Modified corncob as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of environmental restoration and biology, and discloses a modified corncob as well as a preparation method and application thereof. According to the method, a mixed solution of NaOH and acetyl bromide is used for modifying corncobs, lignin in the corncobs is removed through alkalization pretreatment in the modification process, the porosity and the specific surface area of the corncobs are increased, and meanwhile, acetyl bromide is adopted for treatment, so that the adsorption capacity and the immobilization efficiency of the corncobs to microalgae are enhanced. The modified corncob can be crosslinked with an exogenous polymer (EPS) secreted by the microalgae, so that the microalgae can be stably attached and survive for a long time, and the application effect of the corncob in wastewater treatment and ecological restoration is improved. The invention provides an efficient and sustainable biological immobilization technology, provides a new technical path for water pollution treatment and ecological restoration, and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the field of environmental restoration and biotechnology, and specifically relates to a modified corn cob and a preparation method and application thereof. Background Art

[0002] Sustainable development has become an important direction of modern scientific research, especially in addressing global challenges such as environmental pollution, resource shortages and climate change. Microalgae immobilization technology has become an important strategy for environmental governance and sustainable biomanufacturing due to its wide application in wastewater treatment, biofuel production and bioresource recovery. Among them, microalgae, as a type of photosynthetic autotrophic microorganisms, can effectively fix carbon dioxide and nitrogen in the atmosphere, while secreting extracellular polymers (EPS) to promote pollutant adsorption and biofilm formation. Therefore, it has important application value in pollution remediation and ecological engineering.

[0003] The efficiency of the microalgae immobilization system depends largely on the performance of the immobilization carrier and its surface characteristics. At present, the carrier materials for immobilizing microalgae mainly include synthetic polymers, inorganic materials and natural biomass. Among them, lignocellulosic biomass has become an ideal immobilization matrix due to its wide sources, low cost and environmental friendliness. Corncob, as an agricultural by-product, is rich in cellulose and hemicellulose, and has good mechanical stability and degradability, making it an excellent candidate material for immobilizing microalgae. Compared with synthetic matrices, corncobs are not only degradable and recyclable, but also can optimize the surface structure and physicochemical properties through chemical modification, thereby enhancing the adhesion and immobilization efficiency of microalgae. In addition, the use of agricultural waste as biological immobilization materials helps to reduce environmental pollution and achieve efficient resource utilization, which is in line with the concept of circular economy and green sustainable development.

[0004] However, the surface of natural corncobs contains a large amount of lignin. The presence of lignin and structural rigidity will reduce its affinity and adsorption capacity for microalgae. Therefore, it can be appropriately modified to improve its pore structure and chemical composition, thereby improving the immobilization effect of microalgae. Common methods of lignocellulose modification include alkalization, acetylation, methylation, etc., which improve the adsorption capacity and biocompatibility of the immobilization matrix by removing lignin, exposing cellulose and hemicellulose, and changing the surface chemical properties. For example, alkalization can effectively remove lignin and destroy the ester bonds inside the biomass, thereby increasing the specific surface area and porosity; acetylation improves the compatibility of corncobs with the surface of microalgae cells by introducing acetyl groups; methylation further adjusts the surface chemical properties and enhances the binding force between microalgae and corncobs. By optimizing the parameters of different pretreatment processes, such as temperature, time and reagent concentration, the immobilization efficiency can be further improved, the microalgae can maintain stable growth on the fixed matrix, and its EPS secretion and metabolic activity can be improved, thereby enhancing its application value in wastewater treatment and pollution remediation. Based on the above situation, the present invention has developed a method for improving the immobilization performance of microalgae by modifying corncobs, enhancing the attachment ability and growth stability of microalgae, and ultimately improving its application value in the fields of environmental remediation and biotechnology. Summary of the invention

[0005] In view of the problems and shortcomings in the prior art, the present invention aims to provide a modified corncob and a preparation method and application thereof.

