Riverway silt in-situ solidifying agent and implementation method

Abstract

The application discloses a river silt in-situ curing agent and an implementation method, relates to the technical field of silt curing, and comprises a curing material and a coating layer. The curing material comprises the following components in parts by weight: silicate 20-50 parts, calcium-aluminum hydrotalcite 20-30 parts, cement clinker 25-35 parts, polyacrylamide 2-27 parts, polyaluminum chloride 7-15 parts, tannic acid 1-13 parts, and calcium oxide 5-15 parts. The coating layer comprises three layers and is composed of acrylic high polymer materials. The inner coating layer further comprises a hydrophilic material. The hydrophilic material is silicon dioxide, and the usage amount is 0.5%-3% of the mass of the outer coating layer. Through the intelligent release design of the coating layer, the rapid dehydration and alkaline activation of the calcium oxide, and the gelation-adsorption synergy of the silicate and the hydrotalcite, efficient in-situ silt curing is realized, and multi-component interference under complex environments is resisted.

Description

Technical Field

[0001] The present invention relates to the technical field of silt solidification, and in particular to a river silt in-situ solidifying agent and an implementation method. Background Art

[0002] The main causes of river siltation include both natural and human factors. Natural factors include slower water flow and reduced hydrodynamics, which lead to sediment deposition. Climate change, along with natural disasters such as heavy rains and floods, can also exacerbate river siltation. Human factors include the entry of pollutants such as industrial wastewater, domestic sewage, and agricultural emissions into rivers, leading to the deposition of silt and organic matter. Urbanization and industrialization, along with the discharge of large amounts of waste and hazardous substances into rivers, accelerate the formation of silt.

[0003] Microbial decomposition of organic matter in silt consumes significant amounts of dissolved oxygen, degrading water quality and impacting aquatic life. Pollutants such as heavy metals and organic matter in silt accumulate through the food chain, ultimately harming fish, aquatic plants, and even human health. Mud deposits block river channels, hindering water flow and increasing the frequency of floods. Harmful substances in silt can also generate odors as they accumulate, causing secondary pollution to the surrounding environment.

[0004] Technologies and methods for treating river silt include biodegradation and redox processes, which can effectively reduce or transform harmful substances in silt. Furthermore, using solar drying equipment to dewater silt not only saves energy but also prevents secondary pollution.

[0005] For example, the Chinese patent application number CN201710113222.8 is a method for re-dredging in situ hardened silt in rivers and ponds. The solidification reaction of the silt is delayed by multi-layer coating of a curing agent. After stirring is completed, part of the water in the river and pond is pumped out. Since the curing agent sinks to the bottom of the water, it will not flow away with the water, making the silt conditions in the river and pond suitable for the curing reaction. It is suitable for dredging large rivers and will not waste too much curing agent, which greatly optimizes the river dredging method.

[0006] However, in practice, most river channels are polluted, resulting in a complex composition of silt containing large amounts of heavy metal ions, organic matter, and acid ions. These organic matter and heavy metal ions (such as humic acid and iron ions) in the silt chelate or compete for adsorption with the polyacrylamide and polyaluminum chloride in the curing agent, hindering the gelation reaction. Furthermore, organic matter envelops the coating, hindering its decomposition and making it difficult for the curing agent to function, resulting in poor curing performance. Experiments have found that in complex environments, the curing effect can be reduced to 46% of its original value.

[0007] Another example is Chinese patent application number CN202110081486.6, which describes a water conservancy river sludge treatment and curing agent and its preparation method. By exfoliating calcium aluminum hydrotalcite (cationic sheets) and montmorillonite (anionic sheets), the compound undergoes layer-by-layer self-assembly via electrostatic adsorption, forming a complex with high adsorption and surface hydroxyl groups. This complex consolidates heavy metal ions in the sludge through ion exchange and complexation, enhancing the agglomeration of inorganic particles. Furthermore, through anionic polyacrylonitrile copolymer fibers, it binds to polar components in the sludge through electrostatic adsorption and hydrogen bonding. Its micro-nanoscale fiber structure provides a high specific surface area, further enhancing adsorption capacity, and improves the mechanical strength of the cured product through physical interweaving.

