Acid Mine Drainage (AMD) is a liquid waste caused by mining industrial activity. AMD has a very acidic pH and contain heavy metals, such as Fe and Mn. Therefore, the solution of this global problem should be investigated. One of the ways to treat AMD is by adsorption using activated carbon. Activated carbon is made from coals through chemical activation process using ZnCl2 with a composition of 40% ZnCl2 and 60% coals. Afterwards, carbonization process was performed at 500oC for 120 minutes. The synthesis result of activated carbon was analyzed for iodine numbers and characterized using BET. The activated carbon had maximum iodine numbers of 1373 mg/g and maximum surface area of 667 m2/g. Ion content in Fe and Mn in AMD was adsorbed using activated carbon with several variations of activated carbon grain size, mass, and contact duration. The results showed maximum adsorption of 100% for Fe and 56% for Mn, with increased maximum pH from 3 to 6.2. Kinetic and adsorption study was conducted on contact duration variation and obtained that adsorption process followed Langmuir isothermal model with adsorption capacity of 2.54 mg/g.