Uranium Tailings Research Articles

Bioprospecting of a Native Plant Growth-Promoting Bacterium Bacillus cereus B6 for Enhancing Uranium Accumulation by Sudan Grass (Sorghum sudanense (Piper) Stapf)

Phytoremediation technology is viewed as a potential solution for addressing soil uranium contamination. Sudan grass (Sorghum sudanense (Piper) Stapf.), noted for its robust root structure and resilience to heavy metals, has garnered significant attention. This paper investigates a strain of uranium-tolerant bacterium, B6, obtained from the inter-root environment of native plants in soil contaminated with uranium tailings. The bacterium was identified as Bacillus cereus. Genomic analyses and assessment of uranium tolerance-promoting properties showed that strain B6 not only exhibited high uranium tolerance, but also possessed beneficial properties such as phosphorus solubilization and iron-producing carriers. In this study, we used strain B6 as an inoculant in combination with Sudan grass for germination and potting experiments. The findings demonstrated that Bacillus cereus B6 could substantially mitigate the adverse effects of uranium stress on Sudan grass, boost the plant’s antioxidant response, significantly increase the root length and dry biomass of Sudan grass, and facilitate the accumulation of uranium in the roots, as well as its translocation to the aboveground portions. The study showed that PGPB strain B6 can significantly enhance the effect of plant accumulation of uranium and increase the potential of Sudan grass to become a uranium-rich plant, which provides an important scientific basis and application prospect for the use of microbial-assisted Sudan grass remediation technology to treat uranium-contaminated soil.

Uranium Recovery from Uranium Tailings Using the Low-Temperature Chlorination Roasting and Nitric Acid Leaching Process

To address the problems of low leaching efficiency and the fact that the uranium content in leaching residue is higher than the emission standard in the traditional nitric acid leaching uranium tailing and uranium extraction process, the experimental study of low-temperature chlorination roasting and nitric acid leaching was carried out. The effects of roasting temperature, NaCl addition, and roasting time on uranium leaching rate were investigated, and the morphological structure change and phase transformation of roasted minerals were analyzed. After the low-temperature roasting of sodium chloride, the mineral structure was obviously destroyed, the structure became loose, the voids and microcracks increased, and the size of tailing particles decreased. This is mainly due to the reaction of NaCl with metal compounds in minerals. However, when the sodium chloride is excessive, the formation of hydrogen chloride will promote the formation of new compounds, such as Na2Pb2O7 and Zr7O9F10, and form a secondary coating of uranium, resulting in a decrease in the leaching rate. The optimum process conditions of chlorination roasting are as follows: a roasting temperature 250 °C, a 20% addition of NaCl to the tailing mass, a roasting time of 120 min, and a uranium leaching rate of 93.38%. Compared with traditional nitric acid leaching, the leaching rate of uranium increased by 16.64%.

Experimental Research on Permeability and Effective Radon Reduction of Chemical Solidification of Uranium Tailings

To be able to study the permeability coefficient and radon reduction effect of three materials before and after the solidification of uranium tailings. Firstly, uranium tailings, blast furnace slag, lime, fly ash and cement were selected as raw materials for the experiment. Three solidified materials were mixed with 7.5%, 10% and 12.5% of equal proportions of cement. The curing samples of nine kinds of solidified bodies were prepared after curing. Subsequently, the permeability coefficient was determined through the utilization of X-ray diffraction (XRD) and scanning electron microscopy (SEM). And cumulative radon concentrations in uranium tailings and samples were measured by RAD7. Thus, the radon exhalation rate of the original sample and the sample were determined. The experimental results show that the permeability coefficient of nine samples decreased with the quadratic function with the increase in the amount of curing agent. Microscopic scanning results show that there is a positive correlation among the radon exhalation rate, permeability coefficient and cementation degree. The best material for solidifying uranium tailings and radon insulation was blast furnace slag, followed by fly ash.

