Preparation method and application of aluminum-modified grapefruit peel biochar

Abstract

The present application discloses a preparation method and application of aluminum-modified grapefruit peel biochar. 1-4g of grapefruit peel dry powder and 0.1-4g of sodium aluminate dry powder are weighed in a beaker according to a mass-volume ratio, 15-30ml of 70-99% (v / v) ethanol solution is added, and the solution is transferred to a 50ml reactor for a 100-250°C solvent thermal reaction for 140-180min. After the reaction is completed, the reactor is cooled naturally, and the sample in the reactor is taken out for centrifugation. After the centrifugation is completed, the supernatant is removed and the sample is washed. After washing, the sample is transferred to a clean culture dish, placed in an oven at 80°C and dried for 12h, ground and sieved through a 200-mesh sieve to obtain aluminum-modified grapefruit peel biochar. The defluorination adsorbent prepared by the present invention after optimization by response surface methodology has a controllable preparation process, a short preparation time, low energy consumption, and adjustable components of the adsorption material, and will not cause harm to the environment.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection water treatment, and specifically relates to a preparation method of aluminum-modified grapefruit peel biochar and application thereof. Background Art

[0002] Fluoride is a naturally occurring element that can be exposed to humans through food and drinking water. Low fluoride levels <0.5mg / L help treat tooth decay and osteoporosis in humans. Therefore, it is allowed to be added to drinking water, medicines, and toothpaste. In contrast, high concentrations of fluoride >1.5mg / L can cause a variety of health problems, such as skeletal and dental fluorosis, sweating, irritability, and joint deformities. High fluoride concentrations can also cause neurotoxicity in children, leading to lower IQ levels. Therefore, it is imperative to reduce the fluoride content in drinking water.

[0003] There are many methods that have been applied to defluorination, including ion exchange, reverse osmosis, nanofiltration, coprecipitation, electrodialysis and adsorption. Compared with the above technologies, adsorption stands out due to its selective adsorption, low cost, simplicity, recyclability and strong adsorption capacity. Therefore, adsorbents play a vital role in the adsorption process.

[0004] Biochar (a type of black carbon derived from the pyrolysis of biomass) has low cost and environmentally friendly properties, making it an excellent carbon-based adsorbent, which has been widely studied. Biochar has many advantages as a carrier. First, biochar has well-developed pores, certain activity and adsorption capacity, etc., which meet the general characteristics of an excellent carrier; second, biochar has a wide source, low cost, and mainly utilizes waste, which is environmentally friendly. Various biomass resources such as crop straw, rice husks, tea residues, bones, bagasse, vegetables and other agricultural waste can be used; third, the carrier has a strong loading capacity and can be effectively combined with aluminum / iron and other doping elements to form a carbon-loaded multi-doped defluorinating agent, which can play various synergistic roles, enhance its defluorination performance, and even give it the function of purifying and removing a variety of pollutants. Therefore, biochar-loaded aluminum-based doped materials have become a research hotspot in the field of environmentally friendly material development for removing fluoride and other harmful substances in water.

[0005] In addition to being an edible fruit, grapefruit is often processed into juice, beverages and canned food. In general, these consumptions result in a large amount of grapefruit peel as a byproduct, which accounts for about 30% to 50% (w / w) of the fruit. Chemical analysis shows that fresh grapefruit peel is rich in a variety of nutrients and functional compounds such as dietary fiber, pectin, essential oils, as well as a variety of organic acids and polyphenols. Improperly handled grapefruit peel can easily become a source of environmental pollution due to its high perishability. On the other hand, the refined utilization of grapefruit peel can derive a series of high value-added products or ingredients in industries such as food, cosmetics, medicine, environmental engineering, and material research and development.

[0006] With the continuous expansion of grapefruit pulp processed noodle products, the lack of stable and effective disposal of grapefruit peels has become an increasingly serious problem. The current disposal of grapefruit peels is mainly composting and landfilling, but there are problems of environmental pollution and mold pollution. At present, a small number of grapefruit peel biochar environmental remediation utilization methods have been developed, but the effect is not satisfactory. There are few reports on the removal of fluoride by aluminum-modified grapefruit peel biochar.

