Method for extracting gold and silver from waste filter paper filter bag
By incinerating the slag from waste filter paper and filter bags and then performing chlorination and controlled-potential reduction, the problem of low gold and silver recovery rates in waste filter bags has been solved, achieving efficient, low-cost gold and silver extraction and environmentally friendly industrial production.
Patent Information
- Application Number
- CN202511341923.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-19
- Publication Date
- 2025-11-04
AI Technical Summary
In existing technologies, the recovery rate of gold and silver in waste filter paper and filter bags is low and the cost is high. Traditional pyrometallurgical processes result in the loss of precious metals and make them difficult to recycle.
The incineration residue of waste filter paper and filter bags is treated by incineration, and gold and silver are separated and extracted from the incineration residue by chlorination and controlled potential reduction methods, including silver chloride precipitation and replacement and the preparation of pure gold powder, which are further enriched by pyrometallurgical smelting.
It improves the recovery rate of gold and silver, reduces the difficulty and cost of precious metal recycling, reduces environmental pollution, and is suitable for industrial production.
Smart Images
Figure CN120888772A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of non-ferrous metallurgy and noble metal enrichment and extraction, and relates to a method for extracting gold and silver from waste filter paper filter bags. BACKGROUND
[0002] Gold is the most stable metal element, and only forms a natural compound with tellurium in nature, i.e., gold telluride. In non-ferrous heavy metal (copper, nickel, etc.) deposits, gold minerals often occur in association with sulfide minerals and bismuth and arsenic sulfide minerals. Silver exists in nature in the form of an element, but is mainly produced in the form of a compound. Silver minerals often occur in association with non-ferrous metal sulfides such as copper, lead and zinc. Almost all silver and a considerable amount of gold are recovered as by-products in the process of extracting main metals, and the most important source of silver is non-ferrous metal electrolytic anode slime.
[0003] The extraction methods of gold and silver include physical methods and chemical methods. According to the physical properties of gold and silver, the extraction methods of gold and silver mainly include flotation, gravity separation and amalgamation. At present, the physical method is usually used as a pretreatment process for extracting gold and silver, and is mainly used for the enrichment of gold and silver in ores, the treatment of complex and refractory ores and lean ores to obtain gold and silver concentrates, and then the concentrates are treated by fire or wet method. According to the chemical properties of gold and silver, the extraction methods mainly include fire treatment method and wet leaching method. The fire treatment method has high energy consumption and cost, and the wet leaching method is a hot spot in the research of gold and silver extraction in recent years. Commonly used leaching methods of gold and silver mainly include cyanide method, thiosulfate method, thiourea method, aqueous solution chlorination method, ammonia leaching method and sodium sulfite method.
[0004] The wet extraction process of noble metals often uses filter paper, filter bags and filter cloth for solid-liquid separation. For a long time, the waste filter paper and filter bags accumulated over time are directly treated by the Kaldo furnace process to recover gold and silver and other noble metals by fire. However, in this treatment process, noble metals are lost in the form of smelting slag, blowing tailings and soot. The recovery rate of noble metals obtained by burning waste filter paper and filter bags has been kept at 50-75%. It is difficult and costly to obtain noble metals again from the smelting slag and blowing tailings. Therefore, it is urgent to develop new technical methods to realize the enrichment and recovery of gold and silver from waste filter paper and filter bags. SUMMARY
[0005] The purpose of the present application is to solve the technical problem that the recovery of secondary resources of gold and silver is difficult at present. The method for extracting gold and silver from waste filter paper filter bags can effectively improve the reserves of gold and silver resources, help to further improve the recovery rate of gold and silver, and reduce the difficulty of recovering secondary resources of noble metals.
