A method for simultaneously determining a plurality of heavy metals in electroplating discharge wastewater

Abstract

The application discloses a kind of detection methods for simultaneously determining multiple heavy metals in electroplating discharge wastewater, and relates to the technical field of chemical analysis.The method comprises the following steps: multiple heavy metals are used as standard materials, and standard solutions of each heavy metal are prepared; the standard solutions are uniformly mixed according to different proportions to prepare a mixed standard solution; the mixed standard solution is scanned at 470-580 nm by ultraviolet spectrophotometry to obtain absorbance values; the absorbance values are imported into MATLAB to establish a prediction model; and the content of each heavy metal component in the mixed solution sample is output by the prediction model. The application establishes high-precision prediction model A and wide-range prediction model B based on multiple linear regression method, so as to provide a reference for simultaneous determination of multiple heavy metals in electroplating wastewater.

Description

Technical Field

[0001] This invention relates to the field of chemical analysis technology, specifically to a detection method for simultaneously determining multiple heavy metals in electroplating wastewater. Background Technology

[0002] Wastewater discharged from electroplating enterprises typically contains large amounts of toxic substances, such as heavy metals, organic compounds, and inorganic compounds. Currently, spectrophotometry and voltammetric stripping leaching are the main methods used for heavy metal monitoring in electroplating wastewater both domestically and internationally. Voltammetric stripping leaching has poor repeatability, and the mercury electrode used in the testing process poses a risk of secondary pollution; therefore, it has been gradually replaced by colorimetric methods. Traditional spectrophotometry is widely used in heavy metal determination due to its simple principle and certain sensitivity and selectivity. However, in the analysis of multi-component samples, a single chromogenic agent often undergoes complexation reactions with multiple ions, potentially leading to spectral overlap and severe interference with the determination. Although interference can be removed by adding masking agents or performing separation treatment before detection, these methods are complex, wasteful of chemical reagents, and may introduce new interferences, resulting in low efficiency.

[0003] To address the problem of mutual interference among multiple components, many methods have been proposed in recent years to simultaneously determine interfering components using mathematical separation instead of chemical separation. These include partial least squares (PLS), artificial neural networks (ANN), and multiple linear regression (MLR). Among these, multiple linear regression, aiming at dimensionality reduction, can overcome spectral overlap and inter-component interference, offering advantages over PLS and ANN such as simplicity and accuracy. Currently, methods combining MLR with spectrophotometry, based on the additive nature of light, are widely used in heavy metal content determination. However, much of this research remains theoretical, with significant gaps between practical considerations regarding ion selection, concentration settings, and reaction environments, making practical application in production and daily life difficult. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of the aforementioned background technology and provide a method for simultaneously determining multiple heavy metals in electroplating wastewater. This invention is based on MLR spectrophotometry, taking the wastewater discharged by electroplating enterprises as the research object, and establishes two methods for simultaneously determining Cr. 3+ Ni 2+ Zn 2+ Three MLR prediction models for ions: high-precision model A and wide-range model B, respectively targeting the wastewater discharge of electroplating enterprises under different conditions. This method provides a feasible solution for the rapid testing and screening of wastewater discharged during the actual production process of electroplating enterprises.

[0005] The purpose of this invention is to provide a method for simultaneously determining multiple heavy metals in electroplating wastewater, comprising the following steps:

[0006] Multiple heavy metals were used as standard substances, and standard solutions of each heavy metal were prepared separately. The standard solutions were then mixed evenly in different proportions to form a mixed solution. A colorimetric reagent, a buffer solution, an emulsifier, and a triethanolamine solution were added to the mixed solution in sequence and mixed evenly to obtain a mixed standard solution.

[0007] The absorbance values ​​of the mixed standard solution were obtained by scanning the wavelength range of 470-580 nm using an ultraviolet spectrophotometer. The obtained absorbance values ​​were then imported into MATLAB, and a prediction model was established based on the multiple linear regression analysis program.

[0008] The prediction model outputs the content of each heavy metal component in an unknown mixed solution sample containing multiple heavy metals.

[0009] Preferably, multiple heavy metals, including Cr, Ni, and Zn, are prepared into Cr solutions of 100 mg / L. 3+ Standard solution, 100 mg / L Zn 2+ Standard solution of 100 mg / L Ni 2+ Standard solution.

