以玉米秸秆作为生物质活性炭的原材料,CO2作为活化介质,分别以KOH、HNO3和CH3 COOH作活化剂,在800℃下一步法制备出玉米秸秆活性炭,并针对部分样品分别使用KOH、HNO3和CH3 COOH进行化学活化。分别考察CO2活化时间、CO2活化剂浓度、化学活化种类及后续热处理工艺对样品吸附CO2的性能影响。结果表明,化学活化过程可拓展活性炭的空隙结构,显著提高其对CO2的吸附。在最优工艺下(4mol/L HNO3活化+100℃水浴加热1h+600℃热处理),活性炭的比表面积达639.8 m2/g,其CO2捕集效率为7.33%,高于市场商业用活性炭的6.55%。同时,考察活性炭微孔和中孔对CO2吸附的影响规律,并采用Bangham动力学模型探讨样品的吸附性能。
Activated carbons ( ACs) were produced by a one step process with CO2 as the physical activation agent at 800 ℃. The ACs were further activated chemically using KOH, HNO3 or CH3 COOH and heat-treated at 300 or 600℃ for 1 or 2 h to modify their properties. The effect of CO2 concentration, activation time, types of chemical agents and the post heat-treatment conditions on CO2 capture were investigated. Results showed that the optimum conditions for AC production from corn stalks was at 800 ℃ for 30 min with a CO2 concentration of 20% during the physical activation. Chemical agents and further heat-treatment modified the pore structure of the ACs, resulting in a performance improvement for CO2 adsorption. The BET surface area of one sample ( HNO3 activation +100 ℃ water bath 1 h+post heat-treatment at 600℃ for 2 h) was 639. 8 m2/g. The maximum CO2 adsorption capaci-ty of the sample was 7. 33%, which is higher than that of a commercial AC (6. 55%). The CO2 adsorption is dominantly depend-ent on the mesopore volume when the BET surface area is smaller than 500 m2/g while the adsorption is closely associated with mi-cropore area when the BET surface area is larger than 500 m2/g. The adsorption kinetics agreed well with the Bangham kinetic mod-el.
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