A method for extracting iron from coal mine water and preparing superparamagnetic Fe3O4 nanoparticles

Abstract

The present invention discloses a method for extracting iron from coal mine water and preparing superparamagnetic Fe3O4 nanoparticles. The method utilizes aeration oxidation and flocculation precipitation to precipitate all the iron in the coal mine water as Fe(OH)3. The iron is then uniformly mixed and dispersed with a carbon source, followed by calcination to produce the Fe3O4 nanoparticles. Experimental data demonstrates that the Fe3O4 nanoparticles produced by the present invention are highly pure, free of impurities, and are uniform nanoparticles with superparamagnetic properties.

Description

Technical Field

[0001] The invention belongs to the technical field of pollutant treatment, and in particular relates to a method for extracting iron from coal mine water and preparing superparamagnetic Fe3O4 nanoparticles. Background Art

[0002] Although the mine entrances were sealed after closure, significant water accumulation (tens of billions of tons) still accumulates within the mines, gushing out along the mountainside. Chongqing's abundant rainfall contributes to the daily outflow, reaching approximately 100,000 tons per day in Wansheng District alone. Previous water quality analysis revealed that the outflowing water contains significant amounts of iron ions, posing a significant environmental risk. Furthermore, many of Chongqing's mines are located near tributaries of the Yangtze River and key water sources (for example, the Zaodu River Reservoir, which supplies Chongqing's 3 million people, is home to several closed mines). This significantly increases the environmental safety risks of these outflowing waters, necessitating rigorous treatment. Due to the widespread distribution of outflowing points, current treatment methods for these outflowing waters primarily utilize a "pH adjustment-flocculation sedimentation" method, which can bring the effluent to Class I water standards. However, this process produces significant amounts of brick-red sediment. According to incomplete statistics, one cubic meter of outflowing water can produce approximately 80 kilograms of sediment. These sediments will not only cause considerable economic pressure on the treatment and disposal of the effluent, but also cause secondary pollution to the surrounding environment. Therefore, it is urgent to find a safe, effective and economical way to treat these sediments. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a method for extracting iron from coal mine water and preparing superparamagnetic Fe3O4 nanoparticles, recycling the iron ions in coal mine water and preparing Fe3O4 nanoparticles with superparamagnetism.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] The present invention provides a method for extracting iron from coal mine water and preparing superparamagnetic Fe3O4 nanoparticles, comprising the following steps:

[0006] (1) The coal mine water is separated by solid-liquid separation to remove suspended solid impurities; then the water is exposed to air, alkali is added to adjust the pH to 10-12, and flocculants are added to reduce the Fe 2+ Oxidized to Fe 3+ and flocculates and precipitates in the form of Fe(OH)3;

[0007] (2) mixing the flocculated precipitate obtained in step (1) with water and stirring uniformly to form a suspension A; dispersing the carbon source in a corresponding solvent to form a dispersion B, dropping the dispersion B into the suspension A and stirring to mix, and then separating the mixed solution into solid and liquid to obtain a solid C;

[0008] (3) calcining the solid C obtained in step (2) in an inert atmosphere to obtain superparamagnetic Fe3O4 nanoparticles.

[0009] As a preferred technical solution, in step (1), the flocculant is polyacrylamide, and the amount of polyacrylamide added per ton of water is 1-5 kg.

[0010] As a preferred technical solution, in step (1), the base is a 0.5-1.0 mol / L NaOH or KOH aqueous solution.

[0011] As a preferred technical solution, in step (2), the concentration of suspension A is 800-1500 g / L.

[0012] As a preferred technical solution, in step (2), the carbon source is an inorganic carbon source, and the solvent is methanol or ethanol; or, the carbon source is an organic carbon source, and the solvent is water.

[0013] As a preferred technical solution, the inorganic carbon source is carbon black or activated carbon; the organic carbon source is starch, glucose or sucrose.

[0014] As a preferred technical solution, in step (2), the suspension A and the dispersion B are mixed in a ratio of 200:1-600:1 in terms of the mass ratio of Fe(OH)3 to the inorganic carbon source; or, the suspension A and the dispersion B are mixed in a ratio of 400:1-1000:1 in terms of the mass ratio of Fe(OH)3 to the organic carbon source.

