A dynamic circulation type chitosan column treatment system for azo dye wastewater

Abstract

This application relates to the field of wastewater treatment technology and discloses a dynamic circulating chitosan column system for treating azo dye wastewater. The system includes an integrated reaction column, vertically placed, with an inlet at the bottom and an outlet at the top. The integrated reaction column contains a rolled composite functional fiber felt. An inert anode is located at the center of the integrated reaction column, and the composite functional fiber felt itself acts as a distributed cathode. Azo dye wastewater enters the integrated reaction column through the inlet, where dye molecules are adsorbed by the composite functional fiber felt and then discharged through the outlet. The composite functional fiber felt includes a modified chitosan component for adsorbing azo dyes, a conductive component to make it conductive, and a piezoelectric component capable of generating an electric field under mechanical stress. An electric field application device is also included, with two output contacts connected to the inert anode and the distributed cathode respectively, for applying an electric field during the regeneration stage. A mechanical vibration application device is also included. By integrating the "adsorption-regeneration-degradation" process into a single reactor, in-situ self-cleaning and functional recovery are achieved through self-sensing and intelligent control. This completely solves the problem in existing technologies where adsorption columns must be regenerated or replaced offline after saturation.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a dynamic circulating chitosan column system for treating azo dye wastewater. Background Technology

[0002] Azo dyes are a class of synthetic dyes widely used in the textile, printing and dyeing, and leather industries. The large amounts of wastewater generated during their production and use are characterized by high color, high chemical oxygen demand, high toxicity, and poor biodegradability, posing a serious threat to the ecological environment and human health. Currently, the main methods for treating azo dye wastewater include physical, chemical, and biological methods. Among physical methods, adsorption is highly regarded due to its simple operation, relatively low cost, and high efficiency. Chitosan, as a natural polymer material, is widely available, non-toxic, and biodegradable. Its molecular chain contains a large number of active groups such as amino and hydroxyl groups, exhibiting excellent adsorption performance for various pollutants.

[0003] However, natural chitosan is easily soluble under acidic conditions and has poor mechanical strength and chemical stability. Direct application in columnar dynamic adsorption can easily lead to swelling and clogging, limiting its application in practical industrial wastewater treatment. To improve the adsorption performance and application stability of chitosan, modification is usually necessary. For example, modifying chitosan with acrylic acid can increase the number of active adsorption sites on its surface. Existing research mainly focuses on static batch treatment experiments to examine the adsorption performance of modified chitosan on pollutants. However, the relevant technical solutions for applying highly efficient modified chitosan adsorbents to continuous, dynamic industrial wastewater treatment processes and achieving adsorbent regeneration and recycling are still underdeveloped.

[0004] In existing technologies, adsorption and regeneration are two independent, discontinuous steps. The periodic saturation of the adsorption column and offline regeneration are the fundamental bottlenecks of this technical approach, resulting in low processing efficiency and the inability to achieve truly continuous and automated operation. Chemical regenerators not only cause secondary pollution to the environment but also cause irreversible damage to the chitosan substrate itself, limiting its recycling frequency. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide a fully automated, continuous azo dye wastewater treatment system that integrates efficient pollutant adsorption, in-situ degradation, intelligent sensing, and adaptive control. Its core lies in overcoming the fundamental bottlenecks of traditional adsorption technologies—such as fragmented "adsorption-regeneration" processes, secondary pollution, and the inability to achieve intelligent operation—through innovative composite functional material design and multi-physics field synergistic control.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: a dynamic circulating chitosan column system for treating azo dye wastewater, comprising an integrated reaction column, which is placed vertically with an inlet at the bottom and an outlet at the top. The integrated reaction column is provided with a rolled composite functional fiber felt. An inert anode is provided at the center of the integrated reaction column, and the composite functional fiber felt itself serves as a distributed cathode. Azo dye wastewater enters the integrated reaction column through the inlet, and the dye molecules in the wastewater are adsorbed by the composite functional fiber felt and then discharged through the outlet. The composite functional fiber felt includes a modified chitosan component for adsorbing azo dyes, a conductive component that makes it conductive, and a piezoelectric component that can generate an electric field under mechanical stress.

