CN116626136B - Method for detecting different chromium ion forms based on group interaction - Google Patents
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- 239000011651 chromium Substances 0.000 claims abstract description 63
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 22
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- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 2
- UBEWDCMIDFGDOO-UHFFFAOYSA-N cobalt(2+);cobalt(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[Co+2].[Co+3].[Co+3] UBEWDCMIDFGDOO-UHFFFAOYSA-N 0.000 description 2
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/403—Cells and electrode assemblies
- G01N27/406—Cells and probes with solid electrolytes
- G01N27/411—Cells and probes with solid electrolytes for investigating or analysing of liquid metals
- G01N27/4115—Composition or fabrication of the electrodes and coatings thereon, e.g. catalysts
-
- 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
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/20—Controlling water pollution; Waste water treatment
Abstract
The invention discloses a method for realizing detection of different chromium ion forms based on radical interaction, which comprises the steps of carrying out electrochemical action on a functionalized material modified electrode and a chromium-containing solution under the induction of an electric field; the functional material is amino modified cobalt-based graphene and/or carboxylated modified cobalt-based graphene. The invention further fixes HCrO by electrostatic attraction and group interaction under the action of an electric field 4 ‑ And Cr (OH) 2+ The detection lower limit is 0.10 mug/L and 0.12 mug/L respectively, the detection sensitivity is 19.46 mug/L and 13.44 mug/L respectively, and the detection lower limit is improved by 2-3 orders of magnitude compared with the detection lower limit of the traditional spectrometry, the operation process is simple and mild, the cost is low, and the method has good application prospect.
Description
Technical Field
The invention relates to the technical field of morphological analysis and detection of heavy metal chromium, in particular to a method for detecting different chromium ion morphologies based on radical interaction.
Background
In recent years, environmental pollution caused by heavy metal ions has been receiving increasing attention. Heavy metal ions in different forms correspond to different bioavailability and physiological toxicity, so that emphasis is placed on rapid and accurate detection of different forms, rather than comprehensive detection, and the method has important significance. Currently, the sensitive and reliable detection of heavy metal pollutants still depends on the traditional optical instrument methods, such as atomic absorption spectrometry, inductively coupled plasma mass spectrometry and the like to a great extent. But most of the devices have the characteristics of huge equipment, high running cost, high technical requirements on operators and the like. In addition, electrochemical techniques and Laser Induced Breakdown Spectroscopy (LIBS) are also used for detection of heavy metal ions 1-3 But there are characteristic problems often dependent on strong acid electrolytes or noble metal catalysis, which are commonly used for single morphology analysis.
Disclosure of Invention
The invention provides a mechanism based on the special interaction between the oxygen-containing group of the target ion and the functional material under the induction of an electric field, so that the purpose of ultra-low limit, accurate and rapid detection of chromium with different forms can be realized. In order to achieve the purpose, the invention adopts the following technical scheme:
the method for detecting different chromium ion forms based on group interaction comprises the steps of carrying out electrochemical action on a functionalized material modified electrode and a chromium-containing solution under the induction of an electric field; the functional material is amino modified cobalt-based graphene and/or carboxylated modified cobalt-based graphene.
In the above-described method, it is preferable to use cobalt-based graphene Co 3 O 4 Amination modification of rGO to NH 2 -Co 3 O 4 rGO, cobalt-based graphene Co 3 O 4 Carboxylation modification is carried out on rGO to obtain COOH-Co 3 O 4 /rGO. Wherein the amination modification can be a modification of Co 3 O 4 rGO is dissolved in BAdding ammonia water and aminopropyl trimethoxysilane (APTMS) into alcohol and water, and performing ultrasonic oscillation. The amination modification method is a common treatment process. The carboxylation modification is to make Co 3 O 4 And (3) dissolving rGO in ethanol and water, adding carboxylated graphene (COOHGO), and carrying out ultrasonic oscillation. The Co is 3 O 4 rGO is obtainable by known reported literature methods such as RSC Adv.,2015,5,88567. The carboxylated graphene (COOHGO) may also be obtained by a conventional graphene carboxylation method or directly purchased from a professional manufacturer.
