A method for catalytic degradation of pollutants using zero-valent iron nanomaterials

Abstract

The present invention relates to the field of catalytic technology and discloses a method for catalytically degrading pollutants using zero-valent iron nanomaterials. The method comprises: utilizing the zero-valent iron nanomaterials to catalytically degrade pollutants in a reactor, online monitoring of parameters characterizing the state of catalytic activity, and applying ultrasonic pulses to physically strip the surface passivation layer when the parameters reach a preset threshold, thereby restoring catalytic activity. By coupling state monitoring with on-demand physical awakening, the present invention frees conventional zero-valent iron materials from the limitations of disposable consumables and enables periodic in-situ recovery of activity. Based on the rate of parameter change, chemical poisoning patterns can be intelligently identified and differentiated responses triggered. The stripping operation and acoustic verification are both performed using the same ultrasonic device, forming a closed-loop control system.

Description

Technical Field

[0001] The invention relates to a method for catalytic degradation of pollutants using zero-valent iron nanomaterials, belonging to the technical field of catalysis. Background Art

[0002] In the field of catalytic technology, zero-valent iron nanomaterials are widely used in the catalytic degradation of pollutants due to their strong reducing properties. The current mainstream technical solutions rely on the initial high activity of the material and delay the formation of the passivation layer by optimizing the particle size or surface modification. However, in the industrial continuous flow treatment scenario, this solution faces fundamental limitations: First, the surface oxide layer of the material continues to thicken with the reaction, resulting in irreversible blockage of the active sites, and its catalytic ability shows a unidirectional attenuation trend, forcing the system to be frequently shut down to replace materials or add new agents, resulting in a surge in operating costs and fluctuations in treatment efficiency. Second, under complex water inlet conditions, physical passivation and sudden chemical poisoning are difficult to distinguish immediately, and conventional fixed-cycle regeneration is prone to trigger invalid operations under poisoning conditions, which not only increases energy consumption but also delays fault diagnosis.

[0003] It is worth noting that the industry has tried to introduce a continuous ultrasonic field to slow down the passivation process, but this method is difficult to promote due to the imbalance between continuous high energy consumption and economic efficiency, and the sonochemical effect may interfere with the degradation path. Some studies have also indirectly evaluated activity by monitoring parameters such as pH or dissolved oxygen, but these indicators have a weak correlation with the intrinsic state of the catalyst and a slow response, and cannot accurately capture the passivation critical point. In essence, the existing technology has always been trapped in the cognitive paradigm of the inevitability of activity decay, failing to break through the fate of materials as disposable consumables, and lacking the ability to intelligently identify failure modes.

[0004] Specifically, existing technologies have three major deficiencies: 1. The accumulation of a passivation layer leads to irreversible loss of activity, forcing periodic interruptions of operation; 2. It is impossible to distinguish between reversible physical passivation and irreversible chemical poisoning, and the regeneration operation lacks a precise triggering basis; 3. Indirect parameters make it difficult to reflect the intrinsic activity state of the catalyst in real time, which restricts the implementation of closed-loop control. Therefore, how to establish an adaptive regeneration mechanism based on real-time perception of the intrinsic activity state of the catalyst, accurately trigger physical awakening while achieving intelligent identification of failure modes, and thus transform zero-valent iron from a consumable material into a sustainable and recyclable catalytic system, has become the technical problem to be solved by this invention. Summary of the Invention

[0005] The present invention provides a method for catalytic degradation of pollutants using zero-valent iron nanomaterials. Its main purpose is to solve the problems in the prior art caused by the lack of real-time perception of the intrinsic state of the catalyst and precise regeneration mechanism, such as uncontrollable activity attenuation, blind regeneration operation and difficult identification of failure modes.

[0006] To achieve the above objectives, the present invention provides a method for catalytic degradation of pollutants using zero-valent iron nanomaterials, the method comprising the following cyclic steps:

[0007] Step a, catalytic degradation: In a reactor, zero-valent iron nanomaterials are used to catalytically degrade pollutants. A passivation layer forms on the surface of the zero-valent iron nanomaterials during the degradation process, causing their catalytic activity to gradually decrease.

[0008] Step b, activity state monitoring: online monitoring of the oxidation-reduction potential (ORP) in the reactor to reflect the catalytic activity state;

[0009] Step c, passivation identification and awakening triggering: based on the calculation result of the rate of change of the redox potential (ORP) over time, and when the ORP value rises beyond a preset first potential threshold and its rising rate is lower than a preset first rate threshold, a physical awakening operation of the zero-valent iron nanomaterial is triggered. The physical awakening operation includes: ultrasonic pulse application, applying a high-power ultrasonic pulse with a duration of 30 seconds to 120 seconds to the zero-valent iron nanomaterial in the reactor, and using the microjets and local high-pressure impact force generated by the ultrasonic cavitation effect to peel off the passivation layer from the surface of the zero-valent iron nanomaterial to expose its internal active core, thereby restoring its catalytic activity; awakening efficacy verification, after the ultrasonic pulse application is completed, using the same ultrasonic transducer that applies the ultrasonic pulse to emit a low-power detection acoustic pulse into the reactor and receive its echo signal, calculate the total echo energy or the preset frequency band energy, and compare it with the preset threshold to determine whether the passivation layer has been effectively stripped.

[0010] Preferably, in step c, the calculation of the rate of change of the oxidation-reduction potential (ORP) over time is based on differential or regression analysis of a continuously collected ORP value sequence, the first potential threshold is set to a value in the range of -300 mV to -200 mV, and the first rate threshold is set to a positive value.

[0011] Preferably, in step c, the frequency range of the high-power ultrasonic pulse is 20 kHz to 40 kHz.

