阅读说明：本技术 一种电芬顿过程溶解性有机物在线定量的分析方法及系统 (Method and system for analyzing dissolved organic matters in electro-Fenton process in online quantitative manner ) 是由 黄梅珍 富雨超 李婉香 李昊宸 于 2021-07-08 设计创作，主要内容包括：本发明提供一种电芬顿过程溶解性有机物在线定量的分析方法及系统,包括：S1,在激发光波长的激发光条件下,建立激发光波长和水样中被测溶解性有机物的荧光特征波长处的接收光强与被测溶解性有机物的浓度关系的表达式：S2,基于S1表达式,对具体被测的含有铁干扰物的溶解性有机物建立分析模型,确定表达式中的待标定常数S3,待确定标定常数后,利用S2建立的分析模型实时计算出水样中的溶解性有机物的含量。本发明用于在线检测电芬顿过程中溶解性有机物含量,利用两个波长处的吸收光谱和荧光光谱信息,得到被测物浓度与两路光强之间的精确关系,消除了铁离子对光谱的影响,从而精确定量电芬顿过程中溶解性有机物的含量。(The invention provides an on-line quantitative analysis method and system for dissolved organic matters in an electro-Fenton process, which comprises the following steps: s1, under the condition of exciting light with exciting light wavelength, establishing an expression of the relation between the wavelength of the exciting light and the received light intensity at the fluorescence characteristic wavelength of the detected soluble organic matters in the water sample and the concentration of the detected soluble organic matters: and S2, establishing an analysis model for the specifically tested soluble organic matter containing the iron interferent based on the S1 expression, determining a constant S3 to be calibrated in the expression, and calculating the content of the soluble organic matter in the water sample in real time by using the analysis model established in S2 after the calibration constant is determined. The invention is used for detecting the content of the soluble organic matters in the electro-Fenton process on line, obtains the accurate relation between the concentration of the detected matter and the light intensity of two paths by utilizing the information of the absorption spectrum and the fluorescence spectrum at two wavelengths, eliminates the influence of iron ions on the spectrum, and accurately quantifies the content of the soluble organic matters in the electro-Fenton process.)

1. An on-line quantitative analysis method for dissolved organic matters in an electro-Fenton process is characterized by comprising the following steps: the method comprises the following steps:

s1, under the condition of excitation light with excitation light wavelength, establishing an expression (1) of the relation between the excitation light wavelength and the received light intensity at the fluorescence characteristic wavelength of the dissolved organic matter containing the iron interferent to be detected in the water sample and the concentration of the dissolved organic matter:

ln(k₂·c_Trp)+k₃·c_Trp＝k₁·A_λ1-B_λ2 (1)；

A_λ1＝-lnT_λ1，T_λ1＝I_λ1/I₀；

B_λ2＝-lnη_λ2，η_λ2＝I_λ2/I₀；

wherein λ is₁Is the wavelength of the excitation light, λ₂Is the fluorescence characteristic wavelength, I, of the dissolved organic matter containing the iron interferent to be detected₀Is the intensity of the excitation light, I_λ1Is to receive the light intensity of the original wavelength, I_λ2Is receiving the intensity of fluorescence, T_λ1Is a water sample pairTransmittance of excitation light, η_λ2Is the measured fluorescence conversion efficiency, c_TrpIs the concentration, k, of the dissolved organic matter to be measured containing the iron interferent_i(i ═ 1,2,3) is the constant to be calibrated;

s2, establishing an analysis model for the tested soluble organic matter containing the iron interferent based on the expression (1) of S1, and determining the constant k to be calibrated in the expression (1)_i(i＝1，2，3)；

S3, determining a calibration constant k_iAnd (i is 1,2 and 3), calculating the content of the dissolved organic matters containing the iron interferents to be detected in the water sample in real time by using the analysis model established in the S2.

2. The method for on-line quantitative analysis of dissolved organic compounds in electro-Fenton process according to claim 1, wherein S1, under the condition of excitation light with excitation light wavelength, establishes the expression (1) of the relationship between the wavelength of the excitation light and the received light intensity at the fluorescence characteristic wavelength of the dissolved organic compounds containing iron interferents to be detected in the water sample and the concentration of the dissolved organic compounds: wherein the content of the first and second substances,

analysis of dissolved organic concentration c by ultraviolet-visible spectrophotometry_TrpThe ultraviolet-visible spectrophotometry is based on Lambert beer law and analyzes to obtain the intensity of the received original wavelength light and the concentration c of the soluble organic matters at the excitation light wavelength_TrpThe relationship of (1);

analysis of dissolved organic matter concentration c by fluorescence quantitative analysis method_TrpAnalyzing to obtain the received light intensity at the fluorescence characteristic wavelength of the soluble organic matter and the concentration c of the soluble organic matter_TrpThe relationship between them.

3. The method for the on-line quantitative analysis of dissolved organic compounds in electro-Fenton process according to claim 1, wherein the S2 is based on the S1 expression (1) to build an analysis model for the dissolved organic compounds containing iron interferents to be tested, and the method comprises the following steps:

s21, establishing a plurality of groups of standard solution samples containing series gradient concentrations of random interferents, and determining the wavelength lambda of the excitation light₁And fluorescenceReceiving wavelength lambda₂And the concentration c of the standard solution is known_Trp(ii) a Obtaining the received light intensity I corresponding to a plurality of groups of standard solution samples with different series gradient concentrations mixed with random interferents through experiments_λ1And receiving the fluorescence intensity I_λ2；

S22, measuring a plurality of groups of standard solution samples, and respectively calculating and determining A_λ1And B_λ2And using the data as a training set;

s23, solving the nonlinear least square problem fitting expression (1) by using a Levenberg-Marquardt algorithm, thereby determining the parameter k in the expression S1_i(i＝1，2，3)。

4. The analytical method for the on-line quantification of dissolved organics in electro-Fenton process according to claim 3, wherein said S23, solving a non-linear least squares problem fitting expression (1) with 95% confidence level.

