An investigation on the biosorption of inorganic textile dyes by Bacillus subtilis from aqueous solution

In this study, batch experiments were carried out for the biosorption of Acid Blue 225 (AB 225) and Acid Blue 062 (AB 062) onto Bacillus subtilis. The operating variables studied were initial dye concentration, initial solution pH, adsorbent dosage and contact time. Equilibrium biosorption data were fitted to Freundlich and Langmuir isotherms. Langmuir isotherm was found to be an optimum isotherm for two dyes. The maximum adsorption capacity for AB 225 and AB 062 were found to be 89.92 mg g-1 and 74.51mg g-1, respectively, at optimum conditions of pH (1.0) and temperature (25oC). The equilibrium time for the removal of AB 225 and AB 062 by the biomass was reached within 90 min. Two simplified kinetic models were tested to investigate biosorption mechanisms in terms of pseudo-first order and pseudo-second order rate equations. The biosorption rates of Acid Blue 225 and Acid Blue 062 were found to be in consistent with the pseudo-second order model.Keywords: Biosorption, Bacillus subtilis, Acidic dye, Langmuir, Pseudo-second order rate.