A system and method for silver recovery by leaching and adsorption enhanced in sections

Abstract

The application discloses a segmented leaching and adsorption reinforced silver recovery system and method, and belongs to the technical field of metallurgy. The system comprises two pre-leaching tanks, two silver adsorption tanks and at least four gold adsorption tanks connected in series, and the leaching tanks are connected in series. The silver adsorption tanks are filled with modified silver special adsorption carbon, and the gold adsorption tanks are filled with gold active carbon. The last gold adsorption tank is connected with the feeding end of a post-leaching thickener, the overflow supernatant of the post-leaching thickener is connected with the feeding end of a precipitation tank, and the discharging end of the precipitation tank is connected with the pre-leaching tank through a cyanide-resistant centrifugal pump. The system further comprises air lifters respectively inserted into the second silver adsorption tank and the last gold adsorption tank, and the air lifters are sequentially connected with a linear vibrating screen, a silver carbon desorption column or a gold carbon desorption column and an electrodeposition tank. The modified silver special adsorption carbon is loaded with a dithiocarbamate salt group on the surface. The system solves the problems of low silver recovery rate, long carbon extraction period, high reagent consumption and gold-silver adsorption competition in the existing whole mud cyanidation carbon pulp process.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal hydrometallurgy technology. It relates to a system for enhancing silver recovery, and also to a method for segmented leaching and adsorption based on the system. It is mainly applicable to scenarios involving the synergistic and efficient recovery of gold and silver from silver-bearing gold ore resources. Background Technology

[0002] In the gold mining sector, silver, as a typical associated valuable metal, directly impacts the overall profit margin of mining companies through its recovery efficiency. According to industry statistics, the average silver recovery rate in my country's silver-bearing gold mines is only 60%-75%, far lower than the gold recovery rate of over 95%, resulting in a significant loss of silver resources.

[0003] In current mainstream whole-sludge cyanidation carbon-in-pulp processes, activated carbon with a single pore size is commonly used for gold and silver co-adsorption. Gold and silver ions differ significantly in their adsorption kinetics, activated carbon pore size compatibility, and surface binding mechanisms. For example, gold ions (Au(CN)2⁻) have a smaller radius (approximately 0.3 nm), making it easier for them to enter the 10–15 Å microporous structure of traditional activated carbon and be rapidly adsorbed; while silver ions (Ag(CN)2⁻) have a larger radius (approximately 0.35 nm), resulting in greater diffusion resistance within the micropores and weaker non-specific adsorption on the activated carbon surface. Consequently, the silver adsorption kinetic rate is only 1 / 3 to 1 / 2 that of gold, and the adsorption equilibrium time is significantly prolonged.

[0004] Meanwhile, the existing whole-mud cyanidation carbon-in-pulp process has two major problems: First, the carbon extraction cycle is poorly designed. Most mines set the carbon extraction cycle to 36-48 hours to reduce the frequency of operation, which causes the adsorbed carbon to remain in the leaching tank for a long time. In the early stage, the adsorption efficiency decreases due to the saturation of active sites (the silver adsorption capacity decreases by 20%-25% after 48 hours). In the later stage, the compaction of the carbon layer increases the resistance to the flow of the slurry, resulting in local "dead zones". Second, the recycling of cyanide-containing wastewater is insufficient. For example, in the existing process of a beneficiation plant of Shandong Gold Group, the actual consumption of sodium cyanide (0.63 kg / t) is 3.3 times the theoretical leaching consumption (0.19 kg / t). A large amount of residual sodium cyanide is broken down in the cyanide removal section with the leaching residue, which not only increases the cost of reagents, but also causes fluctuations in the concentration of free cyanide in the leaching system, further affecting the leaching and adsorption stability of silver.

