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

Abstract

The present application relates to harmless treatment technology field of deep treatment of groundwater and industrial wastewater, especially to the application of silicification zero-valent iron in organic amine wastewater treatment, the present application utilizes neutral silica gel and micron zero-valent iron to carry out mechanical ball milling treatment to obtain silicification zero-valent iron, then utilizes silicification zero-valent iron to activate ozone to deeply remove organic amine in organic amine wastewater, realizes the removal of various organic amine and efficient denitrification.Compared with the traditional organic amine treatment method (Fenton method and other advanced oxidation technology), the method provided by the present application can not only realize the efficient removal of organic amine in wastewater, but also can significantly improve the total nitrogen removal efficiency in wastewater, reduce the secondary pollution of excessive oxidation products such as nitric nitrogen or nitrous nitrogen, and the process is expected to realize the harmless deep treatment of organic amine in industrial wastewater or groundwater.

Description

Technical Field

[0001] This invention relates to the field of harmless treatment technology for organic amines in groundwater and industrial wastewater undergoing deep treatment, and in particular to the application of silicated zero-valent iron in the treatment of organic amine wastewater. Background Technology

[0002] Excessive total nitrogen in industrial wastewater is particularly prominent in industries such as chemical, pharmaceutical, printing and dyeing, and papermaking, with organic amines contributing over 25% of the total nitrogen load. As amino-containing organic compounds, these substances are widely used in industrial production as solvents, catalysts, and additives due to their excellent water solubility and biological activity. Organic amines account for 5%–10% of annual industrial wastewater discharge, and their environmental hazards are multidimensional: they not only exacerbate excessive total nitrogen levels but also possess biotoxicity, environmental persistence, and health risks—for example, aniline (LC50 for fish = 10 mg / L, Group 2B carcinogen) and dimethylamine (EPA potential carcinogen) pose threats to aquatic ecosystems and the human respiratory / nervous system, respectively.

[0003] Current pollution control technologies face a dual challenge: the simultaneous achievement of efficient removal of organic amines and selective denitrification to prevent secondary pollution. While microbial nitrification-denitrification processes (CN112047534A, CN113105019A) are widely used for ammonia nitrogen treatment, their low decontamination efficiency is hampered by the inhibitory effect of the combined toxicity of organic amines. Adsorption methods (CN112047535A, CN113105020A), despite their economic advantages, only achieve phase transfer of pollutants, requiring subsequent mineralization treatment. Chemical oxidation technologies (Fenton process, ozone oxidation, etc.) can degrade organic amines, but the non-selective oxidation by free radicals easily produces persistent byproducts such as nitrates / nitrites, leading to a decline in denitrification efficiency.

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

[0005] To address the aforementioned problems, the present invention aims to provide an application of zero-valent iron silicate in the treatment of organic amine wastewater. This invention utilizes neutral silica gel and micron-sized zero-valent iron through mechanical ball milling to obtain zero-valent iron silicate. Then, the zero-valent iron silicate is used to activate ozone for deep removal of organic amines from the wastewater, achieving the removal of various organic amines and efficient denitrification. Compared to traditional organic amine treatment methods (advanced oxidation technologies such as the Fenton process), the method provided by this invention not only achieves efficient removal of organic amines from wastewater but also significantly improves the total nitrogen removal efficiency and reduces secondary pollution from excessive oxidation products such as nitrate or nitrite nitrogen. This process holds promise for the harmless deep treatment of organic amines in industrial wastewater or groundwater.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] The first objective of this invention is to provide an application of zero-valent iron silicate in the treatment of organic amine wastewater, wherein the zero-valent iron silicate is combined with ozone.

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

[0009] Neutral silica gel and micron-sized zero-valent iron were mixed and then ball-milled to prepare silica-modified zero-valent iron.

[0010] In one embodiment of the present invention, the mass ratio of the neutral silica gel to micron-sized zero-valent iron is 1:20 to 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] Adjust the pH of the sodium silicate solution to 7 to precipitate neutral silica gel.

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

[0016] A second objective of this invention is to provide a method for treating organic amine wastewater with improved total nitrogen removal efficiency, comprising the following steps:

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

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

[0019] In one embodiment of the present invention, the molar ratio of ozone to ferric silicate is 1:3 to 7;

[0020] Preferably, the molar ratio of ozone to ferric silicate is 1:5.

