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

Abstract

The present application relates to a flocculant for mine water treatment and a preparation method thereof and a water treatment method, wherein the flocculant for mine water treatment contains modified polyacrylamide with a mass fraction of 98%, and the mass fraction of water-insoluble substances in the flocculant is less than or equal to 1.0%; the modified polyacrylamide is a white solid with a molecular weight of 20-40 million; the modified polyacrylamide has carboxyl groups, amino groups and calcium ions introduced into the molecular chain of polyacrylamide; wherein 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 on average. The flocculant can effectively reduce the effluent turbidity of mine water and improve the flocculation and sedimentation efficiency; the molecular structure is stable, the anti-suspended matter difference impact performance of the flocculant is improved, the amount of the flocculant is reduced, and the cost is saved.

Description

TECHNICAL FIELD

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

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

[0003] The treatment technology of mine water containing suspended solids in China usually adopts the process flow of "coagulation sedimentation + filtration treatment". In the process of coagulation sedimentation, the flocculants polyaluminum chloride (PAC) and polyacrylamide (PAM) are added together to remove the positive charge carried on the surface of suspended solids, so as to make them coagulate and settle. However, in the field of mine water treatment, the use of conventional PAM has the following problems: (1) poor coagulation sedimentation effect and high operating cost: the color of coal mine water is usually gray-black, and the main components include coal dust and rock dust with small particle size. The suspended solids content is usually high, and the concentration can reach 2000 mg / L or even higher. Under high suspended solids concentration, the conventional PAM dosage is large, the cost of the flocculant is high, and the coagulation effect is poor. Small suspended solids cannot be completely captured, resulting in high turbidity in the water, which requires the addition of high-concentration PAC to achieve solid-liquid separation. (2) Poor resistance to suspended solids: according to the characteristics of coal production, mine water is first stored in the underground water warehouse. It is usually discharged at night when the electricity consumption is low, and not discharged during the day when the electricity consumption is high. Therefore, the water quality and quantity of mine water fluctuate greatly within the same day. Conventional PAM needs to adjust the dosage of the flocculant greatly or even change the original concentration of the flocculant when facing fluctuating raw water. The adaptability to changes in suspended solids in mine water is poor, and the labor cost is also increased. (3) Long dissolution time, uneven dissolution and short storage time: conventional PAM has a long dissolution time, usually 60-90 min. If the dissolution time is not enough, the flocculant may not fully play its effect, or even cause blockage of the dosing equipment. (4) Unstable molecular structure: in high turbidity water, traditional polyacrylamide is prone to degradation, affecting the flocculation effect and increasing the use cost. SUMMARY

[0004] (I) Technical problems to be solved

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

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0008] In a first aspect, embodiments of the present invention provide a flocculant for mine water treatment, wherein the flocculant contains ≥98% by mass of modified polyacrylamide, and the water-insoluble matter in the flocculant is ≤1.0% by mass; the modified polyacrylamide is a white solid with a molecular weight of 20-40 million; the modified polyacrylamide has carboxyl groups, amino groups, and calcium ions introduced into its molecular chain; wherein, on average, each unit gram of 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.

[0009] Secondly, embodiments of the present invention provide a method for preparing the flocculant for mine water treatment, comprising the following steps, wherein, within a unit reaction system, by mass parts:

[0010] S1. Dissolve 50-200 parts of acrylamide monomer completely in deionized water, heat the solution to 50-55℃, and then add 5-7 parts of glycine to the solution to obtain the first mixture.

[0011] The first mixture is heated to 70-75℃ and the pH is adjusted to 8.0-8.5 to obtain the second mixture;

[0012] S2. Add the second mixture to the initiator, and polymerize for 2-2.5 hours. Add the terminator to terminate the polymerization reaction, remove impurities, and obtain polyacrylamide with carboxyl and amino groups introduced.

[0013] S3. Dissolve the polyacrylamide with introduced carboxyl and amino groups in deionized water to obtain a third mixture. Heat the third mixture to 60-65℃, add 1-5 parts of soluble calcium salt, and stir for 4-5 hours to obtain a modified polyacrylamide solution.

