CN113155558A - Method for extracting, separating and purifying micro-plastic in soil - Google Patents
Method for extracting, separating and purifying micro-plastic in soil Download PDFInfo
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- 239000002689 soil Substances 0.000 title claims abstract description 175
- 229920003023 plastic Polymers 0.000 title claims abstract description 91
- 239000004033 plastic Substances 0.000 title claims abstract description 91
- 238000000034 method Methods 0.000 title claims abstract description 40
- 239000004927 clay Substances 0.000 claims abstract description 35
- 239000005416 organic matter Substances 0.000 claims abstract description 33
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 32
- 239000002245 particle Substances 0.000 claims abstract description 24
- 239000000725 suspension Substances 0.000 claims abstract description 17
- 239000012535 impurity Substances 0.000 claims abstract description 12
- JIAARYAFYJHUJI-UHFFFAOYSA-L zinc dichloride Chemical class [Cl-].[Cl-].[Zn+2] JIAARYAFYJHUJI-UHFFFAOYSA-L 0.000 claims abstract description 7
- 238000006243 chemical reaction Methods 0.000 claims abstract description 5
- 239000000243 solution Substances 0.000 claims description 38
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 26
- 238000001914 filtration Methods 0.000 claims description 13
- 239000012528 membrane Substances 0.000 claims description 12
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 11
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 claims description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 9
- 238000004445 quantitative analysis Methods 0.000 claims description 5
- 239000007864 aqueous solution Substances 0.000 claims description 4
- 238000003756 stirring Methods 0.000 claims description 4
- 239000006228 supernatant Substances 0.000 claims description 4
- 239000008367 deionised water Substances 0.000 claims description 3
- 229910021641 deionized water Inorganic materials 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 3
- 239000007788 liquid Substances 0.000 claims description 3
- 238000007873 sieving Methods 0.000 claims description 3
- 238000011010 flushing procedure Methods 0.000 claims 2
- 238000000926 separation method Methods 0.000 abstract description 16
- 238000000605 extraction Methods 0.000 abstract description 11
- 239000000126 substance Substances 0.000 abstract description 6
- 239000000203 mixture Substances 0.000 abstract description 5
- 230000010355 oscillation Effects 0.000 abstract description 5
- 238000004458 analytical method Methods 0.000 abstract description 3
- 229910052500 inorganic mineral Inorganic materials 0.000 abstract description 3
- 239000011707 mineral Substances 0.000 abstract description 3
- 235000010755 mineral Nutrition 0.000 abstract description 3
- 238000005345 coagulation Methods 0.000 abstract description 2
- 230000015271 coagulation Effects 0.000 abstract description 2
- 238000004090 dissolution Methods 0.000 abstract description 2
- 239000004576 sand Substances 0.000 description 13
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 10
- 229920000426 Microplastic Polymers 0.000 description 9
- 229910052739 hydrogen Inorganic materials 0.000 description 9
- 239000003153 chemical reaction reagent Substances 0.000 description 8
- 239000002688 soil aggregate Substances 0.000 description 7
- 238000011160 research Methods 0.000 description 6
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000005406 washing Methods 0.000 description 4
- 239000002699 waste material Substances 0.000 description 4
- 239000012028 Fenton's reagent Substances 0.000 description 3
- 239000002734 clay mineral Substances 0.000 description 3
- 238000000746 purification Methods 0.000 description 3
- 241000196324 Embryophyta Species 0.000 description 2
- 239000012615 aggregate Substances 0.000 description 2
- 229910000019 calcium carbonate Inorganic materials 0.000 description 2
- 239000003814 drug Substances 0.000 description 2
- 229940079593 drug Drugs 0.000 description 2
- 238000005188 flotation Methods 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000004575 stone Substances 0.000 description 2
- 238000002604 ultrasonography Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical class [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000007605 air drying Methods 0.000 description 1
- 238000003556 assay Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 150000005323 carbonate salts Chemical class 0.000 description 1
- 239000000084 colloidal system Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 229910001448 ferrous ion Inorganic materials 0.000 description 1
- 239000011790 ferrous sulphate Substances 0.000 description 1
- 235000003891 ferrous sulphate Nutrition 0.000 description 1
- 238000005189 flocculation Methods 0.000 description 1
- 230000016615 flocculation Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- MGZTXXNFBIUONY-UHFFFAOYSA-N hydrogen peroxide;iron(2+);sulfuric acid Chemical compound [Fe+2].OO.OS(O)(=O)=O MGZTXXNFBIUONY-UHFFFAOYSA-N 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 235000010446 mineral oil Nutrition 0.000 description 1
