Activated carbon (AC) has been prepared from rice husk (RH) as an agricultural by-product. Different analytical instruments characterized the prepared activated carbon. Fe3+ and Mn2+ were extracted from the aqueous solution. The effects of many different variables namely, pH effect, reaction time, adsorbent amount, starting concentration of metal ions, interfering ions and temperature on the adsorption of ions were evaluated. The optimal adsorption of Fe3+ and Mn2+ was 3 and 6, respectively. The optimal contact time was determined to be 2 hours for both Fe3+ and Mn2+ ions. The kinetic and thermodynamic of adsorption process was found to be a pseudo-second order for both Fe3+ and Mn2+ ions. The equilibrium data was applicable to Langmuir, and Freundlich isotherm. The correlation coefficient (R2) of both isotherms were 0.99 & 0.89 for Fe3+, respectively and 0.99 & 0.77 for Mn2+, respectively. The obtained data predicted also that; the endothermic system governs the adsorption process. Furthermore, the maximum adsorption capacities for Fe3+ and Mn2+ were 72.2 & 49.6 mg/g, respectively and the removal of metal ions were 90.12 & 83.42 %, respectively. Finally, the results revealed that the adsorption process of the two metal ions is consistent with the pseudo-second-order kinetics.