Method for treating non-biodegradable nitrogen-containing wastewater by utilizing three-dimensional electro-Fenton electrolysis system

Abstract

The invention provides a method for treating nonbiodegradable nitrogen-containing wastewater by using a three-dimensional electro-Fenton electrolysis system, which comprises the following steps: (1) adding wastewater to be treated, an electrode material and an electrolyte into an electrolytic bath under the condition that the pH value of the wastewater is not adjusted; (2) adjusting the distance between the cathode and anode plates; (3) starting aeration at the cathode and adjusting the aeration rate; and (4) connecting a power supply, adjusting the current density, and electrolyzing for 5 hours to catalytically oxidize pollutants in the wastewater. Efficient electrolysis is carried out under the catalytic action of the particle electrode, Fenton reaction is promoted, and removal of COD, TN and ammonia nitrogen in wastewater is accelerated.

Description

Technical Field

[0001] The present invention relates to the field of industrial wastewater, and in particular to a method for treating difficult-to-biodegrade nitrogen-containing wastewater by using a three-dimensional electro-Fenton electrolysis system. Background Art

[0002] The sources of nitrogen-containing wastewater are wide and the discharge volume is large. Once it enters the water body, it is easy to cause eutrophication of the water body, trigger natural disasters such as algal blooms, and cause water bodies to become black and smelly due to lack of oxygen, and cause the death of a large number of aquatic organisms, causing serious damage to the aquatic ecology. In addition, this type of wastewater has complex components and poor biodegradability, so it is very necessary to treat this type of wastewater.

[0003] The three-dimensional electro-Fenton technology is an advanced oxidation technology that combines three-dimensional electrochemistry and electro-Fenton technology. The removal of pollutants in wastewater mainly includes the following three aspects: ① direct oxidation of pollutants on the surface of the anode and particle electrode; ② indirect oxidation of pollutants by ·OH produced by electrochemical reactions; ③ the removal of pollutants by H2O2 and Fe 2+ The ·OH generated by the Fenton reaction is oxidized. The particle electrode is a new type of supported catalyst that uses physical or chemical methods to attach Fe elements or new metal elements or some new elements mixed with Fe to relevant carriers, providing the required catalytic effect for research and enhancing the treatment effect of difficult-to-degrade wastewater. Summary of the invention

[0004] The purpose of the present invention is to provide a method for treating difficult-to-biodegrade nitrogen-containing wastewater using a three-dimensional electro-Fenton electrolysis system in response to the shortcomings of the technology for treating difficult-to-biodegrade nitrogen-containing wastewater.

[0005] The present invention is achieved through the following technical solutions: A method for treating difficult-to-biodegrade nitrogen-containing wastewater using a three-dimensional electro-Fenton electrolysis system comprises the following steps: (1) adding wastewater to be treated, electrode materials and electrolytes into an electrolytic cell without adjusting the pH value of the wastewater; (2) adjusting the distance between the anode and cathode plates; (3) starting aeration at the cathode and adjusting the aeration volume; (4) connecting a power source, adjusting the current density, and performing electrolysis for 5 hours to catalytically oxidize pollutants in the wastewater.

[0006] The electrode material is composed of a cathode plate, an anode plate and a particle electrode.

[0007] The cathode plate is a stainless steel plate, and the anode plate is a ruthenium-iridium-titanium plate.

[0008] The particle electrode is Fenton catalytic filler (LFD) with a dosing concentration of 100 g / L.

[0009] The Fenton catalytic filler (LFD) is spherical and has a diameter of 4 mm to 6 mm.

[0010] The Fenton catalytic filler (LFD) needs to be activated before use, and the activation steps are as follows: ① There is no excessive residue on the surface of the packing, so simply rinse the packing with pure water before use; ② Soak in 1% dilute sulfuric acid solution for 1 hour to activate the filler; ③Finally, place the activated filler in an oven and dry it at 80°C for later use.

