Modified diatomite and preparation method thereof, COD (Chemical Oxygen Demand) removing agent and application and utilization method thereof

Abstract

The invention relates to modified diatomite and a preparation method thereof, a COD (Chemical Oxygen Demand) removal agent and application and a utilization method thereof, in particular to the field of secondary utilization of resources, the modified diatomite comprises diatomite and copper, iron and manganese composite metal oxides loaded on the diatomite; the chemical structural formula of the copper, iron and manganese composite metal oxide is CuxFeyMnzOw, and in terms of molar weight, x is 1-2, y is 1-2, z is 1-2, and w is 3-7. According to the modified diatomite provided by the invention, by utilizing the synergistic effect of the copper, iron and manganese composite metal oxide and the diatomite, when the modified diatomite is matched with hydrogen peroxide to remove COD in a liquid phase, the hydrogen peroxide can be efficiently catalyzed to be decomposed to generate hydroxyl free radicals (. OH); and the adsorption capacity of the modified diatomite is synchronously exerted to intercept macromolecular refractory organic matters, so that efficient removal of COD in a liquid phase is realized.

Description

Technical Field

[0001] The present invention relates to the field of secondary utilization of resources, and particularly to a modified diatomite and its preparation method, a COD remover and its uses, and a utilization method, especially to a modified diatomite and its preparation method, a COD remover and its uses, and a utilization method for resource utilization of high-COD fluorosilicate mixed acid. Background Art

[0002] At present, in the fluorochemical industry, electronic etching, and photovoltaic industry, a mixed acid solution of hydrofluoric acid (HF) and hexafluorosilicic acid (H₂SiF₆) is a common by-product or waste liquid, and its chemical oxygen demand (COD) is usually relatively high, mainly derived from residual organic solvents, surfactants, and fluorinated organic compounds. If such mixed acid is directly discharged or treated conventionally, it not only faces environmental protection risks (such as fluoride ion pollution and excessive COD), but also causes waste of fluorine and silicon resources.

[0003] For example, CN117509547A discloses a method for separating hexafluorosilicic acid-hydrofluoric acid by using an anion membrane, which is to effectively separate hexafluorosilicic acid and hydrofluoric acid in a mixed solution of hexafluorosilicic acid-hydrofluoric acid by using an anion exchange membrane. Although the hydrofluoric acid obtained by this method has high purity after membrane separation, the cost of the anion exchange membrane is relatively high and it will age, and the membrane needs to be replaced regularly, increasing the equipment maintenance cost. At the same time, the operating conditions are also more stringent, and the mixed acid needs to be pretreated.

[0004] CN115872406A discloses a resource utilization system device and method for hydrogen fluoride wastewater in the photovoltaic industry. The hexafluorosilicic acid is settled through a hexafluorosilicic acid reaction device, and then the hydrofluoric acid is refined and recovered through a hydrofluoric acid refining device. The precipitated fluorosilicate is reused after cleaning and impurity removal. Although this method realizes the effective recycling of hydrofluoric acid, the equipment and energy consumption costs are relatively high.

[0005] CN117466250A discloses a method for comprehensively utilizing fluorine-containing waste acid to recover hydrofluoric acid. The fluorine-containing waste acid is subjected to ultra-fine bubble stripping to obtain hydrofluoric acid, and the remaining residual liquid after ultra-fine bubble stripping is subjected to reaction treatment to recover the acid solution and fluorosilicate. Although this method improves the resource utilization rate and reduces the impact on the environment, the equipment requirements are high, the operating cost is relatively high, and the operation and maintenance are complex.

[0006] In summary, the current treatment methods have the following limitations:

[0007] 1. The COD degradation efficiency is low and the energy consumption is high. Existing methods for treating high-COD mixed acid solutions mostly rely on physical adsorption or conventional oxidation methods (such as biological methods and membrane filtration). Only through traditional oxidation methods (such as Fenton reagents and ozone oxidation), the degradation of organic matter in the fluorine-containing system has poor selectivity, and may generate secondary pollutants (such as fluorine-containing intermediates), resulting in difficulties in subsequent fluorine resource recovery. At the same time, the COD degradation efficiency is low, and high temperature or complex equipment support is required. For example, some processes use electrolysis or advanced oxidation methods, which have certain effects, but have high energy consumption and complex operations, and are limited in practical applications.

[0008] 2. The selection of adsorbents and the effect of impurity removal are poor. Traditional adsorbents (such as activated carbon and ordinary diatomaceous earth) have limited adsorption capacity for organic matter and metal ions in the mixed acid solution, resulting in impurity residues in subsequent reactions and affecting the product purity.

[0009] 3. Direct neutralization treatment is prone to generate low-value by-products such as calcium fluoride (CaF2), and silicon elements mostly precipitate in the form of silica gel, making it difficult to separate and purify into high-value-added silica (white carbon black), with poor resource utilization effect and being unfavorable for the recovery of useful substances. Summary of the Invention

[0010] In view of the problems existing in the prior art, the purpose of the present invention is to provide a modified diatomaceous earth and its preparation method, a COD remover and its uses, and a utilization method to solve the defects of poor COD removal effect, poor recovery effect of valuable substances, and low product purity during the secondary utilization of high-COD fluorine-containing silicon waste acid.

