Biogenic Silver Nanoparticles for Acid Red Dye Remediation in Aquatic Systems: Structural Characterization and Ecotoxicological Evaluation

Abstract

The increasing discharge of textile dye effluents into aquatic ecosystems poses serious environmental and ecological challenges, necessitating the development of sustainable and efficient remediation strategies. In the present study, biogenic silver nanoparticles (AgNPs) were synthesized using natural pond water as a green reducing and stabilizing medium and evaluated for their potential in Acid Red dye remediation under semi-natural conditions. The biosynthesized AgNPs were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDX). XRD analysis confirmed the formation of crystalline face-centered cubic silver with prominent reflections corresponding to (111), (200), (220), and (311) planes (JCPDS card No. 04-0783), while FE-SEM imaging revealed predominantly spherical nanoparticles with an estimated size range of 150–300 nm. Average crystallite size, estimated via the Debye–Scherrer equation, ranged from 15 to 35 nm, consistent with nanoscale silver formation. EDX spectroscopy confirmed elemental silver as the dominant signal, accompanied by trace chlorine and nitrogen peaks attributable to biogenic capping residues. The remediation efficiency and ecological impact were assessed by monitoring total protein content—measured by the Lowry method at 660 nm—as a biochemical indicator of microbial metabolic activity across control, dye-treated, nanoparticle-treated, and combined exposure systems over a four-day incubation period. A consistent, time-dependent decline in protein concentration was observed in all treatment groups, with comparatively greater inhibition recorded in the combined dye + AgNP system (OD₄ₜₕ = 0.23), suggesting synergistic enhancement of dye transformation coupled with augmented biological stress. Statistical analysis using F-test (p = 0.1092), independent t-test (p = 0.3210), and Wilcoxon Signed-Rank test (p = 0.50) indicated no significant inter-group differences at α = 0.05; however, Pearson’s correlation analysis demonstrated a strong negative relationship between incubation time and protein levels (r = −0.95 to −0.99), indicating progressive and reproducible metabolic suppression across treatments. necessity for careful dosage optimization and environmental risk assessment to mitigate possible ecotoxicological impacts. This study contributes to advancing green nanotechnology approaches for sustainable wastewater management.