Composite material and preparation method and application thereof

Abstract

The present invention relates to the field of water treatment technology, and in particular to a composite material, a preparation method thereof, and an application thereof. The preparation method of the composite material comprises: loading nano-zero-valent iron copper on granular activated carbon, wherein the mesh size of the granular activated carbon is 2 to 10 meshes. The present invention controls the size of the activated carbon particles and uses the granular activated carbon to load bimetallic nanoparticles, which not only solves the problem of easy agglomeration of nano-zero-valent iron (nZVI) and improves its dispersibility in water, but also realizes the modification of GAC, reduces the polar functional groups in GAC, enhances the hydrophobicity of GAC, and further improves the adsorption capacity of activated carbon for nitrosamines in water.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a composite material and a preparation method and application thereof. Background Art

[0002] With the increasing scarcity of global water resources, the reuse of recycled water has become an international research hotspot as an important way to solve the water crisis, and has been put into practical use in countries with long-term water shortages. Direct potable reuse (DPR) of recycled water, as one of the reuse methods, refers to the direct entry of deeply treated recycled water into the water supply system or directly into the water supply network without any type of environmental "buffer". This requires that the effluent water quality must meet drinking water standards. Disinfection is usually at the end of recycled water treatment, which inevitably produces some disinfection by-products that are harmful to the human body. Nitrosamines (N-nitrosamines, NAs) are a common type of water disinfection by-products. They are widely detected in water bodies after disinfection treatment with chlorine, chloramines, and ozone. They are stable in nature and difficult to oxidize, biodegrade, and adsorb. Their toxicity is significantly higher than that of conventional disinfection by-products such as trihalomethanes and haloacetic acids. They are highly carcinogenic and emerging nitrogen-containing disinfection by-products that have attracted much attention in the water treatment field.

[0003] Currently, the main methods for controlling nitrosamine byproducts in drinking water include adsorption, membrane filtration, ultraviolet photolysis, and metal reduction. Adsorption utilizes the porosity of solid adsorbents to adsorb NAs in water onto their surfaces or pores, thereby achieving removal. Commonly used adsorbents include activated carbon, zeolite, and mesoporous silica. Activated carbon adsorption is the most commonly used adsorption technology, but activated carbon is a hydrophobic material. Competitive adsorption with water molecules reduces its adsorption capacity for nitrosamines.

[0004] Membrane filtration removes nitrosamines primarily through interactions between pore sizes. When using membrane filtration, nitrosamine removal is dependent on membrane type, membrane permeate flux, feed pH, membrane fouling, and nitrosamine molecular size. For smaller nitrosamine molecules, such as nitrosodimethylamine (NDMA), membrane filtration is less effective. Furthermore, as membrane flux decreases, the permeate flux of nitrosamines also decreases, leading to poorer removal.

[0005] NAs are highly sensitive to ultraviolet light, so photolysis of NAs can be achieved under a certain ultraviolet radiation intensity. However, studies have shown that better degradation of nitrosamines can only be achieved under slightly acidic conditions, and the economic cost of ultraviolet photolysis is relatively high.

[0006] The metal reduction method refers to the use of metals such as iron, nickel, and palladium as reducing agents to degrade NAs in water, reducing NAs to precursor substances with lower toxicity, and, compared with single metals, bimetallic (such as iron and copper, iron and nickel, etc.) has a better reduction effect on NAs in water. However, in the current metal reduction method, there are still problems such as metals being easily agglomerated, easily oxidized, and not highly dispersed. When removing NAs, the reaction is slow, the removal efficiency is not high, and the product after the NAs reaction is still present in water. For example, CN 104986846 A discloses the application of nano-mesoporous silicon catalysts loaded with nano-zero-valent metals in the reduction and degradation of nitrosamine organic matter in water, but its synthesis method is relatively complex, the synthesis process is easily affected by the environment, and the operation is difficult; the NAs precursor substances with lower toxicity generated after the reaction are still present in water; and, due to the poor stability of mesoporous silicon nanoparticles, defects are easily generated on the surface, and it is easy to adsorb substances such as moisture and gas, thereby affecting its application performance. Summary of the Invention

