CN111398003A - Digestion solution for digesting organic impurities in micro-plastic, preparation method thereof and digestion method based on digestion solution - Google Patents
Digestion solution for digesting organic impurities in micro-plastic, preparation method thereof and digestion method based on digestion solution Download PDFInfo
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Abstract
The invention provides a digestion solution for digesting organic impurities in micro-plastics, a preparation method thereof and a digestion method based on the digestion solution, and relates to the technical field of micro-plastic impurity treatment, wherein the digestion solution comprises potassium persulfate and an alkaline compound, the concentration ratio of the potassium persulfate to the alkaline compound in the digestion solution is 1: 1-3, and the concentration of the potassium persulfate in the digestion solution is 0.1-0.35 mol/L.
Description
Technical Field
The invention relates to the technical field of impurity treatment in micro-plastics, in particular to a digestion solution for digesting organic impurities in micro-plastics, a preparation method thereof and a digestion method based on the digestion solution.
Background
"Microplastic" refers to plastic chips, granules, fibers, films, or the like having a particle size of less than 5 mm. With the development of modern science and technology, plastics are widely used in the global scope, and the distribution of the micro plastics with the particle size below 5mm is in a global trend and brings persistent pollution to marine environment. The micro plastic in the environment migrates to various places including surface water, deep water, sediments and the like through different conveying mechanisms and even in arctic sea ice. Therefore, people pay more and more attention to the research on the harm of the micro-plastic to the marine environment and even the global ecology and the establishment of a convenient, effective, reliable and accurate method for analyzing and identifying the micro-plastic.
The micro plastic sample in the existing environment is generally collected by trawl or filtration, but the micro plastic sample collected by the method is generally mixed with a large amount of organic impurities such as algae, zooplankton and the like. The key of the collected micro plastic sample processing methods lies in how to efficiently remove the organic impurities which interfere with the subsequent qualitative detection of the micro plastic, and the micro plastic sample is not damaged.
Organic impurities in microplastics are typically removed by chemical digestion processes, such as: acid digestion, alkaline digestion or enzyme digestion. Wherein hydrogen peroxide (H)2O2) The method is the simplest, but the time for the crustacean substance which is difficult to digest is longer (more than 24h) if the crustacean substance achieves better digestion effect; fenton's reagent method (Fe)2+And H2O2Composed system) can effectively remove organic impurities in a sample, especially for H2O2The method can effectively remove the carapace of the podomer which is difficult to digest, and simultaneously avoids the defect that the micro-plastics are easy to be damaged in an acid-base method. However, a large amount of gas and heat are often released at the moment of violent reaction of the Fenton reagent, and the operation of the Fenton reagent method cannot be separated from manual work, so that potential experimental danger is caused; especially in the set-up of in-situ automated processing equipment for samples,the device system is easy to have large impact and cannot be effectively applied; on the other hand, the solution generated after the fenton reagent reacts is yellow and rich in a large amount of ferric ions, and certain interference is easily caused in the subsequent design of the micro-plastic qualitative automatic detection method. Therefore, the two conventional methods for digesting organic impurities in the micro plastic have certain defects.
Therefore, it becomes necessary and urgent to research and develop a digestion treatment method for organic impurities in the micro-plastic, which has high digestion rate of organic impurities, no damage to the micro-plastic, short reaction time, mild process, colorless reaction system and no interference to the subsequent qualitative detection of the micro-plastic.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
The first purpose of the invention is to provide a digestion solution for digesting organic impurities in micro-plastics, wherein the digestion solution has a high digestion rate for the organic impurities in the micro-plastics when being used for digesting the organic impurities in the micro-plastics, has no damage to the micro-plastics, is colorless in a reaction system, does not interfere with subsequent micro-plastics qualitative detection, and can effectively alleviate the problem of difficult micro-plastics qualitative detection caused by the fact that a large amount of organic impurities are usually mixed in a micro-plastics sample in the existing environment.
The second purpose of the invention is to provide a preparation method of the digestion solution, which has simple process and easy operation.
The digestion method can effectively remove the organic impurities in the micro-plastic by adopting the digestion solution, has higher digestion rate of the organic impurities, and does not damage the micro-plastic.
The invention provides a digestion solution for digesting organic impurities in micro-plastics, which comprises potassium persulfate and an alkaline compound, wherein:
the concentration ratio of potassium persulfate to alkaline compounds in the digestion solution is 1: 1-3;
the concentration of the potassium persulfate in the digestion solution is 0.1-0.35 mol/L.
Further, the alkaline compound includes sodium hydroxide.
