Method for selectively desiliconizing and enriching vanadium in shale vanadium ore based on hydrothermal alkaline leaching

Abstract

The invention relates to the technical field of vanadium mineral treatment, in particular to a method for selectively desiliconizing and enriching vanadium in shale vanadium ore based on hydrothermal alkaline leaching, which comprises the following steps: drying the shale vanadium ore and then crushing the shale vanadium ore to a target particle size; preparing a mixed solution containing sodium hydroxide, sodium carbonate and a nonionic surfactant; mixing the dried shale vanadium ore with the mixed solution according to a specific liquid-solid ratio; placing the mixture in a high-pressure reaction kettle for hydrothermal reaction; after the reaction is finished, carrying out solid-liquid separation to obtain a vanadium-rich solid product; the vanadium-rich solid product is washed with water; according to the method, the enrichment rate of V2O5 can reach 180%-195%, and the enrichment rate of V2O5 is far higher than that of a traditional physical separation method. Under the optimal process conditions, the enrichment rate of V2O5 can reach 190.6%, the removal rate of SiO2 reaches 68.6%, and the treatment efficiency is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of vanadium mineral processing technology, specifically to a method for selectively desilication and enriching vanadium in shale vanadium ores based on hydrothermal alkaline leaching, which is particularly suitable for processing densely intercalated, difficult-to-process shale vanadium ores. Background Technology

[0002] Vanadium is an important strategic resource, widely used in steel, chemical, and battery industries. In my country, vanadium resources are mainly found in shale vanadium deposits. These ores typically have low grades, dense mineral embedding, and high gangue mineral content, which poses significant challenges for beneficiation and enrichment.

[0003] Currently, methods for improving vanadium grade in shale vanadium deposits mainly include physical separation methods such as magnetic separation, gravity separation, flotation, and combined methods. CN119793677A discloses a beneficiation method for removing calcium and enriching vanadium in vanadium-bearing shale through gravity flotation. This method employs steps such as crushing and ball milling, spiral flow cell gravity separation, reverse flotation, and forward flotation to physically separate vanadium-rich minerals from gangue minerals. However, these physical separation methods have the following shortcomings when processing densely disseminated shale vanadium deposits: Firstly, for densely interbedded ores such as the Songtao shale vanadium deposit, the main phases are mica (density 2.76–3.10 g / cm³) and quartz (density 2.65 g / cm³). These two minerals are interbedded and have a fine grain size. The mica phase is encapsulated by the quartz phase, resulting in low efficiency of physical separation methods. Typically, when using gravity separation, the vanadium recovery rate is only around 70%, with a vanadium loss of up to 30%. Even with a combined flotation-gravity separation process, the vanadium loss is still around 14%.

[0004] Secondly, physical separation methods are complex and require the use of various flotation reagents, which not only increases production costs but also imposes environmental burdens. This is especially true for Songtao shale vanadium deposits, where the minerals are closely interlocked and have similar densities, making effective separation difficult using physical methods.

[0005] Third, traditional physical separation methods typically involve multiple steps, including crushing, grinding, classification, gravity separation, and flotation. These processes are lengthy, require significant equipment investment, and incur high operating costs.

[0006] Given the limitations of physical methods in processing densely embedded shale vanadium deposits, developing a simple and efficient chemical method for vanadium enrichment is of great significance. Hydrothermal alkaline leaching, as a potential chemical treatment method, has advantages such as mild reaction conditions and good selectivity; however, existing hydrothermal alkaline leaching processes still suffer from problems such as significant vanadium leaching losses and insufficient selectivity. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for selectively desilication and enriching vanadium in shale vanadium ores based on hydrothermal alkaline leaching. In particular, it introduces a dual-additive synergistic system to achieve efficient and selective dissolution of the quartz phase (SiO2) while maximizing the retention of the vanadium-bearing mica phase, thereby achieving the goal of efficient vanadium enrichment.

[0008] To achieve the above objectives, the technical solution provided by this invention is: a method for selectively desilication and enriching vanadium in shale vanadium ore based on hydrothermal alkaline leaching, comprising the following steps: The shale vanadium ore is dried and then crushed to the target particle size. Prepare a mixed solution containing sodium hydroxide, sodium carbonate, and a nonionic surfactant; The dried shale vanadium ore is mixed with the mixed solution according to a specific liquid-solid ratio; The mixture was placed in a high-pressure reactor for hydrothermal reaction. After the reaction is complete, solid-liquid separation is performed to obtain a vanadium-rich solid product; The vanadium-rich solid product is washed with water; The treated product is dried to obtain the final vanadium-enriched product.

[0009] Preferably, the shale vanadium ore is dried at 105-110℃ for 4-6 hours, then crushed to a particle size of 0.074-0.150 mm, and dried at 105-110℃ for 4-6 hours.

[0010] Preferably, the concentration of sodium hydroxide in the mixed solution is 140–160 g / L, the concentration of sodium carbonate is 5–10 g / L, and the concentration of nonionic surfactant is 0.1–0.3 g / L.

[0011] More preferably, the concentration of sodium hydroxide in the mixed solution is 145-155 g / L, the concentration of sodium carbonate is 6-8 g / L, and the concentration of nonionic surfactant is 0.15-0.25 g / L.

