Preparation and application of salt and potassium hydroxide composite modified charcoal

Abstract

The invention discloses preparation and application of salt and potassium hydroxide composite modified biochar, and the scheme is as follows: taking chlorella as a biomass raw material, preparing disodium hydrogen phosphate and potassium hydroxide composite modified biochar taking phosphate and potassium hydroxide as modifiers, performing experiments, modifying a plurality of similar schemes, and performing comparison verification to obtain the biochar with the salt and potassium hydroxide composite modified biochar with the salt and potassium hydroxide composite modified biochar with the salt and potassium hydroxide composite modified biochar with the salt and potassium hydroxide composite modified biochar. The invention provides the method for preparing the biochar adsorbed tetracycline by using impregnation-pyrolysis, and the material prepared by the invention has the advantages of shorter adsorption time, lower concentration of the required salt solution, lower dosage of biochar and remarkably improved adsorption efficiency, avoids the introduction of metal elements in the biochar preparation process, and can be used for preparing the biochar adsorbed tetracycline. And the preparation cost of the adsorbent is reduced, and the potential risk that the aquatic environment is affected by metal leaching after adsorption is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to the preparation of salt and potassium hydroxide composite modified biochar and the application of the biochar in adsorbing tetracycline. Background Art

[0002] With the continuous development of the pharmaceutical industry, animal husbandry, and agriculture, antibiotics are widely used in the prevention and treatment of diseases. As a broad-spectrum antibiotic, excessive use of tetracycline will bring various environmental risks, such as inhibiting the growth and development of aquatic organisms, overaccumulating in the food chain, affecting human health, and causing joint diseases, kidney diseases, endocrine disorders, etc. In addition, tetracycline in the environment can induce microorganisms to produce antibiotic resistance genes. Therefore, exploring efficient and environmentally friendly tetracycline removal methods has become an urgent problem to be solved.

[0003] Common methods for removing tetracycline include physical and chemical techniques, biotechnology and advanced oxidation technology. Among them, adsorption is widely regarded as a method with simple process flow and high treatment efficiency. However, the production cost of adsorbents has always been a bottleneck restricting its large-scale application. Biochar is a carbon-rich solid produced by pyrolysis of biomass in an oxygen-deficient environment. It has a porous structure and relatively rich functional groups, and has great potential in adsorption performance. Due to its wide source, cheap raw materials and good adsorption performance, it is widely used to remove tetracycline from water.

[0004] However, due to the small specific surface area and underdeveloped pores of ordinary biochar, the adsorption performance of tetracycline is poor. It needs to be modified to change its physical properties, or to change its chemical properties by introducing functional groups to improve the adsorption performance of the material. KOH, as a common activator, is used to increase the specific surface area of ​​biochar, optimize the pore structure, and increase the surface oxygen-containing functional groups. Many studies have confirmed that KOH-activated biochar can improve the adsorption efficiency of tetracycline. However, in order to further improve the adsorption efficiency of tetracycline by biochar, metal doping has become a research hotspot. For example, CN118440710A discloses a biochar that uses the anaerobic fermentation residue of shrimp pond waste as a biomass raw material, which is modified by FeCl3 and KOH solution and pyrolyzed to obtain a biochar that can adsorb antibiotics. In the optimal preparation method, the adsorption efficiency of 0.5g / L FKBC for 20mg / L tetracycline is about 90%. CN114984909A discloses a method for adsorbing tetracycline by manganese chloride and potassium hydroxide modified grapefruit peel biochar. When the concentration of tetracycline is 30 mg / L, after 6 hours of adsorption, the removal rate of double modified biochar BC-MK is 81.1%. Although the adsorption efficiency of tetracycline can be improved to a certain extent by metal doping biochar, the introduction of metal elements not only increases the complexity of the preparation process and production cost, but more importantly, the precipitation of metal elements on biochar after adsorption brings potential pollution risks to the aquatic ecological environment. Therefore, it is necessary to invent a non-metal modified biochar for adsorbing tetracycline in water. Summary of the invention

[0005] The purpose of the present invention is to use Chlorella as a biomass raw material, phosphate and potassium hydroxide as modifiers, to prepare biochar prepared by a composite modification method of disodium hydrogen phosphate and potassium hydroxide, to provide a method for preparing biochar for adsorbing tetracycline by impregnation-pyrolysis, and to obtain the application of non-metal modified biochar in adsorbing tetracycline.