[0005] Furthermore, from a mineralogical perspective, the occurrence state of silver in silver-bearing gold deposits is complex. For example, mineralogical analysis of the cyanide slag from a certain beneficiation plant showed that silver mainly exists in the form of intergrowths (accounting for 63.83%), and is partially encapsulated within gangue minerals such as quartz and pyrite, requiring longer leaching times for complete dissociation and dissolution. However, traditional leaching and adsorption processes do not incorporate segmented residence times designed for the dissociation characteristics of silver, resulting in some dissolved silver ions being lost with the tailings due to delayed adsorption. Therefore, developing a segmented leaching and adsorption technology that balances silver adsorption specificity, process adaptability, and cost-effectiveness is crucial for the efficient recovery of silver-bearing gold resources. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a system and method for enhanced silver recovery through segmented leaching and adsorption, which solves the problems of low silver recovery rate, long carbon extraction cycle, high reagent consumption and competition between gold and silver adsorption in the existing whole-sludge cyanidation carbon-in-pulp process.

[0007] The technical solution of the present invention is as follows:

[0008] A segmented leaching and adsorption-enhanced silver recovery system includes an adsorption carbon functional module, an online monitoring and control module, a cyanide water circulation module, and an adsorption carbon turnover desorption treatment module. The adsorption carbon functional module includes a first pre-leaching tank, a second pre-leaching tank, a first silver adsorption tank, a second silver adsorption tank, and at least four gold adsorption tanks connected in series as leaching tanks. The outlet of the preceding leaching tank is connected to the inlet of the adjacent subsequent leaching tank via a pipeline. The first and second silver adsorption tanks are respectively filled with modified silver-specific adsorption carbon, and each gold adsorption tank is filled with gold-adsorbing activated carbon. The online monitoring and control module includes pH sensors and free cyanide concentration sensors installed in each leaching tank. The system includes a detector and a slurry flow meter; a cyanide-based circulation module comprising a post-leaching thickener and a sedimentation tank; a final gold adsorption tank connected to the feed end of the post-leaching thickener, with the overflow supernatant from the thickener connected to the feed end of the sedimentation tank; and a sedimentation tank discharge end connected to the replenishment ports of the first and second pre-leaching tanks via a cyanide-resistant centrifugal pump; and an adsorption carbon turnover and desorption treatment module comprising air lifters inserted into the second silver adsorption tank and the final gold adsorption tank, respectively; the air lifter inserted into the second silver adsorption tank is sequentially connected to a linear vibrating screen, a silver-carbon desorption column, and an electrowinning tank; and the air lifter inserted into the final gold adsorption tank is sequentially connected to a linear vibrating screen, a gold-carbon desorption column, and an electrowinning tank.

[0009] Preferably, the modified silver-specific adsorbent carbon has a pore size distribution of 20-30 Å, a mesopore ratio of ≥65%, a surface loaded with dithiocarbamate groups with a loading amount of 0.8-1.2 mmol / g, a BET specific surface area of ​​≥1000 m² / g, and a silver adsorption capacity of ≥80 mg / g; the gold-adsorbing activated carbon has a pore size distribution of 10-15 Å, a micropore ratio of ≥70%, and a BET specific surface area of ​​≥1200 m² / g.

[0010] Preferably, the preparation steps of the modified silver-specific adsorbent carbon are as follows:

[0011] a) Pretreatment: Select coconut shell activated carbon with a particle size of 1.0-3.0 mm, acid wash with 5-10% hydrochloric acid solution at 60-80℃ for 2-4 hours, wash with water until pH 6.5-7.0, and dry at 105-110℃ for 4-6 hours.

[0012] b) Functional modification: Add the pretreated activated carbon to a 0.5-1.5 mol / L sodium diethyldithiocarbamate solution at a solid-liquid ratio of 1:(6~10), and shake and impregnate at 40-60℃ for 4-6 hours.

[0013] c) Drying and activation: Drain the impregnated activated carbon, vacuum dry it at 110-130℃ for 2-3 hours, and then sieve it to obtain modified silver-specific adsorption carbon.

[0014] The method for segmented leaching and adsorption based on the system includes the following steps:

[0015] a) Pre-leaching treatment: The slurry is fed into the pre-leaching tank, sodium cyanide and lime milk are added, the pH is controlled at 11.5-12.0, the free cyanide concentration is 320-350mg / L, and the pre-leaching time is 18-20 hours.

[0016] b) Silver adsorption treatment: The pre-leached slurry enters the silver adsorption section and is in contact with modified silver-specific adsorption carbon for 15-16 hours, with the carbon density controlled at 18-20 g / L.

