Method for measuring sodium dodecyl sulfate in wastewater through magnetic field enhancement

Abstract

The invention provides a magnetic field enhanced method for measuring the content of sodium dodecyl sulfate in wastewater, which comprises the following steps: carrying out solid-liquid separation pretreatment on a wastewater sample, removing suspended solids and solid impurities, uniformly mixing the wastewater sample with a malachite green solution to form a to-be-measured wastewater sample, and fully reacting in a magnetic field environment to obtain the content of sodium dodecyl sulfate in the wastewater. And detecting the absorbance value of the mixture at 582 nm, and calculating the content of sodium dodecyl sulfate in the wastewater sample according to the obtained absorbance value and a standard curve formula. Compared with the prior art, the detection method provided by the invention has the advantages that the bond energy and interaction capability of anions and cations in the sodium dodecyl sulfate and malachite green solution in the wastewater are enhanced through a magnetic field environment, so that a chromogenic association compound of the sodium dodecyl sulfate and malachite green in a wastewater sample is more stable, and the electron cloud distribution of the sodium dodecyl sulfate is changed; therefore, the absorption peak signal is enhanced, and the sensitivity and accuracy of the detection method are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of sodium dodecyl sulfate detection, and particularly relates to a method for detecting sodium dodecyl sulfate in waste water by magnetic field enhancement. Background Art

[0002] Sodium dodecyl sulfate (SDS) is a common anionic surfactant. As the main raw material of synthetic detergents, it is widely used in various fields such as agriculture, textiles, and chemicals. However, with the increasing application of such products, water pollution problems are becoming increasingly serious. In particular, the presence of surfactants reduces the self-purification ability of water bodies, causing algae to reproduce rapidly and destroying the ecological balance. Surfactants remaining in water bodies will enter the human body through the food chain and bioaccumulate. In the long run, it is easy to cause a decrease in human immunity and an increase in the risk of disease. Therefore, it is necessary to conduct targeted testing of the surfactant content in domestic sewage to avoid excessive content and pollution of water resources, which in turn affects human health.

[0003] At present, the commonly used detection methods for sodium dodecyl sulfate mainly include ultraviolet spectrophotometry, high performance liquid chromatography and fluorescence analysis. Among them, high performance liquid chromatography and fluorescence analysis have relatively high sensitivity, but the former has complex separation conditions for gradient elution; the latter is easily affected by environmental factors. Ultraviolet spectrophotometry has the advantages of low cost, high sensitivity and rapid detection. Among them, methylene blue spectrophotometry (GB / T / T 7494-1987) is the current national standard method with high sensitivity, but the operation is complicated and requires repeated extraction with chloroform, which has low safety. Based on this, researchers have also proposed some innovative methods. For example, the prior art CN201910632630.3 simplifies the steps and improves the stability by adding masking agents and Lloyd's purple solution; the prior art CN201710343311.1 directly uses the standard curve of absorbance value for comparative analysis. Although these methods have facilitated the difficulty of determination to a certain extent, the precision, sensitivity and accuracy of detection still need to be improved. Summary of the invention

[0004] In order to solve all or part of the above technical problems, the present invention provides the following technical solutions: One of the purposes of the present invention is to provide a method for determining sodium dodecyl sulfate in waste water by magnetic field enhancement, the method comprising: The wastewater sample to be tested containing sodium dodecyl sulfate is reacted with malachite green in a magnetic field to obtain a reaction solution to be tested; the magnetic field strength of the magnetic field is 0.5-0.8 T; The absorbance value A of the reaction solution to be tested at a wavelength of 582 nm is detected, and the concentration Y of sodium dodecyl sulfate in the wastewater sample to be tested is calculated according to the standard curve Y=28.154AC, where C=0.154~0.473, and the unit of Y is mg / L.

[0005] The detection method provided by the present invention is assisted by magnetic field treatment during the combination process of malachite green and sodium dodecyl sulfate, so as to enhance the bond energy and interaction ability of the anions and cations in the sodium dodecyl sulfate and malachite green solution in the wastewater, so as to promote the structure of the association complex of malachite green and sodium dodecyl sulfate to be more stable, and change the electron cloud distribution of sodium dodecyl sulfate, so as to enhance the absorption peak signal, and improve the sensitivity and accuracy of the detection. The magnetic field intensity of the magnetic field has an impact on the detection effect. If the magnetic field intensity is low, the effect cannot be manifested, the compound structure stability is poor, and the absorption signal is weak; if the magnetic field intensity is large, it is easy to cause the electron cloud center distance of the compound obtained by the reaction to shift, and weaken the binding force between molecules, resulting in a decrease in the absorption peak intensity.

