CN113552186A - Electrochemical method for measuring oxidation-reduction characteristics of micro-plastic and application thereof - Google Patents
Electrochemical method for measuring oxidation-reduction characteristics of micro-plastic and application thereof Download PDFInfo
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Abstract
The invention discloses an electrochemical method for measuring the oxidation-reduction characteristics of micro-plastics and application thereof, wherein the electrochemical method comprises the following steps: s1 assembling an electrolytic cell; s2 discharging oxygen; s3 and S4 electrochemical treatment: applying a potential of 0.4V to-0.7V on a working electrode, introducing an electronic intermediate, adding 200 mu L of micro-plastic suspension after the current is stable, obtaining oxidation and reduction peak currents in a timing current curve, and calculating the areas of the oxidation and reduction peak currents by an integration method after the current is stable to respectively obtain the loss and gain electronic capacities of the micro-plastic; s5 verification: and detecting whether the redox active functional group exists on the surface of the micro plastic by cyclic voltammetry. By applying the method to the measurement of the gain-loss electron capacity of the hydrogen peroxide aged phenolic resin micro plastic, the invention characterizes the redox characteristic of the micro plastic, namely the method of the gain-loss electron capacity of the micro plastic, by an electrochemical method, thereby promoting the research of the influence of the micro plastic on the redox conversion of substances in the environment from the redox angle.
Description
Technical Field
The invention relates to the technical field of environmental remediation, in particular to an electrochemical method for measuring the redox characteristics of micro-plastics and application thereof.
Background
With the discharge of a large number of plastic products into the environment during industrial and agricultural production and daily life, researches in recent years find that micro-plastics are widely distributed in marine, fresh water and land ecosystems, and have caused global pollution problems. The micro plastic is extremely small in size, usually nano or micro-nano, but has a relatively large specific surface area, and after entering the environment, the micro plastic adsorbs heavy metal ions and organic pollutants through a series of physical, chemical and biological decomposition effects, so that the pollutants possibly eaten by aquatic organisms are accumulated in animals and plants, and the pollutants adsorbed by the micro plastic are retained in the organisms to generate long-term and continuous toxic action on the aquatic organisms. Affecting the functions and services of the whole ecosystem and finally entering the human body through food chain transmission, thus endangering human health.
The micro plastic changes the particle size of the micro plastic and forms rich functional groups on the surface of the micro plastic through the aging action of oxidants such as photochemical oxidation, ozone, hydrogen peroxide and the like in the environment, thereby changing the physical and chemical properties of the micro plastic. Numerous studies have reported the transformation, adsorption and toxicity effects during the aging of microplastics. Furthermore, recent studies have found that microplastics can also affect the redox conversion process of carbon and nitrogen in the environment, but it has not been recognized that this may be related to the redox properties of microplastics. Therefore, there is an urgent need to establish a method for characterizing the redox characteristics of the micro-plastics, so as to promote research on the influence of the micro-plastics on the redox conversion of substances in the environment from the redox perspective.
The patent CN112023714B discloses a preparation method of a functional carbon fiber membrane capable of adsorbing and degrading micro-plastics, which comprises the steps of mixing an amidoxime-modified polyacrylonitrile fiber membrane (the content of amidoxime groups is 0.5-15 wt%) and metal salt (MnCl) in a mass ratio of 1: 0.01-0.52·4H2O、MnSO4·4H2O、FeCl3·6H2O、Fe(NO3)3·9H2O、CoCl2·6H2O、Co(NO3)2·6H2O、Co(Ac)2·4H2O、NiCl2·6H2O、Ni(NO3)2·6H2O and Ni (Ac)2·4H2More than one of O) is subjected to self-assembly reaction under hydrothermal condition and then calcined to prepare a functionalized carbon fiber membrane consisting of a PAN-based carbon fiber membrane, carbon nanotubes and metal nanoparticles with graphite layers coated on the surfaces; the membrane is used as a cathode, the BDD electrode is used as an anode, and the micro plastic is degraded by an electro-Fenton oxidation method, so that the high micro plastic degradation rate is realized. However, no further investigation was made on the redox characteristics during electrochemical treatment.
Disclosure of Invention
In order to solve the problems, the invention provides an electrochemical method for measuring the oxidation-reduction characteristics of the micro plastic and application thereof.
