Composite acid for recycling silver-titanium waste and method for recycling silver from silver-titanium waste

Abstract

The invention relates to the field of precious metal recovery, and discloses a composite acid for silver-titanium waste recovery, which comprises hydrofluoric acid and nitric acid, the mass ratio of hydrofluoric acid to nitric acid is 1: (2-4); the concentration of hydrofluoric acid in the composite acid is 50-100g / L. The composite acid is used for recovering silver from the silver-titanium waste, the leaching rate of silver in the silver-titanium waste can be increased, and ignition or explosion caused by instability of titanium can be prevented. Meanwhile, the invention further provides a method for recycling silver from the silver-titanium waste.

Description

Technical Field

[0001] The present invention relates to the field of precious metal recovery, in particular to a composite acid for recovering silver-titanium waste and a method for recovering silver from the silver-titanium waste. Background Art

[0002] Semiconductor manufacturing produces a large amount of silver-containing titanium waste. Conventional acid leaching of this waste with nitric or sulfuric acid yields a low silver recovery rate. Furthermore, titanium, under the action of strong oxidants and simultaneously with external mechanical factors such as impact and friction, can cause fire and explosion, posing a significant risk. Therefore, the challenge of recovering silver from this waste remains unsolved.

[0003] CN202311071960.2 discloses a method for recovering high-purity silver from silver-containing waste, comprising the following steps: S1, placing the silver-containing waste in a reactor, adding nitric acid for a primary reaction to dissolve the silver into silver ions, then filtering to obtain a filtrate and a filter residue, adding nitric acid for a secondary reaction to dissolve the obtained filter residue, and combining the filtrate after the secondary reaction with the filtrate after the primary reaction; S2, adding sufficient sodium chloride to the combined filtrate obtained in step S1 until the silver ions are completely precipitated to obtain a silver chloride precipitate, then washing the silver chloride precipitate with pure water in a centrifuge until the filtrate is neutral, and continuing to centrifuge for a period of time to minimize the amount of water; S3, calcining the silver chloride precipitate after washing and centrifugation in step S2 in stages under the condition of oxygen or compressed air to obtain silver blocks. This method uses nitric acid for secondary dissolution of silver and requires heating. However, in silver-containing titanium waste, heating may cause the titanium to explode, and the use of only nitric acid results in a relatively low silver leaching rate in silver-titanium waste.

[0004] CN107574313A discloses a method for recovering silver from silver-containing electronic scaffolds, comprising the following steps: A. Weighing scrapped silver-containing electronic scaffolds, adding a theoretically calculated amount of nitric acid to the scaffolds, and heating while adding more nitric acid until the scrapped silver-containing scaffolds are completely dissolved; B. Cooling the leachate to room temperature, and slowly adding hydrochloric acid to precipitate silver; C. After the complete precipitation of Ag+ and Cl-, the precipitate is allowed to stand and filtered to obtain a silver chloride precipitate and a post-precipitate solution. The post-precipitate solution is repeatedly circulated to dissolve the silver-containing electronic scaffolds until the post-precipitate solution is saturated, and valuable metals are recovered from the saturated post-precipitate solution; D. The silver chloride precipitate is washed with a saturated sodium chloride solution, slurried with ammonia water, and then reduced with hydrazine hydrate to obtain sponge silver with a purity greater than 98%. This method also uses nitric acid and heating to dissolve the silver-containing scaffolds. The leaching rate of silver in silver-titanium waste is relatively low.

[0005] Therefore, the technical problem to be solved by the present invention is: how to safely increase the leaching rate of silver in silver-titanium waste. Summary of the Invention

[0006] The main purpose of the present invention is to provide a composite acid for recycling silver-titanium waste. The composite acid can dissolve silver and titanium, increase the contact area between silver and the composite acid, and improve the leaching rate of silver. Moreover, the composite acid can be used to acidly leach silver at room temperature, avoiding fire or explosion caused by instability of titanium.

[0007] At the same time, a method for recovering silver from silver-titanium waste is also provided.

[0008] To achieve the above objectives, the technical solutions adopted in this application are:

[0009] A composite acid for recycling silver-titanium waste comprises hydrofluoric acid and nitric acid; the mass ratio of the hydrofluoric acid to the nitric acid is 1:2-4; and the concentration of the hydrofluoric acid in the composite acid is 50-100 g / L.

