Environment-friendly cyanide-free gold leaching agent and process for extracting gold in electronic waste

Abstract

The invention provides an environment-friendly cyanide-free gold leaching agent and a technology for extracting gold in electronic waste through the environment-friendly cyanide-free gold leaching agent, and belongs to the technical field of hydrometallurgy. A series of environment-friendly cyanide-free gold leaching agents are prepared by designing the environment-friendly cyanide-free gold leaching agents, using non-toxic and renewable biomass resources as raw materials, optimizing the molecular structure level of the raw materials through a series of derivatization means and introducing specific functionalized molecular groups. The problem that an existing cyanide-free leaching agent is difficult to treat electronic waste is solved. On the premise that technology feasibility is met, balance of economy and environment is achieved to the maximum extent, the gold leaching technological process is simple, operation is convenient, the gold leaching technological process conforms to original facilities of existing enterprises, and extra equipment upgrading cost does not need to be input.

Description

Technical Field

[0001] The invention relates to the technical field of hydrometallurgy, and in particular to an environmentally friendly cyanide-free gold leaching agent and a process for extracting gold from electronic waste. Background Art

[0002] Gold is not a currency by nature, but currency is gold by nature. As a precious metal, gold has the ability to regulate national economic issues. It can be seen that the amount of gold reserves plays a ballast role in the stability of the national economy. In recent years, with the enhancement of gold's hedging function and cash conversion, value preservation and appreciation characteristics, the value of gold has become more and more obvious.

[0003] Electronic waste is rich in precious metals, such as gold, silver, palladium and other precious metals. The gold content in electronic waste is higher than that in ore resources. According to statistics, when producing the same quality of gold, the process cost of extracting gold from electronic waste is only 1 / 7 of the traditional mining cost. It is worth mentioning that 1 / 10 of the world's gold consumption can be met by extracting gold from electronic waste. It is estimated that the final profit of China's electronic waste treatment companies for recycling metals from 1 ton of electronic waste is about 1.56×10 5 ~1.75×10 5 The economic value of electronic waste is immeasurable.

[0004] However, the existing gold extraction process often uses the cyanide gold extraction process. Since cyanide is a highly toxic chemical and there are safety uncertainties during its use, the cyanide gold extraction process needs to take into account environmental and social factors while considering economic feasibility when processing electronic waste. For example, unlike the mining and metallurgical operating environment in remote areas, electronic waste processing companies are usually built in the suburbs of cities in order to reduce transportation costs. In most countries, the use of cyanide in urban areas is prohibited.

[0005] At present, there are many gold extraction processes that do not use cyanide, including thiosulfate method, halogen method, thiourea method, glycine method, lime sulfur method, etc. While achieving environmental protection and cyanide-free, there are still certain limitations.

[0006] In the prior art, the patent with publication number CN119307734A provides an environmentally friendly gold leaching agent and its application method, which is a mixture of halogen acid salt, thiosulfate and a strengthening agent. The application method of the environmentally friendly gold leaching agent includes the following steps: crushing and grinding the gold ore, adjusting the slurry concentration to 30%-50%, then adding 0.2wt%-5wt% of the gold leaching agent, adjusting the slurry pH to 6-12, and stirring and leaching for 8-36 hours at normal temperature and pressure. The environmentally friendly gold leaching agent provided by the invention is a mixture of common chemical reagents, and the method is simple, the gold leaching rate is high, the reagent stability is high, and gold leaching can be achieved under neutral to alkaline conditions. However, in the process of gold leaching, if there is a large amount of impurity metal in the raw material, a series of complex reactions will occur with the byproducts after the decomposition of thiosulfate, which will interfere with the leaching of gold. The patent with publication number CN110484724A provides a gold leaching agent and a gold leaching method based on ionic liquids. The gold leaching agent based on ionic liquids is prepared by mixing 1-methyl-3-(4-diacetoxyiodobenzyl)imidazolium tetrafluoroborate, ionic liquid and water in a molar ratio of 1:1-20:20-140, and the ionic liquid is an ionic liquid containing halogen anions or dinitrile amide ions. The invention provides a gold leaching method based on ionic liquids, and the gold leaching method comprises: 1) preparing the gold leaching agent based on ionic liquids; 2) adding a sample containing precious metals to the gold leaching agent obtained in step 1), and stirring the precious metals sufficiently to leach the precious metals. During the gold leaching process, this method will also react with other impurity metals, and cannot achieve selective leaching of gold. Summary of the invention

