Sustainable approach for fabrication of pineapple agro-waste mediated cellulose nanocrystals embedded with Ag/Ag2O/ZnO nanocomposites for efficient removal of waterborne pathogens in wastewater.

Biogenic nanocomposites (NCs) effectively purify contaminated water by eliminating pollutants caused by rapid urbanization, unrestrained industrial activities, and the proliferation of pathogenic organisms, addressing the critical water contamination crisis impacting global health. This study describes the synthesis of a sustainable biopolymer NC (BNC) by incorporating pineapple (Murusi variety) crop residue-based Ag/Ag2O/ZnO NCs and cellulose nanocrystals (CNCs) through an eco-friendly and sustainable approach. TEM analysis revealed cross-sectional diameters of 11 nm consisting of spherical-shaped Ag/Ag2O NPs (9 nm) arranged on nanoflower-shaped ZnO NPs (82 nm). XRD analysis confirmed that biogenic Ag, Ag2O, and ZnO NPs exhibit space groups Fm3m, Pn-3m, and P63mc respectively with Ag/Ag2O NPs forming face-centered cubic and ZnO NPs wurtzite crystal structures. FTIR validated the pure CNCs formation, while TGA and differential thermogravimetry (DTG) demonstrated high thermal stability at 370 °C. Ag/Ag2O NPs exhibited outstanding antibacterial activity at 2000 ppm, with inhibition zones of 20 mm against E. coli and 21 mm against S. aureus. In contrast, ZnO NPs demonstrated lower antibacterial activity with inhibition zones of 13 mm against E. coli and 14 mm against S. aureus. The Ag/Ag₂O/ZnO NCs displayed significant antibacterial activity against both strains with inhibition zones of 19 mm. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the NCs were determined to be 31.3 ppm and 62.5 ppm, respectively, for both bacterial strains. These findings highlight the superior antimicrobial properties of silver-based NCs compared to ZnO, suggesting their potential application in antimicrobial treatments. The developed BNC filter comprising of Ag/Ag2O/ZnO NCs 20 mg: CNCs: 50 g effectively removed Salmonella typhi from 1.2 L of contaminated wastewater through sequential filtration, exhibiting significant characteristics including sustainability, low production cost, water stability, easy recoverability, and high bacterial growth inhibition, making it a promising solution for water treatment applications.