A method for recovering valuable metals from tungsten ore phosphogypsum

Abstract

This invention belongs to the field of mineral processing and solid waste resource utilization technology, specifically relating to a method for recovering valuable metals from tungsten ore phosphogypsum. This invention utilizes a specific surfactant formulation combined with a two-stage hydrocyclone centrifugal separation process to efficiently enrich and recover high-density but low-content (typically <1 wt%) valuable metal particles such as tungsten and molybdenum from phosphogypsum. This effectively solves the problem of recovering extremely low-grade valuable metals from tungsten ore phosphogypsum with high pesticide residues and impurities, providing an efficient and low-cost technical solution for the resource recovery of rare and dispersed metals from complex low-grade solid waste.

Description

Technical Field

[0001] This invention belongs to the field of mineral processing and solid waste resource utilization technology, specifically relating to a method for recovering valuable metals from tungsten ore phosphate gypsum. Background Technology

[0002] With the development and utilization of complex and difficult-to-process tungsten ore resources, the amount of flotation reagents used in the upstream beneficiation process has increased. Some reagent residues, along with associated sulfides and gangue impurities, will further enter the hydrometallurgical process and accumulate in the subsequent slag. As a result, phosphogypsum, a byproduct of tungsten hydrometallurgy, often exhibits characteristics such as high reagent residues, high impurities, and fine granulation, posing significant challenges to the recovery of valuable metals such as tungsten and molybdenum. Currently, low-grade, high-sulfur scheelite ore with associated tungsten and molybdenum has become the main raw material for the tungsten smelting industry. Its beneficiation process presents an inherent contradiction: to ensure molybdenum recovery, a large amount of flotation reagents must be used upstream; however, the residues of these reagents severely interfere with the subsequent leaching of scheelite.

[0003] Therefore, a "using reagents to suppress reagents" process has emerged in production: that is, adding excessive amounts of alkaline reagents (such as sodium oleate) to suppress the harmful effects of residual reagents. This directly leads to an inevitable result: the final scheelite concentrate inevitably contains a large amount of residual flotation reagents and sulfides that could not be removed, i.e., high-sulfur scheelite. Statistics from the China Tungsten Industry Association show that before 2024, the sulfur content of scheelite concentrate entering tungsten smelters was generally below 1%, while after 2025, raw materials with a sulfur content above 3% have become commonplace.

[0004] When scheelite with high reagent residues and high sulfur content enters downstream hydrometallurgical processes, the residual reagents cause severe foaming, and various impurities interfere with each other. The hydrometallurgical process requires the addition of large amounts of inorganic flocculants to remove impurities such as silicon and aluminum, resulting in the inclusion of various gangue minerals such as silicon, aluminum, magnesium, and iron in the tungsten ore phosphogypsum. This ultimately forms a tungsten ore phosphogypsum with high sulfur content, high reagent residues, and high impurities, and with a very fine particle size (the D50 of tungsten ore phosphogypsum is 20-30 μm, while the D50 of phosphate ore phosphogypsum is generally above 74 μm). Existing technologies (whether for phosphate ore or weathered tungsten ore) struggle to solve the core challenges of "organic film dissociation" and "enrichment and recovery of extremely low-grade valuable metals."

[0005] This type of high-sulfur scheelite causes a series of serious production problems during hydrometallurgical processing: 1. Severe foaming of slurry and unstable operation: The residual flotation agent continuously generates a large amount of stable foam in the alkaline leaching system, which seriously interferes with liquid-solid separation, deteriorates mass transfer efficiency, and leads to a decrease in leaching rate and a deterioration of the operating environment; 2. Significant interference from impurities and low recovery rate: Impurities such as silicon, aluminum, and magnesium easily form colloidal precipitates, which encapsulate tungsten minerals, hinder their contact with the reactants, and increase the consumption of auxiliary materials and the yield of waste residue.

[0006] Existing cyclone separation technologies (such as CN113492063A) mainly target the interfacial dissociation and flocculation-cyclone enrichment of phosphate rock systems, without addressing the removal of organic coatings and the synergistic removal of impurities in scheelite smelting slag. Weathered tungsten ore beneficiation and smelting combined processes (such as CN119186796A) focus on the particle size classification and differentiated treatment of weathered / semi-weathered tungsten ore, targeting natural weathered ore, rather than phosphogypsum slag with a strong hydrophobic organic film produced during hydrometallurgical processes.

