WO2021163821A1

WO2021163821A1 - Method for quantitative determination of total amount of micro and nano plastics in water environment based on total organic carbon

Info

Publication number: WO2021163821A1
Application number: PCT/CN2020/075469
Authority: WO
Inventors: 刘景富; 李鹏; 谭志强; 李庆存
Original assignee: 中国科学院生态环境研究中心
Priority date: 2020-02-17
Filing date: 2020-02-17
Publication date: 2021-08-26
Also published as: DE112020006738T5; JP7270306B2; JP2022539039A

Abstract

Disclosed is a method for quantitative determination of the total amount of micro and nano plastics in a water environment based on total organic carbon. The method comprises: filtering a water sample using a first concentration membrane, and collecting same to obtain a first solid; adding a digestion reagent to the first concentration membrane bearing the first solid, in order to digest and remove natural organic matter; filtering the resulting mixture using a second concentration membrane to obtain a second concentration membrane bearing a second solid; and drying the digested first concentration membrane and the second concentration membrane bearing the second solid, and then determining the total organic carbon value, i.e. the total organic carbon value of the micro and nano plastics. The use of the TOC value of the micro and nano plastics to express the total amount of the micro and nano plastics enables the determination of the total amount of the micro and nano plastics at a μg C/L level, and is successfully applied for accurate quantitative analysis of the total amount of micro and nano plastics in an actual water sample. The method has a higher sensitivity, simple operations and a low operation cost.

Description

Method for quantitatively determining the total amount of micro-nano plastics in water environment based on total organic carbon

Technical field

The present disclosure relates to the field of environmental analytical chemistry, and in particular to a method for quantitatively determining the total amount of micro-nano plastics in a water environment based on total organic carbon.

Background technique

Due to the excellent physical and chemical properties of plastics, its products are widely used in daily production and life. In the end, these plastic products often form plastic waste into the environment. A large amount of plastic waste will be cracked under the action of solar radiation, water current impact and biodegradation to form micro-nano plastics. On the other hand, micro-nano plastics are also used in industrial raw materials and daily cosmetics. While these products are in use, micro-nano plastics will also be released into the environment.

In recent years, micro-nano plastics have been listed as a new type of pollutant by environmentalists. According to toxicology studies, micro-nano plastics can be ingested by animals and affect their growth and reproduction. In addition, micro-nano plastics can also adsorb heavy metal ions, organic pollutants, etc., resulting in compound toxic effects. Moreover, the toxic effects of micro-nanoplastics are closely related to their concentration levels. Therefore, accurate quantitative analysis of micro-nano plastics is a prerequisite for studying their pollution levels and toxic effects.

At present, the quantitative analysis of micro-nano plastics mainly adopts weighing method, scanning electron microscopy-energy spectroscopy, thermal pyrolysis gas chromatography mass spectrometry, etc. However, these methods have the disadvantages of narrow application range (for example, only suitable for a certain material), time-consuming and labor-intensive, low sensitivity, and expensive instruments, and are difficult to be used for quantitative analysis of the total amount of micro-nano plastics in actual environmental waters.

Summary of the invention

In response to the above technical problems, the present disclosure proposes a method for quantitatively determining the total amount of micro-nano plastics in the water environment based on total organic carbon. Specifically, the present disclosure provides a method for quantitatively determining the total amount of micro-nano plastics in a water environment based on total organic carbon, which includes the following steps:

(1) Filter the water sample with the first enrichment membrane, and collect the first solid;

(2) Add a digestion reagent to the first enrichment membrane with the first solid to digest and remove natural organic matter;

(3) Filter the mixture obtained in step (2) with a second enrichment membrane to obtain a second enrichment membrane with a second solid;

(4) Dry the digested first enrichment membrane and the second enrichment membrane with the second solid in step (3), and then determine the total organic carbon value, which is the total organic carbon value of the micro-nanoplastic.

Description of the drawings

Figure 1 is a schematic diagram of the disclosed method for quantitatively determining micro-nano plastics in a water environment;

Figure 2 is an electron micrograph of the disclosed nano-pore (300nm) glass fiber membrane trapped and enriched with micro-nano plastic particles;

Figure 3 is a graph showing the influence of the volume of filtered water sample (100mL-1000mL) on the recovery rate of micro/nano plastics in the present disclosure;

Figure 4 is a graph showing the influence of Fenton's digestion on the recovery rate of micro-nano plastics.