[0006] In order to achieve the above objectives, the main technical solution adopted by the present invention includes the following steps:

[0007] (1) Prepare a salt solution of a certain concentration, mix it with chlorella powder in a certain proportion, immerse it in a constant temperature oscillator for a certain period of time, wash it with water for multiple times, filter it, and dry it for later use.

[0008] (2) Grind the product of step (1) into powder with a mortar and weigh it, and at the same time weigh a certain mass of potassium hydroxide solid, quickly grind the potassium hydroxide into powder, mix the two solids in a certain mass ratio and place them in a quartz boat. Under N2 protective atmosphere, place the quartz boat in a tube furnace, ventilate 30 minutes in advance to exhaust the air, and control the roasting conditions of the solid powder by setting the parameters of the tube furnace. After the roasting is completed, cool it to room temperature. Take out the quartz boat and wash the pyrolysis product with pure water by suction filtration. Repeat this operation until the last water washing liquid is neutral, and place it in an oven for drying.

[0009] Preferably, the salt solution in step (1) is a phosphate and silicate solution, including but not limited to disodium hydrogen phosphate and sodium silicate.

[0010] Preferably, the concentration of the salt in step (1) is 5 mmol / L-300 mmol / L, and the ratio of the Chlorella powder to the salt solution is 5 g: 50 mL-150 mL.

[0011] Preferably, the oscillation conditions of the biomass and the salt solution in step (1) are as follows: the biomass and the salt solution are immersed in a constant temperature oscillator at 20°C-60°C at a speed of 50-200 r / min, and the reaction time is 2h-48h.

[0012] Preferably, the mass ratio of potassium hydroxide to biomass in step (2) is 0-1:1.

[0013] Preferably, the calcination parameters of the tube furnace in step (2) include: calcination temperature of 500°C-900°C, heating rate of 2°C / min-20°C / min, and holding time of 1h-3h.

[0014] A water treatment catalyst is prepared by the method.

[0015] The invention discloses an application of a water treatment catalyst, wherein the biochar modified by a composite of salt and potassium hydroxide is used for adsorption treatment of wastewater containing tetracycline.

[0016] Secondly, the scheme of the present invention also provides: the product of step (2) is ground and sieved in a mortar and then added to a tetracycline-containing solution for oscillation. After the adsorption is completed, the solution is filtered with a 0.22 μm filter membrane, and the tetracycline concentration in the filtrate is measured to obtain the treatment efficiency of the salt and potassium hydroxide composite modified biochar prepared by the present invention.

[0017] Preferably, in step (3), the dosage of the adsorbent is 0.05 g / L-0.5 g / L, and the adsorption time is 5 min-6 h.

[0018] Preferably, the concentration of the tetracycline solution in step (3) is 0-200 mg / L, and the pH is 1-9.

[0019] Beneficial effects:

[0020] (1) The present invention systematically compares the adsorption effects of seven common metal-modified biochars on tetracycline. The results show that among the metal-modified biochars, the biochar modified with calcium chloride has the best effect. When the impregnation concentration of calcium chloride is 0.1 mol / L, KOH: biomass = 0.75, and the pyrolysis temperature is 700°C, the addition amount is 0.2 g / L, which can achieve an adsorption efficiency of 89.3% for 100 mg / L of tetracycline. The preparation method of biochar is further optimized. When the impregnation concentration of calcium chloride is 25 mmol / L, KOH: biomass = 0.5, and the pyrolysis temperature is 700°C, the addition amount is 0.2 g / L, which can achieve an adsorption efficiency of 99.9% for 100 mg / L of tetracycline within 3 hours. Compared with the existing technical solutions, the solution disclosed in the present invention has a shorter material adsorption time, a lower concentration of the required salt solution, a smaller amount of biochar, and a significantly improved adsorption efficiency.

