A method for adsorptive recovery of precious metals from aqueous samples

Abstract

The application discloses a method for adsorbing and recovering precious metals in an aqueous sample. The method comprises the following steps: adding an adsorbent to the aqueous sample, wherein the adsorbent comprises microalgae and mycelium balls; and adsorbing the precious metals in the aqueous sample, wherein the microalgae and the mycelium balls are used to adsorb the precious metals in the aqueous sample and flocculate the microalgae cells at the same time. The application solves the technical problems that the biological adsorbent often needs chemical pretreatment and modification and solidification, which results in high use cost, serious secondary pollution, and difficulty in solid-liquid separation of the tiny biological cells or micron / nanometer adsorption materials after crushing and grinding, and realizes rapid and selective adsorption of gold ions and synchronous, efficient and low-consumption separation of the microalgae cells by using the simple biological mixed system of the mycelium balls and the microalgae to shorten the preparation time of the adsorbent, save the floor area, and reduce the production cost.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology and relates to a method for adsorbing and recovering precious metals in aqueous samples, particularly a method for simultaneously adsorbing, removing and recovering precious metal ions in wastewater by immobilizing microalgae with mycelial balls. Background Technology

[0002] Gold (Au), an important precious metal, has wide applications in industries such as electroplating, electronics, and catalysis. With the increasing demand for this precious metal in industry and the limited availability of gold in natural ores, the discharge of gold-containing wastewater has become a major threat to environmental and resource sustainability. Therefore, recovering gold from secondary resources is of great significance. Currently, numerous technologies for enriching and extracting gold ions from wastewater have been developed, such as chemical deposition, solvent extraction, membrane separation, ion exchange, electrodialysis, and adsorption. Adsorption, in particular, has shown significant effectiveness in recovering gold ions from low-concentration wastewater. Gold ions are first adsorbed by an adsorbent, and then the loaded gold ions are stripped during desorption, concentrating them in a smaller volume of desorption liquid to improve energy efficiency and reduce the operating costs of the subsequent electrolysis stage.

[0003] Adsorption methods primarily utilize adsorbents prepared from activated carbon, clay minerals, silica gel, nano-zero-valent iron, and natural polymers to adsorb precious metal ions from water. However, several drawbacks exist. While activated carbon boasts high adsorption efficiency for heavy metals, it suffers from high operating costs, difficult regeneration, and inability to be reused. Clay minerals, though widely found in nature, exhibit poor heavy metal removal efficiency. Nano-zero-valent iron and metal-organic frameworks, while highly efficient at removing heavy metals, suffer from poor stability and significant environmental impact. Biological adsorption, on the other hand, offers advantages such as low cost, high removal rate, easy regeneration, simple operation, and no secondary pollution, making it a promising candidate for treating and recovering precious metal wastewater. The most crucial biosorbents in biological adsorption are widely available, including fungi, bacteria, algae, and agricultural and forestry waste. In particular, the abundant functional groups on the cell surfaces of algae, bacteria, and fungi serve as binding sites for gold ions, playing a vital role in the adsorption, removal, and recovery of precious metals from aqueous solutions.

[0004] Currently, while there is considerable research on the removal and recovery of precious metals from water using biosorbents, several potential problems remain, including difficulties in solid-liquid separation, low mechanical strength, slow adsorption rates, and poor reusability. In particular, separating tiny cells such as algae, bacteria, and fungi, or synthetic and modified nano- and micron-sized adsorbents, from dilute solutions remains a significant challenge, especially for large-scale applications. Traditional separation methods such as centrifugation, filtration, flotation, and chemical flocculation are prohibitively expensive and energy-intensive.

[0005] In existing technologies, biosorbents used to adsorb and recover gold ions from wastewater are mainly derived from bacteria and agricultural and forestry waste. Reference 1 utilizes a manganese oxide-producing bacterium, *Lysinibaeillus* sp. M14, to adsorb trivalent gold ions from water, but its adsorption capacity is only 21 mg / g within 1 hour at room temperature and pressure, and solid-liquid separation of the bacterial cells is difficult. Reference 2 uses modified mangosteen residue (particles smaller than 40 mesh) to adsorb gold ions from wastewater, achieving an adsorption capacity of 100 mg / g within 24 hours at room temperature and pressure, but solid-liquid separation of micron-sized particles consumes a lot of energy. Reference 3 uses acidic pretreatment of poultry eggshells, followed by protein hydrolysis and modification / solidification to form a water-soluble adsorbent material to adsorb gold ions from wastewater, achieving a maximum adsorption capacity of 628 mg / g at room temperature and pressure, but requiring a high temperature of 55℃. Reference 4 utilizes mycelial flocculation of microalgae cells to form algae-bacterial symbiotic particles, and then uses these pre-formed algae-bacterial symbiotic particles as adsorbents to adsorb gold ions from wastewater, achieving a capacity of 628 mg / g within 6 hours at room temperature and pressure. The maximum adsorption capacities within h are 104 mg / g (active algae-bacterial symbiotic particles) and 112 mg / g (lyophilized algae-bacterial symbiotic particles), respectively. However, additional time and space are required to prepare and preserve the algae-bacterial symbiotic particles, which is not conducive to their large-scale production and application.

[0006] Therefore, there is an urgent need to develop an economical and efficient biosorption method that has a high affinity for gold ions, good sedimentation performance, and is easy to separate from wastewater.

[0007] References

[0008] Reference 1: CN103421702A

[0009] Reference 2: CN102534211A

[0010] Reference 3: CN103191701A

[0011] Reference 4: Na Shen and Evans MN Chirwa, 2020. Live and lyophilizedfungi-algae pellets as novel biosorbents for gold recovery: Critical parameters, isotherm, kinetics and regeneration studies, BioresourceTechnology, 306, 123041. Summary of the Invention

[0012] The problem the invention aims to solve

[0013] Although existing technologies, such as those cited in references 1-3, have attempted to recover precious metals from water bodies, as mentioned earlier, current biosorbents often require chemical pretreatment, modification, and solidification processes, resulting in high preparation costs, complex processes, and severe secondary pollution, which greatly limits the large-scale production and application of these adsorbent materials. Furthermore, separating tiny biological cells or micron- and nano-sized adsorbent materials after crushing and grinding from solution remains a significant challenge, especially for large-scale applications. Traditional separation methods such as centrifugation, filtration, flotation, and chemical flocculation are too costly and energy-intensive. Although the method of pre-preparing microalgae and mycelial balls into algal-bacterial symbiotic particles (i.e., pre-formed algal-bacterial symbiotic particles) in reference 4 shows some potential for gold ion adsorption, its adsorption performance needs improvement. Moreover, this method, which separates the flocculation and adsorption processes, requires additional time and space to prepare and preserve the algal-bacterial symbiotic particles, which is not conducive to its large-scale production and application.

[0014] To overcome the aforementioned problems in the prior art, this invention provides a method for the simultaneous microalgae flocculation and adsorption of gold ions from wastewater using a microalgae-mycelium ball combination without any chemical pretreatment or modification / solidification. Utilizing the abundant functional groups on the surface of fungal and microalgae cells, and the increased secretion of extracellular polymers by both in response to gold ion stimulation, this method not only enhances the adsorption performance of gold ions by microalgae and fungi, but also allows microalgae cells to rapidly immobilize on the mycelium balls, forming stable and large-particle-size algae-fungus symbiotic particles in situ. This achieves efficient, low-consumption, and rapid solid-liquid separation. Compared to pre-formed algae-fungus symbiotic particles and the adsorption of gold ions by microalgae or fungi alone, the in-situ algae-fungus symbiotic particle formation method provided by this invention not only improves the adsorption performance for gold ions but also combines the adsorption and flocculation processes. It eliminates the need for additional time and space for preparing and storing algae-fungus symbiotic particles, shortening adsorbent preparation time, saving floor space, and reducing the cost of large-scale production and application.

