Solar photocatalytic degradation of Zn2+ using graphene based TiO2

•TiO2-graphene composite catalyst was synthesised by hydrothermal treatment method.•Removal of heavy metal Zinc studied by solar photocatalysis.•Photo-reduction of Zn2+ follows pseudo first-order kinetics.•The reaction rate strongly dependents on pH.•TiO2-G showed increased photo activity under solar light.

The improvement of photocatalytic efficiency under an abundant natural resource, sun light, presents the next step in the large-scale application of photocatalysis for the treatment of dissolved organic and inorganic pollutants in wastewater. In this study, a composite catalyst of TiO2 and Graphene synthesised by a hydrothermal treatment method is used to photo-reduce Zn2+, the most abundant heavy metal found in combined sewer overflows (CSOs). The performance of this composite photo-catalyst was assessed under various process conditions such as pH, light intensity, catalyst loading and light source. The TiO2-Graphene composite photo-catalyst showed a 20.3 ± 0.04% increase in the photo-reduction of Zn2+ under solar light compared to un-doped TiO2 when reaction rate constants are compared. This enhancement is a result of the availability of more sorption sites, decrease in band-gap of the TiO2, and effectiveness of the charge separation in the TiO2-G composite catalyst.