Biological extraction agent and method for extracting gold from cyanide wastewater

Abstract

The present application provides a biological extraction agent and a method for extracting gold from cyanide wastewater, belonging to the field of wastewater purification. Among them, the extraction agent uses histidine as a raw material, and a thioester group is introduced into the main chain of the histidine molecule through a chemical reaction. Utilizing the dissociation characteristics of the mercapto group under alkaline conditions, it combines with gold ions to form a stable polycyclic gold chelate. The special structure of the side chain of the imidazole ring helps the reaction occur and masks other metal ions, ensuring the selective chelation of gold ions. The biological extraction agent provided by the present application can effectively extract gold from cyanide wastewater, and through the reverse extraction process, achieve the gradient recovery of gold and other metal ions, avoiding the influence of impurity ions on the gold extraction effect. By regulating the types, quantities, and molecular structures of functional groups, the present application ensures the efficient chelation of the activation sites of the extraction agent molecules with gold ions, realizing the efficient and selective extraction of low-concentration gold in cyanide-containing wastewater.

Description

Technical Field

[0001] The present invention relates to the technical field of purifying precious metals in cyanide wastewater, and particularly relates to a biological extraction agent and a method for extracting gold from cyanide wastewater using the same. Background Art

[0002] Gold mining has a severely adverse impact on the environment. In particular, cyanide and mercury used in the process of gold extraction generate a large amount of low-concentration gold-containing cyanide wastewater. Currently, common processes for treating such wastewater include electrolysis and extraction. Since there are many types and large amounts of impurity metal ions in low-concentration cyanide-containing gold waste liquid, existing extraction agents are difficult to achieve selective extraction of gold. In actual operation, high-concentration extraction agents often need to be used, which not only extract all metal ions indiscriminately but may also cause the extraction agent to preferentially combine with impurity metal ions to form chelates, thus interfering with the extraction of gold and reducing the extraction efficiency of gold.

[0003] The development difficulty of gold extraction agents lies in achieving both efficient extraction of low-concentration target metal ions and selective extraction of the target ion (gold), while minimizing the co-extraction of other metal ions as much as possible. Currently, research and related technologies in this field are in the development stage. For example, the team of Nobel laureate J. Fraser Stoddart at Northwestern University in the United States proposed an additive-induced gold recovery method based on precisely controlling the mutual transformation and instantaneous assembly of the second-sphere coordination adduct formed between β-cyclodextrin and tetrabromoaurate anions. The additive co-occupies the binding cavity of β-cyclodextrin with tetrabromoaurate anions, triggering a rapid assembly process to form a supramolecular polymer, which precipitates from the aqueous solution in the form of a co-crystal. When dibutyl carbitol is used as the additive, the gold recovery rate can reach 99.8%. This co-crystallization has a high selectivity for square-planar tetrabromoaurate anions and can achieve a gold recovery of over 94% from electronic waste with a gold concentration as low as 9.3 ppm. However, this technology mainly targets tetrabromoaurate anions and is difficult to apply to cyanide-containing gold wastewater, which accounts for the majority of industrial gold-containing wastewater. It requires complex pretreatment processes to convert gold cyanide complexes into tetrabromoaurate anions, which increases the costs and environmental protection expenditures of enterprises.

[0004] In view of this, it is necessary to design a biological extraction agent and a method for extracting gold from cyanide wastewater to solve the above problems. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present application provides a biological extraction agent and a method for extracting gold from cyanide wastewater, aiming to solve the technical problems of poor selectivity of existing extraction agents and difficulty in efficiently treating low-concentration gold-containing waste liquid.

[0006] In a first aspect, the present application provides a biological extraction agent, and the structural formula of the biological extraction agent is as follows:

[0007] .

[0008] In a second aspect, the present application provides a method for extracting gold from cyanide wastewater using the biological extraction agent described in the first aspect. The extraction is carried out using the biological extraction agent, and the method includes the following steps:

[0009] S1. Mix and dissolve the biological extraction agent with a diluent to obtain an extraction agent dilution solution;

[0010] S2. Adjust the pH value of the cyanide wastewater containing gold to 9 - 12, and then add the extraction agent dilution solution to achieve selective extraction of gold in the solution.

[0011] As a further improvement of the present application, the diluent is sulfonated kerosene.

[0012] As a further improvement of the present application, the volume ratio of the biological extraction agent to the sulfonated kerosene is 1:(10 - 100).