[0012] Preferably, the wake-up efficacy verification in step c is based on the comparison of the total energy of the echo signal, the energy change of the preset frequency band, or the sound velocity attenuation coefficient with a preset value. When the following conditions are met, it is determined that the passivation layer has been effectively stripped:

[0013] ,

[0014] in, Indicates the change in the echo signal energy after wake-up relative to the reference echo signal energy before wake-up. Indicates the baseline echo signal energy before wake-up, Indicates the preset acoustic characteristic change threshold, which is a positive value.

[0015] Preferably, in step c, if the wake-up efficacy verification result is that the passivation layer is not effectively stripped, the method further includes selecting one of the following methods: applying a high-power ultrasonic pulse again; or triggering an alarm signal to prompt the operator to perform manual intervention.

[0016] Preferably, the zero-valent iron nanomaterial is micron-scale or nanometer-scale zero-valent iron particles without any surface chemical modification.

[0017] Preferably, the method further comprises: before or while performing the ultrasonic pulse application in step c, temporarily reducing or stopping the feed flow rate of the pollutants.

[0018] Preferably, the method further includes: when the oxidation-reduction potential (ORP) rising rate exceeds a preset first rate threshold, identifying it as a chemical poisoning mode, triggering an emergency alarm, and simultaneously stopping the physical wake-up operation and prompting manual intervention instead.

[0019] Preferably, the zero-valent iron nanomaterial exists in the reactor in the form of any one of a fixed bed, a fluidized bed or a suspended bed.

[0020] Preferably, an oxidation-reduction potential (ORP) online sensor is arranged at the water outlet of the reactor or inside the reactor.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. By coupling online monitoring of catalytic activity, such as ORP, with on-demand physical wake-up operations (ultrasonic pulses), the present invention enables conventional zero-valent iron nanomaterials to break free from the inherent limitations of being disposable consumables. When activity decay reaches a preset threshold, the applied physical stripping force effectively removes the surface passivation layer, re-exposing the active core. This allows for periodic in-situ recovery of catalytic activity without interrupting operation or frequently replacing materials, significantly extending the effective service life of the catalyst and reducing operating costs. Furthermore, the wake-up triggering employed by the present invention is not based on a fixed time or subjective judgment, but rather on a real-time monitoring signal reflecting the intrinsic state of the system. This state-feedback-based triggering mechanism ensures that the wake-up operation is only executed when activity decay truly requires intervention, effectively avoiding excessive or ineffective energy consumption. The wake-up process itself utilizes short, high-power pulsed ultrasonic waves, which ensures effective stripping impact on the passivation layer while confining energy input to the necessary, extremely short time window, achieving an optimal balance between wake-up effect and energy consumption control.

[0023] 2. By further analyzing the activity state monitoring parameters, such as the rate of change of ORP over time, the present invention can effectively distinguish between conventional passivation decay and sudden chemical poisoning. When a sharp deterioration of the activity state is detected, such as a sharp rise in ORP exceeding a preset rate threshold, the system can quickly identify the poisoning mode in which physical wake-up is invalid, trigger an emergency alarm and suspend the wake-up operation, preventing energy waste caused by invalid wake-up in the case of chemical poisoning, and providing a key early warning for operators to intervene in time, thereby improving the robustness and safety of system operation; after the physical wake-up operation is completed, the same ultrasonic device is used to instantaneously switch to low-power detection mode, and by analyzing the changes in the acoustic characteristics of the system represented by the echo signal, the passivation layer stripping effect can be immediately verified in situ; this self-verification mechanism based on physical principles does not require the introduction of additional complex sensors. It only obtains the ability to confirm the effectiveness of the system through functional reuse of existing hardware and intelligent switching of modes, ensuring the closed loop and reliability of the entire wake-up cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart of the method for catalytic degradation of pollutants using zero-valent iron nanomaterials of the present invention;

[0025] Figure 2 This is a flow chart of the zero-valent iron catalyst activity recovery process based on ORP monitoring and acoustic verification according to the present invention;

[0026] Figure 3 This is a comparison chart of ORP changes and dichlorophenol degradation rates of the present invention.

[0027] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0028] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] The present invention provides a method for catalytically degrading pollutants using zero-valent iron nanomaterials, the method comprising the following cyclically performed steps:

[0030] Step a, catalytic degradation: In a reactor, zero-valent iron nanomaterials are used to catalytically degrade pollutants. A passivation layer forms on the surface of the zero-valent iron nanomaterials during the degradation process, causing their catalytic activity to gradually decrease.

[0031] Step b, activity state monitoring: online monitoring of the oxidation-reduction potential (ORP) in the reactor to reflect the catalytic activity state;

[0032] Step c, passivation identification and awakening triggering: based on the calculation result of the rate of change of the redox potential (ORP) over time, and when the ORP value rises beyond a preset first potential threshold and its rising rate is lower than a preset first rate threshold, a physical awakening operation of the zero-valent iron nanomaterial is triggered. The physical awakening operation includes: ultrasonic pulse application, applying a high-power ultrasonic pulse with a duration of 30 seconds to 120 seconds to the zero-valent iron nanomaterial in the reactor, and using the microjets and local high-pressure impact force generated by the ultrasonic cavitation effect to peel off the passivation layer from the surface of the zero-valent iron nanomaterial to expose its internal active core, thereby restoring its catalytic activity; awakening efficacy verification, after the ultrasonic pulse application is completed, using the same ultrasonic transducer that applies the ultrasonic pulse to emit a low-power detection acoustic pulse into the reactor and receive its echo signal, calculate the total echo energy or the preset frequency band energy, and compare it with the preset threshold to determine whether the passivation layer has been effectively stripped.

[0033] In step c, the calculation of the rate of change of the oxidation-reduction potential (ORP) over time is based on differential or regression analysis of a continuously collected ORP value sequence, with the first potential threshold set to a value within the range of -300 mV to -200 mV, and the first rate threshold set to a positive value.

[0034] In step c, the frequency range of the high-power ultrasonic pulse is 20 kHz to 40 kHz.

