It is quite important to ensure the safety and sustainable development of nuclear energy for the treatment of radioactive wastewater. To treat radioactive wastewater efficiently and rapidly, two multi-amine β-cyclode...It is quite important to ensure the safety and sustainable development of nuclear energy for the treatment of radioactive wastewater. To treat radioactive wastewater efficiently and rapidly, two multi-amine β-cyclodextrin polymers(diethylenetriamine β-cyclodextrin polymer(DETA-TFCDP) and triethylenetetramine β-cyclodextrin polymer(TETA-TFCDP)) were prepared and applied to capture uranium. Results exhibited that DETA-TFCDP and TETA-TFCDP displayed the advantages of high adsorption amounts(612.2and 628.2 mg·g-1, respectively) and rapid adsorption rates, which can reach(88 ± 1)% of their equilibrium adsorption amounts in 10 min. Moreover, the adsorbent processes of DETA-TFCDP and TETATFCDP on uranium(Ⅵ) followed the Langmuir model and pseudo-second-order model, stating they were mainly chemisorption and self-endothermic. Besides, TETA-TFCDP also showed excellent selectivity in the presence of seven competing cations and could be effectively reused five times via Na2CO3as the desorption reagent. Meanwhile, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy illustrated that the enriched multi-amine groups and oxygen-containing functional groups on the surface of TETA-TFCDP were the main active sites for capturing uranium(Ⅵ). Hence, multi-amine β-cyclodextrin polymers are a highly efficient, rapid, and promising adsorbent for capturing uranium(Ⅵ)from radioactive wastewater.展开更多
Xiazhuang uranium ore field,located in the southern part of the Nanling Metallogenic Belt,is considered one of the largest granite-related U regions in South China.In this paper,we contribute new apatite fission track...Xiazhuang uranium ore field,located in the southern part of the Nanling Metallogenic Belt,is considered one of the largest granite-related U regions in South China.In this paper,we contribute new apatite fission track data and thermal history modeling to constrain the exhumation history and evaluate preservation potential of the Xiazhuang Uranium ore field.Nine Triassic outcrop granite samples collected from different locations of Xiazhuang Uranium ore field yield AFT ages ranging from 43 to 24 Ma with similar mean confined fission track lengths ranging from 11.8±2.0 to 12.9±1.9μm and Dpar values between 1.01 and 1.51μm.The robustness time-temperature reconstructions of samples from the hanging wall of Huangpi fault show that the Xiazhuang Uranium ore field experienced a time of monotonous and slow cooling starting from middle Paleocene to middle Miocene(~60-10 Ma),followed by relatively rapid exhumation in the late Miocene(~10-5 Ma)and nearly thermal stability in the Pliocene-Quaternary(~5-0 Ma).The amount of exhumation after U mineralization since the Middle Paleogene was estimated as~4.3±1.8 km according to the integrated thermal history model.Previous studies indicate that the ore-forming ages of U deposits in the Xiazhuang ore field are mainly before Middle Paleocene and the mineralization depths are more than 4.4±1.2 km.Therefore,the exhumation history since middle Paleocene plays important roles in the preservation of the Xiazhuang Uranium ore field.展开更多
Leptospirillum ferriphilum cultured using different energy sources(either soluble ferrous ion or pyrite) changed the surface properties of pyrite.Cell adsorption,zeta-potential,hydrophobicty,FT-IR spectra and surface ...Leptospirillum ferriphilum cultured using different energy sources(either soluble ferrous ion or pyrite) changed the surface properties of pyrite.Cell adsorption,zeta-potential,hydrophobicty,FT-IR spectra and surface morphology were investigated.Adhesion of bacterial cells to the pyrite surface is a fast process.Furthermore,the adsorption of cells grown in pyrite is greater than of cells grown in soluble ferrous ion.The Iso-Electric Point(IEP) of pyrite treated with L.ferriphilum approaches that of the cells themselves.The contact angle of the pyrite surface was observed to decrease due to the surface formation of some hydrophilic substances during bio-leaching.Changes in pyrite surface properties after bacterial treatment support the idea that ferric ion plays an important role and that indirect bio-oxidation is the principal mechanism of pyrite bio-leaching.展开更多
