A method and device for treating flotation collector wastewater based on multi-electrode low-temperature plasma surface discharge

Abstract

The present invention discloses a method and device for treating flotation collector wastewater based on multi-electrode low-temperature plasma along-discharge, which relates to the technical field of wastewater treatment. The device comprises: a high-voltage AC power supply; a liquid storage bottle; a along-discharge plasma reactor, which has an air inlet and a liquid inlet, and is provided with a grounding electrode and a high-voltage electrode inside, the high-voltage electrode is coated with an insulating medium, and a saturated solution is sealed in the gap between the high-voltage electrode and the insulating medium, and the high-voltage electrode and the grounding electrode form along-discharge with the wastewater to generate low-temperature plasma. The method comprises: using the above-mentioned device to treat flotation collector wastewater. The beneficial effect of the present invention is that the active substances generated by the along-discharge plasma discharge form are directly in contact with the mineral processing wastewater solution, which is beneficial to gas-liquid mass transfer, has a large plasma generation area, a high ozone generation amount, and strong ultraviolet radiation, and can effectively improve the degradation performance of the flotation collector.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a method and a device for treating flotation collector wastewater by surface discharge based on multi-electrode low-temperature plasma. Background Art

[0002] Mineral resources are one of the most important materials for sustainable development in modern society. People have been using mineral resources for thousands of years. Mining, smelting and processing activities are spread all over the world. The rational development and utilization of mineral resources is crucial to human development. China is one of the world's largest producers and consumers of non-ferrous metals. After nearly a hundred years of over-exploitation, high-grade mineral resources available for mining have become very scarce. In order to utilize low-grade mineral resources more efficiently and at a lower cost, people have developed and used a large number of new and efficient flotation collectors. However, as the main pollutant in mineral processing wastewater, flotation collector residues are often detected in wastewater. This leads to a high COD concentration in the wastewater, and the N element in the reagent will cause eutrophication of the water body, which will have an adverse effect on the ecological environment. Since most flotation collectors contain stable benzene ring structures with physiological toxicity, they are highly mutagenic and carcinogenic. In addition, residual flotation collectors can accumulate and enrich in the tissues of animals and plants through the food chain, and even enter the reproductive cells of organisms, causing changes or even destruction to the genetic material of the organism. If the mineral processing wastewater is treated and reused in the mineral processing process, it can not only reduce the waste of water resources, save the amount of new water and flotation collector, but also reduce the pollution to the environment. Therefore, how to effectively treat the mineral processing wastewater discharged by mines, prevent potential ecological and health risks, and realize the clean production of mines and the comprehensive resource utilization of mineral processing wastewater is of great significance.

[0003] Most of the flotation collectors in mineral processing wastewater are difficult to degrade toxic pollutants. They are not easy to hydrolyze and oxidize in the natural environment. They have relatively stable chemical properties and take a long time to degrade or almost do not degrade naturally. At present, biological electrochemical oxidation is mainly used for degradation. However, in the later stage of the biological method, due to the reduction of carbon sources used by microorganisms, it is easy to cause slow growth or even death of microorganisms. The electrochemical oxidation method has the disadvantages of high energy consumption and easy corrosion and consumption of electrodes, which limits the application of electrochemical oxidation method in the degradation of hydroxamic acid wastewater. By comparison, it is found that traditional mineral processing wastewater treatment technologies have problems such as high energy consumption, secondary pollution, and poor universality. In addition, these methods have the problem that mineral processing wastewater is difficult to meet the discharge or reuse standards. With the proposal of ecological civilization construction in my country, the requirements for environmental protection have become more stringent. Improving the wastewater reuse rate is an inevitable way to solve water environment protection and an advanced productivity to promote sustainable development. Therefore, considering that with the rapid development of the national economy, the amount of mineral processing wastewater treated in industrial production is increasing, and for the sustainable and high-quality development of human society, it is urgently necessary to develop new technologies and methods that are economical, efficient and highly universal for degrading residual flotation collectors in mineral processing wastewater, thereby increasing the reuse rate of wastewater, reducing or even eliminating its pollution to the natural environment and harm to human health. Summary of the invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a method and device for treating flotation collector wastewater based on multi-electrode low-temperature plasma surface discharge.

[0005] In recent years, low-temperature plasma, as a new type of composite advanced oxidation technology, has been widely studied and valued because of its advantages such as simple equipment, strong applicability, high degradation efficiency, and the ability to treat various wastewaters at room temperature and pressure. Dielectric barrier discharge (DBD) is a typical discharge form in low-temperature plasma. It is also a non-equilibrium gas discharge form with an insulating medium inserted into the discharge space. It is also called dielectric barrier corona discharge or silent discharge. Dielectric barrier discharge includes volume dielectric barrier discharge (VDBD) and surface dielectric barrier discharge (SDBD). VDBD and SDBD discharge between electrodes and on the surface of the dielectric, respectively. Among them, SDBD can produce a larger area, more uniform, more stable plasma layer and stronger ultraviolet light on the surface of the medium. Its discharge broadening and frequency shift are larger than those of bulk discharge, and its electron density is higher. The SDBD structure not only makes up for the shortcomings of complex equipment, high noise intensity and easy wear, but also has the advantages of short reaction time, more active substances, wide application range, high oxidizability, high processing efficiency and less secondary pollution. The ultraviolet rays, high-energy electrons, ultrasonic waves, magnetic fields and active substances such as oxygen atoms (•O), hydroxyl groups (•OH), ozone O3, nitric oxide (NO), peroxide (HO) and their excited state particles generated in the SDBD process have broad application prospects.

[0006] The present invention seals a saturated solution between the high-voltage electrode and the insulating medium. The high-voltage electrode directly discharges at the edge where the insulating medium contacts the liquid, i.e., surface discharge plasma discharge. The active substances generated by the high-voltage electrode directly contact the mineral processing wastewater solution. There is no need to blow the generated active substances into the wastewater solution by aeration for reaction, thereby greatly improving the degradation efficiency.

[0007] The technical solution of the present invention is as follows:

[0008] The first aspect of the present invention provides a device for treating flotation collector wastewater based on multi-electrode low-temperature plasma surface discharge, characterized in that it comprises:

[0009] High voltage AC power supply;

[0010] Storage bottles for storing flotation collector wastewater;

[0011] A surface discharge plasma reactor is provided with a gas inlet connected to an oxygen-containing gas and a liquid inlet connected to the liquid storage bottle. A grounding electrode and a high-voltage electrode connected to the high-voltage AC power supply are arranged inside the surface discharge plasma reactor. The high-voltage electrode is coated with an insulating medium. A saturated solution is sealed in the gap between the high-voltage electrode and the insulating medium. The high-voltage electrode and the grounding electrode contact the wastewater entering from the liquid inlet to form surface discharge and generate low-temperature plasma.

