Efficient resourceful treatment method for industrial wastewater
Nitrate nitrogen in industrial wastewater is converted into ammonia nitrogen by a composite reducing agent, and treated with hydrophobic boron nitride and magnesium hydroxide phosphoric acid, which solves the problems of long process, high energy consumption, high cost and secondary pollution in the existing technology, and realizes the efficient resource treatment of inorganic nitrogen and the recovery of nitrogen fertilizer.
Patent Information
- Application Number
- CN202510956803.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-11
- Publication Date
- 2025-10-17
AI Technical Summary
The existing technology for treating inorganic nitrogen in industrial wastewater has problems such as long process, high energy consumption, high cost, risk of secondary pollution and residual metal powder, and the two-stage reduction operation is cumbersome.
A composite reducing agent is used to reduce nitrate nitrogen/nitrite nitrogen in wastewater to ammonia nitrogen, and hydrophobic boron nitride is used as a carrier to load sodium borohydride to increase the reaction contact area. Nitrogen fertilizer is obtained by treating with magnesium hydroxide and phosphoric acid to avoid nitrogen element escape.
It achieves efficient resource utilization of inorganic nitrogen, ensures that wastewater meets standards and avoids nitrogen escape, converts it into usable solid nitrogen fertilizer, improves reduction efficiency and selectivity, and reduces secondary pollution.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of wastewater treatment, and particularly relates to an efficient resource treatment method for industrial wastewater. BACKGROUND
[0002] Currently, the treatment of inorganic nitrogen mainly includes traditional biochemical method, stripping method, ion exchange method, breakpoint chlorination method, and precipitation method. The traditional biochemical method and the ion exchange method are suitable for low-concentration nitrogen-containing wastewater, the stripping method, the breakpoint chlorination method, and the precipitation method are suitable for various concentrations of nitrogen-containing wastewater. The traditional biochemical method has a mature process and good denitrification effect, but has a long process, large occupation, high energy consumption, and high cost. The stripping method has a simple process and low investment, but has high energy consumption and secondary pollution. The ion exchange method has a simple process and convenient operation, but has high cost and secondary pollution. The breakpoint chlorination method has low investment, fast reaction, and high efficiency, but has high operation requirement, high cost, and secondary pollution. The precipitation method has simple operation, few interference factors, and fast reaction, but has high cost and secondary pollution of effluent.
[0003] Patent CN114149067A discloses a resource solidification nitrogen method for inorganic nitrogen in industrial wastewater, which uses metal powder as a reducing agent to reduce nitrate nitrogen and ammonia nitrogen in industrial wastewater to obtain ammonia nitrogen, and then uses the ammonia nitrogen solidification agent to obtain nitrogen fertilizer. The invention uses a large amount of metal powder as a reducing agent, which may cause metal ion residues and increase the risk of heavy metal pollution of wastewater. In addition, the process flow of the invention has a two-stage reduction operation, which is complicated.
[0004] Therefore, it is an important problem to be solved in the field to provide a method for efficiently and resourcefully treating industrial wastewater. SUMMARY
[0005] To solve the problems in the prior art, the present application provides an efficient resource treatment method for industrial wastewater. Specifically, the technical solution of the present application includes the following contents: An efficient resource treatment method for industrial wastewater, which includes the following steps: Adjusting the pH of the wastewater to be treated to 6.8-7.4, then adding a composite reducing agent to obtain a reaction liquid, and then filtering and separating the reaction liquid to obtain a nitrogen-containing filtrate and a filter residue; Mixing the nitrogen-containing filtrate, magnesium hydroxide, and phosphoric acid, adjusting the pH to 8.5-9.2, and then centrifuging to obtain a supernatant and a solid; Post-treating the supernatant to obtain effluent, and drying the solid to obtain nitrogen fertilizer.
[0006] Further, the preparation method of the composite reducing agent includes the following steps: Ultrasonic treatment of hexagonal boron nitride and isopropyl alcohol to obtain boron nitride nanosheets; The boron nitride nanosheets and ammonium dihydrogen phosphate are mixed and calcined to obtain phosphorus-doped boron nitride; The phosphorus-doped boron nitride and hydrophobic silane are reacted to obtain hydrophobic boron nitride; The hydrophobic boron nitride and sodium borohydride are reacted to obtain the composite reducing agent.
[0007] Further, the weight ratio of the hexagonal boron nitride and isopropanol is 1:150-200.
[0008] Further, the ultrasonic treatment conditions include ultrasonic power of 400-500 W and ultrasonic time of 4-6 h.
[0009] Further, the weight ratio of the boron nitride nanosheets and ammonium dihydrogen phosphate is 4-5:2-2.5.
[0010] Further, the calcination conditions include calcination temperature of 800-900℃ and calcination time of 6-8 h.
[0011] Further, the hydrophobic silane includes n-octyl triethoxysilane or dodecyl trimethoxysilane.
[0012] Further, the weight ratio of the phosphorus-doped boron nitride and hydrophobic silane is 1-1.2:0.5-0.7.
[0013] Further, the reaction conditions of the phosphorus-doped boron nitride and hydrophobic silane include reaction temperature of 60-80℃ and reaction time of 24-30 h.
[0014] Further, the weight ratio of the hydrophobic boron nitride and sodium borohydride is 1.2-1.6:0.18-0.38.
