A method for treating salt-containing ammonia-nitrogen wastewater by cyclone electrolysis

Abstract

The application discloses a method for treating salt-containing ammonia-nitrogen wastewater by using a cyclone electrolysis device, and belongs to the technical field of wastewater treatment. The method comprises the following steps: adjusting the pH value of untreated salt-containing ammonia-nitrogen wastewater, adding a chloride salt solution to adjust the chloride ion concentration of the salt-containing ammonia-nitrogen wastewater, and obtaining pretreated salt-containing ammonia-nitrogen wastewater; using the pretreated salt-containing ammonia-nitrogen wastewater as an electrolyte, and placing the electrolyte in a cyclone electrolysis device to perform preliminary cyclone electrolysis; increasing the temperature and the current density of the preliminary cyclone electrolysis, and further performing cyclone electrolysis to obtain treated wastewater. The method for treating salt-containing ammonia-nitrogen wastewater by using a cyclone electrolysis device is based on the oxidation of active chlorine and active oxygen and the step-by-step utilization of chloride ions, realizes deep degradation and removal of ammonia-nitrogen and efficient removal of high-chloride salts, avoids the introduction of other impurities into the reaction system, does not cause any side effects on electrolysis, and has the advantages of mild and easy-to-control reaction conditions, simple reaction device, low cost, no secondary pollution or little secondary pollution, and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment, in particular to a method for treating salt-containing ammonia nitrogen wastewater by cyclone electrolysis. BACKGROUND

[0002] In recent years, with the rapid development of the photovoltaic industry in China, the resource and environmental problems in the photovoltaic manufacturing process have become increasingly apparent. In particular, the problem of wastewater pollution in the production cycle of the photovoltaic industry is particularly prominent, mainly including polysilicon wastewater, cutting and grinding wastewater, organic silicon wastewater, and cleaning silicon wafer wastewater. Therefore, photovoltaic production wastewater exhibits characteristics such as multiple waste components, complex composition, strong acid-base, and poor biodegradability. High concentrations of salt and ammonia nitrogen are the difficulties and keys of photovoltaic wastewater treatment. Traditional ammonia nitrogen treatment technologies can be divided into physical and chemical methods (point chlorination method, chemical precipitation method, membrane separation method, ion exchange method, etc.) and biological methods (activated sludge method, biofilm method, anaerobic ammonia oxidation method, etc.). Among them, the physical and chemical methods have the advantages of simple treatment equipment, convenient operation, and mature technology, but their disadvantages are also obvious, such as high water quality requirements, incomplete oxidation denitrification, and secondary pollution. For the biological method, the high salt concentration in the wastewater can inhibit microbial activity and even cause microbial death, making the ammonia nitrogen treatment highly consumptive and inefficient.

[0003] Electrochemical oxidation method has broad application prospects in the field of wastewater treatment due to its high efficiency, mild and easy-to-control reaction conditions, simple reaction device, and no or little secondary pollution. However, electrochemical treatment of ammonia nitrogen wastewater faces the problem of not being able to remove ammonia nitrogen deeply. The introduction of other salt components into ammonia nitrogen wastewater can effectively improve the removal efficiency of ammonia nitrogen electro-oxidation. However, the addition of multiple salt components increases the subsequent treatment cost of ammonia nitrogen wastewater. Therefore, there is an urgent need to develop an electrolytic technology for efficiently treating high-salt and high-ammonia nitrogen wastewater without secondary pollution. SUMMARY

[0004] To solve the above technical problems, the purpose of the present application is to provide a method for treating salt-containing ammonia nitrogen wastewater by cyclone electrolysis.

[0005] The above purpose of the present application is achieved by the following technical solution:

[0006] A method for treating salt-containing ammonia nitrogen wastewater by cyclone electrolysis, comprising the following steps:

[0007] (1) adjusting the pH value of untreated salt-containing ammonia nitrogen wastewater to 5-9, adding a chloride salt solution to adjust the chloride ion concentration of the salt-containing ammonia nitrogen wastewater to 10-20 g / L, to obtain pretreated salt-containing ammonia nitrogen wastewater;

[0008] (2) The pretreated saline ammonia nitrogen wastewater is used as the electrolyte and placed in a cyclone electrolysis device for preliminary cyclone electrolysis, wherein the temperature is 20-50℃ and the current density is 50-150A / m³. 2 ;

[0009] (3) Increase the temperature of the preliminary swirl electrolysis to 50–90°C and increase the current density to 200–500 A / m. 2 The treated wastewater is obtained after further cyclone electrolysis.