[0021] The technical principles of this invention are as follows:

[0022] Zero-valent iron (ZVI), as a novel environmental remediation material, exhibits significant advantages in pollutant degradation due to its synergistic effects with oxidants such as ozone (O3) and hydrogen peroxide (H2O2). Its catalytic ozone system (ZVI / O3), by enhancing ozone activation rate and utilization, has become an important technological pathway for wastewater treatment. However, this system relies on strongly oxidizing hydroxyl radicals (·OH, E...). 0 = +2.4V) mechanism (Equation (1) to (3)) 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 Formula (2);

[0025] ·HO3 → ·OH + O2 Equation (3);

[0026] To address this technical bottleneck, this invention develops a silicate-based zero-valent iron catalytic ozone technology. Because silicate ions possess the ability to confine free protons, confined protons accumulate on the surface of the silicate-based zero-valent iron. These confined protons gain electrons from the iron nucleus to form confined hydrogen (≡·H). Due to the high reducing activity of this confined hydrogen, it readily reacts with ozone to generate superoxide anions (·O2). - E 0 = +1.3V, Equations (4) to (5) — This active species combines mild oxidation properties with high selectivity, making it easier to attack amino groups without over-oxidizing them, thus providing a possibility for the conversion of organic amines 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· Formula (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) This invention is the first to use the method of activating ozone by silicating zero-valent iron. It is applied to the treatment of simulated and actual organic amine wastewater. After treatment, the concentration of organic amines and total nitrogen in the wastewater are significantly reduced, which reduces the risk of secondary pollution during the removal of organic amines.

[0032] (2) The silicate zero-valent iron catalytic ozone technology is not only applicable to industrial wastewater treatment, but can also treat organic amine pollution in groundwater through in-situ injection. It has great application potential and is expected to be widely used in various organic amine polluted wastewater. Attached Figure Description

[0033] Figure 1 Electron micrographs of zero-valent iron and silicate zero-valent iron prepared in Example 1 of this invention;

[0034] Figure 2 This is a graph showing the trend of urea removal when the present invention is applied to the treatment of simulated organic amine (urea) wastewater.

[0035] Figure 3 This is a diagram showing the effect of the present invention on urea removal in the treatment of simulated organic amine (urea) wastewater;

[0036] Figure 4 This is a diagram showing the total nitrogen removal effect of the present invention in the treatment of simulated organic amine (urea) wastewater;

[0037] Figure 5 The diagram shows the effect of this invention on the removal of pollutants from various simulated organic amine wastewater.

[0038] Figure 6 The diagram shows the effect of this invention on the removal of total nitrogen from various simulated organic amine wastewater.

[0039] Figure 7 The diagram shows the effect of this invention on the removal of total nitrogen from actual organic amine wastewater.

[0040] Figure 8 The graph shows the total nitrogen removal effect of this invention on actual organic amine wastewater under different ozone dosages.

[0041] Figure 9 The diagram shows the effect of different zero-valent iron materials on total nitrogen removal when applied to actual organic amine wastewater. Detailed Implementation

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

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

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

[0045] Sodium silicate powder with a modulus of 3.2–3.4 was prepared into a 10% mass fraction solution, and the pH was adjusted 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 embodiment provides a method for preparing zero-valent iron silicate (Si-ZVI), including the following steps:

[0048] Neutral silica gel and micron-sized zero-valent iron were mixed (mass ratio of neutral silica gel to micron-sized zero-valent iron was 1:20) and then ball-milled (500 r / min for 4 h) to prepare silicated zero-valent iron (morphology of zero-valent iron and silicated zero-valent iron is shown in the figure). Figure 1 (As shown).

[0049] pass Figure 1 It can be observed that the silicated zero-valent iron particles are small and have flocculent material on their surface, indicating that silicic acid has been successfully modified onto the surface of zero-valent iron. The smaller particle size and larger specific surface area may help to improve the reactivity of silicated zero-valent iron.

