Migration of vanadium oxide nanoparticles in saturated porous media

Vanadium oxides nanoparticles (VO_x-NPs) as emerging functional materials are widely applied in high-technology industries. However, their environmental behaviors remain largely known. In this study, the migration of three common VO_x-NPs (V₂O_5, VO₂, and V₂O₃) in saturated porous media has been investigated. V₂O₅ NPs showed the highest migration ability under all conditions, compared to other VO_x-NPs. Increasing ionic strength and decreasing pH hindered their migration, while the presence of Ca^2 + was more effective than Na⁺ in depositing VO_x-NPs. The combined results from multiple analyses (DLVO theory, MMS equations, Traj-Hap module of Parti-Suite and HYDRUS-1D simulation) suggested that high ionic strength and low pH reduced the energy barrier between the VO_x-NPs and quartz sand, and increased the particulate sizes, making VO_X-NPs more difficult to migrate. Changes in VO_x-NPs size effected the contribution of gravity in retention fate. Small VO_x-NPs (< 400 nm) delivered to both the upstream and downstream of the quartz sand surface, while large ones (> 900 nm) remained downstream. This study provides the insight into the geochemical fates of VO_x-NPs, which is helpful to develop regulating strategies to reduce/eliminate their potential environmental risks.