Multifunctional soil conditioner based on lead-zinc tailings as well as preparation method and application of multifunctional soil conditioner

Abstract

The invention discloses a multifunctional soil conditioner based on lead-zinc tailings and a preparation method and application thereof.The preparation method comprises the following steps that the lead-zinc tailings, calcium-containing minerals, silicon-containing minerals, aluminum-containing minerals and magnesium-containing minerals are evenly mixed according to the element proportion of target water-soluble and / or citrate-soluble minerals, carbon-containing substances are added, mixed and ground, and a mixture is obtained; raw materials are obtained; calcining the raw material to obtain solid and flue gas, cooling and collecting the flue gas for lead and zinc recovery, and cooling the solid to obtain clinker; mixing the clinker with functional auxiliary materials, and grinding the mixture into powder to obtain the powdery multifunctional soil conditioner. Or the powdery multifunctional soil conditioner is subjected to a forming process to obtain the granular multifunctional soil conditioner. The soil conditioner disclosed by the invention has the advantages of neutralizing acid soil, fixing heavy metals in the soil, supplementing nutritional ingredients required by the soil and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of large-scale, safe and high-value comprehensive utilization of lead-zinc tailings, and specifically relates to a multifunctional soil conditioner based on lead-zinc tailings, a preparation method thereof and an application thereof. Background Art

[0003] In recent years, a great deal of work has been done in China on the development of lead-zinc tailings. Research work such as re-selection for the recovery of valuable metals, preparation of building materials, use for mine filling and mine environment restoration has been carried out, and certain effects have been achieved. However, there are still a large number of deficiencies in these works, the effects are not good, and the substantial problems of lead-zinc tailings have not been truly solved. For example, the composition of lead-zinc tailings is complex, the particle size is small, and the degree of slimeification is relatively high. It is difficult to re-select and recover valuable metals, and the amount of tailings has not been reduced. Although lead-zinc tailings can be used as raw materials to produce building materials products such as cement, bricks and tiles, plates, ceramics, and glass-ceramics, the high impurity content of the raw materials results in poor product performance and poor benefits, and it is difficult to sustain in the current context of the overall decline of the building materials industry. Although lead-zinc tailings can be used for mine filling or mine area reclamation, the heavy metal ions contained therein are easily transported with surface water and groundwater, causing regional environmental pollution.

[0004] In lead-zinc tailings, except for a small amount of heavy metal elements such as lead and zinc, the vast majority are non-metallic vein stone minerals, including quartz, calcite, dolomite, etc., and their main constituent elements are Ca, Si, Al, Mg, Fe, etc. However, these minerals are insoluble, and these elements cannot be used in soil conditioners. Summary of the Invention

[0005] In view of the above-mentioned deficiencies, the present invention provides a multifunctional soil conditioner based on lead-zinc tailings and a preparation method thereof. First, based on the mineral composition and element composition of the lead-zinc tailings themselves, the aim is to generate water-soluble and / or citrate-soluble alkaline minerals such as wollastonite, calcium feldspar, calcium magnesium feldspar, nepheline, etc. through high-temperature mineral phase reconstruction. A variety of calcium-containing, silicon-containing, and aluminum-containing minerals are incorporated to regulate the composition ratios of SiO2, CaO, Al2O3, and MgO in the raw material to meet the generation requirements of the target minerals. A carbon-containing substance is introduced into the formulation of the present invention. Utilizing its reduction effect at high temperatures, compounds such as lead and zinc in the lead-zinc tailings are reduced so that they volatilize with the flue gas. This can not only reduce the heavy metal content in the soil conditioner to below the safety threshold but also achieve the recovery of heavy metals. The present invention obtains lead-zinc-rich soot through cooling, and lead-zinc products can be obtained after collection and post-treatment. The calcined clinker compounding of the present invention is to further improve the functionality and applicability of the soil conditioner. According to the nature characteristics of the application object itself and the improvement target requirements, a small amount of fertilizer and functional materials are compounded into the clinker to obtain a multifunctional soil conditioner, thereby realizing the targeted development and personalized customization of the product. The preparation method of the soil conditioner of the present invention is well-considered, highly feasible, and has a relatively low cost. It can not only achieve the recovery of lead and zinc metals in the tailings but also produce a multifunctional soil conditioner with good performance and wide application. This technological invention helps to achieve the large-scale, safe, and high-value consumption of lead-zinc tailings and provides a high-quality multifunctional soil conditioner for the treatment and improvement of acidic soils and heavy metal-contaminated soils in China.