[0012] Preferably, the ground electrode and the high-voltage electrode are arranged side by side in the surface discharge plasma reactor, and the lower ends of the ground electrode and the high-voltage electrode are in contact with the wastewater entering from the liquid inlet, and the upper ends are in contact with the oxygen-containing gas entering from the gas inlet.

[0013] Preferably, the surface discharge plasma reactor further has a liquid outlet, and the surface discharge plasma reactor is further provided with:

[0014] A first baffle plate is arranged at one end close to the liquid inlet, and a channel is provided between the first baffle plate and the bottom wall of the surface discharge plasma reactor for the waste water entering from the liquid inlet to pass through;

[0015] A second baffle plate is arranged on a side of the first baffle plate away from the liquid inlet, and an overflow groove is formed between the second baffle plate and the first baffle plate;

[0016] A porous plate, which is arranged on a side of the second baffle plate away from the liquid inlet, and has a plurality of through holes for the wastewater entering from the liquid inlet to pass through;

[0017] a water-blocking baffle, which is arranged at one end close to the liquid outlet, and the height of the water-blocking baffle is lower than the height of the second baffle;

[0018] The ground electrode and the high voltage electrode are arranged between the water blocking baffle and the porous plate.

[0019] Preferably, the surface discharge plasma reactor also has an air outlet, and the air outlet and the liquid outlet are connected to the liquid storage bottle through a pipe; the air outlet and the liquid outlet are arranged at one end of the surface discharge plasma reactor, and the air inlet and the liquid inlet are arranged at the other end of the surface discharge plasma reactor, and the air inlet and the liquid inlet are arranged above the air outlet and the liquid outlet in the height direction.

[0020] As a preference, it also includes:

[0021] An oscilloscope for displaying and recording voltage and current signals collected during the discharge process of the surface discharge plasma reactor, wherein the oscilloscope is connected to the high-voltage AC power supply.

[0022] Preferably, the high-voltage electrode is a copper rod, the insulating medium is a quartz tube, and the saturated solution is at least one of a saturated sodium chloride solution, a saturated KCl solution and a saturated oxalic acid solution.

[0023] The number of the grounding electrodes and the number of the high-voltage electrodes are both several, and the several grounding electrodes and the high-voltage electrodes are arranged side by side in sequence with equal intervals. The number of the high-voltage electrodes is preferably 2 to 4, more preferably 3; the number of the grounding electrodes is preferably 3 to 5, more preferably 4.

[0024] The second aspect of the present invention provides a method for treating flotation collector wastewater based on multi-electrode low-temperature plasma surface discharge, and the flotation collector wastewater is treated using the above-mentioned device.

[0025] As a preference, the method comprises the following steps:

[0026] S1. Pre-treat flotation collector wastewater;

[0027] S2, pouring the flotation collector wastewater into the liquid storage bottle, introducing oxygen-containing gas into the surface discharge plasma reactor through the air inlet, and introducing the flotation collector wastewater into the surface discharge plasma reactor through the liquid inlet, wherein the introduced flotation collector wastewater does not completely immerse the high-voltage electrode and the grounding electrode; turning on the high-voltage AC power supply, the high-voltage electrode and the grounding electrode contact with the flotation collector wastewater to form a surface discharge to generate a low-temperature plasma, and the ultrasonic wave and ultraviolet rays generated by the low-temperature plasma together with the active substances generated by the low-temperature plasma degrade the pollutants in the wastewater.

[0028] In step S1, Na2SO4 is added to adjust the initial conductivity of the flotation collector wastewater so that the initial conductivity is 93~1480µs / cm; the initial conductivity is preferably 200~1000µs / cm; the initial conductivity is more preferably 500~900µs / cm.

[0029] In step S1, the method for pre-treating the flotation collector wastewater includes: adding sodium hydroxide or hydrochloric acid to adjust the pH of the flotation collector wastewater to ., and ultrasonically mixing;

[0030] In step S2, the duty cycle and modulation frequency of the high-voltage AC power supply are 60% and 200 Hz respectively, the peak-to-peak voltage is 21-29 kV, the peak-to-peak voltage is preferably 22-28 kV, and the peak-to-peak voltage is more preferably 24-28 kV;

[0031] In step S2, the thickness of the outer wall of the insulating medium is 1.0-3.0 mm, preferably 1.0-2.5 mm, and more preferably 1.0-2.0 mm.

[0032] In step S2, the depth of the high-voltage electrode immersed in the flotation collector wastewater is 1 / 4 to 3 / 4 of its outer diameter, preferably 1 / 2.

[0033] In step S2, the radius of curvature of the high voltage electrode is 4.5-6.5 mm, preferably 4.5-6.2 mm, and more preferably 5.0-6.0 mm.

[0034] The present invention has at least one of the following beneficial effects:

[0035] The present invention aims at the problem that in the prior art, the active substances generated by discharge need to be blown into the wastewater solution by aeration for reaction, but some short-lived active substances such as ·OH, ·O, ·HO2 may be deactivated before entering the mineral processing wastewater solution, which will lead to problems such as low degradation efficiency and energy waste. The surface discharge plasma discharge form adopted by the present invention is different from other traditional discharges in that the generated active substances directly contact the mineral processing wastewater solution, which is conducive to gas-liquid mass transfer, has the characteristics of a large plasma generation area, high ozone generation, strong ultraviolet radiation, simple and practical reactor structure, etc., which can effectively improve the degradation performance of the flotation collector. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the structure of the device for treating flotation collector wastewater by surface discharge in Example 1 of the present invention.

[0037] Figure 2 This is a cross-sectional view of the high voltage electrode in Example 1 of the present invention.

[0038] Figure 3 This is a graph showing the degradation efficiency of NOP wastewater treated at different peak-to-peak voltages in Examples 2 to 6.

[0039] Figure 4 This is a diagram of energy utilization efficiency for treating NOP wastewater in Examples 2 to 6.

[0040] Figure 5 It is a graph showing the degradation efficiency of treating NOP wastewater in Example 2 and Example 7 to Example 10 at different peak-to-peak voltages.