The technical scheme of the invention is as follows:
an electrochemical method for determining the redox properties of a micro-plastic, comprising the steps of:
s1 cell assembly: sequentially placing a working electrode, a reference electrode and a counter electrode into a closed electrolytic cell, wherein the reference electrode is a saturated Ag/AgCl reference electrode, pouring 25mL of electrolyte into the electrolytic cell, the electrolyte is a mixed solution of 0.1mol of KCl solution and 0.1mol of phosphate, and adjusting the pH value of the electrolyte to be 7;
s2 discharge oxygen: introducing argon into the electrolyte through the air inlet hole for 0.5h, and discharging oxygen in the electrolytic cell through the air outlet hole;
s3 electrochemical oxidation treatment: connecting a working electrode, a reference electrode and a counter electrode of an electrolytic cell with a working electrode, a reference electrode and a counter electrode of an electrochemical workstation respectively, setting by control software of the electrochemical workstation, applying a potential of 0.4V relative to a saturated Ag/AgCl reference electrode on the working electrode, simultaneously adding 1mL of an electron mediator subjected to aeration and deoxygenation into a gas outlet, continuing for 30min, adding 200 muL of a micro plastic suspension subjected to aeration and deoxygenation after the current is stabilized to a baseline current, obtaining an oxidation peak current in a timing current curve immediately, and calculating the area of the oxidation peak current by an integration method after the current is stabilized to the baseline current to obtain the electron loss capacity of the micro plastic;
s4 electrochemical reduction treatment: applying a potential of-0.7V relative to a saturated Ag/AgCl reference electrode on a working electrode, simultaneously adding 1mL of the electron mediator solution subjected to aeration and deoxygenation from a gas outlet, continuing for 30min, adding 200 mu L of the micro plastic suspension subjected to aeration and deoxygenation after the current is stabilized to a baseline current, then obtaining a reduction peak current in a timing current curve, and calculating the area of the reduction peak current through an integration method after the current is stabilized to the baseline current to respectively obtain the electron capacity of the micro plastic;
s5 verification: detecting whether redox active functional groups exist on the surface of the micro plastic through cyclic voltammetry, filtering, freeze-drying the electrochemically treated micro plastic, mixing with conductive carbon black to obtain a mixed suspension, fixing the suspension on a glassy carbon electrode, scanning to obtain a cyclic voltammetry curve, and comparing with a control group.
Further, the working electrode in the step S1 is a carbon felt working electrode with an area of 1 × 1cm, and the counter electrode is a graphite sheet counter electrode, so that the oxidation-reduction reaction can be efficiently completed, and the energy consumption is low.
Further, the amount of argon gas introduced in the step S2 is 0.4-0.6m3The oxygen in the electrolytic cell can be completely removed.
Further, the electron mediator solution in step S3 is 10mmol of ABTS, and the electron mediator solution in step S4 is 10mmol of amphoteric viologen solution ZiV, and the electron response sensitivity is high.
Further, the oxidation current stability value of the electron loss capacity measured in the step S3 is 200-300 muA, the oxidation peak current is 30-80 muA, and the duration is 70 min; the stable value of the reduction current of the electron capacity measured in the step S4 is 15-30 muA, the reduction peak current is 200-500 muA, and the duration is 5 min.
Further, the temperature of the freeze drying in the step S5 is-50 to-80 ℃, so that the impurities are prevented from interfering the test result.
Furthermore, in the step S5, the mass concentration of the micro plastic in the mixed suspension is 4g/L, the mass concentration of the conductive carbon black is 1g/L, and the solute is water, so that the recognition effect on the redox functional group is good.
The application of the electrochemical method for measuring the oxidation-reduction characteristics of the micro plastic is to measure the electron gaining and electron losing capacity of the hydrogen peroxide aged phenolic resin micro plastic by applying the method.
Further, the preparation method of the hydrogen peroxide aged phenolic resin micro plastic comprises the following steps: weighing 3g of phenolic resin micro plastic in a glass bottle, adding 80mL of hydrogen peroxide solution, and reacting for 0, 4, 8, 12, 19, 26 and 42 days respectively to prepare micro plastic suspensions with different hydrogen peroxide aging degrees, wherein the micro plastic suspensions are named as PF-0, PF-4, PF-8, PF-12, PF-19, PF-26 and PF-42 respectively.
Furthermore, the hydrogen peroxide solution has the mass concentration of 5-30%, has good aging effect, and can achieve the effect of simulating long-time aging in nature.