[0007] Currently, the mature adsorption defluorination technology is mainly activated alumina defluorination, but the cost of the defluorination adsorbent is relatively high and the defluorination effect is not ideal. The adsorption capacity is about 10 mg / g, which is relatively low.

[0008] Although pure biochar materials generally have a porous structure, their adsorption capacity for fluorine is very poor. The improvement effect of many materials modified by conventional metal salts on the adsorption capacity cannot meet the requirements of water treatment; in addition, most materials need to be first subjected to high-temperature pyrolysis carbonization and then metal modification in a step-by-step operation, which often consumes a lot of energy and reagents and is time-consuming. These defects limit the widespread application of modified biochar materials. Summary of the invention

[0009] Technical issues solved:

[0010] The present application aims at the deficiencies of the prior art, solves the current technical problems such as environmental pollution and mold pollution, and provides a method for preparing aluminum-modified grapefruit peel biochar and its application for removing fluoride in water. The method has low cost, short preparation time, low preparation temperature, low energy consumption, large adsorption capacity, and the components of the adsorption material are adjustable, thus realizing the utilization of agricultural waste without causing harm to the environment, and opening up a new direction for the disposal of grapefruit peel.

[0011] Technical solution:

[0012] To achieve the above objectives, this application is implemented through the following technical solutions:

[0013] A method for preparing aluminum-modified grapefruit peel biochar specifically comprises the following steps:

[0014] Step 1: Weigh 1-4g of grapefruit peel dry powder and 0.1-4g of sodium aluminate dry powder in a beaker according to the mass-volume ratio, add 15-30ml of 70-99% (v / v) ethanol solution, and stir to mix evenly;

[0015] Step 2: Transfer the stirred mixed solution obtained in the first step to a 50 ml reaction kettle and perform solvothermal treatment at 100-250°C for 140-180 min;

[0016] Step 3: After the solvent heat is over, wait for the reactor to cool naturally, take out the sample in the reactor and centrifuge it;

[0017] Step 4: After centrifugation, remove the supernatant and wash the sample;

[0018] Step 5: Transfer the washed sample in step 4 to a clean Petri dish and dry it in an oven at 80°C for 12 h;

[0019] Step 6: Grind the dried product in step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified grapefruit peel biochar.

[0020] Furthermore, in the first step, the diameter of the grapefruit peel dry powder is less than 0.2 mm.

[0021] Furthermore, in the third step, the centrifugation is performed at 5000 r / min for 3-5 min.

[0022] Furthermore, the washing step in the fourth step is washing once with deionized water, then washing once with ethanol, and then washing twice with deionized water.

[0023] The present application also discloses the use of aluminum-modified grapefruit peel biochar prepared by any of the above preparation methods in water treatment and fluoride removal.

[0024] Beneficial effects:

[0025] The present application provides a preparation method of aluminum-modified grapefruit peel biochar and its application, which has the following beneficial effects compared with the prior art:

[0026] 1. The preparation process of the defluorination adsorbent prepared by the response surface methodology optimization in this application is controllable, the preparation time is short, the energy consumption is low, and the adjustable properties of each component of the adsorption material are achieved;

[0027] 2. This application adopts a one-step solvothermal method for synthesis based on Lewis's hard and soft acid theory; unlike ordinary materials that are synthesized by adding a large amount of artificial organic acid reagents, the synthesis process of this material fully utilizes the carbon source and organic acid components in the grapefruit peel to combine with the added alkali aluminum source, greatly reducing costs and avoiding the generation of harmful wastes during the synthesis process;

[0028] 3. The surface of the modified material (PPB-Al) is rough and has a large number of irregular particles. The XRD diagram of PPB-Al shows that the main component of these particles is AlO(OH), i.e. boehmite. These particles improve the pore structure and specific surface area of ​​the material. Its specific surface area is increased from 1.960 m 2 / g rises to 43.90m 2 / g, the average pore size of this material is between 2-50nm, and it has an excellent mesoporous structure;