[0010] In silver-titanium scrap, silver and titanium are intertwined, with some silver being encapsulated by the titanium. Using a mass ratio of 1:2 to 4 for hydrofluoric acid and nitric acid allows the hydrofluoric acid in the composite acid to react with the titanium, softening the titanium. This increases the contact area between the nitric acid and the silver in the composite acid, further promoting the reaction between the nitric acid and silver and increasing the silver leaching rate. Furthermore, the reaction between hydrofluoric acid and titanium releases heat, which is then provided to the nitric acid and silver reaction, enabling the silver to dissolve at room temperature and preventing titanium instability that could cause fire or explosion.

[0011] In some embodiments of the present invention, the mass ratio of hydrofluoric acid to nitric acid is preferably 1:2, 1:2.5, 1:3, 1:3.5, or 1:4; and the concentration of the hydrofluoric acid is preferably 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, or 100 g / L.

[0012] At the same time, a method for recovering silver from silver-titanium waste is also provided, comprising the following steps:

[0013] Step 1: acid leaching the silver-titanium waste using the composite acid for silver-titanium waste recovery as described above to obtain a silver-containing solution;

[0014] Step 2: Precipitate and reduce the silver-containing solution to obtain sponge silver.

[0015] Preferably, step 1 includes the following steps:

[0016] Step A1: using the composite acid for recycling silver-titanium waste as described above to perform a primary acid leaching on the silver-titanium waste, and filtering to obtain a primary filtrate and a primary filter residue;

[0017] Step A2: performing secondary acid leaching on the primary filter residue using the composite acid for silver-titanium waste recovery as described above, and filtering to obtain a secondary filtrate;

[0018] The silver-containing solution comprises a primary filtrate and a secondary filtrate.

[0019] Preferably, in step A1, the mass ratio of hydrofluoric acid to nitric acid is 1:3-4, and the time for one acid leaching is 0.5-1.5 h.

[0020] In some embodiments of the present invention, the mass ratio of hydrofluoric acid to nitric acid is preferably 1:3, 1:3.5, or 1:4; and the time for one acid leaching is preferably 0.5 h, 1 h, or 1.5 h.

[0021] Preferably, in step A2, the mass ratio of hydrofluoric acid to nitric acid is 1:2-3; and the time of the secondary acid leaching is 0.5-1.5 h.

[0022] In some embodiments of the present invention, the preferred mass ratio of hydrofluoric acid to nitric acid is 1:2, 1:2.5, or 1:3; and the preferred time for the secondary acid leaching is 0.5 h, 1 h, or 1.5 h.

[0023] Preferably, step 2 includes the following steps:

[0024] Step B1: adding sodium hydroxide and / or sodium chloride to a silver-containing solution to obtain a precipitate;

[0025] Step B2: Wash and remove impurities from the precipitate, add hydrazine hydrate or glucose for reduction to obtain sponge silver.

[0026] Preferably, the step 1 further comprises: during the acid leaching, continuously introducing protective gas to blow toward the silver-titanium waste to achieve tumbling and stirring of the silver-titanium waste.

[0027] Preferably, the blowing pressure of the protective gas is 0.2-0.6 MPa.

[0028] The blowing pressure is used to adjust the tumbling and stirring efficiency of the silver-titanium waste in the composite acid. The blowing pressure of 0.2 to 0.6 MPa can improve the silver recovery rate.

[0029] In some embodiments of the present invention, the blowing pressure of the protective gas is preferably 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, or 0.6 MPa.

[0030] Compared with the existing technology, this solution has the following beneficial effects:

[0031] The mass ratio of hydrofluoric acid to nitric acid in the composite acid of the present invention is 1:2-4. In the silver-titanium waste, the hydrofluoric acid reacts with titanium, so that the silver wrapped by the titanium can be separated from the titanium wrapping, the contact area between the silver and the nitric acid is increased, more silver can react with the nitric acid, and the leaching rate of the silver is improved.

[0032] Secondly, the reaction between hydrofluoric acid and titanium releases heat, which provides heat for silver and nitric acid, so that silver and nitric acid can react at room temperature without the need for additional heating, avoiding fire or explosion caused by the instability of titanium. DETAILED DESCRIPTION

[0033] To make the purpose, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the present application shown here can be arranged and designed in various different configurations.

[0034] The following examples and comparative examples detect the mass fraction of silver and the mass fraction of titanium in the silver-titanium waste by fire assay, and convert the mass of silver and the mass of titanium in the silver-titanium waste.

