Gradient high-valued utilization treatment method of quartz tailings and product

Abstract

The invention relates to the technical field of comprehensive utilization of quartz resources, soil improvement, heavy metal solidification and slow-release fertilizer preparation, in particular to a gradient high-value utilization treatment method of quartz tailings and a product. The preparation method comprises the following steps: uniformly mixing quartz tailings with calcium additives such as calcium carbonate, calcium hydroxide and calcium oxide according to a specific mass ratio, calcining and activating to obtain a silicon-calcium fertilizer; secondly, a silicon-calcium fertilizer is converted into a calcium-based hydrotalcite / porous silicon oxide soil heavy metal curing agent through an acid leaching-aluminum (iron) adding-normal pressure hydrothermal method; and finally, carrying out negative-pressure dipping, low-temperature evaporation, mixed granulation and organic coating to obtain the slow-release fertilizer. According to the technology, the low-value quartz tailings are converted into three products including the soil conditioner, the soil heavy metal curing agent and the slow-release fertilizer through three procedures of continuous process steps, different application requirements are met, high-value utilization of the quartz tailings is fully achieved, and the technology has remarkable technical, product and cost advantages.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of comprehensive utilization of quartz resources, soil improvement, heavy metal solidification and preparation of slow-release fertilizers, and particularly relates to a processing method and product for stepwise high-value utilization of quartz tailings. BACKGROUND

[0002] With the rapid development of high-purity quartz processing industry, the production of quartz tailings is increasing year by year. The tailings, which are produced in the process of quartz crushing, grinding, magnetic separation, flotation and acid leaching, have a purity and particle size that do not meet the standards, usually have a high silicon dioxide content (generally greater than 90%, many between 95% and 99%), low impurity element content and extremely low heavy metal content, and have good potential for resource utilization. However, the comprehensive utilization rate is low at present, and most of them are only used for low-value building fillers and other purposes, failing to fully realize the potential value of their high purity and low harmful substance content, resulting in waste of resources and hindering the sustainable development of the industry.

[0003] At the same time, China's agricultural production is facing multiple challenges: soil effective silicon and calcium deficiency restricts the full play of crop growth potential, heavy metal pollution threatens the quality of arable land and the safety of agricultural products, and low fertilizer utilization rate exacerbates resource consumption and environmental pressure. These problems have become key bottlenecks affecting the sustainable development of agriculture. Under this background, silicon and calcium fertilizer, as an important soil conditioner, plays a significant role in improving crop yield and quality, improving soil health and reducing environmental pollution, and is an important fertilizer type for promoting the development of green agriculture; soil heavy metal solidification agent can effectively reduce the migration of active heavy metals in the soil-plant system by converting them into stable state, and reduce the risk of accumulation in crops and diffusion to the environment, which is of great significance to food safety and ecological safety; slow-release fertilizer, with the characteristics of "precise fertilizer supply, efficient utilization and green environmental protection", can not only improve fertilizer utilization rate and reduce production cost, but also reduce non-point source pollution, which is a key technical means to realize the reduction and efficiency of chemical fertilizers. Therefore, the development of low-cost, high-efficiency and environmentally friendly soil conditioner, soil heavy metal solidification agent and slow-release fertilizer has important strategic significance for reducing agricultural production cost, maintaining soil health and promoting sustainable agricultural development.

[0004] In summary, the present application develops various agricultural products using quartz tailings as raw materials through a step-by-step process, realizes the step-by-step utilization of quartz tailings in soil conditioning, heavy metal solidification and slow-release fertilizer, expands the application range of quartz tailings-based materials, and can significantly improve the high-value utilization of quartz tailings. In addition, the step-by-step utilization technology of the present application can realize controllable product cost, excellent performance and significant economic and performance advantages through simple process. SUMMARY

[0005] The application provides a step-by-step high-value utilization treatment method and product of quartz tailings, and aims to solve the problem of low utilization rate of tailings resources and provide a low-cost and high-efficiency soil conditioner, heavy metal solidifying agent and slow-release fertilizer.

[0006] In order to achieve the above-mentioned purpose, the application provides a step-by-step high-value utilization treatment method of quartz tailings, comprising the following steps:

[0007] S1, adding a calcium-containing additive to the quartz tailings, mixing and grinding, high-temperature calcination and activation, and obtaining a calcium-silicon fertilizer;

[0008] S2, acid leaching the calcium-silicon fertilizer obtained in S1, mixing an aluminum source and / or an iron source, and then adding a sodium hydroxide solution for co-precipitation, and then performing normal-pressure hydrothermal reaction after co-precipitation, to obtain a calcium-based hydrotalcite / porous silicon oxide soil heavy metal solidifying agent;

[0009] S3, wet mixing the calcium-based hydrotalcite / porous silicon oxide soil heavy metal solidifying agent obtained in S2 with a chemical fertilizer and performing negative pressure impregnation, low-temperature evaporation and dehydration to obtain a hydrotalcite / porous silicon oxide nutrient composite, adding inorganic auxiliary materials for mixing and granulation to obtain a slow-release fertilizer inner core, and then coating an organic coating material outside the slow-release fertilizer inner core to obtain a hydrotalcite / porous silicon oxide nutrient slow-release fertilizer.

