A modified polyacrylic acid, its preparation method, and its application in iron ore reverse flotation.

Abstract

This invention belongs to the field of mineral processing technology, specifically relating to a modified polyacrylic acid, its preparation method, and its application in iron ore reverse flotation. Through a two-step alkalization-phosphorylation reaction, phosphorous acid groups are introduced into the polyacrylic acid molecular chain, significantly improving its affinity for Fe on the iron ore surface. 3+ Coordination ability of active sites. The modified polyacrylic acid structure possesses bifunctional groups of both carboxyl and phosphite groups, which can enhance adsorption strength through electrostatic and hydrogen bonding interactions, while also providing good water solubility and dispersibility. When the prepared modified polyacrylic acid was used as an inhibitor in the reverse flotation separation of iron ore, it exhibited strong selective inhibition, effectively suppressing the flotation of iron ore while having minimal impact on silicate gangue minerals, demonstrating high potential for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of mineral processing technology, specifically relating to a modified polyacrylic acid, its preparation method, and its application in reverse flotation of iron ore. Background Technology

[0002] In the reverse flotation process of iron ore, iron ore often coexists closely with silicate gangue minerals. The presence of these minerals significantly weakens the separation selectivity, becoming a key factor limiting the improvement of iron ore indicators. Currently, the common solution is to add traditional depressants such as starch and its modified forms, but these reagents still have many shortcomings. First, their selectivity is limited; while inhibiting iron ore, they often also "falsely inhibit" silicate minerals. Existing studies have shown that as the amount of starch increases, the recovery rate of silicate minerals decreases significantly, making it difficult to guarantee the separation effect. Second, conventional depressants have unstable and low-efficiency inhibitory effects on silicate minerals and other structurally complex silicate minerals; at the same time, they usually require large amounts of reagent, which can easily lead to increased pulp viscosity, increased fluctuations in the flotation system, and increased difficulty in process control. Furthermore, although starch has advantages such as wide availability and low price, its residue is high, resulting in high wastewater treatment costs; the preparation process also requires high temperature and alkaline conditions, leading to increased energy consumption and a heavier process burden.

[0003] Polyacrylamide (PAM), a typical water-soluble polymer, possesses excellent flocculation and dispersing properties and is widely used in mineral processing, especially in flotation separation. Its flexible molecular chain contains a large number of amide groups (-CONH2), which can bind to hydroxyl groups and metal ions on the mineral surface through hydrogen bonding, electrostatic interactions, or coordination, thereby altering the surface properties of the minerals. In the separation of fine-grained minerals, polyacrylamide exhibits a significant flocculation effect, effectively improving separation efficiency. To further enhance the effect of polyacrylamide in flotation, researchers have modified its structure. Sodium hydroxide is commonly used to hydrolyze polyacrylamide, yielding polyacrylic acid (PAA). Compared to polyacrylamide, polyacrylic acid has stronger complexing and dispersing properties, and more readily forms stable complexes with metal ions on the mineral surface, thus enhancing its inhibitory effect on iron minerals. However, existing polyacrylic acid inhibitors still have shortcomings; for example, although they have a strong inhibitory effect on iron ore, their selectivity for silicate minerals is not ideal; their molecular structure is simple and their functional groups are insufficient, making it difficult to achieve efficient differentiation of different minerals in complex ore systems; in industrial applications, large doses are often required to achieve good results, which leads to high reagent consumption and increased costs.

[0004] Overall, both starch and polyacrylamide, as alternatives, still have significant shortcomings in terms of selectivity, environmental friendliness, and industrial adaptability, and have not yet effectively solved the problem of efficient separation of iron ore and silicate minerals. Therefore, there is an urgent need to develop a new type of inhibitor for iron ore reverse flotation to overcome the problems of poor selectivity, large inhibitor dosage, poor pH adaptability, and environmental pollution in existing technologies. Summary of the Invention

[0005] The purpose of this invention is to provide a modified polyacrylic acid, its preparation method, and its application in reverse flotation of iron ore. The modified polyacrylic acid can effectively regulate the interfacial interaction of the slurry, improve the separability between iron ore and silicate gangue minerals, thereby achieving efficient reverse flotation separation.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The first aspect of this invention provides a method for preparing modified polyacrylic acid, comprising the following steps:

[0008] S1. Dissolve and pretreat to obtain a polyacrylamide solution;

[0009] S2, Alkali treatment, to obtain mixture 1;

[0010] S3, alkalization reaction, to obtain intermediate raw materials;

[0011] S4, modified with phosphorous acid, yielded mixture 2;

[0012] S5. Increase the temperature to react and obtain the reaction solution;

[0013] S6. Product processing and drying.

