Green and efficient bismuth hydroxide preparation method

Abstract

The invention relates to the technical field of bismuth hydroxide preparation, in particular to a green and efficient bismuth hydroxide preparation method which comprises the following steps: step 1, preparing materials: preparing materials required by bismuth hydroxide preparation, including bismuth oxide, fatty acid, strong acid, alkaline substances and a catalyst; 2, bismuth salt preparation, wherein bismuth oxide and fatty acid react at the high temperature of 70-90 DEG C to prepare organic bismuth salt, and the organic salt is purified; 3, bismuth salt decomposition and precipitation: carrying out acidolysis on the organic bismuth salt by using strong acid, and filtering an acidolysis solution by using a filtering technology after the acidolysis is finished; the bismuth ion release rate can be increased through the pressurized acidolysis-oxygen oxidation method, the product morphology can be controlled through the gradient pH precipitation method, green production can be achieved by combining countercurrent washing and waste liquid circulation, the purity of the obtained product is larger than or equal to 99%, and the method is suitable for the fields of high-end electronic materials and environment-friendly catalysis.

Description

Technical Field

[0001] The invention relates to the technical field of bismuth hydroxide preparation, and in particular to a green and efficient method for preparing bismuth hydroxide. Background Art

[0002] Bismuth hydroxide has a good application prospect in the fields of epoxy system cathode electrodeposition coating for automobile electrophoretic coating, the manufacture of bismuth salts, the absorption of rutin and quercetin, the hydrolysis of ribonucleic acid, etc. For example, the patent CN102027076A disclosed on April 20, 2011 pointed out that the use of dibutyltin oxide can cause shrinkage and form a precipitate to be removed from the dip coating bath. However, the current method for preparing bismuth hydroxide is to react with bismuth salts or sodium hydroxide, or to prepare it by chemical precipitation in a ratio of 5:1 with barium nitrate and ammonium carbonate in water. This chemical precipitation method has the characteristics of simple process and easy adjustment of process parameters as needed.

[0003] For example, a method for preparing bismuth hydroxide with application number CN201310033133.4 and authorization announcement date 20150204 includes the following steps: first preparing bismuth nitrate solution, ammonia solution and dispersant solution; then add bismuth nitrate to the dispersant solution Solution, stir, and add water to dilute bismuth nitrate solution, and then add ammonia solution to adjust bismuth nitrate The solution pH is set, and stirred; after the reaction is completed, the pre-precipitate is filtered, precipitated, and washed; the pre-precipitate after washing is prepared into a suspension, and an ammonia solution is continuously added to adjust its pH, and stirred; after the reaction is completed, the suspension is allowed to stand for aging, and after aging, bismuth hydroxide is The precipitate is washed, separated and dried to obtain dry bismuth hydroxide. Powder, the dried powder is air flow crushed to obtain bismuth hydroxide The bismuth hydroxide prepared by this method has low impurity content and excellent catalytic performance.

[0004] Currently, bismuth hydroxide is mostly produced on the market by two methods: inorganic bismuth salt precipitation method and organic bismuth salt hydrolysis method. However, the above two methods have the following disadvantages: (1) The traditional inorganic bismuth salt precipitation method uses inorganic salts such as bismuth nitrate and bismuth chloride as raw materials, which has the disadvantages of high raw material cost and residual heavy metal impurities (such as , ) and other problems, the product purity is insufficient (≤95%); (2) The decomposition of organic bismuth salts in the organic bismuth salt hydrolysis method requires high temperature and strong acid conditions (such as concentrated nitric acid, above 80°C), which leads to severe corrosion of the equipment, low bismuth ion release rate (<85%), and difficult separation of by-products (organic acids); (3) Environmental issues: Existing process wastewater contains high concentrations of acid and metal ions, and the treatment cost is high.

[0005] In view of this, it is urgent to design a green and efficient method for preparing bismuth hydroxide to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to provide a green and efficient method for preparing bismuth hydroxide to solve the above-mentioned shortcomings in the prior art.

[0007] In order to achieve the above object, the present invention provides the following technical solutions: A green and efficient method for preparing bismuth hydroxide comprises the following steps: Step 1. Prepare materials: prepare the materials required for the preparation of bismuth hydroxide, which include bismuth oxide, fatty acid, strong acid, alkaline substance, and catalyst; It should be noted that the bismuth oxide is microporous bismuth oxide, and the preparation technology is as follows: Step S1-1. Template introduction: The bismuth oxide powder and the mesoporous template are fed into a ball mill, and the ball mill is started to mix and grind the bismuth oxide powder and the mesoporous template, and the pores of the template are used to guide the dispersion of the bismuth oxide particles to form a composite structure; Step S1-2. Template removal: adding hydrofluoric acid to the obtained composite structure, dissolving the template by acid washing, and retaining the microporous framework of bismuth oxide; Step S1-3. Washing and drying: washing the retained bismuth oxide with ultrapure water to obtain pure bismuth oxide, and drying the obtained bismuth oxide to obtain a bismuth oxide powder with a microporous structure; The fatty acid selected is saturated fatty acid, the strong acid selected is nitric acid, the alkaline substance selected is ammonia water, and the catalyst selected is activated carbon, oxygen, and polyvinyl pyrrolidone.

