Aluminum-modified pomegranate peel biochar, and preparation method and application thereof

Abstract

This invention relates to the field of environmental protection and water treatment technology, specifically to an aluminum-modified pomegranate peel biochar, its preparation method, and its application. The invention involves reacting dried pomegranate peel powder with sodium aluminate in an ethanol system via a one-step solvothermal process to obtain aluminum-modified pomegranate peel biochar. The solvothermal process allows the aluminum source to combine in situ with the organic acids and carbon source abundant in the pomegranate peel, achieving optimal biochar production within a pH range of 2-7. ‑ The removal rate was 96.68%, and the mechanism study revealed that it achieves efficient fluoride removal through the synergistic effect of the biochar framework and active sites. This invention uses waste pomegranate peel as raw material to realize the resource utilization of agricultural waste, and provides a low-cost, environmentally friendly and excellent adsorption performance solution for the treatment of fluoride pollution in water bodies.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection and water treatment technology, specifically relating to an aluminum-modified pomegranate peel biochar, its preparation method, and its application. Background Technology

[0002] Fluoride is one of the most common pollutants in water bodies. Modern industrial activities, such as phosphate mining and processing, metal smelting, and fluorochemical production, result in large amounts of reactive fluoride entering the aquatic environment, with highly complex and ecologically interconnected impacts. On the one hand, fluoride ions have a strong migration capacity in acidic or neutral water bodies, easily spreading with surface runoff and causing transboundary pollution. On the other hand, after entering sediments, fluoride can complex with metal ions such as aluminum and iron, affecting benthic communities and potentially being passed down through the food chain, posing a long-term, potential threat to the ecological security of watersheds. Long-term excessive fluoride intake can cause multi-system damage to the human body, primarily affecting bones and teeth. In terms of teeth, excessive fluoride damages enamel development, leading to dental fluorosis; in terms of bones, the continuous accumulation of fluoride in bone tissue disrupts bone metabolism balance, causing skeletal fluorosis. Fluoride also has neurotoxicity, capable of crossing the blood-brain barrier and damaging the central nervous system; it also interferes with thyroid function, affecting iodine absorption and thyroid hormone synthesis. Excessive fluoride can also irritate the gastrointestinal mucosa, increase the burden on the kidneys, and cause varying degrees of damage to the digestive and urinary systems.

[0003] A large amount of pomegranate peel waste is generated in agricultural production and the juice processing industry. Because pomegranate peel has low commercial value and is easily perishable, it is currently usually discarded or landfilled as agricultural waste, which not only wastes biomass resources but may also cause environmental pollution. Therefore, developing modified fluoride-removing materials using pomegranate peel as raw material not only expands the resource utilization pathways of agricultural waste but also realizes the circular economy concept of "treating waste with waste," showing good development prospects and application value.

[0004] To address the problem of fluoride pollution in water bodies, various treatment technologies have been developed, including chemical precipitation, ion exchange, adsorption, and membrane separation. Among these, adsorption is favored due to its low cost, ease of operation, environmental friendliness, and excellent adsorption effect. This technology not only has widely available and cost-controllable adsorbent materials, but also allows for easy control of process conditions, large adsorption capacity, and the regeneration and reuse of some adsorbents. Therefore, it is widely considered to be the most promising fluoride removal technology currently available.

[0005] Biochar, a carbon-rich material prepared from biomass through pyrolysis, has become a highly regarded carbon-based adsorbent due to its low cost, wide availability, and good environmental compatibility. As a carrier material, biochar offers advantages in three aspects: First, it possesses excellent structural characteristics, well-developed pores, and a large adsorption capacity, meeting the basic requirements of an ideal carrier. Second, it is readily available from agricultural byproducts such as straw, rice husks, tea residue, and bagasse, reducing costs and realizing waste resource utilization. Third, it exhibits strong composite modification capabilities, stably loading with metals such as aluminum and iron to form multi-component doped composite materials. This allows for synergistic effects between components, improving fluoride removal efficiency and even achieving simultaneous removal of multiple pollutants. Based on these advantages, biochar-supported aluminum-based composite materials have become a research hotspot in the treatment of fluoride-containing wastewater, demonstrating broad application prospects.

