A method for preparing kaolin using oxygen plasma treatment

Abstract

The application provides a method for preparing kaolin by adopting oxygen plasma treatment, and the method comprises the following steps: (1) a coal-based kaolin raw material is subjected to crushing treatment, grinding and stripping treatment, drying treatment and screening treatment in sequence to obtain coal-based kaolin particles; (2) the coal-based kaolin particles are subjected to oxygen plasma treatment under the condition that the vacuum degree is 6*10 ‑1 ~9*10 ‑ 1 mBar and the power is 45-75 W to obtain kaolin. The method is simple in operation, the coal-based kaolin raw material is cheap and easy to obtain, the temperature of the oxygen plasma treatment is low, and the coal-based kaolin raw material is decarburized while the layered structure of the contained kaolin mineral is not damaged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste resource utilization, and particularly relates to a method for preparing kaolin by using oxygen plasma treatment. BACKGROUND

[0002] Kaolin is a kind of rock, and is a kind of clay and clay rock mainly composed of kaolinite clay mineral. The chemical formula of kaolin is Al2O3·2SiO2·2H2O. Pure kaolin is white or light gray, and when impurities are contained, kaolin is gray, yellow, brown and the like. Kaolin has good plasticity, cohesiveness, insulation, acid resistance, fire resistance and other excellent physical and chemical properties, and is widely used as a raw material in various fields, such as ceramic industry, papermaking industry, refractory material, cement industry, rubber industry, petroleum chemical industry, medicine and textile, and national defense industry.

[0003] At present, common raw materials for preparing kaolin include natural kaolin ore and coal-based kaolin. The methods mainly include gravity separation, magnetic separation, flotation, chemical bleaching and roasting purification. Gravity separation is to remove light organic matter and high-density impurities containing iron, titanium and manganese and the like by using the difference in density and particle size between kaolin and gangue minerals. Magnetic separation is to separate materials by using the attractive force and repulsive force of magnetic substances, and is used to remove weakly magnetic impurities such as hematite, siderite, pyrite and rutile in kaolin. Flotation is to separate minerals by using the difference in physical and chemical properties of the surface of the minerals, and can effectively remove iron, titanium and carbon impurities in kaolin. Chemical bleaching is to remove trivalent iron ions and oxides thereof by using chemical reagents to prepare kaolin. Roasting is to heat the mineral raw material to a temperature lower than the melting point of the mineral raw material in a certain atmosphere, so that the target component and the furnace gas are chemically reacted to be converted into the desired component and form, and the carbon impurities in kaolin can be removed. At present, the methods for preparing kaolin by using coal-based kaolin as raw material mainly include gravity separation, magnetic separation, flotation and roasting. The gravity separation and magnetic separation cannot remove the carbon impurities in kaolin, the flotation and chemical bleaching need to add chemical reagents, which causes the increase of production cost, and the roasting will destroy the layered structure of the kaolinite mineral contained in kaolin.

[0004] CN111533440A discloses a production method of calcined kaolin for glass fiber, comprising the following steps: 1) crushing and finely breaking kaolin raw material, and grinding into fine powder of 200 mesh or more, 2) the fine powder after grinding enters a continuous preheating system of cyclone for preheating, the preheating temperature is 300-800℃, 3) the powder from the upper part of the cyclone is collected and mixed with the powder after grinding, and then enters the cyclone for preheating, the cyclone discharge from the lower part of the cyclone enters the calcining equipment for calcining, the calcining temperature is 500-900℃, the calcining residence time is 10 minutes or more, and the hot powder after calcining is cooled to obtain the kaolin for glass fiber. The production method of calcined kaolin for glass fiber does not need to add additional agents, reduces the raw material input cost, the prepared kaolin for glass fiber has a COD of 300ppm or less, and a little mullite phase, the composition is uniform, the product composition content fluctuation is small, which is beneficial to the melting and drawing of glass fiber, and the production process is easy to realize continuous and large-scale production.

[0005] CN102730709A discloses a method for preparing calcined kaolin from coal gangue. The method can prepare high-quality calcined kaolin by crushing, balling, crushing, washing, drying, adding sulfuric acid solution, NaOH solution and drying treatment of the coal gangue.

