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 m 2 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.