[0015] Further, the reaction conditions of the hydrophobic boron nitride and sodium borohydride include reaction temperature of 35-55℃ and reaction time of 4-8 h.
[0016] Further, the weight ratio of the wastewater to be treated and the composite reducing agent is 900-1000:1.
[0017] Further, the reaction conditions of the wastewater to be treated and the composite reducing agent include reaction temperature of 60-80℃, reaction rotation speed of 150-200 r / min, and reaction time of 30-90 min.
[0018] Further, the filter residue can be treated to obtain a regenerated composite reducing agent.
[0019] Further, the treatment of the filter residue includes the following steps: The filter residue is placed in a nitrogen protective atmosphere, and is treated at 150-200 DEG C for 60-90 min, then is added into 0.1 mol / L sodium borohydride solution with 20 times of the weight of the filter residue, and is reacted at 23-25 DEG C for 2-4 h, and finally is dried under vacuum to obtain the regenerated composite reducing agent.
[0020] Further, the phosphoric acid is a 85% mass fraction phosphoric acid solution.
[0021] Further, the weight ratio of the nitrogen-containing filtrate, magnesium hydroxide and phosphoric acid is 100:0.024-0.026:0.049-0.051.
[0022] Further, the reaction conditions of the nitrogen-containing filtrate, magnesium hydroxide and phosphoric acid include a reaction temperature of 30-50 DEG C and a reaction time of 30-60 min.
[0023] Further, the step of post-treatment is that the supernatant is adjusted to a pH of 6.5-7.4, and then is treated by sand filter tank and ultraviolet disinfection.
[0024] Further, the drying treatment conditions include a drying temperature of 60-80 DEG C and a drying time of 12-24 h.
[0025] Compared with the prior art, the present application has the following beneficial effects: (1) The present application provides a resource utilization and nitrogen fixation method of inorganic nitrogen in industrial wastewater, in which the nitrate nitrogen / nitrite nitrogen in the wastewater is reduced to ammonium nitrogen by a composite reducing agent, and the ammonium nitrogen is solidified and crystallized by a nitrogen fixation agent. The method uses inorganic nitrogen in the wastewater as raw material, and completes the conversion of nitrate nitrogen to ammonium nitrogen by means of a composite reducing agent, so as to realize efficient fixation of ammonium nitrogen. While ensuring that the inorganic nitrogen in the wastewater meets the standard, the nitrogen element is converted into solid nitrogen fertilizer instead of escaping in the form of nitrogen gas, thereby providing available resources for downstream related enterprises.
[0026] (2) The present application uses hydrophobic boron nitride as a carrier to load sodium borohydride to prevent its agglomeration and inactivation, and to increase the reaction contact area. The hydrophobicity of the surface can resist the interference of water molecules, and improve the reduction efficiency, selectivity and stability. The method converts difficult-to-treat nitrate / nitrite nitrogen into ammonium nitrogen which is easy to be crystallized and recovered, so as to realize resource utilization and nitrogen fixation of inorganic nitrogen in industrial wastewater. DETAILED DESCRIPTION
[0027] The technical solutions of the present application will be clearly and completely described below through embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.
[0028] The raw materials and reagents used in the present application below are commercially available or can be prepared by known methods unless otherwise specified.
[0029] Preparation Example 1: The preparation method of the composite reducing agent comprises the following steps: 1. 1 part by weight of hexagonal boron nitride is dispersed in 150 parts by weight of isopropanol, ultrasonic treatment is carried out at a power of 400 W for 4 h, and then the boron nitride nanosheets are collected by centrifugation; 4. 4 parts by weight of boron nitride nanosheets and 2 parts by weight of ammonium dihydrogen phosphate are mixed by ball milling at a speed of 200 rpm for 1 h, and then the mixture is placed in a tube furnace and calcined at 800°C for 6 h in a nitrogen protective atmosphere to obtain phosphorus-doped boron nitride; 1. 1 part by weight of phosphorus-doped boron nitride is dispersed in 200 parts by weight of toluene, 0.5 parts by weight of n-octyl triethoxysilane is added, and stirring reaction is carried out at 60°C for 24 h in a nitrogen protective environment to obtain hydrophobic boron nitride; 1. 2 parts by weight of hydrophobic boron nitride and 0.18 parts by weight of sodium borohydride are dispersed in 100 parts by weight of a mixed solvent (V 乙醇 :V 乙酸 = 9:1), stirring reaction is carried out at 35°C for 4 h, and then vacuum drying is carried out at 60°C for 12 h to prepare the composite reducing agent.
[0030] Preparation Example 2: The preparation method of the composite reducing agent comprises the following steps: 1. 1 part by weight of hexagonal boron nitride is dispersed in 160 parts by weight of isopropanol, ultrasonic treatment is carried out at a power of 420 W for 4.2 h, and then the boron nitride nanosheets are collected by centrifugation; 4.2. 4.2 parts by weight of boron nitride nanosheets and 2.1 parts by weight of ammonium dihydrogen phosphate are mixed by ball milling at a speed of 220 rpm for 1.2 h, and then the mixture is placed in a tube furnace and calcined at 820°C for 6.2 h in a nitrogen protective atmosphere to obtain phosphorus-doped boron nitride; 1.02. 1.02 parts by weight of phosphorus-doped boron nitride are dispersed in 200 parts by weight of toluene, 0.52 parts by weight of dodecyl trimethoxysilane is added, and stirring reaction is carried out at 62°C for 25 h in a nitrogen protective environment to obtain hydrophobic boron nitride; 1.25. 1.25 parts by weight of hydrophobic boron nitride and 0.20 parts by weight of sodium borohydride are dispersed in 100 parts by weight of a mixed solvent (V 乙醇 :V 乙酸 = 9:1), stirring reaction is carried out at 37°C for 4.5 h, and then vacuum drying is carried out at 62°C for 15 h to prepare the composite reducing agent.
