A polysilicate sludge conditioner, its preparation method and use

Abstract

The application provides a polysilicate sludge conditioner, a preparation method and application thereof, and belongs to the technical field of sludge treatment. The conditioner is composed of modified biochar, modified magnesium polysilicate and zirconium-iron sol; the mass ratio of the modified biochar and the modified magnesium polysilicate is 1-3:3-10; the mass ratio of the zirconium-iron sol to the sum of the mass of the former two is 1-2:2-5. The polysilicate sludge conditioner is used for the method for strengthening pretreatment sludge, which comprises the following steps: S1, adjusting the pH of the sludge to 3.0-4.0 by using acid and then adding calcium dihydrogen phosphate; S2, adding the modified biochar and the modified magnesium polysilicate in the sludge; then adding the zirconium-iron sol and stirring and reacting. The sludge conditioner can effectively improve the dewatering performance of the sludge, and greatly reduces the influence of chloride ions on the subsequent drying of the sludge; while ensuring the reduction of sludge organic matter and the improvement of sludge dewatering performance, the comprehensive cost is reduced, and the greatest convenience is provided for the subsequent treatment.

Description

Technical Field

[0001] This invention relates to the technical field of sludge treatment, and in particular to a polysilicate sludge conditioner, its preparation method, and its application in enhancing pretreated sludge. Background Technology

[0002] With the rapid increase in the number of urban wastewater treatment plants, the treatment and disposal of excess sludge has become one of the main factors hindering the development of the wastewater treatment industry. Regardless of the final disposal route chosen, sludge dewatering and volume reduction will be the most crucial step in the entire sludge treatment process. Sludge dewatering significantly reduces the moisture content of the sludge cake and shrinks its volume, thereby reducing sludge transportation costs, extending the lifespan of sludge landfills, and increasing the calorific value during sludge incineration, thus lowering the final disposal costs. Therefore, the screening of highly efficient sludge dewatering conditioning agents is of significant guiding importance for improving sludge dewatering efficiency, reducing energy consumption, and lowering sludge treatment costs.

[0003] Sludge has a high water content, and the strong interaction between water molecules and the surface of solid particles makes sludge dewatering difficult, especially for high-organic-matter sludge in northern regions, which has a high content of EPS (extracellular polymeric substances, polymers composed of proteins, polysaccharides, and small amounts of lipids, nucleic acids, and humic substances). Loose EPS (LB-EPS) mainly consists of sticky capsules, a mucus layer, and surface macromolecules, which significantly affect sludge viscosity and increase the difficulty of subsequent dewatering. Currently, methods to reduce sludge water content include chemical, physical, and biological methods. Among these, chemical methods, especially the application of chemical conditioners, provide important support for subsequent mechanical dewatering.

[0004] Efficient dewatering of high-organic-matter sludge remains a global challenge. The composition, physicochemical properties, and other external factors of dewatered sludge all affect its dewatering performance. Chemical conditioning is an important and commonly used method for improving sludge dewatering performance. Despite extensive research on the chemical conditioning of sludge, many shortcomings still exist. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention provides a polysilicate sludge conditioner, its preparation method, and its applications. The sludge conditioner of this invention effectively improves the dewatering performance of sludge and significantly reduces the impact of chloride ions on subsequent sludge drying. While ensuring the reduction of sludge organic matter and the improvement of sludge dewatering performance, it also reduces overall costs and provides maximum convenience for subsequent treatment.

[0006] The technical solution of the present invention is as follows:

[0007] A polysilicate sludge conditioner, the conditioner being composed of modified biochar, modified magnesium polysilicate, and zirconium-iron sol;

[0008] The mass ratio of the modified biochar to the modified magnesium polysilicate is 1-3:3-10;

[0009] The mass ratio of the zirconium-iron sol to the sum of the masses of the former two is 1-2:2-5.

