Treatment method for removing nitrate ions and application

Abstract

The invention belongs to the technical field of industrial water treatment, and provides a treatment method for removing nitrate ions and application, and the treatment method comprises the following steps: adjusting the pH value of waste liquid containing nitrate ions to be not more than 1; adjusting the temperature of the waste liquid to be not lower than 40 DEG C; and adding urea into the to-be-treated waste liquid subjected to pH and temperature adjustment, and reacting for 15-60 minutes. According to the method disclosed by the invention, nitrate ions are reduced into nitrite ions by changing the acidity and temperature of the waste liquid, and then urea is added for reaction to generate nitrogen, so that the removal of nitrate is realized. Compared with the prior art, the method has the advantages of quick response, high efficiency, lower equipment requirement and easier cost control.

Description

Technical Field

[0001] The invention relates to the technical field of industrial water treatment, and in particular to a treatment method for removing nitrate ions and an application thereof. Background Art

[0002] Fertilizer manufacturing, steel production, gunpowder manufacturing, feed production, meat processing, electronic components and nuclear fuel production and other production activities often produce wastewater containing high concentrations of nitrates and nitrites. Nitrates can destroy the ecological balance of water bodies and cause the death of aquatic plants and animals. When nitrates are ingested into the human body, they will be reduced to nitrites in the stomach, which are carcinogenic. At present, the conventional method for nitrate removal is micro-electrolysis filler biological denitrification, which uses the denitrification of denitrifying bacteria to reduce nitrate nitrogen to nitrogen gas, but the treatment process is long, the operation is difficult and the cost is high; for a small amount of industrial wastewater containing nitrates or nitrites, electrodialysis, reverse osmosis, ion exchange and other methods can also be used, but the treatment capacity is small, the equipment maintenance cost is high, and the energy consumption is high.

[0003] Because nitrates have the characteristics of good solubility and stability, and are easily enriched in water bodies, they are difficult to separate and remove, and require a large amount of capital to treat. Therefore, a method that can quickly remove nitrate ions is needed. Summary of the invention

[0004] Based on the above reasons, one of the purposes of the present invention is to provide a treatment method for removing nitrate ions, which has a simple process, a fast speed and a low cost; the second purpose is to provide the application of the above-mentioned treatment method for removing nitrate ions in the wastewater treatment industry.

[0005] The first technical solution of the present application provides a treatment method for removing nitrate ions, comprising: The pH value of the waste liquid containing nitrate ions is adjusted to not more than 1 and the temperature of the waste liquid is adjusted to not less than 40°C; Urea is added to the waste liquid to be treated after adjusting pH and temperature, and the reaction is carried out for 15-60 minutes.

[0006] Furthermore, the method for adjusting the pH value of the waste liquid is to add a sulfuric acid solution into the waste liquid until the pH value of the waste liquid does not exceed 1.

[0007] Preferably, the sulfuric acid is concentrated sulfuric acid with a mass fraction of not less than 70%.

[0008] Furthermore, the molar concentration ratio of urea to nitrate ion is 1:(1-2).

[0009] Furthermore, the reaction of the waste liquid with urea comprises the following process: Under strong acid and elevated temperature conditions, nitrate is reduced to nitrite; Nitrite reacts with urea to produce nitrogen gas.

[0010] Furthermore, the waste liquid containing nitrate ions comes from industries such as chemical industry, petroleum, food, iron smelting, and electronic manufacturing.

[0011] The present application also provides the application of the above-mentioned treatment method for removing nitrate ions in the wastewater treatment industry.

[0012] The present invention has the following beneficial effects: The present invention reduces nitrate ions to nitrite ions by changing the acidity and temperature of the waste liquid, and then adds urea to react to generate nitrogen gas, thereby achieving the removal of nitrate ions. Compared with the prior art of adding silver ions to generate silver nitrate precipitates and then filtering and removing, the present invention has lower costs and faster reactions. Compared with biological denitrification denitrification, the present invention has a short treatment process and lower requirements on equipment. DETAILED DESCRIPTION

[0013] The scheme of the present invention will be explained below in conjunction with embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. In the embodiments, if specific techniques or conditions are indicated, the techniques or conditions described in the literature in this area or the product specifications are followed.

