Photocatalyst-based treatment method for antibiotic residues in pharmaceutical wastewater

Abstract

The invention relates to the technical field of antibiotic treatment, in particular to a photocatalyst-based pharmaceutical wastewater antibiotic residue treatment method which comprises the following steps: judging whether the interface contact efficiency of light and a catalyst is qualified or not based on an effective photon flux attenuation rate; under the condition that the interface contact efficiency of the light and the catalyst is unqualified, the gas-liquid ratio of the reactor is adjusted by a proportional adjustment coefficient based on the bubble density; fitting a degradation kinetics curve of the target antibiotic based on the real-time concentration of the target antibiotic determined by sampling in a preset duration in the photocatalytic reaction process, and optimizing the proportion adjustment coefficient based on the reaction time point of the degradation inflection point of the degradation kinetics curve; and determining a deviation index between an actual degradation path of the target antibiotic and a preset degradation path based on the intermediate product spectrum so as to determine whether the actual degradation path is qualified, and optimizing a preset addition proportion based on the qualification of the actual degradation path and the residual concentration of the target antibiotic. The treatment efficiency of the antibiotics in the pharmaceutical wastewater is improved.

Description

Technical Field

[0001] This invention relates to the field of antibiotic treatment technology, and in particular to a method for treating antibiotic residues in pharmaceutical wastewater based on photocatalysts. Background Technology

[0002] Pharmaceutical wastewater generated during production processes is complex in composition and contains a wide variety of antibiotic residues with fluctuating concentrations. Direct discharge of this wastewater can severely damage aquatic ecosystems and easily induce the emergence and spread of drug-resistant strains in the environment, posing a significant threat to public health and safety. Current treatment technologies for antibiotic residues in pharmaceutical wastewater mainly include biochemical treatment, physical adsorption, and traditional advanced oxidation. Among these, biochemical treatment technology suffers from drawbacks such as low degradation efficiency and difficulty in achieving acceptable residual antibiotic concentrations in effluent due to the poor tolerance of microorganisms to high concentrations of antibiotics. Physical adsorption technology can only achieve phase transfer of antibiotics and cannot complete complete mineralization, which can easily lead to secondary pollution. Traditional advanced oxidation technologies, such as Fenton oxidation, suffer from problems such as large dosage of reagents, high operating costs, and insufficient mineralization capacity for complex degradation intermediates. Photocatalytic oxidation technology has become a research hotspot for the treatment of antibiotic residues in pharmaceutical wastewater due to its advantages of being green and environmentally friendly, having no secondary pollution, and being able to deeply mineralize organic pollutants. However, existing photocatalytic treatment processes still have many technical bottlenecks. On the one hand, photocatalysts are prone to agglomeration in the reaction system, leading to reduced separation efficiency of photogenerated carriers and insufficient utilization of active sites. On the other hand, the control of process parameters lacks precision and stage adaptability. For example, the gas-liquid ratio is adjusted only based on bubble density, which can easily lead to contradictions such as insufficient dissolved oxygen supply or bubble light shielding. The power of the light source is not dynamically controlled in conjunction with the degradation stage and the transformation law of intermediate products. Furthermore, the lack of a monitoring and correction mechanism for the degradation path often results in the actual degradation path deviating from the preset path and the residual antibiotic concentration in the effluent exceeding the standard, making it difficult to balance treatment efficiency, operational economy, and effluent stability.

[0003] Chinese Patent Application Publication No. CN120136235A discloses a method and apparatus for treating tetracycline antibiotics in wastewater based on solar energy degradation. The photothermal continuous flow reactor includes a copper heat exchanger, the surface of which is coated with a thermally conductive material and a photothermal conversion material sequentially from the inside out. The copper heat exchanger has an inlet and an outlet. The method for treating tetracycline antibiotics in wastewater using the photothermal continuous flow reactor includes the following steps: adding an oxidant to the wastewater containing tetracycline antibiotics, and then introducing it into the copper heat exchanger through the inlet; then irradiating the copper heat exchanger with light to carry out degradation treatment; finally, discharging the degraded wastewater through the outlet. This invention, by converting tetracycline antibiotics into their copper complexes, not only reduces the dependence on temperature but also improves the degradation efficiency, realizing continuous flow degradation of tetracycline antibiotics in wastewater based on solar energy.

[0004] The existing technology still has the following problems: when treating antibiotic residues in pharmaceutical wastewater, the photocatalyst is prone to agglomeration, resulting in insufficient generation of active oxygen, lack of precise staged control of process parameters, and lack of degradation path monitoring and correction mechanisms, resulting in low overall treatment efficiency, incomplete mineralization, and difficulty in meeting the standards for residual concentration in the effluent. Summary of the Invention

[0005] Therefore, this invention provides a photocatalyst-based method for treating antibiotic residues in pharmaceutical wastewater, which overcomes the problems of low overall treatment efficiency in the prior art when treating antibiotic residues in pharmaceutical wastewater, such as insufficient active oxygen generation due to easy aggregation of photocatalysts, lack of precise staged control of process parameters, and lack of degradation path monitoring and correction mechanisms.

[0006] To achieve the above objectives, the present invention provides a method for treating antibiotic residues in pharmaceutical wastewater based on a photocatalyst, comprising: The suspension prepared based on the photocatalyst is mixed with the wastewater to be treated at a preset dosage ratio to form a primary reaction system; An optical monitoring window of the reactor containing the primary reaction system is illuminated with a light source of a specific wavelength that matches the main peak of the absorption spectrum of the photocatalyst. The effective photon flux attenuation rate after the light passes through the primary reaction system is calculated in real time to determine whether the interfacial contact efficiency between the light and the catalyst is qualified. Under the condition that the interfacial contact efficiency between light and catalyst is unqualified, the gas-liquid ratio of the reactor is adjusted by a proportional adjustment coefficient based on the bubble density of the primary reaction system. During the photocatalytic reaction, samples are taken at a preset time to determine the real-time concentration of the target antibiotic. Based on several of the real-time concentrations, the degradation kinetic curve of the target antibiotic is fitted, and the ratio adjustment coefficient is optimized based on the reaction time point of the degradation inflection point of the degradation kinetic curve. After the preset total reaction time is completed, the effluent is subjected to solid-liquid separation to obtain a separated liquid. The separated liquid is analyzed to construct an intermediate product profile based on the intermediate products. Based on the intermediate product spectrum, the deviation index between the actual degradation path of the target antibiotic and the preset degradation path is determined to determine whether the actual degradation path is qualified, and the preset dosage ratio is optimized based on the condition that the actual degradation path is qualified and the residual concentration of the target antibiotic is greater than the preset concentration.