5. An on-line quantitative analysis system for dissolved organic matters in the electro-Fenton process, which is used in the on-line quantitative analysis method for dissolved organic matters in the electro-Fenton process according to any one of claims 1 to 4, so as to obtain the content of the dissolved organic matters in a water sample in real time.

6. The system for on-line quantitative analysis of dissolved organics in electro-Fenton process of claim 5, comprising:

an electro-Fenton reactor for generating H₂O₂And Fe²⁺Providing reactants for the electro-Fenton degradation process to degrade soluble organic matters in a water sample;

the control unit is used for conveying the water sample of the electro-Fenton reactor to the ultraviolet absorption-fluorescence online analyzer in real time;

an ultraviolet absorption-fluorescence online analyzer for measuring the received light intensity of the excitation light wavelengthI_λ1And the received light intensity I at the fluorescence characteristic wavelength of the dissolved organic matter containing the iron interferent to be detected_λ2。

7. The system for on-line quantitative analysis of dissolved organic compounds in electro-Fenton process according to claim 6, wherein the UV absorption-fluorescence on-line analyzer comprises:

the sample pool is used for storing a water sample;

the first light path is arranged on the first side of the sample cell and comprises a first narrow-band optical filter, a collimating lens and a diaphragm which are arranged from inside to outside in sequence;

the excitation light source is arranged on the outer side of the diaphragm and used for emitting excitation light, light emitted by the excitation light source passes through the diaphragm and then is converted into parallel light beams by the collimating lens, the parallel light beams vertically irradiate the water sample in the sample pool after passing through the first narrow-band light filter, and one part of light is absorbed by the water sample while the other part of light is transmitted;

the second light path is arranged on the second side of the sample cell and comprises a second narrow-band optical filter, a first focusing lens and a first photoelectric detector which are sequentially arranged from inside to outside, and after a part of transmission light transmitted from the sample cell passes through the second narrow-band optical filter, the transmission light is focused by the first focusing lens and is received by the first photoelectric detector to be converted into an electric signal;

and the third light path is sequentially provided with a third narrow-band optical filter, a second focusing lens and a second photoelectric detector from inside to outside, the soluble organic matters in the water sample are excited by the exciting light and then emit fluorescence to the periphery, the fluorescence in the direction vertical to the exciting light is collected, and the fluorescence in the direction passes through the third narrow-band optical filter and then is focused by the second focusing lens and received by the second photoelectric detector to be converted into an electric signal.

8. The system for the on-line quantitative analysis of dissolved organic matters in the electro-Fenton process according to claim 6, wherein an inert metal platinum sheet electrode is adopted as an anode of the electro-Fenton reactor, and a ferroferric oxide doped carbon felt electrode is adopted as a cathode of the electro-Fenton reactor.

9. The system for analyzing dissolved organic matters in the electro-Fenton process in an on-line quantitative manner according to claim 6, wherein a pH monitoring component is arranged in the electro-Fenton reactor and is used for monitoring the pH value in the reaction process in an on-line manner.

10. The system for on-line quantitative analysis of dissolved organic compounds in electro-Fenton process according to claim 6, wherein the stirring component in the electro-Fenton reactor is used for stirring and mixing the water sample.

Technical Field

The invention relates to the technical field of quantitative analysis, in particular to an on-line high-precision ultraviolet absorption-fluorescence dual-wavelength quantitative analysis method for soluble organic matters in an electro-Fenton process and a measurement control system for on-line monitoring of content change of the soluble organic matters in the electro-Fenton process.

Background

Electrochemical Advanced Oxidation Processes (EAOPs) are a green water treatment technology. No harm to environment, no need of excessive chemical reagents and no generation of harmful substances. The Fenton (Fenton) process is another Advanced Oxidation Process (AOP). It is one of the most widely used water treatment processes because of its potential and high efficiency for degrading most refractory organic pollutants. The electro-Fenton (EF) process combines the advantages of the electrochemical and Fenton processes. As a water treatment technology with high efficiency, environmental protection and low cost, the method is widely welcomed and has great attention in academia and industry.

The key to the electro-Fenton technique is the generation of hydroxyl radicals (HO.) as strong oxidizing agents. The hydroxyl free radical has no selective degradation capability on a plurality of complex Dissolved Organic Matters (DOM), so that the DOM is mineralized, and the water quality is purified. In the Fenton method, ferrous ions undergo a redox reaction with hydrogen peroxide to generate hydroxyl radicals (Eq (1)). In electrochemical processes, iron ions and hydrogen ions regenerate the desired reactant H at the cathode by electron transfer₂O₂And Fe²⁺。

H₂O₂+Fe²⁺+H⁺→Fe³⁺+H₂O+HO·

O₂+2H⁺+2e^-→H₂O₂

Fe³⁺+e-→Fe²⁺

In the electro-fenton process, it is generally necessary to add an iron salt externally to provide ferrous or ferric ions. Recent studies have demonstrated that ferrous or ferric ions can be provided by a carbon felt cathode doped with iron particles through a multi-step complex fiberization process, or by a cathode having iron oxide nanoparticles embedded in the carbon felt. Because the carbon felt cathode also has the characteristic of a porous structure, more catalyst active sites can be exposed, and the diffusion path of oxygen heterogeneous catalysis is increased. Therefore, the functional iron or iron oxide doped carbon felt electrode can further improve the degradation efficiency of the electro-fenton process.