[0006] In order to achieve the purpose of the present invention, the technical solution adopted by the present invention is as follows:

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

[0008] (1) cutting the washed and dried corn cobs into flakes to obtain flake corn cobs;

[0009] (2) placing the flaky corn cob into a modification liquid for modification, washing and drying the modified flaky corn cob to obtain a modified corn cob; wherein the modification liquid is a mixed solution of NaOH and acetyl bromide.

[0010] Preferably, the modifying solution in step (2) is a mixture of 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 to 75° C., and the modification treatment time is 2 to 8 hours.

[0012] Preferably, in step (2), the usage 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] The third aspect of the present invention provides an application of the modified corncob 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 into a liquid culture medium, culturing and allowing the microalgae to grow on the modified corn cob to obtain immobilized microalgae.

[0017] Preferably, the microalgae is a filamentous cyanobacteria, and the filamentous cyanobacteria is one of the genus Tenuissima, the genus Talsazana, and the genus Nostoc.

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

[0019] Preferably, the culture conditions are: temperature 28-32°C, light intensity 120-130 μmol m -2 s -1 , aeration culture is carried out under a photoperiod of 12h light / 12h dark, and culture time: culture until the microalgae is in the logarithmic growth phase.

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

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

[0022] The seventh aspect of the present 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, culturing, and removing TN, TP and NH in the wastewater. 4 + -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 culture conditions are: temperature 28-32°C, light intensity 120-130 μmol m -2 s -1 , aeration culture is carried out under a photoperiod of 12h light / 12h dark, and the culture time is 12 to 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 cobs by pre-treating them with NaOH and acetyl bromide at the same time, so that the corn cobs have better biocompatibility and adsorption performance. The modified corn cobs undergo cross-linking reactions with exogenous polymers (EPS) secreted by microalgae, effectively enhancing their 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 properties of microalgae.

[0028] (2) The modified corncob immobilized microalgae of the present invention is effective in removing the main nutrients (TN, TP and NH) from wastewater. 4 + -N) and has a broad application prospect in the fields of 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, has low production costs, and is environmentally friendly.

[0030] In summary, the modified corn cob of the present invention has significant advantages in improving the immobilization efficiency of microalgae, extending the service life and enhancing the water treatment effect. It is suitable for being widely used in multiple fields such as water pollution control, wastewater treatment and environmental protection, and has important application value and broad market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a diagram of the immobilization efficiency of corncob microalgae cells treated with different modifications of NaOH, acetyl bromide, and methanol, where Alkalynation represents alkalinization, Acetylation represents acetylation, and Methylation represents methylation, corresponding to NaOH, acetyl bromide, and methanol treatments, respectively;

[0032] Figure 2Figure 1 shows the immobilization mechanism of microalgae on corncobs modified by NaOH-acetyl bromide (Figure A), immobilization efficiency (Figure B), and FTIR characterization of different modified corncobs (Figure C). Raw CC represents unmodified corncobs, Direct Acetylation represents direct acetylation, corresponding to acetyl bromide treatment, and Delignified acetylation represents delignified acetylation, corresponding to NaOH-acetyl bromide treatment.

[0033] Figure 3 Figure 1 is a graph showing the fixation efficiency and biomass of microalgae in corn cobs with different treatments, where Figure A shows the fixation efficiency and biomass production of microalgae in corn cobs with different treatments; Figure B shows the effect of immobilization of microalgae in corn cobs with different treatments, the left figure in Figure B shows the effect of microalgae immobilized in the delignified acetylated corn cob group, and the right figure shows the effect of microalgae immobilized in the unmodified corn cob;

[0034] Figure 4 This is a diagram showing the removal effect of total nitrogen, total phosphorus and ammonia nitrogen in wastewater by modified corn cob immobilized microalgae. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention clearer and more specific, the present invention is further described in detail by examples below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] 1. Effects of different modified corncobs on microalgae immobilization

[0037] Example 1 NaOH modified corncob as carrier for immobilization of microalgae

[0038] The preparation of modified corncob, the specific steps are as follows:

[0039] (1) The corn cobs were washed with distilled water to remove dust, fungi, and other debris. After ensuring cleanliness, the corn cobs were dried in the sun for three days and then placed in an oven at 60°C to completely dry;

[0040] (2) After drying, the corn cobs were cut into round slices with a thickness of 0.5 cm and a diameter of 2 cm;

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

[0042] The method of using modified corncobs as carriers to immobilize microalgae has the following specific steps:

[0043] 15 g of the modified corncob (ptCC) was placed in 500 mL of sterilized BG11 liquid medium (pH 7.0), and inoculated with filamentous cyanobacteria Desertifilum tharense BERC-3 at a 5% inoculation rate. The light intensity was 120 μmol m -2 s -1 , the photoperiod was 12 h light / 12 h dark, ventilation culture was carried out, and the humidity of the incubator was 65%.

