A high purity gold refining process

Abstract

The application discloses a high-purity gold refining process in the technical field of gold refining, which comprises the following steps: after gold raw materials are made into pieces, the gold is dissolved in a hydrochloric acid-sodium chlorate system in steps and then is dissolved in aqua regia for strengthened final solution, gold-containing solutions are combined, a magnetic multi-tooth coordination inorganic modified material is added for deep adsorption of impurities, a purified chloroauric acid solution is obtained through separation under an applied magnetic field, high-purity gold is prepared through reduction precipitation, acid boiling and impurity removal and smelting in an inert atmosphere. The magnetic multi-tooth coordination inorganic modified material is prepared by using ferroferric oxide as a magnetic core, coating a silica layer and a porous zinc-aluminum layered double metal oxide shell layer in sequence, and then performing surface modification through amination, and is prepared through covalent grafting of ethylenediaminetetraacetic dianhydride and nitrilotriacetic acid and coordination anchoring. Through the cooperation of step-by-step gold dissolution and magnetic multi-tooth coordination adsorption, the gold dissolution rate and deep removal of impurities are effectively considered, the operation is simple, the adsorption material can be separated and recycled under an applied magnetic field, and the product has high purity.

Description

Technical Field

[0001] This invention relates to the field of gold refining technology, specifically to a high-purity gold refining process. Background Technology

[0002] Currently, the main chemical methods used in industrial gold refining include the chloride process, the aqua regia process, and the electrolysis process. The chloride process uses hydrochloric acid... When gold is dissolved in a chlorate system, the resulting chloroauric acid solution inevitably contains various impurity ions such as copper, iron, lead, and silver. These impurity ions originate from the gold raw material itself and enter the solution simultaneously with the gold during the dissolution process. Current chlorination processes typically rely solely on filtration to remove insoluble residues after gold dissolution, lacking targeted deep purification methods for dissolved impurity ions. Similarly, the aqua regia method, which uses a mixture of hydrochloric and nitric acids to dissolve gold, also dissolves almost all base metal impurities in the raw material due to its strong oxidizing properties, resulting in a higher concentration and more diverse range of impurities in the gold-containing solution. While electrolysis can achieve some degree of impurity separation by utilizing potential differences, when the content of impurities such as silver and copper in the raw material is high, these impurities continue to accumulate in the electrolyte and co-deposit with gold at the cathode, also facing the problem of incomplete impurity removal.

[0003] The core drawback of the existing processes mentioned above is that the gold-containing solutions obtained through gold dissolution or electrolysis contain various coexisting impurity ions that are difficult to remove deeply through conventional filtration, washing, or simple chemical precipitation. In the subsequent reduction and gold precipitation stage, these residual impurity ions compete with gold ions for reduction, or become trapped within the gold powder through co-precipitation or surface adsorption. Some impurities also form difficult-to-separate colloidal particles during the reduction process, further deteriorating product quality. The subsequent acid boiling process can only perform shallow cleaning of some impurities on the surface of the gold powder, and its effect on impurities trapped inside the particles or encapsulated during the reduction process is very limited. The combination of these multiple factors results in gold products prepared by existing processes having low purity and poor batch-to-batch quality stability, making it difficult to consistently and stably meet the industrial requirements of ultra-high purity of 99.999% and above. Therefore, how to achieve deep and selective impurity removal from the gold-containing solution while efficiently dissolving gold is a technical bottleneck that urgently needs to be overcome in this field.

[0004] This application proposes a gold dissolution route that organically combines chlorination and aqua regia processes. Chlorination uses hydrochloric acid-chlorate as the gold solvent, producing no nitrogen oxides throughout the process, making it environmentally friendly and avoiding the problems of large amounts of nitrogen oxides generated by the aqua regia process, which are difficult to treat and prone to exceeding emission standards. However, while chlorination initially dissolves quickly, the dissolution rate drops sharply as the reagents are consumed, with complete dissolution typically requiring 4-8 hours. Given the high price of gold, this excessively long production cycle leads to significant capital tied up. While the aqua regia process offers rapid dissolution, it generates large amounts of nitrogen oxides, resulting in a heavy treatment burden and high environmental risks. To comprehensively utilize the advantages of both methods, this application adopts a combined strategy: first, chlorination dissolves the gold to approximately 85% dissolution rate, then the remaining difficult-to-dissolve gold material is transferred to the aqua regia system for rapid dissolution. In this way, the vast majority of gold is dissolved under conditions without the release of nitrogen oxides, with only a small amount of gold undergoing short-term terminal dissolution using aqua regia, significantly reducing the total gold dissolution time and capital occupation. At the same time, due to the significant reduction in the amount of aqua regia used and the contact time, the total amount of nitrogen oxides generated and the instantaneous emission intensity are proportionally reduced, alleviating the pressure of waste gas treatment from the source, and reducing the excessive dissolution of impurities in the strong oxidizing aqua regia system, creating favorable liquid conditions for subsequent deep impurity removal and stable preparation of ultra-high purity gold. Summary of the Invention

[0005] The purpose of this invention is to provide a high-purity gold refining process that solves the technical problems of incomplete impurity removal and difficulty in achieving ultra-high product purity in existing processes.

[0006] The present invention achieves the above objectives through the following technical solutions: A high-purity gold refining process includes the following steps: S1. By weight, 100-120 parts of gold raw material are added to a sheet-making machine to form gold sheets; the gold sheets are ultrasonically cleaned with 300-500 parts of deionized water and dried at 78-82°C to obtain dried gold sheets; the dried gold sheets are placed in a dissolving vessel, 500-1000 parts of hydrochloric acid and 100-200 parts of deionized water are added, and then a mixture containing 28-40 parts of sodium chlorate and 50-100 parts of deionized water is added, stirred, and reacted at 60-85°C; after the reaction is completed, the mixture is allowed to stand. S2, add 100-300 parts of hydrochloric acid to the dissolving vessel, stir, and heat; cool to room temperature to obtain the cooled mixture; filter the cooled mixture to obtain a primary chloroauric acid solution and filter residue; S3: Wash the filter residue obtained in S2 with deionized water, and add 25-100 parts of aqua regia; heat to 70-90°C and stir the reaction; after the reaction is complete, filter to obtain a secondary gold-containing solution; place the secondary gold-containing solution in a denitrification vessel, add a solution containing 10-20 parts of urea and 30-60 parts of deionized water, and stir the reaction at 60-80°C to obtain a denitrification reaction mixture; combine the denitrification reaction mixture with the primary chloroauric acid solution obtained in S2, and add NaO dropwise. The pH of the H solution was adjusted to 1.5-2.5 and transferred to a reaction vessel. 0.5-2.0 parts of the magnetic multidentate coordination inorganic modifier were added. The mixture was stirred at 20-30°C. Separation was achieved using an external magnetic field to obtain a clear liquid and the magnetic multidentate coordination inorganic modifier. The clear liquid was filtered to obtain a purified and combined chloroauric acid solution. The magnetic multidentate coordination inorganic modifier was soaked in 100-200 parts of an aqueous solution of disodium ethylenediaminetetraacetate, washed with deionized water, and then dried. S4. Under stirring, the purified and combined chloroauric acid solution is heated to 50-70°C, and 150-200 parts of reducing agent are added. At the same time, NaOH solution is added dropwise to adjust the pH value to 1.5-2.5. After the reduction reaction is completed, stirring is continued, the mixture is allowed to stand, and vacuum filtration is performed to collect the gold powder. The gold powder is mixed with 150-300 parts of impurity removal reagent, heated, and filtered to obtain impurity-removed gold powder. The impurity-removed gold powder is washed with deionized water at 80-90°C, filtered, and the filtered wet gold powder is obtained. The filtered wet gold powder is dried at 105-115°C, naturally cooled to room temperature, transferred to a medium-frequency induction melting furnace, and melted at 1100-1150°C under an inert atmosphere. The melt is then cast into a preheated graphite mold and printed and surface-treated by a hydraulic press.