[0029] 4. The boehmite particles that appear in large quantities on the surface of the modified material provide a large number of -OH and Al-O structure adsorption sites for the adsorption of fluorine. The modified biochar contains a large number of carbon groups and specific surface area, which greatly disperses and protects the original adsorption sites and strengthens the binding opportunities of fluoride ions, so that the material retains more effective adsorption sites, thereby significantly improving the adsorption capacity; under the adsorption conditions of an initial fluoride concentration of 10 mg / L, an adsorbent dosage of 1 g / L, and a pH of 5, the fluorine removal rate of the defluoridation agent can reach 95.28%, and the theoretical maximum adsorption capacity is as high as 88.813 mg / g; compared with the unmodified grapefruit peel biochar, it has increased by 44 times, which is a significant technical progress;

[0030] 5. The composite material of the present application is not a simple combination of aluminum and grapefruit peel, but has a significant coupling advantage and has a "1+1>>2" effect; first, under the same dosage of the equivalent adsorbent (component) and the same conditions of use, the adsorption capacity of grapefruit peel biochar is lower than 1.45-2.33 mg / g, the adsorption capacity of the pure aluminum-based adsorbent is lower than 0.51-1.55 mg / g, and the sum of the two is lower than 1.96-3.88 mg / g, while the average adsorption capacity of the material of the present application is higher than 9.5 mg / g, which is much greater than the sum of the two, and an unexpected effect is obtained; in addition, the adsorption capacity of grapefruit peel biochar prepared by conventional high-temperature pyrolysis-impregnation modification and other complex procedures is only 6.21 mg / g, indicating that the material obtained by the one-step solvothermal method is not only more effective, but also easier to operate, while achieving the beneficial technical effect of increasing efficiency and reducing costs;

[0031] 6. The raw materials of the aluminum-modified grapefruit peel biochar defluoridation agent prepared in this application are cheap and easy to obtain, and grapefruit peel has a wide source: grapefruit product processing plants, fruit farmers, fruit stores, etc., which effectively realizes the recycling of resources; at the same time, the material can treat the fluoride pollution problem in water bodies while also treating waste with waste, effectively controlling the environmental pollution caused by the rotting of grapefruit peel, and achieving the effect of dual treatment;

[0032] 7. The aluminum-modified grapefruit peel biochar prepared in this application has low cost, excellent performance, high defluorination efficiency and a wide pH application range in practical applications of defluorination adsorbents, and has unexpected technical effects. In practical applications, it further saves water treatment costs and has significant social, environmental and economic benefits.

[0033] 8. The aluminum-modified grapefruit peel biochar material prepared in the present application has excellent performance, high fluorine removal efficiency and low use cost. The adsorbent of the present application only requires an adsorbent dosage of 1g / L to achieve a fluorine removal rate of more than 95%, which meets the needs of general fluorine removal applications. Compared with traditional alumina, the amount of activated alumina used is 3-17 times more. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The morphology of the aluminum-loaded grapefruit peel biochar PPB-Al and the grapefruit peel biochar PPB prepared in this application, the XRD structure identification and BET specific surface area analysis diagram of the aluminum-loaded grapefruit peel biochar PPB-Al, wherein a is the morphology of the grapefruit peel biochar PPB, b is the morphology of the aluminum-loaded grapefruit peel biochar PPB-Al, c is the XRD structure identification diagram of the aluminum-loaded grapefruit peel biochar PPB-Al, and d is the BET specific surface area analysis diagram;

[0035] Figure 2 A comparison chart of the adsorption capacity of the defluorination materials prepared by different modification methods in this application;

[0036] Figure 3 It is the adsorption isotherm simulation of fluoride by grapefruit peel biochar PPB and aluminum-loaded grapefruit peel biochar PPB-Al prepared in this application, wherein a is the adsorption isotherm simulation of PPB, and b is the adsorption isotherm simulation of PPB-Al. DETAILED DESCRIPTION

[0037] In order to further illustrate the present invention, the present invention is further described in detail below in conjunction with embodiments.

