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Herein, copper perrhenate (Cu(ReO4)2) was synthesized using a micro-emulsion method and adhered to graphene (Gr) using an ultrasonic process. Then, the as-prepared Cu(ReO4)2/Gr composite was added into the synthetic oil as a lubricant additive with the help of ionic liquid to achieve enhanced dispersion stability within the base oil. The tribological performances of the Cu(ReO4)2/Gr additive were investigated using four-ball tests and the ball-on-disk reciprocating configuration under various temperatures. The potential lubrication mechanisms of the Cu(ReO4)2/Gr additive were performed using a series of characterization methods including XRD, Raman, SEM-EDS, TEM, DSC/TG, and XPS. The results of four-ball tests at room temperature indicated that the Cu(ReO4)2/Gr additive could substantially improve the tribological performances of the base oil. The smallest coefficient of friction (COF) and wear scar diameter (WSD) values were 0.068 and 495 μm, respectively, when 0.05 wt% of Cu(ReO4)2/Gr was added. Additionally, the graphene accelerated friction-induced heat transfer, which led to decreased friction and wear. The results of reciprocating friction experiments at elevated temperatures revealed that the Cu(ReO4)2/Gr additive had excellent friction-reduction properties when the temperature was high. This could be attributed to the generation of a protective layer containing tribo-oxides from the alloy, some residual carbides and copper perrhenate induced by friction heat and stress. This protective layer was uniformly and stably covered on the worn surface, which could effectively alleviate direct contact between the rubbing pair.

The corrosion characteristics of thin coatings (5 µm) with binary and ternary alloys CoW, CoRe, CoWRe, obtained from poly-ligated citrate-pyrophosphate electrolyte, depending on the concentration of potassium perrhenate, were investigated. The methods of impedance spectroscopy and voltammetry have shown that the most corrosion-resistant coatings were obtained with a current density of 10 mA·cm−2. The largest value of corrosion resistance and microhardness is inherent in the CoWRe alloy and is 3.2 kΩ·cm2 in 1 M KOH solution and 644 HV. It has been found that an increase in the rhenium content in the alloy results in an increase in the current efficiency (CE) during the precipitation of the alloy from the alkaline citrate-pyrophosphate electrolyte and CE reaches 84%.

In this article, nano-sized calcium perrhenate was prepared using the microemulsion reaction method. By the aid of surfactant, the calcium perrhenate was suspended in pentaerythritol ester base oil to serve as a lubricating additive. The tribological performances of the oil containing calcium perrhenate at elevated temperatures were investigated by four-ball tests and ball-on-disk reciprocating sliding tests. The underlying lubricating mechanism of the calcium perrhenate additive was explored using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, differential scanning calorimetry/thermogravimetry, Raman spectroscopy, and X-ray photoelectron spectroscopy. The four-ball test results indicated that the oil containing calcium perrhenate featured lower friction coefficients, smaller wear scar diameters, and lower temperature rising performance than the base oil under an applied load of 392 N. The optimum lubricating property was obtained when the additive was at a concentration of 0.05 wt%. The tribological performance in a wide temperature range results showed that the friction coefficients of the oil containing calcium perrhenate were slightly lower than those of the base oil at a relatively low temperature range, and decreased as the temperature increased within a high range. The improved tribological performances owed to the formation of a protective layer, which consisted of the shear-susceptible calcium perrhenate additive as well as some native metal oxides that enhanced the layer carrying capacity during rubbing after chemical degradation of base oil. This protective layer acted as a barrier between the rubbing surfaces, preventing them from directly contacting each other at elevated temperatures.

A polyligand citrate-pyrophosphate electrolyte is proposed, which makes it possible to obtain uniform bright coatings containing 15–40 at.% Re and 10–4 at.% W and a current efficiency of up to 93% depending on the concentration of potassium perrhenate in the solution. The dependence of the chemical composition, current efficiency and morphology of ternary electrolytic alloys CoWRe on the electrolyte components and the electrolysis conditions is presented. The coatings obtained are fine-crystalline and X-ray amorphous and have a high microhardness of 574–788 HV.

Counterions have a significant effect on the efficiency of the deoxydehydration (DODH) reaction. Four perrhenate salts, Z+ReO4− (Z = Na+, K+, NH4+, and Bu4N+), were tested in the DODH reaction of a vicinal diol in the presence of PPh3 as the reductant. In addition, a new perrhenate salt, (2-ppyH)[ReO4] (2-ppyH+ = 2-phenylpyridinium cation), has been synthesized and characterized by X-ray crystallography and utilized as an efficient catalyst in the DODH reaction. Since so far computational studies related to the influence of the counterion in the different steps of the DODH mechanism are scarce, we have carried out a comparative investigation of the counterion effect using density functional theory (DFT) calculations. The DODH mechanism of the conversion of phenyl-1,2-ethanediol to styrene in the presence of the five perrhenate salts mentioned above, as well as bare perrhenate (ReO4−) was studied from an energetic point of view. The catalytic tests and concomitant DFT computations confirmed the general mechanistic aspect in which the counterion plays an active role in all stages of the reaction mechanism including intermediate structures, Gibbs free energy changes (ΔG°g and ΔG°sol), transition states, and activation barrier energies. The role of counterion type has been considered in three key steps of the reaction mechanism, including the proton-transfer from diol to oxo-ligand in the rhenium moiety, the nucleophilic attack of the P atom from PPh3 on the oxo-ligand, the dissociation of the OPPh3 ligand, and the olefin extrusion from the Re(V)-diolate intermediate for each perrhenate salt. The crucial roles played by the counterion in terms of structure arrangement during transition states and the activation energy barriers are finally discussed.

Technetium-99 (99Tc) is a major contaminant at nuclear power plants and several US Department of Energy sites. Its most common aqueous species, pertechnetate (TcO4-), is very mobile in the environment, and currently there are no effective technologies for its sequestration. In this work, a porous iron (pFe) material was investigated for TcO4- and perrhenate (ReO4-) sequestration from artificial groundwater. The pFe was significantly more effective than granular iron for both TcO4- and ReO4- sequestration under oxic conditions. The Tc removal capacity was 27.5 mg Tc/g pFe at pH ˜6.8, while the Re removal capacity was 23.9 mg Re/g pFe at pH ˜10.6. Tc K-edge XANES and EXAFS analyses indicated that the removed Tc species was 70-80% Tc(IV) that was likely incorporated into Fe corrosion products (i.e., Fe(OOH), Fe3O4) and 20-30% unreduced TcO4-. In contrast, the removed Re species was ReO4- only, without detectable Re(IV). In addition, the sequestered ReO4- was not extracted (

A novel (CuII/ReVII)-heterobimetallic complex based on l -Arginine, namely trans-[Cu( l -Arg)2(ReO4)2] (CuLARe), was successfully synthesized and fully characterized using X-ray structure analysis as well as (IR/UV–vis) spectroscopy, molar conductivity and (TG/DTA) thermal methods. The crystal structure determination reveals that CuLARe has a non-symmetrical atomic arrangement and features striking helical chains of {[Cu( l -Arg)2(ReO4)2]}n, which are further assembled into a 3D-supramolecular network through multidirectional N(C, O)-H⋯O hydrogen bonding interactions. Analysis by Hirshfeld surface generation in combination with 2D-fingerprinting was also performed to elucidate the nature of the interactions and their contributions towards the crystal packing. Moreover, a comparative antioxidant screening of CuLARe with the free ligands as well as CuCl2 has been investigated. The results emphasize that the complexation of ligands to the metal ions plays a crucial role in the improvement of the biochemical properties of CuLARe.

