Method for recovering invisible gold from waste cyanide solution of gold mine

Abstract

This invention discloses a method for recovering invisible gold from cyanide extraction wastewater in gold mines, belonging to the field of gold beneficiation technology. First, the pH of the wastewater is adjusted to 6.5-7.5; then, it is fed into a high-speed mixer with a coagulant added and reacted for 5-15 minutes; next, it is fed into a medium-low speed mixer with a flocculant added and reacted for 5-15 minutes; after the reaction, the material undergoes primary solid-liquid separation via a high-frequency stacked screen. The resulting solid-containing material is then subjected to secondary solid-liquid separation via a centrifuge to obtain gold-containing material. The separated wastewater is combined and returned to the production process for recycling. This invention effectively disrupts colloidal stability and generates dense flocs through precise pH adjustment, a dual-stage stirring mode (fast and slow), synergistic use of inorganic and organic agents, and a combination of double-layer screening and high-speed centrifugation, achieving efficient recovery of invisible gold. Examples show a gold recovery rate of 42.6-62.4%, a gold grade of 68-182 g / t in the gold-containing material, and the wastewater is recyclable, demonstrating significant economic and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of gold beneficiation and smelting technology, specifically to a method for recovering invisible gold from cyanide extraction waste liquid in gold mines. Background Technology

[0002] Cyanide leaching has become the dominant process in global gold production due to its high gold extraction efficiency and low production cost, contributing approximately 80% of global gold output. In a typical carbon-in-pulp (CIP) or carbon-leaching process, the ore is finely ground and then reacted with cyanide under alkaline conditions. Gold dissolves into the liquid phase as a gold-cyanide complex, and is subsequently adsorbed and enriched by activated carbon. The gold-loaded carbon undergoes desorption, electrolysis, and smelting to finally obtain the finished gold product. The adsorbed slurry undergoes solid-liquid separation to obtain tailings and tailings liquid. The tailings are transported to a tailings pond, while the tailings liquid is returned to the production process for continued use.

[0003] Industrial production practices show that the gold adsorption rate of activated carbon adsorption is typically only about 95%, leaving a certain concentration of gold residue in the adsorption tailings. For example, in whole-sludge cyanidation plants, the gold content in the tailings is generally 0.1~0.2 mg / L, while in gold concentrate cyanidation plants, the gold content is as high as 0.5~1 mg / L. This lost gold is not entirely in the form of dissolved gold-cyanide complexes; a significant portion is invisible solid-phase gold that is difficult to identify and capture using conventional processes. Its occurrence states are mainly divided into two categories: The first is colloidal gold, with particle sizes ranging from 1 to 100 nm. Due to the charged particle surface, it can form a stable double-layer colloidal system in the liquid phase, keeping it suspended for a long time and unable to settle naturally by gravity. The second category is ultrafine suspended gold, typically less than 1 μm in diameter, which readily adsorbs onto the surface of clay particles or iron-manganese oxides and other suspended matter in wastewater, forming a "carrier-state" complex, further increasing the stability of the particles and the difficulty of separation. Existing processes face significant technical bottlenecks in the recovery of the aforementioned invisible solid-phase gold. On one hand, conventional filtration or natural sedimentation processes suffer from extremely low solid-liquid separation efficiency due to the extremely small size of the target particles, making effective retention difficult. On the other hand, the micropore size of activated carbon is typically below 2 nm, which is orders of magnitude different from the particle size of colloidal gold or carrier composite particles. The latter cannot effectively adsorb into the pores of activated carbon, relying only on weak physical contact on the outer surface of the carbon particles. In the high shear force environment generated by actual slurry agitation, this already unstable physical adsorption is prone to detachment, leading to permanent loss of gold with the tailings, making recovery impossible in existing processes and resulting in gold loss.

