Modified diatomite and preparation method thereof

Abstract

The invention discloses modified diatomite and a preparation method thereof, and the method comprises the following steps: step 1, calcining a diatomite raw material to obtain activated diatomite; step 2, pickling the activated diatomite to obtain acidified diatomite; step 3, carrying out alkali treatment on the acidified diatomite to obtain alkali-regulated diatomite; and step 4, drying the alkali-regulated diatomite to obtain the modified diatomite. The prepared modified diatomite can be used for adsorption separation to the maximum extent.

Description

Technical Field

[0001] The invention belongs to the field of porous adsorption materials and relates to modified diatomaceous earth and a preparation method thereof. Background Art

[0002] Diatomaceous Earth (DME) is a white powder, mainly composed of silicon dioxide (SiO2), and also contains a small amount of aluminum oxide (Al2O3), iron oxide (Fe2O3), calcium oxide (CaO) and magnesium oxide (MgO). Diatomaceous earth has the advantages of high porosity (80-90%), high specific surface area, good adsorption performance, stable chemical properties, environmental friendliness and light weight. It is a natural adsorption material with a unique microporous structure. Due to its excellent microporous structure characteristics, coupled with my country's abundant reserves, large output and economical price, diatomaceous earth is widely used in industrial and civil fields, such as filter aids, adsorbents, catalyst substrates, etc.

[0003] However, natural diatomite has uneven pore structure, low specific surface area, and insufficient chemical purity, which leads to low adsorption efficiency and limits its use in industry and environmental protection. Therefore, modifying natural diatomite, removing impurities from raw materials, correcting its physical and chemical defects, and improving its microscopic pore structure to improve its purity and maximize the use of diatomite's porous structure are important means to improve its application effect.

[0004] Common modification methods include: calcination and acid washing. Calcination is a technology that uses high-temperature calcination technology to remove organic matter and structural water from diatomite. Its main feature is to decompose it and melt the clay impurities in the tiny pores formed inside and on the surface. When the impurities are removed, the specific surface area increases and the pore structure improves, thereby significantly improving the adsorption performance of diatomite. However, excessively high temperatures during the calcination process may destroy the microstructure of diatomite, affect its unique pore properties and adsorption capacity, and the particle size and shape may also change. The acid washing method is to remove impurities such as alkaline metals and oxides through an acidic solution, thereby unblocking the pore structure and expanding the pore size, but acid washing may cause structural damage to the diatomite, reduce its physical strength, and affect subsequent use.

[0005] In view of the above reasons, there is an urgent need to provide a modification method for diatomite to improve its structural stability and adsorption performance. Summary of the invention

[0006] In order to overcome the above problems, the present invention proposes a modified diatomite and a preparation method, the method comprising: step 1, calcining diatomite raw material to obtain activated diatomite; step 2, acid washing the activated diatomite to obtain acidified diatomite; step 3, alkali treating the acidified diatomite to obtain alkali-adjusted diatomite; step 4, drying the alkali-adjusted diatomite to obtain modified diatomite. The obtained modified diatomite can be used for adsorption separation to the maximum extent.

[0007] Specifically, the purpose of the present invention is to provide the following aspects:

[0008] In a first aspect, a method for preparing modified diatomite is provided, the method comprising:

[0009] Step 1, calcining diatomite raw material to obtain activated diatomite;

[0010] Step 2, acid-washing the activated diatomite to obtain acidified diatomite;

[0011] Step 3, treating the acidified diatomaceous earth with alkali to obtain alkali-adjusted diatomaceous earth;

[0012] Step 4, drying the alkali-adjusted diatomaceous earth to obtain modified diatomaceous earth.

[0013] In step 1, the calcination temperature is 450-550°C.

[0014] Furthermore, the calcination temperature is 480-520°C.

[0015] In step 1, the calcination time is 1 to 3 hours.

[0016] Furthermore, the calcination time is 1.5 to 2.5 hours.

[0017] In step 2, the pickling is carried out using hydrochloric acid, sulfuric acid or nitric acid.

[0018] In step 3, the alkali used in the alkali treatment is sodium hydroxide, potassium hydroxide or magnesium hydroxide.

[0019] In step 4, the drying temperature is 100°C to 120°C.

