Emulsified waste oil for flotation reagent as well as preparation method and application of emulsified waste oil

Abstract

The invention relates to emulsified waste oil for a flotation reagent as well as a preparation method and application of the emulsified waste oil, belongs to the technical field of flotation, and is used for solving at least one of the problems of poor stability, poor dispersity, poor flotation effect and the like of the emulsified waste oil prepared by the existing method. PSBMA and Tween 80 are added in the preparation of the emulsified waste oil to serve as compound flotation reagents, the stability of emulsion can be improved, PSBMA is a long-chain polymer and has amphipathy, when PSBMA reacts with the waste oil, each macromolecular polymer adsorbed on an interface is similar to side-by-side aggregation of a plurality of connected small molecules, and the stability of the emulsion is improved. And when the macromolecular polymer is desorbed from an interface, the whole main chain needs to be removed, so that more energy is needed to break through a high-energy barrier, the stability of the emulsion is effectively improved, the collision probability with target minerals is increased, emulsion droplets are more easily in contact with particles and spread on the surface, and the flotation effect is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of flotation, and in particular to an emulsified waste oil used as a flotation agent, and a preparation method and application thereof. Background Art

[0002] China is the world's largest coal producer and consumer. A large amount of coal-based solid waste such as fly ash and coal gasification slag is generated during the mining and processing of coal. At present, the utilization rate of coal-based solid waste is low, mainly because it cannot be directly used as fuel due to its low calorific value, and the relatively high content of unburned carbon cannot be directly mixed with building materials. Therefore, the separation of charcoal ash is the prerequisite for its large-scale utilization. Flotation has the advantages of simple operation and high recovery rate. It is an effective way to achieve the separation of coal gasification slag and charcoal ash. However, the surface of coal gasification slag contains many oxygen functional groups, rich pores, and charcoal ash is mixed with each other. During the flotation process, traditional non-polar hydrocarbon oil collectors are difficult to effectively adsorb and spread on its surface, resulting in large reagent consumption and low economic benefits. As the amount of reagent increases, the flotation effect is not good. Therefore, finding a green, efficient and low-cost collector is the key to realizing the resource utilization of coal gasification slag.

[0003] At present, the annual output of waste oil in my country exceeds 1.2 billion liters. Waste oil usually contains a variety of harmful substances such as hydrocarbons, esters, heteroatoms, etc., which pose a huge threat to the environment and human health. The oxygen-containing functional groups, such as C=O, CO, O=CO, etc., can selectively act on the surface of coal particles, effectively enhancing their hydrophobicity, and have the potential to be flotation agents. However, direct use has problems such as large dosage of agents and poor recovery effect. Emulsion is a dispersion system formed by two incompatible liquids, one of which is evenly dispersed in the other liquid in the form of tiny droplets. Emulsifying the flotation agent can greatly improve the dispersibility of the agent and increase the contact area with coal particles, thereby obtaining a better flotation recovery effect of coal gasification slag with a smaller dosage of agent.

[0004] In the prior art, waste oil is usually emulsified by various emulsifiers, but the emulsion has poor stability, short stability time, serious demulsification problem and other problems. Summary of the invention

[0005] In view of the above analysis, the present invention aims to provide an emulsified waste oil for flotation agent and a preparation method and application thereof, so as to solve at least one of the problems of poor stability, poor dispersibility, and poor flotation effect of the emulsified waste oil prepared by the existing method.

[0006] In a first aspect, the present invention provides a method for preparing emulsified waste oil for flotation reagent, comprising the following steps:

[0007] (1) centrifuging the waste oil to obtain a stable waste oil system;

[0008] (2) Adding polymethacrylate sulfobetaine and Tween 80 to the stable waste oil system to obtain a mixed system, heating, stirring, and adding water to obtain emulsified waste oil.

[0009] Furthermore, in step (1), the centrifugal speed is 9000-15000 r / min, and the centrifugal time is 5-15 min.

[0010] Furthermore, in step (2), the average molecular weight of polymethacrylate sulfobetaine is greater than 3.5 KDa.

[0011] Furthermore, in step (2), the mass of polymethacrylate sulfobetaine is 2-5% of the total mass of the mixed system, and the mass ratio of polymethacrylate sulfobetaine to Tween 80 is 1:3-3:1.

[0012] Furthermore, in step (2), the stirring speed is 400 to 1200 r / min, the stirring time is 6 to 16 min, and the mass ratio of added water to waste oil is 1:2 to 2:1.

[0013] Furthermore, in step (2), the polymethacrylate sulfobetaine is prepared by the following method:

[0014] (a) adding an aqueous solution of sulfobetaine methacrylate (SBMA) to an initiator in a nitrogen atmosphere to obtain a sulfobetaine methacrylate (SBMA) mixed solution;

[0015] (b) stirring and heating the sulfobetaine methacrylate (SBMA) mixed solution in a nitrogen environment to obtain a polysulfobetaine methacrylate (PSBMA) solution;

[0016] (c) dialyzing the poly(methacrylate sulfobetaine) (PSBMA) solution and drying to obtain poly(methacrylate sulfobetaine) (PSBMA) powder.