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention characterizes the oxidation-reduction characteristics of the micro plastic by an electrochemical method, namely a method for obtaining electrons and losing electron capacity of the micro plastic, thereby promoting the research of the influence of the micro plastic on the oxidation-reduction conversion of substances in the environment from the oxidation-reduction angle.
(2) The invention has good aging effect by being applied to the measurement of the electron obtaining and electron losing capacity of the hydrogen peroxide aging phenolic resin micro plastic, and can achieve the effect of simulating long-time aging in nature.
(3) The invention verifies that the redox active functional groups exist in the electrochemically treated micro-plastic through cyclic voltammetry, and mainly generates phenolic, semiquinone and quinone redox active functional groups with different chemical structures.
Drawings
FIG. 1 is a schematic diagram of the determination of the electron gain/loss capacity of the microplastic of the present invention;
FIG. 2 is a schematic diagram of the construction of the electrolytic cell apparatus of the present invention;
FIG. 3 is a schematic diagram of the electron gain/loss of the working electrode micro-plastic of the present invention;
FIG. 4 is a scanning electron microscope image of a phenolic resin micro plastic aged with hydrogen peroxide for 0 day (PF-0) in example 6 of the present invention;
FIG. 5 is a scanning electron micrograph of a phenolic resin microplastic of 42 days (PF-42) hydrogen peroxide aged in example 6 of the present invention;
FIG. 6 is a chronoamperometric response curve of a phenolic resin micro-plastic with different hydrogen peroxide aging times at an electrode potential of-0.70V in example 6 of the present invention;
FIG. 7 is a plot of chronoamperometric response of phenolic resin microplastic with different hydrogen peroxide aging times at an electrode potential of 0.40V in example 6 of the present invention;
FIG. 8 shows the electron gaining/losing capacity of the phenolic resin micro plastic with different hydrogen peroxide aging times at the electrode potentials of-0.70V and 0.40V in example 6 of the present invention;
FIG. 9 is a cyclic voltammogram of a phenolic resin micro plastic aged with hydrogen peroxide for 0 days (PF-0), 8 days (PF-8), and 26 days (PF-26) in example 6 of the present invention.
Detailed Description
Example 1
An electrochemical method for determining the redox properties of a micro-plastic, comprising the steps of:
s1 cell assembly: as shown in fig. 2, a working electrode, a reference electrode and a counter electrode are sequentially arranged in a closed electrolytic cell, the working electrode is a carbon felt working electrode with the area of 1 × 1cm, the reference electrode is a saturated Ag/AgCl reference electrode, the counter electrode is a graphite sheet counter electrode, 25mL of electrolyte is poured into the electrolytic cell, the electrolyte is a mixed solution of 0.1mol of KCl solution and 0.1mol of phosphate, and the pH of the electrolyte is adjusted to 7;
s2 discharge oxygen: introducing argon into the electrolyte through the air inlet for 0.5h, wherein the introduction amount of the argon is 0.4m3/h，Oxygen in the electrolytic cell is discharged through the air outlet;
s3 electrochemical oxidation treatment: respectively connecting a working electrode, a reference electrode and a counter electrode of an electrolytic cell with a working electrode, a reference electrode and a counter electrode of an electrochemical workstation, setting by control software of the electrochemical workstation, applying a potential of 0.4V relative to a saturated Ag/AgCl reference electrode on the working electrode, simultaneously adding 10mmol ABTS of an electronic mediator subjected to aeration and deoxygenation from a gas outlet hole for 30min, adding 200 muL of a micro plastic suspension subjected to aeration and deoxygenation after the current is stabilized to a baseline current, obtaining an oxidation peak current in a timing current curve, calculating the area of the oxidation peak current by an integration method after the current is stabilized to the baseline current to obtain the electron loss capacity of the micro plastic, and determining the stable value of the oxidation current of the electron loss capacity to be 200 muA, the oxidation peak current to be 30 muA and the duration to be 70 min;
s4 electrochemical reduction treatment: applying a potential of-0.7V relative to a saturated Ag/AgCl reference electrode on a working electrode, simultaneously adding 1mL of amphoteric viologen solution ZiV of 10mmol of the electronic mediator solution subjected to aeration and deoxygenation from a gas outlet, continuing for 30min, adding 200 mu L of micro plastic suspension subjected to aeration and deoxygenation after the current is stabilized to a baseline current, then obtaining a reduction peak current in a timing current curve, calculating the area of the reduction peak current by an integration method after the current is stabilized to the baseline current to respectively obtain the electron obtaining capacity of the micro plastic, and measuring the reduction current stability value of the electron capacity to be 15 mu A, the reduction peak current to be 200 mu A and continuing for 5 min;
s5 verification: detecting whether redox active functional groups exist on the surface of the micro plastic through cyclic voltammetry, filtering, freeze-drying the micro plastic after electrochemical treatment, mixing the micro plastic with conductive carbon black to obtain a mixed suspension, wherein the freeze-drying temperature is-50 ℃, the mass concentration of the micro plastic in the mixed suspension is 4g/L, the mass concentration of the conductive carbon black is 1g/L, the solute is water, fixing the suspension on a glassy carbon electrode, scanning to obtain a cyclic voltammetry curve, and comparing the cyclic voltammetry curve with a control group.