[0004] Regarding the specific technical problem of invisible gold loss in cyanide gold extraction wastewater, existing wastewater treatment methods, such as acidification and oxidative cyanide removal, primarily focus on removing cyanide or heavy metal impurities to meet environmental emission or recycling requirements. However, their process design does not consider the physical state control and selective separation of colloidal and ultrafine suspended gold. Patent CN101381175A provides a method for treating cyanide gold extraction wastewater. It involves adding a 10% shell composite additive aqueous solution to the alkaline wastewater and mixing for 4-6 hours to precipitate impurities. Then, anionic polyacrylamide flocculant is added to form a suspension, which settles and is then pressed and filtered to achieve solid-liquid separation. The filter cake, containing copper, zinc, and small amounts of gold and silver, is saleable, while the filtrate is completely reused. However, in essence, it can only recover visible suspended solids and heavy metal precipitates such as copper and zinc that can settle in the waste liquid. It uses anionic polyacrylamide for flocculation, which cannot achieve charge neutralization and destabilization of negatively charged colloidal gold (1~100nm) and ultrafine suspended gold particles (<1μm). In addition, the long natural sedimentation and coarse pressure filtration of 8~12 hours result in a large amount of invisible gold remaining in the waste liquid and being lost. It fails to solve the fundamental problem of efficient capture of invisible gold in cyanide gold extraction waste liquid.

[0005] In view of this, it is necessary to study a special method for recovering invisible gold from solid phase in cyanide gold extraction waste liquid. This method can precisely disrupt colloidal stability, promote the efficient aggregation of ultrafine gold-containing particles, and achieve invisible gold recovery through enhanced separation. It has important industrial application value for improving the comprehensive utilization rate of gold mine resources and reducing the loss of valuable metals. Summary of the Invention

[0006] In view of the technical problems existing in the background art, the present invention provides a method for recovering invisible gold from cyanide gold extraction waste liquid in gold mines. Targeting the colloidal gold and ultrafine suspended gold particles in cyanide gold extraction waste liquid that are difficult to settle, a combined process is proposed, consisting of precise pre-control of neutral pH, fast and slow two-stage flocculation reaction, and two-stage enhanced solid-liquid separation.

[0007] This invention provides a method for recovering invisible gold from cyanide extraction wastewater in gold mines. The invisible gold includes colloidal gold and ultrafine suspended gold particles, and includes the following steps: S1, adjust the pH value of the cyanide gold extraction waste liquid to 6.5~7.5; S2, under the first stirring speed, add a coagulant to the cyanide gold extraction waste liquid after pH adjustment, so that the colloidal gold and ultrafine suspended gold in the cyanide gold extraction waste liquid destabilize and aggregate to form micro flocs; S3, at a second stirring speed lower than the first stirring speed, a cationic flocculant is added to the cyanide gold extraction waste liquid of step S2, so that the micro flocs form dense flocs through bridging. S4. The material obtained in step S3 is subjected to two-stage solid-liquid separation. The first stage of solid-liquid separation is performed by vibrating sieving, and the second stage of solid-liquid separation is performed by centrifugal separation to obtain gold-containing material.

[0008] As a further improvement of the present invention, the first stirring speed is 1400~2500 rpm; the second stirring speed is 40~50 rpm.

[0009] As a further improvement of the present invention, the coagulant is modified polyferric sulfate or modified polyaluminum chloride, and the dosage is 80~150mg / L; the reaction time of step S2 is 5~15min.

[0010] As a further improvement of the present invention, the cationic flocculant is cationic polyacrylamide with a molecular weight of 10 million to 15 million and a dosage of 5 to 15 mg / L; the reaction time of step S3 is 5 to 15 min.

[0011] As a further improvement of the present invention, in step S4, the two-stage solid-liquid separation includes: S41, the material obtained in step S3 is fed into a double-layer high-frequency vibrating screen for the first stage of solid-liquid separation to obtain solid material on the screen and liquid under the screen. S42, the solid material on the sieve is fed into a centrifuge for a second-stage solid-liquid separation to obtain gold-containing material with low water content and centrifugal liquid.

[0012] As a further improvement of the present invention, the upper screen aperture of the double-layer high-frequency vibrating screen is 0.1~0.2mm, and the lower screen aperture is 0.02~0.05mm; the centrifuge speed is 8000~10000rpm.

[0013] As a further improvement of the present invention, the modified polyferric sulfate or modified polyaluminum chloride is a polymer that has undergone structural modification treatment, has a higher positive charge density than conventional polyferric sulfate or conventional polyaluminum chloride, and has more highly active cation sites on its molecular chain than conventional polyferric sulfate or conventional polyaluminum chloride. The modified polyferric sulfate or modified polyaluminum chloride used in this invention has a higher degree of polymerization and charge neutralization capacity compared to conventional products (conventional polyferric sulfate or conventional polyaluminum chloride), and can rapidly destabilize colloidal gold over a wider pH range, thereby significantly improving the collection efficiency of invisible gold in cyanide wastewater.

