Method for directly measuring concentration of high-concentration target species in flowing liquid

Abstract

Disclosed in the present invention is a method for directly measuring the concentration of a high-concentration target species in a flowing liquid. The method comprises the steps of: measuring a qualitative optical path and a quantitative optical path of a target species, and constructing a wavelength-concentration model and an algorithm, wherein a luminosity signal and the concentration of the target species in a liquid can be measured in real time in wavelength regions of ultraviolet visible light and near-infrared light. During operation, a liquid flows through a device; according to a qualitative optical path, the type of a target species is determined; according to a quantitative optical path, a rational high absorbance is maintained, and the wavelength of the liquid is measured; and the concentration of the target species is thus calculated, such that the original valence state, original form, original phase state and concentration of a high-concentration target species in a flowing liquid are measured within 10 seconds without adding a chemical agent or diluting a solution.

Description

A method for directly measuring the concentration of high-concentration target species in flowing liquids Technical Field

[0001] The present invention relates to the technical field of chemical analysis and environmental protection, and in particular to a method for directly measuring the concentration of high-concentration target species in flowing liquid. Background Art

[0002] Process industries often involve complex chemical reactions, with significant linkages between upstream and downstream units. Resource conversion and pollution production depend on the progress and efficiency of the reactions. The ability to monitor and control the valence, morphology, phase, and concentration of species in liquid systems in real-time determines the efficiency of resource conversion, the total amount of pollution produced, and its toxicity. Real-time monitoring of the valence, morphology, phase, and concentration of species in complex industrial liquids is crucial for process control. However, due to the complexity of industrial liquids, which often involve the coexistence of multiple phases and components, and the wide range and rapid changes in concentration, existing monitoring methods are generally based on the Lambert-Beer linear law. This often requires complex pretreatment of the solution before detection, such as the addition of multiple chemicals and large dilutions. This can easily lead to secondary contamination, sample preparation errors, and prolonged analysis times. In most cases, analyzing high-concentration solutions in industrial plants using existing domestic and international equipment takes 3-4 hours, and can even cause changes in the target species. This makes it impossible to quickly and directly determine the original valence, morphology, phase, and concentration of the target species in the high-concentration range, making it unsuitable for real-time guidance of industrial process control. The existing technology urgently needs a method for rapid and direct measurement of microscopic chemical information such as the valence, morphology, phase state and concentration of species in high-concentration industrial liquids.

[0003] Therefore, the existing technology still needs to be improved and developed.

[0004] Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a method and equipment for directly measuring the concentration of high-concentration target species in flowing liquids, aiming to solve the problem that the prior art cannot quickly and directly measure the original valence, original form, original phase and concentration of target species in a high concentration range.

[0006] The technical solutions of the present invention are as follows:

[0007] A method for directly measuring the concentration of a high-concentration target species in a flowing liquid, comprising the steps of:

[0008] Take the flowing liquid containing different concentrations of the target as the sample, measure the absorbance curve of the sample in the ultraviolet visible light and near infrared light range, and obtain the characteristic wavelength corresponding to the sharp peak with the highest absorbance in the absorbance curve as the qualitative wavelength λ qual , and its corresponding optical path is taken as the qualitative optical path b qual ;

[0009] Prepare solution samples of different concentrations according to the actual concentration range of the flowing liquid, scan the absorbance of the solution samples in the ultraviolet-visible light and near-infrared light wavelength range using different optical pathlengths in turn, and produce absorption spectra of the solution samples at each optical pathlength;

[0010] In the absorption spectrum of the solution sample, an adapted absorbance point is selected on the Abs axis, and a straight line parallel to the λ axis is drawn from the absorbance point so that it intersects all spectral curves on the relevant side of the target species at (λ, Abs). At this time, the straight line parallel to the λ axis is the adapted absorbance line;

[0011] Setting screening conditions for the quantitative optical pathlength, and screening to obtain the quantitative optical pathlength based on the adapted absorbance line and the absorption spectrum;

