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The milling of molybdenite under cryogenic conditions in argon has been performed for the first time, and the physicochemical properties of its samples, their catalytic activity in model reactions of hydrodesulfurization of dibenzothiophene and diesel components, and the ability to initiate the isopropylbenzene oxidation reaction have been studied. The samples have been found to exhibit high catalytic activity. [ABSTRACT FROM AUTHOR]

Molybdenum is the most important by-product of Chile's copper mining industry, and during the last decade gained international relevance because of its high price At mining deposits, copper and molybdenum are extracted together and then separated in a process consisting of several stages of flotation using sodium hydrosulfide (NaHS) as key reagent. However, environmental issues related to the potential emissions of toxic hydrosulfide gas (H 2 S), and bad odors make necessary the development of new environmentally friendly processes that incorporate non-toxic reagents. In this work, we hypothesize that a selective separation of chalcopyrite and molybdenite by flotation can be achieved by using lignosulfonates instead of NaHS. This approach was evaluated by testing the effect of lignosulfonates, produced by reacting kraft lignin with sodium sulfite and formaldehyde, and commercially available lignosulfonates, on molybdenite and chalcopyrite flotation. Chemical characterization of lignosulfonates was performed by determination of molecular mass, elemental analysis, fourier transform infrared, and mass spectroscopy with inductively coupled plasma. Also, interactions between molybdenite and lignosulfonates were studied through measurements of electrophoretic mobility. The main conclusions of the work are that molybdenite flotation can be depressed by the action of lignosulfonates, and such depressing effect increases with pH because of the interactions between lignosulfonates with the metallic calcium sites existing on the surface of the mineral particles. The experimental results also indicate that lignosulfonates can depress chalcopyrite flotation when sodium isopropyl xanthate is used as a collector, but this effect can be completely mitigated by using potassium amyl xanthate as a collector, thus, making it possible the potential separation of both minerals. Image 1 • Lignosulfonates from kraft lignin depress molybdenite flotation at alkaline conditions when pH is adjusted with lime. • Lignosulfonates depress chalcopyrite flotation when pH is adjusted with lime using sodium isopropyl xanthate as collector. • Lignosulfonates do not depress chalcopyrite when pH is adjusted with lime using potassium amyl xanthate as collector. • The degree of anionicity is a key variable to explain the interactions between lignosulfonates and molybdenite. [ABSTRACT FROM AUTHOR]

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Understanding the occurrence of Re in ore minerals is the prerequisite for comprehensive recovery of rhenium. The study on the occurrence of Re in copper-molybdenum ores of Fujiawu deposit is lacking. Chemical analysis, optical microscopic identification, electron probe analysis, sieve analysis and balance classification were used to systematically process a mineralogy study on the porphyry type copper-molybdenum ore and phyllite type copper-molybdenum ore from the Fujiawu copper molybdenum mine, in order to understand the present state of Re in ores and the factors affecting the recovery and utilization of Re in ores. No independent rhenium minerals have been found, and Re is dispersed in minerals such as molybdenite chalcopyrite, pyrite, galena, and zircon. The content of Re ranges from 0.001% to 0.267%. Molybdenite is the target mineral for enrichment and recovery of Re with Re content up to 684×10-6. Moreover, the grade change of Re and Mo is similar in different particle sizes. For the comprehensive recovery of Re from two types of copper-molybdenum ores, the differences in molybdenite content and types of gangue minerals should be taken into consideration, and the ore to be used should be classified. Meanwhile, when the ore is crushed and ground, it should not be crushed excessively, in order to improve the comprehensive recovery of Re at +0.023 mm.

Molybdenite from two porphyry copper mineralisation sites within the South Urals was studied by electron microprobe (EMPA), micro x-ray diffraction (μXRD) and electron backscattered diffraction (EBSD) methods. Elevated contents of rhenium (0.2 to 0.4, sometimes up to 1.1 wt.%) form linear zones from several to tens of micrometres wide and up to hundreds of micrometres long parallel to the elongation of molybdenite flakes. In most cases Re-rich zones are composed of the rhombohedral (3 R) polytype of molybdenite, while the rest of the molybdenite flakes with ca. 0.1 wt.% of Re consist of hexagonal (2 H) molybdenite. In rare cases Re-rich zones are confined to grain boundaries of molybdenite-2 H. It is shown that both μXRD and EBSD are the most appropriate tools to distinguish different polytypes within a single grain of molybdenite. [ABSTRACT FROM AUTHOR]

The Xinlu Sn‐polymetallic ore field is located in the western Nanling Polymetallic Belt in northeastern Guangxi, South China, where a number of typical skarn‐, hydrothermal vein‐type tin deposits have developed. There are two types of Sn deposits: skarn‐type and sulfide‐quartz vein‐type. The tin mineralizations mainly occur on the south side of the Guposhan granitic complex pluton and within its outer contact zone. To constrain the Sn mineralization age and further understand its genetic links to the Guposhan granitic complex, a series of geochronological works has been conducted at the Liuheao deposit of the ore field using high‐precision zircon SHRIMP U‐Pb, molybdenite Re‐Os, and muscovite Ar‐Ar dating methods. The results show that the biotite‐monzogranite, which is part of the Xinlu intrusive unit of the Guposhan complex pluton, has a SHRIMP U‐Pb zircon age of 161.0 ± 1.5 Ma. The skarn‐type ore has a 40Ar‐39Ar muscovite plateau age of 160 ± 2 Ma (same as its isochron age), and the sulfide‐quartz vein‐type ore yields an Re‐Os molybdenite isochron age of 154.4 ± 3.5 Ma. The magmatic‐hydrothermal geochronological sequence demonstrated that the hydrothermal mineralization took place immediately following the emplacement of the monzogranite, with the skarn metasomatic mineralization stage predating the sulfide mineralization stage. Geochronologically, we have compared this ore field with 26 typical Sn deposits distributed along the Nanling Polymetallic Belt, leading to the suggestion of the magmatic‐metallogenic processes in the Xinlu ore field (ca. 161–154 Ma) as a component of the Early Yanshanian large‐scale Sn‐polymetallic mineralization event (peaked at 160–150 Ma) in the Nanling Range of South China. Petrogenesis of Sn‐producing granite and Sn‐polymetallic mineralization were probably caused by crust–mantle interaction as a result of significant lithospheric extension and thinning in South China in the Late Jurassic. [ABSTRACT FROM AUTHOR]