[0010] The step-by-step high-value utilization treatment method of quartz tailings provided by the application converts the quartz tailings into three products: a calcium-silicon fertilizer (soil conditioner), a calcium-based hydrotalcite / porous silicon oxide (soil heavy metal solidifying agent) and a hydrotalcite / porous silicon oxide nutrient (slow-release fertilizer) through continuous process steps, and is specifically realized in the following manner:

[0011] First, silicon-calcium fertilizer is obtained by calcining and activating quartz tailings with calcium additives. During this process, the silica in the quartz crystal structure breaks down under the stimulation of the calcium additives, forming active substances such as calcium silicate, dicalcium silicate, and tricalcium silicate with calcium, constituting the silicon-calcium fertilizer. This fertilizer is alkaline and citrate-soluble, and when applied to the soil, it releases silicate and calcium ions that can be directly absorbed by plants and neutralizes soil acidity. Second, after acid dissolution, the silicon-calcium fertilizer produces free silicate and calcium ions. Through aluminum (iron) supplementation, pH adjustment, and atmospheric pressure hydrothermal methods, calcium, aluminum (iron), and silicate ions are simultaneously precipitated and transformed into a calcium-based hydrotalcite / porous silica soil heavy metal solidifier. Because the hydrotalcite and silica phases form simultaneously, it significantly promotes the formation of Ca-O-Si bonds, avoiding steric hindrance caused by differences in particle size. The calcium-based hydrotalcite / porous silica soil heavy metal solidifier prepared by this invention consists of ultrathin nanosheets stacked together, forming a loose and porous structure. This significantly improves the solidification of heavy metals and the adsorption of nutrients. Finally, by utilizing the pore structure, interlayer domains, and surface hydroxyl groups of the calcium-based hydrotalcite / porous silica soil heavy metal solidifier, nitrogen, phosphorus, and potassium fertilizers can be adsorbed and loaded, forming a slow-release fertilizer. This invention patent uses quartz tailings as raw material and transforms it into three agricultural products through a three-stage continuous process, realizing the high-value utilization of quartz tailings.

[0012] The cascade utilization technology of this invention has the following advantages: First, the silicon-calcium fertilizer produced by calcination activation can be widely and directly used for conditioning acidic soils. The technology is simple, low-cost, and easy to implement. Second, the calcination step can promote the activation of silicon and calcium (after calcination, silicon and calcium can be leached at an acid concentration of 0.5 mol / L; without calcination, a very high concentration of acid is required to achieve silicon leaching, but the silicon leaching rate is still very low), which greatly saves energy and acid consumption for the subsequent synthesis of calcium-based hydrotalcite / porous silica soil heavy metal solidifying agent, significantly reducing costs. Third, the calcium-based hydrotalcite / porous silica soil heavy metal solidifying agent has excellent heavy metal solidification effect. The high specific surface area of ​​the composite material is conducive to the adsorption of heavy metal ions, the abundant Si-O broken bonds are conducive to the chemical bonding of heavy metal cations, the interlayer of calcium-based hydrotalcite is conducive to the insertion of heavy metal anion groups, and the hydrotalcite itself can transfer heavy metals through ion exchange. The process involves several key steps: First, ions are converted into ultra-low solubility product products. Second, using calcium-based hydrotalcite / porous silica soil heavy metal solidifier as a base, different slow-release fertilizers can be prepared according to actual needs by adjusting the types, amounts, and process parameters of nutrients, inorganic additives, and organic coating materials, thereby achieving efficient nutrient loading and long-term release. Third, the calcium-based hydrotalcite / porous silica soil heavy metal solidifier has a large adsorption capacity and strong adsorption force for nutrients. A large amount of nutrients exist in the interlayer of hydrotalcite, in the pores of silica, and on the surface of hydrotalcite and silica through different chemical or physical adsorption methods, exhibiting a significant slow-release effect, thus reducing the dependence on coating slow release. The amount of coating agent required for the slow-release fertilizer of this application is reduced by at least half compared to conventional slow-release fertilizers, which can significantly reduce the cost and potential environmental impact of resin-based coating agents.

[0013] Preferably, in step S1, the calcium-containing additive includes one or more of calcium carbonate, calcium oxide, or calcium hydroxide, and the addition ratio of the calcium additive is calculated based on the molar amount of calcium in the calcium-containing additive and silicon in the quartz tailings, with a silicon / calcium molar ratio of 0.75-2.5.

[0014] Preferably, in step S1, the particle size after mixing and grinding is less than 100 mesh; the calcination activation temperature is 1100-1500 ℃, the activation time is 1-5 h, and the particles are directly taken out at high temperature and air-cooled after calcination.

[0015] Preferably, in step S2, the acid used in the acid leaching includes nitric acid and / or hydrochloric acid solution, with an acid concentration of 0.5-1 mol / L, a solid-liquid ratio of 1:10-1:50, an acid leaching temperature of 25-80 ℃, and an acid leaching time of 0.5-4 h.

[0016] Preferably, in step S2, the aluminum source and / or iron source contains trivalent metal ions, and the aluminum source and / or iron source includes one or more of aluminum chloride, aluminum nitrate, aluminum hydroxide, ferric chloride, ferric nitrate, or ferric hydroxide. The addition ratio of the aluminum source and / or iron source is calculated based on the total molar amount of calcium ions in the silicon-calcium fertilizer and the total molar amount of aluminum ions and iron ions in the aluminum source and / or iron source, and the molar ratio of calcium to total aluminum and iron is 2:1-6:1.

[0017] Preferably, in step S2, the concentration of the sodium hydroxide solution is 1-3 mol / L, the pH value is adjusted to 9-11, the temperature of the atmospheric pressure hydrothermal treatment is 40-80 ℃, and the time is 12-72 h.

[0018] Preferably, in step S3, the amount of calcium-based hydrotalcite / porous silica soil heavy metal solidifying agent and chemical fertilizer added is 20-40 parts by mass and 30-100 parts by mass; the wet mixing solvent is water, and the negative pressure impregnation is continuous stirring under negative pressure for 1-6 hours;

[0019] The low-temperature evaporation temperature is 40-70 ℃, and the material is evaporated until the moisture content is 5-15%.

[0020] Preferably, in step S3, the amount of inorganic excipients added is 5-15 parts by mass, and the mixing and granulation adopts an extrusion process;

[0021] The amount of the organic coating material added is 1-5% of the mass of the slow-release fertilizer core.