[0006] In some embodiments, the magnetic field is a pulsed magnetic field.

[0007] In some embodiments, the magnetic field frequency of the pulsed magnetic field is 0.01-0.1 Hz.

[0008] In some embodiments, the pulsed magnetic field is a sawtooth pulsed magnetic field.

[0009] In some embodiments, the pH value of the wastewater sample to be tested is 6.8-7.6. For example, an acidic reagent such as HCl or an alkaline reagent such as NaOH can be used to adjust the pH value of the wastewater sample to be tested.

[0010] In some embodiments, the wastewater sample to be tested includes domestic wastewater. The concentration of sodium dodecyl sulfate in the wastewater is not less than 0.01 mg / L. The domestic wastewater includes, for example, bathroom wastewater, kitchen wastewater, laundry wastewater, etc.

[0011] In some embodiments, before reacting the wastewater sample to be tested with malachite green, the step of pretreating the wastewater sample to be tested is also included, and the pretreatment includes solid-liquid separation of the wastewater sample to be tested to at least remove suspended matter and solid impurities therein.

[0012] In some embodiments, the method specifically includes: preparing malachite green into a malachite green solution with a concentration of 0.5~1.5 mg / L, and mixing the pretreated wastewater sample to be tested with the malachite green solution in a volume ratio of 10:1~1:1 to carry out the reaction.

[0013] In some embodiments, the reaction temperature of the reaction is 20-30° C., and the reaction time is 20-40 min.

[0014] In some embodiments, the method for determining the standard curve includes: taking a series of sodium dodecyl sulfate solutions of different concentrations as standard samples, and allowing the standard samples to react with malachite green in the magnetic field to obtain a standard reaction solution; taking 3 mL of the standard reaction solution in a quartz cuvette, the optical path of the quartz cuvette is 1 cm, and detecting the absorbance value of the standard reaction solution at a wavelength of 582 nm, thereby obtaining the relationship between the concentration of sodium dodecyl sulfate in the standard sample and the absorbance value of the corresponding standard reaction solution at a wavelength of 582 nm, and then establishing the standard curve.

[0015] In some embodiments, the method further comprises: when detecting the absorbance value A of the reaction solution to be tested, a buffer solution with a concentration of 0.1-0.5 mol / L and a pH value of 6.8-7.6 is used as a reference. More specifically, after the reaction of the wastewater sample to be tested and malachite green is completed, 3 mL of the reaction solution to be tested is taken into a quartz cuvette, and the absorbance value at 582 nm is measured with the buffer solution as a reference, and the optical path of the cuvette is 1 cm. The buffer solution can be, for example, a sodium phosphate or potassium salt buffer solution, but is not limited thereto.

[0016] In some embodiments, the detection range of the method is 0.01-20 mg / L.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The present invention applies a magnetic field during the process of combining malachite green and sodium dodecyl sulfate. Since the sodium ions have a large charge, they are subject to a large Lorentz force, and their motion trajectory and speed are enhanced, which affects the signal transmission between different electrons and ions and enhances the ionic bond energy and interaction force. The magnetic field is used to change the electron cloud distribution of sodium dodecyl sulfate, the radius of the cation is reduced, the radius of the anion is increased, the absorption peak signal of the ion association complex is enhanced, and the peak width is narrowed. In addition, the magnetic field can also make the association complex formed by the reaction of the two more stable, thereby improving the sensitivity and accuracy of the detection method; (2) The detection method provided by the present invention does not require the addition of other organic solvents, and can achieve high sensitivity and accuracy by simply applying magnetic field treatment, which effectively simplifies the operation steps and improves the safety of the detection method; (3) The relative standard deviation of the detection results of the method provided by the present invention is within 4%, and the spike recovery rate is higher than 93%, indicating that the method has high precision; compared with the detection results of the GB / T 7494-1987 method, the relative deviation does not exceed ±3%, indicating that the method has high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is an ultraviolet absorption spectrum of the complex formed by the standard solution of sodium dodecyl sulfate and malachite green in the range of 450-700 nm under the conditions of applying a magnetic field and not applying a magnetic field in Example 1 of the present invention. DETAILED DESCRIPTION

[0020] In view of the many defects of the prior art, the inventors of this case, after long-term research and extensive practice, were very pleasantly surprised to find that in the process of combining malachite green and sodium dodecyl sulfate, if assisted by magnetic field treatment, not only can the structure of the complex be made more stable, but also the sensitivity and accuracy of detection can be improved.

