Modified polyferric coagulant for treating papermaking wastewater and preparation method thereof

Abstract

The invention provides a modified polyferric coagulant for treating papermaking wastewater and a preparation method thereof. The preparation method comprises the following steps: reacting trimethoxysilyl propyl with water to obtain a solution A; dissolving silicate minerals in an ethanol solution to obtain a solution B; dissolving cationic starch in water to obtain a solution C; mixing the solution B with the solution A to obtain a mechanically modified mixed solution D; and mixing the solution C and the organic modified mixed solution D with a polyferric sulfate solution to obtain the modified polyferric coagulant. According to the preparation method, cationic starch, silicate minerals, trimethoxysilylpropyl (MPTMS) and polymeric ferric sulfate are introduced, a large number of hydroxyl groups are generated after MPTMS is hydrolyzed, and the hydroxyl groups are subjected to polycondensation combination with the cationic starch, serpentine and Fe-O bonds to generate a large number of polymeric bonds, so that the concrete has enough strength; compared with a conventional coagulant, the flocculant has the advantages that hydrophobicity and selective adsorption performance are increased, meanwhile, molecular chains are increased, and the bridging and net capturing capabilities of the flocculant are improved, so that the coagulation effect is better.

Description

Technical Field

[0001] The present application relates to the technical field of papermaking wastewater treatment, and in particular to a modified polyferric coagulant for treating papermaking wastewater and a preparation method thereof. Background Art

[0002] The flocculation sedimentation method is an important part of water treatment engineering. Its treatment effect depends largely on the performance of the flocculant. However, the traditional flocculants commonly used at present have different advantages and disadvantages.

[0003] Commonly used flocculants mainly include organic polymer flocculants and inorganic polymer flocculants. Organic polymer flocculants include natural and synthetic ones. Among organic polymer flocculants, natural polymer flocculants have the advantages of being non-toxic and biodegradable, but they are not very stable and are not easy to obtain; while synthetic organic polymer flocculants are limited in their development due to secondary pollution caused by toxic monomer residues. Inorganic polymer flocculants mainly include iron and aluminum series. Since the aluminum series contains residual aluminum that is harmful to the human body, iron-based inorganic polymer flocculants have become a research hotspot in recent years and are widely used in water treatment. At present, there are few studies on the copolymerization of iron-based flocculants with other polymers or organic matter. Summary of the invention

[0004] The first aspect of the embodiment of the present application provides a method for preparing a modified polyferric coagulant for treating papermaking wastewater, the preparation method comprising:

[0005] The trimethoxysilylpropyl group is reacted with water to obtain solution A;

[0006] Dissolving silicate minerals in ethanol solution to obtain solution B;

[0007] Dissolving cationic starch in water to obtain solution C;

[0008] Mixing solution B with solution A to obtain an organic modified mixed solution D;

[0009] The solution C and the organic modified mixed solution D are mixed with the polyferric sulfate solution to obtain a modified polyferric coagulant.

[0010] In some embodiments, in the step of reacting trimethoxysilylpropyl with water to obtain solution A, trimethoxysilylpropyl is first added to an anhydrous organic solvent to dissolve, and after dissolution is completed, deionized water is added to trigger a hydrolysis reaction, and then the pH value is adjusted with an acidic buffer and stirred to accelerate the hydrolysis reaction, thereby obtaining solution A.

[0011] In some embodiments, the anhydrous organic solvent is anhydrous ethanol, the acidic buffer is acetic acid, the pH value is adjusted to 4-5, and the stirring time is 30-60 minutes.

[0012] In some embodiments, in the step of dissolving a silicate mineral in an ethanol solution to obtain solution B, the silicate mineral is serpentine powder, and the average particle size of the serpentine powder is 100 nm-10 μm.

[0013] In some embodiments, the step of dissolving the silicate mineral in an ethanol solution to obtain solution B further includes subjecting solution B to ultrasonic treatment for sufficient dispersion; wherein the ethanol mass fraction of the ethanol solution is 1%-2%; the solid-liquid mass ratio of the silicate mineral to the ethanol solution is 1:5 to 1:20; and the ultrasonic treatment time is 20-30 minutes.

