A sludge dewatering conditioner, a preparation method thereof and a sludge dewatering process

Abstract

The present application relates to sludge treatment technical field, disclose a kind of sludge dewatering conditioner and its preparation method and sludge dewatering process, including following weight parts raw materials: modified bentonite 20-30 parts, Si-CNC nano-composite 25-40 parts, graphite phase carbon nitride load iron oxide nano-composite 5-10 parts, aluminum sulfate iron 10-15 parts, citric acid-oxalic acid complex chelating agent 3-6 parts, sodium phosphate slow-release agent 1-3 parts, wherein, the modified bentonite is ammonium persulfate and polyacrylamide monomer in situ grafting polymerization modification, the graphite phase carbon nitride load iron oxide nano-composite is melamine calcination after loading iron ion again calcination and obtain.The present application can reduce the water content of sludge while sludge increment is small, convenient to use.

Description

Technical Field

[0001] This invention relates to the field of sludge treatment technology, and in particular to a sludge dewatering conditioner, its preparation method, and sludge dewatering process. Background Technology

[0002] With the rapid development of industrialization and urbanization, the volume of urban sewage treatment is constantly increasing, resulting in a growing amount of residual sludge. Sludge, as a byproduct of sewage treatment, is characterized by high water content, high organic matter content, poor stability, and susceptibility to decay and spoilage. It not only occupies a large amount of land resources but also causes secondary pollution to the environment if not properly treated. Therefore, efficient sludge dewatering technology has become one of the current research hotspots in the environmental protection field.

[0003] Traditional sludge dewatering mainly relies on physical methods such as mechanical filtration and centrifugation. However, due to the large amount of colloidal substances and hydrophilic groups in sludge, it is difficult to effectively separate free water and capillary water through physical means, resulting in low dewatering efficiency and high moisture content in the sludge cake. Therefore, chemical conditioners are usually introduced to pretreat the sludge, disrupting its structural stability and thus improving dewatering efficiency.

[0004] Currently, the sludge dewatering agents widely used in the market mainly include single polymeric flocculants and inorganic coagulants. However, the application effect of these traditional dewatering agents in complex sludge treatment scenarios often fails to meet actual needs.

[0005] The patent application CN 104649533A, entitled "A Method for Composite Conditioning and Deep Dewatering of Sludge," discloses a method that utilizes free radicals generated by the reaction of zero-valent iron or nano-zero-valent iron with persulfates such as potassium persulfate, persulfate, and persulfate as activators to destroy extracellular polymers in sludge. This is combined with industrial by-product gypsum for synergistic effects, forming conditioned sludge with a newly formed skeletal structure, improving sludge filtration performance and reducing sludge moisture content to below 60%. The disadvantages include complex composition, large dosage, the need for activators to generate active free radicals, gypsum dosage of 10%-40% of dry sludge, significant sludge volume increase, and a cumbersome process.

[0006] Therefore, there is a need to provide a sludge dewatering conditioner, its preparation method, and a sludge dewatering process to solve the problem of high sludge moisture content. Summary of the Invention

[0007] In view of this, the purpose of this invention is to provide a sludge dewatering conditioner, its preparation method, and a sludge dewatering process, which can reduce the water content of sludge while minimizing sludge volume increase and is convenient to use.

[0008] The present invention solves the above-mentioned technical problems through the following technical means:

[0009] In a first aspect, the present invention discloses a sludge dewatering conditioner, comprising the following raw materials in parts by weight: 20-30 parts modified bentonite, 25-40 parts Si-CNC nanocomposite, 5-10 parts graphite phase carbon nitride supported iron oxide nanocomposite, 10-15 parts iron aluminum sulfate, 3-6 parts citric acid-oxalic acid composite chelating agent, and 1-3 parts sodium phosphate slow-release agent, wherein the modified bentonite is modified by in-situ graft polymerization of ammonium persulfate and polyacrylamide monomer, and the graphite phase carbon nitride supported iron oxide nanocomposite is obtained by calcining melamine and then calcining it again with iron ions loaded on it.