[0012] Preferably, the nonionic surfactant is an octylphenol polyoxyethylene ether or a polyethylene glycol alkyl ether surfactant, preferably Triton X-100 or polyethylene glycol dodecyl ether.

[0013] Preferably, the liquid-to-solid ratio is 4–6 mL / g.

[0014] Preferably, the hydrothermal reaction temperature is 175-195℃ and the reaction time is 15-35 minutes.

[0015] More preferably, the temperature of the hydrothermal reaction is 180-190°C, and the reaction time is 15-25 minutes.

[0016] Preferably, the preparation steps of the mixed solution include: first adding sodium carbonate to sodium hydroxide solution and dissolving it completely, then slowly adding a pre-diluted nonionic surfactant and stirring for 10-15 minutes to disperse it evenly.

[0017] Preferably, the water washing process includes washing the solid product 2 to 3 times with deionized water at a liquid-to-solid ratio of 8-12:1, with each washing session lasting 8 to 12 minutes.

[0018] This invention achieves the following beneficial effects by introducing a dual-additive system: 1. Highly efficient enrichment effect: The method of this invention can achieve a V2O5 enrichment rate of 180% to 195%, which is far higher than that of traditional physical sorting methods. Under optimal process conditions, the V2O5 enrichment rate can reach 190.6%, and the SiO2 removal rate can reach 68.6%, significantly improving the processing efficiency.

[0019] 2. Solves the problem of difficult-to-process ores: This invention is particularly suitable for densely embedded shale vanadium ores, effectively overcoming the difficulty of separating densely embedded minerals by traditional physical sorting methods.

[0020] 3. Simplified process and reduced cost: Compared with the traditional multi-step physical sorting process, the present invention adopts a one-step hydrothermal treatment, which greatly simplifies the process, reduces equipment investment by about 40%, and reduces the overall processing cost by about 25%.

[0021] 4. Environmentally friendly: It avoids the use of large amounts of flotation reagents, and the alkali solution can be recycled, reducing the environmental burden.

[0022] 5. Clear selective mechanism: Based on the synergistic effect of Na2CO3 and nonionic surfactant, a dual synergistic control mechanism for accelerating silicon dissolution and protecting vanadium is realized, resulting in good dissolution selectivity and low vanadium loss. Detailed Implementation

[0023] This invention provides a method for selectively desilication and enriching vanadium in shale vanadium ores based on hydrothermal alkaline leaching. Specifically, it introduces a dual-additive system of Na₂CO₃ and a surfactant, achieving selective dissolution of SiO₂ and efficient enrichment of vanadium by controlling the hydrothermal alkaline leaching reaction parameters. The invention is described in detail below with reference to specific embodiments, but the scope of protection of this invention is not limited thereto.

[0024] The principle of this invention for selective desilication and vanadium enrichment through hydrothermal alkaline leaching is based on the difference in solubility selectivity between the main phases in shale vanadium ore—mica and quartz—under alkaline conditions. Under suitable temperature and NaOH concentration conditions, the addition of Na₂CO₃ and a nonionic surfactant constructs a synergistic system, achieving preferential dissolution of SiO₂ and efficient enrichment of vanadium.

[0025] The specific mechanism of action can be summarized in the following three aspects: 1. Mechanism by which sodium carbonate promotes silicon dissolution: CO3²⁻ ions can react with Si-O bonds, accelerating the hydrolysis of Si-O-Si bonds and promoting the conversion of SiO2 to soluble Na2SiO3. The chemical reaction formulas are: SiO2(s) + 2NaOH(aq) → Na2SiO3(aq) + H2O(l) or SiO2(s) + Na2CO3=(s) → Na2SiO3(aq) + CO2(g). 2- It serves to regulate alkalinity and promote the dissolution of SiO2.

[0026] 2. Selective protection mechanism of surfactant: The hydrophilic head group of nonionic surfactant forms hydrogen bonds with oxygen atoms on the surface of vanadium-containing mica, and the hydrophobic tail chain forms a semi-permeable membrane structure on the mica surface, which hinders the diffusion of OH⁻ into the interlayer of mica and reduces the breaking of vanadium-oxygen bonds, thereby forming a dynamic permeable barrier that allows SiO2 dissolution products to diffuse out, but inhibits the dissolution of vanadium.

[0027] 3. Synergistic effect of two components: Na2CO3 increases the alkalinity of the system and promotes the directional adsorption of surfactants on the mineral surface; at the same time, the surfactant reduces the liquid-solid interfacial tension, promotes full contact between sodium carbonate and silicate, and forms a synergistic controlled cycle of accelerated silicon dissolution and vanadium protection, so as to achieve efficient removal of SiO2 and selective enrichment of vanadium.

[0028] Example 1: Basic Process Flow In this embodiment, Songtao shale vanadium ore (initial V2O5 content 0.85%, SiO2 content 65.3%) is used as raw material and processed using the following steps: First, the shale vanadium ore sample is dried at 105℃ for 4 hours. Then, the Songtao shale vanadium ore is crushed to a density of 100% passing through a 100-mesh sieve and 80% passing through a 200-mesh sieve (approximately corresponding to a particle size range of 0.150–0.074 mm).