[0010] Furthermore, the method for preparing the modified biochar includes the following steps:

[0011] A1: First, add the straw to distilled water and soak for 12-15 hours;

[0012] A2: Add mercaptoethylamine solution to it and react at 120-160℃ and 40-60 bar for 8-10 hours. Then, use hydrothermal carbonization technology to make modified hydrothermal carbon.

[0013] A3: Wash with distilled water until the washing solution is free of amines;

[0014] A4: Finally, dry to constant weight in a vacuum environment at 30-40℃, and then grind to obtain modified biochar.

[0015] Preferably, the concentration of the mercaptoethylamine solution in step A2 is 150-200 mg / L, and the mass-to-volume ratio of the straw to the mercaptoethylamine solution is 1-3:15-18 kg / L.

[0016] Furthermore, the preparation method of the modified magnesium polysilicate includes the following steps:

[0017] B1: Dissolve sodium silicate in water to obtain a water glass solution, then gradually add it to a 20% dilute sulfuric acid solution and stir at 30-40℃ until the solution changes color;

[0018] B2: Add magnesium sulfate and stir for 2-3 hours;

[0019] B3: Adjust the alkalinity of the solution to 50% with sodium hydroxide to obtain a magnesium polysilicate solution;

[0020] B4: Modification of magnesium polysilicate by adding sodium sulfate and potassium sulfate solution;

[0021] B5: Dry in an oven, then grind to obtain modified magnesium polysilicate.

[0022] Preferably, in step B1, the mass ratio of sodium silicate to water is 1-2:15-20;

[0023] In step B2, the amount of magnesium sulfate added is such that nMg:nSi = 7:1 in the system;

[0024] In step B4, the volume ratio of magnesium polysilicate solution to sodium sulfate and potassium sulfate solution is 30:0.5-1:0.5-1.

[0025] More preferably, in step B4, the concentration of sodium sulfate is 18-24 g / L, most preferably 20 g / L; and the concentration of potassium sulfate solution is 18-24 g / L, most preferably 20 g / L.

[0026] Furthermore, the preparation method of the zirconium-iron sol includes the following steps:

[0027] C1: Add epoxy silane to ethanol and stir to dissolve;

[0028] C2: Adjust the pH of the solution to 3.0-3.5 using dilute hydrochloric acid;

[0029] C3: Add zirconium acetate solution dropwise to this solution and stir at 50-70℃;

[0030] C4: After stirring for 0.5-1.5 hours, add monolauryl phosphate, continue stirring, and simultaneously add ferric acetate solution dropwise;

[0031] C5: After 5-7 hours, stop stirring. The reaction is complete, and zirconium-iron sol is obtained.

[0032] Preferably, in step C1, the volume ratio of the epoxy silane to ethanol is 1-3:40-50;

[0033] In step C3, the amount of zirconium acetate solution added is 1.0-1.5 vt% of ethanol;

[0034] In step C4, the amount of monolauryl phosphate added is 0.1-1.0 wt% of ethanol, and the amount of ferric acetate added is 1.0-1.5 wt% of ethanol.

[0035] More preferably, the concentration of the zirconium acetate solution in step C3 is 4-6 g / L, most preferably 5 g / L; and the concentration of the ferric acetate solution in step C4 is 4-6 g / L, most preferably 5 g / L.

[0036] Furthermore, after preparing modified biochar, modified magnesium polysilicate, and zirconium-iron sol respectively, the modified biochar and modified magnesium polysilicate were mixed evenly using a stirring device and stored at room temperature; the zirconium-iron sol was stored separately.

[0037] More preferably, the modified biochar and modified magnesium polysilicate need to be ground to a particle size of less than 2 mm.

[0038] The present invention also provides the application of the polysilicate sludge conditioner, namely, for enhancing the pretreatment of sludge.