[0008] Similarly, in a sludge environment with high salt content, salt ions compete for the adsorption of Ca on calcium aluminum hydrotalcite. 2+ , destroying the complexation effect, resulting in insufficient strength of the solidified body, easy cracking of the surface, and increased risk of heavy metal dissolution. Summary of the Invention

[0009] The embodiments of the present application solve the problem of failure of curing agents in complex ions in complex environments in the prior art by providing an in-situ curing agent for river silt and an implementation method, thereby achieving an efficient curing effect in a complex environment.

[0010] The present application provides an in-situ curing agent for river silt, including a curing material and a coating layer. The curing material includes the following components by weight: 20-50 parts of silicate, 20-30 parts of calcium aluminum hydrotalcite, 25-35 parts of cement clinker, 2-27 parts of polyacrylamide, 7-15 parts of polyaluminum chloride, 1-13 parts of tannic acid, and 5-15 parts of calcium oxide.

[0011] The coating layer includes three layers, which are composed of acrylic polymer materials. The inner coating layer also contains hydrophilic material; the hydrophilic material is silicon dioxide, and the usage amount is 0.5%-3% of the mass of the outer coating layer.

[0012] Furthermore, the silicate includes sodium silicate, calcium silicate and magnesium fluorosilicate, the weight ratio of sodium silicate, calcium silicate and magnesium fluorosilicate is 1:0.5:0.2, the calcium aluminum hydrotalcite is Ca-Al nitrate type hydrotalcite; and the particle size of calcium oxide is 1-200 microns.

[0013] Furthermore, the acrylic polymer material is polymerized by unsaturated acrylic ester monomers and carboxyl-containing monomers, the unsaturated acrylic ester monomers are alkyl acrylates, the carboxyl-containing monomers are acrylic acid, and the mass ratio of the unsaturated acrylic ester monomers to the carboxyl-containing monomers is 2:1.

[0014] Furthermore, the weight average molecular weight of the acrylic polymer material in the middle layer and the inner layer coating is 140,000-150,000 and the glass transition temperature is 30-60°C, and the weight average molecular weight of the acrylic polymer material in the outer layer coating is 130,000-140,000 and the glass transition temperature is 5-30°C.

[0015] Furthermore, the inner coating layer also contains 5-15 parts by weight of calcium oxide.

[0016] Furthermore, the inner coating layer also contains 2-8 parts by weight of sulfobetaine.

[0017] Furthermore, the particle size of sulfobetaine is 50-200 nm, and sulfobetaine is added together with calcium oxide in the form of nano-powder.

[0018] Furthermore, the calcium oxide includes small-particle calcium oxide and large-particle calcium oxide, the particle size of the small-particle calcium oxide is 1-10 microns, the large particle size is 50-200 microns, and the mass ratio of small-particle calcium oxide to large-particle calcium oxide is 3:7.

[0019] Furthermore, small-sized calcium oxide particles were sprayed with a 5% sulfobetaine solution and dried to form a charge-controlled coating layer.

[0020] Large-particle calcium oxide and sulfobetaine are mixed in a weight ratio of 7:1, the spraying pressure is 0.3 MPa, the coating layer thickness is 50-80 μm, and hot air drying is performed at 80° C. for 1 hour.

[0021] The above-mentioned construction method of a river silt in-situ solidifying agent comprises the following specific steps:

[0022] S1. Detecting the pH of the pond to be desilted and adjusting the pH to be less than 11, uniformly stirring the silt and curing agent in the pond to be desilted by a pontoon-type excavator mixer traveling in the pond to be desilted;

[0023] S2. Pumping out part of the water in the pond to be desilted, so that the moisture content of the silt in the pond to be desilted is 85%;

[0024] S3. Testing the pH of the sludge in the river and pond to be desilted, and adding additional calcium oxide to make the pH greater than 12, and then allowing the curing agent to undergo a curing reaction, the curing reaction time being between 1 and 3 hours;

[0025] S4. Digging out the solidified silt in the pond to be desilted by an excavator traveling in the pond to be desilted.

[0026] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0027] First, through the intelligent release design of the coating layer, the rapid dehydration and alkaline activation of calcium oxide, and the gelation-adsorption synergy of silicate and hydrotalcite, efficient in-situ solidification of sludge is achieved, and it resists multi-component interference in complex environments.