Geological characteristics, trace element geochemistry, and Re–Os dating of molybdenite are presented and discussed for seven Cu and Mo porphyry, one Cu skarn-porphyry and two Mo and Mo–W greisen deposits. Re contents in molybdenite are discussed versus ore mineralogy, molybdenite polytypes, formation temperature, and whole rock chemistry of parental rocks. They are also evaluated in the light of the geotectonic settings of these deposits and tectonic history of the Urals. Re–Os dating of molybdenite evidences that the porphyry deposits studied are confined to four volcanic arc terranes of the Urals and are linked to four subduction events: Tomino and Birgilda (ca. 430 Ma) and Zeleny Dol (ca. 420 Ma) porphyry deposits linked to the East Uralian volcanic arc; Voznesenskoe porphyry (ca. 395 Ma) and Verkhneuralskoe porphyry (ca. 365 Ma) deposits linked to the Magnitogorsk arc and its collision to the East European continent respectively; Mikheevskoe porphyry and Tarutino skarn-porphyry deposits (ca. 360 Ma) linked to subduction under the East Uralian microcontinent; Benkala porphyry deposit (ca. 335 Ma) linked to the activity of the Valerianovka Andean-type arc. The Talitsa Mo porphyry deposit (ca. 300 Ma) as well as Yuzhno-Shameiskoe (ca. 280 Ma) and Koklanovskoe (ca. 255 Ma) greisen Mo–W deposits are linked to collision between East European and Kazakh continents. Electron microprobe analysis and laser ablation inductively coupled mass-spectrometry of molybdenite demonstrate an extremely irregular distribution of all trace elements on both grain-scale and deposit-scale levels. Most trace elements (Fe, Co, Cu, Zn, As, Se, Ag, Sb, Te, Pb, Bi, etc.) form mineral inclusions within molybdenite while Re and W are commonly incorporated into molybdenite lattice. Re contents and distribution in molybdenite are indicative for tectonic setting of the deposits. Molybdenite from deposits formed within intra-oceanic arcs (Mikheevskoe, Tomino, and Voznesenskoe porphyry Cu deposits) is featured by high Re contents (1000–5000 ppm) and low W contents (<10 ppm). Molybdenite from Verkhneuralskoe (arc-continent collision stage) and Benkala (Andean-type arc) deposits is featured by lower Re contents (mainly 400–900 ppm) and higher W contents (30–120 ppm). Molybdenite from Talitsa Mo-porphyry, and Yuzhno-Shameiskoe and Koklanovskoe greisen deposits (continent-continent collision) is featured by the lowest Re contents (<10 ppm to 370 ppm) and the highest W contents (10 to 150 ppm). Geometrical mean Re content in molybdenite for all ten deposits studied has positive correlation with average Cu/Mo ratio in ore implying mass balance was one of the key controls of Re incorporation in molybdenite. In addition, Re content has a negative correlation with SiO 2 and total REE contents in ore-bearing intrusive rocks as well as with the absolute age of the deposits which correlates with the general evolution of porphyry- and greisen-type deposits of the Urals. For subduction-related porphyry deposits magma composition was generated with strong influence of the shallow subduction component. Fluid-mobile elements and various degrees of partial melting of the mantle wedge strongly depend on Re contents. Collision tectonic settings are marked by low Re concentrations in molybdenite. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Ahadawa deposit is a newly discovered porphyry Cu–Mo system in the North Qaidam. • The Ahadawa formed by more than 25 Ma prolonged magmatic-hydrothermal activity. • The Late Triassic fertile magmas initially had high water and high oxygen fugacity. • Plagioclase-dominated fractionation occurred with magma evolution. Ongoing exploration in the North Qaidam, Northern Qinghai-Tibet Plateau, NW China, has led to the identification of a porphyry Cu-Mo system centered on Ahadawa. In this study, we conducted a detailed geochronological and geochemical study on porphyritic monzogranite from the Ahadawa deposit, which hosts the Cu-Mo mineralization. The weighted mean zircon U-Pb ages for three mineralized porphyritic monzogranite samples from different sites range from 218.8 ± 1.2 Ma (MSWD = 1.5) to 224.7 ± 1.6 Ma (MSWD = 1.8), and finally to 233.1 ± 0.9 Ma (MSWD = 1.4, n = 23). These results, combined with antecrystic grains as old as ∼ 245.7 Ma, collectively indicate more than 25 Ma multi-stage magmatic emplacement activity in the Ahadawa deposit. Corresponding to complex magma episodes, six studied molybdenite samples yielded variable Re-Os model ages ranging from 436.7 ± 6.6 to 232.6 ± 1.2 Ma, with the three youngest dates constraining a weighted mean Re-Os age of 234.0 ± 6.8 Ma. The 234 Ma mineralization age is consistent with the observed Late Triassic magmatism, whereas the Re-Os model ages of 436.7 to 245.7 Ma, if they remain robust through future investigation, may highlight a long-lived hydrothermal activity in the Ahadawa deposit. Whole-rock and zircon compositions indicate that the Late Triassic porphyries occurring at the surface display distinct geochemical features, with the early porphyritic monzogranite of 233.1 Ma characterized by much higher whole-rock Sr/Y, and zircon Eu/Eu* and Ce/Ce* than the younger (218.8 Ma and 224.7 Ma, respectively) porphyritic monzogranite. This suggests that the Late Triassic magmas were initially characterized by high water content and high oxidation state and the differences between the old and two younger groups might be related to plagioclase-dominated fractionation. The finding of the Ahadawa porphyry system highlights the need for ongoing exploration (especially in poorly studied remote areas) and systematically geochronological and geochemical studies to constrain the temporal and spatial evolution of mineralized episodes within a complex, protracted magmatic history. [ABSTRACT FROM AUTHOR]

In this paper, the effect mechanism of calcium hypochlorite on the adsorption of the collector DDTC on the surface of molybdenite and bismuthinite was explored. The single mineral flotation test showed that calcium hypochlorite had significant inhibition on the flotation behavior of bismuthinite, but had no similar effect on that of molybdenite. The results of FT-IR spectra and contact angle measurement indicated that the collector DDTC was not able to adhere to the bismuthinite surface treated with calcium hypochlorite, but could adhere to the molybdenite surface treated with the same way. Synthesizing the results of electrochemical test, thermodynamic analysis, Raman spectra, and Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) test, it could be confirmed that calcium hypochlorite could react on the surface of bismuthinite and molybdenite, and the reaction on the bismuthinite surface first produced Bi3+ and Cl-, which continued to react in solution and finally formed BiOCl precipitation, while the reaction on the molybdenite surface formed soluble components, which dissolved into the solution. Therefore, the hydrophilic BiOCl precipitation covered the bismuthinite surface, hindering the adsorption of DDTC, while the soluble components produced on the molybdenite surface entered the solution without affecting its surface wettability and collector adsorption, which maybe was the root cause of the selective depression of calcium hypochlorite. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • We report the discovery of a Molybdenum (Mo) porphyry deposit at Shuvuutai, central-east Mongolian. • Molybdenum mineralization spatially and genetically related to Early Permian multi-phase porphyry intrusions. • Ore-forming fluids were initially magmatic and later hydrothermal mineralization evolved with four main stages. • We suggest a new strategy for exploration for Mo and related porphyry deposits in Mongolia and China. We document the newly discovered Shuvuutai Molybdenum (Mo) porphyry deposit located in the central-east Mongolian volcanic/-plutonic belt of the southern Altaids. The deposit is characterized by quartz vein- and veinlet-disseminated-type Mo ore bodies mainly hosted in a Late Permian-Early Triassic granitic intrusion. In this study, we provide a detailed study that integrates detailed geology with petrographic, mineralogic, geochemical, and geochronologic date to determine the tectonic setting of the deposit. Fluid inclusion analysis is used to reconstruct the fluid evolution history of the Shuvuutai Mo mineralization system and to understand the origin of the deposit. The ore bodies occur mainly as veins, lenses, and pods in positions from inner intrusions through contact zones to the host rocks distal to causative intrusions. The host rocks are variable in lithology, including granites, porphyries, volcanic breccias and tuffs, and sedimentary rocks. Outward from ore bodies to host rocks, the wall rock alteration is zoned from potassic (K-feldspar-quartz-mica), through phyllic (quartz-sericite-chlorite-epidote), to propylitic or argillic alterations. Two samples from porphyry stock intrusions at Shuvuutai were selected for U–Pb zircon geochronology and trace element composition studies, including the ore-hosting monzodiorite porphyry and quartz syenite porphyry. Our new ages are consistent with, or slightly postdate published zircon U-Pb ages of early phase of monzodiorite porphyry (268–232 Ma) and the main phase of quartz syenite porphyry (251.6 ± 1.7 Ma). Hydrothermal mineralization generally includes four stages, from early to late, represented by (1) potassic feldspar-quartz veins or veinlets, (2) quartz-molybdenite stockworks, (3) quartz-sulfide stockworks, and (4) quartz ± carbonate veins or veinlets. The ore-forming fluids were initially magmatic in origin and show high-temperature and high-salinity, containing daughter mineral and CO 2 -bearing fluid inclusions; and eventually evolved to low-temperature, low-pressure, low-salinity and CO 2 -poor meteoric water. S isotopic compositions of sulfides from the Shuvuutai Mo porphyry deposit indicate that the source of the ore-forming material was derived from the felsic magma. The Central-Eastern Mongolian volcanic-plutonic belt continues from Mongolia into northeast China, where similar Mo deposits are not yet recognized, suggesting that a new exploration strategy, based on the characteristics and history of the Shuvuutai discovery, is needed for the Chinese segment of the Altaids. [ABSTRACT FROM AUTHOR]