[0007] In view of the technical problems existing in the background technology, the present application provides an environmentally friendly cyanide-free gold leaching agent and a process for extracting gold from electronic waste, aiming to solve the problem that existing gold leaching agents cannot selectively leach gold from electronic waste.

[0008] In the first aspect, the present application provides an environmentally friendly cyanide-free gold leaching agent, wherein the environmentally friendly cyanide-free gold leaching agent comprises at least one of B-1, B-2, B-3, and B-4, wherein the structural formula of B-1 is ; The structural formula of B-2 is ; The structural formula of B-3 is ; The structural formula of B-4 is .

[0009] In the technical solution of the embodiment of the present application, an environmentally friendly cyanide-free gold leaching agent is designed, non-toxic and renewable biomass resources are used as raw materials, the molecular structure is optimized through a series of derivatization methods, and specific functionalized molecular groups are introduced to prepare a series of environmentally friendly cyanide-free gold leaching agents. The problem that existing cyanide-free leaching agents are difficult to selectively leach gold from electronic waste is solved.

[0010] In a second aspect, the present application provides a process for extracting gold from electronic waste using an environmentally friendly cyanide-free gold leaching agent, comprising the following steps: S1. Grind the electronic waste into fine powder; S2. adding water to the finely ground sample and stirring to obtain a slurry of a preset concentration; S3. Add the environmentally friendly cyanide-free gold leaching agent to the ore pulp, adjust the pH value of the ore pulp, stir, and obtain a gold-containing precious liquid and a solid residue.

[0011] In the technical solution of the embodiment of the present application, a process for extracting gold from electronic waste is designed by using the prepared gold leaching agent, and the gold leaching agent prepared above is used to extract gold from electronic waste. The gold leaching process is simple and easy to operate, conforms to the original facilities of existing enterprises, and does not require additional investment in equipment upgrade costs.

[0012] In some embodiments, in step S1, the electronic waste includes at least one of discarded circuit boards, integrated chips and discarded electrodes.

[0013] In this embodiment, the prepared gold leaching agent can selectively leach gold from electronic waste containing mixed metals such as discarded circuit boards, integrated chips and discarded electrodes.

[0014] In some embodiments, in step S1, the fineness of the fine grinding is less than 100 mesh and the content is 88.0-92.0%.

[0015] In this embodiment, the electronic waste is finely ground to a specific fineness to facilitate subsequent gold leaching.

[0016] In some embodiments, in step S2, the mass concentration of the slurry is 20%~30%; the mass concentration of the environmentally friendly cyanide-free gold leaching agent in the slurry is 20~60g / L.

[0017] In this embodiment, a certain amount of gold leaching agent is added to the ore pulp of a specific concentration, so that the gold in the ore pulp can be leached out with a better effect.

[0018] In some embodiments, in step S3, the pH value of the slurry is adjusted by adding a pH adjuster; the pH adjuster is sodium hydroxide; and the pH value is adjusted to 8-14.

[0019] In this embodiment, by adjusting the pH value of the gold immersion system to alkaline, the activation sites of the functional groups of the agent are released, thereby achieving efficient chelation with gold ions.

[0020] In some embodiments, in step S3, the stirring temperature is 25-60° C.; and the stirring time is 7-8 h.