[0029] Next, prepare the treatment solution. Weigh 75g of analytical grade sodium hydroxide and dissolve it in an appropriate amount of deionized water. Then add 3.5g of analytical grade sodium carbonate. After it is completely dissolved, slowly add 0.1g of Triton X-100 (Sigma-Aldrich, USA, analytical grade) that has been diluted with 10mL of deionized water. Stir thoroughly for 15 minutes to ensure uniform dispersion. Finally, dilute to 500mL with deionized water to obtain a mixed solution containing 150g / L NaOH, 7g / L Na2CO3 and 0.2g / L Triton X-100.

[0030] Then, weigh 25g of dried shale vanadium ore sample, add 125mL of the above-prepared mixed solution (liquid-solid ratio of 5mL / g), stir thoroughly and transfer to a stainless steel high-pressure reactor lined with polytetrafluoroethylene (model: YZHR-500), tighten the reactor and place it in an electric heating drying oven (model: DHG-9140).

[0031] Next, the temperature was set to 185℃ and the reaction was maintained at that temperature for 20 minutes (excluding the heating time, the heating rate was approximately 5℃ / min). After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The reaction vessel was then opened, and the reaction product was transferred to a Buchner funnel for filtration to separate the solid product.

[0032] Subsequently, the solid product was washed with deionized water at a liquid-to-solid ratio of 10:1, for a total of 3 washes, each lasting 10 minutes, to ensure that the alkaline solution was fully eluted.

[0033] Finally, the washed solid was dried at 105℃ for 4 hours to obtain the final vanadium-enriched product. The product was tested and found to have a V₂O₅ content of 1.62% and an enrichment rate of 190.6% (calculated as: enrichment rate = V₂O₅ content after treatment / V₂O₅ content of the original ore × 100%). Simultaneously, the SiO₂ content decreased to 20.5%, with a removal rate of 68.6%.

[0034] Example 2: Effect of NaOH concentration This example investigated the effect of NaOH concentration on the hydrothermal alkaline leaching desilication and vanadium enrichment effect. The experimental steps were basically the same as in Example 1, except for the change in NaOH concentration, as detailed below: After drying at 105℃ for 4 hours, the Songtao shale vanadium ore was crushed to 0.074-0.150 mm and set aside. Mixed solutions containing different concentrations of NaOH (140 g / L, 145 g / L, 150 g / L, 155 g / L, 160 g / L) were prepared, while maintaining the Na2CO3 concentration at 7 g / L and the Triton X-100 concentration at 0.2 g / L.

[0035] The dried shale vanadium ore was thoroughly mixed with each of the mixed solutions at a liquid-to-solid ratio of 5 mL / g, and placed in a high-pressure reactor. The mixture was then reacted at 185°C for 20 minutes. After the reaction, solid-liquid separation, water washing, and drying were performed to obtain a series of vanadium-enriched products.

[0036] Based on testing and analysis, the performance of the products obtained under different NaOH concentrations is as follows: When the NaOH concentration is 140 g / L, the V2O5 enrichment rate is 170.2% and the SiO2 removal rate is 62.8%. When the NaOH concentration is 145 g / L, the V2O5 enrichment rate is 174.5%, and the SiO2 removal rate is 64.3%. When the NaOH concentration is 150 g / L, the V2O5 enrichment rate is 190.6%, and the SiO2 removal rate is 68.6%. When the NaOH concentration is 155 g / L, the V2O5 enrichment rate is 185.4%, and the SiO2 removal rate is 70.2%. When the NaOH concentration is 160 g / L, the V2O5 enrichment rate is 179.8% and the SiO2 removal rate is 71.5%.

[0037] The results showed that the SiO2 removal rate gradually increased with increasing NaOH concentration. Within the NaOH concentration range of 140–150 g / L, the V2O5 enrichment rate increased with increasing NaOH concentration. However, when the NaOH concentration exceeded 150 g / L, the V2O5 enrichment rate began to decrease. This is mainly because under high NaOH concentrations, the dissolution of the vanadium-containing mica phase is accelerated, leading to more vanadium entering the solution rather than remaining in the solid phase. Considering all factors, a NaOH concentration of 150 g / L yielded the best V2O5 enrichment effect.

[0038] Example 3: Effect of sodium carbonate concentration This example investigated the effect of Na₂CO₃ concentration on the hydrothermal alkaline leaching desilication and vanadium enrichment effect. The experimental procedures were basically the same as in Example 1, except for the change in Na₂CO₃ concentration, as detailed below: After drying at 105℃ for 4 hours, the Songtao shale vanadium ore was crushed to 0.074-0.150 mm and set aside. Mixed solutions containing different concentrations of Na2CO3 (5 g / L, 6 g / L, 7 g / L, 8 g / L, 10 g / L) were prepared, while maintaining the NaOH concentration at 150 g / L and the Triton X-100 concentration at 0.2 g / L.

[0039] The dried shale vanadium ore was thoroughly mixed with each of the mixed solutions at a liquid-to-solid ratio of 5 mL / g, and placed in a high-pressure reactor. The mixture was then reacted at 185°C for 20 minutes. After the reaction, solid-liquid separation, water washing, and drying were performed to obtain a series of vanadium-enriched products.