In the high-resolution HAADF STEM images of the Re-rich area in molybdenite, a large number of layered structures appear (Fig. a), and a rare five-fold twinning was identified (Fig. b). Its formation is related to plastic deformation caused by the low stacking fault energy and stress of hexagonal molybdenite. Re atoms are mainly enriched in the area where the five-fold twinning and other lattice defects occur (Fig. c). It is speculated that the stepwise formation of five-fold twinning may be an important mechanism for the enrichment of Re in molybdenite (Fig. d). [Display omitted] • The extremely heterogeneous of rhenium content and irregular distribution in molybdenite may be a common phenomenon in nature. • The Re atoms were clarified to exist in the Re-rich area in the form of in situ substitution of Mo atoms. • Lattice defects such as five-fold twinning is an important mechanism for the enrichment of Re in molybdenite. • The formation mechanism of Re-rich molybdenite in the Merlin deposit involves the decrease in temperature and oxygen fugacity of the ore-forming fluid, as well as the increase in S2- concentration. Rhenium (Re) is one of the critical metals, and molybdenite (MoS 2) is the main host mineral for Re. Previous studies have shown that the distribution of Re in molybdenite is highly heterogeneous, and the occurrence state and enrichment mechanism of Re in molybdenite is not clear. The molybdenite of Merlin deposit has typical Re rich characteristics, which is an ideal object to study the occurrence state and enrichment mechanism of Re in molybdenite. Based on the geological research of the deposit, this study systematically investigated the Re-rich molybdenite of the Merlin deposit using LA-ICP-MS and STEM techniques. The LA-ICP-MS results showed that the content of Re in molybdenite ranged from 67 to 2726 ppm, and the distribution of Re content in molybdenite was extremely uneven and irregular. The STEM results showed that there was no independent Re mineral in molybdenite, and Re atoms were found to substitute molybdenum (Mo) atoms in situ in the Re-rich area of molybdenite. The substitution mechanism of Re was clarified at the atomic scale in a visual form, and a corresponding rigid sphere stacking model was established. Mo atoms are sandwiched between two layers of S atoms, while Re atoms enter the molybdenite lattice and substitute Mo atoms in situ, thus changing the lattice structure of the original molybdenite matrix. Rare lattice defects such as five-fold twinning were identified in the Re-rich area of molybdenite in high-resolution HAADF STEM images, which are related to plastic deformation caused by the low stacking fault energy and stress of hexagonal molybdenite. It is speculated that lattice defects such as five-fold twinning is an important mechanism for the enrichment of Re in molybdenite. The magmatic-hydrothermal fluids released from the intrusion of igneous rocks may have provided the main source of ore-forming materials for the Merlin deposit. The ore-forming fluids, which are rich in Mo4+ and Re4+, underwent redox reactions with carbonaceous shale, resulting in the decrease in temperature and oxygen fugacity, and the increase in S2- concentration. This ultimately led to the precipitation and enrichment of Re4+ and Mo4+ to form the Re-rich molybdenite in the Merlin deposit. [ABSTRACT FROM AUTHOR]

[Display omitted] • Better flotation and attachment behavior of fine molybdenite were achieved using CTD. • Abundant of aromatic compounds in the CTD were exacted from coal tar. • Aromatic compounds were preferentially adsorbed on the (1 0 0) plane of molybdenite. • Larger adsorption amounts of CTD were responsible for superior flotation efficiency. With the depletion of high-grade molybdenum (Mo) deposits, it is more pressing to separate the low-grade deposits effectively due to the large demand for Mo. However, traditional hydrocarbon oil collectors such as kerosene suffered low collecting capacity for low-grade ores because of the fine disseminated nature and crystal anisotropy of molybdenite. In this study, the effect of a compound collector prepared from coal tar and dodecane (CTD) on the flotation of fine molybdenite was investigated by micro-flotation experiments, bubble-particle attachment tests, gas chromatography-mass spectrometry (GC–MS), density functional theory (DFT) calculations, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The results of micro-flotation experiments demonstrated that CTD improved the flotation recovery of fine molybdenite dramatically compared with dodecane and kerosene, the fine particles pretreated with CTD had a better affinity for bubbles, and a stronger mineralization efficiency was achieved than that with dodecane as the improvement of the surface coverage and attachment rate constant. The results of GC–MS, FTIR, and DFT calculations indicated that there were plenty of compounds with benzene rings in the CTD, especially for phenanthrene and naphthalene, which showed a stronger interaction on the (1 0 0) plane of molybdenite than dodecane, thereby proving a stronger affinity for hydrophilic planes. The results of XPS analysis depicted that more adsorption amounts were achieved on molybdenite by CTD than that of dodecane, and contact angle test results further demonstrated that the effect of CTD was stronger than dodecane in improving the hydrophobicity of fine molybdenite particles. In general, the compound collector (CTD) is beneficial to the improvement of attachment rate of molybdenite particles to bubble and hydrophobicity of molybdenite particles, which improves the flotation recovery of fine molybdenite. The extract from coal tar had more affinity for the (1 0 0) plane of molybdenite compared to the (0 0 1) plane through DFT calculations. The finding has important reference value and guiding significance for the future research on collectors for fine molybdenite flotation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ca(ClO) 2 exhibited a stronger depressing power to bismuthinite than molybdenite. • Bismuthinite surface became rough and hydrophilic due to the deposition of BiOCl. • The presence of BiOCl impeded the adsorption of kerosene onto bismuthinite surface. • Molybdenite surface was not affected by Ca(ClO) 2 and remained affinity to kerosene. • Ca(ClO) 2 showed superior separation performance than conventional depressant Na 2 S. Molybdenite and bismuthinite are valuable components arising from Mo–Bi sulfide ore, and their recoveries are considerably limited by separation efficiency. Herein, calcium hypochlorite (Ca(ClO) 2) was first introduced as bismuth depressant for efficient separation of molybdenite and bismuthinite, and its depression mechanisms were investigated through a series of analytical techniques supplemented with solution chemistry and thermodynamic calculations. Flotation results showed that Ca(ClO) 2 had a stronger depressing ability than conventional depressant sodium sulfide and exhibited superior selectivity for bismuthinite against molybdenite. At pH around 8.0, the high-selective separation of Mo–Bi bulk concentrate was realized, where more than 96% of molybdenite was recovered and over 98% of bismuthinite was depressed. Solution chemistry and thermodynamic analysis indicated that the bismuthinite surface was preferentially oxidized by Ca(ClO) 2 to SO2- 4 and Bi3+. The former dissolved into solution and existed as stable ions, whereas the Bi3+ further interacted with Cl− and was hydrolyzed as BiOCl precipitates. Surface analysis demonstrated that the deposition of BiOCl on the bismuthinite surface not only made its surface rougher but also enhanced its surface hydrophilicity. In comparison, the surface of molybdenite was slightly oxidized and it remained hydrophobic as confirmed from scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and contact angle results. The difference in surface characteristics resulted in the selective adsorption of collector on the surface of molybdenite rather than that of bismuthinite, thus improving the floatability of molybdenite and drastically deteriorating the floatability of bismuthinite. This work suggests that Ca(ClO) 2 could be a promising depressant for bismuthinite in the flotation separation of Mo–Bi sulfide ore. [ABSTRACT FROM AUTHOR]

