Preparation of functionalized magnetic nanoparticles and its application in purification of coal washing wastewater

Abstract

The preparation of functionalized magnetic nanoparticles and its application in coal washing wastewater purification belong to the technical field of coal washing wastewater purification and purification process.The magnetic separation nanoparticles are prepared by adding concentrated ammonia to the ferric chloride and ferrous chloride solution, and then the functionalized magnetic nanoparticles are prepared by coating the magnetic separation nanoparticles with sodium citrate.The functionalized magnetic nanoparticles can effectively adsorb on the fine particle suspensions in the coal washing wastewater, so that the surface of the fine particle suspensions is magnetized, an external magnetic field is applied, and the physical method of external magnetic force is used to accelerate the sedimentation of the fine particle suspensions in the coal washing wastewater.Compared with the existing chemical method, the operation is more stable, the operation is more simple, and the environmental protection is better.

Description

Technical Field

[0001] This invention belongs to the technical field of coal washing wastewater purification and upgrading process, specifically relating to the preparation of functionalized magnetic nanoparticles and their application in coal washing wastewater purification. Background Technology

[0002] To remove dust and waste rock from raw coal and reduce ash and sulfur content, a large amount of water is needed for washing to improve coal utilization. This results in a significant amount of coal washing wastewater being generated at coal preparation sites. This wastewater mainly contains suspended solids with a particle size of less than 50 μm, primarily composed of silicate impurities such as sand, clay, and shale. Untreated coal washing wastewater can have a suspended solids concentration exceeding 5 g / L, and these particles are particularly stable in water, exhibiting slow settling rates, poor filtration performance, and natural settling periods of up to several months, causing serious pollution to the environment near the mining area. Research in this area began in my country in the 1960s. Li Yafeng et al. proposed a flocculation sedimentation treatment method for coal preparation wastewater, which involves first preparing a slurry with 10% lime (or carbide slag), then adding 0.1% polyacrylamide for coagulation and sedimentation. This method yields coal preparation wastewater with a suspended particle concentration of 87 mg / L. The "Integrated Wastewater Discharge Standard" (GB 8978-1996), promulgated by the State on January 1, 2009, clearly stipulates that the suspended solids content in coal washing wastewater must be below 70 mg / L. Therefore, in order to meet the discharge standards and protect the ecological environment, it is imperative to discover a functionalized magnetic nanoparticle for the efficient and rapid removal of fine suspended solids from coal washing wastewater. Summary of the Invention

[0003] The purpose of this invention is to provide a functionalized magnetic nanoparticle for the efficient removal of fine particulate matter suspended in coal washing wastewater. By synthesizing magnetic nanoparticles and functionalizing the surface of the magnetic nanoparticles, they can be adsorbed onto the surface of fine silicate impurity particles, thus giving the fine silicate impurity particles magnetic separation properties. Suspended matter in coal washing wastewater can then be rapidly removed by applying an external magnetic field.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] The preparation of a functionalized magnetic nanoparticle includes the following steps:

[0006] Step 1. Weigh out ferrous chloride and ferric chloride reagents separately and add them to water. Stir to obtain a mixed solution.

[0007] Step 2. Add concentrated ammonia to the mixed solution to obtain magnetically separated nanoparticles;

[0008] Step 3. Add the magnetically separated nanoparticles to water to prepare an aqueous solution of magnetically separated nanoparticles. After stirring evenly, add sodium citrate to obtain a mixed solution. Slowly heat the mixed solution and stir it to finally obtain functionalized magnetic nanoparticles coated with sodium citrate.

[0009] In step 1, the purity of ferrous chloride and ferric chloride is greater than 95%; the water temperature is 65–80°C; and the Fe in the mixed solution… 2+ / Fe 3+ The molar ratio is 0.6 to 1.0, preferably 0.75; the stirring speed is 1600 to 1900 rpm, preferably 1800 rpm; the stirring time is 2 to 4 min, preferably 3 min.

[0010] In step 2, the volume ratio of concentrated ammonia to the mixed solution is 0.4 to 0.8, preferably 0.6.

