Method for recovering gold from solution containing monovalent gold ions under assistance of light

Abstract

The invention belongs to the technical field of precious metal resource recovery, and discloses a light-assisted method for recovering gold from a solution containing monovalent gold ions, which comprises the following steps: S1, mixing the solution containing monovalent gold ions with an adsorbent, and fully stirring under the illumination condition of ultraviolet light with the wavelength of 225-380nm and the intensity of 1-100W / m < 2 > until the adsorption reaction is finished; s2, performing ultrasonic treatment and centrifugation on the reactants to obtain dispersion liquid of the elemental gold and the adsorbent; and S3, the dispersion liquid of the adsorbent is repeatedly utilized, and the gold elementary substance solid is recycled. Wherein the adsorbent is a polymer and a derivative of dopamine, polydopamine, melanin and melanin-like. The method has ultrahigh adsorption capacity and selectivity on gold ions, and is simple and convenient in process, good in material reusability and beneficial to large-scale preparation.

Description

Technical Field

[0001] This invention belongs to the field of precious metal resource recycling technology, specifically relating to a photo-assisted method for recovering gold from a solution containing monovalent gold ions. Background Technology

[0002] Gold, as an important strategic resource, possesses high economic value and a wide range of applications. Therefore, the mining and recycling of gold resources is a crucial issue. Currently, gold mainly originates from two sources: gold mines and various electroplating waste liquids containing gold. In gold mines, although gold primarily exists in its elemental form, it is often accompanied by elements such as antimony, arsenic, and iron. To separate gold from other impurities, hydrometallurgical methods are frequently used during mining. To reduce environmental pollution during leaching, non-cyanide leaching agents are commonly used to first convert elemental gold into gold ions, followed by a reducing agent to reduce the gold ions back to elemental gold, thus obtaining gold with higher purity. For various gold electroplating waste liquids containing gold, a similar process is employed to reduce gold ions back to elemental gold. While the above process is widely used in the recycling of various precious metals, it has the following problems: 1. The reducing agent often lacks selectivity in reducing gold ions, meaning that after reduction, further refining is often required to obtain gold of higher purity; 2. When treating solutions containing gold ions, the concentration of gold ions cannot be too low. If it is below 10 ppm (gold ion concentration of 10 mg / L), the gold ions in the solution cannot be effectively reduced; 3. The gold ions involved in the above process are mostly [Au(S2O3)2]. 3- [Au(SO3)2] 3- Due to their low redox potentials, most existing adsorbents cannot effectively adsorb them. Therefore, developing materials with ultra-high adsorption capacity, high reusability, and unique selectivity to achieve highly selective extraction and recovery of trace gold remains a challenge. Summary of the Invention

[0003] To address the problems of poor selectivity, low reusability, and low adsorption capacity of existing monovalent gold ion adsorption materials, this invention provides a photo-assisted method for recovering gold from solutions containing monovalent gold ions.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a photo-assisted method for recovering gold from a solution containing monovalent gold ions, comprising the following steps: S1. Mix the solution containing monovalent gold ions with the adsorbent and apply the solution at a wavelength of 225-350 nm and an intensity of 1-100 W / m. 2 Stir thoroughly under ultraviolet light irradiation until the adsorption reaction is complete; S2. The reactants obtained in step S1 are subjected to ultrasonic treatment to separate the gold from the adsorbent, and then centrifuged to obtain a dispersion of gold and adsorbent. S3. The dispersion of the adsorbent is reused, and the solid gold is recovered.

[0005] The adsorbent is selected from at least one of polymers and derivatives of dopamine, polydopamine, melanin, and melanin-like substances.

[0006] Preferably, the polymers and derivatives of dopamine, polydopamine, melanin and melanin-like substances are at least one of the following: powder, dispersion, or composite material loaded on macroscopic materials to form a hybrid.

[0007] Preferably, the illumination conditions in step S1 are a wavelength of 225-350 nm and an intensity of 1-100 W / m. 2 The adsorption effect is optimal. When the wavelength range is greater than 350 nm, the adsorption capacity decreases, but effective adsorption and recovery can still be achieved.

[0008] Preferably, the gold ions in the solution containing monovalent gold ions are [Au(S2O3)2]. 3- [Au(SO3)2] 3- At least one of them.

