The influence of adsorbent dose, initial metal ion, pH, other ions, temperature and contact time were studied for the adsorption of ferrous ions on to acid activated carbon prepared from Albizia lebbeck bark. The results were analyzed in the light of Langmuir and Freundlich isotherms From this, the adsorption efficiency, adsorption energy, adsorption capacity, intensity of adsorption and dimensionless separation factor were calculated. From the kinetic studies the rate constant values for the adsorption process was calculated. From the effect of temperature thermodynamic parameters like ΔG°, ΔH°, and ΔS° were calculated. The mechanism of adsorption for that ferrous ion onto carbon have investigated by using the experimental results and confirmed by IR spectra, XRD and SEM images.