Method for preparing gold powder based on ion exchange method

Abstract

The invention relates to the technical field of metal recovery, and discloses a method for preparing gold powder based on an ion exchange method, which comprises the following steps: S1, resin pretreatment: pretreating ion exchange resin by using a saturated saline solution, removing impurities on the surface of the resin, and sequentially cleaning the resin by using an HCl acid solution with the concentration of 3%-7% and an NaOH alkali solution with the concentration of 2%-4%; s2, ion exchange adsorption: the pretreated ion exchange resin is in contact with the waste gold liquid with the pH value of 8.5-9.5, and ion exchange adsorption is carried out at the set flow speed. Through the gold recovery technology based on the ion exchange method, the recovery rate of gold in the low-concentration waste gold liquid is remarkably increased, and the problem that the recovery effect is poor when the gold content is low in a traditional method is solved. Compared with the prior art, by adopting the ion exchange method, the purity of the gold powder is effectively improved, impurities are reduced, the operation steps are simplified, the cost is reduced, and meanwhile, the uniformity of gold powder particles is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of metal recycling, and specifically to a method for preparing gold powder based on the ion exchange method. Background Art

[0002] With the advancement of the industrialization process, the recycling of waste gold liquid has become an important field of resource recycling and utilization. The waste gold liquid contains trace amounts of gold elements. How to efficiently and stably recover gold from these waste liquids is an important problem faced by the current technical field. Existing gold recovery methods include metal displacement method, electrolysis method, dissolution method, reduction method, etc. These methods have achieved gold recovery to a certain extent, but there are still many technical bottlenecks in the treatment of waste gold liquid with low gold concentration, recovery efficiency, and gold powder purity, resulting in unsatisfactory recovery effects and even relatively high treatment costs.

[0003] In the existing gold recovery technologies, the metal displacement method and the electrolysis method often face problems such as low recovery efficiency and complex operation. Especially in waste gold liquid with a gold content below a certain level, the recovery effect is greatly reduced. The metal displacement method performs poorly in low-concentration waste gold liquid because the concentration of gold ions is not sufficient for effective displacement, resulting in low recovery efficiency; the electrolysis method requires strict control of parameters such as current, temperature, and pH value, and by-products are generated during the electrolysis process, affecting the purity of gold. When the traditional dissolution method uses aqua regia to dissolve gold, although gold can be dissolved, the dissolved gold liquid often contains more impurities, resulting in increased difficulty in subsequent purification and low recovery efficiency. At the same time, the reduction process of gold also faces problems of uneven precipitation and unstable gold powder quality. In view of these deficiencies, the present invention proposes a method for preparing gold powder based on the ion exchange method, which effectively solves problems such as low gold recovery rate, poor purity, and complex operation during the recovery process through precise step design and optimization, and improves the efficiency and quality of gold recovery. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention provides a method for preparing gold powder based on the ion exchange method, which solves the problems of low recovery efficiency of waste gold liquid with low concentration, poor gold powder purity, and complex operation during the recovery process in the existing technology.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: A method for preparing gold powder based on the ion exchange method, comprising the following steps: S1. Resin pretreatment: Pretreat the ion exchange resin with saturated brine to remove impurities on the resin surface, and then wash the resin successively with HCl acid solution with a concentration of 3%-7% and NaOH base solution with a concentration of 2%-4%; S2. Ion exchange adsorption: Contact the pretreated ion exchange resin with waste gold solution having a pH value of 8.5 - 9.5, and perform ion exchange adsorption at a set flow rate to adsorb gold in the waste gold solution. The flow rate is 30 m / h - 50 m / h, and the adsorption time is 8 hours - 16 hours; S3. Resin carbonization: After drying the resin adsorbed with gold, carbonize it in a carbonization furnace at 500 °C - 650 °C for 3 hours - 5 hours to obtain gold-containing carbide; S4. Dissolution of gold and denitrification: Add the carbide to aqua regia for dissolution, control the temperature at 35 °C - 45 °C for reaction for 1 hour - 3 hours, and then add hydrochloric acid for denitrification treatment. Stop heating after denitrification; S5. Filtration and washing: Filter the dissolved aqua regia containing gold to remove insoluble substances, and wash with deionized water until the pH value of the solution is neutral; S6. Reduction of gold: Mix the filtered aqua regia containing gold with anhydrous sodium sulfite for reduction reaction until the gold ions in the solution are completely reduced to gold powder. The dosage of anhydrous sodium sulfite is 0.8 kg - 1.2 kg per kg of gold powder; S7. Final filtration, washing and drying: Filter the reduced gold powder, wash it and place it in an oven for drying. After cooling, obtain gold powder, and the purity of the gold powder reaches 90% - 98%.