[0017] Furthermore, in step (a), the mass concentration of methacrylate sulfobetaine water solution is 10-15%, and nitrogen is introduced for 8-12 minutes. Preferably, the initiator is potassium persulfate, and the mass of the initiator is 0.2-0.4% of the mass of SBMA.

[0018] Furthermore, in step (c), the dialysis uses a dialysis bag with a molecular weight of 3.5 KDa, and the dialysis time is 68 to 72 hours.

[0019] In a second aspect, the present invention provides an emulsified waste oil prepared by the above method.

[0020] In a third aspect, the present invention provides an application of the above-mentioned emulsified waste oil in the flotation of coal-based solid waste.

[0021] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0022] (1) The present invention uses polymethacrylate sulfobetaine, a long-chain amphiphilic polymer, and Tween 80 as a composite flotation agent to emulsify waste oil. The sporadic effects of polymethacrylate sulfobetaine and Tween 80 on the interface are combined to effectively improve the stability of the emulsion. At the same time, the waste oil is centrifuged for pretreatment to improve its self-emulsification and emulsification capabilities. Combined with the high energy barrier and multi-factor regulated emulsification process brought about by the side-by-side aggregation of methacrylate sulfobetaine after polymerization, the stability and dispersibility of the waste oil emulsion are greatly improved. The emulsion has a long existence period and more exposed surface functional groups, which can meet the flotation needs of different production scales at different times;

[0023] (2) PSBMA of the present invention is a long-chain polymer with amphiphilicity. When it reacts with waste oil, each macromolecular polymer adsorbed on the interface is similar to a plurality of small molecules connected together and aggregated side by side. When the macromolecular polymer is desorbed from the interface, the entire main chain needs to be removed, resulting in more energy required to break through the high energy barrier, thereby effectively improving the stability of the emulsion, increasing the probability of collision with the target mineral, and making it easier for the emulsion droplets to contact the particles and spread on the surface, thereby effectively improving the flotation effect;

[0024] (3) The PSBMA described in the present invention can improve the flotation effect in two ways. On the one hand, the oxygen-containing functional groups of PSBMA can form hydrogen bonds with the hydrophilic sites on the surface of unburned carbon in coal-based solid waste, thereby improving the hydrophobicity of the hydrophilic region, and the straight-chain alkane structure of PSBMA can also produce van der Waals forces with the methyl and methylene groups on the surface of unburned carbon, thereby improving the floatability of unburned carbon in coal-based solid waste; on the other hand, the PSBMA has an average molecular weight of >3.5KDa, which is larger than that of betaine. The larger molecular weight requires more energy when it is desorbed on the liquid film surface, thereby ensuring the droplet structure of the emulsion. The droplet structure has a larger specific surface area, exposing more surface functional groups in the waste oil, and effectively improving the mineralization efficiency of the coal-based solid waste during the flotation process;

[0025] (4) The present invention adjusts the parameters such as the amount of emulsifier, water-oil ratio, stirring speed, stirring time, etc., so that the waste oil forms a stable emulsified state with good dispersibility and long-term stability, increases the probability of collision with the target mineral, and makes it easier for the emulsion droplets to contact the particles and spread on the surface, thereby effectively improving the flotation effect.

[0026] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be achieved and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0028] Figure 1 This is a microscopic image of the emulsified waste oil prepared in Example 1;

[0029] Figure 2 This is a microscopic image of the emulsified waste oil prepared in Example 2;

[0030] Figure 3 This is a microscopic image of the emulsified waste oil prepared in Example 3;

[0031] Figure 4 This is a microscopic image of the emulsified waste oil prepared in Example 4;

[0032] Figure 5 This is a microscopic image of the emulsified waste oil prepared in Example 5;

[0033] Figure 6 A microscopic image of the emulsified waste oil prepared in Example 6;

[0034] Figure 7 This is a microscopic image of the emulsified waste oil prepared in Example 7;

[0035] Figure 8 This is a microscopic image of the emulsified waste oil prepared in Example 8;

[0036] Fig. 9 A microscopic image of the emulsified waste oil prepared in Example 9;

[0037] Fig.10 This is a microscope image of the emulsified waste oil prepared in Comparative Example 1;

[0038] Fig.11 This is a microscope image of the emulsified waste oil prepared in Comparative Example 2;

[0039] Fig.12 This is a microscope image of the emulsified waste oil prepared in Comparative Example 3;

[0040] Fig.13 This is a microscope image of the emulsified waste oil prepared in Comparative Example 4;

[0041] Fig.14 This is a microscope image of the emulsified waste oil prepared in Comparative Example 5. DETAILED DESCRIPTION

[0042] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0043] A specific embodiment of the present invention discloses a method for preparing emulsified waste oil for flotation reagent, comprising the following steps:

[0044] (1) centrifuging the waste oil to obtain a stable waste oil system;

[0045] (2) Adding poly(methyl methacrylate sulfobetaine) (PSBMA) and Tween 80 to the stable waste oil system to obtain a mixed system, heating, stirring, and adding water to obtain emulsified waste oil.

