High Molybdenum Research Articles

Increased Molybdenum Loading for Vitrified High Level Waste

ABSTRACTThe solubility of molybdenum in borosilicate glasses is low. The UK National Nuclear Laboratory has developed a new glass formulation containing calcium and zinc for the vitrification of high molybdenum containing waste arising from the Post Operational Clean Out of the Highly Active Storage Tanks at Sellafield that will decrease the number of product containers required, reducing both production and disposal costs. The new formulation increases the quantity of molybdenum that can be vitrified through the formation of a durable CaMoO4 phase once the solubility limit of molybdenum in the glass has been exceeded. Extensive laboratory trials confirmed the potential to increase the Mo loading significantly. Recently full scale testing has been performed on the Vitrification Test Rig using highly active liquor simulants to determine the maximum MoO3 loading that can be achieved. This paper explores the full scale testing and product quality of the glass manufactured during this study.

Potential for Application of Special Stainless Steels for Chemical Process Equipments

The most predominant material of construction (MOC) for process equipments in chemical process industries (CPI) is plain carbon steel only. This is because of its lowest cost, easy availability, adequate thermal and mechanical properties, ease of fabrication etc. The only limitation is its low corrosion resistance. When corrosion resistance becomes the deciding factor, for overall resistance to general uniform corrosion, the common austenitic stainless steel Type 304(L) SS, 18/8(L) SS, is used. This has limitation with respect to uniform corrosion in reducing acids and to pitting corrosion, crevice corrosion and stress corrosion cracking in chloride containing media. In such situations, Type 316(L) SS, 18/8/2.5Mo/(L), shows somewhat better performance. These are called Standard Austenitic Stainless Steels. Even 316(L) SS shows unsatisfactory corrosion behavior in strong reducing acids, in concentrated chloride solutions at elevated temperatures and in fluids flowing with high velocities. In such cases, if the process conditions cannot be made milder with respect to corrosion phenomena, then there is a strong potential for upgrading the MOCs to Special Stainless Steels. These special stainless steels are either high nickel high molybdenum (~25 % Ni and ~6 % Mo) Super Austenitic Stainless Steels or low nickel (4 to 7 %) Duplex Stainless Steels. With respect to cost, the former are highly expensive than 316(L) SS because of widely varying amounts of nickel and of the presence of high molybdenum and the latter are marginally comparable with 316L SS. It is a common experience in industry that the usage of such special stainless steels is felt necessary only after facing severe corrosion problems in equipments made of standard stainless steels. The purpose of this paper is to present a few case studies of severe corrosion problems analyzed by the author resulting in recommendation of special stainless steel as the corrosion preventive step. The following case studies would be presented. Fertilizer Industry, Ammonia plant, Synthesis Gas Coolers Petrochemical Plant, Proprietary Amine manufacturing Reactor in the presence of Orthophosphoric Acid Petrochemical Plant, Proprietary Amine manufacturing process, Ammonia recovery column. Petrochemical Plant, Reboiler Tubes processing concentrated acetic acid.

High Capacity Microporous Molybdenum–Vanadium Oxide Electrodes for Rechargeable Lithium Batteries