[0007] In this invention, the reaction mechanism of the high-purity gold refining process encompasses multiple continuous physicochemical processes, including gold oxidation leaching, impurity chelation purification, liquid-phase denitration, and specific reduction purification. During the gold dissolution stage, physical compression increases the specific surface area of ​​the gold raw material. In the acidic chlorination gold dissolution system, sodium chlorate undergoes self-accelerated disproportionation and redox reactions under a strong acid environment, continuously generating nascent chlorine gas and trace amounts of chlorine dioxide gas with extremely strong oxidizing properties. These strong oxides rapidly attack the crystal lattice of elemental gold, causing it to lose electrons and complex with chloride ions in the system, generating stable tetrachloroalloy anions that enter the solution. Simultaneously, the excess dissolved free chlorine gas must be completely removed through a continuous boiling physical gas-liquid mass transfer process to prevent it from poisoning the subsequent reducing agent. For the gold-containing filter residue that is not completely dissolved, a second deep leaching is carried out by taking advantage of the synergistic effect of the strong oxidizing property of nitric acid and the strong complexing property of hydrochloric acid in aqua regia. Urea is introduced as a denitrifying agent before merging. The amino group of urea molecules undergoes a violent disproportionation reaction with free nitric acid under heating conditions, generating non-toxic nitrogen gas and carbon dioxide that escape, thereby completely eliminating the highly oxidizing nitrate ions and avoiding their damage to the subsequent reduction precipitation process. In the core solution purification process, a pre-prepared magnetic multidentate coordination inorganic modified material is introduced. Under specific pH adjustment, the ethylenediaminetetraacetic acid group and the carboxyl oxygen atom and amino nitrogen atom of the hyponitrotriacetic acid group on the surface of this material act as Lewis bases. They undergo a strong multidentate chelation coordination reaction with base metal impurity ions such as copper, iron, and lead, which are also hard acids or interface acids in the solution, forming stable heterocyclic spatial complexes and trapping them in the porous framework. According to the hard acid-soft base theory, the complexed gold ions, which are also soft acids, are completely excluded from the adsorption network, thus achieving deep phase separation of gold and impurities. After adsorption saturation, the material undergoes instantaneous solid-liquid separation by an external magnetic field, and competitive coordination is achieved using a specific eluent with a stronger complexation constant to achieve non-destructive regeneration. In the final reduction stage, ascorbic acid is used as a green reducing agent. Under a strictly controlled acid-base buffer system, ascorbic acid molecules undergo dehydrogenation and oxidation to convert into dehydroascorbic acid. At the same time, electrons are precisely transferred to trivalent gold complex ions, causing them to slowly precipitate a sponge-like high-purity gold powder with high surface energy. The reduction process generates no toxic gaseous byproducts. The precipitated primary gold powder is then boiled and filtered with a specific inorganic strong acid. The protonation effect is used to forcibly dissolve trace amounts of base metal oxides that may be physically entrained or co-precipitated in the crystal lattice. After multiple washings with pure water to reduce the conductivity of the particles and gentle drying and dehydration, the particles are melted by high-frequency induction under an inert atmosphere to completely eliminate grain boundary defects. Finally, the product is cast into an extremely high-purity gold product.

[0008] According to a preferred embodiment of the present invention, in step S1, the reaction time at 60-85°C is 0.5-2 hours.

[0009] According to a preferred embodiment of the present invention, in step S3, the stirring time at 20-30°C is 30-60 minutes.

[0010] According to a preferred embodiment of the present invention, in step S3, the aqua regia is composed of hydrochloric acid and nitric acid.

[0011] According to a preferred embodiment of the present invention, in step S4, the reducing agent is one of sulfur dioxide, sodium sulfite, sodium metabisulfite, hydroxylamine hydrochloride, and ascorbic acid; the impurity removal reagent is selected from one of oxalic acid, dilute sulfuric acid, dilute hydrochloric acid, and dilute nitric acid.

[0012] According to a preferred embodiment of the present invention, the preparation steps of the magnetic multidentate coordination inorganic modified material include: A1, by weight, 7.5-8.0 parts of ferric chloride hexahydrate and 3.2-4.0 parts of anhydrous sodium acetate were dissolved in 85-90 parts of ethylene glycol, stirred, transferred to a reaction vessel, and reacted at 195-205°C. After natural cooling, the mixture was separated by an external magnetic field to obtain a solid. The solid was washed successively with anhydrous ethanol and deionized water, and dried under vacuum at 58-62°C to obtain a dried solid. 1.8-2.2 parts of the dried solid were ultrasonically dispersed in a mixture containing 80-85 parts of anhydrous ethanol and 20-25 parts of deionized water. 1.5-2.0 parts of ammonia and 1.2-1.5 parts of tetraethyl orthosilicate were added, and the mixture was stirred at room temperature. The mixture was separated by an external magnetic field to obtain a solid. The solid was washed with 50-100 parts of anhydrous ethanol and dried under vacuum at 48-52°C to obtain magnetite@silicon dioxide magnetic nanoparticles. A2. 1.4-1.6 parts of magnetite@silicon dioxide magnetic nanoparticles were ultrasonically dispersed in 50-60 parts of deionized water to obtain a magnetic suspension. 3.0-3.5 parts of zinc nitrate hexahydrate and 1.8-2.0 parts of aluminum nitrate nonahydrate were dissolved in 100-110 parts of deionized water to obtain solution A. 1.8-2.0 parts of urea and 1.4-1.6 parts of trisodium citrate were dissolved in 100-110 parts of deionized water to obtain solution B. Under nitrogen protection and stirring, solutions A and B were added dropwise to the magnetic suspension. After the addition was complete, the mixture was heated to 94-96°C and refluxed. The mixture was centrifuged to obtain a solid. The solid was washed with deionized water and anhydrous ethanol and dried to obtain a magnetite@silicon dioxide@zinc-aluminum layered bimetallic hydroxide magnetic composite nanomaterial. A3, 0.9-1.1 parts of magnetite@silicon dioxide@zinc-aluminum layered bimetallic hydroxide magnetic composite nanomaterial were calcined at 448-452°C under a nitrogen atmosphere and allowed to cool naturally to obtain the calcined product; the calcined product was dispersed in 50-60 parts of deionized water and stirred at 58-62°C; separated by an external magnetic field to obtain a solid; the solid was washed with deionized water and dried to obtain a porous magnetite@silicon dioxide@zinc-aluminum layered bimetallic oxide magnetic composite material; A4. 0.7-0.9 parts of a porous iron(III) oxide@silicon(II) oxide@zinc-aluminum layered bimetallic oxide magnetic composite material were ultrasonically dispersed in 40-50 parts of anhydrous ethanol containing 1-2 parts of deionized water. 0.8-1.0 parts of 3-aminopropyltriethoxysilane were added, and the mixture was heated to 78-82°C and stirred under a nitrogen atmosphere. After the reaction was complete, the mixture was separated by an external magnetic field to obtain a solid. The solid was washed with anhydrous N,N-dimethylformamide to obtain an aminated intermediate. The aminated intermediate was re-ultrasonically dispersed in 40-50 parts of deionized water, and pre-activated ethanol containing 0.1-0.2 parts of hypozinotriacetic acid and 0.1-0.15 parts of 1- A mixture of (3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 0.05-0.1 parts of N-hydroxysuccinimide was stirred and reacted at 20-25°C. After the reaction was completed, the mixture was separated by an external magnetic field to obtain a solid. The solid was washed successively with anhydrous ethanol and anhydrous N,N-dimethylformamide, and then redispersed in 40-50 parts of anhydrous N,N-dimethylformamide. 0.2-0.3 parts of ethylenediaminetetraacetic acid dianhydride were added, and the mixture was stirred and reacted again at 20-25°C. After the reaction was completed, the mixture was separated by an external magnetic field to obtain a solid. The solid was washed successively with deionized water and then with anhydrous ethanol, and then dried under vacuum at 38-42°C.