[0021] (2) The biochar prepared by the composite modification method of disodium hydrogen phosphate and potassium hydroxide disclosed in the present invention has a higher adsorption efficiency in adsorbing tetracycline in water than that modified by calcium chloride. When the impregnation concentration of disodium hydrogen phosphate is only 5 mmol / L, KOH: biomass = 0.5, and the pyrolysis temperature is 800°C, the addition amount is 0.2 g / L, which can achieve 100.0% adsorption efficiency of 100 mg / L tetracycline. More importantly, the introduction of metal elements is avoided in the process of preparing biochar, which not only reduces the preparation cost of the adsorbent, but also reduces the potential risk of metal leaching after adsorption affecting the aquatic environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the adsorption effect of tetracycline on the metal and potassium hydroxide composite modified biochar in comparative examples 1 to 2 of the present invention.

[0023] Figure 2 This is the adsorption effect of tetracycline on the non-metal and potassium hydroxide composite modified biochar in Examples 1 to 3 of the present invention.

[0024] Figure 3 The adsorption effects of Comparative Example 3 and Example 4 of the present invention in solutions with different pH values ​​are shown.

[0025] Figure 4 This is the FT-IR spectrum diagram of Example 4 of the present invention. DETAILED DESCRIPTION

[0026] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0027] Comparative Example 1:

[0028] (1) Grind the chlorella powder into powder with a mortar and weigh it. At the same time, weigh a certain amount of potassium hydroxide solid, quickly grind the potassium hydroxide into powder, mix the two solids in a mass ratio of 1:0.75 and place them in a quartz boat. Under a N2 protective atmosphere, place the quartz boat in a tube furnace and calcine at 700°C for 2 hours. After calcination, cool to room temperature. Take out the quartz boat and wash the pyrolysis product with pure water by suction. Repeat this operation until the last water wash is neutral and place it in an oven for drying.

[0029] (2) The product of step (1) is ground and sieved in a mortar and then added to a solution containing tetracycline and shaken. After adsorption, the solution is filtered through a 0.22 μm filter membrane and the tetracycline concentration in the filtrate is measured.

[0030] Comparative Example 2:

[0031] (1) Seven solutions of calcium chloride, magnesium chloride, aluminum chloride, ferric chloride, copper chloride, zinc chloride and manganese chloride were prepared with a concentration of 0.1 mol / L respectively. Each solution was mixed with Chlorella powder at a ratio of 100 mL:5 g. The mixture was immersed in a constant temperature oscillator at 30°C and 120 rpm for 24 h. After immersion, the mixture was washed with water for several times, filtered and dried for later use.

[0032] (2) Grind each product of step (1) into powder using a mortar and weigh it. At the same time, weigh a certain mass of potassium hydroxide solid, quickly grind the potassium hydroxide into powder, mix the two solids in a mass ratio of 1:0.75 and place them in a quartz boat. Under a N2 protective atmosphere, place the quartz boat in a tube furnace and calcine at 700°C for 2h. After calcination, cool to room temperature. Take out the quartz boat and wash the pyrolysis product with pure water by suction filtration. Repeat this operation until the last water wash is neutral and place it in an oven for drying.

[0033] (3) Grind each product of step (2) in a mortar, sieve it, add it to a tetracycline solution and shake it. After adsorption, filter the solution with a 0.22 μm filter membrane and measure the tetracycline concentration in the filtrate.

[0034] Comparative Example 3:

[0035] (1) Prepare a 25 mmol / L calcium chloride solution and mix it with Chlorella powder in a ratio of 100 mL:5 g. Immerse the solution in a constant temperature oscillator at 30°C and 120 rpm for 24 h. After immersion, wash and filter the solution several times, and dry it for later use.