[0028] Secondly, the timing when the inner coating layer takes effect is almost the same as the timing when the curing material takes effect. It can not affect its effect in the inner coating layer, but can also take effect in advance, and has a synergistic effect with the new component to increase the alkali resistance of the coating layer.

[0029] Third, the OH- released by small-particle CaO rapidly raises the local pH to 12, triggering the hydrophobic-hydrophilic transition of sulfobetaine. Its hydrophobic groups adsorb onto the surface of small-particle CaO, forming a "nanoscale charge shield" that reduces competitive adsorption with PAM. Smaller CaO particles produce higher local pH concentrations, ultimately improving the overall effect. Nanosized CaO particles (200-500nm) produce virtually no competitive adsorption of PAM, and the combination of sulfobetaine and small-particle CaO further enhances the curing effect. Large-particle CaO slowly hydrates, continuously releasing Ca2+ (maintaining a concentration of 100-200 mg / L) during the mid-curing period (1-3 hours).

[0030] Fourthly, by coating sulfobetaine on calcium oxide particles, calcium supply is optimized in stages. Sulfobetaine (50-200 nm) is preferentially adsorbed on the CaO surface, and the negative charge repulsion forces PAM (10-50 μm) to preferentially adsorb sludge particles, which improves the flocculation efficiency by more than 30%. Small and large particle size CaO release Ca in stages. 2+ , inhibiting the formation of CSH, so that in the 0-1h of the reaction, it is mainly the small-particle CaO that releases Ca 2+ Nano-AFt (10-100 nm) is generated to fill micron-sized pores. During the reaction time of 1-3 hours, large-particle CaO continuously supplies calcium to generate micron-AFt (1-5μm) to build a rigid skeleton. Calcium is supplied in stages to match the gelation reaction requirements and inhibit side reactions. Charge repulsion guides the efficient adsorption of PAM to optimize the microstructure. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the XRD pattern of Experiment 7;

[0032] Figure 2 This is the XRD pattern of Experiment 5;

[0033] Among them, 9.1°, 15.8° and 22.9° are characteristic peaks of ettringite. DETAILED DESCRIPTION

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains; the terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention; the term "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0035] Example 1: An in-situ curing agent for river silt, comprising a curing material and a coating layer, wherein the curing material comprises the following components by weight: 20-50 parts of silicate, 20-30 parts of calcium aluminum hydrotalcite, 25-35 parts of cement clinker, 2-27 parts of polyacrylamide, 7-15 parts of polyaluminum chloride, 1-13 parts of tannic acid, and 5-15 parts of calcium oxide (CaO);

[0036] The silicate comprises sodium silicate, calcium silicate and magnesium fluorosilicate, the weight ratio of sodium silicate, calcium silicate and magnesium fluorosilicate is 1:0.5:0.2, the calcium aluminum hydrotalcite is Ca-Al nitrate type hydrotalcite; the particle size of calcium oxide is 1-200 microns.

[0037] The coating layer consists of three layers, which are made of acrylic polymer materials. The inner coating layer also contains hydrophilic material; the hydrophilic material is silicon dioxide, and the amount used is 0.5%-3% of the mass of the outer coating layer;

[0038] The acrylic polymer material is polymerized by unsaturated acrylic ester monomer and carboxyl-containing monomer, wherein the unsaturated acrylic ester monomer is alkyl acrylate and the carboxyl-containing monomer is acrylic acid, and the mass ratio of the unsaturated acrylic ester monomer to the carboxyl-containing monomer is 2:1;

[0039] The weight average molecular weight of the acrylic polymer material in the middle layer and the inner layer coating is 140,000-150,000; the glass transition temperature is 30-60°C; the weight average molecular weight of the acrylic polymer material in the outer layer coating is 130,000-140,000; the glass transition temperature is 5-30°C.

[0040] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0041] Through the intelligent release design of the coating layer, the rapid dehydration and alkaline activation of calcium oxide, and the gelation-adsorption synergy of silicate and hydrotalcite, efficient in-situ solidification of sludge is achieved, and it can resist multi-component interference in complex environments.

