Method for preparing ceramsite from hazardous waste zinc-nickel-containing sludge and kyanite flotation tailings and product thereof

Abstract

The invention discloses a method for preparing ceramsite from hazardous waste zinc-nickel-containing sludge and kyanite flotation tailings and a product thereof, and the method comprises the following steps: uniformly mixing fine-grain zinc-nickel-containing sludge, kyanite flotation tailings and palygorskite mineral powder, grinding at a high speed, mixing and stirring with water, and performing low-temperature plasma irradiation treatment to obtain the ceramsite. After the reaction is finished, granulating and drying to obtain raw material balls; sintering under an air atmosphere condition, and cooling to obtain the ceramsite. According to the method, a method of combining high-speed grinding, low-temperature plasma irradiation and sintering is adopted, collaborative recycling and harmless treatment of hazardous waste zinc-nickel-containing sludge and common solid waste kyanite flotation tailings are achieved, and the obtained ceramsite has no dangerous characteristic and has high strength. The method not only eliminates environmental risks of hazardous waste heavy metal sludge and common solid waste kyanite flotation tailings, but also converts the hazardous waste heavy metal sludge and the common solid waste kyanite flotation tailings into available building materials, and has environmental and economic dual benefits.

Description

Technical Field

[0001] The invention relates to a method for preparing ceramsite by utilizing hazardous waste zinc-nickel sludge and kyanite flotation tailings and a product thereof, belonging to the field of harmless disposal and resource utilization of hazardous waste. Background Art

[0002] Zinc-nickel sludge is a highly toxic hazardous waste generated during the treatment of zinc-nickel wastewater in the production process of surface treatment plants. Currently, the main processes for the harmless disposal of zinc-nickel sludge include chemical stabilization, cement kiln co-treatment, and high-temperature sintering. Even after chemical stabilization, zinc-nickel sludge still requires safe landfilling, but landfill capacity is limited and cannot continuously accommodate it. To ensure cement quality, cement kiln co-treatment has strict requirements on the characteristics and quantity of zinc-nickel sludge entering the kiln. High-temperature sintering consumes a lot of energy and can easily lead to the volatilization of some zinc into the flue gas, making flue gas treatment more difficult and, in turn, increasing treatment costs.

[0003] Kyanite flotation tailings, produced after the flotation and purification of medium-grade kyanite, are classified as general industrial solid waste. Currently, large quantities of kyanite flotation tailings are stored in tailings ponds due to their fine particle size, high content of gangue minerals, and low content of kyanite. The complex composition of impurities in kyanite flotation tailings makes purification and separation extremely difficult, limiting their potential for resource utilization. The storage of tailings not only occupies significant land, but also contributes to water pollution due to the adsorption of flotation reagents, such as sodium sulfonate and amines, on the tailings surface.

[0004] Therefore, there is an urgent need for a simple and efficient method for resource-based treatment of hazardous wastes such as zinc-nickel sludge and kyanite flotation tailings. Summary of the Invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a method and product for preparing ceramsite by simple and efficient resource utilization of hazardous waste zinc-nickel sludge and kyanite flotation tailings.

[0006] Technical solution: To solve the above technical problems, the present invention provides a method for preparing ceramsite by using hazardous waste zinc-nickel sludge and kyanite flotation tailings, comprising the following steps: (1) mixing fine zinc-nickel sludge, kyanite flotation tailings and palygorskite ore powder uniformly and grinding to obtain a grinding product; (2) adding water to the ground material obtained in step (1) and stirring to prepare a slurry, and subjecting it to low-temperature plasma irradiation treatment, followed by granulation and drying to obtain raw material balls; (3) The raw material balls obtained in step (2) are sintered in an air atmosphere and cooled to obtain ceramsite.

[0007] The dry mass ratio of the fine zinc-nickel sludge, kyanite flotation tailings and palygorskite powder in step (1) is 30-42:31-50:20-27.