[0036] (2) Grind the product of step (1) into powder with a mortar and weigh it. At the same time, weigh a certain mass of potassium hydroxide solid, quickly grind the potassium hydroxide into powder, mix the two solids in a mass ratio of 1:0.5 and place them in a quartz boat. Under N2 protective atmosphere, place the quartz boat in a tube furnace and calcine at 700°C for 2h. After calcination, cool to room temperature. Take out the quartz boat and wash the pyrolysis product with pure water by suction filtration. Repeat this operation until the last water washing liquid is neutral and place it in an oven for drying.

[0037] (3) The product of step (2) is ground and sieved in a mortar and then added to a tetracycline-containing solution and shaken. After adsorption is completed, the solution is filtered with a 0.22 μm filter membrane and the tetracycline concentration in the filtrate is measured.

[0038] Embodiment 1:

[0039] (1) Prepare 0.1 mol / L disodium hydrogen phosphate solution, mix it with Chlorella powder in a ratio of 100 mL:5 g, and immerse it in a constant temperature oscillator at 30°C and 120 rpm for 24 hours. After immersion, wash it with water several times, filter it, and dry it for later use.

[0040] (2) Grind the product of step (1) into powder with a mortar and weigh it. At the same time, weigh a certain mass of potassium hydroxide solid, quickly grind the potassium hydroxide into powder, mix the two solids in a mass ratio of 1:0.75 and place them in a quartz boat. Under a N2 protective atmosphere, place the quartz boat in a tube furnace and calcine at 700°C for 2h. After calcination, cool to room temperature. Take out the quartz boat and wash the pyrolysis product with pure water by suction filtration. Repeat this operation until the last water wash is neutral and place it in an oven for drying.

[0041] (3) The product of step (2) is ground and sieved in a mortar and then added to a tetracycline-containing solution and shaken. After adsorption is completed, the solution is filtered with a 0.22 μm filter membrane and the tetracycline concentration in the filtrate is measured.

[0042] Embodiment 2:

[0043] (1) Prepare 0.1 mol / L sodium silicate solution, mix it with Chlorella powder in a ratio of 100 mL:5 g, and immerse it in a constant temperature oscillator at 30°C and 120 rpm for 24 hours. After immersion, wash it with water several times, filter it, and dry it for later use.

[0044] (2) Grind the product of step (1) into powder with a mortar and weigh it. At the same time, weigh a certain mass of potassium hydroxide solid, quickly grind the potassium hydroxide into powder, mix the two solids in a mass ratio of 1:0.75 and place them in a quartz boat. Under a N2 protective atmosphere, place the quartz boat in a tube furnace and calcine at 700°C for 2h. After calcination, cool to room temperature. Take out the quartz boat and wash the pyrolysis product with pure water by suction filtration. Repeat this operation until the last water wash is neutral and place it in an oven for drying.

[0045] (3) The product of step (2) is ground and sieved in a mortar and then added to a tetracycline-containing solution and shaken. After adsorption is completed, the solution is filtered with a 0.22 μm filter membrane and the tetracycline concentration in the filtrate is measured.

[0046] Embodiment 3:

[0047] (1) Prepare 5 mmol / L disodium hydrogen phosphate solution, mix it with Chlorella powder in a ratio of 100 mL:5 g, and immerse it in a constant temperature oscillator at 30°C and 120 rpm for 24 hours. After immersion, wash it with water several times, filter it, and dry it for later use.

[0048] (2) Grind the product of step (1) into powder with a mortar and weigh it. At the same time, weigh a certain mass of potassium hydroxide solid, quickly grind the potassium hydroxide into powder, mix the two solids in a mass ratio of 1:0.5 and place them in a quartz boat. Under a N2 protective atmosphere, place the quartz boat in a tube furnace and calcine at 800°C for 2h. After calcination, cool to room temperature. Take out the quartz boat and wash the pyrolysis product with pure water by suction filtration. Repeat this operation until the last water wash is neutral and place it in an oven for drying.

