Lignin branched modified coal washing flocculant and preparation method thereof

Abstract

The invention relates to the technical field of coal washing wastewater treatment, in particular to a lignin branched modified coal washing flocculant and a preparation method thereof. The preparation method of the lignin branched modified coal washing flocculant provided by the embodiment of the invention comprises the following steps: S1, carrying out enzymatic degradation treatment on lignin to obtain pretreated lignin powder; s2, carrying out epoxy group activation pretreatment on the pretreated lignin powder to obtain epoxy group lignin; s3, performing sulfydryl pretreatment on the epoxy lignin to obtain sulfydryl-containing sulfydryl grafted modified lignin; and S4, carrying out branched copolymerization on the sulfhydrylation grafting modified lignin and a cationic monomer to obtain the lignin branched modified coal washing flocculant. The embodiment of the invention provides the lignin branching modified coal washing flocculant, and the lignin branching modified coal washing flocculant which is low in consumption, efficient and environment-friendly can be provided.

Description

Technical Field

[0001] This invention relates to the field of coal washing wastewater treatment technology, and in particular to a lignin-branched modified coal washing flocculant and its preparation method. Background Technology

[0002] Coal washing wastewater is a typical industrial wastewater generated during the coal washing process. Its water quality is complex, containing suspended coal slime particles, clay minerals and residual flotation reagents. Direct discharge will lead to water siltation and soil compaction, seriously threatening the ecological environment.

[0003] Currently, polyacrylamide and its derivatives are the mainstream flocculants used in coal washing wastewater treatment, but they have the following core drawbacks: Performance limitations: Linear polyacrylamide has a low charge density and a weak ability to neutralize the charge of negatively charged coal slime particles. Its bridging effect is easily interfered with by clay particles, resulting in a long settling time and difficulty in subsequent treatment.

[0004] Therefore, there is an urgent need to develop a "low-consumption, high-efficiency, and environmentally friendly" lignin-branched modified coal washing flocculant. By precisely controlling the lignin structure and introducing multifunctional active units, the problems of "low reactivity, poor controllability of branching, and insufficient flocculation efficiency" in existing technologies can be solved, which is of great significance for promoting the green development of the coal industry. Summary of the Invention

[0005] This invention provides a lignin-branched modified coal washing flocculant, which is "low-consumption, high-efficiency, and environmentally friendly." By precisely controlling the lignin structure and introducing multifunctional active units, it solves the problems of "low reactivity, poor controllability of branching, and insufficient flocculation efficiency" in existing technologies, and is of great significance for promoting the green development of the coal industry.

[0006] In a first aspect, embodiments of the present invention provide a method for preparing a lignin-branched modified coal washing flocculant, comprising: S1, lignin is enzymatically degraded to obtain pretreated lignin powder; S2, the pretreated lignin powder is subjected to epoxy group activation pretreatment to obtain epoxy lignin; S3, the epoxy lignin is subjected to thiol pretreatment to obtain thiol-modified grafted lignin including thiol groups; S4, the thiol-grafted modified lignin is branched copolymerized with cationic monomers to obtain lignin-branched modified coal washing flocculant.

[0007] Optionally, S1 includes: After pretreating the broken lignin in an alkaline environment, peroxidase and hydrogen peroxide were added for enzymatic degradation to obtain pretreated lignin powder.

[0008] Optionally, S2 includes: The pretreated lignin powder was reacted with epichlorohydrin under the catalysis of sodium hydroxide in a nitrogen atmosphere to obtain epoxy lignin; wherein the reaction time was 1.5~2.5h and the reaction temperature was 55~65℃.

[0009] Optionally, S3 includes: The epoxy lignin was mixed with mercaptoethanol, diacetone acrylamide, isopropyl mercaptoacetate, and acetic anhydride, and p-hydroxyanisole was added. The mixture was heated to 70°C and reacted for 3 hours under nitrogen protection and stirring at 200 rpm to obtain mercapto-grafted modified lignin.

[0010] Optionally, S4 includes: The thiol-grafted modified lignin, acrylamide, 3-mercaptopropyltrimethoxysilane, cationic monomer, crosslinking agent, co-solvent, and deionized water are mixed, the pH is adjusted to 6.8-7.0, the temperature is adjusted to 3-4℃, a mixed initiator, dithiothreitol, and chain transfer agent are added, and a branching polymerization reaction is carried out under nitrogen atmosphere to obtain lignin branched modified coal washing flocculant.

