CN116282400A - A double-pulse low-voltage electrocoagulation method for treating acidic wastewater containing heavy metals in mines - Google Patents

Abstract

The invention belongs to the technical field of water pollution treatment, and in particular relates to a double-pulse piezoelectric flocculation method for treating mine acid wastewater containing heavy metals, which comprises the following steps: the raw water quantity and the water quality condition are defined; selecting a vertical folded plate flocculation tank, wherein a plurality of columnar iron anodes and folded plate-shaped iron cathodes are arranged in the vertical folded plate flocculation tank, and the speed gradient or flocculation flow rate gradually decreases from a water inlet to a water storage port in the flocculation process; the electric flocculation Chi Yinyang polar plate is electrified with current to select double-pulse low-voltage current, and wastewater is treated by using an intermittent mode of 'electrifying-de-electrifying' of a pulse power supply; the magnetic separation performance of the flocs is changed by combining the double pulse waveform regulation and control with aeration and air-expelling, and the sludge reduction of water treatment is controlled. The invention uses double pulse current to replace direct current, which can greatly save the energy consumption of treatment and reduce the generation amount of sludge.

Description

A double-pulse low-voltage electrocoagulation method for treating acidic wastewater containing heavy metals in mines

technical field

The invention belongs to the technical field of water pollution treatment, and in particular relates to a double-pulse low-voltage electrocoagulation method for treating acidic wastewater containing heavy metals in mines.

Background technique

In recent years, chromium has been widely used in electroplating, chemical industry, leather and other industries, which causes a large amount of chromium to be discharged into water bodies, resulting in frequent occurrence of chromium pollution incidents in recent years. The occurrence of these chromium pollution events has caused a serious threat to human survival and health. The sources of Cr(VI) in water bodies are mainly divided into natural existence and man-made, and the entry of naturally occurring Cr(VI) into water mainly depends on the dissolution of rocks. The artificially produced Cr(VI) mainly comes from the by-products generated in industrial and agricultural production activities. For example, in agricultural production activities, most of the chemical fertilizers or pesticides contain chromium. Applying chemical fertilizers and pesticides to plants will directly make chromium It enters the soil, and then dissolves and leaches into surface water or groundwater through rainfall. In industrial production activities, a large amount of Cr(VI)-containing wastewater will be generated in processes such as refining chromite, electroplating, leather, ferrochrome, paint and textile. Especially in the electroplating industry, a large amount of Cr(VI)-containing wastewater will be produced. If large-scale Cr(VI)-containing wastewater is discharged or treated improperly, it will easily pose a threat to fresh water resources and human health.

Electrocoagulation is an electrochemical technology that is widely used at present. Electrocoagulation mainly relies on the principle of electrochemical reaction to electrolytically reduce heavy metal ions with high valence and strong toxicity to low valence forms. Under the synergistic effect of chemical coagulants Precipitation occurs and is removed from the water body. The reaction mainly includes the following points: the electrolytic reaction at the anode gradually dissolves in the solution to produce a flocculant; under the action of the flocculant, the pollutants in the water gradually become destabilized; Large particles are subsequently removed by precipitation. Iron and aluminum are more anode materials used in electrocoagulation in water treatment. Taking iron as an anode as an example, when the current density is low, the iron anode is gradually oxidized and begins to dissolve ferrous ions into the water, and then reacts with Cr(VI) in the solution. Cr(VI) gets electrons from the cathode and is then reduced to Cr(III). Aluminum ions produced by electrolysis at the anode can form aluminum hydroxide precipitates, which are co-precipitated with Cr(OH)3 as a flocculant.

Electrocoagulation treatment of Cr(VI) is relatively well-developed and has good treatment effect, but there are also shortcomings that need to be improved. For example, the current intensity needs to be adjusted at all times; the surface of the electrode is easily passivated, the anode needs to be replaced from time to time, and the effective product formed after flocculation is unstable and easy to dissolve by itself.