The standard (p° = 0.1 MPa) molar enthalpies of sublimation, at 298.15 K, of methyltrioxorhenium(VII), Δ sub H m o [CH3ReO3] = 70.2 ± 0.4 kJ mol−1, and dirhenium decacarbonyl, Δ sub H m o [Re2(CO)10] = 97.4 ± 0.9 kJ mol−1, corresponding to well characterized crystalline phases, were determined by Calvet microcalorimetry. These results, along with structural information obtained in this work by single crystal X-ray diffraction for CH3ReO3, or previously reported for Re2(CO)10, tetramethylammonium perrhenate(VII), [N1111][ReO4], and hexamethylrhenium(VI), Re(CH3)6, were used to extend our previously developed all-atom force field for organometallic compounds, to rhenium species. The new parametrization was able to reproduce the enthalpies of sublimation and unit cell parameters of the test set with maximum absolute deviations of 3.3 kJ⋅mol−1 and

Rhenium and molybdenum are valuable metals present in the earth's crust in very low concentration and are increasingly used in industry thanks to their multiple properties, but due to the harmful aspects of the production process, there is a need to develop systems of concentration or purification of salts of these elements. For this work a PEG/Na2MoO4 aqueous two phase system (ATPS) was used for the partition of ReO4- anion. By using a central composite design, the effects of PEG concentration, sodium molybdate concentration, temperature, pH and their possible interaction on the partition coefficient were studied, also to estimate the optimal configuration of the factors that influence the process. At the same time, experimental density, sound velocity and isentropic compressibility were also obtained for top and bottom phases. The results showed that the optimal conditions for the partition of ReO4− anion using the ATPS formed by PEG and Na2MoO4 were 14.7 wt% PEG 4000, 16.3 wt% Na2MoO4, 35 °C and pH 6. For these conditions, the partition coefficient (K) obtained was up to 17.8 ± 0.78. The order of factors with high significance on the partition coefficient was: Na2MoO4 concentration > PEG concentration > temperature > pH > interaction between Na2MoO4 and PEG concentrations; the effect of these parameters mainly is related with the speciation, salting-out effect and hydrophobicity. The influence of these factors on the density, and sound velocity of the top phase was minimal, unlike its influence on the properties of the bottom phase, not isentropic compressibility and effect of PEG and Na2MoO4 concentrations on sound velocity. The evaluation of the partitioning behavior was made by experimental design, applying statistical regression analysis and analysis of variance (ANOVA). The statistical models for partition coefficient and for phase densities (and the other properties) as function of parameters with significant effects were obtained, and also a good correlation between experimental and correlated data was observed (R-Squared = 0.9379, ReO4− partition coefficient; 0.9882, bottom phase; and 0.9836 upper phase). This work is oriented to the possible application in stripping of a top phase provided for a co-extraction of rhenium and molybdenum by ATPS in acidic media or in solutions with high contend of Mo such as those provided by pressure oxidative leaching of molybdenite in basic media.

The single extraction of rhenium(VII) and uranium(VI) from nitric acid solution by dicyclohexano-18-crown-6 (DCH) solutions was investigated. The extraction of Re(VII), in the form of perrhenate (ReO4−) anion, was optimum for a nitric acid concentration of 3 M and was explained by the ion-pair extraction of perrhenate anions by the hydroxonium DCH complex. The stoichiometry of the Re(VII) complex was obtained from the distribution data by slope analysis and the extracted specie was identified as {ReO4−(DCH-H3O)+}. The uranyl extraction by DCH solutions was evaluated under the same conditions and the extracted specie was identified as {(NO3−)2(DCH-UO22+)} for a nitric acid concentration above 5 M. The extraction of rhenium(VII) from nitric acid solution by DCH solutions in the presence of large excess of uranium(VI) was then investigated. For a nitric acid concentration of 3 mol/L, the extraction efficiency of perrhenate was found to be almost independent of uranium concentration. Based on the chemical similarities between Re(VII) and Tc(VII), this suggests that DCH could be considered for the separation of technetium (VII)/uranium(VI) from nitric acid solution.

Technetium (99Tc), as a radionuclide produced by the fission of enriched uranium, poses a significant threat to human being due to its long half-life and radioactive toxicity. Therefore, developing highly-efficient functional materials that can rapidly and selectively capture 99Tc is of great significance. In this work, rhenium (Re) was employed as a surrogate of 99Tc, and a mesoporous hybrid anion exchanger with silica framework (SiPyR-N4) was studied for its removal from the simulated groundwater. As the results, SiPyR-N4 exhibited unique advantages over traditional commercial organic resins, including large bulk density in solution (0.56 g/ml), extremely fast adsorption kinetics ( O bonding. Even in the simulated groundwater rhenium was also eliminated completely after flowing through the chromatographic extraction column packed with SiPyR-N4. In general, the research not only exhibited an excellent material that can remove low-level rhenium (surrogate of radioactive technetium) from natural water effectively and efficiently, but also provide a new sight for the synthesis or improvement of ion exchange resin.

The synthesis, structures, and characterization of two new families of trivalent lanthanide perrhenate complexes, [Ln(ReO4)(H2O)4Cl]Cl·H2O (Ln = La – Nd) (1) and [Ln(ReO4)3(H2O)2] (Ln = Tb, Ho, Er) (2), along with the expansion of a third known family, [Ln(ReO4)3(H2O)4] (Ln = Tm, Lu, Y) (3), is presented. Complex 1 is a purely inorganic member of a rare class of compounds known as cationic materials. Single crystal X-ray diffraction analysis reveals that 1 crystallizes in the P21/m space group and is comprised of two-dimensional (2D) sheets constructed from LnO4(H2O)4Cl monocapped square antiprismatic (CN = 9) lanthanide cations, 2 crystallizes in the C2 space group and is a three-dimensional (3D) structure constructed from two unique LnO6(H2O)2 square antiprismatic (CN = 8) lanthanide cations, and 3 crystallizes in the P21/n space group and is comprised of one-dimensional chains constructed from LnO4(H2O)4 square antiprismatic (CN = 8) lanthanide cations. This work provides a comprehensive study on essentially the entire lanthanide series (sans Pm) and its complexation with perrhenate at room temperature. The structural features of these complexes exhibit properties influenced by contracting ionic radii and increasing hardness upon traversing the lanthanide series.