[0007] Furthermore, the process of determining whether the interfacial contact efficiency between light and catalyst is qualified based on the effective photon flux attenuation rate includes: The effective photon flux attenuation rate is compared with a preset attenuation rate; Based on the comparison result that the effective photon flux attenuation rate is less than the preset attenuation rate, it is determined that the interfacial contact efficiency between light and catalyst is unqualified.

[0008] Furthermore, under the condition that the interfacial contact efficiency between light and catalyst is unsatisfactory, the process of adjusting the gas-liquid ratio of the reactor based on bubble density includes: The bubble density was compared with the preset density. Based on the comparison result that the bubble density is greater than a first preset density and less than or equal to a second preset density, the gas-liquid ratio is reduced by a first proportional adjustment coefficient. Based on the comparison result that the bubble density is greater than the second preset density, the gas-liquid ratio is reduced by a second proportional adjustment coefficient. The dispersion uniformity of the photocatalyst is determined based on the comparison results of the bubble density being less than or equal to the first preset density. Wherein, the first preset density is less than the second preset density.

[0009] Furthermore, it also includes a process for determining the dispersion uniformity of the photocatalyst based on the average particle size and particle size distribution index of the photocatalyst particles in the sampled liquid: The average particle size is compared with the preset particle size, and the particle size distribution index is compared with the preset index; Based on the comparison results of the average particle size being greater than the preset particle size, or the particle size distribution index being greater than the preset index, it is determined that the photocatalyst is not uniformly dispersed, and the intermittent working mode of the ultrasonic device is activated.

[0010] Furthermore, the process of determining the degradation inflection point based on the degradation kinetic curve includes: Taking the second derivative of the degradation kinetic curve yields the second derivative function; The zero point of the second derivative is determined as the degradation inflection point.

[0011] Furthermore, the process of optimizing the proportional adjustment coefficient based on the reaction time point of the degradation inflection point includes: The reaction time points are compared with preset time nodes respectively; The ratio adjustment coefficient is optimized based on the comparison results of the reaction time point being greater than or equal to the first time node and less than or equal to the second time node; In this process, several proportional correction coefficients are set based on the relative difference between the oxygen content of the primary reaction system and the preset oxygen content to increase the proportional adjustment coefficient.

[0012] Furthermore, it also includes a process of increasing the power of the light source based on the reaction time point of the degradation inflection point: The reaction time points are compared with preset time nodes respectively; The power of the light source is increased based on the comparison result that the reaction time point is greater than or equal to the second time node and less than or equal to the third time node; Several power adjustment coefficients are set based on the relative concentration difference between the real-time concentration and the standard concentration at the reaction time point to increase the power of the light source.

[0013] Furthermore, the process of determining the deviation index between the actual degradation pathway of the target antibiotic and the preset degradation pathway based on the intermediate product profile includes: Compare the intermediate product spectrum with the standard intermediate product spectrum; Based on the comparison results, the following sub-indices were determined: the matching degree of key intermediate types, the consistency of concentration time series, and the achievement of mineralization endpoint. The deviation index is determined by the weighted sum of the matching degree sub-index of the key intermediate type, the consistency sub-index of concentration time series, and the sub-index of mineralization endpoint attainment.

[0014] Furthermore, the process of determining whether the actual degradation path is qualified based on the deviation index includes: Compare the deviation index with a preset deviation index; The actual degradation path is deemed qualified based on the comparison result that the deviation index is less than or equal to the preset deviation index.

[0015] Furthermore, under the condition that the actual degradation pathway of the target antibiotic is qualified, the process of optimizing the preset dosage ratio based on the residual concentration of the target antibiotic includes: The residual concentration is compared with the preset residual concentration; The preset dosage ratio is optimized based on the comparison results showing that the residual concentration is greater than the preset residual concentration. Based on the residual concentration difference between the residual concentration and the preset residual concentration, several proportional optimization coefficients are set to increase the preset dosage ratio.

[0016] Compared with existing technologies, the advantages of this invention lie in its ability to fundamentally guarantee the energy input efficiency of the photocatalytic reaction by real-time monitoring of the photon flux attenuation rate and correspondingly controlling the state of matter in the reaction system. When the attenuation rate is unacceptable, it is determined whether it is due to bubble obstruction or catalyst agglomeration, and the gas-liquid ratio is reduced or ultrasonic dispersion is initiated accordingly. This ensures that photons of specific wavelengths are absorbed by Fe. 3+ / Ni 2+ The co-doped TiO2 catalyst effectively captures and maximizes the yield of photogenerated electron-hole pairs, providing ample driving force for the subsequent generation of active species such as hydroxyl radicals (·OH), thereby significantly improving the treatment efficiency of antibiotics in pharmaceutical wastewater.

[0017] Furthermore, this invention utilizes the inflection point of the degradation kinetic curve as a real-time control signal to achieve adaptive optimization of the reaction process. An inflection point appearing in the middle of the reaction indicates insufficient degradation kinetics due to the accumulation of intermediate products. At this point, increasing the light source power increases the photon flux, forcibly breaking through the reaction energy barrier of high-bond-energy intermediates. Inflection points appearing in the early stages of the reaction are often related to insufficient dissolved oxygen. Optimizing the gas-liquid ratio ensures the supply of oxygen as an electron acceptor, inhibits electron-hole recombination, and ensures the continuous and efficient generation of reactive oxygen species, allowing the degradation reaction to proceed in depth, thereby further improving the treatment efficiency of antibiotics in pharmaceutical wastewater.

