Screening method for multiple pollutants in sewage

Abstract

The invention belongs to the technical field of water pollutant detection and screening, and particularly relates to a method for screening multiple pollutants in sewage. The method for screening multiple pollutants in sewage mainly comprises the following steps: S1, collecting water, and pretreating the collected water; s2, measuring whether metal exists in the pre-treated water by utilizing an atomic absorption method; step S3, determining whether cyanide exists in the pre-treated water by utilizing a spectrophotometric method; and S4, obtaining data of various pollutants in the sewage. According to the screening method for the various pollutants in the sewage, various metals and various cyanides which are harmful to human bodies in the sewage can be screened and detected, and the detection method is simple to operate and accurate in result.

Description

Technical Field

[0001] The invention belongs to the technical field of water pollutant detection and screening, and specifically relates to a method for screening multiple pollutants in sewage. Background Art

[0002] With the rapid development of industrialization and urbanization, water pollution is becoming increasingly serious. Sewage contains a variety of pollutants, including but not limited to heavy metals, organic pollutants, nutrients, etc. These pollutants pose a threat to the environment and human health.

[0003] There are many metals in sewage, such as lead, thallium, nickel, etc. These metals are not only difficult to degrade naturally, but also accumulate through the food chain and eventually enter the human body, causing chronic poisoning. Therefore, when the metal content in sewage increases and exceeds the normal range, it directly endangers human health and causes environmental quality to deteriorate. At the same time, there are also a lot of cyanides in sewage. Most cyanides are highly acutely toxic to human health. Cyanides can be inhaled through the respiratory tract, absorbed by the digestive tract, and absorbed through skin contact, causing harm to the human body. Long-term exposure to cyanides may cause chronic damage to the blood system, nervous system, heart, liver, kidneys, etc.

[0004] Therefore, it is necessary to detect various metals and cyanides in sewage that are harmful to the human body to prevent them from harming the human body. Although the existing sewage screening method can detect various metals and cyanides separately, its detection steps need to be further optimized. Summary of the invention

[0005] In view of the deficiencies of the prior art, the present invention provides a method for screening multiple pollutants in sewage, the purpose of which is to screen and detect various metals and various cyanides that are harmful to the human body in sewage. The detection method is simple to operate and the results are accurate.

[0006] In order to achieve the above object, the present invention provides a method for screening multiple pollutants in sewage, comprising the following steps:

[0007] Step S1, collecting water quality and pre-processing the collected water quality;

[0008] Step S2, using atomic absorption spectrometry to measure whether there is metal in the pre-treated water;

[0009] Step S3, using spectrophotometry to determine whether cyanide exists in the pre-treated water;

[0010] Step S4, obtaining data of various pollutants in sewage.

[0011] Furthermore, in step S1, the pre-processing steps are:

[0012] Step A1, using an instrument to remove large suspended particles in the sewage;

[0013] Step A2, by stirring or ultrasonic treatment of the collected water, ensure that various pollutants in the collected water are evenly distributed to obtain pre-treated water.

[0014] Furthermore, in step A1, the instrument is a vibrating screen, a belt filter press or a sand filter; the mesh size of the vibrating screen, the belt filter press or the sand filter is 25 to 35 meshes; in step A2, the stirring instrument is a mechanical stirrer or an air stirrer; the rotation speed of the mechanical stirrer is 100 r / min; the gas flow rate of the air stirrer is 13 cfm; the ultrasonic instrument is an ultrasonic generator, and the ultrasonic frequency of the ultrasonic generator is 50 kHz.

[0015] Furthermore, in step S2, the metal is one or more of copper, zinc, lead, chromium, thallium and nickel.

