Activated carbon obtained from orange peel (ACOP) was synthesized and used for the removal of heavy metal ions (Cr, Cd, and Co) from aqueous solutions. Two different adsorption models were used for analyzing data. Adsorption capacities were determined: copper ions exhibit the greatest adsorption on activated carbon orange peel because of its size and pH conditions. Adsorption capacity varies as a function of pH. Adsorption isotherms from aqueous solution of heavy metals on ACOP were determined. Adsorption isotherms are consistent with Langmuir's adsorption model. Adsorbent quantity and immersion enthalpy were studied.