PDMS基涂层活性炭对甲苯、苯和丙酮吸附研究

活性炭疏水性改性是提高其对含水VOCs选择性吸附的重要手段,然而这种改性方法对活性炭吸附不同VOCs的效果研究较少.采用聚二甲基硅氧烷(polydimethylsiloxane,PDMS)对活性炭进行改性处理,并利用BET、Boehm滴定等方法对活性炭进行表征.采用动态吸附法,利用Yoon-Neslon吸附理论模型研究了不同相对湿度条件下,PDMS改性活性炭对VOCs(甲苯、苯、丙酮)吸附穿透曲线、饱和吸附量的影响及关键影响因素.结果表明:PDMS改性活性炭BET比表面积、微孔容积和表面酸碱官能团含量均有减少;经PDMS改性后,活性炭表面疏水性增大.动态吸附实验结果表明:PDMS改性前后活性炭吸附甲苯、苯、丙酮穿透曲线均符合Y-N模型;随着相对湿度增大,未经改性的活性炭(Bare-AC)对甲苯、苯和丙酮吸附速率降低、平衡吸附量减少,PDMS改性活性炭对甲苯、苯分子吸附速率和选择吸附能力提高,其中PDMS改性的活性炭(PDMS/AC-250)对甲苯、苯吸附量为相同条件下Bare-AC的1.86(甲苯)、1.92(苯)倍,但对丙酮分子提高不明显;结合表征结果分析,PDMS改性活性炭对VOCs分子吸附主要依靠化学吸附,同时与VOCs分子极性有关.

Toluene, Benzene and Acetone Adsorption by Activated Carbon Coated with PDMS

To improve the adsorption selectivity of volatile organic compounds(VOCs), activated carbon (AC) was modified by polydimethylsiloxane (PDMS) and characterized by BET analysis and Boehm titration. Dynamic adsorption column experiments were conducted and Yoon-Neslon(Y-N) model was used to identify adsorption effect for toluene, benzene and acetone on AC when relative humidity was 0%, 50% and 90%, respectively. The results showed that the BET area, micropore volume and surface functional groups decreased with the PDMS modification, and surface hydrophobicity of the modified AC was enhanced leading to a lower water adsorption capacity. The results of dynamic adsorption showed that the adsorption kinetics and capacity of Bare-AC decreased with the increase of relative humidity, and the adsorption capacities of PDMS coated AC were 1.86 times (toluene) and 1.92 times (benzene) higher than those of Bare-AC, while a significant improvement of adsorption capacity for acetone was not observed. These findings suggest that polarity of molecule can be an important influencing factor for adsorption on hydrophobic surface developed by PDMS.