[0021] In this embodiment, by stirring the gold leaching system at a specific temperature for a certain period of time, the reagent can fully react with the gold to obtain a higher gold leaching rate.

[0022] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 Schematic diagram of the structure of each gold leaching agent in the embodiments of the present application; Figure 2 Schematic diagram of the reaction formula of each gold leaching agent in the examples of this application; Figure 3 This is the nuclear magnetic resonance hydrogen spectrum of the gold leaching agent B-1 in the example of this application. DETAILED DESCRIPTION

[0025] The following is a detailed description of the embodiments of the technical solution of the present application. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0026] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0027] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0028] In order to solve the problem that existing cyanide-free leaching agents are difficult to selectively leach gold from electronic waste, the present application provides an environmentally friendly cyanide-free gold leaching agent and a process for extracting gold from electronic waste. By designing an environmentally friendly cyanide-free gold leaching agent, using non-toxic and renewable biomass resources as raw materials, optimizing the molecular structure through a series of derivatization methods, introducing specific functionalized molecular groups, and preparing a series of environmentally friendly cyanide-free gold leaching agents. First, the agent molecule has a unique aliphatic molecular skeleton structure. The imino and carboxyl groups in the molecular skeleton give the agent significant hydrophilicity, which is suitable for mass transfer reactions in polar environments, and provides a basis for the agent to leach the target metal. In addition, the core functional group in the agent molecule obtained after the raw material derivatization reaction is connected by two sulfur atoms (S) and an imino group (-NH) through carbon atoms to form a "semi-thiourea" structural fragment. The "semi-thiourea" fragment plays a key role in this molecule. The electronegativity of the sulfur atom in the (C=S) of the "semi-thiourea" structural fragment is low, resulting in the polarity of the thiocarbonyl group (C=S) being significantly weaker than that of the carbonyl group (C=O), which is conducive to the activation of (-CS-). The lone pair of electrons on the sulfur ion in (-CS-) has a higher ability to form coordination bonds with metal ions than the sulfur ions in traditional agents, which ultimately leads to the sulfur atom having a very high affinity for the soft acid metal Au. Therefore, the "semi-thiourea" fragment can effectively chelate the gold ions. The synergistic effect of the carboxyl group and the "semi-thiourea" structural fragment further enhances the selective binding ability of the molecule to the target metal ions. This synergistic effect reduces the nonspecific binding with non-target impurity ions, effectively avoids the interference of impurities, and realizes the selective chelation of the agent to the target metal. This gold leaching agent solves the problem that existing cyanide-free leaching agents are difficult to treat electronic waste.

[0029] In the first aspect, the present application provides an environmentally friendly cyanide-free gold leaching agent, wherein the environmentally friendly cyanide-free gold leaching agent comprises at least one of B-1, B-2, B-3, and B-4, wherein the structural formula of B-1 is ; The structural formula of B-2 is ; The structural formula of B-3 is ; The structural formula of B-4 is .

[0030] In the technical solution of the embodiment of the present application, an environmentally friendly cyanide-free gold leaching agent is designed, non-toxic and renewable biomass resources are used as raw materials, the molecular structure is optimized through a series of derivatization methods, and specific functionalized molecular groups are introduced to prepare a series of environmentally friendly cyanide-free gold leaching agents. The problem that existing cyanide-free leaching agents are difficult to selectively leach gold from electronic waste is solved.

[0031] In a second aspect, the present application provides a process for extracting gold from electronic waste using an environmentally friendly cyanide-free gold leaching agent, comprising the following steps: S1. Grind the electronic waste into fine powder; S2. adding water to the finely ground sample and stirring to obtain a slurry of a preset concentration; S3. Add the environmentally friendly cyanide-free gold leaching agent to the ore pulp, adjust the pH value of the ore pulp, stir, and obtain a gold-containing precious liquid and a solid residue.