[0006] CN104150497A discloses a method for preparing ultra-high whiteness calcined kaolin from coal gangue. The method calcines the raw material composed of coal gangue at a temperature of 945-955℃ for 6 hours or more. The calcined kaolin prepared by the method has a whiteness of 95 or more, and the abrasion value and 325 mesh screen residue are lower than those of the calcined kaolin prepared by other methods, which has high application value.

[0007] However, the above-mentioned methods for preparing kaolin all use calcination, which can destroy the layered structure of the contained kaolinite mineral and limit the application of kaolin. SUMMARY

[0008] In view of the problems in the prior art, the present application provides a method for preparing kaolin by oxygen plasma treatment, which uses cheap and readily available coal-based kaolin raw material to effectively decarbonize by oxygen plasma treatment, can improve the whiteness of kaolin, and will not destroy the layered structure of the contained kaolinite mineral; the method is simple to operate, low in processing cost, and has large-scale application prospect.

[0009] To achieve this purpose, the present application adopts the following technical solutions:

[0010] The present application provides a method for preparing kaolin by oxygen plasma treatment, which comprises the following steps:

[0011] (1) the coal series kaolin raw material is sequentially subjected to crushing treatment, grinding stripping treatment, drying treatment and screening treatment to obtain coal series kaolin particles;

[0012] (2) the coal series kaolin particles are subjected to oxygen plasma treatment under the condition that the vacuum degree is 6*10 -1 ~ 9*10 -1 mBar and the power is 45~75W to obtain kaolin.

[0013] The method for preparing kaolin by adopting oxygen plasma treatment in the application adopts the coal series kaolin as raw material which is widely sourced and low in price, and utilizes oxygen plasma treatment to prepare kaolin, effectively removes carbon in the coal series kaolin raw material, and has simple operation, greatly improved whiteness of kaolin and color change from black to grayish white. The reaction mechanism diagram of the method for preparing kaolin by adopting oxygen plasma treatment in the application is shown in Figure 1 Moreover, the temperature of oxygen plasma treatment is in the range of 50~150℃, compared with the method for preparing kaolin by adopting calcination treatment with the temperature of 1000~1300℃ in the prior art, low-temperature operation does not destroy the layered structure of the contained kaolinite mineral, and the obtained kaolin still has the layered structure of kaolinite mineral, and has wider application range.

[0014] The vacuum degree of the oxygen plasma treatment in the application is 6*10 -1 ~ 9*10 -1 mBar, for example, can be 6*10 -1 mBar, 6.5*10 - 1 mBar, 7*10 -1 mBar, 7.5*10 -1 mBar, 8*10 -1 mBar, 8.5*10 -1 mBar or 9*10 -1 mBar, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0015] The power is 45~75W, for example, can be 45W, 46W, 50W, 55W, 60W, 65W or 75W, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0016] The vacuum degree of the oxygen plasma treatment in the application is 6*10 -1 ~ 9*10 -1mBar, to ensure that the coal-based kaolin decarbonization is well carried out, the vacuum degree is low, the oxygen molecules are few, the gas active particles of the reaction are few, the decarbonization effect is poor, and the quality of the obtained kaolin is poor; when the vacuum degree is higher, the oxygen molecules are more, the energy loss of the flying electron is increased, which can lead to the decrease of the gas active particles of the reaction, the decarbonization effect of the oxygen plasma coal-based kaolin raw material is poor, the whiteness of the obtained kaolin is lower, and the application range is limited.

[0017] The power of the oxygen plasma treatment is 45-75W, when the power is lower, the oxygen plasma cannot be well excited, leading to the poor decarbonization effect of the coal-based kaolin; when the power is higher, the energy consumption of the oxygen plasma treatment is higher, and the economy of the prepared kaolin is poor.

[0018] Preferably, the carbon content of the coal-based kaolin raw material in step (1) is 2-15%, for example, can be 2%, 4%, 6%, 8%, 10%, 12% or 15%, but not limited to the listed values, and other values not listed in the value range are also applicable.

[0019] Preferably, the particle size of the coal-based kaolin raw material after the crushing treatment in step (1) is 0.25-0.85mm, for example, can be 0.25mm, 0.30mm, 0.42mm, 0.50mm, 0.60mm, 0.71mm or 0.85mm, but not limited to the listed values, and other values not listed in the value range are also applicable.