[0046] Compared with the prior art, the present invention uses polymethacrylate sulfobetaine, a long-chain amphiphilic polymer, and Tween 80 as emulsifiers to emulsify waste oil, thereby improving the stability of emulsified waste oil. At the same time, the waste oil is centrifuged for pretreatment to improve its self-emulsification and emulsification capabilities. Combined with the high energy barrier and multi-factor regulated emulsification process brought about by the side-by-side aggregation of methacrylate sulfobetaine after polymerization, the stability and dispersibility of the waste oil emulsion are greatly improved, and the emulsion has a long existence period and more exposed surface functional groups, which can meet the flotation needs of different production scales at different times.

[0047] The PSBMA of the present invention is a long-chain polymer with amphiphilicity. When it reacts with waste oil, each macromolecular polymer adsorbed on the interface is similar to a plurality of small molecules connected together and aggregated side by side. When the macromolecular polymer is desorbed from the interface, the entire main chain needs to be removed, resulting in more energy required to break through the high energy barrier, thereby effectively improving the stability of the emulsion, increasing the probability of collision with the target mineral, and making it easier for the emulsion droplets to contact the particles and spread on the surface, thereby effectively improving the flotation effect.

[0048] In a specific embodiment, in step (1), the waste oil is waste engine oil, waste lubricating oil or waste hydraulic oil.

[0049] Preferably, the viscosity of the waste oil is 1 to 200 mPa·s.

[0050] In a specific embodiment, in step (1), the centrifugal speed is 9000-15000 r / min, for example, 9000 r / min, 9500 r / min, 10000 r / min, 10500 r / min, 11000 r / min, 11500 r / min, 12000 r / min, 12500 r / min, 13000 r / min, 13500 r / min, 14000 r / min, 14500 r / min, 15000 r / min, and the centrifugal time is 5-15 min, for example, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min.

[0051] It should be noted that waste oil usually contains impurity particles such as metal debris and oil sludge, and carbon deposits, colloids and acidic substances will be produced due to thermal decomposition and oxidation under high temperature conditions. Solid impurities will destroy the interfacial tension and lead to poor emulsion stability. The present invention performs centrifugal pretreatment on waste oil to improve its self-emulsification and emulsification capabilities, and further improve the emulsion stability.

[0052] In a specific embodiment, in step (2), the average molecular weight of polymethacrylate sulfobetaine is greater than 3.5 KDa.

[0053] In a specific embodiment, in step (2), the mass of polymethacrylate sulfobetaine is 2-5% of the total mass of the mixed system, for example, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, and the mass ratio of polymethacrylate sulfobetaine to Tween 80 is 1:3-3:1, for example, 1:3, 3:5, 3:4, 1:1, 3:2, 3:1.

[0054] It should be noted that when the emulsifier solution is mixed with oil, the hydrophilic group enters the water phase and the lipophilic group enters the oil phase to form an oil-water interface film. When the emulsifier concentration is too low to form a dense interface film, the emulsion will break quickly and demulsify due to insufficient strength of the interface film. When the emulsifier concentration reaches 5%, further increasing the dosage has little effect on the arrangement of molecules on the surface of the liquid film, so further increasing the dosage does not change the stability of the emulsion.

[0055] When the composite mass ratio of PSBMA to Tween 80 is too small, the decomposition energy barrier of PSBMA is low and it is easy to detach from the liquid film surface, so the emulsion stability is poor; when the composite mass ratio is too large, Tween 80 cannot be evenly distributed on the liquid film surface, which will also reduce the emulsion stability.

[0056] In a specific embodiment, in step (2), the temperature is raised to 40-70°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C.

[0057] It should be noted that as the temperature rises, the thermal motion of the oil, water and emulsifier molecules becomes violent, the diffusion capacity increases, and the adsorption capacity of the molecules at the oil-water interface increases. However, when the temperature is too high, the small droplets formed after emulsification are small in volume and are subject to buoyancy greater than gravity, ultimately resulting in instability in the oil-water separation.

[0058] In a specific embodiment, in step (2), the stirring speed is 400-1200 r / min, for example, 400 r / min, 500 r / min, 600 r / min, 700 r / min, 800 r / min, 900 r / min, 1000 r / min, 1100 r / min, 1200 r / min, the stirring time is 6-16 min, for example, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, and the mass ratio of added water to waste oil is 1:2-2:1, for example, 1:2, 1:1, 2:3, 2:1.

[0059] It should be noted that the stirring speed, stirring time and water-oil mass ratio are key factors. The stirring speed and stirring time will affect the energy input and turbulence intensity of the system, thereby affecting the droplet size and liquid film strength; the water-oil mass ratio mainly controls whether the emulsion formed during the emulsification process is an oil-in-water type or an oil-in-water type. The emulsion prepared by the present invention is an oil-in-water type emulsion and has good dispersibility in the aqueous phase slurry.

