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Iron Oxide Red, red or dark red powder, has the chemical formula α-Fe2O3, particle size 0.5~2μm, density 5.24g/cm3, melting point 1565°C, and decomposes at the same time. Non-toxic. Insoluble in water. It has high hiding power and tinting power, second only to carbon black. Its light resistance, heat resistance, alkali resistance, dilute acid and corrosive gas resistance are all very good. It dissolves when heated in concentrated acid. Iron oxide red is a traditional and important inorganic pigment. Common models include 101 (red iron oxide with brighter color and finer particle size) and 120 (iron oxide with orange-red color and generally coarser particle size). , 130 (darker orange-red iron oxide), 140 (lighter orange-red iron oxide), 180, 190, etc. Due to different preparation methods, the size and shape of the particles produced are also different. The color of iron red varies from red and yellow to red and purple, and different hues can be selected according to different requirements. Iron oxide red has excellent light resistance, high temperature resistance, alkali resistance and atmospheric impact resistance. The raw materials are simple and easy to obtain, and it can make full use of waste and by-product resources from other industries. It is also low in toxicity and has a wide range of uses. It is widely used in various applications. Fields, including coatings, building materials, plastics, rubber, inks, ceramics and other industries. In the rubber industry and construction industry, it is used as a coloring agent for artificial marble, floor terrazzo, and wall decoration; in the electronics and telecommunications industry, it is an important raw material for manufacturing ferrite components; in the chemical industry, it is a catalyst and the production of other iron-containing materials. Raw materials for chemical products. In addition, it is used as a colorant and filler in plastics, asbestos, varnished cloth, artificial leather, leather finishing agents, etc. It can also be used in the polishing of hardware equipment and as a polishing material for eyeglasses, optical instruments and jade. The common production processes of iron oxide red pigment can generally be divided into two types: dry method and wet method. Dry processes typically involve oxidizing or calcining raw materials at high temperatures to form iron oxide red pigments. The wet process performs a chemical reaction in a solution to generate iron oxide red pigment, and then obtains the final product through filtration, drying and other steps. 1. Dry process 1) Green vitriol calcining method: The raw materials of this process mainly come from steel pickling liquid and green vitriol (FeSO4·7H2O), a by-product of titanium dioxide produced by sulfuric acid process. The process flow is as follows: convert the purified FeSO4·7H2O into green vitriol monohydrate at 250-300°C, grind and pulverize it, and then calcine it at 700-800°C to obtain iron red. After washing to remove water-soluble salts and other pigments, the finished product is then dried and crushed. By controlling the calcination temperature and time and the amount of air introduced, many shades of iron red from light red to deep red can be produced, and the particles are spherical. The product can be made into easily dispersed iron red, high-purity iron red and electronic grade iron red. The by-products SO2 and SO3 can be used to produce sulfuric acid. 2) Iron yellow calcination method: Use dry iron yellow powder to be calcined in a calcining furnace at a temperature of 500-600°C and a time of 40-60 minutes to produce brown iron oxide red. After cooling and sieving, the finished product is obtained. The particles of iron red products have a needle-like structure. The color of the product is affected by the calcination temperature, the particle size of the iron yellow and the calcination time. 3) Iron black calcination method: Calculate the washed iron black at high temperature (600-700 ℃) to oxidize the FeO in the iron black into Fe2O3. Since the iron black used is relatively pure, the product does not need to be washed with water and is directly crushed into products. The product particles are spherical, and the chromatogram is also very wide and is mainly affected by the calcination temperature, calcination time and iron black particle size. 4) Ferrous sulfate-soda ash calcination method: Mix soda ash (Na2CO3) and green vitriol (FeSO4·7H2O) at a molar ratio of 1:1.25, grind them into fine pieces and put them into the roasting furnace. At a temperature of 700°C (Na2CO3 will decompose if it is too high). Lower roasting. The burnt material is leached with water at room temperature to dissolve Na2SO4. Then filter, wash with dilute sulfuric acid to remove residual Na2CO3, wash with water and dry at 150-200°C to obtain the finished product. The filtrate is concentrated by evaporation and then crystallized to obtain the by-product Glauber's salt decahydrate. The main disadvantage of the dry method is higher energy consumption. 2. Wet process Sulfate method; nitrate method; mixed salt method. Their process is: first make seed crystals, then put the seeds into a reaction tank filled with Fe2+ solution, add iron filings to it, keep the temperature at 75-85°C, introduce oxygen, oxidize Fe2+ into Fe3+, Then it combines with OH- in water and deposits on the surface of the seed crystal, gradually forming iron oxide red. During the oxidation reaction, hydrogen ions are also generated, and the hydrogen ions interact with the metal to generate Fe2+ and be oxidized to Fe3+. This cycle is repeated until the oxidation reaction is completed. Then, filter the precipitate and dry it at 300 to 400°C to obtain the product. In this method, the oxidation reaction generally takes more than 50h. This method can produce various shades of iron red, and the particles of the product are soft and easy to disperse. Among the three methods, the nitrate method has better product performance, but the cost is higher and nitric acid is highly corrosive. The sulfate method has low cost and less corrosion than nitric acid, but the product performance is slightly worse. The mixed salt method is a compromise. The cost of this method is close to that of the sulfate method, and its performance is close to that of the nitrate method. The main disadvantage of the wet method is the long production cycle.
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