[0012] Observe the changing pattern of characteristic wavelength and spectral curve shape corresponding to different concentrations of target species in actual flowing liquid under qualitative optical path, and compare it with the qualitative wavelength λ measured in static samples with different concentrations of actual liquid target species. qual The qualitative wavelength λ is determined by comparing the changing pattern of the spectral curve shape with the target species at different concentrations under the actual flowing liquid condition. qual f The position and curve shape of

[0013] Obtain quantitative pathlength from the lowest concentration to the highest concentration C in actual flowing liquid conditions j Wavelength λ corresponding to different concentrations within the range j , according to the quantitative optical path (C j， λ j ), make a concentration-wavelength curve with C as the horizontal axis value and λ as the vertical axis value;

[0014] The concentration-wavelength curve is further divided into piecewise linear curves according to statistical indicators, and a piecewise linear function of C=f(λ) is obtained by piecewise linear fitting, that is, a wavelength-concentration method model that meets the requirements is obtained;

[0015] Let the liquid to be measured flow through the qualitative light path b qual The type information of the monitored species is given when it flows through the quantitative light path, and the wavelength information of the monitored species is given when it flows through the quantitative light path. The wavelength information is substituted into the wavelength-concentration model to give the valence, form, phase and concentration of the target species in the flowing liquid to be measured.

[0016] The method for directly measuring the concentration of a high-concentration target species in a flowing liquid, wherein, in the step of sequentially scanning the absorbance of the solution sample using different optical pathlengths and preparing an absorption spectrum of the solution sample at each optical pathlength, the selected optical pathlength ensures that the peak absorbance value of the curve obtained by scanning the solution sample is higher than half of the maximum absorbance of the instrument, and the absorbance curve of the non-peak portion near half of the maximum absorbance of the instrument is a smooth curve without burrs.

[0017] The method for directly measuring the concentration of a high-concentration target species in a flowing liquid comprises the following conditions for selecting an adapted absorbance point on the Abs axis: a) the intersection of a straight line starting from the point with all spectral curves on the relevant side of the target species and the curve segments nearby are smooth and free of burrs, and the curve segments have no intersecting tendency; b) the Abs value of the point is the largest among all points on the Abs axis that meet condition a; c) the spectrum at the intersection of the straight line starting from the point with all spectral curves on the relevant side of the target species is not interfered with by the spectra of other species; and d) the wavelengths at the intersections of the straight line starting from the point with the lowest concentration and highest concentration spectral curves on the relevant side of the target species are both within the optimal energy wavelength range of the light source used.

[0018] The method for directly measuring the concentration of a high-concentration target species in a flowing liquid, wherein the screening conditions for setting the quantitative optical pathlength and screening the quantitative optical pathlength based on the adapted absorbance line and the absorption spectrum graph include:

[0019] Let b i represents the i-th optical path, i = 1, 2, ... m, C j represents the jth concentration, j = 1, 2, ... n, λ ij It represents the wavelength of the intersection of the spectral curve of the jth concentration and the adapted absorbance line measured with the i-th optical path, that is, the wavelength of the foot of the perpendicular line drawn from the intersection of the spectral curve of the jth concentration and the adapted absorbance line in the Abs-λ diagram of the i-th optical path;

[0020] Let ΔC j =C j+1 -C j , j=1, 2,...n-1; let Δλ ij =λ i，j+1 -λ ij , For any i, j = 1, 2, ... n-1, i = 1, 2, ... m, where ΔC j is the jth concentration difference, that is, the difference between the j+1th concentration and the jth concentration; Δλ ij k is the difference in the jth perpendicular wavelength of the ith optical path, that is, the difference in the perpendicular wavelength from the intersection of the curve of the j+1th concentration and the adapted absorbance line to the horizontal axis under the ith optical path, and the difference in the perpendicular wavelength from the intersection of the curve of the jth concentration and the adapted absorbance line to the horizontal axis under the same optical path; ijis the ratio of the jth perpendicular foot wavelength difference to the jth concentration difference of the i-th optical path;

[0021] The optical path length that meets the following two conditions at the same time is the quantitative optical path length: k ij ≥δ, i=1, 2…m, j=1, 2,…n-1, δ is a user-defined positive number greater than 0;

