Modified corncob, and preparation method and application thereof

Abstract

The present application belongs to the field of environmental remediation and biotechnology, and discloses a modified corncob, a preparation method and application thereof. The present application uses a mixed solution of NaOH and acetyl bromide to modify the corncob. The modification process removes lignin in the corncob through alkalization pretreatment, improves the porosity and specific surface area of the corncob, and simultaneously uses acetyl bromide treatment to enhance the adsorption capacity and immobilization efficiency of the corncob to microalgae. The modified corncob can cross-link with exogenous polymers (EPS) secreted by microalgae, so that the microalgae can stably adhere and survive for a long time, and the application effect of the microalgae in wastewater treatment and ecological remediation is improved. The present application provides an efficient and sustainable biological immobilization technology, and provides a new technical path for water pollution control and ecological remediation, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of environmental remediation and biotechnology, specifically relating to a modified corn cob, its preparation method, and its application. Background Technology

[0002] Sustainable development has become an important direction in modern scientific research, especially in addressing global challenges such as environmental pollution, resource scarcity, and climate change. Microalgae immobilization technology, due to its wide application in wastewater treatment, biofuel production, and bioresource recycling, has become a crucial strategy for environmental governance and sustainable biomanufacturing. Microalgae, as a type of photosynthetic autotrophic microorganism, can effectively immobilize atmospheric carbon dioxide and nitrogen while secreting extracellular polymeric substances (EPS), promoting pollutant adsorption and biofilm formation. Therefore, they have significant application value in pollution remediation and ecological engineering.

[0003] The efficiency of microalgae immobilization systems largely depends on the performance and surface properties of the immobilization carrier. Currently, carrier materials for immobilized microalgae mainly include synthetic polymers, inorganic materials, and natural biomass. Among these, lignocellulose biomass has become an ideal immobilization matrix due to its wide availability, low cost, and environmental friendliness. Corn cobs, as an agricultural byproduct, are rich in cellulose and hemicellulose, and possess good mechanical stability and biodegradability, making them an excellent candidate material for immobilized microalgae. Compared to synthetic matrices, corn cobs are not only biodegradable and recyclable, but their surface structure and physicochemical properties can also be optimized through chemical modification, thereby enhancing the adhesion and immobilization efficiency of microalgae. Furthermore, using agricultural waste as a biological immobilization material helps reduce environmental pollution, achieves efficient resource utilization, and aligns with the concepts of circular economy and green sustainable development.

[0004] However, the surface of natural corn cobs contains a large amount of lignin. The presence of lignin and its structural rigidity reduce its affinity and adsorption capacity for microalgae. Therefore, appropriate modification treatment can be performed to improve its pore structure and chemical composition, thereby enhancing the immobilization effect of microalgae. Common lignocellulose modification methods include alkalization, acetylation, and methylation. These methods enhance the adsorption capacity and biocompatibility of the immobilization matrix by removing lignin, exposing cellulose and hemicellulose, and altering surface chemical properties. For example, alkalization can effectively remove lignin and disrupt ester bonds within biomass, thereby increasing specific surface area and porosity; acetylation improves the compatibility between corn cobs and microalgae cell surfaces by introducing acetyl groups; and methylation further adjusts surface chemical properties, enhancing the binding force between microalgae and corn cobs. By optimizing the parameters of different pretreatment processes, such as temperature, time, and reagent concentration, the immobilization efficiency can be further improved, enabling microalgae to maintain stable growth on the immobilization matrix and increasing their EPS secretion and metabolic activity, thus enhancing their application value in wastewater treatment and pollution remediation. Based on the above, this invention develops a method for improving the immobilization performance of modified corn cobs in microalgae, enhancing the adhesion ability and growth stability of microalgae, and ultimately improving their application value in environmental remediation and biotechnology. Summary of the Invention

[0005] In view of the problems and shortcomings of the existing technology, the present invention aims to provide a modified corn cob, its preparation method and application.

[0006] To achieve the objectives of this invention, the technical solution adopted is as follows:

[0007] The first aspect of this invention provides a method for preparing modified corn cob, comprising the following steps:

[0008] (1) Cut the cleaned and dried corn cobs into slices to obtain sliced ​​corn cobs;

[0009] (2) The flaky corn cob is placed in a modification solution for modification treatment, and the modified flaky corn cob is washed and dried to obtain modified corn cob; wherein the modification solution is a mixed solution of NaOH and acetyl bromide.

