Method for testing trace complexing agent in electroplating wastewater

Abstract

The invention relates to the technical field of complexing agent detection, in particular to a method for testing trace complexing agents in electroplating wastewater, which at least comprises the following steps: measuring the content of heavy metal ions in the electroplating wastewater; determining the adding amount of an organic heavy metal ion trapping agent based on the heavy metal ion content; adding an organic heavy metal ion trapping agent into the electroplating wastewater for pretreatment; filtering to obtain supernate, treating the supernate until the supernate meets the LC-MS sampling requirement, and feeding the supernate into a liquid chromatograph-mass spectrometer for detection and analysis; after the electroplating wastewater is simply treated, LC-MS (Liquid Chromatography-Mass Spectrometry) is adopted for detection and analysis, the pretreatment steps are simplified, the trace complexing agent in the electroplating wastewater can be rapidly and accurately detected, and the actual requirements are better met.

Description

Technical Field

[0001] The invention relates to the technical field of complexing agent detection, in particular to a method for testing trace complexing agents in electroplating wastewater. Background Art

[0002] According to the Technical Specifications for Electroplating Wastewater Treatment Engineering, electroplating wastewater must strictly treat complexing agents and their complexed metal ions (such as cyanide, hexavalent chromium, nickel, etc.) to emission limits. Therefore, the detection of complexing agents in electroplating wastewater is an essential step to ensure compliant discharge, optimize treatment processes, and protect ecological safety. However, the complexity of wastewater components, the low concentration and diversity of complexes, and the need for real-time detection significantly increase technical difficulty. A Chinese patent (authorization announcement number CN108169372B) discloses a method for determining complexing agents in electroplating wastewater. The method first stabilizes the complexing agent in electroplating wastewater with formaldehyde, then further stabilizes it with an internal standard and an acidifying agent, and finally purifies the sample with a washing agent and an eluent. Based on gas chromatography-mass spectrometry detection, the type and content of the complexing agent are obtained, but multi-step pretreatment (acidification, concentration, and purification) is required, which is time-consuming and relies on skilled technicians, limiting its widespread application. A Chinese patent application (publication number CN119715747A) discloses a Cu-EDTA detection device and method based on solid-state nanopore detection technology. This method combines the control of nanopore pore size and surface properties with the principle of resistive pulse sensing to achieve high-sensitivity, real-time monitoring of Cu-EDTA (copper-ethylenediaminetetraacetic acid) complexes. However, its applicability to certain substances that do not produce mass spectrometry peaks after complexing with heavy metals, such as nickel citrate and nickel tartrate, is insufficient, limiting its scope of application. Summary of the Invention

[0003] In order to solve the above problems, the present invention provides a method for testing trace complexing agents in electroplating wastewater. After simple treatment of the electroplating wastewater, LC-MS (liquid chromatography-mass spectrometry) is used for detection and analysis, which simplifies the pretreatment steps and can achieve rapid and accurate detection of trace complexing agents in electroplating wastewater, better meeting actual needs.

[0004] On one hand, the present invention provides a method for testing trace complexing agents in electroplating wastewater, which comprises at least the following steps: determining the heavy metal ion content in the electroplating wastewater; determining the amount of an organic heavy metal ion scavenger to be added based on the heavy metal ion content; adding the organic heavy metal ion scavenger to the electroplating wastewater for pretreatment; obtaining a supernatant by filtration, treating the supernatant until it meets LC-MS injection requirements, and then entering the supernatant into a liquid chromatography-mass spectrometry instrument for detection and analysis.

[0005] In one embodiment, the method for determining the content of heavy metal ions in the electroplating wastewater is selected from ICP-OES (inductively coupled plasma optical emission spectroscopy) or AAS (atomic absorption spectroscopy).

[0006] In one embodiment, the organic heavy metal ion trapping agent comprises at least a sulfur-containing organic heavy metal ion trapping agent.

[0007] In one embodiment, the sulfur-containing organic heavy metal ion trapping agent is selected from at least one of sodium dimethyldithiocarbamate, sodium piperazine-N,N-bisdithiocarbamate, trimercaptotriazine trisodium salt (TMT) or dithiocarbamate (DTCR).

[0008] In one embodiment, the sulfur-containing organic heavy metal ion trapping agent is sodium dimethyldithiocarbamate or sodium piperazine-N,N-bisdithiocarbamate.

[0009] In one embodiment, the molar ratio of the heavy metal ion content to the organic heavy metal ion capture agent is 1:(1-10).

[0010] In one embodiment, the molar ratio of the heavy metal ion content to the organic heavy metal ion scavenger can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10.

[0011] In one embodiment, the molar ratio of the heavy metal ion content to the organic heavy metal ion capture agent is 1:5.

