Sludge dewatering flocculant as well as preparation method and application thereof

Abstract

The invention discloses a sludge dewatering flocculant and a preparation method and application thereof.The sludge dewatering flocculant is a natural polymer modified corn straw powder flocculant, natural corn straw is smashed into powder to serve as a base material, and cationic groups are carried by the base material through alkalization and graft copolymerization; and the cation group is quaternary ammonium group methyl. The modified corn straw powder flocculant is used for conditioning municipal sludge, is beneficial to flocculation and dehydration of the sludge, is extremely good in solubility, can be easily and fully dispersed in the sludge, is extremely small in addition amount, and has the characteristics of environment friendliness and high efficiency; the biomass fuel is prepared by modifying the corn straws, so that the biomass fuel also has the advantages of high calorific value similar to that of the corn straws and the like, and subsequent sludge incineration disposal is facilitated. Municipal sludge is conditioned through the modified corn straw powder flocculating agent and dehydrated, the water content of an obtained sludge cake can be as low as 65%, and the specific resistance SRF of the sludge can be as low as 6.25 * 10 <-12 > m.kg <-1 >.

Description

Technical Field

[0001] The invention belongs to the technical field of urban sludge treatment, and in particular relates to a sludge dewatering flocculant and a preparation method and application thereof. Background Art

[0002] In recent years, municipal sludge production has steadily increased, and efficient treatment and disposal has become a pressing challenge. Because municipal sludge is a heterogeneous colloidal system with a high moisture content, composed of bacterial cells, recalcitrant organic matter, and some colloids, it is difficult to separate sludge flocs from the aqueous phase. Therefore, reducing the moisture content (MC) of municipal sludge has become a key issue in sludge treatment and disposal.

[0003] Flocculants are chemicals or polymers that cause tiny suspended particles in water, such as colloids, to aggregate and combine into larger flocs, accelerating their sedimentation or removal by filtration. They are key agents in processes such as water treatment, sewage treatment, and sludge dewatering. The current mainstream sludge flocculants are inorganic salt flocculants like ferric chloride and polyaluminum chloride, and organic synthetic polymer flocculants like cationic polyacrylamide. These sludge flocculants have numerous drawbacks, including high dosages, equipment corrosion, reduced calorific value, potential for secondary pollution after incineration, and lack of biodegradability. They pose significant risks to humans, animals, and plants, and pose a significant environmental burden.

[0004] Therefore, the development of environmentally friendly, cost-effective and efficient sludge flocculants is of great practical significance. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a sludge dewatering flocculant and its preparation method and application, which can achieve rapid dehydration of urban sludge by adding a small amount of sludge dewatering flocculant, thereby ensuring the efficiency and environmental protection of the urban sludge dewatering process.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention first proposes a method for preparing a sludge dewatering flocculant, comprising the following steps: S1, dissolving corn stalk powder, mixing it with sodium hydroxide and heating it in a water bath for alkalization treatment; S2, adding 3-chloro-2-hydroxypropyltrimethylammonium chloride to the reaction system of S1, and then adding chloroacetic acid to carry out graft copolymerization reaction, cooling to room temperature after the reaction is completed, neutralizing, washing, and drying to obtain the sludge dewatering flocculant.

[0007] Preferably, in step S1, the mass ratio of corn straw powder to sodium hydroxide is (2-4):1.

[0008] Preferably, in step S1, the temperature of the water bath heating is 55°C-60°C.

[0009] Preferably, in step S1, the alkalization treatment time is 40 min-60 min.

[0010] Preferably, in step S2, the mass ratio of 3-chloro-2-hydroxypropyltrimethylammonium chloride to corn straw powder is 1:(1-3).

[0011] Preferably, in step S2, the mass ratio of chloroacetic acid to corn straw powder is 1:(1-2).

[0012] The present invention further proposes a sludge dewatering flocculant prepared by the above preparation method.

[0013] The present invention also proposes the application of the above-mentioned sludge dewatering flocculant, and adopts the following steps to carry out sludge dewatering conditioning: Step 1: Mixing a sludge dewatering flocculant with municipal sludge, stirring the mixture, and then allowing the mixture to stand for reaction; Step 2: Filter the product after the standing reaction to obtain a sludge cake, thereby completing the dehydration and conditioning of the sludge.

[0014] Preferably, in step 1, the amount of sludge dewatering flocculant added is 10-20 wt% of the dry municipal sludge.

[0015] Preferably, in step 2, the filtration pressure is 0.5-0.8 MPa, the pressing time is 0.5-1 h; the moisture content of the sludge cake is 65-70%, and the sludge specific resistance SRF is 6.25×10 -12 -8.60×10 -12 m·kg -1 .