[0013] In this invention, the preparation reaction mechanism of the magnetic multidentate coordination inorganic modified material mainly consists of two core stages: the construction of the core-shell structure and the stepwise grafting of surface multidentate chelating groups. First, under solvothermal conditions, ferric chloride hexahydrate and anhydrous sodium acetate undergo coordination and high-temperature alcoholysis reactions in ethylene glycol solvent. Acetate ions act as end-capping agents to control crystal growth, ultimately forming a superparamagnetic iron oxide nanocore through Oswald ripening. Subsequently, this core, under an alkaline ammonia catalytic system, induces the hydrolysis and condensation reaction of tetraethyl orthosilicate, coating its surface with a dense silica protective shell. This prevents the magnetic core from dissolving in subsequent acidic environments and provides abundant hydroxyl active sites for the outer coating. Next, utilizing the high-temperature hydrolysis characteristics of urea, hydroxide ions are slowly and uniformly released in the suspension of the magnetic silicon core, promoting homogeneous co-precipitation of zinc and aluminum ions on the silica shell surface, resulting in the in-situ growth of a zinc-aluminum layered bimetallic hydroxide shell. The layered precursor, after high-temperature calcination, loses interlayer water and carbonate ions, undergoing a topological transformation and collapsing to form a porous layered bimetallic oxide with a high specific surface area and abundant micro-mesoporous structure. In the surface functional group modification stage, alkoxy groups are first hydrolyzed in an alcohol phase system with trace amounts of water using an aminopropylsilane coupling agent. The resulting silanol groups undergo a condensation dehydration reaction with the metal hydroxyl groups on the inorganic support surface, thereby covalently anchoring the amino groups to the material surface. Subsequently, a solvent-switching stepwise grafting strategy is employed. First, hypozinotriacetic acid is pre-activated in a weakly acidic aqueous environment using carbodiimide hydrochloride and hydroxysuccinimide, converting its free carboxyl groups into a highly reactive succinimide ester intermediate. This intermediate undergoes a nucleophilic substitution reaction with some of the amino groups on the material surface, forming stable amide bonds. Finally, in an anhydrous aprotic polar solvent environment, extremely hydrophobic ethylenediaminetetraacetic acid dianhydride is introduced. Its highly reactive anhydride ring undergoes a transient ring-opening amidation reaction with the remaining free amino groups on the material surface. By employing this multi-step grafting strategy of steric hindrance control and reaction thermodynamic window isolation, a high-density composite multidentate chelate ligand was successfully constructed on the surface of a porous inorganic support, enabling it to possess a strong targeted capture capability for trace impurity metal ions.

[0014] According to a preferred embodiment of the present invention, in step A1, the vacuum drying time at 48-52°C is 24-30 hours.

[0015] According to a preferred embodiment of the present invention, in step A2, the reflux reaction time is 24-30 hours.

[0016] According to a preferred embodiment of the present invention, in step A3, the calcination time at 448-452°C is 4-6 hours.

[0017] According to a preferred embodiment of the present invention, in step A4, the stirring time at 78-82°C is 6-8 hours.

[0018] The beneficial effects of this invention are as follows: The high-purity gold refining process provided by this invention achieves significant technical results through the organic coupling of a dual process of gold dissolution via chlorination and aqua regia with a deep adsorption and impurity removal technology using a magnetic multidentate coordination inorganic modified material. Firstly, the invention's uniquely designed magnetic multidentate coordination inorganic modified material, with iron(III) oxide as the magnetic core, silicon dioxide as the protective shell, and zinc-aluminum layered bimetallic oxide as the porous framework, after surface modification with ammoniation, constructs a three-dimensional functionalized network rich in nitrogen and oxygen multidentate coordination sites on the carrier surface through covalent grafting of ethylenediaminetetraacetic acid dianhydride and coordination anchoring with hyponitrotriacetic acid. This material exhibits highly selective chelation and capture capabilities for base metal impurities such as copper, iron, lead, and silver in strongly acidic chloroauric acid solution, while showing extremely low co-adsorption loss of gold ions, achieving efficient deep removal of impurities and efficient gold recovery. Simultaneously, the material's excellent superparamagnetism allows for rapid separation and recovery via an external magnetic field. After competitive elution and regeneration with disodium ethylenediaminetetraacetic acid aqueous solution, it can be recycled, significantly reducing refining costs.

[0019] Secondly, this invention systematically optimizes the gold refining process. The chlorination dissolution step uses a sodium chlorate-hydrochloric acid system, ensuring that most of the gold enters the solution as chloroauric acid, while impurities such as silver are separated as silver chloride precipitate. The dechlorination process effectively removes residual free chlorine, avoiding additional consumption of reducing agent. After the filter residue undergoes a second gold dissolution with aqua regia, this invention employs a process sequence of first separately removing nitrates and then combining it with the chloroauric acid solution, ensuring complete removal of residual nitric acid from the aqua regia solution and overcoming the low efficiency of nitrate removal caused by solution dilution in traditional processes. The reduction step uses ascorbic acid as the reducing agent, and the pH of the system is precisely controlled with sodium hydroxide solution, ensuring efficient reduction reaction and minimal co-precipitation of metal impurities. The gold powder is then treated with an acid-boiling reagent to further remove trace impurities from the surface and grain boundaries. The entire process has few operating units, uses commercially available industrial reagents, requires no complex equipment, offers good production safety, and is easy to scale up.

[0020] Furthermore, this invention offers significant advantages in resource utilization efficiency and environmental friendliness. The coupled design of the dual processes of chlorination and aqua regia dissolution achieves an extremely high total gold recovery rate, realizing highly efficient utilization of gold resources. The magnetic multi-toothed coordination inorganic modified material is recyclable, significantly reducing the cost per use. The entire process avoids the large-scale use and emission of organic solvents. Waste gas is collected and treated through a condensation and alkaline absorption system, and wastewater is discharged in compliance with standards after neutralization and heavy metal precipitation, meeting the requirements of green metallurgy and clean production. The final gold product obtained by this process has extremely high purity, fully meeting the stringent requirements for ultra-high purity gold in cutting-edge technology fields such as semiconductor chip manufacturing, aerospace electronics, high-performance sputtering targets, and precision bonding wires. Detailed Implementation

[0021] The following detailed embodiments are only used to further illustrate this application and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make some non-essential improvements and adjustments to this application based on the above application content.

[0022] Example 1 This embodiment provides a high-purity gold refining process, the steps of which include: S1: Place 5 kg of gold raw material (crude gold content ≥ 99.0%) in a centrifugal sheeter to obtain continuous gold sheets with a thickness of 0.2 mm; ultrasonically clean the gold sheets with 20 kg of deionized water in an ultrasonic cleaner for 4 min (ultrasonic frequency 40 kHz), remove and dry in an 80°C oven to obtain dried gold sheets; put the dried gold sheets into a dissolving vessel (the dissolving vessel is made of titanium and equipped with a stirrer, condenser and jacket heating), add 37.5 kg of 9 mol / L industrial hydrochloric acid and 7.5 kg of deionized water, and start stirring (speed 200 rpm); dissolve 1.7 kg of sodium chlorate in 3.75 kg of deionized water to prepare a sodium chlorate aqueous solution, and slowly add it to the dissolving vessel; after the addition is complete, heat the reaction system to 72.5°C under stirring, and react at a constant temperature for 1.25 h. During the reaction, maintain a slight negative pressure (-0.01 MPa) in the reaction vessel and reflux through the condenser; after the reaction is completed, stop stirring and let stand for 30 min to allow the insoluble residue to settle.

[0023] S2: Add 10 kg of 6 mol / L industrial hydrochloric acid to the dissolving vessel, restart the stirring (200 rpm), heat the system to boiling, maintain boiling for 45 min, collect the volatilized chlorine gas through the condenser into the alkaline absorption bottle; after the chlorine removal is completed, stop heating and allow the solution to cool to room temperature; filter the cooled mixture through a precision filter (5 μm filter cloth pore size) to obtain a primary chloroauric acid solution (filtrate) and filter residue, retaining the filter residue in the dissolving vessel.