[0016] Furthermore, in step S2, the specific steps of measuring metal by atomic absorption spectrometry are as follows:

[0017] Step B1, digest the pre-treated water, after digestion, remove and cool, add water to dissolve the residue, filter into a 100mL volumetric flask through medium-speed filter paper, dilute with water to the mark, and obtain the digested sample to be tested;

[0018] Step B2, setting a blank sample, taking 100 mL of water, adding 5 mL of nitric acid thereto, mixing evenly, to obtain a blank sample, adding 5 mL of nitric acid to the 100 mL of the sample to be tested after digestion, mixing evenly, to obtain a sample to be tested;

[0019] Step B3, preparing standard solutions of metals with different concentrations;

[0020] Step B4, turning on the atomic absorption spectrophotometer, turning on the acetylene gas cylinder connected to the atomic absorption spectrophotometer, and then turning on the air compressor connected to the atomic absorption spectrophotometer;

[0021] Step B5, selecting hollow cathode lamps of different elements according to the different metals to be detected; after the selection is completed, waiting for the instrument to be preheated and stabilized, and the atomic absorption spectrophotometer performs zeroing operation;

[0022] Step B6, injecting the prepared standard solution, measuring the absorbance, and drawing a standard curve of the metal with the concentration of the standard solution of the metal as the abscissa and the absorbance as the ordinate;

[0023] Step B7, injecting a blank sample and a sample to be tested, measuring absorbance, taking the average of three measurements, and calculating the concentration of the metal in the sample to be tested.

[0024] Furthermore, in step B1, the digestion treatment step is: add 5 mL of nitric acid, heat and digest on a hot plate to ensure that the sample does not boil, evaporate to about 1 mL, add 5 mL of nitric acid and 2 mL of perchloric acid, continue digestion, and evaporate to about 1 mL.

[0025] Furthermore, in step B3, the composition of the standard solution is water and nitric acid; the volume ratio of water to nitric acid is 99:1; in step B4, the flow rate of acetylene in the acetylene cylinder is 2.80 L / min; the flow rate of air in the air compressor is 13.80 L / min; in step B5, the instrument preheating time is 15 min to 20 min.

[0026] Furthermore, the heating temperature of the electric heating plate is 240-260°C.

[0027] Further, in step S3, the specific steps of measuring cyanide by spectrophotometry are:

[0028] Step C1, preparing an isonicotinic acid-pyrazolone solution, weighing isonicotinic acid and dissolving it in a sodium hydroxide solution, diluting the solution with water to 100 mL, then weighing pyrazolone and dissolving it in anhydrous ethanol, mixing the pyrazolone solution and the isonicotinic acid solution according to a volume ratio to obtain an isonicotinic acid-pyrazolone solution;

[0029] Step C2, take a 25mL colorimetric tube, add different amounts of potassium cyanide solution, add water to 10mL, add phosphate buffer solution, and then add chloramine T solution, immediately cover the stopper, mix well, and let stand for 6 to 8 minutes to obtain a standard solution of potassium cyanide;

[0030] Step C3, set a blank sample, take 10 mL of water and 10 mL of pre-treated water into a 25 mL colorimetric tube, add phosphate buffer solution, then add chloramine T solution, immediately cover the stopper, mix well, and leave for 6 to 8 minutes to obtain a blank sample and a sample to be tested;

[0031] Step C4, add 4 mL of isonicotinic acid-pyrazolone solution to each colorimetric tube, mix well, dilute to the mark with water, shake well, place in a water bath for 40 minutes, and immediately compare colors;

[0032] Step C5, turning on the UV-visible spectrophotometer, preheating for 10 to 15 minutes, setting the detection wavelength, selecting a cuvette for sample measurement, using water as a reference, measuring the absorbance, using the cyanide content as the abscissa and the absorbance after deducting the reagent blank as the ordinate, and drawing a standard curve for cyanide;

[0033] Step C6, injecting a blank sample into the test sample, measuring the absorbance, taking the average of three measurements, and calculating the concentration of cyanide in the test sample.

[0034] Furthermore, in step C1, the volume ratio is pyrazolone solution: isonicotinic acid solution = 1:4; in step C2, the volume of the phosphate buffer solution is 5 mL; the concentration of the chloramine T solution is 10 g / L, and the volume is 0.20 mL; in step C3, the volume of the phosphate buffer solution is 5 mL; the concentration of the chloramine T solution is 10 g / L, and the volume is 0.20 mL; in step C4, the temperature of the water bath is 38-42°C; in step C5, the instrument preheating time is 10-15 min; the detection wavelength is 638 nm; the specification of the cuvette is a 10 mm cuvette.