[0006] To achieve the purpose, the present application adopts the following technical solutions: A method for extracting gold and silver from waste filter paper filter bags, comprising the following steps: (1) the waste filter paper filter bag produced in the solid-liquid separation in the precious metal wet extraction process is incinerated to obtain incineration slag; (2) sodium chlorate solution is added to the incineration slag for chlorination of gold, then one or any combination of two or more of hydrochloric acid, nitric acid and sulfuric acid is supplemented to destroy the residual sodium chlorate, then filtered to obtain a gold separation liquid, a gold separation tailing and a silver chloride precipitate; (3) the silver chloride precipitate in step (2) is immersed and cooked in boiling water for 3-4 h, filtered to obtain pure silver chloride, then iron powder is used for replacement to obtain crude silver powder, or N2H4•H2O NH4OH is added for stirring reduction to obtain pure silver powder; (4) the gold separation liquid in step (2) is subjected to controlled potential reduction by sodium sulfite, filtered to obtain pure gold powder, and the obtained gold powder is subjected to nitric acid and hydrochloric acid cooking and then soaked in pure water until neutral; (5) the gold separation tailing in step (2) is subjected to fire roasting or fire smelting for further enrichment and recovery of gold and silver.
[0007] As a further optimization of the technical scheme of the application, in step (1), the incineration equipment is an incinerator, a pyrolysis furnace or a muffle furnace, the incineration temperature is 450-650 DEG C, and the incineration time is 4-5 h.
[0008] Further, in step (2), the concentration of the sodium chlorate solution is 0.2-0.3 g / L; and the mass ratio of the incineration slag to the sodium chlorate solution is 1:4-1:2.
[0009] In step (2), the chlorination of gold process has an acidity of 1-5 mol / L and a temperature of 50-95 DEG C, and the chlorination process is violent, so the sodium chlorate addition flow is controlled at 10-55 L / h, the potential is 850-1200 mV, the constant potential time is 15-60 min, then the sodium chlorate is stopped, and 10-50 L of hydrochloric acid is added again to completely decompose the sodium chlorate.
[0010] In step (2), the iron ion concentration in the gold separation liquid is ≤0.05 g / L, the copper ion concentration is ≤0.05 g / L, the platinum ion concentration is ≤0.01 g / L, the palladium ion concentration is ≤0.01 g / L, and the gold ion concentration is ≥150 g / L.
[0011] Further, in step (3), the amount of N2H4•H2O NH4OH added is 25%-65% of the mass fraction of the pure silver chloride. The stirring reduction speed is 30-45 r / min, and the stirring reduction time is 3-5 h.
[0012] Further, in step (4), sodium bisulfite is added to keep the acidity at 2-5 mol / L, the reduction temperature is 55-75 DEG C, the matching flow is 45-100 L / h, the solution oxidation-reduction potential is reduced to 900 mV, the addition of sodium bisulfite is stopped, then the gold powder is separated from the gold separation solution by solid-liquid separation, and the gold powder is obtained.
[0013] In step (4), the sodium bisulfite added in the reduction process is a 45-60% sodium bisulfite aqueous solution.
[0014] Further, the waste filter paper filter bag used in the silver refining, chlorination gold separation and gold refining acid boiling and water washing processes is any one or any two or more combinations thereof.
[0015] By adopting the above technical scheme, the beneficial effects of the present application are as follows: The method for extracting gold and silver from waste filter paper filter bags provided by the present application uses waste filter paper and filter bags produced by solid-liquid separation in the gold and silver wet extraction process as raw materials, which are incinerated in a pyrolysis incinerator, and then the incineration slag produced is used as raw material for wet extraction of gold and silver, and then silver is precipitated and separated in the form of silver chloride by chlorination gold separation, gold is separated in the form of gold separation tailings and gold separation solution, and gold is completely separated into the gold separation solution by secondary chlorination gold separation, and pure gold powder can be obtained by controlled electrochlorination and acid boiling and water washing of the gold separation solution, and pure silver powder can be obtained by water washing and reduction of the silver chloride.