[0035] The wake-up efficacy verification in step c is based on the comparison of the total energy of the echo signal, the energy change in the preset frequency band, or the sound velocity attenuation coefficient with the preset value. When the following conditions are met, it is determined that the passivation layer has been effectively stripped:

[0036] ,

[0037] in, Indicates the change in the echo signal energy after wake-up relative to the reference echo signal energy before wake-up. Indicates the baseline echo signal energy before wake-up, Indicates the preset acoustic characteristic change threshold, which is a positive value.

[0038] In step c, if the wake-up efficacy verification result is that the passivation layer is not effectively stripped, the method further includes selecting one of the following methods: applying a high-power ultrasonic pulse again; or triggering an alarm signal to prompt the operator to perform manual intervention.

[0039] Zero-valent iron nanomaterials are micron-sized or nanometer-sized zero-valent iron particles without any surface chemical modification.

[0040] The method further includes temporarily reducing or stopping the feed flow rate of the pollutant before or while performing the ultrasonic pulse application in step c.

[0041] The method also includes: when the oxidation-reduction potential (ORP) rising rate exceeds a preset first rate threshold, identifying it as a chemical poisoning mode, triggering an emergency alarm, and simultaneously stopping the physical wake-up operation and prompting manual intervention instead.

[0042] The zero-valent iron nanomaterials exist in the reactor in the form of a fixed bed, a fluidized bed or a suspended bed.

[0043] The oxidation reduction potential (ORP) online sensor is arranged at the water outlet of the reactor or inside the reactor.

[0044] During system operation, adaptive regeneration in the present invention refers to the ability to automatically adjust its operating behavior based on real-time parameters collected during the reaction process. For example, after detecting a preset trend change in the redox potential, the control module automatically determines whether to initiate the physical excitation link. This is neither dependent on a fixed cycle nor on manual experience, reflecting a certain degree of operational flexibility and targeted response. State-aware triggering, for example, is based on the correspondence between continuous monitoring signals and set judgment criteria, forming a startup logic with practical execution standards to ensure the timeliness and accuracy of operations. A sustainable circulation system means that under preset operating conditions, after the material is periodically restored to activity, it can maintain continuous operation rather than frequent replacement, thereby supporting the stability and low consumption of the entire process and avoiding unnecessary downtime caused by one-time material failure. In addition, intelligent recognition and intelligent judgment refer to the control system automatically responding to the match between the collected change data, such as the potential rise rate and duration, and the preset judgment conditions, to achieve response to changes in passivation and poisoning situations in the project. It should be noted that the intrinsic state of the catalyst mainly refers to the essential parameter reflecting its surface reactivity under preset reaction conditions, which is mainly reflected by the change trend of the redox potential. This potential is affected by The influence of changes in the catalyst surface structure can also, to a certain extent, reflect the overall reactivity of the reaction system. Therefore, in actual use, the absolute value and trend of the potential change are used as indirect indicators of the intrinsic state to establish a linkage relationship between the judgment basis and the control logic, facilitating engineering deployment and real-time response. At the same time, in the system control involved in the present invention, the relevant identification, judgment, and response processes are all determined based on the relationship between the real-time collected potential change trend and the set judgment conditions. This is a rule-based automated response logic that can achieve on-demand triggering and closed-loop control. On this basis, its intelligence refers to the system's ability to make autonomous decisions based on parameter state changes. It is an automatic monitoring and logical judgment method commonly used in industrial control known to those of ordinary skill in the art. At the same time, with respect to the catalyst's life cycle and material renewal, the present invention can restore its active state to a certain extent by physically stripping the surface passivation layer, thereby extending the material's life cycle and reducing the frequency of replacement. However, it should be noted that this does not mean that the material can be recycled indefinitely. In actual operation, when irreversible poisoning or structural degradation occurs on the catalyst surface, timely manual intervention or material replacement is still required. These are all extension methods known to those of ordinary skill in the art.

[0045] Moreover, in the process of implementing the present invention, in order to ensure that the system has sufficient accuracy in judging the change of the catalyst activity state, when performing the redox potential change trend analysis, for example, the differential analysis and sliding regression methods used are not simple empirical judgments, but a regularity extraction mechanism established based on a large amount of previous operating data. Specifically, differential processing calculates the change amplitude of the redox potential in adjacent time periods to identify the rate change pattern of the potential change; sliding regression is to perform linear fitting on multiple continuous potential values collected within a certain time window to evaluate the stability and significance of the overall upward or downward trend, so as to help smooth the instantaneous anomalies caused by water inlet disturbance or measurement fluctuation, thereby improving the robustness of the judgment basis. At the same time, in order to ensure that the system has sufficient accuracy in judging the change of the catalyst activity state, the redox potential change trend analysis adopts differential analysis. A method combining differential processing with sliding regression, in which differential is used to identify the rate of change characteristics of the potential in adjacent time periods, and sliding regression is used to extract the overall trend of the potential change within a set time window, thereby effectively reducing the risk of misjudgment caused by hydraulic disturbances or measurement fluctuations. For the potential and rate thresholds triggered by awakening, for example, they can be set based on the historical data accumulation and experience summary during the previous system operation. Specifically, in a typical organochlorine pollutant treatment scenario, when the potential is monitored to rise to about negative two hundred and fifty millivolts and its rate is less than two millivolts per minute for five minutes, it can be considered that the catalyst is in a reversible passivation state and is suitable for initiating the awakening operation. Ordinary technicians in this field can make engineering adjustments to the above-mentioned judgment parameters based on the characteristics of the reaction system and the actual operation conditions to achieve reliable activity recovery control, which are all extended implementation methods known to ordinary technicians in this field.

