A method for reducing the solubility of diatom shells, low-solubility diatoms, and applications thereof

Abstract

The present invention relates to the field of marine environment technology, and specifically to a method for reducing the solubility of diatom shells, low-solubility diatoms and applications. The method for reducing the solubility of diatom shells comprises the following steps: preparing an artificial seawater solution and sterilizing the artificial seawater, adding nutrient components to the artificial seawater to form a diatom culture solution, wherein the diatom culture solution comprises a silicon source, a sodium source, an iron source, a copper source, a zinc source, a molybdenum source, a cobalt source, a manganese source, vitamins and biotin; the diatom culture solution is inoculated with diatoms and cultured for 7 to 15 days, and the culture conditions are: the light intensity is 50 to 70 μmolE·m <supgt;‑2< / supgt;s<supgt;‑1< / supgt;,光照周期为12 / 12~16 / 8光暗循环,温度为20~25℃。所述硅藻由上述方法培育而成。所述应用为上述硅藻在固定二氧化碳上的应用。本发明利用有机硅作为硅源,从而形成表面疏水的硅藻壳体,有利于降低壳体的溶解度,提高硅藻的固碳效率。

Description

Technical Field

[0001] The invention relates to the technical field of marine environment, in particular to a method for reducing the solubility of diatom shells, low-solubility diatoms and applications. Background Art

[0002] Carbon fixation technology can be roughly divided into three categories: chemical, physical and biological. 2 It is a green, energy-saving and sustainable method. While marine microalgae absorb carbon dioxide, they can also produce high value-added products such as protein, polysaccharides, and oils, which have important development value in the fields of medicine, food, aquaculture, etc. Compared with traditional physical and chemical methods for fixing CO 2 In comparison, marine microalgae have the characteristics of strong growth and reproduction ability, high photosynthetic rate, and strong environmental adaptability. Therefore, microalgae biocarbon fixation technology is expected to become a feasible CO 2 Fixation method.

[0003] Marine diatoms are one of the main groups of marine microalgae, accounting for a huge proportion of their number and species. Diatoms absorb a large amount of carbon dioxide through photosynthesis and release oxygen, which is beneficial to CO 2 The absorption rate is high and it is considered to be an efficient photosynthetic organism. Marine diatoms fix CO 2 The amount is up to 1×10 12 kg, contributing approximately 20% of global primary productivity, 40% of marine primary productivity, and 50% of marine sedimentary organic carbon. Diatoms are important participants in the carbon cycle and play an important role in the fixation of CO2 by marine microalgae. 2 , maintaining global CO 2 It plays an important role in balancing and mitigating global warming.

[0004] Compared with other microalgae, diatoms have a siliceous cell wall, the main chemical composition of which is amorphous silicon dioxide. The siliceous shell of diatoms can not only fully transmit light for efficient photosynthesis, but also has good mechanical properties, protecting diatoms from the invasion of other microorganisms and changes in the water environment. After the death of diatoms, the diatom shell can also play a role in protecting and carrying organic matter, promoting the fixation of CO by diatoms. 2 The sedimentation and burial depth of diatoms. However, the amorphous silica shell itself is hydrophilic and easily soluble in the water environment. Therefore, most of the dead diatoms dissolve their siliceous shells during the sedimentation and burial depth of the ocean, and the fixed organic carbon returns to the environment through the respiration of microorganisms. Therefore, increasing the hydrophobicity of diatom shells and thus reducing the solubility of diatom shells is the key to improving the carbon fixation efficiency of diatoms.

