Isolation material and its application

Abstract

The present invention provides an isolation material and its application, wherein the isolation material comprises a first isolation layer and a second isolation layer stacked in the thickness direction; the median particle size D1 of particles in the first isolation layer and the median particle size D2 of particles in the second isolation layer satisfy: 2mm≤D1-D2≤2cm; and / or the pH value of the first isolation layer is 9-11, and the pH value of the second isolation layer is 8-10. The isolation material provided by the present invention limits the median particle size of particles in the first isolation layer and the second isolation layer, so that a capillary retardation effect is formed between the first isolation layer and the second isolation layer, thereby increasing the water storage capacity of the isolation material and thus improving the anti-seepage effect.

Description

Technical Field

[0001] The invention belongs to the technical field of materials, and in particular relates to an isolation material and application thereof. Background Art

[0002] Phosphogypsum is a byproduct of wet phosphoric acid production, that is, phosphoric acid and phosphogypsum are generated after the reaction of phosphate rock and sulfuric acid. The main component of phosphogypsum is calcium sulfate dihydrate (CaSO4·2H2O). In addition, it also contains a small amount of impurities, mainly including phosphorus, fluorine, silicon dioxide, organic matter, etc. In the existing phosphogypsum depots where phosphogypsum is mainly stored, phosphogypsum continues to expose a variety of serious environmental problems during long-term storage. If the storage conditions are not properly handled, the soluble phosphorus, fluorine and heavy metals in the phosphogypsum will be washed into the soil, groundwater and surface water with rainwater. Since phosphogypsum is a byproduct of wet phosphoric acid production, the phosphogypsum leachate is usually highly acidic with a pH value of 1.7-3.5, which causes serious harm to the surrounding environment. In order to prevent leaching pollution of the phosphogypsum depot, it is often necessary to lay isolation layers at the bottom and top of the depot respectively. The upper isolation layer is used to directly isolate rainwater and reduce the leaching amount, and the lower isolation layer is used to prevent the infiltrated rainwater from further infiltrating and polluting the groundwater.

[0003] The commonly used isolation materials in the prior art mainly include geomembranes and clay. Among them, geomembranes have the following disadvantages: they are easily pierced by sharp stones; they have aging problems and may be impacted by chemicals and microorganisms; contact openings are prone to occur at the joints during the construction process; they have poor shear resistance, and the film may be damaged due to uneven pressure when the upper covering soil is compacted; they are difficult to degrade and easily cause plastic pollution. The use of clay can solve the above problems, but it requires the consumption of a large amount of clay resources and is costly. In addition, the clay covering layer is prone to shrinkage, frost heave or cracking during long-term service. Over time, the permeability coefficient will increase significantly, and the anti-seepage effect will gradually deteriorate. In addition, the clay has limited water storage capacity and is prone to saturation and leakage in extreme rainfall weather. Therefore, it is urgent to develop an isolation material with strong water storage capacity and good anti-seepage effect to help prevent and control pollution in phosphogypsum depots. Summary of the invention

[0004] The main purpose of the present invention is to provide an isolation material, which has a good anti-seepage effect.

[0005] The present invention also provides a method for preventing seepage in a phosphogypsum reservoir. Since the above-mentioned isolation material is used, the anti-seepage effect can be improved.

[0006] In a first aspect, the present invention provides an isolation material, comprising a first isolation layer and a second isolation layer stacked in a thickness direction;

[0007] The median particle size D1 of the particles in the first isolation layer and the median particle size D2 of the particles in the second isolation layer satisfy: 2mm≤D1-D2≤2cm; and / or,

[0008] The pH value of the first isolation layer is 9-11, and the pH value of the second isolation layer is 8-10.

[0009] In the isolation material as described above, the average particle size of the particles in the first isolation layer is greater than 3 mm, and the median particle size D1 is 5 mm<D1<20 mm.

[0010] In the above-mentioned isolation material, the porosity S of the first isolation layer is 15%<S<50%.

[0011] In the isolation material as described above, the thickness ratio of the first isolation layer to the second isolation layer is 1:1.5-2.

