A tailings-based soil-improving permeable brick and its preparation method

Abstract

The present application provides a tailings-based soil-improving permeable brick and a preparation method thereof, which relates to the field of solid waste recycling. The tailings-based soil-improving permeable brick comprises a surface layer and a base layer; the base layer includes a core layer and a shell layer provided on the surface of the core layer; the raw materials of the surface layer include tailings, cement, binder solution, pigment and water in a mass ratio of 60-80:33-72:4-26:2-12:7-16; the raw materials of the shell layer include tailings, cement, binder solution, adsorbent and water in a mass ratio of 60-80:36-76:5-30:20-30:8-18; the raw materials of the core layer include tailings, potassium feldspar, conversion agent, binder solution, cement and water in a mass ratio of 60-80:20-40:50-80:7-40:19-48:10-24. The tailings-based soil-improving permeable brick has the characteristic of long-lasting improvement effect and can be widely applied to fields such as soil remediation, garden construction, urban greening, etc.

Description

Technical Field

[0001] The present application relates to the field of solid waste recycling, and particularly to a tailings-based soil-improving permeable brick and a preparation method thereof. Background Art

[0002] As solid waste in the beneficiation industry, tailings are one of the largest sources of industrial solid waste globally. Preparing building materials products from tailings is an important direction for the comprehensive utilization of tailings. It not only solves the problem of tailings disposal, alleviates the environmental protection risks and safety hazards brought by tailings storage, but also promotes the recycling of resources and realizes sustainable development.

[0003] A permeable brick is a building material with good water permeability, which can quickly infiltrate the accumulated water after rainfall through pores, reduce surface runoff, and is widely used in the construction of sponge cities, effectively alleviating the problem of urban waterlogging after heavy rain. In recent years, the research on preparing permeable bricks from tailings has received the attention of scholars.

[0004] At present, the permeable brick products prepared from tailings still mainly focus on basic building material functions such as decoration and load-bearing, with a single application scenario and low product added value. Compared with the permeable brick products prepared from conventional raw materials, they have no performance advantages. At the same time, with the decline of the real estate industry, the demand in the building brick and tile market is small, resulting in a narrow sales radius, compressed profit space, and deteriorating market prospects for the permeable brick products prepared from tailings raw materials. It is urgent to enrich the functionality of the tailings-based permeable brick products, improve the product added value, and then broaden the market sales channels.

[0005] Tailings contain valuable elements such as Si, Ca, Mg, K, P, Fe, etc. After processing, they have functions such as promoting plant growth, improving acidic soil, and regulating heavy metal pollution. If the inherent advantages of tailings can be utilized while preparing permeable bricks, and the valuable elements therein can be fully utilized to improve the soil environment, the functions of the tailings-based permeable bricks can be further enriched.

[0006] Based on this, there is an urgent need to provide a technical solution that fully utilizes the inherent advantages of tailings, improves the added value and functionality of tailings-based permeable brick products. Summary of the Invention

[0007] The purpose of the present application is to provide a tailings-based soil-improving permeable brick and a preparation method thereof to solve the above problems.

[0008] To achieve the above purpose, in the first aspect of the present application, a tailings-based soil-improving permeable brick is provided, which includes a surface layer and a base layer;

[0009] The base layer includes a core layer and a shell layer provided on the surface of the core layer;

[0010] The raw materials of the surface layer include tailings, cement, binder solution, pigment and water with a mass ratio of 60 - 80:33 - 72:4 - 26:2 - 12:7 - 16;

[0011] The raw materials of the shell layer include tailings, cement, binder solution, adsorbent and water with a mass ratio of 60 - 80:36 - 76:5 - 30:20 - 30:8 - 18;

[0012] The raw materials of the core layer include tailings, potassium feldspar, conversion agent, binder solution, cement and water with a mass ratio of 60 - 80:20 - 40:50 - 80:7 - 40:19 - 48:10 - 24.

[0013] Optionally, the tailings - based soil - improving permeable brick meets at least one of the following conditions:

[0014] A. The adsorbent includes one or more of rice husk charcoal, attapulgite clay and humic acid;

[0015] B. The conversion agent includes one or more of calcium carbonate, desulfurized gypsum and dolomite;

[0016] C. The binder solution includes one or more of sodium lignosulfonate aqueous solution, calcium lignosulfonate aqueous solution, ammonium chloride aqueous solution and sodium carboxymethylcellulose aqueous solution.

[0017] Optionally, the tailings - based soil - improving permeable brick meets at least one of the following conditions:

[0018] A. The adsorbent includes the rice husk charcoal, the attapulgite clay and the humic acid, wherein the mass ratio of the rice husk charcoal, the attapulgite clay and the humic acid is 60 - 80:20 - 40:0 - 10;

[0019] B. The conversion agent includes the calcium carbonate, the desulfurized gypsum and the dolomite, wherein the mass ratio of the calcium carbonate, the desulfurized gypsum and the dolomite is 50 - 60:20 - 30:20 - 30.

[0020] C. The binder solution includes one or more of the sodium lignosulfonate aqueous solution, the calcium lignosulfonate aqueous solution, the ammonium chloride aqueous solution and the sodium carboxymethylcellulose aqueous solution, and the solution concentration is 5% - 10%.

[0021] Optionally, the content of SiO2 in the tailings is greater than 30%, the content of K2O is greater than 5%, the content of Cr is less than 250 mg / kg, the content of Cd is less than 20 mg / kg, the content of Pb is less than 400 mg / kg, the content of As is less than 100 mg / kg, the content of Hg is less than 10 mg / kg, and the content of Tl is less than 5 mg / kg.

[0022] Optionally, the particle sizes of the pigment, the tailings, the cement, the potassium feldspar, and the conversion agent are each independently less than or equal to 0.074 mm.

[0023] The second aspect of the present application provides a method for preparing the tailings-based soil-improving permeable brick, including:

[0024] Mix the tailings and the cement to obtain a first homogenized raw material and a second homogenized raw material;

[0025] Perform first granulation on the first homogenized raw material and the adsorbent, wherein the adsorbent is disposed on the surface of the first homogenized raw material, and then perform first curing to obtain a shell layer material;

[0026] Perform second granulation on the second homogenized raw material and the pigment, wherein the pigment is disposed on the surface of the second homogenized raw material, and then perform second curing to obtain a surface layer material;

[0027] Mix the tailings, the potassium feldspar, and the conversion agent, perform third granulation and roasting to obtain a core layer material;

[0028] Mix the cement with water to obtain a cement slurry, and mix the core layer material, the shell layer material, and the surface layer material with the cement slurry respectively to obtain a core layer material-cement slurry mixture, a shell layer material-cement slurry mixture, and a surface layer material-cement slurry mixture;

[0029] Stack the core layer material-cement slurry mixture, the shell layer material-cement slurry mixture, and the surface layer material-cement slurry mixture in sequence in a mold, and perform third curing to obtain the tailings-based soil-improving permeable brick;

[0030] When performing the first granulation, the second granulation, and the third granulation, a binder solution is also sprayed.

