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The ocean contains uranium with an approximate concentration of 3.34 ppb, which can serve as an incredible supply source to sustain nuclear energy in the United States. Unfortunately, technology currently available to recover uranium from seawater is not efficient enough and mining uranium on land is still more economical. We have developed polymer-based adsorbents with high uranium adsorption capacities by grafting amidoxime onto high-surface-area polyethylene (PE) fibers. Various process conditions have been screened, in combination with developing a rapid testing protocol (

The Pacific Northwest National Laboratory (PNNL) is evaluating the performance of adsorption materials to extract uranium from natural seawater. Testing consists of measurements of the adsorption of uranium and other elements from seawater as a function of time using flow-through columns and a recirculating flume to determine adsorbent capacity and adsorption kinetics. The amidoxime-based polymer adsorbent AF1, produced by Oak Ridge National Laboratory (ORNL), had a 56-day adsorption capacity of 3.9 ± 0.2 g U/kg adsorbent material, a saturation capacity of 5.4 ± 0.2 g U/kg adsorbent material, and a half-saturation time of 23 ± 2 days. The ORNL AF1 adsorbent has a very high affinity for uranium, as evidenced by a 56-day distribution coefficient between adsorbent and solution of log KD,56day = 6.08. Calcium and magnesium account for a majority of the cations adsorbed by the ORNL amidoxime-based adsorbents (61% by mass and 74% by molar percent), uranium is the fourth most abundant element adsorbed by mass an...

High-surface-area amidoxime and carboxylic acid grafted polymer adsorbents developed at Oak Ridge National Laboratory were tested for sequestering uranium in a flowing seawater flume system at the PNNL-Marine Sciences Laboratory. FTIR spectra indicate that a KOH conditioning process is necessary to remove the proton from the carboxylic acid and make the sorbent effective for sequestering uranium from seawater. The alkaline conditioning process also converts the amidoxime groups to carboxylate groups in the adsorbent. Both Na2CO3–H2O2 and hydrochloric acid elution methods can remove ∼95% of the uranium sequestered by the adsorbent after 42 days of exposure in real seawater. The Na2CO3–H2O2 elution method is more selective for uranium than conventional acid elution. Iron and vanadium are the two major transition metals competing with uranium for adsorption to the amidoxime-based adsorbents in real seawater. Tiron (4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt, 1 M) can remove iron from the adsorben...

Poly(acrylamidoxime) fibers are the current state of the art adsorbent for mining uranium from seawater. While the acid dissociation constants, pKa, of characteristic amidoxime and carboxylate ligands have been reported in the literature, the proton affinity distribution of the poly(acrylamidoxime) fiber is yet to be established. Herein, we report the poly(acrylamidoxime) proton affinity distribution between pH 2 and pH 10 via the stable numerical solution of the adsorption integral equation using splines (SAIUS) algorithm. Two peaks in the proton affinity distribution of poly(acrylamidoxime) were observed: the neutral to anionic dissociation of the carboxylate monomer between pH 3.2 and pH 4.4 (pKa ≈ 4.0) and the protonated to neutral dissociation of the acyclic amidoxime monomer between pH 5.6 and pH 6.8 (pKa ≈ 6.1). The acidity constants obtained for the carboxylate and amidoximate monomers vary from the acidity constants of acetic acid and acetamidoxime, respectively. These variations in acidity can b...

Extraction of uranium (U) from seawater for use as a nuclear fuel is a significant challenge due to the low concentration of U in seawater (∼3.3 ppb) and difficulties to selectively extract U from the background of major and trace elements in seawater. The Pacific Northwest National Laboratory (PNNL)’s Marine Sciences Laboratory (MSL) has been serving as a marine test site for determining performance characteristics (adsorption capacity, adsorption kinetics, and selectivity) of novel amidoxime-based polymeric adsorbents developed at Oak Ridge National Laboratory (ORNL) under natural seawater exposure conditions. This manuscript describes the performance of three formulations (38H, AF1, AI8) of amidoxime-based polymeric adsorbents produced at ORNL in MSL’s ambient seawater testing facility. The adsorbents were produced in two forms, fibrous material (40–100 mg samples) and braided material (5–10 g samples), and exposed to natural seawater using flow-through columns and recirculating flumes. All three formu...

