Phosphogypsum flotation collecting agent and preparation method and application thereof

Abstract

The invention discloses an ardealite flotation collecting agent and a preparation method and application thereof.The ardealite flotation collecting agent is a compound with the structure of the following general formula (I): [R-O-CH2-CH (OH)-CH2-NH-(CH2) e-N + (R1) (R2)-(CH2) m-Si (OR3) 3] X-(I). The preparation method of the ardealite flotation collecting agent comprises the steps that alcohol ROH and epichlorohydrin are subjected to a reaction, and an intermediate I is obtained through amination; carrying out Michael addition on the intermediate I and acrylonitrile, and carrying out reduction to obtain an intermediate II; carrying out methylation on the intermediate II by using a formic acid / formaldehyde system to obtain an intermediate III; and reacting the intermediate III with halogenated silane in an organic solvent, and carrying out quaternization to obtain the ardealite flotation collecting agent. The collecting agent is good in selectivity, can remove various impurities at the same time, is suitable for a strong acid environment, integrates various functional groups, and is suitable for ardealite flotation.

Description

Technical Field

[0001] This invention relates to the field of mineral flotation technology, specifically to a phosphogypsum flotation collector, its preparation method, and its application. Background Technology

[0002] Phosphogypsum is a large-scale industrial solid waste generated during the wet-process phosphoric acid production process, producing approximately 4.5-5.5 tons of phosphogypsum for every ton of phosphoric acid produced. Large stockpiles of phosphogypsum not only occupy land, but the soluble phosphorus, fluorine, and heavy metals it contains also pose a potential threat to the environment. Resource utilization of phosphogypsum is the fundamental way to solve its stockpiling problem. However, phosphogypsum contains impurities such as quartz, undecomposed phosphate rock, organic matter, and soluble phosphorus and fluorine, resulting in low purity, poor whiteness, and unstable performance, severely restricting its high-value application in building materials, soil conditioners, and other fields.

[0003] Flotation is one of the most effective methods for purifying phosphogypsum, with reverse flotation (where impurities are removed by flotation and the phosphogypsum remains as a concentrate in the tank) offering significant advantages. The core of reverse flotation is the collector, whose performance directly determines the separation effect. Currently, commonly used collectors mainly include amines (such as dodecylamine) and quaternary ammonium salts (such as hexadecyltrimethylammonium bromide, CTAB) cationic collectors. These collectors primarily collect negatively charged siliceous impurities such as quartz through electrostatic attraction. However, this type of collector has the following significant drawbacks: 1) Limited selectivity: Amine collectors' collecting ability is greatly affected by pH under strongly acidic conditions, and they also have a certain collecting effect on phosphogypsum itself, resulting in a high concentrate loss rate. Although quaternary ammonium salt collectors have good acid resistance, their synergistic removal effect on complex impurities (such as organic matter) is not good.

[0004] 2) Limited functionality: Existing collectors are mainly for silica impurities, and their removal effect on symbiotic organic matter, fluorides and other impurities is limited. They often require the addition of multiple agents, which increases costs and process complexity.

[0005] 3) Foam properties: Some collectors produce foam that is too viscous and stable, which is not conducive to subsequent defoaming and process control.

[0006] 4) Lengthy Flotation Process: A single reverse flotation process suffers from bottlenecks such as lengthy processes and limited efficiency. Practical experience has shown that reverse flotation alone cannot meet the dual requirements of silica removal and phosphogypsum grade improvement. Therefore, it is necessary to introduce a coupled operation of forward and reverse flotation processes. Through the synergistic effect of multiple stages of forward and reverse flotation, the silica content in phosphogypsum can be further reduced, and the grade of the phosphogypsum product can be improved simultaneously. While this coupled operation can optimize flotation parameters, it inevitably increases costs such as equipment investment and reagent consumption, creating a contradiction between product quality improvement and economic benefits.

[0007] Therefore, to achieve a breakthrough, it is necessary to develop a collector with a more profound mechanism of action and stronger binding force. Summary of the Invention

[0008] The purpose of this invention is to solve the above-mentioned technical problems and provide a phosphogypsum flotation collector that has good selectivity, can remove multiple impurities at the same time, is suitable for strongly acidic environments, and integrates multiple functional groups.

[0009] The present invention also provides a method for preparing the above-mentioned phosphogypsum flotation collector, which is simple in process, low in cost and short in cycle.

[0010] The present invention also provides an application of the above-mentioned phosphogypsum flotation collector.

[0011] The collector of the present invention is a compound having the following general formula (I): [RO-CH2-CH(OH)-CH2-NH-(CH2) e -N + (R 1 (R) 2 )-(CH2) m -Si(OR 3 )3] X - (I) In the formula, R is a C8-C22 straight-chain or branched alkyl or alkenyl group; R 1 R 2 Each is an alkyl group that is independently C1-C4; R 3 It can be methyl, ethyl, or propyl; e and m are each an independent integer of 2, 3 or 4; X - It consists of chloride ions, bromide ions, or iodide ions.

[0012] The preparation method of the phosphogypsum flotation collector includes the following steps: (1) React alcohol ROH with epichlorohydrin and then amination to obtain intermediate I: RO-CH2-CH(OH)-CH2-NH2; (2) Intermediate I undergoes Michael addition with acrylonitrile, followed by reduction to obtain intermediate II: RO-CH2-CH(OH)-CH2-NH-(CH2) e -NH2; (3) Methylation of intermediate II using a formic acid / formaldehyde system to obtain intermediate III: RO-CH2-CH(OH)-CH2-NH-(CH2) e -N(CH3)2; (4) React intermediate III with halosilane X-(CH2) m -Si(OR 3 )3 is reacted in an organic solvent and quaternized to obtain the phosphogypsum flotation collector as described in claim 1 or 2.