[0007] In summary, there is currently a lack of a method for treating tungsten ore phosphogypsum that can simultaneously address the three major challenges of "organic film removal, foam suppression, and impurity removal." While the valuable metals (tungsten and molybdenum) in this type of material are theoretically separable due to their high density, their hydrophobic surface film and extremely low grade (the total tungsten and molybdenum content is typically <1%) often make traditional physical separation methods ineffective. Therefore, developing a synergistic process combining targeted surface modification and cyclone-enhanced separation to achieve efficient pre-enrichment of valuable metals in this type of solid waste is of great significance for improving the overall tungsten and molybdenum recovery rate and reducing smelting costs. Summary of the Invention

[0008] To address the aforementioned problems, the present invention aims to provide a method for recovering valuable metals from tungsten ore phosphogypsum. This invention utilizes a specific surfactant formulation combined with a two-stage hydrocyclone centrifugal separation process to efficiently enrich and recover high-density but low-content (typically <1wt%) valuable metal particles such as tungsten and molybdenum from phosphogypsum. This provides an efficient and low-cost technical solution for the resource recovery of rare and dispersed metals from complex low-grade solid waste.

[0009] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for recovering valuable metals from tungsten ore phosphogypsum, comprising the following steps: (1) Preparation of composite surfactant working solution: Weigh 25-45 parts of wetting and penetrating component, 35-55 parts of dispersion and cleaning component, 8-15 parts of pH buffer and stabilizing component, 4-8 parts of defoaming and stabilizing component, and 0.5-2 parts of additives by weight; under stirring conditions, first dissolve the pH buffer and stabilizing component in water, then add the remaining components in sequence, make up the water volume, stir evenly, and prepare a composite surfactant working solution with a mass concentration of 1%-5%; (2) Surfactant pretreatment of phosphogypsum: mix tungsten ore phosphogypsum raw material with water to prepare a slurry with a solid-liquid mass ratio of 1:5~15, add the composite surfactant working solution to the slurry, the amount of addition is 0.5%~2.5% of the dry basis phosphogypsum mass, and stir thoroughly. (3) Two-stage series hydrocyclone separation and enrichment: The pretreated slurry is fed into a two-stage series hydrocyclone for centrifugal separation. The first-stage hydrocyclone controls the feed pressure at 0.15~0.25MPa. Most of the light phosphogypsum fine mud is removed by low-pressure centrifugal separation. The overflow is discharged as purified phosphogypsum slurry. The underflow is the slurry with preliminarily enriched valuable metals, which is sent to the second-stage hydrocyclone. The second-stage hydrocyclone controls the feed pressure at 0.3~0.35MPa. The valuable metals are deeply enriched by high-pressure centrifugal separation. The underflow is the concentrate enriched with valuable metals such as tungsten and molybdenum.

[0010] Furthermore, the wetting and penetrating component is selected from at least one of alkyl glycosides (APG) and fatty alcohol polyoxyethylene ethers (JFC).

[0011] Furthermore, the dispersing and cleaning components are selected from at least one of ethyl thiocyanate (SN-9#), sodium dodecylbenzene sulfonate (LAS), and sodium α-alkenyl sulfonate (AOS).

[0012] Furthermore, the pH buffer and stabilizing component is sodium carbonate, and the pH value of the slurry after pretreatment in step (2) is 8.0~8.5.

[0013] Furthermore, the defoaming and stabilizing components are selected from at least one of polyether defoamers (such as GP type) and modified silicone defoamers.

[0014] Furthermore, the auxiliary agent is disodium ethylenediaminetetraacetate (EDTA-2Na).

[0015] Furthermore, the dispersing and cleaning component is ethyl thiocyanate, and the amount of ethyl thiocyanate added is 0.2‰~0.4‰ of the mass of dry tungsten ore phosphogypsum raw material.

[0016] Furthermore, the diameter of the first-stage hydrocyclone is 50 mm, and the separation particle size is 5~40 μm; the diameter of the second-stage hydrocyclone is 25 mm, and the separation particle size is 5~20 μm.

[0017] Furthermore, the tungsten ore phosphogypsum is phosphogypsum made from the wet smelting residue of scheelite without roasting pretreatment; wherein the total mass content of valuable metals such as tungsten and molybdenum is <1%, and the particle size D50 of the phosphogypsum is 20~30μm.

[0018] Furthermore, in step (2), the stirring speed is 400~600 r / min and the stirring time is 10~30 min.

[0019] The beneficial effects of this invention are as follows: 1. Overcoming the challenge of organic coating layer shielding physical sorting: Addressing the unique characteristics of organic film coating in raw phosphogypsum, this invention utilizes a compound surfactant system. Through the synergistic effects of wetting, penetration, dispersion, cleaning, and pH control, it efficiently wets, penetrates, and peels off the hydrophobic organic film on the surface of tungsten-molybdenum minerals, restoring their intrinsic physical properties of being hydrophilic and heavy. This allows the particle movement in the aqueous medium to be primarily controlled by density, creating a core prerequisite for density-based centrifugal separation.