[0046] Example 1: The present invention proposes a method for catalytically degrading pollutants using zero-valent iron nanomaterials. By introducing a physical awakening mechanism of online monitoring and on-demand triggering, real-time perception and controllable recovery of the catalyst activity state are achieved, thereby effectively extending the service life of the catalyst and improving the stability and resource utilization efficiency of the pollutant treatment system. The method comprises the following steps: first, introducing zero-valent iron nanomaterials as catalysts into the reactor, making them contact with the pollutants to be treated and causing a reduction reaction, thereby completing the degradation of the pollutants. Since oxides will gradually form a passivation layer on the surface of the catalyst during the reaction, the passivation layer will cover the active sites, causing its catalytic performance to gradually decrease; while the degradation reaction is continuing, an online oxidation-reduction potential (ORP) sensor is provided in the reactor or at its outlet to continuously collect ORP signals reflecting the catalytic activity state, and perform real-time monitoring. ORP, as an electrochemical parameter that can directly reflect the redox characteristics of the system, can characterize the activity status of the catalyst surface to a certain extent. The monitoring system realizes dynamic tracking of the ORP value by connecting with the data processing module; further, the system performs differential or regression analysis on the rate of change of the ORP value over time. When the ORP value is detected to rise and exceeds the preset first potential threshold, and its rate of change is lower than the first rate threshold, the system determines that the catalyst is in a reversible passivation state and triggers a physical awakening operation. The awakening process is carried out in the form of high-power ultrasonic pulses. The ultrasonic frequency is set in the range of 20 kHz to 40 kHz, and the application duration is 30 seconds to 120 seconds. The ultrasonic pulse can effectively strip off the passivation layer on the surface of the catalyst through the microjets and local high-pressure impact generated by the cavitation effect, thereby re-exposing the active core area inside it and realizing the recovery of catalytic performance.

[0047] After the wake-up operation is completed, the system immediately switches to the low-power acoustic detection mode, transmits the detection sound wave through the original ultrasonic transducer and receives its echo signal. Based on the acoustic characteristics of the reaction system reflected by the echo signal, the system makes an in-situ judgment on the wake-up effect. When it is detected that the energy change of the echo energy after wake-up compared with the energy change of the reference signal before wake-up exceeds the preset acoustic change threshold, it is judged that the passivation layer has been effectively stripped off. This verification mechanism does not require additional detection hardware. It can achieve closed-loop confirmation of the wake-up effect only by switching the transducer working mode and adjusting the signal processing algorithm. Under certain operating conditions, if the system detects that the rate of change of the ORP value is much higher than the first rate threshold and the change trend rises sharply, it can be determined that the catalyst has undergone irreversible chemical poisoning. In this case, the system will stop the current physical wake-up process and immediately trigger an alarm to alert The operator is prompted to intervene manually. This intelligent recognition mechanism can effectively avoid energy waste and system loss of control caused by erroneous wake-up operations. At the same time, to further improve system stability, the pollutant feed rate can be selectively reduced or suspended before or simultaneously with the application of the ultrasonic pulse to ensure stable operation of the reaction system during the wake-up process. In addition, the present invention is applicable to various catalyst bed structures, including fixed bed, fluidized bed, and suspended bed, and has good engineering adaptability. The selected zero-valent iron nanomaterial is a micron- or nanometer-sized particle material that has not been surface-modified and has strong reducibility and dispersibility, making it suitable for long-term operation in industrial continuous flow reaction systems. At the same time, in the present invention, the "acoustic characteristic value" is the total energy of the echo signal or the energy of a preset frequency band. The calculation steps are, for example: the echo signal is collected by a transducer with a sampling frequency of 100 kHz; a fast Fourier transform (FFT) is performed on the echo signal to extract the energy in the 20-30 kHz frequency band; the total signal energy is the square integral of the amplitude to form an echo energy value E; if the echo energy after wake-up increases by more than 8% relative to the energy before wake-up (| | / >8%), it is judged that the passivation layer is successfully stripped; this threshold can be determined based on the statistical experimental data of 30 consecutive days of historical operation, which is an extended implementation method known to ordinary technicians in this field.

[0048] Example 2: In this example, the reaction system is set as a continuous flow industrial wastewater treatment process. The reactor adopts a fixed bed structure and is filled with unmodified zero-valent iron nanoparticles with a particle size of less than 100 nanometers. The particles have a high specific surface area and good reducibility and are suitable for long-term continuous use. The treated wastewater contains typical chlorinated aromatic hydrocarbon pollutants. The reaction system integrates an oxidation-reduction potential (ORP) online monitoring module, a data processing and decision-making unit, a controllable ultrasonic excitation module (including a transducer with switchable working modes), and an echo signal detection and analysis module. At the initial stage of system operation, raw water flows into the reactor and undergoes a reduction reaction with the zero-valent iron nanomaterial. The pollutants are reduced and converted into target intermediates. During this process, oxides are gradually generated on the catalyst surface, forming a passivation layer, which in turn hinders the continuous exposure of the active sites, resulting in a decrease in catalytic performance. In order to achieve real-time identification of the catalytic performance attenuation state, the system sets an ORP online sensor at the water outlet of the reactor. The device continuously collects the potential signal reflecting the redox state of the reaction system and records it at one-minute intervals to form an ORP sequence. The sequence is subjected to differential calculation and sliding regression analysis by the data processing module to smooth occasional fluctuations and extract numerical trend changes. When the system detects that the ORP value rises and exceeds the preset first potential threshold (for example, -250 mV) and its rising rate is lower than the first rate threshold (for example, less than 2 mV per minute), it determines that the current catalyst is in a reversible passivation state and triggers a physical awakening operation. During the awakening process, the control system applies high-power ultrasonic pulses with a duration of 30 seconds to 120 seconds and a frequency in the range of 20 kHz to 40 kHz to the transducer built into the reactor. This frequency range can form a stable cavitation effect in the liquid phase system. The generated microjets and local high pressure can effectively peel off the passivation layer on the surface of the catalyst, exposing its internal active area, thereby restoring its catalytic function. The selected frequency and duration are set.

