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 3h. 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 (50–300mg/L). The maximum biosorption capacity of biosorbent reached up to 59±0.6mgg−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.