In the above-described method, it is preferable that NH is used 2 -Co 3 O 4 Modification of electrode by rGO, application of positive voltage to chromium-containing solution HCrO 4 - Detecting; by COOH-Co 3 O 4 Modification of electrode by rGO, application of negative voltage to chromium-containing solution Cr (OH) 2+ And (5) detecting. The electrode can be a common metal electrode such as an aluminum sheet electrode, and of course, other metals such as a copper foil electrode, a titanium electrode and a silver electrode or a non-metal electrode such as a graphite electrode can also be used, and research shows that compared with the graphite electrode, the aluminum sheet electrode has a better electrochemical enrichment effect, which may be the reason that the conductivity of the aluminum sheet is better. In addition, when the electrode is modified, the working electrode is usually pretreated, such as sanded to a bright state, and then 4-6mg/ml NH is applied 2 -Co 3 O 4 rGO and 1-3mg/ml COOH-Co 3 O 4 And (3) uniformly spin-coating/rGO on the surface of the electrode, and drying for later use. Preferably 5mg/ml NH 2 -Co 3 O 4 /rGO、1.5mg/ml COOH-Co 3 O 4 Spin coating is performed on/rGO. The electrode may employ a rotatable electrode that is easily replaced, thus facilitating adjustment of the replacement electrode. The inventor researches find that the excessive concentration of the spin-coating solution can cause the excessive thickness of the dripping material, cover the active sites on the surface of the electrode and influence the interaction with target ions; while spin-on solutions with too low a concentration are not sufficient to provide enough functional groups to interact with the target ions, reducing the generation of spectroscopic signals.
More preferably, the method for detecting and enriching different chromium ion forms can adopt the following steps:
(1) Taking 8-12mg Co 3 O 4 rGO is dissolved in 25-35mL of ethanol and 1-3mL of deionized water, 2-6mL of ammonia water and 200-300 mu L of APTMS are added, and after ultrasonic treatment for 2-4 hours, the solution is oscillated for 6-8 hours at room temperature and 200 rpm; washing with ethanol and water for several times to obtain NH 2 -Co 3 O 4 /rGO；
(2) When COOHGO is used for replacing APTMS, COOH-Co is obtained 3 O 4 rGO; specific: taking 8-12mg Co 3 O 4 rGO is dissolved in 25-35mL of ethanol and 1-3mL of deionized water, 200-300 mu L of COOHGO is added, and after ultrasonic treatment for 2-4 hours, the solution is oscillated for 6-8 hours at room temperature and 200 rpm; washing with ethanol and water for several times to obtain COOH-Co 3 O 4 /rGO。
(3) By NH 2 -Co 3 O 4 Modification of electrode by rGO, application of positive voltage to chromium-containing solution HCrO 4 - Detecting; by COOH-Co 3 O 4 Modification of electrode by rGO, application of negative voltage to chromium-containing solution Cr (OH) 2+ And (5) detecting.
Preferably, the chromium-containing solution has a ph=4-5. Within this pH range, hexavalent chromium and trivalent chromium are present as HCrO4, respectively - And Cr (OH) 2+ In the form of hexavalent chromium, generally in the form of oxygen-containing groups, and trivalent chromium, in the form of oxygen-containing groups Cr (OH) at a pH of 4 to 5 2+ Exists in the form of (int.j. Environ. An. Ch.2019, 1051). Electrochemical analysis can thus be performed using the difference in charge of the two oxygen-containing groups. Of course, the chromium-containing solution may be formulated to a suitable pH using a buffer solution. The positive voltage is preferably applied by 0.5-2V, more preferably 0.8-1.5V, and most preferably 1.0V; applying negative voltage-0.5 to-2V is preferable, -0.8 to-1.5V is more preferable, -0.9V is most preferable; the hydrogen evolution on the surface of the electrode is easily caused by the overlarge applied voltage, bubbles are generated to influence the adsorption and interaction of the nano material on target ions, and the traction force under a sufficient electric field cannot be provided due to the overlarge voltage, so that the electric enrichment efficiency is influenced. The detection combination in the step (3) is preferably LIBS quantitative analysis. The invention uses voltage regulation and chemical combination of amino or carboxylation group under electric fieldCo-action to fix HCrO on electrode surface 4 - Or Cr (OH) 2+ Quantitative analysis can be performed.
According to the invention, the functionalized cobalt-based graphene composite material carrier is prepared by using cobaltosic oxide and graphene as media and through amino and carboxyl functionalization, so that not only can the electron transfer capacity be improved through the valence state circulation of transition metal cobalt, but also the selectivity and anti-interference detection of target ions can be realized through the interaction of oxygen-containing groups and functionalized groups.