[0010] Preferably, the modified solution in step (2) is prepared by mixing a NaOH solution with a concentration of 1% to 3% w / v and an acetyl bromide solution with a concentration of 1% to 3% w / v in a volume ratio of 1:1.

[0011] Preferably, the modification treatment temperature in step (2) is 30-75℃, and the modification treatment time is 2-8h.

[0012] Preferably, in step (2), the ratio of corn cob to modified liquid is (40-50) g: (500-600) mL.

[0013] Preferably, the sheet in step (1) is a round sheet with a thickness of 0.4 to 0.6 cm and a diameter of 2 to 3 cm.

[0014] The second aspect of the present invention provides a modified corn cob prepared by the preparation method described in the first aspect of the present invention.

[0015] A third aspect of the present invention provides an application of the modified corn cob described in the second aspect of the present invention in microalgae immobilization.

[0016] The fourth aspect of the present invention provides a method for preparing immobilized microalgae, comprising the following steps: adding microalgae and the modified corn cob described in the second aspect of the present invention to a liquid culture medium, and culturing the microalgae to grow on the modified corn cob to obtain immobilized microalgae.

[0017] Preferably, the microalgae is a filamentous cyanobacterium, and the filamentous cyanobacterium is one of the genera *Hymenopterus*, *Talsalina*, or *Nostoc*.

[0018] Preferably, the inoculum amount of microalgae is 4% to 10%, and the ratio of modified corn cob to liquid culture medium is (10 to 15) g: 500 mL.

[0019] Preferably, the cultivation conditions are: temperature 28–32℃, light intensity 120–130 μmol m -2 s -1 The microalgae were cultured under a 12-hour light / 12-hour dark cycle with ventilation, and the culture time was until the logarithmic growth phase of the microalgae.

[0020] The fifth aspect of the present invention provides an immobilized microalgae prepared by the preparation method described in the fourth aspect.

[0021] The sixth aspect of the present invention provides an application of the immobilized microalgae described in the fifth aspect in water pollution control and / or wastewater treatment.

[0022] The seventh aspect of this invention provides a method for treating aquaculture wastewater, comprising the following steps: adding the immobilized microalgae described in the fifth aspect to the aquaculture wastewater, and after cultivation, removing TN, TP and NH4 from the wastewater. + -N.

[0023] Preferably, the aquaculture wastewater is treated as follows: centrifuged at 5000-6000 r / min for 10-15 min, the supernatant is collected, the supernatant is transferred to a sterile container, and diluted with water to a concentration of 45%.

[0024] Preferably, the amount of immobilized microalgae added is 15–25 g / L.

[0025] Preferably, the cultivation conditions are: temperature 28–32℃, light intensity 120–130 μmol m -2 s -1 Cultured under a 12-hour light / 12-hour dark cycle with ventilation for 12-14 days.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) The modification method of the present invention optimizes the surface structure of corn cob by simultaneously pretreating it with NaOH and acetyl bromide, giving it better biocompatibility and adsorption performance. The modified corn cob undergoes a cross-linking reaction with the exogenous polymer (EPS) secreted by microalgae, which effectively enhances its adsorption capacity and immobilization efficiency for microalgae, ensuring the stable attachment and continuous growth of microalgae on the carrier, and significantly improving the biomass and functional characteristics of microalgae.

[0028] (2) The modified corn cob immobilized microalgae of the present invention removes the main nutrients (TN, TP and NH4) from wastewater. + It exhibits superior processing capabilities in terms of -N, and has broad application prospects in water pollution control, wastewater treatment, and ecological restoration.

[0029] (3) The modification method of the present invention is simple to operate, green and environmentally friendly, and the chemical reagents used are non-toxic and easy to recycle, which meets the requirements of sustainable development. The modification process does not require complex equipment or expensive raw materials, the production cost is low, and the process is environmentally friendly.

