Chinese Name: Diatomite mbth: Diatomite 1 Chemical Formula: SiO2 Molecular Weight: 60 Mineral Density: 0.47 g/cm3 Melting Point: 1400~ 1650℃ Chinese Synonyms: Diatomite Filter Aid, Diatomite Filler CAS: 61790-. Physical Properties Diatomite has a density of 1.9-2.3g/cm3, a bulk density of 0.34-0.65g/cm3, a specific surface area of 40-65m2/g, a pore volume of 0.45-0.98cm3/g, a water absorption of 2-4 times its own volume and a melting point of1655. The nature of the raw ore contains a small amount of Al 2 O 3, Fe 2 O 3, CaO, MgO, K 2 O, Na 2 O, P 2 O 5 and organic matter. SiO _ 2 usually accounts for more than 80%, up to 94%. The iron oxide content of high-quality diatomite is generally 1~ 1.5%, and the alumina content is 3~6%. The mineral composition of diatomite is mainly opal and its varieties, followed by clay minerals-hydromica, kaolinite and mineral debris. Mineral debris includes quartz, feldspar, biotite and organic matter. The content of organic matter ranges from trace to over 30%. Diatomite is white, off-white, gray and light taupe. It is thin, loose, light, porous, absorbent and breathable. Silica in diatomite is mostly amorphous, and the content of soluble silicic acid in alkali is 50~80%. Amorphous silica turns into crystals when heated to 800 ~ 1000℃, and the soluble silicic acid in alkali can be reduced to 20~30%. Molecular formula of mineral profile: SiO2 molecular weight: 60.08casNoNo.: 6 1790-53-2 Diatomite is a siliceous rock, mainly distributed in China, the United States, Denmark, France, Romania and other countries. China's diatomite reserves are 320 million tons, and the prospective reserves are more than 2 billion tons, mainly concentrated in East China and Northeast China, among which Jilin, Zhejiang, Yunnan, Shandong, Sichuan and other provinces are large in scale and do more work. Although widely distributed, high-quality soil is only concentrated in Changbai, Jilin and diatomite mining areas in Yunnan, and the resources are particularly rich. Most of the other deposits are grade 3~4 soils with high impurity content, so they cannot be directly processed and utilized. Diatomite Diatomite is composed of amorphous silicon dioxide and contains a small amount of iron oxide, calcium oxide, magnesium oxide, aluminum oxide and organic impurities. Diatomite is usually light yellow or light gray, soft, porous and light. It is often used as thermal insulation material, filter material, filler, grinding material, water glass raw material, decolorant, diatomite filter aid and catalyst carrier in industry. The special porous structure of natural diatomite can be observed under the microscope, which is the reason why diatomite has unique physical and chemical properties. Diatomite as a carrier is mainly composed of silicon dioxide. For example, the active component of industrial vanadium catalyst is V 2 O 5, the cocatalyst is alkali metal sulfate, and the carrier is refined diatomite. The experiment shows that silica has a stabilizing effect on active components, which is enhanced with the increase of K 2 O or Na 2 O content. The activity of the catalyst is also related to the dispersion and pore structure of the carrier. After acid treatment, the content of oxide impurities decreases, the content of SiO 2 increases, and the specific surface area and pore volume also increase, so the carrier effect of refined diatomite is better than that of natural diatomite. Diatomite is generally formed by silicate remains after the death of unicellular algae, which is called diatom, and its essence is aqueous amorphous SiO 2. Diatoms can exist in both fresh water and salt water, and there are many kinds, which can be generally divided into "central class" diatoms and "pinnate" diatoms. In each order, there are many "genera", which are quite complicated. The main component of natural diatomite is silicon dioxide. Good quality is white, and the content of SiO _ 2 often exceeds 70%. Monomer diatom is colorless and transparent. The color of diatom depends on clay minerals and organic matter, and the composition of diatom from different mineral sources is also different. Diatomite is a kind of fossil diatom accumulation soil deposit formed after the death of unicellular plants called diatoms for about 65,438+0 to 20,000 years. Diatom is one of the earliest protozoans on the earth. It lives in seawater or lake water. This diatom is deposited from the remains of the unicellular aquatic plant diatom. The unique property of this diatom is that it can absorb free silicon in water to form a skeleton, and when its life ends, it will deposit and form a diatom deposit under certain geological conditions. It has some unique properties such as porosity, low density, large specific surface area, relative incompressibility and chemical stability. After changing the particle size distribution and surface properties of the original soil through crushing, sorting, calcination, airflow classification and impurity removal, it can be applied to various industrial requirements such as coating additives. Purification methods of mineral processing diatomite purification methods are mainly divided into physical method, chemical method and physical-chemical comprehensive method. 1, scrubbing method