[0005] At present, there have been a lot of studies on the cultivation methods, cultivation devices and separation methods of marine diatoms and freshwater diatoms. The Chinese invention patent "A benthic diatom cultivation method" (publication number: CN108004146A) uses the improved F culture medium and intermittent circulation to conveniently and quickly realize the cultivation of benthic freshwater diatoms. The Chinese invention patent "A method and device for cultivating diatoms by adding silicates based on turbidity value feedback" (publication number: CN111944694A) discloses a method for cultivating diatoms by adding silicates based on turbidity value feedback. The addition of silicates is controlled by the turbidity change of the culture medium, and the addition of other nutrients is controlled to effectively improve the growth efficiency of diatoms. However, these studies can only realize the artificial cultivation of background diatoms and increase the growth rate of diatoms, but do not change the physical and chemical properties of the diatom shells, nor improve the carbon fixation capacity of diatoms. As a result, in practical applications (i.e., fixing CO in seawater environments), the growth efficiency of diatoms has increased significantly. 2 ) process, the diatom shells dissolve during the sedimentation process, thus failing to achieve the carbon fixation effect. Summary of the invention

[0006] The present invention aims to solve the existing problem of diatom fixing CO 2 In the process, the solubility of the diatom shells obtained by culture is large and the carbon fixation efficiency is low. In order to solve the above technical problems, a method for culturing organically modified marine diatoms is provided, which regulates the silicon source in the growth environment and uses organic silicon instead of sodium silicate to provide the silicon source for the formation of diatom shells, thereby forming diatom shells with hydrophobic surfaces, which is beneficial to reducing the solubility of the shells and improving the carbon fixation efficiency of diatoms.

[0007] In order to achieve the above object, the present invention mainly provides the following technical solutions:

[0008] A method for reducing the solubility of diatom shells, using an organic modification method to reduce the solubility of diatom shells, comprises the following steps:

[0009] Step 1, preparing an artificial seawater solution and sterilizing the artificial seawater, adding organosilane and nutrients to the artificial seawater to form a diatom culture solution, wherein the molar concentrations of the components of the organosilane and nutrients after being prepared into the diatom culture solution are: organosilane (1-2) 10 -4 M, ferric chloride (2-3) × 10 -5 M, sodium nitrate (1~10)×10 -4 M, sodium dihydrogen phosphate (1-5) × 10 -5 M, disodium ethylenediaminetetraacetate (1~1.5)×10 -5 M, copper sulfate (2-4) × 10 -8 M, Sodium molybdate (1~3)×10 -8 M, zinc sulfate (1~8)×10-8 M, cobalt chloride (1~5)×10 -8 M, manganese chloride (1~10)×10 -7 M, Vitamin B1 (1-3) × 10 -7 M, biotin (1~3)×10 -9 M, Vitamin B12 (1-4) × 10 -10 M;

[0010] Step 2, mixing the diatom culture solution and adjusting the pH value of the diatom culture solution to 7-8;

[0011] Step 3, inoculating diatoms in the diatom culture solution and culturing for 7 to 15 days, the culture conditions are: the light intensity is 50 to 70 μmol·m -2 s -1 , the photoperiod is 12 / 12 to 16 / 8 light-dark cycle, and the temperature is 20 to 25°C.

[0012] In the above method for reducing the solubility of diatom shells, the organosilane includes a first organosilane and a second organosilane, the first organosilane is tetramethoxysilane, and the second organosilane is one or more of 3-mercaptopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane and trimethoxyphenylsilane.

[0013] In the above method for reducing the solubility of diatom shells, the mass ratio of the first organosilane to the second organosilane is 1 to 3:1.

[0014] In the above-mentioned method for reducing the solubility of diatom shells, the components and concentrations of the various substances in the artificial seawater solution are: sodium chloride 20.758 g / L, sodium sulfate 3.477 g / L, potassium chloride 0.587 g / L, sodium bicarbonate 0.170 g / L, potassium bromide 0.0845 g / L, boric acid 0.0225 g / L, sodium fluoride 0.0027 g / L, magnesium chloride 9.395 g / L, calcium chloride 1.316 g / L, and strontium chloride 0.0214 g / L.

