Industrial application of magnesium hydroxide
Magnesium hydroxide is both a product and an intermediate material in the plant. As an intermediate material, it can be used to produce magnesium oxide. Superfine grade magnesium hydroxide is also one of the important raw materials to produce nano magnesium oxide; as a product, it has many aspects of use, among which the consumption is large and the use is significant mainly in two major fields. One is as an inorganic additive non-toxic flame retardant, with a variety of properties such as flame retardant, smoke elimination, drip blocking, filling, etc.; the second is the application in the field of environmental protection. As environmental protection supplies, it has occupied the first place of magnesium hydroxide consumption due to its excellent performance. Magnesium hydroxide has strong adsorption, high activity, especially the slurry product, with non-precipitation, non-cohesion, better fluidity, easy to pump and store, easy to use and adjust control, etc. It can be used for acid-containing wastewater neutralization, heavy metal removal, flue gas desulfurization, land acid rain treatment and pH adjustment, etc. The use of magnesium hydroxide can be specifically divided into the following categories.
1. In the application of flame retardant At present, the actual application of flame retardant mainly has halogen system, organic phosphorus system and inorganic class of antimony system, aluminum system, magnesium system, boron system, molybdenum system, etc.. Among them, the halogen system (mainly bromine) flame retardants is currently one of the world's largest production of organic flame retardants. The use of organic flame retardants synthetic materials, when burning will emit toxic gases and smoke, threatening the safety of human life and property. Moreover, the organic flame retardant production process is difficult to control, the waste is easy to cause pollution to the environment, high production costs and high prices. Magnesium hydroxide is a halogen-free flame retardant, decomposed by heat to produce water, while absorbing heat, and decomposition without corrosive and harmful substances, not only can improve the decomposition temperature of the materials added, and does not cause pollution to the environment, can be widely used in polypropylene, polyvinyl chloride and unsaturated resin and other polymer materials of flame retardant and smoke elimination. High thermal decomposition temperature of magnesium hydroxide is conducive to accelerate the speed of extrusion, shorten the molding time, but also help to improve the efficiency of flame retardant, can be widely used in polyester, epoxy resin, paint, fiber products, polypropylene, polyacrylonitrile, polyvinyl acetate, wire, cable, wood, rubber, paint, PVC and other fields.
2. Sulfur wastewater treatment magnesium hydroxide is a weak base, slurry magnesium hydroxide has the advantages of non-precipitation and non-liquidity, easy to use and adjust. The weak alkali magnesium hydroxide so that it has a unique buffer and neutralization ability, in the use of the highest pH value will not exceed 9, which happens to be the U.S. EPA "clean water regulations" (CleanWaterActs) to allow the highest limit of the discharge pH system, and other alkali substances if the excess will make the pH value of 12 or more. Magnesium hydroxide is slow to neutralize, and the particles produced by neutralization settle quickly, easy to filter, and its adsorption capacity is strong, active, low corrosiveness. These advantages make magnesium hydroxide in the treatment of acid-containing wastewater can reduce the operation process and time, reduce equipment investment. Therefore, magnesium hydroxide in the treatment of acid wastewater can be widely used.
3. Heavy metal removal agent Because of magnesium hydroxide specific surface area, strong adsorption, easy from a variety of different industrial wastewater adsorption and remove the environmental hazards of Ni2+, Cu2+, Cd2+, Mn2+, Zn2+, Cr6+ and other heavy metal ions. Magnesium hydroxide can be used alone or in combination with lime and bentonite. Its as heavy metal removal agent, a Japanese patent detailed review of the unique features of using magnesium hydroxide, and pointed out that compared with Ca (OH) 2 treatment, has unparalleled superiority.
4. Flue gas desulfurization using magnesium material desulfurization, the earliest started in Japan, has become a common concern and research issues internationally. Atmospheric pollution mainly from the combustion of the exhaust gas produced. Most of the exhaust gas, especially the exhaust gas from coal combustion contains a large amount of sulfur dioxide. Since the 1980s, magnesium hydroxide slurry products have emerged in the flue gas desulfurization. This is because, compared with other methods, the use of magnesium hydroxide for desulfurization has the advantages of high efficiency, easy to operate, the process is relatively simple, the by-products can be recycled and have high economic benefits.
5. Printing and dyeing wastewater decolorization printing and dyeing wastewater is a class of industrial wastewater is extremely harmful to the environment, its discharge, complex composition, deep color, especially a variety of water-soluble, strong coloring power of dyes, so that the traditional treatment methods are difficult to work. In recent years, domestic and foreign research on the use of magnesium hydroxide treatment of dyeing wastewater, the basic principle is the use of positively charged Mg (OH) 2 adsorption of negatively charged anionic dyes to decolorize the dye wastewater.
6. Phosphate and ammonium removal from wastewater Phosphate in wastewater will promote the growth of algae and lead to oxygen deprivation of fish, and ammonium will harm the survival of marine life. Excessive discharge of phosphorus and ammonium has caused major lakes and oceans in China to face serious eutrophication and red tide phenomenon. Therefore, it is necessary to reduce the ammonium and phosphorus content of wastewater before discharge. With magnesium compounds such as magnesium hydroxide, lightly burned magnesium oxide, dolomite ash (MgO CaO) to remove phosphorus in addition to ammonium effect is significant.
7. Other with seawater magnesium sand production process of intermediate products of magnesium hydroxide as adsorbent, can remove about 80% of the boron in seawater in advance, for the subsequent production of low boron magnesium sand to lay an important foundation. In the chemical pulp bleaching, magnesium hydroxide can be used as alkali agent and cellulose protector to keep the final whiteness of the pulp unchanged, reduce the COD content in the waste water and can improve the viscosity of the pulp. Magnesium hydroxide can also be used as preservative for meat products containing fat and protein, feed and feed additives, also can be used in combination with antioxidant to prevent biodegradation of meat tissue, and maintain elasticity and softness. As potato preservative, under the condition of 4℃～6℃, a layer of emulsion of magnesium hydroxide containing 3% on the surface of potato as non-toxic protective layer can effectively stop the disease caused by plant pathogens. In addition, magnesium hydroxide can be used as a new type of oil field mud material in oil extraction, and has some applications in medical cosmetics, cigarette paper, smoke suppression coating and magnetic material processing.
