Biological extraction agent and method for extracting gold in cyanidation wastewater by using biological extraction agent

Abstract

The invention provides a biological extraction agent and a method for extracting gold in cyaniding waste water, and belongs to the field of waste water purification. Histidine is used as a raw material, a total sulfur ester group is introduced into a histidine molecule main chain through a chemical reaction, the total sulfur ester group is combined with gold ions through the dissociation characteristic of sulfydryl under the alkaline condition, and the total sulfur ester group is separated from the total sulfur ester group. The stable multi-element annular gold chelate is formed. The special structure of the imidazole ring side chain is beneficial to the reaction, other metal ions are masked, and selective chelation of gold ions is ensured. The biomass extraction agent provided by the invention can effectively extract gold in cyaniding wastewater, gradient recovery of gold and other metal ions is realized through a reverse extraction process, and the influence of impurity ions on the gold extraction effect is avoided. By regulating and controlling the types, the number and the molecular structures of the functional groups, efficient chelation of activation sites of molecules of the extraction agent and gold ions is guaranteed, and efficient selective extraction of low-concentration gold in the cyanide-containing wastewater is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of precious metal purification in cyanide wastewater, and in particular to a biological extractant and a method for extracting gold in cyanide wastewater. Background Art

[0002] Gold mining has a very serious impact on the environment, especially the cyanide and mercury used in the gold extraction process, which produce a large amount of low-concentration gold-containing cyanide wastewater. At present, the common processes for treating this type of wastewater include electrolysis and extraction. Since there are many types of impure metal ions and their content is large in low-concentration cyanide gold-containing wastewater, it is difficult for existing extractants to achieve selective extraction of gold. In actual operation, high-concentration extractants are often required, which will not only extract all metal ions indiscriminately, but may also cause the extractant to preferentially combine with the impurity metal ions to form chelates, thereby interfering with the extraction of gold and reducing the extraction effect of gold.

[0003] The difficulty in developing gold extractants lies in taking into account the efficient extraction of low-concentration target metal ions while taking into account the selective extraction of target ions (gold) and minimizing the co-extraction of other metal ions. At present, research and related technologies in this field are in the development stage. For example, the team of Nobel Prize winner J. Fraser Stoddart of Northwestern University in the United States proposed an additive-induced gold recovery method. Based on the precise control of the mutual transformation and instantaneous assembly of the second sphere coordination adduct formed between β-cyclodextrin and tetrabromoaurate anion, the additive occupies the binding cavity of β-cyclodextrin together with the tetrabromoaurate anion, triggering a rapid assembly process, thereby forming a supramolecular polymer, which is precipitated from the aqueous solution in the form of a cocrystal. When dibutyl carbitol is used as an additive, the gold recovery rate can reach 99.8%. The cocrystal is highly selective for square planar tetrabromoaurate anions and can achieve more than 94% gold recovery from electronic waste with a gold concentration as low as 9.3ppm. However, this technology mainly targets tetrabromoaurate anion, and is difficult to apply to cyanide gold-containing wastewater, which currently accounts for the majority of industrial gold-containing wastewater. It requires a complex pretreatment process to convert the gold cyanide complex into tetrabromoaurate anion, a process that increases the company's costs and environmental protection expenses.

[0004] In view of this, it is necessary to design a biological extractant 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 technology, the present application provides a biological extractant and a method for extracting gold from cyanide wastewater, aiming to solve the technical problems that the existing extractants have poor selectivity and are difficult to efficiently treat low-concentration gold-containing wastewater.

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

[0007] In the second aspect, the present application provides a method for extracting gold from cyanide wastewater using the biological extraction agent. The extraction is carried out using the biological extraction agent described in the first aspect, and includes the following steps: S1. Mix and dissolve the biological extraction agent with a diluent to obtain an extraction agent diluent; S2. Adjust the pH value of the cyanide wastewater containing gold to 9 - 12, and then add the extraction agent diluent to achieve selective extraction of gold in the solution.