[0040] Based on testing and analysis, the performance of the products obtained under different Na2CO3 concentrations is as follows: When the Na2CO3 concentration is 5 g / L, the V2O5 enrichment rate is 178.5%, and the SiO2 removal rate is 65.3%. When the Na2CO3 concentration is 6 g / L, the V2O5 enrichment rate is 185.2%, and the SiO2 removal rate is 67.4%. When the Na2CO3 concentration is 7 g / L, the V2O5 enrichment rate is 190.6%, and the SiO2 removal rate is 68.6%. When the Na2CO3 concentration is 8 g / L, the V2O5 enrichment rate is 189.8%, and the SiO2 removal rate is 68.9%. When the Na2CO3 concentration is 10 g / L, the V2O5 enrichment rate is 184.5% and the SiO2 removal rate is 69.5%.

[0041] The results showed that the SiO2 removal rate increased with increasing Na2CO3 concentration, but the rate of increase gradually decreased. The V2O5 enrichment rate reached its highest value of 190.6% at a Na2CO3 concentration of 7 g / L; further increases in Na2CO3 concentration led to a decrease in the V2O5 enrichment rate. This indicates that an appropriate amount of Na2CO3 can promote the dissolution of SiO2, but excessive Na2CO3 may affect the adsorption effect of surfactants on the mineral surface, reducing the protective effect on the vanadium-containing mica phase. Therefore, a Na2CO3 concentration of 7 g / L is preferable.

[0042] Example 4: Effect of surfactant concentration This example investigated the effect of Triton X-100 concentration on the vanadium enrichment effect of hydrothermal alkaline leaching desilication. The experimental procedures were basically the same as in Example 1, except for the change in Triton X-100 concentration, as detailed below: After drying at 105℃ for 4 hours, the Songtao shale vanadium ore was crushed to 0.074-0.150 mm and set aside. Mixed solutions containing different concentrations of Triton X-100 (0.1 g / L, 0.15 g / L, 0.2 g / L, 0.25 g / L, and 0.3 g / L) were prepared, while maintaining the NaOH concentration at 150 g / L and the Na2CO3 concentration at 7 g / L.

[0043] The dried shale vanadium ore was thoroughly mixed with each of the mixed solutions at a liquid-to-solid ratio of 5 mL / g, and placed in a high-pressure reactor. The mixture was then reacted at 185°C for 20 minutes. After the reaction, solid-liquid separation, water washing, and drying were performed to obtain a series of vanadium-enriched products.

[0044] Based on testing and analysis, the performance of the products obtained under different Triton X-100 concentrations is as follows: When the Triton X-100 concentration is 0.1 g / L, the V2O5 enrichment rate is 178.6% and the SiO2 removal rate is 68.2%. When the Triton X-100 concentration is 0.15 g / L, the V2O5 enrichment rate is 185.3%, and the SiO2 removal rate is 68.4%. When the Triton X-100 concentration is 0.2 g / L, the V2O5 enrichment rate is 190.6% and the SiO2 removal rate is 68.6%. When the Triton X-100 concentration is 0.25 g / L, the V2O5 enrichment rate is 187.2% and the SiO2 removal rate is 68.5%. When the Triton X-100 concentration is 0.3 g / L, the V2O5 enrichment rate is 182.7% and the SiO2 removal rate is 67.9%.

[0045] The results showed that the surfactant concentration had little effect on the SiO2 removal rate, but a significant impact on the V2O5 enrichment rate. With increasing Triton X-100 concentration, V2O5 enrichment initially increased and then decreased, reaching a maximum at 0.2 g / L. This is because an appropriate amount of surfactant can form a protective layer on the vanadium-containing mica surface, inhibiting vanadium dissolution; however, excessive surfactant may increase solution viscosity, affecting mass transfer, and may even form micelle structures, interfering with the normal hydrothermal reaction process. Therefore, a Triton X-100 concentration of 0.2 g / L is optimal.

[0046] Example 5: Effect of reaction temperature This example investigated the effect of reaction temperature on the vanadium enrichment effect of hydrothermal alkaline leaching for desilication. The experimental steps were basically the same as in Example 1, except for the change in reaction temperature, as detailed below: After drying at 105℃ for 4 hours, the Songtao shale vanadium ore was crushed to 0.074-0.150 mm and set aside. A mixed solution containing 150 g / L NaOH, 7 g / L Na2CO3 and 0.2 g / L Triton X-100 was prepared.

[0047] The dried shale vanadium ore was thoroughly mixed with the mixed solution at a liquid-to-solid ratio of 5 mL / g and placed in a high-pressure reactor. The mixture was then reacted for 20 minutes at different temperatures (175℃, 180℃, 185℃, 190℃, and 195℃). After the reaction, solid-liquid separation, water washing, and drying were performed to obtain a series of vanadium-enriched products.

[0048] Based on testing and analysis, the performance of the products obtained under different reaction temperature conditions is as follows: At a reaction temperature of 175℃, the V2O5 enrichment rate was 158.3%, and the SiO2 removal rate was 58.2%. At a reaction temperature of 180℃, the V2O5 enrichment rate was 174.8%, and the SiO2 removal rate was 63.5%. At a reaction temperature of 185℃, the V2O5 enrichment rate was 190.6%, and the SiO2 removal rate was 68.6%. At a reaction temperature of 190℃, the V2O5 enrichment rate was 187.3%, and the SiO2 removal rate was 71.2%. At a reaction temperature of 195℃, the enrichment rate of V2O5 was 173.0%, and the removal rate of SiO2 was 72.4%.

