Search

Abstract Uranium is the most radioactive element using in the nuclear industry and nuclear technology application. However, it is harmful for environment and human health due to its high toxicity and mobility. Thus designing effective material for uranium removal is highly desirable. In this paper, a novel adsorbent of nZVI@Zn-MOF-74 prepared by anchoring nZVI on Zn-MOF-74 was investigated for the removal of uranium from aqueous solutions. Impressively, nZVI was synthesized for the first time by a spraying approach in a simple and convenient manner. The experimental results indicated that nZVI@Zn-MOF-74 can significantly enhance the removal of U(VI) than both Zn-MOF-74 material and nZVI, leading to high adsorption capacity up to 348 mg/g at pH = 3 and 298 K. The origin, as unveiled by XPS, is due to both U(VI) adsorption from Zn-MOF-74 and U(VI)-to-U(IV) reduction by nZVI. Graphical abstract The experimental results indicate that nZVI@Zn-MOF-74 adsorption uranium is synergistic effect by the adsorption of Zn-MOF-74 and reduction by nZVI. fx1 Highlights • This work presents the first case of anchoring Fe0 on MOFs for removal of U(VI). • This resultant material enables ultrahigh U(VI) adsorption capacity. • A significant synergism effect from MOF and Fe0 is observed. [ABSTRACT FROM AUTHOR]

Current studies reveal that the biomineralization of U(VI) by anaerobes normally produces nano-sized U(IV) minerals that can easily re-migrate/re-oxidize, while the biomineralization of U(VI) by aerobes has been constrained because the general mechanism has not yet been fully characterized. The biomineralization of U(VI) by Bacillus cereus 12-2 was investigated in this work. The maximum biosorption capability of intact cells was 448.68 mg U/g biomass (dry weight) at pH 5, while a decrease over 60% was induced when phosphate, amino, and especially carboxyl groups were shielded. X-ray diffraction, electron microscopy, and tracing the concentration of soluble intracellular U(VI) demonstrated that extracellular amorphous uranium particles can directly enter cells as solid, and about 10 nm-sized (NH 4 )(UO 2 )PO 4 ·3H 2 O was formed subsequently. It was also revealed that the biosorption capability was not affected by a high uranium concentration, while biomineralization was inhibited, suggesting that a high concentration of heavy metals may inhibit the enzyme activity involved in biomineralization. Besides, U(VI) could trigger the overexpression of proteins with a molecular weight of 22 kD, including various phosphatases, kinases, and other enzymes that are related to metabolism and stimulus response, which may contribute to the intracellular transformation of U(VI) compounds from amorphous to crystalline phase. Taken together, the immobilization of U(VI) by B. cereus 12-2 contains two major steps: (1) fast immobilization of U(VI) on the cell surface as amorphous compounds, in which the carboxyl groups served as the predominant coordination functional groups and (2) transport of amorphous particles to cells directly and enzyme-related formation of uramphite. [ABSTRACT FROM AUTHOR]

Carbon superstructures with graphitized lamellar microstructures were fabricated through a modified hydrothermal method. The dual oxidation process combining acrylic acid functionalization and air thermal treatment introduced plentiful carboxyl groups on the surface of the carbon superstructures. Adsorption capacity of U(VI) on the as prepared carbon superparticles reached 197.7 mg g −1 , which was 9-fold higher than that of raw glucose-derived hydrothermal carbon microspheres. The thermo-dynamic and kinetic studies demonstrated that the uptake of uranyl ions was a spontaneous and endothermic chemisorption dominated process with the abundant carboxyl groups acting as main binding sites. Impressively, the carbon superstructure adsorbents showed excellent recycling performance. To sum up, this paper proposed a novel high-performance U(VI) adsorbent from hydrothermal carbon, which exhibited potential in real application due to their outstanding reusability and scale-up capability. [ABSTRACT FROM AUTHOR]

