Bio-based magnesium silicate composite material and preparation process thereof

Abstract

The invention provides a method for preparing a magnesium silicate composite material, which is characterized by comprising the following steps: (1) reacting rice hull ash with alkali, and separating to obtain crude carbon and a silicate part; (2) adding sodium sulfate and the silicate obtained in the step (1) into a reaction tank in advance; (3) adding sodium silicate, magnesium salt and acid into the reaction tank in the step (2) for reaction to obtain magnesium silicate slurry; (4) filtering and drying the magnesium silicate slurry in the step (3) to obtain magnesium silicate; (5) drying the crude carbon in the step (1) to obtain a carbon product; and (6) mixing products obtained in the steps (4) and (5) to obtain the magnesium silicate composite material. The composite material disclosed by the invention is used for oil refining, and can be used for efficiently removing 3-MCPD and reducing the acid value in oil.

Description

Technical Field

[0001] This application relates to the field of materials, and particularly to composite materials and their preparation methods. Background Art

[0002] The main components of rice husk ash are silicon dioxide and carbon. Different from the crystalline silicon dioxide in quartz sand, the silicon dioxide in rice husk ash is amorphous and can be dissolved by an alkali solution under certain reaction conditions to form a silicate solution. The prepared silicate solution can produce silicon-containing products with different structures through an acid precipitation reaction.

[0003] The main component of the de-silicated rice husk ash is carbon. After extracting the amorphous silicon dioxide from the rice husk ash, a large number of micropores are formed on the surface of the carbon, and its specific surface area is greatly increased, thereby forming rice husk activated carbon with certain adsorption capacity.

[0004] During the cooking process, the oil undergoes a series of reactions such as thermal decomposition, thermal polymerization, cracking, and hydrolysis with oxygen in the air, water and other components in the fried food, and the oil itself at high temperature, generating aldehydes, ketones, lower fatty acids, oxides, peroxides, epoxides, and high molecular weight thermal polymers, making the oil thicken, become sticky, change color, and even deteriorate, producing malodors or foaming and other deterioration phenomena, and further generating more components harmful to human health. Therefore, the deterioration phenomenon of oil during frying not only shortens the service life of the oil itself, causing economic losses, but also leads to the deterioration of the color and flavor of fried foods, reducing the quality of fried foods. More seriously, it directly affects people's physical health.

[0005] The magnitude of the acid value reflects the content of free acids in fats. The quality of edible oil is closely related to the amount of free fatty acids it contains. Therefore, the quality of oil can generally be measured by the acid value. The smaller the acid value, the better the quality of the edible oil, and the better the freshness and refining degree. However, if the acid value of the edible oil is too high, it will cause discomfort and diarrhea in the human gastrointestinal tract after consumption, and even damage the liver.

[0006] Regarding how to extend the service life of edible oil and slow down the deterioration rate of frying oil, at present, adsorbents are still used to adsorb and treat the oil in the initial stage of deterioration. Commonly used adsorbents include activated clay, silica gel, etc. However, the oil absorption amount is relatively large, which will reduce the yield of the purified oil, and the removal effect on 3-MCPD is relatively poor.

[0007] The synthesized magnesium silicate has good selective and adsorption properties. There are both acidic and basic adsorption centers on the surface of magnesium silicate, so it has both acid and base adsorption properties. The adsorption of magnesium silicate in oils and fats is a simultaneous chemical adsorption and physical adsorption, and it has the ability to react with impurities and remove the reactants, which can greatly enhance its ability to extend the service life of edible oils and slow down the fission rate. Magnesium silicate also has strong chemical stability, environmental friendliness, etc. In current research, the main application methods in the magnesium silicate industry are hydrothermal method and melting method: The hydrothermal method refers to a reaction in a closed reaction vessel with water as the solvent, where magnesium-containing and silicon-containing salt raw materials react at a temperature as high as several hundred degrees Celsius, mainly producing magnesium hydrogen silicate; The melting method mainly uses magnesium oxide and quartz sand solids, which are melted at high temperature to obtain magnesium silicate solids. However, the hydrothermal method and the melting method need to be carried out under high temperature and high pressure conditions, which require high equipment requirements and large energy consumption during the reaction process, and the construction and maintenance costs are high. In addition, single magnesium silicate materials, activated clay, silica gel and other materials have poor effects in removing 3-MCPD because they do not have corresponding adsorption and reaction sites.

[0008] Existing production of magnesium silicate uses ore resources as raw materials. Quartz sand is a non-renewable mineral silicon resource. With the development of industry, the excessive consumption of silicon resources has caused great resource shortages. With the improvement of environmental awareness, the production of adsorption materials from bio-based raw materials has attracted more and more attention. It is becoming more and more urgent to use bio-based raw materials to produce adsorption materials for use in the refining process of oils and fats. Summary of the Invention

[0009] The inventor of the present invention found through a large number of experimental studies that by using rice husk ash as a raw material and controlling the process parameters of the reaction, the present invention obtains the target product through the process of gradually mixing solutions containing silicate and magnesium salt and nucleation and crystal growth under the action of an initiator. The equipment required for synthesis is simple, with low energy consumption and short duration. By controlling conditions such as the temperature, concentration, pH, and time of the solution during the reaction process, the microstructure and component ratio of the product can be adjusted, and the types and quantities of surface groups can be controlled, thereby achieving the purpose of controlling the application performance of the product;

[0010] Finally, a bio-based composite material is obtained. The composite material is used in the refining process of oils and fats to efficiently remove 3-MCPD and reduce the acid value in the oils and fats.

[0011] In the first aspect of the present invention, a method for preparing a magnesium silicate composite material is provided. The method includes the following steps:

[0012] (1) After the rice husk ash reacts with an alkali, the crude carbon and the silicate part are separated;

[0013] (2) Pre-add sodium sulfate and the silicate obtained in step (1) in the reaction tank;

[0014] (3) Add sodium silicate, a magnesium salt, and an acid to the reaction tank described in step (2) for reaction to obtain a magnesium silicate slurry;

[0015] (4) Filter and dry the magnesium silicate slurry in step (3) to obtain magnesium silicate;

[0016] (5) Dry the crude carbon in step (1) to obtain a carbon product;

[0017] (6) Mix the products obtained in steps (4) and (5) to obtain a magnesium silicate composite material.

[0018] In one or more embodiments of the present invention, based on the total mass of the rice husk ash, the carbon content in the rice husk ash is 5 - 25%, and the silica content is 65 - 80%.

[0019] In one or more embodiments of the present invention, the base in step (1) is selected from one or more of sodium hydroxide, potassium hydroxide, magnesium hydroxide, sodium carbonate, potassium carbonate, and magnesium carbonate; preferably sodium hydroxide.

[0020] In one or more embodiments of the present invention, the mass percentage concentration of the base in step (1) is 8 - 20%.

[0021] In one or more embodiments of the present invention, the weight ratio of the rice husk ash to the base in step (1) is about 3:1 to 5:1.

[0022] In one or more embodiments of the present invention, in step (1), the reaction temperature of the rice husk ash and the base is 100 - 300 °C.

[0023] In one or more embodiments of the present invention, in step (1), the reaction time is 3 - 6 h.

[0024] In one or more embodiments of the present invention, in step (1), after the reaction, the slurry is filtered.

[0025] In one or more embodiments of the present invention, in step (1), the filtration pressure is 4 - 6 bar.

[0026] In one or more embodiments of the present invention, in step (3), the magnesium salt is selected from one or more of magnesium sulfate, magnesium chloride, and magnesium nitrate; preferably magnesium sulfate.

[0027] In one or more embodiments of the present invention, in step (3), the concentration of the magnesium salt solution is 5 - 20%.

[0028] In one or more embodiments of the present invention, the dosage of the magnesium salt solution in step (3) is 80% - 240% of the amount of rice husk ash.

[0029] In one or more embodiments of the present invention, the acid in step (3) is selected from sulfuric acid.

