Method for determining fiber microplastics in textile aqueous solution based on fluorophotometry

Abstract

The invention discloses a method for determining fiber micro-plastics in a textile aqueous solution based on fluorophotometry, and relates to the technical field of textile pollutant detection, and the method comprises the following steps: S1, collecting wastewater, and filtering with a filter membrane; s2, washing the filter membrane with a sodium hypochlorite solution; s3, flushing the fiber micro-plastic on the filter membrane into a separating funnel; s4, part of the fiber micro-plastic is poured out from the upper end opening of the separating funnel, and the other part of the fiber micro-plastic is collected from the lower end opening of the separating funnel; s5, repeating the steps S1 to S4, and washing the filter membrane with hydrochloric acid during the period to leave and collect the residual fiber micro-plastic; s6, dyeing the obtained three solutions; s7, taking polyester, polyamide and polypropylene standard linings to respectively prepare standard series solutions; s8, measuring and drawing a standard curve of the fluorescence intensity and the fiber micro-plastic concentration by using a fluorospectro photometer; and S9, determining the fluorescence intensity of the three solutions obtained in the step S6. The method is applied to the field of textile water solutions, unknown samples can be quantitatively analyzed, single samples and mixed samples can be analyzed, and the detection deviation is small.

Description

Technical Field

[0001] The present invention relates to the technical field of textile pollutant detection, and in particular to a method for determining fiber microplastics in a textile aqueous solution based on fluorescence spectrophotometry. Background Art

[0002] Plastic is an indispensable material in our daily life and production. Plastic products are lightweight, strong, durable and corrosion-resistant, making them highly versatile materials. At the same time, due to their low price, plastics are easy to manufacture and can be found in industries such as industry, agriculture, daily use, medicine, military, aerospace, etc. As early as the 1970s, the scientific community began to pay attention to microplastic pollution. In 2004, Thompson et al. first proposed the term microplastics (Microplastics MPs), which aroused the full attention of mankind to the tiny plastic particles in the environment. According to the size of plastics, the International Microplastics Symposium defines microplastics as plastic fragments with a diameter of less than 5 mm. In the past decade, microplastics have become a hot spot and frontier in environmental science research and have developed rapidly. The largest amount found in current research is fibrous microplastics.

[0003] Fibrous microplastics, also known as fiber microplastics, are mainly caused by mechanical friction, collision, chemical reagents, etc. during the production, printing and dyeing, finishing, wearing and washing of textiles, which cause some non-degradable fibers to break from textiles. After being exposed to light, rain, water flow, etc., they become fiber microplastics with a size of less than 5mm. Due to its difficulty in degradation and bioaccumulation, it has caused great harm to the environment, animals, plants and even the human body. Its specific types mainly include polyester fibers, polyamide fibers, polypropylene fibers, etc. Other difficult-to-degrade microplastics such as polyvinyl chloride and polystyrene are basically not used in textile products, so no corresponding fiber microplastics will be produced. Among them, polyester fibers and polyamide fibers are the most commonly used textile fibers for textiles. They are made into textiles of various styles and styles with pure chemical fiber products or blended with other fibers such as cotton, viscose, and linen. In the textile industry, polypropylene fibers are generally used for textile fillings, clothing linings or disposable sanitary protection products, and the amount used is relatively small.

[0004] For the detection of fiber microplastics, the current ISO / DIS 4484-2-2023 (E) "Textiles and textile products-Microplastics from textile sources-Part 2: Qualitative and quantitative evaluation of microplastics" standard uses optical microscopy, and then uses Fourier transform infrared spectrometer and Raman spectrometer to conduct qualitative and quantitative analysis of microplastics dropped from textiles. DB 37 / T4323-2021 "Technical Specifications for Monitoring Microplastics in Marine Aquaculture Areas" and DB 21 / T 2751-2017 "Determination of Microplastics in Seawater by Fourier Transform Microscopic Infrared Spectroscopy" both use stereo microscope inspection, and then use Fourier transform infrared spectrometer to test the material of microplastic particles. The above standards all use large-scale instruments such as Fourier transform infrared spectrometers or Raman spectrometers. The sample preparation is complicated, the detection cycle is long, and professional operation is required. The cost is high. When the amount of fiber microplastics is slightly large, they tend to agglomerate. The agglomerated fiber microplastics cause troubles in counting and infrared and Raman spectroscopy scanning. Fiber microplastics vary in length, and it is difficult to accurately describe the amount of fiber microplastics by using quantitative statistics.

[0005] A Chinese invention patent with patent publication number CN112730368A discloses a thermal cycling method for preparing fluorescently dyed microplastics and a concentration analysis method: the method comprises the following steps: 1. mixing a dye and an organic solvent to prepare a dyeing working solution; 2. mixing the dyeing working solution with microplastics, thermally cycling and oscillating the dyeing, filtering and drying to obtain fluorescently dyed microplastics; 3. dyeing an unknown sample and measuring the fluorescence intensity, and using a standard curve between the concentration of fluorescently dyed microplastics and the fluorescence intensity to analyze the mass concentration of microplastics in the unknown sample. The present invention provides a short, fast and convenient method for quantitatively analyzing microplastics.