[0014] As a further improvement of the present invention, the wastewater generated by the first-stage solid-liquid separation and the second-stage solid-liquid separation in step S4 is combined and returned to the gold production process for recycling; the moisture content of the gold-containing material is less than 30%.

[0015] As a further improvement of the present invention, in step S1, a non-oxidizing inorganic acid is used to adjust the pH of the gold extraction cyanide waste liquid; the non-oxidizing inorganic acid is selected from at least one of hydrochloric acid, dilute sulfuric acid, phosphoric acid, and hydrobromic acid.

[0016] As a further improvement of the present invention, the cyanide gold extraction waste liquid is the tail liquid after activated carbon adsorption in the carbon-in-pulp gold extraction process, and the gold grade is 0.05~1.0 mg / L.

[0017] This invention precisely controls the pH of cyanide gold extraction wastewater from an alkaline environment to 6.5-7.5. Firstly, it transforms the gold-cyanide complex from a stable ionic state to a molecular or colloidal state that is easily adsorbed and trapped. Secondly, it provides optimal hydrolysis conditions for modified polyferric sulfate or polyaluminum chloride, promoting the release of highly active cations. Simultaneously, it allows the cationic polyacrylamide molecular chains to fully extend, exposing more adsorption sites. Based on this precise pH control strategy, it simultaneously achieves gold speciation transformation, activation of inorganic coagulants, and conformation optimization of organic cationic flocculants, laying the foundation for subsequent destabilization and bridging.

[0018] Employing a "fast-slow two-stage" reaction mode, high-speed stirring (1400-2500 rpm) rapidly neutralizes the highly active cations of the inorganic coagulant with the negative charges on the colloidal gold surface, compressing the double layer and instantly breaking down colloidal stability to form micro-flocs. Subsequently, stirring is switched to low speed (40-50 rpm), where low shear force prevents micro-floc breakage and provides sufficient time for the cationic polyacrylamide with a molecular weight of tens of millions to bridge and connect between micro-flocs via long chains, generating coarse and dense flocs. The use of an inorganic-to-organic addition sequence and optimized dosage avoids the problems of poor efficacy and high dosage associated with single agents, achieving a relay enhancement of charge neutralization and bridging aggregation. This mode separates the destabilization process from the floc growth process, resolving the contradiction between "incomplete destabilization" and "easily broken flocs" in traditional single-stage flocculation.

[0019] A two-stage solid-liquid separation process using a double-layer high-frequency vibrating screen and centrifuge replaces the traditional sedimentation tank. Based on the differences in floc particles, a double-layer screen improves separation efficiency, while high-frequency vibration further enhances this efficiency. The wet material separated by the double-layer screen is then fed into a high-speed centrifuge to further strengthen the solid-liquid separation effect, ensuring effective dehydration of the gold-containing flocs and obtaining gold-containing materials with low moisture content, thus achieving efficient recovery of invisible gold from wastewater. The combination of coarse screening and fine centrifugal separation is more efficient and provides more thorough dehydration than sedimentation or single-stage filtration alone.

[0020] In summary, starting with negatively charged colloidal gold and gold cyanide complex ions in alkaline wastewater, the chemical form and reagent activity are transformed through pH adjustment. Charge neutralization and destabilization are achieved under high-speed stirring, followed by polymer bridging under low-speed stirring to form dense flocs that can be efficiently separated. Finally, subsequent solid-liquid separation achieves efficient recovery of invisible gold. The core of this approach is the synergy of chemical regulation and staged fluid dynamics to transform gold, which is originally impossible to capture by traditional processes due to its extremely small particle size and electrostatic stability, into an aggregateable and separable form.

