Preparation method and application of fluorine ion adsorption porous ceramic membrane with oyster shells as main raw material

Abstract

The invention discloses a preparation method and application of a fluorine ion adsorption porous ceramic membrane taking oyster shells as a main raw material, the porous ceramic membrane is prepared by taking activated oyster shell powder prepared from waste oyster shells as a main raw material, magnesium oxide and aluminum oxide as auxiliary materials, sodium glycinate as a pore structure stabilizer and sludge porous activated carbon as a template through a hydrothermal method. The porous ceramic membrane is prepared by adopting a gel template method, and by taking the mass of the porous ceramic membrane as a reference, the mass percentage content of the activated oyster shell powder is 50-70%, the mass percentage content of the magnesium oxide is 10-20%, and the mass percentage content of the aluminum oxide is 20-30%. The efficient adsorption and removal of the fluorine ions in the water body can be realized, and higher economic value and wide market application prospect are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and particularly to a preparation method and application of a porous ceramic membrane for fluoride ion adsorption mainly made of oyster shells. Background Art

[0002] Industries such as bauxite smelting, aluminum fluoride production, and chemical fertilizer production will discharge a large amount of fluoride ions (F-), resulting in their widespread presence in industrial wastewater, urban sewage, and natural water bodies. Excessive fluoride ions will not only cause health problems such as human bone diseases and dental diseases, but also cause serious harm to the ecological environment. For industries with a large amount of fluoride ion emissions, such as bauxite and chemical fluoride production industries, national and local environmental protection departments have formulated more stringent emission standards according to the emission characteristics of specific industries. Therefore, the research on the adsorption of fluoride ions in wastewater has gradually become an important topic in the fields of environmental science and water treatment in recent years.

[0003] On the other hand, shellfish are the main types of seawater aquaculture in China. Among them, the output of oysters is about 4.57 million tons, accounting for more than 34% of the total shellfish output. Entering the 21st century, the scale of shellfish aquaculture has been continuously expanding, the types of cultured shellfish have been increasing, and the aquaculture output has increased significantly. A large amount of waste oyster shells accumulated in coastal areas not only produce odors and breed insects, but also pollute the water quality. Therefore, the resource utilization of shellfish waste such as oyster shells has double significance of environmental protection and economy.

[0004] Due to the high solubility and toxicity of fluoride ions, traditional water treatment methods (such as precipitation method, ion exchange method, etc.) often have problems such as low treatment efficiency and high cost. Adsorption method has become one of the research focuses for removing fluoride ions in wastewater due to its simple operation, high efficiency, and low cost. At present, researchers have developed a variety of adsorption materials, mainly including: (1) natural mineral adsorbents, such as natural minerals like bentonite, activated carbon, and laterite, which have good adsorption performance and low cost; (2) modified materials: improving their adsorption performance through chemical modification or surface modification, such as using polymer composites, metal oxides (such as alumina, iron oxide), etc.; (3) nano-adsorption materials: the introduction of nanotechnology has greatly increased the specific surface area and adsorption capacity of adsorption materials, with higher removal efficiency; (4) biological adsorption materials: such as algae, plant residues, microorganisms, etc. Natural biological materials are not only environmentally friendly but also inexpensive. Although certain progress has been made in fluoride ion adsorption technology, the cost, treatment efficiency, and stability of adsorption materials still restrict their large-scale application. Therefore, the research and development of low-cost and high-efficiency fluoride ion adsorption materials is one of the important directions for current wastewater treatment. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems of low fluoride ion adsorption efficiency and high cost, and to provide a preparation method and application of a porous ceramic membrane for fluoride ion adsorption mainly made of oyster shells.