A new family of high-surface-area polyethylene fiber adsorbents named the AF series was recently developed at the Oak Ridge National Laboratory (ORNL). The AF series adsorbents were synthesized by radiation-induced graft polymerization of acrylonitrile and itaconic acid (at different monomer/comonomer mol ratios) onto high surface area polyethylene fibers. The degree of grafting (%DOG) of AF series adsorbents was found to be 154–354%. The grafted nitrile groups were converted to amidoxime groups by treating with hydroxylamine. The amidoximated adsorbents were then conditioned with 0.44 M KOH at 80 °C followed by screening at ORNL with sodium-based synthetic aqueous solution, spiked with 8 ppm uranium. The uranium adsorption capacity in simulated seawater screening ranged from 170 to 200 g-U/kg-ads irrespective of %DOG. A monomer/comonomer molar ratio in the range of 7.57–10.14 seemed to be optimum for highest uranium loading capacity. Subsequently, the adsorbents were also tested with natural seawater at ...

A high-surface-area polyethylene-fiber adsorbent (AF160-2) has been developed at the Oak Ridge National Laboratory by radiation-induced graft polymerization of acrylonitrile and itaconic acid. The grafted nitriles were converted to amidoxime groups by treating with hydroxylamine. The amidoximated adsorbents were then conditioned with potassium hydroxide (KOH) by varying different reaction parameters such as KOH concentration (0.2, 0.44, and 0.6 M), duration (1, 2, and 3 h), and temperature (60, 70, and 80 °C). Adsorbent screening was then performed with simulated seawater solutions containing sodium chloride and sodium bicarbonate, at concentrations found in seawater, and uranium nitrate at a uranium concentration of ∼7–8 ppm and pH 8. Fourier transform infrared spectroscopy and solid-state NMR analyses indicated that a fraction of amidoxime groups was hydrolyzed to carboxylate during KOH conditioning. The uranium adsorption capacity in the simulated seawater screening solution gradually increased with co...

Oxidation catalysts in emissions control systems generally contain Pd/Pt and require exhaust temperatures above 200 °C to operate, but under low-temperature conditions, oxidation of CO and hydrocarbons are challenging. As engine efficiency improves and exhaust temperature decreases, there is an increasing demand for high emissions control performance at low temperatures. Therefore, it becomes imperative to design new catalysts that are active at low operating temperatures. Au–CuOx catalysts, made through the oxidation of AuCu alloy nanoparticles, have been found to be highly active for the oxidation of CO at low reaction temperatures. The catalytic activity for the conversion of CO using Au–CuOx/SiO2 was evaluated under simulated lean exhaust conditions (CO, C3H6, NO, H2O, O2 and Ar). It was found that the oxidation of CO over the Au–CuOx/SiO2 catalyst was inhibited when C3H6 or NO was introduced into the reaction stream. Interestingly, a physical mixture of Au–CuOx/SiO2 and Pt/Al2O3 worked in synergy to enhance the oxidation of NO to NO2 with 90% conversion near 300 °C in the presence of CO. This reactivity is on par with Pt/Al2O3 NO oxidation activity in the absence of CO. The Au–CuOx/SiO2 catalysts were also found to be thermally stable after being aged up to 700 °C for 10 h. The resistance to particle sintering can be attributed to the CuOx “anchoring” the Au particles to the silica support.

Uranium recovery from seawater has been investigated for several decades for the purpose of securing nuclear fuel for energy production. In this study, field column experiments have been performed at the Marine Sciences Laboratory of the Pacific Northwest National Laboratory (PNNL) using a laboratory-proven, amidoxime-based polymeric adsorbent developed at the Oak Ridge National Laboratory (ORNL). The adsorbent was packed either in in-line filters or in flow-through columns. The maximum amount of uranium uptake from seawater was 3.3 mg of U/g of adsorbent after 8 weeks of contact between the adsorbent and seawater. This uranium adsorption amount was about 3 times higher than the maximum amount achieved in this study by a leading adsorbent developed at the Japan Atomic Energy Agency (JAEA). Both adsorbents were tested under similar conditions. The results were used to update an assessment of the cost of large-scale recovery of uranium from seawater using the ORNL adsorbent. The updated uranium production c...