[0014] In some embodiments, in the step of dissolving the cationic starch in water to obtain solution C, the temperature for dissolving the cationic starch is 55-65° C., and the solution is stirred at a speed of 300-600 rpm.

[0015] In some embodiments, in the step of mixing solution C and organic modified mixed solution D with polyferric sulfate solution to obtain modified polyferric coagulant, the mass concentration of the polyferric sulfate solution is 5-20%; and the reaction temperature after mixing is 46-50°C.

[0016] In some embodiments, the mass ratio of trimethoxysilylpropyl to silicate mineral is 1:100 to 5:100; the mass ratio of polyferric sulfate to silicate mineral is 100:1 to 120:1.

[0017] In some embodiments, the mass ratio of polyferric sulfate to cationic starch is 5:1 to 70:1; the reaction temperature after mixing is 46-50°C, and the standing and aging time is 4-6h.

[0018] In a second aspect, an embodiment of the present application provides a modified polyferric coagulant for treating papermaking wastewater, wherein the modified polyferric coagulant is prepared by the preparation method described in the above embodiment.

[0019] The preparation method of the modified polyferric coagulant for treating papermaking wastewater provided in the embodiment of the present application introduces cationic starch, silicate mineral (serpentine), trimethoxysilylpropyl (MPTMS) and polyferric sulfate (PFS). After hydrolysis, MPTMS produces a large number of hydroxyl groups, which are condensed with cationic starch, serpentine and Fe-O bonds to produce a large number of polymer bonds, which makes the coagulant have sufficient strength, increases the hydrophobicity and selective adsorption properties compared with conventional coagulants, and at the same time increases the molecular chain, the bridging and netting capabilities of the flocculant are improved, and the coagulation effect is better. The modified polyferric flocculant prepared by the method in the embodiment of the present application has mild reaction conditions, low cost, simple preparation, excellent flocculation effect, and has a good market application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 It is a schematic flow chart of an embodiment of a method for preparing a modified polyferric coagulant for treating papermaking wastewater of the present application;

[0022] Figure 2 It is a chemical reaction mechanism diagram of the modified polyferric coagulant reaction in the embodiment of the present application. DETAILED DESCRIPTION

[0023] The present application is further described in detail below in conjunction with the accompanying drawings and examples. It is particularly noted that the following examples are only used to illustrate the present application, but are not intended to limit the scope of the present application. Similarly, the following examples are only some embodiments of the present application rather than all embodiments, and all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0024] The terms "first", "second", and "third" in the embodiments of the present application are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first", "second", and "third" can expressly or implicitly include at least one of the features. In the description of the present application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the embodiments of the present application, all directional indications (such as up, down, left, right, front, back...) are only used to explain the relative position relationship, movement, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication also changes accordingly. The terms "including" and "having" in the embodiments of the present application and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or components inherent to these processes, methods, products, or devices.

[0025] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0026] The present application example first provides a method for preparing a modified polyferric coagulant for treating papermaking wastewater. Figure 1 , Figure 1 It is a flow chart of an embodiment of a method for preparing a modified polyferric coagulant for treating papermaking wastewater according to the present application. The preparation method includes but is not limited to the following steps.

[0027] Step S100, reacting trimethoxysilylpropyl with water to obtain solution A.

[0028] In this step, MPTMS (3-methoxypropyltrimethoxysilane) is slowly added to an anhydrous organic solvent and stirred. After it is completely dissolved, deionized water is added to trigger a hydrolysis reaction, and then the pH is adjusted with an acidic buffer solution to accelerate the hydrolysis reaction. After stirring at room temperature for half an hour, it is fully hydrolyzed to obtain Solution A.

[0029] The anhydrous organic solvent may be anhydrous ethanol, the acidic buffer may be acetic acid, the pH value is adjusted to 4-5, and the stirring time is 30-60 minutes.

[0030] Step S200, dissolving the silicate mineral in an ethanol solution to obtain a solution B.