[0050] Comparative Example 1

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

[0052] Zero-valent iron (XV) powder was prepared by ball milling (500 r / min for 4 h). The morphologies of XV and silicate XV were as follows: Figure 1 (As shown).

[0053] pass Figure 1 It can be observed that the surface of the zero-valent iron powder is smooth and the particles are relatively large. This indicates that the zero-valent iron prepared in this comparative example still maintains a dense and smooth oxide layer structure, and the presence of the oxide layer may inhibit the reactivity of the zero-valent iron.

[0054] Example 2

[0055] This embodiment provides a method for treating organic amine wastewater, as detailed below:

[0056] Preparation of simulated organic amine wastewater: Urea standard, sodium bicarbonate, sodium sulfate, and potassium chloride were mixed in deionized water; wherein, in the simulated organic amine wastewater, the final concentration of urea standard 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.

[0057] The group settings are as follows:

[0058] Control group 1 (ozone treatment only): 2 mmol / L (final concentration) of ozone was added to the simulated organic amine wastewater, and the urea concentration and total nitrogen removal rate in the water were measured after stirring for 1 hour.

[0059] Control group 2 (micron zero-valent iron + ozone treatment group): 4 g / L (final concentration) of zero-valent iron powder (prepared in Comparative Example 1) + 2 mmol / L (final concentration) of ozone were added to simulated organic amine wastewater. After stirring and reacting for 1 hour, the urea concentration and total nitrogen removal rate in the water were measured.

[0060] Experimental group (silicified zero-valent iron + ozone treatment group): 4 g / L (final concentration) of silicified zero-valent iron (prepared in Example 1) + 2 mmol / L (final concentration) of ozone were added to simulated organic amine wastewater. After stirring and reacting for 1 hour, the urea concentration and total nitrogen removal rate in the water were measured.

[0061] The trends of urea concentration changes in each treatment group are as follows: Figure 2 As shown, the results indicate that the experimental group had the best urea removal effect, significantly better than control groups 1 and 2. The urea and total nitrogen removal rates are shown in the figures below. Figure 3 and Figure 4 As shown, the results indicate that after the above treatments, the organic amine urea removal rate of the simulated wastewater reached over 90%, and the total nitrogen removal rate also reached 85%, which is significantly better than ozone oxidation alone and zero-valent iron catalytic ozone technology.

[0062] Example 3

[0063] This embodiment provides a method for treating organic amine wastewater, as detailed below:

[0064] The following are examples of various simulated organic amine wastewater:

[0065] Uracil-simulated wastewater: Uracil standard, sodium bicarbonate, sodium sulfate, and potassium chloride were mixed in deionized water; wherein, in the simulated organic amine wastewater, the final concentration of uracil standard 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.

[0066] Dimethylamine simulated wastewater: Dimethylamine standard, sodium bicarbonate, sodium sulfate, and potassium chloride were mixed in deionized water; wherein, in the simulated organic amine wastewater, the final concentration of dimethylamine standard 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.

[0067] Aniline simulated wastewater: Aniline standard, sodium bicarbonate, sodium sulfate, and potassium chloride were mixed in deionized water; wherein, in the simulated organic amine wastewater, the final concentration of aniline standard 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: Add 4 g / L (final concentration) of ferric silicate + 5 mmol / L (final concentration) of ozone to three types of simulated organic amine wastewater (uracil simulated wastewater, dimethylamine simulated wastewater, and aniline simulated wastewater), stir and react for 1 hour, and then measure the total nitrogen concentration and total nitrogen removal rate in the water.

[0069] Pollutant removal rate and total nitrogen removal rate of each treatment group are as follows: Figure 5 and Figure 6 As shown, the results indicate that the organic amine urea removal rate of the simulated wastewater after treatment by the process of the present invention reaches 80-92%, and the total nitrogen removal rate is 74-88%, which shows that the method of the present invention has good degradation and denitrification effects on various organic amines.

[0070] Example 4

[0071] This embodiment provides a method for treating organic amine wastewater, as detailed below:

[0072] In this embodiment, the organic amine wastewater is actual organic amine wastewater with the following specific composition: total nitrogen concentration of 25 mg / L, inorganic nitrogen (nitrate nitrogen + ammonia nitrogen) concentration of 5 mg / L, organic amine concentration of approximately 20 mg / L, salinity of 2000 mg / L, and pH = 6.5.