[0020] Preferably, the grinding and stripping treatment in step (1) is carried out in a grinding and stripping machine.

[0021] Preferably, the feeding concentration of the grinding and stripping machine is 20-40%, for example, can be 20%, 25%, 30%, 35%, 38% or 40%, but not limited to the listed values, and other values not listed in the value range are also applicable.

[0022] Preferably, grinding aids and grinding and stripping media are added in the grinding and stripping treatment in step (1).

[0023] Preferably, the grinding aid is sodium hexametaphosphate, and the addition amount is 1-4%, for example, can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 3.8% or 4%, but not limited to the listed values, and other values not listed in the value range are also applicable.

[0024] Preferably, the grinding and stripping medium is a zirconium ball, and the mass ratio of the material to the zirconium ball is 5:1-1:1, for example, can be 5:1, 4.5:1, 4:1, 3.8:1, 3.5:1, 3:1, 2.5:1, 2:1 or 1:1, but not limited to the listed values, and other values not listed in the value range are also applicable.

[0025] Preferably, the drying treatment in step (1) is performed in a drying machine.

[0026] Preferably, the inlet temperature of the drying machine is 200-300℃, for example, it can be 200℃, 220℃, 240℃, 250℃, 270℃, 290℃ or 300℃, etc., but not limited to the listed values, other values not listed in this range are also applicable.

[0027] The outlet temperature is 80-180℃, for example, it can be 80℃, 100℃, 120℃, 140℃, 150℃, 170℃ or 180℃, etc., but not limited to the listed values, other values not listed in this range are also applicable.

[0028] Preferably, the moisture content of the coal-based kaolin after the drying treatment is less than 1%, for example, it can be 0.9%, 0.8%, 0.5%, 0.3%, 0.2%, 0.1% or 0.05%, etc., but not limited to the listed values, other values not listed in this range are also applicable.

[0029] Preferably, the particle size of the coal-based kaolin after the screening treatment in step (1) is 0.09-0.125mm, for example, it can be 0.09mm, 0.1mm, 0.15mm, 0.12mm or 0.125mm, etc., but not limited to the listed values, other values not listed in this range are also applicable.

[0030] Preferably, the particle size of the coal-based kaolin after the screening treatment in step (1) is 0.09-0.125mm, which can make the coal-based kaolin raw material fully contact with the oxygen plasma, improving the decarburization efficiency.

[0031] Preferably, the oxygen plasma treatment in step (2) is performed in a low-temperature oxygen plasma ashing instrument.

[0032] Preferably, the carrier gas for the oxygen plasma treatment is oxygen.

[0033] Preferably, the chamber pressure of the low-temperature oxygen plasma ashing instrument is increased from 5x10 -1 to 1x10 0 mBar.

[0034] Preferably, the radio frequency of the oxygen plasma treatment is 13.56MHz.

[0035] Preferably, the ashing time of the oxygen plasma treatment is 4-5h, for example, it can be 4h, 4.2h, 4.4h, 4.5h, 4.7h, 4.9h or 5h, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0036] Preferably, the carbon content of the kaolin is 0.1-0.4%, for example, it can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35% or 0.4%, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0037] As a preferred technical solution of the present application, the method comprises the following steps:

[0038] (1) The coal-based kaolin raw material with a carbon content of 2-15% is crushed to a particle size of 0.25-0.85mm, then subjected to a grinding and stripping treatment in a grinding and stripping machine, and a drying treatment in a drying machine, the water content of the coal-based kaolin after the drying treatment is less than 1%, then subjected to a screening treatment to obtain coal-based kaolin particles with a particle size of 0.09-0.125mm;

[0039] The feeding concentration of the grinding and stripping machine is 20%-40%; grinding aids and grinding and stripping media are added in the grinding and stripping treatment; the grinding aid is sodium hexametaphosphate, and the addition amount is 1-4%; the grinding and stripping medium is zirconium ball, and the mass ratio of the material to the zirconium ball is 5:1-1:1;

[0040] The inlet temperature of the drying machine is 200-300℃, and the outlet temperature is 80-180℃;