The influences of N species and transpiration on the Fe plaque (IP) formation and related aquatic U rhizofiltration had not revealed yet, especially when these factors were co-existed. It was evaluated in a mesocosm experiment in the condition of respective ammonium (NH 4 + )/nitrate (NO 3 − ) cultivation of Phragmites australis Trin ex Steud. coupled with different transpiration rates (TRs). The results suggested that the enhanced transpiration of P. australis improved the aquatic U rhizofiltration in both NO 3 − and NH 4 + rich milieus. However, the NO 3 − dependent oxidizing milieu restricted aquatic U uptake by the root of P. australis (up to 47.6 ± 1.8 mg kg −1 under high TR) via IP assisted rhizofiltration. The high aquatic U availability and limited IP formation in NO 3 − rich milieu benefited the U retention within root tissue. On the contrary, the aquatic U rhizofiltration (up to 62.1 ± 1.0 mg kg −1 under high TR) was enhanced under NH 4 + dependent reductive milieu. It was mainly contributed by U retention within IP. The area related U accumulation in different N species cultured roots was enhanced but did not significantly different under higher TR condition. The result suggested that the supplied NH 4 + coupled with enhanced transpiration was supposed to be more optimized option for IP assisted aquatic U rhizofiltration via P. australis . [ABSTRACT FROM AUTHOR]

In this paper, the defective TiO 2−x with abundant oxygen vacancies were fabricated through a simple modified solvothermal strategy and characterized by SEM, TEM, XRD, FT-IR, EDX, Zeta-potential, and XPS techniques in detail. The prepared TiO 2−x was applied to remove U(VI) and humic acid (HA) from aqueous solutions to evaluate its sorption performance. The sorption of U(VI) and HA on TiO 2−x was examined under various environmental conditions ( e.g. , contact time, pH, ionic strength, initial HA/U(VI) concentrations, the addition sequences of HA/U(VI) and temperature). According to the Langmuir model simulation, the maximum sorption capacities of U(VI) and HA on TiO 2−x at pH = 5.0 were calculated to be 65 and 142 mg g −1 , respectively, which were higher than most current reported materials. The kinetic results indicated that the sorption of U(VI) and HA onto TiO 2−x was better described by the pseudo-second-order kinetic model. The presence of HA enhanced U(VI) sorption on TiO 2−x at pH = 5.0, meanwhile, the surface adsorbed U(VI) on TiO 2−x also enhanced the sorption capacity of HA, which was mainly attributed to the formation of U(VI)-HA-TiO 2−x ternary complexes. Combining FT-IR and XPS analysis, the oxygen vacancies could provide high chemical activity and trap U(VI) in the defective sites of TiO 2−x , while the sorption of HA was dominated by surface complexation. The findings might provide an opportunity to estimate and optimize the efficient simultaneous elimination of radionuclides and natural organic substances by using defective TiO 2−x . [ABSTRACT FROM AUTHOR]

Uranium contamination of groundwater increasingly concerns rural residents depending on home wells for their drinking water in communities where uranium is a source of contamination. Established technologies to clean up contaminated aquifers are ineffective in large contaminated areas or are prohibitively expensive. Permeable reactive barriers (PRBs) are a low-cost alternative to these methods. In this paper, the applicability of clay ceramic pellets was investigated as permeable reactive barriers (PRBs) material for the treatment of uranium-contaminated groundwater. Flow-through columns were fabricated and used to mimic the flow path of a contaminant plume through the reactive media. Experiment results show that clay ceramic pellets effectively remove uranium from uranium-contaminated water and also can be a cost-efficient technique for remediating uranium contaminated groundwater by a clay pellet barrier. Using clay ceramic pellets is also a practical treatment method for uranium removal from drinking water and can supply potable water for households in the affected areas. [ABSTRACT FROM AUTHOR]