- 239000002480 mineral oil Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 229910052604 silicate mineral Inorganic materials 0.000 description 1
- FVAUCKIRQBBSSJ-UHFFFAOYSA-M sodium iodide Chemical class [Na+].[I-] FVAUCKIRQBBSSJ-UHFFFAOYSA-M 0.000 description 1
- 239000004016 soil organic matter Substances 0.000 description 1
- 239000003802 soil pollutant Substances 0.000 description 1
- 238000003900 soil pollution Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 238000009210 therapy by ultrasound Methods 0.000 description 1
- 238000003828 vacuum filtration Methods 0.000 description 1
- 239000011592 zinc chloride Substances 0.000 description 1
- 235000005074 zinc chloride Nutrition 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/34—Purifying; Cleaning
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3563—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing solids; Preparation of samples therefor
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/62—Plastics recycling; Rubber recycling
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- General Physics & Mathematics (AREA)
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- Spectroscopy & Molecular Physics (AREA)
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Abstract
The invention relates to a method for extracting, separating and purifying micro-plastics in soil, belonging to the technical field of soil chemical analysis. The method is based on soil texture: classifying the analyzed soil samples according to the difference of sandy soil, loam and clay, and adopting different extraction and separation methods for different soil type samples; to promote the dissolution of some mineral compositions in the soil, reduce the coagulation of soil particles, add hydrochloric acid in the saturated zinc chloride suspension; the soil suspension is subjected to ultrasonic and oscillation to break the granular structure of the soil and promote the separation of the micro-plastic and the impurity components. And (3) standing and layering the suspension, separating, and removing the organic matter interference of the soil by performing Fenton reaction on the sample.
Description
Technical Field
The invention relates to a method for extracting, separating and purifying micro-plastics in soil, belonging to the technical field of soil chemical analysis.
Background
The soil is a vital natural resource for guaranteeing the sustainable development of agriculture in China, and is an important object for protecting ecology and environment. However, with the rapid development of industrialization in China, the problems of soil pollution and soil quality reduction become more severe. Among a plurality of soil pollutants, micro plastic with the diameter less than 5mm becomes a novel pollutant, and the pollution problem caused by the micro plastic is more and more concerned. The micro-plastics in the soil mainly enter through the ways of using a large amount of agricultural films, recycling the waste containing plastics and the like, and are continuously accumulated in the soil, so that the soil property, the soil function and the soil biological diversity are influenced. Therefore, the method has great significance for strengthening the treatment and research of the micro-plastic pollution in the soil.
The first problem of studying and treating soil micro-plastic pollution is to extract and separate micro-plastic from a complex soil matrix, however, the sources of the micro-plastic in the soil are wide, the residual quantity is large, and the commercialized micro-plastic may have a certain difference with the soil environment micro-plastic, so that it is difficult to separate and identify a sufficient amount of micro-plastic from the actual soil for the evaluation of the ecological environment effect. Although the current reports about the micro-plastic pollution in soil exist, the adopted soil micro-plastic extraction and separation methods are not uniform and are different; in the literature of "separation of micro-plastics in coastal tidal flat soil and surface microscopic characteristics", for example, in the summary of the previous research, a quantitative soil sample is weighed, firstly, a saturated sodium chloride solution is used for flotation to obtain a primary separation sample, then, a saturated sodium iodide solution is used for flotation separation, a vacuum filtration device is used for filtering, salinity is cleaned, and the micro-plastics are placed into a glass culture dish, dried in the air and measured.
Soils are classified according to the proportion of soil texture and grain composition and are generally classified into the following three categories:
(1) sand and soil: the single sand grains can be seen or felt, and are held in the hands when being dry, and then are scattered after being slightly loosened; when wet, the mixture can be kneaded into a mass, but can be dispersed after being collided; the content of clay particles is less than 15 percent.
(2) Loam: when the dry product is dry, the product is held into a ball by hand and cannot be scattered when being carefully held by hand; when the paste is moistened, the paste is held by hands to be conglomerated and is generally not scattered by touch; the content of clay particles is 15-25%.
