Preparation method and application of micro-crosslinked flocculant for mud water dehydration treatment in earth pressure balance shield

Abstract

The present invention discloses a preparation method and application of a micro-crosslinked flocculant for dehydration of mud water in an earth pressure balance shield, and relates to the technical field of dehydration of mud water (sludge) in an earth pressure balance shield. The present invention comprises the following steps: step S1: firstly prepare a reaction solution; uniformly mix the raw materials and deionized water together, and then use sulfuric acid or sodium hydroxide solution to dissolve the solution; step S2: after freeze drying at -5°C, add a trace crosslinking agent. The present invention, by selecting a functional monomer polymerization process, raw materials and a trace crosslinking agent, and optimizing the addition amount of the raw materials and the crosslinking agent, enhances the performance of the composite flocculant in mud water dehydration, and uses a flocculant to dehydrate mud water. In order to control the amount of flocculant, ensure safe construction, reduce secondary pollution, reduce costs and achieve economic benefits, there are strict requirements for the amount of dehydrating agent and specific performance, such as treatment efficiency, feeding range, safety, operability and flocculation effect.

Description

Technical Field

[0001] The invention relates to the technical field of dehydration treatment of earth pressure balance shield mud water (sludge), and in particular to a preparation method and application of a micro-crosslinking flocculant for dehydration treatment of earth pressure balance shield mud water. Background Art

[0002] With the continuous improvement of urbanization level, urban scale and population density are also increasing. The construction scale of municipal construction and urban rail transit has also achieved great development. In addition, the discharge of urban sewage has also shown a rapid growth trend. For the effective treatment of earth pressure balance shield mud water and urban sewage in subway construction, purification and dehydration are currently generally used to remove or reduce nitrogen, phosphorus and other components, and then the clear liquid is reused. Improving the dehydration performance of mud water and improving dehydration efficiency have become important goals in the field of mud water treatment. In this treatment process, flocculants play a vital role. The current development direction of flocculants is mainly low-cost, functional composite, green and easy to recycle. The realization of high-performance flocculants through composite or hybrid methods is receiving more and more attention.

[0003] The flocculant sedimentation technology is used to dehydrate mud water. Due to its significant advantages of simplicity, cost-effectiveness and high efficiency, it has become the most commonly used and most concerned method for treating mud water in earth pressure balance shield. Since there are certain components with high negative ion content in mud water, cationic polyacrylamide can neutralize negatively charged colloidal particles, adsorb and bond them, so that the colloidal particles can be released, aggregated and settled to achieve the effect of efficient flocculation. Therefore, cationic polyacrylamide is widely used in the current mud water dehydration and other wastewater treatment.

[0004] Therefore, a preparation method and application of a micro-crosslinked flocculant for mud dehydration treatment in an earth pressure balance shield are proposed. Summary of the invention

[0005] The purpose of the present invention is to solve the problems raised in the above background technology. The present invention provides a preparation method and application of a micro-crosslinked flocculant for dehydration of mud water in an earth pressure balance shield.

[0006] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:

[0007] The preparation method of a micro-crosslinked flocculant for dehydration treatment of mud water in an earth pressure balance shield comprises the following steps:

[0008] Step S1: first prepare a reaction solution; mix the raw materials and deionized water together, and then use sulfuric acid or sodium hydroxide solution to make the solution;

[0009] Step S2: After freeze-drying at -5°C, adding a trace amount of cross-linking agent, carrying out cross-linking reaction for 10 hours, and then keeping warm for 2-6 hours to obtain a composite flocculant colloid;

[0010] Step S3: ball-milling the composite flocculant colloid obtained above;

[0011] Step S4: drying at 60-80° C., crushing and sieving, and finally obtaining composite flocculant powder with a particle size of less than 500 μm.

[0012] Furthermore, the raw materials are diatom, chitosan and functional monomers, and the trace cross-linking agent is one or more of N,N-methylenebisacrylamide, N,N-dimethylacryloylethylenediamine, pentaerythritol triallyl and triallyl isocyanurate.

[0013] Furthermore, the functional monomer is one or more of acrylamide, pentaerythritol, trimethylolethane and trimethylolpropane.

[0014] Furthermore, the raw materials used in step S1 are diatom and acrylamide.

[0015] Furthermore, the pH value of the solution in step S1 needs to be adjusted to 3-4, and the diatom concentration used is 70%.

