Method for detecting polybrominated diphenyl ethers in water body by using biochar electrochemical sensor

Abstract

This invention discloses a method for detecting polybrominated diphenyl ethers (PDEs) in water using a biochar electrochemical sensor. The method involves constructing an electrochemical sensor using a biochar electrode to electrochemically detect PDEs in a solution. Finally, based on the peak current change of the obtained PDE solution, the concentration of PDEs is calculated using a linear regression equation between the PDE concentration and the peak current change. This method first utilizes biochar to adsorb PDEs, and then detects PDEs in water by observing the changes in the electrochemical signal generated during the adsorption process. It has advantages such as simple operation, low cost, high detection efficiency, and high accuracy, enabling accurate detection of PDEs, and also improving the detection of Na+. + K + Ca 2+ Mg 2+ Fe 2+ and Pb 2+ It has strong anti-interference ability against interference factors, which is of great significance for achieving efficient detection of trace polybrominated diphenyl ethers in the aquatic environment.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical sensor technology and relates to a method for detecting polybrominated diphenyl ethers (PBDEs), specifically a method for detecting PBDEs in water using a biochar electrochemical sensor. Background Technology

[0002] Polybrominated diphenyl ethers (PBDEs) are polybrominated aromatic compounds. Theoretically, there are 209 homologues based on the number of brominators and their positions on the benzene ring. Among them, 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) is one of the most abundant homologues in environmental media. It exhibits strong persistence, toxicity, and potential bioaccumulation, interfering with the normal secretion of thyroid hormones in organisms and leading to hypothyroidism in children and adults. Furthermore, because PBDEs are difficult to decompose in the environment, their pollution is becoming increasingly serious. Therefore, it is urgent to control and treat PBDEs in the aquatic environment, and effective detection of PBDE levels in water bodies is a prerequisite for pollution prevention and control.

[0003] Traditional analytical methods for detecting organic matter include gas chromatography, liquid chromatography, mass spectrometry, and gas chromatography-mass spectrometry (GC-MS). However, most of these methods suffer from drawbacks such as large equipment size, high operating and maintenance costs, and cumbersome sample pretreatment processes. Furthermore, the pretreatment required for most detections is time-sensitive, making it difficult to immediately analyze the content of specific organic compounds in a sample and hindering real-time online detection. Sensor-based detection technology, due to its high sensitivity and specificity, has become a new research hotspot for organic matter detection. Moreover, the required equipment is becoming increasingly miniaturized and easy to operate, enabling rapid, efficient, real-time, and online detection of trace organic matter in aquatic environments.

[0004] Cyclic voltammetry is a commonly used electrochemical sensing technique. However, in existing cyclic voltammetry methods, the glassy carbon electrode surface lacks adsorption sites for polybrominated diphenyl ethers (PBDEs). Therefore, directly using a glassy carbon electrode as the working electrode results in the inability to adsorb PBDEs, hindering effective detection of PBDEs using electrochemical sensing techniques. Furthermore, while loading biochar onto the glassy carbon electrode surface can improve its adsorption capacity, electrochemical sensors constructed using this biochar-based working electrode are primarily used for detecting heavy metals in water; there are no reports on using biochar working electrodes for detecting PBDEs in water. Meanwhile, electrochemical sensors using biochar-based ion-imprinted working electrodes to detect heavy metals in water employ stripping voltammetry, requiring the enrichment of heavy metal ions before obtaining the detection signal through differential pulse voltammetry. However, this method is not suitable for detecting PBDEs in water. Furthermore, non-ionic imprinted biochar electrodes currently used for detecting heavy metals in water are not suitable for detecting polybrominated diphenyl ethers (PBDEs) in water. This is because biochar produced from different raw materials has different physicochemical properties, leading to different mechanisms for detecting heavy metals and organic pollutants, making a direct comparison impossible. Existing methods for preparing biochar-based working electrodes mainly involve loading biochar onto the electrode surface through natural drying, infrared drying, and ionomer-based cellulose gels. However, such loading methods struggle to stably fix the biochar on the electrode surface, causing it to easily detach. This results in decreased sensor accuracy and even potential complete failure. Simultaneously, existing biochar-based working electrodes suffer from drawbacks such as limited adsorption sites and poor conductivity, leading to narrow detection ranges and low sensitivity in the constructed electrochemical sensors. Therefore, obtaining a low-cost, rapid-response, highly sensitive and accurate biochar electrochemical sensor with low detection limits, wide detection range, strong anti-interference capabilities, and good reusability is crucial for achieving efficient and accurate detection of PBDEs in water and for the effective treatment of PBDE-contaminated water bodies. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for detecting polybrominated diphenyl ethers in water using a biochar electrochemical sensor that is simple to operate, low in cost, high in detection efficiency, high in detection accuracy, and strong in anti-interference ability.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for detecting polybrominated diphenyl ethers in water using a biochar electrochemical sensor includes the following steps:

[0008] S1. Construct an electrochemical sensor using a biochar electrode as the working electrode; the biochar electrode includes an electrode, and the surface of the electrode's reaction end is modified with biochar.