Further, the digestion liquid comprises potassium persulfate and sodium hydroxide, wherein:
the concentration of sodium hydroxide in the digestion solution is 0.1-1.05 mol/L, and the concentration of potassium persulfate in the digestion solution is 0.1-0.35 mol/L;
preferably, the digestion liquid comprises potassium persulfate and sodium hydroxide, wherein:
the concentration of sodium hydroxide in the digestion solution is 0.4 mol/L, and the concentration of potassium persulfate in the digestion solution is 0.2 mol/L.
The invention provides a preparation method of the digestion solution, which comprises the following steps:
mixing a potassium persulfate aqueous solution and an alkaline compound aqueous solution to obtain a digestion solution, wherein the concentration of potassium persulfate in the digestion solution is 0.1-0.35 mol/L, and the concentration ratio of potassium persulfate to the alkaline compound is 1: 1-3;
preferably, the temperature for mixing the potassium persulfate aqueous solution and the alkaline compound aqueous solution is 10-30 ℃, and when the temperature is 0.2 mol/L of potassium persulfate, the temperature is preferably 20 ℃.
Further, the preparation method comprises the following steps:
mixing a potassium persulfate aqueous solution and a sodium hydroxide aqueous solution to obtain a digestion solution, wherein the concentration of potassium persulfate in the digestion solution is 0.2 mol/L, and the concentration of sodium hydroxide in the digestion solution is 0.4 mol/L;
preferably, the temperature for mixing the potassium persulfate aqueous solution and the sodium hydroxide aqueous solution is 10-30 ℃.
The invention provides a digestion method of organic impurities in micro plastic based on the digestion solution, which comprises the following steps:
and (3) placing the micro plastic to be treated in the digestion solution, heating for reaction, digesting and removing organic impurities in the digestion solution to obtain the micro plastic.
Furthermore, the material-liquid ratio of the micro-plastic to be treated to the digestion solution is 0.1-1: 20-100 g/m L, and preferably 0.5: 40g/m L.
Further, the heating reaction is carried out at the temperature of 60-65 ℃ for 1-8 h;
preferably, the temperature of the heating reaction is 65 ℃ and the time is 4 h.
Further, the method also comprises a step of pretreatment before the micro-plastic to be treated is placed in a digestion solution;
preferably, the step of pre-treating is: drying the micro plastic to be treated for 3-4 hours at the temperature of 50-60 ℃;
more preferably, the step of pre-treating is: the micro-plastic to be treated is dried for 3h at 55 ℃.
Further, the digestion method comprises the following steps:
drying the micro plastic to be treated at 50-60 ℃ for 3-4 h, then placing the material to be treated in the digestion solution according to the material-liquid ratio of 0.1-1: 20-100 g/m L, and heating and reacting at 60-65 ℃ for 1-8 h to obtain the micro plastic;
preferably, the digestion method comprises the following steps:
drying the micro plastic to be treated at 55 ℃ for 3h, then putting the material to be treated into the digestion solution according to the material-liquid ratio of 0.5: 40g/m L, heating and reacting at 65 ℃ for 4h, and digesting and removing organic impurities to obtain the micro plastic.
Compared with the prior art, the invention has the beneficial effects that:
the digestion solution for digesting organic impurities in micro-plastics comprises potassium persulfate and an alkaline compound, wherein the concentration ratio of potassium persulfate to the alkaline compound in the digestion solution is 1: 1-3, and the concentration of potassium persulfate in the digestion solution is 0.1-0.35 mol/L. when the digestion solution containing the potassium persulfate and the alkaline compound with specific concentrations is used for digesting the organic impurities in the micro-plastics, in an aqueous solution at the temperature of more than 60 ℃, the potassium persulfate can be decomposed to generate hydrogen ions and oxygen, the potassium persulfate is promoted to be completely decomposed in an alkaline medium of sodium hydroxide to generate strong oxidation free radicals-atomic oxygen, and further the organic impurities in the micro-plastics are oxidized and digested.
The invention provides a preparation method of the digestion solution, the method is to mix a potassium persulfate aqueous solution and an alkaline compound aqueous solution to obtain the digestion solution, the concentration of potassium persulfate in the digestion solution is 0.1-0.35 mol/L, and the concentration ratio of potassium persulfate to the alkaline compound is 1: 1-3.
