Coal flotation agent and preparation method thereof

Abstract

The present application relates to the technical field of mining reagent, and particularly relates to a coal flotation agent and a preparation method thereof. The preparation of the coal flotation agent comprises the following steps: filtering and decoloring kitchen waste oil to obtain pretreated kitchen waste oil; adding the pretreated kitchen waste oil, n-hexane, water and immobilized enzyme into a flask, adding methanol for three times for oscillation reaction, filtering and separating after the reaction is completed, and obtaining biodiesel; mixing kerosene, biodiesel, epoxy soybean oil, sodium lignosulfonate, a foaming agent, a surfactant, an emulsifier and water, and emulsifying and dispersing under stirring to obtain the coal flotation agent. The present application uses kitchen waste oil as raw material to obtain biodiesel, and then uses the biodiesel and kerosene to prepare oil-in-water type coal flotation agent, so that the production cost is reduced, the method is green and environment-friendly, and the flotation effect is good; in addition, the immobilized enzyme with core-shell structure is prepared, the catalytic effect on the kitchen waste oil is good, and the service life is long.

Description

Technical Field

[0001] This invention relates to the field of mining reagents technology, and in particular to a coal flotation agent and its preparation method. Background Technology

[0002] Flotation is one of the effective technical means for coal upgrading. Low-quality coal is improved through flotation, significantly enhancing economic benefits. Flotation typically involves adding flotation agents, including collectors, frothers, emulsifiers, and other trace additives. Various collectors are used in coal flotation, primarily non-polar hydrocarbon oils such as diesel, kerosene, and gasoline, as well as insoluble esters. In coal flotation, most frothers also adsorb onto the coal particle surface and exhibit collecting ability, such as alcohols and organic acids. Emulsifiers are mainly used to formulate oil-in-water composite reagents from flotation agents.

[0003] Every year, my country generates a large amount of waste cooking oil. Simply processing this waste oil into edible oil and then re-entering the market poses a direct threat to public health. Under current technological conditions, it is not advisable to continue recycling and consuming waste cooking oil. The rational development and utilization of waste cooking oil can reduce the risk of it returning to the dining table and is a fundamental measure to solve the problem. Waste cooking oil is rich in fatty acids, which can be used to produce biodiesel. Biodiesel can be used to prepare coal flotation agents.

[0004] Chinese patent application CN201210513536.4 discloses a method for preparing a flotation collector from waste cooking oil. The method involves first removing solid impurities and odors from the waste cooking oil to obtain a relatively clean crude oil. Then, the crude oil undergoes simple acid and alkali treatment, with the addition of certain additives, to generate a collector suitable for flotation of metal oxides and non-metallic minerals. However, this technical solution requires the use of strong acids and alkalis for acid and alkali treatment of the waste cooking oil. Strong acids and alkalis not only easily corrode equipment but also cause serious environmental pollution, increasing production and post-processing costs. Furthermore, the biodiesel obtained by this technical solution is mainly used as a collector. Due to its high viscosity, biodiesel spreads slowly on the coal surface, resulting in poor selectivity when used alone, and its foaming effect is unsatisfactory, affecting the flotation effect. Summary of the Invention

[0005] To solve at least one of the above-mentioned technical problems, the present invention provides a method for preparing a coal flotation agent, comprising the following steps: Step S100, Pretreatment of waste cooking oil: Filter and decolorize the waste cooking oil to obtain pretreated waste cooking oil; Step S200: Preparation of biodiesel: Pretreated kitchen waste oil, n-hexane, water and immobilized enzyme are added to a shake flask, methanol is added in three portions and the mixture is shaken to react. After the reaction is complete, the mixture is filtered and separated to obtain biodiesel. Step S300: Preparation of coal flotation agent: Mix kerosene, biodiesel, epoxidized soybean oil, sodium lignosulfonate, foaming agent, surfactant, emulsifier and water, and emulsify and disperse under stirring conditions to obtain coal flotation agent.

[0006] In the above technical solution, biodiesel is prepared using waste cooking oil as raw material, which can effectively utilize waste cooking oil, reduce the production cost of biodiesel, and reduce environmental pollution, making it green and environmentally friendly. The biodiesel is prepared by immobilized enzyme catalysis, without the use of strong acids or alkalis, thus avoiding environmental pollution and corrosion of production equipment. Methanol is added in three stages during the preparation of biodiesel, which can effectively protect the activity of the immobilized enzyme catalyst and extend its service life. At the same time, compared with free lipase, immobilized enzyme is easier to filter, separate and reuse. Combining biodiesel, kerosene, epoxidized soybean oil, and sodium lignosulfonate can improve the stability of the flotation agent, reduce its viscosity, increase the spreading speed of biodiesel and kerosene on the surface of coal particles, and improve the coal flotation effect. In addition, biodiesel has both collecting and foaming functions, and can work synergistically with the foaming agent to improve the foaming effect while ensuring moderate foam strength, thus improving flotation efficiency. Mixing kerosene, biodiesel, epoxidized soybean oil, sodium lignosulfonate, foaming agent, surfactant, emulsifier, and water, and emulsifying and dispersing them under stirring conditions, can obtain an oil-in-water coal flotation agent, which improves the dispersion speed of the coal flotation agent during use and increases flotation efficiency.

[0007] Preferably, in step S100, the waste cooking oil has a moisture content of 2-3 wt%, an impurity content of 7-9 wt%, and a triglyceride content of 87-91 wt%. In step S200, the pretreated kitchen waste oil is 100 parts by weight; the total amount of methanol is 15-21 parts by weight, which is added in three equal parts in three batches; the amount of n-hexane is 25-30 parts by weight; the amount of water is 25-30 parts by weight; and the amount of immobilized enzyme is 10-30 parts by weight. In step S300, the kerosene is 40-60 parts by weight; the biodiesel is 30-40 parts by weight; the epoxidized soybean oil is 10-20 parts by weight; the sodium lignosulfonate is 1-5 parts by weight; the foaming agent is 10-20 parts by weight; the surfactant is 0.1-0.3 parts by weight; the emulsifier is 0.5-2 parts by weight; and the water is 150-300 parts by weight.

