A magnetic hematite-mixed iron ore dressing flotation agent and a preparation method thereof

Abstract

The application discloses a magnetic and hematite mixed iron ore dressing flotation agent and a preparation method thereof. First, quaternary ammonium salt is obtained by reacting alkyl tertiary amine and benzyl chloride as raw materials; then allyl polyoxyethylene ether phosphate is obtained by reacting allyl polyoxyethylene ether and diaphosphorus pentoxide as raw materials; then linear dextrin is obtained by hydrolyzing the first part of corn starch, and oxidized dextrin is obtained by first-time oxidation; then the oxidized dextrin is mixed with the second part of corn starch and water, and pretreated starch slurry is obtained by high-pressure micro-jet and high-pressure pulse electric field treatment; the second-time oxidation is realized by ozone nano-bubbles to obtain an inhibitor; finally, the quaternary ammonium salt, the allyl polyoxyethylene ether phosphate, the inhibitor and diesel oil are uniformly mixed to obtain the flotation agent. The flotation agent is particularly suitable for the reverse flotation of the magnetic and hematite mixed iron ore, and the grade of the iron concentrate is low and the recovery rate is high.

Description

Technical Field

[0001] This invention belongs to the field of mineral processing technology, specifically relating to a flotation agent for magnetohemorrheic mixed iron ore and its preparation method. Background Technology

[0002] Industrially valuable iron ore can be classified into five types: magnetite ore, hematite and pseudomorphous hematite ore, limonite ore, titanium-bearing magnetite ore, and siderite ore. With the accelerating pace of industrialization and modernization, the demand for iron ore resources both domestically and internationally has increased significantly. Consequently, iron ore resources are becoming increasingly scarce. Therefore, the efficient development and utilization of low-grade, lean ores is essential.

[0003] Currently, commonly used methods for processing fine-grained magnetite both domestically and internationally include single weak magnetic separation processes, weak magnetic separation-reverse flotation processes, weak magnetic separation-fine screening-weak magnetic separation processes, or weak magnetic separation-gravity separation processes. All of these methods further improve the quality of the weak magnetic concentrate by discarding tailings from the weak magnetic separation process. However, in practical applications, existing methods suffer from problems such as high energy consumption, inability to significantly increase iron concentrate grade, and excessively low iron concentrate recovery rates, resulting in substantial resource waste.

[0004] For the beneficiation of fine-grained hematite ore, the most commonly used typical beneficiation processes include staged grinding or continuous grinding, coarse and fine separation, gravity separation-weak magnetic separation-high gradient magnetic separation-anion reverse flotation process, continuous grinding, weak magnetic separation-strong magnetic separation-anion reverse flotation process, roasting, staged grinding-high efficiency magnetic separation-cation reverse flotation process, etc.

[0005] Therefore, flotation technology is becoming increasingly important in iron ore beneficiation.

[0006] Magnetite has poorer natural floatability than hematite, and its flotation speed is also lower. Therefore, reverse flotation is usually used to float gangue minerals to improve iron grade and reduce impurity content. Hematite has better floatability and is easily floated by fatty acid collectors. Therefore, a direct flotation process that suppresses gangue minerals to float iron ore can be used, as well as a reverse flotation process that suppresses iron ore to float gangue, but its reverse flotation performance is slightly worse than that of magnetite. Pseudo-hematite has floatability similar to magnetite, but worse than that of hematite.

[0007] There are three main flotation methods for iron ore: 1. Anion flotation method: Iron ores using this process often have characteristics such as a simple composition of iron oxide minerals, low content of primary slime, and difficulty in flotating gangue minerals. Flotation is carried out under weakly alkaline conditions with sodium carbonate as a modifier or weakly acidic conditions with sodium ammonium fluorosilicate as a modifier. Common collectors include fatty acid soaps (crude tar oil, oxidized paraffin soap, oxidized kerosene, oleic acid, pulp waste liquor, etc.) and mixed petroleum sulfonates.

[0008] 2. Anionic reverse flotation method: Quartz is easily activated by calcium, magnesium, and iron ions. Under alkaline conditions, lime and other inhibitors such as starch, sulfonated lignin, and dextrin can effectively suppress iron minerals. Medium conditioning agents include sodium hydroxide and sodium carbonate.

[0009] 3. Cationic reverse flotation method: Starch or dextrin is used to suppress iron minerals, while cationic collectors are used to float quartz. The suppression effect on iron minerals is best in an alkaline medium. Because the surface of quartz or silicate minerals carries a negative charge, it easily interacts with the positively charged cationic collectors.

[0010] Flotation agents are diverse and can be broadly categorized into collectors, frothers, and modifiers. Frosting agents primarily act at the air-water interface, dispersing air into small bubbles within the slurry and improving the stability and mineralization of these bubbles during flotation. Modifiers adjust the interaction between other reagents (mainly collectors) and the mineral surface, modifying slurry properties and enhancing selectivity for the desired minerals. Based on their primary mode of action, modifiers can be classified into activators, inhibitors, pH adjusters, dispersants or flocculants, and defoamers. Collectors are reagents that selectively act on the mineral surface, making mineral particles more hydrophobic and thus enhancing their affinity for organic matter.