• The matching mechanism for bubble and particle sizes in fluidized-bed flotation was investigated. • Stable bubble and particle adhesion did not necessarily result in particle separation. • Only the stable bubble adhesion that effectively decreased particle density led to the separation. • Fluidized-bed flotation was a consequence of matched bubble and particle size affected by mineral exposure pattern. Fluidized-bed flotation is a novel process with combined features of flotation and density separation. The application of fluidized-bed flotation in grinding circuit to reject coarse gangues for sulfide ores has been increasingly attracting attentions. Previous studies have focused on the effect of mineral liberation on coarse particle separation. Little work has yet been conducted to simultaneously investigate the effect of mineral liberation, particle and bubble sizes on the fluidized-bed flotation efficiency. The lack of this work has hindered the process optimization to some extent. In this study, three sizes of bubbles (498 μm, 1200 μm, 1952 μm) were generated to separate molybdenite ores under three particle size fractions (150–450 μm, 450–700 μm and 700–1000 μm) in a fluidized-bed flotation column (80 mm in diameter). For the 150–450 μm and 450–700 μm particles, small bubbles of 498 μm could achieve separation by effectively reducing the particle density. For the 700–1000 μm particles with greater mass, intermediate bubble of 1200 μm was required to reduce the particle density for separation. No separation was observed for the three particle size classes with the oversized bubbles of 1952 μm due to high bubble detachment probability. It was concluded that fluidized-bed flotation is a consequence of matched bubble and particle sizes affected by the exposure rate of hydrophobic mineral and its distributing discreteness, the underlying mechanism for which was discussed. It is believed that the outcomes of this work could facilitate the optimization of fluidized-bed flotation in coarse gangue rejecting for sulfide ores. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tunable ion and phase hybridization is designed in natural molybdenite. • An optimal reflection loss value of − 45.34 dB could be obtained at 1.4 mm. • Defect and interfacial polarizations synergistically attenuate EMW. • This study expands the potential application prospects of natural molybdenite. Responsible utilization of natural mineral resources is essential for mitigating their imminent depletion. In this study, natural molybdenite (MoS 2) containing sulfur vacancies (MoS (2−x)) is modified for the synergistic enhancement of electromagnetic wave (EMW) absorption. Under the influence of thermal motion, negative (O) and positive (Cu) ions are embedded in MoS (2−x) to realize synchronous tunable ion and phase hybridization, affording MoS (2−x) /Cu 2 S/MoO 2 heterogeneous composites. Ion and phase hybridization considerably reduces the bandgap, changing the semiconductor type of MoS 2 from p to n. They also promote the generation of sulfur vacancies and a complex heterojunction, increasing the uneven charge distribution between the polyphase interfaces as well as increasing the number of active sites, thereby improving the probability of polarization. These processes enhance the EMW absorption properties of the Cu/O–codoped MoS 2 matrix composites. Negative (positive) ion and phase hybridization probably enhances the EMW absorption properties by increasing the number of defects and interfacial polarizations for which the heterogeneous structure provides the necessary microenvironment. Thus, this study considerably expands the application of molybdenite in high–efficiency EMW absorption materials and offers new perspectives on mineral resource utilization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Native gold coexists with molybdenite and occurs as chrysanthemum-like aggregates. • Molybdenite has similar S and Pb isotopic compositions to other sulfides minerals. • Molybdenite Re-Os dating yielded a weighted average age of 381.7 ± 2.0 Ma. • Te-Au mineralization was genetically associated with the Devonian alkaline magmatism. The Zhangjiakou goldfield, located in the northern North China Craton (NCC) margin, is a typical gold mineral province in China, containing over 67 gold deposits with 260 t gold reserve. However, gold mineralization age in this district has not been well constrained. Here, we integrate mineral paragenesis, molybdenite Re-Os age and in situ sulfides S and Pb isotopes from the Zhongshangou Te-rich Au deposit to constrain the timing and origin of gold and tellurium mineralization. Molybdenite Re-Os dating yielded a weighted average age of 381.7 ± 2.0 Ma (2 σ , MSWD = 0.37, n = 7). Molybdenite has similar δ 34S value (-12.9 to −8.5‰, n = 10) to other sulfide minerals (23 pyrite, 2 chalcopyrite and 2 bornite, δ 34S = -13.6 to −5.6‰). Lead isotope compositions also show no difference among these sulfide minerals. Considering the mineral paragenesis and S-Pb isotopes, we suggest that molybdenite coprecipitated with gold, tellurides and other types of sulfides from the ore-forming fluids, and that the molybdenite Re-Os data could represent the timing of Zhongshangou gold and tellurium mineralization. New and published age data define a ca. 380 Ma Au-Te mineralization event for the Zhangjiakou goldfield. These Au deposits were genetically associated with the Devonian alkaline magmatism. [ABSTRACT FROM AUTHOR]

• Depression mechanism of the depressants and the collection mechanism of collectors are summarized. • Crystal structure characteristics of chalcopyrite and molybdenite are reviewed. • Molecular structure characteristics of depressants are classified. • Methods for development of new depressants are suggested. • Direction for design of new depressants and usage of combined depressants are prospected. Copper and molybdenum are important metal resources, efficient treatment and utilization of copper and molybdenum ores are of great significance to the development of economy and technology in the world. Flotation separation of chalcopyrite and molybdenite is an enormous challenge faced by mineral processing, since chalcopyrite is usually closely associated with molybdenite in porphyry copper-molybdenum deposits. Similar flotability of chalcopyrite and molybdenite caused by the residual of pre-adsorbed xanthate on the surface of chalcopyrite and molybdenite during the bulk flotation is the main reason for difficult separation of chalcopyrite and molybdenite. Depressants are the key to separation of copper and molybdenum, but most depressants have disadvantages of high dosage, toxicity, instability and high cost. It is necessary to further study the depression mechanism of different depressants, so as to better understand the dissolution, dissociation and adsorption behaviors of the depressants in the pulp, and to provide a theoretical basis for the development of new efficient and environment-friendly depressants. It is also important to clarify the methods for reagent design and provide technical support for the development of novel depressants. These depression mechanism of depressants and the methods for reagent design are systematically summarized and reviewed in this paper, together with a brief description on mechanism of collector and the crystal structure of chalcopyrite and molybdenite which have influence on the action of depressants. The development of environment-friendly organic with high selectivity and the combined use of the depressants are the research direction for copper-molybdenum separation depressants in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • Calcium lignosulfonate depressed chalcopyrite with little effect on molybdenite. • Calcium lignosulfonate adsorbed much more on chalcopyrite than on molybdenite. • Adsorption occurred on molybdenite edges without modifying molybdenite faces. • Adsorption occurred on metal sites of chalcopyrite rather than sulphur-rich phases. • On chalcopyrite lignosulfonate blocked kerosene approaching sulphur-rich phases. Molybdenite is the main mineral for molybdenum extraction, which coexists with chalcopyrite in porphyry copper deposits. However, the separation of molybdenite from chalcopyrite by flotation uses large amounts of toxic depressants, causing financial, health and environmental concerns. In this study, an environmentally friendly depressant, calcium lignosulfonate, with a low price was explored to depress chalcopyrite in the presence of kerosene, a collector widely used to float molybdenite. Adsorption isotherms of calcium lignosulfonate on chalcopyrite and molybdenite surfaces and contact angles of chalcopyrite, molybdenite's basal planes and edge planes in the absence and presence of calcium lignosulfonate and kerosene were determined to understand the adsorptions of calcium lignosulfonate on heterogeneous chalcopyrite and molybdenite surfaces and the subsequent interactions with kerosene. It was found that calcium lignosulfonate effectively depressed chalcopyrite flotation, but had little depression effect on molybdenite because the adsorption density of calcium lignosulfonate on chalcopyrite was significantly higher than that on molybdenite. Calcium lignosulfonate molecules were uniformly adsorbed on chalcopyrite and molybdenite despite the heterogeneous surfaces. In fact, calcium lignosulfonate adsorbed on polar metal ion sites of chalcopyrite surfaces, blocking the adsorption of kerosene from adsorbing on hydrophobic sulphur-rich phases. Analogously, calcium lignosulfonate adsorbed on polar edge planes of molybdenite with little interference with the adsorption of kerosene on hydrophobic basal planes. [ABSTRACT FROM AUTHOR]

• The effect of sodium hypochlorite as an oxidizing agent depressed chalcopyrite in flotation. • A decrease in the recovery of chalcopyrite was observed as the NaClO dosage increased. • Mixed potential measurements were made to confirm the best NaClO concentration. • Molybdenite recovery remained almost constant at different NaClO dosages. • The formation of soluble species was observed upon molybdenite floatability due to oxidation. One alternative to replace conventional depressants in Cu-Mo separation is using oxidizing agents to promote the formation of products on chalcopyrite that render its surface hydrophilic and thus favor its depression. This work provides a study to understand how sodium hypochlorite can act as a depressor for chalcopyrite in Cu-Mo flotation separation. The effect of NaClO in flotation tests was evaluated by means of electrochemical techniques, scanning electron microscopy (SEM), Fourier transform infrared analysis and contact angle measurements. The flotation results showed a selective depressant effect at a dosage of 1,020 g/t NaClO, conditioning time of 5 min, and pH 7. The mixed potential showed that the oxidation of chalcopyrite and molybdenite is possible through the addition of NaClO. The SEM observations showed changes in oxidized chalcopyrite morphology, which is supported by the decreasing contact angle change; no morphological changes were observed on molybdenite. FTIR analyses showed the characteristic peaks of the OH group after chalcopyrite was treated with NaClO; when molybdenite was treated with NaClO, the FTIR spectrum did not show changes. A scheme is proposed for the formation of oxidation species. [ABSTRACT FROM AUTHOR]

• The E-pH dominant region diagrams of Bi-S-H 2 O and Bi-S-Cl-H 2 O systems were drawn. • The mechanism of decomposition of Bi 2 S 3 by HCl was revealed according to thermodynamic analysis. • The experiment result proves the accuracy of the theoretical prediction and provides support for the separation of molybdenite and bismuthinite. Through thermodynamic calculations, the E-pH diagrams of the Bi-S-H 2 O and Bi-S-Cl-H 2 O systems at 298 K were plotted, the dominant regions of the components in the system and their changes with pH were clarified, and the mechanism and thermodynamic conditions for the decomposition of Bi 2 S 3 in acidic systems were clarified. The key to the decomposition of Bi 2 S 3 in acidic systems was based on the coordination of Cl− and Bi3+. The formation of BiCl 4 − can promote the decomposition of Bi 2 S 3 in acidic systems, based on this characteristic, HCl was used to achieve efficient leaching of bismuth in molybdenite-bismuthinite mixed ore. Under the optimized conditions of hydrochloric acid concentration of 6 mol/L, liquid-to-solid ratio of 5:1, temperature of 95 °C, stirring speed of 400 rpm, and time of 300 min, the leaching efficiency of bismuth reached 97.64 %, and the bismuth content in the leaching residue was 0.93 %, while molybdenum remained in the form of MoS 2 in the residue, The efficient separation of molybdenum and bismuth has been achieved, providing a new process to solve the traditional separation of molybdenite-bismuthinite mixed ores. [ABSTRACT FROM AUTHOR]