[0008] Preferably, in step S300, the foaming agent is at least one of 2-octanol, n-octanol, cyclohexanol, and pinyl oil; In step S300, the surfactant is at least one of alkylphenol polyoxyethylene sulfate, alkylphenol polyoxyethylene ether sulfonate, alkylphenol ether sulfonate, and alkylphenol ether sulfate. In step S300, the emulsifier is at least one of Span 80, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, and nonylphenol polyoxyethylene ether; Preferably, in step S200, the shaking speed is 100 r / min, the reaction temperature is 50℃, and the reaction time is 24 h; In step S300, the stirring speed is 1500-3000 rpm, and the emulsification and dispersion time is 30-40 min.

[0009] Preferably, in step S200, the preparation of the immobilized enzyme includes the following steps: Step S210: Preparation of modified attapulgite: Attapulgite is plasma activated, then washed and filtered with deionized water. The filtered attapulgite is then added to a dilute hydrochloric acid solution and acidified by ultrasonic dispersion. The acidified attapulgite is washed and dried with deionized water. The dried attapulgite is then added to a methacryloyloxyethyltrimethylammonium chloride aqueous solution. After the reaction is complete, it is filtered and dried to obtain modified attapulgite. Step S220: Preparation of core-shell microspheres: Modified attapulgite clay, water, N,N-methylenebisacrylamide, potassium oleate, acrylamide, and cellulose are mixed and stirred evenly at 50-60℃ to obtain an aqueous phase; toluene and Span 60 are mixed and stirred evenly at 60-65℃ to obtain an oil phase; under continuous stirring at 60-65℃, the aqueous phase is added to the oil phase in three portions to obtain a reverse emulsion; sodium sulfite solution and ammonium persulfate solution are simultaneously added dropwise to the reverse emulsion; after the addition is complete, the reaction continues for a certain period of time; after the reaction is completed, the reverse emulsion is filtered and dried to obtain core-shell microspheres; Step S230: Preparation of aminated microspheres: Core-shell microspheres are added to an alkaline solution and allowed to stand for a certain period of time. Then, epichlorohydrin and a phase transfer catalyst are added sequentially to react. After the reaction is complete, the mixture is filtered, washed, and dried to obtain epoxidized microspheres. The epoxidized microspheres are then added to hexamethylenediamine and the reaction is completed to obtain aminated microspheres. Step S240: Preparation of immobilized enzyme: Mix and stir aminated microspheres, glutaraldehyde and phosphate buffer for 1-2 hours to obtain activation solution. Mix lipase with phosphate buffer and stir evenly to obtain enzyme solution. Mix activation solution and enzyme solution evenly and place in a shaker to immobilize enzyme. After enzyme immobilization, wash, filter and dry to obtain immobilized enzyme.

[0010] In the above technical solution, during step S210, when preparing modified attapulgite, the attapulgite is activated by arc plasma to break the van der Waals forces between attapulgite molecules and the bonding forces of other ionic bonds, making the structure of the attapulgite loose. This facilitates the removal of impurities and inorganic salts from the pores of the attapulgite by deionized water. Acid modification of the plasma-activated attapulgite can increase its specific surface area and pore volume, which is beneficial for its cationic modification by methacryloyloxyethyltrimethylammonium chloride. During step S220, when preparing core-shell microspheres, core-shell microspheres are prepared by reverse emulsion polymerization. Ammonium chloride, acrylamide, and cellulose can form an interpenetrating network with attapulgite during the reaction process, adhering to the surface of attapulgite to obtain a structurally stable porous microsphere structure. In step S230, when preparing aminated microspheres, epoxy groups are first introduced onto the core-shell microspheres, and then a grafting reaction is carried out with hexamethylenediamine to introduce amino groups into the core-shell microspheres. In step S240, when preparing immobilized enzymes, glutaraldehyde is used as a crosslinking agent to activate the amino groups on the aminated microspheres, so that the amino groups on the aminated microspheres react chemically with the amino acid residues on the surface of the lipase to form covalent bonds, thereby improving the immobilization rate and immobilization stability of the lipase on the aminated microspheres.

[0011] Preferably, in step S210, the DC voltage for plasma activation is 30-50 kV, the activation time is 10-15 min, the ultrasonic dispersion temperature is 60-80 °C, and the ultrasonic dispersion time is 1-1.5 h. In step S220, the sodium sulfite solution and ammonium persulfate solution are added dropwise over a period of 6 hours, and the reaction continues for another 3 to 4 hours after the addition is complete. In step S230, the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution; the phase transfer catalyst is at least one of benzyltriethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, and hexadecyltrimethylammonium bromide.

[0012] In step S230, the standing time is 2-3 hours, the reaction temperature for synthesizing epoxidized microspheres is 60-80°C and the reaction time is 2-3 hours, and the reaction temperature for synthesizing aminated microspheres is 50-60°C and the reaction time is 9-10 hours. In step S240, the temperature of the shaker is 25-35℃, and the enzyme fixation time is 5-8 hours.

