Quasi-full-visible-light absorption by D35-TiO2/g-C3N4 for synergistic persulfate activation towards efficient photodegradation of micropollutants

To utilize the excellent charge separation efficiency of the g-C3N4/TiO2 photocatalyst and broaden its narrow visible-light absorption range, D35 dye-sensitization was employed to synthesize a novel D35 TiO2/g-C3N4 photocatalyst. Due to the complementary co-absorption ability of g-C3N4 and the D35 dye, the D35 TiO2/g-C3N4 nano-composite exhibits a quasi-full-visible-light harvesting range up to 675 nm, and the simultaneous electron injection from the D35 and g-C(3)N(4)to TiO2 synergistically activates persulfate (PS) to produce the active oxidizing species more efficiently. In the D35-TiO2/g-C3N4/PS photocatalytic system, 10 mg/L bis-phenol A (100 mL) could be completely removed in only 15 min with 0.5 g/L photocatalyst and 2 mM PS under visiblelight illumination (lambda > 400 nm); meanwhile, nearly 50% of BPA was mineralized into nontoxic substances. Radical quenching experiments and electron paramagnetic resonance (EPR) spectra revealed that (OH)-O-center dot, SO4(center dot-), O-center dot(2)- and h(+) all contributed to organics elimination, and the radical process was the main degradation pathway. The efficient photodegradation of other typical micropollutants, such as caffeine, phenol, acetaminophen and methylene blue, indicating that the D35-TiO2/g-C3N4/PS photocatalytic system has a strong non-selective oxidative ability to remove micropollutants. Therefore, it has great potential to be applied in water environment remediation.