Preparation method of organic acid modified pyrite material and application thereof

Abstract

The application discloses a kind of small molecule organic acid modified pyrite materials and the method for activating persulfate degradation organic pollutants, the small molecule organic acid modified natural pyrite catalytic material can be obtained by direct ball milling method in the application, the agglomeration phenomenon of pyrite can be avoided, and the catalytic activity of natural pyrite is improved, and the prepared pyrite catalytic material can be applied to the treatment of organic pollutants, and is a kind of catalytic material with far-reaching application prospect.

Description

Technical Field

[0001] This invention belongs to the field of functional composite materials technology, specifically relating to a method for preparing organic acid-modified pyrite materials and their applications. Background Technology

[0002] In recent years, persulfate advanced oxidation technology has attracted widespread attention and has been extensively applied in organically contaminated soils and groundwater environments. Compared with oxidants such as ozone, hydrogen peroxide, and potassium permanganate, persulfate has advantages such as structural stability, convenient transportation, low cost, and high efficiency. Furthermore, persulfate activation generates a large amount of sulfate free radicals (SO42-). ·- It possesses a high redox potential (2.5-3.1 eV), as well as good selectivity and pH adaptability. Furthermore, SO42-... ·- It also generates hydroxyl radicals (·OH), which participate in the degradation of pollutants. Therefore, persulfate advanced oxidation technology shows great promise in the remediation of organic pollutants. However, persulfate has poor direct reactivity and requires activation. Common activation techniques include thermal activation, photoactivation, ultrasonic activation, alkali activation, and transition metal activation. Among these, transition metal activation has significant advantages due to its low cost, low energy consumption, and high activity. Iron and iron-containing compounds have attracted widespread attention due to their low toxicity, high efficiency, and low cost.

[0003] Pyrite is the most abundant sulfide metal mineral on Earth, its main component being FeS2. Due to its rich content of ferrous iron and reducing low-valence sulfur, it is widely used in advanced oxidation processes. Compared to zero-valent iron, pyrite is cheaper and more readily available. Pyrite can slowly release Fe(II) and activate persulfate to produce SO4. ·- Pyrite contains low-valence sulfur, which has strong reducing properties and can reduce high-valence Fe(III) to low-valence Fe(II). Therefore, pyrite can effectively activate persulfate and regulate the iron cycle in solution, promoting the continuous reaction. Pyrite particle size and specific surface area play important roles in its catalytic activity; therefore, reducing particle size is an important means to improve the catalytic effect of pyrite. Pyrite can be synthesized chemically to prepare micro / nano-structured pyrite. However, the chemical synthesis process is complex and costly, which is not conducive to large-scale production and application. Natural pyrite is inexpensive and readily available, but its catalytic effect is poor.

[0004] Currently, there are many methods for modifying natural pyrite, mostly focusing on direct ball milling or adding other active substances, such as ferric iron and organic acids, to the reaction system. Ball milling accumulates surface mechanical energy through grinding, compression, impact, friction, shearing, and stretching, promoting changes in the physicochemical properties and structure of the particles and improving their reactivity. However, during ball milling, agglomeration occurs as the pyrite particle size decreases. Agglomerated pyrite particles have a reduced specific surface area, fewer active reaction sites, and a lower pollutant removal efficiency. Directly adding macromolecular organic matter to the system also consumes the active free radicals generated during the reaction, hindering pollutant degradation. Therefore, the preparation of highly active pyrite materials using a green and environmentally friendly method is of significant environmental and economic importance. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for modifying pyrite materials with molecular organic acids and for activating persulfate to degrade organic pollutants. The introduction of small-molecule acids can improve ball milling efficiency, enhance the activity of pyrite, and further improve its catalytic performance. The prepared pyrite catalytic material can be applied to the treatment of organic pollutants.

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

[0007] A method for preparing organic acid-modified pyrite material includes the following steps:

[0008] S1 adds pyrite particles and organic acid into a ball mill jar, adds ball milling media into the ball mill jar, and performs ball milling under nitrogen conditions, adjusting the ball mill program to alternate between forward and reverse rotation;

[0009] S2 The material prepared in S1 is placed into a centrifuge tube and washed three times each with deoxygenated deionized water and anhydrous ethanol.

[0010] S3. The material obtained in S2 is placed in a vacuum drying oven, dried, and then filled with nitrogen. It is then stored at room temperature away from light to obtain organic acid modified pyrite material.

[0011] Preferably, as a preferred embodiment, in step S1, the pyrite is natural pyrite or artificially synthesized pyrite with a purity greater than 90%.