Bench scale field trials were initiated for the development of effective technology for recovery of uranium from sea water using acrylonitrile absorbents synthesized by radiation grafting. One of the important needs is to ensure quality assurance for the accurate measurement of heavy metal ion concentrations from lean solutions such as sea water and brine. Efforts have been made at Bioassay Laboratory of Radiation Safety Systems Division in India to improve the radiochemical separation and detection techniques for rapid, sensitive and accurate estimation of uranium in sea water samples. The earlier method using ion exchange had disadvantages of being lengthy and required use of sulphuric acid. Hence, a method was developed for estimation of uranium concentration in natural sea water and brine (desalination plant effluents) samples by solid extraction chromatography (SEC) using UTEVA resin (Uranium and TEtraValents Actinides). This resin consists of dipentyl pentylphosphonate sorbed onto an inert polymeric support. Using SEC technique, the complete analysis results are available within a day and as the resin is very specific for uranium extraction from the samples, it is easier to eliminate interfering transition ions like vanadium and iron from the samples. This paper reports the standardization of radiochemical procedure for uranium from sea water and brine samples and its determination by alpha spectrometry. [ABSTRACT FROM PUBLISHER]

The efficiency of two-cascade schemes for purification of regenerated uranium is investigated on the basis of a computational experiment. In the first cascade, by shifting the feed toward the waste the waste flow is purified by removing U with U enrichment to 5%. In the second cascade, the flow is additionally purified by removing U in the intermediate product flow and natural raw material is fed into the main feed flow and low-enrichment commercial-grade uranium is obtained in the main product flow. It is shown that purification can be conducted by feeding it into the step minimizing the total feed flow of the steps or into the first step of the cascade. Low-enrichment commercial-grade uranium hexafluoride meeting ASTM specifications in terms of U can be produced from the purified product obtained in the intermediate product flow. [ABSTRACT FROM AUTHOR]

A new series of amidoxime-based polymer adsorbents were synthesized at the Oak Ridge National Laboratory (ORNL) by electron beam induced grafting of acrylonitrile and itaconic acid onto polyethylene fiber. Hydroxylamine derivatives of poly(acrylonitrile) (PAN) moiety are demonstrated to possess two kinds of functional groups: open-chain amidoxime and cyclic imide dioxime. The open-chain amidoxime is shown to convert to imide dioxime on heat treatment in the presence of an aprotic solvent, like dimethylsulfoxide (DMSO). The formation of amidoxime and imide dioxime was confirmed by 13 C CP-MAS spectra. The adsorbents were evaluated for uranium adsorption efficiency at ORNL with simulated seawater spiked with 8 ppm uranium and 5 gallon seawater in a batch reactor, and in flow-through columns with natural seawater at the Marine Science Laboratory (MSL) of Pacific Northwest National Laboratory (PNNL) at Sequim Bay, WA. The DMSO-heat-treated sorbents adsorbed uranium as high as 4.48 g-U/kg-ads. from seawater. Experimental evidence is presented that the poly(imide dioxime) is primarily responsible for enhanced uranium adsorption capacity from natural seawater. The conjugated system in the imide dioxime ligand possesses increased electron donation ability, which is believed to significantly enhance the uranyl coordination in seawater. [ABSTRACT FROM AUTHOR]

This study reports the removal of uranium in underground wastewater using a Nigerian clay-based membrane. The clay and sintered clay were characterized using XRD, XRF, TGA/DTA, FESEM and PSD. The raw clay was mixed with cassava starch (10, 15, 20 and 25 wt%) and sintered at a temperature of 1300 °C. A multi-point BET analysis of the produced clay-based membranes was conducted to determine the surface area, pore volume and average pore size. Sintering characteristics were determined by apparent porosity, bulk density and flexural strength. The radioactivity of the feed and the permeated water was counted using a gamma spectrometer with an HPGe detector. From the XRD, TGA and FESEM, 1300 °C was found to be optimum for the mullite formation from the clay. The average pore sizes of the produced membranes from the BET results were observed to be in the range from 51 to 70 Å and with a steady state flux range of the tested membranes in the range 1.92×10 −5 –2.09×10 −4 m 3 m −2 s −1 . The permeation flux produced is of high quality with a rejection in the range of 1.78–2.56 Bq/l of the uranium activity by the tested membranes. This low-cost membrane will have an application for the treatment of uranium-containing wastewater from fracking, oil exploration and phosphate mining industries. [ABSTRACT FROM AUTHOR]