The invention provides a digestion method of organic impurities in micro plastic based on the digestion solution, which comprises the following steps: and (3) placing the micro plastic to be treated in the digestion solution, heating for reaction, digesting and removing organic impurities in the digestion solution to obtain the micro plastic. The digestion solution can effectively remove organic impurities in the micro-plastic, has higher organic impurity digestion rate, and does not damage the micro-plastic.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a linear analysis chart of digestion rates of digestion solutions of example 5 and comparative examples 1 to 3 provided in Experimental example 1 of the present invention;
FIG. 2 is a linear analysis chart of the digestion rate of chitin digested by the digestion solutions of the experimental groups 1 to 4 in the experimental example 2 of the present invention;
FIG. 3 shows the digestion recovery rates of 8 detected micro-plastic standards according to Experimental example 3 of the present invention;
FIG. 4 is a comparative chart of surface morphology of digested PA, EVA, PBT and PC micro-plastics and their standards provided in Experimental example 3 of the present invention;
FIG. 5 is a comparative chart of surface morphology of digested PE, PP, PS and PVC micro-plastics and their standards provided in Experimental example 3 of the present invention;
FIG. 6 is a Raman spectrum analysis chart of the PA micro-plastic standard provided in Experimental example 3 of the present invention;
FIG. 7 is a Raman spectrum analysis chart of the digested PA micro plastic provided in the experimental example 3 of the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
According to one aspect of the present invention, a digestion solution for digesting organic impurities in a microplastic, the digestion solution comprising potassium persulfate and an alkaline compound, wherein:
the concentration ratio of potassium persulfate to alkaline compounds in the digestion solution is 1: 1-3;
the concentration of the potassium persulfate in the digestion solution is 0.1-0.35 mol/L.
Note that the concentration units of the potassium persulfate and the alkaline compound in the digestion liquid are both mol/L.
The digestion solution for digesting organic impurities in micro-plastics comprises potassium persulfate and an alkaline compound, wherein the concentration ratio of potassium persulfate to the alkaline compound in the digestion solution is 1: 1-3, and the concentration of potassium persulfate in the digestion solution is 0.1-0.35 mol/L. the digestion solution containing the potassium persulfate and the alkaline compound with specific concentrations can generate strong oxidation free radicals when used for digesting the organic impurities in the micro-plastics, can decompose the potassium persulfate to generate hydrogen ions and oxygen in an aqueous solution at the temperature of more than 60 ℃, and promote the complete decomposition of the potassium persulfate in an alkaline medium of sodium hydroxide to generate strong oxidation free radicals-atomic oxygen so as to oxidize and digest the organic impurities in the micro-plastics.
Typical but non-limiting preferred embodiments of the above-mentioned concentration of potassium persulfate are 0.1 mol/L, 0.15 mol/L, 0.18 mol/L, 0.2 mol/L, 0.22 mol/L, 0.25 mol/L, 0.28 mol/L and 0.35 mol/L.
In a preferred embodiment of the present invention, the alkaline compound comprises sodium hydroxide.
In a preferred embodiment of the invention, the digestion solution comprises potassium persulfate and sodium hydroxide, wherein the concentration of the sodium hydroxide in the digestion solution is 0.1-1.05 mol/L, and the concentration of the potassium persulfate in the digestion solution is 0.1-0.35 mol/L;
in the above preferred embodiment, the digestion solution comprises potassium persulfate and sodium hydroxide, wherein the concentration of the sodium hydroxide in the digestion solution is 0.4 mol/L, and the concentration of the potassium persulfate in the digestion solution is 0.2 mol/L.
In a preferred embodiment, the concentration of sodium hydroxide in the digestion solution is 0.4 mol/L, the concentration of potassium persulfate in the digestion solution is 0.2 mol/L, the potassium persulfate in the digestion solution is a saturated solution at the selected experimental temperature of 20 ℃, and the concentration of the sodium hydroxide solution is 2 times that of the potassium persulfate, because 1 potassium persulfate molecule is decomposed to generate 2 hydrogen ions in the process of generating atomic oxygen by decomposing the potassium persulfate, and the 2 times concentration of sodium hydroxide can completely neutralize the hydrogen ions generated by decomposing the potassium persulfate, so that the potassium persulfate is completely decomposed.
According to an aspect of the present invention, a method for preparing the digestion solution described above includes the steps of:
mixing a potassium persulfate aqueous solution and an alkaline compound aqueous solution to obtain a digestion solution, wherein the concentration of potassium persulfate in the digestion solution is 0.1-0.35 mol/L, and the concentration ratio of potassium persulfate to the alkaline compound is 1: 1-3;
the preparation method of the digestion solution provided by the invention comprises the step of mixing a potassium persulfate aqueous solution and an alkaline compound aqueous solution to obtain the digestion solution, wherein the concentration of potassium persulfate in the digestion solution is 0.1-0.35 mol/L, and the concentration ratio of potassium persulfate to the alkaline compound is 1: 1-3.
In the preferred embodiment, the temperature of mixing the aqueous potassium persulfate solution and the aqueous alkaline compound solution is 10 to 30 ℃.