[0006] However, although this technical solution can realize the quantitative analysis method of fiber microplastics without using large-scale instruments and equipment, this quantitative analysis method requires advance qualitative analysis. Knowing what microplastics are contained in the unknown sample can select the corresponding standard curve, and it cannot meet the quantitative analysis of unknown samples that have not been qualitatively analyzed in advance; and this quantitative analysis method can only meet the quantitative analysis of unknown samples that are single samples, such as the quantitative analysis of single microplastics such as polyethylene microplastics or polyethylene terephthalate microplastics in the unknown sample, and cannot achieve quantitative analysis of mixed samples containing multiple microplastics. Therefore, the quantitative analysis method of fiber microplastics in this technical solution has great limitations and is difficult to use in practice.

[0007] In addition, we know that there are many types of microplastics, which can be divided into flakes, microspheres, foams, fibers, films, etc. in terms of their morphology. In this technical solution, the standard curve given can be understood as being applicable to microplastics of various forms. For granular microplastics, their particle size directly affects the fluorescence intensity after staining, and the standard curves of microplastics of each size interval are different. In other words, for certain specific forms of microplastics, the standard defects in this technical solution are used for quantitative analysis, and the results are seriously biased. It is difficult to achieve reliable quantitative analysis results when this technical solution is applied to the determination of microplastics in the field of textile wastewater.

[0008] In addition, in the determination of fiber microplastics in the field of textile wastewater, we know that in addition to fiber microplastics, textile wastewater also contains other degradable fibers such as cotton, viscose, flax, sheep wool, mulberry silk, and polyacrylonitrile. These degradable fibers will interfere with the determination of fiber microplastics, resulting in inaccurate determination of fiber microplastics. This technical solution is also difficult to solve the above problems.

[0009] Therefore, there is an urgent need to invent a method for the determination of fiber microplastics in textile wastewater that has few limitations, is reliable, accurate, and can be applied. Summary of the invention

[0010] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a method for determining fiber microplastics in textile aqueous solution based on fluorescence spectrophotometry.

[0011] In order to achieve the above object, the present invention adopts the following technical solutions:

[0012] A method for determining fiber microplastics in a textile aqueous solution based on fluorescence spectrophotometry comprises the following steps:

[0013] S1. Collect wastewater from the environment and filter the wastewater using a micro-glass filtration device with a glass fiber filter membrane;

[0014] S2. Rinse the filter membrane with sodium hypochlorite solution, turn off the suction filtration device, and fully immerse the fiber microplastics in the sodium hypochlorite solution. After standing for a period of time, wash the filter membrane with a large amount of water until it is neutral;

[0015] S3, rinse the fiber microplastics on the filter membrane into tertiary water, add it to the separatory funnel, and let it stand until obvious stratification;

[0016] S4, pour out the fiber microplastics floating on the upper layer of the solution from the upper port of the separatory funnel, collect the fiber microplastics deposited at the bottom from the lower port, the liquid collected at the upper port is the test liquid 1, and the liquid collected at the lower port is the test liquid 2;

[0017] S5, repeat S1-S2, then rinse the filter membrane with hydrochloric acid to remove a small part of the fiber microplastics that may exist, collect the remaining fiber microplastics, rinse the filter membrane with a large amount of water until it is neutral, then repeat S3-S4, collect the fiber microplastics deposited at the bottom from the lower port of the separatory funnel, and mark it as test solution 3;

[0018] S6, filtering the obtained three solutions of test solution 1, 2, and 3 respectively, and dyeing them with the prepared Nile red dye solution;

[0019] S7, taking the polyester, polyamide and polypropylene standard lining fiber microplastics that have been dyed and filtered, respectively, and preparing a series of standard solutions with concentration gradients;

[0020] S8. Take appropriate amounts of the standard series solutions from low to high, place them in a cuvette, start the fluorescence spectrophotometer for measurement, and draw a standard curve of fluorescence intensity and fiber microplastic concentration. After exponential fitting of the standard curve, obtain the standard curve fitting equation;

[0021] S9. Disperse the three solutions obtained in S6 evenly and measure their fluorescence intensities on a fluorescence spectrophotometer. Calculate the concentration of fiber microplastics in the aqueous solution using a standard curve fitting equation.

[0022] Furthermore, in S2, the flushing volume of the sodium hypochlorite solution is 20mL-50mL, and the concentration of the sodium hypochlorite solution is 0.9mol / L-1.0mol / L.

[0023] Furthermore, the separatory funnel is a cylindrical separatory funnel.

[0024] Furthermore, in S5, the amount of hydrochloric acid is 20 mL-50 mL, and before flushing the filter membrane with hydrochloric acid, the filter bottle receiving the filtrate is replaced.

[0025] Furthermore, the Nile red dyeing step in S6 is: use 80mL-150mL of the prepared Nile red dye to rinse the three types of fiber microplastics into the dye solution respectively, and let it stand at room temperature for 20min-40min; wherein the concentration of Nile red fluorescent dye is 80ug / mL.