The premise of purifying diatomite by scrubbing method is to refine the raw material particles by scrubbing, so as to separate as many mineral impurities as possible, such as clay consolidated on diatom shells, and create conditions for separation and purification. Then, according to the different mineral properties and particle ranges, timely mud, iron-containing minerals and sand particles can be separated first because of their larger particles, while clay impurity montmorillonite has been dispersed into very small particles after stirring and scrubbing, which have the same negative charge as diatomite and repel each other. Therefore, it has good suspension and dispersibility, and dispersant such as sodium hydroxide can be added to the slurry to enhance the suspension and dispersibility of montmorillonite. Montmorillonite particles are difficult to precipitate, while diatomite particles settle much faster in mud than montmorillonite particles. By separating the suspension mainly composed of montmorillonite, diatom fine soil mainly composed of diatomite can be obtained.
Kong Wei removed some clay minerals such as montmorillonite and coarse sediment by scrubbing method, which increased the specific surface area and pore volume of diatomite slightly. Mr. Ai and others used low-grade diatomite from Chifeng, Inner Mongolia as raw material, and studied the effects of scrubbing concentration, scrubbing time, scrubbing times and dispersant on its physical purification effect.
Scrubbing can remove impurities outside diatom shells, but it has little effect on removing impurities in diatom micropores. The process of purifying diatomite by washing method is simple, with less equipment investment and easy to realize industrial production, but it occupies a large area, consumes a lot of water, has a long production cycle and consumes a lot of energy to dry diatomite. 2, 2.2 Acid leaching method
Wen Fei et al. removed most impurities such as iron and aluminum from the pulp by pickling after peeling, and then obtained diatomite concentrate with silicon content of 9 1.27% through primary sedimentation and classification. After roughing, peeling and acid leaching, the final concentrate reached the expected requirements, and the silicon content increased from 7 1.86% to 9 1.27%, effectively removing impurities. Zhang Guilong and others studied the modification of diatom pore structure by acid leaching, and thought that acid leaching could not only increase diatom content, but also modify diatom pore structure. O *** an San et al. studied the effect of acid leaching on the filtration performance and porosity of diatomite, and prepared diatomite filtration materials and porous ceramic materials by acid leaching diatomite.
However, the conventional acid leaching method has the advantages of long purification time, large acid consumption, high cost and environmental pollution, which is not conducive to industrial production and greatly affects its application prospect. Study on microwave-enhanced acid leaching purification process of diatomite can not only shorten the leaching time, but also improve the leaching rate. Using diatomite to treat urban sewage is a physical and chemical sewage treatment technology, and the key to this technology is to modify diatomite sewage treatment agent efficiently. On this basis, combined with process flow and facilities, this technology can achieve the purpose of treating urban sewage efficiently, stably and cheaply. However, because this is a new technology, there are still some problems to be solved in theoretical and practical engineering applications. Application scope of diatomite industrial filler pesticide industrial application scope: wettable powder, dry land herbicide, paddy field herbicide and various biological pesticides. The advantages of diatomite application are: pH value 1: neutral, non-toxic, good suspension performance, strong adsorption performance, light bulk density, oil absorption rate 1 15%, fineness of 325 -500 mesh, good mixing uniformity, no blockage of agricultural machinery pipelines when in use, moisture retention, loosening soil and prolonging the drug effect in soil. Compound fertilizer industry: compound fertilizer for fruits, vegetables, flowers and other crops. Advantages of diatomite application: strong adsorption performance, light bulk density, uniform fineness, neutral and non-toxic pH value and good mixing uniformity. Diatomite can be used as an efficient fertilizer to promote crop growth and improve soil. Rubber industry: fillers for various rubber products, such as automobile tires, rubber tubes, V-belts, rubber rollers, conveyor belts and automobile mats. Advantages of diatomite application: it can obviously enhance the rigidity and strength of products, and the