CN113149141B - Graphite-phase carbon nitride modified lead dioxide electrode and preparation method and application thereof - Google Patents
Graphite-phase carbon nitride modified lead dioxide electrode and preparation method and application thereof Download PDFInfo
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Abstract
The application discloses a graphite phase carbon nitride modified lead dioxide electrode and a preparation method and application thereof. The graphite-phase carbon nitride modified lead dioxide electrode sequentially comprises a substrate, a metal oxide bottom layer and alpha-PbO from inside to outside 2 Intermediate layer and modified beta-PbO 2 An active layer; wherein, in the modified beta-PbO 2 The active layer comprises beta-PbO modified by graphite-phase carbon nitride 2 。
Description
Technical Field
The application relates to a graphite phase carbon nitride modified lead dioxide electrode and a preparation method and application thereof, belonging to the technical field of lead dioxide electrodes.
Background
With the increasing environmental protection law in recent years, the national requirements for sewage discharge are also more and more strict. The electrocatalytic oxidation technology is an advanced oxidation technology for water treatment with great application prospect, has the advantages of simple operation, no secondary pollution and capability of mineralizing nonbiodegradable organic matters, and becomes a research hotspot of the water treatment technology. The core of electrocatalytic oxidation technology lies in the anode material, and therefore, many researchers have been working on the development of highly catalytically active and stable electrode materials in recent years. Lead dioxide electrodes are researched mostly, and have the advantages of good conductivity, strong oxidation capacity, high oxygen evolution potential, simple preparation method and the like, but lead dioxide can generate a delamination problem in the use process, so that the service life of the lead dioxide electrodes is greatly reduced.
Therefore, in recent years, many researchers have been devoted to the modification of the catalytic activity and stability of the lead dioxide electrode. For example, the patent CN 105110425a provides a method for preparing a carbon nanotube modified three-dimensional porous titanium matrix lead dioxide electrode, and the prepared lead dioxide electrode has the advantages of strong hydrophobicity on the surface of the carbon nanotube, unique electrocatalytic performance, huge specific surface area, long service life and the like; patent CN 106315772A provides a nitrogen-doped lead dioxide electrode and a preparation method thereof, the electrode prepared by the method has the characteristics of low manufacturing cost, high activity, long service life and the like, and has very wide market development prospect in the application of treating 4-CP in wastewater by electrocatalysis; xiaoyue Duan et al (Xiaoyue Duan, fang Ma, zhongxin Yuan, et al, lauryl benzene sulfonic acid sodium-carbon nanotube-modified PbO) 2 The electrode for the degradation of 4-chlorophenol, electrochimica acta.76 (2012) 333-343) utilizes the carbon nano tube and sodium dodecyl benzene sulfonate to modify lead dioxide, thereby increasing the oxygen evolution potential and the surface active charge amount of the electrode, showing better 4-chlorophenol degradation effect and longer service life. Therefore, the lead dioxide electrode can be doped and modified properly to increase the organic matter degrading capacity and the service life of the lead dioxide electrode to a certain extent.
However, in the prior art, the doping amount of doping modification on the lead dioxide electrode is low, and the modification improvement effect is not obvious.
Disclosure of Invention
According to one aspect of the present application, there is provided a graphite-phase carbon nitride modified lead dioxide electrode having high electrocatalytic oxidation activity and a long service life.
The graphite-phase carbon nitride modified lead dioxide electrode sequentially comprises a substrate, a metal oxide bottom layer and alpha-PbO from inside to outside 2 Intermediate layer and modified beta-PbO 2 An active layer;
wherein, in the modified beta-PbO 2 The active layer comprises beta-PbO modified by graphite-phase carbon nitride 2 I.e. graphite phase carbon nitride is doped into beta-PbO in a similar manner 2 In the active layer.
Specifically, in the present application, the substrate may be any one of a titanium substrate, a nickel substrate, and a stainless steel substrate.
The substrate may be plate-shaped or mesh-shaped.
The metal oxide underlayer may be any one of a tin-antimony oxide underlayer, a ruthenium-iridium oxide underlayer, a ruthenium-titanium oxide underlayer, a ruthenium-tantalum oxide underlayer, and an iridium-tantalum oxide underlayer.
Optionally, in the modification of beta-PbO 2 In the active layer, the content of the graphite phase carbon nitride is 0.5-10 wt%.
According to another aspect of the present application, there is also provided a method for preparing a graphite phase carbon nitride modified lead dioxide electrode, the method comprising the steps of:
s100, preparing a metal oxide bottom layer on the surface of a substrate;
s200, preparing alpha-PbO on the metal oxide bottom layer 2 An intermediate layer;
s300 in the alpha-PbO 2 Preparation of modified beta-PbO on intermediate layer 2 And obtaining the lead dioxide electrode through the active layer.