The invention provides a novel method for detecting chromium in different forms of ppb level with high sensitivity and high selectivity under the interaction of an electric field regulation and an amino group and a carboxylation group. Compared with the traditional spectrum method, the method can improve the detection limit and the sensitivity by two orders of magnitude, and further explains that the action mechanism of the selective and sensitive detection is the combined action of electric field induction and chemical combination. The surface of cobalt-based graphene is respectively subjected to amination and carboxylation group modification, and the amino group is protonated to form NH in a buffer solution with pH of 4.0-5.0, especially 4.0 3 + With HCrO 4 - Under the action of positive electric field 1.0V, electrostatic attraction and chemical combination are combined to promote LIBS to recognize HCrO with high sensitivity and high selectivity 4 - Is provided. Deprotonation of carboxylated groups to form COO - And Cr (OH) 2+ Under the action of negative electric field 0.9V, electrostatic attraction and chemical combination are combined to promote LIBS to recognize Cr (OH) with high sensitivity and high selectivity 2+ Is provided. The highly sensitive detection mechanism of the new method in this work is explained by TEM, XPS and XANES. The novel method for selectively detecting the heavy metal pollutants in the water environment is provided from the microscopic angle of radical interaction, and a novel thought is provided for rapid and accurate analysis of the heavy metal pollutants in the water environment.
Here, the inventors propose a new method for detecting different forms of chromium in water with the aid of Laser Induced Breakdown Spectroscopy (LIBS) based on the mechanism of interaction of different oxygen-containing groups with functionalized groups under the influence of an applied electric field. Since the morphological distribution of heavy metal pollutants changes along with the change of the pH value of the solution, the electrochemical parameters are adjustedThe selective enrichment is realized by utilizing the charge difference of two chromium ions, and then quantitative analysis is carried out by LIBS technology. Using Co with excellent conductivity 3 O 4 The composite material can prevent aggregation of graphene sheets, improve conductivity and electrochemical enrichment efficiency, and reduce LIBS detection lower limit. Amino and carboxyl modified Co 3 O 4 Selective enrichment of HCrO by rGO 4 - And Cr (OH) 2+ And then quantitatively detected by LIBS. The result shows that the method has better anti-interference performance and actual water sample analysis effect. FTIR, XPS and XANES showed that the excellent detection performance is due to the strong adsorption capacity of thin graphene, selective adsorption and chemical interaction of functional groups (amino and carboxyl) on chromium ions of different forms, and Co 3 O 4 Synergistic effect of Co (II)/(III) valence state circulation in nanoparticles, co is treated in the present invention 3 O 4 The particle size of the nano particles is not required, and the nano particles mainly play a role in enhancing conductivity and promoting electron transfer by valence state circulation.
The inventors have found that Co 3 O 4 The nano particles enhance the conductivity of the composite material, prevent interlayer agglomeration of the graphene substrate material and improve the enrichment efficiency. COO is disclosed in DFT differential charge density diagram - -Co 3 O 4 rGO and Cr (OH) 2+ When in action, electrons flow from Co sites to Cr (OH) 2+ Cr site, NH in (C) 3 + -Co 3 O 4 rGO and HCrO 4 - When acting, electrons flow from Co sites to HCrO 4 - O site of (a), as shown in figure 3.XPS shows that after the functionalized cobalt-based graphene adsorbs chromium ions, the Co (II) proportion is reduced and the Co (III) proportion is increased. Electron transfer is promoted by Co (II)/(III) valence state cycling. As in fig. 5.
The invention realizes selective electrochemical enrichment of Cr (OH) by modifying the electrode with a functional material under different electric fields 2+ And HCrO 4 - And specific chemical interaction is generated, which is a key factor for improving detection sensitivity and selectivity, and specific surface modification is carried out on the materialFunctional groups (amino and carboxyl) of (a) and further immobilizing HCrO by electrostatic attraction and radical interaction under the action of an electric field 4 - And Cr (OH) 2+ The lower detection limit is 0.10 mug/L and 0.12 mug/L respectively, the detection sensitivity is 19.46 mug/L and 13.44 mug/L respectively, compared with the traditional laser-induced breakdown spectroscopy 4-8 (lower detection limit is 100-1000 mug/L) and is increased by 2-3 orders of magnitude. The operation process is simple and mild, the cost is low, and the method has good application prospect. The mechanism of high sensitivity detection is electric field induction during pre-enrichment and interaction of the functionalized groups with the target ions. The results indicate that the amino group protonates NH 3 + With HCrO 4 - The combined action of electrostatic attraction and chemical bonding takes place while avoiding the interference of cations (electrostatic repulsion) and other anions present in simple form (without oxygen-containing groups) under a positive electric field. Deprotonation of carboxylated groups to form COO - And Cr (OH) 2+ The combined action of electrostatic attraction and chemical bonding takes place while avoiding the interference of anions (electrostatic repulsive force) and the interference of other cations present in a simple form (without oxygen-containing groups) under a negative electric field. Co with excellent conductivity 3 O 4 The nano particles synergistically improve the electric enrichment and electron transfer efficiency, and promote LIBS to detect chromium in different forms with high sensitivity and high selectivity. The invention provides a new thought for an electrochemical method for morphological analysis of heavy metal ions.