[0006] In recent years, the development of highly efficient adsorbents from agricultural waste has become a research hotspot in the field of water purification. Various biomass materials, such as straw, rice husks, and fruit peels, have been widely explored for fluoride ion removal. Pomegranate peel, as a major waste product of the pomegranate processing industry, has a considerable annual output. Research on the application of pomegranate peel biochar in environmental remediation is relatively limited. In existing research, the application of pomegranate peel for fluoride removal mainly adopts two methods: one is to prepare biochar materials through pyrolysis; the other is to modify it with acids and bases. However, the fluoride adsorption performance of both types of materials is not ideal, indicating that conventional pyrolysis or simple modification strategies cannot fully utilize the structural advantages and functional group potential of pomegranate peel. Existing attempts have not yielded satisfactory results, and research on the preparation of pomegranate peel-based defluoridation materials using aluminum modification is even rarer. Therefore, developing novel composite modification technologies to construct highly efficient pomegranate peel-based defluoridation materials is of great significance for achieving "waste-to-waste treatment" and improving the efficiency of water defluoridation. Summary of the Invention

[0007] Technical Problem Solved: Addressing the problems of high cost, complex processes, and low resource utilization rate of agricultural waste such as pomegranate peels in existing water fluoride pollution treatment technologies, this invention proposes an aluminum-modified pomegranate peel biochar, its preparation method, and its application. Aluminum modification endows the pomegranate peel biochar with excellent fluoride adsorption properties, offering advantages such as short preparation cycle, low reaction temperature, low energy consumption, and large adsorption capacity. Furthermore, the material's composition is adjustable, and the preparation process is green and environmentally friendly, realizing the transformation of agricultural waste into valuable resources and opening up new directions for the disposal and high-value utilization of pomegranate peels.

[0008] Technical solution: The first objective of this invention is to provide a method for preparing aluminum-modified pomegranate peel biochar, the steps of which are as follows:

[0009] Step 1: Mix the dried pomegranate peel powder with sodium aluminate, then add ethanol solution and stir to mix evenly;

[0010] Step 2: Perform a solvothermal reaction on the mixed solution after stirring in Step 1;

[0011] Step 3: After the solvothermal process is complete, cool the sample, remove it and centrifuge it. After centrifugation, remove the supernatant and wash the sample.

[0012] Step 4: Dry the washed sample;

[0013] Step 5: After drying, grind the product and sieve it to obtain aluminum-modified pomegranate peel biochar.

[0014] Preferably, in step one, the mass ratio of dried pomegranate peel powder to sodium aluminate is 1-4:1-4, the concentration of the ethanol solution is 70-99% v / v, and the ratio of ethanol solution to dried pomegranate peel powder is 10-20 mL:1-4 g.

[0015] Preferably, in step one, the diameter of the dried pomegranate peel powder is <0.2 mm.

[0016] Preferably, in step two, the solvothermal reaction conditions are: solvothermal reaction at 100-250 ℃ in the reactor for 120-180 min.

[0017] Preferably, in step three, the centrifugation conditions are: centrifugation at 5000 r / min for 3-5 min.

[0018] Preferably, in step three, the washing process specifically involves washing once with deionized water, then once with ethanol, and then twice with deionized water.

[0019] Preferably, in step four, the drying conditions are: drying in an oven at 60 ℃ for 12 h.

[0020] Preferably, in step five, the sample is passed through a 200-mesh sieve.

[0021] The second objective of this invention is to provide aluminum-modified pomegranate peel biochar prepared based on the above-described method.

[0022] The third objective of this invention is to provide the application of the above-mentioned aluminum-modified pomegranate peel biochar as an adsorbent in water treatment for fluoride removal.

[0023] Beneficial effects:

[0024] 1. The raw materials for this invention are extremely widely available and inexpensive, primarily using pomegranate peels as the biochar substrate—these peels can be easily obtained from pomegranate processing plants, fruit farmers, and fruit shops, truly achieving the recycling of waste biomass resources. In practical applications, this material can not only efficiently remove fluoride pollutants from water bodies but also simultaneously solve the problem of rotting pollution caused by the indiscriminate dumping of pomegranate peels, perfectly achieving the dual environmental governance goal of "treating waste with waste," possessing outstanding social value, ecological benefits, and economic development potential.

[0025] 2. This invention achieves quantitative control and precise preparation of the adsorbent synthesis process. Based on response surface methodology (RSM), the preparation process parameters are optimized, and a mathematical model relating key factors to material properties is constructed, thereby enabling precise control of the synthesis conditions. This process not only significantly shortens the preparation cycle and reduces energy consumption, but also provides the flexibility to dynamically adjust material components according to the characteristics of the target water body, demonstrating high engineering adaptability.

[0026] 3. The synthetic route of this invention is based on the Lewis hard and soft acid-base theory and employs a one-step solvothermal method. Unlike conventional methods that rely on added organic acids, this technology fully utilizes the organic acid components contained in pomegranate peel itself, which undergo an in-situ complexation reaction with an added aluminum source, significantly reducing raw material costs while avoiding the environmental risks that may arise from the use of artificial organic acids, thus achieving clean production.

