Iron tailing waste pretreatment method

Abstract

The invention discloses an iron tailing waste pretreatment method, and relates to the field of iron tailing treatment.The iron tailing waste pretreatment method comprises the following steps that S1, iron tailings are crushed into iron tailing powder; s2, adding the iron tailing powder into an aqueous solution of a heavy metal capturing agent, and uniformly stirring to obtain iron tailing slurry; and S3, a wall material solution is added into the iron tailing slurry, after uniform stirring, spray drying is conducted, modified iron tailings are obtained, and after the wall material solution is dried to form a film, the film is resistant to acid and alkali and insoluble in water. According to the method, the heavy metal capturing agent is added to pre-fix heavy metal ions in the iron tailings, then the iron tailings are coated with the wall material solution, dissolution of heavy metal lead and cadmium in the modified iron tailings can be effectively prevented through joint cooperation of the heavy metal capturing agent and the wall material solution, and the problem of environmental pollution can be prevented.

Description

Technical Field

[0001] The present application relates to the field of iron tailings treatment, and in particular to a method for pretreating iron tailings waste. Background Art

[0002] As mining continues to expand, the efficient and environmentally friendly disposal of iron ore tailings has become a major global concern. Iron ore tailings typically contain large amounts of inorganic materials such as silicon, aluminum, and calcium-magnesium compounds, along with various heavy metals such as lead (Pb) and cadmium (Cd). If not properly handled, these components can pose long-term environmental risks.

[0003] Currently, traditional methods for treating iron ore tailings waste include physical separation, chemical solidification, and direct landfill. Physical separation relies on screening and magnetic separation to remove harmful components; chemical solidification involves adding cement or other binders to cause heavy metal ions to precipitate and fix them; and direct landfill involves simply depositing unprocessed iron ore tailings at a designated location.

[0004] Among them, chemical solidification is currently the most common method for iron tailings waste, but this method still has the following disadvantages: when ordinary cement binders are used to fix iron tailings containing various metal ions such as lead (Pb) and cadmium (Cd), due to the internal structure of the system being not tight enough and external factors such as rain erosion, it is easy to cause the originally fixed heavy metals to be released again in large quantities, thereby creating new environmental pollution risks. Summary of the Invention

[0005] The purpose of this application is to provide a method for pretreatment of iron tailings waste, aiming to improve the problem in the related art that when treating iron tailings waste by chemical solidification method, the heavy metals fixed in the iron tailings waste are easily released and dissolved again in large quantities, causing potential environmental pollution risks.

[0006] The present invention discloses a method for pre-processing iron tailings waste, comprising the following steps: S1, crushing the iron tailings into iron tailings powder; S2, adding the iron tailings powder to an aqueous solution of a heavy metal scavenger, stirring evenly, to obtain an iron tailings slurry; S3. Adding a wall material solution to the iron tailings slurry, stirring evenly, and spray drying to obtain a modified iron tailings, wherein the wall material solution is acid- and alkali-resistant and insoluble in water after drying to form a film.

[0007] The present application crushes the iron tailings and adds them to an aqueous solution of a heavy metal scavenger, which can pre-fix the heavy metal ions in the iron tailings through the adsorption and chelation action of the heavy metal scavenger, thereby reducing the risk of heavy metal ions in the iron tailings waste being released into the environment. Furthermore, the iron tailings slurry in which the heavy metal ions are pre-fixed is coated with a wall material solution that is acid- and alkali-resistant and insoluble in water after film formation, and a modified iron tailing is formed through a spray drying process, so that the final modified iron tailings has good environmental stability, which can significantly reduce the risk of dissolution of heavy metals such as lead (Pb) and cadmium (Cd), and reduce the possibility of environmental pollution.

[0008] Preferably, in step S1, the particle size of the iron tailings powder is in the range of 100-200 μm.

[0009] In this application, the iron tailings are crushed into iron tailings powder with a particle size range of 100-200 μm, which can significantly improve the adsorption and chelation efficiency of subsequent heavy metal capture agents for heavy metal ions in the iron tailings, and at the same time help to improve the uniformity of the wall material solution coating on its surface, further reducing the risk of dissolution of heavy metals such as lead (Pb) and cadmium (Cd).