[0038] Example 1

[0039] A method for preparing aluminum-modified grapefruit peel biochar specifically comprises the following steps:

[0040] Step 1: Weigh 4g of grapefruit peel dry powder (diameter <0.2mm) and 2g of sodium aluminate dry powder in a beaker according to the mass-volume ratio, add 15ml of ethanol, and stir with a glass rod for 1min to mix evenly;

[0041] Step 2: Transfer the stirred mixed solution obtained in the first step to a 50 ml reaction kettle and heat at 180 °C for 140 min;

[0042] Step 3: After the solvent heat is over, wait for the reactor to cool naturally, take out the sample in the reactor and centrifuge it at 5000r / min for 5min;

[0043] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then wash once with ethanol, and then wash twice with deionized water;

[0044] Step 5: Transfer the washed sample in step 4 to a clean Petri dish and dry it in an oven at 80°C for 12 h;

[0045] Step 6: Grind the dried product in step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified grapefruit peel biochar P01.

[0046] An application of aluminum-modified grapefruit peel biochar in water treatment and fluoride removal. The above-mentioned P01 sample is placed under the adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5. The fluoride removal rate of the sample can reach 80.76%, and the experimental adsorption amount is 8.076 mg / g.

[0047] Example 2

[0048] A method for preparing aluminum-modified grapefruit peel biochar specifically comprises the following steps:

[0049] Step 1: Weigh 3g of grapefruit peel dry powder (diameter <0.2mm) and 1g of sodium aluminate dry powder in a beaker according to the mass-volume ratio, add 15ml of ethanol, and stir with a glass rod for 1min to mix evenly;

[0050] Step 2: Transfer the stirred mixed solution obtained in the first step to a 50 ml reactor and heat at 200 °C for 160 min;

[0051] Step 3: After the solvent heat is over, wait for the reactor to cool naturally, take out the sample in the reactor and centrifuge it at 5000r / min for 5min;

[0052] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then wash once with ethanol, and then wash twice with deionized water;

[0053] Step 5: Transfer the washed sample in step 4 to a clean Petri dish and dry it in an oven at 80°C for 12 h;

[0054] Step 6: Grind the dried product in step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified grapefruit peel biochar P02.

[0055] An application of aluminum-modified grapefruit peel biochar in water treatment and fluoride removal. When the above-mentioned P02 sample is placed under the adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the fluoride removal rate of the sample can reach 81.02%, and the experimental adsorption amount is 8.102 mg / g.

[0056] Example 3

[0057] A method for preparing aluminum-modified grapefruit peel biochar specifically comprises the following steps:

[0058] Step 1: Weigh 3g of grapefruit peel dry powder (diameter <0.2mm) and 2g of sodium aluminate dry powder in a beaker according to the mass-volume ratio, add 10ml of ethanol, and stir with a glass rod for 1min to mix evenly;

[0059] Step 2: Transfer the stirred mixed solution obtained in the first step to a 50 ml reaction kettle and heat at 170 °C for 140 min;

[0060] Step 3: After the solvent heat is over, wait for the reactor to cool naturally, take out the sample in the reactor and centrifuge it at 5000r / min for 5min;

[0061] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then wash once with ethanol, and then wash twice with deionized water;

[0062] Step 5: Transfer the washed sample in step 4 to a clean Petri dish and dry it in an oven at 80°C for 12 h;

[0063] Step 6: Grind the dried product in step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified grapefruit peel biochar P03.

[0064] An application of aluminum-modified grapefruit peel biochar in water treatment and fluoride removal. The above-mentioned P03 sample is placed under the adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5. The fluoride removal rate of the sample can reach 95.28%, and the experimental adsorption amount is 9.528 mg / g.

[0065] Example 4

[0066] A method for preparing aluminum-modified grapefruit peel biochar specifically comprises the following steps:

[0067] Step 1: Weigh 3g of grapefruit peel dry powder (diameter <0.2mm) and 3g of sodium aluminate dry powder in a beaker according to the mass-volume ratio, add 15ml of ethanol, and stir with a glass rod for 1min to mix evenly;

[0068] Step 2: Transfer the stirred mixed solution obtained in the first step to a 50 ml reaction kettle and heat at 100 °C for 150 min;

[0069] Step 3: After the solvent heat is over, wait for the reactor to cool naturally, take out the sample in the reactor and centrifuge it at 5000r / min for 5min;

[0070] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then wash once with ethanol, and then wash twice with deionized water;

[0071] Step 5: Transfer the washed sample in step 4 to a clean Petri dish and dry it in an oven at 80°C for 12 h;

[0072] Step 6: Grind the dried product in step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified grapefruit peel biochar P04.