[Display omitted] • Acetoacetamide (CSD2) is used as a selective depressant to realize the flotation separation of sulfide minerals. • The collectorless flotation with only CSD2 reduces the cost and simplifies the process. • CSD2 can expand the recovery gaps between molybdenite and chalcopyrite, galena, and pyrite to 60–80%. • –C=O in CSD2 molecule realizes the stable adsorption onto the surfaces of chalcopyrite, galena and pyrite. • –NH 2 in CSD2 molecule bonds to S2– through hydrogen bonding, improving its selectivity and surface hydrophilicity. Molybdenite is usually associated with chalcopyrite and other sulfide minerals, which troubles the efficient utilization of Mo resources. Flotation using various surfactants is a key technology to solve the problem. In this work, acetoacetamide (CSD2) is used as a novel depressant to realize the selective separation of molybdenite from chalcopyrite, galena and pyrite. Any collector is unwanted for the flotation system using CSD2, which not only reduces the cost, but also simplifies the flotation process. Under the optimum and green flotation scheme ([CSD2] = 5 × 10−4 mol/L; the pulp pH = 7), CSD2 can expand the recovery gap between molybdenite and chalcopyrite (or galena or pyrite) to 60% ∼ 80%. The excellent and selective depression of CSD2 has been continued in the flotation systems of mixed minerals and grinding products of quaternary mineral mixtures (GPQMM), confirming the potential industrial application prospect. The selective depression of CSD2 is confirmed by Zeta potential and contact angle measurements. After being treated with CSD2, the Zeta potential and hydrophilicity of the surfaces of chalcopyrite, galena and pyrite have more obvious changes than those of molybdenite surface, meaning a stronger adsorption of CSD2. In addition, the selective depression mechanism of CSD2 is further investigated through Fourier Transform Infrared (FTIR) analysis, X-ray Photoelectron Spectroscopy (XPS) analysis and electrostatic potential surface (EPS). The stable adsorption of CSD2 onto the surfaces of chalcopyrite, galena and pyrite is realized through forming six-membered chelation rings by the bi-carbonyl groups (–C=O) in CSD2 molecules and the metal ions on the mineral surfaces. At the same time, the amino group (–NH 2) in CSD2 molecule also play an auxiliary role in the adsorption process through weak interaction. However, it is difficult to achieve an effective adsorption of CSD2 onto the surface of molybdenite, due to a lack of exposed metal ions. CSD2, as a high-performance depressant, has an industrial application potential in the collectorless/collector-free flotation separation of Mo-containing sulfide minerals. [ABSTRACT FROM AUTHOR]

The effect of microwave activation on the properties of oxidation roasting for molybdenite was investigated under the protection of inert gas, and the specific surface area, the oxidation properties, lattice constant, microstructure, and shape of molybdenite were analyzed and characterized by a laser particle size analyzer, thermogravimetry (TG), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results show that microwave activation could effectively reduce the residual amount of sulfur in the molybdenum calcine and decrease the average particle size of molybdenite while increasing the specific surface area of molybdenite. On increasing the microwave activation power, the crystal cell volume and grain size of MoS2 reduced, and the microstrain increased slightly. At the same time, the surface shape of molybdenite became looser, but the layered structure is not changed. In addition, the oxidation property changed significantly; microwave activation promoted the oxidation reaction of molybdenite above 538 °C, and the rate of weight loss increased from 6.177% to 7.718% at 620 °C.

An occurrence of vein U-Mo mineralization is located in the Majerská valley near Čučma, about 7 km to the NNE of the district town of Rožňava (Eastern Slovakia). Mineralization is hosted in the acidic metapyroclastics of the Silurian Bystrý Potok Fm. (Gemeric Unit), and originated in the following stages: (I.) quartz I, fluorapatite I; (II.) quartz II, fluorapatite II, zircon, rutile chlorite, tourmaline; (III.) uraninite, molybdenite, U-Ti oxides; (IV.) pyrite I, ullmannite, gersdorffite, cobaltite; (Va.) galena, bismuth, tetradymite, joséite A and B, Bi3(TeS)2 mineral phase, (BiPb)(TeS) mineral phase, ikunolite; (Vb.) minerals of the kobellite–tintinaite series, cosalite; (VI.) pyrite II; (VII.) titanite, chlorite; and (VIII.) supergene mineral phases. The chemical in-situ electron-microprobe U-Pb dating of uraninite from a studied vein yielded an average age of around 265 Ma, corresponding to the Guadalupian Epoch of Permian; the obtained data corresponds with the age of Gemeric S-type granites. The age correlation of uraninite with the Gemeric S-type granites and the spatial connection of the studied mineralization with the Čučma granite allows us to assume that it is a Hercynian, granite-related (perigranitic) mineralization.

The objective of this work was to study the effect of muscovite and biotite on the flotation of chalcopyrite and molybdenite in seawater, and the use of sodium hexametaphosphate and sodium silicate to improve copper and molybdenum recoveries. The impact of the inorganic dispersants on the settling properties of the resulting flotation tailings was also studied. It was found that muscovite and biotite depress the flotation of chalcopyrite and molybdenite in seawater, with this depressing effect being stronger at pH 11 than at pH 9. Sodium hexametaphosphate and sodium silicate increased the recoveries of copper and molybdenum in seawater. These dispersants render the mineral particles more negatively charged and remove the hydroxy-complexes of magnesium and calcium from the mineral particles causing dispersion of the slimes. The settling rates of the flotation tailings slightly decrease when sodium hexametaphosphate and sodium silicate were added in the flotation stage. The presence of ultrafine particles dispersed by the action of the inorganic dispersants negatively impacted the flocculation and sedimentation processes leading to high flocculant consumption, low settling rates and high turbidity of the supernatant.

In this study, a novel organic depressant maleyl 5-amino-1,3,4-thiadiazole-2-thiol (MATT) was synthesized and utilized as a galena depressant in the flotation separation of molybdenite and galena. The results of the flotation test indicated that MATT exhibited an excellent depression ability on galena but barely influenced the flotation of molybdenite in the pH range of 6.0–11.0. Zeta potential results suggested that MATT preferentially adsorbed on galena surface. UV-visible spectroscopy analysis indicated that the stoichiometric ratio of lead ion and reagent in the complex compound. XPS analysis demonstrated that the S (-SH) atom and N (1,3,4-thiadiazole group) atom of MATT coordinated with the Pb atom on galena surface.

The Shapoling Mo deposit is located in the Xiong'er rock mass of the southern margin of the North China Craton. The deposit is hosted in a contact zone between granite and wallrocks of the Taihua Soupergroup, which is a recently found discovered vein dissemination type deposit in East Qinling. The ore-bodies are associated with quartz veins and controlled by subsidiary faults. The mineralization styles include veinlet and disseminated types. In order to determine the age of the Shapoling Mo deposit, Re-Os isotopic dating of molybdenite was conducted. Six molybdenite samples yielded Re-Os ages ranging from 158.3±1.5 Ma to 160.7±1.2 Ma, with a weighted mean age of 160±1 Ma (2σ, MSWD=2.1). The Re-Os age shows that the Mo mineralization occurred during the late Jurassic, earlier than the formation of Huashan rock mass (about 30 Ma). In addition, one molybdenite sample in Huashan rock mass yielded a Re-Os age of 130.5±1.0 Ma, which is in accordance with the age of the Huashan pluton and molybdenite age (125.4-129.4 Ma) reported by a previous study. In conclusion, the Shapoling deposit contains two episodes of Mo mineralization from the early Cretaceous and late Jurassic periods. Combining this with geological characteristics and tectonic-metallogenic evolution, it is suggested that Huashan rock mass, granite porphyry, and related hydrothermal deposits in the Xiong'er terrain are the products of extrusion to extension transition during continent-continent collision in the Qinling orogenic belt.