[0021] Beneficial effects: 1. The method provided by this invention significantly improves the recovery rate of invisible gold. By precisely controlling the pH value and adopting a "fast and slow two-stage" reaction mode, a coagulant is added under high-speed stirring to disrupt colloidal stability, and a cationic flocculant is added under low-speed stirring to generate dense flocs, effectively capturing colloidal gold and ultrafine suspended gold particles that are difficult to handle by traditional processes. Examples show that the gold recovery rate can reach 42.6%~62.4%, and the gold grade of the gold-containing material is as high as 68~182 g / t, significantly reducing gold loss.

[0022] 2. The method provided by this invention solves the defects of traditional flocculation process, overcomes the contradiction between "incomplete destabilization" and "fragmentation" in single-stage flocculation, enables ultrafine suspended matter and colloidal gold to aggregate efficiently, forming dense flocs that are easy to separate, and improves the efficiency and stability of subsequent solid-liquid separation.

[0023] 3. The method provided by this invention enhances solid-liquid separation efficiency and reduces water content. It employs a two-stage solid-liquid separation process to replace traditional sedimentation tanks. A double-layer screen combined with high-frequency vibration achieves initial, efficient separation, followed by high-speed centrifugation for further dehydration, yielding gold-containing materials with low water content, facilitating subsequent processing or smelting.

[0024] 4. The method provided by this invention realizes wastewater recycling, which has outstanding environmental and economic benefits. The separated wastewater is combined and returned to the production process for recycling, reducing cyanide wastewater discharge, reducing fresh water consumption and wastewater treatment costs, while recovering valuable resources and improving the economic benefits of enterprises.

[0025] 5. The method provided by this invention has strong process adaptability and controllable operation. It is applicable to the treatment of tailings in various gold production enterprises, such as whole mud cyanidation, gold concentrate cyanidation, and biological oxidation pretreatment. Key parameters such as pH, stirring speed, and reagent dosage can be optimized and controlled, making it easy to implement in industrial applications.

[0026] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0027] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0028] Figure 1 This is a schematic flowchart of a method for recovering invisible gold from cyanide gold extraction waste liquid in gold mines, provided in an embodiment of the present invention. Detailed Implementation

[0029] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the invention, are intended to cover non-exclusive inclusion.

[0031] In the description of the embodiments of this invention, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this invention, "multiple" means two or more, unless otherwise explicitly defined.

[0032] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0033] To address the technical challenge of effectively recovering invisible gold, such as colloidal gold and ultrafine suspended gold particles, from cyanide gold extraction wastewater, this invention provides a method for recovering invisible gold from cyanide gold extraction wastewater in gold mines. By precisely controlling the pH of the wastewater to 6.5-7.5, not only are gold-cyanide complex ions converted into easily trappable forms, but the highly active cations of modified polyferric sulfate / aluminum chloride are also activated, creating a suitable environment for the full extension of cationic polyacrylamide molecular chains. Under high-speed stirring, a coagulant rapidly neutralizes the surface charge of colloidal gold, undermining its stability. Subsequently, under medium-to-low-speed stirring, a high-molecular-weight cationic flocculant, through bridging, aggregates destabilized particles into dense flocs, avoiding the contradiction of "incomplete destabilization" and "easily broken flocs" inherent in traditional single-stage flocculation. Finally, a double-layer high-frequency stacked screen rapidly intercepts coarse flocs using vibrating sieving, followed by high-speed centrifugation for deep dehydration, achieving complete separation of the solid and liquid phases. The separated wastewater is then directly returned to the production process for recycling.

[0034] Please refer to Figure 1 As shown in the figure, this invention provides a method for recovering invisible gold from cyanide extraction wastewater in gold mines. The invisible gold includes colloidal gold and ultrafine suspended gold particles, and includes the following steps: S1, adjust the pH value of the cyanide gold extraction waste liquid to 6.5~7.5; S2, under the first stirring speed, add a coagulant to the cyanide gold extraction waste liquid after pH adjustment, so that the colloidal gold and ultrafine suspended gold in the cyanide gold extraction waste liquid destabilize and aggregate to form micro flocs; S3, at a second stirring speed lower than the first stirring speed, a cationic flocculant is added to the cyanide gold extraction waste liquid of step S2, so that the micro flocs form dense flocs through bridging. S4. The material obtained in step S3 is subjected to two-stage solid-liquid separation. The first stage of solid-liquid separation is performed by vibrating sieving, and the second stage of solid-liquid separation is performed by centrifugal separation to obtain gold-containing material.