[0011] The type of electrolyte is NaCl, and the added concentration is 2 g / L. Beneficial Effects

[0012] The beneficial effects of the method for treating refractory biodegradable nitrogen-containing wastewater using a three-dimensional electro-Fenton electrolysis system provided by the present invention are as follows: (1) The Fenton catalytic filler (LFD) used in electrolysis is made of alumina as a carrier and attached with catalytic materials. It has active sites and catalytic effects, which can make organic matter and hydrogen peroxide adsorb on the active sites on the catalyst surface. Then, under the catalytic effect, hydrogen peroxide decomposes to produce OH, thereby initiating a free radical chain reaction and accompanying the iron cycle process to maintain the smooth progress of the entire catalytic oxidation reaction, thereby oxidizing and degrading pollutants; (2) The compressive strength of the filler is ≥100N / particle, which shows that it has strong stability and can be reused. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is the removal rate of COD, TN and ammonia nitrogen in wastewater by the three-dimensional electro-Fenton electrolysis system; Figure 2 The removal rate of COD in wastewater by three-dimensional electrochemical electrolysis system and three-dimensional electro-Fenton electrolysis system; Figure 3 The removal efficiency of ammonia nitrogen from wastewater by three-dimensional electrochemical electrolysis system and three-dimensional electro-Fenton electrolysis system; Figure 4 Removal rate of TN in wastewater by three-dimensional electrochemical electrolysis system and three-dimensional electro-Fenton electrolysis system. DETAILED DESCRIPTION

[0014] The present invention is further described below with reference to specific embodiments, but is not intended to limit the present invention.

[0015] Example 1 The three-dimensional electro-Fenton electrolysis system was used to treat wastewater: 500 mL of nitrogen-containing wastewater (COD value 1980 mg / L, TN value 296 mg / L, ammonia nitrogen value 98 mg / L) was added to the electrolytic cell, and a NaCl electrolyte with a concentration of 2 g / L and a LFD filler of 100 g / L were added. The stainless steel plate was connected to the negative electrode of the power supply, and the ruthenium-iridium-titanium plate was connected to the positive electrode of the power supply, wherein the anode plate and the cathode plate were kept 4 cm apart; an air stone was placed near the cathode, the air pump was turned on, and the aeration volume was adjusted to 1.5 L / min through the flow meter; Finally, adjust the power supply current and voltage to make the current density 30mA / cm 2 After power is turned on, electrolysis is performed for 5 hours, and samples are taken every hour to determine the COD, TN and ammonia nitrogen concentrations in the wastewater. The treatment results are as follows Figure 1 As shown: Under the treatment of the three-dimensional electro-Fenton electrolysis system, as the electrolysis proceeds, the removal rates of COD, ammonia nitrogen and TN in the wastewater can reach 88.18%, 90.31% and 90.47% respectively after 5 hours of electrolysis.

[0016] Comparative Example 1 The treatment effects of the two electrolysis systems, "three-dimensional electro-Fenton electrolysis system" and "three-dimensional electrochemical electrolysis system" on difficult-to-biodegrade nitrogen-containing wastewater, were compared. The difference between the two systems is that the particle electrode used in the three-dimensional electro-Fenton electrolysis system is LFD filler, and the particle electrode used in the three-dimensional electrochemical electrolysis system is cellulose acetate-coated activated carbon; the three-dimensional electro-Fenton electrolysis system has aeration, and the three-dimensional electrochemical electrolysis system has no aeration.

[0017] The preparation of cellulose acetate coated activated carbon used in the three-dimensional electrochemical electrolysis system is as follows: Rinse the granular activated carbon with tap water to remove excess powder in the activated carbon, then wash it with dilute hydrochloric acid and dilute acetone solution for several times, and dry it at 105°C for later use; prepare 500mL of 85% acetone aqueous solution, weigh 75g of cellulose acetate, slowly dissolve the taken cellulose acetate in the acetone solution, place it on an electric stirrer to accelerate the dissolution rate, and after it is completely dissolved, weigh 500g of washed and dried activated carbon and add it thereto, and soak it for 30 minutes; take out the fully soaked activated carbon, put it on a wire mesh to filter out the solvent, dry it naturally, evaporate and remove the remaining solution, and obtain activated carbon with a white cellulose acetate coating after sufficient drying.

[0018] Specifically, 500 mL of biodegradable nitrogen-containing wastewater (COD value 2048 mg / L) generated by a certain enterprise was placed in an electrolytic cell for two experiments. One group used a three-dimensional electro-Fenton electrolysis system, and the other group used a three-dimensional electrochemical electrolysis system. The removal effects of the two systems on COD in the wastewater were compared. The experimental parameters were set as follows: The particle electrode concentration in both systems was 100 g / L, and 2 g / L of NaCl electrolyte was added to each system. Without adjusting the pH value of the wastewater, the aeration rate was controlled at 1.5 L / min and the current density was 30 mA / cm 2 The distance between the electrode plates was 4 cm, and the electrolysis lasted for 5 hours. After electrolysis, the COD concentration in the wastewater was measured. The treatment results are as follows: Figure 2 As shown: As the electrolysis progressed, the removal rates of COD in wastewater by the two electrolysis systems showed an increasing trend. However, the removal effect of COD by the three-dimensional electrochemical electrolysis system was always inferior to that of the three-dimensional electro-Fenton electrolysis system. After 5 hours of electrolysis, the removal rates of COD in wastewater by the three-dimensional electrochemical electrolysis system and the three-dimensional electro-Fenton electrolysis system were 83.11% and 88.57%, respectively. It can be seen that the three-dimensional electro-Fenton electrolysis system has more advantages in removing COD in wastewater.

