CN112777693B - Modified anode and application thereof in electric flocculation treatment of electroplating wastewater - Google Patents
Modified anode and application thereof in electric flocculation treatment of electroplating wastewater Download PDFInfo
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- CN112777693B CN112777693B CN202110035768.2A CN202110035768A CN112777693B CN 112777693 B CN112777693 B CN 112777693B CN 202110035768 A CN202110035768 A CN 202110035768A CN 112777693 B CN112777693 B CN 112777693B
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
- C02F1/463—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrocoagulation
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
- C02F1/46104—Devices therefor; Their operating or servicing
- C02F1/46109—Electrodes
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
- C02F1/46104—Devices therefor; Their operating or servicing
- C02F1/46109—Electrodes
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/16—Nature of the water, waste water, sewage or sludge to be treated from metallurgical processes, i.e. from the production, refining or treatment of metals, e.g. galvanic wastes
Abstract
The invention discloses a modified anode and application thereof in electric flocculation treatment of electroplating wastewater, belonging to the field of wastewater treatment. The method for preparing the polyaniline/molybdate modified anode plate comprises the following steps: (1) preparing an electrolyte: uniformly mixing aniline and molybdate to form electrolyte; (2) placing the anode plate in electrolyte, and carrying out electropolymerization at an oxidation potential of 0.9-1.0V; and after the end, washing and drying to obtain the polyaniline/molybdate modified anode plate. Then, the obtained polyaniline/molybdate modified anode plate is used for electrocoagulation treatment, wherein the treatment conditions are that the initial pH is 4-6, the treatment time is 40-80 min, and the current density is 20-40 mA cm‑2. The removal rate of the polyaniline/molybdate modified anode plate on copper in electroplating wastewater reaches over 90 percent and can reach 99.99 percent; the chromium removal rate reaches more than 70 percent, can reach 84.24 percent, and the corrosion inhibition efficiency is 33.33 percent.
Description
Technical Field
The invention relates to a modified anode and application thereof in electric flocculation treatment of electroplating wastewater, belonging to the field of wastewater treatment.
Background
In the electroplating process, a large amount of industrial wastewater with complex components is generated, and the wastewater contains heavy metal ions such as chromium, zinc, copper and the like and toxic substances such as acid, alkali, cyanide and the like. The pollutants in the wastewater have the characteristics of complex types, difficult control, strong toxicity and the like, so the pollutants are listed as one of three kinds of pollution in the world at present. Heavy metal wastewater which cannot be effectively treated contains various toxic substances, some of which also belong to carcinogenic and distortional highly toxic substances, which can generate irreversible harm to the environment.
At present, the treatment method of electroplating wastewater mainly comprises a physical method, a chemical method, a physical-chemical method and a biological method, and various methodsAll have advantages and disadvantages. The electric flocculation technology has the advantages of simple design, low cost, less sludge generation, good removal efficiency and the like, and provides an effective and promising method for the treatment of electroplating wastewater. The principle of the electric flocculation process is as follows: in the electrolytic process, the anode loses electrons and is oxidized into corresponding metal cations, the released cations are easy to generate hydrolysis reaction in aqueous solution, and finally, the hydrolyzed ions generate various mononuclear or polynuclear hydroxyl complexes through a series of complex reactions, such as Fe (OH)2，Fe(OH)3These hydrolyzed hydroxides can remove metal ions and charged contaminants in wastewater by the action of adsorption bridges, sludge traps, and the like.
Disclosure of Invention
[ problem ] to
The consumption of plates and the cost problem associated with them are a disadvantage for the electroflocculation process. Iron or aluminum plates are generally used as sacrificial anodes in the electrocoagulation treatment, and anodes made of the materials are also generally more easily corroded in the water treatment process, and excessive release of metal ions occurs in the electrocoagulation process, so that the electrode plates are rapidly consumed and unnecessarily worn, and the service life of the electrode plates is shortened. Therefore, the protection of the electric flocculation anode plate is realized, the corrosion resistance is improved to reduce unnecessary loss, and the service life of the anode is prolonged, which becomes a direction worthy of research.
