Engineering Bi3O4Br/TiO2 nanobelt/glucose hydrochar heterostructures for enhanced visible-light degradation of pharmaceutical pollutants

The existence of pharmaceutical residues, such as paracetamol, in water bodies is extremely risky to the environment and human health, and thus efficient and sustainable remediation technologies should be developed. In this study, a novel ternary Z-scheme photocatalyst consisting of bismuth-rich oxybromide (Bi 3 O 4 Br), TiO 2 nanobelts (TiO 2 NB), and glucose-derived hydrochar (GH) was synthesized to degrade paracetamol under visible light irradiation. The effect of the synthesis procedure was explored through a two-step and one-step hydrothermal synthesis method. The photocatalyst prepared with the two-step procedure showed better efficiency and the increased growth of Bi 3 O 4 Br nanosheets around the hydrochar, resulting in better interface electronic coupling and charge separation efficiency compared to the synthesized one-step material and Bi 3 O 4 Br/TiO 2 NB heterostructure. Photocatalytic experiments showed that the two-step 10% composite displayed the highest paracetamol degradation efficiency of approximately 91% at natural pH, outperforming the pristine TiO 2 NB, Bi 3 O 4 Br, and the Bi 3 O 4 Br/TiO 2 NB heterostructure photocatalyst under visible light irradiation. Scavenger tests and electron paramagnetic resonance (EPR) analysis revealed the role of the reactive species (h + , •OH, and O 2 • - ) during the photocatalytic tests, indicating the primary contributions of holes and superoxide radicals and the minor contribution of hydroxyl radicals. The Z-scheme mechanism was also proven by selective photodeposition of Pt and MnO x . The photocatalysts remained active during five cycles of photocatalytic experiments and demonstrated potential for treating real pharmaceutical wastewater, indicating their promising application in the sustainable remediation of pharmaceutical wastewater.