Azo dyes are among the most signifcant xenobiotics that are resistant to environmental deterioration. In this study, Reactive Black (RB) 5 and Direct Red (DR) 23 dyes were removed from aqueous solutions using biogenic copper oxide nanoparticles synthesized from a cold-tolerant bacterium, namely Stenotrophomonas sp. The efects of physicochemical factors like pH, nanoparticle dose, dye concentration, and mixing speed were examined in batch biosorption experiments. The pseudo-second-order kinetic model and the Langmuir isotherm had better agreement with the biosorption data. Biogenic nanoparticles were studied using the following techniques: scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Zeta potential, X-ray powder difraction (XRD) analysis, and energy-dispersive X-ray spectroscopy (EDS). These nanoparticles had an average size of 52.41 nm in the DLS analysis, and the PDI index was calculated to be 0.26, indicating the uniform size distribution of copper oxide nanoparticles. For the nanoparticles, fower-like and cluster morphology was seen in the SEM images. The oxygen and copper elements were said to have the two most notable EDS analysis peaks. The optimum pH for both dyes’ adsorption was 2. The efective decolorization increased with an increase in the nanoparticle dose and mixing speed. Therefore, with an initial dye concentration of 20 mg/L, a mixing speed of 500 rpm, and a dose of 0.08 g of copper oxide nanoparticles in 80 min, the decolorization efciency of RB5 dye reached 94%. For DR23 dye (20 g/L), 400 rpm mixing speed, and 0.04 g of copper oxide nanoparticles, 97% was measured after 60 min. The Langmuir isotherm and the pseudo-second-order kinetic model were used to explain how the RB5 and DR23 dyes adsorb to CuONPs biosorbent. Because of their superior capacity to adsorb both azo dyes, copper oxide nanoparticles synthesized by bacteria can be used as low-cost, promising, and potential alternatives to traditional wastewater treatment methods.

Keywords