Hydrogel adsorbent for gold extraction, its preparation method, and gold extraction method

Abstract

The present invention relates to a hydrogel adsorbent for gold extraction, a preparation method thereof, and a gold extraction method. The preparation method of the hydrogel adsorbent includes: concentrating and collecting halophilic bacteria cultured to the stationary phase to obtain a concentrated halophilic bacteria solution; using deionized water to swell and rupture the halophilic bacteria cells in the concentrated halophilic bacteria solution to obtain a lysate; injecting the lysate into an acidic solution to obtain a hydrogel adsorbent; wherein, the reducing substances contained in the hydrogel adsorbent reduce gold ions (III) to elemental gold and fix the elemental gold inside the hydrogel adsorbent. In this embodiment, a hydrogel adsorbent is prepared using halophilic bacteria. The preparation method is simple, with low cost and high preparation efficiency; the hydrogel adsorbent contains reducing substances, which can reduce gold ions to elemental gold and fix the elemental gold inside the hydrogel adsorbent, thereby realizing efficient and highly selective extraction of gold elements, effectively reducing the extraction cost of gold, and improving the quality of gold.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic waste recycling, and particularly relates to a hydrogel adsorbent for gold extraction, a preparation method thereof, and a gold extraction method. Background Art

[0002] An increasing amount of electronic waste has gradually become a prominent environmental problem. Printed Circuit Boards (PCBs) produce approximately 50 million tons per year and are growing at a rate of 8.8% per year. A typical PCB contains 40% metal, 30% plastic, and 30% ceramic. The metal part includes 10 - 27% copper, 2 - 8% aluminum, 1 - 4% lead, 1 - 8% iron, 1 - 6% tin, 0.2 - 3.6% nickel, 0.1 - 1.5% zinc, and <0.1% precious metals. Generally, the content of precious metals varies greatly, mainly including 10 - 1600 ppm of gold, 200 - 20000 ppm of silver, and 5 - 970 ppm of palladium. In most cases, the content of precious metals exceeds the expected value of traditional ores. If waste circuit boards are not effectively recycled, they will cause serious harm to air, soil, water quality, and human health. Effective resource treatment of waste circuit boards can not only save precious resources, reduce environmental pollution, and obtain objective profits, but also has an important impact on the overall situation of circuit board production and consumption and is of great significance to sustainable development.

[0003] Currently, 80% of waste circuit boards enter landfills, mainly because there is a lack of cheap, environmentally friendly, and high-yield recycling methods. The methods for recovering precious metals such as gold and platinum from waste circuit boards mainly include pyrometallurgy and hydrometallurgy. Pyrometallurgy is to refine precious metals in circuit boards through high-temperature treatment. This method is technically mature and easy to scale up, but it also has problems such as high energy consumption and serious secondary pollution. Hydrometallurgy uses appropriate solvents to leach metals from electronic waste into the liquid phase, and then uses appropriate methods to recover the target metal from the metal ion mixture solution. This method has low energy consumption and low pollution and has broad application prospects. The leachate of waste circuit boards contains multiple metal ions, and the concentration of precious metals is often very low. Therefore, how to highly selectively extract the target precious metal from the leachate rich in coexisting ions is a current technical problem.

[0004] During the wet gold extraction process, the e-waste leachate contains multiple metal elements, with concentrations of copper, iron, cobalt, and nickel far exceeding those of gold. This makes selective gold extraction very challenging. Traditional gold extraction methods primarily include zinc reduction, activated carbon adsorption, solvent extraction, and ion exchange. In recent years, researchers have synthesized a series of high-performance materials, such as: additive-induced supramolecular polymers of β-cyclodextrin (Nature Comm, 2023, 14: 1284), vinyl-linked two-dimensional silver (I) organic frameworks (Nature Comm, 2022, 13: 7771), porous porphyrin polymers (PNAS, 2020, 117: 16174–16180), caged amine-rich polymer capsules (Chem Eng J, 2022, 438, 135618), poly (ionic liquid)-derived porous organic polycarbene adsorbents (Nature Comm, 2023, 14: 263), reduced graphene oxide (Nature Comm, 2022, 13: 4472), etc. These materials can adsorb and enrich gold ions from the leachate with extremely high selectivity.