[0008] The grinding rate in step (1) is 420-580 rpm, and the grinding time is 8-22 hours.

[0009] The low-temperature plasma irradiation voltage in step (2) is 6-10 kV, and the irradiation time is 45-125 minutes.

[0010] Wherein, the solid mass percentage of the slurry in step (2) is 42% to 52%.

[0011] The particle size of the pellets after granulation in step (2) is 8-15 mm.

[0012] Wherein, the moisture content of the raw material balls in step (2) is 4% to 6%.

[0013] Wherein, the sintering temperature in step (3) is 960-1060°C and the sintering time is 18-28 minutes.

[0014] The present invention also provides ceramsite prepared by the method, wherein the minimum zinc leaching concentration of the ceramsite is 0.36±0.02 mg / L, and the minimum Ni leaching concentration is 0.05±0.01 mg / L.

[0015] The principle of the present invention is that the mechanochemical forces generated by high-speed ball milling transform the ordered, less chemically reactive crystalline forms found in zinc-nickel sludge, kyanite flotation tailings, and palygorskite into a highly reactive, disordered, amorphous, and multiphase system, continuously generating active components such as silicates, aluminosilicates, and aluminoferrites. The ground product is then mixed with water and stirred to form a slurry. After irradiation with a low-temperature plasma, a large number of high-energy electrons, ions, and free radicals bombard the material at high speeds, disrupting the silicon-oxygen tetrahedron, aluminum-oxygen octahedron, and iron-oxygen tetrahedron networks within the material components. This high-energy particle action disrupts these networks, forming numerous unsaturated bonds and defect sites. These highly reactive unsaturated bonds and defect sites rapidly react with surrounding heavy metal ions to form silicon-oxygen, aluminum-oxygen, and silicon-aluminum-oxygen network polymer components, which then encapsulate, stabilize, or solidify the large amounts of zinc and nickel components, achieving stabilization and solidification of the zinc and nickel.

[0016] During the sintering process, the highly active zinc, nickel, aluminum, magnesium, iron, calcium, and silicon components in the raw material balls quickly form phases such as zinc-aluminum spinel, zinc-iron spinel, and nickel-iron spinel, further achieving structural fixation of zinc and nickel, strengthening and solidifying them, and greatly reducing the volatilization of zinc and nickel. At the same time, a large amount of phases such as aluminum silicate and mullite are also produced, enhancing the structural strength of the ceramsite. In addition, due to the synergistic effect of mechanochemistry and plasma irradiation, the activity of the solid-phase reaction of the material is enhanced, and the energy supply of the solid-phase reaction of the material is reduced, thereby reducing the sintering temperature and roasting time of the material, and significantly reducing the energy consumption of the ceramsite sintering process.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. Based on the chemical composition and characteristics of the waste, the present invention adopts a method combining high-speed grinding, low-temperature plasma irradiation and sintering to achieve the coordinated resource utilization and harmless disposal of hazardous waste zinc-nickel sludge and general solid waste kyanite flotation tailings.

[0018] 2. Through the ratio of raw materials, combined with the synergistic effect of mechanochemistry and plasma irradiation, the solid-phase reaction activity of the material is improved, and the energy supply of the solid-phase reaction of the material is reduced, thereby reducing the sintering temperature and roasting time of the material, greatly reducing the volatilization of zinc and nickel, and achieving a significant reduction in energy consumption in the ceramsite sintering process, which is conducive to energy conservation, emission reduction and low carbon emissions.