Microporous Mo2.5+yVO9+δ with channels defined by seven-membered rings of corner-sharing MO6 (M = Mo5+/6+ or V4+/5+) octahedra belongs to the family of isostructural MoVNbTeO compounds, which are very active and selective oxidation catalysts for light alkanes. The large open channels which can accommodate small ions, together with the redox properties of Mo2.5+yVO9+δ, make this material of potential interest as a rechargeable intercalation electrode. Microcrystalline Mo2.5+yVO9+δ was synthesized by hydrothermal reaction of (NH4)6Mo7O24·4H2O and VOSO4·nH2O and exists in the composition range −0.13 ≤ y ≤ 0.05. The electrochemical properties of Mo2.5+yVO9+δ were investigated in Li/1 M LiPF6 in ethylene carbonate (EC) and dimethyl carbonate (DMC)/Mo2.5+yVO9+δ cells. When the cells are discharged between 3.9 and 1.5 V vs Li/Li+, up to 6 Li+ ions per formula unit are electrochemically inserted into the framework. Upon recharge, all of the Li+ ions can be extracted with minimal structural rearrangement. Unit cell dimensions for LixMo2.5+yVO9+δ (0 < x ≤ 6) phases prepared by chemical lithiation with n-BuLi have been determined by powder X-ray analysis and are closely related to those of the parent Mo2.5+yVO9+δ phase with orthorhombic Pba2 symmetry. Lithium cells of Mo2.5+yVO9+δ are rechargeable and exhibit a reversible capacity exceeding 300 mAh/g making Mo2.5+yVO9+δ a potential electrode material for secondary lithium batteries.

Synthesis of carboxylate derivatives of molybdenum and tungsten based on joint insertion of CO2 and PhNCS or N, N′-dicyclohexylcarbodiimide into M-Cl bonds

Reactions of the higher molybdenum and tungsten chlorides with phenyl isothiocyanate or with N, N′-dicyclohexylcarbodiimide and carbon dioxide in dichloroethane are the first to demonstrate the possibility of insertion of carbon dioxide in combination with other heterocumulenes into transition metal-halogen bonds. IR spectroscopy and elemental analysis data show that the reactions result in the attachment of the ligands at the same metal-chlorine bond and the formation of heteromolecular insertion products with the compositions $$\left[ {MoOCl_3 \left\{ {N\left( {Ph} \right)C\left( S \right)} \right\}_2 Nc\left( {Me} \right)Cl} \right]$$ and $$MCl_x \left\{ {OC\left( O \right)\left[ {\left( {Hex} \right)NCN\left( {Hex} \right)} \right]_2 } \right\}Cl,$$ where x = 4 and 5 for the Mo and W derivatives, respectively.

Seeds with high molybdenum concentration improved growth and nitrogen acquisition of rhizobium-inoculated and nitrogen-fertilized common bean plants

Seeds of common bean (Phaseolus vulgaris) with high molybdenum (Mo) concentration can supply Mo plant demands, but to date no studies have concomitantly evaluated the effects of Mo-enriched seeds on plants inoculated with rhizobia or treated with N fertilizer. This work evaluated the effects of seed Mo on growth and N acquisition of bean plants fertilized either by symbiotic N or mineral N, by measuring the activities of nitrogenase and nitrate reductase and the contribution of biological N2 fixation at different growth stages. Seeds enriched or not with Mo were sown with two N sources (inoculated with rhizobia or fertilized with N), in pots with 10 kg of soil. In experiment 1, an additional treatment consisted of Mo-enriched seeds with Mo applied to the soil. In experiment 2, the contribution of N2 fixation was estimated by 15N isotope dilution. Common bean plants grown from seeds with high Mo concentration flowered one day earlier. Seeds with high Mo concentration increased the leaf area, shoot mass and N accumulation, with both N sources. The absence of effects of Mo application to the soil indicated that Mo contents of Mo-enriched seeds were sufficient for plant growth. Seeds enriched with Mo increased nitrogenase activity at the vegetative stage of inoculated plants, and nitrate reductase activity at late growth stages with both N sources. The contribution of N2 fixation was 17 and 61 % in plants originating from low- or high-Mo seeds, respectively. The results demonstrate the benefits of sowing Mo-enriched seeds on growth and N nutrition of bean plants inoculated with rhizobia or fertilized with mineral N fertilizer.

