Method for removing perfluorinated compounds by using magnetic rotor enhanced ultrasound

Abstract

The invention discloses a method for removing perfluorinated compounds by using magnetic rotor enhanced ultrasound. After a magnetic rotor is added into a perfluorooctanoic acid solution, ultrasound is started to complete removal of perfluorooctanoic acid. According to the method, the magnetic rotor in a laboratory environment is used as a contact electrocatalyst, and the method shows good potential for efficiently removing perfluorides in a water body under the action of high-frequency ultrasonic enhancement. Compared with a conventional degradation method, the method does not need to additionally add a catalyst and an oxidizing agent which are complex in preparation. The method provided by the invention is simple to operate, low in energy consumption, low in cost, obvious in pollutant removal effect, green and environment-friendly.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and more particularly to a method for removing perfluorinated compounds by utilizing a magnetic rotor to enhance ultrasound. Background Art

[0002] Perfluorinated compounds (PFASs) are a class of synthetic organic compounds with extremely high chemical stability, which are widely used in industrial and consumer product manufacturing. Due to the characteristics of their CF bonds, perfluorinated compounds are difficult to degrade naturally like plastics, so they are called "permanent pollutants". The widespread presence of PFASs in water bodies around the world has become an environmental issue of international concern. They not only pose a threat to water security, but may also affect biological health, causing health problems such as liver disease, fertility problems and cancer.

[0003] At present, common perfluorinated compound degradation technologies include advanced oxidation technology, electrochemical oxidation, photocatalysis and biodegradation methods. However, the removal effect of these methods on perfluorinated compounds is still unsatisfactory. The electrochemical method has high operating costs and is prone to wear and corrosion of electrode materials; photocatalytic technology is limited by light sources and catalyst recovery is difficult; biodegradation is slow and difficult to cope with high-concentration pollution. Domestic research on PFASs started late, and currently mainly uses traditional physical adsorption and chemical oxidation methods. Although physical adsorption is simple and low-cost, there is a risk of secondary pollution and the adsorbent needs to be replaced frequently; chemical oxidation can effectively destroy the chemical structure of PFASs, but it has limited effect on PFASs with strong stability and may produce toxic intermediates. Therefore, there is an urgent need for a green, efficient and economical treatment technology to deal with the pollution degradation of PFASs.

[0004] Contact electrocatalysis (CEC) degradation technology is an emerging pollutant treatment technology and a green and efficient water treatment technology. It has attracted widespread attention due to its stability and excellent degradation effect. The basic principle is that when the solid-liquid interface contacts and separates rapidly, the electrons or ions are transferred from one material to another, resulting in the surfaces of the two materials carrying opposite charges. Charges accumulate on the solid surface, forming a local potential difference. This potential difference can drive the transfer of electrons from the solid surface to the chemical substances in the solution, thereby driving the chemical reaction. The CEC process does not rely on external power sources or complex chemicals, and has significant advantages in economy and environmental protection compared to traditional methods. However, there are currently few materials that can produce contact electrocatalysis and the cost is high. The exploration of new and efficient materials has become a challenge for the development of contact electrocatalysis.

[0005] PTFE is a high-performance, durable plastic that is commonly used to manufacture a variety of high-temperature, corrosion-resistant and friction-resistant products, such as seals, pipes, valves, coatings, etc. Due to its special properties, it is used as the outer skin material of magnetic rotors in laboratory environments. However, when conducting pollution degradation or other scientific research, the existence of magnetic rotors is often ignored by scientific researchers as a key factor, resulting in some unnecessary errors in their scientific research. Summary of the invention

[0006] In view of this, the present method provides a simple contact electrocatalytic system based on a magnetic rotor, which produces a contact electrocatalytic reaction through ultrasonic cavitation and a magnetic rotor with a surface material of PTFE, thereby achieving efficient degradation of perfluorinated compounds without adding other chemical agents.

[0007] To achieve the above object, the present invention adopts the following technical solution:

[0008] A method for removing perfluorinated compounds by using a magnetic rotor to enhance ultrasound comprises the following steps:

[0009] A magnetic rotor was placed in the target solution containing the perfluorinated compound and then sonicated.

[0010] Preferably, the perfluorinated compound is perfluorooctanoic acid.

[0011] Preferably, the surface material of the magnetic rotor is PTFE.

[0012] Preferably, the molar concentration of the perfluorinated compound in the target solution containing the perfluorinated compound is 0.05 mmol / L.

[0013] Preferably, the ultrasonic power is 100W.

[0014] Preferably, the ultrasonic frequency is 40 kHz.

[0015] Preferably, the ultrasonic treatment temperature is ≤30°C.

[0016] Preferably, the ultrasonic treatment time is ≥ 2.5 h.

