Production method of high-purity silver nitrate

Abstract

The invention relates to the technical field of silver nitrate preparation, in particular to a production method of high-purity silver nitrate. According to the method, impurities are precipitated by adopting an impurity removing agent, then the impurities are removed by utilizing solid-liquid separation, and impurity metals and impurities in the silver nitrate solution are subjected to chemical reaction and physical solid-liquid separation by virtue of three-stage precision filtering equipment, so that the impurity content of the separated silver nitrate solution is relatively low, and meanwhile, the filtering parameter requirements are specified; according to the method, impurities are effectively removed, introduction of other ions is avoided, the purity of silver nitrate is guaranteed, the production efficiency is improved, the risk of secondary pollution is reduced, the product quality is improved, the production period is shortened, the single-batch treatment capacity is large, the product yield is high, the labor amount is reduced, and labor personnel are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of silver nitrate preparation, and in particular to a method for producing high-purity silver nitrate. Background Art

[0002] With technological advancements and growing environmental awareness, silver nitrate has a promising future in the electronics industry. The increasing demand for electronic products such as liquid crystal displays, LEDs, and solar cells is driving a surge in demand for silver nitrate. Furthermore, its increasing use in environmental protection, such as sewage and waste gas treatment, is fueling its market prospects.

[0003] In recent years, the production method of silver nitrate has been continuously improved with the goal of increasing purity and reducing costs. It mainly includes steps such as silver washing, silver dissolving, impurity removal, and evaporation crystallization. The main focus is on how to reduce impurities in silver nitrate. For example, Chinese patent CN102040241A proposes a production method for producing photographic-grade silver nitrate, which uses magnesium carbonate as an impurity remover to produce photographic-grade silver nitrate; Chinese patent CN102040240A discloses a method for producing high-purity silver nitrate, which uses magnesium oxide as an impurity remover to reduce the concentration of impurity metal elements to below 0.1 mg / L. However, the overall effect of impurity removal is still limited, which is not conducive to the industrial production of high-purity silver nitrate.

[0004] Therefore, the present invention provides a production method with simple process, low cost and low impurity content in silver nitrate. Summary of the Invention

[0005] In order to solve the problems of the prior art, the present invention provides a method for producing high-purity silver nitrate, comprising the following steps:

[0006] A method for producing high-purity silver nitrate comprises the following steps:

[0007] Step 1: The silver ingot is subjected to alkaline washing with sodium hydroxide solution, a water wash, an acid wash with nitric acid solution, and a second water wash to obtain a washed silver ingot;

[0008] Step 2: Dissolve the cleaned silver ingot in nitric acid, controlling the temperature to not less than 50°C. After complete dissolution, continue heating to a pH value of 2.5-3.5 to obtain a crude silver nitrate solution;

[0009] Step 3: Add water to the crude silver nitrate solution obtained in step 2 and adjust the density to 1.6 g / cm 3 -1.8g / cm 3 , then add sodium sulfide and adjust the solution pH to 6-8, stir evenly and let it stand for 15-20 hours;

[0010] Step 4: Filter the solution after standing in step 3 to obtain a primary filtrate;

[0011] Step 5: Passing the primary filtrate through three stages of precision filtration equipment connected in series, with the filtration accuracy of the three stages increasing successively, and the maximum filtration pore size does not exceed the pore size of the filtration equipment in step 4, to obtain a secondary filtrate;

[0012] Step 6: adding nitric acid to the secondary filtrate to adjust its pH value to 1-1.2, and performing vacuum evaporation and concentration, cooling and crystallization, filtering, washing, and drying to obtain high-purity silver nitrate.

[0013] Furthermore, the mass concentration of the sodium hydroxide solution in step 1 is 2%, and the mass concentration of the nitric acid solution is 5%.

[0014] Furthermore, the dissolving temperature in step 2 is 50°C-90°C.

[0015] Furthermore, the mass ratio of the sodium sulfide and the silver ingot added in step 3 is 0.02-0.05:1.

[0016] Furthermore, the filtering device in step 4 is a 1500-mesh filtering device.

[0017] Furthermore, the filtration accuracy of the filtration equipment in step 5 is 1 micron, 0.5 micron, and 0.2 micron respectively.