[0015] In the above method for reducing the solubility of diatom shells, the diatom is any one or more of Thalassiosira, Chaetoceros, Nitzschia, Cyclotella, and Navicula;

[0016] In the above method for reducing the solubility of diatom shells, the diatom shells are 1×10 4 ~1×10 5 cells / ml were inoculated into the diatom culture solution.

[0017] In the above method for reducing the solubility of diatom shells, the shells of the diatoms obtained by culture are non-hydrophilic silanes, and the contact angle test value of the shells is 60.8° to 89.7°.

[0018] A low-solubility diatom, the porous material is cultivated by the above-mentioned method for reducing the solubility of the diatom shell, and the contact angle test value of the shell is 60.8° to 89.7°

[0019] Among the above-mentioned low-solubility diatoms, the carbon fixation efficiency of the marine diatoms is increased by more than 20%.

[0020] Application of low-solubility diatom in biological fixation of carbon dioxide.

[0021] By means of the above technical solution, the present invention has at least the following advantages:

[0022] 1) The cultivation method provided in the embodiment of the present invention uses organosilane as a silicon source in the culture solution, so that the organosilane is cross-linked to form the shell of the diatom. In this way, the diatom with hydrophobic surface is cultivated, which has high stability in the water environment, thereby reducing the solubility of the diatom shell;

[0023] 2) The content of iron ions in the culture medium of the present invention is relatively large. After the iron ions enter the diatom cells, they can effectively promote the absorption of organosilane by diatoms. Iron is an essential element for diatoms. Iron ions can promote the activity of diatoms and enhance their active absorption, thereby promoting their capture and absorption of organosilicon.

[0024] 3) In the embodiment of the present invention, the problem that a single organosilane is easy to condense in water and difficult to be absorbed by diatoms is solved through the joint action of tetramethoxysilane and another organosilane. The two silanes can form a metastable molecular binding state, which remains stable in water and is easy to be absorbed by diatoms;

[0025] 4) The embodiments of the present invention effectively solve the problem that diatom shells have high solubility and diatom organic matter is easily decomposed and returned to the environment. 2 And it has broad application prospects in the field of environmental protection.

[0026] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The morphology and element distribution diagrams of a single particle of diatom shell powder according to an embodiment of the present invention are as follows: 1a is a scanning electron microscope image; 1b is an energy spectrum diagram of silicon element distribution; 1c is an energy spectrum diagram of sulfur element distribution. DETAILED DESCRIPTION

[0028] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects proposed according to the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form.

[0029] Method for reducing the solubility of diatom shells Example 1

[0030] This embodiment discloses a method for reducing the solubility of diatom shells, specifically a method of organically modifying Thalassiosira salina by using tetramethoxysilane and 3-mercaptopropyltrimethoxysilane to reduce the solubility of diatom shells, and the specific steps are as follows:

[0031] Step 1: prepare 2L of artificial seawater and sterilize it in a high-temperature steam sterilizer at 121°C for 30 minutes, then cool it to room temperature, sterilize the components of the nutrient components with ultraviolet light for 15 minutes, and add them to the cooled artificial seawater, add tetramethoxysilane and 3-mercaptopropyltrimethoxysilane to the nutrient components in a weight ratio of 1:1, and make the concentration of the organosilane in the diatom culture solution 2×10 -4 M, the concentration of each component of the nutrient substance after being prepared into diatom culture solution is shown in Table 2; Step 2, mixing the diatom culture solution and adjusting the pH value of the diatom culture solution to 8; Step 3, Thalassiosira salsa at 1×10 4 The cells were transferred into diatom culture medium at a density of 10 cells / ml and cultured for 10 days under the following conditions: light intensity of 60 μmol·m -2 s -1 , the photoperiod was 12 / 12 light-dark cycle, the temperature was 25°C, and the Thalassiosira obtained by centrifugation enrichment was the low-solubility diatom.