Porphyry-type deposits are the major sources of copper and molybdenum, and flotation has been adopted to recover them separately. The conventional reagents used for depressing copper minerals, such as NaHS, Na2S, and Nokes reagent, have the potential to emit toxic H2S gas when pulp pH was not properly controlled. Thus, in this study the applicability of microencapsulation (ME) using ferrous and phosphate ions as an alternative process to depress the floatability of chalcopyrite was investigated. During ME treatment, the use of high concentrations of ferrous and phosphate ions together with air introduction increased the amount of FePO4 coating formed on the chalcopyrite surface, which was proportional to the degree of depression of its floatability. Although ME treatment also reduced the floatability of molybdenite, ~92% Mo could be recovered by utilizing emulsified kerosene. Flotation of chalcopyrite/molybdenite mixture confirmed that the separation efficiency was greatly improved from 10.9% to 66.8% by employing ME treatment as a conditioning process for Cu-Mo flotation separation.

O-Carboxymethyl chitosan (O-CMC), a nontoxic and biodegradable derivative of the natural polysaccharide-chitosan, was recently found to be a viable alternative for the toxic depressants used in the flotation separation of chalcopyrite and molybdenite. In this work, the adsorption characteristics of O-CMC on molybdenite/chalcopyrite surfaces and the associated interaction mechanisms were investigated by electrokinetic study, infrared spectroscopy, Atomic force microscopy (AFM) imaging, X-ray photoelectron spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The experimental results demonstrated that O-CMC adsorbed on both mineral surfaces. However, the interactions between O-CMC and chalcopyrite are mostly weak physical interactions such as electrostatic interaction, and most of the adsorbed O-CMC molecules can be removed mechanically (e.g., washing) or displaced by xanthate. In comparison, the adsorption of O-CMC on molybdenite is dictated by hydrophobic interaction and electrostatic interaction, and is barely affected by rinsing or xanthate addition. As a result, the strong adsorption of O-CMC on molybdenite over the chalcopyrite lead to the depression of molybdenite and selective separation of two minerals in flotation. In addition, infrared spectroscopy and XPS revealed that no strong chemical interactions were involved during the adsorption O-CMC on molybdenite and chalcopyrite surfaces. [ABSTRACT FROM AUTHOR]

The Siah Kamar porphyry Mo deposit is the newly discovered deposit of this type in the Neo Tethys-related Urumieh–Dokhtar magmatic arc, northwest Iran. Mineralization occurs as stock-work quartz–molybdenite and mono-mineralic molybdenite veinlets within the porphyry quartz-monzonite stock and the country rocks, accompanied by locally scattered later-stage and cross-cutting quartz-chalcopyrite-pyrite veinlets in the trachy-andesite and trachy-basalt country rocks. U–Pb zircon geochronology of the porphyry stock yielded Early Oligocene dates of 32.7 ± 0.4 to 30.9 ± 0.4 Ma (at 2σ level). The Th/U ratios of the zircons range between 0.48 and 0.77, and they possess initial εHf(t) values of 3.2 to 12.1, which may suggest a dominant mantle source for the magma. Molybdenite separates yielded rhenium contents between ~10 and 41 ppm (average ~26 ppm, n = 4) and slightly younger Re–Os ages compared to the porphyry stock, ranging from 29.1 ± 0.2 to 28.1 ± 0.2 Ma (at 2σ level). The Siah Kamar porphyry Mo deposit is nearly temporally coeval with the Haft Cheshmeh porphyry Cu deposit and the vein-type Cu–Mo–Au mineralization in the Qarachilar area, corresponding to the second porphyry Cu–Mo mineralization epoch in NW Iran. However, it is younger than the majority of the porphyry Cu deposits in the southern Lesser Caucasus and only shows temporal correlation with the Paragachay and first-stage Kadjaran porphyry Cu deposits. Moreover, it is older than all the porphyry Cu–Mo systems across the central and south-eastern parts of the Urumieh–Dokhtar magmatic arc, except the Bondar Hanza deposit, which is nearly coeval with the Siah Kamar porphyry Mo deposit. All these data reveal an old to young trend along the UDMA and the porphyry Cu belt of Iran, further testifying to the diachronous and later closure of the Neo-Tethyan oceanic basin in central and SE Iran. [ABSTRACT FROM AUTHOR]

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Flotation using sea water has been considered as a promising alternative to concentrate molybdenite (MoS2) under alkaline conditions due to scarcity of fresh water and increasingly strict regulations on the quality of discharged water. However, the MoS2 recovery with sea water during flotation has not been satisfactory, owing to the depressing effects from the hydrophilic metallic species onto MoS2 surface. This study combines experimental and theoretical studies of MoS2 flotation to investigate how the physicochemical properties of MoS2 vary with the addition of a dispersant, sodium hexametaphosphate (SHMP), and in sea and fresh water. Our experimental results show that the addition of SHMP during flotation has increased the recovery of MoS2, via reducing the adsorption of the hydrophilic metallic precipitation onto MoS2 surface. The DLVO calculation confirms that the addition of SHMP increases the floatability of MoS2 by dispersing the formed hydrophilic metallic precipitation (Mg(OH)2 colloids) from the MoS2 surface, via reversing attraction force to repulsion force, thereby improving MoS2 flotation recovery. [ABSTRACT FROM AUTHOR]

In the present work, two different methods were used to study the effect of mechanical activation on aluminothermic reduction of MoO 3. In the first method, a stoichiometric amount of Al + MoO 3 and 20% weight percent of aluminum oxide (as the heat absorber) was mixed and mechanically activated by milling process in a planetary ball mill under argon atmosphere. XRD patterns and SEM micrographs of the activated samples indicated that aluminothermic reduction of MoO 3 was done in the milling media after 5 h and increasing the milling time, decreased the remaining non reacted Al and MoO 3. In the second method, as received MoO 3 , was mechanically activated in different times in the range of 3 to 24 h. The effect of mechanical activation on molybdenum trioxide grain size was analyzed by Williamson-Hall method, and it was shown that, by increasing the activation time, the grain size and internal strain was reduced and increased, respectively. In the next step, the activated MoO 3 powders were mixed with stoichiometric amount of Al and 20 wt% Al 2 O 3 (as the heat absorber) and shaped in the form of cylindrical samples of 10 mm in diameter and height of 15–20 mm by applying 70 MPa uniaxial pressure. Aluminothermic reaction was initiated in the prepared pellets by using conventional microwave oven. The XRD patterns of the combustion products showed that, by mechanical activation of MoO 3 , the undesired phases of molybdenum dioxide (MoO 2) and aluminum molybdate Al 2 (MoO 4) 3 was decreased. The aluminothermic reduction of activated MoO 3 also was studied by non-isothermal Differential Scanning Calorimetry (DSC) with heating rate of 10 °C min−1 under argon atmosphere. The results showed that by mechanically activating MoO 3 for 24 h, the ignition temperature of reduction reaction decreased from 910 to 780 °C and the practical efficiency of the reaction increased from 82.9% (for the nonactivated MoO 3) to 92.5%. The comparing results between the milling mixture and the milling molybdenum trioxide indicated that the reaction in mixture cannot be completed during milling and a small amount of Al and MoO 3 remained in the activated powder. But for the activated MoO 3 , and after igniting in a conventional microwave oven the desired reaction went to completion. • It has been shown that. • Mechanical activation of MoO 3 , caused elimination of undesired phases of molybdenum dioxide and aluminum molybdate. • By mechanical activation of MoO 3 , the production of undesired phases of molybdenum dioxide (MoO 2) and aluminum molybdate Al 2 (MoO 4) 3 can be efficiently eliminated. • Mechanical activation decreases the ignition temperature of aluminothermic reduction of MoO 3. [ABSTRACT FROM AUTHOR]

The first data on five primary molybdenite sources within the gabbro-dolerite complex of Pay-Khoy (Pay-Khoy Ridge, Yugra Peninsula, Russia) are presented. The mineral is extended areally in Devonian ore-bearing gabbro-dolerites, contact rocks, and quartz veins. This paper considers the mineralogical–geochemical features of molybdenite, its occurrence, the composition of host rocks, and spectroscopic studies. [ABSTRACT FROM AUTHOR]