[0042] The coating layer adopts three layers of acrylic high molecular materials, and the gradient design of molecular weight and glass transition temperature (Tg) realizes staged release: the high molecular weight (140-150 million) and high Tg (30-60°C) make the middle layer stable in a dry environment, while the inner layer contacts moisture, the hydrophilic silicon dioxide accelerates water absorption and swelling, the inner layer degrades, and the solidified material (calcium oxide, silicate, etc.) is released; the lower molecular weight (130-140 million) and Tg (5-30°C) give flexibility, which gradually breaks down at ambient temperature or mechanical disturbance, prolongs the release period of the curing agent, and avoids the reaction out of control caused by one-time release;

[0043] The staged release optimizes the reaction process: and then uses calcium oxide to first absorb water and release heat, which increases the temperature of the sludge and reduces the water content, and then the silicate and hydrotalcite fully react in the alkaline environment to form a dense structure to complete the curing process, the utilization rate of the curing agent is improved, the sludge curing speed and strength are significantly enhanced, and the component waste is reduced.

[0044] Calcium oxide (CaO) reacts with water to generate Ca(OH)2, which rapidly reduces the water content of the sludge and accelerates the hydration reaction of other components (cement clinker) through heat release; the generated Ca(OH)2 raises the pH of the system to above 12, promotes the dissociation of silicate (sodium silicate releases SiO3 2- ), and reacts with Ca 2+ to generate C-S-H gel;

[0045]

[0046] Ca 2+ +SiO3 2- +H2O→(CaO·SiO2·H2O);

[0047] The carboxylate (-COO - ) and phenolic hydroxyl (-OH) of humic acid, fatty acid and other organic matters are neutralized by OH - to form insoluble salts (calcium humate), which destroys the molecular structure of organic matters; and in an alkaline environment, esters, oils and other organic matters are hydrolyzed to decompose into water-soluble carboxylate and alcohol, which destroys the macromolecular structure of organic matters, reduces the physical wrapping of the curing agent coating layer, and Ca 2+ binds to negatively charged organic colloid particles (humic acid colloid) through electrostatic interaction to form flocculation, accelerate sedimentation, and accelerate the hydrolysis of the acrylic coating layer in an alkaline environment.

[0048] CaO reacts with calcium silicate and tricalcium silicate in cement clinker to further generate gel network, enhance the compactness of the cured body; make the sludge dewatering efficiency improve, the gelation reaction rate accelerate, and the ultimate compressive strength of the cured body improve; sodium silicate (Na2SiO3) provides a soluble silicon source, which generates SiO32- with Ca 2+ forms C-S-H gel; calcium silicate (CaSiO3) directly participates in hydration, early strength contributor; 2CaSiO3+4H2O→3CaO·2SiO2·3H2O+Ca(OH)2;

[0049] magnesium fluorosilicate (MgSiF6): release F - and Mg 2+ , Mg 2+ can replace hydrotalcite interlayer ions, enhance its stability; F - with Ca 2+ generate CaF2microcrystalline, fill the pores;

[0050] MgSiF6→Mg 2+ + SiF6 2- ;

[0051] SiF6 2- + 2H2O→SiO2+ 6F - + 4H + ;

[0052] Ca 2+ + 2F - →CaF2;

[0053] nitrate type hydrotalcite ([CaAl(OH)6]NO3·nH2O) by ion exchange adsorption sludge Cl - , SO4 2- and other harmful anions, reduce pollution risk, hydrotalcite in alkaline environment partial dissolution, release Ca 2+ and Al 3+ , Ca 2+ supplement cementation reaction, Al 3+ and polyacrylamide (PAM) form complex, enhance flocculation effect;

[0054] [CaAl(OH)6]NO3·nH2O+Cl - →[CaAl(OH)6]Cl·nH2O+ NO3 - ;

[0055] [CaAl(OH)6]NO3·nH2O+OH - →Ca 2+ +Al(OH)4 - +NO3 - +(n+2)H2O;

[0056]

[0057] CaO provides initial Ca 2+and OH - , activating silicate dissociation and hydrotalcite ion exchange capacity. The layered skeleton of hydrotalcite is interwoven with CSH gel to form a "reinforced concrete" composite structure, which improves crack resistance and durability. The anions adsorbed by hydrotalcite and the Ca(OH)2 generated by CaO jointly precipitate heavy metals (forming Cd(OH)2), achieving dual stabilization.