[0010] Modified bentonite provides a porous support structure through adsorption and the construction of a physical framework, enhancing water migration pathways and adsorbing colloidal particles; Si-CNC nanocomposites act as nanoscaffolds and regulate surface activity, improving floc stability and cohesion through a high specific surface area nanonetwork structure; graphitic carbon nitride-supported iron oxide nanocomposites release trace amounts of hydroxyl radicals (•OH) through micro-oxidation and colloidal chain scission, autonomously attacking the organic colloidal layer in sludge flocs; ferric aluminum sulfate achieves charge neutralization and rapid flocculation, forming a tight aggregate core by neutralizing the negatively charged colloidal surface; citric acid-oxalic acid composite chelating agents destroy Ca2+ through metal ion chelation and promote dehydration. 2+ Fe 3+ Metal bridging and water-organic matter bonding; sodium phosphate slow-release agent, through pH regulation and synergistic reaction, slowly releases phosphate ions, suppresses acid fluctuations, and maintains the stability of the system's reaction window.

[0011] Among them, modified bentonite and Si-CNC nanocomposite synergistically form a microscopic "skeleton-fiber cross-linked body", providing a three-dimensional support network, enabling the formation of multi-level pores inside the floc; significantly improving water migration efficiency, reducing pressure filtration resistance, and providing a structural basis for subsequent dehydration reactions.

[0012] Graphite-phase carbon nitride-supported iron oxide nanocomposites release a small amount of hydroxyl radicals (•OH) in the sludge microenvironment, precisely attacking the protein and polysaccharide structures of organic flocs in the sludge, thus loosening the structure; simultaneously, the citric acid-oxalic acid composite chelating agent interacts with naturally bridging metals (Ca) in the sludge. 2+ Fe 3+ This process forms stable complexes, disrupts the cross-linking structure of micelles, and promotes the release of capillary bound water. At this time, aluminum ferric sulfate acts as a strong electrolyte flocculant, rapidly neutralizing the charge of the colloidal particles and generating Al / Fe hydroxyl flocs, which stably encapsulate the dispersed particles into clusters, thereby improving the dehydration and flocculation efficiency.

[0013] Chelating agents and oxidants may cause the pH of the system to drop during the reaction, which can easily lead to excessive acidity in the system. Sodium phosphate slow-release agent can gradually release weakly basic phosphate ions, buffer the system, maintain the reaction within a suitable pH range (5.5-7.5), prevent the decrease in flocculation efficiency and reaction overshoot; at the same time, it promotes the persistence of micro-reactions and enhances the time-dependent stability of conditioning agents.

[0014] Preferably, the modified bentonite is prepared as follows: Bentonite is dispersed in deionized water, a silane coupling agent is added, and then ammonium persulfate and polyacrylamide monomer are added for in-situ graft polymerization. The reaction temperature is 55-65℃, and the mixture is stirred for 3-5 hours. After drying, the mixture is pulverized and sieved to obtain the modified bentonite.

[0015] Preferably, the mass ratio of bentonite to deionized water is 1:(9-11).

[0016] More preferably, the mass ratio of bentonite to deionized water is 1:10.

[0017] More preferably, the silane coupling agent is KH550.

[0018] More preferably, the sieving is performed through a 200-mesh sieve.

[0019] Bentonite surface contains numerous hydroxyl groups, which can undergo condensation reactions with silane coupling agents, introducing organic functional groups into the bentonite surface. This provides an organophilic interface for subsequent polymer grafting, improving polymer loading stability and dispersibility. Ammonium persulfate decomposes at suitable temperatures to generate free radicals, inducing in-situ polymerization of polyacrylamide monomers on the bentonite surface, forming a stable organic-inorganic hybrid structure. The polyacrylamide segments form multi-point long-chain "tentacles" on the particle surface, enhancing adsorption, flocculation, and bridging of sludge particles. The grafted bentonite retains the adsorption capacity of its layered structure and also incorporates the high molecular weight flocculation properties of the polyacrylamide monomers. These two elements complement each other, forming a modified flocculation matrix material with high specific surface area, high activity, and multiple functions.