[0018] Furthermore, this invention, by constructing and analyzing intermediate product profiles, deepens the evaluation of treatment effectiveness from simple removal of parent product concentration to compliance management of the degradation pathway. By calculating the deviation index, it scientifically determines whether the degradation process leads to complete mineralization or produces unexpected toxic intermediates. This allows for reverse optimization of the catalyst dosage ratio, essentially precisely matching the number of catalytically active sites based on the actual reactivity of the wastewater, avoiding catalyst waste or insufficiency. Ultimately, while ensuring that both effluent toxicity and residual concentration meet standards, the overall economy and reliability of the treatment process are achieved, further improving the treatment efficiency of antibiotics in pharmaceutical wastewater. Attached Figure Description

[0019] Figure 1 This is a flowchart of a method for treating antibiotic residues in pharmaceutical wastewater based on photocatalysts, as described in an embodiment of the present invention. Figure 2 This is a flowchart illustrating whether the interfacial contact efficiency between light and catalyst is qualified according to an embodiment of the present invention. Figure 3 This is a flowchart illustrating the process of determining the dispersion uniformity of the photocatalyst in an embodiment of the present invention. Figure 4 This is a flowchart for determining whether the actual degradation path is qualified in an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0021] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0022] Please see Figure 1 As shown, it is a flowchart of the method for treating antibiotic residues in pharmaceutical wastewater based on photocatalysts according to an embodiment of the present invention.

[0023] This invention provides a method for treating antibiotic residues in pharmaceutical wastewater based on photocatalysts, comprising: Step S1: The suspension prepared based on the photocatalyst is mixed with the wastewater to be treated at a preset addition ratio to form a primary reaction system; Step S2: Illuminate the optical monitoring window of the reactor containing the primary reaction system with a light source of a specific wavelength that matches the main peak of the photocatalyst absorption spectrum, and calculate the effective photon flux attenuation rate after the light passes through the primary reaction system in real time, so as to determine whether the interface contact efficiency between the light and the catalyst is qualified based on the effective photon flux attenuation rate. Step S3: Under the condition that the interfacial contact efficiency between light and catalyst is not up to standard, adjust the gas-liquid ratio of the reactor or start the ultrasonic device based on the bubble density of the primary reaction system using a proportional adjustment coefficient. Step S4: During the photocatalytic reaction, samples are taken for a preset time to determine the real-time concentration of the target antibiotic. Based on several of the real-time concentrations, the degradation kinetic curve of the target antibiotic is fitted. The power of the light source is increased or the proportional adjustment coefficient is optimized based on the reaction time point of the degradation inflection point of the degradation kinetic curve. Step S5: After completing the preset total reaction time, the effluent is subjected to solid-liquid separation to obtain a separated liquid. The separated liquid is analyzed to construct an intermediate product profile based on the intermediate products. Step S6: Determine the deviation index between the actual degradation path of the target antibiotic and the preset degradation path based on the intermediate product spectrum, so as to determine whether the actual degradation path is qualified, and optimize the preset dosage ratio based on the condition that the actual degradation path is qualified and the residual concentration of the target antibiotic is greater than the preset concentration.

[0024] Specifically, the process of preparing a suspension based on a photocatalyst includes: weighing and drying the photocatalyst; adjusting the pH of deionized water to the same value as the wastewater to be treated; then introducing nitrogen gas with a purity ≥99.99% into the deionized water and aerating for 20 minutes; adding the dried photocatalyst powder to the deionized water at a solid-liquid ratio of 5 g / L and stirring at a speed of 200-300 r / min for 1 hour to form a pre-dispersion; transferring the pre-dispersion to an ultrasonic disperser and sonicating for 35 minutes at an ultrasonic power of 300 W and an ultrasonic frequency of 30 kHz, using an intermittent ultrasonic method of 5 minutes of sonication followed by a 2-minute pause, to obtain the photocatalyst suspension.

[0025] Specifically, the photocatalyst selected in this embodiment of the invention is Fe. 3+ and Ni 2+ Co-doped anatase phase titanium dioxide with a Fe to Ni molar ratio of 1:0.49 can be used to degrade tetracycline hydrochloride and methylene blue in pharmaceutical wastewater.

[0026] Specifically, the preset dosage ratio is the ratio of the volume of the suspension to the volume of the wastewater to be treated. The volume of the suspension can be calculated using the following formula: Where C1 is the concentration of the photocatalyst in the suspension, V1 is the volume of the suspension added, and C 目标 V2 represents the target concentration of the photocatalyst in the wastewater to be treated, with an initial target concentration set at 1.5 g / L.

[0027] Specifically, with Fe 3+ and Ni 2+ The absorption spectrum of the co-doped anatase phase titanium dioxide photocatalyst has a specific wavelength range of 400nm-750nm matching main peak.

[0028] Specifically, the effective photon flux attenuation rate refers to the percentage of the value of (1 - the ratio of the effective photon flux transmitted through the primary reaction system within a specific wavelength range to the initial effective photon flux incident on the optical monitoring window).

[0029] Please continue reading. Figure 2 As shown, it is a flowchart for determining whether the interfacial contact efficiency between light and catalyst is qualified according to an embodiment of the present invention.

[0030] Specifically, the process of determining whether the interfacial contact efficiency between light and catalyst is qualified based on the effective photon flux attenuation rate includes: The effective photon flux attenuation rate is compared with a preset attenuation rate; Based on the comparison result that the effective photon flux attenuation rate is less than the preset attenuation rate, it is determined that the interfacial contact efficiency between light and catalyst is unqualified. The interfacial contact efficiency between light and catalyst is determined to be qualified based on the comparison result that the effective photon flux attenuation rate is greater than or equal to the preset attenuation rate.