[0026] Furthermore, in S7, 0.5000 g ± 0.0002 g of polyester, polyamide, and polypropylene standard linings are weighed respectively and crushed into various types of fiber microplastics with a length of less than 2 mm;

[0027] The dyeing process includes: placing various types of fiber microplastics into conical flasks, adding grade tertiary water and Nile red dye, and standing at room temperature for a period of time, wherein the concentration of Nile red dye is 160ug / mL;

[0028] The filtration includes: washing with a solution of water:acetone=1:1, and drying for standby use.

[0029] Furthermore, in S7, the preparation process of the standard series solution with concentration gradient is as follows:

[0030] Weigh 0.2500 g ± 0.0002 g of the dyed polyester and polyamide standard lining fiber microplastics respectively, add them to an aqueous solution containing a surfactant to prepare a standard solution, and dilute them into at least 6 solutions with a concentration gradient;

[0031] Weigh 0.2500g±0.0002g of dyed polypropylene standard lining fiber microplastics, add it to liquid paraffin to prepare a standard solution, and dilute it into at least 6 solutions with a concentration gradient.

[0032] Furthermore, the standard curve fitting equation in S8 is: I=aC+b; wherein I is the fluorescence intensity of a single type of fiber microplastic, C is the concentration of a single type of fiber microplastic in the sample to be tested, and a and b are the working curve coefficients of a single type of fiber microplastic.

[0033] Furthermore, in S9:

[0034] The fluorescence intensity of the test solution 1 is measured to be I1, and the fluorescence intensity I1 is substituted into the polypropylene fiber microplastic standard curve fitting equation I PP =a PP C PP +b PP The concentration C1 of fiber microplastics in the test solution 1 is obtained;

[0035] The fluorescence intensity of the test solution 3 is measured to be I3, and the fluorescence intensity I3 is substituted into the polyester fiber microplastic standard curve fitting equation I PET =a PET C PET +b PET The concentration of polyester fiber microplastics C3 was obtained;

[0036] The fluorescence intensity of the test liquid 2 is measured as I2. Substituting C1, C3, and I2 into the following formula can obtain the total amount of fiber microplastics in the concentrated or diluted aqueous solution:

[0037]

[0038] C=KC 总

[0039] C——Concentration of fiber microplastics in aqueous solution (ug / mL);

[0040] C 总 ——The total concentration of fiber microplastics in aqueous solution after concentration or dilution (ug / mL);

[0041] K——concentration or dilution multiple. When not concentrated or diluted, K=1 / 10.

[0042] Furthermore, the method of uniformly dispersing the solution in S9 is: placing the solution in a turbine disperser or shaking it manually.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The present invention provides a method for determining fiber microplastics in a textile aqueous solution based on fluorescence spectrophotometry, which is applied to the field of textile wastewater and can realize the determination of textile wastewater of unknown samples. There is no need to pre-qualify the unknown samples before determination. At the same time, the textile wastewater of the unknown samples can be a single sample or a mixed sample, both of which are applicable to the determination method of the present invention. At the same time, the interference of fibers other than fiber microplastics in the textile wastewater can be effectively eliminated. In addition, since the standard curve equation is determined by standard stickers for several types of fiber microplastics in textile aqueous solutions, the deviation is small when it is applied to the determination of these types of fiber microplastics in textile aqueous solutions, and the determination result is more accurate.

[0045] In general, the method for determining fiber microplastics in textile aqueous solutions based on fluorescence spectrophotometry provided in the present invention not only does not require the use of large instruments such as Fourier transform infrared spectrometers and Raman spectrometers, but is also simple to operate, less time-consuming, and helps to improve detection efficiency. Moreover, it is suitable for unknown samples in the field of textile aqueous solutions, and can analyze both single samples and mixed samples with higher detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a schematic diagram showing the effect of fiber microplastic length on fluorescence intensity in Experimental Example 1 of the present invention;

[0047] Figure 2 This is a schematic diagram of the fluorescence intensity of microplastics in shredded 500um polyester fibers in Experimental Example 1 of the present invention. Figure 2 .b is a schematic diagram of the fluorescence intensity of ground 50um polyester fiber microplastics;

[0048] Figure 3 This is a test graph of the fluorescence intensity of polyester fiber microplastics with different diameters in Experimental Example 2 of the present invention;

[0049] Figure 4 This is a test graph of the fluorescence intensity of polyamide fiber microplastics with different diameters in Experimental Example 2 of the present invention;

[0050] Figure 5 To show that the relationship between the concentration of microplastics in polyethylene fibers and the fluorescence intensity of the present invention is consistent with the standard curve of microplastics in polypropylene fibers. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0052] The embodiments given in this application use blue polyacrylonitrile and polyester blended knitted fabric washing wastewater and beige viscose and nylon blended trousers washing wastewater as wastewater samples to determine fiber microplastics. The wastewater samples are not limited to these, but can also be other textile aqueous solutions, such as polypropylene and linen blended mat washing wastewater, etc. It should be pointed out that the choice of wastewater samples is diverse and can be selected according to actual needs.

[0053] The implementation principle of the embodiment of the present invention is: the above-mentioned textile wastewater is taken as an unknown sample. The unknown sample does not need to be qualitatively analyzed in advance for fiber microplastics. It can be a sample mixed with a single fiber microplastic or a sample mixed with multiple fiber microplastics. The unknown sample is filtered and rinsed with sodium hypochlorite solution. Then, a cylindrical separatory funnel is used to separate the fiber microplastics into two parts with a density less than water and a density greater than water to obtain an upper and lower layer of aqueous solution. Then, the sample is dyed with Nile red dye solution, and after secondary dispersion with a reagent, its fluorescence intensity is tested. Then, the content of fiber microplastics in the unknown aqueous solution is obtained by corresponding to the standard curve.

