A novel ZnO/biochar composite catalysts for visible light degradation of metronidazole

In this study, waste pine-attached zinc oxide (ZnO/PiC) composites were synthesized for the degradation of metronidazole (MNZ) over a wide pH range (3, 5, 7, 9, and 11) by using a facile hydrothermal process, where pine alkali hydrolysate was used both as an in-situ carbon source and a bio-template. The microstructure and optical properties of the prepared catalysts were characterized using XRD, SEM, BET, XPS, ESR, FTIR, UV-vis DRS and photoluminescence (PL) spectroscopy techniques. It was observed that the surface area of ZnO/PiC0.1 composite was increased, and the electronic band gap was reduced, after the attachment of ZnO nanoparticles to the PiC surface, which enhanced the active sites and electron-hole pairs as well as reduced the recombination frequency of the photogenerated charges. It enabled ZnO/PiC0.1 to be activated by visible light, thereby improving the photocatalytic activity. The quenching tests and ESR analysis confirmed that the hydroxyl radicals (.OH) played a dominant role in the degradation of MNZ, while h(+) and O-2(.-) contributed to a lesser extent in the photocatalytic process. In addition, the ZnO/PiC0.1 sample exhibited an excellent stability over five cycles and high photocatalytic activity over a wide pH range, thereby confirming its potential use in practical engineering for treating the industrial wastewater over a wide large pH range.

Automated summary

In this study, waste pine-attached zinc oxide composites were synthesized and used for the photocatalytic degradation of metronidazole. The composites showed improved photocatalytic activity due to the increased surface area and reduced electronic band gap. Hydroxyl radicals played a dominant role in the degradation process, and the composites exhibited stability and high photocatalytic activity over a wide pH range.