[0013] In step (1), the molar ratio of alcohol ROH to epichlorohydrin is 1:1.1-1.5. In the presence of an alkaline catalyst, the reaction is carried out at 50-80℃ for 2-6 hours to obtain the etherified product RO-CH2-CH(OH)-CH2Cl. Then, it undergoes an amination reaction with ammonia or liquid ammonia, with a molar ratio of ammonia to the etherified product of 3-10:1. The reaction is carried out in an autoclave at 80-120℃ for 4-12 hours, or at atmospheric pressure using ammonia (mass fraction 25-28%) at 60-80℃ for 6-15 hours to obtain intermediate I: RO-CH2-CH(OH)-CH2-NH2. The alkaline catalyst is sodium hydroxide, potassium hydroxide, or potassium tert-butoxide, and the amount used is 0.5-2% of the molar amount of alcohol ROH.

[0014] Among them, the preferred alcohol ROH is dodecanol (C 12 H 25 OH), n-octanol (C8H) 17 OH), stearyl alcohol (C 18 H 37 OH), isohexadecanol (branched C) 16 H 33 OH) or oleyl alcohol (C 18 H 35 OH (containing a double bond).

[0015] In step (2), the molar ratio of intermediate I to acrylonitrile is 1:1.05-1.3. The reaction is carried out in methanol, ethanol or isopropanol solvent at room temperature to 60°C for 8-24 hours to complete Michael addition and obtain nitrile intermediate RO-CH2-CH(OH)-CH2-NH-(CH2)2-CN. Then, catalytic hydrogenation reduction is carried out using Raney nickel or Pd / C as catalyst, with the catalyst amount being 3-8% of the mass of nitrile intermediate. The reaction is carried out at a hydrogen pressure of 2-5 MPa and a temperature of 50-100°C for 3-8 hours. Alternatively, a sodium borohydride-cobalt chloride system is used for reduction, with the molar ratio of sodium borohydride to nitrile intermediate being 2-4:1 and the amount of cobalt chloride being 5-10% of the molar mass of nitrile intermediate. The reaction is carried out in methanol solvent at 0-25°C for 4-10 hours to obtain intermediate II: RO-CH2-CH(OH)-CH2-NH-(CH2)3-NH2.

[0016] In step (3), the molar ratio of intermediate II, formic acid (mass fraction 85-90%), and formaldehyde solution (mass fraction 37-40%) is 1:2.5-4:2.5-4. The reaction is carried out under reflux at 60-90℃ for 4-12 hours in a water bath to complete the Eschweiler-Clarke methylation reaction. During the reaction, only the terminal primary amine group is dimethylated, while the secondary amine group remains unchanged. After the reaction, sodium hydroxide solution is added to adjust the pH to 10-12, and the mixture is extracted with an organic solvent such as dichloromethane or ethyl acetate. The extract is dried and concentrated with anhydrous sodium sulfate or anhydrous magnesium sulfate to obtain intermediate III: RO-CH2-CH(OH)-CH2-NH-(CH2)3-N(CH3)2. The extraction is performed 2-3 times, and the volume of organic solvent used each time is 0.3-0.5 times the volume of the reaction liquid.

[0017] In step (4), intermediate III reacts with the halosilane X-(CH2). m -Si(OR 3 The molar ratio of intermediate III to intermediate III is 1:1.05-1.2. The quaternization reaction is carried out in organic solvents such as acetonitrile, toluene, isopropanol, or N,N-dimethylformamide, with the solvent amount being 2-5 times the mass of intermediate III. The reaction temperature is 60-100℃, and the reaction time is 8-24 hours. The reaction is carried out in a closed container under nitrogen protection, with potassium iodide or sodium iodide added as a catalyst, at a amount of 1-5% of the molar mass of intermediate III. After the reaction, the mixture is cooled to room temperature, the insoluble matter is removed by filtration, and the solvent is removed by vacuum distillation to obtain the target product: [RO-CH2-CH(OH)-CH2-NH-(CH2)3-N + (CH3)2-(CH2) m -Si(OR 3 )3] X - The product can be purified by recrystallization with ethyl acetate / ethanol mixed solvent or acetone, and after drying, a phosphogypsum flotation collector with a purity ≥95% is obtained.

[0018] The above-mentioned collectors are used as collectors in the reverse flotation of phosphogypsum.

[0019] The collector is added to the phosphogypsum slurry at a rate of 50-600 g / ton of dry phosphogypsum.

[0020] The collector is prepared as a 0.01%-0.1wt% alcohol solution and then added to the phosphogypsum slurry.

[0021] Beneficial effects: 1) The collector of this application creatively integrates long-chain hydrophobic groups, coordinating amine groups, quaternary ammonium salt cations, and covalently anchored silyl groups into one unit. The silyl groups, after hydrolysis, form Si-O-Si covalent bonds with the quartz surface, exhibiting extremely strong binding force and providing unparalleled selectivity and stability. The secondary and tertiary amine groups in the molecule are excellent electron donors, capable of forming coordination bonds or hydrogen bonds with metal ions (such as Fe, Al) on the impurity surface or with polar groups in organic matter. The quaternary ammonium salt cations generate strong electrostatic attraction with the negatively charged quartz surface under acidic conditions. The long-chain alkoxy groups provide excellent hydrophobic properties. This multi-synergistic mechanism of "covalent anchoring + coordination chelation + electrostatic adsorption" enables highly efficient and selective removal of siliceous and organic impurities from phosphogypsum, significantly improving the whiteness and purity of phosphogypsum concentrate, and is suitable for phosphogypsum from different sources with varying impurity compositions.

[0022] 2) The formation of covalent bonds has extremely high substrate specificity, mainly targeting silicon-containing impurities, which greatly reduces the loss of phosphogypsum bulk and simultaneously increases concentrate yield and purity significantly; due to the strong interaction, the amount of reagent used is much lower than that of traditional collectors, making it economically significant.

[0023] 3) The collector of this invention has good flotation effect, high efficiency and wide adaptability. When applied to a single reverse flotation process, it can also effectively reduce the number of flotation stages and the number of equipment sets, and can meet the dual requirements of silica removal and phosphogypsum grade improvement.

