Optimization, equilibrium, kinetic modeling, and thermodynamic studies of biosorption of aniline blue by the dead biomass of Aspergillus fumigatus

The effect of biosorbent concentration, initial pH, temperature, agitation rate, adsorption time, and initial dye concentration was studied for the biosorption of aniline blue dye using dead fungal biomass of Aspergillus fumigatus. The maximum biosorption of aniline blue was observed at the sorbent concentration of 1 g/L, initial pH 10, temperature 30 degrees C, agitation rate 160 rpm, and initial dye concentration of 50 mg/L. The experimental data were analyzed using Freundlich, Temkin, and Scatchard equilibrium isotherm models out of which the Freundlich isotherm (R-2 = 0.98) was found to best fit the experimental data. Thermodynamic parameters such as enthalpy change (-3.08 kJ/mol) and entropy change (8.32 J/mol K) were also calculated. The biosorption kinetics of Aniline blue was found to obey pseudo-second-order kinetic model (R-2 = 0.967). The results showed that biosorption was favorable and spontaneous, thus, indicating the positive affinity of the dye towards the adsorbent. The characteristics of the fungal biosorbent were studied using Fourier transform-infrared spectroscopy (FTIR) and scanning electron microscopic (SEM).