Eco-friendly mechanochemical synthesis of titania-graphene nanocomposites for pesticide photodegradation

Titania graphene hybrid nanocomposites (TiO2-FLG) synthesized from graphite and TiO2 precursors, in a simple and sustainable approach via a three-step method, including the mechanochemical treatment of pre-synthesized FLG and TiO2 NPs are efficient has led to the preparation of TiO2-FLG as efficient nano-catalysts for photo catalytic degradation of a complex mixing of pesticides (isoproturon, pyrimethanil, alachlor and methomyl). The effect of few layer graphene (FLG) loading (0-1.0%) was analyzed to define the optimal ratio of FLG to TiO2 and compared with the corresponding physical mixtures. X-ray Powder Diffraction (XRD) patterns of all these hybrid photocatalysts have presented the same crystal structure, with anatase as the main crystalline phase and brookite as secondary phase. An interaction between the graphene structure and the TiO2 nanoparticles has been observed from Energy Dispersive X-Ray (EDX), X-ray photoelectron (XPS) and Raman spectroscopy studies, indicating that FLG is mainly deposited on the surface wrapping the TiO2 nanoparticles. The presence of FLG in low concentrations and the mechanochemical activation are the key steps to improve the photocatalytic activity of TiO2 nanoparticles on these hybrid nanocomposites. The TiO2-FLG-0.5% hybrid nanocomposite, with circa 1.9 % content of graphitic carbon in surface, has showed the best photocatalytic performance in the degradation of pesticides. Pesticides were completely removed at 350 min, and around 82 % of total organic carbon (TOC) conversion was achieved at 540 min of irradiation time.

Automated summary

Titania graphene hybrid nanocomposites are synthesized and utilized as efficient nano-catalysts for the photo catalytic degradation of complex mixtures of pesticides. The presence of a small amount of few layer graphene and the mechanochemical activation significantly enhance the photocatalytic activity of TiO2 nanoparticles. The TiO2-FLG-0.5% hybrid nanocomposite shows the best photocatalytic performance with complete pesticide removal and about 82% total organic carbon conversion achieved within the irradiation time.