[0007] At present, in the prior art, when using metal reduction methods to remove wastewater, it has been found that using activated carbon as a metal carrier can quickly adsorb pollutants and accelerate the degradation rate of pollutants. CN 111333154A discloses a method for preparing a micro-electrolysis material and its application in treating para-nitrochlorobenzene, but the powdered activated carbon (PAC) used therein is easy to lose and difficult to recycle, is generally used once, and the process is mostly intermittent operation. Therefore, there is still room for further improvement in the prior art when using metal reduction methods for water treatment. The present application has found that compared with nano-activated carbon, activated carbon powder, etc., granular activated carbon (GAC) is more suitable as a carrier for degradation materials. It has more loading sites, bimetallic nanoparticles are easier to load on GAC, and its preparation cost is lower, the restrictions on use are fewer, and the application range is wider; and the addition of nano zero-valent bimetallic can improve the problem that GAC has weaker adsorption capacity than nano-activated carbon and activated carbon powder.

[0008] Based on this, the specific technical solutions of the present invention are as follows:

[0009] The present invention first provides a method for preparing a composite material, comprising: loading nanometer zero-valent iron copper on granular activated carbon, wherein the mesh number of the granular activated carbon is 2 to 10 meshes.

[0010] The present invention has found that when granular activated carbon with the above-mentioned mesh size is used to load bimetallic nanoparticles, not only can the problem of easy agglomeration of nano zero-valent iron (nZVI) be solved and its dispersibility in water be improved, but also the GAC can be modified to reduce the polar functional groups in GAC, enhance the hydrophobicity of GAC, and further improve the activated carbon's adsorption capacity for nitrosamines in water.

[0011] Preferably, the mesh size of the granular activated carbon is 4 to 6 meshes.

[0012] Preferably, the granular activated carbon is pretreated before loading, comprising: mixing the granular activated carbon with water, heat-treating the mixture at 90-110° C., and then washing the mixture with water and drying the mixture.

[0013] Preferably, the water is ultrapure water.

[0014] Preferably, the granular activated carbon is heat treated for 30 to 40 minutes, and then washed and dried at 105°C for 20 to 24 hours.

[0015] Preferably, the loading in the preparation method of the composite material comprises the following steps:

[0016] S1: mixing FeSO4·7H2O, CuSO4·5H2O, the granular activated carbon, polyethylene glycol and ethanol aqueous solution, and stirring the obtained mixed solution under a nitrogen atmosphere;

[0017] S2: adding sodium borohydride dropwise to the mixed solution to react;

[0018] S3: After the reaction is completed, the obtained solid is collected by centrifugation, and the solid is washed and dried to obtain a composite material (i.e., nZVI-Cu@GAC composite material).

[0019] Preferably, in the mixed solution, the mass ratio of FeSO4·7H2O to granular activated carbon is (0.25-0.30):1; and / or

[0020] The copper / iron mass ratio of CuSO4.5H2O and FeSO4.7H2O is 4-6wt%; and / or

[0021] The mass ratio of the polyethylene glycol to FeSO4·7H2O is (0.05-0.07):1.

[0022] The present invention finds that by doping the surface of nZVI with the above-mentioned amount of catalytic metal (such as copper) to construct a nano bimetallic, the surface oxidation of nZVI can be reduced and its reduction efficiency of nitrosamine compounds can be further increased through catalytic electron transfer and hydrogen atom transfer processes.

[0023] Preferably, in the ethanol aqueous solution, the volume ratio of ethanol to water is 3-4:6-7.

[0024] Preferably, in S1, the stirring conditions include: stirring the mixed solution at 160-200 r / min for 20-30 min.

[0025] Preferably, in the S2, the mass ratio of NaBH4 to FeSO4·7H2O is (0.15-0.20):1.

[0026] Preferably, in S3, the drying conditions include: drying the washed solid in a vacuum drying oven at 60-80°C for 8-12 hours.

