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

Abstract

The invention relates to a hydrogel adsorbent for gold extraction, a preparation method of the hydrogel adsorbent and a gold extraction method, and the preparation method of the hydrogel adsorbent comprises the following steps: concentrating and collecting halophilic bacteria cultured to a stable phase to obtain a halophilic bacteria concentrated solution; expanding and breaking halophilic bacteria cells in the halophilic bacteria concentrated solution by using deionized water to obtain a lysis solution; injecting the lysate into an acidic solution to obtain a hydrogel adsorbent; wherein a reducing substance contained in the hydrogel adsorbent is used for reducing gold ions (III) into a gold elementary substance and fixing the gold elementary substance in the hydrogel adsorbent. According to the embodiment, the hydrogel adsorbent is prepared from the halophilic bacteria, the preparation method is simple, the cost is low, and the preparation efficiency is high; the hydrogel adsorbent contains a reducing substance which can reduce gold ions into gold simple substances and fix the gold simple substances in the hydrogel adsorbent, so that high-efficiency and high-selectivity gold element extraction is realized, the gold extraction cost is effectively reduced, and the gold quality is improved.

Description

Technical Field

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

[0002] More and more electronic waste has gradually become a prominent environmental problem. Printed Circuit Board (PCB) is produced at an annual rate of about 50 million tons, and it is growing at an annual rate of 8.8%. A typical PCB contains 40% metal, 30% plastic and 30% ceramic, of which 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. In general, the content of precious metals varies greatly, mainly including 10-1600ppm gold, 200-20000ppm silver and 5-970ppm 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 disposal of waste circuit boards can not only save precious resources, reduce environmental pollution and obtain substantial profits, but also have an important impact on the overall production and consumption of circuit boards and is of great significance to sustainable development.

[0003] At present, 80% of waste circuit boards go to landfills, mainly because of the lack of cheap, environmentally friendly and high-yield recycling methods. The main methods for recovering precious metals such as gold and platinum from waste circuit boards are pyrometallurgy and hydrometallurgy. The pyrometallurgy is to extract precious metals from circuit boards through high-temperature treatment. This method is mature and easy to scale up, but it also has problems such as high energy consumption and serious secondary pollution. The wet method 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. This method has low energy consumption and low pollution and has broad application prospects. The leachate of waste circuit boards contains a variety of metal ions, and the concentration of precious metals is often very low. Therefore, how to highly selectively extract the target precious metals from the leachate rich in coexisting ions is a current technical problem.

[0004] In the process of wet gold extraction, the leaching solution of electronic waste contains a variety of metal elements, and the concentrations of metal elements such as copper, iron, cobalt, and nickel are much higher than the concentration of gold, which makes the selective extraction of gold very difficult. Traditional gold extraction methods mainly 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 leaching solution with extremely high selectivity.

[0005] The wet gold extraction of electronic waste involves multiple links. The recycling, disassembly, leaching, and refining of electronic waste all require cost investment. In addition, environmental costs are also a factor that must be considered. Overall, the benefits of gold extraction from electronic waste are not high, which is also the key reason restricting the recycling and refining of electronic waste. Therefore, reducing the cost of gold extraction and increasing the benefits of gold extraction from all links are the key to developing the electronic waste gold extraction industry. At present, it is technically feasible to extract gold from a mixed solution of metal ions with high selectivity. However, considering its cost and benefits, the existing methods have more or less some problems. For example, the gold impurity content extracted by the zinc reduction method is high, which affects the quality of gold. The activated carbon adsorption method is greatly affected by coexisting ions and pH value, and the extraction conditions are demanding. The solvent extraction method and ion exchange method are too expensive. Although the new synthetic materials have excellent performance, the complex preparation or synthesis methods bring a lot of uncertainty to their large-scale application. In summary, there is still a lack of cheap, efficient and easy-to-scale gold extraction materials on the market. Summary of the invention

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

[0007] The 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 cultured to the stable phase to obtain a halophilic bacteria concentrate;

[0009] S2, using deionized water to swell and rupture the halophilic bacteria cells in the halophilic bacteria concentrate to obtain a lysate;

[0010] 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 gold element and fixing the gold element inside the hydrogel adsorbent.

[0011] In one embodiment of the present invention, the halophilic bacteria include any one of the genus Halobacterium, Halobacterium, Halobacterium, Halococcus, Halobacterium, Halobacterium, Halobacterium, Halobacterium, Natrinum, Natrinum, Halobacter, Halobacter, Halobacterium, Halobacterium, and Halobacterium.