[0054] Among them, the present invention is applied to the detection of fiber microplastics in aqueous solutions of textiles, and the fiber microplastics involved in the determination are polypropylene fiber microplastics, polyethylene fiber microplastics, polyester fiber microplastics, and polyamide fiber microplastics. That is to say, no matter the unknown sample contains a single polypropylene fiber microplastic or polyethylene fiber microplastic or polyester fiber microplastic or polyamide fiber microplastic, or contains any two, three or a combination of three of polypropylene fiber microplastics, polyethylene fiber microplastics, polyester fiber microplastics, and polyamide fiber microplastics, the fiber microplastic determination method provided by the present invention can measure the concentration of fiber microplastics, that is, the present invention is applied to the determination of polypropylene fiber microplastics, polyethylene fiber microplastics, polyester fiber microplastics, and polyamide fiber microplastics in aqueous solutions of textiles, and is not only applicable to the detection of unknown samples, but also to the determination of single samples or mixed samples.

[0055] At the same time, the standard curve provided by the present invention is a standard curve fitting equation obtained by measuring polypropylene fiber microplastics, polyester fiber microplastics and polyamide fiber microplastics using standard stickers, and the standard curve provided is only applicable to polypropylene fiber microplastics, polyester fiber microplastics and polyamide fiber microplastics. Therefore, when the standard in the present invention is applied to the quantitative analysis of textile aqueous solutions, the situation in which the results have serious deviations is avoided, and reliable quantitative analysis results can be achieved.

[0056] It should be noted that there is currently no standard fiber material for polyethylene fibers. In addition, most of them are high-modulus polyethylene fibers, which cannot be cut with scissors, and it is difficult to obtain fiber microplastics within the length range of microplastics. A variety of low-modulus polyethylene fibers and two high-modulus polyethylene fibers were subsequently collected. Short fibers within the length range of fiber microplastics were made by cutting and low-temperature grinding. After staining with Nile red fluorescent dye, it was found that the relationship between its concentration and fluorescence intensity conformed to the standard curve of polypropylene fiber microplastics, see Figure 5 . Figure 5 The two curves in the middle are linear curves between the fluorescence intensity of polypropylene fibers in two bands and the concentration of fiber microplastics. The black data points in the figure are the relationship between the fluorescence intensity measured using multiple batches of polyethylene fiber microplastics and the concentration of polyethylene fiber microplastics. Therefore, a standard curve between the concentration of fiber microplastics and the fluorescence intensity is no longer established for the determination of polyethylene fiber microplastics.

[0057] Example 1

[0058] This embodiment is a method for determining fiber microplastics in a textile aqueous solution based on fluorescence spectrophotometry, wherein the textile aqueous solution is wastewater from washing a knitted fabric blended with blue polyacrylonitrile fiber and polyester fiber, and comprises the following steps:

[0059] S1. Use a water sampler to collect 2L of blue polyacrylonitrile fiber and polyester fiber blended plush fabric washing wastewater, stir to obtain a uniform water sample, and collect parallel samples at the same time; and filter the wastewater using a micro-glass filtration device with a glass fiber filter membrane; the specific method of parallel sample collection refers to the sample collection part of the water sampler stored in the transportation of GB 17378.3 Marine Monitoring Specification Part 3, which will not be repeated here;

[0060] S2. Rinse the filter membrane with sodium hypochlorite solution, turn off the suction filtration device, fully immerse the fiber microplastics in the sodium hypochlorite solution, let it stand for 10 minutes, and wash the filter membrane with a large amount of water until it is neutral; wherein, the flushing volume of the sodium hypochlorite solution is 20mL-50mL, and the concentration of the sodium hypochlorite solution is 0.9mol / L-1.0mol / L;

[0061] S3, rinse the fiber microplastics on the filter membrane into tertiary water, add it to the cylindrical separatory funnel, and let it stand for 1 hour;

[0062] S4, pour out the fiber microplastics floating on the upper layer of the solution from the upper port of the cylindrical separatory funnel, and collect the fiber microplastics deposited at the bottom from the lower port, the liquid collected at the upper port is the test liquid 1, and the liquid collected at the lower port is the test liquid 2;

[0063] S5. Repeat S1-S2, then rinse the filter membrane with hydrochloric acid to remove some of the possible fiber microplastics, collect the remaining fiber microplastics, rinse the filter membrane with a large amount of water until it is neutral, and then repeat S3-S4, collect the fiber microplastics deposited at the bottom from the lower port of the separatory funnel, and mark it as test solution 3; it should be noted that before using hydrochloric acid to rinse the filter membrane, replace the filter bottle receiving the filtrate;

[0064] S6. Filter the obtained test solutions 1, 2, and 3 respectively, and rinse the three fiber microplastics into the dye solution with 80 mL-150 mL of the prepared Nile red dye solution, and let stand at room temperature for 20 min-40 min; wherein the concentration of Nile red fluorescent dye is 80 ug / mL;