[0012] In one embodiment, the pH of the pretreatment is controlled at 3-12.

[0013] In one embodiment, the pH of the pretreatment is controlled at 8-9.

[0014] In one embodiment, the pretreatment temperature is 15-35° C. and the pretreatment time is 0.5-5 min.

[0015] In one embodiment, the pretreatment temperature is 25±2° C. and the time is 1-2 min.

[0016] In one embodiment, the filtering step comprises: filtering through quantitative filter paper (0.22-0.45 um) to obtain a clear liquid.

[0017] In one embodiment, the content of heavy metal ions in the supernatant is less than 1 mg / kg.

[0018] The method of the present invention targets electroplating wastewater as the primary analytical sample, typically discharged from various stages of the entire electroplating process. As such, its composition is complex, and complexes formed between some heavy metal ions and chelating agents are difficult to directly characterize and quantify. The method pre-treats the electroplating wastewater by adding an organic heavy metal ion scavenger to prevent interference of the heavy metals in the complexes with the target organic compounds. After simple subsequent treatment, liquid chromatography-mass spectrometry can be used for qualitative and quantitative analysis, significantly shortening the number of detection and analysis steps and time. Furthermore, the present invention determines the heavy metal ion content in the electroplating wastewater by ICP-OES (inductively coupled plasma emission spectroscopy) or AAS (atomic absorption spectroscopy), and then determines the amount of organic heavy metal ion scavenger added to the electroplating wastewater based on the obtained heavy metal ion content, specifically based on a molar ratio of heavy metal ion content to organic heavy metal ion scavenger of 1:(1-10), ensuring that the heavy metal ion content in the supernatant obtained after treatment is less than 1 mg / kg while minimizing the cost increase and detection interference caused by excessive addition of organic heavy metal ion scavenger, thereby ensuring the accuracy of subsequent test results.

[0019] The detection method provided by the present invention uses sodium dimethyldithiocarbamate or sodium piperazine-N,N-bisdithiocarbamate for pretreatment at pH = 8-9 for 1-2 minutes before filtering, ensuring treatment efficiency and treatment effect and meeting real-time monitoring needs.

[0020] In one embodiment, the LC-MS injection requirements include:

[0021] (1) Sample volume: greater than 2 g, special cases can be discussed separately;

[0022] (2) Applicable to qualitative and quantitative analysis of organic compounds with molecular weight less than 2000. Standards are required for accurate quantification.

[0023] (3) The pH range of the inlet liquid is 7-9;

[0024] (4) The sample system is non-heavy metal or non-high salt system;

[0025] (5) Not suitable for the analysis of non-polar substances;

[0026] (6) Not suitable for the analysis of substances that precipitate when exposed to water, acetonitrile, or methanol.

[0027] In one embodiment, the model of the liquid chromatograph in the liquid chromatography-mass spectrometry instrument is Waters I-Class (Waters ACQUITY I-Class ultra high performance liquid chromatography system).

[0028] In one embodiment, the mass spectrometer in the liquid chromatography-mass spectrometry instrument is a Waters XEVO-TQS micro (Waters Xevo TQ-S Micro triple quadrupole mass spectrometer).

[0029] In one embodiment, the parameter conditions of the liquid chromatograph are set as follows: the injection volume is 1-5 μL; the mobile phase includes positive ions and negative ions, the positive ions include: A-0.05-0.3wt% formic acid aqueous solution, B-acetonitrile; the negative ions include: A-0.02-0.1wt% ammonia water, B-acetonitrile; the flow rate is 0.2-0.5 mL / min.

[0030] In one embodiment, the parameter conditions of the liquid chromatograph are set as follows: the injection volume is 1 μL; the mobile phase includes positive ions and negative ions, the positive ions include: A-0.1wt% formic acid aqueous solution, B-acetonitrile; the negative ions include: A-0.05wt% ammonia water, B-acetonitrile; the flow rate is 0.3 mL / min.

[0031] In one embodiment, the parameter conditions of the mass spectrometer are set as follows: the ion source is ESI (electrospray ionization); the ion source temperature is 130-170°C; the desolvation temperature is 380-420°C; the capillary voltage is 2-3kV; the cone voltage is 25-35V; the desolvation gas flow rate is 700-900L / Hr (hour); and the cone gas flow rate is 40-60L / Hr.

[0032] In one embodiment, the parameter conditions of the mass spectrometer are set as follows: the ion source is ESI (electrospray ionization); the ion source temperature is 150°C; the desolvation temperature is 400°C; the capillary voltage is 2.5kV; the cone voltage is 30V; the desolvation gas flow rate is 800L / Hr; and the cone gas flow rate is 50L / Hr.

[0033] The test method provided by the present invention is applicable to the qualitative analysis of substances that do not produce mass spectrum peaks after complexing with heavy metals by certain complexing agents, and can detect the concentration changes of 1-3 ppm of trace complexed citric acid and tartaric acid.