[0024] 4) The collector preparation method of this invention is simple, easy to operate, and has mild reaction conditions. When used in the reverse flotation process of phosphogypsum, it has the advantages of high impurity removal efficiency, good effect, low dosage, low cost, and good adaptability. Detailed Implementation

[0025] The preparation method of the phosphogypsum flotation collector is as follows: Step (1): The molar ratio of alcohol ROH to epichlorohydrin is 1:1.1-1.5. The reaction is carried out at 50-80℃ for 2-6 hours in the presence of an alkaline catalyst to obtain the etherified product RO-CH2-CH(OH)-CH2Cl. Then, an amination reaction is carried out with ammonia or liquid ammonia. The molar ratio of ammonia to the etherified product is 3-10:1. The reaction is carried out in an autoclave at 80-120℃ for 4-12 hours, or at atmospheric pressure with ammonia (mass fraction 25-28%) at 60-80℃ for 6-15 hours to obtain intermediate I: RO-CH2-CH(OH)-CH2-NH2. The alkaline catalyst is sodium hydroxide, potassium hydroxide or potassium tert-butoxide, and the amount used is 0.5-2% of the molar amount of alcohol ROH.

[0026] Step (2): Intermediate I is reacted with acrylonitrile at a molar ratio of 1:1.05-1.3 in methanol, ethanol or isopropanol solvent at room temperature to 60°C for 8-24 hours to complete Michael addition and obtain nitrile intermediate RO-CH2-CH(OH)-CH2-NH-(CH2)2-CN. Then, catalytic hydrogenation reduction is performed using Raney nickel or Pd / C as catalyst, with the catalyst amount being 3-8% of the mass of the nitrile intermediate. The reaction is carried out at a hydrogen pressure of 2-5 MPa and a temperature of 50-100°C for 3-8 hours. Alternatively, a sodium borohydride-cobalt chloride system is used for reduction, with a molar ratio of sodium borohydride to nitrile intermediate of 2-4:1 and the amount of cobalt chloride being 5-10% of the molar mass of the nitrile intermediate. The reaction is carried out in methanol solvent at 0-25°C for 4-10 hours to obtain intermediate II: RO-CH2-CH(OH)-CH2-NH-(CH2)3-NH2.

[0027] Step (3): The molar ratio of intermediate II, formic acid (mass fraction 85-90%), and formaldehyde solution (mass fraction 37-40%) is 1:2.5-4:2.5-4. The reaction is carried out under reflux at 60-90℃ for 4-12 hours in a water bath to complete the Eschweiler-Clarke methylation reaction. During the reaction, only the terminal primary amine group is dimethylated, while the secondary amine group remains unchanged. After the reaction, sodium hydroxide solution is added to adjust the pH to 10-12. The mixture is extracted with an organic solvent such as dichloromethane or ethyl acetate. The extract is dried and concentrated with anhydrous sodium sulfate or anhydrous magnesium sulfate to obtain intermediate III: RO-CH2-CH(OH)-CH2-NH-(CH2)3-N(CH3)2. The extraction is performed 2-3 times, and the volume of organic solvent used each time is 0.3-0.5 times the volume of the reaction liquid.

[0028] Step (4), intermediate III reacts with halosilane X-(CH2) m -Si(OR 3 The molar ratio of intermediate III to intermediate III is 1:1.05-1.2. The quaternization reaction is carried out in organic solvents such as acetonitrile, toluene, isopropanol, or N,N-dimethylformamide, with the solvent volume being 2-5 times the mass of intermediate III. The reaction temperature is 60-100℃, and the reaction time is 8-24 hours. The reaction is carried out in a closed container under nitrogen protection. If necessary, a small amount of potassium iodide or sodium iodide can be added as a catalyst, with the amount being 1-5% of the molar mass of intermediate III. After the reaction is completed, the mixture is cooled to room temperature, the insoluble matter is removed by filtration, and the solvent is removed by vacuum distillation to obtain the target product: [RO-CH2-CH(OH)-CH2-NH-(CH2)3-N + (CH3)2-(CH2) m -Si(OR 3 )3] X -The product can be purified by recrystallization with ethyl acetate / ethanol mixed solvent or acetone, and after drying, a phosphogypsum flotation collector with a purity ≥95% is obtained.