[0065] S7. Weigh 0.5000 g ± 0.0002 g (accurate to 0.0001 g) and crush various types of fiber microplastics (polyester standard lining, polyamide standard lining and polypropylene standard lining) with a length of <2 mm, put them into conical flasks respectively, add 25 ml of grade 3 water and 25 ml of Nile red dye (160 ug / mL), let stand at room temperature for 30 min, and filter the three types of fiber microplastics after dyeing. Rinse with 50 ml of a solution of water: acetone = 1:1 during filtration, and dry for use;

[0066] Weigh 0.2500 g ± 0.0002 g (accurate to 0.0001 g) of the dyed polyester and polyamide standard lining fiber microplastics respectively, add them into 500 ml of an aqueous solution containing 0.3% of a surfactant to prepare a standard solution;

[0067] Weigh 0.2500 g ± 0.0002 g (accurate to 0.0001 g) of the dyed polypropylene standard lining fiber microplastics, add it to 500 ml of liquid paraffin with a density of 0.86-0.89 g / cm3 to prepare a standard solution; wherein the liquid paraffin is used as a dispersant;

[0068] To prepare two calibration solutions of polyester fiber microplastics and polyamide fiber microplastics, dilute at least six solutions of the standard solution with third-grade water containing 0.3% surfactant in a 250 mL conical flask;

[0069] Preparation of polypropylene fiber microplastic calibration solution: In a 250 mL conical flask, use a density of 0.86 g / cm 3 -0.89g / cm 3 At least 6 solutions of the dilute standard solution of liquid paraffin;

[0070] in:

[0071] 10mL standard solution to 100mL, containing 50ug / mL fiber microplastics;

[0072] 15mL standard solution to 100mL, containing 75ug / mL fiber microplastics;

[0073] 20mL standard solution to 100mL, containing 100ug / mL fiber microplastics;

[0074] 25mL standard solution to 100mL, containing 125ug / mL fiber microplastics;

[0075] 30mL standard solution to 100mL, containing 150ug / mL fiber microplastics;

[0076] 35mL standard solution to 100mL, containing 175ug / mL fiber microplastics;

[0077] 40mL standard solution to 100mL, containing 200ug / mL fiber microplastics;

[0078] 45mL standard solution to 100mL, containing 225ug / mL fiber microplastics;

[0079] 50mL standard solution to 100mL, containing 250ug / mL fiber microplastics;

[0080] 55mL standard solution to 100mL, containing 275ug / mL fiber microplastics;

[0081] 60mL standard solution to 100mL, containing 300ug / mL fiber microplastics;

[0082] S8. Take appropriate amounts of standard series solutions from low to high, place them in a cuvette, start the analysis and testing system for measurement, so as to measure and draw a standard curve of fluorescence intensity and fiber microplastic concentration, and obtain the standard curve fitting equation after exponential fitting of the standard curve;

[0083] in:

[0084] Fitting equation curve of polyester fiber microplastics

[0085] I PET =a PET C PET +b PET Formula (1)

[0086] Fitting equation curve of polyamide fiber microplastics

[0087] I PA =a PA C PA +b PA Formula (2)

[0088] Fitting equation curve of microplastics in polypropylene fibers

[0089] I PP =a PP C PP +b PP Formula (3)

[0090] In the above formula:

[0091] I PET ——The fluorescence signal value (fluorescence intensity) of polyester fiber microplastics;

[0092] I PA ——fluorescence signal value (fluorescence intensity) of polyamide fiber microplastics;

[0093] I PP ——The fluorescence signal value (fluorescence intensity) of polypropylene fiber microplastics;

[0094] C PET ——Concentration of polyester fiber microplastics in the sample to be tested, (ug / mL);

[0095] C PA ——Concentration of polyamide fiber microplastics in the sample to be tested, (ug / mL);

[0096] C PP ——Concentration of polypropylene fiber microplastics in the sample to be tested, (ug / mL);

[0097] a PET ,b PET ——Working curve coefficient of polyester fiber microplastics;

[0098] a PA ,b PA ——Working curve coefficient of polyamide fiber microplastics;

[0099] a PP ,b PP ——Working curve coefficient of polypropylene fiber microplastics;

[0100] S9. Put the three solutions obtained in S6 into a turbine disperser or shake them by hand to disperse them evenly, and then measure their fluorescence intensity on a fluorescence spectrophotometer. Combined with the standard curve fitting equation, calculate the concentration of the three fiber microplastics, specifically:

[0101] The fluorescence intensity of the test solution 1 is measured to be I1, and the fluorescence intensity I1 is substituted into the polypropylene fiber microplastic standard curve fitting equation I PP =a PP C PP +b PP The concentration C1 of fiber microplastics in the test solution 1 is obtained;

[0102] The fluorescence intensity of the test solution 3 is measured to be I3, and the fluorescence intensity I3 is substituted into the polyester fiber microplastic standard curve fitting equation I PET =a PET C PET +b PET The concentration of polyester fiber microplastics C3 was obtained;

[0103] The fluorescence intensity of the test liquid 2 is measured as I2. Substituting C1, C3, and I2 into the following formula can obtain the total amount of fiber microplastics in the concentrated or diluted aqueous solution:

[0104]

[0105] C=KC 总

[0106] C——Concentration of fiber microplastics in aqueous solution (ug / mL);

[0107] C 总 ——The total concentration of fiber microplastics in aqueous solution after concentration or dilution (ug / mL);

[0108] K——concentration or dilution multiple. When not concentrated or diluted, K=1 / 10;.

