基于稻壳灰的高吸收性活性炭制备工艺的优化及其产品性能分析

Optimization of the preparation technology of high absorbency activated carbon based on rice husk ash and its product performance analysis

为了充分利用稻壳这一资源,获得高吸收性活性炭,以稻壳灰(RHA)为原料,分别用NaOH为脱硅剂和KOH为活化剂对其进行脱硅和活化处理,采用单因素分析和正交试验设计法,以活性炭的亚甲基蓝吸附值为考核指标,考察炭碱比、活化温度、活化时间对活性炭吸附性能的影响,确定制备高吸附活性炭的最优工艺条件。结果表明,活化工艺参数最佳组合为炭碱比1∶3、活化温度550℃、活化时间40 min;影响活性炭吸附性能的因素次序为炭碱比>活化温度>活化时间。根据吸附-脱附等温线,经活化后的活性炭等温线属于IV型,具有发达的微孔和介孔结构。利用扫描电子显微镜(SEM)观察到活性炭的孔径和孔容,结果表明经过KOH活化法可制得高比表面积、高吸附性的活性炭。利用X射线衍射(XRD)观察稻壳灰、脱硅稻壳灰和活性炭的微晶结构发现,在衍射角2θ分别为22.3°、24.0°、24.4°附近有衍射峰,表明稻壳灰制备的活性炭具有炭无定型结构。

To thoroughly utilize rice husk resources and obtain high absorbable activated carbon,rice husk ash( RHA) was desiliconized and activated with NaOH as the desiliconizer and KOH as the activator,respectively. Single factor analysis and orthogonal test design were used to determine the effects of carbon-alkali ratio,activation temperature and activation time on the adsorption property of activated carbon with the absorptive value of methylene blue as the index to establish the preparation process of high absorbable activated carbon. The results showed that the optimal combination of activation process parameters were as follow s: carbon-to-alkali ratio 1 ∶ 3,activation temperature 550 ℃,activation time 40 min. Factors affecting the adsorption of activated carbon was in this order: the ratio of carbon to alkali>activation temperature> activation time. Based on the adsorption-desorption isotherm,the activated carbon isotherm belonged to type IV,and the carbon had advanced micropore and mesopore structure. Scanning electron microscope( SEM)was used to determine the pore size and pore volume of activated carbon. The results showed that activated carbon with high specific surface area and high adsorption could be prepared by KOH activation method. Xray diffraction( XRD) was used to observe the microcrystalline structure of rice husk ash,desiliconized rice husk ash and activated carbon,it was found that there were diffraction peaks around 2θ = 22. 3°,2θ =24. 0°,and 2θ = 24. 4°,respectively,indicating that the activated carbon prepared by rice husk ash had an amorphous structure.