In order to prevent iron loss due to iron precipitation during electro-fenton, instead of hydroxide ions forming complexes with ferrous or ferric ions, polyphosphoric acid derivatives such as Tripolyphosphate (TPP) are used as chelating agents. The tripolyphosphoric acid radical is taken as a ligand, so that the generation of hydroxyl active groups influenced by an organic chelating agent such as EDTA can be avoided, the efficiency of the electro-Fenton process is improved, and the reactivity of the complex ferrous ions and the complex ferric ions can be kept under the environment close to neutral pH.

Fe²⁺_TPP+O₂+H⁺→Fe³⁺_TPP+HO₂·

Fe²⁺_TPP+HO₂·+H⁺→Fe³⁺_TPP+H₂O₂

Fe²⁺_TPP+H⁺+H₂O₂→Fe³⁺_TPP+HO·+H₂O

The central goal in the electro-fenton process is to degrade the Dissolved Organics (DOM) in the water body. In order to monitor the concentration of dissolved organic substances in the electro-Fenton process, redox titration and reversed-phase high performance liquid chromatography are generally used. However, these methods are complicated and time-consuming to operate, require taking out a sample for measurement, and are not suitable for on-line efficient monitoring, so that non-destructive and efficient spectroscopic techniques are favored. The fluorescence spectrum technology of the three-dimensional Excitation Emission Matrix (EEM) is a technology for rapidly and sensitively analyzing dissolved organic matters and is commonly used for monitoring the change of the dissolved organic matters in water.

The technology has been successfully applied to characterization of organic matter in seawater, fresh water and estuary water. In addition, it is also used to monitor organic matter and diesel pollution in rivers, to evaluate drinking water treatment processes or to detect pesticides. However, in the fenton process, the presence of ferrous ions and complexes thereof, and ferric ions and complexes thereof can absorb excitation light and fluorescence of soluble organic matters to a certain extent. Therefore, in the process of monitoring the soluble organic matter of the soluble organic matter in the electro-Fenton process by adopting the spectrum technology, the iron-containing interferent can cause great errors to be generated in the measurement, and the measurement precision is influenced. The concentration of the dissolved organic substances cannot be accurately quantified by the widely adopted ultraviolet absorption method and fluorescence analysis method.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide an on-line quantitative analysis method and system for soluble organic matters in an electro-Fenton process.

The invention provides an on-line quantitative analysis method for dissolved organic matters in an electro-Fenton process, which comprises the following steps: the method comprises the following steps:

s1, under the condition of excitation light with excitation light wavelength, establishing an expression (1) of the relation between the excitation light wavelength and the received light intensity at the fluorescence characteristic wavelength of the dissolved organic matter containing the iron interferent to be detected in the water sample and the concentration of the dissolved organic matter:

ln(k₂·c_Trp)+k₃·c_Trp＝k₁·A_λ1-B_λ2 (1)；

A_λ1＝-ln T_λ1，T_λ1＝I_λ1/I₀；

B_λ2＝-ln η_λ2，η_λ2＝I_λ2/I₀；

wherein λ is₁Is the wavelength of the excitation light, λ₂Is the fluorescence characteristic wavelength, I, of the dissolved organic matter containing the iron interferent to be detected₀Is the intensity of the excitation light, I_λ1Is to receive the light intensity of the original wavelength, I_λ2Is receiving the intensity of fluorescence, T_λ1Is the transmittance, eta, of a water sample to the exciting light_λ2Is the measured fluorescence conversion efficiency, c_TrpIs the concentration, k, of the dissolved organic matter to be measured containing the iron interferent_i(i ═ 1,2,3) is the constant to be calibrated;

s2, establishing an analysis model for the tested soluble organic matter containing the iron interferent based on the expression (1) of S1, and determining the expression (1)Constant k to be calibrated_i(i＝1,2,3)；

S3, determining a calibration constant k_iAnd (i is 1,2 and 3), calculating the content of the dissolved organic matters containing the iron interferents to be detected in the water sample in real time by using the analysis model established in the S2.

Preferably, in S1, the expression (1) for the relationship between the wavelength of the excitation light and the received light intensity at the fluorescence characteristic wavelength of the dissolved organic substance containing the iron interferent to be detected in the water sample and the concentration of the dissolved organic substance is established: wherein the content of the first and second substances,

analysis of dissolved organic concentration c by ultraviolet-visible spectrophotometry_TrpThe ultraviolet-visible spectrophotometry is based on Lambert beer law and analyzes to obtain the intensity of the received original wavelength light and the concentration c of the soluble organic matters at the excitation light wavelength_TrpThe relationship of (1);

analysis of dissolved organic matter concentration c by fluorescence quantitative analysis method_TrpAnalyzing to obtain the received light intensity at the fluorescence characteristic wavelength of the soluble organic matter and the concentration c of the soluble organic matter_TrpThe relationship between them.

