Camellia oleifera shell-based composite flocculant and preparation method thereof

Abstract

The invention relates to the field of biological resource utilization, in particular to an oil tea fruit shell-based composite flocculant and a preparation method thereof, and on the whole, oil tea fruit shells are firstly subjected to dipping treatment, and then are subjected to carbonization, enzymolysis modification and microbial attachment. Wherein the first impregnation can reduce the ash content of the system and improve the load performance of microorganisms, so as to improve the overall flocculation effect.

Description

Technical Field

[0001] This application belongs to the field of biological resource utilization and relates to a Camellia oleifera fruit shell-based composite flocculant and its preparation method. Background Technology

[0002] Camellia oleifera fruit shells are a major byproduct of the camellia oil industry, accounting for 50-60% of the fruit's weight. China generates millions of tons of camellia oleifera fruit shell waste annually, the vast majority of which is incinerated or discarded, causing environmental pollution and resource waste. Camellia oleifera fruit shells possess a natural porous structure. Through chemical modification or high-temperature pyrolysis, they can be dehydrated to obtain activated carbon materials. These materials have advantages such as looseness, porosity, and high porosity, and are often used in research on adsorption and energy storage.

[0003] In practical applications, we found that camellia fruit shells produce less ash during carbonization compared to other bio-based materials such as corn cobs and straw, while also exhibiting higher particle strength. Due to its low ash content and high strength, it has certain advantages in preparing flocculants loaded with active biological materials. Summary of the Invention

[0004] Based on the above problems, the purpose of this application is to reduce the fly ash rate of the flocculation system and improve the strength and durability of the flocculant when preparing Camellia oleifera fruit shell into a high-porosity flocculant.

[0005] This application provides a method for preparing a Camellia oleifera fruit shell-based composite flocculant, comprising the following steps: S1. After crushing the camellia fruit shell, soak it in a potassium carbonate or sodium carbonate solution. S2. The soaked camellia fruit shells are heated in an oxygen-free environment at a temperature not exceeding 350°C to prepare biochar. S3. Enzymatically modify the biochar to obtain modified biochar; S4. A composite flocculant is obtained by attaching modified biochar to microorganisms.

[0006] In the above scheme, the biochar is first treated with potassium carbonate or sodium carbonate solution, and then prepared into a flocculant through heating carbonization, enzymatic modification, and microbial attachment. This method can improve the adhesion performance of microorganisms and reduce the ash generated in the flocculation system. Soaking in potassium carbonate or sodium carbonate solution reduces ash generation in the system. This step removes soluble ash and impurities, and also dissolves some of the surface wax structure. During subsequent sintering, this improves the overall strength and load-bearing capacity of the biochar and reduces fly ash clogging of micropores.

[0007] After calcination, enzymatic hydrolysis is performed to further remove residual hydrophobic natural waxes from the biochar. Since the sintering temperature does not exceed 350℃, some biowax remains in the flocculation system along with the biochar. This biowax can undergo partial hydrolysis under enzymatic action, forming functional groups such as hydroxyl groups, thus providing better coordination properties and further improving the adsorption performance of the flocculation system for heavy metals. Simultaneously, the enzymatically hydrolyzed biochar also has better biocapacity, allowing for better adsorption of microorganisms in the system, thereby improving the removal rate of pollutants.

[0008] In summary, the above-mentioned methods comprehensively improve the strength and adhesion properties of biochar prepared from Camellia oleifera fruit shells. Impregnation with potassium carbonate or sodium carbonate solutions mitigates the problem of excessive ash content in the system; simultaneously, enzymatic hydrolysis enhances the system's adsorption capacity for heavy metals and its adhesion to microorganisms, thus providing a superior Camellia oleifera fruit shell-based composite flocculant.

[0009] Preferably, in step S1, the aqueous solution contains the following components according to their mass concentration: Potassium carbonate or sodium carbonate solution 0.5-2.0%; Modified starch 0.5-2.0%.

[0010] In the above system, the addition of a certain amount of modified starch allows the starch to partially fill the camellia fruit shell system. During the subsequent sintering process, the starch binds the camellia fruit shell, which improves the overall strength on the one hand, and adjusts the pore structure by modifying the starch, thereby improving the adsorption performance of the system. At the same time, the starch improves the pores, which has the effect of supporting the pores and preventing the pores from closing during subsequent heating, thus improving the overall flocculation effect.

