Method for sterilization using pomelo peel biochar
By combining grapefruit peel biochar with sulfate, and utilizing its micron-sized macroporous structure and potential free radicals, the safety and efficiency issues of traditional sterilization methods are solved, providing a highly efficient and environmentally friendly sterilization solution.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGSU ACAD OF AGRI SCI
- Filing Date
- 2024-04-02
- Publication Date
- 2026-05-15
AI Technical Summary
Existing sterilization methods such as chlorination, ozone, and ultraviolet sterilization have safety issues or insufficient efficiency. Traditional biochar has limited adsorption of bacteria and may produce environmental toxicity. Therefore, there is a need to develop environmentally friendly and efficient sterilization methods.
The biochar was prepared by combining grapefruit peel biochar with sulfate and carbonizing the grapefruit peel at high temperature. Sulfate solution was added to water to kill pathogens. The micron-sized ultraporous structure and potential persistent free radicals of grapefruit peel biochar were used for sterilization.
It achieves highly efficient sterilization, with a bacterial inactivation rate of 99.8% within 1 hour and 99.97% within 2 hours. Moreover, the material cost is low, it is easy to recycle, and there is no secondary pollution, making it suitable for large-scale promotion.
Smart Images
Figure CN118239577B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of water treatment technology, specifically relating to a sterilization method using grapefruit peel biochar. Background Technology
[0002] Water is a precious natural resource indispensable for human production and daily life. The aquatic environment is highly susceptible to microbial contamination. In recent years, with the intensification of environmental pollution, the types of pathogenic microorganisms in water have increased and their resistance has strengthened, posing a significant threat to human health. Therefore, sterilization and disinfection treatment is essential in the purification of drinking water and wastewater.
[0003] Currently, commonly used sterilization methods include chlorination, ozone, and ultraviolet (UV) sterilization, but each has certain drawbacks. Chlorination is the most widely used disinfection technology, but the storage and transportation of chlorine gas is extremely dangerous. Furthermore, the disinfection process produces carcinogenic disinfection byproducts such as trihalomethanes and haloacetic acids, affecting water quality safety. Ozone is a strong oxidant, but it is extremely unstable in water, decays rapidly, and cannot maintain the residual sterilization capacity in water supply networks. Ozone production, equipment operation, and maintenance costs are high, making it unsuitable for large-scale water supply or wastewater disinfection. Ozone disinfection also easily generates disinfection byproducts such as bromate. UV sterilization is a physical sterilization technology that requires no chemical additives, does not pollute water quality, does not produce disinfection byproducts, and has a fast sterilization speed and high efficiency. Its main drawback is the lack of sustained sterilization; after the water leaves the reactor, some bacteria killed by UV light may revive and regenerate under photoreactivation mechanisms, compromising water safety. In addition, UV lamps and quartz sleeves are prone to scaling, requiring regular replacement, which is costly. The effectiveness of UV sterilization is also greatly affected by water turbidity and suspended solids. The limitations of traditional sterilization and disinfection methods necessitate the development of new sterilization methods.
