Method for recovering silver from liquid after fire assaying detection

Abstract

The invention relates to a method for recovering silver from a solution after fire assaying detection, and belongs to the technical field of precious metal detection, the method comprises the following steps: S1, determination: determining the content of silver ions in a recovered silver nitrate solution by adopting a formald method; step S2, reaction: adding equal amount of sodium chloride into the recovered silver nitrate solution according to the amount of silver ion substance, stirring for 20 minutes, standing for 4 hours, filtering, and washing the precipitate with deionized water to be neutral; the preparation method comprises the following steps: reacting sodium chloride with a recycled silver nitrate solution, precipitating, stirring, standing, filtering and cleaning precipitates of the recycled liquid containing silver thiocyanate, mixing the precipitates of the sodium chloride and the recycled liquid containing silver thiocyanate, adding ammonia water, stirring, standing, clarifying, filtering, collecting filtrate, adding a hydrazine hydrate solution into the filtrate until no bubbles are generated, filtering, cleaning the precipitates with deionized water, and drying to obtain the silver thiocyanate. And melting ingot casting is carried out, 99.9% silver ingots are obtained, and the purpose of recovering silver from the silver nitrate solution and the silver thiocyanate after fire assaying detection at the same time is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of precious metal detection, and in particular relates to a method for recovering silver from liquid after fire assay detection. Background Art

[0002] Fire assay chemical analysis method is the most classic and effective method to determine the content of precious metal components in minerals and metal products through melting and ash blowing process. It is widely used because of its extremely high enrichment ability, simple operation, accurate and reliable results.

[0003] Silver is used as an enricher and protective agent for other precious metals. A certain amount of pure silver is usually added during the detection process. The silver contained in the sample is enriched to form precious metal particles. The silver in the precious metal particles is first dissolved in nitric acid and separated from other precious metals, and converted into silver nitrate solution. The silver content is generally determined in two ways. One is to calculate the silver content by the weight difference before and after separating the silver from the precious metal particles. The other is to titrate the silver nitrate solution with potassium thiocyanate to form silver thiocyanate precipitate. At present, there is no method for simultaneously recovering silver from the silver nitrate solution and silver thiocyanate after fire assay. Summary of the invention

[0004] The object of the present invention is to provide a method for recovering silver from the liquid after fire assay in order to solve the above problems.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0006] The present invention provides a method for recovering silver from a liquid after a fire assay, comprising the following steps:

[0007] Step S1, determination: using Volhard method to determine the silver ion content in the recovered silver nitrate solution;

[0008] Step S2, reaction: adding an equal amount of sodium chloride to the recovered silver nitrate solution according to the amount of silver ion substance, stirring for 20 minutes, standing for 4 hours, filtering, and washing the precipitate with deionized water until it is neutral;

[0009] Step S3, filtration: stirring the recovered liquid containing silver thiocyanate for 10 minutes, standing for 4 hours, filtering, and washing the precipitate with deionized water;

[0010] Step S4, combining: combining the precipitates obtained in step S2 and step S3;

[0011] Step S5, precipitation: slowly add ammonia water in a volume ratio of (1+1) to the precipitate according to 1.1 times the amount of precipitate obtained in step S4 and stir, adjust the pH value to 12-13, stir for 1 hour, let it stand to clarify and then filter, and collect the filtrate;

[0012] Step S6, stirring: adding a hydrazine hydrate solution in a volume ratio of (1+4) to the filtrate in step S5 while stirring until no bubbles are generated, and continuing stirring for 1 hour to obtain a mixture;

[0013] Step S7, precipitation: filtering the mixture in step S6, and washing the precipitate with deionized water;

[0014] Step S8, ingot casting: the precipitate in step S7 is dried, and then melted and cast to obtain a 99.9% silver ingot.

[0015] As a further optimization scheme of the present invention, the silver nitrate solution recovered in step S1 is pre-filtered before being determined by the Volhard method.

[0016] As a further optimization scheme of the present invention, the step S2 also includes pouring the waste liquid into a stirring tank, adding a corrosion inhibitor into the stirring tank for mixing and stirring, controlling the stirring speed to 20 rps, and controlling the stirring time to 30 min.

[0017] As a further optimization scheme of the present invention, the mass ratio of the waste liquid to the corrosion inhibitor is 1:0.2.

[0018] As a further optimization scheme of the present invention, the specific components of the corrosion inhibitor are: glycidyl methacrylate, triethanolamine, sodium gluconate and polyaspartic acid.

