Transport of nano zero-valent iron supported by mesoporous silica microspheres in porous media

Effective in situ remediation of groundwater requires the successful delivery of reactive iron particles through sand. However, the agglomeration of nano zero-valent iron (NZVI) particles limits the migration distance, which inhibits their usefulness. In the study described herein, NZVI supported by mesoporous silica microspheres covered with FeOOH (SiO₂@FeOOH@Fe) was synthesized, and its mobility was demonstrated on the basis of transport in porous media. Degradation of decabromodiphenyl ether (BDE209) was more efficient by SiO₂@FeOOH@Fe than by ‘bare’ NZVI. Breakthrough curves and mass recovery showed the mobility of SiO₂@FeOOH@Fe in granular media was better than that of bare NZVI. It increased greatly in the presence of natural organic matter (NOM) and decreased when high Ca²⁺ and Mg²⁺ concentrations were encountered. Analysis of the transport data on the basis of filtration theory showed diffusion to be the main mechanism for particle removal in silicon sand. Increasing the NOM may decrease agglomeration of the gains of sand, which has a positive effect on the mobility of SiO₂@FeOOH@Fe. Presumably, increasing the concentrations of Ca²⁺ and Mg²⁺ compresses the diffuse double layer of SiO₂@FeOOH@Fe, resulting in a reduction of mobility. Copyright © 2015 IWA Publishing.