[0022] The drying temperature is 40-70 ℃, and the time is 4-8 h; the baking temperature is 50-70 ℃.

[0023] Preferably, the chemical fertilizer includes one or more of urea, ammonium phosphate, ammonium carbonate, ammonium chloride, potassium dihydrogen phosphate, potassium chloride, potassium sulfate, or potassium phosphate.

[0024] The inorganic excipients include one or more of bentonite, attapulgite, kaolin, or gypsum.

[0025] The organic coating agent is a resin-based coating material, including one of urea-formaldehyde resin, alkyd resin, polyurethane, or polyacrylate.

[0026] Under the same technical concept, the present invention also provides a product obtained by the cascade high-value utilization treatment method of the quartz tailings, the product comprising a silicon-calcium fertilizer soil conditioner, a calcium-based hydrotalcite / porous silica soil heavy metal solidifying agent, and a hydrotalcite / porous silica@nutrient slow-release fertilizer.

[0027] The product obtained from the tiered high-value utilization treatment method of quartz tailings in this application can remediate and improve various soil problems. Through a single high-value utilization treatment step, it meets the diverse fertilizer needs of agricultural soils. The silicon-calcium fertilizer can condition acidic soils while providing silicon and calcium nutrients. The heavy metal solidifier primarily aims to solidify and stabilize heavy metal ions in the soil and remediate heavy metal pollution. Excess silicon and calcium components that do not participate in heavy metal solidification can be gradually absorbed and utilized by plants as slow-release nutrients. The slow-release fertilizer focuses on nutrient management, improving nutrient utilization and reducing nutrient loss through slow and controlled release, while achieving soil improvement, silicon and calcium nutrient supply, and heavy metal fixation. This technology maximizes the high-value application of quartz tailings, offering low cost, multiple functions, and ease of implementation, making it highly valuable for industrial applications.

[0028] The above-described solution of the present invention has the following beneficial effects:

[0029] (1) This invention obtains silicon-calcium fertilizer by calcining and activating quartz tailings with calcium additives. During this process, the silicon oxide in the quartz crystal structure breaks down under the stimulation of the calcium additives, forming active substances such as calcium silicate / dicalcium silicate / tricalcium silicate with calcium. After being applied to the soil, it can release silicate and calcium ions that can be directly absorbed by plants and neutralize soil acidity. Secondly, after acid dissolution, the silicon-calcium fertilizer produces free silicate and calcium ions. By supplementing aluminum (iron), adjusting the pH value, and using atmospheric pressure hydrothermal methods, calcium, aluminum (iron), and silicate are simultaneously precipitated and transformed into a calcium-based hydrotalcite / porous silica soil heavy metal solidifying agent. Since the hydrotalcite phase and the silica phase are formed simultaneously, it can significantly promote the formation of Ca-O-Si bonds and avoid steric hindrance caused by differences in particle size. The calcium-based hydrotalcite / porous silica soil heavy metal solidifying agent prepared by this invention is composed of ultrathin nanosheets stacked together to form a porous and loose structure. This is of great significance for the solidification of heavy metals and the adsorption of nutrients. Finally, by utilizing the pore structure, interlayer domains, and surface hydroxyl groups of the calcium-based hydrotalcite / porous silica soil heavy metal solidifier to adsorb and load nitrogen, phosphorus, and potassium fertilizers, a slow-release fertilizer can be formed. This invention patent uses quartz tailings as raw material and transforms it into three agricultural products through a three-stage continuous process, achieving high-value utilization of quartz tailings.

[0030] (2) This invention makes full use of the characteristics of high silicon content, low impurity content, and especially extremely low content of harmful heavy metals in quartz tailings, as well as the wide availability and low price, to prepare three products that are suitable for agricultural use in terms of applicability, safety and economy.

[0031] (3) These three products are designed in a progressive manner. These products can be used directly as end products or as intermediate products to produce products in the next stage, which broadens the use and quantity of each product, thereby fully realizing the large-scale and high-value utilization of quartz tailings.

[0032] (4) These three products utilize components in a tiered manner, transfer performance step by step, and amplify functions in a complementary manner, so that the products of each step become "customized raw materials" for subsequent steps, transforming quartz tailings from "waste" into a series of products with integrated capabilities of "soil improvement - heavy metal remediation - nutrient management", solving the problem that a single process cannot take into account both environmental benefits and agricultural value, and forming an inseparable systematic innovation.

[0033] (5) The three-stage continuous process proposed in this invention has a short process flow, simple operation, conventional equipment, and low process cost; all raw materials used are mature, economical and harmless chemical products, so it is suitable for large-scale production.

[0034] (6) The negative pressure impregnation process can promote the entry of nutrients into the pore structure of calcium-based hydrotalcite / porous silica soil heavy metal solidifier, and improve the slow release performance; the low temperature evaporation process can avoid the decomposition and evaporation of nutrients (especially urea) at high temperature, and can also avoid the migration of nutrients (especially urea) to the material surface with the evaporation of water, thereby reducing the segregation of nutrients (especially urea) and enhancing the retention effect of the material pore structure on nutrients.