[0012] In the above-mentioned insulating material, the moisture content of the second insulating layer is less than 15%, and the saturated moisture content is greater than 50%.

[0013] The isolation material as described above, wherein the first isolation layer is obtained by granulating and compacting a first mixed system, wherein the first mixed system comprises, by weight: 40-60 parts of phosphogypsum, 10-20 parts of fly ash, 5-10 parts of calcite, 1-3 parts of slaked lime, and 20-30 parts of calcium-based bentonite;

[0014] The second isolation layer is obtained by compacting the second mixed system, wherein the second mixed system comprises, by weight: 30-50 parts of river and lake sediment, 20-30 parts of fly ash, 10-20 parts of calcite, and 10-20 parts of expansive soil or loess;

[0015] Wherein, the average particle size of phosphogypsum in the first mixed system is 0.05-1 mm, and the median particle size is greater than 0.1 mm; the average particle size of fly ash, calcite, slaked lime, and calcium-based bentonite is less than 0.2 mm;

[0016] The average particle size of river and lake bottom mud in the second mixed system is less than 100 μm, and the median particle size is less than 50 μm; the average particle size of fly ash is less than 80 μm; and the average particle size of calcite, expansive soil or loess is less than 10 μm.

[0017] The isolation material as described above, wherein the water content of the river and lake bottom mud is less than 30%, and the saturated water content is greater than 70%; and / or,

[0018] The moisture content of the expansive soil is less than 10%, and the expansion rate is greater than 50%.

[0019] The isolation material as described above is prepared by a method comprising the following process:

[0020] 1) granulating a first mixed system including phosphogypsum, fly ash, calcite, slaked lime, and calcium-based bentonite to obtain a first isolation layer precursor;

[0021] 2) performing a first compaction treatment on the first isolation layer precursor to obtain the first isolation layer;

[0022] 3) placing a second mixed system including river and lake sediment, fly ash, calcite, expansive soil or loess on any surface of the first isolation layer in the thickness direction, and performing a second compaction treatment to obtain an isolation material including a first isolation layer and a second isolation layer stacked in the thickness direction.

[0023] The insulating material as described above, wherein the thickness of the first insulating layer precursor is 30-50 cm, and the thickness of the first insulating layer is 27-47 cm; and / or,

[0024] The thickness of the second mixed system is 60-80 cm, and the thickness of the second isolation layer is 50-70 cm; and / or,

[0025] The thickness of the insulating material is 80-110 cm.

[0026] In a second aspect, the present invention provides a method for preventing seepage of a phosphogypsum reservoir, using the above-mentioned isolation material to pave the bottom and top of the phosphogypsum reservoir.

[0027] The isolation material provided by the present invention limits the median particle size of particles in the first isolation layer and the second isolation layer, so that a capillary blocking effect is formed between the first isolation layer and the second isolation layer, thereby improving the anti-seepage effect of the isolation material. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In a first aspect, the present invention provides an isolation material, comprising a first isolation layer and a second isolation layer stacked in a thickness direction;

[0030] The median particle size D1 of the particles in the first isolation layer and the median particle size D2 of the particles in the second isolation layer satisfy: 2mm≤D1-D2≤2cm; and / or,

[0031] The pH value of the first isolation layer is 9-11, and the pH value of the second isolation layer is 8-10.

[0032] The difference between the median particle size D1 of the particles in the first isolation layer and the median particle size D2 of the particles in the second isolation layer of the present invention satisfies: 2mm≤D1-D2≤2cm. In a suitable range, a capillary retardation effect can be formed at the interface of the first isolation layer and the second isolation layer, and the hydraulic conductivity between the two layers is low, which can increase the maximum water storage capacity of the isolation material and enhance the anti-seepage effect. In specific use, the second isolation layer with a smaller particle size can be placed on the upper layer. During the continuous filling of the upper second isolation layer with water, it is difficult for the water in the pores to continue to infiltrate through the interface of the first isolation layer and the second isolation layer, thereby reducing the risk of leaching of phosphogypsum.

