Biosorption of Congo red dye by Aspergillus carbonarius M333 and Penicillium glabrum Pg1: Kinetics, equilibrium and thermodynamic studies

The biosorption of the anionic dye Congo red from aqueous solution onto the novel biosorbents Aspergillus carbonarius and Penicillium glabrum was studied. Optimum sorption conditions were identified by varying solution pH, initial dye concentration, contact time and temperature. The obtained results showed that BET surface area of Penicillium glabrum biosorbent (6.31 m2/g) was larger than that of Aspergillus carbonarius biomass (5.07 m2/g). The microstructures of the fungi were observed with scanning electron micrographs. Chemical characterization of both micro-fungi was carried out by Fourier Transform Infrared Spectroscopy (FT-IR). The biosorption data have been analyzed using Langmuir, Freundlich, Temkin, Dubinin-Radushkevich and Sips isotherms. Based on R2, the equilibrium sorption data was better fitted to Langmuir isotherm model than any other model. The biosorption processes conformed to the pseudo-second-order rate kinetics. Maximum biosorption capacity was found to be 99.01 mg/g for Aspergillus carbonarius and 101.01 mg/g for Penicillium glabrum at pH 4.5, 0.33 g/L sorbent dosage, 180 min contact time and 303 K for dye initial concentration of 50 mg/L. Thermodynamic parameters of the biosorption (ΔG° ΔH° and ΔS°) were also determined and it was found that the biosorption of dye by Aspergillus carbonarius and Penicillium glabrum was a spontaneous process and endothermic in nature.