Biosorption of methylene blue by chaetophora elegans algae: kinetics, equilibrium and thermodynamic studies

Adsorptive removal capacities of renewable and highly available Chaetophora elegans algae have been investigated in this study. To assess the use of this soft water algae to remove organic pollutants from aqueous solution, Methylene blue (MB) dye was used as a model molecule. The effect of dye concentrations, pH, adsorbent mass, temperature, and particle size have been evaluated. The algal biomass showed quite interesting adsorption capacity under optimized operating conditions (333 mg of dye per gram of biomass at 30 °C). Pseudo-first and pseudo-second order kinetic models were applied to the adsorption dynamic data. Pseudo second order model was well in line with the experimental data, therefore suggesting a probable chemically-based adsorption process. Several isotherm models were investigated to monitor the adsorption behavior. The Langmuir-Freundlich isotherm model fitted the experimental data best. The adsorption thermodynamic parameters ΔG°, ΔH° and ΔS° were calculated. The maximum uptake is independent of temperature. From the values of the thermodynamic parameters, we concluded that the adsorption is exothermic, more ordered and spontaneous.