Flocculant for mine water treatment, preparation method thereof and water treatment method

Abstract

The invention relates to a flocculating agent for mine water treatment, a preparation method thereof and a water treatment method, the flocculating agent for mine water treatment contains more than or equal to 98% by mass of modified polyacrylamide, and the mass of water insoluble substances in the flocculating agent is less than or equal to 1.0%; the modified polyacrylamide is a white solid, and the molecular weight of the modified polyacrylamide is 2000-4000 million; according to the modified polyacrylamide, carboxyl, amino and calcium ions are introduced into a molecular chain of polyacrylamide; wherein the modified polyacrylamide with the average gram weight per unit contains 0.32 to 1.60 mmol of introduced amino groups, 0.32 to 1.60 mmol of introduced carboxyl groups and 0.043 to 0.32 mmol of calcium ions. The device has the beneficial effects that the effluent turbidity of mine water can be effectively reduced, and the flocculation precipitation efficiency is improved; the molecular structure is stable, the suspended matter difference impact resistance of the flocculant is improved, the dosage of the flocculant is reduced, and the cost is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of mine water treatment, in particular to a flocculant for mine water treatment and a preparation method thereof, and a water treatment method. Background Art

[0002] With the continuous development of my country's coal industry, the amount of mine water produced has also increased year by year. The quality of mine water is complex and changeable, usually containing suspended matter, coal dust, salts, petroleum and other harmful substances. The presence of these substances not only increases the difficulty of mine water treatment, but also has a serious impact on its direct discharge and utilization. In order to improve the quality of mine water, protect the environment and ensure the sustainable use of water resources, mine water treatment agents play an irreplaceable role.

[0003] The treatment technology for mine water containing suspended matter in my country usually adopts the process of "coagulation and sedimentation + filtration treatment". During the coagulation and sedimentation process, the reagents polyaluminium chloride (PAC) and polyacrylamide (PAM) are added in combination to remove the positive charge carried on the surface of the suspended matter and make it condense and settle. However, in the field of mine water treatment, the use of conventional PAM has the following problems: (1) Poor coagulation and sedimentation effect and high operating cost: Coal mine water is usually gray-black in color, and its main components include fine coal powder and rock dust. The suspended matter content is usually high, and the concentration can reach 2000mg / L or even higher. Under high suspended matter concentration, the conventional PAM dosage is large, the reagent cost is high, and the coagulation effect is poor. Often, fine suspended matter cannot be completely captured, resulting in high turbidity in the water. It is necessary to add high-concentration PAC to achieve solid-liquid separation. (2) Poor resistance to differential impact of suspended matter: According to the characteristics of coal production, mine water is first stored in underground water tanks. It is generally discharged at night when electricity consumption is low, and not discharged during the day when electricity consumption is high. Therefore, the water quality and water volume of mine water fluctuate greatly within the same day. In the face of large fluctuations in raw water, conventional PAM needs to significantly adjust the dosage of the agent, and even needs to change the original ratio and concentration of the agent. It has poor adaptability to changes in suspended solids in mine water, and also increases labor costs. (3) Long dissolution time, uneven dissolution, and short storage time: Conventional PAM takes a long time to dissolve, usually 60-90 minutes. If the dissolution time is insufficient, the agent may not be able to fully exert its effect, and may even cause blockage of the dosing equipment. (4) Unstable molecular structure: In high turbidity water bodies, traditional polyacrylamide is prone to degradation, which affects the flocculation effect and increases the cost of use. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a flocculant for mine water treatment and a preparation method thereof, and a water treatment method, which solves the technical problems of the existing polyacrylamide in mine water treatment, such as poor coagulation and sedimentation effect, poor resistance to differential impact of suspended matter, and high treatment cost.

[0006] (II) Technical solution

[0007] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0008] In the first aspect, an embodiment of the present invention provides a flocculant for mine water treatment, wherein the flocculant contains ≥98% by mass of modified polyacrylamide, and the mass of water-insoluble matter in the flocculant is ≤1.0%; the modified polyacrylamide is a white solid with a molecular weight of 20-40 million; the modified polyacrylamide introduces carboxyl groups, amino groups and calcium ions on the molecular chain of polyacrylamide; wherein the modified polyacrylamide contains, on average, 0.32-1.60 mmol of introduced amino groups, 0.32-1.60 mmol of introduced carboxyl groups and 0.043-0.32 mmol of calcium ions per unit gram weight.