[0006] In order to achieve the above object, the present invention provides a preparation method of a multifunctional soil conditioner based on lead-zinc tailings, comprising the following steps:

[0007] S1. Mix lead-zinc tailings with calcium-containing minerals, silicon-containing minerals, aluminum-containing minerals, and magnesium-containing minerals according to the element ratio of the target water-soluble and / or citrate-soluble minerals, and add a carbon-containing substance for mixed grinding to obtain a raw material;

[0008] S2. Calcinate the raw material to obtain a solid and flue gas; wherein, after the flue gas is cooled and collected, lead-zinc recovery is carried out (the tail gas is discharged up to standard after absorption and purification treatment); the solid is cooled to obtain a clinker;

[0009] S3. Mix the clinker and functional auxiliary materials in proportion, and grind them into powder to obtain a powdery multifunctional soil conditioner; or obtain a granular multifunctional soil conditioner by shaping the powdery multifunctional soil conditioner.

[0010] The mechanism of the present invention:

[0011] The lead-zinc tailings of the present invention mainly contain non-metallic minerals such as quartz and calcite. In the high-temperature calcination system of lead-zinc tailings batching, the thermal decomposition reaction of calcite (CaCO3) in the lead-zinc tailings is the start of the ore phase reconstruction process in the whole process. First, the thermal decomposition of calcite will form calcium oxide (CaO), which then reacts with various added batching materials at high temperature. Specifically:

[0012] When the batching contains potassium feldspar, the lattice vibration energy induced by it under high temperature conditions (above 1100 °C) breaks through the bonding energy threshold of the Si-O-Al bond in potassium feldspar, resulting in the phase change decomposition of potassium feldspar to generate leucite and liquid-phase SiO2 (Equation 1). This process is reversible. During this period, CaO breaks the phase equilibrium of the aluminosilicate system, promoting the directional mineralization reaction of liquid-phase SiO2 and CaO to generate wollastonite (Equation 2). The formation of wollastonite not only consumes liquid-phase SiO2 to reduce the system viscosity, but also drives the reaction equilibrium to continuously shift to the right, forming a typical "calcium-silicate melt - new crystal phase" coupled reaction mechanism, promoting the further decomposition of leucite into soluble kaliophilite.

[0013] When the batching contains potassium feldspar and gypsum, there is a certain synergistic effect between gypsum and calcium oxide. On the one hand, during the calcination process, calcium oxide and feldspar undergo a chain reaction of Equation 1 to Equation 2 to generate kaliophilite and wollastonite. On the other hand, the lattice of CaSO4 in gypsum undergoes relaxation under high temperature conditions, reducing the Ca 2+ activation energy. Based on Wagner's ion diffusion theory, during this process, the Ca 2+ activation energy in gypsum is significantly higher than the migration energy barrier of K + in the feldspar / leucite lattice, forming a cross-crystal-phase cation exchange driven by a concentration gradient. The preferential migration of Ca 2+ results in the reconstruction of the interlayer charge in the feldspar lattice, generating soluble potassium sulfate and rankinite.

[0014] When the batching contains brucite, its thermal decomposition forms magnesium oxide. Under high temperature conditions, magnesium oxide undergoes a composite mineralization reaction with quartz and the decomposition product calcium oxide of calcite in the tailings to generate soluble calcium magnesium feldspar (Equation 4), providing soluble calcium, magnesium, and silicon for the soil conditioner.

[0015] According to phase diagrams such as SiO2-Al2O3-CaO, SiO2-CaO-MgO, and KAlSi3O8-SiO2, the proportion ranges of components such as SiO2, Al2O3, CaO, and MgO required to generate water-soluble and citrate-soluble alkaline minerals such as wollastonite, gehlenite, anorthite, and nepheline can be calculated; then, by fitting the ΔG values of the main reactions at different temperatures, the temperature ranges for the formation of target phases such as kaliophilite, wollastonite, gehlenite, and melilite can be determined. Based on this, different ingredients can be accurately introduced according to the mineral composition and chemical composition of the tailings, and the calcination temperature can be determined. The quantitative conversion from mineral composition analysis to batching scheme design is realized.