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

[0045] Table 1 Conditions for modifying corncobs using NaOH modification solution in Example 1 to Example 16

[0046]

[0047]

[0048] Example 17: Immobilization of microalgae using corncobs modified with acetyl bromide as carriers

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

[0050] The method of immobilizing microalgae using modified corncobs as carriers is basically the same as that of Example 1, except that acetyl bromide is used to modify corncobs to immobilize microalgae.

[0051] The contents of Examples 18 to 32 are basically the same as those of 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 liquid in Examples 17 to 32 are shown in Table 2.

[0052] Table 2 Conditions for modifying corncobs using acetyl bromide modification liquid in Examples 17 to 32

[0053] serial number Temperature treatment (℃) Time (h) Embodiment 17 30 2 Embodiment 18 30 4 Embodiment 19 30 6 Embodiment 20 30 8 Embodiment 21 45 2 Embodiment 22 45 4 Embodiment 23 45 6 Embodiment 24 45 8 Embodiment 25 60 2 Embodiment 26 60 4 Embodiment 27 60 6 Embodiment 28 60 8 Embodiment 29 75 2 Embodiment 30 75 4 Embodiment 31 75 6 Embodiment 32 75 8

[0054] Example 33: Methanol-modified corncobs as carriers for immobilization of microalgae

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

[0056] The method of immobilizing microalgae using modified corncobs as carriers is basically the same as that of Example 1, except that methanol-modified corncobs are used to immobilize microalgae.

[0057] The contents of Examples 34 to 48 are basically the same as those of Example 33, except that the temperature and time of the modification treatment are different. The temperature and time of the modification treatment using the methanol modification liquid in Examples 33 to 48 are shown in Table 3.

[0058] Table 3 Conditions for modifying corn cobs using methanol modification liquid in Examples 33 to 48

[0059] serial number Temperature treatment (℃) Time (h) Embodiment 33 30 2 Embodiment 34 30 4 Embodiment 35 30 6 Embodiment 36 30 8 Embodiment 37 45 2 Embodiment 38 45 4 Embodiment 39 45 6 Embodiment 40 45 8 Embodiment 41 60 2 Embodiment 42 60 4 Embodiment 43 60 6 Embodiment 44 60 8 Embodiment 45 75 2 Embodiment 46 75 4 Embodiment 47 75 6 Embodiment 48 75 8

[0060] In order to compare the immobilization effects of modified corn cobs treated with different modifiers on microalgae, the immobilization efficiency of microalgae cells of corn cobs treated with different modifications in Examples 1 to 48 was measured. The calculation formula for the immobilization efficiency of microalgae cells 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 thereon, and W2 is the dry weight of corn cob.

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

[0064] FW=Free cells+Immobilized cells

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

[0066] The determination method of W1 and Free cells is as follows: the modified corn cobs prepared in Examples 1 to 48 are used to immobilize the microalgae, and the immobilization method is as follows: 15 g of the modified corn cob (ptCC) is placed in 500 mL of sterilized BG11 liquid culture medium (pH 7.0), and the filamentous cyanobacteria Desertifilum tharense BERC-3 is inoculated at an inoculation rate of 5%. The light intensity is 120 μmol m -2 s -1, the light cycle is 12h light / 12h dark, ventilation culture, and the humidity of the incubator is 65%; when the microalgae are cultured to the logarithmic growth phase (about 8 to 12 days), the modified corn cob is taken out, at which time the modified corn cob is covered with microalgae cells, the immobilized microalgae cells adsorbed on the corn cob are harvested, freeze-dried, and the dry weight is measured to obtain W1; the liquid culture medium is centrifuged at 5000-6000r / min for 10-15min, the suspended microalgae cells in the liquid culture medium are collected, freeze-dried, and the dry weight is measured to obtain Free cells.