[0017] It can be seen from the above technical solution that, compared with the prior art, the present invention discloses a method for removing perfluorinated compounds by using a magnetic rotor to enhance ultrasound, which has the following beneficial effects:

[0018] Ultrasonic enhancement can promote the electron transfer process of rapid contact and separation between the solid-liquid interface of the catalytic material and water. The local potential difference is formed during the rapid transfer of electrons, thereby promoting the transfer of electrons from the surface of the catalytic material to the solution, thereby driving the progress of the chemical reaction. In addition to being able to quickly activate chemical reactions and accelerate the reaction process, the use of magnetic rotors to enhance the activation of contact electrocatalysis technology with ultrasonic enhancement eliminates the steps of preparing catalysts and adding external oxidants. In addition, magnetic rotors are extremely easy to obtain, especially under laboratory background conditions. This not only provides inspiration for pollution degradation research in laboratory settings, but also provides greater possibilities for rapid and economical degradation of new pollutants in water bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0020] Figure 1 This is a diagram showing the effect of using a magnetic rotor to enhance the ultrasonic degradation of perfluorinated compounds;

[0021] Figure 2 The experimental results of magnetic rotor-enhanced ultrasonic removal of perfluorooctanoic acid on different surface materials; A is the statistical result of the degradation rate; B is the statistical result of the first-order kinetic reaction rate;

[0022] Figure 3 The experimental results of the magnetic rotor enhanced ultrasonic removal of perfluorooctanoic acid under different pH conditions; A is the statistical result of the degradation rate; B is the statistical result of the first-order kinetic reaction rate;

[0023] Figure 4 The figure shows the effect of magnetic rotor enhanced ultrasound in removing perfluorooctanoic acid in different water bodies; A is the degradation rate of magnetic rotor enhanced ultrasound in removing perfluorooctanoic acid in different water bodies, and B is the removal rate of perfluorooctanoic acid and the removal rate of total organic carbon (TOC) in the reaction system after 150 minutes of reaction;

[0024] Figure 5 The experimental results of the removal of perfluorooctanoic acid by magnetic rotor enhanced ultrasound under different anion conditions at a concentration of 0.5mM;

[0025] Figure 6 These are the experimental results of magnetic rotor-enhanced ultrasonic removal of perfluorooctanoic acid under different humic acid concentrations. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Example 1

[0028] Take 0.0207g of perfluorooctanoic acid powder and dissolve it in 500mL of deionized water to obtain a perfluorooctanoic acid solution with a molar concentration of 0.05mmol / L, and take 20mL into a glass reaction vial;

[0029] The magnetic rotor surface material used is polytetrafluoroethylene (PTFE);

[0030] Add two magnetic rotors with dimensions of 0.4 cm × 0.1 cm × 1.0 cm to the reaction vial;

[0031] Place the reaction vial equipped with a magnetic rotor into a 100W 40kHz ultrasonic device, add a certain amount of water into the ultrasonic device until the liquid level covers the liquid level of the reaction vial, add an ice bag to control the temperature not exceeding 30°C, start the reaction, time for 150 minutes, and take samples at 0, 10, 20, 40, 60, 90, 120, and 150 minutes, respectively.

[0032] Comparative Example 1

[0033] The difference from Example 1 is that the surface of the magnetic rotor is made of glass.

[0034] Comparative Example 2

[0035] The difference from Example 1 is that the surface of the magnetic rotor is made of stainless steel.

[0036] Comparative Example 3

[0037] The difference from Example 1 is that no magnetic rotor is added.

[0038] Experimental Example 1

[0039] The content of perfluorooctanoic acid in the solutions sampled in Example 1 and Comparative Examples 1-3 was detected by high performance liquid chromatography, and the degradation rate of perfluorooctanoic acid was calculated. The results are as follows: Figure 1-2 shown.

[0040] Figure 1 It shows that in Example 1, the degradation rate of perfluorooctanoic acid can reach 99% within 150 minutes by using the magnetic rotor to enhance the ultrasonic-induced contact electrocatalytic effect.

[0041] The statistical results of Example 1 and Comparative Examples 1-3 are as follows Figure 2 As shown in A and B in the figure, the degradation rate of perfluorooctanoic acid in Example 1 using magnetic rotors with PTFE as the surface material can reach 99%, the degradation rates of magnetic rotors with glass (Comparative Example 1) and stainless steel (Comparative Example 2) as the surface material are 60% and 52% respectively, and the degradation rate of perfluorooctanoic acid in Comparative Example 3 without magnetic rotors is 47%. It can be seen that the degradation effect of using magnetic rotors of other materials to enhance ultrasound to remove perfluorooctanoic acid is very limited, while the degradation effect of using magnetic rotors with PTFE as the surface material to enhance ultrasound to remove perfluorooctanoic acid is very obvious, the constant of the first-order kinetic reaction rate is larger, and PTFE magnetic rotors can enhance ultrasound to degrade more than 99% of perfluorooctanoic acid within 150 minutes.