[0021] Sodium dodecyl sulfate is composed of dodecyl sulfonate ion (C 12 H 25 SO3 - ) and sodium ions (Na + ), while the dodecyl sulfonate ion is composed of a dodecyl chain (C 12 H 25 - ) and sulfonic acid groups (-SO3 - ) are combined. Sodium ions, as the cationic part, combine with sulfonate ions to form stable salt compounds. The principle of spectrophotometric detection of sodium dodecyl sulfate is mainly based on the fact that sodium dodecyl sulfate forms an ion association complex with a specific color with malachite green, which has an absorption effect on light within a specific wavelength range. The content of sodium dodecyl sulfate can be determined by measuring its absorbance value. The present invention finds that different ions are affected by the Lorentz force in a magnetic field environment. Sodium ions are affected by a larger Lorentz force due to their large charge, and their motion trajectory and speed are enhanced, which affects the signal transmission between different electrons and ions, enhances the ionic bond energy and interaction force, and further affects the stability of the ion complex. Under magnetic field conditions, the radius of the cation decreases, the radius of the anion increases, and the symmetric center of the electron cloud distribution of sodium dodecyl sulfate shifts, thereby enhancing the light absorption performance of the ion association complex and the absorbance value of the solution, and improving the detection sensitivity and accuracy.

[0022] Based on such unexpected discovery, the applicant has proposed the technical solution of the present invention, and the technical solution, its implementation process and principle, etc. will be further explained in combination with several embodiments as follows. However, it should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described in the following (embodiments) can be combined with each other to form a new or preferred technical solution. Due to space limitations, they will not be described one by one here.

[0023] Calculation of the spike recovery θ (%): add 0.1 mL of 1 g / L sodium dodecyl sulfate standard solution to 10 mL of pretreated sample (sodium dodecyl sulfate concentration Y0), calculate the spike concentration Y1, and detect according to the method of the present invention to obtain the corresponding absorbance value A, and then calculate the measured value Y2 of the sodium dodecyl sulfate content in the wastewater after spiked based on the relationship between A and the standard curve, then the spike recovery θ (%) = (Y2-Y0) / Y1×100.

[0024] Calculation of relative deviation (%) of the test results of different methods: Let the test result of this implementation method be Y a , the control method test result is Y b , then the relative deviation (%) = (Y a -Y b ) / Y c ×100, where Y c is the average of the two test results.

[0025] In the following examples, unless otherwise specified, the various raw materials, reagents, reaction equipment, testing equipment and methods used can be obtained through commercial purchase or other channels.

[0026] Example 1 Example 1 provides a method for determining sodium dodecyl sulfate in bathroom wastewater using a magnetic field-enhanced malachite green reagent method, which specifically comprises the following steps: S1. The bathroom wastewater was filtered through gauze until there were no obvious impurities and suspended matter, and the pH of the filtrate was adjusted to 7.2 with 0.1 mol / L HCl to obtain pretreated bathroom wastewater; S2. Take 2 mL of the above-mentioned pretreated bathroom wastewater and mix it thoroughly with 1 mL of 1 mg / L malachite green solution to obtain a mixed solution; S3. Place the above mixed solution in a constant temperature magnetic field box, set the ambient temperature in the chamber to 25 °C, set the magnetic field type to a sawtooth pulse magnetic field, the magnetic field strength to 0.6 T, the frequency to 0.05 Hz, and allow to react for 30 min. After the reaction, take 3 mL of the reaction solution in a 1 cm optical path quartz cuvette, and use the blank group (the blank group uses 0.2 mol / L, pH 7.2 Na2HPO4-KH2PO4 buffer instead of bathroom wastewater) as a reference to measure the absorbance value A of the sample at 582 nm.