[0049] In order to improve the system stability during the awakening stage, ten seconds before starting the ultrasonic excitation, the system can selectively reduce the pollutant inflow rate to the minimum operating value to reduce the impact of hydrodynamic interference on cavitation stability. After the ultrasonic action is completed, the transducer immediately switches to low-power transmission mode, sends out a detection signal lasting two hundred milliseconds, and receives the echo signal returned by the inner wall of the reactor and the catalyst layer. After the echo signal is analyzed through the spectrum, the total energy change value and the energy proportion of the preset frequency band are extracted and compared with the baseline state before awakening. When the system detects that the total energy of the echo is increased by more than three percent compared with the baseline value, or the energy proportion of the mid-frequency band is increased by more than five percent, it can be judged that the passivation layer has been The peeling is effective and the wake-up operation is successful. If the detection result does not meet the above judgment conditions, the system will automatically perform an ultrasonic wake-up operation again. If the effect threshold is not reached twice in a row, the system alarm will be triggered, prompting manual intervention and terminating the current water inlet process to avoid invalid operation. In addition, when the ORP value continues to rise rapidly within a unit time and the rate of change is much higher than the preset first rate threshold, such as exceeding five millivolts per minute, the system will identify the state as chemical poisoning mode according to the set logic. At this time, the physical wake-up process will be stopped and an alarm signal will be issued immediately. This identification mechanism can effectively avoid the energy waste and operation uncertainty caused by ineffective physical intervention in the irreversible inactivation state.

[0050] Example 3: In the current field of industrial wastewater treatment, zero-valent iron nanomaterials have shown great potential in catalytic degradation of various organic pollutants due to their excellent reducing properties. However, a common challenge in practical applications is that a passivation layer is easily formed on the surface of the material during the reaction, resulting in rapid decay of catalytic activity, which requires frequent shutdown to replace or replenish materials, significantly increasing operating costs and affecting treatment efficiency. Although existing technologies attempt to delay passivation through continuous ultrasonic fields, they have high energy consumption and poor economy, and it is difficult to accurately distinguish between physical passivation and chemical poisoning modes, resulting in blind and inefficient regeneration operations. In view of this, the core purpose of this experiment is to verify the method of catalytic degradation of pollutants by zero-valent iron nanomaterials through actual operation data, which innovatively introduces a closed-loop control strategy of online redox potential (ORP) monitoring and on-demand high-power ultrasonic wake-up, and how to effectively achieve periodic in-situ recovery of catalyst activity under different pollution load conditions and intelligently identify chemical poisoning modes, thereby significantly extending the service life of the catalyst and reducing operating energy consumption.In this experiment, a continuous flow catalytic degradation pilot system based on the principle of the present invention was constructed. The system mainly includes: a reactor unit, which adopts a closed stainless steel continuous stirred reactor (CSTR) with a volume of 50 liters. It is equipped with multi-layer guide plates inside to ensure uniform flow field and integrated ultrasonic transducers. In order to facilitate uniform dispersion of pollutants and product separation, the bottom of the reactor is designed with a sedimentation area of zero-valent iron nanomaterials and a circulating reflux pump. It can be adjusted to a fixed bed, fluidized bed or suspended bed configuration as needed. In this experiment, we chose a fixed bed configuration to simulate a typical industrial application scenario to ensure that the catalyst particles remain stable in the flow field; the catalyst material is selected from zero-valent iron nanoparticles with an average particle size of less than 100 nanometers without surface chemical modification (supplier: a well-known nanomaterial technology company), whose BET specific surface area is about 25 m² / g, with a purity higher than 99.5%, good dispersibility and reduction activity, suitable for long-term continuous use; the online monitoring module is equipped with a high-precision industrial-grade oxidation-reduction potential (ORP) sensor (range: -1000mV to +1000mV, accuracy: ±1mV) at the outlet of the reactor for real-time online monitoring of the redox state of the reaction system. The sensor is connected to the data acquisition and control unit via a standard RS485 interface and collects ORP data at a frequency of once per minute; the ultrasonic excitation and detection module uses an integrated high-power ultrasonic generator (maximum output power 1500W, frequency adjustable range 20kHz) z-40kHz) and its matching immersed piezoelectric ceramic transducer, which realizes the functional switching of high-power pulse excitation and low-power detection on the same physical device; the data acquisition and control unit is built based on an industrial PLC programmable logic controller, integrating ORP signal acquisition, data processing including differential calculation, sliding average, threshold comparison, ultrasonic excitation control, wake-up effect verification signal analysis and alarm output functions. All control logic is implemented through PLC programming to ensure the automatic operation and closed-loop control of the system; the feed and water outlet system includes a peristaltic pump (precisely controls the pollutant feed rate), a raw water tank, a treated water tank, and necessary pipes and valves.