Preferably, the S2, based on the expression (1) of S1, establishes an analysis model for the dissolved organic matter containing random interference, and specifically includes the following steps:

s21, establishing a plurality of groups of standard solution samples containing series gradient concentrations of random interferents, and determining the wavelength lambda of the excitation light₁And fluorescence reception wavelength lambda₂And the concentration c of the standard solution is known_Trp(ii) a Obtaining the received light intensity I corresponding to a plurality of groups of standard solution samples with different series gradient concentrations mixed with random interferents through experiments_λ1And receiving the fluorescence intensity I_λ2；

S22, measuring a plurality of groups of standard solution samples, and respectively calculating and determining A_λ1And B_λ2And using the data as a training set;

s23, solving the nonlinear least square problem fitting expression (1) by using a Levenberg-Marquardt algorithm, thereby determining the parameter k in the expression S1_i(i＝1,2,3)。

Preferably, at S23 above, the non-linear least squares problem is solved to fit expression (1), with a 95% confidence level.

The Levenberg-Marquardt algorithm integrates a steepest descent method and a Taylor series linearization method, and obtains a search direction by solving an optimization model; the optimization model is as follows:

wherein d is_kIn order to search for the direction(s),is n-dimensional real number field, J_kIs a Jacobian matrix, r_kTo believe Domain radius, μ_kFor the damping parameter, h is the step size.

The second aspect of the invention provides an online quantitative analysis system for dissolved organic matters in the electro-Fenton process, which is used in the online quantitative analysis method for dissolved organic matters in the electro-Fenton process to obtain the content of the dissolved organic matters in a water sample in real time.

Preferably, an analytical system for on-line quantification of dissolved organic compounds in electro-fenton process comprises:

an electro-Fenton reactor for generating H₂O₂And Fe²⁺Providing reactants for the electro-Fenton degradation process to degrade soluble organic matters in a water sample;

the control unit is used for conveying the water sample of the electro-Fenton reactor to the ultraviolet absorption-fluorescence online analyzer in real time;

an ultraviolet absorption-fluorescence online analyzer for measuring the received light intensity I of the excitation light wavelength_λ1And the received light intensity I at the fluorescence characteristic wavelength of the dissolved organic matter containing the iron interferent to be detected_λ2。

Preferably, the ultraviolet absorption-fluorescence online analyzer includes:

the sample pool is used for storing a water sample;

the first light path is arranged on the first side of the sample cell and comprises a first narrow-band optical filter, a collimating lens and a diaphragm which are arranged from inside to outside in sequence;

the excitation light source is arranged on the outer side of the diaphragm and used for emitting excitation light, light emitted by the excitation light source passes through the diaphragm and then is converted into parallel light beams by the collimating lens, the parallel light beams vertically irradiate the water sample in the sample pool after passing through the first narrow-band light filter, and one part of light is absorbed by the water sample while the other part of light is transmitted;

the second light path is arranged on the second side of the sample cell and comprises a second narrow-band optical filter, a first focusing lens and a first photoelectric detector which are sequentially arranged from inside to outside, and after a part of transmission light transmitted from the sample cell passes through the second narrow-band optical filter, the transmission light is focused by the first focusing lens and is received by the first photoelectric detector to be converted into an electric signal;

and the third light path is sequentially provided with a third narrow-band optical filter, a second focusing lens and a second photoelectric detector from inside to outside, the soluble organic matters in the water sample are excited by the exciting light and then emit fluorescence to the periphery, the fluorescence in the direction vertical to the exciting light is collected, and the fluorescence in the direction passes through the third narrow-band optical filter and then is focused by the second focusing lens and received by the second photoelectric detector to be converted into an electric signal.

Preferably, the wavelength of the excitation light source and the detection wavelength are determined according to the absorption spectrum of various substances in the water body in the electro-Fenton process and the fluorescence emission spectrum of the detected soluble organic matters. By measuring tryptophan and Fe²⁺、Fe³⁺、STPP、Fe²⁺_TPP、Fe³⁺Absorption spectra of TPP (see FIG. 1), taken together with the consideration that tryptophan is a protein-like soluble organic substance at λ₁λ can be emitted under 270nm ultraviolet light irradiation_Em<38, and an iron-containing interfering substance at λ₂315nm attached toApproximately have similar molar extinction coefficients, so preferably λ is used₁270nm and λ₂315nm is the probe wavelength.

Preferably, the excitation light source is an LED light source, the LED light source is driven by a constant current source, the LED light source keeps stable irradiation, and the effective radiation power is 2 mW. And a 270nm light source is collimated and then parallelly emitted into the water sample to be detected. Parallel light emitted in the original direction is filtered and focused by a 270nm narrow-band filter and then received by a photoelectric detector to measure lambda₁Light intensity signal I at 270nm_λ1. The tryptophan photoluminescence, the fluorescence radiates to all directions, the part vertical to the exciting light is filtered by a 315nm narrow-band filter and focused and then received by another photoelectric detector, and the lambda is measured₂Fluorescence emission intensity signal at 315nm_λ2。

Preferably, the anode of the electro-Fenton reactor adopts an inert metal platinum sheet electrode, and the cathode of the electro-Fenton reactor adopts a carbon felt electrode doped with ferroferric oxide.

Preferably, a pH monitoring part is arranged in the electro-fenton reactor, and the pH monitoring part is used for monitoring the pH value in the reaction process on line.

Preferably, the stirring component in the electro-Fenton reactor is used for stirring and mixing the water sample.

The analysis method comprehensively utilizes the information of the absorption spectrum and the fluorescence spectrum at the two wavelengths, obtains the accurate relation between the concentration of the measured object and the light intensity of the two paths by deduction, eliminates the influence of iron ions on the spectrum, and accurately quantifies the content of the soluble organic matters in the electro-Fenton process. Meanwhile, a prototype model machine of the ultraviolet absorption-fluorescence sensor is designed, the design structure is simple and light, and the method is suitable for detecting the content of soluble organic matters in the electro-Fenton process on line. The experiment takes tryptophan as an example, and researches for on-line high-precision monitoring of the content change of the tryptophan in the electro-Fenton process are carried out by utilizing the established concentration relation between the received light intensity with double wavelengths and the detected soluble organic matter (namely the detected soluble organic matter containing iron interferents).