[0027] Standard curve determination: Sodium dodecyl sulfate solutions with different concentrations of 0, 2, 4, 6, 8, 10, 12, 14, and 16 mg / L were taken as standard samples, and the absorbance values ​​of these solutions at 582 nm were determined according to the methods described in S1-S3. By collecting the obtained data and building a model, the relationship between the sodium dodecyl sulfate content Y in the standard sample and the absorbance value A was obtained, Y=28.154A-0.264, and the detection range was 0.010-15.628 mg / L.

[0028] For bathroom wastewater to be tested with unknown sodium dodecyl sulfate content, the test is performed according to the steps described in S1 to S3 to obtain its corresponding absorbance value A, and then the sodium dodecyl sulfate content in the bathroom wastewater to be tested is calculated based on the relationship between A and the above standard curve.

[0029] The method of this embodiment and the method of GB / T 7494-1987 were used to detect the content of sodium dodecyl sulfate in 6 collected bathroom wastewaters. The results are shown in Table 1. The relative standard deviation of the detection results of the method of this embodiment is always less than 2%, and the spike recovery rate is higher than 96%, indicating that the method has high precision. In addition, compared with the detection results of the method described in GB / T 7494-1987, the relative deviation is always less than ±2%, indicating that the detection method provided by the present invention has high accuracy.

[0030] Table 1 Test results of 6 bathroom wastewater samples tested using the method of Example 1 ; Figure 1 The figure is the ultraviolet absorption spectrum of the complex formed by the standard solution of sodium dodecyl sulfate and malachite green in the range of 450-700 nm under the conditions of applying a magnetic field and not applying a magnetic field in Example 1 of the present invention. It can be seen that under the condition of applying a magnetic field, the absorbance value of the complex formed by sodium dodecyl sulfate and malachite green is significantly enhanced.

[0031] Example 2 Example 2 provides a method for determining sodium dodecyl sulfate in kitchen wastewater using a magnetic field enhanced malachite green reagent method, which specifically comprises the following steps: S1. The kitchen wastewater was filtered through gauze until there were no obvious impurities and suspended matter, and the pH of the filtrate was adjusted to 7.4 with 0.1 mol / L HCl to obtain pretreated kitchen wastewater; S2. Take 10 mL of the pretreated kitchen wastewater obtained above and mix thoroughly with 1 mL of 1.5 mg / L malachite green solution to obtain a mixed solution; S3. Place the mixed solution in a constant temperature magnetic field box, set the ambient temperature in the chamber to 30 °C, set the magnetic field type to a sawtooth pulse magnetic field, set the magnetic field intensity to 0.8 T, set the magnetic field frequency to 0.01 Hz, and allow to react for 20 min. After the reaction, take 3 mL of the reaction solution and place it in a 1 cm optical path quartz cuvette. Use the blank group (the blank group uses 0.5 mol / L Na2HPO4-NaH2PO4 buffer solution with a pH of 7.4 instead of kitchen waste water) as a reference to determine the absorbance value A of the sample at 582 nm.

[0032] Standard curve determination: Sodium dodecyl sulfate solutions with different concentrations of 0, 3, 6, 9, 12, 15, and 18 mg / L were taken as standard samples, and the absorbance values ​​of these solutions at 582 nm were determined according to the methods described in S1-S3. By collecting the obtained data and building a model, the relationship between the sodium dodecyl sulfate content Y in the standard sample and the absorbance value A was obtained, Y=28.154A-0.451, and the detection range was 0.010-16.441 mg / L.

[0033] For kitchen wastewater to be tested with unknown sodium dodecyl sulfate content, the test is performed according to the steps described in S1 to S3 to obtain its corresponding absorbance value A, and then the sodium dodecyl sulfate content in the kitchen wastewater to be tested is calculated based on the relationship between A and the above standard curve.

[0034] The method of this embodiment and the method of GB / T 7494-1987 were used to detect the content of sodium dodecyl sulfate in 8 collected kitchen wastewaters. The results are shown in Table 2. The relative standard deviation of the detection results of the method of this embodiment is always less than 4%, and the spike recovery rate is higher than 95%, indicating that the method has high precision. In addition, compared with the detection results of the method described in GB / T 7494-1987, the relative deviation is always less than ±3%, indicating that the detection method provided by the present invention has high accuracy.