[0011] The mineral-loving groups of flotation reagents for iron minerals are mainly carboxyl, amino, sulfonic acid, and phosphonic acid groups. Based on the groups that interact with the minerals, they are classified into anionic, cationic, and nonionic collectors. Fatty acids and their soaps are typical anionic collectors, mainly including oleic acid, talc oil, oxidized paraffin soap, and naphthenic acids. Due to the highly reactive carboxyl functional group, fatty acids can float almost all minerals. However, their biggest weaknesses are poor mineral selectivity, high dosage requirements, intolerance to hard water, and poor low-temperature flotation performance. When used as a mineral processing collector, a depressant must be used simultaneously to suppress gangue minerals in order to separate the useful minerals from the gangue minerals. Many factors determine the concentration of fatty acid anions in the pulp during flotation, and the concentration of fatty acid anions is related to the pulp pH. Amine collectors are typical cationic collectors used in reverse flotation of iron ore, mainly for the flotation of quartz and silicates. It has the advantages of simple reagent types, low requirements for water quality, better low-temperature flotation performance than anionic reagents, and low reagent dosage. However, amines are very sensitive to mineral slime and easily adsorb onto the surface of negatively charged slime particles. This not only consumes a large amount of collector but also causes the foam to become sticky, reducing the selectivity of amines.

[0012] In summary, magnetochre mixed iron ore is very common in current iron ore development, and selecting appropriate flotation agents is of great significance for the beneficiation of magnetochre mixed iron ore. Summary of the Invention

[0013] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a flotation agent for the beneficiation of magnetic hematite mixed iron ore and its preparation method, which has excellent reverse flotation effect on magnetic hematite mixed iron ore.

[0014] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a flotation agent for magnetohemorrhagic mixed iron ore beneficiation, comprising the following specific steps: (1) First, alkyl tertiary amines and benzyl chloride are reacted to obtain quaternary ammonium salts; (2) Using allyl polyoxyethylene ether and phosphorus pentoxide as raw materials, an allyl polyoxyethylene ether phosphate ester is obtained by reaction. (3) Then the first part of corn starch is hydrolyzed to obtain linear dextrin, and oxidized for the first time to obtain oxidized dextrin; then the oxidized dextrin is mixed with the second part of corn starch and water, and treated with high pressure microjet and high pressure pulse electric field to obtain pretreated starch paste, and then oxidized for the second time through ozone nanobubbles to obtain inhibitor; (4) Finally, the quaternary ammonium salt, allyl polyoxyethylene ether phosphate, inhibitor and diesel oil are mixed evenly to obtain the flotation agent.

[0015] Preferably, the specific method of step (1) is as follows: mix the alkyl tertiary amine with 0.45 to 0.55 times its weight of benzyl chloride, stir and react at 90 to 100°C for 100 to 120 minutes, and then cool naturally to room temperature to obtain the product.

[0016] Preferably, in step (1), the alkyl tertiary amine is tetradecyl tertiary amine or hexadecyl tertiary amine.

[0017] Preferably, the specific method of step (2) is as follows: allyl polyoxyethylene ether is heated to 40°C under a nitrogen atmosphere, phosphorus pentoxide is added while stirring, the temperature is raised to 80-90°C, the reaction is carried out by stirring for 3-5 hours, and then naturally cooled to room temperature to obtain the product.

[0018] Preferably, in step (2), the molar ratio of allyl polyoxyethylene ether to phosphorus pentoxide is 2:1.

[0019] Preferably, in step (2), the stirring rate is 300-500 r / min.

[0020] Preferably, in step (3), the linear dextrin is prepared by the following method: First, the first part of corn starch is stirred and dispersed in water to make a starch milk with a mass concentration of 5%. Then, the starch milk is stirred in a boiling water bath for 1 hour to obtain gelatinized starch milk. The pH of the gelatinized starch milk is adjusted to 6 using 0.01-0.02 mol / L acetic acid solution. α-amylase is added and enzymatically hydrolyzed at 50-60℃ for 1-2 hours to inactivate the enzyme. The temperature is adjusted to 50-60℃, pullulanase is added, and enzymatically hydrolyzed at 50-60℃ for 3-4 hours to inactivate the enzyme. The supernatant is centrifuged, rotary evaporated, and freeze-dried under vacuum to obtain the final product.

[0021] More preferably, the amounts of α-amylase and pullulanase added are 3-4 U / L and 35-45 U / L, respectively.

[0022] More preferably, the centrifugation rate is 5000-6000 r / min for 20-30 minutes.

[0023] Preferably, in step (3), the process conditions for the first oxidation are as follows: linear dextrin is stirred and dispersed in water to prepare a dextrin solution with a mass concentration of 5% and stored at 5°C. At the same time, 2,2,6,6-tetramethylpiperidine-1-oxy free radical and sodium bromide are dissolved in water at 5°C to obtain a premix. The premix is ​​then added to the dextrin solution stored at 5°C. The pH is adjusted to 10-11 using 0.5 mol / L sodium hydroxide solution. Sodium hypochlorite is added, and the mixture is kept warm and stirred for 50-60 minutes to obtain a reaction solution. Finally, 75% ethanol solution is added to the reaction solution, and the mixture is kept warm and allowed to stand for 1-2 hours. The precipitate is then taken, washed, and dried to obtain the final product.

[0024] More preferably, the mass ratio of 2,2,6,6-tetramethylpiperidine-1-oxy radical, sodium bromide, and water in the preparation of the premix is ​​0.2–0.3:2–3:1000.