[0060] In a specific embodiment, in step (2), the polymethacrylate sulfobetaine is prepared by the following method:

[0061] (a) adding an initiator to an aqueous solution of sulfobetaine methacrylate (SBMA) in a nitrogen atmosphere to obtain a sulfobetaine methacrylate (SBMA) mixed solution;

[0062] (b) stirring and heating the sulfobetaine methacrylate (SBMA) mixed solution in a nitrogen environment to obtain a polysulfobetaine methacrylate (PSBMA) solution;

[0063] (c) dialyzing the poly(methacrylate sulfobetaine) (PSBMA) solution and drying to obtain poly(methacrylate sulfobetaine) (PSBMA) powder.

[0064] The structural formula of sulfobetaine methacrylate (SBMA) in the present invention is as follows:

[0065]

[0066] The chemical reaction equation for preparing polymethacrylate sulfobetaine in the present invention is as follows:

[0067]

[0068] In a specific embodiment, in step (a), the mass concentration of the methacrylate sulfobetaine aqueous solution is 10-15%, for example, 10%, 11%, 12%, 13%, 14%, 15%, and nitrogen is introduced for 8-12 minutes, for example, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes.

[0069] It should be noted that when the mass concentration of the aqueous solution is too low, the polymer molecular weight will be small and it will be easily removed during dialysis; when the mass concentration of the aqueous solution is too high, some monomers cannot participate in the reaction and the reaction time will be prolonged. Nitrogen purge > 8min to ensure that the air in the experimental system is completely exhausted to create a nitrogen environment.

[0070] In a specific embodiment, in step (a), the initiator is potassium persulfate, and / or the mass of the initiator is 0.2-0.4% of the mass of SBMA, for example, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%.

[0071] In a specific embodiment, in step (b), the heating temperature is 55-65°C, for example, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, and the heating time is 8-12h, for example, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h.

[0072] It should be noted that when the heating temperature is low, the system energy is insufficient to realize the polymerization reaction of polymethacrylate sulfobetaine. The higher the temperature, the faster the decomposition rate of potassium persulfate. When the temperature is too high, the mixture of potassium persulfate and organic matter is dangerous. The heating time is 8 to 12 hours to ensure that the polymerization reaction can be completed.

[0073] In a specific embodiment, in step (c), the dialysis uses a dialysis bag with a molecular weight of 3.5 KDa, and the dialysis time is 68 to 72 hours, for example, 68 hours, 69 hours, 70 hours, 71 hours, or 72 hours.

[0074] It should be noted that the molecular weight of SBMA is 0.279KDa. A 3.5KDa dialysis bag is used to dialyze to remove potassium persulfate, unpolymerized SBMA monomers and PSBMA oligomers. When the molecular weight of the dialysis bag is too large, the polymerized PSBMA will be dialyzed out. If the molecular weight of the dialysis bag is too small, the monomers cannot be removed, affecting the emulsification effect. The dialysis time is greater than 68h to ensure that potassium persulfate, unpolymerized monomers and PSBMA oligomers are completely removed.

[0075] In a specific embodiment, in step (c), the drying is performed by freeze drying, and the freeze drying temperature is -40 to -45°C, for example, -40°C, -41°C, -42°C, -43°C, -44°C, -45°C.

[0076] Another specific embodiment of the present invention discloses an emulsified waste oil used as a flotation agent prepared by the above method.

[0077] Another specific embodiment of the present invention discloses an application of the above-mentioned emulsified waste oil in the flotation of coal-based solid waste.

[0078] The PSBMA described in the present invention can improve the flotation effect in two aspects. On the one hand, it can directly act. The oxygen-containing functional groups of PSBMA can hydrogen bond with the hydrophilic sites on the surface of unburned carbon in coal-based solid waste to improve the hydrophobicity of the hydrophilic area, and the straight-chain alkane structure of PSBMA can also produce van der Waals forces with the methyl and methylene groups on the surface of unburned carbon, thereby improving the floatability of unburned carbon in coal-based solid waste; on the other hand, it can indirectly act. The average molecular weight of PSBMA is greater than 3.5KDa, and it has a larger molecular weight than betaine. The larger molecular weight requires more energy when it is desorbed on the liquid film surface, thereby ensuring the droplet structure of the emulsion. The droplet structure has a larger specific surface area, exposing more surface functional groups in the waste oil, and effectively improving the mineralization efficiency of the coal-based solid waste during the flotation process.

[0079] In a specific embodiment, the application specifically includes: dispersing coal-based solid waste in water, adding the emulsified waste oil and stirring, then adding a foaming agent, stirring, scraping bubbles, and obtaining unburned charcoal and tail ash.

[0080] In a specific embodiment, the amount of the emulsified waste oil added is 1 to 6 kg / t, for example, 1 kg / t, 2 kg / t, 3 kg / t, 4 kg / t, 5 kg / t, 6 kg / t.