[0006] Preferably, the ion exchange resin is D301 type ion exchange resin.

[0007] Preferably, during the ion exchange adsorption process, the contact time between the waste gold solution and the ion exchange resin is 8 hours - 16 hours.

[0008] Preferably, during the dissolution of gold and denitrification process, the volume ratio of the aqua regia to the gold carbide is 1:3.

[0009] Preferably, in the reduction reaction, the dosage of anhydrous sodium sulfite is 0.8 kg - 1.2 kg per kg of gold powder.

[0010] Preferably, the drying temperature of the gold powder is 100 °C - 130 °C, and the drying time is 3 hours - 5 hours.

[0011] Preferably, the gold content in the waste gold solution is below 2 ppm, and the waste gold solution also contains a small amount of silver and platinum metal impurities.

[0012] The present invention provides a method for preparing gold powder based on the ion exchange method. It has the following beneficial effects: 1. The present invention adopts a gold recovery technical solution based on the ion exchange method, achieving the effect of efficiently and stably recovering gold ions from waste gold liquid. Compared with traditional metal displacement methods or electrolysis methods, the present invention can treat waste liquid with low gold content and significantly improve the gold recovery rate, solving the problems of low recovery rate and difficult treatment in traditional methods.

[0013] 2. During the dissolution and denitration of gold in the present invention, aqua regia is used to dissolve gold powder and denitration treatment is carried out, effectively improving the purity of gold. Compared with the prior art, the present invention has made a more optimized design in removing harmful substances and impurities, solving the problems of incomplete gold dissolution or more impurities in the solution in traditional methods.

[0014] 3. In the gold powder reduction step of the present invention, by precisely controlling the dosage of the reducing agent and the reaction conditions, the reduction efficiency of gold powder is greatly improved. Different from the possible uneven gold powder situation in the reduction process of traditional methods, the present invention ensures that the gold powder has uniform particles and high purity, avoiding the problems of over-reduction and gold powder loss.

[0015] 4. Through precise resin pretreatment and ion exchange adsorption technology, the adsorption capacity of the resin in the present invention is greatly enhanced. Compared with the problem of poor adsorption effect caused by resin surface impurities in traditional technologies, the present invention ensures the efficient utilization of the resin in the gold recovery process, improving the efficiency of the entire recovery process from the source. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flowchart of the method steps of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0018] Please refer to the attached Figure 1 , an embodiment of the present invention provides a method for preparing gold powder based on the ion exchange method, including the following steps: S1. Resin pretreatment: Pretreat the ion exchange resin with saturated brine to remove impurities on the resin surface, and then wash the resin successively with HCl acid solution with a concentration of 3%-7% and NaOH alkali solution with a concentration of 2%-4%. In this embodiment, the resin pretreatment first uses saturated brine for preliminary treatment. The saturated brine can effectively clean the impurities on the resin surface and at the same time promote the expansion of the resin, ensuring that the resin can contact the waste gold solution to the greatest extent in the subsequent process, thereby improving the adsorption effect of gold. Specifically, the resin needs to be immersed in saturated brine for 18 to 20 hours to ensure that the resin fully absorbs water and reaches the best expanded state.

[0019] In some embodiments, the resin pretreatment step further includes using an acid cleaning solution and an alkali cleaning solution to further clean the resin. In this case, the resin will be immersed in a 5% hydrochloric acid solution for 4 to 8 hours. Acid cleaning can effectively remove the metal ions or impurities that may remain on the resin surface and reduce the interfering substances during subsequent exchange. After treatment, it is thoroughly cleaned with deionized water until the drained water contains no yellow precipitate or any contaminants.

