Application of silicified zero-valent iron in organic amine wastewater treatment

Abstract

The invention relates to the technical field of innocent treatment of organic amines in deeply treated underground water and industrial wastewater, in particular to application of silicified zero-valent iron in organic amine wastewater treatment. According to the method, the neutral silica gel and the micron zero-valent iron are subjected to mechanical ball-milling treatment to obtain the silicified zero-valent iron, and then the silicified zero-valent iron is used for activating ozone to deeply remove the organic amine in the organic amine wastewater, so that removal of various organic amines and efficient denitrification are realized. Compared with a traditional organic amine treatment method (advanced oxidation technologies such as a Fenton method), the method provided by the invention not only can realize efficient removal of organic amine in the wastewater, but also can remarkably improve the removal efficiency of total nitrogen in the wastewater, reduce secondary pollution caused by excessive oxidation products such as nitrate nitrogen or nitrite nitrogen and the like, and has a wide application prospect. The process is expected to realize harmless deep treatment of organic amine in industrial wastewater or underground water.

Description

Technical Field

[0001] The present invention relates to the technical field of harmless treatment of organic amines in deeply treated groundwater and industrial wastewater, and in particular to the application of silicified zero-valent iron in the treatment of organic amine wastewater. Background Art

[0002] The problem of excessive total nitrogen in industrial wastewater is particularly prominent in industries such as chemical engineering, pharmaceuticals, printing and dyeing, and papermaking. Among them, the contribution rate of organic amine pollutants exceeds 25% of the total nitrogen load. As organic compounds containing amino groups, these substances are widely used in fields such as solvents, catalysts, and additives in industrial production due to their excellent water solubility and biological activity. Data from the Ministry of Ecology and Environment shows that 5% - 10% of the annual industrial wastewater discharge contains organic amine pollutants, and their environmental hazards present multi-dimensional characteristics: not only exacerbating the excessive total nitrogen, but also having biological toxicity, environmental persistence, and health risks - for example, aniline (fish LC50 = 10mg / L, a class 2B carcinogen) and dimethylamine (a potential carcinogen of the EPA) pose threats to the aquatic ecosystem and the human respiratory / nervous system respectively.

[0003] The current pollution treatment technologies face dual challenges: the need to simultaneously achieve efficient removal of organic amines and selective denitrification to block secondary pollution. Although the microbial nitrification-denitrification process (CN112047534A, CN113105019A) is widely used for ammonia nitrogen treatment, it has the defect of low decontamination efficiency due to the inhibitory effect of the composite toxicity of organic amines. Although the adsorption method (CN112047535A, CN113105020A) has economic advantages, it only completes the phase transfer of pollutants, and subsequent mineralization treatment is still required. Although chemical oxidation technologies (Fenton method, ozone oxidation, etc.) can degrade organic amines, the non-selective oxidation of free radicals easily produces refractory by-products such as nitrates / nitrites, resulting in a decline in denitrification efficiency.

[0004] Therefore, it is crucial to develop a new treatment technology with both efficient mineralization and precise denitrification functions. Summary of the Invention

[0005] In order to solve the above problems, the purpose of the present invention is to provide the application of silicified zero-valent iron in the treatment of organic amine wastewater. The present invention uses neutral silica gel and micron zero-valent iron to carry out mechanical ball milling treatment to obtain silicified zero-valent iron, and then uses silicified zero-valent iron to activate ozone to deeply remove organic amines in organic amine wastewater, realizing the removal of various organic amines and efficient denitrification. Compared with traditional organic amine treatment methods (advanced oxidation technologies such as the Fenton method), the method provided by the present invention can not only achieve efficient removal of organic amines in wastewater, but also significantly improve the total nitrogen removal efficiency in wastewater, reduce the secondary pollution of over-oxidation products such as nitrate nitrogen or nitrite nitrogen, and this process is expected to realize the harmless deep treatment of organic amines in industrial wastewater or groundwater.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] The first object of the present invention is to provide an application of silicified zero-valent iron in the treatment of organic amine wastewater, and the silicified zero-valent iron is combined with ozone.