Adsorption of Molybdenum on Mesoporous Aluminum Oxides for Potential Application in Nuclear Medicine

Inorganic oxides with high surface area find versatile applications in fields ranging from catalysis to medicine. In this study, we have investigated the potential of two mesoporous aluminum oxides with high surface area, MSU-X and Al-TUD-1, as adsorption materials for 99Mo/99mTc generators utilized in nuclear medicine. For this purpose we have studied the molybdenum adsorption kinetics and isotherms of these materials and we have compared them with acid activated aluminum oxide (AA) that is conventionally applied in generators. The results reveal that MSU-X and Al-TUD-1 have much better adsorption performance than AA in terms of kinetics and maximum adsorption capacity. The best results have been obtained for Al-TUD-1 reaching maximum adsorption capacity of 112 mg g−1, more than two times the adsorption capacity of AA materials. Furthermore, 40–50% of 99mTc could be removed from all sorbents in a single elution with negligible loss of 99Mo. Aluminum breakthrough has been found to be higher than the accepted limit in all tested materials when high molybdenum concentrations have been used, indicating that the aluminum oxides may need to be specially pre-treated in order to prevent contamination of the 99mTc eluate.

Electrical control of neutral and charged excitons in a monolayer semiconductor

Monolayer group-VI transition metal dichalcogenides have recently emerged as semiconducting alternatives to graphene in which the true two-dimensionality is expected to illuminate new semiconducting physics. Here we investigate excitons and trions (their singly charged counterparts), which have thus far been challenging to generate and control in the ultimate two-dimensional limit. Utilizing high-quality monolayer molybdenum diselenide, we report the unambiguous observation and electrostatic tunability of charging effects in positively charged (X(+)), neutral (X(o)) and negatively charged (X(-)) excitons in field-effect transistors via photoluminescence. The trion charging energy is large (30 meV), enhanced by strong confinement and heavy effective masses, whereas the linewidth is narrow (5 meV) at temperatures <55 K. This is greater spectral contrast than in any known quasi-two-dimensional system. We also find the charging energies for X(+) and X(-) to be nearly identical implying the same effective mass for electrons and holes.

Features of the Solid Solution (Mo&lt;SUB&gt;0&lt;/SUB&gt;&lt;SUB&gt;.&lt;/SUB&gt;&lt;SUB&gt;9&lt;/SUB&gt;,Cr&lt;SUB&gt;0&lt;/SUB&gt;&lt;SUB&gt;.&lt;/SUB&gt;&lt;SUB&gt;1&lt;/SUB&gt;)Si&lt;SUB&gt;2&lt;/SUB&gt; Formation Depending on the State of Initial Mixture

The regularities of solid state synthesis of the solid solution (Mo0.9 ,Cr0.1)Si2 in vacuum have been investigated in the temperature range 400-1200℃ depending on the dispersity and energetic state of the init ial powders, namely mo lybdenum, chro miu m and silicon. The energetic state of the in itial mixture was established to be a determin ing factor which affects the principal features of solid state interaction whereas an increase in dispersity only influences the temperature of the interaction start. When non-activated initial mixtures and ones mechanically activated in a p lanetary mill with lo w number of dru m revolutions were used, the solid solution formation proceeded owing to diffusion of silicon into metals through successive formation of lo wer and higher molybdenum-based silicide phases followed by their interaction. Mechanical activation in a planetary mill with high number of dru m revolutions was accompanied by not only decrease in particle size but also changes in the energetic state of the reaction mixture, which resulted in changing the regularities of the solid solution formation. Herein solid solutions on the basis of two higher molybdenum silicide phases, tetra- and hexagonal mod ifications, were formed with further poly morphic transition of the unstable high temperature hexagonal β-MoSi2 phase into the lo w temperature tetragonal α-MoSi2 phase. It has been established that temperature of the beginning of interaction decreases by 100℃ as compared with non-activated initial mixtures and temperature of the end of the process depends on the amount of accu mu lated energy: under low energy mechanical activation the process is co mplete at 1200℃, while a h igh energy activation decreases this temperature by 200-400℃ depending on the duration of activation.

