Amphoteric collecting agent AEDA-14 for iron ore flotation and preparation method of amphoteric collecting agent AEDA-14

Abstract

The invention belongs to the technical field of beneficiation collecting agents, and particularly relates to an amphoteric collecting agent AEDA-14 for iron ore flotation and a preparation method of the amphoteric collecting agent AEDA-14. In order to solve the problems that an existing amphoteric collecting agent is complex in synthetic route, insufficient in stability, prone to being interfered by multivalent ions in a complex ore pulp environment and the like, the amphoteric collecting agent AEDA-14 for iron ore flotation is provided, the structural formula is HOOC-CH (NH-CH2-CH2)-(CH2) 11-CH3, and the amphoteric collecting agent AEDA-14 is obtained through a reaction of bromotetradecanoic acid and ethanediamine and has hydrophobic alkyl chains and amido; when being used for iron ore flotation, the composite collecting agent has the characteristics of anionic and cationic collecting agents at the same time, forms a stable adsorption layer on the surface of iron ore, can resist interference of Mg < 2 + > and Al < 3 + > ions and interference of pH fluctuation, and improves the flotation effect.

Description

Technical Field

[0001] This invention belongs to the field of mineral processing collector technology, and in particular relates to an amphoteric collector AEDA-14 for iron ore flotation and its preparation method. Background Technology

[0002] Collectors commonly used in iron ore flotation can be classified into three categories: anionic, cationic, and amphoteric. Anionic collectors, such as carboxylic acids like sodium oleate, hydroxamic acids, phosphoric (phosphonic) acids and their esters, and sulfonates, are widely used, but often suffer from problems such as viscous foam, poor adaptability to hard water, and temperature sensitivity, thus affecting flotation efficiency. Cationic collectors, represented by amines, are typically suitable for neutral to weakly alkaline conditions. They have lower collection efficiency for difficult-to-process minerals and are easily affected by anions in the pulp (such as CO32-). 2- SO4 2- The competitive adsorption of colloidal clay and other materials leads to a decrease in selectivity.

[0003] To overcome the aforementioned shortcomings, some studies have begun to explore the application of amphoteric collectors in iron ore flotation. For example, the study "Study on the Performance and Mechanism of Lauroamide-propyl Betaine in Reverse Flotation of Hematite" (Metal Mines, 2023) used lauroamide-propyl betaine as a collector and starch as an inhibitor for quartz-hematite separation, achieving high iron concentrate grades and recoveries. However, this system is sensitive to the amount of regulator under acidic conditions, and the iron recovery rate decreases significantly under alkaline conditions, limiting its application scope. Overall, existing collectors still suffer from insufficient selectivity, poor temperature adaptability, and large reagent dosages in complex iron ore-silicate systems. Therefore, it is necessary to develop collectors with simple synthesis methods, good solubility and stability, and the ability to maintain excellent collecting performance over a wide pH range and under complex hydrochemical conditions to improve the problems of existing technologies and enhance the separation efficiency and utilization rate of iron ore resources.

[0004] Amphoteric collectors, containing both anionic and cationic groups, have shown potential in iron ore flotation. However, current research still has significant limitations, generally including complex processes, insufficient selectivity, or poor stability. First, the synthetic routes for amphoteric collectors are relatively complex, typically requiring multiple organic synthesis steps (such as amidation and phosphorylation). Compared to traditional reagents like sodium oleate or dodecylamine, their preparation costs are higher, making industrial-scale application difficult. Second, most existing research remains at the laboratory stage, lacking systematic analysis of the adsorption configurations, electron transfer, and coordination modes of molecules on different mineral surfaces, and a complete mechanism of action has not yet been established, resulting in a weak foundation for their technological applications. Furthermore, in complex slurry environments, these collectors exhibit insufficient stability and are susceptible to Mg2+. 2+ Al 3+Interference from polyvalent ions leads to competitive adsorption or complexation, thereby weakening its selectivity and collection efficiency, making it difficult to meet the actual performance requirements of collectors in complex iron ore beneficiation processes. Summary of the Invention

[0005] To address the problems of existing amphoteric collectors, such as complex synthesis routes, high preparation costs, insufficient stability, susceptibility to interference from multivalent ions in complex slurry environments, and unsatisfactory selectivity, this invention provides an amphoteric collector AEDA-14 for iron ore flotation and its preparation method.

