A method for synergistic treatment of hexavalent chromium and sulfadimethylpyrimidine complex wastewater

Abstract

This invention discloses a method for the synergistic treatment of hexavalent chromium and sulfadiazine complex wastewater. The method utilizes a bimetallic node coupled with a metal-organic framework derivative electrode for the synergistic treatment of hexavalent chromium and sulfadiazine complex wastewater. The electrode includes a conductive substrate coupled with ZrO2 and ZnO. In this invention, the bimetallic node coupled with a metal-organic framework derivative electrode is used as the working electrode. The resulting photoelectrocatalytic system has advantages such as strong light utilization, fast electron transfer efficiency, and strong conversion effect between complex free radical chemistry and different active substances. It can not only achieve the synergistic degradation of hexavalent chromium and sulfadiazine in wastewater, but also simultaneously and efficiently remove both hexavalent chromium and sulfadiazine from the wastewater. It has advantages such as good recyclability, high removal efficiency, good cycle performance, and strong practical application, making it a widely applicable photoelectrocatalytic method with high practical value and application prospects.

Description

Technical Field

[0001] This invention belongs to the field of photoelectrocatalytic anode preparation technology, and relates to a method for synergistically treating hexavalent chromium and sulfadimethylpyrimidine complex wastewater, specifically a method for synergistically treating hexavalent chromium and sulfadimethylpyrimidine complex wastewater using bimetallic nodes coupled with metal-organic framework derivative electrodes. Background Technology

[0002] The production processes of refractory materials, leather tanning, metallurgy, and other chemical industries generate large amounts of chromium-containing wastewater. When discharged into water bodies, this wastewater easily causes serious water environment problems, especially wastewater containing Cr(VI). Due to its high solubility and fluidity, Cr(VI) is thousands of times more toxic than Cr(III), making it a typical highly toxic and carcinogenic substance. Therefore, converting Cr(VI) to Cr(III) is generally considered a key strategy for the environmental remediation of chromium pollutants. It is noteworthy that sulfamethazine also coexists in Cr(VI)-containing wastewater. This composite wastewater containing Cr(VI) and sulfamethazine is even more toxic, and the resulting environmental pollution problems have received widespread attention. However, conventional physical adsorption and biological treatment methods are insufficient for the simultaneous removal of Cr(VI) and sulfamethazine. Therefore, there is an urgent need for a method capable of simultaneously removing Cr(VI) and sulfamethazine from wastewater.

[0003] Photoelectrocatalysis based on MOF derivatives is a highly efficient, environmentally friendly, and economical method for pollutant removal, attracting increasing attention in wastewater treatment. It involves applying a certain anodic bias under illumination to promote the separation of photogenerated electrons and holes at the anode, and to generate… 1 O2、·O2 - h +The photoelectrocatalytic system utilizes photogenerated electrons and active substances to remove pollutants from wastewater. However, existing anodes based on MOF derivatives mainly promote the separation of photogenerated electrons and holes and generate active substances by constructing heterostructures. However, this method is difficult to generate a large number of photogenerated electrons and active substances, resulting in poor pollutant removal efficiency. In particular, in this heterostructure-based photoelectrocatalytic system, the low production of photogenerated electrons leads to poor reduction ability, making it unable to reduce high-valence heavy metals to low-valence states. As a result, the aforementioned heterostructure-based photoelectrocatalytic system can only treat organic pollutants, but it is still difficult to use it to reduce heavy metals in wastewater, thus making it difficult to achieve synergistic treatment of Cr(VI) and sulfadimethylpyrimidine in wastewater. Furthermore, in the aforementioned anodes constructed based on MOF derivatives, the MOFs used to prepare the derivatives employ single transition metal nucleation, resulting in a high energy barrier. Consequently, it is difficult to regulate the distribution of interfacial metal ions using only a three-dimensional matrix, leading to uneven distribution of active sites on the catalyst surface and relatively poor stability. This significantly limits the widespread application of existing anodes based on MOF derivatives in wastewater treatment. Therefore, constructing a MOF photoelectric system capable of simultaneously treating Cr(VI) and sulfadimethylpyrimidine in wastewater is of great significance for the effective treatment of Cr(VI) and sulfadimethylpyrimidine complex wastewater. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for synergistic treatment of hexavalent chromium and sulfadimethylpyrimidine complex wastewater, which can achieve efficient removal of hexavalent chromium and sulfadimethylpyrimidine from the wastewater.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0006] A method for synergistically treating a complex wastewater containing hexavalent chromium and sulfadimethylpyrimidine, wherein the method utilizes a bimetallic node-coupled metal-organic framework (MOF) derivative electrode to synergistically treat the wastewater; the bimetallic node-coupled MOF derivative electrode comprises a conductive substrate, on which MOF derivatives are coupled via Zr and Zn as metal nodes; the MOF derivatives are ZrO2 and ZnO.

[0007] A further improvement to the above method is the preparation method of the bimetallic node-coupled metal-organic framework derivative electrode, which includes the following steps:

[0008] S1. A conductive substrate is placed in a zirconium-containing electrolytic solution and pulse electrodeposition is performed to obtain a conductive substrate loaded with zirconium ions;

[0009] S2. A conductive substrate loaded with zirconium ions is mixed with a mixed solution containing N,N-dimethylformamide, zinc nitrate, 2-aminoterephthalic acid, nitric acid and titanium isopropoxide and subjected to a hydrothermal reaction to obtain a conductive substrate loaded with NH2-UiO-66(Zr) and NH2-MOF-5(Zn).

[0010] S3. The conductive substrate loaded with NH2-UiO-66 (Zr) and NH2-MOF-5 (Zn) is calcined to obtain a bimetallic node-coupled metal-organic framework derivative electrode.

[0011] In a further improvement to the above method, in step S1, a three-electrode system is constructed using a conductive substrate as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Pulse electrodeposition is then performed in a zirconium-containing electrolytic solution using multicurrent switching, thereby loading zirconium ions onto the surface and interior of the conductive substrate. The zirconium-containing electrolytic solution is a mixed solution of zirconium salt and electrolyte; the concentration of zirconium salt in the zirconium-containing electrolytic solution is 0.02 mol·L⁻¹. -1 The concentration of the electrolyte is 0.01 mol·L⁻¹. -1 The zirconium salt is zirconium chloride; the electrolyte is sodium sulfate; during the pulse electrodeposition process, the deposition current and diffusion current complete 300 alternating cycles, the buffer voltage of each cycle is set to 0V, and the dwell time between adjacent cycles is 1s; the deposition current is 0.15A for 10ms; the diffusion current is -0.15A for 3ms.

