A process for preparing modified silica from vanadium acid leaching tailings of clay vanadium ore.

Abstract

This invention discloses a process for preparing modified silica from vanadium ore leaching tailings, belonging to the field of industrial waste treatment and utilization technology. The steps include: (1) non-grinding alkaline leaching of silica: vanadium ore leaching tailings are leached without grinding with sodium hydroxide and water in a certain ratio and then heated for leaching; after cooling, the residue and filtrate are obtained by solid-liquid separation, and the filtrate is water glass; (2) preparation and modification: self-composite electrolyte is added to water glass, and a new combination modifier is added, followed by acid neutralization to produce silica gel precipitate, which is dried and ground to obtain modified silica product; the electrolyte includes 60% to 80% sodium sulfate and 20% to 40% sodium carbonate by mass percentage; the modifier includes 40% to 80% hexadecyltrimethylammonium bromide and 20% to 60% sodium dodecyl sulfate by mass ratio. The process of this invention can turn the vanadium acid leaching tailings from clay vanadium ore into a valuable resource, achieving reduced treatment and resource utilization, while also producing high-quality silica products.

Description

Technical Field

[0001] This invention relates to a process for preparing modified silica from vanadium acid leaching tailings of clay vanadium ore, belonging to the field of industrial waste treatment and utilization technology. Background Technology

[0002] Vanadium clay ore is one of my country's important vanadium extraction raw materials. It is a clay mineral with low vanadium grade and a silica matrix (silica content of about 80%). Statistics show that producing 1 ton of vanadium pentoxide generates 150-200 tons of tailings. This vanadium leaching tailings not only retain a large amount of highly corrosive substances but also contain various heavy metals. Traditional stockpiling and landfilling methods not only occupy significant land resources but may also pollute water and soil resources. In recent years, the development and utilization of vanadium clay ore has increased, leading to a corresponding increase in the amount of vanadium leaching tailings and mounting environmental pressure. Therefore, there is an urgent need to explore effective methods for reducing volume and efficiently recovering resources from this tailings. Thus, the efficient extraction of silica from vanadium leaching tailings of vanadium clay ore and the preparation of modified silica is of great significance.

[0003] Silica, also known as hydrated silica (SiO2·nH2O), possesses characteristics such as high temperature resistance, non-combustibility, porosity, high surface activity, and large specific surface area, and is widely used in rubber, plastics, inks, paper, and pharmaceuticals. Preparation methods for silica include gas-phase methods, precipitation methods, microemulsion methods, and sol-gel methods. Gas-phase and precipitation methods are two main methods in industrial production. However, the gas-phase method for producing silica has limitations such as complex processes, high requirements for production equipment, and high production costs, preventing its large-scale industrial application. Therefore, precipitation methods are generally used for large-scale production of silica. It should be noted that the type and amount of electrolyte are crucial in the precipitation method for preparing silica, and further research and development are needed. This is because water glass contains a large amount of silica particles, which are reacted with a large amount of OH- under alkaline conditions. - The silica particles are surrounded and form a stable charged body, making them less prone to aggregation. Adding an electrolyte weakens the electrostatic interaction between the particles, reducing the surface charge of the silica particles and ultimately causing aggregation, which is beneficial for the precipitation process of silica.

[0004] Furthermore, the surface of silica prepared by conventional processes contains a large number of active hydroxyl groups. The presence of these active hydroxyl groups worsens the hydrophobicity of the silica product, increases particle size, and further increases surface energy, enhances aggregation, and reduces dispersibility. Therefore, to further expand the application range of silica, surface modification is necessary. Currently, the main method for silica modification is chemical modification. Chemical modification mainly includes silane coupling agent modification, alcohol ester modification, surfactant modification, and organohalosilane modification. Among these, in-situ grafting modification of silica using surfactants does not alter the phase form and crystal structure of the silica, and significantly improves many properties after modification, making it a promising method. In this method, the surfactant (i.e., the modifier) ​​is of paramount importance.

