Method for synergistically degrading organic pollutants by using pyrite and sodium hypophosphite

Abstract

The invention discloses a method for synergistically degrading organic pollutants by using pyrite and sodium hypophosphite, and belongs to the technical field of water pollution control and advanced oxidation. The method comprises the following steps: carrying out ball milling, sieving, washing and drying on pyrite to obtain treated pyrite, and storing under an anaerobic condition; and then adding the treated pyrite and sodium hypophosphite into the water body containing the organic pollutants, and reacting under the condition of natural light to degrade the organic pollutants. Through the synergistic effect of the pyrite and the sodium hypophosphite, an exogenous oxidant does not need to be added in an organic pollutant degradation system, and free radicals can be generated only through internal reaction of the system, so that the system can still keep high degradation activity on the organic pollutants in an anaerobic or anaerobic environment; dependence of a traditional advanced oxidation technology on dissolved oxygen is broken through, the application potential of the method in in-situ remediation of underground water, bottom mud and other anoxic environments is widened, in addition, the cost is remarkably reduced, and the risk of secondary pollution is eradicated.

Description

Technical Field

[0001] This invention belongs to the field of water pollution control and advanced oxidation technology, specifically relating to a method for the synergistic degradation of organic pollutants using pyrite and sodium hypophosphite. Background Technology

[0002] Carbamazepine is a typical pharmaceutical contaminant widely found in surface water, groundwater, and wastewater treatment plant effluent. Due to its high chemical stability and poor biodegradability, traditional water treatment processes (such as adsorption and biodegradation) have limited removal efficiency. Therefore, developing efficient and economical advanced oxidation technologies is crucial.

[0003] Pyrite (FeS2) is a natural mineral rich in Fe(II) and S. 2- Reducing components such as pyrite can degrade pollutants by generating free radicals through the activation of oxidants. However, using pyrite alone has problems such as low activation efficiency, high iron leaching, and slow reaction rate. Sodium hypophosphite (NaH2PO2), as a mild reducing agent, can promote the conversion of Fe(III) to Fe(II) and maintain the free radical chain reaction, but it cannot effectively degrade pollutants when used alone.

[0004] Currently, there are no reports on the combined use of pyrite and sodium hypophosphite for the degradation of organic pollutants. Existing advanced oxidation technologies (AEOs) largely rely on the external addition of oxidants (such as persulfate and ozone), which not only increases treatment costs and process complexity but also introduces potential secondary pollution risks and process uncertainties due to the introduction of highly oxidizing exogenous substances. Furthermore, the catalytic efficiency and free radical chain reaction of most AEO processes are severely dependent on the participation of dissolved oxygen, making them difficult to operate effectively in typical anoxic environments such as deep groundwater and contaminated sediment. Traditional free radical-based AEO technologies (such as Fenton and persulfate activation) heavily rely on dissolved oxygen molecules to participate in the chain reaction, and their efficiency typically drops significantly when the dissolved oxygen concentration is below approximately 2.0 mg / L, and they almost fail in typical anaerobic environments such as groundwater or sediment below approximately 0.5 mg / L. This invention aims to provide a method for the efficient degradation of organic pollutants even in environments lacking or without dissolved oxygen. Therefore, developing a green degradation method based on natural minerals and inexpensive chemicals that does not rely on the addition of exogenous oxidants or is not limited by dissolved oxygen is of great research significance and engineering value for promoting the safe and economical application of advanced oxidation technologies in actual water remediation. Summary of the Invention

[0005] To address or partially address the problems existing in related technologies, this invention proposes a method for the synergistic degradation of organic pollutants using pyrite and sodium hypophosphite.

[0006] This invention provides a method for the synergistic degradation of organic pollutants using pyrite and sodium hypophosphite, comprising the following steps: (1) Pyrite was ball-milled, sieved, washed with ethanol and water in sequence, and then dried to obtain the treated pyrite; (2) Under light conditions, the treated pyrite and sodium hypophosphite obtained in step (1) are added to the water containing organic pollutants to react and achieve the degradation of organic pollutants.

[0007] In step (1), the treated pyrite is preserved under anaerobic conditions.

[0008] In step (2), the reaction is stirred under room temperature and natural light conditions to achieve the degradation of organic pollutants.

[0009] Preferably, in step (1), the pyrite is dried and then calcined to obtain the treated pyrite. The calcination temperature is 200°C and the time is 2 hours.