[0019] As a further optimization scheme of the present invention, the mass ratio of glycidyl methacrylate, triethanolamine, sodium gluconate and polyaspartic acid is 1:1.2:0.72:0.3.

[0020] As a further optimization scheme of the present invention, the waste liquid obtained after filtration in step S2 is sealed by coating.

[0021] As a further optimization scheme of the present invention, the specific method of coating is: (i) pouring sodium carboxymethyl cellulose powder on a vibrating screen, vibrating and sieving the sodium carboxymethyl cellulose powder using the vibrating screen, controlling the sieve hole diameter of the vibrating screen to be 0.001nm, and obtaining sodium carboxymethyl cellulose powder with a diameter of 0.001nm; (ii) preheating distilled water to 45°C, pouring the sieved sodium carboxymethyl cellulose powder into distilled water, while maintaining the distilled water temperature at 45°C, and stirring the distilled water, controlling the stirring speed to 20r / min, and controlling the time to 30min, to obtain (ii) using the gel method to prepare the dissolved liquid into a gel; (iii) applying the gel on the inner wall of the semi-hollow sphere, controlling the inner diameter of the semi-hollow sphere to be 1 cm, controlling the gel coating thickness to be 1 mm, and then dropping 10 g of waste liquid into the semi-hollow sphere, and bonding the two semi-hollow spheres with the gel coated on the contact surface to form a hollow sphere, and then placing the hollow sphere in a refrigerator, controlling the temperature in the refrigerator to be -140°C, and controlling the placement time to be 6 hours, so that the gel solidifies, thereby forming a coating layer on the outer layer of the waste liquid solution; (iv) according to the operation method in (iii), all the waste liquid is subjected to a weight coating treatment.

[0022] As a further optimization scheme of the present invention, the mass ratio of the sodium carboxymethyl cellulose powder to distilled water is 1:1.3.

[0023] The beneficial effects of the present invention are:

[0024] The method adopts the Volhard method to determine the silver ion content in the recovered silver nitrate solution, uses sodium chloride to react with the recovered silver nitrate solution and precipitate, stirs, stands, filters, washes the precipitate of the recovered liquid containing silver thiocyanate, mixes the precipitates of the two, adds ammonia water, stirs, stands, clarifies, filters, collects the filtrate, adds hydrazine hydrate solution to the filtrate until no bubbles are generated, filters again, washes the precipitate with deionized water, dries, and performs melting ingot casting to obtain a silver ingot with a content of 99.9%, thereby achieving the purpose of simultaneously recovering silver from the silver nitrate solution and silver thiocyanate after fire assay.

[0025] By using a corrosion inhibitor composed of glycidyl methacrylate, triethanolamine, sodium gluconate and polyaspartic acid, adding it into the waste liquid to reduce its corrosion ability, and using a gel made of sodium carboxymethyl cellulose powder to wrap the outside of the waste liquid, the risk of subsequent treatment of the waste liquid, such as use and transportation, is further reduced. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0027] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0028] In the description of the present application, the term "for example" is used to mean "used as an example, illustration or description". Any embodiment described as "for example" in the present application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is given to enable any technician in the field to implement and use the present invention. In the following description, details are listed for the purpose of explanation. It should be understood that a person of ordinary skill in the art can recognize that the present invention can be implemented without using these specific details. In other examples, well-known structures and processes will not be elaborated in detail to avoid unnecessary details to obscure the description of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown, but is consistent with the widest scope consistent with the principles and features disclosed in the present application.

[0029] A method for recovering silver from liquid after fire assay, comprising the following steps:

[0030] Step S1, determination: using the Volhard method to determine the silver ion content in the recovered silver nitrate solution, wherein the Volhard method is a commonly used silver volume method, mainly used to determine the content of silver ions (Ag+) or halogen ions (such as Cl-, Br-, I-);

[0031] The silver nitrate solution recovered in step S1 is pre-filtered before being determined by the Volhard method, wherein the pre-filtering treatment needs to be supplemented by, specifically, preparing a container whose capacity is greater than the amount of the silver nitrate solution, placing a filter membrane on the container, pouring the silver nitrate solution onto the filter net, allowing the silver nitrate solution to pass through the filter membrane and fall into the container for storage, and filtering impurities in the silver nitrate solution by the filter net, so as to avoid the impurities from affecting the subsequent recovery of silver from the silver nitrate solution and the quality of the silver recovery;

[0032] It should be added that the filtration pore size of the filter membrane is 0.001 mm;