Contents of the invention

Aiming at the problems of plate passivation, energy consumption and sludge volume in electrocoagulation treatment of Cr(VI)-containing wastewater, the present invention proposes a double-pulse low-voltage electrocoagulation method for treating acid wastewater containing heavy metals in mines, which can reduce extremely The passivation speed of the plate can reduce energy consumption, reduce the amount of sludge generated, and quickly and efficiently treat Cr(VI)-containing wastewater.

In order to achieve the above-mentioned technical purpose and achieve the above-mentioned technical effect, the present invention is realized through the following technical solutions:

A double-pulse low-voltage electrocoagulation method for treating acidic wastewater containing heavy metals in mines, comprising the following steps:

S1. According to the survey data of mine wastewater and relevant laws and regulations, clarify the raw water volume and water quality, the water quality requirements of the effluent, and determine the design parameters of the electroflocculation tank through tests and operating experience;

S2. The flocculation tank chooses a vertical folded plate flocculation tank. There are several iron columnar anodes and iron folded plate cathodes in the vertical folded plate flocculation tank. The acidic wastewater containing heavy metals in the mine is guided by the iron folded plate cathode. Repeated deflection, the velocity gradient or flocculation flow rate gradually decreases from the water inlet to the water storage port during the flocculation process to ensure the fullness and perfection of the flocculation process;

S3. The current passing through the cathode and anode plates of the electroflocculation tank is selected as a double-pulse low-voltage current, and the intermittent mode of pulse power supply "power-on-power-on" is used to treat wastewater;

S4. Change the magnetic separation performance of the flocs through double pulse waveform regulation combined with aeration and gas drive to control the reduction of water treatment sludge.

Further, in step S2, the data of each segment of the vertical folding plate sedimentation tank:

Relative to the first segment of the folded plate, G=80s ^-1 , t≥240s;

The second section of the parallel folded plate, G=50s ^-1 , t≥240s;

For the third segment of the parallel folded plate, G=25s ^-1 , t≥240s.

Further, the included angle of the folded plate is 90-120°, the width of the folded plate is 0.4-0.6 m, and the length of the folded plate is 0.8-1.5 m.

Further, in step S2, the flocculation tank should have sufficient flocculation time, and the flocculation tank should be merged with the sedimentation tank as much as possible to avoid connecting with pipes and channels. If it is really necessary to use pipes and channels to connect, the flow rate should be controlled to avoid a sudden increase in flow rate causing The water head drops; in order to avoid the breakage of the formed flocs, the flow rate of the perforated wall of the flocculation tank outlet should be controlled; in order to prevent the flocs from settling in the flocculation tank, corresponding mud discharge measures should be adopted if necessary.

Further, in step S3, the iron anode is gradually oxidized after electrification and begins to dissolve ferrous ions in water, and then reacts with Cr(VI) in the solution; Cr(VI) obtains electrons from the cathode, and is then reduced to Cr( III), the aluminum ions produced by anode electrolysis can form aluminum hydroxide precipitates, which are used as flocculants to co-precipitate with Cr(OH) ₃ ; large particle flocs are removed by precipitation, and small particle flocs are removed by air flotation. Then it is added to the sedimentation tank for floc precipitation and removal.

Further, when electrified, the current density is 20Am ^-2 , the peak voltage is 5V, the current frequency is 5000Hz, and the optimal duty ratio is 30%.

Furthermore, when the ratio of the number of positive pulses and negative pulses of double-pulse electrocoagulation is larger, the corresponding Cr(Ⅵ) removal rate is higher; when the ratio of positive pulses to negative pulses is 10, the highest removal rate is 99.2 %, and the corresponding energy consumption is also the lowest.