[0014] S4. The modified polyacrylamide solution is spray-dried and sieved to obtain the flocculant.

[0015] In a preferred embodiment of the present invention, in the method for preparing flocculant for mine water treatment, sodium chloride is added simultaneously with aminoacetic acid in step S1.

[0016] By mass fractions: 100 parts of acrylamide monomer glycine and 10-20 parts of sodium chloride.

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

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

[0019] Thirdly, embodiments of the present invention provide a water treatment method utilizing 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 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] In a preferred embodiment of the present invention, in the second step of the water treatment method, before adding the flocculant solution, an auxiliary agent is added to the mine water to be treated. The auxiliary agent is selected from polyaluminum chloride, polyferric sulfate and lime.

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

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

[0025] (III) Beneficial Effects

[0026] The beneficial effects of this invention are as follows: The flocculant for mine water treatment, its preparation method, and the water treatment method of this invention, wherein the flocculant, by appropriately introducing carboxyl and amino groups into the molecular chain of polyacrylamide, can interact with suspended solids and colloidal particles in water, improving the dispersibility and flocculation performance of the flocculant in highly turbid mine water. Appropriate cross-linking treatment of polyacrylamide forms a network structure, enhancing its stability and treatment capacity in highly turbid water. Utilizing the strong positive charge of calcium ions, calcium ions can interact with the negatively charged portion of polyacrylamide molecules to form a bridging structure, facilitating cross-linking between flocculant molecules, between flocculant molecules and suspended particles, and between suspended particles. Suspended particles mutually adsorb and aggregate, forming larger flocs, which are denser and settle quickly, helping to accelerate the removal of suspended solids during wastewater treatment. By optimizing and controlling the molecular weight of the flocculant to 20-40 million, it can effectively adsorb particulate matter in water without easily degrading, effectively treating high concentrations of suspended solids in mine water. Compared with existing technologies, it can effectively reduce the turbidity of mine water effluent and improve flocculation and sedimentation efficiency; its stable molecular structure improves the flocculant's resistance to differential impact of suspended solids, reduces the amount of flocculant used, and saves costs.

[0027] The flocculant is prepared by adding sodium chloride simultaneously with glycine, in parts by mass: 100 parts glycine and 10-20 parts sodium chloride. Adding an appropriate amount of sodium chloride acts as a salting-out agent, which helps promote the dissolution and uniform dispersion of glycine, 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 polymer formation.

[0028] In water treatment methods, flocculants are prepared into a flocculant solution with a mass concentration of 0.1-0.2% to facilitate uniform dispersion after being added to mine water. The flocculant solution is then added to the mine water to be treated and stirred thoroughly. Maintaining the flocculant concentration in the mine water at 1 mg / L yields the best flocculation effect, but excessive use of flocculant will result in waste.

[0029] Compared to other additives, under the same conditions, using polyaluminum chloride as an additive significantly reduces the settling time and can also reduce the amount of flocculant used to a certain extent, thus saving costs. Attached Figure Description

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

[0031] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] The flocculant for mine water treatment proposed in this invention, along with its preparation method and water treatment method, addresses the technical problems of existing polyacrylamide in mine water treatment, such as poor coagulation and sedimentation effects, poor resistance to differential shock of suspended solids, and high treatment costs. By appropriately introducing carboxyl and amino groups into the polyacrylamide molecular chain, the flocculant can interact with suspended solids and colloidal particles in the water, improving its dispersibility and flocculation performance in highly turbid mine water. Appropriate cross-linking treatment of the polyacrylamide forms a network structure, enhancing its stability and treatment capacity in highly turbid water. Utilizing the strong positive charge of calcium ions, they can interact with the negatively charged parts of the polyacrylamide molecules to form a bridging structure, facilitating cross-linking between flocculant molecules, between flocculant molecules and suspended particles, and among suspended particles themselves. Suspended particles mutually adsorb and aggregate, forming larger, denser flocs with faster settling rates, thus accelerating the removal of suspended solids during wastewater treatment. By optimizing and controlling the molecular weight of the flocculant to 20-40 million, it can effectively adsorb particulate matter in water while remaining resistant to degradation, thus effectively treating high concentrations of suspended solids in mine water. Compared to existing technologies, it can effectively reduce the turbidity of effluent from mine water, improve flocculation and sedimentation efficiency, and its stable molecular structure enhances the flocculant's resistance to differential impacts of suspended solids, reducing the amount of flocculant needed and saving costs.