[0020] Preferably, the Si-CNC nanocomposite is prepared as follows: microcrystalline cellulose is swollen in dilute acid, hydrothermally treated at 115-125℃ for 3-5 hours, γ-aminopropyltriethoxysilane is added, the pH is adjusted to 4-5, and the reaction is carried out at 75-85℃ for 1.5-2.5 hours. After washing, drying and grinding, the Si-CNC nanocomposite is obtained.

[0021] After hydrothermal treatment at 115-125℃ for 3-5 hours in a dilute acid system, the amorphous regions of microcrystalline cellulose are preferentially hydrolyzed, while the crystalline regions are retained, resulting in uniformly sized, highly crystalline cellulose nanocrystals (CNCs), providing high specific surface area and good mechanical support. Under pH 4-5 conditions, APTES hydrolyzes to generate silanols, which dehydrate and condense with hydroxyl groups on the CNC surface to form Si-OC bonds, exposing aminopropyl groups on the surface and endowing it with cationic functional groups and a silicon-based supporting structure, enhancing its electrochemical matching and reactivity with negatively charged sludge particles. The resulting Si-CNC composite combines the flexible support of nanocellulose with the thermal stability and structural rigidity of inorganic silicon components, providing a stable and synergistic framework material for subsequent interfacial composites and network formation with flocculants (such as iron and aluminum salts, bentonite, etc.).

[0022] Preferably, the preparation method of the graphite-phase carbon nitride supported iron oxide nanocomposite is as follows:

[0023] A1. Graphite-phase carbon nitride powder was prepared by calcining melamine at 500-600℃ for 1-3 hours using melamine as a precursor.

[0024] A2. Add graphitic carbon nitride powder to 0.2-0.4 mol / L ferric nitrate solution and ultrasonically disperse for 20-40 minutes;

[0025] A3. Add NaBH4 for reduction, allow to stand for 7-9 hours, filter and wash to obtain graphite phase carbon nitride supported iron oxide nanocomposite.

[0026] Using melamine as a precursor, calcination at 500-600℃ for 1-3 hours induces polymerization and deamination reactions, forming a graphitic carbon nitride material with a porous, layered structure. Its surface contains numerous -NH2, -NH groups and hexazine ring structures, exhibiting excellent adsorption capacity and electron donor properties. The graphitic carbon nitride material is then added to a 0.2-0.4 mol / L ferric nitrate solution and dispersed ultrasonically to allow Fe... 3+ Fe is uniformly adsorbed onto the surface and pores of the graphitic carbon nitride material. 3+ The nitrogen heterocyclic surface groups of the graphitic carbon nitride material coordinate with each other, forming a stable bond. FeOx nanoparticles are generated by adding NaBH4 and loaded onto the surface of the graphitic carbon nitride material. The graphitic carbon nitride material provides an electron transport channel for the reduction process and also acts as a dispersion support, effectively preventing the aggregation of iron oxide nanoparticles and forming a highly efficient and active composite material.

[0027] Secondly, this invention discloses a method for preparing a sludge dewatering conditioner, which includes the following steps:

[0028] Modified bentonite, Si-CNC nanocomposite, graphitic carbon nitride supported iron oxide nanocomposite, iron aluminum sulfate, citric acid-oxalic acid composite chelating agent, and sodium phosphate slow-release agent were mixed, granulated, dried, and packaged after ball milling.

[0029] Preferably, the granulation particle size is controlled within 80-120 μm.

[0030] Preferably, the granulation speed is 35-45 rpm and the granulation time is 20-25 min.

[0031] This invention employs a ball milling mixing process to achieve uniform dispersion of each component, eliminate agglomeration, and improve product stability. Simultaneously, by controlling the granulation particle size at 80-120μm, the rotation speed at 35-45rpm, and the time at 20-25min, powder particles with moderate size and uniform distribution can be obtained, which is beneficial for the rapid dispersion and uniform mixing of the conditioner in sludge, thereby improving its actual application efficiency.

[0032] Thirdly, this invention discloses a sludge dewatering process, the process comprising the following steps:

[0033] S1. Use a weak acid to adjust the pH of the sludge to 5.5-6.0 to promote colloidal stabilization;

[0034] S2. Add the sludge dewatering conditioner at 8-12% of the dry weight of the sludge, mix and react by high-speed stirring for 4-6 minutes and low-speed stirring for 9-11 minutes, and let stand for 10-15 minutes.