[0009] S2. Place the polybrominated diphenyl ether (PBDE) solution to be tested in an electrochemical sensor for electrochemical detection to obtain the peak current change of the PBDE solution to be tested;

[0010] S3. Based on the peak current change of the polybrominated diphenyl ether (PBDE) solution to be tested, the concentration of PBDE in the solution to be tested is calculated using the linear regression equation between PBDE and peak current change.

[0011] In a further improvement to the above method, in step S1, the biochar loading in the biochar electrode is 636.85 g / cm³. 2 The biochar is sludge biochar; the specific surface area of ​​the biochar is 35.65 m². 2 / g~52.91m 2 / g; the electrode is a glassy carbon electrode; the glassy carbon electrode is a glassy carbon electrode.

[0012] In a further improvement to the above method, step S1, the preparation method of the biochar electrode includes the following steps:

[0013] (1) Prepare a biochar dispersion by mixing biochar and adhesive;

[0014] (2) The biochar dispersion is coated on the reaction end surface of the electrode and then glued to obtain the biochar electrode.

[0015] The above method is further improved in step (1), wherein the preparation method of the biochar dispersion includes the following steps: mixing biochar and adhesive, and sonicating for 60 min to 80 min to obtain biochar dispersion; the mass-to-volume ratio of biochar to adhesive is 10 mg: 1 mL; the biochar is obtained by calcining sludge; the heating rate during calcination is 10 °C / min; the calcination temperature is 400 °C to 800 °C; the calcination time is 2 h; and the adhesive is dimethylformamide.

[0016] The above method is further improved in step (2), in which the electrode is further treated as follows before use: the reaction end surface of the electrode is ground, polished and cleaned, the cleaned electrode is placed in an acidic solution, and the cleaned electrode is electrochemically treated by cyclic voltammetry until the current in the electrochemical treatment process reaches stability; the grinding is to first grind the reaction end surface of the electrode with alumina powder with a particle size of 0.3μm and 0.05μm in sequence, and then grind the reaction end surface of the electrode with 2500 mesh, 3000 mesh, 5000 mesh and 7000 mesh sandpaper in sequence; the polishing is to polish the reaction end surface of the working electrode with a polymer synthetic leather polishing cloth; the cleaning is to place the electrode in anhydrous ethanol and ultrasonically clean it in a water bath for 30s to 90s; in the electrochemical treatment process, the scanning potential range of cyclic voltammetry is -0.3V to 0.8V, and the scanning rate is 100mV / S; the acidic solution is a sulfuric acid solution; the concentration of the acidic solution is 0.5mol / L.

[0017] In a further improvement to the above method, in step (2), the adhesive process is carried out under vacuum conditions; the temperature of the adhesive treatment is 100℃~120℃; and the time of the adhesive treatment is 10min~20min.

[0018] In a further improvement to the above method, in step (1), the calcination temperature is 500℃~600℃.

[0019] In a further improvement to the above method, in step (2), the temperature of the adhesive treatment is 110℃~118℃ and the time of the adhesive treatment is 12min~18min.

[0020] In a further improvement to the above method, in step S1, a biochar electrode is used as the working electrode, and a reference electrode and a counter electrode are used to establish a three-electrode system, which is then connected to an electrochemical workstation to form a sludge biochar electrochemical sensor; the reference electrode is Ag-AgCl; and the counter electrode is a platinum electrode.

[0021] In a further improvement to the above method, step S2 involves electrochemical detection of the polybrominated diphenyl ether (PBDE) solution to be tested using cyclic voltammetry. During the electrochemical detection, the control potential is -0.3V to 0.8V, and the scan rate is 100mV / s. The measurement parameters for the cyclic voltammetry are: amplitude 0.001V, frequency 1000Hz, and sensitivity 0.00001V. The concentration of PBDEs in the PBDE solution to be tested is 0.005mg / L to 0.60mg / L. The pH value of the PBDE solution to be tested is ≤7. The PBDE is tetrabromodiphenyl ether.

[0022] A further improvement to the above method, in step S3, the method for constructing the linear regression equation of the polybrominated diphenyl ether and the peak current change includes the following steps:

[0023] S3-1. Place polybrominated diphenyl ether standard solutions of different concentrations into an electrochemical sensor for electrochemical detection to obtain the peak current changes corresponding to polybrominated diphenyl ether standard solutions of different concentrations.

[0024] S3-2. Based on the peak current changes corresponding to standard solutions of polybrominated diphenyl ethers (PBDEs) of different concentrations, suggest a mapping relationship between PBDE concentrations and peak current changes in the solution, and obtain a linear regression equation between PBDEs and peak current changes.

[0025] In a further improvement to the above method, in step S3-1, the concentration of the polybrominated diphenyl ether standard solution is 0.005 mg / L, 0.02 mg / L, 0.04 mg / L, 0.05 mg / L, 0.07 mg / L, 0.10 mg / L, 0.13 mg / L, 0.15 mg / L, 0.18 mg / L, 0.20 mg / L, 0.23 mg / L, 0.25 mg / L, 0.28 mg / L, 0.30 mg / L, 0.33 mg / L, 0.35 mg / L, 0.38 mg / L, 0.40 mg / L, 0.45 mg / L, 0.50 mg / L, 0.55 mg / L, or 0.60 mg / L.

