A wastewater self-purification catalyst and its preparation method and application

Abstract

The present invention discloses a wastewater self-purification catalyst and a preparation method and application thereof, which belongs to the technical field of organic wastewater treatment. The catalyst comprises the following steps: (1) obtaining powder of dried African chinaberry bark and carbonizing it through a hydrothermal reaction to obtain a carbon material; (2) dispersing the carbon material in an aqueous solution of 2,5-diaminoterephthalic acid to obtain a suspension; (3) adding iron salt to the suspension, stirring the mixture until uniform, and evaporating the mixture to obtain a solid product; (4) grinding the solid product and ammonium chloride into powder, and then calcining the powder at a high temperature under inert gas protection to obtain the catalyst; the catalyst of the present invention does not require the addition of additional reagents and energy to the water body, and can effectively self-purify and remove water pollutants such as CIP, SMZ, DP and RhB under conventional conditions, and has excellent water purification efficiency and catalytic stability.

Description

Technical Field

[0001] The present invention relates to the technical field of organic wastewater treatment, and in particular to a wastewater self-purification catalyst and a preparation method and application thereof. Background Art

[0002] In recent years, with the increasing affluence of human production and lifestyles, the number and variety of organic micropollutants in water bodies have increased exponentially. These micropollutants, mostly derived from compounds used extensively in human activities and their residues, are present at concentrations ranging from ng / L to μg / L and are widely distributed in various water bodies, making them difficult to biodegrade and remove. Even at very low concentrations in water bodies, micropollutants still pose a constant threat to the ecosystem and human health, posing significant challenges to existing water treatment processes.

[0003] Advanced oxidation processes (AOPs) are considered effective technologies for degrading organic micropollutants in water. AOPs typically utilize hydrogen peroxide, persulfate, or ozone, or input energy such as light, electricity, or ultrasound, to stimulate a catalytic system to produce reactive oxygen species such as hydroxyl radicals, effectively degrading water pollutants. However, the chemical reagents and energy required for these technologies lead to high energy costs during the water treatment process. Therefore, developing a low-energy, high-efficiency, green water treatment technology to effectively remove water pollutants is crucial.

[0004] Zero-valent iron is low in toxicity and low in price. It can not only catalyze the degradation of pollutants by oxidizing systems such as ozone, oxygen, hydrogen peroxide, peracetic acid, and persulfate, but it can also reduce and degrade a variety of toxic and harmful pollutants by itself. However, its properties are unstable, it is easily oxidized in the air for a long time, and it is easy to agglomerate in aqueous solution, and its degradation efficiency is also low. The existing technology mainly uses biochar as a carrier to load iron on it. Although it can effectively inhibit agglomeration, it still has the problem of low degradation efficiency. Moreover, the load is only dispersed on the surface, and it is very easy for iron to be lost and dissolved, resulting in catalytic failure, and the catalytic stability is poor. Summary of the Invention

[0005] In response to at least one of the above problems, the present invention provides a wastewater self-purification catalyst, a preparation method and an application thereof.

[0006] The purpose of the present invention is achieved by adopting the following technical solutions:

[0007] The first aspect of the present invention is to provide a method for preparing a wastewater self-purification catalyst, comprising the following steps:

[0008] (1) The powder of dried African neem bark is carbonized by hydrothermal reaction to obtain carbon material;

[0009] (2) dispersing the carbon material in an aqueous solution of 2,5-diaminoterephthalic acid to prepare a suspension;

[0010] (3) adding iron salt to the suspension, stirring thoroughly until uniform, and evaporating to dryness to obtain a solid product;

[0011] (4) Grinding the solid product and ammonium chloride into powder, and then calcining at high temperature under inert gas protection conditions to obtain the wastewater self-purification catalyst. Grinding and heating with ammonium chloride can promote the carbon material to generate a graphene-like structure with porous wrinkles.

[0012] In some preferred embodiments, the temperature of the hydrothermal reaction is 120-200° C., more preferably 180° C., and the reaction time is 6-15 h, more preferably 10 h.

[0013] In some preferred embodiments, the concentration of the aqueous solution of 2,5-diaminoterephthalic acid is 3-9 g / L.

[0014] In some preferred embodiments, the dispersion temperature in step (2) is 20-80°C, more preferably 60°C, and the dispersion time is 15-60 min, more preferably 30 min.