Example 2
An electrochemical method for determining the redox properties of a micro-plastic, comprising the steps of:
s1 cell assembly: as shown in fig. 2, a working electrode, a reference electrode and a counter electrode are sequentially arranged in a closed electrolytic cell, the working electrode is a carbon felt working electrode with the area of 1 × 1cm, the reference electrode is a saturated Ag/AgCl reference electrode, the counter electrode is a graphite sheet counter electrode, 25mL of electrolyte is poured into the electrolytic cell, the electrolyte is a mixed solution of 0.1mol of KCl solution and 0.1mol of phosphate, and the pH of the electrolyte is adjusted to 7;
s2 discharge oxygen: introducing argon into the electrolyte through the air inlet for 0.5h, wherein the introduction amount of the argon is 0.5m3The oxygen in the electrolytic cell is discharged through the air outlet;
s3 electrochemical oxidation treatment: respectively connecting a working electrode, a reference electrode and a counter electrode of an electrolytic cell with a working electrode, a reference electrode and a counter electrode of an electrochemical workstation, setting by control software of the electrochemical workstation, applying a potential of 0.4V relative to a saturated Ag/AgCl reference electrode on the working electrode, simultaneously adding 10mmol ABTS of an electronic mediator subjected to aeration and deoxygenation from a gas outlet hole for 30min, adding 200 muL of a micro plastic suspension subjected to aeration and deoxygenation after the current is stabilized to a baseline current, obtaining an oxidation peak current in a timing current curve, calculating the area of the oxidation peak current by an integration method after the current is stabilized to the baseline current to obtain the electron loss capacity of the micro plastic, and determining the stable value of the oxidation current of the electron loss capacity to be 200 muA, the oxidation peak current to be 30 muA and the duration to be 70 min;
s4 electrochemical reduction treatment: applying a potential of-0.7V relative to a saturated Ag/AgCl reference electrode on a working electrode, simultaneously adding 1mL of amphoteric viologen solution ZiV of 10mmol of the electronic mediator solution subjected to aeration and deoxygenation from a gas outlet, continuing for 30min, adding 200 mu L of micro plastic suspension subjected to aeration and deoxygenation after the current is stabilized to a baseline current, then obtaining a reduction peak current in a timing current curve, calculating the area of the reduction peak current by an integration method after the current is stabilized to the baseline current to respectively obtain the electron obtaining capacity of the micro plastic, and measuring the reduction current stability value of the electron capacity to be 15 mu A, the reduction peak current to be 200 mu A and continuing for 5 min;
s5 verification: detecting whether redox active functional groups exist on the surface of the micro plastic through cyclic voltammetry, filtering, freeze-drying the micro plastic after electrochemical treatment, mixing the micro plastic with conductive carbon black to obtain a mixed suspension, wherein the freeze-drying temperature is-50 ℃, the mass concentration of the micro plastic in the mixed suspension is 4g/L, the mass concentration of the conductive carbon black is 1g/L, the solute is water, fixing the suspension on a glassy carbon electrode, scanning to obtain a cyclic voltammetry curve, and comparing the cyclic voltammetry curve with a control group.