[0006] The amphoteric collector AEDA-14 of this invention contains one carboxylic acid group (-COOH) and two amino functional groups (including one primary amine and one secondary amine), possesses a hydrophobic alkyl chain and a protonable primary amine site, and exhibits characteristics of both anionic and cationic collectors. Its structural formula is HOOC-CH(NH-CH2-CH2-NH2)-(CH2). 11 -CH3, theoretical molecular formula is C 16 H 34 N₂O₂, with a relative molecular mass of 290 g / mol; its structural formula is as follows: .

[0007] AEDA-14 exhibits amphoteric forms (anionic and cationic) during flotation in iron ore-silicate symbiotic systems, with the hydrophobic alkyl chain providing the anionic carboxylate form (-COO). - It can coordinate with the metal hydroxyl sites on the mineral surface to form metal-carboxylate bonds, thereby providing adsorption anchoring; its cationic amine groups (-NH2 / -NH3) can coordinate with these sites to form metal-carboxylate bonds on the mineral surface. + AEDA-14 can interact with negatively charged oxygen-containing groups on the mineral surface through electrostatic and hydrogen bonding, promoting the formation of a dense and ordered adsorption layer. The hydrophobic alkyl chains in AEDA-14 provide the collecting driving force, while the protonable primary amine sites impart cationic characteristics, exhibiting both anionic and cationic collector properties. The synergistic adsorption of anions and cations enhances both the affinity and hydrophobicity of the iron-bearing mineral surface. Under the flotation conditions of the iron ore-silicate symbiotic system, it can form a stable adsorption layer on the iron ore surface, resisting Mg... 2+ Al 3+ Interference from ions and pH fluctuations can help to capture minerals and improve flotation efficiency.

[0008] The preparation method of the amphoteric collector AEDA-14 of the present invention includes the following: adding bromotetradecanoic acid to ethylenediamine, adding a catalyst, forming a reaction system to carry out the reaction, and obtaining the amphoteric collector AEDA-14;

[0009] Ethylenediamine is preheated at 60℃~70℃ for 10min~20min, and bromotetradecanoic acid is added dropwise to the preheated ethylenediamine at a uniform rate over 30min~60min; ethanol can be added as a solvent to the reaction system, and the proportion of ethanol to the total mass of ethylenediamine and ethanol shall not exceed 30%;

[0010] The molar ratio of ethylenediamine to bromotetradecanoic acid is 1.0:(1.05~1.80); the catalyst includes any one of p-toluenesulfonic acid, phosphoric acid, or urea; when the catalyst is p-toluenesulfonic acid, the amount used is 0.5wt%~2.0wt% of the mass of bromotetradecanoic acid; when the catalyst is phosphoric acid, the amount used is 0.2wt%~1.0wt% of the mass of bromotetradecanoic acid; when the catalyst is urea, the amount used is 1wt%~5wt% of the mass of bromotetradecanoic acid.

[0011] The reaction system was refluxed at 100℃~110℃ for 3h~5h and then the reaction was stopped. After the reaction was completed, the reaction system was cooled to 30℃~40℃ and hot ethanol was added to promote the precipitation of the product. Then it was washed with deionized water at 40℃~50℃ and finally dried at 45℃~60℃ to obtain the amphoteric collector AEDA-14.

[0012] The beneficial effects of this invention are as follows:

[0013] The amphoteric collector AEDA-14 of this invention is prepared by reacting tetradecanoic acid with ethylenediamine via nucleophilic substitution after bromination at the α-position of the carboxyl group to obtain α-bromotetradecanoic acid. By introducing an ethylenediamine fragment at the α-position of the carboxyl group in tetradecanoic acid, AEDA-14 simultaneously possesses a C14 hydrophobic alkyl chain, a carboxylic acid group, and two protonable amino groups, forming a long-chain amino acid-type amphoteric structure. The hydrophobic alkyl chain provides the driving force for hydrophobic adsorption on the mineral surface; the carboxylic acid group, under suitable pH conditions, can coordinate or exchange ions with the Fe(III)-OH sites on the hematite surface in the form of a carboxylate ion; the α-position and terminal primary amine sites are easily protonated under acidic to weakly alkaline conditions, allowing electrostatic adsorption with negatively charged oxygen-containing groups on the mineral surface, and interaction with surface hydroxyl groups through hydrogen bonding and other mechanisms, forming a relatively dense adsorption layer on the iron ore surface, thereby achieving effective mineral collection and demonstrating an amphoteric collection mechanism of synergistic anion / cation action. AEDA-14 maintains good solubility and dispersibility in complex slurry environments and is not easily affected by Mg. 2+ Al 3+ The interference of polyvalent ions solves the problem of poor stability of existing amphoteric collectors under hard water conditions, which helps to improve the selectivity and stability of AEDA-14 in the iron ore-silicate system and significantly reduces its risk of failure in complex water environments. Attached Figure Description