[0013] Preferably, in step S210, the concentration of the dilute hydrochloric acid solution is 0.5–1 wt%; the concentration of the methacryloyloxyethyltrimethylammonium chloride aqueous solution is 10–15 wt%. In step S220, the sodium sulfite solution concentration is 1.5 wt%; the ammonium persulfate solution concentration is 2 wt%; the modified attapulgite clay is 15-20 parts by weight; water is 80-90 parts by weight; N,N-methylenebisacrylamide is 0.05-0.1 parts by weight; potassium oleate is 0.3-0.5 parts by weight; acrylamide is 20-25 parts by weight; cellulose is 10-15 parts by weight; sodium sulfite solution is 20 parts by weight; ammonium persulfate solution is 20 parts by weight; toluene is 500 parts by weight; and Span 60 is 1-2 parts by weight. In step S230, the concentration of the alkali solution is 10 wt%, and the alkali solution is 100 parts by mass; the core-shell microspheres are 10-15 parts by mass; the epichlorohydrin is 50-55 parts by mass; the phase transfer catalyst is 1-5 parts by mass; the epoxidized microspheres are 10-15 parts by mass; and the hexamethylenediamine is 50-60 parts by mass. In step S240, the amount of aminated microspheres is 10-15 parts by weight, the amount of glutaraldehyde is 3-10 parts by weight, the amount of phosphate buffer is 100 parts by weight, and the concentration of enzyme solution is 0.5-1 wt%.

[0014] Preferably, the modification of the aminated microspheres includes the following steps: Step S250: Mix glutamic acid dialkyl ester ribitol and n-hexane evenly, add immobilized enzyme, sonicate for 10-15 min, let stand at 4℃ for 4 h, and obtain modified immobilized enzyme by vacuum filtration.

[0015] In the above technical solution, glutamic acid dialkyl ester ribitol can coat the surface of the immobilized enzyme, making the immobilized enzyme more resistant to organic solvents and improving the enzyme's activity and lifespan.

[0016] Preferably, the glutamic acid dialkyl ester ribitol is 15-20 parts by weight; n-hexane is 100 parts by weight; and the immobilized enzyme is 20 parts by weight.

[0017] This invention provides a coal flotation agent, which is prepared using the above-mentioned method for preparing a coal flotation agent.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects: 1. Using waste cooking oil as raw material to prepare biodiesel, and then using biodiesel and kerosene together to prepare coal flotation agent, can reduce production costs and reduce environmental pollution, making it green and environmentally friendly; 2. Combining biodiesel, kerosene, epoxidized soybean oil, and sodium lignosulfonate can improve the stability of the flotation agent, reduce its viscosity, increase the spreading speed of biodiesel and kerosene on the surface of coal particles, and improve the coal flotation effect. In addition, biodiesel has both collecting and foaming functions, and can work synergistically with the foaming agent to improve the foaming effect while ensuring moderate foam strength, thus improving flotation efficiency. Mixing kerosene, biodiesel, epoxidized soybean oil, sodium lignosulfonate, foaming agent, surfactant, emulsifier, and water, and emulsifying and dispersing them under stirring conditions, can obtain an oil-in-water coal flotation agent, which improves the dispersion speed of the coal flotation agent during use and increases flotation efficiency. 3. The immobilized enzyme catalysis method is used to prepare biodiesel without the use of strong acids or bases, thus avoiding environmental pollution and corrosion of production equipment; methanol is added in three stages during the preparation of biodiesel, which can effectively protect the activity of the immobilized enzyme catalyst and extend its service life. 4. Using attapulgite as a carrier, immobilized enzymes with core-shell structures were prepared. Methacryloxyethyltrimethylammonium chloride, acrylamide, and cellulose can form an interpenetrating network with attapulgite during the reaction process, resulting in structurally stable porous core-shell microspheres. Amino groups were grafted onto the core-shell microspheres and then activated. The activated amino groups reacted with amino acid residues on the surface of the lipase to form covalent bonds, thereby improving the immobilization rate and stability of the lipase on the aminated microspheres. 5. Surface modification of immobilized enzymes: glutamate dialkyl ester ribitol is coated on the surface of the immobilized enzyme to make it more resistant to organic solvents, thereby improving enzyme activity and lifespan. In summary, the coal flotation agent provided by this invention uses waste cooking oil as raw material to obtain biodiesel, and then uses biodiesel and kerosene together to prepare an oil-in-water coal flotation agent, which reduces production costs, is environmentally friendly, and has a good flotation effect. In addition, a core-shell structured immobilized enzyme was prepared, which has a good catalytic effect on waste cooking oil and a long service life. Detailed Implementation