[ solution ]
In order to solve at least one problem, the invention modifies the anode by coating modification, and then applies the modified anode to the electrocoagulation to treat the electroplating wastewater, thereby realizing the protection and corrosion inhibition of the anode, reducing the irreversible corrosion in the running process of the Electrocoagulation (EC) and prolonging the service life of the steel anode. According to the invention, the conductive polymer (Pani polyaniline) is polymerized on the surface of the anode plate in an electrochemical deposition mode, so that a certain corrosion inhibition and protection effect is achieved on the anode plate under the conditions that the conductivity of the plate is not influenced and a certain water treatment efficiency is ensured, and no relevant electroflocculation research reports that a polyaniline coating is used for protecting the electrode in the anode modification process are provided.
The first purpose of the invention is to provide a method for preparing an anode plate modified by polyaniline/molybdate, which comprises the following steps:
(1) preparing an electrolyte: uniformly mixing aniline and molybdate to form electrolyte;
(2) electropolymerization: placing the anode plate in electrolyte, and carrying out electropolymerization at an oxidation potential of 0.9-1.0V; and after the end, washing and drying to obtain the polyaniline/molybdate modified anode plate.
In one embodiment of the present invention, the electropolymerization of step (2) is carried out at an oxidation potential of 0.95V.
In one embodiment of the present invention, the electropolymerization time in step (2) is related to the area of the anode plate, such as: electropolymerizing the anode plate of 1.5 × 1 × 0.1cm for 700 s.
In one embodiment of the present invention, the concentration of aniline in the electrolyte in step (1) is 0.15 to 0.30M, and more preferably 0.20M.
In one embodiment of the present invention, the concentration of molybdate in the electrolyte in step (1) is 0.01 to 0.1M, and more preferably 0.05M.
In one embodiment of the invention, the electrolyte is purged with nitrogen for 30 minutes prior to electropolymerization.
In one embodiment of the invention, the anode plate needs to be pretreated before being electropolymerized, and the pretreatment is to soak the anode plate in a hydrochloric acid solution with the mass fraction of 15% for 30 min; then washing the mixture by water; then, using 500-mesh coarse sand paper for polishing, and then using 800-mesh coarse sand paper for continuous polishing; then soaking the electrode for 10min by using a hydrochloric acid solution with the mass fraction of 10% to remove oxides on the surface of the electrode; using a mixture of 1: soaking in 1 ethanol/acetone mixed solution for degreasing; and finally, washing the anode plate by using water, and putting the anode plate into an oven for drying to obtain the pretreated anode plate.
In one embodiment of the invention, the anode plate comprises 304 stainless steel.
In one embodiment of the present invention, the electropolymerization temperature is 20 to 30 ℃ (room temperature).
The second purpose of the invention is to obtain the polyaniline/molybdate modified anode plate prepared by the method.
The third purpose of the invention is to apply the polyaniline/molybdate modified anode plate in the invention to the electric flocculation treatment of electroplating wastewater.
In one embodiment of the present invention, the application is to perform an electrocoagulation reaction by using the polyaniline/molybdate-modified anode plate of the present invention as an anode and an aluminum plate as a cathode; wherein the conditions of the electric flocculation reaction are as follows: the initial pH is 4-6, the treatment time is 40-80 min, and the current density is 20-40 mA cm-2。
In one embodiment of the present invention, the conditions of the electrocoagulation reaction in the application are as follows: initial pH of 5, treatment time of 60min, and current density of 35mA cm-2。
In one embodiment of the invention, the distance between the anode and the cathode in the application is 1-3 cm, and more preferably 2 cm.
In one embodiment of the invention, the anode is connected with a direct current power supply in a constant current mode to provide voltage and current of 0-25V and 0-8A.
In one embodiment of the invention, the cathode is connected with a DC power supply in a constant current mode in the application, and the voltage and the current of 0-25V and 0-8A are provided.
In one embodiment of the invention, the parameters of the electroplating wastewater in the application are that copper is 15.66mg/L, chromium is 7.85mg/L, pH is 3.17, conductivity is 4.39mS/cm, and chemical oxygen demand is 377.64 mg/L; wherein both the copper and the chromium exist in a complex state.
