Method for intensively degrading phthalic acid ester pollutants by using natural organic acid

Abstract

The invention discloses a method for intensively degrading phthalic acid ester pollutants through natural organic acid, and belongs to the technical field of underground water organic pollutant remediation. The specific method comprises the following steps: adding pyrite particles and hydrogen peroxide into a to-be-treated water body containing the phthalate pollutants to form a Fenton or Fenton-like reaction system; adding natural organic acid into the Fenton or Fenton-like reaction system to strengthen the reaction so as to degrade the phthalate pollutants in the water body to be treated; the natural organic acid is protocatechuic acid, L ascorbic acid or salicylic acid. The method provided by the invention can efficiently and stably remove the phthalate pollutants in the underground water, and the raw materials are wide in source, green, pollution-free, low in cost, high in operability and convenient to popularize and apply in practice.

Description

Technical Field

[0001] The invention belongs to the technical field of groundwater organic pollutant remediation, and specifically relates to a method for enhancing the degradation of phthalate pollutants using natural organic acids. Background Art

[0002] Phthalates (PAEs) are a typical class of endocrine disruptors. As a major plasticizer, the frequent use of PAEs has caused soil and groundwater pollution. PAEs can enter the human body through ingestion, inhalation and skin contact, posing a serious threat to human health. In addition, leachate from landfills and fracturing flowback fluids produced during shale gas development often contain difficult-to-degrade substances such as phthalates (PAEs), further increasing the risk of soil and groundwater pollution. The main degradation pathways of diethyl phthalate (DEP) in the environment are photolysis and hydrolysis, but its natural degradation rate is extremely slow. How to effectively remove DEP from groundwater has become a research topic of widespread concern.

[0003] The Fenton and Fenton-like reactions of pyrite with hydrogen peroxide are low-cost advanced oxidation technologies that show promising application prospects in the treatment of organically contaminated groundwater due to their ability to generate reactive free radicals. However, under dark, anaerobic, and neutral pH conditions, the reaction rate between pyrite and hydrogen peroxide is low, resulting in slow degradation of pollutants. This has become a core issue in this field that needs to be addressed. Therefore, a method to enhance the activation of hydrogen peroxide with pyrite to remove phthalate esters from groundwater is urgently needed. Summary of the Invention

[0004] The purpose of the present invention is to solve the deficiencies in the prior art and provide a method for enhancing the degradation of phthalate pollutants using natural organic acids.

[0005] The specific technical solutions adopted in the present invention are as follows:

[0006] The present invention provides a method for enhancing the degradation of phthalate pollutants by using natural organic acids. The method is characterized in that pyrite particles and hydrogen peroxide are added to a water body to be treated containing phthalate pollutants to form a Fenton or Fenton-like reaction system; and natural organic acid is added to the Fenton or Fenton-like reaction system to enhance the reaction so as to degrade the phthalate pollutants in the water body to be treated. The natural organic acid is protocatechuic acid, L-ascorbic acid or salicylic acid.

[0007] Preferably, the pyrite particles are synthesized by a hydrothermal method, and the specific preparation method is as follows:

[0008] S1: Mix the ferrous chloride solution and the sodium 2 S 2 O 3 sodium thiosulfate solution evenly and place them in a tetrafluoroethylene autoclave; seal the autoclave and place it at 180-200°C for synthesis reaction;

[0009] S2: The precipitate obtained after the synthesis reaction is washed with CS2, dilute hydrochloric acid, deionized water, and anhydrous ethanol in sequence and then dried to obtain pyrite particles.

[0010] Furthermore, Fe 2+ The molar ratio of S is 1:(2~3).

[0011] Furthermore, the synthesis reaction time is 24 to 36 hours.

[0012] Preferably, the method for preparing the pyrite particles is as follows:

[0013] S1: Unprocessed pyrite from natural groundwater was ground to a particle size of less than 200 mesh, and then ultrasonically removed impurities, and then washed with nitric acid solution to remove the oxide layer and then washed and dried;

[0014] S2: The pyrite obtained in step S1 is placed in an anaerobic zirconia tank, wherein the mass ratio of pyrite to zirconia balls is 1:(10-15); the pyrite particles are ground to nanometer scale using a planetary ball mill, rinsed to remove impurities, and then freeze-dried to obtain pyrite particles.

[0015] Preferably, the added mass ratio of the natural organic acid to the pyrite particles is (1-50):90.

[0016] Preferably, the amount of hydrogen peroxide added to the Fenton or Fenton-like reaction system is 20 mmol / L.