[0015] Solution for solving the problem

[0016] [1]. A method for adsorbing and recovering precious metals from aqueous samples, wherein the method comprises:

[0017] The step of adding an adsorbent to an aqueous sample, wherein the adsorbent comprises microalgae and mycelial balls, and prior to adding the adsorbent to the aqueous sample, the microalgae and mycelial balls in the adsorbent have not flocculated and have not formed symbiotic particles;

[0018] The step of adsorbing precious metals from aqueous samples involves using the adsorbent to adsorb the precious metals from the aqueous samples.

[0019] Preferably, the precious metal includes gold, cobalt, and nickel; more preferably, the precious metal is gold.

[0020] Preferably, in the step of adsorbing precious metals in an aqueous sample, while the adsorbent adsorbs the precious metals in the aqueous sample, the microalgae and mycelial balls in the adsorbent flocculate to form symbiotic particles.

[0021] [2]. According to the method of [1], the step of adjusting pH is further included before the step of adding adsorbent to aqueous sample, wherein the pH value of aqueous sample is adjusted to 2 to 5, preferably 2 to 4.

[0022] [3]. According to the method of [1] or [2], wherein, on a dry weight basis, the mass ratio of the mycelial balls to the microalgae is 1:1 to 10, preferably 1:1 to 5.

[0023] [4]. The method according to any one of [1] to [3], wherein the particle size of the mycelial balls is 5 to 15 mm, preferably 8 to 12 mm;

[0024] Optionally, the mycelial balls are live mycelial balls or freeze-dried mycelial balls.

[0025] [5]. The method according to any one of [1] to [4], wherein the microalgae exist in the form of a suspension;

[0026] Preferably, the absorbance of the microalgae suspension at 680 nm is 0.5~2, more preferably 0.8~1.5.

[0027] [6]. The method according to any one of [1] to [5], wherein the mycelium ball is a mycelium ball formed from fungi or bacteria;

[0028] Optionally, the fungus is selected from at least one of filamentous fungi and yeasts;

[0029] Optionally, the bacteria are selected from at least one of actinomycetes, iron bacteria, and sulfur bacteria;

[0030] Preferably, the fungus is selected from at least one of Aspergillus niger, Aspergillus oryzae, Rhizopus oryzae, Cladosporium cladosporoides, and Aspergillus nidulans.

[0031] More preferably, the fungus includes Aspergillus niger.

[0032] And / or,

[0033] The microalgae are selected from at least one of freshwater microalgae, red algae, and brown algae;

[0034] Preferably, the microalgae are selected from at least one of Tetradesmus obliquus, Chlorella vulgaris, Chlorococcum ellipsoideum, and Phaeodactylumtricornutum; more preferably, the microalgae include Tetradesmus obliquus.

[0035] [7]. The method according to any one of [1] to [6], wherein the aqueous sample is a water sample;

[0036] Optionally, the water sample is selected from at least one of water samples from the aquatic environment, industrial wastewater, mining and mineral processing wastewater, domestic water, solid digestion solution, and eluent.

[0037] [8]. The method according to any one of [1] to [7], wherein, after the step of adsorbing the precious metal in the aqueous sample, a step of recovering the precious metal is further included, wherein,

[0038] Add a desorption solution to the adsorbent obtained in the step of adsorbing precious metals from the aqueous sample to desorb the precious metals from the adsorbent.

[0039] [9]. An adsorbent comprising microalgae and mycelial balls;

[0040] Optionally, the mass ratio of the mycelial balls to the microalgae is 1:1 to 10, preferably 1:1 to 5, based on dry weight.

[0041] Optionally, the mycelial balls have a particle size of 5-15 mm, preferably 8-12 mm;

[0042] Optionally, the mycelial balls are live mycelial balls or freeze-dried mycelial balls;

[0043] Optionally, the microalgae exist in the form of a suspension; preferably, the absorbance of the microalgae suspension at 680 nm is 0.5~2, more preferably 0.8~1.5;

[0044] Preferably, before using the adsorbent, the microalgae and mycelial balls in the adsorbent have not flocculated and have not formed symbiotic particles.

[0045]

[10] . The adsorbent according to [9], wherein the mycelium ball is a mycelium ball formed from fungi or bacteria;

[0046] Optionally, the fungus is selected from at least one of filamentous fungi and yeasts;

[0047] Optionally, the bacteria are selected from at least one of actinomycetes, iron bacteria, and sulfur bacteria;

[0048] Preferably, the fungus is selected from at least one of Aspergillus niger, Aspergillus oryzae, Rhizopus oryzae, Cladosporium cladosporoides, and Aspergillus nidulans.

[0049] More preferably, the fungus includes Aspergillus niger.

[0050] And / or,

[0051] The microalgae are selected from at least one of freshwater microalgae, red algae, and brown algae;

[0052] Preferably, the microalgae are selected from at least one of Tetradesmus obliquus, Chlorella vulgaris, Chlorococcum ellipsoideum, and Phaeodactylumtricornutum;

[0053] More preferably, the microalgae include Tetradesmus obliquus.

[0054]

[11] . An apparatus for adsorbing and recovering precious metals from aqueous samples, wherein the apparatus comprises an adsorbent as described in [9] or

[10] ;

[0055] Preferably, the precious metal includes gold, cobalt, and nickel;

[0056] More preferably, the precious metal is gold.

[0057]

[12] . Use of the adsorbents described in [9] or

[10] in the adsorption and recovery of precious metals from aqueous samples;

[0058] Preferably, the precious metal includes gold, cobalt, and nickel;

[0059] More preferably, the precious metal is gold.

[0060] The effects of the invention

[0061] This invention overcomes the technical problems of high usage costs and serious secondary pollution caused by the need for chemical pretreatment and modification and solidification of bioadsorbents, as well as the difficulty in solid-liquid separation of tiny biological cells or micron- and nano-sized adsorbent materials after crushing and grinding. To shorten the adsorbent preparation time, save floor space, and reduce production costs, the adsorption and flocculation processes are carried out simultaneously. A simple biological hybrid system combining mycelial balls and microalgae achieves rapid and selective adsorption of gold ions and simultaneous, efficient, and low-consumption separation of microalgal cells. Utilizing the abundant functional groups on the surface of fungal and microalgal cells, and the fact that both secrete more extracellular polymers under the stimulation of gold ions, not only is the adsorption performance for gold ions improved, but also a large number of microalgal cells are captured in situ by the mycelial balls, stably forming large algae-fungus symbionts of 9-10 mm. Furthermore, no additional time and space are required to prepare and preserve the algae-fungus symbiont particles, reducing the cost of large-scale production and application. Thus, an economical and efficient bioadsorption method with high gold ion affinity, good sedimentation performance, and easy separation from wastewater is achieved. Attached Figure Description

[0062] Figure 1 Showing active fungal hyphae ( Figure 1 A) and freeze-dried fungal mycelial balls ( Figure 1 The diagram in section B) illustrates the adsorption and recovery of gold ions from wastewater by flocculated microalgae.