[0010] Preferably, during the establishment of the prediction model, the obtained absorbance values ​​are imported into MATLAB, and the MLR program is run automatically in MATLAB to perform calculations. The absorbance values ​​of the mixed standard solution at wavelengths of 470-580 nm, along with the ion concentrations in the scanned wavelength range and the mixed solution, can be used to obtain the following regression equation, where a... w b w c w d w Unknown parameters, establish Cr in mixed solution 3+ Ni 2+ Zn 2+ Prediction models for three ion concentrations;

[0011] The resulting regression equation: a w X1+b w X2+c w X3+d w W = Q w R 2

[0012] Where: a w b w c w d w These are partial regression coefficients;

[0013] Q w The absorbance of the solution at wavelength W;

[0014] R 2 The correlation of the obtained fitted equation;

[0015] X1, X2, and X3 represent Cr respectively. 3+ Ni 2+ Zn 2+ Concentrations of the three ions.

[0016] Preferably, the colorimetric agent is an ethanol solution of 4-(2-pyridineazo)resorcinol, and the amount of 4-(2-pyridineazo)resorcinol is 0.02% of the volume of the ethanol solution.

[0017] Preferably, the buffer solution is an NH3-NH4Cl buffer solution with pH=9.0.

[0018] Preferably, the emulsifier is a 0.001 mol / mL CTMAB solution.

[0019] Preferably, the concentration of the triethanolamine solution is 1 mol / L.

[0020] Preferably, the prediction model is established based on the different concentrations of each heavy metal ion in the mixed standard solution and includes prediction model A or prediction model B;

[0021] The prediction model A is a high-precision model Cr 3+ Ni 2+ Zn 2+ The limits of detection for the three ions were 0.32 mg / L, 0.32 mg / L, and 0.72 mg / L, respectively, and the MRE was between 5.14% and 6.68%.

[0022] The forecast model B is a wide-range model Cr 3+ Ni 2+ Zn 2+ The detection limits for the three ions were 0.20 mg / L, 0.10 mg / L, and 0.30 mg / L, respectively, and the MRE ranged from 6.44% to 9.91%.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] This invention, based on MLR spectrophotometry, takes the wastewater discharged by electroplating enterprises as the research object and establishes two methods for simultaneously determining Cr. 3+ Ni 2+ Zn 2+Three MLR prediction models for ions: high-precision model A and wide-range model B, respectively targeting the wastewater discharge of electroplating enterprises under different conditions. This method provides a feasible solution for the rapid testing and screening of wastewater discharged during the actual production process of electroplating enterprises.

[0025] This invention uses spectrophotometry to analyze Cr in wastewater. 3+ Ni 2+ Zn 2+ The simultaneous determination of ions was studied. Through analysis of wastewater from synthetic processes and actual electroplating plants, and using multiple linear regression analysis, the simultaneous determination of Cr was explored. 3+ Ni 2+ Zn 2+ Experimental methods for three ions. Based on multiple engineering examples, the Cr content in actual electroplating wastewater was obtained. 3+ Ni 2+ Zn 2+ Concentration distribution of three ions, designing high-precision and wide-range models: High-precision model Cr 3+ Ni 2+ Zn 2+ The detection limits for the three ions were 0.32 mg / L, 0.32 mg / L, and 0.72 mg / L, with MRE ranging from 5.14% to 6.68%. The detection limits for the three ions in the wide-range model were 0.20 mg / L, 0.10 mg / L, and 0.30 mg / L, with MRE ranging from 6.44% to 9.91%, which can be applied to different types of electroplating wastewater testing projects as needed. Finally, the Cr content in actual electroplating wastewater was analyzed. 3+ Ni 2+ Zn 2+ The content of [substance name] was determined, and the analytical results were basically similar to those of atomic absorption spectrophotometry. The RE values ​​were all less than 6%, and the coefficients of variation were between 0.431% and 5.301%. The reproducibility was good, the precision was high, and the method was fast, convenient, and simple while also having a certain degree of accuracy.