[0014] In step S1, the specific steps of dissolution and pretreatment are as follows: dissolve polyacrylamide in deionized water, place it in a 40°C water bath and stir continuously at a speed of 200-400 rpm until a uniform colorless viscous liquid is formed, and then sonicate to obtain a polyacrylamide solution.

[0015] Preferably, the polyacrylamide has a relative molecular mass of 5 million to 10 million and is sourced from Shanghai McLean Company.

[0016] Preferably, the mass ratio of the polyacrylamide to deionized water is 1:(15-25).

[0017] Preferably, the specific conditions for the ultrasonic treatment are: ultrasonic power of 250-350W, ultrasonic frequency of 35-45kHz, temperature of 40℃, and time of 10-20min.

[0018] In step S2, the specific steps of the alkalization treatment are as follows: sodium hydroxide solution is slowly added to the polyacrylamide solution obtained in step S1, and the mixture is stirred at 300-400 rpm for 30-45 minutes while maintaining a 40°C water bath. Then, it is ultrasonicated under the same conditions to obtain mixture 1.

[0019] Preferably, the sodium hydroxide solution contains 5%-15% by mass.

[0020] Preferably, the molar ratio of polyacrylamide in the polyacrylamide solution to sodium hydroxide in the sodium hydroxide solution is (1.2-1.5):1.

[0021] In step S3, the specific steps of the alkalization reaction are as follows: adjust the temperature of the mixed solution to 73-77℃, react at a speed of 400-500 rpm for 1-3 hours to obtain intermediate raw materials.

[0022] In step S4, the specific steps for modifying phosphorous acid are as follows: add phosphorous acid and catalyst to the intermediate raw material, and continue stirring at 50-60℃ and 300-400rpm for 20-40min to obtain mixture 2.

[0023] Preferably, the molar ratio of phosphorous acid to intermediate raw material is (0.8-1.2):1.

[0024] Preferably, the catalyst is urea, and the amount added is 1%-2% of the mass of polyacrylamide.

[0025] Preferably, in step S5, the specific steps of the heating reaction are as follows: the mixture 2 is heated to 78-82°C and maintained for 4-6 hours to obtain the reaction solution.

[0026] Preferably, in step S6, the specific steps for product processing and drying are as follows: the reaction solution is allowed to stand and vacuum filtered, the precipitate is collected, washed with ethanol 2-3 times, washed with deionized water 2-3 times, and vacuum dried to constant weight to obtain the product.

[0027] Preferably, the specific conditions for vacuum filtration are as follows: vacuum degree of 0.06-0.08 MPa, using a Buchner funnel and a filtration flask, and using a 0.22 μm mixed cellulose ester microporous filter membrane until no filtrate drips down.

[0028] Preferably, the specific conditions for vacuum drying are: temperature of 50-60℃ and vacuum degree of 0.07-0.09MPa.

[0029] The aforementioned preparation method successfully prepared polyacrylic acid phosphite (PPAA), an inhibitor with bifunctional synergistic effects, which can efficiently and selectively inhibit iron ore at low dosages. The alkalization process, by adjusting the molar ratio, promotes the conversion of PAM carboxyl groups to -COO-, enhancing molecular polarity and water solubility, and providing active sites for subsequent phosphorylation reactions. In the phosphorous acid modification stage, by adjusting the molar ratio of phosphorous acid and adding a small amount of urea as a catalyst, the phosphorous acid groups undergo esterification condensation with the polyacrylic acid segments to form a "carboxyl-phosphite" bifunctional structure. In this structure, the phosphorous acid groups react with Fe... 3+ The coordination ability of the inhibitor significantly enhances the adsorption of the iron ore surface, while the synergistic effect of the carboxyl and phosphite groups forms a dense hydrophilic layer on the gangue surface, hindering the adsorption of the collector. This preparation process achieves targeted regulation of the inhibitor molecular structure by precisely controlling the reaction temperature, raw material ratio, and catalytic conditions. Thus, in the reverse flotation process, it improves the separation selectivity and process stability through a dual mechanism of "iron ore site protection - gangue full coverage inhibition".

[0030] The second aspect of the present invention provides a method for preparing the modified polyacrylic acid.

