Mechanistic, adsorption kinetics and confirmatory study of Congo red dye removal by native fungus Aspergillus niger

The focus of the current research is the removal of Congo red dye by utilizing a variety of native fungi (dead biomass, live biomass, and crude enzyme extract) isolated from carpet manufacturing wastewater. Using ITS region sequencing analysis, the native isolate GS28 was determined to be Aspergillus niger, and isolate GS28 was successfully able to decolorize CR at concentrations up to 1000 mg L⁻¹. Under optimized conditions (pH 6.0–8.0, temperature 25–35 ℃, Mn 100 mg L⁻¹, and IM + G), live biomass decolorize maximum CR (93.942.8%) at 800 mg L⁻¹ within 120 h, and dead biomass (4 g L⁻¹ of dose,) was removed 86.84% at 200 mg L⁻¹ within 72 h as well as extracted metabolites degrade (4 mL of crude enzyme per 50 mL of CR) CR 84.37% at 100 mg L⁻¹ within 32 h. The CR adsorption happened via monolayer adsorption on A. niger biomass and CR adsorption experimental data was best fitted with the Langmuir isotherm model. The pseudo-second-order kinetic model was well fitted with adsorption of CR. Surface sorption mechanisms were involved in the CR decolorization as validated from FTIR analysis. Enzymatic activity and GC–MS studies have also confirmed the degradation mechanism. The degradation of CR entailed a greater amount of LiP and a smaller quantity of laccase, MnP activities, and because of stress circumstances, protein content decreases at higher concentrations of CR. According to a phytotoxicity study, a fungal-processed dye (100 mg L⁻¹) solution showed a higher rate of seedling growth than pure dye. Overall results show that isolate GS28 has an excellent decolorization capacity to CR and a promising future for use in the treatment of dye wastewater.