A ferrocene-modified biochar oxidation reactor, its preparation method, and its application

Abstract

This invention relates to a ferrocene-modified biochar oxidation reactor, which has a sandwich structure, comprising, from left to right: an acrylic plate, a cathode, a water guide net, an anode, and another acrylic plate; wherein the anode material is biochar; the cathode is a composite material of biochar-supported polyvinyl ferrocene; the anode and cathode are externally powered; and the acrylic plate has several water guide holes through which organic wastewater containing persulfate flows into or out of the reactor. This invention achieves the degradation of organic pollutants by persulfate through low-voltage cyclic catalytic degradation, realizing catalyst recycling, reducing input costs, preventing secondary pollution from the catalyst in the system, and achieving green degradation of organic pollutants with low energy consumption, low cost, and low risk of secondary pollution. This is of great significance for expanding the application scope of advanced persulfate oxidation technology.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a ferrocene-modified biochar oxidation reactor, its preparation method, and its application. Background Technology

[0002] Based on sulfate free radicals (SO4· - Persulfate-based advanced oxidation systems (AEOs) have become a research hotspot in recent years due to their advantages over traditional OH-based AEOs, including longer free radical lifetimes, higher redox potentials, and wider pH adaptability. However, since most catalysts in natural water are negatively charged, negatively charged persulfate species may experience reduced catalytic activity due to electrostatic repulsion. Currently, non-metallic catalysts, including graphene, carbon nanotubes (CNTs), nanodiamonds, and biochar (BC), have been successfully used as carbonaceous persulfate catalysts, with biochar attracting significant attention due to its adaptability in adsorption and catalysis. In persulfate AEOs, iron, as an abundant and non-toxic transition metal, is commonly used as a catalyst; however, the oxidative deactivation of iron in iron-based activated persulfate systems often hinders technological implementation. Currently, much research focuses on finding stable iron-based materials or suitable reduction methods to promote the conversion of Fe(III) to Fe(II). Some studies have reported that introducing a reducing agent into the system can effectively promote the conversion of Fe(III), but excessive addition of the reducing agent or quenching of free radicals can affect system efficiency or cause secondary pollution. In contrast, an electric field, as a highly efficient electron-donating reducing agent, holds promise for achieving the green conversion of Fe(III).

[0003] Ferrocene (Fc) is an aromatic organotransition metal compound with the chemical formula Fe(C5H5)2. Mössbauer spectroscopy data shows that the oxidation state of the central iron atom in Fc is +2, and each pentene ring carries a single negative charge. Its molecule is polar and exhibits high thermal stability, chemical stability, and radiation resistance. When the Fe(II) in the core is oxidized to Fe(III), electrons from the pentene ring readily flow into the core, stabilizing the molecule. Studies have shown that this molecule possesses good redox reversibility; when Fe(II) in the molecule is oxidized to Fe(III), it readily gains electrons to return to Fe(II). Based on its excellent electron gain / loss ability and unique redox activity, it is a potential catalyst for activating polystyrene (PS), and its unique redox reversibility gives it the potential to be reduced and reactivated. Furthermore, persulfate can directly gain an electron from the cathode surface to generate SO4· - However, the negative charge on the cathode surface may repel persulfate anions, leading to inefficient activation of PMS. Therefore, a pre-oxidation step is required to convert some Fc to Fc. +This allows it to selectively adsorb PMS anions.

[0004] Therefore, how to use multi-stage oxidation treatment to achieve deep oxidation of organic matter in wastewater is a key focus of our attention. Summary of the Invention