[0010] Preferably, in step (2), the ratio of the amount of hypophosphite, the mass of organic pollutants, and the mass of pyrite is (13~20) mmol:(a~10) mg:(0.1~0.3) g, where 0 ≤ a < 10.

[0011] When reacting under aerobic conditions, the concentration of sodium hypophosphite in the reaction system is 14-20 mM, and the concentration of pyrite is 0.1-0.3 g / L; when reacting under anaerobic or anaerobic conditions, the concentration of sodium hypophosphite in the reaction system is 13-20 mM, and the concentration of pyrite is 0.1-0.3 g / L.

[0012] This invention reveals that the presence of molecular oxygen affects the initiation threshold and reaction pathway of the synergistic effect between pyrite and sodium hypophosphite. Under aerobic conditions, a sodium hypophosphite to pyrite concentration ratio of (14~20) mM:(0.1~0.3) g / L is required to effectively initiate the degradation reaction; while under anaerobic or anaerobic conditions, a sodium hypophosphite to pyrite concentration ratio of (13~20) mM:(0.1~0.3) g / L is required to effectively initiate the degradation reaction; and the system exhibits faster reaction kinetics and wider pH adaptability. This provides a flexible control strategy for practical applications in different oxygen environments (such as surface water and groundwater).

[0013] In this invention, an anaerobic environment refers to an environment devoid of molecular oxygen (including gaseous or dissolved oxygen). An anaerobic environment is an anaerobic habitat, meaning an environment completely lacking or devoid of molecular oxygen; a lack of molecular oxygen means that trace amounts of molecular oxygen exist in the environment, but the concentration is insufficient to support the growth of aerobic organisms or the occurrence of oxygen-dependent chemical reactions. An aerobic environment refers to an environment containing molecular oxygen, with a concentration sufficient to support the growth of aerobic organisms or the occurrence of oxygen-dependent chemical reactions.

[0014] Preferably, the organic pollutant is carbamazepine.

[0015] Preferably, in step (2), the pH of the reaction is 3-9.

[0016] Preferably, the reaction is carried out under aerobic, anaerobic, or anaerobic conditions.

[0017] The technical solution of the present invention has the following beneficial effects: (1) The pyrite used in this invention is a natural mineral, and sodium hypophosphite is inexpensive and readily available, resulting in low overall cost and environmental friendliness. Through the synergistic effect of pyrite and sodium hypophosphite, no external oxidant needs to be added in the system for degrading organic pollutants. Free radicals can be generated through the internal reaction of the system alone, so that the system can maintain high degradation activity for organic pollutants even in anaerobic or anaerobic environments. This breaks through the dependence of traditional advanced oxidation technology on dissolved oxygen, broadens its application potential in in-situ remediation of groundwater, sediment and other oxygen-deficient environments, and significantly reduces costs and eliminates the risk of secondary pollution.

[0018] (2) The method of using pyrite and sodium hypophosphite to synergistically degrade organic pollutants described in this invention can effectively degrade organic pollutants not only when the dissolved oxygen concentration is higher than 2.0 mg / L, but also in anaerobic or anaerobic environments with a dissolved oxygen concentration lower than 0.5 mg / L.

[0019] (3) The method of using pyrite and sodium hypophosphite to synergistically degrade organic pollutants described in this invention can maintain high efficiency in a wide pH range of 3-9 and has strong adaptability to pH fluctuations in actual water bodies. Attached Figure Description

[0020] Figure 1 The graph shows a comparison of the degradation experiments of carbamazepine in Examples 1-3 and Comparative Examples 1-3 of the present invention. In the graph, 0.2 g / LFeS2 is Comparative Example 1, 14 mM sodium hypophosphite is Comparative Example 2, and light-shielded sample is Comparative Example 4. In the graph, C0 is the concentration of carbamazepine in the sample taken at 0 min, C is the concentration of carbamazepine in the sample taken at t min, and t is the sampling time.

[0021] Figure 2This is a comparison diagram of the degradation experiments of carbamazepine under different pH reaction conditions and under anaerobic conditions in Example 3.

[0022] Figure 3 The images show the free radical quenching experimental spectra of aerobic free radicals in Example 2 and anaerobic free radicals in Example 3 of the present invention. In Example 2, 2.5 carbamazepine + 0.2 g / L pyrite + 14 mM sodium hypophosphite + tert-butanol were used, and N2 was used in Example 3.