[0005] This invention is proposed to achieve effective reduction and efficient resource utilization of clay vanadium ore, and to produce high-quality (smaller particle size, stronger hydrophobicity, and larger specific surface area) silica products. Summary of the Invention

[0006] To address the issues of reduced-volume disposal and resource utilization of vanadium acid leaching tailings from vanadium extraction from clay vanadium ore, and to resolve problems such as low precipitation rate and large particle size in existing silica preparation methods, this invention proposes a process for preparing modified silica from vanadium acid leaching tailings from vanadium extraction from clay vanadium ore, specifically including the following steps:

[0007] (1) Non-grinding alkaline leaching of silicon: The vanadium acid leaching tailings of clay vanadium ore are not ground, and are mixed with sodium hydroxide and water in a certain proportion and then heated for leaching reaction. After the reaction is completed, the mixture is cooled to below 50°C, and the filter residue and filtrate are obtained by solid-liquid separation. The tailings are reduced by more than 85%, that is, the weight of the filter residue is less than 15% of the vanadium acid leaching tailings of clay vanadium ore, and the filtrate is water glass.

[0008] (2) Preparation and modification: Add the self-composite electrolyte SC-1 to water glass and add a new combination modifier for in-situ grafting modification. Then add acid to neutralize, age at constant temperature, and produce silica gel precipitate. Dry and grind the silica gel to obtain the modified silica product.

[0009] The self-formulated electrolyte SC-1 comprises 60%–80% sodium sulfate and 20%–40% sodium carbonate by mass.

[0010] The novel combined modifier comprises, by mass ratio: 40%–80% cetyltrimethylammonium bromide (CATB) and 20%–60% sodium dodecyl sulfate (SDS).

[0011] Preferably, the tailings in step (1) come from the acid leaching process of vanadium extraction from clay vanadium ore, with a silica content of more than 85% and a particle size of -2mm to -4mm. No acid leaching or grinding treatment is performed before alkali leaching of silica.

[0012] Preferably, in step (1), the alkali-slag ratio, i.e., the mass ratio of sodium hydroxide to vanadium leaching tailings from clay vanadium ore extraction, is 0.3 to 1; the liquid-solid ratio, i.e., the mass ratio of water to vanadium leaching tailings from clay vanadium ore extraction, is 3 to 6; the heating temperature is 180 to 220°C; the reaction time is 50 to 100 min; and air cooling is used to cool the temperature to below 50°C.

[0013] Preferably, the filter residue obtained from solid-liquid separation in step (1) has a mass of less than 15% of the mass of the vanadium leaching tailings from clay vanadium ore extraction. That is, after non-grinding alkali leaching of silicon, the vanadium leaching tailings from clay vanadium ore extraction are reduced by more than 85%, which can effectively achieve the reduction treatment of vanadium leaching tailings from clay vanadium ore extraction.

[0014] Preferably, the amount of the self-composite electrolyte SC-1 added in step (2) is 2% to 6% of the mass of the vanadium leaching tailings from clay vanadium ore.

[0015] Preferably, in step (2), the preparation and modification of silica are carried out simultaneously, that is, in-situ grafting modification is carried out by adding a novel combination modifier that is self-assembled and compounded. The amount of the novel combination modifier is 2% to 5% of the mass of the vanadium leaching tailings from clay vanadium ore.

[0016] Preferably, in step (2), acid is added to neutralize the solution to a pH of 7.0 to 8.5; the constant temperature aging conditions are controlled as follows: 60 to 90°C, 60 to 120 min.

[0017] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0018] (1) Vanadium extraction from clay ore inevitably produces a large amount of high-silica acid leaching tailings. In recent years, the development and utilization of clay vanadium ore has been increasing, and the amount of vanadium acid leaching tailings has also increased, putting increasing pressure on the environment. It is urgent to explore methods for reducing and recycling these tailings. This invention uses vanadium acid leaching tailings from clay vanadium ore as raw material and performs silicon leaching with non-grinding alkali. This not only reduces the amount of tailings by more than 85%, effectively reducing the amount of tailings, but also provides a cheap and readily available silicon source for the preparation of silica. This can provide a new path for the comprehensive utilization of vanadium acid leaching tailings from clay vanadium ore.

[0019] (2) During the acid leaching process of vanadium extraction from clay vanadium ore, most of the acid-soluble impurities have been dissolved and leached out. The main component of the acid leaching tailings is silicon dioxide, with a content of more than 85%. There are very few other impurities that are harmful to the preparation of silica. Therefore, the present invention does not require acid leaching to remove impurities or grinding before alkaline leaching of silicon.