Example 3
An electrochemical method for determining the redox properties of a micro-plastic, comprising the steps of:
s1 cell assembly: as shown in fig. 2, a working electrode, a reference electrode and a counter electrode are sequentially arranged in a closed electrolytic cell, the working electrode is a carbon felt working electrode with the area of 1 × 1cm, the reference electrode is a saturated Ag/AgCl reference electrode, the counter electrode is a graphite sheet counter electrode, 25mL of electrolyte is poured into the electrolytic cell, the electrolyte is a mixed solution of 0.1mol of KCl solution and 0.1mol of phosphate, and the pH of the electrolyte is adjusted to 7;
s2 discharge oxygen: introducing argon into the electrolyte through the air inlet for 0.5h, wherein the introduction amount of the argon is 0.6m3The oxygen in the electrolytic cell is discharged through the air outlet;
s3 electrochemical oxidation treatment: respectively connecting a working electrode, a reference electrode and a counter electrode of an electrolytic cell with a working electrode, a reference electrode and a counter electrode of an electrochemical workstation, setting by control software of the electrochemical workstation, applying a potential of 0.4V relative to a saturated Ag/AgCl reference electrode on the working electrode, simultaneously adding 10mmol ABTS of an electronic mediator subjected to aeration and deoxygenation from a gas outlet hole for 30min, adding 200 muL of a micro plastic suspension subjected to aeration and deoxygenation after the current is stabilized to a baseline current, obtaining an oxidation peak current in a timing current curve, calculating the area of the oxidation peak current by an integration method after the current is stabilized to the baseline current to obtain the electron loss capacity of the micro plastic, and determining the stable value of the oxidation current of the electron loss capacity to be 200 muA, the oxidation peak current to be 30 muA and the duration to be 70 min;
s4 electrochemical reduction treatment: applying a potential of-0.7V relative to a saturated Ag/AgCl reference electrode on a working electrode, simultaneously adding 1mL of amphoteric viologen solution ZiV of 10mmol of the electronic mediator solution subjected to aeration and deoxygenation from a gas outlet, continuing for 30min, adding 200 mu L of micro plastic suspension subjected to aeration and deoxygenation after the current is stabilized to a baseline current, then obtaining a reduction peak current in a timing current curve, calculating the area of the reduction peak current by an integration method after the current is stabilized to the baseline current to respectively obtain the electron obtaining capacity of the micro plastic, and measuring the reduction current stability value of the electron capacity to be 15 mu A, the reduction peak current to be 200 mu A and continuing for 5 min;
s5 verification: detecting whether redox active functional groups exist on the surface of the micro plastic through cyclic voltammetry, filtering, freeze-drying the micro plastic after electrochemical treatment, mixing the micro plastic with conductive carbon black to obtain a mixed suspension, wherein the freeze-drying temperature is-50 ℃, the mass concentration of the micro plastic in the mixed suspension is 4g/L, the mass concentration of the conductive carbon black is 1g/L, the solute is water, fixing the suspension on a glassy carbon electrode, scanning to obtain a cyclic voltammetry curve, and comparing the cyclic voltammetry curve with a control group.
Example 4
An electrochemical method for determining the redox properties of a micro-plastic, comprising the steps of:
s1 cell assembly: as shown in fig. 2, a working electrode, a reference electrode and a counter electrode are sequentially arranged in a closed electrolytic cell, the working electrode is a carbon felt working electrode with the area of 1 × 1cm, the reference electrode is a saturated Ag/AgCl reference electrode, the counter electrode is a graphite sheet counter electrode, 25mL of electrolyte is poured into the electrolytic cell, the electrolyte is a mixed solution of 0.1mol of KCl solution and 0.1mol of phosphate, and the pH of the electrolyte is adjusted to 7;
s2 discharge oxygen: introducing argon into the electrolyte through the air inlet for 0.5h, wherein the introduction amount of the argon is 0.4m3The oxygen in the electrolytic cell is discharged through the air outlet;
s3 electrochemical oxidation treatment: respectively connecting a working electrode, a reference electrode and a counter electrode of an electrolytic cell with a working electrode, a reference electrode and a counter electrode of an electrochemical workstation, setting by control software of the electrochemical workstation, applying a potential of 0.4V relative to a saturated Ag/AgCl reference electrode on the working electrode, simultaneously adding 10mmol ABTS of an electronic mediator subjected to aeration and deoxygenation from a gas outlet, continuing for 30min, adding 200 muL of a micro plastic suspension subjected to aeration and deoxygenation after the current is stabilized to a baseline current, immediately obtaining an oxidation peak current in a timing current curve, calculating the area of the oxidation peak current by an integration method after the current is stabilized to the baseline current to obtain the electron loss capacity of the micro plastic, and determining the stable value of the oxidation current of the electron loss capacity to be 250 muA, the oxidation peak current to be 20 muA and the duration to be 70 min;