[0032] In the technical solution of the embodiment of the present application, a process for extracting gold from electronic waste is designed by using the prepared gold leaching agent, and the gold leaching agent prepared above is used to extract gold from electronic waste. The gold leaching process is simple and easy to operate, conforms to the original facilities of existing enterprises, and does not require additional investment in equipment upgrade costs.

[0033] Furthermore, in some embodiments, in step S1, the electronic waste includes at least one of discarded circuit boards, integrated chips and discarded electrodes.

[0034] In the technical solution of the embodiment of the present application, the prepared gold leaching agent can selectively leach gold from electronic waste containing mixed metals such as discarded circuit boards, integrated chips and discarded electrodes.

[0035] Furthermore, in some embodiments, in step S1, the fineness of the fine grinding is less than 100 mesh and the content is 88.0-92.0%.

[0036] In the technical solution of the embodiment of the present application, the electronic waste is finely ground to a specific fineness to facilitate subsequent gold leaching.

[0037] Furthermore, in some embodiments, in step S2, the mass concentration of the slurry is 20% to 30%; the mass concentration of the environmentally friendly cyanide-free gold leaching agent in the slurry is 20 to 60 g / L.

[0038] In the technical solution of the embodiment of the present application, a certain amount of gold leaching agent is added to the ore pulp of a specific concentration, so that the gold in the ore pulp can be leached better.

[0039] Furthermore, in some embodiments, in step S3, the pH value of the slurry is adjusted by adding a pH adjuster; the pH adjuster is sodium hydroxide; and the pH value is adjusted to 8-14.

[0040] In the technical solution of the embodiment of the present application, by adjusting the pH value of the gold immersion system to alkaline, the activation sites of the functional groups of the agent are released, thereby achieving efficient chelation with gold ions.

[0041] Furthermore, in some embodiments, in step S3, the stirring temperature is 25-60° C.; and the stirring time is 7-8 h.

[0042] In the technical solution of the embodiment of the present application, by stirring the gold leaching system at a specific temperature for a certain period of time, the reagent can fully react with the gold to obtain a higher gold leaching rate.

[0043] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be obtained commercially.

[0044] Embodiment 1~4 Examples 1 to 4 respectively provide an environmentally friendly cyanide-free gold leaching agent and a process for extracting gold from electronic waste. The environmentally friendly gold leaching agents are B-1, B-2, B-3 and B-4, respectively. The specific structural formula is as follows: Figure 1 shown.

[0045] The preparation method of gold leaching agent B-1 is as follows: add 1 mol of glycine to 1L of sodium hydroxide solution with a mass concentration of 80g / L, then add 1.5 mol of carbon sulfide, stir evenly, and then heat to reflux at 40°C, react for 24 hours, and after the reaction is completed, distill the solution under reduced pressure to remove excess carbon sulfide to obtain gold leaching agent B-1 containing sodium hydroxide.

[0046] The raw materials used in gold leaching agents B-2, B-3 and B-4 are cysteine, proline and glutathione respectively. The specific preparation methods are similar to those of B-1 and will not be described in detail here. The specific reaction formulas of B-1, B-2, B-3 and B-4 are as follows: Figure 2 shown.

[0047] The nuclear magnetic resonance hydrogen spectrum of gold leaching agent B-1 is as follows Figure 3 As shown. Figure 3 It can be seen that the molecular composition of the substances in the solution changed before and after the reaction, and glycine was converted into a glycine derivative, namely B-1.

[0048] The gold leaching agents B-1, B-2, B-3 and B-4 prepared above are used to extract gold from electronic waste, which specifically includes the following steps: (1) Grind the waste circuit boards to a particle size of less than 100 mesh and a content of 90%; (2) Add water to the finely ground sample and stir to obtain a slurry with a concentration of 25%; (3) Add the gold leaching agents B-1, B-2, B-3 and B-4 prepared above at a mass concentration of 50 g / L to the slurry, respectively, then add sodium hydroxide to adjust the pH of the slurry to 10, and stir at 30°C for 8 hours to obtain a precious gold solution and a solid residue.