[0020] (3) Water glass, the filtrate from the non-abrasive alkali leaching process for silicon, has colloidal properties. According to the DLVO theory, the stability of colloidal solutions is related to the balance between van der Waals forces and the double-layer pressure at the solid-liquid interface. Adding sufficient electrolyte to the solution can compress the double-layer around the colloidal particles, reducing the repulsive energy. At this point, the attraction between colloidal particles becomes dominant, reducing the distance between particles and causing the colloidal particles to become unstable and precipitate. However, when the double-layer can no longer be compressed, excessive electrolyte ions will hinder the aggregation between colloidal particles. Adding inorganic salt electrolytes to water glass can increase the number of microcolloidal ions in the water glass-electrolyte system, forming a large number of sodium silicate polymers. The polymers in the system have a porous structure, and the SiO2 precipitate formed on this basis has a rich porous structure and a relatively loose structure. In addition, single electrolytes often have limited effectiveness, but by controlling the type and ratio of electrolytes to achieve a positive synergistic effect, better results can be obtained with reduced dosage. Therefore, in this invention, the electrolyte SC-1 is self-formulated, comprising 60% to 80% sodium sulfate and 20% to 40% sodium carbonate by mass. SC-1 can effectively promote the formation of small aggregates of SiO2 from water glass, improve the precipitation rate, and thus easily form loose and porous SiO2 precipitates to obtain high-quality silica products.

[0021] (4) To further expand the application range of silica, surface modification of silica products is necessary. In-situ grafting modification of silica with surfactants does not alter the phase form and crystal structure of silica, and significantly improves many properties of the modified silica, making it a promising method. In this method, the surfactant, i.e., the modifier, is of paramount importance.

[0022] Cetyltrimethylammonium bromide (CATB) is a cationic surfactant, and sodium dodecyl sulfate (SDS) is an anionic surfactant. Both can be grafted onto the surface of silica via chemisorption to achieve graft modification. Similarly, single surfactants often have limited effectiveness, but by controlling the type and ratio of surfactants to achieve a synergistic effect, better results can be obtained with reduced dosage. Therefore, in this invention, the modifier, i.e., the surfactant, is autonomously compounded and assembled. The mass ratio of the novel combined modifier is: 40%–80% cetyltrimethylammonium bromide (CATB) and 20%–60% sodium dodecyl sulfate (SDS). CATB and SDS can synergistically adsorb onto the hydroxyl groups on the silica surface, improving its hydrophobic properties and forming a network structure on the silica surface, preventing further aggregation of silica particles, reducing their particle size, and creating a loose, porous structure that enhances its various properties.

[0023] In summary, the process of this invention can turn the vanadium acid leaching tailings from clay vanadium ore into a valuable resource, achieving effective volume reduction and efficient resource utilization. At the same time, the prepared silica products meet all industry standard requirements, and the modified silica products have stronger hydrophobicity, larger specific surface area and smaller particle size, which can greatly expand the application range. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of the present invention.

[0025] Figure 2 This is a particle size analysis diagram of the silica product prepared in Example 1.

[0026] Figure 3 This is a particle size analysis diagram of the silica product prepared in Example 2.

[0027] Figure 4 The particle size distribution diagram is shown for the silica product prepared in Comparative Example 1.

[0028] Figure 5 The particle size distribution diagram is shown for the silica product prepared in Comparative Example 2.

[0029] Figure 6 The particle size distribution diagram is shown for the silica product prepared in Comparative Example 3.

[0030] Figure 7 The particle size analysis diagram is shown for the silica product prepared in Comparative Example 4. Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following embodiments are merely simple examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be determined by the claims.