Optimization of Strength Factors in Microbial Solidification of Uranium Tailings Using Response Surface Methodology

Once the uranium tailings dam collapses, it will cause great harm to the surrounding ecological environment and people’s safety. This study experimentally investigates microbial grouting reinforcement of uranium tailings to advance microbial reinforcement technology and facilitate its large-scale engineering applications. The study simulated original environmental conditions and used tap water to prepare the culture medium and cement without sterilization or pH adjustment. The response surface method was employed to optimize parameters affecting the immobilization of uranium tailings, and the results were verified. The mechanical strength of the immobilized uranium tailings was determined through unconfined compression tests, while their microstructures were analyzed using X-ray diffraction, scanning electron microscopy and computed tomography. The findings indicate that the response surface method optimizes test parameters accurately, with the concentration of the cementation solution and the grouting amount being two main factors influencing the compressive strength of the solidified uranium tailings. Without pH adjustment, sterilization, or slurry modification using tap water, the bacteria−cementation ratio was set at 1, the concentration of the cementation solution was 1.3 mol/L, and the grouting volume was 70 mL. Notably, the strength of the uranium tailings increased 27-fold after seven rounds of grouting compared to the water-only group, and 6-fold compared to the cementation solution-only group. This study contributes to reducing the complexity associated with the application of microbial grouting technology in soil stabilization and provides valuable references for other engineering practices.

Advancements in Paper-Based Electrochemical Sensors for Cancer Biomarker Detection

Cancer is currently the third leading cause of death among the people of the Navajo Nation and is the most common cause of death worldwide. American Indians are often diagnosed when cancer has reached the advanced stages compared to other communities. Major contributors for the cancer inside the Navajo Nation is the exposure to uranium, other heavy metals, and radon gas. In the Navajo Nation, uranium mining boomed from 1944 to 1986; decades later, uranium tailings and toxic waste from the milling process have caused an increased rate of cancer in the Navajo Nation.Further cancer detection and monitoring remain critical challenges in healthcare. This research explores the fabrication of paper-based electrochemical sensors modified with nanoparticles and antigens at the Nanoelectrochemical Analysis and Energy Storage Laboratory (NEST LAB) at Navajo Technical University (NTU) for the sensitive and selective detection of cancer biomarkers.These electrochemical sensors harness the unique qualities of paper, such as low cost and ease of fabrication, combined with the specific binding capabilities of nanoparticles and antigens. Modifying paper electrode surfaces enhances sensitivity and selectivity, making these sensors a cost-effective and portable option for early cancer detection. In contrast to traditional methods like imaging and biopsies, electrochemical sensors are low-cost, offer minimally invasive screening, high sensitivity, and affordability, making them valuable tools in the early diagnosis and management of cancer. These sensors' accessibility and potential to detect cancer at its earliest stages can significantly improve patient outcomes, particularly in resource-limited areas such as Native American reservations. Keywords: Cancer biomarkers, paper-based electrochemical sensors, nanoparticle modification, antigen modification, early detection, point-of-care diagnostics, cost-effective healthcare.

Radon and Gamma Radiation Dose to the Population Residing Near the Uranium Mill Tailings Disposal Site in Uranium Mineralized Zone at Jaduguda

Members of the public residing in the villages situated near the uranium mill disposal site, such as those in the vicinity of uranium tailings ponds, may indeed be at risk of radiation exposure. Present study focuses to evaluate the radiological exposure condition for the resident of villages situated in nearby vicinity of the tailing disposal site in the uranium mineralized region of Jaduguda, Jharkhand, India. In this study, the dose from external gamma radiation and radon concentrations, both indoors and outdoors, is evaluated. The natural background radiation dose to the residents of villages located near the uranium mill tailings disposal site is estimated to be 2.99 mSvy-1. Radon and its decay products contribute approximately 57.6% of the radiation dose to the villagers, while gamma radiation accounts for 42.4%. Residents of villages near the uranium tailings ponds receive a radiation dose is within the typical range of global natural background radiation dose of 1-10 mSvy-1 to the members of the public.