[0041] Figure 6 This is a diagram of energy utilization efficiency for treating NOP wastewater in Example 2 and Example 7 to Example 10.

[0042] Figure 7 This is a graph showing the degradation efficiency of treating NOP wastewater in Example 8 and Example 11 to Example 14 at different peak-to-peak voltages.

[0043] Figure 8This is a diagram of energy utilization efficiency for treating NOP wastewater in Example 8 and Example 11 to Example 14.

[0044] Fig. 9 This is a graph showing the degradation efficiency of treating NOP wastewater in Example 2 and Example 15 to Example 16 at different peak-to-peak voltages.

[0045] Fig.10 This is a diagram of energy utilization efficiency for treating NOP wastewater in Example 2 and Example 15 to Example 16.

[0046] Fig.11 This is a graph showing the degradation efficiency of treating NOP wastewater in Example 2 and Example 17 at different peak-to-peak voltages.

[0047] Fig.12 This is the energy utilization efficiency diagram for treating NOP wastewater in Example 2 and Example 17.

[0048] Fig.13 This is a graph showing the degradation efficiency of treating NOP wastewater in Example 2 and Example 18 to Example 19 at different peak-to-peak voltages.

[0049] Fig.14 This is a diagram of energy utilization efficiency for treating NOP wastewater in Example 2 and Example 18 to Example 19.

[0050] Fig.15 This is a graph showing the degradation efficiency of treating NOP wastewater in Example 2 and Example 20 to Example 23 at different peak-to-peak voltages.

[0051] Fig.16 This is a diagram of energy utilization efficiency for treating NOP wastewater in Example 2 and Example 20 to Example 23.

[0052] In the figure: 1-surface discharge plasma reactor; 2-high voltage electrode; 3-ground electrode; 4-conductor; 5-porous plate; 6-overflow trough; 7-liquid inlet; 8-air inlet; 9-water blocking baffle; 10-air outlet; 11-liquid outlet; 12-liquid storage bottle; 13-peristaltic pump; 14-plastic hose; 15-air pump; 16-high voltage AC power supply; 17-high voltage probe; 18-current probe; 19-oscilloscope; 20-insulating medium. DETAILED DESCRIPTION

[0053] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0054] Example 1

[0055] In a preferred embodiment of the present invention, Figure 1-Figure 2 As shown, this embodiment provides a device for treating flotation collector wastewater based on multi-electrode low-temperature plasma surface discharge, the device includes a surface discharge plasma reactor 1, a liquid storage bottle 12 for storing flotation collector wastewater, a peristaltic pump 13 for continuously circulating the wastewater from the liquid storage bottle 12 to the surface discharge plasma reactor 1 to improve the reactor processing capacity, an air pump 15 for providing oxygen-containing gas to the surface discharge plasma reactor 1 to ensure continuous generation of active substances such as ozone in the discharge area, a high-voltage AC power supply 16 for supplying power to the surface discharge plasma reactor 1 to generate plasma, and an oscilloscope 19 for displaying and recording voltage and current signals collected by the surface discharge plasma reactor 1 during the discharge process.

[0056] like Figure 1 As shown, the surface discharge plasma reactor 1 has a liquid inlet 7 and an air inlet 8. The liquid inlet 7 is connected to the liquid storage bottle 12 through a plastic hose 14 and a peristaltic pump 13, so that the waste water in the liquid storage bottle 12 can be passed into the surface discharge plasma reactor 1 through the peristaltic pump 13; the air inlet 8 is connected to the air pump 15 through the plastic hose 14, so that oxygen-containing gas can be passed into the surface discharge plasma reactor 1. The oxygen-containing gas in this embodiment takes air as an example.

[0057] The surface discharge plasma reactor 1 is provided with a surface discharge plasma module, which includes a discharge electrode system having a high-voltage wiring electrode and a low-voltage wiring electrode. Specifically, in this embodiment, it includes a horizontally arranged ground electrode 3 and a high-voltage electrode 2 connected to a high-voltage AC power supply 16. The ground electrode 3 is connected to the ground wire in the high-voltage AC power supply 16 through a wire. Figure 2 As shown, the high-voltage electrode 2 is sleeved or coated with an insulating medium 20, the high-voltage electrode 2 is arranged inside the insulating medium 20, and a saturated solution is sealed between the high-voltage electrode 2 and the insulating medium 20, and the high-voltage electrode 2 and the ground electrode 3 are in contact with the wastewater entering from the liquid inlet 7 and the oxygen-containing gas entering from the gas inlet 8 to form a surface discharge to generate a low-temperature plasma. Specifically, one end of the insulating medium 20 is closed and the other end is open. The outer diameter of the high-voltage electrode 2 is equal to the inner diameter of the insulating medium 20, so that the high-voltage electrode 2 can be inserted into the insulating medium 20 from the open end, and the other end of the high-voltage electrode 2 extends from the insulating medium 20 and is connected to the high-voltage AC power supply 16, and the saturated solution is injected into the gap between the high-voltage electrode 2 and the insulating medium 20, and the open end of the insulating medium 20 is sealed with a sealant to form a sealed state to ensure that the discharge energy is not consumed in the gap.

[0058] In this embodiment, a quartz tube with a closed end having a length of 160 mm and a thickness ranging from 1.0 to 3.0 mm is used as the insulating medium 20, the high-voltage electrode 2 is a copper rod (length 200 mm, diameter 7 mm); a threaded rod stainless steel electrode (length 200 mm, diameter 10 mm) is used as the grounding electrode 3, and the saturated solution is at least one of a saturated sodium chloride solution, a saturated KCl solution and a saturated oxalic acid solution, preferably a saturated sodium chloride solution; the number of high-voltage electrodes 2 is 3, and the 3 high-voltage electrodes 2 are connected in parallel to the high-voltage AC power supply 16, and 4 parallel threaded rod stainless steel electrodes with a length of 200 mm and a diameter of 10 mm are in contact with the liquid as grounding electrodes, and the grounding electrode 3 and the high-voltage electrode 2 are placed at equal intervals, and the high-voltage electrode 2 is connected to the output end of the high-voltage AC power supply 16 through a wire 4, and the grounding electrode 3 is connected to the ground wire in the high-voltage AC power supply 16 through a wire 4; a voltage is applied to the high-voltage electrode 2, so that a discharge plasma is generated at the contact position between the surface of the insulating medium 20 outside the high-voltage electrode 2 and the liquid.