[0081] In a specific embodiment, the foaming agent is methyl isobutyl carbinol (MIBC).

[0082] Specifically, the amount of the foaming agent added is 1 to 5 kg / t, for example, 1 kg / t, 2 kg / t, 3 kg / t, 4 kg / t, 5 kg / t.

[0083] In a specific embodiment, the mass ratio of the coal-based solid waste to water is 1:50 to 1:10, for example, 1:50, 1:45, 1:40, 1:35, 1:30, 1:25, 1:20, 1:15, or 1:10.

[0084] The present invention uses polymethacrylate sulfobetaine, a long-chain amphiphilic polymer, and Tween 80 as a composite flotation agent to emulsify waste oil. The sporadic effects of polymethacrylate sulfobetaine and Tween 80 on the interface are combined to effectively improve the stability of the emulsion. The probability of the composite flotation agent of the present invention colliding with the target mineral is increased, and the emulsion droplets are more likely to contact the particles and spread on the surface, thereby effectively improving the flotation recovery rate of the target mineral.

[0085] The technical solution of the present invention is further explained below in conjunction with specific embodiments.

[0086] Example 1

[0087] A method for preparing emulsified waste oil for flotation reagent comprises the following steps:

[0088] (1) placing a 10% SBMA aqueous solution in a 500 mL three-necked flask, passing nitrogen gas for 12 min to create a nitrogen environment, adding a potassium persulfate initiator accounting for 0.3% of the mass of the SBMA monomer, stirring and heating to 60° C. in a nitrogen environment, and maintaining a constant temperature for 12 h of polymerization reaction; after the polymerization reaction is completed, transferring the solution to a dialysis bag with a molecular weight of 3.5 KDa, and dialyzing in ultrapure water for 72 h to remove monomers and oligomers; after the dialysis is completed, transferring the supernatant to a freeze dryer and drying at -40° C. to obtain PSBMA powder, wherein the average molecular weight of the PSBMA is 42.3 KDa;

[0089] (2) placing the waste oil in a centrifuge and centrifuging at 13000 r / min for 10 min to obtain a stable waste oil system;

[0090] (3) PSBAM and Tween 80 were added to 3 g of the stable waste oil to obtain a mixed system, wherein the mass ratio of PSBAM to Tween 80 was 1:3, and the mixture was placed on a 50° C. magnetic stirrer. After reaching a preset temperature, water was added dropwise while stirring, and stirring was continued at 800 r / min for 12 min to obtain a milky yellow emulsified waste oil; wherein the amount of water added was 1.4 times the mass of the waste oil, and the amount of PSBMA added was 3% of the total mass of the mixed system.

[0091] The waste oil in this embodiment is waste engine oil.

[0092] Example 1-1

[0093] A method for preparing emulsified waste oil for flotation reagent is the same as that of Example 1, except that step (1) is specifically as follows:

[0094] (1) placing a 12.5% ​​SBMA aqueous solution in a 500 mL three-necked flask, passing nitrogen for 8 minutes to create a nitrogen environment, adding a potassium persulfate initiator accounting for 0.2% of the mass of the SBMA monomer, stirring and heating to 55° C. in a nitrogen environment, and maintaining a constant temperature for 8 hours of polymerization reaction; after the polymerization reaction is completed, transferring the solution to a dialysis bag with a molecular weight of 3.5 KDa, and dialyzing in ultrapure water for 68 hours to remove monomers and oligomers; after the dialysis is completed, transferring the supernatant to a freeze dryer and drying at -42° C. to obtain PSBMA powder, wherein the average molecular weight of the PSBMA is 38.5 KDa;

[0095] Example 1-2

[0096] (1) placing a 15% SBMA aqueous solution in a 500 mL three-necked flask, passing nitrogen gas for 10 min to create a nitrogen environment, adding a potassium persulfate initiator accounting for 0.4% of the mass of the SBMA monomer, stirring and heating to 65° C. in a nitrogen environment, and maintaining a constant temperature for 10 h of polymerization reaction; after the polymerization reaction is completed, transferring the solution to a dialysis bag with a molecular weight of 3.5 KDa, and dialyzing in ultrapure water for 72 h to remove monomers and oligomers; after the dialysis is completed, transferring the supernatant to a freeze dryer and drying at -45° C. to obtain PSBMA powder, wherein the average molecular weight of the PSBMA is 46.8 KDa;

[0097] Example 2

[0098] A method for preparing emulsified waste oil for flotation reagent is the same as that of Example 1, except that in step (3), the amount of water added is 1.6 times the mass of the waste oil.

[0099] Example 3

[0100] A method for preparing emulsified waste oil for flotation reagent is the same as that of Example 1, except that in step (3), the amount of water added is 1.8 times the mass of the waste oil.

[0101] Example 4

[0102] A method for preparing emulsified waste oil for flotation reagent is the same as that of Example 1, except that in step (3), the amount of PSBMA added is 2.5% of the total mass of the mixed system.