[0026] The above method is further improved in step S3, when the polybrominated diphenyl ether is tetrabrominated diphenyl ether, the corresponding linear regression equation of polybrominated diphenyl ether and peak current change is shown in equation (1).

[0027] ΔI BDE-47 =16.8125×(C BDE-47 )+22.7186 (1);

[0028] In equation (1), △I BDE-47 The peak current values ​​for tetrabromodiphenyl ether at different concentrations in the solution are given in μA; C BDE-47 The concentration of tetrabromodiphenyl ether in the solution is expressed in mg / L; the correlation coefficient R in equation (1) is... 2 =0.99, detection range is 0.005mg / L~0.60mg / L, and detection limit is 5ng / L.

[0029] Compared with the prior art, the advantages of the present invention are as follows:

[0030] (1) This invention provides a method for detecting polybrominated diphenyl ethers (PDEs) in water using a biochar electrochemical sensor. First, an electrochemical sensor is constructed using a biochar electrode, which includes an electrode with biochar-modified reaction end surface. Then, the electrochemical sensor is used to electrochemically detect the PDE solution, obtaining the peak current change of the PDE solution. Finally, based on the peak current change of the PDE solution, the concentration of PDEs in the solution is calculated using a linear regression equation between PDEs and peak current changes. This method first utilizes biochar to adsorb PDEs, and then detects PDEs in water by observing the changes in the electrochemical signal generated during adsorption. It has advantages such as simple operation, low cost, high detection efficiency, and high detection accuracy, enabling accurate detection of PDEs and improving the detection of Na+. + K + Ca 2+ Mg 2+ Fe 2+ and Pb 2+ It has strong anti-interference ability against interference factors, which is of great significance for achieving efficient detection of trace polybrominated diphenyl ethers in the aquatic environment.

[0031] (2) In this invention, the sludge biochar used is a three-dimensional material with a large specific surface area and many spatial active sites. Therefore, modifying the surface of the working electrode with sludge biochar is beneficial to increasing the number of reaction sites on the surface of the working electrode, thereby improving the detection range of the electrochemical sensor. In this invention, the sludge biochar has good organic matter adsorption performance, so it can be used in the detection process of polybrominated diphenyl ether concentration. In this invention, the sludge biochar used has good conductivity. Therefore, modifying the surface of the working electrode with sludge biochar is beneficial to improving the detection sensitivity and accuracy of the working electrode, as well as lowering the detection limit. In this invention, the sludge biochar used has good stability. Therefore, modifying the surface of the working electrode with sludge biochar is beneficial to improving the structural stability and reliability of the working electrode. Compared to electrochemical sensors with conventional working electrodes, the electrochemical sensor of this invention, constructed with a working electrode whose reaction end surface is modified with sludge biochar, offers advantages such as low cost, rapid response (immediate detection), high detection sensitivity and accuracy (detection range of 0.005–0.60 mg / L), low detection limit (lowest detection limit is 5 ng / L), wide detection range (detection of trace tetrabromodiphenyl ether spans three orders of magnitude), and strong anti-interference capability (even when interacting with common interfering heavy metal ions such as Na+). + K + Ca 2+ Mg 2+ Fe 2+ and Pb 2+With advantages such as minimal impact of heavy metals on the detection of this electrochemical sensor when coexisting with other substances, good reusability (the working electrode modified with sludge biochar can be stored at 4°C, and the current response signal does not show significant decay after multiple detections), it is a high-performance novel electrochemical sensor that can be widely used to detect tetrabromodiphenyl ether in the aquatic environment and can achieve simultaneous detection of tetrabromodiphenyl ether. It has high practical value and good application prospects. In addition, the sludge biochar electrochemical sensor of this invention still maintains good current response after being stored for a period of time, and has good stability and reliability.

[0032] (3) In this invention, the adhesive method is used for the first time to load sludge biochar onto the reaction end surface of glassy carbon electrode, thereby obtaining a working electrode with excellent current response performance and stable structure. At the same time, the method of preparing biochar electrode in this invention has the advantages of simple process, convenient operation and low cost, which is suitable for large-scale preparation and conducive to industrial application.

[0033] (4) In the present invention, the method for preparing biochar electrode is optimized by setting the adhesive treatment temperature to 100℃~120℃ and the time to 10min~20min, especially the adhesive treatment temperature to 110℃~118℃ and the time to 12min~18min, which is more conducive to fixing the sludge biochar completely and firmly on the electrode reaction end surface. This is not only conducive to obtaining a larger peak current, which is more conducive to the accurate detection of polybrominated diphenyl ethers by the electrochemical sensor, but also conducive to improving the service life of the biochar electrode, which is more conducive to the reuse of the electrochemical sensor. Attached Figure Description

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0035] Figure 1 This is a voltammetric curve of the adsorption of different concentrations of tetrabromodiphenyl ether by a glassy carbon electrode supported on sludge biochar in Example 1 of the present invention.

[0036] Figure 2 This is a graph showing the peak current changes corresponding to different concentrations of tetrabromodiphenyl ether standard solutions in Example 1 of the present invention.