[0020] In a second aspect, a modified diatomaceous earth prepared according to the method of the first aspect is provided.

[0021] Wherein, the pore size of the modified diatomaceous earth gradually increases from the inner layer to the outer layer.

[0022] The beneficial effects of the present invention include:

[0023] (1) The preparation method of modified diatomite provided by the present invention sequentially calcines, acid-washes and alkaline-treats the raw diatomite, thereby removing a large amount of impurities in the raw diatomite and enlarging the pores, thereby maximizing the use of the diatomite for adsorption and separation.

[0024] (2) The preparation method of modified diatomite provided by the present invention first enhances the physical and chemical stability of diatomite by calcination and improves its pore structure; then uses acid washing to remove impurities and organic matter, thereby increasing the specific surface area and adsorption performance; and then uses alkali treatment to remove metal ions and harmful components, thereby further improving its purity and functionality. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only used to illustrate the preferred embodiments and are not considered to be limitations of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work.

[0026] In the attached picture:

[0027] Figure 1 The SEM characterization image of the raw material diatomaceous earth in Example 1 at 3000 times magnification is shown;

[0028] Figure 2 The SEM characterization image of the raw material diatomaceous earth in Example 1 at 8000 times is shown;

[0029] Figure 3 The SEM characterization image of the activated diatomaceous earth in Example 1 at 2000 times magnification is shown;

[0030] Figure 4 The SEM characterization image of the activated diatomaceous earth in Example 1 at 3000 times magnification is shown;

[0031] Figure 5 The SEM characterization image of the alkali-adjusted diatomaceous earth in Example 1 at 2000 times magnification is shown;

[0032] Figure 6 The SEM characterization image of the alkali-adjusted diatomaceous earth in Example 1 at 8000 times magnification is shown. DETAILED DESCRIPTION

[0033] The following will refer to the attached Figures 1 to 6Specific embodiments of the present invention are described in more detail. Although specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0034] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.

[0035] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front", "rear", etc. indicate positions or positional relationships based on the working state of the present invention, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", and "fourth" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0036] To facilitate understanding of the embodiments of the present invention, further explanation will be given below by taking specific embodiments as examples in conjunction with the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0037] On the one hand, according to the method for preparing modified diatomite provided by the present invention, the method comprises:

[0038] Step 1, calcining diatomite raw material to obtain activated diatomite;

[0039] Step 2, acid-washing the activated diatomite to obtain acidified diatomite;

[0040] Step 3, treating the acidified diatomaceous earth with alkali to obtain alkali-adjusted diatomaceous earth;

[0041] Step 4, drying the alkali-adjusted diatomaceous earth to obtain modified diatomaceous earth.

[0042] Specifically:

[0043] Step 1, calcining diatomite raw material to obtain activated diatomite.

[0044] According to a preferred embodiment, the diatomite raw material is purified before calcining to remove soluble impurities attached to the surface. The purification includes: repeatedly washing the diatomite raw material in a water bath shaker until there is no foam suspension.

[0045] Furthermore, when washing with a water bath shaker, the oscillation frequency is 150 to 250 times / minute, preferably 180 to 210 times / minute, for example 200 times / minute; the oscillation time is 0.5 to 2 hours, preferably 1 to 1.5 hours, for example 1 hour.

[0046] Among them, 150 to 250 times / minute can provide sufficient mechanical force to help water molecules penetrate into the micropores of diatomaceous earth and remove soluble impurities from the surface of diatomaceous earth; purification requires sufficient time, and 0.5 to 2 hours provides enough time for cleaning to ensure that impurities can be fully removed. Too high an oscillation frequency and / or too long an oscillation time will cause the structure of diatomaceous earth to be destroyed.

[0047] In the present invention, after each water bath shaker cleaning is completed, the suspension is allowed to stand for 10 to 20 minutes, such as 15 minutes, and then the suspension is poured out.

[0048] Preferably, when the diatomaceous earth raw material is washed until there is no foam suspension, the diatomaceous earth is filtered and dried using a water circulation vacuum pump and dried at 100° C. to 120° C. for 1 to 3 hours.

