BIOSORPTION OF Cr(III) FROM AQUEOUS SOLUTION BY ACTIVATED SLUDGE

The biosorption of Cr(III) from aqueous solution using activated sludge (AS) microorganisms was investigated under various experimental conditions regarding pH and temperature. Biosorption equilibrium parameters were determined based on the Langmuir and Freundlich isotherm model. The kinetic parameters were established using the equations of pseudo-first order and pseudo-second order. Moreover thermodynamic parameters have been calculated. Langmuir isotherm provided a better fit to the equilibrium data. The maximum experimentally determined sorption capacity 26.95 mg . g(-1) obtained at 25 degrees C and pH 5.0. The kinetics model of pseudo-second order row has been better describing experimental data. The negative value of free Gibbs energy (Delta G(0)) proves spontaneous Cr(III) biosorption by AS biomass and its decreasing along with temperature increase. The negative value of enthalpy (Delta H-0) and entropy (Delta S-0) indicates exothermic process and limitation of degree of freedom Cr(III) ions on the interphase surface solution/biosorbent. FT-IR spectroscopy analysis indicated the contribution of carboxylate groups towards the biosorption of Cr(III) by AS.