Further, the factors affecting the removal rate are:

a. When the pH of acidic wastewater containing heavy metals in mines is greater than 6, the removal rate changes little as the initial pH increases;

b. The low conductivity of acid wastewater containing heavy metals in mines will lead to a decrease in removal rate and an increase in energy consumption, but too high conductivity will limit the voltage, resulting in a decrease in removal rate;

c. The increase of the plate spacing will increase the removal rate, but too large plate spacing will passivate the plate;

d. When the initial concentration of Cr(VI) is too high, the flocs formed by the dissolved iron ions in the anode are not enough to remove the high concentration of Cr(VI), which will reduce the removal rate.

Further, in step S4, the magnetic separation performance of the flocs is changed through the reversible reverse waveform regulation of the double pulse combined with the aeration/purging and the easy-to-obtain chlorine-containing electrolyte to control the reduction of the water treatment sludge; through the double pulse waveform Control combined with aeration to promote electron transfer to generate γ-FeOOH. When the gas is purged, due to the decrease of dissolved oxygen, the Cl ^- produced by the electrolysis of iron and chlorine-containing electrolyte under double pulse control is converted into green rust, thereby changing the magnetic properties of the flocs.

Further, the chloride-ion-containing electrolyte is at least one of NaCl, KCl, HCl, and perchloric acid.

The beneficial effects of the present invention are:

1. In the present invention, double-pulse electric current is used instead of direct current. Compared with direct-current electric flocculation, double-pulse electric flocculation can greatly save the energy consumption of treatment and reduce the amount of sludge generated. The power-off period of the current in a cycle is conducive to the diffusion of the cations dissolved in the anode into the solution, which is beneficial to inhibit the occurrence of concentration polarization, and achieve the purpose of saving energy and reducing plate passivation. Compared with traditional DC electrocoagulation, double-pulse electrocoagulation has a more stable treatment process.

2. The present invention explores the influence of different numbers of positive and negative pulses on the electrocoagulation effect and power consumption. The ratio of positive pulse to negative pulse with the highest removal rate was obtained.

3. The present invention proves that pulsed double electrocoagulation has good stability in the field of treating Cr(VI) wastewater by exploring the change of floc magnetism during the electrocoagulation process.

4. The present invention obtains the optimal operating conditions by exploring the effects of different water quality conditions and operating parameters on the removal of Cr(VI) in wastewater by electrocoagulation and double-pulse electrocoagulation, and comparing the efficiencies of different electrocoagulation processes.

5. The invention reduces the consumption and replacement frequency of the anode plate by using the columnar anode, the contact area between the sewage and the electrode is large, and the mass transfer effect between substances is improved.

6. The present invention uses a folded plate-shaped cathode plate, which not only takes place in the electrolysis reaction, but also acts as a guide for water flow. It can eliminate the plate passivation phenomenon and improve the flocculation effect.

7. The present invention changes the magnetic separation performance of the flocs through double-pulse waveform regulation combined with aeration/dispelling gas and easy-to-obtain chlorine ion electrolytes to control the reduction of water treatment sludge.

Of course, implementing any product of the present invention does not necessarily need to achieve all the above advantages at the same time.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that are required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. Those of ordinary skill in the art can also obtain other drawings based on these drawings without any creative effort.

Fig. 1 is the structural representation of vertical folding plate flocculation tank;

1-double pulse power supply, 2-positive pole, 3-negative pole, 4-column anode, 5-folded plate cathode, 6-water inlet, 7-water outlet, 8-sedimentation tank, 9-flocculation tank;

Fig. 2 is the structural representation of experimental device in embodiment 2;

10-magnetic stirrer, 11-electrocoagulation reactor, 12-iron anode, 13-DC and pulse power supply;

Fig. 3 is the waveform diagram of pulse current;

Among them, (a) single pulse current, (b) double pulse current waveform;

Fig. 4 is the morphology under the microscope of floc (magnification 400 times);

Among them, (a) DC floc, (b) single-pulse floc, (C) double-pulse floc, (d-f) let the floc stand for 1 hour, and apply a magnetic field to attract: (d) DC floc, (e) single-pulse floc Pulse floc, (f) double pulse floc;