[0012] In a further improvement to the above method, step S1 includes the following treatment before use of the conductive substrate: cleaning the conductive substrate sequentially with acetone, anhydrous ethanol, and ultrapure water, followed by drying; the cleaning time is 10 minutes; the drying is carried out at a temperature of 60℃~80℃; the drying time is 30 minutes~60 minutes; the conductive substrate is carbon fiber; the carbon fiber has a size of 3cm×3cm.

[0013] In a further improvement to the above method, in step S2, the ratio of N,N-dimethylformamide, zinc nitrate, 2-aminoterephthalic acid, nitric acid, and titanium isopropoxide in the mixed solution is 40 mL–50 mL : 0.3 g–0.6 g : 0.4 g–0.6 g : 0.20 mL–0.25 mL : 0.10 mL–0.12 mL; the hydrothermal reaction is carried out at a temperature of 160 °C; the hydrothermal reaction time is 24 h; and after the hydrothermal reaction, the following steps are further included: washing the hydrothermal reaction product sequentially with N,N-dimethylformamide and ultrapure water at a temperature of 60 °C–80 °C for 30 min–60 min.

[0014] In a further improvement to the above method, in step S3, the calcination is carried out under an inert atmosphere; the inert atmosphere is argon; the heating rate during the calcination process is 5℃ / min to 7℃ / min; the calcination is carried out at a temperature of 450℃ to 500℃; and the calcination time is 2h to 3h.

[0015] The above method is further improved by using a bimetallic node coupled with a metal-organic framework derivative electrode to synergistically treat hexavalent chromium and sulfadimethylpyrimidine composite wastewater, including the following steps: mixing the bimetallic node coupled with a metal-organic framework derivative electrode, hexavalent chromium and sulfadimethylpyrimidine composite wastewater for photoelectrocatalytic reaction to complete the synergistic treatment of hexavalent chromium and sulfadimethylpyrimidine in the composite wastewater.

[0016] A further improvement to the above method involves constructing a three-electrode system using a bimetallic node-coupled metal-organic framework derivative electrode as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode. This system is used to perform a photoelectrocatalytic reaction on a mixture of hexavalent chromium and sulfadimethylpyrimidine wastewater. During the photoelectrocatalytic reaction, the voltage is 0–1.5 V, and the light density is 10⁹ mW·cm². -2 ~159mW·cm -2 The photoelectrocatalytic reaction time is 90 min.

[0017] A further improvement to the above method is that the concentration of sulfadiazine in the hexavalent chromium and sulfadiazine composite wastewater is 10 mg·L⁻¹. -1 ~30mg·L -1 The concentration of hexavalent chromium was 10 mg·L⁻¹. -1 ~30mg·L -1 The initial pH value of the hexavalent chromium and sulfadimethylpyrimidine composite wastewater is 1-6.

[0018] A further improvement to the above method is that, during the photoelectrocatalytic reaction process, an electrolyte is added to the hexavalent chromium and sulfadimethylpyrimidine composite wastewater, such that the concentration of the electrolyte in the hexavalent chromium and sulfadimethylpyrimidine composite wastewater is 0.1 mol·L⁻¹. -1 The electrolyte is sodium sulfate.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] (1) To address the shortcomings of existing MOF derivative-constructed anodes, such as poor redox capacity and poor stability, and the resulting difficulties in simultaneously removing hexavalent chromium and sulfadiazine from wastewater, poor recycling efficiency, and secondary pollution, this invention creatively proposes a method for the synergistic treatment of hexavalent chromium and sulfadiazine complex wastewater. This method utilizes a bimetallic node-coupled metal-organic framework (MOF) derivative electrode to synergistically treat the wastewater. The bimetallic node-coupled MOF derivative electrode comprises a conductive substrate on which MOF derivatives are coupled via Zr and Zn as metal nodes. The MOF derivatives are ZrO2 and ZnO. This bimetallic node-coupled MOF derivative electrode, using Zr and Zn as metal nodes, can effectively remove hexavalent chromium and sulfadiazine from wastewater. The framework derivatives are uniformly and stably coupled to the surface of the conductive substrate, exhibiting excellent photocatalytic activity and stability. They also possess advantages such as large specific surface area, numerous surface reaction sites, abundant pore structure, and strong conductivity. Therefore, through the reflection effect of the layered porous structure and the multiple electron transfer effect, the light utilization capacity and electron transfer rate of the electrode can be significantly improved. This allows the bimetallic node-coupled metal-organic framework derivative electrode to generate a large number of photogenerated electrons and holes under photoelectric conditions. On the one hand, these abundant photogenerated electrons can rapidly transfer to hexavalent chromium and reduce hexavalent chromium (Cr(VI)) to reduced pentavalent chromium (Cr(V)), ultimately forming trivalent chromium (Cr(III)). On the other hand, these abundant photogenerated electrons can combine with dissolved oxygen to generate a large number of superoxide radicals (Cr(VI)). · O2 - ), and the · O2 - It can be further converted into hydroxyl radicals using electrons. · OH), thus the large amount of reactive oxygen species formed in the system can be utilized. · O2 - , ·The system efficiently degrades sulfadimethylpyrimidine using OH and holes. More importantly, in the constructed photoelectrocatalytic system, the formation of Cr(V) is a single-electron transfer process. Compared to Cr(VI), the reduced Cr(V) obtained from the reduction of Cr(VI) has higher oxidizing power (E0(Cr(V) / Cr(III)) = 1.75V vs NHE); E0(Cr(VI) / Cr(III)) = 1.33V vs NHE). Cr(V) can be used as an oxidizing active substance to promote the degradation of sulfadimethylpyrimidine (SMT). The intermediate products of SMT can also be further oxidized to CO2 by Cr(V), thereby further improving the removal efficiency of sulfadimethylpyrimidine. In particular, since Cr(V) is consumed in large quantities by SMT, this also further improves the accessibility of hexavalent chromium being continuously reduced to trivalent chromium, thereby further improving the removal efficiency of hexavalent chromium. That is, in the photoelectrocatalytic system constructed in this invention, there is a mutual promoting effect between hexavalent chromium and sulfadimethylpyrimidine, which is conducive to achieving efficient degradation of hexavalent chromium and sulfadimethylpyrimidine in wastewater. Compared to conventional photoelectrocatalytic systems based on MOF derivative heterostructures, this invention utilizes a bimetallic node coupled with a metal-organic framework derivative electrode as the working electrode. The resulting photoelectrocatalytic system exhibits advantages such as strong light utilization, rapid electron transfer efficiency, and strong conversion effects between complex free radical chemistry and different active substances. It not only achieves the synergistic degradation of hexavalent chromium (SMT) and sulfamethoxam (SVI) in wastewater but also simultaneously and efficiently removes both. The degradation rate constant of pollutants in this photoelectrocatalytic system is more than four times that of individual photocatalytic and electrocatalytic systems. The photoelectro-co ...

