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CN115124019B - Method for preparing silicon-carbon material by utilizing fluosilicic acid waste - Google Patents

Method for preparing silicon-carbon material by utilizing fluosilicic acid waste Download PDF

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CN115124019B
CN115124019B CN202210674609.1A CN202210674609A CN115124019B CN 115124019 B CN115124019 B CN 115124019B CN 202210674609 A CN202210674609 A CN 202210674609A CN 115124019 B CN115124019 B CN 115124019B
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CN115124019A (en
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刘建文
贲淼
王石泉
曾嵘
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Wuhan Side Technology Co ltd
Hubei University
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Wuhan Side Technology Co ltd
Hubei University
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
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    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C01B33/021—Preparation
    • C01B33/023—Preparation by reduction of silica or free silica-containing material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/5835—Comprising fluorine or fluoride salts
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    • C01P2006/40—Electric properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area

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Abstract

The invention discloses a method for preparing a silicon-carbon material by utilizing fluosilicic acid waste, which comprises the following steps: s1, taking fluosilicic acid and weak acid root salt as raw materials, and carrying out a neutralization reaction to obtain a fluosilicate solution; s2, heating the fluorosilicate solution, regulating the pH value, continuing the reaction, and cooling to obtain slurry; s3, filtering and separating the slurry, dispersing filter residues obtained by separation in water, and heating and ageing; s4, under inert atmosphere, performing thermal reduction on the aged filter residues by using a reducing agent and a heat removing agent, and reacting with strong acid to obtain a silicon material; s5, compounding the silicon material and the carbon material, and carbonizing to obtain the silicon-carbon material, so that pollution of fluosilicic acid is avoided, and application of fluosilicic acid waste in preparation of battery materials is realized.

Description

Method for preparing silicon-carbon material by utilizing fluosilicic acid waste
Technical Field
The invention relates to the field of hexafluorosilicic acid recovery, in particular to a method for preparing a silicon-carbon material by utilizing fluosilicic acid waste.
Background
As a byproduct of the phosphate industry, a significant amount of hexafluorosilicic acid is produced annually (collection of H 2SiF6).H2SiF6 is typically done by the absorption process of gaseous silicon tetrafluoride (SiF 4) in water scrubbers. Generally, H 2SiF6 is one of the wastes released in phosphate industry production and is a major environmental (hazardous) and economic (end waste disposal) challenge.
The ingredient detection shows that the fluosilicic acid waste material of the phosphate fertilizer plant contains impurities such as sulfuric acid, silica gel, phosphate and the like besides fluosilicic acid; the sodium chloride waste is usually solid or liquid, and mainly contains sodium glycolate, ethanol, sodium carboxymethylcellulose, ammonium chloride and other impurities besides sodium chloride; in the prior art, fluosilicic acid waste of a phosphate fertilizer factory, sodium chloride discarded by an agricultural chemical factory and sodium chloride-containing brine discarded by other pharmaceutical chemical enterprises are piled up or discarded as industrial waste, and are not utilized as resources, so that the waste of fluosilicic resources is caused, and the environment is polluted;
The Chinese patent with publication No. CN106185817A discloses a method for recovering hydrofluoric acid from waste water containing fluosilicic acid, which is to add ammonia or ammonium into the waste water containing fluosilicic acid to decompose fluosilicic acid into ammonium fluoride and silicon dioxide precipitate, then add magnesium sulfate into the solution containing ammonium fluoride to precipitate fluorine therein in the form of magnesium fluoride, filter to obtain magnesium fluoride and solution after precipitating fluorine, then thermally decompose magnesium fluoride with sulfuric acid, thermally decompose steam for condensation and absorption to obtain recovered hydrofluoric acid, but the application range of the recovered product obtained by the method is limited, so the method is very important for recovering the product by using a new method for fluosilicic acid waste, and the resource utilization field is widened.
Disclosure of Invention
The invention aims to overcome the technical defects, and provides a method for preparing a silicon-carbon material by utilizing fluosilicic acid waste, so that the pollution of fluosilicic acid is solved, and the application of a recovered product of fluosilicic acid waste in the aspect of preparing a battery material is realized.
In order to achieve the technical purpose, the invention adopts the following technical scheme.