[0035] Table 2 Test results of 8 samples of kitchen wastewater tested by the method of Example 2

[0036] Example 3 Example 3 provides a method for determining sodium dodecyl sulfate in laundry wastewater using a magnetic field-enhanced malachite green reagent method, which specifically comprises the following steps: S1, the laundry wastewater was filtered through gauze until there were no obvious impurities and suspended matter, and the pH of the filtrate was adjusted to 6.8 with 0.1 mol / L HCl to obtain pretreated laundry wastewater; S2, taking 5 mL of the above-mentioned pretreated laundry wastewater and 5 mL of 0.5 mg / L malachite green solution and mixing them thoroughly to obtain a mixed solution; S3. Place the above mixed solution in a constant temperature magnetic field box, set the ambient temperature in the chamber to 20 ℃, the magnetic field type to a sawtooth pulse magnetic field, the magnetic field strength to 0.5 T, the magnetic field frequency to 0.1 Hz, and allow to react for 40 min. After the reaction, take 3 mL of the reaction solution in a 1 cm optical path quartz cuvette, and use the blank group (the blank group uses 0.1 mol / L Na2HPO4-NaH2PO4 buffer solution with a pH of 6.8 instead of laundry wastewater) as a reference to determine the absorbance value A of the sample at 582 nm.

[0037] Standard curve determination: Sodium dodecyl sulfate solutions with different concentrations of 0, 2.5, 5, 7.5, 10, 12.5, 15, 17.5, and 20 mg / L were taken as standard samples, and the absorbance values ​​of these solutions at 582 nm were determined according to the methods described in S1-S3. By collecting the obtained data and building a model, the relationship between the sodium dodecyl sulfate content Y in the standard sample and the absorbance value A was obtained, Y=28.154A-0.186, and the detection range was 0.010-19.522 mg / L.

[0038] For laundry wastewater with unknown sodium dodecyl sulfate content, the test is performed according to the steps described in S1 to S3 to obtain the corresponding absorbance value A, and then the sodium dodecyl sulfate content in the laundry wastewater is calculated based on the relationship between A and the above standard curve.

[0039] The method of this embodiment and the method of GB / T 7494-1987 were used to detect the content of sodium dodecyl sulfate in 10 collected laundry wastewaters. The results are shown in Table 3. Laundry wastewater generally contains a higher content of sodium dodecyl sulfate. The relative standard deviation of the detection results of the method of this embodiment is always less than 4%, and the spike recovery rate is higher than 93%, indicating that the method has high precision. In addition, compared with the detection results of the method described in GB / T 7494-1987, the relative deviation is always less than ±3%, and the detection results are more accurate.

[0040] Table 3 Test results of 10 portions of laundry wastewater using the method of Example 3

[0041] Comparative Example 1 Comparative Example 1 provides a method for determining sodium dodecyl sulfate in bathroom wastewater using a malachite green reagent method, which specifically comprises the following steps: Steps S1 and S2 are the same as those in Example 1, except that in step S3, the mixed solution is placed in a constant temperature magnetic field box, and only the ambient temperature is set to 25°C without applying a magnetic field treatment, and the mixture is fully reacted for 30 minutes. 3 mL of the reaction solution is placed in a 1 cm optical path quartz cuvette, and the blank group is used as a reference to measure the absorbance value A of the sample at 582 nm.

[0042] Standard curve determination: Sodium dodecyl sulfate solutions with different concentrations of 0, 2, 4, 6, 8, 10, 12, 14, and 16 mg / L were taken as standard samples, and the absorbance of these solutions at 582 nm was determined according to the steps described in the control method. By collecting the obtained data and building a model, the relationship between the sodium dodecyl sulfate content Y in the standard sample and the absorbance value A was obtained, Y=24.269A-0.538, and the detection range was 0.010~9.170 mg / L.

[0043] For bathroom wastewater with unknown sodium dodecyl sulfate content, the test was performed according to the steps described in Comparative Example 1 to obtain the corresponding absorbance value A, and then the sodium dodecyl sulfate content in the bathroom wastewater was calculated based on A and the relationship between the standard curve.