[0109] It should also be noted that the fibers collected from the lower port of the separatory funnel include not only fibrous microplastics but also some possible degradable fibers, but these fibers have little effect on the determination of this application and are therefore not considered here.

[0110] To avoid uneven distribution of fiber microplastics, each solution was tested three times in parallel to obtain three fiber microplastic concentrations, and the average value was taken as the final fiber microplastic concentration. If the difference in the parallel test results is greater than 3.0%, a fourth test is conducted, and the data with large differences are discarded. The final result is the arithmetic mean of the three tests. The final result is rounded to two decimal places according to GB / T 8170.

[0111] Example 2

[0112] This embodiment is a method for determining fiber microplastics in a textile aqueous solution based on fluorescence spectrophotometry, wherein the textile aqueous solution is trouser washing wastewater blended with beige viscose 40% and nylon fiber 60%, comprising the following steps:

[0113] S1. Use a water sampler to collect 5L of blue polyacrylonitrile fiber and polyester fiber blended plush fabric washing wastewater, and stir to obtain a uniform water sample; collect parallel samples at the same time, and filter the wastewater using a micro-glass filtration device with a glass fiber filter membrane; the specific method of parallel sample collection refers to the sample collection part of the water sampler stored in the transportation of GB 17378.3 Marine Monitoring Specification Part 3, which will not be repeated here;

[0114] Then, the same operation steps as in Example 1 were repeated, S2-29 was repeated to obtain C1, C3, C 总 , thereby obtaining the concentration of fiber microplastics in the aqueous solution to be tested.

[0115] Test Example 1

[0116] Fiber microplastics are fibrous microplastics with a size of less than 5 mm that are formed by the mechanical action, wear, etc. of the fibers that are difficult to degrade on textiles during the pre-treatment, printing and dyeing, finishing, wearing and washing of textiles. After being exposed to wind, rain, sun, and microbial action, the fibers fall off the textiles. The length of fiber microplastics is not completely uniform. There are nano-scale, micron-scale, and some larger millimeter-scale microplastics. For unknown samples, we cannot know their size distribution, so the length of fiber microplastics is an important factor affecting dyeing.

[0117] Based on this, the fiber microplastic dyeing method given in this application was used to dye fiber microplastics of different lengths and types. The fiber microplastics measured included polyester fibers, polyamide fibers, and polypropylene fibers.

[0118] The three fiber standard linings were cut into pieces with lengths of 500um, 1mm, 2mm, 3mm, and 4mm. In addition, a freeze grinder was used to grind the fibers into fiber microplastics with a size of 50um.

[0119] The effect of fiber microplastic length on fluorescence intensity was obtained, such as Figure 1 shown.

[0120] Depend on Figure 1 .A It can be seen that the fiber length has little effect on the fluorescence intensity of polyamide fiber microplastics and polypropylene fiber microplastics. The fluorescence intensity of polyester fiber microplastics is stronger when the length is about 50um. This is because the polyester fiber has a tight structure and it is difficult for dye molecules to enter the interior of the fiber at room temperature. The fiber microplastics with a length of about 50um obtained by grinding cause most of the fibers to be damaged by grinding.

[0121] like Figure 2 As shown, Figure 2 .a is to cut up 500um polyester fiber microplastics, Figure 2 .b is grinding 50um polyester fiber microplastics, such as Figure 2In .b, the specific surface area of ​​polyester fiber microplastics suddenly increases, and the ability to adsorb dyes is enhanced, resulting in a higher fluorescence intensity of the fibers than fibers of other lengths. However, some fiber microplastics are less than 0.7um in length and will be filtered out of the glass fiber filter membrane during filtration. Another important reason is that the fiber microplastics are small in length and easy to agglomerate, causing the fluorescence intensity test results to fluctuate, making it impossible to obtain accurate fluorescence intensity test results. However, since the unknown samples of fiber microplastics are composed of fibers of various sizes, and it is difficult to damage the fiber epidermis, other sample preparation methods were used later, and the results are as follows. Figure 1 .B. as shown.

[0122] It can be seen that, using the determination method of the present application, the length of the fiber microplastics has little effect on the fluorescence intensity of the fiber microplastics after staining, and its influence can be eliminated. The staining of unknown samples can obtain a relatively stable fluorescence intensity.

[0123] Test Example 2

[0124] During the spinning and weaving process, textiles are produced, designed, and woven according to the style and design of the textiles, so the fiber diameters used will vary. Some ultrafine fibers are spun using a special process, and the fiber diameters can be as small as a few microns, while fibers with larger diameters can be as large as nearly 100 microns. Therefore, whether the diameters of different fibers will affect the fluorescence intensity after dyeing is also a key factor affecting whether this method is feasible.

