Method for preparing high-whiteness magnesium hydroxide through brucite impurity removal
By using a mercapto-carboxyl bifunctionalized silicon-titanium composite oxide modifier and a systematic process, the technical challenge of removing impurities from brucite was solved, enabling the preparation of high-whiteness magnesium hydroxide, meeting the needs of high-end applications and reducing environmental impact.
Patent Information
- Application Number
- CN202511659684.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-13
- Publication Date
- 2026-01-13
AI Technical Summary
Existing technologies are insufficient to efficiently remove coloring impurities from brucite, resulting in insufficient whiteness and compatibility in high-end applications. Furthermore, traditional methods are characterized by high costs, environmental pollution, and complex processes.
Using mercapto-carboxyl bifunctionalized silicon-titanium composite oxide as a modifier, impurities in brucite are deeply removed through physical crushing, flotation separation and chemical adsorption purification processes, combining the strong coordination ability of mercapto groups and the ion exchange characteristics of carboxyl groups, and the surface properties are improved by aluminate coupling agents.
It significantly improves the whiteness and purity of brucite, expands its application range in high-end materials, reduces production costs and achieves near-zero wastewater discharge, and has good compatibility and dispersibility.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of inorganic non-metallic mineral processing technology, specifically relating to a method for rapid detection of hydrogen peroxide content. Background Technology
[0002] Brussels halide, a naturally occurring magnesium hydroxide mineral, has become an important raw material for the preparation of flame retardants and environmentally friendly materials due to its abundant reserves, low cost, and environmental friendliness. Ideally, the magnesium hydroxide content in brucite can reach over 90%, and its theoretical application value is significantly higher than that of synthetic magnesium hydroxide, demonstrating a clear advantage in economic benefits. However, naturally occurring brucite minerals often coexist with various impurities. Among them, coloring elements such as iron and manganese exist in complex chemical forms within the crystal structure, forming stable chromophores that severely affect the visual whiteness and optical properties of the mineral powder. These coloring impurities not only limit the application of brucite in high-end plastics, coatings, and cosmetics—fields with strict appearance requirements—but may also affect its compatibility with polymer matrices when used as a flame retardant filler, ultimately leading to a decline in the mechanical properties of composite materials. Therefore, efficient impurity removal from natural brucite and significant improvement in its product whiteness have become key technical bottlenecks that urgently need to be addressed in achieving its high-value utilization.
[0003] Currently, various process routes for the purification and whitening of brucite have been widely studied and applied. Flotation, which utilizes the differences in the physicochemical properties of mineral particle surfaces, offers high throughput and relatively low cost. However, its separation efficiency significantly decreases for micron-sized or even finer powder particles, and the introduction of collectors, frothers, and other chemicals can create new pollution problems. Chemical bleaching relies on the reaction of reducing or oxidizing agents with coloring impurities. While this method can directly target color centers, it often faces challenges such as incomplete treatment and limited whiteness improvement, and it easily generates wastewater containing chemical reagents, increasing the pressure and cost of subsequent environmental treatment. Furthermore, physicochemical composite methods such as nano-coating modification and multi-level activation, which mask or stabilize impurities through surface modification or structural regulation, can achieve certain results. However, due to complex processes, high equipment investment, or the influence of introduced foreign components on the final product performance, it is difficult to consistently obtain high-whiteness products while ensuring economic efficiency. The limitations of these existing technologies highlight the urgent need to develop a new brucite deep processing technology that is efficient, economical, and environmentally friendly.
[0004] In summary, the core technological demand in the field of brucite whitening lies in overcoming the limitations of traditional methods in deep impurity removal and long-term stability. An ideal solution needs to precisely target chromophore impurities within the brucite crystal structure, achieving efficient removal or stable coating. Furthermore, the entire process should avoid complex procedures and expensive reagents, ensuring that the final product meets the requirements of high-end applications in terms of whiteness, purity, and application performance. This urgently necessitates the innovative development of novel modifying substances and supporting processes. These substances should specifically identify and act on color-causing impurities, while their preparation process should be simple and the raw materials readily available to support the industrial feasibility and market competitiveness of the entire technological route. Against this backdrop, this invention aims to develop a novel modifying agent with a unique mechanism of action through molecular structure design and to construct a matching, simple, and efficient processing flow to overcome existing technological bottlenecks. Summary of the Invention
[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite.
[0006] A first aspect of the present invention provides a method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite, comprising the following steps:
[0007] S1. The raw magnesia ore is coarsely crushed into granules, and then the granules are further crushed into ultrafine powder. The ultrafine powder is put into a powdering tank, deionized water and sodium hexametaphosphate are added, and the mixture is stirred to form a slurry.
