Sequential flotation separation method based on sulfonated phosphonic acid derivatives and applications thereof

Abstract

This invention belongs to the field of mineral processing engineering technology, and discloses a sequential flotation separation method and its application based on sulfanilamide phosphonic acid derivatives. It utilizes specific organic inhibitors to achieve efficient sequential separation of bastnaesite, fluorite, and calcite through stepwise pH control of the pulp. The process is driven by pH-responsive sulfanilamide phosphonic acid derivative inhibitors. This process requires only a single reagent combined with stepwise pH control, eliminating the need for magnetic separation, resulting in a simple and easily controllable process. By leveraging the drastic variation in inhibitory effects at different pH levels, precise separation of bastnaesite and fluorite can be achieved, significantly improving concentrate quality and recovery rate. Simultaneously, calcite can be recovered, resulting in high resource utilization and significant economic and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of mineral processing engineering technology, and in particular to a sequential flotation separation method and application based on sulfanilamide phosphonic acid derivatives. The method uses specific organic inhibitors to achieve efficient sequential separation of bastnaesite, fluorite and calcite by stepwise control of the pulp pH value. Background Technology

[0002] Fluorocarbonate cerium is a major mineral containing light rare earth elements, and its efficient development and utilization are crucial for strategic industries such as new energy and high-end equipment manufacturing. In nature, fluorocarbonate cerium is often closely intercalated with calcareous gangue minerals such as fluorite and calcite. Due to the high similarity of the surface chemical properties of these three minerals, achieving efficient flotation separation is quite challenging.

[0003] Currently, mainstream flotation processes both domestically and internationally utilize highly selective hydroxamic acid as a collector and water glass and dextrin as depressants for the separation and purification of bastnaesite. While this process has been widely applied in industrial settings such as the Baotou rare earth mine, its recovery rate is low due to the similarity of mineral surface properties and poor depressant selectivity, and the removal of fluorite is also ineffective. Furthermore, a mixed flotation followed by magnetic separation to separate bastnaesite and fluorite is also a common rare earth separation process. However, bastnaesite has weak magnetic properties, and the magnetic separation process easily entrains gangue impurities, resulting in both low concentrate grade and low recovery rate. Moreover, this process involves multiple stages including mixed flotation, concentration, and magnetic separation, leading to high equipment and labor costs and poor adaptability to complex ores.

[0004] Existing flotation technologies suffer from several major problems: Complex reagent systems: Most industrial processes require the simultaneous addition of multiple depressants, and the dosage of depressants must be strictly controlled during the refining stage to stabilize the separation effect. Furthermore, even slight fluctuations in pulp pH can easily lead to a decrease in rare earth concentrate grade, making operational stability difficult to guarantee; Insufficient reagent selectivity: Fluorocarbonate cerium ore and fluorite have highly similar surface charge characteristics in the neutral to weakly alkaline range, making it difficult for existing reagent systems to effectively amplify the differences in their floatability, resulting in flotation concentrates that fail to meet the requirements for preparing high-end permanent magnet materials; Low resource utilization rate: Traditional processes focus solely on rare earth recovery, and fluorite separation requires an additional "regrinding-reflotation" step, increasing industrial operating costs.

[0005] To address the aforementioned issues, a novel flotation technology with a simple process, excellent selectivity, and the ability to recover all components is being developed. This technology not only theoretically reveals the selective inhibition mechanism of inhibitors on calcareous minerals under different pH conditions, but also enriches the fundamental theory of flotation separation of calcareous minerals. Furthermore, at the application level, it simplifies industrial processes, reduces reagent costs and operational complexity, and enables the efficient separation and comprehensive recovery of bastnaesite, fluorite, and calcite. This provides technical support for the efficient utilization of associated rare earth resources in my country and offers significant economic and environmental benefits. Summary of the Invention

[0006] Objective: This invention addresses the challenge of separating fluorite and calcite in bastnaesite by providing a sequential flotation separation method and its application based on sulfanilamide phosphonic acid derivatives. The method employs pH-responsive sulfanilamide phosphonic acid derivative inhibitors. This process requires only a single reagent with stepwise pH control, eliminating the need for magnetic separation and resulting in a simple and easily controllable process. Leveraging the drastic variation in inhibitory effects at different pH levels, precise separation of bastnaesite and fluorite can be achieved, significantly improving concentrate quality and recovery rate. Simultaneously, calcite can be recovered, resulting in high resource utilization and significant economic and environmental benefits.