[0041] (2) The oxygen plasma treatment is carried out in a low-temperature oxygen plasma ashing instrument; before the oxygen plasma treatment, the chamber is first pumped to carry oxygen into the chamber, the chamber pressure is increased from 5x10 -1 to 1x10 0 mBar, the radio frequency power is applied to the entire chamber to excite oxygen molecules;

[0042] The coal-based kaolin particles are subjected to oxygen plasma treatment under the conditions of a radio frequency of 13.56MHz, a vacuum degree of 6x10 -1 -9x10 -1 mBar, a power of 45-75W, and an ashing time of 4-5h, to obtain kaolin with a carbon content of 0.1-0.4%.

[0043] Compared with the prior art, the present application has at least the following beneficial effects:

[0044] The method for preparing kaolin by adopting oxygen plasma treatment provided by the application has simple operation, cheap and easily obtained coal-based kaolin raw material, and low oxygen plasma treatment temperature, which can well realize decarburization of the coal-based kaolin raw material, greatly improve the whiteness of the prepared kaolin, and will not damage the layered structure of kaolinite minerals contained in the kaolin, and has large-scale industrial application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 is a reaction mechanism diagram of the method for preparing kaolin by adopting oxygen plasma treatment provided by the application.

[0046] Figure 2 is an XRD diagram of the Datong coal-based kaolin raw material and the prepared kaolin in Example 1.

[0047] Figure 3 is a picture of the Datong coal-based kaolin raw material in Example 1.

[0048] Figure 4 is a picture of the prepared kaolin in Example 1.

[0049] Figure 5 is an XRD diagram of the Datong coal-based kaolin raw material and the prepared calcined kaolin in Comparative Example 7. DETAILED DESCRIPTION

[0050] The technical solutions of the application will be further described below by combining with the drawings and through specific embodiments.

[0051] The application will be further described below in detail. However, the following examples are only simple examples of the application, and do not represent or limit the protection scope of the application, and the protection scope of the application is subject to the claims.

[0052] Example 1

[0053] The embodiment provides a method for preparing kaolin by adopting oxygen plasma treatment, and the method comprises the following steps:

[0054] (1) the coal-based kaolin raw material with a carbon content of 4% is subjected to crushing treatment, and the particle size is 0.42 mm, and then the coal-based kaolin raw material is subjected to grinding and stripping treatment in a grinding and stripping machine and drying treatment in a drying machine, the water content of the coal-based kaolin after the drying treatment is 0.3%, and then the coal-based kaolin is subjected to screening treatment, and the coal-based kaolin particles with a particle size of 0.1 mm are obtained;

[0055] the feeding concentration of the grinding and stripping machine is 30%; grinding aids and grinding and stripping media are added in the grinding and stripping treatment; the grinding aid is sodium hexametaphosphate, and the addition amount is 1%; the grinding and stripping medium is a zirconium ball, and the mass ratio of the material to the zirconium ball is 2:1;

[0056] The inlet temperature of the drying machine is 230℃, and the outlet temperature is 120℃;

[0057] (2) The oxygen plasma treatment is performed in a low-temperature oxygen plasma ashing instrument; before the oxygen plasma treatment, the chamber is evacuated, oxygen is carried into the chamber, the pressure in the chamber is increased from 5*10 -1 to 1*10 0 mBar, radio frequency power is applied to the whole chamber to excite oxygen molecules;

[0058] The coal-based kaolin particles are subjected to oxygen plasma treatment under the conditions that the radio frequency is 13.56MHz, the vacuum degree is 7*10 -1 mBar, the power is 60W, and the ashing time is 4.5h, and kaolin with a carbon content of 0.08% is obtained.

[0059] The XRD pattern of the Datong coal-based kaolin raw material and the kaolin prepared therefrom in this embodiment is shown in Figure 2 From Figure 2 it can be seen that the obtained kaolin product has been decarburized and the layered structure of the contained kaolinite mineral has not been destroyed after the oxygen plasma treatment.