[0020] As an option, after the resin is pickled, the resin will be immersed in a sodium hydroxide solution with a concentration of 2% to 4%. This process is mainly to remove the organic substances in the resin and further improve the exchange performance of the resin. The alkali cleaning time can be controlled within 4 to 8 hours. After the treatment, the resin will be washed with deionized water again until it reaches a neutral state. The purpose of this step is to remove the harmful components in the resin and provide a cleaner environment for the subsequent adsorption of gold ions.

[0021] Generally, the effect after resin pretreatment directly affects the efficiency of the subsequent ion exchange adsorption process. If the pretreatment step is not in place, some interfering components may remain on the resin surface, resulting in incomplete adsorption or low adsorption efficiency. Therefore, the improvement of resin cleanliness directly enhances the adsorption capacity of the resin and the recovery rate of gold.

[0022] Specifically, the resin used in this embodiment is D301 type ion exchange resin. D301 resin has good exchange capacity and stability and is suitable for the treatment of waste liquid with low gold content. During the resin pretreatment process, through the expansion effect of saturated brine, the purification effects of acid cleaning and alkali cleaning, the performance of the resin has been significantly improved. In this process, the improvement of the resin adsorption capacity provides an important guarantee for the subsequent gold recovery.

[0023] In a possible implementation manner, during the resin pretreatment process, the concentrations of acid cleaning and alkali cleaning and the treatment time can be appropriately adjusted according to the actual use situation. The specific concentration range and time should be optimized according to the composition of the waste gold solution to be treated, the gold content, and the resin type. By reasonably adjusting these parameters, the exchange capacity of the resin can be maximized, thereby achieving more efficient gold recovery.

[0024] In addition, the pre-treatment steps have a significant impact on the final performance of the resin. If a certain link in the pre-treatment process is not properly handled (such as too long pickling time or too low hydrochloric acid concentration), it may lead to insufficient adsorption capacity of the resin, ultimately affecting the gold recovery efficiency. Therefore, ensuring that each link is strictly implemented as required to guarantee the quality of the resin is a prerequisite for the smooth progress of the entire gold recovery process.

[0025] In this embodiment, the resin pre-treatment steps fully consider the cleanliness and activity of the resin, and adopt a series of precise control measures, enabling the resin to exhibit its best performance in the subsequent ion exchange process, thereby effectively improving the gold recovery rate.

[0026] S2. Ion exchange adsorption: Contact the pretreated ion exchange resin with waste gold solution having a pH value of 8.5 - 9.5, and perform ion exchange adsorption at a set flow rate to adsorb the gold in the waste gold solution. The flow rate is 30 m / h - 50 m / h, and the adsorption time is 8 hours - 16 hours. In this embodiment, the pH value of the waste gold solution is maintained at 9, which is the most suitable for the exchange reaction between gold ions and the surface active sites of the resin. Controlling the pH value of the waste gold solution within this range can avoid the competitive exchange of other impurities with gold ions and optimize the adsorption performance of the resin. Specifically, a lower pH value may affect the dissolution state of gold ions, while a higher pH value may lead to a decrease in the adsorption capacity of the resin. Therefore, controlling at pH 9 is an optimal compromise.

[0027] In some embodiments, the gold content in the waste gold solution is relatively low, usually below 2 ppm. Such waste liquid can significantly increase the gold concentration through the ion exchange method, thereby achieving effective recovery. During the contact with the resin, the gold ions in the waste gold solution are adsorbed on the resin surface, while other impurity ions are excluded, gradually increasing the gold ion concentration. The process of the resin adsorbing gold ions depends on the exchange capacity of the resin and the gold concentration in the waste gold solution. For waste liquid with a lower concentration, a longer contact time can ensure more efficient gold recovery.