[0004] Biochar is a low-cost adsorbent material with a high specific surface area. However, in general biochar, micropores (<2nm) account for more than 90% of the total pores, and more than 90% of the specific surface area is provided by micropores. Considering the actual disinfection scenario (taking bacteria as an example), bacteria are mostly in the micrometer range and obviously cannot enter the nanometer-sized pores of general biochar. Therefore, the adsorption of pathogenic microorganisms in the aquatic environment by general biochar is limited, and it cannot kill bacteria itself. Regulating the pore size of general biochar or modifying it by loading active components are the main strategies to improve the bactericidal ability of biochar. Chinese patent CN110550709A discloses a bactericidal biochar loaded with silver particles and its preparation method. This invention prepares biochar loaded with silver particles and silver monoxide by heating silver hydroxide in a biomass-ethanol system. This biochar can adsorb and remove bacteria in water in a short time and also has a bactericidal effect, with a kill rate of 50%. Chinese patent CN110074102A discloses a nano-silver biochar composite bactericidal material, its preparation method, and its application. This invention is a composite material prepared by hydrothermal synthesis of silver ions and biochar under the action of a reducing agent and a protecting agent. The biochar forms stable chemical bonds with nano-silver, slowing down the release of silver ions and greatly improving the antibacterial performance of the composite bactericidal material, resulting in high antibacterial rate, long antibacterial cycle, and long service life. Chinese patent CN114180702A discloses an advanced oxidative bactericidal method for activating permonosulfate with transition metal-supported biochar. It uses transition metal-supported biochar (Cu-BC) to activate permonosulfate (PMS), utilizing the generated hydroxyl radicals (·OH) and sulfate radicals (·SO4). - Biochar can kill pathogens in water. It is evident that loading with certain metal elements (such as Ag and Cu) can enhance the bactericidal ability of biochar; however, most of these metal elements are environmentally toxic, and their leakage into the aquatic environment can affect human health. Therefore, there is still a need to develop environmentally friendly bactericidal methods based on biochar. Summary of the Invention
[0005] To address the limitations of traditional disinfection technologies and achieve efficient disinfection of wastewater / drinking water, this invention provides a sterilization method using grapefruit peel biochar.
[0006] Specifically, the present invention is achieved through the following technical solutions:
[0007] (1) Select grapefruit peel, wash it, and cut it into pieces of about 1-10mm in size; more preferably, pieces of 5-10mm in size.
[0008] (2) Dry the granular grapefruit peel in an oven. Set the oven temperature to 60℃ and the drying time to 12-24 hours.
[0009] (3) The dried grapefruit peel granules were carbonized at high temperature in a tube furnace under nitrogen protection, and then cooled to obtain grapefruit peel biochar. The high temperature carbonization conditions were: heating to 500-700℃ at a rate of 10℃ / min, holding for 2 hours and then cooling naturally to obtain grapefruit peel biochar.
[0010] (4) Add the grapefruit peel biochar prepared in step (3) to the water containing bacteria, and add sulfate to kill the pathogens in the water.
[0011] The sulfate added in step (4) is preferably a soluble salt, such as sodium sulfate or potassium sulfate.
[0012] In the preferred step (4), the amount of grapefruit peel biochar added to the reaction solution is 1-4 g / L.
[0013] In step (4), the final concentration of sulfate ions in the reaction solution is preferably 10-50 mM (because natural water bodies contain a certain concentration of sulfate ions, the concentration of sulfate added is controlled according to the background content of sulfate ions, so that the final concentration of sulfate ions in the reaction solution is 10-50 mM), and more preferably 50 mM.
[0014] Compared with the prior art, the present invention has the following beneficial effects:
[0015] 1) The method provided by this invention uses grapefruit peel biochar and sulfate as bactericides. Grapefruit peel has a unique sponge structure, and the resulting grapefruit peel biochar has a large number of micron-sized macroporous structures adapted to the size of bacteria. Comparative experiments have shown that its surface contains persistent free radicals, which can effectively adsorb and kill bacteria (such as Escherichia coli). Furthermore, when grapefruit peel biochar and sulfate solution are mixed, they can dissolve chemical substances with bactericidal effects. The method of this invention has a significant bactericidal effect, achieving 2.7 log (99.8%) bacterial inactivation in 1 hour and 3.57 log (99.97%) bacterial inactivation in 2 hours.
[0016] 2) The grapefruit peel biochar material used in the method provided by this invention is inexpensive, simple to prepare, and the biochar is a granular solid that is easy to recycle. The sulfate used promotes the dissolution of bactericidal substances and is itself a common, non-toxic, and harmless salt. The overall operation is convenient, produces no secondary pollution, requires no additional energy input, and is suitable for large-scale promotion. Attached Figure Description
[0017] Figure 1 Physical image and scanning electron microscope image of pomelo peel biochar in Example 1 of this invention;
[0018] In the image, A is a photograph of grapefruit peel biochar, and B is a scanning electron microscope image of grapefruit peel biochar.