[0031] The third aspect of this invention provides the application of the modified polyacrylic acid in the field of mineral processing, specifically in the reverse flotation of iron ore.

[0032] In the iron ore reverse flotation process, modified polyacrylic acid is added as an inhibitor in the form of an aqueous solution. The mass concentration of modified polyacrylic acid in the aqueous solution is 0.5%-2%. During reverse flotation, the pH value of the system is 7-11.

[0033] A schematic diagram of the iron ore reverse flotation process is available. Figure 1 .

[0034] The specific process of iron ore reverse flotation is as follows:

[0035] 1) The iron ore is crushed and ground to prepare particle sizes, resulting in the ore sample to be processed;

[0036] 2) Mix the ore sample to be treated with water to prepare slurry 1;

[0037] 3) Adjust the pH of the slurry to 7-11 using a pH adjuster, then add the inhibitor and collector sequentially and stir to obtain slurry 2;

[0038] 4) Perform a three-stage reverse flotation test on the slurry 2 obtained in step 3). The amount of collector used in the roughing test is twice the amount of collector used in the cleaning test.

[0039] Preferably, the particle size of the mineral sample to be treated is ≥80% -0.074mm.

[0040] Preferably, the concentration of the slurry 1 is 25%-35%.

[0041] Preferably, in step 3), the pH adjuster is a sodium hydroxide solution with a mass fraction of 1%-5% or a sulfuric acid solution with a mass fraction of 5%-10%.

[0042] Preferably, in step 3), the amount of inhibitor added is 50 g / t slurry 1, and the amount of collector added is 160 g / t slurry 1.

[0043] Preferably, the collector includes one or more fatty acids and fatty acid derivatives.

[0044] Preferably, the iron grade of the iron ore is 45%-55%, and the iron grade in the concentrate obtained after the reverse flotation can be increased to more than 65%, and the iron recovery rate can reach more than 80%.

[0045] By introducing phosphorous acid groups into the polyacrylic acid molecular chain, polyacrylic acid phosphorite (PPAA) is prepared. The phosphorous acid and carboxyl groups interact with the active sites on the surface of the target gangue minerals, forming a stable hydrophilic layer on their surface, thereby effectively preventing the adsorption of collectors and achieving targeted inhibition of gangue minerals. Simultaneously, this inhibitor exhibits strong adsorption stability on the surface of iron minerals, ensuring the flotation activity of iron ore and significantly improving the selectivity of flotation separation. Compared with traditional starch-based or polyacrylamide-based inhibitors, this invention has advantages such as low dosage, high inhibition efficiency, low energy consumption, and low residue, which helps to reduce production costs, improve the pulp environment, and enhance the feasibility and stability of industrial applications.

[0046] Unlike traditional starch-based or polyacrylamide-based inhibitors, PPAA forms a dense and stable hydrophilic layer on the surface of target gangue minerals (such as silicate minerals) through the synergistic effect of phosphite and carboxyl groups. This significantly weakens the adsorption of collectors on these gangue surfaces, thus achieving highly efficient targeted inhibition. Simultaneously, the phosphite groups can coordinate with the metal active sites on the iron mineral surface, stabilizing its surface structure, preventing accidental inhibition, and ensuring the floatability of the iron ore. Through this "dual-action mechanism," PPAA exhibits higher selectivity, lower dosage, and better environmental adaptability in reverse flotation, effectively improving concentrate grade and recovery rate while reducing wastewater treatment and reagent consumption costs. In iron ore reverse flotation, polyacrylic acid phosphite (PPAA) has a large number of carboxyl groups (-COOH / -COO-) and phosphite groups (-PO3H2 / -PO3) in its molecular backbone. 2-It possesses multiple functional groups, including carboxyl groups, which provide hydrogen bond donor / acceptor capabilities, while phosphite groups exhibit strong metal coordination ability and hydrophilicity. Its role on gangue mineral surfaces is primarily manifested in the interaction of carboxyl and phosphite groups with hydroxyl groups, silicon-oxygen tetrahedra, or magnesium / iron ion coordination sites on the surfaces of silicate minerals and iron-containing silicates, forming hydrogen bonds and electrostatic adsorption. Furthermore, this multi-site adsorption allows PPAA to form a dense hydrophilic layer on the gangue surface, increasing the thickness of the surface hydration film and significantly hindering the approach and adsorption of hydrophobic groups of collectors. On iron ore surfaces, phosphite groups can interact with Fe on the iron ore surface. 3+ / Fe 2+ Coordination occurs at the active sites, forming a stable chemisorption layer. This coordination adsorption differs from the fully covered hydrophilic film on the gangue surface; instead, it primarily relies on site-specific binding, which does not significantly weaken the adsorption of collectors (such as hydroxamic acid and fatty acid derivatives) on the iron ore surface. Therefore, PPAA has a weaker inhibitory effect on iron ore, preserving its floatability and avoiding the "false inhibition" problem of traditional starch. Overall, the reagent selectivity is significantly enhanced; the dosage is reduced, and the system viscosity is lowered; the process stability is improved, with less residue and lower wastewater treatment costs; ultimately, highly efficient and selective reverse flotation is achieved, improving concentrate grade and recovery rate.