[0008] In one embodiment of the present invention, the silicified zero-valent iron is prepared by the following method:

[0009] Neutral silica gel and micron zero-valent iron are mixed evenly and then subjected to ball milling treatment to prepare silicified zero-valent iron.

[0010] In one embodiment of the present invention, the mass ratio of the neutral silica gel to the micron zero-valent iron is 1:20 - 100.

[0011] In one embodiment of the present invention, during the ball milling process, the rotation speed is 400 - 600 r / min and the time is 3 - 5 h;

[0012] Preferably, during the ball milling process, the rotation speed is 500 r / min and the time is 4 h.

[0013] In one embodiment of the present invention, the neutral silica gel is prepared by the following method:

[0014] The pH of the sodium silicate solution is adjusted to 7 to precipitate neutral silica gel.

[0015] In one embodiment of the present invention, the sodium silicate has a modulus of 3.2 - 3.4.

[0016] The second object of the present invention is to provide a method for treating organic amine wastewater to improve the total nitrogen removal efficiency, including the following steps:

[0017] Ozone and silicified zero-valent iron are in-situ added to the organic amine wastewater, mixed evenly and then reacted to complete the treatment of the organic amine wastewater.

[0018] In one embodiment of the present invention, the dosage of ozone is 10 - 100 mg / L.

[0019] In one embodiment of the present invention, the molar ratio of ozone to silicified zero-valent iron is 1:3 - 7;

[0020] Preferably, the molar ratio of ozone to silicified zero-valent iron is 1:5.

[0021] The technical principle of the present invention is specifically as follows:

[0022] Zero-valent iron (ZVI), as a new type of environmental remediation material, has shown significant advantages in the field of pollutant degradation due to its synergistic enhancement characteristics with oxidants such as ozone (O3) and hydrogen peroxide (H2O2). Its catalytic ozone system (ZVI / O3) has become an important technical route for wastewater treatment by enhancing the ozone activation rate and utilization rate. However, this system relies on the action mechanism of strongly oxidizing hydroxyl radicals (·OH, E 0 = +2.4V) (Equations (1) to (3)), which easily leads to non-selective over-oxidation of organic amine pollutants and cannot achieve effective removal of total nitrogen.

[0023] O3 + e - → ·O3 - Equation (1);

[0024] ·O3 - + H + → ·HO3 Equation (2);

[0025] ·HO3 → ·OH + O2 Equation (3);

[0026] To address this technical bottleneck, the present invention develops a silicated zero-valent iron catalytic ozone technology; since silicate has the ability to confine free protons, silicated zero-valent iron surface is enriched with confined protons, and the confined protons form confined hydrogen (≡·H) after obtaining the iron core electrons. Due to the high reduction activity of confined hydrogen, it easily reacts with ozone to generate superoxide anion (·O2 - , E 0 = +1.3V, Equations (4) to (5)) - this active species has both mild oxidation characteristics and high selectivity, can more easily attack amino groups without over-oxidation, providing the possibility for the conversion of organic amine to nitrogen. At the same time, the presence of confined hydrogen can consume some ·OH (Equation (6)), thereby reducing the possibility of over-oxidation of organic amines.

[0027] O3 + ≡·H → HO3· Equation (4);

[0028] HO3· + ≡·H → ·O2 - + ·OH + H + Equation (5);

[0029] ·OH + ≡·H → H2O Equation (6);

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The present invention first adopts the method of activating ozone with silicated zero-valent iron, which is applied to the treatment of simulated and actual organic amine wastewater. After treatment, the organic amine concentration and total nitrogen concentration in the wastewater are both significantly reduced, reducing the risk of secondary pollution during the process of organic amine removal.

