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The thermal analysis behavior of C6H6N3[ReO4] was studied by simultaneous thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) up to 700 °C under argon. Such analysis afforded rhenium metal, which was characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy. XRD peak broadening due to crystallite size and lattice strain was analyzed by both Williamson-Hall (W-H) and Debye-Scherrer (D-S) methods. Efforts to isolate Re metal from the thermal treatment of benzotriazole (BTA = C6H5N3) with NH4ReO4 and Re2O7 under various atmospheres and temperatures are also reported. The results provide a significant insight into the chemistry of group VII transition metals, investigate the potential use of benzotriazole as a reducing agent for metal productions, and demonstrate a successful convenient method for rhenium metal production, which could be applied to other refractory metals.

A new imidazolium functionalized hexapodal polymeric receptor, [PHIm-Br], showed selective and efficient removal (>99%) of perrhenate (ReO4−), from 100% aqueous medium via solid–liquid extraction, which was 13% higher as compared to its monomeric analouge [HIm-Br]. Most importantly, [PHIm-Br] overcomes the drawback of [HIm-Br] in terms of removal of ReO4− at lower anion concentration of ∼100 ppm along with excellent radiation resistivity and reusability within a wide pH range, which implies its potential towards practical applications.

In this work, an ion imprinted polymer (ReO4–-IIP) of the perrhenate ion based on acrylamide (AM) and acrylic acid (AA) was prepared by solution polymerization using ReO4– as a template ion, N,N-me...

The theoretical description of a new sandwich-like rhenium-based polymer composite cathodic electrodeposition has been given. The cathodic process is realized by perrhenate-ion electrochemical reduction to rhenium (IV) oxide, acting as an in situ formed oxidant for 3,4-dimethoxypyrrole polymerization. It is shown that the polymer deposition in this system is realized by more efficient manner than during the direct electropolymerization. The polymer composite has to have a well-developed morphology and enhanced conductivity by sandwich-like structure. The oscillatory behavior, in this case, is also possible, being caused by the DEL influences on both electrochemical and chemical stages of the process. DOI: http://dx.doi.org/10.17807/orbital.v12i2.1193

The extraction process of rhenium was investigated in the room-temperature ionic liquid 1-pentyl-3-methylimidazolium bis((trifluoromethane)-sulfonyl)imide ([C5mim][NTf2]) containing N235. At ionic strength ranging from 0.2 to 2.0 mol·kg–1 and temperatures ranging from 293.15 to 318.15 K, the molalities of perrhenate in the aqueous phase were obtained at an extraction equilibrium. The standard extraction constants K0 at diverse temperatures were gained by the Pitzer polynomial approximation method. Thermodynamic characters for the extraction procedure were calculated.

We report the structural, spectroscopic, and computational studies of two new Re(I) tricarbonyl complexes bearing 2,3,6,7-tetraphenyl-1,4,5,8-tetraazaphenanthrene (Ph4TAP) and 4,5-diazafluoren-9-one (dafone) having a coordinated perrhenate group obtained via in situ superoxidation of Re(I) to Re(VII); intramolecular and intermolecular n → π* interactions are dominant and stabilize the molecular geometry and crystal packing.

The title hydrated salt, tris­[hexa­amminecobalt(III)] tetroxidorhenate(VII) tetra­kis­[hexa­fluorido­rhenate(IV)] hexa­hydrate, arose unexpectedly due to possible contamination of the K2ReF6 starting material with KReO4. It consists of octa­hedral [Co(NH3)6]3+ cation (Co1 site symmetry 1), tetra­hedral [ReVIIO4]− anions (Re1 site symmetry 1) and octa­hedral [ReIVF6]2− anions (Re site symmetries, Re2: 1; Re3 and Re4: ). A network of N—H⋯F hydrogen bonds consolidates the structure., The title hydrated salt, tris­[hexa­amminecobalt(III)] tetraoxidorhenate(VII) tetra­kis­[hexa­fluorido­rhenate(IV)] hexa­hydrate, arose unexpectedly due to possible contamination of the K2ReF6 starting material with KReO4. It consists of octa­hedral [Co(NH3)6]3+ cation (Co1 site symmetry 1), tetra­hedral [ReVIIO4]− anions (Re site symmetry 1) and octa­hedral [ReIVF6]2− anions (Re site symmetries 1and ). The [ReF6]2− octa­hedral anions (mean Re—F = 1.834 Å), [Co(NH3)6]3+ octa­hedral cations (mean Co—N = 1.962 Å), and the [ReO4]− tetra­hedral anion (mean Re—O = 1.719 Å) are slightly distorted. A network of N—H⋯F hydrogen bonds consolidates the structure. The crystal studied was refined as a two-component twin.

