Coal washing water composite flocculant as well as preparation method and application thereof

Abstract

The invention relates to the technical field of sewage treatment flocculants, in particular to a coal washing water composite flocculant as well as a preparation method and application thereof, and the flocculant is prepared from polyaluminum chloride, aluminum potassium sulfate dodecahydrate, modified silica, plant ash, modified anionic polyacrylamide and sodium chloride. The inorganic flocculant A and the organic flocculant B are matched for use, so that coal particles in coal washing water of different types and different particle sizes can be effectively settled, fine coal particles are further adsorbed and decolorized through the matching effect of the modified silica and the plant ash, the turbidity of supernate can be effectively reduced, sodium chloride can sterilize and remove dust, and the water quality is improved. The dissolution of the modified anionic polyacrylamide can be effectively promoted. Experiments prove that the composite flocculant has more remarkable effects on various types of coal washing water of coal mines in different regions than conventional flocculants.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment flocculants, and in particular to a composite flocculant for coal washing water, a preparation method and application thereof. Background Art

[0002] Coal washing water is industrial wastewater with high suspended matter content and difficult to settle discharged from the coal washing plant during the wet coal washing process. These suspended matter are mainly composed of coal particles, clay and some impurities, characterized by small particles, high viscosity, negative charge, strong stability, and extremely difficult to settle naturally. If discharged without treatment, it will not only have a great impact on the environment, but also cause coal slime loss, reduce coal mine yield, and waste water resources. According to statistics, my country loses 1.5 million tons of coal slime in coal washing and processing every year, which is equivalent to the annual output of a large mine. If flocculants are used for flocculation, sedimentation and separation, not only can part of the coal powder be effectively recovered, but the supernatant can also be recycled into the system to reduce water consumption. However, although a single inorganic flocculant can electrically neutralize tiny coal slime molecules and effectively coagulate them, it is difficult to settle and separate them due to its low molecular weight and unclear bridging effect, and excessive use can easily cause secondary pollution of water bodies. Although organic flocculants such as anionic APAM have high molecular weight, strong electrical neutralization ability and good flocculation effect, they are difficult to capture some extremely small coal particles due to their large bridge chains, resulting in high turbidity in the supernatant. At the same time, the dissolution rate of APAM is also slow, and usually requires a lot of dissolution time and a large space for dissolution equipment.

[0003] Therefore, making a composite flocculant for coal washing water that can solve the above-mentioned shortcomings of flocculants not only has great environmental significance, but also has high economic value.

[0004] Purpose of the Invention

[0005] In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a composite flocculant for coal washing water, a preparation method and its application. The present invention uses an inorganic flocculant and an organic flocculant in combination, so that coal particles in coal washing water of different types and particle sizes can be effectively settled. Through the combined action of modified silica and plant ash, fine coal particles are further adsorbed and decolorized, and the turbidity of the supernatant can be effectively reduced. Sodium chloride can not only sterilize and remove dust, but also effectively promote the dissolution of modified anionic polyacrylamide. Experiments have shown that the composite flocculant has a more significant effect on various types of coal washing water in coal mines in different regions than conventional flocculants.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A composite flocculant for coal washing water, comprising an inorganic flocculant A and an organic flocculant B, wherein the inorganic flocculant A comprises, by weight, 30-40 parts of polyaluminium chloride, 20-30 parts of potassium aluminium sulfate dodecahydrate, 15-20 parts of modified silica and 20-30 parts of plant ash;

[0008] The organic flocculant B comprises the following components by weight: 10-15 parts of modified anionic polyacrylamide and 5-10 parts of sodium chloride;

[0009] Wherein, the modified silica is prepared by the following steps:

[0010] S11. 10-20 parts by mass of silica, 40-50 parts of water, 2-5 parts of hexadecyltrimethylammonium bromide were mixed and stirred for 2-3h to obtain a mixed solution;

[0011] S12. The mixed solution obtained in step S11 is transferred to a high pressure reactor, reacted at 150-180°C for 24-48h, cooled to room temperature, the product is filtered, washed with ethanol, and dried at 80-100°C for 2-3h to obtain the modified silica;

