Method for preparing antibacterial functional core-shell silicon dioxide from fluorine-containing silicon slag

Abstract

The invention relates to the technical field of chemical engineering, in particular to a method for preparing antibacterial functional core-shell silicon dioxide from fluorine-containing silicon slag, which comprises the following steps: S1, silicon slag pretreatment: mixing silicon slag with water to prepare slurry, sanding the slurry, and controlling the particle size D50 of SiO2 in the sanded silicon slag to be less than 200nm; s2, alkali activation and silicon release: mixing the sanded slurry with an alkali solution, carrying out a hydrothermal reaction, and controlling the silicon dissolution rate to be within a preset range; s3, constructing a gradient pH core shell: firstly, adjusting the pH of the system to an alkaline interval, and carrying out reaction to form a compact inner shell; adjusting the pH value of the system to an acidic interval, and adding a solution containing zinc and fluorine for reaction to form a composite shell; s4, post-treatment: washing and calcining a product obtained in the step S3 to obtain the core-shell silicon dioxide with the antibacterial function. The silicon slag is purified by a one-step method through a four-step integrated process of pretreatment, activation, gradient coating and post-treatment, and the fluorine-containing waste slag is directionally converted into a high-added-value functional material.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to a method for preparing antibacterial functional core-shell silica from fluorinated silica slag. Background Technology

[0002] Phosphate fertilizer and fluorochemical by-product waste residues (containing 30-50% amorphous SiO2 and 5-15% fluorides) pose a high risk of fluoride leaching pollution when traditionally disposed of by landfill, resulting in unutilized resources. Existing patents propose stripping the fluoride from the waste and further processing the silica into precipitated silica for reuse. However, the fluoride wastewater is difficult to treat, and the resulting precipitated silica has poor performance and has not yet been widely adopted.

[0003] Core-shell silica, with its unique core-shell structure combining the stability of the core with the functionality of the shell, shows broad application prospects in catalysis, adsorption, biomedicine, and antibacterial materials. Among these, antibacterial functional core-shell silica, by loading antibacterial active ingredients (such as metal ions like silver, zinc, and copper, or antibacterial organic compounds) into the shell, can achieve long-lasting antibacterial properties. Furthermore, the core-shell structure effectively reduces the loss of antibacterial components, improving the stability and safety of the material.

[0004] Limitations of traditional core-shell material preparation: Patent CN118851193A uses only silicon sources to prepare silica, without functionalization, resulting in a narrow range of product applications. Patent CN106000285A requires the addition of an extra silicon source, which is costly. Patent CN110996885A uses a metal coating method to prepare core-shell materials, which requires the fluorine element in the silicon slag to be removed beforehand, thus failing to achieve the high-value utilization of fluorine. The gradient coating technology in patent CN115011143A does not solve the problem of harmful component conversion.

[0005] Currently, there is no technology to directly convert fluorinated silica slag into functional core-shell silica. Existing technologies either ignore the functionalization potential of silica slag or fail to simultaneously address the issues of fluorine pollution and the devaluation of silicon resources. This invention innovatively utilizes the inherent SiO2 in silica slag to construct a core-shell structure, converting fluorides into the antibacterial component ZnF2, thus achieving an integrated approach of "waste treatment - resource utilization - high-value products". Summary of the Invention

[0006] This invention provides a method for preparing antibacterial functional core-shell silica from fluorinated silica slag. Through a four-step integrated process of pretreatment, activation, gradient coating and posttreatment, the purification, functionalization and high-value-added transformation of silica slag are completed in one step, realizing the directional transformation of fluorinated waste slag into high-value-added functional materials.

[0007] The technical implementation scheme of the present invention is as follows: A method for preparing antibacterial functional core-shell silica from fluorinated silica slag includes the following steps: S1. Pretreatment of silicon slag: Mix silicon slag with water to prepare a slurry, and then perform sand milling on the slurry to control the particle size D50 of SiO2 in the silicon slag after sand milling to be less than 200nm. S2, Alkali-activated silicon release: The slurry after sand milling is mixed with an alkaline solution and subjected to a hydrothermal reaction, with the silicon solubility controlled within a preset range; S3, Gradient pH Core-Shell Construction: First, adjust the pH of the system to the alkaline range and carry out the reaction to form a dense inner shell; then adjust the pH of the system to the acidic range, add a zinc-fluorine-containing solution and carry out the reaction to form a composite outer shell; S4. Post-processing: The product obtained in step S3 is washed and calcined to obtain antibacterial core-shell silica.