[0016] Furthermore, the flocculant is prepared by compounding chitosan and polyacrylamide, comprising the following steps:

[0017] Step Sa: dissolving chitosan obtained by polymerization of monomers in an acidic aqueous solution to prepare a solution containing chitosan and fully dissolving the chitosan;

[0018] Step Sb: adding ammonium cerium nitrate or ammonium persulfate initiator to the chitosan solution, and then adding acrylamide;

[0019] Step Sc: reacting at 40-60° C. for 1-4 hours to prepare a chitosan and polyacrylamide composite structure in a chitosan / polyacrylamide mixed solution;

[0020] Step Sd: adding isopropanol and then adding sodium hydroxide aqueous solution, reacting at 50-80° C. for 1-4 hours to prepare a chitosan / polyacrylamide composite flocculant.

[0021] Furthermore, the acidic solution used in preparing chitosan / polyacrylamide is acetic acid solution, hydrochloric acid solution or sulfuric acid solution, and the mass percentage concentration of the acid is 0.1%-1%, the mass percentage concentration of the chitosan-containing solution is 1-3%, and the mass percentage concentration of the sodium hydroxide solution is 10%-20%.

[0022] Furthermore, in terms of monomer mass fraction: acrylamide accounts for 5%-25% of the total mass, acrylamide accounts for 0.05-1% of the total mass, ammonium cerium nitrate or ammonium persulfate accounts for 2%-5% of the total mass, and deionized water accounts for 30%-90% of the total mass.

[0023] Application of micro-cross-linked flocculants in mud dewatering treatment of earth pressure balance shield.

[0024] The beneficial effects of the present invention are as follows:

[0025] The performance of composite flocculants in mud water dewatering is enhanced by selecting functional monomer polymerization process, raw materials and trace cross-linking agents, as well as optimizing the addition amount of raw materials and cross-linking agents. Flocculants are used for mud water dewatering. In order to control the amount of flocculants, ensure safe construction, reduce secondary pollution, reduce costs and achieve economic benefits, strict requirements are placed on the amount of dehydrating agents and specific performance, such as treatment efficiency, feed range, safety, operability and flocculation effect. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. The components of the embodiments of the present invention described and shown herein can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In the description of the embodiments of the present invention, it should be noted that the terms "inside", "outside", "upper", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown, or the orientations or positional relationships in which the inventive product is usually placed when used. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0029] The preparation method of a micro-crosslinked flocculant for dehydration treatment of mud water in an earth pressure balance shield comprises the following steps:

[0030] Step S1: first prepare a reaction solution; mix the raw materials and deionized water together, and then use sulfuric acid or sodium hydroxide solution to make the solution;

[0031] Step S2: After freeze-drying at -5°C, adding a trace amount of cross-linking agent, carrying out cross-linking reaction for 10 hours, and then keeping warm for 2-6 hours to obtain a composite flocculant colloid;

[0032] Step S3: ball-milling the composite flocculant colloid obtained above;

[0033] Step S4: drying at 60-80° C., crushing and sieving, and finally obtaining composite flocculant powder with a particle size of less than 500 μm.

[0034] The raw materials are diatom, chitosan and functional monomers, and the trace crosslinking agent is one or more of N,N-methylenebisacrylamide, N,N-dimethylacryloylethylenediamine, pentaerythritol triallyl and triallyl isocyanurate.

[0035] The functional monomer is one or more of acrylamide, pentaerythritol, trimethylolethane and trimethylolpropane. More specifically, the functional monomer is selected as a multifunctional organic molecule, and its functional group includes carbon bond and hydroxyl group, etc. In the polymerization chain initiation stage, these functional monomers are initiated by free radicals and can generate multiple free radical active sites. The prepared composite flocculant has lower viscosity and better solubility than linear polyacrylamide at the same molecular weight.

[0036] The raw materials used in step S1 are diatom and acrylamide.

[0037] The pH value of the solution in step S1 needs to be adjusted to 3-4, and the diatom concentration used is 70%.

[0038] The flocculant is prepared by compounding chitosan and polyacrylamide, and comprises the following steps:

[0039] Step Sa: dissolving chitosan obtained by polymerization of monomers in an acidic aqueous solution to prepare a solution containing chitosan and fully dissolving the chitosan;

[0040] Step Sb: adding ammonium cerium nitrate or ammonium persulfate initiator to the chitosan solution, and then adding acrylamide;

[0041] Step Sc: reacting at 40-60° C. for 1-4 hours to prepare a chitosan and polyacrylamide composite structure in a chitosan / polyacrylamide mixed solution;

[0042] Step Sd: adding isopropanol and then adding sodium hydroxide aqueous solution, reacting at 50-80° C. for 1-4 hours to prepare a chitosan / polyacrylamide composite flocculant.