[0013] As a further improvement of the present application, in the cyanide wastewater containing gold, gold exists in the form of Au(CN)4 - .

[0014] As a further improvement of the present application, in the cyanide wastewater containing gold, the concentration of cyanide is 0.01 g / L - 1 g / L.

[0015] As a further improvement of the present application, the cyanide wastewater containing gold includes one or more of low - concentration gold - containing cyanide waste liquid remaining after activated carbon adsorption of cyanidation gold extraction solution, cyanidation leaching waste liquid of gold / palladium catalyst, and cyanidation leaching waste liquid of pyrometallurgical dust.

[0016] The beneficial effects of the present application are as follows:

[0017] The present application provides a biological extraction agent and a method for extracting gold from cyanide wastewater. The extraction agent uses histidine as a raw material. The amine group in the main chain of the histidine molecule can be derivatized into a full - sulfur thioester group through a series of chemical reactions. The mercapto group can dissociate into S under alkaline conditions -, which is conducive to bonding with gold ions. Under alkaline conditions, the carboxyl groups in the main chain of the molecule cooperate with the sulfhydryl groups in the functionalized functional groups after amine group derivatization to chelate gold ions. The lone pair electrons on the nitrogen atom in the amine group can stably form polycyclic gold chelates, increasing the stability of the final chelation product. In addition, for the specific imidazole ring in the side chain segment, compared with 1,3-imidazole, the electron cloud density of the N atom at the 3rd position on the imidazole ring (IUPAC nomenclature) is relatively large, so it is conducive to the occurrence of the reaction and can also form all-thioester groups. The high-density functionalized functional groups in the extractant can achieve the purpose of efficiently extracting and purifying gold in cyanide-containing wastewater.

[0018] On the basis of achieving efficient gold extraction, the all-thioester groups derived from the N atom at the 3rd position on the imidazole ring can mask other metal ions in the solution to the greatest extent, ensuring that the all-thioester groups and carboxyl groups in the main chain chelate with gold ions. Through subsequent back-extraction procedures, gradient recovery of impurity metal ions and gold ions can be achieved, ultimately avoiding the influence of impurity ions on the gold extraction effect of the extractant.

[0019] By designing the types and quantities of derivatized functional groups, changing the main chain structure of the molecule and its steric hindrance regulation, the activation sites of the extractant molecules are ensured to efficiently chelate with gold ions, achieving efficient and selective extraction of low-concentration gold in cyanide-containing wastewater and achieving the purpose of extracting gold from cyanide-containing wastewater.

[0020] The above description is only an overview of the technical solution of this application. In order to be able to more clearly understand the technical means of this application, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of this application more obvious and understandable, the following specifically gives the specific implementation manners of this application. Brief Description of the Drawings

[0021] In order to more clearly illustrate the technical solution of this application, the drawings used in this application will be briefly introduced below. Obviously, the following described drawings are only some embodiments of this application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0022] Figure 1 It is the action mechanism of the biological extractant provided in the embodiment of this application and gold;

[0023] Figure 2 It is the synthesis route diagram of the biological extractant in Example 16 of this application;

[0024] Figure 3 It is the physical diagram of the biological extractant in Example 16 of this application;

[0025] Figure 4This is the nuclear magnetic resonance hydrogen spectrum of the biological extraction agent in Example 16 of this application. Detailed implementation manners

[0026] The embodiments of the technical solutions of this application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solutions of this application more clearly, so they are only examples and cannot be used to limit the protection scope of this application.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the description and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0028] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, "a plurality of" means more than two unless otherwise specifically defined.

[0029] Referring to "embodiment" herein means that the specific features, structures or characteristics described in connection with the embodiment may be included in at least one embodiment of this application. The phrase appears in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0030] Currently, the extraction agents used in the field of treating low-concentration gold-containing cyanide wastewater have certain limitations: poor selectivity, making it difficult to achieve selective extraction of target metal ions (gold) in wastewater with coexisting multiple metals; existing extraction agents are difficult to efficiently treat low-concentration gold-containing waste liquid.

[0031] To solve the technical problems of poor selectivity and unsatisfactory treatment effect of existing extraction agents for treating low-concentration gold-containing waste liquid, this application provides a biological extraction agent and a method for extracting gold from cyanide wastewater. Among them, through the design of the molecular structure of the extraction agent, the efficient chelation of the activation sites of the extraction agent molecules with gold ions is ensured, realizing the efficient selective extraction of low-concentration gold in cyanide-containing wastewater.