[0011] To achieve this purpose, the present invention adopts the following technical solutions:

[0012] In the first aspect, the present invention provides a modified diatomaceous earth, which includes:

[0013] Diatomaceous earth, and copper, iron, and manganese composite metal oxides supported on the diatomaceous earth;

[0014] The chemical structural formula of the copper, iron, and manganese composite metal oxides is Cu x Fe y Mn z O w , in terms of molar amount, x is 1 - 2, y is 1 - 2, z is 1 - 2, and w is 3 - 7.

[0015] The modified diatomaceous earth provided by the present invention, through the synergistic effect of copper, iron, and manganese composite metal oxides and diatomaceous earth, enables the modified diatomaceous earth and hydrogen peroxide to cooperate to remove COD in the liquid phase, can efficiently catalyze the decomposition of hydrogen peroxide to generate hydroxyl radicals (·OH), and simultaneously play the adsorption capacity of the modified diatomaceous earth to intercept macromolecular and difficult-to-degrade organic matter, thereby achieving efficient removal of COD in the liquid phase.

[0016] In a second aspect, the present invention provides a method for preparing modified diatomite as described in the first aspect, the preparation method comprising: impregnating diatomite with a salt solution containing copper, iron, and manganese, then adjusting the pH value of the solution, and obtaining a precursor through solid-liquid separation;

[0017] Calcining the precursor to obtain modified diatomite.

[0018] As a preferred technical solution of the present invention, the D50 particle size of the diatomite is 10 - 30 μm.

[0019] Preferably, the total concentration of copper, iron, and manganese in the salt solution containing copper, iron, and manganese is 0.5 - 2 mol / L.

[0020] Preferably, the impregnation time is 6 - 12 h.

[0021] Preferably, stirring is assisted during the impregnation at a stirring speed of ≥200 r / min.

[0022] Preferably, the end pH value range for adjusting the pH value of the solution is 8 - 9.

[0023] As a preferred technical solution of the present invention, the calcination temperature is 300 - 600 °C.

[0024] Preferably, the heating rate of the calcination is 2 - 5 °C / min.

[0025] Preferably, the calcination is carried out in an oxidizing atmosphere.

[0026] Preferably, the calcination time is 3 - 6 h.

[0027] In a third aspect, the present invention provides a COD remover, the COD remover comprising:

[0028] Hydrogen peroxide solution and modified diatomite as described in the first aspect.

[0029] As a preferred technical solution of the present invention, the mass of the modified diatomite is 0.1 - 1% of the mass of the hydrogen peroxide solution.

[0030] Preferably, the mass concentration of the hydrogen peroxide solution is 35 - 45%.

[0031] In a fourth aspect, the present invention provides a use of the COD remover as described in the third aspect, the use comprising: removing organic matter using the COD remover.

[0032] As a preferred technical solution of the present invention, the mass of the COD remover in the organic matter removal is 1 - 5% of the liquid mass.

[0033] Preferably, the time for removing organic matter is 2 - 4 h.

[0034] Fifthly, the present invention provides a method for resource utilization of high - COD fluorosilicon mixed acid, and the utilization method includes:

[0035] Mixing high - COD fluorosilicon mixed acid and ammonia water, followed by stirring reaction and first solid - liquid separation in sequence to obtain silicon - containing precipitate and ammonium salt solution;

[0036] The silicon - containing precipitate is calcined to obtain white carbon black product;

[0037] The ammonium salt solution is successively subjected to deammoniation, COD removal and second solid - liquid separation to obtain fluoride salt solution;

[0038] The fluoride salt solution is successively concentrated and crystallized to obtain fluoride salt product;

[0039] Among them, the COD remover used in the COD removal includes the COD remover as described in the third aspect.

[0040] As a preferred technical solution of the present invention, the mass concentration of the ammonia water is 10 - 15%.

[0041] Preferably, the pH value of the mixed liquid phase is 6 - 7.

[0042] Preferably, the stirring speed of the stirring reaction is ≥200 r / min.

[0043] Preferably, the time of the stirring reaction is 2 - 4 h.

[0044] Preferably, the temperature of the calcination is 300 - 500 °C.

[0045] Preferably, the time of the calcination is 2 - 4 h.

[0046] As a preferred technical solution of the present invention, the deammoniation includes: adding alkali to the ammonium salt solution for heating reaction.

[0047] Preferably, the temperature of the heating reaction is 80 - 100 °C.

[0048] Preferably, the ammonia component obtained by deammoniation is returned for use as ammonia water.

[0049] Preferably, the mass of the COD remover in the COD removal is 1 - 5% of the mass of the liquid obtained by deammoniation.

[0050] Preferably, the time of the COD removal is 2 - 4 h.

[0051] Preferably, the solid phase obtained by the second solid - liquid separation is activated and returned for secondary use in COD removal.

[0052] Preferably, the activation temperature is 200 - 400 °C.

[0053] Preferably, the activation time is ≥2 h.

[0054] Preferably, the end point of concentration is that the mass concentration of the material is 40 - 60%.

[0055] Preferably, the concentration methods include: evaporation and / or membrane separation.

[0056] Preferably, the crystallization methods include: one or a combination of at least two of evaporation crystallization, spray drying, or cooling crystallization.

[0057] Preferably, the temperature of spray drying is 260 - 350 °C.

