Boric acid was first prepared by Wilhelm Homberg (1652-1715) and was given the the name "sal sedativum Hombergi", which was produced by a mixture of sulfuric acid and borax. Boric acid is actually a hydrate of boron oxide (B2O3·3H2O). It has a slippery feel and no odor. The specific gravity of boron oxide is 1.435 (15℃). The solubility of boric acid in water increases with increasing temperature and can volatilize with water vapor, and its solubility in inorganic acid is less than that in water. When heated to 70-100 ℃, boric acid gradually dehydrates to form metaboric acid. And when heated to 150-160 ℃, pyrobetic acid is formed, and at 300 ℃, boric anhydride (B2O3) is formed.
Boric acid is used in enamels and ceramics to enhance the gloss and fastness of these products. It is also one of the ingredients of glazes and pigments. In the pharmaceutical industry and metallurgical industry, boric acid can be used as an additive and a co-solvent. For example, boron steel has high hardness and good rolling ductility so it can be used to replace nickel steel. Boric acid is corrosion resistant, so it can be used as preservative such as wood preservative. And it can also be used in the fields of metal welding, leather, photography, dyes, heat-resistant fireproof fabrics, artificial gemstones, capacitors, and cosmetics. Besides, Boric acid can also be used as insecticide and catalyst. In agriculture, the boron-containing trace element fertilizers have fertilizer effect on many crops and can increase the oil content of rapeseed. A variety of borides can be produced from boric acid and they are widely used in defense and other industrial sectors and research institutes. Boric acid has a variety of product standards and specifications, and it can be divided into electronic grade, capacitor grade, atomic grade, spectral grade, industrial grade, food grade and pharmaceutical grade in terms of purity. Boric acid is an important multifunctional raw material for inorganic chemicals, and plays an important role in the development of national economy and industrial production.
At present, the proven reserves of the boron mines in world are about 70,000 kt, and the prospective reserves are about 470,000 kt. The countries with more reserves of boron ore are Turkey, the United States, Russia, China and Kazakhstan. The total reserves of the five countries account for about 90% of the world's total boron ore. Turkey has the world's most abundant boron resource, and its boron ore reserves account for 60% of the world's total boron ore. The boron-containing minerals used to prepare boric acid mainly include orthorhombic borax and natural borax, sodium borate, bauxite, borosilicate, and boric acid extracted from boron-containing brine. Due to the different boron resources in different countries, the methods to produce boric acid is different as well, but the acid method is the main method. For example, the United States, Turkey and Russia use the traditional sulfuric acid method, and the raw materials used generally contain more than 25% of B2O3. This method has the advantages of less impurities, easy processing, low cost and high purity of boric acid. In addition, the United States has successfully extracted boric acid from boron-containing brines by using the extraction method in Sears Salt Lake, California, and Bogaz Bay, Russia, and the method has been put into industrial production. While using traditional methods to produce boric acid, countries continue to research and develop new production processes based on their own conditions.
In the United States, the boric acid production reached 223 kt (in B2O3) in the mid-1980s, and the finished boric acid production reached 396.1 kt. Today, the annual output of boric acid and borate of U.S. Borax, Inc. exceeds 1,000 kt. Borate produced in Turkey accounts for 65% of the world's borate reserves. Boric acid is usually prepared by soaking the colemanite with sulfuric acid, and it is now being studied to extract boric acid from the colemanite by using carbon dioxide gas in a liquid medium. Other countries such as Argentina, Chile, and Italy also have certain boric acid production capacity.
Due to the wide-ranging use of boric acid, the domestic production capacity and processing capacity of boric acid are still increasing in demand. In the United States, the demand for boride in the fiberglass sector accounts for 64%, the glass sector accounts for 6%, the flame retardant sector accounts for 4%, the soap and detergent sector accounts for 4%, the agricultural sector accounts for 3%, the ceramics sector accounts for 3%, and other areas accounted for 16%. Rio Tinto Borates (world's largest boron company) revealed that they will accelerate the development of new applications for borax and boric acid. In terms of market application prospects, TFT liquid crystal displays produced using boron materials have great market potential.