[0033] In the present invention, the pH value of the first isolation layer is 9-11, and the pH value of the second isolation layer is 8-10, which can neutralize the strong acidity of the phosphogypsum leachate and further reduce the risk of leaching.

[0034] The isolation material provided by the present invention limits the median particle size of particles in the first isolation layer and the second isolation layer, so that a capillary blocking effect is formed between the first isolation layer and the second isolation layer, thereby improving the anti-seepage effect of the isolation material.

[0035] In some embodiments of the present invention, the average particle size of the particles in the first isolation layer is greater than 3 mm, and the median particle size D1 is 5 mm < D1 < 20 mm.

[0036] The present invention defines the average particle size of the particles in the first isolation layer as >3 mm, and the median particle size D1 as 5 mm <D1 <20 mm, which is conducive to forming a particle size difference between the particles of the first isolation layer and the second isolation layer, thereby forming a capillary blocking effect at the interface of the first isolation layer and the second isolation layer, and improving the anti-seepage effect of the isolation material. In addition, it can also provide a better support effect to prevent the isolation material from being deformed or damaged when subjected to external force, thereby extending its service life and stability.

[0037] In some embodiments of the present invention, the porosity S of the first isolation layer is 15%<S<50%.

[0038] The porosity S of the first isolation layer is limited in the present invention to 15%<S<50%, which is within a suitable range. The capillary blocking effect formed between the first isolation layer and the second isolation layer can be further improved, thereby improving the anti-seepage effect of the isolation material. In addition, the suitable porosity is also beneficial to improving the structural stability and strength of the isolation material.

[0039] In some embodiments of the present invention, the thickness ratio of the first isolation layer to the second isolation layer is 1:1.5-2.

[0040] The appropriate thickness ratio of the first isolation layer and the second isolation layer in the present invention can further improve the capillary barrier effect formed between the first isolation layer and the second isolation layer. That is, on the one hand, it can avoid the first isolation layer being too thin to form a capillary barrier effect and reduce the penetration effect of the isolation material; it can also avoid the first isolation layer being too thick to cause unnecessary waste and increase material costs.

[0041] In some embodiments of the present invention, the moisture content of the second isolation layer is less than 15%, and the saturated moisture content is greater than 50%.

[0042] The present invention limits the moisture content of the second isolation layer to less than 15%, which is within a lower range, and the saturated moisture content to greater than 50%, which is within a higher range. This allows the second isolation layer to absorb water to the maximum extent, thereby enhancing the water storage capacity of the second isolation layer and preventing excessive water from seeping into the first isolation layer. This can enhance the anti-seepage effect of the isolation material and solve the problem of cracking of traditional clay isolation materials.

[0043] In some embodiments of the present invention, the first isolation layer is obtained by granulating and compacting a first mixed system, wherein the first mixed system comprises, by weight: 40-60 parts of phosphogypsum, 10-20 parts of fly ash, 5-10 parts of calcite, 1-3 parts of slaked lime, and 20-30 parts of calcium-based bentonite;

[0044] The second isolation layer is obtained by compacting the second mixed system, wherein the second mixed system comprises, by weight: 30-50 parts of river and lake sediment, 20-30 parts of fly ash, 10-20 parts of calcite, and 10-20 parts of expansive soil or loess;

[0045] Wherein, the average particle size of phosphogypsum in the first mixed system is 0.05-1 mm, and the median particle size is greater than 0.1 mm; the average particle size of fly ash, calcite, slaked lime, and calcium-based bentonite is less than 0.2 mm;

[0046] The average particle size of river and lake bottom mud in the second mixed system is less than 100 μm, and the median particle size is less than 50 μm; the average particle size of fly ash is less than 80 μm; and the average particle size of calcite, expansive soil or loess is less than 10 μm.

