Patent Application
20250171320
This application claims priority to Chinese Patent Application No. 202410078803.2 with a filing date of Jan. 19, 2024. The content of the aforementioned application, including any intervening amendments thereto, is incorporated herein by reference.
The present disclosure relates to the technical field of processing of non-metallic mineral materials, and in particular to high-purity kaolin and a preparation method thereof.
As a basic material for ceramics, electronic materials, new antimicrobial materials, anticancer carriers, etc., high-purity kaolin plays a key role in different fields. In the ceramic industry, the refined purification of kaolin can improve the whiteness, transparency, and mechanical properties of kaolin, such that the kaolin is suitable for the preparation of high-end ceramics. In the field of electronic materials, the purity of kaolin is directly related to the insulating properties of dielectric materials. In the field of biomedicine, because it is stipulated in the European INventory of Existing commercial Chemical Substances (EINECS) NO. 215-628-1 that the purity of kaolin needs to reach 95% or more, high-purity kaolin is essential for the preparation of materials with excellent biocompatibility and no harm to the human body. The improvement of the purity of kaolin is conducive to improving the properties of materials and expanding the application fields, and also can increase the market value added of mineral products and promote the sustainable utilization of mineral resources. The refined beneficiation can effectively extract the useful components in kaolin, reduce the waste of resources, alleviate the problem that kaolin resources undergo scattered distribution and include many colored impurities, and improve the comprehensive utilization efficiency of mineral resources, which is in line with the strategic requirements of sustainable development.
The main components in crude kaolin ore are kaolinite minerals. The crude kaolin ore also includes a large number of impurities such as quartz, feldspar, mica, and various iron minerals and iron oxides, and even includes organic matters. Kaolin purification methods include gravity concentration, magnetic separation, flotation, leaching, chemical bleaching, roasting, etc. These methods have respective characteristics, and can be used for removing different types of impurities to improve the whiteness and quality of kaolin. The gravity concentration is mainly used to remove organic matters, feldspar, quartz, etc., and achieves the purification based on density and particle size differences. The gravity concentration needs to be used in combination with calcination, magnetic separation, and leaching to produce a final product. The magnetic separation can remove weakly-magnetic staining impurities. The high-gradient strong magnetic separator can effectively achieve the magnetic separation and purification of kaolin. The flotation can be used to treat crude kaolin ore with many impurities, and achieves the purification through the adsorption and separation of bubbles. The leaching allows the removal of some impurities through the dissolution with a leaching agent, and is simple and energy-saving. The chemical bleaching achieves the removal of staining impurities through chemical reactions, including oxidation, reduction, oxidation-reduction combination, etc. However, the above-mentioned different purification processes exhibit prominent removal effects merely for specific types of impurities. Therefore, how to well remove impurities in kaolin and use purified kaolin in the field of biomedicine is an urgent problem to be solved.
An objective of the present disclosure is to provide high-purity kaolin with high purity, low cost, and high biosafety and a preparation method thereof in view of the above-mentioned shortcomings in the prior art. In the preparation method, kaolinite in kaolin is effectively separated from hematite, montmorillonite, and quartz through a physical-chemical combined process to produce high-purity kaolin.
To achieve the above objective, the present disclosure adopts the following technical solutions:
A first objective of the present disclosure is to provide a preparation method of high-purity kaolin, including the following steps:
Further, in the S1, the solid-to-liquid ratio of the kaolin powder to the deionized water is (5-160) g:100 mL, the stirring is conducted at 1,000 rpm to 1,500 rpm for 60 min to 120 min, and the slurry is allowed to stand for 5 min to 60 min.
Further, in the S1, the centrifugal classification is conducted by a centrifuge with a centrifugation speed of 2,000 rpm to 7,000 rpm and a centrifugation time of 5 min to 10 min to produce a supernatant and a precipitate; and the supernatant is retained as a product for subsequent purification, and the precipitate is discarded.
Further, in the S2, a solid-to-liquid ratio of the physically-purified ore to the 16% to 32% sulfuric acid is 1 g:(1-20) mL, and the reaction is conducted at 60° C. to 65° C. for 60 min to 180 min.
Further, in the S2, the drying is conducted at 30° C. to 70° C. for 120 min to 600 min.
Further, in the S3, a solid-to-liquid ratio of the purified kaolin ore to the nonionic polyacrylamide is (1-5):100, the low-speed stirring is conducted at 50 rpm to 500 rpm for 60 min to 240 min, and the dewatering and drying is conducted at 30° C. to 70° C. for 120 min to 600 min.