[0063] Figure 2 The time-concentration curves showing the gold ion and microalgae flocculation efficiency in Example 1 and Comparative Examples 1, 2, and 3 of this invention are displayed. Figure 2 The upper center displays a combination of microalgae and active Aspergillus niger particles; Figure 2 (The image below shows a combination of microalgae and freeze-dried Aspergillus niger granules.)

[0064] Figure 3 This shows the time-concentration curves of gold ions in Example 2 and Comparative Examples 4 and 5 of the present invention.

[0065] Figure 4 This diagram illustrates the process of gold ion recovery from PCB wastewater by immobilizing microalgae with mycelial balls, as shown in Example 4 of the present invention. Detailed Implementation

[0066] Various exemplary embodiments, features, and aspects of the present invention will be described in detail below. The term "exemplary" as used herein means "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments.

[0067] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art should understand that the present invention can be practiced without certain specific details. In other instances, methods, means, apparatus, and steps well known to those skilled in the art have not been described in detail in order to highlight the spirit of the present invention.

[0068] Unless otherwise stated, all units used in this specification are international standard units, and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors that are unavoidable in industrial production.

[0069] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0070] In this specification, references to "some specific / preferred embodiments," "other specific / preferred embodiments," "implementation," etc., refer to specific elements (e.g., features, structures, properties, and / or characteristics) related to that embodiment, which are included in at least one of the embodiments described herein and may or may not be present in other embodiments. Furthermore, it should be understood that these elements may be combined in any suitable manner in various embodiments.

[0071] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0072] In this instruction manual, when "room temperature" or "room temperature" is used, the temperature can be approximately 15-30℃. Invention Details

[0074]

[0075] In some aspects of the present invention, a method for adsorbing and recovering precious metals from an aqueous sample is provided, wherein the method comprises:

[0076] The step of adding an adsorbent to an aqueous sample, wherein the adsorbent comprises microalgae and mycelial balls, and prior to adding the adsorbent to the aqueous sample, the microalgae and mycelial balls in the adsorbent have not flocculated and have not formed symbiotic particles;

[0077] The step of adsorbing precious metals from aqueous samples involves using the adsorbent to adsorb the precious metals from the aqueous samples.

[0078] In some preferred embodiments, during the step of adsorbing precious metals in an aqueous sample, the microalgae and mycelial balls in the adsorbent flocculate to form symbiotic particles while the adsorbent adsorbs the precious metals in the aqueous sample.

[0079] Compared with existing methods that pre-prepare microalgae and mycelial balls into algal-microalgae symbiotic particles, the method of simultaneously adsorbing precious metals and flocculating microalgae cells in this invention not only improves the adsorption performance of precious metals, but also combines the adsorption and flocculation processes, eliminating the need for additional time and space to prepare and preserve algal-microalgae symbiotic particles, thus having a greater advantage in their large-scale production applications.

[0080] Steps for adding adsorbent to aqueous samples

[0081] (Mycelial balls)

[0082] In this invention, there are no special restrictions on the source of mycelial balls. For example, they can be fungi or bacteria that can form mycelial balls when cultured in a liquid culture medium with aeration, stirring or shaking.

[0083] In some embodiments, the fungus may be selected from at least one of filamentous fungi and yeasts.

[0084] In some preferred embodiments, the fungus is selected from at least one of Aspergillus niger, Aspergillus oryzae, Rhizopus oryzae, Cladosporium cladosporoides, and Aspergillus nidulans.

[0085] In some preferred embodiments, the fungus comprises Aspergillus niger. Aspergillus niger is commercially available, for example, from the China Industrial Microbial Culture Collection Center, exemplarily strain number CICC 2487.

[0086] In other embodiments, the bacteria are selected from at least one of actinomycetes, iron bacteria, and sulfur bacteria.

[0087] In this invention, fungal mycelial balls, also known as fungal particles, are a special fermentation form of fungi (such as filamentous fungi). Under conditions of sufficient oxygen and nutrients, low viscosity of the culture medium, and appropriate directional shear hydraulic strength, germinating filamentous fungal spores form mycelia, which intertwine with each other to form a spherical mycelial aggregate with a dense surface and a loose interior.

[0088] In some embodiments of the present invention, the mycelial balls have a particle size of 5-15 mm, preferably 8-12 mm, and more preferably 9-10 mm. At this particle size, when adsorbing and recovering precious metals (e.g., gold ions) from aqueous samples, the in-situ formed algal-bacterial symbiotic particles are easily separated from the wastewater and can quickly settle to the bottom of the reactor within seconds, eliminating the need for other energy-intensive separation methods such as centrifugation, filtration, and flotation.

[0089] In some embodiments of the present invention, the mycelial balls are live mycelial balls or freeze-dried mycelial balls. In some preferred embodiments, the mycelial balls are live mycelial balls, and the adsorbent using live mycelial balls has higher adsorption efficiency and adsorption capacity compared to using freeze-dried mycelial balls.

[0090] (Microalgae)

[0091] In this invention, there are no special requirements for the selection of microalgae, as long as they can be flocculated and captured by hyphal balls (e.g., fungal hyphal balls, more specifically filamentous fungal hyphal balls).

[0092] In some embodiments, the microalgae are selected from at least one of freshwater microalgae, red algae, and brown algae.

[0093] In some preferred embodiments, the microalgae are selected from at least one of Tetradesmus obliquus, Chlorella vulgaris, Chlorococcumellipsoideum, and Phaeodactylum tricornutum.

[0094] In some preferred embodiments, the microalgae includes *Tetradesmus obliquus*. *Tetradesmus obliquus* is commercially available, for example, from the Freshwater Algae Culture Collection of the Chinese Academy of Sciences, with the exemplary species number FACHB-12.

[0095] In some embodiments, the microalgae exist in the form of a suspension. Exemplarily, the suspension is a suspension of microalgae formed in water. In some preferred embodiments, the absorbance of the microalgae suspension at 680 nm is 0.5–2, preferably 0.8–1.5, and more preferably 1.1–1.3. Using a suspension, especially at the aforementioned absorbance, when the microalgae suspension is combined with mycelial balls as an adsorbent, can improve the adsorption efficiency and capacity of the adsorbent for precious metals (e.g., gold ions).

[0096] (Ratio of mycelial balls to microalgae)

[0097] In some embodiments, the mass ratio of the mycelial balls to the microalgae in the adsorbent, based on dry weight, is 1:1 to 10, preferably 1:1 to 5. Within the above mass ratio range, the adsorbent exhibits superior adsorption efficiency, adsorption capacity, etc.

[0098] (precious metals)

[0099] In some embodiments, the precious metal includes gold, cobalt, and nickel. In some preferred embodiments, the precious metal is gold. As demonstrated in Example 4, the adsorbent used in the method of the present invention has a strong selective adsorption capacity for gold.

[0100] (Aqueous sample)

[0101] The aqueous sample applicable to this invention is not particularly limited and can be an aqueous sample of any source and type. In some specific embodiments, the aqueous sample can be a water sample.

[0102] In some specific implementation schemes, the water sample may be industrial wastewater (such as the printed circuit board wastewater in the examples), mining and mineral processing wastewater, domestic water (such as tap water, drinking water, beverage water, etc.), various solid digestion solutions, eluents, etc.

[0103] Steps for adsorbing precious metals from aqueous samples

[0104] In this invention, the step of adsorbing precious metals in an aqueous sample involves using an adsorbent to adsorb the precious metals in the aqueous sample.