[0030] In summary, the modified corn cob of this invention has significant advantages in improving microalgae immobilization efficiency, extending service life, and enhancing water treatment effects. It is suitable for widespread application in multiple fields such as water pollution control, wastewater treatment, and environmental protection, and has important application value and broad market prospects. Attached Figure Description

[0031] Figure 1 The graph shows the immobilization efficiency of corn cob microalgae cells after different modifications with NaOH, acetylation, and methanol. Alkalynation represents alkalization, acetylation represents acetylation, and methylation represents methylation, corresponding to NaOH, acetylation, and methanol treatments, respectively.

[0032] Figure 2The immobilization mechanism (Figure A) and immobilization efficiency (Figure B) of microalgae on NaOH-acetylation modified corn cobs are shown in Figure C. The FTIR characterization of different modified corn cobs is shown in Figure C. Raw CC represents unmodified corn cobs, DirectAcetylation represents direct acetylation, corresponding to acetylation treatment, and Delignifiedacetylation represents delignification acetylation, corresponding to NaOH-acetylation treatment.

[0033] Figure 3 Figure A shows the immobilization efficiency and biomass of corn cob microalgae under different treatments. Figure B shows the immobilization efficiency and biomass production of corn cob microalgae under different treatments. The left figure in B shows the immobilization effect of corn cob microalgae under the delignification acetylation group, and the right figure shows the immobilization effect of corn cob microalgae under the unmodified group.

[0034] Figure 4 The diagram shows the removal effect of modified corn cob immobilized microalgae on total nitrogen, total phosphorus and ammonia nitrogen in wastewater. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer and more explicit, the invention is further described in detail below through embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0036] (I) Effects of different modified corn cobs on microalgae immobilization

[0037] Example 1: NaOH-modified corn cob as a carrier for immobilizing microalgae

[0038] The specific steps for preparing modified corn cobs are as follows:

[0039] (1) Wash the corn cobs with distilled water to remove dust, fungi and other debris. After ensuring cleanliness, dry the corn cobs for three days and then put them in an oven at 60°C to dry completely.

[0040] (2) After drying, cut the corn cob into round slices 0.5cm thick and 2cm in diameter;

[0041] (3) Weigh 50g of corn cob and transfer it to 500mL of modification solution, and modify it at 30℃ for 2h. After pretreatment, take out the corn cob, cool it to room temperature, wash it with distilled water, and dry it at 60℃ to obtain modified corn cob; wherein, the modification solution is a 2% (w / v) NaOH solution.

[0042] The specific steps of the method for immobilizing microalgae using modified corn cobs as a carrier are as follows:

[0043] 15g of the modified corn cob (ptCC) was placed in 500mL of sterile BG11 liquid medium (pH 7.0), and the filamentous cyanobacterium *Desertifilum tharense* BERC-3 was inoculated at a rate of 5%. The light intensity was 120 μmol / m². -2 s -1 The light cycle was 12 hours of light and 12 hours of darkness, with ventilation during incubation and a humidity level of 65% in the incubator.

[0044] Examples 2 through 16 are basically the same as Example 1, except that the temperature and time of the modification treatment are different. The temperature and time of the NaOH modification solution used in Examples 1 through 16 are shown in Table 1.

[0045] Table 1. Conditions for modifying corn cobs using NaOH modified solution in Examples 1 to 16.

[0046]

[0047]

[0048] Example 17: Immobilization of microalgae using acetyl bromide-modified corn cob as a carrier

[0049] The preparation of modified corn cob is basically the same as in Example 1, except that the modified liquid in step (3) is a 2% (w / v) acetyl bromide solution.

[0050] The method for immobilizing microalgae using modified corn cobs as a carrier is basically the same as in Example 1, except that acetyl bromide-modified corn cobs are used to immobilize microalgae.

[0051] Examples 18-32 are basically the same as Example 17, except that the temperature and time of the modification treatment are different. The temperature and time of the modification treatment using acetyl bromide modification solution in Examples 17-32 are shown in Table 2.

[0052] Table 2. Conditions for modifying corn cobs using acetyl bromide modified solution in Examples 17 to 32.

[0053] Example 17 30 2 Example 18 30 4 Example 19 30 6 Example 20 30 8 Example 21 45 2 Example 22 45 4 Example 23 45 6 Example 24 45 8 Example 25 60 2 Example 26 60 4 Example 27 60 6 Example 28 60 8 Example 29 75 2 Example 30 75 4 Example 31 75 6 Example 32 75 8

[0054] Example 33: Methanol-modified corn cob as a carrier for immobilized microalgae

[0055] The preparation of modified corn cob is basically the same as in Example 1, except that the modified liquid in step (3) is a methanol solution with a concentration of 2% (w / v).