Figure 5 is a schematic diagram of the formation of iron flocs and the removal of Cr(VI) by DC and pulse electrocoagulation;

Among them, DC is direct current coagulation, DO is aeration and oxygenation, PC is pulse electrocoagulation, DO abscent+CI ^- is deoxygenation and combined with chloride ions.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Relevant specific embodiments of the present invention are:

Example 1

This embodiment provides a double-pulse low-voltage electrocoagulation method for treating acidic wastewater containing heavy metals in mines, including the following steps:

S1. According to the survey data of mine wastewater and relevant laws and regulations, clarify the raw water volume and water quality, the effluent water quality requirements, and determine the design parameters of the electroflocculation tank through tests and operating experience.

S2. The flocculation tank chooses a vertical folded plate flocculation tank. There are several iron columnar anodes and iron folded plate cathodes in the vertical folded plate flocculation tank. The acidic wastewater containing heavy metals in the mine is guided by the iron folded plate cathode. Repeated deflection, the velocity gradient or flocculation flow rate gradually decreases from the water inlet to the water storage port during the flocculation process to ensure the fullness and perfection of the flocculation process; the data of each section of the vertical folded plate sedimentation tank:

Relative to the first segment of the folded plate, G=80s ^-1 , t≥240s;

The second section of the parallel folded plate, G=50s ^-1 , t≥240s;

For the third segment of the parallel folded plate, G=25s ^-1 , t≥240s.

The included angle of the folded plate is 90-120°, the width of the folded plate is 0.4-0.6m, and the length of the folded plate is 0.8-1.5m.

The flocculation tank should have sufficient flocculation time, and the flocculation tank should be built together with the sedimentation tank as much as possible, and the connection with pipes and channels should be avoided. If it is really necessary to use pipes and channels to connect, the flow rate should be controlled to avoid the sudden increase of the flow rate and the drop of the water head; in order to avoid the formed For the breaking of flocs, the flow rate of the perforated wall of the flocculation tank outlet should be controlled; in order to prevent the flocs from settling in the flocculation tank, corresponding mud discharge measures should be adopted if necessary.

S3. The electric current for the cathode and anode plates of the electrocoagulation pool is double-pulse low-voltage current, and the intermittent mode of pulse power supply "power-on-power-on" is used to treat wastewater; after power-on, the iron anode is gradually oxidized and begins to dissolve in the water. Iron ions then react with Cr(VI) in the solution; Cr(VI) gets electrons from the cathode and is then reduced to Cr(III), aluminum ions produced by anode electrolysis can form aluminum hydroxide precipitates, which are used as flocculants Co-precipitation with Cr(OH) ₃ ; large particle flocs are removed by sedimentation, small particle flocs are removed by air flotation, and after the water outlet, they are added to the sedimentation tank for floc precipitation and removal.

S4. Change the magnetic separation performance of the flocs through double pulse waveform regulation combined with aeration and gas drive to control the reduction of water treatment sludge. Change the magnetic separation performance of flocs through the reversible reverse waveform regulation of double pulse combined with aeration/driver and easy access to chlorine-containing electrolytes, and control the reduction of sludge in water treatment; through the regulation of double pulse waveform combined with aeration to promote electron transfer γ-FeOOH is generated. When the gas is purged, due to the decrease of dissolved oxygen, the Cl- from the electrolysis of iron and chloride-ion-containing electrolyte under the double pulse control is converted into green rust, thereby changing the magnetic properties of the flocs. The chloride-ion-containing electrolyte is at least one of NaCl, KCl, HCl, and perchloric acid.