[0049] Among them, the water content in the diatomite is reduced by filtration, thereby shortening the drying time and improving the drying efficiency; more importantly, it further removes the fine impurities that may remain and improves the purity of the diatomite. Drying helps to maintain the structure of the diatomite and avoid pore collapse caused by too fast evaporation of water during high temperature treatment.

[0050] In step 1, the calcination temperature is 450-550°C, preferably 480-520°C, for example 500°C.

[0051] In the present invention, calcination is used to remove organic matter and water in the pores of diatomite and increase its specific surface area. The structure of diatomite is relatively fragile, and high temperature may cause its pore structure to collapse; too low a temperature cannot completely decompose organic matter. Within the above temperature range, the organic matter in diatomite can be effectively decomposed and removed without destroying the structure of diatomite.

[0052] In step 1, the calcination time is 1 to 3 hours, preferably 1.5 to 2.5 hours, for example 2 hours.

[0053] In the present invention, a sufficiently long calcination time can ensure that the organic matter in the diatomite is fully decomposed and removed, but a too long calcination time may cause irreversible damage to the structure of the diatomite. 1 to 3 hours balances the need to remove organic matter and moisture with maintaining the stability of the diatomite structure.

[0054] Step 2, acid-washing the activated diatomaceous earth to obtain acidified diatomaceous earth.

[0055] In step 2, a large amount of rock debris still remains on the surface of the activated diatomite obtained after calcination, and some pores are still blocked. After acid washing, the metal oxides or mineral impurities in the pore structure are dissolved or chemically reacted, thereby improving the purity and adsorption capacity of the activated diatomite.

[0056] Furthermore, the pickling uses hydrochloric acid, sulfuric acid or nitric acid, preferably hydrochloric acid.

[0057] Among them, hydrochloric acid, sulfuric acid and nitric acid are all strong acids that can effectively dissolve a variety of metal oxides and mineral impurities, thereby removing blockages in the pores of activated diatomite. Hydrochloric acid has a certain volatility, which means that during the pickling process, hydrochloric acid can be easily removed from the surface and pores of activated diatomite; in addition, hydrochloric acid will not introduce new impurities that are difficult to remove during the pickling process, thereby maintaining the purity of the activated diatomite.

[0058] In step 2, H + The concentration is 4 to 6 mol / L, preferably 5 to 5.5 mol / L, for example 5.5 mol / L.

[0059] Among them, 4 to 6 mol / L H + The concentration is helpful to clean the deep impurities of the activated diatomaceous earth, but it also avoids the destruction of the activated diatomaceous earth structure caused by excessively high concentration of hydrogen ions.

[0060] In step 2, the pickling time is 1 to 3 hours, preferably 1.5 to 2.5 hours, for example 2 hours.

[0061] Among them, 1 to 3 hours is sufficient to ensure that the acid fully reacts with the metal oxides and mineral impurities in the activated diatomite, thereby effectively removing these impurities. If the pickling time is too long, the structure of the activated diatomite may be damaged. 1 to 3 hours helps to avoid excessive pickling.

[0062] In step 2, after the acid wash is completed, the upper layer of acid liquid is removed. It is preferred to repeatedly wash the acidified diatomite with water for 3 to 4 times to remove the unreacted acid liquid that may remain on the surface and in the pores of the activated diatomite. This is because the residual acid liquid may react with the alkali used in the subsequent alkali treatment to neutralize, which will not only reduce the efficiency of the alkali treatment, but also may cause unnecessary chemical reactions and affect the quality of the final product.

[0063] Step 3, treating the acidified diatomaceous earth with alkali to obtain alkali-adjusted diatomaceous earth.

[0064] In step 3, the alkali treatment of the acidified diatomite further removes the residual metal ions and harmful components, and improves the purity and functionality of the acidified diatomite. The inventors have found that during the alkali treatment, the acidified diatomite reacts with the alkali to dissolve part of SiO2, thereby increasing the pores of the acidified diatomite. Therefore, the pore structure of the alkali-treated diatomite shows a phenomenon in which the pore size gradually increases from the inner layer to the outer layer.

[0065] In step 3, the alkali used for the alkali treatment can be any one of sodium hydroxide, potassium hydroxide and magnesium hydroxide, preferably sodium hydroxide.