[0014] The embodiment of the present application provides a treatment method for removing nitrate ions, comprising: The pH value of the waste liquid containing nitrate ions is adjusted to not more than 1 and the temperature of the waste liquid is adjusted to not less than 40°C; Urea is added to the waste liquid to be treated after adjusting pH and temperature, and the reaction is carried out for 15-60 minutes.

[0015] In a specific embodiment, the method for adjusting the pH value of the waste liquid is to add a sulfuric acid solution to the waste liquid until the pH value of the waste liquid does not exceed 1.

[0016] In some preferred embodiments, the sulfuric acid is concentrated sulfuric acid with a mass fraction of not less than 70%. Concentrated sulfuric acid has strong acidity, a high degree of ionization when mixed with waste liquid, releases a large amount of heat, and adjusts acidity and temperature at the same time, while dilute sulfuric acid has weaker acidity, weaker ability to adjust acidity, and a lower degree of ionization, releasing less heat.

[0017] It should be noted that, generally, when adjusting the pH value of the waste liquid, the added sulfuric acid will react with the water molecules in the waste liquid to release heat and change the temperature of the waste liquid. If the pH value of the waste liquid is no more than 1, but the temperature of the waste liquid has not reached 40°C, the temperature of the waste liquid can be increased by heating. If the pH value of the waste liquid itself does not need to be adjusted, the temperature of the waste liquid can be increased by adding a small amount of water. When the acidity in the waste liquid is strong, an exothermic neutralization reaction will occur after adding water. Pay attention to the change in pH value when adding water.

[0018] In a specific embodiment, the molar concentration ratio of urea to nitrate ion is 1:(1-2).

[0019] In a specific embodiment, the reaction of the waste liquid with urea comprises the following process: Under strong acid and elevated temperature conditions, nitrate is reduced to nitrite; Nitrite reacts with urea to produce nitrogen gas.

[0020] In the present application, nitrate is unstable in strong acid and above 40°C environment and can be reduced to nitrite. After adding urea, nitrite reacts with urea to generate inert gas nitrogen. When nitrogen is discharged, bubbles are formed on the surface of the waste liquid. The whole process is continuous. The present application can achieve the removal of nitrate, and the generated nitrogen can be directly discharged or collected for further use, generating new economic benefits and realizing the recycling of resources.

[0021] The waste liquid containing nitrate ions comes from industries such as chemical industry, petroleum, food, iron smelting, and electronic manufacturing.

[0022] The invention also provides application of the treatment method for removing nitrate ions in the wastewater treatment industry.

[0023] The following will disclose specific embodiments for implementing the present application, as well as corresponding comparative examples to demonstrate the relevant technical effects of the present application.

[0024] Example 1 A treatment method for removing nitrate ions The original waste liquid was electroplating wastewater with a pH of 6.4 and a nitrate concentration of 389 mg / L. 50 L of the waste liquid was placed in a continuously stirred reaction tank with a stirring rate of 80 r / min. 90% concentrated sulfuric acid was slowly added to the reaction tank to adjust the pH value of the waste liquid to 1. At this time, the temperature of the waste liquid was 45 °C. 11 g of urea was added to react for 30 minutes until no bubbles were generated in the waste water. After the reaction, the nitrate concentration in the waste liquid was 10 mg / L, and the nitrate removal rate was 97.43%.

[0025] In this embodiment 1, the nitrate in the waste liquid is reduced to nitrite in a strong acid and 45°C environment, and then the nitrite reacts with urea to generate nitrogen gas, and bubbles are generated on the surface of the waste liquid due to the discharge of gas. During the reaction, the nitrate is reduced to nitrite and then reacts with urea, which is a continuous process. When no bubbles are generated, the reaction ends.

[0026] Example 2 A treatment method for removing nitrate ions The original waste liquid was chemical wastewater with pH=0.6 and nitrate concentration of 864g / L. 50L of waste liquid was placed in a continuously stirred reaction tank with a stirring rate of 100r / min. Distilled water was slowly added to the reaction tank. The acid in the waste liquid released heat when it met water. After the temperature of the waste liquid rose to 42°C, the pH value was 1. 25g of urea was added and reacted for 45 minutes. When no bubbles were generated in the waste liquid, the nitrate concentration in the waste liquid was 13mg / L after the reaction ended, and the nitrate removal rate was 98.50%.