[0031] In step S200, the silicate mineral can be serpentine powder, and the average particle size of the serpentine powder is 100nm-10μm; the serpentine is ground and put into an ethanol solution for dissolution, and a solution B with good dispersibility is obtained after ultrasonic treatment for a period of time. Among them, the ethanol mass fraction of the ethanol solution is 1%-2%; the solid-liquid mass ratio of the silicate mineral to the ethanol solution is 1:5-1:20, and specifically can be 1:5, 1:6, 1:7.5, 1:10, 1:15, 1:20 and other values; the ultrasonic treatment time is 20-30 minutes. The mass ratio of trimethoxysilylpropyl (MPTMS) to the silicate mineral is 1:100-5:100, and specifically can be 1:100, 1.5:100, 2:100, 3:100, 4:100, 5:100 and other values.

[0032] Step S300, dissolving cationic starch in water to obtain solution C.

[0033] In this step, the cationic starch may be dissolved in deionized water, stirred, and heated to a certain temperature to prepare solution C. The temperature for dissolving the cationic starch is 55-65°C, specifically 55°C, 56°C, 58°C, 60°C, 62°C, 65°C, etc.; the stirring speed is 300-600rpm.

[0034] Step S400, mixing solution B with solution A to obtain an organic-modified mixed solution D.

[0035] In step S400, solution B is added to the fully hydrolyzed MPTMS solution, heated in a water bath and stirred for a period of time to obtain an organic modified mixed solution D.

[0036] Step S500, mixing solution C and organic modified mixed solution D with polyferric sulfate solution to obtain modified polyferric coagulant.

[0037] In this step, solutions C and D can be dropped into the polyferric sulfate solution, heated, and left to stand for aging to obtain a modified polyferric coagulant for treating papermaking wastewater. Figure 2 , Figure 2 This is a chemical reaction mechanism diagram of the modified polyferric coagulant reaction in the embodiment of the present application, in which 101 represents polyferric sulfate, 102 represents silicate (the main component of the mineral), 103 represents cationic starch, 104 represents trimethoxypropylsilyl (MPTMS), and 105 represents a modified polyferric coagulant.

[0038] The mass concentration of the polyferric sulfate solution is 5-20%, specifically 5%, 8%, 10%, 12%, 15%, 18%, 20% and the like; preferably 10-15%. The reaction temperature after mixing is 46-50°C. The mass ratio of polyferric sulfate to silicate mineral is 100:1 to 120:1, specifically 100:1, 105:1, 110:1, 115:1, 118:1, 120:1 and the like.

[0039] Optionally, the mass ratio of polyferric sulfate to cationic starch is 5:1 to 70:1, specifically 5:1, 10:1, 20:1, 35:1, 50:1, 70:1, etc. The reaction temperature after mixing is 46-50°C, preferably 50°C, and the standing aging time is 4-6h, preferably 5h.

[0040] In order to make the measures implemented, the objectives and effects achieved by the present invention easier to understand, the present invention is described in detail using specific embodiments below.

[0041] Example 1

[0042] The following steps are involved:

[0043] S1: According to the solid-liquid ratio of 1:5, 40 g of serpentine with a particle size of 100 nm-10 μm was ground and dissolved in 400 mL of 1% ethanol solution. After ultrasonic treatment at 25°C for 20 minutes, a solution with good dispersion was obtained.

[0044] S2: Take 3 mL of MPTMS in a beaker, add MPTMS to anhydrous ethanol at a solid-liquid ratio of 1:8. After it is completely dissolved, add deionized water, and then adjust the pH to 4.0 with acetic acid. Continue stirring at room temperature for 30 minutes to fully hydrolyze it to obtain an MPTMS solution.

[0045] S3: Add the above serpentine to the fully hydrolyzed MPTMS solution, heat in a water bath at 60°C and stir for 2h to obtain an organic modified mixed solution.

[0046] S4: Dissolve the cationic starch in deionized water and stir, and heat to 55° C. and stir to obtain a cationic starch solution.

[0047] S5: Finally, the organic modified mixed solution and cationic starch solution are slowly dripped into a 10% by mass polyferric sulfate solution, heated to 46° C. and stirred, and allowed to stand and mature for 4 hours to obtain a modified polyferric coagulant T1.