[0035] Beneficial Effects

[0036] The invention discloses a method for screening multiple pollutants in sewage, and screens and detects various metals harmful to human body and various cyanides in sewage. The detection method is simple to operate and has accurate results. When the cyanide in sewage is detected, the invention uses anhydrous ethanol as the solvent when preparing isonicotinic acid-pyrazolone solution, which replaces the currently commonly used N,N-dimethylformamide, and can save detection costs. At the same time, a blank control is set, and the detection is performed three times to ensure the accuracy of the detection result. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The flowchart of the screening method for multiple pollutants in a sewage is shown in FIG.

[0038] Figure 2 is the standard curve diagram of lead in Example 1;

[0039] Figure 3 It is the standard curve diagram of cyanide in Example 1;

[0040] Figure 4 is the standard curve diagram of zinc in Example 2;

[0041] Figure 5 It is the standard curve diagram of cyanide in Example 2. DETAILED DESCRIPTION

[0042] The present invention is further illustrated by specific examples below. These examples are exemplary and are intended to illustrate the problem and explain the present invention, but are not intended to be limiting.

[0043] Example 1

[0044] A method for screening multiple pollutants in paper mill wastewater comprises the following steps:

[0045] Step S1, collecting water quality around the paper mill and pre-processing the collected water quality, the pre-processing steps are:

[0046] Step A1, using a 30-mesh vibrating screen to remove large suspended particles, such as silt, fiber, etc., from the collected water;

[0047] Step A2, using an ultrasonic generator to treat the collected water to break up the aggregation of pollutants, ensure that the pollutants in the collected water are evenly distributed, avoid deviations during detection, and obtain pre-treated water;

[0048] Step S2, determining whether there is metallic lead in the pre-treated water, the specific steps are:

[0049] Step B1, digest the pre-treated water, add 5 mL of nitric acid, heat and digest on a hot plate, the heating temperature of the hot plate is 240 ° C, ensure that the sample does not boil, evaporate to about 1 mL, add 5 mL of nitric acid and 2 mL of perchloric acid, continue to digest, evaporate to about 1 mL, remove and cool, add water to dissolve the residue, filter into a 100 mL volumetric flask through medium-speed filter paper, dilute with water to the mark, and obtain the digested sample to be tested;

[0050] Step B2, setting a blank sample, taking 100 mL of water, adding 5 mL of nitric acid thereto, mixing evenly, to obtain a blank sample, adding 5 mL of nitric acid to the 100 mL of the sample to be tested after digestion, mixing evenly, to obtain a sample to be tested;

[0051] Step B3, preparing standard solutions of lead with different concentrations, wherein the prepared concentrations are 0.1 mg / L, 0.5 mg / L, 1 mg / L, 2 mg / L, 5 mg / L and 10 mg / L;

[0052] Step B4, turn on the atomic absorption spectrophotometer, open the acetylene cylinder connected to the atomic absorption spectrophotometer, the flow rate of acetylene is 2.80 L / min, and then turn on the air compressor connected to the atomic absorption spectrophotometer, the air flow rate in the air compressor is 13.80 L / min;

[0053] Step B5, if the metal to be detected is lead, a hollow cathode lamp of the lead element is selected. After the selection is completed, the machine is preheated for 20 minutes to stabilize, and the atomic absorption spectrophotometer is zeroed;

[0054] Step B6, injecting the prepared standard solution, measuring the absorbance, and drawing a standard curve of lead with the concentration of the standard solution of lead as the abscissa and the absorbance as the ordinate;

[0055] Step B7, injecting a blank sample and a sample to be tested, measuring absorbance, taking the average of three measurements, and calculating the lead concentration in the sample to be tested;

[0056] Step S3, determining whether cyanide exists in the pre-treated water, the specific steps are:

[0057] Step C1, preparing an isonicotinic acid-pyrazolone solution, weighing 2.0 g of isonicotinic acid and dissolving it in 30 mL of 20 g / L sodium hydroxide solution, diluting the volume to 100 mL with water, then weighing 0.3 g of pyrazolone and dissolving it in 25 mL of anhydrous ethanol, and mixing the pyrazolone solution and the isonicotinic acid solution in a ratio of 1:4 to obtain an isonicotinic acid-pyrazolone solution;