[0019] Figure 2 The effect of bacterial inactivation in grapefruit peel biochar and Na2SO4 solution in Example 1 of this invention is shown in the figure.
[0020] Figure 3 Comparative Example 1: The bacterial inactivation effect of grapefruit peel itself and grapefruit peel combined with Na2SO4 solution compared with that of Example 1;
[0021] Figure 4 Comparison of pore size distribution between grapefruit peel biochar and coconut shell biochar in Comparative Example 2 of this invention;
[0022] Figure 5 Comparison of the bacterial inactivation effects of coconut shell biochar and Na2SO4 solution in Comparative Example 2 with those in Example 1;
[0023] Figure 6 Comparison of the bacterial inactivation effect of grapefruit peel biochar in Comparative Example 3 with that in Example 1;
[0024] Figure 7 Comparison of the bacterial inactivation effect of the filtrate after mixing grapefruit peel biochar and Na2SO4 solution in Comparative Example 4 with that in Example 1;
[0025] Figure 8 The bacterial inactivation effect of grapefruit peel biochar and NaCl solution in Comparative Example 5 is compared with that in Example 1. Detailed Implementation
[0026] The present invention will be further described in detail with reference to the accompanying drawings and specific embodiments:
[0027] Example 1
[0028] (1) Select grapefruit peel (commercially available Baishangguo brand), wash it, and cut it into pieces about 5mm in size;
[0029] (2) The granular grapefruit peel was dried in an oven at a temperature of 60°C for 12 hours.
[0030] (3) The dried grapefruit peel granules were carbonized at high temperature in a tube furnace under nitrogen protection. After cooling, grapefruit peel biochar was obtained. The high-temperature carbonization conditions were: heating to 600℃ at 10℃ / min, holding at that temperature for 2 hours, and then naturally cooling to obtain grapefruit peel biochar. The physical image and scanning electron microscope image (Zeiss Gemini 300) are shown below. Figure 1 As shown in A and B;
[0031] (4) Add 250 mL of laboratory-preserved Escherichia coli (E. coli ATCC15597, conventional strain) suspension (initial concentration 10) to the water. 7CFU / mL, the strain and its preparation method are disclosed in the literature "LongYJ, Ni JR, WangZH. Subcellular mechanism of Escherichia coliinactivation during electrochemical disinfection with boron-doped diamond anode: A comparative study of three electrolytes. Water Research, 2015, 84: 198-206.") The laboratory-preserved Escherichia coli was cultured at 37℃ and 200rpm for 13h to reach the stable period. After centrifugation and washing with water, it was resuspended in ultrapure water to prepare a suspension. The grapefruit peel biochar prepared in step (3) (addition amount of 4g / L) and 50mM Na2SO4 solution were reacted under uniform stirring (stirrer speed 200rpm). Only 50mM Na2SO4 solution was added as a control. The sterilization results are as follows. Figure 2 As shown.
[0032] Depend on Figure 1 It can be seen that the grapefruit peel biochar prepared by this method is a black porous particle with a large number of micron-sized ultra-large pores distributed inside. Figure 2 It can be seen that Escherichia coli will not be inactivated in a simple 50mM Na2SO4 solution; however, under the action of grapefruit peel biochar and 50mM Na2SO4 solution, Escherichia coli is rapidly inactivated, with an inactivation rate of 2.7log (99.8%) after 1 hour and 3.57log (99.97%) after 2 hours.
[0033] Example 2
[0034] (1) Select grapefruit peel (same as in Example 1), wash it, and cut it into pieces about 5mm in size;
[0035] (2) The granular grapefruit peel was dried in an oven at a temperature of 60°C for 12 hours.