[0044] The method of this comparative example and the method of GB / T 7494-1987 were used to detect the content of sodium dodecyl sulfate in 8 collected bathroom wastewaters. As shown in Table 4, the relative standard deviation of the detection results of the comparative example method varied in the range of 2% to 9%, with a large difference, and the spike recovery rate was less than 93%, indicating that the method was insufficient in precision and the detection stability was relatively poor. In addition, compared with the detection results of the method described in GB / T 7494-1987, the relative deviation was large, up to -6.07%, and the detection results of multiple samples were lower than the national standard method detection results, which may be related to the poor structural stability of the compound, resulting in a weakened absorption signal at 582nm.

[0045] Table 4 Test results of 8 bathroom wastewaters tested by the method of Comparative Example 1

[0046] Comparative Example 2 Comparative Example 2 provides a method for determining sodium dodecyl sulfate in bathroom wastewater using a magnetic field enhanced malachite green reagent method, which specifically comprises the following steps: Steps S1 and S2 are the same as those of Example 1, except that in step S3, the magnetic field strength of the pulsed magnetic field is 0.2 T.

[0047] Standard curve determination: Sodium dodecyl sulfate solutions with different concentrations of 0, 2, 4, 6, 8, 10, 12, 14, and 16 mg / L were taken as standard samples, and the absorbance of these solutions at 582 nm was determined according to the steps described in the control method. By collecting the obtained data and building a model, the relationship between the sodium dodecyl sulfate content Y in the standard sample and the absorbance value A was obtained, Y=23.164A-0.631, and the detection range was 0.010~10.951 mg / L.

[0048] For bathroom wastewater with unknown sodium dodecyl sulfate content, detection was performed according to the steps described in Comparative Example 2 to obtain its corresponding absorbance value A, and then the sodium dodecyl sulfate content in the bathroom wastewater was calculated based on A and the relationship between the standard curve.

[0049] The content of sodium dodecyl sulfate in 8 collected bathroom wastewaters was tested by the method of this comparative example and the method of GB / T 7494-1987, respectively. As shown in Table 5, the relative standard deviation of the test results of the comparative example method varied in the range of 3% to 7%, with a large difference, and the spike recovery rate was less than 93%, indicating that the method was not precise enough. In addition, compared with the test results of the method described in GB / T 7494-1987, the relative deviation was large, up to -6.71%. This may be related to the low intensity of the applied magnetic field, which could not make the effect manifest, so the compound structure was less stable and the absorption signal at 582 nm was weakened.

[0050] Table 5 Test results of 8 bathroom wastewaters tested by the method of Comparative Example 2

[0051] Comparative Example 3 Comparative Example 3 provides a method for determining sodium dodecyl sulfate in bathroom wastewater using a magnetic field enhanced malachite green reagent method, which specifically comprises the following steps: Steps S1 and S2 are the same as those of Example 1, except that in step S3, the magnetic field strength of the pulsed magnetic field is 1.2 T.

[0052] Standard curve determination: Sodium dodecyl sulfate solutions with different concentrations of 0, 2, 4, 6, 8, 10, 12, 14, and 16 mg / L were taken as standard samples, and the absorbance of these solutions at 582 nm was determined according to the steps described in the control method. By collecting the obtained data and building a model, the relationship between the sodium dodecyl sulfate content Y in the standard sample and the absorbance value A was obtained, Y=21.689A-2.317, and the detection range was 0.010~12.865 mg / L.

[0053] For bathroom wastewater with unknown sodium dodecyl sulfate content, detection was performed according to the steps described in Comparative Example 3 to obtain its corresponding absorbance value A, and then the sodium dodecyl sulfate content in the bathroom wastewater was calculated based on A and the relationship between the standard curve.

[0054] The content of sodium dodecyl sulfate in 8 collected bathroom wastewaters was tested by the method of this comparative example and the method of GB / T 7494-1987, respectively. As shown in Table 6, the relative standard deviation of the test results of the comparative example method varied in the range of 3% to 8%, with a large difference, and the spike recovery rate varied in the range of 87% to 94%, indicating that the method had poor precision. In addition, compared with the test results of the method described in GB / T7494-1987, the relative deviation was large, up to -7.41%. This may be due to the excessively high intensity of the applied magnetic field, which caused the distance between the electron cloud centers of the compound to shift excessively, and weakened the intermolecular binding force, causing the absorption peak intensity at 582 nm to decrease.

