A water treatment method using internal nitrogen-doped biochar to catalyze the oxidation of tetracycline under ozone conditions

Abstract

A water treatment method for catalyzing the oxidation of tetracycline by internal nitrogen-doped biochar under ozone conditions relates to a water treatment method. The present invention utilizes sludge and water hyacinth to co-pyrolyze to prepare internal nitrogen-doped biochar. The nitrogen doping in water hyacinth increases the electronegativity of the biochar, which is conducive to electron transfer. Industrial sludge and fresh water hyacinth are washed with ultrapure water and dried, ground and sieved. The pretreated raw materials are evenly mixed and placed in a tube furnace, heated to 800-1000°C for co-pyrolysis, and cooled to room temperature to obtain internal nitrogen-doped biochar. With tetracycline as the target pollutant, under ozone catalytic oxidation conditions, it shows good performance in removing tetracycline. Its catalytic performance is investigated using real industrial wastewater. The results show good COD removal effect and show certain potential in industrial promotion and use. The preparation method of the present invention not only improves the physical and chemical properties of biochar, but also solves the disposal problems of industrial sludge and invasive species.

Description

Technical Field

[0001] The present invention relates to a water treatment method, in particular to a water treatment method for catalytically oxidizing tetracycline in biochar doped with internal nitrogen under ozone conditions. Background Art

[0002] Antibiotics are widely used in human therapy and veterinary medicine due to their low cost, low toxicity, and ease of administration. However, due to their slow metabolism, most antibiotics are excreted into the environment through feces and urine, potentially contaminating surface water, groundwater, and soil. Antibiotics' high hydrophilicity and low volatility allow them to persist in the environment for extended periods. Residual antibiotics can disrupt ecosystems and reduce human immunity to a certain extent. Therefore, effectively removing residual antibiotics from the environment presents a significant challenge.

[0003] Common antibiotic removal technologies include biological methods, adsorption, membrane separation, and advanced oxidation. Biological methods can only degrade a small portion of readily degradable antibiotic contaminants, presenting certain limitations. Furthermore, the degradation process produces intermediates that may retain toxicity and be difficult to remove. Adsorption involves removing contaminants by adsorbing them onto the surface of a solid adsorbent through intermolecular forces or chemical bonds. While simple to operate, this method does not completely degrade the contaminants, and adsorbent regeneration is difficult. Membrane separation is highly effective in removing contaminants, but its high cost and membrane fouling prevent large-scale application. In contrast, advanced oxidation techniques generate reactive oxygen species such as hydroxyl radicals, which react with organic contaminants, decomposing them into non-toxic intermediates, water, and carbon dioxide. Among advanced oxidation techniques, ozone catalytic oxidation offers significant advantages: its high redox potential, low cost, and disinfection capabilities make it widely used in industrial wastewater treatment. Replacing current metal oxide catalysts with carbon materials offers significant advantages and market prospects. Biochar is a carbon-rich product formed through the thermochemical conversion of biomass under high temperature and an inert atmosphere. Sludge, as a biomass, is the most produced by-product in the sewage treatment process and needs to be treated through methods such as landfill and composting. The treatment process is costly and inefficient. In the current context of resource utilization, it is urgent to develop green and sustainable sludge resource utilization technologies to turn harm into benefit. Therefore, carbonizing sludge into catalytic materials is a feasible treatment method. Studies have confirmed that nitrogen (N) doping can effectively change the electronegativity of carbon-based materials, improve electron transfer ability, and produce more active sites, all of which are conducive to improving the catalytic ability of biochar. Water hyacinth is an alien invasive aquatic plant and also one of the biomasses with the richest nitrogen content. Summary of the Invention

[0004] The purpose of the present invention is to provide a water treatment method for catalytically oxidizing tetracycline under ozone conditions using internally nitrogen-doped biochar. Based on its rich nitrogen content and low cost, the present invention uses it to modify sludge biochar to prepare internally nitrogen-doped biochar, which is of great significance for achieving efficient removal of pollutants in water and can achieve the goal of "using waste to treat pollution."

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for treating water by catalytically oxidizing tetracycline using internally nitrogen-doped biochar under ozone conditions, the method comprising the following steps:

[0007] (1) The raw material selection and preparation of nitrogen-doped carbon are as follows:

[0008] 1) Sludge raw material selection: sludge produced by using polyacrylamide (anionic and cationic types) as coagulant in sewage treatment plants;

[0009] 2) Selection of water hyacinth raw materials: wild water hyacinths grown in eutrophic water bodies are used as raw materials;

[0010] 3) Sludge pretreatment: Wash the industrial sludge with ultrapure water and dry it to constant weight, grind it and sieve it for later use;

[0011] 4) Water hyacinth pretreatment: Wash fresh water hyacinth with water (remove roots and leaves) and place in a drying oven at 80°C for 24 hours. Grind and sieve for later use.

[0012] 5) Preparation of internal nitrogen-doped biochar: Water hyacinth and industrial sludge (mass ratio between 1:5 and 5:1) were weighed and placed in a beaker. After adding water, ultrasonic vibration was performed for 20-50 min. The beaker was then placed in a magnetic stirring water bath and dried and stirred at 80°C until the water in the beaker was completely evaporated. The dried sludge and water hyacinth mixed powder was placed in a tubular furnace for co-pyrolysis.