[0031] Optionally, the method for preparing the tailings-based soil-improving permeable brick satisfies at least one of the following conditions:

[0032] A. The disk rotation speeds of the first granulation, the second granulation, and the third granulation are each independently 20 r / min - 40 r / min, and the granulation times are each independently 5 min - 10 min;

[0033] B. The times of the first curing and the second curing are each independently 12 h - 24 h;

[0034] C. The temperature of the roasting is 1100 °C - 1200 °C, and the time is 30 min - 60 min;

[0035] D. The time of the third curing is not less than 28 days.

[0036] Optionally, the particle size of the shell material is 8 mm - 10 mm;

[0037] The particle size of the surface layer material is 1 mm - 3 mm;

[0038] The particle size of the core layer material is 3 mm - 5 mm.

[0039] Optionally, the preparation method of the tailings-based soil-improving permeable brick satisfies at least one of the following conditions:

[0040] A. When preparing the homogenized raw materials, the mass ratio of the tailings to the cement is 60 - 80:20 - 40;

[0041] B. When preparing the shell material-cement slurry mixture, the mass ratio of the shell material, the cement, and the water is 100:15 - 20:8 - 10;

[0042] C. When preparing the core layer material-cement slurry mixture, the mass ratio of the core layer material, the cement, and the water is 100:15 - 20:8 - 10;

[0043] D. When preparing the surface layer material-cement slurry mixture, the mass ratio of the surface layer material, the cement, and the water is 100:15 - 20:8 - 10.

[0044] Optionally, the sequential stacking and forming in the mold includes:

[0045] First, cover the bottom and four walls of the mold with the shell material-cement slurry mixture, then fill it with the core layer material-cement slurry mixture, and then sequentially lay the shell material-cement slurry mixture and the surface layer material-cement slurry mixture on the upper layer of the core layer material-cement slurry mixture.

[0046] Compared with the prior art, the beneficial effects of this application include:

[0047] The tailings-based soil-improving permeable brick provided by this application, while having excellent mechanical properties and water permeability of traditional building material permeable bricks, applies tailings building materials to the field of soil improvement, further exploiting the advantages of tailings in natural endowment characteristics, having functions such as providing nutrients, improving acidic soil, and fixing heavy metals, and realizing the slow release of valuable components through the "surface layer - shell layer - core layer" structure, with the characteristic of long-lasting improvement effect, and can be widely applied to fields such as soil remediation, garden construction, and urban greening.

[0048] The preparation method of the tailings-based soil-improving permeable brick provided by the present application prepares core layer materials, shell layer materials, and surface layer materials with various functions: the core layer materials contain a certain amount of effective silicon, effective potassium, effective calcium, and effective magnesium elements that can be absorbed by plants, which can be slowly released under soil environment and long-term water immersion conditions, playing the role of supplementing soil nutrients and increasing the pH value of acidic soil; the interior of the shell layer materials is a filler composed of cement and tailings, playing a skeletal role. The adsorbent on the surface gradually falls off in water immersion and soil environment, playing the role of adsorbing heavy metals in the soil. At the same time, the shell layer materials avoid the direct contact between the core layer materials and the surrounding environment, reduce the release rate of valuable elements, effectively extend the duration of soil improvement, and improve the utilization rate of valuable elements; pigments are added during the preparation of the surface layer materials, so the surface layer can also play a decorative role. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and should not be regarded as limiting the scope of the present application.

[0050] Figure 1 is a schematic structural diagram of the tailings-based soil-improving permeable brick;

[0051] Figure 2 is a physical diagram of the tailings-based soil-improving permeable brick prepared in Example 1;

[0052] Figure 3 is a physical diagram of the shell layer material prepared in Example 1;

[0053] Figure 4 is a physical diagram of the surface layer material prepared in Example 1;

[0054] Figure 5 is a physical diagram of the core layer material prepared in Example 1;

[0055] Figure 6 is a schematic flow chart of the preparation method of the tailings-based soil-improving permeable brick provided in Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0056] As used herein, the terms:

[0057] "prepared from" is synonymous with "comprising". As used herein, the terms "comprising", "including", "having", "containing" or any other variation thereof are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or device containing the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or device.

[0058] The conjunctive term "consisting of" excludes any element, step, or component not specified. If used in a claim, this phrase renders the claim closed, excluding materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause within the body of a claim rather than immediately following the subject, it only limits the elements described in that clause; other elements are not excluded from the claim as a whole.

[0059] When an equivalent, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values and lower preferred values, this should be understood to specifically disclose all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, whether or not the range is separately disclosed. For example, when the range "1 to 5" is disclosed, the described range should be interpreted as including the ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values and all integers and fractions within the range.

[0060] In these examples, unless otherwise specified, the parts and percentages are by mass.

[0061] "Parts by mass" refers to the basic measurement unit representing the mass ratio relationship of multiple components. 1 part can represent any unit mass, such as 1 g or 2.689 g, etc. Suppose we say that the mass parts of component A is a parts and the mass parts of component B is b parts, then it represents the mass ratio of component A to component B as a:b. Or, it represents that the mass of component A is aK and the mass of component B is bK (K is any number representing a multiple factor). It should not be misunderstood that, different from the number of mass parts, the sum of the mass parts of all components is not limited to 100 parts.

[0062] "And / or" is used to indicate that either or both of the stated circumstances may occur. For example, A and / or B includes (A and B) and (A or B).

[0063] The first aspect of the present application provides a tailings-based soil-improving permeable brick, comprising a surface layer and a base layer;

[0064] The base layer includes a core layer and a shell layer provided on the surface of the core layer;

[0065] It should be noted that the structural schematic diagram of the tailings-based soil-improving permeable brick is as Figure 1As shown, the shell layer completely wraps the core layer, avoiding direct contact between the core layer and the surrounding environment; exemplarily, in the cross-section of the tailings-based soil-improving permeable brick, the core layer can be of any shape such as square, rectangular, circular, etc., and the shell layer can be set in shape according to the shape of the core layer or actual situation; in some embodiments, the thickness ratio of the surface layer, core layer, and shell layer is 5-20:30-50:30-70, but the thickness ratio of the surface layer, core layer, and shell layer can be set according to actual needs.