[0032] (2) The zero-valent iron-catalyzed ozone technology with silication can not only be applied to the treatment of industrial wastewater, but also treat the pollution of organic amines in groundwater through in-situ injection method, which has great application potential and is expected to be widely used in various organic amine-polluted wastewater. Description of the Drawings

[0033] Figure 1 It is the electron microscope image of the zero-valent iron and the zero-valent iron with silication prepared in Example 1 of the present invention;

[0034] Figure 2 It is the change graph of urea removal trend in the treatment of simulated organic amine (urea) wastewater by the present invention;

[0035] Figure 3 It is the effect graph of urea removal in the treatment of simulated organic amine (urea) wastewater by the present invention;

[0036] Figure 4 It is the effect graph of total nitrogen removal in the treatment of simulated organic amine (urea) wastewater by the present invention;

[0037] Figure 5 It is the effect graph of pollutant removal in the treatment of various simulated organic amine wastewater by the present invention;

[0038] Figure 6 It is the effect graph of total nitrogen removal in the treatment of various simulated organic amine wastewater by the present invention;

[0039] Figure 7 It is the effect graph of total nitrogen removal in the treatment of actual organic amine wastewater by the present invention;

[0040] Figure 8 It is the effect graph of total nitrogen removal in the treatment of actual organic amine wastewater under different ozone dosages by the present invention;

[0041] Figure 9 It is the effect graph of total nitrogen removal in the treatment of actual organic amine wastewater with different zero-valent iron materials by the present invention. Detailed Embodiments

[0042] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0043] In the following embodiments, unless otherwise specified, the reagents used are all commercially available reagents, and the detection means and methods used are all conventional detection means and methods in the art.

[0044] In the following embodiments, the neutral silica gel is prepared by the following method:

[0045] Prepare a solution with a mass fraction of 10% by mixing sodium silicate powder with a modulus of 3.2 - 3.4, and adjust the pH to 7 using 1 mol / L sulfuric acid solution and 1 mol / L sodium hydroxide solution to precipitate neutral silica gel for later use.

[0046] Example 1

[0047] This example provides a method for preparing silicified zero-valent iron (Si-ZVI), which includes the following steps:

[0048] Mix neutral silica gel and micron-sized zero-valent iron (the mass ratio of neutral silica gel to micron-sized zero-valent iron is 1:20), and then perform ball milling (rotation speed is 500 r / min, time is 4 h) to prepare silicified zero-valent iron (the morphologies of zero-valent iron and silicified zero-valent iron are as Figure 1 shown).

[0049] Through Figure 1 it can be found that the particles of silicified zero-valent iron are small and there are flocculants on the surface, indicating that silica has been successfully modified on the surface of zero-valent iron; the smaller particles and larger specific surface area may help improve the reaction activity of silicified zero-valent iron.

[0050] Comparative Example 1

[0051] This example provides a method for preparing zero-valent iron powder (ZVI), which includes the following steps:

[0052] Perform ball milling on micron-sized zero-valent iron (rotation speed is 500 r / min, time is 4 h) to prepare zero-valent iron powder (the morphologies of zero-valent iron and silicified zero-valent iron are as Figure 1 shown).

[0053] Through Figure 1 it can be found that the surface of zero-valent iron powder is smooth and the particles are large, indicating that the zero-valent iron prepared in this comparative example still maintains a dense and smooth oxide layer structure, and the existence of the oxide layer may inhibit the reaction activity of zero-valent iron.

[0054] Example 2

[0055] This example provides a method for treating organic amine wastewater, which is as follows:

[0056] Preparation of simulated organic amine wastewater: Mix urea standard sample, sodium bicarbonate, sodium sulfate, and potassium chloride in deionized water; among them, in the simulated organic amine wastewater, the final concentration of urea standard sample is 1 mmol / L, the final concentration of sodium bicarbonate is 2 mmol / L, the final concentration of sodium sulfate is 1 mmol / L, and the final concentration of potassium chloride is 1 mmol / L.

[0057] The group settings are as follows:

[0058] Control group 1 (only ozone treatment group): Add ozone with a final concentration of 2 mmol / L to the simulated organic amine wastewater, stir and react for 1 hour, and then detect the urea concentration and total nitrogen removal rate in the water;

[0059] Control group 2 (microscale zero-valent iron + ozone treatment group): Add zero-valent iron powder with a final concentration of 4 g / L (prepared in Comparative Example 1) and ozone with a final concentration of 2 mmol / L to the simulated organic amine wastewater, stir and react for 1 hour, and then detect the urea concentration and total nitrogen removal rate in the water;