[0051] This experiment simulates the treatment process of industrial wastewater containing typical chlorinated aromatic hydrocarbon organic pollutants, such as 2,4-dichlorophenol, with an initial concentration set at 200 mg / L. The system is continuously operated to observe and record the changes in key parameters. The specific experimental steps are as follows: system startup and stable operation, an appropriate amount of zero-valent iron nanomaterials are loaded into the reactor, and simulated wastewater is injected, the stirring system is started, the feed pump is turned on, and the simulated wastewater is fed at a constant flow rate (for example, 10 L / h) is continuously pumped into the reactor. In the early stage of the reaction, the rapid decline and stabilization of the ORP value are closely observed, indicating that the catalyst activity is at a high level; catalytic degradation and activity decay monitoring allows the system to continue to operate under the set pollutant load. The online ORP sensor monitors the ORP value of the reactor outlet water in real time. During the degradation process, due to the gradual formation of an oxide passivation layer on the surface of the zero-valent iron nanomaterial, its catalytic activity will gradually decrease, which is manifested as a gradual increase in the ORP value. The data acquisition and control unit continuously collects ORP data and performs differential calculation or regression analysis to obtain the rate of change of ORP over time; passivation identification and physical awakening: awakening trigger, when the ORP value rises and exceeds the preset first potential threshold, for example, the test is set to -250 mV, and its rising rate is lower than the preset first rate threshold, for example, this test is set to 2 per minute. mV, the system determines that the catalyst is in a reversible passivation state and triggers a physical awakening operation. The setting of these thresholds is based on preliminary exploratory tests and engineering experience on the ORP response characteristics of zero-valent iron materials at different passivation levels, aiming to ensure accurate awakening when the activity decays to the critical point; feed flow rate adjustment, 10 seconds before triggering the awakening operation, the system will control the feed pump to temporarily reduce the pollutant feed flow rate to the minimum operating value (for example, 2 L / h) to reduce the interference of hydrodynamics on the ultrasonic cavitation effect and ensure the stability and efficiency of the awakening process; high-power ultrasonic pulse application, the ultrasonic generator is activated, and high-power ultrasonic pulses are continuously applied to the reactor. The pulse duration is set to 90 seconds and the frequency is fixed at 28 kHz, this frequency range is between 20kHz and 40kHz, and it has been verified in the early stage that a stable cavitation effect can be effectively generated within this range. The microjets and local high-pressure impact force generated by the ultrasonic cavitation effect will physically peel off the passivation layer on the surface of the catalyst, exposing the internal active core, thereby restoring the catalytic activity; wake-up efficacy verification, after the high-power ultrasonic pulse is applied, the ultrasonic generator instantly switches to low-power detection mode, and the same transducer emits a low-power detection acoustic pulse (for example, lasting 200 milliseconds) into the reactor and receives its echo signal. The data acquisition and control unit analyzes the changes in the acoustic characteristics of the echo signal, including changes in total energy, changes in the energy proportion of the preset frequency band (such as the mid-frequency band), or the sound velocity attenuation coefficient, and compares it with the baseline echo signal before wake-up;Effective stripping judgment: when it is detected that the total energy of the echo signal after awakening is increased by more than 3% compared with the baseline signal before awakening or the proportion of mid-frequency energy is increased by more than 5%, the system judges that the passivation layer has been effectively stripped and the awakening is successful. The setting of these percentage thresholds is based on the preliminary experimental data analysis of the relationship between the acoustic signal characteristics and the passivation layer stripping effect to ensure the accuracy of the judgment; Failure response: if the awakening efficacy verification result shows that the passivation layer is not effectively stripped, the system will automatically perform a high-power ultrasonic awakening operation again. If the awakening fails to meet the standard after two consecutive times, an emergency alarm will be triggered to prompt the operator to intervene manually and suspend the physical awakening process to avoid ineffective energy consumption and misjudgment; Intelligent recognition and response of chemical poisoning mode: during the operation of the system, the data acquisition and control unit continuously monitors the ORP rise rate. If the ORP rise rate sharply exceeds the preset first rate threshold (for example, more than 5 per minute), the system will automatically perform a high-power ultrasonic awakening operation again. mV) and persists for a period of time (for example, 5 consecutive minutes), the system intelligently identifies that the catalyst may have experienced irreversible chemical poisoning. At this time, the system will immediately stop the physical wake-up operation and trigger an emergency alarm, while prompting manual intervention to avoid ineffective physical wake-up in the case of poisoning, saving energy and improving system robustness. Cyclic operation and long-term stability: The system will continue to operate according to the above cyclic logic, through the closed-loop control of monitoring-wake-up-verification, to achieve periodic in-situ recovery of catalyst activity, and regularly sample and analyze the concentration of pollutants in the effluent to evaluate the long-term degradation efficiency of the system.

[0052] During a 30-day continuous operation test, the pilot system of the present invention demonstrated excellent performance and stability. Key data from a typical operating cycle (e.g., a complete passivation-wake-up-recovery cycle) are analyzed below and compared with a control group that did not adopt the wake-up mechanism of the present invention (zero-valent iron nanomaterials were used once until their activity expired).

[0053] Table 1. Verification data of ORP, pollutant degradation rate and wake-up effect in a typical operation cycle.

[0054]