[0060] The picture of the Datong coal-based kaolin raw material in this embodiment is shown in Figure 3 From Figure 3 it can be seen that the color of the Datong coal-based kaolin raw material is black. The picture of the prepared kaolin in this embodiment is shown in Figure 4 From Figure 4 it can be seen that the color of the kaolin is grayish white. Therefore, it can be known that the method for preparing kaolin by oxygen plasma treatment provided in the present application realizes effective decarburization and greatly improves the whiteness of the kaolin.

[0061] Example 2

[0062] The present embodiment provides a method for preparing kaolin by oxygen plasma treatment, which comprises the following steps:

[0063] (1) The coal-based kaolin raw material with a carbon content of 10% is subjected to crushing treatment, and the particle size is 0.85mm, then the raw material is subjected to grinding and stripping treatment in a grinding and stripping machine, and drying treatment in a drying machine, the water content of the coal-based kaolin after the drying treatment is 0.1%, and then the coal-based kaolin particles with a particle size of 0.12mm are obtained through screening treatment;

[0064] The feeding concentration of the grinding and stripping machine is 20%; grinding aids and grinding and stripping media are added in the grinding and stripping treatment; the grinding aid is sodium hexametaphosphate, and the addition amount is 1%; the grinding and stripping medium is zirconium ball, and the mass ratio of the material to the zirconium ball is 2:1;

[0065] The inlet temperature of the drying machine is 300℃, and the outlet temperature is 180℃;

[0066] (2) The oxygen plasma treatment is performed in a low-temperature oxygen plasma ashing instrument; before the oxygen plasma treatment, the chamber is first evacuated, oxygen is carried into the chamber, the pressure of the chamber is increased from 5x10 -1 to 1x10 0 mBar, radio frequency power is applied to the entire chamber to excite oxygen molecules;

[0067] The coal-based kaolin particles are subjected to oxygen plasma treatment under the conditions of a radio frequency of 13.56 MHz, a vacuum degree of 9x10 -1 mBar, a power of 75W, and an ashing time of 5h, to obtain kaolin with a carbon content of 0.2%.

[0068] Example 3

[0069] The present embodiment provides a method for preparing kaolin by oxygen plasma treatment, which comprises the following steps:

[0070] (1) The coal-based kaolin raw material with a carbon content of 13% is subjected to crushing treatment with a particle size of 0.60mm, and then is subjected to grinding and stripping treatment in a grinding and stripping machine, and drying treatment in a drying machine. After the drying treatment, the moisture content of the coal-based kaolin is 0.8%, and then is subjected to screening treatment to obtain coal-based kaolin particles with a particle size of 0.09mm;

[0071] The feeding concentration of the grinding and stripping machine is 20%-40%; grinding aids and grinding and stripping media are added during the grinding and stripping treatment; the grinding aid is sodium hexametaphosphate, and the addition amount is 1%; the grinding and stripping medium is zirconium ball, and the mass ratio of the material to the zirconium ball is 2:1;

[0072] The inlet temperature of the drying machine is 200℃, and the outlet temperature is 80℃;

[0073] (2) The oxygen plasma treatment is performed in a low-temperature oxygen plasma ashing instrument; before the oxygen plasma treatment, the chamber is first evacuated, oxygen is carried into the chamber, the pressure of the chamber is increased from 5x10 -1 to 1x10 0 mBar, radio frequency power is applied to the entire chamber to excite oxygen molecules;

[0074] The coal-based kaolin particles are subjected to oxygen plasma treatment under the conditions of a radio frequency of 13.56 MHz, a vacuum degree of 6x10 -1 mBar, a power of 45W, and an ashing time of 4h, to obtain kaolin with a carbon content of 0.3%.

[0075] From the examples 1-3, it can be seen that the method for preparing kaolin by oxygen plasma treatment provided by the present application has simple operation and low processing temperature, and can well realize decarburization of the coal-series kaolin raw material, greatly improve the whiteness of the kaolin, and will not destroy the layered structure of the kaolinite mineral contained in the kaolin, and the prepared kaolin has large-scale industrial application prospect.

[0076] The XRF analysis results of the different coal-series kaolin raw materials and the prepared kaolin products in the examples 1-3 are shown in Table 1.

[0077] Table 1

[0078]

[0079]

[0080] From Table 1, it can be seen that the layered structure of the kaolinite mineral contained in the kaolin is not changed before and after the oxygen plasma treatment.