[0033] Step S2, reaction: adding an equal amount of sodium chloride to the recovered silver nitrate solution according to the amount of silver ion substance, stirring for 20 minutes, standing for 4 hours, filtering, and washing the precipitate with deionized water until it is neutral, the purpose is to generate silver chloride precipitate by the reaction of sodium chloride and silver ions, wherein stirring and standing are conducive to the formation and separation of the precipitate, and washing the precipitate to neutrality is to remove excess sodium chloride and other impurities;

[0034] Step S2 also includes pouring the waste liquid into a stirring tank, and adding a corrosion inhibitor into the stirring tank for mixing and stirring, controlling the stirring speed to 20 rps, and controlling the stirring time to 30 min. It should be noted that the main component of the waste liquid is sodium nitrate produced by the reaction of silver nitrate solution and sodium chloride. The sodium nitrate solution is highly corrosive. Adding a corrosion inhibitor helps to reduce the corrosion capacity of sodium nitrate, thereby reducing the danger of subsequent treatment of the waste liquid.

[0035] In addition, the mass ratio of waste liquid to corrosion inhibitor is 1:0.2;

[0036] The specific components of the corrosion inhibitor are: glycidyl methacrylate, triethanolamine, sodium gluconate and polyaspartic acid (the mass ratio of the mercaptobenzothiazole, tripolyphosphate and sulfonated lignin is 1:1.2:0.72:0.3);

[0037] The waste liquid obtained after filtration in step S2 is sealed by coating, and the specific method of coating is as follows: (i) pouring sodium carboxymethyl cellulose powder on a vibrating screen, vibrating and sieving the sodium carboxymethyl cellulose powder by the vibrating screen, controlling the sieve hole diameter of the vibrating screen to be 0.001 nm, and obtaining sodium carboxymethyl cellulose powder with a diameter of 0.001 nm; (ii) preheating distilled water to 45° C., pouring the sieved sodium carboxymethyl cellulose powder into distilled water (the mass ratio of sodium carboxymethyl cellulose powder to distilled water is 1:1.3), while maintaining the distilled water temperature at 45° C., and stirring the distilled water, and controlling the stirring speed to be 20 r / m in, controlling the time to 30min, and obtaining a dissolved solution; (ii) using a gel method to prepare a gel from the dissolved solution; (iii) applying the gel on the inner wall of the semi-hollow sphere, controlling the inner diameter of the semi-hollow sphere to be 1cm, and controlling the gel coating thickness to be 1mm, and then dropping 10g of waste liquid into the semi-hollow sphere, and bonding the two semi-hollow spheres with the gel coated on the contact surface of the two to form a hollow sphere, and then placing the hollow sphere in a refrigerator, controlling the temperature in the refrigerator to be -140°C, and controlling the placement time to be 6h, so that the gel solidifies, thereby forming a coating layer on the outer layer of the waste liquid solution; (iv) according to the operation method in (iii), all the waste liquid is subjected to a weight coating treatment;

[0038] According to the above technical solution, it can be explained that by using a corrosion inhibitor composed of glycidyl methacrylate, triethanolamine, sodium gluconate and polyaspartic acid, adding it into the waste liquid to reduce its corrosion ability, and using a gel made of sodium carboxymethyl cellulose powder to wrap the outside of the waste liquid, the risk of subsequent treatment of the waste liquid, such as use, transportation, etc., is further reduced;

[0039] Step S3, filtration: stirring the recovered liquid containing silver thiocyanate for 10 minutes, standing for 4 hours, filtering, and washing the precipitate with deionized water, the purpose of which is to further recover silver by generating silver thiocyanate precipitate in order to treat the solution containing other silver compounds;

[0040] Step S4, combining: combining the precipitates obtained in step S2 and step S3 for subsequent processing;

[0041] Step S5, precipitation: slowly adding ammonia water in a volume ratio of (1+1) to the precipitate according to 1.1 times the amount of the precipitate obtained in step S4 and stirring, adjusting the pH value to 12-13, stirring for 1 hour, filtering after standing to clarify, and collecting the filtrate, the purpose is: the precipitate is converted into soluble silver ammine ions by ammonia water treatment for subsequent recovery, in addition, the pH value is adjusted to ensure complete reaction, stirring and standing to clarify are conducive to the reaction and separation of the solution;

[0042] Step S6, stirring: adding a hydrazine hydrate solution in a volume ratio of (1+4) to the filtrate in step S5 while stirring until no bubbles are generated, and continuing stirring for 1 hour to obtain a mixture, wherein the hydrazine hydrate acts as a reducing agent to reduce the silver ammine complex ions to metallic silver, wherein no bubbles are generated indicating that the reaction is complete;

[0043] Step S7, precipitation: filtering the mixture in step S6, and washing the precipitate with deionized water, the purpose of which is to collect the generated metallic silver precipitate by filtration, and to wash the precipitate to remove impurities;

[0044] Step S8, ingot casting: the precipitate in step S7 is dried, and then melted and cast to obtain a 99.9% silver ingot.