[0037] Figure 3 This is a comparison of the current-voltage curves before and after the use of the working electrode in Embodiment 1 of the present invention.

[0038] Figure 4 This is a graph showing the peak current changes corresponding to the adsorption of tetrabromodiphenyl ether at different scan rates in Example 1 of the present invention.

[0039] Figure 5This is a graph showing the peak current changes in tetrabromodiphenyl ether solutions at different pH values ​​in Example 1 of the present invention.

[0040] Figure 6 This is a schematic diagram of the preparation process of the biochar electrode in Example 1 of the present invention.

[0041] Figure 7 The images show SEM images of sludge biochar prepared at different calcination temperatures in Example 1 of this invention.

[0042] Figure 8 This is a graph showing the peak current variation of the sludge biochar electrochemical sensor in Example 2 of the present invention under different heavy metal ion interference conditions. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0044] In the following examples, unless otherwise specified, the raw materials and instruments used are commercially available, the processes used are conventional processes, the equipment used is conventional equipment, and the data obtained are the average values ​​of more than three repeated experiments.

[0045] Example 1

[0046] A method for detecting polybrominated diphenyl ethers (PBDEs) in water using a biochar electrochemical sensor, specifically utilizing a sludge biochar electrochemical sensor constructed from biochar electrodes to detect tetrabrominated diphenyl ethers (TBDEs) in water, includes the following steps:

[0047] (1) Construction of sludge biochar electrochemical sensor:

[0048] A three-electrode system was established using a glassy carbon electrode (A2) with biochar modified on the reaction end surface as the working electrode, Ag-AgCl as the reference electrode, and a platinum electrode as the counter electrode. This system was then connected to an electrochemical workstation to form a sludge biochar electrochemical sensor.

[0049] (2) Place the test solution in the sludge biochar electrochemical sensor constructed in step (1), and perform adsorption / electrochemical detection of the test solution using cyclic voltammetry. Specifically, the tetrabromodiphenyl ether in the test solution is adsorbed onto the working electrode through biochar and subjected to cyclic voltammetry testing. Wait for the cyclic voltammetry detection to be complete and the image to stabilize, and obtain the peak current change value of tetrabromodiphenyl ether (ΔI). BDE-47 ),like Figure 1As shown in Table 1. In this step, the test solutions are: Test solution A, which is obtained by mixing tetrabromodiphenyl ether and phosphate buffer solution, wherein the actual concentrations of tetrabromodiphenyl ether in test solution A are 80 μg / L, 300 μg / L, and 500 μg / L, respectively; the phosphate buffer solution is composed of NaH2PO4, Na2HPO4, and H3PO4, and the pH value of the phosphate buffer solution is 2.

[0050] (3) Based on the peak current change value (ΔI) of the tetrabromodiphenyl ether solution to be tested BDE-47 The concentration of tetrabromodiphenyl ether in the solution to be tested was calculated using a linear regression equation of tetrabromodiphenyl ether and peak current change. The results are shown in Table 1.

[0051] Table 1. Validation results of the recovery rate of the test solution in Example 1 of this invention.

[0052]

[0053] As shown in Table 1, the results of the spiked recovery experiment of water samples compared with those of liquid chromatography are basically consistent with those of the traditional detection method, with a recovery rate of 96.79% to 105.04%, which indicates that the method of the present invention has good accuracy.

[0054] In step (3), the method for constructing the linear regression equation between tetrabromodiphenyl ether and the peak current change is as follows: The sludge biochar electrochemical sensor constructed in step (1) is used to detect different concentrations of tetrabromodiphenyl ether standard solutions (the tetrabromodiphenyl ether standard solution gradients are 0.005 mg / L, 0.02 mg / L, 0.04 mg / L, 0.05 mg / L, 0.07 mg / L, 0.10 mg / L, 0.13 mg / L, 0.1 ... Different concentrations of tetrabromodiphenyl ether standard solutions and their peak current changes were obtained at concentrations of 5 mg / L, 0.18 mg / L, 0.20 mg / L, 0.23 mg / L, 0.25 mg / L, 0.28 mg / L, 0.30 mg / L, 0.33 mg / L, 0.35 mg / L, 0.38 mg / L, 0.40 mg / L, 0.45 mg / L, 0.50 mg / L, 0.55 mg / L, and 0.60 mg / L. Figure 2 As shown. However, based on the relationship between the concentration of tetrabromodiphenyl ether standard solutions of different concentrations and the peak current change, a linear regression equation was constructed for the relationship between the concentration of tetrabromodiphenyl ether and the peak current change, as shown in equation (1) below.

[0055] The linear regression equation constructed by the concentration of tetrabromodiphenyl ether and the change in peak current is as follows:

[0056] ΔI BDE-47 =16.8125×(C BDE-47 )+22.7186 (1);

[0057] In equation (1), △I BDE-47 To detect the peak current values ​​of tetrabromodiphenyl ether at different concentrations in a buffer solution, the unit is μA; C BDE-47 The concentration of tetrabromodiphenyl ether in the buffer solution is expressed in mg / L; the relative standard deviation of three parallel determinations of tetrabromodiphenyl ether in the same sample is 2.8%; the correlation coefficient R in equation (1) is... 2 =0.99, detection range is 0.005mg / L~0.60mg / L, and detection limit is 5ng / L.