[0035] (7) The final slow-release fertilizer combines the characteristics of the heavy metal solidifying agent and the soil conditioner. After the fertilizer is released, the remaining calcium-based hydrotalcite / porous silica is the heavy metal solidifying agent, which can effectively solidify the heavy metal ions in the soil. At the same time, the calcium and silicon that did not participate in the solidification of heavy metals will be released to enhance the soil nutrition. Attached Figure Description

[0036] Figure 1 This is a flowchart of the method for the tiered high-value utilization of quartz tailings according to the present invention;

[0037] Figure 2 The images shown are SEM images of the calcium-based hydrotalcite / porous silica soil heavy metal solidifiers prepared in Examples 1-5 of this invention; wherein, a is the SEM image of the calcium aluminum hydrotalcite / porous silica soil heavy metal solidifier of Example 1; b is the SEM image of the calcium aluminum hydrotalcite / porous silica soil heavy metal solidifier of Example 2; c is the SEM image of the calcium aluminum hydrotalcite / porous silica soil heavy metal solidifier of Example 3; d is the SEM image of the calcium iron hydrotalcite / porous silica soil heavy metal solidifier of Example 4; and e is the SEM image of the calcium iron aluminum hydrotalcite / porous silica soil heavy metal solidifier of Example 5. Detailed Implementation

[0038] To make the technical problems, solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0039] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] Comparative Example 1

[0041] 21.79 g of calcium chloride (calcium content 7.86 g) and 8.73 g of aluminum chloride (aluminum ion content 1.77 g) (calcium to aluminum molar ratio approximately 3.0) were added to 1000 mL of water. Subsequently, a 2.0 mol / L sodium hydroxide solution was slowly added to the solution to adjust the pH to 10.5. The mixture was then transferred to a 60 °C oven and subjected to hydrothermal treatment at atmospheric pressure for 18 h. After filtration, drying, and grinding, calcium-aluminum hydrotalcite was obtained.

[0042] Example 1

[0043] A method for the tiered high-value utilization of quartz tailings, the flowchart of which is as follows: Figure 1 As shown, it includes the following steps:

[0044] S1. Take 100 g of -150 mesh quartz tailings (silicon oxide content of 98.67%, i.e., silicon content of 1.64 mol) and 218.2 g (2.18 mol) of calcium carbonate, mix thoroughly, with a silicon-to-calcium molar ratio of 0.75, then calcine at 1200 ℃ for 2 h, and grind to 80 mesh to obtain silicon-calcium fertilizer. According to the national standard GB / T 36207-2018, the available silicon content is 19.31% and the available calcium content is 39.28%.

[0045] S2. Take 20.0 g of the above-mentioned calcium-silicon fertilizer (3.86 g of available silicon and 7.86 g of available calcium) and 8.73 g of aluminum chloride (1.77 g of aluminum ions) (the molar ratio of calcium to aluminum is approximately 3.0) and add it to 400 mL of 0.5 mol / L hydrochloric acid solution. Leach at 60 ℃ for 1 h to obtain a mixed solution, then dilute with water to 1000 mL. Subsequently, slowly add 2.0 mol / L sodium hydroxide solution to the above solution to adjust the pH to 10.5. Then transfer the mixed solution to a 60 ℃ oven and perform hydrothermal treatment at normal pressure for 18 h to obtain a calcium-aluminum hydrotalcite / porous silica composite material. Analysis results show that the calcium content is 25.45%, the silicon content is 14.86%, and the aluminum content is 5.44%. SEM results show that this heavy metal curing agent has a porous structure formed by interwoven nanosheets. Figure 2 a), its specific surface area is 347.86 m². 2 / g. This calcium aluminum hydrotalcite / porous silica has a good solidification and stabilization effect on heavy metal ions in soil. The specific detection process is as follows: Take a soil sample contaminated with Cd (Cd content is 112.34 mg / kg). −1 The concentrations of Cd were far higher than the soil risk screening values. Three groups of 1000 g soil samples were taken and thoroughly mixed with a blank (without any compound), 20 g of calcium aluminum hydrotalcite prepared in Comparative Example 1, and 20 g of calcium aluminum hydrotalcite / porous silica soil heavy metal solidifying agent prepared in Example 1 in 1 L beakers. Then, 500 ml of deionized water was added, and the mixture was left to stand naturally. Samples were taken at regular intervals to determine the effective Cd concentration. The results showed that compared to the blank control, the effective Cd concentration in Example 1 decreased by 93.78% after 28 days; compared to the calcium aluminum hydrotalcite prepared in Comparative Example 1, the effective Cd concentration decreased by 49.00% after 28 days, as shown in Table 1.

[0046] Table 1. Changes in the effective concentration of Cd at different remediation time periods (mg / kg)

[0047]

[0048] S3. Based on mass fractions, continue to weigh 20 parts of the prepared calcium-aluminum hydrotalcite / porous silica composite material, 40 parts of urea, 20 parts of ammonium dihydrogen phosphate, and an appropriate amount of water. Impregnate and mix under negative pressure for 2 hours, then dry at 60°C through low-temperature evaporation until the moisture content is approximately 10%, obtaining a hydrotalcite / porous silica@nutrient mixture. Then, weigh 1.5 parts of gypsum, 1.5 parts of bentonite, and 2 parts of attapulgite and add them to the above mixture, mix thoroughly, and then granulate to obtain a slow-release fertilizer core. Spray a urea-formaldehyde resin solution onto the slow-release fertilizer core, with the amount of urea-formaldehyde resin being 3% of the dry matter mass of the core. After drying at 45°C for 6 hours, and then drying at 60°C, a hydrotalcite / porous silica@nutrient slow-release fertilizer with an N content of 24.09% and a P2O5 content of 14.10% is obtained.

[0049] According to the national standard GB / T 23348-2009, the nitrogen release rate of the hydrotalcite / porous silica@nutrient slow-release fertilizer was 12% in 24 hours, 76% in 28 days, and 88% in 90 days, which meets the national standard requirements for slow-release fertilizers.

[0050] Comparative Example 2

[0051] 19.01 g of calcium chloride (calcium content 6.85 g) and 32.0 g of aluminum nitrate nonahydrate (aluminum ion concentration 2.30) (calcium to aluminum molar ratio approximately 2.0) were added to 1000 mL of water. Subsequently, a 2.0 mol / L sodium hydroxide solution was slowly added to the solution to adjust the pH to 9.5. The mixture was then transferred to a 60 °C oven and subjected to hydrothermal treatment at atmospheric pressure for 18 h. After filtration, drying, and grinding, calcium aluminum hydrotalcite was obtained.