[0022] Beneficial effects: The method provided by the present invention for directly measuring the concentration of high-concentration target species in flowing liquids does not require large-multiple dilution of high-concentration complex solutions or the addition of multiple chemical agents. Therefore, there is no dilution error and secondary contamination risk. The original valence, original form, original phase and concentration and other chemical information of the target species in the high-concentration solution in the flowing liquid can be directly measured within 10 seconds. The problem of changes in the target species in the solution to be measured will not occur. After the measurement, the solution can be directly returned to the original system, and the production process can be guided in real time. The method of the present invention overcomes the problem that the Lambert-Beer linear law cannot be satisfied when directly measuring high-concentration complex solutions, and even the absorbance far exceeds the upper limit of the instrument measurement, and important information such as the valence, form, phase and concentration of the species in the solution cannot be quickly given. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is a flow chart of a method for directly measuring the concentration of a high-concentration target species in a flowing liquid provided by the present invention.

[0024] FIG2 is a graph showing the absorbance curve in the ultraviolet region of a sample with an arsenic ion concentration of 4665.43 mg / L provided by the present invention.

[0025] Figure 3 shows the UV wavelength range, the different optical path lengths are used to analyze the 10-20 g / L trivalent arsenic (As 3+ ) ion sample is subjected to absorbance scanning to prepare absorption spectra of the solution sample at each optical path.

[0026] FIG4 is a schematic diagram of a wavelength-concentration method model that meets the requirements by further dividing the concentration-wavelength curve into piecewise linear curves according to statistical indicators and obtaining a piecewise linear function of C=f(λ) through piecewise linear fitting. DETAILED DESCRIPTION

[0027] The present invention provides a method for directly measuring the concentration of a high-concentration target species in a flowing liquid. To make the objectives, technical solutions, and effects of the present invention more clear and explicit, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention.

[0028] Please refer to FIG1 , which is a flow chart of a method for directly measuring the concentration of a high-concentration target species in a flowing liquid provided by the present invention. As shown in the figure, the method includes the following steps:

[0029] S10, using a flowing liquid containing a target of different concentrations as a sample, measuring the absorbance curve of the sample in the ultraviolet-visible light and near-infrared light range, and obtaining the characteristic wavelength corresponding to the sharp peak with the highest absorbance in the absorbance curve as the qualitative wavelength λ qual , and its corresponding optical path is taken as the qualitative optical path b qual ;

[0030] In this example, without adding any chemical agents, the appropriate optical path length is selected based on the different concentrations of the actual liquid samples in the enterprise. The sample is a flowing liquid containing different concentrations of the target substance. The absorbance curve of the sample in the ultraviolet-visible light and near-infrared light range is measured to ensure that the absorbance curve in the ultraviolet-visible light and near-infrared light wavelength range has a sharp characteristic absorption peak at the top, and the absorbance corresponding to the absorption peak is within a reasonable range. The curve waveform should be complete, smooth and free of burrs. The characteristic wavelength corresponding to the sharp peak with the highest absorbance is the qualitative wavelength λ qual , the corresponding optical path is the qualitative optical path b qual .

[0031] As an example, as shown in FIG2 , the arsenic ion concentration of 4665.43 mg / L is used as a sample, and its absorbance curve in the ultraviolet region is measured. The characteristic wavelength (λmax = 193 nm) corresponding to the sharp peak with the highest absorbance in the absorbance curve is obtained as the qualitative wavelength λ qual , the corresponding optical path (b = 1mm) is used as the qualitative optical path b qual .

[0032] S20, preparing solution samples of different concentrations according to the actual concentration range of the flowing liquid, scanning the absorbance of the solution samples at different optical path lengths within the ultraviolet, visible, and near-infrared wavelength ranges, and producing absorption spectra of the solution samples at each optical path length;

[0033] In this example, absorbance scans were performed on samples of all concentrations at different optical pathlengths within the ultraviolet, visible, and near-infrared wavelengths, without dilution or the addition of any chemical agents. Absorption spectra (λ-Abs plots) were generated for all concentrations at each optical pathlength. The optical pathlength was selected to ensure that the peak absorbance of the curve obtained for each concentration was greater than half the instrument's maximum absorbance (50% Abs value), and that the non-peak portion of the absorbance curve near half the instrument's maximum absorbance was smooth and free of burrs.

