Enrichment and separation process method for thorium in feldspar-based minerals

Abstract

The invention discloses an enrichment and separation process method for thorium in feldspar-based minerals, and relates to the technical field of recovery of radioactive element thorium. The enrichment and separation process method comprises the following steps: S1, pre-crushing: crushing feldspar-based raw ores to-30-+ 150 meshes by using crushing equipment; s2, multi-section collaborative flotation enrichment is conducted, wherein at least three sections of flotation are conducted on the feldspar-based raw materials with the size ranging from-30 meshes to + 150 meshes; s3, wet grinding and crushing, wherein the thorium-rich concentrate is subjected to wet grinding, and the particle size is controlled to be-200 meshes; s4, stepped acid leaching is conducted, specifically, sulfuric acid with the concentration being 0.5-0.8 mol / L is used for conducting multi-tank series connection and staged acid leaching treatment on the ground ore pulp; s5, acid cake washing; s6, circulating enrichment and acid recovery; according to the method, flotation is conducted on feldspar minerals containing fine crystal structures such as iron sulfide and silicon dioxide under the conditions of normal temperature and normal pressure, so that the element thorium and iron-containing impurities are enriched, then acid leaching treatment is conducted on enriched products, thorium is dissolved and leached out under the condition that main components of the minerals are not damaged, and separation and purification of the minerals are achieved.

Description

Technical Field

[0001] This application relates to the field of radioactive thorium recovery technology, specifically a process for enriching and separating thorium from feldspar minerals. Background Technology

[0002] Thorium is a naturally occurring radioactive metallic element with a silvery-white luster. It is soft in texture and has a high energy density. Thorium's energy density per unit is significantly higher than that of uranium and coal. Compared to uranium, thorium is abundant, has low radiation, and cannot be used in weapons manufacturing, making it the future king of energy.

[0003] Thorium is abundant in the Earth's crust. In China, thorium-bearing minerals are mainly concentrated in the Bayan Obo mine in Baotou, the bastnaesite mine in Sichuan, and the Weishan rare earth mine in Shandong. These three major rare earth mining areas account for more than 80% of my country's thorium reserves. Current thorium extraction processes primarily rely on the smelting process of rare earth mines. For example, the "high-temperature concentrated sulfuric acid roasting method" used in the Baotou rare earth mine or the "high-temperature roasting-acid leaching" combined process used in the Sichuan bastnaesite mine aims to extract rare earth elements; thorium is merely a byproduct separated during this process. These traditional processes have inherent and insurmountable flaws.

[0004] 1. Extremely high energy consumption, the process involves high-temperature roasting (usually exceeding 800℃), consuming a large amount of energy and resulting in high production costs;

[0005] 2. Severe environmental pollution: High-temperature roasting and the use of strong acids will generate a large amount of sulfur- and fluorine-containing waste gas, acidic wastewater and radioactive waste residue, which pose a serious threat to the ecological environment.

[0006] 3. The source of resources is singular and limited, and the process relies entirely on the increasingly depleted conventional rare earth mineral resources, failing to explore new thorium resource channels.

[0007] Feldspar minerals are among the most widely distributed rock-forming minerals in the Earth's crust and are important raw materials for industries such as ceramics and glass. In some feldspar mines (such as a high-potassium feldspar mine in Henan Province), rare and valuable elements such as thorium, gold, molybdenum, and silver are often found together. In the traditional feldspar beneficiation process, these valuable elements are discarded as tailings or waste along with impurities such as iron, which not only wastes valuable strategic resources, but also brings significant environmental safety risks due to the accumulation of these wastes rich in radioactive elements and heavy metals.

[0008] Therefore, there is an urgent need in the field for a new technology that can recover thorium in a green and economical way from unconventional resources such as feldspar. Summary of the Invention

[0009] To overcome the shortcomings of the prior art, this invention discloses a process for enriching and separating thorium in feldspar minerals. This invention involves flotation of feldspar group minerals containing fine-grained structures such as iron sulfide and silicon dioxide under normal temperature and pressure conditions, thereby enriching elemental thorium and iron-containing impurities. The enriched product is then subjected to acid leaching treatment, which dissolves and leaches thorium without damaging the main components of the mineral, thus achieving the separation and purification of the mineral.

[0010] To achieve the above objectives, this application provides the following technical solution:

[0011] A process for enriching and separating thorium from feldspar minerals includes the following steps:

[0012] S1. Pre-crushing: Using crushing equipment to crush feldspar-based raw ore to -30 to +150 mesh to obtain feldspar-based raw material;

[0013] S2. Multi-stage synergistic flotation enrichment: Feldspar-based raw materials of -30 to +150 mesh are subjected to at least three stages of flotation, and different collectors are used under different pH conditions to selectively enrich thorium-containing impurity minerals, obtain thorium-rich concentrate and simultaneously improve the grade of feldspar matrix.