The novel pulsed liquid chromatography radionuclide separation method presented here provides a new and promising strategy for the extraction of uranium from seawater.In this study,a new chromatographic separation met...The novel pulsed liquid chromatography radionuclide separation method presented here provides a new and promising strategy for the extraction of uranium from seawater.In this study,a new chromatographic separation method was proposed,and a pulsed nuclide automated separation device was developed,alongside a new chromatographic column.The length of this chromatographic column was 10 m,with an internal warp of 3 mm and a packing size of 1 mm,while the total separation units of the column reached 12,250.The most favorable conditions for the separation of nuclides were then obtained through optimizing the separation conditions of the device:Sample pH in the column=2,sample injection flow rate=5.698 mL/min,chromatographic column heating temperature=60℃.Separation experiments were also carried out for uranium,europium,and sodium ions in mixed solutions;uranium and sodium ions in water samples from the Ganjiang River;and uranium,sodium,and magnesium ions from seawater samples.The separation factors between the different nuclei were then calculated based on the experimental data,and a formula for the separation level was derived.The experimental results showed that the separation factor in the mixed solution of uranium and europium(1:1)was 1.088,while achieving the initial separation of uranium and europium theoretically required a 47-stage separation.Considering the separation factor of 1.50for the uranium and sodium ions in water samples from the Ganjiang River,achieving the initial separation of uranium and sodium ions would have theoretically required at least a 21-stage separation.Furthermore,for the seawater sample separation experiments,the separation factor of uranium and sodium ions was 1.2885;therefore,more than 28 stages of sample separation would be required to achieve uranium extraction from seawater.The novel pulsed liquid chromatography method proposed in this study was innovative in terms of uranium separation and enrichment,while expanding the possibilities of extracting uranium from seawater through chromatography.展开更多
Direct collection of uranium from low uranium systems via adsorption remains challenging.Fibrous sorbent materials with amidoxime(AO)groups are promising adsorbents for uranium extraction from seawater.However,low AO ...Direct collection of uranium from low uranium systems via adsorption remains challenging.Fibrous sorbent materials with amidoxime(AO)groups are promising adsorbents for uranium extraction from seawater.However,low AO adsorption group utilization remains an issue.We herein fabricated a branched structure containing AO groups on polypropylene/polyethylene spun-laced nonwoven(PP/PE SNW)fibers using grafting polymerization induced by radiation(RIGP)to improve AO utilization.The chemical structures,thermal properties,and surface morphologies of the raw and treated PP/PE SNW fibers were studied.The results show that an adsorptive functional layer with a branching structure was successfully anchored to the fiber surface.The adsorption properties were investigated using batch adsorption experiments in simulated seawater with an initial uranium concentration of 500μg·L^(−1)(pH 4,25℃).The maximum adsorption capacity of the adsorbent material was 137.3 mg·g^(−1)within 24 h;moreover,the uranyl removal reached 96%within 240 min.The adsorbent had an AO utilization rate of 1/3.5 and was stable over a pH range of 4–10,with good selectivity and reusability,demonstrating its potential for seawater uranium extraction.展开更多
Undoped nickel-based catalysts supported on depleted uranium oxide allow one to carry out CO_(2)methanation process under extremely low reaction temperature under atmospheric pressure and powered by a contactless indu...Undoped nickel-based catalysts supported on depleted uranium oxide allow one to carry out CO_(2)methanation process under extremely low reaction temperature under atmospheric pressure and powered by a contactless induction heating.By adjusting the reaction conditions,the catalyst is able to perform CO_(2)methanation reaction under autothermal process operated inside a non-adiabatic reactor,without any external energy supply.Such autothermal process is possible thanks to the high apparent density of the UO_x which allows one to confine the reaction heat in a small catalyst volume in order to confine the exothermicity of the reaction inside the catalyst and to operate the reaction at equilibrium heat in-heat out.Such autothermal operation mode allows one to significantly reduce the complexity of the process compared to that operated using adiabatic reactor,where complete insulation is required to prevent heat disequilibrium,in order to reduce as much as possible,the heat exchange with the external medium.The catalyst displays an extremely high stability as a function of time on stream as no apparent deactivation.It is expected that such new catalyst with unprecedented catalytic performance could open new era in the field of heterogeneous catalysis where traditional supports show their limitations to operate catalytic processes under severe reaction conditions.展开更多