In a preferred embodiment, the temperature of the mixture of the potassium persulfate solution and the alkaline compound solution is 10 to 30 ℃, the temperature of the mixture of the potassium persulfate solution and the alkaline compound solution is not more than 60 ℃, and once the temperature exceeds 60 ℃, the potassium persulfate in the solution is easy to generate oxidation reaction, and thus digestion solution cannot be prepared.
Typical but non-limiting preferred embodiments of the temperature at which the potassium persulfate solution and the alkaline compound solution are mixed are as follows: 10 deg.C, 12 deg.C, 15 deg.C, 18 deg.C, 20 deg.C, 22 deg.C, 25 deg.C, 28 deg.C and 30 deg.C.
In a preferred embodiment of the present invention, the preparation method comprises the steps of:
mixing a potassium persulfate aqueous solution and a sodium hydroxide aqueous solution to obtain a digestion solution, wherein the concentration of potassium persulfate in the digestion solution is 0.2 mol/L, and the concentration of sodium hydroxide in the digestion solution is 0.4 mol/L;
preferably, the temperature for mixing the potassium persulfate aqueous solution and the sodium hydroxide aqueous solution is 10-30 ℃, and preferably 20 ℃.
According to one aspect of the invention, the digestion method of organic impurities in the micro plastic based on the digestion solution comprises the following steps:
and (3) placing the micro plastic to be treated in the digestion solution, heating for reaction, digesting and removing organic impurities in the digestion solution to obtain the micro plastic.
The invention provides a digestion method of organic impurities in micro plastic based on the digestion solution, which comprises the following steps: and (3) placing the micro plastic to be treated in the digestion solution, heating for reaction, digesting and removing organic impurities in the digestion solution to obtain the micro plastic. The digestion solution can effectively remove organic impurities in the micro-plastic, has higher organic impurity digestion rate, and does not damage the micro-plastic.
In a preferred embodiment of the invention, the material-liquid ratio of the to-be-treated micro plastic to the digestion solution is 0.1-1: 20-100 g/m L, preferably 0.5: 40g/m L.
In a preferred embodiment, the ratio of the micro-plastic to be treated to the digestion solution is such that organic impurities mixed in the micro-plastic can be removed more completely without generating excessive surplus digestion solution.
In a preferred embodiment of the invention, the temperature of the heating reaction is 60-65 ℃ and the time is 1-8 h;
as a preferable embodiment, the heating reaction temperature is 60-65 ℃ and the time is 1-8 h, compared with the existing hydrogen peroxide method and Fenton reagent digestion method, the digestion method has the advantages of short reaction time, mild process, high efficiency, colorless reaction system and no interference to the subsequent qualitative detection of the micro-plastic.
Typical but non-limiting preferred embodiments of the above-described heating reaction are: 60 ℃, 61 ℃, 62 ℃, 63 ℃, 64 ℃ and 65 ℃; typical but non-limiting preferred embodiments of the above-described heating reaction are: 1h, 2h, 3h, 4h, 5h, 6h, 7h and 8 h.
In the above preferred embodiment, the temperature of the heating reaction is 65 ℃ and the time is 4 hours.
In a preferred embodiment of the invention, the micro plastic to be treated further comprises a pretreatment step before being placed in a digestion solution;
in the above preferred embodiment, the step of pre-treating is: drying the micro plastic to be treated for 3-4 hours at the temperature of 50-60 ℃;
in a preferred embodiment, the temperature for drying the micro plastic to be treated is 50 to 60 ℃, and the temperature is not too high, so that the micro plastic is prevented from being denatured at high temperature, and the micro plastic is dried to the extent that no moisture is visible to naked eyes.
Preferably, the step of pre-treating is: the micro-plastic to be treated is dried for 3h at 55 ℃.
In a preferred embodiment of the present invention, the digestion method comprises the steps of:
drying the micro plastic to be treated at 50-60 ℃ for 3-4 h, then placing the material to be treated in the digestion solution according to the material-liquid ratio of 0.1-1: 20-100 g/m L, and heating and reacting at 60-65 ℃ for 1-8 h to obtain the micro plastic;
preferably, the digestion method comprises the following steps:
drying the micro plastic to be treated at 55 ℃ for 3h, then putting the material to be treated into the digestion solution according to the material-liquid ratio of 0.5: 40g/m L, and heating and reacting at 65 ℃ for 4h to obtain the micro plastic.
The technical solution of the present invention will be further described with reference to examples and comparative examples.