[0017] c) Gold adsorption treatment: The slurry enters the gold adsorption section and is in contact with gold-adsorbing activated carbon for 20-22 hours, with the carbon density controlled at 12-15 g / L.

[0018] Preferably, the carbon extraction cycle is 24 hours. Saturated adsorbed carbon is extracted from the second silver adsorption tank (4) and the last gold adsorption tank by an air lifter. After separation, the silver saturated carbon is sent to the silver carbon desorption column (13) for desorption, and the gold saturated carbon is sent to the gold carbon desorption column (14) for desorption. The desorbed lean carbon is acid washed and regenerated and then returned to the second silver adsorption tank (4) and the last gold adsorption tank for recycling. The desorption liquid is sent to the electrolysis section to recover gold and silver.

[0019] More preferably, the desorbent for silver-saturated carbon is a mixture of sodium hydroxide and thiourea, with a desorption temperature of 120-130℃ and a pressure of 0.3-0.4MPa; the lean carbon is regenerated after being washed with hydrochloric acid.

[0020] Preferably, the ore in the pre-leaching treatment has a hydrocyclone overflow content of ≥85% -200 mesh and a slurry concentration of 39-40%.

[0021] Compared with the prior art, the present invention has the following significant advantages:

[0022] This invention addresses industry pain points such as low silver recovery rate and rapid decay of carbon adsorption efficiency in traditional co-adsorption processes by optimizing the functional characteristics of adsorbent carbon and the matching of process parameters. It can be widely applied to the comprehensive recovery and upgrading of associated silver in the whole-sludge cyanidation carbon slurry gold extraction process, providing technical support for the resource utilization of high-value associated metals.

[0023] Significantly improved silver recovery efficiency: Through the functional design of modified silver-specific adsorbent carbon and a segmented adsorption process, the silver recovery rate has increased from less than 80% in traditional processes to over 89%, increasing the silver recovery per ton of ore by 5.5-6.2g. Based on a gold mine processing 1300t of ore per day, this translates to an annual increase in silver recovery of approximately 2.6-2.9t. Experiments have shown that compared to traditional processes, this invention improves the silver recovery rate by about 15%.

[0024] Gold recovery stability is guaranteed: The targeted design and segmented layout of the gold-adsorbing activated carbon avoids competition between gold and silver adsorption, the gold adsorption rate exceeds 99%, and the gold grade in the tail tank liquid is stable at ≤0.01mg / L, ensuring that the gold recovery index is not lower than the level of traditional processes.

[0025] Significant reduction in reagent and energy costs: The recycling of cyanide-containing wastewater reduces sodium cyanide consumption from 0.63 kg / t to 0.25-0.3 kg / t, saving approximately 150-180 tons of sodium cyanide annually; at the same time, the 24-hour carbon extraction cycle accelerates the turnover efficiency of adsorbent carbon (increasing carbon utilization by 40%-50%), reducing the amount of activated carbon replenishment (saving approximately 20-25 tons of carbon annually), resulting in a 12%-15% reduction in overall reagent and carbon costs.

[0026] High process adaptability and operability: The system upgrade is based on the existing leaching tank layout, without the need for a large number of new equipment (only one thickener and online monitoring instrument need to be added), the upgrade cycle is short (30~45 days), and the return on investment is high (static payback period ≤1.5 years); at the same time, the introduction of the online monitoring system realizes the automated control of process parameters, reducing the intensity of manual operation and errors.

[0027] Significant environmental benefits: The recycling rate of cyanide-containing wastewater has increased to over 60%, reducing the consumption of fresh water (saving approximately 150,000 m³ of water annually) and the discharge of cyanide-containing wastewater; due to the reduced amount of sodium cyanide introduced into the cyanide removal section, the dosage of cyanide-breaking agents (pyroxene, copper sulfate) has decreased by 30% to 35%, reducing pollutant emissions. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the segmented leaching and adsorption system of the present invention.

[0029] Figure 2This is a pore size distribution curve of the gold-adsorbing activated carbon used in this invention and the modified silver-specific adsorbing carbon prepared in this invention.

[0030] Figure 3 This is a comparison chart of the silver recovery rates of the segmented process of this invention and the traditional process.

