Calcination-driven performance enhancement in ZnAl-cl LDH-based photocatalysts for herbicide degradation

In this study, oxygen-vacancy-enriched ZnAl-LDOs were synthesized via coprecipitation followed by calcination at different temperatures (300 °C, 500 °C, and 700 °C) and tested for chloridazon (CLZ) photodegradation. The photocatalysts were thoroughly characterized using XRD, FTIR, TGA, SEM, BET, DRS, XPS, and PL analyses. Among them, the ZnAl-LDO calcined at 500 °C (ZA-500 °C) exhibited the highest photocatalytic performance for CLZ degradation through peroxydisulfate (PDS) activation, outperforming the other ZnAl-LDOs as well as pure ZnO and ZnAl 2 O 4 . Under UVA irradiation for 4 h, 94.3 % of CLZ (100 μM) was degraded using 0.48 g/L of ZA-500 °C and 1 mM PDS. Quenching experiments identified • OH and SO 4 •- as the dominant reactive oxygen species responsible for CLZ degradation. Mechanistic studies indicated that surface oxygen vacancies on ZnAl-LDO played a key role in photocatalysis and PDS activation. Furthermore, possible degradation pathways of CLZ were proposed based on the analysis of its intermediate products. This work not only demonstrates that ZnAl-LDO can act as an efficient photocatalyst for PDS activation and CLZ degradation, but also provides valuable insights into the relationship between the structure of ZnAl-LDOs and their photocatalytic properties. In this study, environmentally relevant conditions were used with the consideration of environmental factors, such as temperature, pH, environmental matrix constituents, and chemical doses for waste removal, within their respective realistic occurrence ranges. • ZnAl-LDO enriched with oxygen vacancies was synthesized via coprecipitation followed by calcination. • ZnAl-LDO was employed for the first time as a persulfate activator for chloridazon degradation. • • OH and SO₄ •- radicals were identified as the dominant reactive species involved in CLZ degradation. • Oxygen vacancies significantly enhanced persulfate activation and improved the photocatalytic performance.