[0031] Preparation Example 3: The preparation method of the composite reducing agent comprises the following steps: 1. 1 part by weight of hexagonal boron nitride is dispersed in 170 parts by weight of isopropanol, ultrasonic treatment is carried out at a power of 440 W for 4.5 h, and then the boron nitride nanosheets are collected by centrifugation; 4.4 4.4 parts by weight of boron nitride nanosheets and 2.2 parts by weight of ammonium dihydrogen phosphate were mixed by ball milling at a rotation speed of 250 rpm for 1.4 h, and then placed in a tube furnace for calcination treatment at 840 °C for 6.5 h in a nitrogen protective atmosphere to obtain phosphorus-doped boron nitride; 1.05 parts by weight of phosphorus-doped boron nitride were dispersed in 200 parts by weight of toluene, 0.55 parts by weight of dodecyltrimethoxysilane was added, and the mixture was stirred and reacted at 65 °C for 26 h in a nitrogen protective environment to obtain hydrophobic boron nitride; 1.3 parts by weight of hydrophobic boron nitride and 0.22 parts by weight of sodium borohydride were dispersed in 100 parts by weight of a mixed solvent (V 乙醇 :V 乙酸 = 9:1), and the mixture was stirred and reacted at 37 °C for 5 h and then vacuum dried at 65 °C for 18 h to prepare a composite reducing agent.
[0032] Preparation Example 4: The method for preparing the composite reducing agent comprises the following steps: 1 part by weight of hexagonal boron nitride was dispersed in 180 parts by weight of isopropanol, and ultrasonic treatment was performed at a power of 460 W for 5 h, and then boron nitride nanosheets were collected by centrifugation; 4.6 parts by weight of boron nitride nanosheets and 2.3 parts by weight of ammonium dihydrogen phosphate were mixed by ball milling at a rotation speed of 300 rpm for 1.6 h, and then placed in a tube furnace for calcination treatment at 860 °C for 7 h in a nitrogen protective atmosphere to obtain phosphorus-doped boron nitride; 1.1 parts by weight of phosphorus-doped boron nitride was dispersed in 200 parts by weight of toluene, 0.6 parts by weight of dodecyltrimethoxysilane was added, and the mixture was stirred and reacted at 70 °C for 28 h in a nitrogen protective environment to obtain hydrophobic boron nitride; 1.4 parts by weight of hydrophobic boron nitride and 0.27 parts by weight of sodium borohydride were dispersed in 100 parts by weight of a mixed solvent (V 乙醇 :V 乙酸 = 9:1), and the mixture was stirred and reacted at 40 °C for 6 h and then vacuum dried at 70 °C for 20 h to prepare a composite reducing agent.
[0033] Preparation Example 5: The method for preparing the composite reducing agent comprises the following steps: 1 part by weight of hexagonal boron nitride was dispersed in 190 parts by weight of isopropanol, and ultrasonic treatment was performed at a power of 480 W for 5.5 h, and then boron nitride nanosheets were collected by centrifugation; 4.8 parts by weight of boron nitride nanosheets and 2.4 parts by weight of ammonium dihydrogen phosphate were mixed by ball milling at a rotation speed of 350 rpm for 1.8 h, and then placed in a tube furnace for calcination treatment at 880 °C for 7.5 h in a nitrogen protective atmosphere to obtain phosphorus-doped boron nitride; 1.15 parts by weight of phosphorus-doped boron nitride is dispersed in 200 parts by weight of toluene, 0.65 parts by weight of n-octyl triethoxysilane is added, and the reaction is stirred at 75°C for 29 hours in a nitrogen protective environment to obtain hydrophobic boron nitride; 1.5 parts by weight of hydrophobic boron nitride and 0.32 parts by weight of sodium borohydride are dispersed in 100 parts by weight of a mixed solvent (V 乙醇 :V 乙酸 = 9:1), and after the reaction is stirred at 47°C for 7 hours, vacuum drying is performed at 75°C for 22 hours to obtain a composite reducing agent.
[0034] Preparation Example 6: The method for preparing the composite reducing agent comprises the following steps: 1 part by weight of hexagonal boron nitride is dispersed in 200 parts by weight of isopropanol, and ultrasonic treatment is performed at a power of 500W for 6 hours, and then boron nitride nanosheets are collected by centrifugation; 5 parts by weight of boron nitride nanosheets and 2.5 parts by weight of ammonium dihydrogen phosphate are ball-mixed at a rotation speed of 400 rpm for 2 hours, and then placed in a tube furnace and calcined at 900°C for 8 hours in a nitrogen protective atmosphere to obtain phosphorus-doped boron nitride; 1.2 parts by weight of phosphorus-doped boron nitride is dispersed in 200 parts by weight of toluene, 0.7 parts by weight of n-octyl triethoxysilane is added, and the reaction is stirred at 80°C for 30 hours in a nitrogen protective environment to obtain hydrophobic boron nitride; 1.6 parts by weight of hydrophobic boron nitride and 0.38 parts by weight of sodium borohydride are dispersed in 100 parts by weight of a mixed solvent (V 乙醇 :V 乙酸 = 9:1), and after the reaction is stirred at 55°C for 8 hours, vacuum drying is performed at 80°C for 24 hours to obtain a composite reducing agent.