The fourth purpose of the invention is to provide a method for treating copper and chromium in electroplating wastewater by electric flocculation, which comprises the following steps:
taking the polyaniline/molybdate modified anode plate as an anode and an aluminum plate as a cathode to perform an electrocoagulation reaction; wherein the conditions of the electric flocculation reaction are as follows: initial pH value of 4-6, and treatmentThe time is 40-80 min, and the current density is 20-40 mA cm-2。
In one embodiment of the present invention, the conditions of the electrocoagulation reaction in the method are as follows: initial pH of 5, treatment time of 60min, and current density of 35mA cm-2。
[ advantageous effects ]
(1) The polyaniline/molybdate modified anode plate provided by the invention plays a certain role in corrosion inhibition and protection on the anode plate under the conditions that the conductivity of the anode plate is not influenced and a certain water treatment efficiency is ensured. The open circuit potential of the polyaniline/molybdate modified anode plate reaches-134 mV, RporeValue 17.78(Ω cm)2)，RctReach 1521.31 omega cm2The corrosion current is only 9.43 mu A cm-2The corrosion potential reaches-138 mV, and the protection efficiency reaches 97.72%.
(2) The polyaniline/molybdate modified anode plate has higher removal rate of copper and chromium in electroplating wastewater, and the removal rate of copper reaches over 90 percent and can reach 99.99 percent; the chromium removal rate reaches more than 70 percent, can reach 84.24 percent, and the corrosion inhibition efficiency is 33.33 percent.
Drawings
FIG. 1 shows SS, Pani/MoO4 2-Pani/BTA and Pani/PTS open circuit potential trends in 0.1M sulfuric acid solution.
FIG. 2 is Pani/MoO4 2-Test results of the AC impedances of Pani/BTA and Pani/PTS; where the inset shows the test results for uncoated ac impedance.
FIG. 3 is Pani/MoO4 2-Pani/BTA and Pani/PTS.
FIG. 4 is Pani/MoO4 2-Pani/BTA and Pani/PTS.
FIG. 5 is a schematic diagram of corrosion inhibition by the electrocoagulation process.
FIG. 6 shows the results of the test of 10 lots in example 6.
FIG. 7 shows Pani/MoO in example 74 2-And the Pani/BTA two-electrode plate is used for testing the chromium removal rate of 10 batchesAnd (5) fruit.
FIG. 8 shows Pani/MoO in example 74 2-And the corrosion inhibition efficiency of 10 batches of the Pani/BTA two-electrode plate is tested.
Detailed Description
The following description of the preferred embodiments of the present invention is provided for the purpose of better illustrating the invention and is not intended to limit the invention thereto.
The parameters of the plating wastewater used in the examples are shown in Table 1:
TABLE 1 parameters of electroplating wastewater
| Index of water quality | Copper (Cu) | Chromium (III) | pH | Electrical conductivity of | Chemical Oxygen Demand (COD) |
| Parameter(s) | 15.66mg L-1 | 7.85mg L-1 | 3.17 | 4.39mS cm-1 | 377.64mg L-1 |
Example 1
Preparation of polyaniline/molybdenumAcid salt (Pani/MoO)4 2-) A method of modifying an anode plate comprising the steps of:
(1) preparing an electrolyte: uniformly mixing aniline and sodium molybdate to form electrolyte; wherein the concentration of aniline is 0.20M, and the concentration of sodium molybdate is 0.05M;
(2) electropolymerization: placing the anode plate 304 stainless steel SS (1.5 multiplied by 1 multiplied by 0.1cm) in the electrolyte, and carrying out 700s of electropolymerization at the oxidation potential of 0.95V; after the reaction is finished, washing with water and drying at 50 ℃ to obtain polyaniline/sodium molybdate Pani/MoO4 2-Modified anode plate.
Comparative example 1
A method for preparing a polyaniline/benzotriazole Pani/BTA modified anode plate comprises the following steps:
(1) preparing an electrolyte: dispersing aniline and benzotriazole in water to form an electrolyte; wherein the concentration of aniline is 0.20M, and the concentration of benzotriazole is 0.05M;
(2) the same procedure as in step (2) of example 1 gave a polyaniline/benzotriazole Pani/BTA modified anode plate.
Comparative example 2
A method for preparing polyaniline/sodium p-toluenesulfonate Pani/PTS modified anode plate comprises the following steps:
(1) preparing an electrolyte: dispersing aniline and sodium p-toluenesulfonate in water to form an electrolyte; wherein the concentration of aniline is 0.20M, and the concentration of sodium p-toluenesulfonate is 0.05M;
(2) the same procedure as in step (2) of example 1 gave a polyaniline/benzotriazole Pani/BTA modified anode plate.