[0035] S3. Dewater the sludge by filter press, with the filter press pressure controlled at 0.5-0.8 MPa.

[0036] Preferably, the high-speed stirring speed in step S2 is 150-250 rpm, and the low-speed stirring speed is 40-60 rpm.

[0037] This invention adjusts the sludge to a weakly acidic environment of pH 5.5-6.0 using a weak acid, effectively breaking the electrostatic balance of colloidal particles in the sludge, promoting cell wall rupture and colloidal particle deagglomeration, and providing favorable reaction conditions for the adsorption and complexation of active components in the subsequent conditioner, thereby significantly improving the initial reaction efficiency of sludge dewatering.

[0038] The conditioner is added precisely at 8-12% of the sludge dry weight. It is mixed in a two-stage process using high-speed (150-250 rpm) and low-speed (40-60 rpm) stirring. The high-speed stirring in the early stage helps to quickly disperse the conditioner and break up agglomerates, while the low-speed stirring in the later stage helps to form and stabilize flocs, avoid shear damage, and ensure that the conditioner fully contacts and reacts with the sludge, thereby improving the uniformity of conditioning and the dewatering effect.

[0039] Allowing the mixture to stand for 10-15 minutes helps to further bridge, expand, and stabilize the flocs formed after the reaction, enhancing their mechanical strength and filterability. This creates ideal preconditions for the subsequent filter press dewatering process, ultimately significantly improving the solids content and structural integrity of the sludge cake.

[0040] The method of this invention is convenient, quick, efficient, and time-saving, with a high dewatering rate and a small increase in sludge volume, effectively achieving a small increase in sludge volume and a significant reduction in sludge quantity.

[0041] The beneficial effects of this invention are:

[0042] (1) This invention achieves synergistic conditioning of multifunctional components, significantly improving sludge dewatering efficiency. Through the synergistic effect of functional materials such as modified bentonite, Si-CNC nanocomposite, and graphite phase carbon nitride supported iron oxide nanocomposite, it has multiple mechanisms of action such as adsorption, bridging, coagulation, and complexation, effectively destroying the colloidal structure of sludge, releasing bound water and capillary water, making sludge easier to filter, and improving dewatering efficiency by more than 20% compared with single-component conditioners.

[0043] (2) This invention constructs a stable and efficient complexation and chelation system to enhance the removal capacity of heavy metals and organic matter in sludge. Through the synergistic effect of citric acid-oxalic acid composite chelating agent and ferric aluminum sulfate, stable complexes can be formed with heavy metal ions and some organic pollutants in sludge, reducing toxicity and migration, while promoting particle aggregation and desorption, further improving sludge cake density and heavy metal removal rate, and enhancing the safety of sludge resource utilization or volume reduction treatment.

[0044] (3) The present invention optimizes the sustained-release control and reaction kinetics of the conditioner, thereby improving the stability and economy of the conditioner. The synergistic design of sodium phosphate sustained-release agent and Si-CNC composite structure enables the conditioner to continuously release effective components during stirring, settling and pressure filtration, avoiding the conditioner from reacting too quickly or becoming ineffective, effectively extending the conditioner time window, reducing the amount of conditioner used by about 15-30%, and achieving a balance between conditioner effect and cost control. Detailed Implementation

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0046] The sludge used in the following examples and comparative examples was from a wastewater treatment plant in Chaohu City, with a moisture content of 98%. The on-site programmable diaphragm plate and frame filter press had a filtration area of ​​200 square meters and could process 0.8 tons of dry sludge per batch. In the following examples and comparative examples, 25 m³ of sludge was taken each time.3 The raw sludge was used for a production trial, and the amount of oven-dried sludge was 0.75 tons.

[0047] Example 1

[0048] 20 kg of modified bentonite, 25 kg of Si-CNC nanocomposite, 5 kg of graphite phase carbon nitride supported iron oxide nanocomposite, 10 kg of iron aluminum sulfate, 3 kg of citric acid-oxalic acid composite chelating agent, and 1 kg of sodium phosphate slow-release agent were mixed, granulated, dried and packaged after ball milling.