[0008] As a further improvement of the present application, the diluent is sulfonated kerosene.

[0009] As a further improvement of the present application, the volume ratio of the biological extraction agent to the sulfonated kerosene is 1:(10 - 100).

[0010] As a further improvement of the present application, in the cyanide wastewater containing gold, gold exists in the form of Au(CN) 4 - form.

[0011] 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.

[0012] As a further improvement of the present application, the cyanide wastewater containing gold includes one or more of the low - concentration gold - containing cyanide waste liquid remaining after activated carbon adsorption of the cyanide gold extraction solution, the cyanide leaching waste liquid of gold / palladium catalyst, and the cyanide leaching waste liquid of pyrometallurgical flue dust.

[0013] The beneficial effects of the present application are as follows: 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 amino group in the main chain of the histidine molecule can be derivatized into a thioester group through a series of chemical reactions. The mercapto group can dissociate into S - , which is beneficial for bonding with gold ions. Under alkaline conditions, the carboxyl group in the main chain of the molecule, in cooperation with the mercapto group in the functionalized functional group after amine group derivatization, chelates gold ions. The lone pair electrons on the nitrogen atom in the amine group can stably form a polycyclic gold chelate, increasing the stability of the final chelation product. In addition, the specific imidazole ring in the side chain segment, compared with 1,3 - imidazole, has a higher electron cloud density at the 3 - position N atom (IUPAC nomenclature) on the imidazole ring, so it is beneficial for the reaction to occur and can also generate a thioester group. The high - density functionalized functional groups in the extraction agent can achieve the purpose of efficient extraction, purification, and extraction of gold from cyanide wastewater.

[0014] On the basis of achieving efficient extraction of gold, the all-thioester groups derived from the N atom at the 3-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 processes, 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.

[0015] 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 wastewater.

[0016] 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 in accordance with 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 specific embodiments of this application are specifically given. Brief Description of the Drawings

[0017] 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 drawings described below are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 The mechanism of action between the bio-based extractant and gold provided in the embodiment of this application; Figure 2 The synthesis route diagram of the bio-based extractant in Example 16 of this application; Figure 3 The physical diagram of the bio-based extractant in Example 16 of this application; Figure 4 The nuclear magnetic resonance hydrogen spectrum diagram of the bio-based extractant in Example 16 of this application. Detailed Description of the Embodiments

[0019] The embodiments of the technical solution of this application will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solution of this application, so they are only examples and cannot be used to limit the protection scope of this application.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs; the terms used herein are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above description of the drawings are intended to cover non-exclusive inclusion.

[0021] 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, the meaning of "a plurality" is two or more unless otherwise specifically defined.

[0022] Referring to "embodiments" herein means that specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appears in various places 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 will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0023] Currently, the extractants applied 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 co-existing multiple metals; existing extractants are difficult to efficiently treat low-concentration gold-containing waste liquid.

[0024] To solve the technical problems of poor selectivity and unsatisfactory treatment effect of existing extractants for treating low-concentration gold-containing waste liquid, this application provides a biologically prepared extractant and a method for extracting gold from cyanide wastewater. Among them, through the design of the molecular structure of the extractant, the efficient chelation of the activation site of the extractant molecule with gold ions is ensured, realizing the efficient selective extraction of low-concentration gold in cyanide-containing wastewater.

[0025] In a first aspect, an embodiment of this application provides a biologically prepared extractant, the structural formula of which is as follows: .

[0026] In the technical solution of the embodiment of this application, the extractant uses the renewable biological resource histidine as a 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 bind with gold ions. The functional groups derivatized with carboxyl 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 this application can effectively extract gold from cyanide wastewater and achieve the gradient recovery of gold and other metal ions through a back-extraction process, avoiding the influence of impurity ions on the gold extraction effect.

[0027] In a second aspect, an embodiment of this 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 it includes the following steps: S1. Mix and dissolve the biological extractant with a diluent to obtain an extractant diluent. 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.