[0043] The acidic solution used in preparing chitosan / polyacrylamide is acetic acid solution, hydrochloric acid solution or sulfuric acid solution, and the mass percentage concentration of the acid is 0.1%-1%, the mass percentage concentration of the chitosan-containing solution is 1-3%, and the mass percentage concentration of the sodium hydroxide solution is 10%-20%.

[0044] In terms of monomer mass fraction: acrylamide accounts for 5%-25% of the total mass, acrylamide accounts for 0.05-1% of the total mass, ammonium cerium nitrate or ammonium persulfate accounts for 2%-5% of the total mass, and deionized water accounts for 30%-90% of the total mass.

[0045] Application of micro-cross-linked flocculants in mud dewatering treatment of earth pressure balance shield.

[0046] Example 1

[0047] A method for preparing a micro-crosslinked composite flocculant for dehydration treatment of mud water in an earth pressure balance shield, wherein the composite flocculant preparation method is carried out according to the following steps:

[0048] 1. First, prepare a reaction solution, mix 25% of acrylamide, 4% of methacryloyloxyethyl trimethyl ammonium chloride, 8% of acryloyloxyethyl trimethyl ammonium chloride, 0.05% of functional monomer pentaerythritol, 3% of monomer additive ammonium sulfate and 59.95% of deionized water, and then adjust the pH of the solution to 3.5 with sulfuric acid and sodium hydroxide solution, put it into a freeze drying device, and cool it to minus 5°C.

[0049] 2. Pour the cooled solution in step 1 into a heat preservation reaction device, then put in a thermometer and a nitrogen blower, first add 1000ppm of azo initiator azobisisobutyronitrile and 80ppm of chelating agent diethylenetriamine pentaacetic acid penta, then add 50ppm of activator zinc sulfate, 200ppm of chain transfer agent sodium formate and 5ppm of cross-linking agent N,N-dimethylacryloylethylenediamine after an interval of 5 minutes, and then add 3ppm of oxidant sodium persulfate and 3ppm of reducing agent ammonium ferrous sulfate after 5 minutes. After the reaction is initiated, take out the nitrogen blower, react for 4-10 hours, and then keep warm for 2-3 hours to obtain a composite flocculant colloid.

[0050] 3. The colloid obtained in step 2 is crushed, dried at high temperature, and then crushed and sieved to obtain a powder with a particle size of less than 500 microns.

[0051] Example 2

[0052] A method for preparing a micro-crosslinked composite flocculant for dehydration treatment of mud water in an earth pressure balance shield, wherein the composite flocculant preparation method is carried out according to the following steps:

[0053] 1. Dissolve chitosan in an acidic aqueous solution to prepare a solution containing chitosan, and allow the chitosan to be fully dissolved.

[0054] 2. Add ammonium cerium nitrate or ammonium persulfate initiator to the chitosan solution obtained in step 1, and then add acrylamide, and react at 40-60° C. for 1-4 hours to prepare a chitosan / polyacrylamide composite structure, wherein the amount of ammonium cerium nitrate or ammonium persulfate initiator added is 2-4% of the molar number of chitosan units, and the mass of acrylamide used is 1-10 times that of chitosan.

[0055] 3. Add isopropanol to the chitosan / polyacrylamide composite structure mixed solution obtained in step 2, and then add sodium hydroxide aqueous solution, and react at 50-80° C. for 0.5-4 hours to prepare a chitosan / hydrolyzed polyacrylamide composite flocculant. The amount of isopropanol added is half to twice the volume of the original solution, and the mass percentage concentration of the sodium hydroxide solution is 10%-50%.

[0056] Example 3

[0057] A method for preparing a micro-crosslinked composite flocculant for dehydration treatment of mud water in an earth pressure balance shield, wherein the composite flocculant preparation method is carried out according to the following steps:

[0058] 1. Dissolve chitosan in 1.0% hydrochloric acid solution to prepare a solution containing 3% chitosan. After the solution is stirred evenly, add ammonium cerium nitrate as an initiator in an amount of 2% of the molar number of chitosan units, and add acrylamide in an amount of 5 times the mass of chitosan. React at 45°C for 2 hours to obtain a chitosan / polyacrylamide composite structure.