[0048] Example 2

[0049] The preparation steps are similar to those of Example 1, except that:

[0050] The solid-liquid ratio in S1 is 1:8, and the mass fraction of ethanol is 1.25%; the pH in S2 is adjusted to 4.5; the water bath heating temperature in S3 is 80° C., and the modified polyferric coagulant T2 is obtained.

[0051] Example 3

[0052] The preparation steps are similar to those of Example 1, except that:

[0053] The solid-liquid ratio in S1 is 1:10, and the mass fraction of ethanol is 1.5%; the pH in S2 is adjusted to 5; the mass fraction of polyferric sulfate in S5 is 13%, and the modified polyferric coagulant T3 is obtained after standing and aging for 5 hours.

[0054] Example 4

[0055] The preparation steps are similar to those of Example 1, except that:

[0056] The mass fraction of ethanol used in S1 is 1.5%; the mass fraction of polyferric sulfate in S5 is 15%, and the modified polyferric coagulant T4 is obtained by standing and aging for 5 hours.

[0057] Example 5

[0058] The preparation steps are similar to those of Example 1, except that:

[0059] The mass fraction of ethanol in S1 is 1.75%; the pH in S2 is adjusted to 5; the mass fraction of polyferric sulfate in S5 is 18%, and the modified polyferric coagulant T5 is obtained by standing and aging for 6 hours.

[0060] Example 6

[0061] The preparation steps are similar to those of Example 1, except that:

[0062] The mass fraction of the ethanol solution used in S1 is 2%; the pH in S2 is adjusted to 5; the water bath temperature in S3 is 65° C.; the mass fraction of polyferric sulfate in S5 is 20%, and the modified polyferric coagulant T6 is obtained by standing and aging for 6 hours.

[0063] Comparative Example: Commercially available conventional polyferric sulfate flocculant.

[0064] Application example: This implementation uses the biochemical tail water from a sewage treatment plant of a pulp and paper company. According to the test report, the pH is 6-9 and the COD concentration is <1600mg / L.

[0065] 10 mL of the coagulants prepared in Examples 1 to 6 and the comparative coagulant were respectively added into 1 L of wastewater at 25°C, stirred rapidly for 30 min and slowly for 10 min. The treatment effects on COD in the wastewater are shown in the following table.

[0066] Sample name Influent COD Outlet COD Removal rate T1 1565mg / L 165mg / L 89.5％ T2 1417mg / L 158mg / L 88.8％ T3 1585mg / L 159mg / L 90.0％ T4 1414mg / L 145mg / L 89.7％ T5 1502mg / L 173mg / L 88.5％ T6 1579mg / L 152mg / L 90.4％ PFS 1574mg / L 387mg / L 75.4％

[0067] It can be found from the comparative experiment that the modified polyferric flocculant for treating papermaking wastewater prepared in the examples of the present application is better than the conventional non-modified polyferric sulfate flocculant, and the COD removal rate can reach 90.4% under the optimal conditions (Example 6). In addition, the flocs are large and dense during the test, and the flocs settle in layers with a fast sedimentation rate. It can be seen that the modified polyferric flocculant provided by the present invention has mild reaction conditions, low cost, simple preparation, excellent flocculation effect, and has a good market application prospect.

[0068] Compared with conventional non-modified polyferric sulfate, the preparation method of the modified polyferric coagulant for treating papermaking wastewater provided in the embodiment of the present application introduces cationic starch, silicate mineral (serpentine), trimethoxysilylpropyl (MPTMS) and polyferric sulfate (PFS). After hydrolysis, MPTMS produces a large number of hydroxyl groups, which are condensed with cationic starch, serpentine and Fe-O bonds to produce a large number of polymer bonds, which makes the coagulant have sufficient strength, increases the hydrophobicity and selective adsorption performance compared with conventional coagulants, and at the same time increases the molecular chain, improves the bridging and net capturing capabilities of the flocculant, and makes the coagulation effect better.