[0058] Therefore, adding calcium oxide to the curing material can not only increase the curing effect, but also increase the chain reaction of the curing agent in a complex curing environment. After some curing agents take effect, the progress of the action of other curing agents will be rapidly accelerated, thereby rapidly accelerating the entire curing reaction.

[0059] In order to verify the effect of the in-situ solidifying agent for river silt, a group experiment was conducted to simulate highly polluted silt. Humic acid (15% of the clay mass) was added to the clay, and then an iron ion solution was added at a dosage of 2000 mg / kg clay. Water was then added to make the moisture content 90%. 1 kg of the solidifying agent was added to every 10 kg of silt. After stirring for 30 minutes, the water was pumped out to a moisture content of 85%. The solidification reaction lasted for 3 hours. The results were tested using the dichromate method (HJ 828-2017). The curing effect of the metal ions was verified by inductively coupled plasma mass spectrometry (HJ 766-2015) using iron ions as the target ions. The strength after solidification was tested by a universal testing machine test (GB / T 50123-2019). The group results are shown in Table 1, and the experimental results are shown in Table 2.

[0060]

[0061] To verify the effect of calcium oxide, an experiment was conducted to simulate highly contaminated sludge. Humic acid (15% of the mass of the clay) was added to the clay, and then an iron ion solution was added at an amount of 2000 mg / kg of clay. Water was then added to a moisture content of 90%, and 1 kg of a curing agent was added to every 10 kg of sludge (the other components of the curing agent used in this example, excluding calcium oxide, were as follows: 30 parts of silicate, 20 parts of calcium aluminum hydrotalcite, 35 parts of cement clinker, 15 parts of polyacrylamide, 10 parts of polyaluminum chloride, and 2 parts of tannic acid). After stirring for 30 minutes, water was pumped out to a moisture content of 85%. The curing reaction was carried out for 3 hours. The results were tested using the dichromate method (HJ 828-2017). The curing effect of the metal ions was verified by inductively coupled plasma mass spectrometry (HJ 766-2015) using iron ions as the target ion. The strength after curing was tested using a universal testing machine test (GB / T 50123-2019). The results are shown in Table 3.

[0062]

[0063] Example 2: The above embodiment achieves efficient in-situ solidification of sludge and resists multi-component interference in a complex environment through the intelligent release design of the coating layer, rapid dehydration and alkaline activation of calcium oxide, and synergistic gelation-adsorption of silicate and hydrotalcite. Although the presence of calcium oxide reduces the release speed due to the influence of the complex environment during release, it will also cause a small part of the coating layer to fail during the stirring process, resulting in a rapid decrease in the overall environmental pH. The acrylic polymer material swells or hydrolyzes in an alkaline environment, causing the curing agent particles to rupture prematurely and the release to be uncontrolled. Therefore, further improvements are made on the basis of Example 1.

[0064] The calcium oxide in the curing material is added to the inner coating layer, or the calcium oxide is directly provided in the inner coating layer in the same amount as that in the curing material, and 2-8 parts of sulfobetaine are additionally added together with the calcium oxide in the form of nano-powder with a particle size of 50-200nm.

[0065] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0066] The timing when the inner coating layer takes effect is almost the same as the timing when the curing material takes effect. It can not affect its effect in the inner coating layer, but can take effect in advance, and has a synergistic effect with the new component to increase the alkali resistance of the coating layer.

[0067] The sulfobetaine molecule consists of three parts: a quaternary ammonium cationic group with a positive charge; a sulfonate anionic group (-SO3 - ) is negatively charged; the hydrophobic alkyl chain provides steric hindrance;

[0068] The zwitterionic properties make it form an "inner salt" structure in solution (positive and negative charge groups are balanced by electrostatic attraction within the molecule), but in a high pH environment, due to OH - As the concentration increases, the sulfonic acid group (-SO3 - ) Partial deprotonation, enhancing electronegativity;

[0069] RN + (CH3)2-R'-SO3H+OH - →RN + (CH3)2-R'-SO3 - + H2O;

[0070] At high pH (>12), OH - H with sulfonic acid group + Combine to form -SO3 - , strengthening the negative charge; the quaternary ammonium group holds a positive charge, forming an intramolecular electrostatic cross-link; the hydrophobic chain and the hydrophilic group self-assemble into a "hydrophilic-hydrophobic micro-region", and the hydrophobic region shields the OH -Penetration, the hydrophilic area adsorbs water molecules to form a hydration layer.