[0058] Compared with the prior art solutions, the present invention has the following beneficial effects:

[0059] (1) The modified diatomaceous earth provided by the present invention and hydrogen peroxide cooperate to efficiently catalyze the decomposition of hydrogen peroxide to generate hydroxyl radicals. At the same time, the modified diatomaceous earth can effectively intercept macromolecular and refractory organic substances, thereby achieving efficient removal of COD in the liquid phase. For a liquid phase with COD ≥ 20000 mg / L, the removal rate of COD can reach over 98%.

[0060] (2) In the COD removal process provided by the present invention, by adopting mild reaction conditions, the requirements for equipment are reduced, and the equipment investment cost and energy consumption during operation are reduced. Using diatomaceous earth, which is widely sourced and relatively inexpensive, as a carrier, after modification, it can efficiently catalyze the decomposition of hydrogen peroxide. At the same time, it meets the adsorption of impurities and the degradation requirements of COD in the mixed acid solution, greatly reducing the treatment cost and improving the practicability and feasibility of the method.

[0061] (3) In the utilization method provided by the present invention, by converting the silicon element in the mixed acid solution into white carbon black (precipitated silica) and the fluorine element into potassium fluoride (prepared by spray drying), it breaks through the limitations of traditional low-value-added products, meets the needs of the materials market, and realizes the secondary utilization of resources. Detailed Embodiments

[0062] To better illustrate the present invention and facilitate understanding of its technical solutions, the typical but non-limiting embodiments of the present invention are as follows:

[0063] This embodiment provides a modified diatomaceous earth, which includes:

[0064] Diatomaceous earth, and copper, iron, and manganese composite metal oxides supported on the diatomaceous earth;

[0065] The chemical structural formula of the copper, iron, and manganese composite metal oxide is Cu x Fe y Mn z O w , in terms of molar quantity, x is 1 - 2, y is 1 - 2, z is 1 - 2, and w is 3 - 7.

[0066] Furthermore, the present invention provides a method for preparing the aforementioned modified diatomaceous earth, and the preparation process is as follows:

[0067] The diatomaceous earth is impregnated with a salt solution containing copper, iron, and manganese, and then the pH value of the solution is adjusted, and a precursor is obtained through solid-liquid separation;

[0068] The precursor is calcined to obtain the modified diatomaceous earth.

[0069] Among them, before the diatomaceous earth is impregnated, it can be optionally pickled and / or washed with water to remove residual metal oxides, organic substances, ions and other impurities.

[0070] Among them, the D50 particle size of the diatomaceous earth is 10 - 30 μm, for example, it can be 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 22 μm, 24 μm, 26 μm, 28 μm or 30 μm, etc., but not limited to the listed values, and other unlisted values within this range also meet the requirements.

[0071] Among them, the pickling includes: washing with an acid solution of 1 - 2 mol / L for 2 - 4 h.

[0072] Among them, the acid used for pickling includes one or a combination of at least two of hydrochloric acid, nitric acid, or sulfuric acid.

[0073] Among them, the water washing includes: washing the diatomaceous earth with water until the pH value of the filtrate is 6.6 - 7.2.

[0074] Optionally, after pickling or water washing, it can be dried at 120 - 200 °C for ≥12 h.

[0075] Among them, the copper salt used in preparing the salt solution containing copper, iron, and manganese includes: one or a combination of at least two of copper sulfate, copper nitrate, or copper chloride.

[0076] Exemplarily, the combinations of copper salts used include: the combination of copper sulfate and copper nitrate, the combination of copper nitrate and copper chloride, the combination of copper sulfate and copper chloride, the combination of copper sulfate, copper nitrate, and copper chloride, etc.

[0077] Among them, the iron salt used in preparing the salt solution containing copper, iron, and manganese includes: one or a combination of at least two of ferric sulfate, ferric nitrate, or ferric chloride.

[0078] Exemplarily, the combinations of iron salts used include: the combination of ferric sulfate and ferric nitrate, the combination of ferric nitrate and ferric chloride, the combination of ferric sulfate and ferric chloride, the combination of ferric sulfate, ferric nitrate and ferric chloride, etc.

[0079] Among them, the manganese salts used in preparing the copper, iron and manganese-containing salt solution include: one or a combination of at least two of manganese sulfate, manganese nitrate or manganese chloride.

[0080] Exemplarily, the combinations of manganese salts used include: the combination of manganese sulfate and manganese nitrate, the combination of manganese nitrate and manganese chloride, the combination of manganese sulfate and manganese chloride, the combination of manganese sulfate, manganese nitrate and manganese chloride, etc.

[0081] Among them, the total concentration of copper, iron and manganese in the copper, iron and manganese-containing salt solution is 0.5 - 2 mol / L. For example, it can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L or 2 mol / L, etc., but not limited to the listed values. Other unlisted values within this range also meet the requirements.

[0082] In the present invention, the concentrations of copper, iron and manganese in the copper, iron and manganese-containing salt solution are specifically configured according to the molar content in the chemical structural formula.

[0083] Furthermore, the loading amounts of copper, iron and manganese on the diatomite are specifically and reasonably selected by controlling the impregnation time and the solid-liquid ratio during the impregnation process according to actual needs. The loading amounts of copper, iron and manganese are added with the corresponding metal salts according to 5 - 10% of the total mass ratio.