[0006] A preparation method of a fluoride ion adsorption porous ceramic membrane using oyster shells as the main raw material, characterized in that: the porous ceramic membrane uses activated oyster shell powder prepared from waste oyster shells as the main raw material, magnesium oxide and alumina as auxiliary materials, sodium glycinate as a pore structure stabilizer, and sludge porous activated carbon as a template, and is prepared by a gel template method. Based on the mass of the porous ceramic membrane, the mass percentage content of the activated oyster shell powder is 50-70%, the mass percentage content of magnesium oxide is 10-20%, and the mass percentage content of alumina is 20-30%. The method includes the following steps:

[0007] (1) Preparation of a mixed gel from waste oyster shells

[0008] Weigh oyster shells, wash them with deionized water and then dry them. Then, ball mill them using a planetary ball mill and sieve them to obtain oyster shell powder. Next, place the oyster shell powder in a muffle furnace and calcine it at high temperature to obtain activated oyster shell powder. Weigh the activated oyster shell powder, magnesium source, aluminum source, pore structure stabilizer, deionized water, and glycerol, mix them evenly to form a mixed solution, and place the mixed solution in a water bath to react to form a mixed gel for standby;

[0009] (2) Preparation of a sludge porous activated carbon template by an electrochemical method

[0010] Weigh the sludge, dry it, and mix it evenly with the electrolyte. Then, place the mixed solution in an electrolytic cell, use graphite electrodes as the positive and negative electrodes, and pass an electric current for electrolysis. After electrolysis is completed, place the obtained carbon-rich particles in an atmosphere furnace, introduce an inert gas and heat them at high temperature to obtain carbon particles. Weigh sodium hydroxide and dissolve it in deionized water to form a sodium hydroxide solution. Then, immerse the carbon particles in the sodium hydroxide solution, dry them, place them in a microwave heater for microwave heating activation, and finally wash and dry them with deionized water to obtain sludge porous activated carbon for standby;

[0011] (3) Preparation of a porous ceramic membrane by the gel template method

[0012] Mix and stir evenly the sludge porous activated carbon prepared in step (2) and the mixed gel prepared in step (1), let it stand and age, then dry it in an oven, and finally roast it in a high-temperature atmosphere furnace to obtain a porous ceramic membrane.

[0013] In the technical solution of the present invention: the mass ratio of the oyster shells to deionized water in step (1) is 1:(30-50), the drying temperature is 100-130°C, the drying time is 12-24h, the rotation speed of the ball mill is 500-700rpm, the mass ratio of oyster shells to zirconia balls during the ball milling process is 1:(5-10), the ball milling time is 3-6h, the mesh number of the metal sieve during the sieving process is 200-400 mesh, the high-temperature calcination temperature is 800-1000°C, and the high-temperature calcination time is 3-6h.

[0014] In the technical solution of the present invention: in step (1), the magnesium source is magnesium nitrate or magnesium chloride, the aluminum source is aluminum chloride, the pore structure stabilizer is sodium glycinate, and the mass ratio of the activated oyster shell powder, the pore structure stabilizer, deionized water, and glycerol is 1: (0.3 - 0.6): (40 - 80): (20 - 40). The temperature of the water bath reaction is 40 - 60 °C, and the time of the water bath reaction is 4 - 8 h.

[0015] In the technical solution of the present invention: in step (2), the drying temperature is 80 - 100 °C, and the drying time is 4 - 6 h. The sludge is the printing and dyeing sludge generated in the production process of the printing and dyeing industry. The electrolyte is a mixed solution of sodium chloride with a mass fraction of 5 - 10% and hydrogen chloride with a mass fraction of 1 - 5%. The mass ratio of the sludge to the electrolyte is 1: (10 - 20).

[0016] In the technical solution of the present invention: in step (2), the diameter of the graphite electrode is 6 - 10 mm, the length of the graphite electrode is 10 - 15 cm, the current during electrolysis is 10 - 30 mA, and the electrolysis time is 2 - 4 h.

[0017] In the technical solution of the present invention: in step (2), the feeding rate of the inert gas is 20 - 40 mL / min, the high-temperature heating temperature is 600 - 800 °C, and the high-temperature heating time is 2 - 6 h.

[0018] In the technical solution of the present invention: in step (2), the mass ratio of sodium hydroxide, deionized water, and carbon particles is 1: (10 - 20): (0.5 - 1). The power of microwave heating activation is 800 - 1000 W, and the microwave heating activation time is 30 - 60 min.

