Dehydrating agent for bauxite tailings slurry and preparation method thereof

Abstract

The present invention provides a method for preparing a dehydrating agent for bauxite tailings slurry, comprising the steps of: uniformly mixing an inorganic silicate coagulant with an acrylamide monomer, an acrylic acid monomer, a hydrophobically associating monomer, a hydrophobically associating solubilizing monomer, and an aqueous emulsifier; adding a water-soluble chain transfer agent, a metal complexing agent, a temperature initiator, and a persulfate oxidant to the mixture; and uniformly mixing to obtain a dispersed phase; wherein the inorganic silicate coagulant is prepared by polymerization reaction of a silane coupling agent, an inorganic aluminum salt, and an alkali solution; and uniformly adding the dispersed phase to a continuous phase to obtain a water-in-oil inverse emulsion mixed system; wherein the continuous phase is obtained by uniformly mixing a base oil, an oil-soluble emulsifier, and an oil-soluble initiator; and adding a reducing agent solution to the water-in-oil inverse emulsion mixed system, and performing polymerization reaction in stages to obtain a dehydrating agent for bauxite tailings slurry. The dehydrating agent prepared in the present invention has both excellent settling velocity and flocculation effect.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical synthesis, in particular to a dehydrating agent for bauxite tailings slurry and a preparation method thereof. Background Art

[0002] The main components of bauxite tailings slurry are kaolinite, diaspore (trihydrate), and hematite, with Al2O3 and SiO2 as the main chemical components. The slurry is highly dispersible and extremely fine, with particles smaller than 0.02 mm accounting for approximately 65%. The slurry is negatively charged, and after thickening, the underflow solids content is approximately 30%. This tailings slurry has a high water content, and the environmental risks of mud storage are high. It also presents an "overhead structure," and even after 10 to 20 years of sedimentation, the lower layer of mud remains in a plastic state. Therefore, in order to reduce the amount of tailings slurry discharged, ensure long-term mineral processing production and safe storage of tailings, and improve water resource utilization, the tailings slurry needs to be further dehydrated after thickening and settling.

[0003] At present, commonly used dehydrating agents include inorganic gelling agents and organic flocculants. Inorganic gelling agents such as polyaluminum chloride, polyferric sulfate or polyaluminum ferric chloride are used to dehydrate the tailings slurry. Although the supernatant is clearer after dehydration treatment with inorganic gelling agents, its sedimentation rate is slow; organic flocculants such as anionic polyacrylamide can significantly increase the sedimentation rate, but their flocculation effect on fine suspended particles is poor, and the supernatant is turbid.

[0004] Therefore, based on the shortcomings of the performance of inorganic gelling agents and organic flocculants in the existing technology, it is necessary to study a dewatering agent with fast settling rate, clear supernatant, low turbidity and suitable for bauxite tailings slurry, which is of great significance to the application and research of tailings slurry dewatering agents. Summary of the Invention

[0005] The invention provides a dehydrating agent for bauxite tailings slurry and a preparation method thereof. The prepared dehydrating agent has the advantages of fast settling speed, good flocculation effect on fine suspended particles, clear supernatant and low turbidity.

[0006] In a first aspect, the present invention provides a method for preparing a dehydrating agent for bauxite tailings slurry, the preparation method comprising the following steps:

[0007] (1) mixing an inorganic silicate coagulant with an acrylamide monomer, an acrylic acid monomer, a hydrophobically associating monomer, a hydrophobically associating solubility-promoting monomer, and an aqueous emulsifier to obtain a first mixed solution; adding a water-soluble chain transfer agent, a metal complexing agent, a temperature initiator, and a persulfate oxidant to the first mixed solution, and mixing to obtain a dispersed phase; wherein the inorganic silicate coagulant is prepared by a polymerization reaction of a silane coupling agent, an inorganic aluminum salt, and an alkali solution;

[0008] (2) adding the dispersed phase to the continuous phase and mixing them to obtain a water-in-oil inverse emulsion mixed system; wherein the continuous phase is obtained by mixing a base oil, an oil-soluble emulsifier, and an oil-soluble initiator;

[0009] (3) Adding a reducing agent solution to the water-in-oil reverse emulsion mixed system, and performing polymerization reaction in stages to obtain the dehydrating agent for the bauxite tailings slurry.

[0010] Preferably, the inorganic silicate coagulant is prepared by the following method:

[0011] (11) mixing water, a silane coupling agent, and an inorganic aluminum salt to obtain a second mixed solution;

[0012] (12) Alkali solution is added dropwise to the second mixed solution to obtain the inorganic silicate coagulant after polymerization reaction.

[0013] Preferably, in the process of preparing the inorganic silicate coagulant, the content of each reaction raw material is, by mass percentage, 40-46% water, 15-17% silane coupling agent, 16-18% inorganic aluminum salt, and 23-25% alkali solution; the mass concentration of the alkali solution is 40-50%.

[0014] Preferably, in step (12), the polymerization reaction temperature is 50-53° C., and the time is 0.5-1 h.

[0015] Preferably, the silane coupling agent is at least one of vinyltriethoxysilane, γ-aminopropyltriethoxysilane, vinyltrimethoxysilane or γ-methacryloxypropyltrimethoxysilane;

[0016] The inorganic aluminum salt is at least one of aluminum chloride, aluminum sulfate or alum;

[0017] The alkali solution is at least one of sodium hydroxide, potassium hydroxide or ammonia water.

[0018] Preferably, in step (1):

[0019] The acrylamide monomer is at least one of acrylamide, N,N-dimethylacrylamide or methacrylamide;

[0020] The acrylic monomer is at least one of acrylic acid, 2-ethylacrylic acid, methacrylic acid, 2-propyl acrylic acid, 2-(bromomethyl)acrylic acid or 3,3-dimethylacrylic acid;

[0021] The hydrophobic associating monomer is at least one of allyl tris(3,3,4,4,5,5,6,6,6-nonafluorohexyl)stannane, N-(1-naphthyl)-N-phenylmethacrylamide, 2-ethylhexyl acrylate or allyloxy-tert-butyldimethylsilane;

[0022] The hydrophobic associating solubility-promoting monomer is at least one of polyoxyethylene (10) lauryl ether, polyoxyethylene (6) lauryl ether, coconut oil polyoxyethylene ether methyl ammonium chloride, caprylylsulfobetaine or 3-(N,N-dimethyldodecylammonium) propane sulfonate;

[0023] The aqueous emulsifier is at least one of Tween-60, Tween-40, Tween-80 or Tween-85;

[0024] The water-soluble chain transfer agent is at least one of sodium formate, ascorbic acid or isopropyl alcohol;

[0025] The metal complexing agent is at least one of diethylenetriaminepentaacetic acid, dihydroxyethylglycine, diethylenetriaminepenta(methylenephosphonic acid) or sodium ethylenediaminetetra(methylenephosphonic acid);

[0026] At least one of the temperature initiator tert-butyl hydroperoxide, dicumyl peroxide or tert-butyl cumyl hydroperoxide;

[0027] The persulfate oxidant is at least one of potassium persulfate, ammonium persulfate, sodium persulfate or manganese persulfate.

[0028] Preferably, in step (1):

[0029] When preparing the dehydrating agent for bauxite tailings slurry, the addition amount of each reaction raw material in the mixed solution is as follows, calculated by mass percentage: 23.7-30.9% of inorganic silicate coagulant, 21.5-23.2% of acrylamide monomer, 16-18% of acrylic acid monomer, 0.3-0.5% of hydrophobic associating monomer, 1.3-1.6% of hydrophobic associating solubilizing monomer, and 1.5-1.7% of water-soluble emulsifier.

[0030] Preferably, in step (1):

[0031] The amount of the water-soluble chain transfer agent added is 0.009-0.012% of the mixed solution, the amount of the metal complexing agent added is 0.014-0.016% of the mixed solution, the amount of the temperature initiator added is 0.0068-0.007% of the mixed solution, and the amount of the persulfate oxidant added is 0.016-0.018% of the mixed solution.

