Fan Ming, Boonfueng Thipnakarin, Xu Ying, Axe Lisa, Tyson Trevor A
Department of Civil and Environmental Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA.
J Colloid Interface Sci. 2005 Jan 1;281(1):39-48. doi: 10.1016/j.jcis.2004.08.050.
Hydrous amorphous Al (HAO), Fe (HFO), and Mn (HMO) oxides are ubiquitous in the subsurface as both discrete particles and coatings and exhibit a high affinity for heavy metal contaminants. To assess risks associated with heavy metals, such as Pb, to the surrounding environment and manage remedial activities requires accurate mechanistic models with well-defined transport parameters that represent sorption processes. Experiments were conducted to evaluate Pb sorption to microporous Al, Fe, and Mn oxides, as well as to montmorillonite and HAO-coated montmorillonite. Intraparticle diffusion, a natural attenuating process, was observed to be the rate-limiting mechanism in the sorption process, where best-fit surface diffusivities ranged from 10(-18) to 10(-15) cm(2) s(-1). Specifically, diffusivities of Pb sorption to discrete aluminum oxide, aluminum oxide-coated montmorillonite, and montmorillonite indicated substrate surface characteristics influence metal mobility where diffusivity increased as affinity decreased. Furthermore, the diffusivity for aluminum oxide-coated montmorillonite was consistent with the concentrations of the individual minerals present and their associated particle size distributions. These results suggest that diffusivities for other coated systems can be predicted, and that oxide coatings and montmorillonite are effective sinks for heavy metal ions.
含水无定形铝（HAO）、铁（HFO）和锰（HMO）氧化物在地下以离散颗粒和涂层的形式普遍存在，并且对重金属污染物具有高亲和力。为了评估与重金属（如铅）相关的对周围环境的风险并管理修复活动，需要具有明确传输参数的准确机理模型来表示吸附过程。进行了实验以评估铅对微孔铝、铁和锰氧化物以及蒙脱石和HAO涂层蒙脱石的吸附。颗粒内扩散是一种自然衰减过程，被观察到是吸附过程中的限速机制，其中最佳拟合表面扩散率范围为10^(-18)至10^(-15) cm² s^(-1)。具体而言，铅吸附到离散氧化铝、氧化铝涂层蒙脱石和蒙脱石的扩散率表明，底物表面特性影响金属迁移率，其中扩散率随着亲和力的降低而增加。此外，氧化铝涂层蒙脱石的扩散率与存在的单个矿物的浓度及其相关的粒度分布一致。这些结果表明，可以预测其他涂层系统的扩散率，并且氧化物涂层和蒙脱石是重金属离子的有效汇。