[0019] 3. The ceramsite obtained by this invention has a minimum zinc leaching concentration of 0.36±0.02 mg / L and a minimum nickel leaching concentration of 0.05±0.01 mg / L. It is non-hazardous and exhibits high strength. This invention not only eliminates the environmental risks of hazardous waste heavy metal sludge and general solid waste kyanite flotation tailings, but also converts them into usable building materials, achieving both environmental and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0022] The zinc-nickel sludge was taken from Rongchang Metal Surface Treatment Co., Ltd. in Suzhou Industrial Park. It is the sludge produced by heavy metal wastewater treatment. Its chemical composition is SiO2 2.69%, Al2O3 5.06%, Fe2O3 21.84%, MgO 1.70%, CaO 37.25%, Na2O 0.19%, K2O 0.23%, TiO2 0.33%, ZnO 16.53%, SO3 7.51%, NiO 1.17%, Cr2O3 0.30%, P2O52.49%, Cl 1.76%, F 0.53%, and loss on ignition 0.42%.

[0023] Kyanite flotation tailings are taken from Kaiyuan Kyanite Mine in Nanyang City, Henan Province. They are tailings produced after the flotation purification of medium-grade kyanite. Their chemical composition is SiO2 46.27%, Al2O3 43.08%, K2O 3.70%, Na2O 0.95%, and other components 6%.

[0024] Palygorskite was obtained from Changzhou Dingbang Mineral Products Technology Co., Ltd., and its chemical composition is SiO2 72.91%, Al2O3 14.28%, Fe2O3 1.01%, CaO 4.95%, Na2O 2.10%, K2O 2.04%, MgO 2.34%, SO3 0.05%, Cl 0.02%, P2O5 0.02%, TiO2 0.11%, BaO 0.09%, and MnO 0.08%.

[0025] Example 1

[0026] A total of 35 g of fine-grained zinc-nickel sludge, kyanite flotation tailings, and palygorskite powder were uniformly mixed in a dry weight ratio of 30:50:20 to obtain a mixture. The mixture was then added to a vertical planetary ball mill and ground for 8 hours at 580 rpm. The ground product was mixed with water to prepare a slurry with a solid phase content of 42%. The slurry was then irradiated with a low-temperature plasma at a voltage of 6 kV for 125 minutes. After the low-temperature plasma irradiation, granulation was performed. After granulation, pellets with a particle size of 15 mm were screened and dried in a vacuum drying oven to obtain green pellets with a moisture content of 4.0%. The green pellets were sintered in a high-temperature furnace at a temperature of 1060°C for 18 minutes in an air atmosphere. After sintering, the pellets were naturally cooled to produce ceramsite A1.

[0027] The heavy metal leaching toxicity of ceramsite A1 was tested using the "Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid and Nitric Acid Method" (HJ / T299-2007). The zinc leaching concentration of ceramsite A1 was measured to be 0.36±0.02 mg / L, and the Ni leaching concentration was 0.05±0.01 mg / L, which were much lower than the concentration limits of zinc and nickel leaching concentrations (100 mg / L and 5 mg / L) in the "Hazardous Waste Identification Standard Leaching Toxicity Identification" (GB 5085.3-2007). The cylinder compressive strength and bulk density of ceramsite A1 were tested in accordance with the "Light Aggregate and Its Test Methods Part 2: Light Aggregate Test Method" (GB / T 17431.2-2010). The results showed that the cylinder compressive strength of ceramsite A1 was 9.40 MPa and the bulk density was 885 kg / m 3 , in line with the requirements of "Light Aggregate and Its Test Methods Part 1: Light Aggregate" (GB / T17431.1-2010).

[0028] Example 2

[0029] A total of 35 g of fine-grained zinc-nickel sludge, kyanite flotation tailings, and palygorskite powder were mixed uniformly in a dry weight ratio of 42:31:27 to obtain a mixture. The mixture was then added to a vertical planetary ball mill and ground for 18 hours at 450 rpm. The ground product was mixed with water to prepare a slurry with a solids content of 50%. The slurry was then irradiated with a low-temperature plasma at an 8 kV voltage for 65 minutes. After the plasma treatment, granulation was performed. After granulation, pellets with a particle size of 10 mm were screened and dried in a vacuum drying oven to obtain green pellets with a moisture content of 5.0%. The green pellets were sintered in a high-temperature furnace at 1000°C for 22 minutes in an air atmosphere. After sintering, the pellets were naturally cooled to produce ceramsite A2.