Example 1
A digestion solution for digesting organic impurities in micro-plastics is prepared by the following steps:
(a) when preparing the 1L digestion solution, 27g of potassium persulfate is dissolved in 700-800m L deionized water at about 30 ℃, 8g of sodium hydroxide is dissolved in 50-100m L deionized water and cooled to respectively prepare a potassium persulfate solution and a sodium hydroxide solution;
(b) mixing the potassium persulfate solution obtained in the step (a) with a sodium hydroxide solution to obtain a mixed solution, and adjusting the concentration of potassium persulfate in the mixed solution to 0.1 mol/L and the concentration of sodium hydroxide to 0.2 mol/L to obtain a digestion solution;
the mixing temperature of the potassium persulfate solution and the alkaline compound solution in the step (b) is 10-30 ℃.
Example 2
A digestion solution for digesting organic impurities in micro-plastics is prepared by the following steps:
(a) when preparing the 1L digestion solution, 94.5g of potassium persulfate is dissolved in 700-800m L deionized water at about 30 ℃, 14g of sodium hydroxide is dissolved in 50-100m L deionized water and cooled to respectively prepare a potassium persulfate solution and a sodium hydroxide solution;
(b) mixing the potassium persulfate solution obtained in the step (a) with a sodium hydroxide solution to obtain a mixed solution, and adjusting the concentration of potassium persulfate in the mixed solution to 0.35 mol/L and the concentration of sodium hydroxide to 0.35 mol/L to obtain a digestion solution;
the mixing temperature of the potassium persulfate solution and the alkaline compound solution in the step (b) is 10-30 ℃.
Example 3
A digestion solution for digesting organic impurities in micro-plastics is prepared by the following steps:
(a) when preparing the 1L digestion solution, 40.5g of potassium persulfate is dissolved in 700-800m L deionized water at about 30 ℃, 10g of sodium hydroxide is dissolved in 50-100m L deionized water and cooled to respectively prepare a potassium persulfate solution and a sodium hydroxide solution;
(b) mixing the potassium persulfate solution obtained in the step (a) with a sodium hydroxide solution to obtain a mixed solution, and adjusting the concentration of potassium persulfate in the mixed solution to 0.15 mol/L and the concentration of sodium hydroxide to 0.25 mol/L to obtain a digestion solution;
the mixing temperature of the potassium persulfate solution and the alkaline compound solution in the step (b) is 10-30 ℃.
Example 4
A digestion solution for digesting organic impurities in micro-plastics is prepared by the following steps:
(a) when preparing the 1L digestion solution, dissolving 72.9g of potassium persulfate in 700-800m L deionized water at about 30 ℃, dissolving 9.6g of sodium hydroxide in 50-100m L deionized water, and cooling to respectively prepare a potassium persulfate solution and a sodium hydroxide solution;
(b) mixing the potassium persulfate solution obtained in the step (a) with a sodium hydroxide solution to obtain a mixed solution, and adjusting the concentration of potassium persulfate in the mixed solution to 0.27 mol/L and the concentration of sodium hydroxide to 0.24 mol/L to obtain a digestion solution;
the mixing temperature of the potassium persulfate solution and the alkaline compound solution in the step (b) is 10-30 ℃.
Example 5
A digestion solution for digesting organic impurities in micro-plastics is prepared by the following steps:
(a) when preparing the 1L digestion solution, dissolving 53g of potassium persulfate in 700-800m L deionized water at about 30 ℃, dissolving 16g of sodium hydroxide in 50-100m L deionized water, and cooling to respectively prepare a potassium persulfate solution and a sodium hydroxide solution;
(b) mixing the potassium persulfate solution obtained in the step (a) with a sodium hydroxide solution to obtain a mixed solution, and adjusting the concentration of potassium persulfate in the mixed solution to 0.2 mol/L and the concentration of sodium hydroxide to 0.4 mol/L to obtain a digestion solution;
the mixing temperature of the potassium persulfate solution and the alkaline compound solution in the step (b) is 10-30 ℃.
Example 6
A method for digesting organic impurities in a micro plastic, the method comprising the steps of:
(A) providing to-be-treated micro plastic containing organic impurities, and drying the to-be-treated micro plastic at 50 ℃ for 3 hours to obtain to-be-treated material;
(B) and (2) putting the material to be treated obtained in the step (A) into the digestion solution described in the example 1 according to the material-liquid ratio of 0.1: 20g/m L, and heating and reacting for 1h at 60 ℃ to obtain the micro plastic.
Example 7
A method for digesting organic impurities in a micro plastic, the method comprising the steps of:
(A) providing to-be-treated micro plastic containing organic impurities, and drying the to-be-treated micro plastic at 60 ℃ for 4 hours to obtain to-be-treated material;
(B) and (3) putting the material to be treated obtained in the step (A) into the digestion solution described in the example 2 according to the material-liquid ratio of 1: 100g/m L, and heating and reacting for 8 hours at 65 ℃ to obtain the micro plastic.