The use of some environmental functional minerals as backfill-modified materials may improve the leaching resistance of cemented uranium tailings backfill created from alkali-activated slag(CUTB),but these materials m...The use of some environmental functional minerals as backfill-modified materials may improve the leaching resistance of cemented uranium tailings backfill created from alkali-activated slag(CUTB),but these materials may participate in the hydration reaction of the cementitious materials,which could have a certain impact on the pore structure of the CUTB,thus affecting its mechanical properties and leaching resistance.In this paper,natural zeolite is selected as the backfill-modified material,and it is added to alkali-activated slag paste(AASP)and CUTB in cementitious material proportions of 4%,8%,12%,and 16%to prepare AASP mixtures and CUTB mixtures containing environmental functional minerals.After the addition of natural zeolite,the porosity of the CUTB generally increases,but when the content is 4%,the porosity decreases to 22.30%.The uniaxial compressive strength(UCS)of the CUTB generally decreases,but the decrease is the smallest when the content is 4%,and the UCS is 12.37 MPa.The addition of natural zeolite mainly reduces the number of fine pores in the CUTB,but the pores with relaxation times T_(2)of greater than 10 ms account for about 10%of the total pores,and there are a certain number of large pores in the CUTB.The main product of alkali-activated slag is calcium(alumino)silicate hydrate(C-(A)-S-H gel).When natural zeolite is added,the hydration products develop towards denser products with a high degree of polymerization and the formation of low polymerization products is reduced.This affects the internal fracture pores of the hydration products and the interface pores of the CUTB,has an irregular effect on the pore characteristics of the CUTB,and influences the UCS.展开更多
Based on machine learning,the high-dimensional fitting of potential energy surfaces under the framework of first principles provides density-functional accuracy of atomic interaction potential for high-precision and l...Based on machine learning,the high-dimensional fitting of potential energy surfaces under the framework of first principles provides density-functional accuracy of atomic interaction potential for high-precision and large-scale simulation of alloy materials.In this paper,we obtained the high-dimensional neural network(NN)potential function of uranium metal by training a large amount of first-principles calculated data.The lattice constants of uranium metal with different crystal structures,the elastic constants,and the anisotropy of lattice expansion of alpha-uranium obtained based on this potential function are highly consistent with first-principles calculation or experimental data.In addition,the calculated formation energy of vacancies in alpha-and beta-uranium also matches the first-principles calculation.The calculated site of the most stable self-interstitial and its formation energy is in good agreement with the findings from density functional theory(DFT)calculations.These results show that our potential function can be used for further large-scale molecular dynamics simulation studies of uranium metal at low pressures,and provides the basis for further construction of potential model suitable for a wide range of pressures.展开更多
Geochemical behaviors of heavy metals are closely related to their chemical state that can be divided by sequential extraction into exchangeable(F1),bound to carbonates(F2),bound to Fe-Mn oxides(F3),bound to organic m...Geochemical behaviors of heavy metals are closely related to their chemical state that can be divided by sequential extraction into exchangeable(F1),bound to carbonates(F2),bound to Fe-Mn oxides(F3),bound to organic matter or sulfide(F4),and residual(F5).Uranium in sediment of the Huanghe(Yellow)River,China,in different chemical states was extracted using the five-step procedure of Tessier and the source and sink were analyzed.Results show that more than 70%of the total uranium was immobile residual F5 in abundance,followed in order of F4>F3>F2>F1,indicating that the main source of uranium in the sediments was from weathered rock in the drainage basin.In addition,the uranium in the sediments presents potential exogenous input in the Lanzhou,Baotou,and Tongguan reach.Fe-Mn oxides are main carriers of unstable uranium,especially those of F1 and F3.Calcite and illite are secondary adsorption minerals of unstable uranium in sediments under natural conditions.Human activities can also produce an obvious impact on uranium speciation.This study provides a reference for the application of sequential extraction in analyzing the source and sink of uranium in river sediments.展开更多
