Phosphate tailing collecting agent and application thereof in phosphate tailing flotation

Abstract

The invention discloses a phosphate tailing collecting agent. The phosphate tailing collecting agent is formed by compounding o-methylbenzohydroxamic acid and sodium laurate according to the mass ratio of 1: 3-1: 6. The o-methylbenzohydroxamic acid is prepared by the following steps: adding sodium hydroxide into an aqueous solution of hydroxylamine hydrochloride in batches, and fully reacting to generate free hydroxylamine; raising the temperature to 40-60 DEG C, slowly dropwise adding methyl o-toluate to react for 3-6 hours, and acidizing the obtained reaction product with hydrochloric acid to obtain a crude product of o-methylbenzohydroxamic acid; purifying to obtain o-methylbenzohydroxamic acid; the novel hydroximic acid compound is synthesized and compounded with a traditional fatty acid collecting agent, the mixed collecting agent with the phosphate tailing collecting capacity and selectivity exceeding the expectation is obtained, and the problems that the fatty acid collecting agent is poor in selectivity and the hydroximic acid collecting agent is high in cost are solved.

Description

Technical Field

[0001] This invention belongs to the field of mineral processing technology, specifically relating to a phosphorus tailings collector and its application. Background Technology

[0002] Phosphate rock is an important non-metallic mineral resource and a major raw material for the production of phosphate fertilizers and phosphate chemical products. During the beneficiation process, a large amount of phosphate resources are lost in tailings. my country's phosphate tailings stockpile exceeds one billion tons, with tens of millions of tons added annually. This massive stockpile not only wastes resources but also poses environmental and safety risks. With the increasing depletion of high-grade phosphate rock resources, recovering phosphate minerals from previously stockpiled phosphate tailings has become increasingly important.

[0003] After beneficiation, the composition and surface properties of phosphate tailings are more complex, with the following mineral characteristics: low content of valuable minerals, with phosphorus grades mostly below 6%; insufficient liberation of individual minerals, with valuable and impurity minerals intermingled, increasing the difficulty of separating them; and severe surface contamination, with a large amount of impurity ions or residual reagents adsorbed on the surface, altering the mineral's floatability and making it difficult for traditional reagents to accurately identify target minerals. These characteristics all render traditional collectors ineffective, and their limited ability to distinguish between phosphate and gangue minerals further hinders the improvement of concentrate grades. Conventional methods for treating phosphate tailings, such as Chinese patent CN102600965A which involves high-temperature calcination and Chinese patent CN111484020A which uses various chemical reagents to leach all elements in the phosphate tailings, can fully utilize all elements in the phosphate tailings, but they require a large amount of energy and chemical reagents, resulting in high costs and making them unsuitable for large-scale use.

[0004] Chinese patent CN 111135947 A discloses a process for treating collophane flotation tailings, specifically a method for recovering phosphorus from collophane tailings through multiple flotation processes, achieving a P2O5 grade of 8.0%~13.0%. Chinese patent CN114653478 A discloses a method for recovering phosphorus concentrate from low-phosphorus collophane tailings, achieving a P2O5 grade of 6.0%~9.0%. While both methods yield good concentrate indicators, the range of phosphorus tailings they process is above 6%, making it difficult to handle tailings with low phosphorus grades. Furthermore, both patents use traditional fatty acid reagents, requiring pre-flotation and multiple reagent-added flotation processes, along with multiple grinding operations, increasing process costs. For tailings with relatively high grades, the economic benefits might cover the costs due to the higher availability of usable elements; however, for tailings with very low grades, the costs may not be offset.

[0005] The key to recycling phosphate tailings using flotation lies in the selection of collectors. Traditional phosphate rock flotation collectors are mainly fatty acid-based. These collectors achieve flotation by chemically adsorbing or reacting with calcium particles on the surface of phosphate minerals through carboxyl groups (-COOH), and then adhering to the floating air bubbles through their long-chain hydrophobic ends. However, the abundant carbonate gangues in tailings are also rich in calcium ions, causing the collector to adsorb indiscriminately onto both phosphate and carbonate minerals, resulting in poor flotation selectivity and low concentrate grades. Furthermore, due to its poor low-temperature performance, heated flotation is often required, increasing energy consumption.