[0019] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other. Example 1

[0020] This embodiment prepares a coal flotation agent, including the following steps: Step S100, Pretreatment of waste cooking oil: Filter and decolorize the waste cooking oil to obtain pretreated waste cooking oil; Step S200: Preparation of biodiesel: 100 parts by weight of pretreated waste cooking oil, 5 parts by weight of methanol, 25 parts by weight of n-hexane, 25 parts by weight of water, and 10 parts by weight of immobilized enzyme are added to a shake flask. The mixture is reacted at 50°C with a shaking speed of 100 r / min for 8 hours. Then, 5 parts by weight of methanol are added, and the reaction continues for another 8 hours. Another 5 parts by weight of methanol are added, and the reaction continues for another 8 hours. After filtration and separation, biodiesel is obtained. The immobilized enzyme can be reused 10 times. Its preparation includes the following steps: Step S210: Preparation of modified attapulgite: Attapulgite is plasma activated at a DC voltage of 30-50 kV for 10-15 min, then washed and filtered with deionized water. The filtered attapulgite is added to a 0.5 wt% dilute hydrochloric acid solution and ultrasonically dispersed at 60-80℃ for 1-1.5 h for acidification modification. The acidified attapulgite is washed and dried with deionized water. The dried attapulgite is added to a 10 wt% aqueous solution of methacryloyloxyethyltrimethylammonium chloride. After the reaction is complete, it is filtered and dried to obtain modified attapulgite. Step S220: Preparation of core-shell microspheres: 15 parts by mass of modified attapulgite, 80 parts by mass of water, 0.05 parts by mass of N,N-methylenebisacrylamide, 0.3 parts by mass of potassium oleate, 20 parts by mass of acrylamide, and 10 parts by mass of cellulose are mixed and stirred evenly at 50-60°C to obtain an aqueous phase; 500 parts by mass of toluene and 1 part by mass of Span 60 are mixed and stirred evenly at 60-65°C to obtain an oil phase; under continuous stirring at 60-65°C, the aqueous phase is added to the oil phase in three portions to obtain a reverse emulsion; 20 parts by mass of a 1.5 wt% sodium sulfite solution and 20 parts by mass of a 2 wt% ammonium persulfate solution are simultaneously added dropwise to the reverse emulsion over a period of 6 hours; after the addition is complete, the reaction continues for 3 hours; after the reaction is complete, the reverse emulsion is filtered and dried to obtain core-shell microspheres; Step S230: Preparation of aminated microspheres: 10 parts by mass of core-shell microspheres were added to 100 parts by mass of 10 wt% alkaline solution. After standing for 2 hours, 50 parts by mass of epichlorohydrin and 1 part by mass of benzyltriethylammonium chloride were added sequentially. The mixture was reacted at 60-80℃ for 2-3 hours. After filtration, washing and drying, epoxidized microspheres were obtained. 10 parts by mass of epoxidized microspheres were added to 50 parts by mass of hexamethylenediamine and reacted at 50-60℃ for 9-10 hours to obtain aminated microspheres. Step S240: Preparation of immobilized enzyme: Mix 10 parts by weight of aminated microspheres, 3 parts by weight of glutaraldehyde and 100 parts by weight of phosphate buffer and stir for 1-2 hours to obtain an activation solution. Mix 0.5 parts by weight of lipase with 100 parts by weight of phosphate buffer and stir evenly to obtain an enzyme solution. Mix the activation solution and the enzyme solution evenly and place them in a shaker at 25-35°C to immobilize the enzyme for 5-8 hours. After washing, filtering and drying, the immobilized enzyme is obtained. Step S300: Preparation of coal flotation agent: Mix 40 parts by weight of kerosene, 40 parts by weight of biodiesel, 20 parts by weight of epoxidized soybean oil, 5 parts by weight of sodium lignosulfonate, 10 parts by weight of 2-octanol, 0.1 parts by weight of alkylphenol polyoxyethylene sulfate, 0.5 parts by weight of Span 80 and 150 parts by weight of water, and emulsify and disperse at a speed of 1500-3000 rpm for 30-40 min to obtain the coal flotation agent. Example 2

[0021] This embodiment prepares a coal flotation agent, including the following steps: Step S100, Pretreatment of waste cooking oil: Filter and decolorize the waste cooking oil to obtain pretreated waste cooking oil; Step S200: Preparation of biodiesel: 100 parts by weight of pretreated waste cooking oil, 5 parts by weight of methanol, 25 parts by weight of n-hexane, 25 parts by weight of water, and 10 parts by weight of immobilized enzyme are added to a shake flask. The mixture is reacted at 50°C with a shaking speed of 100 r / min for 8 hours. Then, 5 parts by weight of methanol are added, and the reaction continues for another 8 hours. Another 5 parts by weight of methanol are added, and the reaction continues for another 8 hours. After filtration and separation, biodiesel is obtained. The immobilized enzyme is a modified immobilized enzyme that can be reused 18 times. Its preparation includes the following steps: Step S210: Preparation of modified attapulgite: Attapulgite is plasma activated at a DC voltage of 30-50 kV for 10-15 min, then washed and filtered with deionized water. The filtered attapulgite is added to a 0.5 wt% dilute hydrochloric acid solution and ultrasonically dispersed at 60-80℃ for 1-1.5 h for acidification modification. The acidified attapulgite is washed and dried with deionized water. The dried attapulgite is added to a 10 wt% aqueous solution of methacryloyloxyethyltrimethylammonium chloride. After the reaction is complete, it is filtered and dried to obtain modified attapulgite. Step S220: Preparation of core-shell microspheres: 15 parts by mass of modified attapulgite, 80 parts by mass of water, 0.05 parts by mass of N,N-methylenebisacrylamide, 0.3 parts by mass of potassium oleate, 20 parts by mass of acrylamide, and 10 parts by mass of cellulose are mixed and stirred evenly at 50-60°C to obtain an aqueous phase; 500 parts by mass of toluene and 1 part by mass of Span 60 are mixed and stirred evenly at 60-65°C to obtain an oil phase; under continuous stirring at 60-65°C, the aqueous phase is added to the oil phase in three portions to obtain a reverse emulsion; 20 parts by mass of a 1.5 wt% sodium sulfite solution and 20 parts by mass of a 2 wt% ammonium persulfate solution are simultaneously added dropwise to the reverse emulsion over a period of 6 hours; after the addition is complete, the reaction continues for 3 hours; after the reaction is complete, the reverse emulsion is filtered and dried to obtain core-shell microspheres; Step S230: Preparation of aminated microspheres: 10 parts by mass of core-shell microspheres were added to 100 parts by mass of 10 wt% alkaline solution. After standing for 2 hours, 50 parts by mass of epichlorohydrin and 1 part by mass of benzyltriethylammonium chloride were added sequentially. The mixture was reacted at 60-80℃ for 2-3 hours. After filtration, washing and drying, epoxidized microspheres were obtained. 10 parts by mass of epoxidized microspheres were added to 50 parts by mass of hexamethylenediamine and reacted at 50-60℃ for 9-10 hours to obtain aminated microspheres. Step S240: Preparation of immobilized enzyme: Mix 10 parts by weight of aminated microspheres, 3 parts by weight of glutaraldehyde and 100 parts by weight of phosphate buffer and stir for 1-2 hours to obtain an activation solution. Mix 0.5 parts by weight of lipase with 100 parts by weight of phosphate buffer and stir evenly to obtain an enzyme solution. Mix the activation solution and the enzyme solution evenly and place them in a shaker at 25-35°C to immobilize the enzyme for 5-8 hours. After washing, filtering and drying, the immobilized enzyme is obtained. Step S250: Preparation of modified immobilized enzyme: Mix 15 parts by mass of glutamic acid dialkyl ester ribitol and 100 parts by mass of n-hexane and stir evenly. Add 20 parts by mass of immobilized enzyme, sonicate for 10-15 min, let stand at 4℃ for 4 h, and filter under reduced pressure to obtain modified immobilized enzyme. Step S300: Preparation of coal flotation agent: Mix 40 parts by weight of kerosene, 40 parts by weight of biodiesel, 20 parts by weight of epoxidized soybean oil, 5 parts by weight of sodium lignosulfonate, 10 parts by weight of 2-octanol, 0.1 parts by weight of alkylphenol polyoxyethylene sulfate, 0.5 parts by weight of Span 80 and 150 parts by weight of water, and emulsify and disperse at a speed of 1500-3000 rpm for 30-40 min to obtain the coal flotation agent. Example 3