[0011] Optionally, in S1, the alkaline environment is adjusted by a 0.5-2% dilute alkaline solution, and the pH of the system is adjusted by a 0.1 mol / L citrate-sodium citrate buffer solution before enzyme degradation. The weight parts of each raw material component are as follows: 150-300 parts by weight of industrial by-product lignin, 500-750 parts by weight of dilute alkali solution, 25-35 parts by weight of pH buffer solution, 0.5-1.5 parts by weight of lignin peroxidase, and 75-100 parts by weight of 6% hydrogen peroxide solution.

[0012] Optionally, in S2, the sodium hydroxide catalyst is a 5% sodium hydroxide solution; The weight parts of each raw material component are as follows: 10-15 parts by weight of pretreated lignin powder, 15-25 parts by weight of epichlorohydrin, and 0.5-1 parts by weight of sodium hydroxide catalyst.

[0013] Optionally, in S3, the weight parts of each raw material component are: 10-20 parts by weight of mercaptoethanol, 0.5-7 parts by weight of diacetone acrylamide, 1-4 parts by weight of isopropyl mercaptoacetate, 3-7 parts by weight of acetic anhydride, and 0.003-0.01 parts by weight of p-hydroxyanisole.

[0014] Optionally, in S4, the cationic monomer is selected from at least two of methacryloyloxyethyl dimethyl butyl ammonium bromide, vinyl benzyl trimethyl ammonium chloride, methacrylamide propyl trimethyl ammonium chloride, and (meth)acryloyloxyethyl dimethyl benzyl ammonium chloride, and includes methacryloyloxyethyl dimethyl butyl ammonium bromide; The chain transfer agent is selected from any one or more of sodium formate, isopropanol, sodium hypophosphite, and sodium methylpropene sulfonate; The mixed initiator comprises an azo initiator and a redox initiator. The azo initiator is selected from one or more of azobisisobutyramidine dihydrochloride, azobisisoheptanenitrile, azobisisobutyronitrile, and 4,4'-azobis(4-cyanopentanoic acid). The redox initiator is selected from benzoyl peroxide, ammonium persulfate, potassium persulfate, sodium bisulfite formaldehyde, ferrous sulfate, and sodium bisulfite. The crosslinking agent is selected from at least two of N-hydroxymethylacrylamide, diacetone methacrylamide, and diallyl phthalate; The co-solvent is a 30% sodium xylenesulfonate aqueous solution; The weight parts of each raw material component are as follows: 120-220 parts by weight of acrylamide crystals, 15-25 parts by weight of thiolized grafted modified lignin, 0.05-0.9 parts by weight of 3-mercaptopropyltrimethoxysilane, 20-115 parts by weight of cationic monomer, 0.5-2 parts by weight of crosslinking agent, 2-6 parts by weight of prosolvent, 600-800 parts by weight of deionized water, 0.05-1.8 parts by weight of chain transfer agent, 0.005-0.05 parts by weight of dithiothreitol, and 0.001-0.5 parts by weight of mixed initiator.

[0015] Secondly, embodiments of the present invention provide a lignin-branched modified coal washing flocculant, which is prepared by any one of the preparation methods described above.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: In this embodiment, a step-by-step process of "degradation pretreatment - thiolization grafting modification - branching copolymerization" is used to achieve precise control of lignin structure. The final product has a synergistic effect of "charge neutralization - adsorption bridging - net trapping and sweeping", which significantly improves the treatment efficiency of coal washing wastewater, while reducing raw material costs and realizing solid waste resource utilization. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 The present invention provides a flowchart of a method for preparing a lignin-branched modified coal washing flocculant. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. 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.

[0020] In the description of the embodiments of the present invention, unless otherwise expressly specified and limited, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; unless otherwise specified or stated, the term "multiple" refers to two or more; the terms "connected," "fixed," etc., should be interpreted broadly. For example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0021] In this specification, it should be understood that the directional terms such as "upper" and "lower" used in the description of the embodiments of the present invention are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of the present invention. Furthermore, in the context, it should also be understood that when it is mentioned that one element is connected "upper" or "lower" to another element, it can be directly connected to the other element "upper" or "lower," or indirectly connected to the other element "upper" or "lower" through an intermediate element.

[0022] like Figure 1 As shown in the figure, this invention provides a method for preparing a lignin-branched modified coal washing flocculant, comprising: S1, lignin is enzymatically degraded to obtain pretreated lignin powder; S2, the pretreated lignin powder is subjected to epoxy group activation pretreatment to obtain epoxy lignin; S3, the epoxy lignin is subjected to thiol pretreatment to obtain thiol-modified grafted lignin including thiol groups; S4, the thiol-grafted modified lignin is branched copolymerized with cationic monomers to obtain lignin-branched modified coal washing flocculant.