[0005] This invention proposes a method for the cyclic catalytic degradation of bisphenol A (BPA) by persulfate using ferrocene-modified biochar. The biochar is modified with an Fc-derived polymer—polyvinyl ferrocene (PVF)—to catalyze the production of SO4·4·4 from permonosulfate (PMS). - Degradation of organic pollutants in wastewater. Considering the electrostatic repulsion between PMS and the PVF-BC cathode, a two-stage synergistic effect is proposed. In the first step, a 0V battery voltage is applied to the reactor, where PMS is catalyzed by the Fc in the PVF-BC to partially generate SO4· - Degradation of organic pollutants. In this process, Fc is partially converted to Fc. + This forms a positively charged PVF-BC surface. In the second stage, a cell voltage of -1.2V is applied, and the PMS directly gains electrons from the cathode to generate a large amount of SO4· - At the same time, Fc + Reverting to Fc, Fc can also activate PMS to produce SO4· - This invention establishes a method for the degradation of organic pollutants by persulfate using PVF-BC composite materials through low-voltage cyclic catalysis. This method enables the recycling of the catalyst, reduces input costs, and prevents secondary pollution caused by the catalyst in the system. It achieves green degradation of organic pollutants with low energy consumption, low cost, and low risk of secondary pollution, which is of great significance for expanding the application scope of persulfate advanced oxidation technology.

[0006] One object of the present invention is to provide a ferrocene-modified biochar oxidation reactor, wherein the ferrocene-modified biochar oxidation reactor has a sandwich structure, comprising the following structures from left to right:

[0007] Acrylic sheet, cathode, water guide net, anode, acrylic sheet;

[0008] in

[0009] The anode material is biochar;

[0010] The cathode is a composite material of biochar-supported polyvinyl ferrocene;

[0011] The anode and cathode are connected to an external power source.

[0012] The acrylic plate has several water guide holes through which organic wastewater containing persulfate flows into or out of the reactor.

[0013] Specifically, organic wastewater containing persulfate is pumped into or out of the reactor through a peristaltic pump via a water guide hole on an acrylic plate near the cathode, ensuring that the organic wastewater in the system is in a dynamic equilibrium state.

[0014] Furthermore, the power supply has a value of 0 to -2.1V.

[0015] Furthermore, in the composite material, the mass ratio of polyvinyl ferrocene to biochar is 1:4 to 2:1.

[0016] Furthermore, the anode surface is sequentially covered with a silica gel layer and a cation exchange membrane.

[0017] Furthermore, the concentration of the persulfate in the organic wastewater is 0.5–4 mmol / L.

[0018] Another object of the present invention is to provide a method for degrading bisphenol A in the above-mentioned ferrocene-modified biochar oxidation reactor, which includes two stages:

[0019] S1. Set the external power supply voltage to 0V for 0.5 to 2 hours;

[0020] S2. The external power supply voltage is set to -0.8 to -2.1V, and the time is 0.5 to 2 hours.

[0021] Furthermore, the method also includes the preparation of the cathode, wherein the preparation of the cathode comprises the following steps: mixing biochar and polyvinyl ferrocene, adding organic solvent and binder, and grinding to obtain a mixture; then coating the mixture onto graphite paper and drying to obtain the cathode.

[0022] Another object of the present invention is to provide the application of the above-mentioned ferrocene-modified biochar oxidation reactor in the degradation of organic wastewater containing bisphenol A.

[0023] The present invention has the following beneficial effects:

[0024] 1. Current advanced oxidation technologies for persulfate still suffer from the difficulty in reusing catalysts, resulting in high application costs. This invention proposes to load stable redox polyvinyl ferrocene and highly conductive, high-specific-surface-area biochar onto a graphite paper substrate. Utilizing the unique electron transport capabilities of polyvinyl ferrocene, free radicals are directly reduced from persulfate using low voltage, while simultaneously reducing the Fc oxidized by persulfate. + This enables the catalyst to be continuously reused.

[0025] 2. Since persulfate is negatively charged, and most catalysts are also negatively charged under natural water pH conditions, electrostatic repulsion may reduce the reaction between the catalyst and persulfate. This invention oxidizes Fc to Fc in the first stage. +This improves the material's ability to interact with persulfate under electrorepulsion, thereby enhancing the ability of persulfate to generate free radicals in the second stage.

[0026] 3. The persulfate advanced oxidation system established in this invention is suitable for the treatment of various recalcitrant organic wastewaters. It has good durability, high efficiency, recyclable materials, is environmentally friendly, and causes no secondary pollution.

[0027] 4. The operation method of this invention is simple and easy to operate. In particular, the parameters of the electroreduction process are easy to control, and the reaction parameters can be adjusted at any time as needed. Attached Figure Description

[0028] Figure 1 This is a reactor configuration diagram of the ferrocene-modified biochar oxidation treatment reactor in Examples 1-2.