[0016] The process technology for extracting gold and silver from waste filter paper filter bags developed by the present application discards the traditional lead matte capture fire smelting technology, has no heavy metal pollution, is widely applicable, has high precious metal yield, and the slag and waste liquid are easy to handle, which is beneficial to protect the ecological environment, and the precious metal recovery cost is low, the economic value is excellent, and it is suitable for industrial production. BRIEF DESCRIPTION OF DRAWINGS
[0017] Figure 1 The figure is a process flow diagram of the present application. DETAILED DESCRIPTION
[0018] The present application will be described in detail below by combining specific embodiments with the accompanying drawings.
[0019] Example 1 Waste filter paper and filter bags are incinerated in a pyrolysis incinerator at 450℃ for 4 hours to obtain incinerator residue. At this point, the ash content reaches 42.3%, and the gold and silver grades in the incinerator residue are 2.1% and 5.3%, respectively. The incinerator residue is then added to a 0.2 g / L sodium chlorate solution at a solid-liquid mass ratio of 1:3 for chlorination. The sodium chlorate solution flow rate is 15 L / h, the solution temperature is 50℃, the acidity is 1.5 mol / L, and the stirring rate is 30 r / min. When the potential reaches 850 mV, it is held at this potential for 15 minutes before chlorination is stopped. 10 L of hydrochloric acid is added to completely decompose the sodium chlorate. Filtration yields gold separation solution, gold separation tailings, and silver chloride precipitate. Silver chloride precipitate was boiled in 100℃ water for 3 hours, filtered, and pure silver chloride was obtained. Then, iron powder was used to replace the silver in the silver chloride to obtain crude silver. The gold and silver grades in the crude silver reached 2.7% and 93%, respectively. The gold chloride separation solution was subjected to potentiometric selective reduction using sodium bisulfite, maintaining an acidity of 2.5 mol / L, a reduction temperature of 55℃, and a sodium bisulfite aqueous solution mass fraction of 45%. To control the selective reduction rate, the flow rate of the sodium bisulfite aqueous solution was limited to 45 L / h. The potential was observed during the reduction process, and the addition of sodium bisulfite aqueous solution was stopped when the potential reached 900 mV. Finally, solid-liquid separation yielded solid gold powder, which was then washed with nitric acid to achieve a purity of 99.95%. Practical calculations showed that the gold and silver recovery rates were 97% and 98.3%, respectively.
[0020] Example 2 Waste filter paper and filter bags are incinerated in a pyrolysis incinerator at 500℃ for 4.5 hours to obtain incinerator residue. At this point, the ash content reaches 31.08%, and the gold and silver grades in the incinerator residue are 3.46% and 7.18%, respectively. The incinerator residue is then added to a 0.3 g / L sodium chlorate solution at a solid-liquid mass ratio of 1:4 for chlorination. The sodium chlorate solution flow rate is 20 L / h, the solution temperature is 65℃, the acidity is 2 mol / L, and the stirring rate is 30 r / min. When the potential reaches 900 mV, it is held at this potential for 30 minutes before chlorination is stopped. 5 L of hydrochloric acid is added to completely decompose the sodium chlorate. Filtration yields gold separation solution, gold separation tailings, and silver chloride precipitate. Silver chloride precipitate was immersed in boiling water at 100℃ for 4.5 hours, filtered, and pure silver chloride was obtained. Then, iron powder was used to replace the silver in the silver chloride to obtain crude silver. The gold and silver grades in the crude silver reached 1.34% and 97.5%, respectively. The gold chloride separation solution was subjected to potentiostatic reduction using sodium bisulfite, maintaining an acidity of 3.5 mol / L, a reduction temperature of 65℃, and a sodium bisulfite aqueous solution mass fraction of 50%. To control the selective reduction rate, the flow rate of the sodium bisulfite aqueous solution was limited to 55 L / h. The potential was observed during the reduction process, and the addition of sodium bisulfite aqueous solution was stopped when the potential reached 900 mV. Finally, solid-liquid separation yielded solid gold powder, which was then washed with nitric acid to achieve a grade of 99.95%. Practical calculations showed that the gold and silver recovery rates were 98% and 98.5%, respectively.