[0103] Example 5

[0104] A method for preparing emulsified waste oil for flotation reagent is the same as that of Example 1, except that in step (3), the amount of PSBMA added is 3.5% of the total mass of the mixed system.

[0105] Example 6

[0106] A method for preparing emulsified waste oil for flotation reagent is the same as that of Example 5, except that in step (3), stirring is continued at 600 r / min for 12 minutes to obtain milky yellow emulsified waste oil.

[0107] Example 7

[0108] A method for preparing emulsified waste oil for flotation reagent is the same as that of Example 5, except that in step (3), stirring is continued at 1000 r / min for 12 minutes to obtain milky yellow emulsified waste oil.

[0109] Example 8

[0110] A method for preparing emulsified waste oil for flotation reagent is the same as that of Example 5, except that in step (3), stirring is continued at 1000 r / min for 6 minutes to obtain milky yellow emulsified waste oil.

[0111] Example 9

[0112] A method for preparing emulsified waste oil for flotation reagent is the same as that of Example 5, except that in step (3), stirring is continued at 1000 r / min for 8 minutes to obtain milky yellow emulsified waste oil.

[0113] Example 10

[0114] An application of the emulsified waste oil prepared in Example 1 in the flotation of coal-based solid waste specifically comprises dispersing 30 g of coal-based solid waste in a plexiglass flotation cell containing 500 mL of deionized water, wherein the loss on ignition of the coal-based solid waste is 32.62%, stirring thoroughly for 1 minute, adding 1 kg / t of the emulsified waste oil prepared in Example 1 to the flotation cell, stirring for 3 minutes, adding 3 kg / t of MIBC foaming agent, stirring thoroughly for another 3 minutes, and then aerating and scraping for 4 minutes; the unburned charcoal and tail ash are obtained.

[0115] Example 10-1

[0116] An application of emulsified waste oil in coal-based solid waste flotation is the same as Example 10, except that the emulsified waste oil is prepared by the method of Example 1-1.

[0117] Example 10-2

[0118] An application of emulsified waste oil in coal-based solid waste flotation is the same as Example 10, except that the emulsified waste oil is prepared by the method of Example 1-2.

[0119] Embodiment 11

[0120] An application of emulsified waste oil in coal-based solid waste flotation is the same as Example 10, except that the emulsified waste oil is prepared by the method of Example 2.

[0121] Example 12

[0122] An application of emulsified waste oil in coal-based solid waste flotation is the same as Example 10, except that the emulsified waste oil is prepared by the method of Example 3.

[0123] Embodiment 13

[0124] An application of emulsified waste oil in coal-based solid waste flotation is the same as Example 10, except that the emulsified waste oil is prepared by the method of Example 4.

[0125] Embodiment 14

[0126] An application of emulsified waste oil in coal-based solid waste flotation is the same as Example 10, except that the emulsified waste oil is prepared by the method of Example 5.

[0127] Embodiment 15

[0128] An application of emulsified waste oil in coal-based solid waste flotation is the same as Example 10, except that the emulsified waste oil is prepared by the method of Example 6.

[0129] Example 16

[0130] An application of emulsified waste oil in coal-based solid waste flotation is the same as Example 10, except that the emulsified waste oil is prepared by the method of Example 7.

[0131] Embodiment 17

[0132] An application of emulsified waste oil in coal-based solid waste flotation is the same as Example 10, except that the emulsified waste oil is prepared by the method of Example 8.

[0133] Embodiment 18

[0134] An application of emulsified waste oil in coal-based solid waste flotation is the same as Example 10, except that the emulsified waste oil is prepared by the method of Example 9.

[0135] Embodiment 19

[0136] An application of emulsified waste oil in coal-based solid waste flotation is the same as Example 10, except that the amount of emulsified waste oil added is 3 kg / t.

[0137] Comparative Example 1

[0138] A method for preparing emulsified waste oil for flotation reagent is the same as that of Example 1, except that in step (1), a dialysis bag with a molecular weight of 3.0 KDa is used.

[0139] Comparative Example 2

[0140] A method for preparing emulsified waste oil for flotation reagent is the same as that of Example 1, except that in step (3), the amount of water added is 2.4 times the mass of the waste oil.

[0141] Comparative Example 3

[0142] A method for preparing emulsified waste oil for flotation reagent is the same as that of Example 1, except that in step (3), the amount of PSBMA added is 1% of the total mass of the mixed system.

[0143] Comparative Example 4

[0144] A method for preparing emulsified waste oil for flotation reagent is the same as that of Example 5, except that in step (3), stirring is continued at 300 r / min for 12 minutes to obtain milky yellow emulsified waste oil.

[0145] Comparative Example 5

[0146] A method for preparing emulsified waste oil for flotation reagent is the same as that of Example 1, except that Tween 80 is not added in step (3).

[0147] Comparative Example 6

[0148] An application of emulsified waste oil in coal-based solid waste flotation is the same as Example 10, except that the emulsified waste oil is prepared by the method of Comparative Example 1.