[0031] Explanation of reference numerals in the attached drawings: 1. First pre-impregnation tank; 2. Second pre-impregnation tank; 3. First silver adsorption tank; 4. Second silver adsorption tank; 5. First gold adsorption tank; 6. Second gold adsorption tank; 7. Third gold adsorption tank; 8. Fourth gold adsorption tank; 9. Post-impregnation thickener; 10. Cyanide-resistant centrifugal pump; 111. First air lift; 112. Second air lift; 121. First linear vibrating screen; 122. Second linear vibrating screen; 13. Silver-carbon desorption column; 14. Gold-carbon desorption column; 15. Sedimentation tank; 161. First electrodeposition tank; 162. Second electrodeposition tank. Detailed Implementation

[0032] The present invention will be further illustrated below with reference to embodiments and experimental data.

[0033] I. System Composition and Structure Implementation Examples

[0034] like Figure 1 An embodiment of the segmented leaching adsorption system of the present invention includes a first pre-leaching tank 1, a second pre-leaching tank 2, a first silver adsorption tank 3, a second silver adsorption tank 4, a first gold adsorption tank 5, a second gold adsorption tank 6, a third gold adsorption tank 7, and a fourth gold adsorption tank 8 as leaching tanks. The outlet of the preceding leaching tank is connected to the inlet of the adjacent subsequent leaching tank via a pipeline.

[0035] The first pre-leaching tank 1 and the second pre-leaching tank 2 are used to achieve two-stage pre-leaching of the ore. The first silver adsorption tank 3 and the second silver adsorption tank 4 constitute the silver adsorption section. The first gold adsorption tank 5, the second gold adsorption tank 6, the third gold adsorption tank 7, and the fourth gold adsorption tank 8 constitute the gold adsorption section. The ore slurry is conveyed by gravity in the order of "pre-leaching, silver adsorption, gold adsorption".

[0036] The above leaching tanks constitute the adsorption carbon functional module. The first silver adsorption tank 3 and the second silver adsorption tank 4 are respectively filled with modified silver-specific adsorption carbon prepared according to this invention, with a carbon density controlled at 20 g / L; the first gold adsorption tank 5, the second gold adsorption tank 6, the third gold adsorption tank 7, and the fourth gold adsorption tank 8 are respectively filled with gold-adsorbing activated carbon, with a carbon density of 12 g / L. The gold-adsorbing activated carbon is a commercially available product, with a pore size distribution concentrated in the 10-15 Å range, a micropore ratio ≥70%, a BET specific surface area greater than 1200 m² / g, and a gold adsorption capacity greater than 15 mg / g.

[0037] The segmented leaching adsorption system of this invention also includes an online monitoring and control module: a pH sensor (measuring range 10~14, accuracy ±0.05), a free cyanide concentration detector (detection limit 0.1mg / L), and a slurry flow meter (range 0~200m³ / h) are installed at the outlet of each leaching tank. Data is transmitted to the central control system in real time. The pH of the first pre-leaching tank 1 and the second pre-leaching tank 2 is controlled at 11.5~12.0 by automatically adjusting the amount of lime slurry added, and the free cyanide is maintained at 300~350mg / L by adjusting the amount of sodium cyanide added. Other leaching tanks only need to add a small amount of lime slurry to fine-tune the pH, without the need for additional sodium cyanide, ensuring a stable leaching adsorption environment in each segment.

[0038] The segmented leaching system of this invention also includes a cyanide-containing wastewater circulation module: the tailings slurry outlet of the fourth gold adsorption tank 8 is connected to the feed end of the post-leaching thickener 9 via a pipeline; the overflow supernatant of the post-leaching thickener 9 is connected to the feed end of the sedimentation tank 15 via a pipeline; and the discharge end of the sedimentation tank 15 is connected to the replenishment ports of the first pre-leaching tank 1 and the second pre-leaching tank 2 via a cyanide-resistant centrifugal pump 10. The cyanide-containing tailings slurry discharged from the fourth gold adsorption tank 8 is concentrated by the post-leaching thickener 9, and the supernatant (containing 30-50 mg / L of free cyanide) is returned to the first pre-leaching tank 1 and the second pre-leaching tank 2 for reuse, achieving a cyanide-containing wastewater recycling rate of ≥60% and reducing the consumption of fresh water and sodium cyanide.