[0005] Hydrometallurgical gold extraction from e-waste involves multiple steps. Recycling, disassembly, leaching, and refining all require significant investment, and environmental costs are also a significant consideration. Overall, the returns from gold extraction from e-waste are low, a key constraint in both recycling and refining. Therefore, reducing extraction costs and increasing returns at every stage are key to developing the e-waste gold extraction industry. Currently, highly selective gold extraction from mixed metal ion solutions is technically feasible. However, existing methods often present challenges, both in terms of cost and profitability. For example, zinc reduction methods produce high levels of impurities, impacting gold quality. Activated carbon adsorption methods are significantly affected by coexisting ions and pH, requiring stringent extraction conditions. Solvent extraction and ion exchange methods are prohibitively expensive. While new synthetic materials offer excellent performance, their complex preparation and synthesis methods pose significant uncertainties for their large-scale application. In summary, the market remains lacking in inexpensive, efficient, and scalable gold extraction materials. Summary of the Invention

[0006] To address the above-mentioned problems in the prior art, the present invention provides a hydrogel adsorbent for gold extraction, a preparation method thereof, and a gold extraction method. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0007] An embodiment of the present invention provides a method for preparing a hydrogel adsorbent for gold extraction, comprising the steps of:

[0008] S1, concentrating and collecting the halophilic bacteria cells cultured to the stable phase to obtain a halophilic bacteria concentrate;

[0009] S2. Use deionized water to swell and rupture the halophilic bacteria cells in the halophilic bacteria concentrate to obtain a lysate.

[0010] S3. Inject the lysate into an acidic solution to obtain a hydrogel adsorbent; wherein, the hydrogel adsorbent contains a reducing substance for reducing gold ions to elemental gold and fixing the elemental gold inside the hydrogel adsorbent.

[0011] In one embodiment of the present invention, the halophilic bacteria include any one of the genera Halobacterium, Haloarcula, Halobaculum, Halococcus, Haloterrigena, Halogeometricum, Halorubrum, Halotalea, Natrialba, Natrinema, Natronobacterium, Natronococcus, Natronomonas, Natronorubrum.

[0012] In one embodiment of the present invention, step S1 includes:

[0013] Centrifuge and collect the halophilic bacteria cells cultured to the stationary phase to obtain the halophilic bacteria concentrate.

[0014] In one embodiment of the present invention, step S2 includes:

[0015] Centrifuge the halophilic bacteria concentrate in a centrifuge tube, discard the supernatant to obtain a precipitate; add deionized water to the precipitate to swell and rupture the halophilic bacteria cells to obtain the lysate;

[0016] Alternatively, place the halophilic bacteria concentrate in a dialysis bag, and then place the dialysis bag in deionized water to swell and rupture the halophilic bacteria cells to obtain the lysate;

[0017] Alternatively, place the halophilic bacteria concentrate in a conical bottom container, add an acidic solution to adjust the pH < 2, let it stand for a period of time, discard the supernatant after the halophilic bacteria cells precipitate to the bottom of the conical bottom container to obtain a precipitate; add deionized water to the precipitate, and then adjust the pH to neutral or alkaline with a dilute alkali solution, and let it stand for a period of time to obtain the lysate.

[0018] In one embodiment of the present invention, the volume ratio of the halophilic bacteria concentrate to the deionized water is 1:1 - 1:2.

[0019] In one embodiment of the present invention, step S3 includes:

[0020] Inject the lysate into an H2SO4 solution or an HCl solution to obtain the hydrogel adsorbent, wherein the pH of the H2SO4 solution or the HCl solution ≤ 2;

[0021] Alternatively, the lysis solution is injected into an e-waste leaching solution with a pH ≤ 2 to obtain the hydrogel adsorbent. Meanwhile, the reducing substances in the hydrogel adsorbent reduce gold ions to elemental gold and fix the elemental gold inside the hydrogel adsorbent, achieving the extraction of gold.