[0052] Example 2

[0053] A method for the tiered high-value utilization of quartz tailings includes the following steps:

[0054] S1. Take 100.0 g of -150 mesh quartz tailings (silicon oxide content of 98.67%, i.e., silicon of 1.64 mol) and 92.05 g (1.64 mol) of calcium oxide, mix thoroughly (silicon-to-calcium molar ratio of 1.0), then calcine at 1300 ℃ for 2 h, and grind to 80 mesh to obtain silicon-calcium fertilizer. According to GB / T 36207-2018, the available silicon content is 22.40%, and the available calcium content is 34.24%.

[0055] S2. Take 20 g of the above-mentioned silicon-calcium fertilizer (effective silicon 4.48 g; effective calcium 6.85 g) and 32.0 g of aluminum nitrate nonahydrate (aluminum ion concentration 2.30) (calcium to aluminum molar ratio approximately 2.0) and add it to 200 mL of 1 mol / L hydrochloric acid solution. Leach at 60 ℃ for 1 h to obtain a mixed solution, then dilute with water to 1000 mL. Subsequently, slowly add 2.0 mol / L sodium hydroxide solution to the above solution to adjust the pH to 9.5. Then transfer the mixed solution to a 60 ℃ oven and perform hydrothermal treatment at normal pressure for 18 h to obtain a calcium-aluminum hydrotalcite / porous silica soil heavy metal solidification agent. Analysis results show that the calcium content is 24.89%, the silicon content is 18.97%, and the aluminum content is 7.48%. SEM results show that the composite material has a porous structure formed by interwoven nanosheets. Figure 2 (b) Its specific surface area is 358.93 m². 2 / g. This calcium aluminum hydrotalcite / porous silica has a good solidification and stabilization effect on heavy metal ions in soil. The specific detection process is as follows: soil samples contaminated with Pb, Zn, and Cu (Pb, Zn, and Cu contents were 2506 mg / kg) were taken. -1 1200.98 mg kg -1 and 432 mg kg -1 (The values ​​far exceeded the soil risk screening values). Three groups of 1000 g soil samples were taken and thoroughly mixed with the blank (without any compound), 20 g of calcium aluminum hydrotalcite prepared in Comparative Example 2, and 20 g of calcium aluminum hydrotalcite / porous silica heavy metal solidifying agent prepared in Example 2 in 1 L beakers. After mixing, 500 ml of deionized water was added, and the mixture was left to stand naturally. The effective concentrations of Pb, Zn, and Cu were measured at regular intervals. The results showed that compared with the blank control, the effective concentrations of Pb, Zn, and Cu decreased by 88.81%, 82.77%, and 91.18% respectively after 28 days; compared with the calcium aluminum hydrotalcite in Comparative Example 2, the effective concentrations of Pb, Zn, and Cu decreased by 42.86%, 50.09%, and 50.00% respectively after 28 days. See Table 2 for details.

[0056] Table 2. Changes in the available concentrations of Pb, Zn, and Cu at different remediation time periods (mg / kg)

[0057]

[0058] S3. Weigh out 30 parts by weight of the prepared calcium-aluminum hydrotalcite / porous silica composite material, 25 parts by weight of urea, 25 parts by weight of potassium dihydrogen phosphate, and an appropriate amount of water. Impregnate and mix under negative pressure for 2 hours. Then, dry at 60°C through low-temperature evaporation until the moisture content is approximately 10%, obtaining a hydrotalcite / porous silica@nutrient mixture. Next, weigh out 2 parts by weight of gypsum, 1.5 parts by weight of bentonite, 1.5 parts by weight of kaolin, and 2 parts by weight of attapulgite, and add them to the above mixture. Mix well and then granulate to obtain a slow-release fertilizer core. Spray an alkyd resin emulsion onto the slow-release fertilizer core, using 3% of the dry matter mass of the fertilizer core. After drying at 45°C for 6 hours, and then drying at 60°C, obtain composite slow-release fertilizer granules with an N content of 13.0%, a K2O content of 9.60%, and a P2O5 content of 14.56%. According to the national standard GB / T 23348-2009, the nitrogen release rate was 13.8% in 24 hours, 74.89% in 28 days, and 84.68% in 90 days, which meets the national standard requirements for slow-release fertilizers.

[0059] Comparative Example 3

[0060] 17.98 g of calcium chloride (calcium content 6.48 g) and 5.40 g of aluminum chloride (aluminum ion content 1.09 g) (calcium to aluminum molar ratio approximately 4.0) were added to 1000 mL of aqueous solution. Subsequently, a 2.0 mol / L sodium hydroxide solution was slowly added to the above solution to adjust the pH to 9.5. The mixed solution was then transferred to a 60 °C oven and subjected to hydrothermal treatment at atmospheric pressure for 18 h. After filtration, drying, and grinding, calcium-aluminum hydrotalcite was obtained.

[0061] Example 3

[0062] A method for the tiered high-value utilization of quartz tailings includes the following steps:

[0063] S1. Take 100 g of -150 mesh quartz tailings (silicon oxide content of 98.67%, i.e., silicon content of 1.64 mol) and mix thoroughly with 110.7 g (1.50 mol) of calcium hydroxide, with a silicon-to-calcium molar ratio of 1.09. Then calcine at 1250 ℃ for 4 h, and grind to 80 mesh to obtain silicon-calcium fertilizer. According to the method of GB / T 36207-2018, the available silicon content is 23.82% and the available calcium content is 32.52%.