[0021] (2) Compared with conventional anodes based on MOFs derivatives, the bimetallic node coupled metal-organic framework derivative electrode used in this invention has the following advantages: (a) For the first time, Zr and Zn with considerable affinity are used together as metal nodes of MOFs to construct the electrode on a carbon fiber substrate. The constructed electrode has a flower-like three-dimensional porous structure, exhibiting stronger light utilization and higher electron transfer rate; (b) The electrode can achieve excellent treatment effects for both organic matter and heavy metals. The constructed photoelectrocatalytic system can synergistically treat hexavalent chromium and sulfadimethylpyrimidine; (c) The electrode has good stability and can still maintain good treatment effect after 6 cycles. The structure has not changed much and the reaction sites have not decreased much.

[0022] (3) In this invention, by optimizing the voltage and light density in the photoelectrocatalytic reaction process, the efficiency of the photoelectrocatalytic system in degrading pollutants can be improved, which is more conducive to the rapid and thorough removal of pollutants in wastewater. Attached Figure Description

[0023] 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.

[0024] Figure 1 The images show scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 1 of this invention.

[0025] Figure 2 The X-ray diffraction pattern is shown for the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 1 of this invention.

[0026] Figure 3 This is a full scanning spectrum of the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 1 of the present invention.

[0027] Figure 4 The O, Ti, Zn, and Zr spectra of the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 1 of this invention are shown.

[0028] Figure 5 This is a diagram showing the synergistic degradation of tetracycline (TC) and hexavalent chromium (Cr(VI)) by the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 2 of this invention.

[0029] Figure 6 This is a diagram showing the synergistic degradation of norfloxacin (NOF) and hexavalent chromium (Cr(VI)) by the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 2 of this invention.

[0030] Figure 7 This is a diagram showing the synergistic degradation of sulfadimethylpyrimidine (SMT) and hexavalent chromium (Cr(VI)) by the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 2 of this invention.

[0031] Figure 8 The diagrams show the synergistic degradation of Cr(VI) and SMT by the bimetallic node-coupled metal-organic framework derivative electrode under different pH conditions in Example 5 of this invention, as well as the morphological changes of hexavalent and trivalent chromium. (a) is the degradation effect diagram, (b) is the reaction rate diagram, (c) is the morphological change diagram of hexavalent chromium, and (d) is the morphological change diagram of trivalent chromium.

[0032] Figure 9The graph shows the degradation effect of the bimetallic node coupled metal-organic framework derivative electrode on Cr(VI) and SMT in different water qualities in Example 7 of this invention.

[0033] Figure 10 This is a diagram showing the cyclic degradation effect of the bimetallic node coupled metal-organic framework derivative electrode on Cr(VI) and SMT in wastewater in Example 8 of the present invention.

[0034] Figure 11 The graph shows the degradation effect of the bimetallic node coupled metal-organic framework derivative electrode on Cr(VI) and SMT under different interference conditions in Example 9 of the present invention. Detailed Implementation

[0035] 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. All materials and instruments used in the following embodiments are commercially available.

[0036] Example 1

[0037] A method for synergistically treating hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, specifically utilizing a bimetallic node coupled with a metal-organic framework derivative electrode for synergistic treatment of hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, includes the following steps:

[0038] A bimetallic node-coupled metal-organic framework derivative electrode was used as the working electrode (anode), a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode. 100 mL of wastewater containing sodium sulfate, Cr(VI), and SMT (the concentration of sodium sulfate in the wastewater was 0.1 mol·L⁻¹) was added. -1 The concentration of SMT is 10 mg·L⁻¹ -1 The concentration of Cr(VI) is 10 mg·L⁻¹. -1 The photoelectrocatalytic reaction was carried out for 90 min at pH = 2.0, with the voltage set at 1.0 V and the electrode light intensity at 159 mW·cm⁻¹. -2 The co-treatment of hexavalent chromium and sulfadimethylpyrimidine in the compound wastewater was completed.

[0039] Control group 1: Sulfamethazine wastewater was treated alone, with all other conditions being the same.

[0040] Control group 2: Hexavalent chromium wastewater was treated alone, with all other conditions being the same.

[0041] In this embodiment, the removal efficiency of different electrodes on hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater was also investigated. Specifically, C-Ti2O3, C-Ti2O3@Zr-MOF, and C-Ti2O3@Zn / ZnO were used as working electrodes to carry out photoelectrocatalytic reactions on hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, with other conditions being the same as in Example 1.

[0042] In this example, the bimetallic node-coupled metal-organic framework derivative electrode uses carbon fiber as the conductive substrate, Zr and Zn as the metal nodes, and ZrO2 and ZnO as the metal-organic framework derivatives, which are derived from the metal-organic frameworks NH2-UiO-66 (Zr) and NH2-MOF-5 (Zn). Specifically, in the bimetallic node-coupled metal-organic framework derivative electrode, ZrO2 and ZnO are coupled on the carbon fiber surface through Zr and Zn as metal nodes.

[0043] A method for preparing a bimetallic node-coupled metal-organic framework derivative electrode according to the present embodiment includes the following steps:

[0044] (1) The carbon fiber with a size of 3cm×3cm was washed with acetone, anhydrous ethanol and ultrapure water for 10min each; then dried in an oven at 60℃ for 30min.

[0045] (2) Using the dried electrode (carbon fiber) from step (1) as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode, a standard three-electrode system was constructed. This system utilized multiple current conversion in zirconium chloride (0.02 mol·L⁻¹) -1 ) and sodium sulfate (0.01 mol·L -1 Pulse electrodeposition was performed in a mixed solution of zirconium ions for 5 min. During the pulse deposition process, 300 alternating cycles were completed between the deposition current (0.15 A, 10 ms) and the diffusion current (-0.15 A, 3 ms). The buffer voltage of each cycle was set to 0 V, and the dwell time between adjacent cycles was 1 s, resulting in an electrode (carbon fiber) loaded with zirconium ions.

[0046] (3) The electrode deposited in step (2) is placed in an oven and dried at 60°C. Then it is immersed in a mixed solution containing 0.6g zinc nitrate, 0.6g 2-aminoterephthalic acid, 0.25mL nitric acid, 0.10mL titanium isopropoxide and 50mL N,N-dimethylformamide. The electrode is hydrothermally heated at 160°C for 24h. NH2-UiO-66(Zr) and NH2-MOF-5(Zn) are formed on the carbon fiber surface through hydrothermal self-assembly reaction, resulting in an electrode (carbon fiber) loaded with NH2-UiO-66(Zr) and NH2-MOF-5(Zn).