We investigate the electronic structure ofβ-uranium,which has five nonequivalent atomic sites in its unit cell,by means of the density functional theory plus Hubbard-U correction with U from linear response calculati...We investigate the electronic structure ofβ-uranium,which has five nonequivalent atomic sites in its unit cell,by means of the density functional theory plus Hubbard-U correction with U from linear response calculation.It is found that the 5f electronic correlations inβ-uranium are moderate.More interestingly,their strengths are site selective,depending on the local atomic environment of the present uranium atom.As a consequence,the occupation matrices and partial 5f density of states ofβ-uranium manifest site dependence.In addition,the complicate experimental structure ofβ-uranium could be well reproduced within this theoretical framework.展开更多
Many scientific domains use gamma-ray spectrometry, but non-destructive gamma scanning and gamma emission tomography of radioactive fuel in particular. In the experimental setting, a collimator is frequently employed ...Many scientific domains use gamma-ray spectrometry, but non-destructive gamma scanning and gamma emission tomography of radioactive fuel in particular. In the experimental setting, a collimator is frequently employed to focus on a particular location of interest in the fuel. Predictive models for the transmitted gamma-ray intensity through the collimator are required for both the optimization of instrument design and the planning of measurement campaigns. Gamma-ray transport accuracy is frequently predicted using Monte Carlo radiation transport methods, but using these tools in low-efficiency experimental setups is challenging due to the lengthy computation times needed. This study focused on the full-energy peak intensity that was transmitted through several collimator designs, including rectangle and cylinder. The rate of photons arriving at a detector on the other side of the collimator was calculated for anisotropic source of SNM (U<sub>3</sub>O<sub>8</sub>). Some geometrical assumptions that depended on the source-to-collimator distance and collimator dimensions (length, radius or length, height, and width) were applied to achieve precise findings.展开更多
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 mechani...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 lowpermeability 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 U6þleaching,and the vibration treatment increased the permeability,causing the U6þleaching 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 lowfrequency vibration in the CO_(2)+O_(2) leaching process.展开更多
Under the new development philosophy of carbon peaking and carbon neutrality,CO_(2)and O_(2)in situ leaching(ISL)has been identified as a promising technique for uranium mining in China,not only because it solves carb...Under the new development philosophy of carbon peaking and carbon neutrality,CO_(2)and O_(2)in situ leaching(ISL)has been identified as a promising technique for uranium mining in China,not only because it solves carbon dioxide utilization and sequestration,but it also alleviates the environmental burden.However,significant challenges exist in assessment of CO_(2)footprint and water-rock interactions,due to complex geochemical processes.Herein this study conducts a three-dimensional,multicomponent reactive transport model(RTM)of a field-scale CO_(2)and O_(2)ISL process at a typical sandstone-hosted uranium deposit in Songliao Basin,China.Numerical simulations are performed to provide new insight into quantitative interpretation of the greenhouse gas(CO_(2))footprint and environmental impact(SO_(4)^(2–))of the CO_(2)and O_(2)ISL,considering the potential chemical reaction network for uranium recovery at the field scale.RTM results demonstrate that the fate of the CO_(2)could be summarized as injected CO_(2)dissolution,dissolved CO_(2)mineralization and storage of CO_(2)as a gas phase during the CO_(2)and O_(2)ISL process.Furthermore,compared to acid ISL,CO_(2)and O_(2)ISL has a potentially smaller environmental footprint,with 20%of SO_(4)^(2–)concentration in the aquifer.The findings improve our fundamental understanding of carbon utilization in a long-term CO_(2)and O_(2)ISL system and provide important environmental implications when considering complex geochemical processes.展开更多
基金National Natural Science Foundation of China(21603064,52102214)Natural Science Foundation of Jiangxi Province(20202BABL203026,20212BAB203001,20202BABL214016)College Student Innovation and Enterprise Programme of Jiangxi Province(S202310405010)provided funding for this study.
