Dual-action water purification against waterborne pathogens and organic pollutants by biofabricated ZnO nanoparticles

Waterborne pathogens and synthetic dyes constitute a major public health threat, especially in low-resource settings where conventional treatment infrastructures are limited. Addressing this issue requires regional, green, cost-effective, and sustainable approaches for clean water access. In this study, zinc oxide nanoparticles were biosynthesized and laboratory scaled-up using Teucrium stocksianum extract (ZnONPs@TS) to evaluatetheir dual-actionfor wastewater remediation. The constituents of the plant extract were identified through GC-MS analysis, and systematic optimization of pH, temperature, and extract concentration successfully yielded spherical ZnO crystallites (26 nm) as confirmed by UV-Vis, FT-IR, SEM, DLS, and XRD analysis. Antibacterial assays against Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, and Streptococcus pneumoniae revealed MIC values of 6.1-8.5 µg mL^-1, underscoring the synergistic effect of ZnO-derived ROS and bioactive plant metabolites. A molecular docking study against key bacterial proteins was conducted to elucidate the role of plant constituents in enhancing the activity of the biofabricated nanoparticles. The biological potential of the synthesized nanoparticles was further evaluated for antioxidant and antidiabetic activities. Photocatalytic tests under simulated sunlight demonstrated pseudo-first order degradation of methylene blue (k = 1.48 × 10^-2 min^-1) and methyl orange (k = 1.76 × 10^-2 min^-1), achieving 76-88 % and 78-84 % removal, respectively. The measured band gap (3.06 eV) and band edge positions (E_CB = 0.41 eV, E_VB = 4.01 eV) favor visible light excitation and efficient ROS generation, corroborating the mechanistic model proposed for green ZnO photocatalysts. Thermodynamic analysis (ΔH > 0, ΔG < 0) confirmed an endothermic yet spontaneous degradation process. Practical application studies in different water matrices (spiked distilled, tap, and wastewater effluent) highlighted an affordable, sustainable,and dual-potential of ZnONPs@TS in wastewater treatment.