Compared with the prior art, the invention has at least one of the following beneficial effects:

the analysis method establishes an analysis model of the relation between the received light intensity at the double wavelength and the concentration of the detected soluble organic matter based on the comprehensive consideration of the absorption spectrum and the fluorescence emission of the soluble organic matter and the absorption spectrum of the iron-containing interferent in the Fenton process, and can strictly prove that the concentration of the soluble organic matter is accurately quantified in the environment containing the iron-containing interferent through the established analysis model.

The analysis method of the invention provides an on-line high-precision ultraviolet absorption-fluorescence dual-wavelength quantitative analysis method aiming at the difficult problem of the quantification of the soluble organic matter due to the existence of the iron-containing interferent in the electro-Fenton process, can be suitable for providing on-line high-precision monitoring of the soluble organic matter in the electro-Fenton process, and can also be suitable for similar situations of interference on both excitation light and fluorescence.

The system of the invention can realize the wavelength (lambda) of the excitation light₁270nm) and fluorescence characteristic wavelength (λ) of dissolved organic matter₂315nm) to provide the related measurement data for the above ultraviolet absorption-fluorescence dual wavelength quantitative analysis method.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 shows Tryptophan and Fe in a preferred embodiment of the present invention²⁺、Fe³⁺、STPP、Fe²⁺_TPP、Fe³⁺Absorption spectrum of TPP;

FIG. 2 is a schematic view showing the internal structure of an ultraviolet absorption-fluorescence on-line analyzer according to a preferred embodiment of the present invention;

FIG. 3 is a result of a quantitative regression of a standard solution using an analytical method for the on-line quantification of dissolved organics in the electro-Fenton process in the presence of a random concentration of an iron-containing interferent in accordance with a preferred embodiment of the present invention;

FIG. 4 is a diagram illustrating the on-line monitoring of dissolved organic compounds in the electro-Fenton process by using the UV absorbance method, the fluorescence quantitative analysis method, and the UV absorption-fluorescence dual-wavelength quantitative analysis method according to a preferred embodiment of the present invention;

FIG. 5 is a table 1 showing the composition of each set of measured standard solutions according to a preferred embodiment of the present invention.

The scores in the figure are indicated as: the device comprises an excitation light source 1, a diaphragm 2, a collimating lens 3, a first narrow-band filter 4, a third narrow-band filter 5, a second focusing lens 6, a second photoelectric detector 7, a second narrow-band filter 8, a first focusing lens 9, a first photoelectric detector 10 and a sample cell 11.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.

The embodiment provides an online quantitative analysis method for soluble organic matters in an electro-Fenton process, which is used for solving the problem that the soluble organic matters are difficult to quantify due to the existence of iron-containing interferents in the electro-Fenton process, can be suitable for providing online high-precision monitoring for the soluble organic matters in the electro-Fenton process, and can also be suitable for similar situations of interference on excitation light and fluorescence at the same time.

The method for analyzing the dissolved organic matters in the electro-Fenton process in an online quantitative mode comprises the following steps: the method comprises the following steps:

s1: at a single wavelength λ₁An expression for establishing a relationship between the received light intensity at two wavelengths and the concentration of a soluble organic substance containing an iron interfering substance to be measured (hereinafter, simply referred to as a soluble organic substance to be measured) under an excitation light condition is as follows:

ln(k₂·c_Trp)+k₃·c_Trp＝k₁·A_λ1-B_λ2 (1)；

A_λ1＝-lnT_λ1,T_λ1＝I_λ1/I₀；

B_λ2＝-lnη_λ2,η_λ2＝I_λ2/I₀；

wherein λ is₁Is the wavelength of the excitation light, λ₂Is the fluorescence characteristic wavelength, I, of the dissolved organic matter containing the iron interferent to be detected₀Is the intensity of the excitation light, I_λ1Is to receive the light intensity of the original wavelength, I_λ2Is receiving the intensity of fluorescence, T_λ1Is the transmittance, eta, of a water sample to the exciting light_λ2Is the measured fluorescence conversion efficiency, c_TrpIs the concentration, k, of dissolved organic matter to be measured containing iron interference_i(i ═ 1,2,3) are the instrument constants to be calibrated, in this example tryptophan.

In this step, a solution (e.g., a solution in a cuvette) of a certain volume is used as a research object, and the lambert beer theorem and a fluorescence quantitative analysis method are integrated, and light absorption in two aspects is considered:

the first aspect is: the excitation light is absorbed by the soluble organic and ferrous interfering substances. The second aspect is photoluminescence of soluble organic substances, and the emitted fluorescence is absorbed by the iron-containing interfering substance.

Assuming that a sample cell is filled with a water sample containing a certain concentration of soluble organic matters containing iron-containing interfering substances with random concentration, a parallel excitation light beam passes through the sample cell along a straight line direction, and the derivation calculation is carried out on the sample cell at a single wavelength lambda₁Receiving the light intensity I of the original wavelength under the condition of exciting light_λ1And receiving the fluorescence intensity I_λ2The above expression of the relationship with the concentration of the dissolved organic matter. Accurately reflects the intensity I of the received original wavelength light through the expression_λ1And receiving the fluorescence intensity I_λ2And the concentration of dissolved organic matter.