[0032] In specific implementation, the composition contents of the artificial seawater and nutrient components are as follows:

[0033] Table 1: Composition and concentration of artificial seawater

[0034]

[0035] Table 2: Components of nutrient components and the concentration of each component after preparation into diatom culture solution

[0036]

[0037]

[0038] Since FeCl 3 6H 2O dissolution rate will change under different pH conditions. Therefore, when adding FeCl 3 6H 2 O to artificial seawater, some of the FeCl 3 In this embodiment, the specific amount of iron ions added to the diatom culture solution is 2.0×10 -5 M.

[0039] The specific structure of the diatom shell is an amorphous silicon-oxygen-organic sulfur-silicon skeleton, so the surface contains organic functional groups, which promotes hydrophobicity. The organic sulfur is sulfur connected to carbon. Since 3-mercaptopropyltrimethoxysilane contains sulfur, Figure 1 From the transmission electron microscope and silicon-sulfur element energy spectrum analysis of sulfur-containing organosilicon-modified Thalassiosira, we can see that: Figure 1 The diatom shell shown in a does not contain sulfur originally. After being cultured with silane containing sulfur as the silicon source, sulfur enters the diatom shell, so sulfur appears (such as Figure 1 c), silicon also enters the diatom shell (as shown in Figure 1 b), which proves that silane has entered the diatom shell, which will have an important impact on the properties of the diatom shell. The diatom shell cultured without organosilane has no sulfur, and a large amount of sulfur appears here, indicating that the sulfur-containing organosilane has entered the diatom shell and become a component of the siliceous skeleton construction.

[0040] Tetramethoxysilane is (CH 3 O) 4 Si is hydrolyzed to H in the culture medium. 4 SiO 4 , 3-mercaptopropyltrimethoxysilane is (CH 3 O) 3 SiC 2 CH 2 CH 2 SH, hydrolyzed in the culture medium to (HO)SiCH 2 CH 2 CH 2 SH, and then the two are transported into diatom cells to form diatom cell walls (i.e. diatom shells).

[0041] The method for testing the solubility of the shell of low-solubility diatoms in this embodiment is as follows:

[0042] Step 1) washing the Thalassiosira with ultrapure water for 3 times, then washing with 70° C. hot water for 3 times, and finally washing with anhydrous ethanol for 3 times to obtain a shell of Thalassiosira; this step removes organic matter on the diatom, and the diatom shell is dried after the organic matter is removed to obtain a shell powder;

[0043] Step 2) 10 mg of Thalassiosira shell powder was dissolved in 400 mL of ultrapure water and shaken at 25° C. for 9 days. The concentration of dissolved silicon in the test solution was 1.19 mg / L. The solubility of 3-mercaptopropyltrimethoxysilane-modified Thalassiosira was calculated to be 10.18%. The solubility (D%) was calculated as follows: 1.19 mg / L×1 mL×10 -3 × 60.1 × 400 mL / 10 mg × % = 10.18%, where 60.1 is SiO 2 The atomic weight of .

[0044] Since the contact angle is a key indicator of hydrophilicity and hydrophobicity, the contact angle of the diatom shell powder formed in this embodiment is 66.4°-79.7°, so the diatom shell in the embodiment of the present invention is a non-hydrophilic silane. The contact angle data is directly tested by a contact angle measuring instrument, and the specific measurement steps are as follows:

[0045] 1. Tablet pressing: Take about 20-30 mg of powder sample and place it between two pieces of aluminum foil, and use a tablet press to press it into a tablet with a smooth surface.

[0046] 2. Transfer: Remove the aluminum foil from the flattened sample and transfer it to the stage of a contact angle meter (Dataphysics OCA20).

[0047] 3. Focus. Adjust the micro-syringe to above the sample and adjust the camera focus to 2-2.5 times to make the sample image clear.

[0048] 4. Liquid dripping. The optimal amount of liquid squeezed out by a microsyringe is generally 6 μL, and clear small droplets can be observed at the lower end of the injector.