The factors that affect the removal rate are:

a. When the pH of acidic wastewater containing heavy metals in mines is greater than 6, the removal rate changes little as the initial pH increases;

b. The low conductivity of acid wastewater containing heavy metals in mines will lead to a decrease in removal rate and an increase in energy consumption, but too high conductivity will limit the voltage, resulting in a decrease in removal rate;

c. The increase of the plate spacing will increase the removal rate, but too large plate spacing will passivate the plate;

d. When the initial concentration of Cr(VI) is too high, the flocs formed by the dissolved iron ions in the anode are not enough to remove the high concentration of Cr(VI), which will reduce the removal rate.

In this example, the Tafel curve during the double-pulse electrocoagulation process was used to explore the electrochemical behavior of the iron electrode. Measure the forward current of the iron electrode to obtain the corrosion voltage of iron through the Tafel curve of Cr(VI), and calculate the corrosion current through the Tafel equation after converting the current direction. The corrosion current decreases with the prolongation of energization time, because during the energization period, a dense oxide film is gradually formed on the surface of the iron electrode, which leads to the passivation of the electrode surface. This proves that applying a reverse current can slow down the formation rate of the passivation film on the iron electrode. Therefore, the periodical reversal of the cathode and anode can be realized by applying double pulse current, which can reduce the formation of passivation film and achieve the purpose of reducing energy consumption.

In this embodiment, the effects of different numbers of positive and negative pulses on the electrocoagulation effect and power consumption are explored. When the number of positive pulses and negative pulses is the same, the removal rate of Cr(VI) in the solution is 7.23%, and the corresponding energy consumption is also the highest. When the ratio of positive pulse to negative pulse is larger, the corresponding removal rate of Cr(VI) is higher. When the ratio of the number of positive pulses to negative pulses is 10, the highest removal rate is 99.2%, and the corresponding energy consumption is also the lowest. In addition, the current density increases with the number of pulses. Through the waveform diagrams of different combinations of positive and negative pulse currents, it can be found that increasing the number of positive and negative pulses is equivalent to increasing the duty cycle of a current cycle. When the peak voltage is constant, the average voltage within the total pulse period increases with the increase of the duty cycle.

Three different electrocoagulation methods were compared in terms of removal rate, energy consumption and sludge volume, and it was found that double-pulse electrocoagulation requires a longer treatment time to achieve a removal rate similar to DC electrocoagulation. However, compared with DC electrocoagulation, double-pulse electrocoagulation can greatly save the energy consumption of treatment and reduce the amount of sludge generated. This is due to the characteristics of the double-pulse current. The power-off period of the current in one cycle is conducive to the diffusion of the cations dissolved in the anode to the solution, which is beneficial to suppress the occurrence of concentration polarization, which in turn will reduce the energy consumption of the reaction process. Achieve sludge reduction.

In this example, the change of the magnetic properties of the flocs was obtained. The flocs produced by direct current flocculation have stronger magnetic properties than those produced by double-pulse electric flocculation, which may be due to the transformation of the flocs into hematite and magnetite. . The composition of iron flocs during electrocoagulation is very complex and easily affected by the external environment, especially the presence of dissolved oxygen (DO) and Cl-. When sufficient DO exists in the solution, the ferrous floc components generated during electrocoagulation can be rapidly oxidized to ferric components. The mixed iron phase then proceeds to transform into γ-FeOOH in the presence of dissolved oxygen. However, when DO is scarce, the mixed-valence iron phase transforms into green rust (GRCl), which is a general term for various green crystalline compounds, in the presence of Cl. Due to the different current characteristics, in the process of water treatment, the energization time of DC electrocoagulation is longer than that of double pulse electrocoagulation, resulting in the formation of a large amount of oxygen on the electrodes. In this case, γ-FeOOH was produced due to the presence of sufficient DO during the electrocoagulation process, while GRCl was produced due to the absence of sufficient DO and the presence of Cl- during the double-pulse electrocoagulation process.