Enhanced Charge Carrier Mobility in Two‐Dimensional High Dielectric Molybdenum Oxide (Adv. Mater. 1/2013)

Extremely high carrier mobilities are achieved in layered molybdenum oxide by Sivacarendran Balendhran, Kourosh Kalantar-zadeh, and co-workers on page 109. This is achieved by intercalation of the octahedral molybdenum oxide lattice with hydrogen, which tunes the bandgap of the material. Carrier mobilities of 1100 cm2 V−1 s−1 and greater are attained, highlighting the potential of ultrathin molybdenum oxide for high speed nanoelectronics.

Vitrification of high molybdenum feeds in the presence of reprocessing waste liquor

ABSTRACTAt Sellafield, the Post Operational Clean Out (POCO) of solids from the base of the highly active waste storage tanks, in preparation for decommissioning, will result in a high molybdenum stream which will be vitrified using the current Waste Vitrification Plant (WVP). In order to minimise the number of containers required for POCO, the high molybdenum feed could be co-vitrified by addition to reprocessing waste, using the borosilicate glass formulation currently utilised on WVP. Co-vitrification of high molybdenum feeds has been carried out using non-active simulants, both in the laboratory and on the Vitrification Test Rig (VTR) which is a full scale working replica of a WVP processing line.In addition, a new borosilicate glass formulation containing calcium has been developed by NNL which allows a higher incorporation of molybdenum through the formation of a durable CaMoO4 phase, after the solubility limit of molybdenum in the glass has been reached. Vitrification of the high molybdenum feed in the presence of varying quantities of reprocessing waste liquor using the new glass formulation has been carried out in the laboratory. Up to ∼10 wt% MoO3 could be incorporated without any detrimental phase separation in the product glass, but increasing the fraction of reprocessing waste was found to decrease the MoO3 incorporation. Soxhlet and static powder leach tests have been performed to assess the durability of the glass products. This paper discusses the results of the vitrification of high molybdenum feeds in the presence of reprocessing liquor in both the borosilicate glass formulation currently utilised on WVP and the modified formulation which contain calcium.

High performance platinum-free counter electrode of molybdenum sulfide–carbon used in dye-sensitized solar cells

A high porous molybdenum sulfide–carbon (MoS2–C) hybrid film was prepared by using an in situ hydrothermal route. The MoS2–C hybrid film served as a low-cost and high efficient platinum-free counter electrode for a dye-sensitized solar cell (DSSC). The cyclic voltammetry, electrochemical impedance spectroscopy and Tafel curve analysis indicate that the MoS2–C electrode possesses low charge transfer resistance on the electrolyte–electrode interface, high electrocatalytic activity and fast reaction kinetics for the reduction of triiodide to iodide at the counter electrode, which is due to large specific surface area and special structure and compositions of MoS2–C film. A DSSC with the novel MoS2–C counter electrode achieve a high power conversion efficiency of 7.69% under standard light illumination, which exceeds that of the DSSC with a Pt counter electrode (6.74%).

The modifier/former role of MoO3 in some calcium-phosphate glasses

This paper report the results obtained by EPR and Raman investigations of xMoO3⋅(100−x)[P2O5⋅CaO] with 0⩽x⩽50mol% glass system. From EPR spectroscopy were evidenced the local symmetry and the interaction between Mo5+ ions. Depending on the content of MoO3 were highlighted the EPR spectra modifications. By Raman spectroscopy were identified and analyzed the modification which appear on the characteristic bands of these glasses. At low concentration of molybdenum oxide the specific Raman bands of long phosphate chains (Q2) dominate the spectra meanwhile for high molybdenum content the most intense bands are those specific to MoO3 and short phosphate groups. From both techniques we can conclude that at low concentration of molybdenum oxide, it acts as a very strong network modifier while for high concentrations it plays the role of network co-former.

Enhanced Charge Carrier Mobility in Two‐Dimensional High Dielectric Molybdenum Oxide

We demonstrate that the energy bandgap of layered, high-dielectric α-MoO(3) can be reduced to values viable for the fabrication of 2D electronic devices. This is achieved through embedding Coulomb charges within the high dielectric media, advantageously limiting charge scattering. As a result, devices with α-MoO(3) of ∼11 nm thickness and carrier mobilities larger than 1100 cm(2) V(-1) s(-1) are obtained.

