Preparation of TiO₂/C₃N₄ heterojunctions on carbon-fiber cloth as efficient filter-membrane-shaped photocatalyst for removing various pollutants from the flowing wastewater

C₃N₄-decorated carbon-fiber (CF) cloth has been demonstrated as flexible filter-membrane-shaped photocatalyst for degrading the flowing wastewater, but its photocatalytic activity should be further improved. To enhance the separation efficiency of photogenerated carrier, herein we inserted TiO₂ between C₃N₄ and CF. With CF cloth as the substrate, the in-situ growth of TiO₂ nanoparticles (diameter: 100-200 nm) was realized by a dip-coating/hydrothermal method; and C₃N₄ nanosheets (thickness: 30-50 nm) were prepared on their surface by thermal polymerization. CF/TiO₂/C₃N₄ cloth shows excellent visible photoabsorption (edge: ∼450 nm). Under visible light irradiation, CF/TiO₂/C₃N₄ cloth exhibits improved photocurrent and photocatalytic activity for degrading various organic pollutants (methylene blue, acid orange 7, 4-chloprophenol, tetracycline hydrochloride (TC)) and reducing heavy-metal ions (Cr(VI)), compared with CF/C₃N₄ and CF/TiO₂ cloth. Especially, when CF/TiO₂/C₃N₄ cloth is used as filter-membrane to photo-degrade the flowing wastewater (rate: 1.5 L h^-1), the removal efficiency of TC and Cr(VI) reaches 87% and 88% after 7 grade, higher than that by CF/C₃N₄ cloth (60% TC, 28% Cr(VI)) and CF/TiO₂ cloth (8% TC, 7% Cr(VI)). Therefore, CF/TiO₂/C₃N₄ cloth can be used as efficient filter-membrane-shaped photocatalyst for removing various organic pollutants and heavy metal in the flowing wastewater.