[0015] In some preferred embodiments, the mass ratio of the carbon material to the 2,5-diaminoterephthalic acid, the iron salt, and the ammonium chloride is (1.0-2.0): (0.3-0.9): (0.02-0.1): (2.0-5.0).

[0016] In some preferred embodiments, the iron salt is ferric chloride hexahydrate, ferrous sulfate or ferric acetate.

[0017] In some preferred embodiments, the high-temperature calcination temperature is 600-800° C., the heating rate is 5-15° C. / min, more preferably 10° C. / min, and the calcination time is 1-3 h, more preferably 2 h.

[0018] The second aspect of the present invention is to provide a wastewater self-purification catalyst, which is prepared by the above-mentioned preparation method.

[0019] The third aspect of the present invention is to provide an application of the aforementioned wastewater self-purification catalyst in reducing organic pollutants in water, specifically, directly dispersing the wastewater self-purification catalyst in water containing organic pollutants.

[0020] In some preferred embodiments, the organic pollutant is one or more of ciprofloxacin, sulfamethoxazole, diphenhydramine, and rhodamine B.

[0021] The beneficial effects of the present invention are:

[0022] (1) In response to the problem that the biochar-loaded iron materials in the prior art have low autocatalytic performance or poor catalytic stability, the present invention provides a self-purification catalyst based on graphene-like biochar loaded with multi-species nano-iron based on the bark of the African neem tree. The catalyst of the present invention does not need to add additional reagents such as hydrogen peroxide and ozone and energy such as light and heating to the water body, and can self-purify and efficiently remove water pollutants such as CIP, SMZ, DP and RhB under normal conditions; for CIP, DP and RhB, the catalyst can remove more than 90% within 10 minutes, and for SMZ, it can also remove more than 80% within 60 minutes. The catalyst has extremely high autocatalytic efficiency; the catalyst can still maintain an 80% removal rate for SMZ during 120 consecutive days of operation, and the release of metallic iron is almost undetectable. The catalyst of the present invention exhibits excellent water purification efficiency and catalytic stability.

[0023] (2) The preparation method of the catalyst of the present invention is simple, the required raw materials are not hazardous or explosive reagents, and the equipment requirements are relatively low; the catalytic conditions are mild, and no secondary pollution of iron sludge is generated, thus avoiding the cost of treating secondary pollutants such as iron sludge and sludge; at the same time, the catalyst of the present invention is a heterogeneous solid catalyst, which is easy to separate and recover from the water body after the reaction and reuse, and is suitable for commercial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention is further described with reference to the accompanying drawings. However, the embodiments in the accompanying drawings do not constitute any limitation to the present invention. A person skilled in the art can obtain other drawings based on the following drawings without creative effort.

[0025] Figure 1 is the X-ray diffraction (XRD) pattern of the catalyst prepared in Example 1;

[0026] Figure 2 is a scanning electron microscope (SEM) image of the catalyst prepared in Example 1;

[0027] Figure 3 This is a transmission electron microscope (TEM) image of the catalyst prepared in Example 1;

[0028] Figure 4 This is an X-ray photoelectron spectroscopy (XPS) graph of the catalyst prepared in Example 1;

[0029] Figure 5 is a degradation curve diagram of the catalyst or carbon material prepared in Example 1 to CIP, SMZ, DP or RhB;

[0030] Figure 6This is a graph showing the evaluation results of a continuous flow column experiment on SMZ degradation using the catalyst prepared in Example 1. DETAILED DESCRIPTION

[0031] The present invention is further described with reference to the following examples.

[0032] An embodiment of the present invention relates to a wastewater self-purification catalyst, the preparation method of which comprises the following steps:

[0033] (1) The powder of dried African neem bark is carbonized by hydrothermal reaction to obtain carbon material;

[0034] (2) dispersing the carbon material in an aqueous solution of 2,5-diaminoterephthalic acid to prepare a suspension;

[0035] (3) adding iron salt to the suspension, stirring thoroughly until uniform, and evaporating to dryness to obtain a solid product;

[0036] (4) Grinding the solid product and ammonium chloride into powder, and then calcining at high temperature under inert gas protection to obtain the wastewater self-purification catalyst;

[0037] In some embodiments, the temperature of the hydrothermal reaction is 120-200° C., for example, 120° C., 140° C., 160° C., 180° C., or 200° C., and the reaction time is 6-15 h, for example, 6 h, 8 h, 10 h, 12 h, 14 h, or 15 h.