[0009] Preferably, in step S1, the concentration of gold ions in the solution containing monovalent gold ions is 0.001-10000 mg / L, and the adsorption reaction temperature is -20℃ to 100℃.

[0010] Preferably, in step S1, the mass ratio of the solution containing monovalent gold ions to the adsorbent is 10:1 to 0.1:1.

[0011] Preferably, in step S1, the initial pH value of the solution containing monovalent gold ions is 0-14.

[0012] More preferably, the initial pH value of the solution containing monovalent gold ions is 6-9.

[0013] Preferably, in step S2, the dispersion of the adsorbent can be regenerated by ultrasonic exfoliation.

[0014] Preferably, in step S2, the ultrasonic treatment power is 80-300 W, the ultrasonic time is 30-180 minutes, the centrifugation speed is 1500-3000 r / min, and the centrifugation time is 30-180 minutes.

[0015] Preferably, in step S3, the gold element can be separated from the adsorbent by solid-liquid separation.

[0016] Preferably, in step S1, the solution containing monovalent metal ions is electroplating waste liquid or hydrometallurgical waste liquid, and the hydrometallurgical waste liquid is mostly leaching solution from cyanide-free and mercury-free alternative processes used for gold mines and placer gold.

[0017] Compared with existing technologies, the present invention has the following beneficial effects: The method for recovering gold from solutions containing monovalent gold ions utilizes the photoresponse properties of polymers and derivatives of dopamine, polydopamine, melanin, and melanin-like substances. These materials exhibit good dispersibility in gold-containing solutions, facilitating efficient gold recovery from solutions containing gold ions. Experiments have demonstrated that this method is effective at wavelengths of 225-350 nm and intensities of 1-100 W / m². 2 Under light irradiation, polydopamine exhibits a reducing adsorption effect on gold ions, directly reducing monovalent gold ions to elemental gold. The adsorbent can be regenerated by ultrasonic centrifugation, exhibiting both high adsorption capacity and selectivity. The method of this invention is simple, achieving adsorbent regeneration and noble metal stripping through simple ultrasonic treatment. The adsorption capacity remains largely unchanged after regeneration, significantly reducing material costs and facilitating large-scale preparation. Attached Figure Description

[0018] Figure 1 This is an image showing the adsorption capacity of the dispersion for gold ions in Example 1 of this invention, as well as the adsorption capacity during ultrasonic regeneration.

[0019] Figure 2 This is a graph showing the change in the adsorption capacity of the dispersion for gold ions in Example 1 of the present invention with the concentration of gold ions.

[0020] Figure 3 This is the X-ray diffraction pattern of the dispersion in Example 1 of the present invention after adsorption and reduction of gold ions.

[0021] Figure 4 This refers to the gold selective recovery performance of the dispersion in Example 3 of the present invention under conditions of coexisting competing ions. Detailed Implementation

[0022] The present invention can be better understood from the following embodiments. However, those skilled in the art will readily understand that the description of the embodiments is for illustrative purposes only and should not, and will not, limit the invention as described in the claims. In the following text, ppm represents mg / L and ppb represents μg / L.

[0023] This invention provides a photo-assisted method for recovering gold from a solution containing monovalent gold ions, comprising the following steps: S1. Mix the solution containing monovalent gold ions with the adsorbent and stir thoroughly under ultraviolet light irradiation until the adsorption reaction is complete. S2. After sonicating and centrifuging the reactants, a dispersion of elemental gold and adsorbent is obtained. S3. The dispersion of the adsorbent is reused, and the solid gold is recovered.

[0024] This invention proposes a method for efficiently treating and recovering various types of gold ion salts under ultraviolet light irradiation, using polymers and derivatives of dopamine, polydopamine, melanin, and melanin-like substances with high Fermi level and wide bandgap, i.e., abundant electron-donating capabilities, as adsorbents. It is particularly suitable for electroplating waste liquid or hydrometallurgical waste liquid containing monovalent gold ions generated under cyanide-free and mercury-free process conditions. This is beneficial for achieving the recycling of gold resources while protecting the environment.

[0025] In a preferred embodiment, the adsorbent material is at least one of polymers and derivatives of dopamine, polydopamine, melanin, and melanin-like substances.

[0026] In a preferred embodiment, the polymers and derivatives of dopamine, polydopamine, melanin and melanin-like substances are at least one of the following: powder, dispersion, or composite material loaded onto macroscopic materials to form a hybrid.