[0030] In one or more embodiments of the present invention, the concentration of the acid in step (3) is 5 - 15%.

[0031] In one or more embodiments of the present invention, the reaction temperature in step (3) is 50 - 70 °C.

[0032] In one or more embodiments of the present invention, the reaction time in step (3) is 40 - 120 min.

[0033] In one or more embodiments of the present invention, the reaction pH in step (3) is 3 - 10.

[0034] In one or more embodiments of the present invention, after the reaction in step (3), it is cured, and the curing time is 60 - 120 min.

[0035] In one or more embodiments of the present invention, the rice husk ash is obtained through pretreatment.

[0036] In one or more embodiments of the present invention, the pretreatment includes the step of screening and removing impurities from the rice husk ash.

[0037] In a second aspect of the present invention, there is provided a magnesium silicate composite material, and the mass ratio of C, Mg, and Si in the material is 20:23:73 - 10:90:60.

[0038] In one or more embodiments of the present invention, the mass ratio of C and magnesium silicate in the material is 10:150 - 20:100.

[0039] In one or more embodiments of the present invention, the magnesium silicate composite material is prepared by the method described in the first aspect of the present invention.

[0040] In a third aspect of the present invention, there is provided a method for reducing 3 - MCPD in oils and fats, and the method is to treat the oils and fats with the composite material prepared by the method described in the first aspect of the present invention; or to treat the oils and fats with the composite material described in the second aspect of the present invention.

[0041] In one or more embodiments of the present invention, in the present invention, the oil and fat can be various types of oil and fat well-known in the art, especially edible oil, including animal oil and vegetable oil. Exemplary vegetable oils include but are not limited to one or any mixture of two or more of rice bran oil, sunflower seed oil, palm oil, palm kernel oil, peanut oil, rapeseed oil (also known as colza oil), cottonseed oil, safflower oil, perilla oil, camellia oil, palm fruit oil, coconut oil, olive oil, cocoa butter, Chinese tallow tree seed oil, almond oil, apricot kernel oil, tung oil, rubber seed oil, rice bran oil, corn germ oil, wheat germ oil, sesame oil, castor oil, linseed oil, evening primrose oil, hazelnut oil, walnut oil, grape seed oil, sesame oil, borage oil, sea buckthorn oil, tomato seed oil, pumpkin seed oil, macadamia oil, cocoa butter, algal oil, etc. Exemplary animal oils can be any mixture of one or two or more of beef tallow, lard, mutton fat, chicken fat, fish oil, seal oil, whale oil, dolphin oil, oyster sauce, etc. The oil and fat can be various oil and fat that need to be decolorized and / or plasticizer-removed. The oil and fat can be crude oil, or oil and fat that have undergone one or more processes in the conventional oil refining process, for example, it can be degummed oil, decolorized oil or deodorized oil, etc. In some embodiments, the oil and fat can be refined oil, that is, finished oil.

[0042] In a fourth aspect of the present invention, there is provided an oil refining method, which includes the step of mixing and adsorbing the oil and fat with the composite material described in the present invention.

[0043] In one or more embodiments of the present invention, the method further includes the step of filtering to remove the composite material.

[0044] Technical effects of the present invention:

[0045] (1) Using rice husk ash as the raw material and making full use of the rice husk ash resources, it is economical and environmentally friendly;

[0046] (2) Used in the oil refining process, it can efficiently remove 3-MCPD and reduce the acid value in the oil and fat.

[0047] (3) The rice husk ash is relatively pure and is easy to extract high-purity silicate solution and carbon material. Description of the drawings

[0048] Appendix Figure 1 : Schematic process diagram for preparing the composite material Detailed implementation manners

[0049] In the present invention, if there is no special description, the percentage (%) or part refers to the weight percentage or weight part relative to the composition.

[0050] In the present invention, if there is no special description, the various components or their preferred components involved can be combined with each other to form a new technical solution.

[0051] In the present invention, unless otherwise specified, all the embodiments and preferred embodiments mentioned herein can be combined with each other to form new technical solutions.

[0052] In the present invention, unless otherwise specified, all the technical features and preferred features mentioned herein can be combined with each other to form new technical solutions.

[0053] In the present invention, unless otherwise stated, the sum of the contents of the components in the composition is 100%.

[0054] In the present invention, unless otherwise stated, the sum of the parts of the components in the composition can be 100 parts by weight.

[0055] In the present invention, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers.

[0056] In the present invention, unless otherwise specified, the integer numerical range "a - b" represents an abbreviated representation of any integer combination between a and b, where a and b are both integers. For example, the integer numerical range "1 - N" represents 1, 2... N, where N is an integer.

[0057] In the present invention, unless otherwise specified, "their combination" refers to a multi-component mixture of the said respective elements, such as a two-component, three-component, four-component, and up to the maximum possible multi-component mixture.

[0058] If not specifically indicated, the term "a" used in this specification means "at least one".

[0059] If not specifically indicated, the basis of the percentages (including weight percentages) described in the present invention is the total weight of the composition.

[0060] The "ranges" disclosed herein are in the form of a lower limit and an upper limit. There can be one or more lower limits, and one or more upper limits respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundaries of a particular range. All ranges that can be defined in this way are inclusive and combinable, that is, any lower limit can be combined with any upper limit to form a range.

[0061] In this article, unless otherwise specified, each reaction is carried out under normal temperature and pressure.

[0062] In this article, unless otherwise specified, each reaction step can be carried out sequentially or non-sequentially. For example, other steps can be included between each reaction step, and the reaction steps can also be reversed in order. Preferably, the reaction methods herein are carried out sequentially.

[0063] The technical solution of the present invention will be further specifically described as follows:

[0064] <First aspect>

[0065] A method for preparing a magnesium silicate composite material, the method controls conditions such as the temperature, concentration, pH, and time of the solution during the reaction process, adjusts the microstructure and component ratio of the product, and controls the type and quantity of its surface groups, so as to achieve the purpose of controlling the application performance of the product; specifically, the method includes the following steps:

[0066] (1) After the rice husk ash reacts with an alkali, crude carbon and a silicate part are separated.

[0067] (2) Sodium sulfate and the silicate obtained in step (1) are pre-added to a reaction tank.

[0068] (3) Sodium silicate, a magnesium salt, and an acid are added to the reaction tank described in step (2) for reaction to obtain a magnesium silicate slurry.

[0069] (4) The magnesium silicate slurry in step (3) is filtered and dried to obtain magnesium silicate.

[0070] (5) The crude carbon in step (1) is dried to obtain a carbon product.

[0071] (6) The products obtained in steps (4) and (5) are mixed to obtain a magnesium silicate composite material.

[0072] According to the embodiment of the present invention, based on the total mass of the rice husk ash, the carbon content in the rice husk ash is 5-25%, and the silicon dioxide content is 65-80%.

[0073] According to the embodiment of the present invention, the rice husk ash is obtained through pretreatment.

[0074] According to the embodiment of the present invention, the pretreatment includes the step of screening and removing impurities from the rice husk ash.

[0075] According to the embodiment of the present invention, the alkali in step (1) is selected from one or more of sodium hydroxide, potassium hydroxide, magnesium hydroxide, sodium carbonate, potassium carbonate, and magnesium carbonate; preferably sodium hydroxide.

[0076] According to the embodiment of the present invention, the mass percentage concentration of the alkali in step (1) is 8-20%.

