RESUMO

This report summarizes the findings of a workshop held at the safeND Research Symposium and hosted by the German Federal Office for the Safety of Radioactive Waste Management (BASE) in Berlin in September 2023. The workshop aimed to channel perspectives from various fields of expertise to discuss key sustainability concepts in terms of radioactive waste management. Therefore, the report highlights that current sustainability concepts, such as the United Nations' Sustainable Development Goals (SDG) as well as the concept of Planetary Boundaries, neglect challenges arising from the production and storage of human-made radioactive materials. The workshop consisted of three group tasks. The first attempted at identifying the interrelations between "sustainability" and radioactive waste management. The second was to map the global nature of the challenges. The third took first steps to determine a human-made radioactive material as a potential planetary sub-boundary for "novel entities". All three groups identified valuable knowledge gaps that should be addressed by future research and concluded that radioactive waste management is underrepresented in these sustainability concepts.


Assuntos
Resíduos Radioativos , Gerenciamento de Resíduos , Humanos
11.
J Contam Hydrol ; 262: 104309, 2024 03.
Artigo em Inglês | MEDLINE | ID: mdl-38308940

RESUMO

The high-level nuclear waste, HLW, from Swedish and Finnish reactors will be deposited in crystalline rock at depths around 500 m. The waste is enclosed in steel canisters protected against corrosion by a 5 cm thick copper shell, which ensures a lifetime far longer than 100 000 years. Should some canister be breached any leaking nuclides will have decayed to so low activity that even if they reached the biosphere, they would cause minimal risk to humans. The cost of the copper is significant. The dismantling of the nuclear reactors, with induced activity must also be disposed of and this waste volume is much larger than that of the HLW, which makes it impossible to protect it in the same way. This paper explores if by locating the waste at larger depth where the ground water is more saline, and where the hydraulic conductivity of the rock is lower up-flow of contaminated water can be ensured to be negligible because the denser water at larger depth counteracts up-flow due to negative buoyancy. Several processes that could cause local up-flow are addressed, such as infiltration of meteoric water, impact of surface topology, heat production of the waste, geothermal gradient, salinity gradient, hydraulic conductivity heterogeneities and salt migration between seeping water and salt in matrix pore water. Flow and transport simulations using data from extensive field investigations over more than ten years with scores of km deep boreholes suggest that a HLW repository at around one km depth may be sufficient to hinder up-flow to the biosphere.


Assuntos
Água Subterrânea , Resíduos Radioativos , Humanos , Modelos Teóricos , Cobre , Água Subterrânea/química , Radioisótopos , Resíduos Radioativos/análise , Água
12.
Sci Rep ; 14(1): 1021, 2024 01 10.
Artigo em Inglês | MEDLINE | ID: mdl-38200072

RESUMO

Legacy radioactive waste can be defined as the radioactive waste produced during the infancy of the civil nuclear industry's development in the mid-20th Century, a time when, unfortunately, waste storage and treatment were not well planned. The marine environment is one of the environmental compartments worth studying in this regard because of legacy waste in specific locations of the seabed. Comprising nearly 70% of the earth's service, the oceans are the largest and indeed the final destination for contaminated fresh waters. For this reason, long-term studies of the accumulation biochemical mechanisms of metallic radionuclides in the marine ecosystem are required. In this context the brown algal compartment may be ecologically relevant because of forming large and dense algal beds in coastal areas and potential important biomass for contamination. This report presents the first step in the investigation of uranium (U, an element used in the nuclear cycle) bioaccumulation in the brown alga Ascophyllum nodosum using a multi-scale spectroscopic and imaging approach. Contamination of A. nodosum specimens in closed aquaria at 13 °C was performed with a defined quantity of U(VI) (10-5 M). The living algal uptake was quantified by ICP-MS and a localization study in the various algal compartments was carried out by combining electronic microscopy imaging (SEM), X-ray Absorption spectroscopy (XAS) and micro X-ray Florescence (µ-XRF). Data indicate that the brown alga is able to concentrate U(VI) by an active bioaccumulation mechanism, reaching an equilibrium state after 200 h of daily contamination. A comparison between living organisms and dry biomass confirms a stress-response process in the former, with an average bioaccumulation factor (BAF) of 10 ± 2 for living specimens (90% lower compared to dry biomass, 142 ± 5). Also, these results open new perspectives for a potential use of A. nodosum dry biomass as uranium biosorbent. The different partial BAFs (bioaccumulation factors) range from 3 (for thallus) to 49 (for receptacles) leading to a compartmentalization of uranium within the seaweed. This reveals a higher accumulation capacity in the receptacles, the algal reproductive parts. SEM images highlight the different tissue distributions among the compartments with a superficial absorption in the thallus and lateral branches and several hotspots in the oospheres of the female individuals. A preliminary speciation XAS analysis identified a distinct U speciation in the gametes-containing receptacles as a pseudo-autunite phosphate phase. Similarly, XAS measurements on the lateral branches (XANES) were not conclusive with regards to the occurrence of an alginate-U complex in these tissues. Nonetheless, the hypothesis that alginate may play a role in the speciation of U in the algal thallus tissues is still under consideration.


