Impact of aquatic chemistries to the fate and transport of engineered nanoparticles in membrane-based water treatment process

Abstract

As technology for production of engineered nanomaterials has been developed, releases of nanomaterials into environments has been increased leading to potential harmfulness for the human body. In this research, influence of aquatic chemistries during membrane filtration of zinc oxide (ZnO) and titanium dioxide (TiO2) were studied. Different pH (5.0, 7.4, 9.0) and presence of natural organic matters (NOM) were investigated, and two membranes (polymeric and ceramic membrane) were used. As a result, removal of ZnO was considerably affected by the change of pH (97-99 % and 8-13 % at pH 9 and pH 5 respectively). On the other hand, TiO2 showed relatively stable rejection at tested pH values (> 97 %). Results from dynamic light scattering presented that the average diameter were 284 ± 23 nm for ZnO and 303 ± 41 nm for TiO2. In the presence of NOM, average diameter was decreased to 171 ± 4 nm and 186 ± 5 nm for ZnO and TiO2 respectively. In the presence of NOM, nanomaterial permeation through polymeric membrane increased. However, in ceramic membrane, the rejection of ZnO and TiO2 were same with or without NOM. That is because the surface filtration was dominant in polymeric membranes, while the depth filtration mechanism played an important role in ceramic membrane. These results indicate that fate and transport of nanomaterials depend on aquatic chemistries.