[0047] (4) The electrode obtained in step (3) was repeatedly rinsed three times with N,N-dimethylformamide and ultrapure water, dried in an oven at 60°C, and then calcined at 450°C for 2 hours in an argon atmosphere at a heating rate of 5°C / min to obtain a bimetallic node coupled metal-organic framework derivative electrode, denoted as C-Ti2O3@Zr-Zn / ZnO.

[0048] In this embodiment, the preparation method of C-Ti2O3 is basically the same as the preparation method of bimetallic node coupled metal-organic framework derivative electrode (C-Ti2O3@Zr-Zn / ZnO), the only difference being that pulse electrodeposition is not performed and zinc nitrate is not added in the hydrothermal reaction.

[0049] In this embodiment, the preparation method of C-Ti2O3@Zr-MOF is basically the same as the preparation method of bimetallic node coupled metal-organic framework derivative electrode (C-Ti2O3@Zr-Zn / ZnO), the only difference being that zinc nitrate is not added during the hydrothermal reaction.

[0050] In this embodiment, the preparation method of C-Ti2O3@Zn / ZnO is basically the same as the preparation method of bimetallic node coupled metal-organic framework derivative electrode (C-Ti2O3@Zr-Zn / ZnO), the only difference being that pulse electrodeposition is not performed.

[0051] Figure 1 The images shown are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 1 of this invention. Figure 1 In the diagram, ad represents the microstructure of the electrode at different scales, ef represents the three diffraction rings of the carbon fiber, gj represents the crystal structure of the electrode, and kl represents the lattice fringe spacing of the electrode. From... Figure 1 As can be seen from the image, Zn clusters are loaded onto Zr clusters to form bimetallic coordination cores. After heat treatment, the morphology undergoes a transformation from a two-dimensional to a three-dimensional structure, ultimately forming a flower-like structure. This change is related to the effect of metal ions on the additional growth of MOF edges. Not only single-crystal diffraction was observed in the TEM images, but also polycrystalline diffraction was observed. Figure 1 gj), which is consistent with the Zn and ZnO crystal phases in the X-ray diffraction pattern. Figure 2 ). Figure 1 kl shows that the electrode has a distinct lattice stripe array structure.

[0052] Figure 2 This is the X-ray diffraction (XRD) pattern of the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 1 of this invention. Figure 2It can be seen that the (101) crystal plane at 36.5° of the electrode proves that a portion of ZnO was successfully reduced to Zn. In addition, the enhancement of various characteristic peaks of the electrode indicates that the crystal content and crystal quality of the catalyst have increased, further verifying the successful synthesis of the catalyst.

[0053] Figure 3 This is a full scanning spectrum of the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 1 of the present invention. Figure 4 The O, Ti, Zn, and Zr spectra of the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 1 of this invention are shown. Figure 3 The chemical composition of C, O, Ti, Zr, and Zn elements in the electrode was confirmed. Figure 4 a shows that different catalysts all have lattice oxygen (O). 2- The presence of Ti is consistent with the crystal structure shown in the XRD pattern. Furthermore, the high proportion of C=O structures provides more active sites, which is beneficial for the catalytic reaction of pollutants. 4+ 2p 3 / 2 and Ti 4+ 2p 1 / 2 There are two distinct peaks at 465.1 eV and 472.2 eV. Argon calcination and reduction cause Ti to form at 461.9 eV on the electrode. 3+ Self-doping improved the photosensitivity of the catalyst. Figure 4 b). Zn and ZnO exhibit typical coexistence characteristics at binding energies of 1022.1 eV and 1045.1 eV. Figure 4 c), while in the vicinity of 185.0 eV, Zr, Ti, and lattice oxygen completed their bonding ( Figure 4 d).

[0054] In the photoelectrocatalytic reaction, 4 mL samples were taken at regular intervals (0 min, 15 min, 30 min, 45 min, 60 min, 75 min, and 90 min) and filtered through a 0.22 μm filter membrane. One mL of this sample was analyzed using high-performance liquid chromatography (HPLC) to determine the peak area change of SMT at different degradation times, thus identifying the SMT degradation concentration and the degradation effect of different photoelectrodes on sulfadimethylpyrimidine. Additionally, the concentration of Cr(VI) in the remaining 3 mL sample was determined using diphenylcarbonyldiamine spectrophotometry, thereby assessing the reduction effect of the photoelectrodes on Cr(VI).

[0055] Table 1 shows that the degradation effect of SMT and Cr(VI) in the synergistic system is greater than that in the individual systems. Furthermore, pseudo-first-order reaction kinetics indicate that the reaction kinetic constant in the synergistic system is higher than that in the individual systems, suggesting that the electrode exhibits good catalytic performance.

[0056] As shown in Table 2, compared with conventional electrodes (C-Ti2O3, C-Ti2O3@Zr-MOF, C-Ti2O3@Zn / ZnO), the bimetallic node coupled metal-organic framework derivative electrode (C-Ti2O3@Zr-Zn / ZnO) used in this invention can not only effectively remove SMT and Cr(VI) from wastewater, but also has a higher removal rate.

[0057] Table 1. Catalytic effects of the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 1 of this invention on the individual and synergistic degradation of pollutants.

[0058]

[0059] Table 2. Catalytic effects of different electrodes on hexavalent chromium and sulfadiazine composite wastewater in Example 1 of this invention.

[0060]

[0061] The results above show that, compared with conventional electrodes (C-Ti2O3, C-Ti2O3@Zr-MOF, C-Ti2O3@Zn / ZnO), the bimetallic node-coupled metal-organic framework derivative electrode (C-Ti2O3@Zr-Zn / ZnO) used in this invention has the following advantages: higher crystallinity and higher catalytic activity; a higher proportion of C=O structures, which can provide more active sites and is conducive to improving catalytic efficiency. Therefore, the bimetallic node-coupled metal-organic framework derivative electrode (C-Ti2O3@Zr-Zn / ZnO) of this invention exhibits better catalytic degradation effect.

[0062] Example 2

[0063] A method for synergistically treating hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, specifically utilizing a bimetallic node coupled with a metal-organic framework derivative electrode to synergistically treat hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater of different concentrations, includes the following steps:

[0064] Using the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 1 as the working electrode (anode), a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode, 100 mL of wastewater containing sodium sulfate, Cr(VI), and SMT at different concentrations (the concentration of sodium sulfate in the wastewater was 0.1 mol·L⁻¹) was placed in each solution. -1 The concentrations of SMT were 10 mg·L⁻¹. -1 20 mg·L -1 30 mg·L -1 The concentration of Cr(VI) was 10 mg·L⁻¹. -1The photoelectrocatalytic reaction was carried out for 90 min at a pH of 2.0 (where the voltage was 1.0 V and the light intensity at the electrode was 159 mW·cm⁻¹). -2 The co-treatment of hexavalent chromium and sulfadimethylpyrimidine in the compound wastewater was completed.