[0008] Preferably, in step S1, the solid-liquid mass ratio of the silicon slag to water is 1:2, and the mass percentage of SiO2 in the slurry is 20%; the grinding media used in the sand milling is zirconia beads with a particle size of 0.05-0.1 mm, the sand mill speed is 3000 r / min, and the sand milling time is 4 h; in step S1, the particle size of SiO2 after sand milling is detected by a laser particle size analyzer.

[0009] It should be noted that in step S1, sand milling can break up the agglomerates in the silicon slag, and reducing the micron-sized particles to the nano-sized particles (D50 < 200 nm) can ensure uniform core size and avoid uneven shell coating due to excessively large particles; it also exposes more SiO2 active sites, providing a reaction interface for subsequent alkali activation and the formation of a new SiO2 inner shell.

[0010] Preferably, in step S2, the alkaline solution is a NaOH solution with a concentration of 1 mol / L; the mass ratio of the sand grinding slurry to the NaOH solution is 1:3.

[0011] Preferably, in step S2, the hydrothermal reaction temperature is 120°C and the reaction time is 2-3 hours; the silicon solubility within the preset range is 18±2%.

[0012] Preferably, in step S3, before adjusting the system to the alkaline range, a cationic surfactant CTAB is added, with the addition amount being 0.1% of the dry basis SiO2 mass.

[0013] Preferably, in step S3, the pH value of the alkaline range is 10.5, and the pH is adjusted using 1 mol / L H2SO4; the reaction temperature in the alkaline range is 80℃, and the reaction time is 3 h; in step S3, the pH value of the acidic range is 3.5, and the pH is adjusted using 1 mol / L H2SO4; the zinc-fluorine-containing solution is a ZnCl2 solution, and the Zn / F molar ratio is 1.8:1.

[0014] Preferably, in step S3, the slurry is injected into the ZnCl2 solution at a rate of 5 ml / min; the reaction temperature in the acidic region is 40°C, and the reaction time is 4 h.

[0015] It should be noted that: the alkaline activation reaction, SiO2 + 2NaOH → Na2SiO3 + H2O, generates active silicic acid (SiO2 = 0.9-1.1 g / L); hydrothermal conditions at 120℃ can promote the depolymerization of amorphous SiO2, while avoiding excessive reaction that could damage the core structure of the silicon slag.

[0016] Meanwhile, a solubility rate of 18±2% is crucial for the formation of the core-shell structure; too low a rate results in insufficient shell material, while too high a rate leads to the collapse of the core.

[0017] Further explanation is needed: CTAB, as a cationic surfactant, adsorbs onto the surface of the SiO2 core through electrostatic interaction, forming a micelle template that guides the directional polymerization of active silicic acid, generating a dense nascent SiO2 inner shell; pH=10.5 is the critical condition for the large-scale polymerization of silicic acid, avoiding the formation of too much precipitation that would lead to a loose shell; the reaction temperature of 80℃ can accelerate the condensation of silicic acid, ensuring that the nascent inner shell is tightly bonded to the core.

[0018] During the construction of the acidic functional layer, at pH=3.5, the hydroxyl groups (-Si-OH) on the SiO2 surface are protonated and become positively charged, which can combine with Zn²+ through electrostatic attraction to form Zn-SiO2 bonds.

[0019] The reverse addition method (slurry injection into ZnCl2 solution) can avoid the precipitation of Zn(OH)2 caused by excessive local concentration of Zn²+, and ensure that Zn²+ reacts preferentially with F⁻ to form ZnF2; The Zn / F ratio design of 1.8:1: an excess of Zn²⁺ (1.8 times the theoretical amount) can compensate for the adsorption loss of Zn²⁺ during the reaction process and ensure complete conversion of F⁻.

[0020] Preferably, in step S4, the product is washed three times alternately with 95% ethanol and water, with the volume of the washing liquid being twice the volume of the solid each time; the calcination temperature is 550℃ and the calcination time is 4h.