[0066] The raw materials of the surface layer include tailings, cement, binder solution, pigment, and water with a mass ratio of 60-80:33-72:4-26:2-12:7-16;

[0067] Optionally, the mass ratio of tailings, cement, binder solution, pigment, and water in the surface layer raw materials can be 60:33:4:2:7, 70:33:4:2:7, 80:33:4:2:7, 60:50:4:2:7, 60:72:4:2:7, 60:33:10:2:7, 60:33:26:2:7, 60:33:4:12:7, 60:33:4:2:16, or any value between 60-80:33-72:4-26:2-12:7-16;

[0068] The raw materials of the shell layer include tailings, cement, binder solution, adsorbent, and water with a mass ratio of 60-80:36-76:5-30:20-30:8-18;

[0069] Optionally, the mass ratio of tailings, cement, binder solution, adsorbent, and water in the shell layer raw materials can be 60:36:5:20:8, 70:36:5:20:8, 80:36:5:20:8, 60:72:5:20:8, 60:36:30:30:18, or any value between 60-80:36-76:5-30:20-30:8-18;

[0070] The raw materials of the core layer include tailings, potassium feldspar, conversion agent, binder solution, cement, and water with a mass ratio of 60-80:20-40:50-80:7-40:19-48:10-24.

[0071] Optionally, the mass ratio of tailings, potassium feldspar, conversion agent, binder solution, cement and water in the core layer raw material can be 60:20:50:7:19:10, 70:20:50:7:19:10, 80:20:50:7:19:10, 60:30:50:7:19:10, 60:40:50:7:19:10, 60:20:70:7:19:10, 60:20:80:7:19:10, 60:20:50:20:19:10, 60:20:50:40:19:10, 60:20:50:7:48:10, 60:20:50:7:19:24, 80:40:80:40:48:24 or any value between 60-80:20-40:50-80:7-40:19-48:10-24.

[0072] It should be noted that in the raw material of the core layer, tailings mainly provide silicon elements, potassium feldspar mainly provides potassium elements, and the conversion agent converts the silicon and potassium elements in tailings and potassium feldspar from an inert state that cannot be absorbed by plants into an effective state that can be absorbed by plants during the high-temperature process, and at the same time provides calcium and magnesium elements; the binder is used to improve the strength of the core layer material and prevent particle damage during transportation, drying and high-temperature processes. Cement and water are used to prepare cement slurry. After the core layer material is evenly mixed with the cement slurry and piled up and cured, a complete core layer can be obtained.

[0073] In some embodiments, the tailings-based soil-improving permeable brick satisfies at least one of the following conditions:

[0074] A. The adsorbent includes one or more of rice husk charcoal, attapulgite clay and humic acid;

[0075] B. The conversion agent includes one or more of calcium carbonate, desulfurized gypsum and dolomite;

[0076] C. The binder is one or more of aqueous solutions of sodium lignosulfonate, calcium lignosulfonate, ammonium chloride and sodium carboxymethylcellulose.

[0077] In some embodiments, the cement includes, but is not limited to, ordinary Portland cement type 42.5.

[0078] In some embodiments, the tailings-based soil-improving permeable brick satisfies at least one of the following conditions:

[0079] A. The adsorbent includes the rice husk charcoal, the attapulgite clay and the humic acid, wherein the mass ratio of the rice husk charcoal, the attapulgite clay and the humic acid is 60-80:20-40:0-10;

[0080] Optionally, in the raw material components of the adsorbent, the mass ratio of rice husk carbon, attapulgite clay, and humic acid can be 60:20:0, 70:20:0, 80:20:0, 60:30:0, 60:40:0, 60:20:5, 60:20:10, or any value between 60 - 80:20 - 40:0 - 10;

[0081] It should be noted that when the adsorbent includes rice husk carbon, attapulgite clay, and humic acid with a mass ratio of 60 - 80:20 - 40:0 - 10, the heavy metal solidification effect is better. The high-porosity structure of rice husk carbon provides physical adsorption sites, the layer-chain structure of attapulgite clay provides ion-exchange sites, and humic acid contains functional groups such as carboxyl and hydroxyl groups, which can chelate heavy metals to form stable complexes. The combination of the three can cover more types of heavy metals and improve the heavy metal solidification effect.

[0082] B. The conversion agent includes the calcium carbonate, the desulfurized gypsum, and the dolomite, wherein the mass ratio of the calcium carbonate, the desulfurized gypsum, and the dolomite is 50 - 60:20 - 30:20 - 30.

[0083] Optionally, in the raw material components of the conversion agent, the mass ratio of calcium carbonate, desulfurized gypsum, and dolomite can be 50:20:20, 55:20:20, 60:20:20, 50:30:20, 50:20:30, or any value between 50 - 60:20 - 30:20 - 30.

[0084] It should be noted that when the conversion agent includes calcium carbonate, desulfurized gypsum, and dolomite with a mass ratio of 50 - 60:20 - 30:20 - 30, the conversion efficiency of silicon and potassium elements in tailings and potassium feldspar is relatively high, and the raw material cost is relatively low. Calcium carbonate, desulfurized gypsum, and dolomite can all react with tailings and potassium feldspar under high-temperature conditions to convert inert silicon and potassium elements into available forms. At the same time, calcium carbonate mainly provides available calcium elements, dolomite mainly provides available magnesium elements, and desulfurized gypsum, as industrial solid waste, can replace part of the calcium carbonate to provide available calcium elements and reduce production costs. However, the conversion effect of desulfurized gypsum on tailings and potassium feldspar is not as good as that of calcium carbonate, so the dosage should not be too high.

[0085] C. The binder solution includes the sodium lignosulfonate aqueous solution, the calcium lignosulfonate aqueous solution, the ammonium chloride aqueous solution, and the sodium carboxymethyl cellulose aqueous solution, wherein the concentration of the binder solution is 5% - 10%.

[0086] Optionally, the concentration of the binder solution can be 5%, 6%, 7%, or any value between 5% - 10%.

[0087] It should be noted that when the concentration of the binder solution is 5% - 10%, the particle strength of the granulated material can be effectively improved. Too low a concentration will result in insufficient bonding force, while too high a concentration will affect the fluidity of the solution, causing the material to agglomerate easily and increasing the cost.