[0065] Control group 1: The antibiotic in the composite wastewater was tetracycline (TC), and the photoelectrocatalytic reaction was carried out for 90 min, with other conditions being the same.

[0066] Control group 2: The antibiotic in the composite wastewater was norfloxacin (NOF), the photoelectrocatalytic reaction was carried out for 90 min, and other conditions were the same.

[0067] In the photoelectrocatalytic reaction, 4 mL samples were taken at regular intervals (0 min, 15 min, 30 min, 45 min, 60 min, 75 min, and 90 min) and filtered through a 0.22 μm filter membrane. One mL of the sample was analyzed using high-performance liquid chromatography (HPLC) to determine the peak area change of the antibiotic at different degradation times, thus determining the antibiotic degradation concentration and obtaining the degradation effect of the photoelectrode on different antibiotics. The other 3 mL of the sample had its Cr(VI) concentration determined using diphenylcarbazide spectrophotometry, thus obtaining the reduction effect of the photoelectrode on Cr(VI). The results are as follows: Figure 5-7 As shown.

[0068] Figure 5 This is a diagram showing the synergistic degradation of tetracycline (TC) and hexavalent chromium (Cr(VI)) by the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 2 of this invention.

[0069] Figure 6 This is a diagram showing the synergistic degradation of norfloxacin (NOF) and hexavalent chromium (Cr(VI)) by the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 2 of this invention.

[0070] Figure 7 This is a diagram showing the synergistic degradation of sulfadimethylpyrimidine (SMT) and hexavalent chromium (Cr(VI)) by the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 2 of this invention.

[0071] contrast Figure 5-7It is evident that in the TC / Cr(VI) and NOF / Cr(VI) systems, especially the TC / Cr(VI) system, the degradation of Cr(VI) was inhibited, while in the SMT / Cr(VI) system, both SMT and Cr(VI) exhibited excellent degradation effects. Cr(VI) reduction is a proton-regulated three-electron transfer process. The proton-donating and proton-accepting abilities of different antibiotics mediate the proton reduction of Cr(VI) in the system. Therefore, in the photoelectrocatalytic system constructed in this invention, there is a synergistic effect between hexavalent chromium and sulfadimethylpyrimidine, which is beneficial for achieving efficient degradation of hexavalent chromium and sulfadimethylpyrimidine in wastewater.

[0072] Example 3

[0073] A method for synergistically treating hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, specifically utilizing a bimetallic node coupled with a metal-organic framework derivative electrode for synergistic treatment of hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, includes the following steps:

[0074] Using the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 1 as the anode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode, 100 mL of wastewater containing sodium sulfate, Cr(VI), and SMT (the concentration of sodium sulfate in the wastewater was 0.1 mol·L⁻¹) was added. -1 The concentration of SMT is 10 mg·L⁻¹ -1 The concentration of Cr(VI) is 10 mg·L⁻¹. -1 The photoelectrocatalytic reaction was carried out for 90 min at pH = 2.0, with the voltage set at 1.0 V and the electrode light intensity at 159 mW·cm⁻¹. -2 The co-treatment of hexavalent chromium and sulfadimethylpyrimidine in the compound wastewater was completed.

[0075] Control group 1: Only visible light source was applied to carry out the photocatalytic reaction, and other conditions were the same.

[0076] Control group 2: Electrocatalytic reaction was carried out under the same conditions with only a voltage of 1.0V applied.

[0077] In the three catalytic reaction conditions, 4 mL samples were taken at intervals (0 min, 15 min, 30 min, 45 min, 60 min, 75 min, and 90 min) and filtered through a 0.22 μm filter membrane. One mL of the sample was analyzed by high-performance liquid chromatography (HPLC) to determine the peak area change of SMT at different degradation times, thus determining the SMT degradation concentration and obtaining the degradation effect of the photoelectrode on SMT under different conditions. The other 3 mL of the sample was analyzed by diphenylcarbazide spectrophotometry to determine the Cr(VI) reduction effect of the photoelectrode. The results are shown in Table 3.

[0078] Table 3. Catalytic effects of the bimetallic node-coupled metal-organic framework derivative electrode on hexavalent chromium and sulfadiazine composite wastewater under different conditions in Example 3 of the present invention.

[0079]

[0080] As shown in Table 3, compared with photocatalysis (PC) and electrocatalysis (EC), the bimetallic node-coupled metal-organic framework derivative electrode of the present invention exhibits the best degradation effect and the fastest degradation rate of SMT and Cr(VI) in wastewater under photoelectrocatalysis (PEC) conditions. Therefore, the bimetallic node-coupled metal-organic framework derivative electrode demonstrates a synergistic effect in utilizing light and electricity, and the synergistic factor (SF) can be calculated using equation (1):

[0081]

[0082] Where, k PEC k PC and k EC These represent the reaction rate constants in the photoelectrocatalysis, photocatalysis, and electrocatalysis processes, respectively. The calculated photoelectrocatalytic synergistic factors for SMT and Cr(VI) are 3.06 and 2.07, respectively.

[0083] Example 4

[0084] A method for synergistically treating hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, specifically utilizing a bimetallic node coupled with a metal-organic framework derivative electrode for synergistic treatment of hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, includes the following steps:

[0085] Using the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 1 as the anode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode, 100 mL of wastewater containing sodium sulfate, Cr(VI), and SMT (the concentration of sodium sulfate in the wastewater was 0.1 mol·L⁻¹) was added. -1 The concentration of SMT is 10 mg·L⁻¹ -1 The concentration of Cr(VI) is 10 mg·L⁻¹.-1 The catalytic reaction was carried out for 90 min at 0 V, 0.5 V, 1.0 V, and 1.5 V in a medium (pH = 2.0), with the photoelectrocatalytic reaction occurring at a light intensity of 159 mW·cm⁻¹. -2 The co-treatment of hexavalent chromium and sulfadimethylpyrimidine in the compound wastewater was completed.