[0055] Data description: The ORP change rate is the average value of the past 1 hour; during the wake-up operation, the feed flow rate is reduced to 2 L / h, data statistics are suspended, and the total echo energy after wake-up is increased as a percentage of the baseline signal before wake-up. Correlation between ORP and catalytic activity: As shown in Table 1, in the early stage of catalytic degradation (0-24 hours), the ORP value remains at a low level (-480mV to -350mV), corresponding to a higher 2,4-dichlorophenol degradation rate (98.5% to 95.2%), which indicates that the zero-valent iron nanomaterial has good activity. As the operating time increases, the ORP value gradually increases, and the degradation rate shows a downward trend, which confirms the formation of a passivation layer on the catalyst surface and its inhibitory effect on catalytic activity. ORP, as an electrochemical parameter that directly reflects the redox potential of the system, can effectively characterize the active state of the catalyst; Passivation identification and precise awakening: At the 60th and 120th hours, when the ORP value rises to -245mV and -238mV (both exceeding the set When the ORP value reaches a predetermined threshold of -250mV and the ORP rising rate is still within a controllable range, the system accurately triggers the physical wake-up operation. This indicates that the intelligent recognition mechanism based on the ORP value and its changing rate can effectively judge the reversible passivation state of the catalyst, avoiding blind or excessive wake-up, thereby optimizing energy consumption. The physical wake-up effect is significant: after each wake-up operation, the ORP value can quickly drop from the high level in the passivation state to a level close to the initial high activity, for example, from -245mV to -475mV, and from -238mV to -468mV. At the same time, the degradation rate of 2,4-dichlorophenol also quickly recovered to more than 97%, fully verifying the effective physical stripping ability of high-power ultrasonic pulses on the passivation layer and successfully restoring the activity of the catalyst.Acoustic verification of wake-up efficacy: After the wake-up operation, the wake-up efficacy verification data showed that the total echo energy increased by more than 8% (such as 8.2%), which is much higher than the set 3% threshold. This strongly proves that the passivation layer has been successfully stripped off. This verification mechanism based on acoustic signals does not require additional sensors and uses the same ultrasonic device to achieve closed-loop control, thereby improving the reliability of system operation. The introduction of this verification method further enhances the system's self-judgment ability of the wake-up effect and reduces the need for manual intervention; Intelligent identification of chemical poisoning mode: During long-term operation, the system simulated a sudden change in the influent composition, causing the ORP rise rate to rise sharply to 8mV / min in a short period of time, exceeding the set 5 mV / min threshold, the system immediately identified it as chemical poisoning mode and triggered an emergency alarm. At the same time, the originally planned physical wake-up operation was stopped and instead prompted manual intervention. This result verified the intelligence of the present invention in distinguishing between physical passivation and chemical poisoning modes, effectively avoiding ineffective physical wake-up in the case of chemical poisoning, thereby saving energy and providing key early warning for operators; Catalyst life and system operation efficiency are improved: Through continuous online monitoring, intelligent wake-up and effect verification, the scheme of the present invention enables zero-valent iron nanomaterials to repeatedly restore their activity within the test cycle, rather than being exhausted all at once as in traditional methods. During the entire 30-day test period, the catalyst activity was always maintained at an efficient degradation level, and there was no situation where shutdown and replacement due to activity decay occurred. Compared with the control group, the present invention significantly extended the effective service life of the catalyst, greatly reduced material consumption and operating costs, while avoiding frequent shutdowns, improving the overall operational reliability of the system and the continuity of pollutant treatment. The dynamic adjustment of the feed flow rate also further ensured the system stability during the wake-up period.

[0056] Example 4: This example combines Figures 1 to 3 , a method for catalytic degradation of pollutants using zero-valent iron nanomaterials is described. Figure 1 As shown, first, in the catalytic degradation phase, zero-valent iron nanoparticles catalyze the degradation of pollutants, creating a passivation layer that affects catalytic activity. Next, in the intelligent monitoring module, the catalyst's passivation state is identified through real-time monitoring of the oxidation-reduction potential (ORP) and calculation of its rate of change. When the ORP value reaches a set threshold and the rate of change is low, the system enters the chemical poisoning treatment phase. ORP rate anomaly detection issues an emergency alarm and prompts manual intervention. In the ultrasonic wake-up phase, high-power ultrasonic pulses of 30 to 120 seconds are applied to effectively strip the passivation layer from the catalyst surface, restoring catalytic activity. Finally, in the acoustic verification phase, low-power acoustic pulses are used to detect the echo signal to confirm whether the passivation layer has been successfully stripped, thereby ensuring the wake-up effect.

[0057] like Figure 2As shown, first, during the catalytic degradation stage (passivation layer formation), a passivation layer gradually forms on the surface of the zero-valent iron nanomaterials in the reaction system, resulting in a decrease in catalytic activity. The system uses real-time ORP monitoring to continuously read the redox potential in the reactor and feed this data into the data analysis (ORP threshold determination) module for analysis. When the ORP value rises and exceeds the set threshold, the system issues a trigger signal, initiating ultrasonic pulse operation (20-40kHz), implementing high-power ultrasonic pulses to strip the passivation layer. The system then switches to a mode, activating the acoustic verification (echo energy analysis) module. By analyzing the energy changes of the ultrasonic echo signal, the stripping effect is determined, and finally the activity recovery confirmation module is entered to verify whether the catalyst activity has been effectively restored. If activity recovery fails, the system will repeat the ultrasonic wake-up process. On the other hand, if the data analysis identifies an abnormal ORP rate (chemical poisoning), the system immediately initiates an emergency alarm and manual intervention to avoid ineffective wake-up operations and prompts for human intervention.

[0058] like Figure 3 As shown, the upper figure shows the change of oxidation-reduction potential (ORP), with the vertical axis in mV and the horizontal axis in time (hours), showing that with the extension of operating time, the ORP value continues to increase from about -450 mV to -250 mV, indicating the gradual passivation of the catalyst surface; at the 60th hour and 120th hour, a wake-up operation was performed respectively, and the operation status was marked in the figure to distinguish the changes in ORP values before and after wake-up. After both wake-ups, the ORP value dropped rapidly to the initial active state, verifying the effectiveness of the physical wake-up operation in restoring catalytic activity; the lower figure shows the change of dichlorophenol degradation rate (%), with the vertical axis as the percentage of degradation rate and the horizontal axis also as time (hours), showing that during the catalyst passivation process, the degradation rate gradually dropped from close to 100% to about 85%, and after each wake-up operation, the degradation rate significantly rebounded to a high level. The figure also marks the two nodes before and after wake-up in the operation state to reflect the recovery effect of the wake-up treatment on the pollutant treatment capacity.

[0059] Example 5: In this example, the present invention is applied to the in-situ remediation of groundwater at a heavily polluted site. The main pollutants in the groundwater at this site are typical halogenated organic chlorides, especially chloroform and trichloroethylene. The pollution source has been stabilized, the pollution plume has not extended to the domestic water area, and the conditions for controllable treatment are available. To achieve efficient and controllable in-situ degradation of pollutants, the zero-valent iron-based composite nanomaterial (hereinafter referred to as ZVI composite material) selected in this example is mainly composed of reduced iron elemental substance, supplemented by a second component that can enhance electron transfer efficiency (such as a metal dopant or surface modifier with a preset valence state). After the ZVI composite material is prepared, it is stabilized and dispersed to form a uniform water-soluble dispersion, which is injected into the target groundwater contaminated layer through a dedicated injection device.