[0032] In the first aspect, the embodiments of this application provide a biological extraction agent, and its structural formula is as follows:

[0033] 。

[0034] In the technical solution of the embodiment of the present application, the extractant uses renewable biological resource histidine as the raw material, and a thioester group is introduced into the main chain of the histidine molecule through a chemical reaction. Under alkaline conditions, the mercapto group dissociates into S - , which helps to combine with gold ions. The functional groups derivatized from carboxyl groups and amino groups act synergistically to form a stable polycyclic gold chelate. The specific imidazole ring in the side chain segment improves the reaction efficiency and helps to mask other metal ions. The biomass extractant provided by the present application can effectively extract gold in cyanide wastewater and achieve gradient recovery of gold and other metal ions through a back-extraction process, avoiding the influence of impurity ions on the gold extraction effect.

[0035] Secondly, the embodiment of the present application provides a method for extracting gold from cyanide wastewater using a biological extractant. The extraction is carried out using the biological extractant described in the first aspect, and the method includes the following steps:

[0036] S1. Mix and dissolve the biological extractant with a diluent to obtain an extractant diluent;

[0037] S2. Adjust the pH value of the cyanide wastewater containing gold to 9-12, and then add the extractant diluent to achieve selective extraction of gold in the solution.

[0038] In the technical solution of the embodiment of the present application, by using a specific biological extractant, gold ions can be efficiently and selectively extracted from cyanide wastewater coexisting with multiple metal ions. The biological extractant based on histidine is derived from renewable biological resources and has less impact on the environment compared to traditional chemical extractants. By introducing a thioester group into the main chain of the histidine molecule, the formed polycyclic gold chelate has high stability, which is beneficial to the subsequent separation and recovery process. Specifically, by using sodium hydroxide to adjust the pH value of the cyanide wastewater containing gold to an alkaline environment of 9-12, adding the extractant diluent to the wastewater, and oscillating in a water bath at 25-28 °C for 5-20 min, the extraction efficiency is improved. After the extraction is completed, the organic phase is separated, and the concentration of gold in the inorganic liquid phase is detected and the extraction rate is calculated.

[0039] Further, in some embodiments, the diluent is sulfonated kerosene.

[0040] In the technical solution of the embodiment of the present application, sulfonated kerosene has good compatibility with the biological extractant, can be effectively mixed and dissolved to form a stable extractant diluent. The density of sulfonated kerosene is different from that of cyanide wastewater containing gold, which helps to form two-phase separation during the extraction process, facilitating the subsequent recovery of gold ions. At the same time, sulfonated kerosene has high chemical stability and will not react adversely with the components in cyanide wastewater, ensuring the stability of the extraction process.

[0041] Further, in some embodiments, the volume ratio of the biological extraction agent to sulfonated kerosene is 1:(10 - 100).

[0042] In the technical solution of the embodiment of the present application, an appropriate volume ratio can ensure that the biological extraction agent reaches the optimal concentration in sulfonated kerosene, thereby improving the extraction efficiency. If the concentration of the extraction agent is too low, it may not be able to effectively complex the metal ions; if the concentration is too high, the cost may increase.

[0043] Further, in some embodiments, in the cyanide-containing wastewater containing gold, gold exists in the form of Au(CN)4 - form.

[0044] In the technical solution of the embodiment of the present application, when treating the cyanide-containing wastewater containing gold, gold exists in the form of Au(CN)4 - (tetracyanoaurate) in the solution. This form of gold complex is formed during the cyanidation process because gold reacts with cyanide ions (CN - ) to form a stable complex, and the biological extraction agent provided by the present application can effectively react with Au(CN)4 - to form a complex that can be extracted into the organic phase.

[0045] Further, in some embodiments, in the cyanide-containing wastewater containing gold, the concentration of cyanide is 0.01 g / L - 1 g / L.

[0046] In the technical solution of the embodiment of the present application, the biological extraction agent can effectively extract gold from the cyanide-containing wastewater containing gold with a cyanide concentration of 0.01 g / L - 1 g / L, and can extract gold at a relatively low cost, improving the economy of the treatment process.