[0020] 2. Suppress severe foaming of slurry and ensure stable operation of hydrocyclone separation process: This invention innovatively introduces defoaming, stabilizing and pH adjusting components into the surfactant formulation, suppressing the severe foaming problem caused by residual flotation agents and surfactants in the slurry from the source, ensuring the stability of the flow field in the hydrocyclone and realizing continuous and efficient centrifugal separation.

[0021] 3. Achieving efficient enrichment of extremely low-grade fine-particle valuable metals: Addressing the characteristics of extremely low (typically <1%) content, fine particle size (D50 approximately 20~30μm), and coexistence with various impurities in tungsten ore phosphogypsum, this invention utilizes a deep synergy between surface modification pretreatment and a two-stage gradient pressure cyclone process. The initial low-pressure desliming stage removes a large amount of light phosphogypsum, while the subsequent high-pressure beneficiation stage achieves deep enrichment of valuable metals. This effectively separates heavy mineral particles with a content below 1% and a particle size in the micrometer range. The tungsten and molybdenum grades are increased by more than 5 times compared to the raw material, with a recovery rate exceeding 90%. This solves the problem of low separation efficiency of traditional physical methods for extremely low-content, fine-particle materials.

[0022] 4. The process is simple and low-cost, making it suitable for industrial applications: This invention avoids the high-energy-consuming roasting process and only requires the addition of a reagent stirring and cyclone separation unit at the end of the existing wet process. The equipment investment and operating costs are low, the process parameters are highly controllable, and it is easy to modify and implement in existing smelting plants. At the same time, the surfactants remaining in the secondary overflow are still active and can be directly returned to the front end for slurry preparation and reuse, further reducing reagent consumption.

[0023] 5. Environmentally friendly with no risk of secondary pollution: The surfactant used in this invention is used in small quantities, and the cyclone separation is a purely physical process. The content of valuable metals in the purified phosphogypsum after treatment is significantly reduced, and it can be safely utilized as a resource, meeting the environmental protection requirements of harmless and resource-based solid waste treatment. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0025] Figure 1 This is a process flow diagram of the method of the present invention.

[0026] Figure 2 This is a schematic diagram showing the morphology and composition of the concentrate after hydrocyclone separation of tungsten ore and phosphogypsum.

[0027] Figure 3 The images shown are electron microscope images of the concentrates obtained in each group in Example 3; where a is Comparative Example 3.1, b is Comparative Example 3.2, c is Comparative Example 3.3, and d is Group 3 of Example 3.

[0028] Figure 4 The images show electron microscope and IR spectra of the tailings obtained in Example 3 and Comparative Example 3.1.

[0029] Figure 5 The images show the state of two slurries, one with and one without surfactant, after standing for 20 minutes.

[0030] Figure 6 Electron micrographs of the phosphogypsum obtained in Example 2 and Comparative Group 2.3 are shown. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. See attached document Figure 1 As shown, the present invention provides a method for recovering valuable metals from tungsten ore phosphogypsum, comprising the following steps: (1) Preparation of composite surfactant working solution: Weigh 25-45 parts of wetting and penetrating component, 35-55 parts of dispersion and cleaning component, 8-15 parts of pH buffer and stabilizing component, 4-8 parts of defoaming and stabilizing component, and 0.5-2 parts of additives by weight.

[0032] Under stirring conditions, the pH buffer and stabilizing components are first dissolved in water, and then the remaining components are added in sequence. After the water volume is replenished, the mixture is stirred evenly to prepare a composite surfactant working solution with a mass concentration of 1% to 5%.

[0033] The wetting and penetrating component is selected from at least one of alkyl glycosides (APG) and fatty alcohol polyoxyethylene ethers (JFC); alkylphenol polyoxyethylene ethers (OP series) can also be used. The dispersing and cleaning component is selected from at least one of ethyl thiocyanate (SN-9#, the amount of ethyl thiocyanate added is 0.2‰~0.4‰ of the dry basis tungsten ore phosphogypsum raw material), sodium dodecylbenzene sulfonate (LAS), and sodium α-alkenyl sulfonate (AOS); sodium fatty alcohol polyoxyethylene ether sulfate (AES) can also be used. The pH buffer and stabilizing component is sodium carbonate, and the pH value of the slurry after pretreatment in step (2) is 8.0~8.5. The defoaming and stabilizing component is selected from at least one of polyether defoamers (such as GP type) and modified organosilicon defoamers; the defoaming and stabilizing component can also be selected from alcohol or ester defoamers according to the foaming characteristics. The additive is disodium ethylenediaminetetraacetate (EDTA-2Na).