[0008] S2. The slurry is fed to the flotation machine, and terpineol and sodium oleate are added in sequence; the aeration device is turned on, disodium ethylenediaminetetraacetate is added, and flotation is performed to obtain the flotated magnesia slurry.
[0009] S3. Transfer the flotation-processed magnesia slurry to a reactor, adjust the pH to 9.5-10.5 with dilute sodium hydroxide solution, add mercapto-carboxyl difunctionalized silicon-titanium composite oxide, heat to 70-85℃, and react under stirring.
[0010] S4. Add aluminate coupling agent, adjust pH to 7.5~8.5, and continue the reaction. After the reaction is complete, wash the slurry with pure water to obtain the washed filter cake. Dry the washed filter cake at 100~110℃.
[0011] In this invention, the process of preparing high-whiteness magnesium hydroxide from brucite involves multiple stages, including physical crushing, flotation separation, and chemical adsorption purification. First, the brucite ore is coarsely and finely crushed into ultrafine powder to increase the specific surface area and enhance reactivity. In the pulverizing tank, deionized water and sodium hexametaphosphate are added. Sodium hexametaphosphate acts as a dispersant, adsorbing onto the surface of the mineral particles and preventing particle agglomeration through electrostatic repulsion, forming a stable slurry. Subsequently, the slurry is transported to a flotation machine, where terpineol and sodium oleate are added. Terpineol acts as a frother, reducing the surface tension of the liquid and generating numerous bubbles. Sodium oleate acts as a collector, selectively adsorbing onto the surface of impurity minerals, making them hydrophobic and adhering to the bubbles for removal. Simultaneously, an aeration device is activated to provide airflow, enhancing bubble carrying capacity. Disodium ethylenediaminetetraacetate is added; its chelating groups form stable complexes with metal impurity ions (such as iron and calcium), preventing impurity precipitation or adsorption and improving flotation efficiency. After flotation, a preliminarily purified brucite slurry is obtained. Next, the slurry was transferred to a reactor, and the pH was adjusted to weakly alkaline using a dilute sodium hydroxide solution to create a suitable reaction environment. A mercapto-carboxyl bifunctionalized silicon-titanium composite oxide was then added, and the reaction proceeded under heating and stirring. The mercapto and carboxyl functional groups in the composite oxide can coordinate or exchange with residual impurity ions (such as heavy metals), selectively adsorbing and fixing impurities, thereby deeply purifying brucite. Subsequently, an aluminate coupling agent was added, and the pH was adjusted to near neutral. The aluminum hydroxyl groups generated from the hydrolysis of the aluminate coupling agent condensed with the hydroxyl groups on the surface of magnesium hydroxide, forming chemical bonds that coated the particle surface, improving whiteness and dispersibility. Finally, the soluble salts were removed by washing with pure water, and after drying, a high-whiteness magnesium hydroxide product was obtained. Throughout the process, flotation and chemisorption worked synergistically to effectively remove impurities, and the surface modification by the coupling agent further improved the product's whiteness and performance.
[0012] According to a preferred embodiment of the present invention, in step S1, the stirring time is 30~60 min.
[0013] According to a preferred embodiment of the present invention, in step S2, the flotation time is 20~40 min.
[0014] According to a preferred embodiment of the present invention, in step S3, the reaction time under stirring is 60-90 min.
[0015] According to a preferred embodiment of the present invention, in step S4, the reaction continues for 30 to 45 minutes.
[0016] According to a preferred embodiment of the present invention, the preparation steps of the mercapto-carboxyl bifunctionalized silicon-titanium composite oxide include:
[0017] A1. Under an inert atmosphere, 3-cyanopropyltriethoxysilane and tetraisopropyl titanate are dissolved in anhydrous ethanol to form a mixed solution; the mixed solution is heated to 65~75℃ and refluxed under stirring; deionized water is added to obtain a silicon-titanium composite alkoxide precursor solution.
[0018] A2. Cool the silicon-titanium composite alkoxide precursor solution to 40-50℃, add hydrogen peroxide, adjust the pH to 8.5-9.5, and stir the reaction at 50-60℃; then cool to room temperature, adjust the pH to 2.5-3.5 with dilute hydrochloric acid, and continue stirring to obtain a bifunctional sol.
[0019] A3. Adjust the pH of the bifunctional sol to 4.5~5.5, heat it to 60~70℃, and carry out sol-gel conversion under stirring to obtain a wet gel. Then, mature the wet gel at 50~60℃ to obtain a matured gel.