Fluorescent sensor for the perrhenate/pertechnetate anions in aqueous media are rarely reported in literature as their large size and low charge density poses great challenge to their detection. Herein, we report the first fluorescent turn-on ratiometric sensor for perrhenate anion, exploiting its weak hydration property which leads to an advantageous formation of a contact ion-pair of perrhenate anion with a well-known cationic ultrafast molecular rotor dye, Auramine O. This ion-pair formation, in turn, leads to a fluorescent aggregate assembly that provides an excellent opportunity to detect perrhenate anion in aqueous solution.

As an analog of technetium (99Tc), rhenium (Re) was incorporated into the tin oxide (SnO2) lattice structure to produce a stable phase. This new bi-metallic oxide consisting of Re4+ and Sn4+ was formed from perrhenate (ReO4−) reduction by tin (Sn2+) and could reduce re-oxidation. After the precipitate was characterized by various techniques, the precipitate morphology and XRD patterns were found to resemble those of cassiterite (SnO2) with narrow crystallite size (Daverage = ∼1.47 nm). The local structure of the precipitate was characterized as Re–O (∼2.02 nm), Re–Sn (∼3.15 nm), and Re–Sn (∼3.70 nm) in the first, second, and third coordination shells, respectively. As Re4+ was doped into the cassiterite phase, the precipitate was much less soluble than α-ReO2 (dissolved Re = ∼0.10 mg L−1 vs. ∼45.20 mg L−1). The precipitate resisted re-oxidation, and the dissolved Re species were re-precipitated after 23 h. A major portion of Re dissolved during the solubility and re-oxidation tests was assigned to the species of Re+1 (12%), Re2+ (47.42%), Re4+ (28.48%), and Re7+ (12.18%) on the surface of precipitate, while Re+1 (1.05%), Re2+ (15.35%), Re5+ (27.77%), and Re7+ (55.82%) species were found on the α-ReO2 surface. These findings suggest that low-temperature reductive co-precipitation can incorporate 99Tc (or Re) into the SnO2 structure which limit the 99Tc (or Re) re-oxidation and solubility.

Several new solid oxo-rhenium and oxo-molybdenum catalysts were tested for the deoxydehydration (DODH) of 1,2-diols to terminal olefins employing aromatic solvents and reaction temperatures of 150–200 °C. A catecholato oxo-rhenium catalyst tethered to silica was prepared and found to have comparably high DODH activity to its soluble analog with triphenylphosphine as the reductant. Catalyst re-use and leach-test experiments show significant leaching into the liquid phase. Silica, ceria and, for the first time, alumina and iron oxide were tested as supports for perrhenate, with ceria producing the least active material in 1,2-decane diol DODH. Decene yields obtained with ReOx/SiO2, ReOx/Fe2O3, ReOx/Al2O3 were highest when triphenylphosphine was the reductant and reached 70 − 78% (at 90–100% conversion) at 150 °C. These three catalysts were also effective with gaseous reductants H2 or CO. Leaching of rhenium species occurred for all supports and was most pronounced for SiO2. New solid oxo-molybdenum catalysts were synthesized. At 200 °C, decene yields observed using MoOx/Fe2O3, MoOx/SiO2, MoOx/Al2O3, MoOx/TiO2 and MoOx/ZrO2 were comparable and did not exceed 20%. There were homogeneous contributions through leached molybdenum species.

The preparation, characteristics and adsorption properties of novel porous carbon-ceramic composite microspheres are presented. The composites were synthesised by a simple ion exchange process involving the cationic Zr tetramer and commonly-available macroporous sulphonated polystyrene-divinylbenzene cation exchange resins, with subsequent carbothermal reduction at 1350 °C. The materials were extensively characterised with respect to composition, chemical structure and porosity. Carbothermal reduction of the Zr-loaded templates resulted in formation of crystallites of the MAX phase zirconium sulphide carbide (Zr 2 SC) embedded within a highly microporous carbon framework with a macroporous secondary structure inherited from the resin template. Despite the high BET surface areas of the Zr 2 SC-carbon composite microspheres (in some cases, greater than 600 m 2 g −1 ), they are extremely mechanically robust. The microspheres displayed high adsorption selectivity for oxoanions relative to cationic solution species, including perrhenate (ReO 4 − ), a pertechnetate (TcO 4 − ) surrogate. Accumulation of ReO 4 − on the Zr 2 SC particles was unequivocally demonstrated by elemental mapping. Such materials are potential candidates as combined 99 Tc sorbents and reusable transmutation hosts.

A newly designed Ru(II) probe, C1 containing iodotriazole (halogen bond unit) and pendent pentafluorophenyl (π-acidic) moiety shows superior dihydrogen phosphate sensing property over perrhenate and other inorganic anions. A supramolecular polymeric chain formation by the probe through halogen bond and anion-π interactions with dihydrogen phosphate is established by solid-state structural studies. On the contrary, C1 forms a dimeric aggregation via halogen bonding interaction with perrhenate. Macroscopic investigations, such as DLS, TEM, and SEM also show the formation of supramolecular polymeric aggregated structures with phosphates, however, such aggregation is not observed in the case of perrhenate. Polymeric aggregation of C1 with phosphate is additionally supported by DOSY NMR spectroscopy. Thus, the combined cooperative action of anti-electrostatic anion–anion (phosphate-phosphate), anion-π (phosphate-π of C6F5) and halogen-bonding (phosphate and C-I of probe C1) interactions are responsible for dihydrogen phosphate induced supramolecular polymeric aggregation. Finally, the formation of larger supramolecular self-assembly in presence of dihydrogen phosphate leads to selective sensing and higher binding towards the ion over perrhenate and other inorganic anions.

Rational design of anion-scavenging materials with high selectivity and stability under high acid/base extreme conditions for removing 99TcO4− is still a significant challenge. Herein, we put forward an anion exchange strategy that utilized an imidazolium-based cationic organic polymer (named ImCOP) for efficient capture of perrhenate (ReO4−), a surrogate for TcO4− with nonradioactive. ImCOP was synthesized via the quaternization reaction using tris (4-(1H-imidazol-1-yl) phenyl) amine, a tripodal flexible ligand, and 1,4-bis (bromomethyl) benzene to forming a semi-rigid structure. ImCOP exhibited high chemical stability even under 3 M HNO3 and 3 M NaOH, which was superior to those of most materials. Attributed to the charged imidazolium moieties and tertiary amine groups that produced rich adsorption sites, ImCOP can produce electrostatic interactions with ReO4−, thereby leading to a record uptake capability (1162 mg g−1) of ReO4−. Furthermore, ImCOP exhibited high selectivity for removing ReO4− in the presence of large excess of competitive anions, which was attributed to the hydrophobic surface of ImCOP. These excellent features endowed ImCOP successfully separated ReO4− from simulated Hanford waste with a high adsorption removal of 93.4%. The excellent performance suggested ImCOP would be a promising material for TcO4−/ReO4− removal, which provided a feasible pathway for designing a high-efficiency and durable material for nuclear-related environmental remediation.