A novel adsorbent preparation method using atom-transfer radical polymerization (ATRP) combined with radiation-induced graft polymerization (RIGP) was developed to synthesize an adsorbent for uranium recovery from seawater. The ATRP method allowed a much higher degree of grafting on the adsorbent fibers (595–2818%) than that allowed by RIGP alone. The adsorbents were prepared with varied compositions of amidoxime groups and hydrophilic acrylate groups. The successful preparation revealed that both ligand density and hydrophilicity were critical for optimal performance of the adsorbents. Adsorbents synthesized in this study showed a relatively high performance (141–179 mg g−1 at 49–62% adsorption) in laboratory screening tests using a uranium concentration of ∼6 ppm. This performance is much higher than that of known commercial adsorbents. However, actual seawater experiment showed impeded performance compared to the recently reported high-surface-area-fiber adsorbents, due to slow adsorption kinetics. The impeded performance motivated the investigation of the effect of hydrophilic block addition on the graft chain terminus. The addition of a hydrophilic block on the graft chain terminus nearly doubled the uranium adsorption capacity in seawater, from 1.56 mg g−1 to 3.02 mg g−1. The investigation revealed the importance of polymer chain conformation, in addition to the ligand and hydrophilic group ratio, for advanced adsorbent synthesis for uranium recovery from seawater.

Polymer-coated mesoporous carbon nanocomposites were prepared from the immobilization of acrylonitrile and acrylic acid copolymers with divinylbenzene as a crosslinker onto a mesoporous carbon framework. High surface areas were maintained after polymerization with accessible porosity. This functional nanocomposite was tested as an adsorbent for uranium from high salinity solutions. Uranium adsorption results have shown that the adsorption capacities are strongly influenced by the density of the amidoxime groups and the specific surface area.

Supported AuCu and AuCuPd catalysts were synthesized through the diffusion of Pd and Cu into Au nanoparticle seeds. When supported on SiO2, the AuCuPd nanoparticles were found to be the most active for the oxidation of CO after being exposed to reductive pretreatment conditions as opposed to oxidative pretreatment conditions. In contrast, AuCu/SiO2 was found to be more active for CO oxidation after the alloy phase was segregated into a Au–CuO x heterostructure. In situ XRD and EXAFS were used to monitor the structural changes of AuCu and AuCuPd catalysts as they were subjected to different pretreatment conditions.

A laboratory study of uranium uptake from seawater has been conducted using batch and flow-through recycling experiments. Uranium adsorption from seawater, using amidoxime-based polymeric adsorbents, has been described by transport and kinetic models under the assumption of transport-limited or reaction-limited process for batch adsorption experiments. Mathematical models based on liquid film mass transfer, diffusion, or reaction kinetics have been evaluated in terms of the Sherwood number and the Thiele modulus to provide insight into the limiting mechanism. The value of the Sherwood number suggests that the external mass-transfer resistance is much smaller than the intraparticle diffusion resistance. The Thiele modulus was estimated on the basis of the rate constants from independent batch tests analyzed by a reaction kinetic model, and its value suggests that the uranium binding is the rate-limiting step compared to diffusion. The uranium uptake in batch experiments reached 4 mg U/g adsorbent over a pe...

The recovery of uranium (U) from seawater has been investigated for over six decades in efforts to secure uranium sources for future energy production. The majority of the research activities have focused on inorganic materials, chelating polymers, and nanomaterials. Previous studies of uranium adsorption from aqueous solutions, mainly seawater, are reviewed here with a focus on various adsorbent materials, adsorption parameters, adsorption characterization, and marine studies. Continuous progress has been made over several decades, with adsorbent loadings approaching 3.2 mg U/g adsorbent in equilibrium with seawater. Further research is needed to improve first, the viability including improved capacity, selectivity, and kinetics, and second, the sorbent regeneration for multicycle use. An overview of the status of the uranium adsorption technology is provided and future research needs to make this technology commercially competitive are discussed.

Amidoxime-based polymer adsorbents have attracted interest within the last decade due to their high adsorption capacities for uranium and other rare earth metals from seawater. The ocean contains an approximated 4–5 billion tons of uranium and even though amidoxime-based adsorbents have demonstrated the highest uranium adsorption capacities to date, they are still economically impractical because of their limited recyclability. Typically, the adsorbed metals are eluted with a dilute acid solution that not only damages the amidoxime groups (metal adsorption sites), but is also not strong enough to remove the strongly bound vanadium, which decreases the adsorption capacity with each cycle. We resolved this challenge by incorporating Le Chatelier's principle to recycle adsorbents indefinitely. We used a solution with a high concentration of amidoxime-like chelating agents, such as hydroxylamine, to desorb nearly a 100% of adsorbed metals, including vanadium, without damaging the metal adsorption sites and preserving the high adsorption capacity. The method takes advantage of knowing the binding mode between the amidoxime ligand and the metal and mimics it with chelating agents that then in a Le Chatelier's manner removes metals by shifting to a new chemical equilibrium. For this reason the method is applicable to any ligand–metal adsorbent and it will make an impact on other extraction technologies.