[0027] 4. The adsorbent material prepared by this invention exhibits excellent performance, with a particularly outstanding ability to remove fluoride ions, and is highly competitive in terms of cost. Experimental verification shows that adding only 1 g / L of adsorbent to polluted water achieves a fluoride removal rate of over 90%, a level sufficient to meet the practical needs of most conventional fluoride removal applications. Compared to traditional activated alumina defluorinators, the material advantages of this invention are even more pronounced: to achieve the same fluoride removal effect, the dosage of traditional activated alumina needs to be several times or even ten times that of this material, fully demonstrating the high efficiency and economy of this invention. Attached Figure Description

[0028] Figure 1 The adsorption isotherm of fluoride by unmodified pomegranate peel biochar PPP;

[0029] Figure 2 The adsorption isotherm of fluorides by PPP-Al in this invention;

[0030] Figure 3 The N2 adsorption-desorption isotherm of PPP-Al in this invention;

[0031] Figure 4 A comparison of the adsorption capacity of PPP-Al of the present invention with that of different modified materials. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to specific embodiments.

[0033] It should be noted that these embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Simple improvements to the method under the premise of the present invention are all within the scope of protection claimed by the present invention.

[0034] Unless otherwise specified, the raw materials used in the examples in this specification are all from common commercially available products. The dried pomegranate peel powder is obtained from pomegranates purchased from fruit stores. The outer peel is dried at 60°C for 12 hours, then pulverized, ground, and sieved through a 200-mesh sieve.

[0035] Example 1

[0036] This embodiment provides a method for preparing aluminum-modified pomegranate peel biochar, which specifically includes the following steps:

[0037] Step 1: Weigh 2 g of dried pomegranate peel powder (diameter < 0.2 mm) and 3 g of dried sodium aluminate powder according to the mass-volume ratio and place them in a beaker. Add 10 mL of 99% v / v ethanol and stir with a glass rod for 1 min to mix evenly.

[0038] Step 2: Transfer the stirred mixture obtained in Step 1 to a 50 mL reaction vessel and solvate at 150 °C for 120 min.

[0039] Step 3: After the solvothermal process is complete, wait for the reactor to cool naturally, then remove the sample from the reactor and centrifuge it at 5000 r / min for 5 min.

[0040] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then once with ethanol, and then twice with deionized water.

[0041] Step 5: Transfer the washed sample from step 4 to a clean petri dish and dry it in a 60 ℃ oven for 12 hours;

[0042] Step 6: Grind the dried product from step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified pomegranate peel biochar P01.

[0043] The above-mentioned aluminum-modified pomegranate peel biochar P01 (adsorbent) was applied to defluoridation in water treatment. Under the adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, pH 5, 25℃, and 24 h, the defluoridation rate of the sample reached 88.65%, and the experimental adsorption capacity was 9.017 mg / g.

[0044] Example 2

[0045] This embodiment provides a method for preparing aluminum-modified pomegranate peel biochar, which specifically includes the following steps:

[0046] Step 1: Weigh 3 g of dried pomegranate peel powder (diameter < 0.2 mm) and 2 g of dried sodium aluminate powder according to the mass-volume ratio and place them in a beaker. Add 15 mL of 99% v / v ethanol and stir with a glass rod for 1 min to mix evenly.

[0047] Step 2: Transfer the stirred mixture obtained in Step 1 to a 50 mL reaction vessel and solvothermal at 180 °C for 180 min;

[0048] Step 3: After the solvothermal process is complete, wait for the reactor to cool naturally, then remove the sample from the reactor and centrifuge it at 5000 r / min for 5 min.

[0049] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then once with ethanol, and then twice with deionized water.

[0050] Step 5: Transfer the washed sample from step 4 to a clean petri dish and dry it in a 60 ℃ oven for 12 hours;

[0051] Step 6: Grind the dried product from step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified pomegranate peel biochar PO2.

[0052] The above-mentioned aluminum-modified pomegranate peel biochar PO2 (adsorbent) was applied to defluoridation in water treatment. Under the adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, pH 5, 25℃, and 24 h, the defluoridation rate of the sample reached 83.43%, and the experimental adsorption capacity was 8.487 mg / g.

[0053] Example 3

[0054] This embodiment provides a method for preparing aluminum-modified pomegranate peel biochar, which specifically includes the following steps:

[0055] Step 1: Weigh 4 g of dried pomegranate peel powder (diameter < 0.2 mm) and 2 g of dried sodium aluminate powder according to the mass-volume ratio and place them in a beaker. Add 15 mL of 99% v / v ethanol and stir with a glass rod for 1 min to mix evenly.