Rhenium is a valuable metal in very low concentration and it is being increasingly used in industry due to its multiples properties, mainly in the aeronautics and oil industries. For this work, the PEG/CuSO 4 aqueous two phase system (ATPS) was used for the partition of perrhenate anion. For the partition tests the NH 4 ReO 4 salt was used. The effects of temperature, pH, salt concentration, PEG concentration and their interactions on the partition were analyzed by using experimental design 2 k . Moreover, density, kinematic viscosity and sound velocity were determined for the top and bottom phases. The optimal conditions obtained by the model for the perrhenate partition in the ATPS formed by PEG and CuSO 4 were 13.7% PEG 4000 ( w /w), 13% CuSO 4 (w/w) and 35 °C, obtaining a distribution coefficient, K ReO4- , of 7.72 ± 0.31. Also, an increase of K ReO4- with increasing PEG and CuSO 4 concentration was observed, i.e. their effects are significant on the perrhenate partition. On the other hand, the effects of temperature and pH do not have high significance on the partition. Of all the studied parameter, the pH had less significance on the partition. Thus, to simplify the statistical model the pH was not considered in the model. For both phases, only density is inversely proportional to pH. With exception of the sound velocity of bottom phase all properties for both phases are inversely proportional to temperature. Moreover, all properties are proportional with the PEG and CuSO 4 concentrations in both phases. The partitioning behavior was evaluated by an experimental design, applying statistical regression analysis and analysis of variance (ANOVA). The statistical model for distribution coefficient as function of the parameters with significant effects was obtained. A good agreement between experimental and correlated data was observed (R-Squared = 0.930).

For the first time the standard formation enthalpy of Bi 12.5 Nd 1.4 In 0.1 ReO 24.5 has been determined by solution calorimetry by combining the solution enthalpies of Bi 12.5 Nd 1.4 In 0.1 ReO 24.5 , 1.4NdCl 3 + 0.1InCl 3 0.1InCl 3 mixture in 2 M HCl and literature data. The lattice energy for Bi 12.5 Nd 1.4 In 0.1 ReO 24.5 has been calculated using Born-Haber cycle. The dependence of lattice energy for Bi 12.5 R 1.5 ReO 24.5 (R – rare earth element) from radius of rare earth metal was constructed. It was established that dependence was linear and had form: U lat = −129450 + 45070 r R . Linear character of experimentally obtained dependence was explained using modified variant of Kapustinskii formula obtained by us as following: U = A + Br R .

Heat capacities of sulfate, perrhenate, chloride, and iodide sodalites with the ideal formula Na8Al6Si6O24X2 (X = SO4, ReO4, Cl, I) were measured from 2 K to 300 K using a Quantum Design Physical Property Measurement System (PPMS). From the heat capacity data, the standard thermodynamic functions were determined. All four sodalites undergo a phase transition below room temperature for which thermodynamic parameters were determined. Additionally, the heat capacity of one of the constituent compounds (NaReO4) was measured.

A series of N -alkylammonium perrhenate salts [N(R 1 ) 3 R 2 ] + [ReO 4 ] − with varying substituents R 1 and R 2 were synthesized and characterized and used as catalysts for the epoxidation of olefins. The effect of the substitution pattern on the catalytic activity was investigated.

We report the cloning, purification and characterization of Bps beta CA, a beta-class carbonic anhydrase (CA, EC 4.2.1.1) from the pathogenic bacterium Burkholderia pseudomallei, the etiological agent of melioidosis, and compare its activity and inhibition with those of the gamma-CA from the same organism, Bps gamma CA, recently investigated by our groups. Bps beta CA showed a significant catalytic activity for the physiologic, CO2 hydration reaction, with the following kinetic parameters, k(cat) of 1.6 x 10(5) s(-1) and k(cat)/K-m of 3.4 x 10(7) M-1 x s(-1). The inhibition of Bps beta CA with a group of anions and small molecules was also investigated. The best inhibitors were sulfamide, sulfamic acid and phenylarsonic acid, which showed K(I)s in the range of 83-92 mu M, whereas phenylboronic acid, fluoride, cyanide, azide, bisulfite, tetraborate, perrhenate, perruthenate, peroxydisulfate, perchlorate, tetrafluoroborate, fluorosulfonate and hexafluorophosphate showed K(I)s > 100 mM. Other inhibitors of this new enzyme were bicarbonate, trithiocarbonate, some complex inorganic anions and N,N-diethyldithiocarbamate, which had inhibition constants of 0.32-8.6 mM. As little is known of the life cycle and virulence of this bacterium, this type of study may bring information of interest for the development of novel strategies to fight bacterial infection and drug resistance to commonly used antibiotics. (C) 2017 Elsevier Ltd. All rights reserved.

Tetraamminepalladium(II) perrhenate, a double complex salt, has significant utility in PdRe catalyst preparation; however, the vibrational spectra of this readily prepared compound have not been described in the literature. Herein, we present the infrared (IR) and Raman spectra of tetraamminepalladium(II) perrhenate and several related compounds. The experimental spectra are complemented by an analysis of normal vibrational modes that compares the experimentally obtained spectra with spectra calculated using DFT (DMol 3 ). The spectra are dominated by features due to the ammine groups and the Re O stretch in T d ReO 4 − ; lattice vibrations due to the D 4h Pd(NH 3 ) 4 2+ are also observed in the Raman spectrum. Generally, we observe good agreement between ab initio calculations and experimental spectra. The calculated IR spectrum closely matches experimental results for peak positions and their relative intensities. The methods for calculating resonance Raman intensities are implemented using the time correlator formalism using two methods to obtain the excited state displacements and electron-vibration coupling constants, which are the needed inputs in addition to the normal mode wave numbers. Calculated excited state energy surfaces of Raman-active modes correctly predict relative intensities of the peaks and Franck-Condon activity; however, the position of Raman bands are predicted at lower frequencies than observed. Factor group splitting of Raman peaks observed in spectra of pure compounds is not predicted by DFT.

