Synthesis, structural characterization and evaluation of a novel floating metal-free photocatalyst based on g-C3N4 grafted expanded perlite for the degradation of dyes

A highly active, low cost and simple water-floating metal-free photocatalysts based on g-C3N4 grafted expanded perlite (EP) were prepared and characterised. g-C3N4 was grafted by the pyrolysis of melamine in the presence of expanded perlite granules at five different temperatures (from 450 to 580 degrees C). The detailed characterisation and analyses clearly revealed that the physicochemical properties of the photocatalysts, such as the texture, surface structure, optical properties and band structure, which can be controlled by adjusting the calcination temperature. The morphology of samples obtained at different temperatures undergoes sequential evolution from monolith-like to nanosheet, moderately rolled nanosheet, nanoflakelet and even nanoparticles. The calcination temperature played a key role in tuning the pore structure, extending the photoactivity to the visible-light region and effectively narrowing the band gap of the floating photocatalysts. The optimal calcination temperature was 520 degrees C and is attributed to the resultant favourable structure and textural characteristics, including a high specific surface area and a high polymerisation degree. EP-CN-520 showed the highest photocatalytic activity and great recyclability, which indicating EP-CN-520 is a promising photocatalyst, and can be employed to remediate contaminated waters using solar irradiation. [GRAPHICS]