Detailed ways

There are many types of micro-nano plastics, and it is very challenging to analyze a certain amount of them. However, micro-nano plastics, as a type of typical carbon-containing particulate matter, can be used to characterize the total amount of micro-nano plastics with the total organic carbon (TOC) value of the micro-nano plastics. The presence of a large amount of natural organic matter (NOM) in the natural water environment will interfere with the TOC determination of micro-nano plastics, and it needs to be digested to remove the interference of NOM. The TOC value of solid samples is generally determined by catalytic combustion method. The solid sample is completely converted into CO ₂ under the combined action of catalyst and high-purity oxygen at 900°C. The generated CO _{2 is} introduced into a non-dispersive infrared absorption detector (NDIR) to obtain TOC content. At present, TOC value is used to characterize the total amount of micro-nano plastics, and the method of quantitatively determining the total amount of micro-nano plastics based on TOC has not been reported.

The present disclosure discloses a method for quantitatively determining the total amount of micro-nano plastics in a water environment based on total organic carbon, including:

In some embodiments of the present disclosure, the pH of the digestion solution in step (2) is less than 3.

In some embodiments of the present disclosure, the digestion temperature in step (2) is 25 to 60° C., and the digestion time is 0.5 to 2 hours.

In some embodiments of the present disclosure, the digestion reagent in step (2) includes Fenton's reagent.

In some embodiments of the present disclosure, the drying temperature in the drying step in step (3) is 60 to 190°C.

In some embodiments of the present disclosure, the drying time in the drying step in step (3) is 0.5 to 6 hours.

In some embodiments of the present disclosure, in the drying step in step (3), the first enrichment membrane and the second enrichment membrane are directly placed in a sample boat for drying.

In some embodiments of the present disclosure, the instrument used in the step of determining the total organic carbon value of micro-nano plastics in step (4) includes a total organic carbon analyzer equipped with a solid accessory;

Wherein, the detector of the total organic carbon analyzer is a non-dispersive infrared detector;

The carrier gas in the total organic carbon analyzer includes oxygen, the carrier gas has a flow rate of 400 to 500 mL/min, a pressure of 190 to 200 kPa, and a reaction furnace temperature of 900 to 1200°C.

In some embodiments of the present disclosure, the first enrichment membrane and the second enrichment membrane both include glass fiber membranes, alumina membranes, and quartz membranes.

In some embodiments of the present disclosure, the pore size of the glass fiber membrane is 1 to 1000 nanometers.

In an exemplary embodiment, the method for quantitatively determining the total amount of micro-nano plastics in environmental water bodies according to the present disclosure includes the following steps:

Use glass fiber membranes to filter environmental water samples to retain micro-nano plastics in the enriched water samples;

Use Fenton's reagent to digest and remove the natural organic matter (NOM) on the membranes enriched with micro-nanoplastics;

Use a new glass fiber membrane to filter the digestion solution, and dry the two membranes (ie glass fiber membranes) at 60°C-190°C for 0.5-6 hours;

Use a TOC meter equipped with a solid accessory to measure the TOC value, and use the TOC value to indicate the total amount of micro-nano plastics.

Among them, TOC is used as a parameter to quantitatively express the total amount of micro-nano plastics.

Wherein, the retention enrichment membrane is a glass fiber membrane.

Wherein, the NOM removal method is Fenton's digestion, and the digestion reagent is Fenton's reagent: an equal volume of 30% (m/v) H ₂ O ₂ solution plus 0.05 mol/L Fe ²⁺ solution.

Among them, Fe ²⁺ is FeSO ₄ ·7H ₂ O or other ferrous salts, and the digestion condition of Fenton’s reagent is pH<3.

Among them, the two films are directly placed in the sample boat, and the TOC value is measured after drying.

Among them, the trapped and enriched micro-nano plastic membrane is subjected to Fenton digestion treatment to remove NOM while also removing inorganic carbon (IC). At this time, the measured total carbon (TC) value is the TOC value.

Among them, the two films are dried at 60°C-190°C for 0.5-6 hours.

Among them, the purpose is to remove the moisture on the film without destroying the micro-nano plastic. 60-190℃ will not affect the determination of micro-nano plastics.