[0056] The method for immobilizing microalgae using modified corn cobs as a carrier is basically the same as in Example 1, except that methanol-modified corn cobs are used to immobilize microalgae.

[0057] Examples 34-48 are basically the same as Example 33, except that the temperature and time of the modification treatment are different. The temperature and time of the methanol modification solution used in Examples 33-48 are shown in Table 3.

[0058] Table 3. Conditions for modifying corn cobs with methanol-modified liquid in Examples 33-48.

[0059] Example 33 30 2 Example 34 30 4 Example 35 30 6 Example 36 30 8 Example 37 45 2 Example 38 45 4 Example 39 45 6 Example 40 45 8 Example 41 60 2 Example 42 60 4 Example 43 60 6 Example 44 60 8 Example 45 75 2 Example 46 75 4 Example 47 75 6 Example 48 75 8

[0060] To compare the immobilization effects of modified corn cobs treated with different modifiers on microalgae, the immobilization efficiency of microalgae cells on corn cobs with different modification treatments in Examples 1 to 48 was measured. The formula for calculating the microalgae cell immobilization efficiency is as follows:

[0061] Immobilized cells = W1 - W2

[0062] Wherein, Immobilized cells is the dry weight of immobilized microalgae cells, W1 is the total dry weight of corn cob and the immobilized microalgae cells on it, and W2 is the dry weight of corn cob.

[0063] Immobilization efficiency (IE)=Immobilized cells / FW

[0064] FW=Free cells+Immobilized cells

[0065] Wherein, Immobilization efficiency (IE) is the microalgal cell immobilization efficiency, FW is the final total dry weight of microalgal cells, and Free cells is the dry weight of free microalgal cells.

[0066] The methods for determining W1 and Free cells were as follows: Microalgae were immobilized using modified corn cobs prepared in Examples 1 through 48. The immobilization method involved placing 15g of modified corn cob (ptCC) in 500mL of sterile BG11 liquid culture medium (pH 7.0), and inoculating the filamentous cyanobacterium *Desertifilum tharense* BERC-3 at a 5% inoculum. The light intensity was 120 μmol / m². -2 s -1The photoperiod was 12 hours of light and 12 hours of darkness, with aeration and a humidity of 65% in the incubator. After culturing to the logarithmic growth phase of the microalgae (approximately 8-12 days), the modified corn cobs were removed. At this point, the modified corn cobs were covered with microalgal cells. The immobilized microalgal cells adsorbed on the corn cobs were harvested, freeze-dried, and their dry weight was measured to obtain W1. The liquid culture medium was centrifuged at 5000-6000 r / min for 10-15 min, and the suspended microalgal cells in the liquid culture medium were collected, freeze-dried, and their dry weight was measured to obtain Free cells.

[0067] The results of the microalgal cell immobilization efficiency of corn cobs with different modifications in Examples 1 to 48 are as follows: Figure 1 As shown, the microalgal cell immobilization efficiency was found to be significantly dependent on the synergistic effect of temperature and time, as well as the chemical modification mechanism. NaOH-modified corn cobs exhibited the highest microalgal cell immobilization efficiency at 60℃ for 6 hours, as the moderate high temperature promoted lignin removal and increased porosity. However, extending the treatment time to 8 hours led to structural collapse and a decrease in microalgal cell immobilization efficiency. Acetylated corn cobs showed the best microalgal cell immobilization efficiency at 60℃ for 8 hours. Methanol-modified corn cobs exhibited the lowest immobilization efficiency under all conditions, showing the worst effect. Figure 1 (A~D). Among all temperatures and treatments, the NaOH-modified corn cob immobilization efficiency was best after treatment at 60℃ for 6 h. Figure 1 C), at 75℃, the immobilization efficiency of corn cobs decreased due to excessively high temperature. Figure 1 D). The effects of different modification treatments on microalgae immobilization show that the immobilization efficiency of corn cobs modified with methanol is the lowest under all conditions. Therefore, the effect of corn cobs modified with a mixture of NaOH and acetyl bromide on microalgae immobilization will be investigated in the next step.