[0105] In some embodiments, the adsorption of precious metals in aqueous samples is carried out using an adsorbent at room temperature, preferably 25 ± 2°C. At this temperature, it is advantageous to improve the adsorption efficiency and capacity of the adsorbent for precious metals (e.g., gold ions).

[0106] In this invention, there are no particular restrictions on the containers or equipment used when using adsorbents to adsorb precious metals (such as gold ions) from aqueous samples, as long as the adsorbent can be in full contact with the aqueous sample, which is conducive to the adsorption of precious metals from the aqueous sample.

[0107] For example, in some embodiments, the step of adsorbing precious metals from an aqueous sample can be carried out in a track shaker, for example at a rotation speed of 150-500 rpm, preferably 200-400 rpm. In other embodiments, the step of adsorbing precious metals from an aqueous sample can be carried out in a tower-type upflow reactor, with aeration at the bottom of the reactor using an air compressor.

[0108] The method for adsorbing and recovering precious metals from aqueous samples provided by this invention has high adsorption efficiency. Therefore, the step of adsorbing precious metals from aqueous samples can be completed within 10 hours, preferably within 8 hours, and more preferably within 6 hours. As demonstrated in Example 3, using the method of this invention, the adsorption rate of gold ions by the microalgae-active fungus particle combination reaches 98.8% within 3 hours.

[0109] Steps to adjust pH

[0110] In some embodiments, prior to the step of adding the adsorbent to the aqueous sample, a step of adjusting the pH is included, wherein the initial pH value of the aqueous sample is adjusted to 2 to 5, preferably 2 to 4 (e.g., 2, 2.5, 3, 3.5, 4), and more preferably 3.5 ± 0.3.

[0111] At this pH value, the adsorption efficiency and adsorption capacity of the adsorbent for gold ions can be improved.

[0112] In this invention, the initial pH value of an aqueous sample refers to the pH value of the aqueous sample before the adsorbent is added to the aqueous sample (e.g., a solution containing gold ions).

[0113] In this invention, there are no particular limitations on the acidic or alkaline reagents used to adjust the initial pH of aqueous samples; commonly used acid and base adjusters in the art can be used. In some specific embodiments, HCl and / or NaOH can be used.

[0114] Steps for recycling precious metals

[0115] In this invention, after the step of adsorbing precious metals from aqueous samples, a step of recovering precious metals from the adsorbent may be included. During desorption, a desorbent (such as an acid, alkali, or complex) is used to strip the precious metal ions loaded on the adsorbent and release them into a smaller desorption liquid, thereby reducing the cost and energy consumption of subsequent recovery processes (such as electrolysis). Electrolysis is one of the commonly used methods for recovering elemental metals from desorption liquids containing precious metal ions. Under the action of direct current, gold ions migrate to the cathode and are deposited on it. When the gold deposited on the cathode accumulates to a certain amount, the cathode is removed, washed, and the elemental gold is recovered. In some specific embodiments, thiourea, acid, alkali, and chelating agents are added to the adsorbent (i.e., algae-bacterial symbiotic particles loaded with precious metals, such as gold ions) obtained in the step of adsorbing precious metals from aqueous samples as a desorption liquid, thereby desorbing the precious metals from the adsorbent.

[0116] In some specific implementations, a step of washing the adsorbent is included before the step of recovering precious metals. Specifically, the adsorbent is washed with deionized water.

[0117] In some preferred embodiments, the desorption solution (thiourea) is an acidic desorption solution with a pH of 3 or less, preferably 2 or less, more preferably 1 or less, for example 0.7.

[0118] In some specific embodiments, the desorption time is within 3 hours, preferably within 2 hours, and more preferably within 1 hour, for example, 30 minutes. As demonstrated in Example 4, 1 M acidic thiourea (pH=0.7) can strip 92.12% of gold ions from algal-bacterial symbiotic particles within 30 minutes. The thiourea desorption solution containing gold ions is placed in an electrolytic cell using an electrolytic method. Under the action of direct current, the gold ions migrate to the cathode and are deposited on it. When a certain amount of gold accumulates on the cathode, the cathode is removed, washed, and the elemental gold is recovered.

[0119] <Adsorbent>

[0120] In some aspects of the present invention, an adsorbent is provided, wherein the adsorbent comprises microalgae and mycelial balls. Prior to use of the adsorbent, the microalgae and mycelial balls in the adsorbent have not flocculated or formed symbiotic particles.

[0121] (Mycelial balls)

[0122] In this invention, there are no special restrictions on the source of mycelial balls. For example, they can be fungi or bacteria that can form mycelial balls when cultured in a liquid culture medium with aeration, stirring or shaking.

[0123] In some embodiments, the fungus may be selected from at least one of filamentous fungi and yeasts.

[0124] In some preferred embodiments, the fungus is selected from at least one of Aspergillus niger, Aspergillus oryzae, Rhizopus oryzae, Cladosporium cladosporoides, and Aspergillus nidulans.

[0125] In some preferred embodiments, the fungus comprises Aspergillus niger. In other embodiments, the bacteria are selected from at least one of actinomycetes, iron bacteria, and sulfur bacteria.

[0126] In some embodiments of the present invention, the mycelial balls have a particle size of 5-15 mm, preferably 8-12 mm, and more preferably 9-10 mm. At this particle size, when adsorbing and recovering precious metals (e.g., gold ions) from aqueous samples, the in-situ formed algal-bacterial symbiotic particles are easily separated from the wastewater and can quickly settle to the bottom of the reactor within seconds, eliminating the need for other energy-intensive separation methods such as centrifugation, filtration, and flotation.

[0127] In some embodiments of the present invention, the mycelial balls are live mycelial balls or freeze-dried mycelial balls. In some preferred embodiments, the mycelial balls are live mycelial balls, and the adsorbent using live mycelial balls has higher adsorption efficiency and adsorption capacity compared to using freeze-dried mycelial balls.

[0128] (Microalgae)

[0129] In this invention, there are no special requirements for the selection of microalgae, as long as they can be flocculated and captured by hyphal balls (e.g., fungal hyphal balls, more specifically filamentous fungal hyphal balls).

[0130] In some embodiments, the microalgae are selected from at least one of freshwater microalgae, red algae, and brown algae.

[0131] In some preferred embodiments, the microalgae are selected from at least one of Tetradesmus obliquus, Chlorella vulgaris, Chlorococcumellipsoideum, and Phaeodactylum tricornutum.

[0132] In some preferred embodiments, the microalgae include Tetradesmus obliquus.

[0133] In some embodiments, the microalgae exist in the form of a suspension. Exemplarily, the suspension is a suspension of microalgae formed in water. In some preferred embodiments, the absorbance of the microalgae suspension at 680 nm is 0.5–2, preferably 0.8–1.5, and more preferably 1.1–1.3. Using a suspension, especially at the aforementioned absorbance, when the microalgae suspension is combined with mycelial balls as an adsorbent, can improve the adsorption efficiency and capacity of the adsorbent for precious metals (e.g., gold ions).

[0134] (Ratio of mycelial balls to microalgae)

[0135] In some embodiments, the mass ratio of the mycelial balls to the microalgae in the adsorbent, based on dry weight, is 1:1 to 10, preferably 1:1 to 5. Within the above mass ratio range, the adsorbent exhibits superior adsorption efficiency, adsorption capacity, etc.