[0010] In some specific embodiments, in step S2, the heavy metal scavenger is copolymerized by sodium acrylate, mercaptoacrylamide, and N-vinylformamide in a molar ratio of (1-5): (2-6): (1-4), and the molecular weight of the heavy metal scavenger is 30,000-80,000.

[0011] In the present application, the heavy metal scavenger is copolymerized by sodium acrylate, mercaptoacrylamide and N-vinylformamide in a specific molar ratio, and its molecular weight is controlled within the range of 30,000-80,000, which can effectively enhance the adsorption and chelation stability of the heavy metal ions in the iron tailings by the heavy metal scavenger, and is conducive to reducing the risk of heavy metal dissolution during subsequent use.

[0012] Further preferably, in step S2, the heavy metal scavenger is copolymerized by sodium acrylate, mercaptoacrylamide, and N-vinylformamide in a molar ratio of (2-3): (3-4): (2-3), and the molecular weight of the heavy metal scavenger is 40,000-50,000.

[0013] The preparation method of the heavy metal scavenger comprises the following steps: Sodium acrylate, mercaptoacrylamide, and N-vinylformamide are respectively diluted with water to prepare aqueous solutions with a mass concentration of 15-20%; a mercaptoacrylamide aqueous solution with a mass concentration of 15-20%, a N-vinylformamide aqueous solution with a mass concentration of 15-20%, and a persulfate aqueous solution are dropwise added to the sodium acrylate aqueous solution with a mass concentration of 15-20%, and the temperature is controlled at 80-85°C for 3-5 hours to obtain a heavy metal scavenger.

[0014] In some specific embodiments, in step S2, the weight ratio of the iron tailings powder to the aqueous solution of the heavy metal scavenger is 1:(2-3), wherein the weight proportion of the heavy metal scavenger in the aqueous solution of the heavy metal scavenger is 5-10%.

[0015] The present application improves the capture efficiency of heavy metal ions by the heavy metal capture agent while ensuring sufficient contact by regulating the ratio between the iron tailings powder and the heavy metal capture agent aqueous solution.

[0016] In some specific embodiments, in step S3, the wall material solution has a hardness of 2H to 3H after film formation, and a porosity of less than 0.5%.

[0017] In the present application, the hardness of the wall material solution after film formation is 2H to 3H, which can effectively form a strong and wear-resistant protective layer, improve the stability of the wall material in the modified iron tailings, and prevent the problem of wall material damage when the modified iron tailings are mixed with concrete raw materials; the porosity is low, less than 0.5%, which greatly limits the possibility of moisture and air penetration. At the same time, the low-porosity wall material can also hinder the dissolution of heavy metal ions, thereby significantly reducing the risk of fixed heavy metal ions being re-dissolved from the modified iron tailings.

[0018] In some specific embodiments, in step S3, the wall material solution is obtained by mixing hydroxy acrylic emulsion, water-based polycarbonate-modified hydroxy polyurethane, bisphenol A epoxy resin and water in a weight ratio of 1: (1-2): (3-4): (1-1.5).

[0019] The wall material solution of the present application is formed by mixing hydroxyl acrylic emulsion, water-based polycarbon-modified hydroxyl polyurethane, bisphenol A epoxy resin and water in a specific ratio. The joint combination of hydroxyl acrylic emulsion, water-based polycarbon-modified hydroxyl polyurethane and bisphenol A epoxy resin is conducive to obtaining a wall material with a hardness of 2H to 3H, a porosity of less than 0.5%, water resistance and excellent acid and alkali corrosion resistance, thereby effectively preventing moisture penetration and improving the problem of heavy metal ion infiltration, ensuring the environmental friendliness of the modified iron tailings in subsequent applications.

[0020] In some specific embodiments, in step S3, during spray drying, the pressure is controlled to be 0.6-1.0 MPa, the hot air inlet temperature is 175-185°C, and the outlet temperature is 85-95°C.