[0028] Generally, the flow rate is a key parameter affecting the ion exchange effect. If the flow rate is too high, the contact time between the gold ions in the waste gold solution and the resin surface is too short, which may lead to low gold adsorption efficiency. Therefore, the flow rate is controlled at 40 m / h to ensure that the contact time between the resin and the waste gold solution is long enough to achieve the maximum adsorption effect. This flow rate has been verified many times in practice and can provide an ideal exchange efficiency.

[0029] Specifically, the contact time between the resin and the waste gold solution is 12 hours. This contact time is sufficient for the resin to adsorb most of the gold ions in the waste gold solution onto the resin surface, forming an effective gold-loaded resin. This time period has been optimized through experiments, which can not only ensure the full adsorption of gold but also avoid the saturation of the adsorption sites on the resin surface and other unnecessary side reactions caused by excessive processing time.

[0030] In a possible implementation, the structure and size of the ion exchange column also affect the adsorption efficiency. Generally, selecting resin particles with a larger surface area and resin types with a higher exchange capacity can further improve the gold adsorption efficiency. For this purpose, in this embodiment, D301 ion exchange resin is selected, which has a high exchange capacity and good selectivity and is particularly suitable for the treatment of low-concentration waste gold solutions.

[0031] During the adsorption process of the resin, the gold ions in the waste gold solution are exchanged with the ions on the resin through an ion exchange reaction. For example, the hydrogen ions (H + ) on the resin surface will be replaced by the gold ions (Au 3+ ) in the waste gold solution. This exchange process enables the gold ions to gradually accumulate on the resin surface, while the concentration of gold ions in the waste gold solution gradually decreases.

[0032] In addition, to improve the gold recovery rate, in this embodiment, the flow rate can also be adjusted regularly or as needed during the ion exchange process to ensure uniform and sufficient exchange of gold ions. In specific implementations, the flow rate, pH value, and the contact time of the resin can be appropriately adjusted according to the actual situation to treat waste gold solutions with different metal concentrations and waste liquid components.

[0033] In some embodiments, the waste gold solution can also be pretreated during the ion exchange process, such as removing some irrelevant ions or impurities therein to reduce the influence of these impurities on the resin's adsorption of gold ions. Especially when there are relatively high concentrations of other metal ions (such as silver, platinum, etc.) in the waste gold solution, it may be necessary to optimize the composition of the waste gold solution to enhance the selective adsorption effect of gold.

[0034] Through this ion exchange adsorption step, the gold ions in the waste gold solution will be efficiently adsorbed onto the resin, thus laying a good foundation for the subsequent gold extraction step. Finally, the gold content of the waste gold solution treated through this process will be significantly reduced, and the gold recovery rate will be greatly improved.

[0035] S3. Resin carbonization: After drying the resin adsorbed with gold, it is carbonized in a carbonization furnace at 500°C - 650°C for 3 hours - 5 hours to obtain gold-containing carbide; In this embodiment, after the ion exchange adsorption process, the resin contains a large amount of adsorbed gold. To effectively extract this gold, the resin needs to be carbonized. After the resin undergoes pretreatment and adsorption, it is placed in a carbonization furnace and carbonized at a temperature of 600 °C. The carbonization process lasts for 4 hours. This processing time has been optimized multiple times and can effectively remove the residual organic substances in the resin and release the adsorbed gold.

[0036] Specifically, controlling the temperature of the carbonization process at 600 °C is crucial for the removal of the organic components in the resin and the release of gold. Too low a temperature may result in incomplete release of gold, while too high a temperature may cause excessive decomposition of the resin and even produce unnecessary by-products. By carbonizing at 600 °C for 4 hours, it can be ensured that the organic components of the resin are completely burned, while not damaging the physical structure of the resin and not causing oxidation or loss of gold.

[0037] In some embodiments, the control of the carbonization temperature and time has a significant impact on the gold recovery effect. Selecting the appropriate carbonization temperature and time is the key to effectively releasing gold while ensuring that the resin performance is not damaged. After carbonization, the gold in the resin will become gold powder, and the gold powder is separated from other substances, facilitating the next steps of gold dissolution and denitrification treatment.