[0029] The specific embodiments and comparative parameters using the above process are as follows. All raw materials and additives in the following embodiments are commercially available: Example 1: Target product: [C] 12 H 25 -O-CH2-CH(OH)-CH2-NH-(CH2)3-N + [(CH3)2-(CH2)3-Si(OCH3)3] Cl - Step (1): Raw material: dodecanol (C 12 H 25 OH) 186g, epichlorohydrin 120g Catalyst: 1.0g sodium hydroxide Reaction conditions: Reaction at 65℃ for 4 hours to obtain RO-CH2-CH(OH)-CH2Cl Amination: 500 mL ammonia solution, react at 70 °C for 10 h. Product: Intermediate I 210g, yield 85% Step (2): Raw materials: Intermediate I 247g, Acrylonitrile 58g Solvent: 300 mL ethanol Reaction conditions: Reaction at 40℃ for 16 h to obtain a nitrile intermediate. Reduction: 15g Raney nickel, hydrogen pressure 3.5 MPa, reaction at 75℃ for 5h. Product: Intermediate II 260g, yield 80% Step (3): Raw materials: Intermediate II 325g, formic acid 156g, formaldehyde solution 237g Reaction conditions: reflux at 75℃ for 8 hours Post-treatment: Adjust pH to 11 with sodium hydroxide solution, extract three times with 200 mL of dichloromethane each time. Product: Intermediate III 305g, yield 86% Step (4): Raw materials: Intermediate III 355g, Chloropropyltrimethoxysilane (Cl-(CH2)3-Si(OCH3)3) 198g Solvent: Acetonitrile 600mL Catalyst: Potassium iodide 3.3g Reaction conditions: 80℃, nitrogen protection, 16h Post-processing: cooling, filtration, solvent removal by vacuum distillation, and recrystallization from acetone. Product: 425g of target collector, yield 78%, purity 97%. Example 2: Target product: [C8H] 17 -O-CH2-CH(OH)-CH2-NH-(CH2)2-N + (C2H5)(CH3)-(CH2)2-Si(OC2H5)3]Br - Step (1): Raw material: n-Octanol (C8H) 17 130g of OH, 102g of epichlorohydrin Catalyst: 0.56g potassium hydroxide Reaction conditions: 50℃ for 6 hours Amination: Liquid ammonia gas is introduced, the molar ratio of ammonia to etherification product is 3:1, and the reaction is carried out in an autoclave at 120°C for 4 hours. Product: Intermediate I 145g, yield 75% Step (2): Raw materials: Intermediate I 189g, Acrylonitrile 55.6g Solvent: 250 mL methanol Reaction conditions: Reaction at room temperature for 24 hours Reduction: 76g sodium borohydride, 11.9g cobalt chloride·6H2O, reacted in methanol at 0℃ for 10h. Product: Intermediate II 155g, yield 70% Step (3): Raw materials: Intermediate II 217g, formic acid 134g, formaldehyde solution 203g Reaction conditions: reflux at 60℃ for 12 hours Post-treatment: Adjust pH to 10 with sodium hydroxide solution, extract twice with 150 mL of ethyl acetate each time. Product: Intermediate III 195g, yield 80% Step (4): Raw materials: Intermediate III 245g, bromoethyltriethoxysilane (Br-(CH2)2-Si(OC2H5)3) 285g Solvent: 500 mL toluene Catalyst: Sodium iodide 1.5g Reaction conditions: 60℃ for 24 hours Post-processing: cooling, filtration, concentration under reduced pressure, recrystallization from ethyl acetate / ethanol (1:1) Product: 380g of target collector, yield 75%, purity 95%. Example 3 Target product: [C 18 H 37 -O-CH2-CH(OH)-CH2-NH-(CH2)4-N + [(C4H9)2-(CH2)4-Si(OC3H7)3] I - Step (1): Raw material: Octadecyl alcohol (C 18 H 37 OH) 270g, epichlorohydrin 139g Catalyst: Potassium tert-butoxide 2.24g Reaction conditions: 80℃ for 2 hours Amination: 1200 mL ammonia solution, reacted at 80°C under normal pressure for 6 hours. Product: Intermediate I 295g, yield 90% Step (2): Raw materials: Intermediate I 331g, Acrylonitrile 69g Solvent: 400 mL isopropanol Reaction conditions: 60℃ for 8 hours Reduction: 25g Pd / C catalyst, 5 MPa hydrogen pressure, 100℃ reaction for 3h Product: Intermediate II 320g, yield 85% Step (3): Raw materials: Intermediate II 389g, formic acid 201g, formaldehyde solution 300g Reaction conditions: reflux at 90℃ for 4 hours Post-treatment: Adjust pH to 12 with sodium hydroxide solution, extract three times with 250 mL of dichloromethane each time. Product: Intermediate III 380g, yield 92% Step (4): Raw materials: Intermediate III 417g, iodobutyltripropoxysilane (I-(CH2)4-Si(OC3H7)3) 465g Solvent: 2000 mL N,N-dimethylformamide Catalyst: Potassium iodide 8.3g Reaction conditions: 100℃, nitrogen protection, 8h Post-processing: cooling, filtration, vacuum distillation, and recrystallization twice with acetone. Product: 680g of target collector, yield 88%, purity 98%. Example 4 Target product: [C 14 H 29-O-CH2-CH(OH)-CH2-NH-(CH2)3-N + (CH3)(C3H7)-(CH2)3-Si(OCH3)3] Cl - Step (1): Raw material: Tetradecyl alcohol (C 14 H 29 OH) 214g, epichlorohydrin 130g Catalyst: 1.6g sodium hydroxide Reaction conditions: 70℃ for 3 hours Amination: 800 mL ammonia solution, react at 65°C under normal pressure for 12 h. Product: Intermediate I 240g, yield 87% Step (2): Raw materials: Intermediate I 275g, Acrylonitrile 63.6g Solvent: 350 mL ethanol Reaction conditions: 50℃ for 12 hours Reduction: 18g Raney nickel, hydrogen pressure 4 MPa, reaction at 80℃ for 4h Product: Intermediate II 275g, yield 82% Step (3): Raw materials: Intermediate II 353g, formic acid 175g, formaldehyde solution 261g Reaction conditions: reflux at 80℃ for 6 hours Post-treatment: Adjust pH to 11 with sodium hydroxide solution, extract three times with 180 mL of dichloromethane each time. Product: Intermediate III 330g, yield 88% Step (4): Raw materials: Intermediate III 381g, chloropropyltrimethoxysilane 210g Solvent: Acetonitrile 800mL Catalyst: Potassium iodide 5.0g Reaction conditions: 85℃, nitrogen protection, 14h Post-processing: cooling, filtration, vacuum concentration, and acetone recrystallization. Product: 460g of target collector, yield 80%, purity 96%. Example 5 Target product: [oleyl-O-CH2-CH(OH)-CH2-NH-(CH2)3-N] + (C2H5)2-(CH2)3-Si(OC2H5)3]Br - Step (1): Raw material: oleyl alcohol (C18 H 35 OH (containing one double bond) 268g, epichlorohydrin 125g Catalyst: 1.12g potassium hydroxide Reaction conditions: 60℃ for 5 hours Amination: 700 mL ammonia solution, reaction at 75°C under normal pressure for 8 hours. Product: Intermediate I 290g, yield 88% Step (2): Raw materials: Intermediate I 329g, Acrylonitrile 60g Solvent: 320 mL ethanol Reaction conditions: 45℃ for 18 hours Reduction: 20g Pd / C catalyst, 3 MPa hydrogen pressure, 60℃ reaction for 6h Product: Intermediate II 310g, yield 78% Step (3): Raw materials: Intermediate II 387g, formic acid 167g, formaldehyde solution 250g Reaction conditions: reflux at 75°C for 7 hours Post-treatment: Adjust pH to 11 with sodium hydroxide solution, extract three times with 200 mL of ethyl acetate each time. Product: Intermediate III 360g, yield 87% Step (4): Raw materials: Intermediate III 415g, Bromopropyltriethoxysilane (Br-(CH2)3-Si(OC2H5)3) 340g Solvent: 1200 mL isopropanol Catalyst: Sodium iodide 2.5g Reaction conditions: 75℃, nitrogen protection, 18h Post-processing: cooling, filtration, concentration under reduced pressure, recrystallization from ethyl acetate / ethanol (2:1) Product: 560g of target collector, yield 77%, purity 96%. Example 6 Target product: [isohexadecyl-O-CH2-CH(OH)-CH2-NH-(CH2)2-N] + (CH3)(C4H9)-(CH2)4-Si(OCH3)3] I - Step (1): Raw material: Isohexadecyl alcohol (branched C) 16 H 33 OH) 242g, epichlorohydrin 111g Catalyst: 1.2g sodium hydroxide Reaction conditions: 68℃ for 4.5 h Amination: Liquid ammonia gas is introduced, and the reaction is carried out in an autoclave at 100°C for 8 hours. Product: Intermediate I 265g, yield 86% Step (2): Raw materials: Intermediate I 303g, Acrylonitrile 59g Solvent: 300 mL methanol Reaction conditions: 35℃ for 20 hours Reduction: 114 g sodium borohydride, 17.8 g cobalt chloride·6H₂O, reacted in methanol at 15 °C for 7 h. Product: Intermediate II 280g, yield 76% Step (3): Raw materials: Intermediate II 361g, formic acid (86%) 189g, formaldehyde solution (38%) 284g Reaction conditions: reflux at 82℃ for 5 hours Post-treatment: Adjust pH to 11.5 with sodium hydroxide solution, and extract three times with 200 mL of dichloromethane each time. Product: Intermediate III 340g, yield 89% Step (4): Raw materials: Intermediate III 389g, iodobutyltrimethoxysilane (I-(CH2)4-Si(OCH3)3) 365g Solvent: 1500 mL acetonitrile Catalyst: Potassium iodide 6.6g Reaction conditions: 90℃, nitrogen protection, 12h Post-processing: cooling, filtration, vacuum distillation, and recrystallization from acetone. Product: 580g of target collector, yield 81%, purity 97%. Comparative Example 1: Comparative Example 1 (with silane groups removed) Except for the halosilane X-(CH2) in step (4) m -Si(OR 3 )3 is changed to a haloalkane X-(CH2). m Except for CH3 (chloropropane), everything else is the same as in Example 1.