[0136] <device>

[0137] In some aspects of the present invention, an apparatus for adsorbing and recovering precious metals from aqueous samples is provided, wherein the apparatus comprises an adsorbent as described in the preceding <Adsorbent> section.

[0138] In some embodiments, the precious metal includes gold, cobalt, and nickel. In some preferred embodiments, the precious metal is gold.

[0139] <Applications>

[0140] In some aspects of the present invention, the use of adsorbents as described in the preceding <Adsorbents> section in the adsorption and recovery of precious metals in aqueous samples.

[0141] In some embodiments, the precious metal includes gold, cobalt, and nickel. In some preferred embodiments, the precious metal is gold.

[0142] Example

[0143] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0144] The experimental materials used in the subsequent reference examples and embodiments are as follows:

[0145] Tetradesmus obliquus: Provided by the School of Life Sciences and Biotechnology, Shanghai Jiao Tong University. Tetradesmus obliquus can also be purchased from the Freshwater Algae Culture Collection, Chinese Academy of Sciences, for example, species number FACHB-12.

[0146] Aspergillus niger: Provided by the Forestry and Agricultural Biotechnology Institute (FABI) at the University of Pretoria, South Africa. Aspergillus niger is also available from the China Industrial Microbial Culture Collection Center, for example, strain number CICC2487.

[0147] The formulation of BG-11 medium is shown in Table 1 below:

[0148] Table 1. BG-11 culture medium formulation (1L)

[0149]

[0150] Potato glucose agar (PDA): 200 g potato, 20 g glucose, 20 g agar, 5 g peptone, 3 g potassium dihydrogen phosphate, 1.5 g magnesium sulfate, 1000 ml water.

[0151] Potato glucose liquid culture medium (PDB): 200 g potato, 20 g glucose, 5 g peptone, 3 g potassium dihydrogen phosphate, 1.5 g magnesium sulfate, 1000 ml water.

[0152] Thiourea: purchased from Merck.

[0153] Example: An exemplary technical solution of the method for adsorption and recovery of precious metals from aqueous samples provided by the present invention is as follows:

[0154] Microalgae cultivation: The freshwater microalga *Tetradesmus obliquus* was used. To obtain a faster growth rate, this pure strain was cultured in sterile BG-11 medium at pH 7 at room temperature (25 ± 2°C) using 60 μmol / L... -2 s -1 Under intense light and with simultaneous air aeration and stirring to provide CO2, the algae were diluted to the appropriate concentration with sterile deionized water after 7 days of growth.

[0155] Formation of fungal mycelial balls: Using the filamentous fungus *Aspergillus niger*, a pure strain of this fungus was placed on sterile potato dextrose agar (PDA) plates and incubated at 28°C for 7 days for activation. When collecting spores, 10 mL of sterile water was added to the PDA plate, and the fungal spore suspension was collected using a sterile syringe. This suspension was then diluted with sterile water to 50 mL before use. The spore suspension was used as inoculum for fungal particle culture, and the initial concentration of the *Aspergillus niger* spore suspension was adjusted to approximately 7.2 × 10⁻⁶ with sterile water. 3 The spore count in the suspension was determined using an optical microscope. The spores were then cultured in potato dextrose liquid medium (PDB) at pH 4 and shaken thoroughly in a track shaker at 28°C and 120 rpm. After 4–5 days of culture, mycelial pellets with a diameter of 9–10 mm formed. These pellets were thoroughly rinsed with sterile deionized water and used as live fungal particles. The live fungal particles were then freeze-dried and stored at room temperature for later use.

[0156] Microalgae-fungus particle combination adsorption and recovery of gold ions from wastewater: A microalgae suspension (Tetradesmus obliquus) was diluted to an absorbance of 1.2 at 680 nm, and 35 mg (dry weight) of active or lyophilized fungal particles (9-10 mm particle size) were added to the microalgae suspension (fungus to microalgae dry weight ratio 1:2). The algal solution and active or lyophilized fungal particles were respectively added to 100 mL of a HAuCl4 gold ion solution with an initial pH of 3.5 and an initial concentration of 100 mg / L. The solution was shaken at 250 rpm for 6 h at 25 ± 2°C in a track shaker. The initial pH was adjusted with HCl and NaOH. Figure 1 As shown.

[0157] Example 1

[0158] The initial concentration was 7.2 × 10⁻⁶. 3 Spores / mL: Aspergillus niger spore suspension was cultured in potato dextrose liquid medium (PDB) at pH 4 and shaken evenly in a track shaker at 28°C and 120 rpm. After 4-5 days of culture, fungal mycelial balls with a particle size of 9-10 mm were formed. These were thoroughly rinsed with sterile deionized water, and one portion was used as active fungal particles. The other portion of active fungal particles was freeze-dried and stored as freeze-dried fungal particles. The centrifuged and concentrated freshwater microalgae *Tetradesmus obliquus* was diluted with sterile deionized water to an absorbance of 1.2 at 680 nm, and two 100 ml OD aliquots were prepared. 680nm =1.2 The above algal solution was concentrated by centrifugation and used as fresh algal solution. 35 mg of dry weight, 9-10 mm particle size, active and lyophilized Aspergillus niger particles were weighed separately. The above microalgae-active Aspergillus niger particle combination and the microalgae-lyophilized Aspergillus niger particle combination were added to 100 mL of HAuCl4 solution with an initial pH of 3.5 and an initial concentration of 80 mg / L. The mixture was shaken at 250 rpm for 6 h at room temperature (25±2°C) on a track shaker. Samples were taken at 60, 120, 180, 240, 300, and 360 min. The samples were centrifuged at 8000 rpm for 5 min, and the supernatant was collected. The gold ion concentration was determined using atomic absorption spectrometry. The results are as follows: Figure 2 As shown.

[0159] Comparative Example 1

[0160] Same as Example 1, except that the initial pH of the solution was 2. The initial concentration was 7.2 × 10⁻⁶. 3Spores / mL: Aspergillus niger spore suspension was cultured in potato dextrose liquid medium (PDB) at pH 4 and shaken evenly in a track shaker at 28°C and 120 rpm. After 4-5 days of culture, fungal mycelial balls with a particle size of 9-10 mm were formed. These were thoroughly rinsed with sterile deionized water, and one portion was used as active fungal particles. The other portion of active fungal particles was freeze-dried and stored as freeze-dried fungal particles. The centrifuged and concentrated freshwater microalgae *Tetradesmus obliquus* was diluted with sterile deionized water to an absorbance of 1.2 at 680 nm, and two 100 ml OD aliquots were prepared. 680nm =1.2 The above algal solution was concentrated by centrifugation and used as fresh algal solution. 35 mg of dry weight, 9-10 mm particle size, active and lyophilized Aspergillus niger particles were weighed separately. The above microalgae-active Aspergillus niger particle combination and the microalgae-lyophilized Aspergillus niger particle combination were added to 100 mL of HAuCl4 solution with an initial pH of 2 and an initial concentration of 80 mg / L. The mixture was shaken at 250 rpm for 6 h at room temperature (25±2°C) on a track shaker. Samples were taken at 60, 120, 180, 240, 300, and 360 min. The samples were centrifuged at 8000 rpm for 5 min, and the supernatant was collected. The gold ion concentration was determined using atomic absorption spectrometry. The results are as follows: Figure 2 As shown.

