A method for catalyst activity evaluation in heterogeneous persulfate oxidation systems

Abstract

The application provides a method for evaluating the activity of a catalyst in a heterogeneous persulfate oxidation system, comprising the following steps: S1: determining a target oxidant, a target pollutant and a catalyst to be evaluated participating in a catalytic reaction, and performing a catalytic reaction using the target oxidant, the target pollutant and the catalyst to be evaluated; S2: determining the amount of electron transfer per active site of the catalyst per unit time during the catalytic reaction; S3: setting a plurality of target pollutant concentrations, calculating the corresponding electron transfer amounts of the plurality of target pollutant concentrations and performing fitting, and determining a corresponding electron transfer efficiency index according to the fitting result; S4: evaluating the activity of the catalyst using the electron transfer efficiency index; and the application realizes quantitative characterization of the intrinsic catalytic activity of the heterogeneous catalyst by constructing an electron transfer efficiency index (k e ).

Description

Technical Field

[0001] This invention relates to the field of pollution treatment technology, and more specifically to a method for evaluating catalyst activity in heterogeneous persulfate oxidation systems. Background Technology

[0002] Currently, heterogeneous persulfate oxidation technology has been widely used in recent years for the removal of recalcitrant toxic organic pollutants in water bodies due to its advantages such as high efficiency and simple operation.

[0003] However, in the existing evaluation of the catalytic activity of heterogeneous persulfate oxidation systems, the most widely used index is the apparent first-order rate constant k. obs k obs Essentially, it is a system-level ensemble of multi-factor parameters, the value of which is influenced by multiple external factors such as the type and concentration of oxidant, the molecular structure of the target pollutant, the background water matrix (such as natural organic matter and inorganic anions), and mass transfer efficiency, rather than a single mapping of the intrinsic properties of the catalyst. Attributing all the contributions of these factors, which should belong to different factors, to the catalyst itself makes it difficult to compare different research results, lacks the ability to characterize the catalytic reaction process in multiple dimensions, and fails to quantify the surface affinity / reaction equilibrium characteristics of the catalyst for specific pollutants; it cannot assess the interference intensity of the background matrix on catalytic performance; and it cannot reflect the dominant type of reaction pathway (radical pathway vs. non-radical pathway), the latter of which directly affects the stability, selectivity, and resistance to interference of the catalyst.

[0004] To overcome the effect of catalyst specific surface area differences on k obs Due to the influence of specific surface area (SA), some researchers have introduced a normalization process to obtain the specific activity rate constant k. SA This method only corrects surface roughness at the geometric level and fails to address k. obs The core of the fundamental flaw is k obs The mixture of multiple non-intrinsic kinetic contributions, such as the oxidizability of pollutants, matrix quenching effect, and oxidant utilization rate, makes it impossible to distinguish between productive and non-productive consumption of oxidant. This obscures information on catalyst selectivity and oxidant utilization efficiency, and cannot fundamentally solve the problem of activity comparability across catalyst systems and experimental conditions.

[0005] Finally, existing assessment methods completely bypass the direct measurement of the ability of a unit active site to mediate electron transfer per unit time, instead relying on the indirect, apparent surrogate indicator of pollutant concentration decay. This approach ignores the quantitative correlation between pollutant degradation, oxidant consumption, and electron transfer, resulting in the assessment of catalytic efficiency remaining at a "semi-quantitative" level.

[0006] Therefore, how to provide a method for evaluating catalyst activity in heterogeneous persulfate oxidation systems that can solve the above problems is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, the present invention provides a method for evaluating catalyst activity in heterogeneous persulfate oxidation systems, by constructing an electron transfer efficiency index (k... e This enables quantitative characterization of the intrinsic catalytic activity of heterogeneous catalysts.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A method for evaluating catalyst activity in heterogeneous persulfate oxidation systems includes the following steps: S1: Identify the target oxide, target pollutant, and catalyst to be evaluated for the catalytic reaction, and use the target oxide, target pollutant, and catalyst to be evaluated to carry out the catalytic reaction; S2: Determines the amount of electrons transferred per unit time at each active site of the catalyst during the catalytic reaction; S3: Set multiple target pollutant concentrations, calculate the electron transfer amount corresponding to the multiple target pollutant concentrations and perform fitting, and determine the corresponding electron transfer efficiency index based on the fitting result; S4: The activity of the catalyst is evaluated using the electron transfer efficiency index.

[0009] Preferably, S2 includes: S21: Calculate the molar concentration of effective electron transfer based on the first molar concentration of the target oxide when the target pollutant is not added and the second molar concentration of the target oxide when the target pollutant is added; S22: Determine the amount of electron transfer for each active site based on the number of active sites per unit time and the molar concentration of effective electron transfer.