[0067] The results of the immobilization efficiency of microalgae cells by corn cobs with different modification treatments in Examples 1 to 48 are as follows Figure 1 As shown in the figure, it was found that the efficiency of microalgae cell immobilization was significantly dependent on the temperature-time synergy and the chemical modification mechanism. The microalgae cell immobilization efficiency of corn cobs modified with NaOH was the highest at 60°C and 6h, because moderately high temperature promoted the removal of lignin and increased the porosity. When the treatment time was extended to 8h, the structure collapsed, resulting in a decrease in the microalgae cell immobilization efficiency. The microalgae cell immobilization efficiency of corn cobs modified with acetylation was the best at 60°C and 8h. The immobilization efficiency of corn cobs modified with methanol was the lowest under various conditions, and the effect was the worst ( Figure 1 A~D). Among all the temperatures and treatments, the NaOH-modified corncob treated at 60℃ for 6h had the best immobilization efficiency ( Figure 1 C), the efficiency of corncob immobilization decreased due to high temperature at 75℃ ( Figure 1 D). From the effects of different modification treatments on the immobilization of microalgae, it can be seen that the immobilization efficiency of corncobs modified with methanol is the lowest under all conditions. Therefore, the effect of corncobs modified with a mixed solution of NaOH and acetyl bromide on the immobilization of microalgae was subsequently investigated.

[0068] (II) Effect of NaOH-acetyl bromide synergistic treatment on microalgae immobilization

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

[0070] The preparation process of the modified corn cob is basically the same as that of Example 1, except that the modification solution in step (3) is a mixed solution of NaOH and acetyl bromide, which is a mixture of 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 corncobs as carriers is basically the same as that of Example 1, except that the microalgae are immobilized using modified corncobs co-treated with NaOH-acetyl bromide.

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

[0073] Table 4 Conditions for modifying corncobs using NaOH-acetyl bromide modification solution in Examples 49 to 64

[0074]

[0075]

[0076] The immobilization mechanism of microalgae by using a mixed solution of NaOH and acetyl bromide to modify corncobs is shown in Figure 2 A. Corncobs are mainly composed of lignin, hemicellulose and cellulose. NaOH alkalization treatment can remove lignin by destroying the bonds between lignin and cellulose, increase the porosity and make cellulose easier to modify. The hydroxyl groups on the surface of corncob cellulose are replaced by acetyl groups. Delignified acetylated corncobs enhance the fixation effect on cyanobacteria.

[0077] The results of the microalgae cell immobilization efficiency of Examples 49 to 64 are as follows Figure 2 As shown in Figure B, the microalgae cell immobilization efficiency of delignified acetylated modified corncobs was the lowest at a lower temperature (30°C) compared to 45°C, 60°C, and 75°C. As the temperature increased, the microalgae cell immobilization efficiency increased, indicating that high temperature led to more effective acetylation after delignification and enhanced the adsorption capacity of corncobs. At 45°C, the microalgae cell immobilization efficiency increased with duration. A significant increase in the microalgae cell immobilization efficiency was observed at 60°C, and the microalgae cell immobilization efficiency reached a maximum value of 76% at 6h.

[0078] Characterization of microalgae immobilized on modified corncobs:

[0079] (1) Infrared characterization

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

[0081] In FTIR analysis, the hydroxyl peak usually exists at 3500cm -1 This is related to the hydroxyl groups of lignin. Figure 2 C, 3500cm-1 The broader peak nearby represents the intensity of the corncob hydroxyl group. Direct acetylation group 3500cm -1 The intensity of the nearby hydroxyl groups decreased compared to the unmodified corncob, indicating that the hydroxyl groups were replaced by acetyl groups. Compared with the direct acetylation group, the delignification acetylation group significantly reduced the intensity of the hydroxyl groups, and effective acetylation occurred on the cellulose after the removal of lignin.