[0033] To better understand the above technical solutions, 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 drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and that the scope of the present invention can be fully conveyed to those skilled in the art.

[0034] Example 1

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

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

[0037] The first mixture was heated to 70°C, and the reaction system was gradually increased to 980 ml with deionized water. The pH of the first mixture was adjusted to 8.0 to obtain the second mixture.

[0038] (2) Dissolve 0.2g of ammonium persulfate (APS) in 20ml of deionized water, and then add the dissolved APS to the second mixture to form a total reaction system of 1000ml. The polymerization reaction is carried out for 2 hours.

[0039] (3) At the end of the reaction, sodium bisulfite, the terminator, is gradually added. The amount added is 1-10 times the amount of the initiator. Stir until the reaction system stops heating and no new bubbles are generated, indicating that the polymerization reaction has been effectively terminated. Then, the reaction system is cooled to room temperature by natural cooling or water bath cooling (water temperature 10℃-25℃). The reaction product is washed with deionized water that is 10 to 20 times the volume of the reaction system to remove liquid impurities and retain solids to obtain polyacrylamide with carboxyl and amino groups introduced.

[0040] (4) Dissolve the polyacrylamide with introduced carboxyl and amino groups in 1000 ml of deionized water to prepare the third mixture. Heat the third mixture to 60-65℃, add 1g of calcium chloride, and stir 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 successfully grafted with amino and carboxyl groups on modified polyacrylamide using Fourier transform infrared spectroscopy (FT-IR). Dynamic light scattering (DLS) and molecular weight analysis confirmed its molecular weight range to be 20 million–40 million.

[0043] Example 2

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

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

[0046] (2) First, add polyaluminum chloride to the mine water to be treated with an initial turbidity of 2500 NTU at a concentration of 80 mg / L. Then add the flocculant solution to the mine water to be treated, stir evenly, keep the concentration of flocculant in the mine water at 1 mg / L, and let the flocculation reaction last for 20-30 minutes. Collect the supernatant to obtain the treated mine water.

[0047] The sedimentation effect of the flocculant is detailed in Table 1 and... Figure 1 .

[0048] Example 3

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

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

[0051] Example 4

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

[0053] In (2), the initial turbidity of the mine water to be treated was 500 NTU, and the concentration of polyaluminum chloride in the mine water to be treated was 60 mg / L. The remaining steps were the same. The sedimentation effect of the flocculant is detailed 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. The difference from Example 2 is that the flocculant in Example 2 is replaced with an equal dosage of commercially available conventional PAM. 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. The difference from Example 3 is that the flocculant in Example 3 is replaced with an equal dosage of commercially available conventional PAM. 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. The difference from Example 4 is that the flocculant in Example 3 is replaced with an equal dosage of commercially available conventional PAM. 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] Based on the sedimentation effect of the flocculant shown in Table 1, the analysis is as follows:

[0064] Example 2, as the preferred embodiment, shows that when the initial turbidity of the mine water is 2500 NTU (high turbidity), the flocculant dosage is 1 mg / L and the additive polyaluminum chloride dosage is 80 mg / L. After only 20 minutes of flocculation and sedimentation, the effluent turbidity drops to 36 NTU, demonstrating a shorter flocculation and sedimentation time and effectively reducing the overall flocculant dosage. In contrast, Comparative Example 1, using commercially available PAM as the flocculant under the same conditions, still shows an effluent turbidity of 88 NTU after 30 minutes of flocculation and sedimentation. Comparatively, in high-turbidity mine water, with the same dosage, the flocculant treatment in Example 1 results in lower effluent turbidity and faster settling speed, ensuring the mine water meets discharge standards. This demonstrates that polyacrylamide modified with appropriate amounts of carboxyl and amino groups and calcium ions (hereinafter referred to as modified polyacrylamide) can effectively interact with suspended particles in mine water.

