The Mesozoic–Cenozoic tectonic movement largely controls the northwest region of the Junggar Basin（NWJB）, which is a significant area for the exploration of petroleum and sandstone-type uranium deposits in China. T...The Mesozoic–Cenozoic tectonic movement largely controls the northwest region of the Junggar Basin（NWJB）, which is a significant area for the exploration of petroleum and sandstone-type uranium deposits in China. This work collected six samples from this sedimentary basin and surrounding mountains to conduct apatite fission track（AFT） dating, and utilized the dating results for thermochronological modeling to reconstruct the uplift history of the NWJB and its response to hydrocarbon migration and uranium mineralization. The results indicate that a single continuous uplift event has occurred since the Early Cretaceous, showing spatiotemporal variation in the uplift and exhumation patterns throughout the NWJB. Uplift and exhumation initiated in the northwest and then proceeded to the southeast, suggesting that the fault system induced a post spread-thrust nappe into the basin during the Late Yanshanian. Modeling results indicate that the NWJB mountains have undergone three distinct stages of rapid cooling： Early Cretaceous（ca. 140–115 Ma）, Late Cretaceous（ca. 80–60 Ma）, and Miocene–present（since ca. 20 Ma）. These three stages regionally correspond to the LhasaEurasian collision during the Late Jurassic–Early Cretaceous（ca. 140–125 Ma）, the Lhasa-Gandise collision during the Late Cretaceous（ca. 80–70 Ma）, and a remote response to the India-Asian collision since ca. 55 Ma, respectively. These tectonic events also resulted in several regional unconformities between the J3/K1, K2/E, and E/N, and three large-scale hydrocarbon injection events in the Piedmont Thrust Belt（PTB）. Particularly, the hydrocarbon charge event during the Early Cretaceous resulted in the initial inundation and protection of paleo-uranium ore bodies that were formed during the Middle–Late Jurassic. The uplift and denudation of the PTB was extremely slow from 40 Ma onward due to a slight influence from the Himalayan orogeny. However, the uplift of the PTB was faster after the Miocene, which led to re-uplift and exposure at the surface during the Quaternary, resulting in its oxidation and the formation of small uranium ore bodies.展开更多
The 300±20 Ma anomalously radioactive trachytes of Wadi El Kareim, central Eastern Desert, are a significant example of U-mineralization related to the alkaline volcanics in Egypt. Extensive portable gamma-ray sp...The 300±20 Ma anomalously radioactive trachytes of Wadi El Kareim, central Eastern Desert, are a significant example of U-mineralization related to the alkaline volcanics in Egypt. Extensive portable gamma-ray spectrometric data has been utilized to identify geological factors controlling uranium mobility in the geological units along the three detailed study locations of Kab Al-Abyad, South Wadi(W) Al-Tarafawy and W. Al-Farkhah; their eT h/eU ratios averaging around 4.1, 3.7 and 5.6 respectively. Quantitative analysis with the integration of mobility maps and geological studies suggest two systems controlling U-migration within the geological units(confined system and unconfined system). In the confined system, the syngenetically formed U have experienced mobility after leaching and are redistributed in the presence of an incorporation carrier during transportation(probably as carbonate complexes). Then the retardant for uranium is achieved by sorption or by coprecipitation with the aid of Fe oxy-hydroxide, and finally the formation of immobile secondary U-bearing minerals takes place along a lithogeochemical trap. In contrast to the confined system, the unconfined one is basically lacking the lithogeochemical trap which influences the final accumulation of U-bearing minerals. The radioactivity of the trachyte rocks arises from the radioactive minerals uranophane and betauranophane with U-and/or Th-bearing minerals samarskite, Th-rich REE silicates, monazite and allanite.展开更多
The authors discovered a new way to clean the ion exchange resin sorption of uranium from silicic acid used solution ＂Ayanat＂. The method reduces the costs of regeneration of ion exchange resin and its reuse in the ...The authors discovered a new way to clean the ion exchange resin sorption of uranium from silicic acid used solution ＂Ayanat＂. The method reduces the costs of regeneration of ion exchange resin and its reuse in the sorption of uranium.展开更多