[0023] In this embodiment, a step-by-step process of "degradation pretreatment - thiolization grafting modification - branching copolymerization" is used to achieve precise control of lignin structure. The final product has a synergistic effect of "charge neutralization - adsorption bridging - net trapping and sweeping", which significantly improves the treatment efficiency of coal washing wastewater, while reducing raw material costs and realizing solid waste resource utilization.

[0024] In some embodiments of the present invention, S1 includes: After pretreating the broken lignin in an alkaline environment, peroxidase and hydrogen peroxide were added for enzymatic degradation to obtain pretreated lignin powder.

[0025] In this embodiment, a combined process of "mechanical pulverization-alkali pretreatment-enzymatic degradation" is used to break the lignin cross-linking structure and expose active groups such as phenolic hydroxyl groups. Specifically, the process includes the following steps: a) Mechanical crushing: Take lignin, an industrial byproduct, and put it into a planetary ball mill. Use agate balls as the grinding media and grind it at 300-500 rpm for 20-30 minutes. Then pass it through a 100-mesh standard sieve and collect the sieve material. b) Alkali pretreatment: Mix pulverized lignin with dilute alkaline solution at a liquid-solid ratio of 10:1-15:1, transfer to a four-necked flask with a stirrer, heat to 50-80℃, and react for 1-2 hours with stirring at 150-200 rpm. c) Enzymatic degradation: To the pretreated lignin suspension, pH buffer was added to adjust the pH of the system, followed by the addition of lignin peroxidase and hydrogen peroxide solution. d) Post-processing: After the enzymatic hydrolysis reaction is completed, the pH of the system is adjusted to 7.0-8.0 with 0.1 mol / L NaOH or HCl. Then the suspension is transferred to a vacuum filter and the filter cake is washed with deionized water. The washed filter cake was transferred to a vacuum freeze dryer and dried for 4 hours. After being pulverized, it was passed through a 100-mesh sieve to obtain pretreated lignin powder.

[0026] In some embodiments of the present invention, S2 includes: The pretreated lignin powder was reacted with epichlorohydrin under the catalysis of sodium hydroxide in a nitrogen atmosphere to obtain epoxy lignin; wherein the reaction time was 1.5~2.5h and the reaction temperature was 55~65℃.

[0027] In this embodiment, the hydroxyl groups of pretreated lignin are activated by epichlorohydrin to facilitate the subsequent introduction of thiol groups. The specific steps are as follows: Preparation of epoxy intermediates: Add pretreated lignin powder, epichlorohydrin, and anhydrous ethanol to a four-necked flask, and ultrasonically disperse for 10-15 minutes until a homogeneous suspension is formed. Add NaOH catalyst and react for 2 hours under nitrogen protection, at 60°C and 180 rpm stirring.

[0028] After the reaction was completed, excess epichlorohydrin and ethanol were removed by vacuum distillation to obtain epoxy-modified lignin.

[0029] In some embodiments of the present invention, S3 includes: The epoxy lignin was mixed with mercaptoethanol, diacetone acrylamide, isopropyl mercaptoacetate, and acetic anhydride, and p-hydroxyanisole was added. The mixture was heated to 70°C and reacted for 3 hours under nitrogen protection and stirring at 200 rpm to obtain mercapto-grafted modified lignin.

[0030] Epoxy-activated lignin is reacted with mercaptoethanol, diacetone acrylamide, isopropyl mercaptoacetate, and acetic anhydride to introduce thiol and tertiary amine sites, providing active sites for subsequent branched copolymerization. The specific steps are as follows: Introduction of thiol groups: Mercaptoethanol, diacetone acrylamide, isopropyl mercaptoacetate, and acetic anhydride were added to epoxy-modified lignin, and a small amount of p-hydroxyanisole was added. The mixture was heated to 70°C and reacted for 3 hours under nitrogen protection and stirring at 200 rpm.

[0031] After the reaction was complete, acetone was added to the system, stirred for 30 min, allowed to stand for 1 h, and the precipitate was collected by centrifugation. The precipitate was washed three times with acetone and then dried at 60°C and a vacuum of -0.08 MPa for 4 hours to obtain thiolized grafted lignin.

[0032] In some embodiments of the present invention, S4 includes: The thiol-grafted modified lignin, acrylamide, 3-mercaptopropyltrimethoxysilane, cationic monomer, crosslinking agent, co-solvent, and deionized water are mixed, the pH is adjusted to 6.8-7.0, the temperature is adjusted to 3-4℃, a mixed initiator, dithiothreitol, and chain transfer agent are added, and a branching polymerization reaction is carried out under nitrogen atmosphere to obtain lignin branched modified coal washing flocculant.