[0028] In the technical solution of the embodiment of this application, by using a specific biological extractant, gold ions can be efficiently and selectively extracted from cyanide wastewater with multiple metal ions coexisting. 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, the pH value of the cyanide wastewater containing gold is adjusted to an alkaline environment of 9 - 12 with sodium hydroxide, the extractant diluent is added to the wastewater, and it is oscillated in a water bath at 25 - 28 °C for 5 - 20 min to improve the extraction efficiency. After 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.

[0029] Further, in some embodiments, the diluent is sulfonated kerosene.

[0030] In the technical solution of the embodiment of this 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 the 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 the cyanide wastewater, ensuring the stability of the extraction process.

[0031] Further, in some embodiments, the volume ratio of the biological extractant to sulfonated kerosene is 1:(10 - 100).

[0032] 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, it may increase the cost.

[0033] Further, in some embodiments, in the cyanide-containing wastewater containing gold, gold exists in the form of Au(CN) 4 - form.

[0034] In the technical solution of the embodiment of the present application, when treating 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.

[0035] Further, in some embodiments, in the cyanide-containing wastewater containing gold, the concentration of cyanide is 0.01 g / L to 1 g / L.

[0036] In the technical solution of the embodiment of the present application, the biological extraction agent can effectively extract gold from cyanide-containing wastewater containing gold with a cyanide concentration of 0.01 g / L to 1 g / L, and can extract gold at a relatively low cost, improving the economy of the treatment process.

[0037] Further, in some embodiments, the cyanide-containing 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, cyanide leaching waste liquid of gold / palladium catalyst, and cyanide leaching waste liquid of pyrometallurgical dust.

[0038] 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 from waste liquid containing other metal ions and impurities.

[0039] 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 a limitation of the present application. For those without specific technologies or conditions indicated in the embodiments, the technologies or conditions described in the literature in the field or according to the product specifications are followed. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0040] Example 1 This embodiment provides a method for extracting gold from cyanide wastewater using a biological extraction agent. The structural formula of the biological extraction agent is as follows: , and specifically includes the following steps: S1. Mix the biological extraction agent and sulfonated kerosene at a volume ratio of 1:10, and ultrasonically dissolve to obtain an extraction agent dilution solution; S2. Adjust the pH value of the cyanide solution containing 100 ppm gold to 9 with sodium hydroxide. At room temperature, take 10 mL of the extraction agent dilution 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, thereby calculating the extraction rate of the biological extraction agent. Among them, the detection error of ICP-OES is ±2%.

[0041] Examples 2 - 4 and Comparative Examples 1 - 5 Examples 2 - 4 and Comparative Examples 1 - 5 respectively provide a method for extracting gold from cyanide wastewater using a biological extraction agent. 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.

[0042] As can be seen from Table 1, the biological extraction agent 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 over 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 biological extraction agent exists in the form of neutral molecules or protons, and the activation sites are not activated, so it cannot undergo a chelation reaction with gold ions, resulting in the inability to extract gold.

[0043] Examples 5 - 12 Examples 5 - 12 respectively provide a method for purifying and extracting gold from cyanide wastewater using a biological extraction agent. The biological extraction agent provided in Example 1 is used to extract and separate gold from a solution containing multiple coexisting ions. The specific operation steps are as follows: S1. Prepare a series of cyanide co - mixed solutions containing different concentration ratios of gold, tungsten, molybdenum, iron, and copper. Adjust the pH value of the cyanide co - mixed solution to 9. Take 10 mL of the extraction agent dilution solution prepared in Example 1 and add it to 50 mL of the co - mixed solution respectively. After shaking in a water bath at 25 °C for 20 min, take the inorganic liquid phase, and use ICP-OES to detect the concentration of each metal ion in the solution to calculate the extraction rate.

[0044] S2. Take 10 mL of the extractant extract obtained in step S1, add 50 mL of saturated ammonium chloride solution, shake in a water bath at 25 °C for 20 min, then take the inorganic phase solution, and detect the concentration of copper ions in the solution by ICP-OES to calculate the copper reverse extraction rate.

