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Properties and Applications of Molybdenum
Published in C. K. Gupta, Extractive Metallurgy of Molybdenum, 2017
While the insoluble molybdates such as the calcium and zinc molybdates have found applications as corrosion-inhibitive pigments as described above, soluble molybdate, typically the sodium molybdate, has found important use as an aqueous corrosion inhibitor. In this capacity it is used for cooling tower applications and in the automotive industry.
Eu3+-Based Orange-Red-Emitting Inorganic Color Convertors: An Overview
Published in Sanjay J. Dhoble, B. Deva Prasad Raju, Vijay Singh, Phosphors Synthesis and Applications, 2018
CaGd2(1-X)Eu2X(MoO4)4(1-y)(WO4)4y (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) solid solutions with a scheelite-type structure were synthesized, and detailed structural studies and optical properties were reported [66]. The detailed structural study reveals that the CaEu2(MoO4)4, CaGd2(MoO4)4, and CaGd2(1-x)Eu2x(MoO4)4 solid-solution compounds as well as their W-based analogs are not disordered scheelites but incommensurately modulated structures contrasting to the literature reports [67]. This is because of ordering of the A cations and vacancies. CaGd2(1-x)Eu2x(MoO4)4(1-y)(WO4)4y solid solutions have either the tetragonal scheelite structure (0 < y < 0.5), which is (3 + 2)D modulated, or the monoclinically distorted scheelite-type structure (0.75 < y < 1), which is (3 + 1)D modulated. The cation and vacancy ordering was observed in the (3 + 1)D-modulated monoclinic CaEu2(WO4)4 structure. The phosphor Eu3+ in CaGd2(1-x)Eu2x(BO4)4 (B = Mo, W) emission intensity of the 5D0-7F2 transition reaches a maximum for x = 0.5 and is well matched with other reported scheelite-related phases [60,65,68,69]. The relatively large Eu-Eu distances could arrest the concentration quenching in the lattice (varying in the range of 3.68 to 4.01 A in the CaEu2(WO4)4 structure). A complete structural study was established in the scheelite-related structures. Detailed crystallographic studies give information about the flexible geometry of MoO42- and WO42- tetrahedrals in CaEu2(WO4)4 and CaEu2(MoO4)4 structures. Changing the A-site by cations with a different charge/size and/or cation vacancies leads to variation in metal-oxygen (M-O) distances and bond angles [70]. A variety of crystal structures and polymorphs are encountered in the double molybdates KR(MoO4)2 and can be categorized in scheelite- type modifications (R = La-Dy) and nonscheelite modifications (R = Dy-Lu) with the KY(MoO4)2-type structure (space group Pbcn), [71]. Scheelite-type modifications can be divided into three groups: (i) tetragonal (R = La-Sm) [72,73] or small monoclinic distortion of the scheelite subcell [70,71], (ii) phases with the incommensurate modulated structure (R = Nd, Sm) [76,77] (superspace group /2/s(aP0)00), and (iii) anorthic phases with the a-KEu(MoO4)2 structure (space group P-1) [78].
Biosorption of hexavalent chromium and molybdenum ions using extremophilic cyanobacterial mats: efficiency, isothermal, and kinetic studies
Published in International Journal of Phytoremediation, 2023
Khairia M. Al-Qahtani, Mohamad S. Abd Elkarim, Foziah F. Al-Fawzan, Afify D. G. Al-Afify, Mohamed H. H. Ali
Molybdenum (Mo) is one of the most biologically active transition elements and is considered significant for plants and animals (Tu et al.2016). Global molybdenum (as Mo metal) mine production was estimated at 281,000 tons in 2014 (Polyak 2016). Half of this amount was converted into molybdenum trioxide (Christensen et al. 2015), and both are slightly soluble in water. Molybdenum concentration becomes toxic when it exceeds 5 mg/L in water, and the molybdate compounds’ toxicity is less than chromate toxicity (Lian et al.2020). Notably, the large effluents of Mo from industrial tailings, such as alloying with steel, printing inks, paints, and ceramics without any treatment, cause serious pollution problems in surface water (Halmi et al.2014). For a long time, workers exposed to Mo(VI) may experience general weakness, irritability, loss of appetite, muscle and joint pain, weight loss, and headache (Brion-Roby et al.2018). There is sufficient evidence for the carcinogenicity of molybdenum trioxide in experimental animals, possibly carcinogenic to humans (IARC 2018). Hexavalent molybdenum, in the form of MoO42 and MoO3, is highly toxic; thus, Mo(VI) removal from aqueous solutions has received considerable attention in recent years (Wu et al.2021).