[0035] Example 1

[0036] A method for recovering silver from silver-titanium waste comprises the following steps:

[0037] Step 1: 200 g of silver-titanium waste (actual detection shows that the mass of silver is 22.8 g and the mass of titanium is 3.8 g) is put into a reaction container, and a composite acid is added to the reaction container for a primary acid leaching. At the same time, argon gas is continuously introduced into the reaction container to blow the silver-titanium waste, so that the silver-titanium waste is tumbled and stirred in the composite acid until the primary acid leaching is completed. The blowing pressure of the argon gas is 0.4 MPa, and the primary acid leaching time is 1 hour. After filtration, a silver-containing solution is obtained;

[0038] In the primary acid leaching, the concentrations of hydrofluoric acid and nitric acid in the composite acid are 80 g / L and 200 g / L respectively; the mass ratio of the composite acid to the silver-titanium waste is 1:5;

[0039] Step 2: adding sodium chloride to the silver-containing solution to obtain a precipitate;

[0040] The mass ratio of the silver-containing solution to sodium chloride is 1:0.2;

[0041] Step 3: After washing the precipitate with pure water to remove impurities, adding clean water to slurry, adding sodium hydroxide to obtain a slurry, and then adding glucose to the slurry for reduction to obtain sponge silver;

[0042] The mass ratio of the precipitate to sodium hydroxide is 1:0.5, and the mass ratio of the slurry to glucose is 1:0.8.

[0043] Example 2

[0044] This embodiment is basically the same as the first embodiment, except that:

[0045] Step 1: 180 g of silver-titanium waste (according to actual testing, the mass of silver is 22.8 g and the mass of titanium is 3.8 g) is put into a reaction container, and a composite acid is added to the reaction container for a primary acid leaching. At the same time, argon gas is continuously introduced into the reaction container to blow the silver-titanium waste, so that the silver-titanium waste is tumbled and stirred in the composite acid until the primary acid leaching is completed. The blowing pressure of the argon gas is 0.4 MPa, and the primary acid leaching time is 1 hour. After filtration, a primary filtrate and a primary filter residue are obtained;

[0046] In the primary acid leaching, the concentrations of hydrofluoric acid and nitric acid in the composite acid are 50 g / L and 200 g / L respectively; the mass ratio of the composite acid to the silver-titanium waste is 1:5;

[0047] Step 2: The primary filter residue is placed in a reaction vessel, and a composite acid is added to the reaction vessel for secondary acid leaching. At the same time, argon is continuously introduced into the reaction vessel to blow the primary filter residue, so that the primary filter residue is tumbled and stirred in the composite acid until the secondary acid leaching is completed. The blowing pressure of the argon gas is 0.4 MPa, and the secondary acid leaching time is 1 hour. After filtration, a secondary filtrate is obtained;

[0048] In the secondary acid leaching, the concentrations of hydrofluoric acid and nitric acid in the composite acid are 100 g / L and 200 g / L, respectively; the mass ratio of the composite acid to the primary filter residue is 1:5;

[0049] Step 3: adding sodium chloride to the primary filtrate and the secondary filtrate to obtain a precipitate;

[0050] Among them, the mass ratio of the primary filtrate to sodium chloride is 1:0.2; the mass ratio of the secondary filtrate to sodium chloride is 1:0.2;

[0051] Step 4: After washing the precipitate with pure water to remove impurities, adding clean water to slurry, adding sodium hydroxide to obtain a slurry, and then adding glucose to the slurry for reduction to obtain sponge silver;

[0052] The mass ratio of the precipitate to sodium hydroxide is 1:0.5, and the mass ratio of the slurry to glucose is 1:0.8.

[0053] Example 3

[0054] This embodiment is substantially the same as embodiment 1, except that in the primary acid leaching, the concentrations of hydrofluoric acid and nitric acid in the composite acid are 100 g / L and 200 g / L, respectively.

[0055] Example 4

[0056] This embodiment is substantially the same as embodiment 1, except that in the primary acid leaching, the concentrations of hydrofluoric acid and nitric acid in the composite acid are 50 g / L and 200 g / L, respectively.

