Biosorption thermodynamic and kinetic of direct dye from aqueous solutions on bacterial cellulose

Abstract

In recent years, dyes pollution has become one of the most serious environmental problems. Biosorption as a biotechnology for removal of dyes pollution from aqueous solutions has been extensively studied and most biosorption research mainly focused on the process kinetics and thermodynamics. Bacterial cellulose is receiving great attention and presently being widely investigated as a new type of cost-efficient biosorbent due to its nanofibers network, biocompatibility, nontoxicity, biodegradability and high water holding capacity. The aim of this study was to determine the thermodynamic and kinetic adsorption of direct blue 15 dye from aqueous solutions with bacterial cellulose as a biosorbent. The effects of pH, contact time and temperature on adsorption of direct dye by bacterial cellulose were also evaluated. Kinetic study of direct blue 15 on bacterial cellulose, were carried out under sorption conditions of pH 3.0, MLR 1:500 and an initial dye concentration 100 mg/L. Kinetic analyses were conducted using pseudo first- and second-order models. The regression results showed that the adsorption kinetic was more accurately represented by a pseudo second-order model. Changes in free energy of adsorption (ΔG#), enthalpy (ΔH#) and entropy (ΔS#) as well as the activation energy (Ea) were determined. ΔH#, ΔS# and Ea with pH control were -26.5, -230 and 43.5 kJ/mol. The result showed that the bacterial cellulose could be employed as an effective sorbent for the removal of direct dye from aqueous solution and the values of ΔH#, ΔG# and Eaindicate that the adsorption of direct dye onto bacterial cellulose was a physisorption process.   Key words: Acetobacter xylinum, biosorbent, kinetic, thermodynamic, bacterial cellulose