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Author |
Zhao, Y.; Li, X.; Lei, L.; Chen, L.; Luo, Z. |
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Title |
Permeability evolution mechanism and the optimum permeability determination of uranium leaching from low-permeability sandstone treated with low-frequency vibration |
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Journal Article |
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Year |
2023 |
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Journal of Rock Mechanics and Geotechnical Engineering |
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15 |
Issue  |
10 |
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2597-2610 |
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Chemical reactive rate, Low-frequency vibration, Low-permeability sandstone, Optimum permeability, Permeability evolution mechanism, Uranium migration |
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Abstract |
Low-frequency vibrations can effectively improve natural sandstone permeability, and higher vibration frequency is associated with larger permeability. However, the optimum permeability and permeability evolution mechanism for uranium leaching and the relationship between permeability and the change of chemical reactive rate affecting uranium leaching have not been determined. To solve the above problems, in this study, identical homogeneous sandstone samples were selected to simulate low-permeability sandstone; a permeability evolution model considering the combined action of vibration stress, pore water pressure, water flow impact force, and chemical erosion was established; and vibration leaching experiments were performed to test the model accuracy. Both the permeability and chemical reactions were found to simultaneously restrict U6+ leaching, and the vibration treatment increased the permeability, causing the U6+ leaching reaction to no longer be diffusion-constrained but to be primarily controlled by the reaction rate. Changes of the model calculation parameters were further analyzed to determine the permeability evolution mechanism under the influence of vibration and chemical erosion, to prove the correctness of the mechanism according to the experimental results, and to develop a new method for determining the optimum permeability in uranium leaching. The uranium leaching was found to primarily follow a process consisting of (1) a permeability control stage, (2) achieving the optimum permeability, (3) a chemical reactive rate control stage, and (4) a channel flow stage. The resolution of these problems is of great significance for facilitating the application and promotion of low-frequency vibration in the CO2 + O2 leaching process. |
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1674-7755 |
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THL @ christoph.kuells @ zhao_permeability_2023 |
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198 |
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Author |
Külls, C. |
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Title |
Rekonstruktion hydrologischer Extreme in der Namibwüste |
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2011 |
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Berichte der naturforschenden Gesellschaft zu Freiburg im Breisgau |
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101 |
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69-81 |
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THL @ christoph.kuells @ |
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71 |
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Author |
Schwiede, M.; Duijnisveld, W.H.M.; Böttcher, J. |
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Title |
Investigation of processes leading to nitrate enrichment in soils in the Kalahari Region, Botswana |
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Journal Article |
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2005 |
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Physics and Chemistry of the Earth, Parts A/B/C |
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30 |
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11 |
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712-716 |
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Nitrate, Arenosol soils, Semi-arid, Kalahari, Cattle, Chloride, Travel time |
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In Southern Africa elevated nitrate concentrations are observed in mostly uninhabited semi-arid areas. In the Kalahari of Botswana groundwater locally exhibits concentrations up to 600mg/l. It is assumed, that nitrate found in the groundwater originates mainly from nitrogen input and transformations in the soils. Our investigations in the Kalahari between Serowe and Orapa show that cattle raising is an important source for enhanced nitrate concentrations in the soils (Arenosols). But also in termite mounds very high nitrate stocks were found, and under natural vegetation (acacia trees and shrubs) nitrate concentrations were mostly unexpectedly high. This nitrate enrichment in the soils poses a serious threat to the groundwater quality. However, calculated soil water age distributions in the unsaturated zone clearly show that today’s nitrate pollution of the groundwater below the investigation area could originate from natural sources, but cannot be caused by the current land use for cattle raising. |
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1474-7065 |
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Integrated Water Resources Management (IWRM) and the Millennium Development Goals: Managing Water for Peace and Prosperity |
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THL @ christoph.kuells @ Schwiede2005712 |
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276 |
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Zeng, S.; Shen, Y.; Sun, B.; Zhang, N.; Zhang, S.; Feng, S. |
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Title |
Pore structure evolution characteristics of sandstone uranium ore during acid leaching |
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Journal Article |
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Year |
2021 |
Publication |
Nuclear Engineering and Technology |
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53 |
Issue |
12 |
Pages |
4033-4041 |
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Keywords |
Acid method, In situ leaching, Nuclear magnetic resonance, Pore characteristic, Sandstone uranium ore |
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To better understand the permeability of uranium sandstone, improve the leaching rate of uranium, and explore the change law of pore structure characteristics and blocking mechanism during leaching, we systematically analyzed the microstructure of acid-leaching uranium sandstone. We investigated the variable rules of pore structure characteristics based on nuclear magnetic resonance (NMR). The results showed the following: (1) The uranium concentration change followed the exponential law during uranium deposits acid leaching. After 24 h, the uranium leaching rate reached 50%. The uranium leaching slowed gradually over the next 4 days. (2) Combined with the regularity of porosity variation, Stages I and II included chemical plugging controlled by surface reaction. Stage I was the major completion phase of uranium displacement with saturation precipitation of calcium sulfate. Stage II mainly precipitated iron (III) oxide-hydroxide and aluminum hydroxide. Stage III involved physical clogging controlled by diffusion. (3) In the three stages of leaching, the permeability of the leaching solution changed with the pore structure, which first decreased, then increased, and then decreased. |
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1738-5733 |
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THL @ christoph.kuells @ zeng_pore_2021 |
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199 |
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Zagana, E.; Obeidat, M.; Külls, C.; Udluft, P. |
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Title |
Chloride, hydrochemical and isotope methods of groundwater recharge estimation in eastern Mediterranean areas: a case study in Jordan |