[0024] S3: Wash the filter residue obtained in S2 twice with 6.25 kg of deionized water (each time add 6.25 kg of deionized water, stir for 5 min and then filter), add 3.125 kg of freshly prepared aqua regia (aqua regia is a mixture of hydrochloric acid and nitric acid in a volume ratio of 3:1, with a hydrochloric acid concentration of 12 mol / L and a nitric acid concentration of 15.8 mol / L); heat the system to 80°C and react for 1.25 h with stirring (200 rpm); after the reaction is complete, filter through a precision filter to obtain a secondary gold-containing solution; place the secondary gold-containing solution in a denitrification vessel, add a solution containing 0.75 kg of urea and 2.25 kg of deionized water (urea pre-dissolved in deionized water), stir at 70°C (200 rpm) and react for 45 min until no reddish-brown nitrogen oxide gas is produced, to obtain the denitrification reaction mixture; combine the denitrification reaction mixture with the primary chloroauric acid solution obtained in S2, and add 25 wt% of the solution dropwise with stirring. The NaOH solution was adjusted to pH 2.0 using a pH meter. The pH-adjusted mixed solution was transferred to a reaction vessel, and 62.5 g of magnetic multidentate coordination inorganic modified material was added. The mixture was stirred at 200 rpm for 45 min at 25°C. After adsorption treatment, an external magnetic field (magnetic field strength 0.3T) was applied through an electromagnetic separation device at the bottom of the reaction vessel to adsorb the magnetic multidentate coordination inorganic modified material to the bottom of the vessel. The supernatant was discharged through the outlet to obtain the separated clear liquid. The separated clear liquid was filtered through a 0.45 μm filter membrane to obtain a purified and combined chloroauric acid solution. The separated magnetic multidentate coordination inorganic modified material was soaked in 7.5 kg of 0.1 mol / L disodium ethylenediaminetetraacetate aqueous solution for 60 min, with stirring three times during the process. Then, the material was separated by an external magnetic field, the regeneration liquid was discarded, and the material was washed with 12.5 kg of deionized water until neutral. Finally, it was dried in a 60°C oven for later use.

[0025] S4: Under stirring, transfer the purified and combined chloroauric acid solution to a reduction vessel and heat to 60°C; add 8.75 kg of sulfur dioxide to the reduction vessel, and simultaneously monitor the pH of the system using a pH meter, adding 7.5 kg of 25 wt% NaOH solution dropwise to maintain the pH value at 2.0 ± 0.1; after the reduction reaction is complete, continue stirring for 30 min, let stand for 30 min to allow the gold powder to completely settle, discard the supernatant, and collect the gold powder by vacuum filtration; transfer the gold powder to a titanium acid boiling tank, and add 11.25 kg of... A 7.5 wt% oxalic acid solution (oxalic acid prepared with deionized water) was heated to boiling and maintained for 40 minutes. After boiling, the solution was filtered while hot to obtain gold powder after impurity removal. The gold powder was washed four times with 15 kg of deionized water at 85°C until the conductivity of the washing solution was lower than 10 μS / cm (measured with a conductivity meter). Then, it was vacuum filtered to obtain wet gold powder. The wet gold powder was evenly spread in a titanium tray and transferred to a programmable oven to dry at 110°C for 2.5 hours. After drying, it was naturally cooled to room temperature and transferred to a medium-frequency induction melting furnace. It was melted at 1125°C under an argon atmosphere for 35 minutes to completely melt the gold powder. The melt was then cast into a preheated graphite mold. After printing and surface treatment by a hydraulic press, the finished gold powder was obtained.

[0026] Preparation steps of magnetic multidentate coordination inorganic modified materials: A1: Dissolve 7.75g of ferric chloride hexahydrate and 3.6g of anhydrous sodium acetate in 87.5g of ethylene glycol. Stir at 300rpm for 1h using a magnetic stirrer until a uniform orange-yellow solution is formed. Transfer the solution to a 100mL high-pressure reactor lined with polytetrafluoroethylene, seal it, and place it in an oven. React at 200°C for 12h. After the reaction, allow it to cool naturally to room temperature. Separate the black solid product using an external neodymium iron boron permanent magnet (magnetic field strength 0.3T), and discard the supernatant. Wash the obtained solid three times each with 70g of anhydrous ethanol and 70g of deionized water (adding solvent each time, discarding the washing liquid after magnetic separation). Dry the solid in a vacuum drying oven at 60°C for 12h (vacuum degree -0.09MPa) to obtain dried iron oxide magnetic nanoparticles. Take 2.0g of the dried particles and place them in a three-necked flask. The mixture was ultrasonically dispersed (ultrasonic frequency 40kHz, power 200W, time 15min) in a mixed solvent of 82.5g anhydrous ethanol and 22.5g deionized water to form a uniform black suspension. 1.75g ​​of 25wt% ammonia and 1.35g of tetraethyl orthosilicate (TEOS) were added to this suspension, and the mixture was mechanically stirred at 250rpm for 6h at room temperature. Subsequently, 0.9g of (3-aminopropyl)triethoxysilane (APTES) was added, and the mixture was stirred at 250rpm for another 12h at room temperature. After the reaction was complete, the solid was separated by an external magnetic field (0.3T), washed three times with 75g anhydrous ethanol (75g ethanol added each time, and the washing liquid discarded after magnetic separation), and dried in a vacuum oven at 50°C for 27h (vacuum degree -0.09MPa) to obtain iron(III) oxide@silica-amino magnetic nanoparticles.

[0027] A2: Weigh 1.5g of iron(II,III) oxide@silica-amino magnetic nanoparticles and place them in a three-necked flask. Add 55g of deionized water and ultrasonically disperse (40kHz, 200W, 20min) to obtain a uniform magnetic suspension. Prepare solutions A and B separately: Solution A is prepared by dissolving 3.25g of zinc nitrate hexahydrate and 1.9g of aluminum nitrate nonahydrate in 105g of deionized water and stirring until dissolved; Solution B is prepared by dissolving 1.9g of urea and 1.5g of trisodium citrate in 105g of deionized water and stirring until dissolved. Under nitrogen protection (nitrogen flow rate 0.5L / min) and mechanical stirring (300rpm), solutions A and B are simultaneously added dropwise to the magnetic suspension at a rate of 1mL / min using a peristaltic pump. Without using NaOH to adjust the pH, the pH of the system gradually changed from the initial 4.5. After the addition was complete (total addition time was about 3.5 h), the reaction mixture was transferred to an oil bath and heated to 95°C. The mixture was refluxed for 27 h with constant temperature stirring (250 rpm). During this period, urea slowly hydrolyzed, and the pH of the system naturally rose to 8.0 and remained thereafter. After the reaction was completed, the mixture was naturally cooled to room temperature, and the solid was separated by an external magnetic field (0.3 T). The supernatant was discarded. The solid was washed five times each with 75 g of deionized water and 75 g of anhydrous ethanol (magnetic separation after each wash), and dried in a vacuum drying oven at 60°C for 48 h (vacuum degree -0.09 MPa) to obtain a magnetic composite nanomaterial of iron(III) oxide@silicon(II) dioxide@zinc-aluminum layered bimetallic hydroxide.

[0028] A3: 1.0 g of magnetite@silicon dioxide@zinc-aluminum layered bimetallic hydroxide magnetic composite nanomaterial was placed in a corundum boat and then placed in a tube furnace. The temperature was increased from room temperature to 450°C at a rate of 2°C / min under a nitrogen atmosphere (nitrogen flow rate 1 L / min), and calcined at 450°C for 5 hours. After calcination, the material was naturally cooled to room temperature under a nitrogen atmosphere to obtain the magnetite@silicon dioxide@zinc-aluminum layered bimetallic oxide material. The calcined product was transferred to… Add 55g of deionized water to a 250mL beaker and stir magnetically at 200rpm for 2h in a 60°C water bath to hydrate and reconstruct pores. After stirring, separate the solid by applying an external magnetic field (0.3T) and discard the supernatant. Wash the solid once with 75g of deionized water (magnetic separation) and dry it in a vacuum drying oven at 60°C for 24h (vacuum degree -0.09MPa) to obtain a porous magnetite@silicon dioxide@zinc aluminum layered bimetallic oxide magnetic composite material.