[0082] (2) Biomass production

[0083] The modified corncobs prepared in Example 11 (alkalization group, Alkalynation), the modified corncobs prepared in Example 28 (acetylation group, Acetylation), the modified corncobs prepared in Example 43 (methylation group, Methyiation), the modified corncobs prepared in Example 59 (delignifiedacetylation group, Delignifiedacetylation) and the unmodified corncobs of the control group (Control) were used to immobilize the microalgae. The immobilization method was as follows: 15 g of the modified corncobs (ptCC) were placed in 500 mL of sterilized BG11 liquid culture medium (pH 7.0), and the filamentous cyanobacteria Desertifilum tharense BERC-3 was inoculated at an inoculation rate of 5%. The light intensity was 120 μmol m -2 s -1 , the light cycle is 12h light / 12h dark, ventilation culture, and the humidity of the incubator is 65%; when the microalgae are cultured to the logarithmic growth phase (about 8 to 12 days), the modified corn cob is taken out, at which time the modified corn cob is covered with microalgae cells, the immobilized microalgae cells adsorbed on the corn cob are harvested, freeze-dried, and the dry weight is measured to obtain W1; the liquid culture medium is centrifuged at 5000-6000r / min for 10-15min, the suspended microalgae cells in the liquid culture medium are collected, freeze-dried, and the dry weight is measured to obtain Free cells.

[0084] The biomass yield and microalgae cell immobilization efficiency corresponding to the five different treatment groups were determined. The calculation formulas for the biomass yield and microalgae cell immobilization efficiency are as follows:

[0085] Biomass Production = (FW-IW) / V, where FW is the final total microalgae cell dry weight, IW is the initial inoculated microalgae cell dry weight, and V is the culture volume 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 thereon, and W2 is the dry weight of corn cob.

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

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

[0091] The immobilization efficiency and biomass production of microalgae cells in five different treatment groups are shown in Figure 2. Figure 3 , the delignification acetylation group showed the highest biomass production (3.3g / L) and the highest microalgae cell immobilization efficiency (76%). The control group used unmodified corn cobs as the immobilization carrier, with a microalgae biomass production of 2.9g / L and a microalgae cell immobilization efficiency of 35%. The microalgae cell immobilization efficiencies of the alkalization and acetylation treatment groups were 47% and 40%, respectively. The biomass production of the alkalization treatment group was equivalent to that of the control group. The biomass production of the acetylation treatment group reached 3.1g / L. The microalgae cell immobilization efficiency and biomass production of the methylation treatment group were the lowest, at 31% and 2.63g / L ( Figure 3 A) Effects of microalgae immobilization Figure 3 As shown in B, the microalgae are fully fixed on the surface of the delignified acetylated corncob in the left figure, while there are many areas on the unmodified corncob in the right figure where the microalgae are not fully attached.

[0092] (III) Modified corncobs as carriers to immobilize microalgae for wastewater treatment

[0093] The specific process of aquaculture wastewater treatment is as follows:

[0094] (1) centrifuging the aquaculture wastewater at 5000 r / min for 10 min, collecting the supernatant, transferring the supernatant to a sterile container, and diluting it with ultrapure water to 45% aquaculture wastewater (45% aquaculture wastewater is obtained by mixing aquaculture wastewater stock solution with ultrapure water in a volume ratio of 9:11);

[0095] (2) The microalgae immobilized with the modified corncob as carrier in Example 59 was 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 m -2 s -1 The culture was cultured with aeration for 12 days under a photoperiod of 12 h light / 12 h dark.

[0096] In order to compare the effect of sewage treatment, a comparative example of using suspended culture microalgae for wastewater treatment was set up.

