Graphene oxide/titania photocatalytic ozonation of primidone in a visible LED photoreactor

Highlights: • GO-TiO₂ catalysts were synthetized and tested for photocatalytic ozonation. • Ozone processes completely remove Primidone from water in minutes. • TiO₂ becomes a visible active catalyst with GO and ozone. • Combination of ozone, GO-TiO₂ and visible light is needed for mineralization. • Catalyst reusability test shows high mineralization after 3 runs. -- Abstract: A graphene oxide-titania (GO/TiO₂) composite was synthesized via sol-gel method, and studied in aqueous Primidone mineralization with ozone and LED visible light. The photocatalyst was characterized by different techniques (XRD, TEM, SBET, TGA, UV–vis diffuse reflectance spectroscopy). The band gap value decrease from 3.14 eV for bare TiO₂ samples to 2.5 eV in GO/TiO₂ composites clearly shows the interaction of GO with TiO₂ structure. Approximately 20 mg L⁻¹ of Primidone was removed in less than 20 min if ozone was applied, regardless of the presence or absence of light and catalyst. However, reactivity tests show a synergism effect between photocatalysis and ozonation for mineralization purposes. The combination of ozone and GO improved the activation of TiO₂ under visible light. Process optimization led us to select a catalyst dosage of 0.25 g L⁻¹, a light radiance of 359 W m⁻² and a GO loading in the catalyst around 0.75%. At these conditions, with photocatalytic ozonation, the presence of GO in the catalyst improved mineralization up to 82% in 2 h compared to 70% reached with bare TiO₂. Catalyst reusability shows no decrease of photocatalytic activity. Scavenger tests point to hydroxyl radicals as the main species responsible for Primidone removal.