[0029] A4: Place 0.8g of porous iron tetroxide@silicon dioxide@zinc-aluminum layered bimetallic oxide magnetic composite material in a three-necked flask, add 45g of anhydrous ethanol containing 1.5g of deionized water, and ultrasonically disperse (40kHz, 200W, 20min); add 0.9g... 3-Aminopropyltriethoxysilane (APTES) was heated to 80°C under a nitrogen atmosphere (0.5 L / min) and stirred at 200 rpm for 7 h. After the reaction, it was naturally cooled to room temperature, and the solid was separated by an external magnetic field (0.3 T). The supernatant was discarded. The solid was washed three times with anhydrous N,N-dimethylformamide (DMF), 50 g of DMF each time. After magnetic separation, the washing liquid was discarded to obtain an aminated intermediate. The aminated intermediate was re-dispersed ultrasonically (40 kHz, 200 W, 15 min) in 45 g of deionized water, and a pre-activated mixture was added (the mixture was prepared by adding 0.15 g of nitric acid (NTA), 0.125 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) and 0.075 g of... N-hydroxysuccinimide (NHS) was dissolved in 10g of deionized water and activated by stirring at room temperature for 30 min. The mixture was then reacted at 22.5°C with stirring at 200 rpm for 12 h. After the reaction was complete, the solid was separated by applying an external magnetic field (0.3T), and the supernatant was discarded. The solid was washed three times each with 75g of anhydrous ethanol and 75g of anhydrous DMF (magnetic separation after each wash). The solid was then redispersed in 45g of anhydrous DMF, and 0.25g of ethylenediaminetetraacetic acid dianhydride (EDTA dianhydride) was added. The mixture was then reacted at 22.5°C with stirring at 200 rpm for 12 h. The reaction was continued at 200 rpm for 12 h under C conditions. After the reaction was completed, the solid was separated by an external magnetic field (0.3 T), and the supernatant was discarded. The solid was washed three times with 75 g of deionized water and then three times with 75 g of anhydrous ethanol (magnetic separation after each wash). It was dried in a vacuum drying oven at 40°C for 48 h (vacuum degree -0.09 MPa) to obtain a composite modified material of iron tetroxide@silicon dioxide@zinc aluminum layered bimetallic oxide@ethylenediaminetetraacetic acid dianhydride-hypo-triacetic acid, which is a magnetic multidentate coordination inorganic modified material.

[0030] Example 2 The specific implementation method is the same as in Example 1, except that this example provides a high-purity gold refining process, the steps of which include: S1: Prepare gold flakes from 5 kg of gold raw material; ultrasonically clean the gold flakes with 15 kg of deionized water for 3 min, and dry them at 78°C to obtain dried gold flakes; put the dried gold flakes into a dissolving vessel, add 25 kg of 6 mol / L hydrochloric acid and 5 kg of deionized water, then add a mixture containing 1.4 kg of sodium chlorate and 2.5 kg of deionized water, stir, and react at 60°C for 0.5 h; after the reaction is complete, let it stand for 30 min.

[0031] S2: Add 5 kg of 6 mol / L hydrochloric acid to the dissolving vessel, stir, heat to boiling and maintain for 30 min; allow to cool naturally to room temperature to obtain the cooled mixture; filter the cooled mixture to obtain a primary chloroauric acid solution and filter residue.

[0032] S3: Wash the filter residue obtained in S2 twice with 5 kg of deionized water, and add 1.25 kg of aqua regia (hydrochloric acid to nitric acid volume ratio 3:1, hydrochloric acid concentration 12 mol / L, nitric acid concentration 15.8 mol / L); heat to 70°C and stir for 0.5 h; after the reaction is complete, filter to obtain a secondary gold-containing solution; place the secondary gold-containing solution in a denitrification vessel, add a solution containing 0.5 kg of urea and 1.5 kg of deionized water, and stir at 60°C for 30 min to obtain the denitrification reaction mixture; combine the denitrification reaction mixture with the primary chloroauric acid solution obtained in S2, and add 20 wt% of [a specific ingredient / component] dropwise. NaOH solution was prepared, pH adjusted to 1.5, and transferred to a reaction vessel. 25g of magnetic multidentate coordination inorganic modified material was added. The mixture was stirred at 20°C for 30min. Separation was performed using an external magnetic field (magnetic field strength 0.3T) to obtain the separated clear liquid and the magnetic multidentate coordination inorganic modified material. The separated clear liquid was filtered to obtain a purified and combined chloroauric acid solution. The magnetic multidentate coordination inorganic modified material was soaked in 5kg of 0.1mol / L disodium ethylenediaminetetraacetate aqueous solution for 60min, washed with 10kg of deionized water, and dried for later use.

[0033] S4: Under stirring, the purified and combined chloroauric acid solution was heated to 50°C, 7.5 kg of sodium sulfite was added, and 5 kg of 20 wt% NaOH solution was added dropwise to adjust the pH to 1.5. After the reduction reaction was completed, stirring was continued for 30 min, and the mixture was allowed to stand for 30 min. The mixture was then vacuum filtered to collect the gold powder. The gold powder was mixed with 7.5 kg of 5 wt% oxalic acid and heated to boiling for 30 min. The mixture was then filtered to obtain the purified gold powder. The purified gold powder was washed three times with 80°C deionized water until the conductivity of the washing solution was less than 10 μS / cm. The mixture was then filtered to obtain the filtered wet gold powder. The filtered wet gold powder was dried at 105°C for 2 h. After naturally cooling to room temperature, the mixture was transferred to a medium-frequency induction melting furnace and melted at 1100°C under an argon atmosphere for 30 min. The melt was then cast into a preheated graphite mold and printed and surface-treated using a hydraulic press to obtain the finished gold product.

[0034] Preparation steps of magnetic multidentate coordination inorganic modified materials: A1: 7.5g of ferric chloride hexahydrate and 3.2g of anhydrous sodium acetate were dissolved in 85g of ethylene glycol. After stirring for 1 hour, the solution was transferred to a reaction vessel and reacted at 195°C for 12 hours. After natural cooling, the mixture was separated by an external magnetic field to obtain a solid. The solid was washed three times each with 60g of anhydrous ethanol and 60g of deionized water, and then dried under vacuum at 58°C for 12 hours to obtain a dried solid. 1.8g of the dried solid was ultrasonically dispersed in a mixture of 80g of anhydrous ethanol and 20g of deionized water. 1.5g of 25wt% ammonia and 1.2g of tetraethyl orthosilicate were added, and the mixture was stirred at room temperature for 12 hours. After separation by an external magnetic field, a solid was obtained. The solid was washed three times with 50g of anhydrous ethanol and then dried under vacuum at 48°C for 24 hours to obtain magnetite@silicon dioxide magnetic nanoparticles.

[0035] A2: 1.4g of iron(II,III) oxide@silicon(II,III) oxide magnetic nanoparticles were ultrasonically dispersed in 50g of deionized water to obtain a magnetic suspension; 3.0g of zinc nitrate hexahydrate and 1.8g of aluminum nitrate nonahydrate were dissolved in 100g of deionized water to obtain solution A; 1.8g of urea and 1.4g of trisodium citrate were dissolved in 100g of deionized water to obtain solution B; under nitrogen protection and stirring, solutions A and B were simultaneously added dropwise to the magnetic suspension at 1mL / min. After the addition was complete, the mixture was heated to 94°C and refluxed for 24h; the mixture was centrifuged to obtain a solid; the solid was washed five times each with 50g of deionized water and 50g of anhydrous ethanol, and dried to obtain iron(II,III) oxide@silicon(II,III) oxide@zinc-aluminum layered bimetallic hydroxide magnetic composite nanomaterials.

[0036] A3: 0.9g of magnetite@silicon dioxide@zinc-aluminum layered bimetallic hydroxide magnetic composite nanomaterial was calcined at 448°C for 4h under a nitrogen atmosphere at a heating rate of 2°C / min, and then naturally cooled to obtain the calcined product. The calcined product was dispersed in 50g of deionized water and stirred at 58°C for 2h. It was then separated by an external magnetic field to obtain a solid. The solid was washed with 50g of deionized water and dried to obtain a porous magnetite@silicon dioxide@zinc-aluminum layered bimetallic oxide magnetic composite material.

[0037] A4: 0.7 g of porous iron(III) oxide@silicon(II) oxide@zinc-aluminum layered bimetallic oxide magnetic composite material was ultrasonically dispersed in 40 g of anhydrous ethanol containing 1 g of deionized water. 0.8 g of 3-aminopropyltriethoxysilane was added, and the mixture was stirred at 78°C for 6 h under a nitrogen atmosphere. After the reaction was complete, the mixture was separated by an external magnetic field to obtain a solid. The solid was washed three times with anhydrous N,N-dimethylformamide to obtain an aminated intermediate. The aminated intermediate was re-ultrasonically dispersed in 40 g of deionized water, and pre-activated solution containing 0.1 g of hypozinotriacetic acid, 0.1 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 0.05 g of... A mixture of N-hydroxysuccinimide was stirred at 20°C for 12 h. After the reaction was completed, the mixture was separated by an external magnetic field to obtain a solid. The solid was washed three times each with 50 g of anhydrous ethanol and 50 g of anhydrous N,N-dimethylformamide, and then redispersed in 40 g of anhydrous N,N-dimethylformamide. 0.2 g of ethylenediaminetetraacetic acid dianhydride was added, and the mixture was stirred at 20°C for another 12 h. After the reaction was completed, the mixture was separated by an external magnetic field to obtain a solid. The solid was washed three times with 50 g of deionized water and three times with 50 g of anhydrous ethanol, and then vacuum dried at 38°C for 48 h to obtain a magnetic multidentate coordination inorganic modified material.