[0059] like Figure 1 As shown, the surface discharge plasma reactor 1 also has a liquid outlet 11 and a gas outlet 10, and the gas outlet 10 and the liquid outlet 11 are connected to the liquid storage bottle 12 through a pipeline, and the pipeline connected to the gas outlet 10 extends into the interior of the surface discharge plasma reactor 1; in this embodiment, the gas outlet 10 and the liquid outlet 11 are arranged at one end of the surface discharge plasma reactor 1, and the gas inlet 8 and the liquid inlet 7 are arranged at the other end of the surface discharge plasma reactor 1, and the gas inlet 8 and the liquid inlet 7 are arranged above the gas outlet 10 and the liquid outlet 11 in the height direction, so that the wastewater can flow from the liquid inlet 7 to the liquid outlet 11 under the action of gravity.

[0060] like Figure 1 As shown, the surface discharge plasma reactor 1 is provided with the following components in sequence from the liquid inlet 7 to the liquid outlet 11:

[0061] A first baffle plate, which is arranged at one end close to the liquid inlet 7, and a channel for the wastewater entering from the liquid inlet 7 to pass through is provided between the first baffle plate and the bottom wall of the surface discharge plasma reactor 1;

[0062] A second baffle plate is arranged on a side of the first baffle plate away from the liquid inlet 7, and an overflow groove 6 is formed between the second baffle plate and the first baffle plate;

[0063] a porous plate 5, which is arranged on a side of the second baffle plate away from the liquid inlet 7, and has a plurality of through holes for the wastewater entering from the liquid inlet 7 to pass through;

[0064] a water-blocking baffle 9, which is arranged at one end close to the liquid outlet 11, and the height of the water-blocking baffle 9 is lower than the height of the water-blocking baffle 9;

[0065] The ground electrode 3 and the high voltage electrode 2 are arranged between the water blocking baffle 9 and the porous plate 5 .

[0066] An overflow trough 6 and a porous plate 5 are arranged at one end of the liquid inlet 7 of the surface discharge plasma reactor 1. This design can avoid uneven liquid layer thickness caused by water flow impact at the water inlet and increase the adjustable flow range. A water blocking baffle (110 mm long, with a height adjustment range of 10-23 mm) is arranged at one end of the liquid outlet 11 of the surface discharge plasma reactor 1 to ensure the thickness of the liquid layer, and at the same time, the immersion depth of the high-voltage electrode 2 in the liquid in the water tank can be adjusted. After the water overflows, it flows into the liquid storage bottle 12 through the liquid outlet 11 pipeline.

[0067] The surface discharge plasma reactor 1 is externally connected to a liquid storage bottle 12 and a peristaltic pump 13 to form a water circulation system. The waste water is circulated from the liquid storage bottle 12 to the liquid inlet 7 by the peristaltic pump 13, which can improve the processing capacity of the reactor. During operation, the flowing water body enhances the gas-liquid mass transfer compared with the static water body, which is beneficial for the active substances generated by the surface discharge to enter the liquid phase. The circulating solution is used to reduce the thermal effect generated by the high-voltage discharge, avoid the waste of electrical energy due to heat generation, and improve the energy utilization efficiency of the reactor.

[0068] The air pump 15 adjusts the rotor flow controller (gas flow 6-60L / min) to blow the ozone generated in the discharge area into the solution in the liquid storage bottle 12 through the outlet 10 for secondary utilization. The newly added air can be used as an oxygen source to ensure the continuous generation of active substances such as ozone in the discharge area, thereby improving the efficiency of plasma water treatment.

[0069] The oscilloscope 19 is connected to the high-voltage AC power supply 16 via a high-voltage probe 17 and a current probe 18 , and is used to display and record voltage and current signals collected by the surface discharge plasma reactor 1 during the discharge process.

[0070] In this embodiment, the high-voltage AC power supply 16 is purchased from Nanjing Suman Company, the model is CTP-2000K, the frequency is 5-20KHz, the power is 0-500W, the modulation pulse frequency is adjustable from 1-1000Hz, and the duty cycle is 1%-99%.

[0071] The principle of this embodiment is: when the air pump 15 inputs air into the surface discharge plasma reactor 1, the peristaltic pump 13 passes the wastewater in the liquid storage bottle 12 into the surface discharge plasma reactor 1. Since a part of the high-voltage electrode 2 is immersed in the wastewater and the other part is exposed to the air, by turning on the high-voltage AC power supply 16, a low-temperature plasma is generated in the contact area between the high-voltage electrode 2 and the wastewater liquid surface. The low-temperature plasma can generate ultrasonic waves and ultraviolet rays, and oxygen-containing substances in the air and the wastewater liquid (including O2 and H2O, etc.) are subjected to the action of high-energy electrons in the plasma and converted into oxygen-containing active substances (including O3, O·, ·OH, etc.). Ultrasonic waves, ultraviolet rays and active substances (hydrogen peroxide, ozone, hydroxyl radicals, etc.) jointly realize the degradation of pollutants in the wastewater, and the air pump 15 blows the ozone generated in the discharge area into the solution in the liquid storage bottle 12 for secondary utilization.

[0072] In view of the need to blow the active substances generated by discharge into the wastewater solution by aeration in the prior art for reaction, some short-lived active substances such as •OH, •O, •HO2 may be deactivated before entering the mineral processing wastewater solution, which will lead to problems such as low degradation efficiency and energy waste. In this embodiment, a saturated solution is sealed between the high-voltage electrode 2 and the insulating medium 20, and the high-voltage electrode 2 is directly discharged at the edge where the insulating medium 20 contacts the liquid, that is, surface discharge plasma discharge, and the active substances generated by the high-voltage electrode 2 are directly in contact with the mineral processing wastewater solution, and there is no need to blow the generated active substances into the wastewater solution by aeration for reaction, which greatly improves the degradation efficiency. In addition, the device in this embodiment is conducive to gas-liquid mass transfer, has a large plasma generation area, high ozone generation, strong ultraviolet radiation, and a simple and practical reactor structure, which can effectively improve the degradation performance of the flotation collector. Compared with the device in the prior art, under the condition of achieving the same degradation effect, the power of the device in this embodiment is only 14W, while the others require 46W, which greatly reduces energy consumption.

[0073] Example 2

[0074] A method for treating flotation collector wastewater based on multi-electrode low-temperature plasma surface discharge, comprising the following steps:

[0075] S1. Sodium hydroxide and hydrochloric acid were added to the ore dressing wastewater solution containing 60 mg / L N-hydroxyphthalimide (NOP) (initial conductivity was 93 µs / cm) to adjust the pH to 7.0, and ultrasonically mixed.