(3) Clay: the dry soil is hard clod, has adhesiveness when being moistened and is extremely plastic, and can be scooped and twisted into a long plastic soil strip by hands; the content of clay particles is more than 25 percent.
Research shows that when the existing soil micro-plastic extraction and separation method is used for extracting micro-plastics in soil with different textures, the micro-plastic extraction efficiency and recovery rate are found to be unstable, the sandy soil sample extraction efficiency is high, the clay and loam efficiency is low, and the extraction is insufficient.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide a method for extracting, separating and purifying micro-plastics in soil. The method classifies the analyzed soil samples according to the difference of soil textures (sandy soil, loam and clay), and different soil type samples adopt different extraction and separation methods; to promote the dissolution of some mineral compositions in the soil and reduce the coagulation of soil particles, hydrochloric acid is added into the saturated zinc chloride suspension; the soil suspension is subjected to ultrasonic and oscillation to break the granular structure of the soil and promote the separation of the micro-plastic and the impurity components. And (3) standing and layering the suspension, separating, and removing the organic matter interference of the soil by performing Fenton reaction on the sample.
In order to achieve the purpose of the invention, the following technical scheme is provided.
A method for extracting, separating and purifying micro-plastics in soil comprises the following steps:
step one, soil sample pretreatment
Classifying soil samples according to the texture, and dividing the soil samples into sandy soil, loam and clay; removing large particle impurities such as crushed stone, plant rhizome and the like in the sample, and then sieving the sample to obtain a pretreated soil sample, wherein the sieve pore diameter is 5.0mm so as to remove impurities such as plastics with particles larger than 5 mm.
Step two, extracting and separating soil micro-plastic
(1) Dissolving the pretreated soil sample in saturated zinc chloride (ZnCl)2) To the aqueous solution, a soil suspension was prepared, and hydrochloric acid was added while stirring.
Wherein the mass fraction of the hydrochloric acid is 36-38%.
H in the hydrochloric acid+With CO in the pretreated soil sample3 2-The molar ratio of (A) is greater than or equal to 3: 1; the CO3 2-Derived from carbonate in the pretreated soil sample.
(2) Ultrasonic and shaking are carried out to be mixed evenly, standing and layering are carried out, and supernatant after layering is filtered; repeating the step for more than 3 times to obtain a sample from which the soil micro-plastics are extracted.
The ultrasonic power is 600W, the frequency is 40KHz, wherein the ultrasonic time of sandy soil is 3-6 min, the ultrasonic time of clay is 10-15 min, and the ultrasonic time of loam is 20-30 min.
When the standing and layering are preferred, the standing and layering time of the sandy soil is more than 2.0 hours; the clay standing and layering time is more than 12.0 h; the standing and layering time of the loam is more than 12.0 h.
Step three, purifying the micro-plastic
Adding FeSO into the sample from which the soil micro-plastic is extracted4Solution and 27.5-50% of H by mass fraction2O2Solution of H2O2With Fe2+The molar ratio of the organic matter to the organic matter is more than or equal to 10:1, and the organic matter in the sample is removed after the reaction is carried out for more than 2 hours at the temperature of 40-80 ℃; filtering, repeatedly washing the filtering device with water for more than three times, and filtering the washing liquid together to enable all the target objects to be gathered on the filter membrane; and taking down the filter membrane and drying to obtain a purified micro-plastic sample on the filter membrane for subsequent identification and quantitative analysis of the micro-plastic.
Wherein, H in the hydrogen peroxide solution2O2The mass ratio of the organic matter to the organic matter is 5-10: 1.
The water is water with the purity of deionized water above.
Advantageous effects
1. The invention provides a method for extracting, separating and purifying micro-plastics in soil, and researches show that the soil is divided into three different soil types, namely sandy soil, clay and loam according to the texture, so that the physical and chemical properties of the three soil types are greatly different; the sand has high content of sand grains, small content of clay grains and low content of organic matters; the clay is opposite to sandy soil, contains less sand grains, is formed by weathering of silicate minerals, is sticky and heavy in texture, is slow in decomposition of organic matters and is rich in humic substances; the soil in the loam has moderate content of sticky grains and sand grains in soil particle composition, the particle size is 0.2-0.02 mm, and the soil aggregate structure is most abundant; therefore, the single micro-plastic extraction and separation method in the prior art is not suitable for all soil types with different textures; according to the method, firstly, soil samples are pretreated and divided into three types of sandy soil, clay and loam, and the soil samples are respectively and pertinently treated in subsequent treatment according to the characteristics of the three types of soil.