[0013] (2) Nitrogen-doped biochar catalyzes the oxidation of tetracycline under ozone conditions. The steps are as follows: internal nitrogen-doped biochar is added as a catalyst to an aqueous solution containing tetracycline. After the adsorption process reaches equilibrium, ozone (20 mL / min-40 mL / min) is added to oxidize and remove tetracycline.

[0014] The method for treating water by catalytically oxidizing tetracycline using internal nitrogen-doped biochar under ozone conditions comprises a tetracycline solution having a concentration of 20-50 mg / L, a volume of 1 L, and a pH of 3-11; and a catalyst dosage of 0.05-0.2 g / L.

[0015] The method for treating water by catalytically oxidizing tetracycline with internal nitrogen-doped biochar under ozone conditions comprises the following pyrolysis conditions: an inert gas flow rate of 0.4-0.8 L / min, a heating rate of 2-10 °C / min, and continuous pyrolysis at 800 °C for 120-240 min.

[0016] The method for treating water by catalytically oxidizing tetracycline with internal nitrogen-doped biochar under ozone conditions comprises the following steps: the ozone catalytic oxidation degrades pollutants, which are then filtered and separated, washed with ultrapure water, and then dried, and this is repeated three times to obtain regenerated internal nitrogen-doped biochar, which maintains stable catalytic power and can continue to be used in subsequent cycles.

[0017] The method for treating water by catalytically oxidizing tetracycline using internal nitrogen-doped biochar under ozone conditions comprises the following steps: the surface of the nitrogen-doped biochar contains macropores and mesoporous structures, and the nitrogen content after doping is 21%. Most of these nitrogen elements exist in the interior of the biochar in the form of functional groups, including pyridinic nitrogen, pyrrolic nitrogen, and graphitic nitrogen. These nitrogen-containing functional groups act as active sites to participate in the catalytic oxidation reaction and accelerate the degradation of pollutants.

[0018] The advantages and effects of the present invention are:

[0019] Internal nitrogen-doped biochar is prepared by co-pyrolysis of sludge and water hyacinth. As a catalyst, it can efficiently remove tetracycline from water under ozone conditions. It can not only effectively reduce the environmental pollution caused by tetracycline, but also realize the resource utilization of industrial sludge, while effectively curbing the destruction of the ecosystem by invasive species. The biochar prepared by this method has strong catalytic activity and shows high potential in treating actual wastewater.

[0020] (1) The internal nitrogen-doped biochar of the present invention has a strong ability to remove tetracycline. A 0.1 g / L dose of internal nitrogen-doped biochar achieved a 93% removal rate for a 25 mg / L tetracycline concentration. After 3 hours of catalytic ozone oxidation of 5 L of printing and dyeing wastewater with a COD of approximately 9900, the COD decreased by 60%, and the biodegradability of the wastewater increased by approximately 6 times.

[0021] (2) Compared with other technologies (biodegradation, adsorption and membrane separation), the method of removing tetracycline from water by using internal nitrogen-doped biochar as a catalyst adopted in the present invention has the advantages of low cost, simple operation, environmental protection and the prospect of mass production and application.

[0022] Figure 1 SEM image of internal nitrogen-doped biochar prepared by co-pyrolysis of sewage sludge and water hyacinth;

[0023] Figure 2Element distribution of internal nitrogen-doped biochar prepared by co-pyrolysis of sewage sludge and water hyacinth;

[0024] Figure 3 Effects of different tetracycline concentrations on degradation;

[0025] Figure 4 Effects of different ozone flow rates on tetracycline degradation;

[0026] Figure 5 Effects of different pH values on tetracycline degradation;

[0027] Figure 6 Repeatability test curve. Implementation Method

[0028] The present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings.

[0029] Figure 1 The SEM images and EDS of internal nitrogen-doped biochar prepared by co-pyrolysis of sludge and water hyacinth demonstrated that water hyacinth and sludge were tightly combined after pyrolysis and nitrogen was successfully doped inside.

[0030] Figure 2 The relationship between tetracycline concentration, ozone dosage, pH change and its degradation ability when internal nitrogen-doped biochar is used as catalyst;

[0031] Figure 3 The internal nitrogen-doped biochar catalytically oxidizes pollutants and is then washed and dried with water to maintain a stable catalytic ability during subsequent recycling.

[0032] The present invention provides a method for preparing biochar for removing internal nitrogen doping of antibiotics in water by ozone catalytic oxidation, comprising the following steps:

[0033] (1) Pretreatment of raw materials: Wash the industrial sludge with water, dry it to constant weight, grind it and sieve it; (2) Wash the fresh water hyacinth (wild) with water and place it in a drying oven, dry it at a constant temperature of 80℃ for 24 hours, grind it and sieve it for later use.