[0010] Preferably, S2 further includes: S23: The electron transfer amount is optimized using the BET surface area method.

[0011] Preferably, S3 includes: S31: Set multiple target pollutant concentrations and calculate the electron transfer amount corresponding to the multiple target pollutant concentrations; S32: Using the reciprocal of the target pollutant concentration and the reciprocal of the electron transfer amount, a linear fit is performed to obtain the corresponding fitted straight line; S33: The reciprocal of the slope of the fitted straight line is the electron transfer efficiency index.

[0012] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a method for evaluating catalyst activity in heterogeneous persulfate oxidation systems, which has the following beneficial effects: 1. This invention proposes to introduce an electron transfer rate constant (k) based on the Langmuir-Hinshelwood kinetic model. e The method of solving the intrinsic activity of a catalyst by using a double reciprocal plotting method can mathematically isolate the influence of non-intrinsic variables such as pollutant concentration and matrix interference, thereby achieving quantitative extraction of the intrinsic activity of the catalyst.

[0013] 2. This invention aims to quantitatively determine the effective oxidant consumption by setting up two sets of control experiments with and without added pollutants in parallel. Combining the electron transfer equivalent number of the oxidant and the specific surface area of ​​the catalyst, it achieves direct measurement of catalytic efficiency based on the core physical quantity of electron transfer.

[0014] 3. This invention uses k e This decoupled intrinsic activity parameter serves as the core response variable. Correlation analysis is performed with the structural characterization parameters of the catalyst to establish a predictive model that truly reflects the intrinsic relationship between "structure and activity".

[0015] 4. While significantly improving the scientific rigor of the evaluation, this invention requires keeping the experimental workload within a reasonable range. Parameter extraction is achieved through a double reciprocal plotting method at multiple concentration points (e.g., 5 concentrations). The experimental procedure is standardized, the data processing method is clear, and it has good operability and scalability. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0017] Figure 1 This invention provides an overall flowchart of a method for evaluating catalyst activity in a heterogeneous persulfate oxidation system. Figure 2 This is a schematic diagram of experimental results provided in an embodiment of the present invention, where (a, b) represent the calculation and determination of k by activating persulfate with cobalt tetroxide (Co3O4) nanoparticles to remove multiple pollutants. e Values; (c,d) represent the iron content and apparent rate constant (k) in persulfate (PMS) activation systems using the original carbonitride and iron-modified carbonitride, respectively. obs ) and k eThe correlation. Fe 2p (at.%) refers to the atomic percentage of Fe 2p orbitals (energy levels) on the surface of a material as measured by X-ray photoelectron spectroscopy. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1

[0020] See Figure 1 As shown in the figure, this invention discloses a method for evaluating catalyst activity in a heterogeneous persulfate oxidation system, comprising the following steps: S1: Identify the target oxide, target pollutant, and catalyst to be evaluated for the catalytic reaction, and use the target oxide, target pollutant, and catalyst to be evaluated to carry out the catalytic reaction; S2: Determines the amount of electrons transferred per unit time at each active site of the catalyst during the catalytic reaction; S3: Set multiple target pollutant concentrations, calculate the electron transfer amount corresponding to the multiple target pollutant concentrations and perform fitting, and determine the corresponding electron transfer efficiency index based on the fitting result; S4: The activity of the catalyst is evaluated using the electron transfer efficiency index. Subsequently, the activity of the catalyst can be comprehensively evaluated by obtaining reported literature and experimental data of other catalysts through big data.

[0021] In one specific embodiment, S2 includes: S21: Calculate the molar concentration of effective electron transfer based on the first molar concentration of the target oxide when the target pollutant is not added and the second molar concentration of the target oxide when the target pollutant is added; S22: Determine the amount of electron transfer for each active site based on the number of active sites per unit time and the molar concentration of effective electron transfer.

[0022] In one specific embodiment, S2 further includes: S23: The electron transfer amount is optimized using the BET surface area method.

[0023] In one specific embodiment, S3 includes: S31: Set multiple target pollutant concentrations and calculate the electron transfer amount corresponding to the multiple target pollutant concentrations; S32: Using the reciprocal of the target pollutant concentration and the reciprocal of the electron transfer amount, a linear fit is performed to obtain the corresponding fitted straight line; S33: The reciprocal of the slope of the fitted straight line is the electron transfer efficiency index.