[0007] An electric field application device, whose two output contacts are connected to an inert anode and a distributed cathode respectively, is used to apply an electric field during the regeneration stage;

[0008] A mechanical vibration application device is used to apply mechanical vibration to the composite functional fiber felt during the regeneration stage to drive its piezoelectric components to generate an endogenous electric field.

[0009] The control module is used to acquire the impedance and voltage signals of the composite functional fiber felt and to control the operation of the electric field application device and the mechanical vibration application device.

[0010] Preferably, the integrated reaction column is made of a chemically stable material and has a columnar structure. An insulating skeleton is embedded inside the column. The insulating skeleton has a hollow cylindrical structure with multiple pores on its wall. Composite functional fiber felt is tightly wound around the outer wall of the insulating skeleton to form a roll structure. The inert anode penetrates the central cavity of the insulating skeleton and is fixedly connected to the inner wall of the integrated reaction column through a support.

[0011] Preferably, a valve is provided at the inlet of the integrated reaction column and is connected to an inlet pump. The azo dye wastewater is pumped into the integrated reaction column by the inlet pump, and the inlet pump is electrically connected to the control module.

[0012] Preferably, the inlet and outlet of the integrated reaction column are also connected to an internal circulation device, which includes a circulation pump. The input end of the circulation pump is connected to the outlet, and the output end is connected to the inlet.

[0013] Preferably, the mechanical vibration application device uses a piezoelectric ceramic ultrasonic transducer. Multiple piezoelectric ceramic ultrasonic transducers are fixedly connected to the outer wall of the integrated reaction column and are evenly and symmetrically distributed along the circumference and axial direction of the integrated reaction column. Multiple piezoelectric ceramic ultrasonic transducers are connected in parallel to the same ultrasonic signal generator, and the ultrasonic signal generator is electrically connected to the control module.

[0014] Preferably, the composite functional fiber felt is prepared by electrospinning, which involves blending modified chitosan, graphene, and piezoelectric polymer to form a composite nanofiber felt with a three-dimensional porous network structure.

[0015] Preferably, the preparation steps of the composite functional fiber felt include:

[0016] Step 1: Preparation of modified chitosan solution. Chitosan is grafted and copolymerized with a modifier, and then crosslinked with a crosslinking agent to prepare modified chitosan. It is then dissolved in an acetic acid aqueous solution of a preset concentration and continuously stirred magnetically at room temperature until a clear, homogeneous, and viscous chitosan solution is formed.

[0017] Step 2: Preparation of graphene and piezoelectric polymer blend solution. Polyvinylidene fluoride is dissolved in a mixed solvent of N,N-dimethylformamide and acetone and magnetically stirred until completely dissolved. Then, a certain amount of graphene oxide slurry is added and subjected to long-term, high-intensity ultrasonic dispersion treatment using an ultrasonic cell disruptor to ensure that the graphene is uniformly dispersed at the single-layer level in the polyvinylidene fluoride solution, forming a stable black suspension.

[0018] Step 3: Preparation of composite spinning solution. The chitosan solution, graphene and piezoelectric polymer blend solution prepared above are mixed in proportion. The mixed solution is then subjected to thorough mechanical stirring and ultrasonic treatment to eliminate the interface and ensure that the three components are uniformly fused at the molecular level to obtain the final composite spinning solution for electrospinning.

[0019] Step 4: Electrospinning process. The above composite spinning solution is loaded into a syringe with a metal needle and fixed to a micro-injection pump. The needle is connected to the positive terminal of a high-voltage DC power supply. A grounded metal roller covered with aluminum foil is placed at a specific distance opposite the needle as a receiving device. The spinning solution is pushed out by the injection pump at a stable rate. At the same time, under the strong electric field applied by the high-voltage power supply, the droplets are stretched to form Taylor cones and finally ejected as nanoscale fiber jets. Before the fibers reach the receiving roller, the solvent evaporates, solidifies, and is randomly laid out to form a three-dimensional porous, non-woven composite nanofiber felt.

