Tandem adsorption-photodegradation activity induced by light on NiO-ZnO p-n couple modified silica nanomaterials

Well dispersed mono and coupled NiO, ZnO oxides modified silica, with a narrow size distribution, less than 10 nm, have been synthesized by “one-pot” microemulsion assisted sol-gel procedure. The composites exhibited significantly enhanced tandem adsorption-photodegradation activity for the degradation of Methylene Blue dye over 90% (under UV light) and 97% (under sun light). These highly homogeneous oxides modified silica, with very low content of NiO (0.01÷1.14%) and ZnO (0.09%) oxides dispersed in silica, are generating a size effect that leads to nanomaterials with superior properties like higher specific surface area (308 m2 g−1), smaller band-gaps energy (2.5 eV) and, consequently, extended light absorption range from UV to natural light. A synergistic effect of mixed n-type ZnO and p-type NiO oxides incorporated in silica has been noticed on the tandem adsorption and photodegradation process. Several influencing process parameters, such as the material and dye loading, stirring speed, NiO/ZnO ratio and light source on the photodegradation performance of NiO-ZnO modified silica related to Methylene Blue cationic dye, were also investigated.