[0026] In this invention, when the volume of the 0.02% PAR-ethanol solution as the colorimetric reagent is 5 mL, the absorbance values ​​of the complexes formed by the colorimetric reagent and the triion are all relatively high and remain essentially constant. Simultaneously, the absorbance of the complexes is highest when the pH of the mixed standard solution is 9.0; the absorbance of the complexes is highest when the volume of the buffer solution is in the range of 4.5-6.0 mL; the addition of TEA optimizes the Cr... 3+ While the complex formed by the ions and PAR develops color, it also accelerates the color development speed and enhances the stability of the compound without affecting the determination of the other two ions.

[0027] This invention uses PAR as a colorimetric agent, and Cr 3+ Ni 2+ Zn2+ Both can react with PAR to form colored substances. 2+ Zn 2 + The compound of the two metal ions develops color rapidly, reaching its maximum absorbance in 20-25 minutes, and forms a very stable colored complex, showing no significant change within 24 hours after development. However, in the PAR colorimetric system where TEA is present, Cr... 3+ The absorbance of the compound formed by the ions reached its maximum and remained constant after 30 min. To accelerate the color development of the complex and enhance the stability of the compound, this invention incorporates water bath heating (70°C). After heating the system in a water bath (70°C) for 20 min, Cr... 3+ The absorbance of the compound formed by the ions and PAR reaches its maximum, and a stable colored compound is formed. Ni 2+ Zn 2+ The absorbance of the compound of the two metal ions reached its maximum after 20 minutes under the above experimental conditions.

[0028] The 0.001 mol / mL CTMAB emulsifier used in this invention can make the mixed standard solution clear and transparent, with maximum absorbance and long stability.

[0029] This invention uses a reagent blank as a reference solution and performs spectral scanning in the wavelength range of 460-580 nm. Cr 3+ Ni 2+ Zn 2+ The maximum absorption wavelengths of the three ions are 515, 530, and 510 nm, respectively. This means that the spectra of the three ions at their maximum absorption wavelengths within the 470-580 nm range severely overlap. Therefore, when measuring the concentrations of these three ions individually in the mixed system using conventional methods, mutual interference will inevitably affect the measurement results. Thus, this invention selects 470-580 nm as the measurement wavelength range and employs MLR-spectrophotometry to measure the concentration of Cr in the mixed system. 3+ Ni 2+ Zn 2+ The concentrations of the three ions were measured simultaneously. Attached Figure Description

[0030] Figure 1 Cr 3+ Ni 2+ Zn 2+ Emission concentration distribution of the three ions. Detailed Implementation

[0031] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below with reference to specific embodiments, but the embodiments are not intended to limit the present invention.

[0032] This invention addresses the water quality characteristics of electroplating wastewater.

[0033] Based on data collection, preliminary research, and mainstream electroplating wastewater treatment processes, it is known that the wastewater discharged by electroplating enterprises after treatment often contains Cr. 3+ Ni 2+ Zn 2+ The emission concentration distributions of the three ions were obtained simultaneously for pollutants such as [list of pollutants]. Figure 1 As shown in the figure, the emission concentrations of the three ions exhibit an approximately normal distribution, with Cr... 3+ Ni 2+ Zn 2+ The concentration ranges were 0.20-1.20 mg / L, 0.08-0.80 mg / L, and 0.20-1.30 mg / L, respectively. Among them, Cr... 3+ Mostly concentrated in the range of 0.32-0.44 mg / L, Ni 2+ Concentrated at 0.32-0.50 mg / L, Zn 2+ The concentration is concentrated between 0.72-0.84 mg / L. Meanwhile, after treatment, the wastewater complies with the emission concentration limits for water pollutants from newly established enterprises stipulated in the "Electroplating Pollutant Discharge Standard" (GB21900-2008), namely: total chromium: 1.0 mg / L, hexavalent chromium: 0.2 mg / L, total nickel: 0.5 mg / L, and total zinc: 1.5 mg / L.

[0034] The Cr used in this invention 3+ Standard solution, Zn 2+ Standard solution, Ni 2+ Standard solution (100 mg / L), diluted as needed before use; 4-(2-pyridylazo)resorcinol (PAR) colorimetric reagent: 0.02% PAR-ethanol solution; 0.001 mol / mL hexadecyl trimethylammonium bromide (CTMAB) solution; NH3-NH4Cl buffer solution; 1 mol / L triethanolamine (TEA) solution. All reagents used were of analytical grade; the water used in the experiment was ultrapure water.