[0022] Another embodiment of the present invention provides a hydrogel adsorbent for gold extraction, which is prepared by the preparation method described in the above embodiment. The hydrogel adsorbent contains reducing substances, which are used to reduce gold ions to elemental gold and fix the elemental gold inside the hydrogel adsorbent.

[0023] In one embodiment of the present invention, the reducing substances include one or more of reducing pigments and reducing polysaccharides.

[0024] Another embodiment of the present invention provides a method for gold extraction based on a halophilic bacterium hydrogel adsorbent, which includes the steps:

[0025] S1. Wash and soak the waste circuit board in aqua regia for dissolution, and adjust the acidity of the dissolution solution to a pH of 2 - 4 with an alkaline adjusting solution. After filtration, an e-waste leaching solution containing gold ions is obtained;

[0026] S2. Add the hydrogel adsorbent to the e-waste leaching solution containing gold ions and stir, then take out the adsorbed hydrogel adsorbent; wherein, the hydrogel adsorbent is the hydrogel adsorbent described in the above embodiment;

[0027] S3. Dissolve the adsorbed hydrogel adsorbent with nitric acid or burn the adsorbed hydrogel adsorbent to obtain gold particles.

[0028] In one embodiment of the present invention, the alkaline adjusting solution in step S1 includes a NaOH solution or a NaHCO3 solution;

[0029] The temperature of stirring in step S2 is room temperature, and the stirring time includes 6 - 12 h.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] The present invention uses halophilic bacteria to prepare a hydrogel adsorbent. The preparation method is simple, the cost is low, and the preparation efficiency is high; the hydrogel adsorbent contains reducing substances, which can reduce gold ions to elemental gold and fix the elemental gold inside the hydrogel adsorbent, thereby achieving efficient and highly selective extraction of gold elements, effectively reducing the extraction cost of gold, and improving the quality of gold. Description of the Drawings

[0032] Figure 1Schematic flow chart of a preparation method of a hydrogel adsorbent for gold extraction provided by an embodiment of the present invention;

[0033] Figures 2a - 2b Schematic diagram of the mechanism of the lysate forming a hydrogel in an acidic solution;

[0034] Figure 3 Schematic diagram and scanning electron microscope image of the concentrated and collected H. e bacterial solution;

[0035] Figure 4 Macrophenotype diagram and scanning electron microscope image of the hydrogel;

[0036] Figure 5 Schematic diagram of the change in gold concentration with time under the adsorption of gold(III) by the hydrogel;

[0037] Figures 6a - 6b Analysis diagram of the adsorption product;

[0038] Figure 7 Color change diagram of the hydrogel material with time in different concentrations of Au(III) solutions;

[0039] Figure 8 Concentration change diagram of the hydrogel material with time in different concentrations of Au(III) solutions;

[0040] Figure 9 Molecular structure diagram of bacterioerythrin;

[0041] Figure 10 Schematic diagram of the redox reaction between bacterioerythrin in the hydrogel and Au(III);

[0042] Figures 11a - 11b Schematic diagram of the selective adsorption test of the hydrogel for gold;

[0043] Figure 12 Schematic diagram of the computer chip to be dissolved. Detailed implementation manners

[0044] The present invention will be further described in detail below with reference to specific embodiments, but the implementation manners of the present invention are not limited thereto.

[0045] Embodiment 1

[0046] Please refer to Figure 1 , Figure 1 which is a schematic flow chart of a preparation method of a hydrogel adsorbent for gold extraction provided by an embodiment of the present invention.

[0047] The preparation method of the hydrogel adsorbent for gold extraction in this embodiment includes the steps:

[0048] S1. Concentrate and collect the halophilic bacteria cells cultured to the stable phase to obtain a halophilic bacteria concentrate.