[0066] Among them, sodium hydroxide, potassium hydroxide, and magnesium hydroxide can effectively react with residual metal ions and harmful components in acidified diatomaceous earth to form soluble complexes or precipitations, thereby improving the purity of diatomaceous earth. In particular, sodium hydroxide has a high solubility in water, and can be quickly and evenly distributed in the pores of diatomaceous earth, fully contacting and reacting with the substances in the pores; it is relatively stable and economical during the treatment process, easy to obtain, and suitable for large-scale industrial applications; finally, sodium ions help to enhance the chemical stability of diatomaceous earth and improve its applicability under different environmental conditions.

[0067] In step 3, OH - The concentration is 1-2 mol / L, preferably 1-1.5 mol / L, for example 1.25 mol / L.

[0068] Among them, although a higher OH- concentration can accelerate the reaction, it may also damage the structure of diatomite and cause the destruction of its pore structure. 1-2 mol / L can ensure the treatment effect and reduce the potential damage to the diatomite structure.

[0069] In step 3, the alkali treatment time is 3 to 8 minutes, preferably 4 to 6 minutes, for example 5 minutes.

[0070] Among them, the appropriate alkali treatment time helps to partially dissolve SiO2 in the acidified diatomite, increase the pores, and optimize the pore structure without excessively damaging the original structure of the acidified diatomite. 3 to 8 minutes is enough to ensure that OH- fully reacts with the residual metal ions and harmful components in the acidified diatomite to form precipitation or complexes, thereby effectively removing these impurities.

[0071] Preferably, the alkali-conditioned diatomaceous earth is immediately vacuum filtered after the alkali treatment is completed to quickly separate the alkali-conditioned diatomaceous earth from the alkali, thereby preventing the alkali-conditioned diatomaceous earth from staying in the alkaline environment for too long, thereby causing secondary reactions or structural damage.

[0072] The inventors have found that if acid washing is performed before calcination, the structure of the modified diatomite obtained will be damaged or deformed. This is because acid washing will remove some important mineral components and microstructures, resulting in a decrease in the physical strength and stability of the diatomite, making it more likely to cause structural damage or deformation during the subsequent calcination process; and the residue after acid washing reacts with the diatomite to form an unfavorable chemical phase, further reducing its performance. Calcination usually requires high-temperature treatment, and the acid-washed diatomite may encounter a greater risk of chemical reactions at high temperatures, resulting in the formation of new phases or substances, affecting the properties and application effects of the final product.

[0073] In the present invention, modified diatomite is prepared by calcination, acid washing and alkali washing in sequence. The calcination improves the physical and chemical stability of the diatomite, improves its pore structure, and removes organic matter and moisture by calcination, which helps to increase its specific surface area. The subsequent acid washing can effectively remove residual metal ions and impurities, improve the purity and adsorption capacity of the diatomite, and further enhance its functional characteristics. On this basis, alkali treatment is used to remove any residual metal ions and harmful components, and improve the purity and functionality of the diatomite. This sequence removes a large amount of impurities in the diatomite, expands the pores, and can be used for adsorption and separation to the maximum extent.

[0074] Step 4, drying the alkali-adjusted diatomaceous earth to obtain modified diatomaceous earth.

[0075] In step 4, the natural drying process has the risk of uneven drying, residual moisture, and exposure to air, which increases the adsorption of pollutants, thereby reducing the quality of the modified diatomite, its adsorption capacity and filtration performance. Removing moisture from the alkali-adjusted diatomite by drying helps stabilize its pore structure and physical form.

[0076] In step 4, the drying temperature is 100° C. to 120° C., preferably 102° C. to 108° C., for example 105° C.; the drying time is 1 to 3 hours, preferably 1.5 to 2.5 hours, for example 2 hours.

[0077] On the other hand, according to the modified diatomaceous earth prepared by the method according to the first aspect provided by the present invention, the pore size of the modified diatomaceous earth gradually increases from the inner layer to the outer layer, and the pore size of the inner layer is 0.18-0.22 microns, for example, 0.2 microns, and the pore size of the outer layer is 0.58-0.63 microns, for example, 0.6 microns.

[0078] The present invention is further described below through specific examples, but these examples are merely exemplary and do not constitute any limitation to the scope of protection of the present invention.