[0058] After the detection in Example 1 was completed, the working electrode was removed and stored at 4°C for 24 hours before cyclic voltammetry scanning was performed. Figure 3 This is a comparison of the current-voltage curves before and after the use of the working electrode in Embodiment 1 of the present invention. Figure 3 In the diagram, A is the working electrode immediately after adsorption of tetrabromodiphenyl ether, and B is the working electrode after storage at 4°C for 24 hours. From... Figure 3 It can be seen that the peak currents did not change much in the two tests, and the volt-ampere curves were almost identical, indicating that the sludge biochar loaded on the glassy carbon electrode is structurally stable and can be stored at 4℃. Moreover, when used for electrochemical detection multiple times within 3 days, the corresponding response signal did not show significant attenuation.

[0059] In this embodiment, the effect of different scan rates on the detection results was also investigated. Specifically, phosphate buffer solutions with the same pH value and a concentration of 0.40 mg / L for tetrabromodiphenyl ether were detected according to the method in Example 1. The results are as follows: Figure 4 As shown.

[0060] Figure 4 This is a graph showing the peak current changes corresponding to the adsorption of tetrabromodiphenyl ether at different scan rates in Example 1 of the present invention. Figure 4 In this study, using a glassy carbon electrode supported on sludge biochar as the working electrode, the effects of different scan rates (0.01–1 V / s, specifically 0.01 V / s, 0.05 V / s, 0.1 V / s, 0.3 V / s, 0.5 V / s, 0.7 V / s, 0.9 V / s, and 1 V / s) on cyclic voltammetry curves containing 0.40 mg / L tetrabromodiphenyl ether were investigated in a phosphate buffer solution at pH 2.0. Figure 4 As shown, when the scan rate increases in the range of 0.01 to 1 V / s, the peak current of tetrabromodiphenyl ether gradually increases, indicating that tetrabromodiphenyl ether is mainly adsorbed on the glassy carbon electrode surface supported by sludge biochar.

[0061] In this embodiment, the current change of the biochar electrode in test solutions with different pH values ​​was also investigated. Specifically, the pH value of the phosphate solution was adjusted to 2, 3, 4, 5, 6, 7, and 8 using 98% concentrated phosphoric acid. The corresponding pH values ​​of the tetrabromodiphenyl ether (TBD) test solutions were 2, 3, 4, 5, 6, 7, and 8, respectively, and the concentration of TDD in these different pH solutions was 0.40 mg / L. The TDD test solutions were tested according to the method in Example 1, and the results are as follows. Figure 5 As shown. Figure 5 As shown, the peak current is highest when the pH of the test solution is 2. Meanwhile, the peak current gradually decreases as the pH of the test solution increases. The peak current is lowest when the pH of the test solution is 8. Therefore, in this invention, when the pH of the test solution is ≤7, the sludge biochar electrochemical sensor can obtain a higher peak current. In particular, the peak current is highest when the pH of the test solution is 2. This makes the sludge biochar electrochemical sensor more sensitive in detection, and more conducive to the adsorption of tetrabromodiphenyl ether in water and the accurate detection of the concentration of tetrabromodiphenyl ether in water.

[0062] In Example 1, the biochar electrode used includes an electrode with biochar modified on the surface of the reaction end. The biochar loading on the surface of the electrode reaction end is 636.85 g / cm³. 2 The biochar is sludge biochar, and its specific surface area is 44.915 m². 2 / g, the electrode is a glassy carbon electrode, the glassy carbon electrode is a glassy carbon electrode.

[0063] The preparation process flow diagram of the biochar electrode used in Example 1 is as follows. Figure 6 As shown, it includes the following steps:

[0064] S1. Preliminary sludge treatment:

[0065] Sludge from the upper part of the wastewater (the upper aerobic sludge portion) is collected from the wastewater treatment plant and transported back to the laboratory by passenger transport. The sludge temperature is maintained at 3℃~13℃ during the journey. After arriving at the laboratory, the sludge is dewatered, and the remaining dewatered sludge sample is used for subsequent operations. The sludge obtained from the wastewater treatment plant is dried at 105℃ until the sludge quality no longer deteriorates.

[0066] S2. Combustion of sludge biochar:

[0067] The dried sludge was ground and pulverized, then placed in a crucible and placed in a tube furnace. The temperature was increased to the carbonization temperature at a rate of 10℃ / min, and calcined / pyrolyzed at this temperature for 2 hours to obtain sludge biochar. The performance data of sludge biochar prepared under different calcination temperature conditions are shown in Table 2.

[0068] Table 2. BJH and BET parameters of sludge biochar prepared at calcination temperatures of 400℃, 600℃, and 800℃.

[0069]

[0070] Table 2 shows that the pore volume, specific surface area, and average pore size of biochar increase significantly with increasing temperature. However, the total pore volume and average pore size decrease between 600 and 800℃, indicating that the physical adsorption effect of biochar initially increases with temperature and then decreases with further increases. Furthermore, the sludge biochar prepared at 600℃ exhibits the highest total pore volume, specific surface area, and pore size. Therefore, using sludge biochar prepared at 600℃ to prepare biochar electrodes and construct sludge biochar electrochemical sensors is more beneficial for improving the detection range and sensitivity.