[0039] Furthermore, the specific steps for using the polysilicate sludge conditioner to enhance the pretreatment of sludge are as follows:

[0040] S1. After adjusting the pH of the sludge to 3.0-4.0 with acid, add 0.1 g / L of calcium dihydrogen phosphate;

[0041] S2. Add the polysilicate sludge conditioner: First, add modified biochar and modified magnesium polysilicate to the sludge at a rate of 10-20g per 1L of sludge, and stir for 20-40 minutes; then add zirconium-iron sol at a rate of 5-10g per 1L of sludge, and stir for 0.5-1 hour.

[0042] Preferably, the acid used in step S1 is sulfuric acid (analytical grade, 1 mol / L) or phosphoric acid; calcium dihydrogen phosphate is analytical grade, or other soluble agents that do not significantly change the pH of the sludge and do not introduce other pollutants can be used instead of calcium dihydrogen phosphate.

[0043] The beneficial technical effects of this invention are as follows:

[0044] 1. This invention, through the acidification treatment in step S1, can solubilize the extracellular polymers of sludge, break down sludge flocs, and simultaneously facilitate the release of intracellular water due to cell rupture caused by acidification, thereby improving sludge dewatering performance. Sulfuric acid is used to adjust the pH; any non-volatile acid, such as phosphoric acid, can be used. The addition of calcium ions reacts with anions in the sludge to form insoluble precipitates, thus promoting solid-liquid separation of the sludge. Furthermore, calcium ions can alter the charge properties of the sludge, making it easier to aggregate and settle.

[0045] 2. The modified biochar of this invention is prepared using mercaptoethylamine and biochar as modifying materials. Activated sludge particles are usually negatively charged, and there is electrostatic repulsion between the particles. Modified biochar contains a large number of cations, which, when applied to municipal sludge, can neutralize the large amount of negative charge in the sludge, condition the sludge, and improve its settling performance. The adsorption performance of the modified biochar is significantly improved, especially for heavy metal ions in water, such as lead, cadmium, and mercury, with a high removal rate. While absorbing heavy metal ions, the modified biochar can also promote the enlargement of sludge flocs, thereby improving the dewatering performance of the sludge.

[0046] The thiol group (-SH) is a strongly reducing functional group that can form stable complexes with heavy metal ions. Therefore, the surface of biochar modified with mercaptoethylamine will have more -SH functional groups, thereby increasing the surface activity and hydrophilicity of the biochar. At the same time, the addition of biochar can increase the calorific value of sludge, which is beneficial for subsequent drying and incineration.

[0047] 3. The modified polysilicate of the present invention is prepared using polysilicate as a matrix and sodium sulfate and potassium sulfate as modifying materials. Sodium sulfate and potassium sulfate provide sodium and potassium ions, respectively, which have high solubility in water and produce a neutral solution that does not affect the pH value of the solution. By selectively adjusting the alkalinity in step B3, the durability and stability of the polysilicate can be improved, and it can also have better adsorption and flocculation capabilities.

[0048] Modified polysilicate possesses both the charge neutralization ability of metal ions and the adsorption and bridging ability inherent in long chains, thereby enhancing the flocculation effect of sludge particles and effectively improving sludge dewatering performance. Modified magnesium polysilicate exerts bridging, adsorption, and charge neutralization effects to increase the dewaterability of sludge, thus improving dewatering efficiency; the roles of magnesium, sodium, and potassium ions in polysilicate are also considered.

[0049] 4. This invention, through the addition of modified biochar and modified magnesium polysilicate in steps S1 and S2, disrupts the flocculent structure of the sludge. Finally, various impurities in the sludge are aggregated and precipitated using a zirconium-iron sol. While ensuring a reduction in sludge organic matter and improving sludge dewatering performance, this invention also lowers overall costs and provides maximum convenience for subsequent treatment.

[0050] 5. The zirconium-iron sol of this invention can penetrate deep layers of matter, causing organic matter, heavy metal ions, inorganic matter, and microorganisms in the water to aggregate. Subsequently, the aggregated organic matter, heavy metal ions, inorganic matter, and microorganisms precipitate at the bottom of the water, purifying the water and improving the dewaterability of the sludge. This invention reduces the dosage of conditioner and treatment costs, and simplifies the process of reagent preparation. Detailed Implementation

[0051] The present invention will now be described in detail with reference to the embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. 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.