[0032] Preferably, in step (2):

[0033] The base oil is at least one of white oil, rapeseed oil, kerosene, tung oil or castor oil;

[0034] The oil-soluble emulsifier is at least one of Span-40, Span-60, Span-80 or Span-85;

[0035] The oil-soluble initiator is at least one of 4,4'-azodiphenyl ether, diisopropyl azodicarboxylate or dibenzyl azodicarboxylate.

[0036] Preferably, when preparing the dehydrating agent for bauxite tailings slurry, the addition amount of each reaction raw material in the continuous phase is as follows, calculated by mass percentage: base oil 25-27%, oil-soluble emulsifier 1.8-2.1%; the addition amount of the oil-soluble initiator is 0.012-0.013% of the addition amount of the base oil and the oil-soluble emulsifier.

[0037] Preferably, in step (3):

[0038] Before adding the reducing agent solution to the water-in-oil inverse emulsion system, the method further comprises the step of passing nitrogen through the water-in-oil inverse emulsion system to remove oxygen; preferably, the time for passing nitrogen through the system to remove oxygen is 30 to 35 minutes;

[0039] The concentration of the reducing agent solution is 1.5-1.8%, and the solute in the reducing agent solution is at least one of sodium metabisulfite, potassium pyrosulfite, sodium thiosulfate or thiourea dioxide.

[0040] Preferably, the polymerization reaction is carried out in two temperature stages; wherein the temperature of the first temperature stage is 45-47°C and the time is 1.8-2.5 hours, and the temperature of the second temperature stage is 66-68°C and the time is 1.8-2.5 hours;

[0041] Preferably, when the polymerization reaction is carried out at each temperature stage, the reducing agent solution is added dropwise to the inverse emulsion mixed system in two stages; wherein the dropping speed of the reducing agent solution in the first stage is 2 to 3 mL / h, and the dropping speed of the reducing agent solution in the second stage is 0.5 to 1 mL / h.

[0042] Preferably, in step (3):

[0043] After the polymerization reaction, a phase inversion agent is added to the reaction system to obtain the dehydrating agent for the bauxite tailings slurry.

[0044] Preferably, the phase transfer agent is at least one of polyethylene glycol (12) tridecyl ether, hexaethylene glycol dodecyl ether or decaethylene glycol monododecyl ether; and the added amount of the phase transfer agent is 1.5-1.8%.

[0045] In a second aspect, the present invention provides a dehydrating agent for bauxite tailings slurry, which is prepared by the preparation method described in any one of the first aspects above.

[0046] Compared with the prior art, the present invention has at least the following beneficial effects:

[0047] (1) In the present invention, a silane coupling agent, an inorganic aluminum salt and an alkaline solution are firstly used to prepare an inorganic silicate coagulant through a hydrolysis copolymerization reaction. The silanol groups formed after the hydrolysis of the silane coupling agent can react with the metal salt ions or metal salt hydroxide polymers distributed around it, so that the formed coagulant has the effects of electrical neutralization, adsorption bridging and netting, thereby ensuring that it has good flocculation effect and system stability; then, the inorganic silicate coagulant is polymerized with acrylamide monomers, acrylic acid monomers, hydrophobic monomers and hydrophobic associating solubilizing monomers by an in-situ polymerization method, thereby obtaining an inorganic-organic hybrid dehydrating agent; the dehydrating agent has the advantages of both an inorganic coagulant and a high molecular organic dehydrating agent, and can give play to the electrical neutralization, adsorption bridging and netting effects of inorganic particles, and can also give play to the bridging advantages of organic polymers, so that the dehydrating agent has the advantages of good flocculation effect, fast floc formation, high particle density and fast sedimentation rate;

[0048] (2) In the present invention, hydrophobic associating monomers and hydrophobic associating solubilizing monomers are added during the preparation of the dehydrating agent, so that the polymer molecules have hydrophobic associating effects, which is beneficial for further improving the flocculation and dehydration performance of the dehydrating agent on the basis of ensuring good solubility of the dehydrating agent;

[0049] (3) In the process of preparing the dehydrating agent, the present invention adds a persulfate oxidant, and the persulfate ion can combine with the hydroxyl hydrolysis product of the positively charged aluminum salt in the inorganic silicate coagulant, thereby allowing the inorganic components and organic components in the dehydrating agent to react with each other through SO4 2- They are connected in the form of ionic bonds, so that the surface of the dehydrating agent presents a tight and solid spatial network structure, which in turn gives it a better flocculation effect;

[0050] (4) The dehydrating agent for bauxite tailings slurry prepared by the present invention has the advantages of fast flocculation speed, clear supernatant, low turbidity, and fast dissolution. It has a colorless and transparent appearance, a hydrolysis degree of 20-25%, a relative turbidity of ≤0.3, a sedimentation mud concentration of ≥50%, a sedimentation rate of ≥15 mm / min, and a supernatant height of ≥20 mm. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0052] In order to solve the shortcomings of inorganic dehydrating agents and organic flocculants in the prior art that they cannot achieve both good settling speed and good flocculation effect, an embodiment of the present invention provides a method for preparing a dehydrating agent for bauxite tailings slurry, characterized in that the preparation method comprises the following steps:

[0053] (1) mixing an inorganic silicate coagulant with an acrylamide monomer, an acrylic acid monomer, a hydrophobically associating monomer, a hydrophobically associating solubility-promoting monomer, and an aqueous emulsifier to obtain a first mixed solution; adding a water-soluble chain transfer agent, a metal complexing agent, a temperature initiator, and a persulfate oxidant to the first mixed solution, and mixing to obtain a dispersed phase; wherein the inorganic silicate coagulant is prepared by a polymerization reaction of a silane coupling agent, an inorganic aluminum salt, and an alkali solution;

[0054] (2) adding the dispersed phase to the continuous phase and mixing them to obtain a water-in-oil inverse emulsion mixed system; wherein the continuous phase is obtained by mixing a base oil, an oil-soluble emulsifier, and an oil-soluble initiator;

[0055] (3) Adding a reducing agent solution to the water-in-oil reverse emulsion mixed system, and performing polymerization reaction in stages to obtain the dehydrating agent for bauxite tailings slurry.

[0056] In an embodiment of the present invention, an inorganic silicate coagulant is first prepared by hydrolyzing and copolymerizing a silane coupling agent as a silicon source with an inorganic aluminum salt and an alkaline solution. The silanol groups formed after the hydrolysis of the silane coupling agent can undergo polymerization reaction with metal salt ions or metal salt hydroxide polymers distributed in the surrounding area, so that the formed coagulant has simultaneous electrical neutralization, adsorption bridging and netting functions, ensuring that it has good flocculation effect and system stability. Then, the inorganic silicate coagulant, acrylamide monomers, acrylic acid monomers, hydrophobic monomers, hydrophobic associating solubilizing monomers, an emulsifier, an initiator and an oxidant are mixed to form a dispersed phase. Finally, after the dispersed phase is mixed with a continuous phase, a reducing agent is added to initiate a reaction, so that the monomers undergo in situ polymerization, thereby obtaining a water-in-oil type inorganic-organic hybrid dehydrating agent product. The present invention adds hydrophobic associating monomers and hydrophobic associating solubilizing monomers during the polymerization reaction, thereby making the polymer molecules have hydrophobic associating effects, which is beneficial to further improve the flocculation and dehydration performance of the dehydrating agent on the basis of ensuring good solubility of the dehydrating agent; at the same time, the present invention adopts a persulfate oxidant, and the persulfate radical can be combined with the hydroxide hydrolysis product of the positively charged aluminum salt in the inorganic silicate coagulant, and after thermal decomposition, free radicals are generated to initiate the polymerization of organic monomers, thereby allowing the inorganic components and organic components in the dehydrating agent to react via SO4 2- They are connected in the form of ionic bonds, which are strong bonds, so that the surface of the dehydrating agent presents a tight and solid spatial network structure, which in turn makes it have a better flocculation effect and ensures that the dehydrating agent flocs have good shear resistance.