[0086] In the photoelectrocatalytic reaction, 4 mL samples were taken at regular intervals (0 min, 15 min, 30 min, 45 min, 60 min, 75 min, and 90 min) and filtered through a 0.22 μm filter membrane. One mL of the sample was analyzed using high-performance liquid chromatography (HPLC) to determine the peak area change of SMT at different degradation times, thus identifying the SMT degradation concentration and the photoelectrode's effect on SMT degradation. The remaining 3 mL of the sample had its Cr(VI) concentration determined using diphenylcarbazide spectrophotometry, thus assessing the photoelectrode's reduction effect on Cr(VI). The results are shown in Table 4.

[0087] Table 4. Catalytic effects of the bimetallic node-coupled metal-organic framework derivative electrode on hexavalent chromium and sulfadiazine composite wastewater under different voltage conditions in Example 4 of this invention.

[0088]

[0089] As shown in Table 4, the degradation rate of pollutants increases with increasing applied voltage. At 1.0V, the removal rate reaches its optimal peak due to the effective separation and transfer of photogenerated charges in the photoelectric system. However, above 1.0V, the reaction efficiency hardly improves due to the limited yield of photogenerated charges. The enhancement of degradation (F) by the applied voltage was calculated using Equation (2), and the results are shown in Table 5.

[0090]

[0091] Where, k E k is the dynamic constant under applied voltage. E-0.5 The values ​​represent the kinetic constants when the applied voltage is 0.5V lower than the applied voltage. Table 5 shows that the enhancement of degradation is greatest when the applied voltage is 1.0V, indicating that the voltage contributes the most. From 1.0V to 1.5V, the voltage enhancement slows down significantly, and the degradation rate does not increase significantly. Considering the degradation effect and cost-effectiveness in a real aquatic environment, we chose 1.0V as the operating energy.

[0092] Table 5. The enhancement of degradation effect by applying different voltages

[0093] Apply voltage Enhancement level Apply voltage Enhancement level 0.5V-SMT 0.3127 0.5V-Cr(VI) 0.2518 1.0V-SMT 0.6569 1.0V-Cr(VI) 0.6354 1.5V-SMT 0.0874 1.5V-Cr(VI) 0.0667

[0094] Example 5

[0095] A method for synergistically treating hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, specifically utilizing a bimetallic node coupled with a metal-organic framework derivative electrode for synergistic treatment of hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, includes the following steps:

[0096] Using the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 1 as the anode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode, 100 mL of wastewater containing sodium sulfate, Cr(VI), and SMT at different pH values ​​(the concentration of sodium sulfate in the wastewater was 0.1 mol·L⁻¹ in all cases) was added. -1 The concentration of SMT was 10 mg·L⁻¹. -1 The concentration of Cr(VI) was 10 mg·L⁻¹. -1 The photoelectrocatalytic reaction was carried out in electrodes with pH values ​​of 1, 2, 3, 4, 5, and 6 for 90 min. The voltage during the photoelectrocatalytic reaction was set to 1.0 V, and the electrode light intensity was 159 mW·cm⁻¹. -2 The co-treatment of hexavalent chromium and sulfadimethylpyrimidine in the compound wastewater was completed.

[0097] In the photoelectrocatalytic reaction, 4 mL samples were taken at regular intervals (0 min, 15 min, 30 min, 45 min, 60 min, 75 min, and 90 min) and filtered through a 0.22 μm filter membrane. One mL of the sample was analyzed using high-performance liquid chromatography (HPLC) to determine the peak area change of SMT at different degradation times, thus determining the SMT degradation concentration and obtaining the degradation effect of the photoelectrode on SMT under different pH conditions. The other 3 mL of the sample had its Cr(VI) concentration determined using diphenylcarbazide spectrophotometry, thus obtaining the reduction effect of the photoelectrode on Cr(VI). The results are shown below. Figure 8 As shown.

[0098] Figure 8 This image shows the synergistic degradation of Cr(VI) and SMT by the bimetallic node-coupled metal-organic framework derivative electrode in Example 5 of this invention under different pH conditions, as well as the morphological changes of hexavalent and trivalent chromium. (a) shows the degradation effect, (b) shows the reaction rate, (c) shows the morphological changes of hexavalent chromium, and (d) shows the morphological changes of trivalent chromium. Figure 8 As shown, Cr(VI) reacts with HCrO4 under acidic conditions. - Cr(III) exists in the form of free Cr at pH = 1-2. 3+ It exists in the form of free Cr. 3+ It has little effect on the degradation of SMT, while Cr2(OH)2 4+ Cr3(OH)4 5+ Cr(OH) 2+The increase of Cr(VI) has a negative impact on the degradation of SMT because Cr(III) hydroxide is deposited on the surface of the C-Ti2O3@Zr-Zn / ZnO electrode, which hinders the utilization of visible light and the transfer of interfacial charge. Therefore, C-Ti2O3@Zr-Zn / ZnO exhibits better degradation of Cr(VI) and SMT at low pH.

[0099] Example 6

[0100] A method for synergistically treating hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, specifically utilizing a bimetallic node coupled with a metal-organic framework derivative electrode for synergistic treatment of hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, includes the following steps:

[0101] Using the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 1 as the anode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode, 100 mL of wastewater containing sodium sulfate, Cr(VI), and SMT (the concentration of sodium sulfate in the wastewater was 0.1 mol·L⁻¹) was added. -1 The concentration of SMT is 10 mg·L⁻¹ -1 The concentration of Cr(VI) is 10 mg·L⁻¹. -1 In a pH of 2, at a light density of 109 mW·cm⁻¹, -2 132mW·cm -2 159mW·cm -2 Under certain conditions, a photoelectrocatalytic reaction was carried out for 90 minutes, with the voltage set to 1.0V during the reaction, to achieve the synergistic treatment of hexavalent chromium and sulfadimethylpyrimidine in the composite wastewater.

[0102] In the photoelectrocatalytic reaction, 4 mL samples were taken at regular intervals (0 min, 15 min, 30 min, 45 min, 60 min, 75 min, and 90 min) and filtered through a 0.22 μm filter membrane. One mL of this sample was analyzed using high-performance liquid chromatography (HPLC) to determine the peak area change of SMT at different degradation times, thus identifying the SMT degradation concentration and the effect of the photoelectrode on SMT degradation under different light intensities. The remaining 3 mL of the sample had its Cr(VI) concentration determined using diphenylcarbazide spectrophotometry, thus obtaining the reduction effect of the photoelectrode on Cr(VI). The results are shown in Table 6.

[0103] Table 6 shows that the catalytic rate of the photoelectric system constructed by coupling a bimetallic node with a metal-organic framework derivative electrode increases with increasing light intensity. Furthermore, compared to SMT, the increased light intensity leads to more photogenerated electrons, resulting in a more significant enhancement of Cr(VI) degradation. Increased light intensity leads to increased current intensity; higher current density is beneficial for pollutant degradation. Experimental results show that a light intensity of 159 mW·cm⁻¹ is optimal. -2 At that time, the first-order rate constants of the degradation reactions of SMT and Cr(VI) were the highest, at 0.03230 min. -1 and 0.03105min -1 Considering the structure and degradation effects of actual optoelectronic devices, 159 mW·cm⁻² was chosen as the optimal optical density for the experiment.