[0033] In this embodiment, thiol-grafted modified lignin is used as the branching core, copolymerized with acrylamide and cationic monomers. The branching density is controlled by a crosslinking agent, and the compatibility with the solvent is improved. The specific steps are as follows: a) Preparation of the mixture: Add the following to the polymerization reactor: acrylamide crystals, thiol-grafted modified lignin, 3-mercaptopropyltrimethoxysilane, cationic monomer, crosslinking agent, co-solvent, and deionized water; Stirring and dispersion: Sonicate for 20 minutes while stirring at 250-300 rpm to form a homogeneous and transparent solution; Adjust the pH value to 6.8-7.0.

[0034] Adjust the temperature to 3-4℃.

[0035] b) Copolymerization: Nitrogen purging and deoxygenation: High-purity nitrogen gas is purged into the mixture for 15-30 minutes, with dissolved oxygen measured every 5 minutes during this period; Mixed initiator, dithiothreitol, and chain transfer agent are added; Granulation: The polymer blocks obtained from the copolymerization reaction are fed into a granulator for granulation, with a particle size of 2-6 mm; Drying: The granules are transferred to a drying oven and dried at 60-80℃ for 2-4 hours, controlling the moisture content of the finished product to ≤8%; Grinding and sieving: The dried granules are ground in a pulverizer and then passed through an 80-mesh standard sieve. The undersize material is collected, which is the finished product of lignin-branched modified coal washing flocculant.

[0036] In some embodiments of the present invention, in S1, the alkaline environment is adjusted by a 0.5-2% dilute alkaline solution, and the pH value of the system is adjusted by a 0.1 mol / L citrate-sodium citrate buffer solution before enzyme degradation. The weight parts of each raw material component are as follows: 150-300 parts by weight of industrial by-product lignin, 500-750 parts by weight of dilute alkali solution, 25-35 parts by weight of pH buffer solution, 0.5-1.5 parts by weight of lignin peroxidase, and 75-100 parts by weight of 6% hydrogen peroxide solution.

[0037] In some embodiments of the present invention, in S2, the sodium hydroxide catalyst is a 5% sodium hydroxide solution; The weight parts of each raw material component are as follows: 10-15 parts by weight of pretreated lignin powder, 15-25 parts by weight of epichlorohydrin, 60-85 parts by weight of anhydrous ethanol, and 0.5-1 parts by weight of sodium hydroxide catalyst.

[0038] In some embodiments of the present invention, in S3, the weight parts of each raw material component are: 10-20 parts by weight of mercaptoethanol, 0.5-7 parts by weight of diacetone acrylamide, 1-4 parts by weight of isopropyl mercaptoacetate, 3-7 parts by weight of acetic anhydride, 0.003-0.01 parts by weight of p-hydroxyanisole, and 50-100 parts by weight of acetone.

[0039] In some embodiments of the present invention, in S4, the cationic monomer is selected from at least two of methacryloyloxyethyl dimethyl butyl ammonium bromide, vinyl benzyl trimethyl ammonium chloride, methacrylamide propyl trimethyl ammonium chloride, and (meth)acryloyloxyethyl dimethyl benzyl ammonium chloride, and includes methacryloyloxyethyl dimethyl butyl ammonium bromide. The chain transfer agent is selected from any one or more of sodium formate, isopropanol, sodium hypophosphite, and sodium methylpropene sulfonate; preferably sodium methylpropene sulfonate. The mixed initiator comprises an azo initiator and a redox initiator. The azo initiator is selected from one or more of azobisisobutyramidine dihydrochloride, azobisisoheptanenitrile, azobisisobutyramidonitrile, and 4,4'-azobis(4-cyanopentanoic acid), preferably azobisisobutyramidine dihydrochloride. The redox initiator is selected from benzoyl peroxide, ammonium persulfate, potassium persulfate, sodium bisulfite formaldehyde, ferrous sulfate, and sodium bisulfite, preferably ammonium persulfate and sodium bisulfite. The crosslinking agent is selected from at least two of N-hydroxymethylacrylamide, diacetone methacrylamide, and diallyl phthalate; the preferred compounding ratio is diacetone methacrylamide: diallyl phthalate = 2:1, which balances the degree of branching and solubility. The co-solvent is a 30% sodium xylenesulfonate aqueous solution; The weight parts of each raw material component are as follows: 120-220 parts by weight of acrylamide crystals, 15-25 parts by weight of thiolized grafted modified lignin, 0.05-0.9 parts by weight of 3-mercaptopropyltrimethoxysilane, 20-115 parts by weight of cationic monomer, 0.5-2 parts by weight of crosslinking agent, 2-6 parts by weight of prosolvent, 600-800 parts by weight of deionized water, 0.05-1.8 parts by weight of chain transfer agent, 0.005-0.05 parts by weight of dithiothreitol, and 0.001-0.5 parts by weight of mixed initiator.