[0149] Comparative Example 7

[0150] An application of emulsified waste oil in coal-based solid waste flotation is the same as Example 10, except that the emulsified waste oil is prepared by the method of Comparative Example 2.

[0151] Comparative Example 8

[0152] An application of emulsified waste oil in coal-based solid waste flotation is the same as Example 10, except that the emulsified waste oil is prepared by the method of Comparative Example 3.

[0153] Comparative Example 9

[0154] An application of emulsified waste oil in coal-based solid waste flotation is the same as Example 10, except that the emulsified waste oil is prepared by the method of Comparative Example 4.

[0155] Comparative Example 10

[0156] An application of emulsified waste oil in coal-based solid waste flotation is the same as Example 10, except that the emulsified waste oil is prepared by the method of Comparative Example 5.

[0157] Comparative Example 11

[0158] An application of waste oil in coal-based solid waste flotation is the same as Example 10, except that the waste oil is not emulsified and waste engine oil is directly used.

[0159] Comparative Example 12

[0160] An application of waste oil in coal-based solid waste flotation is the same as Example 10, except that the amount of emulsified waste oil added is 0.5 kg / t.

[0161] Test Example 1

[0162] (1) Emulsified waste oils prepared by the methods of Examples 1-9 and Comparative Examples 1-5 were subjected to demulsification tests and microscope tests. The results are shown in Tables 1 and Figure 1-14 shown.

[0163] Table 1

[0164]

[0165] It can be seen from Examples 1, 1-1 and 1-2 that the amount of initiator used will affect the average molecular weight of PSBMA. When the average molecular weight is small, the decomposition energy barrier of PSBMA on the liquid membrane is reduced, which is manifested as a shortened demulsification time. It can be seen from Example 1 and Comparative Example 1 that when the molecular weight of the dialysis bag is too small, the monomer cannot be removed, affecting the emulsification effect.

[0166] It can be seen from Examples 1, 2, 3 and Comparative Example 2 that different water-to-oil ratios significantly affect the emulsion stability time and droplet size. When the mass fraction of the surfactant remains unchanged, the greater the mass fraction of water added, the weaker the liquid film strength, which leads to the merging of droplets, thus forming droplets with larger diameters and easy instability.

[0167] It can be seen from Examples 1, 4, 5 and Comparative Example 3 that the emulsifier can reduce the interfacial tension and interfacial energy, making the system stable. Therefore, increasing the amount of emulsifier can extend the stability time of the emulsion and reduce the droplet diameter. When the amount of emulsifier is too low, the emulsifier molecules are not enough to be evenly distributed on the surface of the liquid film, so it is easy to become unstable and the demulsification time is short.

[0168] It can be seen from Examples 5-9 that increasing the stirring speed and stirring time can enhance the turbulence intensity in the system, making the waste oil, water, and emulsifier act more fully, which is manifested in an increase in demulsification time and a decrease in droplet size;

[0169] It can be seen from Example 5 and Comparative Example 4 that when the stirring speed and time are too low, the emulsifier cannot act evenly on the oil-water interface, resulting in reduced emulsion stability;

[0170] It can be seen from Example 1 and Comparative Example 6 that when Tween 80 is not added, the liquid film lacks sporadic distribution of small molecules, resulting in reduced stability of the liquid film, which is manifested in a shortened demulsification time.

[0171] Depend on Figures 1 to 3 and Fig.11 It can be seen that different water-oil ratios will significantly affect the dispersion and droplet size of the emulsion. When the mass fraction of the surfactant remains unchanged, the greater the mass fraction of water added, the weaker the liquid film strength, which leads to the merging of droplets, thus forming droplets with larger diameters, poor uniform dispersion and easy instability.

[0172] Depend on Figure 1 , 4 , 5 and Fig.12 It can be seen that emulsifiers can reduce interfacial tension and interfacial energy, making the system stable. Therefore, increasing the amount of emulsifier can improve the strength of the liquid film, effectively improve the dispersion of the emulsion and reduce the diameter of the emulsion droplets.

[0173] Depend on Figures 5 to 7 It can be seen that the increase in stirring speed can enhance the turbulence intensity in the system, making the waste oil, water and emulsifier act more fully. Therefore, as the stirring speed increases, the droplet size decreases and the dispersion is better.

[0174] Depend on Figures 7 to 9 and Fig.13 It can be seen that when the stirring time is low, the emulsifier cannot act evenly on the oil-water interface, so the liquid film strength is low, resulting in the merger of droplets, which is manifested as an increase in droplet diameter and poor dispersion. If the stirring time is too long, air will be brought into the emulsion system, the system will become unstable, and droplet merger will occur, so the droplet diameter is larger;

[0175] Depend on Fig. 9 and Fig.14It can be seen that when only PSBMA is added as the emulsifier without Tween 80, only the large molecules of PSBMA aggregate side by side on the surface of the liquid film, while there is a lack of sporadic adsorption of small molecules of Tween 80. Therefore, the strength of the liquid film is poor, which makes the droplets deform and easy to merge.