[0084] Among them, the impregnation time is 6 - 12 h. For example, it can be 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h, 10 h, 10.5 h, 11 h, 11.5 h or 12 h, etc., but not limited to the listed values. Other unlisted values within this range also meet the requirements.

[0085] Among them, the stirring speed during the impregnation is ≥200 r / min. For example, it can be 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min or 500 r / min, etc., but not limited to the listed values. Other unlisted values within this range also meet the requirements.

[0086] Among them, the end pH value range for adjusting the pH value of the solution is 8 - 9. For example, it can be 8, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9 or 9, etc., but not limited to the listed values. Other unlisted values within this range also meet the requirements.

[0087] Among them, the temperature of the calcination is 300 - 600 °C. For example, it can be 300 °C, 350 °C, 400 °C, 450 °C, 500 °C, 550 °C or 600 °C, etc., but not limited to the listed values. Other unlisted values within this range also meet the requirements.

[0088] Among them, the heating rate of the calcination is 2 - 5 °C / min. For example, it can be 2 °C / min, 2.5 °C / min, 3 °C / min, 3.5 °C / min, 4 °C / min, 4.5 °C / min or 5 °C / min, etc., but not limited to the listed values. Other unlisted values within this range also meet the requirements.

[0089] Among them, the calcination is carried out in an oxidizing atmosphere.

[0090] Exemplarily, the oxidizing atmosphere includes an atmosphere containing oxidizing gases such as oxygen, air or ozone, etc.

[0091] Among them, the time of the calcination is 3 - 6 h. For example, it can be 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h, etc., but not limited to the listed values. Other unlisted values within this range also meet the requirements.

[0092] Optionally, before the calcination of the precursor, it can be dried at 60 - 80 °C for ≥12 h.

[0093] Furthermore, for the modified diatomite obtained by calcination, according to specific usage requirements, it can be optionally pulverized, or processed such as forming after pulverization, etc.

[0094] Furthermore, the present invention provides a COD removal agent, and the COD removal agent includes:

[0095] Hydrogen peroxide solution and the modified diatomite.

[0096] Among them, the mass of the modified diatomite is 0.1 - 1% of the mass of the hydrogen peroxide solution. For example, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%, etc., but not limited to the listed values. Other unlisted values within this range also meet the requirements.

[0097] Among them, the mass concentration of the hydrogen peroxide solution is 35-45%, for example, it can be 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44% or 45%, etc., but not limited to the listed values, and other unlisted values within this range also meet the requirements.

[0098] Furthermore, the present invention provides a use of a COD remover, and the use includes: removing organic matter by using the COD remover.

[0099] Among them, the mass of the COD remover in the organic matter removal is 1-5% of the liquid mass, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc., but not limited to the listed values, and other unlisted values within this range also meet the requirements.

[0100] Among them, the time for organic matter removal is 2-4h, for example, it can be 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h or 4h, etc., but not limited to the listed values, and other unlisted values within this range also meet the requirements.

[0101] Exemplarily, the objects targeted in the organic matter removal can be selected, such as raffinate produced in the hydrometallurgy process, washing water produced by washing the organic phase, organic wastewater from coal chemical industry, organic wastewater from petrochemical industry, etc., and organic wastewater produced in the industrial and living processes.

[0102] Furthermore, the present invention provides a utilization method for the resource utilization of high-COD fluorosilicon mixed acid, and the utilization method includes:

[0103] Mixing high-COD fluorosilicon mixed acid and ammonia water, and then successively performing stirring reaction and first solid-liquid separation to obtain silicon-containing precipitate and ammonium salt solution;

[0104] The silicon-containing precipitate is calcined to obtain a white carbon black product;

[0105] The ammonium salt solution is successively subjected to deammoniation, COD removal and second solid-liquid separation to obtain a fluoride salt solution;

[0106] The fluoride salt solution is successively concentrated and crystallized to obtain a fluoride salt product;

[0107] Among them, the COD remover used in the COD removal includes: the COD remover as described above.

[0108] In the present invention, the high COD of the high-COD fluorosilicon mixed acid means that COD≥20000mg / L.

[0109] In the present invention, the high-COD fluorosilicon mixed acid exemplarily includes substances such as hydrofluoric acid and fluorosilicic acid.

[0110] Among them, the mass concentration of the ammonia water is 10-15%, for example, it can be 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5% or 15%, etc., but not limited to the listed values, and other unlisted values within this range also meet the requirements.

[0111] Among them, the pH value of the obtained liquid phase after mixing is 6-7, for example, it can be 6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9 or 7, etc., but not limited to the listed values, and other unlisted values within this range also meet the requirements.

[0112] Among them, the stirring speed of the stirring reaction is ≥200 r / min, for example, it can be 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min or 500 r / min, etc., but not limited to the listed values, and other unlisted values within this range also meet the requirements.

[0113] Among them, the time of the stirring reaction is 2-4 h, for example, it can be 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3 h, 3.2 h, 3.4 h, 3.6 h, 3.8 h or 4 h, etc., but not limited to the listed values, and other unlisted values within this range also meet the requirements.

[0114] Among them, the temperature of the roasting is 300-500 °C, for example, it can be 300 °C, 320 °C, 340 °C, 360 °C, 380 °C, 400 °C, 420 °C, 440 °C, 460 °C, 480 °C or 500 °C, etc., but not limited to the listed values, and other unlisted values within this range also meet the requirements.