Optionally, a pretreatment of the substrate is further included before S100.
The pretreatment of the substrate comprises: putting the substrate into a solution containing acetone and NaOH, performing ultrasonic treatment, etching in an oxalic acid solution at a high temperature, cleaning, and storing in an oxalic acid storage solution for later use. The pretreatment of the substrate can increase the electrodeposition area and increase the bonding force between the substrate and the active layer.
The following describes the treatment of a titanium substrate as an example:
pretreating a titanium substrate, wherein the titanium substrate can be a titanium plate or a titanium net, and sequentially polishing the processed titanium substrate by using abrasive paper with different meshes and washing the polished titanium substrate by using deionized water; putting the ground titanium substrate into acetone and 0.5mol L -1 Carrying out ultrasonic treatment on NaOH (v/v = 1:1-1:5) solution for 30-60 min, and then carrying out ultrasonic treatment in deionized water for 30-60 min; then the titanium matrix is placed in 10-30% (mass fraction) oxalic acid etching solution at 70-90 ℃ for etching for 1-5 h, then a large amount of deionized water is used for cleaning the etched titanium matrix, and then the titanium matrix is placed in 0.5-2% (mass fraction) oxalic acid preserving solution for preservation for later use.
Alternatively, in step S100, a metal oxide underlayer is prepared on the surface of the substrate.
The metal oxide underlayer contains at least two metal elements, such as tin and antimony.
Preparing a metal oxide bottom layer: coating the coating liquid containing the metallic element salt compound on a substrate, drying and roasting to obtain a metallic oxide bottom layer.
The preparation steps of the metal oxide bottom layer can be repeated for 9 to 15 times.
The following describes a specific method for preparing the metal oxide underlayer: dissolving a metal element salt compound in a mixed solution of concentrated hydrochloric acid and isopropanol to prepare a coating solution, uniformly coating the coating solution on the surface of the treated titanium matrix, drying the titanium matrix in an oven at 100-140 ℃ for 10-20 min, then placing the dried titanium matrix in a muffle furnace at 500-700 ℃ for roasting for 10-20 min, repeating the steps for 9-15 times, roasting the titanium matrix in the muffle furnace for 1-2 hours for the last time, and naturally cooling to room temperature.
Optionally, in step S200, α -PbO is prepared on the metal oxide underlayer 2 An intermediate layer.
Preparation of alpha-PbO 2 An intermediate layer:
specific α -PbO is described below 2 The preparation method of the intermediate layer comprises the following steps: taking a substrate with a metal oxide bottom layer as an anode, using a proper cathode in a matching way, and carrying out electrodeposition in an alkaline plating solution to obtain the alpha-PbO 2 An intermediate layer.
The matrix with the metal oxide bottom layer is used as an anode, a copper plate with the same area is used as a cathode, the distance between the electrodes is 1 cm-3 cm, and the current density of electrodeposition is 5mA/cm 2 ～30mA/cm 2 At the temperature of 50-90 ℃ for 15-120 min, and electrodepositing alpha-PbO in alkaline plating solution 2 And cleaning the surface of the electrode by deionized water after the electrodeposition is finished.
The graphite phase carbon nitride in the present application may be purchased or prepared.
The following describes a method for preparing graphite-phase carbon nitride:
the urea or the melamine is placed in a muffle furnace to be roasted to 500-700 ℃ to obtain the urea or the melamine, the roasting time is 0.5-3 h, and the heating rate is 1-10 ℃/min.
Optionally, in said step S300, in a bath containing graphite phase carbon nitride and a lead sourceCarrying out electrodeposition under the condition of acid fluorine, thus obtaining the modified beta-PbO containing graphite phase carbon nitride 2 And an active layer.
Optionally, the lead source comprises at least one of lead nitrate, lead sulfate, lead acetate, lead chloride, and lead phosphate.
Optionally, the electrodeposition conditions are: the electrode distance is 1 cm-3 cm; the current density of electrodeposition is 15mA/cm 2 ～75mA/cm 2 (ii) a The deposition temperature is 45-90 ℃; the deposition time is 15 min-120 min.
Specifically, the upper limit of the electrode spacing is independently selected from 2cm, 3cm; the lower limit of the electrode spacing is independently selected from 1cm, 2cm.