[0035] Preferably, the first stirring speed is 1400~2500 rpm; the second stirring speed is 40~50 rpm.

[0036] Preferably, the coagulant is modified polyferric sulfate or modified polyaluminum chloride, and the dosage is 80~150 mg / L; the reaction time of step S2 is 5~15 min.

[0037] Preferably, the cationic flocculant is cationic polyacrylamide with a molecular weight of 10-15 million and a dosage of 5-15 mg / L; the reaction time in step S3 is 5-15 min.

[0038] Preferably, in step S4, the two-stage solid-liquid separation includes: S41, the material obtained in step S3 is fed into a double-layer high-frequency vibrating screen for the first stage of solid-liquid separation to obtain solid material on the screen and liquid under the screen. S42, the solid material on the sieve is fed into a centrifuge for a second-stage solid-liquid separation to obtain gold-containing material with low water content and centrifugal liquid.

[0039] Preferably, the upper screen aperture of the double-layer high-frequency vibrating screen is 0.1~0.2mm, and the lower screen aperture is 0.02~0.05mm; the centrifuge speed is 8000~10000rpm.

[0040] Preferably, the modified polyferric sulfate or modified polyaluminum chloride is a polymer that has undergone structural modification treatment, has a higher positive charge density than conventional polyferric sulfate or conventional polyaluminum chloride, and has more active cation sites on its molecular chain than conventional polyferric sulfate or conventional polyaluminum chloride.

[0041] Preferably, the structural modification treatment is typically achieved through one or more of the following methods: Introducing at least one high-valence metal ion and / or at least one organic compound containing specific functional groups into the molecular chain of polyferric sulfate or polyaluminum chloride generates grafted or cross-linked structures through chemical reactions. For example, introducing other ions or polymers (such as silicates, phosphates, polyacrylamide, etc.) increases the molecular weight and molecular chain complexity, thereby improving the degree of polymerization.

[0042] After activation by physical fields (such as microwaves, ultrasound, and plasma), it undergoes a polymerization reaction with a modifier to increase the molecular chain length and positive charge density.

[0043] Preferably, the structural modification treatment causes at least one of the following changes to the intrinsic structure of polyferric sulfate or polyaluminum chloride: It forms linear or branched polymer chains with higher polymerization degree, thereby enhancing its adsorption and bridging ability; By introducing enhanced coordinating groups or adjusting the coordination mode between hydroxyl groups and iron / aluminum ions, a polynuclear hydroxyl metal cation complex core with higher charge density can be formed. Introducing silicate, phosphate or other anions into the polymer backbone allows for the formation of more stable and higher molecular weight inorganic polymer composite structures through copolymerization or complexation. It promotes moderate cross-linking between molecular chains through oxygen bridges or hydroxyl bridges, forming a partial network structure and enhancing its chemical stability and reactivity. The molar ratio of hydroxyl groups to sulfate / chloride ions in the polymer was optimized to make its characteristic functional group distribution more suitable for maintaining the dominant hydrolytic form over a wide pH range.

[0044] Preferably, the wastewater generated from the first-stage solid-liquid separation and the second-stage solid-liquid separation in step S4 is combined and returned to the gold production process for recycling; the moisture content of the gold-containing material is less than 30%.

[0045] Preferably, in step S1, a non-oxidizing inorganic acid is used to adjust the pH of the gold extraction cyanide waste liquid; the non-oxidizing inorganic acid is selected from at least one of hydrochloric acid, dilute sulfuric acid, phosphoric acid, and hydrobromic acid.

[0046] Preferably, the cyanide gold extraction waste liquid is the tail liquid after activated carbon adsorption in the carbon-in-pulp gold extraction process, and the gold grade is 0.05~1.0 mg / L.

[0047] Example 1 Example 1 of this invention provides a method for recovering invisible gold from cyanide extraction wastewater in gold mines. 1000 ml of tailings from a whole-mud cyanide processing plant after carbon adsorption was taken, and the gold content was determined to be 0.12 mg / L. The recovery was carried out using the method of this invention, with the specific steps as follows: S1, adjust the pH of the waste liquid to 6.8 using 20% ​​dilute sulfuric acid.