[0020] Step 5: Post-treatment. The obtained fiber felt is peeled off from the aluminum foil and placed in a vacuum drying oven at a suitable temperature for thorough drying to completely remove residual solvent. Then, the fiber felt is placed in glutaraldehyde vapor for cross-linking treatment to enhance its structural stability and durability in aqueous solution.

[0021] Preferably, the system operation steps include:

[0022] Step 1: Adsorption and enrichment. Start the inlet pump and pump the azo dye wastewater into the integrated reaction column at a constant flow rate. The dye molecules are adsorbed by the composite functional fiber felt as they flow through the column.

[0023] Step 2: Saturation self-sensing. During the adsorption and enrichment period, the control module applies a detection signal to the composite functional fiber mat through an inert anode and a distributed cathode to measure the AC impedance of the fiber mat in real time. As non-conductive dye molecules continuously fill the graphene conductive network, the system impedance value will show a regular increase, and the control module will continuously record this impedance value.

[0024] Step 3: Regeneration mode is activated. When the control module detects that the impedance value has reached the preset saturation threshold, it automatically determines that the adsorption is saturated, stops the water inlet pump, starts the circulation pump to form an internal circulation mode, and starts the electric field application device to apply pulsed DC current to the electrode. At the same time, the ultrasonic signal generator is activated to drive the external transducer to generate frequency-converted or intermittent ultrasonic waves. In this multi-field coupling environment, an electro-Fenton reaction occurs in situ on the surface of the fiber felt cathode, and the piezoelectric effect enhances catalysis, resulting in rapid and in-situ decomposition of the adsorbed dye.

[0025] Step 4: Regeneration Feedback. During the regeneration process, microscopic events such as pollutant degradation, product desorption, and microbubble activity cause vibrations in the piezoelectric polymer in the fiber, generating an acoustic emission voltage signal. This signal is captured in real time by the control module through electrodes. The control module performs real-time spectrum and amplitude analysis on the acquired acoustic signal, extracting features that characterize the reaction rate and uniformity. This analysis result serves as a feedback signal to dynamically adjust the applied pulse electric field parameters and ultrasonic field parameters in real time.

[0026] Step 5: When the control module analyzes that the intensity of the acoustic emission signal has attenuated to the background baseline level and the system impedance value has returned to the initial state, it determines that the regeneration process has been completely completed. The control module automatically shuts down the electric field application device and the ultrasonic generator, restores the normal operation of the water inlet pump, and starts a new round of adsorption treatment cycle.

[0027] This invention provides a dynamic circulating chitosan column system for treating azo dye wastewater. It offers the following advantages:

[0028] 1. This invention integrates the "adsorption-regeneration-degradation" process into a single reactor, achieving in-situ self-cleaning and functional recovery through self-sensing and intelligent control. This completely solves the problem in existing technologies where adsorption columns must be regenerated or replaced offline after saturation, eliminating the need for a backup system, significantly reducing equipment footprint and process downtime, and transforming wastewater treatment from intermittent operation to truly continuous, unattended operation.

[0029] 2. The regeneration process of this invention is driven by an electric field and a mechanical vibration field, degrading pollutants through physicochemical methods such as electrochemistry, sonochemistry, and piezoelectric catalysis, completely eliminating the need for corrosive chemical regeneration agents such as acids and alkalis. This not only fundamentally eliminates the generation of high-concentration, difficult-to-treat regeneration waste liquid, avoiding secondary pollution to the environment, but also makes the entire treatment process safer and more environmentally friendly. Simultaneously, by avoiding repeated rinsing and chemical erosion of the chitosan substrate by chemical reagents, the gentle regeneration method of this invention greatly protects the structure and active sites of the composite fibers, enabling them to withstand long-term, stable recycling. Combined with the reduced labor costs from automated operation and the absence of chemical reagents, the long-term overall operating cost of the system is significantly reduced.