[0057] The dehydrating agent of the present invention has the advantages of both an inorganic coagulant and a high-molecular organic dehydrating agent. The dehydrating agent has a spatial network structure, the surface of which is dense and solid clusters, and contains a large number of dense and fine pores with a large surface area. This structure enables it to exert the electrical neutralization, adsorption bridging and net-catching effects of inorganic particles, and also exert the bridging advantage of organic polymers, so that the dehydrating agent has the advantages of good flocculation effect, fast floc formation, high particle density and fast sedimentation speed, and has no secondary pollution, high efficiency and low consumption, and a wide range of applications.

[0058] According to some preferred embodiments, the inorganic silicate coagulant is prepared by the following method:

[0059] (11) mixing water, a silane coupling agent, and an inorganic aluminum salt to obtain a second mixed solution;

[0060] (12) Alkali solution is added dropwise to the second mixed solution to obtain the inorganic silicate coagulant after polymerization reaction.

[0061] In an embodiment of the present invention, a silane coupling agent and water can be first added to a reactor, stirred and dissolved at a certain stirring speed (for example, 280 to 320 r / min), the speed is kept constant, and then an inorganic aluminum salt is added to the mixed solution. After fully dissolving, a mixed solution is obtained, the temperature of the reaction system is raised to 50 to 53 ° C, and an alkali solution is added to the mixed solution at a rate of 10 to 15 mL / h using a syringe pump to ensure that the pH value of the reaction system is 7.6 to 7.8. After that, a polymerization reaction is carried out at a constant temperature. After the reaction is completed, the temperature of the reaction system is lowered to room temperature (23 to 25 ° C). At this time, the system is a light yellow transparent liquid, which is an inorganic silicate coagulant. Preferably, the amount of alkali solution added to this reaction system is 23 to 25%.

[0062] According to some preferred embodiments, the silane coupling agent is at least one of vinyltriethoxysilane, γ-aminopropyltriethoxysilane, vinyltrimethoxysilane or γ-methacryloxypropyltrimethoxysilane; the inorganic aluminum salt is at least one of aluminum trichloride, aluminum sulfate or alum;

[0063] The alkali solution is at least one of sodium hydroxide, potassium hydroxide or ammonia water.

[0064] In the embodiment of the present invention, during the hydrolysis and copolymerization process of the silane coupling agent, the inorganic aluminum salt, and the alkaline solution, the silane coupling agent can form a polysilicic acid aluminum polymer flocculant with the inorganic aluminum salt. The use of the above-mentioned type of aluminum salt can slow down the gelation rate of the polysilicic acid and enhance the stability of the system, so that the inorganic silicate coagulant system has the functions of electrical neutralization, adsorption bridging, and net capture. At the same time, the hydrolysis rate of the silane coupling agent used in the present invention is relatively slow, and the silanol groups generated after the hydrolysis can undergo polymerization reaction with the metal salt ions or the hydroxide polymers of the metal salt ions uniformly distributed around it, thereby making the molecular weight of the formed inorganic silicate coagulant larger, and the alkyl group in the silane coupling agent has a steric hindrance effect, which can hinder the network polymerization of the system to form a gel, thereby further improving the stability of the dehydrating agent product.

[0065] According to some preferred embodiments, in the process of preparing the inorganic silicate coagulant, the content of each reaction raw material is, by mass percentage, 40-46% water (for example, 40%, 41%, 42%, 43%, 44%, 45% or 46%), 15-17% silane coupling agent (for example, 15%, 16% or 17%), 16-18% inorganic aluminum salt (for example, 16%, 17% or 18%), 23-25% alkali solution (for example, 23%, 24% or 25%); the mass concentration of the alkali solution is 40-50% (for example, 40%, 45% or 50%);

[0066] Preferably, in step (12), the polymerization reaction temperature is 50-53°C (for example, 50°C, 51°C, 52°C or 53°C), and the polymerization time is 0.5-1h (for example, 0.5h, 0.6h, 0.7h, 0.8h, 0.9h or 1h).

[0067] In the embodiment of the present invention, by controlling the content of each raw material component during the preparation process of the inorganic silicate gelling agent, the inorganic silicate gelling agent can have a better flocculation effect and better system stability; if the amount of inorganic aluminum salt added is too high, and the content of silane coupling agent in the system is relatively low, it is not conducive to the formation of polyaluminum silicate monomer with a large effective content, and thus is not conducive to ensuring the good flocculation effect and good system stability of the inorganic silicate gelling agent; if the amount of inorganic aluminum salt added is too low, and the content of silane coupling agent in the system is relatively high, part of the silane coupling agent will be unable to dissolve, and the amount of polyaluminum silicate monomer formed will also be less, which is not conducive to ensuring the good flocculation effect and good system stability of the inorganic silicate gelling agent.

[0068] According to some preferred embodiments, in step (1):

[0069] The acrylamide monomer is at least one of acrylamide, N,N-dimethylacrylamide or methacrylamide; the acrylic acid monomer is at least one of acrylic acid, 2-ethylacrylic acid, methacrylic acid, 2-propyl acrylic acid, 2-(bromomethyl)acrylic acid or 3,3-dimethylacrylic acid; the hydrophobic associating monomer is at least one of allyl tris(3,3,4,4,5,5,6,6,6-nonafluorohexyl)stannane, N-(1-naphthyl)-N-phenylmethacrylamide, 2-ethylhexyl acrylate or allyloxy-tert-butyldimethylsilane; The hydrophobic associating solubilizing monomer is at least one of polyoxyethylene (10) lauryl ether, polyoxyethylene (6) lauryl ether, coconut oil polyoxyethylene ether methyl ammonium chloride, caprylsulfobetaine or 3-(N,N-dimethyldodecyl ammonium) propane sulfonate; in the embodiment of the present invention, the hydrophobic associating monomer and the hydrophobic associating solubilizing monomer are added during the polymerization reaction, so that the dehydrating agent product can have the performance of a hydrophobic associating polymer, thereby further improving the flocculation and dehydration performance of the dehydrating agent product, and having good solubility. The present invention is an oil-in-water emulsion system, which is stable, easy to use, and has no dust pollution.

[0070] The aqueous emulsifier is at least one of Tween-60, Tween-40, Tween-80 or Tween-85; the water-soluble chain transfer agent is at least one of sodium formate, ascorbic acid or isopropyl alcohol; the metal complexing agent is at least one of diethylenetriaminepentaacetic acid, dihydroxyethylglycine, diethylenetriaminepenta(methylenephosphonic acid) or sodium ethylenediaminetetra(methylenephosphonic acid); the temperature initiator is at least one of tert-butyl hydroperoxide, diisopropylbenzene peroxide or tert-butylisopropylbenzene hydroperoxide; and the persulfate oxidant is at least one of potassium persulfate, ammonium persulfate, sodium persulfate or manganese persulfate.

[0071] In the embodiment of the present invention, a persulfate oxidant is used in the polymerization process. The persulfate ion can combine with the positively charged aluminum salt hydroxide hydrolysis product in the inorganic silicate coagulant, and generate free radicals after thermal decomposition to initiate the polymerization of organic monomers, thereby allowing the inorganic components in the inorganic silicate coagulant to react with the organic components such as acrylamide and acrylic acid through SO4 2- The ionic bonds are connected in a strong bonding manner compared to conventional hydrogen bonds, which makes the flocs formed by the dehydrating agent stable and not easy to disperse, and has good shear resistance.

