Highly Efficient Water Decontamination by Using Sub-10 nm FeOOH Confined within Millimeter-Sized Mesoporous Polystyrene Beads

Millimeter-sized polymer-based FeOOH nanoparticles (NPs) provide a promising option to overcome the bottlenecks of direct use of NPs in scaled-up water purification, and decreasing the NP size below 10 nm is expected to improve the decontamination efficiency of the polymeric nanocomposites due to the size and surface effect. However, it is still challenging to control the dwelled FeOOH NP sizes to sub-10 nm, mainly due to the wide pore size distribution of the currently available polymeric hosts. Herein, we synthesized mesoporous polystyrene beads (MesoPS) via flash freezing to assemble FeOOH NPs. The embedded NPs feature with α-crystal form, tunable size ranging from 7.3 to 2.0 nm and narrow size distribution. Adsorption of As(III/V) by the resultant nanocomposites was greatly enhanced over the α-FeOOH NPs of 18 × 60 nm, with the iron mass normalized capacity of As(V) increasing to 10.3 to 14.8 fold over the bulky NPs. Higher density of the surface hydroxyl groups of the embedded NPs as well as their stronger affinity toward As(V) was proved to contribute to such favorable effect. Additionally, the as-obtained nanocomposites could be efficiently regenerated for cyclic runs. We believe this study will shed new light on how to fabricate highly efficient nanocomposites for water decontamination.