Assuntos
Ascophyllum , Resíduos Radioativos , Urânio , Humanos , Feminino , Bioacumulação , Ecossistema , Espectroscopia por Absorção de Raios X , Alginatos
13.
Sci Total Environ ; 915: 170149, 2024 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-38242445

RESUMO

Deep Geological Repositories (DGRs) consist of radioactive waste contained in corrosion-resistant canisters, surrounded by compacted bentonite clay, and buried few hundred meters in a stable geological formation. The effects of bentonite microbial communities on the long-term stability of the repository should be assessed. This study explores the impact of harsh conditions (60 °C, highly-compacted bentonite, low water activity), and acetate:lactate:sulfate addition, on the evolution of microbial communities, and their effect on the bentonite mineralogy, and corrosion of copper material under anoxic conditions. No bentonite illitization was observed in the treatments, confirming its mineralogical stability as an effective barrier for future DGR. Anoxic incubation at 60 °C reduced the microbial diversity, with Pseudomonas as the dominant genus. Culture-dependent methods showed survival and viability at 60 °C of moderate-thermophilic aerobic bacterial isolates (e.g., Aeribacillus). Despite the low presence of sulfate-reducing bacteria in the bentonite blocks, we proved their survival at 30 °C but not at 60 °C. Copper disk's surface remained visually unaltered. However, in the acetate:lactate:sulfate-treated samples, sulfide/sulfate signals were detected, along with microbial-related compounds. These findings offer new insights into the impact of high temperatures (60 °C) on the biogeochemical processes at the compacted bentonite/Cu canister interface post-repository closure.


Assuntos
Bentonita , Resíduos Radioativos , Bentonita/química , Resíduos Radioativos/análise , Cobre , Corrosão , Temperatura , Sulfatos , Lactatos , Acetatos
14.
Int J Biol Macromol ; 260(Pt 2): 129690, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38266855

RESUMO

Radioactive iodine is considered one of the most dangerous radioactive elements in nuclear waste. Therefore, effective capture of radioactive iodine is essential for developing and using nuclear energy to solve the energy crisis. Some materials that have been developed for removing radioactive iodine still suffer from complex synthesis, low removal capacity, and non-reusability. Herein, covalent organic framework (COF)/chitosan (CS) aerogels were prepared using vacuum freeze-drying, and the COF nanoparticles were tightly attached on the green biomass material CS networks. Due to the synergistic effect of both COF and CS, the composite aerogel shows a three-dimensional porous and stable structure in the recycle usage. The COF/CS aerogel exhibits excellent iodine adsorption capacity of 2211.58 mg g-1 and 5.62 g g-1 for static iodine solution and iodine vapor, respectively, better than some common adsorbents. Furthermore, COF/CS aerogel demonstrated good recyclability performance with 87 % of the initial adsorption capacity after 5 cycles. In addition, the interaction between iodine and imine groups, amino groups, and benzene rings of aerogel are the possible adsorption mechanisms. COF/CS aerogel has excellent adsorption properties, good chemical stability, and reusable performance, which is a potential and efficient adsorbent for industrial radioactive iodine adsorption from nuclear waste.


Assuntos
Quitosana , Iodo , Estruturas Metalorgânicas , Resíduos Radioativos , Neoplasias da Glândula Tireoide , Humanos , Adsorção , Radioisótopos do Iodo
15.
FEMS Microbiol Rev ; 48(1)2024 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-38216518

RESUMO

The potential for microbial activity to occur within the engineered barrier system (EBS) of a geological disposal facility (GDF) for radioactive waste is acknowledged by waste management organizations as it could affect many aspects of the safety functions of a GDF. Microorganisms within an EBS will be exposed to changing temperature, pH, radiation, salinity, saturation, and availability of nutrient and energy sources, which can limit microbial survival and activity. Some of the limiting conditions are incorporated into GDF designs for safety reasons, including the high pH of cementitious repositories, the limited pore space of bentonite-based repositories, or the high salinity of GDFs in evaporitic geologies. Other environmental conditions such as elevated radiation, temperature, and desiccation, arise as a result of the presence of high heat generating waste (HHGW). Here, we present a comprehensive review of how environmental conditions in the EBS may limit microbial activity, covering HHGW and lower heat generating waste (LHGW) in a range of geological environments. We present data from the literature on the currently recognized limits to life for each of the environmental conditions described above, and nutrient availability to establish the potential for life in these environments. Using examples where each variable has been modelled for a particular GDF, we outline the times and locations when that variable can be expected to limit microbial activity. Finally, we show how this information for multiple variables can be used to improve our understanding of the potential for microbial activity to occur within the EBS of a GDF and, more broadly, to understand microbial life in changing environments exposed to multiple extreme conditions.