[0030] 3. This invention utilizes multi-field synergistic effects to generate strong oxidizing substances in situ, which can completely decompose the adsorbed and enriched azo dye molecules into colorless small molecules, thereby achieving fundamental removal of pollutants and solving the problem of subsequent disposal of saturated adsorbents as hazardous waste. Attached Figure Description

[0031] Figure 1 This is a perspective view of the present invention;

[0032] Figure 2 This is a three-dimensional schematic diagram of the insulating frame in this invention;

[0033] Figure 3 This is a schematic diagram of the internal structure of the integrated reaction column in this invention;

[0034] Figure 4 This is a system flowchart of the present invention.

[0035] Among them, 1. Integrated reaction column; 101. Water inlet; 102. Water outlet; 103. Insulating frame; 104. Inert anode; 105. Support; 2. Composite functional fiber felt; 3. Water inlet pump; 4. Circulation pump. Detailed Implementation

[0036] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Please see the appendix Figure 1 -Appendix Figure 4This invention provides a dynamic circulating chitosan column system for treating azo dye wastewater, comprising an integrated reaction column 1, which is placed vertically with an inlet 101 at the bottom and an outlet 102 at the top. The integrated reaction column 1 contains a rolled composite functional fiber felt 2, and an inert anode 104 is disposed at the center of the integrated reaction column 1. The inert anode 104 may be an iridium-tantalum coated titanium mesh electrode or a graphite rod. The composite functional fiber felt 2 itself serves as a distributed cathode. Azo dye wastewater enters the integrated reaction column 1 through the inlet 101, and the dye molecules in the wastewater are adsorbed by the composite functional fiber felt 2 and then discharged through the outlet 102. The composite functional fiber felt 2 includes a modified chitosan component for adsorbing azo dye, a conductive component that makes it conductive, and a piezoelectric component that can generate an electric field under mechanical stress.

[0038] An electric field application device has two output contacts that are connected to an inert anode 104 and a distributed cathode, respectively, for applying an electric field during the regeneration stage;

[0039] A mechanical vibration application device is used to apply mechanical vibration to the composite functional fiber felt 2 during the regeneration stage to drive its piezoelectric components to generate an endogenous electric field. The mechanical vibration application device adopts a piezoelectric ceramic ultrasonic transducer. Multiple piezoelectric ceramic ultrasonic transducers are fixedly connected to the outer wall of the integrated reaction column 1 and are uniformly and symmetrically distributed along the circumference and axial direction of the integrated reaction column 1. Multiple piezoelectric ceramic ultrasonic transducers are connected in parallel to the same ultrasonic signal generator. The ultrasonic signal generator is electrically connected to the control module.

[0040] The control module is used to acquire the impedance and voltage signals of the composite functional fiber felt 2, and to control the operation of the electric field application device and the mechanical vibration application device.

[0041] The integrated reaction column 1 is made of chemically stable materials, such as quartz glass or Teflon. The integrated reaction column 1 has a columnar structure with an embedded insulating skeleton 103. The insulating skeleton 103 has a hollow cylindrical structure with multiple pores on its wall. Composite functional fiber felt 2 is tightly wound around the outer wall of the insulating skeleton 103 to form a rolled structure. The inert anode 104 penetrates the central cavity of the insulating skeleton 103 and is fixedly connected to the inner wall of the integrated reaction column 1 via a support 105. A valve is installed at the inlet 101 of the integrated reaction column 1, and it is also connected to an inlet pump 3. Azo dye wastewater is pumped into the integrated reaction column 1 by the inlet pump 3, which is electrically connected to the control module. An internal circulation device is also connected to the inlet 101 and outlet 102 of the integrated reaction column 1. The internal circulation device includes a circulation pump 4, whose input end is connected to the outlet 102 and its output end is connected to the inlet 101.

