活性炭孔隙结构在其甲苯吸附中的作用

选用4种商用活性炭(AC),利用氮气绝热吸附、扫描电子显微镜(SEM)和傅立叶变换红外光谱(FTIR)测试了活性炭的物化性质。以甲苯为吸附质,在温度为298.15 K下进行了静态和动态吸附实验,研究了活性炭孔结构对其吸附性能、吸附行为、表面覆盖率和吸附能的影响。结果表明:活性炭的比表面积和孔容是其吸附性能主要影响因素,孔径在0.8～2.4 nm之间的孔容和甲苯吸附量之间存在较好的线性关系,且线性斜率随甲苯浓度增加而变大。甲苯吸附行为符合Langmuir吸附等温模型和准一阶动力学方程式。活性炭孔结构是甲苯吸附速率的主要制约因素。在甲苯快速吸附阶段,微孔为吸附速率主要制约因素,在甲苯颗粒内扩散阶段,微孔和表面孔为吸附速率的主要制约因素,在吸附末尾阶段,中孔和大孔为吸附速率的主要制约因素。4种活性积炭对甲苯的吸附能随其比表面变大而变大。

Pore structure effects on activated carbon adsorption behavior for toluene

Four kinds of commercial activated carbon (AC) were chosen as the samples, the physical and chemical properties of the samples were characterized by nitrogen adsorption isotherms, scanning electron microscopy(SEM) and fourier transform infrared spectroscopy (FTIR). To explore effects of activated carbon pore structure on its adsorption properties, adsorption behaviour, surface coverage and adsorption energy, adsorption of toluene onto the chosen samples was investigated by the thermodynamic and kinetic methods at 298.15 K. The results showed that activated carbon surface area and pore volume were the main factors affecting its adsorption properties, there was a good linear relationship between toluene adsorptive capacity and activated carbon pore volume when aperture was 0.8 ~ 2.4 nm, and the linear slope increased with toluene concentration. Langmuir adsorption isotherm model and the quasi-first order kinetic equation were suitable for describing the experimental data of toluene on activated carbons. Pore structure was the major constraint of adsorption rate for toluene, specifically, during fast adsorption stage, adsorption rate was mainly restricted by micropore, at particles diffusion stage and the end stage, micropores, surface pore and mesopores, macropores was the main constraint on adsorption rate, respectively. Adsorption energy of these four kinds of activated carbon varied with the increase of specific surface area.