[0034] (2) Surfactant pretreatment of phosphogypsum: Mix tungsten ore phosphogypsum raw material with water to prepare a slurry with a solid-liquid mass ratio of 1:5~15. Add the composite surfactant working solution to the slurry at a rate of 0.5%~2.5% of the dry phosphogypsum mass and stir at 400~600 r / min for 10~30 min. Further, a short-time, low-intensity ultrasonic treatment (e.g., 100W, 5-10 minutes) can be added during the agent pretreatment stage to enhance the agent's peeling of the particle surface coating and the breaking of particle agglomerates.

[0035] (3) Two-stage series hydrocyclone separation and enrichment: The pretreated slurry is fed into a two-stage series hydrocyclone for centrifugal separation. The first-stage hydrocyclone controls the feed pressure at 0.15~0.25MPa. Most of the light phosphogypsum fine mud is removed by low-pressure centrifugal separation. The overflow is discharged as purified phosphogypsum slurry. The underflow is the slurry with preliminarily enriched valuable metals, which is sent to the second-stage hydrocyclone. The second-stage hydrocyclone controls the feed pressure at 0.3~0.35MPa. The valuable metals are deeply enriched by high-pressure centrifugal separation. The underflow is the concentrate enriched with valuable metals such as tungsten and molybdenum.

[0036] After hydrocyclone separation, high-density valuable mineral particles (such as undecomposed scheelite, MoS2, etc.) are enriched in the underflow product under centrifugal force; while the purified phosphogypsum is discharged from the overflow. The diameter of the first-stage hydrocyclone is 50 mm, and the separation particle size is 5~40 μm; the diameter of the second-stage hydrocyclone is 25 mm, and the separation particle size is 5~20 μm.

[0037] The secondary overflow can be returned to the pretreatment process of step (2) for scavenging or returned to the primary feed to further improve the recovery rate or concentrate grade; the overflow slurry of the primary hydrocyclone is dewatered by pressure filtration to obtain purified phosphogypsum.

[0038] (4) Product collection: Collect the bottom solids, whose main components are high-density impurity mineral phases (such as undecomposed scheelite CaWO4, MoS2, CuS, etc.). The tungsten (WO3) and molybdenum (MoO3) grades can be increased by more than 5 times compared with the raw materials, and can be directly returned to the main process of tungsten and molybdenum smelting as high-value intermediate products.

[0039] Overflow products: The overflow slurry from the first-stage hydrocyclone is mainly purified phosphogypsum. After pressure filtration and dewatering, its content of valuable metal impurities is significantly reduced (tungsten and molybdenum content is less than 0.2%), and it can be utilized for resource recovery or safely disposed of.

[0040] Example 1 A tungsten smelting company produced tungsten phosphate gypsum using a hydrometallurgical process with high-sulfur scheelite. Its main chemical components (wt%) were: WO3 0.82%, MoO3 0.18%, SiO2 4.2%, Al2O3 1.1%, MgO 0.8%, CaO 48.5%, and loss on ignition (mainly organic matter) 2.5%. The raw material slurry had a natural pH of 3.2 and a D50 particle size of 27 μm.

[0041] (1) Preparation of composite surfactant working solution: 35 parts of wetting and penetrating component (APG), 45 parts of dispersion and cleaning component (SN-9#, LAS, SN-9# and LAS are compounded at a mass ratio of 3:5), 12 parts of pH buffer and stabilizing component (anhydrous sodium carbonate, Na2CO3), 6 parts of defoaming and stabilizing component (polyether GP type defoamer), and 2 parts of auxiliary agent (EDTA-2Na). Add the above components to water in sequence and prepare a working solution with a total mass concentration of 3% under stirring conditions.

[0042] (2) Slurry preparation and pretreatment: Weigh 1000g (dry basis) of tungsten ore phosphogypsum raw material, add 10L of water, and prepare a slurry with a solid-liquid ratio of 1:10 in a mixing tank. Add 170mL of the above-prepared working solution (equivalent to 0.51% of the dry basis tungsten ore phosphogypsum raw material), and continue stirring at 500r / min for 20 minutes. After pretreatment, the pH of the slurry stabilizes at 8.0.

[0043] (3) Cyclone Separation: The pretreated slurry is pumped into a two-stage cyclone separation system. First-stage cyclone: ​​A first-stage hydrocyclone is used with a sand discharge nozzle diameter of 8 mm, and the feed pressure is controlled at 0.20 MPa. The overflow (light impurities) is discharged, and the underflow enters the second-stage cyclone. Second-stage cyclone: ​​A second-stage hydrocyclone is used with a sand discharge nozzle diameter of 4 mm, and the feed pressure is controlled at 0.32 MPa.