[0032] Example 1

[0033] A process for preparing modified silica from vanadium acid leaching tailings of clay vanadium ore is implemented as follows:

[0034] (1) Non-grinding alkali leaching of silicon: The vanadium acid leaching tailings from clay vanadium ore were taken from Shangluo, Shaanxi Province, with a particle size of -2 mm and a silicon dioxide content of 86.8%. The vanadium acid leaching tailings from clay vanadium ore were not ground or subjected to acid leaching for impurity removal. They were directly mixed with sodium hydroxide and water for heating and leaching reaction. The alkali-to-slag ratio (mass ratio of sodium hydroxide to vanadium acid leaching tailings from clay vanadium ore) was 0.8; the liquid-to-solid ratio (mass ratio of water to vanadium acid leaching tailings from clay vanadium ore) was 5; the heating temperature was 200℃; and the reaction time was 90 min. After the reaction, the mixture was cooled to below 50℃ by air cooling for solid-liquid separation, yielding filter residue and filtrate (water glass). The yield of filter residue was 10.4%, which means that 89.6% of the vanadium acid leaching tailings from clay vanadium ore were reduced.

[0035] (2) Preparation and modification: Add the self-formulated electrolyte SC-1 to water glass and add a new combination modifier for in-situ grafting modification. The amount of SC-1 is 3% of the mass of the vanadium acid leaching tailings from clay vanadium ore, and the amount of the new combination modifier is 3% of the mass of the vanadium acid leaching tailings from clay vanadium ore. Then add acid to neutralize to pH 8, and age at 80℃ for 120 min to produce silica gel precipitate. The silica gel is dried and ground to obtain the modified silica product. The self-formulated electrolyte SC-1 includes 60% sodium sulfate and 40% sodium carbonate by mass percentage. The new combination modifier includes the following components by mass ratio: 40% cetyltrimethylammonium bromide (CATB) and 60% sodium dodecyl sulfate (SDS).

[0036] In this embodiment, the silica leaching rate reached as high as 98.64%, and the amount of vanadium acid leaching tailings from clay vanadium ore extraction was reduced by nearly 90%. Through the addition of a self-formulated electrolyte and a novel combination modifier, the prepared modified silica product achieved a specific surface area of ​​316.62 m². 2 / g, median particle size (D) 50 Only 3.86μm Figure 2 As shown in the figure, the SiO2 content reaches 99.3%, and the product quality meets the requirements of the HG / T3061-2020 industry standard.

[0037] Example 2

[0038] A process for preparing modified silica from vanadium acid leaching tailings of clay vanadium ore is implemented as follows:

[0039] (1) Non-grinding alkali leaching of silicon: The vanadium acid leaching tailings from clay vanadium ore were taken from Xichuan, Henan Province, with a particle size of -3 mm and a silicon dioxide content of 85.7%. The vanadium acid leaching tailings from clay vanadium ore were not ground or subjected to acid leaching for impurity removal. They were directly mixed with sodium hydroxide and water for heating and leaching reaction. The alkali-to-slag ratio (mass ratio of sodium hydroxide to vanadium acid leaching tailings from clay vanadium ore) was 0.75; the liquid-to-solid ratio (mass ratio of water to vanadium acid leaching tailings from clay vanadium ore) was 3; the heating temperature was 180℃; and the reaction time was 50 min. After the reaction, the mixture was cooled to below 50℃ by air cooling for solid-liquid separation, yielding filter residue and filtrate (water glass). The yield of filter residue was 12.3%, which means that 87.7% of the vanadium acid leaching tailings from clay vanadium ore were reduced.

[0040] (2) Preparation and modification: Add the self-formulated electrolyte SC-1 to water glass and add a new combination modifier for in-situ grafting modification. The amount of SC-1 is 3.5% of the mass of the vanadium acid leaching tailings from clay vanadium ore, and the amount of the new combination modifier is 3% of the mass of the vanadium acid leaching tailings from clay vanadium ore. Then add acid to neutralize to pH 8.5, and age at 60℃ for 60 min to produce silica gel precipitate. The silica gel is dried and ground to obtain the modified silica product. The self-formulated electrolyte SC-1 includes 80% sodium sulfate and 20% sodium carbonate by mass percentage. The new combination modifier includes the following components by mass ratio: 80% cetyltrimethylammonium bromide (CATB) and 20% sodium dodecyl sulfate (SDS).

[0041] In this embodiment, the silica leaching rate reached as high as 97.2%, and the effective reduction in vanadium acid leaching tailings from clay vanadium ore extraction reached 87.7%. Through the addition of a self-formulated electrolyte and a novel combination modifier, the modified silica product prepared achieved a specific surface area of ​​303.15 m². 2 / g, median particle size (D) 50 Only 4.02μm Figure 3 As shown in the figure, the SiO2 content reaches 98.5%, and the product quality meets the requirements of the HG / T3061-2020 industry standard.