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention proposes a method for preparing a sludge dewatering flocculant. The modified corn straw powder flocculant is rich in cationic groups, which can neutralize the negative charge carried by sludge, significantly destroy extracellular polymers in sludge, and promote sludge flocculation and dewatering. The modified corn straw powder flocculant has excellent solubility and is easily dispersed in sludge. It can be added in small amounts, making it environmentally friendly, highly efficient, and low-carbon. The corn straw powder used has the advantages of low cost and high calorific value, facilitating the incineration of treated sludge cake.

[0017] After the modified corn straw powder flocculant proposed in the present invention is used to condition and dehydrate municipal sludge, the sludge moisture content under the optimal addition condition is reduced to 65%, and the sludge specific resistance is reduced to SRF of 6.25×10 -1 m·kg -12The modified corn straw powder flocculant has high economic benefits, is replicable, and easy to promote. It meets the national green development requirements and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings: Figure 1 This is the infrared spectrum of modified corn straw powder; Figure 2 For pore size analysis of modified corn straw powder flocculant; Figure 3 Scanning electron microscopy analysis of modified corn straw powder flocculant before and after modification; Figure 4 Modified corn straw powder flocculant is used to adjust the sludge moisture content before and after dehydration; Figure 5 The modified corn straw powder flocculant is used to adjust the sludge specific resistance before and after sludge dewatering; Figure 6 Modified corn straw powder flocculant to adjust sludge dewatering rate. DETAILED DESCRIPTION

[0019] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing particular embodiments and are not intended to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between the intermediate value within any stated value or stated range and any other stated value or intermediate value within the range is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0020] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0021] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention without departing from the scope or spirit of the present invention. Other embodiments will be apparent to those skilled in the art from the present invention. The present invention description and examples are intended to be exemplary only. As used herein, the terms "comprising," "including," "having," "containing," and the like are intended to be open ended, meaning including but not limited to.

[0022] Organic natural polymers are gaining popularity as environmentally friendly, biodegradable, and non-toxic natural polymer flocculants. Corn, a common crop worldwide, offers a high yield and a wide variety of sources. Flocculants prepared from corn straw not only have great potential in sludge dewatering but can also effectively reduce carbon emissions.

[0023] Based on the above understanding, the present invention proposes a municipal sludge dewatering flocculant - modified corn straw powder flocculant, which uses corn straw as a base material and grafts quaternary ammonium group methyl (-N + (CH3)3).

[0024] The methods of the present invention are further described below with reference to the accompanying drawings and examples. The following examples utilize conventional instruments and equipment in the art. Unless otherwise specified, the various raw materials and reagents used are conventional commercially available products, with specifications conventional in the art, or can be prepared or formulated by known methods or reagent instructions. Experimental procedures in the following examples, where specific conditions are not specified, generally follow conventional conditions or those recommended by the manufacturer.

[0025] The present invention is described in further detail below with reference to the accompanying drawings: Example 1 Preparation of modified corn straw powder flocculant The synthesis was carried out by a one-step method. 5 g of sodium hydroxide was accurately weighed and dissolved in 100 mL of distilled water. 10 g of corn straw powder was added to the sodium hydroxide solution, and the mixture was heated in a 55°C water bath for 40 minutes.

[0026] Add 3-chloro-2-hydroxypropyltrimethylammonium chloride dropwise, the mass ratio of 3-chloro-2-hydroxypropyltrimethylammonium chloride to corn straw powder is 1:1, and continue to stir and add chloroacetic acid mixed solution dropwise, the mass ratio of chloroacetic acid to corn straw powder is 1:1. Continue to react at 55°C for 2h, and neutralize with pre-configured hydrochloric acid with a concentration of 10% to pH = 7.

[0027] The obtained product was precipitated in ethanol for 1 hour, washed, filtered, and dried in a vacuum drying oven at 60° C. to constant weight to obtain a modified corn straw powder flocculant.

[0028] Infrared spectrum of modified corn straw powder flocculant Figure 1 ,from Figure 1 The wave number is 1476cm -1 -N + The characteristic absorption peak of (CH3)3 was observed, which proved that the cationic group was successfully grafted.

[0029] Pore ​​size analysis of modified corn straw powder flocculant Figure 2 ,from Figure 2 It can be seen that the modified corn straw powder flocculant is a mesoporous material.