[0016] The innovation of this reaction mechanism lies in breaking through the empirical batching mode in the traditional pyroprocessing of tailings, breaking the limitation of having to find a suitable formula through a large number of experiments; instead, it constructs a design-type technical path of "product mineral phase target-oriented - thermodynamics-driven regulation", realizing the innovation of the combination of theory and technology from mineral microstructure regulation to macroscopic reaction process control, and providing a general method and technology for the high-value utilization of lead-zinc tailings.

[0017]

[0018] SiO2 + CaO = CaSiO3 Equation 2

[0019] 2KAlSi3O8 + 8CaSO4 + 2CaO = KAlSiO4 + K2SO4 + Ca2Al2SiO7 + 6CaSiO3 + 7SO2 + 3.5O2 + Ca2SiO4 Equation 3

[0020] MgO + 2CaO + 2SiO2 = Ca2MgSi2O7 Equation 4

[0021] According to one aspect of the present invention, in step S1, the carbon-containing substance includes any one or more of coal, biomass, coke, charcoal, graphite, and stone coal, and the addition amount of the carbon-containing substance accounts for 0.5 - 5 wt% of the raw meal.

[0022] It should be noted that the carbon-containing substance is used as a reducing agent to reduce lead and zinc in the tailings at high temperature during calcination. Although a small amount of ash is generated after the carbon-containing substance burns, and it also contains components such as SiO2, Al2O3, CaO, and MgO, due to the small total amount, its influence on the chemical components of the clinker can be ignored.

[0023] According to one aspect of the present invention, in step S1, the calcium-containing minerals include any one or more of calcite, limestone, marble, dolomite, gypsum, apatite, wollastonite; the silicon-containing minerals include any one or more of quartz, feldspar, wollastonite, mica, talc, kaolinite, montmorillonite; the aluminum-containing minerals include any one or more of bauxite, feldspar, kaolinite, montmorillonite, mica; the magnesium-containing minerals include any one or more of magnesite, brucite, dolomite, talc, serpentine.

[0024] According to one aspect of the present invention, in step S1, the water-soluble minerals and / or citrate-soluble minerals include wollastonite, rankinite, calcio-olivine, and nepheline; in step S2, the content of SiO2 in the clinker is 25-50%, the content of CaO is 30-50%, the content of Al2O3 is 1-8%, the content of MgO is 1-8%, the content of SiO2+CaO is 75-85%, and the content of SiO2+CaO+Al2O3+MgO is 80-95%.

[0025] According to one aspect of the present invention, in step S2, the temperature of the calcination treatment is 1100-1300°C, and the time of the calcination treatment is 60-240 min.

[0026] According to one aspect of the present invention, in step S3, the functional auxiliary materials include any one or more of fertilizers and functional materials; the addition amount of the functional auxiliary materials does not exceed 10 wt% of the clinker.

[0027] According to one aspect of the present invention, the fertilizers include any one or more of nitrogen-phosphorus-potassium fertilizers, organic fertilizers, and trace element fertilizers.

[0028] According to one aspect of the present invention, the functional materials include any one or more of heavy metal solidifying agents, water retaining agents, porous materials, and microbial agents.

[0029] Based on the same inventive concept, the present invention also provides a multifunctional soil conditioner prepared by the above preparation method.

[0030] Based on the same inventive concept, the present invention also provides the application of the above multifunctional soil conditioner in acidic soil and / or heavy metal contaminated soil.

[0031] The beneficial effects of the present invention:

[0032] (1) The present invention completely solves the problems that lead and zinc resources are difficult to recover and easily cause pollution, and non-metallic minerals are not fully utilized in the traditional comprehensive utilization process of lead-zinc tailings. The obtained soil conditioner product has a broader market and higher added value, and truly realizes the large-scale, safe, and high-value resource utilization of lead-zinc tailings.

[0033] (2) The present invention uses wollastonite, gehlenite, calcio-magnesium feldspar, nepheline and other water-soluble minerals and / or citrate-soluble minerals as the target products for high-temperature mineral phase reconstruction, and constructs a batching scheme based on lead-zinc tailings with this as the guide, making the selection of batching raw materials wider and the batching addition ratio more reasonable, and fully ensuring the components and properties of the products.