In a first aspect, the present application provides a method for preparing a silicon-carbon material using fluorosilicic acid waste, comprising the steps of:
S1, taking fluosilicic acid waste and weak acid root salt as raw materials, and carrying out a neutralization reaction to obtain fluosilicate solution;
s2, heating the fluorosilicate solution, regulating the pH value, continuing the reaction, and cooling to obtain slurry;
s3, filtering and separating the slurry, dispersing filter residues obtained by separation in water, and heating and ageing;
S4, under inert atmosphere, performing thermal reduction on the aged filter residues by using a reducing agent and a heat removing agent, and reacting with strong acid to obtain a silicon material;
S5, compounding the silicon material and the carbon material, and carbonizing to obtain the silicon-carbon material.
Preferably, in step S3, the method further comprises drying and collecting the filtrate obtained by separation.
Preferably, in step S2, the pH is in the range of 5-6.
Preferably, in step S2, the heating temperature of the fluorosilicate solution is 40-100 ℃ and the heating time is 1-5h.
Preferably, in the step S3, the heating and ageing temperature is 40-100 ℃ and the ageing time is 1-5h.
Preferably, the reducing agent comprises one or more of magnesium, carbon and silicon.
Preferably, the weak acid root salt comprises one or more of carbonate, bicarbonate, sulfite and bisulfite.
Preferably, the heat removing agent is sodium chloride.
Preferably, the carbon material comprises one or more of glucose, chitosan, asphalt and citric acid.
In a second aspect, the application provides an application of a silicon-carbon material prepared by utilizing fluosilicic acid waste in a silicon-carbon composite electrode.
Compared with the prior art, the invention has the beneficial effects that:
1. The scheme uses fluosilicic acid waste as a raw material, performs neutralization reaction with weak acid salt, gas production and pore forming, then performs reduction to obtain a silicon raw material with mesoporous high specific surface area, and then performs compounding with a carbon material to obtain a battery material with large performance capacity and high cycle retention rate;
2. the method has low equipment requirement, mild reaction condition and strong operability;
3. The scheme solves the problem of fluorosilicic acid waste pollutants and simultaneously produces products which can be used in the field of battery materials, and has high industrial utilization value.
Drawings
FIG. 1 is an electron microscope image of mesoporous silica obtained in the present embodiment;
FIG. 2 is an electron microscope image of the silicon material obtained in the present embodiment;
FIG. 3 is an electron microscope image of the silicon carbon material obtained in the present embodiment;
Fig. 4 is a graph of cycle performance of a silicon carbon material assembled battery obtained in this embodiment.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The embodiment of the application provides a method for preparing a silicon-carbon material by utilizing fluosilicic acid waste, which comprises the following steps of:
S1, carrying out neutralization reaction by taking fluosilicic acid waste and weak acid root salt as raw materials to obtain fluosilicic acid solution, wherein the weak acid root salt comprises one or more of carbonate, bicarbonate, sulfite and hydrosulfite, the concentration of the weak acid root salt is 10-50 wt%, and the concentration of fluosilicic acid in the fluosilicic acid waste is 10-50 wt%, wherein the molar ratio of the weak acid root salt to fluosilicic acid is 1:1-5.