[0049] 5. Take a photo. Take a photo when the droplet falls and touches the sample.

[0050] 6. Measure the angle. At this time, the angle between the solid sample interface through the inside of the droplet and the gas-liquid interface between the droplet and the air is called the contact angle, which is between 0° and 180°.

[0051] The comparative data of the low-solubility diatom (Thalassosira salina) cultured in this example and the diatom obtained by culturing without adding organosilane are shown in Tables 3 and 4.

[0052] Method for reducing the solubility of diatom shells Example 2

[0053] The difference between this embodiment and the method for reducing the solubility of diatom shells in embodiment 1 is that this embodiment reduces the solubility of diatom shells by modifying Nitzschia with tetramethoxysilane and 3-aminopropyltrimethoxysilane. The specific steps are as follows:

[0054] Step 1: prepare 1L of artificial seawater and sterilize it in a high-temperature steam sterilizer at 135°C for 15 minutes, then cool it to room temperature, sterilize the components of the nutrient components by ultraviolet for 20 minutes, and add them to the cooled artificial seawater, add tetramethoxysilane and 3-aminopropyltrimethoxysilane to the nutrient components in a weight ratio of 3:1, and make the concentration of the organosilane in the diatom culture solution 2×10 -4 M, the concentration of each component of the nutrient substance is the same as that in Example 1; Step 2, the diatom culture solution is mixed and the pH value of the diatom culture solution is adjusted to 7; Step 3, the Nitzschia algae is cultured at 3×10 4 The cells were transferred into culture medium at a density of 10 cells / ml and cultured for 15 days under the following conditions: light intensity of 60 μmol·m -2 s -1 , the lighting period is 16 / 8 light-dark cycle, the temperature is 25°C, and the Nitzschia algae obtained by centrifugation enrichment are low-solubility diatoms.

[0055] The low-solubility diatom obtained in this example was prepared by removing organic matter from the shell in the manner described in Example 1 to obtain diatom shell powder.

[0056] The comparative data of the low-solubility diatoms (Nitzschia) cultured in this example and the diatoms cultured without adding organosilane are shown in Tables 3 and 4.

[0057] Method for reducing the solubility of diatom shells Example 3

[0058] The difference between this embodiment and the method for reducing the solubility of diatom shells in embodiment 1 is that the concentration of iron ions in the nutrient material after being prepared into the diatom culture solution is 3×10 -5 M.

[0059] Method for reducing the solubility of diatom shells Example 4

[0060] The difference between this embodiment and the method for reducing the solubility of diatom shells in Embodiment 1 is that tetramethoxysilane and 3-mercaptopropyltrimethoxysilane are used to organically modify Chaetoceros hornii.

[0061] Method for reducing the solubility of diatom shells Example 5

[0062] The difference between this embodiment and the method for reducing the solubility of diatom shells in Embodiment 1 is that tetramethoxysilane and 3-mercaptopropyltrimethoxysilane are used to organically modify Cyclotella.

[0063] Method for reducing the solubility of diatom shells Example 6

[0064] The difference between this embodiment and the method for reducing the solubility of diatom shells in Embodiment 1 is that tetramethoxysilane and 3-mercaptopropyltrimethoxysilane are used to organically modify Navicula.

[0065] Comparative Example 1

[0066] The difference between this comparative example and Example 1 of the method for reducing the solubility of diatom shells is that this comparative example uses sodium silicate as a silicon source to culture Thalassiosira, and the concentration of sodium silicate in the diatom culture solution is 2×10 -4 M.

[0067] Comparative Example 2

[0068] The difference between this comparative example and Example 2 of the method for reducing the solubility of diatom shells is that this comparative example uses sodium silicate as a silicon source to culture Nitzschia, and the concentration of sodium silicate in the diatom culture solution is 2×10 -4 M.