[0073] The group settings are as follows:

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

[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. After stirring and reacting for 1 hour, the urea concentration and total nitrogen removal rate in the water were measured.

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

[0077] Total nitrogen removal rate of each treatment group as follows Figure 7As shown, the results indicate that the total nitrogen removal rate of the actual organic amine wastewater treated in the experimental group reached 80%, which was significantly better than that of control group 1 and control group 2. This shows that the combined treatment of silicate zero-valent iron and ozone has a good removal and denitrification effect on the actual organic amine wastewater.

[0078] Example 5

[0079] This embodiment provides a method for treating organic amine wastewater, as detailed below:

[0080] In this embodiment, the organic amine wastewater is actual organic amine wastewater with the following specific composition: total nitrogen concentration of 25 mg / L, inorganic nitrogen (nitrate nitrogen + ammonia nitrogen) concentration of 5 mg / L, organic amine concentration of approximately 20 mg / L, salinity of 2000 mg / L, and pH = 6.5.

[0081] The group settings are as follows:

[0082] Experimental Group 1 (Silicic Zero-Valence Iron + Ozone Treatment Group): 4 g / L (final concentration) of silicated zero-valent iron (prepared in Example 1) + 0.5 mmol / L (final concentration) of ozone were added to the wastewater. After stirring and reacting for 1 hour, the total nitrogen concentration and total nitrogen removal rate in the water were measured.

[0083] Experimental Group 2 (Silicic Zero-Valence Iron + Ozone Treatment Group): 4 g / L (final concentration) of silicated zero-valent iron (prepared in Example 1) + 1 mmol / L (final concentration) of ozone were added to the wastewater. After stirring and reacting for 1 hour, the total nitrogen concentration and total nitrogen removal rate in the water were measured.

[0084] Experimental Group 3 (Silica-based zero-valent iron + ozone treatment group): 4 g / L (final concentration) of silica-based zero-valent iron (prepared in Example 1) + 3 mmol / L (final concentration) of ozone were added to the wastewater. After stirring and reacting for 1 hour, the total nitrogen concentration and total nitrogen removal rate in the water were measured.

[0085] Experimental Group 4 (Silicic Zero-Valence 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. After stirring and reacting for 1 hour, the total nitrogen concentration and total nitrogen removal rate in the water were measured.

[0086] Experimental Group 5 (Silicic Zero-Valence Iron + Ozone Treatment Group): 4 g / L (final concentration) of silicated zero-valent iron (prepared in Example 1) + 7 mmol / L (final concentration) of ozone were added to the wastewater. After stirring and reacting for 1 hour, the total nitrogen concentration and total nitrogen removal rate in the water were measured.

[0087] Total nitrogen removal rate of each treatment group as follows Figure 8As shown, the results indicate that the total nitrogen concentration in the actual wastewater treated by all five experimental groups was significantly reduced. With increasing ozone dosage, the total nitrogen removal rate gradually increased, reaching a maximum of 90% when the ozone concentration reached 5 mmol / L. Further increasing the ozone dosage resulted in a slightly lower total nitrogen removal rate of 88%, suggesting that excessive ozone does not necessarily lead to better total nitrogen removal. This may be because excessive ozone quenches free radicals, reducing ozone utilization. Therefore, under these experimental conditions, an ozone concentration of 5 mmol / L yielded the best total nitrogen removal effect.

[0088] Example 6

[0089] This embodiment provides a method for treating organic amine wastewater, as detailed below:

[0090] In this embodiment, the organic amine wastewater is actual organic amine wastewater with the following specific composition: total nitrogen concentration of 25 mg / L, inorganic nitrogen (nitrate nitrogen + ammonia nitrogen) concentration of 5 mg / L, organic amine concentration of approximately 20 mg / L, salinity of 2000 mg / L, and pH = 6.5.

[0091] Experimental group (silicic zero-valent iron + ozone treatment group): 4 g / L (final concentration) of silicic zero-valent iron (prepared in Example 1) + 5 mmol / L (final concentration) of ozone were added to the wastewater. After stirring and reacting for 1 hour, the total nitrogen concentration and total nitrogen removal rate in the water were measured.