Removal of Molybdate Anions from Water by Adsorption on Zeolite‐Supported Magnetite

Industrial wastewater may contain high molybdenum concentrations, making treatment before discharge necessary. In this paper, the removal of molybdate anions from water is presented, using clinoptilolite zeolite coated with magnetite nanoparticles. In batch experiments the influence of pH, ionic strength, possible interfering (oxy)anions, temperature and contact time is investigated. Besides determination of kinetic parameters and adsorption isotherms, thermodynamic modeling is performed to get better insight into the adsorption mechanism; molybdenum is assumed to be adsorbed as a FeOMoO2(OH).2H2O inner-sphere complex. At the optimum pH of 3, the adsorption capacity is around 18 mg molybdenum per gram adsorbent. The ionic strength of the solution has no influence on the adsorption capacity. Other anions, added to the molybdenum solution in at least a tenfold excess, only have a minor influence on the adsorption of molybdenum, with the exception of phosphate. Adsorption increases when temperature is increased. It is demonstrated that the adsorbent can be used to remove molybdenum from industrial wastewater streams, and that the limitations set by the World Health Organization (residual concentration of 70 microg/l Mo) can easily be met.

Mechanical energy losses in plastically deformed and electron plus neutron irradiated high purity single crystalline molybdenum at elevated temperatures

AbstractMechanical spectroscopy (MS) and transmission electron microscopy (TEM) studies have been performed in plastically deformed and electron plus neutron irradiated high purity single crystalline molybdenum, oriented for single slip, in order to study the dislocation dynamics in the temperature range within one third of the melting temperature. A damping peak related to the interaction of dislocation lines with both prismatic loops and tangles of dislocations was found. The peak temperature ranges between 900 and 1050 K, for an oscillating frequency of about 1 Hz.

Weldability of New Ferritic Stainless Steel for Exhaust Manifold Application

In the current context of fossil energy scarcity, car manufacturers have to optimize vehicles energy efficiency. This and continuous improvement includes a change of the exhaust manifold design. Usually in cast iron, exhaust manifolds tend to be mechanically welded in order to fit new constraints such as lightness, durability, efficiency and small size. To achieve such requirements, ferritic stainless steels with high chromium content (19%) and molybdenum (2%) are developed. For the welding, the use of existing filler wire does not satisfy fully the application requirements. This leads to oxidation problems and / or thermal fatigue strength that drastically reduces assembly lifetime. New flux cored wires are developed in the context of this study in order to provide molten zone characteristics close to those of the base metal. Different chemical compositions are tested in order to highlight the influence of stabilizing element on microstructure. Welding tests revealed the major influence of titanium on the grain refinement in the molten zone. A minimum Ti content of 0.45 weight % in the filler wire is required to be efficient as grain refiner.

Weldability of New Ferritic Stainless Steel for Exhaust Manifold Application

In the current context of fossil energy scarcity, car manufacturers have to optimize vehicles energy efficiency. This and continuous improvement includes a change of the exhaust manifold design. Usually in cast iron, exhaust manifolds tend to be mechanically welded in order to fit new constraints such as lightness, durability, efficiency and small size. To achieve such requirements, ferritic stainless steels with high chromium content (19%) and molybdenum (2%) are developed. For the welding, the use of existing filler wire does not satisfy fully the application requirements. This leads to oxidation problems and / or thermal fatigue strength that drastically reduces assembly lifetime. New flux cored wires are developed in the context of this study in order to provide molten zone characteristics close to those of the base metal. Different chemical compositions are tested in order to highlight the influence of stabilizing element on microstructure. Welding tests revealed the major influence of titanium on the grain refinement in the molten zone. A minimum Ti content of 0.45 weight % in the filler wire is required to be efficient as grain refiner.