We report the first example of linker modification for an N-donor Ag-based cationic material while maintaining and in some cases increasing the anion exchange capacity. Cationic silver(I) pyrazine nitrate selectively traps harmful oxo-anions from water such as permanganate, perrhenate and a variety of α,ω-alkanedicarboxylates. We chose these anions as initial examples of exchange for potential water purification. The host-guest interaction between the cationic layers of π-stacked silver pyrazine polymers and the incoming/outgoing interlamellar anions allows for the exchange. The exchange capacity over 24 h reached 435 and 818 mg/g for permanganate and perrhenate, respectively, a record for a crystalline metal-organic material and over five times the exchange capacity compared to commercial resin. The material also undergoes organic exchange as an analog for pharmaceutical waste, some of which have a carboxylate functionality at the neutral pH range typical of natural water sources. Both the as-synthesized and exchanged materials are characterized by a variety of analytical techniques.

Oxorhenium catalysts effectively transform biomass-derived polyols into corresponding alkenes via deoxydehydration (DODH) with a secondary alcohol as a hydrogen donor. This study describes the preparation of unsupported rhenium oxide nanoparticles (ReOx NPs), their use as DODH heterogeneous catalyst, and changes in the speciation and structure of Re during catalysis leading to a possible mechanism for DODH by a heterogeneous catalyst. The unsupported nanoparticles catalyze various polyols transformation to produce alkenes with high efficiency and recyclability. X-ray spectroscopy analysis shows that the structure of as-prepared ReOx NPs is similar to perrhenate with oxidation state between Re(VI) and Re(VII). Under reaction conditions and postcatalysis, the ReOx NPs are reduced by approximately two oxidation units. Kinetic isotope effect demonstrates that dissociation of a C–H bond during reduction of ReOx NPs by 3-octanol is part of the rate-determining step. Based on all experimental observations, the m...

Environmental contamination by 99Tc(VII) from radioactive wastewater streams is of particular concern due to the long half-life of 99Tc and high mobility of pertechnetate. Herein, we report a novel MXene-polyelectrolyte nanocomposite with three-dimensional networks for enhanced removal of perrhenate, which is pertechnetate simulant. The introduction of poly(diallyldimethylammonium chloride) (PDDA) regulates the surface charge and improves the stability of Ti2CT x nanosheet, resulting in Re(VII) removal capacity of up to 363 mg g-1, and fast sorption kinetics. The Ti2CT x/PDDA nanocomposite furthermore exhibits good selectivity for ReO4- when competing anions (such as Cl- and SO42-) coexist at a concentration of 1800 times. The immobilization mechanism was confirmed as a sorption-reduction process by batch sorption experiments and X-ray photoelectron spectroscopy. The pH-dependent reducing activity of Ti2CT x/PDDA nanocomposite toward Re(VII) was clarified by X-ray absorption spectroscopy. As the pH increases, the local environment gradually changes from octahedral-coordinated Re(IV) to tetrahedral-coordinated Re(VII). The overall results suggest that Ti2CT x/PDDA nanocomposite may be a promising candidate for efficient elimination of Tc contamination. The reported surface modification strategy might result in applications of MXene-based materials in environmental remediation of other oxidized anion pollutants.