[0047] The first isolation layer of the present invention includes calcite and slaked lime, which can act as reactants to induce precipitation and cementation reactions of materials in the first isolation layer to generate substances such as calcium silicate and calcium phosphate, stabilize the particles, and solidify the soluble phosphate therein to prevent leaching; on the other hand, they can react with acidic substances in phosphogypsum, which can not only prevent strong acid from destroying the stability of the isolation layer, but also generate a large amount of CO2 to form gas micropores and enhance the capillary blocking effect between the second isolation layer. The second isolation layer includes an alkaline buffer substance rich in Ca components, namely calcite, which can react with the phosphate in the lower phosphogypsum to form calcium phosphate after flushing, further reducing the risk of phosphorus leaching, which is a preventive measure.

[0048] The present invention limits the average particle size and median particle size of the components contained in the first isolation layer and the second isolation layer, so that the first isolation layer forms particles with larger particle sizes and the second isolation layer forms particles with smaller particle sizes, which is conducive to the median particle size D1 of the particles in the first isolation layer and the median particle size D2 of the particles in the second isolation layer satisfying: 2mm≤D1-D2≤2cm, thereby forming a capillary barrier effect at the interface between the first isolation layer and the second isolation layer, increasing the maximum water storage capacity of the isolation material and enhancing the anti-seepage effect.

[0049] The main materials used for the isolation material provided by the present invention are solid waste materials such as river and lake sediments, fly ash, phosphogypsum, and expansive soil, which can be obtained locally to reduce material costs.

[0050] The present invention limits the composition of the materials contained in the first isolation layer and the second isolation layer and the particle size of each material, which is conducive to forming a capillary blocking effect at the interface of the first isolation layer and the second isolation layer, increasing the water storage capacity of the isolation material and enhancing the anti-seepage effect. In addition, the cost of the material can also be reduced.

[0051] In some embodiments of the present invention, the water content of the river and lake bottom mud is less than 30%, and the saturated water content is greater than 70%; and / or,

[0052] The moisture content of the expansive soil is less than 10%, and the expansion rate is greater than 50%.

[0053] The river and lake bottom mud in the present invention has a lower water content and a higher saturated water content, which can store more leached rainwater; the expansive soil uses its shrinkage and swelling characteristics to gradually expand when it rains, further increasing its water storage capacity and solving the problem of cracking of the traditional clay cover layer, effectively preventing rainwater from seeping along the cracks. In addition, the organic matter content of the river and lake bottom mud is less than 2%, which can prevent the decomposition of organic matter to produce gas that affects the strength of the isolation material.

[0054] In some embodiments of the present invention, the isolation material is prepared by a method comprising the following process:

[0055] 1) granulating a first mixed system including phosphogypsum, fly ash, calcite, slaked lime, and calcium-based bentonite to obtain a first isolation layer precursor;

[0056] 2) performing a first compaction treatment on the first isolation layer precursor to obtain the first isolation layer;

[0057] 3) placing a second mixed system including river and lake sediment, fly ash, calcite, expansive soil or loess on any surface of the first isolation layer in the thickness direction, and performing a second compaction treatment to obtain an isolation material including a first isolation layer and a second isolation layer stacked in the thickness direction.

[0058] The insulating material of the present invention is obtained by double compaction treatment.

[0059] Specifically, in step 1), the first mixed system including phosphogypsum, fly ash, calcite, slaked lime and calcium-based bentonite is mixed evenly and then placed in a granulator for granulation to form a first isolation layer precursor, wherein the first isolation layer precursor is spherical or ellipsoidal, has a certain hardness, a barrel pressure strength>2Mpa, and a bulk density of 800-1300kg / m 3 .

[0060] In step 2), after the surface of the first isolation layer precursor is watered at a rate of 100-200 kg per square meter, a first compaction treatment is performed and the reaction lasts for 5-10 days to form the first isolation layer.

[0061] In step 3), a second mixed system including river and lake sediment, fly ash, calcite, expansive soil or loess is placed on any surface of the first isolation layer in the thickness direction, and the second mixed system is subjected to a second compaction treatment to form a second isolation layer. At this time, the first isolation layer and the second isolation layer are tightly combined to form an isolation material.

[0062] The insulating material prepared by the preparation method of the present invention has a specific material composition, can form a capillary blocking effect between the first insulating layer and the second insulating layer, can improve the anti-seepage effect of the insulating material, and the method is simple and easy to implement with low cost.