[0058] Step C2, take 7 25mL colorimetric tubes, add 0, 0.5, 1, 2, 3, 4 and 5mL of 1.00mg / L potassium cyanide solution, respectively, add water to 10mL, the cyanide content is 0.50μg, 1.00μg, 2.00μg, 3.00μg, 4.00μg and 5.00μg, add 5mL of phosphate buffer solution, and then add 0.20mL of 10g / L chloramine T solution, immediately cover the stopper, mix well, and let stand for 6min to obtain standard solutions of potassium cyanide of different concentrations;

[0059] Step C3, set a blank sample, take 10mL of water and 10mL of pre-treated water into a 25mL colorimetric tube, add 5mL of phosphate buffer solution, then add 0.20mL of 10g / L chloramine T solution, immediately cover the stopper, mix well, and leave for 6min to obtain a blank sample and a sample to be tested;

[0060] Step C4, add 4 mL of isonicotinic acid-pyrazolone solution to each colorimetric tube, mix well, dilute to the mark with water, shake well, place in a 38° C. water bath for 40 min, and immediately perform colorimetric analysis;

[0061] Step C5, turning on the UV-visible spectrophotometer, preheating for 15 minutes, setting the detection wavelength to 638 nm, selecting a 10 mm cuvette for sample measurement, using water as a reference, measuring the absorbance, using the cyanide content as the abscissa and the absorbance after deducting the reagent blank as the ordinate, and drawing a standard curve for cyanide;

[0062] Step C6, injecting a blank sample into the test sample, measuring the absorbance, taking the average of three measurements, and calculating the concentration of cyanide in the test sample.

[0063] Example 2

[0064] A method for screening multiple pollutants in wastewater from a pharmaceutical factory comprises the following steps:

[0065] Step S1, collecting water quality around the pharmaceutical factory and pre-treating the collected water quality. The pre-treatment steps are:

[0066] Step A1, using a 30-mesh vibrating screen to remove large suspended particles, such as silt, fiber, etc., from the collected water;

[0067] Step A2, using an ultrasonic generator to treat the collected water to break up the aggregation of pollutants, ensure that the pollutants in the collected water are evenly distributed, avoid deviations during detection, and obtain pre-treated water;

[0068] Step S2, determining whether there is metallic zinc in the pre-treated water, the specific steps are:

[0069] Step B1, digest the pre-treated water, add 5 mL of nitric acid, heat and digest on a hot plate, the heating temperature of the hot plate is 250 ° C, ensure that the sample does not boil, evaporate to about 1 mL, add 5 mL of nitric acid and 2 mL of perchloric acid, continue to digest, evaporate to about 1 mL, remove and cool, add water to dissolve the residue, filter into a 100 mL volumetric flask through medium-speed filter paper, dilute with water to the mark, and obtain the digested sample to be tested;

[0070] Step B2, setting a blank sample, taking 100 mL of water, adding 5 mL of nitric acid thereto, mixing evenly, to obtain a blank sample, adding 5 mL of nitric acid to the 100 mL of the sample to be tested after digestion, mixing evenly, to obtain a sample to be tested;

[0071] Step B3, preparing standard solutions of zinc with different concentrations, wherein the prepared concentrations are 0.1 mg / L, 0.5 mg / L, 1 mg / L, 2 mg / L, 5 mg / L and 10 mg / L;

[0072] Step B4, turn on the atomic absorption spectrophotometer, open the acetylene cylinder connected to the atomic absorption spectrophotometer, the flow rate of acetylene is 2.80 L / min, and then turn on the air compressor connected to the atomic absorption spectrophotometer, the air flow rate in the air compressor is 13.80 L / min;

[0073] Step B5, if the metal to be detected is zinc, a hollow cathode lamp of zinc element is selected. After the selection is completed, the machine is preheated for 20 minutes to stabilize, and the atomic absorption spectrophotometer is zeroed;

[0074] Step B6, injecting the prepared standard solution, measuring the absorbance, and drawing a standard curve of zinc with the concentration of the standard solution of zinc as the abscissa and the absorbance as the ordinate;

[0075] Step B7, injecting a blank sample and a sample to be tested, measuring absorbance, taking an average of three measurements, and calculating the zinc concentration in the sample to be tested;