[0034] S30. In the absorption spectrum of the solution sample, select an adapted absorbance point on the Abs axis, and draw a straight line parallel to the λ axis from the absorbance point so that it intersects all spectral curves on the relevant side of the target species at (λ, Abs). At this time, the straight line parallel to the λ axis is the adapted absorbance line;

[0035] In this embodiment, in each Abs-λ diagram obtained in step S20 above, an adaptive absorbance point is selected on the Abs axis, and a straight line parallel to the λ axis is drawn from this point so that it intersects with all spectral curves on the relevant side of the target species at (λ, Abs). The principles for selecting the adaptive absorbance point are as follows: a. The intersection of the straight line starting from this point with all spectral curves on the relevant side of the target species and the curve segments nearby are smooth and burr-free, and the curve segments have no intersecting trend; b. The Abs value of this point is the largest among all points on the Abs axis that meet a; c. The spectrum at the intersection of the straight line starting from this point with all spectral curves on the relevant side of the target species is not interfered with by the spectra of other species; d. The wavelengths at the intersection of the straight line starting from this point with the lowest concentration and highest concentration spectral curves on the relevant side of the target species are both within the optimal energy wavelength range of the light source used. In this embodiment, this straight line parallel to the λ axis is called the adaptive absorbance line.

[0036] As an example, as shown in FIG3 , in the ultraviolet wavelength range, different optical path lengths are used to analyze 10-20 g / L trivalent arsenic (As 3+ ) ion sample is subjected to absorbance scanning to prepare absorption spectrum diagrams of the solution sample at each optical path; in the absorption spectrum diagram under the condition of b=3mm, an adapted absorbance point (Abs=3) is selected on the Abs axis, and a straight line parallel to the λ axis is drawn from the absorbance point so that it intersects all spectral curves on the relevant side of the target species at (λ, Abs). At this time, the straight line parallel to the λ axis is the adapted absorbance line.

[0037] S40, setting screening conditions for the quantitative optical path, and screening to obtain the quantitative optical path based on the adapted absorbance line and the absorption spectrum;

[0038] In this embodiment, let b i represents the i-th optical path, i = 1, 2, ... m, C j represents the jth concentration, j = 1, 2, ... n, λ ij It represents the wavelength of the intersection of the spectral curve of the jth concentration measured with the i-th optical path and the adapted absorbance line, that is, the wavelength of the foot of the perpendicular line drawn from the intersection of the spectral curve of the jth concentration and the adapted absorbance line in the λ-Abs diagram of the i-th optical path; let ΔC j =C j+1 -C j , j=1, 2,...n-1; let Δλ ij =λ i，j+1 -λ ij , For any i, j = 1, 2, ... n-1, i = 1, 2, ... m, where: ΔC j is the jth concentration difference, that is, the difference between the j+1th concentration and the jth concentration; Δλ ijk is the difference in the jth perpendicular wavelength of the ith optical path, that is, the difference in the perpendicular wavelength from the intersection of the curve of the j+1th concentration and the adapted absorbance line to the horizontal axis under the ith optical path, and the difference in the perpendicular wavelength from the intersection of the curve of the jth concentration and the adapted absorbance line to the horizontal axis under the same optical path; ij is the ratio of the jth perpendicular wavelength difference of the i-th optical path to the jth concentration difference. The optical path that meets the following two conditions at the same time is the quantitative optical path: ak ij ≥δ, i=1,2,…m, j=1,2,…n-1, δ is a user-defined positive number greater than 0, such as 0.6, 0.65, etc.; b. If the quantitative pathlength that meets all conditions cannot be obtained based on the selected adapted absorbance line, select another point on the Abs axis with an absorbance slightly lower than the adapted absorbance point and use it as the new adapted absorbance point to redetermine the quantitative pathlength.