[0072] According to some preferred embodiments, in step (1):

[0073] When preparing the dehydrating agent for bauxite tailings slurry, the addition amount of each reaction raw material in the mixed solution is as follows, calculated by mass percentage: 23.7-30.9% of inorganic silicate coagulant (for example, 23.7%, 24%, 25%, 27%, 28% or 30.9%), 21.5-23.2% of acrylamide monomer (for example, 21.5%, 22%, 22.5%, 22.8% or 23.2%), 1% of acrylic acid monomer 6-18% (for example, 16%, 16.5%, 17%, 17.5% or 18%), hydrophobic associating monomer 0.3-0.5% (for example, 0.3%, 0.4% or 0.5%), hydrophobic associating solubilizing monomer 1.3-1.6% (for example, 1.3%, 1.4%, 1.5% or 1.6%), water-soluble emulsifier 1.5-1.7% (for example, 1.5%, 1.6% or 1.7%);

[0074] Experiments of the present invention have confirmed that controlling the content of each component in the reaction monomer within the above range can not only ensure that each monomer can fully react in the polymerization reaction, but also enable each monomer to play its best role, thereby ensuring that the overall performance of the dehydrating agent product is better. If the amount of inorganic silicate coagulant added is too low, it is not conducive to ensuring a good flocculation effect of the dehydrating agent product. If the amount of inorganic silicate coagulant added is too high, the molecular weight of the dehydrating agent product will be low. Although the supernatant after flocculation is relatively clear, its flocculation effect is also poor. At the same time, the content of hydrophobically associating monomers and hydrophobically associating solubilizing monomers must be controlled at the same time. If the content of hydrophobically associating monomers is too low, it is not conducive to further improving the flocculation effect of the dehydrating agent product. If the content of hydrophobically associating monomers is too high, the solubility of the dehydrating agent product will be poor, which is not conducive to on-site application.

[0075] According to some preferred embodiments, in step (1): before adding the water-soluble chain transfer agent, metal complexing agent, temperature initiator and persulfate oxidant to the first mixed solution, the step of adjusting the pH of the first mixed solution with a pH regulator is also included; wherein the pH value of the mixed solution is preferably 7.5-7.7; in the embodiment of the present invention, the pH regulator can be a sodium hydroxide solution, an ammonia solution or a potassium hydroxide solution with a mass concentration of 40-50%, preferably a sodium hydroxide solution in the present invention. When the pH of the mixed solution is within the above range, it can ensure that the reaction rate of the reaction system is within an appropriate range during the subsequent initiation reaction, which neither causes the reaction process to be too slow nor causes the reaction process to have an implosion phenomenon. Preferably, the amount of the pH regulator added to the reaction system is 0.2-0.4%.

[0076] According to some preferred embodiments, in step (1): the amount of the water-soluble chain transfer agent added is 0.009-0.012% of the mixed solution (for example, it can be 0.009%, 0.010% or 0.012%), the amount of the metal complexing agent added is 0.014-0.016% of the mixed solution (for example, it can be 0.014%, 0.015% or 0.016%), the amount of the temperature initiator added is 0.0068-0.007% of the mixed solution (for example, it can be 0.0068%, 0.069% or 0.007%), and the amount of the persulfate oxidant added is 0.016-0.018% of the mixed solution (for example, it can be 0.016%, 0.017% or 0.018%).

[0077] According to some preferred embodiments, in step (2):

[0078] The base oil is at least one of white oil, rapeseed oil, kerosene, tung oil or castor oil;

[0079] The oil-soluble emulsifier is at least one of Span-40, Span-60, Span-80 or Span-85;

[0080] The oil-soluble initiator is at least one of 4,4'-azodiphenyl ether, diisopropyl azodicarboxylate or dibenzyl azodicarboxylate.

[0081] In an embodiment of the present invention, when preparing the continuous phase, a base oil, an oil-soluble emulsifier, and an oil-soluble initiator can be added to a reactor in sequence at a temperature of 23 to 25°C, stirred, and fully dissolved to obtain a continuous phase. The present invention has no particular limitation on the stirring speed, as long as it can ensure that the reaction raw materials are fully dissolved. The stirring speed can be, for example, 280 to 320 r / min. Thereafter, the temperature is maintained at 23 to 25°C, and the dispersed phase is added to the continuous phase, and stirred at high speed for 1.5 to 2 hours to obtain an oil-in-water inverse emulsion mixed system. The apparent viscosity of the mixed system is preferably 2600 to 3000 mP·s, which is conducive to the full polymerization of the subsequent reaction monomers. If the apparent viscosity of the mixed system is too low, the dehydrating agent product prepared subsequently will demulsify. If the apparent viscosity of the mixed system is too high, the viscosity of the mixed system will increase, which is not conducive to the uniform and full polymerization reaction between the subsequent reaction monomers. It should also be noted that the rotation speed of the high-speed stirring in the embodiment of the present invention is preferably 2600-3000 r / min.

[0082] According to some preferred embodiments, when preparing the dehydrating agent for bauxite tailings slurry, the addition amount of each reaction raw material in the continuous phase is as follows, in terms of mass percentage: base oil 25-27% (for example, it can be 25%, 26% or 27%), oil-soluble emulsifier 1.8-2.1% (for example, it can be 1.8%, 1.9%, 2.0% or 2.1%); the addition amount of the oil-soluble initiator is 0.012-0.013% of the addition amount of the base oil and the oil-soluble emulsifier (for example, it can be 0.012%, 0.0125% or 0.013%).

[0083] It should be noted that, in the embodiments of the present invention, when preparing the dehydrating agent for bauxite tailings, the addition amount of each reaction raw material is expressed in mass percentage.

[0084] According to some preferred embodiments, in step (3):

[0085] In order to ensure the progress of the polymerization reaction, before adding the reducing agent solution to the water-in-oil inverse emulsion system, the step of passing nitrogen through the water-in-oil inverse emulsion system to deoxygenate is further included; the time for passing nitrogen through the water-in-oil inverse emulsion to deoxygenate is preferably 30 to 35 minutes (for example, 30 minutes, 32 minutes, 33 minutes or 35 minutes);

[0086] The concentration of the reducing agent solution is 1.5-1.8% (for example, 1.5%, 1.6%, 1.7% or 1.8%), and the solute in the reducing agent solution is at least one of sodium metabisulfite, potassium pyrosulfite, sodium thiosulfate or thiourea dioxide.

[0087] According to some preferred embodiments, the polymerization reaction is carried out in two temperature stages; wherein the temperature of the first temperature stage is 45-47° C. (for example, 45° C., 46° C., or 47° C.), and the time is 1.8-2.5 h (for example, 1.8 h, 2.0 h, 2.2 h, or 2.5 h); the temperature of the second temperature stage is 66-68° C. (for example, 66° C., 67° C., or 68° C.), and the time is 1.8-2.5 h (for example, 1.8 h, 2.0 h, 2.2 h, or 2.5 h);

[0088] When the polymerization reaction is carried out in each temperature stage, the reducing agent solution is added dropwise to the inverse emulsion mixed system in two stages; wherein the dropping speed of the reducing agent solution in the first stage is 2 to 3 mL / h (for example, 2 mL / h, 2.2 mL / h, 2.5 mL / h, 2.8 mL / h or 3 mL / h), and the dropping speed of the reducing agent solution in the second stage is 0.5 to 1 mL / h (for example, 0.5 mL / h, 0.6 mL / h, 0.7 mL / h, 0.8 mL / h or 1 mL / h).