[0069] Comparative Example 3

[0070] The difference between this comparative example and Example 2 of the method for reducing the solubility of diatom shells is that this comparative example uses "tetramethoxysilane + 3-mercaptopropyltrimethoxysilane + sodium silicate" as the silicon source to culture Nitzschia, and the concentration of "tetramethoxysilane + 3-mercaptopropyltrimethoxysilane + sodium silicate" in the diatom culture solution is 2×10 -4 M.

[0071] Table 3: Experimental data of Examples 1 to 6 and Comparative Examples 1 to 3

[0072] Contact Angle Dissolution rate of diatom shells Carbon content Example 1 66.4°-79.7° 10.18％ 23.98％ Example 2 60.8°-79.7° 3.50％ 26.99％ Example 3 68.8°-89.8° 8.08％ 27.88％ Example 4 62.1°-76.5° 10.11％ 22.18％ Example 5 63.4°-78.1° 10.12％ 23.45％ Example 6 65.2°-77.8° 10.19％ 22.79％ Comparative Example 1 23.7°-29.4° 15.87％ 7.25％ Comparative Example 2 23.9°-29.6° 13.20％ 9.12％ Comparative Example 3 24.8°-29.8° 14.16％ 10.18％

[0073] It can be seen from the above-mentioned methods for reducing the solubility of diatom shells in Examples 1 and 2 that when the concentration of organic silicon increases, the concentration of dissolved silicon in the diatom culture solution decreases after the diatom shells react in water for a period of time, the dissolution rate of the diatom shells decreases, and the carbon content in the diatom shells increases significantly.

[0074] The following is a further description of the method for measuring the dissolution rate of the diatom shell by taking the Nitzschia algae shell powder obtained in Example 2 and Comparative Example 2 as examples. The method for measuring the dissolution rate of the diatom shell comprises the following steps: Step 1) Wash the Nitzschia algae with ultrapure water 3 times, then wash it with 60°C hot water 3 times, and finally wash it with methanol 3 times to obtain the Nitzschia algae shell. Step 2) Dissolve 2 mg of Nitzschia algae shell powder in 80 mL of ultrapure water and shake it at 20°C for 12 days. The solubility of the modified Nitzschia algae is calculated to be 3.50%. The solubility calculation steps of the modified Nitzschia algae are: the concentration of silicon in the solution × 1 mL × 10 -3 ×60.1 / 28.1×80mL / 2mg×100% (the same below).

[0075] In comparative example 2, the solubility of Nitzschia cultured with sodium silicate was calculated to be 13.20%. Compared with the Nitzschia cultured with sodium silicate in Example 2, the solubility of Thalassiosira modified with 3-aminopropyltrimethoxysilane in comparative example 2 was increased by 73.49% compared with Example 2.

[0076] In the same way, the solubility of Thalassiosira cultured with sodium silicate in Comparative Example 1 was calculated to be 15.87%. Compared with Thalassiosira cultured with sodium silicate in Example 1, the solubility of Thalassiosira modified with 3-mercaptopropyltrimethoxysilane in Comparative Example 1 was increased by 35.48% compared with Example 1.

[0077] The solubility of the diatom shells obtained by the cultivation method of the organically modified marine diatoms of the embodiment of the present application is reduced by 35.6-73.5% compared with the control example, and the improved carbon fixation efficiency of the "biological pump" is increased by more than 58.8%.

[0078] The data on the improvement of carbon fixation efficiency are further explained with the data of carbon content: 1) The carbon content of the sea sorghum shell in Comparative Example 1 using sodium silicate as the silicon source is 7.25%, and the carbon content of Example 1 using organosilicon as the silicon source is 23.98%, and the calculation of carbon fixation efficiency improvement (%) = (23.98% - 7.25%) / 23.98% = 69.77%; 2) The carbon content of Comparative Example 2 is 9.12%, and the carbon content of Example 2 is 26.99%, which is an increase of 66.21%.