[0049] The results showed that the SiO2 removal rate gradually increased with increasing reaction temperature. The V2O5 enrichment rate first increased and then decreased, reaching its highest value at 185℃. This is because higher temperatures accelerate the reaction kinetics and promote the dissolution of SiO2, but excessively high temperatures can destroy the protective layer formed by the surfactant on the mica surface, accelerating the dissolution of the vanadium-containing mica phase and leading to more vanadium entering the solution. Therefore, a reaction temperature of 185℃ is the most suitable.

[0050] Example 6: Effect of reaction time This embodiment investigated the effect of reaction time on the vanadium enrichment effect of hydrothermal alkaline leaching desilication. The experimental steps were basically the same as in Example 1, except for the change in reaction time, as detailed below: After drying at 105℃ for 4 hours, the Songtao shale vanadium ore was crushed to 0.074-0.150 mm and set aside. A mixed solution containing 150 g / L NaOH, 7 g / L Na2CO3 and 0.2 g / L Triton X-100 was prepared.

[0051] The dried shale vanadium ore was thoroughly mixed with the mixed solution at a liquid-to-solid ratio of 5 mL / g and placed in a high-pressure reactor. The mixture was then reacted at 185°C for different times (15 min, 20 min, 25 min, 30 min, and 35 min). After the reaction, solid-liquid separation, water washing, and drying were performed to obtain a series of vanadium-enriched products.

[0052] Based on testing and analysis, the performance of the products obtained under different reaction time conditions is as follows: When the reaction time was 15 min, the V2O5 enrichment rate was 165.4% and the SiO2 removal rate was 61.2%. When the reaction time was 20 min, the V2O5 enrichment rate was 190.6% and the SiO2 removal rate was 68.6%. When the reaction time was 25 min, the V2O5 enrichment rate was 188.7% and the SiO2 removal rate was 69.5%. When the reaction time was 30 min, the V2O5 enrichment rate was 184.2% and the SiO2 removal rate was 70.1%. When the reaction time was 35 min, the enrichment rate of V2O5 was 172.5% and the removal rate of SiO2 was 70.3%.

[0053] The results showed that the SiO2 removal rate gradually increased with increasing reaction time, but the rate of increase gradually decreased. The V2O5 enrichment rate reached its highest value after 20 min of reaction; further extending the reaction time resulted in a decrease in the V2O5 enrichment rate. This indicates that in the chemical treatment system of this invention, the selective dissolution of SiO2 and the enrichment of vanadium reach an optimal balance point at around 20 min. Further extending the reaction time leads to more vanadium dissolution, which is detrimental to vanadium enrichment. Therefore, a reaction time of 20 min is preferable.

[0054] Example 7: Effect of Liquid-to-Solid Ratio This embodiment investigated the effect of the liquid-to-solid ratio on the vanadium enrichment effect of hydrothermal alkaline leaching desilication. The experimental steps were basically the same as in Example 1, except for the change in the liquid-to-solid ratio, as detailed below: After drying at 105℃ for 4 hours, the Songtao shale vanadium ore was crushed to 0.074-0.150 mm and set aside. A mixed solution containing 150 g / L NaOH, 7 g / L Na2CO3 and 0.2 g / L Triton X-100 was prepared.

[0055] The dried shale vanadium ore was thoroughly mixed with the mixed solution at different liquid-to-solid ratios (4 mL / g, 4.5 mL / g, 5 mL / g, 5.5 mL / g, and 6 mL / g), and placed in a high-pressure reactor. The mixture was reacted at 185°C for 20 minutes. After the reaction, solid-liquid separation, water washing, and drying were performed to obtain a series of vanadium-enriched products.

[0056] Based on testing and analysis, the performance of the products obtained under different liquid-to-solid ratio conditions is as follows: At a liquid-to-solid ratio of 4 mL / g, the V₂O₅ enrichment rate was 166.9%, and the SiO₂ removal rate was 63.4%. At a liquid-to-solid ratio of 4.5 mL / g, the V₂O₅ enrichment rate was 180.3%, and the SiO₂ removal rate was 65.9%. When the liquid-to-solid ratio is 5 mL / g, the V2O5 enrichment rate is 190.6%, and the SiO2 removal rate is 68.6%. At a liquid-to-solid ratio of 5.5 mL / g, the V₂O₅ enrichment rate was 187.7%, and the SiO₂ removal rate was 69.1%. When the liquid-to-solid ratio is 6 mL / g, the enrichment rate of V2O5 is 181.2% and the removal rate of SiO2 is 69.3%.

[0057] The results showed that the SiO2 removal rate increased with increasing liquid-to-solid ratio, but the rate of increase gradually decreased. The V2O5 enrichment rate reached its highest value at a liquid-to-solid ratio of 5 mL / g; further increasing the liquid-to-solid ratio resulted in a decrease in the V2O5 enrichment rate. This is because appropriately increasing the liquid-to-solid ratio is beneficial for improving the mass transfer efficiency of the reaction system and promoting the dissolution of SiO2, but an excessively high liquid-to-solid ratio increases the contact opportunities between the vanadium-containing mica phase and the solution, leading to the dissolution of more vanadium. Considering all factors, a liquid-to-solid ratio of 5 mL / g is preferable.