[0012] Preferably, as a preferred embodiment, in step S1, the organic acid includes, but is not limited to, oxalic acid, citric acid, ascorbic acid, hydroxylamine hydrochloride, tartaric acid, and protocatechuic acid, and the organic acid can be one or more used in combination.

[0013] Preferably, as a preferred embodiment, in step S1, the amount of organic acid added is 1-10% of the mass of pyrite.

[0014] Preferably, as a preferred embodiment, in step S2, the ball milling method includes, but is not limited to, dry ball milling and wet ball milling. Dry ball milling involves mixing small molecule acid with pyrite particles and then loading the mixture into a ball milling jar, followed by adding ball milling media to the jar for ball milling. Wet ball milling involves dissolving the small molecule acid in water and then loading the mixture into a ball milling jar, mixing it with pyrite particles, adding ball milling media, and then ball milling.

[0015] Preferably, as a preferred embodiment, in step S2, the ball mill includes, but is not limited to, a planetary ball mill, a vibratory ball mill, or a sand mill, and the ball mill program alternates between forward and reverse rotation.

[0016] Preferably, as a preferred embodiment, in step S2, the organic acid and pyrite are ball-milled and then washed. The washing sequence is to wash three times with distilled water and then three times with ethanol. After vacuum drying, the organic acid modified pyrite material is obtained.

[0017] Another object of the present invention is to provide the application of the organic acid modified pyrite material for degrading organic pollutants, including but not limited to chlorinated hydrocarbons, polycyclic aromatic hydrocarbons, petroleum hydrocarbons, antibiotics, dyes and other organic pollutants.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] (1) The organic acid modified pyrite material of the present invention can avoid the pyrite agglomeration phenomenon caused by direct ball milling and can improve the catalytic activity of pyrite.

[0020] (2) The preparation method of the present invention is simple, no waste liquid is generated during the preparation process, no dangerous gas is generated, the raw material cost is low, and it is safe to use.

[0021] (3) The organic acid modified pyrite material of the present invention can remove organic pollutants in the environment more efficiently. Attached Figure Description

[0022] Figure 1 The SEM image of the organic acid-modified pyrite material prepared according to the present invention is shown.

[0023] Figure 2 The study demonstrated the effect of organic acid-modified pyrite materials on catalyzing the degradation of chlorobenzene in soil by persulfate. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the 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. The specific embodiments described below further illustrate the present invention.

[0025] Unless otherwise specified, all chemical substances of this invention are commercially available.

[0026] I. Preparation Examples

[0027] 1. Example 1

[0028] A method for preparing ascorbic acid-modified pyrite material includes the following steps:

[0029] 25g of ascorbic acid and pyrite particles (20 mesh) in a mass ratio of 0.02:1 were added to a 500mL ball mill jar. Agate beads of 5mm, 8mm, and 10mm in size were added to the jar in a mass ratio of 6:3:1. Nitrogen gas was introduced into the jar, and after sealing, it was placed in a ball mill. The ball mill program was adjusted to alternate between forward rotation for 30 minutes, pause for 10 minutes, reverse rotation for 30 minutes, and pause for 10 minutes, at a milling speed of 300rpm for 10 hours. After milling, the material was removed under a nitrogen atmosphere. The prepared material was then placed in centrifuge tubes and washed three times each with deoxygenated deionized water and anhydrous ethanol. Next, the material was placed in a 65℃ vacuum drying oven and vacuum dried for 6 hours. After drying, the material was removed, purged with nitrogen gas, and stored at room temperature away from light to obtain ascorbic acid-modified pyrite material.

[0030] 2. Example 2

[0031] A method for preparing pyrite material modified with hydroxylamine hydrochloride includes the following steps:

[0032] A total of 25 g of hydroxylamine hydrochloride and pyrite particles (20 mesh) in a mass ratio of 0.02:1 were added to a 500 mL ball mill jar. Agate grinding beads (total mass of filling material in the jar: 200 g, mass ratio of large to small grinding beads: 1:3:6) were added. Nitrogen gas was introduced into the jar, and after sealing, it was placed in a ball mill. The milling speed was set to 300 rpm, and the milling time was 10 h. After milling, the material was removed under a nitrogen atmosphere. Under nitrogen protection, the grinding beads were separated from the milling product, and the mixture was washed three times with deionized water and three times with anhydrous ethanol. After vacuum drying, the hydroxylamine hydrochloride-modified pyrite material was obtained.