[0047] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0048] 1. This invention provides a modified polyacrylic acid, which, through a two-step alkalization-phosphorylation reaction, introduces phosphorous acid groups into the polyacrylic acid molecular chain, significantly improving its affinity for Fe on the surface of iron minerals. 3+ Coordination ability of active sites. The modified polyacrylic acid structure possesses bifunctional groups of both carboxyl and phosphite groups, which can enhance adsorption strength through electrostatic and hydrogen bonding interactions, while also providing good water solubility and dispersibility. When the prepared modified polyacrylic acid was used as an inhibitor in the reverse flotation separation of iron ore, it exhibited strong selective inhibition, effectively suppressing the flotation of iron ore while having minimal impact on silicate gangue minerals, demonstrating high potential for industrial application.

[0049] 2. This invention modifies polyacrylic acid by introducing phosphorous acid groups into the molecular structure of polyacrylic acid, enabling the modified polyacrylic acid to preferentially adsorb onto the surface of iron ore, forming a stable hydrophilic layer and effectively blocking the action of collectors; while the adsorption effect on silicate gangue minerals is weak, thus achieving high selectivity inhibition of iron ore and ensuring the smooth progress of flotation separation.

[0050] 3. Using the modified polyacrylic acid prepared according to this invention as an inhibitor, the iron concentrate grade increased by approximately 2.0 to 2.5 percentage points compared to traditional polyacrylic acid inhibitors, demonstrating superior separation performance. It exerts a stabilizing effect at an inhibitor concentration of 1 to 5 mg / L, requiring low dosage and offering good economic efficiency. Furthermore, this inhibitor exhibits good selectivity in different ore systems, showing minimal inhibitory effect on silicate gangue minerals and demonstrating strong adaptability.

[0051] 4. The modified polyacrylic acid prepared by this invention has a simple preparation process, mild reaction conditions (the reaction can be completed at 80℃), inexpensive and readily available raw materials, and clear steps, making it easy to promote industrialization. No toxic byproducts are generated during the preparation process, and the reagent itself is biodegradable, which aligns with the development direction of green mineral processing and has good prospects for industrial application. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0053] Figure 1 Infrared spectra of polyacrylamide, polyacrylic acid, and the modified polyacrylic acid prepared in Example 1;

[0054] Figure 2 Flowchart of single-mineral reverse flotation operation for pure iron ore / silicate minerals;

[0055] Figure 3 Flowchart for iron ore reverse flotation operation;

[0056] Figure 4 This is a closed-loop flow chart for iron ore reverse flotation operations. Detailed Implementation

[0057] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] The chemical reagents used in this invention can be obtained by purchasing or by preparing them using existing methods, and the instruments and equipment used are conventional equipment in the prior art.

[0059] Polyacrylamide, with a relative molecular mass of 5 million to 10 million, is from Shanghai McLean Company.

[0060] Example 1

[0061] This embodiment provides a method for preparing modified polyacrylic acid, the steps of which are as follows:

[0062] S1. Dissolve and pretreat to obtain a polyacrylamide solution;

[0063] S2, Alkali treatment, to obtain mixture 1;

[0064] S3, alkalization reaction, to obtain intermediate raw materials;

[0065] S4, modified with phosphorous acid, yielded mixture 2;

[0066] S5. Increase the temperature to react and obtain the reaction solution;

[0067] S6. Product processing and drying.

[0068] In step S1, the specific steps of dissolution and pretreatment are as follows: dissolve polyacrylamide in deionized water, place it in a 40°C water bath and stir continuously at 300 rpm until a uniform colorless viscous liquid is formed, and then sonicate to obtain a polyacrylamide solution.

[0069] The mass ratio of polyacrylamide to deionized water is 1:20.