sedimentation volume reaches 95%, which can improve the chemical properties of products such as heat resistance, wear resistance, heat preservation and aging resistance. Building insulation industry: roofing insulation layer, insulation brick, calcium silicate insulation material, porous coal stove, soundproof and fireproof decorative board and other insulation, soundproof and soundproof building materials, wall soundproof decorative board, floor tile, ceramic products, etc. Advantages of using diatomite 2: diatomite should be used as an additive in cement. Adding 5% diatomite in production cement can improve the strength of ZMP, and SiO 2 in cement becomes active and can be used as emergency cement. Plastic industry: living plastic products, building plastic products, agricultural plastics, door and window plastics, various plastic pipes and other light and heavy industrial plastic products. Application advantages of diatomite 3: good ductility, high impact strength, tensile strength and tear strength, light weight, good internal friction and good compressive strength. Paper industry: office paper, industrial paper and other paper; Application advantages of diatomite: it is light and soft, and its fineness is between 120 mesh and 1200 mesh. The addition of diatomite can make the paper smooth, light and strong, reduce the expansion and contraction caused by humidity change, and adjust the burning speed in the roll paper, without toxic side effects. In filter paper, the clarity of filtrate can be improved and the filtration speed can be accelerated. Paint and coating industry: furniture, office paint, building paint, machinery, household appliances paint, mimeographed ink, drainage meter, automobile paint and other paint and coating fillers; Advantages of diatomite 4: neutral 4:pH value, non-toxic, fineness 120 mesh to 1200 mesh, light and soft, and it is a high-quality filler in oil painting pigments. Feed industry: additives for various feeds such as pigs, chickens, ducks, geese, fish, poultry and aquatic products. Application advantages of diatomite: neutral PH value, non-toxic. Diatomite mineral powder has a unique pore structure, light weight, large porosity and strong adsorption performance, and the formed color is light and soft. When it is stopped in feed and mixed with feed particles, it can be evenly dispersed, and it is not easy to separate and precipitate. After eating, it can promote digestion of livestock and poultry, adsorb bacteria in the gastrointestinal tract of livestock and poultry and excrete them, enhance physical fitness, and play a role in strengthening tendons and bones. When aquatic products are put into fish ponds, the water quality becomes clear. Polishing friction industry: brake pad polishing, mechanical steel plate, wooden furniture, glass, etc. In the vehicle; Application advantages of diatomite: strong lubricity. Leather artificial leather industry: artificial leather products and other leather. Advantages of using diatomite 5: strong sun protection, soft and light constitution, and high-quality filler for balloon products that can eliminate leather pollution: light capacity, neutral PH value, non-toxic, soft and smooth powder, good strength, sun protection and high temperature resistance. Diatomite is used in coatings, paints, sewage treatment and other industries. Main advantages Diatomite coating additive products have the characteristics of large porosity, strong adsorption, stable chemical properties, wear resistance and heat resistance, and can provide excellent surface properties for coatings, compatibilize, thicken and improve adhesion. Because of its large pore volume, it can shorten the drying time of the coating film. It can also reduce the amount of resin and reduce the cost. This product is considered to be a kind of high-efficiency matting powder product for coatings with good cost performance, and has been widely used in water-based diatom mud as a designated product by many large coating manufacturers around the world. Many new indoor and outdoor coatings and decorative materials based on diatomite are increasingly favored by consumers at home and abroad. Diatomite is a potential natural material for developing indoor and outdoor coatings in China. It does not contain harmful chemicals, and has the characteristics of incombustibility, sound insulation, waterproof, light weight and heat insulation, and also has the functions of dehumidification, deodorization and indoor air purification. It is an excellent environment-friendly indoor and outdoor decoration material. Diatom is a kind of unicellular algae that first appeared on the earth. It lives in seawater or lake water, and its body is extremely small, usually only a few microns to a dozen microns. Diatoms can carry out photosynthesis and make their own organic matter. Often grow and reproduce at an alarming rate. Its residue is deposited to form diatomite. Diatomite is mainly composed of silicic acid, with numerous pores on the surface, which can absorb