[0034] (3) The present invention adds carbon-containing substances to the batching as reducing agents in the high-temperature process. Through optimizing the calcination process, full reduction and volatilization of heavy metals such as lead and zinc in the lead-zinc tailings can be achieved. Combined with the in-depth treatment of flue gas and tail gas, both the full recovery and utilization of valuable metal resources in the lead-zinc tailings are realized, and there is no heavy metal residue in the clinker, thus making a safe and compliant soil conditioner.

[0035] (4) Using the clinker fired from lead-zinc tailings as the main component, by compounding a small amount of fertilizers and functional materials into the clinker, a multifunctional soil conditioner is obtained, thus realizing the targeted development and personalized customization of the product. This further improves the functionality and applicability of the soil conditioner product, and better meets the property characteristics of the applied soil object itself and the target requirements of improvement.

[0036] All in all, this patent prepares a multifunctional soil conditioner from lead-zinc tailings through scientific proportioning and complete processes, and simultaneously realizes the recovery of valuable metals such as lead and zinc in the tailings. The technological process of this technology is simple, the batching is easy to obtain, the mineral components in the tailings are fully utilized, the soil conditioner product is safe and its performance is controllable, and the heavy metals in the tailings can be fully recovered, providing a new idea for the large-scale, safe and high-value utilization of lead-zinc tailings in China, and providing strong help for the improvement of acidic soil and heavy metal polluted soil in China. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is the process flow diagram of the preparation method of the multifunctional soil conditioner based on lead-zinc tailings described in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] To make the present invention easier to understand, the following specific embodiments are further used to illustrate the present invention. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention. Unless otherwise defined, the professional terms used below have the same meaning as understood by those of ordinary skill in the art; unless otherwise specified, the raw materials and reagents involved in this article can be purchased from the market or prepared by well-known methods.

[0039] In order to solve the problem that existing lead-zinc tailings are difficult to utilize, the inventors of the present application provide a preparation method of a multifunctional soil conditioner based on lead-zinc tailings, and its process flow chart is as shown in Figure 1 shown, including the following steps:

[0040] S1. Mix lead-zinc tailings with calcium-containing minerals, silicon-containing minerals, aluminum-containing minerals, magnesium-containing minerals and carbon-containing substances, and then grind to obtain raw materials; wherein, the lead-zinc tailings are mixed with calcium-containing minerals, silicon-containing minerals, aluminum-containing minerals, and magnesium-containing minerals according to the elemental ratio of target water-soluble minerals and / or citrate-soluble minerals; preferably, the carbon-containing substances include any one or more of coal, biomass, coke, charcoal, graphite, stone coal, and combustible organic substances; the addition amount of the carbon-containing substances accounts for 0.5-5 wt% of the raw materials. Preferably, the calcium-containing minerals include any one or more of calcite, limestone, marble, dolomite, gypsum, apatite, and wollastonite; the silicon-containing minerals include any one or more of quartz, feldspar, wollastonite, mica, talc, kaolinite, and montmorillonite; the aluminum-containing minerals include any one or more of bauxite, feldspar, kaolinite, montmorillonite, and mica; the magnesium-containing minerals include any one or more of magnesite, brucite, dolomite, talc, and serpentine. Preferably, the water-soluble minerals and / or citrate-soluble minerals include wollastonite, calcium yellow feldspar, calcium magnesium feldspar, and nepheline.

[0041] S2. Calcinate the raw materials to obtain solids and flue gas; wherein, after the flue gas is cooled and collected, lead and zinc are recovered (the tail gas is discharged up to standard after absorption and purification treatment); the solids are cooled to obtain clinker. Preferably, the temperature of the calcination treatment is 1100-1300 °C, and the time of the calcination treatment is 60-240 min. Preferably, the content of SiO2 in the clinker is 25-50%, the content of CaO is 30-50%, the content of Al2O3 is 1-8%, the content of MgO is 1-8%, the content of SiO2+CaO is 75-85%, and the content of SiO2+CaO+Al2O3+MgO is 80-95%.