[0025] More preferably, the volume ratio of the premix to the dextrin solution is 1:1, and the amount of sodium hypochlorite used is 10-12% of the mass of the linear dextrin.

[0026] In a further preferred embodiment, the ethanol solution and the reaction solution are of equal volume, and the mixture is washed 3 to 4 times with acetone.

[0027] Preferably, in step (3), oxidized dextrin is mixed with the second part of corn starch and water at a mass ratio of 2-3:8-10:100.

[0028] Preferably, in step (3), the process conditions for high-pressure microjet are: pressure 100-120MPa, treatment 2-3 times.

[0029] Preferably, in step (3), the process conditions for high-voltage pulse electric field treatment are: electric field strength 50-60kV / cm, frequency 120-150Hz, pulse width 30-40μs, and treatment time 45-55 minutes.

[0030] Preferably, in step (3), the specific method for the second oxidation is as follows: the pretreated starch slurry and ozone are introduced into a nanobubble generator, and the ozone nanobubbles are used to achieve the second oxidation.

[0031] Further preferred, the flow rate of the pretreated starch slurry is 8-10 L / min, the ozone flow rate is 0.3-0.5 L / min, the ozone concentration is 40-50 mg / L, and the treatment time is 8-10 minutes.

[0032] Preferably, in step (4), the mass ratio of quaternary ammonium salt, allyl polyoxyethylene ether phosphate, inhibitor, and diesel is 8-10:2-3:8-10:20-30.

[0033] A magnetic hematite mixed iron ore beneficiation flotation agent is obtained by the aforementioned preparation method.

[0034] Compared with the prior art, the present invention has the following beneficial effects: This invention first reacts alkyl tertiary amines and benzyl chloride as raw materials to obtain a quaternary ammonium salt; then, using allyl polyoxyethylene ether and phosphorus pentoxide as raw materials, it reacts to obtain allyl polyoxyethylene ether phosphate ester; next, the first portion of corn starch is hydrolyzed to obtain linear dextrin, which undergoes a first oxidation to obtain oxidized dextrin; then, the oxidized dextrin is mixed with the second portion of corn starch and water, and treated with high-pressure microjet and high-pressure pulsed electric field to obtain a pretreated starch slurry; a second oxidation is achieved through ozone nanobubbles to obtain an inhibitor; finally, the quaternary ammonium salt, allyl polyoxyethylene ether phosphate ester, inhibitor, and diesel oil are mixed evenly to obtain a flotation agent. This flotation agent is particularly suitable for reverse flotation in the beneficiation of magnetochromic mixed iron ore, achieving high recovery rates even with low iron concentrate grades.

[0035] This invention utilizes the synergistic effect of quaternary ammonium salt, allyl polyoxyethylene ether phosphate, inhibitor, and diesel fuel to suppress iron minerals and float quartz and other minerals in maghemite mixed iron ore, thereby achieving reverse flotation of maghemite mixed iron ore.

[0036] To improve the recovery rate of iron concentrate, inhibitors are crucial. The inhibitor of this invention is prepared by the following method: A first portion of corn starch is hydrolyzed to obtain linear dextrin, which is then oxidized for the first time to obtain oxidized dextrin. Next, the oxidized dextrin is mixed with a second portion of corn starch and water, and treated with a high-pressure microjet and a high-pressure pulsed electric field to obtain a pretreated starch slurry. A second oxidation is then achieved using ozone nanobubbles to obtain the inhibitor. Compared to corn starch, linear dextrin is debranched and oxidized, making it more stable and having better solubility, thus providing a better inhibitory effect during flotation. Furthermore, after mixing the oxidized dextrin with another portion of corn starch and treating it with a high-pressure pulsed electric field, the macromolecular chains break down, and hydrophilic carboxyl groups are oxidized at the chain ends, further improving solubility and strengthening the inhibitory effect, resulting in better reverse flotation performance.

[0037] Quaternary ammonium salts, allyl polyoxyethylene ether phosphate, and diesel fuel promote the generation of abundant foam in the slurry. Simultaneously, the allyl polyoxyethylene ether phosphate stabilizes the foam, thereby enriching quartz and other minerals and separating them from iron minerals. Furthermore, the inhibitor effectively prevents iron minerals from entering the foam, thus ensuring a high recovery rate and grade of the iron concentrate. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] Unless otherwise specified, all products in this invention were purchased through market channels.

[0040] Example 1 A method for preparing a flotation agent for magnetohemorrhagic mixed iron ore beneficiation, comprising the following specific steps: (1) First, alkyl tertiary amines and benzyl chloride are reacted to obtain quaternary ammonium salts; (2) Using allyl polyoxyethylene ether and phosphorus pentoxide as raw materials, an allyl polyoxyethylene ether phosphate ester is obtained by reaction. (3) Then the first part of corn starch is hydrolyzed to obtain linear dextrin, and oxidized for the first time to obtain oxidized dextrin; then the oxidized dextrin is mixed with the second part of corn starch and water, and treated with high pressure microjet and high pressure pulse electric field to obtain pretreated starch paste, and then oxidized for the second time through ozone nanobubbles to obtain inhibitor; (4) Finally, mix 8 kg of quaternary ammonium salt, 2 kg of allyl polyoxyethylene ether phosphate, 8 kg of inhibitor and 20 kg of diesel oil evenly to obtain the flotation agent.