[0029] Figure 2 This is a mechanism diagram of the two-stage operation of the ferrocene-modified biochar oxidation reactor in Examples 1-2.

[0030] Figure 3 This describes the removal process of bisphenol A, an organic pollutant, in the ferrocene-modified biochar oxidation reactor corresponding to the biochar ratio in Examples 1-2.

[0031] Figure 4 This describes the removal process of bisphenol A, an organic pollutant, in the ferrocene-modified biochar oxidation reactor under different voltage conditions in Example 2.

[0032] Figure 5 This describes the removal process of bisphenol A, an organic pollutant, in the ferrocene-modified biochar oxidation reactor in Example 2 under different initial sodium perhydrosulfate concentrations.

[0033] Figure 6 This describes the removal process of bisphenol A, an organic pollutant, in the ferrocene-modified biochar oxidation reactor during ten cycles in Example 2. Detailed Implementation

[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. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0036] Unless otherwise specified, the construction of the ferrocene-modified biochar oxidation reactor in the embodiments of the present invention is a conventional method well known to those skilled in the art.

[0037] Example 1

[0038] A ferrocene-modified biochar oxidation reactor, the specific structure of which is shown in [the diagram]. Figure 1 :

[0039] From left to right: acrylic plate (10cm*10cm, 1cm thick) / cathode (7.5cm*7.5cm, 0.3mm thick) / water guide net (7.5cm*7.5cm, 1mm thick) / silicone pad (10cm*10cm, 1cm thick) / cation exchange membrane (10cm*10cm, 0.3mm thick) / anode (7.5cm*7.5cm, 0.3mm thick) / acrylic plate (10cm*10cm, 1cm thick); the volume of the ferrocene-modified biochar oxidation treatment reactor is 5.6mL.

[0040] The anode material is biochar, and its surface is sequentially coated with a silica gel layer and a cation exchange membrane (CEM-Type II FUJIFILM) of the same size, forming a multilayer structure;

[0041] The cathode is a composite material (4.5cm*4.5cm) of polyvinyl ferrocene supported on biochar (7.5cm*7.5cm); wherein the polyvinyl ferrocene composite material is located at the center of the biochar and forms a multilayer structure;

[0042] During operation, the anode and cathode are connected to an external power source via an electrostatic titanium plate. Organic wastewater containing sodium perhydrosulfate flows into the reactor through a peristaltic pump at a flow rate of 10 mL / min, through a water guide hole (inlet) on the acrylic plate near the cathode, and then flows out of the reactor at the same flow rate through the same water guide hole (outlet) on the same acrylic plate near the cathode. The initial concentration of bisphenol A in the organic wastewater is 0.05 mg / L, and the initial concentration of sodium perhydrosulfate is 2 mmol / L.

[0043] The preparation steps of the above cathode are as follows: Polyvinyl ferrocene and biochar are mixed (2:1, 60mg:30mg), and 375μL of organic solvent N-methylpyrrolidone and 10mg of binder polyvinylidene fluoride are added and ground to obtain a mixture; then the mixture is coated on graphite paper (7.5cm*7.5cm in size) and dried in an oven at 60°C to obtain the cathode.

[0044] Example 2

[0045] The ferrocene-modified biochar oxidation reactor obtained in Example 2 is the same as that in Example 1, except that in the cathode preparation step, the mass ratio of polyvinyl ferrocene and biochar is 1:2, 30mg:60mg.

[0046] Example 3

[0047] The ferrocene-modified biochar oxidation reactor obtained in Example 3 is the same as that in Example 1, except that in the cathode preparation step, the mass ratio of polyvinyl ferrocene and biochar is 1:4, 30mg:120mg.

[0048] Test case

[0049] The ferrocene-modified biochar oxidation reactors of Examples 1-3 were prepared and processed in the following two-stage manner:

[0050] S1. The external power supply voltage is set to 0V, and the processing time is 1 hour.

[0051] S2. Then set the external power supply voltage to -1.2V and the processing time to 1 hour.