[0115] Among them, the time of the roasting is 2-4 h, for example, it can be 2 h, 2.5 h, 3 h, 3.5 h or 4 h, etc., but not limited to the listed values, and other unlisted values within this range also meet the requirements.

[0116] Among them, the deammoniation includes: adding an alkali to the ammonium salt solution and heating for reaction.

[0117] Among them, the alkali includes: one or a combination of at least two of sodium hydroxide, potassium hydroxide or calcium hydroxide.

[0118] In the present invention, the type of metal ions in the base added during the deamination process will affect the type of the final fluoride salt product. Specifically, the addition of the base can be reasonably selected according to the type of the final required fluoride salt product. For example, when the final fluoride salt product needs to be potassium fluoride, potassium hydroxide is used for deamination. When the final fluoride salt product needs to be calcium fluoride, calcium hydroxide is used for deamination.

[0119] Among them, the temperature of the heating reaction is 80-100°C. For example, it can be 80°C, 82°C, 84°C, 86°C, 88°C, 90°C, 92°C, 94°C, 96°C, 98°C or 100°C, etc., but it is not limited to the listed values. Other unlisted values within this range also meet the requirements.

[0120] Among them, the ammonia component obtained by deamination is returned for use as ammonia water.

[0121] Among them, the mass of the COD remover in the COD removal is 1-5% of the mass of the liquid obtained by deamination. For example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc., but it is not limited to the listed values. Other unlisted values within this range also meet the requirements.

[0122] Among them, the time for COD removal is 2-4h. For example, it can be 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h or 4h, etc., but it is not limited to the listed values. Other unlisted values within this range also meet the requirements.

[0123] Among them, the solid phase obtained by the second solid-liquid separation is returned for secondary utilization after activation in the COD removal.

[0124] Among them, the temperature of the activation is 200-400°C. For example, it can be 200°C, 220°C, 240°C, 260°C, 280°C, 300°C, 320°C, 340°C, 360°C, 380°C or 400°C, etc., but it is not limited to the listed values. Other unlisted values within this range also meet the requirements.

[0125] Among them, the time for activation is ≥2h. For example, it can be 2h, 2.5h, 3h, 3.5h or 4h, etc., but it is not limited to the listed values. Other unlisted values within this range also meet the requirements.

[0126] Among them, the end point of the concentration is that the mass concentration of the material is 40-60%. For example, it can be 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58% or 60%, etc., but it is not limited to the listed values. Other unlisted values within this range also meet the requirements.

[0127] Among them, the concentration methods include: evaporation and / or membrane separation.

[0128] Among them, the crystallization methods include: one or a combination of at least two of evaporation crystallization, spray drying, or cooling crystallization.

[0129] Among them, the temperature of the spray drying is 260 - 350 °C, for example, it can be 260 °C, 270 °C, 280 °C, 290 °C, 300 °C, 310 °C, 320 °C, 330 °C, 340 °C, or 350 °C, etc., but not limited to the listed values, and other unlisted values within this range also meet the requirements.

[0130] Furthermore, in order to illustrate the effects that can be achieved by the modified diatomaceous earth provided by the present invention in the process of removing COD, the following actual examples are used for illustration, specifically as follows:

[0131] Example 1

[0132] This example provides a modified diatomaceous earth, and the modified diatomaceous earth includes:

[0133] Diatomaceous earth, and copper, iron, and manganese composite metal oxides supported on the diatomaceous earth;

[0134] The chemical structural formula of the copper, iron, and manganese composite metal oxides is Cu x Fe y Mn z O w , in terms of molar amount, x is 2, y is 1, z is 1, and w is 5;

[0135] The preparation process is as follows:

[0136] Diatomaceous earth with a particle size D50 of 15 μm is impregnated with a salt solution with a total concentration of copper, iron, and manganese of 1 mol / L at a stirring speed of 200 r / min for 8 h, and then the pH value of the solution is adjusted to 8.5, and the precursor is obtained through solid-liquid separation;

[0137] The precursor is calcined at 400 °C for 5 h in an air atmosphere to obtain the modified diatomaceous earth.

[0138] Example 2

[0139] This example provides a modified diatomaceous earth, and the modified diatomaceous earth includes:

[0140] Diatomaceous earth, and copper, iron, and manganese composite metal oxides supported on the diatomaceous earth;

[0141] The chemical structural formula of the copper, iron, and manganese composite metal oxides is Cu x Fe y Mn z Ow , in terms of molar amount, x is 1, y is 2, z is 1, and w is 7;

[0142] The preparation process is as follows:

[0143] Diatomaceous earth is impregnated with a salt solution containing copper, iron, and manganese, and then the pH value of the solution is adjusted, and a precursor is obtained through solid-liquid separation;

[0144] The precursor is calcined to obtain modified diatomaceous earth;

[0145] Diatomaceous earth with a particle size D50 of 20 μm is impregnated with a salt solution with a total concentration of copper, iron, and manganese of 0.5 mol / L at a stirring speed of 200 r / min for 10 h, and then the pH value of the solution is adjusted to 8.8, and a precursor is obtained through solid-liquid separation;

[0146] The precursor is calcined at 500 °C for 4 h in an air atmosphere to obtain modified diatomaceous earth.