[0077] According to an embodiment of the present invention, the weight ratio of rice husk ash to alkali in step (1) is not particularly limited as long as the mass of the alkali is in excess relative to the rice husk ash, that is, the mass ratio of rice husk ash to the alkali in the alkali solution is greater than 1:1. Exemplarily, it is about 3:1 to 5:1. During the research process, the inventors found that the alkali content in the alkali solution uses light alkali. If it is higher than 5:1, the amount of alkali is too small, which affects the extraction of silicon, the silicon content in the activated carbon is too high, the adsorption sites and pores are blocked, and the adsorption rate of impurities is reduced; if it is lower than 3:1, the silicon content in the activated carbon is too low, the surface silicon-containing basic groups are reduced, and the reaction amount with impurity substances is reduced, affecting the impurity removal effect. Therefore, an appropriate ash-alkali ratio can ensure that the content of silicon dioxide in the rice husk ash after treatment with the alkaline solution is within an appropriate range, reaching more than 10% by mass, for example, 10% - 50% by mass, so as to meet the subsequent application requirements.

[0078] According to an embodiment of the present invention, in step (1), the reaction temperature of the rice husk ash and the alkali is 100 - 300 °C.

[0079] According to an embodiment of the present invention, in step (1), the reaction time is 3 - 6 h.

[0080] According to an embodiment of the present invention, in step (1), after the reaction, the slurry is filtered.

[0081] According to an embodiment of the present invention, in step (1), the filtration pressure is 4 - 6 bar.

[0082] According to an embodiment of the present invention, the step after filtration further includes a water washing step. Exemplarily, the water washing is to wash the filtered filter cake with water until it is neutral.

[0083] According to an embodiment of the present invention, in step (2), a solution with a sodium sulfate concentration of 0.5 - 4% is prepared in the reaction tank.

[0084] According to an embodiment of the present invention, the filtrate obtained by pressure filtration after the reaction of rice husk ash and alkali is concentrated silicate; the filtrate is temporarily stored for use. The washing liquid obtained after washing the filter cake will contain a small amount of silicate. The washing liquid is collected in the reaction tank and the concentration of silicate in the washing liquid is adjusted; exemplarily, the silicate concentration is adjusted to a solution of 0.5 - 4%. If the silicate concentration in the washing liquid is higher than the maximum value of this range, water is added to the reaction tank for dilution; if it is lower than the minimum value of this range, the reaction tank is heated to remove some water and increase its concentration.

[0085] According to an embodiment of the present invention, in step (3), the magnesium salt is selected from one or more of magnesium sulfate, magnesium chloride, and magnesium nitrate, and preferably magnesium sulfate.

[0086] According to an embodiment of the present invention, in step (3), the concentration of the magnesium salt solution is 5-20%.

[0087] According to an embodiment of the present invention, in step (3), the addition amount of the magnesium salt solution is 4000 g - 12000 g.

[0088] According to an embodiment of the present invention, in step (3), the acid is selected from sulfuric acid.

[0089] According to an embodiment of the present invention, in step (3), the concentration of the acid is 5-15%.

[0090] According to an embodiment of the present invention, in step (3), the reaction temperature is 50-70 °C.

[0091] According to an embodiment of the present invention, in step (3), the reaction time is 40-120 min.

[0092] According to an embodiment of the present invention, in step (3), the change rate of pH in the reaction tank is controlled by the pumping speed of sulfuric acid. For example, the change rate of pH is ≤5 / h, or ≤3 / h, or 2.5 / h.

[0093] According to an embodiment of the present invention, in step (3), the pH at the end point of sulfuric acid titration is greater than or equal to 7; or greater than or equal to 8, or greater than or equal to 9, or greater than or equal to 10; or 7-12 or 8-10.

[0094] According to an embodiment of the present invention, after step (3), a step of constant temperature curing is carried out to grow its crystal nuclei; for example, the curing reaction time is 60-120 min.

[0095] According to an embodiment of the present invention, in step (4), the slurry is filtered and washed until the conductivity of the filtrate <2 ms / cm.

[0096] According to an embodiment of the present invention, the magnesium silicate sample after washing in step (4) is dried and pulverized.

[0097] According to an embodiment of the present invention, in step (6), the magnesium silicate and the carbon product are mixed, and they can be all mixed, or mixed according to a mass ratio of 1:1 to 15:1; or mixed according to a mass ratio of 1:1 to 13:1. For example, they are mixed according to a mass ratio of 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1.

[0098] <Second aspect>

[0099] A magnesium silicate composite material is provided. The mass ratio of C, Mg, and Si in the material is 20:23:73 to 10:90:60.

[0100] In one or more embodiments of the present invention, the mass ratio of C and MgSiO3 in the material is 10:150 to 20:100.

[0101] According to the embodiments of the present invention, the mass ratio of C and MgSiO3 in the material is 10:125, 15:120, 20:117.

[0102] According to the embodiments of the present invention, the magnesium silicate composite material is prepared by the method described in the first aspect of the present invention.

[0103] <Third aspect>

[0104] A method for reducing 3-MCPD in oils and fats, which is to treat oils and fats with the composite material prepared by the method described in the first aspect of the present invention; or to treat oils and fats with the composite material described in the second aspect of the present invention.

[0105] According to the embodiments of the present invention, in the present invention, the oils and fats can be various oils and fats well-known in the art, especially edible oils, including animal oils and vegetable oils. Exemplary vegetable oils include but are not limited to rice bran oil, sunflower oil, palm oil, palm kernel oil, peanut oil, rapeseed oil (also known as rapeseed oil), cottonseed oil, safflower oil, perilla oil, tea seed oil, palm fruit oil, coconut oil, olive oil, cocoa butter, Chinese tallow tree seed oil, almond oil, tung oil, rubber seed oil, rice bran oil, corn germ oil, wheat germ oil, sesame seed oil, castor oil, linseed oil, evening primrose oil, hazelnut oil, walnut oil, grape seed oil, sesame oil, borage oil, seabuckthorn oil, tomato seed oil, pumpkin seed oil, macadamia nut oil, cocoa butter, algal oil, etc., or any mixture of two or more of these oils. Exemplary animal oils can be any mixture of one or more of beef tallow, lard, mutton fat, chicken fat, fish oil, seal oil, whale oil, dolphin oil, oyster sauce, etc.; preferably, the oil and fat is palm oil. The oil and fat can be various oils and fats that need to be decolorized and / or plasticizer-removed. The oil and fat can be crude oil, or oil and fat that has undergone one or more processes in the conventional oil refining process, for example, it can be degummed oil, decolorized oil, or deodorized oil, etc. In some embodiments, the oil and fat can be refined oil, that is, finished oil.

[0106] <Fourth aspect>

[0107] An oil refining method, which includes the step of mixing and adsorbing the oil and fat with the composite material described in the present invention.

[0108] According to an embodiment of the present invention, the method further includes a step of filtering to remove the composite material.

[0109] The present invention will be described below by way of specific examples. It should be understood that these examples are merely illustrative and are not intended to limit the scope of the present invention. The methods, reagents, and materials used in the examples,

[0110] unless otherwise specified, are conventional methods, reagents, and materials in the art. The starting compounds in the examples can all be obtained through commercial channels.

[0111] Source of raw materials:

[0112] Rice husk ash: Purchased from Yihai Kerry Group

[0113] All other raw material reagents are from commercial sources.

[0114] Detection method

[0115] 1. 3-MCPD test method: The AOCS official method Cd 29C-13 GC / MS method is used to determine 3-MCPD fatty acid esters and glycidyl fatty acids in edible oils and fats.

[0116] 2. Acid value test method: Accurately weigh 3.00 - 5.00 g of the oil sample and place it in a 250 ml conical flask. Add 50 ml of a neutral ether-ethanol mixture, shake to dissolve the oil. If necessary, place it in hot water and warm it to promote dissolution. Then cool to room temperature, add 2 - 3 drops of phenolphthalein indicator, and titrate with a 0.1000 mol / L KOH standard solution until a faint pink color appears and does not fade within 30 s, which is the end point.