The complexation, precipitation, and migration behavior of uranium in the presence of humic acid (HA) or fulvic acid (FA) were investigated by cation exchange, ultrafiltration and dynamic experiment, respectively. The...The complexation, precipitation, and migration behavior of uranium in the presence of humic acid (HA) or fulvic acid (FA) were investigated by cation exchange, ultrafiltration and dynamic experiment, respectively. The results showed that (i) complex equilibrium between the uranium and humic substances was achieved at approximately 72 h, (ii) the coordination number varied from 1:1 to 1:2 ( U(Ⅵ) : humic acid) as pH increased from 3 to 6; and (iii) , while the complex stability constant decreased when temperature increased, but increased with pH value. We found that the precipitation of uranyl could only be observed in presence of HA, and the precipitation was influenced by conditions, such as pH, uranium concentration, temperature, and the HA concentration. The maximum precipitation proportion up to 60% could be achieved in the condition of 40 mg/L HA solution at pH 6. We further observed that the migration behavior of uranium in soil in the presence of humic acid (HA) or fulvic acid (FA) was different from that in the presence of inorganic colloid, and the effect of humic substances (HS) was limited.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
A dynamic sorption experiment was performed for removal of uranium （VI or 6＋） from a leachate from an alum shale landfill with a diatomite-bentonite based sorbent in a laboratory scale. Such material was grounded a...A dynamic sorption experiment was performed for removal of uranium （VI or 6＋） from a leachate from an alum shale landfill with a diatomite-bentonite based sorbent in a laboratory scale. Such material was grounded and treated chemically with H3PO4 （phosphoric acid） and thermally for improving its porosity and resistance to water flow. A specific surface area of 209 m2·g-1 was determined by the BET method. A sorption capacity of 30 μg·gl and 0.6 μg·g-1 was obtained at a pH of 7.5 and 4 respectively by means of Langmuir and Freundlich isotherm models. The flow rate was 3 mL·min-1 was effective for controlling the pH inside of the column. The sorption mechanism was investigated along with desorption of the element of interest for further process design considerations for a treatment unit on the landfill site.展开更多
During the chemical weathering of the uranium mill tailings,released uranium could be immobilized by the newly formed secondary minerals such as oxyhydroxides.A deeper understanding of the interaction between uranium ...During the chemical weathering of the uranium mill tailings,released uranium could be immobilized by the newly formed secondary minerals such as oxyhydroxides.A deeper understanding of the interaction between uranium and common oxyhydroxides under environmental conditions is necessary.In this work,uranium sorption behaviors on Al-,Mn-and Fe-oxyhydroxide minerals(boehmite,manganite,goethite,and lepidocrocite)were investigated by batch experiments.Results showed that the uranium sorption on Al-oxyhydroxide behaved significantly differently from the other three minerals.The sorption edge of the Mn-and Fe-oxyhydroxides located around pH 5,while the sorption edge of boehmite shifted about 1.5 pH unit to near neutral.The sorption isotherms of uranium on manganite,goethite and lepidocrocite at pH 5.0 could be well fitted by the Langmuir model.Instead of surface complexation,sorption on boehmite happened mainly by uranium-bearing carbonates and hydroxides precipitation as illustrated by the characterization results.Both carbonate and phosphate strongly affected the uranium sorption behavior.The removal efficiency of uranium by boehmite exceeded 98%after three sorption-desorption cycles,indicating it may be a potential material for uranium removal and recovery.展开更多
Sorption characteristics of ion exchange resins 001 × 7, 005 × 8, D72 regarding rare earth metals （REM） during extraction from barren solution of uranium sorption in dynamic conditions were investigated. I...Sorption characteristics of ion exchange resins 001 × 7, 005 × 8, D72 regarding rare earth metals （REM） during extraction from barren solution of uranium sorption in dynamic conditions were investigated. It was identified that D72 resin capacity on analyzed REM was 2.46 mg.cm-3 after passing 220 BV （bed volume） of initial solution with 95 % recovery of element of REM with the lowest affinity. Researches on REM desorption in dynamic conditions from investigated ion exchange resins by solution of 1.7 mol.L-1 HNO3 and 8.0 mol.L-1 NHnNO3 with 0.2 mol.L-1 HNO3 passing were carded out. It was identified that using desorption solution based on ammonium nitrate allows to achieve acceptable recovery degree of REM from the resin. The possibility of organization of a circulating desorption solution system increases the perspectives of nitrate ammonium solution usage.展开更多