[0011] In step 3, the concentration of the aqueous solution of magnetically separated nanoparticles is 0.05–0.1 g / mL, preferably 0.07 g / mL; the stirring speed of the aqueous solution of magnetically separated nanoparticles is 1600–1900 rpm, preferably 1800 rpm; the stirring time is 2–4 min, preferably 3 min; the concentration of sodium citrate is 0.025–0.075 g / mL, preferably 0.05 g / mL; the mixture solution is heated to 85–95°C, and after heating, the stirring speed is 1600–1900 rpm, and the stirring time is 2–3 h.

[0012] The application of the functionalized magnetic nanoparticles in the purification of coal washing wastewater includes the following steps:

[0013] S1. Add functionalized magnetic nanoparticles to the coal preparation wastewater and stir until homogeneous;

[0014] S2. Pass the above mixture into a magnetic separator for magnetic separation to obtain purified coal preparation wastewater.

[0015] In step S1, the suspended solids content in the coal preparation wastewater is 3-10 g / L; the mass ratio of suspended solids particles to functionalized magnetic nanoparticles in the coal preparation wastewater is (10-15):1, preferably 12:1; the stirring speed is 1600-1900 rpm, and the stirring time is 8-10 min, preferably 9 min.

[0016] In step S2, the magnetic separator current is 4-6A, preferably 5A; the suspended solids content of the purified coal preparation wastewater is 50-70mg / L.

[0017] The application of functionalized magnetic nanoparticles in the purification of coal washing wastewater according to the present invention has the following advantages compared with the prior art:

[0018] 1. This invention develops functionalized magnetic nanoparticles that can be effectively adsorbed onto fine suspended matter in coal washing wastewater, magnetizing the surface of the fine suspended matter. When an external magnetic field is applied, the fine suspended matter is rapidly settled under the influence of the magnetic field, accelerating the sedimentation of fine suspended matter in coal washing wastewater. The sedimentation rate is about 0.5 m / s, which is much higher than that of existing natural sedimentation equipment.

[0019] 2. The method of the present invention uses the physical method of external magnetic force to accelerate the sedimentation of fine suspended solids in coal washing wastewater. Compared with the existing chemical methods such as slurry preparation + flocculation, it is more stable in operation, simpler to operate, and more environmentally friendly. The purified coal washing wastewater has a suspended solids content of 50-70 mg / L, which meets the national emission standards. Attached Figure Description

[0020] Figure 1 This is the particle size distribution curve of fine suspended matter in coal washing wastewater in an embodiment of the present invention.

[0021] Figure 2 This is a scanning electron microscope image of the functionalized magnetic nanoparticles prepared in Example 1 of the present invention adsorbed on the surface of fine suspended matter in coal washing wastewater. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0023] The present invention relates to the application of functionalized magnetic nanoparticles in the purification of coal washing wastewater. The method involves synthesizing magnetic separation nanoparticles, functionalizing the surface of the magnetic separation nanoparticles, adding them to coal washing wastewater, and using magnetic separation equipment to efficiently and rapidly remove suspended impurities from the coal washing wastewater.

[0024] Furthermore, the magnetic nanoparticles are synthesized using FeCl2 and FeCl3 solutions under concentrated ammonia conditions.

[0025] Furthermore, the functionalized magnetic nanoparticles are formed by immersing magnetically separated nanoparticles in a sodium citrate solution and then heating them to allow citrate ions to be carried on the surface of the magnetic nanoparticles.

[0026] In the following examples, the coal washing wastewater used was taken from Xiaoqing Mine of Tiemei Group, Diaobingshan City, Liaoning Province. The concentration of suspended solids in the coal washing wastewater was measured to be 6.2 g / L by drying and weighing. The particle size distribution was detected by laser particle size analyzer, and the results are as follows: Figure 1 As shown, approximately 80% of the fine suspended matter has a particle size less than 10.24 μm (D). 80 =10.24). The nanoscale functionalized magnetically separated particles prepared by this invention can be well adsorbed on the surface of micron-sized suspended particles, magnetizing the suspended particles. When an external magnetic field is applied, the suspended particles settle rapidly. Tap water was used in the experiment.

