Polyoxometalate anchored zinc oxide nanocomposite as a highly effective photocatalyst and bactericide for wastewater decontamination

Abstract

Considering the remediation of water enviroments polluted by antibiotics and bacteria, it is critical to construct cost-effective, high-performance and environmentally friendly composites. In this work, a novel ZnO@PDA/Cu-POMs nanocomposite was first synthesized by post-grafting polyoxometalate (Cu-POMs) onto ZnO with the assistance of polydopamine (PDA) layer and then fully characterized. The nanocomposite exhibits high-efficiency photocatalytic degradation of tetracycline (TC, 90.75%) with good stability. Furthermore, it retains almost 80% removal efficiency in the presence of competing species. The excellent removal ability was derived from the Z-scheme heterostructure with compact interfacial contact and the synergistic effect between adsorption and photocatalysis. The photocatalytic mechanism and degradation pathway of TC also are elucidated. More importantly, the computational eco-toxicity analysis indicated that the degradation products had low biotoxicity compared to the original TC. It's worth noting that the ZnO@PDA/Cu-POMs nanocomposite shows extraordinary antibacterial activities against four gram-positive/negative bacteria (S. aureus, 99.88%, E. coli, 99.93%, B. cereus, 99.68%, P. aeruginosa, 99.60%) and two antibiotic-resistant bacteria (kanamycin-resistant E. coli, 92.27% and ampicillin-resistant E. coli, 88.93%) at low concentrations. Moreover, the antibacterial mechanism revealed that the synergistic action between ZnO@PDA and Cu-POMs damages the cellular membrane, increases oxidative stress levels, and leads to the death of bacteria. The current work provides a new perspective on the construction of multifunctional POM-based composites for environmental cleaning and water purification.