[0057] Example 5

[0058] This embodiment is substantially the same as embodiment 1, except that: step 1: 180 g of silver-titanium waste (actual detection shows that the mass of silver is 22.8 g and the mass of titanium is 3.8 g) is put into a reaction vessel, a composite acid is added into the reaction vessel for primary acid leaching, and at the same time, argon gas is continuously introduced into the reaction vessel to blow the silver-titanium waste so that the silver-titanium waste is tumbled and stirred in the composite acid until the primary acid leaching is completed, the blowing pressure of the argon gas is 0.4 MPa, the primary acid leaching time is 1 h, and a primary filtrate and a primary filter residue are obtained after filtration;

[0059] In the primary acid leaching, the concentrations of hydrofluoric acid and nitric acid in the composite acid are 100 g / L and 200 g / L respectively; the mass ratio of the composite acid to the silver-titanium waste is 1:5;

[0060] Step 2: The primary filter residue is placed in a reaction vessel, and a composite acid is added to the reaction vessel for secondary acid leaching. At the same time, argon is continuously introduced into the reaction vessel to blow the primary filter residue, so that the primary filter residue is tumbled and stirred in the composite acid until the secondary acid leaching is completed. The blowing pressure of the argon gas is 0.4 MPa, and the secondary acid leaching time is 1 hour. After filtration, a secondary filtrate is obtained;

[0061] In the secondary acid leaching, the concentrations of hydrofluoric acid and nitric acid in the composite acid are 100 g / L and 200 g / L, respectively; the mass ratio of the composite acid to the primary filter residue is 1:5;

[0062] Step 3: adding sodium chloride to the primary filtrate and the secondary filtrate to obtain a precipitate;

[0063] Among them, the mass ratio of the primary filtrate to sodium chloride is 1:0.2; the mass ratio of the secondary filtrate to sodium chloride is 1:0.2;

[0064] Step 4: After washing the precipitate with pure water to remove impurities, adding clean water to slurry, adding sodium hydroxide to obtain a slurry, and then adding glucose to the slurry for reduction to obtain sponge silver;

[0065] The mass ratio of the precipitate to sodium hydroxide is 1:0.5, and the mass ratio of the slurry to glucose is 1:0.8.

[0066] Comparative Example 1

[0067] This comparative example is basically the same as Example 1, except that: Step 1: silver-titanium waste is put into a reaction vessel, 200 g / L nitric acid is added to the reaction vessel for acid leaching, and the mixture is heated to 75° C. in a water bath for 2.5 hours, and the mass ratio of nitric acid to silver-titanium waste is 1:5.

[0068] Comparative Example 2

[0069] This comparative example is substantially the same as Example 1, except that in the primary acid leaching, the concentrations of hydrofluoric acid and nitric acid in the composite acid are 40 g / L and 200 g / L, respectively.

[0070] The methods of Examples 1 to 5 and Comparative Examples 1 to 2 were respectively used to recover silver from silver-titanium waste, and the testing method was as follows: the mass fraction of silver in the silver-titanium waste was detected by a fire assay method and the silver mass of the silver-titanium waste was converted; the mass fraction of silver in sponge silver was detected by an ICP-MS detection method and the silver mass of the sponge silver was converted; the silver recovery rate was calculated by the ratio of the silver mass of the sponge silver to the silver mass of the silver-titanium waste.

[0071] The results are shown in Table 1:

[0072] Table 1 Test results of silver titanium scrap

[0073]

[0074] Result analysis:

[0075] As can be seen from Examples 1, 3, and 4, the silver recovery rate fluctuates slightly, proving that a good silver recovery rate can be obtained when the mass ratio of hydrofluoric acid to nitric acid in the composite acid is in the range of 1:2 to 4.

[0076] It can be seen from Examples 1, 2, and 5 that the silver recovery rates in Examples 2 and 5 are significantly higher than that in Example 1. The reason is that Example 1 uses one acid leaching, while Examples 2 and 5 use two acid leachings. Since part of the silver in the silver-titanium waste is wrapped by titanium, some silver wrapped by titanium cannot react with nitric acid during one acid leaching. Using two composite acid leachings can dissolve silver and titanium, and then precipitate silver to obtain sponge silver, thereby improving the silver recovery rate.