[0070] The specific conditions for the ultrasonic treatment are: ultrasonic power of 300W, ultrasonic frequency of 40kHz, temperature of 40℃, and time of 15min.

[0071] In step S2, the specific steps of the alkalization treatment are as follows: sodium hydroxide solution is slowly added to the polyacrylamide solution obtained in step S1, and the mixture is stirred at 350 rpm for 35 minutes while maintaining a 40°C water bath. Then, it is ultrasonicated under the same conditions to obtain mixture 1.

[0072] The sodium hydroxide solution contains 10% sodium hydroxide by mass.

[0073] The molar ratio of polyacrylamide in the polyacrylamide solution to sodium hydroxide in the sodium hydroxide solution is 1.3:1.

[0074] In step S3, the specific steps of the alkalization reaction are as follows: adjust the temperature of the mixed solution to 75°C, react at 450 rpm for 2 hours to obtain intermediate raw materials.

[0075] In step S4, the specific steps for modifying phosphorous acid are as follows: add phosphorous acid and catalyst to the intermediate raw material, and continue stirring at 55°C and 350 rpm for 30 minutes to obtain mixture 2.

[0076] The molar ratio of phosphorous acid to intermediate raw material is 1:1.

[0077] The catalyst is urea, and the amount added is 1.5% of the mass of polyacrylamide.

[0078] In step S5, the specific steps of the heating reaction are as follows: the mixture 2 is heated to 80°C and kept for 5 hours to obtain the reaction solution.

[0079] In step S6, the specific steps for product processing and drying are as follows: the reaction solution is allowed to stand and vacuum filtered, the precipitate is collected, washed three times with ethanol, then washed three times with deionized water, and vacuum dried to constant weight to obtain the product.

[0080] The specific conditions for vacuum filtration are as follows: vacuum degree of 0.07 MPa, using a Buchner funnel and a filtration flask, and using a 0.22 μm mixed cellulose ester microporous filter membrane until no filtrate drips down.

[0081] The specific conditions for vacuum drying are: temperature 55℃ and vacuum degree 0.08MPa.

[0082] The infrared spectrum of the prepared modified polyacrylic acid is shown in the figure. Figure 1 .from Figure 1 It can be seen that, compared with unmodified polyacrylic acid, PPAA at 1160 A new strong absorption appears, attributed to P=O stretching; in the range of 1040–1060. P–O–C expansion belt was observed, and 930 The bands are attributed to the P–OH vibration. These characteristics indicate that phosphorus-containing groups have been introduced into the polymer backbone.

[0083] Comparative Example 1

[0084] The only difference between this comparative example and Example 1 is that the molar ratio of polyacrylamide in the polyacrylamide solution to sodium hydroxide in the sodium hydroxide solution is 1:1.

[0085] Comparative Example 2

[0086] The only difference between this comparative example and Example 1 is that the molar ratio of polyacrylamide in the polyacrylamide solution to sodium hydroxide in the sodium hydroxide solution is 2:1.

[0087] Comparative Example 3

[0088] The only difference between this comparative example and Example 1 is that the molar ratio of phosphorous acid to intermediate raw material is 1:2.

[0089] Comparative Example 4

[0090] The only difference between this comparative example and Example 1 is that the molar ratio of phosphorous acid to intermediate raw material is 2:1.

[0091] Comparative Example 5

[0092] The only difference between this comparative example and Example 1 is that in step S4, the specific steps for modifying phosphorous acid are: adding phosphorous acid to the intermediate raw material and stirring for 30 minutes at 55°C and 350 rpm to obtain mixture 2.

[0093] Application Example 1

[0094] The modified polyacrylic acid prepared in Example 1 was diluted to a 1% aqueous solution and used as an inhibitor in the reverse flotation process. A schematic diagram of the reverse flotation operation process is shown below. Figure 2 The raw ore was pure iron ore with an iron grade of 69.69%; the particle size of the ore sample to be processed was ≥80% for particles of -0.074mm; the concentration of the slurry 1 was 30%; and fatty acids were used as collectors. The experimental results showed that the recovery rate of the concentrate was 97.44%, and the recovery rate of the tailings was 2.56%. This indicates that PPAA can effectively inhibit iron ore at concentrations below 3 mg / L.