[0022] This embodiment prepares a coal flotation agent, including the following steps: Step S100, Pretreatment of waste cooking oil: Filter and decolorize the waste cooking oil to obtain pretreated waste cooking oil; Step S200: Preparation of biodiesel: 100 parts by weight of pretreated waste cooking oil, 7 parts by weight of methanol, 30 parts by weight of n-hexane, 30 parts by weight of water, and 30 parts by weight of immobilized enzyme are added to a shake flask. The mixture is reacted at 50°C with a shaking speed of 100 r / min for 8 hours. Then, 7 parts by weight of methanol are added, and the reaction continues for another 8 hours. Another 7 parts by weight of methanol are added, and the reaction continues for another 8 hours. After filtration and separation, biodiesel is obtained. The immobilized enzyme is a modified immobilized enzyme that can be reused 20 times. Its preparation includes the following steps: Step S210: Preparation of modified attapulgite: Attapulgite is plasma activated at a DC voltage of 30-50 kV for 10-15 min, then washed and filtered with deionized water. The filtered attapulgite is added to a 1 wt% dilute hydrochloric acid solution and ultrasonically dispersed at 60-80℃ for 1-1.5 h for acidification modification. The acidified attapulgite is washed and dried with deionized water. The dried attapulgite is added to a 15 wt% aqueous solution of methacryloyloxyethyltrimethylammonium chloride. After the reaction is complete, it is filtered and dried to obtain modified attapulgite. Step S220: Preparation of core-shell microspheres: 20 parts by mass of modified attapulgite, 90 parts by mass of water, 0.1 parts by mass of N,N-methylenebisacrylamide, 0.5 parts by mass of potassium oleate, 25 parts by mass of acrylamide, and 15 parts by mass of cellulose are mixed and stirred evenly at 50-60°C to obtain an aqueous phase; 500 parts by mass of toluene and 2 parts by mass of Span 60 are mixed and stirred evenly at 60-65°C to obtain an oil phase; under continuous stirring at 60-65°C, the aqueous phase is added to the oil phase in three portions to obtain a reverse emulsion; 20 parts by mass of a 1.5 wt% sodium sulfite solution and 20 parts by mass of a 2 wt% ammonium persulfate solution are simultaneously added dropwise to the reverse emulsion over a period of 6 hours; after the addition is complete, the reaction continues for 3 hours; after the reaction is complete, the reverse emulsion is filtered and dried to obtain core-shell microspheres; Step S230: Preparation of aminated microspheres: 15 parts by mass of core-shell microspheres were added to 100 parts by mass of 10 wt% alkaline solution. After standing for 2 hours, 55 parts by mass of epichlorohydrin and 5 parts by mass of dodecyltrimethylammonium chloride were added sequentially. The mixture was reacted at 60-80°C for 2-3 hours. After filtration, washing and drying, epoxidized microspheres were obtained. 15 parts by mass of epoxidized microspheres were added to 60 parts by mass of hexamethylenediamine and reacted at 50-60°C for 9-10 hours to obtain aminated microspheres. Step S240: Preparation of immobilized enzyme: Mix 15 parts by weight of aminated microspheres, 10 parts by weight of glutaraldehyde and 100 parts by weight of phosphate buffer and stir for 1-2 hours to obtain an activation solution. Mix 0.5 parts by weight of lipase with 100 parts by weight of phosphate buffer and stir evenly to obtain an enzyme solution. Mix the activation solution and the enzyme solution evenly and place them in a shaker at 25-35°C to immobilize the enzyme for 5-8 hours. After washing, filtering and drying, the immobilized enzyme is obtained. Step S250: Preparation of modified immobilized enzyme: Mix 20 parts by mass of glutamic acid dialkyl ester ribitol and 100 parts by mass of n-hexane and stir evenly. Add 30 parts by mass of immobilized enzyme, sonicate for 10-15 min, let stand at 4℃ for 4 h, and filter under reduced pressure to obtain modified immobilized enzyme. Step S300: Preparation of coal flotation agent: Mix 60 parts by weight of kerosene, 30 parts by weight of biodiesel, 10 parts by weight of epoxidized soybean oil, 1 part by weight of sodium lignosulfonate, 20 parts by weight of pine oil, 0.3 parts by weight of alkylphenol polyoxyethylene ether sulfonate, 2 parts by weight of sodium dodecylbenzene sulfonate, and 300 parts by weight of water, and emulsify and disperse at a speed of 1500-3000 rpm for 30-40 min to obtain the coal flotation agent. Example 4