[0081] Comparative example 1

[0082] The present comparative example provides a method for preparing kaolin by oxygen plasma treatment, wherein the method is the same as that of the example 1 except that the vacuum degree of the oxygen plasma treatment is 10x10 -1 mBar.

[0083] Comparative example 2

[0084] The present comparative example provides a method for preparing kaolin by oxygen plasma treatment, wherein the method is the same as that of the example 1 except that the vacuum degree of the oxygen plasma treatment is 5x10 -1 mBar.

[0085] From the examples 1 and the comparative examples 1-2, it can be seen that in the comparative example 1, the vacuum degree of the oxygen plasma treatment is low, the oxygen molecules are less, the active gas particles of the reaction are less, the decarburization effect is poor, and the quality of the prepared kaolin is poor; in the comparative example 2, the vacuum degree of the oxygen plasma treatment is high, the oxygen molecules are more, the energy loss of the flying electrons is increased, which will lead to the decrease of the active gas particles of the reaction, the decarburization effect of the oxygen plasma coal-series kaolin raw material is poor, the whiteness of the prepared kaolin is low, and the application range is limited.

[0086] Comparative example 3

[0087] The present comparative example provides a method for preparing kaolin by oxygen plasma treatment, wherein the method is the same as that of the example 1 except that the power of the oxygen plasma treatment is 40W.

[0088] Comparative example 4

[0089] The comparative example provides a method for preparing kaolin by oxygen plasma treatment, which is the same as example 1 except that the power of the oxygen plasma treatment is 80 W.

[0090] It can be seen from the combination of example 1 and comparative examples 3-4 that the power of the oxygen plasma treatment in comparative example 3 is low, which cannot well excite the oxygen plasma, resulting in poor decarburization effect of the coal-based kaolin and low whiteness of the obtained kaolin; the power of the oxygen plasma treatment in comparative example 4 is high, which has little effect on the decarburization of the coal-based kaolin, but the high power leads to high energy consumption and poor economy of preparing kaolin.

[0091] Comparative example 5

[0092] The comparative example provides a method for preparing kaolin by oxygen plasma treatment, which is the same as example 1 except that the time of the oxygen plasma treatment is 2 h.

[0093] Comparative example 6

[0094] The comparative example provides a method for preparing kaolin by oxygen plasma treatment, which is the same as example 1 except that the time of the oxygen plasma treatment is 7 h.

[0095] It can be seen from the combination of example 1 and comparative examples 5-6 that the time of the oxygen plasma treatment in comparative example 5 is short, which cannot completely decarburize and has poor decarburization effect; the time of the oxygen plasma treatment in comparative example 6 is long, which has little effect on the decarburization of the coal-based kaolin, but the long time leads to high energy consumption and poor economy of preparing kaolin.

[0096] The carbon content of the coal-based kaolin and the kaolin product in comparative examples 1-6 is shown in table 2.

[0097] Table 2

[0098]

[0099]

[0100] Comparative example 7

[0101] The comparative example provides a method for preparing kaolin, which comprises the following steps:

[0102] (1) The Datong coal-based kaolin raw material with a carbon content of 4% is crushed to a particle size of 0.85 mm, and then is subjected to a milling and stripping treatment in a milling and stripping machine and a drying treatment in a drying machine, wherein the water content of the coal-based kaolin after the drying treatment is 0.1%, and then is subjected to a screening treatment to obtain coal-based kaolin particles with a particle size of 0.09 mm;

[0103] The feed concentration of the attrition machine is 20%; grinding aids and attrition media are added in the attrition process; the grinding aid is sodium hexametaphosphate, and the addition amount is 1%; the attrition medium is zirconium ball, and the mass ratio of material to zirconium ball is 2:1;

[0104] The inlet temperature of the drying machine is 300℃, and the outlet temperature is 180℃;

[0105] (2) The coal-based kaolin particles are placed in a muffle furnace, the furnace temperature is controlled at 1000℃, calcination is carried out for 2h, natural annealing is carried out, and cooling is carried out at room temperature, to obtain kaolin.

