Method for producing silica using chaff as raw material
A method using rice husks to produce amorphous silica with controlled porosity and purity addresses the limitations of existing silica production, enhancing safety and efficacy in drug delivery systems.
Patent Information
- Application Number
- JP2024110437
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-07-09
- Publication Date
- 2026-01-22
AI Technical Summary
Existing methods for producing silica, such as crystalline MCM-41, do not effectively utilize plant-derived materials and lack the necessary purity and porosity for safe and effective applications in fields like drug delivery systems.
A method utilizing rice husks as a raw material, involving hydrolysis, low-temperature firing, and impurity removal, produces amorphous silica with controlled pore sizes and smooth surfaces, achieving high purity and porosity without crystallization.
The produced amorphous silica is highly pure and porous, ensuring safety and reducing side effects in applications like drug delivery systems by minimizing surface spikes and enhancing drug absorption.
Smart Images
Figure 2026010517000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to a method for producing amorphous silica using rice husks as a raw material. [Background technology]
[0002] Porous silica is used in many fields, such as food, cosmetics, adsorbents, and pharmaceuticals. Research is also underway into drug delivery systems that utilize this porosity. For example, Non-Patent Document 1 describes research results by Hayami Shinya et al. of Kumamoto University that can be applied to drug delivery systems. However, the porous silica material "MCM-41" (Mobil Crystalline Material 41) is a crystalline silica derived from minerals and is surface-treated, so there was room for further improvement. [Prior art documents] [Non-patent literature]
[0003] [Non-Patent Document 1] SHINYA HAYAMI, KUMAMOTO UNIVERSITY NEWS, RELEASE 23-MAR-2018, "Development of an innovative antimalarial drug delivery system using porous silica materials" Summary of the Invention [Problem to be solved by the invention]
[0004] An object of the present invention is to provide a method for producing amorphous silica using rice husks derived from plants as a raw material. [Means for solving the problem]
[0005] The method for producing silica according to the present invention uses rice husks as a raw material and includes a hydrolysis treatment step, a firing step using a furnace, a crushing step, and a step of removing impurities using a magnetic bar. The method is characterized by the fact that the silica is porous with pore sizes of 5 to 200 nm and does not have spikes on the surface.
[0006] The amorphous silica according to the present invention is characterized in that it is amorphous silica having a purity of at least 98% or more, and an average purity of 99% or more.
[0007] In particular, it is porous with countless pores with diameters of 5 to 200 nm, and has no sharp spikes on its surface. Here, "no thorns" means that even if there are protrusions with rounded tips on the surface of the silica particles, there are no protrusions with sharp angles.
[0008] In the present invention, the firing step is preferably a low-temperature, long-term firing in the range of 400 to 800° C. for 24 hours or more. Rice husks contain approximately 18-20% silica (SiO2), approximately 70% organic components such as cellulose, hemicellulose, and lignin, and the remainder is water. Therefore, it is necessary to remove these organic components. Therefore, in the present invention, in order to facilitate the decomposition of cellulose, lignin, etc., citric acid water, which is obtained by adding 1 to 10% citric acid to pure water, is first added, heated, and subjected to hydrolysis treatment. Next, the organic components were removed by baking. Higher firing temperatures will speed up the removal of carbon, but temperatures above 800°C may cause silica to crystallize. Therefore, the present invention is characterized in that the material is slowly fired at a low temperature of 400 to 800°C, preferably 400 to 650°C, for 24 hours or more.
[0009] In the present invention, porous amorphous silica can be obtained without pulverization, but adjusting the particle size distribution to a predetermined range makes it easier to use according to the application. The silica particles thus obtained have a negatively charged surface potential. [Effects of the Invention]
[0010] The amorphous porous silica obtained by the production method according to the present invention is naturally derived and is therefore highly safe for use in the fields of food, cosmetics, and the like. In particular, when used in the field of drug delivery systems, the absence of thorns on the surface of silica particles and their excellent porosity are expected to reduce side effects such as damage to blood vessels and improve the adsorption of drug ingredients. [Brief explanation of the drawings]
[0011] [Figure 1] Photographs of silica particles are shown, where (a) shows rice husk silica particles according to the present invention, and (b) shows MCM-41 particles. [Figure 2] An enlarged TEM image of rice husk silica particles is shown. [Figure 3] A partially enlarged TEM image of rice husk silica particles is shown. [Figure 4] 1 shows the particle size distribution of rice husk silica particles. [Figure 5] 1 shows the measurement results of the zeta potential of rice husk silica particles. DETAILED DESCRIPTION OF THE INVENTION
[0012] An example of the production of silica according to the present invention will be described below, but the present invention is not limited thereto. (1) Rice husks are put into a hydrolysis device (also called a thermal decomposition device, steam decomposition device, etc.). Using approximately 2 to 5% citric acid water as the hydrolysis solution, hydrolysis treatment was carried out under pressure at approximately 180 to 200°C for approximately 35 minutes to 2 hours. (2) Next, the mixture was fired in a furnace at 500 to 600°C for about 36 hours. The structure of the furnace for firing is not particularly limited, but a circulating furnace with a blower may be used as needed. (3) The silica particles obtained above are large, ranging in size from 40 to 60 μm, and are crushed depending on the intended use. The crushed silica particles were sieved through a 400 mesh sieve. (4) Next, five 10,000-millimeter glass magnetic rods were placed in a row and the silica particles were passed over them. This allows magnetic metal powder and metals to be removed.
[0013] FIG. 1 shows TEM images of (a) rice husk-derived silica particles according to the present invention and (b) MCM-41 particles described in the cited literature. Figure 2 shows an enlarged TEM image of silica particles derived from rice husks, and Figure 3 shows a further enlarged partial TEM image. FIG. 4 shows the particle size distribution of silica particles for three lots, and the surface potential of each lot (1st to 3rd) measured with a zeta potential measuring device, which averaged -34 mV and was slightly negatively charged.
[0014] First, as shown in FIG. 1, the fine pores of the amorphous silica particles according to the present invention were smaller than those of the MCM-41 particles and were distributed throughout the particles. The TEM images in Figures 1 to 3 show that the silica particles derived from rice husks contain countless micropores with diameters of 5 to 200 nm, although there is a large degree of variation. Generally, the pore size is generally in the range of 20 to 50 nm. Furthermore, there were no noticeable spikes on the surface of the silica particles. As shown in FIG. 4, the particle size distribution varies depending on the lot, but it can be seen that most are in the range of 250 to 900 nm, especially 400 to 550 nm. The purity of the silica was 99.01%.
Claims
1. A step of using rice husks as a raw material and subjecting them to hydrolysis treatment; Firing using a furnace; a grinding step; and removing impurities using a magnetic bar; A method for producing silica characterized by being porous with pore sizes of 5 to 200 nm and having no spikes on the surface.
2. 2. The method for producing silica according to claim 1, wherein the calcination step is a low-temperature, long-term calcination step at a temperature in the range of 400 to 800° C. for 24 hours or more.
3. 3. The method for producing silica according to claim 2, wherein the pulverization step is carried out so that the particle size falls within the range of 200 to 1000 nm.
4. 4. The method for producing silica according to claim 3, wherein the surface potential of the particles is negatively charged.
5. 5. The method for producing silica according to claim 4, wherein the purity of the silica is 99% or more.