Example 8
A method for digesting organic impurities in a micro plastic, the method comprising the steps of:
(A) providing to-be-treated micro plastic containing organic impurities, and drying the to-be-treated micro plastic at 52 ℃ for 3.2h to obtain to-be-treated material;
(B) and (2) putting the material to be treated obtained in the step (A) into the digestion solution described in the example 3 according to the material-liquid ratio of 0.2: 30g/m L, and heating and reacting for 3 hours at 62 ℃ to obtain the micro plastic.
Example 9
A method for digesting organic impurities in a micro plastic, the method comprising the steps of:
(A) providing to-be-treated micro plastic containing organic impurities, and drying the to-be-treated micro plastic at 58 ℃ for 3.5 hours to obtain to-be-treated material;
(B) and (B) putting the material to be treated obtained in the step (A) into the digestion solution described in the example 4 according to the material-liquid ratio of 0.8: 60g/m L, and heating and reacting for 7 hours at 64 ℃ to obtain the micro plastic.
Example 10
A method for digesting organic impurities in a micro plastic, the method comprising the steps of:
(A) providing to-be-treated micro plastic containing organic impurities, and drying the to-be-treated micro plastic at 55 ℃ for 3 hours to obtain to-be-treated material;
(B) and (2) putting the material to be treated obtained in the step (A) into the digestion solution described in the example 5 according to the material-liquid ratio of 0.5: 40g/m L, and heating and reacting for 4 hours at 65 ℃ to obtain the micro plastic.
Comparative example 1
Adopting a 10% potassium hydroxide method to digest organic impurities in the micro-plastic, wherein the method comprises the following steps:
after drying the micro plastic sample, adding the micro plastic sample into a beaker, adding 40m of L10% potassium hydroxide solution into the beaker, heating the mixture to 60 ℃ and standing the mixture overnight, wherein the material-liquid ratio is 0.5: 40g/m L.
Comparative example 2
The method for digesting the organic impurities in the micro plastic by adopting a hydrogen peroxide method comprises the following steps:
the micro plastic sample is dried and then added into a beaker, 40m of L30 percent hydrogen peroxide solution is added into the beaker, the material-liquid ratio is 0.5: 40g/m L, and the mixture is heated to 60 ℃ and placed overnight.
Comparative example 3
The method for digesting the organic impurities in the micro-plastic by using a Fenton reagent method comprises the following steps:
drying a micro plastic sample, adding the micro plastic sample into a beaker, adding 20m of a ferrous solution with the L concentration of 0.05 mol/L into the beaker, adding 20m of a hydrogen peroxide solution with the L30% of the hydrogen peroxide solution with the material-liquid ratio of 0.5: 40g/m L, standing at normal temperature for 5min, covering the opening of the beaker by using a watch glass, heating the mixture to 60 ℃ in a fume hood, taking down the beaker when bubbles are generated, preventing the reaction from stopping, adding a proper amount of deionized water if the reaction is too violent, slowing down the reaction rate, and continuing heating the mixture for 30min after the reaction is finished to ensure complete digestion.
Experimental example 1
In order to show that the digestion solution and the digestion method have higher digestion rate on organic impurities in the micro-plastic, the digestion solution prepared in the embodiment 5 and the comparative examples 1-3 is specially used for carrying out the digestion experiment on the chitin.
The experimental method comprises weighing 0.1g pure chitin product respectively, placing into 100m L beaker, adding 40m L digestion solution prepared in example 5 respectively, heating at 65 deg.C for 4h, and calculating digestion rate;
meanwhile, as a control, the digestion method of comparative examples 1-3 is adopted to carry out digestion treatment on 0.1g of pure chitin, and the digestion rate is calculated.
The experiment example does not adopt the optimized material-liquid ratio of 0.5: 40g/m L because the material-liquid ratio is set for a micro plastic sample containing organic impurities, and 0.5g of organic impurity chitin is not required to be selected.
The specific experimental data are as follows:
in order to more intuitively express the digestion effect of the digestion solution, a linear graph analysis is performed by using the digestion method of the digestion solution of embodiment 5 and the digestion rates of the digestion methods of comparative examples 1 to 3, and specifically refer to fig. 1.
FIG. 1 is a linear analysis chart of digestion rates of digestion solutions of example 5 and comparative examples 1 to 3.
As can be seen from fig. 1, the digestion rate equivalent to that of the fenton reagent can be achieved within 1h by adopting the digestion method of the digestion solution in example 5, and the digestion rate is greatly superior to that of the other two digestion agents; meanwhile, the digestion rate of the digestion method adopting the digestion solution in the embodiment 5 is improved along with the increase of time.