[0021] The parameters of the spray drying process of the present application are controlled within the above range, which is conducive to promoting the reaction between the hydroxy acrylic emulsion, water-based polycarbonate-modified hydroxy polyurethane and bisphenol A epoxy resin, and is conducive to forming a wall material that is corrosion-resistant, has high hardness and low porosity.

[0022] In some specific embodiments, in step S3, the weight ratio of the iron tailings slurry to the wall material solution is 1:(4-6).

[0023] In some specific embodiments, the re-dissolution concentrations of Pb and Cd in the modified iron tailings are both less than 0.01 mg / L.

[0024] The re-dissolution concentrations of lead and cadmium in the modified iron tailings obtained in the present application in aqueous solution, acid solution and alkaline solution are all less than 0.01 mg / L. This is due to the strong capture ability of the heavy metal scavenger for heavy metal ions and the dense coating layer formed by the wall material solution, which effectively improves the problem of easy dissolution of heavy metals in the iron tailings in subsequent applications.

[0025] In summary, the above technical solution of this application includes at least the following beneficial technical effects: (1) The present application crushes the iron tailings and adds them to an aqueous solution of a heavy metal scavenger, which can pre-fix the heavy metal ions in the iron tailings through the adsorption and chelation effect of the heavy metal scavenger, thereby reducing the risk of heavy metal ions in the iron tailings waste being released into the environment. Furthermore, the iron tailings slurry in which the heavy metal ions are pre-fixed is coated with a wall material solution that is acid- and alkali-resistant and insoluble in water after film formation, and a modified iron tailing is formed through a spray drying process, so that the final modified iron tailings has good environmental stability, which can significantly reduce the risk of dissolution of heavy metals such as lead (Pb) and cadmium (Cd), and reduce the possibility of environmental pollution.

[0026] (2) In the present application, the heavy metal scavenger is copolymerized by sodium acrylate, mercaptoacrylamide and N-vinylformamide in a specific molar ratio, and its molecular weight is controlled within the range of 30,000-80,000, which can effectively enhance the adsorption and chelation stability of the heavy metal ions in the iron tailings by the heavy metal scavenger, and is conducive to reducing the risk of heavy metal dissolution during subsequent use.

[0027] (3) The wall material solution of the present application is prepared by mixing hydroxy acrylic emulsion, water-based polycarbonate-modified hydroxy polyurethane, bisphenol A type epoxy resin and water in a specific ratio. The combination of hydroxy acrylic emulsion, water-based polycarbonate-modified hydroxy polyurethane and bisphenol A type epoxy resin is conducive to obtaining a wall material with a hardness of 2H to 3H, a porosity of less than 0.5%, water resistance and excellent acid and alkali corrosion resistance, thereby effectively preventing water penetration and improving the problem of heavy metal ion infiltration, thereby ensuring the environmental friendliness of the modified iron tailings in subsequent applications. DETAILED DESCRIPTION

[0028] The present application is further described below with reference to specific experiments. The iron tailings processed in this application comprise 48.7% by weight of SiO2, 29.6% by weight of iron oxide, 9.8% by weight of aluminum oxide, 4.5% by weight of calcium oxide, 4.9% by weight of magnesium oxide, 1.2% by weight of lead, and 1.3% by weight of cadmium.

[0029] Preparation Example [Preparation Example 1-1] A heavy metal scavenger is prepared by copolymerizing 30 mol of sodium acrylate, 180 mol of mercaptoacrylamide and 90 mol of N-vinylformamide. The molecular weight of the obtained heavy metal scavenger is in the range of 30,000-35,000.

[0030] The preparation method of the heavy metal scavenger is as follows: Sodium acrylate, mercaptoacrylamide, and N-vinylformamide were respectively diluted with water to prepare aqueous solutions with a mass concentration of 20%; a 20% mass concentration of mercaptoacrylamide aqueous solution, a 20% mass concentration of N-vinylformamide aqueous solution, and 50 g of a 1% mass concentration of sodium persulfate aqueous solution were dropwise added to the 20% mass concentration sodium acrylate aqueous solution, and the temperature was controlled to 80° C. for 4 hours to obtain a heavy metal scavenger.