[0076] S2, take 1L of mineral processing wastewater solution and pour it into the liquid storage bottle 12 of the flotation collector wastewater treatment device based on multi-electrode low-temperature plasma. The flotation collector wastewater treatment device based on multi-electrode low-temperature plasma used in this embodiment has the same main structure as the device in Example 1, and the only difference is that the number of high-voltage electrodes 2 is 1, the number of grounding electrodes 3 is 2, and the saturated solution is a saturated sodium chloride solution. Turn on the air pump 15 and the peristaltic pump 13, the air pump 15 sends air into the air inlet 8, and then into the reaction chamber, while the peristaltic pump 13 allows the mineral processing wastewater solution to enter the plastic hose 4 from the liquid storage bottle 12, and then flow down along the side wall from the liquid inlet 7. After the cycle is stable, turn on the high-voltage AC power supply 16, and set the duty cycle and modulation frequency of the high-voltage AC power supply to 60% and 200Hz respectively, the thickness (Dt) of the insulating medium 20 is 1.0mm, the immersion depth (D) of the high-voltage electrode 2 is 1 / 2 of its outer diameter, and the curvature radius (Cr) of the high-voltage electrode 2 is 6.0mm, the peak-to-peak voltage of the high-voltage AC power supply is 16kV, 18kV, 20kV, 22kV, 24kV and 26kV respectively, so that the low-temperature plasma generated in the low-temperature plasma device is in contact with the mixed wastewater, and the ultrasonic wave and ultraviolet light generated by the low-temperature plasma and the active substances (hydrogen peroxide, ozone, hydroxyl radicals, etc.) generated by the low-temperature plasma jointly realize the degradation of NOP in the wastewater. After a certain reaction time, 5mL of the treated mineral processing wastewater is taken from the liquid storage bottle 12, and the NOP content is detected by Agilent's high performance liquid chromatograph (1260 InfintyAgilent).

[0077] Example 3

[0078] Except that the thickness of the insulating medium 20 is 1.5 mm, the remaining operations are the same as those of the second embodiment.

[0079] Example 4

[0080] Except that the thickness of the insulating medium 20 is 2.0 mm, the remaining operations are the same as those of the second embodiment.

[0081] Example 5

[0082] Except that the thickness of the insulating medium 20 is 2.5 mm, the remaining operations are the same as those of the second embodiment.

[0083] Example 6

[0084] Except that the thickness of the insulating medium 20 is 3.0 mm, the remaining operations are the same as those of the second embodiment.

[0085] Example 7

[0086] Except that the curvature radius of the high voltage electrode 2 is 4.5 mm, the remaining operations are the same as those in Example 3.

[0087] Example 8

[0088] Except that the curvature radius of the high voltage electrode 2 is 5.0 mm, the remaining operations are the same as those in Example 3.

[0089] Example 9

[0090] Except that the curvature radius of the high voltage electrode 2 is 5.5 mm, the remaining operations are the same as those in Example 3.

[0091] Example 10

[0092] Except that the curvature radius of the high voltage electrode 2 is 6.5 mm, the remaining operations are the same as those in Example 3.

[0093] Embodiment 11

[0094] Except that the immersion depth of the high voltage electrode 2 is 0 mm, the remaining operations are the same as those in Example 8.

[0095] Example 12

[0096] Except that the immersion depth of the high voltage electrode 2 is 1 / 4, the remaining operations are the same as those in Example 8.

[0097] Embodiment 13

[0098] Except that the immersion depth of the high voltage electrode 2 is 3 / 4, the remaining operations are the same as those of Example 8.

[0099] Embodiment 14

[0100] Except that the immersion depth of the high voltage electrode 2 is 1, the remaining operations are the same as those in Example 8.

[0101] Embodiment 15

[0102] Except that the saturated solution is a saturated KCl solution, the remaining operations are the same as those in Example 2.

[0103] Example 16

[0104] Except that the saturated solution is a saturated oxalic acid solution, the remaining operations are the same as those in Example 2.

[0105] Embodiment 17

[0106] Except for the ground electrode 3, there is an insulating medium (the insulating medium is made of quartz and has a thickness of 1.5 mm), and the remaining operations are the same as those in Example 2.

[0107] Embodiment 18

[0108] Except that the number of high-voltage electrodes is 2 and the number of ground electrodes is 3, the rest of the operations are the same as those in Example 2.

[0109] Embodiment 19

[0110] Except that the number of high-voltage electrodes is 3 and the number of ground electrodes is 4, the remaining operations are the same as those in Example 2.

[0111] Embodiment 20

[0112] Except that the initial conductivity of the wastewater is 210 μs / cm, the remaining operations are the same as those in Example 2.

[0113] Embodiment 21

[0114] Except that the initial conductivity of the wastewater is 480 μs / cm, the remaining operations are the same as those in Example 2.

[0115] Embodiment 22

[0116] Except that the initial conductivity of the wastewater is 860 μs / cm, the remaining operations are the same as those in Example 2.

[0117] Embodiment 23

[0118] Except that the initial conductivity of the wastewater is 1480 μs / cm, the remaining operations are the same as those in Example 2.

[0119] Results testing and analysis

[0120] The degradation efficiency of NOP wastewater treated in Examples 2 to 23 and the energy utilization efficiency of NOP wastewater treated were calculated as follows:

[0121] (1) Degradation efficiency of NOP wastewater treatment: NOP concentration was detected by high performance liquid chromatography (HPLC, 1260 Infinty Agilent). The chromatographic column was MS-2C18A column (Eclipse, Ø4.6mmx100mm). The mobile phase consisted of acetonitrile and 18mM phosphate in a ratio of 65:35 v / v, with a flow rate of 0.5mL / min. The detection wavelength, injection volume and retention time were 244 nm, 5μL and 10 min, respectively. During the experiment, the sampling interval was set to 10min, and the NOP degradation efficiency was calculated as follows:

[0122]

[0123] C t -Concentration of pollutants after discharge treatment (g / L); C0-initial concentration of pollutants (g / L)

[0124] (2) Energy efficiency of NOP wastewater treatment: The calculation formula is as follows:

[0125]

[0126] P-discharge power (W); f-discharge frequency (Hz); C m -capacitance (0.47μF); U-peak voltage (V); U m - capacitor voltage (V); S- Lissajous figure area.