[0147] Example 3

[0148] This example provides a modified diatomaceous earth, which includes:

[0149] Diatomaceous earth, and a copper, iron, and manganese composite metal oxide supported on the diatomaceous earth;

[0150] The chemical structural formula of the copper, iron, and manganese composite metal oxide is Cu x Fe y Mn z O w , in terms of molar amount, x is 2, y is 1, z is 2, and w is 7;

[0151] The preparation process is as follows:

[0152] Diatomaceous earth with a particle size D50 of 10 μm is impregnated with a salt solution with a total concentration of copper, iron, and manganese of 0.5 mol / L at a stirring speed of 500 r / min for 6 h, and then the pH value of the solution is adjusted to 8, and a precursor is obtained through solid-liquid separation;

[0153] The precursor is calcined at 300 °C for 6 h in an air atmosphere to obtain modified diatomaceous earth.

[0154] Example 4

[0155] This example provides a modified diatomaceous earth, which includes:

[0156] Diatomaceous earth, and a copper, iron, and manganese composite metal oxide supported on the diatomaceous earth;

[0157] The chemical structural formula of the copper, iron, and manganese composite metal oxide is Cux Fe y Mn z O w , in terms of molar amounts, x is 1, y is 1, z is 2, and w is 6;

[0158] The preparation process is as follows:

[0159] Diatomite with a particle size D50 of 30 μm is impregnated with a salt solution having a total concentration of copper, iron, and manganese of 0.5 - 2 mol / L at a stirring speed of 300 r / min for 12 h. Then, the pH value of the solution is adjusted to 9, and the precursor is obtained through solid-liquid separation;

[0160] The precursor is calcined in an air atmosphere at 600 °C for 3 h to obtain modified diatomite.

[0161] The mass content composition of the high-COD fluorosilicon mixed acid used in the following application examples is shown in Table 1 below:

[0162] Table 1

[0163] COD / mg / L HF <![CDATA[H2SiF6]]> 25000 30.5％ 34.8％

[0164] Application Example 1

[0165] In this application example, the modified diatomite described in Example 1 is used to remove COD in the material, specifically as follows:

[0166] The high-COD fluorosilicon mixed acid and ammonia water with a mass concentration of 12% are mixed until the pH value of the liquid phase is 6.5. Then, after stirring and reacting at a stirring speed of 200 r / min for 3.5 h and the first solid-liquid separation, a silica precipitate and an ammonium fluoride solution are obtained;

[0167] The silica precipitate is calcined at 450 °C for 2.5 h to obtain a white carbon black product;

[0168] The ammonium fluoride solution is mixed with a base (potassium hydroxide) and deaminated at 90 °C. Then, a COD removal agent (hydrogen peroxide solution and the modified diatomite, the mass of the modified diatomite is 0.5% of the mass of the hydrogen peroxide solution, and the mass concentration of the hydrogen peroxide solution is 40%) equal to 2% of the liquid mass is added for COD removal for 3.5 h. Finally, after the second solid-liquid separation, a potassium fluoride solution and a solid phase are obtained. The obtained solid phase is activated at 300 °C for 3 h and then returned for secondary utilization in COD removal;

[0169] The obtained potassium fluoride solution is concentrated to a mass concentration of 50% and then crystallized (spray drying, temperature is 300 °C) to obtain a potassium fluoride product.

[0170] Application Example 2

[0171] This application example uses the modified diatomite described in Example 2 to remove COD from the material, specifically as follows:

[0172] Mix the high-COD fluorosilicon mixed acid and ammonia water with a mass concentration of 13% until the pH value of the liquid phase is 6.8, and then successively stir and react for 3 hours at a stirring speed of 300 r / min and perform the first solid-liquid separation to obtain silica precipitate and ammonium fluoride solution;

[0173] The silica precipitate is calcined at a temperature of 300 °C for 3 hours to obtain a white carbon black product;

[0174] The ammonium fluoride solution is mixed with an alkali (potassium hydroxide) and deammoniated at a temperature of 95 °C, and then a COD remover (hydrogen peroxide solution and the modified diatomite, the mass of the modified diatomite is 0.8% of the mass of the hydrogen peroxide solution, and the mass concentration of the hydrogen peroxide solution is 42%) accounting for 3% of the liquid mass is added for COD removal for 3 hours. Finally, after the second solid-liquid separation, a potassium fluoride solution and a solid phase are obtained. The obtained solid phase is activated at 350 °C for 2.5 hours and then returned to the COD removal for secondary utilization;

[0175] The obtained potassium fluoride solution is concentrated to a mass concentration of 55% and then crystallized (spray drying, temperature is 320 °C) to obtain a potassium fluoride product.

[0176] Application Example 3

[0177] This application example uses the modified diatomite described in Example 3 to remove COD from the material, specifically as follows:

[0178] Mix the high-COD fluorosilicon mixed acid and ammonia water with a mass concentration of 15% until the pH value of the liquid phase is 7, and then successively stir and react for 4 hours at a stirring speed of 200 r / min and perform the first solid-liquid separation to obtain silica precipitate and ammonium fluoride solution;

[0179] The silica precipitate is calcined at a temperature of 500 °C for 2 hours to obtain a white carbon black product;

[0180] The ammonium fluoride solution is mixed with an alkali (potassium hydroxide) and deammoniated at a temperature of 100 °C, and then a COD remover (hydrogen peroxide solution and the modified diatomite, the mass of the modified diatomite is 0.1% of the mass of the hydrogen peroxide solution, and the mass concentration of the hydrogen peroxide solution is 35%) accounting for 5% of the liquid mass is added for COD removal for 4 hours. Finally, after the second solid-liquid separation, a potassium fluoride solution and a solid phase are obtained. The obtained solid phase is activated at 200 °C for 4 hours and then returned to the COD removal for secondary utilization;

[0181] The obtained potassium fluoride solution is concentrated to a mass concentration of 60% and then crystallized (the temperature of spray drying is 260 °C) to obtain a potassium fluoride product.