[0023] Figure 4 This is the EPR spectrum of Example 3 of the present invention under anaerobic conditions. Detailed Implementation

[0024] Example 1 A method for the synergistic degradation of carbamazepine using pyrite and sodium hypophosphite includes the following steps: (1) Natural pyrite was ball-milled (220 r / min) for 40 min, passed through a 200-mesh sieve, washed with ethanol and ultrapure water in sequence to remove surface oxides and impurities, dried in a vacuum drying oven at 60 ℃, and stored under anaerobic conditions.

[0025] (2) Add 0.02 g of pyrite powder (200 mesh) obtained in step (1) and 0.1484 g (14 mM) sodium hypophosphite to 100 mL of 2.5 mg / L carbamazepine solution (pH≈6). Under room temperature and natural light conditions, place the above mixed solution on a constant temperature magnetic stirrer and react for 20 min. DO=10.09 mg / L.

[0026] (3) Samples were taken at 0, 1, 2, 3, 4, 5, 10, 15 and 20 min respectively, filtered through a 0.45 μm filter membrane, and the concentration of carbamazepine was detected by liquid chromatography.

[0027] like Figure 1 As shown, in this Example 1, under aerobic conditions, the degradation rate of carbamazepine reached 65.3% within 20 minutes.

[0028] Example 2 A method for the synergistic degradation of carbamazepine using pyrite and sodium hypophosphite includes the following steps: (1) Natural pyrite was ball-milled (220 r / min) for 40 min, passed through a 200-mesh sieve, and washed successively with ethanol and ultrapure water to remove surface oxides and impurities. It was then dried in a vacuum drying oven at 60 ℃. Finally, it was calcined at 200 ℃ for 2 hours and stored under anaerobic conditions.

[0029] (2) Add 0.02 g of pyrite powder (200 mesh) obtained in step (1) and 0.1484 g (14 mM) sodium hypophosphite to 100 mL of 2.5 mg / L carbamazepine solution (pH≈6). Under room temperature and natural light conditions, place the above mixed solution on a constant temperature magnetic stirrer and react for 20 min. DO=10.07 mg / L.

[0030] (3) Samples were taken at 0, 1, 2, 3, 4, 5, 10, 15 and 20 min respectively, filtered through a 0.45 μm filter membrane, and the concentration of carbamazepine was detected by liquid chromatography.

[0031] like Figure 1 As shown, in this Example 2, under aerobic conditions, the degradation rate of carbamazepine reached 100% within 20 minutes.

[0032] Example 3 A method for the synergistic degradation of carbamazepine using pyrite and sodium hypophosphite includes the following steps: (1) Natural pyrite was ball-milled (220 r / min) for 40 min, passed through a 200-mesh sieve, and washed successively with ethanol and ultrapure water to remove surface oxides and impurities. Then it was dried in a vacuum drying oven at 60 ℃. Then it was calcined at 200 ℃ for 2 hours and stored under anaerobic conditions.

[0033] (2) High-purity nitrogen gas was continuously introduced into the reactor for 60 min to completely remove dissolved oxygen, and a nitrogen atmosphere was maintained throughout the reaction. Under nitrogen protection, 0.02 g of pyrite powder (200 mesh) obtained in step (1) and 0.1484 g (14 mM) sodium hypophosphite were added to 100 mL of 2.5 mg / L carbamazepine solution (pH≈6). The mixture was placed on a thermostatic magnetic stirrer and reacted for 20 min under room temperature and natural light conditions. DO=0.31 mg / L.

[0034] (3) Samples were taken at 0, 1, 2, 3, 4, 5, 10, 15 and 20 min respectively, filtered through a 0.45 μm filter membrane, and the concentration of carbamazepine was detected by liquid chromatography.

[0035] like Figure 1 As shown, under anaerobic or anaerobic conditions, the degradation rate of carbamazepine reached 95% within 20 minutes, which is slightly lower than the 100% degradation rate under aerobic conditions in Example 2. This strongly demonstrates that molecular oxygen is not a necessary condition for the generation of free radicals in the synergistic degradation of carbamazepine by pyrite and sodium hypophosphite as described in this invention. The calcination treatment effectively cleans and activates the pyrite surface, optimizes its electron transport characteristics, and thus further enhances its synergistic effect with sodium hypophosphite under anaerobic or anaerobic conditions, maintaining a high efficiency in free radical generation and pollutant degradation.