[0088] In some embodiments, the content of SiO2 in the tailings is greater than 30%, the content of K2O is greater than 5%, the content of Cr is less than 250 mg / kg, the content of Cd is less than 20 mg / kg, the content of Pb is less than 400 mg / kg, the content of As is less than 100 mg / kg, the content of Hg is less than 10 mg / kg, and the content of Tl is less than 5 mg / kg.

[0089] Optionally, the content of SiO2 in the tailings can be 31%, 34%, 40%, 45% or any value greater than 30%, the content of K2O can be 6%, 7%, 8%, 10% or any value greater than 5%, the content of Cr can be 10 mg / kg, 20 mg / kg, 50 mg / kg, 100 mg / kg, 200 mg / kg, 240 mg / kg or any value less than 250 mg / kg, the content of Cd can be 1 mg / kg, 5 mg / kg, 10 mg / kg, 15 mg / kg, 19 mg / kg or any value less than 20 mg / kg, the content of Pb can be 10 mg / kg, 20 mg / kg, 50 mg / kg, 100 mg / kg, 200 mg / kg, 300 mg / kg, 390 mg / kg or any value less than 400 mg / kg, the content of As can be 10 mg / kg, 20 mg / kg, 50 mg / kg, 90 mg / kg or any value less than 100 mg / kg, the content of Hg can be 1 mg / kg, 2 mg / kg, 4 mg / kg, 5 mg / kg, 9 mg / kg or any value less than 10 mg / kg, and the content of Tl can be 1 mg / kg, 2 mg / kg, 3 mg / kg, 4 mg / kg, 4.5 mg / kg or any value less than 5 mg / kg.

[0090] It should be noted that when the contents of SiO2 and K2O in the tailings are lower than the above values, the contents of available silicon and available potassium in the core layer material are low, affecting the soil improvement effect. When the contents of Cr, Cd, Pb, As, Hg, and Tl in the tailings exceed the above values, the heavy metal content in the core layer material is relatively high, and heavy metal dissolution may occur during subsequent applications, affecting the soil improvement effect.

[0091] In some embodiments, the particle sizes of the pigment, the tailings, the cement, the potassium feldspar, and the conversion agent are each independently less than or equal to 0.074 mm.

[0092] Optionally, the particle sizes of the tailings, cement, pigment, potassium feldspar, and conversion agent can each independently be 0.01 mm, 0.02 mm, 0.05 mm, 0.074 mm, or any value less than or equal to 0.074 mm.

[0093] It should be noted that as the main raw material for pelletizing, tailings with a particle size less than 0.074 mm can effectively reduce the voids between particles, ensure the full mixing of tailings particles and other raw materials, and avoid stratification or agglomeration caused by particle size differences; cement with a particle size less than 0.074 mm can increase the specific surface area and accelerate the hydration reaction; pigment with a particle size less than 0.074 mm can ensure uniform color distribution and prevent color differences caused by the aggregation of coarse particles; potassium feldspar and conversion agent with a particle size less than 0.074 mm can ensure the full reaction between material particles under high-temperature conditions and improve the conversion efficiency of silicon and potassium elements;

[0094] The second aspect of the present application provides a method for preparing the tailings-based soil-improving permeable brick, including:

[0095] Mix the tailings and cement to obtain a first homogenized raw material and a second homogenized raw material;

[0096] Perform first pelletizing on the first homogenized raw material and the adsorbent, where the adsorbent is disposed on the surface of the first homogenized raw material, and then perform first curing to obtain a shell layer material;

[0097] Perform second pelletizing on the second homogenized raw material and the pigment, where the pigment is disposed on the surface of the second homogenized raw material, and then perform second curing to obtain a surface layer material;

[0098] Mix the tailings, potassium feldspar, and conversion agent, perform third pelletizing and roasting to obtain a core layer material;

[0099] Mix the cement with water to obtain a cement slurry, and mix the core layer material, the shell layer material, and the surface layer material with the cement slurry respectively to obtain a core layer material-cement slurry mixture, a shell layer material-cement slurry mixture, and a surface layer material-cement slurry mixture;

[0100] Stack the core layer material-cement slurry mixture, the shell layer material-cement slurry mixture, and the surface layer material-cement slurry mixture in sequence in a mold, and perform third curing to obtain the tailings-based soil-improving permeable brick;

[0101] When performing the first pelletizing, the second pelletizing, and the third pelletizing, a binder solution is also sprayed.

[0102] In some embodiments, the first pelletizing and the second pelletizing adopt the layered pelletizing method.

[0103] Exemplarily, the first homogenized raw material and the adsorbent are granulated for the first time by the layer-by-layer granulation method, so that the adsorbent wraps the homogenized raw material to form a structure of outer adsorbent - inner homogenized raw material. During granulation, the binder solution is evenly sprayed, and then the first curing is carried out to obtain the shell layer material.

[0104] Exemplarily, the second homogenized raw material and the pigment are granulated for the second time by the layer-by-layer granulation method, so that the pigment wraps the homogenized raw material to form a structure of outer pigment - inner homogenized raw material. During granulation, the binder solution is evenly sprayed, and then the second curing is carried out to obtain the surface layer material.

[0105] In some embodiments, the method for preparing the tailings-based soil-improving permeable brick satisfies at least one of the following conditions:

[0106] A. The disk rotation speeds of the first granulation, the second granulation, and the third granulation are each independently 20 r / min - 40 r / min, and the granulation times are each independently 5 min - 10 min;

[0107] Optionally, the disk rotation speeds of the first granulation, the second granulation, and the third granulation can each independently be 20 r / min, 25 r / min, 30 r / min, 35 r / min, 40 r / min, or any value between 20 r / min - 40 r / min, and the granulation times can each independently be 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, or any value between 5 min - 10 min;

[0108] B. The times of the first curing and the second curing are each independently 12 h - 24 h;

[0109] Optionally, the times of the first curing and the second curing can each independently be 12 h, 16 h, 20 h, 24 h, or any value between 12 h - 24 h;

[0110] C. The temperature of the roasting is 1100 °C - 1200 °C, and the time is 30 min - 60 min;

[0111] Optionally, the temperature of the roasting can be 1100 °C, 1150 °C, 1200 °C, or any value between 1100 °C - 1200 °C, and the time can be 30 min, 40 min, 50 min, 60 min, or any value between 30 min - 60 min;

[0112] It should be noted that roasting can effectively promote the reaction between the tailings, potassium feldspar and the conversion agent, converting the inert silicon and potassium elements in the tailings and potassium feldspar into available forms that can be absorbed by plants. At the same time, the low-melting substances in the raw materials melt under high-temperature conditions, forming a liquid phase that fills between the grains and forms a consolidation layer after cooling, significantly improving the mechanical bonding force between the particles, and thus enhancing the strength of the core layer material and the tailings-based soil-improving permeable bricks.