[0030] Product obtained: [C] 12 H 25 -O-CH2-CH(OH)-CH2-NH-(CH2)3-N + [(CH3)2-(CH2)3-CH3] Cl - Yield: 82%, Purity: 96% Comparative Example 2 (Removal of Quaternary Ammonium Salt Cationic Groups) Except for changing the methylation reaction of the formic acid / formaldehyde system in step (3) to not perform methylation and directly using intermediate II for subsequent reactions; changing the halosilane in step (4) to epoxypropoxypropyltrimethoxysilane (CH2(O)CH-CH2-O-(CH2)3-Si(OCH3)3), and changing the reaction conditions to intermediate II reacting with epoxypropoxypropyltrimethoxysilane in ethanol at 60°C for 12 h, the rest is the same as in Example 1.

[0031] Product obtained: C 12 H 25 -O-CH2-CH(OH)-CH2-NH-(CH2)3-NH-(CH2)3-O-CH2-CH(OH)-CH2-O-(CH2)3-Si(OCH3)3 (Nonionic type) Yield: 68%, Purity: 94% Comparative Example 3 (without coordinating amine groups) Except that in step (2) Michael addition and reduction reactions are not performed, intermediate I: RO-CH2-CH(OH)-CH2-NH2 is used directly; in step (3) intermediate I is methylated to obtain RO-CH2-CH(OH)-CH2-N(CH3)2; and in step (4) the methylated product is used to react with a halosilane, the rest is the same as in Example 1.

[0032] Specific operations: Step (3): Reflux 247g of intermediate I with 156g of formic acid and 237g of formaldehyde solution at 75℃ for 8h. Step (4): 275g of the methylated product and 198g of chloropropyltrimethoxysilane were reacted in acetonitrile at 80°C for 16h. Product obtained: [C] 12 H 25 -O-CH2-CH(OH)-CH2-N + [(CH3)2-(CH2)3-Si(OCH3)3] Cl - Yield: 70%, Purity: 95% Comparative Example 4 (removal of long-chain hydrophobic groups) Except for dodecanol (C) in step (1) 12 H 25 Except for replacing OH with 32g of methanol (CH3OH), everything else is the same as in Example 1.

[0033] The product obtained is: [CH3-O-CH2-CH(OH)-CH2-NH-(CH2)3-N] +[(CH3)2-(CH2)3-Si(OCH3)3] Cl - Yield: 75%, Purity: 96% Comparative Example 5 (simultaneous removal of silane and quaternary ammonium salt groups) Except that step (3) does not involve methylation and intermediate II is used directly; the halosilane in step (4) is replaced with n-butyraldehyde (C3H7CHO), and butyl is introduced through a reduction amination reaction; the reaction conditions are changed to a molar ratio of intermediate II to n-butyraldehyde of 1:1.2, and sodium borohydride (molar ratio 2:1) is added to methanol and reacted at 25°C for 8 hours, the rest is the same as in Example 1.

[0034] Product obtained: C 12 H 25 -O-CH2-CH(OH)-CH2-NH-(CH2)3-NH-C4H9 (nonionic, nonsilane type) Yield: 65%, Purity: 93% Comparative Example 6 (short-chain hydrophobic group + lack of coordinating amine group) Except for replacing dodecanol in step (1) with hexanol (C6H) 13 OH) 102g; Step (2) does not involve Michael addition reaction, but uses intermediate I directly for subsequent steps, otherwise it is the same as in Example 3.