[0049] (3) The product of step (2) is ground and sieved in a mortar and then added to a tetracycline-containing solution and shaken. After adsorption is completed, the solution is filtered with a 0.22 μm filter membrane and the tetracycline concentration in the filtrate is measured.

[0050] Embodiment 4:

[0051] (1) Prepare 5 mmol / L disodium hydrogen phosphate solution, mix it with Chlorella powder in a ratio of 100 mL:5 g, and immerse it in a constant temperature oscillator at 30°C and 120 rpm for 24 hours. After immersion, wash it with water several times, filter it, and dry it for later use.

[0052] (2) Grind the product of step (1) into powder with a mortar and weigh it. At the same time, weigh a certain mass of potassium hydroxide solid, quickly grind the potassium hydroxide into powder, mix the two solids in a mass ratio of 1:0.5 and place them in a quartz boat. Under N2 protective atmosphere, place the quartz boat in a tube furnace and calcine at 700°C for 2h. After calcination, cool to room temperature. Take out the quartz boat and wash the pyrolysis product with pure water by suction filtration. Repeat this operation until the last water washing liquid is neutral and place it in an oven for drying.

[0053] (3) The product of step (2) is ground and sieved in a mortar and then added to a tetracycline-containing solution and shaken. After adsorption is completed, the solution is filtered with a 0.22 μm filter membrane and the tetracycline concentration in the filtrate is measured.

[0054] Test example:

[0055] Comparative Examples 1-2 and Examples 1-3 were subjected to tetracycline adsorption experiments. The test conditions were: adsorbent dosage of 0.2 g / L, tetracycline concentration of 100 mg / L, pH = 3, placed in a shaker for oscillation, adsorption conditions: reacted in a shaker at 120 rpm and 30° C. for 3 h. The test results are shown in FIG. Figure 1 and Figure 2 shown.

[0056] Figure 1 It shows that among the seven metal-modified biochars, the biochar modified with calcium chloride has the highest adsorption efficiency for tetracycline, which can reach 89.3% after 3 hours.

[0057] Figure 2 It shows that compared with sodium silicate, disodium hydrogen phosphate has a better modification effect. After 3 hours, the adsorption efficiency can reach 99.8%, and when the concentration of disodium hydrogen phosphate is 5 mmol / L, KOH: biomass = 0.5, and the pyrolysis temperature is 800°C, the adsorption efficiency can reach 100.0%.

[0058] It can be seen that the Chlorella biochar co-modified by disodium hydrogen phosphate and potassium hydroxide has the best performance in the adsorption of tetracycline.

[0059] The samples of Comparative Example 3 and Example 4 were subjected to tetracycline adsorption tests under different pH conditions. The test conditions were: the adsorbent dosage was 0.2 g / L, the concentration of the tetracycline solution was 100 mg / L, and the samples were placed in a shaker for oscillation. The adsorption conditions were: reacting for 3 hours at 120 rpm and 30°C in a shaker.

[0060] Test results such as Figure 3 As shown, Example 4 has a higher adsorption efficiency for tetracycline in the pH range of 1-9. Figure 4 This is the FT-IR spectrum diagram of Example 4 of the present invention.

[0061] Through the above, the present invention systematically compared the adsorption effects of seven common metal-modified biochars on tetracycline in the experiment, and the results showed that among the metal-modified biochars, the biochar modified with calcium chloride had the best effect.

[0062] When the impregnation concentration of calcium chloride is 0.1 mol / L, KOH: biomass=0.75, and the pyrolysis temperature is 700°C, the addition amount of 0.2 g / L can achieve an adsorption efficiency of 89.3% for 100 mg / L tetracycline.

