Method for rapidly removing ammonia nitrogen from wastewater

Abstract

The present application belongs to the technical field of water treatment, and particularly relates to a method for rapidly removing ammonia nitrogen in wastewater. A carbon material containing a carbonyl group and a hydroxyl group is added to a magnesium salt, the pH value of a solution is adjusted to be alkaline, and a product obtained after reaction is sintered at high temperature under an argon protective atmosphere to prepare a composite filler. The prepared composite filler is added to wastewater, a persulfate salt is added, the pH value of the wastewater is adjusted to be alkaline, and stirring reaction is carried out for 0.5-1 h, solid-liquid separation is carried out, and the supernatant is treated effluent. In the present application, magnesium oxide loaded on the surface of an active substance can maintain the solution to be alkaline, which is conducive to the oxidation of ammonia nitrogen. The active oxygen species generated by the activation of the active substance and magnesium oxide on the persulfate salt can rapidly oxidize ammonia nitrogen. Meanwhile, the groups on the surface of the active substance can control the product to be nitrogen instead of by-products nitrate and nitrite. Compared with traditional advanced oxidation technology, the present application has the advantages of fast conversion rate, strong anti-interference ability, no secondary pollution, etc.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a method for rapidly removing ammonia nitrogen from wastewater. Background Technology

[0002] Ammonia nitrogen exists in water in the form of free ammonia (NH3) and ammonium ions. Sources of ammonia nitrogen in water are numerous, including domestic sewage and landfill leachate, as well as industrial wastewater discharges from steel mills, oil refineries, fertilizer plants, tanning plants, petrochemical plants, glass manufacturing plants, and feed production plants. Ammonia nitrogen is a major factor contributing to eutrophication, causing the proliferation of algae and microorganisms in aquatic bodies, leading to a sharp decline in dissolved oxygen levels, resulting in the death of fish and other aquatic organisms due to oxygen depletion, and severely impacting water quality.

[0003] To date, numerous technologies have been developed, such as stripping, ion exchange, adsorption, biological treatment, and chemical oxidation, for oxidizing ammonia nitrogen in wastewater. However, each technology has its limitations and drawbacks from both technical and economic perspectives. For example, stripping technology is heavily restricted by temperature and stripping facility requirements; ion exchange is simple to operate and highly adaptable, but faces the challenge of treating the regenerated liquid from the exchanger; biological treatment is an economical and environmentally friendly denitrification technology, but its low carrying capacity and stringent reaction conditions limit its further application. In recent decades, advanced oxidation processes based on persulfate (PS) (SR-AOPs) have been considered a promising wastewater purification technology with the potential to treat ammonia nitrogen-containing wastewater. However, SR-AOPs struggle to efficiently and selectively oxidize ammonia nitrogen into nitrogen gas, easily leading to over-oxidation and the generation of secondary pollutants such as nitrates and nitrites. Therefore, developing a low-energy-consumption ammonia nitrogen removal technology that can rapidly and efficiently selectively convert ammonia nitrogen into nitrogen gas has significant value and promising application prospects. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for rapidly removing ammonia nitrogen from wastewater.

[0005] The objective of this invention is achieved through the following technical solution: a method for rapidly removing ammonia nitrogen from wastewater, comprising the following steps:

[0006] S1. Preparation of composite filler: Add carbon materials containing carbonyl and hydroxyl groups to magnesium salt, adjust the pH of the solution to alkaline, react for 25-35 min, and sinter the resulting product at 600-800℃ for 50-70 min under argon protection atmosphere;

[0007] S2. Removal of ammonia nitrogen: Add the prepared composite packing to the wastewater and add persulfate to adjust the pH of the wastewater to alkaline. Stir the reaction for 0.5 to 1 hour, separate the solid and liquid, and the supernatant is the treated effluent.

[0008] Furthermore, the magnesium salt is magnesium sulfate or magnesium chloride.

[0009] Furthermore, the carbon material containing carbonyl and hydroxyl groups is at least one of activated carbon, activated coke, or carbon nanotubes.

[0010] Furthermore, the mass ratio of the magnesium salt to the carbon material containing carbonyl and hydroxyl groups is 1:1 to 4.

[0011] Furthermore, in step S1, the pH of the solution is adjusted to 10-12 using sodium hydroxide, and the reaction is carried out under a stirring rate of 100-400 r / min.