[0039] The segmented leaching adsorption system of the present invention also includes an adsorbent carbon turnover and desorption treatment module: this mechanism includes

[0040] The system comprises a first air lift 111, a first linear vibrating screen 121 (0.8 mm aperture), a silver-carbon desorption column 13, and a first electrodeposition cell 161, connected in sequence. The system also includes a second air lift 112, a second linear vibrating screen 122 (0.8 mm aperture), a gold-carbon desorption column 14, and a second electrodeposition cell 162, connected in sequence. The linear vibrating screen is used to separate adsorbed carbon from the slurry.

[0041] The carbon suction ports of the first air lifter 111 and the second air lifter 112 are respectively inserted into the bottom of the second silver adsorption tank 4 and the fourth gold adsorption tank 8, and are used to extract saturated adsorbed carbon through negative pressure.

[0042] The discharge ports of the first air lifter 111 and the second air lifter 112 are respectively connected to the inlet ports of the first linear vibrating screen 121 and the second linear vibrating screen 122 via pipelines.

[0043] The silver-carbon discharge port of the first linear vibrating screen 121 is connected to the inlet of the silver-carbon desorption column 13 via a pipeline, and the gold-carbon discharge port of the second linear vibrating screen 122 is connected to the inlet of the gold-carbon desorption column 14 via a pipeline.

[0044] The outlets of the silver-carbon desorption column 13 and the gold-carbon desorption column 14 are connected to the inlets of the first electrodeposition tank 161 and the second electrodeposition tank 162, respectively. The lean liquor from the first electrodeposition tank 161 and the second electrodeposition tank 162 can be returned to the pre-impregnation tank for reuse. After desorption, the lean carbon is regenerated by acid washing and then returned to the second silver adsorption tank 4 and the fourth gold adsorption tank 8 for recycling, respectively.

[0045] The electrodeposition cell is a core piece of equipment in the electrolysis process, where gold and silver are extracted from the desorbed solution. Gold and silver ions in the desorbed solution are deposited as elemental metals through electrolysis, achieving the final recovery of gold and silver.

[0046] II. Examples of Preparation of Modified Silver-Specific Adsorbent Carbon

[0047] (I) Preparation process

[0048] 1. Pretreatment: Take 10 kg of coconut shell activated carbon with a particle size of 1.5-2.5 mm (ash content ≤5%, strength ≥95%), add 50 L of 8% hydrochloric acid solution, stir and acid wash in a 70℃ constant temperature water bath for 3 hours to remove impurities (such as calcium and magnesium ions) and some tar-like substances that block micropores on the surface of activated carbon; after acid washing, rinse repeatedly with deionized water until the pH of the washing solution is 7.0, and then dry at 105℃ for 5 hours.

[0049] 2. Functionalization modification: All pretreated activated carbon was added to 80L of a 1.0mol / L sodium diethyldithiocarbamate (DDTC) aqueous solution and immersed in the solution at 50℃ with shaking for 5 hours (oscillation frequency 120r / min). This allowed DDTC molecules to bind to the hydroxyl groups on the activated carbon surface through van der Waals forces, forming stable dithiocarbamate functional groups. During this period, samples were taken every hour to test the functional group loading to ensure that the design requirement of 0.8~1.2mmol / g was met. If the design requirement was not met, the shaking and immersion time could be extended or the concentration of the DDTC aqueous solution could be increased to ensure that the functional group loading met the standard.

[0050] 3. Drying and Activation: Take out the functionalized activated carbon, let it drain naturally until there are no free droplets on the surface, and then put it into a vacuum drying oven at 120℃ (vacuum degree -0.08MPa) for 2.5 hours to avoid the decomposition of functional groups caused by high temperature; after drying, it is sieved (to remove carbon fragments with a particle size <1.0mm) to obtain the modified silver adsorption carbon product.