Water-stable [Co3(tib)2(H2O)12](SO4)3 (BUC-17) was hydrothermally synthesized by adding formic acid as a modulator. The as-prepared BUC-17, whose zeta potentials were positive in pH 4.0–10.0, was used as potential adsorbent to capture ReO4− ions. The corresponding kinetics behavior and equilibrium isotherm fitted well to the pseudo-second-order and Langmuir model, in which the maximum sorption capacity of BUC-17 was 401.9 mg ReO4− g−1 sorbent at 298 K. Additionally, BUC-17 demonstrated outstanding removal activity in wide range of pH (4.0 – 10.0) and high salinity. The fixed-bed column packed with BUC-17 powder could continuously eliminate ReO4− solution, which provided the possibility to accomplish potentially large-scale application. At last, the adsorption mechanism was proposed, which was the synergism of electrostatic interactions and ion exchange between SO42− and ReO4−.

Two novel ether-based perrhenate ionic liquids [C22OnIm][ReO4](n = 1,2) were synthesized and characterized. The static properties and transport properties were measured, and the extended properties were calculated and investigated in the certain temperature range. Using the six anions of [ReO4]−, [OAc]−, [DCA]−, [NTF2]−, [SCN]− and [TfO]− as the reference ions, the values of cationic parachor for [C22OnIm]+ (n = 1,2) were obtained for the first time. The predicted values of parachor, surface tension and refractive index of 7 kinds of ionic liquids were obtained by the cationic parachor values, which are correlated quite well with their matching experimental ones. The ether-functionalization of cation could decrease the viscosity of ILs, especially 2-ethoxyethyl (2O2) group.

The efficient decontamination of pertechnetate (99TcO4−) is an essential task for managing radioactive 99Tc in nuclear wastes. Perrhenate, (ReO4−), as a nonradioactive analog, exhibits almost identical physicochemical properties as 99TcO4−. Herein, a novel magnetic amine-functionalized MIL-101(Cr) (NH2-MIL-101(Cr)@Fe3O4) was prepared and used to efficiently remove ReO4− from solution for the facile magnetic separation. A series of environmental parameters were considered to investigate the adsorption performance of NH2-MIL-101(Cr)@Fe3O4. Experimental results suggested that NH2-MIL-101(Cr)@Fe3O4 has reached a satisfied adsorption capacity (~401 mg/g) and a very fast adsorption kinetics at pH 7.0. The selectivity for ReO4− was maintained even in the presence of interfering anions with relatively high concentrations. ReO4− were mainly captured by N-donor sites of the surface-decorated amine via complexation and were trapped in the cavities of modified MIL-101(Cr). NH2-MIL-101(Cr)@Fe3O4 exhibits satisfactory adsorption performance for ReO4− and can be conveniently separated from wastewaters after adsorption.

Two new layered barium perrhenate halides, BaX(ReO4) (X = Cl and Br), were prepared and their structures were refined from single-crystal and powder data, respectively. Both compounds are isostructural to the previously reported BaCl(MnO4), exhibiting a matlockite (PbFCl)-derived motif. The structure of previously reported PbBr(ReO4) was also refined, in order to obtain a complete data set; it is similar to PbCl(ReO4). The structures of Ba and Pb compounds correspond to the centro- and non-centrosymmetric versions (pseudo-polymorphs) of the same motif corresponding to the alternation of [M2X2]2+ litharge-derived slabs and double sheets of perrhenate anions. Strong relationships exist to the structures of LnX(TO4) (X = Cl, Br; T = Mo, W) which are monoclinically distorted versions of the orthorhombic permanganates and perrhenates. Crystal chemistry and further perspectives of the compounds with litharge slabs constructed of Cl, Br, and I-centered tetrahedra are discussed.

The development of fluorescence based sensor for perrhenate anion, which serves as a non-radioactive surrogate of hazardous pertechnetate anion, is an extremely rewarding task but nevertheless has remained rarely investigated in literature. Further, there are no reports in literature that propose a lifetime based sensing of perrhenate anion which provides significant advantage over pure intensity based sensor. Herein, we report an extremely simple fluorescence sensor for perrhenate anion in aqueous media, where we have used 1-pyrenemethylamine (PMA) as fluorescent probe. The fluorescence intensity of PMA is heavily quenched along with drastic reduction in the excited-state lifetime of PMA that provides an excellent opportunity for a very sensitive detection of perrhenate anion (LOD = 14 μM). Importantly, PMA also displays high selectivity towards perrhenate anion when compared with several other environmentally ubiquitous anions. The selective interaction between PMA and perrhenate has been attributed to the high basicity of ReO4− anion which facilitates a strong H-bonding interaction with amino group of the probe and the quenching interaction is attributed to the photoinduced electron transfer between excited PMA and ReO4−. Overall, an extremely simple, selective and sensitive fluorescence sensor for perrhenate anion is reported which also operates through lifetime measurement that is first of its kind.

Technetium(Tc)-99 is one of major risk drivers in low level radioactive liquid waste at the U.S. Department of Energy sites. Cementitious waste technology (CWT) has been considered immobilizing pertechnetate, Tc(VII)O4−, in brine and alkaline waste solutions, as Tc(IV) oxides and/or sulfides with the use of reducing agents like slag. In this study, zero valent iron (ZVI) was evaluated as a potential reducing agent in CWT as a function of pH and [nitrate] (0–0.1 M) using perrhenate, Re(VII)O4−, as an analogue for Tc(VII)O4−. Batch Re(VII)O4− sorption experiments in conjunction with X-ray absorption spectroscopic analysis showed that the Re(VII) sorption occurred via the reductive precipitation of Re(IV)O2(s) and the extent of sorption decreased with increasing pH from 8 to 10. Interestingly, pseudo 2nd order kinetic rates increased with increasing [nitrate] which was attributed to co-adsorption of NH4+ (i.e., a reaction product of reduced nitrate by ZVI), facilitating electrostatic attraction towards ReO4− under alkaline conditions. Considering the thermodynamically favorable reduction of Tc(VII) over Re(VII), ZVI might have potential for improving the reduction capacity of the current CWT.

For the first time the heat capacities of phase Bi12.5Nd1.4In0.1ReO24.5 have been measured in the temperature range of 175–550 K. Differential scanning calorimetry has been used for measurements. The temperature dependence of heat capacity is well described by a polynomial Cop,m (T) = 542.62 + 1.5107 T – 1.0402 · 10−3 T2 – 2.7875 · 106/T2. On the basis of smoothed heat capacities the enthalpy and entropy increments were calculated (T = 175–550 K).

Technetium (Tc) retention during Hanford waste vitrification can be increased if the volatility can be controlled. Incorporating Tc into a thermally stable mineral phase, such as sodalite, is one way to achieve increased retention. Here, rhenium (Re)-bearing sodalite was tested as a vehicle to transport perrhenate (ReO4−), a nonradioactive surrogate for pertechnetate (TcO4−), into high-level (HLW) and low-activity waste (LAW) glass simulants. After melting HLW and LAW simulant feeds, the retention of Re in the glass was measured and compared with the Re retention in glass prepared from a feed containing Re2O7. Phase analysis of sodalite in both these glasses across a profile of temperatures describes the durability of Re-sodalite during the feed-to-glass transition. The use of Re sodalite improved the Re retention by 21% for HLW glass and 85% for LAW glass, demonstrating the potential improvement in Tc-retention if TcO4− were to be encapsulated in a Tc-sodalite prior to vitrification.