[0031] Specifically, the preset attenuation rate is set to a range of [18%, 25%], and in this embodiment of the invention, 20% is preferred.

[0032] It is understandable that the essence of photocatalysis is that after a catalyst absorbs photons of a specific wavelength, valence band electrons jump to the conduction band to form photogenerated electron-hole pairs, thereby generating ·OH and ·O2. -Active oxygen species degrade pollutants. If the interfacial contact efficiency is substandard, it indicates that a large number of effective photons are not captured by the active sites on the catalyst surface. For example, if photons penetrate the system without being absorbed, or if catalyst agglomeration results in internal particles being deprived of light, insufficient charge carriers cannot be excited. The catalytic reaction will fail to start effectively due to insufficient energy source, leading to insufficient production of active species. This not only reduces the antibiotic degradation rate but also causes a temporary increase in wastewater toxicity due to incomplete mineralization of intermediate products, ultimately making it difficult for the effluent to meet discharge standards. Simultaneously, low interfacial contact efficiency results in a double waste: firstly, wasted light source energy, as a large number of photons are not utilized and are only converted into heat or scattering losses, increasing energy consumption per unit volume of water; secondly, wasted catalyst, as catalyst particles cannot function due to lack of light, requiring frequent replenishment of new catalyst, increasing reagent costs. Determining whether the contact efficiency is acceptable can prevent such waste in advance, achieving a highly efficient match between photons, catalyst, and pollutants.

[0033] Specifically, under conditions where the interfacial contact efficiency between light and catalyst is unsatisfactory, the process of adjusting the gas-liquid ratio of the reactor based on bubble density includes: The bubble density was compared with the preset density. Based on the comparison result that the bubble density is greater than a first preset density and less than or equal to a second preset density, the gas-liquid ratio is reduced by a first proportional adjustment coefficient. Based on the comparison result that the bubble density is greater than the second preset density, the gas-liquid ratio is reduced by a second proportional adjustment coefficient. The dispersion uniformity of the photocatalyst is determined based on the comparison results of the bubble density being less than or equal to the first preset density. Wherein, the first preset density is less than the second preset density.

[0034] Specifically, the process of determining bubble density is as follows: a high-speed camera is installed on the side wall of the reactor to acquire image information of the primary reaction system. The number of bubbles per unit volume is determined as bubble density by an image recognition algorithm, such as the YOLO target detection algorithm.

[0035] Specifically, the first preset density is 30 cells / mL, and the second preset density is 50 cells / mL. The first proportional adjustment coefficient is set to a value range of [0.8, 0.9], preferably 0.85 in this embodiment of the invention. The second proportional adjustment coefficient is set to a value range of [0.65, 0.75], preferably 0.7 in this embodiment of the invention. The above values ​​are not limited to these, and those skilled in the art can also choose values ​​according to actual needs.

[0036] Specifically, the dispersion uniformity of the photocatalyst is determined online using an online laser diffraction particle size analyzer. Online sampling points are set up in the reaction device's circulation loop, and representative liquid samples from the reaction system are extracted using an automatic sampling system. The average particle size of the photocatalyst particles is measured in real time using laser diffraction technology. Based on a multi-parameter analysis model of the laser scattering signal, the polydispersity index is accurately analyzed and determined as the particle size distribution index of the photocatalyst, ensuring continuous and dynamic monitoring of the photocatalyst particle size and its dispersion state.

[0037] Specifically, the polydispersity index is a dispersibility index calculated using the standard deviation of particle size and the average diameter. It is the ratio of the square of the standard deviation of particle size to the square of the average particle diameter. The value ranges from 0 to 1, with a smaller value indicating a more uniform particle size distribution.

[0038] Specifically, pharmaceutical wastewater containing antibiotics undergoes physical impurity removal, coagulation and flotation, and selective filtration pretreatment before photocatalytic treatment. Selective filtration uses a 0.45μm microporous membrane to remove fine impurities that may interfere with measurements, thus enabling the final pharmaceutical wastewater to undergo photocatalytic treatment.

[0039] Specifically, before adding the photocatalyst, the particle size distribution of blank wastewater is measured as background data, and the background interference can be deducted from the subsequent measurement results.

[0040] Please continue reading. Figure 3 As shown, it is a flowchart for determining the dispersion uniformity of the photocatalyst in an embodiment of the present invention.

[0041] Specifically, the process of determining the dispersion uniformity of the photocatalyst based on the average particle size and the particle size distribution index includes: The average particle size is compared with the preset particle size, and the particle size distribution index is compared with the preset index. The uniformity of photocatalyst dispersion is determined based on the comparison results of the average particle size being less than or equal to the preset particle size and the particle size distribution index being less than or equal to the preset index. Based on the comparison results of the average particle size being greater than the preset particle size, or the particle size distribution index being greater than the preset index, it is determined that the photocatalyst is not uniformly dispersed, and the intermittent working mode of the ultrasonic device is activated.

[0042] Specifically, the preset particle size is set to a range of [100nm, 130nm], and in this embodiment of the invention, 110nm is preferred; the preset index is set to a range of [0.1, 0.5], and in this embodiment of the invention, 0.2 is preferred.

[0043] Specifically, the intermittent working mode of the ultrasound device is: 2 minutes of ultrasound followed by a 3-minute pause.