[0079] Example 1

[0080] (1) Mix diatomaceous earth and deionized water in a conical flask, place the conical flask in a room temperature water bath shaker, set the shaker to oscillate left and right, the oscillation frequency is 200 times / minute, and the oscillation time is 1 hour. After the water bath shaker is cleaned, place the conical flask for 15 minutes, then pour out the suspension, and repeat the above steps until there is no foam suspension; then use a water circulation vacuum pump to filter the diatomaceous earth and dry it at 105° C. for 1.5 hours; put the dried diatomaceous earth in a crucible, place it in a box-type resistance furnace at 500° C. and calcine it for 2 hours, and then use crucible tongs to take it out to obtain activated diatomaceous earth;

[0081] (2) Add hydrochloric acid to the activated diatomite in an amount sufficient to completely submerge the activated diatomite. + The concentration is 5.5 mol / L, and the mixture is allowed to stand for 2 hours under this condition; then, the upper layer of hydrochloric acid is poured out, and the mixture is repeatedly washed with deionized water for 3 to 4 times to obtain acidified diatomaceous earth;

[0082] (3) The acidified diatomaceous earth is treated with OH - Treat with 1.25 mol / L NaOH for 5 min, and then immediately vacuum filter to obtain alkali-adjusted diatomaceous earth;

[0083] (4) Drying the alkali-adjusted diatomaceous earth at 105° C. for 2 h to obtain modified diatomaceous earth.

[0084] Figure 1 The SEM characterization image of the raw material diatomite at 3000 times is shown, and it can be seen that its basic structure is disc-shaped and cylindrical, and the disc-shaped pore structure is obvious; Figure 2 The SEM characterization image of the raw material diatomite at 8000 times is shown, combined with Figure 1 and Figure 2 It can be seen that more debris is attached to its surface, and some of the circular holes on the surface are blocked by impurities.

[0085] Figure 3 The SEM characterization image of the activated diatomite obtained by calcination at 2000 times is shown. Figure 4 The SEM characterization picture of the activated diatomite obtained by calcination at 3000 times is shown, combined with Figure 3 and Figure 4 It can be seen that the organic matter in the pores of the raw diatomite is removed by calcination, but a large amount of rock debris still remains on the surface of the calcined material and some pores are still blocked.

[0086] Figure 5 The SEM characterization image of alkali-adjusted diatomaceous earth at 2000 times is shown. Figure 6The SEM characterization image of the alkali-adjusted diatomite at 8000 times magnification is shown. It can be seen that the surface cleanliness of the alkali-adjusted diatomite disc has been greatly improved, and some blocked pores have also been cleared. This is because the metal oxides or mineral impurities in the pore structure are dissolved or chemically reacted in the hydrochloric acid environment; the pore structure of the alkali-adjusted diatomite shows a phenomenon of gradually increasing pore size from the inner layer to the outer layer. This change is mainly due to the fact that its main component, silicon dioxide, reacts with sodium hydroxide (NaOH) during alkaline washing, causing part of SiO2 to dissolve, thereby increasing its pores. The inner pore size is 0.2 microns, and the outer pore size is 0.6 microns.

[0087] Comparative Example 1

[0088] The diatomite was modified in a similar manner to Example 1, except that no alkali treatment was performed. The specific steps were as follows:

[0089] (1) Mix diatomaceous earth and deionized water in a conical flask, place the conical flask in a room temperature water bath shaker, set the shaker to oscillate left and right, the oscillation frequency is 200 times / minute, and the oscillation time is 1 hour. After the water bath shaker is cleaned, place the conical flask for 15 minutes, then pour out the suspension, and repeat the above steps until there is no foam suspension; then use a water circulation vacuum pump to filter the diatomaceous earth and dry it at 105° C. for 1.5 hours; put the dried diatomaceous earth in a crucible, place it in a box-type resistance furnace at 500° C. and calcine it for 2 hours, and then use crucible tongs to take it out to obtain activated diatomaceous earth;

[0090] (2) Add hydrochloric acid to the activated diatomite in an amount sufficient to completely submerge the activated diatomite. + The concentration is 5.5 mol / L, and the mixture is allowed to stand for 2 hours under this condition; then, the upper layer of hydrochloric acid is poured out, and the mixture is repeatedly washed with deionized water for 3 to 4 times to obtain acidified diatomaceous earth;

[0091] (3) The acidified diatomaceous earth is washed with water until it is neutral, then vacuum filtered, and dried at 105° C. to constant weight to obtain modified diatomaceous earth.