[0014] S3. Wet grinding and crushing: The thorium-rich concentrate is wet ground to control the particle size to -200 mesh, accounting for 60% to 85%;

[0015] S4. Stepped acid leaching: At normal temperature and pressure, sulfuric acid with a concentration of 0.5-0.8 mol / L is used to perform multi-tank series acid leaching treatment on the milled slurry in stages, controlling the liquid-solid ratio at 2.5:1, to obtain thorium-containing leachate and acid cake.

[0016] S5. Acid cake washing: The acid cake is washed countercurrently with water or dilute acid to obtain a washing solution containing trace amounts of thorium and a purified residue containing valuable elements such as gold, molybdenum, and silver.

[0017] S6. Cyclic enrichment and acid recovery: The thorium-containing leachate produced in step S4 and the trace thorium-containing washing solution produced in step S5 are returned to step S4 for acid leaching of a new batch of thorium-rich concentrate. Multiple cycles of enrichment are performed to obtain a high-concentration thorium leachate.

[0018] S7. Separation and purification of thorium: The high-concentration thorium leachate obtained in S6 is subjected to reduction, hydrolysis precipitation, and solid-liquid separation operations in sequence to obtain crude thorium hydroxide product.

[0019] Furthermore, the multi-stage coordinated flotation enrichment in S1 specifically includes:

[0020] First stage flotation: Under pH conditions of 5-6, xanthate collectors are used to separate sulfide minerals such as pyrite by flotation;

[0021] Second stage flotation: Under pH conditions of 2.5–3.5, amine cationic collectors are used to separate mica minerals by flotation.

[0022] The third stage of flotation: under pH conditions of 3 to 4, sulfonate collectors are used to separate iron-containing alkali metal silicate minerals by flotation.

[0023] Furthermore, the first stage of flotation includes the following steps:

[0024] Step 1, Slurry preparation and drug administration: The feldspar-based raw material is prepared into a slurry with a concentration of about 30-35%. After being introduced into the mixing tank, sulfuric acid is added to adjust and stabilize the pH value of the slurry at 5.0-6.0. Then, flotation reagents are added in sequence to mix and prepare the slurry to form slurry I.

[0025] Step 2, roughing: The slurry I is introduced into the roughing flotation machine for aeration flotation. The sulfide mineral particles with collectors on their surface combine with the air bubbles to float and form a foam layer. After the foam is scraped off, the roughing concentrate I is obtained, and the product in the tank is the roughing tailings I.

[0026] Step 3, Fine Concentration: The roughing concentrate is introduced into the fine flotation machine for aeration flotation. Pure sulfide mineral particles with high degree of liberation float first. After the foam is scraped off, thorium-rich concentrate I is obtained. The product in the tank is the fine tailings I. The fine tailings I is returned to step 2 of the first stage flotation for roughing operation.

[0027] Step 4, First Scavenging: Roughing tailings I are introduced into the first scavenging flotation machine for aeration flotation, a small amount of collector and frother are added, and after the foam is scraped off, the first scavenging concentrate I is obtained. The first scavenging concentrate is returned to Step 2 of the first stage flotation for roughing operation, and the product in the tank is the first scavenging tailings I.

[0028] Step 5, Second Scavenging: The tailings I from the first scavenging are introduced into the second scavenging flotation machine for aeration flotation. A small amount of reagent is added, and after the foam is scraped off, the second scavenging concentrate I is obtained. The second scavenging concentrate I is returned to step 4 of the first stage flotation for scavenging operation. The product in the tank is the tailings from the first stage flotation.

[0029] Furthermore, the second stage of flotation includes the following steps:

[0030] Step 1, Slurry preparation and reagent addition: Add the first stage flotation tailings and sulfuric acid to the slurry mixing tank, and precisely adjust the pH value of the slurry to a strongly acidic range of 2.5 to 3.5. Then add cationic collector, dodecylamine acetate and frother to mix and form slurry II.

[0031] Step 2, roughing: The conditioning slurry II is introduced into the roughing flotation machine for aeration flotation. After the foam is scraped off, the roughing concentrate II is obtained. The product in the tank is the roughing tailings II.

[0032] Step 3, Refinement: The rougher concentrate II is introduced into the refiner flotation machine for aeration flotation. After the foam is scraped off, thorium-rich concentrate II is obtained. The product in the tank is the refiner tailings II.

[0033] Step 4, Scavenging: The roughing tailings II are introduced into the scavenging flotation machine for aeration flotation. A small amount of collector and frother are added. After the foam is scraped off, scavenging concentrate II is obtained. Scavenging concentrate II is returned to step 2 of the second stage flotation for roughing operation. The product in the tank is the second stage flotation tailings.

[0034] Furthermore, the third stage of flotation includes the following steps:

[0035] Step 1, Slurry preparation and reagent addition: The tailings from the second stage flotation are introduced into the slurry mixing tank, and the pH value of the slurry is precisely adjusted to 3.0-4.0 with acid or alkali. Then, sodium hydroxysulfonate and frother are added to mix and form slurry III.

