Folklore
The image originates from the internet
Legend has it that more than 1,000 years ago, in a small mountain village about 40 kilometers from Jingdezhen, there lived a poor man who made a living by helping the kiln owner burn porcelain. One winter morning, he saw an old man lying in the snow pile in front of the door, dying. The poor man carried the old man into the house to warm up, and fed him rice soup. When the old man was parting, he took out a handful of soil from his arms and said, "Later life, you are a good person, quickly dig out the soil and burn porcelain!" ”
Later, this poor man dug up the soil behind the house in front of his house, and after 7749 days, he finally took out the "jade soil", and the porcelain fired from this soil was white and delicate, different. Since the mountain village where this poor man lived was called Gaoling Village, the soil on this mountain was called "Kaolin".
PART 1
Kaolin composition and structure
Kaolin is a non-metallic mineral, kaolin minerals are composed of kaolinite, ground stone, pearlstone, eloite and other kaolinite cluster minerals, the main mineral component is kaolinite, named after Gaoling Village in Jingdezhen, Jiangxi.
Kaolinite belongs to the 1:1 type layered silicate, triclinic crystal system, the crystal monomer is pseudohexagonal plate, and some of it is book-like. Most of the crystalline aggregates of kaolinite are worm-like and accordion-like, with particle sizes ranging from 0.5 to 2 nm, and a few helminth-like aggregates may reach the millimeter size.
PART 2
Characteristics of kaolin properties
Kaolin color is mostly white, the highest whiteness can reach more than 95%, the color of kaolin varies slightly with the difference in metal content or organic matter content, with Fe2O3 is rose red, brownish yellow; contains Fe2+ is light blue, light green; contains MnO2 is light brown; when containing organic matter, it is pale yellow, cyan, gray, black, etc. Kaolin is mostly cryptocrystalline dense or soil-like aggregates. Hardness 2.0 ~ 3.5, specific gravity 2.60 ~ 2.63, melting point 1780 °C, good insulation.
The wide range of uses of kaolin is inseparable from its excellent physicochemical properties. Pure kaolin has high whiteness, soft and easy dispersion suspended in water, good plasticity and high adhesion, excellent electrical insulation properties and good acid resistance, low cation exchange capacity, high fire resistance and other physical and chemical properties.
PART 3
Distribution of kaolin resources in China
China's kaolin mineral resources rank among the top in the world, with 267 proven mineral sites and proven reserves of 2.910 billion tons.
▲Schematic diagram of kaolin (porcelain clay) mineral distribution
China's six major kaolin mineral areas:
(1) Jiepai Town, Hengyang County, Hunan Province, is rich in mineral resources. Kaolin, nanofeldspar, potassium feldspar and quartz stone reserves reach 200 million tons, and there are nearly 40 mining and mineral processing enterprises. The Single Mineral Reserves of the Dapailing Mining Area (dominated by kaolin mines) are the highest in Asia at 80 million tonnes. The annual mining volume of the town is more than 500,000 tons, supplying hundreds of ceramic factories across the country.
(2) Kaolin in Maoming, Guangdong, kaolin ore in Maoming Basin belongs to sedimentary rock weathering residue subtype deposits, and its sand content such as quartz is greater than 50%, so it is called sandy kaolin ore. Maoming kaolin is said to have been weathered by residues from the genesis - carried and ground; ——Re-weathering in three stages, kaolin is completely weathered, the wafer is mainly monolithic, and the particle size is fine. Mainly for paper coating raw materials.
(3) Fujian Longyan kaolin, which belongs to the weathered residual type kaolin deposit. Due to the iron content of less than 0.3%, titanium is less than 0.02%, and contains a certain amount of low-temperature solvent elements (Li2O), it is an ideal raw material for electric porcelain, high-grade daily use, and fine art porcelain.
(4) Suzhou Yangshan kaolin, which is hydrothermal altered kaolin. Suzhou Yangshan mud with pure texture, its chemical composition is very close to the theoretical composition of kaolinite, Al2O3 content can be as high as 39.0%, white color, fine particles. Mainly used for catalyst carriers and chemical raw materials.