[0035] Specific operations: Step (3): 189g of intermediate I (hexanol derivative) was refluxed with 201g of formic acid and 300g of formaldehyde solution at 90℃ for 4h. Step (4): 217g of the methylated product was reacted with 465g of iodobutyltripropoxysilane in DMF at 100℃ for 8h. Product obtained: [C6H] 13 -O-CH2-CH(OH)-CH2-N + [(CH3)2-(CH2)4-Si(OC3H7)3] I - Yield: 72%, Purity: 95% Comparative Example 7 (reaction temperature below the lower limit) Except for reducing the reaction temperature from 50°C to 30°C in step (1) and extending the reaction time to 10h; and reducing the reaction temperature from 60°C to 40°C and extending the reaction time to 36h in step (4), the rest is the same as in Example 2.

[0036] Product obtained: [C8H] 17 -O-CH2-CH(OH)-CH2-NH-(CH2)2-N +(C2H5)(CH3)-(CH2)2-Si(OC2H5)3]Br - Yield: The yield in step (1) decreased to 62%, and the yield in step (4) decreased to 58%, with an overall yield of approximately 45% and a purity of 92%. Comparative Example 8 (reaction temperature exceeded the upper limit) Except for increasing the reaction temperature from 80°C to 110°C and shortening the reaction time to 1 hour in step (1), and increasing the reaction temperature from 100°C to 130°C and shortening the reaction time to 4 hours in step (4), the rest is the same as in Example 3.

[0037] Product obtained: [C] 18 H 37 -O-CH2-CH(OH)-CH2-NH-(CH2)4-N + [(C4H9)2-(CH2)4-Si(OC3H7)3] I - Yield: Significant side reactions occurred in step (1), reducing the yield to 72%; decomposition and polymerization occurred in step (4), reducing the yield to 60%, with an overall yield of approximately 50% and a purity of 89%. Comparative Example 9 (raw material molar ratio exceeds the lower limit) Except for reducing the molar ratio of epichlorohydrin to alcohol in step (1) from 1.1:1 to 0.9:1 and the molar ratio of halosilane to intermediate III in step (4) from 1.05:1 to 0.85:1, the rest is the same as in Example 1.

[0038] Product obtained: [C] 12 H 25 -O-CH2-CH(OH)-CH2-NH-(CH2)3-N + [(CH3)2-(CH2)3-Si(OCH3)3] Cl - Yield: In step (1), a large amount of raw alcohol did not react, resulting in a yield of 68%; in step (4), the quaternization was incomplete, resulting in a yield of 61%, with a total yield of approximately 35% and a purity of 90% (including unreacted intermediates). Comparative Example 10 (Raw material quality ratio exceeds the upper limit) Except for increasing the molar ratio of acrylonitrile to intermediate I in step (2) from 1.3:1 to 1.8:1 and the molar ratio of formic acid to formaldehyde in step (3) from 4:1 to 6:1, the rest is the same as in Example 3.

[0039] Product obtained: [C] 18 H 37 -O-CH2-CH(OH)-CH2-NH-(CH2)4-N +[(C4H9)2-(CH2)4-Si(OC3H7)3] I - Yield: In step (2), a biaddition byproduct appeared, reducing the yield of the target product to 70%; in step (3), hypermethylation and formylation byproducts appeared, reducing the yield to 75%, with an overall yield of approximately 58% and a purity of 88%. Comparative Example 11 (using non-halogenated silanes) Except for changing chloropropyltrimethoxysilane in step (4) to 3-aminopropyltrimethoxysilane (H2N-(CH2)3-Si(OCH3)3), changing the reaction conditions to a molar ratio of intermediate III to aminopropylsilane of 1:1.1, adding triethylamine to ethanol as an acid-binding agent, and reacting at room temperature for 24 hours, everything else is the same as in Example 1.

[0040] Product obtained: C 12 H 25 -O-CH2-CH(OH)-CH2-NH-(CH2)3-N(CH3)2 (Failed to achieve quaternization) Yield: Quaternization reaction hardly occurs, yielding only a physical mixture. Comparative Example 12 (removal of hydroxyl protection) Except for adding a hydroxyl protection step after the amination reaction in step (1): acetylation of the hydroxyl group with acetic anhydride at a molar ratio of 1:1.2, and reaction in pyridine at room temperature for 6 hours; subsequent steps using acetylation intermediates; and finally deprotection of the product by hydrolysis in a sodium hydroxide methanol solution (0.1M) at room temperature for 2 hours, the rest is the same as in Example 4.

[0041] Product obtained: [C] 14 H 29 -O-CH2-CH(OH)-CH2-NH-(CH2)3-N + (CH3)(C3H7)-(CH2)3-Si(OCH3)3] Cl - Overall yield: approximately 55% (due to the added protection / deprotection steps), purity 96%. Comparative Example 13 (using excess catalyst) Except for increasing the amount of alkaline catalyst in step (1) from 1% to 5% of the molar amount of alcohol and increasing the amount of potassium iodide in step (4) from 2% to 15%, the rest is the same as in Example 1.

[0042] Product obtained: [C] 12 H 25 -O-CH2-CH(OH)-CH2-NH-(CH2)3-N + [(CH3)2-(CH2)3-Si(OCH3)3] Cl - Yield: In step (1), ether bond cleavage and epichlorohydrin self-polymerization side reactions occurred, reducing the yield to 70%; in step (4), the reaction rate was too fast, leading to silane self-condensation, reducing the yield to 65%, with a total yield of approximately 52% and a purity of 90%. Reverse flotation experiment: 1. Slurry concentration 30%, pH=2.0 (membrane treatment concentrate adjustment).

[0043] 2. Add the collectors prepared in the examples and comparative examples respectively, at a dosage of 150 g / t dry phosphogypsum, and prepare a 0.05 wt% alcohol solution with methanol before use.

[0044] 3. Stir at 2000 rpm for 5 minutes.

[0045] 4. Flotation for 6 minutes, then manually skim off the bubbles.

[0046] 5. A disc vacuum filter is used to perform efficient solid-liquid separation of concentrate and tailings. The resulting filter cake is placed in a constant temperature drying environment at 45℃ to remove moisture and then transferred to a cool, dry place for proper storage.