Experimental example 2
In order to show that the digestion solution containing potassium persulfate and sodium hydroxide has a better digestion effect compared with other potassium persulfate and sodium hydroxide solutions with other proportions and concentrations, the digestion solution in the embodiment 5 of the application is taken as a basis, and the following grouping experiment analysis is carried out:
the specific grouping is as follows:
experiment group 4, in the digestion solution of the application example 5, the sodium hydroxide solution is diluted to three-quarters concentration, the potassium persulfate is 0.2 mol/L, and the sodium hydroxide is 0.3 mol/L;
the experimental method comprises weighing 0.1g pure chitin product respectively, placing into 100m L beaker, adding 40m L treatment solution prepared by experimental groups 1-4 respectively, heating at 65 deg.C for reaction for 6h, and calculating digestion rate;
the specific experimental results are as follows:
in order to more intuitively express the digestion effect of the digestion solution, the digestion rate result data of the experimental example is subjected to line graph analysis, and specifically refer to fig. 2.
Fig. 2 is a linear analysis chart of the digestion rate of chitin digested by the digestion solutions of experimental groups 1 to 4 in the experimental example.
As can be seen from FIG. 2, the digestion solution prepared by mixing 0.2 mol/L K persulfate saturated at 20 ℃ and 0.4 mol/L NaOH at 20 ℃ by the digestion method of Experimental group 1 (i.e., example 5) can reach the maximum digestion rate of chitin.
Experimental example 3
In order to show that the digestion solution of the present application has no damage to the micro-plastics, the digestion solution prepared in example 5 is specifically taken as an example, and experimental tests are performed on various micro-plastic standard products (PBT, PP, PE, PC, PA, PS, PVC, and EVA), specifically as follows:
experimental method 0.1g of 8 micro-plastic standard substances are respectively weighed and placed in a 100m L beaker, 40m L of digestion solution prepared in example 5 is respectively added, and then the digestion solution is heated and reacted for 4 hours at 65 ℃, and the micro-plastic recovery rate is respectively calculated.
The specific experimental result is shown in fig. 3, and fig. 3 shows the digestion recovery rate of 8 kinds of micro-plastic standard samples detected in this experimental example.
As can be seen from FIG. 3, the sample weight of the 8 kinds of microplastic is not changed basically after being treated with alkaline potassium persulfate, and the loss caused by digestion of a small amount of microplastic may be caused by errors generated in processes such as manual transfer and filtration due to too small particle size of the microplastic itself.
In order to more accurately prove that the digestion solution does not damage the micro-plastics, the method specifically identifies the surface morphology of the 8 micro-plastics after the experiment and respective standard products, and performs raman spectrum contrast analysis and observation on the digested PA micro-plastics and the standard products thereof, and specifically refers to fig. 4 to 7, wherein:
FIG. 4 is a comparative chart of surface morphology of digested PA, EVA, PBT and PC micro-plastics and their standards provided in this experimental example;
FIG. 5 is a comparison chart of surface morphology of digested PE, PP, PS and PVC micro-plastics and their standards provided in this experimental example;
FIG. 6 is a Raman spectrum analysis chart of the PA micro-plastic standard provided in this experimental example;
fig. 7 is a raman spectrum analysis chart of digested PA microplastic provided in this experimental example.
As can be seen from FIGS. 4 to 7, the surface morphology of the 8 types of micro-plastic standard products is not different before and after digestion, and Raman spectrogram analysis shows that the functional groups on the surface of the micro-plastic are not changed, which proves that the digestion solution of the application can not damage the micro-plastic.
Application example
And collecting 1t of seawater sample on the offshore surface layer of the Qingdao by using a filter pump and filter membranes of 500 micrometers and 50 micrometers, and filtering to obtain a micro plastic sample with the particle size of 50-500 micrometers. After drying the sample was digested as in example 5. Photographing respectively before and after digestion to record the form of the sample. After digestion, scanning and identifying are carried out under a micro-Raman spectrometer, and various micro plastic particles or fragments can be observed.
In conclusion, when the digestion solution containing the potassium persulfate and the alkaline compound with the specific concentrations is used for digesting organic impurities in the micro-plastic, the digestion solution has a high digestion rate on the organic impurities in the micro-plastic, does not damage the micro-plastic, is colorless in a reaction system, does not interfere with subsequent micro-plastic qualitative detection, and can effectively solve the problem that the micro-plastic qualitative detection is difficult due to the fact that a large amount of organic impurities are usually mixed in a micro-plastic sample in the existing environment.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A digestion liquid for digesting organic impurities in micro-plastics, which is characterized by comprising potassium persulfate and an alkaline compound, wherein:
the concentration ratio of potassium persulfate to alkaline compounds in the digestion solution is 1: 1-3;
the concentration of the potassium persulfate in the digestion solution is 0.1-0.35 mol/L.
