Molybdenum mineral processing

Flotation or froth flotation is a physicochemical property-based separation process. It is widely utilised in the area of mineral processing also known as ore dressing and mineral beneftciation for mineral concentration. In addition to the mining and metallurgical industries, flotation also finds appHcations in sewage treatment, water purification, bitumen recovery from tar sands, and coal desulfurization. Nearly one biUion tons of ore are treated by this process aimuaHy in the world. Phosphate rock, precious metals, lead, zinc, copper, molybdenum, and tin-containing ores as well as coal are treated routinely by this process some flotation plants treat 200,000 tons of ore per day (see Mineral recovery and processing). Various aspects of flotation theory and practice have been treated in books and reviews (1 9). 

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 section on flowsheets basically aims to provide some illustrative examples of the use of the various mineral processing unit operations that have been described. A general flowsheet involving almost all the unit operations pertinent to mineral processing is shown in Figure 2.32. The others refer specifically to beach sands, lead-zinc concentration, molybdenum, and the rare earths. 

Although flotation was developed as a separation process for mineral processing and applies lo the sulfides of copper, lead, zinc, iron-molybdenum, cobalt, nickel, and arsenic and to nonsullides, such as phosphates, sodium chloride, potassium chloride, iron oxides, limestone, feldspar, fluorite, chromite, tungstates, silica, coal, and rhodochrosilc, flotation also applies to nonmineral separations. Flotation is used in the water disposal field, particularly in connection with petroleum waste water cleanup. 

The raw minerals mined from natural deposits comprise mixtures of different specific minerals. An early step in mineral processing is to use crushing and grinding to free these various minerals from each other. In addition, these same processes may be used to reduce the mineral particle sizes to make them suitable for a subsequent separation process. Non-ferrous metals such as copper, lead, zinc, nickel, cobalt, molybdenum, mercury, and antimony are typically produced from mineral ores containing these metals as sulfides (and sometimes as oxides, carbonates, or sulfates) [91,619,620], The respective metal sulfides are usually separated from the raw ores by flotation. Flotation processes are also used to concentrate non-metallic minerals used in other industries, such as calcium fluoride, barium sulfate, sodium and potassium chlorides, sulfur, coal, phosphates, alumina, silicates, and clays [91,619,621], Other examples are listed in Table 10.2, including the recovery of ink in paper recycling (which is discussed in Section 12.5.2), the recovery of bitumen from oil sands (which is discussed further in Section 11.3.2), and the removal of particulates and bacteria in water and wastewater treatment (which is discussed further in Section 9.4). 

Minerals and Metals. HCl is consumed in many mining operations for ore treatment, extraction, separation, purification, and water treatment (see Mineral recovery and processing). Significant quantities are also used in the recovery ofmolybdenum (see Molybdenum and molybdenum alloys) and gold (see Gold and gold compounds). This market consumed about 36 thousand metric tons in 1993. 

Peters (5) Has reviewed the leaching of copper, nickel, zinc, lead and molybdenum concentrates in terms of the thermodynamic stability of the sulfide minerals of these metals. Process developments associated with the most favorable decomposition paths are considered. 

The Fe and Mn that diffuse downward are subject to precipitation as carbonate and sulfide minerals in which the metals are present in reduced form. These minerals do not undergo any further chemical changes unless tectonic processes (uplift) cause them to come into contact with O2. As with the oxide phase, other metals tend to coprecipitate into the sulfide minerals, such as cadmium, silver, molybdenum, zinc, vanadium, copper, nickel, and uranium. 

Reduction-oxidation processes, which are the dominant control for uranium mobility and deposit formation, are also responsible for elevated molybdenum and vanadium contents observed associated with mineralization. 

Anomalous values of lithium, 207pb/206pb, gpjj molybdenum (and other process-related elements) are observed within the distal uranium halo, and appear to represent intermediate and perhaps proximal halos enveloping mineralization. Local enrichments are also observed associated with structural features distal or intermediate to the main zone of mineralization, the trend of which may be useful for vectoring into the deposit. 

Rhenium was the last naturally occurring chemical element to be discovered in 1925 by Noddack, Tacke, and Berg in the mineral gadolinite. The name of this extremely rare element (the estimated occurrence in the earth s crust is about 0.7 ppb ) is derived from the Rhine river. Residues from the processing of molybdenum ores represent the main source of the metal. 

---