[0052] Example 1:

[0053] This embodiment provides a polysilicate sludge conditioner, which is composed of modified biochar, modified magnesium polysilicate, and zirconium-iron sol. The preparation methods of each component are as follows.

[0054] A. The preparation process of modified biochar includes the following steps:

[0055] A1: First, add 1kg of straw to distilled water and soak for 12 hours. After soaking, drain all the water.

[0056] A2: Add 10L of mercaptoethylamine solution (200mg / L) to it, react at 150℃ and 50bar for 8h, and then make it into modified hydrothermal carbon by hydrothermal carbonization technology.

[0057] A3: Wash with distilled water until the washing solution is free of amines;

[0058] A4: Finally, the modified biochar was dried to constant weight in a vacuum environment at 30°C and then ground to obtain the modified biochar.

[0059] B. A method for preparing modified magnesium polysilicate, comprising the following steps:

[0060] B1: Dissolve 50g of sodium silicate in 1kg of water to obtain a water glass solution, then gradually add it to a 20% dilute sulfuric acid solution and stir at 30℃ until the solution changes color;

[0061] B2: Add magnesium sulfate and stir for 2 hours;

[0062] B3: Adjust the alkalinity of the solution to 50% with sodium hydroxide to obtain a magnesium polysilicate solution;

[0063] B4: Modification of magnesium polysilicate by adding sodium sulfate solution (20 g / L) and potassium sulfate solution (20 g / L);

[0064] B5: Dry in an oven, then grind to obtain modified magnesium polysilicate.

[0065] The basicity of the polysilicate is 50%, the amount of magnesium sulfate added in step B2 is such that the nMg:nSi ratio in the system is 7:1, and the volume ratio of the polysilicate solution to the sodium sulfate and potassium sulfate solution in step B4 is 30:0.5:1.

[0066] C. The preparation method of zirconium-iron sol includes the following steps:

[0067] C1: Add 20 mL of epoxy silane to 1 L of ethanol and stir to dissolve;

[0068] C2: Adjust the pH of the solution to 3.0 using dilute hydrochloric acid;

[0069] C3: Add 10 mL of zirconium acetate solution (5 g / L) dropwise to the solution and stir at 60 °C;

[0070] C4: After stirring for 1 hour, add 1 g of monolauryl phosphate, continue stirring, and simultaneously add 10 mL of ferric acetate solution (5 g / L).

[0071] C5: After 6 hours, stop stirring; the reaction is complete, and zirconium-iron sol is obtained.

[0072] D. After preparing modified biochar, modified magnesium polysilicate and zirconium-iron sol respectively, grind the modified biochar and modified magnesium polysilicate to a particle size of less than 2 mm, mix the modified biochar and modified magnesium polysilicate evenly with a stirring device, and store at room temperature; store the zirconium-iron sol separately.

[0073] The mass ratio of modified biochar to modified magnesium polysilicate is 1:3; the mass ratio of zirconium-iron sol to the sum of the masses of the former two is 1:2.

[0074] Example 2:

[0075] This embodiment provides a polysilicate sludge conditioner, which is composed of modified biochar, modified magnesium polysilicate, and zirconium-iron sol. The preparation methods of each component are as follows.

[0076] A. The preparation process of modified biochar includes the following steps:

[0077] A1: First, add 1 kg of straw to distilled water and soak for 13 hours;

[0078] A2: Add 6L of mercaptoethylamine (150mg / L) to it and react at 120℃ and 60bar for 9h. Then, use hydrothermal carbonization technology to make modified hydrothermal carbon.

[0079] A3: Wash with distilled water until the washing solution is free of amines;

[0080] A4: Finally, the modified biochar was dried to constant weight in a vacuum environment at 35°C and then ground to obtain the modified biochar.