[0182] Application Example 4

[0183] In this application example, the modified diatomite described in Example 4 is used to remove COD in the material, specifically as follows:

[0184] Mix the high-COD fluorosilicon mixed acid and ammonia water with a mass concentration of 10% until the pH value of the liquid phase is 6, and then stir and react for 2 h at a stirring speed of 500 r / min and perform the first solid-liquid separation in sequence to obtain silica precipitate and ammonium fluoride solution;

[0185] The silica precipitate is calcined at 300 °C for 4 h to obtain a white carbon black product;

[0186] The ammonium fluoride solution is mixed with an alkali (potassium hydroxide) and deammoniated at 80 °C, and then 1% of the COD removal agent based on the mass of the liquid (hydrogen peroxide solution and the modified diatomite, the mass of the modified diatomite is 1% of the mass of the hydrogen peroxide solution, and the mass concentration of the hydrogen peroxide solution is 45%) is added for 2 h of COD removal. Finally, after the second solid-liquid separation, a potassium fluoride solution and a solid phase are obtained. The obtained solid phase is activated at 400 °C for 2 h and then returned to the COD removal for secondary utilization;

[0187] The obtained potassium fluoride solution is concentrated to a mass concentration of 40% and then crystallized (the temperature of spray drying is 350 °C) to obtain a potassium fluoride product.

[0188] Comparative Application Example 1

[0189] The difference from Application Example 1 is only that no copper salt is added to the salt solution during the preparation of the modified diatomite, that is, the modified diatomite does not contain copper element, that is, the modified diatomite only loads the composite metal oxide of iron and manganese, and the mass of iron and manganese is increased in equal proportion to ensure that the total mass of the metal oxide on the modified diatomite remains unchanged.

[0190] Comparative Application Example 2

[0191] The difference from Application Example 1 is only that no iron salt is added to the salt solution during the preparation of the modified diatomite, that is, the modified diatomite does not contain iron element, that is, the modified diatomite only loads the composite metal oxide of copper and manganese, and the mass of copper and manganese is increased in equal proportion to ensure that the total mass of the metal oxide on the modified diatomite remains unchanged.

[0192] Comparative Application Example 3

[0193] The difference from Application Example 1 is only that no manganese salt is added to the salt solution during the preparation of the modified diatomite, that is, the modified diatomite does not contain manganese element, that is, the modified diatomite only loads the composite metal oxide of iron and copper, and the mass of iron and copper is increased in equal proportion to ensure that the total mass of the metal oxide on the modified diatomite remains unchanged.

[0194] Comparative Application Example 4

[0195] The difference from Application Example 1 is only that no copper salt and iron salt are added to the salt solution during the preparation of the modified diatomite, that is, the modified diatomite is only loaded with manganese metal oxide, the mass of manganese is increased, and the total mass of the metal oxide on the modified diatomite remains unchanged.

[0196] Comparative Application Example 5

[0197] The difference from Application Example 1 is only that no copper salt and manganese salt are added to the salt solution during the preparation of the modified diatomite, that is, the modified diatomite is only loaded with iron metal oxide, the mass of iron is increased, and the total mass of the metal oxide on the modified diatomite remains unchanged.

[0198] Comparative Application Example 6

[0199] The difference from Application Example 1 is only that no iron salt and manganese salt are added to the salt solution during the preparation of the modified diatomite, that is, the modified diatomite is only loaded with copper metal oxide, the mass of copper is increased, and the total mass of the metal oxide on the modified diatomite remains unchanged.

[0200] Comparative Application Example 7

[0201] The difference from Application Example 1 is only that the carrier diatomite is replaced with an equal amount of ZSM-5 molecular sieve during the preparation of the modified diatomite.

[0202] Application Example 5

[0203] The difference from Application Example 1 is only that the COD remover is replaced with an equal amount of the modified diatomite provided in Example 1.

[0204] Application Example 6

[0205] The difference from Application Example 1 is only that the COD remover is replaced with an equal amount of hydrogen peroxide solution (mass concentration: 40%).

[0206] Application Example 7

[0207] The difference from Application Example 1 is only that the mass of the modified diatomite in the COD remover is 0.05% of the mass of the hydrogen peroxide solution.

[0208] Application Example 8

[0209] The difference from Application Example 1 is only that the mass of the modified diatomite in the COD remover is 2% of the mass of the hydrogen peroxide solution.

[0210] Application Example 9

[0211] The difference from Application Example 1 is only that the hydrogen peroxide solution in the COD remover is replaced with an equal amount of sodium hypochlorite.

[0212] The COD removal rate data of the potassium fluoride aqueous solution in the above application example and the technical indicators of the potassium fluoride product that meets the national standard for industrial anhydrous potassium fluoride (HGT2829-2008) are shown in Table 2 below.