1 Introduction Increasing demand for uranium raw materials for the nuclear industry has stimulated interest in non-traditional sources,including hydromineral ones[Qin,2009].Those are saline lakes located in the uraniu...1 Introduction Increasing demand for uranium raw materials for the nuclear industry has stimulated interest in non-traditional sources,including hydromineral ones[Qin,2009].Those are saline lakes located in the uranium ore districts.Accumulation of uranium in such lakes results from the leaching of uranium from the rocks by surface and ground展开更多
Uranium bio-transformations are the many and varying types of interactions that microbes can have with uranium encountered in their environment. In this review, bio-transformations, including reduction, oxidation, res...Uranium bio-transformations are the many and varying types of interactions that microbes can have with uranium encountered in their environment. In this review, bio-transformations, including reduction, oxidation, respiration, sorption, mineralization, accumulation, precipitation, biomarkers, and sensors are defined and discussed. Consensus and divergences are noted in bioavailability, mechanism of uranium reduction, environment, metabolism and the type of organism. The breadth of organisms with characterized bio-trans formations is also cataloged and discussed. We further debate if uranium biotransformations provide bio-protection or bio-benefit to the microbe and highlight the need for more work in the field to understand if microbes use uranium reduction for energy gain and growth, as having the ability is separate from exercising it. The presentation centers on the fundamental drivers for these processes with an additional exposition of the essential contribution of inorganic chemistry techniques to the molecular characterization of these biological processes.展开更多
1 Introduction The attractiveness of Shaazgai-Nuur Soda Lake(pH9.2-9.4)as an alternative metal source is explained by the high concentration of dissolved uranium(~1 mg/l)due to the location of water drainage territory...1 Introduction The attractiveness of Shaazgai-Nuur Soda Lake(pH9.2-9.4)as an alternative metal source is explained by the high concentration of dissolved uranium(~1 mg/l)due to the location of water drainage territory within the Tsagan-展开更多
Similar to chromium contamination, the environmental contamination caused by uranium in radioactive coal bottom ash（CBA） is primarily dependent on the chemical speciation of uranium. However, the relationship betwee...Similar to chromium contamination, the environmental contamination caused by uranium in radioactive coal bottom ash（CBA） is primarily dependent on the chemical speciation of uranium. However, the relationship between uranium speciation and environmental contamination has not been adequately studied. To determine the relationship between uranium speciation and environmental contamination, X-ray absorption fine structure（XAFS） and X-ray photoelectron spectra（XPS） analyses were performed to determine the uranium speciation in CBA exposed to different chemical environments and simulated natural environments. The leachability of the different forms of uranium in the CBA was studied via a simulated acid rain leaching experiment, and the results showed that 57.0% of the total uranium was leached out as U（VI）. The results of a linear combination fit（LCF）of the X-ray absorption near edge structure（XANES） spectrum revealed that in the raw CBA, the uranium mainly occurred as U_3O_8（71.8%）. However, in the iron-rich particles, the uranium mainly occurred as UO_2（91.9%） after magnetic separation. Magnetite is a ubiquitous ferrousbearing oxide, and it was effective for the sorption of U（IV）. The result of FeSO_4 leaching experiment indicated that 96.57% of total uranium was reduced from U（VI） to U（IV） when infiltrated with the FeSO_4 solution for 6 months. This result clearly demonstrated the changes in chemical valence of uranium in the coal ash and provided a conceptual principle for preventing uranium migration from ash to the surrounding soil and plants.展开更多