Technetium-99 (Tc-99) is an important fission product of nuclear industry. Its characteristics can be predicted by studying rhenium (Re), a chemical analogue of technetium, thus avoiding the use of radioactive elements at high concentrations. The present work focused on the sorption of Re(VII) by hexadecyl trimethylammonium cation (HDTMA) modified bentonite. Our experimental results show that the bentonite sample has been successfully modified. The stability of HDTMA in the sample is satisfactory with the increasing of calcination temperature (

2-pyridyl thiourea and methyl-2-pyridyl ketoxime based perrhenate, Re(VII), UV-vis spectrophotometric methods were evaluated in nitrate and bicarbonate solutions ranging from 0.001 M to 0.5 M. Standard curves at [Re]=2.5-50 mg L(-1) for the Re(IV)-thiourea and the Re ketoxime complexes were constructed at 405 nm and 490 nm, respectively. Detection of limits for N-(2-pyridyl) thiourea and methyl-2-pyridyl ketoxime methods in ultrapure water are 3.06 mg/L and 4.03 mg/L, respectively. Influences of NaHCO3 and NaNO3 concentration on absorbance spectra, absorptivity, and linearity were documented. For both methods, samples in ultrapure water and NaHCO3 have an R(2) value>0.99, indicating strong linear relationships. Statistical analysis supports that NaHCO3 does not affect linearity between standards for either method. NaNO3 causes major interference with the ketoxime method above 0.001 M NaNO3. Data provides information for practical use of Re spectrophotometric methods in environmental media that is high in bicarbonate and nitrate.

The spectroscopic and electrochemical behavior of perrhenate ions was examined in aqueous solutions containing concentrated sulfuric acid. The chronopotentiometric results show a multi-electron reduction process. Additional hydrodynamic experiments reveal generation of an ionic form of Re(V) that undergoes oxidation on the ring electrodes. Reduced rhenium species are transformed in 12 M H2SO4 into soluble species characterized by an absorption band at 366 nm.

Perrhenate oxoanion is a non-radioactive surrogate of the radioactive and hazardous pertechnetate oxoanion. The efficient sensor systems for perrhenate anion in aqueous medium is barely reported and still remains challenging due to low charge density and large size of the anion. In this regard, we have identified a cyanine based molecular rotor probe, pseudoisocyanine, which produces an appreciably larger emission enhancement of ∼60 fold in response to perrhenate anion, which is highest reported, till date, for any turn-on sensor for perrhenate anion leading to a significant improvement in the detection limit (0.17 μM) over existing sensors for perrhenate. Our sensing scheme operates through the ion pairing interaction between perrhenate and pseudoisocyanine which induces the formation of J-aggregates of pseudoisocyanine that yield dramatic changes in its fluorescence properties. The J-aggregate formation of pseudoisocyanine, in the presence of perrhenate anion, also yields significant changes in the absorption properties providing an opportunity of dual sensing of perrhenate, i.e. via fluorimetry and colorimetry. Apart from being sensitive and selective, our probe molecule exhibits a desirable feature of emission and excitation wavelength lying in the red region of the visible specrum which is advantageous for operation of a probe molecule in complex sensing matrix.

There are few effective technologies for the sequestration of highly water-soluble pertechnetate (TcO4−) from contaminated water despite the urgency of environmental and public health concerns. In this work, anion exchanged and cetyltrimethylammonium bromide (CTAB) functionalized MIL-101-Cr-NO3 were investigated for perrhenate (ReO4−), a surrogate of TcO4−, sequestration from artificial groundwater. Cl−, I−, and CF3SO3− exchanged MIL-101-Cr proved more effective at ReO4− removal than the parent MIL-101-Cr-F. Compared to the parent framework, CTAB functionalized MIL-101-Cr-NO3 increased ReO4− removal capacity from 39 to 139 mg/g, improved the reaction kinetics from ~30 to

Technetium (99Tc) mobility in the environment increases when 99Tc(IV) is combined with certain organic ligands under reducing environment. Therefore, it is important to detect and characterize 99Tc-organic ligand complex species to understand 99Tc mobility in various environmental conditions. Rhenium (Re) was used as a 99Tc surrogate with ethylenediaminetetracetic acid (EDTA) to produce Re–EDTA complexes, with perrhenate (ReO4−) reduced in the presence of EDTA with tin ion (Sn2+) in an anoxic glove box. Liquid–liquid and vapor–liquid diffusion methods were applied to isolate the Re complexes from the reaction mixture, and they were characterized using ultraviolet–visible, Raman, Fourier-transform infrared spectroscopy, and matrix-assisted laser desorption/ionization-time of flight mass spectroscopy. Bi-metallic base complex [(Sn)(EDTA)(ReO)(OH)(OH2)] was discovered, which transformed to a charge transfer (CT) complex, [CT complex1]=[(OH)2(H2O)2Re2(μ-O2)(EDTA)2·Sn2)] and [CT complex2]=[Re2(μ-O2)(EDTA)2Na4] over a period of 1 month. These CT complexes and a base complex were detected by matrix-assisted laser desorption/ionization-time of flight in black and yellow products, respectively. Oxidation states of +5 and +4 were assigned to Re in [CT complex1] and [CT complex2], respectively, based on Warner’s structure model. These CT complexes were neither broken apart to form ReO2(s) nor reversely transformed to form a base complex during a dissolution experiment, even in oxic conditions. These results suggest that the CT complexes of Re(IV/V) are highly stable and environmentally persistent with mobility higher than immobile 99Tc(IV) oxide.

The two DOTA-tetraamide ligands, DOTAM-n-butyl (1,4,7,10-tetrakis[(N-n-butyl; carbamoyl)methyl]-1,4,7,10-tetraazacyclododecane) and DOTAM-benzyl (1,4,7,10- tetrakis[(N-benzylcarbamoyl)methyl]-1,4,7,10-tetraazacyclododecane), were synthesized and characterized by MS, NMR and FTIR spectra. In acid solution, DOTAM-n-butyl was liable to be protonated. FTIR, 1H NMR, ESI-MS spectra and X-ray diffraction analyses revealed that the nitrogen atoms of cyclen ring combined two protons to form a cation with two positive charges. The protonated DOTAM-n-butyl had strong extraction ability and good selectivity for ReO4−. It was extracted by means of the substitution of one ReO4− for one NO3− in the 1:2 complex of DOTAM-n-butyl with HNO3. The solvent extraction and X-ray crystallography demonstrated an anion-exchange extraction model. Meanwhile, X-ray crystal structure analyses of ligand complexes with HReO4 or HNO3 also indicated that ReO4− or NO3− ions were located in the gap between the upper and lower protonated ligands through multiple hydrogen bonds and electrostatic interactions.