[0021] Example 3 The waste filter bag is put into a pyrolysis incinerator at 550℃ for 5h to obtain incineration slag, at this time the ash content is 25%, and the gold and silver grade in the incineration slag is 3.7% and 8.5% respectively; the incineration slag is placed in a 0.3 g / L sodium chlorate solution for chlorination reaction according to the solid-liquid mass ratio of 1:2, at this time the sodium chlorate solution flow is 25L / h, the solution temperature is 70℃, the acidity is 2.5mol / L, and the stirring rate is 35r / min, when the potential reaches 850mV, the chlorination is stopped after constant potential for 30min, and 15L of hydrochloric acid is added to completely decompose the sodium chlorate. Filtration is performed to obtain a gold separation liquid, a gold separation tailings and a silver chloride precipitate; The silver chloride precipitate is placed in boiling water at 100℃ for 3.5h, and filtration is performed to obtain pure silver chloride, after which the silver in the silver chloride is replaced by iron powder to obtain crude silver, and the gold and silver grade in the crude silver is 1.4% and 95.6% respectively; the chlorination gold separation liquid is selectively reduced by sodium bisulfite controlled potential, the acidity is maintained at 3mol / L, the reduction temperature is maintained at 75℃, the mass fraction of sodium bisulfite aqueous solution is 60%, and the sodium bisulfite aqueous solution flow is limited to 55L / h to control the selective reduction rate, in this process, the potential is observed during reduction, and when the potential reaches 900mV, the addition of sodium bisulfite aqueous solution is stopped, and finally solid-liquid separation is performed to obtain solid gold powder, which is washed with nitric acid to achieve a grade of 99.95%, and the gold and silver recovery rate is 99.2% and 99.7% respectively according to practical calculation.
[0022] Example 4 The waste filter bag is put into a pyrolysis incinerator at 550℃ for 5h to obtain incineration slag, at this time the ash content is 25%, and the gold and silver grade in the incineration slag is 3.7% and 8.5% respectively; the incineration slag is placed in a 0.3 g / L sodium chlorate solution for chlorination reaction according to the solid-liquid mass ratio of 1:2, at this time the sodium chlorate solution flow is 25L / h, the solution temperature is 70℃, the acidity is 2.5mol / L, and the stirring rate is 35r / min, when the potential reaches 850mV, the chlorination is stopped after constant potential for 30min, and 15L of hydrochloric acid is added to completely decompose the sodium chlorate. Filtration is performed to obtain a gold separation liquid, a gold separation tailings and a silver chloride precipitate; The silver chloride precipitate was immersed in boiling water at 100℃ for 3.5h, filtered to obtain pure silver chloride, and then 60% N2H4•H2O NH4OH was added to reduce the silver chloride. NaOH solution was added to control the pH to 10, the stirring speed was 30r / min, and the reduction was stirred at room temperature for 30min. The sponge silver was obtained by standing, and the qualified silver was obtained after filtration, washing, drying and screening. The chlorinated gold solution was selectively reduced by sodium bisulfite controlled potential, the acidity was maintained at 3mol / L, the reduction temperature was maintained at 75℃, the mass fraction of sodium bisulfite aqueous solution was 60%, and the sodium bisulfite aqueous solution flow was limited to 55L / h to control the selective reduction rate. During the process, the potential was observed, and when the potential reached 900mV, the addition of sodium bisulfite aqueous solution was stopped. Finally, solid-liquid separation was carried out to obtain solid gold powder. The gold powder was washed with nitric acid to reach 99.95% grade, and the practical calculation showed that the gold and silver recovery rates were 99.2% and 99.5% respectively.