[0048] S2, the pH-adjusted waste liquid is transferred to a high-speed stirrer, the stirring speed is set to 2100 rpm, modified polyaluminum chloride is added at a dosage of 100 mg / L, and the reaction is carried out for 10 min.

[0049] S3. The waste liquid after the reaction in step S2 is transferred to a medium-low speed stirrer, the stirring speed is set to 45 rpm, cationic polyacrylamide with a molecular weight of 12 million is added at a dosage of 8 mg / L, and the reaction is carried out for 10 min.

[0050] S4. The material after the reaction in step S3 is conveyed to a high-frequency stacked screen for primary solid-liquid separation (the upper screen aperture size is 0.15 mm, and the lower screen aperture size is 0.035 mm). The obtained solid-containing material is fed into a centrifuge for secondary solid-liquid separation at a speed of 9000 rpm to obtain gold-containing solid material. The wastewater from the primary and secondary solid-liquid separations is combined as tailings.

[0051] The collected gold-containing solid material was weighed to be 0.6g, with a gold grade of 124.8g / t and a gold recovery rate of 62.4%.

[0052] Example 2 Example 2 of this invention provides a method for recovering invisible gold from cyanide extraction wastewater in gold mines. 1000 ml of tailings from a gold concentrate cyanide processing plant after carbon adsorption was taken, and the gold content was determined to be 0.25 mg / L. The recovery was carried out using the method of this invention, with the specific steps as follows: S1, adjust the pH of the waste liquid to 7.0 with 20% dilute sulfuric acid.

[0053] S2, the pH-adjusted waste liquid is transferred to a high-speed stirrer, the stirring speed is set to 2100 rpm, modified polyferric sulfate is added at a dosage of 120 mg / L, and the reaction is carried out for 12 min.

[0054] S3. The waste liquid after the reaction in step S2 is transferred to a medium-low speed stirrer, the stirring speed is set to 40 rpm, cationic polyacrylamide with a molecular weight of 15 million is added at a dosage of 10 mg / L, and the reaction is carried out for 15 min.

[0055] S4. The material after the reaction in step S3 is conveyed to a high-frequency stacked screen for primary solid-liquid separation (the upper screen aperture size is 0.15 mm, and the lower screen aperture size is 0.035 mm). The obtained solid-containing material is fed into a centrifuge for secondary solid-liquid separation at a speed of 8500 rpm to obtain gold-containing solid material. The wastewater from the primary and secondary solid-liquid separations is combined as tailings.

[0056] The collected gold-containing solid material was weighed to be 0.8g, with a gold grade of 182.2g / t and a gold recovery rate of 58.3%.

[0057] Example 3 Example 3 of this invention provides a method for recovering invisible gold from cyanide extraction wastewater in gold mines. 1000 ml of cyanide wastewater after biological oxidation pretreatment was taken, and the gold content was determined to be 0.08 mg / L. The recovery was carried out using the method of this invention, with the specific steps as follows: S1, adjust the pH of the waste liquid to 6.5 using 20% ​​dilute sulfuric acid.

[0058] S2, the pH-adjusted waste liquid is transferred to a high-speed stirrer, the stirring speed is set to 2100 rpm, modified polyaluminum chloride is added at a dosage of 80 mg / L, and the reaction is carried out for 8 min.

[0059] S3. The waste liquid after the reaction in step S2 is transferred to a medium-low speed stirrer, the stirring speed is set to 50 rpm, cationic polyacrylamide with a molecular weight of 15 million is added at a dosage of 5 mg / L, and the reaction is carried out for 12 min.

[0060] S4. The material after the reaction in step S3 is conveyed to a high-frequency stacked screen for primary solid-liquid separation (the upper screen aperture size is 0.15 mm, and the lower screen aperture size is 0.035 mm). The obtained solid-containing material is fed into a centrifuge for secondary solid-liquid separation at a speed of 10,000 rpm to obtain gold-containing solid material. The wastewater from the primary and secondary solid-liquid separations is combined as tailings.

[0061] The collected gold-containing solid material was weighed to be 0.5g, with a gold grade of 68.16g / t and a gold recovery rate of 42.6%.

