CN114682287B - A protonated iron carbon nitride composite material for advanced sewage treatment and its preparation method and application - Google Patents

Abstract

The invention belongs to the technical field of sewage treatment, relates to the technical field of wastewater treatment containing pollutants, and specifically relates to a protonated iron carbon nitride composite material used for advanced treatment of sewage and its preparation method and application. In the present invention, nitrogen-containing carbon sources, oxalic acid and iron salts are first ground evenly and then subjected to pyrolysis treatment, and then the precursor sample is obtained by cooling, washing and drying. The precursor sample is protonated and then washed and dried to prepare a protonated sample. Iron carbon nitride composite. The raw materials of the method of the invention are cheap and easy to obtain, and the preparation process is simple. The prepared protonated iron carbon nitride material has the advantages of high catalytic activity, wide pH application range, strong resistance to water quality substrates, etc., and can greatly increase the peroxymonosulfate content. Or the activation effect of hydrogen peroxide, achieving efficient degradation of micro-pollutants, solving the problems of existing activation technology being greatly interfered by the water matrix, incomplete degradation of pollutants, and low utilization efficiency of permonosulfate, and has great application potential .

Description

A kind of protonated iron carbon nitride composite material for advanced treatment of sewage and its preparation Methods and applications

Technical field

The invention belongs to the technical field of sewage treatment, relates to the technical field of wastewater treatment containing pollutants, and specifically relates to a protonated iron carbon nitride composite material used for advanced treatment of sewage and its preparation method and application.

Background technique

Micropollutants are a new type of pollutants in the environment, mainly including drugs, pesticides, personal care products, endocrine disruptors, etc. They have the characteristics of wide range of pollution, many types, long half-life and high toxicity. They are carcinogenic, teratogenic, The risk of mutagenesis, which is latent and cumulative to a certain extent, may cause damage to the reproductive systems of humans and animals. As the water cycle is the link between various cycles, micropollutants at different concentration levels have been detected in the water environment. These micropollutants will have a non-negligible impact on the aquatic environment and water ecological balance. Therefore, the removal of micropollutants in water environments has received increasing attention.

In recent years, persulfate has been widely used for the degradation and removal of pollutants due to its advantages such as relative stability, ease of transportation, and the ability to generate highly active sulfate radicals. When using persulfate to degrade pollutants, it is necessary to activate the persulfate. Traditional activation technology generally uses UV, electrochemistry and hydroxylamine to break the oxygen-oxygen bond to generate highly active sulfate radicals and other active species. , thereby achieving the degradation and removal of pollutants. The concentration of micropollutants in actual water bodies is generally in the ng/L-μg/L range, while chloride ions (Cl ^- ), sulfate ions (SO ₄ ^2- ), and carbonate ions (CO ₃ The concentrations of ^2- ), bicarbonate ions (HCO ₃ ^- ) and natural organic matter (NOM) are generally at the mg/L level. The reaction rate of these water substrates with active species such as sulfate free radicals is extremely fast, reaching 10 ⁶ - 10 ⁹ mol ^-1 s ^-1 . Therefore, when applying persulfate advanced oxidation to degrade micropollutants in water bodies, the coexisting water matrix in the water body will quench a large number of active species such as sulfate radicals generated in the system, significantly inhibiting the oxidative degradation of pollutants through the free radical pathway. efficiency. In addition, the water matrix may react with free radicals generated during advanced oxidation to produce more toxic by-products, thus limiting its application in water bodies.

Therefore, it is necessary and important to develop low-cost, green, efficient, and highly resistant activation materials with strong resistance to water matrix interference to improve the activation effect of persulfate and its degradation efficiency of pollutants.

Contents of the invention

In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a protonated iron carbon nitride composite material for advanced treatment of sewage and its preparation method. This material can solve the problem that the existing activation technology is greatly interfered by the water matrix. Problems such as incomplete degradation of pollutants and low utilization efficiency of permonosulfate.

In order to achieve the above objects, the present invention is achieved through the following technical solutions:

The invention provides a method for preparing protonated iron carbon nitride composite materials. Specifically, the nitrogen-containing carbon source, oxalic acid and iron salt are ground uniformly and then subjected to pyrolysis treatment, and then the precursor is obtained by cooling, washing and drying. The sample, the precursor sample is protonated, washed and dried to prepare a protonated iron carbon nitride composite material.