[0106] The XRD patterns of the raw material Datong coal-based kaolin and the prepared kaolin in the present comparative example are shown in Figure 5 It can be seen from Figure 5 that higher calcination temperature can destroy the layered structure of kaolinite mineral contained in the kaolin, mineral transformation occurs, and thus the performance of the kaolin is reduced.

[0107] The applicant declares that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought by any person skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing kaolin by using oxygen plasma treatment, characterized by, The method comprises the following steps: (1) the coal series kaolin raw material is sequentially subjected to crushing treatment, grinding and stripping treatment, drying treatment and screening treatment to obtain coal series kaolin particles; (2) The coal-based kaolin particles are subjected to oxygen plasma treatment under the conditions of a vacuum degree of 6*10 -1 9*10 -1 mBar and a power of 45-75 W to obtain kaolin. The oxygen plasma treatment in step (2) is performed in a low-temperature oxygen plasma ashing instrument; The carrier gas for the oxygen plasma treatment is oxygen; The chamber pressure of the low temperature oxygen plasma asher increases from 5 x 10 -1 to 1 x 10 0 mBar; The radio frequency for the oxygen plasma treatment in step (2) is 13.56 MHz; The ashing time for the oxygen plasma treatment is 4-5 h; The carbon content of the kaolin in step (2) is 0.1-0.4%.

2. The method of claim 1, wherein, The carbon content of the coal series kaolin raw material in step (1) is 2-15%.

3. The method of claim 1, wherein, The particle size of the coal series kaolin raw material after the crushing treatment is 0.25-0.85 mm.

4. The method of claim 1, wherein, The grinding and stripping treatment in step (1) is performed in a grinding and stripping machine.

5. The method of claim 4, wherein, The feeding concentration of the grinding and stripping machine is 20-40%.

6. The method of claim 1, wherein, An abrasive aid and a grinding and stripping medium are added in the grinding and stripping treatment in step (1).

7. The method of claim 6, wherein, The abrasive aid is sodium hexametaphosphate, and the addition amount is 1-4%.

8. The method of claim 6, wherein, The grinding and stripping medium is a zirconium ball, and the mass ratio of the material to the zirconium ball is 5:1-1:

1.

9. The method of claim 1, wherein, The drying treatment in step (1) is performed in a drying machine.

10. The method of claim 9, wherein, The inlet temperature of the drying machine is 200-300 DEG C, and the outlet temperature is 80-180 DEG C.

11. The method of claim 1, wherein, The water content of the coal series kaolin after the drying treatment is less than 1%.

12. The method of claim 1, wherein, The particle size of the coal series kaolin particles after the screening treatment in step (1) is 0.09-0.125 mm.

13. The method according to any one of claims 1 to 9, characterized in that, The method comprises the following steps: (1) the coal series kaolin raw material with a carbon content of 2-15% is subjected to crushing treatment to have a particle size of 0.25-0.85 mm, and then subjected to grinding and stripping treatment in a grinding and stripping machine and drying treatment in a drying machine, wherein the water content of the coal series kaolin after the drying treatment is less than 1%, and then subjected to screening treatment to obtain coal series kaolin particles with a particle size of 0.09-0.125 mm; The feeding concentration of the grinding and stripping machine is 20-40%; an abrasive aid and a grinding and stripping medium are added in the grinding and stripping treatment; the abrasive aid is sodium hexametaphosphate, and the addition amount is 1-4%; the grinding and stripping medium is a zirconium ball, and the mass ratio of the material to the zirconium ball is 5:1-1:1; the inlet temperature of the drying machine is 200-300 DEG C, and the outlet temperature is 80-180 DEG C; (2) The oxygen plasma treatment is performed in a low-temperature oxygen plasma ashing instrument; before the oxygen plasma treatment, the chamber is first pumped to carry oxygen into the chamber, the pressure of the chamber is increased from 5x10 -1 to 1x10 0 mBar, radio frequency power is applied to the entire chamber to excite oxygen molecules; The coal series kaolin particles are subjected to oxygen plasma treatment under the conditions of radio frequency of 13.56 MHz, vacuum degree of 6x10 -1 9x10 -1 mBar, power of 45-75 W, and ashing time of 4-5 h to obtain kaolin with carbon content of 0.1-0.4%.

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