[0036] Step 2, roughing: The pulp III is introduced into the roughing flotation machine for aeration flotation. After the foam is scraped off, thorium-rich concentrate III is obtained. The product in the tank is the roughing tailings III.

[0037] Step 3, Scavenging: The roughing tailings III are introduced into the scavenging flotation machine for aeration flotation, and collectors and frothers are added. After the foam is scraped off, scavenging concentrate III is obtained. Scavenging concentrate III is returned to step 2 of the third stage flotation for roughing operation. The product in the tank is the feldspar product.

[0038] Furthermore, the stepped acid leaching in S4 includes the following steps:

[0039] Step 1, Primary acid dissolution: The slurry after wet grinding and crushing in step S3 is introduced into the first-stage acid decomposition tank. Sulfuric acid is slowly added during the stirring process. After mixing and reaction, acid-dissolved slurry I is obtained.

[0040] Step 2, Secondary Leaching: The acid-soluble slurry is introduced into the second-stage acid decomposition tank for continuous stirring and decomposition to obtain acid-soluble slurry II;

[0041] Step 3, Aging and Solid-Liquid Separation: The acid-soluble slurry II is introduced into the third-stage decomposition tank for static solid-liquid separation to obtain thorium-containing leachate and acid cake.

[0042] Furthermore, the S6 cycle enrichment and acid recovery includes the following steps:

[0043] Step 1, Solution Collection and Analysis: The thorium-containing leachate produced in step S4 and the thorium-containing washing solution produced in step S5 are introduced into a circulating storage tank to obtain circulating mother liquor, and the free sulfuric acid concentration and thorium concentration of the circulating mother liquor are measured.

[0044] Step 2, Acid replenishment calculation and adjustment: Adjust the concentration of free sulfuric acid in the circulating mother liquor to the range required in step S4;

[0045] Step 3, Circulating Leaching: The circulating mother liquor with the adjusted free sulfuric acid concentration is introduced into S4 for stepwise acid leaching to obtain a new round of thorium-containing leachate, and the S6 operation is repeated based on its thorium concentration.

[0046] Furthermore, S7 specifically includes:

[0047] Reduction: SO2 is introduced into a high-concentration thorium leachate or iron powder is added to reduce Fe. 3+ Reduced to Fe 2+ ;

[0048] Hydrolysis precipitation: Slowly add ammonia water, controlling the final pH to 5.5-6.5, so that thorium precipitates as thorium hydroxide;

[0049] Solid-liquid separation: Pressure filtration is used to separate crude thorium hydroxide product and iron-rich filtrate.

[0050] Compared with the prior art, the beneficial effects of this application are:

[0051] Through multi-stage synergistic flotation enrichment, using specific collectors under different pH conditions, thorium-containing impurities such as pyrite, mica, and iron-containing silicates are separated step by step. This process not only efficiently enriches low-grade thorium in the raw ore, significantly improving the efficiency and economic benefits of subsequent wet thorium extraction, but also deeply purifies the feldspar matrix, reducing its iron content and increasing its whiteness, turning it into a high-value industrial raw material.

[0052] This invention completely eliminates the high-temperature roasting step required by traditional processes, which not only greatly saves energy consumption, but also uses low-concentration sulfuric acid, which greatly reduces acid consumption while ensuring a high leaching rate, and reduces the corrosion of equipment and the pressure on subsequent wastewater treatment.

[0053] This invention creatively shifts the raw material for thorium extraction from traditional rare earth ores to feldspar-based minerals, which have huge reserves and wide distribution. In particular, it targets thorium-bearing flotation tailings or low-grade raw ore generated during feldspar beneficiation, fundamentally broadening my country's thorium resource supply channels and reducing dependence on a few rare earth ores, which is of great strategic significance. Detailed Implementation

[0054] This invention provides a technical solution:

[0055] The thorium (Th) content in high-potassium feldspar minerals is approximately ≤0.01%, and it is associated with rare and valuable elements such as gold (Au), molybdenum (Mo), and silver (Ag). The raw ore has a high iron content, mainly found in pyrite, mica, and iron-bearing silicate minerals. To achieve the enrichment and separation of thorium, a process for enriching and separating thorium from feldspar-based minerals is proposed, comprising the following steps:

[0056] S1. Pre-crushing: Feldspar-based ore is crushed to (over 99.5%) using jaw crushers and cone crushers to obtain feldspar-based raw materials;

[0057] At this particle size, most of the iron- and thorium-containing impurity minerals loosely associated with feldspar can achieve sufficient individual liberation, that is, "peel off" from the feldspar matrix to form independent particles. At the same time, this relatively coarse particle size can effectively avoid "over-grinding" and the generation of a large amount of secondary slime, which not only ensures the selectivity of subsequent flotation, but also protects the particle size of the feldspar product itself.