[0009] In a second aspect, an embodiment of the present invention provides a method for preparing a flocculant for mine water treatment, comprising the following steps, calculated by mass fraction in a unit reaction system:

[0010] S1, completely dissolving 50-200 parts of acrylamide monomer in deionized water, heating the solution to 50-55° C., and then adding 5-7 parts of aminoacetic acid to the solution to prepare a first mixed solution;

[0011] The first mixed solution is heated to 70-75° C., and the pH is adjusted to 8.0-8.5 to obtain a second mixed solution;

[0012] S2, adding an initiator to the second mixed solution, carrying out polymerization reaction for 2-2.5 hours, adding a terminator to terminate the polymerization reaction, removing impurities, and obtaining polyacrylamide with introduced carboxyl groups and amino groups;

[0013] S3, dissolving the polyacrylamide introduced with carboxyl groups and amino groups in deionized water to obtain a third mixed solution, heating the third mixed solution to 60-65° C., adding 1-5 parts of a soluble calcium salt, stirring and reacting for 4-5 hours, and obtaining a modified polyacrylamide solution;

[0014] S4, spray-drying and sieving the modified polyacrylamide solution to obtain the flocculant.

[0015] As a preferred embodiment of the present invention, the method for preparing a flocculant for mine water treatment, in S1, sodium chloride is added while adding aminoacetic acid;

[0016] Calculated by weight: 100 parts of acrylamide monomer aminoacetic acid, 10-20 parts of sodium chloride.

[0017] As a preferred embodiment of the present invention, in the method for preparing a flocculant for mine water treatment, in S2, the initiator is 0.2-0.3 parts of ammonium persulfate, and the terminator is sodium bisulfite, calculated by weight; wherein the mass of the terminator is 1-10 times the mass of the initiator.

[0018] As a preferred embodiment of the present invention, in the method for preparing a flocculant for mine water treatment, in S3, the soluble calcium salt is 1-2 parts of calcium chloride by weight.

[0019] In a third aspect, an embodiment of the present invention provides a water treatment method, using the aforementioned flocculant, comprising the following steps:

[0020] Step 1: prepare a flocculant solution with a mass concentration of 0.1-0.2%;

[0021] Step 2: Add the flocculant solution to the mine water to be treated, stir evenly, maintain the concentration of the flocculant in the mine water at 0.5-2 mg / L, allow the flocculation reaction to proceed for 20-30 minutes, and collect the supernatant to obtain the treated mine water.

[0022] As a preferred embodiment of the present invention, in the water treatment method, in step 2, before adding the flocculant solution, an auxiliary agent is added to the mine water to be treated, and the auxiliary agent is selected from one of polyaluminium chloride, polyferric sulfate and lime.

[0023] As a preferred embodiment of the present invention, in the water treatment method, in step 2, the auxiliary agent is polyaluminium chloride, and its dosage in the mine water to be treated is 60-100 mg / L.

[0024] As a preferred embodiment of the present invention, in the water treatment method, in step 2, the concentration of the flocculant in the mine water is 1 mg / L.

[0025] (III) Beneficial effects

[0026] The beneficial effects of the present invention are as follows: the flocculant for mine water treatment of the present invention, its preparation method and water treatment method, wherein the flocculant introduces carboxyl and amino groups in appropriate amounts on the molecular chain of polyacrylamide, and these groups can interact with suspended matter and colloidal particles in water, thereby improving the dispersibility and flocculation performance of the flocculant in high turbidity mine water. The polyacrylamide is subjected to appropriate cross-linking treatment to form a network structure, thereby enhancing its stability and treatment capacity in high turbidity water. The calcium ions can interact with the negatively charged parts in the polyacrylamide molecules by utilizing the strong positive charge effect of calcium ions to form a bridging structure, which is conducive to the cross-linking between flocculant molecules, between flocculant molecules and suspended particles, and between suspended particles. The suspended particles adsorb and aggregate with each other to form larger flocs, and the flocs are denser and have a faster sedimentation rate, which is conducive to accelerating the removal of suspended matter in the wastewater treatment process. By optimizing and controlling the molecular weight of the flocculant to be 20 million to 40 million, it can effectively adsorb particles in water and is not easy to degrade, so that it can effectively treat high concentrations of suspended matter in mine water. Compared with the existing technology, it can effectively reduce the turbidity of mine water and improve the flocculation and sedimentation efficiency; the molecular structure is stable, which improves the flocculant's resistance to differential impact of suspended matter, reduces the amount of flocculant used, and saves costs.

