Equilibrium, kinetic and thermodynamic studies on aluminum biosorption by a mycelial biomass ( Streptomyces rimosus)

Abstract

This work focused on kinetic, equilibrium and thermodynamic studies on aluminum biosorption by Streptomyces rimosus biomass. Infrared spectroscopy analysis shows that S. rimosus present some groups: hydroxyl, methyl, carboxyl, amine, thiol and phosphate. The maximum biosorption capacity of S. rimosus biomass was found to be 11.76 mg g −1 for the following optimum conditions: particle size,]250–560] μm, pH 4–4.25, biomass content of 25 g L −1, agitation of 250 rpm and temperature of 25 °C. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models were applied to describe the biosorption isotherms at free pH (pH i 4) and fixed pH (pH f 4). Langmuir model is the most adequate. With fixed pH, the maximum biosorption capacity is enhanced from 6.62 mg g −1 to 11.76 mg g −1. The thermodynamic parameters (Δ G°, Δ H° and Δ S°) showed the feasibility, endothermic and spontaneous nature of the biosorption at 10–80 °C. The activation energy (Ea) was determined as 52.18 kJ mol −1 using the Arrhenius equation and the rate constant of pseudo-second-order model (the most adequate kinetic model). The mean free energy was calculated as 12.91 kJ mol −1 using the D–R isotherm model. The mechanism of Al(III) biosorption on S. rimosus could be a chemical ion exchange and carboxyl groups are mainly involved in this mechanism.