Conventional dating of molybdenite (187Re-187Os) provides one of few options for direct dating of sulfide mineralization. Unfortunately, in situ dating of molybdenite is considered unreliable due to intra-granular decoupling of 187Re-187Os. In this study, we developed a new analytical protocol for studies of micron- to grain scale 187Re-187Os systematics in molybdenite. Online chemical separation using ICP-MS/MS technology enables in situ dating by β-decay systems (e.g., Rb-Sr and K-Ca in micas) using laser ablation. Here, the methodology is extended to the 187Re-187Os system, another β-decay system that cannot be resolved by mass spectrometry. Several reaction gases were evaluated, and production of OsCH2 by reaction with CH4 was found to produce strong separation of Os from Re. However, in contrast to the e.g., 87Rb-87Sr system, 1–2% of the parent isotope Re also reacted to ReCH2, leaving a significant interference. A mathematical correction of this remaining interference is possible, and 187Re-187Os (mass-shifted) can be measured accurately even for fairly extreme ratios. For laser ablation, standards were developed by pressing particulate pellets of conventionally dated molybdenite (Moly Hill and Merlin), because there are no appropriate reference materials available. Six natural molybdenite samples from a range of geological settings, containing > 10 ppm Re, were analyzed by 70 μm laser ablation spots, and ages were calibrated by analysis of molybdenite pellets. Contrary to our expectation, weighted average ages obtained were in agreement (within 1%) with conventional age determinations, with fairly good precision (from ~ 1 to 5% 2σ depending on Re concentration), suggesting limited or essentially nonexistent decoupling within crystals. Two important implications of this result are that decoupling Re-Os is not universal, and that our new analytical protocol is useful both for dating and for studies of decoupling. The benefit of in situ dating compared to conventional dating is, apart from lower cost and time consumption, the possibility of targeting smaller molybdenite crystals (≥ 100 μm) in thin sections and epoxy mounts. The youngest sample in the study is 920 Ma, but we see potential of dating significantly younger Re-rich molybdenite. [ABSTRACT FROM AUTHOR]

The Mo Cu W Azegour skarn, located in the High-Atlas in Morocco, is associated with a Late Hercynian alkaline granitic intrusion. Here the origin of the mineralisation via Re Os geochronology and using Mo, S and Pb isotopes is discussed. The age of mineralisation defined by Re Os molybdenite geochronology is 276 ± 1.2 Ma for the Azegour mine, and 267 ± 1.2 for the Tizgui deposit suggesting for multiple mineralisation events associated with the Hercynian alkaline granitic intrusion. The δ98Mo NIST of molybdenite range from −0.60‰ to 0.42‰ (n = 26) for the Azegour mine and from 0.08‰ to 0.40‰ (n = 2) for the Tizgui mine. Variations of the δ98Mo NIST occur either at the deposit scale with a difference of about 0.72‰, and at the sample scale (few cm), which exhibits a difference of up to 0.40‰. A multi-phased mineralisation is proposed as the main processes explaining the variation in the δ98Mo NIST values although the influence of a Rayleigh fractionation process cannot be precluded. The high δ34S values determined from molybdenite, pyrrhotite, and chalcopyrite (8–14.7‰) suggest a sedimentary origin for sulphur from the Cambrian sedimentary country rocks. Whereas, the initial 206Pb/204Pb compositions of common lead (18.08–18.30) for chalcopyrite and pyrrhotite imply a strong contribution of lead from the host volcano-sedimentary units. • The Mo Cu W Azegour skarn is Permian (276 ± 1.2 Ma, Re Os geochronology). • Multiple Permian mineralisation events associated with the Azegour granite are likely. • δ34S values determined from sulphides suggest a sedimentary origin for sulphur. • Source of common lead has to be sought in the host Cambrian volcano-sedimentary units. [ABSTRACT FROM AUTHOR]

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Slepaya Zalezh', the largest orebody of the Tyrnyauz Mo–W deposit, is considered a first-priority object should mining operations at the deposit be resumed. Molybdoscheelite, scheelite, and molybdenite impregnation in mineable concentrations is genetically related to metasomatites of the productive stage overprinted on skarns, periskarn rocks, hornfelses, and marble. Ore types have been recognized based on the relative amounts of different ore-bearing metasomatite facies and protoliths acting as a diluting mass. Seven ore types have been recognized and mapped in cross section. Types I and II are characterized by predominant (70–90%) aposkarn ores after endo- and exoskarns, accordingly. Type III is characterized by approximately equal proportions of ores after endoskarns and periskarn rocks; type IV differs from type III by a decrease in periskarn rocks replenished by an increase in hornfels. Type V is dominated by ores after exoskarns and, to a lower extent (up to 25%), after marble. Type VI is intermediate between types III and IV. Type VII represents all protoliths in approximately equal proportions. Each type exhibits a stable mineral and chemical composition inherited from the protolith. The ores of each particular type have simple distinguishing features, convenient for logging and mapping, which can be used for manual picking of grab and bulk samples and preliminary ore separation. The ores exhibit narrow ranges of variation in sizes and shapes of ore mineral grains and intergrowths and concentrations of minerals harmful to flotation. The subtle differences in ore mineral concentrations between ore types enable their selective mining and blending. Maps and cross sections contain data on the spatial distribution of the associated components such as garnet and wollastonite in skarns and productive metasomatites, pyroxene–plagioclase periskarn rocks, and hydrothermally altered rocks with Cu, Au, and other mineralization. [ABSTRACT FROM AUTHOR]

Abstract Herein, we employed a range of instrumental techniques to investigate the performance of l -cysteine as a biodegradable and selective depressant in the flotation separation of molybdenite (MoS 2) from galena (PbS), demonstrating that this amino acid exhibited a superior depressing efficiency toward PbS and enabled the separation of the above minerals under alkaline conditions. In the presence of l -cysteine, the zeta potentials of PbS shifted to more negative values, which was indicative of chemisorption. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy measurements indicated that the above chemisorption involved the formation of a five-membered chelate ring via coordination of Pb by S (–SH) and N (–NH 2) atoms, as was further confirmed by time-of-flight secondary ion mass spectrometry measurements. Moreover, the detection of l -cysteine dimer on the surface of PbS was ascribed to the occurrence of oxidation processes. The predicted adsorption modes suggested an appreciable extent of surface interaction between l -cysteine and PbS, whereas density functional theory calculations demonstrated that the interaction between l -cysteine and the PbS (100) slab corresponds to both physical and chemical adsorption. Highlights • PbS was separated from MoS 2 by flotation using l -cysteine as a depressant. • The surface of l -cysteine-treated PbS was examined by a number of techniques. • l -Cysteine was found to coordinate Pb ions via NH 2 and SH groups. • l -Cysteine was concluded to be an excellent alternative to inorganic depressants. [ABSTRACT FROM AUTHOR]

Hexagonal molybdenite (MoS2) is one of the most promising two-dimensional (2D) semiconductors, known with n-type and p-type conduction, with possible applications in electronic, opto-electronic, and spintronic devices. In this work, highly pure geological samples of 2H-MoS2 were investigated by temperature-dependent electron paramagnetic resonance (EPR) and Hall effect measurements. The low-temperature (<55 K) EPR spectra were consistently explained as holes (S = 1/2) trapped on shallow As acceptors on sulfur sites leading to a four-line hyperfine-split spectrum (75As: I = 3/2, 100%) in axial symmetry and with a concentration of 5(1) ppm (∼2 × 1017 cm−3). Electrical measurements indicate p-type conduction with a free carrier concentration of about 5 × 1017 cm−3 at room temperature and an ionization energy of 52 meV associated with the shallow As acceptors, which is consistent with the ionization energy determined from the hydrogenic model of shallow acceptors in 2H-MoS2. These values are in strong contrast to the unrealistic value of 0.7 meV reported in the literature obtained from the analysis of temperature-dependent EPR measurements. Possible explanations are related to temperature-dependent spin-lattice relaxation effects, affecting strongly EPR line intensities and making impossible their use in obtaining the ionization energy. [ABSTRACT FROM AUTHOR]

Hexagonal molybdenite (MoS2) is one of the most promising two-dimensional (2D) semiconductors, known with n-type and p-type conduction, with possible applications in electronic, opto-electronic, and spintronic devices. In this work, highly pure geological samples of 2H-MoS2 were investigated by temperature-dependent electron paramagnetic resonance (EPR) and Hall effect measurements. The low-temperature (<55 K) EPR spectra were consistently explained as holes (S = 1/2) trapped on shallow As acceptors on sulfur sites leading to a four-line hyperfine-split spectrum (75As: I = 3/2, 100%) in axial symmetry and with a concentration of 5(1) ppm (∼2 × 1017 cm−3). Electrical measurements indicate p-type conduction with a free carrier concentration of about 5 × 1017 cm−3 at room temperature and an ionization energy of 52 meV associated with the shallow As acceptors, which is consistent with the ionization energy determined from the hydrogenic model of shallow acceptors in 2H-MoS2. These values are in strong contrast to the unrealistic value of 0.7 meV reported in the literature obtained from the analysis of temperature-dependent EPR measurements. Possible explanations are related to temperature-dependent spin-lattice relaxation effects, affecting strongly EPR line intensities and making impossible their use in obtaining the ionization energy. [ABSTRACT FROM AUTHOR]