[0058] Example 8: The Influence of Surfactant Type This example investigated the effect of different types of nonionic surfactants on the hydrothermal alkaline leaching desilication and vanadium enrichment. The experimental procedures were basically the same as in Example 1, except that different types of surfactants were used, as detailed below: After drying at 105℃ for 4 hours, the Songtao shale vanadium ore was crushed to 0.074-0.150 mm and set aside. Mixed solutions containing 150 g / L NaOH, 7 g / L Na2CO3, and 0.2 g / L of different types of surfactants (Triton X-100, Brij 30, Tween20) were prepared separately.

[0059] The dried shale vanadium ore was thoroughly mixed with each of the mixed solutions at a liquid-to-solid ratio of 5 mL / g, and placed in a high-pressure reactor. The mixture was then reacted at 185°C for 20 minutes. After the reaction, solid-liquid separation, water washing, and drying were performed to obtain a series of vanadium-enriched products.

[0060] Based on testing and analysis, the performance of products obtained under different types of surfactant treatment conditions is as follows: When using Triton X-100, the V2O5 enrichment rate was 190.6%, and the SiO2 removal rate was 68.6%. When using Brij 30, the V2O5 enrichment rate was 186.8%, and the SiO2 removal rate was 67.9%. When using Tween 20, the V2O5 enrichment rate was 174.5%, and the SiO2 removal rate was 66.4%.

[0061] The results showed that different types of nonionic surfactants had varying effects on vanadium enrichment through hydrothermal alkaline leaching and desilication. Triton X-100 showed the best effect, followed by Brij 30, while Tween 20 was relatively weak. This is mainly because the different molecular structures and hydrophilic-lipophilic balance (HLB) values ​​of the various surfactants lead to differences in their adsorption capacity and protective effect on vanadium-containing mica surfaces. Among them, Triton X-100, an octylphenol polyoxyethylene ether surfactant, has the best molecular structure matching the surface characteristics of vanadium-containing mica, and can form a more effective protective layer, inhibiting the dissolution of vanadium.

[0062] Example 9: Effect of Particle Size This embodiment investigated the effect of shale vanadium ore particle size on the vanadium enrichment effect of hydrothermal alkaline leaching desilication. The experimental steps were basically the same as in Example 1, the difference being the change in ore particle size, as detailed below: After drying at 105℃ for 4 hours, the Songtao shale vanadium ore was crushed to different particle sizes (0.15~0.074mm, 0.074~0.045mm, <0.045mm) for later use. A mixed solution containing 150g / L NaOH, 7g / L Na2CO3 and 0.2g / L Triton X-100 was prepared.

[0063] Dry shale vanadium ore of different particle sizes was thoroughly mixed with the mixed solution at a liquid-to-solid ratio of 5 mL / g and placed in a high-pressure reactor. The mixture was then reacted at 185°C for 20 minutes. After the reaction, solid-liquid separation, water washing, and drying were performed to obtain a series of vanadium-enriched products.

[0064] Based on testing and analysis, the performance of products obtained under different particle size conditions is as follows: When the particle size is 0.15–0.074 mm, the V₂O₅ enrichment rate is 190.6%, and the SiO₂ removal rate is 68.6%. When the particle size is 0.074–0.045 mm, the V₂O₅ enrichment rate is 178.2%, and the SiO₂ removal rate is 72.3%. When the particle size is <0.045mm, the V2O5 enrichment rate is 165.8% and the SiO2 removal rate is 75.6%.

[0065] The results show that as the ore particle size decreases, the SiO2 removal rate gradually increases, but the V2O5 enrichment rate decreases. This is because smaller particle size results in a larger specific surface area, allowing for more thorough contact with the reaction solution and more complete dissolution of SiO2; however, it also makes the vanadium-containing mica phase more easily dissolved, leading to more vanadium entering the solution. Considering that the main objective of this invention is vanadium enrichment, a particle size range of 0.15–0.074 mm is most suitable.

[0066] Comparative Example 1: Hydrothermal Alkali Immersion without Additives This comparative study investigated the effect of hydrothermal alkaline leaching using only NaOH without the addition of Na2CO3 and surfactant. The experimental procedures are as follows: After drying at 105℃ for 4 hours, the Songtao shale vanadium ore is crushed to 0.074-0.150 mm and set aside. Prepare a 150 g / L NaOH solution.

[0067] The dried shale vanadium ore was thoroughly mixed with NaOH solution at a liquid-to-solid ratio of 5 mL / g and placed in a high-pressure reactor. The mixture was then reacted at 185°C for 20 minutes. After the reaction, solid-liquid separation, water washing, and drying were performed to obtain the vanadium-enriched product.

[0068] Analysis showed that the treated product had a V₂O₅ enrichment rate of 159.3% and a SiO₂ removal rate of 62.7%. Compared with Example 1 (V₂O₅ enrichment rate of 190.6% and SiO₂ removal rate of 68.6%), the hydrothermal alkaline leaching effect without additives was significantly worse, with the V₂O₅ enrichment rate decreasing by 31.3 percentage points and the SiO₂ removal rate decreasing by 5.9 percentage points. This fully demonstrates the synergistic effect of Na₂CO₃ and surfactants in promoting SiO₂ dissolution and protecting vanadium.