[0081] B. A method for preparing modified magnesium polysilicate, comprising the following steps:

[0082] B1: Dissolve 80g of sodium silicate in 1kg of water to obtain a water glass solution, then gradually add it to a 20% dilute sulfuric acid solution and stir at 35℃ until the solution changes color;

[0083] B2: Add magnesium sulfate and stir for 2.5 hours;

[0084] B3: Adjust the alkalinity of the solution to 50% with sodium hydroxide to obtain a magnesium polysilicate solution;

[0085] B4: Modification of magnesium polysilicate by adding sodium sulfate solution (20 g / L) and potassium sulfate solution (20 g / L);

[0086] B5: Dry in an oven, then grind to obtain modified magnesium polysilicate.

[0087] The basicity of the polysilicate is 50%. In step B2, the amount of magnesium sulfate added is such that the nMg:nSi ratio in the system is 7:1. In step B4, the volume ratio of the polysilicate solution to the sodium sulfate and potassium sulfate solutions is 30:0.8:0.6.

[0088] C. The preparation method of zirconium-iron sol includes the following steps:

[0089] C1: Add 30 mL of epoxy silane to 1 L of ethanol and stir to dissolve;

[0090] C2: Adjust the pH of the solution to 3.0 using dilute hydrochloric acid;

[0091] C3: Add 12 mL of zirconium acetate solution (5 g / L) dropwise to the solution and stir at 60 °C;

[0092] C4: After stirring for 1 hour, add 5g of monolauryl phosphate, continue stirring, and simultaneously add 12mL of ferric acetate solution (5g / L).

[0093] C5: After 6 hours, stop stirring; the reaction is complete, and zirconium-iron sol is obtained.

[0094] D. After preparing modified biochar, modified magnesium polysilicate and zirconium-iron sol respectively, grind the modified biochar and modified magnesium polysilicate to a particle size of less than 2 mm, mix the modified biochar and modified magnesium polysilicate evenly with a stirring device, and store at room temperature; store the zirconium-iron sol separately.

[0095] The mass ratio of modified biochar to modified magnesium polysilicate is 2:3; the mass ratio of zirconium-iron sol to the sum of the masses of the former two is 2:5.

[0096] Example 3:

[0097] This embodiment provides a polysilicate sludge conditioner, which is composed of modified biochar, modified magnesium polysilicate, and zirconium-iron sol. The preparation methods of each component are as follows.

[0098] A. The preparation process of modified biochar includes the following steps:

[0099] A1: First, add 1 kg of straw to distilled water and soak for 15 hours;

[0100] A2: Add 15L of mercaptoethylamine (180mg / L) to it and react at 160℃ and 40bar for 10h. Then, use hydrothermal carbonization technology to make modified hydrothermal carbon.

[0101] A3: Wash with distilled water until the washing solution is free of amines;

[0102] A4: Finally, the modified biochar was dried to constant weight in a vacuum environment at 40°C and then ground to obtain modified biochar.

[0103] B. A method for preparing modified magnesium polysilicate, comprising the following steps:

[0104] B1: Dissolve 120g of sodium silicate in 1kg of water to obtain a water glass solution, then gradually add it to a 20% dilute sulfuric acid solution and stir at 40℃ until the solution changes color;

[0105] B2: Add magnesium sulfate and stir for 3 hours;

[0106] B3: Adjust the alkalinity of the solution to 50% with sodium hydroxide to obtain a magnesium polysilicate solution;

[0107] B4: Modification of magnesium polysilicate by adding sodium sulfate solution (20 g / L) and potassium sulfate solution (20 g / L);

[0108] B5: Dry in an oven, then grind to obtain modified magnesium polysilicate.

[0109] The basicity of the polysilicate is 50%. In step B2, the amount of magnesium sulfate added is such that the nMg:nSi ratio in the system is 7:1. In step B4, the volume ratio of the polysilicate solution to the sodium sulfate and potassium sulfate solutions is 30:1:0.8.