[0095] Application Example 2

[0096] The modified polyacrylic acid prepared in Example 1 was diluted to a 1% aqueous solution and used as an inhibitor in the reverse flotation process. A schematic diagram of the reverse flotation operation process is shown below. Figure 2 The raw ore was a type I silicate mineral with an iron grade of 6.55%; the particle size of the ore sample to be processed was ≥80% for particles of -0.074 mm; the concentration of the slurry 1 was 30%; and fatty acids were used as the collector. The experimental results showed that the concentrate recovery rate was 92.86%, and the tailings recovery rate was 7.14%. This indicates that PPAA has a negligible impact on silicate minerals within a certain range.

[0097] Application Example 3

[0098] The modified polyacrylic acid prepared in Example 1 was diluted to a 1% aqueous solution and used as an inhibitor in the reverse flotation process. A schematic diagram of the reverse flotation operation process is shown below. Figure 2 The raw ore was a type II silicate mineral with an iron grade of 7.12%; the particle size of the ore sample to be processed was ≥80% for particles of -0.074 mm; the concentration of the slurry 1 was 30%; and fatty acids were used as the collector. The experimental results showed that the concentrate recovery rate was 95.73%, and the tailings recovery rate was 4.28%. This indicates that PPAA has a negligible impact on silicate minerals within a certain range.

[0099] Application Example 4

[0100] The modified polyacrylic acid prepared in Example 1 was diluted to a 1% aqueous solution and used as an inhibitor in the reverse flotation process. A schematic diagram of the reverse flotation operation process is shown below. Figure 2The raw ore was a mixture of iron ore and silicate minerals, with an iron grade of 37.49%. The particle size of the ore sample to be treated was ≥80% for particles smaller than 0.074 mm. The concentration of the pulp 1 was 30%. Fatty acids were used as the collector. Experimental results showed that the iron grade in the concentrate was 56.78%, with a recovery rate of 84.15%. This indicates that the PPAA and fatty acid reagent system can effectively enrich hematite.

[0101] Application Example 5

[0102] The modified polyacrylic acid prepared in Example 1 was diluted to a 1% aqueous solution and used as an inhibitor in the reverse flotation process. A schematic diagram of the reverse flotation operation process is shown below. Figure 2 The raw ore was a mixture of iron ore and silicate minerals, with an iron grade of 38.63%. The particle size of the ore sample to be treated was ≥80% -0.074mm. The concentration of the slurry 1 was 30%. Fatty acids were used as the collector. Experimental results showed that the iron grade was 56.78%, and the recovery rate was 91.09%. This indicates that the PPAA and fatty acid reagent system can effectively enrich hematite.

[0103] Application Example 6

[0104] The modified polyacrylic acid prepared in Example 1 was diluted to a 1% aqueous solution and used as an inhibitor in the reverse flotation process. A schematic diagram of the open-circuit reverse flotation operation process is shown below. Figure 3 The raw ore was the actual ore with an iron grade of 48.97%; the particle size of the ore sample to be processed was ≥80% for particles of -0.074mm; the concentration of the pulp 1 was 30%; and fatty acids were used as the collector. Experimental results showed that the iron grade in the refined product reached 68.25%, with a recovery rate of 81.99%; while the iron grade in the tailings product was only 7.87%, with an iron recovery rate of 2.73%. This indicates that the PPAA and fatty acid reagent system can effectively enrich hematite. A schematic diagram of the reverse flotation closed-circuit operation process is shown below. Figure 4 The concentrate grade was 68.64%, concentrate recovery rate was 88.5%, tailings grade was 16.25%, and tailings recovery rate was 12.2%. This verifies that the PPAA and fatty acid reagent system can effectively enrich hematite.

[0105] Application Example 7

[0106] The modified polyacrylic acid prepared in Comparative Example 1 was diluted to a 1% aqueous solution and used as an inhibitor in the reverse flotation process. A schematic diagram of the reverse flotation operation process is shown below. Figure 3The raw ore was the actual ore with an iron grade of 48.97%; the particle size of the ore sample to be processed was ≥80% for particles of -0.074mm; the concentration of the slurry 1 was 30%; and fatty acids were used as the collector. The experimental results showed that the iron grade in the concentrate reached 61.35%, with a recovery rate of 64.28%; while the iron grade in the tailings was 22.2%, with an iron recovery rate of 9.23%. This indicates that a decrease in the molar amount of polyacrylamide in the polyacrylamide solution in Comparative Example 1 affects the inhibitory performance of the prepared PPAA.