[0044] Understandably, when the bubble density exceeds the standard, a large number of bubbles will form a light-shielding layer inside the reactor, strongly scattering and blocking effective photons of the characteristic absorption wavelength of Fe-Ni co-doped TiO2. This leads to a sharp reduction in the effective photon flux reaching the catalyst surface and a decrease in interfacial contact efficiency. In this case, the reduction in attenuation rate is due to bubble interference, not the catalyst itself. Reducing the gas-liquid ratio can quickly reduce the number of bubbles in the system and eliminate the physical obstruction of light transmission by bubbles. When the bubble density is within the acceptable range, if the interfacial contact efficiency is still not up to standard, it indicates that the root cause of the problem has shifted to the dispersion state of the catalyst itself. At this point, it is necessary to specifically determine the dispersion uniformity: catalyst dispersion agglomeration / settling will cause active sites to be shielded. The large-particle aggregates formed by agglomeration can only have surface particles in contact with light, while the internal active sites cannot receive photons at all; settled catalyst will deposit at the bottom of the reactor, completely detached from the light-illuminated area. Both of these situations will directly lead to the interfacial contact efficiency being lower than the preset threshold. By measuring the average particle size and particle size distribution index using a dynamic light scattering instrument, the dispersion problem can be accurately determined, avoiding confusion between catalyst agglomeration and bubble shielding, and achieving precise positioning of the control target. The cavitation effect of ultrasound can generate localized microjets and shear forces, rapidly breaking down catalyst aggregates and reducing large-diameter aggregates into nanoscale monodisperse / quasi-monodisperse particles. This restores the uniform suspension of catalyst particles, thereby re-exposing shielded active sites and increasing the effective area of ​​the photocatalyst interface. Using intermittent ultrasound instead of continuous ultrasound avoids two negative risks: first, continuous ultrasound causes a sudden temperature rise, accelerating the recombination of photogenerated electron-hole pairs and reducing catalytic activity; second, strong ultrasonic impact can cause catalyst crystal distortion, such as the transformation from anatase to rutile, leading to irreversible deactivation. Simultaneously, it prevents microbubbles generated by ultrasound from interfering with light transmission again, achieving a balance between dispersibility restoration and reaction stability.

[0045] Specifically, sampling is performed at preset time intervals of 10 minutes to determine the real-time concentration of the target antibiotic. The least squares method is used to fit several real-time concentrations to obtain the sampling degradation kinetic curve. This is existing technology and will not be described in detail here.

[0046] Specifically, the process of determining the degradation inflection point based on the degradation kinetic curve includes: The second derivative of the degradation kinetic curve is obtained by taking the second derivative function, which characterizes the rate of change of the instantaneous degradation rate. Find the zeros of the second derivative function; The zero point of the second derivative is determined as the degradation inflection point.

[0047] It is understandable that the zero point is the boundary point where the second derivative changes from negative to positive or from positive to negative.

[0048] In practice, the zero point is the boundary where the second derivative changes from negative to positive. For the photocatalytic degradation system of antibiotics, the concentration of the target antibiotic decreases monotonically with reaction time. The first derivative of the degradation kinetic curve of the target antibiotic characterizes the instantaneous rate of change of concentration. Since the concentration decreases, it is always negative, and the absolute value of the first derivative is the instantaneous degradation rate. The larger the absolute value, the faster the degradation rate. The second derivative characterizes the rate of change of the first derivative, that is, the acceleration of the instantaneous degradation rate. When the second derivative is less than 0, the value of the first derivative gradually decreases (becomes more negative) with time, and the corresponding instantaneous degradation rate continues to increase; this stage is the accelerated degradation stage. When the second derivative is greater than 0, the value of the first derivative gradually increases (approaches 0) with time, and the corresponding instantaneous degradation rate continues to decrease; this stage is the deceleration stage. The point where the second derivative changes from negative to positive is the critical point where the first derivative reaches its minimum value, corresponding to the instantaneous degradation rate reaching its maximum value. After crossing this point, the degradation rate changes from continuously increasing to continuously decreasing. Therefore, this point is a key node where the degradation rate changes from accelerating upward to decelerating downward. After this node, the degradation rate begins to decay. If the parameters are not adjusted in time, it will lead to incomplete mineralization of pollutants and a prolonged treatment cycle.

[0049] Specifically, the process of increasing the light source power based on the reaction time point of the degradation inflection point includes: The reaction time points are compared with preset time nodes respectively; The power of the light source is increased based on the comparison results of the reaction time point being greater than or equal to the second time node and less than or equal to the third time node; Several power adjustment coefficients are set based on the relative concentration difference between the real-time concentration and the standard concentration at the reaction time point to increase the power of the light source.

[0050] Specifically, the relative concentration difference refers to the percentage of the absolute difference between the real-time concentration and the standard concentration relative to the standard concentration.

[0051] Specifically, the process of optimizing the proportional adjustment coefficient based on the reaction time point of the degradation inflection point includes: The reaction time points are compared with preset time nodes respectively; The ratio adjustment coefficient is optimized based on the comparison results of the reaction time point being greater than or equal to the first time node and less than or equal to the second time node; In this process, several proportional correction coefficients are set based on the relative difference between the oxygen content of the primary reaction system and the preset oxygen content to increase the proportional adjustment coefficient.

[0052] Specifically, the relative difference in oxygen content refers to the percentage difference between the absolute difference between the oxygen content of the primary reaction system and the preset oxygen content and the preset oxygen content.

[0053] Specifically, the first time point of the photocatalytic reaction is 0 min, the second time point is 30 min, the third time point is 120 min, and the fourth time point is 150 min. The period between the first and second time points is the early stage of the photocatalytic reaction, the period between the second and third time points is the middle stage of the photocatalytic reaction, the period after the third time point is the late stage of the photocatalytic reaction, and the fourth time point is the preset total reaction time of this embodiment of the invention.

[0054] Specifically, the relative difference between the real-time concentration and the standard concentration is determined based on the comparison results of the real-time concentration corresponding to the reaction time node being greater than the standard concentration; Based on the comparison result that the relative concentration difference is less than or equal to the preset relative concentration difference, the power of the light source is increased by the first power adjustment coefficient. Based on the comparison result that the relative concentration difference is greater than the preset relative concentration difference, the power of the light source is increased by the second power adjustment coefficient.

[0055] Specifically, the preset concentration relative difference is set to a range of [20%, 40%], and preferably 30% in this embodiment of the invention. The first power adjustment coefficient is set to a range of [1.1, 1.2], and preferably 1.15 in this embodiment of the invention. The second power adjustment coefficient is set to a range of [1.21, 1.3], and preferably 1.25 in this embodiment of the invention.