The upper limit of the current density of electrodeposition is independently selected from 35mA/cm 2 、75mA/cm 2 (ii) a The lower limit of the current density of electrodeposition is independently selected from 15mA/cm 2 、35mA/cm 2 。
The upper limit of the deposition temperature is independently selected from 85 ℃, 90 ℃; the lower limit of the deposition temperature is independently selected from 45 ℃ and 85 ℃.
The upper limit of the deposition time is independently selected from 45min, 90min, 120min; the lower limit of the deposition time is independently selected from 15min, 45min, 90min.
Optionally, in the step S300, performing electrodeposition in a plating solution containing graphite-phase carbon nitride, a lead source, an acid source, and a fluorine source to obtain β -PbO of the graphite-phase carbon nitride 2 An active layer;
wherein the acid source comprises any one of nitric acid, sulfuric acid, hydrochloric acid, hydrofluoric acid and phosphoric acid;
the fluorine source comprises any one of sodium fluoride, potassium fluoride, calcium fluoride, hydrofluoric acid, magnesium fluoride and aluminum fluoride.
Optionally, in the plating solution, the content of the lead source is 0.35mol/L to 1mol/L; the content of the acid source is 0.1 mol/L-0.6 mol/L; the content of the fluorine source is 0.02 mol/L-0.04 mol/L; the content of the graphite phase carbon nitride is 1 g/L-10 g/L.
Optionally, the plating solution contains a surfactant. The surfactant is added, so that the effects of improving the uniformity of the plating layer and the doping amount of the carbon nitride are achieved.
Preferably, the surfactant comprises at least one of a cationic surfactant and an anionic surfactant;
preferably, the content of the surfactant in the plating solution is 0.1 g/L-2 g/L.
The invention discloses a preparation method of a graphite-phase carbon nitride modified lead dioxide electrode, which comprises the steps of taking titanium as a substrate, carrying out surface pretreatment on the titanium substrate, preparing a tin-antimony oxide bottom layer on the titanium substrate through thermal deposition, then preparing an alpha-PbO 2 intermediate layer on the titanium substrate containing the tin-antimony oxide bottom layer through electrodeposition, and finally preparing a graphite-phase carbon nitride-containing beta-PbO 2 active layer on the alpha-PbO 2 intermediate layer through electrodeposition. Compared with an unmodified electrode, the electrode has higher active surface area and active sites, and is an anode material with development potential and suitable for degrading organic pollutants in wastewater.
The graphite-phase carbon nitride modified lead dioxide electrode provided by the application enables the conversion rate of organic matters to reach 100%; the total organic carbon removal rate is more than 86%;
more preferably, the total organic carbon removal rate is 90% or more.
According to another aspect of the application, a method for degrading organic wastewater is also provided, the graphite phase carbon nitride modified lead dioxide electrode is obtained by using any one of the graphite phase carbon nitride modified lead dioxide electrodes or any one of the preparation methods, and organic wastewater is degraded by catalytic wet electrooxidation.
Optionally, the conditions for degrading the organic wastewater by catalytic wet electro-oxidation are as follows: the temperature is 180-280 ℃; the pressure is 3.5-8 Mpa; the flow rate of the oxygen source is 10-80 ml/min; the current density is 5-50 mA/cm 2 。
Optionally, the organic wastewater contains phenol, acetic acid, methyl orange, bisphenol-A, isophorone, acrylic acid, etc.
In this application, graphite phase carbon nitride (g-C) 3 N 4 ) Is a non-metal layered material, and its special electronic structure makes it exhibit unique performance, at the same time it possesses good thermal stability and chemical stability, and its basic structure is simpleThe element comprising a triazine ring (C) 3 N 3 ) And tri-S-triazine ring (C) 6 N 7 ) Wherein carbon and nitrogen atoms are combined in a gap arrangement manner, and the structural units are mutually connected and continuously extended by taking the nitrogen atoms as nodes to form a planar structure with infinite extension, g-C 3 N 4 The nano material has the characteristics of pressure resistance and wear resistance, and the nano material is introduced into the surface of the material, so that the durability of the material can be enhanced, and the service life of the material can be prolonged, therefore, the g-C is proposed 3 N 4 The lead oxide is introduced into an active layer of a lead dioxide electrode to improve the electrocatalytic oxidation activity of the electrode and the service life of the electrode, and is firstly applied to a catalytic wet-type electrooxidation technology.
The beneficial effect that this application can produce includes:
1) The utility model provides a graphite phase carbon nitride modified lead dioxide electrode, wherein tin antimony oxide bottom can effectively prevent to degrade the oxygen of the new ecology that the organic matter in-process produced and permeate through lead dioxide active layer and titanium substrate reaction, avoids making its passivation, has increased the life of electrode to a certain extent.
