多孔介质中黄原胶改性微米铁的迁移和滞留

Transport and Retention of Xanthan Gum-modified Microscale Zero-valent Iron Particles in Porous Media

为改善微米零价铁(mZVI)在地下水中的迁移性能,该文采用黄原胶(XG)制备稳定化微米铁(XG-mZVI),通过渗流实验研究XG-mZVI的穿透曲线及其在砂柱中的分布规律,探讨XG浓度、孔隙水流速、石英砂粒径和非均质性对XG-mZVI在饱和砂柱中迁移行为和沉积特征的影响。结果表明,XG浓度≥3 g/L时能够明显强化mZVI的迁移能力。XG-mZVI在砂柱中的迁移性能随石英砂粒径和流速的增大而增强。保持其他参数不变,穿透粗粒砂柱(1.0~1.7 mm)的XG-mZVI比穿透细粒砂柱(0.25~0.38 mm)的量多26.4%;在最高流速(0.99×10^(-3) m/s)下穿透砂柱的XG-mZVI比在最低流速下(0.38×10^(-4) m/s)的值高14.2个百分点。XG-mZVI滞留量由砂柱进水端向出水端递减,表明其被截留的主要机制是滤除作用。一维渗流条件下,渗透性变异层对XG-mZVI的沉积/释放机制影响不明显。

To improve the mobility of microscale zero-valent iron(mZVI)in groundwater,xanthan gum(XG)is used to prepare stabilized XG-coated mZVI(XG-mZVI)in the present study.Column transport tests are conducted and the effects of XG concentration,pore water flow rate,quartz sand particle size and heterogeneity on XG-mZVI particle mobility are probed by interpreting its breakthrough curves and retention profiles.The results indicate that XG improves the mobility of mZVI particles through the sand column,especially at higher concentrations(≥3 g/L).According to the transport test results,XG-mZVI particle mobility increases with increasing sand particle size and flow rate.With other conditions kept constant,26.4%more XG-mZVI particles flow through the column filled with the coarsest sand(1.0~1.7 mm)in comparation with the value for the column filled with the finest sand(0.25~0.38 mm),and 14.2 percentage points more XG-mZVI particles pass through the column at the highest flow rate(0.99×10^(-3) m/s)compared with the value at the lowest flow rate(0.38×10^(-4) m/s).The retained XG-mZVI mass decreases from the column inlet to outlet,indicating that straining is the primary mechanism of XG-mZVI retention.Under 1-D flow condition,the influence of heterogeneous layer on deposition/release mechanism of XG-mZVI particles is not obvious.