[0007] The technical solution of the present invention is as follows: a sequential flotation separation method based on sulfanilamide phosphonic acid derivatives, comprising the following steps: Step 1, roughing and waste disposal stage: Adjust the pH of the mixed pulp containing fluorite, cerium carbonate, fluorite and calcite to 7.0~9.0, add sulfaphosphonic acid derivative inhibitors and collectors for the first flotation to obtain froth products containing fluorite and cerium carbonate, as well as tailings products mainly composed of calcite. Step 2, Fine Selection and Separation Stage: The froth product obtained in Step 1 is subjected to a second flotation. By adjusting the pH value of the slurry, bastnaesite and fluorite are separated to obtain bastnaesite concentrate and middlings products mainly composed of fluorite.

[0008] The inhibitor is a sulfanilamide phosphonic acid derivative with the structural formula HO3S-CH2(n)-N(CH2PO3H2)(CH2COOH), and its molecular structure contains phosphonic acid group, carboxylic acid group and sulfonic acid group at the same time.

[0009] Preferably, n=0.

[0010] In step 1, the mass of inhibitor added per liter of mixed slurry is 80 mg to 150 mg.

[0011] The collector is a hydroxamic acid collector, and the mass of the collector added per liter of mixed slurry is 10 mg to 50 mg.

[0012] The hydroxamic acid collector is H2O5.

[0013] In step 2, the separation of fluorite and bastnaesite is achieved simply by raising the pH of the slurry to 10.5-11.0, thereby increasing the inhibitory effect of the inhibitor on fluorite in this strongly alkaline range.

[0014] The obtained fluorocarbon cerium concentrate has a Ce grade >25%; the F recovery rate in the middlings exceeds 55%; and the CaO grade in the tailings is >50%.

[0015] The application of sulfaphosphonic acid derivatives as flotation inhibitors in a sequential flotation separation method for fluorocarbon cerium ore. The sulfaphosphonic acid derivatives, as inhibitors, exhibit different affinity for calcareous minerals at different pH values, thereby achieving sequential inhibition of calcareous minerals.

[0016] The beneficial effects of this invention are: (1) The inhibitor and sequential flotation separation method provided by this invention achieves differentiated control of the floatability of bastnaesite, fluorite, and calcite through precise stepwise pH regulation. Under weakly alkaline conditions, the sulfanilamide phosphonic acid derivative inhibitor selectively inhibits calcite while allowing bastnaesite and fluorite to float effectively. Subsequently, under strongly alkaline conditions, the inhibitory ability of the sulfanilamide phosphonic acid derivative inhibitor on fluorite increases dramatically, thereby achieving efficient and clean separation of bastnaesite and fluorite. This characteristic fundamentally solves the technical bottleneck of poor selectivity and low separation efficiency caused by the similar surface properties of fluorite and bastnaesite.

[0017] (2) Compared with traditional processes that require multiple inhibitors, activators, and complex procedures, this invention uses only one core inhibitor and a simple "two-step pH control method" to achieve sequential separation of the three minerals. This process eliminates the need for frequent switching or addition of multiple reagents, significantly reducing reagent costs and operational complexity, and avoiding interference between multiple reagents, thus improving the stability of process control. Furthermore, the streamlined reagent regimen is beneficial for subsequent wastewater treatment and is environmentally friendly.