When radionuclides migrate in porous media with water serving as carrier, the mechanism of sorption and desorption is not negligible. nonequilibrium conditions exist in sorption and desorption. In this paper,a numeric...When radionuclides migrate in porous media with water serving as carrier, the mechanism of sorption and desorption is not negligible. nonequilibrium conditions exist in sorption and desorption. In this paper,a numerical model of radionuclide migration with nonequilibrium sorption was developed.The algorithm of numerical descretizing and direct substituting was adopted in coupling of the convective-dispersive equation and the nonequilibrium sorption isotherm in this model ,and this makes it easier to solve the model numerically.A quantitative analysis is made for the first time that the influence of nonequilibrium sorption, represented by the rate coefficient which shows how quickly the nonequilibrium condition in sorption and desorption reaches equilibrium on the migration of radionuclide,and results show that it affects the migration perceptibly. Finally the model was verified by using the observed data of radionuclide migration test conducted in the field, and which clarified its availability.展开更多
Cyclodextrin-modified graphene oxide nanosheets(denoted as CD/GO) were synthesized by an in-situ polymerization method and characterized by as well as Fourier transform-infrared spectroscopy, X-ray photoelectron spect...Cyclodextrin-modified graphene oxide nanosheets(denoted as CD/GO) were synthesized by an in-situ polymerization method and characterized by as well as Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and potentiometric acid-base titration. The characterization results indicated that CD was successfully grafted onto GO surfaces by forming a chemical bond. Mutual effects on the simultaneous removal of hexavalent uranium and humic acid by CD/GO from aqueous solution were investigated. The results indicated that U(VI) and humic acid(HA) sorption on CD/GO were greatly affected by pH and ionic strength. The presence of HA enhanced U(VI) sorption at low pH and reduced U(VI) sorption at high pH, whereas the presence of U(VI) enhanced HA sorption. The surface adsorbed HA acted as a "bridge" between U(VI) and CD/GO, and formed strong inner-sphere surface complexes with U(VI). Sorption isotherms of U(VI) or HA on CD/GO could be well fitted by the Langmuir model. This work highlights that CD/GO can be used as a promising material in the enrichment of U(VI) and HA from wastewater in U(VI) and humic substances obtained by environmental pollution cleanup.展开更多
Mesoporous silicas have a very attractive ability of sorption and enrichment of metal ions due to their huge surface area and facile functionalization by organic ligands. In this work, phosphonate-amino hifunctionaliz...Mesoporous silicas have a very attractive ability of sorption and enrichment of metal ions due to their huge surface area and facile functionalization by organic ligands. In this work, phosphonate-amino hifunctionalized mesoporous silica SBA-15 （PA-SBA-15） as U（VI） sorbent was fabricated through post-grafting method. The obtained mesoporous silica was character- ized by SEM, XRD, NMR and nitrogen sorption/desorption experiments, which revealed the existence of ordered mesoporous structure with uniform pore diameter and large surface area. The adsorptivity of PA-SBA-15 for U（VI） from aqueous solution was investigated using batch sorption technique under different experimental conditions. The preliminary results show that the U（VI） sorption by PA-SBA-15 is very quick with equilibrium time of less than 1 h, and the U（VI） uptake is as large as 373 mg/g at pH 5.5 under 95℃. The sorption isotherm has been successfully modeled by the Langmuir isotherm, suggesting a monolayer homogeneous sorption of U（VI） in PA-SBA-15. The sorption is pH-dependent due to the pH-dependent charge of sorbent in the aqueous solution. The thermodynamics research shows that the sorption is a feasible and endothermic process. Based on these results, PA-SBA-15 could be a promising solid phase sorbent for highly-efficient removal of U（VI） ions from waste water and enrichment of U（VI） from a solution at a very low level.展开更多