[0006] Hydroxime acid collectors are typical chelating collectors. The oxygen and nitrogen atoms in their molecules can form stable five-membered ring chelates with metal ions on the mineral surface. This chelation effect has stronger specificity for certain metal ions, thus exhibiting better selectivity for gangues such as carbonates than fatty acid collectors. Their high synthesis cost makes their unit price far higher than that of fatty acid collectors. When processing raw ore, the economic benefits of improving concentrate grade and recovery rate may cover their costs. However, when dealing with tailings with a P2O5 grade of only 3%~6% or even lower, the value of the recovered phosphate concentrate may not be enough to offset the cost of the reagents themselves, making the entire reprocessing project economically unfeasible. Summary of the Invention

[0007] This invention provides a mixed collector for phosphorus tailings. By synthesizing a new hydroxamic acid compound and compounding it with a traditional fatty acid collector, a mixed collector with unexpectedly high collection capacity and selectivity for phosphorus tailings is obtained, overcoming the problems of poor selectivity of fatty acid collectors and high cost of hydroxamic acid collectors.

[0008] To achieve the above objectives, the following technical solution is adopted: A phosphorus tailings collector is prepared by compounding o-methylbenzohydroxyxamic acid and sodium laurate in a mass ratio of 1:3 to 1:6; The molecular structure of the o-methylbenzohydroxyoxime acid is as follows: .

[0009] According to the above scheme, the preferred ratio is 1:4. At this ratio, the two collectors can produce the best synergistic effect.

[0010] According to the above scheme, the o-methylbenzylhydroxamic acid is prepared in the following manner: (1) Sodium hydroxide is added in batches to an aqueous solution of hydroxylamine hydrochloride to allow it to react fully and generate free hydroxylamine; (2) The temperature was raised to 40~60℃ and methyl o-methylbenzoate was slowly added dropwise for 3~6h. The reaction product was acidified with hydrochloric acid to obtain crude o-methylbenzohydroxyxamic acid. (3) Purification treatment yielded o-methylbenzylhydroxyxamic acid.

[0011] According to the above scheme, the molar ratio of the raw materials methyl o-methylbenzoate, hydroxylamine hydrochloride, and sodium hydroxide is 1:(1.1~1.4):(2.2~2.8). The optimized scheme is 1:(1.15-1.2):(2.3-2.4).

[0012] In the optimized scheme, step (1) involves adding sodium hydroxide in batches over half an hour at 25-35°C.

[0013] In the optimized scheme, step (2) involves heating to 45~55℃ and reacting for 4~5 hours, with the hydrochloric acid concentration being 1 mol / L.

[0014] In the optimized scheme, the purification process in step (3) includes: dissolving the obtained crude o-methylbenzohydroxyxamic acid in water at 50~70℃, filtering while hot, cooling and crystallizing, and repeating the purification 2~3 times to obtain high-purity o-methylbenzohydroxyxamic acid.

[0015] In the application of the above-mentioned phosphorus tailings collector in flotation, the dosage of the phosphorus tailings collector is 0.8~2.0 kg / t based on the dry weight of the raw ore.

[0016] In the optimized scheme, the dosage of the phosphorus tailings collector is 1.4~1.6 kg / t based on the dry weight of the raw ore.

[0017] In a more optimized scheme, a frother, terpineol, is added during the flotation process of phosphorus tailings, with a dosage of 0.2 to 1 wt% of the phosphorus tailings collector, preferably 0.5%.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: To address the poor selectivity of traditional flotation reagents, a novel hydroxamic acid reagent was synthesized. A methyl group was introduced at the ortho position of benzohydroxamic acid. Due to the steric hindrance effect of the methyl group, non-specific binding was reduced, thus enhancing its selectivity. At the same time, the hydrophobicity of the entire molecule was enhanced, thereby strengthening its flotation ability and obtaining higher-grade phosphate concentrate.

[0019] To address the poor flotation performance and high cost of single hydroxamic acids, resulting in low economic efficiency, fatty acid-based reagents were introduced in combination. To solve the problem of conventional flotation requiring heating, sodium laurate was chosen for the combination, reducing the need for flotation temperature and enabling effective flotation at room temperature, thus saving the heating energy required by traditional fatty acid collectors. Simultaneously, the shorter carbon chain of sodium laurate weakens its non-specific binding with other minerals, enhancing the selectivity of the reagent.