[0161] Comparative Example 2

[0162] Same as Example 1, except that the initial pH of the solution was 4. The initial concentration was 7.2 × 10⁻⁶. 3 Spores / mL: Aspergillus niger spore suspension was cultured in potato dextrose liquid medium (PDB) at pH 4 and shaken evenly in a track shaker at 28°C and 120 rpm. After 4-5 days of culture, fungal mycelial balls with a particle size of 9-10 mm were formed. These were thoroughly rinsed with sterile deionized water, and one portion was used as active fungal particles. The other portion of active fungal particles was freeze-dried and stored as freeze-dried fungal particles. The centrifuged and concentrated freshwater microalgae *Tetradesmus obliquus* was diluted with sterile deionized water to an absorbance of 1.2 at 680 nm, and two 100 ml OD aliquots were prepared. 680nm=1.2 The above algal solution was concentrated by centrifugation and used as fresh algal solution. 35 mg of dry weight, 9-10 mm particle size, active and lyophilized Aspergillus niger particles were weighed separately. The above microalgae-active Aspergillus niger particle combination and the microalgae-lyophilized Aspergillus niger particle combination were added to 100 mL of HAuCl4 solution with an initial pH of 4 and an initial concentration of 80 mg / L. The mixture was shaken at 250 rpm for 6 h at room temperature (25±2°C) on a track shaker. Samples were taken at 60, 120, 180, 240, 300, and 360 min. The samples were centrifuged at 8000 rpm for 5 min, and the supernatant was collected. The gold ion concentration was determined using atomic absorption spectrometry. The results are as follows: Figure 2 As shown.

[0163] Comparative Example 3

[0164] Same as Example 1, except that the initial pH of the solution was 5. The initial concentration was 7.2 × 10⁻⁶. 3 Spores / mL: Aspergillus niger spore suspension was cultured in potato dextrose liquid medium (PDB) at pH 4 and shaken evenly in a track shaker at 28°C and 120 rpm. After 4-5 days of culture, fungal mycelial balls with a particle size of 9-10 mm were formed. These were thoroughly rinsed with sterile deionized water, and one portion was used as active fungal particles. The other portion of active fungal particles was freeze-dried and stored as freeze-dried fungal particles. The centrifuged and concentrated freshwater microalgae *Tetradesmus obliquus* was diluted with sterile deionized water to an absorbance of 1.2 at 680 nm, and two 100 ml OD aliquots were prepared. 680nm =1.2 The above algal solution was concentrated by centrifugation and used as fresh algal solution. 35 mg of dry weight, 9-10 mm particle size, active and lyophilized Aspergillus niger particles were weighed separately. The above microalgae-active Aspergillus niger particle combination and the microalgae-lyophilized Aspergillus niger particle combination were added to 100 mL of HAuCl4 solution with an initial pH of 5 and an initial concentration of 80 mg / L. The mixture was shaken at 250 rpm for 6 h at room temperature (25±2°C) on a track shaker. Samples were taken at 60, 120, 180, 240, 300, and 360 min. The samples were centrifuged at 8000 rpm for 5 min, and the supernatant was collected. The gold ion concentration was determined using atomic absorption spectrometry. The results are as follows: Figure 2 As shown.

[0165] Experimental Results: Comparison of the results of Example 1 and Comparative Examples 1, 2, and 3 shows that the coexistence of fungal mycelial balls and microalgae under suitable pH conditions is crucial for efficient gold ion adsorption and microalgae flocculation. The flocculation effect was optimal at an initial pH of 3.5, and the microalgae-active Aspergillus niger particle combination was superior to the microalgae-freeze-dried Aspergillus niger particle combination, fixing over 95% of microalgae cells onto the active mycelial balls within 3 hours (Example 1). At an initial pH of 2, only about 80% of microalgae cells were fixed onto the active mycelial balls within 3 hours (Comparative Example 1); at an initial pH of 4, only about 73% of microalgae cells were fixed onto the active mycelial balls within 3 hours (Comparative Example 2); and at an initial pH of 5, only 64% of microalgae cells were fixed onto the active mycelial balls within 3 hours (Comparative Example 3). On the other hand, pH changes within the range of 2-5 have little effect on the adsorption of gold ions. Therefore, when the optimal pH is 3.5, the microalgae-Aspergillus niger particle combination has the best adsorption effect on gold ions, and the microalgae also has the best bioflocculation effect.

[0166] Example 2

[0167] The initial concentration was 7.2 × 10⁻⁶. 3 Spores / mL: Aspergillus niger spore suspension was cultured in potato dextrose liquid medium (PDB) at pH 4 and shaken evenly in a track shaker at 28°C and 120 rpm. After 4-5 days of culture, fungal mycelial balls with a particle size of 9-10 mm were formed. These were thoroughly rinsed with sterile deionized water, and one portion was used as active fungal particles. The other portion of active fungal particles was freeze-dried and stored as freeze-dried fungal particles. The centrifuged and concentrated freshwater microalgae *Tetradesmus obliquus* was diluted with sterile deionized water to an absorbance of 1.2 at 680 nm, and two 100 ml OD aliquots were prepared. 680nm =1.2 The above algal solution was concentrated by centrifugation and used as fresh algal solution. 35 mg of dry weight, 9-10 mm particle size, active and lyophilized Aspergillus niger particles were weighed separately. The above microalgae-active Aspergillus niger particle combination and the microalgae-lyophilized Aspergillus niger particle combination were added to 100 mL of HAuCl4 solution with an initial pH of 3.5 and an initial concentration of 100 mg / L. The mixture was shaken at 250 rpm for 6 h at room temperature (25±2°C) on a track shaker. Samples were taken at 5, 15, 30, 60, 120, 180, 240, 300, and 360 min. The samples were centrifuged at 8000 rpm for 5 min, and the supernatant was collected. The gold ion concentration was determined using atomic absorption spectrometry. The results are as follows: Figure 3 As shown, its adsorption kinetic constant (k2) and its adsorption capacity (q) at adsorption equilibrium are... e As shown in Table 2.

[0168] The Lagergren pseudo-second-order reaction model is a commonly used tool for analyzing adsorption kinetics, and its linear equation can be expressed as:

[0169] (1)

[0170] q t q represents the amount of gold ions adsorbed per unit mass of adsorbent at time t (mg / g). e k1 represents the amount of gold ions adsorbed per unit mass of adsorbent at equilibrium (mg / g), and k2 is the second-order adsorption rate constant. .

[0171] Comparative Example 4

[0172] Same as Example 2, except that microalgae are not added. The initial concentration was 7.2 × 10⁻⁶. 3 Spores / mL of Aspergillus niger spore suspension were cultured in potato dextrose liquid medium (PDB) at pH 4 and shaken at 28°C and 120 rpm in a track shaker. After 4-5 days of culture, fungal mycelial balls with a particle size of 9-10 mm were formed. These balls were thoroughly rinsed with sterile deionized water, and one portion was used as active fungal particles. The other portion of active fungal particles was freeze-dried and stored as freeze-dried fungal particles. The same dry weight of adsorbent as in Example 2 was weighed, and the active and freeze-dried fungal particles were added to 100 mL of HAuCl4 solution with an initial pH of 3.5 and an initial concentration of 100 mg / L. The mixture was shaken at 250 rpm for 6 h at room temperature (25±2°C). Samples were taken at 5, 15, 30, 60, 120, 180, 240, 300, and 360 min. The samples were centrifuged at 8000 rpm for 5 minutes, and the supernatant was collected. The gold ion concentration was determined using atomic absorption spectrometry. The results are as follows: Figure 3 As shown.