[0039] S50, observe the changing pattern of the characteristic wavelength and spectral curve shape corresponding to different concentrations of the target species in the actual flowing liquid under the qualitative optical path, and compare it with the qualitative wavelength λ measured in the static sample with different concentrations of the actual liquid target species. qual The qualitative wavelength λ is determined by comparing the changing pattern of the spectral curve shape with the target species at different concentrations under the actual flowing liquid condition. qual f The position and curve shape of

[0040] S60, obtain the quantitative optical path from the lowest concentration to the highest concentration C in the actual flowing liquid situation. j Wavelength λ corresponding to different concentrations within the range j , according to the quantitative optical path (C j， λ j ), make a concentration-wavelength curve with C as the horizontal axis value and λ as the vertical axis value;

[0041] S70, further dividing the concentration-wavelength curve into piecewise linear curves according to statistical indicators, and obtaining a piecewise linear function of C=f(λ) by piecewise linear fitting, that is, obtaining a wavelength-concentration method model that meets the requirements as shown in FIG4 ;

[0042] S80, let the liquid to be tested flow through the qualitative light path b qual The type information of the monitored species is given when it flows through the quantitative light path, and the wavelength information of the monitored species is given when it flows through the quantitative light path. The wavelength information is substituted into the wavelength-concentration model to give the valence, form, phase and concentration of the target species in the flowing liquid to be measured.

[0043] During the actual operation of this embodiment, when the flowing liquid to be measured flows through the qualitative optical path, the device provides the type information of the monitored species, and when it flows through the quantitative optical path, it provides accurate wavelength information. Substituting the wavelength information into the wavelength concentration model, the valence, morphology, phase state and concentration and other chemical information of the target species in the flowing high-concentration liquid can be accurately given within 10 seconds. The method provided by this embodiment for directly measuring the concentration of high-concentration target species in the flowing liquid does not require large-scale dilution of the high-concentration complex solution or the addition of multiple chemical agents. Therefore, there is no dilution error and secondary contamination risk. Within 10 seconds, the original valence, original morphology, original phase state and concentration and other chemical information of the target species in the high-concentration solution in the flowing liquid can be directly measured. The problem of the target species in the solution to be measured changing will not occur. After the measurement, the solution can be directly returned to the original system, which can guide the production process in real time. The method of this embodiment overcomes the problem that the Lambert-Beer linear law cannot be satisfied when directly measuring high-concentration complex solutions, and even the absorbance far exceeds the upper limit of the instrument measurement, and important information such as the valence, morphology, phase state and concentration of the species in the solution cannot be quickly given.

[0044] The technical principles of the present invention are described above in conjunction with specific embodiments. The embodiments described are only some embodiments of the present invention, rather than all embodiments. The description is relatively specific and detailed, and is only for the purpose of explaining this application, but it should not be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent of the present invention shall be based on the attached claims.

Claims

1. A method for directly measuring the concentration of a high-concentration target species in a flowing liquid, characterized in that: Includes steps: Take the flowing liquid containing different concentrations of the target as the sample, measure the absorbance curve of the sample in the ultraviolet visible light and near infrared light range, and obtain the characteristic wavelength corresponding to the sharp peak with the highest absorbance in the absorbance curve as the qualitative wavelength λ qual , and its corresponding optical path is taken as the qualitative optical path b qual ; According to the actual concentration range of the flowing liquid, solution samples of different concentrations are configured, and within the wavelength range of ultraviolet, visible light and near-infrared light, absorbance scanning of the solution samples is performed in sequence using different optical path lengths to prepare absorption spectra of the solution samples at each optical path length; In the absorption spectrum of the solution sample, a matching absorbance point is selected on the Abs axis, and a straight line parallel to the λ axis is drawn from the absorbance point so that it intersects with all the spectral curves on the relevant side of the target species at (λ, Abs). At this time, the straight line parallel to the λ axis is the matching absorbance line; Setting screening conditions for the quantitative optical path, and screening to obtain the quantitative optical path based on the adapted absorbance line and the absorption spectrum; Observe the changing rules of characteristic wavelength and spectral curve shape corresponding to different concentrations of target species in actual flowing liquid under qualitative optical path, and compare them with the qualitative wavelength λ measured in static samples with different concentrations of target species in actual liquid. qual The qualitative wavelength λ of the target species at different concentrations in the actual flowing liquid is determined by comparing and analyzing the changing rules of the spectral curve shape. qual f The position and shape of the curve; Obtain quantitative pathlength from the lowest concentration to the highest concentration C in actual flowing liquid conditions j The wavelength λ corresponding to different concentrations in the range j , according to the quantitative optical path (C j， λ j ), to produce a concentration-wavelength curve with C as the horizontal axis value and λ as the vertical axis value; The concentration-wavelength curve is further divided into piecewise linear curves according to statistical indicators, and a piecewise linear function of C=f(λ) is obtained by piecewise linear fitting, that is, a wavelength-concentration method model that meets the requirements is obtained; The liquid to be tested flows through the qualitative optical path b. qual The type information of the monitored species is given when it flows through the quantitative light path, and the wavelength information of the monitored species is given when it flows through the quantitative light path. The wavelength information is substituted into the wavelength-concentration model to give the valence state, form, phase state and concentration of the target species in the flowing liquid to be measured.