[0117] The calculation formula for the acid value of the sample (mg / g) is:

[0118] X = (cV / m) × 56.1

[0119] Where: X: Acid value (mg KOH / g)

[0120] V: Titration end point volume (mL)

[0121] 56.1: Molecular weight of potassium hydroxide

[0122] C: Concentration of the titrant KOH (mol / L)

[0123] m: Sample amount (g)

[0124] 3. Carbon content detection method:

[0125] Weigh about 1 g of the dried sample and put it into a ceramic crucible that has been accurately weighed and has a constant mass (accurate to 0.001 g)

[0126] Put the crucible into a high-temperature furnace at (900±25)°C and burn it for half an hour. Then put it into a desiccator to cool to room temperature and weigh it (accurate to 0.001 g). Weigh it twice, and if the difference between the two weighings does not exceed 3 mg, record the smaller weighing value.

[0127] Determine with duplicate samples.

[0128] The carbon content (X) expressed as a mass percentage is calculated by the following formula:

[0129] X = (M0 - M1) / M0 * 100%

[0130] Where: M0---mass of the sample before burning, g

[0131] M1---mass of the sample after burning, g.

[0132] If the difference between the two determination results is less than 10% of the larger value, then calculate the average of the two, and report the result (accurate to 0.1%); between (0 - 0.1)% is "less than 0.1%".

[0133] 4. Detection method for SiO2 content:

[0134] After the sample is burned at 950°C ± 50°C for 1 h, decompose silicon dioxide by heating with excessive hydrofluoric acid, and the generated fluorosilicic acid escapes. Weigh after burning, and the lost mass is the silicon dioxide content.

[0135] Determine the carbon content with a platinum crucible, and record the mass m0 of the sample before burning and the mass M1 after burning

[0136] Add 15 ml of hydrofluoric acid (concentration 40%) and 1 ml of sulfuric acid (concentration 49%) to the platinum crucible with the residue, and evaporate to a paste on a hot plate, while avoiding splashing losses. Cool the crucible and wash down the substances on the wall with water, then add 10 ml of hydrofluoric acid and evaporate to dryness.

[0137] Heat the residue on a hot plate until no more white smoke is emitted, then burn it in a muffle furnace at (900±20)°C for 15 min,

[0138] Take out the crucible from the furnace, cool it to room temperature in a desiccator, and weigh M2 (accurate to 0.1 mg).

[0139] The silicon dioxide content (X) of the dry sample expressed as a mass percentage is calculated according to formula (2):

[0140] X = (M1 - M2) / M0 * 100%

[0141] Where: M0—the mass of the sample when determining the loss on ignition,

[0142] M1—the mass of the sample after determining the loss on ignition,

[0143] M2—the mass after being calcined with hydrofluoric acid.

[0144] If the difference between the two determination results is less than 10% of the larger value, then calculate the average of the two, and report the result (accurate to 0.1%); between (0 - 0.1)% is "less than 0.1%".

[0145] Example 1:

[0146] Select 5000 g of rice husk ash with a carbon content of 23% and a silica content of 68%. After impurity removal, it is mixed evenly with 7500 g of a 20% sodium hydroxide solution and 5000 g of water, and placed in a closed reactor A. React at a temperature of 150 °C for 4 hours. Filter the obtained slurry through a plate and frame filter press (Jingjin BMSY0.5 - 250 - U), control the filtration pressure at 5 bar, and the filtrate is concentrated silicate, which is temporarily stored for use; after filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reactor B; the filter cake is flash - dried to obtain a dried carbon product. Prepare a 5% sulfuric acid solution and a 5% magnesium sulfate solution. Add sodium sulfate solid to reactor B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reactor B), adjust its concentration to 3.5% sodium silicate and 1% sodium sulfate and heat to 70 °C. After reaching the reaction temperature, start the peristaltic pump, and simultaneously pump in 12000 g of concentrated silicate and magnesium sulfate solution. Pump in sulfuric acid to control the pH value in reactor B to increase steadily from 5 to 9 at a rate of 2 / h. After dropping for 2 h, end the reaction and keep it at a constant temperature for aging for 60 min. After the total reaction ends, export the slurry for filtration, wash it until the conductivity of the filtrate < 2 ms / cm, dry and pulverize to obtain a magnesium silicate sample. Mix the magnesium silicate product evenly with the dried carbon product to obtain Composite Material 1.

[0147] Example 2:

[0148] Select 5000 g of rice husk ash with a carbon content of 20% and a silica content of 70%. After impurity removal, mix it evenly with 7500 g of sodium hydroxide solution with a concentration of 20% and 5000 g of water, place it in a closed reactor A, and react at a temperature of 150 °C for 4 hours. Filter the obtained slurry through a plate and frame filter press, control the filtration pressure at 4 bar, and the filtrate is concentrated silicate, which is temporarily stored for use; after filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reactor B; the filter cake is flash dried to obtain a dried carbon product. Prepare a sulfuric acid solution with a concentration of 7% and a magnesium sulfate solution with a concentration of 7%. Add sodium sulfate solid to reactor B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reactor B), adjust its concentration to 3.5% sodium silicate and 1% sodium sulfate, and heat to 70 °C. After reaching the reaction temperature, start the peristaltic pump, and simultaneously pump in 10000 g of concentrated silicate and magnesium sulfate solution. Pump in sulfuric acid to control the pH value to steadily increase from 4 to 8 at a rate of 2 / h. After dropping for 2 h, end the reaction, and carry out constant temperature aging at 60 °C for 70 min. After the total reaction is completed, export the slurry for filtration, wash until the conductivity of the filtrate < 2 ms / cm, dry and crush to obtain a magnesium silicate sample. Mix the magnesium silicate product evenly with the dried carbon product to obtain composite material 2.

[0149] Example 3:

[0150] Select a carbon content of 15％ , and a silica content of 72％ of 5000 g of rice husk ash. After impurity removal, mix it evenly with 7500 g of sodium hydroxide solution with a concentration of 20% and 5000 g of water, place it in a closed reactor A, and react at a temperature of 150 °C for 4 hours. Filter the obtained slurry through a plate and frame filter press, control the filtration pressure at 6 bar, and the filtrate is concentrated silicate, which is temporarily stored for use; after filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reactor B; the filter cake is flash dried to obtain a dried carbon product. Prepare a sulfuric acid solution with a concentration of 11% and 5000 g of magnesium sulfate solution with a concentration of 14%. Add sodium sulfate solid to reactor B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reactor B), adjust its concentration to 4% sodium silicate and 0.5% sodium sulfate, and heat to 50 °C. After reaching the reaction temperature, start the peristaltic pump, and simultaneously pump in concentrated silicate and magnesium sulfate solution. Pump in sulfuric acid to control the pH value to steadily increase from 3 to 8 at a rate of 2.5 / h. After dropping for 2 h, end the reaction, and carry out constant temperature aging for 80 min. After the total reaction is completed, export the slurry for filtration, wash until the conductivity of the filtrate < 2 ms / cm, dry and crush to obtain a magnesium silicate sample. Mix the magnesium silicate product evenly with the dried carbon product to obtain composite material 3.

[0151] Example 4:

[0152] Select the carbon content 10％ , and the silicon dioxide content 75％ of 5000 g of rice husk ash. After impurity removal, it is mixed evenly with 7500 g of sodium hydroxide solution with a concentration of 20% and 5000 g of water, placed in a closed reaction kettle A, and reacted at a temperature of 150 °C for 4 hours. The obtained slurry is filtered through a plate and frame filter press, and the filtration pressure is controlled at 6 bar. The filtrate is concentrated silicate and stored temporarily for use; after filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reaction kettle B; the filter cake is flash-dried to obtain the dried carbon product. Prepare a sulfuric acid solution with a concentration of 15% and a magnesium sulfate solution with a concentration of 14%. Sodium sulfate solid is added to reaction kettle B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reaction kettle B), and its concentration is adjusted to 0.5% sodium silicate and 4% sodium sulfate and heated to 70 °C. After reaching the reaction temperature, start the peristaltic pump, and at the same time pump in 5000 g of concentrated silicate and magnesium sulfate solution. The sulfuric acid is pumped in to control the pH value to increase steadily from 3 to 8 at a change rate of 2.5 / h. After dropping for 2 h, the reaction ends, and it is aged at a constant temperature for 90 min. After the total reaction ends, the slurry is exported and filtered, washed until the conductivity of the filtrate < 2 ms / cm, dried and pulverized to obtain a magnesium silicate sample. The magnesium silicate product is mixed evenly with the dried carbon product to obtain composite material 4.