[0036] (3) The dried grapefruit peel granules were carbonized at high temperature in a tube furnace under nitrogen protection, and then cooled to obtain grapefruit peel biochar. The high temperature carbonization conditions were: heating to 500℃ at 10℃ / min, holding for 2 hours and then cooling naturally to obtain grapefruit peel biochar.
[0037] (4) Add 250 mL of E. coli (ATCC15597) suspension to the water (initial concentration is 10). 7 The reaction was carried out with CFU / mL, grapefruit peel biochar prepared in step (3) (addition amount of 1g / L) and 50mM Na2SO4 solution under uniform stirring.
[0038] Escherichia coli was rapidly inactivated by 1 g / L grapefruit peel biochar and 50 mM Na2SO4 solution, with an inactivation rate of 0.56 log (73%) after 1 hour and 1.05 log (91%) after 2 hours.
[0039] Example 3
[0040] (1) Select grapefruit peel (same as in Example 1), wash it, and cut it into pieces about 5mm in size;
[0041] (2) The granular grapefruit peel was dried in an oven at a temperature of 60°C for 12 hours.
[0042] (3) The dried grapefruit peel granules were carbonized at high temperature in a tube furnace under nitrogen protection, and then cooled to obtain grapefruit peel biochar. The high temperature carbonization conditions were: heating to 700℃ at 10℃ / min, holding for 2 hours and then cooling naturally to obtain grapefruit peel biochar.
[0043] (4) Add 250 mL of E. coli (ATCC15597) suspension to the water (initial concentration is 10). 7 The reaction was carried out with CFU / mL, grapefruit peel biochar prepared in step (3) (addition amount of 4 g / L) and 10 mM Na2SO4 solution under uniform stirring.
[0044] Escherichia coli was rapidly inactivated by 4 g / L grapefruit peel biochar and 10 mM Na2SO4 solution, with an inactivation rate of 0.47 log (67%) after 1 hour and 0.50 log (68%) after 2 hours.
[0045] Comparative Example 1
[0046] (1) Select grapefruit peel (same as in Example 1), wash it, and cut it into pieces about 5mm in size;
[0047] (2) The granular grapefruit peel was dried in an oven at a temperature of 60°C for 12 hours to obtain dried grapefruit peel.
[0048] (3) Add 250 mL of E. coli (ATCC15597) suspension to the water (initial concentration is 10). 7 The reaction was carried out with CFU / mL), the dried granular grapefruit peel obtained in step (2) (addition amount of 4 g / L), and 50 mM Na2SO4 solution (with a control without sodium sulfate added). The sterilization results were compared with those in Example 1. Figure 3 As shown.
[0049] Depend on Figure 3It can be seen that in this comparative example, direct contact between grapefruit peel and E. coli suspension has no bactericidal effect. Even with the addition of Na2SO4 solution to the grapefruit peel, there is essentially no bactericidal effect. However, in Comparative Example 1, under the action of grapefruit peel biochar and 50mM Na2SO4 solution, E. coli was rapidly inactivated, with an inactivation rate of 2.7 log in 1 hour and 3.57 log in 2 hours. Therefore, in the method provided by this invention using grapefruit peel biochar and Na2SO4 solution as bactericides, the role of biochar is irreplaceable.
[0050] Comparative Example 2
[0051] (1) Dry the coconut shells in an oven. Set the oven temperature to 60℃ and the drying time to 12 hours.
[0052] (2) The dried coconut shells were carbonized at high temperature in a tube furnace under nitrogen protection, and then cooled to obtain coconut shell biochar. The high temperature carbonization conditions were: heating to 600℃ at 10℃ / min, holding for 2 hours and then cooling naturally to obtain coconut shell biochar.