[0010] This invention utilizes a cyclone electrolysis device to degrade saline ammonia nitrogen wastewater. At the anode, chloride salts are electrolytically converted into chlorine gas, which is readily soluble in water to produce active chlorine (Cl2, HClO, ClO) with strong oxidizing properties. - This method can enhance the indirect oxidation of ammonia nitrogen. At the cathode, oxygen is electrically induced to become active oxygen (H₂O₂), further improving ammonia nitrogen removal efficiency. This method involves adjusting pH and Cl₂... - By carefully controlling concentration, temperature, current density, and electrolysis time, high concentrations of ammonia nitrogen and chloride salts can be efficiently removed. The operation is simple, the reaction conditions are mild, and energy consumption is low. Ammonia nitrogen-containing wastewater can originate from photovoltaic wastewater, where the high salinity provides favorable conditions for electrochemical treatment. High salinity ensures sufficiently high conductivity, reduces energy consumption, and improves the degradation efficiency of ammonia nitrogen-containing wastewater.

[0011] Traditional electrolysis technology places the anode and cathode in a slowly flowing or stagnant tank. Under the influence of an electric field, anions move directionally towards the anode, and cations move directionally towards the cathode, thus undergoing an electro-oxidation reaction. In contrast, vortex electrolysis eliminates factors detrimental to electrolysis, such as concentration polarization, through high-speed solution flow. It avoids the limitations imposed by various factors (ion concentration, deposition potential, concentration polarization, overpotential, pH, etc.) on the traditional electrolysis process. Mass transfer in the reaction system can be enhanced through simple technical conditions, thereby strengthening the deposition and oxidation of electroinduced active chlorine and electroinduced active oxygen.

[0012] The method provided by this invention, through the synergistic effect of active chlorine, active oxygen and mass transfer enhancement, not only achieves efficient and simultaneous removal of ammonia nitrogen and chloride components in photovoltaic wastewater, but also deeply removes ammonia nitrogen, with an ammonia nitrogen removal rate of up to 99.6% and a total chlorine removal rate of up to 92%.

[0013] Further, in step (1), the ammonia nitrogen concentration of the untreated saline ammonia nitrogen wastewater is 200-1500 mg / L, and the chloride ion concentration of the untreated saline ammonia nitrogen wastewater is 2-6 g / L.

[0014] Further, in step (1), the pH value of the saline ammonia nitrogen wastewater is adjusted to 5 to 9 using acid-base reagents, such as 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, etc.

[0015] Further, the acid-base reagent can be a conventional acid solution or base solution, such as a sulfuric acid aqueous solution, a sodium hydroxide aqueous solution.

[0016] Further, the concentration of the acid-base reagent is 0.1-10M, such as 0.1M, 0.3M, 0.5M, 0.8M, 1M, 1.5M, 2M, 2.5M, 3M, 3.5M, 4M, 4.5M, 5M, 5.5M, 6M, 6.5M, 7M, 7.5M, 8M, 8.5M, 9M, 9.5M, etc., preferably 1M.

[0017] Further, the chloride salt solution can be a sodium chloride aqueous solution.

[0018] Further, the concentration of the chloride salt solution is 0.1-1M, preferably 1M.

[0019] Further, in step (1), the concentration of chloride ions in the pretreated salt-containing ammonia-nitrogen wastewater is 10-20g / L, such as 10g / L, 12.5g / L, 15g / L, 17.5g / L, 20g / L, etc., preferably 15-20g / L.

[0020] Further, in step (2), the cyclone electrolysis device comprises a working electrode (cathode), a counter electrode (anode), a reference electrode, a cyclone electrolysis cell, and a cyclone electrolysis circulating pump.

[0021] Further, the working electrode is a carbon felt electrode, preferably an activated carbon felt electrode, more preferably an activated polyacrylonitrile (PAN)-based carbon fiber felt electrode.

[0022] The preparation method of the activated PAN-based carbon fiber felt electrode comprises the following steps: boiling the PAN-based carbon fiber felt in acid, washing and drying, and then performing activation treatment in an inert gas environment to obtain the activated PAN-based carbon fiber felt electrode.