A comparative study of the sorption properties of N-(2-carboxyethyl)chitosan (CEC), N-(2-sulfoethyl)chitosan (SEC), N-(2,3-dihydroxy)propyl chitosan (HPC) and N-2-(2-pyridyl)ethyl chitosan (PEC) with respect to perrhenate ions in an acidic medium was carried out. On the basis of the analysis of the adsorption isotherms and the perrhenate ion adsorption degrees as functions of pH, it was found that the efficiency of adsorbents decreases in the sequence PEC > SEC > HPC > CEC. The investigated chitosan derivatives are characterized by a higher rate of sorption of perrhenate ions in comparison with known commercial anionites. In the case of PEC, accompanying ions have the least effect on the sorption.

A family of pyridyl-functionalized arylacetylene C–H hydrogen bonding (HB) receptors were synthesized and binding interactions to perrhenate (ReO4–) studied in the solid state. The protonation and alkylation state of the pyridine nitrogen dictate the location and denticity of the interactions. X-ray structures of neutral 1 and singly charged 2a+·ReO4– reveal the formation of favorable self-complementary dimers, owing to the presence of nitrogen HB acceptor sites. Dismissal of these dimers upon elimination of nitrogen HB acceptors on the receptor result in an array of multidentate C–H HB receptor–guest contacts.

A novel ionic liquid (IL) based on catalytic functional metal rhenium, [Smim][ReO4] (1-heptyl-3-methyl-imidazolium perrhenate) was synthesized and characterized. Density and surface tension values of the IL were determined at different temperatures, and the volume and surface properties were calculated and discussed, respectively. Furthermore, the synthesized ionic liquid [Smim][ReO4] was used as a green solvent and catalyst for homogeneous catalyzed epoxidation of olefin with urea hydrogen peroxide (UHP) oxidant. The effect of factors of catalyst, oxidant, reaction time, and reaction temperature was discussed. The conversion of cyclohexene and cyclooctene is over 99% at optimum conditions. The IL [Smim][ReO4] as catalyst and solvent are characterized by high efficiency, long service life and recoverability, which is a better green homogeneous catalyst for epoxidation of olefins. A novel IL based on catalytic functional metal rhenium, [Smim][ReO4] was synthesized and characterized. The volume and surface properties were calculated and discussed by the density and surface tension values at different temperatures, respectively. Furthermore, the as-synthesized [Smim][ReO4] was used as a green solvent and catalyst for homogeneous catalyzed epoxidation of olefin with urea hydrogen peroxide (UHP) oxidant. The results showed that the yield and selectivity of the reaction were up to 99%, and the catalytic efficiency of [Smim][ReO4] did not decrease significantly after five times recycling. Easy separation, recycle, nontoxicity and homogeneous catalysis are the main advantages of perrhenate ionic liquids over other heterogeneous catalysts containing organic solvents.

The rhenium complex, [K(DME)(18-c-6)][ReH4(Bpin)(η2-HBpin)(κ2-H2Bpin)] 1, comprising hydride and boron ligands only, has been synthesized by exhaustive deoxygenation of the commercially available perrhenate anion (ReO4−) with pinacol borane (HBpin). The structure of 1 was analysed by X-ray crystallography, NMR spectroscopy, and DFT calculations. While no hydrides were located in the X-ray crystal structure, it revealed a trigonal arrangement of pinacol boron ligands. Variable-temperature NMR spectroscopy supported the presence of seven hydride ligands but further insight was hindered by the fluxionality of both hydride and boron ligands at low temperature. Further evaluation of the structure by Ab Initio Random Structure Searching (AIRSS) identified the presence of hydride, boryl, σ-borane, and dihydroborate ligands. This complex, either isolated or prepared in situ, is a catalyst for the 1,4-hydroboration of N-heteroaromatic substrates under simple operating procedures. It also acts as a reagent for the stoichiometric C–H borylation of toluene, displaying high meta regioselectivity in the borylated products. Reaction of 1 with 9-BBN resulted in HBpin substitution to form the new anionic tetra(dihydroborate) complex [K(DME)(18-c-6)][Re(κ2-H-9-BBN)4] 4 for which the hydride positions were clearly identified by X-ray crystallography. The method used to generate these isolable yet reactive boron–hydride complexes is direct and straightforward and has potential utility for the exploitation of other metal oxo compounds in operationally simple catalytic reactions., Exhaustive deoxygenation of perrhenate by pinacol borane forms a new Re anion of boron and hydride ligands only that undergoes borane ligand exchange, stoichiometric C–H boration, and catalytic pyridine hydroboration.