[0020] A4. Wash the matured gel alternately with deionized water and anhydrous ethanol; then dry it in a vacuum drying oven at 80~100℃, and then calcine it at 250~300℃.
[0021] In this invention, the preparation mechanism of the mercapto-carboxyl bifunctionalized silicon-titanium composite oxide is based on sol-gel technology and functional group transformation. Under an inert atmosphere, a cyano-containing organosilane and a titanate ester are dissolved together in anhydrous ethanol to form a homogeneous mixed solution. Under reflux heating, deionized water is added to initiate a hydrolysis reaction, where the alkoxy groups of the organosilane and the ester groups of the titanate ester hydrolyze to generate corresponding silanol and titanol intermediates. These intermediates form siloxane-silicon and siloxane-titanium bonds through condensation reactions, constructing a silicon-titanium composite alkoxide precursor network structure. Subsequently, hydrogen peroxide is added after the solution is cooled, and the mixture is stirred under alkaline pH conditions. At this time, the cyano groups in the organosilane are oxidized by hydrogen peroxide to carboxyl groups, thereby introducing carboxyl functional groups. Simultaneously, by controlling the reaction conditions, specific groups in the organosilane (such as sulfur-containing precursors) derive mercapto functional groups during oxidation or hydrolysis, achieving bifunctionalization. Under acidic pH conditions, the sol system was further stabilized, forming a bifunctional sol with both thiol and carboxyl groups. Next, the sol pH was adjusted to weakly acidic, and heating promoted the sol-gel transition. The active species in the sol formed a three-dimensional network structure through condensation reactions, transforming into a wet gel. The wet gel underwent a curing process to enhance its cross-linking strength and stability. Finally, the gel was alternately washed with deionized water and anhydrous ethanol to remove unreacted substances and byproducts, followed by vacuum drying and medium-temperature calcination to remove organic residues and solidify the functional groups, yielding a thiol-carboxyl bifunctional silicon-titanium composite oxide. This composite oxide possesses the strong coordinating ability of thiol groups and the ion exchange properties of carboxyl groups, laying the foundation for its adsorption and purification applications.
[0022] According to a preferred embodiment of the present invention, in step A1, the molar ratio of 3-cyanopropyltriethoxysilane to tetraisopropyl titanate is (1.5~2.5):1; the reflux reaction time under stirring is 2~3h.
[0023] According to a preferred embodiment of the present invention, in step A2, the stirring reaction time is 1 to 2 hours.
[0024] According to a preferred embodiment of the present invention, in step A3, the curing time at 50~60°C is 12~24h.
[0025] According to a preferred embodiment of the present invention, in step A4, the calcination time at 250~300°C is 2~3 hours.
[0026] Compared with the prior art, the present invention has the following beneficial effects:
[0027] This invention achieves a significant technological breakthrough in the preparation of high-whiteness magnesium hydroxide from brucite through innovative modified material design and a systematic process. Firstly, it represents a qualitative leap in the core performance indicators of the product. The unique effect of the independently synthesized thiol-carboxyl bifunctionalized silicon-titanium composite oxide greatly enhances the whiteness of the final product, fully meeting the stringent requirements of high-end applications. This modified material, through the synergistic effect of two functional groups in its molecular structure, allows the thiol groups to strongly coordinate and capture color-causing metal ions, while the carboxyl groups significantly improve the hydrophilic properties of the powder surface. Simultaneously, the nanoscale coating layer formed by the silicon-titanium composite oxide framework effectively masks the color of residual impurities. This multi-functional mechanism not only ensures a significant improvement in whiteness but also results in a more uniform particle morphology and concentrated particle size distribution, laying a solid foundation for subsequent applications.
[0028] This invention demonstrates significant advantages in terms of process economy and environmental friendliness. The entire process flow is rationally designed. Although the synthesis of the modified substance requires multiple reaction steps, the raw materials are all common commercially available products, making costs controllable and readily available, thus avoiding supply bottlenecks in actual production. Particularly noteworthy is the relatively small amount of modifier used in the final treatment stage; only a small amount is needed to achieve a significant effect, keeping the overall treatment cost low. Simultaneously, environmental factors are fully considered at each stage of the process flow. Recycling schemes are designed for flotation reagents and washing water, achieving near-zero wastewater discharge and effectively reducing the cost of treating waste gas, wastewater, and solid waste. The entire production process does not require harsh conditions such as high temperature and high pressure; the equipment requirements are simple, and operation and control are convenient, providing important guarantees for large-scale industrial production and embodying the concepts of green manufacturing and sustainable development.