The anode plates obtained in example 1 and comparative examples 1 and 2 were subjected to an open circuit potential test, an EIS test, and a tafel test; the open circuit potential test comprises the following specific steps: A0.1M sulfuric acid solution is used as a test electrolyte, the test time is 1h, and an electrochemical workstation three-electrode system is used for testing (the working electrode is an anode plate (1.5 multiplied by 1 multiplied by 0.1cm) obtained in example 1 and comparative examples 1 and 2, and a platinum sheet electrode (1.5 multiplied by 0.1cm) and a saturated silver/silver chloride electrode are respectively used as a counter electrode and a reference electrode); details of EIS testingThe method comprises the following steps: using a 0.1M sulfuric acid solution as the test electrolyte, the frequency range of EIS measurements was 5mHz to 80kHz, the amplitude was 10mV, and the EIS data were fitted using ZSimp Win 3.20d fitting software (princeton application study); the tafel test comprises the following specific steps: the initial potential and the terminal potential of the Tafel test are-650 mV and 50mV respectively, and the scanning speed is 10mV s-1The electrolyte was a 0.1M sulfuric acid solution.
FIG. 1 shows SS, Pani/MoO4 2-Pani/BTA and Pani/PTS modified anode plates in 0.1M sulfuric acid solution. As can be seen from fig. 1: for bare steel SS, an initial potential of-209 mV was observed, followed by a sharp drop to a steady state of-551 mV after a short soak time. In contrast, the initial potential of all Pani coatings was 168mV (Pani/MoO), respectively4 2-) 56mV (Pani/BTA) and-57 mV (Pani/PTS), significantly larger than bare steel SS. And the final potential of the Pani coating is far higher than that of a bare steel group (-551mV), which are-134 mV (Pani/MoO) respectively4 2-) 212mV (Pani/BTA) and-267 mV (Pani/PTS). For electrochemical open circuit potential testing, a higher potential indicates better corrosion protection, so it can be seen in the figure that Pani/MoO4 2-The initial potential and the final potential of the coating are always the highest in the three coatings, and the optimal coating protection and corrosion inhibition performance is shown.
FIG. 2 and Table 2 show Pani/MoO4 2-Pani/BTA and Pani/PTS. As can be seen from fig. 2 and table 2: the impedance value (Rct) of the polyaniline-coated electrode is significantly greater than that of a bare steel electrode. Pani/MoO4 2-The impedance values of Pani/BTA and Pani/PTS reach 1521.31, 846.80 and 719.70 omega cm respectively2While the resistance of the SS group of the bare steel only reaches 83.68 omega cm2. In addition, Pani/MoO4 2-The group impedance reaches a maximum value, indicating that the corrosion resistance is optimal. At the same time, RporeTo a certain extent, the ability of the coating to resist corrosive media, Pani/MoO4 2-Exhibits the maximum RporeValue 17.78(Ω cm)2) The protective properties proved to be optimal.
TABLE 2 Pani/MoO4 2-Test results of AC impedance of Pani/BTA and Pani/PTS
FIG. 3 and Table 3 are Pani/MoO4 2-Pani/BTA and Pani/PTS. As can be seen from fig. 3 and table 3: Pani/MoO4 2-The corrosion potential of the coating is at a maximum and the corrosion current is at a minimum.
TABLE 3 Pani/MoO4 2-Tafel test results for Pani/BTA and Pani/PTS
| Index (I) | SS | Pani/MoO4 2- | Pani/BTA | Pani/PTS |
| Corrosion current Icorr(μA cm-2) | 413.07 | 9.43 | 27.56 | 46.22 |
| Corrosion potential Ecorr(mV) | -433 | -138 | -219 | -285 |
| Protective efficiency eta (%) | -- | 97.72 | 93.32 | 87.86 |
FIG. 4 is Pani/MoO4 2-Pani/BTA and Pani/PTS, as can be seen in FIG. 4: at 3200--1Stretching vibration for carbon-hydrogen bond at 965cm-1、1549cm-1And 1702cm-1Vibrations of symmetric and asymmetric aniline rings were observed, respectively. 914cm-1、1041cm-1、1312cm-1And 1469cm-1The other main peaks are respectively C-H plane outer ring deformation vibration, N-H plane inner deformation, C-H plane inner deformation vibration and C-N stretching vibration. In addition, the thickness is 2800-3000 cm-1And 950 to 1250cm-1Region, dopant (MoO)4 2-BTA, PTS) spectrum mainly composed of-CH3and-CH2Asymmetric and symmetric control of the-band, this being by-OSO3-asymmetric and symmetric stretch bands. These demonstrate that polyaniline and various dopants were successfully plated on the plate surface.
