KOH活化法制备汉麻秆活性炭及其微孔结构的研究

Preparation of hemp stem-based activated carbon by KOH activation and study of its microporous structure

采用生物质材料制备比表面积大、微孔结构发达的活性炭,对于缓解资源紧缺、拓展活性炭在气相吸附和双电层电容器等方面的应用具有重大意义。以汉麻秆为原料、KOH为活化剂制备活性炭,通过正交试验探讨碱炭比、活化温度、活化时间对活性炭得率和碘吸附值的影响;采用场电镜、孔径分析仪对样品的微孔结构进行分析。结果表明,影响活性炭得率和碘吸附值的最显著因素分别为碱炭比和活化温度,在碱炭比4∶1、活化温度900℃、活化时间为0.5h的条件下,活性炭得率为72%、碘吸附值为2 047mg/g,比表面积为1 924.08m2/g,总孔容为1.01cm3/g,平均孔径为2.1nm;该活性炭的微孔结构发达(微孔率为81.19%),孔径分布较窄,同时存在超微孔和极微孔,且极微孔含量很高。

Activated carbon with large specific surface area and rich microporous structure was prepared from re-newable biomass materials.It was of great significance for alleviating shortage of resources,expanding applica-tion of activated carbon in gas adsorption and EDLC.In this study,activated carbons were prepared from hemp stem using KOH as an activator.The effects of weight ratio (KOH:straw),temperature and duration of acti-vation on the yields and iodine adsorption values of the activated carbons were evaluated using orthogonal test design.The micro-morphology and pore structure of activated carbons were analyzed using FE-SEM and surface area analyzer.The results showed that weight ratio of KOH to the raw material and temperature of the activa-tion were the most influential factors for the yield and iodine adsorption value,respectively.The optimum ad-sorption capability was obtained when the activation was conducted for 0.5 h at 900 ℃ with a 4∶1 weight ratio of activator to raw material.The activated carbon was obtained with a high yield of 72%,a maximum iodine val-ue of 2 047 mg/g,BET specific surface area of 1 924.08 m2/g,total pore volume of 1.01 cm3/g,average pore size of 2.1 nm.The as-prepared activated carbon exhibited rich microporous structure with a microporosity of 81.1 9% and a narrow pore size distribution.Ultra-micropore and a high content of super-micropore were ob-served in the prepared activated carbon.