[0060] Experimental group (silicified zero-valent iron + ozone treatment group): Add silicified zero-valent iron with a final concentration of 4 g / L (prepared in Example 1) and ozone with a final concentration of 2 mmol / L to the simulated organic amine wastewater, stir and react for 1 hour, and then detect the urea concentration and total nitrogen removal rate in the water;

[0061] The change trend of urea concentration in each treatment group is as Figure 2 shown. The results show that the experimental group has the best reaction effect in removing urea, significantly superior to Control group 1 and Control group 2. The results of urea and total nitrogen removal rates are as Figure 3 and Figure 4 shown. The results show that for the simulated organic amine wastewater treated by the above several groups, the removal rate of organic amine urea reaches more than 90%, and the total nitrogen removal rate also reaches 85%, and the effect is significantly better than that of single ozone oxidation and zero-valent iron-catalyzed ozone technology.

[0062] Example 3

[0063] This example provides a method for treating organic amine wastewater, which is as follows:

[0064] A variety of simulated organic amine wastewaters are as follows:

[0065] Uracil simulated wastewater: Mix uracil standard sample, sodium bicarbonate, sodium sulfate, and potassium chloride in deionized water; among them, in the simulated organic amine wastewater, the final concentration of uracil standard sample is 1 mmol / L, the final concentration of sodium bicarbonate is 2 mmol / L, the final concentration of sodium sulfate is 1 mmol / L, and the final concentration of potassium chloride is 1 mmol / L.

[0066] Dimethylamine simulated wastewater: Mix dimethylamine standard sample, sodium bicarbonate, sodium sulfate, and potassium chloride in deionized water; among them, in the simulated organic amine wastewater, the final concentration of dimethylamine standard sample is 1 mmol / L, the final concentration of sodium bicarbonate is 2 mmol / L, the final concentration of sodium sulfate is 1 mmol / L, and the final concentration of potassium chloride is 1 mmol / L.

[0067] Aniline simulated wastewater: An aniline standard sample, sodium bicarbonate, sodium sulfate, and potassium chloride were mixed in deionized water. Among them, in the simulated organic amine wastewater, the final concentration of the aniline standard sample was 1 mmol / L, the final concentration of sodium bicarbonate was 2 mmol / L, the final concentration of sodium sulfate was 1 mmol / L, and the final concentration of potassium chloride was 1 mmol / L.

[0068] Treatment method: 4 g / L (final concentration) of silicated zero-valent iron + 5 mmol / L (final concentration) of ozone were added to three kinds of simulated organic amine wastewaters (uracil simulated wastewater, dimethylamine simulated wastewater, aniline simulated wastewater), and after stirring and reacting for 1 hour, the total nitrogen concentration and total nitrogen removal rate in the water were detected;

[0069] The pollutant removal rate and total nitrogen removal rate of each treatment group are as Figure 5 as Figure 6 shown. The results show that for various organic amine simulated wastewaters treated by the process of the present invention, the removal rate of organic amine urea reaches 80 - 92%, and the total nitrogen removal rate is 74 - 88%, indicating that the method of the present invention has good degradation and denitrification effects on various organic amines.

[0070] Example 4

[0071] This example provides a method for treating organic amine wastewater, which is as follows:

[0072] In this example, the organic amine wastewater is actual organic amine wastewater, and its specific composition is as follows: the total nitrogen concentration is 25 mg / L, the inorganic nitrogen (nitrate nitrogen + ammonia nitrogen) concentration is 5 mg / L, the organic amine concentration is about 20 mg / L, the salinity is 2000 mg / L, and pH = 6.5.

[0073] The group settings are specifically as follows:

[0074] Control group 1 (only ozone treatment group): 5 mmol / L (final concentration) of ozone was added to the wastewater, and after stirring and reacting for 1 hour, the urea concentration and total nitrogen removal rate in the water were detected;

[0075] Control group 2 (zero-valent iron + ozone treatment group): 4 g / L (final concentration) of zero-valent iron powder (prepared in Comparative Example 1) + 5 mmol / L (final concentration) of ozone were added to the wastewater, and after stirring and reacting for 1 hour, the urea concentration and total nitrogen removal rate in the water were detected;

[0076] Experimental group (silicated zero-valent iron + ozone treatment group): 4 g / L (final concentration) of silicated zero-valent iron (prepared in Example 1) + 5 mmol / L (final concentration) of ozone were added to the wastewater, and after stirring and reacting for 1 hour, the total nitrogen concentration and total nitrogen removal rate in the water were detected;

[0077] The total nitrogen removal rate of each treatment group is as Figure 7As shown, the results indicate that for the actual organic amine wastewater treated by the experimental group, the total nitrogen removal rate reaches 80%, which is significantly better than that of control group 1 and control group 2, demonstrating that the combined treatment of silicified zero-valent iron + ozone has good removal and denitrification effects on actual organic amine wastewater.