[0053] The pore size distribution of the coconut shell biochar in the comparative example and the grapefruit peel biochar obtained in Example 1 was determined by mercury porosimetry using a Micromeritics Autopore 9500. The results are as follows. Figure 4 As shown.
[0054] (3) Add 250 mL of E. coli suspension to the water (initial concentration is 10). 7 The reaction was carried out with CFU / mL, coconut shell biochar prepared in step (2) (addition amount of 4 g / L), or coconut shell biochar prepared in step (2) (addition amount of 4 g / L) and 50 mM Na2SO4 solution (with a control without sodium sulfate added). The reaction was carried out under uniform stirring. The sterilization results were compared with those of Example 1. The results are as follows: Figure 5 As shown.
[0055] Depend on Figure 4 It can be seen that the pore size of grapefruit peel biochar is mainly concentrated in the range of 40nm-60μm in diameter, with a total pore volume of 5.07cm³. 3 / g; while coconut shell biochar has extremely underdeveloped pores in the macroporous range, with the main pores being micropores of <2nm, and a total pore volume of 0.195cm³. 3 / g.
[0056] Depend on Figure 5It is evident that neither adding coconut shell biochar to the E. coli suspension, nor adding coconut shell biochar and Na2SO4 solution, had a bactericidal effect on the bacteria (E. coli). In contrast, in Comparative Example 1, under the action of grapefruit peel biochar and 50mM Na2SO4 solution, E. coli was rapidly inactivated, with an inactivation rate of 2.7 log (99.8%) after 1 hour and 3.57 log (99.97%) after 2 hours. This demonstrates that the grapefruit peel biochar provided in this invention plays a crucial role in the bactericidal process. Analysis of the pore size distribution and scanning electron microscopy results of the grapefruit peel biochar suggests that its micron-sized macroporous structure is well-suited to the size of bacteria, enabling it to effectively adsorb them. Furthermore, it can be inferred that the surface of the grapefruit peel biochar may contain persistent free radicals, which can effectively kill the bacteria adsorbed onto its surface.
[0057] Comparative Example 3
[0058] (1) Select grapefruit peel (same as in Example 1), wash it, and cut it into pieces about 5mm in size;
[0059] (2) The granular grapefruit peel was dried in an oven at a temperature of 60°C for 12 hours.
[0060] (3) The dried grapefruit peel granules were carbonized at high temperature in a tube furnace under nitrogen protection, and then cooled to obtain grapefruit peel biochar. The high temperature carbonization conditions were: heating to 600℃ at 10℃ / min, holding for 2 hours and then cooling naturally to obtain grapefruit peel biochar.
[0061] (4) Add 250 mL of E. coli suspension to the water (initial concentration is 10). 7 The grapefruit peel biochar prepared in step (3) (CFU / mL) and the amount added were 4 g / L. The reaction was carried out under uniform stirring. The sterilization results were compared with those in Example 1. Figure 6 As shown.
[0062] Depend on Figure 6 It can be seen that in this comparative example, with only grapefruit peel biochar and no Na2SO4, the inactivation rate of E. coli was significantly slower, with an inactivation rate of 0.52 log in 1 hour and 1.10 log in 2 hours. In contrast, in Example 1, under the action of grapefruit peel biochar and 50 mM Na2SO4 solution, E. coli was rapidly inactivated, with an inactivation rate of 2.7 log in 1 hour and 3.57 log in 2 hours. Therefore, it is speculated that in addition to the adsorption and bactericidal effects of grapefruit peel biochar, the mixture of grapefruit peel biochar and Na2SO4 solution may dissolve bactericidal chemical substances.
[0063] Comparative Example 4
[0064] (1) Select grapefruit peel (same as in Example 1), wash it, and cut it into pieces about 5mm in size;
[0065] (2) The granular grapefruit peel was dried in an oven at a temperature of 60°C for 12 hours.
