On-site rapid detection and analysis method for zinc content in electroplating wastewater

Abstract

The invention discloses an on-site rapid detection and analysis method for zinc content in electroplating wastewater. According to the method, CN <->, S < 2-> and suspended solids in the wastewater are removed through water pretreatment, sodium thiosulfate is used as a masking agent, a small amount of other metal ions existing in the water can be effectively masked, interference of other metal ions in a wastewater sample is eliminated, an acetic acid-sodium acetate solution is selected as a buffer solution, and the pH value of the buffer solution is adjusted. And the pH value of the wastewater solution is regulated and controlled in a proper range, so that a good color development effect is achieved. According to the method, zinc ions and dithizone generate the red chelate, extraction is not carried out, and the chelate stably exists in a water phase by directly adding a hydrophilic active agent Tween 80, so that the detection time can be remarkably shortened, and the technical effect of accurate and rapid detection is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of electroplating solution analysis methods, and particularly relates to an on-site rapid detection and analysis method for zinc content in zinc-containing wastewater generated by water glass zinc plating and ammonium salt zinc plating. Background Art

[0002] Electroplating is an indispensable part of high-end technology and modern industrial system, and is widely used in the industry. Its application improves the corrosion resistance, wear resistance and decorative performance of products, and gives many products special functions. In recent decades, electroplating technology has made great progress and expansion. The main sources of electroplating wastewater are the water used for cleaning plated parts and filtering plating solution in the electroplating production process, as well as the "running, bubbling, dripping and leaking" caused by poor operation or management. In addition, there is the discharge of self-use water in the wastewater treatment process and the drainage of laboratory tests. If electroplating wastewater is discharged directly without treatment, it will cause extremely serious pollution to the society. Therefore, it is necessary to strengthen the comprehensive treatment of electroplating wastewater so that it can meet the discharge standards. On-site analysis and testing of electroplating wastewater is an important means to ensure that electroplating wastewater meets the discharge standards. The on-site analysis method of electroplating wastewater is the specification and basis for the analysis and testing of electroplating wastewater, and is the technical guarantee for the accurate and reliable data of electroplating wastewater analysis and testing.

[0003] The zinc content in electroplating wastewater is a very important indicator. By measuring the zinc content, the quality of electroplating wastewater can be monitored. Zinc ions and dithizone can form red chelates, which can be extracted with carbon tetrachloride or other non-toxic solvents. However, the extraction, stratification and filtration process requires a lot of time and is complicated to operate. Summary of the invention

[0004] The object of the present invention is to provide an on-site rapid detection and analysis method for zinc content in electroplating wastewater, wherein zinc ions and dithizone generate a red chelate, and no extraction is performed. The chelate is directly stabilized in the aqueous phase by adding a hydrophilic active agent Tween 80, thereby significantly shortening the detection time.

[0005] The technical solution adopted by the present invention is: A method for rapid on-site detection and analysis of zinc content in electroplating wastewater comprises the following steps: S1. Pretreatment of water samples For CN - and S 2- For wastewater with high suspended matter, take 100.00mL of wastewater sample and place it in a 300mL beaker, add 5mL of nitric acid and heat it on a hot plate to digest it to 9~11mL. After cooling, add 50mL of water and adjust the pH value of the solution to 4~5 with ammonia water, then wash it into a 100mL volumetric flask, make up to volume, and shake well. If the wastewater sample does not contain CN - and S2- , and if the sample is clear, no pretreatment is performed and the sample is directly measured; S2. Draw working curve 0.00mL, 1.00mL, 2.00mL, 3.00mL, 4.00mL, 5.00mL, and 6.00mL of the zinc standard solution with a concentration of 0.005mg / mL were respectively taken and placed in 7 50mL volumetric flasks, 10mL of water and 10.00mL of acetic acid-sodium acetate buffer solution were added in sequence to adjust the pH to 4-5.5, and shaken well, 2.00mL of 250g / L sodium thiosulfate solution were added respectively, and shaken well, and then 5.00mL of dithiol-Tween 80 solution were added respectively, and diluted to the scale with water, shaken well, and placed at room temperature for 20min. At 535nm of the spectrophotometer, the absorbance of the solution was measured using a solution with a zinc standard of zero as a reference and a 1cm cuvette, and a working curve was drawn with the absorbance as the ordinate and the corresponding zinc content as the abscissa; S3. Determination of zinc content Pipette 10.00mL of the pretreated water sample, place it in a 50mL volumetric flask, add 10.00mL of acetic acid-sodium acetate buffer solution to adjust the pH to 4-5.5, and shake well; then add 2.00mL of 250g / L sodium thiosulfate solution, shake well, and then add 5.00mL of dithiol-Tween 80 solution, leave it at room temperature for 20min, and measure the absorbance of the solution at 535nm on a spectrophotometer with a solution containing zero zinc standard as a reference and a 1cm colorimetric dish, and obtain the corresponding zinc content from the working curve.