[0027] The preparation method of the flocculant comprises adding sodium chloride while adding aminoacetic acid, wherein the weight percentage is: 100 parts of aminoacetic acid and 10-20 parts of sodium chloride; adding an appropriate amount of sodium chloride plays a role of salting out, which helps to promote the dissolution and uniform dispersion of aminoacetic acid, thereby improving the efficiency of the polymerization reaction. At the same time, sodium chloride can reduce the activity of water, making the reaction system more conducive to the formation of polymers.

[0028] In the water treatment method, the flocculant is prepared into a flocculant solution with a mass concentration of 0.1-0.2%, which is easy to be evenly dispersed after being added to the mine water. The flocculant solution is added to the mine water to be treated, stirred evenly, and the concentration of the flocculant in the mine water is kept at 1 mg / L. The flocculation effect is the best, but excessive use of flocculants will also cause waste.

[0029] Compared with other additives, under the same conditions, the use of polyaluminium chloride as an additive can significantly shorten the sedimentation time, and can also reduce the amount of flocculant used to a certain extent, saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a comparison chart of the effects before and after the sedimentation treatment of the flocculant in Example 2 of the present invention. DETAILED DESCRIPTION

[0031] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0032] The flocculant for mine water treatment and its preparation method and water treatment method proposed in the embodiment of the present invention are aimed at the technical problems that the existing polyacrylamide has poor coagulation and sedimentation effect, poor resistance to differential impact of suspended matter, and high treatment cost in mine water treatment; the flocculant introduces carboxyl and amino groups in appropriate amounts on the molecular chain of polyacrylamide, and these groups can interact with suspended matter and colloidal particles in water, thereby improving the dispersibility and flocculation performance of the flocculant in high turbidity mine water. The polyacrylamide is appropriately cross-linked to form a network structure, thereby enhancing its stability and treatment capacity in high turbidity water. Utilizing the strong positive charge of calcium ions, calcium ions can interact with the negatively charged parts in the polyacrylamide molecules to form a bridging structure, which is conducive to the cross-linking between flocculant molecules, between flocculant molecules and suspended particles, and between suspended particles. The suspended particles adsorb and aggregate with each other to form larger flocs, and the flocs are denser and have a faster settling rate, which helps to accelerate the removal of suspended matter in the wastewater treatment process. By optimizing and controlling the molecular weight of the flocculant to 20-40 million, it can effectively absorb particulate matter in the water and is not easily degraded, and can effectively treat high-concentration suspended matter in mine water. Compared with the existing technology, it can effectively reduce the turbidity of mine water and improve the flocculation and sedimentation efficiency; the molecular structure is stable, which improves the flocculant's resistance to differential impact of suspended matter, reduces the amount of flocculant used, and saves costs.

[0033] In order to better understand the above technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0034] Example 1

[0035] This embodiment provides a method for preparing a flocculant for mine water treatment, comprising the following steps:

[0036] (1) According to a total reaction system of 1000 ml: 100 g of acrylamide monomer was completely dissolved in 700 ml of deionized water, the solution was heated to 50° C., and 5 g of aminoacetic acid was added to the solution to prepare a first mixed solution;

[0037] Heat the first mixed solution to 70°C, gradually add deionized water to the reaction system to 980 ml, adjust the pH of the first mixed solution to 8.0, and prepare the second mixed solution.

[0038] (2) dissolving 0.2 g of ammonium persulfate (APS) in 20 ml of deionized water, and then adding the dissolved APS to the second mixed solution to form a total reaction system of 1000 ml, and performing the polymerization reaction for 2 h;

[0039] (3) At the end of the reaction, gradually add the terminator sodium bisulfite in an amount of 1-10 times the amount of the initiator, and stir evenly until the reaction system stops generating heat and no new bubbles are generated, indicating that the polymerization reaction has been effectively terminated; then cool the reaction system to room temperature by natural cooling or in a water bath (water temperature 10° C.-25° C.), wash the reaction product with deionized water 10 to 20 times the volume of the reaction system, remove liquid impurities, retain solid matter, and obtain polyacrylamide with introduced carboxyl and amino groups;

[0040] (4) dissolving the polyacrylamide introduced with carboxyl groups and amino groups in 1000 ml of deionized water to obtain a third mixed solution, heating the third mixed solution to 60-65° C., adding 1 g of calcium chloride, and stirring the mixture for 4-5 hours to obtain a calcium ion-modified polyacrylamide solution;

[0041] (5) The modified polyacrylamide solution was spray dried at 150°C and then passed through a 100-mesh sieve to obtain a flocculant.