We report on the facile, reliable fabrication of novel magnetic cucurbit[6]uril/graphene oxide (CB[6]/GO/Fe 3 O 4 ) composite by using an in-situ co-precipitation method, for which the formation process and possible formation mechanism were also investigated. Moreover, the composite was used as an adsorbent for the removal of uranium(VI) from aqueous solution. Herein, GO nanosheets were chosen as a substrate to immobilize CB[6] and Fe 3 O 4 . During the co-precipitation of Fe 3 O 4 nanoparticles on surface of GO nanosheets, CB[6] molecules was fixed through hydrogen bonding simultaneously. The as-prepared composite exhibited a high efficiency of magnetic separability, competitive adsorption performance and acceptable reusability and stability for U(VI) removal, indicating a potential application in uranium-bearing wastewater treatment. [ABSTRACT FROM AUTHOR]

The present study evaluated uranium (U) removal ability and tolerance to low level nuclear waste (LLNW) of an aquatic weed Hydrilla verticillata . Plants were screened for growth in 10%–50% waste treatments up to 3 d. Treatments of 20% and 50% waste imposed increasing toxicity with duration assessed in terms of change in fresh weight and in the levels of photosynthetic pigments and thiobarbituric acid-reactive substances. U concentration, however, did not show a progressive increase and was about 42 μg g −1 dw from 20% to 50% waste at 3 d. This suggested that a saturation stage was reached with respect to U removal due to increasing toxicity. However, in another experiment with 10% waste and 10% waste+10 ppm U treatments, plants showed an increase in U concentration with the maximum level approaching 426 μg g −1 dw at 3 d without showing any toxicity as compared to that at 20% and 50% waste treatments. Hence, plants possessed significant potential to take up U and toxicity of LLNW limited their U removal ability. This implies that the use of Hydrilla plants for U removal from LLNW is feasible at low concentrations and would require repeated harvesting at short intervals. [ABSTRACT FROM AUTHOR]

Click This study evaluates the feasibility of biosorption of uranium from aqueous solutions using living and dried S. punctata . The uranium maximum removal efficiency for the plant cultivar occurrs in the soluation at pH 4-5 and the uranium removal efficiency exceeds 90%. In the kinetics studies, the dried powder of duckweed can reach nearly 80% adsorption within 5 min, and the batch adsorption equilibrium can be reached within 24 h for the living and dried powder of duckweed. Both for the living and dried powder of duckweed, the experimental data were fitted by the pseudo-second-order rate model with the degree of fitting (R 2 ) higher than 0.99. The uranium was deposited onto the root surface of living S. punctata as 100-500 nanometer size schistose structures that consist of primarily U (82.5%,wt%) and P(8.76%,wt %), and no carbon; while no similar uranium phosphate minerals were found on the dried powder of S. punctata , as revealed by scanning electron microscope and energy dispersive spectrometer analysis. The results suggest that there is one particularly promising biosportion processes, namely, biomineralization. And the root surface of the living S. punctata plays an important role in the uranium phosphate precipitate processes, not only play as a carrier of the functional groups but also as a substrate inducing the nucleation of uranium-phosphate nanoparticles. The dried powder of S. punctata adsorption of U is mainly through the effect of electrostatic attraction, ion exchange, and complexation coordination. [ABSTRACT FROM AUTHOR]

