Kaolin or china clay is a mineral material of the hydrated aluminum silicates group. Kaolin is naturally white or yellowish-gray in powder form. Al2Si2O5(OH)4 is its chemical formula. China clay is well compatible with water and dissolves easily in it. kaolinite has very well stickiness and for this mineral; more stickiness means more purity.
Kaolinite has various industrial applications; it is chemically inert. This white powder can be helpful in the ceramic industry and it increases the strength of the product in terms of heat resistance and helps to improve its ductility.
China clay can also be used as a paper coating, a thin layer of it which is used as a final coating for the paper to give it a smooth, light white color, or as a filler for plastics or used as an alternative to titanium as a pigment in the polymer industry.
The chemical structure of kaolin is as follows:
This mineral is hardly found in some European countries such as Germany, England, and France or Asian countries such as China.
Physical and chemical properties of kaolinite:
The color of kaolinite changes in the presence of air and turns brown. Due to high heat, it decomposes into aluminum oxide and silicon dioxide, which are used in the production of refractory bricks. High melting point, low water capacity, and stability against high temperature are the features of this material. Kaolin is an important material among refractory clay.
The most important physical and chemical properties of this mineral can be summarized in the following table:
|Molecular weight (g/mol)||258.16|
|Density (g/mL at 25°C)||2.6|
|Melting point (°C)||1750|
|Boiling point (°C)||740-1785|
|Solubility||Completely soluble in water|
The production of this mineral starts in the first stage by extracting the stone from the mine. After extracting the stone from the mine, the crushing operation is started by the crushers, then the crushed stones are homogenized and crushed by large mills. After concentrating and purifying, kaolinite is obtained.
Processing of this material can be done in different ways and each method obtains a specific type and grade of this material; the number of impurities is also different.
The best kaolins also have impurities and should be reduced to less than 5.1% by concentrating. In the presence of iron compounds and andesitic and basaltic volcanic rocks and metamorphic feldspars reduces the quality of kaolin.
APPLICATIONS AND USUES OF KAOLIN:
As mentioned, the uses of kaolin are very diverse, we will describe the most important uses of this material:
- This white powder can be very helpful for the digestive system, because it does not decompose and is not absorbed by the body, it is very helpful in cases such as wound healing or swelling treatment. Workers or people who have been dealing with this substance for a long-time face lung problem because the powder of kaolin penetrates the air and affects the lungs.
- In the agricultural industry, it can help repel pests. Kaolin creates a white layer coating and its reflection misleads the insects and prevents them from laying eggs. This substance causes the insects to annoy and move away by creating a special adhesion. Reduces the damage caused by overheating of pistachio orchards, has a positive effect in many agricultural areas of the country, especially in areas with scorching sun, to prevent spoilage of fruits and agricultural products. Over time, because this mineral is non-toxic, it has been widely welcomed by organic farmers.
- In the paint industry, it is a good alternative to titanium oxide, calcined kaolin is the most important material in the paint industry.
- It is also used in adhesives, cosmetics, and pharmaceuticals, such as toothpaste, and as a catalyst in water treatment and the oil industry.
Safety items such as wearing safety goggles, masks, and special clothing should be carefully considered when working with this substance, do not work with this substance for as long as possible because the dust suspended in the air can cause lung diseases. Eating this substance will not pose a risk to most people, but it can cause constipation in children and the elderly. Inhalation of this substance can cause lung inflammation.
TRANSPORTING AND STORAGE:
Use proper packaging to store this material and its storage warehouse should be away from moisture. Keep packages of this material away from heat and direct sunlight and in a cool place.