[0173] Comparative Example 5

[0174] Same as Example 2, except that Aspergillus niger is not added. Weigh the same amount of adsorbent as in Example 2, and calculate the absorbance of 0.1 g dry weight of microalgae as required by formula (2), which is 1.43. Dilute the centrifuged and concentrated freshwater microalgae Tetradesmus obliquus with sterile deionized water until the absorbance of the algal solution at 680 nm is 1.43, and prepare two 100 ml OD solutions. 680nm=1.43 The above algal solution was used in two ways: one portion was concentrated by centrifugation and kept as fresh algal solution, and the other portion was freeze-dried into algal powder. The fresh algal solution and the freeze-dried algal powder were added to 100 mL of HAuCl4 solution with an initial pH of 3.5 and an initial concentration of 100 mg / L, respectively. The solutions were mixed at 250 rpm for 6 h at room temperature (25 ± 2°C) on a rocker. Samples were taken at 5, 15, 30, 60, 120, 180, 240, 300, and 360 min. The samples were centrifuged at 8000 rpm for 5 min, and the supernatant was collected. The gold ion concentration was determined using atomic absorption spectrometry. The results are as follows: Figure 3 As shown.

[0175] (2)

[0176] Comparative Example 6

[0177] The initial concentration was 7.2 × 10⁻⁶. 3 Spores / mL of *Aspergillus niger* spore suspension were cultured in potato dextrose liquid (PDB) at pH 4 and shaken at 28°C and 120 rpm on a track shaker for 4–5 days to form fungal mycelial balls with a particle size of 9–10 mm. These mycelial balls were then thoroughly rinsed with sterile deionized water. The fungal mycelial balls were then added to a culture medium of *Tetradesmus obliquus* at pH 5.0 and a fungus-to-algae ratio of 1:2. The mixture was shaken at 25±2°C and 200 rpm for 3 h, and then thoroughly rinsed with deionized water to form algae-fungus symbiotic particles, which were then used as active algae-fungus symbiotic particles. A portion of these algae-fungus symbiotic particles were freeze-dried and stored as freeze-dried algae-fungus symbiotic particles for later use. Weigh the same amount of adsorbent as in Example 2 (dry weight). Add 100 mL of HAuCl4 solution (optimal initial pH = 3.5 for active algae-bacterial symbiotic particles with a particle size of 9-10 mm) and 100 mL of lyophilized algae-bacterial symbiotic particles (optimal initial pH = 2.0 for lyophilized algae-bacterial symbiotic particles) with an initial concentration of 100 mg / L. Shake at 250 rpm for 6 h at room temperature (25 ± 2°C) on a track shaker. Take samples at 5, 15, 30, 60, 120, 180, 240, 300, and 360 min. Centrifuge the samples at 8000 rpm for 5 min, collect the supernatant, and determine the gold ion concentration, adsorption kinetic constant (k2), and adsorption capacity (q) at adsorption equilibrium using atomic absorption spectrometry. e As shown in Table 2.

[0178] Table 2 Adsorption kinetic constants of algae-bacterial symbiotic particles and microalgae-mycelium ball combinations

[0179]

[0180] *Including the time for preparing the algal-microbe symbiotic particles and the time for adsorption to reach equilibrium.

[0181] Experimental Results: Comparing the results of Example 2 and Comparative Examples 4 and 5, it can be seen that in terms of gold ion adsorption efficiency, the microalgae-active fungal particle combination (Example 2, 99%) > microalgae-lyophilized fungal particle combination (Example 2, 95%) > active / lyophilized fungal particles (Comparative Example 4, 83%-85%) > active / lyophilized microalgae (Comparative Example 5, 80%-81%), and almost 100% of the microalgae cells were immobilized on the active or lyophilized fungal particles within 3-6 hours. Compared with the adsorption of gold ions by microalgae or fungi alone, the microalgae-fungus hyphae combination not only improves the adsorption performance of gold ions, but also stably immobilizes microalgae cells on fungal hyphae to form algae-fungus symbiotic particles with a larger particle size (9-10 mm) in situ, achieving rapid solid-liquid separation through simple sedimentation.

[0182] R 2 The closer the value is to 1, the better the model fits the data. In Example 2 and Comparative Example 6, the behavior of adsorbing gold ions closely matches the Lagergren pseudo-second-order reaction model. Compared with the method in Comparative Example 6 where microalgae and mycelial balls were prepared into algae-bacterial symbiotic particles in advance, the method in Example 2, which combines microalgae-mycelial ball adsorption of gold ions with simultaneous microalgae flocculation, has advantages in adsorption capacity, reaction rate, and running time. In Example 2, the adsorption capacity (100 mg / g) and adsorption rate of the microalgae-active Aspergillus niger particle combination are shown. All were higher than the microalgae-freeze-dried Aspergillus niger granule combination. In Comparative Example 6, the adsorption capacity (94.34 mg / g) and adsorption rate of the freeze-dried algae-bacteria symbiotic particles were... The activity level of algae-bacteria symbiotic particles is higher. Compared to methods that pre-prepare microalgae and mycelial balls into algae-bacterial symbiotic particles, the method of combining microalgae and mycelial balls to adsorb gold ions and simultaneously flocculate microalgae cells not only improves the adsorption performance of gold ions, but also combines the adsorption and flocculation processes. It eliminates the need for additional time and space to prepare and preserve algae-bacterial symbiotic particles, making it more advantageous for large-scale production applications.

[0183] Example 3

[0184] The microalgae-active Aspergillus niger granule combination and the microalgae-lyophilized Aspergillus niger granule combination from Example 1 were added to 100 mL of HAuCl4 solution with an initial pH of 3.5 and initial concentrations of 80, 100, 120, 150, and 200 mg / L, respectively. The solutions were then shaken at 250 rpm for 6 h at room temperature (25 ± 2°C) in a track shaker. Samples were taken after 360 min when adsorption reached stability, and the gold ion concentration, isothermal constant (b), and maximum adsorption capacity (q) of the two adsorbent combinations were determined using atomic absorption spectrometry. m As shown in Table 3. The Langmuir isotherm is one of the models describing the adsorption process, and its linear equation can be expressed as:

[0185] (3)

[0186] Ce is the concentration of gold ions in the solution at equilibrium (mg / L), and q is the concentration of gold ions in the solution at equilibrium. e q represents the amount of gold ions adsorbed per unit mass of adsorbent at equilibrium (mg / g). m denoted as σb, where σb is the maximum adsorption capacity of the adsorbent (mg / g), and b is a constant related to the adsorption energy (L / mg).

[0187] Table 3 Langmuir adsorption isotherms

[0188]

[0189] Experimental results: R 2 The closer the value is to 1, the better the model fits the data. In Example 3, the adsorption behavior of gold ions by the microalgae-fungus mycelium ball combination closely matches the Langmuir model. The maximum adsorption capacity of the microalgae-active fungus particle combination is significantly higher than that of the microalgae-freeze-dried fungus particle combination (163.93 mg / g), with a maximum adsorption capacity of 196.08 mg / g within 6 hours at room temperature and pressure. In contrast, in Reference 4, the maximum adsorption capacity of the freeze-dried pre-formed algae-fungus symbiotic particles (112 mg / g) within 6 hours at room temperature and pressure is higher than that of the active pre-formed algae-fungus symbiotic particles (104 mg / g). Compared with the method in Reference 4 that prepares microalgae and mycelium balls into algae-fungus symbiotic particles in advance, the method of simultaneous microalgae flocculation and adsorption of gold ions by the microalgae-mycelium ball combination in Example 3 improves the maximum adsorption capacity of gold ions by 75%.