[0110] C. The preparation method of zirconium-iron sol includes the following steps:

[0111] C1: Add 70 mL of epoxy silane to 1 L of ethanol and stir to dissolve;

[0112] C2: Adjust the pH of the solution to approximately 3.0 using dilute hydrochloric acid;

[0113] C3: Add 15 mL of zirconium acetate solution (5 g / L) dropwise to the solution and stir at 60 °C;

[0114] C4: After stirring for 1 hour, add 10g of monolauryl phosphate, continue stirring, and simultaneously add 15mL of ferric acetate solution (5g / L).

[0115] C5: After 6 hours, stop stirring; the reaction is complete, and zirconium-iron sol is obtained.

[0116] D. After preparing modified biochar, modified magnesium polysilicate and zirconium-iron sol respectively, grind the modified biochar and modified magnesium polysilicate to a particle size of less than 2 mm, mix the modified biochar and modified magnesium polysilicate evenly with a stirring device, and store at room temperature; store the zirconium-iron sol separately.

[0117] The mass ratio of modified biochar to modified magnesium polysilicate is 3:5; the mass ratio of zirconium-iron sol to the sum of the masses of the former two is 1:3.

[0118] Application example:

[0119] This application example provides a method for enhancing the pretreatment of sludge using the polysilicate sludge conditioner prepared in Examples 1-3. The specific steps are as follows:

[0120] S1. After adjusting the pH of the sludge to 3.0 with acid, add 0.1 g / L of calcium dihydrogen phosphate;

[0121] S2. Add the polysilicate sludge conditioner: First, add 15g of modified biochar and modified magnesium polysilicate to every 1L of sludge, stir and react for 30min, and the mass ratio of the two is 1:3, 2:3, and 3:5 as shown in Examples 1-3;

[0122] S3. Then continue to add zirconium-iron sol, wherein the mass ratio of zirconium-iron sol to the sum of the previous two is 1:2, 2:5, and 1:3 as shown in Examples 1-3, respectively. Stir for 30 minutes after adding zirconium-iron sol.

[0123] Specifically, the enhanced pretreatment process of this polysilicate sludge conditioner is designed for municipal sludge that is difficult to dewater. It employs acidification pretreatment to break down sludge flocs; the addition of calcium ions reacts with anions in the sludge to generate insoluble precipitates, thus promoting solid-liquid separation; the abundant cations in biochar further neutralize the negative charges in the sludge, while the addition of biochar increases the calorific value of the sludge, facilitating subsequent drying and incineration processes. Furthermore, the modified biochar exhibits significantly improved dewatering capacity and a markedly enhanced removal effect for heavy metals and organic matter; magnesium polysilicate acts as a bridging adsorption and charge neutralization agent, increasing the dewaterability of the sludge and thus improving the dewatering effect. Zirconium-iron sol aggregates organic matter, heavy metal ions, inorganic matter, and microorganisms in the sludge, which ultimately settle at the bottom of the water, further improving the sludge's dewatering performance.

[0124] Comparative Example 1:

[0125] Based on the application example, the polysilicate sludge conditioner was replaced with biochar alone, with a dosage of 15g biochar per 1L of sludge, and the mixture was stirred and reacted for 30min.

[0126] The method for producing biochar is as follows: a) Crush the straw, wash it three times with deionized water, and dry it at 60°C for 5 hours; b) Place the dried straw in an atmosphere furnace for carbonization, wherein a protective gas is introduced into the atmosphere furnace, the temperature is increased by 20°C per minute to reach 500°C, and the residence time is 2 hours to obtain biochar; c) Grind the biochar and sieve it to a particle size of 0.5-1 mm.

[0127] Comparative Example 2:

[0128] Based on the application example, the polysilicate sludge conditioner was replaced with the modified biochar prepared in step A of Example 1 and the modified magnesium polysilicate prepared in step B of Example 1. The dosage was 10g of modified biochar and 5g of modified magnesium polysilicate per 1L of sludge, and the mixture was stirred and reacted for 30min.