[0073] An application of aluminum-modified grapefruit peel biochar in water treatment and fluoride removal. The above-mentioned P04 sample is placed under the adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5. The fluoride removal rate of the sample can reach 82.76%, and the experimental adsorption amount is 8.276 mg / g.

[0074] Example 5

[0075] A method for preparing aluminum-modified grapefruit peel biochar specifically comprises the following steps:

[0076] Step 1: Weigh 2g of grapefruit peel dry powder (diameter <0.2mm) and 4g of sodium aluminate dry powder in a beaker according to the mass-volume ratio, add 15ml of ethanol, and stir with a glass rod for 1min to mix evenly;

[0077] Step 2: Transfer the stirred mixed solution obtained in the first step to a 50 ml reactor and heat at 200 °C for 180 min;

[0078] Step 3: After the solvent heat is over, wait for the reactor to cool naturally, take out the sample in the reactor and centrifuge it at 5000r / min for 5min;

[0079] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then wash once with ethanol, and then wash twice with deionized water;

[0080] Step 5: Transfer the washed sample in step 4 to a clean Petri dish and dry it in an oven at 80°C for 12 h;

[0081] Step 6: Grind the dried product in step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified grapefruit peel biochar P05.

[0082] The invention discloses an application of aluminum-modified grapefruit peel biochar in water treatment and fluoride removal. When the P05 sample is placed under the adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the fluoride removal rate of the sample can reach 86.72%, and the experimental adsorption amount is 8.672 mg / g.

[0083] Example 6

[0084] A method for preparing aluminum-modified grapefruit peel biochar specifically comprises the following steps:

[0085] Step 1: Weigh 3g of grapefruit peel dry powder (diameter <0.2mm) and 2g of sodium aluminate dry powder in a beaker according to the mass-volume ratio, add 15ml of ethanol, and stir with a glass rod for 1min to mix evenly;

[0086] Step 2: Transfer the stirred mixed solution obtained in the first step to a 50 ml reaction kettle and heat at 120 °C for 160 min;

[0087] Step 3: After the solvent heat is over, wait for the reactor to cool naturally, take out the sample in the reactor and centrifuge it at 5000r / min for 5min;

[0088] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then wash once with ethanol, and then wash twice with deionized water;

[0089] Step 5: Transfer the washed sample in step 4 to a clean Petri dish and dry it in an oven at 80°C for 12 h;

[0090] Step 6: Grind the dried product in step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified grapefruit peel biochar P06.

[0091] The invention discloses an application of aluminum-modified grapefruit peel biochar in water treatment and fluoride removal. When the P06 sample is placed under the adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the fluoride removal rate of the sample can reach 96.36%, and the experimental adsorption amount is 9.636 mg / g.

[0092] Example 7

[0093] A method for preparing aluminum-modified grapefruit peel biochar specifically comprises the following steps:

[0094] Step 1: Weigh 3g of grapefruit peel dry powder (diameter <0.2mm) and 4g of sodium aluminate dry powder in a beaker according to the mass-volume ratio, add 15ml of ethanol, and stir with a glass rod for 1min to mix evenly;

[0095] Step 2: Transfer the stirred mixed solution obtained in the first step to a 50 ml reaction kettle and heat at 250 °C for 200 min;

[0096] Step 3: After the solvent heat is over, wait for the reactor to cool naturally, take out the sample in the reactor and centrifuge it at 5000r / min for 5min;

[0097] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then wash once with ethanol, and then wash twice with deionized water;

[0098] Step 5: Transfer the washed sample in step 4 to a clean Petri dish and dry it in an oven at 80°C for 12 h;

[0099] Step 6: Grind the dried product in step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified grapefruit peel biochar P07.

[0100] The invention discloses an application of aluminum-modified grapefruit peel biochar in water treatment and fluoride removal. When the P07 sample is placed under the adsorption conditions of 20 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the fluoride removal rate of the sample can reach 87.36%, and the experimental adsorption amount is 17.472 mg / g.