[0079] Method for obtaining carbon content: Take about 2.00 mg of diatom samples obtained by culture in Examples 1 to 6 and Comparative Examples 1 to 3, put them into a 6×12 mm tin boat, and use Vario ELⅢ element analyzer to analyze carbon for the corresponding diatoms. Each sample is tested three times in parallel, and the average value is used for analysis. The detection limit of the Vario ELⅢ element analyzer is 40 ppm.

[0080] From Example 3 we can see that the higher the iron concentration, the better the silane absorption and the lower the diatom shell solubility.

[0081] In Comparative Example 3, the silicon sources of the culture solution are the three substances of "tetramethoxysilane + 3-mercaptopropyltrimethoxysilane + sodium silicate". Due to the presence of sodium silicate, the diatoms basically do not absorb tetramethoxysilane and 3-mercaptopropyltrimethoxysilane during the growth process. Therefore, the diatoms cultured in Comparative Example 3 have a small contact angle and a high dissolution rate.

[0082] The test data of Examples 1 to 6 and Comparative Examples 1 to 3 show that the contact angle of diatom shell powder using organosilane as the silicon source is tested, and it is found that the contact angle is in the range of 60.8°-89.7°, compared with the sample using only sodium silicate as the silicon source, and the contact angle is 23.7°-29.8°. After different diatom species are modified by the method provided by the present invention, the dissolution rate of diatom shells can be greatly reduced, and the carbon fixation efficiency is greatly improved.

[0083] Comparative Example 4

[0084] The difference between this comparative example and Example 2 of the method for reducing the solubility of diatom shells is that in this comparative example, tetramethoxysilane is used alone as a silicon source to culture Nitzschia, and the concentration of tetramethoxysilane in the diatom culture solution is 2×10 -4 M.

[0085] Comparative Example 5

[0086] The difference between this comparative example and Example 2 of the method for reducing the solubility of diatom shells is that in this comparative example, 3-aminopropyltrimethoxysilane is used as a silicon source to culture Nitzschia, and the concentration of 3-aminopropyltrimethoxysilane in the diatom culture solution is 2×10 -4 M.

[0087] Comparative Example 6

[0088] The difference between this comparative example and Example 2 of the method for reducing the solubility of diatom shells is that the concentration of iron ions added to the diatom culture solution in this comparative example is 1×10 -5 M.

[0089] During the diatom cultivation process of Examples 1 to 6 and Comparative Examples 1 to 6, the number of cells in the diatom culture solution was counted at different cultivation days. The specific data are shown in the following table:

[0090] Table 4: Number of cells in diatom culture medium

[0091]

[0092]

[0093] As can be seen from the above table, using only a single organosilane as a silicon source often leads to a decrease in the growth rate of diatoms and slow division. In order to solve this problem, the ideas for solving this problem of the present invention include the following two: the first way is to increase the content of iron ions in the diatom culture solution; the second way is to use two organosilanes as a silicon source. In the first way, after the iron ions enter the diatom cells, they can effectively promote the absorption of organosilanes by diatoms; iron is an essential element for diatoms, and iron ions can promote the activity of diatoms, enhance their active absorption, thereby promoting their capture and absorption of organosilicon; in the second way, a single organosilane is easy to condense in the water body, thereby forming larger molecules and producing precipitation, which is difficult to be absorbed by diatoms, and the two silanes can form a metastable molecular binding state, remain stable in the water body, and are easy to be absorbed by diatoms, thus, the two organosilanes form the shell of diatoms by cross-linking. Both methods can promote the cross-linking and polymerization of silanes in the diatom body, thereby ensuring the growth and division of diatoms.

[0094] Application examples of low solubility diatoms

[0095] The application of low-solubility diatoms provided in this embodiment is used for biological fixation of carbon dioxide. After the low-solubility diatoms die, they fix carbon dioxide by burying them deep. Since the solubility of the diatom shell is reduced, the organic carbon carried by the diatom after death is fixed in the diatom shell. The organosilicon in the diatom shell contains carbon, and the carbon in the diatom skeleton is also fixed, thereby greatly increasing the amount of carbon fixation.