[0023] This embodiment prepares a coal flotation agent, including the following steps: Step S100, Pretreatment of waste cooking oil: Filter and decolorize the waste cooking oil to obtain pretreated waste cooking oil; Step S200: Preparation of biodiesel: 100 parts by weight of pretreated waste cooking oil, 6 parts by weight of methanol, 28 parts by weight of n-hexane, 28 parts by weight of water, and 20 parts by weight of immobilized enzyme are added to a shake flask. The mixture is reacted at 50°C with a shaking speed of 100 r / min for 8 hours. Then, 6 parts by weight of methanol are added, and the reaction continues for another 8 hours. Another 6 parts by weight of methanol are added, and the reaction continues for another 8 hours. After filtration and separation, biodiesel is obtained. The immobilized enzyme is a modified immobilized enzyme that can be reused 22 times. Its preparation includes the following steps: Step S210: Preparation of modified attapulgite: Attapulgite is plasma activated at a DC voltage of 30-50 kV for 10-15 min, then washed and filtered with deionized water. The filtered attapulgite is added to a 0.5 wt% dilute hydrochloric acid solution and ultrasonically dispersed at 60-80℃ for 1-1.5 h for acidification modification. The acidified attapulgite is washed and dried with deionized water. The dried attapulgite is added to a 15 wt% aqueous solution of methacryloyloxyethyltrimethylammonium chloride. After the reaction is complete, it is filtered and dried to obtain modified attapulgite. Step S220: Preparation of core-shell microspheres: 18 parts by mass of modified attapulgite, 85 parts by mass of water, 0.08 parts by mass of N,N-methylenebisacrylamide, 0.4 parts by mass of potassium oleate, 23 parts by mass of acrylamide, and 13 parts by mass of cellulose are mixed and stirred evenly at 50-60°C to obtain an aqueous phase; 500 parts by mass of toluene and 1.5 parts by mass of Span 60 are mixed and stirred evenly at 60-65°C to obtain an oil phase; under continuous stirring at 60-65°C, the aqueous phase is added to the oil phase in three portions to obtain a reverse emulsion; 20 parts by mass of a 1.5 wt% sodium sulfite solution and 20 parts by mass of a 2 wt% ammonium persulfate solution are simultaneously added dropwise to the reverse emulsion over a period of 6 hours; after the addition is complete, the reaction continues for 3 hours; after the reaction is complete, the reverse emulsion is filtered and dried to obtain core-shell microspheres; Step S230: Preparation of aminated microspheres: 13 parts by mass of core-shell microspheres were added to 100 parts by mass of 10 wt% alkaline solution. After standing for 2 hours, 55 parts by mass of epichlorohydrin and 3 parts by mass of tetradecyltrimethylammonium chloride were added sequentially. The mixture was reacted at 60-80°C for 2-3 hours. After filtration, washing and drying, epoxidized microspheres were obtained. 13 parts by mass of epoxidized microspheres were added to 55 parts by mass of hexamethylenediamine and reacted at 50-60°C for 9-10 hours to obtain aminated microspheres. Step S240: Preparation of immobilized enzyme: Mix 13 parts by weight of aminated microspheres, 7 parts by weight of glutaraldehyde and 100 parts by weight of phosphate buffer and stir for 1-2 hours to obtain an activation solution. Mix 1 part by weight of lipase with 100 parts by weight of phosphate buffer and stir evenly to obtain an enzyme solution. Mix the activation solution and the enzyme solution evenly and place them in a shaker at 25-35°C to immobilize the enzyme for 5-8 hours. After washing, filtering and drying, the immobilized enzyme is obtained. Step S250: Preparation of modified immobilized enzyme: Mix 20 parts by mass of glutamic acid dialkyl ester ribitol and 100 parts by mass of n-hexane and stir evenly. Add 25 parts by mass of immobilized enzyme, sonicate for 10-15 min, let stand at 4℃ for 4 h, and filter under reduced pressure to obtain modified immobilized enzyme. Step S300: Preparation of coal flotation agent: Mix 50 parts by weight of kerosene, 35 parts by weight of biodiesel, 15 parts by weight of epoxidized soybean oil, 3 parts by weight of sodium lignosulfonate, 15 parts by weight of cyclohexanol, 0.2 parts by weight of alkylphenol ether sulfonate, 1 part by weight of nonylphenol polyoxyethylene ether, and 250 parts by weight of water, and emulsify and disperse at a speed of 1500-3000 rpm for 30-40 min to obtain the coal flotation agent. Example 5