[0069] Comparative Example 2: Hydrothermal alkaline leaching with only Na2CO3 added This comparative study investigated the effect of hydrothermal alkaline leaching with only Na2CO3 added and no surfactant. The experimental procedure is as follows: After drying at 105℃ for 4 hours, the Songtao shale vanadium ore was crushed to 0.074-0.150 mm and set aside. A mixed solution containing 150 g / L NaOH and 7 g / L Na2CO3 was prepared.

[0070] The dried shale vanadium ore was thoroughly mixed with the mixed solution at a liquid-to-solid ratio of 5 mL / g, and placed in a high-pressure reactor. The mixture was then reacted at 185°C for 20 minutes. After the reaction, solid-liquid separation, water washing, and drying were performed to obtain the vanadium-enriched product.

[0071] Analysis showed that the treated product had a V2O5 enrichment rate of 175.8% and a SiO2 removal rate of 67.5%. Although this was an improvement over Comparative Example 1, it was still lower than Example 1 (V2O5 enrichment rate of 190.6%, SiO2 removal rate of 68.6%). This indicates that Na2CO3 can indeed promote the dissolution of SiO2, but the lack of surfactant protection for the vanadium-containing mica phase resulted in significant vanadium loss and limited enrichment effect.

[0072] Comparative Example 3: Hydrothermal alkaline leaching with only surfactant added This comparative study investigated the effect of hydrothermal alkaline leaching with only surfactant added and without the addition of Na2CO3. The experimental procedure is as follows: After drying at 105℃ for 4 hours, the Songtao shale vanadium ore was crushed to 0.074-0.150 mm and set aside. A mixed solution containing 150 g / L NaOH and 0.2 g / L Triton X-100 was prepared.

[0073] The dried shale vanadium ore was thoroughly mixed with the mixed solution at a liquid-to-solid ratio of 5 mL / g, and placed in a high-pressure reactor. The mixture was then reacted at 185°C for 20 minutes. After the reaction, solid-liquid separation, water washing, and drying were performed to obtain the vanadium-enriched product.

[0074] Analysis of the test results showed that the V2O5 enrichment rate of the treated product was 172.1%, and the SiO2 removal rate was 61.8%. Compared with Example 1, the V2O5 enrichment rate decreased by 18.5 percentage points, and the SiO2 removal rate decreased by 6.8 percentage points. This indicates that although adding surfactants can protect the vanadium-containing mica phase to some extent and reduce vanadium dissolution, the lack of Na2CO3's effect of promoting SiO2 dissolution results in low SiO2 removal efficiency and an unsatisfactory overall enrichment effect.

[0075] Comparative Example 4: Hydrothermal Alkali Immersion at Excessively High Temperature This comparative study investigated the effect of hydrothermal alkaline leaching at higher temperatures. The experimental procedures are as follows: After drying at 105℃ for 4 hours, the Songtao shale vanadium ore was crushed to 0.074-0.150 mm and set aside. A mixed solution containing 150 g / L NaOH, 7 g / L Na2CO3 and 0.2 g / L Triton X-100 was prepared.

[0076] The dried shale vanadium ore was thoroughly mixed with the mixed solution at a liquid-to-solid ratio of 5 mL / g, and placed in a high-pressure reactor. The mixture was then reacted at 220°C for 20 minutes. After the reaction, solid-liquid separation, water washing, and drying were performed to obtain the vanadium-enriched product.

[0077] Analysis of the test results showed that the V2O5 enrichment rate of the treated product was 142.5%, and the SiO2 removal rate was 76.8%. Although the SiO2 removal rate was high, the V2O5 enrichment rate decreased significantly, lower than the 190.6% of Example 1. This is because excessively high temperatures can damage the structure and function of the surfactant and accelerate the dissolution of the vanadium-containing mica phase, resulting in a large amount of vanadium entering the solution, which is not conducive to vanadium enrichment.

[0078] Comparative Example 5: Processing using conventional physical sorting methods This comparative example uses the traditional combined gravity flotation beneficiation method to process the same Songtao shale vanadium ore. The specific steps are as follows: The Songtao shale vanadium ore was crushed to below 0.074 mm, wet-milled, and then classified. The classification products were subjected to spiral sluice gravity separation to obtain coarse-grained and fine-grained vanadium ore products. The coarse-grained vanadium ore product was subjected to reverse flotation, while the fine-grained vanadium ore product was deslimed and then subjected to direct flotation. Finally, the various concentrate products were combined to obtain the final vanadium concentrate.

[0079] After testing and analysis, the final V2O5 enrichment rate of the vanadium concentrate was 155.8%, and the vanadium recovery rate was 86.2%. Compared with Example 1 of the present invention, the enrichment effect of the physical separation method is significantly worse, and the process is more complex, requiring the use of multiple flotation reagents, resulting in a heavier environmental burden.

[0080] To more intuitively compare the differences between the present invention and the comparative examples, the main performance indicators of each embodiment and the comparative examples are summarized in Table 1 below: Table 1 Performance comparison of each embodiment and comparative example As shown in Table 1, under suitable process conditions (Example 1), the dual-additive synergistic system of the present invention achieves the highest V2O5 enrichment rate (190.6%) and an ideal SiO2 removal rate (68.6%). Compared with Comparative Example 1, which uses NaOH alone, the V2O5 enrichment rate is increased by 31.3 percentage points; compared with Comparative Example 2, which only adds Na2CO3, the increase is 14.8 percentage points; compared with Comparative Example 3, which only adds surfactant, the increase is 18.5 percentage points; and compared with Comparative Example 5, which uses the traditional physical sorting method, the increase is 34.8 percentage points.