[0051] (ii) Performance Characterization

[0052] The modified silver-specific adsorbent carbon was determined using the liquid nitrogen adsorption-desorption method. The results are shown in [link to results]. Figure 2The modified silver-specific adsorbent carbon of this invention has a pore size distribution concentrated in the range of 22-28 Å (mesopores account for 68.5%); the gold-adsorbing activated carbon used in this invention has a micropore content of ≥70%. The modified silver-specific adsorbent carbon of this invention has a BET specific surface area of ​​1086 m² / g; the gold-adsorbing activated carbon has a BET specific surface area of ​​≥1200 m² / g.

[0053] X-ray photoelectron spectroscopy (XPS) analysis showed that the surface sulfur content was 2.35%, confirming the successful loading of dithiocarbamate groups. Chemical titration determined the dithiocarbamate functional group loading to be 1.05 mmol / g. Under conditions of 25℃ and pH 11.5, its silver adsorption capacity reached 82.6 mg / g, which is much higher than the 45.3 mg / g of traditional activated carbon.

[0054] III. Segmented Leaching and Adsorption Process Control Examples

[0055] The following section, based on on-site testing and experimental data from a beneficiation plant of Shandong Gold Group, further illustrates the process control method and implementation effects of the segmented leaching adsorption method of this invention. The comparison results between the implementation effects and traditional processes are shown in [link to relevant documentation]. Figure 3 .

[0056] (I) Process Control Example 1

[0057] Experimental conditions: A production line of a beneficiation plant of Shandong Gold Group was selected, with a raw ore processing capacity of 45.01 t / h (daily processing capacity of 1080 t), a raw ore Au grade of 4.97 g / t, an Ag grade of 64.26 g / t, and a grinding fineness of -200 mesh content of 86.88%. The process was operated for 30 days according to the optimized process parameters of this invention.

[0058] Pre-leaching stage treatment: The crushed and ground ore is prepared into a 40% (mass concentration) slurry (cyclone overflow - 200 mesh content 86.88%), which is first fed into the first pre-leaching tank 1, and then flows by gravity into the second pre-leaching tank 2. The two stages are pre-leached in series. When the liquid level in the second pre-leaching tank 2 is lower than the set value, slurry is added to the second pre-leaching tank 2 through the replenishment port at a rate of 0.3~0.4 kg / t. 矿石 Add 30% sodium cyanide aqueous solution and lime slurry to adjust the pH of the slurry to 11.5-12.0. Stir at 18-20 r / min and pre-leaching for 19 hours. This stage utilizes a high concentration of free cyanide (335 mg / L) to promote the dissociation and dissolution of intergrowth silver minerals.

[0059] The results showed that the silver leaching rate reached 72.3% (5% to 8% higher than the traditional pre-leaching process) and the gold leaching rate reached 92.2%.

[0060] Silver adsorption stage treatment: The pre-leached slurry flows by gravity through pipes into the first silver adsorption tank 3 and the second silver adsorption tank 4. The carbon density is controlled at 19 g / L (higher than the traditional level of 9.89 g / L), the stirring rate is 16 r / min, and the adsorption time is 15.5 hours. The remaining 8.5 hours are for the smooth transition of the slurry and the pretreatment of the carbon layer, ensuring uniform carbon layer distribution and a stable adsorption environment in the tanks. Highly efficient silver capture is achieved through the specific coordination of functionalized functional groups with silver ions (the S atom in dithiocarbamate forms a stable five-membered ring chelate with Ag⁺).

[0061] Measurements showed that the silver adsorption rate reached 88.5% at this stage, and the silver ion concentration in the slurry decreased to 4.2 mg / L.

[0062] Gold adsorption stage treatment: The slurry after silver adsorption flows sequentially through the first gold adsorption tank 5, the second gold adsorption tank 6, the third gold adsorption tank 7, and the fourth gold adsorption tank 8. The carbon density is controlled at 13 g / L, the stirring rate is 16 r / min, and the adsorption time is 21 hours. The remaining 3 hours are used for uniform distribution of adsorbed carbon and fine-tuning of system parameters to ensure sufficient gold adsorption.

[0063] Measurements showed that the gold adsorption rate reached 99.6% at this stage, and the gold content in the tailings liquid was 0.008 mg / L.