[0008] Step 2. Preparation of bismuth salt: preparing organic bismuth salt by reacting bismuth oxide and fatty acid at a high temperature of 70-90°C, and purifying the organic salt; It should be noted that the preparation method of the organic bismuth salt is as follows: Step S2-1. Material preparation: Add a certain amount of bismuth oxide and fatty acid to the organic bismuth synthesis reactor and start stirring; Step S2-2. Heating and insulation: raising the temperature inside the organic bismuth synthesis reactor, the temperature is specifically: 85 ° C, and the reaction is kept warm for 1-3 hours; It should be noted that in step S2-2, the following method is specifically used to accelerate the reaction speed, and the specific method is as follows: (1) Introducing a bimetallic catalyst into the organic bismuth synthesis reactor to reduce the reaction activation energy, shorten the reaction time to within 1 hour, and reduce the generation of by-products; (2) Ultrasonic-assisted dispersion technology was used to enhance the interfacial contact between bismuth oxide and fatty acids and increase the rate of transesterification reaction; The heating steps are as follows: (1) In the early stage, the temperature inside the organic bismuth synthesis reactor is raised to 60-70°C, and low temperature is used to promote mass transfer; (2) In the later stage, the temperature in the organic bismuth synthesis reactor is raised to 85-90°C to accelerate the reaction of bismuth oxidation and fatty acid and avoid the oxidation of fatty acid; Step S2-3. Adjusting pH: Lower the internal temperature of the organic bismuth synthesis reactor to 15-20°C, add a certain amount of process water for cleaning, and use ammonia water to adjust the pH of the water layer to 7-8; Step S2-4. Stirring and stratifying: Stop stirring, let stand for a period of time to stratify, and send the stratified water layer to sewage treatment; Step S2-5. Dehydration and drainage: Open the vacuum dehydration device, control the temperature of the organic bismuth synthesis reactor to not exceed 85 ° C, vacuum -0.095Mpa, remove moisture from the material layer, obtain a dehydrated material layer, and send the dehydrated water to sewage treatment; It should be noted that after dehydration, a molecular distillation step is added to separate low-boiling impurities and increase the purity of the organic bismuth salt to ≥98%; Step S2-6 cooling treatment: lowering the temperature in the organic bismuth synthesis reactor, specifically cooling to 20-25 ° C, to obtain a finished organic bismuth salt; Step 3. Decomposition and precipitation of bismuth salt: The organic bismuth salt is subjected to acid hydrolysis by a strong acid. After the acid hydrolysis is completed, the acid hydrolysis solution is filtered by a filtration technique, the filtered acid hydrolysis solution is neutralized to obtain a precipitate, and then the precipitate is separated by a separation technique; It should be noted that the specific steps of decomposition of bismuth salt are as follows: Step S3-1. Raw material pretreatment: add organic bismuth salt and 3-5 mol / L nitric acid into a reactor, start the stirrer on the reactor to mix, and add activated carbon to adsorb heavy metal impurities during the mixing process, and the pre-reaction temperature of the reactor is 40-50°C during the reaction; Step S3-2. Pressurized acid hydrolysis: The reaction material is transferred into an acid-resistant high-pressure reactor and rapidly heated to 60-80°C. During the heating process, oxygen is introduced at an oxygen flow rate of 10-20 L / h. The temperature is raised to react within 1-2 hours. After the reaction is completed, an acid hydrolysis solution is obtained. The precipitation steps are as follows: S4-1. Gradient pH control: 10% ammonia water was added dropwise to the acid hydrolyzate. In the first stage, the pH was controlled at 3-4 and the stirring rate was 300 rpm to pre-precipitate impurities. In the second stage, ammonia water was gradually added to adjust the acid hydrolyzate to pH 8-9 and the stirring rate was 50 rpm to generate nano-scale colloids. S4-2. Addition of dispersant: Add polyvinyl pyrrolidone to the neutralized acid hydrolyzate to inhibit the agglomeration of particles in the acid hydrolyzate.

[0009] Step 4. Purification and drying: washing the obtained precipitate using washing technology, and after washing, drying the precipitate; It should be noted that the specific methods of purification and drying are as follows: S5-1. Countercurrent washing: Ultrapure water with a conductivity of ≤5μS / cm is used to remove impurities through a three-stage countercurrent washing tower (solid-liquid ratio 1:5). The conductivity of the filter cake after washing is ≤50μS / cm; S5-2. Low-temperature vacuum drying: Place the filter cake obtained by washing into a vacuum drying device, start the vacuum device, and dry it at 80-90°C and vacuum degree -0.08MPa for 2-3 hours to obtain a white powder.

[0010] Step 5. Waste recovery: The strong acid and alkaline substances in step 3 are recovered through recycling technology. The specific waste recovery method is as follows: Step S6-1. Acid recovery: distilling the acid hydrolysis waste liquid to recover nitric acid; Step S6-2. Ammonia regeneration: Use ion exchange resin to exchange the neutralized wastewater, remove the neutralized wastewater, and obtain ammonia water.