[0101] Example 8

[0102] A method for preparing aluminum-modified grapefruit peel biochar specifically comprises the following steps:

[0103] Step 1: Weigh 1g of grapefruit peel dry powder (diameter <0.2mm) and 2g of sodium aluminate dry powder in a beaker according to the mass-volume ratio, add 15ml of ethanol, and stir with a glass rod for 1min to mix evenly;

[0104] Step 2: Transfer the stirred mixed solution obtained in the first step to a 50 ml reaction kettle and heat at 200 °C for 200 min;

[0105] Step 3: After the solvent heat is over, wait for the reactor to cool naturally, take out the sample in the reactor and centrifuge it at 5000r / min for 5min;

[0106] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then wash once with ethanol, and then wash twice with deionized water;

[0107] Step 5: Transfer the washed sample in step 4 to a clean Petri dish and dry it in an oven at 80°C for 12 h;

[0108] Step 6: Grind the dried product in step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified grapefruit peel biochar P08.

[0109] The invention discloses an application of aluminum-modified grapefruit peel biochar in water treatment and fluoride removal. The above-mentioned P08 sample is placed under the adsorption conditions of 40 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5. The fluoride removal rate of the sample can reach 83.63%, and the experimental adsorption amount is 33.452 mg / g.

[0110] Comparative Example 1

[0111] An application of activated alumina (Al2O3) in water treatment and defluorination specifically comprises the following steps:

[0112] The first step: dissolving aluminum chloride in water to form an aluminum ion solution;

[0113] Step 2: Add ammonia water dropwise to the aluminum chloride solution and adjust the pH to between 6 and 8. After standing for 6 hours, aluminum hydroxide precipitation is obtained;

[0114] Step 4: The sample was filtered by vacuum and washed several times with deionized water;

[0115] Step 5: Dry the washed sample at 100-120°C until constant weight;

[0116] Step 6: calcine the dried aluminum hydroxide at 500-1000°C to convert it into activated alumina.

[0117] Step 7: Grind and sieve the calcined activated alumina to obtain a suitable particle size.

[0118] In the application of water treatment and fluoride removal, the initial fluoride ion concentration is 10 mg / L, the adsorbent dosage is 5 g / L, and the adsorption condition is pH 6 (optimal pH condition). The fluoride removal rate is 63%. The experimental adsorption amount is only 1.26 mg / g.

[0119] Comparative Example 2

[0120] A method for preparing solvent-thermal pomelo peel biochar (PPB), specifically comprising the following steps:

[0121] Step 1: Weigh 3g of grapefruit peel dry powder (diameter < 0.2mm) and place it in a beaker, add 10ml of ethanol, and stir with a glass rod for 1min to mix evenly;

[0122] Step 2: Transfer the stirred mixed solution obtained in the first step to a 50 ml reaction kettle and heat at 170 °C for 140 min;

[0123] Step 3: After the solvent heat is over, wait for the reactor to cool naturally, take out the sample in the reactor and centrifuge it at 5000r / min for 5min;

[0124] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then wash once with ethanol, and then wash twice with deionized water;

[0125] Step 5: Transfer the washed sample in step 4 to a clean Petri dish and dry it in an oven at 80°C for 12 h;

[0126] Step 6: Grind the dried product in step 5 and pass it through a 200-mesh sieve to obtain pure grapefruit peel biochar.

[0127] In the application of water treatment and fluoride removal, the initial fluoride ion concentration is 10 mg / L, the adsorbent dosage is 1 g / L, and the adsorption condition is pH 5 (optimal pH condition). The fluoride removal rate is 14.88%. The experimental adsorption amount is only 1.488 mg / g.