[0071] Ca 2+ With sulfonic acid group (-SO3 - ) oxygen atoms form coordination bonds (Ca 2+ The empty 3d orbital of the O is combined with the lone pair of electrons of O), the bond length is about 2.4 Å; a single Ca 2+ Can react with -SO3 of multiple sulfobetaine molecules at the same time - Group coordination, forming "Ca 2+ -sulfobetaine cross-linked network", enhancing the density of the coating layer;

[0072] Ca 2+ +2R-N + (CH3)2-R'-SO3 - →[Ca(SO3-R'-RN + (CH3)2)2] 2+ ;

[0073] The positive charge of the quaternary ammonium group and the negative charge of the coating surface (-COO - ) are combined by electrostatic attraction to form a tight interface; Ca 2+ As an "ion bridge", connecting -SO3 of sulfobetaine - -COO with coating layer - , forming a "sandwich structure" (Ca 2+ -(SO3 - )-Ca 2+ -(COO - ));

[0074] COO - +Ca 2+ +RN + (CH3)2-R'-SO3 - →-COO - ---Ca 2+ ---RN + (CH3)2-R'-SO3 - ;

[0075] Ca 2+ With OH in solution - and SO3 - The reaction generates CaSO3·H2O precipitate, which is embedded in the hydrophobic micro-region of sulfobetaine, forming an "organic-inorganic composite barrier" to physically block OH - Diffusion paths;

[0076] Ca 2+ +SO3 -+ H2O → CaSO3·H2O;

[0077] From the above, Ca 2+ The coordination bond and precipitation reaction with sulfobetaine form a chemically stable protective layer; intramolecular electrostatic cross-linking and hydrophobic microdomain self-assembly physically block OH - erosion, Ca 2+ The bridging coating layer and sulfobetaine enhance the interfacial bonding force; the organic-inorganic composite barrier inhibits the diffusion of OH - by size exclusion effect.

[0078] Verification of the added sulfobetaine in Example Two was carried out in simulated high-alkali sludge, which was different from the simulated high-pollution sludge in Example One only in that sodium hydroxide was added to the simulated high-alkali sludge to pH 12. The experimental process was the same as that in Example One, and additional coating layer decomposition rate detection was carried out to detect the mass change of the coating layer, and the percentage of mass reduction in the original mass was calculated as the decomposition rate. The results are shown in Table 4.

[0079]

[0080] Example Three: In Example Two, calcium oxide is added to the inner layer of the coating and sulfobetaine is added to resist the premature release caused by the external alkaline environment. In subsequent experiments, it was found that sulfobetaine and polyacrylamide (PAM) in the curing agent form competitive adsorption at the molecular level due to charge repulsion, hindering the flocculation of PAM on the sludge particles, reducing the coagulation efficiency, and making the sludge particles loose. Based on Example Two, further improvements were made.

[0081] Calcium oxide includes small particle size and large particle size. The small particle size calcium oxide has a particle size of 1-10 microns, and the large particle has a particle size of 50-200 microns. The small particle size: large particle size = 3:7 (weight ratio).

[0082] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0083] Small particle size CaO rapidly hydrates (CaO + H2O → Ca 2+ + 2OH - ) at the beginning of stirring, providing high concentration Ca 2+ (> 500 mg / L), which preferentially generates ettringite (AFt) with sulfate (SO4 2- ): 3Ca 2+ + Al 3+ + 3SO4 2- + 32H2O → Ca6Al2(SO4)3(OH) 12 · 26H2O;

[0084] Small particle size CaO releases OH- The local pH rises rapidly to 12, triggering the hydrophobic-hydrophilic transition of sulfobetaine. Its hydrophobic groups are adsorbed on the surface of small-particle CaO to form a "nanoscale charge shielding layer", reducing competitive adsorption with PAM. The smaller the calcium oxide particles, the higher the local pH concentration produced, and the better the final effect. There is almost no competitive adsorption of PAM in nanoscale calcium oxide particles (200-500nm), and the combination of sulfobetaine and small-particle CaO can further enhance the curing effect.