[0014] Figure 1The nuclear magnetic resonance spectrum of AEDA-14, the amphoteric harvester prepared in Example 1;

[0015] Figure 2 The infrared spectrum of AEDA-14, the amphoteric collector prepared in Example 1. Detailed Implementation

[0016] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. It should be noted that the embodiments described in this invention are only for further explanation and illustration, and not for limiting their application scope. Based on this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention.

[0017] Example 1

[0018] Raw materials: 0.10 mol of ethylenediamine (EDA, purity ≥99%), 0.15 mol of bromotetradecanoic acid (307 g / mol), and 0.5 g of urea as catalyst; that is, the molar ratio of ethylenediamine to bromotetradecanoic acid is 1:1.5, and the amount of urea as catalyst is 1% of the mass of bromotetradecanoic acid.

[0019] Reaction: Ethylenediamine was preheated by stirring at 65°C for 20 min. Pre-dissolved bromotetradecanoic acid was added dropwise to the ethylenediamine at a uniform rate over 30 min, maintaining a stable system temperature during the addition. After adding the catalyst, the temperature was slowly increased to 105°C and refluxed for 4 h to carry out the reaction. Good stirring was maintained throughout the reaction to prevent localized overheating. Samples were taken every 60 min to measure the acid value and infrared spectral density.

[0020] Post-treatment: After the reaction was complete, the reaction system was cooled to 30℃, and 30mL of hot ethanol was added to soften the reaction system and promote product precipitation. The precipitate was washed with 50mL of deionized water at 40℃~50℃ to remove free ethylenediamine and catalyst. Trace amounts of acidic byproducts were removed by washing with an alkaline solution at pH 8~9, followed by washing with deionized water until neutral. The product was then dried under reduced pressure at 45℃~60℃ to constant weight to obtain the amphoteric collector AEDA-14. It was stored in a sealed brown light-proof bottle to prevent amine oxidation / hygroscopic absorption.

[0021] Example 2

[0022] Raw materials: ethylenediamine and bromotetradecanoic acid in a molar ratio of 1:1.05, urea as catalyst, and the amount used is 2wt% of the mass of bromotetradecanoic acid.

[0023] Reaction: Ethylenediamine was preheated by stirring at 60°C for 10 min. Pre-dissolved bromotetradecanoic acid was added dropwise to the ethylenediamine at a uniform rate over 30 min, maintaining a stable system temperature during the addition. After adding the catalyst, the temperature was slowly increased to 110°C and refluxed for 5 h to carry out the reaction. Good stirring was maintained throughout the reaction to prevent localized overheating. Samples were taken every 60 min to measure the acid value and infrared spectrum.

[0024] Post-processing: After the reaction was complete, the reaction system was cooled to 30°C, and hot ethanol was added to soften the reaction system and promote product precipitation. The precipitate was washed with deionized water at 40°C–50°C to remove free ethylenediamine and catalyst. Trace amounts of acidic byproducts were removed by washing with an alkaline solution at pH 8–9, followed by washing with deionized water until neutral. The product was then dried under reduced pressure at 45°C–60°C to constant weight to obtain the amphoteric collector AEDA-14. This was stored in a sealed brown light-proof bottle to prevent amine oxidation and moisture absorption.

[0025] Example 3

[0026] Raw materials: ethylenediamine and bromotetradecanoic acid in a molar ratio of 1:1.2, urea as catalyst, and the amount used is 2wt% of the mass of bromotetradecanoic acid.