[0190] Compared with other reported biosorbents, the microalgae-fungus mycelium ball combination in Example 3 showed a 2-9 fold increase in the adsorption performance of gold ions. Reference 1 used a manganese oxide-producing bacterium, Lysinibaeillus sp. M14, to adsorb trivalent gold ions from water, achieving an adsorption capacity of only 21 mg / g within 1 hour at room temperature and pressure; Reference 2 used modified mangosteen residue (particles smaller than 40 mesh) to adsorb gold ions from wastewater, achieving an adsorption capacity of 100 mg / g within 24 hours at room temperature and pressure. Furthermore, the reported water-soluble adsorbents (Reference 3), micron-sized particles (Reference 2), or bacterial cells (Reference 1) were difficult to separate from the solution. In Examples 1 and 2, almost 100% of the microalgae cells were stably fixed on the fungal mycelium balls after 3-6 hours of adsorption, forming large algae-fungus symbiotic particles with a diameter of 9-10 mm in situ. These particles settled to the bottom of the container within seconds, achieving rapid solid-liquid separation.

[0191] Example 4

[0192] like Figure 4 As shown, in a tower-type upflow reactor with a height-to-diameter ratio (H / D) of 5.9 (inner diameter 6 cm, effective liquid height 35.4 cm), 1 L of simulated printed circuit board (PCB) wastewater (with a gold ion concentration of 30 mg / L) with an initial pH of 3.5 was added. Centrifuged and concentrated fresh algal solution *Tetradesmus obliquus* (1 L of this algal solution has an absorbance of 1.2 at 680 nm) and 0.35 g of dry weight active fungal *Aspergillus niger* particles with a particle size of 9–10 mm were added, with a fungal to microalgae dry weight ratio of 1:2. The reactor was operated at room temperature (25 ± 2 °C), with aeration at the bottom using an air compressor. The concentrations of each component in the wastewater before and after adsorption are shown in Table 4.

[0193] After 3 h of adsorption, samples were extracted from heights of 1 / 4, 1 / 2, and 3 / 4 of the reactor bottom. Subsequently, the resulting algae-bacterial symbiotic particles rapidly settled to the bottom without aeration, and the treated wastewater was discharged from the bottom. Finally, the gold-ion-loaded algae-bacterial symbiotic particles were thoroughly washed in situ with deionized water, and 500 mL of 1 M thiourea was added as the desorption solution. The pH was adjusted to 0.7 with HNO3 / NaOH, and the concentrations of each component in the wastewater were determined using inductively coupled plasma mass spectrometry (ICP-MS).

[0194] Table 4. Components and concentrations in PCB wastewater before and after adsorption (pH=3.5, 25±2 °C)

[0195]

[0196] Experimental Results: In Example 4, the microalgae-active fungus particle combination achieved an adsorption rate of 98.8% for gold ions within 3 hours. Competitive adsorption results showed that despite the presence of some coexisting heavy metal ions, such as Ni and Co, the microalgae-active fungus particle combination only removed 9.49% of Ni and 9.52% of Co, respectively, but still exhibited strong selective adsorption for gold ions. Furthermore, the PCB wastewater contained 354.4 mg / L K... + The concentration was almost 12 times that of 30 mg / L gold ions, but it had no effect on the adsorption of gold ions. After 3 h of adsorption, nearly 80% of the microalgal cells were immobilized on the active fungal particles. The in-situ formed algal-fungus symbiotic particles could rapidly settle to the bottom of the reactor within seconds, eliminating the need for other energy-intensive separation methods such as centrifugation, filtration, and flotation. Finally, 1M acidic thiourea (pH=0.7) could remove 92.12% of the gold ions from the algal-fungus symbiotic particles within 30 min, concentrating them in 500 mL of solution, greatly reducing the cost and energy consumption of the next stage of electrolysis.

[0197] It should be noted that although the technical solution of the present invention has been described with specific examples, those skilled in the art will understand that the present invention should not be limited thereto.

[0198] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for adsorbing and recovering precious metals from aqueous samples, wherein, The method includes: The step of adding an adsorbent to an aqueous sample, wherein the adsorbent comprises microalgae and mycelial balls, and prior to adding the adsorbent to the aqueous sample, the microalgae and mycelial balls in the adsorbent have not flocculated and have not formed symbiotic particles; The step of adsorbing precious metals from aqueous samples involves using the adsorbent to adsorb the precious metals from the aqueous samples. The precious metals include gold, cobalt, and nickel; In the step of adsorbing precious metals in aqueous samples, while the adsorbent adsorbs the precious metals in the aqueous samples, the microalgae and mycelial balls in the adsorbent flocculate to form symbiotic particles. The mycelial ball is a mycelial ball formed from fungi, wherein the fungi are selected from at least one of filamentous fungi and yeasts; The microalgae are selected from at least one of Tetradesmus obliquus, Chlorella vulgaris, Chlorococcum ellipsoideum, and Phaeodactylum tricornutum.

2. The method according to claim 1, wherein, The precious metal in question is gold.

3. The method according to claim 1, wherein, Before the step of adding the adsorbent to the aqueous sample, a step of adjusting the pH is included, wherein the pH value of the aqueous sample is adjusted to 2-5.

4. The method according to claim 1, wherein, Before the step of adding the adsorbent to the aqueous sample, a step of adjusting the pH is included, wherein the pH value of the aqueous sample is adjusted to 2-4.

5. The method according to any one of claims 1 to 4, wherein, On a dry weight basis, the mass ratio of the mycelial balls to the microalgae is 1:1 to 10.

6. The method according to any one of claims 1 to 4, wherein, On a dry weight basis, the mass ratio of the mycelial balls to the microalgae is 1:1 to 5.

7. The method according to any one of claims 1 to 4, wherein, The mycelial balls have a particle size of 5-15 mm.

8. The method according to any one of claims 1 to 4, wherein, The mycelial balls have a particle size of 8-12 mm.

9. The method according to any one of claims 1 to 4, wherein, The mycelial balls are either live mycelial balls or freeze-dried mycelial balls.

10. The method according to any one of claims 1 to 4, wherein, The microalgae exist in the form of a suspension.

11. The method according to claim 10, wherein, The absorbance of the microalgae suspension at 680 nm is 0.5~2.

12. The method according to claim 10, wherein, The absorbance of the microalgae suspension at 680 nm is 0.8~1.

5.

13. The method according to any one of claims 1 to 4, wherein, The fungus is selected from at least one of Aspergillus niger, Aspergillus oryzae, Rhizopus oryzae, Cladosporium cladosporoides, and Aspergillus nidulans.

14. The method according to any one of claims 1 to 4, wherein, The fungi include Aspergillus niger.

15. The method according to any one of claims 1 to 4, wherein, The microalgae include Tetradesmus obliquus.

16. The method according to any one of claims 1 to 4, wherein, The aqueous sample is a water sample.

17. The method according to claim 16, wherein, The water sample is selected from at least one of the following: water samples from the aquatic environment, industrial wastewater, mining and mineral processing wastewater, domestic water, solid digestion solution, and eluent.

18. The method according to any one of claims 1 to 4, wherein, Following the step of adsorbing precious metals from the aqueous sample, a step of recovering the precious metals is also included, wherein... Add a desorption solution to the adsorbent obtained in the step of adsorbing precious metals from the aqueous sample to desorb the precious metals from the adsorbent.

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