[0076] Step S3, determining whether cyanide exists in the pre-treated water, the specific steps are:

[0077] Step C1, preparing an isonicotinic acid-pyrazolone solution, weighing 1.5 g of isonicotinic acid and dissolving it in 25 mL of 20 g / L sodium hydroxide solution, diluting the volume to 100 mL with water, then weighing 0.25 g of pyrazolone and dissolving it in 20 mL of anhydrous ethanol, and mixing the pyrazolone solution and the isonicotinic acid solution in a ratio of 1:4 to obtain an isonicotinic acid-pyrazolone solution;

[0078] Step C2, take 7 25mL colorimetric tubes, add 0, 0.5, 1, 2, 3, 4 and 5mL of 1.00mg / L potassium cyanide solution respectively, add water to 10mL, the cyanide content is 0.50μg, 1.00μg, 2.00μg, 3.00μg, 4.00μg and 5.00μg respectively, add 5mL of phosphate buffer solution, then add 0.20mL of 10g / L chloramine T solution, immediately cover the stopper, mix well, and let stand for 8min to obtain standard solutions of potassium cyanide of different concentrations;

[0079] Step C3, set a blank sample, take 10mL of water and 10mL of pre-treated water into a 25mL colorimetric tube, add 5mL of phosphate buffer solution, then add 0.20mL of 10g / L chloramine T solution, immediately cover the stopper, mix well, and leave for 8min to obtain a blank sample and a sample to be tested;

[0080] Step C4, add 4 mL of isonicotinic acid-pyrazolone solution to each colorimetric tube, mix well, dilute to the mark with water, shake well, place in a 40° C. water bath for 40 min, and immediately compare colors;

[0081] Step C5, turning on the UV-visible spectrophotometer, preheating for 15 minutes, setting the detection wavelength to 638 nm, selecting a 10 mm cuvette for sample measurement, using water as a reference, measuring the absorbance, using the cyanide content as the abscissa and the absorbance after deducting the reagent blank as the ordinate, and drawing a standard curve for cyanide;

[0082] Step C6, injecting a blank sample into the test sample, measuring the absorbance, taking the average of three measurements, and calculating the concentration of cyanide in the test sample.

[0083] Contents of various pollutants in paper mill wastewater

[0084] Figure 2 is the standard curve of lead in Example 1, where R 2 =0.9997, which is higher than 0.999, indicating that the fitting degree is good, the quality of the prepared lead standard curve is high, and the accuracy of the results of determining the lead concentration in the paper mill wastewater sample is improved. Subsequently, the lead concentration in Example 1 is calculated according to the absorbance value determined by the sample to be tested. The determined data are summarized in Table 1. The results show that the lead concentration in the paper mill wastewater is 4.2985 mg / L.

[0085] Example 1 also measured the cyanide content in paper mill wastewater. Figure 3 is the standard curve of cyanide in Example 1, where R 2 =0.9992, which is higher than 0.999, indicating that the fitting degree is good, the quality of the prepared standard curve of cyanide is high, and the accuracy of the results of determining the cyanide concentration in the paper mill wastewater sample is improved. Subsequently, according to the absorbance value determined by the sample to be tested, the concentration of cyanide in Example 1 is calculated. The determined data are summarized in Table 2. The results show that the concentration of cyanide in the paper mill wastewater is 0.9272 μg / mL.

[0086] At the same time, in Example 1, when determining whether cyanide exists in the pre-treated water, it is necessary to use isonicotinic acid-pyrazolone solution for colorimetry. In the process of preparing isonicotinic acid-pyrazolone solution, the solvent anhydrous ethanol is used to replace the commonly used N,N-dimethylformamide. The cost of anhydrous ethanol is lower than that of N,N-dimethylformamide, so it can save costs. At the same time, in Example 1, when determining whether metallic lead exists in the pre-treated water and when determining whether cyanide exists in the pre-treated water, a blank control is set, and the results are measured three times to ensure the accuracy of the measured results.