[0085] Large-particle CaO slowly hydrates and continuously releases Ca in the middle stage of curing (1-3 hours). 2+ (maintain concentration at 100-200 mg / L);

[0086] Steric hindrance inhibits CSH: the surface of large-particle CaO is coated with sulfonic acid groups of sulfobetaine (-SO3 - ), through electrostatic repulsion to block SiO2 and Ca 2+ Contact, inhibitory reaction: Ca 2+ +SiO2+H2O→CaO·SiO2·H2O(CSH);

[0087] The sulfobetaine on the surface of small-particle CaO repels PAM through negative charge, forcing PAM to preferentially adsorb on the surface of sludge particles, thereby improving flocculation efficiency. The Ca released by large-particle CaO 2+ -SO3 with sulfobetaine - Formation of "Ca 2+ -sulfobetaine cross-linked network", filling the pores and enhancing the interface bonding; AFt generated by small-particle CaO fills the micron-sized pores; large-particle CaO continuously supplies calcium to form micron-sized AFt crystals, constituting a rigid skeleton; PAM floccules are embedded in the gaps of the AFt skeleton to form a "fiber-crystal" composite reinforcement phase.

[0088] Sulfobetaine is a zwitterionic polymer, but sulfobetaine is selected for its specificity and high stability coordination bond with Ca 2++ The strong coordination ability of the quaternary ammonium group (much higher than that of the carboxylic acid and phosphate groups) ensures the stability of the precipitation barrier; the electrostatic attraction between the positive charge of the quaternary ammonium group and the negative charge of the coating layer enhances the interfacial binding force; the self-assembly ability of the alkyl chain at high pH realizes the dual functions of physical barrier and chemical regulation; it maintains functional stability in extreme alkaline (pH>12) and complex ionic environments, while other zwitterionic polymers either have low calcium ion binding ability (betaine carboxylate), or porous precipitation (betaine phosphate), or have other groups interfering (betaine hydroxysulfonate), as well as molecular flexibility (polyzwitterionic electrolyte) and other problems. Sulfobetaine is specific and difficult to replace.

[0089] Further experiments were conducted based on Example 3. The experimental process was consistent with that of Example 2. The ettringite content (JC / T 1083-2019) was quantitatively analyzed by X-ray diffraction (XRD). The porosity (GB / T3810.12-2016) was tested by mercury intrusion porosimetry (MIP). The results are shown in Table 5. The XRD results of experimental groups 5 and 7 are as follows: Figure 1 、 Figure 2 As shown;

[0090]

[0091] Example 4: Example 3 improves alkali resistance by using a combination of calcium oxides of different particle sizes. In order to further optimize the curing agent and adapt the implementation method, further improvements are made on the basis of Example 3.

[0092] Small-sized calcium oxide is sprayed with a sulfobetaine solution (5% concentration) and dried to form a charge-regulating coating layer;

[0093] Large-particle calcium oxide and sulfobetaine (weight ratio 7:1) were mixed, sprayed at a pressure of 0.3 MPa, and the coating thickness was 50-80 μm; then dried with hot air at 80°C for 1 hour.

[0094] The implementation method of the above-mentioned curing agent is:

[0095] S1. Detecting the pH of the pond to be desilted and adjusting the pH to be less than 11, uniformly stirring the silt and curing agent in the pond to be desilted by a pontoon-type excavator mixer traveling in the pond to be desilted;

[0096] S2. Pumping out part of the water in the pond to be desilted, so that the moisture content of the silt in the pond to be desilted is 85%;

[0097] S3. Testing the pH of the sludge in the river and pond to be desilted, and adding additional calcium oxide to make the pH greater than 12, and then allowing the curing agent to undergo a curing reaction, the curing reaction time being between 1 and 3 hours;

[0098] S4, digging out the solidified silt in the river and pond to be desilted by an excavator traveling in the river and pond to be desilted;

[0099] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0100] By coating sulfobetaine on calcium oxide particles, calcium supply is optimized in stages. Sulfobetaine (50-200 nm) is preferentially adsorbed on the CaO surface, and the negative charge repulsion forces PAM (10-50 μm) to preferentially adsorb sludge particles, which improves the flocculation efficiency by more than 30%. Small and large particle size CaO release Ca in stages. 2+, inhibiting the formation of CSH, so that in the 0-1h of the reaction, it is mainly the small-particle CaO that releases Ca 2+ Nano-AFt (10-100 nm) is generated to fill micron-sized pores. During the 1-3h reaction, large-particle CaO continuously supplies calcium to generate micron-AFt (1-5 μm) and build a rigid skeleton. Calcium is supplied in stages to match the gelation reaction requirements and inhibit side reactions. Charge repulsion guides the efficient adsorption of PAM and optimizes the microstructure.