(5) Guangxi Hepu kaolin: it is a weathered residual kaolin deposit. Mainly used as raw materials for architectural ceramics.
(6) Northern coal kaolin: it is a sedimentary kaolinite, mainly distributed in China's domestic coal area, which can be used for construction, coatings, paints and paper coatings - coal soil.
The above six major production areas account for more than 80% of China's output, and they are also mainly representative in terms of resource types.
PART 4
Application areas of kaolin
1 Paper industry
Kaolinite clay has a small particle size, has good scale and flake form after peeling, has a large proportion of diameter and thickness, and has stable chemical properties, so it is widely used in the papermaking industry, and can be used as a papermaking filler and paper coating to improve the glossiness of paper, fill the gap between paper fibers, improve opacity, etc.
▲Kaolin is an indispensable raw material for the paper industry
2 Ceramics industry
The ceramic industry is the main application area of kaolin, capable of reaching 20-30%. In the process of firing ceramics, kaolin decomposes mullite to form an embryonic framework, which makes the ceramic body less susceptible to deformation, broadens the firing temperature range, and improves the whiteness of the ceramic.
▲ Kaolin is widely used in the ceramic industry and has a large number of applications
3 Refractory materials
Kaolin has good fire resistance and is commonly used to produce refractory materials, and its products can withstand loads at high temperatures without deformation. The main refractory material products are refractory bricks, silicon aluminum cotton two categories. Some colored kaolin, which cannot be used in ceramics and papermaking, is a good raw material for refractory materials.
▲Kaolin can be used to prepare silicon aluminum cotton refractory products
4 Coatings industry
Kaolin has long been used as a filler for coatings and paints due to its white color, low price, good fluidity, stable chemical properties and large amount of cation exchange on the surface, which can be used to improve the brushability of paints, the storage stability of paint systems, and the moisture absorption resistance of coatings.
▲Kaolin can adapt to various types of coating systems
5 Rubber industry
Kaolin is filled into a colloidal mixture of rubber. It can enhance the chemical stability, wear resistance and mechanical strength of rubber, prolong the hardening time, and also improve the rheology, mixing and vulcanization of rubber, improve the viscosity of unsulcanized products, and prevent its depression, collapse, sagging, deformation, flat pipe, etc.
▲Kaolin affects the comprehensive performance of rubber products
6 Cable industry
The production of highly insulating cables undoubtedly requires the addition of electrical performance modifiers in excess. Kaolin, on the other hand, is a product that can be made into an excellent electrical property modifier. Kaolin calcination after the appropriate temperature has a very high resistivity, different calcination temperature of kaolin porosity is not the same, the void on some of the more active harmful components in the cable material has a certain adsorption effect, can improve the cable insulation.
▲ Kaolin can be used for insulated cables
7 Cosmetics and medicine
The main ingredient of kaolin is aqueous aluminum silicate, which has good adhesion to the skin, inhibits sebum and sweat absorption, and can be used with talc in cosmetics. In the field of medicine, kaolin has good biocompatibility, and after intercalation expands the layer spacing, it can provide new active sites for drug molecules, promote drug entry into the interlayer, and realize drug loading and release.
Kaolin is widely used in cosmetics
Layered silicate (synthetic hydrotallite, series montmorillonite, kaolinite) clay minerals do not release heat during in vitro hemostasis, and have a wide range of coagulation characteristics, both low price, stable and non-toxic characteristics, and can also be used as a new coagulant instead of traditional commercial zeolite-based hemostatic agent.
8 Applications in water treatment and environmental protection engineering
The natural two-dimensional layered structure makes kaolin have a large specific surface area and good adsorption performance, and after modification as a high-quality adsorbent, it has far-reaching significance for the solution of environmental pollution problems such as organic pollutants, heavy metals and suspended solids in water bodies.
▲Modified kaolin can be used for sewage treatment
Source:
Powder circle public number, China powder network public number
MENG Yuhang,SHANG Xi,ZHANG Qian,YANG Huaming. Functional modification of kaolin and its strategic application[J].Mineral Conservation and Utilization,2019(06):69-76.