[0064] Cyanide-containing wastewater recycling: The tailings slurry (containing 270 mg / L of free cyanide) discharged from the fourth gold adsorption tank 8 is sent to the post-leaching thickener 9. The thickened underflow (concentration 51%) enters the cyanide removal section. The supernatant (containing 40 mg / L of free cyanide) is settled in the sedimentation tank 15 and then transported back to the pre-leaching tank for reuse by the cyanide-resistant centrifugal pump 10.

[0065] Measurements showed that the recycling rate of cyanide-containing wastewater reached 61%, reducing the actual consumption of sodium cyanide to 0.28 kg / t (a 55% reduction compared to the traditional process of 0.63 kg / t).

[0066] Overall metrics: Final total gold recovery rate 98.0%, total silver recovery rate 91.5% (an improvement of 15.91% compared to the traditional process's 75.59%). Figure 3 The carbon extraction cycle is 24 hours, and the turnover efficiency of activated carbon is increased by 42%.

[0067] (II) Process Control Example 2

[0068] Experimental conditions and process: Another batch of ore (Au grade 3.85 g / t, Ag grade 48.32 g / t) from a beneficiation plant of Shandong Gold Group was selected. The pre-leaching time was adjusted to 20 hours, the silver adsorption time to 16 hours, and the gold adsorption time to 22 hours. Other parameters were the same as in Process Control Example 1. The experiment was run for 15 days.

[0069] Experimental results:

[0070] Measurements showed that the recycling rate of cyanide-containing wastewater reached 62%, reducing the actual consumption of sodium cyanide to 0.26 kg / t.

[0071] Pre-leaching section: silver leaching rate 69.8%, gold leaching rate 91.5%; silver adsorption section: silver adsorption rate 87.2%, silver ion concentration at slurry outlet 3.9 mg / L; gold adsorption section: gold adsorption rate 99.6%, gold grade in tailings liquid 0.009 mg / L.

[0072] Overall indicators: The final total gold recovery rate was 97.8%, the total silver recovery rate was 89.8%, the sodium cyanide consumption was 0.26 kg / t, and the cyanide-containing wastewater recycling rate was 62%, proving that this process still has good adaptability and stability under different ore grades.

[0073] (III) Examples of Adsorption Carbon Turnover and Desorption Treatment

[0074] Using a 24-hour carbon extraction cycle, saturated adsorbed carbon is extracted from the second silver adsorption tank 4 and the fourth gold adsorption tank 8 respectively through an air lifter (negative pressure -0.06MPa). After separation by a linear vibrating screen (0.8mm sieve aperture), the silver saturated carbon is sent to the silver-carbon desorption column 13 for desorption (the desorbent is a mixture of 1.5% sodium hydroxide and 0.5% thiourea, temperature 120~130℃, pressure 0.3~0.4MPa), and the gold saturated carbon is sent to the gold-carbon desorption column 14 for desorption using a traditional medium-temperature cyanide-free desorption process.

[0075] After desorption, the lean carbon is regenerated by acid washing (5% hydrochloric acid, 60℃ for 2 hours) and then returned to the second silver adsorption tank 4 and the fourth gold adsorption tank 8 for recycling. The desorbed solution is sent to the electrolysis section to recover gold and silver.

[0076] The gold resolution was measured to be 98.2%, and the silver resolution was measured to be 96.6%.

[0077] Additional note: Control valves are installed on the relevant pipelines. Since the installation and operation of control valves are conventional technologies, they are omitted in this embodiment.