[0045] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0046] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for recovering silver from a liquid after a fire assay, characterized in that: The following steps are involved: Step S1, determination: using Volhard method to determine the silver ion content in the recovered silver nitrate solution; Step S2, reaction: adding an equal amount of sodium chloride to the recovered silver nitrate solution according to the amount of silver ion substance, stirring for 20 minutes, standing for 4 hours, filtering, and washing the precipitate with deionized water until it is neutral; Step S3, filtration: stirring the recovered liquid containing silver thiocyanate for 10 minutes, standing for 4 hours, filtering, and washing the precipitate with deionized water; Step S4, combining: combining the precipitates obtained in step S2 and step S3; Step S5, precipitation: slowly add ammonia water in a volume ratio of (1+1) to the precipitate according to 1.1 times the amount of precipitate obtained in step S4 and stir, adjust the pH value to 12-13, stir for 1 hour, let it stand to clarify and then filter, and collect the filtrate; Step S6, stirring: adding a hydrazine hydrate solution in a volume ratio of (1+4) to the filtrate in step S5 while stirring until no bubbles are generated, and continuing stirring for 1 hour to obtain a mixture; Step S7, precipitation: filtering the mixture in step S6, and washing the precipitate with deionized water; Step S8, ingot casting: The precipitate in step S7 is dried, and then melted and cast to obtain a 99.9% silver ingot.

2. A method for recovering silver from liquid after fire assay according to claim 1, characterized in that: The silver nitrate solution recovered in step S1 is pre-filtered before being measured by the Volhard method.

3. A method for recovering silver from liquid after fire assay according to claim 1, characterized in that: The step S2 also includes pouring the waste liquid into a stirring tank, adding a corrosion inhibitor into the stirring tank for mixing and stirring, controlling the stirring speed to 20 rps, and controlling the stirring time to 30 min.

4. A method for recovering silver from liquid after fire assay according to claim 3, characterized in that: The mass ratio of the waste liquid to the corrosion inhibitor is 1:0.

2.

5. A method for recovering silver from liquid after fire assay according to claim 4, characterized in that: The specific components of the corrosion inhibitor are: glycidyl methacrylate, triethanolamine, sodium gluconate and polyaspartic acid.

6. A method for recovering silver from liquid after fire assay according to claim 5, characterized in that: The mass ratio of glycidyl methacrylate, triethanolamine, sodium gluconate and polyaspartic acid is 1:1.2:0.72:0.

3.

7. A method for recovering silver from a liquid after fire assay according to claim 1, characterized in that: The waste liquid obtained after filtration in the step S2 is sealed by coating.

8. A method for recovering silver from a liquid after a fire assay according to claim 7, wherein the coating is specifically performed by: (i) pouring sodium carboxymethyl cellulose powder onto a vibrating screen, vibrating and sieving the sodium carboxymethyl cellulose powder using the vibrating screen, controlling the sieve hole diameter of the vibrating screen to be 0.001 nm, and obtaining sodium carboxymethyl cellulose powder with a diameter of 0.001 nm; (ii) preheating distilled water to 45° C., pouring the sieved sodium carboxymethyl cellulose powder into the distilled water, while maintaining the distilled water temperature at 45° C., and stirring the distilled water, controlling the stirring speed to be 20 r / min, and controlling the time to be 30min to obtain the dissolved solution; (ii) using the gel method to prepare the dissolved solution into gel; (iii) applying the gel on the inner wall of the semi-hollow sphere, controlling the inner diameter of the semi-hollow sphere to be 1cm, controlling the gel coating thickness to be 1mm, and then dropping 10g of waste liquid into the semi-hollow sphere, and bonding the two semi-hollow spheres with the gel coated on the contact surface to form a hollow sphere, and then placing the hollow sphere in a refrigerator, controlling the temperature in the refrigerator to be -140℃, and controlling the placement time to be 6h to solidify the gel, thereby forming a coating layer on the outer layer of the waste liquid solution; (iv) according to the operation method in (iii), all the waste liquid is subjected to a portion coating treatment.

9. A method for recovering silver from a liquid after fire assay according to claim 8, wherein the mass ratio of the sodium carboxymethyl cellulose powder to the distilled water is 1:1.3.