[0011] In the above technical scheme, the present invention provides a green and efficient method for preparing bismuth hydroxide, which has the following beneficial effects: (1) The present invention can improve the bismuth ion release rate through the pressurized acid hydrolysis-oxygen oxidation method, and can control the product morphology through the gradient pH precipitation method. Combined with countercurrent washing and waste liquid circulation, green production can be achieved to obtain a product purity of ≥99%, which is suitable for the fields of high-end electronic materials and environmental protection catalysis.

[0012] (2) The present invention can improve the effect of the reaction between bismuth oxide and fatty acids by preparing bismuth oxide with a microporous structure, and during the reaction process, the purity of the prepared organic bismuth salt is greatly improved by introducing bimetallic catalysts, ultrasonic assistance, two-stage heating and other technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0014] Figure 1 The present invention provides a method flow diagram of a green and efficient method for preparing bismuth hydroxide.

[0015] Figure 2 A schematic flow chart of a method for preparing bismuth oxide with a microporous structure provided in an embodiment of a green and efficient method for preparing bismuth hydroxide of the present invention.

[0016] Figure 3 A schematic diagram of a method for preparing an organic bismuth salt is provided in an embodiment of a green and efficient method for preparing bismuth hydroxide of the present invention.

[0017] Figure 4 A schematic diagram of a bismuth salt decomposition method provided in an embodiment of a green and efficient method for preparing bismuth hydroxide of the present invention.

[0018] Figure 5 A schematic diagram of the precipitation steps provided in an embodiment of a green and efficient method for preparing bismuth hydroxide of the present invention.

[0019] Figure 6 A schematic diagram of a specific method for purification and drying provided in an embodiment of a green and efficient method for preparing bismuth hydroxide of the present invention.

[0020] Figure 7 A schematic diagram of a waste recovery method is provided for an embodiment of a green and efficient method for preparing bismuth hydroxide of the present invention. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0022] like Figure 1-7 As shown, a green and efficient method for preparing bismuth hydroxide provided by an embodiment of the present invention comprises the following steps: Step 1. Prepare materials: prepare the materials required for the preparation of bismuth hydroxide, which include bismuth oxide, fatty acid, strong acid, alkaline substance, and catalyst; It should be noted that the bismuth oxide is microporous bismuth oxide, and the preparation technology is as follows: Step S1-1. Template introduction: The bismuth oxide powder and the mesoporous template are fed into a ball mill, and the ball mill is started to mix and grind the bismuth oxide powder and the mesoporous template, and the pores of the template are used to guide the dispersion of the bismuth oxide particles to form a composite structure; Step S1-2. Template removal: adding hydrofluoric acid to the obtained composite structure, dissolving the template by acid washing, and retaining the microporous framework of bismuth oxide; Step S1-3. Washing and drying: washing the retained bismuth oxide with ultrapure water to obtain pure bismuth oxide, and drying the obtained bismuth oxide to obtain a bismuth oxide powder with a microporous structure; The fatty acid selected is saturated fatty acid, the strong acid selected is nitric acid, the alkaline substance selected is ammonia water, and the catalyst selected is activated carbon, oxygen, and polyvinyl pyrrolidone.

[0023] Step 2. Preparation of bismuth salt: preparing organic bismuth salt by reacting bismuth oxide and fatty acid at a high temperature of 70-90°C, and purifying the organic salt; It should be noted that the preparation method of the organic bismuth salt is as follows: Step S2-1. Material preparation: Add a certain amount of bismuth oxide and fatty acid to the organic bismuth synthesis reactor and start stirring; Step S2-2. Heating and insulation: raising the temperature inside the organic bismuth synthesis reactor, the temperature is specifically: 85 ° C, and the reaction is kept warm for 1-3 hours; It should be noted that in step S2-2, the following method is specifically used to accelerate the reaction speed, and the specific method is as follows: (1) Introducing a bimetallic catalyst into the organic bismuth synthesis reactor to reduce the reaction activation energy, shorten the reaction time to within 1 hour, and reduce the generation of by-products; (2) Ultrasonic-assisted dispersion technology was used to enhance the interfacial contact between bismuth oxide and fatty acids and increase the rate of transesterification reaction; The heating steps are as follows: (1) In the early stage, the temperature inside the organic bismuth synthesis reactor is raised to 60-70°C, and low temperature is used to promote mass transfer; (2) In the later stage, the temperature in the organic bismuth synthesis reactor is raised to 85-90°C to accelerate the reaction of bismuth oxidation and fatty acid and avoid the oxidation of fatty acid; Step S2-3. Adjusting pH: Lower the internal temperature of the organic bismuth synthesis reactor to 15-20°C, add a certain amount of process water for cleaning, and use ammonia water to adjust the pH of the water layer to 7-8; Step S2-4. Stirring and stratifying: Stop stirring, let stand for a period of time to stratify, and send the stratified water layer to sewage treatment; Step S2-5. Dehydration and drainage: Open the vacuum dehydration device, control the temperature of the organic bismuth synthesis reactor to not exceed 85 ° C, vacuum -0.095Mpa, remove moisture from the material layer, obtain a dehydrated material layer, and send the dehydrated water to sewage treatment; It should be noted that after dehydration, a molecular distillation step is added to separate low-boiling impurities and increase the purity of the organic bismuth salt to ≥98%; Step S2-6 cooling treatment: lowering the temperature in the organic bismuth synthesis reactor, specifically cooling to 20-25 ° C, to obtain a finished organic bismuth salt; It should be noted that the high temperature reaction formula of bismuth oxide and fatty acid is as follows:

[0024] (1) Bismuth soap ( ) is a composite salt of metallic bismuth and fatty acid, which has lubricating or catalytic properties.