In the step, fluosilicic acid reacts with weak acid salt solution capable of generating gas at normal temperature, and the generated product has a mesoporous structure, so that a solution containing fluosilicate is obtained after the reaction, the obtained solution is a colloidal solution, weak acid salt is taken as sodium carbonate as an example, and the chemical reaction involved in the step is as follows:
H2SiF6+Na2CO3→Na2SiF6+CO2↑+H2O
S2.40-100 ℃ heating the fluorosilicate solution for 1-5h, regulating the pH value to 5-6 by using weak acid radical salt, continuing the reaction, and cooling to room temperature to obtain slurry;
S3, filtering and separating the slurry, wherein the solid component obtained by separation is mainly mesoporous silica, the liquid component is mainly sodium fluoride solution, dispersing the filter residue obtained by separation in water, heating and ageing for 1-5h at 40-100 ℃, washing the filter residue after ageing, drying and collecting, in the process, the ageing step is favorable for stabilizing the formed mesoporous structure, drying the filtrate part at the drying temperature of (100-160 ℃), cleaning the dried solid, and spray-drying the cleaned solid at the temperature of (100-200 ℃) to obtain commercially available sodium fluoride solid;
The reaction process in step S2 and step S3 is as follows:
≡Si(OH)+(HO)Si≡→≡Si-O-Si≡↓(s)+H2O(l)
Si(OH)4＝SiO2+H2O
Na+(aq)+F-(aq)→NaF(s)
Converting the filter residue into porous silicon dioxide, and converting the filtrate into sodium fluoride;
in summary, the overall reaction process of steps S1-S3 is:
H2SiF6+3Na2CO3→6NaF+SiO2↓+3CO2↑+H2O
s4, under inert atmosphere (nitrogen), carrying out thermal reduction on aged filter residues by using a reducing agent and a heat removing agent, wherein the heating temperature of the thermal reduction is 400-700 ℃, the obtained product is a earthy yellow or black solid, then the earthy yellow or black solid reacts with strong acid to obtain a silicon material with high specific surface area, the reducing agent comprises one or more of magnesium, carbon and silicon, the reducing agent is selected as the reducing agent because the silicon dioxide is difficult to reduce by other reducing agents, the silicon has reducibility, metal with reducibility stronger than that of the silicon reacts with the silicon dioxide to easily form silicate, the heat removing agent is sodium chloride, the weight of the reducing agent accounts for 1/5 of the mixture in the mixture of the reducing agent, the heat removing agent and the filter residues, the heat removing agent accounts for 1/3, the strong acid comprises 3-10 wt.% hydrochloric acid and 5-10 wt.% hydrofluoric acid;
taking magnesium as an example of a reducing agent, the reaction process is as follows:
SiO2(s)+2Mg(g)→Si(s)+2MgO(s)
The reaction end point of the step is that no gas is generated after hydrochloric acid is added, and then hydrofluoric acid is added to hardly generate gas.
S5, compounding the silicon material with the high specific surface area obtained by the steps with a carbon material, and carbonizing the silicon material under the protection of nitrogen, wherein the carbonization temperature is 700-1000 ℃, so that the silicon-carbon material for preparing the battery material is obtained, and the carbon material comprises one or more of glucose, chitosan, asphalt and citric acid, wherein the molar ratio of the silicon material to the carbon material is 1:3-10.
The reaction process of the step is as follows:
Si+CxH2nOn→xC/Si+nH2O
The product obtained by the step is yellow-black, is developed into micron-sized or nano-sized powder, and is collected.
In a second aspect, the present application provides the use of a silicon-carbon material prepared from fluorosilicic acid waste in a silicon-carbon composite electrode, i.e. the resulting silicon-carbon material is directly used as a silicon-carbon composite electrode in a battery.
The present invention will be described below by way of specific examples.
Example 1
A method for preparing a silicon-carbon material by utilizing fluosilicic acid waste, comprising the following steps:
s1, weighing 16753g of fluosilicic acid solution with the concentration of 27.45wt.% and sodium carbonate solution with the concentration of 31.59wt.% to react for 30 minutes to obtain a gelatinous fluosilicate solution;
S2, adding 1500g of deionized water into the gelatinous fluorosilicate solution, heating to 80 ℃, maintaining for 3 hours, maintaining the pH at 5.5 during the period, and cooling to room temperature to obtain slurry;
S3, separating slurry through a plate-frame filter after the reaction is finished, adding 1000g of water into a filter residue part, heating to 80 ℃, and aging for 2 hours to obtain precursor mesoporous silica, wherein an electron microscope diagram of the precursor mesoporous silica is shown in FIG. 1; heating the filtrate to 130 ℃ for drying, adding 300g of water for cleaning after the drying, and then carrying out spray drying at 150 ℃ after the cleaning is finished, and collecting the dried product to obtain sodium fluoride, wherein the filtering pressure of a plate-frame filter is 30bar, and the temperature is 20-30 ℃;
S4, weighing 50g of mesoporous silica prepared by the reaction, and mixing according to a proportion of 1:3, weighing magnesium powder and sodium chloride according to the proportion of 1:2.4; uniformly mixing the materials, placing the materials in a tube furnace, protecting the materials for 30 minutes by nitrogen in the furnace, then heating to 650 ℃ at a speed of 5 ℃/min, and keeping the temperature for 4 hours to obtain earthy yellow or black solid powder, taking 70g of the solid powder, adding 100g of 7wt.% hydrochloric acid and 100g of 5wt.% hydrofluoric acid, and reacting to obtain a silicon material, wherein an electron microscope diagram of the silicon material is shown in figure 2;
S4, 15g of silicon material and 250g of citric acid are taken and compounded, the compounded material is placed in a tube furnace, the furnace is protected by nitrogen for 30 minutes, then the silicon-carbon material is obtained after the temperature is maintained for 3 hours at the speed of 5 ℃/min and the temperature of 850 ℃, the electron microscope diagram of the silicon-carbon material is shown in figure 3, and the battery cycle performance of the carbon-silicon material assembled in a battery as a carbon-silicon composite electrode is shown in figure 4.