[0055] Table 6 Test results of 8 bathroom wastewaters tested by the method of Comparative Example 3

[0056] In summary, the present invention applies a magnetic field treatment during the combination process of malachite green and sodium dodecyl sulfate to make the structure of the complex of malachite green and sodium dodecyl sulfate more stable and improve the detection sensitivity and accuracy of sodium dodecyl sulfate.

[0057] The various aspects, embodiments, features and examples of the present invention should be considered as illustrative in all aspects and are not intended to limit the present invention, the scope of the present invention is defined only by the claims. Other embodiments, modifications and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.

[0058] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0059] Although the present invention has been described with reference to illustrative embodiments, it will be appreciated by those skilled in the art that various other changes, omissions and / or additions may be made without departing from the spirit and scope of the present invention and that the elements of the embodiments may be replaced by substantial equivalents. In addition, many modifications may be made without departing from the scope of the present invention to adapt specific circumstances or materials to the teachings of the present invention. Therefore, it is not intended herein to limit the present invention to the disclosed specific embodiments for performing the present invention, but it is intended that the present invention will include all embodiments within the scope of the appended claims. In addition, unless specifically stated, any use of the terms first, second, etc. does not indicate any order or importance, but rather uses the terms first, second, etc. to distinguish one element from another element.

Claims

1. A method for determining sodium dodecyl sulfate in wastewater by magnetic field enhancement, characterized in that: include: The wastewater sample to be tested containing sodium dodecyl sulfate is reacted with malachite green in a magnetic field to obtain a reaction solution to be tested; the magnetic field strength of the magnetic field is 0.5-0.8 T; The absorbance value A of the reaction solution to be tested at a wavelength of 582 nm is detected, and the concentration Y of sodium dodecyl sulfate in the wastewater sample to be tested is calculated according to the standard curve Y=28.154AC, where C=0.154~0.473, and the unit of Y is mg / L.

2. The method according to claim 1, characterized in that: The magnetic field is a pulsed magnetic field.

3. The method according to claim 2, characterized in that: The magnetic field frequency of the pulsed magnetic field is 0.01-0.1 Hz.

4. The method according to claim 2, characterized in that: The pulse magnetic field is a sawtooth wave pulse magnetic field.

5. The method according to claim 1, characterized in that: The pH value of the wastewater sample to be tested is 6.8-7.6; And / or, the wastewater sample to be tested includes domestic wastewater, and the domestic wastewater includes bathroom wastewater, kitchen wastewater or laundry wastewater.

6. The method according to claim 1, characterized in that Before the wastewater sample to be tested is reacted with malachite green, the method further includes a step of pre-treating the wastewater sample to be tested, wherein the pre-treatment includes solid-liquid separation of the wastewater sample to be tested to at least remove suspended matter and solid impurities therein.

7. The method according to claim 6, characterized in that Specifically include: The malachite green is prepared into a malachite green solution with a concentration of 0.5-1.5 mg / L, and the wastewater sample to be tested after the pretreatment is mixed with the malachite green solution in a volume ratio of 10:1-1:1 to carry out the reaction; And / or, the reaction temperature of the reaction is 20-30°C, and the reaction time is 20-40 min.

8. The method according to claim 1, characterized in that The method for determining the standard curve includes: taking a series of sodium dodecyl sulfate solutions of different concentrations as standard samples, and reacting the standard samples with malachite green in the magnetic field to obtain a standard reaction solution; taking 3 mL of the standard reaction solution in a quartz cuvette, the optical path of the quartz cuvette is 1 cm, detecting the absorbance value of the standard reaction solution at a wavelength of 582 nm, thereby obtaining the relationship between the concentration of sodium dodecyl sulfate in the standard sample and the absorbance value of the corresponding standard reaction solution at a wavelength of 582 nm, and then establishing the standard curve.

9. The method according to claim 1, characterized in that: Also includes: When detecting the absorbance value A of the reaction solution to be tested, a buffer solution with a concentration of 0.1-0.5 mol / L and a pH value of 6.8-7.6 is used as a reference.

10. The method according to claim 1, characterized in that: The detection range of the method is 0.01~20 mg / L.

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