A method for preparing cementitious material using copper tailings

Abstract

This invention discloses a method for preparing cementitious materials using copper tailings, comprising the following steps: 1) ball milling the copper tailings; 2) adding acid to the ball-milled copper tailings for reaction; 3) adding alkali to the filtered precipitate for reaction; 4) adding acid again for reaction; 5) adding ethanol to the filtered solution for reaction, followed by centrifugation after the reaction is complete; 6) adding alkali to the filtrate for reaction, followed by adding hydrogen peroxide; 7) adding sodium hydroxide and Al2O3 after the reaction; 8) stirring the reaction for at least 2 hours. Using this method, the content of arsenic and heavy metals in the cementitious material product prepared from copper tailings is significantly reduced, with an arsenic removal rate exceeding 92%. The calcium sulfite content in the cementitious material product is also significantly reduced.

Description

Technical Field

[0001] This invention belongs to the field of copper ore beneficiation and tailings resource utilization technology, specifically relating to a method for preparing cementitious materials using copper tailings. Background Technology

[0002] Copper tailings are a large-scale industrial byproduct generated throughout the copper mining, beneficiation, and smelting processes. As an inevitable derivative of mineral resource development, their production scale is highly correlated with the development of the copper mining industry. Copper tailings are among the most difficult types of industrial solid waste to manage. Their composition is significantly complex, enriched with basic minerals such as silicon, iron, calcium, and magnesium, and some also contain valuable elements such as copper, lead, zinc, gold, and silver, possessing extremely high potential for resource reuse. At the same time, they contain pollutants such as arsenic, cadmium, and mercury, and are generally mixed with components such as calcium sulfite that can easily cause secondary pollution, forming a special form where "resource attributes" and "environmental risks" are intertwined, posing multiple potential threats to the ecological environment.

[0003] Traditional tailings disposal methods are centered on "passive stockpiling," involving the construction of tailings dams for centralized storage, supplemented by simple basic protective measures such as impermeable layers and surface covering. However, this approach has several unavoidable drawbacks: Firstly, tailings dam construction requires substantial land resources and incurs high construction and maintenance costs. Long-term stockpiling can easily trigger geological disasters such as landslides and dam failures. Especially under extreme rainfall and earthquake conditions, heavy metals such as arsenic in the tailings can seep into the soil and groundwater with leachate, while calcium sulfite may generate acidic wastewater through oxidation, causing continuous pollution to surrounding water bodies and soil, and disrupting the balance of the ecosystem. Secondly, the long-term idleness of various valuable elements and mineral resources contained in the tailings not only results in a serious waste of mineral resources but also violates the concept of sustainable development. Therefore, the safe disposal, hazardous element control, and resource recovery of copper tailings have long been key and challenging issues in the field of mining environmental management, hindering the green transformation of the copper mining industry.

[0004] In recent years, with the increasing demands for global ecological and environmental protection and the growing popularity of the concept of resource recycling, the resource utilization of copper tailings has shifted from "passive treatment" to "active development." In particular, targeted treatment technologies for harmful components such as arsenic and calcium sulfite have become a core research focus in the industry. Currently, there is an urgent need for a method to prepare cementitious materials from copper tailings that yields materials with lower arsenic and heavy metal content, thereby achieving resource utilization and reducing environmental harm during subsequent utilization. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for preparing cementitious materials using copper tailings.