and decompose the odor in the air and has the function of humidity control and deodorization. The building materials produced by diatomite not only have the characteristics of incombustibility, dehumidification, deodorization and good air permeability, but also can purify the air, sound insulation, waterproof and heat insulation. This new building material has many advantages and low cost, so it is widely used in various decoration projects. Since 1980s, a large number of decorative materials containing many chemicals have been used in the interior decoration of Japanese houses, resulting in "indoor decoration pollution syndrome" and affecting some people's health. In order to reduce the negative impact of residential decoration, on the one hand, Japan revised the Building Standards Law, strictly restricted the indoor use of building materials emitting harmful chemicals, and strictly stipulated that indoor ventilation equipment must be equipped and forced ventilation should be implemented. On the other hand, actively encourage and support enterprises to develop new interior decoration materials without harmful chemicals. The research results of humidity regulation in Kitajima University of Technology in Japan show that indoor and outdoor coatings and decorative materials produced from diatomite can not only emit chemicals harmful to human body, but also improve living environment. The first is diatomite, which can automatically adjust the indoor humidity. The main component of diatomite is silicic acid. Indoor and outdoor coatings and wall materials produced by diatomite have the characteristics of super fiber and porosity, and its ultra-fine pores are 5000 to 6000 times that of charcoal. When the indoor humidity rises, the ultra-fine pores on the diatomite wall material can automatically absorb the moisture in the air and store it. If the moisture in the indoor air decreases and the humidity decreases, the diatomite wall material can release the moisture stored in the ultra-fine pores. Secondly, diatomite wall material also has the function of eliminating odor and keeping indoor clean. The research and experimental results show that diatomite can deodorize. If titanium oxide is added into diatomite to make a composite material, it can eliminate odor, adsorb and decompose harmful chemicals for a long time, and keep indoor walls clean for a long time, even if there are smokers at home, the walls will not turn yellow. Third, the research report believes that diatomite decorative materials can also adsorb and decompose allergic substances, resulting in medical effects. The absorption and release of water by diatomite wall material can produce waterfall effect and decompose water molecules into positive and negative ions. Because water molecules are wrapped, forming positive and negative ion groups, and then floating around in the air with water molecules as carriers, it has bactericidal ability. Positive and negative ion groups floating everywhere in the air can be immediately surrounded and isolated when they encounter allergic substances and other harmful substances such as bacteria, mold and formaldehyde. Then, the most active hydroxyl ions in the positive and negative ion groups react violently with these harmful substances, and finally completely decompose into harmless substances such as water molecules. Diatomite has been used for coating extinction and odor absorption abroad for many years, and domestic enterprises have gradually realized the excellent performance of diatomite used in coatings and diatom mud.
Indoor and outdoor coatings, decoration materials and diatom mud produced by diatomite will not emit chemicals harmful to human body, but also improve the living environment.
After diatomaceous earth is added into diatomaceous earth coatings, it is widely used in diatom mud, latex paint, interior and exterior wall coatings, alkyd resin coatings, polyester paint and other coating systems, especially in the production of architectural coatings. When applied to paints and coatings, it can uniformly control the surface gloss of the coating film, increase the wear resistance and scratch resistance of the coating film, remove moisture and deodorize, and purify the air, with good sound insulation, waterproof, heat insulation and air permeability. Diatomite belongs to siliceous rocks, which can be divided into two types according to their genesis: biological or biochemical origin-diatomite, tabular diatomite, protein soil, radiolarian rock and sponge rock. Abiotic genesis (chemistry, volcanism, secondary genesis)-jasper, flint, silica and quartzite. The main associated minerals in diatomite are clay minerals and carbonaceous (organic matter). When the content of these minerals reaches more than 50%, they belong to clay rocks and carbonaceous shale, and are named diatom X X X rocks. When the content of these minerals is less than 50%, they belong to diatomite and are named after ×× diatomite. Mineral composition The main mineral composition of