[0042] Comparative Example 1

[0043] In contrast, the difference between this comparative example and Example 1 is that when preparing and modifying in step (2), the added electrolyte is a single sodium carbonate, and its amount is 6% of the mass of the vanadium leaching tailings from clay vanadium ore. The remaining steps are exactly the same as in Example 1.

[0044] In this comparative example, the silica leaching rate was also as high as 98.64%, and the amount of vanadium leaching tailings from clay vanadium ore was reduced by nearly 90%. However, due to the addition of sodium carbonate as a single electrolyte, even at a dosage as high as 6%, the specific surface area of ​​the prepared modified silica product was only 255.99 m². 2 / g, median particle size (D) 50 ) is 7.60μm ( Figure 4 As shown in the figure, the SiO2 content is only 96.1%. At this time, the specific surface area, particle size index and uniformity of the resulting silica product all decreased to varying degrees. It can be seen that when using a single electrolyte, the aggregation of SiO2 particles cannot achieve the ideal effect, and the dispersibility cannot be improved more effectively under the premise of smaller particle size, thereby reducing the performance parameters of the product and failing to obtain the high-quality silica product as when the self-formulated electrolyte SC-1 is added.

[0045] Comparative Example 2

[0046] In contrast, the difference between this comparative example and Example 2 is that when preparing and modifying in step (2), the added electrolyte is a single sodium sulfate, and its amount is 5% of the mass of the vanadium leaching tailings from clay vanadium ore. The remaining steps are exactly the same as in Example 2.

[0047] In this comparative example, the silica leaching rate was also as high as 97.2%, and the vanadium extraction tailings from clay vanadium ore also achieved an effective reduction of 87.7%; however, due to the addition of a single electrolyte, sodium sulfate, even at a dosage of 5%, the specific surface area of ​​the prepared modified silica product was only 269.53 m². 2 / g, median particle size (D) 50 The value is 6.94 μm. Figure 5 As shown in the figure, the SiO2 content is only 95.8%. At this time, the specific surface area, particle size index and uniformity of the resulting silica product also decreased to varying degrees. It can be seen that without the use of self-blended electrolytes, and only using a single electrolyte, the positive synergistic effect between different single electrolytes formed by controlling and optimizing the type and blending ratio of electrolytes is lacking. The agglomeration of SiO2 particles does not achieve the ideal effect, and the dispersibility cannot be improved more effectively under the premise of smaller particle size. The agglomerated SiO2 particles are relatively large in size and have insufficient pore structure, thereby reducing the performance parameters of the product and failing to obtain the high-quality silica product as when self-blended electrolytes are added.

[0048] Comparative Example 3

[0049] In contrast, the difference between this comparative example and Example 1 is that, in the preparation and modification of step (2), the added modifier is a single cetyltrimethylammonium bromide (CATB), and its dosage is up to 5% of the mass of the vanadium leaching tailings from clay vanadium ore. The remaining steps are exactly the same as in Example 1.

[0050] In this comparative example, the silica leaching rate was also as high as 98.64%, and the amount of vanadium leaching tailings from clay vanadium ore was reduced by nearly 90%. However, due to the addition of a single modifier, cetyltrimethylammonium bromide (CATB), even at a dosage as high as 5%, the specific surface area of ​​the prepared modified silica product was only 284.37 m². 2 / g, median particle size (D) 50 ) is 5.35μm ( Figure 6 As shown in the figure, the SiO2 content is only 96.3%. At this time, the specific surface area, particle size index and uniformity of the obtained silica product all decrease within a certain range. It can be seen that although a single modifier can achieve in-situ grafting modification of hydroxyl groups on the surface of unmodified silica products, change the surface properties of hydroxyl groups adsorbed on the silica surface, and benefit the formation of porous and network structures in silica, the degree of modification is still not ideal even when the dosage is high. This is because the single modifier has limited ability to cover the hydroxyl groups on the surface of silica particles, resulting in a decrease in the quality of silica products.