[0006] The objective of this invention is achieved through the following technical solution: a method for preparing cementitious materials using copper tailings, comprising the following steps: 1) Ball milling of copper tailings; 2) Add acid to the ball-milled copper tailings for reaction, react for more than 2 hours, at a temperature of more than 50℃, with a liquid-to-solid ratio of ≥2L / kg, to initially remove impurities; 3) Add alkali to the filtered precipitate and react. The alkali mass concentration is above 5%, the reaction temperature is above 90℃, the liquid-to-solid ratio is ≥5 L / kg, and the reaction time is above 30 min. Take the filtrate. This step activates Si in the tailings, separates copper, and removes some heavy metals, As, and Fe. 4) Add acid to the filtrate and react for more than 30 minutes at a reaction temperature of 30-90℃ and a liquid-to-solid ratio of 5 L / kg. After the main active substances are initially gelled, they are dissolved again to remove some heavy metals. 5) Add ethanol to the filtered solution to react and fully disperse the dissolved gelling substances, thereby increasing the specific surface area and uniformity. Centrifuge after the reaction is complete. 6) Add alkali with a mass concentration of 10% or more to the filtrate for reaction. The volume ratio of the alkali added to the filtrate is 1 / 30-1 / 60. The reaction temperature is above 60℃. Add hydrogen peroxide with a mass concentration of 30% in a volume of 1 / 20-1 / 100 of the reaction liquid volume in this step. React for 2 hours to oxidize and remove the calcium sulfite precipitate, and remove AS after oxidation by calcium encapsulation. 7) Sodium hydroxide and Al2O3 are added to the filtrate after the reaction. The molar ratio of Na to Si in the filtrate is 6:1, and the molar ratio of Al to Si in the filtrate is 8:10-15:10. This provides a highly alkaline environment, depolymerizes silicon-oxygen bonds, and enhances the activity of silicon components. It also synergistically forms a Na2O-Al2O3-SiO2-H2O gelling system with Al2O3, regulates the Na / Si and Al / Si molar ratios, promotes the stable formation of hydration products, and promotes the formation of gelling materials. 8) Stir the reaction for more than 2 hours, let it stand for 24 hours, and then filter to obtain the gelling material.

[0007] Furthermore, in step 1, the ball is milled to below 100 mesh for 30-60 minutes at a speed of 300-500 r / min; after milling, it is dried at 90°C for 2 hours.

[0008] Furthermore, in step 2, the acid is sulfuric acid or nitric acid.

[0009] Furthermore, in step 3, the alkali is sodium hydroxide or potassium hydroxide.

[0010] Furthermore, in step 4, the acid is nitric acid.

[0011] Furthermore, in step 5, an equal volume of ethanol as the filtrate is added, and the mixture is reacted at room temperature for 10-30 minutes.

[0012] Furthermore, in step 6, the alkali is sodium hydroxide.

[0013] The beneficial effects of this invention are: by using the method of this invention, the arsenic content in the cementitious material product prepared from copper tailings is greatly reduced, with an arsenic removal rate of over 92%; the heavy metal content in the cementitious material product is low; the calcium sulfite content in the cementitious material product is greatly reduced; and the cementitious material product causes less environmental harm during subsequent utilization. Detailed Implementation

[0014] The present invention will now be described in detail.

[0015] Experimental Example 1 Copper tailings were collected, containing 6.45% copper by mass, heavy metal concentrations (including Pb, Zn, Cu, Mn, Co, and Ni) exceeding 8794.56 mg / kg, 2.12% arsenic by mass, 16.3% iron by mass, and 6.78% calcium sulfite. The copper tailings were treated using the following steps: 1) Ball mill the tailings to a mesh size of less than 100 mesh, ball mill for 30 minutes at a speed of 500 r / min, and then dry at 90℃ for 2 hours after ball milling.

[0016] 2) The ball-milled copper tailings were reacted with a 4 mol / L nitric acid solution at a liquid-to-solid ratio of 6 L / kg, a reaction time of 4 h, and a reaction temperature of 50 °C to promote the separation of heavy metals and some As and Fe. 3) Add 20% sodium hydroxide solution to the filtered precipitate, react at 110℃, liquid-to-solid ratio of 7 L / kg, react for 30 min, and take the filtrate. 4) Add 4 mol / L nitric acid solution to the filtrate and react for 30 min at a reaction temperature of 30℃ and a liquid-to-solid ratio of 5 L / kg, then filter. 5) Add an equal volume of ethanol to the filtered solution, react at room temperature for 10 minutes, and centrifuge after the reaction is complete; 6) Add 10% sodium hydroxide solution (the volume ratio of sodium hydroxide solution added to the filtrate is 1 / 30) to the filtrate and react at 60℃. Add 30% hydrogen peroxide (the volume of hydrogen peroxide added is 1 / 20 of the volume of the reaction liquid in this step) and react for 2 hours. 7) After the reaction, add sodium hydroxide (the mass concentration of sodium hydroxide is 5%, and after adding sodium hydroxide, the molar ratio of Na:Si in the filtrate is 6:1) and Al2O3 (after adding Al2O3, the molar ratio of Al:Si in the filtrate is 4:5). 8) Stir the reaction for 2 hours, let it stand for 24 hours, and then filter (pressure vacuum filtration, filter membrane pore size 0.45μm) to obtain the gelling material.

