Selective efficient photocatalytic degradation of antibiotics and direct Z-type migration pathway for hierarchical...

Constructing superior Z-type photocatalytic heterojunction is beneficial to effectively enlarge interface contact, improve the photo-generated carrier separation rate, and retain the high redox ability. In this work, we designed a hierarchical core-shell g-C₃N₄/TiO₂ structure to build Z-type heterojunction via combining simple template method and pyrolysis process. A close-knit Z-type heterojunction was constructed using TiO₂ as a thick core and g-C₃N₄ as an ultra-thin shell. The effects of lamp source, wavelength, tetracycline (TC) concentration, and photocatalyst dose on the degradation performance on TC of g-C₃N₄/TiO₂ were inspected. 0.1TiO₂/g-C₃N₄ photocatalyst had the best degradation rate and highest removal rate within 30 min, and its degradation rate was about 49, 23, and 5 times than pure g-C₃N₄, TiO₂, and commercial TiO₂/g-C₃N₄ in respect. Moreover, compared with degradation ability under Xenon lamp, LED irradiation for g-C₃N₄/TiO₂ composites showed a remarkable selective degradation. The fast and efficient Z-type transfer pathway of 0.1 g-C₃N₄/TiO₂ was realized by forming an optimized interface and abundant surface active sites ascribed to the combined action of thick TiO₂ core and ultra-thin g-C₃N₄ shell. In addition, the degradation intermediates were analyzed by LC-MS and suggested pathways of degradation. The work could provide novel design concept to obtain reliable Z-type photocatalysts with hierarchical core-shell structure applied in degradation of antibiotic wastewater.