For a century ferroelectricity has attracted widespread interest from science and industry. Inorganic ferroelectric ceramics have dominated multibillion dollar industries of electronic ceramics, ranging from nonvolatile memories to piezoelectric sonar or ultrasonic transducers, whose polarization can be reoriented in multiple directions so that they can be used in the ceramic and thin-film forms. However, the realization of macroscopic ferroelectricity in the polycrystalline form is challenging for molecular ferroelectrics. In pursuit of low-cost, biocompatible, and mechanically flexible alternatives, the development of multiaxial molecular ferroelectrics is imminent. Here, from quinuclidinium perrhenate, we applied fluorine substitution to successfully design a multiaxial molecular ferroelectric, 3-fluoroquinuclidinium perrhenate ([3-F-Q]ReO4), whose macroscopic ferroelectricity can be realized in both powder compaction and thin-film forms. The fluorination effect not only increases the intrinsic polarization but also reduces the coercive field strength. More importantly, it is also, as far as we know, the softest of all known molecular ferroelectrics, whose low Vickers hardness of 10.5 HV is comparable with that in poly(vinylidene difluoride) (PVDF) but almost 2 orders of magnitude lower than that in BaTiO3. These attributes make it an ideal candidate for flexible and wearable devices and biomechanical applications.

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.

Spectrophotometric method is a simple and effective in situ analytical method for contaminants monitoring, but further improvement of its sensitivity and detection limit for radionuclides determination remains highly desirable. Herein, we report a simple and highly sensitive thiocyanate spectrophotometric method for the determination of radioactive Tc(VII) by studying its chemical analogue Re(VII) in different aqueous media. The colorless thiocyanate reacted with Re(VII) in hydrochloric acid solution in the presence of SnCl2 producing a stable colored Re(IV)-SCN complex, which was extracted into ethyl acetate and then measured at 427 nm. Under optimized conditions, a strong linear relationship can be obtained in the range of 0.25–10 mg L−1 for Re(VII) with R2 value > 0.9942, and the sensitivity of the method was found to be 0.004 μg cm−2 with detection limit of 0.027 mg L−1. This assay provides highly sensitive detection of Re(VII) in environmental media that is high in NO3−, Cu2+, and Fe3+. We applied it to the determination of Re(VII) in the wide range of background solutions, including deionized water, groundwater, and seawater, and analysis results showed that none of the molar absorptivities for both groundwater and seawater backgrounds was statistically different from the deionized water background when the paired Student’s t test, at 95% confidence level, was applied. The operational simplicity, accuracy, and precision of the proposed method suggest that it can be a good alternative for the in situ analysis of pertechnetate in environmental media.

The process to extract rhenium from a superalloy is an immense technical challenge due the complex chemistry involved. Being one of the rarest elements in the earth’s crust the scarcity and cost of rhenium makes it advantageous to recover the element from scrap superalloy. In this research the separation and monitoring of the different stages of the recycling process to extract rhenium from CMSX-4 superalloys using a distillation process were performed. This novel method combining distillation and use of exchange resins was used to separate rhenium from a complex mixture of metals in the CMSX-4 superalloy. The identification and quantitation of perrhenate and contaminants were performed by atomic absorption spectroscopy (AAS), Fourier transform infrared spectroscopy (FTIR), ion chromatography (IC) and Scanning Electron Microscopy- Energy Dispersive X-Ray (SEM-EDX). Perrhenate ions were extracted with purity close to 93%. The analytical characteristics for a novel infrared method to quickly identify perrhenate anions from CMSX-4 are presented. The main characteristics of the analytical validation were: LoD: 0.5% w/w; LoQ: 1.5% w/w; linear range 1.5-100% w/w; correlation coefficient R2 = 0.9905; precision (%RSD) for 10%w/w = 6.6 and 75%w/w = 4.1, respectively; accuracy (%) for 10% w/w 99.6% and 75% w/w=101.1, respectively.