[0027] Reaction: Ethylenediamine was preheated by stirring at 60°C for 10 min; pre-dissolved bromotetradecanoic acid was added dropwise to ethylenediamine at a uniform rate over 40 min, while maintaining a stable system temperature during the addition. After adding the catalyst, the temperature was slowly raised to 110°C and refluxed for 5 h to carry out the reaction; good stirring was maintained during the reaction to prevent local overheating of the reaction system.

[0028] Post-processing: After the reaction was complete, the reaction system was cooled to 30°C, and hot ethanol was added to soften the reaction system and promote product precipitation. The precipitate was washed with deionized water at 40°C–50°C to remove free ethylenediamine and catalyst. Trace amounts of acidic byproducts were removed by washing with an alkaline solution at pH 8–9, followed by washing with deionized water until neutral. The product was then dried under reduced pressure at 45°C–60°C to constant weight to obtain the amphoteric collector AEDA-14. This was stored in a sealed brown light-proof bottle to prevent amine oxidation and moisture absorption.

[0029] Example 4

[0030] Raw materials: ethylenediamine and bromotetradecanoic acid in a molar ratio of 1:1.5, urea as catalyst, and the amount used is 2wt% of the mass of bromotetradecanoic acid.

[0031] Reaction: Ethylenediamine was preheated by stirring at 60°C for 10 min; pre-dissolved bromotetradecanoic acid was added dropwise to ethylenediamine at a uniform rate over 45 min, while maintaining a stable system temperature during the addition. After adding the catalyst, the temperature was slowly raised to 110°C and refluxed for 5 h to carry out the reaction; good stirring was maintained during the reaction to prevent local overheating of the reaction system.

[0032] Post-processing: After the reaction was complete, the reaction system was cooled to 30°C, and hot ethanol was added to soften the reaction system and promote product precipitation. The precipitate was washed with deionized water at 40°C–50°C to remove free ethylenediamine and catalyst. Trace amounts of acidic byproducts were removed by washing with an alkaline solution at pH 8–9, followed by washing with deionized water until neutral. The product was then dried under reduced pressure at 45°C–60°C to constant weight to obtain the amphoteric collector AEDA-14. This was stored in a sealed brown light-proof bottle to prevent amine oxidation and moisture absorption.

[0033] Example 5

[0034] Raw materials: ethylenediamine and bromotetradecanoic acid in a molar ratio of 1:1.05, urea as catalyst, and the amount used is 2wt% of the mass of bromotetradecanoic acid.

[0035] Reaction: Ethylenediamine was preheated by stirring at 60°C for 10 min; pre-dissolved bromotetradecanoic acid was added dropwise to ethylenediamine at a uniform rate over 30 min, while maintaining a stable system temperature during the addition. After adding the catalyst, the temperature was slowly raised to 110°C and refluxed for 3 h to carry out the reaction; good stirring was maintained during the reaction to prevent local overheating of the reaction system.

[0036] Post-processing: After the reaction was complete, the reaction system was cooled to 30°C, and hot ethanol was added to soften the reaction system and promote product precipitation. The precipitate was washed with deionized water at 40°C–50°C to remove free ethylenediamine and catalyst. Trace amounts of acidic byproducts were removed by washing with an alkaline solution at pH 8–9, followed by washing with deionized water until neutral. The product was then dried under reduced pressure at 45°C–60°C to constant weight to obtain the amphoteric collector AEDA-14. This was stored in a sealed brown light-proof bottle to prevent amine oxidation and moisture absorption.

[0037] Example 6

[0038] Raw materials: ethylenediamine and bromotetradecanoic acid in a molar ratio of 1:1.05, urea as catalyst, and the amount used is 2wt% of the mass of bromotetradecanoic acid.

[0039] Reaction: Ethylenediamine was preheated by stirring at 60°C for 10 min; pre-dissolved bromotetradecanoic acid was added dropwise to ethylenediamine at a uniform rate over 30 min, while maintaining a stable system temperature during the addition. After adding the catalyst, the temperature was slowly raised to 110°C and refluxed for 4 h to carry out the reaction; good stirring was maintained during the reaction to prevent local overheating of the reaction system.