[0078] Example 5

[0079] This example provides a method for treating organic amine wastewater, which is as follows:

[0080] In this example, the organic amine wastewater is actual organic amine wastewater, and its specific composition is as follows: the total nitrogen concentration is 25 mg / L, the inorganic nitrogen (nitrate nitrogen + ammonia nitrogen) concentration is 5 mg / L, the organic amine concentration is about 20 mg / L, the salinity is 2000 mg / L, and pH = 6.5.

[0081] The group settings are specifically as follows:

[0082] Experimental group 1 (silicified zero-valent iron + ozone treatment group): Add 4 g / L (final concentration) of silicified zero-valent iron (prepared in Example 1) + 0.5 mmol / L (final concentration) of ozone to the wastewater, stir and react for 1 hour, and then detect the total nitrogen concentration and total nitrogen removal rate in the water;

[0083] Experimental group 2 (silicified zero-valent iron + ozone treatment group): Add 4 g / L (final concentration) of silicified zero-valent iron (prepared in Example 1) + 1 mmol / L (final concentration) of ozone to the wastewater, stir and react for 1 hour, and then detect the total nitrogen concentration and total nitrogen removal rate in the water;

[0084] Experimental group 3 (silicified zero-valent iron + ozone treatment group): Add 4 g / L (final concentration) of silicified zero-valent iron (prepared in Example 1) + 3 mmol / L (final concentration) of ozone to the wastewater, stir and react for 1 hour, and then detect the total nitrogen concentration and total nitrogen removal rate in the water;

[0085] Experimental group 4 (silicified zero-valent iron + ozone treatment group): Add 4 g / L (final concentration) of silicified zero-valent iron (prepared in Example 1) + 5 mmol / L (final concentration) of ozone to the wastewater, stir and react for 1 hour, and then detect the total nitrogen concentration and total nitrogen removal rate in the water;

[0086] Experimental group 5 (silicified zero-valent iron + ozone treatment group): Add 4 g / L (final concentration) of silicified zero-valent iron (prepared in Example 1) + 7 mmol / L (final concentration) of ozone to the wastewater, stir and react for 1 hour, and then detect the total nitrogen concentration and total nitrogen removal rate in the water;

[0087] The total nitrogen removal rates of each treatment group are as Figure 8As shown, the results indicate that the total nitrogen concentration of the actual wastewater in the 5 experimental groups decreased significantly after treatment. With the increase in ozone dosage, the total nitrogen removal rate of the wastewater also gradually increased. When the ozone concentration reached 5 mmol / L, the total nitrogen removal rate was 90%, reaching the highest. Further increasing the ozone dosage, it was found that the total nitrogen removal rate was 88%, slightly decreasing, indicating that excessive ozone does not necessarily have a better total nitrogen removal effect. It may be that excessive ozone quenched the free radicals, resulting in a decrease in ozone utilization rate. Therefore, under the experimental conditions, when the ozone concentration is set at 5 mmol / L, it has the best total nitrogen removal effect.

[0088] Example 6

[0089] This example provides a method for treating organic amine wastewater, which is as follows:

[0090] In this example, the organic amine wastewater is actual organic amine wastewater, and its specific composition is as follows: the total nitrogen concentration is 25 mg / L, the inorganic nitrogen (nitrate nitrogen + ammonia nitrogen) concentration is 5 mg / L, the organic amine concentration is about 20 mg / L, the salinity is 2000 mg / L, and pH = 6.5.