[0063] In some embodiments of the present invention, the thickness of the first isolation layer precursor is 30-50 cm, and the thickness of the first isolation layer is 27-47 cm; and / or,

[0064] The thickness of the second mixed system is 60-80 cm, and the thickness of the second isolation layer is 50-70 cm; and / or,

[0065] The thickness of the insulating material is 80-110 cm.

[0066] The thickness of the first isolation layer precursor is limited in the present invention, and the pressure of the first compaction treatment is within an appropriate range, so that the particles of the first isolation layer can be bonded to each other, have a distinct honeycomb pore structure, increase the overall pore complexity, form a relatively stable structure, and be conducive to the formation of a capillary retardation effect. The moisture content of the first isolation layer is less than 20%.

[0067] The thickness of the second mixed system is limited in the present invention, and the pressure of the second compaction treatment is within an appropriate range, so that the second isolation layer has an appropriate particle size, and the appropriate thicknesses of the first isolation layer and the second isolation layer can further enhance the capillary blocking effect and improve the anti-seepage effect of the isolation material.

[0068] The thickness of the insulating material of the present invention can make it have high strength and stability, and can withstand greater pressure and impact. And the maximum water storage capacity of the prepared insulating material can be increased by more than 90%.

[0069] In a second aspect, the present invention provides a method for preventing seepage of a phosphogypsum reservoir, using the above-mentioned isolation material to pave the bottom and top of the phosphogypsum reservoir.

[0070] The method for preventing the seepage of the phosphogypsum reservoir in the present invention can be to lay the above-mentioned isolation material at the bottom and top of the phosphogypsum reservoir, the top isolation material is used to directly isolate rainwater and reduce the leaching amount; the bottom isolation material is used to prevent the infiltrated rainwater from further infiltrating and polluting the groundwater. The method for preventing the seepage of the phosphogypsum reservoir in the present invention has a good anti-seepage effect.

[0071] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0072] Example 1

[0073] The method for preparing the isolation material of this embodiment comprises the following steps:

[0074] 1) 50 parts by mass of coarse-grained phosphogypsum, 15 parts by mass of fly ash, 8 parts by mass of calcite, 2 parts by mass of slaked lime, and 25 parts by mass of calcium-based bentonite are mixed evenly, and then placed in a granulator for granulation to form a first isolation layer precursor; wherein the average particle size of the phosphogypsum is 0.12 mm, the median particle size is 0.26 mm, the average particle size of the fly ash is 0.07 mm, the average particle size of the calcite is 0.13 mm, the average particle size of the slaked lime is 0.09 mm, and the average particle size of the calcium-based bentonite is 0.15 mm;

[0075] 2) A 40.5 cm thick first isolation layer precursor is covered on the top and bottom of the phosphogypsum reservoir, and after water is sprinkled on the surface at a rate of 120 kg per square meter, a first compaction treatment is carried out and the reaction lasts for 7 days to form a 35.2 cm first isolation layer; wherein, the average particle size of the particles in the first isolation layer is 5.6 mm, the median particle size D1 is 7.3 mm, the pH value is 10.1, and the porosity is 39.2%.

[0076] 3) Take 35 parts by mass of river and lake sediment, 25 parts by mass of fly ash, 15 parts by mass of calcite and 25 parts by mass of expansive soil, mix them evenly to form a second mixed system, wherein the average particle size of the river and lake sediment is 52.2 μm, the median particle size is 31.7 μm, the moisture content is 26.1%, the saturated moisture content is 83.5%, the average particle size of the fly ash is 49.1 μm, the average particle size of the calcite is 3.1 μm, the average particle size of the expansive soil is 5.7 μm, the moisture content is 6.3%, the expansion rate is 73.2%, and the thickness of the second mixed system is 75.3 cm. The second mixed system is placed on any surface of the first isolation layer in the thickness direction, and a second compaction treatment is performed to form an isolation material including a first isolation layer and a second isolation layer stacked in the thickness direction; wherein the thickness of the second isolation layer is 61.2 cm, the median particle size D2 of the particles in the second isolation layer is 0.042 mm, the pH value is 9.2, the water content is 14.3%, and the saturated water content is 59.6%. The overall thickness of the isolation material is 95.2 cm. In the saturated rainfall leaching test, the pH value of the bottom phosphogypsum leaching solution was measured to be 7.2, and the total phosphorus content was 0.92 mg / L.