[0012] Furthermore, in step S2, the mass ratio of the composite filler, persulfate, and ammonia nitrogen in the wastewater is 5-30:5-30:1.

[0013] Furthermore, in step S2, the pH of the solution is adjusted to 8-10.

[0014] In this invention:

[0015] Preparation of active filler: When magnesium salt, carbon material containing carbonyl and hydroxyl groups (active substance) are reacted with sodium hydroxide solution, the generated magnesium hydroxide covers the active substance. The solid is then sintered at high temperature, and the magnesium hydroxide decomposes into active magnesium oxide.

[0016] Oxidation of ammonia nitrogen: When the composite packing material is placed in wastewater containing ammonia nitrogen, the magnesium oxide and active substances in the composite packing material activate persulfate into active oxide species, which rapidly oxidize the ammonia nitrogen. The magnesium oxide in the composite packing material can maintain the solution under weakly alkaline conditions, so that ammonia nitrogen mainly exists as NH3 with strong reducing properties, which is easily oxidized, thereby improving its oxidation efficiency.

[0017] Regulation of nitrogen gas in the oxidation products of ammonia nitrogen: Since the active oxides activated by magnesium oxide and active substances for persulfate are mainly singlet oxygen, intermediates of ammonia nitrogen oxidation, such as hydrazine, are easily oxidized directly to nitrogen gas by persulfate. The active substances can also catalyze the oxidation of ammonia nitrogen by persulfate through electron transfer, reducing the over-oxidation of ammonia nitrogen. Furthermore, the surface of the active substances is rich in hydroxyl and carbonyl groups, which can reduce nitrogen-containing oxygen intermediates from ammonia nitrogen oxidation to nitrogen gas, thus achieving rapid and efficient oxidation of ammonia nitrogen to nitrogen gas. After solid-liquid separation, the supernatant is the treated effluent.

[0018] The present invention has the following advantages:

[0019] (1) The active substances and magnesium salts containing carbonyl and hydroxyl groups used in this invention are widely available, inexpensive and environmentally friendly.

[0020] (2) In this invention, magnesium oxide loaded on the surface of the active material can maintain the solution as alkaline, which is conducive to the oxidation of ammonia nitrogen. The active oxygen species generated by the activation of persulfate by the active material and magnesium oxide can rapidly oxidize ammonia nitrogen. At the same time, the groups on the surface of the active material can regulate the product to nitrogen gas instead of the by-products nitrate and nitrite. Compared with traditional advanced oxidation technology, it has the advantages of fast conversion rate, strong anti-interference ability and no secondary pollution.

[0021] (3) This invention only requires magnesium oxide-active material composite filler and persulfate to quickly achieve the goal of selectively converting ammonia nitrogen into nitrogen gas at room temperature and pressure. Therefore, the method for removing ammonia nitrogen from wastewater in this invention is simple to operate, removes ammonia nitrogen quickly, and has significant economic and environmental benefits. Detailed Implementation

[0022] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited to the following description:

[0023] Example 1: A method for rapidly removing ammonia nitrogen from wastewater, comprising the following steps:

[0024] S1. Preparation of composite filler: Activated carbon containing carbonyl and hydroxyl groups is added to magnesium sulfate, wherein the mass ratio of magnesium sulfate to activated carbon containing carbonyl and hydroxyl groups is 1:1; the pH of the solution is adjusted to 10 with sodium hydroxide, and the reaction is carried out for 25 min under a stirring rate of 100 r / min; the resulting product is sintered at 600℃ for 50 min under an argon protective atmosphere.

[0025] S2. Removal of ammonia nitrogen: The prepared composite packing is added to the wastewater, wherein the mass ratio of the composite packing, persulfate and ammonia nitrogen in the wastewater is 5:5:1. Persulfate is added, the pH of the wastewater is adjusted to 8, the mixture is stirred and reacted for 0.5 hours, solid and liquid are separated, and the supernatant is the treated effluent.

[0026] Example 2: A method for rapidly removing ammonia nitrogen from wastewater, comprising the following steps:

[0027] S1. Preparation of composite filler: Activated coke containing carbonyl and hydroxyl groups is added to magnesium chloride, wherein the mass ratio of magnesium chloride to activated coke containing carbonyl and hydroxyl groups is 1:4; the pH of the solution is adjusted to 12 with sodium hydroxide, and the reaction is carried out for 35 min under a stirring rate of 400 r / min; the resulting product is sintered at 800℃ for 70 min under an argon protective atmosphere.