[0027] The present invention further provides a composite material, which is prepared by the above preparation method.

[0028] The present invention also provides a method for treating water containing nitrosamine compounds, which comprises adding the above composite material into the water containing nitrosamine compounds to carry out a reduction reaction.

[0029] Preferably, the composite material is added to water containing nitrosamine compounds and then mechanically stirred at a rotation speed of 150 to 200 r / min for 60 to 90 minutes.

[0030] Preferably, the concentration of nitrosamine compounds in water is 60 to 200 ng / L.

[0031] Preferably, the mass of the composite material and water used per ton of water containing nitrosamine compounds is 2-3 kg.

[0032] Preferably, the treatment method further comprises: after the reduction reaction, filtering out the composite material and subjecting the filtrate to nanofiltration.

[0033] The present invention finds that the nanofiltration technology can effectively remove the reduction products generated after the reduction and degradation of nitrosamines by the nZVI-Cu@GAC composite material.

[0034] In the present invention, GAC and loaded nZVI-Cu jointly adsorb and reduce and degrade nitrosamine byproducts in drinking water, and the NAs precursor substances with low toxicity generated after the reaction are removed by nanofiltration technology.

[0035] The molecular weight cut-off of NF membrane is 200-1000Da, and it removes trace small molecular organic matter through the combined effects of steric hindrance, electrostatic repulsion, solute-membrane interaction, and dielectric repulsion effect.

[0036] Preferably, the nanofiltration membrane of the present invention is a hollow fiber NF membrane, which can better overcome concentration polarization than the rolled NF membrane in the present invention, and has the advantages of low operating pressure, high membrane flux, low wastewater rate, etc., and has greater advantages in application in the field of drinking water.

[0037] Preferably, the filtration method is cross-flow filtration.

[0038] The present invention also provides a system for treating water containing nitrosamine compounds, comprising a reduction reaction unit and a nanofiltration unit.

[0039] Based on the above technical solution, the beneficial effects of the present invention are:

[0040] By controlling the size of activated carbon particles and using them to load bimetallic nanoparticles, the present invention not only addresses the issues of easy agglomeration, oxidation, and poor stability of nano-zero-valent iron (nZVI), improving its dispersibility and stability in water, but also modifies GAC, reducing its polar functional groups and enhancing its hydrophobicity, further improving the activated carbon's adsorption capacity for nitrosamines in water. Using granular activated carbon as a carrier is more efficient and stable than other methods, increasing the loading sites for nano-bimetallics while also leveraging their adsorption and catalytic properties. Furthermore, the present invention utilizes inexpensive and readily available raw materials, resulting in low cost, ease of preparation, and high practical value. DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0042] Unless otherwise specified, the various raw materials used in the examples are commercially available conventional raw materials, and the technical means used are conventional means well known to those skilled in the art.

[0043] Example 1

[0044] This embodiment first provides a nZVI-Cu@GAC composite material, the preparation method of which includes the following steps:

[0045] 1) The granular activated carbon was heated and boiled in an electric furnace for 30 minutes, washed with ultrapure water, and dried in an oven at 105°C for 24 hours for later use; the particle size of the granular activated carbon was 4 mesh.

[0046] 2) The nano-zero-valent iron and copper are loaded onto the granular activated carbon by the following method:

[0047] The above-mentioned granular activated carbon, CuSO4·5H2O and FeSO4·7H2O and ethanol aqueous solution are added to a reaction container, the mass ratio of FeSO4·7H2O to granular activated carbon is 0.26:1, CuSO4·5H2O and FeSO4·7H2O are mixed and dissolved with ethanol aqueous solution (ethanol / water, v / v=3 / 7) according to a copper / iron mass ratio of 5wt%; polyethylene glycol-4000 is added as a dispersant, the mass ratio of polyethylene glycol-4000 to FeSO4·7H2O is 0.05:1, and the mixture is stirred at 160r / min for 20 minutes under nitrogen protection; then 0.5mol / L sodium borohydride (NaBH4) solution is added dropwise, the mass ratio of NaBH4 to FeSO4·7H2O is 0.16:1, and stirring is continued at 160r / min for 30 minutes to fully stir and mix;

[0048] 3) The obtained composite material was collected by centrifugation, washed with deionized water and ethanol three times, and then dried in a vacuum drying oven at 60° C. for 8 hours.

