Iron Oxide Pigment

>>>Introduction Of Iron Oxide Pigments For Concrete

As the man-made pigments from natural elements, iron oxide pigment has much stronger tinting strength and hiding power. Meanwhile, it also has excellent light resistance and weather resistance, which makes it the only colorant that can withstand the extreme alkaline environment of concrete without fading or leaching. So they are an excellent choice for concrete and stucco.
Iron oxide particles used in the construction industry are 10 times finer than cement particles. When added to the concrete mixture, the iron oxide pigment particles actually surround and cover the cement particles, thereby achieving the purpose of coloring. However, not all iron oxides have the same coloring power. Different production processes will not only affect the color strength, but also dilute or reduce the tinting intensity of pigments when adding inert filler in mixed color. In order to ensure to purchase the iron oxide power with strong coloring power, customers need to know about the production processes of various manufacturers.

>>>Introduction Of Iron Oxide Powder For Paintings

With the characteristics of non-toxic, non-bleeding, low cost and the ability to form a variety of different shades, iron oxide pigments are widely used in coatings, paints and inks. Iron oxide pigments can be used for coloring of various coatings, including water-based paints, powder coatings, to protect materials and colors. It can also be used in paints including epoxy resin, alkyd, amino and various primers and paints, as well as toy paint, decorative paint, furniture paint, electrophoretic paint and enamel. In addition, read iron oxide primer has the function of anti-rust, which can replace expensive red lead paint, saving non-ferrous metals.

High chemical stability and physical endurance.

• Alkali resistance. It is very stable to any concentration of alkalis and other types of alkaline materials, especially cement and lime mortar commonly used in construction, and won’t powder or affect the strength of cement building components.
• Acid resistance. It has certain resistance to general weak acids and dilute acids, but it can also dissolve in strong acids, especially when heated and concentrated.
• Light fastness. Color invariable under intense sunlight exposure.
• Heat resistance. It is stable within a certain temperature limit, and the color will start to change beyond its temperature limit. As the temperature increases, the degree of change will become more and more significant. The temperature limit of each variety is as follows:
  Iron oxide yellow gradually changes color to red phase over 130℃.
  Iron oxide red becomes dark red gradually over 300℃.
  Iron oxide purple over 400℃ gradually change color to deep red.
  Iron oxide black over 100℃ gradually change color to dark red.
  Iron oxide brown gradually changes color to red phase over 130℃.
  Iron green gradually changes color to dark red over 200℃.
• Weather resistance. It isn’t affected by climatic conditions, such as, cold, hot, dry and wet atmosphere.
• Dirty air resistance. It is very stable in any dirty gas, such as, hydrogen sulfide, carbon oxide, sulfur oxide, hydrogen chloride, nitrogen oxide and other gases.
• Water, oil, solvent resistance permeability. Insoluble in water, various mineral oils, vegetable oils and ethers, esters, ketones and other organic solvents, and no penetration.

Bright and clear color and unique hue. The color of iron oxide pigments is very clear and pure, and it doesn’t need to be embellished with other organic or inorganic pigments.

Excellent economic effect. The iron oxide pigment has a high coloring power, fine and uniform particle size, which ensures its use value, coupled with a lower selling price, which can ensure the economic effect of the users.

The production methods of iron oxide are mainly divided into dry method and wet method. The dry method mainly includes the calcination method of green alum, the calcination method of iron yellow, the calcination method of iron black, as well as natural iron oxide mineral ultrafine crushing method using hematite as raw material. The wet process mainly includes sulfate method, nitrate method and mixed acid method. According to the different neutralizer used in the two-step oxidation process, it can also be divided into iron sheet method and ammonia method.
The advantages of dry process is that the production process is simple, the technological process is short, the equipment investment is relatively small.
The disadvantages is that the quality is a little poor, the harmful gases are produced in the calcination process, which has a significant impact on the environment. For example, a large amount of sulfur-containing gas is produced during the calcination process of iron alum. In recent years, based on the comprehensive utilization of iron-containing wastes, dry processes such as sulfuric acid cinder method, iron ore powder acidification roasting method have appeared. These methods are simple in technology and low in investment, but the quality of products is low, so they can only be used in low-end fields.