[0023] Further, the activation treatment is performed at 950-1000℃ for 2-3h.

[0024] Further, the counter electrode is an iridium-tantalum electrode, a tin-antimony electrode, a platinum-gold electrode, or a graphite electrode.

[0025] The platinum-gold electrode is expensive, which limits its application in industry. The graphite electrode is inexpensive, but its chlorine evolution performance is poor, and as an anode, it is easily carbonized to generate CO2, causing the electrolyte to become black and the electrode structure to fall off. The service life of the tin-antimony electrode is short. Compared with the titanium electrode and the graphite electrode used in traditional cyclone electrolysis, the iridium-tantalum electrode exhibits better chlorine evolution performance and current efficiency, and therefore, the counter electrode is preferably an iridium-tantalum electrode.

[0026] Preferably, the counter electrode is iridium tantalum (Ti / IrO2-Ta2O5) electrode.

[0027] The preparation method of iridium tantalum (Ti / IrO2-Ta2O5) electrode comprises the following steps: coating iridium tantalum solution on titanium substrate rod, standing in hydrogen peroxide solution after air drying, washing and drying, and then heat treatment in inert gas environment to obtain the iridium tantalum (Ti / IrO2-Ta2O5) electrode.

[0028] Further, the heat treatment condition is to heat to 200-250℃ at a heating rate of 5-10℃ / min.

[0029] Further, the cyclone electrolysis tank is a normal pressure open cylindrical electrolysis tank.

[0030] Further, the cyclone electrolysis circulating pump is used to control the flow state of electrolyte, and the opening indicates that the electrolyte in the cyclone electrolysis device forms a cyclone field to generate mass transfer enhancement, and the closing indicates that the electrolyte is in a static state.

[0031] Further, the specific electrochemical reaction in the cyclone electrolysis device is as follows:

[0032] 2Cl - →Cl2+2e - (anode)

[0033] O2+2H + +2e - →H2O2 (cathode)

[0034] (electrolyte)

[0035] (electrolyte)

[0036] 3HClO+2NH3→N2+3H2O+3H + +3Cl - (electrolyte)

[0037] 3H2O2+2NH3→2N2+6H2O (electrolyte)

[0038] Further, in step (2), the preliminary cyclone electrolysis can be carried out at room temperature to avoid the decrease of Cl2 solubility caused by high temperature, and therefore the temperature is preferably 25-30℃.

[0039] Further, in step (2), the current density of the preliminary cyclone electrolysis is preferably 100-150A / m 2 , for example 100A / m 2 , 110A / m 2, 130A / m 2 , 150A / m 2 .

[0040] Further, in step (2), the time of the preliminary cyclone electrolysis is 1.5-3h, for example, 1.5h, 2.0h, 2.5h, 3.0h, etc., preferably 2-2.5h.

[0041] The method provided by the application improves the utilization rate of chlorine ions (increases the dissolution of Cl2) and the precipitation of active oxygen, and reduces the reaction temperature and current density compared with the traditional electrolysis process, thereby reducing the energy consumption and cost.

[0042] Further, in step (3), the temperature of the further cyclone electrolysis can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, etc., preferably 65-70℃.

[0043] Further, in step (3), the current density of the further cyclone electrolysis can be 200A / m 2 , 250A / m 2 , 300A / m 2 , 350A / m 2 , 400A / m 2 , 450A / m 2 , 500A / m 2 , etc., preferably 250-350A / m 2 , more preferably 300-350A / m 2 .

[0044] Further, in step (3), the time of the further cyclone electrolysis is 0.5-3h, for example, 0.5h, 1.0h, 1.5h, 2.0h, 2.5h, 3.0h, etc., preferably 1-2h.

[0045] The method provided by the application removes total chlorine under high temperature and high current density conditions, based on the strong mass transfer effect of cyclone electrolysis, which can shorten the electrolysis time and improve the removal efficiency, and reduce the energy consumption by about 40% compared with the conventional electrolysis process.