[0062] Comparative Example 1 Comparative Example 1 uses a conventional recovery method, specifically 1000 ml of the cyanidation tailings from Example 1. The pH of the waste liquid is adjusted to 6.8 with dilute sulfuric acid, and anionic polyacrylamide (molecular weight approximately 8 million, dosage 5 mg / L) is added. The mixture is allowed to settle naturally in a settling tank for 5 hours. After settling, the material is pumped into a vacuum filter for solid-liquid separation to obtain filter cake and filtrate.

[0063] The collected filter cake was weighed and found to be 0.08 g. The gold content in the filter cake was analyzed to be 28.6 g / t. The total amount of gold recovered was calculated to be 0.0023 mg, and the gold recovery rate was 1.9%, which is significantly lower than the recovery rate of the embodiment of the present invention.

[0064] Comparative Example 2 The difference from Example 1 is that steps S2 and S3 do not differentiate between high-speed and medium-low speed stirring; a single stirring speed of 90 rpm is used throughout. Specifically, after adjusting the pH to 6.8, 100 mg / L of modified polyaluminum chloride is added, and the mixture is stirred at 90 rpm for 10 minutes. Then, 8 mg / L of cationic polyacrylamide is added, and the mixture is stirred at 90 rpm for another 10 minutes. Subsequent solid-liquid separation steps are the same as in Example 1.

[0065] The collected gold-containing solid material was weighed to be 0.21g, with a gold grade of 31.4g / t and a gold recovery rate of 5.5%, which is significantly lower than the recovery rate of the embodiment of the present invention.

[0066] Comparative Example 3 The difference from Example 1 is that step S4 does not employ a two-stage enhanced separation combining a high-frequency stacked screen and a centrifuge, but instead uses a conventional natural sedimentation and vacuum pressure filtration process. Specifically, after the reaction in step S3, the material is allowed to settle for 4 hours, the supernatant is discharged, and the lower layer containing solids is filtered by a vacuum filter press to obtain a gold-containing filter cake.

[0067] The collected gold-containing solid material was weighed to be 0.28g, with a gold grade of 29.1g / t and a gold recovery rate of 6.8%, which is significantly lower than the recovery rate of the embodiment of the present invention.

[0068] Comparative Example 4 The difference from Example 1 is that the combination of inorganic coagulants and organic cationic flocculants is not used; only conventional polyaluminum chloride is used as the flocculant. Specifically, after adjusting the pH to 6.8, 100 mg / L of conventional polyaluminum chloride is added at 2100 rpm, and the reaction is allowed to proceed for 10 minutes; cationic polyacrylamide is not added. Subsequent solid-liquid separation steps are the same as in Example 1.

[0069] The collected gold-containing solid material was weighed to be 0.09 g, with a gold grade of 39.5 g / t and a gold recovery rate of 3.0%, which is significantly lower than the recovery rate of the embodiment of the present invention.

[0070] In summary, this invention discloses a method for recovering invisible gold from cyanide gold extraction wastewater in gold mines, belonging to the field of gold beneficiation technology. Addressing the technical problem of effectively recovering invisible gold, such as colloidal gold and ultrafine suspended gold particles, from cyanide gold extraction wastewater, this invention employs the following steps: adjusting the pH of the wastewater to 6.5-7.5; then feeding it to a high-speed mixer with the addition of a coagulant for 5-15 minutes; followed by feeding it to a medium-low speed mixer with the addition of a cationic flocculant for 5-15 minutes; after the reaction, the material undergoes primary solid-liquid separation via a high-frequency stacked screen; the resulting solid-containing material is then subjected to secondary solid-liquid separation via a centrifuge to obtain gold-containing material; the separated wastewater is combined and returned to the production process for recycling. This invention effectively disrupts colloidal stability and generates dense flocs through precise pH adjustment, a "fast and slow dual-stage" stirring mode, synergistic use of inorganic and organic agents, and a combination of double-layer screening and high-speed centrifugation, achieving efficient recovery of invisible gold. Examples show that the gold recovery rate reaches 42.6-62.4%, the gold grade of the gold-containing material is 68-182 g / t, and the wastewater can be recycled, which has significant economic and environmental benefits.