[0047] Test conditions: Raw material source: Phosphogypsum from certain phosphate chemical enterprises in Xiangyang, Jingmen, Yichang and other places in Hubei Province. Raw material characteristics: whiteness 25-30%, SiO2 content 5-10wt%, P2O5 content 1.0-1.6wt%, pH 2-5 Test methods: Whiteness was determined according to GB / T 5950, and chemical composition was analyzed using XRF. The results are as follows: Table 1 Comparison of flotation performance of reagents in the examples Table 2 Comparison of flotation performance of comparative reagents Table 3 Comparison of characteristics of phosphogypsum from different raw material origins Table 4: Performance Comparison of Xiangyang Phosphogypsum Examples and Comparative Examples Note: Selectivity index = grade × whiteness / yield Table 5: Performance Comparison of Example and Comparative Examples of Phosphogypsum from a Phosphate Chemical Company in Jingmen Table 6: Performance Comparison of Example and Comparative Examples of Phosphogypsum from a Phosphochemical Company in Yichang Table 7: Average Performance Comparison of Examples and Comparative Examples (by Country of Origin) Table 8: Effects of each component on flotation performance (phosphogypsum from a phosphate chemical company in Xiangyang) Table 9: Effect of carbon chain length on flotation performance (Xiangyang phosphogypsum) Table 10: Effects of process parameters on flotation performance (Xiangyang phosphogypsum) Based on the above system implementation examples and comparative study results, it can be concluded that: 1. Comparison with other products from the same country of origin shows that the example is significantly superior to the comparative example: Xiangyang phosphogypsum: The average whiteness of the examples was 67.5%, and that of the comparative examples was 50.1% (34.7% higher); Jingmen phosphogypsum: The average whiteness of the examples was 68.6%, and that of the comparative examples was 52.7% (30.2% higher); Yichang phosphogypsum: The whiteness of the examples was 65.7%, and that of the comparative examples was 59.7% (10.1% higher).

[0048] 2. The balance between yield and selectivity: The example yield was low (82.9-86.3%), but the selectivity was high and the concentrate quality was excellent; the comparative yield was falsely high (86.8-92.1%), and a large number of impurities floated to the surface due to poor selectivity; collectors with intact structures can selectively adsorb phosphogypsum, while collectors with structural defects float to the surface indiscriminately.

[0049] 3. Structural integrity is crucial (data from Xiangyang phosphogypsum): Removal of hydrophobic chains (Comparative Example 4): lowest whiteness 45.2%, highest yield 94.8%, SiO2 as high as 4.23%, completely losing selectivity; Removal of quaternary ammonium salt (Comparative Example 2): whiteness 47.6%, yield 93.2%, SiO2 3.42%, with a large amount of impurities; Removal of silane (Comparative Example 1): whiteness 52.3%, yield 91.5%, SiO2 2.18%, lacking chemical bonding ability; Removal of coordinated amine (Comparative Example 3): whiteness 54.2%, yield 89.8%, SiO2 1.85%, with excessively short chain segments. Complete structure (Example 3): whiteness 71.2%, yield 86.3%, SiO2 only 0.16%, achieving optimal balance.

[0050] 4. Carbon chain length has a significant impact (Xiangyang phosphogypsum): C 18 Long chain: Whiteness 71.2%, grade 96.8%, selectivity index 82.4 (optimal) C 12 Medium chain residue: Whiteness 68.5%, Grade 94.2%, Selectivity Index 76.6 C8 short chain: whiteness 62.8%, grade 89.8%, insufficient hydrophobicity. C6 ultrashort chain: whiteness 48.8%, yield falsely inflated at 92.7%, loss of selectivity. 5. Adaptability of raw material origin: Yichang phosphogypsum (pH 4.1, SiO2 5.3%): The raw material quality is relatively good, and the difference between the examples and the comparative examples is relatively small; Xiangyang phosphogypsum (pH 3.2, SiO2 6.8%): The performance is moderate, and the difference between the examples and the comparative examples is the most obvious; Jingmen phosphogypsum (pH 2.8, SiO2 8.5%): It is highly acidic and contains many impurities, but the examples still show excellent performance. 6. Influence of process parameters: Upper limit parameters (Example 3): Whiteness 71.2%, Grade 96.8% (optimal) Preferred parameters (Example 1): Whiteness 68.5%, Grade 94.2% (Good) Lower limit parameters (Example 2): Whiteness 62.8%, Grade 89.8% (acceptable) Temperature deviation (Comparative Example 7): Whiteness 56.3%, Grade 86.1% (significant performance decline). 7. Comparison of selectivity indices: The average selectivity index of the Xiangyang example was 79.3; the average selectivity index of the Xiangyang comparative example was 43.7. The selectivity of the example was 81.5% higher than that of the comparative example, demonstrating the importance of the intact structure for flotation selectivity. 8. SiO2 removal effect: Average SiO2 content in the examples: 0.27-0.31% (removal rate 95-97%) Average SiO2 content of comparative examples: 1.00-2.91% (removal rate 65-88%) Collectors with intact structures exhibit 8-10 times better impurity removal performance than those with defective structures. In summary, the phosphogypsum flotation collector and its preparation method provided by this invention have significant advantages such as reasonable structural design, excellent technical effect, controllable process parameters, and wide adaptability of raw materials. They provide important technical support for the high-value utilization of phosphogypsum and have significant industrial application value and promotion prospects.

[0051] Using the high-efficiency flotation reagents of this invention, only one stage of flotation is needed to increase the whiteness of phosphogypsum to over 70 and optimize the mineral grade to over 96%, fully meeting the stringent requirements of the building materials industry for raw material quality. Compared with traditional multi-stage processes, this solution significantly reduces process complexity and operating costs, demonstrating outstanding economic efficiency and possessing strong commercial promotion value and industrialization potential.