Extraction of trace pertechnetate (99mTcO4–) from aqueous media using hydrophobic deep eutectic solvents (DESs) is reported for the first time. The hydrophobic DESs studied comprise a 1:2 molar rat...

A new quaternary phosphonium modified hierarchically macro/mesoporous silica (named HPS-P) was prepared by a sol–gel method accompanied by phase separation by using PEG-10000 as surfactant and tetramethoxysilane as silicon source, followed by reacting with quaternary phosphonium. The resultant HPS-P containing large macroporous skeleton with an average diameter of 0.67 μm and mesopores with an average diameter of 10.3 nm has a specific area of ca. 254.7 m2 g–1. The adsorption of HPS-P for ReO4– was investigated, and the adsorption equilibrium could be achieved within 1 min; the adsorption isotherm data for ReO4– could be well fitted with a modified Langmuir model. Moreover, HPS-P has excellent adsorption selectivities toward ReO4– with competing anions, including NO3–, SO42–, and Cl–. The ΔHΘ and ΔSΘ of the Cl–/ReO4– ion-exchange reaction of HPS-P were calculated to be −4.5 kJ mol–1 and 12.6 J mol–1 K–1, respectively, indicating that the adsorption of ReO4– onto HPS-P is a spontaneous physical adsorption ...

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.

At the Hanford Site in southeastern Washington state, the U.S. Department of Energy intends to treat 56 million gallons of legacy nuclear waste by encasing it in borosilicate glass via vitrification. This process ineffectively captures radioactive pertechnetate (TcO4–) because of the ion’s volatility, thereby requiring a different remediation method for this long-lived (t1/2 = 2.1 × 105 years), environmentally mobile species. Currently available sorbents lack the desired combination of high uptake capacity, fast kinetics, and selectivity. Here, we evaluate the ability of the chemically and thermally robust Zr6-based metal–organic framework (MOF), NU-1000, to capture perrhenate (ReO4–), a pertechnetate simulant, and pertechnetate. Our material exhibits an excellent perrhenate uptake capacity of 210 mg/g, reaches saturation within 5 min, and maintains perrhenate uptake in the presence of competing anions. Additionally, experiments with pertechnetate confirm perrhenate is a suitable surrogate. Single-crystal...

Receptors bearing hydrogen and halogen bond donors for recognition of perrhenate and pertechnetate were designed and studied. Acyclic hosts with N-H and C-H binding sites showed the best selectivity for TcO4- and ReO4- over spherical and more basic tetrahedral 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.

Ammonium perrhenate (APR) is an intermediate product in rhenium extraction process, by which it is possible to produce rhenium powder. The main purpose of this research is to investigate the behaviour of APR in different atmospheres as a part of reduction process. In this research, differential thermal analysis and thermo gravimetric analysis are used to peruse the APR behaviour in nitrogen, argon and hydrogen atmospheres. Also for further validation, X-ray diffraction analysis and the scanning electron microscopy were used. The results indicate that APR behaves almost the same in the argon and nitrogen atmospheres. In these conditions, APR decomposes to rhenium oxides during thermal decomposition. However, APR in hydrogen reductive atmosphere is reduced to pure rhenium powder without any reactions. SEM images showed that hydrogen reduced APR had a spherical morphology, but on the other hand the directly reduced rhenium powder in hydrogen atmosphere showed flake morphology.

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.

A static-batch technique was used to demonstrate the adsorption behavior of Re (VII) and Mo ions onto Dowex 21K at equilibrium in single and binary component systems. The single equilibrium adsorption data were modeled through a linear form of four widely used equilibrium isotherm equations. The results indicated that Freundlich and D-R models for Re, and Temkin and D–R isotherms for Mo fitted the obtained data satisfactorily. Binary adsorptions of Re and Mo ions onto Dowex 21K were also analyzed using Extended Langmuir, Modified Langmuir, Extended Freundlich and Langmuir–Freundlich models. The competitive Extended Freundlich model fitted the binary adsorption equilibrium data adequately. Studies on mutual interference effects of Mo ions on Re adsorption capacity indicated that the adsorption of perrhenate ions is always suppressed. In this perspective, the results from EDX studies confirmed the rhenium atom decrease in the simulated Re–Mo adsorption. However, under the studied conditions the affinity of the Dowex 21K for rhenium ions is marginally greater than that of molybdenum ions.