[0052] In the first stage, persulfate gains electrons from ferrocene to generate sulfate radicals that degrade bisphenol A, while ferrocene (Fc) is oxidized to Fc. + In the second stage, a negative charge was applied to the biochar-supported polyvinyl ferrocene composite, and sodium perhydrosulfate was added to the Fc... + Attracted by the cathode, the composite material of polyvinyl ferrocene supported on biochar is brought close to the cathode and directly gains electrons to generate sulfate radicals that degrade bisphenol A, while simultaneously reducing Fc. + Fc is the catalyst that enables Fc to continuously catalyze the formation of sulfate radicals from sodium perhydrosulfate. The relevant mechanism is as follows: Figure 2 As shown.

[0053] The removal rate curve of bisphenol A for the biochar-supported polyvinyl ferrocene composite is shown in the figure below. Figure 3 As shown. From Figure 3As can be seen from the results, the reactors obtained in Examples 1-3 all achieved a bisphenol A removal rate of over 90%. When the PVF:BC ratio changed from 2:1 to 1:4, the bisphenol A removal rate first showed a significant increase, and then slightly decreased.

[0054] like Figure 4 As shown, when the initial concentration of bisphenol A was 0.05 mg / L and the initial concentration of sodium perhydrosulfate was 2 mmol / L, in Example 2, the removal efficiency first increased and then decreased with increasing voltage. The lowest BPA degradation rate was observed at 0.8 V, reaching 66.77% after 120 min. The degradation efficiencies at 1.2 V and 1.5 V were similar, at 90.12% and 92.16%, respectively. Further increasing the voltage to 2.1 V slightly worsened the degradation effect (89.51%). This is because under excessively high voltage conditions, side reactions occur on the electrode surface, such as i) hydrogen evolution reaction and ii) oxygen reduction reaction, leading to a decrease in the utilization rate of electrons available for sodium perhydrosulfate activation.

[0055] like Figure 5 As shown in Example 2, when the second-stage voltage is -1.2V, the degradation efficiency of the 1 mmol / L sodium perhydrosulfate system is the lowest, while the degradation efficiency of the 2 mmol / L and 3 mmol / L sodium perhydrosulfate systems is not significantly different.

[0056] like Figure 6 As shown in Example 2, when the initial concentration of sodium perhydrosulfate was 2 mmol / L, the degradation experiment was repeated 10 times using the same electrode to evaluate the electrode's stability. As the figure shows, with the increase in the number of experiments, the degradation efficiency first increased and then tended to stabilize, and the degradation rate remained above 90% for 2 hours.

[0057] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0058] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for degrading bisphenol A in a reactor using ferrocene-modified biochar oxidation, characterized in that, The ferrocene-modified biochar oxidation reactor has a sandwich structure, which includes the following structures from left to right: Acrylic sheet, cathode, water guide net, anode, acrylic sheet; in The anode material is biochar; The cathode is a composite material of biochar-supported polyvinyl ferrocene; The anode and cathode are connected to an external power source; The acrylic plate has several water guiding holes, through which organic wastewater containing persulfate flows into or out of the reactor. The power supply value is 0 to -2.1 V; The method for degrading bisphenol A in the ferrocene-modified biochar oxidation reactor includes two stages: S1. Set the external power supply voltage to 0 V for 0.5~2 hours; S2. The external power supply voltage is set to -0.8~-2.1 V, and the time is 0.5~2 h.

2. The method for degrading bisphenol A in a ferrocene-modified biochar oxidation reactor according to claim 1, characterized in that, In the composite material, the mass ratio of polyvinyl ferrocene to biochar is 1:4 to 2:

1.

3. The method for degrading bisphenol A in a ferrocene-modified biochar oxidation reactor according to claim 1, characterized in that, The anode surface is sequentially covered with a silica gel layer and a cation exchange membrane.

4. The method for degrading bisphenol A in a ferrocene-modified biochar oxidation reactor according to claim 1, characterized in that, The concentration of persulfate in the organic wastewater is 0.5~4 mmol / L.

5. The method for degrading bisphenol A in a ferrocene-modified biochar oxidation reactor according to claim 4, characterized in that, It also includes the preparation of the cathode, wherein the preparation steps of the cathode are as follows: mixing biochar and polyvinyl ferrocene, adding organic solvent and binder, and grinding to obtain a mixture; then coating the mixture on graphite paper and drying to obtain the cathode.

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