[0068] (II) Effects of NaOH-acetyl bromide synergistic treatment on microalgal immobilization

[0069] Example 49: NaOH-acetyl bromide synergistic treatment for microalgae immobilization

[0070] The preparation of modified corn cob is basically the same as that in Example 1, except that the modified solution in step (3) is a mixed solution of NaOH and acetyl bromide, which is made by mixing a 2% w / v NaOH solution and a 2% w / v acetyl bromide solution in a volume ratio of 1:1.

[0071] The method for immobilizing microalgae using modified corn cobs as a carrier is basically the same as in Example 1, except that modified corn cobs treated with NaOH-acetyl bromide are used to immobilize microalgae.

[0072] Examples 50-64 are basically the same as Example 49, except that the temperature and time of the modification treatment are different. The temperature and time of the modification treatment using the modifying liquid in Examples 49-64 are shown in Table 4.

[0073] Table 4 shows the conditions for modifying corn cobs using NaOH-acetyl bromide modification solution in Examples 49 to 64.

[0074]

[0075]

[0076] The immobilization mechanism of microalgae on corn cobs modified with a mixed solution of NaOH and acetyl bromide is described in [reference needed]. Figure 2 A. Corn cobs are mainly composed of lignin, hemicellulose, and cellulose. NaOH alkalization treatment can remove lignin by breaking the bonds between lignin and cellulose, thereby increasing porosity and making cellulose easier to modify. The hydroxyl groups on the surface of corn cob cellulose are replaced by acetyl groups. Deligninated acetylated corn cobs enhance the fixation effect on cyanobacteria.

[0077] The results of microalgal cell immobilization efficiency in Examples 49 to 64 are as follows: Figure 2 As shown in Figure B, compared to 45℃, 60℃, and 75℃, the lowest temperature (30℃) resulted in the lowest microalgal cell immobilization efficiency in delignified acetylated corn cobs. The microalgal cell immobilization efficiency increased with increasing temperature, indicating that higher temperatures led to more effective acetylation after delignification and enhanced the adsorption capacity of the corn cobs. At 45℃, the microalgal cell immobilization efficiency increased with duration. A significant increase in microalgal cell immobilization efficiency was observed at 60℃, reaching a maximum of 76% after 6 hours.

[0078] Characterization of microalgae immobilized on modified corn cobs:

[0079] (1) Infrared characterization

[0080] Modified corn cob (ptCC) and unmodified corn cob (RCC) were ground into fine powder. The modified corn cob was divided into a direct acetylation group and a delignification acetylation group. The direct acetylation group used acetyl bromide-modified corn cob prepared in Example 28, and the delignification acetylation group used NaOH-acetyl bromide-modified corn cob prepared in Example 59. 98 mg of corn cob was pressed into 2 mg Kbr and analyzed by FTIR. The infrared results are shown in [Figure number missing]. Figure 2 C.

[0081] In FTIR analysis, the hydroxyl peak is typically found at 3500 cm⁻¹. -1 Nearby, this is related to the hydroxyl groups of lignin. Figure 2 In C, 3500cm-1 The broader peaks nearby represent the intensity of the hydroxyl groups in corn cob. Direct acetylation group: 3500 cm⁻¹ -1 The strength of the nearby hydroxyl groups was lower than that of the unmodified corn cob, indicating that the hydroxyl groups were replaced by acetyl groups. Compared with the direct acetylation group, the delignification acetylation group significantly reduced the strength of the hydroxyl groups, indicating that effective acetylation occurred on the cellulose after lignin removal.