[0056] Specifically, the standard concentration refers to the theoretical concentration of the target antibiotic at the reaction time point determined based on an ideal photocatalytic degradation kinetic curve without an inflection point.

[0057] Specifically, the relative difference in oxygen content between the preset oxygen content and the oxygen content is determined based on the comparison result that the oxygen content is less than the preset oxygen content; Based on the comparison result that the relative difference of oxygen content is greater than or equal to the preset relative difference of oxygen content, the proportional adjustment coefficient is increased by a first proportional correction coefficient. Based on the comparison result that the relative difference in oxygen content is less than the preset relative difference in oxygen content, the proportional adjustment coefficient is increased by a second proportional correction coefficient.

[0058] Specifically, the preset oxygen content range is set to [4 g / L, 6 g / L], and preferably 5 g / L in this embodiment of the invention. The first proportional correction coefficient range is set to [1.06, 1.09], and preferably 1.07 in this embodiment of the invention. The second proportional correction coefficient range is set to [1.02, 1.05], and preferably 1.04 in this embodiment of the invention.

[0059] Specifically, the oxygen content of the primary reaction system is detected in real time using an electrochemical method, which is existing technology and will not be elaborated further.

[0060] Specifically, the degradation inflection point occurs in the early stage of the photocatalytic reaction, when the active sites on the catalyst surface are not occupied by intermediate products and the antibiotic molecules have not undergone deep bond breaking. At this time, the core mechanism of the reaction is: photoexcitation generates electron-hole pairs → O2 captures photogenerated electrons and inhibits recombination → ·O2 is generated. - Active oxygen species rapidly attack antibiotic functional groups. The bottleneck at this stage is insufficient electron acceptor O2 or bubble shielding preventing photons from reaching the catalyst surface, thus requiring regulation of O2 supply. When the oxygen content is low, the electron-hole recombination rate increases, leading to a sharp decrease in active oxygen production. Therefore, it is necessary to appropriately increase the gas-liquid ratio to restore the balance of the electron capture mechanism, while avoiding excessive bubble density.

[0061] The degradation inflection point occurs in the middle of the photocatalytic reaction, when the parent antibiotic has already partially degraded. The core degradation sites of the parent antibiotic, such as tetracycline, are amide bonds and phenolic hydroxyl groups. These functional groups interact with ·O2. - The reaction barrier for ·OH is relatively low, and rapid bond breaking can be achieved with a small amount of reactive oxygen species in the early stages. However, in the middle stage, the system mainly consists of ring-opening intermediates, such as monocyclic carboxylic acids and small molecule derivatives containing amino groups. These substances have higher CN and CO bond energies, increasing the reaction barrier with reactive oxygen species by 2-3 times, requiring a higher concentration of reactive oxygen species for deep oxidation. The generation of reactive oxygen species depends entirely on photogenerated charge carriers. When the charge carrier generation decreases due to blockage of active sites, the reactive oxygen species production will also decrease sharply, making it impossible to overcome the degradation barrier of intermediate products. Increasing the power of the light source to increase the photon flux can directly increase the total charge carrier generation, thereby increasing the concentration of reactive oxygen species and meeting the high degradation barrier requirements of intermediate products.

[0062] Specifically, the core hazard of excessive bubble density is the induction of light scattering, causing effective photons to attenuate prematurely in the liquid phase and fail to reach the catalyst surface to excite carriers. Therefore, the initial goal of adjusting the gas-liquid ratio is to reduce the number of bubbles and restore the photon-catalyst-carrier excitation pathway. If the gas-liquid ratio is excessively reduced, the dissolution rate of O2 in the liquid phase will be lower than the consumption rate, disrupting the mechanism balance of O2 capturing electrons, triggering rapid electron-hole recombination, insufficient reactive oxygen production, and the early degradation inflection point will still occur. Therefore, optimizing the ratio adjustment coefficient by the relative difference in oxygen content is to precisely control the O2 concentration under the premise that photons can reach the catalyst normally, and rebuild the complete pathway of photoexcited carriers-O2 capturing electrons-generating reactive oxygen.

[0063] It is understandable that the intermediate products of the photocatalytic reaction process of antibiotics are mostly low-concentration polar / nonpolar small molecules, such as demethylated derivatives, open-ring carboxylic acids, nitrogen-containing heterocycles, etc., and may contain trace amounts of catalyst particles or matrix impurities, which need to be enriched and purified first.

[0064] Specifically, the process of constructing the intermediate product profile includes: 1. Enrichment and Purification: For polar intermediates, such as tetracycline deamidation derivatives, solid-phase extraction is used with C18 or hydrophilic-lipophilic balanced (HLB) packed columns. Through the steps of "activation-loading-rinsing-elution", the intermediates are enriched 10-100 times, while removing interfering substances such as inorganic salts and humic substances from the water sample. For volatile intermediates, such as small molecule fatty acids, liquid-liquid extraction is used with dichloromethane / ethyl acetate as the extractant to separate the target analyte from the aqueous matrix.

[0065] 2. Derivatization (as needed): If the intermediate product contains polar functional groups such as amino or carboxyl groups, such as aminobenzoic acid, or is not sufficiently volatile, derivatization treatment is required, such as silanization or methyl esterification, to improve its resolution in gas chromatography and mass spectrometry response value.

[0066] 3. Filtration and volume adjustment: The sample after the above treatment is filtered through a 0.22μm organic filter membrane to remove small particles, and then adjusted to a fixed volume with methanol / acetonitrile for later detection.

[0067] 4. Detection: Based on the product type, the detection technology is matched. Liquid chromatography-tandem mass spectrometry is used to identify polar / non-volatile organic intermediates, gas chromatography-mass spectrometry is used to identify volatile / derivative organic intermediates, and ion chromatography is used to detect inorganic mineralization products. The product structure is qualitatively determined by comparison with mass spectrometry databases and verification with standards. At the same time, the external standard method is used to achieve quantitative analysis of each product.