[0153] Example 5:

[0154] Select the carbon content 20％ , and the silicon dioxide content 70％5000 g of rice husk ash, after impurity removal, is mixed evenly with 7500 g of sodium hydroxide solution with a concentration of 20% and 5000 g of water, placed in a closed reaction kettle A, and reacted at a temperature of 150 °C for 4 hours. The obtained slurry is filtered through a plate and frame filter press, and the filtration pressure is controlled at 6 bar. The filtrate is concentrated silicate and is temporarily stored for use; after filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reaction kettle B; the filter cake is flash dried to obtain a dried carbon product. A sulfuric acid solution with a concentration of 14% and a magnesium sulfate solution with a concentration of 15% are prepared. Sodium sulfate solid is added to reaction kettle B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reaction kettle B), and its concentration is adjusted to 3.5% sodium silicate and 1% sodium sulfate and heated to 70 °C. After reaching the reaction temperature, a peristaltic pump is started, and at the same time, 5000 g of concentrated silicate and magnesium sulfate solution are pumped in. The sulfuric acid is pumped in to control the pH value to steadily increase from 4 to 10 at a change rate of 3 / h. After dropping for 2 h, the reaction ends, and it is thermally aged at a constant temperature for 100 min. After the total reaction ends, the slurry is filtered out, washed until the conductivity of the filtrate < 2 ms / cm, dried and pulverized to obtain a magnesium silicate sample. The magnesium silicate product is mixed evenly with the dried carbon product to obtain composite material 5.

[0155] Example 6:

[0156] Select rice husk ash with a carbon content 20％ , and a silicon dioxide content 70％ 5000 g of rice husk ash, after impurity removal, is mixed evenly with 7500 g of sodium hydroxide solution with a concentration of 20% and 5000 g of water, placed in a closed reaction kettle A, and reacted at a temperature of 150 °C for 4 hours. The obtained slurry is filtered through a plate and frame filter press, and the filtration pressure is controlled at 5 bar. The filtrate is concentrated silicate and is temporarily stored for use; after filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reaction kettle B; the filter cake is flash dried to obtain a dried carbon product. A sulfuric acid solution with a concentration of 5% and a magnesium sulfate solution with a concentration of 7% are prepared. Sodium sulfate solid is added to reaction kettle B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reaction kettle B), and its concentration is adjusted to 3.5% sodium silicate and 1% sodium sulfate and heated to 70 °C. After reaching the reaction temperature, a peristaltic pump is started, and at the same time, 10000 g of concentrated silicate and magnesium sulfate solution are pumped in. The sulfuric acid is pumped in to control the pH value to steadily increase from 3 to 8 at a change rate of 2.5 / h. After dropping for 2 h, the reaction ends, and it is thermally aged at a constant temperature for 120 min. After the total reaction ends, the slurry is filtered out, washed until the conductivity of the filtrate < 2 ms / cm, dried and pulverized to obtain a magnesium silicate sample. The magnesium silicate product is mixed evenly with the dried carbon product to obtain composite material 6.

[0157] Comparative Example 1:

[0158] Select the carbon content 2％ , the silicon dioxide content 92％ of 5000 g of rice husk ash. After impurity removal, it is mixed evenly with 7500 g of sodium hydroxide solution with a concentration of 20% and 5000 g of water, and placed in a closed reactor A. React at 150 °C for 4 hours. Filter the obtained slurry through a plate and frame filter press, control the filtration pressure at 5 bar, and the filtrate is concentrated silicate, which is temporarily stored for use; after filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reactor B; the filter cake is flash dried to obtain a dried carbon product. Prepare a sulfuric acid solution with a concentration of 15% and a magnesium sulfate solution with a concentration of 14%. Add sodium sulfate solid to reactor B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reactor B), adjust its concentration to 3.5% sodium silicate and 1% sodium sulfate, and heat to 70 °C. After reaching the reaction temperature, start the peristaltic pump, and simultaneously pump in 5000 g of concentrated silicate and magnesium sulfate solution. Pump in sulfuric acid to control the pH value to steadily increase from 3 to 8 at a change rate of 2.5 / h. After dropping for 2 h, end the reaction and keep it at a constant temperature for 120 min. After the total reaction is completed, drain the slurry for filtration, wash it until the conductivity of the filtrate < 2 ms / cm, dry and crush it to obtain a magnesium silicate sample. Mix the magnesium silicate product evenly with the dried carbon product to obtain composite material 7.

[0159] Comparative Example 2:

[0160] Select the carbon content 5％ , the silicon dioxide content 90％5000 g of rice husk ash is mixed with 7500 g of 20% sodium hydroxide solution and 5000 g of water after impurity removal, and the mixture is evenly placed in a closed reaction kettle A and reacted at 150 °C for 4 hours. The obtained slurry is filtered through a plate and frame filter press, and the filtration pressure is controlled at 4 - 6 bar. The filtrate is concentrated silicate and is temporarily stored for use. After filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reaction tank B. The filter cake is flash dried to obtain a dried carbon product. A sulfuric acid solution with a concentration of 15% and a magnesium sulfate solution with a concentration of 14% are prepared. Sodium sulfate solid is added to reaction tank B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reaction tank B), and its concentration is adjusted to 3.5% sodium silicate and 1% sodium sulfate and heated to 70 °C. After reaching the reaction temperature, a peristaltic pump is started, and 5000 g of concentrated silicate and magnesium sulfate solution are pumped in simultaneously. The sulfuric acid is pumped in to control the pH value to increase steadily from 3 to 8 at a rate of 2.5 / h. After dropping for 2 h, the reaction ends, and it is kept at a constant temperature and aged for 120 min. After the total reaction ends, the slurry is filtered out, washed until the conductivity of the filtrate < 2 ms / cm, dried and pulverized to obtain a magnesium silicate sample. The magnesium silicate product is evenly mixed with the dried carbon product to obtain composite material 8.

[0161] Comparative Example 3:

[0162] Select rice husk ash with a carbon content 30％ , and a silicon dioxide content 53％ 5000 g of rice husk ash is mixed with 7500 g of 20% sodium hydroxide solution and 5000 g of water after impurity removal, and the mixture is evenly placed in a closed reaction kettle A and reacted at 150 °C for 4 hours. The obtained slurry is filtered through a plate and frame filter press, and the filtration pressure is controlled at 6 bar. The filtrate is concentrated silicate and is temporarily stored for use. After filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reaction tank B. The filter cake is flash dried to obtain a dried carbon product. A sulfuric acid solution with a concentration of 15% and a magnesium sulfate solution with a concentration of 7% are prepared. Sodium sulfate solid is added to reaction tank B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reaction tank B), and its concentration is adjusted to 3.5% sodium silicate and 1% sodium sulfate and heated to 70

[0163] °C. After reaching the reaction temperature, a peristaltic pump is started, and 10000 g of concentrated silicate and magnesium sulfate solution are pumped in simultaneously. The sulfuric acid is pumped in to control the pH value to increase steadily from 3 to 8 at a rate of 2.5 / h. After dropping for 2 h, the reaction ends, and it is kept at a constant temperature and aged for 120 min. After the total reaction ends, the slurry is filtered out, washed until the conductivity of the filtrate < 2 ms / cm, dried and pulverized to obtain a magnesium silicate sample. The magnesium silicate product is evenly mixed with the dried carbon product to obtain composite material 9.