[0019] In the technical solution of the present invention: in step (3), the mass ratio of the sludge porous activated carbon to the mixed gel is 1: (1 - 2). The standing and aging time is 24 - 36 h, the drying temperature is 80 - 100 °C, the drying time is 12 - 24 h, the roasting temperature is 900 - 1200 °C, and the roasting time is 12 - 24 h.

[0020] In the technical solution of the present invention, the application of the porous ceramic membrane prepared by the above method in the field of wastewater treatment.

[0021] Further: the wastewater treatment is fluoride ion adsorption and removal.

[0022] Beneficial effects:

[0023] (1) The present invention first uses the ball milling and calcination method to make activated oyster shell powder from waste oyster shells, and then adds a magnesium source and an aluminum source to form a gel. Among them, magnesium oxide, calcium oxide, and aluminum oxide can not only be co-calcined at high temperature to form a composite oxide structure similar to hydrotalcite, but also form a porous ceramic membrane to enhance the adsorption performance of fluoride ions. In addition, sodium glycinate is used as a pore structure stabilizer, which can improve the surface characteristics of the activated oyster shell powder, magnesium source, and aluminum source, thus facilitating the formation of a stable pore structure in the gel and the subsequent porous ceramic membrane.

[0024] (2) The present invention uses the electrochemical method to convert printing and dyeing sludge with a high organic matter content into porous activated carbon. At the same time, the organic matter is further converted by heating at high temperature by introducing an inert gas, and the porous carbon particles are activated by sodium hydroxide using the microwave heating method to finally form sludge porous activated carbon.

[0025] (3) To form the porous structure of the ceramic membrane, the present invention not only uses sodium glycinate as a pore structure stabilizer for the gel, but also uses sludge porous activated carbon as a template to couple the gel and the activated carbon, thereby ensuring the pore structure of the porous ceramic membrane during the calcination process.

[0026] (4) When preparing the porous ceramic membrane, the present invention uses waste oyster shells and printing and dyeing sludge, which can realize the high-value resource utilization of waste oyster shells and printing and dyeing sludge while reducing the preparation cost of the porous ceramic membrane, and uses the main active ingredients in waste oyster shells and printing and dyeing sludge, which has an enhancing effect on the adsorption and removal of fluoride ions.

[0027] (5) This preparation method has a simple process and common raw materials, and has broad market application prospects and high economic value. Description of the Drawings

[0028] Appendix Figure 1 Field emission scanning electron microscope image of the catalyst in Example 1;

[0029] Appendix Figure 2 Fluoride ion adsorption and removal efficiency diagrams of Examples 1 to 3. Detailed Description of the Invention

[0030] Example 1

[0031] (1) Preparation of a mixed gel from waste oyster shells

[0032] Weigh 50 g of oyster shells, wash them with 1500 g of deionized water, dry them at 100 °C for 12 h, then take 40 g of the dried oyster shells, place them in a planetary ball mill, add 200 g of zirconia balls, ball mill at a rate of 500 rpm for 3 h, and then pass through a 200-mesh metal sieve to obtain oyster shell powder. Then place it in a muffle furnace and calcine it at 800 °C for 3 h to obtain activated oyster shell powder; Weigh 10 g of activated oyster shell powder, 14.72 g of magnesium nitrate, 15.7 g of aluminum chloride, 3 g of sodium glycinate, 400 g of deionized water, and 200 g of glycerol, mix them evenly to prepare a mixed solution, place the mixed solution in a water bath at 60 °C for 4 h to react to form a mixed gel for standby;

[0033] (2) Preparation of sludge porous activated carbon template by electrochemical method