[0046] The beneficial effects of the application are:

[0047] The method for treating salt-containing ammonia-nitrogen wastewater by the cyclone electrolysis provided by the application realizes deep degradation and removal of ammonia-nitrogen based on oxidation of active chlorine (anode) and active oxygen (cathode) at low temperature and low current density, realizes step-by-step utilization (addition, indirect oxidation and removal) of chlorine ions and efficient removal of high-chloride salt at high temperature and high current density; the method avoids introduction of other impurities into the reaction system and does not cause any side effects on electrolysis, and has the advantages of mild and easy-to-control reaction conditions, simple reaction device, low cost, no secondary pollution or little secondary pollution, etc. Meanwhile, the cyclone electrolysis reaction operation has high automation degree, reduces labor input, can bring good economic and social benefits and has good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 The process flow chart of the method for treating salt-containing ammonia-nitrogen wastewater by the cyclone electrolysis provided by the application.

[0049] Figure 2 The schematic diagram of the principle of electrochemical reaction in the cyclone electrolysis equipment provided by the application.

[0050] Figure 3 The data graph of the mass concentration of active chlorine produced by different anode electrodes and current efficiency in the cyclone electrolysis equipment.

[0051] Figure 4 The data change graph of the ammonia-nitrogen removal rate with the initial cyclone electrolysis time under the condition of 25℃ and 100A / m 2 DETAILED DESCRIPTION

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0053] The application will be further described below with reference to the drawings and specific embodiments, so that those skilled in the art can better understand the application and implement it, but the embodiments are not limiting to the application.

[0054] The experimental methods used in the following examples are conventional methods, and the materials, reagents, etc. used are commercially available, unless otherwise specified.

[0055] The application provides a method for treating salt-containing ammonia-nitrogen wastewater by cyclone electrolysis, comprising the following steps:

[0056] ​(1) adjusting the pH value of untreated salt-containing ammonia nitrogen wastewater to 5-9, adding a chlorate solution to adjust the chloride ion concentration of the salt-containing ammonia nitrogen wastewater to 10-20 g / L, to obtain pretreated salt-containing ammonia nitrogen wastewater;

[0057] (2) placing the pretreated salt-containing ammonia nitrogen wastewater as an electrolyte in a cyclone electrolysis device for preliminary cyclone electrolysis, wherein the temperature is 20-50 DEG C, and the current density is 50-150 A / m 2 ;

[0058] (3) increasing the temperature of the preliminary cyclone electrolysis to 50-90 DEG C, and increasing the current density to 200-500 A / m 2 , to further cyclone electrolyze to obtain treated wastewater.

[0059] The process flow diagram of the method for treating salt-containing ammonia nitrogen wastewater by cyclone electrolysis provided by the application is shown in Figure 1 , the untreated salt-containing ammonia nitrogen wastewater can be derived from photovoltaic wastewater, after adjusting the pH value of the photovoltaic wastewater by using an acid-base reagent and adjusting the chloride ion concentration of the photovoltaic wastewater by using a chlorate solution, the pretreated photovoltaic wastewater is placed in a cyclone electrolysis device as an electrolyte, under low temperature and low current density, based on the oxidation of active chlorine (anode) and active oxygen (cathode), deep degradation and removal of ammonia nitrogen is realized; under high temperature and high current density, stepwise utilization (addition, indirect oxidation and removal) of chloride ions is realized, efficient removal of high chlorate is realized, and the treated wastewater can be discharged up to standard.

[0060] The schematic diagram of the electrochemical reaction principle in the cyclone electrolysis device provided by the application is shown in Figure 2 , on the anode, the chlorate is electrochemically converted into chlorine gas, the chlorine gas is easily dissolved in water to generate active chlorine (Cl2, HClO, ClO - ) with strong oxidizing property, which can improve the effect of indirect oxidation of ammonia nitrogen; on the cathode, oxygen is electrochemically induced into active oxygen (H2O2), which further improves the ammonia nitrogen removal efficiency.

[0061] In the following examples and comparative examples, the untreated salt-containing ammonia nitrogen wastewater is derived from photovoltaic wastewater, the ammonia nitrogen concentration of the photovoltaic wastewater is 1056 mg / L detected by using a Nash reagent spectrophotometry method, the chloride ion concentration of the photovoltaic wastewater is 3.8 g / L detected by using a N, N-diethyl-p-phenylenediamine (DPD) spectrophotometry method, and the pH value of the photovoltaic wastewater is 4.6 detected by using a pH meter.