[0089] In an embodiment of the present invention, when the polymerization reaction is carried out, the polymerization reaction is carried out in two temperature stages, and during the polymerization reaction process in each temperature stage, the reducing agent solution is added dropwise in two stages, and the dropping speed of the reducing agent solution in each stage is different; for example, the reducing agent solution is first added dropwise to the inverse emulsion mixing system at a rate of 2 to 3 mL / h, and at the same time, the reaction system is controlled by a water bath to rise to 45 to 47°C within 0.3 to 0.5h, and the temperature of the reaction system is kept unchanged. Thereafter, the dropping speed of the reducing agent solution is adjusted to 0.5 to 1 mL / h, and the reaction is continued for 1.5 to 2h to complete the polymerization reaction in the first temperature stage. Afterwards, the dropping speed of the reducing agent solution was adjusted to 2-3 mL / h, and the temperature of the reaction system was controlled by a water bath to rise to 66-68°C within 0.3-0.5 h, while keeping the temperature of the reaction system unchanged. Finally, the dropping speed of the reducing agent solution was adjusted to 0.5-1 mL / h, and the reaction was continued for 1.5-2 h to complete the polymerization reaction. At this time, the system was in a transparent and stable emulsion state, and the system temperature was lowered to room temperature (23-25°C).

[0090] It should be noted that, in the embodiments of the present invention, the time for adding the reducing agent solution is the time for the polymerization reaction; for example, during the polymerization reaction in the first temperature stage, the time for adding the reducing agent at a rate of 2 to 3 mL / h is 0.3 to 0.5 h, and the time for adding the reducing agent at a rate of 0.5 to 1 mL / h is 1.5 to 2 h.

[0091] In the embodiment of the present invention, the polymerization reaction is carried out in two temperature stages, and the reducing agent solution with different dripping speeds is used to initiate the polymerization reaction in each temperature stage. This not only ensures that the various reaction monomers can fully contact each other, thereby better causing the polymerization reaction, but also ensures that the molecular weight of the polymer during the polymerization reaction is within a controllable range. If the reducing agent solution is added to the inverse emulsion mixing system at one time during the polymerization reaction and the temperature of the reaction system is suddenly increased to 66-68°C, it is not only not conducive to the full polymerization between the various reaction monomers, but also difficult to control the molecular weight of the polymer formed by the reaction.

[0092] According to some preferred embodiments, in step (3):

[0093] After the polymerization reaction, a phase inversion agent is added to the reaction system to obtain the dehydrating agent for the bauxite tailings slurry;

[0094] The phase inversion agent is at least one of polyethylene glycol (12) tridecyl ether, hexaethylene glycol dodecyl ether or decaethylene glycol monododecyl ether;

[0095] The added amount of the phase inversion agent is 1.5-1.8% (for example, 1.5%, 1.6%, 1.7% or 1.8%).

[0096] In the embodiment of the present invention, in order to obtain a dehydrating agent product with relatively stable performance, a certain amount of phase inversion agent is added to the reaction system after the polymerization reaction is completed, and an inverse oil-in-water emulsion can be obtained after stirring and mixing; if the amount of the phase inversion agent added is too low, it is not conducive to ensuring good solubility of the dehydrating agent product; if the amount of the phase inversion agent added is too high, then

[0097] The present invention also provides a dehydrating agent for bauxite tailings slurry, which is prepared by any of the preparation methods described above. The dehydrating agent for bauxite tailings slurry prepared in the present invention has the advantages of good flocculation effect, fast sedimentation rate, clear supernatant, low turbidity and fast dissolution. It has a colorless and transparent appearance, an apparent viscosity of 1% aqueous solution of 600-800mPa·s, a viscosity-average relative molecular mass of 10 million to 12 million, a degree of hydrolysis of 20-25%, a relative turbidity of ≤0.3, a sedimentation mud concentration of ≥50%, a sedimentation rate of ≥15mm / min, and a supernatant height of ≥20mm.

[0098] In order to more clearly illustrate the technical solutions and advantages of the present invention, a dehydrating agent for bauxite tailings slurry and a preparation method thereof are described in detail below through several embodiments.

[0099] Example 1:

[0100] (1) Preparation of inorganic silicate coagulant:

[0101] (11) Start stirring and set the speed to 295 r / min. Add 35.55 g of silane coupling agent (vinyl triethoxysilane) and 109.02 g of deionized water into the reactor and mix well to obtain a colorless transparent liquid. Then, add 37.92 g of inorganic aluminum salt (aluminum trichloride) and fully dissolve to obtain a second mixed solution.

[0102] (12) The temperature of the reactor was raised to 52° C., and 54.51 g of 50% alkali solution (sodium hydroxide) was added to the second mixed solution at a rate of 12 mL / h using a syringe pump to ensure that the pH value of the reaction system was 7.71. After the polymerization reaction was carried out for 0.6 h, an inorganic silicate coagulant was obtained;

[0103] Stirring was started, the speed was set to 295 r / min, and the system temperature was controlled at 24° C. 237 g of the prepared inorganic silicate coagulant was mixed in sequence with 232 g of an acrylamide monomer (methacrylamide), 180 g of an acrylic acid monomer (methacrylic acid), 5 g of a hydrophobically associating monomer (2-ethylhexyl acrylate), 16 g of a hydrophobically associating solubilizing monomer (octanoylsulfobetaine), and 17 g of an aqueous emulsifier (Tween-60) to obtain a first mixed solution; the pH value of the first mixed solution was adjusted to 7.61 using 4 g of a 50% pH adjuster (sodium hydroxide) solution; then 0.069 g of a water-soluble chain transfer agent (sodium formate), 0.104 g of a metal complexing agent (dihydroxyethylglycine), 0.048 g of a temperature initiator (tert-butyl hydroperoxide), and 0.117 g of a persulfate oxidant (potassium persulfate) were added to the first mixed solution, and the mixture was mixed evenly to obtain a dispersed phase;

[0104] (2) Start stirring, set the speed to 295 r / min, maintain the temperature of the reaction system at 24°C, add 270 g of base oil (white oil), 21 g of oil-soluble emulsifier (Span-85) and 0.035 g of oil-soluble initiator (4,4'-azodiphenyl ether) into the reactor in sequence and mix well to obtain a continuous phase;

[0105] Stirring was started and the speed was set to 2850 r / min. The dispersed phase was added to the continuous phase and stirred for 1.8 h to obtain a water-in-oil inverse emulsion mixture system. The apparent viscosity of the mixture system was 2750 mPa·s.

[0106] (3) After nitrogen was passed through the oil-in-water reverse emulsion mixed system for deoxygenation for 33 minutes, stirring was started and the speed was set to 295 r / min. First, a reducing agent solution (sodium metabisulfite) with a concentration of 1.58% was added to the mixed system at a drop rate of 2.4 mL / h, and the temperature of the reaction system was raised to 46°C within 0.4 h by water bath control, and the temperature was kept constant. Then, the drop rate of the reducing agent solution was adjusted to 0.7 mL / h, and the reaction was continued for 1.6 h; the drop rate of the reducing agent solution was adjusted to 2.4 mL / h, and the temperature of the reaction system was raised to 67°C within 0.4 h by water bath control, and the temperature was kept constant. Then, the drop rate of the reducing agent solution was adjusted to 0.7 mL / h, and the reaction was continued for 1.6 h to obtain a stable and transparent emulsion;

[0107] After the temperature of the transparent emulsion dropped to 24° C., 18 g of a phase inversion agent (polyethylene glycol (12) tridecyl ether) was added to the transparent emulsion and mixed at a speed of 295 r / min to obtain a dehydrating agent for bauxite tailings slurry.

[0108] Example 2:

[0109] (1) Preparation of inorganic silicate coagulant:

[0110] (11) Stirring was started and the speed was set to 280 r / min. 52.53 g of silane coupling agent (vinyl trimethoxysilane) and 132.87 g of deionized water were added to the reactor and mixed to obtain a colorless transparent liquid. Then, 52.53 g of inorganic aluminum salt (aluminum trichloride) was added and fully dissolved to obtain a second mixed solution.