[0091] Experimental group (silicified zero-valent iron + ozone treatment group): Add 4 g / L (final concentration) of silicified zero-valent iron (prepared in Example 1) + 5 mmol / L (final concentration) of ozone to the wastewater, stir and react for 1 hour, and then detect the total nitrogen concentration and total nitrogen removal rate in the water;

[0092] Control group 1 (oxalic acid-modified zero-valent iron + ozone treatment group): Add 4 g / L (final concentration) of oxalic acid-modified zero-valent iron + 5 mmol / L (final concentration) of ozone to the wastewater, stir and react for 1 hour, and then detect the total nitrogen concentration and total nitrogen removal rate in the water;

[0093] The preparation method of oxalic acid-modified zero-valent iron is the same as that of silicified zero-valent iron: Mix oxalic acid powder with micron zero-valent iron (the mass ratio of oxalic acid to micron zero-valent iron is 1:20), and then perform ball milling treatment (rotation speed is 500 r / min, time is 4 h) to prepare oxalic acid-modified zero-valent iron.

[0094] Control group 2 (phosphoric acid-modified zero-valent iron + ozone treatment group): Add 4 g / L (final concentration) of phosphoric acid-modified zero-valent iron + 5 mmol / L (final concentration) of ozone to the wastewater, stir and react for 1 hour, and then detect the total nitrogen concentration and total nitrogen removal rate in the water;

[0095] The preparation method of phosphoric acid-modified zero-valent iron is the same as that of silicified zero-valent iron: Mix potassium dihydrogen phosphate powder with micron zero-valent iron (the mass ratio of potassium dihydrogen phosphate to micron zero-valent iron is 1:20), and then perform ball milling treatment (rotation speed is 500 r / min, time is 4 h) to prepare phosphoric acid-modified zero-valent iron.

[0096] The total nitrogen removal rates of each treatment group are as follows Figure 9 As shown, the results indicate that the total nitrogen concentrations of the actual wastewater after treatment in the experimental group and the control groups (Control Group 1 and Control Group 2) have both decreased. Among them, the experimental group can achieve a 90% removal of total nitrogen in the wastewater, which is significantly better than Control Group 1 (55%) and Control Group 2 (62%).

[0097] The above description of the embodiments is to enable those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art based on the interpretation of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. Application of silicated zero-valent iron in the treatment of organic amine wastewater, characterized in that: The silicated zero-valent iron is combined with ozone.

2. The use of silicated zero-valent iron in the treatment of organic amine wastewater according to claim 1, characterized in that: The silicated zero-valent iron is prepared by the following method: Neutral silica gel and micronized zero-valent iron are mixed and then ball-milled to prepare silicated zero-valent iron.

3. The use of silicated zero-valent iron in the treatment of organic amine wastewater according to claim 2, characterized in that: The mass ratio of the neutral silica gel to the micron zero-valent iron is 1:20-100.

4. The use of silicated zero-valent iron in the treatment of organic amine wastewater according to claim 2, characterized in that: During the ball milling process, the rotation speed is 400-600 r / min and the time is 3-5 h.

5. The use of silicated zero-valent iron in the treatment of organic amine wastewater according to claim 3, characterized in that: The neutral silica gel is prepared by the following method: The pH of the sodium silicate solution was adjusted to neutral to precipitate neutral silica gel.

6. The use of silicated zero-valent iron in the treatment of organic amine wastewater according to claim 5, characterized in that: The modulus of the sodium silicate is 3.2 to 3.

4.

7. A method for treating organic amine wastewater to improve total nitrogen removal efficiency, characterized in that: The following steps are involved: Ozone and silicated zero-valent iron are added in situ into the organic amine wastewater, mixed and reacted, and the organic amine wastewater treatment is completed.

8. The method for treating organic amine wastewater to improve total nitrogen removal efficiency according to claim 7, characterized in that: The dosage of ozone is 10-100 mg / L.

9. The method for treating organic amine wastewater to improve total nitrogen removal efficiency according to claim 8, characterized in that: The molar ratio of ozone to silicated zero-valent iron is 1:3-7.

10. The method for treating organic amine wastewater to improve total nitrogen removal efficiency according to claim 9, characterized in that: The molar ratio of ozone to silicated zero-valent iron is 1:5.

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