2. The invention provides a method for extracting, separating and purifying micro-plastics in soil, and researches show that the particle size of carbonate particles contained in the soil is small and the particles have strong adsorbability; for example, in northern calcareous soil, calcium carbonate is contained in a large amount, and the calcium carbonate has the effect of agglomerating soil particles; if the substances in the soil are not removed, the soil suspension is not stable and is often in a flocculation state, the coated micro plastic is difficult to separate from the soil suspension, and the aperture of the filter membrane is easy to block, so that the difficulty of filtration is increased; therefore, in the method, the influence of carbonate particles is removed and the separation efficiency is improved by dropwise adding hydrochloric acid into the saturated zinc chloride suspension.
3. The invention provides a method for extracting, separating and purifying soil micro-plastics, which is found by research that the establishment of the method for extracting and separating the soil micro-plastics in the prior art ignores the influence of the existence of soil aggregates and inorganic colloid on the soil micro-plastics; soil aggregates are the basic units of the soil structure, and granular structures are the basic structures thereof; in the process of forming the soil aggregate structure, soil particles are easily combined with small-particle-size micro plastics, organic matters and the like to form a part of the aggregate structure; the separation method in the prior art can not fully separate the micro-plastic wrapped in the soil granules, and the obtained result can not reflect the real pollution condition of the soil micro-plastic; therefore, breaking the soil aggregate, namely fully breaking the granular structure of the soil is a prerequisite for fully extracting the soil micro-plastic; in the method, the granular structure of the soil is fully broken through ultrasound and oscillation, so that the coated micro plastic is separated, and the dissociation of impurities such as mineral salt and the like adsorbed on the surface of the micro plastic is promoted;
furthermore, because the content of the clay particles in the sand is low, the content of the sand particles is high, and the soil particles with aggregate structures in the sand are low; however, the clay has the property opposite to that of sandy soil, and the clay contains more clay particles; therefore, during extraction and separation, the ultrasonic oscillation time of the sandy soil sample is short, and the time for standing and layering treatment is short; the clay treatment needs relatively longer ultrasonic oscillation and standing layering time compared with sandy soil; different treatment methods are adopted for soil samples with different textures, so that the time is saved, the working efficiency is improved, the reagent is saved, and the resource waste is reduced.
4. The invention provides a method for extracting, separating and purifying micro-plastics in soil, which finds that the soil contains rich organic matters, the organic matters are easy to wrap with the micro-plastics, and the density of some organic matters is similar to that of the micro-plastics, so that a sample subjected to primary separation not only contains a micro-plastic target object to be detected, but also contains a large amount of soil organic matters, a small amount of clay minerals, mineral oil and other impurities, and the impurities not only influence the separation of the micro-plastics, but also influence the identification and quantitative analysis of the micro-plastics; therefore, in the method of the present invention, a Fenton's reagent is added to the sample from which the soil micro-plastics are extracted, and the organic matter is dissolved in hydrogen peroxide (H)2O2) Ferrous ion (Fe)2+) The mixed solution is quickly oxidized; through the purification treatment, a large amount of soil organic matters, clay minerals and other impurities adsorbed on the micro-plastic are removed, so that the micro-plastic is further purified, and a foundation is laid for accurate identification and quantitative analysis of the micro-plastic;
furthermore, the content of organic matters in the sandy soil is low; however, the clay is opposite to sandy soil in nature and contains abundant organic matters; therefore, in the purification treatment, the sandy soil needs less Fenton reagent, and the clay needs relatively more Fenton reagent; different treatment methods are adopted for soil samples with different textures, so that the time is saved, the working efficiency is improved, the reagent is saved, and the resource waste is reduced.
Detailed Description
The invention will be described in more detail with reference to specific examples, which should not be construed as limiting the scope of the invention.
In the following examples:
the main instruments and reagents used were as follows:
(1) reagent
Zinc chloride (ZnCl)2): analytically pure, Yongda chemical from TianjinReagent, Inc.;
hydrochloric acid: 36-38% of mass fraction, high-grade purity, purchased from chemical reagents of national drug group, ltd;
hydrogen peroxide (H)2O2): 30 percent of mass percent, analytically pure, purchased from Tianjin chemical reagent, Inc.;
ferrous sulfate (FeSO)4): analytically pure, purchased from chemical reagents of national drug group, ltd.