2) The application provides a graphite phase carbon nitride modified lead dioxide capacitor, wherein the graphite phase carbon nitride is introduced with beta-PbO 2 The active layer obviously improves the stability of the electrode and prolongs the service life of the electrode.
3) According to the graphite-phase carbon nitride modified lead dioxide electrode provided by the application, the graphite-phase carbon nitride is introduced into the beta-PbO 2 active layer, so that active sites on the surface of the electrode are increased, and the capacity of the electrode for degrading organic matters is increased.
Drawings
FIG. 1 shows g-C in the present application 3 N 4 Two possible basic building block diagrams: triazine ring and tris-S-triazine ring.
FIG. 2 shows g-C in one embodiment of the present application 3 N 4 Modified cyclic voltammogram
FIG. 3 shows g-C in one embodiment of the present application 3 N 4 And an electron microscope image of the lead dioxide modified by the anionic surfactant.
Detailed Description
The present application will be described in detail with reference to examples, but the present application is not limited to these examples.
The object of the present invention is achieved by a graphite-phase carbon nitride-modified lead dioxide electrode comprising:
a titanium substrate;
a bottom layer of tin antimony oxide thermally deposited on the titanium substrate;
alpha-PbO electrodeposited on tin antimony oxide underlayer 2 An intermediate layer;
preparing graphite phase carbon nitride;
is electrodeposited on alpha-PbO 2 Graphite phase carbon nitride modified beta-PbO on intermediate layer 2 And an active layer.
The preparation method of the graphite phase carbon nitride modified lead dioxide electrode comprises the following steps:
(1) the method comprises the following steps of (1) pretreating a titanium substrate, wherein the titanium substrate can be a titanium plate or a titanium net, grinding the cut titanium substrate by abrasive paper with different meshes in sequence, and washing the ground titanium substrate by deionized water; putting the ground titanium substrate into acetone and 0.5mol L -1 Carrying out ultrasonic treatment on NaOH (v/v = 1:1-1:5) for 30-60 min, and then carrying out ultrasonic treatment in deionized water for 30-60 min; then placing the titanium substrate in 10-30% (mass fraction) oxalic acid etching solution at 70-90 ℃ for etching for 1-5 h, then washing the etched titanium substrate with a large amount of deionized water, and then placing the titanium substrate in 0.5-2% (mass fraction) oxalic acid preserving solution for preservation for later use;
(2) preparing a tin antimony oxide bottom layer, dissolving tin tetrachloride and antimony trichloride in a mixed solution of concentrated hydrochloric acid and isopropanol to prepare a coating solution, uniformly coating the coating solution on the surface of the treated titanium matrix, drying the titanium matrix in an oven at 100-140 ℃ for 10-20 min, then placing the dried titanium matrix in a muffle furnace at 500-700 ℃ for roasting for 10-20 min, repeating the steps for 9-15 times, wherein the roasting time in the muffle furnace for the last time is 1-2 hours, and naturally cooling to room temperature;
③、α-PbO 2 preparing a middle layer, namely taking a titanium substrate with a tin-antimony oxide bottom layer as an anode, taking a copper plate with equal area as a cathode, wherein the electrode distance is 1-3 cm, and performing electro-depositionThe integrated current density is 5mA/cm 2 ～30mA/cm 2 At the temperature of 50-90 ℃ for 15-120 min, and electrodepositing alpha-PbO in alkaline plating solution 2 The middle layer is used for cleaning the surface of the electrode by using deionized water after the electrodeposition is finished;
(4) preparing graphite phase carbon nitride, namely putting urea, melamine and the like into a muffle furnace to roast to 500-700 ℃, wherein the roasting time is 0.5-3 h, and the heating rate is 1-10 ℃/min;
(5) graphite phase carbon nitride modified beta-PbO 2 Preparation of active layer, which will carry alpha-PbO 2 The titanium substrate of the middle layer is taken as an anode, the copper plate with the same area is taken as a cathode, the electrode distance is 1 cm-3 cm, and the current density of electrodeposition is 15mA/cm 2 ～75mA/cm 2 Depositing at 45-85 deg.c for 15-120 min, and electrodepositing modified beta-PbO in acid fluoric lead nitrate solution 2 And cleaning the lead dioxide electrode by using deionized water after the deposition of the active layer is finished.
Optionally, the coating solution in the step (2) is prepared from stannic chloride and antimony trichloride in a mass ratio of 5:1-20.
Optionally, the alkaline plating solution in the step (3) is prepared by adding lead oxide and sodium hydroxide into deionized water, and ultrasonically vibrating for 10min to 30min until the lead oxide and the sodium hydroxide are completely dissolved and uniformly mixed, wherein the solution comprises the following components in percentage by weight: 0.1 mol/L-0.6 mol/L of lead oxide and 0.05 mol/L-0.5 mol/L of sodium hydroxide.