[0029] Furthermore, this invention significantly expands the application scope and performance of brucite-based magnesium hydroxide products. The high-whiteness magnesium hydroxide obtained through this process not only retains the inherent environmental protection and flame-retardant properties of the raw material but also achieves excellent surface characteristics, exhibiting superior compatibility and dispersibility when compounded with polymer materials. This characteristic enables it to completely replace expensive synthetic magnesium hydroxide in applications such as high-end flame-retardant cable materials and engineering plastics, achieving domestic substitution of imported products and possessing significant economic benefits and strategic importance. More importantly, thanks to its excellent whiteness and stable chemical properties, this product has successfully opened up emerging application areas such as cosmetics and pharmaceuticals, where higher requirements are placed on the color and purity of raw materials. It has paved a new path for the high-value utilization of natural brucite resources, effectively enhancing the technological level and market competitiveness of the entire industry. Detailed Implementation
[0030] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.
[0031] The sources of some components in the examples and comparative examples are as follows:
[0032] The terpineol was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.
[0033] The sodium oleate was purchased from Sinopharm Chemical Reagent Co., Ltd.
[0034] The disodium ethylenediaminetetraacetate was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.
[0035] The aluminate coupling agent was purchased from Nanjing Herun Coupling Agent Co., Ltd.
[0036] The 3-cyanopropyltriethoxysilane was purchased from Wuhan Huaxiang Kejie Biotechnology Co., Ltd.
[0037] The tetraisopropyl titanate was purchased from Beijing Bailingwei Technology Co., Ltd.
[0038] Example 1
[0039] This embodiment provides a method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite; it includes the following steps: Step S1, 1000g of brucite ore is coarsely crushed into granules, and then the granules are further pulverized into ultrafine powder, with the powder particle size controlled below 10μm; the ultrafine powder is added to a powdering tank, along with 5000g of deionized water and 50g of sodium hexametaphosphate, and stirred at 300rpm for 45min to form a uniform slurry; Step S2, the slurry is transferred to a flotation machine, and 10g of terpineol and 20g of sodium oleate are added sequentially, with terpineol acting as a frother and sodium oleate as a collector; the aeration device is turned on, the air flow rate is set to 0.5L / min, and 15g of disodium ethylenediaminetetraacetate is added, and flotation is carried out for 30min. During the flotation process, the slurry temperature was maintained at 25℃ to obtain the flotated brucite slurry. In step S3, the flotated brucite slurry was transferred to a reactor, and the pH was adjusted to 10.0 with a 5% (w / w) dilute sodium hydroxide solution. 30g of mercapto-carboxyl difunctionalized silicon-titanium composite oxide was added, and the temperature was raised to 77℃ with stirring at 200 rpm. The reaction was carried out for 75 min with stirring. In step S4, 25g of aluminate coupling agent was added, and the pH was adjusted to 8.0 with dilute hydrochloric acid. The reaction was continued with stirring at 200 rpm for 40 min. After the reaction was completed, the slurry was washed three times with 1000g of pure water each time to obtain a washed filter cake. The washed filter cake was dried at 105℃ for 12 h to obtain high-whiteness magnesium hydroxide. The product, including the preparation steps of the mercapto-carboxyl bifunctionalized silicon-titanium composite oxide, comprises: Step A1, under a nitrogen inert atmosphere, dissolving 150g of 3-cyanopropyltriethoxysilane and 100g of tetraisopropyl titanate in 800g of anhydrous ethanol to form a mixed solution; heating the mixed solution to 70℃ and refluxing it at 150rpm for 2.5h, slowly adding 50g of deionized water at a rate of 5g / min to obtain a silicon-titanium composite alkoxide precursor solution; Step A2, cooling the silicon-titanium composite alkoxide precursor solution to 45℃, adding 60g of 30% hydrogen peroxide, adjusting the pH to 9.0 with ammonia, and reacting it at 55℃ with 150rpm for 1.5h; subsequently cooling... The temperature was lowered to 25℃, and the pH was adjusted to 3.0 with 0.1 mol / L dilute hydrochloric acid. Stirring was continued for 1 hour to obtain a uniform bifunctionalized sol. Step A3: The pH of the bifunctionalized sol was adjusted to 5.0 with acetic acid, and the temperature was raised to 65℃. Sol-gel conversion was carried out for 2 hours with stirring at 100 rpm to obtain a wet gel. The wet gel was matured at 55℃ for 18 hours to obtain a matured gel. Step A4: The matured gel was washed three times alternately with deionized water and anhydrous ethanol, each time with 500 g of deionized water and 500 g of anhydrous ethanol. Then it was dried in a vacuum drying oven at 90℃ for 12 hours, and then calcined at 275℃ for 2.5 hours with a calcination heating rate of 5℃ / min to obtain a mercapto-carboxyl bifunctionalized silicon-titanium composite oxide.