[0064] S2. Take 20 g of the above-mentioned silicon-calcium fertilizer (4.76 g of available silicon and 6.50 g of available calcium) and 5.40 g of aluminum chloride (1.09 g of aluminum ions) (the molar ratio of calcium to aluminum is approximately 4.0) and add it to 200 mL of 2 mol / L hydrochloric acid solution. Leach at 60℃ for 1 h to obtain a mixed solution, then dilute with water to 1000 mL. Subsequently, slowly add 2.0 mol / L sodium hydroxide solution to the above solution to adjust the pH to 9.5. Then transfer the mixed solution to a 60℃ oven and perform hydrothermal treatment at normal pressure for 18 h to obtain a calcium-aluminum hydrotalcite / porous silica soil heavy metal solidification agent. Analysis results show that the calcium content is 25.43%, the silicon content is 18.67%, and the aluminum content is 4.48%. SEM results show that the composite material has a porous structure formed by interwoven nanosheets. Figure 2 c), its specific surface area is 332.67 m². 2 / g. This calcium aluminum hydrotalcite / porous silica has a good solidification and stabilization effect on heavy metal ions in soil. The specific detection process is as follows: Soil samples contaminated with As and Hg (As and Hg content of 2380 mg / kg) were taken. -1 and 1300 mg kg -1 (The concentrations of soil samples were far higher than the soil risk screening values). Three groups of 1000 g soil samples were taken and thoroughly mixed with a blank (without any compound), 20 g of calcium aluminum hydrotalcite prepared in Comparative Example 3, and 20 g of calcium aluminum hydrotalcite / porous silica soil heavy metal solidifying agent prepared in Example 3 in 1 L beakers. 500 ml of deionized water was added, and the mixture was left to stand naturally. Samples were taken at regular intervals, and the effective concentrations of As and Hg were measured. The results showed that compared with the blank control, the effective concentrations of As and Hg decreased by 90.48% and 89.38%, respectively, after 28 days; compared with the calcium aluminum hydrotalcite in Comparative Example 3, the effective concentrations of As and Hg decreased by 45.16% and 43.90%, respectively, after 28 days. Details are shown in Table 3.

[0065] Table 3. Changes in the effective concentrations of As and Hg at different remediation time periods (mg / kg)

[0066]

[0067] S3. Based on mass fractions, continue to weigh 30 parts of the prepared calcium-aluminum hydrotalcite / porous silica composite material, 10 parts of urea, 20 parts of diammonium hydrogen phosphate, 20 parts of potassium dihydrogen phosphate, and an appropriate amount of water. Impregnate and mix under negative pressure for 2 hours, then dry at 60 °C to a moisture content of approximately 10% through low-temperature evaporation to obtain a hydrotalcite / porous silica@nutrient mixture. Then, weigh 2 parts of gypsum, 2 parts of kaolin, and 2 parts of bentonite and add them to the above mixture, mix thoroughly, and then granulate to obtain a slow-release fertilizer core. Spray a polyurethane solution onto the slow-release fertilizer core, with the polyurethane amount being 1.5% of the dry matter mass of the fertilizer core. After drying at 45 °C for 6 hours, and then drying at 60 °C, obtain composite slow-release fertilizer granules with an N content of 10.20%, a K2O content of 7.88%, and a P2O5 content of 24.28%.

[0068] According to the national standard GB / T 23348-2009, the nitrogen release rate was 14.38% in 24 hours, 68.45% in 28 days, and 88.67% in 90 days, which meets the national standard requirements for slow-release fertilizers.

[0069] Comparative Example 4

[0070] 18.07 g of calcium chloride (calcium content 6.51 g) and 13.16 g of ferric chloride (iron ion content 4.54 g) (calcium to iron molar ratio approximately 2.0) were added to 1000 mL of water. Subsequently, a 2.0 mol / L sodium hydroxide solution was slowly added to the above solution to adjust the pH to 9.5. The mixed solution was then transferred to a 60 °C oven and subjected to hydrothermal treatment at atmospheric pressure for 18 h. After filtration, drying, and grinding, calcium-iron hydrotalcite was obtained.

[0071] Example 4

[0072] A method for the tiered high-value utilization of quartz tailings includes the following steps:

[0073] S1. Take 100 g of -150 mesh quartz tailings (silicon oxide content of 98.67%, i.e., silicon content of 1.64 mol) and mix thoroughly with 110.7 g (1.50 mol) of calcium hydroxide, with a silicon-to-calcium molar ratio of 1.09. Then calcine at 1250 ℃ for 4 h, and grind to 80 mesh to obtain silicon-calcium fertilizer. According to the method of GB / T 36207-2018, the available silicon content is 23.78% and the available calcium content is 32.56%.

[0074] S2. Take 20 g of the above-mentioned silicon-calcium fertilizer (4.76 g of available silicon and 6.51 g of available calcium) and 13.16 g of ferric chloride (4.54 g of iron ions) (the molar ratio of calcium to iron is approximately 2.0) and add it to 200 mL of 2 mol / L hydrochloric acid solution. Leach at 60℃ for 1 h to obtain a mixed solution, then dilute with water to 1000 mL. Subsequently, slowly add 2.0 mol / L sodium hydroxide solution to the above solution to adjust the pH to 9.5. Then transfer the mixed solution to a 60℃ oven and perform hydrothermal treatment at normal pressure for 18 h to obtain a calcium-iron hydrotalcite / porous silica soil heavy metal solidification agent. Analysis results show that the calcium content is 26.56%, the silicon content is 21.48%, and the iron content is 17.43%. SEM results show that the composite material has a porous structure formed by interwoven nanosheets. Figure 2 d), its specific surface area is 351.45 m². 2 / g. This calcium-iron hydrotalcite / porous silica heavy metal solidifying agent has a good solidification and stabilization effect on soil heavy metal ions. The specific detection process is as follows: Soil samples contaminated with Cr and As (Cr and As content is 1335 mg kg / kg) -1 and 63.9 mg kg -1 (The concentrations of Cr and As were far exceeded by the soil risk screening value). Three groups of 1000 g soil samples were taken and thoroughly mixed with a blank (without any compound), 20 g of calcium-iron hydrotalcite prepared in Comparative Example 4, and 20 g of calcium-aluminum hydrotalcite / porous silica soil heavy metal solidifying agent prepared in Example 4 in 1 L beakers. After adding 500 ml of deionized water, the mixture was left to stand naturally. Samples were taken at regular intervals, and the effective concentrations of Cr and As were measured. The results showed that compared with the blank control, the effective concentrations of Cr and As decreased by 94.22% and 98.70% respectively after 28 days; compared with the calcium-iron hydrotalcite in Comparative Example 4, the effective concentrations of Cr and As decreased by 68.10% and 62.07% respectively after 28 days. Details are shown in Table 4.