[0062] The active chlorine mass concentration and current efficiency generated by different anode electrodes (iridium tantalum electrode, tin antimony electrode, platinum gold electrode and graphite electrode) in the cyclone electrolysis device are tested, and the active chlorine mass concentration and current efficiency data graphs of different anode electrodes are shown in Figure 3 . Figure 3As can be seen, the platinum-gold electrode produces the highest active chlorine mass concentration and current efficiency, but the platinum-gold electrode is expensive, which limits its application in industry; the graphite electrode is cheap, but its chlorine evolution performance and current efficiency are poor, and as an anode, it is easy to carbonize to generate CO2, causing the electrolyte to become black; the tin-antimony electrode has good performance, but has a short service life; therefore, the iridium-tantalum electrode with good chlorine evolution performance and current efficiency is selected as the anode electrode.

[0063] In the following examples and comparative examples, the preparation method of the active PAN-based carbon fiber felt electrode includes the following steps: boiling the PAN-based carbon fiber felt in HNO3 for 5 min, washing with ultrapure water and drying at 60℃ for 2 h, then performing activation treatment in a tube furnace under a nitrogen atmosphere, and calcining at 1000℃ for 2 h to obtain the active PAN-based carbon fiber felt electrode.

[0064] In the following examples and comparative examples, the preparation method of the iridium-tantalum (Ti / IrO2-Ta2O5) electrode includes the following steps: coating an iridium-tantalum solution on a titanium base rod, naturally air-drying for 24 h, then standing in a 20% hydrogen peroxide solution for 5 h, washing with distilled water multiple times, and then drying in a vacuum drying oven at 80℃ for 4 h, heating to 200℃ at a heating rate of 5℃ / min in a tube furnace under a nitrogen atmosphere, and then obtaining the iridium-tantalum (Ti / IrO2-Ta2O5) electrode after reaction.

[0065] Example 1

[0066] A method for treating photovoltaic wastewater by cyclone electrolysis, comprising the following steps:

[0067] (1) Adjusting the pH value of the photovoltaic wastewater to 7 using a 1M NaOH aqueous solution, and adjusting the chloride ion concentration of the photovoltaic wastewater to 15 g / L by adding a 1M sodium chloride aqueous solution to obtain pretreated photovoltaic wastewater.

[0068] (2) Placing the pretreated photovoltaic wastewater as an electrolyte in a cyclone electrolysis tank of a cyclone electrolysis device to perform preliminary cyclone electrolysis for 2 h, and turning on the cyclone electrolysis circulating pump, with a temperature of 25℃ and a current density of 100 A / m 2 ; wherein the working electrode is an active PAN-based carbon fiber felt electrode, the counter electrode is an iridium-tantalum (Ti / IrO2-Ta2O5) electrode, and the Ag / AgCl electrode is used as the reference electrode.

[0069] (3) Further cyclone electrolysis for 1.5 h, with a temperature of 65℃ and a current density of 300 A / m 2 , to obtain treated wastewater, and detection shows that the ammonia nitrogen removal rate in the photovoltaic wastewater is 99.5%, and the total chlorine removal rate is 92%.

[0070] In addition, the effect of the initial cyclone electrolysis time on the ammonia nitrogen removal rate in test step (2) was tested at 25℃ and 100 A / m 2 The data variation graph of the ammonia nitrogen removal rate with the initial cyclone electrolysis time under the condition of 25℃ and 100 A / m Figure 4 As can be seen from the graph, the ammonia nitrogen removal rate increases with the increase of the initial cyclone electrolysis time.

[0071] Example 2

[0072] A method for treating photovoltaic wastewater by cyclone electrolysis, which is basically the same as that in Example 1, except that in step (1), 1M NaOH aqueous solution is used to adjust the pH value of the photovoltaic wastewater to 5.

[0073] It is detected that the ammonia nitrogen removal rate in the photovoltaic wastewater is 99.45%, and the total chlorine removal rate is 91.3%.

[0074] Example 3

[0075] A method for treating photovoltaic wastewater by cyclone electrolysis, which comprises the following steps:

[0076] (1) 1M NaOH aqueous solution is used to adjust the pH value of the photovoltaic wastewater to 9, and sodium chloride aqueous solution is added to adjust the chlorine ion concentration of the photovoltaic wastewater to 15g / L, to obtain pretreated photovoltaic wastewater.