[0056] Step 2: Transfer the stirred mixture obtained in Step 1 to a 50 mL reaction vessel and solvate at 150 °C for 120 min.

[0057] Step 3: After the solvothermal process is complete, wait for the reactor to cool naturally, then remove the sample from the reactor and centrifuge it at 5000 r / min for 5 min.

[0058] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then once with ethanol, and then twice with deionized water.

[0059] Step 5: Transfer the washed sample from step 4 to a clean petri dish and dry it in a 60 ℃ oven for 12 hours;

[0060] Step 6: Grind the dried product from step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified pomegranate peel biochar PO3.

[0061] The above-mentioned aluminum-modified pomegranate peel biochar PO3 (adsorbent) was applied to defluoridation in water treatment. Under the adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, pH 5, 25℃, and 24 h, the defluoridation rate of the sample reached 91.60%, and the experimental adsorption capacity was 9.172 mg / g.

[0062] Example 4

[0063] This embodiment provides a method for preparing aluminum-modified pomegranate peel biochar, which specifically includes the following steps:

[0064] Step 1: Weigh 1 g of dried pomegranate peel powder (diameter < 0.2 mm) and 4 g of dried sodium aluminate powder according to the mass-volume ratio and place them in a beaker. Add 10 mL of 99% v / v ethanol and stir with a glass rod for 1 min to mix evenly.

[0065] Step 2: Transfer the stirred mixture obtained in Step 1 to a 50 mL reaction vessel and solvate at 200 °C for 150 min.

[0066] Step 3: After the solvothermal process is complete, wait for the reactor to cool naturally, then remove the sample from the reactor and centrifuge it at 5000 r / min for 5 min.

[0067] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then once with ethanol, and then twice with deionized water.

[0068] Step 5: Transfer the washed sample from step 4 to a clean petri dish and dry it in a 60 ℃ oven for 12 hours;

[0069] Step 6: Grind the dried product from step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified pomegranate peel biochar PO4.

[0070] The above-mentioned aluminum-modified pomegranate peel biochar PO4 (adsorbent) was applied to defluoridation in water treatment. Under the adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, pH 5, 25℃, and 24 h, the defluoridation rate of the sample reached 85.04%, and the experimental adsorption capacity was 8.650 mg / g.

[0071] Example 5

[0072] This embodiment provides a method for preparing aluminum-modified pomegranate peel biochar, which specifically includes the following steps:

[0073] Step 1: Weigh 2 g of dried pomegranate peel powder (diameter < 0.2 mm) and 3 g of dried sodium aluminate powder according to the mass-volume ratio and place them in a beaker. Add 20 mL of 99% v / v ethanol and stir with a glass rod for 1 min to mix evenly.

[0074] Step 2: Transfer the stirred mixture obtained in Step 1 to a 50 mL reaction vessel and solvate at 180 °C for 120 min.

[0075] Step 3: After the solvothermal process is complete, wait for the reactor to cool naturally, then remove the sample from the reactor and centrifuge it at 5000 r / min for 5 min.

[0076] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then once with ethanol, and then twice with deionized water.

[0077] Step 5: Transfer the washed sample from step 4 to a clean petri dish and dry it in a 60 ℃ oven for 12 hours;

[0078] Step 6: Grind the dried product from step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified pomegranate peel biochar P05.

[0079] The above-mentioned aluminum-modified pomegranate peel biochar P05 (adsorbent) was applied to defluoridation in water treatment. Under the adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, pH 5, 25℃, and 24 h, the defluoridation rate of the sample reached 91.74%, and the experimental adsorption capacity was 9.332 mg / g.

[0080] Example 6

[0081] This embodiment provides a method for preparing aluminum-modified pomegranate peel biochar, which specifically includes the following steps:

[0082] Step 1: Weigh 3 g of dried pomegranate peel powder (diameter < 0.2 mm) and 1 g of dried sodium aluminate powder according to the mass-volume ratio, place them in a beaker, add 10 mL of 99% v / v ethanol, and stir with a glass rod for 1 min to mix evenly.

[0083] Step 2: Transfer the stirred mixture obtained in Step 1 to a 50 mL reaction vessel and solvothermal at 250 °C for 150 min.

[0084] Step 3: After the solvothermal process is complete, wait for the reactor to cool naturally, then remove the sample from the reactor and centrifuge it at 5000 r / min for 5 min.

[0085] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then once with ethanol, and then twice with deionized water.

[0086] Step 5: Transfer the washed sample from step 4 to a clean petri dish and dry it in a 60 ℃ oven for 12 hours;

[0087] Step 6: Grind the dried product from step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified pomegranate peel biochar P06.