[0042] Experimental Example 2

[0043] Take 0.0207 g of perfluorooctanoic acid powder and dissolve it in 500 mL of deionized water to obtain a perfluorooctanoic acid solution with a molar concentration of 0.05 mmol / L. Take 20 mL of it and put it into 4 glass reaction vials respectively, which are recorded as groups 1-4.

[0044] The magnetic rotor surface material used is polytetrafluoroethylene (PTFE);

[0045] The pH of group 1 was adjusted to 2.0 using hydrochloric acid as a pH adjuster, the pH of group 2 was the initial pH of the perfluorooctanoic acid solution = 4.6, and the pH of groups 3 and 4 were adjusted to 8.0 and 10.0 using sodium hydroxide as a pH adjuster;

[0046] Add two magnetic rotors to the reaction vials of groups 1-4 respectively, place the reaction vials of groups 1-4 into a 100W 40kHz ultrasonic device, add a certain amount of water to the ultrasonic device until the liquid level covers the liquid level of the reaction vials, add ice bags to control the temperature not exceeding 30°C, start the reaction, time for 150 minutes, and take samples at 0, 10, 20, 40, 60, 90, 120, and 150 minutes respectively.

[0047] The content of perfluorooctanoic acid in the solution was detected by high performance liquid chromatography, and the degradation rate of perfluorooctanoic acid was calculated. The results are as follows: Figure 3 As shown in A and B in the figure, the degradation rate of perfluorooctanoic acid can reach 99% under different initial pH conditions by using magnetic rotor to enhance ultrasonic degradation. However, the result of B shows that when the initial pH of the reaction solution is weakly alkaline, the constant of the first-order kinetic reaction rate is greater than that when the initial pH of the reaction solution is acidic, indicating that the reaction rate is greater when the initial pH of the reaction solution is alkaline than that of acidic. Therefore, pH has no effect on the degradation rate.

[0048] Experimental Example 3

[0049] Take 0.0828g of perfluorooctanoic acid powder and dissolve it in 500mL of deionized water to obtain a perfluorooctanoic acid solution with a molar concentration of 0.4mmol / L. Take 2.5mL each and put it into 5 glass reaction vials, recorded as groups 1-5. Add 17.5ml of deionized water, lake water samples, reservoir water samples, rainwater samples, and domestic sewage samples to glass reaction vials 1-5 respectively to establish a 20ml reaction system of different water bodies with a PFOA molar concentration of 0.05mmol / L. Add two magnetic rotors with dimensions of 0.4cm×0.1cm×1.0cm to each reaction vial, and the surface material of the magnetic rotor used is polytetrafluoroethylene (PTFE).

[0050] Place the reaction vial equipped with a magnetic rotor into a 100W 40kHz ultrasonic device, add a certain amount of water into the ultrasonic device until the liquid level covers the liquid level of the reaction vial, add an ice bag to control the temperature not exceeding 30°C, start the reaction, time for 150 minutes, and take samples at 0, 10, 20, 40, 60, 90, 120, and 150 minutes, respectively.

[0051] The content of perfluorooctanoic acid in the solution was detected by high performance liquid chromatography, and the degradation rate of perfluorooctanoic acid was calculated; the content of total organic carbon in the solution was detected by total organic carbon analyzer, and the removal rate of total organic carbon was calculated.

[0052] The experimental results are as follows Figure 4 As shown in A and B in the figure, in different water bodies, the degradation rate of perfluorooctanoic acid can reach 99% within 150 minutes by using a magnetic rotor with PTFE as the surface material to enhance ultrasonic degradation; at the same time, the removal rate of total organic carbon (TOC) in the solution by the reaction system was determined. In different actual water bodies, the TOC removal rate in the PTFE magnetic rotor enhanced ultrasonic system gradually increased with the extension of the reaction time, and finally reached a removal rate of 61% after the reaction ended after 150 minutes. In actual water bodies, the reaction system also showed obvious TOC removal effect, but due to the large number of impurities in the actual water body, the contact electrode system could not completely remove the TOC in the water body, so the TOC removal effect in the actual water body was slightly inferior to that under laboratory conditions.

[0053] Experimental Example 4

[0054] Take 0.0207g of perfluorooctanoic acid powder and dissolve it in 500mL of deionized water to obtain a perfluorooctanoic acid solution with a molar concentration of 0.05mmol / L. Take 20mL of each and put it into 5 glass reaction vials, which are recorded as groups 1-5;

[0055] The surface material of the magnetic rotor used in this example is polytetrafluoroethylene (PTFE). Two magnetic rotors were added to the reaction vials of groups 1-5 respectively. Group 1 was used as the control group and no additional additions were made. 0.0008 g potassium chloride (KCl), 0.0014 g potassium dihydrogen phosphate (KH 2 PO 4 )、0.0011g sodium carbonate (Na 2 CO 3 ), 0.0010 g potassium nitrate (KNO 3 ) so that the concentration of each ion in the solution is 0.5 mM.