[0077] (2) The pretreated photovoltaic wastewater is used as an electrolyte and placed in a cyclone electrolysis tank of a cyclone electrolysis device for initial cyclone electrolysis for 2h, and a cyclone electrolysis circulating pump is started, with a temperature of 25℃ and a current density of 150 A / m 2 ; wherein the working electrode (cathode) is an active PAN-based carbon fiber felt electrode, the counter electrode (anode) is an iridium tantalum (Ti / IrO2-Ta2O5) electrode, and an Ag / AgCl electrode is used as a reference electrode.

[0078] (3) Further cyclone electrolysis is performed for 1.5h, with a temperature of 65℃ and a current density of 300 A / m 2 , to obtain treated wastewater, and it is detected that the ammonia nitrogen removal rate in the photovoltaic wastewater is 99.54%, and the total chlorine removal rate is 92.2%.

[0079] Example 4

[0080] A method for treating photovoltaic wastewater by cyclone electrolysis, which is basically the same as that in Example 1, except that in step (1), sodium chloride aqueous solution is added to adjust the chlorine ion concentration of the photovoltaic wastewater to 10g / L.

[0081] It is detected that the ammonia nitrogen removal rate in the photovoltaic wastewater is 98.9%, and the total chlorine removal rate is 93.2%.

[0082] Example 5

[0083] A method for treating photovoltaic wastewater by cyclone electrolysis, which is basically the same as that in Example 1, except that in step (1), the concentration of chloride ions in the photovoltaic wastewater is adjusted to 20 g / L by adding an aqueous sodium chloride solution.

[0084] It is detected that the removal rate of ammonia nitrogen in the photovoltaic wastewater is 99.66%, and the removal rate of total chlorine is 89.6%.

[0085] Example 6

[0086] A method for treating photovoltaic wastewater by cyclone electrolysis, which is basically the same as that in Example 1, except that in step (2), the temperature of the preliminary cyclone electrolysis is 30°C.

[0087] It is detected that the removal rate of ammonia nitrogen in the photovoltaic wastewater is 99.06%, and the removal rate of total chlorine is 89.7%.

[0088] Example 7

[0089] A method for treating photovoltaic wastewater by cyclone electrolysis, which is basically the same as that in Example 1, except that in step (3), the temperature of the further cyclone electrolysis is 70°C.

[0090] It is detected that the removal rate of ammonia nitrogen in the photovoltaic wastewater is 99.5%, and the removal rate of total chlorine is 93.6%.

[0091] Example 8

[0092] A method for treating photovoltaic wastewater by cyclone electrolysis, which is basically the same as that in Example 1, except that in step (2), the current density of the preliminary cyclone electrolysis is 110 A / m 2 .

[0093] It is detected that the removal rate of ammonia nitrogen in the photovoltaic wastewater is 94.2%, and the removal rate of total chlorine is 90.3%.

[0094] Example 9

[0095] A method for treating photovoltaic wastewater by cyclone electrolysis, which is basically the same as that in Example 1, except that in step (2), the current density of the preliminary cyclone electrolysis is 130 A / m 2 .

[0096] It is detected that the removal rate of ammonia nitrogen in the photovoltaic wastewater is 92.86%, and the removal rate of total chlorine is 89%.

[0097] Example 10

[0098] A method for treating photovoltaic wastewater by cyclone electrolysis, which is basically the same as that in Example 1, except that in step (2), the current density of the preliminary cyclone electrolysis is 80 A / m 2 .

[0099] The removal rate of ammonia nitrogen in the photovoltaic wastewater is 86.32%, and the removal rate of total chlorine is 89%.

[0100] Example 11

[0101] A method for treating photovoltaic wastewater by cyclone electrolysis, comprising the following steps:

[0102] (1) Adjust the pH value of the photovoltaic wastewater to 7 by using 1M NaOH aqueous solution, and adjust the chloride ion concentration of the photovoltaic wastewater to 15g / L by adding sodium chloride aqueous solution, to obtain pretreated photovoltaic wastewater.

[0103] (2) The pretreated photovoltaic wastewater is used as an electrolyte and placed in a cyclone electrolysis tank of a cyclone electrolysis device for preliminary cyclone electrolysis for 2h, a cyclone electrolysis circulating pump is turned on, the temperature is 25℃, and the current density is 150A / m 2 ; wherein the working electrode is an active PAN-based carbon fiber felt electrode, the counter electrode is an iridium tantalum (Ti / IrO2-Ta2O5) electrode, and an Ag / AgCl electrode is used as a reference electrode.