[0041] The specific method of step (1) is as follows: mix tetradecylamine with 0.45 times its weight of benzyl chloride, stir at 90°C for 100 minutes, and then cool naturally to room temperature to obtain the product.

[0042] The specific method for step (2) is as follows: Allyl polyoxyethylene ether is heated to 40°C under a nitrogen atmosphere, and phosphorus pentoxide is added while stirring. The temperature is raised to 80°C, and the reaction is carried out at 300 r / min with stirring for 3 hours. The mixture is then naturally cooled to room temperature to obtain the final product. The molar ratio of allyl polyoxyethylene ether to phosphorus pentoxide is 2:1.

[0043] In step (3), the linear dextrin is prepared by the following method: First, the first part of corn starch is stirred and dispersed in water to make a starch milk with a mass concentration of 5%. Then, the starch milk is stirred in a boiling water bath for 1 hour to obtain gelatinized starch milk. The pH of the gelatinized starch milk is adjusted to 6 using 0.01 mol / L acetic acid solution. α-amylase is added and enzymatically hydrolyzed at 50°C for 1 hour. The enzyme is then inactivated. The temperature is adjusted to 50°C, pullulanase is added, and enzymatically hydrolyzed at this temperature for 3 hours. The enzyme is then inactivated. The mixture is centrifuged at 5000 r / min for 20 minutes, and the supernatant is collected, rotary evaporated, and then freeze-dried under vacuum to obtain the final product. The amounts of α-amylase and pullulanase added are 3 U / L and 35 U / L, respectively.

[0044] In step (3), the process conditions for the first oxidation are as follows: linear dextrin is stirred and dispersed in water to prepare a 5% (w / w) dextrin solution, which is then stored at 5°C. Simultaneously, at 5°C, 2,2,6,6-tetramethylpiperidine-1-oxy radical and sodium bromide are dissolved in water to obtain a premix. This premix is ​​then added to the dextrin solution stored at 5°C. The pH is adjusted to 10 using 0.5 mol / L sodium hydroxide solution. Sodium hypochlorite is added, and the mixture is stirred and kept warm for 50 minutes to obtain a reaction solution. Finally, an equal volume of 75% (v / v) ethanol solution is added to the reaction solution, and the mixture is kept warm and allowed to stand for 1 hour. The precipitate is then collected, washed three times with acetone, and dried to obtain the final product. The mass ratio of 2,2,6,6-tetramethylpiperidine-1-oxy radical, sodium bromide, and water in the premix is ​​0.2:2:1000. The volume ratio of the premix to the dextrin solution is 1:1, and the amount of sodium hypochlorite used is 10% of the mass of the linear dextrin.

[0045] In step (3), oxidized dextrin is mixed with the second part of corn starch and water at a mass ratio of 2:8:100. The process conditions for high-pressure microjet are: pressure 100MPa, treatment twice. The process conditions for high-pressure pulsed electric field treatment are: electric field strength 50kV / cm, frequency 120Hz, pulse width 30μs, and treatment time 45 minutes.

[0046] In step (3), the specific method for the second oxidation is as follows: the pretreated starch slurry and ozone are introduced into a nanobubble generator, and the ozone nanobubbles are used to achieve the second oxidation. The flow rate of the pretreated starch slurry is 8 L / min, the ozone flow rate is 0.3 L / min, the ozone concentration is 40 mg / L, and the treatment time is 8 minutes.

[0047] Example 2 A method for preparing a flotation agent for magnetohemorrhagic mixed iron ore beneficiation, comprising the following specific steps: (1) First, alkyl tertiary amines and benzyl chloride are reacted to obtain quaternary ammonium salts; (2) Using allyl polyoxyethylene ether and phosphorus pentoxide as raw materials, an allyl polyoxyethylene ether phosphate ester is obtained by reaction. (3) Then the first part of corn starch is hydrolyzed to obtain linear dextrin, and oxidized for the first time to obtain oxidized dextrin; then the oxidized dextrin is mixed with the second part of corn starch and water, and treated with high pressure microjet and high pressure pulse electric field to obtain pretreated starch paste, and then oxidized for the second time through ozone nanobubbles to obtain inhibitor; (4) Finally, mix 10 kg of quaternary ammonium salt, 3 kg of allyl polyoxyethylene ether phosphate, 10 kg of inhibitor and 30 kg of diesel oil evenly to obtain the flotation agent.

[0048] The specific method of step (1) is as follows: mix hexadecylamine with 0.55 times its weight of benzyl chloride, stir at 100°C for 120 minutes, and then cool naturally to room temperature to obtain the product.

[0049] The specific method for step (2) is as follows: Allyl polyoxyethylene ether is heated to 40°C under a nitrogen atmosphere, and phosphorus pentoxide is added while stirring. The temperature is raised to 90°C, and the mixture is stirred at 500 r / min for 5 hours. The mixture is then naturally cooled to room temperature to obtain the final product. The molar ratio of allyl polyoxyethylene ether to phosphorus pentoxide is 2:1.