[0082] (2) Biomass production

[0083] Microalgae were immobilized using modified corn cobs prepared in Example 11 (alkalynation group), modified corn cobs prepared in Example 28 (acetylation group), modified corn cobs prepared in Example 43 (methylation group), modified corn cobs prepared in Example 59 (delignified acetylation group), and unmodified corn cobs (control group). The immobilization method was as follows: 15g of modified corn cobs (ptCC) were placed in 500mL of sterile BG11 liquid medium (pH 7.0), and the filamentous cyanobacterium *Desertifilum tharense* BERC-3 was inoculated at a 5% inoculum size. The light intensity was 120 μmol / m². -2 s -1 The photoperiod was 12 hours of light and 12 hours of darkness, with aeration and a humidity of 65% in the incubator. After culturing to the logarithmic growth phase of the microalgae (approximately 8-12 days), the modified corn cobs were removed. At this point, the modified corn cobs were covered with microalgal cells. The immobilized microalgal cells adsorbed on the corn cobs were harvested, freeze-dried, and their dry weight was measured to obtain W1. The liquid culture medium was centrifuged at 5000-6000 r / min for 10-15 min, and the suspended microalgal cells in the liquid culture medium were collected, freeze-dried, and their dry weight was measured to obtain Free cells.

[0084] Biomass yield and microalgal cell immobilization efficiency were measured for five different treatment groups. The formulas for calculating biomass yield and microalgal cell immobilization efficiency are as follows:

[0085] Biomass Production = (FW - IW) / V, where FW is the final total dry weight of microalgal cells, IW is the initial dry weight of inoculated microalgal cells, and V is the volume of culture medium in g / L.

[0086] FW=Free cells+Immobilized cells

[0087] Immobilized cells = W1 - W2

[0088] Wherein, Immobilized cells is the dry weight of immobilized microalgae cells, W1 is the total dry weight of corn cob and the immobilized microalgae cells on it, and W2 is the dry weight of corn cob.

[0089] Immobilization efficiency (IE)=Immobilized cells / FW

[0090] Wherein, Immobilization efficiency (IE) is the microalgal cell immobilization efficiency, FW is the final total dry weight of microalgal cells, and Free cells is the dry weight of free microalgal cells.

[0091] The microalgal cell immobilization efficiency and biomass production of the five different treatment groups are shown in the figure. Figure 3 The delignification acetylation group exhibited the highest biomass production (3.3 g / L) and the highest microalgal cell immobilization efficiency (76%). The control group, using unmodified corn cob as the immobilization carrier, had a microalgal biomass production of 2.9 g / L and a microalgal cell immobilization efficiency of 35%. The alkalization and acetylation treatment groups had microalgal cell immobilization efficiencies of 47% and 40%, respectively. The biomass production in the alkalization group was comparable to the control group, while the acetylation group achieved a biomass production of 3.1 g / L. The methylation treatment group had the lowest microalgal cell immobilization efficiency and biomass production, at 31% and 2.63 g / L, respectively. Figure 3 A) Microalgae immobilization effect, such as Figure 3 As shown in Figure B, the corn cob surface of the delignified acetylated group in the left figure has sufficient microalgae immobilization, while the corn cob of the unmodified group in the right figure has many areas where microalgae are not fully attached.

[0092] (III) Modified corn cob as a carrier to immobilize microalgae for wastewater treatment

[0093] The treatment method for aquaculture wastewater, specifically the process is as follows:

[0094] (1) Centrifuge the aquaculture wastewater at 5000 r / min for 10 min, collect the supernatant, transfer the supernatant to a sterile container, and dilute it with ultrapure water to 45% aquaculture wastewater (45% aquaculture wastewater is made by mixing the original aquaculture wastewater with ultrapure water at a volume ratio of 9:11).

[0095] (2) Microalgae immobilized on modified corn cob (Example 59) were inoculated into 500 mL of 45% aquaculture wastewater at a ratio of 25 g / L, and incubated at 30°C and a light intensity of 120 μmol / L. -2 s -1 The cells were cultured for 12 days with a light cycle of 12 hours in the light and 12 hours in the dark, and then aerated.

[0096] To compare the effectiveness of wastewater treatment, a comparative study was conducted using suspended microalgae culture for wastewater treatment.

[0097] The method for treating aquaculture wastewater using suspended microalgae culture is as follows:

[0098] (1) Centrifuge the aquaculture wastewater at 5000 r / min for 10 min, collect the supernatant, transfer the supernatant to a sterile container, and dilute it with ultrapure water to 45% aquaculture wastewater (45% aquaculture wastewater is made by mixing the original aquaculture wastewater with ultrapure water at a volume ratio of 9:11).