Radioactive pertechnetate (TcO4−) has been detected in nuclear waste affected soil and groundwater, posing significant effect on human health and the environment. Yet, cost-effective remediation of Tc-contaminated soil and groundwater remains challenging. To address this critical technology need, we prepared a class of pyrite (FeS2) particles for effective immobilization of pertechnetate. Using perrhenate (ReO4−) as a non-radioactive surrogate of TcO4−, we tested the immobilization effectiveness of the material through batch kinetic experiments, and evaluated the remobilization potential of immobilized Re under anoxic (sealed from air) and oxic (exposed to air) conditions and in the presence of humic acid (HA), EDTA, nitrate, and a Chinese loess soil. The results showed that more acidic pH gave faster Re(VII) removal due to more abundant electron sources (Fe2+ and S22−). X-ray diffraction (XRD) and/or X-ray photoelectron spectroscopy (XPS) analyses confirmed formation of ReO2/ReS2 as the major reduction products. The immobilized Re remained highly stable when aged for 360 days under anoxic conditions at different influence factors. Yet, the immobilized Re was vulnerable to oxygen oxidation, and about 78% of Re was remobilized after 40 days of exposure to air regardless of the initial pH (3.5–9.0) due to excessive pyrite oxidation and the associated pH drop (~2). HA at 120 mg/L inhibited Re remobilization under oxic conditions, which lowered the Re remobilization by ~21% after 40 days of oxic aging. The presence of EDTA facilitated dissolution of Fe but inhibited the dissolution of Re under oxic conditions. Nitrate showed negligible effect on Re remobilization. The presence of a Chinese loess soil effectively inhibited Re remobilization under both oxic and anoxic conditions, lowering the leachable Re by ~32% under oxic conditions. The findings may guide engineered application of pyrite particles as a long-lasting reducing material for immobilization pertechnetate or similar redox-active contaminants in soil and water.

In our previous work, the selective precipitation of rhenium from an acidic washing solution present in the copper smelting process was studied. The precipitate formed is a polymetallic sulfide that contains rhenium, copper, arsenic, and bismuth. To recover rhenium from the precipitate, the separation of perrhenate ions from industrial leach solutions using synergistic solvent extraction was investigated. For the synergistic extraction system of Alamine 336 and TBP, Alamine 336 is the primary compound that combines with the anions in the leach solution. The solubility of the extraction complex in the organic phase is enhanced by TBP bonding with the neutral complex. For the extraction of perrhenate ion from the chloridizing leach solution, the difference in the distribution coefficient of rhenium and bismuth is small due to the formation of bismuth polychloride complex ion in aqueous solution. For the acidic leach solution using sulfuric acid and ammonia persulfate, the separation percentage of perrhenate ion is more than 99.90 wt% using four-stage countercurrent extraction. This is because the bismuth and arsenic in the leach solution forms an insoluble compound (BiO)2SO4 and arsenic acid. The loaded organic phase is stripped by a 4 mol/L ammonium solution, recovering 98.78% Re. The content of arsenic, copper, bismuth, and lead in the ammonia perrhenate formed from the evaporation and crystallization process using the stripping liquor is less than 0.5 mg/kg and 1.0 mg/kg, respectively.

Tungsten‑rhenium wire is used in thermocouple and lamp filament manufacturing due to its good thermal sensitivity and high temperature plasticity, and many waste wires are generated in processing and after use. This work focuses on the efficient recovery of high value rhenium from tungsten‑rhenium wire waste with a mass composition represented by W95Re5. The main steps for recovery include alkali fusion, recrystallization, hydrogen reducing and washing. First, W Re wire was decomposed by KOH-K2CO3 molten salt to produce potassium perrhenate, where the decomposition ratios of W and Re reached 99.36% and 99.80% using a mass ratio of salt to wire of 3:1, m(KOH) of 80% (m representing the mass fraction of KOH in binary salt), a temperature of 800 °C and a reaction time of 60 min. Then, the decomposed product was leached by water, and from the resulting lixivium high purity KReO4 crystals were obtained by segregation, which had a perfect rhombic dipyramid morphology and average size of 73.26 μm. Last, the material was reduced to Re powder at 350 °C with a H2 flow rate of 10 L/min. Re powder, with a purity of higher than 99.5% and fine grain size of 19.37 μm, was obtained after washing with acid and water. This method provided a potential economic process for the recovery of waste W Re wire.

Biochar has a good adsorption ability for perrhenate (ReO4−), which can be attributed to its abundant oxygen-containing groups, yet the effects of oxygen-containing groups on ReO4− adsorption are still unclear. Here, the interaction of ReO4− and acidic/basic oxygen-containing groups (hydroxyl, carboxyl, pyrone and chromene) on biochar were investigated by density functional theory (DFT) calculation with conductor-like screening model (COSMO). According to the calculated results, it was evidenced that the adsorption of oxygen-containing group functionalized BC towards ReO4− was gradually strengthened as decreased pH, and the protonated positively charged oxygen-containing groups presented stronger chemisorption to ReO4− mainly through electrostatic interaction, complexation and atomic orbital hybridization. The protonated hydroxyl and carboxyl and the protonated etheric oxygen of pyrone and chromene can offer favorable binding sites to ReO4−. Compared with the acidic oxygen-containing groups, the higher adsorption energy values, and the larger Mayer bond order indexes of interacting atoms identified that the basic oxygen-containing groups have stronger affinity with ReO4−. Pyrone had the strongest adsorption stability toward ReO4−. Our results can provide new ideas into the design and preparation of separation materials for ReO4− or the other anions capture from the aqueous solution.

Aqueous solution was simulated by ammonium perrhenate and sodium sulfate in sulphuric acid system according to waste water from metallurgy process of copper and molybdenum. Molalities of perrhenate after extraction were measured at ionic strength from 0.2 to 2.0 mol kg−1 at temperature range 278.15 K to 303.15 K, using tri-n-octylamine as extractant. Optimization condition of extraction was determined in this sulphuric acid medium. The standard extraction constants K0 at various temperatures were obtained by method of polynomial approximation. Thermodynamic quantities for the extraction process were calculated.