Functionalized magnetic Fe_3O_4@SiO_2 composite nanoparticles were prepared by simply embedding iron oxide nanoparticles into MCM-41 through one-step synthesis process, followed by aminopropyls grafting on the mesopor...Functionalized magnetic Fe_3O_4@SiO_2 composite nanoparticles were prepared by simply embedding iron oxide nanoparticles into MCM-41 through one-step synthesis process, followed by aminopropyls grafting on the mesopore channels, aiming to efficiently and conveniently uptake U(VI) from aqueous solution. The resultant material possesses highly ordered mesoporous structure with large surface area, uniform pore size, excellent thermal stability, quick magnetic response, and desirable acids resistance, confirmed by Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), N_2 adsorption/desorption experiments, powder X-ray diffraction(PXRD), and thermogravimetric analysis(TGA). Detailed U(VI) sorption test indicated that this material is indeed an effective U(VI) sorbent with fast sorption kinetics of less than 2 h, large sorption capacity of 160 mg/g at p H 5.0±0.1, and desirable selectivity towards U(VI) ions over a range of competing metal ions. The absorbed U(VI) can be easily desorbed by 0.01 mol/L or more concentrated HNO_3 solution, and the reclaimed sorbent can be reused with no obvious decrease of sorption capacity even after 4 sorption-desorption cycles. The present results suggest the vast opportunities of this kind of magnetic composite on the solid-phase extraction of U(VI).展开更多
基金jointly conjugal supported by the Nuclear energy development project(grant No.H1142)Nation Pre-research Project(grant No.3210402)
文摘The Mesozoic–Cenozoic tectonic movement largely controls the northwest region of the Junggar Basin（NWJB）, which is a significant area for the exploration of petroleum and sandstone-type uranium deposits in China. This work collected six samples from this sedimentary basin and surrounding mountains to conduct apatite fission track（AFT） dating, and utilized the dating results for thermochronological modeling to reconstruct the uplift history of the NWJB and its response to hydrocarbon migration and uranium mineralization. The results indicate that a single continuous uplift event has occurred since the Early Cretaceous, showing spatiotemporal variation in the uplift and exhumation patterns throughout the NWJB. Uplift and exhumation initiated in the northwest and then proceeded to the southeast, suggesting that the fault system induced a post spread-thrust nappe into the basin during the Late Yanshanian. Modeling results indicate that the NWJB mountains have undergone three distinct stages of rapid cooling： Early Cretaceous（ca. 140–115 Ma）, Late Cretaceous（ca. 80–60 Ma）, and Miocene–present（since ca. 20 Ma）. These three stages regionally correspond to the LhasaEurasian collision during the Late Jurassic–Early Cretaceous（ca. 140–125 Ma）, the Lhasa-Gandise collision during the Late Cretaceous（ca. 80–70 Ma）, and a remote response to the India-Asian collision since ca. 55 Ma, respectively. These tectonic events also resulted in several regional unconformities between the J3/K1, K2/E, and E/N, and three large-scale hydrocarbon injection events in the Piedmont Thrust Belt（PTB）. Particularly, the hydrocarbon charge event during the Early Cretaceous resulted in the initial inundation and protection of paleo-uranium ore bodies that were formed during the Middle–Late Jurassic. The uplift and denudation of the PTB was extremely slow from 40 Ma onward due to a slight influence from the Himalayan orogeny. However, the uplift of the PTB was faster after the Miocene, which led to re-uplift and exposure at the surface during the Quaternary, resulting in its oxidation and the formation of small uranium ore bodies.
文摘The 300±20 Ma anomalously radioactive trachytes of Wadi El Kareim, central Eastern Desert, are a significant example of U-mineralization related to the alkaline volcanics in Egypt. Extensive portable gamma-ray spectrometric data has been utilized to identify geological factors controlling uranium mobility in the geological units along the three detailed study locations of Kab Al-Abyad, South Wadi(W) Al-Tarafawy and W. Al-Farkhah; their eT h/eU ratios averaging around 4.1, 3.7 and 5.6 respectively. Quantitative analysis with the integration of mobility maps and geological studies suggest two systems controlling U-migration within the geological units(confined system and unconfined system). In the confined system, the syngenetically formed U have experienced mobility after leaching and are redistributed in the presence of an incorporation carrier during transportation(probably as carbonate complexes). Then the retardant for uranium is achieved by sorption or by coprecipitation with the aid of Fe oxy-hydroxide, and finally the formation of immobile secondary U-bearing minerals takes place along a lithogeochemical trap. In contrast to the confined system, the unconfined one is basically lacking the lithogeochemical trap which influences the final accumulation of U-bearing minerals. The radioactivity of the trachyte rocks arises from the radioactive minerals uranophane and betauranophane with U-and/or Th-bearing minerals samarskite, Th-rich REE silicates, monazite and allanite.