[0042] The prepared flocculant was analyzed by infrared spectroscopy (FT-IR) to confirm that amino and carboxyl groups were successfully grafted onto the modified polyacrylamide. Dynamic light scattering (DLS) and molecular weight analysis confirmed that its molecular weight ranged from 20 million to 40 million.

[0043] Example 2

[0044] This embodiment provides a method for water treatment using the flocculant in Embodiment 1, comprising the following steps:

[0045] (1) preparing a flocculant solution with a mass concentration of 0.1% by weight using water;

[0046] (2) First, polyaluminium chloride is added to the treated mine water with an initial turbidity of 2500 NTU at a concentration of 80 mg / L, and then the flocculant solution is added to the treated mine water, stirred evenly, and the concentration of the flocculant in the mine water is maintained at 1 mg / L. The flocculation reaction is carried out for 20-30 minutes, and the supernatant is collected to obtain the treated mine water.

[0047] The sedimentation effect of flocculants is shown in Table 1 and Figure 1 .

[0048] Example 3

[0049] This embodiment provides a method for water treatment using the flocculant in embodiment 1, which differs from embodiment 2 in that:

[0050] In (2), the concentration of polyaluminium chloride in the mine water to be treated is 100 mg / L, and the remaining steps are the same. The sedimentation effect of the flocculant is shown in Table 1.

[0051] Example 4

[0052] This embodiment provides a method for water treatment using the flocculant in embodiment 1, which differs from embodiment 2 in that:

[0053] In (2), the initial turbidity of the mine water to be treated is 500 NTU, the concentration of polyaluminium chloride in the mine water to be treated is 60 mg / L, and the remaining steps are the same. The sedimentation effect of the flocculant is shown in Table 1.

[0054] Comparative Example 1

[0055] This comparative example provides a method for water treatment using commercially available conventional PAM as a flocculant, which differs from Example 2 in that the flocculant in Example 2 is replaced by commercially available conventional PAM with the same dosage. The remaining steps are the same, and the sedimentation effect of the flocculant is detailed in Table 1.

[0056] Comparative Example 2

[0057] This comparative example provides a method for water treatment using commercially available conventional PAM as a flocculant, which differs from Example 3 in that the flocculant in Example 3 is replaced by commercially available conventional PAM with the same dosage. The remaining steps are the same, and the sedimentation effect of the flocculant is detailed in Table 1.

[0058] Comparative Example 3

[0059] This comparative example provides a method for water treatment using commercially available conventional PAM as a flocculant, which differs from Example 4 in that the flocculant in Example 3 is replaced by commercially available conventional PAM with the same dosage. The remaining steps are the same, and the sedimentation effect of the flocculant is detailed in Table 1.

[0060] Table 1 Sedimentation effect of flocculants

[0061]

[0062]

[0063] According to the sedimentation effect of the flocculant shown in Table 1, the analysis is as follows:

[0064] Example 2 is the best example. When the initial turbidity of the mine water is 2500NTU (high turbidity), the flocculant dosage is 1mg / L, and the auxiliary agent polyaluminium chloride dosage is 80mg / L. After only 20 minutes of flocculation and sedimentation, the effluent turbidity drops to 36NTU. The flocculation and sedimentation time is shorter, which can effectively reduce the overall flocculant dosage. While Comparative Example 1 uses commercially available ordinary PAM as a flocculant under the same conditions. After 30 minutes of flocculation and sedimentation in Comparative Example 1, the effluent turbidity is still 88NTU. In contrast, in high turbidity mine water, under the same dosage of the agent, the effluent turbidity of the high turbidity mine water treated with the flocculant under the conditions of Example 1 is lower, and the sedimentation rate is faster, ensuring that the mine water meets the discharge standards. It shows that polyacrylamide (hereinafter referred to as modified polyacrylamide) modified with appropriate amounts of carboxyl and amino groups and appropriate amounts of calcium ions can effectively interact with suspended particles in mine water.

[0065] See also Figure 1 , showing the effect of flocculant before and after treating high turbidity mine water in Example 2, it can be seen that the black flocs formed are large and dense, the sedimentation effect is good, the water body is clear, and there is no degradation or performance degradation. Modified polyacrylamide has strong molecular stability in high turbidity water, effectively avoiding the degradation of flocculant when treating high turbidity water. At the same time, modified polyacrylamide can realize adaptive adjustment of dosing, reduce the influence of mine water quality and water volume fluctuation on flocculant, and improve dosing stability and water treatment automation.

