Efficiency enhancement of indole photodegradation under visible and UV-light irradiation using g-C3N4/TiO2 hetero-nanostructures

g-C3N4/TiO2 photocatalysts were in-situ synthesized via a straightforward high-temperature calcination method and used to activate persulfate (PS) to degrade indole under different light irradiation. The prepared g-C3N4/TiO2 photocatalysts were characterized by SEM, TEM, XRD, BET, XPS, FTIR, and photocurrent response analysis. The CNT1:5 (mass ratio of g-C3N4 to TiO2 of 1:5) and CNT 24:1 (mass ratio of g-C3N4 to TiO2 of 24:1) showed the best performance in degradation of indole solution under UV and visible light, respectively. Free radical quenching experiments and band structure analysis determined that the UV/CNT1:5 and PS-Vis/CNT24:1 systems followed an S-scheme and type-II transfer mechanism, respectively. A detailed analysis using GC-MS revealed the indole's intermediate products and proposed the indole's degradation pathway. Furthermore, using natural water matrices, the removal of other typical organic compounds, including quinoline, pyridine, and phenol, was investigated in the UV/CNT1:5 and PS-Vis/CNT24:1 systems. The results of this study promote the application of gC3N4/TiO2 composites as organic degradation catalysts, reflecting the potential of composite materials in the removal of toxic organic compounds in coal chemical wastewater.