[0021] Alternating washing with ethanol and water can effectively remove free CTAB (ethanol solubility > 10g / 100ml) and inorganic salts (such as NaCl, Na2SO4), avoiding residual impurities from affecting antibacterial properties; Calcination at 550℃ transforms amorphous ZnF2 into crystalline form, stabilizing the crystal structure and reducing the fluoride ion dissolution rate to <100ppm. Calcination also removes residual organic matter (e.g., CTAB decomposition temperature is 200-300℃), improving product purity (SiO2+ZnF2 content >95%).

[0022] The present invention has the following advantages: This invention features a short and simple process route; waste resource utilization: high utilization rate of silicon slag, replacing purchased silicon sources and reducing costs; fluorine is converted into ZnF2 antibacterial components, turning waste into treasure and maximizing the utilization of fluorine-containing silicon slag raw materials; process innovation: gradient coating and fusion reverse addition method avoids Zn(OH)2 precipitation; precise control of Zn / F molar ratio ensures complete fluorine fixation; through solubility control (18±2%) + pH gradient switching (10.5→3.5), and ternary synergy of reverse addition method, the first time fluorine-containing waste slag has been directionally converted into high-value-added functional materials. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below. It is hereby declared that the directional terms such as up, down, left, right, front, back, inside, and outside used in this text are for illustrative purposes only and are not intended to limit the invention. Example 1:

[0024] 100g of fluorinated silicon slag (SiO2 42wt%, F 8.5wt%) First, sand milling: Add 200ml distilled water and 0.1mm zirconia beads, and mill at 3000r / min for 4 hours to obtain D. 50 =185nm slurry; Secondly, alkali activation: Add 300g of 1M NaOH, transfer to a 500ml high-pressure reactor, react at 120℃ for 3h → take a sample to test the silicon solubility rate, which is 19%, and the SiO2 concentration in the solution is 1.0g / L; Next, gradient wrapping: Construction of alkaline layer: Add 0.42g CTAB (0.1% of dry SiO2), adjust pH to 10.5 with 1M H2SO4, and stir at 80℃ for 3h; Construction of acidic layer: 1M H2SO4 was added dropwise until pH=3.5, and the slurry was injected into a solution containing 15.4g ZnCl2 at 5ml / min, and reacted at 40℃ for 4h; Finally, calcination: wash with ethanol and water three times alternately, and calcine at 550℃ for 4 hours to obtain a white powder product.

[0025] Performance data: index result Test methods Fluorine leaching 13 ppm HJ 557-2010 Escherichia coli inhibition rate 99.3% GB / T 21510-2008 Staphylococcus aureus inhibition rate 98.1% GB / T 21510-2008 Example 2:

[0026] Raw material: 100g of fluorinated silicon slag (SiO2 30wt%, F 5wt%, MgO 8wt%).

[0027] First, sand milling: solid-liquid ratio 1:2, using 0.05mm zirconia beads, sand milling for 4 hours to achieve D50=170nm; Secondly, alkali activation: Add 300g of 1M NaOH, transfer to a 500ml high-pressure reactor, react at 120℃ for 2 hours, and take samples to test the silicon solubility rate, which is 17%. Next, gradient wrapping: Construction of the alkaline layer: Add 0.03 g of CTAB (0.1% of dry SiO2), adjust the pH to 10.5 with 1 M H2SO4, and react for 3 h; Construction of acidic layer: 1M H2SO4 was added dropwise until pH=3.5, and the slurry was injected into a solution containing 6.8g ZnCl2 (Zn / F=1.8:1) at a rate of 5ml / min, and the reaction was carried out at 40℃ for 4h; Finally, calcination: wash with ethanol and water three times alternately, and calcine at 550℃ for 4 hours to obtain a white powder product.