Uranium (VI) is highly toxic and radioactive in water, and may pose the great risk to human health and environment. A new adsorbent is reported here for highly efficient removal of uranyl ions from aqueous solution. Specifically, poly(acrylic acid)-block-polystyrene (PAA-b-PSt) block copolymers were synthesized as macromolecular surfactant for the emulsion polymerization of styrene. The obtained PSt microspheres had the controlled density and length of PAA chain on the surface, which lead to a controlled high adsorption capacity. The effects of pH, adsorbent dose, coexisting ions, temperature, contact time, initial concentration were evaluated on the removal of uranyl ions. Adsorption equilibrium could be achieved within 4 h, and the kinetic data could be well described by pseudo-second-order kinetics equation, and the maximum adsorption capacity calculated from Langmuir equation was ~990 mg/g at 298.15 K and pH 4.5. This work indicates that PAA-functionalized microspheres can be used as a new adsorbent for highly efficient removal of uranium (VI) from aqueous solutions. [ABSTRACT FROM AUTHOR]

Highlights: [•] Waste product of oil shale industry was utilized as sorbent for uranium. [•] Hydrotalcite-like compound was synthesized using oil shale ash. [•] Composition, microstructure and absorptive property were investigated. [•] It was an Mg–Al-based hydrotalcite compound with a lamellar morphology. [•] The maximum adsorption capacity toward uranium is 156mg/g at 298K. [ABSTRACT FROM AUTHOR]

Highlights: [•] Rice husk has the potential to treat U(VI) in wastewater. [•] pH of the medium strongly affected the removal of U(VI). [•] Langmuir model provided the best correlation to the experimental data. [•] Thermodynamics showed that removal of U was spontaneous at low temperature. [•] H2SO4 and EDTA proved most successful as eluting agents. [ABSTRACT FROM AUTHOR]

The current work examines the pilot-scale activities required to utilize a zero valent iron (ZVI) sand bed, incorporated into a biological drinking water treatment system, to remove contaminants, particularly uranium (U) from a rural Canadian water well. Available technologies for U removal tend to be unsuitable for many small communities which lack resources. While ZVI has been acknowledged to be an attractive option, the technology has not achieved successful full-scale implementation. This work included a small-scale column and onsite pilot study. A loading capacity of 5962 mg U/kg ZVI was determined by column study. A ZVI sand filter integrated into a biological pilot system reduced contaminants to within acceptable standards, meeting our objectives including reducing U to <4 μg/L. Disposal of residuals (solid and liquid) was examined and the process was determined to be economically feasible and efficient [ABSTRACT FROM AUTHOR]

Abstract: We prepared a magnetic Schiff base (ferroferric oxide/Schiff base composite) which could efficiently remove uranium(VI) ions from aqueous solutions. In this study, the effect of adsorption parameters such as pH value, adsorbent dose, shaking time, and temperature has investigated and optimized. It is found that the maximum adsorption capacity of the magnetic composite toward uranium(VI) is 94.30mgg−1 obtained at pH=6.0, adsorbent dose=0.02g, contact time=6h and temperature=25°C. Both kinetics and thermodynamic parameters of the adsorption process are estimated. It is found that the pseudo-second-order model is more suitable for our experiment. These data show that the process is exothermic and spontaneous. The Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models have been applied to evaluate the removal efficiency and the data were correlated well with Langmuir model. The adsorbed uranium(VI) can be desorbed effectively (about 98.57%) by 0.1M NaOH and the adsorption capacity is not significantly reduced after three cycles. Present study suggests that this magnetic Schiff base can be used as a potential adsorbent for sorption uranium(VI) and also provide a simple, fast separation method for removal of uranium(VI) ions from aqueous solution. [Copyright &y& Elsevier]