[0050] In step (3), the linear dextrin is prepared by the following method: First, the first part of corn starch is stirred and dispersed in water to make a starch milk with a mass concentration of 5%. Then, the starch milk is stirred in a boiling water bath for 1 hour to obtain gelatinized starch milk. The pH of the gelatinized starch milk is adjusted to 6 using 0.02 mol / L acetic acid solution. α-amylase is added and enzymatically hydrolyzed at 60℃ for 2 hours. The enzyme is then inactivated. The temperature is adjusted to 60℃, pullulanase is added, and enzymatically hydrolyzed at this temperature for 4 hours. The enzyme is then inactivated. The mixture is centrifuged at 6000 r / min for 30 minutes, and the supernatant is collected, rotary evaporated, and then freeze-dried under vacuum to obtain the final product. The amounts of α-amylase and pullulanase added are 4 U / L and 45 U / L, respectively.

[0051] In step (3), the process conditions for the first oxidation are as follows: linear dextrin is stirred and dispersed in water to prepare a 5% (w / w) dextrin solution, which is then stored at 5°C. Simultaneously, at 5°C, 2,2,6,6-tetramethylpiperidine-1-oxy radical and sodium bromide are dissolved in water to obtain a premix. This premix is ​​then added to the dextrin solution stored at 5°C. The pH is adjusted to 11 using 0.5 mol / L sodium hydroxide solution. Sodium hypochlorite is added, and the mixture is stirred and kept warm for 60 minutes to obtain a reaction solution. Finally, an equal volume of 75% (v / v) ethanol solution is added to the reaction solution, and the mixture is kept warm and allowed to stand for 2 hours. The precipitate is then collected, washed four times with acetone, and dried to obtain the final product. The mass ratio of 2,2,6,6-tetramethylpiperidine-1-oxy radical, sodium bromide, and water in the premix is ​​0.3:3:1000. The volume ratio of the premix to the dextrin solution is 1:1, and the amount of sodium hypochlorite used is 12% of the mass of the linear dextrin.

[0052] In step (3), oxidized dextrin is mixed with the second part of corn starch and water at a mass ratio of 3:10:100. The process conditions for high-pressure microjet are: pressure 120MPa, treatment 3 times. The process conditions for high-pressure pulsed electric field treatment are: electric field strength 60kV / cm, frequency 150Hz, pulse width 40μs, and treatment time 55 minutes.

[0053] In step (3), the specific method for the second oxidation is as follows: the pretreated starch slurry and ozone are introduced into a nanobubble generator, and the ozone nanobubbles are used to achieve the second oxidation. The flow rate of the pretreated starch slurry is 10 L / min, the ozone flow rate is 0.5 L / min, the ozone concentration is 50 mg / L, and the treatment time is 10 minutes.

[0054] Example 3 A method for preparing a flotation agent for magnetohemorrhagic mixed iron ore beneficiation, comprising the following specific steps: (1) First, alkyl tertiary amines and benzyl chloride are reacted to obtain quaternary ammonium salts; (2) Using allyl polyoxyethylene ether and phosphorus pentoxide as raw materials, an allyl polyoxyethylene ether phosphate ester is obtained by reaction. (3) Then the first part of corn starch is hydrolyzed to obtain linear dextrin, and oxidized for the first time to obtain oxidized dextrin; then the oxidized dextrin is mixed with the second part of corn starch and water, and treated with high pressure microjet and high pressure pulse electric field to obtain pretreated starch paste, and then oxidized for the second time through ozone nanobubbles to obtain inhibitor; (4) Finally, mix 8 kg of quaternary ammonium salt, 3 kg of allyl polyoxyethylene ether phosphate, 8 kg of inhibitor and 30 kg of diesel oil evenly to obtain the flotation agent.

[0055] The specific method of step (1) is as follows: mix tetradecylamine with 0.45 times its weight of benzyl chloride, stir at 100°C for 100 minutes, and then cool naturally to room temperature to obtain the product.

[0056] The specific method for step (2) is as follows: Allyl polyoxyethylene ether is heated to 40°C under a nitrogen atmosphere, and phosphorus pentoxide is added while stirring. The temperature is raised to 90°C, and the reaction is carried out at 300 r / min with stirring for 5 hours. The mixture is then naturally cooled to room temperature to obtain the final product. The molar ratio of allyl polyoxyethylene ether to phosphorus pentoxide is 2:1.

[0057] In step (3), the linear dextrin is prepared by the following method: First, the first part of corn starch is stirred and dispersed in water to make a starch milk with a mass concentration of 5%. Then, the starch milk is stirred in a boiling water bath for 1 hour to obtain gelatinized starch milk. The pH of the gelatinized starch milk is adjusted to 6 using 0.01 mol / L acetic acid solution. α-amylase is added and enzymatically hydrolyzed at 60°C for 1 hour. The enzyme is then inactivated. The temperature is adjusted to 60°C, pullulanase is added, and enzymatically hydrolyzed at this temperature for 3 hours. The enzyme is then inactivated. The mixture is centrifuged at 6000 r / min for 20 minutes, and the supernatant is collected, rotary evaporated, and then freeze-dried under vacuum to obtain the final product. The amounts of α-amylase and pullulanase added are 4 U / L and 35 U / L, respectively.