Efficient preparation of phosphazene chitosan derivatives and its applications for the adsorption of molybdenum from spent hydrodesulfurization catalyst
Published in Journal of Dispersion Science and Technology, 2022
Hala. A. Ibrahium, Bahig M. Atia, Nasser. S. Awwad, A. A. Nayl, Hend A. Radwan, Mohamed A. Gado
Micronutrient moly bdenum is considered to be one of the most important transition elements for various animate beings because of its critical function in geochemical and enzymatic activities.[1] molybdenum present in water samples is of tremendous environmental and chemical significance as a bio-essential element.[2] The rapidly consumption of because of human activity highlights the possibility for massive of harmful releases into the environment. Molybdenum often manifests in the oxidation state of hexavalent, Mo(VI) and molybdate (MoO42−) ions.[3] As long as the concentration of molybdate oxyanions reaches 5 ppm, they pose an environmental hazard.[4] Molybdate anions pose a significant threat to the quality of drinking water sourced from wells.[5]
Facile synthesize of CdS QDs decorated Bi2MoO6/Bi2Mo3O12 heterojunction photocatalysts and enhanced performance of visible light removal of organic pollutants
Published in Environmental Technology, 2021
Jingling Wang, Wensong Lin, Manru Dong, Yue Xing, Qicheng Zhang
Nowadays, environmental pollution and energy shortage are becoming serious issues [1]. Despite conventional photocatalysts such as TiO2 [2], ZnO [3], and WO3 [4] or some emerging photocatalysts such as BMO [5], BiVO4 [6], SrTiO3 [7]and g-C3N4 [8,9], etc. all exhibit pollutant degradation ability, and their photocatalytic performance continues to be lower than expected. The development of efficient photocatalyst is a great significance for better utilization of the solar spectrum. Recently, Bi-based semiconductor materials play a novel role in photocatalysis field. Such as BiOX (X = Cl, Br and I), BiVO4, Bi2MO6(M = Cr, Mo and W), BiPO4, (BiO)2CO3 and Bi5+ have been developed and applied to degrade organic wastewater [10–16], gas pollutants (NO) [17] and photoreduction of CO2 [18,19]. As far as bismuth molybdate was concerned, three kinds of bismuth molybdate crystals, namely α-Bi2Mo3O12, β-Bi2Mo2O9 and γ-Bi2MoO6 were found, corresponding to atomic ratios of molybdenum to bismuth of 2/3, 2/2 and 2/1[20]. Among them, γ-Bi2MoO6 has more mobile oxygen, while α-Bi2Mo3O12 and β-Bi2Mo2O9 have more hydrocarbon adsorption points. Although α-Bi2Mo3O12 has a highly selective oxidation ability, its practical application in visible light photocatalysis is limited for its high band-gap energy (3.0 eV) [21]. Recently, many researchers have improved the photocatalytic performance of bismuth molybdate by forming heterojunctions [22]. Liu et al. [23] prepared Bi2Mo3O12/MoO3 nano-heterostructure catalyst, which displays a significantly enhanced degradation rate to methylene blue under visible light. Wu et al. [21] constructed a Bi2MoO6:Bi2Mo3O12 heterojunction and compared with pure Bi2Mo3O12 and Bi2MoO6, and found that the Bi2MoO6/Bi2Mo3O12 heterojunction obviously improved the oxidation ability of photocatalytic water. It’s well known that the photocatalytic activity of polyphase bismuth molybdate is better than that of single phase due to its synergistic effect. However, the role of this polyphase bismuth molybdate in the degradation of organic dyes has not yet been demonstrated. Therefore, it is worthwhile to develop heterogeneous heterojunction photocatalyst based on Bi2MoO6 and study its degradation effect on organic pollutants.