[0111] (12) The temperature of the reactor was raised to 52° C., and 71.07 g of 50% alkali solution (sodium hydroxide) was added to the second mixed solution at a rate of 10 mL / h using a syringe pump to ensure that the pH value of the reaction system was 7.71. After the polymerization reaction was carried out for 0.6 h, an inorganic silicate coagulant was obtained;

[0112] Stirring was started, the speed was set to 280 r / min, the system temperature was controlled at 24° C., 309 g of the prepared inorganic silicate coagulant was mixed in sequence with 215 g of an acrylamide monomer (acrylamide), 160 g of an acrylic acid monomer (methacrylic acid), 3 g of a hydrophobically associating monomer (2-ethylhexyl acrylate), 13 g of a hydrophobically associating solubilizing monomer (coconut oil polyoxyethylene ether methyl ammonium chloride), and 15 g of an aqueous emulsifier (Tween-60) to obtain a first mixed solution; the pH value of the first mixed solution was adjusted to 7.61 using 2 g of a 50% pH adjusting agent (sodium hydroxide) solution; then 0.072 g of a water-soluble chain transfer agent (sodium formate), 0.108 g of a metal complexing agent (dihydroxyethylglycine), 0.049 g of a temperature initiator (tert-butyl hydroperoxide), and 0.122 g of a persulfate oxidant (sodium persulfate) were added to the first mixed solution, and the mixture was uniformly mixed to obtain a dispersed phase;

[0113] (2) Start stirring, set the speed to 280 r / min, maintain the temperature of the reaction system at 24°C, add 250 g of base oil (white oil), 18 g of oil-soluble emulsifier (Span-85) and 0.034 g of oil-soluble initiator (4,4'-azodiphenyl ether) into the reactor in sequence and mix well to obtain a continuous phase;

[0114] Stirring was started and the speed was set to 2600 r / min. The dispersed phase was added to the continuous phase and stirred for 1.8 h to obtain a water-in-oil inverse emulsion mixture system. The apparent viscosity of the mixture system was 2600 mPa·s.

[0115] (3) After nitrogen was passed through the oil-in-water reverse emulsion mixed system for deoxygenation for 33 minutes, stirring was started and the speed was set to 280 r / min. First, a reducing agent solution (sodium metabisulfite) with a concentration of 1.5% was added to the mixed system at a drop rate of 2 mL / h, and the temperature of the reaction system was raised to 46°C within 0.4 h by water bath control, and the temperature was kept constant. Then, the drop rate of the reducing agent solution was adjusted to 0.5 mL / h, and the reaction was continued for 1.6 h; the drop rate of the reducing agent solution was adjusted to 2 mL / h, and the temperature of the reaction system was raised to 67°C within 0.4 h by water bath control, and the temperature was kept constant. Then, the drop rate of the reducing agent solution was adjusted to 0.5 mL / h, and the reaction was continued for 1.6 h to obtain a stable and transparent emulsion;

[0116] After the temperature of the transparent emulsion dropped to 24° C., 15 g of a phase inversion agent (polyethylene glycol (12) tridecyl ether) was added to the transparent emulsion and mixed at a speed of 280 r / min to obtain a dehydrating agent for bauxite tailings slurry.

[0117] Example 3:

[0118] (1) Preparation of inorganic silicate coagulants:

[0119] (11) Start stirring and set the speed to 295 r / min. Add 48 g of silane coupling agent (vinyl triethoxysilane) and 132 g of deionized water into the reactor and mix well to obtain a colorless transparent liquid. Then, add 48 g of inorganic aluminum salt (aluminum trichloride) and fully dissolve to obtain a second mixed solution.

[0120] (12) The temperature of the reactor was raised to 50° C., and 72 g of 50% alkali solution (sodium hydroxide) was added to the second mixed solution at a rate of 12 mL / h using a syringe pump to ensure that the pH value of the reaction system was 7.6. After the polymerization reaction was carried out for 0.5 h, an inorganic silicate coagulant was obtained;

[0121] Stirring was started, the speed was set to 295 r / min, the system temperature was controlled at 24 ° C, and 300 g of the prepared inorganic silicate coagulant was sequentially mixed with 218.5 g of acrylamide monomer (methacrylamide), 161 g of acrylic acid monomer (acrylic acid), 3.1 g of hydrophobic associating monomer (2-ethylhexyl acrylate), 13.1 g of hydrophobic associating solubilizing monomer (octanoyl sulfobetaine) and 15.2 g of aqueous emulsifier (Tween-60). After mixing, a first mixed solution was obtained; the pH value of the first mixed solution was adjusted to 7.61 using 3 g of a 50% pH adjuster (sodium hydroxide) solution; then, 0.071 g of a water-soluble chain transfer agent (sodium formate), 0.107 g of a metal complexing agent (dihydroxyethylglycine), 0.049 g of a temperature initiator (tert-butyl hydroperoxide), and 0.121 g of a persulfate oxidant (potassium persulfate) were added to the first mixed solution, and the mixture was mixed uniformly to obtain a dispersed phase;

[0122] (2) Start stirring, set the speed to 295 r / min, maintain the temperature of the reaction system at 24°C, add 251 g of base oil (white oil), 18.6 g of oil-soluble emulsifier (Span-85) and 0.034 g of oil-soluble initiator (4,4'-azodiphenyl ether) into the reactor in sequence and mix well to obtain a continuous phase;

[0123] Stirring was started and the speed was set to 2850 r / min. The dispersed phase was added to the continuous phase and stirred for 1.5 h to obtain a water-in-oil inverse emulsion mixture system. The apparent viscosity of the mixture system was 2750 mPa·s.

[0124] (3) After nitrogen was passed through the oil-in-water reverse emulsion mixed system for deoxygenation for 33 minutes, stirring was started and the speed was set to 295 r / min. First, a reducing agent solution (sodium metabisulfite) with a concentration of 1.58% was added to the mixed system at a drop rate of 2.4 mL / h, and the temperature of the reaction system was raised to 45°C within 0.3 h by water bath control, and the temperature was kept constant. Then, the drop rate of the reducing agent solution was adjusted to 0.7 mL / h, and the reaction was continued for 1.5 h; the drop rate of the reducing agent solution was adjusted to 2.4 mL / h, and the temperature of the reaction system was raised to 66°C within 0.3 h by water bath control, and the temperature was kept constant. Then, the drop rate of the reducing agent solution was adjusted to 0.7 mL / h, and the reaction was continued for 1.5 h to obtain a stable and transparent emulsion;

[0125] After the temperature of the transparent emulsion dropped to 24° C., 16.5 g of a phase inversion agent (polyethylene glycol (12) tridecyl ether) was added to the transparent emulsion and mixed at a speed of 295 r / min to obtain a dehydrating agent for bauxite tailings slurry.

[0126] Example 4:

[0127] Example 4 is basically the same as Example 1, except that: in step (3), the polymerization reaction is carried out at the same temperature, and the reducing agent solution is added to the oil-in-water inverse emulsion mixed system at the same temperature at one time; that is, a reducing agent solution (sodium metabisulfite) with a concentration of 1.58% is added to the mixed system at one time, and the reaction system is directly raised to 67°C for reaction for 4 hours to obtain a stable and transparent emulsion.

[0128] Example 5:

[0129] Example 5 is basically the same as Example 1, except that: in step (3), the polymerization reaction is carried out in two temperature stages, but the reducing agent solution is added to the oil-in-water inverse emulsion mixed system at one time; that is, a reducing agent solution (sodium metabisulfite) with a concentration of 1.58% is first added to the mixed system at a dropwise addition rate of 2.4 mL / h, and the temperature of the reaction system is raised to 46° C. within 0.4 h by water bath control, and the temperature is maintained constant and the reaction is continued for 1.6 h; then, the temperature of the reaction system is raised to 67° C. within 0.4 h by water bath control, and the temperature is maintained constant and the reaction is continued for 1.6 h to obtain a stable and transparent emulsion.

[0130] Example 6:

[0131] Example 6 is basically the same as Example 1, except that in step (11), the amount of silane coupling agent (vinyltriethoxysilane) added is 47.4 g.

[0132] Example 7:

[0133] Example 7 is basically the same as Example 1, except that in step (11), the amount of inorganic aluminum salt (aluminum trichloride) added is 50 g.