[0038] In specific implementations, the design of the carbonization furnace may also affect the treatment effect. The carbonization furnace needs to be able to heat the resin evenly to ensure temperature uniformity. Generally, using a furnace body with high temperature uniformity can effectively avoid excessive decomposition or incomplete carbonization of the resin caused by too large a temperature difference. In addition, the atmosphere control of the carbonization furnace is also very important. Using an environment with a low oxygen content helps prevent the oxidation of gold and ensures the purity of the gold powder.

[0039] As an option, after the carbonization process, the gold powder can also be quickly cooled through a cooling system. This cooling process can prevent excessive oxidation of the gold powder and maintain the particle form of the gold powder, providing conditions for subsequent gold extraction. In actual operation, the time and speed of the cooling process can be adjusted according to the specific equipment and requirements of the gold powder.

[0040] In one possible implementation, the gold powder obtained after carbonization may still need further physical separation, such as removing incompletely carbonized substances or impurities through filtration or other separation techniques. This can ensure that the purity of gold is maximally guaranteed in subsequent steps such as dissolution and reduction.

[0041] Through this carbonization step, the organic matter in the resin is completely removed, and the gold on the resin surface is also effectively released, providing a basis for subsequent gold dissolution, reduction, and final purification processes. This process not only improves the efficiency of gold recovery but also optimizes the economy and operability of the entire recovery process.

[0042] S4. Dissolution of Gold and Denitrification: Add the carbide to aqua regia for dissolution, control the temperature at 35°C - 45°C for a reaction time of 1 - 3 hours, then add hydrochloric acid for denitrification treatment, and stop heating after denitrification; In this embodiment, in this step, the carbonized gold powder is slowly added to the reaction kettle and reacts with aqua regia. Aqua regia is a mixture of concentrated hydrochloric acid and concentrated nitric acid in a ratio of 1:3, which can provide strong enough oxidation ability to completely dissolve the gold in the gold powder. The temperature during the dissolution process is usually controlled at about 40°C, and the duration is 2 hours. This can not only ensure the full dissolution of gold but also avoid damage to gold or the occurrence of side reactions caused by too high temperature.

[0043] In some embodiments, the rate of the dissolution reaction is closely related to the amount of gold powder, the concentration of the solvent, and the temperature. Higher temperature and concentration help to accelerate the dissolution process of gold, but too high conditions may cause excessive oxidation of gold, resulting in difficulties in subsequent purification. Therefore, the temperature and time of dissolution need to be optimized through experiments to ensure the dissolution efficiency and purity of gold.

[0044] Specifically, the addition ratio of aqua regia and the control of temperature are crucial. If the ratio of acid in aqua regia is too low, the dissolution rate of gold will decrease significantly, and it may take a longer time to complete the dissolution process. On the other hand, if the acid concentration or temperature is too high, although the dissolution can be accelerated, it may lead to excessive oxidation of gold and affect the final purity of gold. Therefore, through strict temperature control and reaction time control in this step, it can be ensured that the dissolution of gold is both efficient and does not bring adverse side reactions.

[0045] In a possible implementation, after dissolution, add hydrochloric acid for denitrification treatment. By slowly adding hydrochloric acid to the reaction kettle, the nitrates in aqua regia can be effectively removed, reducing the impact on subsequent steps. The denitrification process requires very fine control. Too fast addition may cause the release of nitric acid gas, which not only affects the safety of the reaction but also leads to the loss of gold. Usually, the denitrification process needs to be carried out slowly, gradually adding hydrochloric acid until the solution reaches the predetermined conditions.

[0046] In some embodiments, the combination of the dissolution and denitrification steps is particularly important. The dissolution process is not only to reduce gold to gold ions in the solution for facilitating subsequent reduction steps; while denitrification can remove the nitrides therein, ensuring the purity of the gold solution and avoiding the interference of impurities in subsequent treatment processes. After denitrification is completed, stop heating and carry out further treatment.

[0047] Generally, the dissolved gold solution must be strictly filtered and washed to ensure the removal of residual impurities. The filtration process of the dissolution solution helps to remove the solid substances generated during the reaction, which are usually composed of the unreacted substances in aqua regia and the residues of the resin. Through this filtration step, a purer gold solution can be obtained, providing high-quality raw materials for the subsequent reduction reaction.