[0027] In the present embodiment 2, since the waste liquid itself is highly acidic, there is no need to add sulfuric acid to adjust the pH value. Water is added to react with the acid in the waste liquid to neutralize it, releasing heat to increase the temperature of the waste liquid. The nitrate in the waste liquid is reduced to nitrite in a strong acid and 42°C environment. The nitrite then reacts with urea to generate nitrogen. Bubbles are generated on the surface of the waste liquid due to the generation of gas. When no bubbles are generated, the reaction is terminated.

[0028] Example 3 A treatment method for removing nitrate ions The original solution was petroleum wastewater with a pH of 1.5 and a nitrate concentration of 108 mg / L. 50 L of waste liquid was placed in a continuously stirred reaction tank with a stirring rate of 60 r / min. 80% concentrated sulfuric acid was slowly added to the reaction tank to adjust the pH value of the waste liquid to 1. At this time, the temperature of the waste liquid was 28°C. The temperature of the waste liquid was heated to 41°C, and 5 g of urea was added to react for 15 minutes until no bubbles were generated in the waste liquid. After the reaction, the nitrate concentration in the waste liquid was 8 mg / L, and the nitrate removal rate was 92.59%.

[0029] In this embodiment 3, since the acidity of the waste liquid is relatively strong, after adding sulfuric acid for adjustment, the temperature of the waste liquid does not reach 40°C. At this time, adding water will cause the pH to rise, so the waste liquid is directly heated to 41°C at this time to make the reaction environment reach a suitable range, and the nitrate is reduced to nitrite in a strong acid and 41°C environment. Thereafter, the nitrite reacts with urea to generate nitrogen. Bubbles are generated on the surface of the waste liquid due to the generation of gas. When no bubbles are generated, the reaction is terminated.

[0030] Example 4 A treatment method for removing nitrate ions The original solution was chemical wastewater with a pH of 3.3 and a nitrate concentration of 1.52 g / L. 50 L of waste liquid was placed in a continuously stirred reaction tank with a stirring rate of 90 r / min. 85% concentrated sulfuric acid was slowly added to the reaction tank to adjust the pH value of the waste liquid to 1. At this time, the temperature of the waste liquid rose to 43 °C. 15 g of urea was added to react. When no bubbles were generated in the waste liquid, 15 g of urea was added again to react. This was repeated 3 times, with a total of 45 g of urea added for 55 minutes. After the reaction, the nitrate concentration in the waste liquid was 15 mg / L, and the nitrate removal rate was 99.01%.

[0031] In this embodiment 4, the nitrate ions in the waste liquid are reduced to nitrite ions. Since the concentration of nitrate ions in the waste liquid is relatively high, urea can be added in small amounts and multiple times to avoid violent reactions in the reaction tank and splashing of waste liquid after adding a large amount of urea at one time, which may lead to safety accidents.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A treatment method for removing nitrate ions, characterized in that, Include: The pH value of the waste liquid containing nitrate ions is adjusted to not more than 1 and the temperature of the waste liquid is adjusted to not less than 40°C; Urea is added to the waste liquid to be treated after adjusting pH and temperature, and the reaction is carried out for 15-60 minutes.

2. The method for removing nitrate ions according to claim 1, wherein The method for adjusting the pH value of the waste liquid is to add a sulfuric acid solution into the waste liquid until the pH value of the waste liquid does not exceed 1.

3. The method for removing nitrate ions according to claim 2, wherein: The sulfuric acid is concentrated sulfuric acid with a mass fraction of not less than 70%.

4. The method for removing nitrate ions according to claim 1, wherein: The molar concentration ratio of the urea to the nitrate ion is 1:(1-2).

5. The method for removing nitrate ions according to claim 1, wherein: The reaction of the waste liquid with urea comprises the following process: Under strong acid and elevated temperature conditions, nitrate is reduced to nitrite; Nitrite reacts with urea to produce nitrogen gas.

6. The method for removing nitrate ions according to claim 1, wherein: The waste liquid containing nitrate ions comes from the chemical, petroleum, food, iron smelting and electronic manufacturing industries.

7. Application of the treatment method for removing nitrate ions according to any one of claims 1 to 6 in wastewater treatment industry.