[0025] (2) Before the reaction, the fatty acid needs to be molten (high temperature > 200°C) to overcome the interfacial resistance; Step 3. Decomposition and precipitation of bismuth salt: The organic bismuth salt is subjected to acid hydrolysis by a strong acid. After the acid hydrolysis is completed, the acid hydrolysis solution is filtered by a filtration technique, the filtered acid hydrolysis solution is neutralized to obtain a precipitate, and then the precipitate is separated by a separation technique; It should be noted that the specific steps of decomposition of bismuth salt are as follows: Step S3-1. Raw material pretreatment: add organic bismuth salt and 3-5 mol / L nitric acid into a reactor, start the stirrer on the reactor to mix, and add activated carbon to adsorb heavy metal impurities during the mixing process, and the pre-reaction temperature of the reactor is 40-50°C during the reaction; Step S3-2. Pressurized acid hydrolysis: The reaction material is transferred into an acid-resistant high-pressure reactor and rapidly heated to 60-80°C. During the heating process, oxygen is introduced at an oxygen flow rate of 10-20 L / h. The temperature is raised to react within 1-2 hours. After the reaction is completed, an acid hydrolysis solution is obtained. The precipitation steps are as follows: S4-1. Gradient pH control: 10% ammonia water was added dropwise to the acid hydrolyzate. In the first stage, the pH was controlled at 3-4 and the stirring rate was 300 rpm to pre-precipitate impurities. In the second stage, ammonia water was gradually added to adjust the acid hydrolyzate to pH 8-9 and the stirring rate was 50 rpm to generate nano-scale colloids. S4-2. Addition of dispersant: Add polyvinyl pyrrolidone to the neutralized acid hydrolyzate to inhibit the agglomeration of particles in the acid hydrolyzate.

[0026] It should be noted that the bismuth hydrochloride acid solution process is as follows: Bismuth soap (as stearic acid): (R is a long chain alkyl group, such as ); Nitric acid (dilute or concentrated): participates in double decomposition reactions as a strong acid; Product: Bismuth nitrate ( ) and the corresponding carboxylic acids (such as stearic acid ).

[0027]

[0028] The precipitation reaction formula is as follows:

[0029] Step 4. Purification and drying: washing the obtained precipitate using washing technology, and after washing, drying the precipitate; It should be noted that the specific methods of purification and drying are as follows: S5-1. Countercurrent washing: Ultrapure water with a conductivity of ≤5μS / cm is used to remove impurities through a three-stage countercurrent washing tower (solid-liquid ratio 1:5). The conductivity of the filter cake after washing is ≤50μS / cm; S5-2. Low-temperature vacuum drying: Place the filter cake obtained by washing into a vacuum drying device, start the vacuum device, and dry it at 80-90°C and vacuum degree -0.08MPa for 2-3 hours to obtain a white powder.

[0030] Step 5. Waste recovery: The strong acid and alkaline substances in step 3 are recovered through recycling technology. The specific waste recovery method is as follows: Step S6-1. Acid recovery: distill the acid hydrolysis waste liquid to recover nitric acid; Step S6-2. Ammonia regeneration: Use ion exchange resin to exchange the neutralized wastewater, remove the neutralized wastewater, and obtain ammonia water.

[0031] Experimental data and effect verification

[0032] ‌Conclusion‌: The microporous structure significantly improves the specific surface area and reaction activity of bismuth oxide, increases the ester exchange reaction rate to 2.8 times that of the traditional method, and shortens the synthesis time of organic bismuth salts.

[0033]

[0034] Test conditions: (1) Bimetallic catalysts: (loading amount 5wt%); (2) Ultrasonic frequency: 40kHz, power 300W; (3) Detection method: HPLC (organic phase analysis).

[0035] ‌Conclusion‌: The synergistic effect of bimetallic catalyst and ultrasound assistance shortened the reaction time to within 1.5 hours, increased the purity to ≥98.5%, and increased the fatty acid utilization rate to more than 95%.

[0036]

[0037] Experimental parameters: (1) Oxygen flow rate: 15L / h; (2) Acid hydrolysis time: 1.5h; (3) Detection methods: ICP-OES (bismuth ion concentration), atomic absorption spectroscopy (heavy metals).

[0038] ‌Conclusion‌: Oxygen oxidation promotes the decomposition of organic bismuth salts, the bismuth ion release rate is increased to ≥95%, and the heavy metal residues are reduced to below 5 ppm after activated carbon adsorption.