[0018] (3) This invention can not only obtain high-grade bastnaesite concentrate, but also simultaneously obtain economically valuable fluorite concentrate and calcite products in the same process. This process transforms fluorite and calcite, which are traditionally difficult to process or are discarded as tailings, into marketable products, greatly enhancing the overall economic value of the ore, maximizing the recovery of rare earth resources and associated calcium resources, and achieving full-component recovery, which is in line with the development concept of green mines and circular economy. Attached Figure Description

[0019] Figure 1 The results of flotation tests of bastnaesite with fluorite and calcite under different inhibitor dosages are shown. Figure 2The results of flotation tests of bastnaesite with fluorite and calcite under different collector dosages are shown. Figure 3 The results of flotation tests of bastnaesite with fluorite and calcite under different pH conditions; Figure 4 The results are from a stepwise flotation test of a three-phase artificially mixed ore. Figure 5 This is a flowchart of a single-mineral flotation test. Figure 6 Flowchart of a stepwise flotation test for ternary artificially mixed ores; Figure 7 The results of flotation tests of physically compounded inhibitors on bastnaesite with fluorite and calcite under different pH conditions; Figure 8 The results of flotation tests on bastnaesite with fluorite and calcite using different structure inhibitors are presented. Detailed Implementation

[0020] This invention provides a sequential flotation separation method based on sulfanilamide phosphonic acid derivatives for the efficient recovery of valuable components from rare earth ores containing fluorocarbon cerium ore, fluorite, and calcite.

[0021] The core of this method lies in employing a sulfaphosphonic acid derivative with the structural formula HO3S-CH2(n)-N(CH2PO3H2)(CH2COOH), where n = 0, 1, or 2. Preferably, the sulfaphosphonic acid derivative (CPMS) with n = 0 is selected as the most selective inhibitor. The simultaneous presence of phosphonic acid, carboxylic acid, and sulfonic acid groups in this type of inhibitor molecule allows it to selectively act on different mineral surfaces according to changes in the pH environment of the slurry. Furthermore, the rigidity and strong electronic effect resulting from the direct connection of the sulfonic acid group to the nitrogen atom give CPMS unique pH responsiveness.

[0022] As the chain length increases, the methylene group partially blocks the strong electron-withdrawing effect of the sulfonic acid group, and the molecular flexibility increases. The molecule can more easily adjust the spatial positions of the phosphonic acid group and the carboxylic acid group by rotating the C / C bond of the methylene group to better match the Ca on the fluorite surface. 2+ The arrangement of these elements enhances their ability to suppress fluorite and calcite, ultimately evolving into a highly effective inhibitor of calcium-containing minerals.

[0023] The core advantage of this inhibitor lies in the fact that three polar groups are covalently fixed to the same molecular backbone, forming a multifunctional unit with a relatively fixed spatial configuration. This covalent connection determines its unique pH-responsive behavior and mineral selectivity, which cannot be simulated by simple mixtures of groups. In covalently linked molecules, the relative positions of intramolecular functional groups are fixed, allowing for the formation of a well-defined adsorption conformation during adsorption. This directional assembly is key to the inhibitor's ability to both adsorb and provide strong hydrophilicity. Furthermore, the dissociation states of each group influence each other, and intramolecular electronic effects give the entire molecule a synergistic and holistic pH-responsive behavior. In addition, in the covalent molecule, the sulfonic acid group is designed as a functional group that does not participate in strong adsorption and always points towards the solution, providing continuous and stable hydrophilicity and electrostatic repulsion. This division of labor between the "anchoring group and the functional group" is the core of molecular design.

[0024] In physical mixtures, each component independently competes for adsorption sites on the mineral surface, resulting in a disordered and uneven mixed adsorption layer that cannot form a dense hydrophilic barrier. Furthermore, each component responds independently to pH changes, failing to produce a synergistic effect of overall molecular conformational change with pH, ​​thus preventing the realization of the unique pH-switching behavior of fluorite surfaces.

[0025] A typical separation process includes the following steps: First, the raw ore or pretreated slurry is adjusted to a weakly alkaline environment, preferably with a pH of 7.0 to 9.0; a measured amount of the aforementioned inhibitor is added, ranging from 80 mg / L to 150 mg / L; simultaneously, a hydroxamic acid collector, H2O5, is added, ranging from 10 mg / L to 50 mg / L. Under these conditions, a first flotation is performed, where calcite is selectively inhibited, and bastnaesite and some fluorite are collected into the froth product, thus achieving separation from the calcite tailings. Subsequently, the froth product is transferred to a second flotation system, where the slurry pH is adjusted to a more alkaline range, preferably from 10.5 to 11. With little or no addition of the aforementioned inhibitor and collector, fluorite is strongly inhibited while bastnaesite maintains good floatability, thereby obtaining high-grade bastnaesite concentrate and fluorite concentrate through a second flotation.