[0164] Comparative Example 4:

[0165] Select 5000 g of rice husk ash with a carbon content of 40% and a silica content of 40%. After impurity removal, mix it evenly with 7500 g of sodium hydroxide solution with a concentration of 20% and 5000 g of water, and place it in a closed reaction kettle A. React at a temperature of 150 °C for 4 hours. Filter the obtained slurry through a plate and frame filter press, control the filtration pressure at 6 bar, and the filtrate is concentrated silicate, which is temporarily stored for use; after filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reaction kettle B; the filter cake is flash dried to obtain the dried carbon product. Prepare a sulfuric acid solution with a concentration of 15% and a magnesium sulfate solution with a concentration of 7%. Add solid sodium sulfate to reaction kettle B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reaction kettle B), adjust its concentration to 3.5% sodium silicate and 1% sodium sulfate and heat to 70

[0166] ℃. After reaching the reaction temperature, start the peristaltic pump and pump in 10000 g of concentrated silicate and magnesium sulfate solution at the same time. Pump in sulfuric acid to control the pH value to increase steadily from 3 to 8 at a rate of 2.5 / h. After dropping for 2 h, end the reaction and keep it at a constant temperature for 120 min. After the total reaction is completed, export the slurry for filtration, wash it until the conductivity of the filtrate < 2 ms / cm, dry and crush it to obtain magnesium silicate samples. Mix the magnesium silicate product evenly with the dried carbon product to obtain Composite Material 10.

[0167] Comparative Example 5:

[0168] Select 5000 g of rice husk ash with a carbon content of 50% and a silica content of 26%. After impurity removal, mix it evenly with 7500 g of sodium hydroxide solution with a concentration of 20% and 5000 g of water, and place it in a closed reaction kettle A. React at a temperature of 150 °C for 4 hours. Filter the obtained slurry through a plate and frame filter press, control the filtration pressure at 6 bar, and the filtrate is concentrated silicate, which is temporarily stored for use; after filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reaction kettle B; the filter cake is flash dried to obtain the dried carbon product. Prepare a sulfuric acid solution with a concentration of 15% and a magnesium sulfate solution with a concentration of 7%. Add solid sodium sulfate to reaction kettle B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reaction kettle B), adjust its adjusted concentration to 3.5% sodium silicate and 1% sodium sulfate and heat to 70 °C. After reaching the reaction temperature, start the peristaltic pump and pump in concentrated silicate and magnesium sulfate solution at the same time

[0169] 10,000 g, pump in sulfuric acid to control the pH value to steadily increase from 4 to 9 at a rate of 2.5 / h. After dropping for 2 h, end the reaction and keep it at a constant temperature for aging for 120 min. After the total reaction ends, export the slurry for filtration, wash it until the conductivity of the filtrate < 2 ms / cm, dry and pulverize to obtain the magnesium silicate sample. Mix the magnesium silicate product evenly with the dried carbon product to obtain Composite Material 11.

[0170] Comparative Example VI:

[0171] Select 5,000 g of rice husk ash with a carbon content of 62% and a silicon dioxide content of 20%. After impurity removal, mix it evenly with 7,500 g of 20% sodium hydroxide solution and 5,000 g of water, and place it in a closed reaction kettle A. React at a temperature of 150 °C for 4 hours. Filter the obtained slurry through a plate and frame filter press, control the filtration pressure at 6 bar, and the filtrate is concentrated silicate, which is temporarily stored for use; after filtration, the filter cake is washed with 5,000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reaction kettle B; the filter cake is flash dried to obtain the dried carbon product. Prepare a 15% sulfuric acid solution and a 7% magnesium sulfate solution. Add sodium sulfate solid to reaction kettle B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reaction kettle B), adjust its concentration to 3.5% sodium silicate and 1% sodium sulfate and heat to 70

[0172] °C. After reaching the reaction temperature, start the peristaltic pump, and at the same time pump in 10,000 g of concentrated silicate and magnesium sulfate solution. Pump in sulfuric acid to control the pH value to steadily increase from 3 to 8 at a rate of 2.5 / h. After dropping for 2 h, end the reaction and keep it at a constant temperature for aging for 120 min. After the total reaction ends, export the slurry for filtration, wash it until the conductivity of the filtrate < 2 ms / cm, dry and pulverize to obtain the magnesium silicate sample. Mix the magnesium silicate product evenly with the dried carbon product to obtain Composite Material 12.

[0173] Comparative Example VII:

[0174] Select 5000 g of rice husk ash with a carbon content of 15% and a silica content of 72%. After impurity removal, it is mixed evenly with 7500 g of sodium hydroxide solution with a concentration of 20% and 5000 g of water, and placed in a closed reactor A. React at a temperature of 150 °C for 4 hours. Filter the obtained slurry through a plate and frame filter press, and control the filtration pressure at 6 bar. The filtrate is concentrated silicate and is temporarily stored for later use; after filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reactor B; the filter cake is flash dried to obtain the dried carbon product. Prepare a sulfuric acid solution with a concentration of 11% and a magnesium sulfate solution with a concentration of 14%. Add solid sodium sulfate to reactor B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reactor B), adjust its concentration to 3.5% sodium silicate and 1% sodium sulfate, and heat to 70 °C. After reaching the reaction temperature, start the peristaltic pump, and simultaneously pump in 5000 g of concentrated silicate and magnesium sulfate solution. Pump in sulfuric acid to control the pH value to increase steadily from 3 to 8 at a change rate of 2.5 / h. After dropping for 2 h, end the reaction and keep it at a constant temperature for aging for 0 min. After the total reaction is completed, export the slurry for filtration, wash it until the conductivity of the filtrate < 2 ms / cm, dry and pulverize it to obtain a magnesium silicate sample. Mix the magnesium silicate product evenly with the dried carbon product to obtain composite material 13.

[0175] Comparative Example VIII:

[0176] Select 5000 g of rice husk ash with a carbon content of 15% and a silica content of 72%. After impurity removal, it is mixed evenly with 7500 g of sodium hydroxide solution with a concentration of 20% and 5000 g of water, and placed in a closed reactor A. React at a temperature of 150 °C for 4 hours. Filter the obtained slurry through a plate and frame filter press, and control the filtration pressure at 6 bar. The filtrate is concentrated silicate and is temporarily stored for later use; after filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reactor B; the filter cake is flash dried to obtain the dried carbon product. Prepare a sulfuric acid solution with a concentration of 11% and a magnesium sulfate solution with a concentration of 14%. Add solid sodium sulfate to reactor B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reactor B), adjust its concentration to 3.5% sodium silicate and 1% sodium sulfate, and heat to 70 °C. After reaching the reaction temperature, start the peristaltic pump, and simultaneously pump in 5000 g of concentrated silicate and magnesium sulfate solution. Pump in sulfuric acid to control the pH value to increase steadily from 5 to 8 at a change rate of 2.5 / h. After dropping for 2 h, end the reaction and keep it at a constant temperature for aging for 30 min. After the total reaction is completed, export the slurry for filtration, wash it until the conductivity of the filtrate < 2 ms / cm, dry and pulverize it to obtain a magnesium silicate sample. Mix the magnesium silicate product evenly with the dried carbon product to obtain composite material 14.

[0177] Comparative Example IX:

[0178] Select 5000 g of rice husk ash with a carbon content of 15% and a silica content of 72%. After impurity removal, it is mixed evenly with 7500 g of a 20% sodium hydroxide solution and 5000 g of water, and placed in a closed reaction kettle A. React at a temperature of 150 °C for 4 hours. Filter the obtained slurry through a plate and frame filter press, and control the filtration pressure at 6 bar. The filtrate is concentrated silicate, which is temporarily stored for use; after filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reaction kettle B; the filter cake is flash dried to obtain a dried carbon product. Prepare a 1% sulfuric acid solution and a 1% magnesium sulfate solution. Add sodium sulfate solid to reaction kettle B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reaction kettle B), adjust its concentration to 3.5% sodium silicate and 1% sodium sulfate, and heat to 70 °C. After reaching the reaction temperature, start the peristaltic pump and pump in 20000 g of concentrated silicate and magnesium sulfate solution at the same time. Pump in sulfuric acid to control the pH value to increase steadily from 5 to 8 at a rate of 2.5 / h. After dropping for 2 hours, end the reaction and keep it at a constant temperature for 120 min. After the total reaction is completed, drain the slurry for filtration, wash it until the conductivity of the filtrate < 2 ms / cm, dry and crush it to obtain a magnesium silicate sample. Mix the magnesium silicate product evenly with the dried carbon product to obtain composite material 15.