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

[0013] The halophilic bacteria cells cultured to the stable phase are collected by centrifugation and concentration to obtain the halophilic bacteria concentrate.

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

[0015] 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;

[0016] 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;

[0017] Alternatively, the halophilic bacteria concentrate is placed in a conical bottom container, an acidic solution is added to adjust the pH to <2, and then the solution is allowed to stand for a period of time, and after the halophilic bacteria are precipitated 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 solution is allowed to 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] 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;

[0021] Alternatively, the lysate is injected into an electronic waste leaching solution with a pH value of ≤2 to obtain the hydrogel adsorbent, and 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 to achieve gold extraction.

[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 a reducing substance for reducing gold ions to gold element and fixing the gold element inside the hydrogel adsorbent.

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

[0024] Another embodiment of the present invention provides a method for extracting gold based on a halophilic bacteria hydrogel adsorbent, comprising the steps of:

[0025] S1, washing 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 adjusting solution, and filtering to obtain a leaching solution containing gold ions;

[0026] S2, adding a hydrogel adsorbent to the gold ion-containing leaching solution and stirring, and taking out the adsorbed hydrogel adsorbent; wherein the hydrogel adsorbent is the hydrogel adsorbent described in the above embodiment;

[0027] S3, dissolving the adsorbed hydrogel adsorbent with nitric acid or burning the adsorbed hydrogel adsorbent to obtain gold particles.

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

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

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention utilizes halophilic bacteria to prepare a hydrogel adsorbent, and the preparation method is simple, the cost is low, and the preparation efficiency is high; the hydrogel adsorbent contains a reducing substance, and the reducing substance can reduce gold ions to gold element and fix the gold element 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1A schematic flow chart of a method for preparing a hydrogel adsorbent for gold extraction provided in an embodiment of the present invention;

[0033] Figure 2a-2b The diagram is the mechanism of the formation of hydrogel by lysate in acidic solution;

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

[0035] Figure 4 The macroscopic phenotype and scanning electron microscopy images of the hydrogel;

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

[0037] Figure 6a-6b It is the analysis diagram of adsorption products;

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

[0039] Figure 8 It is a graph showing the concentration variation of the hydrogel material in Au(III) solutions with different concentrations over time;

[0040] Fig. 9 The molecular structure diagram of bacteriorubin;

[0041] Fig.10 Schematic diagram of the redox reaction between bacteriocyanin and Au(III) in the hydrogel;

[0042] Figure 11a-Figure 11b Schematic diagram of the selective adsorption experiment of gold by hydrogel;

[0043] Fig.12 Schematic diagram of a computer chip to be dissolved. DETAILED DESCRIPTION

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

[0045] Embodiment 1

[0046] See also Figure 1 , Figure 1 A schematic flow chart of a method for preparing a hydrogel adsorbent for gold extraction provided in an embodiment of the present invention.

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

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

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

[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 expand and rupture rapidly to obtain 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 centrifugal time is 10-20min; illustratively, the volume ratio of the halophilic bacteria concentrate to deionized water is 1:1, the centrifugal speed is 8000×g, and the centrifugal time is 10min.

[0052] Alternatively, the halophilic bacteria concentrate is placed in a dialysis bag, and then the dialysis bag is placed in deionized water, and the halophilic bacteria cells are rapidly expanded and ruptured by using the osmotic pressure difference inside and outside the halophilic bacteria cells to obtain a lysate. The volume ratio of the halophilic bacteria concentrate to the deionized water is 1:1-1:2. Exemplarily, the volume of the halophilic bacteria concentrate is 0.6 ml, and the volume of the deionized water is 1 ml.

[0053] Alternatively, the halophilic bacteria concentrate is placed in a conical bottom container, a dilute acid solution is added to adjust the pH to <2, and then the solution is allowed to stand for a period of time (e.g., 24 hours), and after the halophilic bacteria are precipitated 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 solution is allowed to stand for a period of time (e.g., 6 hours), and the halophilic bacteria cells are rapidly expanded and ruptured by utilizing the osmotic pressure difference inside and outside the halophilic bacteria cells to obtain a lysate. The volume ratio of the halophilic bacteria concentrate to the 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 gold element and fixing the gold element 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 Figure 2a-2b , Figure 2a-2b The diagram shows the mechanism of the formation of hydrogel by lysate in acidic solution. Figure 2a Schematic diagram of DNA chain and extracellular polysaccharide 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 an 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 chains contain carboxylic acid groups -COOH and 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 make the DNA and extracellular polysaccharides in the cell lysate form a tight network structure, which is beneficial 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 enrich gold well and is not conducive to the selective extraction of gold.