A second objective of the present disclosure is to provide high-purity kaolin prepared by the preparation method.
Further, in the high-purity kaolin, a content of kaolinite is not less than 98.5% and a content of quartz is not more than 0.4%.
Further, a particle size distribution of the high-purity kaolin is as follows: D50: 361 nm to 365 nm, and D90: 635 nm to 670 nm.
Further, a zeta potential of the high-purity kaolin is −36 mV to −37 mV.
Compared with the prior art, the present disclosure has the following beneficial effects:
In order to make the objective, technical solutions, and advantages of the present disclosure clear, the embodiments of the present disclosure are described below in detail. Examples of the embodiments are shown in the accompanying drawings. The same or similar numerals represent the same or similar elements or elements having the same or similar functions throughout the specification. The embodiments described below with reference to the accompanying drawings are exemplary. These embodiments are only used to explain the present disclosure, and should not be construed as a limitation to the present disclosure.
The crude kaolin ore adopted in the present disclosure comes from Nankang District, Ganzhou City, Jiangxi Province.
The term “high-purity,” as used herein, refers to kaolin that has a content of kaolinite not less than 95%.
In this example, physically-purified kaolin was prepared through physical purification with different dispersant contents (0% to 0.8%).
A dispersing agent was added at 0%, 0.2%, 0.4%, 0.6%, and 0.8% to 1,000 mL of a kaolin slurry, and high-speed stirring was conducted by a stirrer for 120 min. After the high-speed stirring was completed, free sedimentation was allowed for 60 min. After the free sedimentation was completed, a resulting supernatant was collected through siphonage, then transferred to a 50 mL centrifuge tube, and washed multiple times through centrifugation at 2,000 rpm until a clear supernatant was produced. The clear supernatant was kept at 65° C. for 300 min to allow drying to produce physically-purified kaolin.
In this example, physically-purified kaolin was prepared at different centrifugation speeds (500 rpm to 7,000 rpm).
0.4% of a dispersing agent was added to 1,000 mL of a kaolin slurry, and centrifugal classification was conducted for 5 min by a centrifuge with centrifugation speeds of 500 rpm, 1,000 rpm, 2,000 rpm, 3,000 rpm, 5,000 rpm, and 7,000 rpm. After the centrifugal classification was completed, a resulting supernatant was transferred to a 50 mL centrifuge tube and centrifuged multiple times at 7,000 rpm until a clear supernatant was produced. The clear supernatant was kept at 65° C. for 300 min to allow drying to produce physically-purified kaolin.
In this example, hematite was removed with different solid-to-liquid ratios of physically-purified kaolin to a sulfuric acid solution (1:(1-20)) to produce chemically-purified kaolin.
0.4% of a dispersing agent was added to 1,000 mL of a kaolin slurry, mechanical stirring was conducted for 120 min, and standing was allowed for 60 min. A resulting slurry supernatant was collected through siphonage, and subjected to centrifugal classification for 5 min by a centrifuge with a centrifugation speed of 2,000 rpm to produce a product. The product was dried to produce physically-purified kaolin. According to solid-to-liquid ratios of 1:1, 1:5, 1:10, 1:15, and 1:20, 16% to 32% sulfuric acid was added at 60° C. to the physically-purified kaolin, and low-speed stirring was conducted with a low-speed stirrer. A resulting acid-leaching system was subjected to centrifugal classification for 5 min by a centrifugal classifier at 7,000 rpm. A leached product was discarded with a centrifugal supernatant. A purified product was retained with a centrifugal precipitate, and finally kept at 65° C. for 300 min to allow drying to produce chemically-purified kaolin.
In this example, montmorillonite was removed with different flocculating agents to produce high-purity kaolin.
1 g of chemically-purified kaolin was weighed and subjected to a reaction for 180 min with each of 1 L of deionized water, 5 mg/L of anionic polyacrylamide, 5 mg/L of cationic polyacrylamide, and 5 mg/L of nonionic polyacrylamide in a low-speed stirrer to produce mixtures. The mixtures each were washed multiple times until a pH was 7.0, and finally dried to produce high-purity kaolin concentrates with purities of 97.8%, 92.4%, and 98%, respectively. The results indicated that nonionic polyacrylamide is an important optimization condition.
In this example, montmorillonite was removed at different flocculation pH values (3 to 10) to prepare high-purity kaolin.