[0059] 2. Add half the volume of isopropanol and half the volume of sodium hydroxide solution of the original solution, with a mass percentage concentration of 10%, and then react at 85°C for 4 hours to prepare a chitosan / polyacrylamide composite flocculant, in which the carboxylic acid group content is 10% and the mass ratio content of polyacrylamide is 30.

[0060] In summary: by selecting functional monomer polymerization process, raw materials and trace cross-linking agents, as well as optimizing the addition amount of raw materials and cross-linking agents, the performance of composite flocculants in mud water dewatering is enhanced. When flocculants are used for mud water dewatering, in order to control the amount of flocculants, ensure safe construction, reduce secondary pollution, reduce costs and achieve economic benefits, strict requirements are placed on the amount of dehydrating agents and specific performance, such as treatment efficiency, feed range, safety, operability and flocculation effect.

[0061] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a micro-crosslinked flocculant for dehydration of mud water in an earth pressure balance shield, characterized in that: The following steps are involved: Step S1: first prepare a reaction solution; mix the raw materials and deionized water together, and then use sulfuric acid or sodium hydroxide solution to make the solution; Step S2: After freeze-drying at -5°C, adding a trace amount of cross-linking agent, carrying out cross-linking reaction for 10 hours, and then keeping warm for 2-6 hours to obtain a composite flocculant colloid; Step S3: ball-milling the composite flocculant colloid obtained above; Step S4: drying at 60-80° C., crushing and sieving, and finally obtaining composite flocculant powder with a particle size of less than 500 μm.

2. The method for preparing a micro-crosslinked flocculant for dehydration of mud water in an earth pressure balance shield according to claim 1, characterized in that: The raw materials are diatom, chitosan and functional monomers, and the trace crosslinking agent is one or more of N,N-methylenebisacrylamide, N,N-dimethylacryloylethylenediamine, pentaerythritol triallyl and triallyl isocyanurate.

3. The method for preparing a micro-crosslinked flocculant for dehydration of mud water in an earth pressure balance shield according to claim 2, characterized in that: The functional monomer is one or more of acrylamide, pentaerythritol, trimethylolethane and trimethylolpropane.

4. The method for preparing a micro-crosslinked flocculant for dehydration of mud water in an earth pressure balance shield according to claim 3, characterized in that: The raw materials used in step S1 are diatom and acrylamide.

5. The method for preparing a micro-crosslinked flocculant for dehydration of mud water in an earth pressure balance shield according to claim 3, characterized in that: The pH value of the solution in step S1 needs to be adjusted to 3-4, and the diatom concentration used is 70%.

6. The method for preparing a micro-crosslinked flocculant for dehydration of mud water in an earth pressure balance shield according to claim 3, characterized in that: The flocculant is prepared by compounding chitosan and polyacrylamide, and comprises the following steps: Step Sa: dissolving chitosan obtained by polymerization of monomers in an acidic aqueous solution to prepare a solution containing chitosan and fully dissolving the chitosan; Step Sb: adding ammonium cerium nitrate or ammonium persulfate initiator to the chitosan solution, and then adding acrylamide; Step Sc: reacting at 40-60° C. for 1-4 hours to prepare a chitosan and polyacrylamide composite structure in a chitosan / polyacrylamide mixed solution; Step Sd: adding isopropanol and then adding sodium hydroxide aqueous solution, reacting at 50-80° C. for 1-4 hours to prepare a chitosan / polyacrylamide composite flocculant.

7. According to the method for preparing a micro-cross-linked flocculant for mud dehydration treatment of an earth pressure balance shield as described in claim 6, the acidic solution used in the preparation of chitosan / polyacrylamide is an acetic acid solution, a hydrochloric acid solution or a sulfuric acid solution, and the mass percentage concentration of the acid is 0.1%-1%, the mass percentage concentration of the solution containing chitosan is 1-3%, and the mass percentage concentration of the sodium hydroxide solution is 10%-20%.

8. According to the preparation method of the micro-cross-linked flocculant for mud dehydration treatment of earth pressure balance shield as described in claim 6, in terms of monomer mass fraction: acrylamide accounts for 5%-25% of the total mass, acrylamide accounts for 0.05-1% of the total mass, ammonium cerium nitrate or ammonium persulfate accounts for 2%-5% of the total mass, and deionized water accounts for 30%-90% of the total mass.

9. Application of micro-cross-linked flocculants in mud dehydration treatment of earth pressure balance shield.