(2) Laboratory apparatus
HYPERION 2000 microscopic Fourier transform infrared spectrometer, manufacturer: bruker, germany;
OLYM-PUS SZ61 style microscope, manufacturer: olympus Corporation, japan;
FA2204 electronic balance, manufacturer: shanghaineqi instruments science and technology Co., Ltd., China;
DH-101 electric heat forced air drying cabinet, the producer: zhong experimental electric furnace ltd, tianjin, china;
KQ-600DV desktop digital control ultrasonic cleaner, manufacturer: kunshan ultrasonic instruments, Inc.;
DB-2EFS graphite electric hot plate, manufacturer: shanghai Bangxi Instrument science and technology, Inc., China.
Determination of carbonate in pretreated soil samples:
see LY/T1251-1999 forest soil water-soluble salinity analysis.
And (3) measuring organic matters in the pretreated soil sample:
see NY/T85-1988 soil organic matter assay.
The method for identifying and quantitatively analyzing the micro-plastics comprises the following steps:
the purified microplastic samples prepared in the examples were observed using a microscope of the body type, and the shape, color, size and number were recorded, followed by measuring at a wave number of 4000cm-1～400cm-1Scanning times of 32 times and resolution of 4cm-1Under the condition of (1), further identifying and analyzing the sample on the filter membrane by using a microscopic infrared spectrometer, analyzing the micro-plastics, and determining the number of the micro-plastics.
Quantitative calculation of the abundance of micro-plastics (MPs) in soil: according to the formula: and calculating the content of the micro-plastics in the soil, wherein A is the abundance of the micro-plastics in the soil, N is the number of the micro-plastics, and M is the soil sample after pretreatment.
Example 1
Step one, soil sample pretreatment
Classifying soil samples according to the texture, and dividing the soil samples into sandy soil, loam and clay; removing large particle impurities such as crushed stone, plant rhizome and the like in the sample, and then sieving the sample to obtain a pretreated soil sample, wherein the sieve pore diameter is 5.0mm so as to remove impurities such as plastics with particles larger than 5 mm.
The carbonate and the organic matter in the pretreated soil sample are measured, and the results are as follows:
carbonate salt:
the carbonate content in the sandy soil is 0.065g/100g, so that CO is contained therein3 2-0.004g/100 g;
carbonate in the loam is 0.131g/100g, and therefore CO is contained therein3 2-0.008g/100 g;
the carbonate in the clay is 0.128g/100g, so that the CO content therein3 2-It was 0.0078g/100 g.
Organic matter:
the sand soil of 100g contains 0.50g of organic matter,
100g of loam contains 2.82g of organic matter,
100g of clay contains 3.63g of organic matter.
Step two, extracting and separating soil micro-plastic
(1) 50.0g of the pretreated soil sample was placed in a 500mL beaker and saturated ZnCl was added2200mL of the aqueous solution was dissolved to prepare a soil suspension, and hydrochloric acid was added thereto with stirring in an amount shown in Table 1.
(2) Ultrasonically treating, shaking for 2min, standing for layering, and filtering the layered supernatant; repeating the step for 3 times to obtain a sample from which the soil micro-plastics are extracted.
The ultrasonic power is 600W, the frequency is 40KHz, wherein the ultrasonic time of sandy soil is 3min, the ultrasonic time of clay is 10min, and the ultrasonic time of loam is 20 min.
Standing and layering time, wherein the standing and layering time of the sandy soil is 2.0 h; the standing and layering time of the clay is 12.0h, and the standing and layering time of the loam is 12.0 h.
Step three, purifying the micro-plastic
To the sample from which the soil micro-plastic was extracted:
sand and soil: adding 2mol/L FeSO44mL of solution and 30 percent of H by mass fraction2O2Solution 10mL, H2O2With Fe2+Is equal to 10:1, H in hydrogen peroxide solution2O2The mass ratio of the organic matter to the organic matter is 10: 1;
clay: adding 2mol/L FeSO426mL of solution and 30 percent of H by mass fraction2O2Solution 60mL, H2O2With Fe2 +Is equal to 10:1, H in hydrogen peroxide solution2O2The mass ratio of the organic matter to the organic matter is 10: 1;
loam: adding 2mol/L FeSO416mL of solution and 30 percent of H by mass fraction2O2Solution 40mL, H2O2With Fe2 +Is equal to 10:1, H in hydrogen peroxide solution2O2The mass ratio of the organic matter to the organic matter is 10: 1.