[0097] The method of treating aquaculture wastewater by suspended culture of microalgae is as follows:

[0098] (1) centrifuging the aquaculture wastewater at 5000 r / min for 10 min, collecting the supernatant, transferring the supernatant to a sterile container, and diluting it with ultrapure water to 45% aquaculture wastewater (45% aquaculture wastewater is obtained by mixing aquaculture wastewater stock solution with ultrapure water in a volume ratio of 9:11);

[0099] (2) The suspended cultured microalgae were centrifuged and inoculated into 500 mL of 45% aquaculture wastewater at a weight equal to the dry weight of the immobilized microalgae. The cultured microalgae were inoculated into 500 mL of 45% aquaculture wastewater at 30 °C and a light intensity of 120 μmol m -2 s -1 The culture was cultured with aeration for 12 days under a photoperiod of 12 h light / 12 h dark.

[0100] During the treatment process of 0 to 12 days, 5 mL of wastewater was sampled every 2 days, centrifuged at 6000 rpm for 5 min, and the supernatant was filtered through a 0.22 μm filter membrane to determine the total nitrogen (TN), total phosphorus (TP) and ammonia nitrogen (NH 4 + -N) concentration. All indicators were measured and analyzed by a multi-parameter water quality analyzer to evaluate the role and removal efficiency of immobilized microalgae and suspended cultured microalgae in the purification of aquaculture wastewater.

[0101] The results of aquaculture wastewater treatment are as follows Figure 4 As shown in the figure, compared with the suspension culture system, the modified corncob immobilized microalgae is more effective in removing the main substances (TN, TP and NH) from wastewater. 4 + -N) shows better processing capabilities. From the trend of TN changes ( 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 suspended system. After 12 days, the TN level in the immobilized microalgae system almost dropped to the detection limit, while a relatively high concentration of TN still remained in the suspended system. Removal trend of TP ( Figure 4 B) Similar to TN, the immobilized system showed better phosphorus removal ability throughout the culture period and reduced the TP concentration to a level significantly lower than that of the suspension system on the 12th day.

[0102] In addition, in NH 4 + -N removal aspects ( Figure 4C), the immobilized system showed a faster degradation rate than the suspended system, which may be attributed to the ability of immobilized microalgae to stably attach to the corncob carrier, thereby enhancing the absorption capacity of nutrients such as nitrogen and phosphorus. At the same time, the immobilized carrier may provide a more suitable microenvironment for the growth and metabolic activities of algal cells, further improving its decontamination effect. 4 + -N removal rate ( Figure 4 D), the total removal efficiency of the immobilized system was significantly higher than that of the suspended system. At the end of the culture (day 12), the removal efficiency of TN, TP and NH 4 + The removal efficiency of -N exceeded 80%, while the removal efficiency of the suspension system was relatively low.

[0103] As mentioned above, the above examples are only used to explain the technical solutions of the present invention, rather than 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 it is still possible to modify the technical solutions described in the above embodiments, or to replace some technical features equivalently; and such changes or substitutions will not cause the essence of the respective technical solutions to deviate from the spirit and scope of each implementation mode in the present invention.

Claims

1. A method for preparing a modified corncob, characterized in that: The following steps are involved: (1) cutting the washed and dried corn cobs into flakes to obtain flake corn cobs; (2) placing the flaky corn cob into a modification liquid for modification, washing and drying the modified flaky corn cob to obtain a modified corn cob; wherein the modification liquid is a mixed solution of NaOH and acetyl bromide.

2. The preparation method according to claim 1, characterized in that: 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.

3. The preparation method according to claim 2, characterized in that: The modification treatment temperature in step (2) is 30 to 75° C., and the modification treatment time is 2 to 8 hours.

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

5. The modified corn cob prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the modified corncob according to claim 5 in the immobilization of microalgae.

7. A method for preparing immobilized microalgae, characterized in that: The following steps are involved: Add microalgae and the modified corn cob according to claim 5 into a liquid culture medium, and culture the microalgae so that the microalgae grow on the modified corn cob to obtain immobilized microalgae.

8. Immobilized microalgae prepared by the preparation method according to claim 7.

9. Use of the immobilized microalgae according to claim 8 in water pollution control and / or wastewater treatment.

10. A method for treating aquaculture wastewater, characterized in that: The following steps are involved: Add the immobilized microalgae described in claim 8 to the aquaculture wastewater, and remove TN, TP and NH4 in the wastewater after cultivation. + -N.

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