Method for preparing white carbon black by fermenting pre-activated rice husks

Abstract

The invention discloses a method for preparing white carbon black by fermenting pre-activated rice husks. The method comprises the following steps: preparing an ammonia water dilute solution; putting the rice hulls into an ammonia water dilute solution for soaking; performing fermentation treatment on the wet rice hulls, periodically soaking the rice hulls again with an ammonia water solution, and discarding a soaking solution; and heating the fermented rice husks in an air atmosphere to ash the rice husks to obtain the rice husk-based white carbon black. Through fermentation pretreatment, the carbon content in the rice hull-based white carbon black is reduced, hydrochloric acid is not used, and acid pollution is avoided. The firing temperature is reduced, the collapse of a silicon dioxide skeleton is reduced, and the cost is reduced.

Description

Technical Field

[0001] The invention relates to the field of adsorbents, and more specifically to the preparation of a porous silica adsorbent, and in particular to a method for preparing white carbon black by fermenting pre-activated rice husks. Background Art

[0002] Heating rice husks in an air atmosphere below 600°C can produce rice husk ash with silicon dioxide as the main component and a certain amount of amorphous carbon, which has a strong adsorption capacity. (Ouyang Dong, Chen Kai. Microstructure and chemical activity of low-temperature incinerated rice husk ash [J]. Journal of the Chinese Ceramic Society, 2003, 31(11):1121-1124., Yao Xinding, Zhang Yuling, Sun Xiaomin, et al. Research progress in comprehensive utilization of rice husk ash [J]. 2008.) The adsorption capacity of rice husk ash can be further improved by microbial fermentation (Chinese patent application number CN 200810100635). The carbon element contained in the rice husk ash produced by this method is significantly increased. Liu Houfan and others found that pre-treatment of rice husks with dilute hydrochloric acid can reduce the residual carbon in rice husk ash and increase the content of silica in the product with higher wear resistance (Liu Houfan, Gan Lu, Li Risheng, et al. Research on a new method for preparing white carbon black from rice husks [J]. Inorganic Salt Industry, 2007, 39(2):3.). This rice husk ash with a low carbon content is white in appearance and is also called rice husk-based white carbon black. In addition, the temperature of burning rice husks in air also affects the ratio of silica to carbon in the product rice husk ash. A higher burning temperature will result in less carbon in the rice husk ash, but high temperature will also cause the silica skeleton structure in the rice husk ash to partially collapse, resulting in a decrease in its surface area and, in turn, a decrease in adsorption capacity. Summary of the invention

[0003] In view of the problem of preparing porous rice husk-based white carbon black, the present invention aims to provide a method for preparing white carbon black by fermenting pre-activated rice husk.

[0004] The object of the present invention is achieved by the following scheme: A method for preparing white carbon black by fermenting pre-activated rice husks, comprising the following steps: (1) Prepare a dilute ammonia solution.

[0005] (2) Soak the rice husks in the dilute ammonia solution obtained in step (1), and drain the excess solution.

[0006] (3) The wet rice husks obtained in step (2) are placed in a fermentation box with low-speed air blowing and maintained at 100% relative humidity for 15 days. The wet rice husks are soaked in a dilute ammonia solution every 3 days, and the soaking solution is discarded. The rice husks gradually turn brown.

[0007] (4) Drying the wet rice husk obtained in step (3) and then burning it in an air atmosphere to obtain rice husk-based white carbon black.

[0008] Based on the above scheme, the ammonia solution in step (1) is prepared as follows: Add 20 mL of commercially available 25% concentrated ammonia water to a 1000 mL volumetric flask, add pure water to make up to the mark of 1000 mL and shake well.

[0009] Preferably, in step (3), the fermentation temperature is 38°C.

[0010] Preferably, in step (4), the dried pre-activated rice husk is placed in a muffle furnace, heated to 500° C. at a rate of 4° C. / min and maintained for 3 h; after cooling, the pre-activated rice husk is washed with a small amount of pure water to obtain rice husk-based silica.

[0011] Experiments show that the higher the proportion of inorganic salts in rice husks, the higher the proportion of carbon components remaining after burning at the same temperature, and the lower the degree of ashification. This can be proved by reverse experiments. If rice husks are soaked in 3% NaCl solution for 4 hours and then burned at 500 degrees Celsius for 3 hours, the resulting rice husk ash not only contains more carbon and appears darker, but also has a significantly larger particle size, indicating that the ashification is not complete (see Appendix). Figure 1 Left). Control group (attached Figure 1 Right) is the rice husk ash obtained by soaking rice husk in pure water for 4 hours and then burning it in the same way. The inorganic salt components in the rice husk can be reused by microorganisms through the fermentation process, and then the inorganic salt components are removed by repeated soaking. The remaining carbon elements in the remaining rice husk will be reduced after burning, thus obtaining a purer rice husk-based white carbon black.

[0012] Advantages of the present invention: (1) The carbon content in rice husk-based silica is reduced by fermentation pretreatment, and the use of hydrochloric acid is avoided to avoid acid pollution.

[0013] (2) Lowering the burning temperature reduces the collapse of the silica skeleton and reduces costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Photo of the reverse experiment on the effect of inorganic salts.