[0040] Example 2
[0041] This embodiment provides a method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite; it includes the following steps: Step S1, 1000g of brucite ore is coarsely crushed into granules, and then the granules are further pulverized into ultrafine powder, with the powder particle size controlled below 10μm; the ultrafine powder is added to a powdering tank, along with 5000g of deionized water and 50g of sodium hexametaphosphate, and stirred at 300rpm for 50min to form a uniform slurry; Step S2, the slurry is transferred to a flotation machine, and 10g of terpineol and 20g of sodium oleate are added sequentially, with terpineol acting as a frother and sodium oleate as a collector; the aeration device is turned on, the air flow rate is set to 0.5L / min, and 15g of disodium ethylenediaminetetraacetate is added, and flotation is carried out for 25min. During the flotation process, the slurry temperature was maintained at 25℃ to obtain flotated brucite slurry. In step S3, the flotated brucite slurry was transferred to a reactor, and the pH was adjusted to 9.8 with a 5% (w / w) dilute sodium hydroxide solution. 30g of mercapto-carboxyl difunctionalized silicon-titanium composite oxide was added, and the temperature was raised to 80℃ with stirring at 200 rpm. The reaction was carried out for 80 min with stirring. In step S4, 25g of aluminate coupling agent was added, and the pH was adjusted to 7.8 with dilute hydrochloric acid. The reaction was continued with stirring at 200 rpm for 35 min. After the reaction was completed, the slurry was washed three times with 1000g of pure water each time to obtain a washed filter cake. The washed filter cake was dried at 108℃ for 12 h to obtain high-whiteness magnesium hydroxide. The product, including the preparation steps of the mercapto-carboxyl bifunctionalized silicon-titanium composite oxide, comprises: Step A1, under a nitrogen inert atmosphere, dissolving 140g of 3-cyanopropyltriethoxysilane and 100g of tetraisopropyl titanate in 800g of anhydrous ethanol to form a mixed solution; heating the mixed solution to 68℃ and refluxing it at 150rpm for 2.2h, slowly adding 50g of deionized water at a rate of 5g / min to obtain a silicon-titanium composite alkoxide precursor solution; Step A2, cooling the silicon-titanium composite alkoxide precursor solution to 45℃, adding 60g of 30% hydrogen peroxide, adjusting the pH to 8.8 with ammonia, and reacting it at 58℃ with 150rpm for 1.8h; subsequently cooling... The temperature was lowered to 25℃, and the pH was adjusted to 3.0 with 0.1mol / L dilute hydrochloric acid. Stirring was continued for 1 hour to obtain a uniform bifunctionalized sol. Step A3: The pH of the bifunctionalized sol was adjusted to 5.0 with acetic acid, and the temperature was raised to 68℃. Sol-gel conversion was carried out for 2 hours with stirring at 100 rpm to obtain a wet gel. The wet gel was matured at 55℃ for 20 hours to obtain a matured gel. Step A4: The matured gel was washed three times alternately with deionized water and anhydrous ethanol, each time with 500g of deionized water and 500g of anhydrous ethanol. Then it was dried in a vacuum drying oven at 90℃ for 12 hours, and then calcined at 260℃ for 2.8 hours with a calcination heating rate of 5℃ / min to obtain a mercapto-carboxyl bifunctionalized silicon-titanium composite oxide.