[0101] An experimental verification was conducted based on Example 3. The experimental process was consistent with Example 3, and Zeta potential measurement was additionally performed. The surface charge distribution of sulfobetaine and PAM was measured using a Zeta potential analyzer. The results are shown in Table 6.

[0102]

[0103] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Various modifications and variations are readily apparent to those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A river silt in-situ solidifying agent, characterized in that: The invention comprises a curing material and a coating layer, wherein the curing material comprises the following components by weight: 20-50 parts of silicate, 20-30 parts of calcium aluminum hydrotalcite, 25-35 parts of cement clinker, 2-27 parts of polyacrylamide, 7-15 parts of polyaluminium chloride, 1-13 parts of tannic acid and 5-15 parts of calcium oxide; The coating layer consists of three layers, which are made of acrylic polymer materials. The inner coating layer also contains hydrophilic material; the hydrophilic material is silicon dioxide, and the amount used is 0.5%-3% of the mass of the outer coating layer; The acrylic polymer material is polymerized by unsaturated acrylic ester monomer and carboxyl-containing monomer, wherein the unsaturated acrylic ester monomer is alkyl acrylate and the carboxyl-containing monomer is acrylic acid, and the mass ratio of the unsaturated acrylic ester monomer to the carboxyl-containing monomer is 2:1; The weight average molecular weight of the acrylic polymer material in the middle layer and the inner layer coating is 140,000-150,000; the glass transition temperature is 30-60°C; the weight average molecular weight of the acrylic polymer material in the outer layer coating is 130,000-140,000; the glass transition temperature is 5-30°C; the inner layer coating also contains 5-15 parts of calcium oxide and 2-8 parts of sulfobetaine by weight.

2. The river sludge in-situ solidifying agent according to claim 1, characterized in that: The silicate comprises sodium silicate, calcium silicate and magnesium fluorosilicate, the weight ratio of sodium silicate, calcium silicate and magnesium fluorosilicate is 1:0.5:0.2, the calcium aluminum hydrotalcite is Ca-Al nitrate type hydrotalcite; the particle size of calcium oxide is 1-200 microns.

3. The river sludge in-situ solidifying agent according to claim 1, characterized in that: The particle size of sulfobetaine is 50-200 nm, and sulfobetaine is added together with calcium oxide in the form of nano-powder.

4. The river sludge in-situ solidifying agent according to claim 1, characterized in that: The calcium oxide includes small-particle calcium oxide and large-particle calcium oxide. The particle size of the small-particle calcium oxide is 1-10 microns, and the large-particle calcium oxide is 50-200 microns. The mass ratio of the small-particle calcium oxide to the large-particle calcium oxide is 3:

7.

5. The river sludge in-situ solidifying agent according to claim 4, characterized in that: Small-sized calcium oxide particles are sprayed with a 5% sulfobetaine solution, and a charge-controlled coating is formed after drying. Large-particle calcium oxide and sulfobetaine are mixed in a weight ratio of 7:1, the spraying pressure is 0.3 MPa, the coating layer thickness is 50-80 μm, and hot air drying is performed at 80° C. for 1 hour.

6. A construction method for a river sludge in-situ solidifying agent according to any one of claims 1 to 5, characterized in that: The specific steps are: S1. Detecting the pH of the pond to be desilted and adjusting the pH to be less than 11, uniformly stirring the silt and curing agent in the pond to be desilted by a pontoon-type excavator mixer traveling in the pond to be desilted; S2. Pumping out part of the water in the pond to be desilted, so that the moisture content of the silt in the pond to be desilted is 85%; S3. Testing the pH of the sludge in the river and pond to be desilted, and adding additional calcium oxide to make the pH greater than 12, and then allowing the curing agent to undergo a curing reaction, the curing reaction time being between 1 and 3 hours; S4. Digging out the solidified silt in the pond to be desilted by an excavator traveling in the pond to be desilted.

Images