[0068] 5. Construct spectra based on the generation sequence of each intermediate product, such as the early generation of demethylated products, the mid-term generation of ring-opening carboxylic acids, and the late generation of inorganic ions, as well as the concentration change trend. Combined with the photocatalytic degradation mechanism, construct a dynamic intermediate product spectrum with time as the x-axis and intermediate product concentration as the y-axis.

[0069] The process of constructing the intermediate product profile is existing technology and will not be described in detail here.

[0070] Specifically, the process of determining the deviation index between the actual degradation pathway of the target antibiotic and the preset degradation pathway based on the intermediate product spectrum includes: Compare the intermediate product spectrum with the standard intermediate product spectrum; Based on the comparison results, the following sub-indices were determined: the matching degree of key intermediate types, the consistency of concentration time series, and the achievement of mineralization endpoint. The weighted sum of the key intermediate type matching sub-index, the concentration time series consistency sub-index, and the mineralization endpoint attainment sub-index is determined as the deviation index; The weighting coefficients for the key intermediate type matching degree sub-index, the concentration time series consistency sub-index, and the mineralization endpoint attainment degree sub-index are 0.45, 0.35, and 0.2, respectively. However, the above values ​​are not limited to these values, and those skilled in the art can also choose values ​​according to actual needs.

[0071] Specifically, the standard intermediate product spectrum refers to the benchmark product dynamic distribution and transformation spectrum based on the photocatalytic degradation mechanism, relying on multiple sets of ideal reaction system blank verification experiments without process interference and combined with the degradation kinetic model. It includes the types, molecular structures, concentration thresholds, generation and degradation sequences, transformation links and core node conversion rates of key intermediates and final inorganic mineralization products that must appear in the degradation process of the target antibiotic.

[0072] Specifically, the process of determining the matching degree sub-index of the key intermediate type includes: The number of key intermediates N0 in the statistical standard intermediate product spectrum; The number of missing key intermediates N1 and the number of newly added non-standard intermediates N2 in the intermediate product profile were statistically analyzed. The ratio of the sum of N1 and N2 to N0 is determined as the key intermediate type matching degree; Among them, the key intermediates for tetracycline degradation are TC-DM, deamidated tetracycline, and open-ring carboxylic acid.

[0073] For example: N0=3, one key intermediate is missing, and one non-standard intermediate is added, such as cyanide generated by over-oxidation. Then the key intermediate type matching degree = (1+1) / 3≈0.67.

[0074] Specifically, the process of determining the concentration time-series consistency sub-index includes: Based on a single key intermediate, the relative deviation X1 between the actual peak time and the standard peak time and the relative deviation X2 between the actual peak concentration and the standard peak concentration are calculated. The arithmetic mean of X1 and X2 of all key intermediates was determined as the concentration-time consistency sub-index.

[0075] For example: the standard peak time of the key intermediate of deamidinated tetracycline is 30 min, with a peak concentration of 3 mg / L, and the actual peak time is 40 min, with a peak concentration of 2 mg / L. Therefore, X11≈0.33, X12≈0.33; the standard peak time of the key intermediate of TC-DM is 20 min, with a peak concentration of 4 mg / L, and the actual peak time is 25 min, with a peak concentration of 3 mg / L. Therefore, X21=0.25, X22=0.25; the standard peak time of the key intermediate of open-ring carboxylic acid is 60 min, with a peak concentration of 6 mg / L, and the actual peak time is 75 min, with a peak concentration of 4 mg / L. Therefore, X31=0.25, X32≈0.33; the concentration-time consistency sub-index is [(0.25+0.25)+(0.33+0.33)+(0.25+0.33)] / 6≈0.29.

[0076] Specifically, the mineralization endpoint attainment index refers to the percentage difference between the absolute difference of the proportion of inorganic carbon / nitrogen in the intermediate product spectrum and the standard proportion in the standard intermediate product spectrum and the standard proportion.

[0077] Please continue reading. Figure 4 As shown, it is a flowchart for determining whether the actual degradation path is qualified according to an embodiment of the present invention.

[0078] Specifically, the process of determining whether the actual degradation pathway is qualified based on the deviation index includes: Compare the deviation index with a preset deviation index; Based on the comparison results where the deviation index is greater than the preset deviation index, the actual degradation path is determined to be unqualified. The actual degradation path is deemed qualified based on the comparison result that the deviation index is less than or equal to the preset deviation index.

[0079] Specifically, the preset deviation index is set to a range of [0.2, 0.5], and in this embodiment of the invention, 0.4 is preferred.

[0080] Specifically, under the condition that the actual degradation pathway of the target antibiotic is qualified, the process of optimizing the preset dosage ratio based on the residual concentration of the target antibiotic includes: The residual concentration is compared with the preset residual concentration; The preset dosage ratio is optimized based on the comparison results showing that the residual concentration is greater than the preset residual concentration. Based on the residual concentration difference between the residual concentration and the preset residual concentration, several proportional optimization coefficients are set to increase the preset dosage ratio.

[0081] Specifically, based on the comparison result that the residual concentration difference is greater than the preset residual concentration difference, the preset addition ratio is increased by a first ratio optimization coefficient. Based on the comparison result that the residual concentration difference is less than or equal to the preset residual concentration difference, the preset addition ratio is increased by the second ratio optimization coefficient.

[0082] Specifically, the preset residual concentration range is set to [0.1 mg / L, 0.3 mg / L], and preferably 0.2 mg / L in this embodiment of the invention; the preset residual concentration difference range is set to [0.05 mg / L, 0.2 mg / L], and preferably 0.2 mg / L in this embodiment of the invention; the first proportional optimization coefficient range is set to [1.2, 1.35], and preferably 1.25 in this embodiment of the invention; the second proportional optimization coefficient range is set to [1.05, 1.19], and preferably 1.18 in this embodiment of the invention.