[0049] Specifically, the halophilic bacteria are first cultured in a culture medium until the stable phase, and then the halophilic bacteria cells cultured to the stable phase are collected by centrifugation to obtain a halophilic bacteria concentrate. The centrifugation speed is 3000-8000×g and the centrifugation time is 10-20 minutes; illustratively, the centrifugation speed is 6000×g and the centrifugation time is 15 minutes.

[0050] S2. Using deionized water, the halophilic bacteria cells in the halophilic bacteria concentrate are expanded and ruptured to obtain a lysate.

[0051] Specifically, the halophilic bacteria concentrate is centrifuged in a centrifuge tube, and the supernatant is discarded to obtain a precipitate; deionized water is added to the precipitate, and the osmotic pressure difference between the inside and outside of the halophilic bacteria cells is used to cause the halophilic bacteria cells to rapidly swell and rupture, thereby obtaining a lysate. The volume ratio of the halophilic bacteria concentrate to deionized water is 1:1-1:2, the centrifugal speed is 3000-8000×g, and the centrifugation time is 10-20 minutes. For example, the volume ratio of the halophilic bacteria concentrate to deionized water is 1:1, the centrifugal speed is 8000×g, and the centrifugation time is 10 minutes.

[0052] Alternatively, the halophilic bacteria concentrate is placed in a dialysis bag, which is then placed in deionized water. The osmotic pressure difference between the inside and outside of the halophilic bacteria cells is used to cause the halophilic bacteria cells to rapidly swell and rupture, thereby obtaining a lysate. The volume ratio of the halophilic bacteria concentrate to deionized water is 1:1-1:2. For example, the volume of the halophilic bacteria concentrate is 0.6 ml, and the volume of the deionized water is 1 ml.

[0053] Alternatively, a halophilic bacteria concentrate is placed in a conical bottom container, a dilute acid solution is added to adjust the pH to <2, and the mixture is allowed to stand for a period of time (e.g., 24 hours). After the halophilic bacteria settle to the bottom of the conical bottom container, the supernatant is discarded to obtain a precipitate; after deionized water is added to the precipitate, the pH is adjusted to neutral or alkaline with a dilute alkaline solution, and the mixture is allowed to stand for a period of time (e.g., 6 hours). The osmotic pressure difference between the inside and outside of the halophilic bacteria cells causes the halophilic bacteria cells to rapidly swell and rupture, thereby obtaining a lysate. The volume ratio of the halophilic bacteria concentrate to deionized water is 1:1-1:2.

[0054] S3. Injecting the lysate into an acidic solution to obtain a hydrogel adsorbent; wherein the hydrogel adsorbent contains a reducing substance for reducing the gold ions to elemental gold and fixing the elemental gold inside the hydrogel adsorbent.

[0055] Specifically, the lysate is injected into a dilute H2SO4 solution or a dilute HCl solution to obtain a hydrogel adsorbent, wherein the pH of the H2SO4 solution or the HCl solution is ≤ 2. Exemplarily, the acidic solution is a 0.1 mol / L H2SO4 solution.

[0056] See also Figures 2a - 2b , Figures 2a - 2b The diagram shows the mechanism of hydrogel formation by lysate in acidic solution. Figure 2a Schematic diagram of DNA chain and exopolysaccharide chain. Figure 2b The schematic diagram of the cross-linking network formed by DNA chains and extracellular polysaccharide chains through hydrogen bonds. Specifically, the lysate is injected into the acidic solution. Since there are DNA chains, extracellular polysaccharide chains and other substances in the cell lysate, the DNA chains contain phosphate PO4 3- , the extracellular polysaccharide chain contains carboxylic acid groups -COOH, phosphate groups -PO2 - The carboxylic acid group -COOH is cross-linked under the action of hydrogen bonds to form a hydrogel adsorbent with a network structure.