Table 4 shows Pani/MoO4 2-Atomic force microscope coating surface roughness data for Pani/BTA and Pani/PTS, as can be seen from table 4: Pani/MoO4 2-The roughness of the coating is the lowest, which indicates that the coating surface is more flat and smooth, and the minimum gaps are presented between peaks and valleys, and is consistent with the electrochemical test result.
TABLE 4 Pani/MoO4 2-Atomic force microscope coating surface roughness data for Pani/BTA and Pani/PTS
| Coating layer | Pani/MoO4 2- | Pani/BTA | Pani/PTS |
| Coating surface roughness (nm) | 61 | 79 | 92 |
Example 2
The Pani/MoO of example 1 was used4 2-The method is used for treating electroplating wastewater by electric flocculation (the process is shown as figure 5), and comprises the following steps:
a304 stainless steel electrode plate (10X 6X 0.2cm) is used as a working electrode, a platinum sheet electrode (1.5X 0.1cm) is used as a counter electrode, a saturated silver/silver chloride electrode is used as a reference electrode, and constant potential electropolymerization of 1200s is carried out in polyaniline/molybdate electrolyte (the concentration of aniline is 0.20M, and the concentration of sodium molybdate is 0.05M) at an oxidation potential of 0.95V, so that Pani/MoO is prepared4 2-And modifying the anode plate.
Subsequently, Pani/MoO4 2-Modifying the anode plate as anode, aluminum plate as cathode, and treating at initial pH of 5, treatment time of 60min and current density of 35mA cm-2Carrying out an electrocoagulation reaction under the condition of (1); copper and chromium were removed.
Example 3
As shown in Table 5, the pH in example 2 was adjusted so that the reaction time was 50min and the current density was 30mA cm-2Otherwise, the electrocoagulation treatment was carried out in accordance with example 2.
As can be seen from tables 5 and 6: at an initial pH of 5, the removal rate of heavy metals is highest, and the removal rates of copper and chromium can reach 99.99% and 81%, while at low pH (1 and 2), the metal removal efficiency is low due to insufficient accumulation of metal hydroxides. The corrosion inhibition efficiency decreases slowly with increasing initial pH because bare steel surfaces are more susceptible to attack under strong acid conditions, which increases the weight loss of the anode compared to neutral and weak acid conditions. Under strong acid condition, the polyaniline coating can effectively inhibit the corrosion of the plate and ensure the limited iron ion dissolution, thereby having higher corrosion inhibition efficiency.
Table 5 results of copper and chromium removal rate test in example 3
| Initial pH value | pH＝1 | pH＝2 | pH＝3 | pH＝4 | pH＝5 | pH＝6 | pH＝7 | pH＝8 |
| Coated anode// Cu (%) | 87.44 | 93.72 | 96.34 | 98.74 | 99.45 | 98.88 | 98.54 | 97.86 |
| Coated anode// Cr (%) | 29.85 | 51.52 | 65.19 | 74.146 | 79.34 | 73.56 | 68.21 | 66.86 |
| Bare steel anode// Cu (%) | 90.61 | 95.70 | 97.99 | 98.95 | 99.53 | 98.90 | 98.78 | 97.85 |
| Bare steel anode// Cr (%) | 40.97 | 57.51 | 69.97 | 75.79 | 80.05 | 73.87 | 69.47 | 66.47 |
Table 6 test results of corrosion inhibition efficiency in example 3
| Initial pH value | pH＝1 | pH＝2 | pH＝3 | pH＝4 | pH＝5 | pH＝6 | pH＝7 | pH＝8 |
| Inhibition efficiency (%) | 45.35 | 41.42 | 38.55 | 35.43 | 34.73 | 33.25 | 33.67 | 33.50 |
Example 4
The reaction time in adjusting example 2 was as shown in Table 7, and the initial pH was 5 and the current density was 30mA cm-2Otherwise, the electrocoagulation treatment was carried out in accordance with example 2.
As can be seen from tables 7 and 8: as the reaction time increases, the removal rate of both copper and chromium increases because the anode produces more metal hydroxide as the reaction proceeds, thereby increasing the metal removal efficiency. The modified anodes reached maximum 99.99% and 84% removal within 80min, respectively, with results similar to uncoated steel anodes, which also demonstrated that the coated anodes did not affect the removal of heavy metals. The corrosion inhibition efficiency is obviously reduced along with the reaction and then tends to be stable, which is consistent with the protective performance of the coating. In view of running cost, a reaction time of 60min is preferable.