The pertechnetate anion (99TcO4–) is a long-lived radioactive species that is soluble in aqueous solution, in contrast to sparingly soluble 99TcO2. Results are reported for photocatalytic reduction...

Capture of radioactive TcO4- from nuclear wastes is extremely desirable for waste disposal and environmental restoration. Here, we report the synthesis of hydrolytically stable cationic covalent organic nanosheets (iCON) for efficient uptake of ReO4-, a nonradioactive surrogate of TcO4-. The iCON combines cationic guanidine-based knots with hydroxyl anchored neutral edge units and chloride ions loosely bonded in the pores, rendering extremely fast exchange kinetics toward ReO4- with high uptake capacity of 437 mg g-1 and prominent distribution coefficient of 5.0 × 105. The removal efficiency remains stable over a pH range of 3-12 and allows selective capture of ReO4- in the presence of excessive competing anions such as NO3-, CO32-, PO43- and SO42- with good removal efficiency for ReO4- in a simulated Hanford LAW Melter Recycle Stream. Anion exchange between the ReO4- in solution and the chloride ion in iCON plays dominant role in the adsorption of ReO4-. The iCON shows promise for effective removal of radioactive 99Tc from nuclear waste.

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.

Rhenium is one of the most valuable elements found in nature, and its capture and recycle are highly desirable for resource recovery. However, the effective and efficient collection of this material from industrial waste remains quite challenging. Herein, a tetraphenylmethane-based cationic polymeric network (CPN-tpm) nanotrap is designed, synthesized, and evaluated for ReO4 - recovery. 3D building units are used to construct imidazolium salt-based polymers with positive charges, which yields a record maximum uptake capacity of 1133 mg g-1 for ReO4 - collection as well as fast kinetics ReO4 - uptake. The sorption equilibrium is reached within 20 min and a kd value of 8.5 × 105 mL g-1 is obtained. The sorption capacity of CPN-tpm remains stable over a wide range of pH values and the removal efficiency exceeds 60% for pH levels below 2. Moreover, CPN-tpm exhibits good recyclability for at least five cycles of the sorption-desorption process. This work provides a new route for constructing a kind of new high-performance polymeric material for rhenium recovery and rhenium-contained industrial wastewater treatment.

Alpha-cyclodextrin based anion receptors functionalised with pendant arms containing halogen and hydrogen bond donor motifs display selective association of perrhenate in aqueous media at neutral pH. NMR and ITC anion binding investigations reveal the halogen bonding receptor to be the superior host.

Lanthanum perrhenate for use as a lubricating additive was prepared via the aqueous solution method in this study, and was dispersed into a pentaerythritol ester (PETE) base oil accompanied by surface active agents. The thermal stability of the complex oil with/without lanthanum perrhenate and surface active agents was evaluated by thermogravimetry. The influences of lanthanum perrhenate as a solid lubricating additive on the extreme pressure performance and friction-reducing property of the complex lubricants in a wide temperature range were investigated by four-ball tests and ball-on-disc frictional tests with a silicon nitride ball and Ni-base superalloy frictional pair. The results suggested that the added lanthanum perrhenate did not significantly affect the thermal stability and anti-oxidation properties of PETE, and improved the extreme pressure performance of the base oil. Additionally, it decreased the friction coefficient and wear scar diameter to a certain degree. The complex oil had a similar lubricating performance to the base oil below the decomposition temperature point; within the scope of 350 °C to 600 °C, the friction coefficients of oil containing the lanthanum perrhenate additive were markedly lower than that of the base oil, and this was attributed to lanthanum perrhenate's intrinsic shear susceptibility and resistance to phase transformation under high temperature conditions, enabling it to form an effective antifriction layer with native oxides of the superalloy matrix, thus reducing the friction in high-temperature environments.