[0035] The experimental instruments used in this invention are: a UV-2600i ultraviolet-visible spectrophotometer (Shimadzu Corporation, Japan) and an FE-20 pH meter (Mettler-Toledo International Trading (Shanghai) Co., Ltd.).

[0036] This invention provides a method for simultaneously determining multiple heavy metals in electroplating wastewater, comprising the following steps:

[0037] Take an appropriate amount of Cr 3+Zn 2+ Ni 2+ The standard solution was placed in a 50 mL volumetric flask, and then 0.02% PAR-ethanol solution, NH3-NH4Cl buffer solution, CTMAB solution and TEA solution were added in sequence. After mixing well, the solution was placed in a water bath at 70 °C for 20 min, cooled and then diluted to volume to obtain a mixed standard solution.

[0038] Among these, when using 5 mL of 0.02% PAR-ethanol solution as the colorimetric reagent, the absorbance values ​​of the complexes formed by the colorimetric reagent and the triion were all relatively high and remained essentially unchanged; simultaneously, the absorbance of the complexes was highest when the pH of the mixed standard solution was 9.0; the absorbance of the complexes was highest when the volume of the buffer solution was in the range of 4.5-6.0 mL; the addition of TEA optimized the Cr... 3+ While the complex formed by the ions and PAR develops color, it also accelerates the color development speed and enhances the stability of the compound without affecting the determination of the other two ions.

[0039] PAR was used as the colorimetric agent, and Cr 3+ Ni 2+ Zn 2+ Both can react with PAR to form colored substances. 2+ Zn 2+ The compound of the two metal ions develops color rapidly, reaching its maximum absorbance in 20-25 minutes, and forms a very stable colored complex, showing no significant change within 24 hours after development. However, in the PAR colorimetric system where TEA is present, Cr... 3+ The absorbance of the compound formed by the ions reached its maximum and remained constant after 30 min. To accelerate the color development of the complex and enhance the stability of the compound, this invention incorporates water bath heating (70°C). After heating the system in a water bath (70°C) for 20 min, Cr... 3+ The absorbance of the compound formed by the ions and PAR reaches its maximum, and a stable colored compound is formed. Ni 2+ Zn 2+ The absorbance of the compound of the two metal ions reached its maximum after 20 minutes under the above experimental conditions.

[0040] The 0.001 mol / mL CTMAB emulsifier used ensures that the mixed standard solution is clear and transparent, achieves maximum absorbance, and remains stable for a long time.

[0041] Then, the mixed standard solution was placed in a 1cm cuvette, and the reagent blank was used as a reference. The mixed standard solution was scanned in the 470-580nm wavelength range using a UV spectrophotometer to obtain the absorbance value. The obtained absorbance value was imported into MATLAB, and a prediction model was established based on the multiple linear regression analysis program. MLR was implemented using the Regress function package.

[0042] Using a reagent blank as a reference solution, spectral scanning was performed in the wavelength range of 460-580 nm. Cr 3+ Ni 2 + Zn 2+ The maximum absorption wavelengths of the three ions are 515, 530, and 510 nm, respectively. This means that the spectra of the three ions at their maximum absorption wavelengths within the 470-580 nm range severely overlap. Therefore, when measuring the concentrations of these three ions individually in the mixed system using conventional methods, mutual interference will inevitably affect the measurement results. Thus, this invention selects 470-580 nm as the measurement wavelength range and employs MLR-spectrophotometry to measure the concentration of Cr in the mixed system. 3+ Ni 2+ Zn 2+ The concentrations of the three ions are measured simultaneously; a high-precision prediction model A or a wide-range prediction model B is established based on the different concentrations of each heavy metal ion in the mixed standard solution.

[0043] To ensure the accuracy of the forecast models, a high-precision forecast model A and a wide-range forecast model B were set up, and the corresponding ion concentration configurations for the forecast models are shown in Table 1.

[0044] Finally, the prediction model is used to output the content of each heavy metal component in an unknown mixed solution sample containing multiple heavy metals.