[0127]

[0128] C0-initial concentration of pollutants (g / L); V-volume of treated solution (L); η-removal rate (%); P-discharge power (kW); T-discharge time (h).

[0129] Test results such as Figures 3 to 16 shown.

[0130] like Figure 3 As shown in the figure, the thickness of the quartz dielectric is an important parameter that affects the electrical characteristics of the plasma reactor. When examining the influence of the thickness of the discharge dielectric in the discharge reactor structure, the thickness of the dielectric tube can change the impedance of the reaction system, thereby affecting the current size, discharge power, and the generation of active substances. The dielectric thickness affects the high-voltage resistance of the discharge reactor, that is, the resistance to damage and bursting due to increased discharge voltage. The thicker the dielectric, the stronger the high-voltage resistance of the discharge reactor. Therefore, when selecting the dielectric thickness, the high-voltage resistance of the discharge reactor should be comprehensively considered. Figure 3 The effect of dielectric thickness on NOP degradation under different voltage driving.

[0131] from Figure 3 It can be seen that with the increase of applied voltage, the degradation efficiency of NOP with different dielectric thicknesses shows a trend of gradual increase; at the same time, under the same voltage conditions, increasing dielectric thickness is not conducive to the degradation of NOP. When the quartz dielectric thickness increases from 1.0 mm to 3.0 mm, the degradation efficiency of NOP under 26 kV conditions decreases by 30%, but when the dielectric thickness is 1.0 mm and 1.5 mm, the degradation efficiency of NOP is less affected. However, as the dielectric thickness increases, the breakdown voltage decreases. Therefore, considering the high-voltage resistance of the discharge reactor, the dielectric thickness is selected as 1.5 mm and the voltage is selected at 26 kV.

[0132] like Figure 4As shown in the figure, at the same voltage of 26kV, different dielectric thicknesses affect the energy utilization efficiency of NOP degradation. The increase in dielectric thickness leads to a trend of energy utilization efficiency first slowly decreasing and then rapidly decreasing, especially when the dielectric thickness is 3.0mm, its energy utilization efficiency is only 0.22 g / (kW•h), while when the dielectric thickness is 1.0mm and 1.5mm, the energy utilization efficiency is close, which is 1.62 and 1.59 g / (kW•h) respectively. This is because, on the one hand, the greater the dielectric thickness, the greater the impedance, resulting in a decrease in current and maximum electric field intensity; on the other hand, the dielectric thickness will affect the diffusion state of heat. The thicker the dielectric, the less conducive it is to the diffusion of heat, which in turn affects the density of active substances in the tube. Therefore, considering the utilization efficiency and the high-voltage resistance of the discharge reactor, the dielectric thickness of 1.5mm is selected.

[0133] like Figure 5 As shown, the electrode curvature radius also plays a decisive role in the overall discharge performance. This embodiment changes the electrode curvature radius under the discharge structure conditions of the high-voltage electrode 2 to explore the effect of the curvature radius on the degradation of NOP along the surface discharge. As can be seen from the figure, when the curvature radius decreases, the degradation effect first increases and then decreases. When the curvature radius is 5.0mm, the degradation effect of NOP is the best, and as the discharge voltage increases, its degradation efficiency shows a trend of gradually increasing. At 26kV, its degradation efficiency can reach 64.2%. As the curvature radius increases to 6.0mm or 6.5mm, the degradation efficiency drops to 44.6% and 37.9%, respectively. Therefore, combined with the degradation efficiency, the electrode curvature radius is suitable at 5.0mm.

[0134] like Figure 6 As shown in the figure, the effect of curvature radius on energy utilization efficiency at the same voltage of 26kV was investigated. Obviously, with the increase of curvature radius, the energy utilization efficiency of NOP shows a trend of increasing first and then decreasing. When the curvature radius is 6.5mm, its energy utilization efficiency is only 0.96 g / (kW·h), while when the curvature radius is reduced to 5mm, its energy utilization efficiency reaches 2.17 g / (kW·h), an increase of 126%. Therefore, considering comprehensively, it is appropriate to select an electrode curvature radius of 5.0mm.

[0135] like Figure 7 As shown, the high voltage electrode 2 of this embodiment is wrapped by a quartz medium, and the electrode is immersed to a depth of ( Figure 7D in the figure is one of the objects for investigating the effect of the structure of the high-voltage electrode 2 on the degradation efficiency of NOP. When investigating the effect of the high-voltage electrode structure in the discharge reactor structure, the immersion depth of the high-voltage electrode can affect the electric field distribution, electric field density and the generation of discharge active substances. Therefore, it is very necessary to investigate the effect of D when optimizing the high-voltage electrode of the discharge reactor. In order to study the effect of the electrode immersion depth on the plasma parameters, the water surface electrode was placed at the immersion depths of 0, 1 / 4, 1 / 2, 3 / 4 and 1 of the entire electrode. As shown in the figure, as the voltage increases from 16kV to 16kV, the degradation efficiency of NOP increases at different immersion depths; in addition, under the same applied voltage, as the immersion depth increases, the degradation efficiency of NOP decreases significantly. At 26kV, the immersion depth is 0, that is, when the high-voltage electrode is tangent to the liquid phase, its degradation efficiency is 70.9%, which is 3.94 times that of the immersion depth of 1; at the same time, we found that the degradation efficiency of NOP is equivalent at immersion depths of 0 and 1 / 4. Since the liquid is flowing during the embodiment, and considering the influence of factors such as liquid surface tension, it is easy to cause body discharge, affecting the discharge effect. Therefore, by comparing the degradation efficiency of NOP when the immersion depth is 0 and 1 / 4, combined with the actual process of plasma treatment, placing the electrode at a position 1 / 4 of the water surface can effectively improve the working efficiency and performance of the electrode.

[0136] like Figure 8 As shown in the figure, the effect of immersion depth on energy utilization efficiency shows that the energy utilization efficiency decreases slowly first and then decreases significantly with the increase of immersion depth. When the immersion depth is 0 and 1 / 4, the energy utilization efficiency of NOP is 2.76 g / (kW·h) and 2.68 g / (kW·h), respectively, while when the immersion depth is 3 / 4 and 1, its energy utilization efficiency is only 0.68 g / (kW·h) and 0.29 g / (kW·h). Therefore, it is appropriate to choose the position where the electrode is immersed to a depth of 1 / 4 after comprehensive consideration.