[0069] The modified poly-iron coagulant for treating papermaking wastewater prepared by the present invention has greatly improved adsorption bridging and net-filling sweeping capabilities compared with conventional flocculants, and the flocs are formed faster, and the flocs are larger, stronger, and have a faster sedimentation rate. In addition, the preparation method of the present invention is simple to operate and the required raw materials are inexpensive. No coagulant is required to be added during the coagulation process, and no pollutants remain in the treated water, which can ensure that the effluent water quality is safe and free of secondary pollution. Due to the introduction of cationic starch, serpentine, and MPTMS in the present invention, the chain structure of the poly-iron molecule is increased, the flocculation ability of the flocculant is greatly improved, and the amount of flocculant used is less, and the processing cost is lower.

[0070] The present invention provides a method for preparing a modified polyferric coagulant for treating papermaking wastewater. A large number of polymer bonds are generated, and the prepared novel flocculant has a network structure and a relatively long molecular chain, thereby enhancing its net-catching ability, and the formed flocs have greater strength, faster sedimentation speed, and are not easily compressed and destroyed by water flow, thereby achieving the result of obtaining better flocculation performance by using a smaller flocculant dosage.

[0071] The above descriptions are only some embodiments of the present application, and do not limit the protection scope of the present application. Any equivalent device or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for preparing a modified polyferric coagulant for treating papermaking wastewater, characterized in that: The preparation method comprises: The trimethoxysilylpropyl group is reacted with water to obtain solution A; Dissolving silicate minerals in ethanol solution to obtain solution B; Dissolving cationic starch in water to obtain solution C; Mixing solution B with solution A to obtain an organic modified mixed solution D; The solution C and the organic modified mixed solution D are mixed with the polyferric sulfate solution to obtain a modified polyferric coagulant.

2. The preparation method according to claim 1, characterized in that: In the step of reacting trimethoxysilylpropyl with water to obtain solution A, trimethoxysilylpropyl is first added to an anhydrous organic solvent to dissolve, and after the dissolution is completed, deionized water is added to trigger a hydrolysis reaction, and then the pH value is adjusted with an acidic buffer and stirred to accelerate the hydrolysis reaction, thereby obtaining solution A.

3. The preparation method according to claim 2, characterized in that: The anhydrous organic solvent is anhydrous ethanol, the acidic buffer is acetic acid, the pH value is adjusted to 4-5, and the stirring time is 30-60 minutes.

4. The preparation method according to claim 1, characterized in that: In the step of dissolving a silicate mineral in an ethanol solution to obtain solution B, the silicate mineral is serpentine powder, and the average particle size of the serpentine powder is 100 nm-10 μm.

5. The preparation method according to claim 4, characterized in that: The step of dissolving the silicate mineral in the ethanol solution to obtain solution B also includes subjecting solution B to ultrasonic treatment for sufficient dispersion; wherein the ethanol mass fraction of the ethanol solution is 1%-2%; the solid-liquid mass ratio of the silicate mineral to the ethanol solution is 1:5-1:20; and the ultrasonic treatment time is 20-30 minutes.

6. The preparation method according to claim 1, characterized in that: In the step of dissolving the cationic starch in water to obtain solution C, the temperature for dissolving the cationic starch is 55-65° C., and the solution is stirred at a speed of 300-600 rpm.

7. The preparation method according to claim 1, characterized in that: In the step of mixing solution C and organic modified mixed solution D with polyferric sulfate solution to obtain modified polyferric coagulant, the mass concentration of the polyferric sulfate solution is 5-20%; and the reaction temperature after mixing is 46-50°C.

8. The preparation method according to claim 7, characterized in that: The mass ratio of trimethoxysilylpropyl to silicate mineral is 1:100-5:100; the mass ratio of polyferric sulfate to silicate mineral is 100:1-120:

1.

9. The preparation method according to claim 8, characterized in that: The mass ratio of polyferric sulfate to cationic starch is 5:1-70:1; the reaction temperature after mixing is 46-50°C, and the standing and aging time is 4-6h.

10. A modified polyferric coagulant for treating papermaking wastewater, characterized in that: The modified polyferric coagulant is prepared by the preparation method described in any one of claims 1 to 9.

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