The analysis of the concentration of dissolved organic compounds by UV-Vis spectrophotometry is based on Lambert beer's law. Assuming that the concentration of the soluble organic matter in the water body is c_TrpAccording to lambert beer's law:

c_Trp＝ζ₁·A_λ1

therein, ζ₁Is an instrument constant to be calibrated and is calibrated by a standard solution. T is_λ1Is the transmittance of the measured water at the wavelength of the excitation light, i.e. T_λ1Is equal to T_λ1Divided by the reference incident light intensity I₀. Reference incident light intensity I₀Is detected by detecting lambda when the water sample is pure water₁Measured by the detector of (1).

The fluorescence quantitative analysis method is characterized in that different kinds of soluble organic matters can radiate fluorescence with specific wavelength under the irradiation of ultraviolet light with specific wavelength. To eliminate the influence of light source fluctuations on the measurement, the fluorescence conversion efficiency η is defined_λ2，η_λ2Equal to the fluorescence emission intensity I_λ2Divided by the reference incident light intensity I₀. When the concentration of the soluble organic matter is analyzed by a quantitative fluorescence analysis method, the soluble organic matter c_TrpConversion efficiency eta with fluorescence in a certain concentration range_λ2Is in direct proportion. Order:

the fluorescence quantification method can be written as:

ln(ζ₂·c_Trp)＝-B_λ2

wherein ζ₂And is also an instrument constant to be calibrated, and is calibrated by a standard solution.

S2: modeling analytical data using standard solutions of known reference concentrations to determine k for the expression of S1_i(i＝1,2,3)；

Based on the expression (1), an analysis model is established for the specific tested dissolved organic matter containing random interference, and the specific method is as follows:

firstly, establishing a series of gradient concentration samples mixed with random iron-containing interferents to be detected, and determining the wavelength lambda of excitation light₁And fluorescence reception wavelength lambda₂Concentration c of these standard solutions_TrpAre known. For example: the typical solubility organic matter tryptophan represents the solventAnd (4) degrading organic matters, and measuring the concentration of a standard solution and the concentration of the electro-Fenton degradation process. The wavelength of the excitation light source and the detection wavelength are determined according to the absorption spectrum of various substances in the water body in the electro-Fenton process and the fluorescence emission spectrum of the detected soluble organic matters. Referring to FIG. 1, tryptophan and Fe were measured²⁺、Fe³⁺、STPP、Fe²⁺_TPP、Fe³⁺Absorption spectrum of TPP, taking into account that tryptophan is a protein-like soluble organic substance, at lambda₁λ can be emitted under 270nm ultraviolet light irradiation_Em<38, and an iron-containing interfering substance at λ₂Around 315nm, a molar extinction coefficient close to that of λ is preferably used₁270nm and λ₂315nm is the probe wavelength. Obtaining the corresponding received light intensity I of the series of tryptophan solutions with gradient concentration of different mixed random iron-containing interferents through experiments_λ1And receiving the fluorescence intensity I_λ2Measuring the batch of standard solution by using a soluble organic matter ultraviolet absorption-fluorescence online analyzer, and respectively calculating and determining A_λ1And B_λ2These data are used as a training set.

Then, the least square method and the Levenberg-Marquardt algorithm are adopted to carry out optimization fitting, so as to determine the parameter k in the formula (1)_i(i＝1,2,3)。

The Levenberg-Marquardt algorithm integrates the steepest descent method and the Taylor series linearization method, and solves the problem Optimizing the model and obtaining the search direction.

Therefore, an analysis model of the relation between the light intensity of the received original wavelength and the concentration of the detected soluble organic matter at the double wavelengths is established. This analytical model works over a wide range of concentrations and constants therein are consistent experimentally and can be determined.

The above-described absorbance-fluorescence quantitative analysis in the specific measurement includes: measuringMeasuring absorbance while measuring fluorescence, while measuring A_λ1And B_λ2Establishing and dissolving organic concentration c_TrpThe influence of the iron-containing interferents on the fluorescence spectrum can be effectively eliminated by the quantitative relation. Specifically, when analyzing the concentration of a soluble organic substance by using a nondestructive and efficient spectroscopy, the conventional common methods include an ultraviolet-visible spectrophotometry and a fluorescence quantitative analysis. However, because the iron interferents absorb exciting light and also absorb fluorescence emitted by soluble organic matters, the influence of the iron interferents cannot be eliminated only by an ultraviolet-visible spectrophotometry method or a fluorescence quantitative analysis method, and the absorption parts of the spectrum of the iron interferents are removed by selecting absorption and fluorescence information at two wavelengths through comprehensive analysis, so that an accurate quantitative relation is obtained.

S3: receive the original wavelength light intensity I based on the above_λ1And receiving the fluorescence intensity I_λ2And the concentration of the dissolved organic matters, and the analysis model is applied to online high-precision quantitative monitoring of the dissolved organic matters in the electro-Fenton degradation process.

In another aspect, the present invention provides an online quantitative analysis system for dissolved organic compounds in an electro-fenton process, and the system is used in the online quantitative analysis method for dissolved organic compounds in an electro-fenton process to obtain the content of the dissolved organic compounds in a water sample in real time.

The on-line quantitative analysis system for dissolved organic matters in the electro-Fenton process comprises: an electro-Fenton reactor, a control unit and an ultraviolet absorption-fluorescence online analyzer.