[0092] Compared with Example 1, the surface of the modified diatomite disc that has not been alkali washed has some mineral impurities such as iron and aluminum, and there is obvious pore clogging, which affects the purity of the material and reduces the adsorption performance and filtration capacity of the material.

[0093] Comparative Example 2

[0094] The diatomite was modified in a similar manner to Example 1, except that no acid treatment was performed. The specific steps were:

[0095] (1) Mix diatomaceous earth and deionized water in a conical flask, place the conical flask in a room temperature water bath shaker, set the shaker to oscillate left and right, the oscillation frequency is 200 times / minute, and the oscillation time is 1 hour. After the water bath shaker is cleaned, place the conical flask for 15 minutes, then pour out the suspension, and repeat the above steps until there is no foam suspension; then use a water circulation vacuum pump to filter the diatomaceous earth and dry it at 105° C. for 1.5 hours; put the dried diatomaceous earth in a crucible, place it in a box-type resistance furnace at 500° C. and calcine it for 2 hours, and then use crucible tongs to take it out to obtain activated diatomaceous earth;

[0096] (2) Add sodium hydroxide to the activated diatomite in an amount that completely submerges the activated diatomite. - The concentration is 1.25 mol / s, and the mixture is allowed to stand for 2 hours under this condition; then, the upper layer of sodium hydroxide is poured out, and the mixture is repeatedly washed with deionized water for 3 to 4 times to obtain alkalinized diatomaceous earth;

[0097] (3) The alkalized diatomaceous earth is washed with water until it is neutral, then vacuum filtered, and dried at 105° C. to constant weight to obtain modified diatomaceous earth.

[0098] Compared with Example 1, the modified diatomite prepared has inorganic impurities such as calcium, aluminum, etc., as well as some free inorganic acid salts and acidic substances in the diatomite that has not been acid-washed, which does not meet the use standards, and the residual impurities will also affect its stability and service life; in addition, the pores on the surface of the diatomite disc that has not been acid-washed are relatively rough, and the pore micromorphology is uneven, which will reduce its adsorption and filtration effects.

[0099] The present invention has been described in detail above in conjunction with preferred embodiments and exemplary examples. However, it should be noted that these specific embodiments are only illustrative explanations of the present invention and do not constitute any limitation on the protection scope of the present invention. Without exceeding the spirit and protection scope of the present invention, various improvements, equivalent substitutions or modifications may be made to the technical content of the present invention and its embodiments, all of which fall within the protection scope of the present invention. The protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing modified diatomite, characterized in that: The method comprises: Step 1, calcining diatomite raw material to obtain activated diatomite; Step 2, acid-washing the activated diatomite to obtain acidified diatomite; Step 3, treating the acidified diatomaceous earth with alkali to obtain alkali-adjusted diatomaceous earth; Step 4, drying the alkali-adjusted diatomaceous earth to obtain modified diatomaceous earth.

2. The method according to claim 1, characterized in that: Preferably, in step 1, the calcination temperature is 450-550°C.

3. The method according to claim 2, characterized in that The calcination temperature is 480-520°C.

4. The method according to claim 1, characterized in that: In step 1, the calcination time is 1 to 3 hours.

5. The method according to claim 4, characterized in that The calcination time is 1.5 to 2.5 hours.

6. The method according to claim 1, characterized in that In step 2, the pickling is carried out using hydrochloric acid, sulfuric acid or nitric acid.

7. The method according to claim 1, characterized in that In step 3, the alkali used in the alkali treatment is sodium hydroxide, potassium hydroxide or magnesium hydroxide.

8. The method according to claim 1, characterized in that In step 4, the drying temperature is 100°C to 120°C.

9. Modified diatomaceous earth obtained according to the method according to any one of claims 1 to 8.

10. The method according to claim 9, characterized in that The pore size of the modified diatomaceous earth gradually increases from the inner layer to the outer layer.

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