[0011] More preferably, the aqueous solution further contains 0.1 to 0.5% tartaric acid or soluble tartrate.

[0012] In the above scheme, tartaric acid or tartrates can be adsorbed into the system, further providing chelation and adsorption sites, improving the system's adsorption performance for heavy metals. Simultaneously, tartaric acid can form a buffer-complex system with potassium carbonate or sodium carbonate solutions, acting more gently on the camellia oleifera fruit shell raw material. Furthermore, tartaric acid or tartrates can improve the subsequent enzymatic hydrolysis process. Utilizing the strong chelating properties of tartaric acid, the hydrolysis effect of the enzyme system on biochar is enhanced, thus providing better adsorption.

[0013] More preferably, before soaking in potassium carbonate or sodium carbonate solution in step S1, an acid pretreatment step is included, specifically as follows: the crushed camellia fruit shell is added to a 0.01-0.1% hydrochloric acid solution and heated at a temperature of 60-80°C for 5-20 minutes, and then washed until neutral.

[0014] In the above scheme, acid hydrolysis can dissolve and remove some inorganic minerals in the system, further reducing the ash content of the system from the source, so as to avoid the generation of high melting point inert substances in subsequent processes, which would cause pore blockage.

[0015] More preferably, the modified starch is acetate starch.

[0016] In the above scheme, the modified starch used is further specified as acetate starch, because it has better water-cooled dispersibility and good film-forming properties. It can be uniformly attached to the surface of the camellia fruit shell, better control the pyrolysis behavior in the subsequent carbonization process, thereby improving the uniformity of the pores and improving the loading effect on microorganisms.

[0017] Preferably, in step S2, the heating temperature is 250–300°C and the heating time is 4–6 hours.

[0018] In the above scheme, a relatively low temperature is used for heating and carbonization. On the one hand, this helps to maintain the oxygen-containing organic structure in the camellia fruit shell, which is conducive to the formation of a biochar skeleton with more active groups, providing more anchor points for subsequent chemical modification and microbial attachment. At the same time, this temperature range also helps to maintain the mechanical strength of the biochar structure and avoid pore collapse caused by excessive temperature.

[0019] Preferably, in step S3, the mass fraction of the enzyme system is 2-10% of the biochar mass, and the enzyme system contains tanninase and esterase, with a mass ratio of tanninase to esterase of (1-10):1.

[0020] In the above scheme, tanninase and esterase are combined. Tanninase can hydrolyze tannins (tannins) and waxy esters on the surface of camellia fruit shell, which can maximize the exposure of the internal pore structure of biochar and active sites such as hydroxyl and carboxyl groups. On the one hand, it improves the hydrophilicity of biochar, enabling it to achieve better dispersion and flocculation effects, and on the other hand, it provides more microbial adhesion performance.

[0021] Preferably, in step S3, an anionic surfactant with a biochar mass fraction of 1-10% is also added.

[0022] In the above scheme, the introduction of anionic surfactants during the enzymatic hydrolysis process can significantly reduce the interfacial tension of the enzymatic hydrolysis system, improve the permeability of the enzymatic hydrolysate to the micropores of biochar, and enhance the reaction rate within the biochar pores. On the other hand, it can also improve the dispersibility of biochar and prevent it from agglomerating.

[0023] Preferably, in step S4, the microorganism is Bacillus mucilaginosus, and the inoculation amount is 0.05-0.2%.

[0024] In the above scheme, Bacillus mucilaginosus is a relatively safe and efficient flocculant strain that is environmentally friendly and has a high loading efficiency.

[0025] In summary, this application provides a Camellia oleifera fruit shell-based composite flocculant and its preparation method. By first impregnating the Camellia oleifera fruit shell, and then subjecting it to carbonization, enzymatic modification, and microbial adhesion, a high-performance Camellia oleifera fruit shell-based composite flocculant is finally obtained. Detailed Implementation

[0026] The following specific implementation methods will further illustrate the solution in this application.

[0027] In the following examples, a specific batch of Camellia oleifera fruit shells was used to prepare flocculants, and the results were tested in a simulated wastewater environment with a turbidity ≥50 NTU.