[0077] Secondly, Example 2 uses two composite acids to carry out acid leaching on the silver-titanium waste and the primary filter residue respectively, and the concentration of hydrofluoric acid in the composite acid used for the silver-titanium waste is lower than that in the composite acid used for the primary filter residue. In this way, the purity of silver in the sponge silver can be improved. Moreover, it can be seen from Example 5 that when the same concentration of composite acid is used for the silver-titanium waste and the primary filter residue, the purity of the silver in the sponge silver is relatively low. It may be that the concentration of added hydrofluoric acid is too high, which dissolves more titanium, and the recovery rate also decreases slightly. Therefore, considering the difficulty of subsequent purification of the sponge silver, Example 2 is the best solution.

[0078] Compared with Comparative Example 1, the silver recovery rate in Example 1 is significantly higher than that in Comparative Example 1. The reason is that part of the silver in the silver-titanium waste is wrapped by titanium, and nitric acid can only dissolve silver but not titanium, so that nitric acid can only react with part of the silver, resulting in the silver recovery rate in Comparative Example 1 being lower than that in Example 1. Secondly, the use of only nitric acid requires heating, which may make titanium unstable and cause fire or explosion. However, when using a composite acid, hydrofluoric acid reacts with titanium to release heat, which is provided to the reaction of silver and nitric acid, so that silver can react with the composite acid at room temperature.

[0079] Compared with Comparative Example 2, the recovery rate of silver in Example 1 is significantly higher than that in Comparative Example 2. The reason is that although a composite acid is also used, the hydrofluoric acid concentration of the composite acid in Comparative Example 2 is lower. This may be because the concentration of hydrofluoric acid is less than 50 g / L, which cannot soften the titanium. The silver wrapped by titanium cannot be exposed to nitric acid. Therefore, most of the silver wrapped by titanium cannot react with nitric acid.

[0080] However, when the amount of hydrofluoric acid in the composite acid is too high, although it can slightly improve the silver recovery rate, due to the strong corrosiveness of hydrofluoric acid, excessive use can easily cause harm to workers. In addition, the reaction between hydrofluoric acid and titanium is exothermic, and excessive hydrofluoric acid can easily cause titanium instability, resulting in fire or explosion. Based on cost and safety considerations, the mass ratio of hydrofluoric acid to nitric acid in the composite acid is 1:2-4.

[0081] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A composite acid for recycling silver-titanium waste, characterized in that: The composite acid comprises hydrofluoric acid and nitric acid; the mass ratio of the hydrofluoric acid to the nitric acid is 1:2-4; and the concentration of the hydrofluoric acid in the composite acid is 50-100 g / L.

2. A method for recovering silver from silver-titanium waste, characterized in that: The steps include: Step 1: using the composite acid for recycling silver-titanium waste as claimed in claim 1 to acidly leach the silver-titanium waste to obtain a silver-containing solution; Step 2: Precipitate and reduce the silver-containing solution to obtain sponge silver.

3. The method for recovering silver from silver-titanium waste according to claim 2, characterized in that: The step 1 comprises the following steps: Step A1: using the composite acid for recycling silver-titanium waste as claimed in claim 1 to carry out acid leaching on the silver-titanium waste, and filtering to obtain a primary filtrate and a primary filter residue; Step A2: using the composite acid for recycling silver-titanium waste as claimed in claim 1 to perform secondary acid leaching on the primary filter residue, and filtering to obtain a secondary filtrate; The silver-containing solution is a primary filtrate and a secondary filtrate.

4. The method for recovering silver from silver-titanium waste according to claim 3, characterized in that: In the step A1, the mass ratio of the hydrofluoric acid to the nitric acid is 1:3-4, and the time for one acid leaching is 0.5-1.5 hours.

5. The method for recovering silver from silver-titanium waste according to claim 3, characterized in that: In the step A2, the mass ratio of the hydrofluoric acid to the nitric acid is 1:2-3; and the time of the secondary acid leaching is 0.5-1.5h.

6. The method for recovering silver from silver-titanium waste according to claim 2, characterized in that: The step 2 comprises the following steps: Step B1: adding sodium hydroxide and / or sodium chloride to a silver-containing solution to obtain a precipitate; Step B2: Wash and remove impurities from the precipitate, add hydrazine hydrate or glucose for reduction, and obtain sponge silver.

7. The method for recovering silver from silver-titanium waste according to claim 2, characterized in that: The step 1 also includes: during the acid leaching, continuously introducing protective gas to blow toward the silver-titanium waste to achieve tumbling and stirring of the silver-titanium waste.

8. The method for recovering silver from silver-titanium waste according to claim 7, characterized in that: The blowing pressure of the protective gas is 0.2-0.6 MPa.

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