[0018] The process flow of the present invention is simple. First, the silver ingot is cleaned with alkali and acid in sequence to remove metal impurities adhering to the surface of the silver ingot, especially to dissolve some impurities on the surface of the silver ingot. Then, nitric acid is used for dissolution: silver reacts with concentrated / dilute nitric acid under heating conditions to generate silver nitrate, while releasing nitrogen oxide gas (NO3 or NO2). After dissolution, heating is continued to drive out the nitrate and remove the nitride. Then, sodium sulfide is added to precipitate the impurity elements iron, copper and lead. The precipitation is controlled to be close to neutral conditions, so that no Ag is lost and the impurities are completely removed. Then, primary filtration is combined with three-stage precision filtration. The impurity removal process is as follows: the reaction solution is diluted to a relative density of 1.6-1.8 g / cm 3 After cooling and standing for 15-20 hours, impurities such as bismuth nitrate are precipitated. Sodium sulfide is then added to adjust the pH to neutral, forming a metal hydroxide precipitate. The solution is then filtered through multi-layer filter paper or a microporous membrane to remove submicron particles and ensure clarity. The pH of the filtrate is then adjusted to increase the pH of the crystals and subsequent products to ensure purity, and then evaporated and concentrated. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The embodiments of the present invention are further described below with reference to the accompanying drawings, in which:

[0020] Figure 1A flow chart for preparing silver nitrate according to the present application is shown. DETAILED DESCRIPTION

[0021] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application is further described in detail below with reference to specific examples. It should be understood that the specific examples described herein are only used to explain the present application and are not used to limit the present application.

[0022] Example 1

[0023] A production method of high-purity silver nitrate, specifically comprising the following steps:

[0024] Step (1) washing silver: using 2wt% sodium hydroxide solution and 5wt% nitric acid solution, sequentially performing sodium hydroxide solution alkaline washing, once water washing, nitric acid solution acid washing, and twice water washing, to obtain 100kg of cleaned silver ingot;

[0025] Step (2) dissolving silver: placing the cleaned silver material into a reaction kettle, using nitric acid for dissolution, controlling the reaction temperature at 50℃, after reaction, heating to remove nitrate, and adjusting the pH value of the dissolution solution from 0-1.0 to 2.5.

[0026] Step (3) impurity removal: adding water to the solution obtained in step 2 to adjust the density to 1.6g / cm 3 , then adding 2kg of sodium sulfide, adjusting the pH value to 6, stirring uniformly, and then standing for 15 hours;

[0027] Step (4) filtration: using a solid-liquid separation method for the solution after standing in step 3, using a 1500-mesh filtration device to obtain a first filtrate;

[0028] Step (5) secondary filtration: using a three-stage precision filtration device in series for the solution obtained in step 4, the filtration precision being 1 micron, 0.5 micron and 0.2 micron respectively, to obtain a secondary filtrate;

[0029] Step (6) evaporation and crystallization: adding nitric acid solution to the secondary filtrate obtained in step 5 to adjust the pH value to 1-1.1, vacuum evaporation and concentration, cooling and crystallization, filtration, and drying, to obtain silver nitrate.

[0030] The silver nitrate obtained through the above steps has a silver nitrate content of 99.8%, and the total content of impurities Bi, Cu, Fe and Pb is 0.2%.

[0031] Example 2

[0032] A production method of high-purity silver nitrate, specifically comprising the following steps:

[0033] Step (1) washing silver: using 2wt% sodium hydroxide solution and 5wt% nitric acid solution, sequentially performing sodium hydroxide solution alkaline washing, one water washing, nitric acid solution acid washing, and two water washings to obtain 100kg of washed silver ingots;

[0034] Step (2) silver dissolution: the washed silver material is placed in a reactor and dissolved using nitric acid. The reaction temperature is controlled at 70°C. After the reaction, the nitric acid is driven out by heating, and the pH value of the solution is increased from 0-1.0 to 3.0.

[0035] Step (3) impurity removal: add water to the solution obtained in step 2 and adjust the density to 1.7 g / cm 3 , then add 3kg of sodium sulfide, adjust the pH value to 7, stir evenly and let it stand for 18 hours;

[0036] Step (4) Filtration: After step 3 is allowed to stand, the solution is first subjected to a solid-liquid separation method using a 1500-mesh filter to obtain a primary filtrate;

[0037] Step (5) secondary filtration: the solution obtained in step 4 is passed through three stages of precision filtration equipment connected in series, with filtration accuracies of 1 micron, 0.8 micron, and 0.3 micron, respectively, to obtain a secondary filtrate;

[0038] Step (6) Evaporation and crystallization: adding nitric acid solution to the secondary filtrate obtained in step 5 to adjust the pH value to 1-1.2, concentrating by vacuum evaporation, cooling and crystallizing, filtering, and drying to obtain silver nitrate.