[0058] S2. Multi-stage synergistic flotation enrichment: Feldspar matrix raw materials of -30 to +150 mesh (accounting for more than 99.5%) are subjected to first-stage flotation, second-stage flotation and third-stage flotation in sequence. Different collectors are used under different pH conditions to selectively enrich thorium-containing impurity minerals, obtain thorium-rich concentrate and simultaneously improve the grade of feldspar matrix.

[0059] Specifically, the first stage of flotation involves separating sulfide minerals such as pyrite using xanthate collectors at a pH of 5-6. Under weakly acidic conditions, the xanthate collectors selectively chemically adsorb onto the surface of sulfide minerals such as pyrite, making them hydrophobic and thus allowing them to be captured and floated by air bubbles. This stage removes most of the iron sulfide, and thorium is initially enriched in thorium-rich concentrate I. Simultaneously, it deeply desulfurizes the feldspar product, specifically including the following steps:

[0060] Step 1, Slurry preparation and drug administration: The feldspar-based raw material is prepared into a slurry with a concentration of about 30-35%. After being introduced into the mixing tank, sulfuric acid is added to adjust and stabilize the pH value of the slurry at 5.0-6.0. Then, flotation reagents are added in sequence to mix and prepare the slurry to form slurry I.

[0061] Step 2, roughing: The slurry I is introduced into the roughing flotation machine for aeration flotation. The sulfide mineral particles with collectors on their surface combine with the air bubbles to float and form a foam layer. After the foam is scraped off, the roughing concentrate I is obtained, and the product in the tank is the roughing tailings I.

[0062] Step 3, Fine Concentration: The roughing concentrate is introduced into the fine flotation machine for aeration flotation. Pure sulfide mineral particles with high degree of liberation float first. After the foam is scraped off, thorium-rich concentrate I is obtained. The product in the tank is the fine tailings I. The fine tailings I is returned to step 2 of the first stage flotation for roughing operation.

[0063] Step 4, First Scavenging: Roughing tailings I are introduced into the first scavenging flotation machine for aeration flotation, with a small amount of collector and frother added to capture the target minerals that "escaped" during roughing. After the froth is scraped off, the first scavenging concentrate I is obtained. The first scavenging concentrate is returned to Step 2 of the first stage flotation for roughing operation. The product in the tank is the first scavenging tailings I.

[0064] Step 5, Second Scavenging: The tailings I from the first scavenging are introduced into the second scavenging flotation machine for aeration flotation. A small amount of reagent is added, and after the foam is scraped off, the second scavenging concentrate I is obtained. The second scavenging concentrate I is returned to step 4 of the first stage flotation for scavenging operation. The product in the tank is the tailings from the first stage flotation.

[0065] The second stage of flotation involves separating mica minerals using an amine cationic collector at a pH of 2.5–3.5. Under strongly acidic conditions, the edges of mica are negatively charged, and the cationic collector is adsorbed onto its surface through electrostatic attraction, making it hydrophobic. This stage is the most crucial step in improving the whiteness of feldspar. The removal of mica significantly enhances the whiteness of the feldspar product, multiplying its value. Thorium is further enriched in thorium-rich concentrate II, specifically through the following steps:

[0066] Step 1, Slurry Preparation and Reagent Addition: Add the first-stage flotation tailings and sulfuric acid to the slurry mixing tank. After precisely adjusting the pH of the slurry to a strongly acidic range of 2.5–3.5, add a cationic collector, dodecylamine acetate, and a frother to form Slurry II. The amine cations will selectively adsorb onto the negatively charged mica surface.

[0067] Step 2, roughing: The conditioning slurry II is introduced into the roughing flotation machine for aeration flotation. The mica flakes captured on the surface adhere to the air bubbles. After the foam is scraped off, the roughing concentrate II is obtained. The product in the tank is the roughing tailings II.

[0068] Step 3, Refinement: The rougher concentrate II is introduced into the refiner flotation machine for aeration flotation. After the foam is scraped off, thorium-rich concentrate II is obtained. The product in the tank is the refiner tailings II.

[0069] Step 4, Scavenging: The roughing tailings II are introduced into the scavenging flotation machine for aeration flotation. A small amount of collector and frother are added. After the froth is scraped off, scavenging concentrate II is obtained. Scavenging concentrate II is returned to Step 2 of the second stage flotation for roughing operation. The product in the tank is the second stage flotation tailings.

[0070] The third stage of flotation involves separating iron-containing alkali metal silicate minerals using sulfonate collectors at a pH of 3-4. Sulfonate collectors, at specific pH levels, can effectively collect iron-containing silicate minerals with complex surface properties through chelation. This stage also performs a "sweeping" recovery of residual thorium impurities, ensuring a high overall thorium recovery rate. The resulting feldspar product has extremely low iron content and high whiteness, making it a high-quality industrial raw material. The specific steps include:

[0071] Step 1, Slurry preparation and reagent addition: The tailings from the second stage flotation are introduced into the slurry mixing tank, and the pH value of the slurry is precisely adjusted to 3.0-4.0 with acid or alkali. Then, sodium hydroxysulfonate and frother are added to mix and form slurry III.