[0057] In this embodiment, the pH of the H2SO4 solution or the HCl solution is ≤2. Sufficient H+ in the solution can enable the DNA and extracellular polysaccharides in the cell lysate to form a tight network structure, which is conducive to the attachment of gold. If the pH of the acidic solution is too high, the amount of H+ in the solution is insufficient, and the formed hydrogel is relatively loose, which cannot effectively enrich gold and is not conducive to the selective extraction of gold.

[0058] Furthermore, this embodiment provides a hydrogel adsorbent prepared by the above-described preparation method. The hydrogel adsorbent contains a reducing substance that can undergo a redox reaction with gold ions, reducing the gold ions to elemental gold and immobilizing the elemental gold within the hydrogel adsorbent, thereby achieving gold extraction. Specifically, the reducing substance includes one or more of a reducing pigment and a reducing polysaccharide. For example, for halophilic bacteria of the genus Halorhus (Halorubrum), the reducing pigment is bacteriorubin.

[0059] In this embodiment, the hydrogel adsorbent prepared by halophilic bacteria is beneficial for subsequent applications.

[0060] In a specific embodiment, after the lysis solution is obtained in step S2, gold can be extracted even without making a hydrogel, that is, the lysis solution is injected into an electronic waste leaching solution (or an acidic gold-containing solution) with a pH ≤ 2 to obtain a hydrogel adsorbent. At the same time, the reducing substance in the hydrogel adsorbent reduces the gold ions to gold element and fixes the gold element inside the hydrogel adsorbent, thereby achieving gold extraction.

[0061] It should be noted that the halophilic bacteria of the present embodiment include any one of the genus Halobacterium, Haloarcula, Halobaculum, Halococcus, Haloferax, Halogeometricum, Halorubrum, Haloterrigena, Natrialba, Natrinema, Natronobacterium, Natronococcus, Natronomonas or Natronorubrum. The cells of these halophilic bacteria all contain unique reducing pigments and / or reducing polysaccharides, which can react with gold to achieve an extraction effect through redox reaction.

[0062] In this embodiment, a hydrogel adsorbent is prepared using halophilic bacteria. The preparation method of the hydrogel adsorbent is simple, low-cost, and high-efficiency. The hydrogel adsorbent contains a reducing substance that can reduce gold ions to elemental gold and fix the elemental gold inside the hydrogel adsorbent, thereby achieving efficient and highly selective gold extraction, effectively reducing the extraction cost of gold and improving the quality of gold.

[0063] Example 2

[0064] Based on Example 1, this example provides a gold extraction method based on a halophilic bacteria hydrogel adsorbent, the extraction method comprising the steps of:

[0065] S1. Wash the waste circuit boards and dissolve them in aqua regia solution. After the circuit boards are completely dissolved, remove the remaining circuit boards and adjust the acidity of the solution to a pH of 2-4 with an alkaline adjustment solution. Filter and obtain a leachate containing gold ions. The alkaline adjustment solution includes a NaOH solution or a NaHCO3 solution.

[0066] S2. Adding a hydrogel adsorbent to the gold ion-containing leachate and stirring the mixture, and removing the adsorbed hydrogel adsorbent after a period of time; wherein the hydrogel adsorbent is the hydrogel adsorbent of Example 1. The stirring temperature is room temperature, and the stirring time is 6-12 hours.

[0067] S3. Dissolve the adsorbed hydrogel adsorbent with nitric acid or directly calcine the adsorbed hydrogel adsorbent at high temperature to obtain gold particles.

[0068] Example 3

[0069] Based on Example 1 and Example 2, the present example further illustrates the hydrogel adsorbent, its preparation method, and the gold extraction effect of the hydrogel adsorbent through the following examples.

