Popularization - Detailed description of pyrite (FeS2)

Pyrite Introduction

Pyrite (FeS2) copper because of its light yellow color and bright metallic luster, is often mistaken for gold, it is also known as "Fool's Gold." The composition usually contains cobalt , nickel and selenium , and has a NaCl-type crystal structure. It is called pyrite with the same composition and belonging to the orthogonal (orthortic) crystal system. Trace amounts of cobalt, nickel, copper, gold, selenium and other elements are often present in the composition. When the content is high, it can be comprehensively recovered and utilized in the process of extracting sulfur.

Pyrite (FeS2) is often referred to as "fool gold" because of its light brass color and bright metallic luster, which is often mistaken for gold. The composition usually contains cobalt, nickel and selenium, and has a NaCl-type crystal structure. It is called pyrite with the same composition and belonging to the orthogonal (orthortic) crystal system. Trace amounts of cobalt, nickel, copper, gold, selenium and other elements are often present in the composition. When the content is high, it can be comprehensively recovered and utilized in the process of extracting sulfur.

chemical composition

The theoretical composition (wB%) is: Fe 46.55, S 53.45.

There are often Co and Ni-like homogeneous images instead of Fe to form FeS2-CoS2 and FeS2-NiS2 series. As the content of Co and Ni instead of Fe increases, the unit cell increases, the hardness decreases, and the color becomes lighter. As, Se, and Te can replace S. It usually contains finely dispersed mixed materials of Sb, Cu, Au, Ag, and the like. There may also be trace elements such as Ge and In. Au is often present in the cleavage plane or lattice of pyrite by microscopic gold or ultramicroscopic gold.

Physical properties

Pyrite is light brass yellow with a yellowish brown surface. The streak is greenish black or brownish black. Has a strong metallic luster. opaque. No cleavage, the fracture is staggered, the hardness is 6~6.5, and the relative density is 4.9~5.2. Can be detected.

Pyrite is a semiconductor mineral. Since the non-equivalent impurity component is substituted, such as Co3 or Ni3 instead of Fe2 or [As]3, [AsS]3 instead of [S2]2-, an electron core (n-type) or a hole core (p-type) is generated. Electrical conductivity. Under the action of heat, the trapped electrons are easy to flow and have directionality, forming a stream of electrons, generating a thermoelectromotive force and being pyroelectric.

Birth and combination

Pyrite is unstable in the oxidation zone and easily decomposes to form iron hydroxide such as goethite, fibrite, etc. After dehydration, it can form stable limonite, and often forms an illusion according to pyrite. This effect is often formed on the surface outcrop of the metal oxide bed oxidation zone to form limonite or goethite, fibrite, etc. over the ore body, so it is called iron cap. Under the condition of strong acidity in the oxidation zone, jarosite can be formed, which is second only to limonite.

application

The main raw material for the production of sulfur and sulfuric acid. Associated elements can be extracted when Au, Co, and Ni are contained.

Medicinal natural copper is pyrite (chopped or calcined), alias stone core lead . Efficacy: Sanyu pain, bone healing. Medicine preparations: Huoxue Zhitong San, the army broke down.

Application in middle school chemistry: sulfuric acid

The sulfur or pyrite is first burned or calcined in air to obtain sulfur dioxide gas.

Oxidation of sulfur dioxide to sulfur trioxide is the key to the production of sulfuric acid. The reaction is: 2SO2+O2→2SO3

This reaction was practically impossible at room temperature and in the absence of a catalyst.

The method for producing sulfuric acid can be classified into a contact method and a nitrification method depending on the way in which sulfur dioxide is converted into sulfur trioxide.

Contact method is supported on diatomaceous earth containing potassium hydroxide, or (cocatalyst) of vanadium pentoxide V2O5 as a catalyst, the conversion of sulfur dioxide to sulfur trioxide.

Nitrification is the use of nitrogen oxides as oxygen scavengers to oxidize sulfur dioxide to sulfur trioxide: SO2+N2O3+H2O→H2SO4+2NO

According to the different equipment used, the nitrification method is divided into a lead chamber method and a tower method; and the contact method can produce sulfuric acid having a concentration of 98% or more;

The main equation:

4FeS2+11O2=2Fe2O3+8SO2

2SO2+O2=2SO3

SO3+H2O=H2SO4

distributed

World famous places of origin are Spain, the Czech Republic, Slovakia, the United States and China. Pyrite our proven reserves in the world, famous origin have Yingde, Guangdong and Yunfu, Maanshan, Anhui, Gansu and other white silver factory.

Pyrite pyrite is the most widely distributed sulfide in the earth's crust. In the magmatic rock, the pyrite is in the form of fine dissemination, which is the product of hydrothermal action after the magma period. In the contact metasomatic deposit, pyrite is often symbiotic with other sulfides and formed in the later stage of hydrothermal action. In hydrothermal deposits, pyrite is symbiotic with other sulfides, oxides, quartz, etc.; sometimes a huge accumulation of pyrite is formed. In sedimentary rocks, sedimentary deposits, and coal-based, pyrite form clumps, tuberculosis or output lens. In metamorphic rocks, pyrite is often a new product of metamorphism.

Identification feature

The crystal form of pyrite is intact, the crystal plane is striped, and the dense block is similar to chalcopyrite, but according to its light brass yellow color, it has high hardness and its conductivity can be distinguished from chalcopyrite. Sexually brittle, it is easy to break when knocked, and the broken surface is uneven.

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