[0071] In step S2, the sludge biochar prepared at calcination temperatures of 400, 600, and 800℃ are designated as A1, A2, and A3, respectively. SEM images of the sludge biochar prepared at these different calcination temperatures are shown below. Figure 7 As shown.

[0072] Figure 7 The images show SEM images of sludge biochar prepared at different calcination temperatures in Example 1 of this invention. Figure 7 In the diagram, a, b, and c correspond to sludge biochar (A1, A2, A3) respectively. (The remaining text appears to be incomplete and requires further context.) Figure 7 It can be seen that the sludge biochar has a distinct three-dimensional structure, with relatively large particles and pore sizes. The numerous and concentrated pores significantly increase the specific surface area of ​​the sludge biochar, providing more adsorption sites. (See Table 2 and...) Figure 7 The conclusion is that using sludge biochar prepared at a calcination temperature of 600℃ to construct electrochemical sensors is more conducive to improving the detection performance of electrochemical sensors.

[0073] S3, Electrode activation:

[0074] (a) Gently wipe the electrode surface with damp lens paper to remove dirt and ensure the electrode surface is smooth.

[0075] (b) The reaction end surface of the working electrode is polished sequentially using alumina powder and sandpaper. Specifically, when polishing with alumina powder, alumina powder with a particle size of 0.3μm and 0.05μm is used sequentially to polish the reaction end surface of the working electrode. When polishing with sandpaper, 2500 grit, 3000 grit, 5000 grit and 7000 grit sandpaper are used sequentially. The glassy carbon electrode is held vertically, and the elbow is used to apply even force to make the glassy carbon electrode move slowly on the sandpaper. The path is circular or figure-eight. The electrode is polished for 10 minutes. During the polishing process, it is important to ensure that the electrode surface is pressed on the polishing disc and is not tilted. Otherwise, the electrode surface after polishing will easily deform instead of being flat.

[0076] (c) Rinse the electrode surface with ultrapure water.

[0077] (d) Polish the reaction end surface of the working electrode using a polymer synthetic leather polishing cloth.

[0078] (e) Place the glassy carbon electrode in anhydrous ethanol and ultrasonically clean it in a water bath for 1 min.

[0079] (f) The cleaned electrode was placed in a 0.5 mol / L H2SO4 solution and cyclic voltammetry (CV) scan was performed in the potential range of -0.3 to 0.8 V (scan rate of 100 mV / s). The electrochemical treatment was repeated until the detected current stabilized. During the electrochemical treatment, the oxide layer on the electrode surface was removed and more active sites on the electrode surface were exposed to obtain an activated glassy carbon electrode.

[0080] S4. Modification of sludge biochar:

[0081] Take 5 mg of the sludge biochar (A1, A2, A3) prepared in step S2 and mix them separately in 0.5 mL of DMF (dimethylformamide), then sonicate for 75 min to prepare a dispersion. Use a pipette to drop the dispersion onto the surface of the activated glassy carbon electrode reaction end obtained in step S3, and then use a vacuum drying oven for high-temperature bonding, specifically bonding at 115℃ for 15 min, to stably load the sludge biochar onto the surface of the activated glassy carbon electrode reaction end, thus obtaining the biochar electrode.

[0082] After modification, at 5 mmol / L Fe(CN)6 3- / Fe(CN)6 4- Cyclic voltammetry was performed in a detection solution containing 100 mmol / L KCl.

[0083] In this invention, potassium ferricyanide solution (5 mmol / L Fe(CN)6) is used. 3-Cyclic voltammetry (CV) was performed using 100 mmol / L KCl as the base solution to characterize the electrochemical properties of the bare glassy carbon electrode surface. This allows for comparison and evaluation of the changes in the electrochemical properties of the glassy carbon electrode surface loaded with sludge biochar in subsequent steps such as sludge biochar modification and adsorption of tetrabromodiphenyl ether.

[0084] In this embodiment, the effect of sludge biochar prepared at different calcination temperatures on the corresponding current when used to construct an electrochemical sensor was also investigated, with other conditions remaining the same as in Example 1. The test results showed that the currents generated when sludge biochar calcined at 400℃, 600℃, and 800℃ were used to construct the electrochemical sensor were 22.58 μA, 26.58 μA, and 20.08 μA, respectively. This indicates that the current generated in the electrochemical sensor gradually increases with increasing calcination temperature, reaching its maximum at 600℃, and then gradually decreasing. Therefore, when the calcination temperature is between 500-700℃, the prepared sludge biochar can obtain a larger peak current when loaded onto the electrode, indicating that the sludge biochar electrode has better conductivity and more adsorption sites, especially with superior performance obtained at a calcination temperature of 600℃.

[0085] In this embodiment, the effects of different adhesive treatment temperatures and times on the peak current of the biochar electrode were also investigated, as shown in Tables 3 and 4.