[0087] Table 1 Data of blank sample and lead sample to be tested in Example 1

[0088]

[0089] Table 2 Data of blank sample and cyanide sample in Example 1

[0090]

[0091]

[0092] Contents of various pollutants in wastewater from pharmaceutical factories

[0093] Figure 4 is the standard curve of zinc in Example 2, where R 2 =0.9999, which is higher than 0.999, indicating that the fitting degree is good, the prepared zinc standard curve is of high quality, and the accuracy of the results of determining the zinc concentration in the pharmaceutical factory wastewater sample is improved. Subsequently, the zinc concentration in Example 2 is calculated according to the absorbance value determined by the sample to be tested. The determined data are summarized in Table 3. The results show that the zinc concentration in the pharmaceutical factory wastewater is 1.1581 mg / L.

[0094] Example 2 also measured the cyanide content in the wastewater of the pharmaceutical factory. Figure 5 is the standard curve of cyanide in Example 2, where R 2=0.9991, which is higher than 0.999, indicating that the fitting degree is good, the quality of the prepared cyanide standard curve is high, and the accuracy of the results of measuring the cyanide concentration in the pharmaceutical factory wastewater sample is improved. Subsequently, according to the absorbance value measured by the sample to be tested, the concentration of cyanide in Example 2 is calculated. The measured data are summarized in Table 4. The results show that the concentration of cyanide in the paper mill wastewater is 0.6383 μg / mL.

[0095] At the same time, in Example 2, when determining whether cyanide exists in the pre-treated water, it is necessary to use isonicotinic acid-pyrazolone solution for colorimetry. In the process of preparing isonicotinic acid-pyrazolone solution, the solvent anhydrous ethanol is used to replace the commonly used N,N-dimethylformamide. The cost of anhydrous ethanol is lower than that of N,N-dimethylformamide, so it can save costs. At the same time, in Example 2, when determining whether metallic zinc exists in the pre-treated water and when determining whether cyanide exists in the pre-treated water, a blank control is set, and the results are measured three times to ensure the accuracy of the measured results.

[0096] Table 3 Data of blank sample and zinc sample to be tested in Example 2

[0097]

[0098] Table 4 Data of blank sample and cyanide sample in Example 2

[0099]

[0100]

Claims

1. A method for screening multiple pollutants in sewage, characterized in that: The steps include: Step S1, collecting water quality and pre-processing the collected water quality; Step S2, using atomic absorption spectrometry to measure whether there is metal in the pre-treated water; Step S3, using spectrophotometry to determine whether cyanide exists in the pre-treated water; Step S4, obtaining data of various pollutants in sewage.

2. The method for screening multiple pollutants in sewage according to claim 1, characterized in that: In step S1, the pre-processing steps are: Step A1, using an instrument to remove large suspended particles in the sewage; Step A2, by stirring or ultrasonic treatment of the collected water, ensure that various pollutants in the collected water are evenly distributed to obtain pre-treated water.

3. The method for screening multiple pollutants in sewage according to claim 2, characterized in that: In step A1, the instrument is a vibrating screen, a belt filter press or a sand filter; the mesh size of the vibrating screen, the belt filter press or the sand filter is 25 to 35 meshes; in step A2, the stirring instrument is a mechanical stirrer or an air stirrer; the rotation speed of the mechanical stirrer is 100 r / min; the gas flow rate of the air stirrer is 13 cfm; the ultrasonic instrument is an ultrasonic generator; the ultrasonic frequency of the ultrasonic generator is 50 kHz.

4. The method for screening multiple pollutants in sewage according to claim 1, characterized in that: In step S2, the metal is one or more of copper, zinc, lead, chromium, thallium and nickel.