[0024] Specifically, the implementation process of S3 includes: 1. The derivation process of the electron transfer efficiency index includes: Regardless of the reaction pathway (e.g., a radical pathway or a pathway involving high-valence metals), the type of contaminant, or background matrix interference, the electron transfer process from the reducing agent (usually the contaminant) to the oxidizing agent is accelerated by a catalyst. Based on the Langmuir-Hinshelwood theory, embodiments of the present invention can further deduce the establishment of the electron transfer amount r. e The specific expression for the quantitative relationship between pollutant concentration and concentration is as follows: (1) In the formula, r e k represents the amount of electrons transferred per active site per unit time. e K represents the electron transfer efficiency index. ec ∑K represents the adsorption / reaction equilibrium constant. i ×Q i The pol indicates the overall influence of the background matrix, while pol represents the concentration of the target pollutant.

[0025] Taking the double reciprocal of formula (1) yields the corresponding linear equation, where r e The specific expression is: (2) In the formula, electron transfer number represents the molar concentration of effective electron transfer, t represents the unit time, and active site number represents the number of active sites.

[0026] It is important to note that the consumption of oxidant during the treatment process includes both effective contaminant removal (oxidation and polymerization) and non-productive losses (such as free radical scavenging). Therefore, the specific expression for the molar concentration of effective electron transfer is: (3) In the formula, Δ[oxi] wt and Δ[oxi] wo These represent the molar concentrations of oxidant consumed in actual water bodies with and without added pollutants, respectively. The molar concentration of the oxidant can be quantified by periodically collecting samples of the reaction solution. per,oxi This represents the number of moles of electrons per mole of oxidant (Me).- M -1 ).

[0027] Regarding the quantification of the number of active sites, techniques such as chemisorption or electrochemical analysis are preferred to determine the absolute number. However, if these methods are difficult to use for carbon catalysts, this embodiment of the invention recommends using the BET surface area (ST). cat As a simplified approximation, r is calculated by normalizing the active sites (surface area normalized) and time. e It can reflect the efficiency of electron transfer mediated by active sites per unit area per unit time, eliminate the amplification effect of catalyst dosage and reaction time on apparent rate, and provide a fair benchmark for cross-sectional comparison between catalysts with different specific surface areas.

[0028] Substituting formula (3) into formula (2), we get: (4) From formulas (1) and (4), the electron transfer rate constant k is derived in the embodiments of the present invention. e The general formula, specifically the expression, is: (5) In the experiment, at least five gradients of initial pollutant concentrations were set (e.g., concentration range from 0.5 mM to 10.0 mM), and the corresponding r values ​​were measured. e ; Plot 1 / [pol] (the reciprocal of pollutant concentration) on the x-axis and 1 / r on the y-axis. e A standard curve is plotted with the reciprocal of the electron transfer rate as the ordinate, and a linear fit is performed. The reciprocal of the intercept of the fitted line is the intrinsic electron transfer rate constant k. e (i.e., Equation 5). Equation (5) quantifies the intrinsic ability of a catalyst to mediate electron transfer. This is an index decoupled from reactant properties and matrix effects. This constant mathematically eliminates the influence of pollutant concentration variations on the reaction rate and represents the maximum electron transfer capacity of the catalyst's active sites under pollutant saturation conditions. It is independent of specific oxidant types, background water quality, or target pollutant structures, and is therefore an intrinsic, cross-system comparable descriptor of catalytic activity. This solves the problem of the traditional k... obs The fundamental flaw is that it depends on the test conditions and therefore cannot reflect the true performance of the catalyst.

[0029] 2. Auxiliary dynamic parameters (K) ec and ∑K i ×Q i Acquisition and application of ) K ec (Pollutant adsorption / reaction equilibrium constant): This value reflects the catalyst's affinity for the target pollutant. High K ecThis value indicates that the catalyst has a strong enrichment effect on specific pollutants. This parameter guides catalyst surface modification strategies (such as introducing Lewis acid sites) to improve selectivity for electron-rich pollutants.

[0030] ∑K i ×Q i (Background matrix interference coefficient): This value quantifies the competitive consumption effect of non-target components (such as anions and dissolved organic matter) on active species in the reaction system. This parameter can be used as a pretreatment decision threshold: when this value exceeds the preset threshold, it is recommended to add a coagulation or filtration pretreatment step before catalytic oxidation; at the same time, this value can be used to evaluate the stability of the catalyst in actual water bodies, the lower the value, the stronger the catalyst's resistance to interference.

[0031] 3. Regarding the determination of the effective electron transfer number: Two parallel experiments were conducted under identical reaction conditions: a test group containing the target contaminant and a blank control group without the contaminant. The oxidation reaction was terminated by periodic sampling and the use of a quencher (such as NaNO2 for persulfate (PMS / PDS) or catalase for H2O2). The consumption of the oxidant (PMS, PDS, or H2O2) in both reaction systems was determined using spectrophotometry (such as the iodide method or DPD method), high-performance liquid chromatography (HPLC), or fluorescence methods.