[0045] Table 1. Configuration of mixed ions

[0046]

[0047]

[0048] The MLR program can be run automatically using MATLAB to calculate a, which can be obtained by using the absorbance of the solution at different wavelengths, the scanning band, and the known concentrations of each ion in the mixed solution. w b w c w d w Correlation R between unknown parameters and fitting equation 2 Establishment of Cr in electroplating wastewater 3+ Ni 2+ Zn 2+ Three ion prediction models.

[0049] The specific analysis process is as follows: input independent and dependent variables → perform multiple linear regression analysis → derive the regression equation → establish a prediction model → determine the concentration of the solution. The independent variable is: Cr in the mixed solution. 3+ Ni 2+ Zn 2+The concentrations of the three ions; dependent variable: absorbance of the mixed solution in the 470-580 nm wavelength range.

[0050] The resulting regression equation: a w X1+b w X2+c w X3+d w W = Q w R 2

[0051] Where: a w b w c w d w These are partial regression coefficients;

[0052] Q w The absorbance of the solution at wavelength W;

[0053] R 2 The correlation of the obtained fitted equation;

[0054] X1, X2, and X3 represent Cr respectively. 3+ Ni 2+ Zn 2+ Concentrations of the three ions.

[0055] The formulas for calculating relative error (RE), mean relative error (MRE), and recovery (R) are as follows:

[0056]

[0057]

[0058]

[0059] Among them, C add ---True concentration; C pred ---Concentration measured in the experiment.

[0060] To verify the accuracy of this forecasting model, a configuration containing Cr was used. 3+ Ni 2+ Zn 2+ Sixteen groups of mixed solutions were prepared (numbered A1-A8, B1-B8), corresponding to prediction model A and prediction model B, respectively. The absorbance of these solutions in the 470-580 nm wavelength range was measured. The obtained absorbance values ​​were input into the pre-calibrated models A and B, and the output values ​​were calculated. The RE (resonance response) was then calculated. Specific results are shown in Tables 2 and 3.

[0061] In prediction model A, Cr3+ Ni 2+ Zn 2+ The MREs were 5.14%, 5.97%, and 6.68%, respectively; the R values ​​ranged from 98.53% to 102.90%. In forecast model B, Cr... 3+ Ni 2+ Zn 2+ The MRE rates were 8.66%, 6.44%, and 9.91%, respectively; the R rates ranged from 98.26% to 106.67%.

[0062] Table 2 Prediction by Simulated Sample Analysis of Prediction Model A

[0063]

[0064] Table 3 Predictions from Simulated Sample Analysis using Prediction Model B

[0065]

[0066]

[0067] Note: V PAR =5mL, pH=9.0±0.2V NH3-NH4Cl =4.5mL, V TEA =4mL, T=70℃t=20min, V CTMAB = 4mL.

[0068] Compared to model A, model B has a larger RE, mainly due to the difference in their limits of determination (LODs), as shown in Table 4. It is evident that prediction model B has a wider LOD than model A, making it more adaptable to actual wastewater, but its accuracy is relatively lower; while prediction model A, although having a smaller measurement range, has a higher LOD than model A. 3+ Ni 2 + Zn 2+ The triion concentration range covers the concentrations emitted by most electroplating enterprises and has high accuracy. Therefore, the two forecasting models mentioned above can be applied as needed to wastewater monitoring projects of electroplating enterprises with different treatment levels and production processes.

[0069] Table 4 shows the LOD and MRE of the three ions in forecast models A and B.

[0070]

[0071] This invention utilizes multiple regression analysis, which employs regression equations to quantitatively explain the linear dependence between a dependent variable and two or more independent variables. The basic idea is to find the mathematical expression that best represents the relationship between the independent and dependent variables.

[0072] To establish a multiple linear regression model, it is first necessary to measure the degree of correlation between multiple explanatory variables and the explained variable through correlation analysis, and retain variables with significant correlation.

[0073] Secondly, to further investigate the influence and degree of influence of each independent variable on the dependent variable, stepwise regression is typically used to select the independent variables that have a significant impact on the dependent variable one by one. After obtaining the regression equation based on stepwise regression, the coefficient of determination is usually used to measure the linear regression effect of the model. The coefficient of determination is the ratio of the regression sum of squares to the sum of squares of deviations. The larger the proportion of the regression sum of squares, the better the goodness of fit between the regression line and the sample data, and the better the model regression effect.