[0040] This invention provides a lignin-branched modified coal washing flocculant, which is prepared using any of the preparation methods described above.

[0041] To more clearly illustrate the technical solution and advantages of the present invention, the preparation method of a lignin-branched modified coal washing flocculant is described in detail below through several embodiments.

[0042] Example 1 The raw material composition for preparing a lignin-branched modified coal washing flocculant includes: S1 contains: 180 parts by weight of lignin (an industrial byproduct), 625 parts by weight of dilute alkali solution, 27 parts by weight of pH buffer solution, 0.6 parts by weight of lignin peroxidase, and 85 parts by weight of 6% hydrogen peroxide solution.

[0043] S2 contains: 13.5 parts by weight of pretreated lignin powder, 19 parts by weight of epichlorohydrin, 75 parts by weight of anhydrous ethanol, and 0.7 parts by weight of NaOH catalyst.

[0044] S3 contains: 12 parts by weight of mercaptoethanol, 2 parts by weight of diacetone acrylamide, 2.4 parts by weight of isopropyl mercaptoacetate, 3.7 parts by weight of acetic anhydride, 0.005 parts by weight of p-hydroxyanisole, and 68 parts by weight of acetone.

[0045] S4 contains: 210 parts by weight of acrylamide crystals, 19 parts by weight of thiol-grafted modified lignin, 0.15 parts by weight of 3-mercaptopropyltrimethoxysilane, 20 parts by weight of methacryloyloxyethyl dimethylbutylammonium bromide, 35 parts by weight of vinylbenzyltrimethylammonium chloride, 0.6 parts by weight of diacetone methacrylamide, 0.3 parts by weight of diallyl phthalate, 4 parts by weight of 30% sodium xylenesulfonate aqueous solution, 690 parts by weight of deionized water, 0.16 parts by weight of sodium methacrylate sulfonate, 0.02 parts by weight of dithiothreitol, 0.003 parts by weight of ammonium persulfate, 0.002 parts by weight of sodium bisulfite, and 0.2 parts by weight of azobisisobutyramidine dihydrochloride.

[0046] S1: Lignin degradation pretreatment The combined process of "mechanical crushing - alkali pretreatment - enzymatic degradation" breaks down the lignin cross-linking structure, exposing active groups such as phenolic hydroxyl groups. The specific steps are as follows: a) Mechanical crushing: Take lignin, an industrial byproduct, and put it into a planetary ball mill. Use agate balls as the grinding media and grind it at 300-500 rpm for 20-30 minutes. Then pass it through a 100-mesh standard sieve and collect the sieve material. b) Alkali pretreatment: Mix pulverized lignin with dilute alkaline solution at a liquid-solid ratio of 10:1-15:1, transfer to a four-necked flask with a stirrer, heat to 50-80℃, and react for 1-2 hours with stirring at 150-200 rpm. c) Enzymatic degradation: To the pretreated lignin suspension, pH buffer was added to adjust the pH of the system, followed by the addition of lignin peroxidase and hydrogen peroxide solution. d) Post-processing: After the enzymatic hydrolysis reaction is completed, the pH of the system is adjusted to 7.0-8.0 with 0.1 mol / L NaOH or HCl. Then the suspension is transferred to a vacuum filter and the filter cake is washed with deionized water. The washed filter cake was transferred to a vacuum freeze dryer and dried for 4 hours. After being pulverized, it was passed through a 100-mesh sieve to obtain pretreated lignin powder.

[0047] S2: Epoxy group activation treatment The hydroxyl groups of pretreated lignin are activated by epichlorohydrin, and the specific steps are as follows: Preparation of epoxy intermediates: Add pretreated lignin powder, epichlorohydrin, and anhydrous ethanol to a four-necked flask, and ultrasonically disperse for 10-15 minutes until a homogeneous suspension is formed. Add NaOH catalyst and react for 2 hours under nitrogen protection, at 60°C and 180 rpm stirring.

[0048] After the reaction was completed, excess epichlorohydrin and ethanol were removed by vacuum distillation to obtain epoxy-modified lignin.