文摘The authors discovered a new way to clean the ion exchange resin sorption of uranium from silicic acid used solution ＂Ayanat＂. The method reduces the costs of regeneration of ion exchange resin and its reuse in the sorption of uranium.
基金Supported by China National Natural Science Foundation(Nos.21071102 and 91126013)Joint Funds of China National Natural Science Foundation and China Academy of Engineering Physics(No.10476015)National Fund of China for Fostering Talents in Basic Science(No.J1210004)
文摘The complexation, precipitation, and migration behavior of uranium in the presence of humic acid (HA) or fulvic acid (FA) were investigated by cation exchange, ultrafiltration and dynamic experiment, respectively. The results showed that (i) complex equilibrium between the uranium and humic substances was achieved at approximately 72 h, (ii) the coordination number varied from 1:1 to 1:2 ( U(Ⅵ) : humic acid) as pH increased from 3 to 6; and (iii) , while the complex stability constant decreased when temperature increased, but increased with pH value. We found that the precipitation of uranyl could only be observed in presence of HA, and the precipitation was influenced by conditions, such as pH, uranium concentration, temperature, and the HA concentration. The maximum precipitation proportion up to 60% could be achieved in the condition of 40 mg/L HA solution at pH 6. We further observed that the migration behavior of uranium in soil in the presence of humic acid (HA) or fulvic acid (FA) was different from that in the presence of inorganic colloid, and the effect of humic substances (HS) was limited.
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.
文摘A dynamic sorption experiment was performed for removal of uranium （VI or 6＋） from a leachate from an alum shale landfill with a diatomite-bentonite based sorbent in a laboratory scale. Such material was grounded and treated chemically with H3PO4 （phosphoric acid） and thermally for improving its porosity and resistance to water flow. A specific surface area of 209 m2·g-1 was determined by the BET method. A sorption capacity of 30 μg·gl and 0.6 μg·g-1 was obtained at a pH of 7.5 and 4 respectively by means of Langmuir and Freundlich isotherm models. The flow rate was 3 mL·min-1 was effective for controlling the pH inside of the column. The sorption mechanism was investigated along with desorption of the element of interest for further process design considerations for a treatment unit on the landfill site.
基金National Natural Science Foundation of China(NSFC,No.11475008)。
文摘During the chemical weathering of the uranium mill tailings,released uranium could be immobilized by the newly formed secondary minerals such as oxyhydroxides.A deeper understanding of the interaction between uranium and common oxyhydroxides under environmental conditions is necessary.In this work,uranium sorption behaviors on Al-,Mn-and Fe-oxyhydroxide minerals(boehmite,manganite,goethite,and lepidocrocite)were investigated by batch experiments.Results showed that the uranium sorption on Al-oxyhydroxide behaved significantly differently from the other three minerals.The sorption edge of the Mn-and Fe-oxyhydroxides located around pH 5,while the sorption edge of boehmite shifted about 1.5 pH unit to near neutral.The sorption isotherms of uranium on manganite,goethite and lepidocrocite at pH 5.0 could be well fitted by the Langmuir model.Instead of surface complexation,sorption on boehmite happened mainly by uranium-bearing carbonates and hydroxides precipitation as illustrated by the characterization results.Both carbonate and phosphate strongly affected the uranium sorption behavior.The removal efficiency of uranium by boehmite exceeded 98%after three sorption-desorption cycles,indicating it may be a potential material for uranium removal and recovery.
基金financially supported by LLP ‘‘Institute of High Technologies’’(No.RMK-D-018)
文摘Sorption characteristics of ion exchange resins 001 × 7, 005 × 8, D72 regarding rare earth metals （REM） during extraction from barren solution of uranium sorption in dynamic conditions were investigated. It was identified that D72 resin capacity on analyzed REM was 2.46 mg.cm-3 after passing 220 BV （bed volume） of initial solution with 95 % recovery of element of REM with the lowest affinity. Researches on REM desorption in dynamic conditions from investigated ion exchange resins by solution of 1.7 mol.L-1 HNO3 and 8.0 mol.L-1 NHnNO3 with 0.2 mol.L-1 HNO3 passing were carded out. It was identified that using desorption solution based on ammonium nitrate allows to achieve acceptable recovery degree of REM from the resin. The possibility of organization of a circulating desorption solution system increases the perspectives of nitrate ammonium solution usage.