The ability of cross-linked chitosan to take up perrhenate ions was studied systematically. The degree of sorption from acetate buffer solution at pH in the interval 2.8–3.1 reaches 85% and more. N-Sulfoethylation decreases the sorption ability of chitosan, but expands the pH interval of sorption and shifts the optimum pH value toward higher acidities. The sorption materials exhibit higher sorption rate than standard synthetic ion exchangers do. The data obtained suggest predominant ion-exchange mechanism of sorption of perrhenate ions onto chitosan and its sulfoethyl derivative.

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 (

In the rhenium solvent extraction process, molalities of perrhenate after extraction were measured from 278.15 to 303.15 K at impurity ionic strength from 0.2 to 2.0 mol·kg–1 in aqueous phase. Optimization condition of extraction was determined in this sulfuric acid medium. The standard extraction constants K0 at various temperatures were obtained by method of polynomial approximation. Thermodynamic quantities for the solvent extraction process were calculated.

The selective binding and trapping of perrhenate/pertechnetate is of great interest in the contamination remediation of nuclear waste. Herein, we report a cationic metal–organic framework (TJNU-216, TJNU = Tianjin Normal University), with ultra-high selectivity in trapping perrhenate/pertechnetate in the presence of a large excess of SO42− (20 000 times) or NO3− (300 times), and the highest exchange capacity of 417 mg g−1 (1 mol mol−1). The exchange mechanism can be confirmed by the crystal structure of TJNU-216(Re) via single-crystal-to-single-crystal transformation.

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.

This manuscript describes the application of Re_2O_7 to the syntheses of diarylmethanes from benzylic alcohols through solvolysis followed by Friedel–Crafts alkylation. The reactions are characterized by broad substrate scope, low catalyst loadings, high chemical yields, and minimal waste generation. The intermediate perrhenate esters are superior leaving groups to chlorides and bromides in these reactions. The polarity and water sequestering capacity of hexafluoroisopropyl alcohol are critical to the success of these processes. Re_2O_7 is a precatalyst for HOReO_3, which serves as a less costly and easily handled promoter for these reactions. Oxorhenium catalysts selectively activate alcohols in the presence of similarly substituted acetates, indicating a unique chemoselectivity and mechanism in comparison to Brønsted acid catalysis.

Devising sensors for the perrhenate anion in aqueous media is extremely challenging, and has seldom been reported in the literature. Herein, we report a fluorescence turn-on sensor for the perrhenate anion in aqueous media based on the aggregation-induced emission of a popular ultrafast molecular rotor dye, Thioflavin-T. The selective response towards the perrhenate anion has been rationalized in terms of matching water affinity, with the weakly hydrated perrhenate anion spontaneously forming a contact ion pair with the weakly hydrated ultrafast molecule-rotor-based organic cation, Thioflavin-T, which in turn leads to an aggregate assembly that provides a fluorescence turn-on response towards perrhenate. The sensing response of Thioflavin-T has been found to be quite selective towards the perrhenate anion when tested against anions that are ubiquitously present in the environment, such as chloride, nitrate, and sulfate anions. The formation of self-assembled Thioflavin-T aggregates has also been investigated by time-resolved emission and temperature-dependent measurements.

Low-symmetry metal–organic architectures that feature unusual binding motifs are useful for exploring new modes of guest recognition. Such structures remain difficult to create using current rational design principles. One approach to constructing such architectures is to employ ligands with coordination vectors oriented to preclude the formation of simple, low nuclearity molecular assemblies upon complexation to metal ions. Here we report two new supramolecular assemblies generated from such a ligand: a simple metastable [Zn3L3]6+ assembly, which was observed to convert to a more complex [Zn9L5(μ-OH)6]12+ twisted half-pipe architecture. Two chemically distinct stimuli—an anionic template and a base—must be applied for the conversion to occur. Perchlorate, perrhenate, trifluoromethanesulfonate and 2-naphthalenesulfonate were found to act as competent templates for the [Zn9L5(μ-OH)6]12+ structure.