Assuntos
Microbiologia Ambiental , Ambientes Extremos , Resíduos Radioativos , Resíduos Radioativos/análise
16.
Sci Total Environ ; 912: 169242, 2024 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-38072256

RESUMO

Research on eco-friendly bioremediation strategies for mitigating the environmental impact of toxic metals has gained attention in the last years. Among all promising solutions, bentonite clays, to be used as artificial barriers to isolate radioactive wastes within the deep geological repository (DGR) concept, have emerged as effective reservoir of microorganisms with remarkable bioremediation potential. The present study aims to investigate the impact of bentonite fungi in the speciation and mobility of selenium (Se) and tellurium (Te), as natural analogues 79Se and 132Te present in radioactive waste, to screen for those strains with bioremediation potential within the context of DGR. For this purpose, a multidisciplinary approach combining microbiology, biochemistry, and microscopy was performed. Notably, Aspergillus sp. 3A demonstrated a high tolerance to Te(IV) and Se(IV), as evidenced by minimal inhibitory concentrations of >16 and >32 mM, respectively, along with high tolerance indexes. The high metalloid tolerance of Aspergillus sp. 3A is mediated by its capability to reduce these mobile and toxic elements to their elemental less soluble forms [Te(0) and Se(0)], forming nanostructures of various morphologies. Advanced electron microscopy techniques revealed intracellular Te(0) manifesting as amorphous needle-like nanoparticles and extracellular Te(0) forming substantial microspheres and irregular accumulations, characterized by a trigonal crystalline phase. Similarly, Se(0) exhibited a diverse array of morphologies, including hexagonal, irregular, and needle-shaped structures, accompanied by a monoclinic crystalline phase. The formation of less mobile Te(0) and Se(0) nanostructures through novel and environmentally friendly processes by Aspergillus sp. 3A suggests it would be an excellent candidate for bioremediation in contaminated environments, such as the vicinity of deep geological repositories. It moreover holds immense potential for the recovery and synthesis of Te and Se nanostructures for use in numerous biotechnological and biomedical applications.


Assuntos
Resíduos Radioativos , Selênio , Selênio/química , Telúrio , Bentonita , Biodegradação Ambiental
17.
Environ Sci Pollut Res Int ; 31(2): 2732-2744, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38066266

RESUMO

The crystalline phase of molybdenum titanium tungsto-phosphate (MoTiWPO4) as an inorganic sorbent material was synthesized via the sol-gel method. The physicochemical characteristics of MoTiWPO4 were evaluated by using Fourier transform infrared (FT-IR), scanning electron microscope (SEM), energy dispersive X-ray (EDX), thermal analysis (TGA-DTA), and X-ray diffraction (XRD). MoTiWPO4 sorbent material exhibits a high chemical resistance to HNO3, HCl, and alkaline media. MoTiWPO4 has good thermal stability as it retained about 75.63% of its saturation capacity upon heating at 500 °C. The sorption studies for several metal ions revealed marked high sorption efficiency of MoTiWPO4 towards Cs+ and Sr2+ ions which reached 99% and 95%, respectively. The saturation capacity of MoTiWPO4 for Cs+ and Sr2+ is 113 and 109 mg/g, respectively. MoTiWPO4 is approved to be successfully eliminating both 137Cs and 85Sr from liquid radioactive waste streams by %eff. of 92.5 and 90.3, respectively, in the presence of competing ions from 60Co(divalent) and 152Eu (trivalent), confirming the batch experiment results for the removal of Cs+ and Sr2+ metal ions. Furthermore, the decontamination factor exceeds 13.3 in the case of 137Cs and 10.3 for 85Sr.