[0028] Example 1: This example includes a method for preparing a camellia oleifera fruit shell-based composite flocculant, specifically comprising the following steps: S1. After simple impurity removal, the camellia fruit shells are crushed and passed through a 60-mesh sieve. They are then added to a 0.5% hydrochloric acid solution at a solid-liquid ratio of 1:4, heated to 60℃, and treated for 20 minutes. Afterward, they are washed with water until neutral. The shells are then placed in a mixed solution containing 1% potassium carbonate, 1% starch acetate (degree of substitution 1.8%), and 0.5% potassium tartrate. The camellia fruit shells are soaked at 60℃ for 4 hours at a solid-liquid ratio of 1:4. After completion, the solids are filtered and washed until neutral.

[0029] S2. The camellia fruit shells treated in step S1 are heated in a muffle furnace at 300°C in an oxygen-free state for 6 hours to obtain camellia fruit shell biochar.

[0030] S3. Prepare an acidic enzymatic hydrolysate (Tris buffer solution, pH 5.5) containing 0.5% tanninase (CAS: 9025-71-2) + 0.5% esterase (CAS: 9016-18-6) by mass fraction. Add the camellia fruit shell biochar at a solid-liquid ratio of 1:4, and simultaneously add 5% sodium lauryl sulfate, an anionic surfactant, to the biochar. React at 60℃ for 4 hours, and obtain modified camellia fruit shell biochar after filtration.

[0031] S4. Using Bacillus mucilaginosus as the floc-producing microorganism, Bacillus mucilaginosus was inoculated into a liquid culture medium with a composition of 2.0% sucrose, 0.5% urea, 0.1% Na2HPO4, pH 4.5, and an inoculation amount of 0.1%. Modified Camellia oleifera fruit shell biochar was added to the medium at a solid-liquid ratio of 1:4, and cultured at 30℃ for 72 hours. After centrifugation, the solid portion was dried at room temperature to obtain the finished Camellia oleifera fruit shell-based composite flocculant.

[0032] Examples 2-10: The formulation of the "potassium carbonate-acetic acid starch-potassium tartrate" soaking solution after acid washing in step S1 was adjusted; in addition, we also adjusted the acetate starch and selected a variety of modified starches, as shown in Table 1.

[0033] Table 1: Example groups of different soaking solution formulations and modified starch Examples 11-20: Several details in steps S1, S2, S3, and S4 were adjusted in the design. The differences from Example 1 are shown in Table 2.

[0034] Table 2: Example groups of different processing methods The above embodiments were evaluated through the following experiments.

[0035] 1. Flocculation effect: Simulated wastewater with turbidity of 50 NTU, copper content of 50 mg / L, and COD of 100 mg / L was prepared by using kaolin, yeast extract powder, and copper sulfate. 0.1 g / kg of the camellia oleifera shell-based composite flocculant from the above embodiment was added, and the suspended solids removal rate, COD removal rate, copper ion removal rate, and settling time were evaluated after 24 hours.

[0036] 2. Mechanical properties: After sintering in step S2, dust passing through 200 mesh is collected in the system by a vibrating screen, and the dust content after sintering is measured.

[0037] The experimental results of the above experiments are shown in Table 3.

[0038] Table 3. Experimental results of Examples 1-20 In the table above, " / " indicates that no measurement was performed.

[0039] The above experimental data show that, in this application, soaking the camellia fruit shell in potassium carbonate solution has a significant promoting effect on ash removal. Compared with Example 2, Example 1 not only has less ash but also has a significant advantage in flocculation effect. In Example 5, the excessive addition of potassium carbonate actually increased the ash content, indicating that a high amount of potassium carbonate solution leads to a decrease in the overall strength of the system during the soaking process, resulting in an increase in ash content. Compared with Example 12, it can be seen that the acid washing pretreatment step before soaking can further reduce the ash content of the system. At the same time, the active groups generated by acid washing can significantly improve the flocculation effect of the system, making the system more effective against Cu. 2+ It significantly improves the removal effect and the reduction effect on COD.