[0031] [Preparation Example 1-2] A heavy metal scavenger is prepared by copolymerizing 45 mol of sodium acrylate, 270 mol of mercaptoacrylamide and 135 mol of N-vinylformamide. The molecular weight of the obtained heavy metal scavenger is in the range of 40,000-50,000.

[0032] The preparation method of the heavy metal scavenger is as follows: Sodium acrylate, mercaptoacrylamide, and N-vinylformamide were respectively diluted with water to prepare aqueous solutions with a mass concentration of 20%; a 20% mass concentration of mercaptoacrylamide aqueous solution, a 20% mass concentration of N-vinylformamide aqueous solution, and 65 g of a 1% mass concentration of sodium persulfate aqueous solution were dropwise added to the 20% mass concentration sodium acrylate aqueous solution, and the temperature was controlled to 80° C. for 4 hours to obtain a heavy metal scavenger.

[0033] [Preparation Examples 1-3] A heavy metal scavenger is prepared by copolymerizing 70 mol of sodium acrylate, 420 mol of mercaptoacrylamide and 210 mol of N-vinylformamide. The molecular weight of the obtained heavy metal scavenger is in the range of 70,000-80,000.

[0034] The preparation method of the heavy metal scavenger is as follows: Sodium acrylate, mercaptoacrylamide, and N-vinylformamide were respectively diluted with water to prepare aqueous solutions with a mass concentration of 20%; a 20% mass concentration of mercaptoacrylamide aqueous solution, a 20% mass concentration of N-vinylformamide aqueous solution, and 100 g of a 1% mass concentration of sodium persulfate aqueous solution were dropwise added to the 20% mass concentration sodium acrylate aqueous solution, and the temperature was controlled to 80° C. for 4 hours to obtain a heavy metal scavenger.

[0035] [Preparation Examples 1-4] A heavy metal scavenger, which differs from [Preparation Example 2] in that the molar amounts of sodium acrylate, mercaptoacrylamide, and N-vinylformamide are different. In this Preparation Example, the amount of sodium acrylate is 150 mol, the amount of mercaptoacrylamide is 200 mol, and the amount of N-vinylformamide is 150 mol.

[0036] [Preparation Example 2-1] A wall material solution is prepared by mixing a hydroxylated acrylic emulsion, a waterborne polycarbonate-modified hydroxylated polyurethane, a bisphenol A epoxy resin, and water in a weight ratio of 1:2:3:1. The hydroxylated acrylic emulsion is BASF's JONCRYL OH 8710 hydroxylated acrylic dispersion, the waterborne polycarbonate-modified hydroxylated polyurethane is Jufeng Chemical's PT-528T waterborne polycarbonate-modified hydroxylated polyurethane, and the bisphenol A epoxy resin is bisphenol A epoxy resin DER3414.

[0037] [Preparation Example 2-2] A wall material solution is prepared by mixing a hydroxylated acrylic emulsion, a waterborne polycarbonate-modified hydroxylated polyurethane, a bisphenol A epoxy resin, and water in a weight ratio of 1:1:4:1.5. The hydroxylated acrylic emulsion is BASF's JONCRYL OH 8710 hydroxylated acrylic dispersion, the waterborne polycarbonate-modified hydroxylated polyurethane is Jufeng Chemical's PT-528T waterborne polycarbonate-modified hydroxylated polyurethane, and the bisphenol A epoxy resin is bisphenol A epoxy resin DER3414.

[0038] [Preparation Example 2-3] A wall material solution, which differs from [Preparation Example 2-1] in that: The hydroxylated acrylic emulsion is replaced by water-based polycarbonate-modified hydroxylated polyurethane of equal mass.