Optionally, the acidic fluorine-containing lead nitrate plating solution in step (5) is prepared by dissolving lead nitrate, nitric acid and sodium fluoride in deionized water, and ultrasonically vibrating for 10min to 30min until the lead nitrate, the nitric acid and the sodium fluoride are completely dissolved and uniformly mixed, wherein the solution contains the following components in percentage by weight: 0.35-1 mol/L of lead nitrate, 0.1-0.6 mol/L of nitric acid, 0.02-0.04 mol/L of sodium fluoride and 1-10 g/L of carbon nitride.
Preferably, a small amount of surfactant may be added to the acidic fluorine-containing lead nitrate plating solution.
In the examples, the organic matter degrading performance of the samples was measured by using an Shimadzu total organic carbon analyzer.
In the examples, the conversion of organic substances was measured by HPLC-P1201 type high performance liquid chromatography.
Organic conversion = (C) 0 -C t )/C 0 ×100％
C 0 Is the initial organic concentration, C t Initial organic matter concentration at time t
Total organic carbon removal = (TOC) 0 -TOC t )/TOC 0 ×100％
TOC 0 As initial total organic carbon, TOC t Is the total organic carbon at the time t,
in this application, the total organic carbon includes at least one of phenol, acetic acid, methyl orange, bisphenol-a, isophorone, acrylic acid.
Comparative example
For ease of comparison with the products of the invention, unmodified lead dioxide electrodes are also provided as comparative examples.
The specific preparation method of the electrode comprises the following steps:
pretreating a titanium substrate, namely sequentially polishing abrasive paper with different meshes on the cut titanium substrate (3 cm by 4 cm), and cleaning with deionized water; putting the ground titanium mesh into acetone and 0.5mol L -1 Carrying out ultrasonic treatment in NaOH (v/v = 1:3) for 30min, and then placing in deionized water for ultrasonic treatment for 30min; then placing the titanium substrate in 20 percent (mass fraction) oxalic acid etching solution at 90 ℃ for etching for 1h, then washing the etched titanium substrate with a large amount of deionized water, and then placing the titanium substrate in 0.5 percent (mass fraction) oxalic acid preserving solution for preservation for later use;
preparing a tin-antimony oxide bottom layer, namely dissolving 20g of tin tetrachloride and 1g of antimony trichloride (the mass ratio is 20;
(tri) alpha-PbO 2 Preparing an intermediate layer, namely taking a titanium substrate with a tin-antimony oxide bottom layer as an anode, taking a copper plate with equal area as a cathode, wherein the distance between the electrodes is 1cm, and performing electro-depositionThe integrated current density is 15mA/cm 2 At the temperature of 90 ℃ for 30min, the plating solution contains the following components: 0.6mol/L lead oxide and 0.1mol/L sodium hydroxide, and cleaning the surface of the electrode by deionized water after the electrodeposition is finished;
(tetra) beta-PbO 2 Preparation of active layer, which will carry alpha-PbO 2 The titanium substrate of the middle layer is used as an anode, the copper plate with the same area is used as a cathode, the distance between the electrodes is 1cm, and the current density of electrodeposition is 75mA/cm 2 The deposition temperature is 85 ℃, the deposition time is 45min, and the contents of all components in the plating solution are as follows: 0.35mol/L of lead nitrate, 0.1mol/L of nitric acid and 0.04mol/L of sodium fluoride, and after the deposition is finished, the lead dioxide electrode is cleaned by deionized water.