[0104] Table 6. Catalytic effect of the bimetallic node-coupled metal-organic framework derivative electrode in Example 6 of the present invention on hexavalent chromium and sulfadimethylpyrimidine composite wastewater under different light densities.

[0105]

[0106] Example 7

[0107] A method for synergistically treating hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, specifically utilizing a bimetallic node coupled with a metal-organic framework derivative electrode for synergistic treatment of hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, includes the following steps:

[0108] Using the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 1 as the anode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode, 100 mL of tap water, river water (Xiangjiang River water), and medical wastewater containing sodium sulfate, Cr(VI), and SMT were added (the concentration of sodium sulfate in these wastewaters was 0.1 mol·L⁻¹). -1 The concentration of SMT was 10 mg·L⁻¹. -1 The concentration of Cr(VI) was 10 mg·L⁻¹. -1 The photoelectrocatalytic reaction was carried out at pH 2 for 90 min, with the voltage set at 1.0 V and the electrode light intensity at 159 mW·cm⁻¹. -2 The co-treatment of hexavalent chromium and sulfadimethylpyrimidine in the compound wastewater was completed.

[0109] In the photoelectrocatalytic reaction, 4 mL samples were taken at regular intervals (0 min, 15 min, 30 min, 45 min, 60 min, 75 min, and 90 min) and filtered through a 0.22 μm filter membrane. One mL of this sample was analyzed using high-performance liquid chromatography (HPLC) to determine the peak area change of SMT at different degradation times, thus determining the SMT degradation concentration and obtaining the degradation effect of the photoelectrode on SMT in different water qualities. The remaining 3 mL of the sample had its Cr(VI) concentration determined using diphenylcarbazide spectrophotometry, thus obtaining the reduction effect of the photoelectrode on Cr(VI). The results are shown below. Figure 9 As shown.

[0110] Figure 9 This image shows the degradation effect of the bimetallic node-coupled metal-organic framework derivative electrode on Cr(VI) and SMT in different water qualities in Example 7 of the present invention. Figure 9 As shown, the removal rates of SMT and Cr(VI) in the three types of water bodies remained above 80%, indicating that the photoelectrocatalytic system has the potential for application in actual water bodies, and the C-Ti2O3@Zr-Zn / ZnO electrode can still maintain good stability in complex water bodies.

[0111] Example 8

[0112] A method for synergistically treating hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, specifically utilizing a bimetallic node coupled with a metal-organic framework derivative electrode for synergistic treatment of hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, includes the following steps:

[0113] (1) Using the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 1 as the anode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode, 100 mL of wastewater containing sodium sulfate, Cr(VI) and SMT (the concentration of sodium sulfate in the wastewater was 0.1 mol·L⁻¹) was added. -1 The concentration of SMT is 10 mg·L⁻¹ -1 The concentration of Cr(VI) is 10 mg·L⁻¹. -1 The photoelectrocatalytic reaction was carried out at pH 2 for 90 min, with the voltage set at 1.0 V and the electrode light intensity at 159 mW·cm⁻¹. -2 The co-treatment of hexavalent chromium and sulfadimethylpyrimidine in the compound wastewater was completed.

[0114] (2) Repeat step (1) using the same electrodes to treat the wastewater containing sodium sulfate, Cr(VI) and SMT repeatedly for a total of 6 times.

[0115] After each photoelectrocatalytic reaction, 4 mL of sample was taken and filtered through a 0.22 μm filter membrane. One mL of this sample was analyzed by high-performance liquid chromatography (HPLC) to determine the peak area change of SMT at different degradation times, thus determining the SMT degradation concentration and obtaining the degradation effect of the photoelectrode on SMT in different water qualities. The other 3 mL of sample was analyzed by diphenylcarbazide spectrophotometry to determine the Cr(VI) concentration, thus obtaining the reduction effect of the photoelectrode on Cr(VI). The results are as follows: Figure 10 As shown.

[0116] Figure 10 This is a diagram illustrating the cyclic degradation effect of the bimetallic node-coupled metal-organic framework derivative electrode on Cr(VI) and SMT in wastewater in Example 8 of the present invention. Figure 10 As shown, after 6 cycles, the photoelectric system still maintained a degradation efficiency of over 85% for Cr(VI) and SMT, indicating that C-Ti2O3@Zr-Zn / ZnO did not undergo irreversible changes such as decomposition or deactivation during the reaction process, confirming the high activity and stability of the reaction sites within the catalyst.

[0117] Example 9

[0118] A method for synergistically treating hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, specifically utilizing a bimetallic node coupled with a metal-organic framework derivative electrode for synergistic treatment of hexavalent chromium (Cr(VI)) and sulfadimethylpyrimidine (SMT) composite wastewater, includes the following steps:

[0119] Using the bimetallic node-coupled metal-organic framework derivative electrode prepared in Example 1 as the anode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode, 100 mL of wastewater containing sodium sulfate, Cr(VI), and SMT with different interfering substances (chloride ions, phosphate ions, nitrate ions, and humic acid) was placed in each of the wastewater samples (the concentration of sodium sulfate in each wastewater sample was 0.1 mol·L⁻¹). -1 The concentration of SMT was 10 mg·L⁻¹. -1 The concentration of Cr(VI) was 10 mg·L⁻¹. -1 The photoelectrocatalytic reaction was carried out in an atmosphere with a pH of 2 for 90 min, with the voltage set at 1.0 V and the electrode light intensity at 159 mW·cm⁻¹. -2 The co-treatment of hexavalent chromium and sulfadimethylpyrimidine in the compound wastewater was completed.

[0120] In the photoelectrocatalytic reaction, 4 mL samples were taken at regular intervals (0 min, 15 min, 30 min, 45 min, 60 min, 75 min, and 90 min) and filtered through a 0.22 μm filter membrane. One mL of this sample was analyzed using high-performance liquid chromatography (HPLC) to determine the peak area change of SMT at different degradation times, thus identifying the SMT degradation concentration and the effect of the photoelectrode on SMT degradation under different interference conditions. The remaining 3 mL of the sample had its Cr(VI) concentration determined using diphenylcarbazide spectrophotometry, thus determining the reduction effect of the photoelectrode on Cr(VI). The results are shown below. Figure 11 As shown.