[0040] Post-processing: After the reaction was complete, the reaction system was cooled to 30°C, and hot ethanol was added to soften the reaction system and promote product precipitation. The precipitate was washed with deionized water at 40°C–50°C to remove free ethylenediamine and catalyst. Trace amounts of acidic byproducts were removed by washing with an alkaline solution at pH 8–9, followed by washing with deionized water until neutral. The product was then dried under reduced pressure at 45°C–60°C to constant weight to obtain the amphoteric collector AEDA-14. This was stored in a sealed brown light-proof bottle to prevent amine oxidation and moisture absorption.

[0041] The amphoteric collector AEDA-14 was tested:

[0042] The amphoteric collector AEDA-14 prepared in the above examples achieved a yield of 78%; its appearance was a white to light yellow solid or waxy solid with a slight amine odor; its purity (HPLC) was ≥95%; its acid value was ≤5 mg KOH / g; and its moisture content (Karlsky method) was ≤0.5 wt%. The prepared agent has an ethylenediamine fragment linked to the α-position of the carboxyl group, and simultaneously possesses a carboxylic acid group and two protonable amino groups, forming an amphoteric structure in which a hydrophobic C14 alkyl segment and a hydrophilic ionic group coexist.

[0043] The nuclear magnetic resonance spectrum of the AEDA-14 product prepared in Example 1 is as follows: Figure 1 As shown, 1 ¹H NMR (400MHz, DMSO-d6, δ / ppm): 0.84ppm-0.90ppm, t, 3H-terminal CH3(-CH3), 1.20ppm-1.40ppm, m, ~20-24H-long chain (CH2)_n host (-(CH2) n -), 1.50ppm-1.70ppm, m, 2H-β-CH2(-CH2-CH2-COOH, near the carboxyl group), 2.18ppm-2.35ppm(t, 2H)-“-CH2-COOH”, 2.65ppm-3.15ppm, m, 4H- -NH-CH2-CH2-NH2 (two groups of CH2 in the ethylenediamine fragment), 3.05ppm-3.45ppm, dd / m, 1H-α-CH(-CH(NH-CH2CH2NH2)-COOH), this is the diagnostic peak for “α-position substitution”, 7.5ppm-9.0ppm, Br- -NH3 + (Amino salt) / -NH broad peak, with a series of broad peaks at 7.5ppm-8.8ppm, strongly suggesting that the amine terminus in the sample is protonated (NH3). + This forms an amine salt. The above signal is consistent with the structure of the target product AEDA-14.

[0044] The infrared spectrum (FT-IR) of the AEDA-14 product prepared in Example 1 is as follows: Figure 2 As shown. 3270cm-1 3188cm -1 and 3043cm -1 A relatively broad absorption band appears nearby, corresponding to the stretching vibration of -NH / -OH, indicating that the molecule contains amino and carboxyl groups; 2921 cm⁻¹ -1 and 2852cm -1 The strong absorption peak at this point is attributed to the asymmetric and symmetric stretching vibrations of -CH2-, indicating that the product possesses C... 14 Alkyl long chain; 1661 cm -1 and 1578cm -1 The absorption peak can be attributed to the carboxylate (-COO) group. - Asymmetric stretching and -NH3 + Bending vibration; 1468cm -1 ~1401cm -1 The region's peaks and -CH2- shear vibrations and -COO - Related to symmetrical stretching; 1326cm -1 ~1148cm -1 and 983cm -1 ~942cm -1 The multiple absorption peaks are related to CN and CO bond vibrations. These characteristic peaks indicate that the product simultaneously contains long-chain alkyl groups, carboxylic acid / carboxylic acid groups, and polyamino functional groups, consistent with the expected structural characteristics of the long-chain amino acid-type amphoteric collector AEDA-14.

[0045] Comparison of the solubility of AEDA-14 and dodecylamine:

[0046] The amphoteric collector AEDA-14 prepared in Example 1 and dodecylamine were dissolved in deionized water at 60°C, with a concentration of 100 mg·L⁻¹ for both. -1 The solution containing dodecylamine was observed to be partially turbid, indicating the presence of incompletely dissolved flocculent precipitate; the solution containing the amphoteric collector AEDA-14 was clear and transparent, with no obvious precipitation. This demonstrates that the solubility of collector AEDA-14 is significantly better than that of dodecylamine, making it more suitable for flotation applications under low-temperature or hard water conditions.