[0042] Composite functional fiber felt 2 is prepared by electrospinning modified chitosan, graphene, and piezoelectric polymer to form a composite nanofiber felt with a three-dimensional porous network structure. The preparation steps of composite functional fiber felt 2 include:

[0043] Step 1: Preparation of modified chitosan solution. Chitosan is grafted and copolymerized with a modifier, and then crosslinked with a crosslinking agent to prepare modified chitosan. It is then dissolved in an acetic acid aqueous solution of a preset concentration and continuously stirred magnetically at room temperature until a clear, homogeneous, and viscous chitosan solution is formed.

[0044] The modifier is selected from one or more of itaconic acid and maleic acid, and the crosslinking agent is glutaraldehyde. Chitosan is modified with itaconic acid by mixing chitosan with glacial acetic acid, then adding glutaraldehyde, itaconic acid, and ammonium persulfate. This creates an acidic environment that allows the carboxyl groups of itaconic acid to undergo nucleophilic substitution with the amino groups on the chitosan surface, forming amide bonds and achieving chemical modification. The introduction of hydrophilic carboxyl groups makes the modified chitosan more soluble in water.

[0045] Single-factor comparative experiments were conducted to compare chitosan and modified chitosan in terms of pH, adsorption time, initial concentration, and ambient temperature. The results showed that the adsorption effect of modified chitosan was far superior to that of chitosan.

[0046] Step 2: Preparation of graphene and piezoelectric polymer blend solution. Polyvinylidene fluoride is dissolved in a mixed solvent of N,N-dimethylformamide and acetone and magnetically stirred until completely dissolved. Then, a certain amount of graphene oxide slurry is added and subjected to long-term, high-intensity ultrasonic dispersion treatment using an ultrasonic cell disruptor to ensure that the graphene is uniformly dispersed at the single-layer level in the polyvinylidene fluoride solution, forming a stable black suspension.

[0047] Step 3: Preparation of composite spinning solution. The chitosan solution, graphene and piezoelectric polymer blend solution prepared above are mixed in proportion. The mixed solution is then subjected to thorough mechanical stirring and ultrasonic treatment to eliminate the interface and ensure that the three components are uniformly fused at the molecular level to obtain the final composite spinning solution for electrospinning.

[0048] Step 4: Electrospinning process. The above composite spinning solution is loaded into a syringe with a metal needle and fixed to a micro-injection pump. The needle is connected to the positive terminal of a high-voltage DC power supply. A grounded metal roller covered with aluminum foil is placed at a specific distance opposite the needle as a receiving device. The spinning solution is pushed out by the injection pump at a stable rate. At the same time, under the strong electric field applied by the high-voltage power supply, the droplets are stretched to form Taylor cones and finally ejected as nanoscale fiber jets. Before the fibers reach the receiving roller, the solvent evaporates, solidifies, and is randomly laid out to form a three-dimensional porous, non-woven composite nanofiber felt.

[0049] Step 5: Post-treatment. The obtained fiber felt is peeled off from the aluminum foil and placed in a vacuum drying oven at a suitable temperature for thorough drying to completely remove residual solvent. Then, the fiber felt is placed in glutaraldehyde vapor for cross-linking treatment to enhance its structural stability and durability in aqueous solution.

[0050] The operation steps of the dynamic circulating chitosan column system for treating azo dye wastewater include:

[0051] Step 1: Adsorption and enrichment. Start the inlet pump 3 to pump the azo dye wastewater into the integrated reaction column 1 at a constant flow rate. The dye molecules are adsorbed by the composite functional fiber felt 2 as they flow through the column.