[0049] The composite material was characterized, and the results showed that the nano bimetallic particles were evenly distributed on the granular activated carbon, most of which were embedded in the surface of the activated carbon, and some were loaded into the pores of the activated carbon. This embedded loading can prevent the nano bimetallic particles from reducing the target object and then transferring Fe 2+ or Fe 3+ Release into aqueous solution causes secondary pollution.

[0050] This embodiment further provides a method for treating water containing N-nitrosodimethylamine (NDMA) using the composite material, wherein the water is effluent from a reclaimed water plant and the concentration of N-nitrosodimethylamine in the water is 68.9 ng / L. The method specifically includes:

[0051] The composite material was added to water and mechanically stirred to accelerate the reaction. The mass ratio of the composite material to water was 2 kg / t water. The mechanical stirring speed was controlled at 160 r / min for 60 minutes. After the reaction was completed, the composite material was filtered out of the water. The concentration of NDMA in the water was 10.3 ng / L, and the concentration of dimethylamine (DMA) was 59.0 ng / L. The water was then introduced into a nanofiltration device using a hollow fiber nanofiltration membrane and cross-flow filtration. The concentration of NDMA in the filtered water was 10.3 ng / L, and the concentration of DMA was 5.80 ng / L.

[0052] Example 2

[0053] This embodiment first provides a nZVI-Cu@GAC composite material, the preparation method of which includes the following steps:

[0054] 1) The granular activated carbon was heated and boiled in an electric furnace for 30 minutes, washed with ultrapure water, and dried in an oven at 105°C for 24 hours for later use; the particle size of the granular activated carbon was 4 mesh, and its specific surface area was about 800 m 2 / g.

[0055] 2) The nano-zero-valent iron and copper are loaded onto the granular activated carbon by the following method:

[0056] The above-mentioned granular activated carbon, CuSO4·5H2O and FeSO4·7H2O and ethanol aqueous solution are added to a reaction vessel (the mass ratio of FeSO4·7H2O to granular activated carbon is 0.28:1), and FeSO4·7H2O and CuSO4·5H2O are mixed and dissolved with ethanol aqueous solution (ethanol / water, v / v=3 / 7) according to a copper / iron mass ratio of 5wt%; and polyethylene glycol-4000 is added as a dispersant (the mass ratio of polyethylene glycol-4000 to FeSO4·7H2O is 0.05:1), and stirred at 170 / min for 15 minutes under nitrogen protection, and then sodium borohydride (NaBH4) solution (0.5mol / L, the mass ratio of NaBH4 to FeSO4·7H2O is 0.16:1) is added dropwise, and stirring is continued at 170r / min for 25 minutes to fully stir and mix;

[0057] 3) collecting the obtained composite material by centrifugation, washing it three times with deionized water and ethanol, and then drying it in a vacuum drying oven at 70° C. for 7.5 hours;

[0058] This embodiment further provides a method for treating water containing N-nitrosodimethylamine (NDMA) using the composite material. The water is effluent from a reclaimed water plant, and the concentration of N-nitrosodimethylamine in the water is 72.4 ng / L. The method specifically includes:

[0059] The composite material was added to water and mechanically stirred to accelerate the reaction. The mass ratio of the composite material to water was 2 kg / t water. The mechanical stirring speed was controlled at 160 r / min for 60 minutes. After the reaction was completed, the composite material was filtered out of the water. The NDMA concentration in the water was 10.1 ng / L and the dimethylamine concentration was 60.9 ng / L. The water was then introduced into a nanofiltration device using a hollow fiber nanofiltration membrane and a cross-flow filtration method. The NDMA concentration in the filtered water was 10.1 ng / L and the DMA concentration was 6.70 ng / L.