[0128] Comparative Example 3

[0129] A method for preparing aluminum chloride solvent thermally modified grapefruit peel biochar (Al-PPB(S)) specifically comprises the following steps:

[0130] Step 1: Weigh 3g of grapefruit peel dry powder (diameter <0.2mm) and 4g of aluminum chloride dry powder in a beaker according to the mass-volume ratio, add 10ml of ethanol solution, and stir with a glass rod for 1min to mix evenly;

[0131] Step 2: Transfer the stirred mixed solution obtained in the first step to a 50 ml reaction kettle and heat at 170 °C for 140 min;

[0132] Step 3: After the solvent heat is over, wait for the reactor to cool naturally, take out the sample in the reactor and centrifuge it at 5000r / min for 5min;

[0133] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then wash once with ethanol, and then wash twice with deionized water;

[0134] Step 5: Transfer the washed sample in step 4 to a clean Petri dish and dry it in an oven at 80°C for 12 h;

[0135] Step 6: Grind the dried product in step 5 and pass it through a 200-mesh sieve to obtain aluminum chloride-modified grapefruit peel biochar.

[0136] In the application of water treatment and fluoride removal, the initial fluoride ion concentration is 10 mg / L, the adsorbent dosage is 1 g / L, and the adsorption condition is pH 5 (optimal pH condition). The fluoride removal rate is 46.12%. The experimental adsorption amount is only 4.612 mg / g.

[0137] Comparative Example 4

[0138] A conventional aluminum chloride modified grapefruit peel biochar (Al-PPB(C)) specifically comprises the following steps:

[0139] Step 1: Grapefruit powder was rinsed with 0.1 M hydrochloric acid solution and dried at 100 °C for 4 h;

[0140] Step 2: The dried grapefruit peel samples were placed in a muffle furnace under anoxic conditions at 10 °C min -1 The temperature was heated to 450℃ for pyrolysis and maintained for 2 hours. Grapefruit peel biochar (BC) was obtained.

[0141] Step 3: Immerse the prepared BC sample in an aluminum chloride solution with a solid-solubility ratio of 1:10 (m(g) / v(mL)); adjust the pH of the mixture to 7.0 using 0.5 M sodium hydroxide and maintain for 2 hours;

[0142] Step 4: After equilibration for 48 hours, wash the sample 7-8 times with excess deionized water and anhydrous ethanol, and then dry it in an oven at 60 °C for 8 hours.

[0143] In the application of water treatment and fluoride removal, the initial fluoride ion concentration is 10 mg / L, the adsorbent dosage is 1 g / L, and the adsorption condition is pH 6 (optimal pH condition). The fluoride removal rate is 62.1%. The experimental adsorption amount is only 6.21 mg / g.

[0144] Comparative Example 5

[0145] A conventional lanthanum nitrate modified grapefruit peel biochar (La-PPB(C)) specifically comprises the following steps:

[0146] Step 1: Wrap 20.0 g of dried grapefruit peel sample (particle size: 5-10 mm) with tin foil and carry out under low oxygen conditions; carbonize in a muffle furnace at 800 °C for 1 hour to obtain 4 g of grapefruit peel biochar;

[0147] Step 2: 0.5 g of grapefruit peel biochar was added to 50 mL of 0.08 M La(NO3)3 solution, and the mixture was shaken in a constant temperature rotary shaker at 30 °C and 150 rpm for 12 h;

[0148] Step 3: The samples were filtered by vacuum filtration and washed three times with deionized water;

[0149] Step 4: Dry the generated sample at 60°C for 12 hours to obtain lanthanum-modified grapefruit peel biochar.

[0150] In the application of water treatment and fluoride removal, the initial fluoride ion concentration is 10 mg / L, the adsorbent dosage is 2 g / L, and under the adsorption conditions of pH 6.5 (optimal pH conditions), the fluoride removal rate is 90.5%, and the experimental adsorption amount is only 4.55 mg / g.

[0151] Figure 1 The morphology of the aluminum-loaded grapefruit peel biochar PPB-Al and grapefruit peel biochar PPB prepared in this application, the XRD structure identification and BET specific surface area analysis of the aluminum-loaded grapefruit peel biochar PPB-Al, wherein a is the morphology of grapefruit peel biochar PPB, b is the morphology of aluminum-loaded grapefruit peel biochar PPB-Al, c is the XRD structure identification diagram of aluminum-loaded grapefruit peel biochar PPB-Al, and d is the BET specific surface area analysis diagram; it proves that the method successfully loads aluminum oxide with a boehmite structure on the surface of biochar. Enhances its adsorption sites and specific surface area. The surface of the modified material PPB-Al is rough and grows a large number of irregular particles, such as Figure 1 b, XRD pattern of PPB-Al shows that the main component of these particles is AlO(OH), such as Figure 1C, namely boehmite, these particles improve the pore structure and specific surface area of ​​the material, and its specific surface area increases from 1.960m 2 / g rises to 43.90m 2 / g, the average pore size of this material is between 2-50nm, and it has an excellent mesoporous structure, such as Figure 1 As shown in middle d.