[0047] Further, in some embodiments, the cyanide-containing wastewater containing gold includes one or more of the low-concentration gold-containing cyanide waste liquid remaining after the activated carbon adsorption of the cyanidation gold extraction solution, the cyanide leaching waste liquid of gold / palladium catalyst, and the cyanide leaching waste liquid of pyrometallurgical dust.

[0048] In the technical solution of the embodiment of the present application, the biological extraction agent can treat low-concentration gold-containing cyanide waste liquid from different sources. The extraction agent has high selectivity for gold ions and can effectively separate and extract gold in the waste liquid containing other metal ions and impurities.

[0049] The following lists some specific embodiments. 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 a limitation to the present application. For those embodiments where specific technologies or conditions are not indicated, the technologies or conditions described in the literature in the art or according to the product specifications are followed. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0050] Example 1

[0051] This example provides a method for extracting gold from cyanide wastewater using a biologically produced extractant. The structural formula of the biologically produced extractant is as follows:

[0052] , and specifically includes the following steps:

[0053] S1. Mix the biologically produced extractant and sulfonated kerosene at a volume ratio of 1:10, and ultrasonically dissolve to obtain a diluted extractant solution;

[0054] S2. Adjust the pH value of the cyanide solution containing 100 ppm of gold to 9 with sodium hydroxide. At room temperature, take 10 mL of the diluted extractant solution and add it to 50 mL of the cyanide solution containing gold. After shaking in a water bath oscillator at 25 °C for 5 min, separate the organic phase, and use ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometer) to detect the concentration of gold in the inorganic liquid phase solution, so as to calculate the extraction rate of the biologically produced extractant. Among them, the detection error of ICP-OES is ±2%.

[0055] Examples 2-4 and Comparative Examples 1-5

[0056] Examples 2-4 and Comparative Examples 1-5 respectively provide a method for extracting gold from cyanide wastewater using a biologically produced extractant. Compared with Example 1, the only difference is that the pH value of the cyanide waste liquid containing gold is different. As shown in Table 1, other parameters and conditions are basically the same as those in Example 1, and will not be elaborated here.

[0057]

[0058] As can be seen from Table 1, the biologically produced extractant provided in this application has high extraction ability for gold in cyanide waste liquid containing gold within a specific pH range (9-12), and the extraction effect reaches more than 98%. Its action mechanism is as Figure 1 shown. When the pH value is greater than 12, part of the gold in the liquid phase precipitates and separates from the solution system and cannot be extracted, thus reducing the extraction effect. When the pH value is less than 8, the biologically produced extractant exists in the form of neutral molecules or protons, and the activation sites are not activated, and cannot chelate with gold ions, resulting in the inability to extract gold.

[0059] Examples 5-12

[0060] Examples 5-12 respectively provide a method for purifying and extracting gold from cyanide wastewater using a biologically produced extractant. The biologically produced extractant provided in Example 1 is used to extract and separate gold from a variety of coexisting ion solutions respectively. The specific operation steps are as follows:

[0061] S1. Prepare a series of cyanide blended solutions containing gold and tungsten, molybdenum, iron, and copper with different concentration ratios, adjust the pH value of the cyanide blended solutions to 9, add 10 mL of the diluent of the extractant prepared in Example 1 to 50 mL of each blended solution respectively. After shaking in a water bath at 25°C for 20 min, take the inorganic liquid phase, and detect the concentration of each metal ion in the solution by ICP-OES to calculate the extraction rate.

[0062] S2. Take 10 mL of the extractant extraction solution obtained in step S1, add 50 mL of saturated ammonium chloride solution. After shaking in a water bath at 25°C for 20 min, take the inorganic phase solution, and detect the concentration of copper ions in the solution by ICP-OES to calculate the copper back-extraction rate.

[0063] S3. Take the remaining 10 mL of the extractant in step S2, add 10 mL of hydrazine hydrate, shake for 20 min, collect the precipitated gold mud, dissolve it in 50 mL of aqua regia solution, heat to 80°C, react for 30 min, and detect the concentration of gold ions in the solution by ICP-OES to calculate the gold back-extraction rate.