[0015] As a preferred technical solution, in step (3), the calcination temperature is 500-700° C. and the calcination time is 2-3 hours.

[0016] The present invention also provides superparamagnetic Fe3O4 nanoparticles prepared by the method.

[0017] The beneficial effects of the present invention are:

[0018] The present invention utilizes aeration oxidation and flocculation precipitation to precipitate all the iron in coal mine water as Fe(OH)3. The iron is then uniformly mixed and dispersed with a carbon source, followed by calcination to produce Fe3O4 nanoparticles. Experimental data demonstrates that the Fe3O4 nanoparticles produced by the present invention are highly pure, free of impurities, and are uniform nanoparticles with superparamagnetic properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to make the purpose, technical solutions and beneficial effects of the present invention more clear, the present invention provides the following drawings for illustration:

[0020] Figure 1 XRD patterns of Fe3O4 nanoparticles prepared in Example 1 and Example 2.

[0021] Figure 2 This is the SEM image of Fe3O4 nanoparticles prepared in Example 1.

[0022] Figure 3 This is the VSM image of Fe3O4 nanoparticles prepared in Example 1.

[0023] Figure 4 This is the SEM image of Fe3O4 nanoparticles prepared in Example 2.

[0024] Figure 5 This is the VSM image of Fe3O4 nanoparticles prepared in Example 2. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0026] Unless otherwise specified, the methods used in the following examples are all conventional methods. The materials or reagents required in the following examples are all commercially available unless otherwise specified.

[0027] Example 1: Preparation of superparamagnetic Fe3O4 nanoparticles using an inorganic carbon source

[0028] (1) The coal mine water was separated by solid-liquid separation to remove suspended solid impurities; then the water was exposed to air, 1.0 mol / L NaOH aqueous solution was added to adjust the pH to 11, and polyacrylamide was added at a rate of 3 kg per ton of water to reduce the Fe 2+ Oxidized to Fe 3+ and flocculates and precipitates in the form of Fe(OH)3;

[0029] (2) mixing the flocculated precipitate obtained in step (1) with water and stirring evenly to form a suspension A with a concentration of 1000 g / L; dispersing the activated carbon in methanol to form a dispersion B, dropping the dispersion B into the suspension A at a mass ratio of Fe(OH)3 to activated carbon of 600:1, stirring and mixing, and then separating the mixed solution into solid and liquid to obtain solid C;

[0030] (3) The solid C obtained in step (2) was calcined at 650° C. for 2 hours in an inert atmosphere to obtain superparamagnetic Fe 3 O 4 nanoparticles.

[0031] The XRD pattern of Fe3O4 nanoparticles prepared in Example 1 is as follows: Figure 1As shown, the main peaks of the Fe3O4 nanoparticles prepared in Example 1 are basically consistent with those of the standard PDF card of Fe3O4, indicating that Fe3O4 is obtained, and no impurity diffraction peaks appear in the figure, indicating that the product has high purity.

[0032] The SEM image of Fe3O4 nanoparticles prepared in Example 1 is as follows: Figure 2 As shown, uniform Fe3O4 nanoparticles can be seen.

[0033] The VSM image of the Fe3O4 nanoparticles prepared in Example 1 is as follows: Figure 3 As shown, it can be seen that the hysteresis loop of the Fe3O4 nanoparticles has almost no coercive force and remanence, indicating that the Fe3O4 nanoparticles prepared in Example 1 have superparamagnetism.