基金SB RAS Interdisciplinary Integration Projects 38 and 110RFBR Research Project 13-05-00556the Tomsk State University Program to improve competitiveness
文摘1 Introduction Increasing demand for uranium raw materials for the nuclear industry has stimulated interest in non-traditional sources,including hydromineral ones[Qin,2009].Those are saline lakes located in the uranium ore districts.Accumulation of uranium in such lakes results from the leaching of uranium from the rocks by surface and ground
文摘Uranium bio-transformations are the many and varying types of interactions that microbes can have with uranium encountered in their environment. In this review, bio-transformations, including reduction, oxidation, respiration, sorption, mineralization, accumulation, precipitation, biomarkers, and sensors are defined and discussed. Consensus and divergences are noted in bioavailability, mechanism of uranium reduction, environment, metabolism and the type of organism. The breadth of organisms with characterized bio-trans formations is also cataloged and discussed. We further debate if uranium biotransformations provide bio-protection or bio-benefit to the microbe and highlight the need for more work in the field to understand if microbes use uranium reduction for energy gain and growth, as having the ability is separate from exercising it. The presentation centers on the fundamental drivers for these processes with an additional exposition of the essential contribution of inorganic chemistry techniques to the molecular characterization of these biological processes.
基金supported by the SB RAS Interdisciplinary Integration project 110by the RFBR grant 13-0500032by program to improve the competitiveness of Tomsk State University
文摘1 Introduction The attractiveness of Shaazgai-Nuur Soda Lake(pH9.2-9.4)as an alternative metal source is explained by the high concentration of dissolved uranium(~1 mg/l)due to the location of water drainage territory within the Tsagan-
基金supported by the Talent Support Fund of Tsinghua University(No.413405001)
文摘Similar to chromium contamination, the environmental contamination caused by uranium in radioactive coal bottom ash（CBA） is primarily dependent on the chemical speciation of uranium. However, the relationship between uranium speciation and environmental contamination has not been adequately studied. To determine the relationship between uranium speciation and environmental contamination, X-ray absorption fine structure（XAFS） and X-ray photoelectron spectra（XPS） analyses were performed to determine the uranium speciation in CBA exposed to different chemical environments and simulated natural environments. The leachability of the different forms of uranium in the CBA was studied via a simulated acid rain leaching experiment, and the results showed that 57.0% of the total uranium was leached out as U（VI）. The results of a linear combination fit（LCF）of the X-ray absorption near edge structure（XANES） spectrum revealed that in the raw CBA, the uranium mainly occurred as U_3O_8（71.8%）. However, in the iron-rich particles, the uranium mainly occurred as UO_2（91.9%） after magnetic separation. Magnetite is a ubiquitous ferrousbearing oxide, and it was effective for the sorption of U（IV）. The result of FeSO_4 leaching experiment indicated that 96.57% of total uranium was reduced from U（VI） to U（IV） when infiltrated with the FeSO_4 solution for 6 months. This result clearly demonstrated the changes in chemical valence of uranium in the coal ash and provided a conceptual principle for preventing uranium migration from ash to the surrounding soil and plants.
文摘When radionuclides migrate in porous media with water serving as carrier, the mechanism of sorption and desorption is not negligible. nonequilibrium conditions exist in sorption and desorption. In this paper,a numerical model of radionuclide migration with nonequilibrium sorption was developed.The algorithm of numerical descretizing and direct substituting was adopted in coupling of the convective-dispersive equation and the nonequilibrium sorption isotherm in this model ,and this makes it easier to solve the model numerically.A quantitative analysis is made for the first time that the influence of nonequilibrium sorption, represented by the rate coefficient which shows how quickly the nonequilibrium condition in sorption and desorption reaches equilibrium on the migration of radionuclide,and results show that it affects the migration perceptibly. Finally the model was verified by using the observed data of radionuclide migration test conducted in the field, and which clarified its availability.