[0026] Example 1: In this example, the inhibitor CPMS, collector H2O5, and pH adjusters (NaOH, HCl) were all mixed with deionized water to prepare a 0.3% solution, along with industrial grade No. 2 oil. 2 g of pure bastnaesite, fluorite, or calcite minerals were placed in a flotation cell with 30 mL of deionized water and stirred for 2 min. After thorough mixing, the pH of the pulp was adjusted using the pH adjuster. Then, the inhibitor CPMS was added and stirred for 2 min. Next, 50 mg / L of collector H2O5 was added and stirred for 2 min. Finally, No. 2 oil was added, and after stirring for 1 min, aeration was performed, and the froth product was collected. The flotation time was 2-3 min, and the flotation machine speed was set to 1700-1900 r / min. The final product was froth concentrate and tailings. The flotation test results are as follows: Figure 1 As shown.

[0027] Depend on Figure 1 The study investigated the effect of increasing the inhibitor concentration from 0 mg / L to 150 mg / L under fixed pH 9.0 and collector H2O5 concentration of 50 mg / L. The results showed that the yield of bastnaesite remained above 90%, almost unaffected by changes in inhibitor concentration, while calcite and fluorite exhibited more significant inhibitory effects. Calcite was more sensitive to changes in inhibitor concentration, with its yield decreasing to 3.16% at 80 mg / L; while fluorite's yield decreased to 8.30% at an inhibitor concentration of 120 mg / L.

[0028] Example 2: In this example, the inhibitor CPMS, collector H2O5, and pH adjuster (NaOH, HCl) were all mixed with deionized water to prepare a 0.3% solution, along with industrial grade No. 2 oil. 2 g of pure bastnaesite, fluorite, or calcite minerals were placed in a flotation cell with 30 mL of deionized water and stirred for 2 min. After mixing evenly, the pH of the pulp was adjusted using the pH adjuster. Then, 120 mg / L of inhibitor CPMS was added and stirred for 2 min. Subsequently, collector H2O5 was added and stirred for another 2 min. No. 2 oil was added and stirred for 1 min. After aeration, the froth product was collected. The flotation time was 2-3 min, and the flotation machine speed was set to 1700-1900 r / min. Finally, froth concentrate and tailings in the cell were obtained.

[0029] Depend on Figure 2The effect of collector H2O5 dosage on mineral separation was investigated under the conditions of a fixed pulp pH of 9.0 and a depressant dosage of 120 mg / L. The results showed that bastnaesite maintained good floatability within a concentration range of 10 mg / L to 100 mg / L. In contrast, the flotation behavior of fluorite and calcite exhibited a highly synchronous concentration dependence. When the collector dosage did not exceed 50 mg / L, the yields of both were effectively suppressed to below 10%; however, when the dosage increased to 80 mg / L or even higher, the yields rose to 35.64% and 46.31%, respectively, demonstrating that excessive collector significantly weakens the selectivity of the depressant.

[0030] Example 3: In this example, the inhibitor CPMS, collector H2O5, and pH adjusters (NaOH, HCl) were all mixed with deionized water to prepare a 0.3% solution, along with industrial grade No. 2 oil. 2 g of pure bastnaesite, fluorite, or calcite minerals were placed in a flotation cell with 30 mL of deionized water and stirred for 2 min. After thorough mixing, the pH of the pulp was adjusted using the pH adjuster. Then, 50 mg / L of the inhibitor CPMS was added and stirred for 2 min. Next, 50 mg / L of the collector H2O5 was added and stirred for another 2 min. Finally, No. 2 oil was added and stirred for 1 min. Aeration was then performed, and the froth product was collected. The flotation time was 2-3 min, and the flotation machine speed was set to 1700-1900 r / min. The final product was froth concentrate and tailings. The flotation test results are as follows: Figure 3 As shown.