[0033] 3. Example 3

[0034] A method for preparing oxalic acid-modified pyrite material includes the following steps:

[0035] Oxalic acid and pyrite particles (20 mesh) with a total mass ratio of 0.02:1 (25 g) were added to a 500 mL ball mill jar. Agate beads of 5 mm, 8 mm, and 10 mm in size were added to the jar at a mass ratio of 6:3:1. Nitrogen gas was introduced into the jar, and after sealing, it was placed in a ball mill. The ball mill program was adjusted to alternate between forward rotation for 30 min, pause for 10 min, reverse rotation for 30 min, and pause for 10 min, with a milling speed of 300 rpm and a milling time of 10 h. After milling, the material was removed under a nitrogen atmosphere. The prepared material was then placed in centrifuge tubes and washed three times each with deoxygenated deionized water and anhydrous ethanol. Next, the material was placed in a 65 °C vacuum drying oven and vacuum dried for 6 h. After removal, the material was purged with nitrogen gas and stored at room temperature in the dark to obtain oxalic acid-modified pyrite material.

[0036] 4. Example 4

[0037] A method for preparing citric acid-modified pyrite material includes the following steps:

[0038] Citric acid and pyrite particles (20 mesh) in a mass ratio of 0.02:1 (total weight 25g) were added to a 500mL ball mill jar. Agate beads of 5mm, 8mm, and 10mm in size were added to the jar in a mass ratio of 6:3:1. Nitrogen gas was introduced into the jar, which was then sealed and placed in a ball mill. The ball mill program was adjusted to alternate between forward rotation for 30 minutes, pause for 10 minutes, reverse rotation for 30 minutes, and pause for 10 minutes. The milling speed was 300rpm, and the milling time was 10 hours. After milling, the material was removed under a nitrogen atmosphere. The prepared material was then transferred to centrifuge tubes and washed three times each with deoxygenated deionized water and anhydrous ethanol. Next, the material was placed in a 65℃ vacuum drying oven and vacuum dried for 6 hours. After drying, the material was removed, purged with nitrogen gas, and stored at room temperature in the dark to obtain citric acid-modified pyrite material.

[0039] 5. Example 5

[0040] A method for preparing a composite small-molecule acid-modified pyrite material includes the following steps:

[0041] A total of 25 g of modifier (hydroxylamine hydrochloride and ascorbic acid in a mass ratio of 1:3) and pyrite particles (20 mesh) were added to a 500 mL ball mill jar. Agate grinding beads (total mass of filling material in the ball mill jar: 200 g, mass ratio of large, medium, and small grinding beads: 1:3:6) were added. Nitrogen gas was introduced into the ball mill jar, which was then sealed and placed in a ball mill. The grinding speed was set to 300 rpm, and the grinding time was 10 h. After grinding, the material was removed under a nitrogen atmosphere. Under nitrogen protection, the grinding beads were separated from the grinding product, and the mixture was washed three times with deionized water and anhydrous ethanol, respectively. After vacuum drying, the composite small-molecule acid-modified pyrite material was obtained.

[0042] II. Comparative Example

[0043] 1. Comparative Example 1

[0044] A method for preparing natural pyrite particles includes the following steps:

[0045] The pyrite particles were initially crushed, passed through a 20-mesh sieve, and then placed in a brown glass bottle filled with nitrogen. The bottle was then stored at room temperature away from light.

[0046] 2. Comparative Example 2

[0047] A method for preparing ball-milled pyrite material includes the following steps:

[0048] 25g of pyrite particles (20 mesh) were added to a 500mL ball mill jar. Agate beads of 5mm, 8mm, and 10mm in size were added to the jar in a mass ratio of 6:3:1. Nitrogen gas was introduced into the jar, which was then sealed and placed in a ball mill. The ball mill program was adjusted to alternate between forward rotation for 30min, pause for 10min, reverse rotation for 30min, and pause for 10min. The milling speed was 300rpm, and the milling time was 10h. After milling, the material was removed under a nitrogen atmosphere. The prepared material was then placed in centrifuge tubes and washed three times each with deoxygenated deionized water and anhydrous ethanol. Next, the material was placed in a 65℃ vacuum drying oven and vacuum dried for 6h. After drying, the material was removed, purged with nitrogen gas, and stored at room temperature away from light to obtain the ball-milled pyrite material.