Among them, a TOC meter connected with a solid accessory is used to measure the TOC value of the micro-nano plastic on the glass fiber membrane.

Among them, the detector is a non-dispersive infrared detector (NDIR), the carrier gas is high-purity oxygen, the flow rate is 400-500 mL/min, the air pressure is 190-200 kPa, and the TC reactor temperature is 900-1200°C.

The technical solutions of the present disclosure will be further elaborated below through specific embodiments in combination with the drawings. It should be noted that the following specific embodiments are merely examples, and the protection scope of the present disclosure is not limited thereto.

The chemicals and raw materials used in the following examples are all commercially available or self-made by well-known preparation methods.

This embodiment provides a method for quantitatively determining micro-nano plastics in a water environment, as shown in FIG. 1, including the following steps:

(1) Filter the water sample to be tested with a nano-pore glass fiber membrane, and the micro-nano plastic particles are trapped and enriched on the glass fiber membrane;

(2) Use Fenton's reagent digestion treatment to remove the natural organic matter (NOM) on the membrane enriched with micro-nano plastic particles;

(3) Filter with another new glass fiber membrane, and clean the container wall three times with ultrapure water (18.3MΩ), and dry the two membranes at 60℃-190℃ for 0.5-6 hours;

(4) Finally, a TOC meter connected with a solid accessory is used to determine the TOC value, and the TOC value is used to indicate the total amount of micro-nano plastics.

In step (1), the glass fiber membrane with nano-pore size (1-1000nm) is selected. The glass fiber membrane is made of carbon-free glass fiber, which will not interfere with the TOC measurement; the dense fibrous structure is conducive to trapping and enriching micro Nanoplastic particles, as can be seen from Figure 1, micro-nanoplastics are trapped and enriched in the dense glass fiber membrane structure, playing the role of enriching micro-nanoplastics.

As shown in Figure 2, the arrow points to the micro-nano plastic, and the plastic particles are trapped on the glass fiber membrane.

As shown in Figure 3, the influence of the filtration volume of the water sample on the recovery rate of micro-nano plastics was investigated. 100-1000mL ultrapure water was spiked with micro-nano plastics with different carbon content, and the recovery rate was 84%-99%. It is found that when the volume of the filtered water sample reaches 1000 mL, the recovery rate of micro-nano plastics will not be significantly reduced, and the membrane will not be completely blocked or penetrated. It can be seen from Figure 3 that when the water sample filtration volume is increased from 100 mL to 1000 mL, the recovery rate of micro-nano plastics does not decrease significantly.

In step (2), there is a large amount of NOM in the natural environmental water body. If it is filtered with a membrane, some NOM will inevitably be trapped on the membrane. If it is not treated, it will interfere with the TOC determination. Use Fenton’s reagent (5mL 30%(m/v) ) H ₂ O ₂ plus 5mL 0.05mol/L Fe ²⁺ ) digestion treatment to remove the interference of NOM. As shown in Figure 4, in two different matrix (river water, sea water) spiked water samples, the spiked recovery rates of undigested micro/nano plastics were: river water 119%-206%, sea water 124%-218%; The recovery rates of the digested micro-nano plastics are respectively: 90%-96% for river water and 95%-111% for sea water. It shows that Fenton's reagent can remove NOM interference very well, and does not affect the recovery rate of micro/nanoplastic standard addition. It can be seen from Figure 4 that whether it is river water or sea water, the recovery rate of micro-nano plastics is far greater than 100% without Fenton digestion, and the recovery rate of micro-nano plastics is close to 90% after digestion.

In step (3), washing with ultrapure water three times is to transfer the micro-nano plastic adsorbed on the container wall to the film as much as possible, and drying the two films at 60℃-190℃ for 0.5-6 hours is to remove Moisture can be used for subsequent TOC measurement, and controlling the temperature at 60°C will not affect micro-nano plastics.

In step (4), the two membranes to be tested are directly placed in a ceramic sample boat without additional treatment. The micro-nano plastic can fully contact with high-purity oxygen under high-temperature catalysis and completely convert it into CO ₂ .

Under the above-mentioned optimal experimental conditions, the linear range of micro/nanoplastics measured by the method of the present disclosure is 0.02-3.6 mg C (correlation coefficient 0.998), and the detection limit is 14-19 μg C/L.