[0032] By calculating the oxidant consumption of the test group (Δ[oxi)) wt "Oxi" and "Oxidant consumption of the blank group (Δ[oxi])" wo The difference between "" and "" is used to exclude the self-decomposition of the oxidant and its non-productive consumption with the background matrix (such as natural organic matter and inorganic anions), thereby accurately obtaining the effective electron transfer amount for pollutant degradation (Formula 2). This is the fundamental step in achieving deconvolution of the intrinsic activity of the catalyst, ensuring that the accuracy of subsequent calculations is not affected by fluctuations in the water matrix.

[0033] Example 2

[0034] The method provided in Example 1 was verified, specifically including: 1. Using commercially available nano-Co3O4 as a catalyst, the degradation of 2,6-dichlorophenol (DCP) was tested in two systems: peroxymonosulfate (PMS) and peroxydisulfate (PDS), with ultrapure water and campus lake water as background solutions, respectively (see [link to relevant documentation]). Figure 2 (ab in the text). The results show that, under the six conditions of significant difference, the calculated k... e The relative standard deviation (RSD) of the value is less than 17%, while the traditional k... obs The value varies greatly (usually by several times). This confirms the k provided in the embodiments of the present invention. eThe index exhibits excellent cross-condition robustness, as shown in Table 1: Table 1 Experimental Results

[0035] aUW:ultrapure water;SW:surface water.V=20mL,m cat =0.1g, BET=24.2m2g -1 ,S cat =121m 2 L -1 ,[PMS]0=[PDS]0=1mM;[DCP]0=0.5,1.0,2.0,5.0,10.0mM.SolutionpH:7.0.e per,PMS =e per,PDS =2.Δt=10min. 2. A series of Fe-doped modified carbon nitride catalysts (Fe-CN-1, Fe-CN-2, Fe-CN-3, and pure CN) were prepared for PMS activation degradation of 2,6-dimethylphenol (DMP) (see [link to PMS]). Figure 2 (cd in the middle). XPS quantitative analysis of the surface Fe atomic percentage. The results showed that the Fe content was related to kJ / kJ. obs It showed only a weak positive correlation (R² < 0.7), while Fe content and k e A strong linear positive correlation is observed (R²>0.95). This result proves that the k proposed in this embodiment of the invention... e It can effectively eliminate external interference and establish a reliable quantitative structure-activity relationship (QSAR), providing a solid foundation for predicting catalyst performance and rational design. Specific results are shown in Table 2: Table 2 Experimental Results

[0036] a V =20mL, m cat =0.1g,[PMS]0=1mM;[DMP]0=0.5,1.0,2.0,5.0,10.0mM.

[0037] S catvaluesofCN,Fe-CN-1,Fe-CN-2,andFe-CN-3were104.5,12.5,9.5,and11.0,respectively.Solution pH:7.0.

[0038] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0039] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for evaluating catalyst activity in heterogeneous persulfate oxidation systems, characterized in that, Includes the following steps: S1: Identify the target oxide, target pollutant, and catalyst to be evaluated for the catalytic reaction, and use the target oxide, target pollutant, and catalyst to be evaluated to carry out the catalytic reaction; S2: Determines the amount of electrons transferred per unit time at each active site of the catalyst during the catalytic reaction; S3: Set multiple target pollutant concentrations, calculate the electron transfer amount corresponding to the multiple target pollutant concentrations and perform fitting, and determine the corresponding electron transfer efficiency index based on the fitting result; S4: The activity of the catalyst is evaluated using the electron transfer efficiency index.

2. The method for evaluating catalyst activity in a heterogeneous persulfate oxidation system according to claim 1, characterized in that, S2 includes: S21: Calculate the molar concentration of effective electron transfer based on the first molar concentration of the target oxide when the target pollutant is not added and the second molar concentration of the target oxide when the target pollutant is added; S22: Determine the amount of electron transfer for each active site based on the number of active sites per unit time and the molar concentration of effective electron transfer.

3. The method for evaluating catalyst activity in a heterogeneous persulfate oxidation system according to claim 2, characterized in that, S2 further includes: S23: The electron transfer amount is optimized using the BET surface area method.

4. The method for evaluating catalyst activity in a heterogeneous persulfate oxidation system according to claim 1, characterized in that, S3 includes: S31: Set multiple target pollutant concentrations and calculate the electron transfer amount corresponding to the multiple target pollutant concentrations; S32: Using the reciprocal of the target pollutant concentration and the reciprocal of the electron transfer amount, a linear fit is performed to obtain the corresponding fitted straight line; S33: The reciprocal of the slope of the fitted straight line is the electron transfer efficiency index.

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