[0012] Wherein, the modified anionic polyacrylamide is prepared by the following steps:

[0013] S21. Add 20-25 parts of anionic polyacrylamide to 150 parts of water by mass and stir to fully dissolve it to form a uniform solution;

[0014] S22. Add 3-5 parts of methacryloyloxyethyl trimethylammonium chloride and 1-3 parts of 2-acrylamide-2-methylpropane sulfonic acid to the solution obtained in step S21 in parts by mass, and stir until dissolved to obtain a precursor solution;

[0015] S23. Add 0.1-0.3 parts of an initiator dropwise to the precursor solution by mass, stir the precursor solution and react at 50-60° C. for 5-7 hours to obtain a modified anionic polyacrylamide solution;

[0016] S24. The modified anionic polyacrylamide solution is dialyzed for 36-48 hours, and the treated product is dried to obtain the modified anionic polyacrylamide.

[0017] Preferably, the initiator is a mixture of ammonium persulfate, sodium bisulfite and water in a mass ratio of 1:1:10-15.

[0018] Preferably, the molecular weight cut-off of the dialysis bag used in the dialysis treatment is 1000-5000 Daltons.

[0019] A method for preparing a composite flocculant for coal washing water, for preparing the composite flocculant for coal washing water, comprises the following steps:

[0020] S1. Preparation of inorganic flocculant A: 30-40 parts by mass of polyaluminium chloride, 20-30 parts of potassium aluminium sulfate dodecahydrate and 15-20 parts of modified silica were mixed and ground to obtain an inorganic flocculant A after being fully mixed and then adding 20-30 parts of wood ash;

[0021] S2. Preparation of organic flocculant B: 10-15 parts by mass of modified anionic polyacrylamide and 5-10 parts by mass of sodium chloride crystals are mixed evenly to obtain organic flocculant B.

[0022] Preferably, the average particle size of the modified anionic polyacrylamide is 80-100 meshes, the average particle size of the wood ash is 140-160 meshes, and the average particle size of the sodium chloride is 200-300 meshes.

[0023] Application of the coal washing water composite flocculant according to the coal washing water composite flocculant or the coal washing water composite flocculant prepared by the preparation method in coal washing water.

[0024] Preferably, the method comprises the following steps:

[0025] S31. The inorganic flocculant A is prepared into a 10-30% aqueous solution, and the organic flocculant B is prepared into a 1-3‰ aqueous solution;

[0026] S32. Adding an inorganic flocculant A to the coal washing water, stirring and mixing the particles in the coal washing water to form small flocs;

[0027] S33. Add organic flocculant B to the coal washing water treated in step S32, stir and mix again, flocculate the particles in the coal washing water into large flocs for sedimentation, and perform solid-liquid separation.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The positively charged aluminum chloride and aluminum potassium sulfate dodecahydrate react with the negatively charged coal particles to neutralize, reduce the surface potential of the coal particles, destroy the stable colloidal structure of the coal particles, and aggregate the coal particles. The adsorption and decolorization effect of modified silica and plant ash further adsorbs the fine coal particles and impurities that are not easy to aggregate, and has a decolorization effect on the pigments produced by the impurities;

[0030] 2. The fragment molecular sieve structure in the modified silica has a rich pore structure and a large specific surface area, which can adsorb coal particles after aluminum chloride aggregates them; the fragment molecular sieve structure also provides adsorption sites for aluminum hydroxide colloid formed by the hydrolysis of potassium aluminum sulfate dodecahydrate, making it easier for the colloid to adhere to the molecular sieve surface, accelerating the sedimentation of impurities, thereby enhancing the overall flocculation effect;