[0064]

[0065] As can be seen from Table 2, the bio-produced extractant has a selective extraction effect on gold and copper in cyanide wastewater, and does not extract metal ions such as iron, tungsten, and molybdenum, ensuring the subsequent selective separation of gold by the bio-produced extractant. After the processes of extracting copper and gold, a gradient back-extraction process can be selected to achieve the separation of copper and gold. Other types of extractants do not have the above advantages. The main reason is attributed to the unique molecular structure of the bio-produced extractant, resulting in differences in the mechanism of chelating copper and gold, and enabling the effects of efficient extraction of copper and gold and gradient recovery of copper and gold.

[0066] Examples 13 - 15

[0067] Examples 13 - 15 respectively provide a method for extracting gold from cyanide wastewater using a bio-produced extractant. Compared with Example 1, the only difference is the type of cyanide wastewater containing gold, as shown in Table 3. Other parameters and conditions are basically the same as those in Example 1 and will not be elaborated here.

[0068]

[0069] As can be seen from Table 3, for cyanide wastewater containing gold from different sources, the bio-produced extractant provided in this application has high selectivity for gold ions.

[0070] Example 16

[0071] Example 16 provides a synthesis method for preparing the bio-produced extractant in Example 1. The synthesis route diagram is as Figure 2 shown, and specifically includes the following steps:

[0072] Add 1 mol of histidine to 1L of 80g / L sodium hydroxide solution, add 1.5 mol of carbon sulfide, heat to 40°C to reflux, and react for 24 hours. After the reaction is complete, the solution is distilled under reduced pressure to remove excess carbon sulfide. Use dilute hydrochloric acid (V hydrochloric acid: V deionized water = 1:10) to adjust the pH of the residual solution to neutral, and vacuum evaporation is performed in a water bath at 70°C until the liquid is completely evaporated to obtain a clear yellow oily compound such as Figure 3 As shown, the biological extractant has a yield of 87%. The nuclear magnetic resonance hydrogen spectrum of the biological extractant is as follows Figure 4 As shown in the figure, since the biological extractant is unstable under neutral and acidic conditions, sodium hydroxide solution needs to be added to adjust it to alkalinity before analysis can be carried out. As shown in the figure, the peak intensity of the deuterated solvent D2O is much higher than the peak intensity of the biological extractant, indicating that the biological extractant has limited solubility in the aqueous phase under alkaline conditions, which is conducive to avoiding the residue of the extractant in the aqueous phase and causing secondary pollution to the water body. Specifically, the results of the nuclear magnetic resonance test are as follows: 1HNMR (D2O, 400MHZ): δ6.80-7.80 (2H, imidazole ring H), δ2.50~3.50 (2H, -CH2-), δ4.75~5.00 (H, -CH-). The (NH) in the N-containing structural fragment rapidly exchanges with the D of the solvent D2O, and the NH proton may be deuterated (H→D exchange), and the signal is masked by the baseline noise, resulting in the disappearance of the signal.

[0073] 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. A biological extraction agent, characterized in that, The structural formula of the biological extraction agent is as follows: 。 2. A method for extracting gold from cyanide wastewater using a biological extraction agent, which uses the biological extraction agent described in claim 1 for extraction, and is characterized in that, It includes the following steps: S1. Mix and dissolve the biological extraction agent with a diluent to obtain an extraction agent diluent solution; S2. Adjust the pH value of the gold-containing cyanide wastewater to 9 - 12, and then add the extraction agent diluent solution to achieve selective extraction of gold in the solution.

3. The method for extracting gold from cyanide wastewater by using the biological extraction agent according to claim 2, wherein The diluent is sulfonated kerosene.

4. The method for extracting gold from cyanide wastewater by using the biological extraction agent according to claim 3, characterized in that The volume ratio of the biological extraction agent to the sulfonated kerosene is 1:(10 - 100).

5. The method for extracting gold from cyanide wastewater by using the biological extraction agent according to claim 2, wherein, In the cyanide wastewater containing gold, gold exists in the form of Au(CN)4 - form.

6. The method for extracting gold from cyanide wastewater by using the biological extraction agent according to claim 5, characterized in that, In the gold-containing cyanide wastewater, the concentration of cyanide is 0.01 g / L - 1 g / L.

7. The method for extracting gold from cyanide wastewater by using the biological extraction agent according to claim 6, characterized in that The gold-containing cyanide wastewater includes one or more of the low-concentration gold-containing cyanide waste liquid remaining after activated carbon adsorption of the cyanidation gold extraction solution, the cyanidation leaching waste liquid of gold / palladium catalyst, and the cyanidation leaching waste liquid of pyrometallurgical dust.

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