[0107] Application Example 8

[0108] The modified polyacrylic acid prepared in Comparative Example 2 was diluted to a 1% aqueous solution and used as an inhibitor in the reverse flotation process. A schematic diagram of the reverse flotation operation process is shown below. Figure 3 The raw ore was the actual ore with an iron grade of 48.97%; the particle size of the ore sample to be processed was ≥80% for particles of -0.074mm; the concentration of the slurry 1 was 30%; and fatty acids were used as the collector. The experimental results showed that the iron grade in the concentrate reached 60.55%, with a recovery rate of 63.44%; while the iron grade in the tailings was 19.34%, with an iron recovery rate of 11.43%. This indicates that an excessive molar amount of polyacrylamide in the polyacrylamide solution in Comparative Example 2 would affect the inhibitory performance of the prepared PPAA.

[0109] Application Example 9

[0110] The modified polyacrylic acid prepared in Comparative Example 3 was diluted to a 1% aqueous solution and used as an inhibitor in the reverse flotation process. A schematic diagram of the reverse flotation operation process is shown below. Figure 3 The raw ore was the actual ore with an iron grade of 48.97%; the particle size of the ore sample to be processed was ≥80% for particles of -0.074mm; the concentration of the slurry 1 was 30%; and fatty acids were used as the collector. The experimental results showed that the iron grade in the concentrate reached 60.75%, with a recovery rate of 62.4%; while the iron grade in the tailings was only 21.54%, with an iron recovery rate of 12.4%. This indicates that the insufficient molar amount of phosphorous acid in Comparative Example 3 will affect the inhibitory performance of the prepared PPAA.

[0111] Application Example 10

[0112] The modified polyacrylic acid prepared in Comparative Example 4 was diluted to a 1% aqueous solution and used as an inhibitor in the reverse flotation process. A schematic diagram of the reverse flotation operation process is shown below. Figure 3The raw ore was the actual ore with an iron grade of 48.97%; the particle size of the ore sample to be processed was ≥80% for particles of -0.074mm; the concentration of the slurry 1 was 30%; and fatty acids were used as collectors. The experimental results showed that the iron grade in the concentrate reached 61.75%, with a recovery rate of 64.7%; while the iron grade in the tailings was 26.56%, with an iron recovery rate of 11.2%. This indicates that an excessive molar amount of phosphorous acid in Comparative Example 4 would affect the inhibitory performance of the prepared PPAA.

[0113] Application Example 11

[0114] The modified polyacrylic acid prepared in Comparative Example 5 was diluted to a 1% aqueous solution and used as an inhibitor in the reverse flotation process. A schematic diagram of the reverse flotation operation process is shown below. Figure 3 The raw ore was the actual ore with an iron grade of 48.97%; the particle size of the ore sample to be processed was ≥80% for particles of -0.074mm; the concentration of the slurry 1 was 30%; and fatty acids were used as the collector. The experimental results showed that the iron grade in the concentrate reached 64.15%, with a recovery rate of 68.71%; while the iron grade in the tailings was 16.3%, with an iron recovery rate of 6.16%. This indicates that the absence of uric acid as a catalyst in Comparative Example 5 affects the inhibitory performance of the prepared PPAA.

[0115] Application Example 12

[0116] Polyacrylic acid was diluted to a 1% aqueous solution and used as an inhibitor in the reverse flotation process. A schematic diagram of the reverse flotation operation process is shown below. Figure 3 The raw ore was an actual ore with an iron grade of 48.97%; the particle size of the ore sample to be processed was ≥80% for particles of -0.074mm; the concentration of the slurry 1 was 30%; and fatty acids were used as collectors. Experimental results showed that the iron grade in the concentrate reached 64.12%, with a recovery rate of 80.25%; while the iron grade in the tailings was only 24.98%, with an iron recovery rate of 19.75%. This indicates that conventional polyacrylic acid, as an inhibitor, is less effective than the PPAA prepared in this invention.

[0117] Application Example 13

[0118] Polyacrylamide was diluted to a 1% aqueous solution and used as an inhibitor in the reverse flotation process. A schematic diagram of the reverse flotation operation process is shown below. Figure 3The raw ore was an actual ore with an iron grade of 48.97%. The particle size of the ore sample to be processed was ≥80% for particles of -0.074 mm. The concentration of the slurry 1 was 30%. Fatty acid was used as the collector. Experimental results showed that the iron grade in the concentrate reached 61.75%, with a recovery rate of 62.99%; while the iron grade in the tailings was only 28.73%, with an iron recovery rate of 12.91%. This indicates that conventional polyacrylamide as an inhibitor is less effective than the PPAA prepared in this invention.