[0027] Example 1

[0028] The application of functionalized magnetic nanoparticles in the purification of coal washing wastewater includes the following steps:

[0029] Step 1: Synthesis of magnetic nanoparticles

[0030] Weigh out ferrous chloride and ferric chloride reagents with a purity of 97% and add them to a 75℃ aqueous solution to prepare Fe. 2+ / Fe 3+ A mixed solution with a molar ratio of 0.6 was prepared and stirred at 1600 rpm for 2 minutes. Then, concentrated ammonia was added at a ratio of 0.4 to the mixed solution to obtain magnetically separated nanoparticles.

[0031] Step 2: Preparation of Functionalized Magnetic Nanoparticles

[0032] The synthesized magnetically separated nanoparticles were weighed and added to water to prepare an aqueous solution with a concentration of 0.05 g / mL. The solution was stirred at 1600 rpm to ensure uniform dispersion of the nanoparticles. Sodium citrate was then added to achieve a concentration of 0.025 g / mL. The mixture was slowly heated to 90°C and stirred at this temperature for 2.5 hours. The resulting sodium citrate-coated functionalized magnetic nanoparticles were then collected.

[0033] Step 3: Purification of Coal Preparation Wastewater

[0034] Functionalized magnetic nanoparticles were added to coal preparation wastewater to achieve a mass ratio of suspended particles to functionalized magnetic nanoparticles of 10. The mixture was stirred at 1600 rpm for 8 minutes. After stirring, to observe whether the functionalized magnetic nanoparticles adsorbed onto the suspended particles, 1 mL of the mixture was extracted, filtered, and the solid particles were rinsed with water, dried, and then examined using a scanning electron microscope. The results are shown below. Figure 2 As shown. By Figure 2 It can be seen that the surface of the suspended particles is rough and there are obvious fine particles attached, indicating that they contain C5H7O5COO. — Magnetic separation allows nanomaterials to be adsorbed onto the surface of suspended particles. The material is then passed into a magnetic separator with a current of 4A to obtain purified coal preparation wastewater. After filtration and drying, the concentration of fine suspended solids is found to be 57 mg / L, meeting national emission standards.

[0035] Example 2

[0036] Step 1: Synthesis of magnetic nanoparticles

[0037] Weigh out ferrous chloride and ferric chloride reagents with a purity of 98% respectively, and add them to a 75℃ aqueous solution to prepare Fe 2 + / Fe 3+ A mixed solution with a molar ratio of 1.0 was prepared and stirred at 1700 rpm for 4 min. Then concentrated ammonia was added, with the ratio of concentrated ammonia to the mixed solution being 0.8, to obtain magnetically separated nanoparticles.

[0038] Step 2: Preparation of Functionalized Magnetic Nanoparticles

[0039] The synthesized magnetically separated nanoparticles were weighed and added to water to prepare an aqueous solution with a concentration of 0.1 g / mL. The solution was stirred at 1700 rpm to ensure uniform dispersion of the nanoparticles. Sodium citrate was then added to achieve a concentration of 0.075 g / mL. The mixture was slowly heated to 90°C and stirred at this temperature for 2.5 hours. The resulting sodium citrate-coated functionalized magnetic nanoparticles were then collected.

[0040] Step 3: Purification of Coal Preparation Wastewater

[0041] Functionalized magnetic nanoparticles were added to coal preparation wastewater to achieve a mass ratio of suspended particles to functionalized magnetic nanoparticles of 15. The mixture was stirred at 1700 rpm for 10 minutes, and then passed into a magnetic separator with a current of 6A. The resulting purified wastewater was then filtered and dried to obtain a fine suspended solids concentration of 66 mg / L, meeting national emission standards.

[0042] Example 3

[0043] Step 1: Synthesis of magnetic nanoparticles

[0044] Weigh out ferrous chloride and ferric chloride reagents with a purity of 98% respectively, and add them to a 75℃ aqueous solution to prepare Fe 2 + / Fe 3+ A mixed solution with a molar ratio of 0.8 was prepared and stirred at 1800 rpm for 3 minutes. Then concentrated ammonia was added, with the ratio of concentrated ammonia to the mixed solution being 0.6, to obtain magnetically separated nanoparticles.