[0070] Example 1

[0071] Taking the halophilic bacterium Halorubrum ejinoor sp (H.e.) as an example, the preparation of the hydrogel adsorbent specifically includes:

[0072] (1) Cultivation of Halorubrum ejinoor sp (H.e.): The H.e. cells were cultured in a medium at 30 °C and 120 rpm / min until the stationary phase. The medium contained 200 g / L NaCl, 30 g / L MgSO4·7H2O, 25 g / L MgCl2·6H2O, 5.8 g / L KCl, 5 g / L peptone (source: Oxoid), 1 g / L yeast extract (source: Oxoid), 0.555 g / L CaCl2. After mixing evenly, the pH was adjusted to 7.0 with 1.0 mol / L HCl or 1.0 mol / L NaOH. The bacteria in the stationary phase were concentrated and collected by centrifugation (6000×g, 15 min) to obtain a concentrated halophilic bacterium solution. Please refer to Figure 3 , Figure 3 For the schematic diagram and scanning electron micrograph of the concentrated H.e. bacterial solution, Figure 3 The left figure in Figure 3 is the bacterial solution figure, and the concentrated bacterial solution appears red, Figure 3 The right figure in

[0073] (2) Preparation of the hydrogel: Take a certain amount of the concentrated halophilic bacterium solution in a centrifuge tube, centrifuge (8000×g, 10 min), discard the supernatant, add a certain volume of deionized water to expand and rupture the cells, and inject the viscous lysate into a 0.1 mol / L H2SO4 solution to obtain the hydrogel material. Refer to Figure 4 , Figure 4 For the macroscopic phenotype diagram and scanning electron micrograph of the hydrogel, Figure 4 The left figure in Figure 4 is the macroscopic phenotype diagram of the hydrogel. Among them, the diameter of the container is 35 mm, and the hydrogel appears red, Figure 4 The right figure in

[0074] Example 2

[0075] Adsorption experiment of gold using hydrogel: Prepare gold solutions with different concentrations (10mg / L, 20mg / L, 40mg / L, 80mg / L, 120mg / L) using KAuCl4, each with a volume of 10mL. Place them in 50mL Erlenmeyer flasks. Then add the hydrogel prepared in Example 1 above. After shaking for a certain time at 30°C and 120rpm, take 0.2mL of the solution, dilute it with water by a certain multiple, and measure the gold concentration using ICP-MS.

[0076] Please refer to Figure 5 , Figure 5 Figure showing the change of gold concentration with time under the adsorption of gold(III) by hydrogel. From Figure 5 it can be seen that as the shaking time increases, the gold concentration in gold solutions with different concentrations continuously decreases, indicating that the hydrogel material may have an adsorption effect on gold ions in the solution.

[0077] To confirm the adsorption effect of hydrogel on gold, add the hydrogel material to a 10mL, 200mg / L Au(III) solution. After shaking for 24h, take it out and place it in a 1.5mL centrifuge tube. Add 0.4mL of concentrated nitric acid to the centrifuge tube for digestion. Then centrifuge to collect the precipitate, wash the precipitate three times with water, place it in an oven at 60°C to dry, and then characterize the precipitate using SEM-EDS. The results are as Figures 6a - 6b shown, Figures 6a - 6b Figure for the analysis of the adsorption product, Figure 6a SEM image of the adsorption product, Figure 6b EDS image of the adsorption product. From Figures 6a - 6b it can be seen that gold particles are detected, indicating that the hydrogel can enrich gold ions in the solution and reduce them to elemental gold.

[0078] Furthermore, to study the adsorption mechanism of hydrogel on gold, prepare Au(III) solutions with concentrations of 1.0mg / L, 10mg / L, and 100mg / L respectively, and use a solution with a Au concentration of 0mg / L as a control. Add the hydrogel material to the four solutions, observe the color changes of the hydrogel material at 2min, 1.0h, 2.0h, 6.5h, and 31h, and measure the reduction in Au concentration in the four solutions. The results are as Figure 7 and Figure 8 shown, Figure 7 Figure showing the color change of the hydrogel material with time in Au(III) solutions with different concentrations, Figure 8 Figure showing the concentration change of the hydrogel material with time in Au(III) solutions with different concentrations. Combining Figure 7 and Figure 8It can be seen that at the initial concentration, the hydrogel appears red due to the presence of bacterioerythrin; as the gold concentration decreases more, the color of the hydrogel becomes lighter. This may be because bacterioerythrin contains 13 pairs of conjugated double bonds, as Figure 9 shown, Figure 9 is the molecular structure diagram of bacterioerythrin. The presence of conjugated double bonds makes bacterioerythrin have good antioxidant effects, so it can provide electrons to Au(III), undergo an oxidation-reduction reaction with Au(III), and reduce Au(III) to elemental gold, as Figure 10 shown, Figure 10 is the schematic diagram of the oxidation-reduction reaction between bacterioerythrin in the hydrogel and Au(III). In addition, since bacterioerythrin may exactly undergo an oxidation-reduction reaction with gold and does not react with other metal ions such as Cu, Co, and Ni, the hydrogel has high selectivity for gold.

