The biosorption capability of Acacia (Acacia auriculiformis A.Cunn. ex Benth.) leaf powder in batch and a small scale column was investigated. The adsorption properties were analyzed with di erent 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. auriculiformis leaf powder was calculated to be 41.410 μg g^sup -1^. The kinetic data were well fitted using a pseudo-first-order model with a correlation coefficient greater than 0.989. The surface morphology of the biosorbent was analyzed using Scanning Electron Microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) was employed to characterize the surface functional groups of A. auriculiformis leaf powder. The activation energy (E^sub a^) and heat of biosorption (ΔH) were calculated to be 27.549 and 43.380 kJ mol^sup -1^, respectively. The thermodynamic parameters, such as Gibbs free energy (ΔG), enthalpy (ΔH), and entropy (ΔS), revealed the spontaneous nature of the biosorption followed by a physical activated process. Small Scale Column Tests (SSCT) were also conducted to discover the breakthrough characteristics of the column packed with biosorbent.