[0048] As an option, the dissolved gold solution can also be further processed through a vacuum filtration system to ensure the complete cleanliness of the solution and avoid any solid impurities affecting the subsequent steps. The amount of water and temperature during the washing process also need to be adjusted according to the solubility of gold and the substances remaining during the reaction. Through these optimization steps, the dissolved gold solution will enter the reduction step in a high-purity state, ensuring the recovery rate and final purity of the gold powder.

[0049] Through this gold dissolution and denitrification step, the gold in the waste gold solution is effectively extracted, and the purity of gold is further improved by removing impurities such as nitrates. The precise control of the dissolution and denitrification step not only ensures the complete dissolution of gold but also effectively removes the unwanted components, thus laying a solid foundation for the subsequent steps.

[0050] S5. Filtration and Washing: Filter the dissolved aqua regia gold solution to remove insoluble substances, and wash it with deionized water until the pH value of the solution is neutral. In this embodiment, the gold solution after dissolution and denitrification treatment needs to undergo vacuum filtration. This process helps to remove the substances that are not completely dissolved in the solution, such as impurity particles and precipitates that may be generated during the reaction. During the filtration process, the filtration medium usually adopts an appropriate filter membrane or filter, which can effectively prevent solid particles from entering the subsequent steps. Vacuum filtration can accelerate the filtration process and ensure the completeness of the filtration effect.

[0051] Specifically, the gold solution enters the filtration device through the vacuum filtration system. After being filtered through the filter membrane or filter paper, the solid substances in the solution are effectively removed. Generally, the filtered gold solution will remain clear and have no obvious impurities. The waste residue or insoluble substances generated during the filtration process need to be properly treated to prevent environmental pollution. In actual operation, according to the concentration of the solution and the types of impurities, the filtration medium and processing equipment may be adjusted to ensure the best filtration effect.

[0052] As an option, the filtered solution can also be washed. During the washing process, the solution is washed multiple times with deionized water to further remove the residual impurities and substances that are not completely dissolved. The control of the washing water volume is crucial. The volume and temperature of the washing water should be optimized according to the concentration and dissolution situation of the gold solution to ensure that the solution after each washing reaches neutral and does not contain other interfering substances.

[0053] Specifically, the washed solution should reach a neutral pH value to avoid the adverse effects of unremoved acidic or alkaline substances on the subsequent reduction reaction. Usually, the pH value of the solution is monitored using a pH meter, and deionized water is added as needed for dilution. Ensure that the filtered and washed solution meets the predetermined purity requirements to provide the best raw materials for the subsequent steps.

[0054] In some embodiments, optimizing the filtration and washing process can not only remove inorganic impurities in the dissolution solution but also effectively remove nitrides and other harmful substances that may affect gold reduction during the dissolution process. Through this step, the gold ions in the solution will enter the reduction reaction with almost no impurities, thereby improving the efficiency of gold reduction and the purity of the gold powder.

[0055] Through this filtration and washing step, the purity of the gold solution is significantly improved, and insoluble substances and impurities in the solution are effectively removed, laying the foundation for the subsequent gold reduction process. This process is crucial for gold extraction, ensuring the purity of gold ions and the smooth progress of subsequent purification.

[0056] S6. Reduction of gold: Mix the filtered aqua regia with anhydrous sodium sulfite for a reduction reaction until the gold ions in the solution are completely reduced to gold powder, where the dosage of anhydrous sodium sulfite is 0.8 kg - 1.2 kg per kg of gold powder; In this embodiment, after the gold solution is filtered and washed, it will then enter the reduction tank for reduction treatment. To reduce the gold ions dissolved in the gold solution to gold powder, anhydrous sodium sulfite is slowly added to the solution as a reducing agent. When anhydrous sodium sulfite reacts with the gold solution, it reduces the gold ions to solid gold powder while being oxidized to sulfite itself.