5. The method for screening multiple pollutants in sewage according to claim 1, characterized in that: In step S2, the specific steps of measuring metal by atomic absorption spectrometry are: Step B1, digest the pre-treated water, after digestion, remove and cool, add water to dissolve the residue, filter into a 100mL volumetric flask through medium-speed filter paper, dilute with water to the mark, and obtain the digested sample to be tested; Step B2, setting a blank sample, taking 100 mL of water, adding 5 mL of nitric acid thereto, mixing evenly, to obtain a blank sample, adding 5 mL of nitric acid to the 100 mL of the sample to be tested after digestion, mixing evenly, to obtain a sample to be tested; Step B3, preparing standard solutions of metals with different concentrations; Step B4, turning on the atomic absorption spectrophotometer, turning on the acetylene gas cylinder connected to the atomic absorption spectrophotometer, and then turning on the air compressor connected to the atomic absorption spectrophotometer; Step B5, selecting hollow cathode lamps of different elements according to the different metals to be detected; After the selection is completed, wait for the instrument to warm up and stabilize, and the atomic absorption spectrophotometer to perform zero adjustment; Step B6, injecting the prepared standard solution, measuring the absorbance, and drawing a standard curve of the metal with the concentration of the standard solution of the metal as the abscissa and the absorbance as the ordinate; Step B7, injecting a blank sample and a sample to be tested, measuring absorbance, taking the average of three measurements, and calculating the concentration of the metal in the sample to be tested.

6. The method for screening multiple pollutants in sewage according to claim 5, characterized in that: In step B1, the digestion treatment steps are: add 5 mL of nitric acid, heat and digest on a hot plate to ensure that the sample does not boil, evaporate to about 1 mL, add 5 mL of nitric acid and 2 mL of perchloric acid, continue to digest, and evaporate to about 1 mL.

7. The method for screening multiple pollutants in sewage according to claim 5, characterized in that: In step B3, the standard solution is composed of water and nitric acid; the volume ratio of water to nitric acid is 99:1; in step B4, the flow rate of acetylene in the acetylene cylinder is 2.80 L / min; the flow rate of air in the air compressor is 13.80 L / min; in step B5, the preheating time of the instrument is 15 min to 20 min.

8. The method for screening multiple pollutants in sewage according to claim 6, characterized in that: The heating temperature of the electric heating plate is 240-260°C.

9. The method for screening multiple pollutants in sewage according to claim 1, characterized in that: In step S3, the specific steps of measuring cyanide by spectrophotometry are: Step C1, preparing an isonicotinic acid-pyrazolone solution, weighing isonicotinic acid and dissolving it in a sodium hydroxide solution, diluting the solution with water to 100 mL, then weighing pyrazolone and dissolving it in anhydrous ethanol, mixing the pyrazolone solution and the isonicotinic acid solution according to a volume ratio to obtain an isonicotinic acid-pyrazolone solution; Step C2, take a 25mL colorimetric tube, add different amounts of potassium cyanide solution, add water to 10mL, add phosphate buffer solution, and then add chloramine T solution, immediately cover the stopper, mix well, and let stand for 6-8 minutes to obtain a standard solution of potassium cyanide; Step C3, set a blank sample, take 10 mL of water and 10 mL of pre-treated water into a 25 mL colorimetric tube, add phosphate buffer solution, then add chloramine T solution, immediately cover the stopper, mix well, and leave for 6-8 minutes to obtain a blank sample and a sample to be tested; Step C4, add 4 mL of isonicotinic acid-pyrazolone solution to each colorimetric tube, mix well, dilute to the mark with water, shake well, place in a water bath for 40 minutes, and immediately compare colors; Step C5, turning on the UV-visible spectrophotometer, preheating for 10-15 minutes, setting the detection wavelength, selecting a cuvette for sample measurement, using water as a reference, measuring the absorbance, using the cyanide content as the abscissa and the absorbance after deducting the reagent blank as the ordinate, and drawing a standard curve for cyanide; Step C6, injecting a blank sample into the sample to be tested, measuring the absorbance, taking the average of three measurements, and calculating the concentration of cyanide in the sample to be tested.

10. The method for screening multiple pollutants in sewage according to claim 9, characterized in that: In step C1, the volume ratio is pyrazolone solution: isonicotinic acid solution = 1:4; in step C2, the volume of the phosphate buffer solution is 5 mL; the concentration of the chloramine T solution is 10 g / L, and the volume is 0.20 mL; in step C3, the volume of the phosphate buffer solution is 5 mL; the concentration of the chloramine T solution is 10 g / L, and the volume is 0.20 mL; in step C4, the temperature of the water bath is 38-42° C.; in step C5, the preheating time of the instrument is 10-15 min; the detection wavelength is 638 nm; the specification of the cuvette is a 10 mm cuvette.

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