[0038] Example 3 The specific implementation method is the same as in Example 1, except that this example provides a high-purity gold refining process, the steps of which include: S1: Press 5 kg of gold raw material at 200°C to obtain gold flakes; ultrasonically clean the gold flakes with 25 kg of deionized water for 5 min, and dry them at 82°C to obtain dried gold flakes; put the dried gold flakes into a dissolving vessel, add 50 kg of 12 mol / L hydrochloric acid and 10 kg of deionized water, then add a mixture containing 2.0 kg of sodium chlorate and 5.0 kg of deionized water, stir, and react at 85°C for 2 h; after the reaction is completed, let it stand for 30 min.

[0039] S2: Add 15 kg of 6 mol / L hydrochloric acid to the dissolving vessel, stir, heat to boiling and maintain for 60 min; allow to cool naturally to room temperature to obtain the cooled mixture; filter the cooled mixture to obtain a primary chloroauric acid solution and filter residue.

[0040] S3: Wash the filter residue obtained in S2 twice with 7.5 kg of deionized water, and add 5.0 kg of aqua regia (hydrochloric acid to nitric acid volume ratio 3:1, hydrochloric acid concentration 12 mol / L, nitric acid concentration 15.8 mol / L); heat to 90°C and stir for 2 h; after the reaction is complete, filter to obtain a secondary gold-containing solution; place the secondary gold-containing solution in a denitrification vessel, add a solution containing 1.0 kg of urea and 3.0 kg of deionized water, and stir at 80°C for 60 min to obtain the denitrification reaction mixture; combine the denitrification reaction mixture with the primary chloroauric acid solution obtained in S2, and add 30 wt% of [a specific ingredient / component] dropwise. NaOH solution was prepared, pH adjusted to 2.5, and transferred to a reaction vessel. 100g of magnetic multidentate coordination inorganic modifier was added. The mixture was stirred at 30°C for 60min. Separation was performed using an external magnetic field (magnetic field strength 0.3T) to obtain the separated clear liquid and the magnetic multidentate coordination inorganic modifier. The separated clear liquid was filtered to obtain a purified and combined chloroauric acid solution. The magnetic multidentate coordination inorganic modifier was soaked in 10kg of 0.1mol / L disodium ethylenediaminetetraacetate aqueous solution for 60min, washed with 15kg of deionized water, and dried for later use.

[0041] S4: Under stirring, the purified and combined chloroauric acid solution was heated to 70°C, 10 kg of hydroxylamine hydrochloride was added, and 10 kg of 30 wt% NaOH solution was added dropwise to adjust the pH to 2.5. After the reduction reaction was completed, stirring was continued for 30 min, and the mixture was allowed to stand for 30 min. The mixture was then vacuum filtered to collect the gold powder. The gold powder was mixed with 15 kg of 10 wt% oxalic acid and heated to boiling for 50 min. The mixture was then filtered to obtain the purified gold powder. The purified gold powder was washed 5 times with 90°C deionized water until the conductivity of the washing solution was less than 10 μS / cm. The mixture was then filtered to obtain the filtered wet gold powder. The filtered wet gold powder was dried at 115°C for 3 h. After naturally cooling to room temperature, the mixture was transferred to a medium-frequency induction melting furnace and melted at 1150°C under an argon atmosphere for 40 min. The melt was then cast into a preheated graphite mold and printed and surface-treated by a hydraulic press to obtain the finished gold product.

[0042] Preparation steps of magnetic multidentate coordination inorganic modified materials: A1: 8.0 g of ferric chloride hexahydrate and 4.0 g of anhydrous sodium acetate were dissolved in 90 g of ethylene glycol. After stirring for 1 h, the solution was transferred to a reaction vessel and reacted at 205°C for 12 h. After natural cooling, the solution was separated by an external magnetic field to obtain a solid. The solid was washed three times each with 80 g of anhydrous ethanol and 80 g of deionized water, and then dried under vacuum at 62°C for 12 h to obtain a dried solid. 2.2 g of the dried solid was ultrasonically dispersed in a mixture of 85 g of anhydrous ethanol and 25 g of deionized water. 2.0 g of 25 wt% ammonia and 1.5 g of tetraethyl orthosilicate were added, and the mixture was stirred at room temperature for 12 h. After separation by an external magnetic field, a solid was obtained. The solid was washed three times with 100 g of anhydrous ethanol and then dried under vacuum at 52°C for 30 h to obtain magnetite@silicon dioxide magnetic nanoparticles.

[0043] A2: 1.6g of iron(III) oxide@silicon(II) oxide magnetic nanoparticles were ultrasonically dispersed in 60g of deionized water to obtain a magnetic suspension; 3.5g of zinc nitrate hexahydrate and 2.0g of aluminum nitrate nonahydrate were dissolved in 110g of deionized water to obtain solution A; 2.0g of urea and 1.6g of trisodium citrate were dissolved in 110g of deionized water to obtain solution B; under nitrogen protection and stirring, solutions A and B were simultaneously added dropwise to the magnetic suspension at 1mL / min. After the addition was complete, the mixture was heated to 96°C and refluxed for 30h; the mixture was centrifuged to obtain a solid; the solid was washed five times each with 100g of deionized water and 100g of anhydrous ethanol, and dried to obtain iron(III) oxide@silicon(II) oxide@zinc-aluminum layered bimetallic hydroxide magnetic composite nanomaterials.

[0044] A3: 1.1g of magnetite@silicon dioxide@zinc-aluminum layered bimetallic hydroxide magnetic composite nanomaterial was calcined at 452°C for 6h under a nitrogen atmosphere at a heating rate of 2°C / min, and then naturally cooled to obtain the calcined product. The calcined product was dispersed in 60g of deionized water and stirred at 62°C for 2h. It was then separated by an external magnetic field to obtain a solid. The solid was washed with 100g of deionized water and dried to obtain a porous magnetite@silicon dioxide@zinc-aluminum layered bimetallic oxide magnetic composite material.

[0045] A4: 0.9 g of porous iron(III) oxide@silicon(II) oxide@zinc-aluminum layered bimetallic oxide magnetic composite material was ultrasonically dispersed in 50 g of anhydrous ethanol containing 2 g of deionized water. 1.0 g of 3-aminopropyltriethoxysilane was added, and the mixture was stirred at 82°C for 8 h under a nitrogen atmosphere. After the reaction was complete, the mixture was separated by an external magnetic field to obtain a solid. The solid was washed three times with anhydrous N,N-dimethylformamide to obtain an aminated intermediate. The aminated intermediate was re-ultrasonically dispersed in 50 g of deionized water, and pre-activated solution containing 0.2 g of hypozinotriacetic acid, 0.15 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 0.1 g of... A mixture of N-hydroxysuccinimide was stirred at 25°C for 12 h. After the reaction was completed, the mixture was separated by an external magnetic field to obtain a solid. The solid was washed three times each with 100 g of anhydrous ethanol and 100 g of anhydrous N,N-dimethylformamide, and then redispersed in 50 g of anhydrous N,N-dimethylformamide. 0.3 g of ethylenediaminetetraacetic acid dianhydride was added, and the mixture was stirred at 25°C for another 12 h. After the reaction was completed, the mixture was separated by an external magnetic field to obtain a solid. The solid was washed three times with 100 g of deionized water and three times with 100 g of anhydrous ethanol, and then vacuum dried at 42°C for 48 h to obtain a magnetic multidentate coordination inorganic modified material.