[0086] Table 3. Effect of different adhesive treatment temperatures on peak current of biochar electrode

[0087] Adhesive bonding temperature (°C) Peak current (μA) 100 25.59 110 26.04 115 26.58 118 26.13 120 25.98

[0088] Table 4. Effect of different adhesive treatment times on peak current of biochar electrode

[0089] Adhesive bonding time (min) Peak current (μA) 10 24.64 12 24.94 15 26.58 18 25.09 20 24.75

[0090] In Table 3, the adhesive treatment time is 15 min; in Table 4, the adhesive treatment temperature is 115℃.

[0091] In addition, when the adhesive treatment temperature is 132℃ and the heat treatment time is 25min, the electrode signal is abnormal and no effective peak current can be detected.

[0092] The results above show that, in this invention, optimizing the adhesive treatment temperature to 100℃~120℃ and the time to 10min~20min, particularly to 110℃~118℃ and 12min~18min, is more conducive to the complete and firm fixation of sludge biochar onto the electrode reaction end surface. Specifically, if the adhesive treatment time is too short or the adhesive treatment temperature is too low, the sludge biochar may not be properly loaded onto the glassy carbon electrode, potentially leading to detachment when placed in water for tetrabromodiphenyl ether detection, resulting in poor stability. If the adhesive treatment temperature is too high or the adhesive treatment time is too long, it will damage the conductivity between the sludge biochar and the electrode, making electron transfer more difficult and significantly reducing sensitivity. Therefore, optimizing the adhesive treatment conditions in this invention not only facilitates obtaining a larger peak current, thus improving the accurate detection of polybrominated diphenyl ethers by the electrochemical sensor, but also extends the lifespan of the biochar electrode, thereby promoting the reusability of the electrochemical sensor.

[0093] Example 2

[0094] The anti-interference ability of the sludge biochar electrochemical sensor was investigated. Specifically, the sludge biochar electrochemical sensor constructed in Example 1 was used to detect tetrabromodiphenyl ether solutions containing different interfering substances. The steps included: adding 100 times the concentration of sodium ions (Na₂O₃) to phosphate buffer solutions containing tetrabromodiphenyl ether at concentrations of 0.10 mg / L, 0.15 mg / L, 0.20 mg / L, 0.25 mg / L, 0.30 mg / L, and 0.35 mg / L. + ), potassium ions (K) + ), calcium ions (Ca 2+ ), magnesium ions (Mg 2+ ), ferrous ions (Fe) 2+ ) and lead (Pb 2+ This resulted in concentrations of the aforementioned ions in the various tetrabromodiphenyl ether solutions of 10 mg / L, 15 mg / L, 20 mg / L, 25 mg / L, 30 mg / L, and 35 mg / L, respectively. The concentrations of various heavy metal ions in the above samples (test solutions) were detected according to the method described in Example 1. Figure 8 As shown.

[0095] The results showed that Na + K + Ca 2+ Mg 2+ Fe 2+ and Pb 2+The impact on the detection results was all <10% (peak current change), indicating that the chemical sensor has good anti-interference ability. The reasons are as follows: (1) The electrochemical detection method used is cyclic voltammetry, not anodic stripping voltammetry, so it does not need to be pre-enriched with metal ions like ion-imprinted biochar electrodes; (2) Biochar made from different raw materials contains different functional groups and has different physicochemical properties. Furthermore, the sludge biochar used in this invention can both physically adsorb tetrabromodiphenyl ether and chemically adsorb it by combining specific functional groups on the carbon with the groups of tetrabromodiphenyl ether. The two adsorption processes occur simultaneously and generate electrochemical signals, which greatly increases the weight of tetrabromodiphenyl ether being preferentially adsorbed by sludge biochar. At the same time, since the molecule of tetrabromodiphenyl ether is much larger than that of heavy metal ions, the more adsorption sites occupied by tetrabromodiphenyl ether, the more the pores are blocked, and the lower the probability of heavy metal ions being adsorbed. Ultimately, it leads to the coexistence of tetrabromodiphenyl ether and tetrabromodiphenyl ether in water without generating an electrochemical signal that interferes with the detection.

[0096] As can be seen from the above, this invention first utilizes biochar to adsorb polybrominated diphenyl ethers (PBDEs), and then detects PBDEs in water by observing the changes in electrochemical signals generated during the adsorption process. This method has advantages such as simple operation, low cost, high detection efficiency, and high detection accuracy. It can accurately detect PBDEs and is effective against Na+. + K + Ca 2+ Mg 2 + Fe 2+ and Pb 2+ It has strong anti-interference ability against interference factors, which is of great significance for achieving efficient detection of trace polybrominated diphenyl ethers in the aquatic environment.

[0097] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for detecting polybrominated diphenyl ethers in a water body using a biochar electrochemical sensor, characterized in that, Includes the following steps: S1. Constructing an electrochemical sensor using a biochar electrode as the working electrode; the biochar electrode includes an electrode, the reaction end surface of which is modified with biochar; the preparation method of the biochar electrode includes the following steps: (1) Biochar and adhesive are mixed to prepare a biochar dispersion; the biochar is obtained by calcining sludge; The heating rate during the calcination process is 10℃ / min; the calcination temperature is 400℃~800℃; the calcination time is 2h; and the adhesive is dimethylformamide. (2) The biochar dispersion is coated onto the reaction end surface of the electrode and then adhesive-bonded to obtain a biochar electrode; S2. The polybrominated diphenyl ether (PBDE) solution to be tested is placed in an electrochemical sensor for electrochemical detection to obtain the peak current change of the PBDE solution to be tested; the PBDE in the PBDE solution to be tested is tetrabromodiphenyl ether. S3. Based on the peak current change of the polybrominated diphenyl ether (PBDE) solution to be tested, the concentration of PBDE in the solution to be tested is calculated using the linear regression equation between PBDE and peak current change.