Leaching Peculiarity of Uranium-Containing Layered Double Hydroxide Sediment Varied with Environmental Anions.

In this research, we focus our attention on the leaching peculiarity of uranium-containing Mg-Al layered double hydroxide (LDH) which is one kind of waste sediment in uranium tailings, generated by the alkalinization of uranyl raffinate. The effect of inorganic (CO32-, SO42-, PO43-) and organic (C2O42-, C6H6O72-, C6H16O24P62-) anions were investigated. Atomic force microscopy result showed that the thickness of CO32--LDH increased to 8.6 nm compared to original LDH whose thickness was 6.7 nm. Compared with the control sample (5.58 μm), the grain size with C6H16O24P62- anion grew to 7.04 μm. A large amount of CO32- can stay in LDH, up to 1.78 mol percent, while the C6H16O24P62- anion was only 0.41 mol percent. X-ray diffraction results showed that the anions could change the crystal structure of LDH, especially the C6H18O24P6 anion, and theoretical calculation also conformed this result. The leaching tests showed that the introduction of anions improved the leaching efficiency of UO22+ from LDH. The introduction of anions destroyed the super buffer property of LDH. Theoretical calculation results indicated that the anions could grab UO22+ and help the UO22+ escape from the LDH. This research gave guidance for long-term disposal of uranium-containing tailings.

Characterization of Seismic Dynamic Response of Uranium Tailings Dams Based on Discrete Element Method

Tailings dams play a critical role in ensuring the safety of mining operations. However, earthquakes can cause breaches in these dams, resulting in significant casualties and property damage. This study investigates the dynamic response characteristics of uranium tailings dams subjected to seismic loading, employing the discrete element method. It specifically analyzes how seismic wave amplitude, frequency, and the friction angle of tailings sand affect the dams’ dynamic response. The results reveal that the peak ground acceleration ratio (PGAR) exhibits an increasing–decreasing–increasing pattern with elevation. When the friction angle of the tailings sand exceeds 35°, the overall stability of the dam improves. Conversely, a friction angle below 25° significantly increases the risk of dam failure. Additionally, the dam shows a reduced dynamic response to seismic waves with frequencies exceeding 15 Hz. At lower frequencies, deformation and damage are primarily concentrated on the slope face, while at higher frequencies, damage is predominantly located at the bottom of the model. These findings provide a theoretical foundation and reference for the safe operation of tailings dams, highlighting their practical significance.

Response surface prediction model of radon exhalation rate on beach surface of uranium tailings pond based on single factor law

Response surface prediction model of radon exhalation rate on beach surface of uranium tailings pond based on single factor law

Paper-Based Electrochemical Sensors for Cancer Biomarkers Detection

Cancer is currently the third leading cause of death among the people of the Navajo Nation and is the most common cause of death worldwide. American Indians are often diagnosed when cancer has reached the advanced stages compared to other communities. Major contributors for the cancer inside the Navajo Nation is the exposure to uranium, other heavy metals, and radon gas. In the Navajo Nation, uranium mining boomed from 1944 to 1986; decades later, uranium tailings and toxic waste from the milling process have caused an increased rate of cancer in the Navajo Nation.Further cancer detection and monitoring remain critical challenges in healthcare. This research explores the fabrication of paper-based electrochemical sensors modified with nanoparticles and antigens at the Nanoelectrochemical Analysis and Energy Storage Laboratory (NEST LAB) at Navajo Technical University (NTU) for the sensitive and selective detection of cancer biomarkers.These electrochemical sensors harness the unique qualities of paper, such as low cost and ease of fabrication, combined with the specific binding capabilities of nanoparticles and antigens. Modifying paper electrode surfaces enhances sensitivity and selectivity, making these sensors a cost-effective and portable option for early cancer detection. In contrast to traditional methods like imaging and biopsies, electrochemical sensors are low-cost, offer minimally invasive screening, high sensitivity, and affordability, making them valuable tools in the early diagnosis and management of cancer. These sensors'accessibility and potential to detect cancer at its earliest stages can significantly improve patient outcomes, particularly in resource-limited areas such as Native American reservations.Keywords: Cancer biomarkers, paper-based electrochemical sensors, nanoparticle modification, antigen modification, early detection, point-of-care diagnostics, cost-effective healthcare.