[0031] Depend on Figure 3 The results showed that the concentrations of both collector and depressant were fixed at 50 mg / L, and the effect of pH on mineral separation performance was investigated within the range of 7.0 to 12.0. Fluorocarbonate cerium ore exhibited good floatability across a wide pH range of 7.0 to 11.0, with a stable yield exceeding 90%. Calcite was effectively suppressed throughout the entire pH range, while the flotation behavior of fluorite revealed a key pH-dependent inflection point. When the pH was below 9.03, the yield reached as high as 87.14%; however, when the pH rose to between 10.01 and 10.64, the yield rapidly decreased to 13.88%, laying a theoretical foundation for sequential flotation through stepwise pH control.

[0032] Example 4: This example achieves efficient separation by precisely adjusting the pH of the flotation system and utilizing the inherent differences in the surface electrical properties of minerals. In this example, the inhibitor CPMS, collector H2O5, and pH adjusters (NaOH, HCl) are all mixed with deionized water to prepare a 0.3% solution, along with industrial-grade No. 2 oil. 2 g of artificially mixed ore (a 1:1:1 ratio of bastnaesite, fluorite, and calcite) is mixed with 30 mL of deionized water in a flotation cell and stirred for 2 min. After thorough mixing, the pulp pH is adjusted to 9±0.3, and 50 mg / L of the inhibitor CPMS is added and stirred for 2 min. Then, 50 mg / L of the collector H2O5 is added and stirred for another 2 min. Finally, No. 2 oil is added and stirred for 1 min. Aeration is then performed, and the froth product is collected. The product in the cell is the tailings. The froth product is placed in the flotation cell, the pH is adjusted to 10.5, and No. 2 oil is added for secondary cleaning, ultimately yielding froth concentrate and middlings. The flotation test results are as follows: Figure 4 As shown.

[0033] Experimental results show that through a two-step flotation process, the final bastnaesite concentrate obtained has a Ce grade as high as 28.20% and a yield of 23.30%, while its CaO grade is significantly reduced to 5.76%, demonstrating extremely strong impurity removal capabilities. Simultaneously, the fluorite produced in the second flotation step has an F grade of 29.01% and a recovery rate of 55.55%, achieving effective enrichment of fluorite. The tailings mainly consist of calcite, with a CaO grade of 56.05%, close to the theoretical grade of calcite, and the Ce loss rate in the tailings is only 12.79%. This example demonstrates that, within a specific pH window, the collector can exhibit extremely high selectivity for bastnaesite, while calcite and fluorite are naturally inhibited, resulting in a simple process and excellent separation performance.

[0034] Comparative Example 1: This comparative example prepared an inhibitor solution containing phosphoric acid, sulfonic acid, and carboxylic acid groups by compounding the raw materials (aminosulfonic acid, phosphorous acid, and chloroacetic acid) of the synthetic reagent in a 1:1:1 ratio using a simple physical mixing method. In this comparative example, the physical mixing inhibitor, collector H2O5, pH adjuster (NaOH, HCl) were all mixed with deionized water to prepare a 0.3% solution, along with industrial grade No. 2 oil. 2 g of pure bastnaesite, fluorite, or calcite minerals were mixed with 30 mL of deionized water in a flotation cell and stirred for 2 min. After thorough mixing, the pulp pH was adjusted to the specified conditions, and 50 mg / L of the physical mixing inhibitor was added and stirred for 2 min. Then, 50 mg / L of collector H2O5 was added and stirred for another 2 min. Finally, No. 2 oil was added and stirred for 1 min. Aeration was then performed, and the frothy concentrate product was collected. The product in the cell was the tailings. The flotation test results are as follows: Figure 7 As shown.

[0035] Experimental results showed that at pH 9, the flotation rates of bastnaesite, fluorite, and calcite were 93.21%, 94.84%, and 82.06%, respectively. At pH 10.5, the flotation rates of bastnaesite, fluorite, and calcite remained almost unchanged at 91.03%, 90.15%, and 80.72%, respectively. This indicates that inhibitors obtained solely through physical mixing are insufficient for the selective separation of bastnaesite, fluorite, and calcite. The selective function of this inhibitor is achieved through a covalently bonded, holistic structure with specific structure and function, and its performance far surpasses that of simple physical combinations.