[0046] Comparative Example 1 The specific implementation method is the same as in Example 1, except that no magnetic multidentate coordination inorganic modified material is added in S3 for adsorption treatment, and the remaining steps are exactly the same as in Example 1.

[0047] Comparative Example 2 The specific implementation method is the same as in Example 1, except that the magnetic multidentate coordination inorganic modified material added in S3 is only prepared up to step A3 to prepare a porous iron tetroxide@silicon dioxide@zinc aluminum layered bimetallic oxide magnetic composite material (i.e., without the amination and grafting modification in step A4), and the remaining steps are exactly the same as in Example 1.

[0048] Comparative Example 3 The specific implementation method is the same as in Example 1, except that the magnetic multidentate coordination inorganic modified material added in S3 is only subjected to amination in step A4 to obtain an amination intermediate. Specifically, after obtaining the porous iron tetroxide@silica@zinc-aluminum layered bimetallic oxide magnetic composite material according to A1-A3 of Example 1, only the first part of step A4 of Example 1 is performed: 0.8g of the porous iron tetroxide@silica@zinc-aluminum layered bimetallic oxide magnetic composite material is ultrasonically dispersed in 45g of anhydrous ethanol containing 1.5g of deionized water, 0.9g of 3-aminopropyltriethoxysilane is added, the mixture is stirred at 80°C for 7h, washed, and dried to obtain the amination intermediate. The remaining steps are exactly the same as in Example 1.

[0049] Performance testing The high-purity gold refining processes prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance testing according to the following method, which includes the following steps: Gold purity and impurity content test: Take 1.00g of the final gold sample obtained from each example and comparative example, place it in a 50mL polytetrafluoroethylene digestion vessel, add 10.0mL of aqua regia (hydrochloric acid to nitric acid volume ratio 3:1, hydrochloric acid concentration 12mol / L, nitric acid concentration 15.8mol / L), cover the vessel, and digest in a 120°C electric heating oven for 2.0h. After digestion, allow it to cool naturally to room temperature, open the vessel, transfer the digestion solution to a 100mL volumetric flask, rinse the inner wall of the digestion vessel three times with deionized water, 10mL each time, and transfer the washing solution into the volumetric flask as well. Finally, dilute to the mark with deionized water and shake well. Inductively coupled plasma mass spectrometry (ICP-MS) was used for determination. The instrument operating conditions were: RF power 1550W, nebulizing gas flow rate 1.0L / min (argon), auxiliary gas flow rate 0.8L / min (argon), cooling gas flow rate 15.0L / min (argon), sampling depth 8.0mm, integration time 0.3s, and 3 scans. Standard solutions of Ag, Cu, Fe, Pb, and Bi were prepared with concentrations of 0ppb, 1ppb, 5ppb, 10ppb, 50ppb, and 100ppb, respectively, and a standard working curve was established. The test solution was introduced into ICP-MS to determine the mass concentration (in ppb) of Ag, Cu, Fe, Pb, and Bi. The mass fraction (in ppm, i.e., μg / g) of each impurity element in the finished gold was calculated based on the dilution factor (digestion solution to 100mL, sample 1.00g, dilution factor 100). Gold purity was calculated using the formula: Purity (%) = 100% - (w / g) Ag +w Cu +w Fe +w Pb +w Bi The value is calculated as w, where w is the mass fraction (%) of each impurity element. Each sample is measured in triplicate, and the arithmetic mean is taken.

[0050] Total gold recovery rate test: Weigh the gold raw materials (m) used in step S1 of each example and comparative example respectively. 原料 (unit: g, accurate to 0.01 g) and the final gold weight (m) obtained after printing and surface treatment by the hydraulic press. 成品 (Unit: g, accurate to 0.01 g). Total gold recovery rate is calculated using the formula: Recovery rate (%) = (m 成品 / m 原料 Calculate by multiplying by 100%. Each sample was measured in triplicate, and the arithmetic mean was taken.

[0051] Impurity ion adsorption rate test (only for Examples 1-3 and Comparative Examples 2-3; Comparative Example 1, which did not use magnetic multidentate coordination inorganic modification material, was not included in this test): In step S3, samples were taken at two time points: the first sampling point was the mixed solution before the addition of the magnetic multidentate coordination inorganic modification material (i.e., the solution after denitrification of the aqua regia solution and the initial chloroauric acid solution, adjusted to the target pH value with NaOH); the second sampling point was the clear liquid obtained after separation by an external magnetic field after adsorption treatment. 5.00 mL of each of the above two solutions were taken and diluted 10 times with deionized water (5.00 mL of solution was brought to a final volume of 50.00 mL). The mass concentrations (in ppb) of Cu, Fe, Pb, and Ag ions in the diluted solution were determined using ICP-MS, under the same instrument operating conditions as the purity test. The mass concentration (C) of each ion in the original solution was calculated based on the dilution factor. 吸附前 and C 吸附后 (Unit: mg / L). The adsorption rate of each impurity ion is calculated using the formula: Adsorption rate (%) = (C... 吸附前 -C 吸附后 ) / C 吸附前 Calculate using ×100%. Each sample was measured in triplicate, and the arithmetic mean was taken.

[0052] Test results: Table 1: Test results of each embodiment and comparative example ; As can be seen from Table 1, Comparative Example 1 did not use any magnetic multidentate coordination inorganic modification materials, and its finished gold purity was only 99.991%. The contents of impurities such as silver, copper, iron, lead, and bismuth were significantly higher (silver 12.5ppm, copper 8.2ppm, iron 15.6ppm, lead 3.8ppm, bismuth 1.2ppm). This indicates that relying solely on filtration and chemical reduction treatment in the chloroauric acid solution-aqua regia solution dual process cannot effectively remove the various impurity ions coexisting in the chloroauric acid solution. These impurities compete with gold ions for reduction during the reduction stage, resulting in the product purity failing to meet the ultra-high requirements.

[0053] Comparative Example 2 used a porous layered bimetallic oxide material (porous iron tetroxide@silicon dioxide@zinc-aluminum layered bimetallic oxide magnetic composite material) that was only calcined and reconstituted by hydration without any organic modification. Its adsorption rates for copper, iron, lead, and silver were only 32.5%, 28.9%, 35.2%, and 30.1%, respectively, indicating very limited adsorption capacity. The purity of the finished product was only increased to 99.993%, and although the impurity content decreased, it was still at a high level (silver 5.8 ppm, copper 3.2 ppm, iron 6.5 ppm, lead 1.5 ppm, bismuth 0.8 ppm). This shows that although the inorganic framework without polydentate ligand modification has a certain physical adsorption and ion exchange capacity, its selective recognition and chelation capture capacity for various impurity ions is seriously insufficient, and it cannot meet the requirements for deep impurity removal.

[0054] Comparative Example 3 used a material modified only by amination (aminated intermediate), which increased the adsorption rates of copper, iron, lead, and silver to 68.3%, 62.7%, 71.5%, and 65.8%, respectively, with the finished product purity reaching 99.995% and the impurity content further reduced (silver 3.2 ppm, copper 1.8 ppm, iron 3.5 ppm, lead 0.9 ppm, bismuth 0.6 ppm). However, there were still about 0.5-1.8 ppm of residual impurities, indicating that the single amino functional group mainly adsorbs impurities through electrostatic interaction and weak coordination. Its coordination sites are of a single type and the binding strength is insufficient, making it impossible to achieve synergistic capture of impurity ions with multiple different electronic configurations.

[0055] In contrast, Examples 1-3 employed a magnetic multidentate coordination inorganic modified material covalently grafted with ethylenediaminetetraacetic acid dianhydride and coordinated and anchored with hyponitrotriacetic acid. This material's surface simultaneously contains various coordinating atoms such as carboxyl groups, amide groups, and tertiary amine nitrogen, forming a multidentate chelating network. The adsorption rates for copper, iron, lead, and silver all reached over 92%, and the purity of the finished gold product consistently reached over 99.999% (99.9993% in Example 1, 99.9991% in Example 2, and 99.9999% in Example 3). The content of impurities such as silver, copper, iron, lead, and bismuth was reduced to below 1.5 ppm, with lead and bismuth content below 0.5 ppm. The total gold recovery rate remained at 99.92% or higher. This fully demonstrates that the present invention, through deep adsorption and impurity removal using magnetic multidentate coordination inorganic modified materials, successfully solved the technical problems of incomplete impurity removal and difficulty in achieving ultra-high product purity requirements in existing processes.