[0049] S3: Lignin thiol-modified grafting The reaction with mercaptoethanol, diacetone acrylamide, isopropyl mercaptoacetate, and acetic anhydride introduces thiol and tertiary amine sites, providing active sites for subsequent branched copolymerization. The specific steps are as follows: Introduction of thiol groups: Mercaptoethanol, diacetone acrylamide, isopropyl mercaptoacetate, and acetic anhydride were added to epoxy-modified lignin, and a small amount of p-hydroxyanisole was added. The mixture was heated to 70°C and reacted for 3 hours under nitrogen protection and stirring at 200 rpm.

[0050] After the reaction was complete, acetone was added to the system, stirred for 30 min, allowed to stand for 1 h, and the precipitate was collected by centrifugation. The precipitate was washed three times with acetone and then dried at 60°C and a vacuum of -0.08 MPa for 4 hours to obtain thiolized grafted lignin.

[0051] S4: Branched copolymerization and post-processing Using thiol-grafted modified lignin as the branching core, it is copolymerized with acrylamide and cationic monomers. The branching density is controlled by crosslinking agents, and the compatibility with solvents is improved. The specific steps are as follows: a) Preparation of the mixture: Add the following to the polymerization reactor: acrylamide crystals, thiol-grafted modified lignin, 3-mercaptopropyltrimethoxysilane, cationic monomer, crosslinking agent, co-solvent, and deionized water; Stirring and dispersion: Sonicate for 20 minutes while stirring at 250-300 rpm to form a homogeneous and transparent solution; Adjust the pH value to 6.8-7.0.

[0052] Adjust the temperature to 3-4℃.

[0053] b) Copolymerization: Nitrogen purging and deoxygenation: High-purity nitrogen gas is purged into the mixture for 15-30 minutes, with dissolved oxygen measured every 5 minutes during this period; mixed initiator, dithiothreitol, and chain transfer agent are added; granulation: The polymer blocks obtained from the copolymerization reaction are fed into a granulator for granulation, with a particle size of 2-6 mm; drying: The granules are transferred to a drying oven and dried at 60-80℃ for 2-4 hours, controlling the moisture content of the finished product to ≤8%; grinding and sieving: The dried granules are ground by a pulverizer and then passed through an 80-mesh standard sieve. The undersize material is collected, which is the finished product of lignin-branched modified coal washing flocculant; Example 2 The difference from Example 1 lies in the amount of components used. Example 2: The raw material composition for preparing a lignin-branched modified coal washing flocculant includes: S1 contains: 180 parts by weight of lignin (an industrial byproduct), 625 parts by weight of dilute alkali solution, 27 parts by weight of pH buffer solution, 0.6 parts by weight of lignin peroxidase, and 85 parts by weight of 6% hydrogen peroxide solution.

[0054] S2 contains: 13.5 parts by weight of pretreated lignin powder, 19 parts by weight of epichlorohydrin, 75 parts by weight of anhydrous ethanol, and 0.7 parts by weight of NaOH catalyst.

[0055] S3 contains: 12 parts by weight of mercaptoethanol, 2 parts by weight of diacetone acrylamide, 2.4 parts by weight of isopropyl mercaptoacetate, 3.7 parts by weight of acetic anhydride, 0.005 parts by weight of p-hydroxyanisole, and 68 parts by weight of acetone.

[0056] S4 contains: 190 parts by weight of acrylamide crystals, 22 parts by weight of thiol-grafted modified lignin, 0.2 parts by weight of 3-mercaptopropyltrimethoxysilane, 29 parts by weight of methacryloyloxyethyl dimethylbutylammonium bromide, 41 parts by weight of vinylbenzyltrimethylammonium chloride, 0.8 parts by weight of diacetone methacrylamide, 0.4 parts by weight of diallyl phthalate, 3.5 parts by weight of 30% sodium xylenesulfonate aqueous solution, 690 parts by weight of deionized water, 0.14 parts by weight of sodium methacrylate sulfonate, 0.015 parts by weight of dithiothreitol, 0.003 parts by weight of ammonium persulfate, 0.002 parts by weight of sodium bisulfite, and 0.2 parts by weight of azobisisobutyramidine dihydrochloride.

[0057] Example 3 The difference from Example 1 lies in the amount of components used. Example 3: The raw material composition for preparing a lignin-branched modified coal washing flocculant includes: S1 contains: 220 parts by weight of industrial by-product lignin, 679 parts by weight of dilute alkali solution, 29 parts by weight of pH buffer solution, 0.6 parts by weight of lignin peroxidase, and 85 parts by weight of 6% hydrogen peroxide solution.

[0058] S2 contains: 15 parts by weight of pretreated lignin powder, 18 parts by weight of epichlorohydrin, 75 parts by weight of anhydrous ethanol, and 0.7 parts by weight of NaOH catalyst.