Table 7 results of copper and chromium removal test in example 4
| Treatment time (min) | 10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 |
| Coated anode// Cu (%) | 77.39 | 90.77 | 97.25 | 98.54 | 99.45 | 99.98 | 99.99 | 99.99 |
| Coated anode// Cr (%) | 28.12 | 47.75 | 61.05 | 71.37 | 79.34 | 81.89 | 83.02 | 84.29 |
| Bare steel anode// Cu (%) | 80.30 | 91.15 | 91.94 | 99.19 | 99.53 | 99.98 | 99.99 | 99.99 |
| Bare steel anode// Cr (%) | 37.35 | 53.56 | 65.29 | 73.75 | 80.05 | 82.13 | 83.12 | 84.51 |
Table 8 test results of corrosion inhibition efficiency in example 4
| Treatment time (min) | 10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 |
| Inhibition efficiency (%) | 45.25 | 40.5 | 37.33 | 35.65 | 34.73 | 34.25 | 33.73 | 33.25 |
Example 5
Current density in example 2 was adjusted as shown in Table 9, the initial pH was 5, the reaction time was 60min, and the electrocoagulation treatment was carried out in conformity with example 2.
As can be seen from tables 9 and 10: from 5 to 40mA cm with increasing current density-2The removal efficiency of the heavy metal ions is obviously improved. The corrosion inhibition efficiency tends to decrease with increasing current density, since further increasing current density promotes electrochemical dissolution of the steel anode Fe ions. Under the condition of low current density, the modified anode Pani coating has better corrosion inhibition performance on the anode. With the gradual increase of the current density, the impact of Fe ions on the Fe-Pani interface is gradually enhanced, the protective performance is slightly reduced, and then the Fe-Pani interface tends to be stable. The differences and trends in Cr removal for bare steel anodes and modified anodes are similar due to the corrosion inhibition of the modified anodes, which limits Fe release at lower current densities. In addition, more agglomerates are required for Cr removal than for Cu removal, thereby expanding the difference in Cr and Cu removal efficiency. Considering that an excessive current increases power consumption, a current density of 35mA cm is selected-2The current density of (1).
Table 9 results of copper and chromium removal test in example 5
| Current Density (mA/cm)2) | 5 | 10 | 15 | 20 | 25 | 30 | 35 (example 2) | 40 |
| Coated anode// Cu (%) | 77.29 | 92.39 | 96.85 | 99.52 | 99.97 | 99.98 | 99.99 | 99.99 |
| Coated anode// Cr (%) | 26.78 | 47.02 | 59.73 | 70.85 | 77.19 | 81.89 | 84.24 | 84.81 |
| Bare steel anode// Cu (%) | 81.32 | 94.36 | 98.75 | 99.85 | 99.98 | 99.98 | 99.99 | 99.99 |
| Bare steel anode// Cr (%) | 43.87 | 55.64 | 65.25 | 72.32 | 78.62 | 82.13 | 84.77 | 84.89 |
TABLE 10 test results for corrosion inhibition efficiency in example 5
| Current Density (mA/cm)2) | 5 | 10 | 15 | 20 | 25 | 30 | 35 (example 2) | 40 |
| Inhibition efficiency (%) | 45.30 | 43.45 | 39.62 | 35.75 | 35.33 | 34.25 | 33.33 | 32.37 |
Example 6
Example 2 was run in multiple batches (10) with test results as shown in 6:
as can be seen from fig. 6: for bare steel anodes, the removal rate of copper ions and chromium ions of each batch is basically stabilized at about 99.99% and 84%, and the removal rate of the copper ions and the removal rate of the chromium ions after electrode modification respectively reach about 99.99% and 84%. Meanwhile, after 10 batches of electrocoagulation treatment, the corrosion inhibition effect is relatively stable about 33.33%.
Comparative example 3
The Pani/MoO of example 1 was mixed4 2-And Pani/BTA of comparative example 2 were tested for chromium removal and corrosion inhibition efficiency in a multi-batch electrocoagulation corrosion inhibition experiment performed according to the method of example 2.
The test results are shown in fig. 7 and 8, and it can be seen from fig. 7 and 8 that: Pani/MoO4 2-The coating anode can ensure higher heavy metal chromium removal rate, and the difference of the chromium removal rates of the two coating electrode plates is more than 10 percent, which means Pani/MoO4 2-The coating modified electrode is more suitable for treating the copper-chromium alloy heavy metal wastewater by electric flocculation. Meanwhile, the corrosion inhibition efficiency of the two has a certain difference.