[0057] Generally, the dosage of sodium sulfite needs to be calculated based on the concentration of gold ions in the gold solution. In this embodiment, the dosage of sodium sulfite is about 1 kg of sodium sulfite per kg of gold powder. Specifically, according to the concentration of gold in the gold solution, the amount of sodium sulfite required can be calculated using the following formula: where, is the mass of sodium sulfite required, C Au is the concentration of gold in the gold solution, is the molar ratio of sodium sulfite to gold ions, M Au is the mass of gold. Through calculation, the required dosage of the reducing agent can be accurately determined to ensure the complete reduction of gold.

[0058] As an option, during the specific implementation process, the addition of the reducing agent can be carried out in batches. That is, after adding a certain amount of sodium sulfite to the gold solution, observe the reaction progress, and then gradually add the remaining sodium sulfite. This method of adding in batches can more precisely control the progress of the reaction, avoiding uneven generation of gold powder particles or incomplete reaction of sodium sulfite caused by excessive reducing agent.

[0059] Specifically, during the reduction reaction process of gold ions, sodium sulfite acts as a reducing agent, providing electrons to the solution, enabling the reduction of gold ions to gold powder. The reduction process is generally carried out under stirring conditions to ensure the uniformity of the reduction reaction. The stirring speed and time can be adjusted according to the progress of the reaction. Appropriate stirring can not only accelerate the reaction rate but also ensure the uniformity of the gold powder particles and avoid the phenomenon of incomplete reduction.

[0060] In a possible implementation, the reaction temperature can also affect the reduction process. Generally, too low a temperature will result in too slow a reduction reaction rate, and too high a temperature may trigger side reactions. Therefore, the temperature should be controlled between 40°C and 50°C to ensure the smooth progress of the reduction reaction.

[0061] After the reduction is completed, the gold powder will precipitate in the solution. At this time, the gold powder can be separated from the solution by methods such as standing and filtration. During the filtration process, a fine mesh filter or filter paper is used to effectively separate the gold powder from the residual substances in the solution.

[0062] In some embodiments, the precipitation rate and particle size of the gold powder may be affected by factors such as solution concentration, stirring rate, and temperature. In order to obtain high-purity gold powder, it may be necessary to appropriately optimize the precipitation process, such as adjusting the temperature, stirring rate, or selecting a suitable filtration medium to ensure the uniformity and high purity of the gold powder.

[0063] Through this reduction step, the gold ions in the gold solution are converted into solid gold powder, further improving the gold recovery rate. After reduction, the obtained gold powder can be used for subsequent purification or direct application. This step not only ensures the complete recovery of gold but also improves the quality of the gold powder, laying the foundation for the ultimate success of the entire gold recovery process.

[0064] S7. Final filtration, washing, and drying: Filter the reduced gold powder, wash it, and place it in an oven to dry. After cooling, gold powder is obtained, and the purity of the gold powder reaches 90%-98%; In this embodiment, first, the reduced gold powder is filtered to ensure the removal of any unreacted residual substances. This step is usually carried out using a suitable fine-mesh filter or filter paper. Since the gold powder particles are generally small, filter materials with good filtering performance are required to ensure that the filtered gold powder is pure and free of impurities. During the filtering process, the gold powder will be retained on the filter medium, while the solution is effectively separated out.

[0065] Generally, the filtered gold powder may still contain a small amount of solvent or other dissolved components. Therefore, the next step is washing. The gold powder is washed several times with deionized water to further remove the solvent and other impurities. The volume and temperature of the washing water should be optimized according to the properties of the gold powder to ensure thorough cleaning without having an adverse effect on the gold powder particles. In some embodiments, the washing water temperature is controlled between 30°C and 40°C, which can effectively remove the dissolved substances without causing the dissolution or loss of the gold powder particles.

[0066] Specifically, during the washing process, the water should circulate sufficiently through the gold powder to ensure that each particle is cleaned. During this process, the pH value of the water should be kept neutral to avoid an acidic or alkaline environment affecting the quality of the gold powder. After several washings, the gold powder will reach an ideal clean state, and at this time, the pH value of the filtrate should also gradually return to neutral to ensure that there are no residual acidic or alkaline components.

