In a narrow sense, boron chemicals are generally referred to the process of the boron-containing minerals, the industrial production activities of preparing borax, boric acid.
In a broad perspective,
Borax also known as sodium pyroborate, scientific name is ten water sodium tetraborate. Chemical formula is Na2B4O7•10H2O. Relative atomic mass is 381.37. It is a colorless translucent crystals or white crystalline powder, monoclinic, odorless, salty taste, weathering in dry air. Heated to 60 losing eight molecules water, when heated to 350-400 is completely dehydrate become anhydrous salt melts, when heated to 878 is a glass form product. Melted borax can dissolve many metal oxides, generated a complex salt of metaborate which with a characteristic color.
Borax is easy to soluble in water and glycerin, insoluble in ethanol and acid, aqueous solution is weak alkaline. When higher than 56, the solution separate out five salt precipitates; while below 56 will separate out ten salt precipitates. Solubility in water was rising as the temperature. In borax products also have borax pentahydrate. Of which borax pentahydrate is a white crystalline powder. When heated to 122 will completely loss crystal water become anhydrous salt.
Boric acid, chemical formula is H3BO3. Relative atomic mass is 61.83. According to metal powder supplier, boric acid is white crystalline powder or three oblique axial plane scaly with shiny crystals, no odor, have greasy feel. Dissolved in water, ethanol, glycerol, ethers and essential oils, the solubility in water increases with temperature rise, the solubility in inorganic acid is less than in water, slightly solubility in acetone. The aqueous solution is acidic. When heated to 70-100 will gradually dehydrate become metaboric acid, when 150-160 become pyroborate, when 300 become boric anhydride (B2O3), easy to form esters with alcohols. However, with polyols, especially can with structural position form two hydroxy groups ester type complex ions. Aqueous solution has weak bactericidal effect, a small amount showing a gentle physiological role, a large dose can cause shock then affect the central nervous system.
Produce borax methods include acid, ordinary pressure alkaline hydrolysis, carbon alkaline and water leaching solution method. Among them, the ordinary pressure alkaline hydrolysis is suitable for processing ascharite and boron sodium solution mining, carbon alkaline method is suitable for treating lower grade ascharite, water leaching solution method is suitable for handling natural borax mines. Currently is mainly used carbon alkaline method.
The method of producing boric acid by treatment method can be divided into one-step and two-step method. One-step method is used inorganic acids directly treat boron-containing mineral. Of which including sulfuric acid, hydrochloric acid, nitric acid method. At present, Chinese boron acid industry is mainly used sulfuric acid method. Two-step method is based on sulfuric acid, hydrochloric acid, nitric acid treat industrial borax (decahydrate borax or borax pentahydrate) to prepare boric acid, wherein the sulfuric acid method was an earlier production process adopted in China. In recent years, nitric acid treating borax decahydrate and borax pentahydrate to produce boric acid, the nitrate method process of sodium nitrate developed rapidly and has become China's important two-step process for boric acid.
Sulfuric acid as decomposers treating boron minerals one step process, the advantage is mature technology, the process is simple, less investment in equipment, easy operation. Therefore, has long been subject to people's attention. But there are also requirements for higher grade, not suitable for processing low-grade boron; serious corrosion of equipment; product quality control in larger limitations, boron with low yield. Lack of reliable liquor utilization method, have greater impact on environment and other disadvantages.
Source:http://www.mhcmp.com
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