[0121] Figure 11 This image shows the degradation effects of the bimetallic node-coupled metal-organic framework derivative electrode on Cr(VI) and SMT under different interference conditions in Example 9 of this invention. Figure 11 As shown, the presence of coexisting anions has little effect on the degradation of Cr(VI), but it hinders the degradation of SMT. This is because the coexisting anions can act as scavengers of free radicals or holes, generating low-activity free ions. Furthermore, HA also inhibits the degradation of SMT. On one hand, the large presence of HA reduces the electrolyte transmittance, leading to a lack of reactive oxygen species. On the other hand, HA also binds to free radicals, reducing their number. Simultaneously, the adsorption of HA byproducts hinders the active sites of SMT, leading to catalyst deactivation.

[0122] In summary, compared with conventional photoelectrocatalytic systems constructed based on MOF derivative heterostructures, the photoelectrocatalytic system constructed in this invention, using a bimetallic node coupled with a metal-organic framework derivative electrode as the working electrode, possesses advantages such as strong light utilization, fast electron transfer efficiency, and strong conversion effect between complex free radical chemistry and different active substances. It can not only achieve the synergistic degradation of hexavalent chromium and sulfadiazine in wastewater, but also simultaneously and efficiently remove hexavalent chromium and sulfadiazine from wastewater. The degradation rate of pollutants in the photoelectrocatalytic system is [not specified in the original text]. The rate constant is more than four times that of individual photocatalytic and electrocatalytic systems. The photoelectro-co-coefficients (SF) of SMT and Cr(VI) are 3.06 and 2.07, respectively, demonstrating excellent photoelectro-co ...

[0123] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for synergistically treating a complex wastewater containing hexavalent chromium and sulfadimethylpyrimidine, characterized in that, The method utilizes a bimetallic node-coupled metal-organic framework (MOF) derivative electrode to synergistically treat hexavalent chromium and sulfadiazine (SAM) composite wastewater, comprising the following steps: mixing the bimetallic node-coupled MOF derivative electrode and the hexavalent chromium and SAM composite wastewater for photoelectrocatalytic reaction to achieve synergistic treatment of hexavalent chromium and SAM in the composite wastewater; the bimetallic node-coupled MOF derivative electrode comprises a conductive substrate, on which MOF derivatives are coupled via Zr and Zn as metal nodes; the MOF derivatives are ZrO2 and ZnO; the preparation method of the bimetallic node-coupled MOF derivative electrode comprises the following steps: S1. A conductive substrate is placed in a zirconium-containing electrolytic solution and pulse electrodeposition is performed to obtain a conductive substrate loaded with zirconium ions; S2. A conductive substrate loaded with zirconium ions is mixed with a mixed solution containing N,N-dimethylformamide, zinc nitrate, 2-aminoterephthalic acid, nitric acid and titanium isopropoxide and subjected to a hydrothermal reaction to obtain a conductive substrate loaded with NH2-UiO-66 (Zr) and NH2-MOF-5 (Zn). S3. The conductive substrate loaded with NH2-UiO-66 (Zr) and NH2-MOF-5 (Zn) is calcined to obtain a bimetallic node-coupled metal-organic framework derivative electrode.

2. The method according to claim 1, characterized in that, In step S1, a three-electrode system is constructed using a conductive substrate as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Pulse electrodeposition is performed in a zirconium-containing electrolytic solution using multiple current conversion to load zirconium ions onto the surface and interior of the conductive substrate. The zirconium-containing electrolytic solution is a mixed solution of zirconium salt and electrolyte; the concentration of zirconium salt in the zirconium-containing electrolytic solution is 0.02 mol•L. -1 The concentration of the electrolyte is 0.01 mol•L. -1 The zirconium salt is zirconium chloride; the electrolyte is sodium sulfate; during the pulse electrodeposition process, the deposition current and diffusion current complete 300 alternating cycles, the buffer voltage of each cycle is set to 0 V, and the dwell time between adjacent cycles is 1 s; the deposition current is 0.15 A for 10 ms; the diffusion current is -0.15 A for 3 ms.

3. The method according to claim 2, characterized in that, In step S1, the conductive substrate is further treated as follows before use: the conductive substrate is cleaned sequentially with acetone, anhydrous ethanol, and ultrapure water, and then dried; the cleaning time is 10 min; the drying is carried out at a temperature of 60℃~80℃; the drying time is 30 min~60 min; the conductive substrate is carbon fiber; the carbon fiber has a size of 3 cm × 3 cm.

4. The method according to claim 1, characterized in that, In step S2, the ratio of N,N-dimethylformamide, zinc nitrate, 2-aminoterephthalic acid, nitric acid, and titanium isopropoxide in the mixed solution is 40 mL–50 mL: 0.3 g–0.6 g: 0.4 g–0.6 g: 0.20 mL–0.25 mL: 0.10 mL–0.12 mL; the hydrothermal reaction is carried out at a temperature of 160 °C; the hydrothermal reaction time is 24 h; after the hydrothermal reaction, the following steps are further included: the hydrothermal reaction product is washed sequentially with N,N-dimethylformamide and ultrapure water at a temperature of 60 °C–80 °C for 30 min–60 min.

5. The method according to claim 1, characterized in that, In step S3, the calcination is carried out under an inert atmosphere, which is argon; the heating rate during the calcination process is 5℃ / min to 7℃ / min; the calcination is carried out at a temperature of 450℃ to 500℃; and the calcination time is 2h to 3h.

6. The method according to any one of claims 1 to 5, characterized in that, A three-electrode system was constructed using a bimetallic node-coupled metal-organic framework derivative electrode as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode to conduct a photoelectrocatalytic reaction on a mixture of hexavalent chromium and sulfadimethylpyrimidine wastewater. During the photoelectrocatalytic reaction, the voltage was 0–1.5 V and the light intensity was 10⁹ mW•cm². -2 ~159 mW•cm -2 The photoelectrocatalytic reaction time is 90 min.

7. The method according to claim 6, characterized in that, The concentration of sulfadiazine in the hexavalent chromium and sulfadiazine combined wastewater was 10 mg•L. -1 ~30 mg•L -1 The concentration of hexavalent chromium was 10 mg•L. -1 ~30 mg•L -1 The initial pH value of the hexavalent chromium and sulfadimethylpyrimidine composite wastewater is 1-6.

8. The method according to claim 7, characterized in that, The photoelectrocatalytic reaction process also includes adding an electrolyte to the hexavalent chromium and sulfadimethylpyrimidine composite wastewater, such that the concentration of the electrolyte in the hexavalent chromium and sulfadimethylpyrimidine composite wastewater is 0.1 mol•L. -1 The electrolyte is sodium sulfate.

Images