Abstract: In this work, activated carbon models modified with different hydroxy contents were constructed by implanting hydroxyl groups at the edges of coronene. The physical properties, atomic partial charges and pore size distribution of the modified activated carbon model were studied by molecular dynamics and giant canonical Monte Carlo simulation, and the kinetic characteristics and adsorption mechanism of toluene in modified activated carbon were further analyzed. The results showed that the introduction of hydroxyl can improve the adsorption capacity of activated carbon to toluene, and hydroxyl content significantly affected the adsorption capacity. At high relative pressure, the best concentration of the hydroxyl group was 39.4%, and when hydroxyl concentration exceeded this value, the adsorption amount of toluene decreased. The strong electronegative oxygen atom in the hydroxyl group of modified activated carbon and the hydrogen atom in the methyl of toluene were combined to form a Lewis acid-base pair, which led to a stable adsorption structure and then increased the adsorption capacity of activated carbon to toluene. At low relative pressure, the main factors affecting the adsorption capacity were porosity and pore size. The modified activated carbon with hydroxyl content of 20.8% and 31.4% had massive micropores and a relatively compact structure, which was favorable for toluene adsorption. The self-diffusion coefficient of the toluene molecule in activated carbon was decreased by hydroxyl modification, and the diffusion coefficient was the lowest in activated carbon containing 39.4% hydroxyl. This was because the non-bond interaction between the toluene molecule and modified activated carbon hindered the movement of the toluene molecule. In addition, according to the variable-temperature adsorption research, the increase in temperature was not conducive to the adsorption of toluene by activated carbon since it was an exothermic process. This study can provide a theoretical basis for the improvement of the adsorption performance of activated carbon materials.

Key words: activated carbon, hydroxyl modification, adsorption, molecular dynamics, diffusion

摘要： 本工作通过在六苯并苯分子边缘植入羟基构建不同羟基含量的改性活性炭，采用分子动力学和巨正则蒙特卡罗模拟研究了改性活性炭模型的物理性质、局部电荷和孔径分布，进一步分析了甲苯分子在改性活性炭中的动力学特性和吸附机理。结果表明，引入羟基可加强活性炭对甲苯的吸附能力。在较高相对压强下，羟基含量为39.4%是活性炭改性的最佳浓度，超过此浓度后甲苯的吸附量下降。改性活性炭羟基中强电负性的氧原子与甲苯甲基中的氢原子配合成Lewis酸碱对，形成稳定的吸附结构，进而增强活性炭对甲苯的吸附能力。在较低相对压强下，影响吸附量的主要因素为孔隙率和孔径大小；羟基含量为20.8%和31.4%的改性活性炭内多为微孔且结构较为紧密，使得其吸附甲苯效果较好。羟基改性使得甲苯分子在活性炭内的自扩散系数降低，且在含39.4%羟基的活性炭中扩散系数最低，这是由于甲苯分子与改性活性炭之间的非键相互作用阻碍了甲苯分子的运动。此外通过变温吸附研究发现，由于活性炭吸附甲苯过程具有放热性质，温度升高不利于甲苯的吸附。

关键词: 活性炭, 羟基改性, 吸附, 分子动力学, 扩散