2. The method of claim 1, wherein, In step S1, the biochar is sludge biochar; the specific surface area of the biochar is 35.65 m 2 / g~52.91 m 2 / g; the electrode is a glassy carbon electrode; and the glassy carbon electrode is a glassy carbon electrode.

3. The method of claim 2, wherein, In step (1), the preparation method of the biochar dispersion includes the following steps: mixing biochar and adhesive, sonicating for 60 min to 80 min to obtain biochar dispersion; the mass-volume ratio of biochar to adhesive is 10 mg: 1 mL; In step (2), the electrode further includes the following treatment before use: grinding, polishing, and cleaning the reaction end surface of the electrode; placing the cleaned electrode in an acidic solution; and performing electrochemical treatment on the cleaned electrode using cyclic voltammetry until the current during the electrochemical treatment reaches stability; the grinding is performed by sequentially using particles with a particle size of 0.3 μm and 0.05 μm. The electrode's reaction end surface is polished with μm alumina powder, followed by sequential polishing with 2500-mesh, 3000-mesh, 5000-mesh, and 7000-mesh sandpaper. Polishing is performed using a polymer synthetic leather polishing cloth. Cleaning involves placing the electrode in anhydrous ethanol and ultrasonically cleaning it in a water bath for 30-90 seconds. During the electrochemical treatment, the cyclic voltammetry scan potential range is -0.3V to 0.8V, and the scan rate is 100mV / s. The acidic solution is a sulfuric acid solution with a concentration of 0.5mol / L. The adhesive bonding process is carried out under vacuum conditions, at a temperature of 100℃ to 120℃, and for 10-20 minutes.

4. The method according to claim 3, characterized in that, In step (1), the calcination temperature is 500℃~600℃; In step (2), the temperature of the adhesive treatment is 110℃~118℃, and the time of the adhesive treatment is 12min~18min.

5. The method according to any one of claims 1 to 4, characterized in that, In step S1, a three-electrode system is established using a biochar electrode as the working electrode, along with a reference electrode and a counter electrode. This system is then connected to an electrochemical workstation to form a sludge biochar electrochemical sensor. The reference electrode is Ag-AgCl, and the counter electrode is a platinum electrode.

6. The method according to any one of claims 1 to 4, characterized in that, In step S2, cyclic voltammetry is used to perform electrochemical detection on the polybrominated diphenyl ether (PBDE) solution to be tested. During the electrochemical detection process, the control potential is -0.3V to 0.8V, and the scan rate is 100mV / s. The concentration of PBDEs in the PBDE solution to be tested is 0.005mg / L to 0.60mg / L, and the pH value of the PBDE solution to be tested is ≤7.

7. The method according to any one of claims 1 to 4, characterized in that, In step S3, the method for constructing the linear regression equation of the polybrominated diphenyl ether and the peak current change includes the following steps: S3-1. Place polybrominated diphenyl ether standard solutions of different concentrations into an electrochemical sensor for electrochemical detection to obtain the peak current changes corresponding to polybrominated diphenyl ether standard solutions of different concentrations. S3-2. Based on the peak current changes corresponding to standard solutions of polybrominated diphenyl ethers (PBDEs) of different concentrations, establish the mapping relationship between PBDEs of different concentrations in the solution and the peak current changes, and obtain the linear regression equation between PBDEs and peak current changes.

8. The method according to claim 7, characterized in that, In step S3-1, the concentration of the polybrominated diphenyl ether standard solution is 0.005 mg / L, 0.02 mg / L, 0.04 mg / L, 0.05 mg / L, 0.07 mg / L, 0.10 mg / L, 0.13 mg / L, 0.15 mg / L, 0.18 mg / L, 0.20 mg / L, 0.23 mg / L, 0.25 mg / L, 0.28 mg / L, 0.30 mg / L, 0.33 mg / L, 0.35 mg / L, 0.38 mg / L, 0.40 mg / L, 0.45 mg / L, 0.50 mg / L, 0.55 mg / L, or 0.60 mg / L.

9. The method according to claim 7, characterized in that, In step S3, when the polybrominated diphenyl ether is tetrabrominated diphenyl ether, the corresponding linear regression equation of the polybrominated diphenyl ether and the peak current change is shown in equation (1). （1）； In formula (1), ΔI BDE-47 is the peak current value of tetrabromobisphenol A in different concentrations of solution, unit: μA; C BDE-47 is the concentration of tetrabromobisphenol A in solution, unit: mg / L; the correlation coefficient R 2 in formula (1) = 0.99, the detection range is 0.005 mg / L-0.60 mg / L, and the lower limit of detection is 5 ng / L.

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