[0137] like Fig. 9 As shown, the device of this embodiment is a surface discharge reactor, which uses a copper rod inserted into a quartz medium. Since there is a gap between the two solid contacts, in order to avoid discharge in the gap between the high-voltage electrode and the quartz medium, which leads to energy waste. Therefore, a saturated solution is injected into the gap to eliminate the effect of the gap on the discharge and improve the reaction performance. In order to further study the effect of the high-voltage electrode filling liquid on the overall discharge effect, the embodiment selected saturated KCl, saturated NaCl and saturated oxalic acid solutions, and investigated the degradation effects of these three solutions on the flotation collector NOP. The results of the embodiment are shown in FIG. Fig. 9As shown in the figure, the three saturated solutions gradually increase with the increase of discharge voltage, and the degradation efficiency of the three saturated solutions for NOP is slightly different. For example, at 26 kV, the degradation efficiency is 67.8%, 69.2%, and 70.8% when the filling liquid is saturated KCl, saturated NaCl, and saturated oxalic acid solution, respectively, and the degradation efficiency fluctuates within 3%. Therefore, considering economic factors, it is appropriate to use saturated NaCl solution.

[0138] like Fig.10 As shown, through the energy utilization efficiency, we found that the energy utilization efficiency of different saturated solutions on NOP fluctuates around 2.68 g / (kW·h), and the impact is small. By comparison, the three saturated solutions have little effect on the energy utilization efficiency of NOP, indicating that the substances in the saturated solution have no significant effect on the degradation of NOP by the new surface-type DBD reactor developed in this embodiment. This is because the role of the saturated solution is to fill the solution to reduce the impact of the gap on the discharge, and on the other hand, the ion concentration in the saturated solution is higher, which can enhance the conductivity. However, the solutions used in the embodiments are all saturated solutions, and they can achieve the same effect. Therefore, taking into account factors such as economic practicality, the commonly used saturated NaCl is selected as the ideal electrolytic salt for this embodiment.

[0139] like Fig.11 As shown, in order to study the influence of the ground electrode dielectric on the discharge characteristics, this embodiment investigates the degradation efficiency of NOP in the ground electrode with and without dielectric. As shown in the figure, with the increase of voltage, the degradation efficiency of NOP in the ground electrode with dielectric is low and the change is not significant, while the degradation efficiency of NOP in the ground electrode without dielectric increases significantly; by comparing the ground electrode with and without dielectric at the same voltage, it can be seen that the degradation efficiency of NOP in the ground electrode without dielectric is much greater than that in the ground electrode with dielectric. For example, when the voltage is 26 kV, the degradation efficiency is 23.9% when the ground electrode has dielectric, which is only 33.7% of that without dielectric. Therefore, it is appropriate to select the ground electrode without dielectric.

[0140] like Fig.12 As shown in the figure, the energy utilization efficiency is given. Regardless of whether the grounding electrode has a dielectric or not, the energy utilization efficiency of 24 kV is greater than that of 22 kV. It is not difficult to find from the bar graph that the energy utilization efficiency of the grounding electrode without a dielectric is much greater than that with a dielectric. For example, when the voltage is 22 kV, the energy utilization efficiency of the grounding electrode without a dielectric for NOP is 2.34 g / (kW·h), which is 6.3 times that of the dielectric at the same voltage. Therefore, it is appropriate to choose a grounding electrode without a dielectric.

[0141] like Fig.13As shown, the electrode structure has a great influence on the distribution of plasma and the generation of active substances. The selection of a surface discharge reactor with different electrode structures directly affects the degradation efficiency and energy utilization efficiency of organic wastewater. Therefore, in order to further obtain a stable and uniform plasma area, this embodiment establishes a research on an equipotential multi-electrode parallel surface discharge reactor for organic wastewater treatment. As shown in the figure, with the increase of the driving voltage, the degradation efficiency of NOP with different high-voltage pole numbers shows an increasing trend. When the number of high-voltage poles is 3, the voltage is 26kV and the degradation efficiency is 95.9%, which is 2.59 times that of the discharge voltage at 16kV. Under the same voltage, the increase in the number of high-voltage poles significantly increases the degradation efficiency of NOP, such as 1.39 times when the number of high-voltage poles is 3. Therefore, it is appropriate to select 3 high-voltage poles.

[0142] like Fig.14 As shown in the figure, through the influence of the number of high-voltage poles on the energy utilization efficiency of NOP, the study found that with the increase in the number of high-voltage poles, its energy utilization efficiency has also been greatly improved. For example, when the number of high-voltage poles is three, its energy utilization efficiency is 4.16 g / (kW·h), which is 1.55 times that of the number of 1. Therefore, it is appropriate to choose 3 high-voltage poles.

[0143] like Fig.15 As shown, in a sense, the initial conductivity of the wastewater solution is an important factor affecting the surface discharge system, because it affects the nature of the discharge and the generation of chemically active substances, so it is relevant to evaluate its impact on pollutant degradation. Since the conductivity of the solution changes during the discharge treatment process, the conductivity investigated in this embodiment is the effect of the initial conductivity of the solution. The conductivity of the NOP solution was adjusted using Na2SO4. As shown in the figure. With the extension of the discharge time, the degradation efficiency of NOP under different conductivities of the solution gradually increases; when the solution conductivity is increased from 93 µs / cm to 480 µs / cm, the degradation efficiency of NOP increases slowly; when the solution conductivity is increased from 480 µs / cm to 860 µs / cm, the degradation efficiency of NOP increases from 74.9% to 86.2%, with a large increase; however, when the solution conductivity continues to increase to 1480 µs / cm, its degradation efficiency does not change significantly, only increasing by 1.6%. Therefore, considering all factors, it is appropriate to select a conductivity of 860 µs / cm.

[0144] like Fig.16As shown in the figure, within the low conductivity range of 480 µs / cm, as the solution conductivity increases, the kinetic constant increases slightly; when the conductivity is further increased to 860 µs / cm, the kinetic constant increases significantly; and further increasing the conductivity has little effect on the kinetic constant. For example, when the solution conductivity is adjusted to 860 µs / cm, the kinetic constant is 0.0667 min -1 , which is 1.46 times that of 480 µs / cm. When the conductivity is adjusted to 1480 µs / cm, the kinetic constant increases by only 0.002 min compared to 860 µs / cm. -1 Therefore, after comprehensive consideration, the conductivity of 860 µs / cm is appropriate.