[0113] D. The time of the third curing is not less than 28 days.

[0114] Optionally, the third curing time can be 28 days, 30 days, 32 days or any value not less than 28 days;

[0115] In some embodiments, the particle size of the shell layer material is 8 mm - 10 mm;

[0116] Optionally, the particle size of the shell layer material can be 8 mm, 9 mm, 10 mm or any value between 8 mm - 10 mm;

[0117] The particle size of the surface layer material is 1 mm - 3 mm;

[0118] Optionally, the particle size of the surface layer material can be 1 mm, 2 mm, 3 mm or any value between 1 mm - 3 mm;

[0119] The particle size of the core layer material is 3 mm - 5 mm.

[0120] Optionally, the particle size of the core layer material can be 3 mm, 4 mm, 5 mm or any value between 3 mm - 5 mm.

[0121] It should be noted that the particle size of the surface layer material is 1 - 3 mm. On the one hand, it can intercept large particle pollutants (such as gravel and leaves), prevent the deep pores from being blocked, and extend the service life of the permeable bricks. On the other hand, while ensuring the permeability coefficient, it can slow down the rainwater flow rate and promote the uniform infiltration of rainwater. The particle size of the core layer material is 3 - 5 mm, and the particle size of the shell layer material is 8 - 10 mm, which is coarser than that of the surface layer material. On the one hand, it can increase the permeability coefficient and enable the rainwater to quickly penetrate to the foundation or drainage system. On the other hand, the coarse particle skeleton structure has high strength, improving the load-bearing capacity of the permeable bricks.

[0122] In some embodiments, the preparation method of the tailings-based soil-improving permeable bricks satisfies at least one of the following conditions:

[0123] A. When preparing the homogenized raw materials, the mass ratio of the tailings to the cement is 60 - 80:20 - 40;

[0124] Optionally, when preparing the homogenized raw material particles, the mass ratio of the tailings to the cement can be 60:20, 60:30, 60:40, 70:20, 80:20, 80:40, or any value between 60 - 80:20 - 40;

[0125] B. When preparing the shell material - cement slurry mixture, the mass ratio of the shell material, the cement, and the water is 100:15 - 20:8 - 10;

[0126] Optionally, when preparing the shell material - cement slurry mixture, the mass ratio of the shell material, the cement, and the water can be 100:15:8, 100:17:9, 100:20:10, or any value between 100:15 - 20:8 - 10;

[0127] C. When preparing the core material - cement slurry mixture, the mass ratio of the core material, the cement, and the water is 100:15 - 20:8 - 10;

[0128] Optionally, when preparing the core material - cement slurry mixture, the mass ratio of the shell material, the cement, and the water can be 100:15:8, 100:17:9, 100:20:10, or any value between 100:15 - 20:8 - 10;

[0129] D. When preparing the surface material - cement slurry mixture, the mass ratio of the surface material, the cement, and the water is 100:15 - 20:8 - 10.

[0130] Optionally, when preparing the surface material - cement slurry mixture, the mass ratio of the shell material, the cement, and the water can be 100:15:8, 100:17:9, 100:20:10, or any value between 100:15 - 20:8 - 10.

[0131] In some embodiments, the sequential stacking and molding in the mold includes:

[0132] First, cover the bottom and four walls of the mold with the shell material - cement slurry mixture, then fill it with the core material - cement slurry mixture, and then sequentially lay the shell material - cement slurry mixture and the surface material - cement slurry mixture on the upper layer of the core material - cement slurry mixture.

[0133] The following will describe the implementation scheme of the present application in detail with specific embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0134] Example 1

[0135] This embodiment provides a tailings-based soil-improving permeable brick, which is composed of a surface layer and a base layer. The base layer includes a core layer and a shell layer arranged on the surface of the core layer. The specific structure is as Figure 1 shown, and the physical object is as Figure 2 shown;

[0136] Among them, the raw materials of the surface layer are tailings, cement, binder solution, pigment and water with a mass ratio of 80:44:11:10:12. The raw materials of the shell layer are tailings, cement, binder solution, adsorbent and water with a mass ratio of 80:46:12:20:13. The raw materials of the core layer are tailings, potassium feldspar, conversion agent, binder solution, cement and water with a mass ratio of 60:20:50:12:26:13;

[0137] Among them, the adsorbent is rice husk charcoal, attapulgite and humic acid with a mass ratio of 60:30:10; the conversion agent is calcium carbonate, desulfurized gypsum and dolomite with a mass ratio of 50:20:30; the binder solution is an aqueous solution of sodium lignosulfonate with a concentration of 5%; the cement is ordinary Portland cement type 42.5, and the pigment is iron oxide red;

[0138] The tailings used are copper tailings, in which the SiO2 content is 62.97%, the K2O content is 6.71%, the Cr content is 52.47 mg / kg, the Cd content is 10.67 mg / kg, the Pb content is 74.12 mg / kg, the As content is 15.80 mg / kg, the Hg content is 0.02 mg / kg, and the Tl content is 0.01 mg / kg.