[0034] Beneficial effects

[0035] 1. The present invention provides a method for testing trace complexing agents in electroplating wastewater. After simple treatment of the electroplating wastewater, LC-MS (liquid chromatography-mass spectrometry) is used for detection and analysis, which simplifies the pretreatment steps and can achieve rapid and accurate detection of trace complexing agents in electroplating wastewater, better meeting actual needs.

[0036] 2. The present invention adds an organic heavy metal ion scavenger to the electroplating wastewater for pretreatment to avoid the interference of heavy metals in the complex with the target organic matter. After simple subsequent treatment, liquid chromatography-mass spectrometry can be used for qualitative and quantitative analysis, which greatly shortens the detection and analysis steps and shortens the detection and analysis time.

[0037] 3. The present invention determines the heavy metal ion content in the electroplating wastewater by ICP-OES (inductively coupled plasma emission spectroscopy) or AAS (atomic absorption spectroscopy), and then determines the amount of organic heavy metal ion scavenger added to the electroplating wastewater based on the obtained heavy metal ion content, specifically based on a molar ratio of heavy metal ion content to organic heavy metal ion scavenger of 1:(1-10), ensuring that the heavy metal ion content in the supernatant obtained after treatment is less than 1 mg / kg while avoiding the cost increase and detection interference caused by excessive addition of organic heavy metal ion scavenger as much as possible, thereby ensuring the accuracy of subsequent test results.

[0038] 4. The detection method provided by the present invention uses sodium dimethyldithiocarbamate or sodium piperazine-N,N-bisdithiocarbamate for pretreatment at pH = 8-9 for 1-2 minutes before filtration, ensuring treatment efficiency and treatment effect to meet real-time monitoring needs.

[0039] 5. The test method provided by the present invention is applicable to the qualitative analysis of substances that do not produce mass spectrometry peaks after complexing with heavy metals by certain complexing agents, and can detect concentration changes of 1-3 ppm of trace complexed citric acid and tartaric acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is the LS-MS spectrum obtained in Example 1.

[0041] Figure 2 This is the LS-MS spectrum obtained in Example 2.

[0042] Figure 3 This is the LS-MS spectrum obtained in Comparative Example 1.

[0043] Figure 4 This is the LS-MS spectrum obtained in Comparative Example 2. DETAILED DESCRIPTION

[0044] Example 1

[0045] Example 1 of the present invention provides a method for testing trace complexing agents in electroplating wastewater, comprising the following steps: determining the heavy metal ion content in the electroplating wastewater; determining the amount of an organic heavy metal ion scavenger to be added based on the heavy metal ion content; adding the organic heavy metal ion scavenger to the electroplating wastewater for pretreatment; obtaining a supernatant by filtration, and subjecting the supernatant to detection and analysis by a liquid chromatography-mass spectrometer.

[0046] The electroplating wastewater is electroplating wastewater containing nickel tartrate.

[0047] The method for determining the content of heavy metal ions in the electroplating wastewater is ICP-OES (inductively coupled plasma optical emission spectroscopy).

[0048] The organic heavy metal ion trapping agent is a sulfur-containing organic heavy metal ion trapping agent, and the sulfur-containing organic heavy metal ion trapping agent is sodium dimethyldithiocarbamate.

[0049] The molar ratio of the heavy metal ion content to the organic heavy metal ion trapping agent is 1:5.

[0050] The pH of the pretreatment was controlled at 8.5.

[0051] The pretreatment temperature is 25±2° C. and the pretreatment time is 2 minutes.

[0052] The filtering step comprises: filtering through quantitative filter paper (0.45 μm) to obtain a clear liquid.

[0053] The content of heavy metal ions in the supernatant is less than 1 mg / kg, which meets the LC-MS injection requirements.

[0054] The model of the liquid chromatograph in the liquid chromatography-mass spectrometry instrument is Waters I-Class (Waters ACQUITY I-Class ultra-high performance liquid chromatography system).

[0055] The mass spectrometer in the liquid chromatography-mass spectrometry instrument is a Waters XEVO-TQS micro (Waters Xevo TQ-S Micro triple quadrupole mass spectrometer).

[0056] The parameters of the liquid chromatograph are set as follows: the injection volume is 1 μL; the mobile phase includes positive ions and negative ions, the positive ions include: A-0.1 wt% formic acid aqueous solution, B-acetonitrile; the negative ions include: A-0.05 wt% ammonia water, B-acetonitrile; the flow rate is 0.3 mL / min.