[0079] Example 3

[0080] The selectivity of the hydrogel for gold was tested by continuous flow reaction. Please refer to Figures 11a - 11b , Figures 11a - 11b is the schematic diagram of the selective adsorption test of the hydrogel for gold, Figure 11a is the reaction device diagram, Figure 11b is the schematic diagram of the recovery amounts of the hydrogel for different metal ions.

[0081] Figure 11a In , the feed liquid in the raw material bottle contains common metal ions such as cobalt (100 mg / L), nickel (100 mg / L), and copper (100 mg / L) in the leachate of electronic waste, as well as 5 mg / L Au(III) ions and 0.01 mol / L H2SO4. The feeding rate is 6.8 mL / h, and the residence time is about 15 h. After reacting for two days, the hydrogel was picked out, washed with deionized water, and then dissolved in 0.4 mL of aqua regia. After diluting the dissolved solution by a certain multiple, the contents of elements such as Co, Ni, Cu, and Au in the hydrogel were determined by ICP-MS method, and the recovery amounts of these elements were calculated. The measurement results are as Figure 11b shown. From Figure 11b it can be seen that although the contents of metal ions such as cobalt, nickel, and copper in the feed liquid are much higher than the gold ion content, the recovery rate of the hydrogel for gold is far higher than that of other metal ions, indicating that the hydrogel prepared in the embodiment of the present invention has extremely high selective adsorption effect on gold.

[0082] Example 4

[0083] The hydrogel was used to extract gold from electronic waste.

[0084] Take 2 computer chips, about 5 g each, as Figure 12 shown, Figure 12The figure is a schematic diagram of the computer chip to be dissolved. After washing the chip with water, the chip was extracted with 20mL of aqua regia for 5h, then the residual chip was removed, 100mL of water was added, and the acidity of the extract was adjusted to pH 2-3 with solid NaHCO3. After filtering, a gold-containing extract was obtained. The extract was blue and then dissolved to 200mL with water (for convenience, the solution is referred to as chip extract). 2.4mL of concentrated bacterial solution was taken to prepare four portions of hydrogel material (0.6ml of concentrated bacterial solution per portion), which were added to the chip extract at one time and stirred at room temperature for 6-12h. The gel was then removed. The gold concentration of the chip extract before and after adsorption was measured, and the results are shown in Table 1.

[0085] Table 1 Extraction results of gold in chip leaching solution

[0086]

[0087] As shown in Table 1, the gold extraction rate of the hydrogel material reached 81.8%, which can effectively recover gold in the electronic waste leachate.

[0088] This embodiment uses halophilic bacteria to prepare a cheap and efficient gold extraction hydrogel material. The material can be used to efficiently and selectively extract gold from electronic waste leachate, effectively reducing the cost of gold extraction and improving the quality of gold.