In addition, chloride ions also accelerated the settling of the flocs and increased the particle size of the flocs. Compared with GRCl, the adsorption capacity of γ-FeOOH to Cr(VI) is not very strong, so double-pulse electrocoagulation has a higher Cr(VI) removal rate than DC electrocoagulation. As the reaction proceeded, DO was gradually consumed, and the γ-FeOOH generated during the DC electrocoagulation began to transform into magnetite (Fe ₃ O ₄ ). This leads to the release of the Cr(VI) originally adsorbed by the flocs and returning to the solution, which reduces the final removal rate. The removal mechanism of Cr(VI) by double-pulse electrocoagulation relies on the adsorption of GRCl with effective adsorption sites, and Cr(VI) can be adsorbed to the adsorption sites of GRCl to be removed. Another mechanism is that Cr(VI) replaces Fe ²⁺ in GRCl, which makes the combination of Cr(VI) and flocs more tightly, which makes it difficult for Cr(VI) adsorbed by GRCl to return from the flocs to the solution middle. In addition, in the presence of DO, a small amount of GRCl is converted into γ-FeOOH, so double-pulse electrocoagulation has good stability in the field of Cr(VI) wastewater treatment.

Example 2

In this example, a potassium dichromate (K ₂ Cr ₂ O ₇ ) solution with a concentration of 200 mg/L was prepared as a simulated water sample stock solution, and other concentrations required in the experiment were prepared by diluting the stock solution. The simulated water sample uses sodium chloride (NaCI) as the electrolyte, adjusts the conductivity of the solution to 2mS/cm, and uses 1M sodium hydroxide solution and dilute sulfuric acid to adjust the pH of the solution to be between 7.5-8.0. A 500mL plexiglass reactor (100mm×100mm×50mm) was used as the reactor device, and two pure iron sheets were used as electrodes connected to the cathode and anode of the pulse power supply. The waveform of the current (DC and pulse) can be achieved by adjusting the duty cycle of the power supply. The effective area of the iron electrode immersed in the solution is 50cm ² (50mm×100mm×1mm). The electrode needs to be sanded before use, and then placed in an ultrasonic machine for 10 minutes to remove the oxide layer on the surface, and the electrode is treated with ultrapure water. Rinse thoroughly. The spacing of the electrode plates can be adjusted from 5mm to 25mm. All experiments were performed at room temperature (25±2°C) with a stirring speed of 300 rpm/min for enhanced mass transfer.

According to the national standard GB7467-87, adopt diphenylcarbazide spectrophotometry, prepare the solution required for the corresponding standard curve according to the steps shown in the standard, measure the respective absorbance at 540nm wavelength, make the corresponding standard curve, and then After the wastewater treated by electrocoagulation at different times is filtered through a 0.45um inorganic filter head, the sample is measured by the same method as the standard curve, and the concentration of the sample is calculated according to the formula of the standard curve.

Use an electrochemical workstation for electrochemical characterization, use three electrodes to form a test system (Ag/AgCI as a reference electrode, platinum as an auxiliary electrode, and iron as a working electrode) forward scan followed by reverse scan, simulating double pulse The current conduction method realizes the measurement of the Tafel curve of the iron anode to judge the passivation degree of the iron anode during the reaction process.

A laser particle size analyzer was used to measure the particle size of the flocs generated during the electrocoagulation process. Before the measurement, the flocs were stirred for 3 minutes to obtain a longer growth cycle, and the aggregation of the flocs generated under different current conditions was measured.