[0134] Example 8:

[0135] Example 8 is basically the same as Example 1, except that in step (1), the amount of inorganic silicate coagulant added is 20 g.

[0136] Example 9:

[0137] Example 9 is basically the same as Example 1, except that in step (1), the amount of inorganic silicate coagulant added is 35 g.

[0138] Example 10:

[0139] Example 10 is substantially the same as Example 1, except that in step (1), the amount of hydrophobic associating monomer added is 1 g.

[0140] Example 11:

[0141] Example 11 is basically the same as Example 1, except that in step (1), the amount of hydrophobic associating solubilizing monomer added is 20 g.

[0142] Comparative Example 1:

[0143] Comparative Example 1 is basically the same as Example 1, except that: in step (1), no inorganic silicate coagulant is added to the dispersed phase; that is, stirring is started, the speed is set to 295 r / min, the system temperature is controlled at 24° C., 232 g of acrylamide monomer (methacrylamide), 180 g of acrylic acid monomer (methacrylic acid), 5 g of hydrophobic associating monomer (2-ethylhexyl acrylate), 1 g of hydrophobic associating solubilizing monomer (octanoyl sulfobetaine) are added to the dispersed phase. After mixing 6 g of ethanol and 17 g of an aqueous emulsifier (Tween-60), the pH value of the mixture was adjusted to 7.61 using 4 g of a 50% pH adjuster (sodium hydroxide) solution; then, 0.1 g of a water-soluble chain transfer agent (sodium formate), 0.15 g of a metal complexing agent (dihydroxyethylglycine), 0.069 g of a temperature initiator (tert-butyl hydroperoxide) and 0.17 g of a persulfate oxidant (potassium persulfate) were added to the mixture, and the mixture was mixed uniformly to obtain a dispersed phase.

[0144] Comparative Example 2:

[0145] Comparative Example 2 is substantially the same as Example 1, except that in step (1), no hydrophobic associating solubilizing monomer (octanoyl sulfobetaine) is added to the dispersed phase.

[0146] Comparative Example 3:

[0147] Comparative Example 3 is substantially the same as Example 1, except that: in step (1), stirring is started, the speed is set to 295 r / min, 37.92 g of inorganic aluminum salt (aluminum trichloride) and 109.02 g of deionized water are added to the reactor to obtain a mixed solution; (12) the temperature of the reactor is raised to 52° C., 54.51 g of 50% alkali solution (sodium hydroxide) is added to the mixed solution at a dropwise rate of 12 mL / h using a syringe pump, ensuring that the pH value of the reaction system is 7.71, and the coagulant is obtained after the polymerization reaction for 0.6 h. Comparative Example 4:

[0148] Comparative Example 4 is substantially the same as Example 1, except that in step (1), the inorganic silicate coagulant is replaced with polyaluminium ferric chloride of the same mass.

[0149] Comparative Example 5:

[0150] Comparative Example 5 is substantially the same as Example 1, except that: in step (1), no hydrophobic associating monomers and hydrophobic associating solubilizing monomers are added.

[0151] Comparative Example 6:

[0152] Comparative Example 6 is substantially the same as Example 1, except that in step (1), the same mass of hydrogen peroxide is used instead of the persulfate oxidant (potassium persulfate).

[0153] The dehydrating agents prepared in Examples 1 to 11 and Comparative Examples 1 to 6 (hereinafter referred to as samples) were subjected to performance tests. The test results are shown in Table 1. The test method is as follows:

[0154] (1) Apparent viscosity test of 1% aqueous solution: Accurately weigh 4.0 g of sample, set the stirrer speed to 300 r / min, and slowly add it to 400 mL of distilled water while stirring. Then set the speed to 1500 r / min and stir at high speed for 5 minutes. Then measure the apparent viscosity using a rotational viscometer according to method 6.3 of GB / T16783.1;

[0155] (2) Viscosity-average molecular weight and degree of hydrolysis test: 20.000 g of sample (recorded as m1) was accurately weighed on an electronic balance, washed with 100.0 g of anhydrous ethanol, and the obtained solid was filtered using a vacuum pump, repeated 5 times, and placed in a 50°C oven for 5 h. The obtained white powder was weighed on an analytical balance, recorded as m2. The white powder was placed in a moisture analyzer to measure its solid content, recorded as G0. The effective content was calculated according to formula (1):

[0156]

[0157] Where:

[0158] G——effective content, %;

[0159] G0——white powder solid content, %;

[0160] m1——mass of emulsion polymer, g;

[0161] m2——mass of white powder, g.

[0162] The obtained white powder was tested for viscosity-average molecular weight and degree of hydrolysis according to GB / T 17514-2017.

[0163] (3) Supernatant height test: During the sedimentation process of ore mud, the particles move downward to form a clear mud-water separation surface. The liquid above the separation surface is clear and is called the supernatant. The particle content below the separation surface is called the sedimentation mud. The height from the initial liquid surface to the separation surface is called the supernatant height H. The sedimentation velocity can be calculated by the change of the supernatant height with the sedimentation time. Take a graduated cylinder with a range of 200 mL, add the dehydrating agent of the above sample, record the separation surface as V0 after sedimentation for 2 minutes, and calculate the supernatant height according to formula (2):

[0164]

[0165] Where, H is the height of the supernatant, mm;

[0166] V0——liquid level reading, mL;

[0167] D——inner diameter of measuring cylinder, mm.

[0168] (4) Sedimentation rate test: Sedimentation rate refers to the height that the supernatant drops in unit time. It is a dynamic process. In order to better reflect the change in speed, the height difference of adjacent page readings is divided by the corresponding time difference of adjacent page readings. The sedimentation rate is calculated according to formula (3):

[0169]

[0170] Where V t ——sedimentation rate, mm / min;

[0171] H n+1 , H n ——Real-time height of supernatant, mm;

[0172] T n+1 , T n ——Time passed through this scale, min.

[0173] (3) Settled mud concentration: The higher the sedimentation mud concentration, the more favorable it is for dehydration and subsequent solidification. During the sedimentation process, coarse particles will settle first, and the sedimentation mud concentration will decrease from the bottom to the top. It is difficult to collect sedimentation mud in a measuring cylinder, so it can only be calculated by weighing method, as shown in formulas (4) and (5):

[0174] M2=M1-M0……(4)

[0175] Where, M0 is the mass of the measuring cylinder, g;

[0176] M1 - total mass of sludge and measuring cylinder, g;

[0177] M2——mass of ore mud, g;

[0178]

[0179] C0——initial mass concentration of sludge, %;

[0180] C1——mass concentration of sedimentation mud, %;

[0181] ρ w ——density of supernatant, g / cm 3 ;

[0182] V——supernatant volume, mL.

[0183] (4) Specific test of relative turbidity:

[0184] Preparation of TiO2 turbid solution: TiO2 powder (190 nm, density 3.95 g / mL) was dispersed in NaCl brine (concentration 1000 ppm) at a concentration of 1500 ppm. After being sealed and placed for 24 hours, it was stirred at 700 r / min for 2 hours to ensure uniform dispersion of particles. The pH was adjusted to 9-9.2 with 50% NaOH solution to obtain TiO2 turbid solution, which was set aside.

[0185] Relative turbidity test: Use a turbidity meter to test the blank turbidity of TiO2 turbidity solution and record it as T0. Dissolve the dehydrating agent sample in deionized water at a concentration of 1000ppm. After fully dissolving, obtain a flocculant aqueous solution for standby use. According to the concentration of 2000ppm, weigh a certain amount of flocculant aqueous solution and add it to the TiO2 turbidity solution. Stir at a temperature of 25℃ and a speed of 700r / min for 15min. After standing for 10min, test the turbidity and record it as T1. Calculate the relative turbidity T according to formula (6): r :

[0186] T r =T1 / T0……(6).