[0047] Using pure hematite, type 1 silicate minerals, and type 2 silicate minerals as research objects, and with a pulp concentration of 35% and room temperature, the addition amount of AEDA-14 prepared in Example 1 was fixed at 30 mg / L. The effects of different activator ions (Mg) were investigated. 2+ Al 3+ The effects of pH conditions on the flotation performance of the amphoteric collector AEDA-14 were investigated.

[0048] Without adjusting the pH, Al 3+When the added amounts were 10 mg / L, 20 mg / L, 40 mg / L, 60 mg / L, 80 mg / L, and 100 mg / L, the recovery rates of hematite and two types of silicate minerals were ≥90%, and the recovery rate of one type of silicate mineral was ≥70%; Mg 2+ When the added amounts are 10 mg / L, 20 mg / L, 40 mg / L, 60 mg / L, 80 mg / L, and 100 mg / L, the recovery rates of hematite and type 2 silicate minerals are ≥90%, and the recovery rate of type 1 silicate minerals is ≥80%.

[0049] Without the addition of activating ions, the recoveries of hematite and the two types of silicate minerals were ≥80% at pH values ​​of 3, 5, 7, 9, and 11; Al 3+ When the addition amount was 60 mg / L and the pH was 3, 5, 7, 9, and 11, the recovery rate of hematite and the two types of silicate minerals was ≥73%; Mg 2+ When the addition amount is 60 mg / L and the pH is 3, 5, 7, 9 and 11 respectively, the recovery rate of hematite and the two types of silicate minerals is ≥89%.

[0050] Comparative Example 1

[0051] The molar ratio of ethylenediamine to bromotetradecanoic acid is 1.05:1.05~1.80 (ethylenediamine slightly in excess), urea is used as a catalyst, and the amount used is 2wt% of the mass of bromotetradecanoic acid; other preparation methods are the same as in Example 1.

[0052] When ethylenediamine is in slight excess, the small amount of excess ethylenediamine can be basically removed after the reaction by "precipitation with hot ethanol + washing with deionized water", which has a limited impact on the reaction system and the purity of the final product.

[0053] Comparative Example 2

[0054] The molar ratio of ethylenediamine to bromotetradecanoic acid is 1.5~2.0:0.8~1.0 (ethylenediamine in excess), and urea is used as a catalyst at an amount of 2wt% of the mass of bromotetradecanoic acid; other preparation methods are the same as in Example 1.

[0055] Excess ethylenediamine alters the pH and cationic strength of the reaction system, shifting the ionization equilibrium of the target amphoteric collector. Furthermore, the reaction products at the end contain a large amount of unreacted ethylenediamine and the salt formed by ethylenediamine and the generated HBr. This also significantly increases the alkalinity and ionic strength of the reaction system, altering the ionization state of AEDA-14.

[0056] Comparative Example 3

[0057] The molar ratio of ethylenediamine to bromotetradecanoic acid is 1:2.0 (exceeding the upper limit of 1:1.80), and urea is used as a catalyst at an amount of 2 wt% of the mass of bromotetradecanoic acid; other preparation methods are the same as in Example 1.

[0058] Ethylenediamine molecules contain two primary amino groups. Theoretically, both –NH2 terminal groups can undergo nucleophilic substitution reactions at the -CHBr- site on the α-bromotetradecanoic acid molecule. When bromotetradecanoic acid is significantly in excess (e.g., the molar ratio of ethylenediamine to α-bromotetradecanoic acid is 1:2.0 or higher), the second amino group is also easily further substituted, generating "double-terminal substitution" byproducts with long-chain α-amino acid fragments attached to both ends. In this case, the number of primary amino groups at both ends of the ethylenediamine backbone decreases, the strongly basic and easily protonated cation center is weakened, and the molecule as a whole exists as a multi-electrolyte with polycarboxylic acid groups coordinating with relatively weak basic amino groups, exhibiting interfacial behavior closer to neutral or anionic surfactants. If the system is dominated by these "double-terminal substitution" byproducts, it will reduce the amphoteric characteristics of the target product AEDA-14, which features both a prominent cation adsorption center and a carboxylic acid coordination site, thus hindering the design intent of achieving both cation adsorption and anion coordination.

[0059] Comparative Example 4

[0060] The molar ratio of ethylenediamine to bromotetradecanoic acid is 3.0:0.8-1.0, and urea is used as a catalyst at an amount of 2 wt% of the mass of bromotetradecanoic acid; other preparation methods are the same as in Example 1.