[0071] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A method for recovering invisible gold from cyanide extraction wastewater in gold mines, characterized in that, The invisible gold includes colloidal gold and ultrafine suspended gold, and includes the following steps: S1, adjust the pH value of the cyanide gold extraction waste liquid to 6.5~7.5; S2, under the first stirring speed, add a coagulant to the cyanide gold extraction waste liquid after pH adjustment, so that the colloidal gold and ultrafine suspended gold in the cyanide gold extraction waste liquid destabilize and aggregate to form micro flocs; S3, at a second stirring speed lower than the first stirring speed, a cationic flocculant is added to the cyanide gold extraction waste liquid of step S2, so that the micro flocs form dense flocs through bridging. S4. The material obtained in step S3 is subjected to two-stage solid-liquid separation. The first stage of solid-liquid separation is performed by vibrating sieving, and the second stage of solid-liquid separation is performed by centrifugal separation to obtain gold-containing material.

2. The method for recovering invisible gold from cyanide extraction waste liquid in gold mines according to claim 1, characterized in that, The first stirring speed is 1400~2500 rpm; the second stirring speed is 40~50 rpm.

3. The method for recovering invisible gold from cyanide extraction waste liquid in gold mines according to claim 1, characterized in that, The coagulant is modified polyferric sulfate or modified polyaluminum chloride, and the dosage is 80~150 mg / L; the reaction time of step S2 is 5~15 min.

4. The method for recovering invisible gold from cyanide extraction wastewater in gold mines according to claim 1, characterized in that, The cationic flocculant is cationic polyacrylamide with a molecular weight of 10-15 million and a dosage of 5-15 mg / L; the reaction time in step S3 is 5-15 min.

5. The method for recovering invisible gold from cyanide extraction waste liquid in gold mines according to claim 1, characterized in that, In step S4, the two-stage solid-liquid separation includes: S41, the material obtained in step S3 is fed into a double-layer high-frequency vibrating screen for the first stage of solid-liquid separation to obtain solid material on the screen and liquid under the screen. S42, the solid material on the sieve is fed into a centrifuge for a second-stage solid-liquid separation to obtain gold-containing material with low water content and centrifugal liquid.

6. The method for recovering invisible gold from cyanide extraction waste liquid in gold mines according to claim 5, characterized in that, The upper screen of the double-layer high-frequency vibrating screen has an aperture of 0.1~0.2mm, and the lower screen has an aperture of 0.02~0.05mm; the centrifuge has a rotation speed of 8000~10000rpm.

7. The method for recovering invisible gold from cyanide extraction waste liquid in gold mines according to claim 3, characterized in that, The modified polyferric sulfate or modified polyaluminum chloride is a polymer that has undergone structural modification treatment; The structural modification treatment causes at least one of the following changes to the intrinsic structure of polyferric sulfate or polyaluminum chloride: To form linear or branched polymer chains with higher degrees of polymerization; By introducing enhanced coordinating groups or adjusting the coordination mode between hydroxyl groups and iron / aluminum ions, a polynuclear hydroxyl metal cation complex core with higher charge density can be formed. Anions are introduced into the polymer backbone to form inorganic polymer composite structures through copolymerization or complexation. It promotes moderate cross-linking between molecular chains through oxygen bridges or hydroxyl bridges, forming a partial network structure; Optimize the molar ratio of hydroxyl groups to sulfate / chloride ions in the polymer.

8. The method for recovering invisible gold from cyanide extraction waste liquid in gold mines according to claim 1, characterized in that, The wastewater generated from the first-stage solid-liquid separation and the second-stage solid-liquid separation in step S4 is combined and returned to the gold production process for recycling; the moisture content of the gold-containing material is less than 30%.

9. The method for recovering invisible gold from cyanide extraction wastewater in gold mines according to claim 1, characterized in that, In step S1, a non-oxidizing inorganic acid is used to adjust the pH of the gold extraction cyanide waste liquid; the non-oxidizing inorganic acid is selected from at least one of hydrochloric acid, dilute sulfuric acid, phosphoric acid, and hydrobromic acid.

10. The method for recovering invisible gold from cyanide extraction wastewater in gold mines according to claim 1, characterized in that, The cyanide gold extraction waste liquid is the tail liquid after activated carbon adsorption in the carbon-in-pulp gold extraction process, with a gold grade of 0.05~1.0 mg / L.

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