Preferably, the nitrogen-containing carbon source includes thiourea, urea and melamine, and the iron salt includes anhydrous ferric chloride and ferric nitrate. Further, the nitrogen-containing carbon source is urea, and the iron salt is anhydrous ferric chloride.

Through the preparation method of the present invention, a protonated iron carbon nitride composite material can be prepared, the raw materials for preparation are cheap and easy to obtain, and the preparation process is simple. At the same time, the prepared protonated iron carbon nitride composite material contains a carrier of protonated graphite-like phase carbon nitride and iron atoms combined with the carrier, and the protonated graphite-like phase carbon nitride has protons The iron atom coordinates with the nitrogen atom in the carrier to form an Fe-N bond.

Preferably, the mass ratio of the nitrogen-containing carbon source, oxalic acid and iron salt is 15: (0.1-2): (0.01-0.2).

Preferably, the pyrolysis treatment is to raise the temperature from room temperature to 450-600°C at a heating rate of (4-6)°C/min, and maintain it at this temperature for 1-3 hours.

Preferably, the protonation treatment involves mixing the precursor sample and the inorganic acid and stirring for 3-5 hours.

More preferably, the inorganic acid includes hydrochloric acid, sulfuric acid and nitric acid, and the material-liquid ratio of the precursor sample to the inorganic acid is 100-300 mg: 1-4 mL. Further, the hydrochloric acid is 20-100% hydrochloric acid.

Preferably, the two washes are centrifugal washes.

Further, the washing after pyrolysis treatment is to first centrifuge and wash with ultrapure water 3-5 times, and then centrifuge and wash with ethanol 1-3 times, and the material obtained after cooling by pyrolysis needs to be mixed with the washing liquid before each centrifugation. Uniformly, the number of centrifugation times is 7000-10000 rpm, the centrifugation temperature is 4-25°C, and the centrifugation time is 3-10 minutes. The centrifugal washing after protonation treatment is to first centrifuge and wash with ultrapure water for 15-30 times, and then centrifuge and wash with ethanol for 1-3 times. Before each centrifugation, the material obtained after protonation and the washing liquid need to be mixed evenly. The number of revolutions of each centrifugation is 7000-10000 revolutions, the centrifugation temperature is 4-25°C, and the centrifugation time is 3-10 minutes.

Preferably, the drying after pyrolysis treatment is to place the lower layer material obtained after centrifugal washing in a drying box, and the drying temperature is 40-80°C.

Preferably, the cooling treatment after the pyrolysis treatment is natural cooling to room temperature.

The invention also provides protonated iron carbon nitride composite materials prepared by the above preparation method.

The invention also provides the application of the above-mentioned protonated iron carbon nitride composite material in sewage treatment.

Preferably, the sewage is wastewater containing pollutants. Further, the organic micropollutants in the pollutant-containing wastewater include but are not limited to bisphenol A (BPA), p-hydroxybenzoic acid (PHBA), p-chlorophenol (PCP), bisphenol A (BPA), p-chlorophenol Aniline (PCA), mefenamic acid (MFA), p-cyanoaniline (4-ABZ), sulfamethoxazole (SMX), aniline, triclosan.

The protonated iron carbon nitride composite catalyst provided by the invention has high catalytic activity towards persulfate (permonosulfate) and can also activate hydrogen peroxide, thereby achieving efficient degradation of micro-pollutants, and the application process does not require pH control. , the catalytic activity is not interfered by the water matrix and has a wide range of applications.

The invention also provides an advanced treatment method for sewage, which involves putting the above-mentioned protonated iron carbon nitride composite material and permonosulfate or hydrogen peroxide into the sewage to be treated, and activating the permonosulfate or hydrogen peroxide. Thereby achieving the purpose of degrading pollutants in water.

Preferably, the dosage of the protonated iron carbon nitride composite material is 0.1g/L, the dosage of peroxymonosulfate is 0.01-0.2mM, and the dosage of hydrogen peroxide is 0.2-2mM.