[0059] S3 contains: 16 parts by weight of mercaptoethanol, 3 parts by weight of diacetone acrylamide, 3.5 parts by weight of isopropyl mercaptoacetate, 5.5 parts by weight of acetic anhydride, 0.005 parts by weight of p-hydroxyanisole, and 70 parts by weight of acetone.

[0060] S4 contains: 210 parts by weight of acrylamide crystals, 21 parts by weight of thiolized grafted lignin, 0.15 parts by weight of 3-mercaptopropyltrimethoxysilane, 20 parts by weight of methacryloyloxyethyl dimethylbutylammonium bromide, 35 parts by weight of vinylbenzyltrimethylammonium chloride, 0.4 parts by weight of diacetone methacrylamide, 0.2 parts by weight of diallyl phthalate, 4 parts by weight of 30% sodium xylenesulfonate aqueous solution, 690 parts by weight of deionized water, 0.16 parts by weight of sodium methacrylate sulfonate, 0.02 parts by weight of dithiothreitol, 0.003 parts by weight of ammonium persulfate, 0.002 parts by weight of sodium bisulfite, and 0.2 parts by weight of azobisisobutyramidine dihydrochloride.

[0061] Comparative Example 1 The difference from Example 1 is that there is no thiol branching step in S1-S3, only S4, in which industrial by-product lignin replaces the thiol-grafted modified lignin.

[0062] Comparative Example 2 The difference from Example 1 is that diacetone methacrylamide and diallyl phthalate are not added in S4.

[0063] Comparative Example 3 The difference from Example 1 is that the cationic monomer used in S4 is methacryloyloxyethyltrimethylammonium chloride.

[0064] Comparative Example 4 The difference from Example 1 is that there is no S2 epoxy group activation step.

[0065] Test method: 1. Relative molecular mass, cationicity, and water-insoluble matter The relative molecular mass M and cationicity were tested according to the test methods in the national standard GB / T 31246-2014. Water-insoluble matter .

[0066] 2. Specific testing steps A) Preparation of flocculant solution Weigh (1.000 ± 0.001) g of the PAM powder to be tested and slowly add it to a beaker containing approximately 500 mL of water, while stirring at 200-400 r / min. After the powder is completely dispersed, continue stirring for at least 1 hour to ensure complete dissolution. Finally, dilute to 1000 mL with water to prepare a 0.1% (w / v) stock solution. This stock solution should be prepared immediately before use and should not be stored for more than 2 hours.

[0067] Simulated coal slurry water configuration Weigh 10g of quartz and 10g of kaolinite and add them to 700mL of pure water. Use a magnetic stirrer to stir at 500r / min for 5min to ensure complete dispersion and form a simulated coal slurry suspension.

[0068] B) Test Procedure Standard beaker sedimentation test This experiment was conducted to determine the settling properties of flocculants.

[0069] Sampling: Take 500 mL of a uniform simulated coal slurry suspension and pour it into six 500 mL stoppered graduated cylinders.

[0070] Add flocculant: Use a pipette or micropipette to add 1 ml of 0.1% PAM stock solution to each graduated cylinder.

[0071] Mixing and flocculation: Tighten the stopper of the measuring cylinder and flip it up and down 10 times with uniform force and frequency (completed within about 30 seconds) to ensure that the flocculant and coal slurry are fully mixed.

[0072] Settling: Place the graduated cylinder vertically on the experimental table and start the stopwatch at the same time.

[0073] Observation and Recording: Settling time: The time (t, unit: seconds) required for the interface between the clear liquid and flocculent to drop from the 500 mL mark to the 300 mL mark (i.e., settling 200 mL).

[0074] Turbidity of the supernatant: After standing for 5 minutes, carefully aspirate about 50 mL of the supernatant from the top of the graduated cylinder using the siphon method, and measure its turbidity (NTU) using a turbidimeter.

[0075] Observation of floc characteristics: Qualitatively record the size, density, and interface clarity of the flocs.

[0076] Test results:

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a lignin branched modified coal washing flocculant, characterized in that, The method comprises the following steps: S1, lignin is subjected to enzymatic degradation treatment to obtain pretreated lignin powder; S2, the pretreated lignin powder is subjected to epoxy group activation pretreatment to obtain epoxy group lignin; S3, the epoxy group lignin is subjected to mercapto group pretreatment to obtain mercapto group-containing mercapto group grafted modified lignin; S4, the mercapto group grafted modified lignin is subjected to branched copolymerization with cationic monomers to obtain lignin branched modified coal washing flocculant.