[0034] Weigh 200 g of printing and dyeing sludge, dry it at 80 °C for 4 h, then mix it evenly with 2000 g of electrolyte containing 5% sodium chloride and 1% hydrogen chloride, place the mixed solution in an electrolytic cell, use graphite electrodes with a diameter of 6 mm and a length of 10 cm as positive and negative electrodes, pass a current of 10 mA for 2 h to obtain carbon-rich particles, then place them in an atmosphere furnace with an inert gas inlet rate of 20 mL / min and heat them at 600 °C for 2 h to obtain carbon particles; Weigh 20 g of sodium hydroxide and dissolve it in 200 g of deionized water to prepare a sodium hydroxide solution, then place 10 g of carbon particles in the sodium hydroxide solution and soak them for 12 h, filter, dry them at 80 °C for 8 h, then place them in a microwave heater and heat them with 800 W of microwave for 30 min for activation, and finally wash them with deionized water and dry them at 80 °C for 12 h to obtain sludge porous activated carbon for standby;

[0035] (3) Preparation of porous ceramic membrane by gel template method

[0036] Mix 5 g of the sludge porous activated carbon prepared in step (2) and 5 g of the mixed gel prepared in step (1) evenly by stirring, let it stand and age for 24 h, then place it in an oven and dry it at 80 °C for 12 h, and finally place it in a high-temperature atmosphere furnace and roast it at 900 °C for 12 h to obtain a porous ceramic membrane;

[0037] (4) Fluoride ion adsorption performance test

[0038] Take 1 g of the porous ceramic membrane, pour it into a beaker, add 100 mL of an aqueous solution with a fluoride ion concentration of 1000 ppm for performance evaluation, and use ion chromatography to measure the fluoride ion concentration. Under normal temperature and pressure, the adsorption and removal efficiency of the porous ceramic membrane reaches 86.7% in 30 min.

[0039] Example 2

[0040] (1) Preparation of mixed gel from waste oyster shells

[0041] Weigh 50 g of oyster shells, wash them with 2000 g of deionized water, dry them at 120 °C for 18 h, then take 40 g of the dried oyster shells and place them in a planetary ball mill. Add 300 g of zirconia balls and mill at a rate of 600 rpm for 4 h. Then pass through a 300-mesh metal sieve to obtain oyster shell powder. Then place it in a muffle furnace and calcine it at 900 °C for 5 h to obtain activated oyster shell powder; Weigh 10 g of activated oyster shell powder, 7.87 g of magnesium chloride, 8.71 g of aluminum chloride, 4.5 g of sodium glycinate, 600 g of deionized water, and 300 g of glycerol, mix them evenly to make a mixed solution, and place the mixed solution in a water bath at 50 °C for 6 h to react to form a mixed gel for standby;

[0042] (2) Preparation of sludge porous activated carbon template by electrochemical method

[0043] Weigh 200 g of printing and dyeing sludge, dry it at 90 °C for 5 h, then mix it evenly with 3000 g of an electrolyte solution containing 8% sodium chloride and 3% hydrogen chloride, and place the mixed solution in an electrolytic cell. Use graphite electrodes with a diameter of 8 mm and a length of 13 cm as the positive and negative electrodes, pass a current of 20 mA for electrolysis for 3 h to obtain carbon-rich particles, then place them in an atmosphere furnace with an inert gas inlet rate of 30 mL / min and heat them at 700 °C for 4 h to obtain carbon particles; Weigh 20 g of sodium hydroxide and dissolve it in 300 g of deionized water to make a sodium hydroxide solution. Then place 14 g of carbon particles in the sodium hydroxide solution and soak for 12 h. After filtration, dry it at 80 °C for 12 h, then place it in a microwave heater and activate it with 900 W of microwave for 45 min. Finally, wash it with deionized water and dry it at 80 °C for 12 h to obtain sludge porous activated carbon for standby;

[0044] (3) Preparation of porous ceramic membrane by gel template method

[0045] Mix 5 g of the sludge porous activated carbon prepared in step (2) with 10 g of the mixed gel prepared in step (1) and stir evenly. Let it stand and age for 30 h, then place it in an oven and dry it at 90 °C for 18 h. Finally, place it in a high-temperature atmosphere furnace and roast it at 1100 °C for 18 h to obtain a porous ceramic membrane;

[0046] (4) Fluoride ion adsorption performance test

[0047] Take 1 g of the porous ceramic membrane, pour it into a beaker and add 100 mL of an aqueous solution with a fluoride ion concentration of 1000 ppm for performance evaluation. Use ion chromatography to measure the fluoride ion concentration. Under normal temperature and pressure, the adsorption and removal efficiency of the porous ceramic membrane reaches 89.2% in 30 min.