[0044] (4) Product Collection: The underflow from the secondary cyclone is collected as the final concentrate, the secondary overflow is returned to the primary feed, and the primary overflow is used as the final tailings (purified phosphogypsum). The morphology and composition of the concentrate after cyclone separation of tungsten ore and phosphogypsum are shown in the attached figure. Figure 2 As shown.

[0045] In this embodiment, the slurry exhibits minimal foaming, good fluidity, and stable hydrocyclone operation. The concentrate particles have a hydrophilic surface, the tailings are grayish-white, and the impurity content is significantly reduced. The resulting concentrate contains 12.05% WO3 and 2.68% MoO3, representing increases of 14.7 times and 14.9 times respectively compared to the raw material; the WO3 recovery rate is 85.2%, and the MoO3 recovery rate is 86.3%; the total tungsten and molybdenum content in the tailings is less than 0.2%, achieving highly efficient enrichment and recovery of valuable tungsten and molybdenum metals.

[0046] Example 2 This embodiment investigates the effect of the dosage of pH buffer and stabilizing component (sodium carbonate) on the recovery effect. Except for the amount of sodium carbonate added, the other raw materials, formulations and process parameters are the same as in Example 1. Four groups of experiments were set up, as follows: Example 2: Sodium carbonate was added at 0.12% of the dry basis raw material, and the measured pH of the slurry after pretreatment was 8.5; Comparative group 2.1: Sodium carbonate addition accounted for 0.02% of the dry basis raw material, and the measured pH value of the slurry after pretreatment was 5.5; Comparative group 2.2: Sodium carbonate addition accounted for 0.25% of the dry basis raw material, and the measured pH value of the slurry after pretreatment was 10.5; Comparative group 2.3: Sodium carbonate addition was 0, and the measured pH of the slurry after pretreatment was 3.2, which was the natural pH of the raw material.

[0047] Chemical analysis was performed on the concentrates obtained from each group, and the recovery rates of valuable tungsten and molybdenum were calculated. The results are shown in the table below:

[0048] The results showed that the WO3 recovery rate of Example 2 was 89.5%, and the MoO3 recovery rate was 88.7%, with the concentrate grade and recovery rate being the best. Furthermore, the tailings (purified phosphogypsum) obtained from Example 2 was clear, mainly consisting of 20-30 μm fine mud, and was grayish-white. This was primarily due to the fact that the weakly alkaline environment allowed for complete ionization of the anionic surfactants, resulting in optimal dispersion and cleaning efficiency; simultaneously, it effectively neutralized the acidity of the raw materials, inhibiting the formation of silica-alumina colloids and creating ideal interfacial conditions for cyclone separation.

[0049] In contrast, the lower pH of control group 2.1 resulted in insufficient ionization of anionic surfactants, leading to reduced dispersion and cleaning capabilities. Silica and aluminum impurities easily formed colloidal encapsulations of the target minerals, resulting in poor separation selectivity and loss of some heavy minerals with overflow. In control group 2.1, the recovery rate of WO3 was only 71.2%, and the recovery rate of MoO3 was only 69.8%. Furthermore, the tailings obtained were relatively turbid, containing a large number of medium-sized particles, and were grayish in color.

[0050] In control group 2.3, due to the excessively low pH (strongly acidic environment), the sulfonic acid groups of the anionic surfactants (LAS, AOS) exist in molecular form (-SO3H), with almost no ionization, resulting in a complete loss of dispersion and cleaning capabilities; the organic film cannot be peeled off, and the particles are severely aggregated, leading to frequent clogging of the hydrocyclone and complete failure of separation; the resulting overflow is extremely turbid, with a large amount of heavy minerals lost with the overflow, and the tailings are grayish-black.

[0051] In contrast group 2.2, the high pH (strong alkaline environment) resulted in better cleaning but also caused serious foaming problems. It also caused some impurities (such as silicon) to redissolve or form colloids, disrupting the flow field stability and leading to discontinuous operation and large fluctuations in indicators. In contrast group 2.1, the WO3 recovery rate was only 80.3% and the MoO3 recovery rate was only 79.1%. Because the foam carried a large number of fine particles into the overflow, the resulting tailings slurry had a high solids content and a black color.

[0052] from Figure 6 As can be seen, without the addition of sodium carbonate, there is significant agglomeration, coating, and adhesion between the phosphogypsum particles and on their surface. CaWO4 and other particles are embedded or attached to the phosphogypsum matrix, which is not conducive to the effective dissociation of valuable minerals from the phosphogypsum matrix. After the addition of sodium carbonate, the overall dispersibility of the phosphogypsum particles is significantly improved, the morphology of needle-like or platy crystals is clearer, the degree of adhesion between particles is reduced, and the exposure of CaWO4 and other particles is increased. These results indicate that the addition of sodium carbonate helps to improve the chemical environment of the slurry system, weakens the adverse effects of residual acidic components, surfactants, and impurity films on the particle surface, thereby improving the cleanliness of the mineral surface and the dispersibility of particles, promoting the dissociation of valuable minerals such as CaWO4 and MoS2 from the CaSO4 matrix particles, and providing favorable conditions for the enrichment of valuable metals such as tungsten and molybdenum in the underflow during subsequent cyclone separation.