[0104] (3) Further cyclone electrolysis for 1.5h, the temperature is 65℃, and the current density is 250A / m 2 , to obtain treated wastewater, and the removal rate of ammonia nitrogen in the photovoltaic wastewater is 99.5%, and the removal rate of total chlorine is 86.8%.

[0105] Example 12

[0106] A method for treating photovoltaic wastewater by cyclone electrolysis, comprising the following steps:

[0107] (1) Adjust the pH value of the photovoltaic wastewater to 7 by using 1M NaOH aqueous solution, and adjust the chloride ion concentration of the photovoltaic wastewater to 15g / L by adding sodium chloride solution, to obtain pretreated photovoltaic wastewater.

[0108] (2) The pretreated photovoltaic wastewater is used as an electrolyte and placed in a cyclone electrolysis tank of a cyclone electrolysis device for preliminary cyclone electrolysis for 2h, a cyclone electrolysis circulating pump is turned on, the temperature is 25℃, and the current density is 150A / m 2 ; wherein the working electrode is an active PAN-based carbon fiber felt electrode, the counter electrode is an iridium tantalum (Ti / IrO2-Ta2O5) electrode, and an Ag / AgCl electrode is used as a reference electrode.

[0109] (3) Further cyclone electrolysis for 1.5h, the temperature is 65℃, and the current density is 350A / m 2 , to obtain treated wastewater, and the removal rate of ammonia nitrogen in the photovoltaic wastewater is 99.5%, and the removal rate of total chlorine is 93.7%.

[0110] Comparative Example 1

[0111] A method for treating photovoltaic wastewater by hydrocyclone electrolysis is substantially the same as that of Example 1, except that in step (2), the hydrocyclone electrolysis circulating pump is turned off.

[0112] It is detected that the removal rate of ammonia nitrogen in the photovoltaic wastewater is 58.2%, because the hydrocyclone electrolysis does not provide mass transfer enhancement, and the removal rate of ammonia nitrogen is reduced.

[0113] Comparative Example 2

[0114] A method for treating photovoltaic wastewater by hydrocyclone electrolysis is substantially the same as that of Example 1, except that in step (1), 1M H2SO4 aqueous solution is used to adjust the pH value of the photovoltaic wastewater to 3.

[0115] It is detected that the removal rate of ammonia nitrogen in the photovoltaic wastewater is 73.44%, because the acidic condition is not conducive to the reaction proceeds to the right, thereby reducing the solubility of Cl2 in the electrolyte, causing a large amount of Cl2 to escape, thereby reducing the mass concentration of active chlorine in the electrolyte and the current efficiency.

[0116] Comparative Example 3

[0117] A method for treating photovoltaic wastewater by hydrocyclone electrolysis is substantially the same as that of Example 1, except that in step (1), 1M NaOH aqueous solution is used to adjust the pH value of the photovoltaic wastewater to 11.

[0118] It is detected that the removal rate of ammonia nitrogen in the photovoltaic wastewater is 80.6%, because the alkaline condition converts active chlorine ClO - to ClO3 - , and part of ClO - is reduced to Cl - (reaction formula as follows) at the cathode, thereby reducing the mass concentration of active chlorine and the current efficiency.

[0119] ClO - + 4OH - → ClO3 - + 2H2O + 4e -

[0120] ClO - + 2HClO → ClO3 - + 2Cl - + 2H +

[0121] ClO - + H2O → Cl - + 2OH - - 2e -

[0122] Comparative Example 4

[0123] A method for treating photovoltaic wastewater by cyclone electrolysis, which is basically the same as Example 1, except that in step (1), the sodium chloride aqueous solution is added to adjust the chloride ion concentration of the photovoltaic wastewater to 5 g / L.

[0124] It is detected that the ammonia nitrogen removal rate in the photovoltaic wastewater is 53.8%, and the chloride ion concentration is too low to produce enough active chlorine to promote the degradation of ammonia nitrogen.

[0125] Comparative Example 5

[0126] A method for treating photovoltaic wastewater by cyclone electrolysis, which is basically the same as Example 1, except that in step (2), the current density of the preliminary cyclone electrolysis is 170 A / m 2 .