[0048] Example 3

[0049] (1) Preparation of mixed gel from waste oyster shells

[0050] Weigh 50 g of oyster shells, wash them with 2500 g of deionized water, dry them at 130 °C for 24 h. Then take 40 g of the dried oyster shells, place them in a planetary ball mill, add 400 g of zirconia balls, ball mill at a rate of 700 rpm for 6 h, and then pass through a 400-mesh metal sieve to obtain oyster shell powder. Then place it in a muffle furnace and calcine it at a high temperature of 1000 °C for 6 h to obtain activated oyster shell powder; Weigh 10 g of activated oyster shell powder, 3.38 g of magnesium chloride, 7.47 g of aluminum chloride, 6 g of sodium glycinate, 800 g of deionized water, and 400 g of glycerol, mix them evenly to form a mixed solution, place the mixed solution in a water bath at 60 °C and react for 8 h in a water bath to form a mixed gel for standby;

[0051] (2) Preparation of sludge porous activated carbon template by electrochemical method

[0052] Weigh 200 g of printing and dyeing sludge, dry it at 100 °C for 6 h, then mix it evenly with 4000 g of an electrolyte containing 10% sodium chloride and 53% hydrogen chloride, place the mixed solution in an electrolytic cell, use graphite electrodes with a diameter of 10 mm and a length of 15 cm as positive and negative electrodes, pass a current of 30 mA and electrolyze for 4 h to obtain carbon-rich particles, then place them in an atmosphere furnace with an inert gas inlet rate of 40 mL / min and heat at a high temperature of 800 °C for 6 h to obtain carbon particles; Weigh 20 g of sodium hydroxide and dissolve it in 400 g of deionized water to make a sodium hydroxide solution. Then place 20 g of carbon particles in the sodium hydroxide solution and soak for 12 h, filter, dry at 80 °C for 12 h, then place them in a microwave heater and activate them with microwave heating at 800 W for 60 min. Finally, wash them with deionized water and dry at 80 °C for 12 h to obtain sludge porous activated carbon for standby;

[0053] (3) Preparation of porous ceramic membrane by gel template method

[0054] Mix 5 g of the sludge porous activated carbon prepared in step (2) with 8 g of the mixed gel prepared in step (1), stir evenly, let it stand and age for 36 h, then place it in an oven and dry at 100 °C for 24 h. Finally, place it in a high-temperature atmosphere furnace and calcine at 1200 °C for 24 h to obtain a porous ceramic membrane;

[0055] (4) Fluoride ion adsorption performance test

[0056] Take 1 g of the porous ceramic membrane, pour it into a beaker, add 100 mL of an aqueous solution with a fluoride ion concentration of 1000 ppm for performance evaluation, and use ion chromatography to measure the fluoride ion concentration. Under normal temperature and pressure, the adsorption and removal efficiency of the porous ceramic membrane reaches 92.3% in 30 min.