Reacting for 2 hours at the temperature of 60 ℃ to remove organic matters in the sample; filtering, namely repeatedly washing the filtering device by deionized water for three times and filtering the washing liquid together to ensure that the target object is completely gathered on the filter membrane; taking down the filter membrane by using toothless stainless steel tweezers, putting the filter membrane into a culture dish, drying the filter membrane to obtain a purified micro-plastic sample, carrying out micro-plastic identification and quantitative analysis on the micro-plastic sample, and calculating the abundance of the micro-plastics (MPs) in the soil, wherein the results are shown in table 1.
TABLE 1 amount of hydrochloric acid added to soil suspensions of different textures and results
Example 2
Step one, soil sample pretreatment
Same as example 1 step one.
Step two, extracting and separating soil micro-plastic
(1) 50.0g of the pretreated soil sample was placed in a 500mL beaker and saturated ZnCl was added2Dissolving 200mL of the aqueous solution to prepare a soil suspension solution, and adding hydrochloric acid while stirring, wherein the addition amount of the hydrochloric acid is as follows:
adding 0.5mL of sand sample, 1.0mL of loam sample and 1.0mL of clay sample.
Otherwise, the same procedure as in the second step (1) of example 1 was repeated.
(2) Ultrasonically treating, shaking for 2min, standing for layering, and filtering the layered supernatant; repeating the step for 3 times to obtain a sample from which the soil micro-plastics are extracted.
The ultrasonic power is 600W, the frequency is 40KHz, wherein the ultrasonic time of sandy soil, clay and loam is shown in Table 2.
Standing and layering time, wherein the standing and layering time of the sandy soil is 2.0 h; the standing and layering time of the clay is 12.0h, and the standing and layering time of the loam is 12.0 h.
Step three, purifying the micro-plastic
The same procedure as in step three of example 1, the results are shown in Table 2.
TABLE 2 soil suspensions of different textures ultrasound time and results
Example 3
Step one, soil sample pretreatment
Same as example 1 step one.
Step two, extracting and separating soil micro-plastic
(1) The same as the second step (1) of the example 2;
(2) the same as in step two (1) of example 1.
Step three, purifying the micro-plastic
To the sample from which the soil micro-plastic was extracted:
sand and soil: adding 2mol/L FeSO42mL of solution and 30 percent of H by mass fraction2O2Solution 5mL (as shown in Table 3), H2O2With Fe2+In a molar ratio of 10:1, H in the hydrogen peroxide solution2O2The mass ratio of the organic matter to the organic matter is 5: 1;
adding 2mol/L FeSO43mL of solution and 30 percent of H by mass fraction2O2Solution 10mL (as shown in Table 3), H2O2With Fe2+In a molar ratio of 15:1, H in the hydrogen peroxide solution2O2The mass ratio of the organic matter to the organic matter is 10: 1;
clay: adding 2mol/L FeSO413mL of solution and 30 percent of H by mass fraction2O2Solution 30mL (as shown in Table 3), H2O2With Fe2+In a molar ratio of 10:1, H in the hydrogen peroxide solution2O2The mass ratio of the organic matter to the organic matter is 5: 1;
adding 2mol/L FeSO418mL of solution and 30 percent of H by mass fraction2O2Solution 60mL (as shown in Table 3), H2O2With Fe2+In a molar ratio of 15:1, H in the hydrogen peroxide solution2O2The mass ratio of the organic matter to the organic matter is 10: 1;
loam: adding 2mol/L FeSO48mL of solution and 30 percent of H by mass fraction2O2Solution 20mL (as shown in Table 3), H2O2With Fe2+In a molar ratio of 10:1, H in the hydrogen peroxide solution2O2The mass ratio of the organic matter to the organic matter is 5: 1;
adding 2mol/L FeSO412mL of solution and 30 percent of H by mass fraction2O2Solutions of40mL (as shown in Table 3), H2O2With Fe2+In a molar ratio of 15:1, H in the hydrogen peroxide solution2O2The mass ratio of the organic matter to the organic matter is 10: 1.
The rest steps are the same as the third step of the example 1, and the results are shown in the table 3.