[0039]

[0040] Characterization methods: (1) SEM (morphology analysis); (2) Laser particle size analyzer (particle size distribution); (3) XRF (element purity).

[0041] ‌Conclusion‌: Gradient pH control combined with dispersant (PVP) can obtain nanoscale (80-120nm) uniform particles with a purity of 99.2%.

[0042]

[0043] Process Description: (1) Nitric acid recovery: vacuum distillation (boiling point 86°C, vacuum degree -0.09MPa); (2) Ammonia water regeneration: D113 weak acid ion exchange resin treatment.

[0044] ‌Conclusion‌: The recycling rate of waste liquid is ≥85%, which reduces the raw material cost by more than 30%, and the recycling does not affect the product performance.

[0045]

[0046] Testing basis: (1) Energy consumption calculation: covering the entire process of synthesis, acid hydrolysis and drying; (2) Environmental protection data: evaluated according to the “Identification Standards for Hazardous Wastes” (GB5085.3).

[0047] ‌Conclusion‌: The present invention is superior to the traditional process in terms of purity, resource utilization and environmental protection, and is suitable for the production of electronic-grade bismuth hydroxide (99.5%+).

[0048] Embodiment 1 A green and efficient method for preparing bismuth hydroxide comprises the following steps: Step 1. Prepare materials: prepare the materials required for the preparation of bismuth hydroxide, which include bismuth oxide, fatty acid, strong acid, alkaline substance, and catalyst; It should be noted that the bismuth oxide is ordinary bismuth oxide, the fatty acid is saturated fatty acid, the strong acid is nitric acid, the alkaline substance is ammonia water, and the catalyst is activated carbon, oxygen, and polyvinyl pyrrolidone.

[0049] Step 2. Preparation of bismuth salt: preparing organic bismuth salt by reacting bismuth oxide and fatty acid at a high temperature of 70-90°C, and purifying the organic salt; Step 3. Decomposition and precipitation of bismuth salt: The organic bismuth salt is hydrolyzed by strong acid. After the acid hydrolysis is completed, the acid hydrolysis solution is filtered by filtering technology, the filtered acid hydrolysis solution is neutralized to obtain the precipitate, and then the precipitate is separated by separation technology.

[0050] Step 4. Purification and drying: Use washing technology to wash the obtained precipitate. After washing, dry the precipitate.

[0051] Step 5. Waste recovery: Recover the strong acid and alkaline substances in step 3 through recycling technology.

[0052] It should be noted that the comparison of the synthesis efficiency of organic bismuth salts is as follows:

[0053] Embodiment 2 A green and efficient method for preparing bismuth hydroxide comprises the following steps: Step 1. Prepare materials: prepare the materials required for the preparation of bismuth hydroxide, which include bismuth oxide, fatty acid, strong acid, alkaline substance, and catalyst; It should be noted that the bismuth oxide is microporous bismuth oxide, and the preparation technology is as follows: Step S1-1. Template introduction: The bismuth oxide powder and the mesoporous template are fed into a ball mill, and the ball mill is started to mix and grind the bismuth oxide powder and the mesoporous template, and the pores of the template are used to guide the dispersion of the bismuth oxide particles to form a composite structure; Step S1-2. Template removal: adding hydrofluoric acid to the obtained composite structure, dissolving the template by acid washing, and retaining the microporous framework of bismuth oxide; Step S1-3. Washing and drying: washing the retained bismuth oxide with ultrapure water to obtain pure bismuth oxide, and drying the obtained bismuth oxide to obtain a bismuth oxide powder with a microporous structure; The fatty acid selected is saturated fatty acid, the strong acid selected is nitric acid, the alkaline substance selected is ammonia water, and the catalyst selected is activated carbon, oxygen, and polyvinyl pyrrolidone.

[0054] Step 2. Preparation of bismuth salt: preparing organic bismuth salt by reacting bismuth oxide and fatty acid at a high temperature of 70-90°C, and purifying the organic salt; It should be noted that the preparation method of the organic bismuth salt is as follows: Step S2-1. Material preparation: Add a certain amount of bismuth oxide and fatty acid to the organic bismuth synthesis reactor and start stirring; Step S2-2. Heating and heat preservation: Raise the temperature inside the organic bismuth synthesis reactor to 85° C. and keep the temperature for 1-3 hours.

[0055] Step 3. Decomposition and precipitation of bismuth salt: The organic bismuth salt is subjected to acid hydrolysis by a strong acid. After the acid hydrolysis is completed, the acid hydrolysis solution is filtered by a filtration technique, the filtered acid hydrolysis solution is neutralized to obtain a precipitate, and then the precipitate is separated by a separation technique; It should be noted that the specific steps of decomposition of bismuth salt are as follows: Step S3-1. Raw material pretreatment: add organic bismuth salt and 3-5 mol / L nitric acid into a reactor, start the stirrer on the reactor to mix, and add activated carbon to adsorb heavy metal impurities during the mixing process, and the pre-reaction temperature of the reactor is 40-50°C during the reaction; Step S3-2. Pressurized acid hydrolysis: The reaction material is transferred into an acid-resistant high-pressure reactor and rapidly heated to 60-80°C. During the heating process, oxygen is introduced at an oxygen flow rate of 10-20 L / h. The temperature is raised to react within 1-2 hours. After the reaction is completed, an acid hydrolysis solution is obtained. The precipitation steps are as follows: S4-1. Gradient pH control: 10% ammonia water was added dropwise to the acid hydrolyzate. In the first stage, the pH was controlled at 3-4 and the stirring rate was 300 rpm to pre-precipitate impurities. In the second stage, ammonia water was gradually added to adjust the acid hydrolyzate to pH 8-9 and the stirring rate was 50 rpm to generate nano-scale colloids. S4-2. Addition of dispersant: Add polyvinyl pyrrolidone to the neutralized acid hydrolyzate to inhibit the agglomeration of particles in the acid hydrolyzate.