[0081] The results of each embodiment further demonstrate that process parameters such as NaOH concentration, Na2CO3 concentration, surfactant concentration, reaction temperature, reaction time, and liquid-solid ratio have a significant impact on the hydrothermal alkaline leaching desiliconization and vanadium enrichment effect. Optimizing these parameters can yield the best treatment results. The synergistic effect of Na2CO3 and the surfactant is the core innovation of this invention; their combined use achieves a dual control effect of accelerating silicon dissolution and protecting vanadium, significantly improving the vanadium enrichment rate.

[0082] In practical applications, the parameters provided by this invention can be appropriately adjusted according to the specific ore characteristics and production needs to achieve the best processing effect. For example, for ores with high SiO2 content, the Na2CO3 concentration or reaction temperature can be appropriately increased to improve the SiO2 removal rate; for ores where vanadium is easily soluble, the surfactant concentration can be appropriately increased to enhance the protection of vanadium-containing minerals.

[0083] The method of this invention has been verified on a laboratory scale and has been scaled up to a small scale. Compared with traditional physical sorting methods, this invention has the following advantages: 1. Simplified process flow: The process is simplified from multiple physical sorting steps to a single hydrothermal treatment, reducing the number of steps by more than 50% and equipment investment by about 40%.

[0084] 2. Improved processing efficiency: The enrichment rate of V2O5 can reach over 190%, which is much higher than the approximately 155% of the traditional physical separation method, and the vanadium recovery rate is increased by about 15 percentage points.

[0085] 3. Wide applicability: It is particularly suitable for densely interbedded shale vanadium deposits that are difficult to process using traditional physical separation methods, providing a new approach for the efficient utilization of such difficult-to-process ores.

[0086] 4. Environmentally friendly: It avoids the use of large amounts of flotation reagents, and the reaction waste liquid can be recycled, reducing the environmental burden. Sodium silicate in the waste liquid can be recovered and reused through crystallization, realizing comprehensive resource utilization.

[0087] 5. Significant economic benefits: Although the introduction of additives slightly increases the cost of the reagents (about 15%), the overall processing cost is reduced by about 25% due to the simplification of the process, the reduction of equipment investment and the improvement of vanadium recovery rate, resulting in significant economic benefits.

[0088] In summary, the method for selective desilication enrichment of vanadium in shale vanadium ore based on hydrothermal alkaline leaching provided by this invention, especially the synergistic system of Na2CO3 and surfactant dual additives, has a clear technical principle and significant application effect, providing a new technical path for the efficient utilization of shale vanadium ore.

Claims

1. A method for selectively desilication and enriching vanadium in shale vanadium ores based on hydrothermal alkaline leaching, characterized in that, Includes the following steps: The shale vanadium ore is dried and then crushed to the target particle size. Prepare a mixed solution containing sodium hydroxide, sodium carbonate, and a nonionic surfactant; The dried shale vanadium ore is mixed with the mixed solution according to a specific liquid-solid ratio; The mixture was placed in a high-pressure reactor for hydrothermal reaction. After the reaction is complete, solid-liquid separation is performed to obtain a vanadium-rich solid product; The vanadium-rich solid product is washed with water; The treated product is dried to obtain the final vanadium-enriched product.

2. The method according to claim 1, characterized in that, The shale vanadium ore is dried at 105-110℃ for 4-6 hours, then crushed to a particle size of 0.074-0.150 mm, and dried at 105-110℃ for 4-6 hours.

3. The method according to claim 1, characterized in that, The concentration of sodium hydroxide in the mixed solution is 140–160 g / L, the concentration of sodium carbonate is 5–10 g / L, and the concentration of nonionic surfactant is 0.1–0.3 g / L.

4. The method according to claim 3, characterized in that, The concentration of sodium hydroxide in the mixed solution is 145–155 g / L, the concentration of sodium carbonate is 6–8 g / L, and the concentration of nonionic surfactant is 0.15–0.25 g / L.

5. The method according to claim 1, characterized in that, The nonionic surfactant is an octylphenol polyoxyethylene ether or a polyethylene glycol alkyl ether surfactant, preferably Triton X-100 or polyethylene glycol dodecyl ether.

6. The method according to claim 1, characterized in that, The liquid-to-solid ratio is 4–6 mL / g.

7. The method according to claim 1, characterized in that, The hydrothermal reaction is carried out at a temperature of 175-195℃ for 15-35 minutes.

8. The method according to claim 7, characterized in that, The hydrothermal reaction is carried out at a temperature of 180-190℃ for 15-25 minutes.

9. The method according to claim 1, characterized in that, The preparation steps of the mixed solution include: first, adding sodium carbonate to sodium hydroxide solution and dissolving it completely, then slowly adding a pre-diluted nonionic surfactant and stirring for 10 to 15 minutes to disperse it evenly.

10. The method according to claim 1, characterized in that, The water washing process includes washing the solid product 2 to 3 times with deionized water at a liquid-to-solid ratio of 8-12:1, with each washing session lasting 8 to 12 minutes.

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