[0053] Example 3 This embodiment investigates the effect of the amount of ethyl thionitrogen (SN-9#) added to the dispersion and cleaning components on the recovery effect.

[0054] Raw materials: The same tungsten ore-phosphogypsum raw materials as in Example 1. Testing revealed that the residual flotation agents in the raw materials were mainly xanthates (butyl xanthate) and sodium oleate, with an organic carbon content of 0.8% and a sulfide content (mainly molybdenite and pyrite) of approximately 1.5%.

[0055] Experimental method: The following components were added at fixed concentrations: wetting and penetrating component (APG) 0.3‰ (dry basis), dispersing and cleaning component (LAS) 0.5‰ (dry basis), pH buffering and stabilizing component (sodium carbonate) 0.12% (dry basis), defoaming and stabilizing component (polyether GP type defoamer) 0.1‰ (dry basis), and auxiliary agent (EDTA-2Na) 0.05‰ (dry basis). Only the amount of SN-9# added was changed; all other process parameters remained the same as in Example 1. Four sets of experiments were set up, as detailed below: Example 3: SN-9# was added at a rate of 0.3‰ of the dry basis of the raw material; Comparative Example 3.1: The amount of SN-9# added was 0; Comparative Example 3.2: The amount of SN-9# added was 0.1‰ of the dry basis raw material; Comparative Example 3.3: The amount of SN-9# added was 0.6‰ of the dry base material.

[0056] Chemical analysis was performed on the concentrates obtained from each group, and the recovery rates of valuable tungsten and molybdenum were calculated. The results are shown in the table below:

[0057] The results showed that in control group 3.1 without SN-9#, even with LAS and sodium carbonate, the WO3 recovery rate was only 79.5%, the MoO3 recovery rate was only 78.2%, and the tailings organic carbon content was 0.32%. As the SN-9# addition increased from 0 to 0.3‰, the WO3 recovery rate increased to 92.1%, the MoO3 recovery rate increased to 91.8%, and the tailings organic carbon content decreased from 0.32% to 0.18%. When the SN-9# addition increased to 0.6‰, the WO3 and MoO3 recovery rates decreased slightly, and foam accumulation occurred, proving that around 0.3‰ is the optimal addition range for SN-9#, which can form a ternary synergistic effect with LAS and sodium carbonate, significantly improving the tungsten and molybdenum recovery effect.

[0058] In addition, from Figure 3 As can be seen, the enrichment of valuable mineral particles in the concentrate is significantly improved after the addition of SN-9#, and the surface coatings of the particles are reduced; this indicates that the addition of SN-9# is beneficial to removing residual reagent films and organic contaminant layers on the mineral surface, and promotes the effective enrichment of tungsten and molybdenum minerals.

[0059] from Figure 4 As can be seen from the data, the organic coating on the surface of the tailings in Example 3 was significantly less than that in Comparative Example 3.1, and the characteristic peaks of organic matter in the infrared spectrum were weakened. This indicates that SN-9# can effectively strip the residual flotation reagents and organic film layer from the mineral surface, reduce the loss of valuable metals, and improve the recovery effect.

[0060] In summary, based on LAS and sodium carbonate fixation, the addition of SN-9# resulted in an additional 8-13 percentage point improvement in recovery rate, with a particularly significant improvement in molybdenum (13.6 percentage points). SN-9# has a short molecular chain (ethyl), allowing it to penetrate thick mixed oil films (fouling layers), disrupting the integrity of the oil film structure and causing it to detach from the mineral surface (similar to dish soap washing an oily dish), thus exposing the fresh surface of the minerals. (SN-9# is an amphiphilic molecule composed of a "lipophilic group" and a "polar group"; after inserting into the oil film, it uses emulsification / solubilization to "roll up" the aged oil film.)

[0061] Example 4 This embodiment includes a blank control experiment, where only water is used to treat phosphogypsum slurry without adding any surfactants. The remaining process equipment is the same as in Example 1, and the specific steps are as follows: Take 1000g of dry phosphogypsum raw material and mix it with 10L of tap water in a mixing tank. After stirring for 5 minutes, the pH of the slurry is approximately 5.5. After stopping stirring, the solid particles quickly settle and agglomerate significantly, forming an uneven mud layer at the bottom of the tank and a clear water layer on top (as shown in the attached image). Figure 5 As shown in the middle right figure. Figure 5 The left-middle image shows the state of Group 3 of the above-mentioned Examples after pretreatment with added surfactant and standing for 30 minutes.