[0052] Step Two: Saturation Self-Sensing. During adsorption and enrichment, the control module applies a weak, high-frequency AC detection signal to the composite functional fiber felt 2 via the inert anode 104 and distributed cathodes. The signal intensity is insufficient to trigger any electrochemical reaction; it is only used to measure the AC impedance of the composite functional fiber felt 2 in real time. As non-conductive dye molecules continuously fill the graphene conductive network, the system impedance value shows a regular increase, and the control module continuously records this impedance value. In this step, the control module continuously monitors the overall resistivity reflected by the weak current flowing through the composite fiber felt. As non-conductive dye molecules are continuously adsorbed and fill the pores of the graphene conductive network, the resistivity of the fiber felt will increase regularly and measurably. Based on a preset resistivity threshold, this module can accurately determine the saturation level of the adsorption column in real time, without relying on any external online water quality analysis instruments.

[0053] Step 3: Regeneration mode is started. When the control module detects that the impedance value reaches the preset saturation threshold, it automatically determines that the adsorption is saturated, stops the water inlet pump 3, starts the circulation pump 4 to form an internal circulation mode, and starts the electric field application device to apply pulsed DC current to the electrode. At the same time, the ultrasonic signal generator is started to drive the external transducer to generate frequency-converted or intermittent ultrasonic waves. In this multi-field coupling environment, the fiber felt cathode surface undergoes an in-situ electro-Fenton reaction, and the piezoelectric effect enhances catalysis, resulting in rapid and in-situ decomposition of the adsorbed dye.

[0054] In this step, an electric field application device applies pulsed direct current to the electrodes, causing an electrochemical reaction on the composite fiber cathode. Hydrogen peroxide is generated in situ, which then reacts with trace amounts of iron ions added to the wastewater to generate highly oxidizing hydroxyl radicals. These radicals are generated directly on the fiber surface where pollutants are concentrated, efficiently chemically degrading the adsorbed azo dyes.

[0055] The activation of the ultrasonic transducer serves a dual purpose:

[0056] Physical enhancement: Ultrasonic cavitation enhances mass transfer, strips away degradation products, and generates additional hydroxyl radicals.

[0057] Endogenous electric field catalysis: The mechanical vibration of ultrasound acts on the polyvinylidene fluoride piezoelectric material in the fiber, causing it to generate a high-frequency alternating endogenous electric field. This endogenous electric field works synergistically with the applied electric field to greatly promote charge separation and the rate of interfacial electrochemical reactions, thereby enhancing the generation efficiency of hydroxyl radicals.

[0058] It should be noted that at this stage, the control module does not apply a constant energy field, but rather executes a refined dynamic pulse drive strategy:

[0059] Pulsed electric field: Apply optimized, asymmetric electric pulses to suppress side reactions and improve current efficiency and energy utilization while ensuring degradation efficiency.

[0060] Variable frequency / intermittent ultrasound: The frequency and power of ultrasound are dynamically adjusted according to the regeneration process, or an intermittent working mode is adopted to maintain efficient piezoelectric catalysis and sonochemical effects with minimal energy consumption.

[0061] Step 4: Regeneration Feedback. During the regeneration process, microscopic events such as pollutant degradation, product desorption, and microbubble activity cause vibrations in the piezoelectric polymer in the fiber, generating an acoustic emission voltage signal. This signal is captured in real time by the control module through electrodes. The control module performs real-time spectrum and amplitude analysis on the acquired acoustic signal, extracting features that characterize the reaction rate and uniformity, thereby accurately judging the degree of completion and uniformity of regeneration. The analysis result serves as a feedback signal to dynamically adjust the applied pulse electric field parameters and ultrasonic field parameters in real time.

[0062] Step 5: When the control module analyzes that the intensity of the acoustic emission signal has attenuated to the background baseline level and the system impedance value has returned to the initial state, it determines that the regeneration process has been completely completed. The control module automatically shuts down the electric field application device and the ultrasonic generator, restores the normal operation of the water inlet pump 3, and starts a new round of adsorption treatment cycle.

[0063] This enables the system to operate in a fully automated closed loop of "adsorption-sensing-regeneration-monitoring-restart".