[0125] Polyester fiber microplastics and polyamide fibers with different diameters were dyed with Nile red fluorescent dye, and then their fluorescence intensity was tested. The results are as follows Figure 3 Shown with Figure 4 As shown, Figure 3 Shown is a test chart of the fluorescence intensity of polyester fiber microplastics with different diameters; Figure 4 Shown is a graph showing the fluorescence intensity test of polyamide fiber microplastics with different diameters.

[0126] Depend on Figure 3 , Figure 4 The results show that polyester fiber microplastics and polyamide fibers of different diameters do not affect the final fluorescence intensity, and the fluorescence intensity and fiber concentration still follow the above linear relationship.

[0127] At the same time, the determination method of the present application was used to verify polyester fiber microplastics and polyamide fiber microplastics with different diameters, as shown in Tables 1 and 2.

[0128] Table 1 Verification of polyester fiber microplastics with different diameters

[0129]

[0130] Table 2 Verification of microplastics in polyamide fibers with different diameters

[0131]

[0132]

[0133] It can be verified from Tables 1 and 2 that, using the measurement method of the present application, polyester fiber microplastics and polyamide fibers of different diameters do not affect the final fluorescence intensity, and the concentration of fiber microplastics calculated by the fluorescence intensity is highly consistent with the known concentration.

[0134] Test Example 3

[0135] Textile products are all products that have undergone a series of dyeing and finishing processes such as dyeing, printing, and finishing. Therefore, most of the fiber microplastics formed by textiles through mechanical, sun exposure, and biological processes carry dyes and present colorful colors. Whether the various types of dyes carried by the fiber microplastics themselves have an effect on the dyeing of Nile red dye is also the key to the qualitative and quantitative identification of fiber microplastics using this method. The following selected textiles of various colors and cut them into fiber microplastics of about 50um in length, and then tested their solutions to obtain Table 3.

[0136] Table 3 Verification results of fiber microplastics of different colors

[0137]

[0138]

[0139] It can be seen from the above table that the dye color of the fiber itself does not affect the dyeing of Nile red dye, nor does it affect the fluorescence intensity of the confined microplastics. The concentration of fiber microplastics calculated by the fluorescence intensity is highly consistent with the known concentration.

[0140] Test Example 4

[0141] There are more than a dozen types of fibers commonly used in textiles, most of which will be degraded after being exposed to light, rain, and microorganisms when released into the environment, such as natural fibers such as cotton, linen, wool, and silk, and some chemical synthetic fibers such as viscose, modal, lyocell, protein-modified polyvinyl alcohol fiber (soy fiber), protein-modified polyacrylonitrile fiber (milk fiber), and nylon, as well as polyacrylonitrile fiber that takes 20 to 30 years to degrade. Of course, it also includes difficult-to-degrade polyester fibers, polyamide fibers, polypropylene fibers, polyethylene fibers, etc. that belong to the category of fiber microplastics.

[0142] In order to make textiles have better wearing performance, clothing fabric manufacturers often use two or more fiber blends during production and processing. Therefore, the aqueous solutions containing fiber microplastics we collected often contain a variety of fiber microplastics, including incompletely degraded or undegraded degradable fibers in addition to difficult-to-degrade fiber microplastics. Whether the presence of these fibers interferes with the testing of fiber microplastics is an urgent problem that needs to be solved.

[0143] When Nile red was used to dye various biodegradable fibers, it was found that protein fibers such as mulberry silk and wool would be dyed and obtain higher fluorescence intensity. Therefore, 0.9-1.0 mol / L sodium hypochlorite solution was used for immersion and washing during pretreatment to remove the influence of protein fibers.

[0144] Polyamide fiber microplastics and polyacrylonitrile fibers with a length of about 500 um were manually mixed in the following proportions, and their fluorescence intensity was tested. The concentration of solution fiber microplastics was calculated and compared with the mixing results (Table 4).

[0145] Table 4 Polyamide fiber microplastics mixed with polyacrylonitrile fiber

[0146]

[0147] It can be seen from Table 4 that the calculated concentration of microplastics in polyamide fibers is close to the actual blending concentration, that is, the presence of polyacrylonitrile fibers has no effect on the concentration determination of microplastics in polyamide fibers. Nile red dye does not dye degradable polyacrylonitrile fibers, and its effect can be ignored.

[0148] Therefore, the influence of other fibers in the determination method of this application can be ignored.