[0017] Experimental Example 2 Copper tailings were collected, containing 6.45% copper by mass, heavy metal concentrations (including Pb, Zn, Cu, Mn, Co, and Ni) exceeding 8794.56 mg / kg, 0.78% arsenic by mass, 16.3% iron by mass, and 11.45% calcium sulfite. The copper tailings were treated using the following steps: 1) Ball mill the tailings to a mesh size of less than 100 mesh, with a ball milling time of 60 min and a rotation speed of 300 r / min. After ball milling, dry the tailings at 90℃ for 2 h.

[0018] 2) The ball-milled copper tailings were added to a 4 mol / L sulfuric acid solution for reaction, with a liquid-to-solid ratio of 4 L / kg, a reaction time of 3 h, and a reaction temperature of 70 °C, to promote the separation of heavy metals and some As and Fe. 3) Add 10% potassium hydroxide solution to the filtered precipitate, react at 100℃, with a liquid-to-solid ratio of 6 L / kg, for 45 min, and then collect the filtrate. 4) Add 4 mol / L nitric acid solution to the filtrate and react for 45 min at a reaction temperature of 60℃ and a liquid-to-solid ratio of 5 L / kg, then filter. 5) Add an equal volume of ethanol to the filtered solution, react at room temperature for 20 minutes, and centrifuge after the reaction is complete; 6) Add a 20% sodium hydroxide solution (the volume ratio of the added sodium hydroxide solution to the volume of the filtrate is 1 / 40) to the filtrate and react at a temperature of 70°C. Add 30% hydrogen peroxide (the volume of the added hydrogen peroxide is 1 / 60 of the volume of the reaction liquid in this step). 7) After the reaction, add sodium hydroxide (the mass concentration of sodium hydroxide is 6%, and after adding sodium hydroxide, the molar ratio of Na:Si in the filtrate is 6:1) and Al2O3 (after adding Al2O3, the molar ratio of Al:Si in the filtrate is 6:5). 8) Stir the reaction for 2.5 h, let it stand for 24 h, and then filter (pressure vacuum filtration, filter membrane pore size 0.45 μm) to obtain the gelling material.

[0019] Experimental Example 3 Copper tailings were collected, containing 6.45% copper by mass, heavy metal concentrations (including Pb, Zn, Cu, Mn, Co, and Ni) exceeding 8794.56 mg / kg, 4.39% arsenic by mass, 16.3% iron by mass, and 16.21% calcium sulfite. The copper tailings were treated using the following steps: 1) Ball mill the tailings to a mesh size of less than 100 mesh, with a milling time of 50 min and a rotation speed of 400 r / min. After ball milling, dry the tailings at 90℃ for 2 h.

[0020] 2) The ball-milled copper tailings were added to a 4 mol / L sulfuric acid solution for reaction, with a liquid-to-solid ratio of 2 L / kg, a reaction time of 2 h, and a reaction temperature of 90℃, to promote the separation of heavy metals and some As and Fe. 3) Add 5% sodium hydroxide solution to the filtered precipitate, react at 90℃, with a liquid-to-solid ratio of 5 L / kg, react for 60 min, and then take the filtrate. 4) Add 4 mol / L nitric acid solution to the filtrate and react for 60 min at a reaction temperature of 90℃ and a liquid-to-solid ratio of 5 L / kg, then filter. 5) Add an equal volume of ethanol to the filtered solution, react at room temperature for 30 minutes, and centrifuge after the reaction is complete; 6) Add a 30% sodium hydroxide solution (the volume ratio of the added sodium hydroxide solution to the volume of the filtrate is 1 / 60) to the filtrate for reaction. The reaction temperature is 80℃. Add a 30% hydrogen peroxide solution (the volume of the added hydrogen peroxide solution is 1 / 100 of the volume of the reaction liquid in this step). 7) After the reaction, add sodium hydroxide (the mass concentration of sodium hydroxide is 6%, and after adding sodium hydroxide, the molar ratio of Na:Si in the filtrate is 6:1) and Al2O3 (after adding Al2O3, the molar ratio of Al:Si in the filtrate is 3:2). 8) Stir the reaction for 3 hours, let it stand for 24 hours, and then filter (pressure vacuum filtration, filter membrane pore size 0.45μm) to obtain the gelling material.