>>>Wet Process

The wet process uses ferrous sulfate or ferrous nitrate, ferric sulfate and ferric nitrate as raw materials. It adopts the production method of ferric oxide res, which first prepares seed crystal and then oxidizes to prepare red iron oxide. Th raw materials can be either ferrous sulfate or ferrous nitrate solid raw material, also can be aqueous solution containing ferrous sulfate, ferrous nitrate, iron sulfate, iron nitrate. The neutralizer used can be either iron sheet, iron filings or alkali, ammonia.
In recent years, based on the comprehensive utilization of waste industrial waste, a method of preparing iron oxide red industrial pigments by using titanium dioxide by-product ferrous sulfate or ferric sulfate solution and using steel plant pickling waste acid or waste water as raw materials has been produced, but they all belong to the category of wet process technology. The neutralizing solution used is still iron scale, iron filings, alkali or ammonia.
The advantages of wet process is that the produced products has excellent quality and performance, and the different series of iron oxide products can be prepared. The disadvantages is that the process flow is long, the consumption in the production process is high, a large amount of acid waste water is generated, and currently there is a lack of effective comprehensive utilization of acid waste water.

>>>Sulfuric Acid Process

Taking ferrous sulfate or iron sulfate heptahydrate, or waste acid containing ferrous sulfate or iron sulfate, and aqueous solution as raw materials, firstly purity the iron salt or iron salt solution to remove impurities, then the crystal seed can be prepared with sodium hydroxide or ammonia as the neutralizing agent under strict control the process conditions. The prepared crystallization nucleus is transferred to a two-step oxidation synthesis reactor, the process conditions are strictly controlled under heating conditions. Sodium hydroxide or ammonia is added to adjusted the PH value of the system, and then the air is passed through for oxidation to obtain seed crystals. Transfer the prepared qualified seed crystals to the oxidation synthesis reactor, adjust the PH value and temperature conditions, add iron or iron filings to neutralize the acid generated in the oxidation process. The oxidation reaction is carried out through the air and the iron salt solution is continuously added during the oxidation process. When the color of the reaction system reaches the target color standard, the reaction can be stopped and the iron oxide products is separated by filtration. The mother liquor produced by the separation is acidic wastewater containing sodium sulfate. The obvious disadvantage of this process is that a large amount of acid wastewater is produced, and there is no reliable control and recycling method.

>>>Nitric Acid Process

The basic principle is the same as the sulfuric acid process, the difference is that the iron salt used is nitrate. The advantage is that the quality of product obtained is better than the sulfuric acid method. The disadvantage is that the production cost is high, harmful gases and a large amount of acid wastewater is produced in the production process. Acid wastewater contains a large amount of nitrate, and there is currently no reliable comprehensive utilization way.

>>>Mixed acid process

Prepare ferrous sulfate solution and ferrous nitrate solution first, then use ferrous nitrate solution as raw material, and alkali or ammonia as neutralizer to prepare seed crystal. Then transfer the seed crystal to the oxidative synthesis reactor, adjust the temperature and PH value, put the iron sheet or iron filings as the neutralizer, ventilate and oxidize. In the oxidation process, add ferrous sulfate and ferrous nitrate solutions to carry out the oxidation reaction. When the color of the reaction system reaches the target color standard, the reaction can be stopped and the iron oxide product is separated by filtration. The mother liquor produced by the separation is acidic wastewater containing sulfate and nitrate. The quality of products produced is good, which can meet the quality standards of nitric acid products, but a large amount of acid wastewater is generated, and there is no reliable control and recycling method.

>>>Ammonia process

The main component contained in the acidic process wastewater generated by the smmonia process is ammonium sulfate. And it is ammonium chloride when ferric chloride or ferrous chloride is used as the raw material. Since ammonium sulfate or ammonium chloride products can be recovered after wastewater treatment, there is no wastewater discharge. It is considered as a harmless and environmentally friendly production process. However, due to the lack of research on the process and imperfect conditions for the preparation of seed crystals, which has an impact on product quality, resulting in unstable product quality, the process is limited.
The raw material can be used for the production of iron oxide by the ammonia method are ferrous sulfate heptahydrate, ferric nitrate, ferrous chloride, ferric sulfate and ferric chloride crystals. They can also be waste acid, waste water containing the above iron salts or iron industrial solid waste, etc…

>>>Disposal Measures of Waste Residue in Production

The process of producing iron oxide from sulfuric acid waste residues. In the waste residue produced, except for a small amount of impurities insoluble in sulfuric acid, it is mainly composed of unacidified ilmenite, which is discharge after treatment. For the sludge treatment method, the plate and frame filter is generally used. With this treatment method, the recovery rate of the titanium liquid in the sedimentation process can reach 98.8%-99.0%.
The acid digested sludge from the sedimentation process enters the mud storage tank. The iron oxide sludge is diluted and stirred, and then sent to the plate and fame filter by the mud pump. The liquid goes to the small-degree water storage tank, and the filter cake is dried by compressed air for about 20 minutes, then guided by a guide plate to a belt conveyor, and then manually transported to the slag yard. The dilute waste acid in the mud storage tank is used to adjust the concentration of mud residue, and the water is used to clean the mud storage tank.