Evaluation of accurate measurement methods for radon exhalation rate with advection effect and application in field

In decommissioning of a uranium tailings pond, radon exhalation rates on a beach surface should meet regulatory standards. Accurate measurements of the radon exhalation rate are demanded. However, current studies fail to consider the impact of advection under temperature variations or pressure gradients caused by gas movement on measurements using an accumulation chamber. Two proposed methods were therefore evaluated to accurately measure radon exhalation rates on the loose medium surface under advective conditions. Repeated experiments were conducted on a laboratory experimental platform filled with uranium tailings sand under advective flow rates of 0.03 and 0.3 L/min to validate the stability and reliability. Deviations between measured and true values were 0.1–6.1 % and 6.3–29.2 % for the two methods, respectively. Subsequently, numerical simulation was used to analyze defects of traditional methods and mechanisms of the new methods. In a field study, all methods were compared, and a predictive map of radon exhalation rates was created using interpolated data from 20 random sites using the new method. Results from the proposed methods, compared with traditional ones, were closer to true values under advective conditions, and accurate assessment of beach surface treatment was expected.

"Clinical Features of the Integumentary System in Persons Living in the Vicinity of Uranium Tailings in Mountain Conditions"

"Clinical Features of the Integumentary System in Persons Living in the Vicinity of Uranium Tailings in Mountain Conditions"

Distribution characteristics and pollution evaluation of heavy metals in surface water of a uranium tailing area based on spatial interpolation

Distribution characteristics and pollution evaluation of heavy metals in surface water of a uranium tailing area based on spatial interpolation

Research on the influence of surface crack development on radon exhalation in uranium tailing ponds under wet and dry cycles

Compacted soil layers effectively prevent the migration of radon gas from uranium tailings impoundments to the nearby environment. However, surface damage caused by wet and dry cycles (WDCs) weakens this phenomenon.In order to study the effect of crack network on radon exhalation under WDCs, a homemade uranium tailing pond model was developed to carry out radon exhalation tests under five WDCs. Based on image processing and morphological methods, the area, length, mean width and fractal dimension of the drying cracks were quantitatively analyzed, and multiple linear regression was used to establish the relationship between the geometric characteristics of the cracks and the radon exhalation rate under multiple WDCs. The results suggested that the radon release rate and crack network of the uranium tailings pond gradually stabilized as the water content decreased, following rapid development in a single WDC process. The radon release rate increased continuously after each cycle, with a cumulative increase of 25.9% over 5 cycles. The radon release rate and average crack width remained consistent in size, and a binary linear regression considering width and fractal dimension could explain the changes in radon release rate after multiple WDCs.

Quantifying heavy metal and radionuclide contamination in fish and water proximal to a uranium tailings facility: A Linshui River basin investigation, China