[0089] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A preparation method of a hydrogel adsorbent for gold extraction, characterized in that, Including steps: S1. Concentrating and collecting the halophilic bacteria cultured to the stable phase to obtain a halophilic bacteria concentrate; the halophilic bacteria include any one of the genus Halobacterium, Halobacterium, Halobacterium, Halobacterium, Halobacterium, Halobacterium, Halobacterium, Halobacterium, Sodium Leucobacter, Sodium Linear Bacteria, Halobacter, Halobacter, Halobacter, Halobacter, Halobacter, Halobacter, Halobacter, Halobacter, and Halobacter; S2. Using deionized water to swell and rupture the halophilic bacteria cells in the halophilic bacteria concentrate to obtain a lysate; the volume ratio of the halophilic bacteria concentrate to the deionized water is 1:1-1:2; S3. Injecting the lysate into an acidic solution to obtain a hydrogel adsorbent; wherein the hydrogel adsorbent contains a reducing substance for reducing gold ions to elemental gold and fixing the elemental gold inside the hydrogel adsorbent.

2. The preparation method of the hydrogel adsorbent for gold extraction according to claim 1, characterized in that, Step S1 includes: The halophilic bacteria cells cultured to the stable phase are collected by centrifugation and concentration to obtain the halophilic bacteria concentrate.

3. The preparation method of the hydrogel adsorbent for gold extraction according to claim 1, wherein, Step S2 includes: Centrifuging the halophilic bacteria concentrate in a centrifuge tube, discarding the supernatant to obtain a precipitate; adding deionized water to the precipitate to cause the halophilic bacteria cells to swell and rupture, thereby obtaining the lysate; Alternatively, the halophilic bacteria concentrate is placed in a dialysis bag, and then the dialysis bag is placed in deionized water to cause the halophilic bacteria cells to swell and rupture, thereby obtaining the lysate; Alternatively, the halophilic bacteria concentrate is placed in a conical-bottomed container, an acidic solution is added to adjust the pH to <2, and then the container is allowed to stand for a period of time. After the halophilic bacteria settle to the bottom of the conical-bottomed container, the supernatant is discarded to obtain a precipitate; after deionized water is added to the precipitate, the pH is adjusted to neutral or alkaline with a dilute alkaline solution, and the container is allowed to stand for a period of time to obtain the lysate.

4. The preparation method of the hydrogel adsorbent for gold extraction according to claim 1, characterized in that, Step S3 includes: Injecting the lysate into a H2SO4 solution or a HCl solution to obtain the hydrogel adsorbent, wherein the pH of the H2SO4 solution or the HCl solution is ≤ 2; Alternatively, the lysis solution is injected into an electronic waste leaching solution with a pH of ≤2 to obtain the hydrogel adsorbent. At the same time, the reducing substance in the hydrogel adsorbent reduces the gold ions to elemental gold and fixes the elemental gold inside the hydrogel adsorbent to achieve gold extraction.

5. A hydrogel adsorbent for gold extraction, characterized in that, Prepared by the preparation method according to any one of claims 1 to 4, the hydrogel adsorbent contains a reducing substance for reducing gold ions to gold element and fixing the gold element inside the hydrogel adsorbent.

6. The hydrogel adsorbent for gold extraction according to claim 5, wherein The reducing substance includes one or more of reducing pigments and reducing polysaccharides.

7. A gold extraction method based on a halophilic bacterium hydrogel adsorbent, characterized in that, Including steps: (1) cleaning the waste circuit board and soaking it in aqua regia solution to dissolve it, and adjusting the acidity of the solution to a pH of 2-4 with an alkaline regulating solution, and filtering to obtain a leachate containing gold ions; (2) adding a hydrogel adsorbent to the gold ion-containing leaching solution and stirring the solution, and taking out the adsorbed hydrogel adsorbent; wherein the hydrogel adsorbent is the hydrogel adsorbent according to claim 5 or 6; (3) dissolving the adsorbed hydrogel adsorbent with nitric acid or burning the adsorbed hydrogel adsorbent to obtain gold particles.

8. The gold extraction method based on the halophilic bacteria hydrogel adsorbent according to claim 7, characterized in that, The alkaline adjusting solution in step (1) includes NaOH solution or NaHCO3 solution; In step (2), the stirring temperature is room temperature and the stirring time is 6 - 12 h.

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