[0088] The above-mentioned aluminum-modified pomegranate peel biochar PO6 (adsorbent) was applied to defluoridation in water treatment. Under the adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, pH 5, 25℃, and 24 h, the defluoridation rate of the sample reached 81.98%, and the experimental adsorption capacity was 8.339 mg / g.

[0089] Example 7

[0090] This embodiment provides a method for preparing aluminum-modified pomegranate peel biochar, which specifically includes the following steps:

[0091] Step 1: Weigh 2 g of dried pomegranate peel powder (diameter < 0.2 mm) and 3 g of dried sodium aluminate powder according to the mass-volume ratio and place them in a beaker. Add 15 mL of 99% v / v ethanol and stir with a glass rod for 1 min to mix evenly.

[0092] Step 2: Transfer the stirred mixture obtained in Step 1 to a 50 mL reaction vessel and solvate at 200 °C for 150 min.

[0093] Step 3: After the solvothermal process is complete, wait for the reactor to cool naturally, then remove the sample from the reactor and centrifuge it at 5000 r / min for 5 min.

[0094] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then once with ethanol, and then twice with deionized water.

[0095] Step 5: Transfer the washed sample from step 4 to a clean petri dish and dry it in a 60 ℃ oven for 12 hours;

[0096] Step 6: Grind the dried product from step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified pomegranate peel biochar P07.

[0097] The above-mentioned aluminum-modified pomegranate peel biochar P07 (adsorbent) was applied to defluoridation in water treatment. Under the adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, pH 5, 25℃, and 24 h, the defluoridation rate of the sample reached 96.68%, and the experimental adsorption capacity was 9.681 mg / g.

[0098] Example 8

[0099] This embodiment provides a method for preparing aluminum-modified pomegranate peel biochar, which specifically includes the following steps:

[0100] Step 1: Weigh 3 g of dried pomegranate peel powder (diameter < 0.2 mm) and 1 g of dried sodium aluminate powder according to the mass-volume ratio, place them in a beaker, add 15 mL of 99% v / v ethanol, and stir with a glass rod for 1 min to mix evenly.

[0101] Step 2: Transfer the stirred mixture obtained in Step 1 to a 50 mL reaction vessel and solvothermal at 150°C for 170 min.

[0102] Step 3: After the solvothermal process is complete, wait for the reactor to cool naturally, then remove the sample from the reactor and centrifuge it at 5000 r / min for 5 min.

[0103] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then once with ethanol, and then twice with deionized water.

[0104] Step 5: Transfer the washed sample from step 4 to a clean petri dish and dry it in a 60 ℃ oven for 12 hours;

[0105] Step 6: Grind the dried product from step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified pomegranate peel biochar P08.

[0106] The above-mentioned aluminum-modified pomegranate peel biochar P08 (adsorbent) was applied to defluoridation in water treatment. Under the adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, pH 5, 25℃, and 24 h, the defluoridation rate of the sample reached 87.80%, and the experimental adsorption capacity was 8.931 mg / g.

[0107] Comparative Example 1

[0108] This comparative example provides a method for preparing basic aluminum acetate-modified pomegranate peel biochar (Al-PPP), which specifically includes the following steps:

[0109] Step 1: Weigh 3 g of dried pomegranate peel powder (diameter < 0.2 mm) and 3 g of dried basic aluminum acetate powder according to the mass-volume ratio, place them in a beaker, add 15 mL of 99% v / v ethanol, and stir with a glass rod for 1 min to mix evenly.

[0110] Step 2: Transfer the stirred mixture obtained in Step 1 to a 50 mL reaction vessel and solvate at 150 °C for 120 min.

[0111] Step 3: After the solvothermal process is complete, wait for the reactor to cool naturally, then remove the sample from the reactor and centrifuge it at 5000 r / min for 5 min.

[0112] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then once with ethanol, and then twice with deionized water.

[0113] Step 5: Transfer the washed sample from step 4 to a clean petri dish and dry it in a 60 ℃ oven for 12 hours;

[0114] Step 6: Grind the dried product from step 5 and pass it through a 200-mesh sieve to obtain basic aluminum acetate modified pomegranate peel biochar.

[0115] The above-mentioned basic aluminum acetate modified pomegranate peel biochar (adsorbent) was applied in water treatment for fluoride removal. Under the adsorption conditions of an initial fluoride ion concentration of 10 mg / L, an adsorbent dosage of 1 g / L, pH of 5, 25℃, and 24 h, the fluoride removal rate was 41.40%, and the experimental adsorption capacity was 4.227 mg / g.