[0127] It is detected that the ammonia nitrogen removal rate in the photovoltaic wastewater is 81.22%.

[0128] Comparative Example 6

[0129] A method for treating photovoltaic wastewater by cyclone electrolysis, which is basically the same as Example 1, except that in step (2), the current density of the preliminary cyclone electrolysis is 40 A / m 2 .

[0130] It is detected that the ammonia nitrogen removal rate in the photovoltaic wastewater is 38.6%.

[0131] Comparative Example 7

[0132] A method for treating photovoltaic wastewater by cyclone electrolysis, which is basically the same as Example 1, except that in step (2), the temperature of the preliminary cyclone electrolysis is 55°C.

[0133] It is detected that the ammonia nitrogen removal rate in the photovoltaic wastewater is 29.56%, and the temperature is too high to reduce the solubility of Cl2, causing a large amount of Cl2 to escape, and the ammonia nitrogen removal rate to decrease.

[0134] Comparative Example 8

[0135] A method for treating photovoltaic wastewater by cyclone electrolysis, which is basically the same as Example 1, except that in step (3), the current density of the further cyclone electrolysis is 150 A / m 2 .

[0136] The total chlorine removal rate of the treated wastewater is 61.3%, and Comparative Example 8 proves that the current density of the further cyclone electrolysis cannot be lower than that of the preliminary cyclone electrolysis.

[0137] Comparative Example 9

[0138] A method for treating photovoltaic wastewater by cyclone electrolysis is substantially the same as that of Example 1, except that in step (3), the temperature for further cyclone electrolysis is 45°C.

[0139] It is detected that the removal rate of total chlorine in the photovoltaic wastewater is 53.1%, and Comparative Example 9 proves that the further cyclone electrolysis needs a temperature of at least higher than 50°C.

[0140] Obviously, the above examples of the present application are only examples for clearly illustrating the present application, and are not intended to limit the embodiments of the present application. It should be understood by those skilled in the art that other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and also impossible to exhaust all the embodiments. Any modification, equivalent replacement and improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A method for treating salt-containing ammonia-nitrogen wastewater by a cyclone electrolysis process, characterized in that, The method comprises the following steps: (1) adjusting the pH value of untreated salt-containing ammonia-nitrogen wastewater to 5-9, adding a chloride salt solution to adjust the chloride ion concentration of the salt-containing ammonia-nitrogen wastewater to 10-20 g / L, to obtain pretreated salt-containing ammonia-nitrogen wastewater; the ammonia-nitrogen concentration of the untreated salt-containing ammonia-nitrogen wastewater is 200-1500 mg / L, and the chloride ion concentration of the untreated salt-containing ammonia-nitrogen wastewater is 2-6 g / L; (2) The pretreated salt-containing ammonia nitrogen wastewater is used as electrolyte and placed in a cyclone electrolysis device for preliminary cyclone electrolysis, wherein the temperature is 20-50 ℃, and the current density is 100-150 A / m 2 ; (3) increasing the temperature of the above preliminary cyclone electrolysis to 50~90 ℃, increasing the current density to 200~500 A / m 2 , obtaining treated wastewater after further cyclone electrolysis; At low temperature and low current density, deep degradation and removal of ammonia-nitrogen are realized based on the oxidation of active chlorine and active oxygen; at high temperature and high current density, step-by-step utilization of chloride ions is realized, and efficient removal of high-chloride salt is realized.

2. The method of claim 1, wherein, In step (1), the concentration of the chloride salt solution is 0.1-1 M.

3. The method of claim 1, wherein, In step (2), the cyclone electrolysis equipment comprises a working electrode, a counter electrode, a reference electrode, a cyclone electrolysis cell and a cyclone electrolysis circulating pump.

4. The method of claim 3, wherein, The working electrode is a carbon felt electrode.

5. The method of claim 3, wherein, The counter electrode is an iridium tantalum electrode, a tin antimony electrode, a platinum gold electrode or a graphite electrode.

6. The method of claim 1, wherein, In step (2), the temperature of the preliminary cyclone electrolysis is 25-30 ℃.

7. The method of claim 1, wherein, In step (3), the temperature of the further cyclone electrolysis is 65-70 ℃.

8. The method of claim 1, wherein, In step (3), the current density of the further flow-by electrolysis is 250 to 350 A / m 2 .

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