[0045] Step 2: Preparation of Functionalized Magnetic Nanoparticles

[0046] The synthesized magnetically separated nanoparticles were weighed and added to water to prepare an aqueous solution of magnetically separated nanoparticles with a concentration of 0.075 g / mL. The solution was stirred at 1800 rpm to ensure uniform dispersion of the nanoparticles. Sodium citrate was then added to achieve a concentration of 0.05 g / mL. The mixture was slowly heated to 90 °C and stirred at this temperature for 2.5 hours. The resulting sodium citrate-coated functionalized magnetic nanoparticles were then collected.

[0047] Step 3: Purification of Coal Preparation Wastewater

[0048] Functionalized magnetic nanoparticles were added to coal preparation wastewater to achieve a mass ratio of suspended particles to functionalized magnetic nanoparticles of 1:3. The mixture was stirred at 1800 rpm for 9 minutes, and then passed into a magnetic separator with a current of 5A. The resulting purified coal preparation wastewater was then filtered and dried to obtain a fine suspended solids concentration of 60 mg / L, meeting the national emission standards.

[0049] Example 4

[0050] Step 1: Synthesis of magnetic nanoparticles

[0051] Weigh out ferrous chloride and ferric chloride reagents with a purity of 99% and add them to a 75℃ aqueous solution to prepare Fe. 2 + / Fe 3+ A mixed solution with a molar ratio of 0.7 was prepared and stirred at 1900 rpm for 3 minutes. Then concentrated ammonia was added, with the ratio of concentrated ammonia to the mixed solution being 0.5, to obtain magnetically separated nanoparticles.

[0052] Step 2: Preparation of Functionalized Magnetic Nanoparticles

[0053] The synthesized magnetically separated nanoparticles were weighed and added to water to prepare an aqueous solution with a concentration of 0.06 g / mL. The solution was stirred at 1900 rpm to ensure uniform dispersion of the nanoparticles. Sodium citrate was then added to achieve a concentration of 0.03 g / mL. The mixture was slowly heated to 90°C and stirred at this temperature for 2.5 hours. The resulting sodium citrate-coated functionalized magnetic nanoparticles were then collected.

[0054] Step 3: Purification of Coal Preparation Wastewater

[0055] Functionalized magnetic nanoparticles were added to coal preparation wastewater to achieve a mass ratio of suspended particles to functionalized magnetic nanoparticles of 1:1. The mixture was stirred at 1900 rpm for 8.5 minutes. Subsequently, the mixture was fed into a magnetic separator with a current of 4.5A to obtain purified coal preparation wastewater. After filtration and drying, the concentration of fine suspended solids was found to be 51 mg / L, meeting the national emission standards.

[0056] Example 5

[0057] Step 1: Synthesis of magnetic nanoparticles

[0058] Weigh out ferrous chloride and ferric chloride reagents with a purity of 96% respectively, and add them to a 75℃ aqueous solution to prepare Fe. 2 + / Fe 3+ A mixed solution with a molar ratio of 0.9 was prepared and stirred at 1750 rpm for 3.5 min. Then concentrated ammonia was added, with the ratio of concentrated ammonia to the mixed solution being 0.75, to obtain magnetically separated nanoparticles.

[0059] Step 2: Preparation of Functionalized Magnetic Nanoparticles

[0060] The synthesized magnetically separated nanoparticles were weighed and added to water to prepare an aqueous solution with a concentration of 0.65 g / mL. The solution was stirred at 1750 rpm to ensure uniform dispersion of the nanoparticles. Sodium citrate was then added to achieve a concentration of 0.065 g / mL. The mixture was slowly heated to 90°C and stirred at this temperature for 2.5 hours. The resulting sodium citrate-coated functionalized magnetic nanoparticles were then collected.

[0061] Step 3: Purification of Coal Preparation Wastewater

[0062] Functionalized magnetic nanoparticles were added to coal preparation wastewater to achieve a mass ratio of suspended particles to functionalized magnetic nanoparticles of 12. The mixture was stirred at 1750 rpm for 9.5 minutes. Subsequently, the mixture was fed into a magnetic separator with a current of 5.5A to obtain purified coal preparation wastewater. After filtration and drying, the concentration of fine suspended solids was found to be 67 mg / L, meeting the national emission standards.