Example 1
Pretreating a titanium substrate, namely sequentially polishing sand paper (specifically, 240#,600#,1200 #) with different mesh numbers on the cut titanium substrate (3 cm × 4 cm), and cleaning with deionized water; putting the ground titanium mesh into acetone and 0.5mol L -1 Carrying out ultrasonic treatment in NaOH (v/v = 1:3) for 30min, and then placing in deionized water for ultrasonic treatment for 30min; then, the titanium substrate is placed in 20 percent (mass fraction) oxalic acid etching solution at the temperature of 90 ℃ for etching for 1 hour, then a large amount of deionized water is used for cleaning the etched titanium substrate, and then the titanium substrate is placed in 0.5 percent (mass fraction) oxalic acid preserving solution for preservation for standby;
preparing a tin-antimony oxide bottom layer, namely dissolving 20g of tin tetrachloride and 1g of antimony trichloride (mass ratio is 20;
(tri) alpha-PbO 2 Preparing an intermediate layer, namely taking a titanium substrate with a tin-antimony oxide bottom layer as an anode, taking a copper plate with equal area as a cathode, wherein the distance between the electrodes is 1cm, and the current density of electrodeposition is 15mA/cm 2 At the temperature of 90 ℃ for 30min, and the contents of the components in the plating solution are as follows: lead oxide 0.6mol/L and sodium hydroxide 0.1mol/L, and deionized water is used for reaction after the electrodeposition is finishedCleaning the surface of the electrode;
fourthly, preparing graphite-phase carbon nitride, namely placing melamine in a muffle furnace to roast the melamine to 550 ℃, wherein the roasting time is 2 hours, and the heating rate is 2 ℃/min, so as to obtain the graphite-phase carbon nitride;
(V) beta-PbO 2 Preparation of active layer, which will carry alpha-PbO 2 The titanium substrate of the middle layer is used as an anode, the copper plate with the same area is used as a cathode, the distance between the electrodes is 1cm, and the current density of electrodeposition is 75mA/cm 2 The deposition temperature is 85 ℃, the deposition time is 45min, and the contents of all components in the plating solution are as follows: 0.35mol/L of lead nitrate, 0.1mol/L of nitric acid, 0.04mol/L of sodium fluoride and 1g/L of graphite-phase carbon nitride, and cleaning the lead dioxide electrode by using deionized water after the deposition is finished to obtain the graphite-phase carbon nitride modified lead dioxide electrode which is recorded as sample No. 1.
In sample # 1, the modification of beta-PbO was performed 2 The content of graphite-phase carbon nitride in the active layer was 1 wt.% (tested by XRF.)
Taking the prepared modified electrode sample No. 1 as an anode, a titanium mesh with the same area as the anode and two electrodes which are opposite in parallel, carrying out a catalytic wet electrocatalytic oxidation degradation experiment on 300mL of wastewater with the concentration of the isophorone of 10000ppm, adding 308g of sodium sulfate (the concentration is 0.2 mol/L) as an electrolyte, wherein the electrode distance is 6cm, the temperature is 250 ℃, the pressure is 6.5MPa, the oxygen flow is 30mL/min, and the current density is 50mA/cm 2 The conversion rate of isophorone can reach 100% in two hours, and the total organic carbon removal rate is 89%, which is higher than that of unmodified electrode 71%.
Example 2
Pretreating a titanium substrate, namely sequentially polishing (240 #,600#,1200 #) the cut titanium substrate (3 cm × 4 cm) by using abrasive paper with different meshes, and cleaning by using deionized water; putting the ground titanium mesh into acetone and 0.5mol L -1 Carrying out ultrasonic treatment in NaOH (v/v = 1:3) for 30min, and then placing in deionized water for ultrasonic treatment for 30min; then placing the titanium substrate in 20 percent (mass fraction) oxalic acid etching solution at 90 ℃ for etching for 1h, then washing the etched titanium substrate with a large amount of deionized water, and then placing the titanium substrate in 0.5 percent (mass fraction) oxalic acid preserving solution for preservation for later use;
preparing a tin-antimony oxide bottom layer, namely dissolving 30g of tin tetrachloride and 1.5g of antimony trichloride (mass ratio is 20;
(tri) alpha-PbO 2 Preparing an intermediate layer, namely taking a titanium substrate with a tin-antimony oxide bottom layer as an anode, taking a copper plate with equal area as a cathode, wherein the distance between the electrodes is 1cm, and the current density of electrodeposition is 15mA/cm 2 At the temperature of 90 ℃ for 30min, and the contents of the components in the plating solution are as follows: lead oxide 0.6mol/L, sodium hydroxide 0.1mol/L, after the electrodeposition, the deionized water is used for cleaning the surface of the electrode;
fourthly, preparing graphite-phase carbon nitride, namely placing melamine in a muffle furnace to roast the melamine to 550 ℃, wherein the roasting time is 2 hours, and the heating rate is 2 ℃/min, so as to obtain the graphite-phase carbon nitride;
(V) beta-PbO 2 Preparation of active layer, which will carry alpha-PbO 2 The titanium substrate of the middle layer is used as an anode, the copper plate with the same area is used as a cathode, the distance between the electrodes is 2cm, and the current density of electrodeposition is 35mA/cm 2 The deposition temperature is 90 ℃, the deposition time is 90min, and the contents of all components in the plating solution are as follows: 0.35mol/L of lead chloride, 0.1mol/L of hydrochloric acid, 0.04mol/L of hydrofluoric acid, 3g/L of graphite-phase carbon nitride and 1g/L of active surfactant LAS, and after the deposition is finished, the lead dioxide electrode is cleaned by deionized water to obtain the graphite-phase carbon nitride modified lead dioxide electrode which is recorded as sample No. 2.