[0056] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A high-purity gold refining process, characterized in that, Includes the following steps: S1. By weight, 100-120 parts of gold raw material are added to a sheet-making machine to form gold sheets; the gold sheets are ultrasonically cleaned with 300-500 parts of deionized water and dried at 78-82°C to obtain dried gold sheets; the dried gold sheets are placed in a dissolving vessel, 500-1000 parts of hydrochloric acid and 100-200 parts of deionized water are added, and then a mixture containing 28-40 parts of sodium chlorate and 50-100 parts of deionized water is added, stirred, and reacted at 60-85°C; after the reaction is completed, the mixture is allowed to stand. S2, add 100-300 parts of hydrochloric acid to the dissolving vessel, stir, and heat; cool to room temperature to obtain the cooled mixture; filter the cooled mixture to obtain a primary chloroauric acid solution and filter residue; S3, wash the filter residue obtained in S2 with deionized water and add 25-100 parts of aqua regia; Heating to 70-90°C and stirring the reaction; after the reaction is complete, filtering to obtain a secondary gold-containing solution; placing the secondary gold-containing solution in a denitrification vessel, adding a solution containing 10-20 parts urea and 30-60 parts deionized water, stirring the reaction at 60-80°C to obtain a denitrified reaction mixture; combining the denitrified reaction mixture with the primary chloroauric acid solution obtained in S2, adding NaOH solution dropwise to adjust the pH to 1.5-2.5, transferring to a reaction vessel, and adding 0.5-2.0 parts of magnetic multidentate coordination inorganic modification material; stirring at 20-30°C; separating by an external magnetic field to obtain a separated clear liquid and magnetic multidentate coordination inorganic modification material; filtering the separated clear liquid to obtain a purified and combined chloroauric acid solution; soaking the magnetic multidentate coordination inorganic modification material in 100-200 parts of ethylenediaminetetraacetic acid disodium aqueous solution, washing with deionized water, and drying; S4. Under stirring, the purified and combined chloroauric acid solution is heated to 50-70°C, and 150-200 parts of reducing agent are added. At the same time, NaOH solution is added dropwise to adjust the pH value to 1.5-2.

5. After the reduction reaction is completed, stirring is continued, the mixture is allowed to stand, and vacuum filtration is performed to collect the gold powder. The gold powder is mixed with 150-300 parts of impurity removal reagent, heated, and filtered to obtain impurity-removed gold powder. The impurity-removed gold powder is washed with deionized water at 80-90°C, filtered, and the filtered wet gold powder is obtained. The filtered wet gold powder is dried at 105-115°C, naturally cooled to room temperature, transferred to a medium-frequency induction melting furnace, and melted at 1100-1150°C under an inert atmosphere. The melt is then cast into a preheated graphite mold and printed and surface-treated by a hydraulic press.

2. The high-purity gold refining process according to claim 1, characterized in that, In step S1, the reaction time is 0.5-2 hours at 60-85°C.

3. The high-purity gold refining process according to claim 1, characterized in that, In step S3, the stirring time at 20-30°C is 30-60 minutes.

4. The high-purity gold refining process according to claim 1, characterized in that, In step S3, the aqua regia is composed of hydrochloric acid and nitric acid.

5. The high-purity gold refining process according to claim 1, characterized in that, In step S4, the reducing agent is one of sulfur dioxide, sodium sulfite, sodium metabisulfite, hydroxylamine hydrochloride, and ascorbic acid; the impurity removal reagent is selected from one of oxalic acid, dilute sulfuric acid, dilute hydrochloric acid, and dilute nitric acid.

6. The high-purity gold refining process according to any one of claims 1-5, characterized in that, The preparation steps of the magnetic multidentate coordination inorganic modified material include: A1, by weight, 7.5-8.0 parts of ferric chloride hexahydrate and 3.2-4.0 parts of anhydrous sodium acetate were dissolved in 85-90 parts of ethylene glycol, stirred, transferred to a reaction vessel, and reacted at 195-205°C. After natural cooling, the mixture was separated by an external magnetic field to obtain a solid. The solid was washed successively with anhydrous ethanol and deionized water, and dried under vacuum at 58-62°C to obtain a dried solid. 1.8-2.2 parts of the dried solid were ultrasonically dispersed in a mixture containing 80-85 parts of anhydrous ethanol and 20-25 parts of deionized water. 1.5-2.0 parts of ammonia and 1.2-1.5 parts of tetraethyl orthosilicate were added, and the mixture was stirred at room temperature. The mixture was separated by an external magnetic field to obtain a solid. The solid was washed with 50-100 parts of anhydrous ethanol and dried under vacuum at 48-52°C to obtain magnetite@silicon dioxide magnetic nanoparticles. A2. 1.4-1.6 parts of magnetite@silicon dioxide magnetic nanoparticles were ultrasonically dispersed in 50-60 parts of deionized water to obtain a magnetic suspension. 3.0-3.5 parts of zinc nitrate hexahydrate and 1.8-2.0 parts of aluminum nitrate nonahydrate were dissolved in 100-110 parts of deionized water to obtain solution A. 1.8-2.0 parts of urea and 1.4-1.6 parts of trisodium citrate were dissolved in 100-110 parts of deionized water to obtain solution B. Under nitrogen protection and stirring, solutions A and B were added dropwise to the magnetic suspension. After the addition was complete, the mixture was heated to 94-96°C and refluxed. The mixture was centrifuged to obtain a solid. The solid was washed with deionized water and anhydrous ethanol and dried to obtain a magnetite@silicon dioxide@zinc-aluminum layered bimetallic hydroxide magnetic composite nanomaterial. A3, 0.9-1.1 parts of magnetite@silicon dioxide@zinc-aluminum layered bimetallic hydroxide magnetic composite nanomaterial were calcined at 448-452°C under a nitrogen atmosphere and allowed to cool naturally to obtain the calcined product; the calcined product was dispersed in 50-60 parts of deionized water and stirred at 58-62°C; separated by an external magnetic field to obtain a solid; the solid was washed with deionized water and dried to obtain a porous magnetite@silicon dioxide@zinc-aluminum layered bimetallic oxide magnetic composite material; A4. 0.7-0.9 parts of a porous iron(III) oxide@silicon(II) oxide@zinc-aluminum layered bimetallic oxide magnetic composite material were ultrasonically dispersed in 40-50 parts of anhydrous ethanol containing 1-2 parts of deionized water. 0.8-1.0 parts of 3-aminopropyltriethoxysilane were added, and the mixture was heated to 78-82°C and stirred under a nitrogen atmosphere. After the reaction was complete, the mixture was separated by an external magnetic field to obtain a solid. The solid was washed with anhydrous N,N-dimethylformamide to obtain an aminated intermediate. The aminated intermediate was re-ultrasonically dispersed in 40-50 parts of deionized water, and pre-activated ethanol containing 0.1-0.2 parts of hypozinotriacetic acid and 0.1-0.15 parts of 1- A mixture of (3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 0.05-0.1 parts of N-hydroxysuccinimide was stirred and reacted at 20-25°C. After the reaction was completed, the mixture was separated by an external magnetic field to obtain a solid. The solid was washed successively with anhydrous ethanol and anhydrous N,N-dimethylformamide, and then redispersed in 40-50 parts of anhydrous N,N-dimethylformamide. 0.2-0.3 parts of ethylenediaminetetraacetic acid dianhydride were added, and the mixture was stirred and reacted again at 20-25°C. After the reaction was completed, the mixture was separated by an external magnetic field to obtain a solid. The solid was washed successively with deionized water and then with anhydrous ethanol, and then dried under vacuum at 38-42°C.

7. The high-purity gold refining process according to claim 6, characterized in that, In step A1, the vacuum drying time at 48-52°C is 24-30 hours.

8. The high-purity gold refining process according to claim 6, characterized in that, In step A2, the reflux reaction time is 24-30 hours.

9. The high-purity gold refining process according to claim 6, characterized in that, In step A3, the calcination time at 448-452°C is 4-6 hours.

10. The high-purity gold refining process according to claim 6, characterized in that, In step A4, the stirring time is 6-8 hours after heating to 78-82°C.