[0042]

[0043] The following is further elaborated in combination with specific examples and comparative examples.​

[0044] Example 1

[0045] The mineral composition of the lead-zinc tailings in this example is mainly: quartz, calcite, etc., and the chemical composition is shown in Table 1.

[0046] Table 1 Chemical composition of the lead-zinc tailings in Example 1 (%)

[0047] <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Na2O]]> <![CDATA[K2O]]> CaO MgO 22.827 2.40 0.74 0.676 35.8 0.81 <![CDATA[Fe2O3]]> ZnO PbO BaO <![CDATA[SO3]]> LOI 6.103 1.446 0.505 0.635 1.402 26.653

[0048] (1) Dolomite (calcium-containing mineral, magnesium-containing mineral), quartz (silicon-containing mineral), potassium feldspar (aluminum-containing mineral, silicon-containing mineral), magnesite (magnesium-containing mineral) are used as raw materials. They are mixed with the lead-zinc tailings according to the calculated amount. Subsequently, 98.2 g of this mixture is mixed evenly with 1.8 g of coal and ground to obtain raw meal;

[0049] (2) The raw meal is put into a tubular furnace and calcined at 1180 °C for 120 minutes. During the calcination process, a flue gas cooling bottle and a tail gas absorption bottle are respectively connected behind the tubular furnace. After the calcination is completed, the powder in the cooling bottle is recovered to obtain lead-zinc-rich soot; it is determined that the SiO2 content in the prepared clinker is 31.7%, the CaO content is 46.7%, the Al2O3 content is 3.1%, the MgO content is 6.4%, the SiO2+CaO content is 78.4%, and the SiO2+CaO+Al2O3+MgO content is 87.9%;

[0050] (3) The calcined clinker is taken out, 8 wt% of humic acid is added thereto, and after mixing evenly, it is extruded into short strips to obtain an alkaline humic acid soil conditioner that meets the requirements of the HG / T 5782-2020 standard.

[0051] Example 2

[0052] The mineral composition of the lead-zinc tailings in this example is mainly: quartz, calcite, etc., and the chemical composition is shown in Table 2.

[0053] Table 2 Chemical composition of the lead-zinc tailings in Example 2 (%)

[0054] <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Na2O]]> <![CDATA[K2O]]> CaO MgO 40.434 4.46 0.39 0.983 24.793 0.658 <![CDATA[Fe2O3]]> ZnO PbO BaO <![CDATA[SO3]]> LOI 2.503 0.81 0.148 0.131 4.107 20.588

[0055] (1) Gypsum (calcium-containing mineral), apatite (calcium-containing mineral), potassium feldspar (aluminum-containing mineral, silicon-containing mineral), brucite (magnesium-containing mineral) are used as raw materials. They are mixed with the lead-zinc tailings according to the calculated amount. Subsequently, 98.6 g of this mixture is mixed evenly with 1.4 g of charcoal and ground to obtain raw meal;

[0056] (2) Put the raw materials into a tubular furnace and calcine them at 1200 °C for 90 minutes. During the calcination process, a flue gas cooling bottle and a tail gas absorption bottle are respectively connected behind the tubular furnace. After the calcination is completed, recover the powder in the cooling bottle to obtain lead-zinc-rich soot; measure that the SiO2 content in the prepared clinker is 43.5%, the CaO content is 37.7%, the Al2O3 content is 4.8%, the MgO content is 3.4%, the SiO2+CaO content is 81.2%, and the SiO2+CaO+Al2O3+MgO content is 89.4%.

[0057] (3) Take out the calcined clinker, add 7 wt% potassium dihydrogen phosphate to it, mix evenly and granulate into balls to obtain an alkaline inorganic compound soil conditioner that meets the requirements of the DB44 / T 1598-2015 standard.

[0058] Example 3

[0059] The mineral composition of the lead-zinc tailings in this example is mainly: quartz, calcite, etc., and the chemical composition is shown in Table 3.