[0062] The above slurry was pumped into the first-stage hydrocyclone, with the feed pressure controlled at 0.25 MPa. About 2 minutes after startup, a very small amount of slurry flowed out of the underflow outlet and then completely stopped. The feed pressure rose abnormally. Upon inspection after shutdown, it was found that the underflow nozzle was completely blocked by densely bonded fine phosphogypsum particles. After cleaning and restarting, it was still unable to operate stably, and the experiment had to be stopped.

[0063] This embodiment demonstrates that, for the fine-particle, high-drug-residue, and high-impurity tungsten phosphate gypsum targeted by this invention, the composite surfactant is not simply an synergist, but a key and essential component for achieving particle dispersion, stable equipment operation, and effective sorting. Without surfactant pretreatment, not only is it impossible to recover valuable metals, but the separation equipment will also fail to operate normally.

[0064] Example 5 This embodiment explores the effect of pressure combination of two-stage hydrocyclones on recovery efficiency.

[0065] Experimental method: The surfactant formulation in this example is the same as that in Example 3 of Example 3. The raw materials, pretreatment process and other process ratios are basically the same as those in Example 1. The only difference is that the hydrocyclone feed pressure parameter is changed. Three sets of experiments are set up, as follows: Example 5 group: First-stage swirling pressure 0.2 MPa, second-stage swirling pressure 0.32 MPa; Control group A: A single-stage hydrocyclone was used, with a feed pressure of 0.26 MPa; Control group B: The pressures of the two swirling stages are reversed, with the first-stage swirling pressure at 0.32 MPa and the second-stage swirling pressure at 0.20 MPa.

[0066] Chemical analysis was performed on the concentrates obtained from each group, and the recovery rates of valuable tungsten and molybdenum were calculated. The results are shown in the table below:

[0067] The experimental results show that the present invention achieves simultaneous maximization of concentrate grade and recovery rate through the synergistic effect of low-pressure desliming in the front stage and high-pressure cleaning in the back stage. The recovery rates of WO3 and MoO3 are 89.5% and 88.7%, respectively, and the grades of WO3 and MoO3 in the concentrate are 10.82% and 2.38%, respectively. In contrast, the single-stage cyclone in control group A cannot simultaneously achieve desliming and cleaning, with WO3 and MoO3 recovery rates of only 55.2% and 53.8%, and concentrate grades of only 4.35% and 0.95%. In control group B, the high-pressure single-stage cyclone forces a large number of light and heavy particles into the underflow, resulting in frequent equipment blockage. The recovery rates of WO3 and MoO3 are only 49.8% and 48.1%, respectively, and concentrate grades of only 2.91% and 0.63%, respectively. This demonstrates that the two-stage gradient pressure combination of the present invention is the key process parameter for achieving efficient separation.

[0068] In summary, the low-pressure primary cyclone of this invention effectively removes light and fine mud, creating a high-grade feed for the high-pressure secondary cyclone purification process, resulting in a significant synergistic effect. In control group A, the single-stage pressure cannot simultaneously achieve both "desliming" and "purification," making it difficult to simultaneously achieve product grade and recovery rate. In control group B, the high-pressure primary stage forcibly squeezes a large number of light and heavy particles into the underflow, causing equipment blockage, and the material fed to the secondary stage is no longer suitable for purification.

[0069] Example 6 This embodiment investigates the effect of the dosage of the composite surfactant on the recovery effect. The composite surfactant formulation of Example 1 was used, with only the amount of working solution added changed. The other process parameters were the same as in Example 1. Three groups of experiments were set up, as detailed below: Example 6: The surfactant addition amount was 0.5% of the dry basis phosphogypsum raw material mass; Comparative group 6.1: The surfactant addition amount was 0.2% of the dry basis phosphogypsum raw material mass; Comparative group 6.2: The amount of surfactant added was 2.5% of the dry basis phosphogypsum raw material.

[0070] Chemical analysis was performed on the concentrates obtained from each group, and the recovery rates of valuable tungsten and molybdenum were calculated. The results are shown in the table below:

[0071] The experimental results show that the dosage of the reagent in Example 6 is moderate, achieving a balance between effective surface modification, foam suppression, and cost, with the best recovery rate and grade of WO3 and MoO3. In contrast, the dosage of the reagent in the control group 6.1 is insufficient, resulting in incomplete cleaning of the organic film and particle dispersion. The recovery rates of WO3 and MoO3 are only 62.4% and 61.2%, respectively, and the grades of WO3 and MoO3 in the concentrate are only 5.21% and 1.15%, respectively. In contrast, the dosage of the reagent in the control group 6.2 is excessive, causing serious foaming problems, disrupting the stability of the hydrocyclone flow field, and reducing the recovery rates of WO3 and MoO3 to 85.1% and 83.8%, respectively. At the same time, it significantly increases the cost of the reagent, proving that about 0.5% is the optimal addition range for the composite surfactant.