[0083] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for treating pharmaceutical wastewater containing antibiotic residues based on a photocatalyst, characterized by, The method comprises the following steps: Mixing the suspension prepared based on the photocatalyst with the wastewater to be treated at a preset addition ratio to form a primary reaction system; Irradiating the optical monitoring window of the reactor containing the primary reaction system with a light source of a specific wavelength matching the main peak of the light absorption spectrum of the photocatalyst, and calculating the effective photon flux attenuation rate of the light after passing through the primary reaction system in real time to determine whether the interface contact efficiency of the light and the catalyst is qualified; Under the condition that the interface contact efficiency of the light and the catalyst is not qualified, adjusting the gas-liquid ratio of the reactor based on the bubble density of the primary reaction system by a proportional adjustment coefficient; Sampling during the photocatalytic reaction process for a preset time length to determine the real-time concentration of the target antibiotic, fitting the degradation kinetics curve of the target antibiotic based on a plurality of the real-time concentrations, and optimizing the proportional adjustment coefficient based on the reaction time point of the degradation inflection point of the degradation kinetics curve; After completing the preset total reaction time, performing solid-liquid separation on the effluent to obtain a separated liquid, and analyzing the separated liquid to construct an intermediate product spectrum according to the intermediate product; Based on the intermediate product spectrum, determining the deviation index of the actual degradation path of the target antibiotic from the preset degradation path to determine whether the actual degradation path is qualified, and optimizing the preset addition ratio based on the condition that the actual degradation path is qualified and the residual concentration of the target antibiotic is greater than the preset concentration.

2. The method for treating pharmaceutical wastewater according to claim 1, wherein, The process of determining whether the interface contact efficiency of the light and the catalyst is qualified based on the effective photon flux attenuation rate comprises: Comparing the effective photon flux attenuation rate with a preset attenuation rate; Based on the comparison result that the effective photon flux attenuation rate is less than the preset attenuation rate, determining that the interface contact efficiency of the light and the catalyst is not qualified. 3.The method of claim 2, wherein the method is characterized by, Under the condition that the interface contact efficiency of the light and the catalyst is not qualified, the process of adjusting the gas-liquid ratio of the reactor based on the bubble density comprises: Comparing the bubble density with a first preset density and a second preset density respectively; Based on the comparison result that the bubble density is greater than the first preset density and less than or equal to the second preset density, determining to reduce the gas-liquid ratio by a first proportional adjustment coefficient; Based on the comparison result that the bubble density is greater than the second preset density, determining to reduce the gas-liquid ratio by a second proportional adjustment coefficient; Based on the comparison result that the bubble density is less than or equal to the first preset density, determining the dispersion uniformity of the photocatalyst; Wherein, the first preset density is less than the second preset density.

4. The method for treating pharmaceutical wastewater according to claim 3, wherein the photocatalyst is titanium oxide. The process of determining the dispersion uniformity of the photocatalyst based on the average particle size and the particle size distribution index of the photocatalyst particles in the sampling liquid comprises: Comparing the average particle size with a preset particle size, and comparing the particle size distribution index with a preset index; Based on the comparison result that the average particle size is greater than the preset particle size, or the particle size distribution index is greater than the preset index, determining that the dispersion of the photocatalyst is not uniform, and starting the intermittent operation mode of the ultrasonic device. 5.The method for treating antibiotic residues in pharmaceutical wastewater based on a photocatalyst according to claim 4, characterized in that, The process of determining the degradation inflection point based on the degradation kinetics curve comprises: Taking the second derivative of the degradation kinetics curve to obtain a second derivative function; Determining the zero point of the second derivative as the degradation inflection point. 6.The method of claim 5, wherein the method is characterized by, The process of optimizing the proportional adjustment coefficient based on the reaction time point of the degradation inflection point comprises: The reaction time point is compared with a preset time node respectively; The proportion adjustment coefficient is optimized based on the comparison result that the reaction time point is greater than or equal to a first time node and less than or equal to a second time node; Wherein, a plurality of proportion correction coefficients are set based on the oxygen content relative difference between the oxygen content of the primary reaction system and a preset oxygen content to increase the proportion adjustment coefficient. 7.The method of claim 6, wherein the method is characterized by, The process of increasing the light source power based on the reaction time point of the degradation inflection point also includes: The reaction time point is compared with a preset time node respectively; The light source power is increased based on the comparison result that the reaction time point is greater than or equal to the second time node and less than or equal to a third time node; Wherein, a plurality of power adjustment coefficients are set based on the concentration relative difference between the real-time concentration corresponding to the reaction time point and a standard concentration to increase the light source power. 8.The method of claim 7, wherein the method is characterized by, The process of determining the deviation index of the actual degradation path of the target antibiotic from the preset degradation path based on the intermediate product spectrum includes: The intermediate product spectrum is compared with a standard intermediate product spectrum; Based on the comparison result, the key intermediate species matching degree sub-index, the concentration time sequence consistency sub-index and the mineralization end point meeting degree sub-index are determined; The weighted sum of the key intermediate species matching degree sub-index, the concentration time sequence consistency sub-index and the mineralization end point meeting degree sub-index is determined as the deviation index. 9.The method of claim 8, wherein the method is characterized by, The process of determining whether the actual degradation path is qualified based on the deviation index includes: The deviation index is compared with a preset deviation index; Based on the comparison result that the deviation index is less than or equal to the preset deviation index, it is determined that the actual degradation path is qualified. 10.The method of claim 9, wherein the method is characterized by, Under the condition that the actual degradation path of the target antibiotic is qualified, the process of optimizing the preset addition proportion based on the residual concentration of the target antibiotic includes: The residual concentration is compared with a preset residual concentration; Based on the comparison result that the residual concentration is greater than the preset residual concentration, the preset addition proportion is optimized; Based on the residual concentration difference between the residual concentration and the preset residual concentration, a plurality of proportion optimization coefficients are set to increase the preset addition proportion.

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