Preparation and characterization of a novel magnetic biosorbent functionalized with biomass of Bacillus Subtilis: Kinetic and isotherm studies of biosorption processes in the removal of Methylene Blue

Abstract

A novel magnetic biosorbent (M-BSub) was successfully prepared by the immobilization of Bacillus subtilis (B. subtilis) with nano-sized magnetic silica which was confirmed by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), scanning electron microscope (SEM). Optimum biosorption conditions were determined as a function of pH, contact time and initial concentration of Methylene Blue (MB). The maximum biosorption efficiency of MB was obtained at pH 6.8 and 30 °C. The uptake of dye was very fast initially, and achieved equilibrium after 3 h. The isotherm models like Langmuir, Freundlich, Dubinin-Radushkevich (D-R) were used to analyze the equilibrium data. The equilibrium data fit better to the Freundlich model compared to the Langmuir model in concentration range studied (50-300 mg/L). The maximum biosorption capacity of biosorbent reached up to 59 ± 0.6 mg g-1 at pH value of 6.8 and 30 °C. The kinetics data were analyzed using adsorption kinetic models like the pseudo-first order, pseudo-second order and intraparticle diffusion equation. Kinetic data showed good agreement with the pseudo-second order kinetic model. In addition, biosorbent can be easily regenerated and reused for five cycles with high biosorption capacity. This study indicated that M-BSub is a reusable biosorbent for rapid, convenient, and efficient removal of MB from contaminated aquatic systems. © 2017 Elsevier Ltd. All rights reserved.