Claims
1. A method for extracting gold and silver from waste filter paper and filter bags, characterized in that, The method includes the following steps: (1) The waste filter paper and filter bags generated during the solid-liquid separation process of precious metal wet extraction are incinerated to obtain incineration residue; (2) Add sodium chlorate solution to the incinerator residue for chlorination and gold separation, then add one or any combination of two or more of hydrochloric acid, nitric acid, and sulfuric acid to destroy the residual sodium chlorate, then filter to obtain gold separation liquid, gold separation tailings and silver chloride precipitate. (3) The silver chloride precipitate in step (2) is placed in boiling water for immersion and washing for 3-4 hours, filtered, and pure silver chloride is obtained. Then, iron powder is used to replace it to obtain crude silver powder, or N2H4·H2O NH4OH is added and stirred to reduce it to obtain pure silver powder. (4) The gold separation solution in step (2) is reduced by sodium sulfite under controlled potential, filtered, and pure gold powder is obtained. The obtained gold powder is boiled with nitric acid and hydrochloric acid and then soaked in pure water until neutral. (5) The gold tailings from step (2) are baked or smelted by fire to further enrich and recover gold and silver.
2. The method for extracting gold and silver from waste filter paper and filter bags as described in claim 1, characterized in that, In step (1), the incineration equipment is an incinerator, pyrolysis furnace or muffle furnace, the incineration temperature is 450~650℃ and the incineration time is 4~5h.
3. The method for extracting gold and silver from waste filter paper and filter bags as described in claim 2, characterized in that, In step (2), the concentration of sodium chlorate solution is 0.2~0.3 g / L; the mass ratio of incinerator residue to sodium chlorate solution is 1:4~1:
2.
4. The method for extracting gold and silver from waste filter paper and filter bags as described in claim 3, characterized in that, In step (2), the acidity of the gold chlorination process is 1~5 mol / L and the temperature is 50~95℃. The flow rate of sodium chlorate is controlled at 10~55L / h. When the potential is 850~1200mV and the constant potential time is 15~60min, the addition of sodium chlorate is stopped. Then, 10~50L of hydrochloric acid is added again to completely decompose the sodium chlorate.
5. The method for extracting gold and silver from waste filter paper and filter bags as described in claim 4, characterized in that, Step (2) The concentration of iron ions in the gold separation solution is ≤0.05g / L, the concentration of copper ions is ≤0.05g / L, the concentration of platinum ions is ≤0.01g / L, the concentration of palladium ions is ≤0.01g / L, and the concentration of gold ions is ≥150g / L.
6. The method for extracting gold and silver from waste filter paper and filter bags as described in claim 5, characterized in that, In step (3), the amount of N2H4·H2O NH4OH added is 25%~65% of the mass fraction of pure silver chloride.
7. The method for extracting gold and silver from waste filter paper and filter bags as described in claim 6, characterized in that, In step (3), the stirring speed is 30r / min~45r / min and the stirring reduction time is 3~5h.
8. The method for extracting gold and silver from waste filter paper and filter bags as described in claim 7, characterized in that, In step (4), sodium bisulfite is added to maintain the acidity at 2~5 mol / L, the reduction temperature at 55~75℃, and the addition flow rate at 45~100L / h. When the redox potential of the solution decreases to 900mV, the addition of sodium bisulfite is stopped. Then, the gold powder is separated from the gold-separated liquid by solid-liquid separation method to obtain gold powder.
9. A method for extracting gold and silver from waste filter paper and filter bags as described in claim 8, characterized in that, In step (4), the sodium bisulfite added during the reduction process is an aqueous solution of sodium bisulfite with a mass fraction of 45-60%.
10. A method for extracting gold and silver from waste filter paper and filter bags as described in any one of claims 1-9, characterized in that, The waste filter paper and filter bags are any one type or any combination of two or more types of filter paper and filter bags used in the processes of silver refining, gold chloride separation, and gold refining acid boiling and washing.