[0116] Comparative Example 2

[0117] This comparative example provides a method for preparing solvothermal pure pomegranate peel biochar (PPP), which specifically includes the following steps:

[0118] Step 1: Weigh 3 g of dried pomegranate peel powder (diameter < 0.2 mm) and place it in a beaker. Add 10 mL of 99% v / v ethanol and stir with a glass rod for 1 min to mix thoroughly.

[0119] Step 2: Transfer the stirred mixture obtained in Step 1 to a 50 mL reaction vessel and solvate at 150 °C for 120 min.

[0120] Step 3: After the solvothermal process is complete, wait for the reactor to cool naturally, then remove the sample from the reactor and centrifuge it at 5000 r / min for 5 min.

[0121] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then once with ethanol, and then twice with deionized water.

[0122] Step 5: Transfer the washed sample from step 4 to a clean petri dish and dry it in a 60 ℃ oven for 12 hours;

[0123] Step 6: Grind the dried product from step 5 and pass it through a 200-mesh sieve to obtain solvent-thermal pure pomegranate peel biochar.

[0124] The application of the above-mentioned solvothermal pure pomegranate peel biochar (adsorbent) in water treatment for fluoride removal, under the adsorption conditions of an initial fluoride ion concentration of 10 mg / L, an adsorbent dosage of 1 g / L, pH of 5, 25℃, and 24 h, showed a fluoride removal rate of 33.01% and an experimental adsorption capacity of only 3.358 mg / g.

[0125] Comparative Example 3

[0126] This comparative example provides a method for preparing sodium aluminate-modified pomegranate peel biochar (Al-PPP(b)) using a muffle furnace, specifically including the following steps:

[0127] Step 1: Weigh 5 g of dried pomegranate peel powder (diameter < 0.2 mm) and heat it in a muffle furnace under oxygen-deficient conditions at 10 °C for 1 min. −1 The mixture was heated to 400°C at a rate of [missing information] and kept at that temperature for 1 hour to obtain pomegranate peel biochar.

[0128] Step 2: Grind the obtained biochar into powder, take 4 g of dried pomegranate peel powder and mix it with 6 g of sodium aluminate and pour it into a beaker. Add 100 mL of deionized water to the beaker at a solid-liquid ratio of 1:10 (g / mL) and stir for 1 min.

[0129] Step 3: Transfer the beaker to a 70°C water bath and react for 120 min;

[0130] Step 4: Remove the sample and pour it into a centrifuge tube. Centrifuge at 5000 r / min for 5 min, and repeat 5 times.

[0131] Step 5: Transfer the centrifuged sample to a clean petri dish and dry it in a 60 ℃ oven for 12 h;

[0132] Step 6: Grind the dried product from step 5 and pass it through a 200-mesh sieve to obtain sodium aluminate muffle furnace modified pomegranate peel.

[0133] The above-mentioned sodium aluminate muffle furnace modified pomegranate peel (adsorbent) was used in water treatment for defluoridation. Under the adsorption conditions of an initial fluoride ion concentration of 10 mg / L, an adsorbent dosage of 1 g / L, pH of 5, 25℃, and 24 h, the defluoridation rate was 50.25%, and the experimental adsorption capacity was only 5.111 mg / g.

[0134] Comparative Example 4

[0135] This comparative example provides a method for preparing acid-modified pomegranate peel biochar (APP), which specifically includes the following steps:

[0136] Step 1: Mix 20 g of dried pomegranate peel powder with 2 wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and treat with constant temperature shaking at 25℃ for 24 h;

[0137] Step 2: Pour the solution sample obtained in Step 1 into a centrifuge tube, centrifuge at 5000 r / min for 5 min, and repeat 5 times.

[0138] Step 3: After centrifugation, transfer the sample to a clean petri dish and dry it in a 60 ℃ oven for 12 h.

[0139] Step 4: Grind the dried product from step 2 and pass it through a 200-mesh sieve. Take 4 g of dried pomegranate peel powder, add 10 mL of acetic acid, and stir with a glass rod for 1 min to mix evenly.

[0140] Step 5: Transfer the resulting stirred mixture to a 50 mL reaction vessel and solvate at 180 °C for 120 min.

[0141] Step 6: After the solvothermal process is complete, wait for the reactor to cool naturally, then remove the sample from the reactor and centrifuge it at 5000 r / min for 5 min.

[0142] Step 7: After centrifugation, remove the supernatant, wash the sample once with deionized water, then once with ethanol, and then twice with deionized water.

[0143] Step 8: Transfer the sample to a clean petri dish and dry it in a 60 ℃ oven for 12 h;

[0144] Step 9: Grind the dried product and pass it through a 200-mesh sieve to obtain acid-modified pomegranate peel.

