Iron-rich sludge-derived ceramsite for catalytic ozonation of tetracycline hydrochloride: Performance, mechanism, and potential application as a constructed wetland substrate

Tetracycline hydrochloride (TCH) is a persistent antibiotic contaminant with potential ecological risks. Iron-rich sludge, a by-product of water treatment, contains abundant iron and heavy metals, and its conventional disposal leads to resource loss and secondary pollution. In this study, iron-rich sludge-derived ceramsite (FeSC) was prepared and applied for catalytic ozonation of TCH. Under optimal conditions, 60 min reaction achieved 96% TCH removal and 61.5% total organic carbon removal, outperforming commercial wetland substrates. After 20 consecutive cycles in real surface water, FeSC maintained over 89% TCH removal with minimal heavy metal leaching, and its production cost (15.888 USD/t) was far lower than commercial substrates. Mechanistic analysis revealed that surface Fe redox cycling, oxygen vacancies, and oxygen-containing functional groups synergistically activated ozone to generate reactive oxygen species, promoting efficient TCH degradation and mineralization. In a simulated constructed wetland system, water treated with the FeSC/O 3 system had minimal impact on plant growth, with root and shoot lengths showing no significant difference compared to the deionized water control (p > 0.05), indicating effective reduction of phytotoxicity. These results demonstrate that FeSC is a low-cost, environmentally compatible multifunctional material with high catalytic performance and application potential in advanced wastewater treatment and wetland systems.