A new imidazolium-based polymeric ionic liquid (PC2vimBr) gel was prepared by γ-radiation induced polymerization and crosslinking of 1-vinyl-3-ethylimidazolium bromide and a functional crosslinker 3,3′-divinyl-1,1′(1,6-hexanediyl) diimidazolium dibromide. A high gel fraction of ca. 95% could be achieved under 40 kGy, and the equilibrium degree of swelling and mechanical properties could be adjusted by crosslinker content and absorbed dose. The highest fracture compressive strength of PC2vimBr could be as high as 0.21 MPa. PC2vimBr could strongly adsorb perrhenate (ReO4−) with an adsorption capacity as high as ca. 8.6 × 102 mg g−1 (Re/gel), following a Langmuir model by an ion exchange mechanism, which was confirmed by IR and XPS. Competitive adsorption with the electrolytes or sodium dodecyl benzene sulfonate showed that the PC2vimBr gel has good efficiency for ReO4− removal from a low concentration of electrolyte solution or laundry waste water. Considering ReO4− is the natural analogue of TcO4−, PC2vimBr may be used in decontamination of low level wastes such as laundry wastes. Interestingly, PC2vimBr would shrink strongly after adsorbing ReO4−, which is meaningful for volume reduction of radioactive wastes.

A novel strong-base anion exchanger (PS-g-4VP-IE) is prepared by γ-irradiation-induced grafting of 4-vinyl pyridine onto polystyrene microspheres, followed by a quaternization process. The effects of absorbed dose and monomer concentration on grafting yield and quaternization time on conversion ratio were investigated in order to obtain optimum synthesis conditions. The FTIR and XPS results effectively manifest the successful synthesis of PS-g-4VP-IE. Furthermore, the effect of solution acidity on adsorption efficiency, adsorption kinetics and adsorption isotherm were investigated in batch-wise experiments. The results reveal that the adsorption towards perrhenate (ReO4−) not only has rather fast adsorption kinetics, but also matches well with the Langmuir isotherm model. Thus, its theoretical maximum adsorption capacity is deduced to be 252 mg g−1, while that of the couterpart is 247 mg g−1 in column experiments. The concentrated elution peak shows the potential application of PS-g-4VP-IE in concentrating ReO4−.

Technetium-99 (99Tc), largely produced by nuclear fission of 235U or 239Pu, is a component of radioactive waste. This study focused on a remediation strategy for the reduction of pertechnetate (TcO4-) by studying its chemical analogue rhenium (Re(VII)) to avoid the complication of directly working with radioactive elements. Nanoscale zero-valent iron particles supported on graphene (NZVI/rGOs) from GOs-bound Fe ions were prepared by using a H2/Ar plasma technique and were applied in the reductive immobilization of perrhenate (ReO4-). The experimental results demonstrated that NZVI/rGOs could efficiently remove Re from the aqueous solution, with enhanced reactivity, improved kinetics (50 min to reach equilibrium) and excellent removal capacity (85.77 mg/g). The results of X-ray photoelectron spectroscopy analysis showed that the mechanisms of Re immobilization by NZVI/rGOs included adsorption and reduction, which are significant to the prediction and estimation of the effectiveness of reductive TcO4- by NZVI/rGOs in the natural environment.

Silver compound [Ag(Quinox)](ReO4) (I) (Quinox is quinoxaline, C8H6N2) is synthesized, and its crystal structure is determined. The crystals are monoclinic: space group P21/c, a = 7.217(1), b = 15.238(1), c = 9.446(1) A, β = 93.77(2)°, V = 1036.6(2) A3, Z = 4, ρcalcd = 3.128 g/cm3. The structure includes cationic polymer chains [Ag(Quinox)]+∞. The Ag+ ion has an almost linear geometry (Ag(1)–N(1) 2.28(1) A, Ag(1)–N(2) 2.23(1) A, angle N(1)Ag(1)N(2) 169.0(5)°). The 3D supramolecular structure is formed due to a weak interaction of the oxygen atoms of the ReO4− anions with the silver ions. The compound is luminescent.