Molybdenum compounds are also widely used in agricultural fertilizers
Characteristics of molybdenum raw materials
The element abundance of molybdenum in the earth's crust is about 1 10-6, and the highest molybdenum content is 2 10-6 in the magmatic rocks.Molybdenum is a transitional ferrophilic element in geochemical classification.Molybdenum is mainly combined with sulfur to form molybdenite.Other common molybdenum-containing minerals include ferromolybdenum bloom ([Fe3+(MoO4)8·8H2O)), calcium molybdate (CaMoO4), color molybdenum lead ore (PbMoO4), collosulfide molybdenum ore (MoS2), blue molybdenum ore (Mo3O8·nH2O), etc.
Molybdenite (MoS2) is the most widely distributed molybdenum mineral with realistic industrial value among more than 30 known molybdenum minerals in nature.Molybdenum ore is lead-gray, similar to graphite, with metallic luster, is a hexagonal crystal system, the crystals are often hexagonal flake, often have patterns on the bottom, soft and slippery, thin flexible.Proportion of 4.7 ~ 4.8, hardness of 1 ~ 1.5, melting point is 795 ℃, MoS 2 stroke streaks on the ceramic plate is light green black, gray or pale green heating to 400 ~ 500 ℃ MoS 2 easily generated MoS 3 oxidation, nitric acid and aqua regia can make molybdenite (MoS 2) decomposition.Molybdenum molybdenite MoS 2 is used to produce ferromolybdenum alloy, metal molybdenum, calcium molybdate, ammonium molybdate, lubricant and so on.
There are many types of molybdenite, the experiment shows that the polytype is related to the forming temperature, the forming temperature of 2H type molybdenite is higher than that of 3R type molybdenite.Temperature from low to high to form amorphous MoS2 colloidal MoS2 3MoS2 2HMoS2.The temperature data show that the molybdenite forming temperature has a wide range, from fairly high temperature to relatively low temperature, and a large number of molybdenite formed in the high to medium temperature stage.Under hydrothermal action, MoS2 precipitates under acidic conditions, that is, molybdenite is the most stable under acidic conditions. When the solution turns to neutral, molybdenum turns to soluble molybdate and molybdate and then moves again.At low temperature and normal temperature, Mo4+ was reduced in strong acid environment to generate molybdenum collosulfide ore (MoS2), and its oxidized product was blue molybdenum ore (Mo3O8·nH2O).In the exogenous process, mo is Mo6+ and has strong activity.Similar to uranium, it is stable in a transition environment of oxidation and reduction close to neutral or alkaline, so as to generate a variety of uranium-containing molybdate minerals, such as molybdenum uranium [(UO2)MoO4·4H2O] and molybdenum calcium uranium [Ca(UO2)3(MoO4)·(OH)2·11H2O].Fe2(MoO4)3·nH2O] is a common mineral formed in sulfide ores under acidic conditions (pH= 3-5).Color molybdenum lead ore is the product of molybdenum-containing lead-zinc ore under neutral conditions.
Rhenium and molybdenum have similar ionic radius, so it is often substituted for molybdenum and enriched in molybdenite, becoming the main source of rhenium for industrial use.The rhenium content in molybdenite is often related to the type 3R content in molybdenite and the rhenium content in the ore-forming solution.
Molybdenum ore assay technology
Molybdenum ore test: molybdenum can be determined by gravimetric method, volumetric method, colorimetric method, polarographic method, atomic absorption spectrophotometry, X-ray spectrophotometry and spectrophotometry.Because the content of molybdenum in ore is generally low, colorimetric method is mostly used for determination, and catalytic polarography method is also used.Is the most widely used thiocyanate colorimetric method, namely the molybdenum (Ⅵ) reduction in acid solution for molybdenum (Ⅴ), molybdenum (Ⅴ) with complex thiocyanate form orange red color.Can be in nitric acid or sulfuric acid solution, with the corresponding weak reductant such as tin chloride, thiourea reduction.This method is simple, rapid, less disturbing elements, good stability and high accuracy.The higher content of molybdenum can be determined by differential spectrophotometry and the trace molybdenum can be extracted by ethyl acetate.
For determination of high content molybdenum (molybdenum concentrate), gravimetric and volumetric methods can be used.The gravimetric methods include lead molybdate method, benzooxime method and 8-hydroxyquinoline method.Among them, lead molybdate method has many interfering elements and complicated procedures, but the range of acidity during precipitation is wide and the composition of lead molybdate is stable, so it has high accuracy and is widely used in production.Benzoxime method has fewer interfering elements, but the composition of precipitated lead is stable, so it has high accuracy and is widely used in production.