[0006] Further, in S1, the density of nitric acid is 1.40 g / mL.

[0007] Furthermore, in S2, the pH of the acetic acid-sodium acetate buffer solution is adjusted to 4-5.

[0008] Furthermore, in S3, the mass fraction of dithiol in the dithiol-Tween 80 solution is not higher than 10%, preferably 1% to 6%.

[0009] Furthermore, in S3, the calculation formula of zinc content is: Zn(mg / L)= , In the formula, A —Zinc content obtained from the working curve, in mg.

[0010] The above pretreatment can effectively remove CN from wastewater. - and S 2- As well as suspended matter, the wastewater sample is clear and free of suspended matter, achieving the desired effect.

[0011] Sodium thiosulfate, as a masking agent, can effectively mask other small amounts of metal ions in water, eliminating the effects of other metal ions on the absorbance of the solution and eliminating the interference of other metal ions in the wastewater sample.

[0012] The red chelate formed by zinc ions and dithizone has the best color development reaction when the pH is 4.0-5.5. Therefore, acetic acid-sodium acetate solution was selected as the buffer solution. Through experiments, it was finally determined that 10 mL was added to each sample and standard sample, and the pH value of the wastewater solution was between 4.0 and 5.5 to achieve a good color development effect.

[0013] The present invention does not use organic solvent extraction, and by adding Tween 80, the chelate can be stably present in the water phase, thereby achieving the effect of accurate and rapid measurement.

[0014] The beneficial effects of the present invention are: (1) The present invention can effectively improve the detection efficiency and increase the original detection cycle by 4 times, effectively ensuring the needs of electroplating production tasks.

[0015] (2) The dithizone, Tween 80, sodium thiosulfate, etc. used in the entire detection process are all commonly used chemical reagents in laboratories. They are low-cost, safe and environmentally friendly. They do not require the use of toxic and carcinogenic reagents such as carbon tetrachloride, meet the process technical parameter requirements, and ensure the quality of wastewater analysis.

[0016] (3) The detection method of the present invention is simple, the detection process is convenient and fast, and the detection accuracy is high and the error is small. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below with reference to specific embodiments, but the present invention is not limited thereto. Example 1

[0018] (1) Pretreatment of water samples.

[0019] For CN - and S 2- For wastewater with high suspended matter, take 100.00mL of wastewater sample and place it in a 300mL beaker, add 5mL of nitric acid (ρ1.40 g / mL) and heat it on a hot plate to digest it to about 10mL. After cooling, add 50mL of water, adjust the pH value of the solution to 4 with ammonia water, carefully wash it into a 100mL volumetric flask, make up to volume, and shake well.

[0020] If the wastewater sample does not contain CN - and S 2- , and it is clear, so it can be directly sampled and measured without pretreatment.

[0021] (2) Working curve Pipette zinc standard solution (0.005 mg / mL): 0.00mL, 1.00mL, 2.00mL, 3.00mL, 4.00mL, 5.00mL, and 6.00mL into 7 50mL volumetric flasks, add 10mL of water in turn, 10.00mL of acetic acid-sodium acetate buffer solution to adjust the pH to about 4.7, shake well, add 2.00mL of sodium thiosulfate solution (250g / L) respectively, shake well, then add 5.00mL of dithiol-Tween 80 solution (the mass fraction of dithiol is 5%) respectively, dilute to the scale with water, shake well, and place at room temperature for 20min. At 535nm of the spectrophotometer, use the solution with zinc standard added as zero as reference and a 1cm colorimetric dish to measure the absorbance of the solution, and draw a working curve with absorbance as the ordinate and the corresponding zinc content as the abscissa.

[0022] (3) Determination Take 10.00mL of the pretreated water sample and place it in a 50mL volumetric flask, add 10.00mL of acetic acid-sodium acetate buffer solution to adjust the pH to about 4.7, and shake well. Then add 2.00mL of sodium thiosulfate solution (250g / L), shake well, and then add 5.00mL of dithiothiolide-Tween 80 solution (the mass fraction of dithiothiolide is 5%), and place it at room temperature for 20 minutes. At 535nm of the spectrophotometer, use the solution with zinc standard as zero as reference, and use a 1cm colorimetric dish to measure the absorbance of the solution, and find the corresponding zinc content from the working curve.

