Efficient solar removal of acetaminophen contaminant from water using flexible graphene composites functionalized with Ni@TiO:W nanoparticles.

This work presents the morphological, structural and photocatalytic properties of flexible graphene composites decorated with Ni@TiO:W nanoparticles (TiNiW NPs) with an average size of 27 ± 2 nm. The TiNiW NPs were immobilized on the surface of a flexible graphene composite using a PVA-based slurry-paste (FG/TiNiW composite). The SEM study showed that the TiNiW NPs remained exposed on the surface of the FG/TiNiW composite, which benefited its photocatalytic activity. The photocatalytic performance for the degradation of acetaminophen (ACT) was evaluated using both the TiNiW powders and the FG/TiNiW composite, obtaining maximum degradation efficiencies of 100 and 86%, respectively, after 3 h under natural solar irradiation. The degradation of ACT was caused mainly by the reactive oxygen species such as OH radicals and h, which was confirmed by scavenger experiments. Photoluminescence, XPS and absorbance experiments revealed that oxygen vacancy defects were created by i) doping the TiNiW NPs with W and by ii) introducing graphene into the composites. These defects enhanced the absorbance of light in the range of 400-800 nm, which in turn, promoted the photocatalytic degradation of ACT. Moreover, the reuse experiments confirmed that both the TiNiW NPs and FG/TiNiW composite were very stable for the degradation of ACT, since degradation efficiencies >82% were obtained after 4 reuse cycles for both photocatalysts. The experimental findings of this work demonstrate that the flexible TiO/graphene composites are a feasible option for the removal of pharmaceutical contaminants from water using natural solar irradiation.