[0061] Under these conditions, most of the α-bromotetradecanoic acid is rapidly consumed. However, due to the significant excess of ethylenediamine, the dominant component in the product is actually free ethylenediamine and its protonated salt, with AEDA-14 existing only as a minor component. The resulting solid is essentially closer to a mixture of ethylenediamine and its salts as the main component, with a small amount of long-chain amino acid-type AEDA-14 mixed in, rather than a product of a single amphoteric collector.

[0062] Comparative Example 5

[0063] The molar ratio of ethylenediamine to bromotetradecanoic acid is 1:1.5, and urea is used as a catalyst at 8% of the mass of bromotetradecanoic acid; other preparation methods are the same as in Example 1.

[0064] In this invention, urea is used only as a co-catalyst / fluxant. However, when urea is in significant excess (e.g., >5wt%), it will undergo a side reaction with ethylenediamine, consuming the effective amine. At 100℃~110℃, urea will slowly decompose to generate isocyanate and NH3. Isocyanate easily condenses with ethylenediamine to generate urea or cyclic urea byproducts (such as ethylene urea), which is equivalent to wasting some of the ethylenediamine and reducing the formation rate of AEDA-14. The increase in byproducts leads to a decrease in product purity.

Claims

1. An amphoteric collector AEDA-14 for iron ore flotation, characterized in that, The amphoteric collector contains a hydrophobic alkyl chain, a carboxylic acid functional group, and an amino functional group, with the molecular formula C0. 16 H 34 N2O2, structural formula as follows: 。 2. The amphoteric collector AEDA-14 for iron ore flotation according to claim 1, characterized in that, During iron ore flotation, the hydrophobic alkyl chain forms a metal-carboxylate bond on the mineral surface, and the amino functional group interacts with the negatively charged oxygen-containing groups on the mineral surface through electrostatic and hydrogen bonding interactions, giving the amphoteric collector both anionic and cationic collector characteristics, and forming a stable adsorption layer on the iron ore surface.

3. The amphoteric collector AEDA-14 for iron ore flotation according to claim 1, characterized in that, The amphoteric collector AEDA-14 can resist Mg during iron ore flotation. 2+ Al 3+ Interference from ions and pH fluctuations.

4. The preparation method of AEDA-14, an amphoteric collector for iron ore flotation according to claim 1, is characterized in that, Bromotetradecanoic acid was added to ethylenediamine, and a catalyst was added to form a reaction system to obtain the amphoteric collector AEDA-14.

5. The preparation method of AEDA-14, an amphoteric collector for iron ore flotation according to claim 4, is characterized in that, The ethylenediamine is preheated at 60℃~70℃ for 10min~20min, and the bromotetradecanoic acid is added to the preheated ethylenediamine at a uniform rate over 30min~60min.

6. The preparation method of AEDA-14, an amphoteric collector for iron ore flotation according to claim 4, is characterized in that, The molar ratio of ethylenediamine to bromotetradecanoic acid is 1.0:(1.05~1.80).

7. The preparation method of AEDA-14, an amphoteric collector for iron ore flotation according to claim 4, is characterized in that, The catalyst includes any one of p-toluenesulfonic acid, phosphoric acid, or urea.

8. The preparation method of AEDA-14, an amphoteric collector for iron ore flotation according to claim 7, is characterized in that, When the catalyst is p-toluenesulfonic acid, the amount used is 0.5wt% to 2.0wt% of the mass of bromotetradecanoic acid; when the catalyst is phosphoric acid, the amount used is 0.2wt% to 1.0wt% of the mass of bromotetradecanoic acid; when the catalyst is urea, the amount used is 1wt% to 5wt% of the mass of bromotetradecanoic acid.

9. The preparation method of AEDA-14, an amphoteric collector for iron ore flotation according to claim 4, is characterized in that, The reaction system was terminated after reacting at 100℃~110℃ for 3h~5h.

10. The method for preparing the amphoteric collector AEDA-14 for iron ore flotation according to claim 4, characterized in that, After the reaction is completed, the reaction system is cooled to 30℃~40℃, hot ethanol is added to precipitate the product, and after washing with deionized water at 40℃~50℃, it is dried at 45℃~60℃ to obtain the amphoteric collector AEDA-14.

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