[0051] Comparative Example 4

[0052] In contrast, the difference between this comparative example and Example 2 is that when preparing and modifying in step (2), the modifier added is a single sodium dodecyl sulfate (SDS), and its amount is 4% of the mass of the vanadium leaching tailings from clay vanadium ore. The remaining steps are exactly the same as in Example 2.

[0053] In this comparative example, the silica leaching rate was also as high as 97.2%, and the vanadium acid leaching tailings from clay vanadium ore also achieved an effective reduction of 87.7%. However, due to the addition of a single modifier, sodium dodecyl sulfate (SDS), even at a dosage of 4%, the specific surface area of ​​the prepared modified silica product was only 271.21 m². 2 / g, median particle size (D) 50 The value is 6.27 μm. Figure 7 As shown in the figure, the SiO2 content is only 96.5%. At this time, the specific surface area, particle size index and uniformity of the obtained silica product all decreased within a certain range, which is the same as that of Comparative Example 3, which used only hexadecyltrimethylammonium bromide (CATB) as a single modifier. It can be seen that, similarly, although a single modifier can achieve in-situ grafting modification of the hydroxyl groups on the surface of the unmodified silica product and improve the performance of the obtained silica product, even when the dosage is high, the degree of modification is still not ideal. This is because the single modifier has limited ability to cover the hydroxyl groups on the surface of silica particles, and fails to achieve the positive synergistic effect between the two modifiers as the new combination modifier. The degree of in-situ grafting modification of the hydroxyl groups on the surface of silica is insufficient, resulting in a decline in the quality of the silica product.

Claims

1. A process for preparing modified silica from vanadium acid leaching tailings of clay vanadium ore, characterized in that: Specifically, the steps include the following: (1) Non-grinding alkaline leaching of silicon: The vanadium leaching tailings of clay vanadium ore are not ground, and then mixed with sodium hydroxide and water in a certain proportion and heated for leaching reaction; after the reaction is completed, the mixture is cooled and the filter residue and filtrate are obtained by solid-liquid separation. The filtrate obtained is water glass. (2) Preparation and modification: Add the self-composite electrolyte SC-1 to water glass and add the combined modifier for in-situ grafting modification. Then add acid to neutralize, age at constant temperature, and produce silica gel precipitate. Dry and grind the silica gel to obtain the modified silica product. The self-formulated electrolyte SC-1 comprises 60%–80% sodium sulfate and 20%–40% sodium carbonate by mass. The combined modifier comprises, by mass ratio: 40%–80% hexadecyltrimethylammonium bromide and 20%–60% sodium dodecyl sulfate.

2. The process for preparing modified silica from vanadium acid leaching tailings of clay vanadium ore according to claim 1, characterized in that: The tailings in step (1) come from the acid leaching process in the extraction of vanadium from clay vanadium ore. The silica content is above 85% and the particle size is -4mm. No acid leaching or grinding treatment is performed before alkali leaching for silica removal.

3. The process for preparing modified silica from vanadium acid leaching tailings of clay vanadium ore according to claim 1, characterized in that: In step (1), the alkali-to-slag ratio, i.e., the mass ratio of sodium hydroxide to vanadium leaching tailings from clay vanadium ore extraction, is 0.3 to 1; the liquid-to-solid ratio, i.e., the mass ratio of water to vanadium leaching tailings from clay vanadium ore extraction, is 3 to 6; the heating temperature is 180 to 220°C; the reaction time is 50 to 100 min; and air cooling is used to cool the temperature to below 50°C.

4. The process for preparing modified silica from vanadium acid leaching tailings of clay vanadium ore according to claim 1, characterized in that: In step (2), the amount of the self-prepared electrolyte SC-1 added is 2% to 6% of the mass of the vanadium leaching tailings from clay vanadium ore extraction.

5. The process for preparing modified silica from vanadium acid leaching tailings of clay vanadium ore according to claim 1, characterized in that: In step (2), the amount of self-assembled and compounded modifier added is 2% to 5% of the mass of the vanadium leaching tailings from clay vanadium ore.

6. The process for preparing modified silica from vanadium acid leaching tailings of clay vanadium ore according to claim 1, characterized in that: In step (2), acid is added to neutralize the solution to a pH of 7.0–8.5; the constant temperature aging conditions are controlled as follows: 60–90℃, 60–120 min.

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