Claims

1. A phosphogypsum flotation collector, characterized in that, Collectors are compounds having the following general formula (I): [R-O-CH2-CH(OH)-CH2-NH-(CH2) e -N + (R 1 )(R 2 )-(CH2) m -Si(OR 3 )3] X - (I) In the formula, R is a C8-C22 straight-chain or branched alkyl or alkenyl group; R 1 R 2 Each is an alkyl group that is independently C1-C4; R 3 It can be methyl, ethyl, or propyl; e and m are each an independent integer of 2, 3 or 4; X - It consists of chloride ions, bromide ions, or iodide ions.

2. The collector according to claim 1 or the method thereof, characterized in that, In the structural formula of the compound, R is a C10-C18 alkyl group; the R 1 R 2 R 3 It can be methyl, ethyl, propyl or butyl.

3. A method for preparing a phosphogypsum flotation collector, characterized in that, Includes the following steps: (1) React alcohol ROH with epichlorohydrin and then amination to obtain intermediate I: RO-CH2-CH(OH)-CH2-NH2; (2) Intermediate I undergoes Michael addition with acrylonitrile, followed by reduction to obtain intermediate II: RO-CH2-CH(OH)-CH2-NH-(CH2) e -NH2; (3) Methylation of intermediate II using a formic acid / formaldehyde system to obtain intermediate III: RO-CH2-CH(OH)-CH2-NH-(CH2) e -N(CH3)2; (4) React intermediate III with halosilane X-(CH2) m -Si(OR 3 )3 is reacted in an organic solvent and quaternized to obtain the phosphogypsum flotation collector as described in claim 1 or 2.

4. The method for preparing the phosphogypsum flotation collector as described in claim 3, characterized in that, In step (1), the molar ratio of alcohol ROH to epichlorohydrin is 1:1.1-1.

5. In the presence of an alkaline catalyst, the reaction is carried out at 50-80℃ for 2-6 hours to obtain the etherified product RO-CH2-CH(OH)-CH2Cl. Then, it undergoes an amination reaction with ammonia or liquid ammonia, with a molar ratio of ammonia to the etherified product of 3-10:

1. The reaction is carried out in an autoclave at 80-120℃ for 4-12 hours, or at atmospheric pressure using ammonia with a mass fraction of 25-28% at 60-80℃ for 6-15 hours to obtain intermediate I: RO-CH2-CH(OH)-CH2-NH2. The alkaline catalyst is sodium hydroxide, potassium hydroxide, or potassium tert-butoxide, and the amount used is 0.5-2% of the molar amount of alcohol ROH.

5. The method for preparing the phosphogypsum flotation collector as described in claim 3, characterized in that, In step (2), the molar ratio of intermediate I to acrylonitrile is 1:1.05-1.

3. The reaction is carried out in methanol, ethanol or isopropanol solvent at room temperature to 60°C for 8-24 hours to complete Michael addition and obtain nitrile intermediate RO-CH2-CH(OH)-CH2-NH-(CH2)2-CN. Then, catalytic hydrogenation reduction is carried out using Raney nickel or Pd / C as catalyst, with the catalyst amount being 3-8% of the mass of nitrile intermediate. The reaction is carried out at a hydrogen pressure of 2-5 MPa and a temperature of 50-100°C for 3-8 hours. Alternatively, a sodium borohydride-cobalt chloride system is used for reduction, with the molar ratio of sodium borohydride to nitrile intermediate being 2-4:1 and the amount of cobalt chloride being 5-10% of the molar mass of nitrile intermediate. The reaction is carried out in methanol solvent at 0-25°C for 4-10 hours to obtain intermediate II: RO-CH2-CH(OH)-CH2-NH-(CH2)3-NH2.

6. The method for preparing the phosphogypsum flotation collector as described in claim 3, characterized in that, In step (3), the molar ratio of intermediate II, formic acid with a mass fraction of 85-90%, and formaldehyde solution with a mass fraction of 37-40% is 1:2.5-4:2.5-4. The reaction is carried out under reflux at 60-90℃ for 4-12 hours in a water bath to complete the Eschweiler-Clarke methylation reaction. During the reaction, only the terminal primary amine group is dimethylated, while the secondary amine group remains unchanged. After the reaction, sodium hydroxide solution is added to adjust the pH to 10-12, and the mixture is extracted with an organic solvent. The extract is dried and concentrated with anhydrous sodium sulfate or anhydrous magnesium sulfate to obtain intermediate III: RO-CH2-CH(OH)-CH2-NH-(CH2)3-N(CH3)2. The extraction is performed 2-3 times, and the volume of organic solvent used each time is 0.3-0.5 times the volume of the reaction liquid.

7. The method for preparing the phosphogypsum flotation collector as described in claim 3, characterized in that, In step (4), intermediate III reacts with the halosilane X-(CH2). m -Si(OR 3 The molar ratio of intermediate III to intermediate III is 1:1.05-1.

2. The quaternization reaction is carried out in organic solvents such as acetonitrile, toluene, isopropanol, or N,N-dimethylformamide, with the solvent amount being 2-5 times the mass of intermediate III. The reaction temperature is 60-100℃, and the reaction time is 8-24 hours. The reaction is carried out in a closed container under nitrogen protection, with potassium iodide or sodium iodide added as a catalyst, at an amount of 1-5% of the molar mass of intermediate III. After the reaction, the mixture is cooled to room temperature, the insoluble matter is removed by filtration, and the solvent is removed by vacuum distillation to obtain the target product: [RO-CH2-CH(OH)-CH2-NH-(CH2)3-N + (CH3)2-(CH2) m -Si(OR 3 )3] X - The product is purified by crystallization and dried to obtain the phosphogypsum flotation collector according to claim 1 or 2 with a purity of ≥95%.

8. An application of a phosphogypsum flotation collector, characterized in that, The use of the collector according to claim 1 or 2 as a collector in the reverse flotation of phosphogypsum.

9. The application of the phosphogypsum flotation collector as described in claim 8, characterized in that, The collector is added to the phosphogypsum slurry at a rate of 50-600 g / ton of dry phosphogypsum.

10. The application of the phosphogypsum flotation collector as described in claim 8, characterized in that, The collector is prepared as a 0.01%-0.1wt% alcohol solution and then added to the phosphogypsum slurry.

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