文摘It is quite important to ensure the safety and sustainable development of nuclear energy for the treatment of radioactive wastewater. To treat radioactive wastewater efficiently and rapidly, two multi-amine β-cyclodextrin polymers(diethylenetriamine β-cyclodextrin polymer(DETA-TFCDP) and triethylenetetramine β-cyclodextrin polymer(TETA-TFCDP)) were prepared and applied to capture uranium. Results exhibited that DETA-TFCDP and TETA-TFCDP displayed the advantages of high adsorption amounts(612.2and 628.2 mg·g-1, respectively) and rapid adsorption rates, which can reach(88 ± 1)% of their equilibrium adsorption amounts in 10 min. Moreover, the adsorbent processes of DETA-TFCDP and TETATFCDP on uranium(Ⅵ) followed the Langmuir model and pseudo-second-order model, stating they were mainly chemisorption and self-endothermic. Besides, TETA-TFCDP also showed excellent selectivity in the presence of seven competing cations and could be effectively reused five times via Na2CO3as the desorption reagent. Meanwhile, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy illustrated that the enriched multi-amine groups and oxygen-containing functional groups on the surface of TETA-TFCDP were the main active sites for capturing uranium(Ⅵ). Hence, multi-amine β-cyclodextrin polymers are a highly efficient, rapid, and promising adsorbent for capturing uranium(Ⅵ)from radioactive wastewater.
基金the Foundation of State Key Laboratory of Nuclear Resources and Environment(Grant Nos.NRE2021-01,2022NRE34)the National Natural Science Foundation of China(Grant No.42162013)+1 种基金the Third Xinjiang Scientific Expedition Program(Grant No.2022xjkk1301)the Fund of National Key Laboratory of Science and Technology on Remote Sensing Information and imagery Analysis,Beijing Research Institute of Uranium Geology(Grant No.6142A01210405).
文摘Xiazhuang uranium ore field,located in the southern part of the Nanling Metallogenic Belt,is considered one of the largest granite-related U regions in South China.In this paper,we contribute new apatite fission track data and thermal history modeling to constrain the exhumation history and evaluate preservation potential of the Xiazhuang Uranium ore field.Nine Triassic outcrop granite samples collected from different locations of Xiazhuang Uranium ore field yield AFT ages ranging from 43 to 24 Ma with similar mean confined fission track lengths ranging from 11.8±2.0 to 12.9±1.9μm and Dpar values between 1.01 and 1.51μm.The robustness time-temperature reconstructions of samples from the hanging wall of Huangpi fault show that the Xiazhuang Uranium ore field experienced a time of monotonous and slow cooling starting from middle Paleocene to middle Miocene(~60-10 Ma),followed by relatively rapid exhumation in the late Miocene(~10-5 Ma)and nearly thermal stability in the Pliocene-Quaternary(~5-0 Ma).The amount of exhumation after U mineralization since the Middle Paleogene was estimated as~4.3±1.8 km according to the integrated thermal history model.Previous studies indicate that the ore-forming ages of U deposits in the Xiazhuang ore field are mainly before Middle Paleocene and the mineralization depths are more than 4.4±1.2 km.Therefore,the exhumation history since middle Paleocene plays important roles in the preservation of the Xiazhuang Uranium ore field.
基金supported by the National NaturalScience Foundation of China (Nos.50621063 and50674102)the National Basic Research Programof China (No.2004CB619204)
文摘Leptospirillum ferriphilum cultured using different energy sources(either soluble ferrous ion or pyrite) changed the surface properties of pyrite.Cell adsorption,zeta-potential,hydrophobicty,FT-IR spectra and surface morphology were investigated.Adhesion of bacterial cells to the pyrite surface is a fast process.Furthermore,the adsorption of cells grown in pyrite is greater than of cells grown in soluble ferrous ion.The Iso-Electric Point(IEP) of pyrite treated with L.ferriphilum approaches that of the cells themselves.The contact angle of the pyrite surface was observed to decrease due to the surface formation of some hydrophilic substances during bio-leaching.Changes in pyrite surface properties after bacterial treatment support the idea that ferric ion plays an important role and that indirect bio-oxidation is the principal mechanism of pyrite bio-leaching.