[0035] Preparation Example 7: The method for preparing the composite reducing agent comprises the following steps: 1 part by weight of hexagonal boron nitride is dispersed in 200 parts by weight of isopropanol, and ultrasonic treatment is performed at a power of 500W for 6 hours, and then boron nitride nanosheets are collected by centrifugation; 1.2 parts by weight of boron nitride nanosheets is dispersed in 200 parts by weight of toluene, 0.7 parts by weight of n-octyl triethoxysilane is added, and the reaction is stirred at 80°C for 30 hours in a nitrogen protective environment to obtain hydrophobic boron nitride; 1.6 parts by weight of hydrophobic boron nitride and 0.38 parts by weight of sodium borohydride are dispersed in 100 parts by weight of a mixed solvent (V 乙醇 :V 乙酸 = 9:1), and after the reaction is stirred at 55°C for 8 hours, vacuum drying is performed at 80°C for 24 hours to obtain a composite reducing agent.
[0036] Preparation Example 8: The method for preparing the composite reducing agent comprises the following steps: 1 part by weight of hexagonal boron nitride was dispersed in 200 parts by weight of isopropanol and ultrasonicated at a power of 500 W for 6 h, followed by centrifugation to collect the boron nitride nanosheets; 5 parts by weight of boron nitride nanosheets and 2.5 parts by weight of ammonium dihydrogen phosphate were ball-milled at 400 rpm for 2 h, and then placed in a tube furnace in a nitrogen atmosphere and calcined at 900° C. for 8 h to obtain phosphorus-doped boron nitride; 1.6 parts by weight of phosphorus-doped boron nitride and 0.38 parts by weight of sodium borohydride are dispersed in 100 parts by weight of a mixed solvent (V 乙醇 :V 乙酸 =9:1), stirred at 55 °C for 8 h, and then vacuum dried at 80 °C for 24 h to prepare a composite reducing agent.
[0037] Preparation Example 9: The preparation method of the composite reducing agent comprises the following steps: 1 part by weight of hexagonal boron nitride was dispersed in 200 parts by weight of isopropanol and ultrasonicated at a power of 500 W for 6 h, followed by centrifugation to collect the boron nitride nanosheets; 5 parts by weight of boron nitride nanosheets and 2.5 parts by weight of ammonium dihydrogen phosphate were ball-milled at 400 rpm for 2 h, and then placed in a tube furnace in a nitrogen atmosphere and calcined at 900° C. for 8 h to obtain phosphorus-doped boron nitride; 1.2 parts by weight of phosphorus-doped boron nitride were dispersed in 200 parts by weight of toluene, 0.7 parts by weight of n-octyltriethoxysilane was added, and the mixture was stirred and reacted at 80° C. for 30 hours in a nitrogen atmosphere to prepare a composite reducing agent.
[0038] Preparation Example 10: The preparation method of the composite reducing agent comprises the following steps: 1 part by weight of hexagonal boron nitride was dispersed in 200 parts by weight of isopropanol and ultrasonicated at a power of 500 W for 6 h, followed by centrifugation to collect the boron nitride nanosheets; 5 parts by weight of boron nitride nanosheets and 2.5 parts by weight of ammonium dihydrogen phosphate were ball-milled at 400 rpm for 2 h, and then placed in a tube furnace in a nitrogen atmosphere and calcined at 900° C. for 8 h to obtain phosphorus-doped boron nitride; 1.2 parts by weight of phosphorus-doped boron nitride was dispersed in 200 parts by weight of toluene, 0.7 parts by weight of ethyltriethoxysilane was added, and the mixture was stirred at 80° C. for 30 hours in a nitrogen atmosphere to obtain hydrophobic boron nitride; 1.6 parts by weight of hydrophobic boron nitride and 0.38 parts by weight of sodium borohydride are dispersed in 100 parts by weight of a mixed solvent (V 乙醇 :V 乙酸 =9:1), stirred at 55 °C for 8 h, and then vacuum dried at 80 °C for 24 h to prepare a composite reducing agent.
[0039] Example 1: An efficient resource treatment method of industrial wastewater comprises the following steps: 900 parts by weight of the wastewater to be treated is adjusted to pH 6.8, then 1 part by weight of the composite reducing agent prepared in Preparation Example 1 is added, and the temperature is raised to 60°C for stirring at 150 r / min for 30 min to obtain a reaction liquid. The reaction liquid is separated by filtration to obtain a nitrogen-containing filtrate and a filter residue; The filter residue is placed in a nitrogen protective atmosphere, and treated at 150°C for 60 min. Then, the filter residue is added to 0.1 mol / L sodium borohydride solution with a weight of 20 times that of the filter residue, and reacted at 23°C for 2 h. Finally, vacuum drying is performed to obtain the regenerated composite reducing agent; 0.24 parts by weight of magnesium hydroxide and 0.49 parts by weight of 85% phosphoric acid solution are added to 1000 parts by weight of the nitrogen-containing filtrate, and the pH is adjusted to 8.5. After stirring at 120 r / min at 30°C for 30 min, centrifugation is performed at 3000 r / min for 5 min to separate the supernatant and the solid; The supernatant is adjusted to pH 6.5, and then subjected to sand filter tank and ultraviolet disinfection to obtain effluent water. The solid is dried at 60°C for 12 h to obtain nitrogen fertilizer.
