Kaolinit - Thesun.vn

What is Kaolinit?:

Kaolinit is a clay mineral with the chemical formula AlSiO(OH), formed by the weathering process of feldspar.
It is a silicate mineral with a tetrahedral sheet linked through oxygen atoms with an octahedral sheet of alumina.

Origin and Naming

Kaolinit was first described as a mineral in 1867 from deposits in the Jari River valley in Brazil.
The name comes from the Chinese word 高岭 (Cao Lĩnh) in the town of Cangwu, Guangxi province, China.

Properties of Kaolinit:

Kaolinit has low elasticity and cation exchange capacity (1-15 meq/100g).
It is a soft, earthy mineral, usually white in color, formed by the chemical weathering of aluminum silicate minerals such as feldspar.
It can also have a pink-red color due to the presence of iron oxide, giving it a rust-brown color.
Small amounts of kaolinit can produce white, yellow, or light orange colors.

Kaolinit in Tropical Soils:

Kaolinit-containing clay is common in soils formed by the chemical weathering of rocks in hot and humid climates, such as in tropical rainforests.
The proportion of kaolinit decreases along a gradient of drier or cooler climates, while the proportion of other clay minerals, such as illite or smectite, increases.
These differences in clay mineral content can be used to infer past climate changes in geological history.

Structural Changes in Kaolinit:

Kaolinit undergoes a series of phase changes under the influence of heat in air at normal pressure.
The loss of hydroxyl groups begins at 550-600°C to produce metakaolin (AlSiO) without order.
The loss of hydroxyl groups continues up to 900°C and contributes to the gradual oxidation of metakaolin.

Metakaolin structure:

Metakaolin is not a simple mixture of silica and alumina, but a complex amorphous structure that maintains some long-range order due to the stacking of its hexagonal layers.
When heated to 925-950°C, metakaolin transforms into a spinel form of aluminum-silicon, sometimes referred to as gamma-alumina.

Metakaolin applications:

Metakaolin is used in ceramics, medicine, papermaking, food additives, toothpaste, and cosmetics
It is also used in paint to disperse titanium dioxide and change the degree of gloss, in rubber for semi-reinforcing properties, and in adhesives to modify rheological properties.
The largest application is in papermaking, including creating gloss on some types of paper.
Traditional uses:
Metakaolin has been traditionally used to soothe digestive disorders, similar to how primitive parrots (and later humans) in South America used it.
Until the early 1990s, it was the activating agent in the anti-diarrheal drug Kaopectate.
Recent developments:
In April 2008, the US Navy Medical Research Center announced the successful use of nano-sized aluminosilicate particles derived from kaolinite in traditional gauze such as QuikClot® Combat Gauze.
More recently, it has been used as a spray to repel or prevent harmful insects on fruits and vegetables, and at least for apples, to prevent sunburn.
Vietnam’s kaolin reserves:
Vietnam has an estimated 15 million tons of high-quality kaolin reserves, with a high AlO content in the kaolin of around 29-38%.
Kaolin is mainly concentrated in provinces such as Lao Cai, Yen Bai, Phu Tho, Quang Ninh, Tuyen Quang, Lam Dong, and Dong Nai.
Notable kaolin deposits in Vietnam:
Lam Dong’s kaolin, formed by the phong hóa process of sodium-calcium feldspar, is noteworthy due to the dominance of alkali feldspar.
Dalat’s kaolin is concentrated in Prenn, Trai Mat, and Bao Loc.
Metakaolin:
Kaolinite loses water to create metakaolin when heated to 650-900°C.
Metakaolin is a supplementary cementitious material (SCM) that affects the hydration rate of Portland cement when added to a concrete mix, replacing up to 20% of the weight of Portland cement.
Kaolinite in ceramics:
Ceramicists often represent kaolinite as oxides, writing its formula as Al2O3▪2SiO2▪2H2O with a theoretical composition of Al2O3: 39.48%; SiO2: 46.6%; H2O: 13.92%.
This formula is also useful for describing the process of firing clay, as kaolin loses two water molecules, known as “chemical water,” when fired to a high enough temperature.
Other uses of kaolin:
Eden Project, an environmental complex near St Austell, Cornwall, UK, was built in a disused white clay mine.
Sandersville, a small town in Georgia, USA, holds an annual kaolin festival and has large kaolin mines throughout the town and surrounding areas.
Kaolinite in mineralogy:
Kaolinite plays a role in Linus Pauling’s work on the nature of chemical bonding.
Kaolinite is one of several clay minerals, including dickite, halloysite, and nacrite.
Related topics:
List of minerals
Ceramics
Papermaking
Clay mining
References:
Deer W.A., Howie R.A., Zussman J. (1992) An introduction to the rock-forming minerals (2nd ed.). Harlow: Longman ISBN 0-582-30094-0.
Hurlbut, Cornelius S., Klein, Cornelis (1985) Manual of Mineralogy – after J. D. Dana, 20th ed., Wiley, pp. 428-429, ISBN 0-471-80580-7.
Breck D.W. (1984)Zeolite Molecular Sieves, Robert E. Brieger Publishing Company: Malabar, FL, pp. 314-315, ISBN 0-89874-648-5.
Bellotto M., Gualtieri A., Artioli G., Clark S.M. (1995) Kinetic study of the kaolinite-mullite reaction sequence. Part I: kaolinite dehydroxylation’, Phys. Chem. Minerals, Vol 22, 207-214.
The Mineral KAOLINITE
Kaolinit is a rock-forming mineral:
It is a clay mineral with the chemical composition Al2Si2O5(OH)4.
It is a common mineral in soils and sediments and is used in various industries.
Uses of Kaolinit:
It is used in the paper industry as a coating and filler.
It is used in the ceramics industry to make porcelain and other products.
Other Interesting Facts:
Kaolinit is also used in the production of toothpaste and cosmetics.
It has been studied for its potential use in wound healing and drug delivery systems.

Kaolinit and Máng cáp

As a filtration aid: Kaolinit is often used in filtration processes due to its ability to remove particles and impurities. It could potentially be used as a filter aid in Máng cáp processing to help clarify the solution.
To modify rheological properties: Kaolinit can help modify the rheological properties of a solution or suspension, making it more stable or easier to handle. This could be particularly useful if the Máng cáp is being processed in a suspension or emulsion.
As a binder: Kaolinit is often used as a binder in ceramics due to its ability to improve the strength and plasticity of the clay. It could be used in a similar way in Máng cáp processing to improve the texture and binding of the final product.
To improve gloss: Kaolinit can be used in paint to improve the degree of gloss. If Máng cáp is being processed into a final product with a glossy finish, Kaolinit could potentially be used to improve the shine and glossiness of the product.

It’s important to note that these are just potential applications and would need to be tested to determine their effectiveness in Máng cáp processing. Additionally, the specific processing method being used may impact how Kaolinit could be incorporated. It may be best to consult with an expert in Máng cáp processing to determine the best use of Kaolinit in your specific application.