MoS2, molybdenite

It is shown as a solid bar. This solid solution series coexists with metallic molybdenum, M02.06S3, and MoS2 (molybdenite). Copper coexists with a Cu-rich member i.e., pure X-phase) up to a Y-content of approximately 18%. Iron coexists with the solid solution series from 18 to 75% Y-content, whereas the remainder of the solid solution series forms divariant regions with both Fe and Fe3Mo2. Fe3Mo2 is also stable with Cu and with an iron-rich member of the bornite solid solution series. A large portion of the X—Y solid solution is in equilibrium with the metal-rich portion of the chalcocite-bornite solid solution series. The more Y-rich members are stable with pyrrhotite or FeS (ie., troilite). 

Molybdenum is not found naturally in its elemental form. It is obtained primarily from the mineral molybdenite (MoS2), which contains an average 59.9% of molybdenum. It is the only source of molybdenum which accounts for most of the world s molybdenum supply. Processing flowsheet of molybdenum from this commercial source into principal commercial forms is illustrative of the wide and diverse applications of molybdenum and its chemicals (Figure 1.19). 

This is a layer structure similar to the Cdl2 structure except that the pairs of S layers are directly superimposed upon each other, so that the central cation is in trigonal prismatic coordination, not octahedral or tetrahedral. In the structures derived from this S-Mo-S unit, these layers can be stacked like the simple layers in atomic close-packed sequences. The molybdenite ((3-MoS2) structure has these layers in... 

Occurrence. The most important ore of Mo is molybdenite, the sulphide MoS2. Another mineral is wulfenite (PbMo04). The recovery of Mo from spent petroleum catalysts is widely used. 

Molybdenite is the only common concentrator and economic source of Re. This is because MoS2-ReS2 effectively comprises a solid solution. The association of Re with Mo in this manner suggests that Mo and Re may also behave similarly during magmatic processes. 

Layered sulfides predominate in Groups IV to VII except for MnS, which is isotropic. The main structural feature of this class is a strong chemical anisotropy that greatly affects their catalytic properties. In the molybdenite structure (MoS2), the metal is in trigonal prismatic coordination. Other layered sulfides are octahedrally coordinated or distorted octahedrally coordinated (ReS2) with the metal surrounded by six sulfur atoms. It should also be noted that some TMS sulfides have structures that fall in between isotropic and layered sulfides. Rh2S3 is an example and others are completely amorphous, such as IrSt and OsSr. 

Sulfur is widely distributed as sulfide ores, which include galena, PbS cinnabar, HgS iron pyrite, FeS2 and sphalerite, ZnS (Fig. 15.12). The mineral molybdenite, MoS2, is a soft rock with a metallic sheen and properties similar to those of graphite. Sulfur is also found as deposits of the native element (called brimstone), which are formed by bacterial action on H2S. 

Amine salts have been used to recover molybdenum from solutions arising from a variety of sources. Most of the western world s supply of this metal is derived from molybdenite (MoS2) concentrates obtained as a byproduct of copper production in the USA and Chile. Such concentrates are roasted to molybdenum(VI) oxide (volatile Re207 can often be recovered as a valuable byproduct from the roaster gases) and leached with dilute sulfuric acid to remove the copper from the crude M0O3 product. Some molybdenum also dissolves and can be recovered, for example, by the same technique as that practised at Kennecott s Utah Copper Division smelter,213 i.e. by extraction into a solution of a tertiary amine in kerosene at an aqueous pH value of about 1. 

Molybdenum disulfide or molybdenite (MoS2) is the principal natural source of molybdenum and is widely distributed throughout the world2. The largest world... 

Although the molybdenite obtained from commercial ores is hexagonal, a rhom-bohedral modification of MoS2 has also been found in nature9). Polytypism in molybdenite and the distribution of naturally occurring polytypes of this mineral have been discussed in the literature9-11). 

Fig. 4. A macroscopic picture of an incongruently melted molybdenum sesquisulfide regulus. A melting reaction has formed molybdenite (MoS2) at the edges. The initial charge (pure M°2 06 3) was heated to approx. 1700 °C and chilled within 30 min to room temperature. Regulus size 3.5 mm diameter. Photo Udubasa...

Fig. 8. Partly corroded molybdenite (MoS2) fragments, strongly pleochroic, floating in a metal-rich sulfidic melt. Heated in a plasma-jet melting apparatus, chilled from above 2000 °C x 2000, oil immersion...

C Molybdenite (MoS2) becomes unstable with metallic iron ... 

Molybdenite (MoS2) becomes unstable with pyrite (FeS2) MoS2 + FeS2=i ternary monotcctic( iqujd> + Fe, XS + v... 

C Since the X-phase is unstable, molybdenite (MoS2) coexists with all the phases of the system, and divariant relations exist in the diagram with MoS2 and Cu, MoS2 and Cu2 xS (s.s.), and with MoS2 and CuS. 

C Copper and molybdenite become unstable a switch of tie lines Cu + MoS2 = Cu2S + X-phase + v... 

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