[0145] The above-mentioned acid-modified pomegranate peel (adsorbent) was used in water treatment for fluoride removal. Under the adsorption conditions of an initial fluoride ion concentration of 10 mg / L, an adsorbent dosage of 1 g / L, pH of 5, 25℃, and 24 h, the fluoride removal rate was 24.69%, and the experimental adsorption capacity was 2.522 mg / g.

[0146] Comparative Example 5

[0147] Step 1: Weigh 2 g of dried pomegranate peel powder (diameter < 0.2 mm) and 3 g of dried sodium aluminate powder according to the mass-volume ratio and place them in a beaker. Add 15 mL of 99% v / v ethanol and stir with a glass rod for 1 min to mix evenly.

[0148] Step 2: Transfer the stirred mixture obtained in Step 1 to a 50 mL reaction vessel and solvate at 200 °C for 150 min.

[0149] Step 3: After the solvothermal process is complete, wait for the reactor to cool naturally, then remove the sample from the reactor and centrifuge it at 5000 r / min for 5 min.

[0150] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then once with ethanol, and then twice with deionized water.

[0151] Step 5: Transfer the washed sample from step 4 to a clean petri dish and dry it in a 60 ℃ oven for 12 hours;

[0152] Step 6: Grind the dried product from step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified pomegranate peel biochar.

[0153] The above-mentioned aluminum-modified pomegranate peel biochar (adsorbent) was applied to defluoridation in water treatment. Under the adsorption conditions of an initial fluoride ion concentration of 10 mg / L, an adsorbent dosage of 1 g / L, a pH of 1, a temperature of 25℃, and an adsorption time of 24 h, the defluoridation rate of the sample reached 67.21%, and the experimental adsorption capacity was 6.862 mg / g.

[0154] Comparative Example 6

[0155] Step 1: Weigh 2 g of dried pomegranate peel powder (diameter < 0.2 mm) and 3 g of dried sodium aluminate powder according to the mass-volume ratio and place them in a beaker. Add 15 mL of 99% v / v ethanol and stir with a glass rod for 1 min to mix evenly.

[0156] Step 2: Transfer the stirred mixture obtained in Step 1 to a 50 mL reaction vessel and solvate at 200 °C for 150 min.

[0157] Step 3: After the solvothermal process is complete, wait for the reactor to cool naturally, then remove the sample from the reactor and centrifuge it at 5000 r / min for 5 min.

[0158] Step 4: After centrifugation, remove the supernatant, wash the sample once with deionized water, then once with ethanol, and then twice with deionized water.

[0159] Step 5: Transfer the washed sample from step 4 to a clean petri dish and dry it in a 60 ℃ oven for 12 hours;

[0160] Step 6: Grind the dried product from step 5 and pass it through a 200-mesh sieve to obtain aluminum-modified pomegranate peel biochar.

[0161] The above-mentioned aluminum-modified pomegranate peel biochar (adsorbent) was applied to defluoridation in water treatment. Under the adsorption conditions of an initial fluoride ion concentration of 10 mg / L, an adsorbent dosage of 1 g / L, a pH of 8, a temperature of 25℃, and an adsorption time of 24 h, the defluoridation rate of the sample reached 57.27%, and the experimental adsorption capacity was 5.825 mg / g.

[0162] The prepared products were analyzed as follows:

[0163] Example 7 exhibited the best defluorination performance under the same test conditions, with a defluorination rate of 96.68% and an experimental adsorption capacity of 9.681 mg / g, significantly superior to other examples. Its preparation conditions were: pomegranate peel:sodium aluminate mass ratio of 2:3, solvothermal temperature of 200℃, time of 150 min, and ethanol dosage of 15 mL. This combination ensures efficient modification while also possessing good operational controllability and energy efficiency. Compared to other ratios (such as 1:4, 3:1, etc.), the synergistic effect between the aluminum source and the biochar matrix in Example 7 was most complete, with uniform distribution of aluminum active sites and well-developed pore structure, significantly improving the adsorption affinity and mass transfer efficiency of fluoride ions. Compared to various modification methods in the comparative examples (such as acid modification, modification with other aluminum sources, muffle furnace pyrolysis, etc.), the adsorption performance of Example 7 was improved by more than 90%, fully demonstrating the technical advantages of the one-step solvothermal method proposed in this invention in the preparation of aluminum-modified pomegranate peel biochar.

