The discharge of azo-dye-containing wastewater from textile and related industries rep-
resents a major environmental challenge because of the persistence, toxicity, and poor
bio-degradability of synthetic dyes. Congo red dye (CR), one of the most widely used
azo dyes, poses serious ecological and public health risks when released into aquatic
ecosystems. Although numerous biological adsorbents have been investigated for dye re-
moval, the development of sustainable fungal-based nanocomposites with high adsorption
efficiency, optimized operational conditions, and verified environmental safety remains
limited. Therefore, the present work describes the development and evaluation of a novel
Aspergillus terreus–silver oxide nanoparticle (Ag2O NPs) myco-nanocomposite as a promis-
ing eco-friendly biosorbent for CR dye removal from aqueous solutions and real wastew-
ater. Aspergillus terreus (GenBank accession PX920301) isolated from dye-contaminated
wastewater, the adsorption efficiencies of dried mycelia, and the myco-nanocomposite
were compared. Myco-nanocomposite was characterized using ultraviolet visible spec-
troscopic analysis (UV/Vis), Fourier transform infrared spectroscopy (FTIR), and X-ray
diffraction (XRD). A. terreus–Ag2O NPs myco-nanocomposite exhibited the highest ad-
sorption efficiency 92.73%, adsorption capacity (qe) 118.7 mg/g and lowest CR dye residual
by 3.81 mg/L, while A. terreus non-autoclaved dried mycelia recorded 78.28% CR removal,
adsorption capacity (qe) 100.2 mg/g and CR dye residual by 11.39 mg/L. Adsorption
parameters were optimized using a four-factor Box–Behnken experimental design, produc-
ing a highly significant quadratic model (R2 = 0.986). The highest optimized conditions
were obtained at run 17 in which 100 mg L−1 CR dye, pH 8, 0.05 g adsorbent dosage, and
48 h contact time, with removal efficiency of 96.88%, followed by run 14 using 50 mg L−1
CR dye, pH 6, 0.05 g adsorbent dosage, and 48 h contact time, with removal efficiency of
95.79%. Phytotoxicity and microbial toxicity assays demonstrated that the treated wastew-
ater was environmentally safer than untreated CR dye, exhibiting no inhibitory effects
on representative bacteria, yeast, and filamentous fungi while improving wheat seedling
growth. Furthermore, application of the myco-nanocomposite to real industrial wastewater
achieved 94.92% decolorization. This study provides a sustainable myco-nanocomposite of
A. terreus–Ag2O NPs which represents a promising green technology for the remediation of
dye-contaminated industrial effluents and supports the development of environmentally sus-
tainable wastewater management strategies and applicability of reusing treated wastewater.