[0036] Comparative Example 2: This comparative example selected three sulfaphosphonic acid derivatives with the structural formula HO3S-CH2(n)-N(CH2PO3H2)(CH2COOH) as inhibitors, where n=0, 1, and 2. In this comparative example, the three inhibitors, collector H2O5, and pH adjusters (NaOH, HCl) were mixed with deionized water to prepare a 0.3% solution, along with industrial-grade No. 2 oil. 2 g of pure bastnaesite, fluorite, or calcite minerals were placed in a flotation cell with 30 mL of deionized water and stirred for 2 min. After thorough mixing, the pulp pH was adjusted to pH=9±0.3. 50 mg / L of inhibitor was added and stirred for 2 min, followed by 50 mg / L of collector H2O5 and stirring for another 2 min. Finally, No. 2 oil was added and stirred for 1 min. Aeration was then performed, and the frothy concentrate product was collected. The product in the cell was tailings. The flotation test results are as follows: Figure 8 As shown.

[0037] Experimental results show that when n=0, the flotation rate of fluorite is 88.26%. As n increases to 1 and 2, the flotation rate of fluorite reaches 35.25% and 12.34%, respectively. The inhibitor molecules can achieve a stronger inhibitory effect on fluorite by adjusting the spatial position of the polar groups, leading to the disappearance of the pH response mechanism. Stepwise pH control for sequential flotation can only be achieved when n=0. When n=1 and 2, this type of sulfaphosphonic acid derivative is more suitable for the beneficiation and purification steps of fluorocarbonate cerium ore without considering gangue mineral recovery.

Claims

1. A sequential flotation separation method based on sulfanilamide phosphonic acid derivatives, characterized in that, Includes the following steps: Step 1, roughing and waste disposal stage: Adjust the pH of the mixed pulp containing fluorite, cerium carbonate, fluorite and calcite to 7.0~9.0, add sulfaphosphonic acid derivative inhibitors and collectors for the first flotation to obtain froth products containing fluorite and cerium carbonate, as well as tailings products mainly composed of calcite. Step 2, Fine Selection and Separation Stage: The froth product obtained in Step 1 is subjected to a second flotation. By adjusting the pH value of the slurry, bastnaesite and fluorite are separated to obtain bastnaesite concentrate and middlings products mainly composed of fluorite.

2. The sequential flotation separation method based on sulfanilamide phosphonic acid derivatives according to claim 1, characterized in that, The inhibitor is a sulfanilamide phosphonic acid derivative with the structural formula HO3S-CH2(n)-N(CH2PO3H2)(CH2COOH), and its molecular structure contains phosphonic acid group, carboxylic acid group and sulfonic acid group at the same time.

3. The sequential flotation separation method based on sulfanilamide phosphonic acid derivatives according to claim 2, characterized in that, n=0。 4. The sequential flotation separation method based on sulfanilamide phosphonic acid derivatives according to claim 1, characterized in that, In step 1, the mass of inhibitor added per liter of mixed slurry is 80 mg to 150 mg.

5. The sequential flotation separation method based on sulfanilamide phosphonic acid derivatives according to claim 1, characterized in that, The collector is a hydroxamic acid collector, and the mass of the collector added per liter of mixed slurry is 10 mg to 50 mg.

6. The sequential flotation separation method based on sulfanilamide phosphonic acid derivatives according to claim 5, characterized in that, The hydroxamic acid collector is H2O5.

7. The sequential flotation separation method based on sulfanilamide phosphonic acid derivatives according to claim 1, characterized in that, In step 2, the separation of fluorite and bastnaesite is achieved simply by raising the pH of the slurry to 10.5-11.0, thereby increasing the inhibitory effect of the inhibitor on fluorite in this strongly alkaline range.

8. The sequential flotation separation method based on sulfanilamide phosphonic acid derivatives according to claim 1, characterized in that, The obtained fluorocarbon cerium concentrate has a Ce grade >25%; the F recovery rate in the middlings exceeds 55%; and the CaO grade in the tailings is >50%.

9. The use of sulfanilamide phosphonic acid derivatives as flotation depressants in the sequential flotation separation method according to any one of claims 1-8, characterized in that, The sulfaphosphonic acid derivative, acting as an inhibitor, exhibits varying affinity for calcium minerals at different pH values, thereby achieving sequential inhibition of calcium-containing minerals.

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