Abstract: This paper report on the efficient removal of uranium ions from aqueous solution with a novel magnetic composite adsorbent, calcined magnetic layered double hydroxide/hydroxyapatite (CMLH). This adsorbent was obtained via in situ grown of nano-hydroxyapatite on magnetic CaAl-layered double hydroxides and followed with calcining. The morphology and microstructure of the as-prepared adsorbents were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. The influences of conditions for uranium removal, including dosage of LDHs, pH of aqueous solution, and temperature on anion-exchange have been investigated, respectively. The thermodynamic parameters including Gibbs free energy (ΔG 0), standard enthalpy change (ΔH 0) and standard entropy change (ΔS 0) for the process were calculated using the Langmuir constants. It was found from kinetics test that the pseudo-second order kinetics model could be used to well describe the uptake process. Furthermore, the CMLH could be regenerated through the desorption of the uranium using 0.5M NaHCO3 solution and could be reused to adsorb after calcination. [Copyright &y& Elsevier]

Groundwater in the north-eastern suburb of Tallinn was analysed to determine the content of iron, manganese, sulphides, ammonia, and radionuclides (Ra226, Ra228) and total radioactivity. It was established that for several wells of the Cambrian--Vendian water layer the annual effective dose would exceed the EU guideline for drinking water (0.1 mSv/yr). The purpose was to find a technology for simultaneous purification of groundwater from iron, manganese, sulphides, ammonia, and some radionuclides (Ra226, Ra228). A pilot plant consisting of a Venturi-type aeration unit GDT (Gas-Degas Technology, Mazzei Corp., USA), an oxidation tank, and two-stage filtration columns was constructed. Several non-catalytic (Everzit Special Plus, sand) and catalytic filter materials (Filtersorb FMH, Pyrolox) were tested. Along the flow sheet from the aerator to the II stage filter outlet the pH, dissolved oxygen and carbon dioxide, turbidity, the content of iron, manganese, and ammonia were monitored, mainly by using spectrophotometry (HACH DR/2000). Radioactivity of water samples was determined by the Estonian Radiation Centre using the liquid scintillation counting method and γ-spectrometry. It was established that by intensive aeration of groundwater followed by oxidation for a certain contact time and appropriate selection of filter materials of different properties, it was possible to remove together with iron and manganese also radium isotopes. The total effectiveness of the process was 90% removal of gross-alfa and 70% removal of gross-beta activity of groundwater. Since the uranium content in the well water was marginal and radon was almost totally (99%) removed in the degas separator, the total effective dose was calculated by Ra226 and Ra228. It was about 0.067 mSv/yr, which is lower than the EU DWD guideline (0.1 mSv/yr). The theoretical assumption that radionuclides were already removed with Fe(OH)3 flocks in the first filtration step was verified by examining wash water. The radioactivity of wash water containing precipitate and the filtered wash water were measured. Results showed 4.6 times higher gross-alfa and 5.3 times higher gross-beta activity in the water containing precipitate. The co-precipitation process, where MnO2 and Fe(OH)3 flocks played an essential role, resulted in simultaneous removal of radium isotopes. Co-precipitation of radium with MnO2 was more effective than with Fe(OH)3. [ABSTRACT FROM AUTHOR]

The ever-increasing growth of biorefineries is expected to produce huge amounts of lignocellulosic biochar as a byproduct. The hydrothermal carbonization (HTC) process to produce biochar from lignocellulosic biomass is getting more attention due to its inherent advantage of using wet biomass. In the present study, biochar was produced from switchgrass at 300 °C in subcritical water and characterized using X-ray diffraction, fourier transform infrared spectroscopy, scanning electron micrcoscopy, and thermogravimetric analysis. The physiochemical properties indicated that biochar could serve as an excellent adsorbent to remove uranium from groundwater. A batch adsorption experiment at the natural pH (∼3.9) of biochar indicated an H-type isotherm. The adsorption data was fitted using a Langmuir isotherm model and the sorption capacity was estimated to be ca. 2.12 mg of U g−1 of biochar. The adsorption process was highly dependent on the pH of the system. An increase towards circumneutral pH resulted in the maximum adsorption of ca. 4 mg U g−1 of biochar. The adsorption mechanism of U(VI) onto biochar was strongly related to its pH-dependent aqueous speciation. The results of the column study indicate that biochar could be used as an effective adsorbent for U(VI), as a reactive barrier medium. Overall, the biochar produced via HTC is environmentally benign, carbon neutral, and efficient in removing U(VI) from groundwater. [Copyright &y& Elsevier]

The article presents a research study which looks at the role of Geobacter conductive pili in the extracellular reduction of uranium from groundwater. It evaluates the contribution of pili expression to uranium reduction, stressing its function in enhancing the rate and extent of uranium immobilization. The result illustrates the significant function of Geobacter as a catalytic and protective cellular mechanism, inferred to be of interest for remediation of uranium-contaminated groundwater.

