In recent years, biogenic nanoparticles have attracted considerable attention as efficient adsorbents for removing pollutants from industrial wastewater, owing to their small size, low toxicity, cost-effectiveness, and environmentally friendly nature. In this study, copper oxide nanoparticles (CuO-NPs) synthesized by the psychrotolerant Microbacterium sp. were employed for the removal of two common azo dyes, Reactive Red 24 (RR24) and Acid Orange 7 (AO7). The biogenic nanoparticles were characterized using UV-Vis Spectroscopy, FTIR, Zeta Potential, XRD, SEM, EDS, and AFM. The average size of these nanoparticles was 63.21 nm, with a PDI value of 0.27, indicating a relatively uniform size distribution of CuO-NPs. EDS analysis revealed that the highest weight percentages of O and Cu were 38.32% and 35.17%, respectively. Batch biosorption experiments were conducted to evaluate the effects of pH, nanoparticle dose, dye concentration, and mixing speed. Under optimized conditions, the removal efficiency of RR24 reached 95% at an initial concentration of 20 mg/L, pH 2, a mixing speed of 300 rpm, and a nanoparticle dose of 80 mg after 140 minutes, whereas AO7 exhibited an 82% removal efficiency under similar conditions with a mixing speed of 500 rpm over 80 minutes. The adsorption data were well fitted by the Freundlich isotherm and pseudo-second-order kinetic model, indicating chemisorption onto heterogeneous surfaces. Overall, the results demonstrate that biogenic CuO-NPs are highly effective, cost-efficient, and environmentally sustainable adsorbents, presenting a promising alternative to conventional wastewater treatment technologies for the removal of azo dyes.

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