Wherein the electro-Fenton reactor generates H by utilizing an electrochemical mechanism₂O₂And Fe²⁺And a reactant is provided for the electro-Fenton degradation process, and the degradation of soluble organic matters in a water sample is realized. The electrolysis is carried out with the current density kept constant. The effective volume of the reaction cell of the electro-Fenton reactor is 500 mL. Oxygen was pumped into the reaction cell at an average flow rate of 600mL/min using a small air pump. As a preferable mode, a pH meter probe is arranged in the electro-Fenton reactor to monitor the pH value in the reaction process on line. In an electro-Fenton reactorThe bottom of which is provided with a mechanical mixing device.

The control unit is used for conveying the water sample of the electro-Fenton reactor to the ultraviolet absorption-fluorescence online analyzer in real time.

The ultraviolet absorption-fluorescence on-line analyzer is used for measuring a water sample and measuring the received light intensity I of the wavelength of excitation light_λ1And the received light intensity I at the fluorescence characteristic wavelength of the detected dissolved organic matter_λ2. In a preferred embodiment, in order to better realize the simultaneous measurement of fluorescence intensity and absorbance, the structure diagram of the ultraviolet absorption-fluorescence online analyzer is shown in fig. 2. The method comprises the following steps: the sample pool 11 is used for storing a water sample; the first light path is arranged on the first side of the sample cell 11 and comprises a first narrow-band optical filter 4, a collimating lens 3 and a diaphragm 2 which are arranged in sequence from inside to outside; the device comprises an excitation light source 1, a collimating lens 3 and a first narrow-band optical filter 4, wherein light emitted by the excitation light source 1 passes through a diaphragm 2 and then is converted into parallel light beams by the collimating lens 3, the parallel light beams vertically irradiate a water sample in a sample cell 11 after passing through the first narrow-band optical filter 4, one part of the light is absorbed by the water sample, and the other part of the light is transmitted; the second optical path is arranged on the second side of the sample cell 11, the second optical path comprises a second narrow-band filter 8, a first focusing lens 9 and a first photoelectric detector 10 which are arranged in sequence from inside to outside, and after a part of transmission light transmitted from the sample cell 11 passes through the second narrow-band filter 8, the transmission light is focused by the first focusing lens 9 and is received by the first photoelectric detector 10 to be converted into an electric signal; the third light path is arranged on the third side of the sample cell 11, the third pipeline is perpendicular to the first pipeline, the third light path is sequentially provided with a third narrow-band optical filter 5, a second focusing lens 6 and a second photoelectric detector 7 from inside to outside, soluble organic matters in the water sample are excited by the exciting light and then emit fluorescence to the periphery, the direction perpendicular to the exciting light is selected for collecting the fluorescence, and the fluorescence in the direction passes through the third narrow-band optical filter 5, is focused by the second focusing lens 6 and is received by the second photoelectric detector 7 and converted into an electric signal. And the measured parameters are used for the ultraviolet absorption-fluorescence dual-wavelength quantitative analysis method.

In specific implementation, the electro-Fenton degradation process is carried out in an electro-Fenton reactor to degrade soluble organic matters in a water sample. The water matrix for experiment is obtained from ShanghaiThe water source of the remote lake in the school of the university of transportation mainly comes from natural rainfall and seepage, and the lake has abundant species diversity. After the water matrix is filtered by 0.45 mu m glass fiber filter paper, the turbidity is about 3NTU, and the method can be used for experiments. And feeding the water sample in the degradation process into a dissolved organic matter ultraviolet absorption-fluorescence online analyzer in real time for online analysis. From measured intensity of received primary wavelength light I_λ1And receiving the fluorescence intensity I_λ2And calculating the content of the soluble organic matters in the water sample in real time by combining the established model of the concentration relation between the light intensity of the received original wavelength at the double wavelengths and the detected soluble organic matters.

In order to better illustrate the method for analyzing the dissolved organic compounds in the electro-fenton process on-line and quantitatively, the following description is provided with specific application examples to understand the details of the implementation, but it should be understood that the following application examples are not intended to limit the invention.

In this application example, an online quantitative analysis method for dissolved organic matters in an electro-fenton process includes: the method comprises the following steps:

firstly, a dual-wavelength analysis system for online quantification of soluble organic matters in the electro-Fenton process is built.

The configuration of the fluorescence measuring system used in this step is shown in FIG. 2. In order to measure the concentration of tryptophan, the specific structure parameter selection and measurement process of the online ultraviolet absorption-fluorescence analyzer system for the soluble organic matters comprises the following steps:

1) the excitation light source 1 adopts a 270nm ultraviolet LED, and 270nm excitation light is a common excitation light source 1 for dissolved organic matters, and can excite tryptophan to generate 340 +/-40 nm fluorescence.

2) Ultraviolet light emitted by an excitation light source 1 passes through a circular diaphragm 2 with the aperture phi of 5mm and is collimated by a plano-convex lens 3, and the ultraviolet light becomes a parallel Gaussian beam serving as an excitation beam.

3) The effective luminous power of the LED light source is 2 mW.

4) A tetrahedral light quartz cuvette with an optical path length L of 10mm is selected as the sample cell 11 for containing the tryptophan solution.

5) Before incidence, the exciting light passes through the first narrow-band filter 4, and the central wavelength of the first narrow-band filter 4 is 270nm, so that the exciting light is purer monochromatic light.

6) The second narrowband filter 8 in the emitting direction of the exciting light is also a narrowband filter with the center wavelength of 270nm and is used for filtering fluorescence generated in a water sample.

7) The intensity of light I received by the first photodetector 10_λ1The absorbance A of the tryptophan solution can be calculated_λ1。

8) And a third narrow-band filter 5 is arranged on a fluorescence receiving optical path vertical to the exciting light direction, and the third narrow-band filter 5 is a narrow-band filter with the central wavelength of 315nm and used for filtering scattered exciting light.