[0072] Step 2, roughing: The pulp III is introduced into the flotation machine for aeration flotation. The iron-containing silicate minerals are captured and floated to the surface, forming foam. After the foam is scraped off, thorium-rich concentrate III is obtained. The product in the tank is the roughing tailings III.

[0073] Step 3, Scavenging: The roughing tailings III are introduced into the scavenging flotation machine for aerated flotation, and collectors and frothers are added. This is because the minerals remaining in the roughing tailings may have poor floatability and need to be added to be collected. After the foam is scraped off, scavenging concentrate III is obtained. Scavenging concentrate III is returned to step 2 of the third stage flotation for roughing operation. The product in the tank is the feldspar product.

[0074] S3. Wet grinding and crushing: The thorium-rich concentrate is wet ground to control the particle size to -200 mesh, accounting for 60% to 85%. The particle size is controlled at -200 mesh because a large amount of thorium is still wrapped inside the mineral particles in the concentrate after flotation enrichment. The purpose of this step is to completely "break the shell" through ultrafine grinding, fully dissociate the thorium carrier minerals, expose the huge reaction specific surface area, and create the necessary kinetic conditions for efficient acid leaching under mild conditions in the subsequent process.

[0075] S4. Stepped acid leaching: Under normal temperature and pressure, the milled slurry is subjected to multi-tank series acid leaching in stages using sulfuric acid with a concentration of 0.5–0.8 mol / L, controlling the liquid-to-solid ratio at 2.5:1, to obtain thorium-containing leachate and acid cake. The specific operation steps are as follows:

[0076] Step 1, Primary Acid Dissolution: The slurry after wet grinding and crushing in Step S3 is introduced into the first-stage acid decomposition tank. Sulfuric acid is slowly added during stirring, and the concentration of sulfuric acid is controlled at 0.5-0.8 mol / L. The slurry is thoroughly mixed with fresh acid or circulating acid for the first time. The most reactive thorium-containing minerals (such as thorium compounds that have been fully exposed by grinding) dissolve rapidly in this stage. After the mixing reaction, acid-dissolved slurry I is obtained.

[0077] Step 2, Secondary Leaching: The acid-soluble slurry is introduced into the second-stage acid decomposition tank for continuous stirring and decomposition to obtain acid-soluble slurry II. The goal is to dissolve those thorium-containing minerals with slightly lower reactivity or slightly tighter encapsulation. The slurry undergoes a relatively long period of continuous stirring and acid decomposition (about 1 hour or more) to ensure that the acid has enough time to diffuse and act on the target mineral particles.

[0078] Step 3, Aging and Solid-Liquid Separation: The acid-soluble slurry II is introduced into the third-stage decomposition tank for static solid-liquid separation to obtain thorium-containing leachate and acid cake;

[0079] In the acid leaching process of thorium-containing concentrate, the separation of thorium from pyrite and mica impurities is achieved by controlling the slurry concentration, solid-liquid ratio, acid concentration, and acid leaching stirring time. In specific experiments, the experimental parameters were controlled at 15-85℃, sulfuric acid concentration at 5-65%, slurry concentration at 15-60%, and acid leaching time at 0.5-4h. Through multiple orthogonal experiments on the controlled variables under the above parameters, the results show that under normal pressure, maintaining an appropriate acid leaching time within the above temperature, sulfuric acid concentration, and slurry concentration ranges can achieve the separation of thorium from the pyrite matrix. After acid leaching, the thorium content in the thorium-containing concentrate decreased from ≥0.2% to below 0.01%, and the thorium leaching rate reached over 95%. The concentrate mass loss after acid leaching was approximately 5%. Under conditions of increased temperature, the acid leaching dissolution time can be appropriately reduced. A sulfuric acid concentration greater than 5% does not significantly enhance the dissolution effect. The slurry concentration affects the subsequent filtration efficiency.

[0080] S5. Acid cake washing: The acid cake is washed countercurrently with water or dilute acid to obtain a washing solution containing trace amounts of thorium and a purified residue containing valuable elements such as gold, molybdenum, and silver. The washing process can recover the thorium-containing solution entrained in the pores of the acid cake, thereby improving the thorium recovery rate. The purified residue is a high-quality raw material for extracting valuable elements such as gold, molybdenum, and silver.