[0017] Preferably, the Fenton or Fenton-like reaction system is carried out in the dark, anaerobic conditions and at a pH of 4-7.

[0018] Preferably, the phthalate pollutant is diethyl phthalate.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The method for treating phthalates in groundwater provided by the present invention has a simple reaction process, is easy to operate, has low requirements on equipment, and has low operating costs. In addition, the method has mild reaction conditions and low energy consumption. The reaction can be carried out at room temperature and pressure with a neutral pH, without the need for energy consumption such as heating, refrigeration, and pressurization.

[0021] (2) The method for treating phthalates in groundwater provided by the present invention can rapidly and efficiently remove phthalates from the groundwater, with a phthalate removal rate exceeding 95%. Compared with methods without the addition of natural organic acids, the addition of natural organic acids can produce more active substances and rapidly remove pollutants. This technology can be widely used in the fields of environmental pollution control and environmental remediation, and has a promising market prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a scanning electron microscope image of the pyrite particles prepared in Example 1;

[0023] Figure 2 This is the X-ray diffraction pattern of the pyrite particles prepared in Example 1;

[0024] Figure 3 This is a comparison chart of the degradation rates of adding 0.1 mM / L protocatechuic acid, L ascorbic acid, and salicylic acid in Examples 2 to 4 and the comparative example;

[0025] Figure 4 This is a comparison chart of degradation rates of Examples 2 to 4 and the comparative example;

[0026] Figure 5 Comparison of the effects of different pH conditions on the enhanced degradation of organic pollutants by protocatechuic acid, L-ascorbic acid, and salicylic acid, where (a), (b), and (c) are under pH conditions of 4, 7, and 10, respectively. DETAILED DESCRIPTION

[0027] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention may be combined accordingly without conflict.

[0028] Example 1

[0029] This embodiment provides a method for synthesizing nano-sized pyrite particles using an artificial hydrothermal method. The specific method is as follows:

[0030] (1) Weigh 8.34 g of Na2S2O3·5H2O in 40 mL of deionized water to prepare a Na2S2O3 solution. Weigh 2.45 g of FeCl2·4H2O in 40 mL of deionized water to prepare a ferrous chloride solution.

[0031] (2) The Na2S2O3 solution was added to the ferrous chloride solution under a magnetic stirrer and stirred evenly to completely disperse the solute. The mixed solution was then transferred to a 100 mL tetrafluoroethylene autoclave. The autoclave was sealed and subjected to a hydrothermal synthesis reaction at 200°C for 24 hours.

[0032] (3) After the mixture from the synthesis reaction in step (2) is naturally cooled, the precipitate is washed twice with CS2, dilute hydrochloric acid, deionized water, and anhydrous ethanol in sequence. Finally, the product is vacuum-dried at 60° C. for 6 hours to obtain nano-sized pyrite particles.

[0033] Figure 1 and Figure 2 The following are the scanning electron microscope images and XRD patterns of the nano-sized pyrite particles prepared in this example. Figure 1 and Figure 2 It can be seen that nano-sized pyrite particles were prepared using the method of this embodiment. The diffraction peaks in the X-ray diffraction pattern were sharp and prominent, and SEM also showed that the sample had a high degree of crystallinity. The XRD diffraction peak position of the sample coincided with the diffraction peak position on the pyrite-type FeS2 standard PDF card (JCPDS No. 42-1340), proving that the synthesized product is relatively pure pyrite-type FeS2.

[0034] Example 2

[0035] This example uses the nano-sized pyrite particles prepared in Example 1, hydrogen peroxide, and varying concentrations of protocatechuic acid (PCA) to degrade diethyl phthalate in contaminated water at pH 7. This example was conducted in a 250 mL conical flask, with the actual reaction system being a mixture of 200 mL of deionized water. The specific method is as follows:

[0036] A 1 mg / L diethyl phthalate (DEP) solution was prepared in an Erlenmeyer flask and deoxygenated by nitrogen aeration. Protocatechuic acid (0.01, 0.05, 0.1, and 0.5 mM / L) was then added, followed by sonication for 30 minutes to promote dissolution and diffusion. Hydrogen peroxide was then added to a concentration of 20 mM / L. Finally, 0.02 g of the pyrite particles prepared in Example 1 was added to initiate the reaction. A ground glass stopper was used to prevent oxygen ingress and moisture escape. DEP degradation and conversion experiments were conducted at 25°C in the dark, under anaerobic conditions, and at a pH of 7. The effect of protocatechuic acid on the anaerobic conversion of DEP was investigated.