Compared with the prior art, the beneficial effects of the present invention are:

The invention discloses a method for preparing protonated iron carbon nitride composite materials for advanced treatment of sewage. First, nitrogen-containing carbon sources, oxalic acid and iron salts are ground uniformly and then subjected to pyrolysis treatment, and then cooled, washed and The precursor sample is obtained by drying, and the precursor sample is protonated, washed, and dried to prepare a protonated iron carbon nitride composite material. The method of the invention has cheap and easy raw materials, low production cost, simple preparation process, short preparation cycle, low requirements on equipment, good material stability and strong repeatability. The prepared protonated iron carbon nitride material has the advantages of high catalytic activity, wide pH range, and strong resistance to water quality substrates. It can greatly improve the activation effect of peroxymonosulfate or hydrogen peroxide and achieve micro-pollution control. It can efficiently degrade substances and have a low dissolution amount of iron in the material. It can also solve the problems of existing activation technology, which is greatly interfered by the water matrix, incomplete degradation of pollutants, and low utilization efficiency of permonosulfate, and has great application potential.

Description of drawings

Figure 1 shows the XRD of protonated carbon nitride (PCN), protonated oxygen-doped carbon nitride (POCN), protonated iron-doped carbon nitride (PFeCN), and protonated iron-oxygen-doped carbon nitride (PFeOCN). map;

Figure 2 is the degradation curve of PCN, POCN, PFeCN and PFeOCN activated PMS for the degradation of bisphenol A (BPA) (the degradation rate is expressed by C _t /C ₀ , C ₀ is the concentration of micropollutants before degradation, C _t is after degradation concentration of micropollutants);

Figure 3 is a graph showing the influence of PMS dosage on the degradation of BPA by PFeOCN material activated PMS;

Figure 4 is a graph showing the influence of the initial pH of the solution on the degradation of BPA by PFeOCN material activated PMS;

Figure 5 is a graph showing the influence of water quality matrix on the degradation of BPA by PFeOCN material activated PMS;

Figure 6 is the degradation curve of BPA by activated H ₂ O ₂ of PFeOCN material;

Figure 7 shows the degradation effect of PFeOCN material activated PMS on various pollutants.

Detailed ways

The specific embodiments of the present invention will be further described below. It should be noted here that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

The experimental methods in the following examples, unless otherwise specified, are all conventional methods. The test materials used in the following examples, unless otherwise specified, can be purchased through conventional commercial channels.

Example 1 Preparation method of protonated iron carbon nitride (PFeOCN) composite material

The specific preparation method includes the following steps:

(1) Weigh 15g of urea in a mortar, grind and stir evenly to obtain substance a; weigh 15g of urea and 0.25g of anhydrous oxalic acid in a mortar, grind and stir evenly to obtain substance b; weigh 15g of urea and 100mg of anhydrous oxalic acid Put aqueous ferric chloride in a mortar, grind and stir evenly to obtain substance c; weigh 15g urea, 0.25g anhydrous oxalic acid and 100mg anhydrous ferric chloride in a mortar, grind and stir evenly to obtain substance d;

(2) Transfer substances a, b, c, and d to a 50mL crucible, cover it, wrap it tightly with thick aluminum foil, put it into a muffle furnace, and heat it from room temperature to 500°C at a heating rate of 5°C/min. ℃, keep it at this temperature for 2 hours, then naturally cool to room temperature, and centrifuge and wash the cooled material (after centrifugal washing with ultrapure water 5 times, then wash with absolute ethanol 2 times, the centrifugal speed is 9000 rpm each time , centrifugation temperature 4°C, centrifugation time 5min), and finally dried at 60°C for 24h to obtain substances A, B, C, and D, which were labeled CN, OCN, FeCN, and FeOCN respectively, and grinded for use.

(3) Weigh 150 mg of each of substances A, B, C, and D into a 5 mL beaker, add 2 mL of 50% hydrochloric acid, stir for 4 hours, and then centrifuge and wash the mixture (first centrifuge and wash with ultrapure water 20 times, and then anhydrous Wash with ethanol twice, centrifuge at 9000 rpm, centrifuge temperature 4°C, and centrifuge time 5 min). Finally, each substance was obtained by drying at 60°C for 24 hours, which were marked as PCN, POCN, PFeCN, and PFeOCN respectively, and were ground and set aside for use.

As shown in Figure 1, only the peaks of graphite-like carbon nitride appear in the XRD patterns of PCN, POCN, PfeCN and PFeOCN, indicating that the incorporation of Fe and O does not destroy the structure of graphite-like carbon nitride.