Drawings
Fig. 1 is a TEM image of prepared amino and carboxylated cobalt-based graphene.
Fig. 2 is a schematic diagram of the detection. The detection of chromium in different forms is divided into two parts of electrochemical separation and enrichment and LIBS quantitative analysis. Electrocatalytic adsorption was performed on a replaceable rotating electrode, after which both electrodes were subjected to in situ LIBS quantitative analysis. And establishing a linear equation through the spectrum signal result to obtain analysis results of chromium in different forms.
FIG. 3 is a diagram of DFT adsorption configuration (adsorption energy).
(a)Co 3 O 4 /rGO,(b)NH 3 + -Co 3 O 4 rGO vs HCrO 4 - Adsorption configuration and adsorption energy at 1V; (c) Co (Co) 3 O 4 /rGO,(d)COO--Co 3 O 4 rGO vs. Cr (OH) 2+ Adsorption configuration and adsorption energy at-0.9V.
FIG. 4 is a) NH in example 2 -Co 3 O 4 rGO vs HCrO 4 - LIBS response plot of (a), the inset is the corresponding linear fit plot, b) COOH-Co 3 O 4 rGO vs. Cr (OH) 2+ Is shown, the inset is a corresponding linear fit. (50-500 ppb)
FIG. 5 is a) to e) NH prepared in the examples 2 -Co 3 O 4 rGO and COOH-Co 3 O 4 XPS high-resolution spectrum contrast of each element before and after adsorbing Cr by rGO, f) Cr foil, crO 3 ,Cr(OH) 2+ /COOH-Co 3 O 4 /rGO,Cr 2 O 3 ,HCrO 4 - /NH 2 -Co 3 O 4 Comparison of Cr K edge near side spectra of/rGO, the inset is a partial enlarged view.
FIG. 6 simple electric field induction for 100ppb (a) HCrO 4 - And (b) Cr (OH) 2+ Is provided.
Figure 7 selectivity and anti-interference test.
FIG. 8NH 3 + -Co 3 O 4 PerGO at 1V for (a) HCrO 4- And (b) Cr (OH) 2+ Adsorption configuration and adsorption energy of (a); COO-Co 3 O 4 R GO at-0.9V for (c) Cr (OH) 2+ And (d) HCrO 4 - Adsorption configuration and adsorption energy of (a).
Detailed Description
The following examples are further illustrative of the technical content of the present invention, but the essential content of the present invention is not limited to the examples described below, and those skilled in the art can and should know that any simple changes or substitutions based on the essential spirit of the present invention should fall within the scope of the present invention as claimed.
Example 1
(1) The preparation process of the functional material comprises the following steps: first, co 3 O 4 rGO (10 mg) was dissolved in ethanol (30 mL) and deionized water (2 mL), ammonia (5 mL) and APTMS (200. Mu.L) were added, and after sonication for 2h, the mixture was shaken at room temperature (200 rpm) for 6h. Washing with ethanol and water for several times to obtain NH 2 -Co 3 O 4 /rGO；
In the above step, when APTMS is replaced with COOHGO, COOH-Co can be obtained 3 O 4 /rGO. Specifically, co is taken 3 O 4 rGO (10 mg) was dissolved in ethanol (30 mL) and deionized water (2 mL), COOHGO (300. Mu.L) was added, and after 3h of sonication, it was shaken at room temperature (200 rpm) for 8h. Washing with ethanol and water for several times to obtain COOH-Co 3 O 4 /rGO. Fig. 1 shows a TEM image of the aminated and carboxylated cobalt-based graphene prepared in the examples.