基金supported by the National Natural Science Foundation of China(91326202,21375148,21207136,21225730)the Hefei Center for Physical Science and Technology(2012FXZY005)
文摘Cyclodextrin-modified graphene oxide nanosheets(denoted as CD/GO) were synthesized by an in-situ polymerization method and characterized by as well as Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and potentiometric acid-base titration. The characterization results indicated that CD was successfully grafted onto GO surfaces by forming a chemical bond. Mutual effects on the simultaneous removal of hexavalent uranium and humic acid by CD/GO from aqueous solution were investigated. The results indicated that U(VI) and humic acid(HA) sorption on CD/GO were greatly affected by pH and ionic strength. The presence of HA enhanced U(VI) sorption at low pH and reduced U(VI) sorption at high pH, whereas the presence of U(VI) enhanced HA sorption. The surface adsorbed HA acted as a "bridge" between U(VI) and CD/GO, and formed strong inner-sphere surface complexes with U(VI). Sorption isotherms of U(VI) or HA on CD/GO could be well fitted by the Langmuir model. This work highlights that CD/GO can be used as a promising material in the enrichment of U(VI) and HA from wastewater in U(VI) and humic substances obtained by environmental pollution cleanup.
基金supported by the National Natural Science Foundation of China (91026007)the "Strategic Priority Research program" of the Chinese Academy of Sciences (XDA03010401,XDA03010403)
文摘Mesoporous silicas have a very attractive ability of sorption and enrichment of metal ions due to their huge surface area and facile functionalization by organic ligands. In this work, phosphonate-amino hifunctionalized mesoporous silica SBA-15 （PA-SBA-15） as U（VI） sorbent was fabricated through post-grafting method. The obtained mesoporous silica was character- ized by SEM, XRD, NMR and nitrogen sorption/desorption experiments, which revealed the existence of ordered mesoporous structure with uniform pore diameter and large surface area. The adsorptivity of PA-SBA-15 for U（VI） from aqueous solution was investigated using batch sorption technique under different experimental conditions. The preliminary results show that the U（VI） sorption by PA-SBA-15 is very quick with equilibrium time of less than 1 h, and the U（VI） uptake is as large as 373 mg/g at pH 5.5 under 95℃. The sorption isotherm has been successfully modeled by the Langmuir isotherm, suggesting a monolayer homogeneous sorption of U（VI） in PA-SBA-15. The sorption is pH-dependent due to the pH-dependent charge of sorbent in the aqueous solution. The thermodynamics research shows that the sorption is a feasible and endothermic process. Based on these results, PA-SBA-15 could be a promising solid phase sorbent for highly-efficient removal of U（VI） ions from waste water and enrichment of U（VI） from a solution at a very low level.
基金supported by the National Natural Science Foundation of China (11275219, 11275090, U1432103)the “Strategic Priority Research program” of the Chinese Academy of Sciences (XDA030104)+1 种基金the State Key Laboratory of NBC Protection for Civilian (SKLNB201412)the Scientific Research Fund of Hunan Provincial Education Department (12A116)
文摘Functionalized magnetic Fe_3O_4@SiO_2 composite nanoparticles were prepared by simply embedding iron oxide nanoparticles into MCM-41 through one-step synthesis process, followed by aminopropyls grafting on the mesopore channels, aiming to efficiently and conveniently uptake U(VI) from aqueous solution. The resultant material possesses highly ordered mesoporous structure with large surface area, uniform pore size, excellent thermal stability, quick magnetic response, and desirable acids resistance, confirmed by Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), N_2 adsorption/desorption experiments, powder X-ray diffraction(PXRD), and thermogravimetric analysis(TGA). Detailed U(VI) sorption test indicated that this material is indeed an effective U(VI) sorbent with fast sorption kinetics of less than 2 h, large sorption capacity of 160 mg/g at p H 5.0±0.1, and desirable selectivity towards U(VI) ions over a range of competing metal ions. The absorbed U(VI) can be easily desorbed by 0.01 mol/L or more concentrated HNO_3 solution, and the reclaimed sorbent can be reused with no obvious decrease of sorption capacity even after 4 sorption-desorption cycles. The present results suggest the vast opportunities of this kind of magnetic composite on the solid-phase extraction of U(VI).