The selective oxidation of ethanol with molecular O2 is increasingly becoming an important process to develop fine chemicals because it can be obtained from renewable biomass feedstock while reducing the demand on fossil fuels. We have synthesized silica-supported Au–Cu alloy nanoparticles, and through an oxidative dealloying process, we have developed Au–CuOx hybrid catalysts for the selective oxidation of ethanol into acetaldehyde. Using a combination of XRD, XPS, and HR-STEM experiments, we have confirmed that the active catalyst is a Au core with a thin CuOx shell. Oxidation of the AuCu/SiO2 alloy catalyst at 300 °C was found to produce the most active and stable catalyst for ethanol conversion (∼90%) with the highest selectivity (∼80–90%) at a reaction temperature of 200 °C for 50 h on-stream. TEM and XRD results show that Au–CuOx/SiO2 catalysts calcined at 300 and 500 °C are also more resistant to sintering during pretreatment and catalytic conditions than pure gold supported on silica. Furthermore,...

A series of novel thiazolium-bis(triflamide) based ionic liquids has been synthesized and characterized. Physicochemical properties of the ionic liquids such as thermal stability, phase transitions, and infrared spectra were analyzed and compared to the imidazolium-based congeners. Several unique classes of ancillary substitutions are examined with respect to impacts on overall structure, in addition to their carbon dioxide absorption properties in supported ionic-liquid membranes for gas separation.

Fatty acid synthase (FAS) is necessary for growth and survival of tumor cells and is a promising drug target for oncology. Here, we report on the syntheses and activity of novel inhibitors of the thioesterase domain of FAS. Using the structure of orlistat as a starting point, which contains a beta-lactone as the central pharmacophore, 28 novel congeners were synthesized and examined. Structural features such as the length of the alpha- and beta-alkyl chains, their chemical composition, and amino ester substitutions were altered and the resulting compounds explored for inhibitory activity toward the thioesterase domain of FAS. Nineteen congeners show improved potency for FAS in biochemical assays relative to orlistat. Three of that subset, including the natural product valilactone, also display an increased potency in inducing tumor cell death and improved solubility compared to orlistat. These findings support the idea that an orlistat congener can be optimized for use in a preclinical drug design and for clinical drug development.

This report describes work on the successful completion of Milestone M2FT-15OR0310041 (1/30/2015) entitled, Demonstrate braided material with 3.5 g U/kg sorption capacity under seawater testing condition . This effort is part of the Seawater Uranium Recovery Program, sponsored by the U.S. Department of Energy, Office of Nuclear Energy, and involved the development of new adsorbent braided materials at the Oak Ridge National Laboratory (ORNL) and marine testing at the Pacific Northwest National Laboratory (PNNL). ORNL has recently developed four braided fiber adsorbents that have demonstrated uranium adsorption capacities greater than 3.5 g U/kg adsorbent after marine testing at PNNL. The braided adsorbents were synthesized by braiding or leno weaving high surface area polyethylene fibers and conducting radiation-induced graft polymerization of itaconic acid and acrylonitrile monomers onto the braided materials followed by amidoximation and base conditioning. The four braided adsorbents demonstrated capacity values ranging from 3.7 to 4.2 g U/kg adsorbent after 56 days of exposure in natural coastal seawater at 20 oC. All data are normalized to a salinity of 35 psu.

This report describes work on the successful completion of Milestone M2FT-14OR03100115 (8/20/2014) entitled, “Complete new adsorbent materials for marine testing to demonstrate 4.5 g-U/kg adsorbent”. This effort is part of the Seawater Uranium Recovery Program, sponsored by the U.S. Department of Energy, Office of Nuclear Energy, and involved the development of new adsorbent materials at the Oak Ridge National Laboratory (ORNL) and marine testing at the Pacific Northwest National Laboratory (PNNL). ORNL has recently developed two new families of fiber adsorbents that have demonstrated uranium adsorption capacities greater than 4.5 g-U/kg adsorbent after marine testing at PNNL. One adsorbent was synthesized by radiation-induced graft polymerization of itaconic acid and acrylonitrile onto high surface area polyethylene fibers followed by amidoximation and base conditioning. This fiber showed a capacity of 4.6 g-U/kg adsorbent in marine testing at PNNL. The second adsorbent was prepared by atom-transfer radical polymerization of t-butyl acrylate and acrylonitrile onto halide-functionalized round fibers followed by amidoximation and base hydrolysis. This fiber demonstrated uranium adsorption capacity of 5.4 g-U/kg adsorbent in marine testing at PNNL.

