Preparation method of silver powder capable of being continuously synthesized

Abstract

The invention belongs to the technical field of silver powder preparation, and particularly relates to a silver powder preparation method capable of being continuously synthesized, which comprises the following steps: (1) preparing a silver nitrate solution, a surface treatment solution and an ascorbic acid solution; (2) deionized water, a surface treatment solution and an ascorbic acid solution are used as base solutions, then the silver nitrate solution and the ascorbic acid solution are added according to a certain proportion for a reaction, and in the reaction process, the pH value of the reaction solution is adjusted by using a pH regulator to be kept at 4-6; (3) when the total volume of the liquid in the reaction kettle in the step (2) accounts for 80% of the volume of the reaction kettle, stopping feeding, stopping stirring, discharging from the bottom after sedimentation, discharging until the residual liquid in the reaction kettle accounts for 30-40% of the volume of the reaction kettle, and restarting stirring for feeding after discharging is completed; and (4) the materials discharged from the bottom are subjected to centrifugal separation, washing and drying, and then the silver powder is obtained. The method has the beneficial effects that the silver powder output speed is stable, so that the surface of the silver powder is smooth, and the dispersity is good.

Description

Technical Field

[0001] The invention belongs to the technical field of silver powder preparation, and in particular relates to a method for preparing silver powder that can be continuously synthesized. Background Art

[0002] Silver has excellent electrical conductivity, thermal conductivity and anti-oxidation properties. When using solar energy to generate electricity, photovoltaic silver powder is an important material for the manufacture of solar cells. Silver powder is mainly used to make the conductive grid of the battery. These conductive grids are similar to the skeleton of the battery, converting the light energy collected on the solar panel into electrical energy and outputting it. Silver powder is an ideal choice for making conductive solar cell grids due to its excellent electrical conductivity and chemical stability.

[0003] Patent CN115055673A discloses a method for preparing silver powder, in which a pH regulator is added to an ascorbic acid solution to adjust the pH. However, as the silver powder is generated, the pH value in the reaction solution gradually increases, resulting in reduced stability of the output silver powder. At the same time, the preparation method can only produce silver powder in batches, and cannot produce continuously in multiple batches, resulting in low production efficiency, and the waste liquid cannot be reused, increasing production costs. Therefore, a method for preparing silver powder that can produce continuously in multiple batches, has a stable pH value of the reaction liquid during preparation, and can reuse the waste liquid is particularly important. Summary of the invention

[0004] The purpose of the present invention is to solve the above problems and provide a method for preparing silver powder which can be synthesized continuously.

[0005] The present invention relates to a method for preparing silver powder which can be continuously synthesized, comprising the following steps: (1) dissolving silver nitrate in deionized water to obtain a silver nitrate solution; dissolving a surface treatment agent in a solvent to obtain a surface treatment solution; dissolving ascorbic acid in deionized water and adding the surface treatment solution to obtain an ascorbic acid solution; (2) adding deionized water, surface treatment solution and ascorbic acid solution as base solution into the reactor, starting stirring, and then adding silver nitrate solution and ascorbic acid solution into the reactor in a certain proportion, controlling the temperature of the reactor at 10-15° C. for reaction, and using a pH adjuster to adjust the pH value of the reaction solution to maintain at 4-6 during the reaction; (3) When the total volume of the liquid in the reactor in step (2) accounts for 80% of the volume of the reactor, stop feeding and turn off stirring, and discharge the material from the bottom of the reactor after settling for 5 minutes until the remaining liquid in the reactor accounts for 30-40% of the volume of the reactor; use the remaining liquid as the bottom liquid for the next batch of reactions, restart stirring, and add the silver nitrate solution and ascorbic acid solution to the reactor in a certain proportion to carry out the next batch of reactions; (4) The material discharged from the bottom is centrifuged, washed and dried to obtain silver powder.

[0006] Preferably, in the silver nitrate solution, the concentration of silver nitrate is 4 to 6.5 mol / L.

[0007] Preferably, in the ascorbic acid solution, the concentration of ascorbic acid is 1 to 1.5 mol / L.

[0008] Preferably, in the ascorbic acid solution, the amount of the surface treatment solution added is 5-10% of the weight of silver in the silver nitrate solution.

[0009] Preferably, in the surface treatment liquid, the concentration of the surface treatment agent is 0.1 g / ml.

[0010] Preferably, in the surface treatment liquid, the surface treatment agent is selected from at least one of lauric acid, stearic acid and oleic acid; and the solvent is selected from at least one of methanol, ethanol, ethylene glycol, propanol and propylene glycol.

[0011] Preferably, the pH regulator is selected from at least one of ammonia water, ammonium bicarbonate and sodium hydroxide.

[0012] Preferably, in the reaction base liquid, the volume of deionized water is 20-30% of the volume of the reactor, the volume of the surface treatment liquid is 5-10% of the volume of the reactor, and the volume of the ascorbic acid solution is 2-3% of the volume of the reactor.