diatomite is opal, which contains clay (kaolinite, crystal and a small amount of hornblende), carbon (organic matter), iron (limonite, hematite and pyrite), carbonate minerals (calcite, dolomite and a small amount of siderite), quartz, muscovite, glauconite and feldspar. Environmental protection wall materials diatomite 1 and opal SiO _ 2 N H _ 2O are standard group hydrogel minerals, which are dehydrated from aqueous silica gel and are generally called aqueous colloidal minerals or colloidal minerals. Opal itself is colorless and translucent, giving off milky light. Due to the absorption of colored impurities and ions, opal presents various colors. For example, iron mixed dyeing makes opal yellowish brown and brown, while carbon mixed dyeing is grayish black. Opal usually forms dense lumps, stalactites, nodular lumps, nodular and spherical structures and secondary fillings in various sedimentary rocks. When opal is dehydrated, aged or stressed, it will produce electric cracks and breccia-like appearance, which will be transformed into colloidal minerals such as timely and chalcedony, or opal will show local heterogeneity under polarization. 2. Clay minerals, carbonaceous clay minerals and carbonaceous minerals are the main associated minerals in diatomite. Clay minerals are distributed around diatom particles on a microscopic scale, and when clay minerals are the main components, they play a role in cementing diatoms. Carbon-containing substances are granular, massive or layered, and are generated by diatoms. Carbonaceous materials are peat and lignite with low metamorphic degree, and still retain plant structure. Diatomite Diatomite is a kind of rock with biological structure, with mineral characteristics and environmental protection. It is mainly composed of 80~90%, and part of it is above 90%. The main consumer of silica in seawater and lake water is diatom, which constitutes diatom mud. Diatomite is formed by the petrochemical stage of diagenesis. Diatom shells are composed of opal. In the process of growth and reproduction, diatoms absorb colloidal silica from water and gradually transform it into opal. The more diatoms in diatomite, the less impurities, the whiter the color and the lighter the weight. The specific gravity is generally 0.4-0.9g/cm3. Because diatoms have many shell holes, diatoms have a porous structure with a porosity of 90-92%, strong water absorption and sticky tongue. Diatom is fine and smooth because of its fine particles. Diatomite is insoluble in acids (HCl, H 2 SO 4, HNO 3), but soluble in HF and KOH. Mineral Diatomite is a kind of biogenic siliceous sedimentary rock, which is mainly composed of the remains of ancient diatoms. Its chemical composition is mainly silicon dioxide, with a small amount of alumina, iron oxide, calcium oxide, magnesium oxide, potassium oxide, sodium oxide, phosphorus oxide and organic matter. Diatoms in diatomite have many different shapes, such as disc, needle, tube and feather. The bulk density is 0.3-0.5g/cm3, Mohs hardness 1- 1.5 (diatom bone particles are 4.5-5mm), porosity is 80-90%, and it can absorb water which is 0/.5-4 times its own weight/kloc-0, so it is a poor conductor of heat, electricity and sound. Market Status There are three kinds of diatomite decorative materials in Japan's building materials market: one is natural dried products containing impurities, which are cheap. The other kind is ordinary kiln-fired products. It is made of diatomite into various shapes of plates and bricks, and then fired at a high temperature of 800 degrees Celsius, which is a bit like ceramic tiles and the price is average. The third category is kiln-fired products with various additives. This kind of high-grade products with special materials adopts high-quality diatomite, and additives such as salt, soda ash or photocatalyst are added. Impure organic matter, carbon and other substances were removed in a high-temperature kiln at about 1 100 degrees Celsius, and various high-grade and gorgeous diatomite interior decoration materials were fired. Diatomite decorative materials sold in the Japanese market mainly include wall materials (plates), floor materials, sanitary ware and ceiling materials. In Tokyo building materials market, the price of ordinary diatomite wall materials is more than 2,000 yen per square meter. Some companies have also developed a diatomite waterborne coating, which can further enhance the environmental protection effect of diatomite decorative materials. At the 2nd China Green Building Materials Expo, which closed from June 5th to1October 5th, 2003, the application of environmental protection wall material diatomite was listed in Beijing. This new material formula and functional interior wall facing material that inherits the traditional construction method can effectively remove harmful substances such as free formaldehyde, benzene, ammonia and VOC in the air, as well as the odor generated by pet body odor, smoking and domestic garbage, and completely solve indoor air pollution.