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.