[0149] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for determining fiber microplastics in textile aqueous solution based on fluorescence spectrophotometry, characterized in that: The following steps are involved: S1. Collect wastewater from the environment and filter the wastewater using a micro-glass filtration device with a glass fiber filter membrane; S2. Rinse the filter membrane with sodium hypochlorite solution, turn off the suction filtration device, and fully immerse the fiber microplastics in the sodium hypochlorite solution. After standing for a period of time, wash the filter membrane with a large amount of water until it is neutral; S3, rinse the fiber microplastics on the filter membrane into tertiary water, add it to the separatory funnel, and let it stand until obvious stratification; S4, pour out the fiber microplastics floating on the upper layer of the solution from the upper port of the separatory funnel, collect the fiber microplastics deposited at the bottom from the lower port, the liquid collected at the upper port is the test liquid 1, and the liquid collected at the lower port is the test liquid 2; S5, repeat S1-S2, then rinse the filter membrane with hydrochloric acid to remove a small part of the fiber microplastics that may exist, collect the remaining fiber microplastics, rinse the filter membrane with a large amount of water until it is neutral, then repeat S3-S4, collect the fiber microplastics deposited at the bottom from the lower port of the separatory funnel, and mark it as test solution 3; S6, filtering the obtained three solutions of test solution 1, 2, and 3 respectively, and dyeing them with the prepared Nile red dye solution; S7, taking the polyester, polyamide and polypropylene standard lining fiber microplastics that have been dyed and filtered, respectively, and preparing a series of standard solutions with concentration gradients; S8. Take appropriate amounts of the standard series solutions from low to high, place them in a cuvette, start the fluorescence spectrophotometer for measurement, and draw a standard curve of fluorescence intensity and fiber microplastic concentration. After exponential fitting of the standard curve, obtain the standard curve fitting equation; S9. Disperse the three solutions obtained in S6 evenly and measure their fluorescence intensities on a fluorescence spectrophotometer. Calculate the concentration of fiber microplastics in the aqueous solution using a standard curve fitting equation.

2. The method for determining fiber microplastics in textile aqueous solution based on fluorescence spectrophotometry according to claim 1 is characterized in that: In the S2, the flushing volume of the sodium hypochlorite solution is 20mL-50mL, and the concentration of the sodium hypochlorite solution is 0.9mol / L-1.0mol / L.

3. The method for determining fiber microplastics in textile aqueous solution based on fluorescence spectrophotometry according to claim 2 is characterized in that: The separating funnel is a cylindrical separating funnel.

4. The method for determining fiber microplastics in textile aqueous solution based on fluorescence spectrophotometry according to claim 1 is characterized in that: In S5, the amount of hydrochloric acid is 20 mL-50 mL, and before washing the filter membrane with hydrochloric acid, the filter bottle receiving the filtrate is replaced.

5. The method for determining fiber microplastics in textile aqueous solution based on fluorescence spectrophotometry according to claim 1 is characterized in that: The step of dyeing with Nile red dye in S6 is: rinse the three types of fiber microplastics into the dye solution with 80mL-150mL of the prepared Nile red dye solution respectively, and let it stand at room temperature for 20min-40min; wherein the concentration of Nile red fluorescent dye is 80ug / mL.

6. The method for determining fiber microplastics in textile aqueous solution based on fluorescence spectrophotometry according to claim 1, characterized in that: In S7, 0.5000 g ± 0.0002 g of polyester, polyamide, and polypropylene standard linings are weighed respectively and crushed into various types of fiber microplastics with a length of < 2 mm; The dyeing process includes: placing various types of fiber microplastics into conical flasks, adding grade tertiary water and Nile red dye, and standing at room temperature for a period of time, wherein the concentration of Nile red dye is 160ug / mL; The filtration includes: washing with a solution of water:acetone=1:1, and drying for standby use.

7. The method for determining fiber microplastics in textile aqueous solution based on fluorescence spectrophotometry according to claim 1, characterized in that: In S7, the preparation process of the standard series solution with concentration gradient is: Weigh 0.2500 g ± 0.0002 g of the dyed polyester and polyamide standard lining fiber microplastics respectively, add them to an aqueous solution containing a surfactant to prepare a standard solution, and dilute them into at least 6 solutions with a concentration gradient; Weigh 0.2500g±0.0002g of dyed polypropylene standard lining fiber microplastics, add it to liquid paraffin to prepare a standard solution, and dilute it into at least 6 solutions with a concentration gradient.

8. The method for determining fiber microplastics in textile aqueous solution based on fluorescence spectrophotometry according to claim 1, characterized in that: The standard curve fitting equation in S8 is: I=aC+b; wherein I is the fluorescence intensity of a single type of fiber microplastic, C is the concentration of a single type of fiber microplastic in the sample to be tested, and a and b are the working curve coefficients of a single type of fiber microplastic.

9. The method for determining fiber microplastics in textile aqueous solution based on fluorescence spectrophotometry according to claim 1, characterized in that: In the S9: The fluorescence intensity of the test solution 1 is measured to be I1, and the fluorescence intensity I1 is substituted into the polypropylene fiber microplastic standard curve fitting equation I PP =a PP C PP +b PP The concentration C1 of fiber microplastics in the test solution 1 is obtained; The fluorescence intensity of the test solution 3 is measured to be I3, and the fluorescence intensity I3 is substituted into the polyester fiber microplastic standard curve fitting equation I PET =a PET C PET +b PET The concentration of polyester fiber microplastics C3 was obtained; The fluorescence intensity of the test liquid 2 is measured as I2. Substituting C1, C3, and I2 into the following formula can obtain the total amount of fiber microplastics in the concentrated or diluted aqueous solution: C=KC 总 C——Concentration of fiber microplastics in aqueous solution (ug / mL); C 总 ——The total concentration of fiber microplastics in aqueous solution after concentration or dilution (ug / mL); K——concentration or dilution multiple. When not concentrated or diluted, K=1 / 10.

10. The method for determining fiber microplastics in textile aqueous solution based on fluorescence spectrophotometry according to claim 1, characterized in that: The method for uniformly dispersing the solution in S9 is: Place the solution in a turbine disperser or shake by hand.

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