[0129] Example of detection:

[0130] Performance tests were conducted on the sludge after enhanced pretreatment, corresponding to the use cases and comparative examples 1 and 2. The test sludge samples before treatment had the following parameters: moisture content 95.8%; organic matter content 53.6%; capillary suction time (CST) 21 s; and sludge specific resistance (SRF) 0.78 × 10⁻⁶. 9 s 2 / g; Zeta potential is -12.8mV.

[0131] The detection method is as follows:

[0132] 1. Organic matter and moisture content of sludge: CJ / T 221-2005 "Test Methods for Sludge from Urban Wastewater Treatment Plants" were adopted;

[0133] 2. Capillary absorption time: This was measured using a CST meter. The specific steps are as follows:

[0134] (1) Determine the solids concentration of the sludge.

[0135] (2) Prepare cationic, anionic and nonionic polyacrylamide flocculant solutions (1g / L).

[0136] (3) Place Whatman 17# filter paper on the bottom polyethylene or polypropylene plastic plate, place a polyethylene or polypropylene plastic plate with electrical contacts on the filter paper, and put the stainless steel inner cylindrical (straight groove) with the smaller diameter end facing down into the round hole of the plastic plate.

[0137] (4) Add the polyacrylamide flocculant solution to a beaker containing sludge at a certain amount (the amount of flocculant added is 0.5‰, 1.0‰, 1.5‰, 2.0‰, 2.5‰, 3.0‰, 3.5‰, and 4.0‰ of the dry weight of the sludge, respectively), and stir with a six-unit mixer at a speed of 100-400 rpm.

[0138] (5) After the sludge is stirred, it is immediately added to the CST trough. The CST meter is turned on and the timing is started. When the timing stops, the time displayed on the CST meter is the CST of the sludge.

[0139] 3. Method for determining sludge specific resistance: Vacuum filtration was used for the determination, with the experimental pressure set at 0.05 MPa. Paper was placed in a Buchner funnel and moistened, ensuring it adhered tightly to the bottom of the funnel. 150 mL of prepared sludge was poured into the funnel, and a direct-flow pump was turned on to start the flow. The volume of filtrate corresponding to different filtration times was recorded. Recording was stopped when the filter cake cracked. The filter cake was weighed, its moisture content was tested, and the sludge specific resistance was calculated.

[0140] 4. Zeta potential: Measured using a Zeta potential meter.

[0141] The test results are shown in Table 1.

[0142] Table 1

[0143] Testing items Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Moisture content / % 82.9 69.7 45.5 36.7 41.2 Organic matter / % 45.1 37.2 25.1 23.6 26.9 Capillary absorption time (CST) / s 18.2 15.7 6.7 6.4 6.8 <![CDATA[Specific Resistance to Filtration of Sludge (SRF) / s 2 / g]]> <![CDATA[0.68×10 9 ]]> <![CDATA[0.62×10 9 ]]> <![CDATA[0.35×10 9 ]]> <![CDATA[0.29×10 9 ]]> <![CDATA[0.38×10 9 ]]> Zeta potential / mV -9.5 -8.7 -2.3 -2.1 -2.6

[0144] As shown in Table 1, the polysilicate sludge conditioner prepared by this invention can effectively improve the dewatering performance of sludge and avoid the influence of chloride ions on subsequent sludge drying. This conditioner material is easy to prepare, the pretreatment process is simple to operate, and it is easy to apply. While ensuring improved sludge dewatering performance, it reduces overall costs and provides maximum convenience for subsequent treatment. The use of this conditioner can be determined according to the specific properties of the activated sludge in the actual application environment.

[0145] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, and for those of ordinary skill in the art, various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. Therefore, the present invention is not limited to the specific details without departing from the general concept defined by the claims and their equivalents.

