Aluminum hydroxide colloid facilitated transport of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) in porous media

Abstract

In this study, aluminum hydroxide colloids, which widely exist in soils, were selected to investigate their effect on the infiltration of an abundant congener of PBDEs (BDE-47) to groundwater. The batch and column experiments were conducted to study the co-migration of aluminum hydroxide colloid and BDE-47 in two sand media with particle sizes of 2–4.75 and 0.15 mm. The results indicated that the colloid significantly increased the transport of BDE-47 to 24.32% and 65.84% in the vadose zone of coarse and fine sand columns, respectively. The adsorption and blocking effect were found to be the two main functions during the co-migration of aluminum hydroxide colloids with BDE-47. Specifically, BDE-47 that adsorbed on colloids moved faster in the coarse porous media, and the breakthrough peak of BDE-47 appeared early in the media at an approximate pore volume of 0.15. In comparison, colloids that adsorbed onto the fine porous media formed a layer that blocked the adsorption of BDE-47 onto the fine porous media. This weakened the protection capacity of the vadose zone and led to a greater than 80% amount of BDE-47 breakthrough to the vadose zone.