BackgroundThe objective of this study is to evaluate the concentrations of heavy metals and radionuclides in water and fish samples collected from six designated sampling stations along the Linshui River, in close proximity to a Uranium Tailing Pond situated in China. Additionally, it seeks to estimate the bioaccumulation of heavy metals and conduct risk assessments, both carcinogenic and non-carcinogenic, for consumers. MethodsWater and fish samples (yellowhead catfish and common carp) were systematically collected from six stations along the river from January to June 2023, adhering to ethical standards and standard protocols for assessing water quality. Samples underwent chemical preparation and analysis for heavy metals using Graphite Furnace Atomic Absorption Spectrophotometry and Cold Vapor Atomic Absorption Spectroscopy, and for radionuclides using gamma spectrometry, with all methods validated for accuracy. ResultsThe water samples showed metal and radionuclide concentrations within acceptable limits, except for higher levels of U and Th compared to background values. Heavy metal concentrations were higher in common carp compared to yellowhead catfish, with both species exhibiting a similar trend. While non-carcinogenic health risk, as indicated by target hazard quotients, was low for consumers, the health risk data emphasized the carcinogenic threats posed by U238 and Th234. ConclusionsThe study highlights the importance of implementing comprehensive river restoration measures. Additionally, the bioconcentration factor values indicate minimal accumulation of heavy metals in the muscle tissue of fish.

Release of Radioactive Particles to the Environment.

When environmental impact and risks associated with radioactive contamination of ecosystems are assessed, the source term and deposition must be linked to ecosystem transfer, biological uptake and effects in exposed organisms. Thus, a well-defined source term is the starting point for transport, dose, impact and risk models. After the Chornobyl accident, 3-4 tons of spent nuclear fuel were released and radioactive particles were important ingrediencies of the actual source term. As Chornobyl particles were observed in many European countries, some scientists suggested that radioactive particles were "a peculiarity of the Chornobyl accident." In contrast, research over the years has shown that a major fraction of refractory elements such as uranium (U) and plutonium (Pu) released to the environment has been released as particles following a series of past events such as nuclear weapons tests, non-criticality accidents involving nuclear weapons, military use of depleted uranium ammunition, and nuclear reactor accidents. Radioactive particles and colloids have also been observed in discharges from nuclear installations to rivers or to regional seas and are associated with nuclear waste dumped at sea. Furthermore, radioactive particles have been identified at uranium mining and tailing sites as well as at other NORM sites such as phosphate or oil and gas industrial facilities. Research has also demonstrated that particle characteristics such as elemental composition depend on the emitting source, while characteristics such as size distribution, structure, and oxidation state influencing ecosystem transfer will also depend on the release scenarios. Thus, access to advanced particle characteristic techniques is essential within radioecology. After deposition, localized heterogeneities such as particles will be unevenly distributed in the environment. Thus, inventories can be underestimated, and impact and risk assessments of particle contaminated areas may suffer from unacceptable large uncertainties if radioactive particles are ignored. The present paper will focus on key sources contributing to the release of radioactive particles to the environments, as well as linking particle characteristics to ecosystem behavior and potential biological effects.

Enhanced microbial remediation of uranium tailings through red soil utilization

Seepage of uranium tailings has become a focus of attention in the uranium mining and metallurgy industry, and in-situ microbial remediation is considered an effective way to treat uranium pollution. However, this method has the drawbacks of easy biomass loss and unstable remediation effect. To overcome these issues, spare red soil around the uranium mine was used to enhance the efficiency and stability of bioremediation. Furthermore, the bioremediation mechanism was revealed by employing XRD, FTIR, XPS, and 16S rRNA. The results showed that red soil, as a barrier material, had the adsorption potential of 8.21–148.00 mg U/kg soil, but the adsorption is accompanied by the release of certain acidic and oxidative substances. During the dynamic microbial remediation, red soil was used as a cover material to neutralize acidity, provide a higher reduction potential (<-200 mV), and increase the retention rate of microbial agent (19.06 mL/d) compared to the remediation group without red soil. In the presence of red soil, the anaerobic system could maintain the uranium concentration in the solution below 0.3 mg/L for more than 70 days. Moreover, the generation of new clay minerals driven by microorganisms was more conducive to the stability of uranium tailings. Through alcohol and amino acid metabolism of microorganisms, a reducing environment with reduced valence states of multiple elements (such as S2−, Fe2+, and U4+) was formed. At the same time, the relative abundance of functional microbial communities in uranium tailings improved in presence of red soil and Desulfovirobo, Desulfocapsa, Desulfosporosinus, and other active microbial communities reconstructed the anaerobic environment. The study provides a new two-in-one solution for treatment of uranium tailings and resource utilization of red soil through in-situ microbial remediation.