[0058] Furthermore, the present embodiment also provides a hydrogel adsorbent prepared by the above-mentioned preparation method, wherein the hydrogel adsorbent contains a reducing substance, and the reducing substance can undergo an oxidation-reduction reaction with gold ions, reduce the gold ions to gold elements, and fix the gold elements inside the hydrogel adsorbent to achieve gold extraction. Specifically, the reducing substance includes one or more of reducing pigments and reducing polysaccharides. Exemplarily, for Halorubrum, a halophilic bacterium, the reducing pigment refers to 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 if it is not made into a hydrogel, that is, the lysis solution is injected into an electronic waste leaching solution (or an acidic gold-containing solution) with a pH of ≤2 to obtain a hydrogel adsorbent, and 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 to achieve gold extraction.

[0061] It should be noted that the halophilic bacteria of the present embodiment include any one of 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 undergo redox reaction with gold to achieve extraction effect.

[0062] In this embodiment, halophilic bacteria are used to prepare a hydrogel adsorbent. The preparation method of the hydrogel adsorbent is simple, the cost is low, and the preparation efficiency is high. The hydrogel adsorbent contains a reducing substance, which can reduce gold ions to gold element and fix the gold element 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.

[0063] Embodiment 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 soak them in aqua regia solution to dissolve them. After the circuit boards are completely dissolved, take out the remaining circuit boards, and adjust the acidity of the solution to a pH of 2-4 with an alkaline adjusting solution, and filter to obtain a leaching solution containing gold ions. The alkaline adjusting solution includes a NaOH solution or a NaHCO3 solution.

[0066] S2, adding a hydrogel adsorbent to the gold ion-containing leaching solution and stirring, and taking out the adsorbed hydrogel adsorbent after a period of time; wherein the hydrogel adsorbent is the hydrogel adsorbent of Example 1. wherein 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 burn the adsorbed hydrogel adsorbent at high temperature to obtain gold particles.

[0068] Embodiment 3

[0069] On the basis of Example 1 and Example 2, this example further illustrates the hydrogel adsorbent and its preparation method, as well as the extraction effect of the hydrogel adsorbent on gold through the following examples.

[0070] Example 1

[0071] Taking halophilic bacteria Halorubrum ejinoor sp (He) as an example, a hydrogel adsorbent is prepared, which specifically includes:

[0072] (1) Cultivation of Halorubrum ejinoor sp (He): He cells were cultured in a culture medium at 30°C and 120 rpm to the stationary phase. The culture 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 (Oxoid), 1 g / L yeast extract (Oxoid), and 0.555 g / L CaCl2. After mixing well, the pH was adjusted to 7.0 with 1.0 mol / L HCl or 1.0 mol / L NaOH. The cells cultured to the stationary phase were concentrated and collected by centrifugation (6000×g, 15 min) to obtain a halophilic bacteria concentrate. Please refer to Figure 3 , Figure 3 Schematic diagram and scanning electron microscope image of the concentrated and collected He bacterial solution. Figure 3 The left picture in the figure is a bacterial solution. The concentrated bacterial solution appears red. Figure 3 The right picture is a scanning electron microscope picture. Figure 3 Extracellular polysaccharides can be observed around the bacteria.

[0073] (2) Preparation of hydrogel: Take a certain amount of halophilic bacteria concentrate in a centrifuge tube, centrifuge (8000×g, 10 min), discard the supernatant, add a certain volume of deionized water to make the cells swell and rupture, and inject the viscous lysate into 0.1 mol / L H2SO4 solution with a syringe to obtain the hydrogel material. Figure 4 , Figure 4 The macroscopic phenotype and scanning electron microscopy images of the hydrogel are shown in Figure 2. Figure 4 The left picture is a macroscopic phenotype of the hydrogel, where the container diameter is 35 mm and the hydrogel appears red. Figure 4 The right picture is a scanning electron microscope picture. Figure 4 It can be observed that the hydrogel has numerous pore structures.