[0145] In summary, after the above tests, 1.5 mm is the appropriate dielectric thickness, 26 kV is the appropriate voltage, 5.0 is the appropriate high-voltage electrode curvature radius, 1 / 4 is the appropriate high-voltage electrode immersion depth, saturated NaCl is the appropriate high-voltage electrode filling liquid, no dielectric is the appropriate grounding electrode, 3 is the appropriate number of high-voltage electrodes, and 860 µs / cm is the appropriate wastewater solution conductivity.

[0146] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A device for treating flotation collector wastewater based on multi-electrode low-temperature plasma surface discharge, characterized in that: include: High voltage AC power supply (16); A storage bottle (12) for storing flotation collector wastewater; A surface discharge plasma reactor (1) having a gas inlet (8) connected to an oxygen-containing gas and a liquid inlet (7) connected to the liquid storage bottle (12); a grounding electrode (3) and a high-voltage electrode (2) connected to the high-voltage AC power supply (16) are arranged inside the surface discharge plasma reactor (1); the high-voltage electrode (2) is coated with an insulating medium (20); a saturated solution is sealed in the gap between the high-voltage electrode (2) and the insulating medium (20); the high-voltage electrode (2) and the grounding electrode (3) are in contact with wastewater entering from the liquid inlet (7) to form surface discharge and generate low-temperature plasma; The ground electrode (3) and the high-voltage electrode (2) are arranged side by side in the surface discharge plasma reactor (1), and the lower ends of the ground electrode (3) and the high-voltage electrode (2) are in contact with the wastewater entering from the liquid inlet (7), and the upper ends are in contact with the oxygen-containing gas entering from the gas inlet (8); The surface discharge plasma reactor (1) also has a liquid outlet (11), and the surface discharge plasma reactor (1) is also provided with: a first baffle plate, which is arranged at one end close to the liquid inlet (7), and a channel for wastewater entering from the liquid inlet (7) to pass through is provided between the first baffle plate and the bottom wall of the surface discharge plasma reactor (1); A second baffle plate, which is arranged on a side of the first baffle plate away from the liquid inlet (7), and an overflow groove (6) is formed between the second baffle plate and the first baffle plate; a porous plate (5) arranged on a side of the second baffle plate away from the liquid inlet (7), the porous plate (5) having a plurality of through holes for the wastewater entering from the liquid inlet (7) to pass through; a water-blocking baffle (9) arranged at one end close to the liquid outlet (11), the height of the water-blocking baffle (9) being lower than the height of the second baffle; The grounding electrode (3) and the high-voltage electrode (2) are arranged between the water-blocking baffle (9) and the porous plate (5); The number of the grounding electrodes (3) and the number of the high-voltage electrodes (2) are both multiple, and the multiple grounding electrodes (3) and the multiple high-voltage electrodes (2) are arranged side by side in sequence and at equal intervals; The saturated solution is at least one of a saturated sodium chloride solution, a saturated KCl solution and a saturated oxalic acid solution; The thickness of the outer wall of the insulating medium (20) is 1.0-3.0 mm, the depth of the high-voltage electrode (2) immersed in the flotation collector wastewater is 1 / 4-3 / 4 of its outer diameter, and the radius of curvature of the high-voltage electrode (2) is 4.5-6.5 mm.

2. The device for treating flotation collector wastewater based on multi-electrode low-temperature plasma surface discharge according to claim 1 is characterized in that: The surface discharge plasma reactor (1) also has a gas outlet (10), and the gas outlet (10) and the liquid outlet (11) are connected to the liquid storage bottle (12) through a pipeline; the gas outlet (10) and the liquid outlet (11) are arranged at one end of the surface discharge plasma reactor (1), and the gas inlet (8) and the liquid inlet (7) are arranged at the other end of the surface discharge plasma reactor (1), and the gas inlet (8) and the liquid inlet (7) are arranged above the gas outlet (10) and the liquid outlet (11) in the height direction.

3. The device for treating flotation collector wastewater based on multi-electrode low-temperature plasma surface discharge according to claim 1 is characterized in that: Also includes: An oscilloscope (19) for displaying and recording voltage and current signals collected by the surface discharge plasma reactor (1) during the discharge process, wherein the oscilloscope (19) is connected to the high-voltage AC power supply (16).

4. The device for treating flotation collector wastewater based on multi-electrode low-temperature plasma surface discharge according to claim 1 is characterized in that: The high-voltage electrode (2) is a copper rod, and the insulating medium (20) is a quartz tube.

5. A method for treating flotation collector wastewater based on multi-electrode low-temperature plasma surface discharge, characterized in that: The flotation collector wastewater is treated by using the device as described in any one of claims 1 to 4.

6. The method for treating flotation collector wastewater based on multi-electrode low-temperature plasma surface discharge according to claim 5 is characterized in that: The following steps are involved: S1. Pre-treat flotation collector wastewater; S2, pouring the flotation collector wastewater into the liquid storage bottle (12), introducing oxygen-containing gas into the surface discharge plasma reactor (1) through the gas inlet (8), and introducing the flotation collector wastewater into the surface discharge plasma reactor (1) through the liquid inlet (7), wherein the introduced flotation collector wastewater does not completely immerse the high-voltage electrode (2) and the grounding electrode (3); turning on the high-voltage AC power supply (16), the high-voltage electrode (2) and the grounding electrode (3) contact the flotation collector wastewater to form a surface discharge and generate a low-temperature plasma, and the ultrasonic wave and ultraviolet rays generated by the low-temperature plasma, together with the active substances generated by the low-temperature plasma, degrade the pollutants in the wastewater.

7. The method for treating flotation collector wastewater based on multi-electrode low-temperature plasma surface discharge according to claim 6, characterized in that: In step S1, Na2SO4 is added to adjust the initial conductivity of the flotation collector wastewater to 93-1480µs / cm; the method for pre-treating the flotation collector wastewater includes: adding sodium hydroxide or hydrochloric acid to adjust the pH of the flotation collector wastewater to 7.0, and ultrasonically mixing; In step S2, the duty cycle and modulation frequency of the high-voltage AC power supply (16) are 60% and 200 Hz respectively, the peak-to-peak voltage is 21-29 kV, the thickness of the outer wall of the insulating medium (20) is 1.0-3.0 mm, the depth of the high-voltage electrode (2) immersed in the flotation collector wastewater is 1 / 4-3 / 4 of its outer diameter, and the radius of curvature of the high-voltage electrode (2) is 4.5-6.5 mm.

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