[0099] (2) Centrifuge the suspended microalgae and inoculate them into 500 mL of 45% aquaculture wastewater at the same weight as the dry weight of the immobilized microalgae. Incubate at 30°C and a light intensity of 120 μmol / m². -2 s -1 The cells were cultured for 12 days with a light cycle of 12 hours in the light and 12 hours in the dark, and then aerated.

[0100] During the 0–12 day treatment period, 5 mL of wastewater was sampled every 2 days, centrifuged at 6000 rpm for 5 min, and the supernatant was collected and filtered through a 0.22 μm filter membrane before determining its total nitrogen (TN), total phosphorus (TP), and ammonia nitrogen (NH4). + The concentration of (-N) was measured. All indicators were analyzed using a multi-parameter water quality analyzer to evaluate the role and removal efficiency of immobilized and suspended microalgae in the purification of aquaculture wastewater.

[0101] The results of aquaculture wastewater treatment are as follows: Figure 4 As shown, compared to the suspension culture system, modified corn cob immobilized microalgae significantly improved the removal of major substances (TN, TP, and NH4) from wastewater. + It exhibits superior processing capabilities in terms of TN (-N). From the trend of TN change ( Figure 4 A) It can be seen that the TN concentration in both culture systems gradually decreased with the extension of culture time, but the removal rate of the immobilized system was significantly faster than that of the suspension system. Furthermore, after 12 days, the TN level in the immobilized microalgae system almost reached the detection limit, while a relatively high concentration of TN remained in the suspension system. TP removal trend ( Figure 4 B) Similar to TN, the immobilized system exhibited superior phosphorus removal capacity throughout the entire culture period and reduced TP concentration to a level significantly lower than that of the suspension system by day 12.

[0102] In addition, in NH4 + -N removal aspect ( Figure 4C) The immobilized system exhibited a faster degradation rate compared to the suspended system. This may be attributed to the stable attachment of immobilized microalgae to the corn cob carrier, thereby enhancing the absorption of nutrients such as nitrogen and phosphorus. Simultaneously, the immobilized carrier may have provided a more suitable microenvironment for algal cell growth and metabolic activities, further improving its decontamination effect. (Combined TN, TP, and NH4) + -N removal rate ( Figure 4 From D) perspective, the overall removal efficiency of the immobilized system was significantly higher than that of the suspension system. At the end of the culture (day 12), the immobilized system showed significantly higher removal efficiency for TN, TP, and NH4+. + The removal rates of -N all exceeded 80%, while the removal efficiency of the suspended system was relatively low.

[0103] As described above, the examples are merely for explaining the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the above embodiments, or some technical features can be equivalently substituted. Furthermore, such changes or substitutions will not cause the substance of the respective technical solutions to deviate from the spirit and scope of each embodiment in the present invention.

Claims

1. A method for preparing modified corn cob, characterized in that, Includes the following steps: (1) Cut the cleaned and dried corn cobs into slices to obtain sliced ​​corn cobs; (2) The flaky corn cobs are placed in a modifying solution for modification treatment, and the modified flaky corn cobs are washed and dried to obtain modified corn cobs; wherein, the modifying solution is a mixed solution of NaOH and acetyl bromide; The modification solution is prepared by mixing a 1%–3% w / v NaOH solution and a 1%–3% w / v acetyl bromide solution in a volume ratio of 1:

1. The modification treatment temperature is 30–75℃, and the modification treatment time is 2–8 hours.

2. The preparation method according to claim 1, characterized in that, In step (2), the ratio of corn cob to modified liquid is (40-50) g: (500-600) mL.

3. Modified corn cob prepared using the preparation method described in any one of claims 1 to 2.

4. The application of the modified corn cob according to claim 3 in microalgae immobilization.

5. A method for preparing immobilized microalgae, characterized in that, Includes the following steps: Microalgae and the modified corn cob as described in claim 3 are added to a liquid culture medium, and the microalgae are cultured to grow on the modified corn cob to obtain immobilized microalgae.

6. Immobilized microalgae prepared using the preparation method described in claim 5.

7. The application of the immobilized microalgae of claim 6 in water pollution control and / or wastewater treatment.

8. A method for treating aquaculture wastewater, characterized in that, Includes the following steps: Immobilized microalgae as described in claim 6 are added to aquaculture wastewater, and after cultivation, TN, TP and NH4 in the wastewater are removed. + -N.

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