[0179] 20000 g, pump in sulfuric acid to control the pH value to increase steadily from 5 to 8 at a rate of 2.5 / h. After dropping for 2 hours, end the reaction and keep it at a constant temperature for 120 min. After the total reaction is completed, drain the slurry for filtration, wash it until the conductivity of the filtrate < 2 ms / cm, dry and crush it to obtain a magnesium silicate sample. Mix the magnesium silicate product evenly with the dried carbon product to obtain composite material 15.

[0180] Comparative Example Ten:

[0181] Select 5000 g of rice husk ash with a carbon content of 15% and a silica content of 72%. After impurity removal, it is mixed evenly with 7500 g of a 20% sodium hydroxide solution and 5000 g of water, and placed in a closed reaction kettle A. React at a temperature of 150 °C for 4 hours. Filter the obtained slurry through a plate and frame filter press, and control the filtration pressure at 6 bar. The filtrate is concentrated silicate, which is temporarily stored for use; after filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reaction kettle B; the filter cake is flash dried to obtain a dried carbon product. Prepare a 30% sulfuric acid solution and a 30% magnesium sulfate solution. Add sodium sulfate solid to reaction kettle B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reaction kettle B), adjust its concentration to 3.5% sodium silicate and 1% sodium sulfate, and heat to 70 °C. After reaching the reaction temperature, start the peristaltic pump and pump in 2000 g of concentrated silicate and magnesium sulfate solution at the same time. Pump in sulfuric acid to control the pH value to increase steadily from 3 to 8 at a rate of 2.5 / h. After dropping for 2 hours, end the reaction and keep it at a constant temperature for 120 min. After the total reaction is completed, drain the slurry for filtration, wash it until the conductivity of the filtrate < 2 ms / cm, dry and crush it to obtain a magnesium silicate sample. Mix the magnesium silicate product evenly with the dried carbon product to obtain composite material 16.

[0182] Comparative Example XI:

[0183] Prepare a sodium silicate solution with a concentration of 20% and a magnesium sulfate solution with a concentration of 7%. Adjust the pH of the sodium silicate from 11.5 to 11 with 9% sulfuric acid. Slowly and constantly drip 4000 g of the magnesium sulfate solution into 5000 g of the sodium silicate solution to prepare magnesium silicate precipitate. After standing for aging, perform suction filtration, wash with water until there is no sulfate ion in the solution, dry in an oven at 105 °C, and grind to obtain Material 17.

[0184] Add it to palm oil at a ratio of 1% for adsorption, and test the removal rate of 3-MCPD in the oil to be 0% and the acid value reduction rate to be 20%.

[0185] Comparative Example XII:

[0186] Select 5000 g of rice husk ash with a carbon content of 15% and a silica content of 72%. After impurity removal, mix it evenly with 7500 g of a 20% sodium hydroxide solution and 5000 g of water, and place it in a closed reaction kettle A. React at a temperature of 150 °C for 4 hours. Filter the obtained slurry through a plate and frame filter press, and control the filtration pressure at 6 bar. The filtrate is concentrated silicate, which is temporarily stored for use; after filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reaction kettle B; the filter cake is flash dried to obtain a dried carbon product. Prepare a sulfuric acid solution with a concentration of 30% and a magnesium sulfate solution with a concentration of 30%. Add sodium sulfate solid to reaction kettle B (the dosage is adjusted according to the total amount of the dilute silicate solution pumped into reaction kettle B), adjust it to 3.5%, and heat to 70 °C. After reaching the reaction temperature, start the peristaltic pump, and simultaneously pump in 2000 g of concentrated silicate and magnesium sulfate solution. Pump in sulfuric acid to control the pH value to steadily increase from 3 to 8 at a rate of 2.5 / h. After dropping for 2 hours, end the reaction and keep it at a constant temperature for aging for 120 min. After the total reaction ends, drain the slurry for filtration, wash until the conductivity of the filtrate < 2 ms / cm, dry and crush to obtain a magnesium silicate sample. Mix the magnesium silicate product evenly with the dried carbon product to obtain Composite Material 18.

[0187] Example VII:

[0188] Select 5000 g of rice husk ash with a carbon content of 15% and a silica content of 72%. After impurity removal, it is mixed evenly with 7500 g of a 10% sodium hydroxide solution and 5000 g of water, placed in a closed reaction kettle A, and reacted at a temperature of 250 °C for 4 hours. The obtained slurry is filtered through a plate and frame filter press, and the filtration pressure is controlled at 6 bar. The filtrate is concentrated silicate and is temporarily stored for use; after filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reaction kettle B; the filter cake is flash dried to obtain a dried carbon product. Prepare a sulfuric acid solution with a concentration of 7% and a magnesium sulfate solution with a concentration of 7%. Sodium sulfate solid is added to reaction kettle B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reaction kettle B), and its concentration is adjusted to 3.5% sodium silicate and 1% sodium sulfate and heated to 70

[0189] ℃. After reaching the reaction temperature, start the peristaltic pump, and pump in the concentrated silicate and magnesium sulfate solution at the same time. The sulfuric acid is pumped in to control the pH value to steadily increase from 4 to 9 at a change rate of 2.5 / h. After dropping for 2 h, the reaction ends, and it is kept at a constant temperature and aged for 70 min. After the total reaction ends, the slurry is filtered out, washed until the conductivity of the filtrate < 2 ms / cm, dried and pulverized to obtain a magnesium silicate sample. The magnesium silicate product is mixed evenly with the dried carbon product to obtain composite material 19.

[0190] Example 8:

[0191] Select 5000 g of rice husk ash with a carbon content of 15% and a silica content of 72%. After impurity removal, it is mixed evenly with 7500 g of a 25% sodium hydroxide solution and 5000 g of water, placed in a closed reaction kettle A, and reacted at a temperature of 120 °C for 3 hours. The obtained slurry is filtered through a plate and frame filter press, and the filtration pressure is controlled at 6 bar. The filtrate is concentrated silicate and is temporarily stored for use; after filtration, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C, and the washing liquid (i.e., dilute silicate solution) is collected in reaction kettle B; the filter cake is flash dried to obtain a dried carbon product. Prepare a sulfuric acid solution with a concentration of 7% and a magnesium sulfate solution with a concentration of 7%. Sodium sulfate solid is added to reaction kettle B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reaction kettle B), and its concentration is adjusted to 3.5% sodium silicate and 1% sodium sulfate and heated to 70 °C. After reaching the reaction temperature, start the peristaltic pump, and pump in 10000 g of the concentrated silicate and magnesium sulfate solution at the same time. The sulfuric acid is pumped in to control the pH value to steadily increase from 4 to 9 at a change rate of 2.5 / h. After dropping for 2 h, the reaction ends, and it is kept at a constant temperature and aged for 70 min. After the total reaction ends, the slurry is filtered out, washed until the conductivity of the filtrate < 2 ms / cm, dried and pulverized to obtain a magnesium silicate sample. The magnesium silicate product is mixed evenly with the dried carbon product to obtain composite material 19.