[0049] III. Characterization of Examples and Comparative Examples

[0050] The microstructures of Examples 1, 2, 5, Comparative Example 1, and Comparative Example 2 were characterized, and the results are as follows: Figure 1 As shown, by Figure 1It is known that direct ball milling can significantly reduce the particle size of natural pyrite, but agglomeration occurs, with the maximum particle size reaching 4.35 μm. Adding ascorbic acid or hydroxylamine hydrochloride alone to co-ball mill with pyrite somewhat suppresses agglomeration, resulting in average particle sizes of approximately 0.63 and 0.80 μm, respectively, but the particle size distribution is uneven. Adding a complex small-molecule acid for co-ball milling further suppresses agglomeration, reducing the average particle size to 0.45 μm, and the prepared micro / nano pyrite particles have a more uniform distribution. These results indicate that the organic acid-modified pyrite prepared in this invention exhibits significantly suppressed agglomeration and a more uniform particle size distribution, demonstrating great application potential.

[0051] IV. Examples and Comparative Catalytic Applications

[0052] 2g of chlorobenzene-contaminated soil was weighed into a 15mL capped glass bottle. 0.03g of pyrite material prepared in different embodiments and deionized water were added and mixed thoroughly (water-to-soil ratio 2:1). Persulfate (100mM) was added to initiate the reaction. The glass bottle was sealed and placed in a shaker at 150rpm. Destructive sampling was performed at a preset time. After centrifugation, the water and soil were separated, and the remaining pollutants in the system were detected. Extraction of pollutants from the water: After centrifugation, 1mL of the supernatant was added to a centrifuge tube containing 10mL of n-hexane. After vortexing for 10min, the solution was diluted, filtered through a 0.22μm organic filter membrane, and then transferred to a sample vial. Extraction of pollutants from soil: 2g of anhydrous magnesium sulfate desiccant was added to a glass bottle after removing the supernatant, followed by 10mL of an organic extractant consisting of acetone and n-hexane (volume ratio = 1:1). After mixing, the mixture was sonicated at 100Hz for 30min, and the extract was separated by centrifugation. The extraction steps were repeated 3 times. The extracts were combined, diluted, filtered through a 0.22μm organic filter membrane, and then placed into a sample vial. Gas chromatography-mass spectrometry was used for on-machine testing, and the degradation rate of each pollutant in the system was calculated.

[0053] The test results are as follows Figure 2 As stated, by Figure 2 As can be seen, Examples 1-5 and Comparative Examples 1 and 2 compared the effects of ball milling and organic acid modification on the performance of pyrite in catalyzing the degradation of chlorobenzene in soil by persulfate. Direct ball milling can improve the catalytic activity of natural pyrite, but the degradation rate of chlorobenzene is only 56.1%, indicating a mediocre degradation effect. Using pyrite modified with a single organic acid significantly improved the catalytic effect of persulfate degradation of chlorobenzene. Among them, ascorbic acid-modified pyrite (Example 1) showed the best effect, with a chlorobenzene removal rate of approximately 90%. In Example 5 of this invention, the catalytic activity of the composite small-molecule acid-modified pyrite material was further improved, with a chlorobenzene removal rate of almost 100%. The organic acid-modified pyrite prepared by this invention can be used as a highly active iron-based material in advanced oxidation processes, effectively remediating organically contaminated soil and demonstrating great application potential.

[0054] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A method of preparing a hydroxylamine-modified pyrite material, characterized in that, The method comprises the following steps: hydroxylamine hydrochloride and pyrite particles with a total mass of 25 g and a mass ratio of 0.02:1 are added into a ball mill tank with a capacity of 500 mL, agate ball milling beads are added, the ball mill tank is filled with nitrogen, and after being sealed, the ball mill tank is placed in a ball mill, the ball milling speed is set to 300 rpm, and the ball milling time is 10 h; after the ball milling is completed, the material is taken out under a nitrogen atmosphere; under the condition of nitrogen protection, the ball milling beads are separated from the ball milling product, and the ball milling product is washed with deionized water and anhydrous ethanol three times respectively, and after vacuum drying, hydroxylamine hydrochloride modified pyrite material is obtained; the total mass of the filling in the ball mill tank is 200 g, and the mass ratio of large, medium and small agate ball milling beads is 1:3:

6.

2. Hydroxylamine hydrochloride modified pyrite material prepared by the preparation method of claim 1.

3. Use of a hydroxylamine hydrochloride modified pyrite material according to claim 2 for the degradation of organic pollutants, characterized in that, The organic pollutants are chlorinated hydrocarbon organic pollutants.

4. Use according to claim 3, characterized in that, The chlorinated hydrocarbon organic pollutants are chlorobenzene.

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