[0139] This application also provides a preparation method of the tailings-based soil-improving permeable brick. The specific steps are as follows:

[0140] (1) Preparation of the shell layer material: Weigh tailings, cement, adsorbent and binder solution with a mass ratio of 80:20:20:12. Mix the tailings and cement evenly to obtain a homogenized raw material. Granulate the homogenized raw material and the adsorbent in a disk pelletizer. The rotation speed of the disk pelletizer is 30 r / min, and the granulation time is 8 min. During the granulation process, the layered granulation method is adopted. First, add the homogenized raw material, and finally add the adsorbent to make the adsorbent wrap the homogenized raw material, forming a structure of outer adsorbent-inner homogenized raw material. Sprinkle the binder solution evenly during granulation, and control the particle size to be 8 mm. After short-term curing for 24 h, the shell layer material is obtained. The physical object of the shell layer material is as Figure 3 shown;

[0141] (2) Preparation of surface layer material: Weigh tailings, cement, pigment, and binder solution with a mass ratio of 80:20:10:11. Mix the tailings and cement evenly to obtain homogenized raw materials. Granulate the homogenized raw materials and pigment in a disk pelletizer. The rotation speed of the disk pelletizer is 30 r / min, and the granulation time is 5 min. During the granulation process, the layered granulation method is adopted. First, add the homogenized raw materials, and finally add the pigment to make the pigment wrap the homogenized raw materials, forming a structure of outer pigment - inner homogenized raw materials. Sprinkle the binder solution evenly during granulation, control the particle size to be 3 mm, and perform short-term curing for 24 h to obtain the surface layer material; The physical object of the surface layer material is as Figure 4 shown;

[0142] (3) Preparation of core layer material: Weigh tailings, potassium feldspar, conversion agent, and binder solution with a mass ratio of 60:20:50:12. Mix the tailings, potassium feldspar, and conversion agent evenly and then use a disk pelletizer for granulation. The rotation speed of the disk pelletizer is 30 r / min, and the granulation time is 6 min. Sprinkle the binder solution evenly during the granulation process, control the particle size to be 5 mm, dry it, and then place it in a muffle furnace for roasting. The roasting temperature is 1200 °C, and the roasting time is 40 min. After cooling, obtain the core layer material. The physical object of the core layer material is as Figure 5 shown;

[0143] (4) Molding with a mold: Weigh cement, shell layer material, core layer material, surface layer material, and water with a mass ratio of 15:50:35:15:7.5. First, stir the cement and water evenly to make cement slurry. Then divide the cement slurry into three parts according to the mass ratio of the shell layer material, core layer material, and surface layer material (50:35:15). Stir the weighed shell layer material, core layer material, and surface layer material evenly with the corresponding cement slurry respectively to obtain a shell layer material - cement slurry mixture, a core layer material - cement slurry mixture, and a surface layer material - cement slurry mixture. Then perform stacking and molding.

[0144] First, cover the bottom and four walls of a mold with dimensions of 10 cm × 10 cm × 10 cm with the shell layer material - cement slurry mixture. Then fill the core layer material - cement slurry mixture into it. Finally, lay the shell layer material - cement slurry mixture and the surface layer material - cement slurry mixture flat on the upper layer. Then place the mold in a curing room and cure it for 28 days to obtain the tailings-based soil-improving permeable brick. The process flow of this preparation method is as Figure 6 shown.

[0145] (5) Testing: Measure the water permeability coefficient of the permeable brick according to "GB / T 25993-2023 Permeable Pavement Bricks and Permeable Pavement Panels" to be 2.37×10 -2cm / s, the flexural strength is 3.2 MPa, with good water permeability and mechanical properties. At the same time, the prepared tailings-based soil-improving permeable bricks are placed in acidic soil for cultivation. During the cultivation process, the soil moisture content is maintained at 15%. According to the mass change, a certain amount of water is supplemented to the surface layer every three days. The changes in the physical and chemical properties of the test soil within 180 days are shown in Table 1.

[0146] Table 1 Changes in the physical and chemical properties of the soil

[0147]

[0148] As can be seen from Table 1, within 180 days, the contents of available silicon, available calcium, available potassium, and available magnesium in the soil have all increased significantly, the pH has increased, and the content of available heavy metals has decreased, indicating that the tailings-based soil-improving permeable bricks prepared by this method have the effects of improving acidic soil, supplementing nutrients, and solidifying heavy metals, and the improvement effect lasts for a long time.

[0149] Example 2

[0150] The difference from Example 1 is that the mass ratio of rice husk charcoal, attapulgite clay, and humic acid in the adsorbent is changed to 70:25:5.

[0151] According to "GB / T 25993-2023 Permeable Pavement Bricks and Permeable Pavement Panels", the water permeability coefficient of the permeable bricks is measured to be 2.31×10 -2 cm / s, the flexural strength is 3.2 MPa, with good water permeability and mechanical properties. According to the method in Example 1, the soil cultivation test is carried out, and the test results are shown in Table 2.

[0152] Table 2 Changes in the physical and chemical properties of the soil

[0153]

[0154] As can be seen from Table 2, within 180 days, the contents of available silicon, available calcium, available potassium, and available magnesium in the soil have all increased significantly, the pH has increased, and the content of available heavy metals has decreased, indicating that the tailings-based soil-improving permeable bricks still have good soil improvement effects under this adsorbent ratio.

[0155] Example 3

[0156] The difference from Example 1 is that the mass ratio of calcium carbonate, desulfurized gypsum, and dolomite in the converter is changed to 60:20:20.

[0157] According to "GB / T 25993-2023 Permeable Pavement Bricks and Permeable Pavement Panels", the tailings-based soil-improving permeable bricks are detected, and the water permeability coefficient is 2.31×10 -2cm / s, the flexural strength is 3.4 MPa, and it has good water permeability and mechanical properties. The soil culture test was carried out according to the method in Example 1, and the test results are shown in Table 3.

[0158] Table 3 Changes in soil physical and chemical properties

[0159]

[0160] As can be seen from Table 3, within 180 days, the contents of available silicon, available calcium, available potassium and available magnesium in the soil increased significantly, the pH increased, and the content of available heavy metals decreased, indicating that the tailings-based soil-improving permeable brick still had good soil improvement effect under this converter ratio.

[0161] Example 4

[0162] The difference from Example 1 is that the copper tailings used are replaced with gold tailings: the SiO2 content is 55.64%, the K2O content is 5.73%, the Cr content is 35.29 mg / kg, the Cd content is 3.50 mg / kg, the Pb content is 94.12 mg / kg, the As content is 45.73 mg / kg, the Hg content is 0.17 mg / kg, and the Tl content is 0.21 mg / kg.

[0163] The tailings-based soil-improving permeable brick was tested according to "GB / T 25993-2023 Permeable Pavement Bricks and Permeable Pavement Panels", and the permeability coefficient was 2.42×10 -2 cm / s, the flexural strength is 3.0 MPa, and it has good water permeability and mechanical properties. The soil culture test was carried out according to the method in Example 1, and the test results are shown in Table 4.

[0164] Table 4 Changes in soil physical and chemical properties

[0165]

[0166] As can be seen from Table 4, the tailings-based soil-improving permeable brick has obvious soil improvement effect. Within 180 days, the contents of available silicon, available calcium, available potassium and available magnesium in the soil increased significantly, the pH increased, the content of available heavy metals decreased, and the improvement effect lasted for a long time.