[0213] Table 2

[0214]

[0215]

[0216] Combined with Table 1 and Table 2, it can be seen from the comparison of Application Examples 1-6 that the trimetallic composite oxide is significantly superior to the bimetallic and monometallic systems in catalytic activation and adsorption capacity through multi-metal synergy, structural regulation and surface chemical optimization, and then catalyzes hydrogen peroxide to decompose hydroxyl radicals to oxidize and decompose organic matter, which can achieve a higher COD removal rate, and effectively adsorb the remaining impurities to prepare a better quality potassium fluoride product. It can be seen from Application Examples 5-6 that the single use of modified diatomite performs poorly in degrading COD, and the use of hydrogen peroxide alone can effectively degrade COD to a certain extent, but it is not good in the adsorption of other impurities. It can be seen from Application Examples 7-8 that the amount of modified diatomite and hydrogen peroxide used has a greater impact on the synergistic effect. If the amount of modified diatomite used is too little, it will lead to weakened adsorption and catalytic ability, and the amount used is too much. Not only can the adsorption and catalytic ability not be improved again, but it may also have a counter-effect due to the competitive effect. It can be seen from Application Example 9 that in this system, the use of hydrogen peroxide is more conducive to the removal of COD.

[0217] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0218] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0219] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A modified diatomaceous earth, characterized in that: The modified diatomaceous earth comprises: Diatomaceous earth, and composite metal oxides of copper, iron and manganese supported on the diatomaceous earth; The chemical structural formula of the copper, iron and manganese composite metal oxide is Cu x Fe y Mn z O w , based on molar amount, x is 1-2, y is 1-2, z is 1-2, and w is 3-7.

2. A method for preparing modified diatomite according to claim 1, characterized in that: The preparation method comprises: impregnating diatomite with a salt solution containing copper, iron and manganese, then adjusting the pH value of the solution, and obtaining a precursor through solid-liquid separation; The precursor is calcined to obtain modified diatomite.

3. The preparation method according to claim 2, characterized in that: The D50 particle size of the diatomaceous earth is 10-30 μm; Preferably, the total concentration of copper, iron and manganese in the salt solution containing copper, iron and manganese is 0.5-2 mol / L; Preferably, the immersion time is 6-12 hours; Preferably, the impregnation is assisted by stirring at a stirring speed of ≥ 200 r / min; Preferably, the end point pH value range of the pH value of the adjusted solution is 8-9.

4. The preparation method according to claim 2 or 3, characterized in that: The calcination temperature is 300-600°C; Preferably, the heating rate of the calcination is 2-5°C / min; Preferably, the calcination is carried out under an oxidizing atmosphere; Preferably, the calcination time is 3-6 hours.

5. A COD remover, characterized in that: The COD remover comprises: A hydrogen peroxide solution and the modified diatomaceous earth as claimed in claim 1.

6. The COD remover according to claim 5, characterized in that The mass of the modified diatomaceous earth is 0.1-1% of the mass of the hydrogen peroxide solution; Preferably, the mass concentration of the hydrogen peroxide solution is 35-45%.

7. A use of the COD remover as claimed in claim 5 or 6, characterized in that: The use includes: using the COD remover to remove organic matter.

8. The use according to claim 7, characterized in that The mass of the COD remover in the organic matter removal is 1-5% of the mass of the liquid; Preferably, the time for removing the organic matter is 2-4 hours.

9. A method for resource utilization of high COD fluorine-containing silicon mixed acid, characterized in that: The utilization method includes: The high COD fluorine-containing silicon mixed acid and ammonia water are mixed, and then stirred for reaction and first solid-liquid separation are performed in sequence to obtain silicon-containing precipitate and ammonium salt solution; The silicon-containing precipitate is calcined to obtain a white carbon black product; The ammonium salt solution is sequentially subjected to deammoniation, COD removal, and second solid-liquid separation to obtain a fluoride salt solution; The fluoride salt solution is concentrated and crystallized in sequence to obtain a fluoride salt product; Wherein, the COD removal agent used in the COD removal includes: the COD removal agent as described in claim 5 or 6.

10. The utilization method according to claim 9, characterized in that: The mass concentration of the ammonia water is 10-15%; Preferably, the pH value of the liquid phase obtained by mixing is 6-7; Preferably, the stirring speed of the stirring reaction is ≥200r / min; Preferably, the stirring reaction time is 2-4h; Preferably, the calcination temperature is 300-500°C; Preferably, the calcination time is 2-4h; Preferably, the deamination comprises: adding a base to the ammonium salt solution for heating reaction; Preferably, the temperature of the heating reaction is 80-100°C; Preferably, the ammonia component obtained by deamination is returned for use as aqueous ammonia; Preferably, the mass of the COD removal agent in the COD removal is 1-5% of the mass of the liquid obtained by deammoniation; Preferably, the COD removal time is 2-4h; Preferably, the solid phase obtained from the second solid-liquid separation is activated and then returned to COD removal for secondary utilization; Preferably, the activation temperature is 200-400°C; Preferably, the activation time is ≥2h; Preferably, the end point of the concentration is a mass concentration of the material of 40-60%; Preferably, the concentration method includes: evaporation and / or membrane separation; Preferably, the crystallization method includes: one or a combination of at least two of evaporation crystallization, spray drying or cooling crystallization; Preferably, the spray drying temperature is 260-350°C.

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