[0060] Example 3

[0061] This embodiment first provides a nZVI-Cu@GAC composite material, the preparation method of which is the same as that of Example 1, except that the mass ratio of FeSO4·7H2O to granular activated carbon is 0.25:1.

[0062] This example further uses the composite material to treat the water described in Example 1, and uses the same treatment conditions as Example 1. After the water is discharged, the concentration of NDMA in the water is 10.8 ng / L, and the concentration of DMA in the water is 5.40 ng / L.

[0063] Example 4

[0064] This embodiment first provides a nZVI-Cu@GAC composite material, the preparation method of which is the same as that of Example 1, except that the copper / iron mass ratio of CuSO4·5H2O and FeSO4·7H2O is 4 wt%.

[0065] This example further uses the composite material to treat the water described in Example 1, and uses the same treatment conditions as Example 1. After the water is discharged, the concentration of NDMA in the water is 11.30 ng / L, and the concentration of DMA in the water is 6.20 ng / L.

[0066] Example 5

[0067] This embodiment first provides a nZVI-Cu@GAC composite material, the preparation method of which is the same as that of Example 1, except that the mass ratio of polyethylene glycol-4000 to FeSO4·7H2O is 0.06:1, and the addition ratio of NaBH4 to FeSO4·7H2O is 0.17:1.

[0068] In this example, the composite material was further used to treat the water described in Example 1, and the treatment was carried out under the same conditions as in Example 1. After the water was discharged, the concentration of NDMA in the water was 9.60 ng / L, and the concentration of DMA in the water was 5.50 ng / L.

[0069] Comparative Example 1

[0070] This comparative example first provides a nZVI-Cu@GAC composite material, the preparation method of which is the same as that of Example 1, except that the granular activated carbon is replaced by powdered activated carbon with a mesh size of 150 mesh.

[0071] This example further uses the composite material to treat the water described in Example 1, and uses the same treatment conditions as Example 1. After the water is discharged, the concentration of NDMA in the water is 15.4 ng / L, and the concentration of DMA in the water is 5.40 ng / L.

[0072] In the present invention, the nZVI-Cu@GAC composite material prepared by using 2-10 mesh granular activated carbon as a carrier has the same effect as that of the 4 mesh granular activated carbon used in Examples 1-5, and both are better than the treatment effect of Comparative Example 1.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. Application of a composite material in the treatment of water containing nitrosamine compounds, characterized in that: The application method is to add the composite material to water containing nitrosamine compounds to carry out a reduction reaction. The preparation method of the composite material includes: loading nano-zero-valent iron copper on granular activated carbon, wherein the mesh size of the granular activated carbon is 2-10 mesh; The granular activated carbon is pretreated before loading, including: mixing the granular activated carbon with water, heat treating at 90-110° C., and then washing with water and drying; The load includes: S1: mixing FeSO4·7H2O, CuSO4·5H2O, the granular activated carbon, polyethylene glycol and ethanol aqueous solution, and stirring the obtained mixed solution under a nitrogen atmosphere; S2: adding sodium borohydride dropwise to the mixed solution to react; S3: After the reaction is completed, the obtained solid is collected by centrifugation, and the solid is washed and dried to obtain a composite material; In the mixed solution, the mass ratio of FeSO4·7H2O to granular activated carbon is (0.25-0.30):1; and / or The copper / iron mass ratio of CuSO4·5H2O and FeSO4·7H2O is 4-6wt%; and / or The mass ratio of polyethylene glycol to FeSO4·7H2O is (0.05-0.07):1; In the application, the concentration of nitrosamine compounds in water is 60-200 ng / L.

2. The use according to claim 1, characterized in that The mesh number of the granular activated carbon is 4 to 6 meshes.

3. The use according to claim 2, characterized in that In the S2, the mass ratio of NaBH4 to FeSO4·7H2O is (0.15~0.20):

1.

4. The use according to claim 1, characterized in that The method further comprises: after the reduction reaction, filtering out the composite material, and further performing nanofiltration on the filtrate.