[0040] Based on the above, comparing Examples 1 and 3, it can be seen that adding starch acetate during the impregnation process can effectively improve the flocculation performance of the system, resulting in a higher suspended solids removal rate, shorter settling time, and improved COD and Cu removal rates. 2+ The removal rate was also significantly improved, indicating that it had a significant effect on improving the pore structure of biochar. However, excessive addition (Example 6) led to an increase in the ash content of the system. This may be because the excess starch could not be fully adsorbed into the pores of the system, and it also caused some pore blockage. Further comparison with Examples 8-10 showed that the adhesion of ordinary corn starch in the system was significantly worse, which led to a significant increase in ash content. Oxidized starch, regardless of the amount used, had a weaker overall adsorption effect than acetate starch. This may be because acetate starch has better dispersibility in the system and is more likely to bind into the pores.

[0041] In Examples 12 and 13, it can be seen that using tanninase alone or esterase alone, compared to using them together, significantly reduces the effectiveness even with the same total enzyme concentration. This may be because, in the absence of tanninase, the tannic acid in the system significantly weakens the growth and adhesion of microorganisms, leading to a significant decrease in COD degradation rate; while in the absence of esterase, the system contains a waxy structure that is not fully carbonized at low temperatures, resulting in a significant decrease in the system's adsorption performance.

[0042] In Examples 14-19, the amount and type of anionic surfactant were adjusted. The results showed that without the addition of anionic surfactant, sedimentation performance significantly decreased, the removal rate of suspended solids significantly decreased, and sedimentation time significantly increased. (The text then abruptly shifts to a completely unrelated topic: "and the effects on COD and Cu...") 2+ The removal rate also decreased slightly. Meanwhile, various anionic surfactants had similar flocculation-promoting effects, while nonionic or cationic surfactants would cause Cu... 2+The sedimentation and adsorption properties are somewhat weakened.

[0043] In Example 20, the flocculating microorganism Bacillus licheniformis showed a slight decrease in sedimentation and adsorption performance compared to Bacillus mucilaginosus.

[0044] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing a Camellia oleifera fruit shell-based composite flocculant, characterized in that, Includes the following steps: S1. After crushing the camellia fruit shell, heat and soak it in a potassium carbonate or sodium carbonate solution. S2. The soaked camellia fruit shells are heated in an oxygen-free environment at a temperature not exceeding 350°C to produce biochar. S3. Enzymatically modify the biochar to obtain modified biochar; S4. A composite flocculant is obtained by attaching modified biochar to microorganisms.

2. The preparation method of the camellia oleifera fruit shell-based composite flocculant according to claim 1, characterized in that, In step S1, the aqueous solution contains the following components by mass concentration: 0.5-2% sodium carbonate or potassium carbonate; 0.5-2% modified starch.

3. The preparation method of the camellia oleifera fruit shell-based composite flocculant according to claim 2, characterized in that, The aqueous solution also contains tartaric acid or tartrate at a mass concentration of 0.1 to 0.5%.

4. The preparation method of the camellia oleifera fruit shell-based composite flocculant according to claim 2, characterized in that, The modified starch is preferably acetate starch.

5. The preparation method of the camellia oleifera fruit shell-based composite flocculant according to claim 1, characterized in that, In step S3, the enzyme system comprises tanninase and esterase, wherein the mass ratio of tanninase to esterase is (1-10):1; the mass of the enzyme system is 2-10% of the mass of biochar.

6. The method for preparing a Camellia oleifera fruit shell-based composite flocculant according to claim 1, characterized in that, In step S3, an anionic surfactant of 1-10% by weight of biochar is also added.

7. The method for preparing a Camellia oleifera fruit shell-based composite flocculant according to claim 1, characterized in that, In step S2, the heating temperature is 250–300°C, and the heating time is 4–6 hours.

8. The preparation method of the camellia oleifera fruit shell-based composite flocculant according to claim 1, characterized in that, Before soaking in sodium carbonate or potassium carbonate aqueous solution in step S1, an acid pretreatment step is also included, as follows: the crushed camellia fruit shell is added to a 0.01-0.1% hydrochloric acid solution and heated at a temperature of 60-80°C for 5-20 minutes, and then washed until neutral.

9. The method for preparing a Camellia oleifera fruit shell-based composite flocculant according to claim 1, characterized in that, In step S4, the microorganism is Bacillus mucilaginosus, and the inoculation amount is 0.05-0.2%.

10. The camellia oleifera fruit shell-based composite flocculant prepared by the preparation method according to any one of claims 1 to 9.

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