(2) When ph=4 of the solution, cr (VI) was expressed as HCrO 4 - In the form of Cr (III) in the form of Cr (OH) 2+ Is present in the form of (c). Different voltages are applied according to the difference of charges carried by the two ions. The electrochemical separation enrichment can be described as the following steps: by using an electrochemical workstation, when a positive voltage is applied, NH is passed through 2 -Co 3 O 4 Electrode modified by rGO as working electrode, COOH-Co 3 O 4 The electrode modified by rGO is used as a reference electrode/a counter electrode; COOH-Co when negative voltage is applied 3 O 4 An electrode modified by rGO is used as a working electrode and is subjected to NH 2 -Co 3 O 4 the/rGO modified electrode served as reference/counter electrode. Specifically, NH 2 -Co 3 O 4 The rGO modified aluminum sheet is used as a working electrode 1 to apply positive voltage to form a positive electrode area, and NH is induced and protonated by an electric field 3 + Chemical binding of hexavalent chromate ions for HCrO 4 - Is fixed at NH 2 -Co 3 O 4 On the rGO electrode; when negative voltage is applied to COOH-Co 3 O 4 When rGO modified aluminum electrode, the migration of negative electric field assists Cr (OH) 2+ Focusing around the working electrode 2, cr (OH) 2+ Is immobilized on COOH-Co under the action of negative electric field and deprotonated COO- 3 O 4 On the rGO electrode, LIBS laser performs in-situ analysis on the rotatable electrochemical electrode slice,a spectral signal is obtained.
(3) DFT calculations verify that the introduction of functional groups enhances the interaction of the substrate material with the target ions, contributing to the generation of a mechanism for highly selective and sensitive detection of different chromium ions. Fig. 3 shows a comparison of the adsorption configuration and the adsorption energy values of the substrate material for the target ions in both the presence and absence of the functional groups.
(4) The method takes an amination and carboxylation cobalt-based graphene material as a substrate, and realizes quantitative analysis of chromium in different forms based on an LIBS method through electrochemical enrichment and interaction between groups. The results show that HCrO is immobilized by electrostatic attraction under the action of an electric field 4 - And Cr (OH) 2+ The detection lower limit is 0.10 mug/L and 0.12 mug/L respectively, the detection sensitivity is 19.46 mug/L and 13.44 mug/L respectively, and the detection lower limit is improved by 2-3 orders of magnitude compared with the detection lower limit of the traditional spectrometry. FIG. 4 shows the composition prepared for (a) HCrO 4 - And (b) Cr (OH) 2+ Is a spectrum detection signal diagram of the (a).
(5) XPS results reveal the mechanism of chemical displacement generated by the interaction of oxygen-containing groups and functional groups of target ions, and prove the anti-interference and selectivity of the functional material (composite material) prepared by us for detecting chromium ions in different forms. FIG. 5 shows XPS high resolution spectra of the interactions of the composite materials with target ions.
In addition, as shown in FIG. 6, the inventors have found that, in the case where no functional material is modified, simple electric field induction is performed on HCrO 4 - And Cr (OH) 2+ The spectral signal of (2) is very weak. Illustrating that the interaction of the material with the target ion is a key factor in enhancing the spectral signal.
Meanwhile, the inventor also carries out related interference experiments, and the result shows that the spectrum signal of the interference ions in a certain concentration range to the target ions is smaller as shown in figure 7, and the interference of other cations is avoided due to the induction of a positive electric field of 1.0V, and the oxygen-containing group HCrO 4 - With protonated NH 3 + The combined effect of chemical binding and electric field attraction is greater than that of other simple (oxygen-free) anionsAdsorption, thus other anions are bound to the target ion HCrO 4 - Less interference. Negative 0.9V negative field induction avoids the interference of anions and contains oxygen groups Cr (OH) 2+ With deprotonated COO - The combined effect of chemical binding and electric field attraction is greater than that of other simple (oxygen-free) cations, so that the other cations are attracted to the target ion Cr (OH) 2+ Less interference.
FIG. 8 shows the optimization of DFT configuration and adsorption energy, as can be seen, NH at applied field of 1V 3 + -Co 3 O 4 rGO vs HCrO 4 - The adsorption energy of (C) is larger than that of Cr (OH) 2+ Is a natural gas; when the applied electric field is minus 0.9V, COO - -Co 3 O 4 rGO vs. Cr (OH) 2+ Is greater than the adsorption energy of HCrO 4 - Is a high-pressure gas. Protonated NH in the presence of two different forms of chromium ions 3 + -Co 3 O 4 PerGO tends to adsorb HCrO under positive electric field 4 - And interact with, deprotonated COO - -Co 3 O 4 rGO tends to adsorb Cr (OH) under negative electric field 2+ And interact therewith. The above results illustrate the selectivity of the specific groups for two target ions.
