Solid molybdenite

Specific fillers (layer-lattice solids) molybdenite or molysulfide (M0S2) and graphite. 

Solid effluents arising from metallurgical operations occur principally in two forms fine particulate solids or dusts, and solid wastes. As an example, blast furnace gas may contain up to 170 kg of dust per ton of pig iron produced. Suitable methods must be devised for processing the solid effluents for two reasons (i) to prevent pollution of the environment and (ii) to recover their valuable content, if any. As far as the latter is concerned, reference may be drawn, as an example, to the recovery of rhenium from the exit gas from molybdenite roasting in a multiple-hearth furnace. 

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. 

Elemental composition Mo 59.94%, S 40.06%. The compound or mineral molybdenite may be identified nondestructively by x-ray and from physical properties. Molybdenum content of the material may be determined by various instrumental techniques after digestion of the solid in concentrated HNO3 or aqua regia followed by appropriate dilution of acid extract (See Molybdenum.)... 

In water the wetted solid is termed hydrophilic , whereas the non-wetted solid is hydrophobic . Naturally hydrophobic minerals, such as some types of coal, talc and molybdenite are easily separated from the unwanted hydrophilic quartz sand (referred to as gangue ). However, surfactants and oils are usually added as collectors . These compounds adsorb onto the hydrophilic mineral surface and make it hydrophobic. 

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). 

Molybdenite (MoS2) forms stable assemblages with the sulfur-rich portion of the chalcocite-bornite solid solution, with chalcopyrite solid solution, with the iron-deficient portion of the pyrrhotite solid solution, and with pyrite. Similar intergrowths between the respective ore minerals, stable at low temperatures, are known from numerous localities. 

Preferred orientation of metal films can be clearly achieved by depositing the metal on the smooth surface of a well-crystallized solid in vacuo. For example, Uyeda (94) and Kainuma (95) obtained (lll)-oriented films of nickel, copper, and platinum when these metals were deposited on a cleavage surface of molybdenite (0001) at temperatures ranging from 20° to 500°C. Miyake and Kubo (96) observed a temperature dependency of the orientation of deposited films of face-centered cubic metals when they were deposited on a cleavage surface of zinc blende (110). 

After purification and conversion into appropriate grade powders, the mineral molybdenite, M0S2, has widespread commercial applications as a solid lubricant. It is applied to reduce wear and friction, and is able to withstand high-temperature working conditions. The lubricating properties are a consequence of the solid state layer structure... 

Fig. 47. Schematic diagram of molybdenite structure. Mo atoms (solid circles) are located at B sites, and the S atoms (open circles) at A sites which are above and below the plane in which the B sites lie. In hexagonal molybdenite the stacking sequence is AbBaAb. (In the rhombohedral variety the C sites assume importance.) (8 7)...

Molybdenum has a special affinity for sulfur and the close energy match of the Mo 4d and S 3p orbitals often leads to fascinating but unpredictable chemistry. " Molybdenum forms many solid-state sulfides, including the principal ore molybdenite (M0S2), MO2S3, M02SS, non-stoichiometric sulfides and Chevrel phases. These compounds enjoy increasing use as lubricants, electronic materials and catalysts. " ... 

Surface Property Modifiers with further division into a) solid lubricants/tribological additives that include molybdenite, graphite, PTFE and boron nitride and b) antiblocking fillers such as silica. Chapter 19. 

---