[0038] In some embodiments, the concentration of the aqueous solution of 2,5-diaminoterephthalic acid is 3-9 g / L, for example, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L or 9 g / L;

[0039] In some embodiments, the dispersion temperature in step (2) is 20-80°C, for example, 20°C, 40°C, 60°C or 80°C, and the dispersion time is 15-60 min, for example, 15 min, 25 min, 30 min, 40 min, 50 min or 60 min;

[0040] In some embodiments, in step (2), the amount of the carbon material is 1-2 parts by mass, the amount of the 2,5-diaminoterephthalic acid is 0.3-0.9 parts by mass; in step (3), the amount of the iron salt is 0.02-0.1 parts by mass; and the amount of ammonium chloride is 2.0-5.0 parts by mass.

[0041] In some embodiments, the iron salt is ferric chloride hexahydrate, ferrous sulfate, or ferric acetate;

[0042] In some embodiments, the high temperature calcination temperature is 600-800°C, for example, 600°C, 650°C, 700°C, 750°C or 800°C, the heating rate is 5-15°C / min, for example, 5°C / min, 7°C / min, 9°C / min, 10°C / min, 11°C / min, 13°C / min, 15°C / min, and the calcination time is 1-3h, for example, 1h, 2h or 3h;

[0043] The wastewater self-purification catalyst is in the form of a black solid powder. Its microstructure includes graphene-like carbon with a porous wrinkled structure and multi-species iron nanoparticles. The iron nanoparticles are coated by the graphene-like carbon. The nanoparticles in the catalyst are mainly composed of zero-valent iron (Fe 0 ), iron carbide (Fe3C), ferric oxide (Fe2O3) and ferrosoferric oxide (Fe3O4);

[0044] The wastewater self-purification catalyst prepared by the above preparation method can be directly dispersed in water under normal conditions to effectively remove organic pollutants such as antibiotics (such as ciprofloxacin and sulfamethoxazole), drugs (such as diphenhydramine) and rhodamine B in the water without the need for additional reagents and energy input.

[0045] Example 1

[0046] A wastewater self-purification catalyst, the preparation method of which comprises the following steps:

[0047] (1) Wash and dry the bark of the African neem tree and crush it into powder using a crusher. Weigh 10.0 g of the bark powder and disperse it in a polytetrafluoroethylene liner reactor filled with 50 mL of deionized water. The liner is placed in a stainless steel reactor and placed in an oven. The reactor is kept at 180°C for 10 h for hydrothermal reaction. After cooling, it is filtered and dried to obtain a carbon material.

[0048] (2) 0.6 g of 2,5-diaminoterephthalic acid was added to 100 mL of deionized water and stirred vigorously for 30 min to fully dissolve it. 1.5 g of the carbon material was added and stirred vigorously in a water bath at 60 °C for 30 min to fully disperse it to obtain a suspension.

[0049] (3) Add 0.05 g of ferric chloride hexahydrate to the suspension and continue stirring until it is completely evaporated to obtain a solid product;

[0050] (4) The solid product was mixed with 3.50 g of ammonium chloride, fully ground into powder in an agate mortar, and placed in a 25 mL covered quartz crucible. Under nitrogen protection, the crucible was placed in a tube furnace for high-temperature calcination: the calcination temperature was 700 °C, the heating rate was 10 °C / min, and the catalyst was obtained after natural cooling.

[0051] The catalyst prepared in Example 1 was characterized by its structure. Figure 1-4 , Figure 1 This is the X-ray diffraction (XRD) pattern of the catalyst prepared in Example 1. The XRD pattern can intuitively reflect the crystalline species present in the catalyst. By comparing with the standard card, the composition of the species in the catalyst is carbon, Fe 0 , Fe2O3, Fe3O4 and Fe3C; Figure 2 This is a scanning electron microscope (SEM) image of the catalyst prepared in Example 1. From the SEM image, it can be observed that the surface of the catalyst is full of wrinkles and pores; Figure 3 This is a transmission electron microscope (TEM) image of the catalyst prepared in Example 1. From the TEM image, it can be observed that the substrate has a graphene-like layered structure and obvious nanoparticles. The element distribution map shows that iron is concentrated on the nanoparticles, further indicating that the iron species exists in the form of nanoparticles and is coated with a graphene-like carbon layer, so that the iron species does not directly interact with water molecules, thereby further stabilizing the catalytic structure and greatly controlling the dissolution of iron ions. Figure 4 This is an X-ray photoelectron spectroscopy (XPS) graph of the catalyst prepared in Example 1. From the XPS graph, it can be seen that Fe in the catalyst mainly exists in valence states of 0, +2 and +3.