[0045] 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 reverse extraction rate.

[0046] As can be seen from Table 2, the bio-based 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-based extractant. After the processes of extracting copper and gold, a gradient reverse 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-based extractant, resulting in differences in the mechanism of chelating copper and gold, and the effects of efficient extraction of copper and gold and gradient recovery of copper and gold can be achieved.

[0047] Examples 13 - 15 Examples 13 - 15 respectively provide a method for extracting gold from cyanide wastewater using a bio-based extractant. Compared with Example 1, the difference is only that the types of cyanide wastewater containing gold are different, as shown in Table 3. Other parameters and conditions are basically the same as those in Example 1 and will not be elaborated here.

[0048] As can be seen from Table 3, for cyanide waste liquids containing gold from different sources, the bio-based extractant provided in this application has high selectivity for gold ions.

[0049] Example 16 Example 16 provides a synthesis method for preparing the bio-based extractant in Example 1. The synthesis route diagram is as Figure 2 shown, and specifically includes the following steps: Add 1 mol of histidine to 1 L of sodium hydroxide solution with a mass concentration of 80 g / L, add 1.5 mol of carbon disulfide, heat to reflux at 40 °C, and react for 24 h. After the reaction is completed, distill the solution under reduced pressure to remove the excess carbon disulfide. Adjust the pH of the residual solution to neutral with dilute hydrochloric acid (V hydrochloric acid:V deionized water = 1:10), and perform vacuum rotary evaporation at 70 °C in a water bath until all the liquid evaporates to obtain a clear yellow oily compound as Figure 3 shown, which is the bio-based extractant with a yield of 87%. The nuclear magnetic resonance hydrogen spectrum of the bio-based extractant is asFigure 4 As shown, since the biological extraction agent is unstable under neutral and acidic conditions, sodium hydroxide solution needs to be added to adjust it to alkaline before analysis can be carried out. As can be seen from the figure, the peak intensity of deuterated solvent D 2 O is much higher than that of the biological extraction agent, indicating that the biological extraction agent has limited solubility in the aqueous phase under alkaline conditions, which is beneficial to avoiding the residue of the extraction agent in the aqueous phase and causing secondary pollution to the water body. Specifically, the NMR test results are as follows: 1HNMR (D2O, 400MHZ): δ6.80 - 7.80 (2H, imidazole ring H), δ2.50~3.50 (2H, -CH 2 -), δ4.75~5.00 (H, -CH-). The (N-H) in the N-containing structural fragment undergoes rapid exchange with the D of solvent D 2 O, 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.

[0050] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same composition and the same effect as the technical idea within the technical solution scope of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that those skilled in the art can think of to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of this application.

Claims

1. A biological extractant, characterized in that: The structural formula of the biological extractant is as follows: 。 2. A method for extracting gold from cyanide wastewater using a biological extractant, using the biological extractant according to claim 1 for extraction, characterized in that: The following steps are involved: S1. The biological extractant and the diluent are mixed and dissolved to obtain an extractant diluent; S2. adjusting the pH value of the gold-containing cyanide wastewater to 9-12, and then adding the extractant diluent to achieve selective extraction of gold in the solution.

3. The method for extracting gold from cyanide wastewater using a biological extractant according to claim 2, characterized in that: The diluent is sulfonated kerosene.

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

5. The method for extracting gold from cyanide wastewater using a biological extractant according to claim 2, characterized in that: In the gold-containing cyanide wastewater, gold is in the form of Au(CN)4 - Form exists.

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

7. The method for extracting gold from cyanide wastewater using a biological extractant according to claim 6, characterized in that: The gold-containing cyanide wastewater includes one or more of the following: low-concentration gold-containing cyanide wastewater remaining after activated carbon adsorption of gold cyanide extraction solution, gold / palladium catalyst cyanide leaching wastewater, and pyrometallurgical smoke cyanide leaching wastewater.

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