In sample 2#, the modification of beta-PbO was performed 2 In the active layer, the content of graphite phase carbon nitride was 6.3wt%.
Taking the prepared modified electrode sample No. 2 as an anode, a titanium mesh with the same area as the anode and two electrodes which are opposite in parallel, carrying out a catalytic wet electrocatalytic oxidation degradation experiment on 300ml of wastewater with the concentration of isophorone of 10000ppm, adding 308g of sodium sulfate 0.2mol/L, the distance between the electrodes is 6cm, the temperature is 250 ℃, the pressure is 6.5Mpa, the oxygen flow is 20ml/min, and the current density is 50mA/cm 2 The conversion rate of the isophorone can reach 100% in two hours, and the total organic carbon removal rate is 96%, which is higher than that of an unmodified electrode by 71%.
Example 3
Degrading wastewater with acrylic acid concentration of 50000ppm, selecting a lead dioxide electrode modified in example 2 as an anode, namely sample No. 2, selecting a titanium plate as a cathode, selecting a double-cathode double-anode cathode ring-shaped internal cathode ring-shaped external arrangement mode, adding a catalyst into the whole reaction device and the electrode at the lower end of the reaction device, adding the catalyst into irregular active carbon, adding 300g of 10wt% sodium sulfate as electrolyte, controlling the oxygen flow to be 40mL/min, the temperature to be 260 ℃, the pressure to be 7MPa, and controlling the current density to be 20mA/cm 2 The retention time is 1.5h, and the measured total organic carbon removal rate of the effluent can reach 94.5 percent.
Example 4
Pretreating a titanium substrate, namely sequentially polishing abrasive paper with different meshes on the cut titanium substrate (3 cm by 4 cm), and cleaning with deionized water; putting the ground titanium mesh into acetone and 0.5mol L -1 Carrying out ultrasonic treatment in NaOH (v/v = 1:3) for 30min, and then placing in deionized water for ultrasonic treatment for 30min; then placing the titanium substrate in 20 percent (mass fraction) oxalic acid etching solution at 90 ℃ for etching for 1h, then washing the etched titanium substrate with a large amount of deionized water, and then placing the titanium substrate in 0.5 percent (mass fraction) oxalic acid preserving solution for preservation for later use;
preparing a tin antimony oxide bottom layer, namely dissolving 20g of tin tetrachloride and 1g of antimony trichloride (mass ratio is 20;
(tri) alpha-PbO 2 Preparing an intermediate layer, namely taking a titanium substrate with a tin-antimony oxide bottom layer as an anode, taking a copper plate with equal area as a cathode, wherein the distance between the electrodes is 1cm, and the current density of electrodeposition is 30mA/cm 2 At 85 deg.C for 60min, and plating in bathThe content of each component is as follows: 0.6mol/L lead oxide and 0.1mol/L sodium hydroxide, and cleaning the surface of the electrode by deionized water after the electrodeposition is finished;
fourthly, preparing graphite-phase carbon nitride, namely putting urea into a muffle furnace to be roasted to 500 ℃, roasting for 2 hours, and heating at the rate of 1 ℃/min to obtain the graphite-phase carbon nitride;
(V) beta-PbO 2 Preparation of active layer, which will carry alpha-PbO 2 The titanium substrate of the middle layer is used as an anode, the copper plate with the same area is used as a cathode, the distance between the electrodes is 1cm, and the current density of electrodeposition is 75mA/cm 2 The deposition temperature is 85 ℃, the deposition time is 45min, and the contents of all components in the plating solution are as follows: 0.5mol/L of lead phosphate, 0.1mol/L of phosphoric acid, 0.02mol/L of magnesium fluoride, 2g/L of graphite-phase carbon nitride and 1g/L of active surfactant CTAB, and after the deposition is finished, the lead dioxide electrode is cleaned by deionized water to obtain the graphite-phase carbon nitride modified lead dioxide electrode which is marked as a sample No. 3.
In sample # 3, the modification of beta-PbO was performed 2 In the active layer, the content of graphite phase carbon nitride was 4.7wt%.