[0063] The preparation method of biochar was further optimized. When the impregnation concentration of calcium chloride was 25 mmol / L, KOH:biomass=0.5, and the pyrolysis temperature was 700°C, the dosage of 0.2 g / L could achieve an adsorption efficiency of 99.9% for 100 mg / L tetracycline within 3 hours.

[0064] Compared with the existing technical solutions, the solution disclosed in the present invention has a shorter material adsorption time, requires a lower concentration of salt solution, requires less biochar addition, and significantly improves the adsorption efficiency.

[0065] In addition, the biochar prepared by the composite modification method of disodium hydrogen phosphate and potassium hydroxide disclosed in the present invention has a higher adsorption efficiency when adsorbing tetracycline in water than that modified by calcium chloride. When the impregnation concentration of disodium hydrogen phosphate is only 5 mmol / L, KOH:biomass=0.5, and the pyrolysis temperature is 800°C, the addition amount of 0.2 g / L can achieve an adsorption efficiency of 100.0% for 100 mg / L of tetracycline.

[0066] More importantly, the introduction of metal elements is avoided during the preparation of biochar, which not only reduces the preparation cost of the adsorbent, but also reduces the potential risk of metal leaching after adsorption affecting the aquatic environment.

[0067] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing biochar composite modified by salt and potassium hydroxide, characterized in that: The method comprises the following steps: (1) preparing a salt solution of a certain concentration, mixing the salt solution with chlorella powder in a certain proportion, immersing the salt solution in a constant temperature oscillator for a certain period of time, washing and filtering the salt solution for multiple times, and drying the solution for later use; (2) Grinding the product of step (1) into powder using a mortar and weighing it, and at the same time weighing a certain mass of potassium hydroxide solid, quickly grinding the potassium hydroxide into powder, and mixing the two solids in a certain mass ratio and placing them in a quartz boat; placing the quartz boat in a tube furnace under a N2 protective atmosphere, and passing N2 gas 30 minutes in advance to exhaust the air in the tube furnace, and controlling the roasting conditions of the solid powder by setting the parameters of the tube furnace; after the roasting is completed, cooling to room temperature, taking out the quartz boat and washing the pyrolysis product with pure water by suction, repeating this operation until the last water washing liquid is neutral, and placing it in an oven for drying to obtain a salt and potassium hydroxide composite modified biochar based on Chlorella.

2. The preparation method according to claim 1, characterized in that: The salt solution in step (1) includes phosphate and silicate solutions.

3. The preparation method according to claim 1, characterized in that: The salt in the salt solution in step (1) includes disodium hydrogen phosphate, sodium silicate, calcium chloride, magnesium chloride, aluminum chloride, ferric chloride, copper chloride, zinc chloride and manganese chloride.

4. The preparation method according to claim 1, characterized in that: The concentration of the salt in step (1) is 5 mmol / L-300 mmol / L, and the ratio of the Chlorella powder to the salt solution is 5 g: 50 mL-150 mL.

5. The preparation method according to claim 1, characterized in that: The oscillation conditions of the biomass and the salt solution in the step (1) are as follows: the biomass and the salt solution are immersed in a constant temperature oscillator at 20°C-60°C at a speed of 50-200 r / min, and the reaction time is 2h-48h.

6. The preparation method according to claim 1, characterized in that: The mass ratio of potassium hydroxide to biomass in step (2) is 0-1:

1.

7. The preparation method according to claim 1, characterized in that: The calcination parameters of the tubular furnace in step (2) include: a calcination temperature of 500°C-900°C, a heating rate of 2°C / min-20°C / min, and a holding time of 1h-3h.

8. A catalyst for adsorbing tetracycline, characterized in that: It is prepared by a composite modification method of disodium hydrogen phosphate and potassium hydroxide.

9. Application of salt and potassium hydroxide composite modified biochar in tetracycline adsorption wastewater treatment, characterized by: The biochar modified by salt and potassium hydroxide was ground and used for adsorption treatment of wastewater containing tetracycline.

10. The use according to claim 9, characterized in that: The pH of the tetracycline wastewater is 1-9.

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