[0064] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A dynamic circulating chitosan column system for treating azo dye wastewater, characterized in that, include: An integrated reaction column (1) is placed vertically with an inlet (101) at the bottom and an outlet (102) at the top. The integrated reaction column (1) contains a roll-shaped composite functional fiber felt (2). An inert anode (104) is located in the center of the integrated reaction column (1). The composite functional fiber felt (2) itself serves as a distributed cathode. Azo dye wastewater enters the integrated reaction column (1) through the inlet (101). Dye molecules in the wastewater are adsorbed by the composite functional fiber felt (2) and then discharged through the outlet (102). The composite functional fiber felt (2) includes a modified chitosan component for adsorbing azo dyes, a conductive component that makes it conductive, and a piezoelectric component that can generate an electric field under mechanical stress. An electric field application device has two output contacts connected to an inert anode (104) and a distributed cathode, respectively, for applying an electric field during the regeneration stage; A mechanical vibration application device is used to apply mechanical vibration to the composite functional fiber felt (2) during the regeneration stage to drive its piezoelectric components to generate an endogenous electric field. The control module is used to acquire the impedance signal and voltage signal of the composite functional fiber felt (2) and to control the operation of the electric field application device and the mechanical vibration application device. The composite functional fiber felt (2) is prepared by electrospinning, which involves blending modified chitosan, graphene and piezoelectric polymer to form a composite nanofiber felt with a three-dimensional porous network structure.

2. The dynamic circulating chitosan column system for treating azo dye wastewater according to claim 1, characterized in that, The integrated reaction column (1) is made of a chemically stable material and has a columnar structure. An insulating skeleton (103) is embedded inside it. The insulating skeleton (103) has a hollow cylindrical structure with multiple pores on its cylindrical wall. Composite functional fiber felt (2) is tightly wound around the outer wall of the insulating skeleton (103) to form a rolled structure. The inert anode (104) penetrates the central cavity of the insulating skeleton (103) and is fixedly connected to the inner wall of the integrated reaction column (1) through a bracket (105).

3. The dynamic circulating chitosan column system for treating azo dye wastewater according to claim 2, characterized in that, A valve is provided at the inlet (101) of the integrated reaction column (1), and it is connected to the inlet pump (3). Azo dye wastewater is pumped into the integrated reaction column (1) by the inlet pump (3). The inlet pump (3) is electrically connected to the control module.

4. The dynamic circulating chitosan column system for treating azo dye wastewater according to claim 3, characterized in that, The integrated reaction column (1) is also connected to an internal circulation device at its inlet (101) and outlet (102). The internal circulation device includes a circulation pump (4), the input end of which is connected to the outlet (102) and the output end of which is connected to the inlet (101).

5. The dynamic circulating chitosan column system for treating azo dye wastewater according to claim 1, characterized in that, The mechanical vibration application device uses a piezoelectric ceramic ultrasonic transducer. Multiple piezoelectric ceramic ultrasonic transducers are fixedly connected to the outer wall of the integrated reaction column (1) and are evenly and symmetrically distributed along the circumference and axial direction of the integrated reaction column (1). Multiple piezoelectric ceramic ultrasonic transducers are connected in parallel to the same ultrasonic signal generator. The ultrasonic signal generator is electrically connected to the control module.