[0030] Scanning electron microscopy analysis of modified corn straw powder flocculant before and after modification Figure 3 ,from Figure 3 It can be seen that compared with the raw corn straw powder, the modified corn straw powder flocculant exhibits a unique three-dimensional porous structure.

[0031] Example 2 The amount of corn straw powder used was 20 g, and the rest of the preparation process and parameters were the same as in Example 1.

[0032] Example 3 The amount of corn straw powder used was 15 g, and the rest of the preparation process and parameters were the same as in Example 1.

[0033] Example 4 The mass ratio of 3-chloro-2-hydroxypropyltrimethylammonium chloride to corn straw powder is 1:2, and the rest of the preparation process and parameters are the same as in Example 1.

[0034] Example 5 The mass ratio of 3-chloro-2-hydroxypropyltrimethylammonium chloride to corn straw powder is 1:3, and the rest of the preparation process and parameters are the same as in Example 1.

[0035] Example 6 The mass ratio of chloroacetic acid to corn straw powder is 1:2, and the rest of the preparation process and parameters are the same as in Example 1.

[0036] Application Example 1 Method for conditioning municipal sludge dewatering using modified corn straw powder flocculant Fresh municipal sludge without dehydration was used, with an initial moisture content of 95% and an initial sludge specific resistance of 13.25×10 - 1 m·kg -12 250 mL of fresh municipal sludge was placed in a stirring barrel at a speed of 500 rpm, and modified corn straw powder flocculant was added at a dosage of 10% of the sludge dry weight, and stirred for 15 minutes.

[0037] After stirring, let it stand for 1 hour and then send it to a vacuum filter. Set the filter pressure to 0.5MPa and filter for 1 hour to obtain a sludge cake.

[0038] The sludge moisture content and sludge ratio before and after dehydration of sludge conditioned by modified corn straw powder flocculant Figure 4 and Figure 5 .from Figure 4 It can be seen that the sludge moisture content is 65%. Figure 5 It can be seen that the sludge specific resistance is 6.25×10 -1 m·kg -12 .

[0039] The dewatering rate of sludge conditioned by modified corn straw powder flocculant is shown in Figure 6 ,from Figure 6 It can be seen that the modified corn straw powder flocculant greatly improves the dewatering rate of sludge.

[0040] The above are merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for preparing a sludge dewatering flocculant, characterized in that: The following steps are involved: S1, dissolving corn stalk powder, mixing it with sodium hydroxide and heating it in a water bath for alkalization treatment; S2, adding 3-chloro-2-hydroxypropyltrimethylammonium chloride to the reaction system of S1, and then adding chloroacetic acid to carry out graft copolymerization reaction, cooling to room temperature after the reaction is completed, neutralizing, washing, and drying to obtain the sludge dewatering flocculant.

2. The method for preparing a sludge dewatering flocculant according to claim 1, characterized in that: In step S1, the mass ratio of corn straw powder to sodium hydroxide is (2-4):

1.

3. The method for preparing a sludge dewatering flocculant according to claim 1, characterized in that: In step S1, the water bath is heated at a temperature of 55°C-60°C.

4. The method for preparing a sludge dewatering flocculant according to claim 1, characterized in that: In step S1, the alkalization treatment time is 40 min-60 min.

5. The method for preparing a sludge dewatering flocculant according to claim 1, characterized in that: In step S2, the mass ratio of 3-chloro-2-hydroxypropyltrimethylammonium chloride to corn straw powder is 1:(1-3).

6. The method for preparing a sludge dewatering flocculant according to claim 1, characterized in that: In step S2, the mass ratio of chloroacetic acid to corn straw powder is 1:(1-2).

7. A sludge dewatering flocculant prepared according to the preparation method according to any one of claims 1 to 6.

8. The use of the sludge dewatering flocculant according to claim 7, characterized in that: The following steps are used to dewater the sludge: Step 1: Mixing a sludge dewatering flocculant with municipal sludge, stirring the mixture, and then allowing the mixture to stand for reaction; Step 2: Filter the product after the standing reaction to obtain a sludge cake, thereby completing the dehydration and conditioning of the sludge.

9. The use of the sludge dewatering flocculant according to claim 8, characterized in that: In the step 1, the amount of the sludge dewatering flocculant added is 10-20 wt% of the dry municipal sludge.

10. The use of the sludge dewatering flocculant according to claim 8, characterized in that: In step 2, the filtration pressure is 0.5-0.8 MPa, and the pressing time is 0.5-1 h; the moisture content of the sludge cake is 65-70%, and the sludge specific resistance SRF is 6.25×10 -12 -8.60×10 -12 m·kg -1 .

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