[0164] Figure 1 and 2The adsorption capacity of unmodified pomegranate peel biochar (PPP) and aluminum-modified pomegranate peel biochar (PPP-Al, using the product prepared in Example 7 as the sample) for fluoride ions was compared at different equilibrium concentrations (10, 20, 40, 60, 80, 100, 120, 140, 160, 180, 200 mg / L) (pH=5, dosage 1 g / L, initial fluoride ion concentration 10 mg / L, temperature 25 ℃, time 24 h). With increasing initial fluoride ion concentration, the adsorption capacity of both materials increased, but the adsorption capacity of PPP-Al was significantly higher than that of PPP, indicating that aluminum modification significantly improved the adsorption capacity of the material. Adsorption isotherms were used to evaluate the maximum adsorption capacity and adsorption affinity of the adsorbent. This figure shows that PPP-Al did not reach saturation at high concentrations and has good adsorption potential. The product of this invention demonstrates significant technological advancements due to its superior performance, including low dosage, low cost, high defluorination efficiency, wide pH range applicability, and large adsorption capacity (theoretical value up to 96.859 mg / g).

[0165] Figure 3 The specific surface area and pore structure characteristics of PPP-Al were demonstrated, as measured by nitrogen adsorption-desorption experiments. The isotherm type indicates a mesoporous structure, and the presence of a hysteresis loop in the medium-pressure region suggests abundant pores. Larger specific surface area and pore volume are more favorable for adsorbing the F- group. ⁻ The diffusion and adsorption of PPP-Al are facilitated. PPP-Al possesses a favorable pore structure, which contributes to improving the adsorption rate and capacity. This provides a physical structural basis for the synergistic effect of the biochar framework.

[0166] Figure 4 The adsorption capacity of various modified materials (including acid-modified, unmodified, and modified with other aluminum sources) for fluorine was compared under optimal pH conditions. The PPP-Al material of this invention showed the best performance and the highest adsorption capacity among all comparisons. This demonstrates that the adsorption performance of the material of this invention is superior to existing modified materials under various conditions.

[0167] In Example 7, the fluoride removal rates were 67.21% and 57.27% at pH 1 and 8, respectively. When the pH was 2 ≤ pH ≤ 7 and the dosage of PPP-Al was 1 g / L, the fluoride removal rate of this material remained above 80%.

[0168] The above comparison clearly demonstrates that the novel aluminum-modified pomegranate peel biochar (PPP-Al) of this invention successfully integrates the dual advantages of traditional aluminum-based adsorbents and biochar materials, achieving complementary and leapfrog performance and exhibiting a significant synergistic effect of "1+1≫2". In practical applications, this material effectively reduces water treatment costs and has outstanding social, environmental, and economic benefits.

[0169] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described with reference to preferred embodiments, those skilled in the art should understand that various changes in form and detail can be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A method of preparing an aluminum-modified Punica granatum char, characterized by, The steps are as follows: Step 1: Mix the dried pomegranate peel powder with sodium aluminate, then add ethanol solution and stir to mix evenly; Step 2: Perform a solvothermal reaction on the mixed solution after stirring in Step 1; Step 3: After the solvothermal process is complete, cool the sample, remove it and centrifuge it. After centrifugation, remove the supernatant and wash the sample. Step 4: Dry the washed sample; Step 5: After drying, grind the product and sieve it to obtain aluminum-modified pomegranate peel biochar.

2. A process for the preparation of an aluminum-modified Punica granatum char according to claim 1, characterized by, In step one, the mass ratio of dried pomegranate peel powder to sodium aluminate is 1-4:1-4, the concentration of the ethanol solution is 70-99% v / v, and the ratio of ethanol solution to dried pomegranate peel powder is 10-20 mL:1-4 g.

3. The method of claim 1, wherein the aluminum-modified Punica granatum charcoal is characterized by, In step one, the diameter of the dried pomegranate peel powder is <0.2 mm.

4. The method of claim 1, wherein the aluminum-modified Punica granatum charcoal is characterized by, In step two, the solvothermal reaction conditions are: solvothermal reaction at 100-250 ℃ in the reaction vessel for 120-180 min.

5. The method of claim 1, wherein the aluminum-modified Punica granatum charcoal is characterized by, In step three, the centrifugation conditions are: 5000 r / min for 3-5 min.

6. The method of claim 1, wherein the aluminum-modified Punica granatum charcoal is characterized by, In step three, the washing process specifically involves washing once with deionized water, then once with ethanol, and then twice with deionized water.

7. The method for preparing aluminum-modified pomegranate peel biochar according to claim 1, characterized in that, In step four, the drying conditions are: drying in an oven at 60 ℃ for 12 h.

8. The method for preparing aluminum-modified pomegranate peel biochar according to claim 1, characterized in that, In step five, the sample is passed through a 200-mesh sieve.

9. Aluminum-modified pomegranate peel biochar prepared according to the method described in any one of claims 1-8.

10. The application of the aluminum-modified pomegranate peel biochar according to claim 9 as an adsorbent in water treatment for defluorination.

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