[0096] The low-solubility diatom captures carbon dioxide from the atmosphere through photosynthesis, and captures and fixes carbon dioxide through photosynthesis through the carbon dioxide concentration mechanism (CCM), forming organic carbon that is stored in the organism and transported to the deep part of the water body. During the sedimentation of organic carbon from the low-solubility diatom, the diatom shell will not dissolve, so that the organic carbon will not decompose during the sedimentation process and can be completely deposited on the seabed.

[0097] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for reducing the solubility of diatom frustules, characterized in that, the method of using organic modification to reduce the solubility of diatom frustules includes the following steps: Step 1, prepare an artificial seawater solution and sterilize the artificial seawater solution, add organosilane and nutrients to the artificial seawater solution to form a diatom culture solution. The molar concentrations of the components of organosilane and nutrients after being configured into the diatom culture solution are respectively: organosilane (1-2)×10 -4 M, ferric chloride (2-3)×10 -5 M, sodium nitrate (1-10)×10 -4 M, sodium dihydrogen phosphate (1-5)×10 -5 M, disodium ethylenediaminetetraacetate (1-1.5)×10 -5 M, copper sulfate (2-4)×10 -8 M, sodium molybdate (1-3)×10 -8 M, zinc sulfate (1-8)×10 -8 M, cobalt chloride (1-5)×10 -8 M, manganese chloride (1-10)×10 -7 M, vitamin B1 (1-3)×10 -7 M, biotin (1-3)×10 -9 M, vitamin B12 (1-4)×10 -10 M; Step 2, mix the diatom culture solution and adjust the pH value of the diatom culture solution to 7-8; Step 3: Inoculate the diatom culture solution with diatoms and culture for 7 to 15 days. The culture conditions are as follows: the light intensity is 50 to 70 μmol·m -2 s -1 , the light cycle is 12 / 12 to 16 / 8 light / dark cycle, and the temperature is 20 to 25 °C; Wherein: The organosilane includes a first organosilane and a second organosilane. The first organosilane is tetramethoxysilane, and the second organosilane is 3-mercaptopropyltrimethoxysilane and / or 3-aminopropyltrimethoxysilane. The mass ratio of the first organosilane to the second organosilane is 1-3:1; The components and concentrations of each substance in the artificial seawater solution are: sodium chloride 20.758 g / L, sodium sulfate 3.477 g / L, potassium chloride 0.587 g / L, sodium bicarbonate 0.170 g / L, potassium bromide 0.0845 g / L, boric acid 0.0225 g / L, sodium fluoride 0.0027 g / L, magnesium chloride 9.395 g / L, calcium chloride 1.316 g / L, strontium chloride 0.0214 g / L.

2. The method for reducing the solubility of diatom frustules according to claim 1, characterized in that, the diatom is any one or more of Thalassiosira, Chaetoceros, Nitzschia, Cyclotella, Navicula.

3. The method for reducing the solubility of diatom frustules according to claim 1, characterized in that, The diatoms are inoculated into the diatom culture solution at 1×10 4 to 1×10 5 cells / mL.

4. The method for reducing the solubility of diatom frustules according to claim 1, characterized in that, The frustule of the cultured diatom is a non-hydrophilic silane, and the measured contact angle value of the frustule is 60.8°-89.7°.

5. A diatom with low solubility, characterized in that, the diatom with low solubility is cultured by the method for reducing the solubility of diatom frustules according to any one of claims 1-4, and the measured contact angle value of the frustule is 60.8°-89.7°.

6. The diatom with low solubility according to claim 5, characterized in that, the carbon fixation efficiency of the diatom is increased by more than 20%.

7. An application of the diatom with low solubility in claim 5 or 6 in biological carbon dioxide fixation.

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