[0057] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a fluoride ion adsorption porous ceramic membrane using oyster shells as the main raw material, characterized in that: The porous ceramic membrane is prepared by the gel template method, with activated oyster shell powder obtained from waste oyster shells as the main raw material, magnesium oxide and alumina as auxiliary materials, sodium glycinate as the pore structure stabilizer, and sludge porous activated carbon as the template. Based on the mass of the porous ceramic membrane, the mass percentage content of the activated oyster shell powder is 50-70%, the mass percentage content of magnesium oxide is 10-20%, and the mass percentage content of alumina is 20-30%. The method includes the following steps: (1) Preparation of mixed gel from waste oyster shells Weigh oyster shells, wash them with deionized water and then dry them. Then, ball-mill them using a planetary ball mill and sieve them to obtain oyster shell powder. Next, place the oyster shell powder in a muffle furnace for high-temperature calcination to obtain activated oyster shell powder. Weigh the activated oyster shell powder, magnesium source, aluminum source, pore structure stabilizer, deionized water, and glycerol, mix them evenly to form a mixed solution, and place the mixed solution in a water bath for a water bath reaction to form a mixed gel for standby. (2) Preparation of sludge porous activated carbon template by electrochemical method Weigh the sludge, dry it, and mix it evenly with the electrolyte solution. Place the mixed solution in an electrolytic cell, use graphite electrodes as the positive and negative electrodes, and pass an electric current for electrolysis. After electrolysis is completed, place the obtained carbon-rich particles in an atmosphere furnace, introduce an inert gas, and heat them at a high temperature to obtain carbon particles. Weigh sodium hydroxide, dissolve it in deionized water to make a sodium hydroxide solution, then immerse the carbon particles in the sodium hydroxide solution, dry them, place them in a microwave heater for microwave heating activation, and finally wash and dry them with deionized water to obtain sludge porous activated carbon for standby. (3) Preparation of porous ceramic membrane by gel template method Mix and stir evenly the sludge porous activated carbon prepared in step (2) and the mixed gel prepared in step (1), let it stand and age, then dry it in an oven, and finally roast it in a high-temperature atmosphere furnace to obtain the porous ceramic membrane.

2. The preparation method according to claim 1, wherein: In step (1), the mass ratio of the oyster shells to deionized water is 1:(30-50), the drying temperature is 100-130 °C, the drying time is 12-24 h, the rotation speed of the ball mill is 500-700 rpm, the mass ratio of the oyster shells to zirconia balls during the ball milling process is 1:(5-10), the ball milling time is 3-6 h, the mesh number of the metal sieve during the sieving process is 200-400 mesh, the high-temperature calcination temperature is 800-1000 °C, and the high-temperature calcination time is 3-6 h.

3. The preparation method according to claim 1, wherein: In step (1), the magnesium source is magnesium nitrate or magnesium chloride, the aluminum source is aluminum chloride, the pore structure stabilizer is sodium glycinate, and the mass ratio of the activated oyster shell powder, pore structure stabilizer, deionized water, and glycerol is 1:(0.3-0.6):(40-80):(20-40). The water bath reaction temperature is 40-60 °C, and the water bath reaction time is 4-8 h.

4. The preparation method according to claim 1, characterized in that: In step (2), the drying temperature is 80-100 °C, the drying time is 4-6 h, the sludge is printing and dyeing sludge generated during the production process of the printing and dyeing industry, the electrolyte solution is a mixed solution of sodium chloride with a mass fraction of 5-10% and hydrogen chloride with a mass fraction of 1-5%, and the mass ratio of the sludge to the electrolyte solution is 1:(10-20).

5. The preparation method according to claim 1, characterized in that: The diameter of the graphite electrode described in step (2) is 6-10 mm, the length of the graphite electrode is 10-15 cm, the current during electrolysis is 10-30 mA, and the electrolysis time is 2-4 h.

6. The preparation method according to claim 1, characterized in that: The introduction rate of the inert gas described in step (2) is 20-40 mL / min, the temperature of high-temperature heating is 600-800 °C, and the high-temperature heating time is 2-6 h.

7. The preparation method according to claim 1, characterized in that: The mass ratio of sodium hydroxide, deionized water, and carbon particles described in step (2) is 1:(10-20):(0.5-1), the power of microwave heating activation is 800-1000 W, and the microwave heating activation time is 30-60 min.

8. The preparation method according to claim 1, characterized in that: The mass ratio of the sludge porous activated carbon and the mixed gel described in step (3) is 1:(1-2), the standing and aging time is 24-36 h, the drying temperature is 80-100 °C, the drying time is 12-24 h, the roasting temperature is 900-1200 °C, and the roasting time is 12-24 h.

9. Application of the porous ceramic membrane prepared by the method according to claim 1 in the field of wastewater treatment.

10. The application according to claim 9, characterized in that: The wastewater treatment described is fluoride ion adsorption and removal.

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