[0063] Example 6

[0064] Step 1: Synthesis of magnetic nanoparticles

[0065] Weigh out ferrous chloride and ferric chloride reagents with a purity of 98% respectively, and add them to a 75℃ aqueous solution to prepare Fe 2 + / Fe3+ A mixed solution with a molar ratio of 0.6 was prepared and stirred at 1850 rpm for 4 min. Then concentrated ammonia was added, with the ratio of concentrated ammonia to the mixed solution being 0.4, to obtain magnetically separated nanoparticles.

[0066] Step 2: Preparation of Functionalized Magnetic Nanoparticles

[0067] The synthesized magnetically separated nanoparticles were weighed and added to water to prepare an aqueous solution with a concentration of 0.05 g / mL. The solution was stirred at 1850 rpm to ensure uniform dispersion of the nanoparticles. Sodium citrate was then added to achieve a concentration of 0.025 g / mL. The mixture was slowly heated to 90°C and stirred at this temperature for 2.5 hours. The resulting sodium citrate-coated functionalized magnetic nanoparticles were then collected.

[0068] Step 3: Purification of Coal Preparation Wastewater

[0069] Functionalized magnetic nanoparticles were added to coal preparation wastewater to achieve a mass ratio of suspended particles to functionalized magnetic nanoparticles of 15. The mixture was stirred at 1850 rpm for 8 minutes, and then passed into a magnetic separator with a current of 4A. The resulting purified coal preparation wastewater was filtered and dried to obtain a fine suspended solids concentration of 61 mg / L, which meets the national emission standards.

[0070] Example 7

[0071] Step 1: Synthesis of magnetic nanoparticles

[0072] Weigh out ferrous chloride and ferric chloride reagents with a purity of 97% and add them to a 75℃ aqueous solution to prepare Fe. 2 + / Fe 3+ A mixed solution with a molar ratio of 1.0 was prepared and stirred at 1650 rpm for 3 minutes. Then concentrated ammonia was added, with the ratio of concentrated ammonia to the mixed solution being 0.8, to obtain magnetically separated nanoparticles.

[0073] Step 2: Preparation of Functionalized Magnetic Nanoparticles

[0074] The synthesized magnetically separated nanoparticles were weighed and added to water to prepare an aqueous solution with a concentration of 0.1 g / mL. The solution was stirred at 1650 rpm to ensure uniform dispersion of the nanoparticles. Sodium citrate was then added to achieve a concentration of 0.075 g / mL. The mixture was slowly heated to 90°C and stirred at this temperature for 2.5 hours. The resulting sodium citrate-coated functionalized magnetic nanoparticles were then collected.

[0075] Step 3: Purification of Coal Preparation Wastewater

[0076] Functionalized magnetic nanoparticles were added to coal preparation wastewater to achieve a mass ratio of suspended particles to functionalized magnetic nanoparticles of 10. The mixture was stirred at 1650 rpm for 10 minutes, and then passed into a magnetic separator with a current of 4A. The resulting purified coal preparation wastewater was then filtered and dried to obtain a fine suspended solids concentration of 65 mg / L, meeting the national emission standards.

[0077] Example 8

[0078] Step 1: Synthesis of magnetic nanoparticles

[0079] Weigh out ferrous chloride and ferric chloride reagents with a purity of 96% respectively, and add them to a 75℃ aqueous solution to prepare Fe. 2 + / Fe 3+ A mixed solution with a molar ratio of 0.85 was prepared and stirred at 1650 rpm for 2.5 min. Then concentrated ammonia was added, with the ratio of concentrated ammonia to the mixed solution being 0.78, to obtain magnetically separated nanoparticles.