[0034] Example 2: Preparation of superparamagnetic Fe3O4 nanoparticles using an organic carbon source

[0035] (1) The coal mine water was separated by solid-liquid separation to remove suspended solid impurities; then the water was exposed to air, 1.0 mol / L NaOH aqueous solution was added to adjust the pH to 11, and polyacrylamide was added at a rate of 3 kg per ton of water to reduce the Fe 2+ Oxidized to Fe 3+ and flocculates and precipitates in the form of Fe(OH)3;

[0036] (2) mixing the flocculated precipitate obtained in step (1) with water and stirring uniformly to form a suspension A with a concentration of 1000 g / L; dispersing starch in water to form a dispersion B, dropping the dispersion B into the suspension A at a mass ratio of Fe(OH)3 to starch of 1000:1, stirring and mixing, and then separating the mixed solution into a solid-liquid state to obtain a solid C;

[0037] (3) The solid C obtained in step (2) was calcined at 650° C. for 2 hours in an inert atmosphere to obtain superparamagnetic Fe 3 O 4 nanoparticles.

[0038] The XRD pattern of Fe3O4 nanoparticles prepared in Example 2 is as follows: Figure 1 As shown, the main peaks of the Fe3O4 nanoparticles prepared in Example 2 are basically consistent with those of the standard PDF card of Fe3O4, indicating that Fe3O4 is obtained, and no impurity diffraction peaks appear in the figure, indicating that the product purity is high.

[0039] The SEM image of Fe3O4 nanoparticles prepared in Example 2 is as follows: Figure 4 As shown, uniform Fe3O4 nanoparticles can be seen.

[0040] The VSM image of Fe3O4 nanoparticles prepared in Example 2 is as follows: Figure 5As shown, it can be seen that the hysteresis loop of the Fe3O4 nanoparticles has almost no coercive force and remanence, indicating that the Fe3O4 nanoparticles prepared in Example 2 have superparamagnetism.

[0041] The above embodiments are merely preferred embodiments for the purpose of fully illustrating the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

Claims

1. A method for extracting iron from coal mine water and preparing superparamagnetic Fe3O4 nanoparticles, characterized by: The steps include: (1) The coal mine water is separated by solid-liquid separation to remove suspended solid impurities; then the water is exposed to air, alkali is added to adjust the pH to 10-12, and flocculants are added to reduce the Fe 2+ Oxidized to Fe 3+ and flocculates and precipitates in the form of Fe(OH)3; (2) mixing the flocculated precipitate obtained in step (1) with water and stirring uniformly to form a suspension A; dispersing a carbon source in a corresponding solvent to form a dispersion B, dropping the dispersion B into the suspension A and stirring to mix, and then separating the mixed liquid into a solid and a liquid to obtain a solid C; the carbon source is an inorganic carbon source, and the solvent is methanol or ethanol; or the carbon source is an organic carbon source, and the solvent is water; In the step (2), the suspension A and the dispersion B are mixed in a ratio of 200:1 to 600:1 in terms of the mass ratio of Fe(OH)3 to the inorganic carbon source; or the suspension A and the dispersion B are mixed in a ratio of 400:1 to 1000:1 in terms of the mass ratio of Fe(OH)3 to the organic carbon source; (3) calcining the solid C obtained in step (2) in an inert atmosphere to obtain superparamagnetic Fe3O4 nanoparticles.

2. The method for extracting iron from coal mine water and preparing superparamagnetic Fe3O4 nanoparticles according to claim 1, characterized in that: In the step (1), the flocculant is polyacrylamide, and the amount of polyacrylamide added per ton of water is 1-5 kg.

3. The method for extracting iron from coal mine water and preparing superparamagnetic Fe3O4 nanoparticles according to claim 1, characterized in that: In the step (1), the base is a 0.5-1.0 mol / L NaOH or KOH aqueous solution.

4. The method for extracting iron from coal mine water and preparing superparamagnetic Fe3O4 nanoparticles according to claim 1, characterized in that: In the step (2), the concentration of suspension A is 800-1500 g / L.

5. The method for extracting iron from coal mine water and preparing superparamagnetic Fe3O4 nanoparticles according to claim 1, characterized in that: The inorganic carbon source is carbon black or activated carbon; the organic carbon source is starch, glucose or sucrose.

6. The method for extracting iron from coal mine water and preparing superparamagnetic Fe3O4 nanoparticles according to claim 1, characterized in that: In the step (3), the calcination temperature is 500-700° C. and the calcination time is 2-3 hours.

7. Superparamagnetic Fe3O4 nanoparticles prepared according to the method according to any one of claims 1 to 6.

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