6. The dynamic circulating chitosan column system for treating azo dye wastewater according to claim 1, characterized in that, The preparation steps of the composite functional fiber felt (2) include: Step 1: Preparation of modified chitosan solution. Chitosan is grafted and copolymerized with a modifier, and then crosslinked with a crosslinking agent to prepare modified chitosan. It is then dissolved in an acetic acid aqueous solution of a preset concentration and continuously stirred magnetically at room temperature until a clear, homogeneous, and viscous chitosan solution is formed. Step 2: Preparation of graphene and piezoelectric polymer blend solution. Polyvinylidene fluoride is dissolved in a mixed solvent of N,N-dimethylformamide and acetone and magnetically stirred until completely dissolved. Then, a certain amount of graphene oxide slurry is added and subjected to long-term, high-intensity ultrasonic dispersion treatment using an ultrasonic cell disruptor to ensure that the graphene is uniformly dispersed at the single-layer level in the polyvinylidene fluoride solution, forming a stable black suspension. Step 3: Preparation of composite spinning solution. The chitosan solution, graphene and piezoelectric polymer blend solution prepared above are mixed in proportion. The mixed solution is then subjected to thorough mechanical stirring and ultrasonic treatment to eliminate the interface and ensure that the three components are uniformly fused at the molecular level to obtain the final composite spinning solution for electrospinning. Step 4: Electrospinning process. The above composite spinning solution is loaded into a syringe with a metal needle and fixed to a micro-injection pump. The needle is connected to the positive terminal of a high-voltage DC power supply. A grounded metal roller covered with aluminum foil is placed at a specific distance opposite the needle as a receiving device. The spinning solution is pushed out by the injection pump at a stable rate. At the same time, under the strong electric field applied by the high-voltage power supply, the droplets are stretched to form Taylor cones and finally ejected as nanoscale fiber jets. Before the fibers reach the receiving roller, the solvent evaporates, solidifies, and is randomly laid out to form a three-dimensional porous, non-woven composite nanofiber felt. Step 5: Post-treatment. The obtained fiber felt is peeled off from the aluminum foil and placed in a vacuum drying oven at a suitable temperature for thorough drying to completely remove residual solvent. Then, the fiber felt is placed in glutaraldehyde vapor for cross-linking treatment to enhance its structural stability and durability in aqueous solution.

7. The dynamic circulating chitosan column system for treating azo dye wastewater according to claim 4, characterized in that, The system operation steps include: Step 1: Adsorption and enrichment. Start the inlet pump (3) to pump the azo dye wastewater into the integrated reaction column (1) at a constant flow rate. The dye molecules are adsorbed by the composite functional fiber felt (2) when flowing through the column. Step 2: Saturation self-sensing. During the adsorption and enrichment period, the control module applies a detection signal to the composite functional fiber felt (2) through the inert anode (104) and the distributed cathode to measure the AC impedance of the fiber felt in real time. As non-conductive dye molecules continuously fill the graphene conductive network, the system impedance value will show a regular increase. The control module continuously records this impedance value. Step 3: Regeneration mode is started. When the control module detects that the impedance value reaches the preset saturation threshold, it automatically determines that the adsorption is saturated, stops the water pump (3), starts the circulation pump (4) to form an internal circulation mode, and starts the electric field application device to apply pulsed DC current to the electrode. At the same time, the ultrasonic signal generator is started to drive the external transducer to generate frequency-converted or intermittent ultrasonic waves. Under this multi-field coupling environment, the fiber felt cathode surface undergoes an in-situ electro-Fenton reaction, and the piezoelectric effect enhances catalysis, which rapidly and in-situ decomposes the adsorbed dye. Step 4: Regeneration Feedback. During the regeneration process, microscopic events such as pollutant degradation, product desorption, and microbubble activity cause vibrations in the piezoelectric polymer in the fiber, generating an acoustic emission voltage signal. This signal is captured in real time by the control module through electrodes. The control module performs real-time spectrum and amplitude analysis on the acquired acoustic signal, extracting features that characterize the reaction rate and uniformity. This analysis result serves as a feedback signal to dynamically adjust the applied pulse electric field parameters and ultrasonic field parameters in real time. Step 5: When the control module analyzes that the intensity of the acoustic emission signal has attenuated to the background baseline level and the system impedance value has returned to the initial state, it determines that the regeneration process has been completely completed. The control module automatically shuts down the electric field application device and the ultrasonic generator, restores the normal operation of the water pump (3), and starts a new round of adsorption treatment cycle.

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