[0040] Example 2: An efficient resource treatment method of industrial wastewater comprises the following steps: 920 parts by weight of the wastewater to be treated is adjusted to pH 6.9, then 1 part by weight of the composite reducing agent prepared in Preparation Example 2 is added, and the temperature is raised to 62°C for stirring at 160 r / min for 40 min to obtain a reaction liquid. The reaction liquid is separated by filtration to obtain a nitrogen-containing filtrate and a filter residue; The filter residue is placed in a nitrogen protective atmosphere, and treated at 160°C for 65 min. Then, the filter residue is added to 0.1 mol / L sodium borohydride solution with a weight of 20 times that of the filter residue, and reacted at 24°C for 2.5 h. Finally, vacuum drying is performed to obtain the regenerated composite reducing agent; 0.242 parts by weight of magnesium hydroxide and 0.492 parts by weight of 85% phosphoric acid solution are added to 1000 parts by weight of the nitrogen-containing filtrate, and the pH is adjusted to 8.6. After stirring at 125 r / min at 32°C for 35 min, centrifugation is performed at 3000 r / min for 6 min to separate the supernatant and the solid; The supernatant is adjusted to pH 6.6, and then subjected to sand filter tank and ultraviolet disinfection to obtain effluent water. The solid is dried at 62°C for 15 h to obtain nitrogen fertilizer.
[0041] Example 3: An efficient resource treatment method of industrial wastewater comprises the following steps: 940 parts by weight of the wastewater to be treated were adjusted to pH 7.0, then 1 part by weight of the composite reducing agent prepared in Preparation Example 3 was added, and the temperature was raised to 65°C for stirring at 170 r / min for 60 min to obtain a reaction liquid, which was separated by filtration to obtain a nitrogen-containing filtrate and a filter residue; The filter residue was placed in a nitrogen protective atmosphere, and was treated at 170°C for 70 min, then was added to 20 times the weight of the filter residue of 0.1 mol / L sodium borohydride solution, and reacted at 25°C for 3 h, and finally was vacuum dried to obtain the regenerated composite reducing agent; 0.245 parts by weight of magnesium hydroxide and 0.495 parts by weight of 85% phosphoric acid solution were added to 1000 parts by weight of the nitrogen-containing filtrate, and the pH was adjusted to 8.7, and the stirring was carried out at 130 r / min at 35°C for 40 min, and then the centrifugation was carried out at 3000 r / min for 7 min to separate the supernatant and the solid; The supernatant was adjusted to pH 6.8, and then was subjected to sand filter tank and ultraviolet disinfection to obtain effluent; and the solid was dried at 65°C for 18 h to obtain nitrogen fertilizer.
[0042] Example 4: A method for efficient resource treatment of industrial wastewater comprises the following steps: 960 parts by weight of the wastewater to be treated were adjusted to pH 7.2, then 1 part by weight of the composite reducing agent prepared in Preparation Example 4 was added, and the temperature was raised to 70°C for stirring at 180 r / min for 70 min to obtain a reaction liquid, which was separated by filtration to obtain a nitrogen-containing filtrate and a filter residue; The filter residue was placed in a nitrogen protective atmosphere, and was treated at 180°C for 75 min, then was added to 20 times the weight of the filter residue of 0.1 mol / L sodium borohydride solution, and reacted at 23°C for 3.5 h, and finally was vacuum dried to obtain the regenerated composite reducing agent; 0.25 parts by weight of magnesium hydroxide and 0.50 parts by weight of 85% phosphoric acid solution were added to 1000 parts by weight of the nitrogen-containing filtrate, and the pH was adjusted to 8.9, and the stirring was carried out at 140 r / min at 40°C for 50 min, and then the centrifugation was carried out at 3000 r / min for 8 min to separate the supernatant and the solid; The supernatant was adjusted to pH 7.0, and then was subjected to sand filter tank and ultraviolet disinfection to obtain effluent; and the solid was dried at 70°C for 20 h to obtain nitrogen fertilizer.
[0043] Example 5: A method for efficient resource treatment of industrial wastewater comprises the following steps: 980 parts by weight of the wastewater to be treated were adjusted to pH 7.3, then 1 part by weight of the composite reducing agent prepared in Preparation Example 5 was added, and the temperature was raised to 75°C for stirring at 190 r / min for 80 min to obtain a reaction liquid, which was separated by filtration to obtain a nitrogen-containing filtrate and a filter residue; The filter residue was placed in a nitrogen atmosphere and kept warm at 180°C for 80 minutes. It was then added to a 0.1 mol / L sodium borohydride solution (20 times the weight of the filter residue) and reacted at 24°C for 4 hours. Finally, it was vacuum dried to obtain a regenerated composite reducing agent. 0.255 parts by weight of magnesium hydroxide and 0.505 parts by weight of 85% phosphoric acid solution were added to 1000 parts by weight of the nitrogen-containing filtrate, the pH was adjusted to 9.0, and the mixture was stirred at 45°C for 55 minutes at a speed of 145 r / min. The mixture was then centrifuged at a speed of 3000 r / min for 9 minutes to separate the supernatant and the solid. The pH of the supernatant is adjusted to 7.2, and then the effluent is obtained by sand filtration and ultraviolet disinfection; the solid matter is dried at 75° C. for 22 hours to obtain nitrogen fertilizer.
