菲在不同性质黑炭上的吸附动力学和等温线研究

在300、500和700℃3种条件下加热木屑制备得到3种黑炭,并对其结构和组成进行了表征。通过吸附动力学实验和平衡吸附实验,研究了菲在这些黑炭样品上的吸附动力学和平衡吸附,分别应用拟一阶、拟二阶和叶洛维奇3种动力学模型及Freundlich吸附等温方程对实验数据进行了拟合。结果表明,菲在黑炭样品上的吸附可以分为极快吸附、快吸附和慢吸附3个阶段,拟一阶动力学和叶洛维奇动力学方程仅能对菲在黑炭上吸附动力学的某个阶段拟合较好,而拟二阶动力学模型可较好地拟合菲的整体吸附动力学过程。说明菲在黑炭上的吸附由多个过程控制,水膜扩散、吸附剂颗粒表面扩散和吸附剂内部微孔扩散等多个过程导致了其吸附动力学的复杂性。在快吸附阶段,菲在各个黑炭上吸附动力学的差异,主要受黑炭疏水性影响。Freundlich模型对吸附等温数据的拟合结果进一步证实,多环芳烃菲在黑炭样品上的吸附受多种机制影响。

Sorption Kinetics and Isotherms of Phenanthrene in Charcoals with Different Properties

Three charcoals were obtained by heating sawdust at 300, 500 and 700 ℃, respectively. The structures and compositions of the charcoals were characterized. Sorption kinetics and isotherms of phenanthrene onto these charcoals were determined. The data were fitted to the pseudo-first-order, the pseudo-second-order, the Elovich kinetic, and the Freundlich models, respectively. The sorption was divided into very fast,fast and slow stages. The pseudo-second-order model fitted the sorption kinetics data well over the entire sorption duration; The pseudo-first-order and Elovich models did comparatively well for only selected sorption periods. These observations indicated that multiprocesses controlled the sorption of phenanthrene on charcoals including diffusion into water film, diffusion on particle surfaces of the charcoals, and diffusion in the internal micropores, which resulted in the observed complexity in the sorption kinetics. The differences in fast sorption on charcoals were attributed to their varying hydrophobicities. The results from the Freundlich model analysis further suggested that the multiple processes controlled the sorption of phenanthrene onto charcoals.