[0080] Step 2: Preparation of Functionalized Magnetic Nanoparticles

[0081] The synthesized magnetically separated nanoparticles were weighed and added to water to prepare an aqueous solution with a concentration of 0.08 g / mL. The solution was stirred at 1650 rpm to ensure uniform dispersion of the nanoparticles. Sodium citrate was then added to achieve a concentration of 0.065 g / mL. The mixture was slowly heated to 90°C and stirred at this temperature for 2.5 hours. The resulting sodium citrate-coated functionalized magnetic nanoparticles were then collected.

[0082] Step 3: Purification of Coal Preparation Wastewater

[0083] Functionalized magnetic nanoparticles were added to coal preparation wastewater to achieve a mass ratio of suspended particles to functionalized magnetic nanoparticles of 11.5. The mixture was stirred at 1650 rpm for 8.2 minutes. Subsequently, the mixture was fed into a magnetic separator with a current of 5.7 A to obtain purified coal preparation wastewater. After filtration and drying, the concentration of fine suspended solids was found to be 70 mg / L, meeting the national emission standards.

[0084] Example 9

[0085] Step 1: Synthesis of magnetic nanoparticles

[0086] Weigh out ferrous chloride and ferric chloride reagents with a purity of 98% respectively, and add them to a 75℃ aqueous solution to prepare Fe 2 + / Fe 3+ A mixed solution with a molar ratio of 0.73 was prepared and stirred at 1720 rpm for 3.8 min. Then concentrated ammonia was added, with the ratio of concentrated ammonia to the mixed solution being 0.75, to obtain magnetically separated nanoparticles.

[0087] Step 2: Preparation of Functionalized Magnetic Nanoparticles

[0088] The synthesized magnetically separated nanoparticles were weighed and added to water to prepare an aqueous solution with a concentration of 0.09 g / mL. The solution was stirred at 1720 rpm to ensure uniform dispersion of the nanoparticles. Sodium citrate was then added to achieve a concentration of 0.065 g / mL. The mixture was slowly heated to 90°C and stirred at this temperature for 2.5 hours. The resulting sodium citrate-coated functionalized magnetic nanoparticles were then collected.

[0089] Step 3: Purification of Coal Preparation Wastewater

[0090] Functionalized magnetic nanoparticles were added to coal preparation wastewater to achieve a mass ratio of suspended particles to functionalized magnetic nanoparticles of 13.5. The mixture was stirred at 1720 rpm for 9.2 minutes. Subsequently, the mixture was fed into a magnetic separator with a current of 5.2 A to obtain purified coal preparation wastewater. After filtration and drying, the concentration of fine suspended solids was found to be 51 mg / L, meeting the national emission standards.

Claims

1. The application of functionalized magnetic nanoparticles in the purification of coal washing wastewater, characterized in that, Includes the following steps: S1. Add functionalized magnetic nanoparticles to coal preparation wastewater and stir until homogeneous to obtain a mixed liquid; S2. Pass the above mixture into a magnetic separator for magnetic separation to obtain purified coal preparation wastewater; In step S1, the suspended solids content in the coal preparation wastewater is 3~10g / L; the mass ratio of suspended solids particles to functionalized magnetic nanoparticles in the coal preparation wastewater is 10~15:1; the stirring speed is 1600~1900rpm; and the stirring time is 8~10min. In step S2, the magnetic separator current is 4~6A; the suspended solids content in the purified coal preparation wastewater is 50~70mg / L; The method for preparing the functionalized magnetic nanoparticles includes the following steps: Step 1. Weigh out ferrous chloride and ferric chloride reagents separately and add them to water. Stir to obtain a mixed solution. Step 2. Add concentrated ammonia to the mixed solution to obtain magnetically separated nanoparticles; Step 3. Add the magnetically separated nanoparticles to water to prepare an aqueous solution of magnetically separated nanoparticles. After stirring evenly, add sodium citrate to obtain a mixed solution. The mixture solution was slowly heated and stirred to obtain functionalized magnetic nanoparticles coated with sodium citrate.

2. The application of functionalized magnetic nanoparticles according to claim 1 in the purification of coal washing wastewater, characterized in that, The mass ratio of suspended particles to functionalized magnetic nanoparticles in the coal preparation wastewater is 12:1; the stirring time is 9 minutes; and the magnetic separator current is 5A.

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