Claims

1. A polysilicate sludge conditioner, characterized in that, The conditioning agent is composed of modified biochar, modified magnesium polysilicate, and zirconium-iron sol; The mass ratio of the modified biochar to the modified magnesium polysilicate is 1-3:3-10; The mass ratio of the zirconium-iron sol to the sum of the masses of the former two is 1-2:2-5; The preparation method of the zirconium-iron sol includes the following steps: C1: Add epoxy silane to ethanol and stir to dissolve; C2: Adjust the pH of the solution to 3.0-3.5 using dilute hydrochloric acid; C3: Add zirconium acetate solution dropwise to this solution and stir at 50-70℃; C4: After stirring for 0.5-1.5 hours, add monolauryl phosphate, continue stirring, and simultaneously add ferric acetate solution dropwise; C5: After 5-7 hours, stop stirring. The reaction is complete, and zirconium-iron sol is obtained. In step C1, the volume ratio of the epoxy silane to ethanol is 1-3:40-50; In step C3, the amount of zirconium acetate solution added is 1.0-1.5 vt% of ethanol; In step C4, the amount of monolauryl phosphate added is 0.1-1.0 wt% of ethanol, and the amount of ferric acetate added is 1.0-1.5 wt% of ethanol.

2. The polysilicate sludge conditioner according to claim 1, characterized in that, The method for preparing the modified biochar includes the following steps: A1: First, add the straw to distilled water and soak for 12-15 hours; A2: Add mercaptoethylamine solution to it and react at 120-160℃ and 40-60 bar for 8-10 hours. Then, use hydrothermal carbonization technology to make modified hydrothermal carbon. A3: Wash with distilled water until the washing solution is free of amines; A4: Finally, dry to constant weight in a vacuum environment at 30-40℃, and then grind to obtain modified biochar.

3. The polysilicate sludge conditioner according to claim 2, characterized in that, The concentration of the mercaptoethylamine solution in step A2 is 150-200 mg / L, and the mass-to-volume ratio of the straw to the mercaptoethylamine solution is 1-3:15-18 kg / L.

4. The polysilicate sludge conditioner according to claim 1, characterized in that, The preparation method of the modified magnesium polysilicate includes the following steps: B1: Dissolve sodium silicate in water to obtain a water glass solution, then gradually add it to a 20% dilute sulfuric acid solution and stir at 30-40℃ until the solution changes color; B2: Add magnesium sulfate and stir for 2-3 hours; B3: Adjust the alkalinity of the solution to 50% with sodium hydroxide to obtain a magnesium polysilicate solution; B4: Modification of magnesium polysilicate by adding sodium sulfate and potassium sulfate solution; B5: Dry in an oven, then grind to obtain modified magnesium polysilicate.

5. The polysilicate sludge conditioner according to claim 4, characterized in that, In step B1, the mass ratio of sodium silicate to water is 1-2:15-20; In step B2, the amount of magnesium sulfate added is such that nMg:nSi = 7:1 in the system; In step B4, the volume ratio of magnesium polysilicate solution to sodium sulfate and potassium sulfate solution is 30:0.5-1:0.5-1.

6. The polysilicate sludge conditioner according to claim 1, characterized in that, After preparing modified biochar, modified magnesium polysilicate, and zirconium-iron sol, the modified biochar and modified magnesium polysilicate were mixed evenly using a stirring device and stored at room temperature; the zirconium-iron sol was stored separately.

7. The application of the polysilicate sludge conditioner according to any one of claims 1-6, characterized in that, Used to enhance the pretreatment of sludge.

8. The application according to claim 7, characterized in that, The specific steps for using the polysilicate sludge conditioner to enhance the pretreatment of sludge are as follows: S1. After adjusting the pH of the sludge to 3.0-4.0 with acid, add 0.1 g / L of calcium dihydrogen phosphate; S2. Add the polysilicate sludge conditioner: First, add 10-20g of modified biochar and modified magnesium polysilicate to each 1L of sludge, and stir for 20-40min; then add 5-10g of zirconium-iron sol and stir for 0.5-1h.