[0031] 3. By grafting functional groups on anionic polyacrylamide (APAM), strong ionization groups are introduced, the charge density of polyacrylamide is enhanced, and thus the charge and bridging net capture effect of anionic polyacrylamide are enhanced. The modified high molecular weight long-chain APM and small flocs form larger flocs, which make the flocs settle quickly and have a synergistic effect with modified silica. The long-chain cationic monomers can interact with the anionic groups on the surface of the modified silica, so that the polyacrylamide is firmly adsorbed on the surface of the modified silica to form a composite flocculation structure, enhance the ability to remove pollutants, make the coal particles in the coal washing water settle completely, reduce the loss of coal slime, increase the yield of coal slime, and at the same time reduce the turbidity of the supernatant to a greater extent, so that it can be recycled back to the system and reduce water consumption;

[0032] 4. When sodium chloride is mixed with modified anionic polyacrylamide, the tiny modified anionic polyacrylamide particles will not clump due to surface tension, and can be easily mixed with the sodium chloride particles. The tiny modified anionic polyacrylamide particles will swell and have enough time to fully absorb water and swell fully. During transportation and storage, the modified anionic polyacrylamide particles will be quickly and evenly dispersed in the water and dissolved in the water because they have been fully swollen during use, which accelerates the dissolution rate of the modified anionic polyacrylamide and reduces the uneven distribution of the modified anionic polyacrylamide in the water and the clumping. At the same time, the solubility of sodium chloride itself further promotes the dissolution of the modified anionic polyacrylamide. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a process flow chart for preparing the composite flocculant for coal washing water of the present invention;

[0034] Figure 2 The present invention is a process flow chart for preparing the modified silica;

[0035] Figure 3 This is a process flow chart for preparing the modified anionic polyacrylamide of the present invention;

[0036] Figure 4 It is a schematic diagram of the flocculation effect of the composite flocculant for coal washing water prepared in Examples 1-2 of the present invention and the flocculants described in Comparative Examples 1-2 on coal washing water, wherein from left to right are Example 1, Example 2, Comparative Example 1, and Comparative Example 2. DETAILED DESCRIPTION

[0037] The present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] See also Figure 1-4 , the present invention provides a technical solution:

[0039] Example 1

[0040] A method for preparing a composite flocculant for coal washing water:

[0041] S1. Preparation of inorganic flocculant A: 30 g of polyaluminium chloride, 20 g of potassium aluminium sulfate dodecahydrate and 15 g of modified silica were mixed and ground to obtain an inorganic flocculant A after sufficient mixing was added and 20 g of wood ash was mixed;

[0042] S2. Preparation of organic flocculant B: 10 g of modified anionic polyacrylamide and 5 g of sodium chloride crystals were mixed evenly to obtain organic flocculant B.

[0043] In the above process, the modified silica is prepared by the following steps:

[0044] S11. 10 g of silica, 40 g of water and 2 g of hexadecyltrimethylammonium bromide were mixed and stirred for 2 h to obtain a mixed solution;

[0045] S12. The mixed solution obtained in step S11 was transferred to a high pressure reactor, reacted at 150°C for 24 hours, cooled to room temperature, the product was filtered, washed with ethanol, and dried at 80°C for 2 hours to obtain the modified silica;

[0046] In the above process, the modified anionic polyacrylamide is prepared by the following steps:

[0047] S21. 20g of anionic polyacrylamide model A936 purchased from Anhui Tianrun Chemical Industry Co., Ltd. was added to 150g of water and stirred to fully dissolve to form a uniform solution;

[0048] S22. Sequentially, 3 g of methacryloyloxyethyl trimethylammonium chloride and 1 g of 2-acrylamido-2-methylpropanesulfonic acid were added to the solution obtained in step S21 and stirred until dissolved to obtain a precursor solution.

[0049] S23. Adding 0.1 g of an initiator dropwise to the precursor solution by mass, stirring the precursor solution and reacting at 50° C. for 5 h to obtain a modified anionic polyacrylamide solution;

[0050] S24. The modified anionic polyacrylamide solution is dialyzed for 36 hours, and the treated product is dried to obtain the modified anionic polyacrylamide.