[0067] After the washing is completed, the gold powder needs to be dried to remove all residual moisture. The drying temperature of the gold powder is usually controlled at about 120°C, and the drying time is 4 hours. Appropriate drying temperature and time can ensure that the gold powder is completely dry without damaging the structure or purity of the gold powder. During the drying process, the gold powder particles will gradually lose moisture, become drier, looser, and be ready for further processing or use.

[0068] In a possible implementation, the drying process of the gold powder can also be adjusted according to the particle size of the gold powder. Larger gold powder particles may require a longer drying time, while smaller particles can be dried in a shorter time. The choice of drying equipment is also important. Common ovens or drying towers can be used, but it must be ensured that the drying process is uniform to prevent uneven heating of the gold powder, resulting in adhesion between particles or over-drying of the gold powder.

[0069] Finally, the gold powder will be cooled to room temperature after drying, and the final yield is ensured by precise weighing. The dried gold powder should be moisture-free, with loose and uniform particles, meeting the standards for industrial applications. Through this series of processing steps, the purity and quality of the gold powder have been significantly improved, meeting the requirements for subsequent further applications or sales.

[0070] Through this final filtering, washing, and drying step, the gold powder is completely separated from the solution, obtaining high-purity solid gold powder. This process not only removes impurities and moisture but also ensures the quality and uniformity of the gold powder, providing an ideal gold powder raw material for subsequent use and applications.

[0071] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing gold powder based on the ion exchange method, characterized in that, It includes the following steps: S1. Resin pretreatment: Pretreat the ion exchange resin with saturated brine to remove impurities on the resin surface, and then wash the resin successively with HCl acid solution with a concentration of 3%-7% and NaOH alkali solution with a concentration of 2%-4%; S2. Ion exchange adsorption: Contact the pretreated ion exchange resin with waste gold solution with a pH value of 8.5-9.5, and carry out ion exchange adsorption at a set flow rate to adsorb gold in the waste gold solution. The flow rate is 30m / h-50m / h, and the adsorption time is 8 hours-16 hours; S3. Resin carbonization: After drying the resin adsorbed with gold, carbonize it in a carbonization furnace at 500℃-650℃ for 3 hours-5 hours to obtain gold-containing carbide; S4. Dissolution and denitrification of gold: Add the carbide into aqua regia for dissolution, control the temperature at 35℃-45℃ and react for 1 hour-3 hours, then add hydrochloric acid for denitrification treatment, and stop heating after denitrification; S5. Filtration and washing: Filter the dissolved aqua regia to remove insoluble substances, and wash with deionized water until the pH value of the solution is neutral; S6. Reduction of gold: Mix the filtered aqua regia with anhydrous sodium sulfite for reduction reaction until the gold ions in the solution are completely reduced to gold powder. The dosage of anhydrous sodium sulfite is 0.8 kg-1.2 kg per kg of gold powder; S7. Final filtration, washing and drying: Filter the reduced gold powder, wash it and place it in an oven for drying. After cooling, obtain gold powder, and the purity of the gold powder reaches 90%-98%.

2. The method for preparing gold powder based on the ion exchange method according to claim 1, characterized in that, The ion exchange resin is D301 type ion exchange resin.

3. A method for preparing gold powder based on the ion exchange method according to claim 1, characterized in that, During the ion exchange adsorption process, the contact time between the waste gold solution and the ion exchange resin is 8 hours-16 hours.

4. A method for preparing gold powder based on the ion exchange method according to claim 1, characterized in that During the dissolution and denitrification of gold, the volume ratio of aqua regia to gold carbide is 1:

3.

5. A method for preparing gold powder based on the ion exchange method according to claim 1, characterized in that, In the reduction reaction, the dosage of anhydrous sodium sulfite is 0.8 kg-1.2 kg per kg of gold powder.

6. A method for preparing gold powder based on the ion exchange method according to claim 1, characterized in that, The drying temperature of the gold powder is 100℃-130℃, and the drying time is 3 hours-5 hours.

7. A method for preparing gold powder based on the ion exchange method according to claim 1, characterized in that, The gold content of the waste gold solution is below 2 ppm, and the waste gold solution also contains a small amount of silver and platinum metal impurities.

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