The present work addresses the recovery of rhenium from scrub liquor of molybdenite concentrate roasting fume and dust by solvent extraction method. According to the results, recovery of rhenium from the scrub liquor is not practical unless molybdenum is removed in advance. The extraction of molybdenum was carried out using a D2EHPA-TBP system which resulted in up to 99.8% Mo extraction in a two-stage solvent extraction at pH = 1 and O/A = 1. Up to 99.6% of Re was extracted subsequently using TOA in a single-stage extraction at pH = −0.3 and O/A = 1:20. The organic phase was stripped by ammonium hydroxide 32% and the resultant liquor was further subjected to evaporation as a result of which, an enriched purified solution was obtained. Ammonium perrhenate was precipitated from the enriched liquor by adjusting the pH to 6.5–7. • A new approach in separation of molybdenum over rhenium from aqueous solutions • Separation and purification of rhenium from the high-sulfate Mo-bearing liquors • High efficient molybdenum extraction using synergistic effect of TBP and D2EHPA • Study of synergistic effect of TBP and D2EHPA on extraction of molybdenum from the high-sulfate solutions • Production of ammonium perrhenate through a low-cost process with high potential of industrial application [ABSTRACT FROM AUTHOR]

• Orebodies are controlled by F1 in the Caledonian Miao'ershan granite batholith. • Monzogranite at Pingtan is a highly fractionated peraluminous granite. • Molybdenite Re–Os age coincident with zircon U–Pb age. • Ore-forming materials were derived from a predominantly crustal source. The Pingtan deposit in southwestern Hunan Province is a newly-discovered, large-sized W-(Mo) deposit. This deposit is situated in the northwestern part of the Miao'ershan granite batholith, western Nanling Range. The tungsten mineralization is mainly hosted in biotite monzogranite, and the alteration related to mineralization is controlled by a NE-trending fault zone. In this paper, we present new molybdenite Re–Os and zircon U–Pb ages, zircon Lu–Hf isotope and REE geochemical data, aiming to constrain the W (Mo) mineralization age and ore-hosting granite petrogenesis in the Pingtan W (Mo) deposit. Molybdenite Re–Os dating of eight ore samples yielded a weighted average model age of 427.0 ± 5.4 Ma (MSWD = 0.24). The LA-ICP-MS Zircon U-Pb analysis of two biotite monzogranite yielded 206Pb/238U ages of 430.8 ± 2.4 Ma and 431.0 ± 1.8 Ma, respectively, suggesting that the W-(Mo) mineralization is spatial-temporally associated with the biotite monzogranite. The ore-related granites have high contents of SiO 2 and K 2 O, belong to weakly to strongly peraluminous (A/CNK = 1.00–1.30), and geochemically classified as S-type affinity. Molybdenite Re contents (2.262–7.297 μg/g), zircon ε Hf (t) (−10.34–−5.87) and 176Hf/177Hf (0.282241–0.282376) values of the biotite monzogranite suggest that the ore-forming materials are predominantly derived from the crust. This is the first identification of tungsten mineralization related to Silurian S-type granites Caledonian granites in the Miao'ershan granite intrusion, indicating Caledonian is an important mineralization period of W in the western part of Nanling Range, South China. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • LIBS is successfully used to perform automatic mineral imaging and quantification. • QMA_EDS-SEM is used to guide the LIBS training and to validate the final results. • MCR-ALS allows element-to-mineral conversion of mixed-mineral-phase LIBS data. • Method can use laser spot size large enough to be suitable for field applications. • The point counting absolute errors are <3.5% for major minerals and <1% for minor minerals. Abstract Quantitative mineral analysis (QMA) performed using energy-dispersive x-ray spectrometry and scanning electron microscopes (EDS-SEM) provide reliable information on the mineral abundance and texture of prepared rocks. This information helps in the optimization of the mining and milling processes, and to define the value of a deposit. Real-time analysis of coarse rock streams would greatly enhance the decision-making processes driving the mining operation efficiency; however electron-microscope-based instruments are not yet adaptable for in-field measurements. Laser-induced breakdown spectroscopy (LIBS) has been used for elemental analysis in many environments but has not been employed for true mineral quantification and identification. This work presents a new method for mineral identification and quantification using LIBS, which could be scalable to perform automated mineralogy measurement in coarse rock streams. A set of rock tiles from mining operations in Australia had QMA performed using an EDS-SEM instrument and the resulting data were used to guide and validate the results obtained by LIBS. The use of a multivariate curve resolution – alternating least square (MCR-ALS) method applied to the LIBS data allowed the identification, quantification and imaging of minerals on rock tiles, even in the presence of mixed mineral phases within the laser spot area. Mineral abundance and imaging are obtained with success for the mineral phases selected in the present work, which includes bornite, chalcopyrite, pyrite, molybdenite, quartz, chlorite, K-feldspar, albite, fluorite and calcite. The method presented a mineral quantification root mean square error below 10% for the main minerals. In addition, mineral quantification by point-counting using single laser shots per LIBS measurement is demonstrated, achieving absolute errors below 3.5% for major minerals and below 1% for minor minerals. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Chalcopyrite flotation was not affected by O-CMC. • O-CMC strongly depress molybdenite flotation from pH 3–11. • Selective Cu-Mo separation was achieved by O-CMC from pH 3–11. • The interactions between O-CMC and chalcopyrite are weak. • O-CMC adsorbs strongly on molybdenite surface. Abstract The flotation separation of molybdenite from copper sulfide minerals (mostly chalcopyrite) typically relies on the use of toxic inorganic depressants such as cyanides and sodium sulfide/hydrosulfide. In this work, a nontoxic, biodegradable and cost-effective derivative of the natural polysaccharide chitosan, O-Carboxymethyl chitosan (O-CMC), is investigated as an alternative depressant for molybdenite during the Cu-Mo separation. The flotation tests on single minerals showed that O-CMC strongly depresses molybdenite flotation from pH 3–11, while chalcopyrite flotation is not affected by O-CMC except at pH 3. The flotation tests on mineral mixtures confirmed O-CMC could efficiently depress the molybdenite flotation without dramatically reducing chalcopyrite recovery and selective separation of molybdenite and chalcopyrite was achieved over the entire pH range tested from pH 3 to pH 11. To explain the flotation results, the adsorption characteristics of O-CMC on both minerals were investigated by atomic force microscopy (AFM) imaging. The experimental results indicate that the strong adsorption of O-CMC onto molybdenite surface over the chalcopyrite surface is responsible for the selective separation. [ABSTRACT FROM AUTHOR]

Highlights • Chalcopyrite flotation was not affected by humic acids after adding xanthate. • Humic acids strongly depress molybdenite flotation from pH 3 to 11. • Selective Cu-Mo separation was achieved by humic acids from pH 3 to 11. • Humic acids adsorb onto molybdenite surface mainly via hydrophobic interaction. Abstract Humic acids (HA), a major component of humus or soil, was explored as a selective depressant for molybdenite during the flotation separation of molybdenite and chalcopyrite. Microflotation tests on single minerals revealed that chalcopyrite flotation was not affected by HA from pH 3 to 11, while molybdenite was strongly depressed by HA in the same pH range. Microflotation tests on chalcopyrite-molybdenite mixtures proved that HA could selectively depress the molybdenite flotation without significantly affecting the flotation of chalcopyrite. Infrared spectroscopy revealed that HA strongly adsorbs on molybdenite surfaces while no detectable HA was observed on chalcopyrite surfaces after being wash thoroughly with Milli-Q water. In addition, the infrared spectroscopy also indicates the adsorption of HA on molybdenite (basal planes) is likely governed by hydrophobic interaction while chemical interaction is absent. However, the interactions between HA and chalcopyrite are most likely to be weak interactions such as electrostatic interaction etc., and the adsorbed HA are likely detached (or partially detached) after rinsing or xanthate addition. Our work showed that HA could be utilized as a promising depressant for molybdenite during the flotation separation of copper-molybdenum sulfides over a wide range of pH. [ABSTRACT FROM AUTHOR]