[0024] This embodiment prepares a coal flotation agent, including the following steps: Step S100, Pretreatment of waste cooking oil: Filter and decolorize the waste cooking oil to obtain pretreated waste cooking oil; Step S200: Preparation of biodiesel: 100 parts by weight of pretreated waste cooking oil, 7 parts by weight of methanol, 25 parts by weight of n-hexane, 25 parts by weight of water, and 10 parts by weight of immobilized enzyme are added to a shake flask. The mixture is reacted at 50°C with a shaking speed of 100 r / min for 8 hours. Then, 7 parts by weight of methanol are added, and the reaction continues for another 8 hours. Another 7 parts by weight of methanol are added, and the reaction continues for another 8 hours. After filtration and separation, biodiesel is obtained. The immobilized enzyme can be reused 19 times. Its preparation includes the following steps: Step S210: Preparation of modified attapulgite: Attapulgite is plasma activated at a DC voltage of 30-50 kV for 10-15 min, then washed and filtered with deionized water. The filtered attapulgite is added to a 0.5 wt% dilute hydrochloric acid solution and ultrasonically dispersed at 60-80℃ for 1-1.5 h for acidification modification. The acidified attapulgite is washed and dried with deionized water. The dried attapulgite is added to a 10 wt% aqueous solution of methacryloyloxyethyltrimethylammonium chloride. After the reaction is complete, it is filtered and dried to obtain modified attapulgite. Step S220: Preparation of core-shell microspheres: 15 parts by mass of modified attapulgite, 80 parts by mass of water, 0.1 parts by mass of N,N-methylenebisacrylamide, 0.3 parts by mass of potassium oleate, 22 parts by mass of acrylamide, and 12 parts by mass of cellulose are mixed and stirred evenly at 50-60°C to obtain an aqueous phase; 500 parts by mass of toluene and 1.5 parts by mass of Span 60 are mixed and stirred evenly at 60-65°C to obtain an oil phase; under continuous stirring at 60-65°C, the aqueous phase is added to the oil phase in three portions to obtain a reverse emulsion; 20 parts by mass of a 1.5 wt% sodium sulfite solution and 20 parts by mass of a 2 wt% ammonium persulfate solution are simultaneously added dropwise to the reverse emulsion over a period of 6 hours; after the addition is complete, the reaction continues for 3 hours; after the reaction is complete, the reverse emulsion is filtered and dried to obtain core-shell microspheres; Step S230: Preparation of aminated microspheres: 10 parts by mass of core-shell microspheres were added to 100 parts by mass of 10 wt% alkaline solution. After standing for 2 hours, 50 parts by mass of epichlorohydrin and 1 part by mass of hexadecyltrimethylammonium bromide were added sequentially. The mixture was reacted at 60-80℃ for 2-3 hours. After filtration, washing and drying, epoxidized microspheres were obtained. 10 parts by mass of epoxidized microspheres were added to 50 parts by mass of hexamethylenediamine and reacted at 50-60℃ for 9-10 hours to obtain aminated microspheres. Step S240: Preparation of immobilized enzyme: Mix 10 parts by weight of aminated microspheres, 3 parts by weight of glutaraldehyde and 100 parts by weight of phosphate buffer and stir for 1-2 hours to obtain an activation solution. Mix 0.8 parts by weight of lipase with 100 parts by weight of phosphate buffer and stir evenly to obtain an enzyme solution. Mix the activation solution and the enzyme solution evenly and place them in a shaker at 25-35°C to immobilize the enzyme for 5-8 hours. After washing, filtering and drying, the immobilized enzyme is obtained. Step S250: Preparation of modified immobilized enzyme: Mix 15 parts by mass of glutamic acid dialkyl ester ribitol and 100 parts by mass of n-hexane and stir evenly. Add 20 parts by mass of immobilized enzyme, sonicate for 10-15 min, let stand at 4℃ for 4 h, and filter under reduced pressure to obtain modified immobilized enzyme. Step S300: Preparation of coal flotation agent: Mix 50 parts by weight of kerosene, 40 parts by weight of biodiesel, 10 parts by weight of epoxidized soybean oil, 3 parts by weight of sodium lignosulfonate, 5 parts by weight of 2-octanol, 5 parts by weight of pine oil, 0.1 parts by weight of alkylphenol ether sulfate, 0.5 parts by weight of sodium dodecyl sulfate, and 200 parts by weight of water, and emulsify and disperse at a speed of 1500-3000 rpm for 30-40 min to obtain the coal flotation agent.

[0025] Performance testing The coal flotation agents in Examples 1-5 were used to conduct coal flotation tests. 100g of coal flotation agent was added to each ton of raw coal particles. The test results are shown in Table 1.

[0026]

[0027] As shown in Table 1, when using the coal flotation agents in Examples 1-5, the yield of clean coal is high, the ash content of clean coal is low, and the flotation effect on coal is good.

[0028] The embodiments described above are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a coal flotation agent, characterized in that, Includes the following steps: Step S100, Pretreatment of waste cooking oil: Filter and decolorize the waste cooking oil to obtain pretreated waste cooking oil; Step S200: Preparation of biodiesel: Pretreated kitchen waste oil, n-hexane, water, and immobilized enzyme are added to a shake flask. Methanol is added in three portions, and the mixture is shaken during the reaction. After the reaction is complete, the mixture is filtered to obtain biodiesel. The preparation of the immobilized enzyme includes the following steps: Step S210: Preparation of modified attapulgite: Attapulgite is plasma activated, then washed and filtered with deionized water. The filtered attapulgite is then added to a dilute hydrochloric acid solution and acidified by ultrasonic dispersion. The acidified attapulgite is washed and dried with deionized water. The dried attapulgite is then added to a methacryloyloxyethyltrimethylammonium chloride aqueous solution. After the reaction is complete, it is filtered and dried to obtain modified attapulgite. Step S220: Preparation of core-shell microspheres: Modified attapulgite clay, water, N,N-methylenebisacrylamide, potassium oleate, acrylamide, and cellulose are mixed and stirred evenly at 50-60℃ to obtain an aqueous phase; toluene and Span 60 are mixed and stirred evenly at 60-65℃ to obtain an oil phase; under continuous stirring at 60-65℃, the aqueous phase is added to the oil phase in three portions to obtain a reverse emulsion; sodium sulfite solution and ammonium persulfate solution are simultaneously added dropwise to the reverse emulsion; after the addition is complete, the reaction continues for a certain period of time; after the reaction is completed, the reverse emulsion is filtered and dried to obtain core-shell microspheres; Step S230: Preparation of aminated microspheres: Core-shell microspheres are added to an alkaline solution and allowed to stand for a certain period of time. Then, epichlorohydrin and a phase transfer catalyst are added sequentially to react. After the reaction is complete, the mixture is filtered, washed, and dried to obtain epoxidized microspheres. The epoxidized microspheres are then added to hexamethylenediamine and the reaction is completed to obtain aminated microspheres. Step S240: Preparation of immobilized enzyme: Mix and stir aminated microspheres, glutaraldehyde and phosphate buffer for 1-2 hours to obtain activation solution. Mix lipase with phosphate buffer and stir evenly to obtain enzyme solution. Mix activation solution and enzyme solution evenly and place in a shaker to immobilize enzyme. After enzyme immobilization, wash, filter and dry to obtain immobilized enzyme. Step S300: Preparation of coal flotation agent: Mix kerosene, biodiesel, epoxidized soybean oil, sodium lignosulfonate, foaming agent, surfactant, emulsifier and water, and emulsify and disperse under stirring conditions to obtain coal flotation agent.