[0049] The sources and performance parameters of raw materials are as follows: Waste circuit boards containing precious metal resources after processing low-value metals (copper, lead, zinc, tin, nickel, etc.) are selected. The main components of the waste circuit boards are shown in Table 1.

[0050] Table 1 Main components of precious metals in waste circuit boards The content of each precious metal in the solid residues in Examples 1 to 4 was tested by fire assay method. The test and analysis method was based on GB / T 7739 "Chemical Analysis Methods for Gold Concentrates". The leaching rate η of each precious metal is Among them, η represents the leaching rate of each precious metal, in units of %; m1 represents the mass of the original material, in units of g; β1 represents the grade of the original material, in units of g / t; m2 represents the mass of the solid residue after leaching, in units of g; β2 represents the grade of the solid residue after leaching, in units of g / t.

[0051] The concentration of each precious metal in the gold-containing precious solution in Examples 1 to 4 was then tested by ICP-OES; the test results of the two methods were compared, and when the deviation of the test results of the two methods was less than 1%, it was considered valid data. The leaching rates of each precious metal in Examples 1 to 4 were finally measured as shown in Table 2.

[0052] Table 2 Leaching rate of precious metals from waste circuit boards in Examples 1 to 4 It can be seen from the leaching rates of the precious metals in Examples 1 to 4 that the four gold leaching agents all have a high leaching rate for gold in the waste circuit boards and have a selective leaching effect on gold.

[0053] Examples 5-6 and Comparative Examples 1-2 Examples 5-6 and Comparative Examples 1-2 respectively provide a process for extracting gold from electronic waste using an environmentally friendly cyanide-free gold leaching agent. Compared with Example 1, the difference is that the concentration of the gold leaching agent in step (3) is different. The concentrations of the gold leaching agents corresponding to the embodiments and comparative examples are shown in Table 3. The other steps are substantially the same as those in Example 1 and are not described in detail here.

[0054] Table 3 Concentration of gold leaching agent in Examples 5-6 and Comparative Examples 1-2 The leaching rates of gold in Examples 5-6 and Comparative Examples 1-2 were analyzed according to the method in Example 1, and the results are shown in Table 4.

[0055] Table 4 Gold leaching rate in Examples 5-6 and Comparative Examples 1-2 It can be seen from the leaching rate of gold in Examples 5-6 and Comparative Examples 1-2 that a suitable environmentally friendly non-cyanide gold leaching agent concentration can achieve efficient leaching of gold in electronic waste. When the agent concentration is 20g / L, the gold leaching rate is 90%. Taking this as the dividing point, when the agent concentration is less than 20g / L, the gold leaching effect is difficult to achieve high efficiency. With the increase of the agent concentration, when the agent concentration reaches 60g / L, a stable point appears, at which the gold leaching rate is 98%. Subsequently, the gold leaching rate is no longer affected by the continued increase in the agent concentration. Considering factors such as actual on-site operation and economic perspectives, it is more reasonable when the agent concentration is in the range of 20-60g / L, and the gold leaching rate is ≥90%.

[0056] Examples 7-8 and Comparative Example 3 Examples 7-8 and Comparative Example 3 respectively provide a process for extracting gold from electronic waste using an environmentally friendly cyanide-free gold leaching agent. Compared with Example 1, the difference lies in the different pH values ​​in step (3). The pH values ​​corresponding to the examples and comparative examples are shown in Table 5. The other steps are substantially the same as those in Example 1 and will not be described in detail herein.

[0057] Table 5 pH values ​​in Examples 7-8 and Comparative Example 3 The leaching rates of gold in Examples 7-8 and Comparative Example 3 were analyzed according to the method in Example 1, and the results are shown in Table 6.