Example 2 PFeOCN composite activated PMS degrades BPA (bisphenol A) in water

At pH=7±0.2, the solid-liquid ratio of carbon nitride materials (PCN, POCN, PFeCN, PFeOCN) and BPA aqueous solution is 0.1g/L, the dosage of PMS is 0.2mM, the activation temperature is 25°C, and the degradation time Under the condition of 15 minutes, the degradation effects of PCN, POCN, PFeCN, and PFeOCN on BPA in 100 mL of 2 μM BPA aqueous solution were investigated respectively. The results are shown in Figure 2.

As shown in Figure 2, when no carbon nitride material is added, the degradation of BPA by pure PMS is 0 within 15 minutes; when PCN is added, BPA is degraded by 5% after 15 minutes of reaction; when POCN is added, the reaction BPA was degraded by 10% after 15 minutes; when PfeCN was added, BPA was almost completely degraded after 15 minutes of reaction; and when PFeOCN was added, BPA was completely degraded in 6 minutes. This shows that the optimization of PFeOCN materials is effective, and subsequent experiments can be conducted using PFeOCN.

Example 3 Factors influencing the degradation of BPA in water by PFeOCN composite activated PMS

1) Effect of PMS dosage on BPA degradation

Under the conditions of pH=7±0.2, the solid-liquid ratio of PFeOCN and BPA aqueous solution is 0.1g/L, the activation temperature is 25℃, and the degradation time is 15min, different PMS dosages (0.01 , 0.06, 0.1, 0.2mM) on the degradation of BPA by PFeOCN material activated PMS, the results are shown in Figure 3.

As shown in Figure 3, when the PMS dosage is in the range of 0.01-0.2mM, the rate at which PFeOCN material activates PMS to degrade BPA obviously accelerates as the PMS concentration increases, and when the PMS dosage is 0.01mM, PFeOCN material activated PMS can achieve complete removal of BPA within 15 minutes. When the concentration of PMS is greater than 0.1mM, as the concentration of PMS increases, the rate at which PFeOCN material activates PMS to degrade BPA remains basically stable. This shows that in the system where the PFeOCN material activates PMS to degrade BPA, the material can activate and utilize trace amounts of PMS in the aqueous solution. It has relatively high sensitivity to PMS and can improve the utilization rate of PMS.

2) Effect of initial pH of aqueous solution on the degradation of BPA

Under the conditions that the solid-liquid ratio of PFeOCN and BPA aqueous solution is 0.1g/L, the PMS dosage is 0.2mM, the activation temperature is 25°C, and the degradation time is 15min, the initial pH of the aqueous solution (3 ±0.2, 5±0.2, 7±0.2, 9±0.2, 11±0.2) on the degradation of BPA by PFeOCN material activated PMS. The experimental results are shown in Figure 4.

As shown in Figure 4, FeOCNH composite activated PMS can efficiently degrade BPA in the range of pH=3-11, and achieve complete degradation of BPA within 6 minutes, indicating that PFeOCN materials have a wide range of pH applications and can be used in practical applications. It is not necessary to control the pH of the system.

3) The impact of water quality matrix on the degradation of BPA

In actual water bodies, there are a large number of coexisting ions and natural organic matter. The presence of such substances will greatly affect the degradation of micropollutants. Therefore, at pH=7±0.2, the solid-liquid ratio of PFeOCN and BPA aqueous solution is 0.1g/L, the PMS dosage is 0.2mM, the activation temperature is 25°C, the degradation time is 15min, and the coexisting ions (Cl ^- , SO ₄ ^{2 -} , NO ₃ ^- , HCO ₃ ^- , HPO ₄ ^- , ClO ₄ ^- , K ⁺ , Ca ²⁺ , Na ⁺ , Mg ²⁺ ) at a concentration of 50mM and a natural organic matter (NOM) concentration of 20mgC/L ( Using an aqueous solution without coexisting ions and natural organic matter as a control), the effect of the water quality matrix in the water environment on the degradation of BPA by PFeOCN material activated PMS was examined in 100 mL of 2 μM BPA aqueous solution. The experimental results are shown in Figure 5.

As shown in Figure 5, in the presence of various water quality matrices, BPA can basically be completely degraded within 6 minutes. However, within 4 minutes, compared with the control group, HCO ₃ ^- and Mg ²⁺ had a relatively small impact on the degradation of BPA. Overall, the presence of water quality matrix will not significantly affect the degradation of BPA by PFeOCN material-activated PMS, indicating that the PFeOCN material-activated PMS degradation of BPA has a relatively high anti-interference ability.