2. The method for preparing the coal flotation agent according to claim 1, characterized in that, In step S100, the waste cooking oil has a moisture content of 2-3 wt%, an impurity content of 7-9 wt%, and a triglyceride content of 87-91 wt%. In step S200, the pretreated kitchen waste oil is 100 parts by weight; the total amount of methanol is 15-21 parts by weight, which is added in three equal parts in three batches; the amount of n-hexane is 25-30 parts by weight; the amount of water is 25-30 parts by weight; and the amount of immobilized enzyme is 10-30 parts by weight. In step S300, the kerosene is 40-60 parts by weight; the biodiesel is 30-40 parts by weight; the epoxidized soybean oil is 10-20 parts by weight; the sodium lignosulfonate is 1-5 parts by weight; the foaming agent is 10-20 parts by weight; the surfactant is 0.1-0.3 parts by weight; the emulsifier is 0.5-2 parts by weight; and the water is 150-300 parts by weight.

3. The method for preparing the coal flotation agent according to claim 1, characterized in that, In step S300, the foaming agent is at least one of 2-octanol, n-octanol, cyclohexanol, and pinyl oil; In step S300, the surfactant is at least one of alkylphenol polyoxyethylene sulfate, alkylphenol polyoxyethylene ether sulfonate, alkylphenol ether sulfonate, and alkylphenol ether sulfate. In step S300, the emulsifier is at least one of Span 80, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, and nonylphenol polyoxyethylene ether.

4. The method for preparing the coal flotation agent according to claim 1, characterized in that, In step S200, the shaking speed is 100 r / min, the reaction temperature is 50℃, and the reaction time is 24 h; In step S300, the stirring speed is 1500-3000 rpm and the emulsification and dispersion time is 30-40 min.

5. The method for preparing the coal flotation agent according to claim 1, characterized in that, In step S210, the DC voltage for plasma activation is 30–50 kV, the activation time is 10–15 min, the ultrasonic dispersion temperature is 60–80 °C, and the ultrasonic dispersion time is 1–1.5 h. In step S220, the sodium sulfite solution and ammonium persulfate solution are added dropwise over a period of 6 hours, and the reaction continues for another 3 to 4 hours after the addition is complete. In step S230, the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution; the phase transfer catalyst is at least one selected from benzyltriethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, and hexadecyltrimethylammonium bromide. In step S230, the standing time is 2-3 hours, the reaction temperature for synthesizing epoxidized microspheres is 60-80°C and the reaction time is 2-3 hours, and the reaction temperature for synthesizing aminated microspheres is 50-60°C and the reaction time is 9-10 hours. In step S240, the temperature of the shaker is 25-35℃, and the enzyme fixation time is 5-8 hours.

6. The method for preparing the coal flotation agent according to claim 1, characterized in that, In step S210, the concentration of the dilute hydrochloric acid solution is 0.5–1 wt%; the concentration of the aqueous solution of methacryloyloxyethyltrimethylammonium chloride is 10–15 wt%. In step S220, the sodium sulfite solution concentration is 1.5 wt%; the ammonium persulfate solution concentration is 2 wt%; the modified attapulgite clay is 15-20 parts by weight; water is 80-90 parts by weight; N,N-methylenebisacrylamide is 0.05-0.1 parts by weight; potassium oleate is 0.3-0.5 parts by weight; acrylamide is 20-25 parts by weight; cellulose is 10-15 parts by weight; sodium sulfite solution is 20 parts by weight; ammonium persulfate solution is 20 parts by weight; toluene is 500 parts by weight; and Span 60 is 1-2 parts by weight. In step S230, the concentration of the alkali solution is 10 wt%, and the alkali solution is 100 parts by mass; the core-shell microspheres are 10-15 parts by mass; the epichlorohydrin is 50-55 parts by mass; the phase transfer catalyst is 1-5 parts by mass; the epoxidized microspheres are 10-15 parts by mass; and the hexamethylenediamine is 50-60 parts by mass. In step S240, the amount of aminated microspheres is 10-15 parts by weight, the amount of glutaraldehyde is 3-10 parts by weight, the amount of phosphate buffer is 100 parts by weight, and the concentration of enzyme solution is 0.5-1 wt%.

7. The method for preparing the coal flotation agent according to claim 1, characterized in that, The modification of aminated microspheres includes the following steps: Step S250: Mix glutamic acid dialkyl ester ribitol and n-hexane evenly, add immobilized enzyme, sonicate for 10-15 min, let stand at 4℃ for 4 h, and obtain modified immobilized enzyme by vacuum filtration.

8. The method for preparing the coal flotation agent according to claim 7, characterized in that, The dialkyl glutamate ester ribitol is 15-20 parts by weight; n-hexane is 100 parts by weight; and the immobilized enzyme is 20 parts by weight.

9. A coal flotation agent, characterized in that, It is prepared by the method of any one of claims 1 to 8 for preparing a coal flotation agent.

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