[0049] in

[0050] The modified bentonite was prepared as follows: 40 kg of bentonite was dispersed in 360 L of deionized water, 400 g of silane coupling agent was added, and then 200 g of ammonium persulfate and 2.0 kg of polyacrylamide monomer were added for in-situ graft polymerization. The reaction temperature was 55 °C, and the mixture was stirred for 3 hours. After drying, the mixture was pulverized and sieved to obtain 42 kg of modified bentonite.

[0051] The preparation method of Si-CNC nanocomposite is as follows: 40 kg of microcrystalline cellulose was swollen in 300 L of dilute sulfuric acid, hydrothermally treated at 115 °C for 5 h, 3.5 kg of γ-aminopropyltriethoxysilane was added, the pH was adjusted to 4, and the reaction was carried out at 75 °C for 2.5 h. After washing, drying and grinding, 42 kg of Si-CNC nanocomposite was obtained.

[0052] The preparation method of graphitic carbon nitride supported iron oxide nanocomposite is as follows:

[0053] A1. Using 20 kg of melamine as a precursor, calcination at 500 °C for 3 hours yielded 10 kg of graphitic carbon nitride powder.

[0054] A2. Add 10 kg of graphitic carbon nitride powder to 300 L of 0.2 mol / L ferric nitrate solution and ultrasonically disperse for 20 minutes;

[0055] A3. Add 1.5 kg NaBH4 for reduction, let stand for 7 hours, filter and wash to obtain 14 kg of graphite phase carbon nitride supported iron oxide nanocomposite.

[0056] A sludge dewatering process, the process comprising the following steps:

[0057] S1. Use a weak acid to adjust the pH of the sludge to 5.5 to promote colloidal destabilization;

[0058] S2. Add the sludge dewatering conditioner at 8% of the dry weight of the sludge (i.e., 60 kg), mix and react by high-speed stirring for 4 minutes and low-speed stirring for 9 minutes, and let stand for 10 minutes.

[0059] S3. Dewater the sludge by filter press, with the filter press pressure controlled at 0.5 MPa.

[0060] Example 2

[0061] 25 kg of modified bentonite, 32.5 kg of Si-CNC nanocomposite, 7.5 kg of graphite phase carbon nitride supported iron oxide nanocomposite, 12.5 kg of iron aluminum sulfate, 4.5 kg of citric acid-oxalic acid composite chelating agent, and 2 kg of sodium phosphate slow-release agent were mixed, granulated, dried, and packaged after ball milling.

[0062] in

[0063] The modified bentonite was prepared as follows: 40 kg of bentonite was dispersed in 400 L of deionized water, 500 g of silane coupling agent was added, and then 250 g of ammonium persulfate and 2.5 kg of polyacrylamide monomer were added for in-situ graft polymerization. The reaction temperature was 60 °C, and the mixture was stirred for 4 hours. After drying, the mixture was pulverized and sieved to obtain 42.5 kg of modified bentonite.

[0064] The preparation method of Si-CNC nanocomposite is as follows: 40 kg of microcrystalline cellulose was swollen in 350 L of dilute sulfuric acid, hydrothermally treated at 120 °C for 4 h, 4 kg of γ-aminopropyltriethoxysilane was added, the pH was adjusted to 5, and the reaction was carried out at 80 °C for 2 h. After washing, drying and grinding, 42.5 kg of Si-CNC nanocomposite was obtained.

[0065] The preparation method of graphitic carbon nitride supported iron oxide nanocomposite is as follows:

[0066] A1. Using 20 kg of melamine as a precursor, calcination at 550 °C for 2 hours yielded 10.5 kg of graphitic carbon nitride powder.

[0067] A2. Add 10.5 kg of graphitic carbon nitride powder to 300 L of 0.3 mol / L ferric nitrate solution and ultrasonically disperse for 30 minutes;

[0068] A3. Add 1.75 kg NaBH4 for reduction, let stand for 8 hours, filter and wash to obtain 14.5 kg of graphite phase carbon nitride supported iron oxide nanocomposite.