[0027] In a preferred embodiment, the illumination conditions in step S1 are a wavelength of 225-350 nm and an intensity of 1-100 W / m. 2 The adsorption effect is optimal. When the wavelength range is greater than 350 nm, the adsorption capacity decreases, but effective adsorption and recovery can still be achieved.

[0028] In a preferred embodiment, the gold ions in the solution containing noble metal ions are [Au(S2O3)2]. 3- [Au(SO3)2] 3- At least one of them.

[0029] In a preferred embodiment, the gold ions in the solution are [Au(S2O3)2]. 3- When the adsorbent is polydopamine, the research of this invention shows that polydopamine has an effect on [Au(S2O3)2]. 3- The ions exhibit an extremely high adsorption capacity, reaching 1800 mg / g, which is far higher than the adsorption capacity of existing adsorbents.

[0030] In a preferred embodiment, in step S1, the concentration of gold ions in the gold ion-containing solution is 0.001-10000 mg / L, and the adsorption reaction temperature is -20℃ to 100℃. For example, the initial concentration of gold ions is preferably 10 ppm, 50 ppm, or 100 ppm, and the adsorption reaction temperature is preferably 40℃. The adsorbent in this invention exhibits reducing adsorption of gold ions, especially in trace amounts such as gold solutions below 10 ppm, where it still has a high adsorption capacity and can directly reduce gold ions to elemental gold.

[0031] In a preferred embodiment, the initial pH of the gold ion-containing solution can be between 0 and 14. Preferably, the initial pH can be 6, 7, 8, or 9 to ensure the stability of the monovalent gold ion ligand. For example, the pH of the solution can be adjusted by adding a 0.1 mol / L HCl or NaOH solution.

[0032] In a preferred embodiment, in step S1, the mass ratio of the noble metal ions to the adsorbent is 10:1 to 0.1:1.

[0033] In a preferred embodiment, the adsorbent regeneration in step S2 can be achieved by ultrasonic exfoliation. For example, polydopamine can be used for [Au(S2O3)2]. 3- After ion adsorption, a polydopamine dispersion was obtained by ultrasonic exfoliation, with an adsorption capacity of up to 1800 mg / g, which is the same as the adsorption capacity at the time of first use.

[0034] The power and time of ultrasonic stripping affect the degree of adsorbent regeneration. In a preferred embodiment, in step S2, the ultrasonic power is 80-300 W, the ultrasonic time is 30-180 minutes, the centrifugation speed is 1500-3000 r, and the centrifugation time is 30-180 minutes. The inventors observed the surface morphology of the adsorbent after adsorption equilibrium and found that a large number of gold particles accumulated on the adsorbent surface, and these gold particles could be stripped off by ultrasonication. Subsequently, centrifugation can separate the polydopamine and gold particles. Experiments verified that the above steps can be achieved not only in single gold ion solutions, but also in solutions containing gold ions and other metal ions, such as solutions or precipitates of metal elements in electronic waste, and gold ore leaching solutions.

[0035] In a preferred embodiment, in step S3, the gold element can be separated from the adsorbent by solid-liquid separation.

[0036] In a preferred embodiment, the solution containing precious metal ions in S1 is electroplating waste liquid or hydrometallurgical waste liquid (mostly leaching solutions from cyanide-free and mercury-free alternative processes used in gold mining and placer gold production). Experiments have shown that in solutions containing multiple coexisting metal ions, over 99% adsorption of gold ions can be achieved, while the adsorption rate of other ions does not exceed 5%.

[0037] The present invention will be further illustrated below through some specific embodiments.

[0038] Example 1: Preparation of polydopamine dispersion Dopamine was dispersed in a tris(hydroxymethyl)aminomethane hydrochloride buffer solution for mixing and reaction. The pH of the solution was maintained at 8.5-10. Experiments showed that different alkaline reagents did not affect the adsorption performance of the prepared polydopamine. Dopamine and the alkaline solution were mixed and reacted at 25°C for 24 hours. After the reaction, deionized water was added and the mixture was centrifuged and washed. Then, deionized water was added to the final product to obtain a polydopamine dispersion with a concentration of 1 mg / ml. The tris(hydroxymethyl)aminomethane hydrochloride buffer solution can be replaced with one or more of ammonia, sodium hydroxide, potassium hydroxide, etc.

