Porous organic semiconductor/PET composite fibre for the synergistic removal of hexavalent chromium and organic pollutants under sunlight

In this study, the porous graphite phase carbon nitride photocatalyst (P-g-C₃N₄) is prepared by the CaCO₃ template method, and then P-g-C₃N₄/T-polyethylene terephthalate (T-PET) catalytic fibre is prepared by the padding method. P-g-C₃N₄ can provide more active sites than g-C₃N₄ as proved by the Brunauer–Emmett–Teller and the UV–Visible diffuse reflectance test. P-g-C₃N₄ powder catalyst successfully supports PET fibre as proved by scanning electron microscope, Fourier infrared spectroscopy and X-ray diffraction spectroscopy. The photocatalytic performance of P-g-C₃N₄/T-PET catalytic fibre is tested by constructing a single hexavalent chromium or hexavalent chromium/organic pollutant binary pollution system. The potential application value of P-g-C₃N₄/T-PET catalytic fibre is further explored by simulating the complex actual water environment. After five recycles, P-g-C₃N₄/T-PET catalytic fibre shows good catalytic performance. The mechanism of P-g-C₃N₄/PET photocatalytic degradation of organic pollutants is proposed through the capture agent experiment and electron paramagnetic resonance spectroscopy. Among them, •O₂⁻ is the most important active species of P-g-C₃N₄ catalytic fibre, which is used for the oxidation of organic pollutants. At the same time, photoelectrons generated by the catalytic fibre are used to reduce hexavalent chromium. The efficiency of P-g-C₃N₄ to remove pollutants is improved by using PET fibre as a carrier, which not only solves the problem of difficult recovery of powder catalysts but also provides more active sites.