Example 2
A method for preparing a silicon-carbon material by utilizing fluosilicic acid waste, comprising the following steps:
S1, weighing a fluorosilicic acid solution with the concentration of 50wt.% and a sodium bicarbonate solution with the concentration of 50wt.% to react for 30 minutes to obtain a gelatinous fluorosilicate solution;
s2, adding 1500g of deionized water into the gelatinous fluorosilicate solution, heating to 40 ℃, maintaining the temperature for 3 hours, maintaining the pH at 5 during the period, and cooling to room temperature to obtain slurry;
S3, separating slurry through a plate-frame filter after the reaction is finished, adding 1000g of water into the filter residue part, heating to 40 ℃, and aging for 5 hours to obtain mesoporous silica; heating the filtrate to 130 ℃ for drying, adding 300g of water for cleaning after the drying, and then carrying out spray drying at 150 ℃ after the cleaning is finished, and collecting the dried product to obtain sodium fluoride, wherein the filtering pressure of a plate-frame filter is 30bar, and the temperature is 20-30 ℃;
S4, weighing 50g of mesoporous silica prepared by reaction, weighing carbon powder according to a ratio of 1:3, and weighing sodium chloride according to a ratio of 1:2.4; uniformly mixing the materials, placing the materials in a tube furnace, protecting the tube furnace for 30 minutes by nitrogen, then heating to 400 ℃ at 5 ℃/min, and keeping the temperature for 4 hours to obtain earthy yellow or black solid powder, taking 70g of the solid powder, adding 100g of 7wt.% hydrochloric acid, adding 100g of 5wt.% hydrofluoric acid, and reacting to obtain the silicon material;
s5, taking 15g of silicon material and 250g of glucose, compounding, placing the compounded material in a tube furnace, protecting the furnace for 30 minutes by nitrogen, and then keeping the temperature for 3 hours at the temperature of 5 ℃/min and 700 ℃ to obtain the silicon-carbon material.
Example 3
A method for preparing a silicon-carbon material by utilizing fluosilicic acid waste, comprising the following steps:
S1, weighing a fluosilicic acid solution with the concentration of 10wt.% and a sodium carbonate solution with the concentration of 10wt.% to react for 30 minutes to obtain a gelatinous fluosilicate solution;
S2, adding 1500g of deionized water into the gelatinous fluorosilicate solution, heating to 100 ℃, maintaining the temperature for 1h, maintaining the pH at 6 during the period, and cooling to room temperature to obtain slurry;
S3, separating slurry through a plate-frame filter after the reaction is finished, adding 1000g of water into the filter residue part, heating to 100 ℃, and aging for 1h to obtain mesoporous silica; heating the filtrate to 130 ℃ for drying, adding 300g of water for cleaning after the drying, and then carrying out spray drying at 150 ℃ after the cleaning is finished, and collecting the dried product to obtain sodium fluoride, wherein the filtering pressure of a plate-frame filter is 30bar, and the temperature is 20-30 ℃;
s4, weighing 50g of mesoporous silica prepared by the reaction, weighing magnesium powder according to the proportion of 1:3, and weighing sodium chloride according to the proportion of 1:2.4; uniformly mixing the materials, placing the materials in a tube furnace, protecting the tube furnace for 30 minutes by nitrogen, then heating to 700 ℃ at 5 ℃/min, and keeping the temperature for 4 hours to obtain earthy yellow or black solid powder, taking 70g of the solid powder, adding 100g of 7wt.% hydrochloric acid and 100g of 5wt.% hydrofluoric acid, and reacting to obtain a silicon material;
S5, taking 15g of silicon material and 250g of chitosan, compounding, placing the compounded material in a tube furnace, protecting the furnace for 30 minutes by nitrogen, and then keeping the temperature at 5 ℃/min and 1000 ℃ for 3 hours to obtain the silicon-carbon material.