[0066] In addition, preparing a modified polyacrylamide flocculant solution with a mass concentration of 0.1% before adding the drug can effectively reduce the drug dissolution time and difficulty, give full play to the flocculation effect of the drug, and extend the effective use time of the drug.

[0067] Comparison between Example 3 and Comparative Example 2 shows that, under the same conditions, the effluent turbidity of the high turbidity mine water treated with the flocculant in Example 3 is reduced to 29 NTU compared with the high turbidity mine water treated with the commercially available ordinary PAM. Compared with Example 2, Example 3 shows that when treating high turbidity mine water, adding the auxiliary agent polyaluminium chloride can reduce the effluent turbidity to a certain extent, but the reduction is limited. Therefore, considering the cost comprehensively, the addition amount of the auxiliary agent polyaluminium chloride is 80 mg / L as the optimal dosage.

[0068] Comparison of Example 4 with Comparative Example 3 shows that the initial turbidity of the mine water is 500 NTU (low turbidity). When the same flocculant dosage is used, the turbidity of the effluent after treatment with the two flocculants is not much different, indicating that the flocculant used in the example is more suitable for the treatment of high turbidity mine water.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A flocculant for mine water treatment, characterized in that: The flocculant contains ≥98% by weight of modified polyacrylamide, and the weight of water-insoluble matter in the flocculant is ≤1.0%; The modified polyacrylamide is a white solid with a molecular weight of 20-40 million; The modified polyacrylamide introduces carboxyl groups, amino groups and calcium ions into the molecular chain of polyacrylamide; The modified polyacrylamide contains 0.32-1.60 mmol of introduced amino groups, 0.32-1.60 mmol of introduced carboxyl groups and 0.043-0.32 mmol of calcium ions per unit gram weight.

2. A method for preparing a flocculant for mine water treatment according to claim 1, characterized in that: The method comprises the following steps, which are calculated by mass fractions within a unit reaction system: S1, completely dissolving 50-200 parts of acrylamide monomer in deionized water, heating the solution to 50-55° C., and then adding 5-7 parts of aminoacetic acid to the solution to prepare a first mixed solution; The first mixed solution is heated to 70-75° C., and the pH is adjusted to 8.0-8.5 to obtain a second mixed solution; S2, adding an initiator to the second mixed solution, carrying out polymerization reaction for 2-2.5 hours, adding a terminator to terminate the polymerization reaction, removing impurities, and obtaining polyacrylamide with introduced carboxyl groups and amino groups; S3, dissolving the polyacrylamide introduced with carboxyl groups and amino groups in deionized water to obtain a third mixed solution, heating the third mixed solution to 60-65° C., adding 1-5 parts of a soluble calcium salt, stirring and reacting for 4-5 hours, and obtaining a modified polyacrylamide solution; S4, spray-drying and sieving the modified polyacrylamide solution to obtain the flocculant.

3. The method for preparing a flocculant for mine water treatment according to claim 2, characterized in that: In S1, sodium chloride is added while adding aminoacetic acid; Calculated by weight: 100 parts of acrylamide monomer aminoacetic acid, 10-20 parts of sodium chloride.

4. The method for preparing a flocculant for mine water treatment according to claim 3, characterized in that: In S2, the initiator is 0.2-0.3 parts of ammonium persulfate, and the terminator is sodium bisulfite, calculated by weight; wherein the weight of the terminator is 1-10 times the weight of the initiator.

5. The method for preparing a flocculant for mine water treatment according to claim 3, characterized in that: In S3, the soluble calcium salt is 1-2 parts of calcium chloride by weight.

6. A water treatment method, characterized in that: The flocculant prepared by the flocculant according to claim 1 or the preparation method according to any one of claims 2 to 5 comprises the following steps: Step 1: prepare a flocculant solution with a mass concentration of 0.1-0.2%; Step 2: Add the flocculant solution to the mine water to be treated, stir evenly, maintain the concentration of the flocculant in the mine water at 0.5-2 mg / L, allow the flocculation reaction to proceed for 20-30 minutes, and collect the supernatant to obtain the treated mine water.

7. The water treatment method according to claim 6, characterized in that: In the second step, before adding the flocculant solution, an auxiliary agent is added to the mine water to be treated, and the auxiliary agent is selected from one of polyaluminium chloride, polyferric sulfate and lime.

8. The water treatment method according to claim 7, characterized in that: In step 2, the auxiliary agent is polyaluminium chloride, and its dosage in the mine water to be treated is 60-100 mg / L.

9. The water treatment method according to claim 6, characterized in that: In step 2, the concentration of flocculant in mine water was 1 mg / L.

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