Dipartimento di Ingegneria del Territorio, dell'Ambiente e delle Geotecnologie, Politecnico di Torino, Corso Duca degli Abruzzi, 24, 10129 Torino, Italy.
Environ Sci Technol. 2010 Dec 1;44(23):9062-8. doi: 10.1021/es100868n. Epub 2010 Nov 8.
The use of zerovalent iron micro- and nanoparticles (MZVI and NZVI) for groundwater remediation is hindered by colloidal instability, causing aggregation (for NZVI) and sedimentation (for MZVI) of the particles. Transportability of MZVI and NZVI in porous media was previously shown to be significantly increased if viscous shear-thinning fluids (xanthan gum solutions) are used as carrier fluids. In this work, a novel modeling approach is proposed and applied for the simulation of 1D flow and transport of highly concentrated (20 g/L) non-newtonian suspensions of MZVI and NZVI, amended with xanthan gum (3 g/L). The coupled model is able to simulate the flow of a shear thinning fluid including the variable apparent viscosity arising from changes in xanthan and suspended iron particle concentrations. The transport of iron particles is modeled using a dual-site approach accounting for straining and physicochemical deposition/release phenomena. A general formulation for reversible deposition is herein proposed, that includes all commonly applied dynamics (linear attachment, blocking, ripening). Clogging of the porous medium due to deposition of iron particles is modeled by tying porosity and permeability to deposited iron particles. The numerical model proved to adequately fit the transport tests conducted using both MZVI and NZVI and can develop into a powerful tool for the design and the implementation of full scale zerovalent iron applications.
使用零价铁微纳米颗粒（MZVI 和 NZVI）进行地下水修复受到胶体不稳定性的阻碍，导致颗粒聚集（对于 NZVI）和沉淀（对于 MZVI）。如果将粘性剪切稀化流体（黄原胶溶液）用作载体流体，MZVI 和 NZVI 在多孔介质中的迁移能力会显著提高。在这项工作中，提出并应用了一种新的建模方法，用于模拟用黄原胶（3 g/L）改性的高浓度（20 g/L）非牛顿悬浮液的一维流动和传输。耦合模型能够模拟剪切稀化流体的流动，包括由于黄原胶和悬浮铁颗粒浓度变化引起的表观粘度变化。使用双位模型来模拟铁颗粒的传输，该模型考虑了应变和物理化学沉积/释放现象。本文提出了一种通用的可逆沉积公式，其中包括所有常用的动力学（线性附着、阻塞、成熟）。由于铁颗粒的沉积而导致多孔介质堵塞，通过将孔隙率和渗透率与沉积的铁颗粒联系起来进行建模。数值模型被证明能够很好地拟合使用 MZVI 和 NZVI 进行的传输测试，并可能发展成为设计和实施全规模零价铁应用的有力工具。
