Catalytic synthesis of selenium nanoparticles by gram-negative Aeromonas sobria and their application for removal of toxic dyes

The hazardous dyes used in various industries pose significant threats to human health, underscoring the urgent need for eco-friendly methods of dye removal. This study explores the catalytic synthesis of selenium nanoparticles (SeNPs) by the gram-negative bacterium Aeromonas sobria, which demonstrated remarkable tolerance to sodium selenite concentrations of up to 20 mM. Characterization of the synthesized SeNPs revealed a distinctive UV-vis absorption peak at 300 nm, indicative of successful nanoparticle formation. Fourier-transform infrared spectroscopy (FTIR) analysis identified key biomolecules involved in the synthesis, while X-ray diffraction (XRD) confirmed the crystalline structure of the SeNPs. Transmission electron microscopy (TEM) revealed that the SeNPs ranged in size from 40 to 100 nm, exhibiting predominantly oval shapes with irregular surfaces. The efficacy of these biosynthesized SeNPs in dye removal was evaluated against methylene blue (MB), Congo red, methyl red, and Eriochrome Black T (EBT). Ultrasonication significantly enhanced the catalytic activity, achieving a remarkable 49% removal rate for MB, while the removal rate for Congo red was consistent at approximately 8.6% across all agitation conditions. Kinetic analysis indicated that the degradation of MB followed a pseudo-first-order model with a rate constant of 2.49 × 10⁻² min⁻¹. Mechanistic studies highlighted hydroxyl radicals as the primary active species in the degradation process. This research emphasizes the potential of A. sobria as a promising bio-factory for the sustainable synthesis of SeNPs, offering innovative solutions for the efficient environmental remediation of dye-contaminated waste and contributing to the advancement of nanotechnology in pollution management.