[0065] See also Figure 1 The diagram illustrates the effect of the flocculant on treating high-turbidity mine water in Example 2 before and after treatment. It shows that the formed black flocs are large and dense, exhibiting good settling effect, resulting in clear water, and no degradation or performance deterioration was observed. Modified polyacrylamide possesses strong molecular stability in high-turbidity water, effectively preventing flocculant degradation during treatment. Furthermore, modified polyacrylamide allows for adaptive adjustment of dosage, reducing the impact of fluctuations in mine water quality and quantity on the flocculant, and improving dosage stability and the degree of automation in water treatment.

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

[0067] Comparing Example 3 with Comparative Example 2, under the same conditions, the effluent turbidity of the high-turbidity mine water treated with the flocculant in Example 3 decreased to 29 NTU compared to that treated with commercially available ordinary PAM. Compared to Example 2, Example 3 shows that adding the auxiliary agent polyaluminum chloride can reduce the effluent turbidity to some extent when treating high-turbidity mine water, but the reduction is limited. Therefore, considering the overall cost, the optimal dosage of the auxiliary agent polyaluminum chloride is 80 mg / L.

[0068] Comparing Example 4 with Comparative Example 3, it can be seen that the initial turbidity of the mine water was 500 NTU (low turbidity). When the same amount of flocculant was added, the turbidity of the effluent after treatment by the two flocculants was not much different, indicating that the flocculant used in the example is more suitable for treating 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, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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 method for preparing a flocculant for mine water treatment, characterized in that, The following steps are included, per unit mass fraction within the reaction system: S1. Dissolve 50-200 parts of acrylamide monomer completely in deionized water, heat the solution to 50-55°C, and then add 5-7 parts of glycine to the solution to obtain the first mixture. The first mixture is heated to 70-75°C, and the pH is adjusted to 8.0-8.5 to obtain the second mixture; S2. Add the second mixture to the initiator, and polymerize for 2-2.5 hours. Add the terminator to terminate the polymerization reaction, remove impurities, and obtain polyacrylamide with carboxyl and amino groups introduced. S3. Dissolve the polyacrylamide with introduced carboxyl and amino groups in deionized water to prepare a third mixture. Heat the third mixture to 60-65°C, add 1-5 parts of soluble calcium salt, and stir the reaction for 4-5 hours to obtain a modified polyacrylamide solution. S4. The modified polyacrylamide solution is spray-dried and sieved to obtain the flocculant. The flocculant contains ≥98% by mass of modified polyacrylamide, and the water-insoluble matter in the flocculant is ≤1.0% by mass. The modified polyacrylamide is a white solid with a molecular weight of 20-40 million. The modified polyacrylamide has carboxyl groups, amino groups, and calcium ions introduced into its molecular chain. 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 weight.

2. The method for preparing the flocculant for mine water treatment as described in claim 1, characterized in that, In S1, sodium chloride is added at the same time as aminoacetic acid; By mass fractions: 100 parts of acrylamide monomer glycine and 10-20 parts of sodium chloride.

3. The method for preparing the flocculant for mine water treatment as described in claim 2, characterized in that, In S2, the initiator is 0.2-0.3 parts by mass of ammonium persulfate, and the terminator is sodium bisulfite; wherein the mass of the terminator is 1-10 times the mass of the initiator.

4. The method for preparing the flocculant for mine water treatment as described in claim 2, characterized in that, In S3, the soluble calcium salt is 1-2 parts calcium chloride by mass.

5. A water treatment method, characterized in that, Includes the following steps: Preliminary step: Prepare flocculant according to the preparation method of any one of claims 1-4; 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 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.

6. The water treatment method as described in claim 5, characterized in that, In step 2, before adding the flocculant solution, an auxiliary agent is added to the mine water to be treated. The auxiliary agent is selected from polyaluminum chloride, polyferric sulfate and lime.

7. The water treatment method as described in claim 6, characterized in that, In step 2, the auxiliary agent is polyaluminum chloride, and its dosage in the mine water to be treated is 60-100 mg / L.

8. The water treatment method as described in claim 5, characterized in that, In step 2, the concentration of flocculant in the mine water is 1 mg / L.

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