Evaluation of substrate and amendment materials for soil reclamation at a diamond mine in the Northwest Territories, Canada

Drozdowski, B. L., Naeth, M. A. and Wilkinson, S. R. 2012. Evaluation of substrate and amendment materials for soil reclamation at a diamond mine in the Northwest Territories, Canada. Can. J. Soil Sci. 92: 77–88. Mine waste materials with potential for use in soil construction at a diamond mine in the Northwest Territories were evaluated to address physical and chemical limitations for plant establishment, growth and development. Substrates were glacial till, gravel, processed kimberlite, and 50:50 and 25:75 mixes of processed kimberlite and till. Amendments were salvaged topsoil, sewage sludge, inorganic fertilizer and sludge from a water treatment facility. Reclamation soils constructed with these materials were adequate for revegetation. Mixes of processed kimberlite and glacial till enhanced soil structure and diluted adverse concentrations of elements. The original gravel pad, alone or amended, was a suitable substrate for plants. Addition of organic amendments topsoil and sludge, to any substrate, increased organic matter, nutrients and surface water retention. Of amendments evaluated, salvaged topsoil provided the most consistent increase in plant density among substrates. Inorganic fertilizer applied to gravel or till provided results similar to those with topsoil. Sludge had potential to amend mixes of processed kimberlite and till, although results were variable. Sewage was a good source of organic matter, increasing soil water content and macro nutrients. Vegetation response was poor in sewage-amended treatments likely due to combined effects of high copper, molybdenum, phosphorus, selenium, sulphate and zinc.

Effects of Zinc Supplementation on the Element Distribution in Kidney Tissue of Diabetic Rats Subjected to Acute Swimming

In this study, we report the effect of zinc supplementation on the distribution of elements in kidney tissue of diabetic rats subjected to acute swimming exercise. Diabetes was induced by two subcutaneous injections of 40 mg/kg of streptozotocin within a 24-h period. Zinc was given intraperitoneally at a dose of 6 mg/kg per day for a period of 4 weeks. The rats (n = 80) were equally divided into eight study groups: controls, zinc-supplemented, swimming, diabetic, zinc-supplemented diabetic, zinc-supplemented swimming, diabetic swimming, and zinc-supplemented diabetic swimming. The levels of lead, cobalt, molybdenum, chromium, boron, magnesium, iron, copper, calcium, zinc, and selenium were determined in the kidney tissue samples by ICP-AES. Higher molybdenum, calcium, zinc, and selenium values were found in both swimming and nonswimming diabetic rats. Significantly higher iron values were found in swimming, diabetic, diabetic swimming, and zinc-supplemented diabetic swimming rats (p < 0.001). Diabetic, zinc-supplemented diabetic, diabetic swimming, and zinc-supplemented diabetic swimming rats had the highest copper values. These results show that zinc supplementation normalized the higher levels of molybdenum, calcium, selenium, and iron levels seen in diabetic rats, indicating that zinc may have a regulatory effect on element metabolism in kidney tissue.

THE EXTREME OVERABUNDANCE OF MOLYBDENUM IN TWO METAL-POOR STARS

We report determinations of the molybdenum abundances in five mildly to extremely metal-poor turnoff stars using five Mo II lines near 2000A. In two of the stars, the abundance of molybdenum is found to be extremely enhanced, as high or higher than the neighboring even-Z elements ruthenium and zirconium. Of the several nucleosynthesis scenarios envisioned for the production of nuclei in this mass range in the oldest stars, a high-entropy wind acting in a core-collapse supernova seems uniquely capable of the twin aspects of a high molybdenum overproduction confined to a narrow mass range. Whatever the details of the nucleosynthesis mechanism, however, this unusual excess suggests that very few individual nucleosynthesis events were responsible for the synthesis of the light trans-Fe heavy elements in these cases, an unexpected result given that both are only moderately metal-poor.