[0051] In the above process, the initiator is a mixture of ammonium persulfate, sodium bisulfite and water in a mass ratio of 1:1:10;

[0052] In the above process, the molecular weight cut-off of the dialysis bag used in the dialysis treatment is 1000-5000 Daltons;

[0053] In the above process, the average particle size of the modified anionic polyacrylamide is 80-100 meshes, the average particle size of the wood ash is 140-160 meshes, and the average particle size of the sodium chloride is 200-300 meshes.

[0054] Example 2

[0055] A method for preparing a composite flocculant for coal washing water:

[0056] S1. Preparation of inorganic flocculant A: 40 g of polyaluminium chloride, 30 g of potassium aluminium sulfate dodecahydrate and 20 g of modified silica were mixed and ground to obtain an inorganic flocculant A after sufficient mixing was added and 30 g of wood ash was mixed;

[0057] S2. Preparation of organic flocculant B: 15 g of modified anionic polyacrylamide and 10 g of sodium chloride crystals were mixed evenly to obtain organic flocculant B.

[0058] In the above process, the modified silica is prepared by the following steps:

[0059] S11. 20 g of silica, 50 g of water and 5 g of hexadecyltrimethylammonium bromide were mixed and stirred for 2 h to obtain a mixed solution;

[0060] S12. The mixed solution obtained in step S11 was transferred to a high pressure reactor, reacted at 150°C for 32 hours, cooled to room temperature, the product was filtered, washed with ethanol, and dried at 80°C for 2 hours to obtain the modified silica;

[0061] In the above process, the modified anionic polyacrylamide is prepared by the following steps:

[0062] S21. 25g of anionic polyacrylamide model A936 purchased from Anhui Tianrun Chemical Industry Co., Ltd. was added to 160g of water and stirred to fully dissolve to form a uniform solution;

[0063] S22. Sequentially, 5 g of methacryloyloxyethyl trimethylammonium chloride and 3 g of 2-acrylamide-2-methylpropanesulfonic acid were added to the solution obtained in step S21 and stirred until dissolved to obtain a precursor solution;

[0064] S23. Add 0.3 g of initiator dropwise to the precursor solution by mass, stir the precursor solution and react at 50 ° C for 5 h to obtain a modified anionic polyacrylamide solution;

[0065] S24. The modified anionic polyacrylamide solution is dialyzed for 36 hours, and the treated product is dried to obtain the modified anionic polyacrylamide.

[0066] In the above process, the initiator is a mixture of ammonium persulfate, sodium bisulfite and water in a mass ratio of 1:1:12;

[0067] In the above process, the molecular weight cut-off of the dialysis bag used in the dialysis treatment is 1000-5000 Daltons;

[0068] In the above process, the average particle size of the modified anionic polyacrylamide is 80-100 meshes, the average particle size of the wood ash is 140-160 meshes, and the average particle size of the sodium chloride is 200-300 meshes.

[0069] Comparative Example

[0070] Comparative Example 1: Comparative Example 1 is anionic polyacrylamide A for conventional coal washing water, model A936, purchased from Anhui Tianrun Chemical Industry Co., Ltd.

[0071] Comparative Example 2: Comparative Example 2 is anionic polyacrylamide B for conventional coal washing water, model A458, purchased from Anhui Tianrun Chemical Industry Co., Ltd.

[0072] Performance Testing:

[0073] The inorganic flocculant A in Example 1-2 was dissolved into a 10% aqueous solution, and the organic flocculant B was dissolved into a 1‰ aqueous solution. Two commercially available coal washing waters were selected and dissolved into a 1‰ aqueous solution with conventional APAM. The coal washing water of Pansan Mine of Huainan Mining Group was selected, and four 50mL test tubes were used for small-scale comparison. The amount of the agent solution added was 0.2mL. The sedimentation rate and supernatant turbidity were tested. The filtrate turbidity was measured using a turbidity meter (equipment model HACH-2100Q). The test results are shown in Tables 1 and Figure 4 As shown:

[0074] Table 1. Comparison results of composite flocculants and conventional flocculants

[0075] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Supernatant turbidity 38 33 72 54 Sedimentation velocity (s) 9 8 16 12

[0076] As shown in Table 1, Examples 1 and 2 are superior to the control sample in flocculation sedimentation rate and supernatant turbidity, indicating that the synergistic effect of the components of the composite flocculant of the present invention makes the composite flocculant have better flocculation sedimentation and purification effects.