[0030] The heavy metal leaching toxicity of ceramsite A2 was tested using the "Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid and Nitric Acid Method" (HJ / T299-2007). The zinc leaching concentration of ceramsite A2 was measured to be 0.87±0.01 mg / L, and the Ni leaching concentration was 0.16±0.01 mg / L, which were much lower than the zinc and nickel leaching concentration limits (100 mg / L and 5 mg / L) in the "Hazardous Waste Identification Standard Leaching Toxicity Identification" (GB 5085.3-2007). The cylinder compressive strength and bulk density of ceramsite A2 were tested in accordance with the "Light Aggregate and Its Test Methods Part 2: Light Aggregate Test Method" (GB / T 17431.2-2010). The results showed that the cylinder compressive strength of ceramsite A2 was 7.23 MPa and the bulk density was 812 kg / m 3, in line with the requirements of "Light Aggregate and Its Test Methods Part 1: Light Aggregate" (GB / T17431.1-2010).

[0031] Example 3

[0032] A total of 35 g of fine-grained zinc-nickel sludge, kyanite flotation tailings, and palygorskite powder were uniformly mixed in a dry weight ratio of 35:40:25 to obtain a mixed material. The mixed material was then added to a vertical planetary ball mill and ground for 22 hours at 420 rpm. The ground product was mixed with water to prepare a slurry with a solids content of 52%. The slurry was then irradiated with a low-temperature plasma at a voltage of 10 kV for 45 minutes. After the low-temperature plasma irradiation, granulation was performed. After granulation, pellets with a particle size of 8 mm were screened and dried in a vacuum drying oven to obtain green pellets with a moisture content of 6.0%. The green pellets were sintered in a high-temperature furnace at a temperature of 960°C for 28 minutes in an air atmosphere. After sintering, the pellets were naturally cooled to produce ceramsite A3.

[0033] The heavy metal leaching toxicity of ceramsite A3 was tested using the "Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid and Nitric Acid Method" (HJ / T299-2007). The zinc leaching concentration of ceramsite A3 was measured to be 0.66±0.02 mg / L, and the Ni leaching concentration was 0.10±0.01 mg / L, which are much lower than the zinc and nickel leaching concentration limits (100 mg / L and 5 mg / L) in the "Hazardous Waste Identification Standard Leaching Toxicity Identification" (GB 5085.3-2007). The cylinder compressive strength and bulk density of ceramsite A3 were tested in accordance with the "Light Aggregate and Its Test Methods Part 2: Light Aggregate Test Method" (GB / T 17431.2-2010). The results showed that the cylinder compressive strength of ceramsite A3 was 7.41 MPa and the bulk density was 833 kg / m 3 , in line with the requirements of "Light Aggregate and Its Test Methods Part 1: Light Aggregate" (GB / T17431.1-2010).

[0034] Comparative Example 1 A total of 35 g of fine-grained zinc-nickel sludge, kyanite flotation tailings, and palygorskite powder were mixed uniformly in a dry weight ratio of 30:50:20 to obtain a mixed material. The mixed material was then mixed with water to prepare a slurry with a solids content of 42%. The slurry was then subjected to low-temperature plasma irradiation at a voltage of 6 kV for 125 minutes. After the plasma irradiation, pellets were granulated. After granulation, pellets with a particle size of 15 mm were screened and dried in a vacuum drying oven to obtain green pellets with a moisture content of 4.0%. The green pellets were then sintered in a high-temperature furnace at a temperature of 1060°C for 18 minutes in an air atmosphere. After sintering, the pellets were naturally cooled to produce ceramsite B1.