[0058] In step (3), the process conditions for the first oxidation are as follows: linear dextrin is stirred and dispersed in water to prepare a 5% (w / w) dextrin solution, which is then stored at 5°C. Simultaneously, at 5°C, 2,2,6,6-tetramethylpiperidine-1-oxy radical and sodium bromide are dissolved in water to obtain a premix. This premix is ​​then added to the dextrin solution stored at 5°C. The pH is adjusted to 11 using 0.5 mol / L sodium hydroxide solution. Sodium hypochlorite is added, and the mixture is stirred and kept warm for 50 minutes to obtain a reaction solution. Finally, an equal volume of 75% (v / v) ethanol solution is added to the reaction solution, and the mixture is kept warm and allowed to stand for 2 hours. The precipitate is then collected, washed three times with acetone, and dried to obtain the final product. The mass ratio of 2,2,6,6-tetramethylpiperidine-1-oxy radical, sodium bromide, and water in the premix is ​​0.3:2:1000. The volume ratio of the premix to the dextrin solution is 1:1, and the amount of sodium hypochlorite used is 12% of the mass of the linear dextrin.

[0059] In step (3), oxidized dextrin is mixed with the second part of corn starch and water at a mass ratio of 2:10:100. The process conditions for high-pressure microjet are: pressure 100MPa, treatment 3 times. The process conditions for high-pressure pulsed electric field treatment are: electric field strength 50kV / cm, frequency 150Hz, pulse width 30μs, and treatment time 55 minutes.

[0060] In step (3), the specific method for the second oxidation is as follows: the pretreated starch slurry and ozone are introduced into a nanobubble generator, and the ozone nanobubbles are used to achieve the second oxidation. The flow rate of the pretreated starch slurry is 8L / min, the ozone flow rate is 0.5L / min, the ozone concentration is 40mg / L, and the treatment time is 10 minutes.

[0061] Example 4 A method for preparing a flotation agent for magnetohemorrhagic mixed iron ore beneficiation, comprising the following specific steps: (1) First, alkyl tertiary amines and benzyl chloride are reacted to obtain quaternary ammonium salts; (2) Using allyl polyoxyethylene ether and phosphorus pentoxide as raw materials, an allyl polyoxyethylene ether phosphate ester is obtained by reaction. (3) Then the first part of corn starch is hydrolyzed to obtain linear dextrin, and oxidized for the first time to obtain oxidized dextrin; then the oxidized dextrin is mixed with the second part of corn starch and water, and treated with high pressure microjet and high pressure pulse electric field to obtain pretreated starch paste, and then oxidized for the second time through ozone nanobubbles to obtain inhibitor; (4) Finally, mix 9 kg of quaternary ammonium salt, 2.5 kg of allyl polyoxyethylene ether phosphate, 9 kg of inhibitor and 25 kg of diesel oil evenly to obtain the flotation agent.

[0062] The specific method of step (1) is as follows: mix hexadecylamine with 0.5 times its weight of benzyl chloride, stir and react at 95°C for 110 minutes, and then cool naturally to room temperature to obtain the product.

[0063] The specific method for step (2) is as follows: Allyl polyoxyethylene ether is heated to 40°C under a nitrogen atmosphere, and phosphorus pentoxide is added while stirring. The temperature is raised to 85°C, and the reaction is carried out at 400 r / min with stirring for 4 hours. The mixture is then naturally cooled to room temperature. The molar ratio of allyl polyoxyethylene ether to phosphorus pentoxide is 2:1.

[0064] In step (3), the linear dextrin is prepared by the following method: First, the first part of corn starch is stirred and dispersed in water to make a starch milk with a mass concentration of 5%. Then, the starch milk is stirred in a boiling water bath for 1 hour to obtain gelatinized starch milk. The pH of the gelatinized starch milk is adjusted to 6 using 0.02 mol / L acetic acid solution. α-amylase is added and enzymatically hydrolyzed at 55°C for 1.5 hours. The enzyme is then inactivated. The temperature is adjusted to 55°C, pullulanase is added, and enzymatically hydrolyzed at this temperature for 3.5 hours. The enzyme is then inactivated. The mixture is centrifuged at 6000 r / min for 25 minutes, and the supernatant is collected, rotary evaporated, and then freeze-dried under vacuum to obtain the final product. The amounts of α-amylase and pullulanase added are 4 U / L and 40 U / L, respectively.

[0065] In step (3), the process conditions for the first oxidation are as follows: linear dextrin is stirred and dispersed in water to prepare a 5% (w / w) dextrin solution, which is then stored at 5°C. Simultaneously, 2,2,6,6-tetramethylpiperidine-1-oxy radical and sodium bromide are dissolved in water at 5°C to obtain a premix. The premix is ​​then added to the dextrin solution stored at 5°C, and the pH is adjusted to 11 using 0.5 mol / L sodium hydroxide solution. Sodium hypochlorite is then added, and the mixture is stirred at this temperature for 55 minutes to obtain a reaction solution. Finally, an equal volume of 75% (v / v) ethanol solution is added to the reaction solution, and the mixture is kept at this temperature and allowed to stand for 1.5 hours. The precipitate is then collected, washed four times with acetone, and dried to obtain the final product. The mass ratio of 2,2,6,6-tetramethylpiperidine-1-oxy radical, sodium bromide, and water in the premix is ​​0.25:2.5:1000. The volume ratio of the premix to the dextrin solution was 1:1, and the amount of sodium hypochlorite used was 11% of the mass of the linear dextrin.

[0066] In step (3), oxidized dextrin is mixed with the second part of corn starch and water at a mass ratio of 2.5:9:100. The process conditions for high-pressure microjet are: pressure 110MPa, treatment 3 times. The process conditions for high-pressure pulsed electric field treatment are: electric field strength 55kV / cm, frequency 130Hz, pulse width 35μs, treatment time 50 minutes.