Example 1

Quantitative determination of micro-nano plastics in different substrates of water.

First, 100-1000mL of water samples from different substrates are passed through glass fiber membranes with a pore size of 300nm. The micro-nano plastic particles are trapped and enriched on the glass fiber membranes. The glass fiber membranes are transferred to a glass container, and Fenton’s reagent (5mL 30% (m/v) H ₂ O ₂ plus 5mL 0.05M Fe ²⁺ ) to eliminate the interference of NOM. Immediately use another membrane to filter the digested solution, and wash it with ultrapure water (18.3MΩ) three times, then transfer the two membranes to the sample boat and dry them at 60°C-190°C for 0.5-6 hours to remove water. Finally, the TOC is measured with a TOC meter connected with a solid accessory. The TOC value is used to express the total amount of micro/nano plastics. The results are shown in Table 1. Among them, no micro/nano plastics were detected in the water samples of Daliao River, Luanhe River and Bohai, indicating that these samples do not contain micro/nano plastics or The concentration is far below the detection limit of this method. 17-67μg C/L was detected in several samples of Bohai 1, Bohai 3, Bohai 4, and Bohai 5, indicating that this method can be used to determine the micro-nanoplastics in the environment at the micro-concentration level.

Table 1 The measurement results of the total amount of micro-nano plastics in actual environmental waters using this method

ND*: lower than the detection limit

For the above specific embodiments, the method for quantitatively determining the total amount of micro-nano plastics in the water environment based on total organic carbon of the present disclosure has at least one of the following advantages over the prior art:

1. The present disclosure uses the TOC value of micro-nano plastics to indicate the total amount of micro-nano plastics, and realizes the determination of the total amount of micro-nano plastics at the level of μg C/L, and has been successfully applied to the accuracy of the total amount of micro-nano plastics in actual water samples. Quantitative analysis

2. The sensitivity is high, and the detection limit of the method is 14-19μg C/L;

3. Easy to operate and low operating cost.

The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present disclosure in further detail. It should be understood that the above are only specific embodiments of the present disclosure and are not intended to limit the present disclosure. Within the spirit and principle of the present disclosure, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present disclosure.

Claims

A method for quantitatively determining the total amount of micro-nano plastics in the water environment based on total organic carbon, including:

(1) Filter the water sample with the first enrichment membrane, and collect the first solid;

(2) Add a digestion reagent to the first enrichment membrane with the first solid to digest and remove natural organic matter;

(3) Filter the mixture obtained in step (2) with a second enrichment membrane to obtain a second enrichment membrane with a second solid;

(4) Dry the digested first enrichment membrane and the second enrichment membrane with the second solid in step (3), and then determine the total organic carbon value, which is the total organic carbon value of the micro-nanoplastic.
The method of claim 1, wherein:

The pH of the digestion solution in step (2) is less than 3.
The method of claim 1, wherein:

In step (2), the digestion temperature is 25 to 60°C, and the digestion time is 0.5 to 2 hours.
The method of claim 1, wherein:

The digestion reagent in step (2) includes Fenton's reagent.
The method of claim 1, wherein:

The drying temperature in the drying step in step (3) is 60 to 190°C.
The method of claim 1, wherein:

The drying time in the drying step in step (3) is 0.5 to 6 hours.
The method of claim 1, wherein:

In the drying step in step (3), the first enrichment membrane and the second enrichment membrane are directly placed in a sample boat for drying.
The method of claim 1, wherein:

The instrument used in the step of determining the total organic carbon value of micro-nano plastic in step (4) includes a total organic carbon analyzer equipped with a solid accessory;

Wherein, the detector of the total organic carbon analyzer is a non-dispersive infrared detector;

The carrier gas in the total organic carbon analyzer includes oxygen, the carrier gas has a flow rate of 400 to 500 mL/min, a pressure of 190 to 200 kPa, and a reaction furnace temperature of 900 to 1200°C.
The method of claim 1, wherein:

The first enrichment membrane and the second enrichment membrane both include glass fiber membranes, alumina membranes, and quartz membranes.
The method of claim 1, wherein:

The pore diameter of the glass fiber membrane is 1 to 1000 nanometers.