Advanced strategies for enhanced decolorization and detoxification of textile dyes using biofilm NAS

As the most diverse prokaryotes, bacteria can decolorize dyes and produce nanoparticles. In this research, a mixture of four commonly used textile dyes, Reactive Red 120, Acid Red 18, Acid Red 137, and Direct Yellow 12, was effectively decolorized using three bacterial strains (S2, N, and A) isolated from wastewater in textile facilities. These strains were applied as a consortium NAS2, and in biofilm form, combined with an Ag/AgCl/Fe3O4 nanocomposite on a peach pit. Furthermore, strain S2 was explicitly employed to synthesize the Ag/AgCl/Fe3O4 nanocomposite, which exhibits antimicrobial properties. The combination of four dyes was decolorized entirely by consortium NAS2 within 24 h and by the biofilm NAS2–Ag/AgCl/Fe3O4 nanocomposite (B-NAS2-NC/PP) within 12 h, as confirmed by UV–Vis spectroscopy. FTIR analysis of the decolorized dye mixture revealed the breakdown of dye bonds. GC-MS analysis indicated that the bacterial strains degraded the dyes into more minor compounds, primarily decanoic acids and esters. SEM/EDX analysis of B-NAS2-NC/PP showed successful stabilization of the bacterial strains and the nanocomposite on the peach stone. The Ag/AgCl/Fe3O4 nanocomposite was synthesized and characterized by UV–Vis, FTIR, XRD, and SEM, with an average nanocomposite size of 22 nm. The impact of the nanocomposite, dyes, and decolorized products was determined through radish seed germination and brine shrimp assays. Radish seed growth reached 77% in the presence of the nanocomposites, compared to 67% with the decolorized product. Notably, radish seeds failed to germinate in the presence of the four-dye mixture. The brine shrimp lethality rate was 11% at a nanocomposite concentration of 25 µg/ml, rising to 40% at 2500 µg/ml. The decolorized product at a 1250 µg/ml concentration of the dye mixture showed a 0% lethality rate.