[0075] Table 4. Changes in the effective concentrations of Cr and As at different remediation time periods (mg / kg)

[0076]

[0077] S3. Continue to weigh 30 parts by weight of the prepared calcium-iron hydrotalcite / porous silica composite material, 15 parts by weight of urea, 10 parts by weight of potassium nitrate, 15 parts by weight of potassium phosphate, and an appropriate amount of water. Impregnate and mix under negative pressure for 2 hours, then dry at 60 °C until the moisture content is approximately 10% by low-temperature evaporation, obtaining a calcium-iron hydrotalcite / porous silica@nutrient mixture. Then, weigh 1 part by weight of gypsum, 2 parts by weight of bentonite, 1 part by weight of kaolin, and 3 parts by weight of attapulgite, add them to the above mixture, mix well, and then granulate to obtain a slow-release fertilizer core. Spray a polyacrylate emulsion onto the slow-release fertilizer core, with the amount of polyacrylate being 2% of the dry matter mass of the fertilizer core. After drying at 45 °C for 6 hours, and then drying at 60 °C, composite slow-release fertilizer granules with an N content of 10.67%, a K2O content of 18.562%, and a P2O5 content of 6.39% are obtained.

[0078] According to the national standard GB / T 23348-2009, the nitrogen release rate was 11.56% in 24 hours, 72.68% in 28 days, and 90.15% in 90 days, which meets the national standard requirements for slow-release fertilizers.

[0079] Comparative Example 5

[0080] 12.04 g of calcium hydroxide (calcium content 6.51 g), 6.60 g of ferric chloride (iron ion content 2.29 g), and 5.40 g of aluminum chloride (aluminum ion content 1.09 g) (the molar ratio of calcium to total aluminum and iron is approximately 2.0) were added to 1000 mL of water. Subsequently, a 2.0 mol / L sodium hydroxide solution was slowly added to the above solution to adjust the pH to 9.5. The mixed solution was then transferred to a 60°C oven and subjected to hydrothermal treatment at atmospheric pressure for 18 h. After filtration, drying, and grinding, calcium-iron-aluminum hydrotalcite was obtained.

[0081] Example 5

[0082] A method for the tiered high-value utilization of quartz tailings includes the following steps:

[0083] S1. Take 100 g of -150 mesh quartz tailings (silicon oxide content of 98.67%, i.e., silicon content of 1.64 mol) and mix thoroughly with 110.7 g (1.50 mol) of calcium hydroxide, with a silicon-to-calcium molar ratio of 1.09. Then calcine at 1250 ℃ for 4 h, and grind to 80 mesh to obtain silicon-calcium fertilizer. According to the method of GB / T 36207-2018, the available silicon content is 23.78% and the available calcium content is 32.56%.

[0084] S2. Take 20 g of the above-mentioned silicon-calcium fertilizer (4.76 g of available silicon and 6.51 g of available calcium), 6.60 g of ferric chloride (2.28 g of iron ions), and 5.40 g of aluminum chloride (1.09 g of aluminum ions) (the molar ratio of calcium to aluminum and iron is approximately 2.0) and add it to 200 mL of 2 mol / L hydrochloric acid solution. Leach at 60 ℃ for 1 h to obtain a mixed solution, then dilute with water to 1000 mL. Subsequently, slowly add 2.0 mol / L sodium hydroxide solution to the above solution to adjust the pH to 9.5. Then transfer the mixed solution to a 60 ℃ oven and perform hydrothermal treatment at normal pressure for 18 h to obtain a calcium-iron-aluminum hydrotalcite / porous silica soil heavy metal solidification agent. XRF results show that the calcium content is 27.28%, silicon content is 21.38%, iron content is 7.63%, and aluminum content is 4.88%. SEM results show that the composite material has a porous structure formed by interwoven nanosheets. Figure 2 e), its specific surface area is 351.45 m². 2 / g. This calcium-iron-aluminum hydrotalcite / porous silica has a good solidification and stabilization effect on heavy metal ions in soil. The specific detection process is as follows: Soil samples contaminated with Cr and As (Cr and As content is 1335 mg / kg) -1 and 63.9 mg kg -1 (The concentrations of Cr and As were far exceeded by the soil risk screening value). Three groups of 1000 g soil samples were taken and thoroughly mixed with the blank (without any compound), 20 g of calcium-iron-aluminum hydrotalcite prepared in Comparative Example 5, and 20 g of calcium-aluminum hydrotalcite / porous silica soil heavy metal solidifying agent prepared in Example 5 in 1 L beakers. After adding 500 ml of deionized water, the mixture was left to stand naturally. Samples were taken at regular intervals to determine the effective concentrations of Cr and As. The results showed that compared with the blank control, the effective concentrations of Cr and As decreased by 93.83% and 94.91% respectively after 28 days; compared with the calcium-iron-aluminum hydrotalcite in Comparative Example 5, the effective concentrations of Cr and As decreased by 68.22% and 62.93% respectively after 28 days.