[0074] Example 2

[0075] Gold adsorption test was carried out using hydrogel: gold solutions of different concentrations (10 mg / L, 20 mg / L, 40 mg / L, 80 mg / L, 120 mg / L) were prepared with KAuCl4, 10 mL of each solution was placed in a 50 mL conical flask, and then the hydrogel prepared in Example 1 was added. After shaking for a certain period of time at 30°C and 120 rpm, 0.2 mL of the solution was taken, diluted with water a certain multiple, and the gold concentration was determined by ICP-MS.

[0076] See also Figure 5 , Figure 5 Schematic diagram of the change of gold concentration over time under the adsorption of gold (III) by hydrogel. Figure 5 It can be seen that with the increase of oscillation time, the gold concentration in gold solutions of different concentrations continues to decrease, indicating that the hydrogel material may have an adsorption effect on the gold ions in the solution.

[0077] To confirm the adsorption effect of hydrogel on gold, hydrogel material was added to 10mL, 200mg / L Au(III) solution, shaken for 24h, taken out and placed in a 1.5mL centrifuge tube, 0.4mL concentrated nitric acid was added to the centrifuge tube for digestion, and then centrifuged to collect the precipitate. The precipitate was washed with water three times and then dried in an oven at 60℃. The precipitate was then characterized by SEM-EDS. The results are as follows: Figure 6a-6b As shown, Figure 6a-6b is the analysis diagram of adsorption products. Figure 6a is the SEM image of the adsorption product. Figure 6b is the EDS diagram of the adsorption product. Figure 6a-6b It can be seen that gold particles were detected, indicating that the hydrogel can enrich the gold ions in the solution and reduce them to gold element.

[0078] Furthermore, in order to study the adsorption mechanism of gold by hydrogel, Au(III) solutions with concentrations of 1.0 mg / L, 10 mg / L, and 100 mg / L were prepared, and a solution with an Au concentration of 0 mg / L was used as a control. Hydrogel materials were added to the four solutions, and the color changes of the hydrogel materials were observed at 2 min, 1.0 h, 2.0 h, 6.5 h, and 31 h, and the reduction in Au concentration in the four solutions was measured. The results are shown in Figure 2. Figure 7 and Figure 8 As shown, Figure 7 The color change diagram of the hydrogel material in Au(III) solutions with different concentrations over time. Figure 8 The concentration of the hydrogel material changes with time in Au(III) solutions of different concentrations. Figure 7 and Figure 8It can be seen that at the initial concentration, the hydrogel is red due to the presence of bacteriocyanin; as the gold concentration decreases, the color of the hydrogel becomes lighter, which may be due to the fact that bacteriocyanin contains 13 pairs of conjugated double bonds, such as Fig. 9 As shown, Fig. 9 The molecular structure of bacteriorubin is shown in Figure 2. The presence of conjugated double bonds makes bacteriorubin have a good antioxidant effect, which can provide electrons to Au(III), undergo redox reaction with Au(III), and reduce Au(III) to a single substance, such as Fig.10 As shown, Fig.10 Schematic diagram of the redox reaction between bacteriocyanate and Au(III) in the hydrogel. In addition, since bacteriocyanate may just undergo a redox reaction with gold and does not react with other metal ions such as Cu, Co, and Ni, the hydrogel has a high selectivity for gold.

[0079] Example 3

[0080] The selectivity of the hydrogel for gold was tested by continuous flow reaction. Figure 11a-Figure 11b , Figure 11a-Figure 11b Schematic diagram of the selective adsorption experiment of gold by hydrogel. Fig.11a is the reaction device diagram, Fig.11b Schematic diagram of the recovery of different metal ions by hydrogel.

[0081] Fig.11a The feed liquid in the raw material bottle contains common metal ions in the leached liquid of electronic waste, such as cobalt (100 mg / L), nickel (100 mg / L), copper (100 mg / L), as well as 5 mg / L Au (III) ions and 0.01 mol / L H2SO4. The feed rate is 6.8 mL / h and the residence time is about 15 h. After two days of reaction, the hydrogel is picked up, washed with deionized water, and then dissolved with 0.4 mL of aqua regia. After the dissolved solution is diluted a certain multiple, the content of elements such as Co, Ni, Cu, and Au in the hydrogel is determined by ICP-MS, and the recovery of these elements is calculated. The measurement results are as follows: Fig.11b As shown. Fig.11b It can be seen that although the content of metal ions such as cobalt, nickel, and copper in the feed solution is much higher than the content of gold ions, the recovery rate of gold by the hydrogel is much higher than that of other metal ions, indicating that the hydrogel prepared in the embodiment of the present invention has a very high selective adsorption effect on gold.