Example 3

Based on the device shown in Figure 1, the waste water is passed into the electroflocculation tank, and the columnar anode is oxidized after electrification, the anode ions are dissolved in water and hydrolyzed, and Cr(Ⅵ) is reduced to Cr(Ⅲ) through the folded plate-shaped cathode, followed by coagulation. Form flocs, these flocs with strong adsorption capacity can adsorb Cr(Ⅲ), form floc chromium hydroxide and chromium-iron co-precipitation, large particle flocs are removed by precipitation, small particle flocs are removed by air flotation Remove and add to the sedimentation tank after the water outlet for floc precipitation. Designing the cathode as a folded plate not only takes place the electrolytic reaction but also plays the role of diversion of the water flow. This method can eliminate the plate passivation phenomenon and improve the flocculation effect. During the DC electrocoagulation process, a large amount of oxygen will be generated to oxidize the flocs to α-Fe2O3 and γ-Fe2O3, resulting in the release of Cr(Ⅵ) originally adsorbed by the flocs and returning to the solution, which reduces the final removal rate. . The removal mechanism of Cr(Ⅵ) by pulse electrocoagulation relies on the adsorption of GRCl, which makes the process of pulse electrocoagulation more stable. The commutation of the current during the double-pulse electrocoagulation process can increase the corrosion current of the electrode and play a role in alleviating the passivation of the plate. The optimal current density of the double-pulse low-voltage current is 20Am ^-2 , the peak voltage is 5V, the current frequency is 5000Hz, and the duty cycle of 30% is the most suitable. When the ratio of the number of positive pulses and negative pulses in double-pulse electrocoagulation is larger, the corresponding removal rate of Cr(Ⅵ) is higher. When the ratio of positive pulse to negative pulse is 10, the removal rate is the highest at 99.2%, and the corresponding energy consumption is also the lowest. In addition, the current density increases with the increase of the number of pulses. Through the waveform diagrams of different combinations of positive pulse current and negative pulse current, it can be found that increasing the number of positive and negative pulses is equivalent to increasing the duty cycle of a current cycle. When the peak voltage is constant, the average voltage within the total pulse period increases with the increase of the duty cycle.

The present invention innovatively introduces an improved electroflocculation technology in which double pulse current replaces direct current. The introduction of pulse power can effectively solve the problem of concentration polarization, achieve energy saving, reduce plate passivation, and adjust water treatment Sludge magnetism improves magnetic separation performance, effectively promotes sludge reduction, and reduces sludge disposal costs after water treatment.

The preferred embodiments of the invention disclosed above are only to help illustrate the invention. The preferred embodiments do not exhaust all details nor limit the invention to specific implementations. Obviously, many modifications and variations can be made based on the contents of this specification. This description selects and specifically describes these embodiments in order to better explain the principle and practical application of the present invention, so that those skilled in the art can well understand and utilize the present invention. The invention is to be limited only by the claims, along with their full scope and equivalents.

Claims (10)