s4 electrochemical reduction treatment: applying a potential of-0.7V relative to a saturated Ag/AgCl reference electrode on a working electrode, simultaneously adding 1mL of amphoteric viologen solution ZiV of 10mmol of the electronic mediator solution subjected to aeration and deoxygenation from a gas outlet, continuing for 30min, adding 350 mu L of micro plastic suspension subjected to aeration and deoxygenation after the current is stabilized to a baseline current, then obtaining a reduction peak current in a timing current curve, calculating the area of the reduction peak current by an integration method after the current is stabilized to the baseline current to respectively obtain the electron obtaining capacity of the micro plastic, and measuring the reduction current stability value of the electron capacity to be 15 mu A, the reduction peak current to be 200 mu A and continuing for 5 min;
s5 verification: detecting whether redox active functional groups exist on the surface of the micro plastic through cyclic voltammetry, filtering, freeze-drying the micro plastic after electrochemical treatment, mixing the micro plastic with conductive carbon black to obtain a mixed suspension, wherein the freeze-drying temperature is-70 ℃, the mass concentration of the micro plastic in the mixed suspension is 4g/L, the mass concentration of the conductive carbon black is 1g/L, the solute is water, fixing the suspension on a glassy carbon electrode, scanning to obtain a cyclic voltammetry curve, and comparing the cyclic voltammetry curve with a control group.
Example 5
An electrochemical method for determining the redox properties of a micro-plastic, comprising the steps of:
s1 cell assembly: as shown in fig. 2, a working electrode, a reference electrode and a counter electrode are sequentially arranged in a closed electrolytic cell, the working electrode is a carbon felt working electrode with the area of 1 × 1cm, the reference electrode is a saturated Ag/AgCl reference electrode, the counter electrode is a graphite sheet counter electrode, 25mL of electrolyte is poured into the electrolytic cell, the electrolyte is a mixed solution of 0.1mol of KCl solution and 0.1mol of phosphate, and the pH of the electrolyte is adjusted to 7;
s2 discharge oxygen: introducing argon into the electrolyte through the air inlet for 0.5h, wherein the introduction amount of the argon is 0.4m3The oxygen in the electrolytic cell is discharged through the air outlet;
s3 electrochemical oxidation treatment: respectively connecting a working electrode, a reference electrode and a counter electrode of an electrolytic cell with a working electrode, a reference electrode and a counter electrode of an electrochemical workstation, setting by control software of the electrochemical workstation, applying a potential of 0.4V relative to a saturated Ag/AgCl reference electrode on the working electrode, simultaneously adding 10mmol ABTS of an electronic mediator subjected to aeration and deoxygenation from a gas outlet, continuing for 30min, adding 200 muL of a micro plastic suspension subjected to aeration and deoxygenation after the current is stabilized to a baseline current, immediately obtaining an oxidation peak current in a timing current curve, calculating the area of the oxidation peak current by an integration method after the current is stabilized to the baseline current to obtain the electron loss capacity of the micro plastic, and determining the oxidation current stabilization value of the electron loss capacity to be 300 muA, the oxidation peak current to be 80 muA and the duration to be 70 min;
s4 electrochemical reduction treatment: applying a potential of-0.7V relative to a saturated Ag/AgCl reference electrode on a working electrode, simultaneously adding 1mL of amphoteric viologen solution ZiV of 10mmol of the electronic mediator solution subjected to aeration and deoxygenation from a gas outlet, continuing for 30min, adding 200 mu L of micro plastic suspension subjected to aeration and deoxygenation after the current is stabilized to a baseline current, then obtaining a reduction peak current in a timing current curve, calculating the area of the reduction peak current by an integration method after the current is stabilized to the baseline current to respectively obtain the electron obtaining capacity of the micro plastic, and measuring the reduction current stability value of the electron capacity to be 30 mu A, the reduction peak current to be 500 mu A and the duration to be 5 min;
s5 verification: detecting whether redox active functional groups exist on the surface of the micro plastic through cyclic voltammetry, filtering, freeze-drying the micro plastic after electrochemical treatment, mixing the micro plastic with conductive carbon black to obtain a mixed suspension, wherein the freeze-drying temperature is-80 ℃, the mass concentration of the micro plastic in the mixed suspension is 4g/L, the mass concentration of the conductive carbon black is 1g/L, the solute is water, fixing the suspension on a glassy carbon electrode, scanning to obtain a cyclic voltammetry curve, and comparing the cyclic voltammetry curve with a control group.
