Enhanced photocatalytic and settling performance of a mesoporous graphene/titanium oxide composite for wastewater treatment

A reduced graphene oxide-P25 (rGO-P25) composite was synthesized by one-step hydrothermal method. The photocatalytic degradation of Rhodamine B (RhB) by the rGO-P25 composite and its settling performance was investigated with P25 as a control. The results showed that the rGO-P25 composite has a mesoporous structure, with the average particle size increased from 4.99 to 399.0 µm, and the specific surface area of the composite increased from 54.0 to 74.3 m 2 /g. The rGO-P25 composite has a much better photocatalytic and settling performance as compared to P25, which were 1.56 and 2.4 times higher. The increased photocatalytic performance by the rGO-P25 composite was mainly attributed to the increased adsorption capacity and charge transfer ability due to the introduction of rGO flakes in the composite. However, the improved settling performance mainly lies on the increase of the average particle size. The electron spin resonance (ESR) results shows that hydroxyl radical, superoxide radical and photogenerated hole were all generated in the degradation of RhB but the hydroxyl radicals are the leading reactive oxygen species. The as-synthesized rGO-P25 composite showed a good recycling ability as RhB degradation rate could still reach 98.6% after five times reuse. This study indicates that the rGO-P25 composite is a promising photocatalyst for practical wastewater treatment. Graphical abstract