[0067] In step (3), the specific method for the second oxidation is as follows: the pretreated starch slurry and ozone are introduced into a nanobubble generator, and the ozone nanobubbles are used to achieve the second oxidation. The flow rate of the pretreated starch slurry is 9 L / min, the ozone flow rate is 0.4 L / min, the ozone concentration is 45 mg / L, and the treatment time is 9 minutes.

[0068] Comparative Example A method for preparing a flotation agent for magnetohemorrhagic mixed iron ore beneficiation, comprising the following specific steps: (1) First, alkyl tertiary amines and benzyl chloride are reacted to obtain quaternary ammonium salts; (2) Using allyl polyoxyethylene ether and phosphorus pentoxide as raw materials, an allyl polyoxyethylene ether phosphate ester is obtained by reaction. (3) Then the first part of corn starch is hydrolyzed to obtain linear dextrin, which is oxidized for the first time to obtain oxidized dextrin, which is used as an inhibitor; (4) Finally, mix 8 kg of quaternary ammonium salt, 2 kg of allyl polyoxyethylene ether phosphate, 8 kg of inhibitor and 20 kg of diesel oil evenly to obtain the flotation agent.

[0069] The specific method of step (1) is as follows: mix tetradecylamine with 0.45 times its weight of benzyl chloride, stir at 90°C for 100 minutes, and then cool naturally to room temperature to obtain the product.

[0070] The specific method for step (2) is as follows: Allyl polyoxyethylene ether is heated to 40°C under a nitrogen atmosphere, and phosphorus pentoxide is added while stirring. The temperature is raised to 80°C, and the reaction is carried out at 300 r / min with stirring for 3 hours. The mixture is then naturally cooled to room temperature to obtain the final product. The molar ratio of allyl polyoxyethylene ether to phosphorus pentoxide is 2:1.

[0071] In step (3), the linear dextrin is prepared by the following method: First, the first part of corn starch is stirred and dispersed in water to make a starch milk with a mass concentration of 5%. Then, the starch milk is stirred in a boiling water bath for 1 hour to obtain gelatinized starch milk. The pH of the gelatinized starch milk is adjusted to 6 using 0.01 mol / L acetic acid solution. α-amylase is added and enzymatically hydrolyzed at 50°C for 1 hour. The enzyme is then inactivated. The temperature is adjusted to 50°C, pullulanase is added, and enzymatically hydrolyzed at this temperature for 3 hours. The enzyme is then inactivated. The mixture is centrifuged at 5000 r / min for 20 minutes, and the supernatant is collected, rotary evaporated, and then freeze-dried under vacuum to obtain the final product. The amounts of α-amylase and pullulanase added are 3 U / L and 35 U / L, respectively.

[0072] In step (3), the process conditions for the first oxidation are as follows: linear dextrin is stirred and dispersed in water to prepare a 5% (w / w) dextrin solution, which is then stored at 5°C. Simultaneously, at 5°C, 2,2,6,6-tetramethylpiperidine-1-oxy radical and sodium bromide are dissolved in water to obtain a premix. This premix is ​​then added to the dextrin solution stored at 5°C. The pH is adjusted to 10 using 0.5 mol / L sodium hydroxide solution. Sodium hypochlorite is added, and the mixture is stirred and kept warm for 50 minutes to obtain a reaction solution. Finally, an equal volume of 75% (v / v) ethanol solution is added to the reaction solution, and the mixture is kept warm and allowed to stand for 1 hour. The precipitate is then collected, washed three times with acetone, and dried to obtain the final product. The mass ratio of 2,2,6,6-tetramethylpiperidine-1-oxy radical, sodium bromide, and water in the premix is ​​0.2:2:1000. The volume ratio of the premix to the dextrin solution is 1:1, and the amount of sodium hypochlorite used is 10% of the mass of the linear dextrin.

[0073] The reverse flotation of magnetohemorrheic mixed iron ore was carried out using the flotation agents obtained in Examples 1-4 and the comparative example, respectively. The specific methods are as follows: S1. First, crush the magnesite mixed iron ore into ore powder with a fineness of -200 mesh, and then use water to prepare a slurry with a mass concentration of 45%. S2. Then, the flotation agents obtained in Examples 1 to 4 or the comparative examples are added to the slurry respectively. The amount of flotation agent is 0.6‰ of the mass of the mineral powder. Reverse flotation is carried out by 1 roughing, 1 cleaning, and 3 scavenging. The reverse flotation tailings are discharged as tailings and the iron concentrate is collected.

[0074] Among them, the magnesite mixed iron ore is mainly composed of magnetite, followed by hematite. The gangue minerals are mainly quartz. The magnetite is fine-grained with a particle size of 0.02 to 0.03 mm, and the hematite is disseminated in the gangue minerals with a particle size between 0.02 and 0.03 mm. The iron grade is 21.8%.

[0075] The iron grade in iron concentrates obtained with different flotation agents was tested, specifically in accordance with GB / T 6730.73-2016 "Determination of Total Iron Content in Iron Ore by EDTA Photometric Titration".

[0076] The recovery rate is calculated using the following formula: Recovery rate = Iron concentrate mass × Iron concentrate grade / (Magnetic hematite mixed iron ore mass × Magnetic hematite mixed iron ore grade) × 100%.