Example 6
The application of an electrochemical method for measuring the redox characteristics of the micro plastic comprises the following steps of: weighing 3g of phenolic resin micro plastic in a glass bottle, adding 80mL of hydrogen peroxide solution with the mass concentration of 5%, reacting for 0, 4, 8, 12, 19, 26 and 42 days respectively to prepare micro plastic suspensions with different hydrogen peroxide aging degrees, wherein the micro plastic suspensions are named as PF-0, PF-4, PF-8, PF-12, PF-19, PF-26 and PF-42 respectively, and the shapes of the phenolic resin micro plastic before and after aging are shown in figures 4 and 5.
Example 7
The application of an electrochemical method for measuring the redox characteristics of the micro plastic comprises the following steps of: weighing 3g of phenolic resin micro plastic in a glass bottle, adding 80mL of hydrogen peroxide solution with the mass concentration of 20%, reacting for 0, 4, 8, 12, 19, 26 and 42 days respectively to prepare micro plastic suspensions with different hydrogen peroxide aging degrees, which are named as PF-0, PF-4, PF-8, PF-12, PF-19, PF-26 and PF-42 respectively, as shown in figures 4 and 5.
Example 8
The application of an electrochemical method for measuring the redox characteristics of the micro plastic comprises the following steps of: weighing 3g of phenolic resin micro plastic in a glass bottle, adding 80mL of hydrogen peroxide solution with the mass concentration of 30%, reacting for 0, 4, 8, 12, 19, 26 and 42 days respectively to prepare micro plastic suspensions with different hydrogen peroxide aging degrees, which are named as PF-0, PF-4, PF-8, PF-12, PF-19, PF-26 and PF-42 respectively, as shown in figures 4 and 5.
Examples of the experiments
As shown in FIGS. 6-8, the response peak current of the timing current of the phenolic resin micro-plastic added with different aging times in example 6, the response time of the peak current was 5min in the process of measuring the obtained electron capacity, and the obtained electron capacities from PF-0 to PF-42 are shown in Table 1; the peak current response time in the electron loss capacity measurement process was 70min, and the electron loss capacities from PF-0 to PF-42 are shown in Table 1.
Table 1 electron capacity gain/loss in example 6
| Micro plastic | Obtaining the electron capacity mmol/e g | Electron loss capacity mmol/e g |
| PF-0 | 0.30752 | 0.65745 |
| PF-4 | 0.44189 | 0.26356 |
| PF-8 | 0.36548 | 0.68024 |
| PF-12 | 0.41722 | 0.44690 |
| PF-19 | 0.26717 | 0.60523 |
| PF-26 | 0.41881 | 0.98001 |
| PF-42 | 0.27876 | 1.15431 |
To verify that the microplastic does have electron gain/loss capacity, the presence of redox active functional groups on the surface of the microplastic was further examined by cyclic voltammetry. Mixing the micro plastic with the aging time of 0 day, 8 days and 26 days with conductive carbon black to prepare suspension, fixing the suspension on a glassy carbon electrode, scanning to obtain a cyclic voltammetry curve, and comparing the cyclic voltammetry curve with a control group C to obtain redox peaks which are reversible in oxidation and reduction, wherein the redox active functional groups exist in the micro plastic, and as shown in figure 9, for the original micro plastic PF-0, a pair of redox peaks exist at a position of-0.07V; PF-8 aged for 8 days showed a new pair of redox peaks at 0.015V; PF-26 aged for 26 days showed a new pair of redox peaks at 0.145V, indicating that the micro-plastics showed an increased number of species for forming redox active functional groups, mainly phenolic, semiquinone and quinone redox active functional groups of different chemical structures. An increase in peak current intensity indicates an increase in the redox-active functional group content.