[0021] Comparative Example 1 In this comparative example, steps 2 and 3 were skipped. The ball-milled copper tailings were directly fed into step 4 to react with acid. The remaining steps were the same as in Experimental Example 1.

[0022] Comparative Example 2 In this comparative example, step 2 was skipped; the copper tailings from step 1 (ball milling) were directly fed into step 3 to react with alkali. Step 5 was also skipped; the filtered solution from step 4 was directly fed into step 6 to react with alkali. The remaining steps in this comparative example were the same as in Experimental Example 2.

[0023] Comparative Example 3 In this comparative example, 1.2 mol / L hydrochloric acid was used to replace sulfuric acid in step 2, and calcium hydroxide solution was used for all subsequent alkaline solutions. The remaining steps were the same as in Experimental Example 3.

[0024] The contents of arsenic and calcium sulfite in the copper tailings and the contents of arsenic and calcium sulfite in the cementitious materials obtained in the above experiments are shown in Table 1.

[0025] Table 1

[0026] Table 1 shows that after treatment with copper tailings in Examples 1-3, the arsenic content in the resulting cementitious material was significantly reduced, with an arsenic removal rate exceeding 92%. The calcium sulfite content in the cementitious material was also significantly reduced, and the total heavy metal content was less than 38.22 mg / kg. In contrast, in Comparative Examples 1-3, due to changes in the process method, the arsenic, calcium sulfite, and total heavy metal content in the cementitious material were all higher, failing to meet the process requirements.

[0027] The cementitious materials produced in Examples 1-3 of this invention can be applied in the fields of cemented backfilling in mines and road engineering, and can also be directly used for backfilling tailings in mining areas. These cementitious materials have low As and heavy metal content, avoiding the impact of As and heavy metals on subsequent applications.

[0028] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing cementitious materials using copper tailings, characterized in that... Includes the following steps: 1) Ball milling of copper tailings; 2) Add acid to the ball-milled copper tailings and react for more than 2 hours at a temperature of more than 50°C and a liquid-to-solid ratio of ≥2 L / kg. 3) Add alkali to the filtered precipitate and react. The alkali concentration should be 5% or higher, the reaction temperature should be 90℃ or higher, the liquid-to-solid ratio should be ≥5 L / kg, and the reaction time should be ≥30 min. Take the filtrate. 4) Add acid to the filtrate and react for at least 30 minutes at a temperature of 30-90℃, with a liquid-to-solid ratio of 5 L / kg; 5) Add ethanol to the filtered solution to allow the reaction to proceed, and centrifuge after the reaction is complete; 6) Add alkali with a mass concentration of 10% or more to the filtrate for reaction. The volume ratio of the alkali added to the filtrate is 1 / 30-1 / 60. The reaction temperature is above 60℃. Add hydrogen peroxide with a mass concentration of 30%. The amount of hydrogen peroxide added is 1 / 20-1 / 100 of the volume of the reaction liquid in this step. React for 2 hours. 7) Add sodium hydroxide and Al2O3 to the filtrate after the reaction. The molar ratio of Na to Si in the filtrate is 6:1, and the molar ratio of Al to Si in the filtrate is 8:10-15:

10. 8) Stir the reaction for more than 2 hours, let it stand for 24 hours, and then filter to obtain the gelling material.

2. The method for preparing cementitious materials using copper tailings according to claim 1, characterized in that: In step 1, the ball is milled to below 100 mesh for 30-60 minutes at a speed of 300-500 r / min; after milling, it is dried at 90°C for 2 hours.

3. The method for preparing cementitious materials using copper tailings according to claim 1, characterized in that: In step 2, the concentration of the acid is 4 mol / L, and the acid is sulfuric acid or nitric acid.

4. The method for preparing cementitious materials using copper tailings according to claim 1, characterized in that: In step 3, the alkali is sodium hydroxide or potassium hydroxide.

5. The method for preparing cementitious materials using copper tailings according to claim 1, characterized in that: In step 4, the acid is nitric acid.

6. The method for preparing cementitious materials using copper tailings according to claim 1, characterized in that: In step 5, add an equal volume of ethanol to the filtrate and react at room temperature for 10-30 minutes.

7. The method for preparing cementitious materials using copper tailings according to claim 1, characterized in that: In step 6, the alkali is sodium hydroxide.

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