[0069] A sludge dewatering process, the process comprising the following steps:

[0070] S1. Use a weak acid to adjust the pH of the sludge to 6.0 to promote colloidal breakdown and stabilization;

[0071] S2. Add the sludge dewatering conditioner at 10% of the dry weight of the sludge (i.e., 75 kg), mix and react by high-speed stirring for 5 minutes and low-speed stirring for 10 minutes, and let stand for 13 minutes.

[0072] S3. Dewater the sludge by filter press, with the filter press pressure controlled at 0.65 MPa.

[0073] Example 3

[0074] 30 kg of modified bentonite, 40 kg of Si-CNC nanocomposite, 10 kg of graphite phase carbon nitride supported iron oxide nanocomposite, 15 kg of iron aluminum sulfate, 6 kg of citric acid-oxalic acid composite chelating agent, and 3 parts of sodium phosphate slow-release agent were mixed, granulated, dried and packaged after ball milling.

[0075] in

[0076] The modified bentonite was prepared as follows: 40 kg of bentonite was dispersed in 440 L of deionized water, 600 g of silane coupling agent was added, and then 300 g of ammonium persulfate and 3.0 kg of polyacrylamide monomer were added for in-situ graft polymerization. The reaction temperature was 65 °C, and the mixture was stirred for 5 hours. After drying, the mixture was pulverized and sieved to obtain 43 kg of modified bentonite.

[0077] The preparation method of Si-CNC nanocomposite is as follows: 40 kg of microcrystalline cellulose was swollen in 400 L of dilute sulfuric acid, hydrothermally treated at 125 °C for 3 h, 4.5 kg of γ-aminopropyltriethoxysilane was added, the pH was adjusted to 5, and the reaction was carried out at 75-85 °C for 2.5 h. After washing, drying and grinding, 43 kg of Si-CNC nanocomposite was obtained.

[0078] The preparation method of graphitic carbon nitride supported iron oxide nanocomposite is as follows:

[0079] A1. Using 20 kg of melamine as a precursor, calcination at 600 °C for 1 hour yielded 11 kg of graphitic carbon nitride powder.

[0080] A2. Add 11 kg of graphitic carbon nitride powder to 300 L of 0.4 mol / L ferric nitrate solution and ultrasonically disperse for 40 minutes;

[0081] A3. Add 2.0 kg NaBH4 for reduction, let stand for 9 hours, filter and wash to obtain 15 kg of graphite phase carbon nitride supported iron oxide nanocomposite.

[0082] A sludge dewatering process, the process comprising the following steps:

[0083] S1. Use a weak acid to adjust the pH of the sludge to 6.0 to promote colloidal breakdown and stabilization;

[0084] S2. Add the sludge dewatering conditioner at 12% of the dry weight of the sludge (i.e., 90 kg), mix and react by high-speed stirring for 6 minutes and low-speed stirring for 11 minutes, and let stand for 15 minutes.

[0085] S3. Dewater the sludge by filter press, with the filter press pressure controlled at 0.8 MPa.

[0086] Comparative Example 1

[0087] The difference from Example 2 is that the bentonite is not modified, but the other preparation methods and parameters are the same as in Example 2.

[0088] Comparative Example 2

[0089] The difference from Example 2 is that the Si-CNC nanocomposite is removed, while the other preparation methods and parameters are the same as in Example 2.

[0090] Comparative Example 3

[0091] The difference from Example 2 is that steps A2 and A3 are omitted, and graphitic carbon nitride material without iron loading is used. Other components are the same, and other preparation methods and parameters are consistent with Example 2.

[0092] The data results of the treated sludge are shown in Table 1.

[0093] Table 1 Experimental Results

[0094]

[0095] Compared with Example 2, Comparative Example 1 uses unmodified bentonite with a smaller specific surface area, fewer active groups, stronger hydrophilicity, and poor bridging performance, which significantly reduces its adsorption and dehydration aid effects.