2. The method for directly measuring the concentration of high-concentration target species in flowing liquid according to claim 1, characterized in that: In the step of successively scanning the absorbance of the solution sample using different optical pathlengths to prepare the absorption spectrum of the solution sample under each optical pathlength, the selected optical pathlength ensures that the peak absorbance value of the curve obtained by scanning the solution sample is higher than half of the maximum absorbance of the instrument, and the absorbance curve of the non-peak part near half of the maximum absorbance of the instrument is a smooth curve without burrs.

3. The method for directly measuring the concentration of high-concentration target species in flowing liquid according to claim 1, characterized in that: The conditions for selecting an adapted absorbance point on the Abs axis include: a. The intersection of the straight line starting from this point and all the spectral curves on the relevant side of the target species and the curve segments nearby are smooth and free of burrs, and the curve segments have no intersecting tendency; b. The Abs value of this point is the largest among all the points on the Abs axis that meet condition a; c. The spectrum at the intersection of the straight line starting from this point and all the spectral curves on the relevant side of the target species is not interfered by the spectra of other species; d. The wavelengths at the intersection of the straight line starting from this point and the lowest concentration and highest concentration spectral curves on the relevant side of the target species are both within the optimal energy wavelength range of the light source used.

4. The method for directly measuring the concentration of high-concentration target species in flowing liquid according to claim 1, characterized in that: The screening conditions for setting the quantitative optical path length and screening the quantitative optical path length based on the adapted absorbance line and the absorption spectrum diagram include: Let b i represents the i-th optical path, i = 1, 2, ... m, C j represents the jth concentration, j = 1, 2, ... n, λ ij It represents the wavelength of the intersection of the spectral curve of the jth concentration and the adapted absorbance line measured by the i-th optical path, that is, the wavelength of the foot of the perpendicular line drawn from the intersection of the spectral curve of the jth concentration and the adapted absorbance line to the λ axis in the Abs-λ diagram of the i-th optical path; Let ΔC j = C j+1 - C j , where j = 1, 2, … n - 1; Let Δλ ij = λ i，j+1 - λ ij , For any i, j = 1, 2, ... n-1, i = 1, 2, ... m, where ΔC j is the jth concentration difference, that is, the difference between the j+1th concentration and the jth concentration; Δλ ij k is the difference in the jth perpendicular wavelength of the ith optical path, that is, the difference in the perpendicular wavelength from the intersection of the curve of the j+1th concentration and the adapted absorbance line to the horizontal axis under the ith optical path, and the difference in the perpendicular wavelength from the intersection of the curve of the jth concentration and the adapted absorbance line to the horizontal axis under the same optical path; ij is the ratio of the jth perpendicular foot wavelength difference to the jth concentration difference of the i-th optical path; The optical path length that meets the following two conditions at the same time is the quantitative optical path length: k ij ≥δ, i=1, 2…m, j=1, 2,…n-1, δ is a user-defined positive number greater than 0;

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