[0082] Example 4

[0083] Extracting gold from electronic waste using hydrogel.

[0084] Take 2 computer chips, each weighing about 5g. Fig.12 As shown, Fig.12The figure is a schematic diagram of the computer chip to be dissolved. After washing the chip with water, extract the chip with 20mL aqua regia for 5h, then take out the residual chip, add 100mL of water, adjust the acidity of the extract to pH 2-3 with solid NaHCO3, filter, and obtain a gold-containing extract, which is blue, and then use water to dissolve to 200mL (for convenience, the solution is called chip extract). Take 2.4mL of concentrated bacterial solution, prepare four portions of hydrogel material (0.6ml of concentrated bacterial solution each), add it to the chip extract at one time, stir at room temperature for 6-12h, and then take out the gel. Determine the gold concentration of the chip extract before and after adsorption, 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 the gold in the electronic waste leaching solution.

[0088] This embodiment uses halophilic bacteria to prepare a cheap and efficient gold extraction hydrogel material. The material can be used to efficiently and highly selectively extract gold from electronic waste leaching liquid, which can effectively reduce the gold extraction cost and improve 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 method for preparing a hydrogel adsorbent for gold extraction, characterized in that: Includes steps: S1, concentrating and collecting the halophilic bacteria cultured to the stable phase to obtain a halophilic bacteria concentrate; S2, using deionized water to swell and rupture the halophilic bacteria cells in the halophilic bacteria concentrate to obtain a lysate; 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 gold element and fixing the gold element inside the hydrogel adsorbent.

2. The method for preparing a hydrogel adsorbent for gold extraction according to claim 1, characterized in that: The halophilic bacteria include any one of the genus Halobacterium, Halobacterium, Halobacterium, Halococcus, Halobacterium, Halobacterium, Halobacterium, Halobacterium, Natrinum, Natrinum, Halobacter, Halobacter, Halobacterium, Halobacterium, and Halobacterium.

3. The method for preparing a 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.

4. The method for preparing a hydrogel adsorbent for gold extraction according to claim 1, characterized in that: 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 swell and rupture the halophilic bacteria cells to obtain 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 bottom container, an acidic solution is added to adjust the pH to <2, and then the solution is allowed to stand for a period of time, and after the halophilic bacteria are precipitated 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 solution is allowed to stand for a period of time to obtain the lysate.

5. The method for preparing a hydrogel adsorbent for gold extraction according to claim 1, characterized in that: The volume ratio of the halophilic bacteria concentrate to the deionized water is 1:1-1:

2.

6. The method for preparing a 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 lysate is injected into an electronic waste leaching solution with a pH value of ≤2 to obtain the hydrogel adsorbent, and 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 to achieve gold extraction.

7. A hydrogel adsorbent for gold extraction, characterized in that: The hydrogel adsorbent is prepared by the preparation method according to any one of claims 1 to 6, wherein the hydrogel adsorbent contains a reducing substance for reducing gold ions to gold element and fixing the gold element inside the hydrogel adsorbent.

8. The hydrogel adsorbent for gold extraction according to claim 7, characterized in that The reducing substances include one or more of reducing pigments and reducing polysaccharides.

9. A method for extracting gold based on halophilic bacteria hydrogel adsorbent, characterized in that: Includes steps: S1, washing 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 adjusting solution, and filtering to obtain a leaching solution containing gold ions; S2, adding a hydrogel adsorbent to the gold ion-containing leaching solution and stirring, and taking out the adsorbed hydrogel adsorbent; wherein the hydrogel adsorbent is the hydrogel adsorbent as claimed in claim 7 or 8; S3, dissolving the adsorbed hydrogel adsorbent with nitric acid or burning the adsorbed hydrogel adsorbent to obtain gold particles.

10. The gold extraction method based on halophilic bacteria hydrogel adsorbent according to claim 9, characterized in that: The alkaline adjustment solution in step S1 includes NaOH solution or NaHCO3 solution; The stirring temperature in step S2 is room temperature, and the stirring time is 6-12 hours.

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