Chlorella vulgaris-mediated ZrO2 nanostructures for sustainable adsorption of congo red/crystal violet and antibacterial treatment

The development of sustainable nanomaterials by biogenic strategies has emerged as an effective approach for addressing water pollution and microbial contamination. In this study, ZrO 2 nanostructures (ZrO 2 NSs) were successfully synthesized via a rapid microwave-assisted green route using Chlorella vulgaris extract. Comprehensive characterization by XRD, FTIR, FESEM, HRTEM, XPS, and BET analyses confirmed the formation of highly crystalline cubic ZrO 2 NSs with an average crystallite size of 6.65 nm, quasi-spherical morphology, mesoporous architecture, and a specific surface area of 46 m 2 .g −1 . The adsorption performance of the biosynthesized ZrO 2 NSs was evaluated for the removal of Congo Red (CR) and Crystal Violet (CV) from aqueous solutions. The maximum adsorption capacities were 45.1 mg.g −1 for CR and 63.1 mg.g −1 for CV, corresponding to removal efficiencies of 95% and 91%, respectively. Both linear and nonlinear adsorption analyses demonstrated that the equilibrium data were best described by the Langmuir isotherm, while the adsorption kinetics followed the pseudo-second-order model, as supported by higher correlation coefficients and lower χ 2 and RMSE values. Furthermore, the ZrO 2 NSs retained high adsorption efficiency after five regeneration cycles. The nanostructure found potential antibacterial performance exhibiting antibacterial activity against Klebsiella pneumoniae (14 mm inhibition zone) among the studied clinical pathogens. The biosynthesized ZrO 2 NSs demonstrate strong potential for scalable industrial applications as sustainable bioremediation agents in wastewater treatment and antimicrobial technologies.