Example 4 PFeOCN composite material activates hydrogen peroxide (H ₂ O ₂ ) to degrade BPA in water

At pH=7±0.2, the solid-liquid ratio of PFeOCN and BPA aqueous solution is 0.1g/L, the dosage of H ₂ O ₂ is 0.2mM, 0.5mM, 1mM, 2mM, the activation temperature is 25℃, and the degradation time is 15min. Under the conditions, the degradation of BPA in water by FeOCNH composite activated H ₂ O ₂ was investigated in 100 mL of 2 μM BPA aqueous solution. The experimental results are shown in Figure 6.

As shown in Figure 6, within 15 minutes, as the concentration of H ₂ O ₂ increases, the efficiency of the PFeOCN material in catalyzing the degradation of BPA by H ₂ O ₂ becomes higher. When the concentration of H ₂ O ₂ is 0.2mM, BPA degrades within 15 minutes. 63%; when the concentration of H ₂ O ₂ is increased to 2mM, BPA can be degraded by 91% within 15 minutes, indicating that PFeOCN materials are also suitable for activated H ₂ O ₂ systems.

Example 5 PFeOCN composite material activates PMS to degrade various pollutants in water bodies

Under the conditions of pH=7±0.2, the solid-liquid ratio of PFeOCN and BPA aqueous solution is 0.1g/L, the PMS dosage is 0.2mM, the activation temperature is 25℃, and the degradation time is 15min, 100mL of 2μM various contaminants Aqueous solution (para-hydroxybenzoic acid PHBA, p-chlorophenol PCP, bisphenol ABPA, p-chloroaniline PCA, mefenamic acid MFA, p-cyanoaniline 4-ABZ, sulfamethoxazole SMX, aniline, triclosan) The degradation of various pollutants in water by FeOCNH composite activated PMS was investigated. The experimental results are shown in Figure 7.

As shown in Figure 7, within 15 minutes, PFeOCN composite material-activated PMS can degrade a variety of pollutants in water, and the degradation efficiency is greater than 90%, indicating that PFeOCN material-activated PMS can degrade a variety of micro-pollutants, not just limited to BPA.

In summary, the protonated iron carbon nitride composite catalyst (PFeOCN) prepared by the present invention can efficiently activate PMS and H ₂ O ₂ , and has a relatively wide pH range, and is suitable for most coexisting ions and Water matrices such as natural organic matter have relatively high anti-interference capabilities and can be used to degrade a variety of micropollutants, which has great potential for practical application.

The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and modifications can be made to these embodiments without departing from the principle and spirit of the invention, and they still fall within the protection scope of the invention.

Claims (4)

1. The application of a protonated iron carbon nitride composite material in the treatment of bisphenol A-containing sewage, which is characterized in that the protonated iron carbon nitride composite material and peroxymonosulfate are put into the sewage to be treated. Activating permonosulfate to achieve the purpose of degrading pollutants in water. The sewage contains the pollutant bisphenol A; the preparation method of the protonated iron carbon nitride composite material is: nitrogen-containing carbon source, oxalic acid and iron After grinding the salt evenly, pyrolysis treatment is performed, and then the precursor sample is obtained by cooling, washing and drying. The precursor sample is protonated, washed and dried to prepare a protonated iron carbon nitride composite material; the nitrogen-containing carbon The source is selected from thiourea, urea or melamine, and the iron salt is selected from anhydrous ferric chloride or ferric nitrate; the pyrolysis treatment is to heat up from room temperature to 450-600 at a heating rate of (4-6)°C/min. ℃, and keep at this temperature for 1-3h; the protonation treatment involves mixing and stirring the precursor sample with an inorganic acid for 3-5h, and the inorganic acid is selected from hydrochloric acid, sulfuric acid or nitric acid. 2. The application according to claim 1, characterized in that the mass ratio of the nitrogen-containing carbon source, oxalic acid and iron salt is 15: (0.1-2): (0.01-0.2). 3. The application according to claim 1, characterized in that the material-to-liquid ratio of the precursor sample and the inorganic acid is 100-300 mg: 1-4 mL. 4. The application according to claim 1, characterized in that the dosage of the protonated iron carbon nitride composite material is 0.1g/L, and the dosage of peroxymonosulfate is 0.01-0.2mM.