[0044] Example 6: A method for efficiently recycling industrial wastewater comprises the following steps: After adjusting the pH of 1000 parts by weight of the wastewater to be treated to 7.4, 1 part by weight of the composite reducing agent prepared in Preparation Example 6 was added, the temperature was raised to 80° C., and the mixture was stirred at 200 r / min for 90 minutes to obtain a reaction solution, which was then filtered to obtain a nitrogen-containing filtrate and a filter residue; The filter residue was placed in a nitrogen atmosphere and kept warm at 200°C for 90 minutes. It was then added to a 0.1 mol / L sodium borohydride solution (20 times the weight of the filter residue) and reacted at 25°C for 4 hours. Finally, it was vacuum dried to obtain a regenerated composite reducing agent. 0.26 parts by weight of magnesium hydroxide and 0.51 parts by weight of 85% phosphoric acid solution were added to 1000 parts by weight of the nitrogen-containing filtrate, the pH was adjusted to 9.2, and the mixture was stirred at 50° C. for 60 minutes at a speed of 150 r / min. The mixture was then centrifuged at a speed of 3000 r / min for 10 minutes to separate the supernatant and the solid; The pH of the supernatant is adjusted to 7.4, and then the effluent is obtained by sand filtration and ultraviolet disinfection; the solid matter is dried at 80° C. for 24 hours to obtain nitrogen fertilizer.
[0045] Comparative Example 1: A method for efficiently recycling industrial wastewater comprises the following steps: After adjusting the pH of 1000 parts by weight of the wastewater to be treated to 7.4, 1 part by weight of the composite reducing agent prepared in Preparation Example 7 was added, the temperature was raised to 80° C., and the mixture was stirred at 200 r / min for 90 minutes to obtain a reaction solution, which was then filtered to obtain a nitrogen-containing filtrate and a filter residue; The filter residue was placed in a nitrogen atmosphere and kept warm at 200°C for 90 minutes. It was then added to a 0.1 mol / L sodium borohydride solution (20 times the weight of the filter residue) and reacted at 25°C for 4 hours. Finally, it was vacuum dried to obtain a regenerated composite reducing agent. 0.26 parts by weight of magnesium hydroxide and 0.51 parts by weight of 85% phosphoric acid solution were added to 1000 parts by weight of the nitrogen-containing filtrate, the pH was adjusted to 9.2, and the mixture was stirred at 50° C. for 60 minutes at a speed of 150 r / min. The mixture was then centrifuged at a speed of 3000 r / min for 10 minutes to separate the supernatant and the solid; The pH of the supernatant is adjusted to 7.4, and then the effluent is obtained by sand filtration and ultraviolet disinfection; the solid matter is dried at 80° C. for 24 hours to obtain nitrogen fertilizer.
[0046] Comparative Example 2: A method for efficiently recycling industrial wastewater comprises the following steps: After adjusting the pH of 1000 parts by weight of the wastewater to be treated to 7.4, 1 part by weight of the composite reducing agent prepared in Preparation Example 8 was added, the temperature was raised to 80° C., and the mixture was stirred at 200 r / min for 90 minutes to obtain a reaction solution, which was then filtered to obtain a nitrogen-containing filtrate and a filter residue; The filter residue was placed in a nitrogen atmosphere and kept warm at 200°C for 90 minutes. It was then added to a 0.1 mol / L sodium borohydride solution (20 times the weight of the filter residue) and reacted at 25°C for 4 hours. Finally, it was vacuum dried to obtain a regenerated composite reducing agent. 0.26 parts by weight of magnesium hydroxide and 0.51 parts by weight of 85% phosphoric acid solution were added to 1000 parts by weight of the nitrogen-containing filtrate, the pH was adjusted to 9.2, and the mixture was stirred at 50° C. for 60 minutes at a speed of 150 r / min. The mixture was then centrifuged at a speed of 3000 r / min for 10 minutes to separate the supernatant and the solid; The pH of the supernatant is adjusted to 7.4, and then the effluent is obtained by sand filtration and ultraviolet disinfection; the solid matter is dried at 80° C. for 24 hours to obtain nitrogen fertilizer.