[0074] Finally, to establish a simpler regression equation and eliminate an independent variable that has no significant effect on the dependent variable, it is necessary to perform a significance test on the regression coefficients of the multiple linear regression equation; this can be done using t-tests, multiple co-occurrence tests, or residual analysis.

[0075] The above steps are the specific steps for establishing an MLR model. The "specific analysis process" in the following text, "the specific analysis process is: input independent variables and dependent variables → perform multiple linear regression analysis → derive the regression equation → establish a prediction model → determine the unknown concentration solution," is actually the "specific procedural analysis process," and can be modified as appropriate.

[0076] The following describes a method for simultaneously determining multiple heavy metals in electroplating wastewater provided by the present invention, based on specific embodiments.

[0077] Example

[0078] In this embodiment, the wastewater was taken from electroplating enterprises in two industrial parks in Guangxi. After simple filtration, it was placed in a 50mL volumetric flask, and then 5mL of 0.02% PAR-ethanol solution, 4.5mL of pH=9.0 NH3-NH4Cl buffer solution, 4mL of 0.001mol / mL CTMAB emulsifier, and 4mL of 1mol / LTEA solution were added sequentially. The solution was incubated in a water bath at 70℃ for 20min, cooled, and then diluted to volume. Using a 1cm cuvette and with a reagent blank as a reference, the absorption spectrum of the solution was scanned in the wavelength range of 470-580nm to obtain the absorption spectrum. The Cr content can be obtained using prediction models A and B. 3+ Ni 2+ Zn 2+ The content of the three ions was measured, and the results were compared with those obtained by atomic absorption spectrometry. The results are shown in Table 5.

[0079] As shown in the table, Cr was measured by both MLR-spectrophotometry and atomic absorption spectrometry. 3+ Ni 2+ Zn 2+The content of Cr was basically similar. Meanwhile, prediction model A showed higher accuracy for sample 2, making it suitable for wastewater with relatively stable water quality characteristics and minimal fluctuations in water quality indicators; prediction model B, although less accurate, had strong adaptability to both samples, making it suitable for wastewater with large water quality fluctuations or where the water quality status could not be estimated. The coefficient of variation was 0.431%-5.301%, indicating good reproducibility and high precision of the measurement data. Both models showed similarities in Cr content. 3+ Ni 2+ Zn 2+ The prediction results of the three ions fully demonstrate the reliability and feasibility of the MLR-spectrophotometric method for simultaneously determining the content of heavy metal ions in electroplating wastewater.

[0080] Table 5 Comparison of results from the two methods

[0081]

[0082] In summary, to address the problem of mutual interference among multiple components, this study takes the wastewater discharged from electroplating enterprises as the research object and establishes a high-precision prediction model A and a wide-range prediction model B based on the multiple linear regression method, aiming to provide a reference for the simultaneous determination of multiple heavy metals in electroplating wastewater.

[0083] The high-precision forecasting model A provided by this invention contains Cr 3+ Ni 2+ Zn 2+ The limits of detection (LODs) for the three ions are 0.32-0.44 mg / L, 0.32-0.50 mg / L, and 0.72-0.84 mg / L, basically covering the wastewater discharge from most electroplating enterprises. The mean reactivity ratio (MRE) is between 5.14% and 6.68%, demonstrating strong specificity and high accuracy. The wide-range prediction model B has LODs for the three ions of 0.2-1.0 mg / L, 0.1-0.7 mg / L, and 0.3-1.5 mg / L. Due to its wide detection range, it is suitable for electroplating wastewater analysis in a few special cases, with an MRE between 6.44% and 9.91%. Both prediction models show good accuracy and meet the testing requirements.

[0084] The method provided by this invention is used for treating Cr in wastewater discharged from actual electroplating enterprises. 3+ Ni 2+ Zn 2+ The three-ion determination, in the actual wastewater samples corresponding to the prediction models A and B, showed that the reproducibility (RE) was less than 6% compared with that of atomic absorption spectrophotometry, and the coefficient of variation was between 0.431% and 5.301%, indicating good reproducibility and high precision. Therefore, it can be applied to the determination of Cr in the wastewater discharged by electroplating enterprises. 3+ Ni 2+ Zn 2+Simultaneous determination of three heavy metal ions. Furthermore, the method's detection limit is lower than the water pollutant discharge concentration limit stipulated in the "Electroplating Pollutant Discharge Standard" (GB21900-2008), meeting the daily monitoring needs of electroplating wastewater. Therefore, it can also provide a convenient method for monitoring multi-component heavy metals in electroplating wastewater and offer a new approach for online monitoring of wastewater discharged by electroplating enterprises.

