Grinding kaolin

Thermal analysis, and to a lesser extent infrared spectroscopy, has shown that grinding kaolin reduces the number of structural hydroxyls and increases the amount of sorbed water. However, the infrared studies have been restricted to... 

Sodium sihcate (41°Bh, 1 3.22 ratio Na20 Si02) is added in the milling operation to disperse the slime, mosdy kaolin. Dispersion also aids the grinding process. The rod mill serves to grind the ore to 0.833 mm (—20 mesh) or to the point where mica, quart2, feldspar, and iron minerals are Hberated. Cyclones, or rake, hydrauhc, or other types of classifiers, are used after grinding to produce coarse and fine mica fractions that are treated separately. 

Kaolin (HciO washed and partially dried) 10 0.5 Imp-mill type grind to 99.9%—325 mesh... 

Ceramic powder processing technology is discussed in the Tao Shuo [9]. This text describes how kaolin raw materials had to be foimd and ground to the desirable size distribution. After grinding, the earth was washed and purified. This was done by mixing it with water in a large... 

Takahachi H. Wet grinding on kaolin minerals. Bull. Chem. Soc. Japan 1959 32 235-54. 

However, different studies have revealed that the amorphization of kaolin produces solids more reactive under chemical treatments. This amorphization can be performed by calcination, obtaining metakaolin by heating from 550 C to 900 C. The metakaolin is an amorphous phase formed by the dehydroxylation of the octahedral layers and the deformation of the tetrahedral sheets [5-7]. Also the grinding produces the amorphization of kaolin [8], by means of delaminating [9,10]. 

Carthew (91), who also studied the decomposition of kaolinite. in the particle-size range of >2 to 0.25-0.1 ju. agreed with the work of Norton (89) and Grimshaw et al. (90). For particle sizes from 2-1 u to 0.25-0.1 ju. the peak areas were essentially constant, as were the A7 in values. The disagreement with Spiel et al. (2) was attributed to the fact that they obtained their particle-size fractions by a grinding process, which could reduce die degree of crystallinity of the kaolin. 

Mica ores contain from 15% to 80% mica and other minerals such as silica, feldspar, and kaolin. Mica producers use a variety of purification processes to purify mica before grinding into finished products. 

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