[0077] Example 2

[0078] The preparation method of the isolation material of Example 2 is basically the same as that of Example 1, except that the median particle size D1 of the particles in the first isolation layer is 5.4 mm, the average particle size is 4.1 mm, the median particle size D2 of the particles in the second isolation layer is 0.059 mm, and D1-D2 is 5.341 mm.

[0079] Example 3

[0080] The preparation method of the isolation material of Example 3 is basically the same as that of Example 1, except that the first isolation layer precursor is uniformly mixed by 55 parts by mass of coarse-grained phosphogypsum, 18 parts by mass of fly ash, 5 parts by mass of calcite, 2 parts by mass of slaked lime, and 30 parts by mass of calcium-based bentonite, and then placed in a granulator for granulation. The average particle size of the first isolation layer is 5.3 mm, the median particle size D1 is 6.9 mm, the pH value is 9.4, and the porosity is 43.2%.

[0081] Example 4

[0082] The preparation method of the isolation material of Example 4 is basically the same as that of Example 1, except that the second mixed system consists of 30 parts by mass of river and lake sediment, 30 parts by mass of fly ash, 20 parts by mass of calcite and 20 parts by mass of expansive soil. The moisture content of the second isolation layer is 13.3%, and the saturated moisture content is 53.5%.

[0083] Example 5

[0084] The preparation method of the isolation material of Example 5 is basically the same as that of Example 1, except that the moisture content of the expansive soil is 7.9% and the expansion rate is 57.6%.

[0085] Example 6

[0086] The preparation methods of the isolation materials of Example 6 and Example 1 are basically the same, except that the thickness of the first isolation layer precursor is 40.5 cm, and the first compaction treatment is not performed.

[0087] Example 7

[0088] The preparation methods of the isolation materials of Example 7 and Example 1 are basically the same, except that the thickness of the second mixed system is 55.3 cm, and after the second compaction treatment, the thickness of the second isolation layer is 46.1 cm.

[0089] Comparative Example 1

[0090] The preparation methods of the insulating materials of this comparative example and Example 1 are basically the same, except that the insulating material does not include the first insulating layer, but only has the second insulating layer with a thickness of 95.2 cm.

[0091] Comparative Example 2

[0092] The preparation method of the isolation material of this comparative example is basically the same as that of Example 1, except that the median particle size D1 of the particles in the first isolation layer is 1.90 mm, the median particle size D2 of the particles in the second isolation layer is 0.13 mm, and D1-D2 is 1.77 mm.

[0093] Comparative Example 3

[0094] The preparation method of the isolation material of this comparative example is basically the same as that of Example 1, except that the median particle size D1 of the particles in the first isolation layer is 3.22 cm, the median particle size D2 of the particles in the second isolation layer is 1.56 mm, and D1-D2 is 30.6 mm.

[0095] Comparative Example 4

[0096] The isolation material of this comparative example is clay, with a moisture content of 12.7%, a laying thickness of 115.2 cm, and compacted to a thickness of 95.2 cm.

[0097] Comparative Example 5

[0098] The preparation method of the isolation material of Comparative Example 5 is basically the same as that of Example 1, except that no calcite is added to the second isolation layer and the pH value is 7.2. In the saturated rainfall leaching test, the pH value of the bottom phosphogypsum leaching solution was measured to be 5.9, and the total phosphorus content was 4.63 mg / L.

[0099] The maximum water storage capacity refers to the maximum amount of precipitation that the anti-seepage layer can store before rainwater breaks through the anti-seepage layer and begins to leak, measured in mm.