[0167] Comparative Example 1

[0168] The difference from Example 1 is that the core layer is not set, and the permeable brick is only composed of the upper surface layer and the lower shell layer.

[0169] The tailings-based soil-improving permeable brick was tested according to "GB / T 25993-2023 Permeable Pavement Bricks and Permeable Pavement Panels", and the permeability coefficient was 2.32×10 -2cm / s, the flexural strength is 3.4 MPa. Compared with Example 1, the water permeability coefficient and flexural strength change little. The soil cultivation test was carried out according to the method in Example 1, and the test results are shown in Table 5.

[0170] Table 5 Changes in soil physical and chemical properties

[0171]

[0172] As can be seen from Table 5, compared with Example 1 and without setting the core layer, since the surface layer material and shell layer material basically do not contain effective silicon, effective calcium, effective potassium and effective magnesium elements, the effective silicon, effective calcium, effective potassium and effective magnesium in the soil hardly increase after a period of cultivation. Due to the increase in the proportion of the shell layer material, the heavy metal solidification effect has been improved.

[0173] Comparative Example 2

[0174] The difference from Example 1 is that the shell layer is not set, and the permeable brick is only composed of the upper surface layer and the lower core layer.

[0175] The tailings-based soil-improved permeable brick was tested in accordance with "GB / T 25993-2023 Permeable Pavement Bricks and Permeable Pavement Slabs". The water permeability coefficient is 2.12×10 -2 cm / s, and the flexural strength is 2.5 MPa. Compared with Example 1, the water permeability and flexural strength decreased. The soil cultivation test was carried out according to the method in Example 1, and the test results are shown in Table 6.

[0176] Table 6 Changes in soil physical and chemical properties

[0177]

[0178] As can be seen from Table 6, without setting the shell layer, the release rate of valuable components in the core layer increases significantly, resulting in a short-term significant increase in the pH value and the content of effective elements. However, plants cannot fully utilize these valuable elements in a short time, leading to the leaching of valuable components and the risk of soil salinization. In addition, without setting the shell layer, the heavy metal solidification effect decreases significantly.

[0179] Comparative Example 3

[0180] The difference from Example 1 is that the raw materials of the shell layer and the core layer are replaced.

[0181] The tailings-based soil-improved permeable brick was tested in accordance with "GB / T 25993-2023 Permeable Pavement Bricks and Permeable Pavement Slabs". The water permeability coefficient is 2.30×10 -2 cm / s, and the flexural strength is 3.0 MPa. The soil cultivation test was carried out according to the method in Example 1, and the test results are shown in Table 7.

[0182] Table 7 Changes in physical and chemical properties of soil

[0183]

[0184] It can be seen that, compared with Example 1, after swapping the core layer material and the shell layer material, the shell layer material lacks the coating layer, and the release rate of valuable components increases significantly, causing the pH value and the content of available elements to increase substantially in a short time. However, plants cannot fully utilize these valuable elements in a short time, resulting in the leaching loss of valuable components. At the same time, there is also a risk of soil salinization. In addition, the heavy metal solidification effect decreases.

[0185] Comparative Example 4

[0186] The difference from Example 1 is that no roasting is performed when preparing the core layer material.

[0187] The tailings-based soil-improving permeable bricks were tested in accordance with "GB / T 25993-2023 Permeable Pavement Bricks and Permeable Road Panels". The permeability coefficient was 2.30×10 -2 cm / s, and the flexural strength was 1.4 MPa. Compared with Example 1, the flexural strength decreased significantly. The tailings-based soil-improving permeable bricks prepared were tested for the changes in the physical and chemical properties of the soil for 180 days. The test results are shown in Table 8.

[0188] Table 8 Changes in physical and chemical properties of soil

[0189]

[0190] It can be seen that, compared with Example 1, the contents of available silicon and available potassium in the soil did not change significantly under the condition that the core layer material was not roasted. This is because the silicon and potassium elements in the tailings and potassium feldspar were not activated by roasting and remained in an inert state.

[0191] Comparative Example 5

[0192] The difference from Example 1 is that during the preparation of the shell layer material, the particle size was controlled to be 15 mm.

[0193] The tailings-based soil-improving permeable bricks were tested in accordance with "GB / T 25993-2023 Permeable Pavement Bricks and Permeable Road Panels". The permeability coefficient was 3.27×10 -2 cm / s, and the flexural strength was 0.7 MPa. It can be seen that, compared with Example 1, when the particle size of the shell layer material increased to 15 mm, the strength of the permeable brick decreased significantly. This is because the particles of the shell layer material were too large, the contact area between the particles was small, and the cement slurry bonding points were insufficient. At the same time, the excessive particle gaps led to too high a permeation rate, and surface runoff was likely to be triggered during heavy rain.

[0194] Comparative Example 6

[0195] The difference from Example 1 is that during the preparation of the surface layer material, the particle size is controlled to be 0.5 mm.

[0196] The tailings-based soil-improved permeable bricks were tested in accordance with "GB / T 25993-2023 Permeable Pavement Bricks and Permeable Pavement Panels". The permeability coefficient was 0.81×10 -2 cm / s, and the flexural strength was 3.1 MPa. It can be seen that compared with Example 1, when the particle size of the surface layer is smaller, the permeability coefficient of the permeable brick decreases significantly.

[0197] Comparative Example 7

[0198] The difference from Example 1 is that during the preparation of the core layer material, the particle size is controlled to be 1 mm.

[0199] The tailings-based soil-improved permeable bricks were tested in accordance with "GB / T 25993-2023 Permeable Pavement Bricks and Permeable Pavement Panels". The permeability coefficient was 0.97×10 -2 cm / s, and the flexural strength was 2.8 MPa. Compared with Example 1, after the particle size of the core layer material was reduced to 1 mm, the permeability coefficient decreased significantly. This is because the number of contact points between the core layer particles increased, the pore size decreased, and the connectivity became worse.

[0200] Comparative Example 8

[0201] The difference from Example 1 is that the copper tailings used are replaced with lead-zinc tailings: the SiO2 content is 42.66%, the K2O content is 2.06%, the Cr content is 85.07 mg / kg, the Cd content is 69.60 mg / kg, the Pb content is 715.66 mg / kg, the As content is 90.96 mg / kg, the Hg content is 0.28 mg / kg, and the Tl content is 0.21 mg / kg. Among them, the K2O content is lower than the specified requirement, and the Cd and Pb contents exceed the specified requirements.