[0187] Table 1

[0188]

[0189]

[0190] As can be seen from Table 1, compared with the comparative example, the dehydrating agent for bauxite tailings slurry prepared by the present invention has the advantages of fast flocculation speed, clear supernatant, low turbidity, fast dissolution, etc., its appearance is colorless and transparent, the hydrolysis degree is 20-25%, the relative turbidity is ≤0.3, the sedimentation mud concentration is ≥50%, the sedimentation rate is ≥15 mm / min, and the supernatant height is ≥20 mm.

[0191] Note: The tailings mud used in the above test is thickener tailings mud with a mass concentration of 25%. Its main components are shown in Table 2:

[0192] Table 2

[0193]

[0194] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a dehydrating agent for bauxite tailings slurry, characterized in that: The preparation method comprises the following steps: (1) An inorganic silicate coagulant is mixed with an acrylamide monomer, an acrylic acid monomer, a hydrophobic associating monomer, a hydrophobic associating solubilizing monomer and an aqueous emulsifier to obtain a first mixed solution; a water-soluble chain transfer agent, a metal complexing agent, a temperature initiator and a persulfate oxidant are added to the first mixed solution, and the mixture is mixed to obtain a dispersed phase; wherein the inorganic silicate coagulant is prepared by polymerization reaction of a silane coupling agent, an inorganic aluminum salt and an alkali solution; the silane coupling agent is at least one of vinyl triethoxysilane, γ-aminopropyl triethoxysilane, vinyl trimethoxysilane or γ-methacryloxypropyl trimethoxysilane; the inorganic aluminum salt is at least one of aluminum trichloride, aluminum sulfate or alum; When preparing the dehydrating agent for bauxite tailings slurry, the addition amount of each reaction raw material in the first mixed solution is as follows, calculated by mass percentage: inorganic silicate coagulant 23.7-30.9%, acrylamide monomer 21.5-23.2%, acrylic acid monomer 16-18%, hydrophobic associating monomer 0.3-0.5%, hydrophobic associating solubilizing monomer 1.3-1.6%, water-soluble emulsifier 1.5-1.7%; The acrylamide monomer is at least one of acrylamide, N,N-dimethylacrylamide or methacrylamide; the acrylic acid monomer is at least one of acrylic acid, 2-ethylacrylic acid, methacrylic acid, 2-propyl acrylic acid, 2-(bromomethyl) acrylic acid or 3,3-dimethylacrylic acid; the hydrophobic associating monomer is at least one of allyl tris(3,3,4,4,5,5,6,6,6-nonafluorohexyl)stannane, N-(1-naphthyl)-N-phenylmethacrylamide, 2-ethylhexyl acrylate or allyloxy-tert-butyldimethylsilane; the hydrophobic associating solubilizing monomer is at least one of polyoxyethylene (10) lauryl ether, polyoxyethylene (6) lauryl ether, coconut oil polyoxyethylene ether methyl ammonium chloride, caprylsulfobetaine or 3-(N,N-dimethyldodecyl ammonium) propane sulfonate; (2) adding the dispersed phase to the continuous phase and mixing them to obtain a water-in-oil inverse emulsion mixed system; wherein the continuous phase is obtained by mixing a base oil, an oil-soluble emulsifier and an oil-soluble initiator; (3) adding a reducing agent solution to the water-in-oil reverse emulsion mixed system, and performing polymerization reaction in stages to obtain the dehydrating agent for bauxite tailings slurry; The polymerization reaction is carried out in two temperature stages; wherein the temperature of the first temperature stage is 45-47° C. and the time is 1.8-2.5 hours, and the temperature of the second temperature stage is 66-68° C. and the time is 1.8-2.5 hours. When the polymerization reaction is carried out in each temperature stage, the reducing agent solution is added dropwise to the inverse emulsion mixed system in two stages; wherein the dropping speed of the reducing agent solution in the first stage is 2-3 mL / h, and the dropping speed of the reducing agent solution in the second stage is 0.5-1 mL / h.

2. The preparation method according to claim 1, characterized in that The inorganic silicate coagulant is prepared by the following method: (11) mixing water, a silane coupling agent, and an inorganic aluminum salt to obtain a second mixed solution; (12) Alkali solution is added dropwise to the second mixed solution to obtain the inorganic silicate coagulant after polymerization reaction.

3. The preparation method according to claim 2, characterized in that In the process of preparing the inorganic silicate coagulant, the contents of the reaction raw materials are as follows, by mass percentage: water 40-46%, silane coupling agent 15-17%, inorganic aluminum salt 16-18%, alkali solution 23-25%; the mass concentration of the alkali solution is 40-50%; and / or In step (12), the polymerization reaction temperature is 50-53° C., and the time is 0.5-1 h.

4. The preparation method according to claim 1, characterized in that The alkali solution is at least one of sodium hydroxide, potassium hydroxide or ammonia water.

5. The preparation method according to claim 1, characterized in that In step (1): The aqueous emulsifier is at least one of Tween-60, Tween-40, Tween-80 or Tween-85; The water-soluble chain transfer agent is at least one of sodium formate, ascorbic acid or isopropyl alcohol; The metal complexing agent is at least one of diethylenetriaminepentaacetic acid, dihydroxyethylglycine, diethylenetriaminepenta(methylenephosphonic acid) or sodium ethylenediaminetetra(methylenephosphonic acid); The temperature initiator is at least one of tert-butyl hydroperoxide, dicumyl peroxide or tert-butyl cumyl hydroperoxide; and / or The persulfate oxidant is at least one of potassium persulfate, ammonium persulfate, sodium persulfate or manganese persulfate.

6. The preparation method according to claim 1, characterized in that In step (1): The amount of the water-soluble chain transfer agent added is 0.009-0.012% of the mixed solution, the amount of the metal complexing agent added is 0.014-0.016% of the mixed solution, the amount of the temperature initiator added is 0.0068-0.007% of the mixed solution, and the amount of the persulfate oxidant added is 0.016-0.018% of the mixed solution.

7. The preparation method according to claim 1, characterized in that In step (2): The base oil is at least one of white oil, rapeseed oil, kerosene, tung oil or castor oil; The oil-soluble emulsifier is at least one of Span-40, Span-60, Span-80 or Span-85; The oil-soluble initiator is at least one of 4,4'-azodiphenyl ether, diisopropyl azodicarboxylate or dibenzyl azodicarboxylate.

8. The preparation method according to claim 1, characterized in that When preparing the dehydrating agent for bauxite tailings slurry, the addition amount of each reaction raw material in the continuous phase is as follows, calculated by mass percentage: base oil 25~27%, oil-soluble emulsifier 1.8~2.1%; the addition amount of the oil-soluble initiator is 0.012~0.013% of the addition amount of the base oil and the oil-soluble emulsifier.

9. The preparation method according to claim 1, characterized in that In step (3): Before adding the reducing agent solution to the water-in-oil inverse emulsion system, the method further comprises the step of passing nitrogen through the water-in-oil inverse emulsion system for deoxygenation; the time for passing nitrogen through the system for deoxygenation is 30 to 35 minutes; and / or The concentration of the reducing agent solution is 1.5-1.8%, and the solute in the reducing agent solution is at least one of sodium metabisulfite, potassium metabisulfite, sodium thiosulfate or thiourea dioxide.

10. The preparation method according to claim 1, characterized in that In step (3): After the polymerization reaction, a phase inversion agent is added to the reaction system to obtain the dehydrating agent for the bauxite tailings slurry.

11. The preparation method according to claim 10, characterized in that: In step (3): The phase inversion agent is at least one of polyethylene glycol (12) tridecyl ether, hexaethylene glycol dodecyl ether or decaethylene glycol monododecyl ether; The added amount of the phase inversion agent is 1.5-1.8%.

12. A dehydrating agent for bauxite tailings slurry, characterized in that: The method is prepared according to any one of claims 1 to 11.

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