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Whether natural silica is hydrophilic or hydrophobic

2018-10-20
Whether natural silica is hydrophilic or hydrophobic
 
Natural silica is generally hydrophilic and hydrophobic must be post-treated.
 
Silica (chemical formula: SiO2) is an acidic oxide, and the corresponding hydrate is silicic acid (H2SiO3). Silica is the most important compound of silicon. The natural silica present on the earth accounts for about 12% of the mass of the earth's crust. Its existence is crystalline and amorphous. It is collectively called silica.
 
Silica is also known as silica and has the chemical formula SiO2. There are two kinds of crystalline silica and amorphous silica in nature. Crystalline silica is classified into quartz, tridymite and cristobalite due to its different crystal structure. Pure quartz is a colorless crystal, and large, transparent prismatic quartz is called crystal. If the crystal containing trace impurities has different colors, there are amethyst, sap, crystal and so on. Ordinary sand is a fine quartz crystal with yellow sand (more iron impurities) and white sand (less impurities, purer). In the silica crystal, the four valence electrons of the silicon atom form four covalent bonds with four oxygen atoms, the silicon atoms are located at the center of the regular tetrahedron, and the four oxygen atoms are located at the four vertex angles of the regular tetrahedron.

Such tetrahedrons are in turn connected by oxygen atoms in the apex, each oxygen atom being shared by two tetrahedra, ie each oxygen atom is combined with two silicon atoms. SiO2 is the simplest form of composition, and is only the ratio of the number of atoms of silicon and oxygen in the silica crystal. Silica is an atomic crystal.

 
The bond energy of Si—O bond in SiO 2 is very high, and the melting point and boiling point are high (melting point 1723 ° C, boiling point 2230 ° C). The refractive index is approximately 1.6.
 
The refractive indices of various silica products were: 1.547 for quartz sand, 1.544 for powdered quartz, 1.542 for vein quartz, 1.42 to 1.48 for diatomite, 1.46 for fumed silica, and 1.46 for precipitated silica.
 
The diatomaceous earth existing in nature is amorphous silica, which is the remains of lower aquatic plant diatoms. It is a white solid or powdery, porous, light and soft solid with strong adsorption.