Leaching behaviour of 226Ra from uranium tailings and adsorption behaviour in geotechnical medias

The leaching process of uranium tailings is a typical water-rock interaction. The release of 226Ra from uranium tailings depends on the nuclides outside the intrinsic properties of uranium tailings on the one hand, and is influenced by the water medium on the other. In this paper, a uranium tailings repository in southern China was used as a research object, and uranium tailings at different depths were collected by drilling samples and mixed to analyze the 226Ra occurrence states. Static dissolution leaching experiments of 226Ra under different pH conditions, solid-liquid ratio conditions, and ionic strength conditions were carried out, and the adsorption and desorption behaviours of 226Ra in five representative stratigraphic media were investigated. The results show that 226Ra has a strong adsorption capacity in representative strata, with adsorption distribution coefficient Kd values ranging from 1.07E+02 to 1.29E+03 (mL/g) and desorption distribution coefficients ranging from 4.97E+02 to 2.71E+03 (mL/g), but the adsorption is reversible. The 226Ra in uranium tailings exists mainly in the residual and water-soluble states, and the release of 226Ra from uranium tailings under different conditions is mainly from the water-soluble and exchangeable state fractions. Low pH conditions, low solid-liquid ratio conditions and high ionic strength conditions are favourable to the release of 226Ra from uranium tailings, so the release of 226Ra from uranium tailings can be reduced by means of adjusting the pH in the tailings and setting up a water barrier. The results of this research have important guiding significance for the management of existing uranium tailings ponds and the control of 226Ra migration in groundwater, which is conducive to guaranteeing the long-term safety, stability and sustainability of uranium mining sites.

Decoration of phosphoric acid groups onto Ti3C2Tx MXene for enhanced uranium removal

The construction of novel MXene-based composites with superb abilities through functionalization is an effective strategy to enhance the potential of this emerging inorganic lamellar material for environmental adsorption applications. The present work systematically investigated the adsorption performance of Ti3C2Tx MXene modified with phosphate functional groups that facilitate the capture of uranyl ions. After introducing phosphate groups via a two-step modification of 3-aminopropyltriethoxysilane (APTES) and phytic acid (PA), the synthesized Ti3C2-APTES-PA is significantly superior to pristine Ti3C2Tx nanosheets in terms of adsorption capacity, adsorption selectivity and reusability for uranium. The maximum uptake capacity of Ti3C2-APTES-PA at pH = 5 reaches 323 mg/g, which is 2.5 times higher than that of unmodified MXene. Furthermore, the large selectivity coefficient (SU/M > 16.2) declares that Ti3C2-APTES-PA preferentially adsorbs uranium among substantial competing ions. Ti3C2-APTES-PA also shows good cycling performance that its adsorption capacity remained 92.3 % after 6 cycles. When it comes to treating simulated uranium tailings pond leachate and radioactive wastewater from mines, high U(VI) removal rates of 88.9 % and 96.8 % can be achieved by our ternary composite at a dosage of 0.05 g/L. The underlying adsorption mechanism was unraveled by spectroscopic analysis to be the formation of coordination complexes of uranyl ions with phosphate groups on PA and hydroxyl groups on Ti3C2Tx substrate, as well as the reduction of a small amount of adsorbed U(VI) to U(IV) by MXene. The overall results imply that Ti3C2-APTES-PA is an effective uranium chelating scavenger for the treatment of environmental radioactive wastewater.

Phosphorus additives driving the bacterial community succession during Bacillus spp. remediation of the uranium tailings

Phosphorus additives driving the bacterial community succession during Bacillus spp. remediation of the uranium tailings