[0072] Analysis of the phenomenon: The dosage of reagents in this invention is moderate, achieving a balance between effective surface modification, foam suppression, and cost. Control group C had insufficient reagent dosage, resulting in incomplete cleaning of the organic film and particle dispersion of tungsten ore phosphogypsum, leading to low dissociation and separation efficiency, and low recovery rate and grade. Control group D used excessive dosage; although the cleaning effect was good, it caused serious foaming problems, disrupting process stability and increasing reagent costs.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for the recovery of valuable metals from tungsten ore phosphogypsum, characterized by, Includes the following steps: (1) Preparation of composite surfactant working solution: Weigh 25-45 parts of wetting and penetrating component, 35-55 parts of dispersion and cleaning component, 8-15 parts of pH buffer and stabilizing component, 4-8 parts of defoaming and stabilizing component, and 0.5-2 parts of additives by weight; under stirring conditions, first dissolve the pH buffer and stabilizing component in water, then add the remaining components in sequence, make up the water volume, stir evenly, and prepare a composite surfactant working solution with a mass concentration of 1%-5%; (2) Surfactant pretreatment of phosphogypsum: mix tungsten ore phosphogypsum raw material with water to prepare a slurry with a solid-liquid mass ratio of 1:5~15, add the composite surfactant working solution to the slurry, the amount of addition is 0.5%~2.5% of the dry basis phosphogypsum mass, and stir thoroughly. (3) Two-stage series hydrocyclone separation and enrichment: The pretreated slurry is fed into a two-stage series hydrocyclone for centrifugal separation. The first-stage hydrocyclone controls the feed pressure at 0.15~0.25MPa. Most of the light phosphogypsum fine mud is removed by low-pressure centrifugal separation. The overflow is discharged as purified phosphogypsum slurry. The underflow is the slurry with preliminarily enriched valuable metals, which is sent to the second-stage hydrocyclone. The second-stage hydrocyclone controls the feed pressure at 0.3~0.35MPa. The valuable metals are deeply enriched by high-pressure centrifugal separation. The underflow is the concentrate enriched with valuable metals such as tungsten and molybdenum.

2. The method for recovery of valuable metals from tungsten ore phosphogypsum according to claim 1, characterized in that, The wetting and penetrating component is selected from at least one of alkyl glycosides and fatty alcohol polyoxyethylene ethers.

3. The method for recovery of valuable metals from tungsten ore phosphogypsum according to claim 1, characterized in that, The dispersing and cleaning components are selected from at least one of ethyl thiocyanate, sodium dodecylbenzene sulfonate, and sodium α-alkenyl sulfonate.

4. The method for recovery of valuable metals from tungsten ore phosphogypsum according to claim 1, characterized in that, The pH buffer and stabilizing component is sodium carbonate, and the pH value of the slurry after pretreatment in step (2) is 8.0~8.

5.

5. The method for recovery of valuable metals from tungsten ore phosphogypsum according to claim 1, characterized in that, The defoaming and stabilizing components are selected from at least one of polyether defoamers and modified silicone defoamers.

6. The method for recovering valuable metals from tungsten ore phosphogypsum according to claim 1, characterized in that, The auxiliary agent is disodium ethylenediaminetetraacetate.

7. The method for recovery of valuable metals from tungsten ore phosphogypsum according to claim 3, characterized in that, The dispersion and cleaning component is ethyl thiocyanate, and the amount of ethyl thiocyanate added is 0.2‰~0.4‰ of the mass of dry tungsten ore phosphogypsum raw material.

8. The method for recovery of valuable metals from tungsten ore phosphogypsum according to claim 1, characterized in that, The diameter of the first-stage hydrocyclone is 50 mm, and the particle size it separates is 5~40 μm; the diameter of the second-stage hydrocyclone is 25 mm, and the particle size it separates is 5~20 μm.

9. The method for recovery of valuable metals from tungsten ore phosphogypsum according to claim 1, characterized in that, The tungsten ore phosphogypsum is phosphogypsum made from the wet smelting residue of scheelite without roasting pretreatment; wherein the total mass content of valuable metals such as tungsten and molybdenum is <1%, and the particle size D50 of the phosphogypsum is 20~30μm.

10. The method for recovery of valuable metals from tungsten ore phosphogypsum according to claim 1, characterized in that, In step (2), the stirring speed is 400~600 r / min and the stirring time is 10~30 min.

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