Preparation method for coproduction of high-specific-capacitance active carbon and nano silicon dioxide from rice hull

Abstract

The invention discloses a preparation method for coproduction of high-specific-capacitance active carbon and nano silicon dioxide from rice hull, and belongs to the technical field of resource comprehensive utilization and electrochemical supercapacitors. The preparation method comprises the steps of (1) cleaning, drying and grinding rice hull; (2) carbonizing the rice hull ground in the step (1) under a non-oxidizing condition, processing the carbonized rice hull through an acid solution, washing with water and drying to obtain carbide; (3) mixing the carbide obtained from the step (2) with strong base by a certain proportion, adding a certain amount of water, uniformly mixing, drying, controlling a temperature-increasing speed and activating to obtain an activated product; (4) soaking the activated product obtained from the step (3) in hot water, filtering and washing to be neutral, drying and grinding the product to 150-300 meshes to obtain a high-specific capacitance rice hull-based active carbon material; and (5) recovering filtrate obtained from the step (4), adding the acid solution at certain temperature, controlling a speed of dropping acid, regulating pH, aging, filtering and drying to obtain a nano silicon dioxide product.

Description

technical field [0001] The invention belongs to the technical field of comprehensive utilization of resources and electrochemical supercapacitors, and relates to a method for coproducing activated carbon with high specific capacitance and nano silicon dioxide from rice husks. Background technique [0002] Electrochemical supercapacitor is a new type of high-efficiency energy storage device between rechargeable batteries and traditional capacitors. Supercapacitors with high energy density, which can provide powerful burst power in an instant and their key materials have been researched and developed by people. hotspot. Carbon materials with high specific capacity are one of the key materials for supercapacitors. Typical carbon materials include carbon fibers, activated carbon, carbon nanotubes, and carbon gels. The current commercial electrode material for electrochemical supercapacitors is mainly activated carbon, which has low production cost, mature technology and stable...

AI Technical Summary

Problems solved by technology

[0004] Among the various utilization methods of rice husks, the patent CN101708845A uses rice husks and straws as raw materials to prepare activated carbon, and performs pretreatment, carbonization, acid treatment, and alkali activation on the raw materials. More than 135mg / g, the patent is activated by alkali boiling method, which cannot effectively remove the silica in the activated carbon, and the obtained activated carbon has a high ash content, which is not suitable for use as capacitor carbon; the patent CN1203887A uses rice husk as raw material, uses rice husk carbide and alkali The activator is mixed according to a certain mass ratio, and after pretreatment, it is activated by heating to obtain a specific surface area of ​​2500-3500m 2 / g of activated carbon products, the purpose of the prepared activated carbon with high specific surface is as a high-efficiency adsorption material. This method directly activates the rice husk carbide and alkali solid phase after mixing, it is difficult to mix the carbide and alkali evenly, and The activation product is not treated, resulting in unstable performance of the obtained activated carbon and relatively high ash content; patent CN102205963A combines biomass raw materials such as rice husks with 32-72wt% inorganic acid at a solid-to-liquid ratio of 1:5-10 (Kg / L) mixing, using the sugar-acid solution obtained after hydrolysis to undergo polycondensation carbonization reaction, filtration, washing, and drying to prepare hydrothermal carbon, and then activate to prepare activated carbon with high specific surface area for supercapacitors. The preparation method is relatively complicated, and there are many types of raw materials. The time is longer, the energy consumption is larger, and the product cost is higher; the patent CN102431993A uses rice husk as a carbon source, zinc chloride as an activator, and prepares mesoporous carbon materials through microwave-assisted heating of zinc chloride activation, and the prepared mesoporous The specific surface area of ​​carbon material is between 1409-1738m 2 / g, the specific capacitance is less than 200F / g, and the specific surface area of ​​the carbon material prepared by this method is not large, and the specific capacitance is not high. Since zinc chloride is used as the activator, it is very effective for the removal of silicon dioxide and ash in rice husks. not effectively

Although the activated carbon material with high specific surface area has been prepared in the above-mentioned patent, there are still many deficiencies in the preparation method, and only the carbon source in the rice husk is used, and the full utilization of the rice husk has not been realized.

Considering that rice husk contains a large amount of natural silica, patent CN101486460A uses rice husk as raw material to prepare activated carbon and silica with high adsorption performance, but the quality of the prepared silica is not high; patent CN101804988A discloses a A method for preparing nano-silica and activated carbon from rice husk ash, which realizes the comprehensive utilization of rice husk, but due to the use of carbonate as an activator, the specific surface area of ​​the prepared activated carbon is low (2 / g), which limits the application of the prepared activated carbon. At the same time, this method does not control the formation conditions of silica, such as the concentration of acid, the solution drop rate, the end pH, etc., so it is difficult to obtain nano-scale silica

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