[0015] This can be proved by reverse experiment. If rice husk is soaked in 3% NaCl solution for 4 h and then burned at 500 °C for 3 h, the resulting rice husk ash not only contains more carbon and appears darker, but also has a significantly larger particle size, indicating that the ashification is incomplete (see Appendix). Figure 1 Left). Control group (attached Figure 1Right) is the rice husk ash obtained by soaking rice husk in pure water for 4 hours and then burning it in the same way. The inorganic salt components in the rice husk can be reused by microorganisms through the fermentation process, and then the inorganic salt components are removed by repeated soaking. The remaining carbon elements in the remaining rice husk will be reduced after burning, thus obtaining a purer rice husk-based white carbon black. DETAILED DESCRIPTION

[0016] The present invention will be further described below in conjunction with specific examples. The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial sources. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0017] Example 1. A method of preparing rice husk-based white carbon black by fermentation and pre-activation for 15 days, according to the following steps (1) Preparation of ammonia solution: Add 20 mL of commercially available 25% concentrated ammonia water to a 1000 mL volumetric flask, add pure water to the mark and shake well. This solution can also be prepared as needed. (2) Soaking rice husks in ammonia solution: Weigh 25 g of dry rice husks and place them in a 200 mL beaker. Add 100 mL of the ammonia solution obtained in step (1). Stir with a glass rod to completely immerse the rice husks in the solution. Let stand for 4 h. (3) Fermentation pre-activation: Drain the wet rice husks obtained in step (2), loosen the wet rice husks with a glass rod, place them in an incubator at a constant temperature of 38°C, and fill the water tank of the incubator with water. On the 3rd, 6th, 9th and 12th day after the start of the culture, take out the wet rice husks and add 100 mL of the ammonia solution obtained in step (1) again, soak for 2 hours, then drain the wet rice husks and put them back into the incubator to continue fermentation culture; on the 15th day, soak the wet rice husks in 150 mL of pure water for 4 hours and then drain; the liquid drained out each time is wheat color or brown, and the wet rice husks eventually turn into brown; (4) Ashing reaction.

[0018] The wet rice husk obtained in step (3) was transferred to a 100 mL quartz beaker, dried at 115°C for 8 h, placed in a muffle furnace, heated to 500°C at 4°C / min and maintained for 3 h; after cooling, washed with a small amount of pure water to obtain rice husk-based silica. The obtained rice husk-based silica is as shown in the attached Figure 1 As shown in the right figure.

[0019] Table 1 compares the amount of white carbon black obtained from dry rice husks that were pre-activated by fermentation, unactivated, and reversed by 3% NaCl. The above embodiments are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for preparing white carbon black by fermenting pre-activated rice husks, characterized in that: The steps include: (1) Prepare a dilute ammonia solution; (2) soaking the rice husks in the dilute ammonia solution obtained in step (1), draining the excess solution, and obtaining wet rice husks treated with the dilute ammonia solution; (3) placing the wet rice husk obtained in step (2) in a fermentation box with low-speed air blowing, maintaining a relative humidity of 100% for fermentation for 15 days, re-immersing the wet rice husk in a dilute ammonia solution every 3 days, and discarding the filtrate to obtain pre-activated wet rice husk; (4) The pre-activated wet rice husk obtained in step (3) is dried and then burned in an air atmosphere to obtain rice husk-based white carbon black.

2. The method for preparing white carbon black by fermenting preactivated rice husk according to claim 1, characterized in that: In step (1), the aqueous ammonia solution is prepared as follows: Add 20 mL of commercially available 25% concentrated ammonia water to a 1000 mL volumetric flask, add pure water to make up to the mark of 1000 mL and shake well.

3. The method for preparing white carbon black by fermenting pre-activated rice husk according to claim 1, characterized in that: The fermentation temperature in step (3) is 38°C.

4. The method for preparing white carbon black by fermenting preactivated rice husk according to claim 1, characterized in that: In step (4), the dried pre-activated rice husk is placed in a muffle furnace, heated to 500°C at a rate of 4°C / min and maintained for 3 h; after cooling, the pre-activated rice husk is washed with a small amount of pure water to obtain rice husk-based silica.

5. The method for preparing white carbon black by fermenting pre-activated rice husk according to any one of claims 1 to 4, characterized in that: Follow the steps below (1) Preparation of ammonia solution: Add 20 mL of commercially available 25% concentrated ammonia water to a 1000 mL volumetric flask, add pure water to the mark and shake well. This solution can also be prepared as needed. (2) Soaking rice husks in ammonia solution: Weigh 25 g of dry rice husks and place them in a 200 mL beaker. Add 100 mL of the ammonia solution obtained in step (1). Stir with a glass rod to completely immerse the rice husks in the solution. Let stand for 4 h. (3) Fermentation pre-activation: Drain the wet rice husks obtained in step (2), loosen the wet rice husks with a glass rod, place them in an incubator at a constant temperature of 38°C, and fill the water tank of the incubator with water. On the 3rd, 6th, 9th and 12th day after the start of the culture, take out the wet rice husks and add 100 mL of the ammonia solution obtained in step (1) again, soak for 2 hours, then drain the wet rice husks and put them back into the incubator to continue fermentation culture; on the 15th day, soak the wet rice husks in 150 mL of pure water for 4 hours and then drain; the liquid drained out each time is wheat color or brown, and the wet rice husks eventually turn into brown; (4) Ashing reaction: The wet rice husk obtained in step (3) was transferred to a 100 mL quartz beaker, dried at 115°C for 8 h, placed in a muffle furnace, heated to 500°C at a rate of 4°C / min and maintained for 3 h; after cooling, the rice husk was washed with a small amount of pure water to obtain rice husk-based silica.

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