[0077] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A composite flocculant for coal washing water, characterized in that: It comprises an inorganic flocculant A and an organic flocculant B, wherein the inorganic flocculant A comprises, by weight, 30-40 parts of polyaluminium chloride, 20-30 parts of potassium aluminium sulfate dodecahydrate, 15-20 parts of modified silica and 20-30 parts of plant ash; The organic flocculant B comprises the following components by weight: 10-15 parts of modified anionic polyacrylamide and 5-10 parts of sodium chloride; Wherein, the modified silica is prepared by the following steps: S11. 10-20 parts by mass of silica, 40-50 parts of water, 2-5 parts of hexadecyltrimethylammonium bromide were mixed and stirred for 2-3h to obtain a mixed solution; S12. The mixed solution obtained in step S11 is transferred to a high pressure reactor, reacted at 150-180°C for 24-48h, cooled to room temperature, the product is filtered, washed with ethanol, and dried at 80-100°C for 2-3h to obtain the modified silica; Wherein, the modified anionic polyacrylamide is prepared by the following steps: S21. Add 20-25 parts of anionic polyacrylamide to 150 parts of water by mass and stir to fully dissolve it to form a uniform solution; S22. Add 3-5 parts of methacryloyloxyethyl trimethylammonium chloride and 1-3 parts of 2-acrylamide-2-methylpropane sulfonic acid to the solution obtained in step S21 in parts by mass, and stir until dissolved to obtain a precursor solution; S23. Add 0.1-0.3 parts of an initiator dropwise to the precursor solution by mass, stir the precursor solution and react at 50-60° C. for 5-7 hours to obtain a modified anionic polyacrylamide solution; S24. The modified anionic polyacrylamide solution is dialyzed for 36-48 hours, and the treated product is dried to obtain the modified anionic polyacrylamide.

2. A composite flocculant for coal washing water according to claim 1, characterized in that: The initiator is a mixture of ammonium persulfate, sodium bisulfite and water in a mass ratio of 1:1:10-15.

3. A composite flocculant for coal washing water according to claim 1, characterized in that: The molecular weight cut-off of the dialysis bag used in the dialysis treatment is 1000-5000 Daltons.

4. A method for preparing a composite flocculant for coal washing water, used for preparing the composite flocculant for coal washing water according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Preparation of inorganic flocculant A: 30-40 parts by mass of polyaluminium chloride, 20-30 parts of potassium aluminium sulfate dodecahydrate and 15-20 parts of modified silica were mixed and ground to obtain an inorganic flocculant A after being fully mixed and then adding 20-30 parts of wood ash; S2. Preparation of organic flocculant B: 10-15 parts by mass of modified anionic polyacrylamide and 5-10 parts by mass of sodium chloride crystals are mixed evenly to obtain organic flocculant B.

5. The method for preparing a composite flocculant for coal washing water according to claim 4, characterized in that: The average particle size of the modified anionic polyacrylamide is 80-100 meshes, the average particle size of the plant ash is 140-160 meshes, and the average particle size of the sodium chloride is 200-300 meshes.

6. Use of the composite flocculant for coal washing water according to claim 1 or the composite flocculant for coal washing water prepared by the preparation method according to any one of claims 4 to 5 in coal washing water.

7. The use of a coal washing water composite flocculant in coal washing water according to claim 6, characterized in that: The method of application comprises the following steps: S31. The inorganic flocculant A is prepared into a 10-30% aqueous solution, and the organic flocculant B is prepared into a 1-3‰ aqueous solution; S32. Adding an inorganic flocculant A to the coal washing water, stirring and mixing the particles in the coal washing water to form small flocs; S33. Add organic flocculant B to the coal washing water treated in step S32, stir and mix again, flocculate the particles in the coal washing water into large flocs for sedimentation, and perform solid-liquid separation.

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