[0039] The silver nitrate obtained through the above steps contains 99.9% silver nitrate and 0.1% impurities of Bi, Cu, Fe and Pb.

[0040] Example 3

[0041] A method for producing high-purity silver nitrate specifically comprises the following steps:

[0042] Step (1) washing silver: using 2wt% sodium hydroxide solution and 5wt% nitric acid solution, sequentially performing sodium hydroxide solution alkaline washing, one water washing, nitric acid solution acid washing, and two water washings to obtain 100kg of washed silver ingots;

[0043] Step (2) silver dissolution: the washed silver material is placed in a reactor and dissolved using nitric acid. The reaction temperature is controlled at 90°C. After the reaction, the nitric acid is driven out by heating, and the pH value of the solution is increased from 0-1.0 to 3.0.

[0044] Step (3) impurity removal: add water to the solution obtained in step 2 and adjust the density to 1.8g / cm 3 , then add 5kg of sodium sulfide, adjust the pH value to 8, stir evenly and let it stand for 20 hours;

[0045] Step (4) Filtration: After step 3 is allowed to stand, the solution is first subjected to a solid-liquid separation method using a 1500-mesh filter to obtain a primary filtrate;

[0046] Step (5) secondary filtration: the solution obtained in step 4 is passed through three stages of precision filtration equipment connected in series, with filtration accuracies of 1 micron, 0.6 micron, and 0.2 micron, respectively, to obtain a secondary filtrate;

[0047] Step (6) Evaporation and crystallization: adding nitric acid solution to the secondary filtrate obtained in step 5 to adjust the pH value to 1-1.2, concentrating by vacuum evaporation, cooling and crystallizing, filtering, and drying to obtain silver nitrate.

[0048] The silver nitrate obtained through the above steps contains 99.8% silver nitrate and 0.2% impurities of Bi, Cu, Fe and Pb.

[0049] Example 4

[0050] A method for producing high-purity silver nitrate specifically comprises the following steps:

[0051] Step (1) washing silver: using 2wt% sodium hydroxide solution and 5wt% nitric acid solution, sequentially performing sodium hydroxide solution alkaline washing, one water washing, nitric acid solution acid washing, and two water washings to obtain 100kg of washed silver ingots;

[0052] Step (2) silver dissolution: the washed silver material is placed in a reactor and dissolved using nitric acid. The reaction temperature is controlled at 80°C. After the reaction, the nitric acid is driven out by heating, and the pH value of the solution is increased from 0-1.0 to 3.5.

[0053] Step (3) impurity removal: add water to the solution obtained in step 2 and adjust the density to 1.8g / cm 3 , then add 4kg of sodium sulfide, adjust the pH value to 7, stir evenly and let it stand for 20 hours;

[0054] Step (4) Filtration: After step 3 is allowed to stand, the solution is first subjected to a solid-liquid separation method using a 1500-mesh filter to obtain a primary filtrate;

[0055] Step (5) secondary filtration: the solution obtained in step 4 is passed through three stages of precision filtration equipment connected in series, with filtration accuracies of 1 micron, 0.5 micron, and 0.2 micron, respectively, to obtain a secondary filtrate;

[0056] Step (6) Evaporation and crystallization: adding nitric acid solution to the secondary filtrate obtained in step 5 to adjust the pH value to 1-1.2, concentrating by vacuum evaporation, cooling and crystallizing, filtering, and drying to obtain silver nitrate.

[0057] The silver nitrate obtained through the above steps contains 99.8% silver nitrate and 0.2% impurities of Bi, Cu, Fe and Pb.

[0058] Comparative Example 1

[0059] A method for producing high-purity silver nitrate specifically comprises the following steps:

[0060] Step (1) washing silver: using 2wt% sodium hydroxide solution and 5wt% nitric acid solution, sequentially performing sodium hydroxide solution alkaline washing, one water washing, nitric acid solution acid washing, and two water washings to obtain 100kg of washed silver ingots;

[0061] Step (2) silver dissolution: the washed silver material is placed in a reaction kettle and dissolved using nitric acid, with the reaction temperature controlled at 90°C.

[0062] Step (3) impurity removal: add 5 kg of sodium sulfide to the solution obtained in step 2 to adjust the pH value to 8-9, stir evenly and let it stand for 10 hours;

[0063] Step (4) Filtration: After step 3 is allowed to stand, the solution is first subjected to a solid-liquid separation method using a 0.5 micron filter to obtain a primary filtrate;

[0064] Step (5) evaporation crystallization: add nitric acid solution to the primary filtrate obtained in step 4 to adjust the pH value to 1-1.2, concentrate by vacuum evaporation, cool and crystallize, filter, and dry to obtain silver nitrate.