[0052] Example 2

[0053] A method for degrading organic pollutants in water, specifically, adding 0.05 g of the catalyst powder prepared in Example 1 to 100 mL of simulated wastewater with a pollutant concentration of 10 mg / L, maintaining a natural pH, constant temperature in a water bath at 30° C., turning on magnetic stirring, and sampling at different time points (0, 2, 4, 6, 8, 10, 20, 30, 40, 50, and 60 min) to detect the concentration of the pollutant;

[0054] The contaminants included ciprofloxacin (CIP), sulfamethoxazole (SMZ), diphenhydramine (DP), and rhodamine B (RhB).

[0055] See attached Figure 5 , Figure 5 The figure shows the degradation curves of the catalyst prepared in Example 1 for CIP, SMZ, DP and RhB. For the three pollutants CIP, SMZ, DP and RhB, more than 90% can be removed within 10 minutes. The removal effect of SMZ is relatively poor, but more than 80% of SMZ can be removed within 60 minutes.

[0056] Example 3

[0057] An ordinary chromatography column was used as the filling column, and the catalyst was filled between the upper and lower layers of quartz sand to form a reaction column. The water containing SMZ was used as the inlet water. Water was introduced from the upper end of the reaction column and flowed through the packing layer by gravity. The hydraulic retention time was about 30 minutes. The lower end was the outlet. Samples were taken regularly to determine the residual concentration of SMZ. Figure 6 The continuous flow column test results of the catalyst prepared in Example 1 for SMZ degradation are shown in FIG. Figure 6 It can be seen that during the long-term operation of 120 consecutive days, the catalytic system can still maintain an 80% removal rate for SMZ, and no Fe ions can be detected in the effluent, demonstrating the excellent degradation efficiency and long-term operation stability of the wastewater self-purification catalyst.

[0058] 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 the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a wastewater self-purification catalyst, characterized in that: The following steps are involved: (1) The powder of dried African neem bark is carbonized by hydrothermal reaction to obtain carbon material; (2) dispersing the carbon material in an aqueous solution of 2,5-diaminoterephthalic acid to prepare a suspension; (3) adding iron salt to the suspension, stirring thoroughly until uniform, and evaporating to dryness to obtain a solid product; (4) Grinding the solid product and ammonium chloride into powder, and then calcining at high temperature under inert gas protection conditions to obtain the wastewater self-purification catalyst; the temperature of the high-temperature calcination is 600-800°C.

2. The method for preparing a wastewater self-purification catalyst according to claim 1, characterized in that: The temperature of the hydrothermal reaction in step (1) is 120-200° C., and the reaction time is 6-15 h.

3. The method for preparing a wastewater self-purification catalyst according to claim 1, characterized in that: The concentration of the aqueous solution of 2,5-diaminoterephthalic acid in step (2) is 3-9 g / L.

4. The method for preparing a wastewater self-purification catalyst according to claim 1, characterized in that: The dispersion temperature in step (2) is 20-80°C, and the dispersion time is 15-60 minutes.

5. The method for preparing a wastewater self-purification catalyst according to claim 1, characterized in that: The iron salt is ferric chloride hexahydrate, ferrous sulfate or ferric acetate.

6. The method for preparing a wastewater self-purification catalyst according to claim 1, characterized in that: The mass ratio of the carbon material to the 2,5-diaminoterephthalic acid, the iron salt, and the ammonium chloride is (1.0-2.0): (0.3-0.9): (0.02-0.1): (2.0-5.0).

7. The method for preparing a wastewater self-purification catalyst according to claim 1, characterized in that: The heating rate of the high-temperature calcination is 5-15°C / min, and the calcination time is 1-3h.

8. A wastewater self-purification catalyst, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 7.

9. Use of a wastewater self-purification catalyst according to claim 8 in reducing organic pollutants in water, characterized in that: The wastewater self-purification catalyst is directly dispersed in water containing organic pollutants.

10. The use according to claim 9, characterized in that The organic pollutants are one or more of ciprofloxacin, sulfamethoxazole, diphenhydramine and rhodamine B.

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