[0056] Place the reaction vials of groups 1-5 into a 100W 40kHz ultrasonic device, add a certain amount of water into the ultrasonic device until the liquid level covers the liquid level of the reaction vials, add ice bags to control the temperature not exceeding 30°C, start the reaction, and time for 150 minutes. Take samples at 0, 10, 20, 40, 60, 90, 120, and 150 minutes respectively; detect the content of perfluorooctanoic acid in the solution by HPLC, and calculate the degradation rate of perfluorooctanoic acid.

[0057] The experimental results are as follows Figure 5 As shown, among different anions, the degradation rate of perfluorooctanoic acid in 150 minutes using the magnetic rotor with the surface material of PTFE to enhance ultrasonic degradation can reach 99%. The results show that anions have almost no effect on the degradation effect of perfluorooctanoic acid in the removal of perfluorooctanoic acid using the magnetic rotor with the surface material of PTFE to enhance ultrasonic degradation.

[0058] Experimental Example 5

[0059] Take 0.0207 g of perfluorooctanoic acid powder and dissolve it in 500 mL of deionized water to obtain a perfluorooctanoic acid solution with a molar concentration of 0.05 mmol / L. Take 20 mL each and put it into 5 glass reaction vials, which are recorded as groups 1-5.

[0060] The surface material of the magnetic rotor used in this example is polytetrafluoroethylene (PTFE), and two magnetic rotors are added to the reaction vials of groups 1 to 5 respectively. Group 1 is used as the control group and no additional addition is made. Humic acid 0.0005 g, 0.0023 g, 0.0091 g, and 0.0227 g are added to the reaction vials of groups 2 to 5 respectively, so that the concentration of humic acid in the solution is 0.1 mM, 0.5 mM, 2.0 mM, and 5.0 mM.

[0061] Place the reaction vials of groups 1-5 into a 100W 40kHz ultrasonic device, add a certain amount of water into the ultrasonic device until the liquid level covers the liquid level of the reaction vials, add ice bags to control the temperature not exceeding 30°C, start the reaction, and time for 150 minutes. Take samples at 0, 10, 20, 40, 60, 90, 120, and 150 minutes, respectively. Detect the content of perfluorooctanoic acid in the solution by HPLC, and calculate the degradation rate of perfluorooctanoic acid.

[0062] The experimental results are as follows Figure 6 As shown, in different concentrations of humic acid, the degradation rate of perfluorooctanoic acid can reach 99% within 150 minutes by using a magnetic rotor with a surface material of PTFE to enhance ultrasonic degradation. The results show that different concentrations of humic acid have almost no effect on the degradation effect of perfluorooctanoic acid by using a magnetic rotor with a surface material of PTFE to enhance ultrasonic removal.

[0063] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other. The above description of the disclosed embodiments enables professionals and technicians in this field to implement or use the present invention. Various modifications to these embodiments will be obvious to professionals and technicians in this field, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown in this article, but will comply with the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for removing perfluorinated compounds by using a magnetic rotor to enhance ultrasound, characterized in that: The following steps are involved: A magnetic rotor was placed in the target solution containing the perfluorinated compound and then sonicated.

2. The method for removing perfluorinated compounds by using magnetic rotor enhanced ultrasound according to claim 1, characterized in that: The perfluorinated compound is perfluorooctanoic acid.

3. The method for removing perfluorinated compounds by using magnetic rotor enhanced ultrasound according to claim 1, characterized in that: The surface material of the magnetic rotor is PTFE.

4. The method for removing perfluorinated compounds by using magnetic rotor enhanced ultrasound according to claim 1, characterized in that: The molar concentration of the perfluorinated compound in the target solution containing the perfluorinated compound is 0.05 mmol / L.

5. The method for removing perfluorinated compounds by using magnetic rotor enhanced ultrasound according to claim 1, characterized in that: Ultrasonic power: 100W.

6. The method for removing perfluorinated compounds by using magnetic rotor enhanced ultrasound according to claim 1, characterized in that: Ultrasonic frequency 40kHz.

7. The method for removing perfluorinated compounds by using magnetic rotor enhanced ultrasound according to claim 1, characterized in that: The ultrasonic treatment temperature is ≤30°C.

8. The method for removing perfluorinated compounds by using magnetic rotor enhanced ultrasound according to claim 1, characterized in that: The ultrasonic treatment time is ≥2.5h.

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