[0081] S6. Cyclic Enrichment and Acid Recovery: The thorium-containing leachate from step S4 and the trace thorium-containing washing solution from step S5 are returned to step S4 for acid leaching of a new batch of thorium-rich concentrate. This process involves multiple cycles of enrichment to obtain high-purity thorium sulfate. The cyclic enrichment and acid recovery are achieved through a closed-loop cycle, concentrating the thorium from a large volume of low-concentration leachate into a small volume solution. With each cycle, the thorium concentration in the leachate cumulatively increases. The specific operating steps are as follows:

[0082] Step 1, Solution Collection and Analysis: The thorium-containing leachate produced in step S4 and the thorium-containing washing solution produced in step S5 are introduced into a circulating storage tank to obtain circulating mother liquor, and the free sulfuric acid concentration and thorium concentration of the circulating mother liquor are measured.

[0083] Step 2, Acid Replenishment Calculation and Adjustment: Adjust the concentration of free sulfuric acid in the circulating mother liquor to the range required in step S4.

[0084] Step 3, Circulating Leaching: The circulating mother liquor with the adjusted free sulfuric acid concentration is introduced into S4 for stepwise acid leaching to obtain a new round of thorium-containing leachate;

[0085] S7. Separation and purification of thorium: The high-thorium concentration leachate after recycling and enrichment undergoes reduction, hydrolysis precipitation, and solid-liquid separation operations, specifically including:

[0086] Reduction: SO2 is introduced into a high-concentration thorium leachate or iron powder is added to reduce Fe. 3+ Reduced to Fe2+ ;

[0087] Hydrolysis precipitation: Slowly add ammonia water, controlling the final pH to 5.5-6.5, so that thorium precipitates as thorium hydroxide;

[0088] Solid-liquid separation: Pressure filtration is used to separate crude thorium hydroxide product and iron-rich filtrate;

[0089] The crude thorium hydroxide product is obtained, and the iron-rich filtrate can be further processed into ferrous sulfate by-product, realizing the comprehensive utilization of all elements of resources.

[0090] Example 1: This example uses a high-potassium feldspar ore with a thorium (Th) grade of 0.009% as raw material. The specific recovery process steps are as follows:

[0091] S1, Pre-crushing:

[0092] Jaw crushers and cone crushers are used to crush the raw ore to -30 to +150 mesh, with the material accounting for ≥99.5% of the total material within this particle size range;

[0093] S2, Multi-stage cooperative flotation enrichment:

[0094] First stage flotation: Adjust the pulp pH to 5.5, and use pentyl xanthate (100g / t) with higher selectivity as collector to preferentially remove thorium-loaded pyrite by flotation, and obtain thorium-rich concentrate I with Th grade enriched to 0.08%;

[0095] Second stage flotation: Adjust the pulp pH to 3.0, use a mixed amine collector (150g / t) to efficiently collect thorium-loaded mica minerals, and obtain thorium-rich concentrate II, with its Th grade enriched to 0.18%;

[0096] Third stage flotation: Adjust the pulp pH to 3.5, and use a high-efficiency hydroxysulfonate collector (200g / t) to deeply remove residual thorium-loaded impurities such as iron-containing silicates, to obtain thorium-rich concentrate III, with a Th grade enriched to 0.25%;

[0097] After the three-stage flotation process was combined, the th content of the thorium-rich concentrate was increased from 0.009% in the original ore to 0.20%, and the thorium recovery rate in the flotation operation reached 84.5%. At the same time, the iron content in the final feldspar product was reduced to 0.12%, and the whiteness was increased to 88%.

[0098] S3, Wet grinding and crushing:

[0099] Wet milling of thorium-rich concentrate to control the proportion of -200 mesh in the product to reach 75%;

[0100] S4, Stepped acid leaching:

[0101] Under normal temperature and pressure, using sulfuric acid with a concentration of 0.6 mol / L and controlling the liquid-to-solid ratio at 2.5:1, a three-stage series countercurrent leaching process was carried out.

[0102] The thorium leaching rate in this step reaches 93%, producing a thorium-containing leachate (Th concentration: 0.18 g / L) and acid cake;

[0103] S5. Recycling and recovery:

[0104] The above leachate was mixed with the washing liquid of the acid cake and returned to be used for acid leaching of the next batch of thorium-rich concentrate. After five cycles, the Th concentration in the leachate was enriched to 0.85 g / L.

[0105] S7. Separation and purification of thorium:

[0106] SO2 was introduced into the enriched leachate for reduction, and then ammonia was slowly added to adjust the pH to 6.0 for hydrolysis and precipitation.

[0107] After pressure filtration, washing, and drying, crude thorium hydroxide product is finally obtained, with a ThO2 purity of ≥92%. The overall thorium recovery rate from raw ore to product is 84.7%.

[0108] Example 2: This example describes the processing of a low-grade feldspar ore with a thorium grade of 0.008% and complex mineral distribution. The specific recovery process steps are as follows:

[0109] S1, Pre-crushing:

[0110] After crushing, the proportion of particles ranging from -30 to +150 mesh in the raw ore is 99.7%.