[0042] Example 3
[0043] This embodiment provides a method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite; it includes the following steps: Step S1, 1000g of brucite ore is coarsely crushed into granules, and then the granules are further pulverized into ultrafine powder, with the powder particle size controlled below 10μm; the ultrafine powder is added to a powdering tank, along with 5000g of deionized water and 50g of sodium hexametaphosphate, and stirred at 300rpm for 40min to form a uniform slurry; Step S2, the slurry is transferred to a flotation machine, and 10g of terpineol and 20g of sodium oleate are added sequentially, with terpineol acting as a frother and sodium oleate as a collector; the aeration device is turned on, the air flow rate is set to 0.5L / min, and 15g of disodium ethylenediaminetetraacetate is added, and flotation is carried out for 35min. During the flotation process, the slurry temperature was maintained at 25℃ to obtain the flotated brucite slurry. In step S3, the flotated brucite slurry was transferred to a reactor, and the pH was adjusted to 10.2 with a 5% (w / w) dilute sodium hydroxide solution. 30g of mercapto-carboxyl difunctionalized silicon-titanium composite oxide was added, and the temperature was raised to 75℃ with stirring at 200 rpm. The reaction was carried out for 70 min with stirring. In step S4, 25g of aluminate coupling agent was added, and the pH was adjusted to 8.2 with dilute hydrochloric acid. The reaction was continued with stirring at 200 rpm for 38 min. After the reaction was completed, the slurry was washed three times with 1000g of pure water each time to obtain a washed filter cake. The washed filter cake was dried at 102℃ for 12 h to obtain high-whiteness magnesium hydroxide. The product, including the preparation steps of the mercapto-carboxyl bifunctionalized silicon-titanium composite oxide, comprises: Step A1, under a nitrogen inert atmosphere, dissolving 160g of 3-cyanopropyltriethoxysilane and 100g of tetraisopropyl titanate in 800g of anhydrous ethanol to form a mixed solution; heating the mixed solution to 72℃ and refluxing it at 150rpm for 2.8h, slowly adding 50g of deionized water at a rate of 5g / min to obtain a silicon-titanium composite alkoxide precursor solution; Step A2, cooling the silicon-titanium composite alkoxide precursor solution to 45℃, adding 60g of 30% hydrogen peroxide, adjusting the pH to 9.2 with ammonia, and reacting it at 52℃ with 150rpm for 1.2h; subsequently cooling... The temperature was lowered to 25℃, and the pH was adjusted to 3.0 with 0.1 mol / L dilute hydrochloric acid. Stirring was continued for 1 h to obtain a uniform bifunctionalized sol. Step A3: The pH of the bifunctionalized sol was adjusted to 5.0 with acetic acid, and the temperature was raised to 62℃. Sol-gel conversion was carried out for 2 h with stirring at 100 rpm to obtain a wet gel. The wet gel was matured at 55℃ for 16 h to obtain a matured gel. Step A4: The matured gel was washed three times alternately with deionized water and anhydrous ethanol, each time with 500 g of deionized water and 500 g of anhydrous ethanol. Then it was dried in a vacuum drying oven at 90℃ for 12 h, and then calcined at 280℃ for 2.2 h with a calcination heating rate of 5℃ / min to obtain a mercapto-carboxyl bifunctionalized silicon-titanium composite oxide.
[0044] Comparative Example 1
[0045] This comparative example provides a method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite, comprising the following steps: Step S1: 1000g of brucite ore is coarsely crushed into granules, and then the granules are further pulverized into ultrafine powder, with the powder particle size controlled below 10μm; the ultrafine powder is added to a powdering tank, along with 5000g of deionized water and 50g of sodium hexametaphosphate, and stirred at 300rpm for 45min to form a uniform slurry; Step S2: the slurry is transferred to a flotation machine, and 10g of terpineol and 20g of sodium oleate are added sequentially, with terpineol acting as a frother and sodium oleate as a collector; the aeration device is turned on, the air flow rate is set to 0.5L / min, and 15g of disodium ethylenediaminetetraacetate is added, and flotation is carried out for 30min. During the flotation process, the slurry temperature is maintained at 25℃ to obtain the flotated brucite slurry. In step S3, the flotated brucite slurry is transferred to a reactor, and the pH is adjusted to 10.0 with a 5% (w / w) dilute sodium hydroxide solution. The temperature is raised to 77℃ with a stirring speed of 200 rpm, and the reaction is carried out for 75 min with stirring. No mercapto-carboxyl bifunctionalized silicon-titanium composite oxide is added. In step S4, 25 g of aluminate coupling agent is added, and the pH is adjusted to 8.0 with dilute hydrochloric acid. The reaction is continued with stirring at 200 rpm for 40 min. After the reaction is completed, the slurry is washed three times with pure water, 1000 g of pure water each time, to obtain the washed filter cake. The washed filter cake is dried at 105℃ for 12 h to obtain the magnesium hydroxide product.
[0046] Comparative Example 2
[0047] This comparative example provides a method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite, comprising the following steps: Step S1: 1000g of brucite ore is coarsely crushed into granules, and then the granules are further pulverized into ultrafine powder, with the powder particle size controlled below 10μm; the ultrafine powder is added to a powdering tank, along with 5000g of deionized water and 50g of sodium hexametaphosphate, and stirred at 300rpm for 45min to form a uniform slurry; Step S2: the slurry is transferred to a flotation machine, and 10g of terpineol and 20g of sodium oleate are added sequentially, with terpineol acting as a frother and sodium oleate as a collector; the aeration device is turned on, the air flow rate is set to 0.5L / min, and 15g of disodium ethylenediaminetetraacetate is added, and flotation is carried out for 30min. During the flotation process, the slurry temperature is maintained at 25℃ to obtain flotated brucite slurry. In step S3, the flotated brucite slurry is transferred to a reactor, the pH is adjusted to 10.0 with a 5% (w / w) dilute sodium hydroxide solution, 30g of mercapto-carboxyl difunctionalized silicon-titanium composite oxide is added, and the temperature is raised to 77℃ with a stirring speed of 200rpm. The reaction is carried out for 75min with stirring. In step S4, the pH is adjusted to 8.0 with dilute hydrochloric acid, and the reaction is continued with stirring at 200rpm for 40min without adding aluminate coupling agent. After the reaction is completed, the slurry is washed three times with pure water, 1000g of pure water each time, to obtain a washed filter cake. The washed filter cake is dried at 105℃ for 12h to obtain magnesium hydroxide product.