[0035] The heavy metal leaching toxicity of ceramsite B1 was tested using the "Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid and Nitric Acid Method" (HJ / T299-2007). The measured zinc leaching concentration of ceramsite B1 was 198.23±0.06 mg / L, and the Ni leaching concentration was 12.35±0.04 mg / L, which were higher than the zinc and nickel leaching concentration limits (100 mg / L and 5 mg / L) in the "Hazardous Waste Identification Standard Leaching Toxicity Identification".

[0036] Comparative Example 2 A total of 35 g of fine-grained zinc-nickel sludge, kyanite flotation tailings, and palygorskite fines were mixed uniformly in a dry weight ratio of 30:50:20 to obtain a mixture. The mixture was then added to a vertical planetary ball mill and ground for 8 hours at 580 rpm. The ground product was mixed with water to prepare a slurry with a solids content of 42%, which was then granulated. After granulation, pellets with a particle size of 15 mm were screened and dried in a vacuum drying oven to obtain green pellets with a moisture content of 4.0%. The green pellets were sintered in a high-temperature furnace at 1060°C for 18 minutes in an air atmosphere. After sintering, the pellets were naturally cooled to produce ceramsite B2.

[0037] The heavy metal leaching toxicity of ceramsite B2 was tested using the "Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid and Nitric Acid Method" (HJ / T299-2007). The zinc leaching concentration of ceramsite B2 was measured to be 76.35±0.04 mg / L, which is lower than the zinc leaching concentration limit (100 mg / L) in the "Hazardous Waste Identification Standard Leaching Toxicity Identification"; the Ni leaching concentration was 9.67±0.03 mg / L, which is higher than the nickel leaching concentration limit (5 mg / L) in the "Hazardous Waste Identification Standard Leaching Toxicity Identification".

[0038] Comparative Example 3 According to the method of Example 1, ceramsite was prepared under different raw material ratios, grinding conditions, low-temperature plasma conditions, and sintering conditions. The heavy metal leaching toxicity of the ceramsite was tested using the "Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid and Nitric Acid Method" (HJ / T299-2007). The results are shown in Table 1.

[0039] Table 1

[0040] The results in Table 1 show that the zinc leaching concentrations of ceramsite samples No. 1, No. 3, No. 4, No. 7 and No. 8 in Comparative Example 3 are higher than the environmental threshold, and the nickel leaching concentrations of all ceramsite samples are higher than the environmental threshold and are still dangerous.

Claims

1. A method for preparing ceramsite by utilizing hazardous waste zinc-nickel sludge and kyanite flotation tailings, characterized in that: The following steps are involved: (1) uniformly mixing the zinc-nickel sludge, kyanite flotation tailings and palygorskite ore powder, and grinding them to obtain a grinding product; (2) adding water to the ground product obtained in step (1) and stirring to prepare a slurry, then subjecting it to low-temperature plasma irradiation, and then granulating and drying it to obtain raw material balls; (3) The raw material balls obtained in step (2) are sintered in an air atmosphere and cooled to obtain ceramsite.

2. The method according to claim 1, characterized in that The dry mass ratio of the zinc-nickel sludge, kyanite flotation tailings and palygorskite ore powder in step (1) is 30-42:31-50:20-27.

3. The method according to claim 1, characterized in that The grinding rate in step (1) is 420-580 rpm, and the grinding time is 8-22 hours.

4. The method according to claim 1, characterized in that The solid mass percentage of the slurry in step (2) is 42% to 52%.

5. The method according to claim 1, characterized in that The voltage of the low-temperature plasma irradiation in step (2) is 6-10 kV, and the irradiation time is 45-125 minutes.

6. The method according to claim 1, characterized in that The particle size of the pellets after granulation in step (2) is 8-15 mm.

7. The method according to claim 1, characterized in that: The moisture content of the raw material balls in step (2) is 4% to 6%.

8. The method according to claim 1, characterized in that: The sintering temperature in step (3) is 960-1060° C. and the sintering time is 18-28 minutes.

9. A ceramsite prepared by the method according to any one of claims 1 to 8.

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