Biosorption of As(III) from aqueous solution by Acacia auriculiformisleaves

The biosorption capability of Acacia (Acacia auriculiformis A.Cunn. ex Benth.) leaf powder in batch and small scale column was investigated. The adsorption properties were analyzed with different experimental variables such as solution pH, amount of biosorbent, initial As(III) concentration and temperature. The maximum adsorption was observed at pH 6.0 while the equilibrium was attained in 5 h. Langmuir and Freundlich equilibrium adsorption isotherm models were utilized for fitting the experimental data. The maximum adsorption capacity of A. auriculiformisleaf powder was calculated to be 41.410 μg g-1. The kinetic data were well fitted by pseudo-first-order model with the correlation coefficient greater than 0.989. Surface morphology of the biosorbent was analyzed by scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) was employed to characterize the surface functional groups of A. auriculiformisleaf powder.The activation energy (Ea) and heat of biosorption (∆H) were calculated to be 27.549 and 43.380 kJ mol-1 respectively. The thermodynamic parameters such as Gibbs free energy (∆G), enthalpy (∆H), and entropy (∆S) revealed the spontaneous nature of the biosorption followed by physical activated process. Small scale column tests (SSCT) were also conducted to find out the breakthrough characteristics of the column packed with biosorbent.