[0039] [Preparation Example 2-4] A wall material solution, which differs from [Preparation Example 2-1] in that: The water-based polycarbonate-modified hydroxy polyurethane is replaced by an equal mass of hydroxy acrylic emulsion. Example

[0040] [Example 1] A method for pretreating iron tailings waste comprises the following steps: S1, crushing the iron tailings into iron tailings powder with a particle size range of 100-200 μm; S2. Add the iron tailings powder to the aqueous solution of the heavy metal scavenger and stir evenly to obtain an iron tailings slurry; wherein the weight ratio of the heavy metal scavenger in the aqueous solution of the heavy metal scavenger is 5%, the heavy metal scavenger is the heavy metal scavenger prepared in [Preparation Example 1-1], and the weight ratio of the iron tailings powder to the aqueous solution of the heavy metal scavenger is 1:3; S3. Add the wall material solution to the iron tailings slurry, stir evenly, and spray dry to obtain modified iron tailings, wherein the wall material solution adopts the wall material solution prepared in [Preparation Example 2-1], and the weight ratio of the iron tailings slurry to the wall material solution is 1:4. During spray drying, the pressure is controlled to be 0.6 MPa, the hot air inlet temperature is 175°C, and the outlet temperature is 85°C.

[0041] [Example 2] A method for pretreating iron tailings waste comprises the following steps: S1, crushing the iron tailings into iron tailings powder with a particle size range of 100-200 μm; S2. Add the iron tailings powder to the aqueous solution of the heavy metal scavenger and stir evenly to obtain an iron tailings slurry; wherein the weight ratio of the heavy metal scavenger in the aqueous solution of the heavy metal scavenger is 10%, the heavy metal scavenger is the heavy metal scavenger prepared in [Preparation Example 1-1], and the weight ratio of the iron tailings powder to the aqueous solution of the heavy metal scavenger is 1:2; S3. Add the wall material solution to the iron tailings slurry, stir evenly, and spray dry to obtain modified iron tailings, wherein the wall material solution adopts the wall material solution prepared in [Preparation Example 2-2], and the weight ratio of the iron tailings slurry to the wall material solution is 1:6. During spray drying, the pressure is controlled to be 0.8 MPa, the hot air inlet temperature is 185°C, and the outlet temperature is 95°C.

[0042] [Example 3] A method for pretreating iron tailings waste, which differs from [Example 1] in that: In step S2, the heavy metal scavenger is the heavy metal scavenger prepared in [Preparation Example 1-2].

[0043] [Example 4] A method for pretreating iron tailings waste, which differs from [Example 1] in that: In step S2, the heavy metal scavenger is the heavy metal scavenger prepared in [Preparation Example 1-3].

[0044] [Example 5] A method for pretreating iron tailings waste, which differs from [Example 1] in that: In step S2, the heavy metal scavenger is the heavy metal scavenger prepared in [Preparation Example 1-4].

[0045] [Example 6] A method for pretreating iron tailings waste, which differs from [Example 1] in that: In step S3, the wall material solution adopts the wall material solution prepared in [Preparation Example 2-3].

[0046] [Example 7] A method for pretreating iron tailings waste, which differs from [Example 1] in that: In step S3, the wall material solution adopts the wall material solution prepared in [Preparation Example 2-4].

[0047] Comparative Example [Comparative Example 1] A method for pretreating iron tailings waste, which differs from [Example 1] in that: In step S2, the aqueous solution of the heavy metal scavenger is replaced with water of equal mass. [Comparative Example 2] A method for pretreating iron tailings waste, which differs from [Example 1] in that: In step S3, the wall material solution is replaced by water of equal mass.

[0048] Performance testing Prepare dense concrete specimens according to the mix ratios in Table 1 below: Table 1 Dense concrete mix ratio (unit: kg) Three groups of concrete samples were randomly selected from the concrete samples prepared in each embodiment and comparative example, with 6 concrete samples in each group, and each concrete sample weighing about 1 kg. Three of the concrete samples were immersed in 5 L of deionized water, and the other three were immersed in 5 L of 0.1 mol / L acetic acid solution. The immersion time was 90 days at an ambient temperature of 25°C. After the immersion, the immersion solution was taken for lead and cadmium concentration testing.