[0020] Sodium lauryl precipitate is an anionic collector that can adhere to the surfaces of apatite and dolomite through physical adsorption. o-Toluene-2-hydroxyxamic acid is a chelating collector; its O and N atoms can donate lone pairs of electrons to form stable five-membered ring chelates with metal ions. Under acidic conditions, free H₂PO₄ in solution... - Ions preferentially adsorb onto the calcium sites on the apatite surface, thus hindering the approach and adsorption of the collector. Meanwhile, the active sites of dolomite are exposed, allowing o-methylbenzyl hydroxamic acid to specifically chelate with it. Through intermolecular forces, it interacts with sodium laurate molecules also adsorbed on the mineral surface. This is equivalent to forming a more stable and hydrophobic mixed adsorption layer on the dolomite surface, significantly enhancing the dolomite's buoyancy.

[0021] Combining inexpensive fatty acid collectors with highly selective hydroxamic acids in a certain proportion can achieve a synergistic effect, where "1+1>2". The inexpensive collector serves as the main component, ensuring basic harvesting capacity; the high-priced, high-efficiency collector acts as a "guide" or "enhancer," improving the overall selectivity of the combined agent. Simultaneously, a small amount of frother can be introduced to increase the foaming ability of the agent, thereby improving efficacy and reducing the total dosage. Detailed Implementation

[0022] The following embodiments further illustrate the technical solution of the present invention, but are not intended to limit the scope of protection of the present invention.

[0023] A specific embodiment provides a method for preparing o-methylbenzohydroxyxamic acid: (1) Prepare raw materials, using methyl o-toluene, hydroxylamine hydrochloride and sodium hydroxide as raw materials, with a molar ratio of 1:(1.1~1.4):(2.2~2.8).

[0024] (2) To prepare a free hydroxylamine solution, dissolve hydroxylamine hydrochloride in distilled water, heat it in a water bath at 30°C, add the required sodium hydroxide in batches over half an hour, and then wait for it to react fully to generate free hydroxylamine.

[0025] (3) To prepare o-methylbenzoic acid, methyl methylbenzoate was slowly added dropwise to the solution obtained in step (2), and the solution was heated in an oil bath at a constant temperature of 40~60℃ for 3~6h. After the reaction was completed, the resulting reaction solution was acidified with 1mol / L hydrochloric acid to obtain crude o-methylbenzoic acid.

[0026] (4) Dissolve the crude o-methylbenzohydroxyxamic acid obtained in step (3) in water at 50~70℃, then filter while hot, cool and crystallize, and repeat the purification process 2~3 times to obtain high-purity o-methylbenzohydroxyxamic acid.

[0027] The specific reaction equation is shown below:

[0028]

[0029] A specific embodiment provides a phosphorus tailings collector, which is prepared by compounding the above-mentioned o-methylbenzyl hydroxamic acid and sodium laurate in a mass ratio of 1:3 to 1:6.

[0030] A specific implementation also provides a flotation method for phosphorus tailings, including the following steps: Raw material preparation: Prepare the phosphate tailings sample into a slurry, controlling the slurry concentration to 20wt%~35wt%; Preparation of collector solution: Prepare a 1-10 wt% aqueous solution by combining the phosphorus tailings collector and the foaming agent terpineol; Stirring pretreatment: Thoroughly stir the slurry in the flotation cell to ensure uniform dispersion; Addition of adjusting agent: Add sulfuric acid to adjust the pH of the slurry to a weakly acidic range of 4-6.5; Inhibitor addition: Inhibitors (such as sodium pyrophosphate) can be selectively added. Collector addition: Add the mixed collector solution and stir vigorously for 1-2 minutes to ensure the agent reacts fully with the mineral; the amount of collector used is 0.8-2.0 kg / t based on the dry weight of the raw ore. Flotation separation: Perform flotation operations to scrape off the foam product.

[0031] The phosphorus tailings used in this specific implementation are discarded phosphorus tailings piled up in a tailings dam by a company in Hubei Province. The specific content of each component is shown in Table 1. Unless otherwise specified, all other raw materials were obtained through commercial purchase.

[0032] Table 1

[0033] Example 1 Add 240g of tailings sample to a 0.75L flotation cell, and adjust the slurry with tap water to prepare a 30% concentration slurry. Adjust the pH to 4.5 and stir for 2 minutes. Mix o-toluidine hydroxamic acid and sodium lauryl acid at a ratio of 1:4, with a total dosage of 1.5kg / t, and add 75g / t of terpineol to prepare a 2% aqueous solution. Add this solution to the flotation cell, stir for 3 minutes, aerate and bubble, and then float for 5 minutes.