基金the Natural Science Foundation of Jiangxi Province,China(No.20202BABL203004)the Opening Project of the State Key Laboratory of Nuclear Resources and Environment(East China University of Technology)(No.2022NRE23)the Opening Project of Jiangxi Province Key Laboratory of Polymer Micro/Nano Manufacturing and Devices(No.PMND202101).
文摘The novel pulsed liquid chromatography radionuclide separation method presented here provides a new and promising strategy for the extraction of uranium from seawater.In this study,a new chromatographic separation method was proposed,and a pulsed nuclide automated separation device was developed,alongside a new chromatographic column.The length of this chromatographic column was 10 m,with an internal warp of 3 mm and a packing size of 1 mm,while the total separation units of the column reached 12,250.The most favorable conditions for the separation of nuclides were then obtained through optimizing the separation conditions of the device:Sample pH in the column=2,sample injection flow rate=5.698 mL/min,chromatographic column heating temperature=60℃.Separation experiments were also carried out for uranium,europium,and sodium ions in mixed solutions;uranium and sodium ions in water samples from the Ganjiang River;and uranium,sodium,and magnesium ions from seawater samples.The separation factors between the different nuclei were then calculated based on the experimental data,and a formula for the separation level was derived.The experimental results showed that the separation factor in the mixed solution of uranium and europium(1:1)was 1.088,while achieving the initial separation of uranium and europium theoretically required a 47-stage separation.Considering the separation factor of 1.50for the uranium and sodium ions in water samples from the Ganjiang River,achieving the initial separation of uranium and sodium ions would have theoretically required at least a 21-stage separation.Furthermore,for the seawater sample separation experiments,the separation factor of uranium and sodium ions was 1.2885;therefore,more than 28 stages of sample separation would be required to achieve uranium extraction from seawater.The novel pulsed liquid chromatography method proposed in this study was innovative in terms of uranium separation and enrichment,while expanding the possibilities of extracting uranium from seawater through chromatography.
基金supported by the National Natural Science Foundation of China(Nos.11675247,22176194).
文摘Direct collection of uranium from low uranium systems via adsorption remains challenging.Fibrous sorbent materials with amidoxime(AO)groups are promising adsorbents for uranium extraction from seawater.However,low AO adsorption group utilization remains an issue.We herein fabricated a branched structure containing AO groups on polypropylene/polyethylene spun-laced nonwoven(PP/PE SNW)fibers using grafting polymerization induced by radiation(RIGP)to improve AO utilization.The chemical structures,thermal properties,and surface morphologies of the raw and treated PP/PE SNW fibers were studied.The results show that an adsorptive functional layer with a branching structure was successfully anchored to the fiber surface.The adsorption properties were investigated using batch adsorption experiments in simulated seawater with an initial uranium concentration of 500μg·L^(−1)(pH 4,25℃).The maximum adsorption capacity of the adsorbent material was 137.3 mg·g^(−1)within 24 h;moreover,the uranyl removal reached 96%within 240 min.The adsorbent had an AO utilization rate of 1/3.5 and was stable over a pH range of 4–10,with good selectivity and reusability,demonstrating its potential for seawater uranium extraction.
