Biogenic ZnO Nanoparticles Derived from Eichhornia crassipes: Synthesis and Application in the Degradation of Multiple Organic Dyes and Chlorpyrifos Ethyl

The green synthesis of zinc oxide (ZnO) nanoparticles using plant biomass offers a sustainable approach for developing photocatalytic materials for water treatment. In this study, ZnO nanoparticles were biosynthesized using aqueous extracts of Eichhornia crassipes from the Medio Atrato region, Chocó, Colombia, at 1%, 2%, and 4% (w/v). The materials were characterized by FTIR, UV-Vis, XRD, and SEM–EDX. All samples exhibited the hexagonal wurtzite structure of ZnO without detectable secondary crystalline phases. Average crystallite sizes were 38.66, 38.16, and 31.52 nm for EC-1%, EC-2%, and EC-4%, respectively, decreasing with increasing extract concentration. Photocatalytic activity was evaluated under UV irradiation using six organic dyes: amido black 10B, eosin yellow, methylene blue, methyl orange, methyl red, and rhodamine B. Performance depended on both pollutant type and extract concentration. EC-2% showed the most consistent overall performance, achieving 87% degradation of amido black 10B, 92% of methyl orange, 81% of methyl red, and 93% of rhodamine B. Eosin yellow reached approximately 97% removal at 90 min, while EC-4% achieved 95% methylene blue degradation after 180 min. EC-2% also removed approximately 56.78% of chlorpyrifos ethyl after 180 min. Overall, E. crassipes-mediated ZnO nanoparticles demonstrate promising photocatalytic activity toward diverse organic pollutants and provide a potential route for valorizing invasive aquatic biomass.