Comparative example 1
A method for preparing a silicon carbon material using fluorosilicic acid waste, the other steps being the same as in example 1, except that sodium sulfite is replaced with sodium carbonate.
Comparative example 2
A method for preparing a silicon carbon material using fluorosilicic acid waste, the other steps being the same as in example 1, except that sodium hydroxide is replaced with sodium carbonate.
Comparative example 3
A method for preparing a silicon carbon material using fluorosilicic acid waste, the other steps are the same as in example 1, except that the pH is changed from 5.5 to 1.7.
Comparative example 4
A method for preparing a silicon carbon material using fluorosilicic acid waste material, the other steps being the same as in example 1, except that the reducing agent is replaced with sodium by magnesium.
Test case
Component analysis was performed on the residue treated products and filtrate treated products obtained in step S3 of examples 1 to 3 and comparative examples 1 to 3, and the specific surface area of the intermediate mesoporous silica was analyzed, wherein the specific surface area of the silica was measured by a specific surface area analyzer, the weight ratio of the silica in the residue was measured by a weight method, and the mass ratio of sodium fluoride in the filtrate was measured by YS/T535.1 to 2006, and the results are shown in table 1.
TABLE 1 analysis results of filter residues and filtrate products
It is explained that the specific surface area of silica obtained with sodium carbonate as weak acid salt is larger than that of silica obtained with sodium hydroxide and sodium sulfite as weak acid salt, and the content of silica is higher, the recovery efficiency is high, and in step S2, the specific surface area of mesoporous silica generated is large at pH of 5 to 6.
The silicon materials obtained in step S4 of example 1 and comparative example 4 were subjected to composition analysis, and the silicon material powder obtained in example 1 had 47g and a silicon content of 76%, whereas the silicon material powder obtained in comparative example 4 had almost no reduction of silica, and all of the silica was converted to silicate, indicating that the conversion rate of silica reduced with magnesium was high and the reduction with sodium was impossible to obtain the desired silicon material.
The carbon-silicon materials obtained in example 1 and comparative examples 1 to 4 were subjected to a battery cycle performance test, and the test results are shown in table 2.
Table 2 battery performance test of carbon-silicon materials
The above-described embodiments of the present invention do not limit the scope of the present invention. Any other corresponding changes and modifications made in accordance with the technical idea of the present invention shall be included in the scope of the claims of the present invention.

Claims (6)

1. A method for preparing a silicon-carbon material by utilizing fluosilicic acid waste, which is characterized by comprising the following steps:
S1, taking fluosilicic acid waste and weak acid root salt as raw materials, and carrying out a neutralization reaction to obtain fluosilicate solution; the weak acid salt is sodium carbonate or sodium bicarbonate, the concentration of the weak acid salt is 10-50 wt%, the concentration of fluorosilicic acid in the fluorosilicic acid waste is 10-50 wt%, and the molar ratio of the weak acid salt to the fluorosilicic acid is 1:1-5;
S2.40-100 ℃ heating the fluorosilicate solution for 1-5h, regulating the pH value to 5-6 by using weak acid radical salt, continuing the reaction, and cooling to room temperature to obtain slurry;
s3, filtering and separating the slurry, dispersing filter residues obtained by separation in water, and heating and ageing;
S4, under inert atmosphere, performing thermal reduction on the aged filter residues by using a reducing agent and a heat removing agent, and reacting with strong acid to obtain a silicon material; the reducing agent is magnesium or carbon;
S5, compounding the silicon material and the carbon material, and carbonizing to obtain the silicon-carbon material.
2. The method for producing a silicon carbon material using fluorosilicic acid waste as claimed in claim 1, wherein in step S3, the filtrate obtained by separation is further dried and collected.
3. The method for preparing silicon-carbon material using fluorosilicic acid waste as claimed in claim 1, wherein in step S3, the temperature of the heating aging is 40-100 ℃ and the aging time is 1-5h.
4. The method for preparing a silicon carbon material using fluorosilicic acid waste according to claim 1, wherein the heat removing agent is sodium chloride.
5. The method for preparing a silicon carbon material by utilizing fluosilicic acid waste according to claim 1, wherein the carbon material comprises one or more of glucose, chitosan, asphalt and citric acid.
6. Use of a silicon-carbon material prepared according to the method of any one of claims 1-5 in a silicon-carbon composite electrode.
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