[0036] This invention explores the pH of the reaction system in Example 3. Figure 2 The only difference between the experiments with pH=3, 5, 7, 9, 11 and Example 3 is the change in the pH value of the carbamazepine solution in step (2).

[0037] according to Figure 2 It is known that the present invention utilizes pyrite and sodium hypophosphite to synergistically degrade carbamazepine. The pH range applicable under anaerobic or anaerobic conditions is relatively wide, and carbamazepine can be efficiently degraded in a system with pH=3-9, with a degradation rate of over 90%.

[0038] The present invention conducted free radical quenching experiments on the reaction systems of Examples 2 and 3: In step (2) of Examples 2 and 3, when adding pyrite and sodium hypophosphite, 97.5 mL of tert-butanol was added in Example 2, and 9.5 μL of tert-butanol was added in Example 3 to carry out the reaction. Figure 3 It can be seen that no carbamazepine degradation occurred in Examples 2 and 3, indicating that hydroxyl radicals are the main active species in the carbamazepine degradation system of this invention. Furthermore, through... Figure 4 The EPR diagram shows that, under anaerobic or anaerobic conditions, pyrite and sodium hypophosphite contribute to the carbamazepine degradation system by the presence of hydroxyl radical active species.

[0039] Example 4 A method for the synergistic degradation of carbamazepine using pyrite and sodium hypophosphite includes the following steps: (1) Natural pyrite was ball-milled (220 r / min) for 40 min, passed through a 200-mesh sieve, and washed successively with ethanol and ultrapure water to remove surface oxides and impurities. Then it was dried in a vacuum drying oven at 60 ℃. Then it was calcined at 200 ℃ for 2 hours and stored under anaerobic conditions.

[0040] (2) High-purity nitrogen gas was continuously introduced into the reactor for 60 min to completely remove dissolved oxygen, and a nitrogen atmosphere was maintained throughout the reaction. Under nitrogen protection, 0.01 g of pyrite powder (200 mesh) obtained in step (1) and 0.212 g (20 mM) sodium hypophosphite were added to 100 mL of 10 mg / L carbamazepine solution (pH≈6). The mixture was placed on a thermostatic magnetic stirrer and reacted for 20 min at room temperature and under natural light. DO=0.30 mg / L.

[0041] (3) Samples were taken at 0, 1, 2, 3, 4, 5, 10, 15 and 20 min respectively, filtered through a 0.45 μm filter membrane, and the concentration of carbamazepine was detected by liquid chromatography.

[0042] In this example, the degradation rate of carbamazepine reached 24.4% within 20 minutes.

[0043] Example 5 A method for the synergistic degradation of carbamazepine using pyrite and sodium hypophosphite includes the following steps: (1) Natural pyrite was ball-milled (220 r / min) for 40 min, passed through a 200-mesh sieve, and washed successively with ethanol and ultrapure water to remove surface oxides and impurities. Then it was dried in a vacuum drying oven at 60 ℃. Then it was calcined at 200 ℃ for 2 hours and stored under anaerobic conditions.

[0044] (2) High-purity nitrogen gas was continuously introduced into the reactor for 60 min to completely remove dissolved oxygen, and a nitrogen atmosphere was maintained throughout the reaction. Under nitrogen protection, 0.01 g of pyrite powder (200 mesh) obtained in step (1) and 0.1378 g (13 mM) sodium hypophosphite were added to 100 mL of 10 mg / L carbamazepine solution (pH≈6). The mixture was placed on a thermostatic magnetic stirrer and reacted for 20 min under room temperature and natural light conditions. DO=0.29 mg / L.

[0045] (3) Samples were taken at 0, 1, 2, 3, 4, 5, 10, 15 and 20 min respectively, filtered through a 0.45 μm filter membrane, and the concentration of carbamazepine was detected by liquid chromatography.

[0046] In this example, the degradation rate of carbamazepine reached 99.6% within 20 minutes.

[0047] Comparative Example 1 The only difference between this comparative example and Example 3 is that sodium hypophosphite is not added in step (2).

[0048] Depend on Figure 1 It can be seen that carbamazepine in Comparative Example 1 did not degrade, indicating that when sodium hypophosphite is lacking, the degradation capacity of carbamazepine by pyrite alone is limited.