[0085] This invention describes preferred embodiments and their effects. However, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to include both the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0086] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for simultaneously determining multiple heavy metals in electroplating wastewater, characterized in that, Includes the following steps: Multiple heavy metals were used as standard substances, and standard solutions of each heavy metal were prepared separately. The standard solutions were then mixed evenly in different proportions to form a mixed solution. A colorimetric agent, a buffer solution, an emulsifier, and a triethanolamine solution were added to the mixed solution in sequence. After mixing evenly, the solution was placed in a water bath at 70 °C for 20 min to obtain a mixed standard solution. The colorimetric agent is an ethanol solution of 4-(2-pyridineazo)resorcinol, wherein the amount of 4-(2-pyridineazo)resorcinol is 0.02% of the volume of the ethanol solution. The emulsifier is a 0.001 mol / mL CTMAB solution; The absorbance values ​​of the mixed standard solution were obtained by scanning the wavelength range of 470-580 nm using an ultraviolet spectrophotometer. The obtained absorbance values ​​were then imported into MATLAB, and a prediction model was established based on the multiple linear regression analysis program. The prediction model outputs the content of each heavy metal component in an unknown mixed solution sample containing multiple heavy metals. Various heavy metals, including Cr, Ni, and Zn.

2. The detection method for simultaneously determining multiple heavy metals in electroplating wastewater according to claim 1, characterized in that, Prepare Cr at 100 mg / L respectively 3+ Standard solution, 100 mg / L Zn 2+ Standard solution of 100 mg / L Ni 2+ Standard solution.

3. The detection method for simultaneously determining multiple heavy metals in electroplating wastewater according to claim 1, characterized in that, In the process of establishing the forecast model, the obtained absorbance values ​​are imported into MATLAB, and the MLR program is run automatically in MATLAB to perform calculations. The absorbance values ​​of the mixed standard solution at wavelengths of 470-580 nm, as well as the concentrations of each ion in the scanned wavelength range and the mixed solution, can be used to obtain the following regression equation, where a... w b w c w d w Unknown parameters, establish Cr in mixed solution 3+ Ni 2+ Zn 2+ Prediction models for three ion concentrations; The resulting regression equation: a w X1+b w X2 +c w X3 +d w W=Q w R 2 Where: a w b w c w d w These are partial regression coefficients; Q w The absorbance of the solution at wavelength W; R 2 The correlation of the obtained fitted equation; X1, X2, and X3 represent Cr respectively. 3+ Ni 2+ Zn 2+ Concentrations of the three ions.

4. The detection method for simultaneously determining multiple heavy metals in electroplating wastewater according to claim 1, characterized in that, The buffer solution is an NH3-NH4Cl buffer solution with pH=9.

0.

5. The detection method for simultaneously determining multiple heavy metals in electroplating wastewater according to claim 1, characterized in that, The concentration of the triethanolamine solution is 1 mol / L.

6. The detection method for simultaneously determining multiple heavy metals in electroplating wastewater according to claim 1, characterized in that, The prediction model is established based on the different concentrations of each heavy metal ion in the mixed standard solution, including prediction model A or prediction model B; The prediction model A is a high-precision model Cr 3+ Ni 2+ Zn 2+ The limits of detection for the three ions were 0.32 mg / L, 0.32 mg / L, and 0.72 mg / L, respectively, with MRE ranging from 5.14% to 6.68%. The forecast model B is a wide-range model Cr 3+ Ni 2+ Zn 2+ The limits of detection for the three ions were 0.20 mg / L, 0.10 mg / L, and 0.30 mg / L, respectively, with MRE ranging from 6.44% to 9.91%.

7. The detection method for simultaneously determining multiple heavy metals in electroplating wastewater according to claim 1, characterized in that, The pH of the mixed standard solution is 9.0 ± 0.2.

Images