Kaolin, a hydrated aluminum silicate, which also known as China clay, Argilla, Glomax & Porcelain clay, is a white powder and commonly obtained by extraction from mineral deposits. It is found naturally in mineral sources and the main component of it is Kaolinite. This substance has a different size from 0.1 to 10 micrometers or more & widely used in production of Porcelain and Paper. The best sources of this material are found in France, Britain, Czech and United states.
Physical and chemical properties
|Molecular weight||258.16 gr/mol|
|Color||White to yellowish or grayish|
|Solubility||Insoluble in water, ether & dilute acids|
The production of this material can be either laboratory or extracted from natural mines. Today, natural mineral extraction is known as the most economical and best way to produce this material and is widely used in many countries around the world. There are two ways to kaolin purification, dry process or wet process.
Dry process major steps are crushing the deposit, drying and trituration. Usually, at the end of the dry process, the powders are separated by size.
In this process, the raw mined is converted into egg-sized particles by roll crushers. The materials are then transferred to rotary dryers and aerial floaters. The next steps usually involve pouring and separating by air. Finally, suitable powders are collected and coarse grains are again used as input feed.
In the wet process, a slurry is first formed of kaolin and then the separation processes are applied, and the dewatering and drying process is also carried out.
In this method, the mined is first dispersed in water. The next step is the separation of coarse particles on the shaking plates, at which point particles with a size greater than 44 microns are removed. The remaining slurry is sent to the centrifuge separator, which separates the particles into appropriate, medium and coarse sizes.
Particles may be used to whiten the chemical because of the presence of non-white colored iron. The particles then become free of water during a filtration process, drying can be done by rotate or spray driers. After this stage, China clay is ready for transportation. This process is performed to produce high purity kaolin by controlled properties.
Uses and benefits
In ceramic industries this substance used widely. Some special properties such as: high fusion temperature, color, hardness and burning properties makes this mineral a good choose to production of ceramics. In manufacturing of whiteware, it is mixed with some other materials like feldspar, silica and ball clay, these materials improve plastic properties of whiteware.
Although Porcelain clay is the main ingredient in ceramic and china manufacture, but contrary to the general perception of people, this material also has other applications in the rubber, paper and paint industries.
In paper production it is used as a filler and a coating agent. About 40% of produced China clay is used in filling and coating paper. Color, printability and giving glass are the properties of paper that improve by appearance of this substance.
In color, China clay enjoys a high coating capability due to neutrality and insolubility in the paint, and improves the flow properties of paint at low cost.
Adding this material to thermosetting and thermoplastic mixtures increases surface fineness, good secondary stability and increases resistance to chemicals.
In addition to the industrial applications mentioned for this article, it is also used in medicine.
Porcelain clay seems to be beneficial in the treatment of oral ulcers due to some radiation.
Using kaolin impregnated pads and inserting them on the cuts causes the hemorrhage to be wider than usual. In post-surgical recovery, the use of a pad impregnated with this substance also suggests faster wound healing.
In some cases, it is also used to treat diarrhea and colon inflammation, but there is still insufficient evidence to prove its usefulness in this area.
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.
COA of kaolin
Murray, H. H. (1963). Industrial applications of kao.lin. Clays and Clay Minerals, 10, 291-298.
Britannica, T. E. (2015, October 19). Kaolin. Retrieved February 17, 2019, from https://www.britannica.com
Kaolin. (n.d.). Retrieved February 17, 2019, from https://pubchem.ncbi.nlm.nih.gov