TABLE 3 soil suspension oxidation purification effect of different textures
Through the above examples, those skilled in the art can see that, compared with the existing soil micro-plastic extraction method, the method of the present invention proposes: (1) the extraction of the soil micro-plastics is based on different soil textures, and different treatment methods are selected, so that the time is saved, the working efficiency is improved, the reagent is saved, and the resource waste is reduced. (2) Adding acid into the suspension and carrying out ultrasonic treatment on the soil mixed solution, so that flocculent precipitate and soil aggregate structures caused by carbonate in the soil are broken, and the micro plastic wrapped by the flocculent precipitate and the soil aggregate structures is released, so that the micro plastic is more completely extracted; (3) the micro-plastic sample subjected to primary separation is purified, so that the influence of organic matters and clay mineral particles is eliminated, and the efficiency and the accuracy of micro-plastic identification are improved.
Claims (7)
1. A method for extracting, separating and purifying micro-plastics in soil is characterized by comprising the following steps: the method comprises the following steps:
step one, soil sample pretreatment
Classifying soil samples according to the texture, and dividing the soil samples into sandy soil, loam and clay; removing large particle impurities, and then sieving the large particle impurities to obtain a pretreated soil sample, wherein the aperture of a sieve is 5.0 mm;
step two, extracting and separating soil micro-plastic
(1) Dissolving the pretreated soil sample in a saturated zinc chloride aqueous solution to prepare a soil suspension solution, and adding hydrochloric acid while stirring;
h in hydrochloric acid+With the pretreated soilCO in the sample3 2-The molar ratio of (A) is greater than or equal to 3: 1;
(2) ultrasonic and shaking are carried out to be mixed evenly, standing and layering are carried out, and supernatant after layering is filtered; repeating the step for more than 3 times to obtain a sample from which soil micro-plastics are extracted;
the ultrasonic power is 600W, the frequency is 40KHz, the ultrasonic time of sandy soil is 3-6 min, the ultrasonic time of clay is 10-15 min, and the ultrasonic time of loam is 20-30 min;
step three, purifying the micro-plastic
Adding FeSO into the sample from which the soil micro-plastic is extracted4Solution and 27.5-50% of H by mass fraction2O2Solution of H2O2With Fe2+The molar ratio of the reaction solution is more than or equal to 10:1, and the reaction is carried out for more than 2 hours at the temperature of 40-80 ℃; filtering, repeatedly flushing the filtering device with water for more than three times, filtering the flushing liquid together, and collecting the target object on the filter membrane; taking down the filter membrane and drying to obtain a purified micro-plastic sample on the filter membrane for subsequent identification and quantitative analysis of the micro-plastic;
h in hydrogen peroxide solution2O2The mass ratio of the organic matter to the organic matter is 5-10: 1.
2. The method for extracting, separating and purifying the micro-plastics in the soil as claimed in claim 1, wherein the method comprises the following steps: in the second step (1), the mass fraction of the hydrochloric acid is 36-38%.
3. The method for extracting, separating and purifying the micro-plastics in the soil as claimed in claim 1, wherein the method comprises the following steps: in the second step (1), the CO is3 2-Derived from carbonate in the pretreated soil sample.
4. The method for extracting, separating and purifying the micro-plastics in the soil as claimed in claim 1, wherein the method comprises the following steps: in the second step (1), the mass fraction of the hydrochloric acid is 36-38%; the CO is3 2-Derived from carbonate in the pretreated soil sample.
5. The method for extracting, separating and purifying the micro-plastics in the soil as claimed in claim 1, wherein the method comprises the following steps: in the step two (2), when standing and layering, the standing and layering time of the sandy soil is more than 2.0 h; the clay standing and layering time is more than 12.0 h; the standing and layering time of the loam is more than 12.0 h.
6. The method for extracting, separating and purifying the micro-plastics in the soil as claimed in claim 1, wherein the method comprises the following steps: in the second step (1), the mass fraction of the hydrochloric acid is 36-38%; the CO is3 2-Carbonate derived from the pretreated soil sample;
in the step two (2), when standing and layering, the standing and layering time of the sandy soil is more than 2.0 h; the clay standing and layering time is more than 12.0 h; the standing and layering time of the loam is more than 12.0 h.
7. The method for extracting, separating and purifying the micro-plastics in the soil according to any one of claims 1 to 6, wherein the method comprises the following steps: in the third step, the water is water with the purity higher than that of deionized water.
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