9) A first condensing lens 9 and a second condensing lens 6 (plano-convex lens) for condensing light.

10) The third photodetector 7 is used for receiving the fluorescence intensity I_λ2The parameter B can be calculated_λ2。

Secondly, in order to determine parameters in a relation model between the light intensity of the receiving original wavelength at the two wavelengths of the tryptophan solution and the concentration of the detected soluble organic matter, the following operations are carried out:

1) 17 sets of tryptophan solutions containing random iron interference with different concentration gradients for modeling were prepared, 10 samples were prepared for each concentration, and as standard solutions, iron-containing interferents were randomly mixed into the individual standard solutions.

2)170 samples were randomly divided into a training set and a test set, which were used to test whether the parameterized models had the ability to generalize and the instrument's ability to react to the iron-containing interfering tryptophan fluorescent chromophore.

3) The composition configuration of the standard solution measured in each group is shown in table 1 of fig. 5.

4) All sample solutions were contained in 15mL reagent tubes and analyzed after 48 hours of storage at 4 ℃ in the dark.

5) After 48 hours, the test solution was allowed to be brought to 25 ℃ in a dark thermostated chamber and subsequently transferred to a quartz cuvette for analytical testing.

6) And (4) washing the quartz cuvette five times by using deionized water after the test of each sample is finished, and adding the next group of samples for testing after the water in the quartz cuvette is volatilized.

7) The test time for each sample was guaranteed to be within 1min to reduce the effect of fluorescence bleaching on the measurements.

And thirdly, preprocessing the original data obtained by testing as follows.

1) The baseline of the photodetector produced by the drift of the electrical signal and the dark current during the measurement is removed, ensuring that the spectra at each time have the same base.

2) Removing the measurement data containing the gross error according to Laplace criterion, wherein the Laplace criterion is expressed as the following formula: (b ═ 1,2, …, n). In the formula, x_b∈{x_II ∈ 1,2, …, n } represents one sample data in each concentration;represents the arithmetic mean of the samples; | v_b| represents the absolute value of the residual error; σ is the standard deviation calculated by Bessel's equation. Consider x if the sample satisfies the above equation_bBad values with large error values should be eliminated.

Analysis of the results of the above application examples:

17 sets of different concentration gradients of tryptophan solutions containing random iron interference were measured, each set containing 10 samples.

Received intensity I measured from these concentration gradient solutions_λ1And I_λ2For the change of the tryptophan concentration in the sample, a relation between the received original wavelength light intensity at the two wavelengths and the concentration of the detected soluble organic matters can be used for fitting.

For the same excitation light source, the same fluorescence receiving range and the same detector integration time, the expression (1) given by the relational expression of the light intensity of the receiving original wavelength at the double wavelengths and the concentration of the detected soluble organic matters is well fitted to experimental data.

The maximum number of iterations for the optimized fit using the Levenberg-Marquardt algorithm at 95% confidence limits was 1000 rounds over the tryptophan concentration range of 1.2-10 mg/L.

Referring to FIG. 3, the UV absorption-fluorescence dual wavelength analysis method can quantify the tryptophan concentration under random interference with high precision, and the quantitative analysis linear regression result of the analytical expression (1) on the prediction set reaches R²0.9942. Compared with the common ultraviolet visible spectrophotometry and fluorescence quantitative analysis method, the quantitative analysis result of the ultraviolet absorption-fluorescence dual-wavelength analysis method is obviously better. The analytical expression (1) of the ultraviolet absorption-fluorescence dual-wavelength analysis method can also be used in scenes with interference in similar fluorescence quantitative analysis.

The results of on-line monitoring of tryptophan concentration for the actual electro-fenton degradation process are shown in fig. 4. By Fe₃O₄The nano particles are embedded into the carbon felt electrode, provide an iron source for the electro-Fenton process, and are made of Fe with rich cracks₃O₄And abundant active centers are provided in the embedded structure, so that the rate of electro-Fenton degradation reaction is improved.

The results of on-line monitoring of the electro-fenton degradation reaction using uv-vis spectrophotometry, a quantitative fluorescence analysis method, and a uv absorption-fluorescence dual wavelength analysis method are shown in fig. 4. Initial concentration of tryptophan is C_Trp0Initial pH was 4.7 at 3.5 mg/L. Recording the concentration C on-line monitoring once every 5min_Trp. The degradation of tryptophan by the electro-Fenton method follows the kinetics of a pseudo-first order chemical reaction with an apparent rate constant k_app＝(4.496±0.150)×10^-2min^-1(shown in solid lines in FIG. 4).

And the data points of the square data points and the circular data points are respectively the prediction results of the online monitoring of the ultraviolet-visible spectrophotometry and the fluorescence quantitative analysis method. The concentration of tryptophan cannot be quantitatively analyzed completely by ultraviolet-visible spectrophotometry under the influence of iron-containing interferents with variations, and the tryptophan can be roughly monitored by the fluorescent quantitative analysis methodThe degradation trend is not accurate and quantitative. The ultraviolet absorption-fluorescence dual-wavelength analysis method provided by the invention is a triangular data point in a graph, and linear fitting goodness R can be achieved after the negative logarithm is taken on the ordinate of the triangular data point²0.9882, the root mean square error RMSE of the online monitoring is 0.0131mg/L, and the monitoring precision is high.

During this on-line monitoring, Fe was also demonstrated₃O₄The nano particles are embedded into the carbon felt electrode to change the iron content in the water body, and simultaneously, the Fe is proved from another angle²⁺The TPP complexes contribute to the degradation of tryptophan.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.