Recovery of rhenium from aqueous solutions by photoinduced-electron transfer from an electron donor to excited-state ReO4− is reported for the first time. Specifically, irradiation of aqueous ReO4− in the presence of 2-propanol as the electron donor efficiently decreased the ReO4− concentration in the solution and resulted in formation of a precipitate consisting of amorphous ReO2 and ReO3 and formation of acetone by oxidation of 2-propanol. After 19 h of irradiation, ReO4− had completely disappeared, and 89.1% of the initial rhenium content was recovered in the collected precipitate. Although an induction period prior to the decrease in the ReO4− concentration was observed, the induction period could be eliminated by introduction of acetone to the reaction system, which afforded 94.7% recovery of rhenium within 6 h of irradiation. The acceleration of the reaction induced by acetone could be explained by an increase in the light absorption of ReO4− via precomplexation with acetone, which resulted in an increase in the emission intensity from the excited rhenium species.

Analogous to the non-linear optical properties of L-alaninium perrhenate ionic crystals with three-dimensional hydrogen bonds, we have synthesized various chiral bimetallic assemblies, [CuL2][Ni(CN)4]·2H2O (Cu(II)–Ni(II)), [CuL2]3[Co(CN)6]2·5H2O·4DMSO (Cu(II)–Co(III)), [CuL2]2[Fe(CN)6]·10H2O (Cu(II)–Fe(II)), [CuL2]2[CrO4]2·5H2O (Cu(II)–Cr(VI)) and [CuL2]2[MoO4]2·3H2O·2DMSO (Cu(II)–Mo(VI)) (L = (1R,2R)-diphenylethylenediamine), determined their crystal structures at different temperatures; measured their spectroscopic and magnetic properties and confirmed their non-linear optical properties. One-dimensional Cu(II)–Ni(II) crystallizes in the P1 space group and exhibits no NLO properties. However, two-dimensional Cu(II)–Co(III) crystallizes in the P21 space group and three-dimensional Cu(II)–Fe(II) crystallizes in the C2 space group; both exhibit NLO properties. Moreover, the complexes Cu(II)–Cr(VI) and Cu(II)–Mo(VI) crystallize in polar crystals of P21 symmetry involving two-dimensional hydrogen bonding and exhibit NLO properties. These Cu(II)–Cr(VI) and Cu(II)–Mo(VI) crystals are so flexible that they exhibit anisotropic thermal negative expansion. Therefore, their second-harmonic generation efficiency makes them potentially useful as new materials for non-linear optics.

The crystal structure of Cu+Re7+O4 is capable of a quasi-reversible incorporation of C3H7OH molecules. A room-temperature reaction between CuReO4 and C3H7OH under oxidizing conditions leads to the formation of a novel metal-organic hybrid compound Cu2+(C3H7OH)2(ReO4)2. Upon heating under reducing conditions, this compound transforms back into CuReO4, albeit with ReO2 and metallic Cu as by-products. The crystal structure of Cu(C3H7OH)2(ReO4)2 solved from single-crystal X-ray diffraction (Pbca, a=10.005(3) A, b=7.833(2) A, and c=19.180(5) A) reveals layers of corner-sharing CuO6-octahedra and ReO4-tetrahedra, whereas isopropyl groups are attached to both sides of these layers, thus providing additional connections within the layers through hydrogen bonds. Cu(C3H7OH)2(ReO4)2 is paramagnetic down to 4 K because the spatial arrangement of the Cu2+ half-filled orbitals prevents magnetic superexchange. The paramagnetic effective moment of 2.0(1) μB is slightly above the spin-only value and typical for Cu2+ ions.

It is significant for environment and human health to develop new materials for the sorption of radioactive technetium. We report herein a novel method to synthesize surface ion-imprinted magnetic microspheres for efficient capture of technetium ions. Specifically, perrhenate anion as the structural surrogate for pertechnetate anion, was employed as template to prepare ion-imprinted magnetic microsphere by “one-pot” radical polymerization and quaternization. The sorption behavior is closely related with the surface chemical composition: the more nitrogen content, the higher sorption efficiency. The sorption is an exothermic spontaneous sorption process and kinetically followed pseudo-second-order model. A sorption capacity of 62.8 mg of Re/g could be achieved at 298.15 K and pH = 6. Compared with non-imprinted composites, imprinted microspheres showed higher selectivity, faster kinetics, and larger sorption capacity of perrhenate ions. This work may provide a promising approach for the efficient sorption of pertechnetate.

We investigated volatilization of rhenium (Re), sulfur, cesium, and iodine during the course of conversion of high-level waste melter feed to glass and compared the results for Re volatilization with those in low-activity waste borosilicate glasses. Whereas Re did not volatilize from high-level waste feed heated at 5 K min−1 until 1000 °C, it began to volatilize from low-activity waste borosilicate glass feeds at ∼600 °C, a temperature ∼200 °C below the onset temperature of evaporation from pure KReO4. Below 800 °C, perrhenate evaporation in low-activity waste melter feeds was enhanced by vigorous foaming and generation of gases from molten salts as they reacted with the glass-forming constituents. At high temperatures, when the glass-forming phase was consolidated, perrhenates were transported to the top surface of glass melt in bubbles, typically together with sulfates and halides. Based on the results of this study (to be considered preliminary at this stage), the high-level waste glass with less foaming and salts appears a promising medium for technetium immobilization.

Highly alkaline nuclear tank wastes containing key anionic contaminants have leaked into the subsurface at the U.S. Department of Energy's Hanford Site. Laboratory studies showed that when simulated caustic tank wastes contact subsurface sediments, mineral dissolution and precipitation result in feldspathoid formation. Feldspathoids are environmentally important for waste management and disposal purposes because of their purported potential to sequester contaminants of interest (e.g., 99 TcO 4 − , 137 Cs + , 90 Sr 2+ ) into their structure. We investigated the incorporation of perrhenate (ReO 4 − ), a surrogate for TcO 4 − , in the presence of competing anions (X) including OH − , NO 2 − , NO 3 − and Cl − on feldspathoid formation and under conditions mimicking tank waste solution compositions. The resulting solids were characterized by their chemical composition, structure and morphology. Regardless of solution pH, sodalite formed in the presence of Cl − and NO 2 − whereas NO 3 − promoted either cancrinite formation in 16-mol OH − /kg (16 m ) or mixed sodalite/cancrinite phases in 1-mol OH − /kg (1 m ) solutions. In the presence of Cl − , NO 2 − , and NO 3 − less than 0.02 mol fraction of ReO 4 − was incorporated into the feldspathoid phase(s). Although, the NO 2 -sodalite and mixed NO 3 -cancrinite/sodalite phases incorporated significantly more ReO 4 − than NO 3 -cancrinite or Cl-sodalite phases, the total ReO 4 − fraction was ∼1% or less of the total sites. The ReO 4 − immobilized in ReO 4 -sodalite, NO 2 -sodalite, mixed NO 3 -cancrinite/sodalite and NO 3 -cancrinite was resistant to ion exchange with either NO 2 − or NO 3 − . The results imply that ReO 4 − , and thus by analogy 99 TcO 4 − , does not compete well with smaller ions for incorporation into feldspathoids, but, once sequestered, is difficult to exchange.