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2007 |
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Hydrological Processes: An International Journal |
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21 |
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16 |
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2112-2123 |
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John Wiley & Sons, Ltd. Chichester, UK |
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THL @ christoph.kuells @ Zagana2007chloride |
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29 |
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Zagana, E.; Külls, C.; Udluft, P.; Constantinou, C. |
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Methods of groundwater recharge estimation in eastern Mediterranean water balance model application in Greece, Cyprus and Jordan |
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2007 |
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Hydrological Processes: An International Journal |
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21 |
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18 |
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2405-2414 |
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John Wiley & Sons, Ltd. Chichester, UK |
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THL @ christoph.kuells @ Zagana2007methods |
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30 |
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Strandmann, P.A.E.P. von; Reynolds, B.C.; Porcelli, D.; James, R.H.; Calsteren, P. van; Baskaran, M.; Burton, K.W. |
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Assessing continental weathering rates and actinide transport in the Great Artesian Basin |
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2006 |
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Geochimica et Cosmochimica Acta |
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70 |
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18, Supplement |
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497 |
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0016-7037 |
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THL @ christoph.kuells @ strandmann_assessing_2006 |
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116 |
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Garvelmann, J.; Külls, C.; Weiler, M. |
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A porewater-based stable isotope approach for the investigation of subsurface hydrological processes |
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2012 |
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Hydrology & Earth System Sciences |
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16 |
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2 |
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THL @ christoph.kuells @ Garvelmann2012porewater |
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24 |
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Lawrinenko, M.; Kurwadkar, S.; Wilkin, R.T. |
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Long-term performance evaluation of zero-valent iron amended permeable reactive barriers for groundwater remediation – A mechanistic approach |
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2023 |
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Geoscience Frontiers |
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14 |
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2 |
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101494 |
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Geochemistry, Iron, Permeable reactive barrier, Plating reactions, Reduction potential, Surface passivation |
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Permeable reactive barriers (PRBs) are used for groundwater remediation at contaminated sites worldwide. This technology has been efficient at appropriate sites for treating organic and inorganic contaminants using zero-valent iron (ZVI) as a reductant and as a reactive material. Continued development of the technology over the years suggests that a robust understanding of PRB performance and the mechanisms involved is still lacking. Conflicting information in the scientific literature downplays the critical role of ZVI corrosion in the remediation of various organic and inorganic pollutants. Additionally, there is a lack of information on how different mechanisms act in tandem to affect ZVI-groundwater systems through time. In this review paper, we describe the underlying mechanisms of PRB performance and remove isolated misconceptions. We discuss the primary mechanisms of ZVI transformation and aging in PRBs and the role of iron corrosion products. We review numerous sites to reinforce our understanding of the interactions between groundwater contaminants and ZVI and the authigenic minerals that form within PRBs. Our findings show that ZVI corrosion products and mineral precipitates play critical roles in the long-term performance of PRBs by influencing the reactivity of ZVI. Pore occlusion by mineral precipitates occurs at the influent side of PRBs and is enhanced by dissolved oxygen and groundwater rich in dissolved solids and high alkalinity, which negatively impacts hydraulic conductivity, allowing contaminants to potentially bypass the treatment zone. Further development of site characterization tools and models is needed to support effective PRB designs for groundwater remediation. |
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1674-9871 |
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THL @ christoph.kuells @ lawrinenko_long-term_2023 |
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143 |
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Zeng, S.; Song, J.; Sun, B.; Wang, F.; Ye, W.; Shen, Y.; Li, H. |
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Title |
Seepage characteristics of the leaching solution during in situ leaching of uranium |
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Journal Article |
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2023 |
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Nuclear Engineering and Technology |
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55 |
Issue |
2 |
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566-574 |
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In situ leaching, Leaching solution viscosity, Seepage characteristics, Seepage pressure, Uranium-bearing sandstone |
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Investigating the seepage characteristics of the leaching solution in the ore-bearing layer during the in situ leaching process can be useful for designing the process parameters for the uranium mining well. We prepared leaching solutions of four different viscosities and conducted experiments using a self-developed multifunctional uranium ore seepage test device. The effects of different viscosities of leaching solutions on the seepage characteristics of uranium-bearing sandstones were examined using seepage mechanics, physicochemical seepage theory, and dissolution erosion mechanism. Results indicated that while the seepage characteristics of various viscosities of leaching solutions were the same in rock samples with similar internal pore architectures, there were regular differences between the saturated and the unsaturated stages. In addition, the time required for the specimen to reach saturation varied with the viscosity of the leaching solution. The higher the viscosity of the solution, the slower the seepage flow from the unsaturated stage to the saturated stage. Furthermore, during the saturation stage, the seepage pressure of a leaching solution with a high viscosity was greater than that of a leaching solution with a low viscosity. However, the permeability coefficient of the high viscosity leaching solution was less than that of a low viscosity leaching solution. |
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1738-5733 |
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THL @ christoph.kuells @ zeng_seepage_2023 |
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211 |
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