Abstract: Adsorption of uranyl ions onto talc from aqueous solutions was investigated in batch adsorption experiments. The study has been conducted to investigate the effects of the pH of solution, contact time, initial concentration and presence of other metals that could compete with uranium for adsorption sites. The kinetic sorption data were found to fit the first-order kinetic model. The experimental isotherm data of uranium sorption were examined using the Freundlich, the Langmuir and the BET models. The results obtained showed three segments separated by characteristic steep slopes in the respective experimental isotherms. This could be indicative of uranium adsorption in multimolecular or cluster states onto talc. Moreover, the detected talc surface area of 3.5m2/g was too small for adsorption of uranium as a monolayer. The surface area occupied by the maximum amount of uranium adsorbed (41.6mg/g) as a monolayer was 58.3m2/g. [Copyright &y& Elsevier]

In this report, synthesis and characterization data for françoisite-(Nd), Nd[(UO2)3O(OH) (PO4)2]⋅6H2O are presented. Experimental studies including chemical digestion, thermogravimetric analysis (TG), attenuated total reflection infrared spectroscopy (ATR-IR), Raman spectroscopy, and X-ray powder diffraction (XRD) were conducted. The local bonding environments of uranyl and water were investigated with ATR-IR and Raman spectroscopy. The average axial uranium-oxygen bond lengths [R(U=O)] and the oxygen-oxygen hydrogen bond distances [R(O⋯O)] in water were calculated from the vibrational frequencies of the stretching modes of uranyl and water, respectively. The IR spectra of protiated and deuterated françoisite-(Nd) appear to confirm a coordinated hydroxyl group bridging vicinal uranyl groups in the structural unit. These studies provide the basis for further thermodynamic (e.g., calorimetry, solubility, and sorption) and geochemical modeling investigations of hydrated uranyl phosphate compounds. [ABSTRACT FROM AUTHOR]

Massively parallel sequencing has provided a more affordable and high-throughput method to study microbial communities, although it has mostly been used in an exploratory fashion. We combined pyrosequencing with a strict indicator species statistical analysis to test if bacteria specifically responded to ethanol injection that successfully promoted dissimilatory uranium(VI) reduction in the subsurface of a uranium contamination plume at the Oak Ridge Field Research Center in Tennessee. Remediation was achieved with a hydraulic flow control consisting of an inner loop, where ethanol was injected, and an outer loop for flow-field protection. This strategy reduced uranium concentrations in groundwater to levels below 0.126 μM and created geochemical gradients in electron donors from the inner-loop injection well toward the outer loop and downgradient flow path. Our analysis with 15 sediment samples from the entire test area found significant indicator species that showed a high degree of adaptation to the three different hydrochemical-created conditions. Castellaniella and Rhodanobacter characterized areas with low PH, heavy metals, and low bloactivity, while sulfate-, Fe(III)-, and U(VI)-reducing bacteria (Desulfovibrio, Anaeromyxobacter, and Desulfosporosinus) were indicators of areas where U(VI) reduction occurred. The abundance of these bacteria, as well as the Fe(III) and U(VI) reducer Geobacter, correlated with the hydraulic connectivity to the substrate injection site, suggesting that the selected populations were a direct response to electron donor addition by the groundwater flow path. A false-discoveryrate approach was implemented to discard false-positive results by chance, given the large amount of data compared. [ABSTRACT FROM AUTHOR]

