Investigation of the Potential of Wild Lettuce for the Biosynthesis of Silver-Zinc Oxide Nanocomposites as Antimicrobial Agents for Water Treatment
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Date
2025-05
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NM-AIST
Abstract
Silver-zinc oxide nanocomposites (Ag-ZnO NCs) are highly effective antimicrobial agents for point-of-use water treatment. However, chemically synthesized Ag-ZnO NCs pose potential health risks due to the use of toxic and carcinogenic chemicals as reducing and stabilizing agents raising a concern for the use of safe, non-toxic, readily available, and non-carcinogenic biochemicals. This study explored the potential of wild lettuce as a natural source of biochemicals that can serve as safe and eco-friendly reducing and stabilizing agents for the biosynthesis of Ag-ZnO NCs. The study further investigated the use of water hyacinth activated
carbon (AC) as a potential impregnation precursor for the biosynthesized Ag-ZnO NCs and evaluated their antimicrobial efficacy. The biochemicals were extracted using 0, 50 and 100% ethanolic solvents (EtOH) in different extraction circles and volumes. The wild lettuce leaf extracts were used to biosynthesize Ag-ZnO NCs and eventually were impregnated in the AC. The antimicrobial activity was performed using ager plate and the water treatment was analysed using synthetic and natural water in a batch reaction. The FTIR results confirmed the presence of alkaloids, flavonoids, tannins, saponins, and proteins which are essential for the biosynthesis process. Phytochemical analysis confirmed the presence of high amounts of biochemicals in wild lettuce leaves. Total phenolic and antioxidant contents of the leaf extract followed the trend 100<0<50% EtOH with the highest yield of about 11 044 ± 63 and 44 112 ± 894 µg/g, respectively (p<0.05). The XRD analysis of Ag-ZnO NCs confirmed their crystalline nature with an average particle size of 21.51 nm. The SEM and TEM images confirmed formation of
spherical shaped nanocomposites with a successful doping of Ag into ZnO. It further confirmed a successful impregnation of Ag-ZnO into AC. The BET results of Ag-ZnO-AC indicated an increase of surface area with activation creating more surface for the Ag-ZnO attachment. The antibacterial activity of Ag-ZnO NCs indicated high microbial inhibition on E. coli (21 ± 1.08 mm) and S. aureus (19.67 ± 0.47 mm). The Ag-ZnO-AC had significant antimicrobial activities against E. coli (14.00 ± 0.37 mm) and S. aureus (17.33 ± 0.36 mm). The water treatment analysis of Ag-ZnO-AC indicated complete microbial elimination on synthetic (2 h) and natural water (1 h). These results confirm wild lettuce as a potential natural source of biochemicals for the biosynthesis of Ag-ZnO NCs and water hyacinth as a potential impregnation material due to its high porosity and high surface area
Sustainable Development Goals
SDG-3: Good Health and Well-being
SDG-6: Clean Water and Sanitation
SDG-9: Industry, Innovation and Infrastructure
SDG-12: Responsible Consumption and Production
SDG-13: Climate Action
SDG-15: Life on Land