[0119] Application Examples 1-13 demonstrate that modified polyacrylic acid possesses the following technical advantages: ① Strong selectivity: The modified molecules exhibit stronger complexation and steric hindrance effects, enabling them to preferentially adsorb onto the iron ore surface, hindering the action of the collector and thus showing a significant inhibitory effect on iron ore; ② Weak influence on silicate minerals: Under conventional collector systems, modified polyacrylic acid has almost no inhibitory effect on silicate minerals, thereby significantly improving the selectivity of flotation separation; ③ Simple preparation and controllable cost: The synthesis method of this modified polyacrylic acid inhibitor is simple to operate, with mild reaction conditions and readily available raw materials, making it suitable for large-scale industrial production; ④ Outstanding application value: This modified polyacrylic acid inhibitor can significantly improve the separation efficiency of iron ore and silicate minerals, providing a new approach for the efficient utilization of iron ore resources.

[0120] In summary, the modified polyacrylic acid inhibitor proposed in this invention not only overcomes the problems of poor selectivity and large dosage of existing polyacrylic acid inhibitors, but also has a simple preparation process and low cost, and has broad industrial application prospects and promotion value.

[0121] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a modified polyacrylic acid, characterized by, It comprises the following steps: S1, dissolving and pretreating to obtain a polyacrylamide solution; S2, alkali treatment: slowly adding a sodium hydroxide solution to the polyacrylamide solution obtained in step S1, maintaining a 40℃ water bath, stirring at a speed of 300-400 rpm for 30-45 min, and obtaining a mixture 1; S3, alkali reaction, to obtain an intermediate raw material; S4, phosphorous acid modification: adding phosphorous acid and a catalyst to the intermediate raw material, continuing to stir at a speed of 300-400 rpm at 50-60℃ for 20-40 min, and then obtaining a mixture 2 under the same conditions by ultrasonic treatment; The molar ratio of phosphorous acid to the intermediate raw material is (0.8-1.2):1; The catalyst is urea, and the addition amount is 1%-2% of the mass of the polyacrylamide; S5, temperature rising reaction, to obtain a reaction liquid; S6, product treatment and drying; In the step S1, the specific steps of dissolving and pretreating are as follows: dissolving the polyacrylamide in deionized water, placing it in a 40℃ water bath, and continuously stirring at a speed of 200-400 rpm until a uniform colorless viscous liquid is formed, and then obtaining the polyacrylamide solution after ultrasonic treatment; The relative molecular mass of the polyacrylamide is 5-10 million; The molar ratio of the polyacrylamide in the polyacrylamide solution to the sodium hydroxide in the sodium hydroxide solution is (1.2-1.5):

1.

2. A modified polyacrylic acid prepared by the preparation method of the modified polyacrylic acid according to claim 1.

3. The application of the modified polyacrylic acid according to claim 2 in iron ore reverse flotation.

4. The use of modified polyacrylic acid according to claim 3 in the reverse flotation of iron ores, characterized in that, In the process of the iron ore reverse flotation, the modified polyacrylic acid is used as an inhibitor and is added in the form of an aqueous solution, the mass concentration of the modified polyacrylic acid in the aqueous solution is 0.5%-2%, and the pH value of the system during the reverse flotation is 7-11.

5. The use of modified polyacrylic acid according to claim 4 in the reverse flotation of iron ores, characterized in that, The specific process of the iron ore reverse flotation is as follows: 1) preparing a particle size by crushing and grinding the iron ore to obtain a to-be-treated ore sample; 2) mixing the to-be-treated ore sample with water to prepare an ore slurry 1; 3) adjusting the pH value of the ore slurry 1 to 7-11 by using a pH regulator, adding an inhibitor and a collector in sequence, and stirring to obtain an ore slurry 2; 4) performing one roughing and one cleaning and three scavenging reverse flotation tests on the ore slurry 2 obtained in step 3), and the dosage of the collector for the roughing test is 2 times the dosage of the collector for the cleaning.

6. The use of the modified polyacrylic acid according to claim 5 in the reverse flotation of iron ores, characterized in that, In step 3), the addition amount of the inhibitor is 50 g / t of the ore slurry 1, and the addition amount of the collector is 160 g / t of the ore slurry 1.

7. The use of the modified polyacrylic acid according to claim 6 in the reverse flotation of iron ores, characterized in that, The collector comprises one or more of a fatty acid and a fatty acid derivative.

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