大孔隙对纳米CeO_2在多孔介质中迁移行为的影响

Effect of macropores on the transport behavior of CeO_2 nanoparticles in porous media

研究了不同类型大孔隙对纳米CeO_2在石英砂柱中迁移的影响,并运用两区物理化学非平衡模型对纳米CeO_2流出曲线进行拟合和参数估算.结果表明,含横孔(垂直水流运动方向)石英砂柱中纳米CeO_2的流出曲线与均匀石英砂柱十分接近,横孔对于纳米CeO_2在石英砂介质中的迁移影响较弱.与均匀石英砂柱相比,含竖孔(平行水流运动方向)石英砂柱中纳米CeO_2流出曲线明显不同于均匀石英砂柱,其初始穿透时间明显提前,初始穿透浓度和初始回收率显著增加,竖孔对于纳米CeO_2在石英砂介质中的迁移起促进作用,特别是贯通竖孔.两区物理化学非平衡模型可以很好地拟合纳米CeO_2在含有大孔隙石英砂柱中的迁移.通过分析模型参数质量交换系数(ωph、αch)和分配系数(Kd)得出,含横孔石英砂柱中纳米CeO_2在两区间的质量交换能力和吸附作用较强,而含有竖孔石英砂柱中纳米CeO_2在两区间的质量交换能力和吸附作用较弱.

This study investigated the effect of macropores on the transport behaviors of CeO2nanoparticles（n CeO2） in quartz sand columns.The breakthrough curves（BTCs） were fitted by two-region physico-chemical non-equilibrium model,and the transport parameters were also estimated.Similar BTCs were observed between the columns with homogeneous and horizontal macropores,indicating there was little effect of horizontal macropores on the transport behavior of n CeO2.However,compared with the homogeneous column,the BTCs of n CeO2 were significantly different in columns containing vertical macropores,which had much earlier initial breakthrough time,much higher initial transport concentration and much higher initial recovery rate.It demonstrated that the mobility of n CeO2 was significantly enhanced by vertical macropores,especially the continuous vertical macropores.The two-region physical and chemical nonequilibrium model provided a good description for transport of n CeO2 s in quartz sand containing macropores.From the analysis of model parameters of mass transfer coefficient（ωph,αch） and distribution coefficient（Kd）,we could draw a conclusion that mass transfer and adsorption of n CeO2 between the two regions were strong in columns containing horizontal macropores,but were weak in columns containing vertical macropores.