[0049] Comparative Example 2 The only difference between this comparative example and the embodiment of the method for degrading carbamazepine is that pyrite is not added in step (2).

[0050] Depend on Figure 1 It can be seen that carbamazepine in Comparative Example 2 did not degrade, and sodium hypophosphite cannot degrade carbamazepine when pyrite is lacking.

[0051] Depend on Figure 1 It is known that only when pyrite and sodium hypophosphite are used together can pollutants be efficiently degraded under aerobic, anaerobic, or anaerobic conditions, and that molecular oxygen is not a necessary condition for the system to generate free radicals.

[0052] Comparative Example 3 The only difference between this comparative example, which describes a method for the synergistic degradation of carbamazepine using pyrite and sodium hypophosphite, and Example 3 is that in step (1), the dried pyrite is not calcined but stored directly under anaerobic conditions.

[0053] In this comparative example, carbamazepine could not be degraded within 20 minutes under anaerobic conditions.

[0054] Comparative Example 4 The only difference between this comparative example, which describes a method for the synergistic degradation of carbamazepine using pyrite and sodium hypophosphite, and Example 3 is that in step (2), the reaction is carried out at room temperature and in the dark.

[0055] like Figure 1 As shown, carbamazepine cannot be degraded under light-protected conditions in this comparative example.

[0056] Comparative Example 5 A method for the synergistic degradation of carbamazepine using pyrite and sodium hypophosphite includes the following steps: (1) Natural pyrite was ball-milled (220 r / min) for 40 min, passed through a 200-mesh sieve, and washed successively with ethanol and ultrapure water to remove surface oxides and impurities. Then it was dried in a vacuum drying oven at 60 ℃. Then it was calcined at 200 ℃ for 2 hours and stored under anaerobic conditions.

[0057] (2) Add 0.03 g of pyrite powder (200 mesh) obtained in step (1) and 0.1378 g (13 mM) sodium hypophosphite to 100 mL of 10 mg / L carbamazepine solution (pH≈6). Under room temperature and natural light conditions, place the above mixed solution on a constant temperature magnetic stirrer and react for 20 min. DO=10.08 mg / L.

[0058] (3) Samples were taken at 0, 1, 2, 3, 4, 5, 10, 15 and 20 min respectively, filtered through a 0.45 μm filter membrane, and the concentration of carbamazepine was detected by liquid chromatography.

[0059] according to Figure 1 It can be seen that carbamazepine cannot be degraded within 20 minutes in this comparative example.

[0060] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for synergistic degradation of organic pollutants using pyrite and sodium hypophosphite, characterized in that: Includes the following steps: (1) Pyrite is ball-milled, sieved, washed and dried in sequence to obtain the processed pyrite; (2) Under light conditions, the treated pyrite and sodium hypophosphite obtained in step (1) are added to the water containing organic pollutants to react and achieve the degradation of organic pollutants.

2. The method for synergistic degradation of organic pollutants using pyrite and sodium hypophosphite as described in claim 1, characterized in that: In step (1), the pyrite is dried and then calcined to obtain the treated pyrite. The calcination temperature is 200℃ and the time is 2 hours.

3. The method for synergistic degradation of organic pollutants using pyrite and sodium hypophosphite as described in claim 1, characterized in that: In step (2), the ratio of the amount of hypophosphite, the mass of organic pollutants, and the mass of pyrite is (13~20) mmol: (a~10) mg: (0.1~0.3) g, where 0≤a<10.

4. The method for synergistic degradation of organic pollutants using pyrite and sodium hypophosphite as described in claim 1, characterized in that: The organic pollutant is carbamazepine.

5. The method for synergistic degradation of organic pollutants using pyrite and sodium hypophosphite as described in claim 1, characterized in that: In step (2), the pH of the reaction is 3-9.

6. The method for synergistic degradation of organic pollutants using pyrite and sodium hypophosphite as described in claim 3, characterized in that: The reaction is carried out under aerobic, anaerobic, or anaerobic conditions.

7. The method as described in claim 6, characterized in that: When the reaction is carried out under aerobic conditions, the concentration ratio of sodium hypophosphite to pyrite is (14~20) mM:(0.1~0.3) g / L.

8. The method as described in claim 6, characterized in that: When the reaction is carried out under anaerobic or non-anaerobic conditions, the concentration ratio of sodium hypophosphite to pyrite is (13~20) mM:(0.1~0.3) g / L.

Images