2. A digestion liquid according to claim 1, characterized in that the basic compound comprises sodium hydroxide.
3. A digestion liquid according to claim 1, characterized in that the digestion liquid comprises potassium persulfate and sodium hydroxide, wherein:
the concentration of sodium hydroxide in the digestion solution is 0.1-1.05 mol/L, and the concentration of potassium persulfate in the digestion solution is 0.1-0.35 mol/L;
preferably, the digestion liquid comprises potassium persulfate and sodium hydroxide, wherein:
the concentration of sodium hydroxide in the digestion solution is 0.4 mol/L, and the concentration of potassium persulfate in the digestion solution is 0.2 mol/L.
4. A method for producing a digestion liquid according to any one of claims 1 to 3, characterized by comprising the steps of:
mixing a potassium persulfate aqueous solution and an alkaline compound aqueous solution to obtain a digestion solution, wherein the concentration of potassium persulfate in the digestion solution is 0.1-0.35 mol/L, and the concentration ratio of potassium persulfate to the alkaline compound is 1: 1-3;
preferably, the temperature for mixing the potassium persulfate aqueous solution and the alkaline compound aqueous solution is 10-30 ℃, and when the temperature is 0.2 mol/L of potassium persulfate, the temperature is preferably 20 ℃.
5. The method for preparing a digestion liquid according to claim 4, characterized by comprising the steps of:
mixing a potassium persulfate aqueous solution and a sodium hydroxide aqueous solution to obtain a digestion solution, wherein the concentration of potassium persulfate in the digestion solution is 0.2 mol/L, and the concentration of sodium hydroxide in the digestion solution is 0.4 mol/L;
preferably, the temperature for mixing the potassium persulfate aqueous solution and the sodium hydroxide aqueous solution is 10-30 ℃.
6. A digestion method for organic impurities in micro plastic based on the digestion liquid as claimed in any one of claims 1 to 3, characterized by comprising the following steps:
and (3) placing the micro plastic to be treated in the digestion solution of any one of claims 1-3, heating for reaction, and digesting to remove organic impurities to obtain the micro plastic.
7. The digestion method according to claim 6, wherein the feed-liquid ratio of the micro plastic to be treated to the digestion liquid is 0.1-1: 20-100 g/m L, preferably 0.5: 40g/m L.
8. The digestion method according to claim 6, wherein the temperature of the heating reaction is 60-65 ℃ and the time is 1-8 h;
preferably, the temperature of the heating reaction is 65 ℃ and the time is 4 h.
9. The digestion method according to claim 6, wherein the micro plastic to be treated further comprises a step of pretreatment before being placed in the digestion solution;
preferably, the step of pre-treating is: drying the micro plastic to be treated for 3-4 hours at the temperature of 50-60 ℃;
more preferably, the step of pre-treating is: the micro-plastic to be treated is dried for 3h at 55 ℃.
10. The digestion method according to claim 6, characterized in that it comprises the steps of:
drying the micro plastic to be treated at 50-60 ℃ for 3-4 h, then placing the material to be treated in the digestion solution of any one of claims 1-3 according to the material-to-liquid ratio of 0.1-1: 20-100 g/m L, and heating and reacting at 60-65 ℃ for 1-8 h to obtain the micro plastic;
preferably, the digestion method comprises the following steps:
drying the micro plastic to be treated at 55 ℃ for 3h, then placing the material to be treated in the digestion solution of any one of claims 1 to 3 at a material-to-liquid ratio of 0.5: 40g/m L, heating at 65 ℃ for reaction for 4h, and digesting to remove organic impurities to obtain the micro plastic.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113588608A (en) * | 2021-07-12 | 2021-11-02 | 生态环境部南京环境科学研究所 | Method for evaluating electron loss capability of micro plastic through oxidation rate of trivalent arsenic of micro plastic |
| CN114486476A (en) * | 2021-12-27 | 2022-05-13 | 江苏省疾病预防控制中心(江苏省公共卫生研究院) | Pretreatment method for detecting polyethylene micro-plastic in liquid sample and application thereof |
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2020
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113588608A (en) * | 2021-07-12 | 2021-11-02 | 生态环境部南京环境科学研究所 | Method for evaluating electron loss capability of micro plastic through oxidation rate of trivalent arsenic of micro plastic |
| CN114486476A (en) * | 2021-12-27 | 2022-05-13 | 江苏省疾病预防控制中心(江苏省公共卫生研究院) | Pretreatment method for detecting polyethylene micro-plastic in liquid sample and application thereof |
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Application publication date: 20200710 |