[0037] After initiating the reaction, 1 mL of liquid sample was taken at predetermined intervals and extracted with 1 mL of n-hexane, followed by thorough vortexing. The n-hexane supernatant was aspirated and dehydrated with anhydrous sodium sulfate. The sample was then filtered through a 0.22 μm filter membrane, and the filtrate was transferred to a brown injection vial. DEP concentration was determined using a gas chromatography-mass spectrometer (GC-MS, Agilent 5977B MSD Bundle, Agilent Technologies, USA). The GC-MS was equipped with an EI ion source, an FID detector, and an HP-5MS column (30 m, 0.25 mm × 0.25 mm). The following parameters were set: 50°C for 1 min, followed by a temperature increase of 15°C / min to 220°C for 1 min. The carrier gas was nitrogen and helium at a flow rate of 0.9 mL / min, and the injection volume was 1 mL.

[0038] Example 3

[0039] This example uses the nano-sized pyrite particles, hydrogen peroxide and L-ascorbic acid (VC) prepared in Example 1 to degrade diethyl phthalate in polluted water at pH = 7. The specific method is as follows:

[0040] A 1 mg / L diethyl phthalate (DEP) solution was prepared in a conical flask and deoxygenated by nitrogen aeration. Different concentrations of L-ascorbic acid (0.01, 0.05, 0.1, and 0.5 mM / L) were added, and ultrasound was applied for 30 min to promote dissolution and diffusion. Hydrogen peroxide was then added to 20 mM / L. Finally, 0.02 g of the pyrite particles prepared in Example 1 was added to initiate the reaction. A ground glass stopper was used to prevent oxygen ingress and moisture escape during the reaction. DEP degradation and conversion tests were conducted at 25°C in the dark, under anaerobic conditions, and at a pH of 7. The effect of L-ascorbic acid on the anaerobic conversion of DEP in the system was investigated. After initiating the reaction, the sampling and testing procedures were consistent with those in Example 2.

[0041] Example 4

[0042] This example uses the nano-sized pyrite particles prepared in Example 1, hydrogen peroxide, and salicylic acid (SA) to degrade diethyl phthalate in contaminated water at pH = 7. The specific method is as follows:

[0043] A 1 mg / L diethyl phthalate (DEP) solution was prepared in a conical flask and deoxygenated by nitrogen aeration. Salicylic acid was added at different concentrations of 0.01, 0.05, 0.1, and 0.5 mM / L, respectively. Ultrasonication was performed for 30 min to promote dissolution and diffusion. Hydrogen peroxide was then added to 20 mM / L. Finally, 0.02 g of the pyrite particles prepared in Example 1 was added to initiate the reaction. A ground glass stopper was used to prevent oxygen ingress and moisture escape. DEP degradation and conversion experiments were conducted at 25°C in the dark, under anaerobic conditions, and at a pH of 7. The effect of salicylic acid on the anaerobic conversion of DEP in the system was investigated. After initiation of the reaction, sampling and testing were performed as in Example 2.

[0044] Comparative Example

[0045] In this comparative example, no natural organic acid was added, and the nano-sized pyrite particles prepared in Example 1 and hydrogen peroxide were directly used to degrade diethyl phthalate in the polluted water. The specific method is as follows:

[0046] A 1 mg / L diethyl phthalate (DEP) solution was prepared in an Erlenmeyer flask and deoxygenated by nitrogen aeration. Hydrogen peroxide was added to 20 mM / L, and finally, 0.02 g of the pyrite particles prepared in Example 1 was added to initiate the reaction. A ground glass stopper was used to prevent oxygen ingress and moisture escape. DEP degradation and conversion experiments were conducted at 25°C in the dark, under anaerobic conditions, and at a pH of 7. After initiation, sampling and testing were performed in the same manner as in Example 2.

[0047] The experimental results of Examples 2 to 4 and Comparative Examples are as follows: Figure 3 and Figure 4 As shown. Figure 3 It can be seen that the addition of 0.1 mM / L protocatechuic acid, L-ascorbic acid, and salicylic acid, respectively, increased the reaction rate constants by 16, 15, and 15 times the original values, significantly accelerating the degradation of DEP compared to the control without the addition of organic matter.

[0048] Example 5

[0049] In this example, the nano-sized pyrite particles prepared in Example 1, hydrogen peroxide, and 0.1 mM / L protocatechuic acid (PCA) were used to degrade diethyl phthalate in contaminated water at pH = 4.