[0047] Comparative Example 3: A method for efficiently recycling industrial wastewater comprises the following steps: After adjusting the pH of 1000 parts by weight of the wastewater to be treated to 7.4, 1 part by weight of the composite reducing agent prepared in Preparation Example 9 was added, the temperature was raised to 80° C., and the mixture was stirred at 200 r / min for 90 minutes to obtain a reaction solution, which was then filtered to obtain a nitrogen-containing filtrate and a filter residue; The filter residue was placed in a nitrogen atmosphere and kept warm at 200°C for 90 minutes. It was then added to a 0.1 mol / L sodium borohydride solution (20 times the weight of the filter residue) and reacted at 25°C for 4 hours. Finally, it was vacuum dried to obtain a regenerated composite reducing agent. 1000 parts by weight of the nitrogen-containing filtrate were added with 0.26 parts by weight of magnesium hydroxide and 0.51 parts by weight of an 85% by mass phosphoric acid solution, the pH was adjusted to 9.2, and after stirring at 150 r / min at 50°C for 60 min, the supernatant and solid were separated by centrifugation at 3000 r / min for 10 min; The supernatant was adjusted to pH 7.4, and then subjected to sand filter tank and ultraviolet disinfection to obtain effluent water; the solid was dried at 80°C for 24 h to obtain nitrogen fertilizer.
[0048] Comparative Example 4: An efficient resource treatment method of industrial wastewater includes the following steps: 1000 parts by weight of the nitrogen-containing filtrate were added with 0.26 parts by weight of magnesium hydroxide and 0.51 parts by weight of an 85% by mass phosphoric acid solution, the pH was adjusted to 9.2, and after stirring at 150 r / min at 50°C for 60 min, the supernatant and solid were separated by centrifugation at 3000 r / min for 10 min; The filter residue was placed in a nitrogen protective atmosphere and treated at 200°C for 90 min, then added to 0.1 mol / L sodium borohydride solution 20 times the weight of the filter residue, reacted at 25°C for 4 h, and finally vacuum dried to obtain regenerated composite reducing agent; 1000 parts by weight of the nitrogen-containing filtrate were added with 0.26 parts by weight of magnesium hydroxide and 0.51 parts by weight of an 85% by mass phosphoric acid solution, the pH was adjusted to 9.2, and after stirring at 150 r / min at 50°C for 60 min, the supernatant and solid were separated by centrifugation at 3000 r / min for 10 min; The supernatant was adjusted to pH 7.4, and then subjected to sand filter tank and ultraviolet disinfection to obtain effluent water; the solid was dried at 80°C for 24 h to obtain nitrogen fertilizer.
[0049] Comparative Example 5: An efficient resource treatment method of industrial wastewater includes the following steps: 1000 parts by weight of the nitrogen-containing filtrate were added with 0.26 parts by weight of magnesium hydroxide and 0.51 parts by weight of an 85% by mass phosphoric acid solution, the pH was adjusted to 9.2, and after stirring at 150 r / min at 50°C for 60 min, the supernatant and solid were separated by centrifugation at 3000 r / min for 10 min; The filter residue was placed in a nitrogen protective atmosphere and treated at 200°C for 90 min, then added to 0.1 mol / L sodium borohydride solution 20 times the weight of the filter residue, reacted at 25°C for 4 h, and finally vacuum dried to obtain regenerated composite reducing agent; 1000 parts by weight of the nitrogen-containing filtrate were added with 0.26 parts by weight of magnesium hydroxide and 0.51 parts by weight of an 85% by mass phosphoric acid solution, and the pH was adjusted to 9.2. After stirring at 150 r / min at 50°C for 60 min, the supernatant and solid were separated by centrifugation at 3000 r / min for 10 min; The supernatant was adjusted to pH 7.4, and then filtered through a sand filter tank and disinfected with ultraviolet light to obtain the effluent. The solid was dried at 80°C for 24 h to obtain a nitrogen fertilizer.
[0050] Comparative Example 6: An efficient resource treatment method for industrial wastewater includes the following steps: 1000 parts by weight of the wastewater to be treated were adjusted to pH 7.4, and then 0.4 parts by weight of the composite reducing agent prepared in Preparation Example 6 was added. The mixture was heated to 80°C and stirred at 200 r / min for 90 min to obtain a reaction liquid. The reaction liquid was separated by filtration to obtain a nitrogen-containing filtrate and a filter residue; The filter residue was placed in a nitrogen protective atmosphere and heat-treated at 200°C for 90 min. Then, the filter residue was added to 20 times its weight of a 0.1 mol / L sodium borohydride solution and reacted at 25°C for 4 h. Finally, the regenerated composite reducing agent was obtained by vacuum drying; 1000 parts by weight of the nitrogen-containing filtrate were added with 0.26 parts by weight of magnesium hydroxide and 0.51 parts by weight of an 85% by mass phosphoric acid solution, and the pH was adjusted to 9.2. After stirring at 150 r / min at 50°C for 60 min, the supernatant and solid were separated by centrifugation at 3000 r / min for 10 min; The supernatant was adjusted to pH 7.4, and then filtered through a sand filter tank and disinfected with ultraviolet light to obtain the effluent. The solid was dried at 80°C for 24 h to obtain a nitrogen fertilizer.
[0051] Test Example: The effluent obtained after treatment in Examples 1-6 and Comparative Examples 1-6 was subjected to water quality testing, and the results are shown in Table 1.