[0028] S2. Removal of ammonia nitrogen: The prepared composite packing is added to the wastewater. The mass ratio of the composite packing, persulfate, and ammonia nitrogen in the wastewater is 30:10:1. Persulfate is added, the pH of the wastewater is adjusted to 10, and the mixture is stirred for 1 hour. Solid-liquid separation is performed, and the supernatant is the treated effluent.

[0029] Example 3: A method for rapidly removing ammonia nitrogen from wastewater, comprising the following steps:

[0030] S1. Preparation of composite filler: An active substance containing carbonyl and hydroxyl groups is added to a magnesium salt, wherein the mass ratio of the magnesium salt to the active substance containing carbonyl and hydroxyl groups is 1:2; the pH of the solution is adjusted to 11 with sodium hydroxide, and the reaction is carried out for 28 min under a stirring rate of 200 r / min; the resulting product is sintered at 680℃ for 55 min under an argon protective atmosphere; wherein the magnesium salt is a mixture of magnesium sulfate and magnesium chloride in a weight ratio of 2:1, and the active substance containing carbonyl and hydroxyl groups is a mixture of activated carbon and activated coke in a weight ratio of 1:2;

[0031] S2. Removal of ammonia nitrogen: The prepared composite packing is added to the wastewater. The mass ratio of the composite packing, persulfate, and ammonia nitrogen in the wastewater is 20:30:1. Persulfate is added, the pH of the wastewater is adjusted to 9, and the mixture is stirred for 0.8 hours. Solid-liquid separation is performed, and the supernatant is the treated effluent.

[0032] Example 4: A method for rapidly removing ammonia nitrogen from wastewater, comprising the following steps:

[0033] S1. Preparation of composite filler: An active substance containing carbonyl and hydroxyl groups is added to magnesium sulfate, wherein the mass ratio of magnesium sulfate to the active substance containing carbonyl and hydroxyl groups is 1:3.5; the pH of the solution is adjusted to 11.5 with sodium hydroxide, and the reaction is carried out for 32 min under a stirring rate of 300 r / min. The resulting product is sintered at 720℃ for 65 min under an argon protective atmosphere; wherein the active substance containing carbonyl and hydroxyl groups is a mixture of activated carbon, activated coke and carbon nanotubes in a weight ratio of 1:1:2.

[0034] S2. Removal of ammonia nitrogen: The prepared composite packing is added to the wastewater. The mass ratio of the composite packing, persulfate, and ammonia nitrogen in the wastewater is 18:25:1. Persulfate is added, and the pH of the wastewater is adjusted to 8-10. The mixture is stirred and reacted for 0.5-1 hours. Solid-liquid separation is performed, and the supernatant is the treated effluent.

[0035] The following experiments illustrate the beneficial effects of this invention:

[0036] Experimental Example 1:

[0037] Experimental subject: The effluent from a landfill leachate MBR biological treatment process was treated by nanofiltration. The TOC, total nitrogen, and ammonia nitrogen contents in the wastewater were 83.75 mg / L, 205.7 mg N / L, and 14.52 mg N / L, respectively, and the pH was 7.60 ± 0.2.

[0038] Experimental methods:

[0039] Preparation of activated coke-magnesium oxide composite material: Magnesium chloride and activated coke containing carbonyl and hydroxyl groups were mixed evenly in an aqueous solution, with the mass ratio of magnesium chloride to activated coke containing carbonyl and hydroxyl groups being 1:4; the pH of the solution was adjusted to 11 with sodium hydroxide, and the reaction was carried out for 30 min at a stirring rate of 200 r / min. The resulting product was sintered at 700 °C for 60 min under an argon protective atmosphere, and then ground to obtain the activated coke-magnesium oxide composite material.

[0040] 5 L of the wastewater was collected into a 10 L acid and alkali resistant container 1. The pH of the wastewater was adjusted to 8.5 with sodium hydroxide. 40 g of activated coke-magnesium oxide composite material and 40 g of potassium persulfate were added to container 1 respectively. The mixture was reacted for 30 min at a stirring rate of 150 r / min. After the reaction was stopped, the solid and liquid were separated, and the supernatant was the final treated effluent.