[0060] During the injection process, the injection pressure, speed and volume are controlled to ensure that the material can form a continuous reaction interface zone in the pollution plume. In order to improve the contact efficiency with the pollutants and avoid material agglomeration or pore clogging, the particle size of the material is preferably controlled between tens of nanometers and hundreds of nanometers. Its fluidity and dispersibility have been confirmed in experimental simulation injection. In actual operation, after the composite material comes into contact with chlorinated organic matter in the groundwater environment, a multi-stage in-situ reduction reaction is triggered. The core reaction mechanism is that the material surface releases electrons, which react with the active halogen bonds in the halogenated organic matter molecules and are gradually reduced to harmless or low-toxic products. This process does not rely on external power or auxiliary energy and has autonomous reaction capabilities. At the same time, in order to further strengthen In order to improve the treatment efficiency, a preset type of conductive additive, such as a graphene derivative or a doped conductive polymer, is introduced into the ZVI composite material to construct a more efficient electron channel structure, which helps to expand the overall electrochemical active area of the material. In the in-situ environment of groundwater, fluctuations in parameters such as temperature, pH and dissolved oxygen may affect the reaction rate and path. Therefore, this embodiment adopts a layered pH buffer coating design on the surface of the material, so that the material can maintain a high catalytic reduction efficiency even in a weakly alkaline or neutral environment. In addition, the buffer layer also has a certain degree of anti-passivation ability, which can delay the process of oxidative inactivation on the surface of the material. These are all extended implementation methods known to ordinary technicians in this field.

[0061] 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 present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for catalytic degradation of pollutants using zero-valent iron nanomaterials, characterized in that: The method comprises the following steps which are performed in a loop: Step a, catalytic degradation: In a reactor, zero-valent iron nanomaterials are used to catalytically degrade pollutants. A passivation layer forms on the surface of the zero-valent iron nanomaterials during the degradation process, causing their catalytic activity to gradually decrease. Step b, activity state monitoring: online monitoring of the redox potential in the reactor reflecting the catalytic activity state; Step c, passivation identification and wake-up triggering: Based on the calculation result of the rate of change of the redox potential over time, and when the ORP value rises beyond a preset first potential threshold and its rising rate is lower than a preset first rate threshold, triggering a physical wake-up operation on the zero-valent iron nanomaterial, the physical wake-up operation comprising: applying an ultrasonic pulse, applying a high-power ultrasonic pulse with a duration of 30 to 120 seconds to the zero-valent iron nanomaterial in the reactor, utilizing the microjets and local high-pressure impact force generated by the ultrasonic cavitation effect to peel off the passivation layer from the surface of the zero-valent iron nanomaterial to expose the active core inside it, thereby restoring its catalytic activity; To verify the wake-up effect, after the ultrasonic pulse is applied, the same ultrasonic transducer that applies the ultrasonic pulse is used to transmit a low-power detection acoustic pulse into the reactor and receive its echo signal. The total echo energy or the energy of the preset frequency band is calculated and compared with the preset threshold to determine whether the passivation layer has been effectively stripped off.

2. The method for catalytic degradation of pollutants using zero-valent iron nanomaterials according to claim 1, wherein: In step c, the calculation of the rate of change of the redox potential over time is based on differential or regression analysis of the continuously collected ORP value sequence, with the first potential threshold set to a value within the range of -300 mV to -200 mV, and the first rate threshold set to a positive value.

3. The method for catalytic degradation of pollutants using zero-valent iron nanomaterials according to claim 1, wherein: In step c, the frequency range of the high-power ultrasonic pulse is 20 kHz to 40 kHz.

4. The method for catalytic degradation of pollutants using zero-valent iron nanomaterials according to claim 1, wherein: The wake-up efficacy verification in step c is based on the comparison of the total energy of the echo signal, the energy change in the preset frequency band, or the sound velocity attenuation coefficient with the preset value. When the following conditions are met, it is determined that the passivation layer has been effectively stripped: ， in, Indicates the change in the echo signal energy after wake-up relative to the reference echo signal energy before wake-up. Indicates the baseline echo signal energy before wake-up, Indicates the preset acoustic characteristic change threshold, which is a positive value.

5. The method for catalytic degradation of pollutants using zero-valent iron nanomaterials according to claim 1, wherein: In step c, if the wake-up efficacy verification result is that the passivation layer is not effectively stripped, the method further includes selecting one of the following methods: applying a high-power ultrasonic pulse again; or triggering an alarm signal to prompt the operator to perform manual intervention.

6. The method for catalytic degradation of pollutants using zero-valent iron nanomaterials according to claim 1, wherein: Zero-valent iron nanomaterials are micron-sized or nanometer-sized zero-valent iron particles without any surface chemical modification.

7. The method for catalytic degradation of pollutants using zero-valent iron nanomaterials according to claim 1, wherein: The method further includes temporarily reducing or stopping the feed flow rate of the pollutant before or while performing the ultrasonic pulse application in step c.

8. The method for catalytic degradation of pollutants using zero-valent iron nanomaterials according to claim 1, wherein: The method also includes: when the redox potential rising rate exceeds a preset first rate threshold, identifying it as a chemical poisoning mode, triggering an emergency alarm, and simultaneously stopping the physical wake-up operation and prompting manual intervention instead.

9. The method for catalytic degradation of pollutants using zero-valent iron nanomaterials according to claim 1, wherein: The zero-valent iron nanomaterials exist in the reactor in the form of a fixed bed, a fluidized bed or a suspended bed.

10. The method for catalytic degradation of pollutants using zero-valent iron nanomaterials according to claim 1, wherein: The redox potential online sensor is arranged at the water outlet of the reactor or inside the reactor.

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