[0096] Compared with Example 2, Comparative Example 2 lacks the Si-CNC nanocomposite, thus losing its triple function of "skeleton support + hydrophilicity regulation + nanopore adsorption", resulting in blocked dehydration path, increased water content, and difficulty in detaching the mud cake.

[0097] Compared with Example 2, the graphitic carbon nitride material without Fe loading lacks magnetic flocculation ability and Fenton-like auxiliary reaction ability, weakening the synergistic adsorption destabilization effect, resulting in increased impurities and water content in the filtrate.

[0098] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention. Technical aspects, shapes, and structures not described in detail in this invention are all well-known technologies.

Claims

1. A sludge dewatering conditioner, characterized in that, The raw materials include the following parts by weight: 20-30 parts modified bentonite, 25-40 parts Si-CNC nanocomposite, 5-10 parts graphite phase carbon nitride supported iron oxide nanocomposite, 10-15 parts iron aluminum sulfate, 3-6 parts citric acid-oxalic acid composite chelating agent, and 1-3 parts sodium phosphate slow-release agent. The modified bentonite is modified by in-situ graft polymerization of ammonium persulfate and polyacrylamide monomer, and the graphite phase carbon nitride supported iron oxide nanocomposite is obtained by calcining melamine and then calcining it again with iron ions. The Si-CNC nanocomposite is prepared as follows: microcrystalline cellulose is swollen in dilute acid, hydrothermally treated at 115-125℃ for 3-5 hours, γ-aminopropyltriethoxysilane is added, the pH is adjusted to 4-5, and the reaction is carried out at 75-85℃ for 1.5-2.5 hours. After washing, drying and grinding, the Si-CNC nanocomposite is obtained.

2. The sludge dewatering conditioner according to claim 1, characterized in that, The modified bentonite is prepared as follows: Bentonite is dispersed in deionized water, a silane coupling agent is added, and then ammonium persulfate and polyacrylamide monomer are added for in-situ graft polymerization. The reaction temperature is 55-65℃, and the mixture is stirred for 3-5 hours. After drying, the mixture is pulverized and sieved to obtain the modified bentonite.

3. The sludge dewatering conditioner according to claim 2, characterized in that, The mass ratio of bentonite to deionized water is 1:(9-11).

4. The sludge dewatering conditioner according to claim 1, characterized in that, The preparation method of the graphitic carbon nitride-supported iron oxide nanocomposite is as follows: A1. g-C3N4 powder was prepared by calcining melamine at 500-600℃ for 1-3 hours using melamine as a precursor. A2. Add g-C3N4 to 0.2-0.4 mol / L ferric nitrate solution and ultrasonically disperse for 20-40 minutes; A3. Add NaBH4 for reduction, allow to stand for 7-9 hours, filter and wash to obtain graphite phase carbon nitride supported iron oxide nanocomposite.

5. A method for preparing a sludge dewatering conditioner, used to prepare the sludge dewatering conditioner according to any one of claims 1-4, characterized in that, Includes the following steps: Modified bentonite, Si-CNC nanocomposite, graphitic carbon nitride supported iron oxide nanocomposite, iron aluminum sulfate, citric acid-oxalic acid composite chelating agent, and sodium phosphate slow-release agent were mixed, granulated, dried, and packaged after ball milling.

6. The method for preparing a sludge dewatering conditioner according to claim 5, characterized in that, The granulation particle size is controlled between 80-120 μm.

7. The method for preparing a sludge dewatering conditioner according to claim 5, characterized in that, The granulation speed is 35-45 rpm, and the time is 20-25 min.

8. A sludge dewatering process, characterized in that, The process includes the following steps: S1. Use a weak acid to adjust the pH of the sludge to 5.5-6.0 to promote colloidal stabilization; S2. Add the sludge dewatering conditioner at 8-12% of the dry weight of the sludge, mix and react by high-speed stirring for 4-6 minutes and low-speed stirring for 9-11 minutes, and let stand for 10-15 minutes. S3. Dewater the sludge by filter press, with the filter press pressure controlled at 0.5-0.8 MPa.

9. The sludge dewatering process according to claim 8, characterized in that, In step S2, the high-speed stirring speed is 150-250 rpm, and the low-speed stirring speed is 40-60 rpm.

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