Assuntos
Radioisótopos de Césio , Resíduos Radioativos , Molibdênio , Titânio , Descontaminação , Espectroscopia de Infravermelho com Transformada de Fourier , Adsorção , Íons , Fosfatos
18.
Environ Sci Pollut Res Int ; 31(2): 2419-2436, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38063959

RESUMO

The use of phyllite (Phy) instead of quartz in mixtures with bentonite (B) is recommended as a buffer material for engineering barriers in a geological repository of nuclear waste. The recommendation is based on experimentally determined sorption properties of various Phy/B mixtures. The adsorption capacity of Phy/B mixtures (Phy/B: 75/25, 50/50, and 25/75), the removal efficacy of Eu(III) ions (an analog for fissiongenic lanthanides and actinides), and the rate of their binding reaction were studied using the batch adsorption equilibrium and kinetic experiments at different Eu(III) initial concentrations, solution pH, and solution to adsorbent (L/S) ratio. The adsorption capacity of the Phy/B mixtures increased with the increased bentonite content in the mixture depending on the L/S ratio and solution pH. The highest increase in the adsorption capacity of the Phy/B mixtures compared to phyllite was observed for the Phy/B proportions of 25/75 and 50/50. The rate of the Eu(III) adsorption was the best fitted by the pseudo-second-order kinetic model indicating that the adsorption rate was controlled by chemisorption. The Sips model provided the best correlation of the adsorption experimental data, indicative of more than one adsorption site. The results of this study show the advantage of the Phy/B mixtures in immobilizing Eu and certain fission products by combining adsorption properties of the materials.


Assuntos
Resíduos Radioativos , Poluentes Químicos da Água , Bentonita/química , Adsorção , Quartzo , Concentração de Íons de Hidrogênio , Cinética , Poluentes Químicos da Água/análise
19.
Chemosphere ; 350: 141050, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38154672

RESUMO

At present, the deep geological repository concept for spent nuclear fuel is considered the most reliable and safe technique for the permanent disposal of this type of waste. One of the many safety elements used is an engineered barrier made of compacted bentonite. This material allows the encapsulated waste to be isolated from the host rock. Therefore, there is great interest in a detailed study of the behavior of bentonites to different changes in the composition of the surrounding groundwater. In this context, this work presents a new reactive transport model for bentonites implemented in the COMSOL Multiphysics platform. The model contemplates a non-simplistic geochemical system composed of 42 species and 4 minerals. Reactive transport involves the diffusive-dispersive-advective processes defined by the Nernst Planck equations for two overlapping modeling levels (macro- and microstructural) to simulate the behavior of double-porosity media. The uniqueness of this model is that the system of equations used to calculate the chemical speciation problem and the advective-diffusive-dispersive transport can be integrally solved in COMSOL. The model has been satisfactorily verified and validated using the benchmark exercise consisting of the simulation of the multicomponent advective-diffusive column experiment conducted on a compacted bentonite core extracted from a field experiment (LOT project) in the Äspö Hardrock laboratory (Sweden).


Assuntos
Bentonita , Resíduos Radioativos , Bentonita/química , Benchmarking , Porosidade , Simulação por Computador , Suécia , Modelos Teóricos
20.
World J Microbiol Biotechnol ; 40(1): 41, 2023 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-38071262

RESUMO

As bentonite hosts a diverse spectrum of indigenous microorganisms with the potential to influence the long-term stability of deep geological repositories, it is essential to understand the factors influencing microbial activity under repository conditions. Here, we focus on two factors, i.e., temperature and swelling pressure, using a suspension of Cerny Vrch bentonite to boost microbial activity and evaluate microbial response. Suspensions were exposed either to different pressures (10, 12 and 15 MPa; to simulate the effect of swelling pressure) or elevated temperatures (60, 70, 80 and 90 °C; to simulate the effect of cannister heating) for four weeks. Each treatment was followed by a period of anaerobic incubation at atmospheric pressure/laboratory temperature to assess microbial recovery after treatment. Microbial load and community structure were then estimated using molecular-genetic methods, with presence of living cells confirmed through microscopic analysis. Our study demonstrated that discrete application of pressure did not influence on overall microbial activity or proliferation, implying that pressure evolution during bentonite swelling is not the critical factor responsible for microbial suppression in saturated bentonites. However, pressure treatment caused significant shifts in microbial community structure. We also demonstrated that microbial activity decreased with increasing temperature, and that heat treatment strongly influenced bentonite microbial community structure, with several thermophilic taxa identified. A temperature of 90 °C proved to be limiting for microbial activity and proliferation in all bentonite suspensions. Our study emphasizes the crucial role of a deep understanding of microbial activity under repository-relevant conditions in identifying possible strategies to mitigate the microbial potential within the deep geological repository and increase its long-term stability and safety.


Assuntos
Bentonita , Resíduos Radioativos , Bentonita/análise , Bentonita/química , Resíduos Radioativos/análise , Temperatura , Fenômenos Químicos , Proliferação de Células
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