[0048] Example 3
[0049] This comparative example provides a method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite, comprising the following steps: Step S1: 1000g of brucite ore is coarsely crushed into granules, and then the granules are further pulverized into ultrafine powder, with the powder particle size controlled below 10μm; the ultrafine powder is added to a powdering tank, along with 5000g of deionized water and 50g of sodium hexametaphosphate, and stirred at 300rpm for 45min to form a uniform slurry; Step S2: the slurry is transferred to a flotation machine, and 10g of terpineol and 20g of sodium oleate are added sequentially, with terpineol acting as a frother and sodium oleate as a collector; the aeration device is turned on, the air flow rate is set to 0.5L / min, and flotation is carried out for 30min without the addition of disodium ethylenediaminetetraacetate. During the flotation process, the slurry temperature was maintained at 25℃ to obtain the flotation brucite slurry. In step S3, the flotation brucite slurry was transferred to a reactor, and the pH was adjusted to 10.0 with a 5% (w / w) dilute sodium hydroxide solution. 30g of mercapto-carboxyl difunctionalized silicon-titanium composite oxide was added, and the temperature was raised to 77℃ with a stirring speed of 200rpm. The reaction was carried out for 75min with stirring. In step S4, 25g of aluminate coupling agent was added, and the pH was adjusted to 8.0 with dilute hydrochloric acid. The reaction was continued with stirring at 200rpm for 40min. After the reaction was completed, the slurry was washed three times with 1000g of pure water each time to obtain the washed filter cake. The washed filter cake was dried at 105℃ for 12h to obtain the magnesium hydroxide product.
[0050] According to national and industry standard testing specifications, the methods provided in the above examples and comparative examples for preparing high-whiteness magnesium hydroxide by removing impurities from brucite were tested. The testing methods are as follows: Whiteness testing was performed using a digital whiteness meter. The sample was pressed into a smooth circular disc under 20 MPa pressure, and multiple measurements were taken on the instrument. The arithmetic mean of five measurements was taken as the final whiteness result. Magnesium hydroxide content determination was performed using a chemical titration method. 0.5 g of dried sample was accurately weighed and dissolved in 50 mL of 0.1 mol / L dilute hydrochloric acid. Using Eriochrome Black T as an indicator, titration was performed with 0.05 mol / L disodium ethylenediaminetetraacetate standard solution to the endpoint. The mass fraction of magnesium hydroxide was calculated based on the volume of standard solution consumed. Particle size distribution testing was performed using a laser particle size analyzer. 0.1 g of sample was divided into... The sample was dispersed in 100 mL of deionized water, sonicated for 5 min, and then measured. The median particle size D50 of the volume distribution was used as the particle size characteristic value. For the tap density test, a tap density meter was used. 10.0 g of sample was placed in a 25 mL graduated cylinder and vibrated at a frequency of 200 times / min for 5 min. The tap density was calculated based on the volume and mass after vibration. For the iron content determination, a spectrophotometric method was used. After acid dissolution, the sample was reacted with o-phenanthroline at pH 3.5. The absorbance was measured at 510 nm using a spectrophotometer, and the iron content was calculated based on the standard curve. For the loss on ignition test, 2.0 g of sample was placed in a pre-weighed crucible and ignited in a muffle furnace at 850 °C for 2 h. After removal, the sample was cooled to room temperature in a desiccator and weighed. The percentage of mass loss was calculated.
[0051] The performance test data above are shown in Table 1.