Claims (10)
1. An electrochemical method for measuring the redox characteristics of a micro plastic, comprising the steps of:
s1 cell assembly: sequentially placing a working electrode, a reference electrode and a counter electrode into a closed electrolytic cell, wherein the reference electrode is a saturated Ag/AgCl reference electrode, pouring 25mL of electrolyte into the electrolytic cell, the electrolyte is a mixed solution of 0.1mol of KCl solution and 0.1mol of phosphate, and adjusting the pH value of the electrolyte to be 7;
s2 discharge oxygen: introducing argon into the electrolyte through the air inlet hole for 0.5h, and discharging oxygen in the electrolytic cell through the air outlet hole;
s3 electrochemical oxidation treatment: connecting a working electrode, a reference electrode and a counter electrode of an electrolytic cell with a working electrode, a reference electrode and a counter electrode of an electrochemical workstation respectively, setting by control software of the electrochemical workstation, applying a potential of 0.4V relative to a saturated Ag/AgCl reference electrode on the working electrode, simultaneously adding 1mL of an electron mediator subjected to aeration and deoxygenation into a gas outlet, continuing for 30min, adding 200 muL of a micro plastic suspension subjected to aeration and deoxygenation after the current is stabilized to a baseline current, obtaining an oxidation peak current in a timing current curve immediately, and calculating the area of the oxidation peak current by an integration method after the current is stabilized to the baseline current to obtain the electron loss capacity of the micro plastic;
s4 electrochemical reduction treatment: applying a potential of-0.7V relative to a saturated Ag/AgCl reference electrode on a working electrode, simultaneously adding 1mL of the electron mediator solution subjected to aeration and deoxygenation from a gas outlet, continuing for 30min, adding 200 mu L of the micro plastic suspension subjected to aeration and deoxygenation after the current is stabilized to a baseline current, then obtaining a reduction peak current in a timing current curve, and calculating the area of the reduction peak current through an integration method after the current is stabilized to the baseline current to respectively obtain the electron capacity of the micro plastic;
s5 verification: detecting whether redox active functional groups exist on the surface of the micro plastic through cyclic voltammetry, filtering, freeze-drying the electrochemically treated micro plastic, mixing with conductive carbon black to obtain a mixed suspension, fixing the suspension on a glassy carbon electrode, scanning to obtain a cyclic voltammetry curve, and comparing with a control group.
2. The electrochemical method for determining the redox properties of a micro-plastic according to claim 1, wherein the working electrode in step S1 is a carbon felt working electrode with an area of 1 x 1cm, and the counter electrode is a graphite sheet counter electrode.
3. The electrochemical method for determining the redox characteristics of micro-plastics according to claim 1, wherein the amount of argon gas introduced in step S2 is 0.4-0.6m3/h。
4. The electrochemical method for determining the redox property of a micro-plastic according to claim 1, wherein the electron mediator solution in step S3 is 10mmol ABTS, and the electron mediator solution in step S4 is 10mmol amphoteric viologen solution ZiV.
5. The electrochemical method for determining the oxidation-reduction characteristics of micro plastic as claimed in claim 1, wherein the stable oxidation current value of the electron loss capacity determined in step S3 is 200-300 μ A, the oxidation peak current is 30-80 μ A, and the duration is 70 min; the stable value of the reduction current of the electron capacity measured in the step S4 is 15-30 muA, the reduction peak current is 200-500 muA, and the duration is 5 min.
6. The electrochemical method for measuring the redox properties of a micro plastic according to claim 1, wherein the temperature of freeze-drying in step S5 is-50 to-80 ℃.
7. The electrochemical method for measuring the redox property of a micro plastic as claimed in claim 1, wherein the mass concentration of the micro plastic in the mixed suspension in step S5 is 4g/L, the mass concentration of the conductive carbon black is 1g/L, and the solute is water.
8. Use of an electrochemical method for the determination of the redox properties of a micro plastic according to any of claims 1 to 7, characterized in that the electron gain and electron loss capacity of a hydrogen peroxide aged phenolic resin micro plastic is determined using the above method.
9. The application of the electrochemical method for determining the redox characteristics of the micro-plastic according to claim 8, wherein the preparation method of the hydrogen peroxide aged phenolic resin micro-plastic comprises the following steps: weighing 3g of phenolic resin micro plastic in a glass bottle, adding 80mL of hydrogen peroxide solution, and reacting for 0, 4, 8, 12, 19, 26 and 42 days respectively to prepare micro plastic suspensions with different hydrogen peroxide aging degrees, wherein the micro plastic suspensions are named as PF-0, PF-4, PF-8, PF-12, PF-19, PF-26 and PF-42 respectively.
10. The use of an electrochemical method for the determination of the redox properties of a micro-plastic according to claim 9, wherein the hydrogen peroxide solution has a mass concentration of 5-30%.
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