[0039] Example 2: Adsorption capacity for single-component noble metal ion solutions Add 10 ppm of [Au(S₂O₃)₂] to 200 ml of solution. 3- Add 2 ml of dispersion to the aqueous solution, the solution pH is 6, and under ultraviolet light (350 nm, 5 W / m²), 2 After a certain period of stirring and reaction, polydopamine achieves maximum adsorption of gold ions. The product is then subjected to ultrasonication and centrifugation to obtain a dispersion of elemental gold and polydopamine. The polydopamine dispersion can then further adsorb gold ions. The above changes are as follows: Figure 1 As shown, after ultrasound, polydopamine can re-adsorb monovalent gold ions, demonstrating good reusability of the adsorbent.

[0040] Using the same method as in Example 2, adsorption was performed on aqueous solutions of individual gold ions at concentrations of 50 ppm and 100 ppm, respectively. The adsorption capacity of the dispersion for gold ions as a function of gold ion concentration is shown in the graph below. Figure 2 As shown, from Figure 2 It can be seen that the dispersion in this embodiment has an adsorption capacity of 630 mg / g at a gold ion concentration of 10 ppm (trace level), and still exhibits a high adsorption capacity at concentrations above 10 ppm; from Figure 3 It can be seen that the polydopamine of the present invention exhibits a reducing adsorption of gold ions, directly reducing gold ions to elemental gold.

[0041] Example 3: Selective recovery of gold from polymetallic ion solution Add 2 ml of dispersion to 200 ml of an aqueous solution containing gold, copper, nickel, and iron ions (each at a concentration of 10 ppm), mix thoroughly, and set the solution pH to 6. Then, under ultraviolet light (350 nm, 5 W / m²), apply the dispersion. 2 After a certain period of stirring and reaction, such as Figure 4 As shown, the adsorption rates for gold ions, copper ions, nickel ions, and iron ions were 99%, 1%, 0.3%, and 0.8%, respectively. It can be seen that the polydopamine of the present invention can still selectively recover gold ions in an environment containing other competing ions, and has great application potential.

[0042] Example 4: Selective recovery of gold from gold ore leaching solution Gold ore was leached using thiosulfate to obtain a gold ore leaching filtrate containing 100 ppm gold ions, 760 ppm iron ions, and 50 ppm calcium ions. 15 ml of dispersion was added to 100 ml of the gold ore leaching filtrate, mixed thoroughly, and the pH of the solution was measured to be 10. The mixture was stirred for a period of time. After the reaction was complete, tests showed that the adsorption rate of gold ions was 99%, and the adsorption rates of other ions were all less than 1.5%.

[0043] Variation Example 1: Polydopamine dispersion can be loaded onto materials such as filter paper or inorganic substrates and placed in the same gold ore leaching filtrate as described above. After the reaction is completed, the adsorption rate of gold ions is measured to be 99%, and the removal rate of other ions is less than 1.5%, achieving specific and selective adsorption.

[0044] Example 5: Selective recovery of gold from electroplating waste liquid The electroplating wastewater mainly contained 100 ppm gold ions. 5 mg of polydopamine powder was added to 50 ml of the wastewater, mixed thoroughly, and the solution pH was measured to be 6. The mixture was then stirred to allow the reaction to proceed. After the reaction was complete, tests showed that the adsorption rate for gold ions was 99.6%.

[0045] Example 6: Adsorption capacity of melanin for single-component noble metal ion solutions Melanin can be purchased from commercially available brands, with a concentration of 10 ppm [Au(SO3)2] in a solution of 200 mg / L. 3- Add 2 mg of melanin powder to an aqueous solution, the solution pH is 6, and under ultraviolet light (350 nm, 5 W / m²), 2 After a certain period of stirring and reaction, melanin can achieve the highest adsorption of gold ions.

[0046] Variation Example 2: Polymers and derivatives of dopamine and melanin-like substances can be purchased from commercially available brands. Add 2 mg of adsorbent powder to the same monovalent gold ion solution as described above, and expose to ultraviolet light (350 nm, 5 W / m²). 2 After a certain period of stirring and reaction, the adsorbent achieves maximum adsorption of gold ions.