[0023] Zn(mg / L)= , In the formula, A —Zinc content obtained from the working curve, in mg.

[0024] Comparative Example 1 The rest is the same as Example 1, except that the masking agent sodium thiosulfate is not added.

[0025] Compared with using a sufficient amount of sodium thiosulfate to effectively mask the interference of other small amounts of metal ions present in the water, without adding sodium thiosulfate, the influence of other metal ions on the absorbance of the solution will cause interference, thereby causing inaccurate measurement results.

[0026] Comparative Example 2 The rest is the same as Example 1, except that Tween is replaced by organic solvent ethanol and the extraction time is 1 hour.

[0027] Ethanol, as a commonly used extraction agent, can extract chelates to a certain extent, but cannot completely extract the chelates. As a result, not only the detection time is significantly prolonged due to the extraction, but also the detection results are inaccurate.

[0028] Comparative Example 3 The rest is the same as Example 1, except that Tween is replaced by an organic solvent, carbon tetrachloride, and the extraction time is 1 hour.

[0029] Carbon tetrachloride can extract chelates well, but the extraction significantly prolongs the detection time, and carbon tetrachloride is highly toxic and unfavorable to the environment.

Claims

1. A method for rapid on-site detection and analysis of zinc content in electroplating wastewater, characterized in that: The steps include: S1. Pretreatment of water samples For CN - and S 2- For wastewater with high suspended matter, take 100.00mL of wastewater sample and place it in a 300mL beaker, add 5mL of nitric acid and heat it on a hot plate to digest it to 9~11mL. After cooling, add 50mL of water, adjust the pH value of the solution to 4~5 with ammonia water, then wash it into a 100mL volumetric flask, make up to volume, and shake well. If the wastewater sample does not contain CN - and S 2- , and if the sample is clear, no pretreatment is performed and the sample is directly measured; S2. Draw working curve 0.00mL, 1.00mL, 2.00mL, 3.00mL, 4.00mL, 5.00mL, and 6.00mL of the zinc standard solution with a concentration of 0.005mg / mL were respectively taken and placed in 7 50mL volumetric flasks, 10mL of water and 10.00mL of acetic acid-sodium acetate buffer solution were added in sequence to adjust the pH to 4-5.5, and shaken well, 2.00mL of 250g / L sodium thiosulfate solution were added respectively, and shaken well, and then 5.00mL of dithiol-Tween 80 solution were added respectively, and diluted to the scale with water, shaken well, and placed at room temperature for 20min. At 535nm of the spectrophotometer, the absorbance of the solution was measured using a solution with a zinc standard of zero as a reference and a 1cm cuvette, and a working curve was drawn with the absorbance as the ordinate and the corresponding zinc content as the abscissa; S3. Determination of zinc content Pipette 10.00mL of the pretreated water sample, place it in a 50mL volumetric flask, add 10.00mL of acetic acid-sodium acetate buffer solution to adjust the pH to 4-5.5, and shake well; then add 2.00mL of 250g / L sodium thiosulfate solution, shake well, and then add 5.00mL of dithiol-Tween 80 solution, leave it at room temperature for 20min, and measure the absorbance of the solution at 535nm on a spectrophotometer with a solution containing zero zinc standard as a reference and a 1cm colorimetric dish, and obtain the corresponding zinc content from the working curve.

2. The on-site rapid detection and analysis method for zinc content in electroplating wastewater according to claim 1, characterized in that: In S1, the density of nitric acid is 1.40 g / mL.

3. The on-site rapid detection and analysis method for zinc content in electroplating wastewater according to claim 1, characterized in that: In S2, the pH of the acetic acid-sodium acetate buffer solution is adjusted to 4-5.

4. The on-site rapid detection and analysis method for zinc content in electroplating wastewater according to claim 1, characterized in that: In S3, the mass fraction of dithiol in the dithiol-Tween 80 solution is not higher than 10%.

5. The on-site rapid detection and analysis method for zinc content in electroplating wastewater according to claim 1, characterized in that: In S3, the mass fraction of dithiol in the dithiol-Tween 80 solution is 1%~6%.

6. The on-site rapid detection and analysis method for zinc content in electroplating wastewater according to claim 1, characterized in that: In S3, the calculation formula for zinc content is: Zn(mg / L)= , In the formula, A —Zinc content obtained from the working curve, in mg.

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