1. a double-pulse low-voltage electrocoagulation method for processing mine acidic waste water containing heavy metals, is characterized in that, comprises the steps: S1. According to the survey data of mine wastewater and relevant laws and regulations, clarify the raw water volume and water quality, the water quality requirements of the effluent, and determine the design parameters of the electroflocculation tank through tests and operating experience; S2. The flocculation tank chooses a vertical folded plate flocculation tank. There are several iron columnar anodes and iron folded plate cathodes in the vertical folded plate flocculation tank. The acidic wastewater containing heavy metals in the mine is guided by the iron folded plate cathode. Repeated deflection, the velocity gradient or flocculation flow rate gradually decreases from the water inlet to the water storage port during the flocculation process; S3. The current passing through the cathode and anode plates of the electroflocculation tank is selected as a double-pulse low-voltage current, and the intermittent mode of pulse power supply "power-on-power-on" is used to treat wastewater; S4. Change the magnetic separation performance of the flocs through double pulse waveform regulation combined with aeration and gas drive to control the reduction of water treatment sludge. 2. The double-pulse low-voltage electrocoagulation method for processing acidic wastewater containing heavy metals in mines according to claim 1, characterized in that, in step S2, the data of each section of the vertical folding plate sedimentation tank: Relative to the first segment of the folded plate, G=80s ^-1 , t≥240s; The second section of the parallel folded plate, G=50s ^-1 , t≥240s; For the third segment of the parallel folded plate, G=25s ^-1 , t≥240s. 3. The double-pulse low-voltage electrocoagulation method for treating acidic wastewater containing heavy metals in mines according to claim 2, characterized in that the angle of the folded plates is 90-120°, the width of the folded plates is 0.4-0.6m, and the length of the folded plates It is 0.8 ~ 1.5m. 4. The double-pulse low-voltage electrocoagulation method for processing acidic waste water containing heavy metals in mines according to claim 1, characterized in that, in step S2, the flocculation tank should have sufficient flocculation time, and the flocculation tank should be merged with the sedimentation tank as much as possible Construction, avoid using pipes and channels to connect, if it is really necessary to use pipes and channels to connect, the flow rate should be controlled to avoid the sudden increase of the flow rate and the drop of the water head; in order to avoid the breakage of the formed flocs, the flow rate of the perforated wall of the flocculation tank outlet should be controlled; in order to avoid The flocs are settled in the flocculation tank, and corresponding mud discharge measures are adopted if necessary. 5. The double-pulse low-voltage electrocoagulation method for processing acidic wastewater containing heavy metals in mines according to claim 1, characterized in that, in step S3, after electrification, the iron anode is gradually oxidized and begins to dissolve ferrous ions in water, and then dissolves ferrous ions with the solution The Cr(VI) in the reaction reacts; Cr(VI) gets electrons from the cathode and is then reduced to Cr(III), and the aluminum ions produced by anode electrolysis can form aluminum hydroxide precipitates, which are used as flocculants and Cr(OH) ₃ Co-sedimentation; large particle flocs are removed by sedimentation, small particle flocs are removed by air flotation, and are added to the sedimentation tank after the water outlet to remove the flocs by sedimentation. 6. The double-pulse low-voltage electrocoagulation method for treating acidic wastewater containing heavy metals in mines according to claim 5, characterized in that: when electrified, the current density is 20Am ^-2 , the peak voltage is 5V, the current frequency is 5000Hz, and the best empty The proportion is 30%. 7. the double-pulse low-voltage electrocoagulation method of processing mine acidic wastewater containing heavy metals according to claim 5, is characterized in that: when the positive pulse of double-pulse electrocoagulation and the ratio of negative pulse number are bigger, corresponding Cr( Ⅵ) The removal rate is higher; when the ratio of positive pulse and negative pulse is 10, the removal rate is up to 99.2%, and the corresponding energy consumption is also the lowest. 8. The double-pulse low-voltage electrocoagulation method for processing acidic waste water containing heavy metals in mines according to claim 5, wherein the factors affecting the removal rate are: a. When the pH of acidic wastewater containing heavy metals in mines is greater than 6, the removal rate changes little as the initial pH increases; b. The low conductivity of acid wastewater containing heavy metals in mines will lead to a decrease in removal rate and an increase in energy consumption, but too high conductivity will limit the voltage, resulting in a decrease in removal rate; c. The increase of the plate spacing will increase the removal rate, but too large plate spacing will passivate the plate; d. When the initial concentration of Cr(VI) is too high, the flocs formed by the dissolved iron ions in the anode are not enough to remove the high concentration of Cr(VI), which will reduce the removal rate. 9. The double-pulse low-voltage electrocoagulation method for processing acidic wastewater containing heavy metals in mines according to claim 1, characterized in that, in step S4, the reversible reverse waveform of the double pulse is regulated in combination with aeration/purging and easy to obtain Chlorine-containing electrolytes change the magnetic separation performance of flocs and control the reduction of sludge in water treatment; through double-pulse waveform regulation combined with aeration to promote electron transfer to generate γ-FeOOH, when purging, due to the decrease of dissolved oxygen, double-pulse regulation Under the electrolysis of iron and chloride ion electrolyte, the ^Cl- is transformed into patina, thus changing the magnetic properties of the flocs. 10. The double-pulse low-voltage electrocoagulation method for processing acidic wastewater containing heavy metals in mines according to claim 9, wherein the chloride-containing electrolyte is at least one of NaCl, KCl, HCl, and perchloric acid.

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