[0047] Example 7: Selective recovery of gold from melanin in gold sand leachate Leaching of gold sand with thiosulfate yielded a gold sand leachate containing 99.2 ppm gold ions, 786 ppm iron ions, and 49.5 ppm calcium ions. 5 mg of melanin powder was added to 100 ml of the gold sand leachate, mixed thoroughly, and the solution pH was measured to be 10. The mixture was stirred for a period of time. After the reaction was complete, tests showed that the adsorption rate of gold ions was 99%, while the adsorption rates of other ions were all less than 1.5%.

[0048] Variation Example 3: Polymers and derivatives of dopamine, melanin, and melanin-like pigments were loaded onto filter paper, inorganic substrates, and other materials. These were then placed in the same gold sand leaching solution as described above. After the reaction, the adsorption rate for gold ions was measured to be 99%, and the removal rates for other ions were all less than 1.5%, achieving specific and selective adsorption. Monovalent gold ions are widely used in electroplating, metallurgy, and other industries due to their good stability. However, traditional monovalent gold ion ligands are mostly cyanides, which are harmful to humans and the environment. To solve this problem, novel monovalent gold ions using thiosulfate and sulfite as monovalent gold ligands have been developed. However, due to their low redox potential, suitable adsorbents have long been lacking for their recovery. This invention utilizes the photoresponse properties of polymers and derivatives of dopamine, polydopamine, melanin, and melanin-like pigments, using shorter wavelength ultraviolet light as the excitation wavelength, to further efficiently recover gold from electroplating or hydrometallurgical wastewater. This has great application potential in addressing the global sustainability challenge of gold recyclability.

[0049] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several equivalent substitutions or obvious modifications can be made without departing from the concept of the present invention, and all such modifications, achieving the same performance or purpose, should be considered within the scope of protection of the present invention.

Claims

1. A method for photo-assisted recovery of gold from a solution containing monovalent gold ions, characterized in that, Includes the following steps: S1. Mix the solution containing monovalent gold ions with the adsorbent and apply the solution at a wavelength of 225-350 nm and an intensity of 1-100 W / m. 2 Stir thoroughly under ultraviolet light irradiation until the adsorption reaction is complete; S2. The reactants obtained in step S1 are subjected to ultrasonic treatment to separate the gold from the adsorbent, and then centrifuged to obtain a dispersion of gold and adsorbent. S3. The dispersion of the adsorbent is reused, and the solid gold is recovered. The adsorbent is selected from at least one of polymers and derivatives of dopamine, polydopamine, melanin and melanin-like substances.

2. The method for recovering gold as described in claim 1, characterized in that, The polymers and derivatives of dopamine, polydopamine, melanin and melanin-like substances are at least one of the following: powder, dispersion, or composite material loaded onto macroscopic materials to form a hybrid.

3. The method for recovering gold as described in claim 1, characterized in that, The gold ions in the solution containing monovalent gold ions are [Au(S2O3)2]. 3- [Au(SO3)2] 3- At least one of them.

4. The method for recovering gold as described in claim 1, characterized in that, In step S1, the concentration of gold ions in the solution containing monovalent gold ions is 0.001-10000 mg / L, and the adsorption reaction temperature is -20℃ to 100℃.

5. The method for recovering gold as described in claim 1, characterized in that, In step S1, the mass ratio of the solution containing monovalent gold ions to the adsorbent is 10:1 to 0.1:

1.

6. The method for recovering gold as described in claim 1, characterized in that, In step S1, the initial pH value of the solution containing monovalent gold ions is 0-14.

7. The method for recovering gold as described in claim 1, characterized in that, In step S2, the dispersion of the adsorbent is regenerated by ultrasonic stripping; the ultrasonic treatment power is 80-300 W, the ultrasonic time is 30-180 minutes; the centrifugation speed is 1500-3000 r / min, and the centrifugation time is 30-180 minutes.

8. The method for recovering gold as described in claim 1, characterized in that, In step S3, the gold element is separated from the adsorbent by solid-liquid separation.

9. The method for recovering gold as described in claim 1, characterized in that, In step S1, the solution containing monovalent gold ions is electroplating waste liquid or hydrometallurgical waste liquid, and the hydrometallurgical waste liquid is a leaching solution of a cyanide-free and mercury-free alternative process used for gold mines and placer gold.

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