TABLE 11 shows the use of molecules for the plates of example 1 and comparative examples 1 and 2The kinetic method simulates the results of the interaction of the polyaniline Pani coating with the steel surface, as can be seen from table 11: the adsorption energy of Pani and each coating on the surface of Fe is negative, which shows that the surfaces of the polar plates have certain protection effect, wherein Pani/MoO4 2-The adsorption energy of (A) is the most negative, which indicates that the binding capacity is the strongest and the protective performance is the best, and the result is consistent with the result of the previous experiment.
Table 11 test results of the electrode plates of example 1 and comparative examples 1 and 2
| Coating layer | Pani | Pani/MoO4 2- | Pani/BTA | Pani/PTS |
| Adsorption energy (kJ mol)-1) | -77.82 | -115.39 | -102.57 | -95.63 |
Comparative example 4
The specific method for modifying the anode electrode by adopting polypyrrole/p-toluenesulfonate comprises the following steps:
electropolymerization: placing stainless steel SS (10 × 6 × 0.2cm) of the anode plate 304 in polypyrrole/p-toluenesulfonate electrolyte (concentration of polypyrrole is 0.15M, concentration of sodium p-toluenesulfonate is 0.01M), and performing constant potential electropolymerization for 1200s at oxidation potential of 0.95V; and after the reaction is finished, washing with water, and drying at 50 ℃ to obtain the polypyrrole-modified anode plate.
The resulting electrode was subjected to the electroflocculation test in the manner of example 2, with the following test results:
table 12 test results of comparative example 4
| Example (b) | Copper removal (%) | Chromium removal Rate (%) | Inhibition efficiency (%) |
| Example 2 | 99.99 | 84.24 | 33.33 |
| Comparative example 4 | 89.37 | 71.58 | 28.82 |
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (4)
1. Polyaniline/molybdic acidThe application of the salt-modified anode plate in the electric flocculation treatment of electroplating wastewater is characterized in that the application is to take the polyaniline/molybdate-modified anode plate as an anode and an aluminum plate as a cathode to carry out electric flocculation reaction; wherein the conditions of the electric flocculation reaction are as follows: the initial pH is 4-6, the treatment time is 40-80 min, and the current density is 20-40 mA-cm-2；
Parameters of the electroplating wastewater in the application are that copper is 15.66mg/L, chromium is 7.85mg/L, pH is 3.17, conductivity is 4.39mS/cm, and chemical oxygen demand is 377.64 mg/L; wherein, the copper and the chromium exist in a complex state;
the preparation method of the polyaniline/molybdate modified anode plate comprises the following steps:
(1) preparing an electrolyte: uniformly mixing aniline and molybdate to form electrolyte; wherein the concentration of the aniline is 0.15-0.30M; the concentration of the molybdate is 0.01-0.1M;
(2) electropolymerization: placing the anode plate in electrolyte, and carrying out electropolymerization at an oxidation potential of 0.9-1.0V; and after the end, washing and drying to obtain the polyaniline/molybdate modified anode plate.
2. The application of claim 1, wherein the anode and the cathode are connected to a DC power supply in a constant current mode to provide a voltage and a current of 0-25V and 0-8A.
3. The use according to claim 1 or 2, wherein the distance between the anode and the cathode is 1-3 cm.
4. A method for treating copper and chromium in electroplating wastewater by electrocoagulation is characterized by comprising the following steps:
performing an electrocoagulation reaction by taking an anode plate modified by polyaniline/molybdate as an anode and an aluminum plate as a cathode; wherein the conditions of the electric flocculation reaction are as follows: the initial pH is 4-6, the treatment time is 40-80 min, and the current density is 20-40 mA-cm-2；
The preparation method of the polyaniline/molybdate modified anode plate comprises the following steps:
(1) preparing an electrolyte: uniformly mixing aniline and molybdate to form electrolyte; wherein the concentration of the aniline is 0.15-0.30M; the concentration of the molybdate is 0.01-0.1M;
(2) electropolymerization: placing the anode plate in electrolyte, and carrying out electropolymerization at an oxidation potential of 0.9-1.0V; and after the end, washing and drying to obtain the polyaniline/molybdate modified anode plate.
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