[0202] The tailings-based soil-improved permeable bricks were tested in accordance with "GB / T 25993-2023 Permeable Pavement Bricks and Permeable Pavement Panels". The permeability coefficient was 2.28×10 -2 cm / s, and the flexural strength was 3.2 MPa. The soil culture test was carried out according to the method in Example 1, and the test results are shown in Table 9.

[0203] Table 9 Changes in soil physical and chemical properties

[0204]

[0205] As can be seen from Table 9, compared with Example 1, the increase in available potassium in the soil becomes smaller, the effect of fixing heavy metals in the soil becomes worse, and even the contents of available Cd and Pb increase. This indicates that when the K2O is lower than the limit value and the heavy metal content is higher than the limit value, it is not suitable for preparing tailings-based soil-improving permeable bricks.

[0206] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and 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 application.

[0207] In addition, those skilled in the art can understand that although some embodiments herein include certain features included in other embodiments rather than other features, the combination of the features of different embodiments means that it is within the scope of the present application and forms different embodiments. For example, in the above claims, any one of the claimed embodiments can be used in any combination. The information disclosed in this background art section is only intended to deepen the understanding of the overall background art of the present application, and should not be regarded as an admission or any form of implication that this information constitutes the prior art known to those skilled in the art.

Claims

1. A preparation method of a tailing-based soil-improving permeable brick, characterized in that, Including: Mixing tailings and cement to obtain a first homogenized raw material and a second homogenized raw material; Performing first granulation on the first homogenized raw material and an adsorbent, wherein the adsorbent is disposed on the surface of the first homogenized raw material, and then performing first curing to obtain a shell layer material; Performing second granulation on the second homogenized raw material and a pigment, wherein the pigment is disposed on the surface of the second homogenized raw material, and then performing second curing to obtain a surface layer material; Mixing tailings, potassium feldspar and a conversion agent, and performing third granulation and roasting to obtain a core layer material; Mixing cement and water to obtain a cement slurry, and mixing the core layer material, the shell layer material and the surface layer material with the cement slurry respectively to obtain a core layer material-cement slurry mixture, a shell layer material-cement slurry mixture and a surface layer material-cement slurry mixture; Stacking and molding the core layer material-cement slurry mixture, the shell layer material-cement slurry mixture and the surface layer material-cement slurry mixture in a mold in sequence, and performing third curing to obtain a tailings-based soil-improving permeable brick; When performing the first granulation, the second granulation and the third granulation, a binder solution is also sprayed; The prepared tailings-based soil-improving permeable brick includes a surface layer and a base layer; The base layer includes a core layer and a shell layer disposed on the surface of the core layer; the shell layer completely covers the core layer; The raw materials of the surface layer include tailings, cement, binder solution, pigment and water with a mass ratio of 60-80:33-72:4-26:2-12:7-16; The raw materials of the shell layer include tailings, cement, binder solution, adsorbent and water with a mass ratio of 60-80:36-76:5-30:20-30:8-18; The raw materials of the core layer include tailings, potassium feldspar, conversion agent, binder solution, cement and water with a mass ratio of 60-80:20-40:50-80:7-40:19-48:10-24; The binder solution includes one or more of sodium lignosulfonate aqueous solution, calcium lignosulfonate aqueous solution, ammonium chloride aqueous solution and sodium carboxymethylcellulose aqueous solution; The adsorbent includes rice husk charcoal, attapulgite and humic acid, wherein the mass ratio of the rice husk charcoal, the attapulgite and the humic acid is 60-80:20-40:0-10, and the mass of the humic acid is not 0; The conversion agent includes calcium carbonate, desulfurized gypsum and dolomite, wherein the mass ratio of the calcium carbonate, the desulfurized gypsum and the dolomite is 50-60:20-30:20-30; 2. The preparation method of the tailings-based soil-improving permeable brick according to claim 1, characterized in that The concentration of the binder solution is 5%-10%; 3. The preparation method of the tailings-based soil-improving permeable brick according to claim 1, characterized in that, The content of SiO2 in the tailings is greater than 30%, the content of K2O is greater than 5%, the content of Cr is less than 250 mg / kg, the content of Cd is less than 20 mg / kg, the content of Pb is less than 400 mg / kg, the content of As is less than 100 mg / kg, the content of Hg is less than 10 mg / kg, and the content of Tl is less than 5 mg / kg; 4. The preparation method of the tailings-based soil-improving permeable brick according to claim 1, characterized in that The particle sizes of the pigment, the tailings, the cement, the potassium feldspar and the conversion agent are each independently less than or equal to 0.074 mm; 5. The preparation method of the tailings-based soil-improving permeable brick according to claim 1, wherein, Satisfying at least one of the following conditions: A. The disk rotation speeds of the first granulation, the second granulation, and the third granulation are each independently 20 r / min - 40 r / min, and the granulation times are each independently 5 min - 10 min; B. The times of the first curing and the second curing are each independently 12 h - 24 h; C. The temperature of the roasting is 1100 °C - 1200 °C, and the time is 30 min - 60 min; D. The time of the third curing is not less than 28 days.

6. The preparation method of the tailings-based soil-improving permeable brick according to claim 1, characterized in that, The particle size of the shell layer material is 8 mm - 10 mm; The particle size of the surface layer material is 1 mm - 3 mm; The particle size of the core layer material is 3 mm - 5 mm.

7. The preparation method of the tailing-based soil-improving permeable brick according to claim 1, characterized in that, Meet at least one of the following conditions: A. When preparing the homogenized raw material, the mass ratio of the tailings to the cement is 60 - 80:20 - 40; B. When preparing the shell layer material - cement slurry mixture, the mass ratio of the shell layer material, the cement, and the water is 100:15 - 20:8 - 10; C. When preparing the core layer material - cement slurry mixture, the mass ratio of the core layer material, the cement, and the water is 100:15 - 20:8 - 10; D. When preparing the surface layer material - cement slurry mixture, the mass ratio of the surface layer material, the cement, and the water is 100:15 - 20:8 - 10.

8. The preparation method of the tailings-based soil-improving permeable brick according to any one of claims 1-7, characterized in that, The sequential stacking and forming in the mold includes: First, spread the shell layer material - cement slurry mixture over the bottom and four walls of the mold, then fill the core layer material - cement slurry mixture into it, and then sequentially lay the shell layer material - cement slurry mixture and the surface layer material - cement slurry mixture on the upper layer of the core layer material - cement slurry mixture.

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