2. The production method according to claim 1, characterized by, S1 comprises the following steps: After the broken lignin is pretreated in an alkaline environment, peroxidase and hydrogen peroxide are added for enzymatic degradation to obtain pretreated lignin powder.

3. The method of claim 1, wherein S2 The method comprises the following steps: The pretreated lignin powder is reacted with epichlorohydrin under the catalysis of sodium hydroxide in a nitrogen environment to obtain epoxy group lignin; wherein the reaction time is 1.5-2.5 h, and the reaction temperature is 55-65℃.

4. The production method according to claim 1, characterized by S3 The method comprises the following steps: The epoxy group lignin is mixed with mercaptoethanol, diacetone acrylamide, isopropyl mercaptoacetate, and acetic anhydride, and p-hydroxyanisole is added, and the temperature is raised to 70℃, and the mixture is reacted under nitrogen protection and 200 rpm stirring for 3 h to obtain mercapto group grafted modified lignin.

5. The production method according to claim 1, wherein S4 The method comprises the following steps: The mercapto group grafted modified lignin, acrylamide, 3-mercaptopropyl trimethoxysilane, cationic monomers, crosslinking agent, solubilizing agent, and deionized water are mixed, the pH value is adjusted to 6.8-7.0, the temperature is adjusted to 3-4℃, and the mixed initiator, dithiothreitol, and chain transfer agent are added to perform branched polymerization reaction in a nitrogen environment to obtain lignin branched modified coal washing flocculant.

6. The preparation method according to claim 2, characterized in that, In S1, the alkaline environment is adjusted by 0.5-2% dilute alkali solution, and before the enzymatic degradation, the system pH value is adjusted by 0.1 mol / L citric acid-sodium citrate buffer; The weight parts of each raw material component are as follows: industrial by-product lignin 150-300 parts by weight, dilute alkali solution 500-750 parts, pH buffer 25-35 parts by weight, lignin peroxidase 0.5-1.5 parts by weight, and 6% hydrogen peroxide solution 75-100 parts by weight.

7. The preparation method according to claim 3, characterized in that, In S2, the sodium hydroxide catalyst is 5% sodium hydroxide solution; The weight parts of each raw material component are as follows: pretreated lignin powder 10-15 parts by weight, epichlorohydrin 15-25 parts by weight, and sodium hydroxide catalyst 0.5-1 part by weight.

8. The preparation method according to claim 4, characterized in that, In S3, the weight parts of each raw material component are as follows: mercaptoethanol 10-20 parts by weight, diacetone acrylamide 0.5-7 parts by weight, isopropyl mercaptoacetate 1-4 parts by weight, acetic anhydride 3-7 parts by weight, and p-hydroxyanisole 0.003-0.01 parts by weight.

9. The preparation method according to claim 5, characterized in that, In S4, the cationic monomers are selected from at least two of methyl acryloyloxyethyl dimethyl butyl ammonium bromide, vinyl benzyl trimethyl ammonium chloride, methacrylamide propyl trimethyl ammonium chloride, and (methyl) acryloyloxyethyl dimethyl benzyl ammonium chloride, and contain methyl acryloyloxyethyl dimethyl butyl ammonium bromide; The chain transfer agent is selected from any one or more of sodium formate, isopropyl alcohol, sodium hypophosphite, and sodium methacrylate. The mixed initiator comprises an azo initiator selected from one or more of azobisdimethylamidino dihydrochloride, azobisdimethylhexyne, azobisdimethylacrylonitrile, 4,4'-azobis(4-cyanopentanoic acid) and a redox initiator selected from benzoyl peroxide, ammonium persulfate, potassium persulfate, sodium hydroxymethanesulfinate formaldehyde, ferrous sulfate, sodium bisulfite; The crosslinking agent is selected from at least two of N-hydroxymethyl acrylamide, diacetone methacrylamide, and diallyl phthalate; The solubilizing agent is 30% sodium xylene sulfonate aqueous solution; The weight parts of each raw material component are as follows: acrylamide crystals 120-220 parts by weight, thiolated graft-modified lignin 15-25 parts by weight, 3-mercaptopropyl trimethoxysilane 0.05-0.9 parts by weight, cationic monomer 20-115 parts by weight, crosslinking agent 0.5-2 parts by weight, solubilizing agent 2-6 parts by weight, deionized water 600-800 parts by weight, chain transfer agent 0.05-1.8 parts by weight, dithiothreitol 0.005-0.05 parts by weight, and mixed initiator 0.001-0.5 parts by weight.

10. A lignin branched modified coal washing flocculant, characterized in that, The preparation method is prepared by any one of claims 1-9. The preparation method is prepared by any one of claims 1-9.

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