The invention discloses a mechanism of interaction between different functional groups and different oxygen-containing groups of target ions, and discovers that the existence of the oxygen-containing groups is an important factor for realizing the specific combination of the groups so as to realize the anti-interference detection, and the oxygen-containing groups HCrO 4 - With protonated NH 3 + Is induced by a positive electric field of 1.0V, avoids the interference of cations and other anions, and contains oxygen groups Cr (OH) 2+ With deprotonated COO - And negative field induction of-0.9V, avoiding the interference of anions and other cations. In addition, the valence state circulation of Co (II)/(III) in the substrate material promotes the transfer of electrons to Cr, promotes the reduction and fixation of Cr on the electrode, and is beneficial to obtaining enhanced spectrum signals. The coordination ring of the target ion is further analyzed by combining DFT theoretical calculation and XPS characterizationIn addition, a synergistic action mechanism of electric field induction and chemical combination is provided, and the method for detecting chromium ions in different forms with high sensitivity and high selectivity is realized.
It should be noted that the foregoing technical disclosure is only for explanation and illustration to enable one skilled in the art to know the technical spirit of the present invention, and the technical disclosure is not intended to limit the scope of the present invention. The essential scope of the invention is as defined in the appended claims. Those skilled in the art should understand that any modification, equivalent substitution, improvement, etc. made based on the spirit of the present invention should fall within the spirit and scope of the present invention.
Reference is made to:
1.Aragay,G.；Pons,J.；Merkoci,A.Recent trends in macro-,micro-,and nanomaterial-based tools and strategies for heavy-metal detection.Chem.Rev.2011,111,3433-3458.
2.Gu,Y.H.；Zhao,N.J.；Ma,M.J.；Meng,D.S.；Yu,Y.；Jia,Y.；Fang,L.；Liu,J.G.；Liu,W.Q.Monitoring the heavy element of Cr in agricultural soils using a mobile laser-induced breakdown spectroscopy system with support vector machine.Chin.Phys.Lett.2016,33,085201.
3.T.-J.Jiang,M.Yang,S.-S.Li,M.-J.Ma,N.-J.Zhao,Z.Guo,J.-H.Liu,X.-J.Huang In Situ Underwater Laser-Induced Breakdown Spectroscopy Analysis for Trace Cr(VI)in Aqueous Solution Supported by Electrosorption Enrichment and a Gas-Assisted Localized Liquid Discharge Apparatus.Anal.Chem.2017,89,10,5557–5564。
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Claims (4)
1. a method for detecting different chromium ion forms based on group interaction, comprising the following steps:
(1) Taking 8-12mg Co 3 O 4 -rGO is dissolved in 25-35mL ethanol and 1-3mL deionized water, 2-6mL ammonia and 200-300 μl APTMS are added, and after sonication of 2-4h, 6-8h is shaken at 200rpm at room temperature; washing with ethanol and water for several times to obtain NH 2 -Co 3 O 4 /rGO；
(2) When COOHGO is used for replacing APTMS, COOH-Co is obtained 3 O 4 rGO; specific: taking 8-12mg Co 3 O 4 rGO is dissolved in 25-35mL ethanol and 1-3mL deionized water, 200-300 mu L COOHGO is added, and after ultrasonic treatment of 2-4h, the solution is oscillated at 200rpm at room temperature for 6-8h; washing with ethanol and water for several times to obtain COOH-Co 3 O 4 /rGO；
(3) By NH 2 -Co 3 O 4 Modification of electrode/rGO, application of positive voltage to chromium-containing solution HCrO with ph=4-5 4 - Detecting; by COOH-Co 3 O 4 Modification of electrode/rGO, application of negative voltage to chromium-containing solution Cr (OH) at ph=4-5 2+ And (5) detecting.
2. The method of claim 1, wherein the positive voltage is applied at 0.5-2V and the negative voltage is applied at-0.5-2V.
3. The method of claim 1, wherein the electrode is a rotating electrode.
4. The method of claim 1, wherein step (3) employs NH 2 -Co 3 O 4 Modification of electrode/rGO, application of positive voltage 1V to chromium-containing solution HCrO with ph=4-5 4 - Detecting; by COOH-Co 3 O 4 Modification of electrode/rGO, application of negative voltage 0.9V to chromium-containing solution Cr (OH) with pH=4-5 2+ And (5) detecting.
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