Zhovty Vody city, located in south-central Ukraine, has long been an important center for the Ukrainian uranium and iron industries. Uranium and iron mining and processing activities during the Cold War resulted in poorly managed sources of radionuclides and heavy metals. Widespread groundwater and surface water contamination has occurred, which creates a significant risk to drinking water supplies. Hydrogeologic and geochemical conditions near large uranium mine tailings storage facility (TSF) were characterized to provide data to locate, design and install a permeable reactive barrier (PRB) to treat groundwater contaminated by leachate infiltrating from the TSF. The effectiveness of three different permeable reactive materials was investigated: zero-valent iron (ZVI) for reduction, sorption, and precipitation of redox-sensitive oxyanions; phosphate material to transform dissolved metals to less soluble phases; and organic carbon substrates to promote bioremediation processes. Batch and column experiments with Zhovty Vody site groundwater were conducted to evaluate reactivity of the materials. Reaction rates, residence time and comparison with site-specific clean-up standards were determined. Results of the study demonstrate the effectiveness of the use of the PRB for ground water protection near uranium mine TSF. The greatest decrease was obtained using ZVI-based reactive media and the combined media of ZVI/phosphate/organic carbon combinations. [ABSTRACT FROM AUTHOR]

Cavitation is mostly considered as an operational problem and not desirable phenomena. The rapid creation and collapse of bubbles can destroy pump and erode other equipment. Recently, cavitation has been explored to enhance mass transfer and also to enhance or alter chemical reactions. Cavitation by definition is the formation, growth and rapid collapse of bubbles. Cavitation can be generated by different techniques. Hydrodynamic (hydraulic) and acoustic cavitations are the results of overcoming the tension existing in a liquid using fluid and sound energy, respectively. Optic, charge particle and steam bubble cavitations are the consequence of local deposition of energy using light, high energy elementary particles beam and steam bubble, respectively. For industrial application, hydrodynamic and acoustic cavi- tations are more important. Steam bubble cavitation is a recent invention and is a highly promising candidate for industrial applications in future. Improvement in recovery and enhancement in rate of recovery during leaching by ultrasound is documented in literature. Uranium leaching from carnotite ore with ultrasound was reported in 1968 by Russia and ultrasonic leaching of urania impregnated in graphite fuel was reported in 1961 by the USA. There is no other published literature available on uranium leaching with cavitation. However, lot more research has been carried out under sonochemistry for process intensification. Different types of cavitation reactor schemes are proposed by researchers for the process intensification. In this paper, we have reviewed uranium leaching with cavitation using different cavitation mechanisms. Effect of cavitation-aided leaching of uranium from MgF2 has been experimentally established. Uranium leaching of Narwapahar ore with acoustic and hydrodynamic cavitation also has been studied. [ABSTRACT FROM AUTHOR]

In the present article, the major treatment methods applied for uranium removal from ground water, with specific applications in drinking water treatment, are reviewed. These include pump-and-treat technologies, such as membrane filtration methods, anion exchange, and the use of adsorbents, such as iron oxides, or titanium dioxide, as well as the application of coagulation processes with the addition of Fe/Al salts, or by lime softening. In all cases, uranium removal is mainly dependent on its speciation, which is greatly affected by the (usually coexisting) carbonate ions in the contaminated water. Under circumneutral pH values, uranium forms anionic complexes with carbonate of the type UO2(CO3)22-, or UO2(CO3)34-. In situ treatment technologies comprise mainly the use of permeable reactive barriers. These contain reactive materials, such as zero valent iron or hydroxyapatite, and uranium is usually removed by reduction to the respective insoluble products of U(IV); reducing bacteria, when present, can play a supplementary role. [ABSTRACT FROM AUTHOR]

The article cites a report in a 2011 issue of the journal "Proceedings of the National Academy of Sciences of the United States of America" regarding microbiology research by Cologgi and colleagues investigating the use of bacteria to clean up uranium-contaminated groundwater.