[0034] Example 2 Add 240g of tailings sample to a 0.75L flotation cell, and adjust the slurry with tap water to prepare a 30% concentration slurry. Adjust the pH to 4.5 and stir for 2 minutes. Mix o-toluidine hydroxamic acid and sodium lauryl acid at a ratio of 1:4, with a total dosage of 1kg / t, and add 50g / t of terpineol to prepare a 2wt% aqueous solution. Add this solution to the flotation cell, stir for 3 minutes, aerate and bubble, and then float for 5 minutes.

[0035] Example 3 Add 280g of tailings sample to a 0.75L flotation cell, and adjust the slurry with tap water to prepare a 35% concentration slurry. Adjust the pH to 4.5 and stir for 2 minutes. Mix o-toluidine hydroxamic acid and sodium lauryl acid at a ratio of 1:4, with a total dosage of 1.5kg / t, and add 75g / t of terpineol to prepare a 2% aqueous solution. Add this solution to the flotation cell, stir for 3 minutes, aerate and bubble, and then float for 5 minutes.

[0036] Example 4 Add 240g of tailings sample to a 0.75L flotation cell, and adjust the slurry with tap water to prepare a 30% concentration slurry. Adjust the pH to 5 and stir for 2 minutes. Mix o-toluidine hydroxamic acid and sodium lauryl acid at a ratio of 1:4, with a total dosage of 1.5kg / t, and add 75g / t of terpineol to prepare a 2% aqueous solution. Add this solution to the flotation cell, stir for 3 minutes, aerate and bubble, and then float for 5 minutes.

[0037] Example 5 Repeat Example 1, mixing o-methylbenzohydroxyxamic acid and sodium lauryl laurate in a 1:3 ratio, with the rest remaining unchanged.

[0038] Example 6 Repeat Example 1, mixing o-methylbenzyl hydroxamic acid and sodium lauryl laurate in a 1:5 ratio, with the rest remaining unchanged.

[0039] Example 7 Repeat Example 1, mixing o-methylbenzyl hydroxamic acid and sodium lauryl acid in a 1:6 ratio, with the rest remaining unchanged.

[0040] Comparative Example 1 Repeat Example 1, mixing o-methylbenzyl hydroxamic acid and sodium lauryl laurate in a 1:2 ratio, with the rest remaining unchanged.

[0041] Comparative Example 2 Repeat Example 1, mixing o-methylbenzyl hydroxamic acid and sodium lauryl laurate in a 1:7 ratio, with the rest remaining unchanged.

[0042] Comparative Example 3 Repeat Example 1, except that the addition of terpineol is omitted, and everything else remains the same.

[0043] Comparative Example 4 Repeat Example 1, except that sodium lauryl ester is replaced with sodium oleate, and everything else remains the same.

[0044] Comparative Example 5 Repeat Example 1, except that o-methylbenzohydroxyxamic acid is replaced with benzylhydroxyxamic acid, and the rest remains the same.

[0045] The flotation concentrate and tailings of the above embodiments and comparative examples were weighed after treatment, and the data are shown in Table 2.

[0046] Table 2

[0047] In Comparative Examples 1 and 2, the ratio of o-toluidine hydroxamic acid to sodium laurate was outside the scope of the technical solution, resulting in poor performance. When there was a higher proportion of sodium laurate, although the adsorption layer was thicker, it was mainly due to weak physical adsorption of sodium laurate. Its selectivity and stability were inferior to the mixed layer formed by co-adsorption with hydroxamic acid. Furthermore, excess sodium laurate formed micelles, preventing effective adsorption onto the mineral surface and leading to a decrease in the actual effective collector concentration. When there was a higher proportion of o-toluidine hydroxamic acid, adsorption was mainly chelate adsorption. While this enhanced its adsorption capacity, when there was an excess, the excess hydroxamic acid molecules might physically adsorb onto the already hydrophobic mineral surface with their hydrophilic groups facing the aqueous phase. This is equivalent to covering the hydrophobic surface with a hydrophilic film, weakening its hydrophobicity and making it difficult for bubbles to adhere.