[0176] (2) The yield, ignition loss and recovery rate of the unburned carbon and tailings obtained in Examples 10-19 and Comparative Examples 6-12 were tested respectively. The results are shown in Table 2.

[0177] Table 2

[0178]

[0179]

[0180] It can be seen from Examples 10, 10-1, 10-2 and Comparative Example 6 that as the molecular weight of PSBMA increases, the decomposition energy barrier of PSBMA on the liquid film increases, so the stability of the emulsion is enhanced, which is manifested in the increase of the unburned carbon recovery rate in flotation;

[0181] It can be seen from Example 10 and Comparative Example 7 that as the water-oil ratio increases, the stability of the emulsion droplets deteriorates, and the droplets merge, resulting in a decrease in the exposed surface functional groups, and thus a decrease in the unburned carbon recovery rate;

[0182] It can be seen from Example 10 and Comparative Example 8 that as the amount of PSBMA increases, the stability of the liquid film is enhanced, the particle size of the emulsion droplets is smaller, and the probability of collision with the unburned carbon is higher. At the same time, the polar functional groups of PSBMA can generate hydrogen bonding forces with the surface of the oxygen-containing functional groups of the unburned carbon, thereby assisting the recovery of the unburned carbon.

[0183] It can be seen from Example 10 and Comparative Example 9 that as the stirring speed and stirring time increase, the particle size of the emulsion droplets becomes smaller, and the probability of collision with the unburned carbon during the flotation process is higher, so the unburned carbon recovery rate increases accordingly;

[0184] It can be seen from Example 10 and Comparative Example 11 that emulsification can significantly improve the dispersibility of waste oil in the slurry, and the emulsified waste oil exposes more surface functional groups than the unemulsified waste oil. Therefore, using emulsified waste oil as a collector can obtain a lower tail ash loss on ignition and a higher unburned carbon recovery rate.

[0185] It can be seen from Example 10 and Comparative Example 12 that as the amount of emulsified waste oil increases, the selectivity of the waste oil and the surface effect of the unburned carbon are enhanced, the hydrophobicity of the unburned carbon surface is improved, the unburned carbon recovery rate is higher and the tail ash loss on ignition is reduced. When the amount of emulsified waste oil is too low, the hydrophilic functional groups on the surface of the unburned carbon cannot be fully covered, so the hydrophobicity is poor, resulting in a low unburned carbon recovery rate.

[0186] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing emulsified waste oil for flotation reagent, characterized in that: The steps include: (1) centrifuging the waste oil to obtain a stable waste oil system; (2) Adding polymethacrylate sulfobetaine and Tween 80 to the stable waste oil system to obtain a mixed system, heating, stirring, and adding water to obtain emulsified waste oil.

2. The method for preparing emulsified waste oil for flotation reagent according to claim 1, characterized in that: In step (1), the centrifugal speed is 9000-15000 r / min, and the centrifugal time is 5-15 min.

3. The method for preparing emulsified waste oil for flotation reagent according to claim 1, characterized in that: In step (2), the average molecular weight of polymethacrylate sulfobetaine is greater than 3.5 KDa.

4. The method for preparing emulsified waste oil for flotation reagent according to any one of claims 1 to 3, characterized in that: In step (2), the mass of polymethacrylate sulfobetaine is 2-5% of the total mass of the mixed system, and the mass ratio of polymethacrylate sulfobetaine to Tween 80 is 1:3-3:

1.

5. The method for preparing emulsified waste oil for flotation reagent according to any one of claims 1 to 3, characterized in that: In step (2), the stirring speed is 400-1200 r / min, the stirring time is 6-16 min, and the mass ratio of added water to waste oil is 1:2-2:

1.

6. The method for preparing emulsified waste oil for flotation reagent according to any one of claims 1 to 3, characterized in that: In step (2), the polymethacrylate sulfobetaine is prepared by the following method: (a) adding an initiator to an aqueous solution of methacrylate sulfobetaine in a nitrogen atmosphere to obtain a methacrylate sulfobetaine mixed solution; (b) stirring and heating the methacrylate sulfobetaine mixed solution in a nitrogen environment to obtain a polymethacrylate sulfobetaine solution; (c) dialyzing the polymethacrylate sulfobetaine solution and drying to obtain polymethacrylate sulfobetaine powder.

7. The method for preparing emulsified waste oil for flotation reagent according to claim 6, characterized in that: In step (a), the mass concentration of the methacrylate sulfobetaine aqueous solution is 10-15%, nitrogen is introduced for 8-12 minutes, and / or the initiator is potassium persulfate, and the mass of the initiator is 0.2-0.4% of the mass of the methacrylate sulfobetaine.

8. The method for preparing emulsified waste oil for flotation reagent according to claim 6, characterized in that: In step (c), the dialysis uses a dialysis bag with a molecular weight of 3.5 KDa, and the dialysis time is 68 to 72 hours.

9. An emulsified waste oil prepared by the method according to any one of claims 1 to 8.

10. Use of the emulsified waste oil according to claim 9 in flotation of coal-based solid waste.

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