[0049] Table 2 Lead dissolution concentration Table 3 Dissolution concentration of cadmium Combining the above-mentioned Example 1 with the comparative examples 1-2 and the test data in Table 2-3, it can be seen that: adding a heavy metal scavenger to pre-fix the heavy metal ions in the iron tailings, and then coating the iron tailings with a wall material solution, the two together can effectively prevent the dissolution of heavy metals lead and cadmium in the modified iron tailings, and can prevent environmental pollution problems.

[0050] Combining the above-mentioned Example 1 and Example 3-5 and the test data in Table 2-3, it can be seen that the heavy metal scavenger is copolymerized by sodium acrylate, mercaptoacrylamide, and N-vinylformamide in a molar ratio of (2-3): (3-4): (2-3), and the molecular weight of the heavy metal scavenger is 40,000-50,000, which is beneficial to further improve the stability of heavy metals in the modified iron tailings and reduce the risk of heavy metal dissolution during subsequent use.

[0051] Combining the above-mentioned Example 1 with Examples 6-7 and the test data in Table 2-3, it can be seen that the combination of hydroxylated acrylic emulsion, water-based polycarbonate-modified hydroxylated polyurethane and bisphenol A epoxy resin can effectively prevent the penetration of water and improve the problem of heavy metal ion extravasation, thereby ensuring the environmental friendliness of the modified iron tailings in subsequent applications.

[0052] This specific implementation manner is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the specific implementation manner as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for pretreating iron tailings waste, characterized in that: The following steps are involved: S1, crushing the iron tailings into iron tailings powder; S2, adding the iron tailings powder to an aqueous solution of a heavy metal scavenger, stirring evenly, to obtain an iron tailings slurry; S3. Adding a wall material solution to the iron tailings slurry, stirring evenly, and spray drying to obtain a modified iron tailings, wherein the wall material solution is acid- and alkali-resistant and insoluble in water after drying to form a film.

2. A method for pretreating iron tailings waste according to claim 1, characterized in that: In step S1, the particle size of the iron tailings powder is in the range of 100-200 μm.

3. A method for pretreating iron tailings waste according to claim 1, characterized in that: In step S2, the heavy metal scavenger is copolymerized by sodium acrylate, mercaptoacrylamide, and N-vinylformamide in a molar ratio of (1-5): (2-6): (1-4), and the molecular weight of the heavy metal scavenger is 30,000-80,000.

4. A method for pretreating iron tailings waste according to claim 3, characterized in that: In step S2, the heavy metal scavenger is copolymerized by sodium acrylate, mercaptoacrylamide, and N-vinylformamide in a molar ratio of (2-3): (3-4): (2-3), and the molecular weight of the heavy metal scavenger is 40,000-50,000.

5. A method for pretreating iron tailings waste according to any one of claims 1 to 4, characterized in that: In step S2, the weight ratio of the iron tailings powder to the aqueous solution of the heavy metal scavenger is 1:(2-3), wherein the weight proportion of the heavy metal scavenger in the aqueous solution of the heavy metal scavenger is 5-10%.

6. A method for pretreating iron tailings waste according to claim 5, characterized in that: In step S3, the wall material solution has a hardness of 2H to 3H after film formation, and a porosity of less than 0.5%.

7. A method for pretreating iron tailings waste according to claim 6, characterized in that: In step S3, the wall material solution is obtained by mixing hydroxy acrylic emulsion, water-based polycarbonate-modified hydroxy polyurethane, bisphenol A epoxy resin and water in a weight ratio of 1: (1-2): (3-4): (1-1.5).

8. The iron tailings waste pretreatment method according to claim 7, characterized in that: In step S3, during spray drying, the pressure is controlled to be 0.6-1.0 MPa, the hot air inlet temperature is 175-185°C, and the outlet temperature is 85-95°C.

9. The method for pretreating iron tailings waste according to claim 7, wherein: In step S3, the weight ratio of the iron tailings slurry to the wall material solution is 1:(4-6).

10. The iron tailings waste pretreatment method according to claim 7, characterized in that: The re-dissolution concentrations of Pb and Cd in the modified iron tailings are both less than 0.01 mg / L.

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