[0048] Comparative Example 3, without the addition of terpineol, performed poorly. Terpineol is a frother that adsorbs onto the air-water interface, significantly reducing the surface tension of water. This makes it easier to generate more numerous and smaller bubbles during mechanical agitation and aeration. Without its addition, a sufficiently thick and stable foam layer could not be formed on the surface of the flotation cell. Even if a small number of large bubbles were generated, they would quickly burst, failing to form a persistent foam capable of carrying mineral particles. Without stable foam, the vast majority of useful mineral particles, which had already reacted with the collector and had hydrophobic surfaces, could not be carried to the surface by the bubbles, or even if they were carried to the surface, they would fall back into the pulp due to foam collapse.

[0049] Comparative Example 4, which replaced sodium laurate with sodium oleate, performed poorly. Sodium oleate has an unsaturated carbon chain, which is highly hydrophobic, but its selectivity deteriorates. At the same time, the rigidity and size of the olefin chain may interfere with co-adsorption and destroy the synergistic effect. Moreover, sodium oleate has a low critical micelle concentration, making it prone to micelle formation and reducing the effective collector concentration.

[0050] Comparative Example 5, where o-methylbenzohydroxyxamic acid was replaced with benzohydroxyxamic acid, performed poorly. Benzohydroxyxamic acid, lacking the methyl group, exhibits reduced overall hydrophobicity compared to o-methylbenzohydroxyxamic acid. When co-adsorbed with sodium laurate on the dolomite surface, the hydrophobic association between o-methylbenzohydroxyxamic acid and the hydrocarbon chain of sodium laurate is weakened, resulting in a weaker hydrophobic barrier than that formed by o-methylbenzohydroxyxamic acid. Simultaneously, the methyl group, as an electron-donating group, slightly alters the electron cloud density of the benzene ring and the hydroxyxamic acid group through an inductive effect, enhancing the chelating ability of o-methylbenzohydroxyxamic acid.

Claims

1. A phosphorus tailings collector, characterized in that... It is prepared by compounding o-methylbenzohydroxyxamic acid and sodium laurylate in a mass ratio of 1:3 to 1:6; The molecular structure of the o-methylbenzohydroxyoxime acid is as follows: 。 2. The phosphorus tailings collector as described in claim 1, characterized in that... The optimized solution uses o-methylbenzohydroxyxamic acid and sodium lauryl acid in a mass ratio of 1:

4.

3. The phosphorus tailings collector as described in claim 1, characterized in that... The o-methylbenzohydroxyoxime acid is prepared in the following manner: (1) Sodium hydroxide is added in batches to an aqueous solution of hydroxylamine hydrochloride to allow it to react fully and generate free hydroxylamine; (2) The temperature was raised to 40~60℃ and methyl o-methylbenzoate was slowly added dropwise for 3~6h. The reaction product was acidified with hydrochloric acid to obtain crude o-methylbenzohydroxyxamic acid. (3) Purification treatment yielded o-methylbenzylhydroxyxamic acid.

4. The phosphorus tailings collector as described in claim 3, characterized in that... The molar ratio of the raw materials methyl o-methylbenzoate, hydroxylamine hydrochloride, and sodium hydroxide is 1:(1.1~1.4):(2.2~2.8).

5. The phosphorus tailings collector as described in claim 3, characterized in that... Step (1) Add sodium hydroxide in batches over half an hour at 25-35℃.

6. The phosphorus tailings collector as described in claim 3, characterized in that... Step (2) Heat to 45~55℃ and react for 4~5 hours, the concentration of hydrochloric acid is 1mol / L.

7. The phosphorus tailings collector as described in claim 3, characterized in that... The purification process in step (3) includes: dissolving the crude o-methylbenzohydroxyxamic acid in water at 50-70°C, filtering while hot, cooling and crystallizing, and repeating the purification process 2-3 times to obtain high-purity o-methylbenzohydroxyxamic acid.

8. The application of the phosphorus tailings collector according to claim 1 in the flotation of phosphorus tailings, characterized in that... The dosage of the phosphorus tailings collector is 0.8~2.0 kg / t based on the dry weight of the raw ore.

9. The application of the phosphorus tailings collector as described in claim 9 in the flotation of phosphorus tailings, characterized in that... In the flotation of phosphorus tailings, frother terpineol was also added, at a dosage of 0.2 to 1 wt% of the phosphorus tailings collector.

10. The application of the phosphorus tailings collector as described in claim 9 in the flotation of phosphorus tailings, characterized in that... The dosage of the phosphorus tailings collector is 1.4~1.6 kg / t based on the dry weight of the raw ore, and the dosage of the foaming agent terpineol is 0.5% of the dosage of the phosphorus tailings collector.

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