基金ORANO Chimie-Enrichissement Co.for the financial support of this project。
文摘Undoped nickel-based catalysts supported on depleted uranium oxide allow one to carry out CO_(2)methanation process under extremely low reaction temperature under atmospheric pressure and powered by a contactless induction heating.By adjusting the reaction conditions,the catalyst is able to perform CO_(2)methanation reaction under autothermal process operated inside a non-adiabatic reactor,without any external energy supply.Such autothermal process is possible thanks to the high apparent density of the UO_x which allows one to confine the reaction heat in a small catalyst volume in order to confine the exothermicity of the reaction inside the catalyst and to operate the reaction at equilibrium heat in-heat out.Such autothermal operation mode allows one to significantly reduce the complexity of the process compared to that operated using adiabatic reactor,where complete insulation is required to prevent heat disequilibrium,in order to reduce as much as possible,the heat exchange with the external medium.The catalyst displays an extremely high stability as a function of time on stream as no apparent deactivation.It is expected that such new catalyst with unprecedented catalytic performance could open new era in the field of heterogeneous catalysis where traditional supports show their limitations to operate catalytic processes under severe reaction conditions.
基金funded by the National Natural Science Foundation of China(No.51904154)Natural Science Foundation of Hunan Province(No.2020JJ5491).
文摘The use of some environmental functional minerals as backfill-modified materials may improve the leaching resistance of cemented uranium tailings backfill created from alkali-activated slag(CUTB),but these materials may participate in the hydration reaction of the cementitious materials,which could have a certain impact on the pore structure of the CUTB,thus affecting its mechanical properties and leaching resistance.In this paper,natural zeolite is selected as the backfill-modified material,and it is added to alkali-activated slag paste(AASP)and CUTB in cementitious material proportions of 4%,8%,12%,and 16%to prepare AASP mixtures and CUTB mixtures containing environmental functional minerals.After the addition of natural zeolite,the porosity of the CUTB generally increases,but when the content is 4%,the porosity decreases to 22.30%.The uniaxial compressive strength(UCS)of the CUTB generally decreases,but the decrease is the smallest when the content is 4%,and the UCS is 12.37 MPa.The addition of natural zeolite mainly reduces the number of fine pores in the CUTB,but the pores with relaxation times T_(2)of greater than 10 ms account for about 10%of the total pores,and there are a certain number of large pores in the CUTB.The main product of alkali-activated slag is calcium(alumino)silicate hydrate(C-(A)-S-H gel).When natural zeolite is added,the hydration products develop towards denser products with a high degree of polymerization and the formation of low polymerization products is reduced.This affects the internal fracture pores of the hydration products and the interface pores of the CUTB,has an irregular effect on the pore characteristics of the CUTB,and influences the UCS.
基金Beijing Computational Science Research Center(CSRC)the National Natural Science Foundation of China(Grant Nos.52161160330 and U2230402)。
文摘Based on machine learning,the high-dimensional fitting of potential energy surfaces under the framework of first principles provides density-functional accuracy of atomic interaction potential for high-precision and large-scale simulation of alloy materials.In this paper,we obtained the high-dimensional neural network(NN)potential function of uranium metal by training a large amount of first-principles calculated data.The lattice constants of uranium metal with different crystal structures,the elastic constants,and the anisotropy of lattice expansion of alpha-uranium obtained based on this potential function are highly consistent with first-principles calculation or experimental data.In addition,the calculated formation energy of vacancies in alpha-and beta-uranium also matches the first-principles calculation.The calculated site of the most stable self-interstitial and its formation energy is in good agreement with the findings from density functional theory(DFT)calculations.These results show that our potential function can be used for further large-scale molecular dynamics simulation studies of uranium metal at low pressures,and provides the basis for further construction of potential model suitable for a wide range of pressures.
基金Supported by the National Natural Science Foundation of China(Nos.41876077,41376085)。
文摘Geochemical behaviors of heavy metals are closely related to their chemical state that can be divided by sequential extraction into exchangeable(F1),bound to carbonates(F2),bound to Fe-Mn oxides(F3),bound to organic matter or sulfide(F4),and residual(F5).Uranium in sediment of the Huanghe(Yellow)River,China,in different chemical states was extracted using the five-step procedure of Tessier and the source and sink were analyzed.Results show that more than 70%of the total uranium was immobile residual F5 in abundance,followed in order of F4>F3>F2>F1,indicating that the main source of uranium in the sediments was from weathered rock in the drainage basin.In addition,the uranium in the sediments presents potential exogenous input in the Lanzhou,Baotou,and Tongguan reach.Fe-Mn oxides are main carriers of unstable uranium,especially those of F1 and F3.Calcite and illite are secondary adsorption minerals of unstable uranium in sediments under natural conditions.Human activities can also produce an obvious impact on uranium speciation.This study provides a reference for the application of sequential extraction in analyzing the source and sink of uranium in river sediments.