[0060] Table 3 Chemical composition of lead-zinc tailings in Example 3 (%)

[0061] <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Na2O]]> <![CDATA[K2O]]> CaO MgO 27.36 2.62 0.42 0.607 33.01 0.414 <![CDATA[Fe2O3]]> ZnO PbO BaO <![CDATA[SO3]]> LOI 7.316 1.06 0.46 0.337 2.067 24.329

[0062] (1) Use dolomite (calcium-containing mineral, magnesium-containing mineral), apatite (calcium-containing mineral), phosphogypsum (calcium-containing mineral), potassium feldspar (aluminum-containing mineral, silicon-containing mineral) as raw materials, mix them with lead-zinc tailings according to the calculated amount, and then mix 97.9 g of this mixture with 2.1 g of biomass evenly and grind to obtain raw materials;

[0063] (2) Put the raw materials into a tubular furnace and calcine them at 1250 °C for 100 minutes. During the calcination process, a flue gas cooling bottle and a tail gas absorption bottle are respectively connected behind the tubular furnace. After the calcination is completed, recover the powder in the cooling bottle to obtain lead-zinc-rich soot; measure that the SiO2 content in the prepared clinker is 30.7%, the CaO content is 45.9%, the Al2O3 content is 2.9%, the MgO content is 4.2%, the SiO2+CaO content is 76.6%, and the SiO2+CaO+Al2O3+MgO content is 83.7%.

[0064] (3) Take out the calcined clinker, add 5 wt% urea and 5 wt% potassium dihydrogen phosphate to it, mix evenly and granulate into balls to obtain an alkaline soil conditioner that meets the requirements of the T / HNPCIA 11-2019 standard.

[0065] Example 4

[0066] The mineral composition of the lead-zinc tailings in this example is mainly: quartz, calcite, etc., and the chemical composition is shown in Table 4.

[0067] Table 4 Chemical composition of lead-zinc tailings in Example 3 (%)

[0068] <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Na2O]]> <![CDATA[K2O]]> CaO MgO 38.98 3.54 0.76 0.983 28.21 0.617 <![CDATA[Fe2O3]]> ZnO PbO BaO <![CDATA[SO3]]> LOI 4.575 1.09 0.37 0.112 1.203 19.560

[0069] (1) Quartz (silicon-containing mineral), potassium feldspar (aluminum-containing mineral, silicon-containing mineral), bauxite (aluminum-containing mineral), dolomite (calcium-containing mineral, magnesium-containing mineral), and gypsum (calcium-containing mineral) were used as raw materials. They were mixed with lead-zinc tailings according to the calculated amounts, and then 95 g of the mixture was mixed evenly with 5 g of pulverized coal and ground to obtain raw meal;

[0070] (2) The raw meal B was placed in a tubular furnace and calcined at 1200 °C for 120 minutes. During the calcination process, a flue gas cooling bottle and a tail gas absorption bottle were connected to the rear of the tubular furnace respectively. After the calcination was completed, the powder in the cooling bottle was recovered to obtain lead-zinc-rich soot; it was determined that the SiO2 content in the prepared clinker was 40.4%, the CaO content was 38.5%, the Al2O3 content was 7.2%, the MgO content was 2.1%, the SiO2+CaO content was 78.9%, and the SiO2+CaO+Al2O3+MgO content was 88.2%.

[0071] (3) The calcined clinker was taken out, and 4 wt% of magnesium chloride and 4 wt% of potassium chloride were added thereto. After mixing evenly, a silicon-calcium-potassium-magnesium fertilizer soil conditioner meeting the requirements of the GB / T 36207-2018 standard was obtained.

[0072] Comparative Example 1

[0073] The difference between this comparative example and Example 1 is that the calcination temperature was 1000 °C, and the other steps and parameters were the same as those in Example 1. The finally obtained product was in an underburned state, and the mass fraction of available silicon was less than 10%, not meeting the requirements of the HG / T 5782-2020 standard.

[0074] Comparative Example 2

[0075] The difference between this comparative example and Example 1 is that the calcination temperature was 1350 °C, and the other steps and parameters were the same as those in Example 1. The finally obtained product was in an overburned state, and the mass fraction of available calcium was less than 15%, and the mass fraction of available magnesium was less than 3%, not meeting the requirements of the HG / T 5782-2020 standard.

[0076] Comparative Example 3

[0077] The difference between this comparative example and Example 1 is that no carbon-containing substance was added, and the other steps and parameters were the same as those in Example 1. Because of the lack of the reduction effect of the carbon-containing substance during the calcination process, the total lead content in the finally obtained product exceeded the limit requirement of harmful elements by dozens of times, not meeting the requirements of the HG / T5782-2020 standard.