[0111] S2, Multi-stage cooperative flotation enrichment:

[0112] First stage flotation: Ethyl xanthate was used as the collector at a pH of 5.0;

[0113] Second stage flotation: Under conditions of pH 2.8, amine cationic collectors are used;

[0114] The third stage of flotation: using sulfonate collectors at a pH of 3.2;

[0115] Results: The final thorium-rich concentrate had a Th grade of 0.18% and a flotation recovery rate of 81.0%.

[0116] S3, Wet grinding and crushing:

[0117] Thorium-rich concentrate was wet-milled to -200 mesh, accounting for 80% of the total.

[0118] S4, Stepped acid leaching:

[0119] Under normal temperature and pressure, sulfuric acid with a concentration of 0.65 mol / L was used, and the liquid-to-solid ratio was controlled at 2.5:1 for three-stage leaching.

[0120] The thorium leaching rate in this step was 91.5%;

[0121] S5. Recycling and recovery:

[0122] The leachate and washing solution are recycled. After five cycles, the Th concentration in the leachate is enriched to an economically treatable level.

[0123] S6. Separation and purification of thorium:

[0124] Iron powder was added to the high-concentration leachate for reduction, and then the pH was adjusted to 5.8 with ammonia to precipitate thorium.

[0125] After solid-liquid separation, crude thorium hydroxide product was obtained. The overall thorium recovery rate from raw ore to product was 69.5%.

[0126] The parts of this invention not described in detail are prior art. It will be obvious to those skilled in the art that this invention is not limited to the details of the above exemplary embodiments, and that this invention can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention.

Claims

1. A process for enriching and separating thorium from feldspar-based minerals, comprising the following steps: S1. Pre-crushing: Using crushing equipment to crush feldspar-based raw ore to -30 to +150 mesh to obtain feldspar-based raw material; S2. Multi-stage synergistic flotation enrichment: Feldspar-based raw materials of -30 to +150 mesh are subjected to at least three stages of flotation, and different collectors are used under different pH conditions to selectively enrich thorium-containing impurity minerals, obtain thorium-rich concentrate and simultaneously improve the grade of feldspar matrix. S3. Wet grinding and crushing: The thorium-rich concentrate is wet ground to control the particle size to -200 mesh, accounting for 60% to 85%; S4. Stepped acid leaching: At normal temperature and pressure, sulfuric acid with a concentration of 0.5-0.8 mol / L is used to perform multi-tank series acid leaching treatment on the milled slurry in stages, controlling the liquid-solid ratio at 2.5:1, to obtain thorium-containing leachate and acid cake. S5. Acid cake washing: The acid cake is washed countercurrently with water or dilute acid to obtain a washing solution containing trace amounts of thorium and a purified residue containing valuable elements such as gold, molybdenum, and silver. S6. Cyclic enrichment and acid recovery: The thorium-containing leachate produced in step S4 and the trace thorium-containing washing solution produced in step S5 are returned to step S4 for acid leaching of a new batch of thorium-rich concentrate. Multiple cycles of enrichment are performed to obtain a high-concentration thorium leachate. S7. Separation and purification of thorium: The high-concentration thorium leachate obtained in S6 is subjected to reduction, hydrolysis precipitation, and solid-liquid separation operations in sequence to obtain crude thorium hydroxide product.

2. The enrichment and separation process for thorium in feldspar-based minerals according to claim 1, characterized in that: The multi-stage coordinated flotation enrichment in S1 specifically includes: First stage flotation: Under pH conditions of 5-6, xanthate collectors are used to separate sulfide minerals such as pyrite by flotation; Second stage flotation: Under pH conditions of 2.5–3.5, amine cationic collectors are used to separate mica minerals by flotation. The third stage of flotation: under pH conditions of 3 to 4, sulfonate collectors are used to separate iron-containing alkali metal silicate minerals by flotation.

3. The enrichment and separation process for thorium in feldspar-based minerals according to claim 2, characterized in that: The first stage of flotation includes the following steps: Step 1, Slurry preparation and drug administration: The feldspar-based raw material is prepared into a slurry with a concentration of about 30-35%. After being introduced into the mixing tank, sulfuric acid is added to adjust and stabilize the pH value of the slurry at 5.0-6.

0. Then, flotation reagents are added in sequence to mix and prepare the slurry to form slurry I. Step 2, roughing: The slurry I is introduced into the roughing flotation machine for aeration flotation. The sulfide mineral particles with collectors on their surface combine with the air bubbles to float and form a foam layer. After the foam is scraped off, the roughing concentrate I is obtained, and the product in the tank is the roughing tailings I. Step 3, Fine Concentration: The roughing concentrate is introduced into the fine flotation machine for aeration flotation. Pure sulfide mineral particles with high degree of liberation float first. After the foam is scraped off, thorium-rich concentrate I is obtained. The product in the tank is the fine tailings I. The fine tailings I is returned to step 2 of the first stage flotation for roughing operation. Step 4, First Scavenging: Roughing tailings I are introduced into the first scavenging flotation machine for aeration flotation, a small amount of collector and frother are added, and after the foam is scraped off, the first scavenging concentrate I is obtained. The first scavenging concentrate is returned to Step 2 of the first stage flotation for roughing operation, and the product in the tank is the first scavenging tailings I. Step 5, Second Scavenging: The tailings I from the first scavenging are introduced into the second scavenging flotation machine for aeration flotation. A small amount of reagent is added, and after the foam is scraped off, the second scavenging concentrate I is obtained. The second scavenging concentrate I is returned to step 4 of the first stage flotation for scavenging operation. The product in the tank is the tailings from the first stage flotation.