[0056] Step 4. Purification and drying: Use washing technology to wash the obtained precipitate. After washing, dry the precipitate.

[0057] S5-1. Countercurrent washing: Ultrapure water with a conductivity of ≤5μS / cm is used to remove impurities through a three-stage countercurrent washing tower (solid-liquid ratio 1:5). The conductivity of the filter cake after washing is ≤50μS / cm; S5-2. Low-temperature vacuum drying: Place the filter cake obtained by washing into a vacuum drying device, start the vacuum device, and dry it at 80-90°C and vacuum degree -0.08MPa for 2-3 hours to obtain a white powder.

[0058] Step 5. Waste recovery: Recover the strong acid and alkaline substances in step 3 through recycling technology.

[0059] It should be noted that the verification of bismuth ion release rate is as follows:

[0060] Embodiment 3 A green and efficient method for preparing bismuth hydroxide comprises the following steps: Step 1. Prepare materials: prepare the materials required for the preparation of bismuth hydroxide, which include bismuth oxide, fatty acid, strong acid, alkaline substance, and catalyst; It should be noted that the bismuth oxide is microporous bismuth oxide, and the preparation technology is as follows: Step S1-1. Template introduction: The bismuth oxide powder and the mesoporous template are fed into a ball mill, and the ball mill is started to mix and grind the bismuth oxide powder and the mesoporous template, and the pores of the template are used to guide the dispersion of the bismuth oxide particles to form a composite structure; Step S1-2. Template removal: adding hydrofluoric acid to the obtained composite structure, dissolving the template by acid washing, and retaining the microporous framework of bismuth oxide; Step S1-3. Washing and drying: washing the retained bismuth oxide with ultrapure water to obtain pure bismuth oxide, and drying the obtained bismuth oxide to obtain a bismuth oxide powder with a microporous structure; The fatty acid selected is saturated fatty acid, the strong acid selected is nitric acid, the alkaline substance selected is ammonia water, and the catalyst selected is activated carbon, oxygen, and polyvinyl pyrrolidone.

[0061] Step 2. Preparation of bismuth salt: preparing organic bismuth salt by reacting bismuth oxide and fatty acid at a high temperature of 70-90°C, and purifying the organic salt; It should be noted that the preparation method of the organic bismuth salt is as follows: Step S2-1. Material preparation: Add a certain amount of bismuth oxide and fatty acid to the organic bismuth synthesis reactor and start stirring; Step S2-2. Heating and insulation: raising the temperature inside the organic bismuth synthesis reactor, the temperature is specifically: 85 ° C, and the reaction is kept warm for 1-3 hours; It should be noted that in step S2-2, the following method is specifically used to accelerate the reaction speed, and the specific method is as follows: (1) Introducing a bimetallic catalyst into the organic bismuth synthesis reactor to reduce the reaction activation energy, shorten the reaction time to within 1 hour, and reduce the generation of by-products; (2) Ultrasonic-assisted dispersion technology was used to enhance the interfacial contact between bismuth oxide and fatty acids and increase the rate of transesterification reaction; The heating steps are as follows: (1) In the early stage, the temperature inside the organic bismuth synthesis reactor is raised to 60-70°C, and low temperature is used to promote mass transfer; (2) In the later stage, the temperature in the organic bismuth synthesis reactor is raised to 85-90°C to accelerate the reaction of bismuth oxidation and fatty acid and avoid the oxidation of fatty acid; Step S2-3. Adjusting pH: Lower the internal temperature of the organic bismuth synthesis reactor to 15-20°C, add a certain amount of process water for cleaning, and use ammonia water to adjust the pH of the water layer to 7-8; Step S2-4. Stirring and stratifying: Stop stirring, let stand for a period of time to stratify, and send the stratified water layer to sewage treatment; Step S2-5. Dehydration and drainage: Open the vacuum dehydration device, control the temperature of the organic bismuth synthesis reactor to not exceed 85 ° C, vacuum -0.095Mpa, remove moisture from the material layer, obtain a dehydrated material layer, and send the dehydrated water to sewage treatment; It should be noted that after dehydration, a molecular distillation step is added to separate low-boiling impurities and increase the purity of the organic bismuth salt to ≥98%; Step S2-6 cooling treatment: lowering the temperature in the organic bismuth synthesis reactor, specifically cooling to 20-25 ° C, to obtain a finished organic bismuth salt; Step 3. Decomposition and precipitation of bismuth salt: The organic bismuth salt is subjected to acid hydrolysis by a strong acid. After the acid hydrolysis is completed, the acid hydrolysis solution is filtered by a filtration technique, the filtered acid hydrolysis solution is neutralized to obtain a precipitate, and then the precipitate is separated by a separation technique; It should be noted that the specific steps of decomposition of bismuth salt are as follows: Step S3-1. Raw material pretreatment: add organic bismuth salt and 3-5 mol / L nitric acid into a reactor, start the stirrer on the reactor to mix, and add activated carbon to adsorb heavy metal impurities during the mixing process, and the pre-reaction temperature of the reactor is 40-50°C during the reaction; Step S3-2. Pressurized acid hydrolysis: The reaction material is transferred into an acid-resistant high-pressure reactor and rapidly heated to 60-80°C. During the heating process, oxygen is introduced at an oxygen flow rate of 10-20 L / h. The temperature is raised to react within 1-2 hours. After the reaction is completed, an acid hydrolysis solution is obtained. The precipitation steps are as follows: S4-1. Gradient pH control: 10% ammonia water was added dropwise to the acid hydrolyzate. In the first stage, the pH was controlled at 3-4 and the stirring rate was 300 rpm to pre-precipitate impurities. In the second stage, ammonia water was gradually added to adjust the acid hydrolyzate to pH 8-9 and the stirring rate was 50 rpm to generate nano-scale colloids. S4-2. Addition of dispersant: Add polyvinyl pyrrolidone to the neutralized acid hydrolyzate to inhibit the agglomeration of particles in the acid hydrolyzate.