[0085] Table 5. Changes in the effective concentrations of Cr and As at different remediation time periods (mg / kg)

[0086]

[0087] S3. According to the mass fraction, continue to weigh 20 parts of the prepared calcium-iron-aluminum hydrotalcite / porous silica composite material, 20 parts of urea, 20 parts of potassium nitrate, 15 parts of potassium chloride, 30 parts of diammonium hydrogen phosphate, and an appropriate amount of water. Impregnate and mix under negative pressure for 2 hours, then dry at 60 ℃ to a moisture content of approximately 10% to obtain a calcium-iron-aluminum hydrotalcite / porous silica@nutrient mixture. Then, weigh 1 part of gypsum, 2 parts of kaolin, 1 part of bentonite, and 5 parts of attapulgite and add them to the above mixture. Mix well and then granulate to obtain a slow-release fertilizer core. Spray a polyurethane solution onto the slow-release fertilizer core, with the amount of polyurethane being 2% of the dry matter mass of the fertilizer core. After drying at 45 ℃ for 6 h and then drying at 60 ℃, a compound slow-release fertilizer granule with N content of 15.88%, K2O content of 16.09%, and P2O5 content of 13.87% was obtained.

[0088] According to the national standard GB / T 23348-2009, the nitrogen release rate was 11.96% in 24 hours, 62.47% in 28 days, and 81.15% in 90 days, which meets the national standard requirements for slow-release fertilizers.

Claims

1. A method for the tiered high-value utilization of quartz tailings, characterized in that, Includes the following steps: S1. Add calcium-containing additives to quartz tailings, mix and grind, and activate by high-temperature calcination to obtain silicon-calcium fertilizer. S2. The silicon-calcium fertilizer obtained in S1 is acid-leached, mixed with an aluminum source and / or an iron source, and then sodium hydroxide solution is added for co-precipitation. After co-precipitation, a hydrothermal reaction is carried out at atmospheric pressure to obtain a calcium-based hydrotalcite / porous silica soil heavy metal solidification agent. S3. The calcium-based hydrotalcite / porous silica soil heavy metal solidifying agent obtained in S2 is wet-mixed with chemical fertilizer and impregnated under negative pressure. It is then evaporated at low temperature and dehydrated to obtain a hydrotalcite / porous silica@nutrient composite. Inorganic additives are added and granulated to obtain a slow-release fertilizer core. An organic coating material is then coated on the outside of the slow-release fertilizer core, and the mixture is dried to obtain a hydrotalcite / porous silica@nutrient slow-release fertilizer.

2. The processing method as described in claim 1, characterized in that, In step S1, the calcium-containing additive includes one or more of calcium carbonate, calcium oxide, or calcium hydroxide. The addition ratio of the calcium additive is calculated based on the molar amount of calcium in the calcium-containing additive and silicon in the quartz tailings, and the silicon / calcium molar ratio is 0.75-2.

5.

3. The processing method as described in claim 1, characterized in that, In step S1, the particle size after mixing and grinding is less than 100 mesh; the calcination activation temperature is 1100-1500 ℃, the activation time is 1-5 h, and the particles are directly taken out at high temperature and air-cooled after calcination.

4. The processing method as described in claim 1, characterized in that, In step S2, the acid used in the acid leaching includes nitric acid and / or hydrochloric acid solutions, with an acid concentration of 0.5-1 mol / L, a solid-liquid ratio of 1:10-1:50, an acid leaching temperature of 25-80 ℃, and an acid leaching time of 0.5-4 h.

5. The processing method as described in claim 1, characterized in that, In step S2, the aluminum source and / or iron source includes one or more of aluminum chloride, aluminum nitrate, aluminum hydroxide, ferric chloride, ferric nitrate, or ferric hydroxide. The addition ratio of the aluminum source and / or iron source is calculated based on the total molar amount of calcium ions in the silicon-calcium fertilizer and the total molar amount of aluminum ions and iron ions in the aluminum source and / or iron source. The molar ratio of calcium to total aluminum and iron is 2:1-6:

1.

6. The processing method as described in claim 1, characterized in that, In step S2, the concentration of the sodium hydroxide solution is 1-3 mol / L, the pH value is adjusted to 9-11, the temperature of the atmospheric pressure hydrothermal treatment is 40-80 ℃, and the time is 12-72 h.

7. The processing method as described in claim 1, characterized in that, In step S3, the amount of calcium-based hydrotalcite / porous silica soil heavy metal solidification agent and chemical fertilizer added is 20-40 parts by mass and 30-100 parts by mass; the wet mixing solvent is water, and the negative pressure impregnation is continuous stirring under negative pressure for 1-6 hours. The low-temperature evaporation temperature is 40-70 ℃, and the material is evaporated until the moisture content is 5-15%.

8. The processing method as described in claim 1, characterized in that, In step S3, the amount of inorganic excipients added is 5-15 parts by mass, and the mixing and granulation adopts an extrusion process. The amount of the organic coating material added is 1-5% of the mass of the slow-release fertilizer core. The drying temperature is 40-70 ℃, and the time is 4-8 h; the baking temperature is 50-70 ℃.

9. The processing method as described in claim 4, characterized in that, The chemical fertilizer includes one or more of urea, ammonium phosphate, ammonium carbonate, ammonium chloride, potassium dihydrogen phosphate, potassium chloride, potassium sulfate, or potassium phosphate. The inorganic excipients include one or more of bentonite, attapulgite, kaolin, or gypsum. The organic coating agent is a resin-based coating material, including one of urea-formaldehyde resin, alkyd resin, polyurethane, or polyacrylate.

10. A product obtained from the tiered high-value utilization treatment method of quartz tailings as described in any one of claims 1-9, characterized in that, The products include silicon-calcium fertilizer soil conditioner, calcium-based hydrotalcite / porous silica soil heavy metal solidifier, and hydrotalcite / porous silica@nutrient slow-release fertilizer.

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