[0057] The parameters of the mass spectrometer were as follows: the ion source was ESI (electrospray ionization); the ion source temperature was 150°C; the desolvation temperature was 400°C; the capillary voltage was 2.5 kV; the cone voltage was 30 V; the desolvation gas flow rate was 800 L / Hr; and the cone gas flow rate was 50 L / Hr.

[0058] LS-MS spectrum information can be found at Figure 1 The results show that: under the method of the present invention, tartaric acid-complexed nickel in electroplating wastewater is converted into free tartaric acid, thereby effectively detecting trace tartaric acid.

[0059] Example 2

[0060] Example 2 of the present invention provides a method for testing trace complexing agents in electroplating wastewater. The specific implementation method is the same as that of Example 1, except that the electroplating wastewater is electroplating wastewater containing nickel citrate. LS-MS spectrum information can be found at Figure 2 The results show that: under the method of the present invention, citric acid-complexed nickel in electroplating wastewater is converted into free citric acid, thereby effectively detecting trace citric acid.

[0061] Comparative Example 1

[0062] Comparative Example 1 of the present invention provides a test method, comprising the following steps: treating electroplating wastewater containing nickel tartrate to meet the LC-MS sampling requirements, entering the liquid chromatography-mass spectrometry instrument for detection and analysis, the specific implementation method is the same as that of Example 1, and the LS-MS spectrum information can be found in Figure 3 The results show that it is impossible to effectively detect trace tartaric acid in electroplating wastewater containing nickel tartaric acid without pretreatment.

[0063] Comparative Example 2

[0064] Comparative Example 2 of the present invention provides a test method, comprising the following steps: treating the electroplating wastewater containing nickel citrate to meet the LC-MS sampling requirements, entering the liquid chromatography-mass spectrometry instrument for detection and analysis, the specific implementation method is the same as that of Example 1, and the LS-MS spectrum information can be found in Figure 4 The results show that it is impossible to effectively detect trace amounts of citric acid in electroplating wastewater containing nickel citrate without pretreatment.

Claims

1. A method for testing trace complexing agents in electroplating wastewater, characterized in that: At least the following steps are included: Determine the content of heavy metal ions in electroplating wastewater; determine the amount of organic heavy metal ion scavenger to be added based on the heavy metal ion content; An organic heavy metal ion scavenger is added to the electroplating wastewater for pretreatment; a supernatant is obtained by filtration, the supernatant is treated until it meets the LC-MS injection requirements, and then enters the liquid chromatography-mass spectrometry instrument for detection and analysis.

2. The method for testing trace complexing agents in electroplating wastewater according to claim 1, wherein: The method for determining the heavy metal ion content in the electroplating wastewater is selected from inductively coupled plasma emission spectrometry or atomic absorption spectrometry.

3. The method for testing trace complexing agents in electroplating wastewater according to claim 1, wherein: The organic heavy metal ion trapping agent at least includes a sulfur-containing organic heavy metal ion trapping agent.

4. The method for testing trace complexing agents in electroplating wastewater according to claim 3, wherein: The sulfur-containing organic heavy metal ion trapping agent is selected from at least one of sodium dimethyldithiocarbamate, sodium piperazine-N,N-bisdithiocarbamate, trimercaptotriazine trisodium salt or dithiocarbamate.

5. The method for testing trace complexing agents in electroplating wastewater according to claim 1, wherein: The molar ratio of the heavy metal ion content to the organic heavy metal ion trapping agent is 1:(1-10).

6. The method for testing trace complexing agents in electroplating wastewater according to claim 1, wherein: The pH of the pretreatment is controlled at 3-12.

7. The method for testing trace complexing agents in electroplating wastewater according to claim 6, wherein: The pretreatment temperature is 15-35° C. and the pretreatment time is 0.5-5 min.

8. The method for testing trace complexing agents in electroplating wastewater according to claim 1, wherein: The content of heavy metal ions in the supernatant is less than 1 mg / kg.

9. The method for testing trace complexing agents in electroplating wastewater according to claim 1, wherein: The parameters of the liquid chromatograph in the liquid chromatography-mass spectrometry instrument are set as follows: the injection volume is 1-5 μL; the mobile phase includes positive ions and negative ions, the positive ions include: A-0.05-0.3 wt% formic acid aqueous solution, B-acetonitrile; the negative ions include: A-0.02-0.1 wt% ammonia water, B-acetonitrile; the flow rate is 0.2-0.5 mL / min.

10. The method for testing trace complexing agents in electroplating wastewater according to claim 1, characterized in that: The parameter conditions of the mass spectrometer in the liquid chromatography-mass spectrometry instrument are set as follows: the ion source is ESI; the ion source temperature is 130-170°C; the desolvation temperature is 380-420°C; the capillary voltage is 2-3kV; the cone voltage is 25-35V; the desolvation gas flow rate is 700-900L / Hr; and the cone gas flow rate is 40-60L / Hr.

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