[0050] A 1 mg / L diethyl phthalate (DEP) solution was prepared in an Erlenmeyer flask and deoxygenated by nitrogen aeration. 0.1 mM / L protocatechuic acid was added and sonicated for 30 minutes to promote dissolution and diffusion. Hydrogen peroxide was then added to a concentration of 20 mM / L. Finally, 0.02 g of the pyrite particles prepared in Example 1 was added to initiate the reaction. A ground glass stopper was used to prevent oxygen ingress and moisture escape. DEP degradation and conversion experiments were conducted at 25°C in the dark, under anaerobic conditions, and at a pH of 4. The effect of protocatechuic acid on the anaerobic conversion of DEP in the system under acidic conditions was examined. After initiation of the reaction, sampling and testing were performed as in Example 2.

[0051] Example 6

[0052] In this example, the nano-sized pyrite particles prepared in Example 1, hydrogen peroxide, and 0.1 mM / L protocatechuic acid (PCA) were used to degrade diethyl phthalate in contaminated water at pH = 10.

[0053] A 1 mg / L diethyl phthalate (DEP) solution was prepared in an Erlenmeyer flask and deoxygenated by nitrogen aeration. 0.1 mM / L protocatechuic acid was added and sonicated for 30 minutes to promote dissolution and diffusion. Hydrogen peroxide was then added to a concentration of 20 mM / L. Finally, 0.02 g of the pyrite particles prepared in Example 1 was added to initiate the reaction. A ground glass stopper was used to prevent oxygen ingress and moisture escape. DEP degradation and conversion experiments were conducted at 25°C in the dark, under anaerobic conditions, and at a pH of 10. The effect of protocatechuic acid on the anaerobic conversion of DEP under alkaline conditions was examined. After initiation, sampling and testing were performed as in Example 2.

[0054] Example 7

[0055] In this example, the nano-sized pyrite particles prepared in Example 1, hydrogen peroxide, and 0.1 mM / LL ascorbic acid (VC) were used to degrade diethyl phthalate in contaminated water at pH = 4.

[0056] A 1 mg / L diethyl phthalate (DEP) solution was prepared in an Erlenmeyer flask and deoxygenated by nitrogen aeration. 0.1 mM / L L-ascorbic acid (VC) was added and sonicated for 30 minutes to promote dissolution and diffusion. Hydrogen peroxide was then added to 20 mM / L. Finally, 0.02 g of the pyrite particles prepared in Example 1 was added to initiate the reaction. A ground glass stopper was used to prevent oxygen ingress and moisture escape. DEP degradation and conversion experiments were conducted at 25°C in the dark, under anaerobic conditions, and at a pH of 4. The effect of L-ascorbic acid on the anaerobic conversion of DEP in the system under acidic conditions was investigated. After initiation of the reaction, sampling and testing were performed as in Example 2.

[0057] Example 8

[0058] In this example, the nano-sized pyrite particles prepared in Example 1, hydrogen peroxide, and 0.1 mM / LL ascorbic acid (VC) were used to degrade diethyl phthalate in contaminated water at pH = 10.

[0059] A 1 mg / L diethyl phthalate (DEP) solution was prepared in an Erlenmeyer flask and deoxygenated by nitrogen aeration. 0.1 mM / L L-ascorbic acid was added and sonicated for 30 min to promote dissolution and diffusion. Hydrogen peroxide was then added to 20 mM / L. Finally, 0.02 g of the pyrite particles prepared in Example 1 was added to initiate the reaction. A ground glass stopper was used to prevent oxygen ingress and moisture escape. DEP degradation and conversion experiments were conducted at 25°C in the dark, under anaerobic conditions, and at a pH of 10. The effect of L-ascorbic acid on the anaerobic conversion of DEP in the system under alkaline conditions was investigated. After initiation of the reaction, sampling and testing were performed as in Example 2.

[0060] Example 9

[0061] In this example, the nano-sized pyrite particles prepared in Example 1, hydrogen peroxide, and 0.1 mM / L salicylic acid (SA) were used to degrade diethyl phthalate in contaminated water at pH = 4.

[0062] A 1 mg / L diethyl phthalate (DEP) solution was prepared in an Erlenmeyer flask and deoxygenated by nitrogen aeration. 0.1 mM / L salicylic acid was added and sonicated for 30 minutes to promote dissolution and diffusion. Hydrogen peroxide was then added to a 20 mM / L concentration. Finally, 0.02 g of the pyrite particles prepared in Example 1 was added to initiate the reaction. A ground glass stopper was used to prevent oxygen ingress and moisture escape. DEP degradation and conversion experiments were conducted at 25°C in the dark, under anaerobic conditions, and at a pH of 4. The effect of salicylic acid on the anaerobic conversion of DEP under acidic conditions was investigated. After initiation, sampling and testing were performed as in Example 2.