Selecting the prepared modified electrode as an anode, selecting a ruthenium-titanium electrode as a cathode, selecting a cathode and an anode, arranging the electrodes coaxially in a ring shape, arranging the anode inside and the cathode outside, adding a catalyst in the whole reaction device, arranging the electrode at the lower end of the reaction device, adding a catalyst which is irregular activated carbon, adding 300g of a 1wt% sodium chloride aqueous solution as an electrolyte, controlling the electrode spacing to be 6cm, controlling the oxygen flow to be 50mL/min, controlling the temperature to be 260 ℃, controlling the pressure to be 6.5Mpa, and controlling the current density to be 30mA/cm 2 The retention time is 2 hours, and the measured total organic carbon removal rate of the effluent can reach 86.7 percent.
Example 5
And respectively carrying out cyclic voltammetry characteristic tests on the sample 1# electrode, the sample 3# electrode and the comparative example, wherein the test instrument is an electrochemical workstation (CHI 630 Shanghai Chenghua), and the test conditions are that the scanning speed is 50mV/s and the room temperature is adopted.
The test results are shown in FIG. 2, from which it can be seen that the doping C is 3 N 4 The latter electrode has a larger active surface area, meaning that the modified electrode has a larger active surface areaA plurality of electrochemically active sites.
Example 6
And respectively carrying out scanning electron microscope testing on the electrode 1# and the electrode 3# of the sample, wherein the instrument is a scanning electron microscope. Test results show that samples 1# to 3# all show uniform particle size;
taking sample 2# as a typical representative, and fig. 3 is a scanning electron micrograph of sample 2#, it can be seen from the micrograph that the electrode particles are uniform in size and uniform in particle size, and exhibit a good "pyramid" morphology.
Although the present application has been described with reference to a few embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims.
Claims (11)
1. A method for degrading organic wastewater is characterized in that a lead dioxide electrode modified by graphite-phase carbon nitride is used for catalyzing wet electrooxidation to degrade the organic wastewater;
the conditions for degrading the organic wastewater by catalytic wet electrooxidation are as follows: the temperature is 180 to 280 ℃; the pressure is 3.5 to 8Mpa; the flow rate of an oxygen source is 10 to 80ml/min; the current density is 5 to 50mA/cm 2 ；
The lead dioxide electrode comprises a substrate, a metal oxide bottom layer and alpha-PbO from inside to outside in sequence 2 Intermediate layer and modified beta-PbO 2 An active layer;
wherein in the modified beta-PbO 2 The active layer comprises beta-PbO modified by graphite-phase carbon nitride 2 。
2. The method of claim 1, wherein the modified β -PbO is modified by a reaction of beta-PbO with a base 2 In the active layer, the content of the graphite-phase carbon nitride is 0.5-10wt%.
3. The method according to claim 1, wherein the lead dioxide electrode preparation method comprises the following steps:
s100, preparing a metal oxide bottom layer on the surface of a substrate;
s200, preparing alpha-PbO on the metal oxide bottom layer 2 An intermediate layer;
s300 in the alpha-PbO 2 Preparation of modified beta-PbO on intermediate layer 2 And obtaining the lead dioxide electrode through the active layer.
4. The method according to claim 3, wherein in step S300, the graphite-phase carbon nitride-modified β -PbO is obtained by electrodepositing a plating bath containing graphite-phase carbon nitride and a lead source under acidic fluorine-containing conditions 2 An active layer.
5. The method of claim 4, wherein the lead source comprises at least one of lead nitrate, lead sulfate, lead acetate, lead chloride, lead phosphate.
6. The method according to claim 4, characterized in that the conditions of electrodeposition are: the electrode distance is 1cm to 3cm; the current density of electrodeposition is 15mA/cm 2 ~75mA/cm 2 (ii) a The deposition temperature is 45-90 ℃; the deposition time is 15min to 120min.
7. The method according to claim 4, wherein in step S300, the β -PbO of the graphite-phase carbon nitride is obtained by electrodeposition in a bath containing the graphite-phase carbon nitride, a lead source, an acid source, and a fluorine source 2 An active layer;
wherein the acid source comprises any one of nitric acid, sulfuric acid, hydrochloric acid, hydrofluoric acid and phosphoric acid;
the fluorine source comprises any one of sodium fluoride, potassium fluoride, calcium fluoride, hydrofluoric acid, magnesium fluoride and aluminum fluoride.
8. The method according to claim 7, wherein the content of the lead source in the plating solution is 0.35-1 mol/L; the content of the acid source is 0.1-0.6 mol/L; the content of the fluorine source is 0.02-0.04 mol/L; the content of the graphite-phase carbon nitride is 1 g/L-10 g/L.
9. The method of claim 7, wherein the plating solution comprises a surfactant.
10. The method of claim 9, wherein the surfactant comprises a cationic surfactant and an anionic surfactant.
11. The method according to claim 9, wherein the surfactant is contained in the plating solution in an amount of 0.1 to 2g/L.
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