[0078] Comparative Example 4

[0079] The difference between this comparative example and Example 1 is that the SiO2 content in the clinker is 52.6%, the CaO content is 25.8%, and the other steps and parameters are the same as those in Example 1. In the finally obtained product, the mass fraction of effective silicon is less than 10%, the mass fraction of effective calcium is less than 15%, and the mass fraction of effective magnesium is less than 3%, which does not meet the requirements of the HG / T 5782-2020 standard.

[0080] Comparative Example 5

[0081] The difference between this comparative example and Example 1 is that no humic acid is added, and the other steps and parameters are the same as those in Example 1. In the finally obtained product, the mass fractions of total humic acid and activated humic acid are both 0, which does not meet the requirements of the HG / T 5782-2020 standard.

[0082] As mentioned above, the above are only the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A preparation method of a multifunctional soil conditioner based on lead-zinc tailings, characterized in that, It includes the following steps: S1. Mix lead-zinc tailings with calcium-containing minerals, silicon-containing minerals, aluminum-containing minerals, and magnesium-containing minerals according to the elemental ratio of target water-soluble and / or citric acid-soluble minerals, and add carbon-containing substances for mixing and grinding to obtain raw materials; S2. Calcinate the raw materials to obtain solids and flue gas; among them, after the flue gas is cooled and collected, lead and zinc are recovered; the solids are cooled to obtain clinker; S3. Mix the clinker and functional auxiliary materials in proportion, grind them into powder to obtain a powdery multi-functional soil conditioner; or obtain a granular multi-functional soil conditioner by shaping the powdery multi-functional soil conditioner.

2. The preparation method of the multifunctional soil conditioner based on lead-zinc tailings according to claim 1, characterized in that, In step S1, the carbon-containing substances include any one or more of coal, biomass, coke, charcoal, graphite, and stone coal; the addition amount of the carbon-containing substances accounts for 0.5-5wt% of the raw materials.

3. The preparation method of the multifunctional soil conditioner based on lead-zinc tailings according to claim 1, characterized in that, In step S1, the calcium-containing minerals include any one or more of calcite, limestone, marble, dolomite, gypsum, apatite, and wollastonite; the silicon-containing minerals include any one or more of quartz, feldspar, wollastonite, mica, talc, kaolinite, and montmorillonite; the aluminum-containing minerals include any one or more of bauxite, feldspar, kaolinite, montmorillonite, and mica; the magnesium-containing minerals include any one or more of magnesite, brucite, dolomite, talc, and serpentine.

4. The preparation method of the multifunctional soil conditioner based on lead-zinc tailings according to claim 1, characterized in that, In step S1, the water-soluble minerals and / or citric acid-soluble minerals include wollastonite, calcium yellow feldspar, calcium magnesium feldspar, and nepheline; in step S2, the SiO2 content in the clinker is 25-50%, the CaO content is 30-50%, the Al2O3 content is 1-8%, the MgO content is 1-8%, the SiO2+CaO content is 75-85%, and the SiO2+CaO+Al2O3+MgO content is 80-95%.

5. The preparation method of the multifunctional soil conditioner based on lead-zinc tailings according to claim 1, wherein, In step S2, the temperature of the calcination treatment is 1100-1300°C, and the time of the calcination treatment is 60-240 min.

6. The preparation method of the multifunctional soil conditioner based on lead-zinc tailings according to claim 1, characterized in that, In step S3, the functional auxiliary materials include any one or more of fertilizers and functional materials; the addition amount of the functional auxiliary materials does not exceed 10wt% of the clinker.

7. The preparation method of the multifunctional soil conditioner based on lead-zinc tailings according to claim 6, characterized in that, The fertilizers include any one or more of nitrogen-phosphorus-potassium fertilizers, organic fertilizers, and trace element fertilizers.

8. The preparation method of the multifunctional soil conditioner based on lead-zinc tailings according to claim 6, characterized in that, The functional materials include any one or more of heavy metal solidifying agents, water retaining agents, porous materials, and microbial agents.

9. A multifunctional soil conditioner, characterized in that, Prepared by the preparation method according to any one of claims 1-8.

10. Application of the multi-functional soil conditioner according to claim 9 in acidic soil and / or heavy metal contaminated soil.

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