Inventory the characteristics of various
magnesium oxides and hydroxides
Magnesium oxide has been continuously developed and widely used in various fields in recent years. Magnesium oxide is a white powder that exists in the form of free magnesite in nature. The main component of magnesite is magnesium carbonate, while the main component of dolomite is MgCO3 and CaCO3 eutectic.
The specific gravity of artificial marble is 3.65-3.9, the melting point is 2800 ℃, and the relative molecular weight is 40.3. Magnesium oxide can be roughly divided into the following categories according to different production processes and uses:
Calcined magnesium oxide
According to operating temperature: The magnesium oxide produced by high-temperature calcination of raw magnesite is calcined magnesium oxide; Magnesium oxide produced by burning coke at 1400-1800 ℃ is a type of heavy burned magnesium, also known as dead burned magnesium; Magnesium oxide produced by burning coal or gas as fuel at 700-1000 ℃ is a light burned powder, also known as caustic magnesium; Low grade magnesium oxide, also known as bitter clay powder, is produced by burning a mixture of low-grade magnesite and anthracite.
The chemical composition of magnesite is MgCO3, with a relative molecular weight of 84.31. MgCO3 is the main component, while SiO2, CaO, Al2O3, and Fe2O3 are secondary components. The content of MgO is usually between 35% and 47%. Reburned magnesia is mainly used for refractory materials, and also has applications in the manufacturing of magnesium chromium bricks and calcium magnesium carbon bricks, insulation fillers for electric heating components, feed, building materials, and other fields.
Industrial magnesium oxide
Industrial magnesium oxide, also known as light magnesium oxide, has a bulk density between 0.2-0.3g/ml. Magnesium oxide produced from MgCl · 6H2O or sea brine as raw materials belongs to light magnesium oxide, and magnesium oxide produced by the dolomite carbonization method is also classified as light magnesium oxide.
Lightweight magnesium oxide is a odorless, odorless, and non-toxic white amorphous powder mainly used in the manufacturing of enamel, ceramics, refractory materials, etc; Serve as a filler in the production of polishing adhesives and paints; Act as a promoter and catalyst in artificial fibers and rubber (fluororubber, chloroprene rubber); Used as a decolorizing agent for sugar refining and a pH regulator for ice cream powder in food processing; Used as a laxative and antacid in medicine, for the treatment of duodenal ulcers and excessive stomach acid; Used as animal feed and fertilizer in agriculture; In the construction industry, special cement and insulation boards containing magnesium can be produced and manufactured.
In addition, it can also be used for water treatment, flue gas cleaning, and has applications in industries such as cables, glass dyes, uranium processing, silicon steel industry, insulation material industry, petroleum additives, electronics industry, casting, phenolic plastics, etc.
Heavy magnesium oxide
The bulk density of heavy magnesium oxide obtained by further processing and separating impurities from lightly burned magnesium oxide ranges from 0.5 to 0.7 g/ml. Heavy magnesium oxide can replace light magnesium oxide in magnetic materials for color TV deflection coils (ferrite soft magnets) and other ferrite magnetic materials; Serve as a polishing agent in the steel ball polishing industry; The dye industry serves as an auxiliary material for the production of aminophenol; The electrical industry serves as a raw material for phenolic resins.
Secondly, it is also applied in ceramic glass, industrial catalysts, feed, and environmental protection industries.
Active magnesium oxide
Active magnesium oxide is one of the many varieties of magnesium oxide products, and activity refers to the difficulty of magnesium oxide reaction, which is determined by the thickness (specific surface area) of magnesium oxide solid particles.
Some indicators of active magnesium oxide are different from those of ordinary magnesium oxide. If there is a suitable particle size distribution, the average particle size should be<2 μ M (2000nm); The microstructure is irregular particles, nearly spherical particles, or sheet-like crystals, and the activity indicated by citric acid (CAA value) is 12 25 seconds (the smaller the value, the higher the activity); The activity expressed by iodine absorption value is 80-120 (mgI2/100gMgO); The specific surface area is between 5-20m2/g, and the apparent specific volume is between 6 ^ 8.5ml/g.
It can be said that heavy magnesium oxide is pure Mg0, while light magnesium oxide is xMg0 * YMg (0H) 2, which is basic magnesium oxide. The percentage content of light magnesium oxide plays an important role in its activity. Generally, highly active magnesium oxide is obtained by long-term decomposition of basic magnesium carbonate at low temperatures. The furnace structure is special, and the energy consumption is high, resulting in a larger apparent volume of the product.
Magnesium hydroxide is an inorganic weakly alkaline product, known as a "green neutralizer", "environmentally friendly flame retardant", and "third alkali" due to its strong buffering performance, high activity and adsorption capacity, as well as many unique properties such as non corrosiveness, non-toxicity, and harmlessness. It is one of the products that are highly favored and respected in promoting sustainable development strategies, environmental protection, and beneficial ecological development.
Magnesium hydroxide can also be used as an intermediate material to produce magnesium oxide. Ultrafine magnesium hydroxide is also one of the important raw materials for producing nano magnesium oxide; As a product, it has many uses, among which the high consumption and significant use effects are mainly in two major fields. Firstly, as an inorganic additive non-toxic flame retardant, it has various properties such as flame retardancy, smoke suppression, droplet inhibition, and filling; The second is its application in the field of environmental protection. As an environmentally friendly product, due to its excellent performance, it has occupied the top few positions in the consumption of magnesium hydroxide.
The preparation methods of magnesium hydroxide include:
1. The physical crushing method refers to the direct crushing of ore, followed by dry coarse grinding and wet ultrafine grinding to obtain the required particle size grade of magnesium hydroxide product. The commonly used ore is brucite.
2. The ore calcination hydration method involves calcining the ore and preparing magnesium hydroxide by hydration of the obtained magnesium oxide. This process involves the dissolution of magnesium oxide and the precipitation of magnesium hydroxide, with the dissolution of magnesium oxide being the control step. Due to the different composition of the ore, magnesite is commonly used.
3. There are two sources of raw materials for the liquid phase precipitation method. One is magnesite, dolomite, serpentine, etc., which are processed by acid hydrolysis or other methods to obtain magnesium salts and undergo precipitation reaction with alkali to prepare magnesium hydroxide. One method is to precipitate magnesium salts obtained from seawater, salt lake water, and well brine with alkali to prepare magnesium hydroxide.