[0066] (3) The dried grapefruit peel granules were carbonized at high temperature in a tube furnace under nitrogen protection, and then cooled to obtain grapefruit peel biochar. The high temperature carbonization conditions were: heating to 600℃ at 10℃ / min, holding for 2 hours and then cooling naturally to obtain grapefruit peel biochar.
[0067] (4) Add the grapefruit peel biochar prepared in step (3) (addition amount of 4 g / L) and 250 mL of 50 mM Na2SO4 solution to the water, stir at a constant speed, and filter the liquid after 2 hours. Add Escherichia coli suspension (initial concentration of 10) to the filtrate. 7 The reaction was carried out under uniform stirring (CFU / mL), and the sterilization results were compared with those of Example 1. Figure 7 As shown.
[0068] Depend on Figure 7 It can be seen that although the bactericidal effect is different from that in Example 1 (rapid inactivation of E. coli, 2.7 log inactivation in 1 hour, 3.57 log inactivation in 2 hours), the filtrate after mixing grapefruit peel biochar and Na2SO4 solution in this comparative example still has a certain bactericidal effect, with 0.29 log (49%) inactivation in 1 hour and 0.55 log (72%) inactivation in 2 hours. Therefore, in addition to the adsorption and bactericidal effects of grapefruit peel biochar, the mixture of grapefruit peel biochar and Na2SO4 solution can indeed dissolve chemical substances with bactericidal effects.
[0069] Comparative Example 5
[0070] (1) Select grapefruit peel (same as in Example 1), wash it, and cut it into pieces about 5mm in size;
[0071] (2) The granular grapefruit peel was dried in an oven at a temperature of 60°C for 12 hours.
[0072] (3) The dried grapefruit peel granules were carbonized at high temperature in a tube furnace under nitrogen protection, and then cooled to obtain grapefruit peel biochar. The high temperature carbonization conditions were: heating to 600℃ at 10℃ / min, holding for 2 hours and then cooling naturally.
[0073] (4) Add 250 mL of E. coli suspension to the water (initial concentration is 10). 7The biochar from grapefruit peel (CFU / mL), prepared in step (3) (addition amount of 4 g / L), and a 150 mM NaCl solution with an ionic strength equivalent to 50 mM Na2SO4 solution were reacted under uniform stirring. The sterilization results were compared with those in Example 1, and the results are as follows: Figure 8 As shown.
[0074] Depend on Figure 8 It can be seen that in Example 1, under the action of grapefruit peel biochar and 50mM Na2SO4 solution, E. coli was rapidly inactivated, with an inactivation rate of 2.7 log in 1 hour and 3.57 log in 2 hours. However, in this comparative example, under the action of grapefruit peel biochar and NaCl solution of equivalent ionic strength, the inactivation rate of E. coli was significantly slower, with an inactivation rate of 0.61 log in 1 hour and 0.68 log in 2 hours. This demonstrates that grapefruit peel biochar can dissolve more and stronger bactericidal substances in Na2SO4 solution.
[0075] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention are within the scope of protection claimed by the present invention.
Claims
1. A sterilization method using grapefruit peel biochar, characterized in that: Grapefruit peel biochar and sulfate were added to the water to kill bacteria, specifically Escherichia coli; the dosage of the grapefruit peel biochar was 1-4 g / L; after addition, the final concentration of sulfate ions in the water was 10-50 mM. The sulfate is sodium sulfate; The grapefruit peel biochar is prepared by the following method: (1) Dry grapefruit peel particles with a size of 1-10 mm to obtain dried grapefruit peel particles; (2) Place the dried pomelo peel granules into a tube furnace and carbonize them at high temperature under nitrogen protection. After cooling, the pomelo peel biochar is obtained. The high temperature carbonization refers to heating to 500-700°C at a rate of 10°C / min, holding the temperature for 2 hours, and then cooling down naturally.
2. The sterilization method using grapefruit peel biochar according to claim 1, characterized in that, The drying mentioned in step (1) refers to drying at 60°C.