[0034] Preparation of internal nitrogen-doped biochar: After steps (1) and (2), take the powder (mass ratio between 1:5 and 5:1) and place it in a beaker. After adding water, ultrasonically vibrate it for 20-50 minutes. Then place the beaker in a magnetic stirring water bath and dry and stir it in an 80°C water bath until the water in the beaker is completely evaporated. The dried sludge water hyacinth mixed powder is placed in a tubular furnace for co-pyrolysis.

[0035] The present invention provides a method for preparing internal nitrogen-doped biochar for removing pollutants in water, further comprising some or all of the following:

[0036] In steps (1) and (2), the drying temperature is 60-90 °C; the pyrolysis conditions are an inert gas flow rate of 0.4-0.8 L / min, a heating rate of 2-10 °C / min, and continuous pyrolysis at 400-800 °C for 120 min-240 min.

[0037] The catalyst product prepared in the above scheme degraded a 1 L tetracycline solution with a concentration of approximately 20-50 mg / L by catalytic ozone oxidation, with a removal rate of 93% after 130 minutes.

[0038] Example 1:

[0039] (1) Wash the industrial sludge with water, dry it to constant weight, grind it and sieve it;

[0040] (2) Wash the fresh water hyacinth with water (remove the roots and leaves) and place it in a drying oven at 80°C for 24 hours. Grind and sieve it for later use.

[0041] The raw materials described in steps (1) and (2) are weighed, water hyacinth and industrial sludge (mass ratio is 1:5) are placed in a beaker, and after adding water, ultrasonic vibration is performed for 20-50 minutes. Then, the beaker is placed in a magnetic stirring water bath, and dried and stirred in an 80°C water bath until the water in the beaker is completely evaporated; the dried sludge and water hyacinth mixed powder is placed in a tubular furnace for co-pyrolysis.

[0042] (3) The internal nitrogen-doped biochar was obtained by pyrolysis at 800 °C for 120 min in a high-temperature tube furnace (N2 flow rate of 0.5 L / min, heating rate of 5 °C / min).

[0043] Take 0.1 g of internal nitrogen-doped biochar as described in steps (1), (2) and (3) and add it to a 1 L tetracycline solution with a concentration of 20 mg / L. Catalytic degradation is carried out at a constant temperature of 25 °C. Adsorption equilibrium is reached after 10 minutes. Ozone is introduced using an ozone generator (20 mL / min). Samples are taken within the set time (0-130 minutes). The residual concentration of tetracycline is measured at λ = 355 nm using a spectrophotometer, and the removal rate of tetracycline at different times is calculated.

[0044] In addition, the internal nitrogen-doped biochar of the present invention can also be applied to other organic wastewater treatment fields besides tetracycline wastewater.

Claims

1. A method for treating water by catalytic oxidation of tetracycline by internal nitrogen-doped biochar under ozone conditions, characterized in that: The method includes the following steps: (1) The raw material selection and preparation of nitrogen-doped biochar are as follows: 1) Sludge raw material selection: sludge produced when polyacrylamide is used as a coagulant in sewage treatment plants; 2) Selection of water hyacinth raw materials: wild water hyacinths grown in eutrophic water bodies are used as raw materials; 3) Sludge pretreatment: Wash the industrial sludge with ultrapure water and dry it to constant weight, grind it and sieve it for later use; 4) Water hyacinth pretreatment: Wash the fresh water hyacinth with water and remove the roots and leaves; Place in a drying oven at 80°C for 24 hours, grind and sieve for later use; 5) Preparation of internal nitrogen-doped biochar: Water hyacinth and industrial sludge were weighed in a mass ratio of 1:5 to 5:1, placed in a beaker, and ultrasonically vibrated for 20-50 minutes after adding water. The beaker was then placed in a magnetically stirred water bath and dried at 80°C with stirring until the water in the beaker was completely evaporated. The dried sludge and water hyacinth mixed powder was placed in a tubular furnace for co-pyrolysis. Nitrogen-doped biochar has a macroporous and mesoporous structure on its surface. The nitrogen content after doping is 21%. Most of the doped nitrogen exists in the form of functional groups inside the biochar, including pyridinic nitrogen, pyrrolic nitrogen and graphitic nitrogen. These nitrogen-containing functional groups act as active sites to participate in catalytic oxidation reactions and accelerate the degradation of pollutants. The pyrolysis conditions were an inert gas flow rate of 0.4-0.8 L / min, a heating rate of 2-10 °C / min, and continuous pyrolysis at 800 °C for 120-240 min. (2) Nitrogen-doped biochar catalyzes the oxidation of tetracycline under ozone conditions. The steps are as follows: internal nitrogen-doped biochar is added as a catalyst to an aqueous solution containing tetracycline. After the adsorption process reaches equilibrium, ozone at a rate of 20 mL / min-40 mL / min is added to oxidize and remove tetracycline. After the pollutants are degraded by ozone catalytic oxidation, they are filtered and separated, washed with ultrapure water and then dried. This process is repeated three times to obtain regenerated internal nitrogen-doped biochar, which maintains stable catalytic power and can be used in subsequent cycles. The tetracycline solution has a tetracycline concentration of 20-50 mg / L, a volume of 1 L, a pH of 3-11, and a catalyst dosage of 0.05-0.2 g / L.

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