[0077] The mineral processing results are shown in Table 1.

[0078] Table 1. Mineral Processing Results

[0079] As can be seen from Table 1, the iron concentrate obtained by reverse flotation using the flotation agents obtained in Examples 1 to 4 has a high grade and a high recovery rate.

[0080] In the comparative study, oxidized dextrin was used as an inhibitor, resulting in a significant decrease in recovery rate and a marked reduction in iron concentrate grade. This indicates that the inhibitor of the present invention, by mixing oxidized dextrin with corn starch and then subjecting it to high-voltage pulsed electric field treatment and ozone nanobubble oxidation, can adjust the inhibitor composition, improve the inhibitory effect on iron ore, and thus achieve a high recovery rate and high grade of iron concentrate.

[0081] The present invention has been illustrated through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of individual raw materials in the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a flotation agent for magnetohemorrhagic mixed iron ore beneficiation, characterized in that, The specific steps are as follows: (1) First, alkyl tertiary amines and benzyl chloride are reacted to obtain quaternary ammonium salts; (2) Using allyl polyoxyethylene ether and phosphorus pentoxide as raw materials, an allyl polyoxyethylene ether phosphate ester is obtained by reaction. (3) Then the first part of corn starch is hydrolyzed to obtain linear dextrin, and oxidized for the first time to obtain oxidized dextrin; then the oxidized dextrin is mixed with the second part of corn starch and water, and treated with high pressure microjet and high pressure pulse electric field to obtain pretreated starch paste, and then oxidized for the second time through ozone nanobubbles to obtain inhibitor; (4) Finally, the quaternary ammonium salt, allyl polyoxyethylene ether phosphate, inhibitor and diesel oil are mixed evenly to obtain the flotation agent.

2. The preparation method according to claim 1, characterized in that, The specific method of step (1) is as follows: mix the alkyl tertiary amine with 0.45 to 0.55 times its weight of benzyl chloride, stir and react at 90 to 100°C for 100 to 120 minutes, and then cool naturally to room temperature to obtain the product.

3. The preparation method according to claim 1, characterized in that, The specific method of step (2) is as follows: Heat allyl polyoxyethylene ether to 40°C under a nitrogen atmosphere, add phosphorus pentoxide while stirring, raise the temperature to 80-90°C, keep the temperature and stir for 3-5 hours, and then cool naturally to room temperature to obtain the product.

4. The preparation method according to claim 1, characterized in that, In step (2), the molar ratio of allyl polyoxyethylene ether to phosphorus pentoxide is 2:1; the stirring rate is 300-500 r / min.

5. The preparation method according to claim 1, characterized in that, In step (3), the linear dextrin is prepared by the following method: First, the first part of corn starch is stirred and dispersed in water to make a starch milk with a mass concentration of 5%. Then, the starch milk is stirred in a boiling water bath for 1 hour to obtain gelatinized starch milk. The pH of the gelatinized starch milk is adjusted to 6 using 0.01-0.02 mol / L acetic acid solution. α-amylase is added and enzymatically hydrolyzed at 50-60℃ for 1-2 hours to inactivate the enzyme. The temperature is adjusted to 50-60℃, pullulanase is added, and enzymatically hydrolyzed at 50-60℃ for 3-4 hours to inactivate the enzyme. The supernatant is collected by centrifugation, rotary evaporation, and vacuum freeze-drying to obtain the final product.

6. The preparation method according to claim 1, characterized in that, In step (3), the process conditions for the first oxidation are as follows: linear dextrin is stirred and dispersed in water to prepare a dextrin solution with a mass concentration of 5% and stored at 5°C. At the same time, 2,2,6,6-tetramethylpiperidine-1-oxy free radical and sodium bromide are dissolved in water at 5°C to obtain a premix. The premix is ​​then added to the dextrin solution stored at 5°C. The pH is adjusted to 10-11 using 0.5 mol / L sodium hydroxide solution. Sodium hypochlorite is then added, and the mixture is kept warm and stirred for 50-60 minutes to obtain a reaction solution. Finally, 75% ethanol solution is added to the reaction solution, and the mixture is kept warm and allowed to stand for 1-2 hours. The precipitate is then taken, washed, and dried to obtain the final product.

7. The preparation method according to claim 1, characterized in that, In step (3), oxidized dextrin is mixed with corn starch and water in the second part at a mass ratio of 2-3:8-10:

100.

8. The preparation method according to claim 1, characterized in that, In step (3), the process conditions for high-pressure microjet are: pressure 100-120MPa, treatment 2-3 times; The process conditions for high-voltage pulsed electric field treatment are: electric field strength 50-60 kV / cm, frequency 120-150 Hz, pulse width 30-40 μs, and treatment time 45-55 minutes. The specific method for the second oxidation is as follows: pretreated starch slurry and ozone are introduced into a nanobubble generator, and ozone nanobubbles are used to achieve the second oxidation.

9. The preparation method according to claim 1, characterized in that, In step (4), the mass ratio of quaternary ammonium salt, allyl polyoxyethylene ether phosphate, inhibitor, and diesel is 8-10:2-3:8-10:20-30.

10. A flotation agent for beneficiation of magnetohemorrhagic mixed iron ore, characterized in that, It is obtained by the preparation method described in any one of claims 1 to 9.

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