[0052] Table 1. Water quality test results It can be seen from the detection results in Table 1 that the effluent obtained by the treatment method of Examples 1-6 of the present application has a lower total nitrogen content. The reason for the increase in total nitrogen content in Comparative Example 1 may be that phosphorus doping may introduce active sites, improving the performance of the composite reducing agent, while the composite reducing agent used in Comparative Example 1 is not doped with phosphorus elements, affecting its reduction efficiency, resulting in the nitrate nitrogen / nitrite nitrogen not being reduced and being unable to be captured by magnesium hydroxide and phosphoric acid. These unreduced nitrogen forms eventually enter the supernatant, resulting in an increase in the total nitrogen content of the effluent. The reason for the increase in total nitrogen content in Comparative Example 2 may be that hydrophobic treatment helps the composite reducing agent to disperse well in the wastewater system, increasing the contact area with pollutants. The composite reducing agent that is not hydrophobic is prone to aggregation and has poor dispersibility, reducing the effective reaction sites and reducing the reduction efficiency, resulting in an increase in residual nitrate nitrogen, thereby affecting the removal efficiency of total nitrogen in industrial wastewater. The reason for the increase in total nitrogen content in Comparative Example 3 may be that the composite reducing agent is not loaded with sodium borohydride, reducing the ability to reduce nitrate nitrogen, and most of the nitrate nitrogen / nitrite nitrogen in industrial wastewater will not be converted to ammonia nitrogen, resulting in an increase in the total nitrogen content of the effluent. The reason for the increase in total nitrogen content in Comparative Example 4 may be that the modification with ethyl triethoxysilane is less hydrophobic, and the dispersibility and anti-aggregation ability are poor, resulting in a decrease in the effective reaction area, a decrease in the reduction efficiency, and the residual of part of the nitrate nitrogen / nitrite nitrogen, resulting in an increase in the total nitrogen content of the effluent. The low total nitrogen content in Comparative Example 5 may be that the excess composite reducing agent completely reduces the nitrate nitrogen to ammonia nitrogen, but the excess composite reducing agent may have the risk of over-reduction, which may further reduce part of the ammonia nitrogen to nitrogen gas and escape. Although this reduces the total nitrogen content in the effluent, it violates the original intention of resource treatment and reduces the recoverable nitrogen fertilizer; in addition, the excess composite reducing agent may damage the subsequent magnesium hydroxide and phosphoric acid. The reason for the increase in total nitrogen content in Comparative Example 6 may be that the amount of composite reducing agent is insufficient to fully reduce the nitrate nitrogen / nitrite nitrogen in industrial wastewater to ammonia nitrogen, and the residual nitrate nitrogen / nitrite nitrogen cannot be removed by the subsequent nitrogen fixation step, resulting in an increase in the total nitrogen content of the effluent.
[0053] The above-described examples have described the technical solutions and beneficial effects of the present application in detail. It should be understood that the above-described examples are only specific embodiments of the present application and are not intended to limit the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.
Claims
1. A method for efficiently recycling industrial wastewater, characterized in that: The processing method comprises the following steps: The pH of the wastewater to be treated is adjusted to 6.8-7.4, and then a composite reducing agent is added to react to obtain a reaction solution, and the reaction solution is filtered and separated to obtain a nitrogen-containing filtrate and a filter residue; The nitrogen-containing filtrate, magnesium hydroxide and phosphoric acid are mixed and the pH is adjusted to 8.5-9.
2. After the reaction, the supernatant and solid are obtained by centrifugation; The supernatant is post-treated to obtain effluent, and the solid matter is dried to obtain nitrogen fertilizer.
2. A method for efficiently recycling industrial wastewater according to claim 1, characterized in that: The preparation method of the composite reducing agent comprises the following steps: Boron nitride nanosheets were obtained by ultrasonic treatment of hexagonal boron nitride and isopropyl alcohol; Boron nitride nanosheets and ammonium dihydrogen phosphate are mixed and calcined to obtain phosphorus-doped boron nitride; Phosphorus-doped boron nitride reacts with hydrophobic silane to obtain hydrophobic boron nitride; The composite reducing agent is prepared by reacting hydrophobic boron nitride with sodium borohydride.
3. A method for efficiently recycling industrial wastewater as claimed in claim 2, characterized in that: The weight ratio of the hexagonal boron nitride to isopropyl alcohol is 1:150-200.
4. A method for efficiently recycling industrial wastewater according to claim 2, characterized in that: The weight ratio of the boron nitride nanosheets to ammonium dihydrogen phosphate is 4-5:2-2.
5.
5. The method for efficiently recycling industrial wastewater according to claim 2, wherein: The hydrophobic silane includes n-octyltriethoxysilane or dodecyltrimethoxysilane.
6. A method for efficiently recycling industrial wastewater according to claim 2, characterized in that: The weight ratio of the phosphorus-doped boron nitride to the hydrophobic silane is 1-1.2:0.5-0.
7.
7. The method for efficiently recycling industrial wastewater according to claim 2, wherein: The weight ratio of the hydrophobic boron nitride to sodium borohydride is 1.2-1.6:0.18-0.
38.
8. The method for efficiently recycling industrial wastewater according to claim 1, wherein: The weight ratio of the wastewater to be treated to the composite reducing agent is 900-1000:
1.
9. The method for efficiently recycling industrial wastewater according to claim 1, wherein: The weight ratio of the nitrogen-containing filtrate, magnesium hydroxide and phosphoric acid is 100: 0.024-0.026: 0.049-0.
051.
10. The method for efficiently recycling industrial wastewater according to claim 1, characterized in that: The post-treatment step comprises adjusting the pH of the supernatant to 6.5-7.4, and then performing sand filtration and ultraviolet disinfection.