[0013] Preferably, the volume of the silver nitrate solution added to the reactor per hour is 0.3 to 0.5 times the volume of the reactor, and the volume of the ascorbic acid solution added to the reactor per hour is 0.4 to 0.6 times the volume of the reactor.

[0014] Preferably, the stirring speed of the reactor is 140-170 r / min.

[0015] Compared with the prior art, the advantages and positive effects of the present invention are: Compared with the prior art, the method for preparing silver powder that can be continuously synthesized by the present invention can (1) The pH adjuster is not added to the ascorbic acid solution, but is added at any time during the reaction to stabilize the pH value, thereby avoiding the problem of pH value changing from low to high during the reaction, thereby stabilizing the rate of silver powder production, making the prepared silver powder smooth and well dispersed; (2) The surface treatment agent is added during the preparation of the silver powder, rather than after the preparation of the silver powder is completed, so that the remaining liquid after sedimentation can be used for the preparation of the next batch of silver powder without causing agglomeration of the silver powder; (3) The remaining liquid after sedimentation is used to prepare the next batch of silver powder, saving raw material costs and reducing waste liquid discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the following briefly introduces the drawings required for describing the embodiment. Figure 1 This is a scanning electron microscope image of the silver powder 1 provided in Example 1; Figure 2 This is a scanning electron microscope image of the silver powder 2 provided in Example 1; Figure 3 This is a scanning electron microscope image of the silver powder 3 provided in Example 2; Figure 4 This is a scanning electron microscope image of the silver powder 4 provided in Example 2; Figure 5 This is a scanning electron microscope image of the silver powder 5 provided in Comparative Example 1; Figure 6 This is a scanning electron microscope image of the silver powder 6 provided in Comparative Example 1. DETAILED DESCRIPTION

[0017] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described below with reference to the accompanying drawings and embodiments.

[0018] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments of the following disclosure.

[0019] Example 1 A method for preparing silver powder that can be continuously synthesized comprises the following steps: (1) Silver nitrate solution: Dissolve 6600 g of silver nitrate in 5400 g of deionized water to prepare a silver nitrate solution with a molar concentration of 5.7 mol / L.

[0020] Surface treatment liquid: Disperse 240 g of oleic acid in 2160 ml of ethanol to prepare a surface treatment liquid with a mass concentration of 0.1 g / ml.

[0021] Ascorbic acid solution: 3.6 kg of ascorbic acid was dissolved in 12 kg of deionized water and stirred to dissolve, and then 200 g of surface treatment solution was added to prepare an ascorbic acid solution. The weight of ascorbic acid in the ascorbic acid solution was 0.53 times the weight of silver nitrate in the silver nitrate solution, wherein the molar concentration of ascorbic acid was 1.31 mol / L, and the amount of surface treatment solution added was 5% of the weight of silver in the silver nitrate solution.

[0022] (2) 7600 g of deionized water, 2200 g of surface treatment solution and 800 g of ascorbic acid solution were added to a 30 L glass kettle as the base solution. The feed rate of the silver nitrate solution was set to 12 kg / h, the feed rate of the ascorbic acid solution was set to 15.5 kg / h, and the stirring speed of the reactor was set to 150 r / min. Then, the silver nitrate solution and the ascorbic acid solution were added to the reactor at the same time. The temperature of the reactor was controlled at 10°C. During the reaction, ammonium bicarbonate was used to adjust the pH value of the reaction solution to 5.

[0023] (3) When the total volume of liquid in the reactor reaches 24 L, stop feeding and turn off stirring. After settling for 5 minutes, discharge the material from the bottom of the reactor. When 10 L of liquid remains in the reactor, stop discharging the material. Use the remaining liquid as the bottom liquid for the next batch of reactions. Restart stirring and add the silver nitrate solution and ascorbic acid solution to the reactor again to carry out the next batch of reactions.

[0024] (4) When the total volume of liquid in the reactor reaches 24 L again, stop feeding and turn off stirring. After settling for 5 min, discharge the liquid from the bottom of the reactor for the second time. When 10 L of liquid remains in the reactor, stop discharging the liquid again.

[0025] (5) The material released for the first time in step (3) is centrifuged, washed and dried to obtain silver powder 1.

[0026] The material discharged for the second time in step (4) is centrifuged, washed and dried to obtain silver powder 2.

[0027] Example 2 The difference between this embodiment and embodiment 1 is that: (1) Surface treatment solution: Disperse 340 g of oleic acid in 3060 ml of ethanol to prepare a surface treatment solution with a mass concentration of 0.1 g / ml.

[0028] Ascorbic acid solution: Dissolve 3.6 kg of ascorbic acid in 12 kg of deionized water and stir to dissolve, then add 400 g of surface treatment solution to prepare ascorbic acid solution. The amount of surface treatment solution added to the ascorbic acid solution is 10% of the weight of silver in the silver nitrate solution.

[0029] (2) Add 7600 g of deionized water, 3000 g of surface treatment solution and 800 g of ascorbic acid solution into a 30 L glass kettle as a bottom solution.