[0062] Step 4. Purification and drying: washing the obtained precipitate using washing technology, and after washing, drying the precipitate; It should be noted that the specific methods of purification and drying are as follows: S5-1. Countercurrent washing: Ultrapure water with a conductivity of ≤5μS / cm is used to remove impurities through a three-stage countercurrent washing tower (solid-liquid ratio 1:5). The conductivity of the filter cake after washing is ≤50μS / cm; S5-2. Low-temperature vacuum drying: Place the filter cake obtained by washing into a vacuum drying device, start the vacuum device, and dry it at 80-90°C and vacuum degree -0.08MPa for 2-3 hours to obtain a white powder.

[0063] Step 5. Waste recovery: The strong acid and alkaline substances in step 3 are recovered through recycling technology. The specific waste recovery method is as follows: Step S6-1. Acid recovery: distilling the acid hydrolysis waste liquid to recover nitric acid; Step S6-2. Ammonia regeneration: Use ion exchange resin to exchange the neutralized wastewater, remove the neutralized wastewater, and obtain ammonia water.

[0064] It should be noted that the economic data of waste liquid recycling are as follows:

[0065] It can be seen from Example 1, Example 2 and Example 3 that the bismuth oxide structures selected in Example 1 and Example 3 are different, and the preparation methods of the organic bismuth salts in Example 2 and Example 3 are different. The following chart can be obtained for the preparation quality and speed of bismuth hydroxide:

[0066] It can be seen from the above table that embodiment 3 is the best embodiment.

[0067] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A green and efficient method for preparing bismuth hydroxide, characterized in that: The following steps are involved: Step 1. Prepare materials: prepare the materials required for the preparation of bismuth hydroxide, which include bismuth oxide, fatty acid, strong acid, alkaline substance, and catalyst; Step 2. Preparation of bismuth salt: preparing organic bismuth salt by reacting bismuth oxide and fatty acid at a high temperature of 70-90°C, and purifying the organic salt; Step 3. Decomposition and precipitation of bismuth salt: The organic bismuth salt is subjected to acid hydrolysis by a strong acid. After the acid hydrolysis is completed, the acid hydrolysis solution is filtered by a filtration technique, the filtered acid hydrolysis solution is neutralized to obtain a precipitate, and then the precipitate is separated by a separation technique; Step 4. Purification and drying: washing the obtained precipitate using washing technology, and after washing, drying the precipitate; Step 5. Waste recovery: Recover the strong acid and alkaline substances in step 3 through recycling technology.

2. A green and efficient method for preparing bismuth hydroxide according to claim 1, characterized in that: In the step 1, the fatty acid is saturated fatty acid, the strong acid is nitric acid, the alkaline substance is ammonia water, and the catalyst is activated carbon, oxygen, and polyvinyl pyrrolidone. In the step 1, the bismuth oxide is microporous bismuth oxide, and the preparation technology is as follows: Step S1-1. Template introduction: The bismuth oxide powder and the mesoporous template are fed into a ball mill, and the ball mill is started to mix and grind the bismuth oxide powder and the mesoporous template, and the pores of the template are used to guide the dispersion of the bismuth oxide particles to form a composite structure; Step S1-2. Template removal: adding hydrofluoric acid to the obtained composite structure, dissolving the template by acid washing, and retaining the microporous framework of bismuth oxide; Step S1-3. Washing and drying: Wash the retained bismuth oxide with ultrapure water to obtain pure bismuth oxide, and dry the obtained bismuth oxide to obtain bismuth oxide powder with a microporous structure.