Uranium adsorbed on amidoxime-based polyethylene fiber in simulated seawater can be quantitatively eluted at room temperature using 1 M Na2CO3 containing 0.1 M H2O2. This efficient elution process is probably due to the formation of an extremely stable uranyl-peroxo-carbonato complex in the carbonate solution. After washing with water, the sorbent can be reused with minimal loss of uranium loading capacity. Possible existence of this stable uranyl species in ocean water is also discussed.

The reaction of benzyl 3-formylpiperidine-1-carboxylate and aryl hydrazines under standard Fisher Indole conditions followed by reductive work-up affords azepino[3,4b]indoles in moderate to good yields. The products are proposed to be derived via a Plancher rearrangement [(a) Plancher, G. Gazz. Chim. Ital. 1898, 28, II, 374; (b) Plancher, G. Atti. Accad. Lincei 1900, 9, 5, 115; (c) Boyd-Barrett, H. S. J. Chem. Soc. 1932, 321].

Aryl hydrazines react with formyl-substituted saturated N-heterocycles to form fused indoles after reductive work-up.

Transition state theory fails to accurately predict the selectivity in an example where it is ubiquitously invoked, hydroboration. The hydroboration of terminal alkenes with BH(3) is moderately regioselective, affording an 88:12-90:10 ratio of anti-Markovnikov/Markovnikov adducts. High-level ab initio calculations predict too large of an energy difference between anti-Markovnikov and Markovnikov transition structures to account for the observed product ratio, and consideration of calculational error, solvent, tunneling, and entropy effects does not resolve the discrepancy. Trajectory studies, however, predict well the experimental selectivity. The decreased selectivity versus transition state theory arises from the excess energy generated as the BH(3) interacts with the alkene, and the observed selectivity is proposed to result from a combination of low selectivity in direct trajectories, moderate RRKM selectivity, and high selectivity after thermal equilibration.

Concise syntheses of orlistat (Xenical), a two-carbon transposed orlistat derivative, and valilactone are described that employ the tandem Mukaiyama aldol-lactonization (TMAL) process as a key step. This process allows facile modification of the alpha-side chain. Versatile strategies for modifying the delta-side chain are described, involving cuprate addition and olefin metathesis. Comparative antagonistic activity of these derivatives toward a recombinant form of the thioesterase domain of fatty acid synthase is reported along with comparative activity-based profiling.

Brown's DCME reaction was successfully performed employing B-alkyl-9-oxa-10-borabicyclo[3.3.2]decanes (1) to provide carboxylic acids (2) in good to excellent yields with complete retention of configuration.

A series of 1,2,4-triazolium-based ionic liquids have been synthesized and evaluated for their use in supported ionic liquid membrane based CO2 separations. The properties of these triazolium-based compounds have proven sensitive to isomeric substitutions, such as isopropyl and propyl groups, as well as ortho and para substitutions in the aryl derivative compounds. While physical properties such as viscosity did not vary significantly between structural isomers, the CO2 permeability, selectivity, and solubility exhibited significant changes allowing for development of task-specific triazolium-based ionic liquids for separation applications. COSMOtherm studies were also completed to gain a better understanding of the ionic liquids which demonstrated a strong correlation between experimental and computational values for the alkyl bearing ionic liquids. Hence, 1,2,4-triazolium-based liquids comprise a class of compounds offering unique opportunities to examine how structural changes affect the physicochemical properties which are necessary for the continuous development of ionic liquids with enhanced adsorption capacity and selectivity in separations.

Irradiation-induced co-grafting of acrylonitrile and vinylsulfonic acid (or vinylphosphonic acid) monomers on polyethylene fiber was studied for the heterogeneous catalysis of fructose dehydration into 5-hydroxymethylfurfural (HMF) solely in water. The acidic co-polymer exhibited excellent catalytic activity and maintained a high yield after being regenerated. We attribute these catalytic properties to a branched environment created by grafted chains, hydrophilic enough to interact with fructose in water but collectively dense enough to form a unique local phase mimicking organic solvents.

Hierarchical nanoporous nitrogen-doped carbons were prepared from task specific ionic liquids having a bis-imidazolium motif linked with various organic groups. While ethyl chains linking the imidazolium ions afforded microporous-mesoporous carbons, long or aromatic groups resulted in microporous samples.