[0100] Table 1

[0101]

[0102] It can be seen from Table 1 that compared with the comparative example, the isolation material provided by the present invention, by limiting the median particle size of the particles in the first isolation layer and the second isolation layer, forms a capillary blocking effect between the first isolation layer and the second isolation layer, thereby improving the water storage effect of the isolation material and the anti-seepage ability, especially improving the water storage and anti-seepage ability under extreme rainfall weather conditions.

[0103] From the comparison between Example 1 and Comparative Examples 1-5, it can be seen that the maximum water storage capacity of the isolation material provided by the present invention is larger and the anti-seepage effect is better. From the comparison between Example 1 and Comparative Example 5, it can be seen that the isolation material provided by the present invention can reduce the total phosphorus content in the leachate after the isolation material is leaked, and has a preventive effect.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An isolation material, characterized in that: including a first isolation layer and a second isolation layer stacked in a thickness direction; The median particle size D1 of the particles in the first isolation layer and the median particle size D2 of the particles in the second isolation layer satisfy: 2mm≤D1-D2≤2cm; The first isolation layer is obtained by granulating and compacting a first mixed system, wherein the first mixed system comprises, by weight: 40-60 parts of phosphogypsum, 10-20 parts of fly ash, 5-10 parts of calcite, 1-3 parts of slaked lime, and 20-30 parts of calcium-based bentonite; The second isolation layer is obtained by compacting the second mixed system, wherein the second mixed system comprises, by weight: 30-50 parts of river and lake sediment, 20-30 parts of fly ash, 10-20 parts of calcite, and 10-20 parts of expansive soil or loess; Wherein, the average particle size of phosphogypsum in the first mixed system is 0.05-1 mm, and the median particle size is greater than 0.1 mm; the average particle size of fly ash, calcite, slaked lime, and calcium-based bentonite is less than 0.2 mm; The average particle size of river and lake bottom mud in the second mixed system is less than 100 μm, and the median particle size is less than 50 μm; the average particle size of fly ash is less than 80 μm; and the average particle size of calcite, expansive soil or loess is less than 10 μm.

2. The insulating material according to claim 1, characterized in that The average particle size of the particles in the first isolation layer is greater than 3 mm, and the median particle size D1 is 5 mm<D1<20 mm.

3. The insulating material according to claim 2, characterized in that The porosity S of the first isolation layer is 15%<S<50%.

4. The insulating material according to claim 3, characterized in that The thickness ratio of the first isolation layer to the second isolation layer is 1:1.5-2.

5. The insulating material according to claim 1, characterized in that The moisture content of the second isolation layer is less than 15%, and the saturated moisture content is greater than 50%.

6. The insulating material according to claim 1, characterized in that The water content of the river and lake sediment is less than 30%, and the saturated water content is greater than 70%; and / or, The moisture content of the expansive soil is less than 10%, and the expansion rate is greater than 50%.

7. The insulating material according to any one of claims 1 to 6, characterized in that: The isolation material is prepared by a method comprising the following steps: 1) granulating a first mixed system including phosphogypsum, fly ash, calcite, slaked lime, and calcium-based bentonite to obtain a first isolation layer precursor; 2) performing a first compaction treatment on the first isolation layer precursor to obtain the first isolation layer; 3) placing a second mixed system including river and lake sediment, fly ash, calcite, expansive soil or loess on any surface of the first isolation layer in the thickness direction, and performing a second compaction treatment to obtain an isolation material including a first isolation layer and a second isolation layer stacked in the thickness direction.

8. The insulating material according to claim 7, characterized in that The thickness of the first isolation layer precursor is 30-50 cm, and the thickness of the first isolation layer is 27-47 cm; The thickness of the second mixed system is 60-80 cm, and the thickness of the second isolation layer is 50-70 cm; and / or, The thickness of the insulating material is 80-110 cm.

9. The insulating material according to any one of claims 1 to 6, characterized in that: The pH value of the first isolation layer is 9-11, and the pH value of the second isolation layer is 8-10.

10. A method for preventing seepage in a phosphogypsum reservoir, characterized in that: The isolation material according to any one of claims 1 to 8 is used to pave the bottom and top of the phosphogypsum reservoir.

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