[0152] The PPB-Al defluoridation agent prepared in this application maintains a defluoridation rate of more than 80% when the dosage is 1g / L and 3≤pH≤6, and the experimental adsorption amount is 8.08-9.53mg / g. The average value of the actual adsorption amount under this condition is compared with that of materials obtained by other conventional modification methods, such as Figure 2 As shown, it can be found that the adsorption capacity of the material of the present application far exceeds the experimental adsorption capacity of many biochar materials such as conventional alumina Al2O3, grapefruit peel biochar PPB, aluminum chloride solvent thermally modified grapefruit peel biochar Al-PPB (S), aluminum chloride conventional modified grapefruit peel biochar Al-PPB (C) and lanthanum conventional modified biochar La-PPB (C). In particular, as a similar combination-type creation, the adsorption capacity of the obtained PPB-Al also far exceeds the sum of the adsorption capacities of each component, such as alumina and PPB alone, achieving unexpected effects and having substantial characteristics.

[0153] Figure 3 The adsorption isotherm simulation of fluoride by grapefruit peel biochar PPB and aluminum-loaded grapefruit peel biochar PPB-Al prepared in this application shows that the maximum theoretical adsorption capacity of the modified material is as high as 88 mg / g or more. The adsorption and isotherm simulation results of fluoride with different initial concentrations by material PPB-Al of Example 3 of this application and material PPB of Comparative Example 2 are shown in Figure 3 The experiments were carried out at pH = 5, dosage 1g / L, and temperature 25°C. Both materials conformed to the Langmuir adsorption isotherm model, and the calculated maximum theoretical adsorption capacities were 88.81 and 2.45 mg / g, respectively. The adsorption capacity after modification increased by more than 40 times that before modification, with significant efficiency enhancement.

[0154] Through the above comparison, it is not difficult to find that the new aluminum-loaded grapefruit peel biochar of the present invention effectively couples the functions of traditional aluminum-based adsorbents and biochar materials, achieving the technical effect of "1+1>>2", and compared with other conventional modification methods, it also has significant technical advantages, further saves water treatment costs in practical applications, and has significant social, environmental and economic benefits; in short, the material of the present invention realizes the utilization of waste resources, and has obvious beneficial technical progress characteristics such as simple operation, low cost, large adsorption capacity, and small dosage.

[0155] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A method for preparing aluminum-modified grapefruit peel biochar, characterized in that: The specific steps include: Step 1: Weigh 1-4 g of grapefruit peel dry powder and 0.1-4 g of sodium aluminate dry powder in a beaker according to the mass-to-volume ratio, add 15-30 ml of 70-99% ethanol solution, and stir to mix evenly; Step 2: Transfer the stirred mixed solution obtained in the first step to a 50 ml reaction vessel and perform solvothermal treatment at 100-250 °C for 140-180 min; Step 3: After the solvent heat is over, wait for the reactor to cool naturally, take out the sample in the reactor and centrifuge it; Step 4: After centrifugation, remove the supernatant and wash the sample; the washing step is to wash once with deionized water, then wash once with ethanol, and then wash twice with deionized water; Step 5: Transfer the washed sample in step 4 to a clean Petri dish and dry it in an oven at 80 °C for 12 h; Step 6: Grind the dried product in step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified grapefruit peel biochar.

2. The method for preparing aluminum-modified grapefruit peel biochar according to claim 1, characterized in that: In the first step, the diameter of the grapefruit peel dry powder is less than 0.2 mm.

3. The method for preparing aluminum-modified grapefruit peel biochar according to claim 1, characterized in that: The centrifugation in the third step is specifically performed at 5000 r / min for 3-5 min.

4. Use of aluminum-modified grapefruit peel biochar prepared by the preparation method according to any one of claims 1 to 3 in water treatment and fluoride removal.

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