[0092] Control group 1 (oxalic acid zero-valent iron + ozone treatment group): 4 g / L (final concentration) oxalic acid zero-valent iron + 5 mmol / L (final concentration) ozone were added to the wastewater. After stirring and reacting for 1 hour, the total nitrogen concentration and total nitrogen removal rate in the water were measured.

[0093] The preparation method of oxalic acid-modified zero-valent iron is the same as that of silicate preparation: oxalic acid powder and micron-sized zero-valent iron are mixed (the mass ratio of oxalic acid to micron-sized zero-valent iron is 1:20) and then ball-milled (the rotation speed is 500 r / min and the time is 4 h) to prepare oxalic acid-modified zero-valent iron.

[0094] Control group 2 (zero valent iron phosphate + ozone treatment group): 4 g / L (final concentration) of zero valent iron phosphate + 5 mmol / L (final concentration) of ozone were added to the wastewater. After stirring and reacting for 1 hour, the total nitrogen concentration and total nitrogen removal rate in the water were measured.

[0095] The preparation method of phosphorylated zero-valent iron is the same as that of silicate preparation method: potassium dihydrogen phosphate powder and micron-sized zero-valent iron are mixed (the mass ratio of potassium dihydrogen phosphate to micron-sized zero-valent iron is 1:20) and then ball-milled (rotation speed is 500 r / min, time is 4 h) to prepare phosphorylated zero-valent iron.

[0096] Total nitrogen removal rate of each treatment group as follows Figure 9 As shown, the results indicate that the total nitrogen concentration in the actual wastewater was reduced after treatment in both the experimental group and the control group (control group 1 and control group 2). The experimental group achieved a 90% removal of total nitrogen in the wastewater, which was significantly better than control group 1 (55%) and control group 2 (62%).

[0097] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any 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 invention, should be within the protection scope of the present invention.

Claims

1. An application of silicated zero-valent iron in the treatment of organic amine wastewater, characterized in that, The silicified zero-valent iron combines with ozone; The zero-valent iron silicate is prepared by the following method: Neutral silica gel and micron-sized zero-valent iron were mixed and then ball-milled to prepare silica-based zero-valent iron. The mass ratio of the neutral silica gel to micron-sized zero-valent iron is 1:20~100; During the ball milling process, the rotation speed is 400~600 r / min, and the time is 3~5 h; The surface of silicated zero-valent iron is enriched with confined protons, which then gain electrons from the iron nucleus to form confined hydrogen.

2. The application of silicated zero-valent iron in the treatment of organic amine wastewater according to claim 1, characterized in that, The neutral silica gel is prepared by the following method: Adjust the pH of the sodium silicate solution to neutral to precipitate neutral silica gel.

3. The application of silicated zero-valent iron in the treatment of organic amine wastewater according to claim 2, characterized in that, The sodium silicate has a modulus of 3.2 to 3.

4.

4. A method for treating organic amine wastewater to improve total nitrogen removal efficiency, characterized in that, Includes the following steps: Ozone and ferric silicate are added in situ to the organic amine wastewater, mixed and reacted to complete the treatment of the organic amine wastewater. The zero-valent iron silicate is prepared by the following method: Neutral silica gel and micron-sized zero-valent iron were mixed and then ball-milled to prepare silica-based zero-valent iron. The mass ratio of the neutral silica gel to micron-sized zero-valent iron is 1:20~100; During the ball milling process, the rotation speed is 400~600 r / min, and the time is 3~5 h; The surface of silicated zero-valent iron is enriched with confined protons, which then gain electrons from the iron nucleus to form confined hydrogen.

5. The method for treating organic amine wastewater with improved total nitrogen removal efficiency according to claim 4, characterized in that, The ozone dosage is 10~100 mg / L.

6. The method for treating organic amine wastewater with improved total nitrogen removal efficiency according to claim 5, characterized in that, The molar ratio of ozone to ferric silicate is 1:3~7.

7. The method for treating organic amine wastewater with improved total nitrogen removal efficiency according to claim 6, characterized in that, The molar ratio of ozone to ferric silicate is 1:5.

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