[0065] The silver nitrate obtained through the above steps contains 99.3% silver nitrate, and the impurities Bi, Cu, Fe, and Pb account for a total of 0.7%.

[0066] Comparative Example 2

[0067] A method for producing high-purity silver nitrate specifically comprises the following steps:

[0068] Step (1) washing silver: using 2wt% sodium hydroxide solution and 5wt% nitric acid solution, sequentially performing sodium hydroxide solution alkaline washing, one water washing, nitric acid solution acid washing, and two water washings to obtain a washed silver ingot;

[0069] Step (2) silver dissolution: the washed silver material is placed in a reactor and dissolved using nitric acid. The reaction temperature is controlled at 90°C. After the reaction, the nitric acid is driven out by heating, and the pH value of the solution is increased from 0-1.0 to 1.5.

[0070] Step (3) impurity removal: add water to the solution obtained in step 2 and adjust the density to 1.5g / cm 3 Then add 1kg of sodium sulfide, adjust the pH value to 6, stir evenly and let it stand for 15 hours;

[0071] Step (4) filtration: After step 3 is allowed to stand, the solution is first subjected to a solid-liquid separation method using a 1500-mesh filter to obtain a primary solution;

[0072] Step (5) secondary filtration: the solution obtained in step 4 is then filtered through three stages of precision filtration equipment connected in series, with filtration accuracies of 1 micron, 0.5 micron, and 0.2 micron, respectively, to obtain a secondary filtrate;

[0073] Step (6) evaporation crystallization: add nitric acid solution to the secondary filtrate obtained in step 5 to adjust the pH value to 1-1.2, concentrate by vacuum evaporation, cool and crystallize, filter, and dry to obtain silver nitrate.

[0074] The silver nitrate obtained through the above steps contains 99.1% silver nitrate, and the impurities Bi, Cu, Fe, and Pb account for a total of 0.9%.

[0075] Some exemplary embodiments of the present invention are described above. It will be understood that the above embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention. The features in these embodiments can be recombined in an appropriate manner, and the solutions obtained thereby are still within the scope of protection claimed by the present invention. Based on the above embodiments, all other embodiments obtained by those skilled in the art without making creative work, that is, all modifications, equivalent substitutions and improvements made within the spirit and principles of this application, fall within the scope of protection claimed by the present invention.

Claims

1. A method for producing high-purity silver nitrate, characterized in that, The following steps are involved: Step 1: The silver ingot is subjected to alkaline washing with sodium hydroxide solution, a water wash, an acid wash with nitric acid solution, and a second water wash to obtain a washed silver ingot; Step 2: Dissolve the cleaned silver ingot in nitric acid, controlling the temperature to not less than 50°C. After complete dissolution, continue heating to a pH value of 2.5-3.5 to obtain a crude silver nitrate solution; Step 3: Add water to the crude silver nitrate solution obtained in step 2 and adjust the density to 1.6 g / cm 3 -1.8g / cm 3 , then add sodium sulfide and adjust the solution pH to 6-8, stir evenly and let it stand for 15-20 hours; Step 4: Filter the solution after standing in step 3 to obtain a primary filtrate; Step 5: Passing the primary filtrate through three stages of precision filtration equipment connected in series, with the filtration accuracy of the three stages increasing successively, and the maximum filtration pore size does not exceed the pore size of the filtration equipment in step 4, to obtain a secondary filtrate; Step 6: adding nitric acid to the secondary filtrate to adjust its pH value to 1-1.2, and performing vacuum evaporation and concentration, cooling and crystallization, filtering, washing, and drying to obtain high-purity silver nitrate.

2. a production method of high-purity silver nitrate according to claim 1, is characterized in that, The mass concentration of the sodium hydroxide solution in step 1 is 2%, and the mass concentration of the nitric acid solution is 5%.

3. A production method of high-purity silver nitrate according to claim 1, characterized in that, The dissolving temperature in step 2 is 50°C-90°C.

4. a production method of high-purity silver nitrate according to claim 1, is characterized in that, The mass ratio of sodium sulfide and silver ingot added in step 3 is 0.02-0.05:

1.

5. A method for producing high-purity silver nitrate according to claim 1, wherein The filtering device in step 4 is a 1500-mesh filtering device.

6. A method for producing high-purity silver nitrate according to claim 5, characterized in that, The filtration accuracy of the filtration equipment in step 5 is 1 micron, 0.5 micron, and 0.2 micron, respectively.

Images