[0041] Experimental results:

[0042] The total nitrogen and ammonia nitrogen in the treated effluent were measured to be 163.7 mg N / L and 0.58 mg N / L, respectively. The total nitrogen adsorbed on the surface of the composite material was 30.15 mg N / L. The total nitrogen removed by ammonia nitrogen oxidation was 11.85 mg N / L, with an ammonia nitrogen removal rate of 96% and a nitrogen selectivity of 85% for the ammonia nitrogen oxidation products.

[0043] Experimental Example 2:

[0044] Experimental subjects:

[0045] The effluent from the secondary biological treatment of domestic sewage in a certain town has TOC, total nitrogen, and ammonia nitrogen of 13.80 mg / L, 13.77 mg N / L, and 12.20 mg N / L, respectively, and pH = 8.5 ± 0.2.

[0046] Experimental methods:

[0047] Preparation of carbon nanotube-magnesium oxide composite material: Carbon nanotubes containing carbonyl and hydroxyl groups were added to magnesium sulfate, with a mass ratio of magnesium sulfate to carbon nanotubes containing carbonyl and hydroxyl groups of 1:2; the pH of the solution was adjusted to 12 with sodium hydroxide, and the reaction was carried out for 25 min under a stirring rate of 300 r / min. The resulting product was sintered at 800 °C for 50 min under an argon protective atmosphere, and then ground to obtain the carbon nanotube-magnesium oxide composite material.

[0048] 5L of the wastewater was collected into a 10L acid and alkali resistant container 1. The pH of the wastewater was adjusted to 9.5 with sodium hydroxide. 2L of the biologically treated effluent was collected into a 5L acid and alkali resistant container 1. 5g of carbon nanotube-magnesium oxide composite material and 3g of potassium persulfate were added to container 1. The mixture was reacted for 30min at a stirring rate of 150r / min. After the reaction was stopped, the solid and liquid were separated, and the supernatant was the final treated effluent.

[0049] Experimental results:

[0050] Ammonia nitrogen was not detected in the treated effluent, the total nitrogen content was 1.27 mg N / L, the total nitrogen adsorbed on the surface of the composite material was 0.87 mg N / L, the total nitrogen removed by ammonia nitrogen oxidation was 11.63 mg N / L, the ammonia nitrogen removal rate was 100%, and the nitrogen selectivity of the oxidation products was 95.3%.

[0051] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, are covered within the scope of protection of the present invention.

Claims

1. A method for rapidly removing ammonia nitrogen from wastewater, characterized in that, It includes the following steps: S1. Preparation of composite filler: Carbon materials containing carbonyl and hydroxyl groups are added to magnesium salt, the pH of the solution is adjusted to alkaline, the reaction is carried out for 25-35 min, and the resulting product is sintered at 600-800℃ for 50-70 min under an argon protective atmosphere; wherein, the magnesium salt is magnesium sulfate or magnesium chloride; the carbon material containing carbonyl and hydroxyl groups is at least one of activated carbon, activated coke or carbon nanotubes; S2. Removal of ammonia nitrogen: The prepared composite packing is added to the wastewater, along with persulfate, and the pH of the wastewater is adjusted to alkaline. The mixture is stirred and reacted for 0.5 to 1 hour. The singlet oxygen generated by the activated persulfate is used to convert ammonia nitrogen into nitrogen gas. Solid-liquid separation is performed, and the supernatant is the treated effluent.

2. The method for rapidly removing ammonia nitrogen from wastewater according to claim 1, characterized in that, The mass ratio of the magnesium salt to the carbon material containing carbonyl and hydroxyl groups is 1:1 to 4.

3. The method for rapidly removing ammonia nitrogen from wastewater according to claim 1, characterized in that, In step S1, the pH of the solution is adjusted to 10-12 with sodium hydroxide, and the reaction is carried out under a stirring rate of 100-400 r / min.

4. The method for rapidly removing ammonia nitrogen from wastewater according to claim 1, characterized in that, In step S2, the mass ratio of the composite filler, persulfate, and ammonia nitrogen in the wastewater is 5-30:5-30:

1.

5. The method for rapidly removing ammonia nitrogen from wastewater according to claim 1, characterized in that, In step S2, the pH value of the wastewater solution is adjusted to 8-10.