1 g of chemically-purified kaolin and 5 mg/L of nonionic polyacrylamide were weighed and subjected to a reaction for 240 min at 300 rpm in solutions with pH values of 3, 4, 6, 7, 9, and 10 to produce mixtures. The mixtures each were washed multiple times until a pH was 7.0, and finally dried to produce high-purity kaolin concentrates with purities of 93%, 92.6%, 94.3%, 95.1%, 98.6%, and 96.7%, respectively. The results indicated that the pH affected the ability of a flocculating agent to flocculate gangue minerals, and the optimal pH was 9.
In this example, montmorillonite was removed at different mashing speeds (50 rpm to 500 rpm) to prepare high-purity kaolin.
1 g of chemically-purified kaolin and 5 mg/L of nonionic polyacrylamide were weighed and subjected to a reaction at mashing speeds of 50 rpm, 100 rpm, 200 rpm, 300 rpm, 400 rpm, and 500 rpm in a solution with a pH of 9 to produce mixtures. The mixtures each were washed multiple times until a pH was 7.0, and finally dried to produce high-purity kaolin concentrates with purities of 90.2%, 92.5%, 95.3%, 98.9%, 98.4%, and 95.7%, respectively. The results indicated that the mashing speed also affected the ability of a flocculating agent to flocculate gangue minerals, and the optimal mashing speed was 300 rpm.
In this example, the correlation between steps was investigated by adjusting an order of S2 and S3.
A natural crude kaolin ore was crushed and screened to produce a kaolin powder. The kaolin powder was mixed with deionized water and a dispersing agent at a mass 0.4% of a mass of the kaolin powder according to a specified solid-to-liquid ratio, and stirring was conducted at a specified speed for a specified time to produce a slurry. The slurry was allowed to stand for 90 min. A resulting slurry supernatant was collected through siphonage, subjected to centrifugal classification, and dried to produce physically-purified kaolin. The physically-purified kaolin and nonionic polyacrylamide were subjected to a reaction for a specified time at a specified temperature under low-speed stirring. An upper waste supernatant liquid was removed through siphonage. A lower flocculent precipitate was subjected to centrifugal classification and dewatering and drying to produce chemically-purified kaolin. Finally, the chemically-purified kaolin was subjected to a reaction for a specified time with sulfuric acid according to a solid-to-liquid ratio of 1:5 to produce a mixture. The mixture was washed multiple times with deionized water until a pH was 7.0, and then dried to produce purified kaolin. The above process was repeated three times. Purified kaolin ores of the above processhad purities of 73.3%, 70.3%, and 68.2%, respectively, indicating that the purity was greatly reduced. Zeta potentials corresponding to the different purities were −16.17 mV, −2.41 mV, and 0.95 mV, respectively, which did not meet the potential requirement of high-purity kaolin. The results indicated that the adjustment of the experimental steps made flocculation products agglomerate and greatly reduced the acid-leaching effect.
In order to well elaborate the properties of the high-purity kaolin prepared in the present disclosure, the applicants carried out the following research:
The high-purity kaolin concentrates prepared in Examples 4 to 6 had similar performance characteristics. The high-purity kaolin concentrate prepared in Example 6 was taken as a representative for explanation below.
Table 1 shows the comparison of specific surface areas, pore volumes, and pore sizes of the crude kaolin ore and the high-purity kaolin concentrate. The high-purity kaolin concentrate produced after treating the crude kaolin ore by the physical-chemical combined process has a specific surface area increasing from 13.92 m2/g to 73.44 m2/g, a pore volume increasing from 0.05 cm3/g to 0.31 cm3/g, and a pore size increasing slightly to 16.65 nm.
In some embodiments, the high-purity kaolin concentrate has a small particle size of 200 nm to 640 nm, a high porosity of 1 nm to 10 nm, an enhanced ion-exchange capacity, and an absolute zeta potential value of greater than 30 mV, and exhibits excellent biocompatibility. The high-purity kaolin can be widely used in the field of biomedicine, including, but not limited to the following examples, preparation of hemostatic materials, drug carriers, and antimicrobial materials, and tissue engineering.
What is not mentioned above can be acquired in the prior art.
Although some specific embodiments of the present disclosure have been described in detail by way of examples, those skilled in the art will appreciate that the above examples are provided for illustration only and not for limiting the scope of the present disclosure. A person skilled in the art can make various modifications or supplements to the specific embodiments described or replace them in a similar manner, but it may not depart from the direction of the present disclosure or the scope defined by the appended claims. Those skilled in the art should understand that any modification, equivalent replacement, and improvement made to the above embodiments according to the technical essence of the present disclosure shall be included in the protection scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202410078803.2 | Jan 2024 | CN | national |