Claims

1. A system for segmental leaching adsorption enhanced silver recovery, comprising an adsorption carbon functional module, an online monitoring and regulation module, a cyanide water system circulation module and an adsorption carbon turnover desorption treatment module, characterized in that: The adsorption carbon functional module comprises a first pre-leaching tank (1), a second pre-leaching tank (2), a first silver adsorption tank (3), a second silver adsorption tank (4) and at least four gold adsorption tanks connected in series as leaching tanks; the outlet of the previous leaching tank is connected to the inlet of the next leaching tank through a pipeline; the first silver adsorption tank (3) and the second silver adsorption tank (4) are respectively filled with modified silver special adsorption carbon, and each gold adsorption tank is respectively filled with gold adsorption activated carbon; The online monitoring and control module comprises a pH sensor, a free cyanide concentration detector and a slurry flow meter installed in each leaching tank; the cyanide water circulation module comprises a post-leaching thickener (9) and a sedimentation tank (15); the last gold adsorption tank is connected to the feed end of the post-leaching thickener (9), the overflow supernatant of the post-leaching thickener (9) is connected to the feed end of the sedimentation tank (15), and the outlet of the sedimentation tank (15) is connected to the liquid supplementing ports of the first pre-leaching tank (1) and the second pre-leaching tank (2) through a cyanide-resistant centrifugal pump (10); the adsorption carbon turnover and desorption treatment module comprises air lifters inserted into the second silver adsorption tank (4) and the last gold adsorption tank; the air lifter inserted into the second silver adsorption tank (4) is sequentially connected with a linear vibrating screen, a silver carbon desorption column (13) and an electrodeposition tank; the air lifter inserted into the last gold adsorption tank is sequentially connected with a linear vibrating screen, a gold carbon desorption column (14) and an electrodeposition tank; The modified silver special adsorption carbon has a pore size distribution of 20-30 Å, a mesopore ratio of ≥65%, a surface loaded dithiocarbamate salt group and a loading amount of 0.8-1.2 mmol / g, a BET specific surface area of ≥1000 m² / g and a silver adsorption capacity of ≥80 mg / g; The gold adsorption activated carbon has a pore size distribution of 10-15 Å, a micropore ratio of ≥70% and a BET specific surface area of ≥1200 m² / g.

2. The system for recovery of silver by leaching-adsorption-intensification in sections according to claim 1, characterized by The preparation steps of the modified silver special adsorption carbon are as follows: a) pretreatment: coconut shell activated carbon with a particle size of 1.0-3.0 mm is selected, acid washing is performed at 60-80 °C for 2-4 hours with 5-10% hydrochloric acid solution, water washing is performed until the pH is 6.5-7.0, and drying is performed at 105-110 °C for 4-6 hours; b) functional modification: the pretreated activated carbon is added into 0.5-1.5 mol / L sodium diethyl dithiocarbamate solution at a solid-liquid ratio of 1: (6-10), and oscillation immersion is performed at 40-60 °C for 4-6 hours; c) drying and activation: the immersed activated carbon is drained, vacuum dried at 110-130 °C for 2-3 hours, and then sieved to obtain the modified silver special adsorption carbon.

3. A method for performing fractional leaching adsorption based on the system of claim 1 or 2, characterized in that The method comprises the following steps: a) pre-leaching treatment: the ore slurry is sent into the pre-leaching tank, sodium cyanide and lime milk are added, the pH is controlled at 11.5-12.0, the free cyanide concentration is controlled at 320-350 mg / L, and pre-leaching is performed for 18-20 hours; b) silver adsorption treatment: the pre-leached ore slurry enters the silver adsorption section, contacts with the modified silver special adsorption carbon for 15-16 hours, and the carbon density is controlled at 18-20 g / L; c) gold adsorption treatment: the ore slurry enters the gold adsorption section, contacts with the gold adsorption activated carbon for 20-22 hours, and the carbon density is controlled at 12-15 g / L.

4. The process for staged leaching and adsorption according to claim 3, characterized in that: The carbon extraction cycle is 24 hours, saturated adsorption carbon is extracted from the second silver adsorption tank (4) and the last gold adsorption tank by air lift respectively, after separation, silver saturated carbon is sent into silver carbon desorption column (13) for desorption, gold saturated carbon is sent into gold carbon desorption column (14) for desorption; after desorption, the lean carbon is sent back to the second silver adsorption tank (4) and the last gold adsorption tank for recycling after acid washing and regeneration, and the desorption liquid is sent into the electrolysis section for recovery of gold and silver.

5. The process for staged leaching and adsorption according to claim 4, characterized in that: The desorption agent of silver saturated carbon is a mixture of sodium hydroxide and thiourea, the desorption temperature is 120-130 DEG C, and the pressure is 0.3-0.4 MPa; the lean carbon is regenerated after hydrochloric acid washing.

6. The process for staged leach adsorption according to claim 3 or 4 or 5, characterised by: In the pre-leaching treatment, the cyclone overflow of the ore is -200 mesh content≥85% and the pulp concentration is 39-40%.

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