4. The enrichment and separation process for thorium in feldspar-based minerals according to claim 3, characterized in that: The second stage of flotation includes the following steps: Step 1, Slurry preparation and reagent addition: Add the first stage flotation tailings and sulfuric acid to the slurry mixing tank, and precisely adjust the pH value of the slurry to a strongly acidic range of 2.5 to 3.

5. Then add cationic collector, dodecylamine acetate and frother to mix and form slurry II. Step 2, roughing: The conditioning slurry II is introduced into the roughing flotation machine for aeration flotation. After the foam is scraped off, the roughing concentrate II is obtained. The product in the tank is the roughing tailings II. Step 3, Refinement: The rougher concentrate II is introduced into the refiner flotation machine for aeration flotation. After the foam is scraped off, thorium-rich concentrate II is obtained. The product in the tank is the refiner tailings II. Step 4, Scavenging: The roughing tailings II are introduced into the scavenging flotation machine for aeration flotation. A small amount of collector and frother are added. After the foam is scraped off, scavenging concentrate II is obtained. Scavenging concentrate II is returned to step 2 of the second stage flotation for roughing operation. The product in the tank is the second stage flotation tailings.

5. The enrichment and separation process for thorium in feldspar-based minerals according to claim 4, characterized in that: The third stage of flotation includes the following steps: Step 1, Slurry preparation and reagent addition: The tailings from the second stage flotation are introduced into the slurry mixing tank, and the pH value of the slurry is precisely adjusted to 3.0-4.0 with acid or alkali. Then, sodium hydroxysulfonate and frother are added to mix and form slurry III. Step 2, roughing: The pulp III is introduced into the roughing flotation machine for aeration flotation. After the foam is scraped off, thorium-rich concentrate III is obtained. The product in the tank is the roughing tailings III. Step 3, Scavenging: The roughing tailings III are introduced into the scavenging flotation machine for aeration flotation, and collectors and frothers are added. After the foam is scraped off, scavenging concentrate III is obtained. Scavenging concentrate III is returned to step 2 of the third stage flotation for roughing operation. The product in the tank is the feldspar product.

6. The enrichment and separation process for thorium in feldspar-based minerals according to claim 1, characterized in that: The stepped pickling process in S4 includes the following steps: Step 1, Primary acid dissolution: The slurry after wet grinding and crushing in step S3 is introduced into the first-stage acid decomposition tank. Sulfuric acid is slowly added during the stirring process. After mixing and reaction, acid-dissolved slurry I is obtained. Step 2, Secondary Leaching: The acid-soluble slurry is introduced into the second-stage acid decomposition tank for continuous stirring and decomposition to obtain acid-soluble slurry II; Step 3, Aging and Solid-Liquid Separation: The acid-soluble slurry II is introduced into the third-stage decomposition tank for static solid-liquid separation to obtain thorium-containing leachate and acid cake.

7. The enrichment and separation process for thorium in feldspar-based minerals according to claim 1, characterized in that: S6 cycle enrichment and acid recovery includes the following steps: Step 1, Solution Collection and Analysis: The thorium-containing leachate produced in step S4 and the thorium-containing washing solution produced in step S5 are introduced into a circulating storage tank to obtain circulating mother liquor, and the free sulfuric acid concentration and thorium concentration of the circulating mother liquor are measured. Step 2, Acid replenishment calculation and adjustment: Adjust the concentration of free sulfuric acid in the circulating mother liquor to the range required in step S4; Step 3, Circulating Leaching: The circulating mother liquor with the adjusted free sulfuric acid concentration is introduced into S4 for stepwise acid leaching to obtain a new round of thorium-containing leachate, and the S6 operation is repeated based on its thorium concentration.

8. The enrichment and separation process for thorium in feldspar-based minerals according to claim 1, characterized in that: S7 specifically includes: Reduction: SO2 is introduced into a high-concentration thorium leachate or iron powder is added to reduce Fe. 3+ Reduced to Fe 2+ ; Hydrolysis precipitation: Slowly add ammonia water, controlling the final pH to 5.5-6.5, so that thorium precipitates as thorium hydroxide; Solid-liquid separation: Pressure filtration is used to separate crude thorium hydroxide product and iron-rich filtrate.