3. A green and efficient method for preparing bismuth hydroxide according to claim 1, characterized in that: In the step 2, the preparation method of the organic bismuth salt is as follows: Step S2-1. Material preparation: Add a certain amount of bismuth oxide and fatty acid to the organic bismuth synthesis reactor and start stirring; Step S2-2. Heating and insulation: raising the temperature inside the organic bismuth synthesis reactor, the temperature is specifically: 80-90 ° C, and the reaction is kept warm for 1-3 hours; Step S2-3. Adjusting pH: Lower the internal temperature of the organic bismuth synthesis reactor to 15-20°C, add a certain amount of process water for cleaning, and use ammonia water to adjust the pH of the water layer to 7-8; Step S2-4. Stirring and stratifying: Stop stirring, let stand for a period of time to stratify, and send the stratified water layer to sewage treatment; Step S2-5. Dehydration and drainage: Open the vacuum dehydration device, control the temperature of the organic bismuth synthesis reactor to not exceed 85 ° C, vacuum -0.095Mpa, remove moisture from the material layer, obtain a dehydrated material layer, and send the dehydrated water to sewage treatment; Step S2-6. Cooling treatment: lowering the temperature in the organic bismuth synthesis reactor, specifically to 20-25° C., to obtain a finished organic bismuth salt.

4. A green and efficient method for preparing bismuth hydroxide according to claim 3, characterized in that: In step S2-2 of the method for preparing the organic bismuth salt, the following method is specifically used to accelerate the reaction speed, and the specific method is as follows: (1) Introducing a bimetallic catalyst into the organic bismuth synthesis reactor to reduce the reaction activation energy, shorten the reaction time to within 1 hour, and reduce the generation of by-products; (2) Ultrasonic-assisted dispersion technology was used to enhance the interfacial contact between bismuth oxide and fatty acids and increase the rate of ester exchange reactions.

5. A green and efficient method for preparing bismuth hydroxide according to claim 3, characterized in that: In step S2-2 of the method for preparing the organic bismuth salt, the heating step is as follows: (1) In the early stage, the temperature inside the organic bismuth synthesis reactor is raised to 60-70°C, and low temperature is used to promote mass transfer; (2) In the later stage, the temperature in the organic bismuth synthesis reactor is raised to 85-90°C to accelerate the reaction of bismuth oxidation and fatty acid and avoid the oxidation of fatty acids.

6. A green and efficient method for preparing bismuth hydroxide according to claim 3, characterized in that: In step S2-5 of the method for preparing the organic bismuth salt, a molecular distillation step is added after dehydration to separate low-boiling impurities and increase the purity of the organic bismuth salt to ≥98%.

7. A green and efficient method for preparing bismuth hydroxide according to claim 1, characterized in that: In step 3, the specific steps of decomposing the bismuth salt are as follows: Step S3-1. Raw material pretreatment: add organic bismuth salt and 3-5 mol / L nitric acid into a reactor, start the stirrer on the reactor to mix, and add activated carbon to adsorb heavy metal impurities during the mixing process, and the pre-reaction temperature of the reactor is 40-50°C during the reaction; Step S3-2. Pressurized acid hydrolysis: The material obtained by the reaction is transferred into an acid-resistant high-pressure reactor and rapidly heated to 60-80°C. During the heating process, oxygen is introduced at an oxygen flow rate of 10-20 L / h. The heating reaction is carried out within 1-2 hours. After the reaction is completed, an acid hydrolysis solution is obtained.

8. A green and efficient method for preparing bismuth hydroxide according to claim 7, characterized in that: In the step 3, the precipitation step is as follows: S4-1. Gradient pH control: 10% ammonia water was added dropwise to the acid hydrolyzate. In the first stage, the pH was controlled at 3-4 and the stirring rate was 300 rpm to pre-precipitate impurities. In the second stage, ammonia water was gradually added to adjust the acid hydrolyzate to pH 8-9 and the stirring rate was 50 rpm to generate nano-scale colloid; S4-2. Addition of dispersant: Add polyvinyl pyrrolidone to the neutralized acid hydrolyzate to inhibit the agglomeration of particles in the acid hydrolyzate.

9. A green and efficient method for preparing bismuth hydroxide according to claim 1, characterized in that: In step 4, the specific method of purification and drying is as follows: S5-1. Countercurrent washing: Ultrapure water with a conductivity of ≤5μS / cm is used to remove Impurities, the conductivity of the filter cake after washing is ≤50μS / cm; S5-2. Low-temperature vacuum drying: Put the washed filter cake into a vacuum drying device, start the vacuum device, and dry it at 80-90℃ and vacuum degree -0.08MPa for 2-3 hours to obtain a white powder.

10. A green and efficient method for preparing bismuth hydroxide according to claim 1, characterized in that: In the step 5, the waste recycling method is specifically as follows: Step S6-1. Acid recovery: distill the acid hydrolysis waste liquid to recover nitric acid; Step S6-2. Ammonia regeneration: Use ion exchange resin to exchange the neutralized wastewater to remove , and obtain ammonia water.

Images