[0019] Comparative Example 2 The implementation content of Comparative Example 2 is basically the same as that of Comparative Example 1, the difference being that the two systems are compared in terms of the removal effect of ammonia nitrogen (ammonia nitrogen value 95 mg / L) in wastewater. The experimental conditions are set the same as those of Comparative Example 1. The treatment results are shown in Table 2. Figure 3 As shown: As the electrolysis progressed, the removal rates of ammonia nitrogen in wastewater by both systems showed an increasing trend. The removal rate of TN in wastewater by the three-dimensional electro-Fenton electrolysis system was always higher than that by the three-dimensional electrochemical electrolysis system. After 5 hours of electrolysis, the removal rates of ammonia nitrogen in wastewater by the three-dimensional electrochemical electrolysis system and the three-dimensional electro-Fenton electrolysis system were 90.76% and 92.55%, respectively. It can be seen that the three-dimensional electro-Fenton electrolysis system also has more advantages in removing ammonia nitrogen in wastewater.

[0020] Comparative Example 3 The implementation content of Comparative Example 3 is basically the same as that of Comparative Example 1. The difference is that the two systems are compared to remove TN (TN value 285 mg / L) in wastewater. The experimental conditions are set the same as those of Comparative Example 1. The treatment results are as follows: Figure 4 As shown: As the electrolysis progressed, the removal rate of TN in the wastewater by the three-dimensional electro-Fenton electrolysis system was significantly higher than that by the three-dimensional electrochemical electrolysis system at 1h, 2h and 3h of electrolysis. At 4h and 5h of electrolysis, the removal rate of TN in the wastewater by the two systems did not increase significantly and the difference was not large, but it was still slightly higher by the three-dimensional electro-Fenton electrolysis system; at 5h of electrolysis, the removal rates of TN in the wastewater by the three-dimensional electrochemical electrolysis system and the three-dimensional electro-Fenton electrolysis system were 92.33% and 92.26%, respectively. It can be seen that the three-dimensional electro-Fenton electrolysis system also has more advantages in removing TN in wastewater.

[0021] The above is only a further explanation of the present invention and is not intended to limit this patent. Equivalent implementations that do not deviate from the spirit and scope of the present invention should be included in the scope of the claims of this patent.

Claims

1. A method for treating refractory biodegradable nitrogen-containing wastewater using a three-dimensional electro-Fenton electrolysis system, characterized in that: The method comprises the following steps: (1) adding wastewater to be treated, electrode materials and electrolyte into an electrolytic cell without adjusting the pH value of the wastewater; (2) adjusting the distance between the cathode and cathode plates; (3) starting aeration at the cathode and adjusting the aeration volume; (4) connecting a power source, adjusting the current density, and performing electrolysis for 5 hours to catalytically oxidize pollutants in the wastewater.

2. The method for treating refractory biodegradable nitrogen-containing wastewater using a three-dimensional electro-Fenton electrolysis system according to claim 1, characterized in that: The electrode material is composed of a cathode plate, an anode plate and a particle electrode.

3. The method for treating refractory nitrogen-containing wastewater using a three-dimensional electro-Fenton electrolysis system according to claim 1, characterized in that: The cathode plate is a stainless steel plate, and the anode plate is a ruthenium-iridium-titanium plate.

4. The method for treating refractory biodegradable nitrogen-containing wastewater using a three-dimensional electro-Fenton electrolysis system according to claim 1, characterized in that: The particle electrode is Fenton catalytic filler (LFD) with a dosing concentration of 100 g / L.

5. The method for treating refractory nitrogen-containing wastewater using a three-dimensional electro-Fenton electrolysis system according to claim 4, characterized in that: The Fenton catalytic filler (LFD) is spherical and has a diameter of 4 mm to 6 mm.

6. The method for treating refractory biodegradable nitrogen-containing wastewater using a three-dimensional electro-Fenton electrolysis system according to claim 1, characterized in that: The type of electrolyte is NaCl, and the added concentration is 2 g / L.

Images