[0028] Performance data: index result Test methods Fluorine leaching 34 ppm HJ 557-2010 Escherichia coli inhibition rate 98.7% GB / T 21510-2008 Staphylococcus aureus inhibition rate 97.5% GB / T 21510-2008 Comparative example:

[0029] Group Deviation parameters result Comparative Example 1 <![CDATA[Not sanded (original residue D 50 = 42μm)]]> Antibacterial rate 65% Comparative Example 2 Solubility 25% Fewer nuclear structure collapses and fewer crust-forming particles. Comparative Example 3 Zn / F=1.2:1 Fluoride ions were not completely converted; the fluoride content in the filtrate was 255 ppm. Comparative Example 4 <![CDATA[Positive mixed ZnCl2]]> The filtrate F content was 1.6 times that of the reverse addition. Comparative Example 5 Calcination at 400℃ Fluorine leaching 136 ppm Based on the comparison of the above embodiments, the antibacterial rates of Escherichia coli and Staphylococcus aureus in Embodiment 1 are higher than those in Embodiment 2, making it the optimal technical solution.

[0030] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing antibacterial functional core-shell silica from fluorinated silica slag, characterized in that, Includes the following steps: S1. Pretreatment of silicon slag: Mix silicon slag with water to prepare a slurry, and then perform sand milling on the slurry to control the particle size D50 of SiO2 in the silicon slag after sand milling to be less than 200nm. S2, Alkali-activated silicon release: The slurry after sand milling is mixed with an alkaline solution and subjected to a hydrothermal reaction, with the silicon solubility controlled within a preset range; S3, Gradient pH Core-Shell Construction: First, adjust the pH of the system to the alkaline range and carry out the reaction to form a dense inner shell; then adjust the pH of the system to the acidic range, add a zinc-fluorine-containing solution and carry out the reaction to form a composite outer shell; S4. Post-processing: The product obtained in step S3 is washed and calcined to obtain antibacterial core-shell silica.

2. The method for preparing antibacterial functional core-shell silica from fluorinated silica slag according to claim 1, characterized in that the steps are as follows: In S1, the solid-liquid mass ratio of silicon slag to water is 1:2, and the mass percentage of SiO2 in the slurry is 20%. The grinding media used in the sand mill is zirconia beads with a particle size of 0.05-0.1 mm. The sand mill speed is 3000 r / min, and the sand milling time is 4 h.

3. The method for preparing antibacterial functional core-shell silica from fluorinated silica slag according to claim 1, characterized in that, In step S1, a laser particle size analyzer is used to detect the particle size of SiO2 after sand milling.

4. A method for preparing antibacterial functional core-shell silica from fluorinated silica slag according to claim 1, characterized in that, In step S2, the alkaline solution is a NaOH solution with a concentration of 1 mol / L; the mass ratio of the sand grinding slurry to the NaOH solution is 1:

3.

5. A method for preparing antibacterial functional core-shell silica from fluorinated silica slag according to claim 1, characterized in that, In step S2, the hydrothermal reaction temperature is 120℃ and the reaction time is 2-3 hours; the silicon solubility within the preset range is 18±2%.

6. A method for preparing antibacterial functional core-shell silica from fluorinated silica slag according to claim 1, characterized in that, In step S3, before adjusting the system to the alkaline range, the cationic surfactant CTAB is added at an amount of 0.1% of the dry SiO2 mass.

7. A method for preparing antibacterial functional core-shell silica from fluorinated silica slag according to claim 6, characterized in that, In step S3, the pH value of the alkaline zone is 10.5, and the pH is adjusted using 1 mol / L H2SO4; the reaction temperature in the alkaline zone is 80℃, and the reaction time is 3 hours.

8. A method for preparing antibacterial functional core-shell silica from fluorinated silica slag according to claim 7, characterized in that, In step S3, the pH value of the acidic range is 3.5, and the pH is adjusted using 1 mol / L H2SO4; the zinc-fluorine-containing solution is a ZnCl2 solution with a Zn / F molar ratio of 1.8:

1.

9. A method for preparing antibacterial functional core-shell silica from fluorinated silica slag according to claim 8, characterized in that, In step S3, the slurry is injected into the ZnCl2 solution at a rate of 5 ml / min; the reaction temperature in the acidic region is 40℃, and the reaction time is 4 h.

10. A method for preparing antibacterial functional core-shell silica from fluorinated silica slag according to claim 1, characterized in that, In step S4, the product is washed three times with alternating washes of 95% ethanol and water, with the volume of the washing liquid being twice the volume of the solid each time; the calcination temperature is 550℃ and the calcination time is 4h.