[0192] Example 9:

[0193] Select 5000 g of rice husk ash with a carbon content of 15% and a silica content of 72%. After impurity removal, it is mixed evenly with 7500 g of a 20% sodium hydroxide solution and 5000 g of water, and placed in a closed reaction kettle A. React at a temperature of 300 °C for 2 hours. Filter the obtained slurry through a plate and frame filter press, and control the filtration pressure at 6 bar. The filtrate is concentrated silicate and is temporarily stored for use. After filtration is completed, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C. The washing liquid (i.e., dilute silicate solution) is collected in reaction kettle B. The filter cake is flash dried to obtain a dried carbon product. Prepare a 7% sulfuric acid solution and a 7% magnesium sulfate solution. Add sodium sulfate solid to reaction kettle B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reaction kettle B), adjust its concentration to 3.5% sodium silicate and 1% sodium sulfate, and heat to 70 °C. After reaching the reaction temperature, start the peristaltic pump, and simultaneously pump in 10000 g of concentrated silicate and magnesium sulfate solution. Pump in sulfuric acid to control the pH value to steadily increase from 4 to 9 at a change rate of 2.5 / h. After dropping for 2 hours, end the reaction and keep it at a constant temperature for aging for 70 min. After the total reaction is completed, export the slurry for filtration, wash it until the conductivity of the filtrate < 2 ms / cm, dry and crush it to obtain a magnesium silicate sample. Mix the magnesium silicate product evenly with the dried carbon product to obtain composite material 20.

[0194] Example ten:

[0195] Select 5000 g of rice husk ash with a carbon content of 15% and a silica content of 72%. After impurity removal, it is mixed evenly with 7500 g of a 20% sodium hydroxide solution and 5000 g of water, and placed in a closed reaction kettle A. React at a temperature of 300 °C for 2 hours. Filter the obtained slurry through a plate and frame filter press, and control the filtration pressure at 5 bar. The filtrate is concentrated silicate and is temporarily stored for use. After filtration is completed, the filter cake is washed with 5000 g of hot water at a water temperature of 60 °C. The washing liquid (i.e., dilute silicate solution) is collected in reaction kettle B. The filter cake is flash dried to obtain a dried carbon product. Prepare a 7% sulfuric acid solution and a 7% magnesium sulfate solution. Add sodium sulfate solid to reaction kettle B (the dosage is adjusted according to the total amount of dilute silicate solution pumped into reaction kettle B), adjust its concentration to 2.5% sodium silicate and 2% sodium sulfate, and heat to 70 °C. After reaching the reaction temperature, start the peristaltic pump, and simultaneously pump in 10000 g of concentrated silicate and magnesium sulfate solution. Pump in sulfuric acid to control the pH value to steadily increase from 4 to 9 at a change rate of 2.5 / h. After dropping for 2 hours, end the reaction and keep it at a constant temperature for aging for 70 min. After the total reaction is completed, export the slurry for filtration, wash it until the conductivity of the filtrate < 2 ms / cm, dry and crush it to obtain a magnesium silicate sample. Mix the magnesium silicate product evenly with the dried carbon product to obtain composite material 21.

[0196] Table 1 Reaction conditions in Examples 1-6 and Comparative Examples 1-10

[0197]

[0198]

[0199]

[0200] Table 2 Reaction conditions in Comparative Examples Eleven, Twelve and Examples Seven-Nine

[0201]

[0202] Application test

[0203] The composite materials obtained in the examples and comparative examples were added to palm oil at a ratio of 1% for mixing adsorption and filtration, and the removal rate of 3-MCPD in the oil and the change in acid value were tested. The results are shown in Table 3.

[0204] Removal rate (reduction rate) = (initial value - end value) / end value

[0205] Table 3 Application test results of the composite material

[0206]

[0207]

[0208]

[0209] It can be seen from the data in Tables 1-3 that the composite material obtained by the solution of the present invention has a significantly higher removal rate of 3-MCPD than the comparative examples; the reduction rate of the acid value in the oil is also significantly higher than that of the comparative examples.

[0210] The above-described embodiments merely represent several embodiments of the present invention, and their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims. At the same time, all the documents mentioned in the present invention are cited in this application as references, just as each document is cited separately as a reference.

Claims

1. A method for preparing a magnesium silicate composite material, characterized in that, The method includes the following steps: Steps: (1) After the rice husk ash reacts with an alkali, crude carbon and a silicate part are separated; (2) Sodium sulfate and the silicate obtained in step (1) are pre-added into a reaction tank; (3) Sodium silicate, a magnesium salt, and an acid are added into the reaction tank described in step (2) for reaction to obtain a magnesium silicate slurry; (4) The magnesium silicate slurry in step (3) is filtered and dried to obtain magnesium silicate; (5) The crude carbon in step (1) is dried to obtain a carbon product; (6) The products obtained in steps (4) and (5) are mixed to obtain a magnesium silicate composite material.

2. The method according to claim 1, wherein The method satisfies one or more of the following conditions: (a) Based on the total mass of the rice husk ash, the carbon content in the rice husk ash is 5-25%, and the silicon dioxide content is 65-80%; and / or, (b) The alkali in step (1) is selected from one or more of sodium hydroxide, potassium hydroxide, magnesium hydroxide, sodium carbonate, potassium carbonate, and magnesium carbonate; preferably sodium hydroxide; and / or, (c) The mass percentage concentration of the alkali in step (1) is 8-20%; and / or, (d) The weight ratio of the rice husk ash to the alkali in step (1) is about 3:1 to 5:1; and / or, (e) In step (1), the reaction temperature of the rice husk ash and the alkali is 100-300°C; and / or, (f) In step (1), the reaction time is 3-6 h; and / or, (g) In step (1), the slurry is filtered after the reaction; and / or, (h) In step (1), the filtration pressure is 4-6 bar.

3. The method according to claim 1, characterized in that, The method satisfies one or more of the following conditions: (i) In step (3), the magnesium salt is selected from one or more of magnesium sulfate, magnesium chloride, and magnesium nitrate; preferably magnesium sulfate; and / or, (j) In step (3), the concentration of the magnesium salt solution is 5-20%; and / or, (k) In step (3), the dosage of the magnesium salt solution is 4000 g-12000 g; and / or, (l) In step (3), the acid is selected from sulfuric acid, and preferably the concentration of the acid is 5-15%; and / or, (m) In step (3), the reaction temperature is 50-70°C, and / or the reaction time is 40-120 min, and / or, the reaction pH is 3-10; and / or, (n) After the reaction in step (3), it is aged, and the aging time is 60-120 min.

4. A magnesium silicate composite material, characterized in that, The mass ratio of C, Mg, and Si in the material is 20:23:73 to 10:90:

60.

5. The material according to claim 4, characterized in that, The mass ratio of C and MgSiO3 in the material is 10:150 to 20:

100.

6. The material according to claim 4, characterized in that, The magnesium silicate composite material is prepared by the method described in any one of claims 1-3.

7. A method for reducing 3-MCPD in oils and fats, characterized in that, The method is to treat oil and fat with the composite material prepared by the method described in any one of claims 1-3; or to treat oil and fat with the composite material described in any one of claims 4-6.

8. The method according to claim 7, characterized in that, The oil and fat is edible oil. Preferably, the oil and fat is selected from any one or a mixture of two or more of rice bran oil, sunflower seed oil, palm oil, palm kernel oil, peanut oil, rapeseed oil, cottonseed oil, safflower seed oil, perilla seed oil, camellia seed oil, palm fruit oil, coconut oil, olive oil, cocoa butter, Chinese tallow tree seed oil, almond oil, apricot kernel oil, tung oil tree seed oil, rubber seed oil, rice bran oil, corn germ oil, wheat germ oil, sesame seed oil, castor oil, linseed oil, evening primrose oil, hazelnut oil, walnut oil, grape seed oil, sesame oil, borage oil, sea buckthorn oil, tomato seed oil, pumpkin seed oil, macadamia nut oil, cocoa butter, algal oil, etc.

9. A method for refining oil and fat, characterized in that, The method includes a step of mixing and adsorbing the oil and fat with the composite material prepared according to any one of claims 1-3, or the composite material according to any one of claims 4-6.

10. The method according to claim 9, characterized in that, The method further includes a step of filtering to remove the composite material.

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