[0058] Table 6 Gold leaching rate in Examples 7-8 and Comparative Example 3 It can be seen from the gold leaching rates in Examples 7 to 8 and Comparative Example 3 that a suitable pulp pH is a prerequisite for achieving efficient leaching of gold from electronic waste. Under neutral acidic conditions, the agent cannot exist in the solution system in anionic form, and the functional group activation sites are protonated and cannot chelate with gold ions. Only under alkaline conditions are the activation sites of the agent functional groups released and efficiently chelate with gold ions. In addition, under strong alkaline conditions (pH ≥ 12), the leaching rate of gold is not affected, and the side reaction agent can exist stably in a strong alkaline environment.

[0059] In summary, the present application provides an environmentally friendly cyanide-free gold leaching agent and a process for extracting gold from electronic waste. By designing an environmentally friendly cyanide-free gold leaching agent, using non-toxic and renewable biomass resources as raw materials, optimizing the molecular structure through a series of derivatization methods, introducing specific functionalized molecular groups, and preparing a series of environmentally friendly cyanide-free gold leaching agents. This is to solve the problem that existing cyanide-free leaching agents are difficult to handle electronic waste. Under the premise of meeting technical feasibility, the balance between economy and environment is achieved to the greatest extent, and the gold leaching process is simple, easy to operate, and in line with the existing facilities of existing enterprises, without the need for additional investment in equipment upgrade costs.

[0060] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. An environmentally friendly cyanide-free gold leaching agent, characterized in that: The environmentally friendly cyanide-free gold leaching agent includes at least one of B-1, B-2, B-3, and B-4, wherein the structural formula of B-1 is ; The structural formula of B-2 is ; The structural formula of B-3 is ; The structural formula of B-4 is .

2. A process for extracting gold from electronic waste using an environmentally friendly cyanide-free gold leaching agent, wherein the environmentally friendly cyanide-free gold leaching agent described in claim 1 is used for gold leaching, characterized in that: The steps include: S1. Grind the electronic waste into fine powder; S2. adding water to the finely ground sample and stirring to obtain a slurry of a preset concentration; S3. Add the environmentally friendly cyanide-free gold leaching agent to the ore pulp, adjust the pH value of the ore pulp, stir, and obtain a gold-containing precious liquid and a solid residue.

3. The process for extracting gold from electronic waste using an environmentally friendly cyanide-free gold leaching agent according to claim 2, characterized in that: In step S1, the electronic waste includes at least one of discarded circuit boards, integrated chips and discarded electrodes.

4. The process for extracting gold from electronic waste using an environmentally friendly cyanide-free gold leaching agent according to claim 2 is characterized in that: In step S1, the fineness of the fine grinding is less than 100 mesh and the content is 88.0-92.0%.

5. The process for extracting gold from electronic waste using an environmentally friendly cyanide-free gold leaching agent according to claim 2 is characterized in that: In step S2, the mass concentration of the slurry is 20% to 30%.

6. The process for extracting gold from electronic waste using an environmentally friendly cyanide-free gold leaching agent according to claim 2 is characterized in that: In step S3, the mass concentration of the environmentally friendly cyanide-free gold leaching agent in the ore pulp is 20-60 g / L.

7. The process for extracting gold from electronic waste using an environmentally friendly cyanide-free gold leaching agent according to claim 2, characterized in that: In step S3, the pH value of the slurry is adjusted by adding a pH adjuster; the pH adjuster is sodium hydroxide.

8. The process for extracting gold from electronic waste using an environmentally friendly cyanide-free gold leaching agent according to claim 2, characterized in that: In step S3, the pH value is adjusted to 8-14.

9. The process for extracting gold from electronic waste using an environmentally friendly cyanide-free gold leaching agent according to claim 2, characterized in that: In step S3, the stirring temperature is 25-60°C.

10. The process for extracting gold from electronic waste using an environmentally friendly cyanide-free gold leaching agent according to claim 2, characterized in that: In step S3, the stirring time is 7 to 8 hours.

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