基金supported by the National Natural Science Foundation of China (Grant Nos.22176181,11874329,11934020,and U1930121)the Foundation of the President of China Academy of Engineering Physics (Grant No.YZJJZQ2022011)the Foundation of Science and Technology on Surface Physics and Chemistry Laboratory (Grant No.WDZC202101)。
文摘We investigate the electronic structure ofβ-uranium,which has five nonequivalent atomic sites in its unit cell,by means of the density functional theory plus Hubbard-U correction with U from linear response calculation.It is found that the 5f electronic correlations inβ-uranium are moderate.More interestingly,their strengths are site selective,depending on the local atomic environment of the present uranium atom.As a consequence,the occupation matrices and partial 5f density of states ofβ-uranium manifest site dependence.In addition,the complicate experimental structure ofβ-uranium could be well reproduced within this theoretical framework.
文摘Many scientific domains use gamma-ray spectrometry, but non-destructive gamma scanning and gamma emission tomography of radioactive fuel in particular. In the experimental setting, a collimator is frequently employed to focus on a particular location of interest in the fuel. Predictive models for the transmitted gamma-ray intensity through the collimator are required for both the optimization of instrument design and the planning of measurement campaigns. Gamma-ray transport accuracy is frequently predicted using Monte Carlo radiation transport methods, but using these tools in low-efficiency experimental setups is challenging due to the lengthy computation times needed. This study focused on the full-energy peak intensity that was transmitted through several collimator designs, including rectangle and cylinder. The rate of photons arriving at a detector on the other side of the collimator was calculated for anisotropic source of SNM (U<sub>3</sub>O<sub>8</sub>). Some geometrical assumptions that depended on the source-to-collimator distance and collimator dimensions (length, radius or length, height, and width) were applied to achieve precise findings.
基金supported by the National Natural Science Foundation of China(Grant No.11705086)the National Science Foundation of Hunan Province,China(Grant No.2018JJ3424)the Foundation of Hunan Educational Committee(Grant No.16C1387).
文摘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 lowpermeability 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 U6þleaching,and the vibration treatment increased the permeability,causing the U6þleaching 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 lowfrequency vibration in the CO_(2)+O_(2) leaching process.
基金supported by the National Natural Science Foundation of China(Grant No.U2167212)。
文摘Under the new development philosophy of carbon peaking and carbon neutrality,CO_(2)and O_(2)in situ leaching(ISL)has been identified as a promising technique for uranium mining in China,not only because it solves carbon dioxide utilization and sequestration,but it also alleviates the environmental burden.However,significant challenges exist in assessment of CO_(2)footprint and water-rock interactions,due to complex geochemical processes.Herein this study conducts a three-dimensional,multicomponent reactive transport model(RTM)of a field-scale CO_(2)and O_(2)ISL process at a typical sandstone-hosted uranium deposit in Songliao Basin,China.Numerical simulations are performed to provide new insight into quantitative interpretation of the greenhouse gas(CO_(2))footprint and environmental impact(SO_(4)^(2–))of the CO_(2)and O_(2)ISL,considering the potential chemical reaction network for uranium recovery at the field scale.RTM results demonstrate that the fate of the CO_(2)could be summarized as injected CO_(2)dissolution,dissolved CO_(2)mineralization and storage of CO_(2)as a gas phase during the CO_(2)and O_(2)ISL process.Furthermore,compared to acid ISL,CO_(2)and O_(2)ISL has a potentially smaller environmental footprint,with 20%of SO_(4)^(2–)concentration in the aquifer.The findings improve our fundamental understanding of carbon utilization in a long-term CO_(2)and O_(2)ISL system and provide important environmental implications when considering complex geochemical processes.