[0030] (5) The material released for the first time in step (3) is centrifuged, washed and dried to obtain silver powder 3.

[0031] The material discharged for the second time in step (4) is centrifuged, washed and dried to obtain silver powder 4.

[0032] Comparative Example 1 The difference between this embodiment and embodiment 1 is that: (3) During the reaction, ammonium bicarbonate was used to adjust the pH value of the reaction solution to 7.

[0033] (5) The material released for the first time in step (3) is centrifuged, washed and dried to obtain silver powder 5.

[0034] The material discharged for the second time in step (4) is centrifuged, washed and dried to obtain silver powder 6.

[0035] Performance Testing The silver powders 1-6 prepared in the above-mentioned Examples 1 and 2 and Comparative Example 1 were observed by scanning electron microscope. Figure 1-Figure 6 ; The particle size, specific surface area, tap density and ignition loss of silver powders 1-6 were tested, and the results are shown in Table 1.

[0036] Table 1 from Figure 1-Figure 6 Compared with Table 1, the silver powders 1-4 prepared in Examples 1 and 2 have high surface smoothness and good powder dispersibility, while the silver powders 5 and 6 prepared in Comparative Example 1 have rough surfaces and the powders agglomerate, indicating that adjusting the pH value of the reaction solution during the reaction can effectively prevent the pH value from gradually increasing during the reaction, stabilize the synthesis rate of the silver powder, prevent the silver powder from agglomerating, and improve the dispersibility of the silver powder. Compared with Example 2, the particle size of the silver powders 1 and 2 in Example 1 is larger than that of the silver powders 3 and 4, indicating that adjusting the amount of the surface treatment solution added to the base solution and the ascorbic acid solution can adjust the particle size of the silver powder.

[0037] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes for application in other fields. However, any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing silver powder that can be continuously synthesized, characterized in that: The following steps are involved: (1) dissolving silver nitrate in deionized water to obtain a silver nitrate solution; dissolving a surface treatment agent in a solvent to obtain a surface treatment solution; dissolving ascorbic acid in deionized water and adding the surface treatment solution to obtain an ascorbic acid solution; (2) adding deionized water, surface treatment solution and ascorbic acid solution as base solution into the reactor, starting stirring, and then adding silver nitrate solution and ascorbic acid solution into the reactor in a certain proportion, controlling the temperature of the reactor at 10-15° C. for reaction, and using a pH adjuster to adjust the pH value of the reaction solution to maintain at 4-6 during the reaction; (3) When the total volume of the liquid in the reactor in step (2) accounts for 80% of the volume of the reactor, stop feeding and turn off stirring, and discharge the material from the bottom of the reactor after settling for 5 minutes until the remaining liquid in the reactor accounts for 30-40% of the volume of the reactor; use the remaining liquid as the bottom liquid for the next batch of reactions, restart stirring, and add the silver nitrate solution and ascorbic acid solution to the reactor in a certain proportion to carry out the next batch of reactions; (4) The material discharged from the bottom is centrifuged, washed and dried to obtain silver powder.

2. The method for preparing silver powder that can be continuously synthesized according to claim 1, characterized in that: In the silver nitrate solution, the concentration of silver nitrate is 4-6.5 mol / L.

3. The method for preparing silver powder capable of continuous synthesis according to claim 2, characterized in that: In the ascorbic acid solution, the concentration of ascorbic acid is 1-1.5 mol / L.

4. The method for preparing silver powder capable of continuous synthesis according to claim 3, characterized in that: In the ascorbic acid solution, the amount of the surface treatment solution added is 5-10% of the weight of silver in the silver nitrate solution.

5. The method for preparing silver powder capable of continuous synthesis according to claim 4, characterized in that: In the surface treatment liquid, the concentration of the surface treatment agent is 0.1 g / ml.

6. The method for preparing silver powder capable of continuous synthesis according to claim 5, characterized in that: In the surface treatment liquid, the surface treatment agent is selected from at least one of lauric acid, stearic acid and oleic acid; and the solvent is selected from at least one of methanol, ethanol, ethylene glycol, propanol and propylene glycol.

7. The method for preparing silver powder capable of continuous synthesis according to claim 6, characterized in that: The pH regulator is selected from at least one of ammonia water, ammonium bicarbonate and sodium hydroxide.

8. The method for preparing silver powder capable of continuous synthesis according to claim 7, characterized in that: In the reaction base liquid, the volume of deionized water is 20-30% of the volume of the reactor, the volume of the surface treatment liquid is 5-10% of the volume of the reactor, and the volume of the ascorbic acid solution is 2-3% of the volume of the reactor.

9. The method for preparing silver powder capable of continuous synthesis according to claim 8, characterized in that: The volume of the silver nitrate solution added to the reactor per hour is 0.3 to 0.5 times the volume of the reactor, and the volume of the ascorbic acid solution added to the reactor per hour is 0.4 to 0.6 times the volume of the reactor.

10. The method for preparing silver powder capable of continuous synthesis according to claim 9, characterized in that: The stirring speed of the reactor is 140-170 r / min.

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