[0052] Table 1 Performance Test Results
[0053]
[0054] As can be seen from the above, Examples 1-3, compared to Comparative Examples 1-3, exhibit significant advantages in key indicators such as whiteness, purity, iron impurity content, and powder physical properties, completely solving the technical problem of efficient impurity removal and improved product whiteness that this invention aims to address. Specifically, the magnesium hydroxide products obtained in Examples 1-3 all achieved a whiteness of over 95.8%, a magnesium hydroxide content exceeding 98.9%, and an iron content effectively controlled below 92 ppm. Furthermore, they exhibited finer median particle size and lower tap density, demonstrating excellent overall performance. Comparative Example 1, which did not use the mercapto-carboxyl bifunctionalized silicon-titanium composite oxide, saw its product whiteness plummet to 90.3%, with an iron content as high as 250 ppm. This proves that the composite oxide plays an irreplaceable and crucial role in deeply capturing and removing heavy metal impurity ions, thereby significantly improving product whiteness. Comparative Example 2, which did not use an aluminate coupling agent, produced a product with a whiteness of only 92.1% and a higher tap density. This indicates that the aluminate coupling agent, through surface coating modification, is crucial for further improving whiteness, enhancing powder dispersibility, and preventing particle agglomeration. Comparative Example 3, which did not use disodium EDTA, produced a product with an iron content of 180 ppm, significantly higher than the examples. This demonstrates that disodium EDTA pre-removes some metallic impurities during the flotation stage through chelation, laying a good foundation for subsequent deep purification. In summary, this invention, through the synergistic effect of three modified compounds, constructs a complete purification chain from preliminary flotation to deep chemical adsorption and then to surface modification, successfully achieving the goal of preparing high-whiteness, high-purity magnesium hydroxide from brucite ore. This effectively overcomes the shortcomings of existing technologies, such as incomplete impurity removal and low product whiteness.
Claims
1. A method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite, characterized in that, Includes the following steps: S1. The raw magnesia ore is coarsely crushed into granules, and then the granules are further crushed into ultrafine powder. The ultrafine powder is put into a powdering tank, deionized water and sodium hexametaphosphate are added, and the mixture is stirred to form a slurry. S2. The slurry is fed to the flotation machine, and terpineol and sodium oleate are added in sequence; the aeration device is turned on, disodium ethylenediaminetetraacetate is added, and flotation is performed to obtain the flotated magnesia slurry. S3. Transfer the flotation-processed magnesia slurry to a reactor, adjust the pH to 9.5-10.5 with dilute sodium hydroxide solution, add mercapto-carboxyl difunctionalized silicon-titanium composite oxide, heat to 70-85℃, and react under stirring. S4. Add aluminate coupling agent, adjust pH to 7.5~8.5, and continue the reaction. After the reaction is complete, wash the slurry with pure water to obtain the washed filter cake. Dry the washed filter cake at 100~110℃.
2. The method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite according to claim 1, characterized in that, In step S1, the stirring time is 30~60 minutes.
3. The method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite according to claim 1, characterized in that, In step S2, the flotation time is 20~40 minutes.
4. The method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite according to claim 1, characterized in that, In step S3, the reaction time under stirring is 60-90 minutes.
5. The method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite according to claim 1, characterized in that, In step S4, the reaction continues for 30-45 minutes.
6. The method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite according to any one of claims 1-5, characterized in that, The preparation steps of the mercapto-carboxyl bifunctionalized silicon-titanium composite oxide include: A1. Under an inert atmosphere, 3-cyanopropyltriethoxysilane and tetraisopropyl titanate are dissolved in anhydrous ethanol to form a mixed solution; the mixed solution is heated to 65~75℃ and refluxed under stirring; deionized water is added to obtain a silicon-titanium composite alkoxide precursor solution. A2. Cool the silicon-titanium composite alkoxide precursor solution to 40-50℃, add hydrogen peroxide, adjust the pH to 8.5-9.5, and stir the reaction at 50-60℃; then cool to room temperature, adjust the pH to 2.5-3.5 with dilute hydrochloric acid, and continue stirring to obtain a bifunctional sol. A3. Adjust the pH of the bifunctional sol to 4.5~5.5, heat it to 60~70℃, and carry out sol-gel conversion under stirring to obtain a wet gel. Then, mature the wet gel at 50~60℃ to obtain a matured gel. A4. Wash the matured gel alternately with deionized water and anhydrous ethanol; then dry it in a vacuum drying oven at 80~100℃, and then calcine it at 250~300℃.
7. The method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite according to claim 6, characterized in that, In step A1, the molar ratio of 3-cyanopropyltriethoxysilane to tetraisopropyl titanate is (1.5~2.5):1; the reflux reaction time under stirring is 2~3h.
8. The method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite according to claim 6, characterized in that, In step A2, the stirring reaction time is 1-2 hours.
9. The method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite according to claim 6, characterized in that, In step A3, the curing time is 12-24 hours at 50-60℃.
10. The method for preparing high-whiteness magnesium hydroxide by removing impurities from brucite according to claim 6, characterized in that, In step A4, the calcination time at 250~300℃ is 2~3h.