[0063] Example 10

[0064] In this example, the nano-sized pyrite particles prepared in Example 1, hydrogen peroxide, and 0.1 mM / L salicylic acid were used to degrade diethyl phthalate in contaminated water at pH = 10.

[0065] A 1 mg / L diethyl phthalate (DEP) solution was prepared in an Erlenmeyer flask and deoxygenated under nitrogen. 0.1 mM / L salicylic acid was added and sonicated for 30 minutes to promote dissolution and diffusion. Hydrogen peroxide was then added to 20 mM / L. Finally, 0.02 g of the pyrite particles prepared in Example 1 was added to initiate the reaction. A ground glass stopper was used to prevent oxygen ingress and moisture escape. DEP degradation and conversion experiments were conducted at 25°C in the dark, under anaerobic conditions, and at a pH of 10. The effect of salicylic acid on the anaerobic conversion of DEP under alkaline conditions was investigated. After initiation of the reaction, sampling and testing were performed as in Example 2.

[0066] The results of DEP removal rates of protocatechuic acid (PCA), L-ascorbic acid (VC) and salicylic acid (SA) within 90 minutes under different pH conditions are as follows: Figure 5 As shown. Figure 5 Under acidic and neutral conditions, the DEP removal rates of the control group (no natural organic acid added) reached 90% and 43% within 90 minutes, respectively. The groups supplemented with 0.1 mM / L protocatechuic acid, ascorbic acid, and salicylic acid achieved 100% removal within 30 minutes. Under alkaline conditions, the DEP removal rates of the control group, protocatechuic acid, ascorbic acid, and salicylic acid groups were inhibited to 16%, 43%, 80%, and 71%, respectively, within 30 minutes. This suggests that the addition of organic matter can activate the pyrite and hydrogen peroxide degradation reactions under both acidic and neutral conditions.

[0067] The embodiment described above is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Persons skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent substitution or equivalent transformation falls within the scope of protection of the present invention.

Claims

1. A method for enhancing the degradation of phthalate pollutants using natural organic acids, characterized in that: Pyrite particles and hydrogen peroxide are added to a water body to be treated containing phthalate pollutants to form a Fenton or Fenton-like reaction system; a natural organic acid is added to the Fenton or Fenton-like reaction system to enhance the reaction so as to degrade the phthalate pollutants in the water body to be treated; the natural organic acid is protocatechuic acid, L-ascorbic acid or salicylic acid.

2. The method for degrading phthalate pollutants according to claim 1, wherein: The pyrite particles are synthesized by hydrothermal method, and the specific preparation method is as follows: S1: Mix the ferrous chloride solution and the sodium 2 S 2 O 3 sodium thiosulfate solution evenly and place them in a tetrafluoroethylene autoclave; seal the autoclave and place it at 180-200°C for synthesis reaction; S2: The precipitate obtained after the synthesis reaction is washed with CS2, dilute hydrochloric acid, deionized water, and anhydrous ethanol in sequence and then dried to obtain pyrite particles.

3. The method for degrading phthalate pollutants according to claim 2, wherein: Fe in the reaction system 2+ The molar ratio of S is 1:(2~3).

4. The method for degrading phthalate pollutants according to claim 2, wherein: The synthesis reaction time is 24 to 36 hours.

5. The method for degrading phthalate pollutants according to claim 1, wherein: The pyrite particle preparation method is as follows: S1: Unprocessed pyrite from natural groundwater was ground to a particle size of less than 200 mesh, and then ultrasonically removed impurities, and then washed with nitric acid solution to remove the oxide layer and then washed and dried; S2: The pyrite obtained in step S1 is placed in an anaerobic zirconia tank, wherein the mass ratio of pyrite to zirconia balls is 1:(10-15); the pyrite particles are ground to nanometer scale using a planetary ball mill, rinsed to remove impurities, and then freeze-dried to obtain pyrite particles.

6. The method for degrading phthalate pollutants according to claim 1, wherein: The added mass ratio of the natural organic acid to the pyrite particles is (1-50):

90.

7. The method for degrading phthalate pollutants according to claim 1, wherein: The amount of hydrogen peroxide added to the Fenton or Fenton-like reaction system is 20 mmol / L.

8. The method for degrading phthalate pollutants according to claim 1, wherein: The Fenton or Fenton-like reaction system is carried out in darkness, anaerobic conditions and at a pH of 4-7.

9. The method for degrading phthalate pollutants according to claim 1, wherein: The phthalate pollutant is diethyl phthalate.

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